Research Article Preparation of Nanostructured Microporous

Research ArticlePreparation of Nanostructured Microporous Metal Foamsthrough Flow Induced Electroless Deposition

Galip Akay123 and Burak Calkan14

1School of Chemical Engineering and Advanced Materials Newcastle University Newcastle upon Tyne NE1 7RU UK2Canik Basarı University Canik 55080 Samsun Turkey3GAP Technologies 1 Grosvenor Place 8th Floor London SW1X 7HU UK4Optimum Domodedovskiy Rayon Starosyanova Village Sadovaya Street No 4 Moscow 142030 Russia

Correspondence should be addressed to Galip Akay galipakay1gmailcom

Received 15 May 2015 Revised 20 June 2015 Accepted 12 July 2015

Academic Editor Ovidiu Ersen

Copyright copy 2015 G Akay and B Calkan This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

Monolithic nanostructured metallic porous structures with a hierarchy of pore size ranging from ca 10 120583m to 1 nm are processedfor use as microreactors The technique is based on flow induced electroless deposition of metals on a porous template known asPolyHIPE Polymer The process is conducted in a purpose built flow reactor using a processing protocol to allow uniform andefficient metal deposition under flow Nickel chloride and sodium hypophosphite were used as the metal and reducing agentrespectively Electroless deposition occurs in the form of grains with a composition of Ni

119909P119910in which the grain size range was ca

20ndash02 120583m depending on the composition of the metal deposition solution Structure formation in the monoliths starts with heattreatment above 600∘C resulting in the formation of a 3-dimensional network of capillary-like porous structures which form thewalls of large arterial pores These monoliths have a dense but porous surface providing mechanical strength for the monolith Theporous capillary-like arterial pore walls provide a large surface area for any catalytic activity The mechanisms of metal depositionandnanostructure formation are evaluated using scanning electronmicroscopy energy dispersiveX-ray analysis XRD BET-surfacearea and mercury intrusion porosimetry

1 Introduction

11 Structured Catalysts Although catalysis accelerates reac-tion rates and chemical conversions accessibility of the reac-tants to and removal of products from the catalytic sites areimportant to realize the full potential of catalysts Supportedcatalyst systems are intended for these provisions Catalystsare either deposited as a thin film on the walls of reactorsor deposited on high surface area porous support particlesand subsequently palletized for use in particulate form inpackedfluidized bed reactors or stirred tanks These twotechniques have certain drawbacks in coated systems cata-lyst adhesion can be nonuniform and weak while the accessi-bility of the active sites within the interior of the catalyst pal-lets is hindered due to low porosity small pore size and con-nectivityTherefore when the reactions are transport-limitedeven such systems cannot provide adequate accessibility of

the catalytic sites since the high surface area supportmaterialsthemselves restrict transport processes

In recent years the so-called ldquostructured catalystsrdquobecame available in order to address these problems Thecatalyst supports are often in the form of macroporous foamsormonolithswhich actually form the reactor acting as a staticmixer at the same time In order to increase the surface areaof themonolithic catalyst supports without excessive pressuredrop macrochannel systems are utilized in industry such asthose in catalytic converters In these systems not only thelocal hydrodynamic conditions but also the catalyst coatingthickness can be controlled to obtain well-defined catalyticreactors and they invariably outperform reactors with catalystparticles in packed bed or stirred tank configuration [1ndash3]Monolithic reactors combine the advantages of fixed bed(ease of handling) and turbulent stirred tank reactors (intense

Hindawi Publishing CorporationJournal of NanomaterialsVolume 2015 Article ID 275705 17 pageshttpdxdoiorg1011552015275705

2 Journal of Nanomaterials

contacting) while providing a narrow residence time distri-bution avoiding mal-distribution and scale-up problems

12 Monolithic Reactors with Hierarchic Pore Structure Mon-olithic catalyst systems with nonporouslow porosity wallsalso suffer from certain disadvantages such as cost lowcatalyst loading integrity of the catalyst coating on themono-lith channel walls and the presence of two independentlycontrolled length scales which only provide partial accessi-bility of the catalytic sites The accessibility of the nanosizedcatalytic sites is achieved most effectively by a hierarchicalchannel or pore network structures which are ubiquitous innature [4ndash6] In these systems the main chemical processesare principally controlled at the molecularnanoscale asmany of these processes are transport-limited while thecontinuous supplyremoval of reactantsproducts is achievedthrough capillariespores of ever increasing diameter Sucha system provides an optimum architecture incorporatingmicro-nanoscale with chemically functional features withinthe macrosystem at an optimum surface area for catalyticapplications Such hierarchically structured catalyst systemswith fractal-like meso- to macropore size distribution can beexpected to be more efficient and robust due to the enhancedsurface area and accessibility leading to the intensification ofchemical processes [6]

13 Production of Porous Metallic Structures There are sev-eral important applications of metallic foams as both struc-turalengineering and specialized materials Excellent peri-odical reviews are available describing themanufacture char-acterization properties and application of thesematerials [7ndash9] One particularmetallic foam is produced through electro-chemical metal deposition on polyurethane foam followed byheat treatmentwhen the template polymer is burnt off [10 11]These materials are commonly used for catalyst support toobtain supported catalyst systems as well as electrode infuel cells These materials are marketed as Metapore CelnetRetimet and Recemet Their macrostructure is very similarto some of the materials produced by the current techniqueexcept that these materials do not have a hierarchy of poreswhile their surface area density (surface area per unit volume)is some 100-fold smaller and pore size is some 50 timessmaller than those produced in this work

14 PolyHIPE Polymers as Monolithic Microreactors and asTemplates for Electroless Metal Deposition In the design ofnovel monoliths with hierarchical porous catalytic reactorshaving a pore size range of ca 100 120583mto a fewnanometers thefirst step is to obtain structures with controlled pore size andporosity and functionalize them to impart both nanostruc-ture and catalytic activities One such highly versatile mono-lithic (or indeed particulate) system is known as PolyHIPEPolymer (PHP) which was developed at Unilever ResearchLaboratory at Port Sunlight (UK) during the 1980s by a teamincluding one of the present authors (Galip Akay) who alsodeveloped the processing of the basic material and advancedits use in both small and large scale applications [12 13] Asummary of PolyHIPE Polymer chemistry can be found in[14]

PolyHIPE Polymers are prepared through a high internalphase emulsion (HIPE) polymerization route and hence theacronymic name PolyHIPE which reflects the processinghistory Depending on the composition of the HIPE process-ing and polymerization history PHPs can have hierarchicalpore and interconnects over a size range ca 100 120583m tonanometre while the pore volume can reach as high as 97for practical applications Chemicalbiochemical functionali-zation processes of PHPs are relatively easy [15] and coupledwith their easy manufacture in monolithic form with well-defined macro- meso- and nanostructures providing a hier-archy of pores they are ideally suited for process intensifica-tion [6] in agricultural biological and chemical processesin both small scale or large scale applications Further accel-eration efficiency and selectivity in processing are obtainedwhen PHPs are used as monoliths

PolyHIPE Polymers can be chemically and biologicallyfunctionalized [16ndash20] in order to achieve mimicking ofnaturersquos processing strategy and applied to tissue engineeringbioprocess intensification and agroprocess intensificationFurthermore nonbiological functionalization processes wereused for specific applications such as separation processes[21] fast response ion-exchange resins [22] and environmen-tal and energy conversion processes [23]

Monolithic chemical or biochemical reactors have severaladvantages over packed bedfluidised bed or stirred tankreactors even when hierarchic catalysts are used in particu-late form In monolithic flow-through reactors there is nochanneling and the distribution of flow across the cross-section of the monolithic reactor is more uniform and thecatalytic sites are only micrometers away from the reactantsFurthermore in some reactions when the rate is limited byproduct concentration flow through the monolith allowsthe removal of the product from the catalytic sites into thebulkconvective flow These characteristics result in processintensification and direct comparison of packed bed andmonolithic reactor performance is available when PolyHIPEPolymer was used in particulate form (packed bed) [17] andin monolithic form [18]

As reviewed above PolyHIPE Polymer monoliths havebeen used successfully for intensifying processes in agricul-ture biology chemicalphysical-chemical and energy con-version processes due to their unique hierarchic pore struc-ture in which large arterial pores with large interconnectingholes (windows) facilitate convective mass transfer whilewalls of the arterial pores provide the catalytic sites whichare connected to the arterial pores via mesoscale (typically100 nm) pores [15] However to the best of our knowledgethere is nometallic equivalent form of suchmonolithic struc-tures Therefore the manufacture of such metallic mono-liths will increase the temperature and pressure range ofchemicalphysical-chemical processes and catalyst reactantand product ranges of these reactors

15 Electroless Deposition There are different mechanisms inthe literature suggested for the chemical reduction of nickelsalts by hypophosphites Probably the most widely acceptedmechanism is the one suggested by Brenner and Riddell [24]as also reported in [25 26]They stated that atomic hydrogen

Journal of Nanomaterials 3

is the real nickel reductant With sufficient energy and acatalytic surface hypophosphite ions react with water andthey are oxidized to orthophosphiteThe hydrogen generatedby this reaction is absorbed onto the catalytic surface

(H2PO2)minus

+H2O 997888rarr H2PO3minus

+ 2Habs (1)

Nickel ions at the catalytic surface are reduced by the absorbedactive hydrogen

Ni+2 + 2Habs 997888rarr (Ni+2+ 2H+ + 2e) 997888rarr Ni0 + 2H+ (2)

The liberation of hydrogen gas in the catalytic nickel reduc-tion is the result of recombination of the hydrogen atoms

2Habs 997888rarr (H+H) 997888rarr H2 (3)

The mechanism of atomic hydrogen being the real nickelreductant has found support frommany researchers But stillit has failed to explain certain issues like the simultaneousreduction of nickel and hydrogen Also there is no clarifi-cation of why stoichiometric consumption of hypophosphitenever exceeds 50 Usually 5 kg of sodium hypophosphiteis required to reduce 1 kg of nickel for an average efficiencyof 37 In another source [27] this problem was explainedby the catalytic oxidation of most of the hypophosphitepresent to orthophosphate and gaseous hydrogen evolutionaccording to the reaction which occurs independently of thedeposition of nickel and phosphorus hence causing the lowefficiency of electroless nickel solutions

(H2PO2)minus

+H2O 997888rarr H+ + (HPO3)minus2+H2 (4)

The most important application of electroless deposition isthe coating of plastic surfaces with metal or indeed metalcoating of surfaces In these applications coating thicknessis small (a few tens of microns) and then the removal ofhydrogen is simple In the present case metal deposition isextensive and confined to micron size pore walls Further-more the walls of the porous template polymer surface werenot catalyzed to achieve metal deposition and polymermetalintegration was not necessary Nevertheless the above chem-ical reactions indicate that the removal of hydrogen is ofparamount importance in order to sustain metal deposition

