2010-2013

CENTER ODLIČNOSTI NAMASTE Zavod za raziskave in razvoj naprednih nekovinskih

materialov s tehnologijami prihodnosti

CENTRE OF EXCELLENCE NAMASTE Advanced Materials and Technologies for the Future

Izdaja | Publisher: Center odličnosti NAMASTE, Zavod za raziskave in razvoj naprednih nekovinskih materialov s tehnologijami prihodnosti | Centre of Excellence (CoE) NAMASTE, Advanced Materials for the Future Jamova cesta 39 SI-1000 Ljubljana T: + 386 (0)590 54 356 F: + 386 (0)590 54 355 http://www.conamaste.si Avtorji teksta | Authors of the text: Alenka Rožaj Brvar, Darko Belavič, Slavko Bernik, Janez Trontelj, Slobodan Žumer, Janez Štrancar, Danjela Kuščer Urednik | Editor: Janez Štrancar Oblikoval | Design: Janez Štrancar Lektoriranje | Lecturing: Paul McGuiness in Jože Gasperič Tisk | Print: Infokart d.o.o. December 2013

2

Center odličnosti NAMASTE Centre of Excellence NAMASTE

NEKAJ OSNOVNIH DEJSTEV O CENTRU ODLIČNOSTI NAMASTE

Center odličnosti NAMASTE je zasebni raziskovalni zavod, ki je bil ustanovljen 15. 12. 2009 na osnovi Javnega razpisa za razvoj centrov odličnosti v obdobju 2009–2013 s sklepom Ministrstva za visoko šolstvo, znanost in tehnologijo št. 430-36/2009/292 z dne 18. 9. 2009.

Program centra odličnosti je sofinanciran v okviru razvojne prioritete: 1 Konkurenčnost podjetij in raziskovalna odličnost in prednostne usmeritve, 1.1 Izboljšanje konkurenčnih sposobnosti podjetij in raziskovalna odličnost v okviru Operativnega programa krepitve regionalnih razvojnih potencialov 2007–2013. V centru so povezani: tri institucije iz akademske sfere in 17 partnerjev iz gospodarstva, privatne institucije, negospodarstva.

V obdobju delovanja od aprila 2010 naprej je Center odličnosti NAMASTE postal prepoznavna mednarodno odlična interdisciplinarna skupina. Temelji našega delovanja so znanstvena, poslovna in raziskovalna odličnost.

Na prioritetnem področju Nekovinski materiali smo naredili preboj z ustvarjenim strateškim partnerstvom med akademsko in gospodarsko sfero na področju raziskav, razvoja, izobraževanja ter prenosa znanja in tehnologij. Rezultati našega delovanja so zavidljivi, saj smo presegli vse zastavljene cilje, in to v dobrih treh letih in pol delovanja. Veliko novo ustvarjenih povezav med gospodarsko in negospodarsko sfero, kakor tudi med različnimi vrstami znanosti, torej močno inter- in transdisciplinarnost, je lepo pokazala raziskava, ki jo je o učinkih nove strukture raziskovalnega omrežja, ki ga spodbujajo državni ukrepi, torej o vlogi centrov odličnosti in kompetenčnih centrov, izvedla Ekonomska fakulteta in je bila predstavljena v okviru Mednarodnega programa na 8. Slovenskem forumu inovacij.

Zaposleni

Število sodelavcev je v Centru odličnosti NAMASTE z leti delovanja naraščalo, kot prikazujejo naslednji podatki:

Leto Število sodelavcev

2010 78

2011 92

2012 100

2013 102

To pomeni, da se je krepila povezovalna vloga CO. Raziskovalci svoje znanje in izkušnje iz delovanja na univerzah, inštitutih in v industriji na različnih raziskovalnih področjih uspešno izmenjujejo in nadgrajujejo v mešanih skupinah. Prav tako igra Center odličnosti NAMASTE pomembno vlogo pri izobraževanju novih kadrov. Sodelavci centra so bili mentorji pri 83 diplomskih nalogah, 14 magistrskih in 36 doktorskih delih. V času delovanja centra je 7 zaposlenih uspešno doktoriralo, 7 jih je zagovarjalo magistrsko delo, 5 zaposlenih pa je diplomiralo (skupaj 19).

62,1%

6,4%

28,5%

3,0%

doktor znanosti

magister univ. dipl. inž.

tehnik

0%

10%

20%

30%

40%

50%

60%

70%

Izobrazbena struktura

dr.Alenka Rožaj Brvar, MBA, direktorica

4

Od aprila 2010 do konca leta 2013 so raziskovalci opravili 101.523 delovnih ur, kar je 59,72 FTE. Raziskovalci svoje znanje in izkušnje iz delovanja na univerzah, inštitutih in v industriji na različnih raziskovalnih področjih uspešno izmenjujejo in nadgrajujejo v mešanih skupinah.

Finance

Za štiriletno delovanje operacije Centra odličnosti NAMASTE je bilo na podlagi javnega razpisa za razvoj centrov odličnosti dodeljenih 9.417.264 EUR finančnih sredstev, od tega je bilo 57 % od celotnih sredstev porabljenih za investicije v raziskovalno in merilno opremo.

Znanstveni in tehnološki dosežki

Znanstveno in tehnološko odličnost delovanja Centra potrjujejo naslednji podatki:

8 inovacij,

37 patentov (4 CO) in 6 patentnih prijav (1 CO),

22 prototipov in

86 demonstracijskih projektov in preizkusnih struktur.

Center ima izjemno število objav z afiliacijo (188) v prestižnih tujih revijah, kot so: Proc. Nat. Acad. Sci. USA, Nature Comm., Phys. Rev. Lett., Chem. Comm., sodelavci so objavili 513 znanstvenih člankov iz tematik s področja delovanja CO, svoje vrhunske rezultate so predstavili na 126 vabljenih predavanjih po vsem svetu in s 150 objavljenimi znanstvenimi prispevki na konferencah. Izjemni raziskovalni rezultati naših sodelavcev so bili tudi tema na štirih naslovnicah eminentnih znanstvenih publikacij. Sodelavci CO so v teh letih prejeli kar 16 nagrad in priznanj.

O rezultatih in dosežkih obveščamo tako znanstveno kot širšo skupnost v obliki javnih predstavitev na konferencah in posebnih dogodkih, na seminarjih, predavanjih, delavnicah. V nadaljevanju predstavljamo poglavitne dosežke po posameznih projektih.

V prihodnosti vidimo Center odličnosti NAMASTE kot še močnejšega povezovalca in pospeševalca pretoka znanja med akademsko sfero in gospodarstvom. Svojo pomembno vlogo igra v usposabljanju mladih in jih pripravlja za vstop v gospodarsko okolje. Najmočnejši vpliv pa ima CO lahko kot zakladnica znanja in praks, kjer lahko zajemamo iz različnih ved, različnih tehnologij, ustvarjamo nove načine in presajamo dobre prakse na nova področja ter tako bogatimo klasične načine in uvajamo inovativne uporabe specialnih materialov.

M 71%

Ž 29%

Struktura po spolu

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CoE NAMASTE

CoE NAMASTE is a multi-disciplinary and trans-disciplinary private research institution that was established on 15 December 2009, selected on a public tender by the decision of the Ministry of Education, Science and Sport No. 430-36/2009/292 dated 18 September 2009.

The research programme of the centre is co-financed up to 85% by the European Regional Development Fund. The operation is carried out under the Operational programme for Strengthening Regional Development Potentials 2007–2013, development priority: Competitiveness of enterprises and research excellence, policy priorities: Improving the Competitive abilities of enterprises and research excellence.

In course of the operation the Centre of Excellence NAMASTE (Advanced Materials for the Future) has developed into an internationally recognized excellent interdisciplinary group. Maintaining and constantly upgrading research, technological and business excellence is our important guideline.

An important breakthrough in the priority area of inorganic materials has been achieved by creating a strategic alliance of academic and entrepreneurial worlds in research, development, education, knowledge and technology transfer. We have achieved and surpassed the goals set in 2009. The interconnecting role of centres of excellence and competence centres and their building of new research frameworks between enterprises and academia, between various scientific areas, i.e., strong inter- and trans-disciplinary activity, was presented in the results of a study, conducted by Faculty of Economics in the course of 8th Slovene Innovation Forum.

Personnel

In the course of the operation the number of co-workers gradually grew, as shown in the table below:

YEAR Number of co-workers

2010 78

2011 92

2012 100

2013 102

On average, CoE NAMASTE has been the employer to 82.5 researchers from a variety of research areas, such as Solid State Physics, Soft Matter, Biophysics, Photonics, Zoology and Zoophysiology, Chemistry, Biochemistry and Molecular Biology, Chemical Engineering, Inorganic Non-Metallic Materials, Electronic Components & Technologies, Materials for Electronic Components, Textiles and Technical Fibres, Microbiology and Immunology, and Health protection - food animal sources.

The integrative role of CoE NAMASTE is reinforcing. Our researchers are upgrading their knowledge and experience from university or institute laboratories, and from the industrial environment in a variety of research areas by working in mixed teams. Within the CoE strong attention is paid to the education of new cadres, and also to the dissemination of the results of the scientific community.

62,1%

6,4%

28,5%

3,0%

Ph.D. M.Sc. B.Sc. College

0%

10%

20%

30%

40%

50%

60%

70%

Educational structure

dr.Alenka Rožaj Brvar, MBA, director

6

The members of CoE NAMASTE have been mentors to 83 B.Sc., 14 Master degrees and 36 Ph.D. theses.

Among the members of CoE, 7 Ph.D. studies, 7 Master and 5 bachelor degrees (in total 19) were performed.

As a consequence of co-financing until the end of December, 2013, a total of 101,523 hours of research have been conducted, i.e., 59.72 FTE of researchers.

Budget

The CoE was granted financing for a 4-year operation with the sum of €9.4m, of which 57% were investments in research equipment.

Scientific and technological results

The technological excellence of this CoE NAMASTE is demonstrated by the following numbers:

8 innovations,

37 patents ( 4CoE), 6 patent applications,

22 prototypes,

86 demonstration projects and test structures.

The number of publications is remarkable – 513 scientific papers, and so is the rank of the journals which have been chosen for publication, including Proc. Nat. Acad. Sci. USA, Nature Comm., Phys. Rev. Lett., or Chem. Comm. Our co-workers have performed 126 invited lectures worldwide, and had 150 published conference contributions. The remarkable scientific results were the themes on 4 cover pages of eminent scientific publications. The excellent results of co-workers have been acknowledged by 16 rewards and recognitions.

The future role of the CoE NAMASTE is seen as an even stronger integrator and catalyst between entrepreneurial and academic worlds. We see it as an important player in preparing the young scientists to move to the enterprises. CoE NAMASTE is a treasury of scientific and practical knowledge, and technologies, where good practice can be creatively employed to innovatively enrich the classical approach and thus open new possibilities.

M 71%

F 29%

Structure by gender

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R&R-poudarki R&D highlights

LTCC-senzor tlaka LTCC pressure sensor

Funkcionalni material na LTCC Functional material on LTCC

Detajl kemijskega reaktorja Detail of chemical reactor

Hibridna keramična struktura Hybrid ceramic structure

RRP1

2D in 3D keramične strukture Ceramic 2D and 3D structures

Mikrosistemi s 3D-strukturami in senzorji Microsystems with 3D structures and sensors

2D in 3D keramične strukture

Poslanstvo projekta "2D in 3D keramične strukture" je spodbuditi raziskovalne in razvojne sinergije raziskovalnih in industrijskih partnerjev na področju keramičnih mikrosistemov.

Smer razvoja na področju mikrosistemske tehnike gre izrazito v povezovanje in integracijo različnih funkcij, ki se realizirajo z različnimi tehnikami, kot so: mikroelektronika, mikromehanika, mikrofluidika, mikrokemija, mikrooptika, mikroakustika, mikrotermika, mikromagnetika. Mikrosistemi so lahko izdelani iz različnih materialov in z različnimi tehnologijami. Večinoma je material silicij, tehnologije pa so polprevodniške. Do leta 2020 pa se načrtuje znatno povečanje uporabe organskih in drugih materialov, ki bodo uporabni na novih področjih, kot sta mikromedicina in pametni tekstil. Med te materiale spadajo tudi keramični in z njimi tudi debeloplastna tehnologija. Praviloma so keramični mikrosistemi večji, vendar so bolj robustni in primerni za delovanje v zahtevnejših razmerah.

Keramične tehnologije se že vrsto let uporabljajo v elektronski industriji. Za izdelavo elektronskih sklopov se večinoma uporablja hibridna debeloplastna tehnologija, ki uporablja keramično podlago. Poleg navadne keramike obstaja tudi tista z nizko temperaturo žganja, imenovana LTCC (ang. Low Temperature Cofired Ceramics). Ta tehnologija se množično uporablja predvsem v avtomobilski elektroniki zaradi zanesljivosti delovanja in v visokofrekvenčni elektroniki zaradi boljših karakteristik pri zmerni ceni. Inovativna nekonvencionalna uporaba tehnologije LTCC pa omogoča izdelavo keramičnih mikrosistemov. Z ustreznim načinom se lahko v LTCC-strukturo vgradijo poleg elektronskih komponent tudi 3D-strukture (kanali, votline, …) ter senzorji (temperature, tlaka, kemijski), aktuatorji, grelniki, hladilniki, optični elementi in razne kemično aktivne plasti.

Rezultati

Materiali in tehnologija

Izdelava keramičnih večplastnih struktur, v katerih so odprte ali zaprte praznine, je zahteven tehnološki postopek. Materiali in tehnološki postopek morajo biti taki, da ne pride do mehanskih deformacij in kemijskih sprememb v večplastni keramični strukturi oziroma materialu. Obvladovanje tehnoloških postopkov za izdelovanje praznin v keramičnih strukturah je omogočil tehnološki preboj pri raziskovalno-razvojnem delu na področju keramičnih mikrosistemov. Mogoče je izdelati kanale (do dolžine 4 m), velike votline (do prostornine 18 cm

3) in tanke

(do 100 µm) membrane nad praznino (premera do 20 mm). Primeri različnih 3D keramičnih struktur so prikazani na sliki 1.1.

