Search

To improve the damping properties of rubbers, organic tackifiers such as hydrocarbon resins, rosin esters, and polyterpenes are often incorporated to increase the intermolecular friction of the rubber, thus increasing the energy dissipation (damping) during dynamic loading. However, this is often at the expense of the cross-linking density and mechanical properties of the rubbers. Ionic cross-links introduce unique properties to rubbers, such as a combination of mechanical reinforcement and high extensibility, as well as self-healing and damping, thanks to the reversible ionic association. Hence creating an ionic network would be an interesting alternative to adding small molecular tackifiers to rubbers. The reversible ionic association inevitably causes structural instability over time (i.e., creep) or at elevated temperatures (ionic transition generally happens at 60–80 °C). To balance the dynamic damping, viscoelasticity, and mechanical stability of these materials, we prepared 1-vinyl imidazole modified brominated poly(isobutylene-co-isoprene) (BIIR) elastomers by solid-state rubber compounding and curing processes, and we investigated the effects of ionic networks and an aliphatic petroleum resin (C5) on the viscoelastic and electromechanical properties of the ionic-cross-linked elastomers. We found that the mechanical reinforcement can be achieved simultaneously with a broad effective damping temperature range through optimizing the ionic network and C5 concentrations. The polar ionic clusters also increased the dielectric permittivity while maintaining a low dielectric loss of the elastomers. The ionic modified BIIR exhibited actuation and energy harvesting properties similar to those of the commercial VHB-4910 elastomer under similar configurations, which provides alternative dielectric elastomers with reprocessability for vibration and energy harvesting applications.\ud \ud

Crack initiation and propagation in a peroxide-cured polybutadiene rubber reinforced with silanised silica nanofiller were studied under a cyclic loading condition. The fatigue properties of the semi-transparent rubber samples were tested at a constant strain amplitude, test frequency and temperature. Initiation and subsequent growth of cracks in the rubber samples were observed using an optical microscope as a function of the number of cycles until the rubber samples failed, indicating that there are two distinct stages in the fatigue failure of the rubber vulcanisate. The cracks were initiated after the rubber was flexed for about 2817 cycles and then the cracks grew from 500 μm and reached to a critical length of 4.6 mm and followed a further 897 cycles, leading to a catastrophic failure of the rubber samples. Correlation between the rate of crack growth, dc/dn, and the strain energy release rate, T, was investigated using the power law index, and a new expression for the measurement of the cyclic fatigue life of the rubber vulcanisate was proposed.

Star copolymers with good film-forming and mechanical properties were in situ synthesized for fabricating proton exchange membranes. The monomers of 3,4-diaminobenzoic acid were first grafted onto glycidyl-polyhedral oligomeric silsesquioxane (G-POSS) cores and then propagated to the poly(2,5-benzimidazole) (ABPBI) chains. The introduction of the star copolymer improves the movement of the ABPBI polymer chains, resulting in a lower internal viscosity and larger free volume that favor increased membrane flatness and absorbilities of water and phosphoric acid molecules, respectively. It was found that the star copolymers with 1.0 wt% of incorporated POSS (ABPBI-1.0POSS) had the best balance of the acid retentivity and film-forming property as well as mechanical properties that are desirable for proton exchange membranes without PA loss operating at high temperatures. The enhanced cell performance characteristics obtained using the ABPBI-1.0POSS-based membranes indicate that star copolymers are promising materials for use in high-temperature proton exchange membrane fuel cells.

Developmental engineering (DE) aims to culture mammalian cells on corresponding modular scaffolds (scale: micron to millimeter), then assemble these into functional tissues imitating natural developmental biology processes. This research intended to investigate the influences of polymeric particles on modular tissue cultures. When poly(methyl methacrylate) (PMMA), poly(lactic acid) (PLA) and polystyrene (PS) particles (diameter: 5–100 µm) were fabricated and submerged in culture medium in tissue culture plastics (TCPs) for modular tissue cultures, the majority of adjacent PMMA, some PLA but no PS particles aggregated. Human dermal fibroblasts (HDFs) could be directly seeded onto large (diameter: 30–100 µm) PMMA particles, but not small (diameter: 5–20 µm) PMMA, nor all the PLA and PS particles. During tissue cultures, HDFs migrated from the TCPs surfaces onto all the particles, while the clustered PMMA or PLA particles were colonized by HDFs into modular tissues with varying sizes. Further comparisons revealed that HDFs utilized the same cell bridging and stacking strategies to colonize single or clustered polymeric particles, and the finely controlled open pores, corners and gaps on 3D-printed PLA discs. These observed cell–scaffold interactions, which were then used to evaluate the adaptation of microcarrier-based cell expansion technologies for modular tissue manufacturing in DE.

