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A one step approach to prepare hybrid nanoparticle embedded polymer fibres using pressurised gyration is presented. Two types of novel antimicrobial nanoparticles and poly(methylmethacrylate) polymer were used in this work. X-ray diffraction analysis of the nanoparticles revealed Ag, Cu and W are the main elements present in them. The concentration of the polymer solution and the nanoparticle concentration had a significant influence on the fibre diameter, pore size and morphology. Fibres with a diameter in the range of 6-20μm were spun using 20wt% polymer solutions containing 0.1, 0.25 and 0.5 wt% nanoparticles under 0.3MPa working pressure and a rotational speed of 36,000rpm. Continuous, bead-free fibre morphologies were obtained for each case. The pore size in the fibres varied between 36 and 300nm. Successful incorporation of the nanoparticles in polymer fibres was confirmed by energy dispersive x-ray analysis. The fibres were also gyrospun on to metallic discs to prepare filters which were tested for their antibacterial activity on a suspension of Pseudomonas aeruginosa. Nanoparticle loaded fibres showed higher antibacterial efficacy than pure poly(methylmethacrylate) fibres.

This work focuses on forming bead on string poly(caprolactone) (PCL) by using gyration under pressure. The fibre morphology of bead on string is an interesting feature that falls between bead-free fibres and droplets, and it could be effectively controlled by the rheological properties of spinning dopes and the major processing parameters of the pressurised gyration system which are working pressure and rotating speed. Bead products were not always spherical in shape and tended to be more elliptical, therefore both their width and length were measured. The average bead width and length produced spanned a range 145-660μm and 140-1060μm, respectively. The average distance between two adjacent beads (i.e. inter-bead distance) and the bead size (width and length) are shown to be a function of processing parameters and polymer concentration. An interesting morphology i.e. beads with short fibre was observed when using a high polymer concentration. Bead on string structure agglomeration was promoted by a low polymer concentration. Formation of droplets or agglomerated bead on string is promoted below 5wt% polymer concentration, and beads with short fibre were present in the microstructure beyond a polymer concentration of 20wt%.

This paper reports for the very first time a facile and simple method, consisting of simultaneous centrifugal spinning and solution blowing, to mass produce ceramic fibres from preceramic polymers. Solutions of two different commercially available silicone resins and a mixture of a silicone resin and graphene were used, and a polymer (polyvynilpyrolidone) was added to aid the fibre generation process. The fibre diameter and the morphology of the spun and the pyrolysed fibres were shown to be influenced by rotating speed, working pressure and the polymer concentration. Non-porous fibres were obtained using a low volatility binary solvent system and, after pyrolysis at high temperature, dense SiOC ceramic fibre bundles were produced. This fabrication method based on pressurised gyration shows great promise in the mass production of ceramic fibre bundles.

The preparation of capsules for medical and industrial use can be achieved via several conventional routes, yielding either hard or soft receptacles, depending on the type and the content of the material to be encapsulated. Together with tablets, capsules are amongst the most commonly used means of administering medication and this makes progress in capsule preparation technology a key area of drug delivery research. Here we uncover new technology for the preparation of capsules with porous chambers. The novelty is signified in the use of an electrohydrodynamic process engineering route and its potential is elucidated using a polymeric material; polymethylsilsesquioxane, which can be converted into an identical ceramic form by means of simple pyrolysis. Thus, both polymeric and ceramic capsules have been prepared. The effects of process control parameters such as the applied voltage and flow rate, on the characteristics of the capsules prepared are discussed.

Porous polymeric near-spherical capsules, ~ 3.6 mm in diameter, were prepared using an electrodydrodynamic process. These capsules were pyrolysed to porous ceramics, ~ 3 mm in diameter. The ceramic capsules had interconnected pores of ~ 1.3 μm in size, and large cells with a mean size of 28 μm. The larger pores resemble the cells in a typical ceramic foam and were evenly distributed throughout the structure. A large proportion of the ceramic capsules contained 65-70% porosity, and their compressive strength was 0.2-0.4 MPa. © 2008 Elsevier B.V. All rights reserved.

Nanometre hydroxyapatite (nHA) coated metallic materials have been successfully used for bone tissue implantation for several decades now due to its sound biological and mechanical properties. The microstructure and surface topography of the implant material are well-known to play a crucial role in influencing cellular responses to implants and bone tissue regeneration ultimately. Recently, a novel jet-based patterning technique, template-assisted electrohydrodynamic atomisation (TAEA) spraying, has been devised to prepare depositions with defined surface topography for guiding the cellular response. In this study, an improvement investigation of this patterning process was carried out to precisely control the nHA surface structure in terms of geographies and dimensions via an angular needle jetting during the patterning process. More importantly, the mechanism of such improvement of the TAEA patterning technique was also discussed and uncovered. A range of diverse nHA surface structures with high-resolution was therefore achieved, which paves the way for the research of the new generation implant materials with defined cellular response.