Pomemben napredek pri razvoju LTCC-senzorjev in drugih keramičnih mikrosistemov je bil dosežen z rezultati raziskav na področju funkcionalnih materialov in tehnologij. Nekateri materiali (uporovni, prevodni, dielektrični, piezouporovni in nekateri piezoelektrični) so v obliki debeloplastnih past in se nanašajo s sitotiskom. Po drugi strani pa nekateri materiali (piezoelektrični, drugi keramični materiali, kremen itd.) še niso kompatibilni z LTCC-tehnologijo in se uporabljajo kot diskretne komponente.

LTCC-senzorji tlaka

Keramični oz. debeloplastni senzorji tlaka so večinoma narejeni na keramični podlagi, kjer je osnova tanka okrogla in upogljiva membrana. Rob membrane je pritrjen na obroč, ta pa na trdo (neupogljivo) podlago. Merjeni tlak upogne membrano, debeloplastni senzorski upori pa zaznajo mehansko deformacijo in jo pretvorijo v električni signal. Upogibek je odvisen od geometrije in materialnih lastnosti membrane. Konvencionalni keramični senzorji tlaka ne morejo konkurirati po občutljivosti, miniaturnosti in ceni polprevodniškim senzorjem, so pa zaradi svoje robustnosti primerni za uporabo v zahtevnejših okoliških razmerah (velike temperaturne razlike, vibracije, kemijsko agresivni mediji itd.). Uporaba LTCC-tehnologije spreminja to

Slika 1.1: Tipične 3D LTCC-strukture:

a – kanali; b – velika votlina; c – praznina in tanka membrana

Slika 1.2: Primer integracije senzorja tlaka in senzorja temperature za uporabo v zahtevnih razmerah

Darko Belavič, vodja RRP1

10

razmerje, saj omogoča trikrat večjo senzorsko občutljivost, miniaturizacijo in lažjo integracijo. Zaradi tega se lahko LTCC-senzorji tlaka uporabljajo od relativno nizkih tlačnih področij (0–5 kPa) do relativno visokih (0–5 MPa). Na sliki 1.2 je prikazan primer LTCC-senzorja tlaka z integriranim temperaturnim senzorjem.

Kemijski mikroreaktorji

V zadnjem času so vedno bolj pomembni t. i. kemijski mikrosistemi. To je skupina miniaturnih naprav, v katerih lahko izvajamo kemijske reakcije ali analize in jih sestavljajo reaktorji, mešalniki, analizatorji, senzorji, aktuatorji itd. Zato so kemijski mikrosistemi velik potencial kot orodje za kemijsko sintezo in analizo. Ker imajo mikrokemijski sistemi veliko razmerje med površino in prostornino, je prenos toplote zelo hiter, zaradi majhne prostornine pa je hiter tudi prenos mase. V mikrosistemih so zadrževalni časi izredno kratki, prehod tekočin in plinov pa laminaren. Kemijske reakcije se izvajajo z manjšo porabo energije. Na sliki 1.3 je prikazan primer LTCC-strukture za kemijski reaktor za dokončno odstranjevanje ogljikovega monoksida iz plinov, ki prihajajo iz reaktorja za razklop goriva.

Veriga vrednosti

Rezultat projekta je tudi vzpostavljena veriga vrednosti pri sodelovanju z naslednjimi partnerji: Odsek za elektronsko keramiko in Odsek za sisteme in vodenje na Institutu »Jožef Stefan«, Fakulteta za kemijo in kemijsko tehnologijo Univerze v Ljubljani, Kemijski inštitut, HIPOT-RR, KEKO Oprema, KEKON in HYB. Veriga vrednosti vključuje aktivnosti od osnovnih in uporabnih raziskav, preko razvoja do trženja. Potek nekaterih inovacij v tem okviru je prikazan na sliki 1.4.

Področja uporabe

Keramični mikrosistemi so pomemben segment različnih sektorjev industrije, predvsem tam, kjer je potrebna miniaturnost, integracija različnih funkcij, velika zanesljivost in delovanje v ekstremnih razmerah, kot so na primer: medicina, biologija, kemija, avtomobilska industrija, aeronavtika itd. Uporabljajo se na področjih mikroelektronike, mikrorobotike, mikromehanike, mikrofluidike, mikrooptike in mikrokemije. Inovativna nekonvencionalna uporaba tehnologije LTCC omogoča izdelavo keramičnih mikrosistemov, primernih za senzorje tlaka za uporabo v zahtevnejših okoljskih razmerah (velike temperaturne razlike, vibracije, kemijsko agresivni mediji itd.). Poleg tega omogoča večjo fleksibilnost pri konstrukciji, večje senzorske občutljivosti in lažjo integracijo z elektronskim delom senzorja ter večjo stopnjo miniaturizacije; pri proizvodnji večjega obsega pa tudi cenovno konkurenčnost. Tehnologija LTCC postaja vedno bolj uporabna tudi v drugih mikrosistemskih aplikacijah. Zaradi kemične, termične in mehanske stabilnosti je primerna za kemične reaktorje (miniaturne laboratorijske), v katerih potekajo kemične reakcije tudi pri višjih temperaturah in z višjo stopnjo učinkovitosti.

Na hitro rastočem mikrosistemskem področju so nišno podpodročje keramični mikrosistemi. Slovenski akterji imajo že sedaj pomembne reference na posameznih segmentih, ki so potrebni za to podpodročje. Zato mislimo, da ima lahko Slovenija eno izmed vodilnih vlog na področju keramičnih mikrosistemov. Povezanost akterjev tudi v prihodnje bi zelo povečala uspešnost posameznikov.

Slika 1.3: LTCC-struktura za kemijski reaktor za dokončno odstranjevanje ogljikovega monoksida iz plinov

Slika 1.4: Potek inovacij

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Ceramic 2D&3D structures

The mission of the project “Ceramic 2D&3D structures” is to motivate the research and development synergies of the research and industrial partners in the field of ceramic microsystems.

Microsystems are miniaturized devices that perform electronic and non‐electronic functions. Typical microsystems have mechanical parts; electrical parts; different fluidic, thermal and optical structures; different sensors and actuators; etc. Microsystems are one of the fastest-growing technologies, and most microsystems are made by the micro-machining of silicon. On the other hand, complex microsystems combine different materials (silicon, ceramic, metal, polymer, etc.) and technologies (semiconductor, thin and thick film, etc.). In some demanding applications, thick-film technologies and ceramic materials are a very useful alternative. In comparison with silicon microsystems the ceramic microsystems are larger, more robust and operate over a wider operating-temperature range.

Low-temperature co-fired ceramic (LTCC) technology has been used for many years for interconnections technology in the electronics industry. Its main advantage is the compatibility with thick-film technologies. Electronic devices and systems based on a combination of these two technologies are reliable and the characteristics are stable. In comparison with other technologies, the LTCC and thick-film technologies enable the rapid and easy fabrication of electronic devices and systems. Therefore, it could both reduce the cost of devices and shorten the development time. The nonconventional application of LTCC technology and materials makes them suitable for producing three-dimensional ceramic structures, such as cantilevers, bridges, diaphragms, and buried channels and cavities. Thick-film technology is used for the lateral and vertical electrical interconnections, and the embedded and surface passive electronic components, such as resistors, thermistors, heaters, inductors, capacitors, piezoresistors, piezoelectric devices, etc.

Results

Materials and technology

The fabrication of 3D ceramic structures with cantilevers, bridges, diaphragms, buried channels and cavities is a demanding technological process. Both the materials and the technological processes must provide the accurate geometry of the structure with no mechanical deformation, and no chemical changes in the materials. The results of the research activities allowed us to construct long channels (up to 4 m), large cavities (up to 18 cm

3) and a thin

(down to 100 µm) diaphragm over the cavity (up to a diameter of 20 mm). Examples of different 3D structures are shown in Figure 1.1.

Important progress in LTCC-based sensors and other ceramic microsystems has been made by the successful implementation of functional materials

and technologies. Some of these materials (resistor, thermistor, conductor, dielectric, piezoresistor, piezoelectric) are used as thick-film pastes and they are deposited by screen-printing. On the other hand, some of the materials (advanced piezoelectric, other types of ceramic, quartz, etc.) are not compatible with the LTCC technology and they are integrated as discrete components with one of the bonding methods.

LTCC pressure sensors

The pressure-sensor market is dominated by silicon pressure sensors. However, ceramic pressure sensors with a flexible diaphragm have been available for many years, mostly for use in a physically and/or chemically demanding environment. Ceramic pressure sensors, in comparison with semiconductor sensors, are larger, more robust and have a lower sensitivity. However, the innovative and nonconventional application of LTCC technology increases the pressure sensitivity and enables miniaturization and integration, which makes these

Figure 1.1: Typical 3D LTCC structures:

a – channel(s); b – large volume cavity; c – cavity and thin diaphragm

Figure 1.2: An example of the integration of pressure and temperature sensors for application in a harsh environment

Darko Belavič, head of RRP1

12

sensors more competitive. LTCC-based ceramic pressure sensors can be designed for different pressure ranges from relatively low (0–5 kPa) to relatively high (0–5 MPa) pressures.

Typical ceramic pressure sensors are made with a circular edge-clamped deformable diaphragm. The piezoresistive type sensor has four thick-film resistors screen-printed and fired onto the deformable diaphragm. The resistors act as strain gauges and are electrically connected in a Wheatstone-bridge configuration. An example of an LTCC pressure sensor with an integrated temperature sensor for applicationa in a harsh environment is shown in Figure 1.2.

Ceramic micro-reactors

A chemical reactor is a typical device or system where the chemical stability, the thermal stability and the mechanical stability are important factors. Many micro-reactors have dimensions in the millimetre and micrometre ranges and they integrate different fluidic elements (channel, cavity, valve, mixer, diffusor, distributor, collector, flow limiter, etc.), sensors (pressure, temperature), actuators, heaters, etc. Therefore, the combination of LTCC and thick-film technologies is suitable for the fabrication of a ceramic structure for the chemical micro-reactors. In addition to the basic design guide (based on technology and materials) the most important requirements in the design issue are: microfluidics, temperature management, mechanical strength, chemical inertness and resistance, and some additional functions like the integration of discrete devices. An example of an LTCC structure designed and fabricated for a preferential oxidation reactor (PROX) is shown in Figure 1.3.

Value chain

The result of the project “Ceramic 2D&3D structures” is a value chain created with other partners, as follows: the Electronic Ceramics Department and the Department of System and Control at the Jožef Stefan Institute, the Faculty of Chemistry and Chemical Technology, University of Ljubljana, the National Institute of Chemistry, HIPOT-RR, KEKO Equipment, KEKON, and HYB. The value chain includes all the activities from the basic and applied research to the marketing. The innovative scenario of different products is presented in Figure 1.4.

Areas of application

Research results in the field of basic and functional materials, technologies and design have enabled the nonconventional application of LTCC technology for the design and fabrication of different three-dimensional structures, such as cantilevers, bridges, diaphragms, buried channels and cavities. This advanced and innovative technology in combination with thick-film technology, functional materials and discrete components is a new, challenging opportunity for the ceramic-microsystems market, especially in two segments. The first is the pressure-sensors market. This is mainly because the LTCC pressure sensors are suitable for the use in harsh conditions, and because the use of specially designed LTCC material and technology increases the pressure sensitivity and enables more flexibility in designing and construction, which leads to miniaturization and lower cost. The second market segment is chemical micro-reactors. 3D LTCC structures enable chemical stability, thermal stability and mechanical stability, which are important factors for chemical reactors. In addition, ceramic chemical micro-reactors in comparison with large conventional reactors have a higher surface-to-volume ratio, and higher rates of reaction, mass and heat transfer.

Figure 1.3: Open and final LTCC structure for the preferential oxidation reactor (PROX)

Figure 1.4: Innovation scenario

13

R&R-poudarki R&D highlights

Prosojna plast ZnO na steklu Transparent ZnO film on glass

Energijski DC-varistorji Energy DC varistors

EM absorpcijske folije EM absorbing foils

Magnetni nanodelci Ni67,5Cu32,5 Magnetic nanoparticles of Ni67.5Cu32.5

RRP2

Prenapetostne in elektromagnetne zaščite Overvoltage and electromagnetic protection

Magnetno polje v orodju Magnetic field in the tool

Materiali, komponente in tehnologije za višji nivo prenapetostnih in elektromagnetnih zaščit

Elektronska oprema, informacijske in telekomunikacijske tehnologije so del našega vsakdanjega življenja. Njihova varna in nemotena uporaba je bistvena za ekonomsko učinkovitost in tudi kvaliteto življenja. Učinkovita zaščita električnega omrežja in opreme pred škodljivimi prehodnimi motnjami je zato zelo pomembna. ZnO-varistorji in plinski odvodniki (GDT) dajejo najboljše rešitve za izdelavo visokoučinkovitih zaščitnih sistemov (SPD). Z vse večjim pomenom obnovljivih virov energije narašča potreba po varistorjih z visoko dc-stabilnostjo za zaščito solarnih panelov in vetrnih generatorjev. ZnO-keramika pa ponuja nove izzive tudi v tehnologijah prosojnih in prevodnih plasti, mikrogeneratorjev energije ali kot obetaven termoelektrični (TE) material, stabilen do 1 000

oC na zraku,

nestrupen in poceni, kar so bistvene prednosti pred klasičnimi TE-zlitinami.