16 Novelty of the Current Process Thecharacteristics of flow-through monolithic reactors have been used in this research(most importantly the removal of reaction products) inorder to obtain electroless deposition In this study weuse PolyHIPE Polymers to electrolessly deposit metals andsubsequently heat-treat the resulting constructs to obtainmonoliths which can be used as gas separation and reactionmedia at high temperatures Previous attempts to producemonolithic porous metal systems through electroless depo-sition using PolyHIPE Polymer as template failed because theprocessing setup did not allow the continuous removal ofreaction products during depositionHence only small weakporous metallic particles could be obtained [28]

As we aim to demonstrate that catalytic microreactorswith hierarchic pore structure can be produced through

this method we need to choose the composition of themetal deposition solution carefully In this case the intro-duction of phosphorous in the reactor should be avoided asphosphorus is a well-known catalyst poison [29] Instead adimethylamine borane system was chosen in order to obtainmonoliths with catalyst activity in which the presence ofboron enhances resistance of nickel catalyst against poisoning[30]The results with dimethylamine borane will be reportedseparately

2 Experimental Section

21 Preparation of Template PolyHIPE Polymer (PHP) forMetal Deposition PHP is conveniently prepared throughthe polymerization of a polymerizable continuous phase ofa high internal phase water-in-oil emulsion (HIPE) usingthe equipment in Figure 1 The effects of temperature andthe non-Newtonian fluid mechanics aspects of the HIPEformation and dispersed phase (water) droplet size reductionwithout phase inversion to oil-in-water have been describedin [31] The techniques used in this study ensure thepreparation of macroporous polymers with well-controlledinternal architecture pore and interconnect sizes and theirdistributions The continuous (oil) phase of HIPE consistedof styrene 78wt (monomer) divinylbenzene 8 wt (cross-linking agent) and sorbitan monooleate (Span80) 14 wt(surfactant) all obtained in reagent grade from Aldrich andused without any further treatmentThe dispersed (aqueous)phase is comprised of double distilled water containing 1 wtpotassium persulfate as initiator for polymerization

The total volume of the aqueous phase and oil phasecombined was 225mL which was the optimum amount forthis particular mixing vessel (internal diameter was 12 cm)(Figure 1) Mixing was conducted using two flat paddles(diameter 9 cm) that were stacked 1 cm apart from each otherat right angles The bottom impeller was 05 cm above thebottom of the vessel Rotational speed of the impellers was300 rpm The phase volume of the aqueous phase was 95in order to obtain highly open pore polymer (pore sizes ca50ndash60 120583m) Agitation of aqueous phase and oil phase wasperformed in the mixing vessel which was heated by a waterjacket that circulated hot water at 60∘C by using a waterbath Prior to the mixing of the constituents the hot watercirculation was started to ensure that the reactor reached therequired temperature The aqueous phase was also preheatedto 60∘C on a hot plate When the aqueous phase and themixing vessel temperatureswere set all the oil phase (113mL)was poured into the vessel at onceThemixingwas conductedin a closed environment to prevent monomercross-linkerloss through evaporation Emulsification at relatively hightemperatures results in large pores at a given mixer speed of220 rpm and 3 minutes mixing time

Feeding of the aqueous phase (214mL) was performed byfour tubes connected to two peristaltic pumps The rate ofpumping was adjusted at such a speed that all the aqueousphase was dosed into the vessel in 2 minutes The impellerwas started at the same time as the dosing of the aqueousphase into the vessel After dosing all the aqueous phaseinto the oil phase the mixture was stirred for another


Emulsion

Peristaltic pumps

Impeller(300 rpm)

Oil phase

Water bath

Aqueousphase (60∘C)

Hot plate Oven (60∘C)

60∘C

Figure 1 Schematic representation of PHP preparation adopted from [15]

minute for homogenization The emulsion was then put into50mL plastic containers with internal diameters of 26mm(Figure 1) The plastic containers were then placed in apreheated (60∘C) oven where polymerization took place inabout 8 hours After the HIPE polymerized the solidifiedPHP blocks were removed from the containers and cut into4mm thick disks with sharp razors Drying of the disks didnot require any specific equipment as the disks were leftto dry overnight on tissues in a fume cupboard In orderto remove the surfactant and residual monomer the diskswere washed in a Soxhlet extractor First they were washedwith isopropanol for 3 hours followed by another 3 hours ofwashing with double distilled water to clean any remainingresidues in the pores and interconnecting wallsThe pore sizeof the disks was evaluated by scanning electron microscopy

22 Electroless Deposition Solution The electroless deposi-tion was conducted under flow conditions Therefore someof the common electroless deposition problems such asconstant change in pH (caused by hydrogen liberation duringdeposition) and difficulty to control reduction of free nickelwere not encountered Hence employment of bufferingagents inhibitors or complexing agentswas not requiredTheelectroless deposition solution (plating bath) was composedof nickel source reducing agent and ammonium hydroxideto adjust the pH Sodium hypophosphite hydrate was used asa reducing agent Accordingly the plating bath compositionswere very simple compared with the well-established plating

bath compositions often used in commercial applicationssuch as metal coating of plastic parts [25]

Metal Deposition Solutions (Plating Bath) Nickel chloridewas used as the metal source The main study is focusedon the use of sodium hypophosphite as the reducing agentHowever in order to demonstrate the effect of reducingagent on the characteristics of metal deposition we also useddimethylamine borane as the reducing agent

Plating Bath-1 Consider the following

(i) Metal source is nickel chloride with fixed concentra-tion at [Ni] = 013M

(ii) Reducing Agent-1 is sodium hypophosphite hydrate(NaH

2PO2sdotH2O) with variable concentration at [P] =

013M 126M 252M Here we represent the reduc-ing agent concentration through the molar concen-tration of phosphorous

(iii) pH regulator is ammonium hydroxide (35 concen-tration) to set pH = 115



(ii) Reducing Agent-2 is dimethylamine borane[(CH3)2NHBH

3] at a fixed concentration of [B] =

026M


Syringe pump Deposition

cell(see detail)

Outlet

Water bath

Wash heating

water

Metal solution

168

at 97∘C

(a)

A

A

B

B

C

C

D

D

EE

T

0 10(mm)

20

S

A PTFE holderB heating holderC inletoutletD flow distributors

E band heaterT thermocoupleS sample

(b)

Figure 2 (a) Diagrammatic illustration of the metal deposition setup (b) Details of the metal deposition cell

(iii) Solution stabilizers are 027M sodium acetate and388 times 10minus4M sodium lauryl sulphate

(iv) pH regulator is ammonium hydroxide (35 concen-tration) to set pH = 75

23 Metal Deposition Process The metal deposition setupused through this study is shown in Figure 2 The flowdiagramof themetal deposition setup is shown in Figure 2(a)A metal deposition cell was constructed as illustrated inFigure 2(b) The deposition cell housed the template PHPin the form of a disk (4mm thick and 26mm in diameter)Referring to Figure 2(b) PHP template sample (S) wassandwiched between two PTFE flow distributors (D) at theend of the PTFE flow channel (C) bored into the holders (A)which also acted as support for PHP The whole assemblywas then placed between two circular brass blocks (B) whichwas electrically heated using a band heater (E) Note that thePHP template was in direct contact with the brass holderto provide direct heating Temperature of the PHP templatewas monitored using a thermocouple (T) in contact with thepolymer All parts of the flow cell whichwere in direct contactwith the plating bath were made of PTFE in order to preventmetal deposition in the flow channels

The metal deposition solution was kept at room tem-perature and was pumped into the deposition cell usinga syringe driver at a rate of 2mLmin In order to causemetal deposition within the pores of the template polymerthe temperature of the solution was raised to 90 plusmn 3∘C inthe polymer In order to achieve this the deposition cellwas heated to 90∘C by using the band heater and chargedwith dematerialized water at 97∘C for 4 minutes at a rateof 40mLmin This was followed by the syringe pumping ofthe metal bath solution After pumping 50mL solution thedeposition was stopped and hot water washing was renewedand the cycle was repeated Throughout the experimentthe band heater and hot water washing kept the polymerconstantly at 90∘C After using 340mL metal bath solutionthe direction of flow was reversed until a sufficient amount ofmetal was deposited It is possible to reverse the flowdirectionafter each 50mL deposition and washing in order to obtainmore uniform deposition

24 Heat Treatment After the completion of the metaldeposition and final washing the samples were put into ahigh temperature oven and the temperature of the oven isincreased from room temperature to the heat treatment tem-perature (119879) which was dominantly 600∘C The heating rate


(a) (b)

Figure 3 Pore morphology of the PHP disks with porosity of 95 and average pore size of 55 plusmn 5 120583m that were used in the metallizationexperiments (a) general appearance (scale bar = 500120583m) (b) details (scale bar = 100 120583m)

(119867119903) was such that total heating period was 1 hour After

reaching this heat treatment temperature the samples wereannealed at this temperature for a period of 119905

119886 In themajority

of cases 119905119886= 60min

25 Scanning Electron Microscopy (SEM) and Energy Disper-sive X-Ray (EDX) Analysis The scanning electron micro-scope used in the present work was an environmentalscanning electron microscopy (XL30 ESEM-FEG) fitted witha Rontec Quantax system for energy dispersive X-ray (EDX)analysis to obtain local atomic concentration of variouselements in metallic samples after heat treatment Sincethe metallic samples were conductive they were not coatedalthough the nonconductive polymeric samples could alsobe examined in their natural state without significant samplemodification or preparation However polymeric sampleswere coated with gold for SEM imaging

26 X-Ray Diffraction (XRD) The X-ray diffraction (XRD)equipment was a PANalytical XrsquoPert Pro diffractometer fittedwith an XrsquoCelerator The XrsquoCelerator is a relatively newattachment to the XrsquoPert and has the effect of giving a goodquality pattern in a fraction of the time of the traditionaldiffractometer

27 BET Surface Area Analysis A Beckman-Coulter SA 3100analyzerwas usedThis instrument uses the gas sorption tech-nique to obtain the surface area and pore size distributionsat room temperature using helium Specific surface area ofthemetallizedmonoliths was calculated aftermeasuring bulkdensity of the samples in order to compare these materialswith the commercially available porous metals

28 Mercury Porosimetry In this study the mercury intru-sion porosimetry technique was used tomeasure the porosityand pore size distribution of the metal foamsThe equipment(Autopore II 9220) was manufactured by Micromeritics Ltd

3 Results and Discussion

Our aim is to demonstrate the feasibility of obtaining mono-lithic metal foams which can also be used as catalytic reactors

or as supported membranes Therefore in the first instancewe aim to establish the method of production which can bescaled up evaluate the mechanism of electroless depositionas well as nanostructure formation through heat treatmentand evaluate the characteristics of themetallicmonolithswitha hierarchic pore structure in which the pore size rangesfrom nanometers to micrometers For this purpose we useda nickel chloridehypophosphite system in a very simpledeposition solution which did not contain any stabilizersand surface sensitization (by palladium) of the templatedeposition medium (ie PHP) to promote deposition andreduction reactions

