~1J11f.1<l~ 1RT~ ~~ -ti~: mg~ fii~ mg, ~~ cwR 1RT~, ql~yR¢ q~ 1RT~ 3fR~~ 'J'l~ Ncf ~ I~ ~~Cl?T~ lRTm,~~~~ 3fR !'I~~lrrl¢1 q \3qxlCfd~ -ti~ 3fR~Cl?1 ~¢ff1d cwrr ~ I~~ ~ ~tlR~~ \3t:t1l~'i -ti ~xhtJfl ~~~¢ "flTIllfI, Cl541ft1<fl, ~~ cwR~,

~~,~ qlfc;JJix:l, 3lm ~~~If.1Cffi~,~~~ 3fR m 3lT!?; ~TTfi:RVr ~ I~ xl cgt9

1RT~ Cl?T m flIJiR¢ q ~~W1¢ ~ -ti fcfJm \jffiIT ~ I~~ -:r 3lkl~I~I~(YJ 3l~ ~~ fii~mg ettf.1&filfl'i !'I~~lrrlcp"l ~~ 1N~ 1ft~ ~ "fll~ ~ fllFll JA qR<ll\Jl'i1 em ~1<11ft1d fcfJm ~ I 3fr<l~~

R(YJltifl ~'S«1\Jl, ~'J'l ~ ~'S«1\Jl ~"fll~ 3fR3lm~ 3f1~lrrl¢ ~m1N~~~~cwrr~ I

"Cf"ffilcr-ti~~~~~~ ~¢lfl~A(YJ qR<11\Jl'iIJO'-ti~m~~ 3ffi~, MI<11ft1d, fli5l<ldl~

(lJtc~ ~), fli5<1I JA3fR~ qR<11\Jl'iIJO' Cl?1~~tlR ~~~ \JlT~ 3fR~ cIT'il~~~, ~~ fllf)(YJdllf4¢ c;rrrj~ fcfJm \JIT~~ I

ENGINEERING MATERIALS

The Division of Engineering Materials mainly comprises of Metals & Alloys, Advanced CarbonProducts, Polymeric & Soft Materials and Liquid Crystal groups. The objective of this division is todevelop materials, processes and technologies for components, devices and systems in the abovementioned areas. The R&D output of the division includes the development of aerospace metallicmaterials, composites, advanced carbon products, liquid crystals, conducting polymers, optoelectronicdevices, organic electronic devices and sensors etc. A few ofthese materials find applications in strategicand industrial areas; General Motors have sponsored a collaborative project to NPL on the developmentof extrusion technology ofMg alloys for automobile applications. More such industrial linkages withother industries like Reliance Industries, Rane Group of Industries are envisaged for future. In fact,under this division several developmental projects, such as, CSIR network, sponsored, grant-in-aid,collaborative and consultancy are successfully being implemented! completed for different R&Dorganizations, both in the public and private sectors.

Devf'lopmentor different grades of light'Weight Magnesium alloys and fetal atrixComposites

Work was concentrated on developing light

weight magnesium & aluminium alloys andMetal Matrix Composites lmder different

sponsored, network and consultancy projects,four of which have successfully concluded this

year realizing the specific deliverables laid outin each of these projects. The thmst, however,

was on developing extruded rods, tubes andsections of different grades of Mg-alloys for

their possible automobile applications lmder aconsultancy project sponsored by General

Motors on "Advanced Magnesium ExtmsionAlloys" which was successfully concluded this

year. CSIR Network project on the developmentof different grades of magnesium alloys

employing rapid solidification and using spray­forming was successfully completed this year.

Under this project, the process for spray­forming ofMg-alloys has been developed (~4­

5 kgs of melt) and the spray-formed depositexhibits equiaxed microstructure, fine sized

intermetallics and with properties better thancast mother alloy. The project sponsored by

Vikram Sarabhai Space Centre on"development of spray-forming technology for

Mg-alloys" was also completed this year and afew spray-formed deposits were sent to VSSC

for testing and evaluation. Another CSIRNetwork project on the development of Cu­

based MMCs using Powder Metallurgytechnique for prototype brakepad applications

was also completed this year. Under an in-house

project, in order to synthesize cylindrical tubesof fimctionally gradient MMC, a vertical

centrifugal casting unit was set-up at NPL.

M i ,"1.8

•

LO S 1\- agnesilln AUo s

Gener~d Motors Sponsored Project utili d" dvanced agnesium ExtrusiollAllo}'s"

Successfully completed joint projectbetween NPL and General Motors on thedevelopment of extrusion technology ofmagnesium (Mg) alloys with the objective ofachieving high ductility and formability at roomtemperature. Under this project, effect ofseveralprocessing parameters, such as die design, alloycomposition, extrusion temperature, pressingspeed, etc. was investigated on themicrostructure and mechanical properties ofMgalloys that were extruded in the form of rods,tubes and strips. A wide range of Mg alloysincluding novel compositions, e.g., pure Mg,Mg-RE, AM30, AM50, Mg-Al-RE, etc wereinvestigated. The extruded products werethoroughly characterized for their metallurgicaland mechanical properties at NPL and GMlaboratory in Bangalore. An important outcomeof this project was that room temperatureductility of Mg was enhanced significantlyunder optimized process parameters of hotextmsion. It is believed that the investigationresults of this project would play an importantrole in the replacement ofconventionalAl alloyswith novel Mg alloys in the near future.

csm Network project on synthesis of l\fg­a Ho)'s using rap id solid Uica lion nndemplo}'ingspray forming

This CSIR Network project on the sprayforming of Mg-alloys was successfullycompleted this year. The main deliverables ofthis project were the synthesis of Mg-alloysemploying spray forming to obtain low porosity,equiaxed microstructure, low grain size andimproved mechanical properties (w.r.t. the castmother alloy).

fjAN UAl REPO 1-2006--2007

ENGINEERING MATERIALS

The spray-formed deposits werecharacterized using optical microscope,scanning electron micro scope /energydispersive spectrometer and X-ray diffraction.The microstructure spray-formed depositindicated (Fig.3.l) homogeneous magnesium

equiaxed matrix with grain size of 20-40 /-lmthroughout the interior of the deposit with fmeuniformly distributed Mg17Al12 intermetallic

particles of6-9 /-lm. The porosity was observedto be about 2.5-3.5% in the central core of thespray-formed deposit but increases near theperipheral region and becomes very high in theextreme peripheral region of the spray-formeddeposit, where the microstructure exhibitedloosely bound pre-solidified particles of

1-4 /-lm. The microstructural features, observedat different regions in the spray formed deposit,have been explained in the light ofsolidificationof droplets in-flight and subsequent dropletconsolidation on the deposition surface.