Količina elektromagnetnega (EM) sevanja v okolju drastično narašča, še zlasti s hitrim razvojem brezžičnih povezav. Da bi zmanjšali škodljive vplive EM-smoga na ljudi, na vsa druga živa bitja in tudi opremo, potrebujemo efektivne sisteme za EM-absorpcijo. Bistveni absorpcijski materiali so spinelni in heksagonalni feriti. Kompoziti s spinelom so pomembni za razvoj absorberjev frekvenc do nekaj gigahertzov (GHz), kompoziti s heksaferitom pa za EM-absorberje nad 10 GHz. Ta razvoj se sklada z razvojem drugih magnetnih materialov in nanoprahov za izredno aktualne magnetne tekočine. Regulativa glede emisij CO2 je močna spodbuda za prehod iz tehnologije motorjev z notranjim zgorevanjem na tehnologije transporta z električnim pogonom, kjer vitalni deli zahtevajo magnetne materiale in magnetne kompozite. Omejene zaloge in visoka cena so močni motivi za razvoj trdomagnetnih zlitin NdFeB z manjšim deležem elementov redkih zemelj. Amorfni magnetokaloriki na osnovi železa omogočajo rešitev problemov, ki se pojavljajo v materialih s prvim redom magnetnega prehoda, kar je do sedaj zaviralo razvoj tehnologije magnetnega hlajenja.

Rezultati

Osnovne raziskave inverznih mej (IBs) in razumevanje njihovega vpliva na rast zrn so omogočili razvoj nizko dopirane varistorske keramike z odličnimi tokovno-napetostnimi karakteristikami v širokem področju prebojnih napetosti od 60 V/mm do 350 V/mm, vse z dodatkom Sb2O3 kot dopanta, ki povzroči nastanek inverznih mej. Ta keramika vsebuje le dodatek z masnim deležem od 3 % do 4 % varistorskih dopantov k ZnO, navadni dodatki pa so od 7 % do 12 %. TiO2 prav tako sproži nastanek inverznih mej, vendar le v nekaterih zrnih ZnO, ki zato zrastejo izredno velika. Z dodatkom Bi4Ti3O12 (BIT) k ZnO in šokovnim sintranjem keramike, hitra sprostitev Bi2O3-taline, bogate s TiO2 zaradi razpada BIT, povzroči nastanek inverznih mej v večjem številu zrn ZnO in homogen razvoj grobo zrnate mikrostrukture.

Razvili smo paste z visokim 70-odstotnim deležem varistorskega prahu kot polnila, da bi zagotovili čim

višjo zeleno gostoto plasti, pripravljene s sitotiskom, ki bi omogočila sintranje in razvoj mikrostrukture debeloplastnega varistorja med žganjem pri nizkih temperaturah pod 1 000

oC za dobre tokovno-

napetostne karakteristike.

Razvili smo postopek nizkotemperaturne hidrotermalne sinteze gladkih, gostih in visoko (0001)-orientiranih prosojno-prevodnih plasti ZnO in urejene mreže ZnO-nanopaličic na steklo.

Za razvoj oksidne termoelektrične (TE) keramike na osnovi ZnO in Ca-Co-O smo konstruirali Z-meter, ki nam omogoča sočasno meritev Seebeckovega koeficienta, električne prevodnosti in termične prevodnosti do 650

oC na istem vzorcu, za določitev

njegovega faktorja TE kvalitete ZT.

Izdelali smo prahove MnZn-ferita z EM-absorpcijo od 500 kHz do 3 GHz, Sr-heksaferita z absorpcijo med 10

Slika 2.1: Homogena mikrostruktura z inverznimi mejami v šokovno sintrani ZnO-keramiki, dopirani z Bi4Ti3O12

Slika 2.2: Prototipi stekla z različnimi dodatki prahu MnZn-ferita in končni izdelek

doc.dr. Slavko Bernik, vodja RRP2

16

GHz in 30 GHz ter MnCu-ferita z absorpcijo v IR- področju in jih uporabili z organskimi polimeri za razvoj EM absorpcijskih kompozitov v obliki folij in fasadnih premazov. Razvili smo postopek izdelave nanoprahu hematita z delci v obliki ploščic za izdelavo različnih premazov.

Razvili smo postopek izdelave biokompatibilnih magnetnih nanoprahov Ni67,5Cu32,5 z ozko porazdelitvijo velikosti delcev in kontrolirano Curiejevo temperaturo pri 43

0C za izdelavo magnetnih

tekočin.

Razvili smo izdelavo termoplastičnih magnetnih kompozitov in monolitnih kompozitov mehko-/trdo-magnetnih materialov z duroplasti v enem postopku z in situ lepljenjem, kar omogoča izdelavo komponent s kompleksnimi oblikami in rotorsko aplikacijo, ki hkrati združuje obe funkciji, motorsko in senzorsko.

EPD-proces nam omogoča fino oblikovanje mej med zrni v trdomagnetnih zlitinah NdFeB, tako da z bistveno manjšimi količinami DyF3 in optimalnim režimom žganja dosežemo povečanje koercitivnosti do 1 620 kA/m.

Z dodatkom Ni smo magnetokalorični efekt zlitine Fe84Zr6B10 izboljšali za 25 % in njeno hladilno kapaciteto dvignili od 210 J/kg do 245 J/kg pri spremembi magnetnega polja 5 T, kar je boljše kot pri do sedaj najbolj znani zlitini Gd5Ge1,9Si2Fe0,1.

Področja uporabe

Nizko dopirano varistorsko keramiko lahko v prihodnje uporabljamo za razvoj vseh tipov varistorjev. Omogoča bistveno izboljšanje energijskih karakteristik varistorjev, zmanjšanje porabe oksidov Bi, Sb, Co, Mn in Ni pa ob znižanju stroškov prinaša tudi ekološke prednosti. Šokovno sintranje ZnO varistorske keramike z dodatkom Bi4Ti3O12 daje možnost zanesljive izdelave visokokvalitetnih nizkovoltnih varistorjev z nazivnimi napetostmi 10 V in 40 V.

Debeloplastni varistorji, izdelani s tehnologijo sitotiska bi omogočili visoko stopnjo integracije varistorjev z drugimi komponentami v hibridnih vezjih.

Prosojno-prevodne plasti ZnO so mogoča zamenjava za drage tanke plasti ITO (In-Sn-O) v tehnologijah ravnih zaslonov, zaslonov na dotik, solarnih panelov in LED diod. Urejena mreža ZnO-nanopaličic daje možnost izdelave mikropiezogeneratorjev energije.

Termoelektrični moduli na osnovi n- in p-tipa oksidnih termoelektričnih materialov dajejo edino realno možnost izrabe odpadne toplote, ki pomeni 70 % vse primarno pridelane energije, in sicer z direktno pretvorbo v električno energijo brez gibajočih se delov ali škodljivih stranskih produktov.

Energijski varistorji z visoko dc-stabilnostjo omogočajo učinkovito prenapetostno zaščito za vetrne turbinske generatorje.

Različne vrste plinskih odvodnikov (GDT) z izboljšano samougasnitvijo in patentirani ploščati GDT za izdelavo miniaturiziranih komponet varistor/GDT so nova generacija prenapetostnih zaščit.

Feritni prahovi in njihovi kompoziti so namenjeni EM-absorpciji, in sicer v območju od 500 kHz do 30 GHz, v IR-območju pa kot prevleke za solarne panele. MnZn-ferit je zanimiv tudi kot barvilo v steklarski industriji. Mogoča uporaba prahu nanodelcev hematita z obliko ploščic pa obsega premaze za korozijsko zaščito, tesnjenje, dušenje, prenos toplote, separacijo in senzoriko.

Magnetne tekočine imajo pomembne možnosti uporabe na področju biomedicine za zdravljenje s hipertermijo, ciljno dostavo zdravil in za slikanje z magnetno resonanco.

Trdomagnetne zlitine in magnetni kompoziti so pomembni v avtomobilski industriji za različne rotorske aplikacije, senzorje, črpalke, instrumente in aktuatorje, prav tako pa tudi kot orodja v beli tehniki, za vodne črpalke in druge pripomočke v gospodinjstvu.

Nizkoenergijsko magnetno hlajenje na osnovi magnetokalorikov bi lahko povsem spremenilo tehnologijo hlajenja in izpodrinilo klasične kompresorske sisteme.

Slika 2.3: Mikrostruktura kompozita mehko/trdo magnetnega materiala in integrirani rotor in senzor

Slika 2.4: Vpliv Ni na magnetokaloričen efekt Fe84Zr6B10 pri spremembi magnetnega polja 1,4 T

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Materials, components and technologies for the next level of overvoltage and electromagnetic protection

Electronic equipment, information and telecommunications technologies are part of our everyday life at work and in our homes. Their safe and undisturbed use is essential for economic efficiency as well as our quality of life. The effective protection of power-supply systems and equipment against transient surges is therefore of essential importance. The ZnO-based varistors and their combinations with gas-discharge tubes (GDT) offer the best solutions for the construction of highly efficient surge-protection devices (SPDs). With the growing importance of renewable energy systems (photovoltaic, wind generator) varistors with high stability in dc electric fields are required. ZnO-based ceramics also open up new challenges in the technologies of transparent-conductive films, micro-power generators and as promising thermoelectric materials with key advantages in comparison to classic thermoelectric alloys, being stable up to 1000

oC in air, non-toxic and much cheaper.

The amount of electromagnetic (EM) radiation in our environment has drastically increased, especially with the rapid development of wireless communications. To minimize the negative effects of EM smog on humans, other life and also electronic equipment, effective systems for EM absorption are needed. Significant absorption materials are mainly spinel and hexagonal ferrites. Composites with the spinel phase are important for the development of absorbers in the frequency range up to several GHz, and composites with hexagonal ferrite are usable at frequencies above 10 GHz. This research complies with the development of other magnetic materials and nanopowders for highly interesting magnetic fluids. The CO2 emissions regulations represent a strong driving force in the transition from internal combustion engines to technologies of electric transport in which vital parts require magnetic materials and magnetic composites. Limited resources and high prices are strong motives to develop the hard magnetic Nd-Fe-B alloys with a reduced content of heavy rare-earth elements. Iron-based amorphous magnetocalorics are very promising materials to overcome problems that occur in materials with a first-order magnetic transition, which hinders the development of technologies for magnetic refrigeration.

Results

Fundamental research on inversion boundaries (IBs) and their influence on grain growth enabled us to develop low-doped varistor ceramics with excellent current-voltage characteristics in a broad range of breakdown voltages from 60 V/mm up to 350 V/mm, all with Sb2O3 as the IBs-triggering dopant. They have mass fractions of only 3 % to 4 % of varistor dopants added to ZnO, while the standard additions are 7 % to 12 %. TiO2 also triggers the formation of IBs; however, only in some ZnO grains, which grow extremely large. With the addition of Bi4Ti3O12 (BIT) to ZnO ceramics and shock-sintering, the rapid release of a TiO2-rich Bi2O3 liquid phase with the decomposition of BIT results in the enhanced formation of IBs in the ZnO grain and hence the homogeneous development of a coarse-grained microstructure.

High-solids-load ink with 70 % of varistor powder was developed to ensure the highest possible green density of screen-printed films in support of the sintering and microstructure development of thick-film varistors at firing temperatures below 1000

oC for good current-

voltage characteristics.

The syntheses of smooth, dense and highly (0001)-oriented transparent-conductive ZnO films on glass and ZnO-nanorod arrays with low-temperature hydrothermal growth were developed.

For the development of oxide thermoelectric ceramics based on ZnO and Ca-Co-O a Z-meter was constructed to analyse the figure of merit ZT of a sample based on simultaneous measurements of their Seebeck coefficient, electrical conductivity and

Figure 2.1: Uniform microstructure with inversion boundaries in 'shock-sintered' ZnO keramiki doped with Bi4Ti3O12

Figure 2.2: Prototypes of glass with varying additions of MnZn-ferrite powder and final product

doc.dr. Slavko Bernik, head of RRP2

18

thermal conductivity up to 650 oC.

Powders of Mn-Zn-ferrite with EM absorption from 500 kHz to 3 GHz, Sr-hexaferrite with absorption from 10 GHz to 30 GHz and MnCu-ferrite with absorption in the IR range were synthesized and used with organic polymers to develop EM absorption composites in the form of foils and putty. The synthesis of plate-like nano-powder of hematite was developed for the preparation of various coating systems.

Biocompatible magnetic nanoparticles of Ni67.5Cu32.5 with a narrow particle size distribution and a controlled Curie temperature at 43

oC

were synthesized to prepare magnetic fluids.

The processing of thermoplastic magnetic composites and monolithic magnetic composites combining soft/hard magnetic materials with thermosets in a single step was developed for the preparation of components with complex geometries, also enabling rotor applications, combining the functions of a motor and a sensor.

The EPD process for the fine tuning of the grain boundaries in hard-magnetic Nd-Fe-B alloys with noticeably reduced amounts of DyF3, while still enhancing their coercively to 1 620 kA/m after an optimal heat treatment, was developed.

The magnetocaloric effect of the Fe84Zr6B10 alloy was increased by 25 % with the addition of Ni, enhancing its refrigeration capacity from 210 J/kg to 245 J/kg for a magnetic field change of 5 T, a result even better than for the well-known Gd5Ge1.9Si2Fe0.1.

Areas of application

Low-doped ZnO-based varistor ceramics can be used for the development of all types of varistors; a significant enhancement of their energy performance can be obtained and the reduced use of oxides of Bi, Sb, Co, Mn and Ni brings a cost benefit, together with ecological benefits. High-quality low-voltage varistors with nominal voltages from 10 V to 40 V can be made reproducibly by exploiting the shock sintering of BIT-doped ZnO-based varistor ceramics.

Screen-printed thick-film varistors open up the possibility for the increased integration of varistors with other components in hybrid circuits.

