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An investigation has been carried out into the production of tungsten oxide coatings from tungstic chloride and tungstic acid precursors, via a sol–gel type process, using various combinations of ethanediol and block co-polymers as stabilising additives to achieve microstructural control. The products were characterised by scanning electron microscopy, X-ray diffraction, FTIR spectroscopy and thermal analysis, with colour changes investigated by UV/Vis spectroscopy. Strongly photochromic transparent coatings were successfully prepared by the reaction of tungstic acid under basic conditions in the presence of ethanediol.

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.

Different dispersants were used to develop ethanol-based silver inks for continuous ink-jet printing. Inks were made using varying amounts of dispersant and silver. Various parameters, such as sedimentation behaviour, sediment volume, half-value time and viscosity, were used to assess the dispersion and stability of these inks over 10 days.

Two types of polymeric precursors for silicon carbide (SiC) were dissolved in dichloromethane. Subsequently, between 10–80 wt% of silicon nitride (Si3N4) and titanium carbide (TiC) powder were added separately into the solutions to make SiC-Si3N4 and SiC-TiC suspensions. Cubes of polyurethane (PU) foams were soaked in precursor solution and suspensions and pyrolyzed in flowing nitrogen to produce SiC, SiC-Si3N4 and SiC-TiC composite foams. Some foams were heated further in nitrogen to 1600°C. Shrinkage observed after pyrolysis and further heating the foams was measured and can be reduced by varying the concentration of polymeric precursor, Si3N4 and TiC content. The foams produced have porosities in the range 85–96%. The average compressive strength of the foams is in the range of 1.1–1.6 MPa.

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.

Cisplatin forms the basis for many chemotherapy regimens, however the maximum permissible dose is limited by its systemic toxicity. Nanoencapsulation of drugs has been shown to reduce off-target side effects and can potentially improve treatment burden on patients. However, uptake of nanoformulations at tumor sites is minimal without some form of active delivery. We have developed a submicron, polymeric nanoparticle based on biocompatible and degradable poly(lactic-co-glycolic acid) (PLGA) capable of encapsulating cisplatin and which can be bound to the surface of a phospholipid coated microbubble. The acoustic behavior and stability of the resulting nanoparticle loaded microbubbles will be compared with those of unloaded microbubbles. Results will also be presented on the extravasation of particles in a tissue mimicking phantom using a novel long working distance confocal microscope that enables particle distributions to be measured in situ and in real time.

Polymeric nanofibers are a fascinating class of material that has been widely used in a myriad of applications, including fiber reinforced composites, protective clothing, and chemical sensors. Here, the science of the combined application of external pressure, controlled infusion of polymer solution and gyration, which allows mass production of uniform polymeric nanofibers in a single step, is uncovered. Using poly(ethylene oxide) as an example this study shows the use of this novel method to fabricate polymeric nanofibers and nanofibrous mats under different combinations of processing parameters such as working pressure (1 × 105 to 3 × 105 Pa), rotational speed (10 000–36 000 rpm), infusion rate (500–5000 µL min−1), and fiber collection distance (4–15 cm). The morphologies of the nanofibers are characterized using scanning electron microscopy and anisotropy of alignment of fiber is studied using 2D fast Fourier transform analysis. A correlation between the product morphology and the processing parameters is established. The produced fibers are in a range of 50–850 nm at an orifice-to-collector distance of 10 cm. The results indicate that the pressure coupled infusion gyration (PCIG) offers a facile way for forming nanofibers and nanofiber assemblies.

A one-pot single-step novel process has been developed to form microbubbles up to 250 μm in diameter using a pressurized rotating device. The microbubble diameter is shown to be a function of rotational speed and working pressure of the processing system, and a modified Rayleigh-Plesset equation has been derived to explain the bubble-forming mechanism. A parametric plot is constructed to identify a rotating speed and working pressure regime, which allows for continuous bubbling. Bare protein (lysozyme) microbubbles generated in this way exhibit a morphological change, resulting in microcapsules over a period of time. Microbubbles prepared with gold nanoparticles at the bubble surface showed greater stability over a time period and retained the same morphology. The functionalization of microbubbles with gold nanoparticles also rendered optical tunability and has promising applications in imaging, biosensing, and diagnostics.