The comparison of mechanical propertiesof the spray formed (& cast) Mg-alloys AZ31(Mg-Al-Zn) were found to be UTS (MPa) : 202209 (176-190); %elong : 10-11 (8-9);Microhardness ( HV100 ): 76.3(67.2). Similar

comparison of properties for Mg-alloys EZ33(Mg-RE-Zn-Zr) exhibited UTS (MPa) : 215-228(117-123); %elong: 8-92.8-3.3; Microhardness(HV10oJ: 79.3(60.2). The results of the

mechanical property measurement suggestedthat these were reasonably lmiform throughoutthe central interior region of the spray-formeddeposit and there is an improvement in thetensile strength, ductility and micro-hardness ofthe spray-formed alloy as compared to the castmother alloy, used for spray forming. Thefractured surfaces of the tensile test samples ofAZ31 were examined using a scanning electronmicroscope and Fig. 3.1 depict typical SEMfractographs of the tensile fracture surfaces.

Fig. 3.1: Seaming electron micrographs of tensilefractures surfaces of spray-formedMg-alloy

These microstructures reveal macroscopicallybrittle fracture due to the presence offme cracks.However, at a microscopic level the fracturedsurfaces also reveal isolated pockets of shallowductile dimples, voids of varying sizeintermingled with tear ridges, featuresreminiscent ofductile failure. This suggests thatfmal failure in spray-formed alloys is due to amixture of ductile and brittle mode of fracture,which is also corroborated by the moderatevalues ofductility observed in this alloy.

Vikram Sarabhai pace Ce tr (VS C)spon 'or p oj -t on " pra)' formingtecbnolo ofMg-aUoys

This project sponsored by Vikram SarabhaiSpace Centre (VSSC) was completed this year.Under this project, spray-forming experimentsto synthesize Rare-earth based EZ33 Mg-alloywere conducted in order to synthesize spray­formed alloys in nearly-gaussian shapes with aminimum height of50 mm and base diameter of100 mm and with target properties ofUTS 225MPa, YS - 190 MPa & elong - 3%. Differentprocess parameters like, melt temperature, flightdistance, atomization pressure, design ofatomizing nozzle and delivery tube, wereoptimized in order to spray-form Mg-alloys in

u •POR ·20 6·20 7 •

B d"an ed Carbo Products

A leading centre in India dedicated to research in

both pure and applied science of Carbon withPrincipal motives:

Trial runs were undertaken on the vertical

centrifugal casting lmit using a hollow

cylindrical moulds to make MMC tubular

sections and their process parameters

optimization and characterization is currently

lmderway.

To develop the process technology of

newer carbon products which hold

strategic importance and are notavailable to the cOlmtry at any cost;

To develop products which can be madecost-effective by innovative process

suitable to available infrastructure,

expertise and resources in India;

To promote overall growth of carbonscience and technology in the country

through sustained R&D, research

publications, patents, technology

transfer, consultancy to industry, national& international conferences and refresher

courses etc.

microstructure varies in one specific direction.

Cylindrical tubes offunctionally gradient MMC

find applications in high wear resistant

components, such as cylinder liners, gears, etc.

In order to synthesize cylindrical tubes of

functionally gradient MMC, a vertical

centrifugal casting unit was set-up at NPL. The

density difference between the reinforcement

and matrix alloy produces redistribution of the

two phases due to centrifugal action leading to

formation of a gradient in reinforcement across

the thickness ofthe MMC cylinder tube.

(i)

(iii)

(ii)

In-house proj~t on the "development offunctionally gradient metal matr"composites'

Functionally gradient materials are a new

class of materials where the composition!

Fig. 3.2 : Copper sintered brakepads

A powder metallurgy processing route wasadopted which involved ball milling ofingredient powders followed by compaction forprototype brakepads and sintering underprotective atmosphere. Detailedcharacterization of the brakepads was carriedout.

nearly-gaussian shape with low porosity, goodyield and equiaxed microstmcture and with notraces ofMgO phase. A final batch often sprayformed deposits, meeting the dimensional andproperty targets, was supplied to VSSC,Trivandmm for testing and evaluation.

omposites

C SIR N ttwo rl p roj ec t ntitled"Development of Cu-based I.\B'1C~ usingPowder Metallurgy technique for brake padapplications

Under Xth Five Year plan, a CSIR networkproject entitled "Development of copper basedsintered composites prototype brakepads" has beencompleted successfully. Under this project, copperbased sintered metallic prototype brakepads havebeendevelopedas showninFig. 3.2.

• ~AN UAl REPO 1-2006--2007

ENGINEERING MATERIALS

car on-ceramithrough .in- itu

CFig. 3.4: (a) SEM, (b) TEM, (c) TEM of selected

area diffraction pattern showing the ringpattern ofC-SiC-B4C

nano wires, nano fibres and nano rods while theproduct from TEOS + Carbon Black led toformation of SiC nano fibres. The diameter ofthe SiC nano wires, nano fibres and nano rodswere found to be 25-35 nm, 40-45 nm and 75-90nm respectively. Impregnated jute cloth whilethe pyrolysed products of pre-carbonised andcarbonised jute cloths impregnated withMTEOS derived silica showed coiled andstraight nano fibres. SiC nano material was alsosynthesized using jute cloth (as such andpyrolysed fomls) and silicon alkoxides. It wasobserved from SEM and TEM studies (Fig.3.3)that formation of silicon nano fibres and nanorods were observed from TEOS/MTEOSderived

D v lopment ofomp-it {C-SiC-B..

formation ofnano-SiC

Composites were prepared by isostaticallymoulding the ball milled NPL developed coal tarbased green coke, sol-gel silica, silicon, carbonblack and boron carbide and heat-treating themoulds at 1400 °c and then at 2200 °c. Theproducts showed oxidation resistance at 800°C

e

b

c

a

Fig. 3.3 : SEM photographs of Nano SiC from (a)TEOS + Carbon black (1400°C) (b)DMEOS TEOS + Carbon black (oxidizedand HF treated) (c) MTEOS+ Carbonised(1400'C) TEM photographs ofNano SiCfrom (d) MTEOS Silica + carbon black (e)carbonized (lOOO'C jute cloth + MTEOSsilica

Synth sis and chars t risation of SiCano· terinls.