Transparent-conductive ZnO films could be used as possible replacements for expensive ITO (In-Sn-O) in technologies of transparent conductive films (TCF) for flat-screen displays, photovoltaic (PV) panels and LEDs. ZnO-nanorod arrays can be used for piezo-energy micro-generators.

Thermoelectric modules based on n- and p-type oxide thermoelectric materials open only a viable possibility to exploit waste heat, which equals about 70 % of the total primary-produced energy, by direct conversion into electricity.

Energy varistors with a high DC stability were developed for the overvoltage protection of wind-turbine generators.

Various types of gas-discharge tubes (GDTs) with enhanced self-extinguishing characteristics were developed, including a patented disc-shaped GDT for miniaturised varistor/GDT surge-protection devices (SPDs).

Ferrite powders and their composites can be used as EM absorbers, covering the range from 500 kHz to 30 GHz, and in the IR range as coatings for solar cells. MnZn-ferrite is also interesting as a pigment in the glass industry, while the applications of plate-like hematite include corrosion protection, sealing, damping, heat transfer, separation and sensors.

Magnetic fluids have important biomedical applications in hyperthermia treatment, targeted drug delivery and magnetic resonance imaging.

Hard-magnetic Nd-Fe-B alloys and magnetic composites are important for the automotive industry, in various rotor applications for sensors, fuel pumps, analogue instruments, actuators and drives; as well as in power tools and home appliances.

Low-energy magnetic refrigeration based on magnetocalorics can revolutionize cooling technologies by replacing conventional compressor systems.

Figure 2.3: Microstructure of composite soft/hard magnetic material and integrated rotor and sensor

Figure 2.4: Effect of Ni on magnetocaloric effect of Fe84Zr6B10 alloy with a magnetic field change of 1.4 T

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R&R-poudarki R&D highlights

Senzorsko polje za zajem 3D THz-slike Sensor array for 3D THz picture capture

Detekcija nevarnih snovi v zraku Detection of dangerous substances in the air

Jedkanje mikrostruktur z velikim razmerjem med višino in širino Etching of microstructures with high aspect ratios

RRP3

Napredni senzorski sistemi Advanced sensor systems

Napredni senzorski sistemi Advanced sensor systems

Napredni senzorski sistemi

THz-senzor

Teraherčna tehnologija ponuja novo orodje za vizualizacijo, odkrivanje, prepoznavanje in analizo predmetov v embalaži oziroma v katerem koli materialu, ki je za THz-valovanje prosojen. Teraherčno področje elektromegnetnega valovanja leži v frekvenčnem pasu od 300 GHz pa do 3 THz. THz-valovanje je neionizirajoče in zato celic ne poškoduje.

Cilj naše skupine je bil prikaz slike, zajete pri frekvenci 300 GHz, ter nadalje zajem in prikaz tridimenzionalne podobe predmetov z veliko natančnostjo položaja predmeta in njegove oblike. Poleg tega pa smo z metodo opazovanja pri različnih frekvencah ugotovili tudi nekatere snovne lastnosti predmeta z analizo njegovega spektralnega podpisa.

Rezultati

THz-sistem, ki je bil zasnovan v laboratoriju za mikroelektroniko (LMFE), zajame THz sliko s površino približno 0,1 m × 0,1 m z ločljivostjo 32 × 32 slikovnih točk. Deluje na centralni frekvenci 300 GHz in za zajem uporablja metodo FM modulacije ter heterodinskega mešalnika. V sistemu se uporablja linijski zajem 32 horizontalnih točk (linijsko polje 32 senzorjev), ki s sočasno obdelavo vseh kanalov zagotavlja ob preletu prek celotne scene tudi vertikalno dimenzijo slike, medtem ko je globina (oddaljenost) določena s frekvenco mešalnega produkta odbitega signala in osnovnega signala za osvetlitev opazovanega predmeta. Jedro sistema je polje senzorjev, katerih razvoj in izdelava je potekala v LMFE. Senzor in njegova izdelava sta patentno zaščitena. Senzor temelji na principu merjenja spremembe upornosti zaradi segrevanja uporovnega materiala. Za svoje delovanje potrebuje električni tok,

kot rezultat meritve vpadlega valovanja pa se zajema vrednost padca napetosti na termistorskem elementu. THz žarki z lahkoto prodirajo skozi večino oblačil, plastike, papirja, kartona, zato slike, zajete s sistemom, izdelanim v LMFE, podajo osnovno predstavo položaja in obliko predmetov, ki so bodisi v embalaži ali kako drugače zakriti za vidno svetlobo.

Področja uporabe

Teraherčni senzorji so uporabni na veliko področjih, predvsem pa kot polja senzorjev za zajem slike v medicini (zaznavanje sprememb tkiv in drugih anomalij), prehrambni industriji (zaznavanje tujkov v produktih ter kontrola kvalitete), farmaciji (pregled debeline prevleke tablet, pregled razporeditve zdravilne učinkovine), avtomobilski industriji (merjenje debeline premazov, detekcija poškodb na površinah), papirni industriji (debelina papirja/kartona, gostota, gramatura, homogenost) itd.

Umetni nos

Detekcija različnih molekul v zraku zahteva poceni in za uporabo enostaven instrument. Sedaj so na razpolago drage in velike naprave, ki zahtevajo izobraženega operaterja, dolge merilne čase, veliko količino materiala za analizo, poleg tega je detekcija nezanesljiva. Meritve so težavne zato, ker je število izparjenih molekul majhno (v razredu 10

–9–10

–14).

Molekulska detekcija temelji na adsorpciji ciljnih molekul na receptorske plasti na površini senzorjev. Pokritost površine senzorja je odvisna od parnega tlaka snovi, temperature in maskiranja z drugimi molekulami. Ciljne molekule so navadno zelo majhne, pokritost senzorja je majhna, zato so signali iz senzorjev zelo šibki; detekcija je izjemno zahtevna. Pred kratkim smo demonstrirali, da je mogoča detekcija par eksplozivov v majhni koncentraciji z uporabo diferencialnega kapacitivnega senzorja COMB, ki je polovično kemijsko modificiran. Realiziran senzorski sistem je izjemno občutljiv (občutljivost 0,3 aF – je med najobčutljivejšimi na svetu) in uporablja nizkošumno CMOS elektronsko vezje. Sistem je robusten, neobčutljiv za mehanske in temperaturne vplive iz okolja in ima velik potencial. Sedaj se trudimo izboljšati občutljivost za dva velikostna razreda, kar pomeni, da

Slika 3.1: Prenosen THz sistem, ki omogoča zajem 3D THz slike ter spektralno analizo pri 300GHz

Slika 3.2: THz senzor ima občutljivost 1000 V/W, NEP = 5 pW/√Hz pri sobni temperaturi in ne potrebuje hlajenja

prof.dr. Janez Trontelj, vodja RRP3

22

bo mogoče zaznati kapacitivno spremembo v razredu 10 zF (10-21

F). Iščemo tudi rešitve za povečanje kemijske selektivnosti in zanesljivosti zaznavanja, kar nameravamo storiti z realizacijo polja različno funkcionaliziranih senzorjev in tako posnemati pasji vohalni organ; sedaj izvajamo meritve pri štirih različno modificiranih senzorjih. Adsorpcije različnih molekul so različne na drugače funkcionaliziranih površinah, zato predvidevamo, da bomo dobili različne »prstne odtise« odzivov na polju različno modificiranih senzorjev za vsako vrsto ciljnih molekul.

Rezultati

V članku, objavljenem v reviji IEEE Sensors, smo pred kratkim objavili rezultate meritev občutljivosti kapacitivnega senzorja za pare TNT in RDX, kjer dosegamo detekcijski nivo 3 molekule TNT in 0,3 molekule RDX na 10

+12 molekul nosilnega plina. Ta rezultat je med najboljšimi,

objavljenimi za to vrsto detekcije. Sedaj nadaljujemo delo s ciljem povečati občutljivost za dva velikostna razreda ter izboljšati selektivnost.

Področja uporabe

Uporabo umetnega nosu predvidevamo v širokem naboru področij: od medicine, varnosti, vojaških apliakcij, kontrole okolja, prehranske proizvodnje, znanosti itd.

3D obdelava silicija za napredne mikrosisteme

3D mikroobdelava silicija z globokim reaktivnim ionskim jedkanjem (DRIE) je eden od ključnih procesnih postopkov za izdelavo naprednih mikroelektromehanskih sistemov (MEMS). Njegova glavna prednost je v jedkanju, neodvisnem od kristalografske orientacije podlage, in izdelavi visokih struktur z vertikalnimi stenami. V okviru CO NAMASTE nabavljenega sistema DRIE Plasmalab 100-ICP180 je bil postavljen dvostopenjski Boschev postopek usmerjenega jedkanja, ki je bil nadgrajen s tristopenjskim in drugimi modificiranimi postopki suhega jedkanja.

Rezultati

Raziskani so bili fizikalni mehanizmi in osnovni procesni parametri jedkanja ter njihov vpliv na rezultat le-tega, kot npr. homogenost jedkanja, odvisnost jedkanja od geometrije, hitrost jedkanja, profil jedkanja, hrapavost in selektivnost jedkanja na masko. Za primere jedkanj z omejeno debelino maskirnih plasti je bil dvostopenjski Boschev postopek nadgrajen s tristopenjskim postopkom jedkanja, s katerim smo selektivnost jedkanja silicija na oksidno masko in masko iz fotorezista v večini primerov povečali za več kot 50 %. Za primere jedkanja velikih površin silicija, odprtih, a hkrati visokih struktur ter dolgem času jedkanja je bil razvit večzančni dvostopenjski Boschev postopek jedkanja. S kombinacijo kratkih izmenjajočih se izotropnih in anizotropnih (usmerjenih) Boschevih jedkanj v istem sistemu je bil razvit postopek jedkanja, katerega rezultat so stene jedkanih mikrostruktur z ošiljenim profilom.

Področja uporabe

Področje uporabe DRIE je široko in ključno za realizacijo naprednih senzorjev, aktuatorjev in mikrosistemov (pospeškometri, giroskopi, odjemniki energije idr.). Tako so bile na področju kemijskega procesnega inženirstva za izvajanje različnih katalitskih procesov izdelane mikrofluidne komponente, kot npr. uparjevalniki, gorilniki in parni reformerji metanola in vode, enota za parcialno oksidacijo ogljikovega monoksida in plinski distributor gorivnih celic. Za potrebe doziranja in analize fluidnih substanc v biomedicini so bile izdelane silicijeve mikroigle za podkožno vnašanje zdravil, mikrofluidni elementi z integriranimi Au elektrodami za impedančno spektroskopijo in mikročrpalke kot osnovni elementi mikrofluidnih sistemov. Mikrofluidni elementi in mikročrpalke so zgrajeni iz stekla in PDMS-polimera. Kot ključni postopek pri izdelavi le-teh so bili uporabljeni zgoraj navedeni razviti postopki DRIE-jedkanja silicija za izdelavo silicijevih kalupov za ulivanje PDMS mikrostruktur.

Slika 3.3: Adsorbcija ciljnih molekul na modificirano površino sensor-ja ter SEM slika COMB kapacitivnega senzorja.

Slika 3.4: Izmerjen odziv na pare RDX v zraku na štirih različno modificiranih senzorjih

Slika 3.5: Detajl izostrene mikroigle s trirobno konico

Slika 3.6: Piezoelektrična mikročrpalka z mikropregradnimi ventili

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Advanced sensor systems

THz sensor

Terahertz technology offers a new tool for the visualization, detection, identification and analysis of items in a package or behind barriers that are transparent to terahertz (THz) waves. THz waves lie in the frequency range from 300 GHz up to 3 THz in the electromagnetic spectra. THz radiation is non-ionizing and therefore does not cause damage to cells or tissue.

The goal of our group was to capture THz images at a frequency of 300 GHz and display three-dimensional THz images of the scene with a high-precision position determination of the object and its shape. In addition, the method of several frequencies material response observation was used to identify some of the material properties using an analysis of its spectral signature.

Results

The THz system designed in the laboratory for microelectronics (LMFE) captures the THz image with approximately 0.1 m × 0.1 m area and a resolution of 32 × 32 pixels. It operates on the central frequency of 300 GHz and uses FM modulation for the illumination and a heterodyne mixer on the sensor side. The system captures 32 horizontal pixels (linear array of 32 sensors) that are processed simultaneously. With additional optics and mechanics, a scan through the scene is made, which provides the vertical dimension of the image. The depth (distance) is determined by the product frequency of the mixing of the objects’ reflected signal and the illumination signal. The core of the system is the THz sensor array developed and produced in LMFE. The sensor and its production steps are patented. The sensor is based on the bolometer principle - on measuring the resistance change due to the material heating by microwave power. As a result of the present THz radiation an

additional voltage drop appears on the thermistor element, which is detected and digitalized. The THz radiation can easily penetrate most types of clothing, plastics, paper, cardboard etc, The images captured with the presented system, give the approximate position and shape of objects that are either in containers or otherwise obscured for visible light.

Areas of application

THz sensors can be used as sensor arrays in many fields for image capturing in medicine (detection of changes in the tissue and other abnormalities), the food industry (detection of impurities in the products and quality control), pharmacy (coating thickness inspection of tablets, monitoring of the active substance distribution), automotive industry (thickness of the coating measurement, detection of surface damage), paper industry (paper/cardboard thickness, density, homogeneity), etc.