Nanoparticles are considered to be one of the most advanced tools for drug delivery applications. In this research, alginate (a model hydrophilic polymer) nanoparticles 80 to 200 nm in diameter were obtained using microbubble bursting. The natural process of bubble bursting occurs through a number of stages, which consequently produce nano- and microsized droplets via two main production mechanisms, bubble shell disintegration and a jetting process. In this study, nano-sized droplets/particles were obtained by promoting the disintegrating mechanism and suppressing (limiting) the formation of larger microparticles resulting from the jetting mechanism. A T-junction microfluidic device was used to prepare alginate microbubbles with different sizes in a well-controlled manner. The size of the bubbles was varied by controlling two processing parameters, the solution flow rate and the bubbling pressure. Crucially, the bubble size was found to be the determining factor for inducing (or limiting) the bubble shell disintegration mechanism and the size needed to promote this process was influenced by the properties of the solution used for preparing the bubbles, particularly the viscosity. The size of alginate nanoparticles produced via the disintegration mechanism was found to be directly proportional to the viscosity of the alginate solution.

Bovine serum albumin (BSA) microbubbles were generated using coaxial electrohydrodynamic atomization (CEDHA) using various concentrations of BSA solutions. The bubble characteristics and the long-term stability of the microbubbles were studied through adjustment of processing parameters and the collection media. Bubbles in the range of 40–800 µm were obtained in a controlled fashion, and increasing the flow rate of the BSA solution reduced the polydispersity of the microbubbles. Use of distilled water–glutaraldehyde, glycerol, and glycerol–Tween 80 collection media allowed a remarkable improvement in bubble stability compared to BSA solution collection medium. Possible physical mechanisms were developed to explain the stability of the microbubbles. The collection distance showed a marked influence on stability of the microbubbles. Near-monodisperse particle-reinforced microbubbles were formed with various concentrations of 2,2'-azobis(isobutyramidine) dihydrochloride (AIBA)–polystyrene particle in BSA solution. The bubble size and the size distribution showed negligible change over a period of time irrespective of the concentration of particles at the bubble surface. The compression stiffness of the microbubbles was determined using nanoindentation at ambient temperature and showed that the stiffness of the microbubbles increased from 8 N/m to 20 N/m upon changing the concentration of BSA solution from 5 wt % to 15 wt %.

Itraconazole is widely used as an anti-fungal drug to treat infections. However, its poor aqueous solubility results in low bioavailability. The aim of the present study was to improve the drug release profile by preparing surface itraconazole adsorbed polymethylsilsesquioxane (PMSQ) nanospheres using a V-junction microfluidic (VJM) device. In order to generate nanospheres with rough surface, the process flow rate of perfluorohexane (PFH) was set between 50 and 300 μl min(-1) while the flow rate of PMSQ and itraconazole solution were constant at 300 μl min(-1). Variations in the PFH flow rate enable the controlled size generation of nanospheres. PMSQ nanospheres adsorbing itraconazole were characterized by SEM, FTIR and Zetasizer. The release of itraconazole from PMSQ nanosphere surface was measured using UV spectroscopy. Nanosphere formulations with a range of sphere size (120, 320 and 800 nm diameter) were generated and drug release was studied. 120 nm itraconazole coated PMSQ nanospheres were found to present highest drug encapsulation efficiency and 13% drug loading in a more reproducible manner compared to 320 nm and 800 nm sized nanosphere formulations. Moreover, 120 nm itraconazole coated PMSQ nanospheres (encapsulation efficiency: 88%) showed higher encapsulation efficiency compared to 320 nm (encapsulation efficiency: 74%) and 800 nm (encapsulation efficiency: 62%) sized nanosphere formulations. The itraconazole coated PMSQ nanospheres were prepared continuously at the rate of 2.6 × 10(6) per minute via VJM device. Overall the VJM device enabled the preparation of monodisperse surface itraconazole adsorbed nanospheres with controlled in vitro drug release profile.