SiC nanomaterials were synthesized usingTEOS/MTEOS/DMTEOS+TEOS as siliconsource and carbon black as carbon source. TheSiC precursors were heat-treated to 1400 °c inargon atmosphere to obtain pyrolysed product(SIC nm). The final product was characterizedby X-ray, FTIR, SEM and TEM studies. It wasfound that SiC obtained from carbon blackincorporated sol gel silica synthesized fromMTEOS/DMTEOS+TEOS were mixtures of

~NU R PORT.2006.2007 ..

Fig. 3.5: I-V performance of the NPL compositeBipolar plates carried out at CECRI.

Development or specialty carbon materialsfor no el nuclear reactor

composites will be tested for mechanical andthermal properties.

D velopment of Cu I ells ba don h)Tdrogen(NMITLI Project)

Under the project sponsored by BARC,NPL is working on the development of specificCarbon/carbon composite tubes for newgeneration high temperature nuclear reactors.Initially prototype tubes with dimensions OD60 mm, ID 20 mm and Length 100 mm werefabricated by filament winding technique using

T-300 CFs, angle ofwinding being ±55° and T­

300 CFs based fabric. These tube samples were

·1110

.. HHJ

1,••14

'(1 ~'0.

~.,

"

ParmI. cOlfducti"g Carbon paper and. d 'UJICl!d composite, bipolarplate

The major objective during the period wasto optimize the properties of the bipolar platesand porous carbon paper and to supply carbonpaper and bipolar plates ofsize 20 cm x 15 cm toCECRI as per specifications for evaluation inthe unit fuel cell. These samples of desiredcharacteristics were evaluated by CECRI,Chennai center, for their I-V performance on theunit fuel cell assembly and the results arereproduced below. As shown in Fig.3.5, thepower density obtained from NPL plates isalmost matching with Schunk plates at lowercurrent densities and is nearly 100 % 0 f the peakvalue.

and 1000"C for about 10 hrs. The X-ray studiesshowed the formation of SiC and crystallite sizecalculated from the X-ray data was found to be56 urn. The SEM and TEM studies (Fig.3.4)showed the nano-sized SiC and TEM showedthe formation of SiC nanoparticles in the rangeofI4-30nm.

Development of high thermal conducrnit)rarbonmaterials for specialized applications

Studies on the development ofhigh thermalconductivity carbon materials, namely Carbon­Carbon Composites and Special Graphite werecontinued under the special project sanctionedby CSIR. The samples of 3-D carbon-carboncomposites of size 45 mm x 45 mm x 20 mmprepared from T-300 carbon fibres andimpregnated with performing pitch and novelpitch (developed in-house) showed a density of

1.68 gcm-3 at NPL. The determination ofthermalconductivity and mechanical properties are inprogress. The isostatically-molded blocks madefrom green coke possessed the characteristicsdesired under the project.

Development of ,carbon-carboD ompositesfor thermal management

The major objective is to develop of highthermal conductivity carbon-carbon composites

possessing bulk density of 1.8 cm-3, thermal

conductivity values of the order of 250-275W/mK in the longitudinal direction and 75-90W/mK in the transverse direction. Threedifferent types of carbon fibre performs of size100 mm x 50 mm x 50 mm with balanced andunbalanced weave using PAN based and pitchbased carbon fibres subjected to differentimpregnation/Graphitization cycles at NPL

possessed bulk density of 1.2 gcm-3• The samples

have been sent to ASL, Hyderabad for

densification to achieve a density of 1.8 cm-3

using HIPIC assembly available there. These

.. u4)PORT·2006.2007

ENGINEERING MATERIALS

10 12

and C IPS

8642

1.00E+01-,--------------,

1.00E+OO~ 1.00E-01

'E 1.00E·02Jl 100E·03J::' 1.00E-04

~ 1.00E-05:::l 1.00E·06

"'Cl5 1.00E-07£ 1.00E·08

1.00E-09 +--r--r--r--,....--,....----j

o

possible to develop CNT/Phenolic compositespossessing flexural strength of 160±10 MPaeven with small volume i.e 2% ofCNT loadings.The neat phenoilc resin value is around 60±5MPa only. These strength values for MWNT­Phenolic isotropic composites are maXImumachieved so far (Fig. 3.7).

Prepa lion of CNT/P~y.Ll""""

omp it

The use of multi-walled carbon nanotubes(MWCNT) as reinforcing material forthermoplastic polymer matrices polymethylmethacrylate (PMMA) and polystyrene (PS) hasbeen studied. As-prepared MWCNT from CVDtechnique were ultrasonically dispersed intoluene and subsequently dispersed in PMMAand PS. Thin polymer composite films werefabricated by solvent casting. The effect of

Fig.3.6: T-300 Carbon fiber based composites tubesafter carbonization

further processed at NPL using number ofimpregnationlcarbonizationlgraphitisationcycles using coal tar pitch as matrix to achievethe desired bulk density of 1.65 to 1.70 glee.Fig. 3.6 shows the photograph of tubes aftercarbonization stage.

ea 'bon Nanotubes: utbesis anda tication in Polymer-Com osi-es

MWNT produced by CVD technique weredispersed in phenolic resin matrix to produce

isotropic composites of 50x5x3 mm3 size.Flexural strength ofthi s type ofcomposites werereached upto 160 MPa which is approximately2.5 times higher than as such phenolic resin evenwith small volume i.e 2% of CNT loadings. Byemploying a suitable dispersion technique it was

180 MWCNT (Vol. %)

160 • a140

•...&1205..j 100

to! BO

j 60IL

40

20

•

'. Sample 1Sample 2

Sample 3

-Mean

I 20+ + + .050"';'+

15 050"'1.