In traditional ceramic processing techniques, high sintering temperature is necessary to achieve fully dense microstructures. But it can cause various problems including warpage, overfiring, element evaporation, and polymorphic transformation. To overcome these drawbacks, a novel processing technique called “cold sintering process (CSP)” has been explored by Randall et al. CSP enables densification of ceramics at ultra-low temperature (⩽300°C) with the assistance of transient aqueous solution and applied pressure. In CSP, the processing conditions including aqueous solution, pressure, temperature, and sintering duration play critical roles in the densification and properties of ceramics, which will be reviewed. The review will also include the applications of CSP in solid-state rechargeable batteries. Finally, the perspectives about CSP is proposed.

There are very few studies that have investigated directly the effect of an oxide film on tin whisker growth, since the ‘cracked oxide theory’ was proposed by Tu in 1994. The current study has inve...

To broaden the operating temperature range of phosphoric acid (PA) doped polybenzimidazole membrane-based proton exchange membrane fuel cells (PEMFCs) toward low temperatures, a novel series of poly(2,5-benzimidazole) (ABPBI)/sulfonated sepiolite (S-Sep) composite membranes (ABPBI/S-Sep) with low PA doping levels (DLs) were prepared via in-situ synthesis. The desirably enhanced mechanical, thermal, and oxidative stabilities of ABPBI/S-Sep composite membranes were achieved by constructing ABPBI chains arranged along the sepiolite (Sep) fibers and acid-base crosslinks formed between S-Sep fibrous particles and ABPBI chains. Benefiting from the richness of high temperature stable bound water and the excellent water absorbability of Sep particles that enable the formation of additive proton conducting paths, the composite membranes retained bounded PA and achieved much higher proton conductivities under both anhydrous and hydrous conditions compared to PA-doped ABPBI membranes. Proton conductivity values above 0.01 S/cm at 40–90 °C/20–98% RH conditions and 90–180 °C/anhydrous conditions as well as peak power density of 0.13 and 0.23 W/cm2 at 80 and 180 °C with 0% RH, respectively from the ABPBI/2S-Sep composite membrane are more holistic compared to Nafion at low temperatures and polybenzimidazole-based membranes at high temperatures, respectively. The excellent properties of ABPBI/S-Sep composite membranes suggest them as prospective candidates for PEMFCs applications in a wide temperature range.

Tissue engineering (TE) was initially designed to tackle clinical organ shortage problems. Although some engineered tissues have been successfully used for non-clinical applications, very few (e.g., reconstructed human skin) have been used for clinical purposes. As the current TE approach has not achieved much success regarding more broad and general clinical applications, organ shortage still remains a challenging issue. This very limited clinical application of TE can be attributed to the constraints in manufacturing fully functional tissues via the traditional top–down approach, where very limited cell types are seeded and cultured in scaffolds with equivalent sizes and morphologies as the target tissues. The newly proposed developmental engineering (DE) strategy towards the manufacture of fully functional tissues utilises a bottom–up approach to mimic developmental biology processes by implementing gradual tissue assembly alongside the growth of multiple cell types in modular scaffolds. This approach may overcome the constraints of the traditional top–down strategy as it can imitate in vivo-like tissue development processes. However, several essential issues must be considered, and more mechanistic insights of the fundamental, underpinning biological processes, such as cell–cell and cell–material interactions, are necessary. The aim of this review is to firstly introduce and compare the number of cell types, the size and morphology of the scaffolds, and the generic tissue reconstruction procedures utilised in the top–down and the bottom–up strategies; then, it will analyse their advantages, disadvantages, and challenges; and finally, it will briefly discuss the possible technologies that may overcome some of the inherent limitations of the bottom–up strategy.