31 PolyHIPE Polymer Templates Throughout this study weused one type of PolyHIPE Polymer (PHP) template withphase volume 95 pore size 55 plusmn 2 120583m A scanning electronmicrograph of the PHP template is shown in Figure 3 Wehave chosen this material because smaller pore size or phasevolume PHP requires pressurization to pump the metaldeposition solution and it does not allow the deposition ofsufficient metal to provide mechanical strength

32MetalDepositionCharacteristics Thedeposition ofmetalwithin the pores is in the form of metal grains Figures 4(a)and 4(b) illustrate the metal deposition behavior in whichthe metallic grains as well as the polymer structure can beidentified clearly as the deposition is at the early stages of theexperiments (340mL solution passed) The deposition wascarried out until all the strands of the polymer were totallycovered with metal grains which required 600mL solutionin this example illustrated in Figure 4(b) The weight of atypical construct (template polymer and nickel deposit) was32 g when the deposition was stopped An example of afully deposited polymer disk is shown in Figure 4(b) whichindicates the autocatalytic nature of the deposition kineticsInitial deposition ratewas low since the template polymerwasnot sensitized and the size of the metal grains was some 70larger compared with the average size of the grains depositedat the later stages as shown in Figure 4(a)

X-ray diffraction patterns of the electroless Ni-P grainsin the as-deposited condition are given in Figure 5 which


(a) (b)

Figure 4 Nickel deposition fromNiCl2[Ni] = 013M solution with sodium hypophosphite as reducing agent [P] = 252M (a) Inner structure

at the early stages of deposition after passing 300mL solution through the template when the dry weight of the resulting construct (PolyHIPEPolymer and metal deposit) was 087 g (scale bar = 20 120583m) (b) Inner structure after passing 600mL solution when the weight of the resultingconstruct was 32 g (scale bar = 10 120583m)

20000

10000

0

Cou

nts

30 40 50 60

Position (∘2120579)

Peak list

04-0850 Ni nickel syn

05-0628 Na Cl balte syn

16-npoCAF

Figure 5 XRD pattern of the as-deposited Ni-P grains before heattreatment of the construct obtained through nickel deposition usinga plating bath with 013M NiCl

2and 126M sodium hypophosphite

after using 600mL solution

exhibited a single broad peak indicative of the amorphousnature of the metal deposits It also indicates the presenceof small amounts of NaCl generated during the reduction ofNiCl2by NaH

2PO3

The effect of reducing agent concentration [P] in themetal deposition solution on the size of the nickel-phosphor-ous grains is illustrated in Figure 6 The grain size decreasedwith increasing reducing agent concentration Regarding thesizes of the deposits Ni-P grain diameters ranged from 7 to18 120583m from 25 to 105 120583m and from 075 to 2 120583m when thereducing agent concentration increased from 063 to 126 andthen to 252M

As seen in these micrographs the concentration ofdeposited grains increases with increasing reducing agentconcentration In order to illustrate the effect of the type ofreducing agent on grain size we also used 063M boranedimethylamine instead of sodium hypophosphite As seen inFigure 6(d) the grain size for borane dimethylamine is ca200 nm

33 Heat Treatment and Skin-Core Structure Development Inorder to understand themechanism of structure formation inthese constructs (ie template PolyHIPE Polymer and metaldeposit) after passing 600mL plating bath solution throughthe template PolyHIPE Polymer the resulting samples wereheat-treated In these experiments we used 013M nickelchloride and 126M reducing agent and sodium hypophos-phite After full deposition was achieved (weight of thewashed and dried constructs was typically 32 g) the resultingconstructs were washed in water and then heat-treated

Starting from room temperature the sample already inthe oven temperature was increased to a prescribed tempera-ture at a variable rate so that the heating period was 60minutes After reaching the target temperature (ie 500 600and 800∘C) samples were either removed immediately (sothat annealing time 119905

119886= 0) and subsequently cooled to the

room temperature in air or alternatively kept at the targettemperature for a fixed period of time (usually 60min) andthen removed from the oven and allowed to cool down inair Final heat treatment procedure involved a prolongedannealing After reaching the heat treatment temperature andremaining at this temperature for 60 minutes (119905

119886= 60min)

the heating was switched off and the samples were graduallycooled in the oven over a period of 12 hours

The reason for this heat treatment protocol was to under-stand the structure formation as a result of the solid-statereaction that took place during heat treatment The fracturesurface of these heat treated samples was examined underscanning electron microscopy (SEM) The location of theexamination was typically at the center of the samples inall cases The reason for this is that these monoliths form


(a) (b)

(c) (d)

Figure 6 Size of the spherical grain deposits varied depending on the concentration of the plating bath Amount of the reducing agentsodium hypophosphite and volume of solution used were (a) 063M and 200mL (b) 126M and 200mL and (c) 252M and 600mL (d)In this example we also used 026M dimethylamine borane as the reducing agent and 600mL solution was used Regarding the size of thedeposits (a) Ni-P grain diameters ranged from 5 to 20120583m (scale bar = 50 120583m) (b) Ni-P grain diameters ranged from 2 to 12120583m (scale bar =20 120583m) (c) Ni-P grain diameters ranged from 05 to 2120583m (scale bar = 5 120583m) (d) Ni-B grain diameters were in the order of a few hundrednanometers (scale bar = 2 120583m)

a skincore structure in which the skin has reduced porositybut provides strength to the monolith These results areillustrated in Figures 7(a)ndash7(f) which reveal the mechanismof structure formation through a solid state reaction

The transformation of the Ni-P grains began on thesurface of the grains As the reaction proceeded densemetallic strands appeared which eventually covered the innerpart of the grains (Figures 7(a)ndash7(d)) These strands alsofused but formed a porous skin (Figure 7(e)) with pore size ofca 200 nm and thickness ca 1 120583m Further SEM examinationof the fracture surface of the grains indicated that core of thegrains is phase separated from the porous skin (Figure 7(e))During heat treatment the original discrete spherical grainsnow merged to form a continuous undulating capillary withporous walls forming the walls of the micron sized largepores which are connected to each other throughmicron sizearterial interconnecting windows

Figures 7(a)ndash7(f) show that during heat treatment thefused grains forming the walls of the porous monolithundergo a solid-state reaction which also causes a phaseseparation resulting in a porous skin and a detached coreHowever as these grains are all connected the resulting wallstructure is in the form of undulating porous capillaries filled

with nickel-phosphorus compound as revealed by XRD andenergy dispersive X-ray analysis

When the core material was removed from the brokengrain skin the remaining structure looked like an empty shellExtensive SEM examination indicated that these grains fusetogether to form undulating partially filled capillaries Thesestructures can be termed as ldquocapillary-like or capillaricrdquo andindeed they are also formed in nature as part of angiogenesis[32 33] The materials within these capillaries are the unre-acted Ni-P compounds Ni

2P Ni12P5 and Ni

3P with the latter

being themost stable of theseNi-P compounds as shown laterusing XRD The inner part of the grain skin (shell) can beseen in Figure 8(a) As this structure was examined in moredetail it was observed that the inner part of grain skin wascomposed of nanosized pores as shown in Figure 8(b)

34 Structure of the Grains and Capillaric Walls of the ArterialPores After heat treatment the formation of a grain skinaround the core was not the only change in the solid depositsThe core material itself was also subjected to reaction anda second skin appeared in the grains The presence ofmultiple skins was only observed when the reducing agentconcentrationwas high ([P] = 126 or 252M)This feature can


Solid metal deposit (core)

Strands

(a) (b)

(c) (d)

(e)

Core material

Grain skin

(f)

Figure 7 Development of hierarchic pore structure during heat treatment of the Ni-P metal deposits Sample characteristics [Ni] = 013M[P] = 126M Amount of deposition solution used was 600mL (a) First stage of the formation of grain surface skin after temperature reached119879 = 500

∘Cduring heating at119867119903= 10∘Cmin 119905

119886= 0 (scale bar = 1 120583m) (b) Skin formation after temperature reaches119879 = 600∘Cduring heating

at 119867119903= 10∘Cmin 119905

119886= 0 (scale bar = 1 120583m) (c) Skin formation after temperature reaches 119879 = 600∘C during heating at 119867

119903= 10∘Cmin

119905119886= 15min (scale bar = 2 120583m) (d) Full grain skin formation after heat treatment at 119879 = 600∘C when119867

119903= 10∘Cmin 119905

119886= 60min followed

by cooling in the closed oven until reaching room temperature over a period of 12 hours (scale bar = 2120583m) (e) Details of the skin at highmagnification (sample as in Figure 7(d)) showing the existence of the pores with size ca 200 nm (scale bar = 1 120583m) (f)The inner structure ofthe grains revealed by the fractured grains showing a porous skin and a dense inner core Sample same as in Figure 7(d) (scale bar = 10 120583m)

be best explained by the expression ldquoRussian dollrdquo structureas shown in Figure 9 The sample in Figure 9 had a grainsize of ca 12 120583m The first skin had a thickness of ca 2 120583mwhile the thickness of the second skin was ca 1120583m Theseskins were separated from each other although the secondskin was connected in part to the inner unreacted core whichhad a diameter of ca 6 120583m The erosion of the core can beobserved in the SEM image at highmagnification in Figure 9

As the grains got smaller in size they became more difficultto find broken cores to be examined Innermost cores as smallas 05 120583mwere observed in other samples as seen in Figure 10which also indicates that the capillary-like (capillaric) wallsof the arterial pores have large porosity

Inward oxygen diffusion and oxygen gas transportthrough the voids and microchannels in the NiO scaleresulted in the formation of a duplex NiO structure [34ndash37]


(a) (b)

Figure 8 Details of the porous undulating capillaries forming the walls of the large arterial pores Sample characteristics [Ni] = 013M[P] = 126M Amount of deposition solution used was 600mL Heat treatment conditions 119879 = 600∘C during heating at 119867

119903= 10∘Cmin

119905119886= 60min (a) Inner structure of an empty capillary wall (Scale bar 2 120583m) (b) Details of the inner structure of the capillary walls of the

arterial pores (scale bar = 500 nm)

Figure 9 Russian doll structures after heat treatment when[Ni] = 013M [P] = 126M Heat treatment temperature 119879 = 800∘C(heating rate 119867

119903= 13∘Cmin) and annealing time 119905

119886= 60min

followed by cooling in air Scale bar = 2 120583m and 200 nm (scale bar ofinset)

Further inward oxygen diffusion and oxygen transport canalso cause triplex or quadruplex oxide scale formation Thebalance between oxygen supply (activity) and phosphoruscontent determines exactly which structures form at whichtime during oxidation Formation of a complete NiPO

119909layer

between Ni-P and NiO layers must be validated by furtherinvestigation with TEM

The summary of the effect of reducing agent concentra-tion on the grain structure is given in Table 1