The biological performance of orthopaedic and oral metallic implants can be enhanced significantly by the application of bioactive coatings. In this work, a cost-efficient alternative to the traditional technique to produce a hydroxyapatite (HA) coating with a nanostructured feature onto a metallic implant surface at room temperature via electrospray deposition, is presented. To evaluate the bioactive capacity of these nanoHA (nHA) coatings in vitro, an acellular simulated body fluid soaking experiment and a human osteoblast (HOB) cell culture work were conducted. Under these physiological conditions, the accelerated apatite precipitation process occurred on the nHA-coated titanium surfaces as compared to the uncoated titanium surfaces. HOB cells developed mature cytoskeletons with distinct evidence of actin stress fibres and vinculin adhesion plaques, on these nHA coatings. Hence, this deposition technique holds great potential in producing high quality nHA coatings for biomedical applications. (C) 2010 Elsevier B.V. All rights reserved.

A novel class of ultra-thin fibres, which affect microbial growth, were explored. The microbial properties of poly(methyl methacrylate) fibres containing 2, 4 and 8 wt% of graphene nanoplatelets (GNPs) were studied. GNPs were dispersed in a polymeric solution and processed using pressurized gyration. Electron microscopy was used to characterize GNP and fibre morphology. Scanning electron microscopy revealed the formation of beaded porous fibres. GNP concentration was found to dictate fibre morphology. As the GNP concentration increased, the average fibre diameter increased from 0.75 to 2.71 µm, while fibre porosity decreased. Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa were used to investigate the properties of 2, 4 and 8 wt% GNP-loaded fibres. GNP-loaded fibres (0 wt%) were used as the negative control. The fibres were incubated for 24 h with the bacteria; bacterial colony-forming units were enumerated by adopting the colony-counting method. The presence of 2 and 4 wt% GNP-loaded fibres promoted microbial growth, while 8 wt% GNP-loaded fibres showed antimicrobial activity. These results indicate that the minimum inhibitory concentration of GNPs required within a fibre is 8 wt%.

Spark plasma sintering has been used for the first time to prepare the ASTM F75 cobalt–chromium–molybdenum (Co–Cr–Mo) orthopaedic alloy composition using nanopowders. In the preliminary work presented in this report, the effect of processing variables on the structural features of the alloy (phases present, grain size and microstructure) has been investigated. Specimens of greater than 99.5 per cent theoretical density were obtained. Carbide phases were not detected in the microstructure but oxides were present. However, harder materials with finer grains were produced, compared with the commonly used cast/wrought processing methods, probably because of the presence of oxides in the microstructure.

Template-assisted electrohydrodynamic atomisation (TAEA) spraying of nanometer-sized siliconsubstituted hydroxyapatite (nanoSiHA) was used to pattern implant surfaces for guided cell growth to improve the repair and regeneration of medical implants. A suspension of nanoSiHA was prepared and characterized. Patterns of pillars and tracks of various dimensions were prepared using the suspension. It was found that the resolution of the pattern was affected by TAEA processing parameters, such as applied voltage, flow rate, distance between needle and substrate, and spray time. Fifteen minutes spraying time provided the most clear and uniform patterned topography with a distance between nozzle and substrate of 50mm and a flow rate of 4?l/min. Therefore, well-defined nanoSiHA patterns can be achieved by TAEA deposition, it thus offers great potential for patterning the surface of medical implants.