Artificial nose

Detecting vapor traces of different molecules in the atmosphere with a simple and cheap instrument is very useful. At the moment different bulky and expensive instruments exist for that task. The measurements take long times, the operator must be trained and false detection is often because the number of targeted molecules in the atmosphere is usually very low (density 10

–9 to 10

–14). Molecular detection is based on the adsorption of target

molecules to the receptor molecules attached to the surface of the sensors. The coverage of adsorbed molecules depends on the vapor pressure of the matter and the temperature; surface interactions might be hidden by the presence of other substances, like water vapor. The target molecules are usually very small, their surface coverage is incomplete and electrical signals from the sensors are usually weak. We have recently demonstrated that low-concentration detection is possible using a differential pair of chemically

Figure 3.1: Mobile THz system consists of five units and provides 3D THz image as well as spectral analysis at 300 GHz

Figure 3.2: The THz sensor has a sensitivity of 1000 V/W, NEP = 5 pW/√Hz at room temperature without additional cooling

prof.dr. Janez Trontelj, head of RRP3

24

functionalized COMB micro-capacitor and a low-noise-detection electronics. To the best of our knowledge, the results are at the cutting edge of the sensitivity of any COMB sensor ever realized. The method uses low-noise CMOS technology with the sensitivity in the range below 0.3 aF. It is very robust, inherently insensitive to temperature and acoustic noise and has a great potential. Currently, we are trying to increase the sensitivity of this system by two orders of magnitude (down to 10 zF) and in addition, we are looking for a solution to the inherent problem of the poor chemical selectivity of the system. At the moment the measurements of four differently modified sensors are on going, thus mimicking the architecture of a dog's nose, which is of course much more complex and by far the best molecular detection system in nature.

Results

We have recently demonstrated that concentrations as low as 3 molecules of TNT and 0.3 molecules of RDX in 10

+12 molecules of

carrier gas can be measured. To the best of our knowledge, these results are at the cutting edge of the sensitivity of any COMB sensor ever realized for that purpose. Currently, we are working on improving the sensitivity by two orders of magnitude and increasing the selectivity.

Areas of application

An artificial nose is believed to be applied within a wide range of applications, from medicine, security, military applications, environmental control, food processing, science, etc.

3D micromachining of silicon for advanced microsystems

The 3D micro-machining of silicon by deep reactive ion etching (DRIE) is one of the key fabrication processes for the manufacturing of advanced micro-electro-mechanical systems (MEMS). The main advantage is etching, independent of substrate crystallographic orientation and fabrication of high-aspect-ratio structures with vertical walls. On the basis of the CO NAMASTE purchased system DRIE Plasmalab 100 ICP180, a two-step Bosch etching process was realized and upgraded with a developed three-step process, and other dry-etching modified procedures.

Results

The influence of process parameters and the relevant physical mechanisms of etching, having an impact on the result of etching, such as etch rate, uniformity and the geometry dependency of etching, influence on verticality profile, surface roughness and the selectivity of etching to mask materials have been investigated. In the cases where a reduced thickness of the masking film is required, a two-step Bosch process was upgraded to a three-step etching process, by which the etching selectivity of silicon with respect to oxide or the photoresist mask was increased in most cases by more than 50 %. For structures where a large silicon surface area is etched, for widely spaced but at the same time high structures and for long etching time, a multi-loop two-step Bosch process was developed. In addition, an etching process resulting in the etched microstructures with tapered walls has been developed, combining short alternating isotropic and anisotropic etching sequences.

Areas of application

The application of the DRIE process is versatile and crucial for the realization of advanced sensors, actuators and microsystems (accelerometers, gyroscopes, energy harvesters, etc.). In the field of chemical process engineering for the implementation of various catalytic processes, microfluidic components such as the evaporator, combustor and steam reformer of methanol and water, a unit for the partial oxidation of carbon monoxide and gas distributors for fuel cells were realized. For the delivery and analysis of fluid substances in biomedicine, silicon microneedles for the subcutaneous introduction of drugs were fabricated. Furthermore, microfluidic elements with integrated Au electrodes for impedance spectroscopy and micropumps as basic microfluidic elements were elaborated. Microfluidic elements and micropumps are composed of glass and PDMS polymer layers. Here, the developed DRIE etching processes play a key role in the fabrication of silicon molds for PDMS casting.

Figure 3.3: Adsorption of target molecu-les to the modified sensor surface and SEM micrograph of COMB capacitive sensor

Figure 3.4: Measured response to RDX vapours in the air on 4 differently modified sensors

Figure 3.5: Detail of sharpened micro-needle with triangular tip

Figure 3.6: Piezoelectric micropump with microthrottle valves

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R&R-poudarki R&D highlights

Topološki „živalski vrt“ Topological Zoo

Zavozlan nematski koloid Knotted nematic colloid

Enoplastni nanokosmiči MoS2 MoS2 single-layer nanoflakes

Kotno omejeni filtri za očala Spatial filtering glasses

RRP4

Mehki kompoziti Soft composites

Tekočekristalni mikrolaser Liquid-crystal microlaser

Mehki kompoziti za optične, elektronske, fotonske in senzorske aplikacije

Naši mehki kompoziti so kompleksni topološki materiali (Poudarek 1), zanimivi za uporabo v optičnih, fotonskih in nanotehnoloških napravah. V okviru CO NAMASTE smo povezali raziskovalce iz različnih okolij (fizika, kemija, nanoznanosti in optika), da bi prispevali k raziskavam novih naprednih materialov in tehnologij. Znanstvene raziskave dopolnjuje razvoj v dveh partnerskih podjetjih. Predstavljamo izbor svojih dosežkov. Nekateri rezultati so prvi te vrste na svetu, med njimi koloidni mikroskopski vozli in zanke, učinkoviti in prilagodljivi kapljični resonatorji, 3D izotropni laserji, lasersko inducirano odtiskovanje optičnih defektov, samosestavljanje 3D koloidnih kristalov v fluidu, elastomerski aktuatorji za umetne mišice, nanomaterialni dodatki mazivnim oljem in optični tekočekristalni ščiti za zaščito oči.

Rezultati in področja uporabe

Nematski koloidi: sestavljanje topološke mehke snovi

Nadzor nad geometrijskimi/topološkimi omejitvami na mikroskali omogoča nov način oblikovanja mehkih topoloških materialov. Prvi na svetu smo realizirali poljubne vozle in zanke, ki jih lahko sestavimo iz topoloških defektnih zank, ki obkrožajo mikrokroglice v kiralnem tekočem kristalu (TK). Z optično pinceto smo naredili različne mreže koloidnih delcev, ob uporabi fokusirane laserske svetlobe pa smo lahko poljubno prepletli zavozlane strukture (Poudarek 2). Možnost urejanja vozlov smo napovedali z računalniškim modeliranjem in upoštevanjem invariant vozlov, specifikacij prepleta in želene oblike. Predstavljen sistem ponuja novo strategijo za izdelavo fotonskih struktur z netrivialno topologijo, ki bi lahko nadzorovala tok svetlobe v nastajajočih aplikacijah.

Nematske kapljice kot prilagodljivi optični mikroresonatorji

Nematske kapljice se vedejo kot električno nastavljivi mikroresonatorji. V polimerni matriki razpršene kapljice smo aktivirali z lasersko svetlobo. Z električnim poljem smo vsilili deformacijo dvolomnega nematika, s čimer smo dosegli premik resonančne

frekvence, nastavljiv dva velikostna reda nad tistimi v trdninskih resonatorjih. Svetloba v kapljicah ustreza različnim resonančnim načinom “whispering-gallery” (WGM), za katere so značilne majhne izgube. Predstavljeni nematski resonatorji bi lahko bili uporabljeni kot sestavni deli fotonskih vezij, zmožni naprednega svetlobno-svetlobnega nadzora (slika 4.1).

Tekočekristalni mikrolaserji

Kot prvi na svetu smo naredili 3D izotropni laser v barvno dopiranih kiralnih nematskih sfernih votlinicah, razpršenih v polimeru (naslovna slika). Izdelava temelji na spontanem sestavljanju majhnih holesteričnih TK-kapljic v kapljevini, s katero se ne meša. Ob vzbujanju s kratkovalovno zunanjo svetlobo dodano barvilo oddaja fluorescenčno svetlobo. V delcu sekunde lahko proizvedemo milijone enakih enobarvnih mikrolaserjev. Holesterični TK se v kapljici samouredi v niz koncentričnih Braggovih ogledal. Ta delujejo kot optični resonatorji in usmerjajo fluorescenčno svetlobo proti središču kapljice, tako da nastane stoječi val. Povečanje vzbujevalne moči poveča emisijo laserja. Kapljica je izotropen vir koherentne svetlobe in je prvi proizvedeni 3D-mikrolaser. Valovna dolžina oddane laserske svetlobe je temperaturno odvisna/nastavljiva. Taki mikrolaserji so zanimivi za fotonske naprave v zaslonih, senzorjih in pri slikanju.

Lasersko inducirano vtiskovanje nematskih defektov

Z računalniškim modeliranjem smo pokazali, da lahko z laserji odtisnemo različne dvolomne nano- in mikrooptične vzorce. Kompleksna optična polja Laguerre-Gaussovih (LG) laserskih žarkov lahko v nematskem TK svoje polarizacijsko polje vtisnejo v molekulski red. Zaradi močne prostorske raznolikosti LG-polarizacije se v nematskem redu pojavijo defekti; konformacije defektov so neposredno odvisne od indeksa LG-žarka. Z optičnim odtiskovanjem lahko

Slika 4.1: “Whispering-gallery” resonančni način nihanja (WGM) svetlobe v nematski kapljici

Slika 4.2: Simulirana koloidna tekočekristalna modra faza

prof.dr.Slobodan Žumer, vodja RRP4

28

naredimo nove kompleksne dvolomne materiale, v katerih se dvolomnost spreminja na mikro- do nanoskali. Z njimi bi lahko nadzorovali tok svetlobe v širokem intervalu valovnih dolžin. Po drugi strani bi odtisnjeni nematski defekti lahko nato ustvarili analogne defekte v svetlobnih poljih.

Koloidne in ograjene modre faze

Pokazali smo prvo samogradnjo 3D, kvazi-2D in 2D koloidnih kristalov, temelječo na regularni notranji strukturi kompleksne modre faze (slika 4.2). Pokazali smo, da modre faze v 3D dajejo možnost ujetja koloidnih delcev v pravilno mrežo in tvorijo kristale FCC v modrih fazah I. vrste ter kristale BCC v modrih fazah II. vrste. Odkrili smo tudi več novih eksotičnih defektnih mikrostruktur v ograjenih celicah modrih faz (skyrmioni, vijačne defektne strukture). Njihova stabilnost je odvisna od temperature, debeline celice in sidranja, kar nakazuje izboljšano vedenje sistemov v močni ograditvi. Ta rezultat je tehnološko zanimiv za spontano tvorbo anizotropnih nanovzorcev in mikromodulacij.

Aktuacija tekočekristalnih elastomerov

Razvili smo nov kompozitni tekočekristalni elastomer (TKE), uporaben v aktuacijski tehnologiji in strukturni manipulaciji na mikro- in nanoskali. Pokazali smo, da je nanos zlate plasti obetaven v aktuaciji TKE z uporovnim gretjem, z dobro ponovljivostjo pri zmerni deformaciji in nizko napetostjo. Nanoplasti PEDOT:PSS, ki izkazujejo odlično stabilnost in adhezijo na TKE-podlago, smo uporabili pri razvoju dvoslojnega kompozita s temperaturno odvisno periodo površinskih gub. Razvili smo tudi molekulski model TKE. V obsežnih simulacijah Monte Carlo smo spreminjali temperaturo, natezno obremenitev in električno poljsko jakost (slika 4.3). Prehod med nematsko in izotropno fazo ter vklop prečnega električnega polja povzročita dramatično spremembo oblike vzorca. Deformacija je v zadnjem primeru mehka, kar je obetavno pri načrtovanju aktuatorjev.

Nanomaterialni aditivi za mazivna olja

Razvili smo sintezni proces za proizvodnjo gramskih količin čistih Mo/W oksidnih/sulfidnih nanodelcev (Poudarek 3), kar že omogoča industrijsko preizkušanje. V raziskavah MoS2 smo prvi izmerili trenje nanocevk in nanočebulic ter predlagali nov tip namazovanja. Trenje na jeklu ali stiku DLC pade za več kot 40 %, če mazivno olje vsebuje nekaj odstotkov nanocevk MoS2. Sintetizirali smo tudi prve polimerne nanokompozite, temelječe na nanocevkah MoS2, in opravili njihovo strukturno, električno in mehanično karakterizacijo. Nanocevke smo pretvorili v enoplastne nanokosmiče (slika 4.4), analogne grafenu, in pojasnili njihove optične lastnosti s kvantno ograditvijo. Predvidevamo njihovo uporabo v sončnih celicah ter nadzoru visokohlapnih snovi. Našli smo tudi novo vrsto makromolekul, temelječih na hidratih Mo-oksidov. Opravili smo meritev litijeve interkalacije v nanomateriale, primerne za litijeve baterije.

Optične tekočekristalne zaslonke za zaščito oči

Institut »Jožef Stefan« (IJS) in njegovo odcepljeno podjetje Balder, d. o. o., sta razvila nove tekočekristalne svetlobne zaslonke, temelječe na optično kompenzirani dvolomnosti v superzvitem TK-zaslonu in zaščitene s 6 mednarodnimi patenti (USA, EU). Balder je s tem postal edini svetovni proizvajalec TK-filtrov za varilce in sme označevati svoje izdelke s prestižnim certifikatom CE 1/1/1/1. Mednarodna organizacija za standardizacijo (ISO) je povabila IJS k sodelovanju v ekspertnih skupinah ISO/TC94/SC6/WG2 in WG4 z namenom priprave novega ISO-standarda za zaščito oči. Naša nova tehnologija TK svetlobnih zaslonk, ki je bila nedavno še izboljšana s prostorskim filtriranjem svetlobe, omogoča uporabo omenjenih filtrov pri zaščiti oči pred kolimiranimi svetlobnimi prameni, npr. pred avtomobilskimi žarometi (Poudarek 4).