Although it can be clearly seen that the grain sizesdecrease with increasing sodium hypophosphite molaritythere is not a uniform distribution of grain sizes before orafter the heat treatment However after heat treatment thesample produced by using 063M sodium hypophosphitehad the most regular size and shape of grains When 252Msodium hypophosphite was used as a reducing agent a veryhigh degree of sinteringagglomeration of the grains wasobserved Grain surface pore size was similar in the first two

Figure 10 Formation of capillaric walls of the arterial poresafter heat treatment following the solid state oxidation of Ni

119909P119910

compounds in the grains Sample characteristics [Ni] = 013M[P] = 252M heat treatment temperature 119879 = 600∘C (heating rate119867119903= 10

∘Cmin) and annealing time 119905119886= 60min followed by

cooling in air Scale bar = 1 120583m

Table 1 The properties of three samples prepared by using [Ni]= 013M and sodium hypophosphite as reducing agent at con-centrations [P] = 063M 126M and 252M Heat treatment wasconducted with gradual heating from room temperature to 600∘Cat a rate of 10∘Cmin followed by annealing at 600∘C for 60 minutesand cooling in air

Sodium hypophosphiteconcentration (M) 063 126 252

Grain size (120583m)Before heat treatment 5ndash10 2ndash11 05ndash2

Grain size (120583m)After heat treatment 6ndash12 3ndash12 05ndash4

Grain surface pores (nm)After heat treatment 100ndash400 100ndash400 20ndash200

samples The high concentration of sodium hypophosphatedecreased the size of the surface pores drastically althoughthese pores were not well defined


100000

50000

0

30 40 50 60

Cou

nts

02-npCAF


Peak list04-0850 Ni nickel syn44-1159 NiO nickel oxide

74-1385 Ni2P nickel phosphide

74-1381 Ni12P5 nickel phosphide74minus1384 Ni3P nickel phosphide

Figure 11 XRD pattern of the Ni-P structure (same sample inFigure 10) after heat treatment at 600∘C Sample details platingbath composition [Ni] = 013M [P] = 126M and heat treatmentconditions 119879 = 600∘C heating rate = 10∘C and curingannealingtime 119905

119888= 60min followed by cooling in air

35 Chemical Distribution within Grains XRD and EDXAnalysis In order to obtain the overall chemical compositionof the porous monoliths after heat treatment the XRDpatterns are taken These patterns change with plating bathcomposition and heat treatment A typical XRD pattern ofthe whole sample is shown in Figure 11The sharp XRD peaksindicate crystalline structure formed by various compoundswhich were identified as Ni NiO Ni

12P5 Ni3P and Ni

2P

Although XRD study is useful in the identification of thecompounds and their crystal structure the distribution ofnickel oxygen and phosphorous across the grains and indeedin different locations was studied using energy dispersive X-ray (EDX) analysis

For EDX analysis we used 3 different samples producedunder different conditions and an additional sample wastested as a duplicate to test the reproducibility of the methodA grain in the sample chosen and its center was locatedunder SEM Several EDX measurements were performed atvarious distances from the center of the grainThis scheme isillustrated in Figure 12

From the EDX spectrum atomic fractions of nickel oxy-gen and hosphorous were calculated The results are shownin Figure 13 where the atomic weight percent of phosphorousis plotted as a function of distance from the center of thegrain The range of overall phosphorous concentration inthe samples before heat treatment ranged from 105 to 154atomic percent (at) when the phosphorous concentrationin the plating bath ranged from 063 to 252M As seen inFigure 13 the maximum phosphorous concentration is ca16 at although phosphorous concentration in the platingbath was 063M and 152M As discussed earlier not all ofthe reducing agents are utilized in the reduction of sodiumhypophosphite to Ni [26] and it therefore appears that theeffect of the reducing agent is to change the morphology of

Figure 12 Typical example of the EDX analysis on a fractured grainusing spotmeasurements starting from the center of the grain (Point0) as a function of distance from the center Sample characteristics[Ni] = 013M [P] = 126M heat treatment temperature 119879 = 600∘Cheating rate 119867

119903= 10

∘Cmin and annealing time 119905119886= 60 min

followed by cooling in air Scale bar = 2 120583m

000200400600800

100012001400160018002000

0 1000 2000 3000 4000 5000 6000 7000 8000 9000

Phos

phor

us (a

t)

Distance from center of the core (nm)

P (31A-5)P (38A-4)P (G3-8)

P (P5)Series5

Figure 13 Distribution of phosphorus in grains as a function ofdistance from the center of the grain Identification of the samplesSample 31A [P] = 063M 119879 = 600∘C and 119905

119886= 60min Sample 38A

[P] = 126M and 119879 = 800∘C Samples G3 and P5 [P] = 126M and119879 = 600

∘C In all cases time to reach the heat treatment temperatureis 60 minutes and curingannealing time 119905

119886= 60min followed by

cooling in air

the grains (and hence the structure of the monolith) ratherthan change the chemical composition of Ni

119909P119910compounds

In commercial applications for nickel coating of plasticsurfaces the phosphorous content also ranges from ca 46 to231 at

It is clear from Figure 13 that within the core of thegrains phosphorous concentration remains constant but itis reduced sharply outside the core when the skin is reachedwhere it is typically less than 1 at within the accuracy of theexperiments

36 Overall Structure of the Monoliths Crust Formation Theforegoing analysis of the foam structure was performed nearthe center of the monolith in order to illustrate the mecha-nism of structure formationHowever for practical purposes


(a)

Surfa

ce

Cross-section

(b)

Fused core material around pores

(c)

Grain skin

Core

(d)

Figure 14 Structure of the skin produced on the top and bottom surface of the monoliths after heat treatment Sample characteristics[Ni] = 013M [P] = 126M 119879 = 600∘C 119867

119903= 10∘Cmin 119905

119886= 60min followed by cooling in air (a) General appearances of top surfaces

of metal disks after heat treatment (b) Cross-section of the crust (c) Large pore was formed by the fusion of numerous grains All the corematerial in these grains was fused to form one extended core surrounding the large pores (d) Details of how the core material and grain skinwere shared As a result the core can be obtained in tubular form with very high porosity

the mechanical strength of the monoliths is important andhence the full structure evaluation is necessary

It was found that even at the initial stages of metaldeposition a dense layer is formed on the surface of thetemplate PolyHIPE Polymer This dense layer is describedas ldquocrustrdquo as it can be separated from the inner bulk ofthe monolith although both regions are connected Crust isformed on both sides of the template when the flow directionis reversed as well as around the perimeter of the circularmonoliths as plating bath solution leaks through the sides ofthe template disk When these polymermetal constructs areheat-treated the resulting porosity of the dense layer (crust)is considerably smaller than that of the inner structureFigure 14 illustrates the structure of crust after heat treatmentat 600∘C of a typical monolith with crust

The thickness (crust) is dependent on the plating bathcomposition as well as on the deposition conditions Further-more by using another nickel source (such as NiSO

4) the

dense crust layer can be completely eliminatedIt is possible to isolate the crust from the bulk and

examine its structure separately Figure 14(a) illustrates thesurface appearance of the crust indicating the reducedporosity of the surface The cross-section of the crust isshown in Figure 14(b) which shows that the porosity ofthe crust increases with distance from the surface This isfurther illustrated in Figure 14(c) at larger magnification

Table 2 Energy dispersive X-ray analysis of the crust Variation ofNi O and P concentration as a function of distance from the topsurface of the crust ([Ni] = 013M [P] = 126M 119879 = 600∘C 119867

119903=

10∘Cmin 119905119888= 60min)

Distance from thecrust surface (120583m)

Nickel(at)

Oxygen(at)

Phosphorous(at)

0 830 169 01300 991 08 01500 993 05 02700 994 03 03

Further investigation of the crust structure indicates thatthe pore walls are formed by the fusion of the grains whichsubsequently became hollow during heat treatment as seen inFigure 14(d) From Figure 14(d) it can also be observed thatthe pore walls (which can be described as capillaric) are alsoporous similar to those observed for the inner core structure

EDX analysis of the crust shows that within the crustphosphorous level is very low and the surface of the crust isoxidized which explains the formation of hollow walls withinthe crust The results are shown in Table 2

37 Inner Structure of Monoliths The inner structures of themonoliths are examined by using SEMand they are illustrated


(a) (b)

(c) (d)

Figure 15 Inner bulk structures of themonoliths showing the effect of reducing agent concentration Experimental conditions [Ni] = 013M119879 = 600

∘C 119867119903= 10∘Cmin 119905

119886= 60min followed by cooling in air (a) General appearance of the bulk structure showing the presence of

pore hierarchy with large arterial pores (interconnectswindows) with size range 10ndash30120583m and pore walls made from the porous capillaricstructures of ca 10 120583msize Reducing agent concentration [P] = 063M scale bar = 50 120583m (b) Sample as in Figure 15(a) at largermagnificationScale bar = 10120583m (c) Reducing agent concentration [P] = 126M Scale bar = 10120583m (d) Reducing agent concentration [P] = 252M Scalebar = 10 120583m

in Figure 15 which shows the presence of large arterialpores and arterial interconnecting holeswindows (Figures15(a) and 15(b)) The walls of the arterial pores are madefrom porous grains The grain size decreases with increasingreducing agent concentration (compare Figures 15(b) 15(c)and 15(d)) The effect of reducing agent concentration on thepore size of the grains is illustrated in Figures 16(a)ndash16(c)As seen from these SEM images when the reducing agentconcentration is [P] = 063Mor 126M grain surface porosityis similar but when [P] = 252M the grain surface porosity issmaller but less well defined

38 Overall Chemical Structure of Crust and Bulk The chem-ical composition of the crust and the bulk were evaluated byXRD studies In the first instance the crust and the bulk ofthemonoliths were separated out and each part was subjectedto XRD analysis These results are shown in Figure 17 whichindicates that Ni NiO and Ni

3P are present in both the inner

structure and crust but Ni2P and Ni

12P5are only present in

the inner structure See Figure 11 for the identification of theXRD peaks

39 Surface Area and Porosity The surface area of the crustand the internal structure of the monoliths were measured

using BET surface area analysis After measuring the densityof the these two parts (crust and bulk) of the monolithsthe specific surface area was calculated Mercury intrusiontechnique was used to calculate the porosity The results ofthe mercury intrusion technique for the inner structure andcrust are shown in Figures 18(a) and 18(b) respectively

Figure 18 indicates that the porosity of the crust was635 while the inner bulk structure had a porosity of 756From Figure 18 it can be seen that both the crust and thebulk of the monolith have bimodal pore size distributionThe arterial pores in the range 5ndash30 120583m are in a majoritywhile the second set of pores were in the range of 2ndash6 nmNanopores were more dominant in the bulk of the monolithThese results were further validated by measuring the BETsurface area which also provides the range of pore sizes Thesurface area of the crust and bulk of the monoliths describedin Figure 18 and Table 3 were 0238m2g and 0626m2grespectively The pore size distribution obtained by BETsurface area analysis was confined to the range of 2 to 160 nm(Table 3) Within this range 177 of all the pores werebetween 2 to 6 nm which verified the peak in Figure 18(b)obtained by the mercury porosimeter These results for thecrust and the bulk are shown in Table 3