A novel nanocomposite polymer with a polycarbonate soft segment (PCU) and polyhedral oligomeric silsesquioxanes (POSS) nanoparticle (POSS-PCU) has been selected for a synthetic heart valve due to its superior biocompatibility and in vivo biostability. However, the development of synthetic heart valves from polymeric materials requires an understanding of the basic mechanical and surface properties of the polymer. In this study, the mechanical properties of POSS-PCU, including tensile strength, tear strength and hardness, were tested and compared to control (PCU). The surface property was analyzed using contact angle measurement and the resistance to platelet adhesion was also investigated. POSS-PCU (hardness 84+/-0.8 Shore A) demonstrated significantly higher tensile strength 53.6+/-3.4 and 55.9+/-3.9Nmm(-2) at 25 and 37 degrees C, respectively) than PCU (33.8+/-2.1 and 28.8+/-3.4Nmm(-2) at 25 and 37 degrees C, respectively). Tensile strength and elongation at break of POSS-PCU was significantly higher than PCU at both 25 and 37 degrees C (P0.001). POSS-PCU showed a relatively low Young's modulus (25.9+/-1.9 and 26.2+/-2.0Nmm(-2)) which was significantly greater in comparison with control PCU (9.1+/-0.9 and 8.4+/-0.5Nmm(-2)) at 25 and 37 degrees C, respectively, with 100mum thickness. There was no significant difference (P0.05) in tear strength between POSS-PCU and PCU at 25 degrees C. However, tear strength increased significantly (P0.001) (at 37 degrees C) as the thickness increased from 100microm (51.0+/-3.3Nmm(-1)) to 200microm (63+/-1.5Nmm(-1)). The surface of POSS-PCU was significantly less hydrophilic than that of PCU.

The gradation of porosity in a biomaterial can be very useful for a variety of medical engineering applications such as filtration, bone replacement and implant development. However, the preparation of such structures is not a technologically trivial task and replication methods do not offer an easy solution. In this work, we elucidate the preparation of structures having a graded porosity by electrohydrodynamic spraying, using zirconia (ZrO 2 ), which is widely used in biomedical and other applications. The processes are generic and can be achieved using other bioactive ceramics with similar particle characteristics. The pores on the sprayed surface, the innermost surface and lengthwise cross sections have been analysed in addition to the change in depth of penetration as a function of spraying time. Control of porosity, pore size and depth of penetration has been obtained by varying parameters such as the spraying time, sintering temperature and the sacrificial template. It has been possible to obtain structures with interconnected pore networks of pore size greater than 100 μm as well as scattered pores smaller than 10 μm in size.

Apatite nanocrystals, which mimic the dimensions of natural bone mineral, were electrosprayed on glass substrates, as a suitable synthetic biomedical material for osteoblast outgrowth was explored. A variety of topographic patterns were deposited and the influence of these designs on osteoblast alignment and cell differentiation was investigated. Patterned cell growth and enhanced cell differentiation were seen. Osteoblasts were also cultured on apatite nanocrystals chemically modified with either carbonate or silicon ions. Enhanced cell proliferation and early formation of mineral nodules were observed on apatite nanocrystals with silicon addition. This work highlights the importance of the combined effects of surface topography and surface chemistry in the guidance of cell behaviour.

Fine nanoapatite relics were deposited on glass substrates by electrohydrodynamic atomisation, using nanohydroxyapatite (nHA), nano-carbonated hydroxyapatite (nCHA) and nanosilicon- substituted hydroxyapatite (nSiHA) suspensions. These electrosprayed nanoapatites were evaluated in-vitro using simulated body fluid (SBF) and human osteoblast (HOB) cells. The SBF study revealed that newly-formed apatite layers were observed on the surface of the relics. Furthermore, enhanced HOB cell growth was observed on each of the nanoapatites at all time points. Hence, this work demonstrated that electrosprayed nanoapatites offer considerable potential as biomaterials.

The ability to create patterns of bioactive nanomaterials particularly on metallic and other types of implant surfaces is a crucial feature in influencing cell response, adhesion and growth. In this report, we uncover and elucidate a novel method that allows the easy deposition of a wide variety of predetermined topographical geometries of nanoparticles of a bioactive material on both metallic and non-metallic surfaces. Using different mesh sizes and geometries of a gold template, hydroxyapatite nanoparticles suspended in ethanol have been electrohydrodynamically sprayed on titanium and glass substrates under carefully designed electric field conditions. Thus, different topographies, e.g. hexagonal, line and square, from hydroxyapatite nanoparticles were created on these substrates. The thickness of the topography can be controlled by varying the spraying time.

Direct writing, consisting of the directed deposition of individual droplets of ceramic suspension using ink jet printing can be used to produce piezoelectric structures with feature sizes in excess of 100 μm. This work presents an alternative direct writing technique, consisting of directed individual droplets produced by electrohydrodynamic atomisation (EHDA), where feature sizes an order of magnitude smaller can be achieved. This technique opens up the possibility of using direct writing technology to produce integrated MEMS devices. Low toxicity lead zirconate titantate (PZT) sol has been used in conjunction with the EHDA process to produce isolated features and lines with dimensions as small as 20 μm. These features, when fired, form the perovskite PZT crystal structure. Using an X–Y stage to move the sample, it is possible to create a variety of structures.