Microparticles of Celecoxib, dispersed in a matrix of poly(lactic-co-glycolic acid) (PLGA), were pre- pared by electrospraying using different solvent mixtures to investigate the influence upon particle formation and the resulting particle characteristics. Mixtures consisting of a good solvent, acetone, and an anti-solvent, methanol, for PLGA were studied in different ratios. Properties of the spraying solutions were examined and the resulting mi- croparticles were characterized with regard to size, mor- phology, porosity, solid state form, surface chemistry and drug release. Particle formation was strongly influenced by the polymer molecular conformation during droplet for- mation and by the anti-solvent concentration during droplet drying. A strong correlation was found between particle morphology and the solubility of the polymer in the solvent mixtures. The lack of chain entanglements in droplets containing anti-solvent resulted in compact polymer conformation and grain-like particle morphology. Further, the early precipitation of polymer and low chain interaction with increasing content of anti-solvent resulted in surface enrichment of drug (from 10 and 20 % up to 41 and 57 % respectively), also demonstrated by the increasingly higher drug release rates. The results demonstrate the importance of solvent composition in particle preparation and indicate potential for exploiting this dependence to improve phar- maceutical particle design and performance.

Synthetic hydroxyapatite (HA) nanoparticles, that mimic natural HA, are widely used as biocompatible coatings on prostheses to repair and substitute human bones. In this study, HA nanoparticles are prepared by precipitating them from a precursor solution containing calcium sucrate and ammonium dihydrogen orthophosphate, at a Ca/P mole ratio of 1.67:1, at temperatures, ranging from 10°C to 95°C. A set of products, prepared at different temperatures, is analyzed for their crystallinity, crystallite size, morphology, thermal stability and composition, by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and Fourier transform infrared (FT-IR) spectroscopic techniques, while the other set is analyzed after calcining the respective products, soon after their synthesis, for 3h, at 700°C. The as-prepared products, after 2h of drying, without any calcination, are not crystalline, but they grow very slowly into needle-like morphologies, as they are ripened with time. The percentage crystallinity of the final products increases from 15% to 52%, with increasing the preparative temperature. The calcined samples always produce spherical nanoparticles of essentially the same diameter, between 90 nm and 100 nm, which does not change due to aging and preparative temperatures. Therefore, the same method can be utilized to synthesize both spherical and needle-like nanoparticles of hydroxyapatite, with well-defined sizes and shapes. The ability to use readily available cheap raw materials, for the synthesis of such well-defined crystallites of hydroxyapatite, is an added advantage of this method, which may be explored further for the scaling up of the procedures to suit to industrial scale synthesis of such hydroxyapatite nanoparticles.

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.

A simple method was developed to produce silicon carbide foams using polysilane polymeric precursors. Polyurethane foams were immersed in polysilane precursor solutions to prepare pre-foams. Subsequently, these were heated in nitrogen at different temperatures in the range of 900°C to 1300°C. The silicon carbide foams produced in this manner showed well-defined open-cell structures and the struts in the foams were free of voids. The shrinkage which accompanies pyrolysis of the pre-foams was reduced with increasing the concentration of the polymeric precursor solutions.

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.

Some microstructural elements, such as microtwins in tetragonal ZrO 2 grains (t-ZrO 2 ), were identified in a plasma-sprayed ZrO 2 -Y 2 O 3 -TiO 2 coating by using transmission electron microscopy. These elements are similar to those described in plasma-sprayed ZrO 2 -Y 2 O 3 coatings and are characteristic of nontransformable t-ZrO 2 . This microstructure could promote some toughening mechanisms. The monoclinic ZrO 2 phase (m - ZrO 2 ), produced by a martensitic transformation of the metastable t-ZrO 2 phase, also was observed. The variation in the concentration of Ti in the ZrO 2 -Y 2 O 3 -TiO 2 coating body was found to be appreciable. The energy-dispersive spectroscopic analyses showed that a high concentration of Ti was associated with t-ZrO 2 whereas a relatively lower content of Ti was found in m-ZrO 2 . ZrO 2 -Y 2 O 3 -TiO 2 thermally treated at 1400 and 1600°C showed signs of grain growth. A higher incidence of m- and t-ZrO 2 twins indicated higher constraints of the polycrystalline structure as a result of the grain growth and rapid cooling rate.