Slika 4.3: Simulacija elektromehaničnega pojava v nematskem elastomeru: polje povzroči deformacijo

Slika 4.4: Monoplasti MoS2: enoplastni nanokosmiči

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Soft composites for optical, electronic, photonic, and sensor applications

Our soft composites are advanced materials often characterized by a complex topology (Highlight 1) that are designed for possible applications in different optic, photonic, and nanotechnological applications. Our CO-NAMASTE research module joined partners from different backgrounds (physics, chemistry, nanosciences & optics) to contribute to the fundamental goal of developing new, advanced materials and technologies. The academic research is complemented by the developments in two partner companies. Here we show selected highlights of our work, some concepts are worldwide firsts, including colloidal microscopic knots and links, efficient and tunable droplet resonators, 3D omnidirectional lasers, the laser-induced printing of optical defects, the fluid-driven self-assembly of 3D colloidal crystals, actuated elastomers for artificial muscles, nanomaterial additives for lubricant oils, and optical LCD shutters for eye protection.

Results and Areas of application

Nematic colloids: assembling topological soft matter

The control of geometrical/topological constraints at the microscale provides a new route for designing soft topological materials. We demonstrated the worldwide-first realization of arbitrary knots and links that can be assembled from topological defect loops encircling microspheres in a chiral liquid crystal (LC). Using optical tweezers, we created different arrays of colloidal particles and by applying focused laser light we rewired the knotted structures at will (Highlight 2). Tailoring knots to order was proved possible through the computer modeling of knot invariants, tangle specifications and targeted made-to-order design. This soft-matter system provides a new fabrication strategy for photonic structures with a nontrivial topology that could control the flow of light in emerging applications.

Nematic droplets as tunable optical microresonators

Nematic droplets are shown to work as electrically tunable microresonators. The droplets are dispersed in a polymer host and then activated by laser light. In such resonators, the resonant frequency shift is achieved via the electric field-induced distortion of the

birefringent nematic, tunable for two orders of magnitude above the achievements in solid-state resonators. The light inside the resonators adopts various low-loss whispering-gallery-modes. The demonstrated nematic resonators could be used as elements in soft matter photonic circuits capable of cutting-edge light-by-light control (Figure 4.1).

Liquid crystal microlasers

A worldwide-first 3D isotropic laser was demonstrated in polymer-dispersed and dye-doped chiral nematic spherical cavities (Front page). It is formed by the spontaneous self-assembly of small cholesteric LC droplets in an immiscible fluid. A small amount of added fluorescent dye produces fluorescent light when excited with an external short-wavelength light. Millions of identical monochromatic microlasers can be produced in a fraction of a second. Cholesteric LC self-organizes inside the droplet into a series of concentric Bragg mirrors, acting as an optical resonator and directing the fluorescent light towards the droplet center; thus an optical standing wave is created. Increasing the excitation power results in stimulated laser emission. The droplet therefore acts as an isotropic source of coherent light, being the first 3D microlaser ever produced. The wavelength of the emitted light can be tuned by the temperature. These microlasers are interesting for photonic applications in displays, sensors and imaging.

Laser-induced printing of nematic defects

The laser-induced imprinting of variable birefringent nano- and microoptical patterns is demonstrated by using computer modeling. Laguerre-Gaussian (LG) laser beams are applied to the nematic LC, where complex LG optical fields imprint their polarization profile into the molecular order. Because of the strong spatial modulation of the LG

Figure 4.1: Whispering-gallery-mode in a nematic liquid crystal droplet

Figure 4.2: Simulated colloidal liquid-crystalline blue phase

prof.dr.Slobodan Žumer, head of RRP4

30

polarization, defects emerge in nematic ordering, which have their conformations directly controlled by the index of the LG beams. This demonstrated optical imprinting process creates new complex birefringent materials with the birefringence modulation at micro- to nanoscale, allowing for the control of the flow-of-light over a wide and continuous wavelength spectrum. Imprinted nematic defects could be back-coupled to generate analogous defects in the light fields.

Colloidal and confined blue phases

The first self-assembly of 3D, quasi-2D and 2D colloidal crystals, based on the regular internal structure of a complex blue phase fluid, is demonstrated (Figure 4.2). We show that the blue phases provide a 3D template of the trapping sites for colloidal particles, forming FCC colloidal crystals in type-I blue phases and BCC crystals in type-II blue phases. We also demonstrate multiple, new, exotic micro-structures in blue phases confined to thin cells (Skyrmions, undulations). The stability of these structures depends on the temperature, cell thickness, and anchoring, which ensures that the LCs perform differently and more in strong confinement. Technologically, this is interesting for the spontaneous formation of anistropic nano-patterns and micro-modulations.

Actuation of liquid-crystal elastomers

We have developed new, composite, LC elastomer (LCE) structures, applicable for actuation technologies and structural manipulation on the micro- and nanoscales. Gold layer deposition has been shown to be promising in the resistive heating actuation of LCE, with good repeatability at moderate strains and low voltage supplies. PEDOT:PSS nanofilms, exhibiting excellent stability and adhesion to the LCE substrate, have been employed in prototyping a bilayered composite with a temperature-tunable periodicity of surface wrinkles. Moreover, a molecular model for the LCE was developed. In large-scale Monte Carlo simulations we performed temperature scans and stress-strain experiments, and explored the electric field behavior (Figure 4.3). The nematic-isotropic transition, as well as transversal electric field application, results in a dramatic sample shape change. In the latter case, the elastic deformation is rather soft, which may be promising for actuator design.

Nanomaterial additives for lubricating oils

We developed a synthesis process for gram quantities of pure Mo/W oxide/sulfide nanoparticles, enabling industrial testing (Highlight 3). Investigating MoS2, we measured single nanotube and nano-onion friction for the first time, proposing a new lubrication type. Friction for the steel or diamond-like carbon (DLC) contact drops by >40 % if the lubricating oil contains a few percent of MoS2 nanotubes. We synthesized the first polymer nanocomposites based on MoS2 nanotubes and performed their structural, electrical, and mechanical characterization. We exfoliated the nanotubes to single-layer nanoflakes (Figure 4.4), representing an analogy with graphene, and explained the optical properties with quantum confinement. Their application is foreseen in solar cells and in the control of highly volatile substances. We discovered a new sort of macromolecules based on Mo-ox hydrates. We performed a measurement of lithium intercalation into the nanomaterials appropriate for lithium batteries.

Optical liquid-crystal shutters for eye protection

Jožef Stefan Institute (JSI) and its spin-off, Balder Ltd, have developed novel LCD optical light shutters based on optically compensated birefringence in Super-twisted LCDs (protected by 6 international patents, USA & EU). Balder hence became the only LCD welding filters’ producer worldwide that can label its products with the prestigious CE 1/1/1/1 certificate. The International Standard Organization (ISO) invited JSI to participate in the expert groups ISO/TC94/SC6/WG2 and WG4, preparing the new ISO standard on Eye Protection. The JSI’s new LCD light-shutter technology, recently upgraded by emerging spatial light filtering, allows for the application of our LCD filters into the field of light-hazard eye protection against collimated light sources (car head-lights, Highlight 4).

Figure 4.3: Simulated electromechanical effect in nematic elastomer: field-induced deformation

Figure 4.4: Monolayers of MoS2: single-layer nanoflakes

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R&R-poudarki R&D highlights

Protimikrobni nanomateriali Antimicrobial nanomaterials

Biokompatibilni materiali Biocompatible materials

Keramični zobni zatički Zirconia dental posts

Novi načini slikanja nanostrukturiranosti New approaches to nanostructure imaging

RRP5

Bioaktivnost in biokompatibilnost Bioactivity and biocompatibility

Interakcija med membrano in nanocevkami Membrane-nanotubes interaction

Napredni bioaktivni, biokompatibilni in bioinertni materiali

Razvoj materialov in funkcionaliziranih površin je v zadnjih letih prinesel nove priložnosti na področjih medicine in medinskih materialov, saj lahko novi koncepti prinesejo dramatično povečanje kvalitete življenja. Na primer, bolnišnične okužbe so med petimi najpogostejšimi vzroki smrti, še večje gospodarsko breme pa so okužbe s hrano. Dezinfekcija z uporabo kemičnih snovi (biocidov) in ultravijolično svetlobo (UV) je zato razširjena v živilskopredelovalni industriji, kot tudi v bolnišnicah, ima pa svojo ceno – agresivna je tako do drugih materialov kot tudi do okolja. Zato so bile razvite površine zaščitene z bioaktivnimi nanomateriali, ki lahko preprečijo rezistentne okužbe, povezane z infrastrukturo tako v živilskopredelovalni industriji kot tudi v zdravstvenem sektorju. Nekatere med temi materiali smo preizkusili tudi pri tem projektu.

Po drugi strani pa sedanje demografske usmeritve kažejo na razkorak med povečevanjem življenjske dobe in premajhnim vplivom novih tehnologij na povečevanje kvalitete življenja. Področje regenerativne medicine je zato v razcvetu, saj bi lahko imelo izjemen vpliv na zdravstvene sisteme široko po svetu. Primanjkuje pa izobraženih kadrov, saj so specialisti ujeti bodisi v premalo usmerjenem akademskem sektorju ali preveč omejenem razvoju v zasebnih podjetjih. Eden od ciljev tega projekta je bil tudi premostiti to razklanost in povezati sektorje ter eksperte, ki naj bi se ukvarjali z najbolj relevantnim vprašanjem obdobja novih materialov: kako varni so ti materiali, ko pridejo v stik z našim telesom. Pri nanomaterialih, ki so bili razviti za protimikrobne površine ali za ojačevanje različnih nosilnih struktur, smo v okviru tega projekta preizkusili njihovo učinkovitost skupaj s koncentracijo v okolju, v tkivih živih organizmov ter v njihovih celicah.

Rezultati in področja uporabe

Protimikrobne površine

Da bi izboljšali antibakterijske lastnosti površin smo razvili stabilen nanos nanocevk TiO2 na polietilen tereftalatnih (PET) površinah, na material, ki se ga pogosto uporablja v živilsko- predelovalni industriji in v bolnišnicah. PET- površine s tovrstnim antibakterijskim nano-nanosom (ABnN), ki so osvetljene z navadnimi fluorescenčnimi svetilkami, zavirajo rast bakterij tudi do enega velikostnega reda. Uporaba enodimenzionalnih nanodelcev, kot so nanocevke TiO2, ponuja poceni in učinkovito alternativo sodobnim metodam razkuževanja, ki se uporabljajo v živilskopredelovalni industriji ter v bolnišnicah. Sedaj je prototip naše tehnologije naprodaj po ceni proizvodnje na laboratorijski skali 7,10 EUR/m

2, zmogljivosti

proizvodnje najmanj 400 m2 na teden in pri

stroških nanašanja zaščitene površine 2,08 EUR/m

2.

Vstop nanomaterialov v celice in vitro ter in vivo

Osrednje vprašanje našega dela je bilo, ali nanodelci in nanovlakna vstopajo v membrane in nadalje v celice tako v sistemu in vitro kot in vivo. Vstop v/skozi membrano smo dokazali s FMS-FRET-eksperimenti na modelnih membranah, ki so bile izpostavljene valu difundirajočih nanodelcev na mikrometrski skali. Nanodelci so se najprej akumulirali na membranah ter zato prišli v molekulsko bližino membranskih sond, zaradi česar se je signal zadnjih povečal (pojav FRET). Po pribl. 40 min

je oblika liposomov začela razpadati, signal membrane pa se je začel pojavljati vsepovsod v mikrometrski okolici.

Da bi detektirali nanodelce v tkivih organizmov, smo študije izvajali na modelnem nevretenčarskem organizmu in študirali celice prebavnih žlez, ki pridejo direktno v stik z zaužitimi nanomateriali. Ugotovili smo, da po zaužitju srebrovih nanodelcev v celice vstopijo le ioni, ne pa tudi delci, če celična membrna ni poškodovana. Pri zaužitju

Slika 5.1: SEM-slika Listerie Innocua na površini, ki je neoptimalno prekrita s titanatnimi nanodelci

Slika 5.2: Preživetje Listerie Innocua na ABnN pri dolgotrajni osvetlitvi s fluorescenčnimi lučmi z nizko jakostjo

prof. dr. Janez Štrancar, vodja RRP5

34

volframovih nanovlaken pa smo dokazali, da se zaužita vlakna v celice zapičijo. Pridobljeno znanje je uporabno na področjih, kjer naomateriali lahko pridejo v direkten stik s celcami in tkivi. Za uspešno in varno uporabo je namreč treba poznati njihove interakcije z netarčnimi celicami.

Spremljanje nanodelcev v okolju

Ustanovili smo enoto za vzorčenje zraka, ki je opremljena s komplementarnimi aparaturami za meritve onesnaženosti zraka z nanodelci. Izvedli smo preizkusne meritve na lokacijah na prostem (Luka Koper, Zagorje) ter v zaprtih prostorih (kovinska delavnica, zobozdravstveni laboratoriji, Kongresni center Brdo pri Kranju). Nadzorne merilne storitve so pripravljene za komercializacijo. Navezali smo stike z ustreznimi podjetji preko Obrtne zbornice in Gospodarske zbornice RS. Prototip, ki temelji na inovativni merilni metodi, je bil obnovljen in računalniško simuliran v okviru končanega doktorskega dela. Okrepili ali začeli smo sodelovanje z javnimi organi na področju varne proizvodnje in uporabe nanomaterialov (Urad za kemikalije, Inštitut za varovanje zdravja, Agencija za okolje), kar se je izrazilo tudi v 3-letni vlogi nacionalne ekspertinje pri EFSA za področje nanotehnologije v hrani in krmi. Sodelovali smo pri raziskavah toksičnosti nanodelcev in v zdravniških komisijah s tega področja. Nadaljevali smo aktivnosti javnega dialoga na področju nanovarnosti.