Preparation of hydroxyapatite coated custom-made metallic bone-implants is very important for the replacement of injured bones of the body. Furthermore, these bone-implants are more stable under the corrosive environment of the body and biocompatible than bone-implants made up of pure metals and metal alloys. Herein, we describe a novel, simple and low-cost technique to prepare biocompatible hydroxyapatite coated titanium metal (TiM) implants through growth of self-formed TiO2 thin-layer (SFTL) on TiM via a heat treatment process. SFTL acts as a surface binder of HA nanoparticles in order to produce HA coated implants. Colloidal HA nanorods prepared by a novel surfactant-assisted synthesis method, have been coated on SFTL via atomized spray pyrolysis (ASP) technique. The corrosion behavior of the bare and surface-modified TiM (SMTiM) in a simulated body fluid (SBF) medium is also studied. The highest corrosion rate is found to be for the bare TiM plate, but the corrosion rate has been reduced with the heat-treatment of TiM due to the formation of SFTL. The lowest corrosion rate is recorded for the implant prepared by heat treatment of TiM at 700 °C. The HA-coating further assists in the passivation of the TiM in the SBF medium. Both SMTiM and HA coated SMTiM are noncytotoxic against osteoblast-like (HOS) cells and are in high-bioactivity. The overall production process of bone-implant described in this paper is in high economic value.

Nano-sized HA (nHA) was applied to the surface of glass and titanium substrates using electrostatic atomisation spray (EAS) deposition. The phase purity of nHA was confirmed by X-ray diffraction. The nHA suspension consisted of rod–like particles 20-30nm in width and 50-100nm in length. The viscosity and conductivity of nHA suspension were 321 mPa s and 5.6 x 10-4 S/m, respectively. EAS of nHA in cone-jet mode was achieved at flow rate of 10-9 m3s-1 with the applied voltage between the needle and the ring-shaped ground electrode of ~6 kV. Micrometer- to submicrometerscaled nHA islands were successfully deposited on the substrate surface. Image analysis showed that the area percentage of nHA increased with deposition time, it covered 50% of the surface area after 10s of spraying. Partial dissolution of nHA was observed after immersion in deionised water for 1 month, particularly on the submicrometer sized nHA islands. Formation of a bone-like apatite layer was found after incubation in simulated body fluid (SBF K9) for 5 days, indicating the high bioactivity of the nHA deposits. In vitro culture with human osteoblast cells showed that the nHA islands were able to support the growth of HOB cells during 7 days of culture; the HOB cell activity increased with culture time as well as EAS deposition time. Immunofluorescence study showed that HOB cells expressed well-organised actin stress fibres on nHA deposited surfaces after 3 days of culture. The result indicated that nHA deposition provided more favourable surfaces for cell attachment. Therefore, electrostatic atomization spray deposition of nHA offers great potential for the creation of bioactive surfaces on bioinert implant surface to provide improved interfacial bonding with host tissues.

In this work we demonstrate a novel method of preparing composite ceramic microstructures, using alumina–zirconia as an example. Suspensions of these two ceramics, containing a similar solids content, were simultaneously subjected to electrohydrodynamic atomization (EHDA) in the stable cone-jet mode and the resulting relics were analyzed by microscopical techniques before and after partial sintering at 1200°C. We show that the new method, coaxial EHDA (CEHDA), is capable of forming different annular microstructures, which are mainly controlled by the speed of the jetting.

A general equation applicable to a sphere, an infinite plate, and an infinite cylinder is used to calculate the transient diffusion of degradation product in a ceramic molding during pyrolysis. The solution includes the concentration-dependent diffusion coefficient for diffusion of monomer in its parent polymer which forms the continuous phase in the ceramic in the as-molded state. In the early stages of pyrolysis, before continuous porosity has developed, the model searches for the critical heating rate above which defects are produced. Reasonable agreement is obtained with experimentally measured critical heating rates for 3-mm-thick plates.

A ceramic ink that contains 30 vol% of zirconia in butyl acetate and 2 wt% of a commercial oligomeric dispersant is considered. The dispersion and viscosity of this ink was optimized in previous work; however, its conductivity is too low for continuous ink-jet printing. The conductivity has been improved by the addition of ethanol and ammonium nitrate, but this addition detrimentally affects the dispersion, viscosity, and surface tension of the ink. This problem has been largely overcome by reducing the amount of ceramic in the ink. The ceramic inks that have been developed are tested in a pressurized, continuous ink-jet printer, and, depending on their performance, the ink composition is modified further.