(a) (b) (c)

Figure 16 Effect of reducing agent concentration on the surface pore structure of the arterial walls (in the form of porous undulatinginterconnecting capillaries) Experimental conditions [Ni] =013M 119879 = 600∘C 119867

119903= 10∘Cmin 119905


Scale bar = 500 nm (a) Reducing agent concentration [P] = 063M (b) Reducing agent concentration [P] = 126M (c) Reducing agentconcentration [P] = 252M

0

40000

80000

120000

25 30 35 40 45 50 55 60 65Position

Inner structureCrust

Ni

(2θ)

NiO

Cou

nt

Ni 12

P 5Ni 3P

Ni 2

P

Figure 17 Superimposed XRD patterns of the crust and the innerbulk structure of themonolith Processing conditions [Ni] = 063M[P] = 126M 119879 = 600∘C 119867

119903= 10∘Cmin 119905


cooling in air Ni NiO and Ni3P are present in both the crust and

inner structure while Ni2P and Ni

12P5are only present in the inner

structure

4 Conclusions

Unlike the previous attempts to produce strong microporousmonolithic metal foams from PolyHIPE Polymer templatea simple metal deposition solution was successfully used ina flow-enhanced deposition process which resulted in grainformation and faster deposition The important element ofthis technique is the electroless deposition under flow whilepreventing deposition outside the template This is achievedby the cyclic charge of deposition solution and washingsolution coupled with the reversal of the flow direction toobtain uniform distribution of metal deposition The effectsof flow can be summarized as follows

(a) Flow removes hydrogen generated during electrolessdeposition Failure to remove hydrogen stops electro-less deposition

(b) The deposition template is heated locally to acceleratethe electroless deposition However the deposition

Table 3 Pore size distribution by surface area analysis Processingconditions [Ni] = 063M [P] = 126M 119879 = 600∘C 119867

119903= 10∘Cmin


Pore diameter range Crust Inner structure(nm) () ()2 to 6 109 1776 to 8 54 918 to 10 31 5010 to 12 37 5612 to 16 43 6216 to 20 51 6220 to 80 403 30280 to 160 272 200

solution is charged into the template at room tem-perature to prevent premature deposition in the flowpath

(c) After deposition for a certain length of time deion-ized water at high temperature (97∘C) was passedthrough the deposition template in order to removereduction products from the electroless deposition aswell as heating the deposition template which is alsoheated externally to prevent heat losses

(d) As the deposition proceeds the deposition cycle timecan be increased due to the increase in the heatcapacity of the monolith which allows faster deposi-tion

(e) Combination of washing and heating at 90∘C allowsthe removal of reaction products such as sodiumchloride thus removing such impurities from thefinal monolith

(f) Depending on the metal and reducing agent sourcea dense layer is also formed on both sides of themonolith

Metal deposition from NiCl2solution with NaH

2PO2as the

reducing agent takes place in the form of grains Depending


0010203040506070809

1

1 10 100 1000 10000 100000Incr

emen

talc

umul

ativ

e por

osity

Pore radius (nm)

Cumulative porosityIncremental pore radius

(a)

0

02

04

06

08

1

12

1 10 100 1000 10000 100000Incr

emen

talc

umul

ativ

e por

osity

Pore radius (nm)


(b)

Figure 18 Variation of the cumulative and incremental pore radius with pore size of the crust and bulk Processing conditions [Ni] = 063M[P] = 126M 119879 = 600∘C119867

119903= 10∘Cmin 119905

119886= 60min followed by cooling in air (a) Crust (b) Bulk of the monolith

on the composition of the metal deposition solution and thetype of the reducing agent metal grain size ranges from ca20120583m to 02 120583mThese grains also form the walls of the largearterial pores During heat treatment these discrete grainsundergo a solid state chemical reaction which results in thefollowing

(a) Formation of a porous metallic Ni skin covers theunreacted inner core which contains mainly NiO andNi119909P119910compounds

(b) These grains also undergo sintering thus forming acontinuous porous capillary-like (capillaric) structureconstituting the walls of the arterial pores

(c) With further increase in the heat treatment the solidstate reaction continues and the inner structure ofthe capillaric walls becomes void thus increasing theoverall porosity of the monoliths

(d) The dense layers on the surfaces of the monolith aretransformed into a strong metal crust with reducedporosity compared with the bulk of the monolithwhich is sandwiched between the crustsThe pores ofthe crust have the same capillaric walls except the sizeof the arterial pores which are now reduced and thethickness of the walls is increased

These structures are also encountered in the human bodywhere capillary-like conduits are formed In the present casethe monoliths have a hierarchy of pores Convective masstransfer is provided by the arterial pores which have porouscapillaric walls providing catalytic sites for reactions wherethe diffusional resistance to mass transfer is significantlyreduced due to the presence of mesoscale pores between theconvective and conductive mass transfer regions

The mechanisms of electroless metal deposition andsubsequent structure development during heat treatmentare evaluated The chemical and physical structures of themonoliths were evaluated The formation of a strong top

surface with reduced porosity (crust) in the monoliths canbe desirable as it imparts mechanical strength as well asproviding a self-filtering system in gaseous reactions due tothe formation of a reduced porosity The pore volumes of thecrust and the bulk are large 635 and 756 respectively

Conflict of Interests

The authors declare that there is no conflict of interestsregarding this publication

Acknowledgments

The authors acknowledge with thanks that this research wasinitially supported by Engineering and Physical SciencesResearch Council (EPSRC) and Department of Trade andIndustry of the UK (Grant no GRR59212) through a LINKproject with additional grant provided by Intensified Tech-nologies Incorporated (ITI) Ltd through a PhD supportto Dr Burak Calkan Further research was funded by anEU FP7 Project (COPIRIDE CP-IP 228853-2) carried out atNewcastle University directed by Prof G Akay

References

[1] M T Kreutzer F Kapteijn J A Moulijn and J J HeiszwolfldquoMultiphase monolith reactors chemical reaction engineeringof segmented flow in microchannelsrdquo Chemical EngineeringScience vol 60 no 22 pp 5895ndash5916 2005

[2] J Gascon J R van Ommen J A Moulijn and F KapteijnldquoStructuring catalyst and reactormdashan inviting avenue to processintensificationrdquo Catal Sci Technol vol 5 no 2 pp 807ndash8172015

[3] A G Gil Z Wu D Chadwick and K Li ldquoMicro-structuredcatalytic hollow fiber reactor for methane steam reformingrdquoIndustrial and Engineering Chemistry and Research vol 54 no21 pp 5563ndash5571 2015


[4] M-O Coppens J Sun and T Maschmeyer ldquoSynthesis of hier-archical porous silicas with a controlled pore size distributionat various length scalesrdquo Catalysis Today vol 69 no 1ndash4 pp331ndash335 2001

[5] M-O Coppens ldquoA nature-inspired approach to reactor andcatalysis engineeringrdquo Current Opinion in Chemical Engineer-ing vol 1 no 3 pp 281ndash289 2012

[6] G Akay ldquoBioprocess and chemical process intensificationrdquo inEncyclopaedia of Chemicals Processing S Lee Ed vol 1 pp 183ndash199 Taylor amp Francis New York NY USA 2006

[7] G J Davies and S Zhen ldquoMetallic foams their productionproperties and applicationsrdquo Journal of Materials Science vol18 no 7 pp 1899ndash1911 1983

[8] J Banhart ldquoManufacture characterisation and application ofcellular metals and metal foamsrdquo Progress in Materials Sciencevol 46 no 6 pp 559ndash632 2001

[9] L-P Lefebvre J Banhart and D C Dunand ldquoPorous metalsand metallic foams current status and recent developmentsrdquoAdvanced Engineering Materials vol 10 no 9 pp 775ndash7872008

[10] X Badiche S Forest T Guibert et al ldquoMechanical propertiesand non-homogeneous deformation of open-cell nickel foamsapplication of the mechanics of cellular solids and of porousmaterialsrdquoMaterials Science and Engineering A vol 289 no 1-2pp 276ndash288 2000

[11] Recemet International Standard Specification Recemet Inter-national 2009

[12] G Akay ldquoFlow induced phase inversion in powder structuringby polymersrdquo in Polymer Powder Technology M Narkis andN Rosenzweig Eds pp 542ndash587 Wiley New York NY USA1995

[13] G Akay ldquoFlow-induced phase inversion in the intensiveprocessing of concentrated emulsionsrdquo Chemical EngineeringScience vol 53 no 2 pp 203ndash223 1998

[14] M S Silverstein and N R Cameron Encyclopaedia of PolymerScience and Technology Wiley New York NY USA 2010

[15] G Akay B Calkan H Hasan and R Mohamed ldquoPreparationof nano-structured microporous composite foamsrdquo EuropeanPatent 2342272 2013

[16] G Akay M A Birch and M A Bokhari ldquoMicrocellular poly-HIPE polymer supports osteoblast growth and bone formationin vitrordquo Biomaterials vol 25 no 18 pp 3991ndash4000 2004

[17] E Erhan E Yer G Akay B Keskinler and D KeskinlerldquoPhenol degradation in a fixed-bed bioreactor using micro-cellular polymer-immobilized Pseudomonas syringaerdquo Journalof Chemical Technology andBiotechnology vol 79 no 2 pp 195ndash206 2004

[18] G Akay E Erhan and B Keskinler ldquoBioprocess intensificationin flow-throughmonolithicmicrobioreactorswith immobilizedbacteriardquo Biotechnology and Bioengineering vol 90 no 2 pp180ndash190 2005

[19] G Akay and D R Burke ldquoAgro-process intensification throughsynthetic rhizosphere media for nitrogen fixation and yieldenhancement in plantsrdquo American Journal of Agricultural andBiological Science vol 7 no 2 pp 150ndash172 2012

[20] G Akay and S Fleming ldquoAgro-process intensificationsoilborne micro-bioreactors with nitrogen fixing bacteriumAzospirillum brasilense as self-sustaining biofertiliser source

for enhanced nitrogen uptake by plantsrdquo Green Processing andSynthesis vol 1 no 5 pp 227ndash237 2012

[21] G Akay T Pekdemir A M Shakorfow and J VickersldquoIntensified demulsification and separation of thermal oxidereprocessing interfacial crud (THORP-IFC) simulantsrdquo GreenProcessing and Synthesis vol 1 no 1 pp 109ndash127 2012

[22] N Barlık B KeskinlerMM Kocakerim andG Akay ldquoSurfacemodification of monolithic PolyHIPE Polymers for anionicfunctionality and their ion exchange behaviorrdquo Journal ofApplied Polymer Science vol 132 no 29 2015