I fir• • • • . • .1.3%•10 x • ,. .. .. • ~

.. x.l%

~! • • • • I I II :s5%":;; 5 .. 5%

I • • • + 10°/",0

i a 10 11 12III

Fr-equ ency (GHz)

10 20

Dispersion Time

30 40

bFig. 3.7: Effect of dispersion conditions on the

flexural properties of the CNTlPhenoliccomposites with 2 vol% CNTs dispersedin the resin

Fig. 3.8 : (a) Electrical Conductivity and (b) EMIShielding Effectiveness of MWCNT ­PMMA composites with different CNTcontent

~NU R PORT.2006.2007 •

. er"alMWCNT content on the mechanical andelectrical properties ofthe nanocomposites wasinvestigated. Results showed an improvement inelectrical conductivity from insulating toconducting with increasing MWCNT content.MWCNT network showed a classicalpercolating network behaviour with a lowpercolation threshold. These composites showspercolation threshold at 0.5 vol% (Fig. 3.8 a)and EMI shielding effectiveness of 20 dB(Fig. 3.8 b)

Development ofcnrbo-graphite sponsored byDM8RDE, Kanpur

Green coke was prepared, characterizedand mixed (dry and wet) with 0,10,20 of finelyground and purified natural graphite (NG). Themixtures were molded into blocks usingisostatic press which were characterized andcarbonised to 1000, 1400 and 2500 °C. The bulkdensity of the carbonised blocks (dry mixed)increased from 1.7 to 1.75 gcm-3 with NGaddition at 1000 "C where it remained constantarOlmd 1.82 gcm-3 at 1400"Cand 1.87-1.91 gcm-3

at 2500 °C. The compressive strength andelectrical resistivity of the dry mixed block atHTT of 1400 °C changed from 1030 to 1385 kg

cm-2 and 3.0 mncm to 2.3 mOcm respectively,

with increase in NG content to 20%. The bulkdensity and compressive strength were found tobe better for wet-mixed GC-NG material thanthose of dry-mixed materiaL Two importedsamples ofcarbographite supplied by DMSRDEwere characterized in detail and it was found thatthe sample no. 2 possessed better propertiesincluding oxidation resistance compared to thesample no. 1. The interim progress report of theproject was prepared and submitted toDMSRDE Kanpur. A patent for theimprovement in the properties of the specialgraphite by suitable modification has beenapplied for.

r. t e·can 'uf

FerroelectricLiquid Crystal

Of all the interesting materials emergingfrom the field of nanotechnology, materialscontinue to attract immense research interest.The size dependent properties of metal nanoparticles are unique as they have both bulk andmolecular metal characteristic, hybrid organicand inorganic materials have emerged as a classof electronic and optical materials with anumber of potential applications. Nanocomposites consisting of inorganic nanoparticles and functional polymers have shownpromises of various applications such as lightemitting diodes and photovoltaic devices. Overa number ofyears, liquid crystals have been thesubject of intense research because of itsapplications in flat panel displays, spatial lightmodulators, optical antennas etc.

Ferroelectric liquid crystals are wellknown for their good optical contrast, lowthreshold voltage, memory effect etc. But acloser look shows that all these characteristicproperties have a scope for further improvementas they are limited by one or other factors. Oneof the methods discovered in NPL recentlyinvolves doping of ferroelectric liquid crystals(FLCs) with gold nanoparticles, which bringsout a phase of FLCs with enhances opticalcontrast and yields a much lower thresholdvoltage with memory effect independent of thethickness of the sample celL The dopingprocedure is shown to enhance the FLC materilsoriginal properties and reveals the significantinterction ofnanoparticles with FLC materials.

The gold nano particles doped FLCmaterial has been investigated for its opticalproperties. Five-fold increase in optical tilt isobtained in the doped FLC case at an appliedbias ofmere 0.1 V. Adding goldnanoparticles in

fjAN UAl REPO 1-2006--2007

ENGINEERING MATERIALS

CHrS.oOOVlD!V DC CH2' 050wOlV DC TSA'lOOOms TR·CH2·AC PT'O

CHr5.oOQVlOIv DC CH2··O~VlOlv DC iBA'IO·OOm:aTR"CH2·AC PT'O

FLC brings memory in the celllU1like the case ofpure ferroelectric liquid crystal (as shown inFig. 3.9).

The electrochemical polymerization ofaniline with EDOT was carried out on Ptelectrode in protonic acid solution bypotentiostatic technique at a potential of0.8 Vorcyclic voltammetry technique by cycling the

Fig. 3.10: Fonnation of conducting polymerscomplex

PEDOT-ferrite and copolymer of(EDOT+Aniline) ferrites were synthesizedsothat the resultant polymer composite possessboth the electrical and magnetic properties.Thermo-magnetic measurements were carriedout to determine the curie temperature of thenano ferrite particles encapsulated inconducting polymer matrix. Proposedcoordination of ethylenedioxy thiophenemoieties with ferrites resulting in the formationof conducting polymer complex is as shownbelowinFig.3.10.

I\r\~o 0 0 0 ~

·Con acting Polymers

Copolymers of aniline with substitutedaniline were synthesized by taking copolymersin specific ratio sothat the copolymerizationretains the conductivity of the parent polymer.The thermal stability of the copolymer dopedwith specific dopant was found to be 280-290"Cwhich was well suited for an industrialrequirement for which Reliance Industriesshowed interest. TG-Mass studies of theconducting Polyaniline and its analogue wascarried out at 300°C and the results indicated theabsence ofbenzidine.