Different amounts (0.5-10.0 wt%) of an oligomeric dispersant were added to a ceramic ink containing 30 vol% of zirconia in butyl acetate, The sediment packing densities of the resulting suspensions were measured. The viscosities of the suspensions were determined using a syringe that was adapted as a capillary viscometer suitable for the measurement of the low viscosities encountered (up to 400 mPa . s). The highest sediment-packing density coincided with the lowest viscosity and occurred when 1-2 wt% of dispersant, based on the ceramic, was added. Investigation of the supernatant of the suspensions by thermogravimetric analysis indicated that this amount corresponded to the highest level of adsorption of the dispersant on the ceramic. The sediment from this suspension yielded a high density on subsequent sintering.

This paper describes the preparation of ceramic inks for forming ceramic components by multilayer printing using a continuous-ink-jet printer. The selection of appropriate binders and dispersants combined with high shear and ultrasonic mixing has enabled zirconia-containing inks to be printed successfully to produce 2.5 mm thick bars. Printing trials show that the method of dispersion of the ceramic powder in the ink is decisive for accurate ink droplet positioning. The quality of the vertical walls and the top surface of the bars are related closely to the rate of drying of each printed layer. Inks with higher ceramic volume loadings (up to 10%) were also studied and produced useful information for further investigations.

An alumina suspension, containing ∼20 vol.% of powder was pumped through a needle held at a high voltage, with respect to a point-like ground electrode, and subjected to electrostatic atomisation. The flow rate and voltage was varied between 10−9 and 10−8 m3 s−1, and 5 and 12 kV, respectively and the mode of atomisation observed was recorded to construct mode selection (M-S) maps. In the stable cone-jet mode, the jet diameter was measured as a function of flow rate and applied voltage. Alumina relics obtained in the stable cone-jet mode regime were collected and studied by optical microscopy to establish the conditions which generated the finest relics.

Solid-state magic angle spinning nuclear magnetic resonance (MAS NMR), X-ray diffraction (XRD), and scanning electron and transmission electron microscopy (SEM and TEM) are used to study thermal degradation of a Si−Al−C−O ceramic precursor in nitrogen. A polysilane (PS) and aluminum acetylacetonate (AlAce) in the weight ratio AlAce/PS = 2 were reacted to synthesize the precursor. Solid state 29Si and 27Al MAS NMR spectra of the precursor confirm the occurrence of chemical reactions between PS and AlAce during synthesis. A complete three-dimensional Si−O−Al network forms at 900 °C. Crystalline phases appear at 1300 °C, and the pyrolyzed product at 1700 °C is a solid solution of 2H−SiC and AlN. Solid state 29Si and 27Al MAS NMR and XRD provide detailed information about the phase formation and transformation. The morphological development and microstructure evolution are further characterized by SEM and TEM.

Over the past two decades it has been established that bone repair in the presence of implant materials can be optimized by control of their surface chemistry. Certain calcium phosphate materials are similar in composition to bone mineral and have been found to be osteoconductive [1–3]. These ceramic materials have therefore been developed as biomaterials for a range of different applications. However, although they promote direct bone apposition, their mechanical properties are relatively poor compared with other monolithic ceramics. Therefore, classes of applications have been developed to exploit the excellent biological properties of the materials while maintaining mechanically viable implants [4, 5]. There is now increasing evidence that surface topography both on the micro and nano-scale are important in determining the cell response to biomaterials [6– 11]. A number of studies have indicated that cell activity can be up-regulated through optimization of the surface properties of the substrate. Investigations originally concentrated on surface features of several tens of micrometers in scale, but more recently, evidence suggests that surface topography at a much finer scale may influence the cell response. Hydroxyapatite (HA) has been used in a number of different forms and several powder processing routes have been investigated in conjunction with HA [12– 18]. The application of jet-based suspension processing methods, such as ink-jet printing (IJP) [19, 20] and electrostatic atomization printing (EAP) [21, 22] allows solid freeforming of fine structures of advanced materials. In particular, EAP in the cone-jet mode enables the formation of

Several alumina suspensions were subjected to electrostatic atomisation at a constant applied voltage and constant flow rate. Various spray modes were observed and the sizes of droplets produced from each suspension were measured using laser diffraction. The sizes of relics obtained by depositing these droplets on a silicone release paper substrate were measured using optical microscopy. Using volume equivalence the relic sizes were used to calculate the size of the droplets, thus allowing a comparison with the laser diffraction results. The calculated and measured droplet distributions showed excellent agreement.

