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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.

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.

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.

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...

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.

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 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 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 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.

The use of polymeric precursors to produce ceramics is generating considerable interest . Owing to distinct advantages in processability, polymeric precursors have found applications in many areas such as ceramic fibers, foams and coatings. Ceramic coatings, in particular, are of immediate value in industry as a means of providing wear and corrosion resistance for articles used in adverse environments. The coating of engineering parts with ceramics using polymeric precursors is a relatively easy, quick and low-cost process compared with other processing methods such as chemical vapor deposition and plasma-coating.

During the last decade porous ceramic materials have been finding increasing applications due to their favorable properties such as high temperature stability, high permeability, low mass, low specific heat capacity and low thermal conductivity. These characteristics are essential for many technological applications such as catalyst supports, filters for molten metals and hot gases, refractory linings, thermal and fire insulators and porous implants [1, 2]. Ceramic foams can be produced by different methods, principally impregnation of polymer foams with slurries containing appropriate binders and ceramic particles followed by pressureless sintering at elevated temperatures [2–5]. This involves coating an open-cell polymeric sponge with a ceramic slurry several times, pyrolysis of the polymer to form a ceramic skeleton followed by sintering. Ceramic foams produced by this method are generally of low strength as their struts are thin and can contain a hole in the center [2, 6–8]. Recently, a new method to produce silicon carbide (SiC) foams using polymeric precursor solutions was developed by Bao et al. [9] where a polyurethane foam was immersed in a polymeric precursor solution to form a pre-foam which was pyrolyzed in nitrogen. The main advantages of this new approach are the simplicity and ease of control of structure of the final product. This new process was exploited further to prepare silicon carbide-silicon nitride (SiC-Si3N4) composite foams [10]. In this letter we provide microstructural evidence of the improvements in structure of the ceramic foams produced by our method. The polysilane precursor discussed in this study was synthesized by the alkali dechlorination of a combination of chlorinated silane monomers in refluxing toluene/tetrahydrofuran with molten sodium as described previously [11, 12]. The structure of the SiC polysilane precursor synthesized is given below. Ph indicates a phenyl group.

The use of polymeric precursors for the preparation of ceramic materials is generating a great deal of interest, and silicon carbide (SiC) has been produced by the pyrolysis of several polymers. However, it is desirable to develop precursors that can be prepared with a high polymer yield, are melt-processable, and give a high SiC yield on pyrolysis close to the theoretical maximum that can be obtained (with a low amount of impurities).