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.

A printing device, which operates on an electrohydrodynamic principle, was used to deposit 100 layers of a 10 vol% zirconia suspension. Thus, a wall ∼100 μm in thickness was freeformed. The wall thickness achieved in this work is almost 30% less than that of similar structures built by ink-jet printing and therefore we demonstrate a novel print deposition based solid freeform fabrication method, which can be developed further for preparing fine ceramic structures.

Several polymer processing techniques, such as extrusion, injection molding, vacuum forming, blow molding and film blowing can be used to mass produce complex shape components from engineering ceramic powders with a high degree of dimensional accuracy and good process control. In these processes the ceramic powder is dispersed in one or several additive(s), usually polymeric. These additives are only useful as the vehicle of the forming process and therefore have to be removed subsequently whilst retaining the architecture of the ceramic particle assembly which is densified by the conventional process of sintering. The removal of the additives, usually referred to as the debinding stage, is carried out usually by slow heating (thermolysis) to about 400°C. This is a crucial and a difficult stage as many unforgiving strength-limiting defects could appear during thermolysis. Defects which occur during thermolysis are difficult to prevent because these can be caused by several factors. Several variab...

Ceramic electrolytes based on yttria-stabilized zirconia (YSZ) are the state-of-the-art for the production of solid oxide fuel cells (SOFCs). However, the cells must operate in the temperature range 800 to 1,000 C to achieve acceptable efficiencies and are limited in the choice of electrode materials and fabrication methods if undesirable reactions between the electrolyte and electrodes are to be avoided. In order to design optimum structures for SOFCs, and to be able to make predictions of service life-times, it is necessary to have reliable data on the mechanical properties of the component materials. There is little information on the fracture properties of doped-ceria ceramics in the published literature. The present study is an investigation of the fracture toughness of well-characterized samples of samaria-doped ceria ceramics, with compositions typical of those of interest for SOFC electrolytes, using both indentation fracture and single-edge notched beam (SENB) techniques. The materials studied here were all ceria solid solutions with the cubic fluorite structure and so were not expected to display anomalous K{sub c} values due to transformation toughening effects.

Recently jet printers have been used in this laboratory for solid freeforming of ceramics. The development of ceramic inks, which are well-dispersed dilute suspensions of powder in a liquid carrier, is a critical stage of this process. The ink is put through the printer to directly print ceramic shapes. The conductivity of the ink is a crucial parameter for most jet printing operations. Several ceramic inks have been prepared and characterized. Their conductivities have been measured using a standardized cell. Several ceramic inks that can be used in direct ceramic jet printing have been developed.

The formulation of a stabilized ceramic ink and the adaptation of a piezoelectric-activated drop- on-demand jet printer with a 65 mm nozzle for the direct solid freeforming of ceramics by multilayer jet printing is reported. The procedure has exciting implications for the miniaturization of ceramic circuits and for the fabrication of solid oxide fuel cells, ordered ceramic composites and small monolithic ceramic components of complex shape.