This paper describes the methodology for simulating a reprographic ink with a ceramic ink based on a commercially available zirconia powder for direct ceramic ink-jet printing. Of over-riding importance was matching viscosity and this was tested systematically by using a mineral oil–hexane binary system. Of secondary importance was adjustment of the pressure defect behind the nozzle to compensate for small differences in surface tension. The inks tested in the wide array print-head were based on low electrical conductivity liquids to avoid damage to the electroding system. The organic binder for the zirconia ink was paraffin wax and the dispersant was a hydroxystearic acid based polyester.

Ceramic ink droplets have been deposited on two fundamentally different types of substrate and the evolution of contact angle, width of the ink–substrate interface and droplet height was measured as a function of time from digital images of the droplet captured on video. On substrate type I, with a lower surface free energy than the surface tension of the ceramic ink, after reaching stability in a few seconds, the contact angle decreased and the width of the ink–substrate interface remained stationary. Subsequently, the contact angle stayed constant and thereafter reduced again, while the width of the ink–substrate interface decreased and remained constant thereafter. On substrate type II, with a higher surface free energy than the surface tension of the ceramic ink, stability was achieved instantaneously and the contact angle decreased rapidly, while the width of the ink–substrate interface increased initially but thereafter remained constant. The corresponding variation of droplet height due to spreading and evaporation, and volume shrinkage rate were also found to be much faster on the type–II substrate.

A novel computer-controlled method of depositing ceramic droplets, according to a pre-determined architecture is described. A 21 vol% alumina suspension flowing through a nozzle was subjected to electrostatic atomization in the cone-jet mode at different applied voltages. By using a point-like ground electrode the resulting spray was focused and printed on a substrate placed between the nozzle and the ground electrode. The substrate was moved with the aid of a 2-axis computer controlled stepper motor driven system which enabled the forming of different ceramic architectures. As an example, the word CERAMIC was printed. At an applied voltage of 10 kV, droplet relics in the print were in the size range 30–60 µm.

A solution of a polymeric precursor for silicon carbide (SiC) was subjected to electrostatic atomization in the cone-jet mode to spray droplets on a zirconia substrate. The resulting deposit was heated to 1300 °C to obtain SiC relics. Precursor and ceramic relics were characterized by microscopy. The size distribution of the droplet relics was studied at several flow rates of the solution to the electrostatic atomization chamber. The results show that by controlling the flow rate SiC relics approximately 5 μm in diameter can be produced.

A high performance 500 nozzle in-line piezoelectric drop-on-demand print-head mounted on a linear table with z-axis control was used to prepare arrays of fine ceramic pillars. Such structures may find applications in miniature heat exchangers, catalyst supports, for cell up-regulation in prosthetics or in polymer-ceramic piezoelectric 1–3 composites. The ink conveyed 14 vol% fine zirconia and deposited a wax-based suspension in an octane-alcohol mixture. The dried ink contained 63 vol% zirconia.

An organic gold precursor was dissolved to form a jet printing ink and deposited using a modified IBM piezoelectric drop-on-demand printer. The substrates were glass slides, glazed tiles and alumina plates. On firing in air, at temperatures below 500 °C, the gold pattern was developed on the substrate by decomposition of the organometallic compound to form tracks that were electrically conducting. The best quality conducting tracks were obtained on glazed tile or glass. The problems that can attend this process have been identified and include spreading and blistering of thick films on pyrolysis and delamination on cooling caused partly by differential thermal contraction. The thickness of the gold was 1.4 μm per layer of deposition.

An alumina slurry containing 21 vol% solids was subjected to electrostatic atomization in the cone-jet mode producing droplets in the size range 0.5–53 μm. Polyurethane foam was exposed to this electrospray and pyrolyzed to prepare open-cell alumina foam. Scanning electron microscopy showed that the struts of the ceramic foam produced did not contain holes or cracks and the total porosity of the foam was ∼96%. A hollow porous house and a twisted artefact was produced using the electrosprayed foam.

The juxtaposition of direct ceramic ink-jet printing with high throughput screening, data-mining and interpretation methods using artificial neural networks is bringing to the ceramics community a capability for combinatorial analysis presently enjoyed mainly by the pharmaceutical industry. This paper attempts to set out the potential and scope for high speed, high resolution sample preparation, high throughput screening and informatics-driven local optimisation methods. It describes the distinct philosophical basis for this approach to discovery and identifies it as primarily Baconian. It examines in detail the aspirating-dispensing systems being used for ceramic sample preparation from powder suspensions, explores their likely strengths and limitations and how these may be mitigated through the application of sophisticated computational methods.