Dentalna keramika

Na področju dentalne keramike smo reševali nekaj perečih problemov, ki spremljajo izdelavo polnokeramičnih zobnoprotetičnih konstrukcij s cirkonijevo oksidno keramiko kot ogrodnim materialom, njihovo cementiranje in vedenje v kliničnih razmerah. Z in vitro in in vivo raziskavami fazne nestabilnosti te keramike smo prišli do boljšega razumevanja procesov staranja in utrujanja ter s tem do zanesljivejše ocene predvidene trajnostne

dobe v kliničnih razmerah. Za izboljšanje oprijema keramike z zobnimi cementi smo razvili in klinično preizkusili sorazmerno enostaven neinvaziven postopek sinteze adhezijskega nanosa na sintrano keramično ogrodje, ki izboljša adhezijo za faktor 2–4, trdnost spoja pa tudi po dolgotrajnem termocikliranju v vodi ostane praktično nespremenjena. Da bi zmanjšali nevarnost odpovedi marginalne zapore in s tem verjetnost nastanka sekundarnega kariesa, smo razvijali zmerno porozno keramiko z visoko trdnostjo, vendar z nižjim modulom, kot ga ima sedanja ogrodna keramika.

Slika 5.3: Razpad liposomske membrane zaradi interakcije z nanodelci – dokaz s FRET; FMS-informacije so razstavljene na dve komponenti – del signala prihaja iz nanodelcev, označenih z Alexo, del pa iz membrane, ki je označena z Bodipyjem.

Slika 5.4: Zaužita volframova nanovlakna se zapičijo v celice prebavnih žlez. Zgornja slika prikazuje celice prebavnega epitela, v katere se zapičijo nanovlakna, kar prikazuje spodnja slika.

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membrane signal

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ne

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nanoparticle enhancement of membrane signal due to FRET

nanoparticle-induced destruction of membrane

Slika 5.5: Nanostrukturna adhezijska prevleka

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Advanced bioactive, biocompatible and bioinert materials

Recent developments in materials and functionalized surfaces have brought new opportunities in the fields of medicine and medical materials. New concepts dramatically increase the quality of our lives. For example, hospital-acquired infections are one of the top five causes of death overall, whereas an even greater economic burden was estimated for the annual number of foodborne illnesses. Disinfection with the use of chemical agents (biocides) and ultraviolet light (UV) is widely employed in the food-processing industry as well as in hospitals at the cost of being more aggressive to other materials and our environment. Recently, bioactive nanomaterial-enriched surfaces were developed to prevent infrastructure-related (resistant) diseases both in the food-processing and the health sector, some new materials have also been tested within this project.

On the other hand, recent demographic trends have clearly shown that life expectancy is increasing, but not matched by an improvement in the quality of life. The regenerative medicine markets thus expand every year, having a critical impact on healthcare systems all around the world. A shortage of qualified people in the sector is expected, with the experts trapped either within a too dispersed academic sector or a too restricted development in private companies. The goal of this project is therefore also to bridge the gap and connect the sectors and experts involved by also addressing one of the most relevant questions of the new materials era: how sure are we that these materials are safe enough to make close contacts with the human body. Nanomaterials that are developed to fight against bacteria or to reinforce the various scaffold structures have therefore been tested for their efficiency together with their concentration in the environment, in tissues of livings organisms and in their cells.

Results and field of application

Antimicrobial surfaces

In order to improve the antibacterial properties of surfaces we developed a stable deposition of TiO2 nanotubes on various surfaces. For example, on polyethylene terephthalate (PET) surface, a material commonly used in the food-processing industry and hospital environment, antibacterial nanocoating (ABnC) retard growth of bacteria by up to one order of magnitude when illuminated by ordinary fluorescent light bulbs. The use of these one-dimensional nanoparticles – TiO2 nanotubes – therefore promises low cost and an effective alternative to current disinfection methods used in the food-processing industry and in the hospital environment. Currently, our technology prototype is on sale, with the lab production of cost 7.10 €/m

2, a production rate of at least

400 m2per week and an application cost of

2.08 €/m2 for the protected surface.

Nanomaterial internalization in membranes and cells in vitro and in vivo

The basic questions are: do nanoparticles and nanofibres enter cell membranes and can they be uptaken further into the cells in vitro and in vivo. The partitioning of the nanoparticles was studied via FMS-FRET experiments on model membranes, exposed to the diffusing nanoparticles on a micron scale. The nanoparticles first accumulated on membranes coming into the molecular neighborhood of the

membrane probes, which enhanced the membrane probe signal due to FRET. After approximately 40 min. the liposomes start to degrade and the membrane signal was detected everywhere within the micrometer neighborhood. To assess the cellular internalization of the nanoparticles in vivo the studies were conducted with a model terrestrial isopod exposed to nanoparticles via food. Results so far have confirmed that the ingestion of Ag nanoparticles resulted in the cellular accumulation of ions, but not

Figure 5.1: SEM image of Listeria Innocua on poorly optimized nanomaterial-coated surface

Figure 5.2: Survival of Listeria Innocua on ABnC under low intensity long-term exposure to common fluorescent lights

prof. dr. Janez Štrancar, head of RRP5

36

particles when the cell membrane is intact. In the case of feeding the animals with tungsten nanofibers, the ingested fibers were thirsted into cells. This knowledge could significantly contribute to efficient and safe applications in different medical fields. In addition, the experimental data provided in our study could make a contribution in the food industry.

Nanoparticle monitoring in the environment

A knowledge-supported monitoring unit equipped with complementary apparatus has been established for the detection of pollution in the air from nanoparticles. Test measurements have been performed in outdoor locations (Luka Koper, Zagorje) and at indoor sites (metal workshop, dental laboratories, Congress centre Brdo pri Kranju). The monitoring service is ready for commercialization. Contacts with relevant industry have been established through the Chamber of Craft and the Chamber of Commerce of the Republic of Slovenia. A prototype based on an innovative measuring technique was reconstructed and computer simulated. One PhD work was completed on this topic. A collaboration with public bodies in the field of safe production and the use of nanomaterials was strengthened or initiated (Chemical Office, Institute of Public Health, Agency of Environment) resulting in a 3-years period of activity as a national expert in EFSA for nanotechnology in food and feed. We participated in nanoparticle toxicity studies and as evaluators of PhD theses in this area. We continued public dialogue activities in the field of nanosafety.

Dental ceramics

In the field of dental ceramics we have addressed some of the emerging problems related to the fabrication of zirconia-based all-ceramic fixed partial dentures (FPDs), their cementation and performance under clinical conditions. In-vitro and in-vivo investigations of the phase instability of the tetragonal zirconia were aimed at a better understanding of the ageing and fatigue behavior of this core

material as a prerequisite for the expected lifetime prediction of FPDs. A relatively simple process involving a non-invasive functionalization of the core ceramic was developed and clinically tested that has the potential for durable improvement of the adhesive bond between the coated core and the dental cements by a factor of 2–4. In order to reduce the magnitude of the elastic stresses developed at the margin of the tooth and the restoration, a novel, moderately porous ceramic material has been developed exhibiting a practical strength and considerably lower elastic modulus than are currently available.

Figure 5.3: Destruction of liposome membrane due to interaction with nanoparticles identified through FRET; FMS data was decomposed to two components – part of the signal originates from Alexa-labeled nanoparticles, and part of the signal originates from Bodipy probes in the membrane.

Figure 5.4: Ingested tungsten nanotubes thrust into cells. SEM images of digestive gland epithelium (upper image) and the nanotubes thrust into cells (lower image).

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nanoparticle-induced destruction of membrane

Figure 5.5: Nanostructured adhesive coating

37

R&R-poudarki R&D highlights

Izobraževanje Education

Termično obstojni kordieritni izdelki Thermally stable cordierite products

Shema elektrokaloričnega cikla Scheme of the electrocaloric cycle

Preizkušanje CISPR 25 v EMC-laboratoriju Letrika Testing CISPR 25 in EMC Lab Letrika

RRP6

Projekt odprtih možnosti Project of new opportunities

Kordieritni granulati Cordierite granulates

Projekt odprtih možnosti

Člani centra odličnosti NAMASTE smo zasnovali »Projekt odprtih možnosti« zato, da bi lahko razvijali dejavnosti na področjih, ki ob zasnovi centra niso bile vključene v nobenega ob obstoječih projektov ter za te dejavnosti tudi zagotovili finančno podporo. Raziskovali smo najbolj napredne smeri na področju materialov za elektroniko, v raziskave smo vključili najboljše strokovnjake iz raziskovalnih organizacij in industrije, ki smo imeli dostop do vrhunskega znanja ter najsodobnejše opreme, ki jo združuje center. Motivirala nas je želja, da bi z aktivnostjo in hitrim odzivom članov centra izboljšali njihovo konkurenčnost na svetovnem trgu ter tako aktivno sledili najnovejšim smerem razvoja na izbranem področju.

Dejavnost CO smo predstavili domači in tuji širši javnosti na različnih sejmih, objavljali smo prispevke v številnih revijah, na radiu in televiziji, obiskali smo števila podjetja. Skupaj smo CO predstavili devetindvajsetkrat. Partnerjem CO in zunanjim članom smo ponudili izobraževanje. Organizirali smo dvanajst delavnic in različnih konferenc, ki so omogočale izpopolnjevanje znanja na izbranih področjih. Organizirali smo devetindvajset predavanj svetovno priznanih strokovnjakov iz Evrope, Amerike in Azije. Poleg tega smo ponudili svetovanje pri reševanju problemov, pretežno industrijskim partnerjem. Strokovnjaki CO so opravili meritve na najsodobnejših aparaturah, ki smo jih nabavili v okviru centra, in ponudili interpretacijo rezultatov ter svetovanje o nadaljnjih postopkih raziskav. Za zunanje uporabnike smo izvedli 270 analiz. Pripravili smo tudi več predlogov projektov za različne razpise ter tako omogočili boljše povezovanje industrijskih partnerjev in akademske sfere za obdobje po končanem financiranju centra.

V okviru »Projekta odprtih možnosti« smo izvajali tri raziskovalne projekte, in sicer »Keramični materiali za elektrokalorične meritve« v sodelovanju z Institutom »Jožef Stefan«, »Virtualni EMC-laboratorij” v sodelovanju z Zavodom SEMTO ter partnerji SIQ, Iskra MIS, IskraTEL, Iskraemeco, Iskra Zaščite, ETI Elektroelement in Hidria AET ter projekt “Raziskave vpliva velikosti delcev in drugih karakteristik keramičnih surovin in keramičnih suspenzij na karakteristike žganih kordieritnih materialov« v sodelovanju s podjetjem ETI Elektroelement, d. d., iz Izlak in Institutom »Jožef Stefan«.

Projekt »Keramični materiali za elektrokalorične meritve«

V okviru podprojekta »Keramični materiali za elektrokalorične meritve« smo preučevali elektrokalorične materiale na osnovi svinca in tudi okolju prijazne materiale brez svinca. Raziskovali smo feroelektrične in relaksorske keramike, antiferoelektrike in monokristale, ker je znano, da v teh materialih obstaja izrazit elektrokalorični pojav in do sedaj na tem področju še ni bilo narejenih veliko raziskav. Najboljši elektrokalorični odziv (ΔTEC = 3,5 K pri E = 160 kV/cm; T = 127 °C) v volumenskih keramikah (1–x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 (PMN–PT) smo dosegli na 0,9PMN–0,1PT. Dosedaj največji elektrokalorični odziv (ΔTEC = 40 K pri E = 120 MV/m in T = 45 °C) pa je bil izmerjen v tankih plasteh (Pb1– 3x/2Lax)Zr0,65Ti0,35O3 (PLZT). V okolju prijazni volumenski keramiki brez svinca K0,5Na0,5NbO3–SrTiO3 (KNN–STO) smo izmerili temperaturno spremembo ΔTEC = 2 K pri E = 159 kV/cm, T = 67 °C, kar je primerljivo z vrednostmi elektrokaloričnega odziva nekaterih keramik na osnovi svinca. Tako lahko v bližnji prihodnosti KNN-STO-materiali nadomestijo elektrokalorične materiale, ki vsebujejo svinec. V antiferoelektrikih PbZrO3 (PZ) in (Pb0,04Ba0,06)ZrO3 smo opazili negativni elektrokalorični pojav, tj. ohladitev vzorcev ob vklopu in segrevanje ob izklopu električnega polja. Preučili smo tudi možnost uporabe debeloplastnih kompozitnih struktur 0,65PMN–0,35PT/Pt za zbiranje energije. To lastnost lahko uporabimo pri izdelavi prototipa hladilne strukture, ki bi temeljila tako na elektrokaloričnem kot tudi na piezoelektričnem efektu (odmik 1 600 μm pri E = 21 kV/cm). Dokaz obstoja velikega elektrokaloričnega odziva v omenjenih materialih omogoča razvoj popolnoma novih tehnoloških rešitev pri vrsti aplikacij hlajenja, stabilizacije temperature in pridobivanja električne energije iz odvečne toplote, ki imajo boljšo energijsko učinkovitost od vseh sedanjih tehnologij, so ekološko bolj sprejemljive in lahko posežejo na vsa področja aplikacije od hladilnih sistemov in klimatizacijskih naprav do točkovnega hlajenja mikroelektronskih komponent.