-rl11 1----

c--r~'Ir=-.- - li....--.-. L_

III

-- , - II

lI,

rn I I [ 1I

I I

rb= nr . ...--:=-, - I..L-!

-11

- --

- .-

-

Chll

~h'

The enhanced intrinsic field created in thesample because ofnano gold particles attributedto the high tilt and strong memory effect. Theinteraction of the collective electron wave fromthe photon of incident light traversing throughFLC molecules probably bring out the observedextraordinary results. These enhanced electro­optical properties could thus pave way for nano­composite FLCs to be utilized in devices fromwith reduced threshold voltage and much betteroptical contrast. The detail dynamic studies ofthe effect of nano-gold particles in FLC mediaare being carried out.

Chll

~hl

Fig. 3.9: Optical response of (a) pure Felix 17/100and (b)AuNPdopedFelix 17/100,in3 f.lillcell at20V and 25 Hz. CHI: [5.000 VIDIV]shows driving square voltage andCH2:[0.050 VIDIV] shows its opticalresponse, outside mark on Y-axis (voltageaxis) shows zero voltage level forrespective channels. TBA shows the timescale per division (10.00 ms) on X-axis,which is same for both channels.

~NU R PORT.2006.2007 •

CV

0.15OxlO·0

0.20OxlO·0

I-V-L Characteristics of Device

All the depositions were carried out be thermalevaporation of the materials in vacuum at about4x10-6 Torr. After preparation the device wastransferred to glove box that resulted exposureofthe sample to the ambient. In the glove box thesample was sealed with glass cap using UVepoxy. A maximlilll efficiency of28.9 cd/A was

achieved at 2.45 mAlcm2• Device had a

continuous running life-time of400 h at 28°C.

The I-V-L characteristics of the device areshown in Fig. 3.12.

0.250 0.500 0.750 1.000

EIV

-O.lOOxlO·O+-~~~~~-,_____~___,__~___1-0.250

0.05OxlO·0

-0.05 Ox 10'0

0.25OxlO"°-,------------------,

potential between 0.2 V to 0.8 V vs SCE at a scanrate of 20 mY/sec. The growth behaviour ofcopolymer is shown in Fig. 3.11.

Fig. 3.11 : Growth behaviour of aniline and EOOTin OBSA medium on cycling thepotential between 0.2 V to 0.8 V onplatinum electrode at a scan rate of 20mY/sec

Organic Light EnuttingDiodes

During the period 2006-2007, R&D wascarried out towards the development of SmallMolecular Organic LEDs. Device life timetesting was main focus of our work.Phosphorescent materials like Ir(PPY)3 has been

studied as a electro luminescent material. Thedevices parameters have been optimized. Thedevices were fabricated on the pre-patterned andpre-cleaned indium tin oxide (ITO) coated glasssubstrates via thermal evaporation of thematerials. The cleaned ITO substrates weretreated to oxygen plasma lmder reducedpressure for 5 min. A thin film (50 nm) of-NPD,0.4 % doped with F4-TCNQ, which works as

hole transport layer was deposited on ITO. ThenIr(PPY)3:CBP (30 nm) was deposited over F4­

TCNQ:-NPD. Subsequently 7 nm of BCP and20 nm ofAlq3 were deposited on Ir(ppY)3:CBP.

Here BCP and Alq3 work as hole blocking and

electron transporting materials. Finally LiF(1nm)!AI(200 nm) cathode was deposited onAI~.

25000 6.00E+01

It""'E 20000

5.00E+01;;

C!:!. 4.00E+01III 15000 gu ..c - 3.00E+01III Cu 10000 ~..III 2.00E+01 ::::IIc (J

E 5000 1.00E+01::::II...0 O.OOE+OO

0 5 10 15

Voltage (volts)

Fig. 3.12: I-V-L characteristics of the OLEO device

CllOlestrol bioseonso.r

Cholesterol biosensor based on N-(2­aminoethyl)-3-aminopropyl-trimethoxysilaneself-assembled monolayer.

Cholesterol oxidase (ChOx) has beencovalently immobilized onto two-dimensionalself-assembled monolayer (SAM) of N-(2­aminoethyl)-3-aminopropyl-trimethoxysilane(AEAPTS) deposited on the indiumtin oxide(ITO) coated glass plates using N-ethyl-NO-(3­dimethylaminopropyl) carbodiimide and N­hydroxysuccinimide (EDC/NHS) chemistry.These ChOX/AEAPTS/ITO bioelectrodes arecharacterized using contact angle (CA)measurements, UVvisible spectroscopy, atomic

• uij)PORT·2006.2007

ENGINEERING MATERIALS

force microscopy (AFM), electrochemicalimpedance technique, and Fourier transforminfrared (FTIR) technique. The covalentlyimmobilized ChOx-modified AEAPTSbioelectrodes are used for the estimation ofcholesterol in solution using UVvisibletechnique. These cholesterol sensingbioelectrodes show linearity as 50 to 500 mg/dlfor cholesterol solution (Fig. 3.13), detectionlimit as 25 mg/dl, sensitivity as 4.499 x 10 -5 Abs

(mgdlr\ Km value as 58.137 mg/dl (1.5 mM),apparent enzyme activity as 1.81 x 10-3 U cm-z

,

shelf life of approximately 10 weeks, andelectrode reusability as 10 times.