[23] G Akay C A Jordan and A H Mohamed ldquoSyngas cleaningwith nano-structured micro-porous ion exchange polymers inbiomass gasification using a novel downdraft gasifierrdquo Journalof Energy Chemistry vol 22 no 3 pp 426ndash435 2013

[24] A Brenner and G Riddell United States Patent No 25322831950

[25] S S Djokic ldquoElectroless deposition of metals and alloysrdquoModern Aspects of Electrochemistry vol 35 pp 51ndash133 2002

[26] G O Mallory ldquoInfluence of the electroless plating bath on thecorrosion resistance of the depositsrdquo Plating vol 61 no 11 p1005 1974

[27] W D Fields R N Duncan and J R Zickgraf ldquoElectrolessnickel platingrdquo inMetals Handbook Volume 5mdashSurface Clean-ing Finishing and Coating ASMHandbook Committee MetalsPark Ohio USA 1982

[28] S Sotiropoulos I J Brown G Akay and E Lester ldquoNickelincorporation into a hollow fibre microporous polymer apreparation route for novel high surface area nickel structuresrdquoMaterials Letters vol 35 no 5-6 pp 383ndash391 1998

[29] V Kroger M Hietikko D Angove et al ldquoEffect of phosphoruspoisoning on catalytic activity of diesel exhaust gas catalystcomponents containing oxide and Ptrdquo Topics in Catalysis vol42-43 no 1ndash4 pp 409ndash413 2007

[30] W-J Wang H-X Li and J-F Deng ldquoBoron role on sulfurresistance of amorphous NiBSiO

2catalyst poisoned by carbon

disulfide in cyclopentadiene hydrogenationrdquo Applied CatalysisA General vol 203 no 2 pp 293ndash300 2000

[31] G Akay M Dogru B Calkan and O F Calkan ldquoFlow inducedphase inversion phenomenon in process intensification andmicro-reactor technologyrdquo in Microreaction Technology andProcess Intensification YWang and J Halladay Eds chapter 18pp 286ndash308 American Chemical Society New York NY USA2005

[32] Y Kubota H K Kleinman G R Martin and T J LawleyldquoRole of laminin and basementmembrane in themorphologicaldifferentiation of human endothelial cells into capillary-likestructuresrdquoThe Journal of Cell Biology vol 107 no 4 pp 1589ndash1598 1988

[33] D C Darland and P A Drsquoamore ldquoTGF120573 is required forthe formation of capillary-like structures in three-dimensionalcocultures of 10T12 and endothelial cellsrdquo Angiogenesis vol 4no 1 pp 11ndash20 2001

[34] A Atkinson and D W Smart ldquoTransport of nickel and oxygenduring the oxidation of nickel and dilute nickelchromiumalloyrdquo Journal of the Electrochemical Society vol 135 no 11 pp2886ndash2893 1988

[35] A W Harris and A Atkinson ldquoOxygen transport in growingnickel oxide scales at 600ndash800∘Crdquo Oxidation of Metals vol 34no 3-4 pp 229ndash258 1990


[36] H Kyung and C K Kim ldquoMicrostructural evolution of duplexgrain structure and interpretation of the mechanism for NiOscales grown on pure Niand Cr-doped substrates during hightemperature oxidationrdquo Materials Science and Engineering BSolid-State Materials for Advanced Technology vol 76 no 3 pp173ndash183 2000

[37] S Chevalier F Desserrey and J P Larpin ldquoOxygen transportduring the high temperature oxidation of pure nickelrdquo Oxida-tion of Metals vol 64 no 3-4 pp 219ndash234 2005

Submit your manuscripts athttpwwwhindawicom

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Journal of

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contacting) while providing a narrow residence time distri-bution avoiding mal-distribution and scale-up problems

12 Monolithic Reactors with Hierarchic Pore Structure Mon-olithic catalyst systems with nonporouslow porosity wallsalso suffer from certain disadvantages such as cost lowcatalyst loading integrity of the catalyst coating on themono-lith channel walls and the presence of two independentlycontrolled length scales which only provide partial accessi-bility of the catalytic sites The accessibility of the nanosizedcatalytic sites is achieved most effectively by a hierarchicalchannel or pore network structures which are ubiquitous innature [4ndash6] In these systems the main chemical processesare principally controlled at the molecularnanoscale asmany of these processes are transport-limited while thecontinuous supplyremoval of reactantsproducts is achievedthrough capillariespores of ever increasing diameter Sucha system provides an optimum architecture incorporatingmicro-nanoscale with chemically functional features withinthe macrosystem at an optimum surface area for catalyticapplications Such hierarchically structured catalyst systemswith fractal-like meso- to macropore size distribution can beexpected to be more efficient and robust due to the enhancedsurface area and accessibility leading to the intensification ofchemical processes [6]

13 Production of Porous Metallic Structures There are sev-eral important applications of metallic foams as both struc-turalengineering and specialized materials Excellent peri-odical reviews are available describing themanufacture char-acterization properties and application of thesematerials [7ndash9] One particularmetallic foam is produced through electro-chemical metal deposition on polyurethane foam followed byheat treatmentwhen the template polymer is burnt off [10 11]These materials are commonly used for catalyst support toobtain supported catalyst systems as well as electrode infuel cells These materials are marketed as Metapore CelnetRetimet and Recemet Their macrostructure is very similarto some of the materials produced by the current techniqueexcept that these materials do not have a hierarchy of poreswhile their surface area density (surface area per unit volume)is some 100-fold smaller and pore size is some 50 timessmaller than those produced in this work

14 PolyHIPE Polymers as Monolithic Microreactors and asTemplates for Electroless Metal Deposition In the design ofnovel monoliths with hierarchical porous catalytic reactorshaving a pore size range of ca 100 120583mto a fewnanometers thefirst step is to obtain structures with controlled pore size andporosity and functionalize them to impart both nanostruc-ture and catalytic activities One such highly versatile mono-lithic (or indeed particulate) system is known as PolyHIPEPolymer (PHP) which was developed at Unilever ResearchLaboratory at Port Sunlight (UK) during the 1980s by a teamincluding one of the present authors (Galip Akay) who alsodeveloped the processing of the basic material and advancedits use in both small and large scale applications [12 13] Asummary of PolyHIPE Polymer chemistry can be found in[14]

PolyHIPE Polymers are prepared through a high internalphase emulsion (HIPE) polymerization route and hence theacronymic name PolyHIPE which reflects the processinghistory Depending on the composition of the HIPE process-ing and polymerization history PHPs can have hierarchicalpore and interconnects over a size range ca 100 120583m tonanometre while the pore volume can reach as high as 97for practical applications Chemicalbiochemical functionali-zation processes of PHPs are relatively easy [15] and coupledwith their easy manufacture in monolithic form with well-defined macro- meso- and nanostructures providing a hier-archy of pores they are ideally suited for process intensifica-tion [6] in agricultural biological and chemical processesin both small scale or large scale applications Further accel-eration efficiency and selectivity in processing are obtainedwhen PHPs are used as monoliths

PolyHIPE Polymers can be chemically and biologicallyfunctionalized [16ndash20] in order to achieve mimicking ofnaturersquos processing strategy and applied to tissue engineeringbioprocess intensification and agroprocess intensificationFurthermore nonbiological functionalization processes wereused for specific applications such as separation processes[21] fast response ion-exchange resins [22] and environmen-tal and energy conversion processes [23]

Monolithic chemical or biochemical reactors have severaladvantages over packed bedfluidised bed or stirred tankreactors even when hierarchic catalysts are used in particu-late form In monolithic flow-through reactors there is nochanneling and the distribution of flow across the cross-section of the monolithic reactor is more uniform and thecatalytic sites are only micrometers away from the reactantsFurthermore in some reactions when the rate is limited byproduct concentration flow through the monolith allowsthe removal of the product from the catalytic sites into thebulkconvective flow These characteristics result in processintensification and direct comparison of packed bed andmonolithic reactor performance is available when PolyHIPEPolymer was used in particulate form (packed bed) [17] andin monolithic form [18]

As reviewed above PolyHIPE Polymer monoliths havebeen used successfully for intensifying processes in agricul-ture biology chemicalphysical-chemical and energy con-version processes due to their unique hierarchic pore struc-ture in which large arterial pores with large interconnectingholes (windows) facilitate convective mass transfer whilewalls of the arterial pores provide the catalytic sites whichare connected to the arterial pores via mesoscale (typically100 nm) pores [15] However to the best of our knowledgethere is nometallic equivalent form of suchmonolithic struc-tures Therefore the manufacture of such metallic mono-liths will increase the temperature and pressure range ofchemicalphysical-chemical processes and catalyst reactantand product ranges of these reactors

15 Electroless Deposition There are different mechanisms inthe literature suggested for the chemical reduction of nickelsalts by hypophosphites Probably the most widely acceptedmechanism is the one suggested by Brenner and Riddell [24]as also reported in [25 26]They stated that atomic hydrogen



(H2PO2)minus


+ 2Habs (1)






(H2PO2)minus











Emulsion

Peristaltic pumps

Impeller(300 rpm)

Oil phase

Water bath



60∘C
















026M



cell(see detail)

Outlet

Water bath

Wash heating

water

Metal solution

168

at 97∘C

(a)

A

A

B

B

C

C

D

D

EE

T

0 10(mm)

20

S



(b)








(a) (b)





of cases 119905119886= 60min












(a) (b)



20000

10000

0

Cou

nts

30 40 50 60


Peak list



16-npoCAF





2PO3







119886= 60min)




(a) (b)

(c) (d)







2P Ni12P5 and Ni

3P with the latter





Strands

(a) (b)

(c) (d)

(e)

Core material

Grain skin

(f)




at 119867119903= 10∘Cmin 119905


119903= 10∘Cmin


119903= 10∘Cmin 119905







(a) (b)


119903= 10∘Cmin





119886= 60min



119909layer





119909P119910











100000

50000

0

30 40 50 60

Cou

nts

02-npCAF








12P5 Ni3P and Ni

2P





119903= 10



000200400600800

100012001400160018002000

0 1000 2000 3000 4000 5000 6000 7000 8000 9000

Phos

phor

us (a

t)


P (31A-5)P (38A-4)P (G3-8)

P (P5)Series5






cooling in air







(a)

Surfa

ce

Cross-section

(b)


(c)

Grain skin

Core

(d)


119903= 10∘Cmin 119905






4) the




119903=

10∘Cmin 119905119888= 60min)


Nickel(at)

Oxygen(at)

Phosphorous(at)

0 830 169 01300 991 08 01500 993 05 02700 994 03 03





(a) (b)

(c) (d)


∘C 119867119903= 10∘Cmin 119905













(a) (b) (c)


119903= 10∘Cmin 119905



0

40000

80000

120000

25 30 35 40 45 50 55 60 65Position


Ni

(2θ)