For the application of proton exchange membrane fuel cells (PEMFCs) in a wide temperature range, an ionogel incorporated into poly(2,5-benzimidazole) (ABPBI) membranes with low phosphoric acid doping levels was designed. The natural sepiolite was first acid-treated to obtain one-dimensional silicon nanorods (SNRs) with a large specific surface area and a hierarchical porous structure. The SNRs were then filled with imidazolium ionic liquid (IL) to prepare IL@SNR ionogels. Analysis of related spectra and thermal behavior verified that the IL molecules were confined in the inner channels of SNRs. The as-prepared IL@SNRs were embedded in the ABPBI to form composite membranes (ABPBI/IL@SNRs) via in situ synthesis. By immobilizing proton conductors, the ABPBI/IL@SNR composite membranes markedly improved proton conductivity with low phosphoric acid doping levels in a wide temperature range. A single-cell based on 5 wt% IL@SNRs embedded in a composite membrane achieved a maximum power density of 0.15 and 0.28 W cm−2 at 80 °C and 180 °C, respectively, with 0% RH. The proton conductivities were comparable to those of Nafion-based PEMFCs under the same temperature and humidity conditions and competed with those of reported polybenzimidazole–inorganic composite membrane-based PEMFCs at high temperatures. By using a facile method to prepare nanostructured fillers, the strategy of avoiding proton carrier wastage can be potentially used in the production of high-performance membranes for PEMFCs.

Antiplasticization of glassy polymers, arising from the addition of small amounts of plasticizer, was examined to highlight the developments that have taken place over the last few decades, aiming to fill gaps of knowledge in the large number of disjointed publications. The analysis includes the role of polymer/plasticizer molecular interactions and the conditions leading to the cross-over from antiplasticization to plasticization. This was based on molecular dynamics considerations of thermal transitions and related relaxation spectra, alongside the deviation of free volumes from the additivity rule. Useful insights were gained from an analysis of data on molecular glasses, including the implications of the glass fragility concept. The effects of molecular packing resulting from antiplasticization are also discussed in the context of physical ageing. These include considerations on the effects on mechanical properties and diffusion-controlled behaviour. Some peculiar features of antiplasticization regarding changes in Tg were probed and the effects of water were examined, both as a single component and in combination with other plasticizers to illustrate the role of intermolecular forces. The analysis has also brought to light the shortcomings of existing theories for disregarding the dual cross-over from antiplasticization to plasticization with respect to modulus variation with temperature and for not addressing failure related properties, such as yielding, crazing and fracture toughness.

Novel organic-inorganic composites were in-situ synthesized by using TriSilanolPhenyl polyhedral oligomeric silsesquioxane (SO-POSS) as fillers and poly(2,5-benzimidazole) (ABPBI) as polymer matrix. The uniformly dispersed 3% SO-POSS particles in ABPBI matrix increased the thermal stability of the composite membranes. It was found that both the water and H3PO4 uptakes were increased significantly with the addition of SO-POSS due to the formation of hydrogen bonds between the POSS and H2O/H3PO4, which played a critical role in the improvement of the conductivity of the composite membranes at temperature over 100 °C. Proton conductivities of H3PO4 doped with 3wt% SO-POSS contained ABPBI membranes increased with the increase of H3PO4 absorbance, reaching the maximum proton conductivity of 2.55 × 10-3 S·cm-1 at 160 °C, indicating that the ABPBI/SO-POSS composite membrane could be a promising candidate for mid-temperature PEMFCs.