0.040

O.03S

~ 0.0'30

~~ 0.02S

'"~~ o,o:!O.;:

0.0\5

0.0\0+-~.---~.---~--.--~--.--~--.--~

o 100 200 300 4Q0 500

Chol<>slerol ConcerrtraUon (mgldl)

time as 180 s, linearity up to 780 mg/dl (12mM), shelflife of 1 month, detection limit of 12mg dt and sensitivity as 5.4x 10-5Abs. ImgdL

D Abio ensor

Polypyrrole-Polyvinyl sulfonate basedDNAbiosensor

Double-stranded calf thymus (dsCT)DNAwas electrochemically entrapped intopolypyrrole-polyvinyl sulfonate (PPy-PVS)films deposited onto indium tin oxide (ITO)coated glass plates. These dsCTDNA entrappedPPy-PVS/ITO films were characterized usingcyclic voltammetry, UV-visible, Fouriertransform infrared (FTIR), scanning tunnelingmicroscopy (STM), and electrochemicalimpedance measurements. Attempts weremade to use these dsCTDNA entrapped PPy­PVS/ITO films for detection of 2-aminoanthracene (0.001 6 ppm) and 3-chloro phenol(0.055 ppm) (Fig. 3.14) revealed a responsetime of30 s and a shelflife ofapproximately 25weeks when stored under desiccated conditionsat 25°C. The addition ofsalts such as Caz+(250

Fig. 3.14 : Typical CVs obtained for dsCTDNAentrapped PPy-PVS fihns showing adecrease in the peak height of guanineoxidation for increasing concentrationof 3-CP at a scan rate of 20 mV/s inphosphate buffer (0.05 M, pH 7.0). Theinset shows a linear plot of percentagepeak area reduction as a function ofconcentrationof3-CP (0.055 ppm)

Fig. 3.13 : UVvisible absorbance curve as a functionofcholesterol concentration.

Sol-gel based ehol sterol bios nsor

Cholesterol oxidase (ChOx) andcholesterol esterase (ChEt) have beencovalently immobilized ontotetraethylorthosilicate (TEOS) solgel films. Thetetraethylorthosilicate sol-gel/ChEt/ChOxenzyme films thus prepared have beencharacterized using scanning electronmicroscopic (SEM), UVvis spectroscopic,Fourier-transform- infrared (F TI R)spectroscopic and amperometric techniques,respectively. The results of photometricmeasurements carried out ontetraethylorthosilicate sol-gel/ChEt/ChOxreveal thermal stability up to 55

0

C, response

3 i::.. )"

E 2§v

o

-SOO 500 tooovl>h.~< (rn V)

1S00 2000

fjAN UAl REPORT.2006-2007 •

~AN UAl REPO 1-2006--2007

Organic Inorganic Hybrid Nanocompositesfor Seu ingApplication

120EtOoa

100Et008

8 800EtOO7

~

'" 6 OOEtOO7.~

'" 4 OOEtOQ7

200EtOO7

oOOEtOOO

500 1000 1500 2000

'Time (second)

Fig. 3.15 NOx gas sensing characteristics ofpreparedAFC-W03 thin films

formaldehyde condensate (AFC)-W03 was

synthesized by in situ chemical polymerizationin acidic medium and its thin film has beenfabricated successfully using vacuumdeposition technique on Platinum inter digitatedelectrodes deposited on glass substrate. X-raydiffraction ofas grown film shows the reflectionofW03 and H20. W03 along with broad peak of

AFC. The surface morphology ofnanocomposite films investigated usingscanning electron microscopy reveals theuniform distribution nanosizedW03 embeded in

polymer matrix. The NOx gas sensingcharacteristics of prepared AFC-W03 thin films

were studies by measuring the change inresistance with time (as shown in Fig. 3.15).The sensor was operated at room temperatureshowing a response time of 15 second andrecovery time of5minute.

Hybrid cros-s-linked pol~raniUne WO~

nanocomposite thin mm using thermalvacuum deposition technique lor 0 gassensin.g

The nanocomposite thin film of cross­linked polyaniline (derived from polyanilineand aniline formaldehyde condensate (AFC)i.e., CLPANI) and W03 has been fabricated

using vacuum thermal evaporation technique.

condensate-tungtonhin film for the

Aniline Formaldeh3"deoxide nanocompositedetection ofNOx gases.

The nanocomposite of aniline

ppm), Mg2+(200 ppm), CI-1560 ppm), andNa+(150 ppm) ions contained in water does notaffect the observed amperometric response ofthe disposable dsCT-DNA entrapped PPy PVSfilm-based electrochemical biosensor.

The following nanocomposite thin films ofconducting polymer and metal oxidenanoparticlea have been fabricated successfullyusing vacuum evaporation technique. The asgrown thin was found to sensitive for the gassensing application

Fabrication and Characterization ofPolyanilille ZnO Hybridnll()Composit~

hinFilms

Polyailine (PANI) - ZnO nanocompositethin film have been successfully fabricated onglass substrates by using vacuum depositiontechnique. The as-grown PANI-ZnOnanocomposite thin films have beencharacterized using analytical techniques. X-raydiffiaction ofas-grown film shows the reflectionofZnO nanoparticles along with a broad peak ofPANI. The surface morphology ofnanocomposite films has been investigatedusing scanning electron microscopy and atomicforce microscopy. The hypsochromic shift inIN absorption band corresponding to 1I-1I*

transition in polymeric chainofPANI and a bandat 504 cm-]due ZnO nanoparticle has beenobserved in the FTIR spectra. The hydrogenbonding between the imine group of PANI andZnO nanoparticle has been confirmed from thepresence ofthe absorbance band at 1151 cm-! inthe FTIR spectra of the nanocomposite thinfilms.

..

ENGINEERING MATERIALS

fjAN UAl REPORT.2006-2007

X-ray diffraction pattern ofas grown film showsthe broad reflection of polymer along with themixed reflection of nonhydrated and hydratedW03 particles. The uniform dispersion ofW03

nanoparticles in CLPANI network has beeninvestigated using scanning electronmicroscopy. The broadness in the absorptionband at 320 nm corresponds to PANI andAFC­W03 nanocomposite confirming the cross­linking between the polymer units. The NOxgas sensing characteristics ofvacuum depositedCLPANI -W03 thin films have been studied

(Fig. 3.16) by measuring the change inresistance with respect to time. The sensor wasoperated at room temperature, which couldextend the shelf life of the sensor. The responsetime of 15 second and recovery time of5 minutehave been achieved.