A lead zirconate titanate (PZT) sol was subjected to electrohydrodynamic atomization in the stable cone-jet mode. The droplets generated were sized by laser diffraction before deposition and heating to 600 °C. The droplets were 20–35 μm in size and transmission electron microscopy showed that their relics consisted of PZT powder particles

This work investigates the rheology and spinning of starch and starch-loaded poly(ethylene oxide) (PEO) by pressurised gyration in order to prepare nanofibres. The spinning dope's rheological properties played a crucial role in fibre formation. Newtonian behaviour is observed in 1–20 wt% starch suspensions and non-Newtonian behaviour is found in all the PEO–starch mixtures. Pressurised gyration of the starch suspensions produced beads only but PEO–starch mixtures generated fibres. The fibre diameter of the PEO–starch samples is shown to be a function of polymer concentration and rotating speed of the gyration system. Fibre formation can only be facilitated below a certain working pressure. The concentration of starch in the PEO–starch mixtures is crucial in defining whether beaded or continuous fibres were generated and this is related to the composition of the spinning dope. FT-IR, XRD and microscopy studies indicated very good miscibility of starch and PEO in the nanofibres. The storage modulus of the PEO–starch were also studied as a function of temperature (30–150 °C) and showed interesting results but it was not possible to deduce general trends valid for the entire temperature range.

One of the hallmarks of urinary tract infection, a serious global disease, is its tendency to recur. Uropathogenic bacteria can invade cells lining the bladder, where they form longer-term intracellular reservoirs shielded from antibiotics, re-emerging at a later date to initiate flare-ups. In these cases, only lengthy systemic antibiotic treatment can eradicate all the reservoirs. Yet, long courses of antibiotics are not ideal, as they can lead to side effects and an increase in antibiotic resistance. Moreover, most antibiotics lose some potency by the time they reach the bladder, and many cannot permeate cells, so they cannot access intracellular reservoirs. Here, using coaxial electrohydrodynamic forming, we developed novel core–shell capsules containing antibiotics as a prototype for a future product that could be infused directly into the bladder. Gentamicin was encapsulated in a polymeric carrier (polymethylsilsesquioxane) and these capsules killed Enterococcus faecalis , a common chronic uropathogen, in vitro in a dose-responsive, slow-release manner. Capsules containing a fluorescent tracer dye in place of gentamicin penetrated human bladder cells and released their dye cargo with no apparent toxicity, confirming their ability to successfully permeate cells. These results suggest that such antibiotic capsules could prove useful in the treatment of recalcitrant UTI.

Levator palpebrae superioris (LPS) is a muscle responsible for lifting the upper eyelid and its malfunction leads to a condition called "ptosis", resulting in disfigurement and visual impairment. Severe ptosis is generally treated with "brow-suspension" surgery, whereby the eyelid is cross-connected to the mobile tissues above the eyebrow using a cord-like material, either natural (e.g. fascia lata harvested from the patient) or a synthetic cord. Synthetic brow-suspension materials are widely used, due to not requiring the harvesting of fascia lata that can be associated with pain and donor-site complications. The mechanical properties of some commonly-used synthetic brow-suspension materials were investigated--namely, monofilament polypropylene (Prolene®), sheathed braided polyamide (Supramid Extra® II), silicone frontalis suspension rod (Visitec® Seiff frontalis suspension set), woven polyester (Mersilene® mesh), and expanded polytetrafluoroethylene (Ptose-Up). Each material underwent a single tensile loading to the failure of the material, at three different displacement rates (1, 750 and 1500 mm/min). All the materials exhibited elastic-plastic tensile stress-strain behaviour with considerable differences in elastic modulus, ultimate tensile strength, elastic limit and work of fracture. The results suggest that, as compared to other materials, the silicone brow-suspension rod (Visitec® SFSS) might be the most suitable, providing relatively long-lasting stability and desirable performance. These findings, together with other factors such as commercial availability, cost and clinical outcomes, will provide clinicians with a more rational basis for selection of brow-suspension materials.