Silicon carbide (SiC) coatings and films have been prepared for the first time by electrostatic atomization of a solution of a polymeric precursor and deposition on to alumina and zirconia substrates. The deposits were heated to 1300 degreesC prior to their examination by X-ray energy-dispersive spectra and selected-area diffraction in scanning and transmission electron microscopes. The results show that these coatings and films are crystalline and probably consist of co-existing alpha -SiC and beta -SiC phases.

A ceramic ink was prepared, characterised, and subjected to continuous ink-jet printing. The optimum modulation frequency for printing was estimated. The surface free energies of several substrates were determined and different patterns of the ink droplets were printed on these. Phenomena occurring during the process were investigated. The drop-by-drop resolution and ink spreading were found to be dependent on the dispersive/total surface free energy ratio of the substrates. Ink drying was accompanied by powder migration in the droplets deposited on substrates with a surface free energy lower than the surface tension of the ink. Printing of multiple layers was accompanied by the appearance of ridges, splattering, and non-vertical walls. The causes of these phenomena are discussed in this paper.

A polysilane solution used as a silicon carbide (SiC) precursor was mixed with different amounts of titanium carbide (TiC) powder and open cell polyurethane (PU) foams were dipped in these suspensions. The resulting pre-foams were pyrolyzed at 900°C in nitrogen and then heated further at various temperature between 1100 and 1600°C in the same atmosphere to produce SiC–TiC composite foams. The evolution of the composite foams has been studied using thermogravimetry and X-ray diffraction. The PU foam, pre-foams and the SiC–TiC composite foams were characterized by optical and scanning electron microscopy. These studies show that the pre-foams retained their shape well during pyrolysis and the composite foams produced consist of an open cell structure and hole-free solid struts. Prevention of cracking in the foams were dependent on the TiC content. The shrinkage observed during the conversion of the pre-foams to the composite ceramic foams can be controlled by varying the TiC content and the sintering temperature.

A polysilane was used as the precursor for silicon carbide (SiC) and different amounts of it was dissolved in dichloromethane. Subsequently, between 10 to 80 %wt of alumina (Al2O3) powder was added into the solutions to make SiC-Al2O3 suspensions. Cubes of polyurethane (PU) foams with open cells in the size range 500-1200μm were soaked in these suspensions and pyrolysed in flowing nitrogen to produce SiC-Al2O3 composite foams. Some foams were heated further in nitrogen to 1300°C. The foams produced consist of an open cell structure and hole-free solid struts which were also cracks free in the polysilane-Al2O3 80:2Owt% formulation. The retention of shape during processing was excellent. Shrinkage observed after pyrolysis and further heating the foams was measured and can be controlled by varying the Al2O3 content. The foams produced have porosities in the range 87 to 95%. The maximum compressive strength of the pyrolysed foams prepared using the polysilane-Al2O3 80:20 wt% formulation was 2.3MPa.

A new method of forming silicon carbide–silicon nitride composite foams is presented. These are prepared by immersing a polyurethane foam in a polysilane precursor solution mixed with Si3N4 powder to form a pre-foam followed by heating it in nitrogen at >900°C. X-ray diffraction patterns indicate that a SiC–Si3N4 composite was formed after sintering the ceramic foam at >1500°C. Micrographs show that most of these foams have well-defined open-cell structures and macro-defect free struts. The shrinkage is reduced considerably due to the addition of Si3N4 particles.

Several new polycyclodisilazanes with different molecular structures were synthesized and characterized using gel permeation chromatography and Fourier-transform infrared spectroscopy. All the polymers synthesized were tractable. The pyrolysis of these polymers at 900°C in nitrogen in a thermal balance indicated that the ceramic yields were very dependent on the compositions of the precursors. The polycyclodisilazanes with reactable groups (Si–H, N–H) showed higher ceramic yields due to the cross-linked structures formed during pyrolysis. The pyrolyzed residues were crystallized by heating to >1500°C. X-Ray diffraction of the crystallized residues showed that they were mixtures containing silicon nitride and silicon carbide. Chemical analysis of one crystallized residue which gave the highest ceramic yield showed that it contained 70 wt% Si3N4 and 25 wt% SiC after heat treatment at 1600°C. The compositions of the ceramic residues produced depended on the compositions of the polymeric precursors. More silicon carbide was formed in the residues derived from the polymers with phenyl group substituents.

A new method that can be used for the synthesis of SiC-Si3N4 composites using a single polymeric precursor is described. A co-polysilane-cyclodisilazane precursor was prepared and characterized. Subsequently, it was heated to 1650oC to form SiC and Si3N4 simultaneously. The ceramic products have been characterized using X-ray diffraction and secondary-ion mass spectrometry.