500 1000 1500 2000

Time (second)

Fig. 3.16 : Resistance vs Time for CLPANI-W03 onthe exposure ofNOx

Ie Ps based Bio po lymer-metal oxidenanocomposites for sensor probes

The current prospective of materialresearch has been devoted to reformation oftechnologies in cheaper and eco-friendlymanners. The electrically conducting polymers(ICPs) based nanocomposite materials arewidely used in the solar cells, sensors, electronicshielding, environmental sensitive membranes,etc. as a principal component. Currently, I amengaged in the synthesis of electrically

conducting-redox biopolymer-metal oxidenanocomposite for the chemical, gas andbiosensor applications. Bio-based polymershave unique physiochemical properties andmake attractive an excellent electroactive redoxenvironmental friendly biocompatible materialthrough wet chemical routes. Thesenanocomposites have mesopores that iscontrolled by thermal curing or by in situprocess. The development of mesopores on thematerials provides significant extension bycreating large surface areas for the interaction ofanalytes. It is observed that such materials haveadvocate electrical and ion conducting featuresthat provide unique physical signals for thedetection of analytes. Hence, nanocompositesof biopolymer ICPs could be used assemiconductor, superionic conductor, ionsensitive semiconductor field-effect transistor(ISFET) probes for the fabrication of electronicsensor devices.

Organic Pho 0 oHair D 'it

To develop improved materials for organicsolar cells fundamental investigations werecarried out in a potential conj ugated polymerviz. poly (3-hexylthiophene) (P3HT) that findsapplications as electron donor in donor-acceptorinterpenetrating bulk heterojunctions, the mostefficient combination used globally in thedevelopment of organic solar cells. In fact, aninnovative work was carried out in P3HT byway of studying the effect of interface layer,curing temperature and polarization on itscharge transport behaviour in the configurationITO/PEDOT:PSS/P3HT/Au diode structure.Some unique features were observed in theseinvestigations. After spin depositing P3HT filmswere cured at different temperatures viz 80, 100,120 and 140°C, respectively. It was found thatthe best possible J-V behaviour in P3HT wasobtained at ~120°C. Further, it was found that

•

Fig. 3.17 : (a) J-V curves for unpolarized case and(b) for polarized case

incorporation of PEDOT:PSS interface layerenhances the hole injection into P3HT andswitches the conduction from ohmic to spacecharge limited conduction. Subsequently the J­V behavior of P3HT was studied at differenttemperatures in the range 110-295 K with no­polarization (Fig. 3.17 a) and under polarization(Fig. 3.17 b) of the films prior to conductivitymeasurements. Symbols represent theexperimental data and solid lines represent thetheoretical plots at different temperatures. Thevalues of calculated transport parameters are

Hb=5.9xl0 17 cm-\ Nv=2xl0 17 cm-\ Tc=450 K

and E. ~39 meV for unpolarized case whereas

the values of the same parameters for the17 -3 2 1017polarized case are Hb=5.3xl0 em ,Nv= x

cm-\ Tc=270 K and E.~ 23 meV Inset in

0,5 .-----------7Z7----,

Fig.3.17b shows the observed J- Vcharacteristics of the polarized and unpolarizedsamples at 110 K.

From these parameters it is seen that thepolarization effect in P3HT results in i) decreasein T from 450 K to 270 K, ii) decrease in Hb fromc

5.9xlO17 to 5.3 xl017, iii) making traps shallower

i.e. that the characteristic depth reduces from 39meV (unpolarized case) to 23 meV (polarizedcase). All these effects of hole transport wereattributed to trap model having traps distributedexponentially in space. In essence, this work isan important fundamental contribution on thecharge transport aspect ofP3HT that may resultin the development improved devices,especially organic solar cells.

A lomal' U 'oup

Developed the several computer controlledsystems like:

Fully Computer controlled CoaxialMicrocalorimeter set-up (a primary standardsetup) for the measurement of power in thefrequency range 10 MHz to 20 GHz all theinstruments, required for measurement andcontrol, have been successfully interfaced withthe computer using Visual BASIC-5.0 language.

Electronic circuitry for 89C51microcontrolLer based water pollutionmonitoring system for taking data fromdeveloped 8 different BOD sensors usingembedded technology along with the interfacecircuit with Keithley Instruments Inc 61;2 digitmultimeter Model 2700. This 61;2 digitmultimeter when interfaced with computergives resolution of O.OlnA. The program for89C51 is written in 89C51 assembly languageand the program for online data acquisition andgraph plotting on the screen is written in VisualBSAIC-5.0 language. This system has beendeveloped in collaboration with Institute of

(a)

(b)

•U R PORT.2006 2007

50

50

295 K195 K

- 135 K, 110K

G 285 K

0245 K

n 210 K

0175 K

.I:lOK

v 110 K

10Vollage (V)

10Voltage (V)

"10-4 -1--.L-.L,-----'---'-"TTTT"'rr---::""="Q,.',-,S)---r---.--I

..

ENGINEERING MATERIALS

Fig. 3.18 shows the SEM pictures ofHDT,HDT & PEG and fibronectin deposited regionsofHDT. It is clearly seen from the above figurethat fibronectin is selectively deposited on HDTcoated regions while there is very little

Design, n ". lopment and Fabri.cntion ofArraJo' Sensor Chip For BiologicalApplications

Micropatterning of biological molecules(proteins.. immu.noglobu.lin~ peptides) ontovarious surfaces using soft Iithographitechniques

Patterning of biomolecules with micronand submicron resolution on to different solidsurfaces is central to the development ofadvanced biosensors, fundamental studies ofcell biology and tissue engineering. All roundefforts are being made to develop simpletechniques for patterning of biomolecules withhigh resolution. Soft lithography techniques(microcontact printing ofself-assembly formingthiols and silanes and microfluidic networks anddevices) have witnessed a tremendous growth inrecent years for forming two dimensionalpatterns of functional biomolecules suitable forbinding primary and secondary antibodies tofabricate advancedbiosensor chips.

A simple techniques based on microcontactprinting of hexadecane thiol (HDT) andpolyethylene glycoL-thiol (PEG-thiol) has beenused to create pattern structure on gold-coatedsubstrate exhibiting high hydrophobicity andhigh hydrophillicity, respectively. Thehydrophobic regions strongly support theadsorption of proteins while the hydrophilicregions strongly resist the adsorption ofproteins.