In this study，nanocomposites of LaCePr-oxide (LCP) and Ni 0.8 Co 0.15 Al 0.05 LiO 2-δ (NCAL) with different contents of polyvinylidene fluoride (PVDF) were prepared and applied to solid oxide fuel cells. The composite materials were characterized by X-ray diffraction analysis (XRD), scanning electron microscope (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and electrochemical impedance spectrum (EIS). The effect of PVDF concentration on the conductivity and performance of the fuel cells was investigated. It was found that PVDF plays a template role of pore forming in the nanocomposites, and the changed microstructure by as-formed pores greatly influences the electrochemical property of the nanocomposites. The cell with 3 wt% PVDF heat-treated at 210 °C achieved the highest power density of 982 mW cm −2 at 520 °C, which enhanced performance by more than 57% than when no heat-treatment was implemented. It is 66% higher than the cell with no PVDF and no heat-treatment. Pores formed by PVDF after heat-treatment enlarged the triple phase boundary (TPB), which results in improved fuel cell performance.

Phosphoric acid doped polybenzimidazoles are among the most interesting proton exchange membrane materials for high temperature proton exchange membrane fuel cell applications. As a major challenge the proton conducting decline due to free phosphoric acid leaching during the long term fuel cell operation is addressed by fixing overmuch phosphoric acid in the polymer matrix. Novel organic-inorganic composite membranes are prepared via in situ synthesis of poly(2,5-benzimidazole) (ABPBI) and OctaAmmonium POSS (AM-POSS) hybrid composites (ABPBI/AM-POSS) following phosphoric acid doping and membrane casting procedures. Compared with the pristine ABPBI membrane, the introduction of AM-POSS into ABPBI polymer membrane caused water and phosphoric acid absorbilities increasing dramatically, resulting in the significant increase of proton conductivities at whether hydrous or anhydrous condition. ABPBI/3AM composite membranes with phosphoric acid uptake above 250% showed best proton conductivities from room temperature to 160 °C, indicating these composite membranes could be excellent candidates as a polymer electrolyte membrane for low and intermediate temperature applications.

Although the investigation of thermal damage in composite materials has increased, the short-term thermal degradation and decomposition mechanisms in a non-oxidative environment have not been well established, as the reported thermal damage results were heavily influenced by the analyses of delicately collected volatiles and the presence of oxygen. The aim of this study, using scanning electron microscopy, Fourier transform infrared spectroscopy and thermogravimetry, along with kinetics, was to develop a post-mortem solid residual-based microscopic characterising methodology for thermal damage in carbon/epoxy composites induced by simulated lightning strikes. Fibre tufting, resin sublimation and discolouration were found to represent the severity of damage in three damage zones. Whilst fibre tufting was caused not by thermal sublimation but by returning shock waves, resin sublimation and discolouration were dominated by Joule heating. The carbon concentration in the damaged zones was found to radially decrease outwards and vice versa with oxygen. Decomposition started from epoxy dehydration, accompanied by discolouration and formation of water and carbonyl, and released chemical compounds like 2-propenal, acetylene and carbonyl-containing aromatic ether. The successful identification of these unique heating-formed functional groups provided the confirmation of the proposed methodology.

The effect of nanoclay cloisite Na + on the mechanical and conductive properties of ionic liquids (ILs) doped sulfonated ABPBI (SABPBI) composite membranes for high temperature proton electrolyte membrane (PEM) applications were investigated in this report. The composite SABPBI membranes with well-dispersed cloisite Na + showed great improvement in mechanical properties with the increase of over 90% in ultimate tensile strength and 40% in Young's modulus, respectively, compared with those of pristine ABPBI membrane. The ILs absorption was also increased due to the incorporation of well-dispersed cloisite Na + , resulting in significant increase in the ionic conductivities of SABPBI membranes at the temperatures above 100 °C. The highest conductivities were 4.0 × 10 −2 S/cm at 220 °C for [HMIM]Cl doped 3 wt% SABPBI composite membranes (doping level 1.32), and 9.6 × 10 −3 S/cm × 10 −3 S/cm at 220 °C for [TMG][BF 4 ] doped SABPBI composite membranes (doping level 1.37), respectively.