NiO

Cou

nt

Ni 12

P 5Ni 3P

Ni 2

P


119903= 10∘Cmin 119905





structure

4 Conclusions





119903= 10∘Cmin









2PO2as the



0010203040506070809

1

1 10 100 1000 10000 100000Incr

emen

talc

umul

ativ

e por

osity

Pore radius (nm)


(a)

0

02

04

06

08

1

12

1 10 100 1000 10000 100000Incr

emen

talc

umul

ativ

e por

osity

Pore radius (nm)


(b)


119903= 10∘Cmin 119905












Acknowledgments


References


















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





(H2PO2)minus


+ 2Habs (1)






(H2PO2)minus











Emulsion

Peristaltic pumps

Impeller(300 rpm)

Oil phase

Water bath



60∘C
















026M



cell(see detail)

Outlet

Water bath

Wash heating

water

Metal solution

168

at 97∘C

(a)

A

A

B

B

C

C

D

D

EE

T

0 10(mm)

20

S



(b)








(a) (b)





of cases 119905119886= 60min












(a) (b)



20000

10000

0

Cou

nts

30 40 50 60


Peak list



16-npoCAF





2PO3







119886= 60min)




(a) (b)

(c) (d)







2P Ni12P5 and Ni

3P with the latter





Strands

(a) (b)

(c) (d)

(e)

Core material

Grain skin

(f)




at 119867119903= 10∘Cmin 119905


119903= 10∘Cmin


119903= 10∘Cmin 119905







(a) (b)


119903= 10∘Cmin





119886= 60min



119909layer





119909P119910











100000

50000

0

30 40 50 60

Cou

nts

02-npCAF








12P5 Ni3P and Ni

2P





119903= 10



000200400600800

100012001400160018002000

0 1000 2000 3000 4000 5000 6000 7000 8000 9000

Phos

phor

us (a

t)


P (31A-5)P (38A-4)P (G3-8)

P (P5)Series5






cooling in air







(a)

Surfa

ce

Cross-section

(b)


(c)

Grain skin

Core

(d)


119903= 10∘Cmin 119905






4) the




119903=

10∘Cmin 119905119888= 60min)


Nickel(at)

Oxygen(at)

Phosphorous(at)

0 830 169 01300 991 08 01500 993 05 02700 994 03 03





(a) (b)

(c) (d)


∘C 119867119903= 10∘Cmin 119905













(a) (b) (c)


119903= 10∘Cmin 119905



0

40000

80000

120000

25 30 35 40 45 50 55 60 65Position


Ni

(2θ)

NiO

Cou

nt

Ni 12

P 5Ni 3P

Ni 2

P


119903= 10∘Cmin 119905





structure

4 Conclusions





119903= 10∘Cmin









2PO2as the



0010203040506070809

1

1 10 100 1000 10000 100000Incr

emen

talc

umul

ativ

e por

osity

Pore radius (nm)


(a)

0

02

04

06

08

1

12

1 10 100 1000 10000 100000Incr

emen

talc

umul

ativ

e por

osity

Pore radius (nm)


(b)


119903= 10∘Cmin 119905












Acknowledgments


References


















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




Emulsion

Peristaltic pumps

Impeller(300 rpm)

Oil phase

Water bath



60∘C
















026M



cell(see detail)

Outlet

Water bath

Wash heating

water

Metal solution

168

at 97∘C

(a)

A

A

B

B

C

C

D

D

EE

T

0 10(mm)

20

S



(b)








(a) (b)





of cases 119905119886= 60min












(a) (b)



20000

10000

0

Cou

nts

30 40 50 60


Peak list



16-npoCAF





2PO3







119886= 60min)




(a) (b)

(c) (d)







2P Ni12P5 and Ni

3P with the latter





Strands

(a) (b)

(c) (d)

(e)

Core material

Grain skin

(f)




at 119867119903= 10∘Cmin 119905


119903= 10∘Cmin


119903= 10∘Cmin 119905







(a) (b)


119903= 10∘Cmin





119886= 60min



119909layer





119909P119910











100000

50000

0

30 40 50 60

Cou

nts

02-npCAF








12P5 Ni3P and Ni

2P





119903= 10



000200400600800

100012001400160018002000

0 1000 2000 3000 4000 5000 6000 7000 8000 9000

Phos

phor

us (a

t)


P (31A-5)P (38A-4)P (G3-8)

P (P5)Series5






cooling in air







(a)

Surfa

ce

Cross-section

(b)


(c)

Grain skin

Core

(d)


119903= 10∘Cmin 119905






4) the




119903=

10∘Cmin 119905119888= 60min)


Nickel(at)

Oxygen(at)

Phosphorous(at)

0 830 169 01300 991 08 01500 993 05 02700 994 03 03





(a) (b)

(c) (d)


∘C 119867119903= 10∘Cmin 119905













(a) (b) (c)


119903= 10∘Cmin 119905



0

40000

80000

120000

25 30 35 40 45 50 55 60 65Position


Ni

(2θ)

NiO

Cou

nt

Ni 12

P 5Ni 3P

Ni 2

P


119903= 10∘Cmin 119905





structure

4 Conclusions





119903= 10∘Cmin









2PO2as the



0010203040506070809

1

1 10 100 1000 10000 100000Incr

emen

talc

umul

ativ

e por

osity

Pore radius (nm)


(a)

0

02

04

06

08

1

12

1 10 100 1000 10000 100000Incr

emen

talc

umul

ativ

e por

osity

Pore radius (nm)


(b)


119903= 10∘Cmin 119905












Acknowledgments


References


















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





cell(see detail)

Outlet

Water bath

Wash heating

water

Metal solution

168

at 97∘C

(a)

A

A

B

B

C

C

D

D

EE

T

0 10(mm)

20

S



(b)








(a) (b)





of cases 119905119886= 60min












(a) (b)



20000

10000

0

Cou

nts

30 40 50 60


Peak list



16-npoCAF





2PO3







119886= 60min)




(a) (b)

(c) (d)







2P Ni12P5 and Ni

3P with the latter





Strands

(a) (b)

(c) (d)

(e)

Core material

Grain skin

(f)




at 119867119903= 10∘Cmin 119905


119903= 10∘Cmin


119903= 10∘Cmin 119905







(a) (b)


119903= 10∘Cmin





119886= 60min



119909layer





119909P119910











100000

50000

0

30 40 50 60

Cou

nts

02-npCAF








12P5 Ni3P and Ni

2P





119903= 10



000200400600800

100012001400160018002000

0 1000 2000 3000 4000 5000 6000 7000 8000 9000

Phos

phor

us (a

t)


P (31A-5)P (38A-4)P (G3-8)

P (P5)Series5






cooling in air







(a)

Surfa

ce

Cross-section

(b)


(c)

Grain skin

Core

(d)


119903= 10∘Cmin 119905






4) the




119903=

10∘Cmin 119905119888= 60min)


Nickel(at)

Oxygen(at)

Phosphorous(at)

0 830 169 01300 991 08 01500 993 05 02700 994 03 03





(a) (b)

(c) (d)


∘C 119867119903= 10∘Cmin 119905













(a) (b) (c)


119903= 10∘Cmin 119905



0

40000

80000

120000

25 30 35 40 45 50 55 60 65Position


Ni

(2θ)

NiO

Cou

nt

Ni 12

P 5Ni 3P

Ni 2

P


119903= 10∘Cmin 119905





structure

4 Conclusions





119903= 10∘Cmin









2PO2as the



0010203040506070809

1

1 10 100 1000 10000 100000Incr

emen

talc

umul

ativ

e por

osity

Pore radius (nm)


(a)

0

02

04

06

08

1

12

1 10 100 1000 10000 100000Incr

emen

talc

umul

ativ

e por

osity

Pore radius (nm)


(b)


119903= 10∘Cmin 119905












Acknowledgments


References


















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a) (b)





of cases 119905119886= 60min












(a) (b)



20000

10000

0

Cou

nts

30 40 50 60


Peak list



16-npoCAF





2PO3







119886= 60min)




(a) (b)

(c) (d)







2P Ni12P5 and Ni

3P with the latter





Strands

(a) (b)

(c) (d)

(e)

Core material

Grain skin

(f)




at 119867119903= 10∘Cmin 119905


119903= 10∘Cmin


119903= 10∘Cmin 119905







(a) (b)


119903= 10∘Cmin





119886= 60min



119909layer





119909P119910











100000

50000

0

30 40 50 60

Cou

nts

02-npCAF








12P5 Ni3P and Ni

2P





119903= 10



000200400600800

100012001400160018002000

0 1000 2000 3000 4000 5000 6000 7000 8000 9000

Phos

phor

us (a

t)


P (31A-5)P (38A-4)P (G3-8)

P (P5)Series5






cooling in air







(a)

Surfa

ce

Cross-section

(b)


(c)

Grain skin

Core

(d)


119903= 10∘Cmin 119905






4) the




119903=

10∘Cmin 119905119888= 60min)


Nickel(at)

Oxygen(at)

Phosphorous(at)

0 830 169 01300 991 08 01500 993 05 02700 994 03 03





(a) (b)

(c) (d)


∘C 119867119903= 10∘Cmin 119905













(a) (b) (c)


119903= 10∘Cmin 119905



0

40000

80000

120000

25 30 35 40 45 50 55 60 65Position


Ni

(2θ)

NiO

Cou

nt

Ni 12

P 5Ni 3P

Ni 2

P


119903= 10∘Cmin 119905





structure

4 Conclusions





119903= 10∘Cmin









2PO2as the



0010203040506070809

1

1 10 100 1000 10000 100000Incr

emen

talc

umul

ativ

e por

osity

Pore radius (nm)


(a)

0

02

04

06

08

1

12

1 10 100 1000 10000 100000Incr

emen

talc

umul

ativ

e por

osity

Pore radius (nm)


(b)


119903= 10∘Cmin 119905












Acknowledgments


References


















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a) (b)



20000

10000

0

Cou

nts

30 40 50 60


Peak list



16-npoCAF





2PO3







119886= 60min)




(a) (b)

(c) (d)







2P Ni12P5 and Ni

3P with the latter





Strands

(a) (b)

(c) (d)

(e)

Core material

Grain skin

(f)




at 119867119903= 10∘Cmin 119905


119903= 10∘Cmin


119903= 10∘Cmin 119905







(a) (b)


119903= 10∘Cmin





119886= 60min



119909layer





119909P119910











100000

50000

0

30 40 50 60

Cou

nts

02-npCAF








12P5 Ni3P and Ni

2P





119903= 10



000200400600800

100012001400160018002000

0 1000 2000 3000 4000 5000 6000 7000 8000 9000

Phos

phor

us (a

t)


P (31A-5)P (38A-4)P (G3-8)

P (P5)Series5






cooling in air







(a)

Surfa

ce

Cross-section

(b)


(c)

Grain skin

Core

(d)


119903= 10∘Cmin 119905






4) the




119903=

10∘Cmin 119905119888= 60min)


Nickel(at)

Oxygen(at)

Phosphorous(at)