Three strategies for the synthesis of silicon carbide–silicon nitride composites from organosilicon preceramic polymers were investigated. Firstly, polymeric precursors with reactive groups for silicon carbide and silicon nitride were synthesized, blended and pyrolyzed. Secondly, a polymeric precursor for silicon carbide was mixed with silicon powder which acts as a reactive filler and the resulting mixtures were pyrolyzed. Thirdly, a co-polycyclodisilazane–silane single polymeric precursor was synthesized and pyrolyzed. The precursors and the various stages of processing were studied using gel permeation chromatography, Fourier transform-infrared spectroscopy, thermo-mechanical analysis, thermogravimetry and X-ray diffraction. In each instance silicon carbide–silicon nitride composites were prepared successfully.

Polycarbosilane was synthesised directly from chloromethyltrichlorosilane and specimens were heat treated at 200, 300 and 400°C in nitrogen. The as-synthesised polymer and heat treated specimens were characterised using infra-red and Fourier transform infra-red spectroscopy, solid-state nuclear magnetic resonance and differential scanning calorimetry and were also subjected to thermogravimetric analysis in nitrogen. All types of specimens were pyrolysed in nitrogen at 1500°C. The ceramic residue obtained from thermogravimetric and pyrolysis experiments was characterised using X-ray diffraction and scanning electron microscopy. Heating the polymer before pyrolysis improved significantly the yield of the ceramic but the gain beyond 200°C was minimal. It was shown that the heat treatment initially caused the as-synthesised polymer to lose volatile oligomers and subsequently to cross-link. Pyrolysis at 900°C and subsequent crystallisation by further heating to 1500°C of the cross-linked polymer produced homogeneous and fine grained silicon carbide.

Several polysilanes with different overall functionalities have been synthesized and pyrolyzed to produce porous silicon carbide. The polysilanes and their ceramic products have been characterized using gel permeation chromatography, Fourier transform-infrared spectroscopy, thermogravimetry, X-ray diffractometry and microscopy. Some products were foams while others were micro-porous ceramics. The effect of the final pyrolytic yield on the Type of ceramic produced, its pore structure and shape retention are discussed. Two polysilanes were blended in various ratios to control the pyrolysis process more precisely. This allowed the Type, shape and pore-structure of the silicon carbide produced to be controlled more efficiently. There exists a relationship between the composition and structure of the precursors and their final pyrolytic yield and this determines the Type, shape retainability and pore structure of the ceramics produced. In this work, precursors or their blends which gave a final pyrolytic yield of 50–60 wt % produced the best silicon carbide foams.

In this paper a novel and versatile 3D print-patterning technique coupling electrohydrodyanmics and a specially designed and constructed plotting device is elucidated. This unit is capable of free-forming advanced ceramics and we demonstrate this by using it to print-pattern a 5mm × 5mm × 1mm walled zirconia structure layer by layer. The wall thickness achieved is ~150$m, almost half that of similar structures prepared using ink-jet printing. The as-printed structure was studied by scanning electron microscopy and some of its typical features are discussed and related to the forming process.

A mechanically-ground doped ceria powder with 10 mol% SmO1.5 was incorporated by high shear mixing into a polystyrene-based organic vehicle. At 45 vol.% solids loading, the suspension could be subjected to elongational flow processes and was prepared in thin film form by tubular film blowing; the manufacturing process used to make thermoplastic polymer film. This provides a potential route for the manufacture of ceramic electrolyte plates for solid oxide fuel cells for which doped ceria is a candidate material. After sintering, film thickness down to 50 μm could be achieved with relative densities >95%. The main problem with this route is in retaining flatness of films of less than 100 μm in thickness during sintering; a problem which exists whatever the particle assembly route.

Several polysilanes, including two groups of copolymers and a group of ter-polymers, with overall functionalities ranging between 2 and 3 were prepared using the alkali metal dechlorination reaction. The yields of the soluble solid fractions of these polymers (the potential ceramic precursor) were in the range 40–70% wt and decreased with increasing overall functionalities in both cases of co- and terpolymers. The molecular weights and FT-IR spectra of the precursors have been determined and the ceramic in the residue after pyrolysis has been identified as silicon carbide. The pyrolytic yield can be increased by using a polymeric precursor of higher overall functionality. The reasons for this are discussed with reference to pyrolysis mechanisms. In particular, some of the ter-polymeric precursors synthesised with a high yield also give a high yield on pyrolysis due to the presence of branched structures and potential cross-linking sites.