Two different synthesis methods, viz. precipitation and hydrothermal treatment, were used to synthesise ultra-fine α-alumina powders from aluminium chloride, ammonia solution and TEAH (tetraethyl ammonium hydroxide). XRD, BET surface area analysis, TEM and FEG-SEM were used to characterise the powders produced. The presence of industrial α-alumina powder as seed particles did not affect the transformation to α-alumina phase during the hydrothermal treatment at 220 °C, either in basic or acidic environments. The results obtained from the precipitation route, however, showed that the combined effect of adding α-alumina seeds and surfactants to the precursor solution could lower the transformation temperature of α-alumina from about 1200 °C for unseeded samples to about 800 °C, as well as reducing the level of agglomeration in the alumina powders. The difference in transformation temperature mainly results from the nucleation process caused by the α-alumina seeds, which enhanced the θ→ α transformation kinetics. The lower level of agglomeration present in the final powders could be due to a surface modifying role of the surfactants, preventing the particles from coalescing during the synthesis process.

Hydroxyapatite/polyetheretherketone (HA/PEEK) composite materials were prepared via an in situ synthesis process in order to achieve strong bonding between PEEK matrix and hydroxyapatite fillers, and ultimately to improve the mechanical properties of the composites. In the study, the biocompatibility of the synthesized HA/PEEK materials was investigated by acute toxicity test, hemolytic test, sensitization test, pyrogen test, intradermal test, and toxicity assay test on animal tissue and cells for the purpose of examining the possible adverse effects of the residue organic chemicals from the in situ synthesis process. In vivo bioactivity of both lab-synthesized PEEK and HA/PEEK composites with various HA content was also studied. It is found that the in situ synthesized composite materials possess good biocompability without toxicity. Although the bioactivity of the material increases with HA content, the composite material with 5.6 vol % HA exhibits satisfactory bioactivity without compromising its excellent mechanical performance, which hints to a potential use as load-bearing orthopedic material.

Novel organic-inorganic composite membranes involving poly(2,5-benzimidazole) (ABPBI) and polyhedral oligomeric silsesquioxane (POSS) were prepared via in-situ synthesis followed by phosphoric acid doping. The formation of composites was characterized by SEM, XRD and FTIR. The results of water uptake showed that POSS cores emerged extraordinary water absorbability. When doping in phosphoric acid solution, phosphoric acid absorption in composites was dominated by functional groups linked to POSS cores. The excellent proton conductivities i.e. above 0.1S/cm at 100~160oC achieved from anhydrous ABPBI/OA-POSS composite membranes with 241wt.% of phosphoric acid absorption, make them very good candidates as the membranes for high temperature polymer electrolyte membrane fuel cell (PEMFC) applications.

Embedding carbon nanotubes (CNTs) in load-bearing composite laminate hosts to turn them into nano-laminates is a rapidly emerging field and has tremendous potential in enhancing the mechanical performance of the host laminates. This state-of-the-art review intends to provide a physical insight into the understanding of the enhancing mechanisms of the processed and controlled CNTs in the nano-laminates. It focuses on four aspects: (1) physical characteristics of CNTs, including CNT length, diameter, weight percentage and surface functionalization; (2) processing and control techniques of CNTs in the fabrication of nano-laminates, including distribution, dispersion and orientation controls of CNTs; (3) mechanical properties along with their testing methods, including tension, in-plane compression, in-plane and interlaminar shear (ILS), flexure, mode I and mode II fracture toughness as well as compression-after-impact (CAI), ballistic protection and fatigue; and (4) CNT–matrix load transfer and enhancing mec...

Sodium-montmorillonite (MMT) was modified with two types of AP-POSS and OA-POSS and dual-surfactants (POSS with a ditallow-based second surfactant: 04AP-POSS/08DTDMA and 04OA-POSS/08DTDMA), respectively, via ion-exchange reaction. The interlayer space, interlamellar structure, thermal and surface properties of these organo-montmorillonites were investigated by X-ray diffraction, thermogravimetric analysis, and contact angle measurement. The interlayer space of POSS modified clay was strongly dependent on the arrangement of POSS surfactants, but less on the POSS concentration. The POSS modified montmorillonites have partially exchanged silicate surfaces and good thermal stabilities due to steric hindering and thermal stability of the POSS molecules. Dual-surfactant modified montmorillonites showed higher exchange ratio and possessed better compatibility with PA12 due to the lower interfacial free energy. Polyamide 12-montmorillonite nanocomposites were prepared by conventional melt compounding with the four POSS based organo-montmorillonites. The best dispersion of modified montmorillonite was observed for 3 mass% 04AP-POSS/08DTDMA/MMT filled PA12 nanocomposites, which resulted in the best mechanical performance with an increase of 60% in tensile modulus and 10% in yield strength, respectively, compared to that of pure PA12. Compatibility between montmorillonites and polymer was not the only key factor affecting dispersion, thermal stability and interlayer space were also crucial for good dispersion of montmorillonites in polymer matrix.