0 830 169 01300 991 08 01500 993 05 02700 994 03 03





(a) (b)

(c) (d)


∘C 119867119903= 10∘Cmin 119905













(a) (b) (c)


119903= 10∘Cmin 119905



0

40000

80000

120000

25 30 35 40 45 50 55 60 65Position


Ni

(2θ)

NiO

Cou

nt

Ni 12

P 5Ni 3P

Ni 2

P


119903= 10∘Cmin 119905





structure

4 Conclusions





119903= 10∘Cmin









2PO2as the



0010203040506070809

1

1 10 100 1000 10000 100000Incr

emen

talc

umul

ativ

e por

osity

Pore radius (nm)


(a)

0

02

04

06

08

1

12

1 10 100 1000 10000 100000Incr

emen

talc

umul

ativ

e por

osity

Pore radius (nm)


(b)


119903= 10∘Cmin 119905












Acknowledgments


References


















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a) (b)

(c) (d)







2P Ni12P5 and Ni

3P with the latter





Strands

(a) (b)

(c) (d)

(e)

Core material

Grain skin

(f)




at 119867119903= 10∘Cmin 119905


119903= 10∘Cmin


119903= 10∘Cmin 119905







(a) (b)


119903= 10∘Cmin





119886= 60min



119909layer





119909P119910











100000

50000

0

30 40 50 60

Cou

nts

02-npCAF








12P5 Ni3P and Ni

2P





119903= 10



000200400600800

100012001400160018002000

0 1000 2000 3000 4000 5000 6000 7000 8000 9000

Phos

phor

us (a

t)


P (31A-5)P (38A-4)P (G3-8)

P (P5)Series5






cooling in air







(a)

Surfa

ce

Cross-section

(b)


(c)

Grain skin

Core

(d)


119903= 10∘Cmin 119905






4) the




119903=

10∘Cmin 119905119888= 60min)


Nickel(at)

Oxygen(at)

Phosphorous(at)

0 830 169 01300 991 08 01500 993 05 02700 994 03 03





(a) (b)

(c) (d)


∘C 119867119903= 10∘Cmin 119905













(a) (b) (c)


119903= 10∘Cmin 119905



0

40000

80000

120000

25 30 35 40 45 50 55 60 65Position


Ni

(2θ)

NiO

Cou

nt

Ni 12

P 5Ni 3P

Ni 2

P


119903= 10∘Cmin 119905





structure

4 Conclusions





119903= 10∘Cmin









2PO2as the



0010203040506070809

1

1 10 100 1000 10000 100000Incr

emen

talc

umul

ativ

e por

osity

Pore radius (nm)


(a)

0

02

04

06

08

1

12

1 10 100 1000 10000 100000Incr

emen

talc

umul

ativ

e por

osity

Pore radius (nm)


(b)


119903= 10∘Cmin 119905












Acknowledgments


References


















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





Strands

(a) (b)

(c) (d)

(e)

Core material

Grain skin

(f)




at 119867119903= 10∘Cmin 119905


119903= 10∘Cmin


119903= 10∘Cmin 119905







(a) (b)


119903= 10∘Cmin





119886= 60min



119909layer





119909P119910











100000

50000

0

30 40 50 60

Cou

nts

02-npCAF








12P5 Ni3P and Ni

2P





119903= 10



000200400600800

100012001400160018002000

0 1000 2000 3000 4000 5000 6000 7000 8000 9000

Phos

phor

us (a

t)


P (31A-5)P (38A-4)P (G3-8)

P (P5)Series5






cooling in air







(a)

Surfa

ce

Cross-section

(b)


(c)

Grain skin

Core

(d)


119903= 10∘Cmin 119905






4) the




119903=

10∘Cmin 119905119888= 60min)


Nickel(at)

Oxygen(at)

Phosphorous(at)

0 830 169 01300 991 08 01500 993 05 02700 994 03 03





(a) (b)

(c) (d)


∘C 119867119903= 10∘Cmin 119905













(a) (b) (c)


119903= 10∘Cmin 119905



0

40000

80000

120000

25 30 35 40 45 50 55 60 65Position


Ni

(2θ)

NiO

Cou

nt

Ni 12

P 5Ni 3P

Ni 2

P


119903= 10∘Cmin 119905





structure

4 Conclusions





119903= 10∘Cmin









2PO2as the



0010203040506070809

1

1 10 100 1000 10000 100000Incr

emen

talc

umul

ativ

e por

osity

Pore radius (nm)


(a)

0

02

04

06

08

1

12

1 10 100 1000 10000 100000Incr

emen

talc

umul

ativ

e por

osity

Pore radius (nm)


(b)


119903= 10∘Cmin 119905












Acknowledgments


References


















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a) (b)


119903= 10∘Cmin





119886= 60min



119909layer





119909P119910











100000

50000

0

30 40 50 60

Cou

nts

02-npCAF








12P5 Ni3P and Ni

2P





119903= 10



000200400600800

100012001400160018002000

0 1000 2000 3000 4000 5000 6000 7000 8000 9000

Phos

phor

us (a

t)


P (31A-5)P (38A-4)P (G3-8)

P (P5)Series5






cooling in air







(a)

Surfa

ce

Cross-section

(b)


(c)

Grain skin

Core

(d)


119903= 10∘Cmin 119905






4) the




119903=

10∘Cmin 119905119888= 60min)


Nickel(at)

Oxygen(at)

Phosphorous(at)

0 830 169 01300 991 08 01500 993 05 02700 994 03 03





(a) (b)

(c) (d)


∘C 119867119903= 10∘Cmin 119905













(a) (b) (c)


119903= 10∘Cmin 119905



0

40000

80000

120000

25 30 35 40 45 50 55 60 65Position


Ni

(2θ)

NiO

Cou

nt

Ni 12

P 5Ni 3P

Ni 2

P


119903= 10∘Cmin 119905





structure

4 Conclusions





119903= 10∘Cmin









2PO2as the



0010203040506070809

1

1 10 100 1000 10000 100000Incr

emen

talc

umul

ativ

e por

osity

Pore radius (nm)


(a)

0

02

04

06

08

1

12

1 10 100 1000 10000 100000Incr

emen

talc

umul

ativ

e por

osity

Pore radius (nm)


(b)


119903= 10∘Cmin 119905












Acknowledgments


References


















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




100000

50000

0

30 40 50 60

Cou

nts

02-npCAF








12P5 Ni3P and Ni

2P





119903= 10



000200400600800

100012001400160018002000

0 1000 2000 3000 4000 5000 6000 7000 8000 9000

Phos

phor

us (a

t)


P (31A-5)P (38A-4)P (G3-8)

P (P5)Series5






cooling in air







(a)

Surfa

ce

Cross-section

(b)


(c)

Grain skin

Core

(d)


119903= 10∘Cmin 119905






4) the




119903=

10∘Cmin 119905119888= 60min)


Nickel(at)

Oxygen(at)

Phosphorous(at)

0 830 169 01300 991 08 01500 993 05 02700 994 03 03





(a) (b)

(c) (d)


∘C 119867119903= 10∘Cmin 119905













(a) (b) (c)


119903= 10∘Cmin 119905



0

40000

80000

120000

25 30 35 40 45 50 55 60 65Position


Ni

(2θ)

NiO

Cou

nt

Ni 12

P 5Ni 3P

Ni 2

P


119903= 10∘Cmin 119905





structure

4 Conclusions





119903= 10∘Cmin









2PO2as the



0010203040506070809

1

1 10 100 1000 10000 100000Incr

emen

talc

umul

ativ

e por

osity

Pore radius (nm)


(a)

0

02

04

06

08

1

12

1 10 100 1000 10000 100000Incr

emen

talc

umul

ativ

e por

osity

Pore radius (nm)


(b)


119903= 10∘Cmin 119905












Acknowledgments


References


















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a)

Surfa

ce

Cross-section

(b)


(c)

Grain skin

Core

(d)


119903= 10∘Cmin 119905






4) the




119903=

10∘Cmin 119905119888= 60min)


Nickel(at)

Oxygen(at)

Phosphorous(at)

0 830 169 01300 991 08 01500 993 05 02700 994 03 03





(a) (b)

(c) (d)


∘C 119867119903= 10∘Cmin 119905













(a) (b) (c)


119903= 10∘Cmin 119905



0

40000

80000

120000

25 30 35 40 45 50 55 60 65Position


Ni

(2θ)

NiO

Cou

nt

Ni 12

P 5Ni 3P

Ni 2

P


119903= 10∘Cmin 119905





structure

4 Conclusions





119903= 10∘Cmin









2PO2as the



0010203040506070809

1

1 10 100 1000 10000 100000Incr

emen

talc

umul

ativ

e por

osity

Pore radius (nm)


(a)

0

02

04

06

08

1

12

1 10 100 1000 10000 100000Incr

emen

talc

umul

ativ

e por

osity

Pore radius (nm)


(b)


119903= 10∘Cmin 119905












Acknowledgments


References


















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a) (b)

(c) (d)


∘C 119867119903= 10∘Cmin 119905













(a) (b) (c)


119903= 10∘Cmin 119905



0

40000

80000

120000

25 30 35 40 45 50 55 60 65Position


Ni

(2θ)

NiO

Cou

nt

Ni 12

P 5Ni 3P

Ni 2

P


119903= 10∘Cmin 119905





structure

4 Conclusions





119903= 10∘Cmin









2PO2as the



0010203040506070809

1

1 10 100 1000 10000 100000Incr

emen

talc

umul

ativ

e por

osity

Pore radius (nm)


(a)

0

02

04

06

08

1

12

1 10 100 1000 10000 100000Incr

emen

talc

umul

ativ

e por

osity

Pore radius (nm)


(b)


119903= 10∘Cmin 119905












Acknowledgments


References


















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a) (b) (c)


119903= 10∘Cmin 119905



0

40000

80000

120000

25 30 35 40 45 50 55 60 65Position


Ni

(2θ)

NiO

Cou

nt

Ni 12

P 5Ni 3P

Ni 2

P


119903= 10∘Cmin 119905





structure

4 Conclusions





119903= 10∘Cmin









2PO2as the



0010203040506070809

1

1 10 100 1000 10000 100000Incr

emen

talc

umul

ativ

e por

osity

Pore radius (nm)


(a)

0

02

04

06

08

1

12

1 10 100 1000 10000 100000Incr

emen

talc

umul

ativ

e por

osity

Pore radius (nm)


(b)


119903= 10∘Cmin 119905












Acknowledgments


References


















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0010203040506070809

1

1 10 100 1000 10000 100000Incr

emen

talc

umul

ativ

e por

osity

Pore radius (nm)


(a)

0

02

04

06

08

1

12

1 10 100 1000 10000 100000Incr

emen

talc

umul

ativ

e por

osity

Pore radius (nm)


(b)


119903= 10∘Cmin 119905












Acknowledgments


References


















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials

















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



Documents

Research Article Preparation of Nanostructured Microporous