PURPOSE: To produce electrospun polymeric fibrous wound dressing patches that can release the antibiotic drug amoxicillin in a controlled manner. METHODS: Poly(D,L-lactide-co-glycolide) acid (PLGA) fibrous dressings with entrapped amoxicillin were produced by electrospinning. The morphology and successful entrapment of amoxicillin in the PLGA fibrous dressings were validated by scanning electron microscopy (SEM) and Fourier Transform Infrared (FTIR) spectroscopy. The rate of drug release from the dressing patches was measured in various media for a period of 21 days using UV spectroscopy. RESULTS: PLGA fibres entrapping amoxicillin were collected for 300 s and then cut to form square patches with an average weight of 55 mg. Each dressing patch contained ~2 mg of amoxicillin. The mean fibre diameter was 2.2 ± 0.4 μm. The drug release from the PLGA dressings was found to be different for each medium during the 21-day release period with the highest and lowest concentration of drug released observed when the dressings were immersed in simulated body fluid (SBF) and phosphate buffered saline (PBS), respectively. CONCLUSIONS: The release profiles obtained in this study and the well-established biocompatibility of PLGA indicate that the fibre-based patches with entrapped amoxicillin fabricated in this work are very well suited for applications in wound healing and infection control.

It is well established that three-dimensional honeycomb-like nanofibrous structures enhance cell activity. In this work, we report that electrospun polymer nanofibres self-assemble into three-dimensional honeycomb-like structures. The underlying mechanism is studied by varying the polymer solution concentration, collecting substrates and working distance. The polymer solution concentration has a significant effect on the size of the electrospun nanofibres. The collection substrate and working distance affect the electric field strength, the evaporation of solvent and the discharging of nanofibres and consequently these two had a significant influence on the self-assembly of nanofibres.

A new route consisting of simultaneous centrifugal spinning and solution blowing to form polymer nanofibers is reported. The fiber diameter (60-1000 nm) is shown to be a function of polymer concentration, rotational speed, and working pressure of the processing system. The fiber length is dependent on the rotational speed. The process can deliver 6 kg of fiber per hour and therefore offers mass production capabilities compared with other established polymer nanofiber generation methods such as electrospinning, centrifugal spinning, and blowing.

A mathematical model is developed to quantify the degradation of binder used for plastic forming of ceramic components and the mass transport of the degradation products. A fully-implicit finite-difference method is used to obtain numerical solutions of a non-linear differential equation governing the degradation rate, diffusion coefficient and concentration. It is able to predict the critical linear heating rate below which defects due to boiling can be avoided. Examples are given to illustrate the use of the model to investigate the effect of ceramic powder, supporting powder bed and binder properties on the critical heating rate.

A thermal barrier coating comprising a zirconia-yttria-titania ceramic coat deposited by plasma spraying on an alloy steel substrate using an NiCrAlCoY intermediate bond coat has been soaked at various temperatures in the range 700–1400 °C and cooled to room temperature in static air. Some thermal treatments were also carried out in an argon atmosphere. Scanning electron microscopy (SEM) studies show that a discontinuous thickness of the bond coat is the reason for the failure of the coating due to thermal treatment. The phase transformations and microstructural changes due to thermal treatment have been investigated using X-ray diffraction and SEM. Thermal treatment did not affect the monoclinic phase of the ZrO 2 content present in the ceramic coat. In the case of thermal treatment in air and argon (below 800 °C) the cubic→tetragonal phase transformation occurred. The appearance of the fracture surfaces of the ceramic coat suggests that interlamellar fracture in the as-sprayed condition changed to intralamellar fracture after thermal treatment below 1200 °C. At higher temperatures the fractures were intergranular in appearance. Reasons for these changes in the appearance of the fracture surfaces are suggested with reference to the microstructure. Microstructural investigations also show some changes in the area of porosity distribution of the ceramic coat. Thermal treatment heals some pores, but other voids appear (cracking of the coating).

The mass transport during pyrolysis of the degradation product of a polymeric binder used for ceramic molding is analyzed. Two series resistances to transport are incorporated: the diffusion of the product of degradation through its parent polymer during decomposition and the permeation of vapor through a static powder bed used to support the molding. The model predicts the critical rate of heating, Z(c), above which defects caused by boiling of the organic phase occur at the center of the molding. For the system modeled, the permeability of the powder bed has little effect on Z(c) if the moldings are small but this is not the case for large moldings where well-packed fine powders should be avoided and the thickness of the powder bed should be kept to a minimum.