Sodium montmorillonite (Na-MMT) was modified with various amounts of aminopropylisooctyl polyhedral oligomeric silsequioxane (POSS) and a second surfactant (alkyl ammonium based) via ion-exchange reactions. Interlayer spacing, interlamellar structure, and thermal and surface properties of these organoclays were characterized by wide angle X-ray diffraction, thermogravimetric analysis, and contact angle measurement. The interlayer space of POSS-modified clay (POSS-MMT) was strongly dependent on the arrangement of POSS surfactant but less dependent on the POSS concentration. The sodium ions in Na-MMT were only partially exchanged by protonized POSS due to the steric hindrance effect. In addition, the dual-surfactant-modified clays exhibited increased exchange ratios by controlling the amount of the second surfactant, resulting in a good balance in hydrophobicity and polarity of the modified clays. The resultant organoclays were mixed with polypropylene (PP) via a melt-compounding method. It was found that the dual-surfactant-modified clays with low polarity and similar hydrophobicity to PP were well dispersed in the PP matrix.

Polyamide 12/Trisilanolphenyl-POSS (PA 12/POSS) composites were prepared via melt-compounding. The effect of polyhedral oligomeric silsesquioxane (POSS) on crystalline structure and crystalline transition of PA 12 was investigated by wide-angle X-ray diffraction (WAXD) and real time fourier transform infrared spectroscopy (FTIR). WAXD results indicated that PA 12 crystallized into γ-form as slowly cooling from melt and the presence of POSS did not influence the crystalline structure of PA 12. Both PA 12 and PA 12/POSS composites underwent Brill transitions when they were heated from room temperature to melt point. Real time FTIR patterns showed that an absorption band at 697 cm−1 ascribed to Amide V (α) mode was emerged along with the disappearance of Amide VI (γ) band at 628 cm−1 with the increase of the temperature for PA 12 and PA 12/POSS composites, which suggested that the γ-form crystalline has transformed into α form. The Brill bands were identified and the transformed mechanism was discussed based on the real FTIR results. The addition of POSS enhanced the tensile strength and thermal stability of PA 12.

Commercially available organoclay (Closite 30B) was modified by using 3-aminopropyltriethoxysilane (APS) via a silylation reaction. Sodium clay (Closite Na) was treated by APS directly as a control. Such modified clays were further melt-compounded with polybutylene terephthalate (PBT). The morphology and properties of the modified organoclays were characterized with X-ray diffraction (XRD), transmission electrical microscopy (TEM), Infra-red spectroscopy, contact angle measurement, and thermogravimetric analysis (TGA). The effects of modified clays on the crystallization behavior of PBT were characterized by differential scanning calorimetry. The basal spacing of Closite Na was enlarged from 1.01 to 1.41 nm after APS treatment, indicating that the APS was intercalated into the clay intergalleries as a monolayer. The basal spacing of Closite 30B increased slightly after APS treatment, partially resulted from the reactions between the APS and hydroxyl groups on the intercalant of Closite 30B. Closite 30B was found to be exfoliated disorderly after melt-compounded with PBT. The APS-modified Closite 30B only dispersed as swollen elliptical clay aggregates, in which the silicate layers were orderly intercalated. TGA results showed that the decomposition temperature at 5% weight loss of Closite 30B was increased from 250 to 270°C after APS treatment. A significant increase in the degree of crystallinity of PBT was observed in the exfoliated PBT/30B composite.