Genomics and Integrative Biology (IGIB),(CSIR) Mall Road, University of Delhi andCentral Pollution Control Board (CPCB),Karkar Dooma Court, Delhi. Rigoroustesting ofthe same is going on in CPCB, Delhi.

Brought the liquid helium plant in order bystudying it's electronic and electrical circuitryfrom the manual and sequentially checkingthem, correcting the faults after locating themand if found necessary replacing the oldelectronic circuit with new developed modifiedones. The helium plant is functioningsatisfactorily.

Developed an electronic circuit around89C51 for controlling the very old existingMLW-MK-70 bath. For the measurement oftemperature of the bath one industrial pLatinumresistance thermometer (Pt-100) has beenemployed and the data acquisition fromthermometer has been done using 4'i2 digitADC.

This way a resolution of0.01 °C is obtained. Thecontrolling of the power has been done bycontrolling the firing angle by a developed firingangle control circuitry and a triac. Theinstructions for controlling the firing angle aregiven by the 89C51. In the bath a specialprovision for creating the varying environmenthas also been incorporated. The complete circuithas beentested and is functioning satisfactorily.

The program for controlling the electroniccircuit, which will be controlling the MLW-MK­70 bath, has been developed in 89C51 assemblylanguage and is working satisfactorily.

Developed an analog electronic circuitryfor PID controller to compare it with the digitalPID controller (i.e. to compare hardware controlcircuit with the software controlled system).

Helped several scientists in bringing theirsystems in operation.

i id cr' aldevice'

a cl"a cad

fjAN UAl REPORT.2006-2007 •

deposition of the protein on the PEG-coatedregions. This will form the template for thedeposition ofprimary and secondary antibodies.

Deposition of fibronectin on HDT

Fig. 3.18 : SEM of HOT, HOT & PEG andfibronectin deposited on HOT

Fig. 3.19: Fluorescence micrographs of selectivelydeposited BSA_FITC conjugatedmolecules on HOT coated regions.

HOT & PEG thiol(SOX)SEM of: HDT (SOX),

The pattern hydrophobic and hydrophilicregions have been further utilized to selectivelydeposit bovine serum albumin (BSA) taggedwith FITC dyes. The following Fig.3.19 showsthe selective deposition of BSA-FITCconjugated molecules as seen under afluorescence microscope. These experimentswould form the basis to fabricate fluorescencebased array biosensors for various biologicalapplications.

Micropatterning of Alignment La en ToProduce PatternLiquid CrystalDisplays

A new technique has been developed toproduce patterned liquid crystal displaysshowing homeotropic and planar orientationwith a few micron resolution in the sameazimuthal plane. The technique is primarily

based on microcontact printing of alignmentlayer ofOTS to produce homeotropic alignmentto the specified region of the substrate andformation of planar orienting layer by self­assembly technique in the remaining region ofthe substrate. Fig. 3.20 shows the homeotropicalignment in the selected regions shown by darklines and the remaining region shows nopreferred alignment ofliquid crystals. It is quiteclearly seen from this figure that there is novariation in the intensity ofdark lines on rotatingbetween crossed polarizers.

Fig. 3.21 shows the homeotropic andplanar orientation in the selected regions. Thehomeotropic alignment (dark strips) showed novariation in the intensity on rotating betweencross polarizers while the planar regions showed

• NU •£PO 1-2006--2007

ENGINEERING MATERIALS

Fig. 3.20 : Photographs showing Homeotropic alignment (B) of a liquid crystal cell rotated clockwise betweencross polarizers from 00 to 1350 at an interval of45 o. Uncoated area shows nopreferred alignment (C).

self-deaning coatings onand design6f coating

creating new storage liquid crystal displays. Thetechnique may also be used to produce patternedLiquid crystal displays. Both the alignments havebeen found to be stable with time andtemperature.

An equipment have been designed for

obtaining thin films of metal oxides by sol-geldip coating technique. The equipment described

here is cheap as compared to the conventional

coating equipment. Further its operation is

simple, as adjustment ofcoating parameters can

be done by simple knob operation. This

equipment gives thin film coating on both sides

of the substrate simultaneously. Uniform film

thickness can be obtained on large area

substrates up to 1 m x 1 m with the equipmentreported here.

The coating solution is partially hydrolyzed

metal alkoxide solution with catalyst. The

composition ofdifferent constituents is adjusted

in such a manner that the solution can be reused

for coating up to six months if stored under

sealed conditions. The solid films obtained from

Development ofgins substrateequipment.

Sun-Shielding & SelfCleaning Coating on

Window Glass•

!~ :. .

dark and bright regions at intervals of45° due tobirefringence ofliquidcrystalline materiaL

Fig. 3.21: Photographs showing Planer alignment(A) as well as Homeotropic alignment(B) of a liquid clystal cell rotatedclockwise between cross polarizers fromOOto 1350at an interval of45°.

The planar alignment of Liquid crystalstakes place only on the area having bilayer ofAPTES & cinnamoyl moieties. Area patternedwith OTS showed homeotropic alignment ofliquid crystals. Alignment direction is governedby the polarization direction ofthe UV-light andcan be varied locally. These two independenttechniques have been combined to producesamples showing both homeotropic as well asplaner alignment of liquid crystals in a singlecelL This has given rise to the possibility of

+

~ANNUAl REPORT.2006-2007

this solution are scratch proof and are stable

lmder various environmental conditions.

Simple glass window panes coated withfilms using the said technique blocks up to 30%if IR radiations and allows up to 80% of thevisible part of the spectrum. These films absorbUV radiations to excite electrons from thevalence band to the conduction band. Valenceband electrons converts helps in dissociating the

organic matter which make the window pane

dirty while valence band holes helps adsorb OH

groups on the surface thereby making the

surface superhydrophillic. Both these properties

are very important from architectural point of

view. Such glass used as window pane reduces

the heating and cooLing cost ofthe building also

their cleaning require little labour and less

detergents which saves onthe cleaning costs.

• fjAN UAl REPO 1-2006--2007