Projekt »Virtualni EMC-laboratorij”

Projekt “Virtualni EMC-laboratorij” je bil vključen v CO kot možnost vertikalnega povezovanja materialov z elementi in izdelki, kar je v strategiji CO posebej poudarjeno. Projekt tako dodatno omogoča uporabne nastavke rezultatov raziskovanj na področju materialov, ki jih

Slika 6.1: Opravljanje storitev za

uporabnike na opremi CO NAMASTE

Slika 6.2: Elektrokalorični odziv v x/65/36

PLZT tankih plasteh

dr. Danjela Kuščer, vodja RRP6

40

nadgrajuje s praktičnimi vsebinami in uporabnostjo pri razvoju novih elementov in izdelkov. Prav zahteve po elektromagnetni združljivosti in zahteve po odpornosti, robustnosti in varnosti pa so tiste, ki jih je za dosego optimalnih rezultatov potrebno v okviru raziskav in razvoja upoštevati po vsej verigi.

Rezultat projekta je izdelana podatkovna baza, v katero so vključeni vodilni laboratoriji na področju elektromagnetne združljivost (EMC) in varnosti v Sloveniji in ki potencialnim uporabnikom posreduje informacijo o meritvah v teh laboratorijih. Ker so EMC-meritve povezane z zelo visokimi stroški investicij v merilno opremo in zahtevajo specifično znanje merilcev, projekt razpršene laboratorije povezuje, izboljšuje izkoriščenost kapacitet in informira strokovno javnost o meritvah v posameznih laboratorijih. V bazi podatkov so dostopne relevantne informacije o razpoložljivi opremi, izkoriščenosti opreme, merilnih postopkih in usposobljenosti za meritve. Nadgradnja informacij o meritvah in preizkusih v posameznih laboratorijih so tudi podatki o izkušnjah in usposobljenosti za reševanje problemov, to je odpornosti proti EMC-motnjam, odpornost proti stresnim preizkusom, in varnostni preizkusi. Potencialni uporabnik s povezovanjem znanja laborantov, merilcev in razvijalcev svoj problem z uporabo meritev in preizkusov ne le okarakterizira, ampak lahko tudi razvojno razreši.

V okviru projekta sta bili organizirani tudi dve konferenci s področja EMC-meritev. Na prvi konferenci v septembru 2011 so bili predstavljeni cilji projekta. Rezultati in razprave med konferenco in po njej so omogočili dobro definiranje vsebine in metodologijo dela. Pridobljeni so bili partnerji projekta, to je vodilni industrijski laboratoriji s področja EMC- meritev in preizkusov. Po konferenci je bilo organiziranih nekaj strokovnih sestankov, kot rezultat pa je bila določena vsebina podatkovne baze in način dela projektnih partnerjev.

Druga konferenca je bila organizirana v oktobru 2013. Njen namen je bil predstaviti rezultate projekta, podatkovno bazo in v neformalnem smislu tudi zaključek projekta. Namen je bil tudi popularizacija rezultatov projekta in povabilo partnerjem k nadaljnjem sodelovanju pri vnosu novih meritev v bazo “EMC-meritve”. Konferenca je ponudila tudi nekaj idej za nadaljevanje projekta v smislu širitve vsebine na trajnostne preizkuse in preizkuse trajnostne dobe izdelkov, na integracijo standardne baze podatkov in razvoj mobilne aplikacije za pregledovanje baze.

Projekt “Raziskave vpliva velikosti delcev in drugih karakteristik keramičnih surovin in keramičnih suspenzij na karakteristike žganih kordieritnih materialov«

ETI, d. d., proizvaja keramične izdelke, ki se uporabljajo v elektrotehniki kot toplotni in električni izolatorji iz različnih keramičnih materialov. Ena izmed skupin materialov so kordieritni materiali, ki vsebujejo mineral kordierit. Ta je magnezijev alumosilikat z oksidno sestavo 2MgO2Al2O35SiO2 in nizkim koeficientom linearnega termičnega raztezka okoli 2,5 10

–6 K

–1, zato se

kordieritni materiali uporabljajo za izdelavo delov, ki so izpostavljeni hitrim temperaturnim spremembam. Kordieritne materiale pripravljamo iz naravnih surovin talkov, gline in glinice, zato je priprava kordieritne keramike kompleksen proces. V prvi fazi MgO in Al2O3 tvorita spinel, ki nato reagira s SiO2 in nastaja kordierit. Nastajati začne pri temperaturi 1 250 C. Proces nastajanja kordierita je odvisen od temperature žganja in od časa izotermnega zadrževanja pri maksimalni temperaturi. Za doseganje želenih karakteristik kordieritnega materiala, to sta visoka odpornost proti temperaturnim spremembam in dobre mehanske lastnosti, je pomembna količina kordierita ter homogena in gosta mikrostruktura. Raziskovali smo vpliv sestave in morfologije surovin ter procesa sintranja na mikrostrukturo, koeficient linearnega termičnega raztezka in mehansko trdnost kordieritnega materiala. Z optimimalno količino in porazdelitvijo Al2O3 v mikrostrukturi smo znižali koeficient linearnega termičnega raztezka, obenem pa smo ohranili dobre mehanske lastnosti materiala. Kordieritne materiale z optimalno sestavo smo pripravili v laboratorijskih razmerah in v proizvodnem procesu. S kontrolo procesnih parametrov smo pripravili kordieritni material s homogeno mikrostrukturo in želenimi mehanskimi ter termičnimi lastnostmi, ki so ključnega pomena za ponovljivo proizvodnjo. Nov material ima želen in ponovljiv koficient termičnega raztezka, zaradi česar se lahko uporablja v zahtevnih proizvodih.

Pridobljeno znanje omogoča načrtovanje in proizvodnjo izdelkov z definiranimi želenimi lastnostmi, ki so pomembne za končnega uporabnika. Primeri uporabe kordieritnih materialov so nosilci grelnih spiral za sušilne stroje in za potopne grelnike, izolacijske elemente grelnikov, zaščitne tulce sond za metalurgijo, elemente variabilnega upora za električne lokomotive in podstavke za sintranje kovinskih prahov.

Slika 6.3: Vplivi in okolje EMC-meritev in

preizkusov

Slika 6.4: Homogena porazdelitev Al2O3 v

mikrostrukturi novega kordieritnega materiala

10 mm

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Project of new opportunities

The “Project of new opportunities” within the Centre of Excellence NAMASTE was established to address the advanced topics that have not been included in any of the projects within the CO and also to financially support selected research work. Thus, the partners of the CO as well as the non-members from the industry and research institutions have the possibility to investigate the advanced phenomena and benefit from access to the advanced knowledge and modern, up-to-date equipment within the CO. The activities within the “Project of new opportunities” and the very fast response of the members present an advanced approach that improves the competitiveness of industrial partners in the global market and gives the possibility to the partners to be actively involved in advanced trends in the field of materials for electronic applications.

The CO presented its activities to the public by attending various fairs, publishing contributions in numerous journals, on radio and television, and visiting a range of companies. Altogether, the activities of the CO were presented at twenty-nine events. The CO has also offered education to the partners and non-members. We organised or co-organised twelve workshops and conferences from the selected fields. We invited twenty-nine experts from Europe, America and Asia to present their work and share their knowledge with the consortium of the CO. The advising and servicing have been important activities of this project. The partners within the consortium have shared the equipment and the experts from the selected field helped with the interpretation of the results. Having access to up-to-date equipment is especially important for industry. We did 270 analyses for the non-members and gave support to the interpretation of the results. The CO prepared numerous project proposals for various calls, hoping for an effective collaboration between the industry and research institutions for the period after 2013.

Three sub-projects have been initiated within the “Project of new opportunities”, namely “Ceramics materials for electrocaloric measurements” in collaboration with the Jožef Stefan Institute, Ljubljana, “Virtual EMC” in collaboration with the Zavod SEMTO, SIQ, Iskra MIS, IskraTEL, Iskraemeco, Iskra Zaščite, ETI Elektroelement and Hidria AET all from

Slovenia, and “The influence of particle size and other ceramic raw materials and ceramic suspensions on sintered cordierite materials” in colaboration with ETI Elektroelement d.d. from Izlake and Jožef Stefan Institute from Ljubljana.

Project “Ceramics materials for the electrocaloric measurement”

Within the sub-project “Ceramics materials for electrocaloric measurements”, electrocaloric materials based on lead and environmentally friendly materials with no lead were studied. We investigated the ferroelectric and relaxor ceramics, antiferroelectrics and monocrystals, since it is known that these materials show a prominent electrocaloric effect and up now it has not been done to any great extent in this field. The best electrocaloric effect, in bulk ceramics (1–x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 (PMN–PT), was observed in 0.9PMN–0.1PT (ΔTEC = 3.5 K at E = 160 kV/cm; T = 127 °C). Until now, the largest electrocaloric response (ΔTEC = 40 K at E = 120 MV/m in T = 45 °C) was measured in (Pb1– 3x/2Lax)Zr0.65Ti0.35O3 (PLZT). Environmentally friendly lead-free K0.5Na0.5NbO3–SrTiO3 (KNN–STO) bulk ceramics show the temperature change ΔTEC = 2 K at E = 159 kV/cm, T = 67 °C. This is comparable with the magnitude of the electrocaloric effect observed in some lead-based ceramics. Thus, in the near future, the KNN-STO materials could replace the lead-based electrocaloric materials. In antiferroelectrics PbZrO3 (PZ) and (Pb0.04Ba0.06)ZrO3 a negative electrocaloric response has been observed, i.e., the cooling and heating of the sample at switching the electric field on and off, respectively. Furthermore, we studied the possibility of using thick composite structures 0.65PMN–0.35PT/Pt for energy harvesting. This feature can be used in the manufacture of a prototype cooling structure, which would be based on both the electrocaloric as well as the piezoelectric effect (displacement 1600 μm at E = 21 kV/cm). The proof of the existence of a large electrocaloric response in these materials allows the development of new technological solutions for a number of applications for cooling, temperature stabilization and generating electricity from waste heat, which have better energy efficiency in comparison to any existing technologies. However, they cover all areas of applications, for example, cooling systems, air-conditioning equipment and the spot cooling of microelectronic components.

Figure 6.1: Servicing for clients using CO

NAMASTE equipment

Figure 6.2: The electrocaloric effect as a

function of the applied electric field in x/65/36 PLZT thin films

dr. Danjela Kuščer, head of RRP6

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Project “Virtual EMC Lab”

The project "Virtual EMC Lab" was included in the Center of Excellence NAMASTE to vertically integrate materials with the elements and products and, in particular, to emphasize the strategy of the Center of Excellence. The project produces results in the area of materials with a practical content and usefulness, developing new products. Demands for electromagnetic compatibility, resistance, robustness and safety have to be taken into consideration in order to achieve optimal results.

The result of the project is a database that provides measurements of all the leading laboratories in the field of EMC and security in Slovenia to the potential users. As the EMC measurements are related to a very large investment in equipment and require specific knowledge, the project connects dispersed laboratories, thereby improving capacity utilization and informing professionals about the measurements in the individual laboratories. The database provides information about the availability and utilization of the equipment, measurement procedures and the capacity of the measurements, as well as about the laboratories and the users’ experiences, their problem-solving skills, resistance to EMC interferences, stress tests resistance and security tests. Shared knowledge will therefore foster more efficient characterization and problem solving.

Two conferences in the field of EMC measurements have been organized in connection with the project. At the first conference, in September 2011, there were presentations of the objectives. Results and discussion during and after the conference enabled us to define the content and methodology of the work. The partners, the leading industrial laboratories for EMC measurements and tests, were also obtained. After the conference, several expert meetings were organized and as a result the contents of the database and methods of work were determined. The second conference was held in October 2013. Its purpose was to present the results of the database and the conclusion of the project in an informal sense. The aim was also to popularize the results of the project and invite partners to continue cooperation with the addition of new measurements to the database "EMC measurements". The conference also offered a few ideas for the continuation of the project in terms of the expansion of sustainable tests, product lifecycle tests, the integration of standard databases and the development of mobile interdface applications.

Project “The influence of particle size and other ceramic raw materials and ceramic suspensions on sintered cordierite materials”

ETI d.d. produces ceramic products, mostly used in electrical engineering as thermal and electrical insulators, made of different ceramic materials. Cordierite materials are one of the main ceramic material groups. The main phase of cordierite material is mineral cordierite, magnesium aluminum silicate with the composition 2MgO

.2Al2O3

.5SiO2. The most important

characteristic of cordierite is its low linear thermal expansion coefficient; therefore, the cordierite materials are mainly used for segments that are exposed to rapid temperature changes. The preparation of cordierite materials based on natural raw materials, i.e., talc, clays and alumina, therefore their production is a complex procedure. In the first step, MgO and Al2O3 form a spinel that reacts with SiO2, and at a temperature higher than 1250 °C the cordierite is formed. The formation process depends on the sintering temperature and the time of the isothermal step at the maximum temperature. To achieve the desired characteristics of the cordierite material, i.e., a high thermal shock resistance and good mechanical properties, a large amount of cordierite phase and a homogeneous, dense microstructure are required. We investigated the effect of the composition and morphology of the raw materials and the sintering conditions, microstructure, linear thermal expansion coefficient and mechanical strength of the cordierite material. With the optimal amount and distribution of Al2O3 in the microstructure, we lowered the linear thermal expansion coefficient and maintained good mechanical properties of the material. Cordierite materials with an optimised composition were prepared under laboratory conditions and in the production process. We prepared the cordierite material with a homogeneous microstructure and the desired mechanical and thermal properties, significant for repeatable production, with careful control of the process parameters. This new material with the desired and reproducible linear thermal expansion coefficient can be used in products with high requirements. The knowledge that was gained within this project allows us to fabricate products with defined, tailored properties, which are important for the end-users. Cordierite materials can be used in the field of heating coils, holders for driers, immersion heaters, the insulating elements of the heaters, ceramic housings for probes for immersion temperature measurements in molten metals, elements of variable resistors for electric locomotives and refractories for sintering metal powders.

Figure 6.3: Influences and environment on

EMC Measurements and Testing

Figure 6.4: Homogenous distribution of Al2O3 in new cordierite material microstructure

10 mm

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PARTNERJI

PARTNERS