© 2014 Society of Plastics Engineers. The influence of untreated and stearic acid surface pretreated calcium carbonate (CaCO3) nanofiller (U1 - untreated CaCO3 and U1S2 - stearic acid treated CaCO3) on the properties of polyurethane/poly(vinyl acetate) (PUR/PVAC) polymer blends was investigated. Adhesion between fillers and polymers in the polymer blend composite, and filler position in regard to the polymer phases, are predicted on the basis of calculated adhesion parameters and wetting factor ωa of PUR, PVAC, U1, and U1S2. U1 is located in the PUR matrix phase and U1S2 is located at the interface between matrix PUR domain and dispersed PVAC domain. Polymer blend composites with predominant U1S2 showed lower tensile strength and elongation compared to these of polymer blend composites with predominant U1 mainly due to the fillers' different surface properties, which confirmed that the mechanical properties of polymer blend composites were dependent on overall system morphology rather than the filler location.

A water-in-oil microemulsion, water-in-cyclohexane stabilized by poly(ethylene glycol) tert-octylphenyl, was developed to prepare poly(methacrylic acid) (PMAA) particles. Up to 100% conversion of the amphiphilic monomer, methacrylic acid (MAA), which could not be converted to the polymer efficiently in a dioctylsulfosuccinate sodium salt/toluene microemulsion, was achieved. The viscosity-average molecular weight of the PMAA prepared was 1.45 105 g/mol. The effects of some polymerization parameters, including the reaction temperature and the concentrations of the initiator and the monomer, on the polymerization of MAA were investigated. The results showed that the polymerization rate of MAA was slower than that of acrylamide in the microemulsions reported in the literature. The degree of conversion increased with the initiator concentration, reaction temperature, and monomer concentration. However, the stable microemulsions became turbid during the polymerization when the reaction temperature was at 70°C or at a high monomer concentration (40 wt %) The synthesized PMAA particles were spherical and had diameters in the range of 50 nm.

The composite nanoparticles and corresponding self-reinforcing composites comprising tricalcium phosphate (TCP) and alumina (Al2O3) were synthesized by simultaneous precipitation from the CaCl2, AlCl3 and (NH4)2HPO4 aqueous solutions, using aqueous NH4OH as precipitant. Influences of the precipitating media pH and the Ca/P atomic ratios on phase composition and morphology of the composites were investigated. Results showed that except for the major phases β-TCP and α-Al2O3, there was always a third minor phase in the calcined composites coprecipitated either in neutral or alkaline condition. Formation of β-TCP is, however, favored at pH 9.2, whereas more of the third phase, mainly AlPO4, is formed under neutral condition. High Ca/P ratios suppress the formation of α-Al2O3 phase under alkaline precipitating condition, but the effect is less significant in neutral condition. TEM observation showed that the ‘as prepared’ composite particles are nano-sized but interconnected to form a network-like morphology. They were changed to a core-shell-like structure after calcination, while their nano-scale dimension was retained. FEGSEM analysis revealed that the α-Al2O3 phase in the sintered composite compacts was in the form of fibrils dispersed in the phosphate phases. These in situ formed fibrils impart a unique role in self-reinforcement of the sintered composites. Mechanical measurements showed that the incorporation of alumina reinforced β-TCP effectively: the flexural strength increased from 15 MPa of the pure β-TCP to 84 MPa of the composite with 40 wt% of α-Al2O3.

Tellurite thin films have potential to be applied in optical and electronic areas, but it is difficult to prepare from tellurium(IV) alkoxides by sol–gel processing due to the instability of tellurium(IV) alkoxides and their derivatives. The precursor of tellurium(VI) complex is synthesized and applied to make tellurium oxide thin films without addition of any modifiers in the study. The decomposition process of the complex is investigated, and the thin films derived from this precursor are characterized structurally, morphologically and optically.

Nano-sized hydroxyapatite (HA) particles were prepared by chemical precipitation through aqueous solutions of calcium chloride and ammonium hydrogenphosphate. The influence of temperature, ripening time and calcination on the crystallinity and morphology of the HA nanoparticles were investigated. It was found that the crystallinity and crystallite size increased with the increase of synthetic temperature and ripening time. XRD and TEM results showed that the morphology change of HA nanoparticles was related to their crystallinity. High crystallinity of HA led to regular shape and smooth surface of the nanoparticles. The crystallinity of HA powders increased greatly after calcination at 650 °C for 6 h but the change of the crystallite size after calcination was dependent on the crystallinity and crystallite size of “as prepared” HA nanoparticles.

Hydroxyapatite/polyetheretherketone (HA/PEEK) composite materials have potentials for use as load-bearing orthopedic materials due to PEEK outstanding properties, which could overcome the disadvantages of currently used metallic and ceramic materials. In the study HA/PEEK composite materials were successfully prepared via an in situ process, for the first time, in order to improve the mechanical performance of the existing HA/PEEK composites. The structure of the lab-synthesized materials was characterized by infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM), and the mechanical performance was investigated by a tensile strength test. The results exhibit the strong bonding between hydroxyapatite fillers and PEEK matrix and good mechanical properties of the composites, suggesting that the in situ synthesized HA/PEEK composite materials are promising for orthopedic applications.

Sol–gel processing is an advantageous route to produce PZT thin film materials with high quality. PZT powders and thin films with good properties were fabricated by sol–gel processing, using acetylacetone as modifier, in the study. The morphologies of PZT powders and thin films were observed by field emission microscopy, and the dielectric and properties of the PZT thin films were measured. Thermal analysis, XRD and FTIR were used to investigate the influence of ligands on the phase transformation in PZT materials, and it is found that the difficulty of decomposing acetylacetone ligands completely resulted in a higher pyrolysis temperature to form PZT with pure phase.

A new water-in-oil microemulsion, consisting of the non-ionic surfactant Triton X-114, cyclohexane as the oil phase and 1.0 M AlCl3 aqueous solution as the aqueous phase, was developed and used to synthesise aluminium oxide (Al2O3) nanoparticles. The partial phase diagram of this ternary system was also determined at 38 °C. Syntheses of Al2O3 nanoparticles were carried out in a range of microemulsions with a fixed oil∶surfactant ratio of 70∶30 (w/w), but with different aqueous phase contents. For the purposes of comparison, Al2O3 particles were also synthesised in the corresponding emulsion and by direct precipitation from aqueous solution. Nano-sized Al2O3 particles were only obtained via microemulsions, whereas the emulsion route led to hollow ball-shaped particles with sub-micron apparent sizes and the direct precipitation process resulted in angular particles about 250 nm in dimension. The nanoparticles synthesised in the microemulsion with 20 wt% aqueous phase content have smaller particle sizes (5–15 nm) and a lower transformation temperature into α-form Al2O3 crystallites. Pure α-Al2O3 nanocrystals were obtained by calcination at 1000 °C for 12 h, while the nano-sized dimension of the particles retained though the apparent particle size increased to some extent. This transformation temperature is about 200 °C lower than that for the Al2O3 particles synthesised by direct precipitation.

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.

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 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 series of 4′-[(carbonyloxy-1,1,2,2 Tetrahydrofluorodecyl)]-4 -(ω-bromo-alkenyloxy) azobenzenes, 4′-[(carbonyloxy-1,1,2,2-Tetrahydrofluorodecyl)]-4-(alk-1-enyloxy) azobenzenes have been synthesized. Also, a polyacrylate has been formed by phase transfer catalyzed reaction between one of the ω-bromo-alkenyloxy compounds and sodium polyacrylate as well as two polysiloxanes formed by hydrosilylation of the alkenyloxy compounds and a polyhydrosilane. All of the low molar mass compounds show the S A phase on heating and an increase in perfluoroalkyl chain length results in an increase in clearing temperature whilst an increase in the hydrocarbon chain length shows a decrease in clearing temperature. Upon grafting these low molar mass units to a polymer backbone, the resulting materials also show smectic mesophases despite having quite low clearing entropies (ΔS/R to approximately 0.2-0.6). The precursor polymers are of low molar mass (Mw 1200-1800 g mol -1) and this may be the reason why the polymers do not show glass transition temperatures.

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.