Advanced Materials Research Vols. 123-125

Abstract: The ceramic coatings were prepared on the T6-tempered Al6061 alloy substrate under a hybrid voltage by PEO treatment in 5-30 min in a phosphate electrolyte. The X-Ray diffraction (XRD) and scanning electron microscopy (SEM) were used to investigate the coating microstructures. With increasing the PEO treating time, the different compositions of coatings eliminate the sharp slope of the microhardness profile. The coatings PEO-treated in 30min presents excellent abrasive resistance property.

Abstract: By the use of a coaxial pulsed vacuum arc discharge deposition method (APD), we have developed the catalyst deposition system onto support powders or sheet under vacuum. In this letter, we introduce Pt catalysis processing for fuel cell and evaluation for the electrode property.

Abstract: Poly(ethylenetarepthalate) (PET)-based polymer electrolyte membranes (PEMs) for fuel cells were successfully prepared by grafting of allyl methacrylate (AMA) and allyl acetate separately onto PET films under UV- radiation. A consequent selective sulfonation of the grafted films was performed by chlorosulfonic acid (ClSO¬3H) under milder condition. The sulfonation reaction proceeded at the grafted chains, as a result the grafted films successfully transformed to a PEM. It has been confirmed by titrimetric and gravimetric analyses as well as FTIR spectroscopy. The ion exchanges capacities (IECs) of the PEMs were studied by changing the degree of grafting and sulfonation. IECs of the PEMs prepared by grafting of allylmethacrylate (AMA) and allyl acetate onto PET were found in the ranges of 0.013-0.035 mmol/g and 0.03114-0.04125 mmol/g respectively. Water uptake, acid and hydrogen peroxide tolerance, tensile strength and proton transfer rate of the PEMs were studied. Electrical properties such as resistance, dielectric loss, and capacitance of the PEMs were also studied using impedance analyzer.

Abstract: This article deals with the classification of glassy and polymer electrolytes for lithium-ion batteries into the so-called “strong/fragile” scale, by the means of the bond-strength-coordination number fluctuation model. We have evaluated the strength parameter, which plays a key role in the understanding of the relaxation phenomena, of each lithium-ion conductor under consideration. We have derived a relationship that not only describes accurately the experimental results, but also provides important details on the interrelation between the strength parameter, the bond strength of the structural unit, the binding energy, the coordination number and the glass transition temperature.

Abstract: The bipolar plates were fabricated using compression molding of graphite (GR), carbon black (CB), multi-wall carbon nanotubes (MWNTs), carbon fibers (CF) and powder type epoxy resin. The electrical conductivity and flexural properties of the composites was increased with increasing the content of fibrous conducting fillers e.g., MWNTs and CF. However, when particulate fillers such as CB and GR were used, the electrical conductivity was increased, but the flexural properties deteriorated with increasing filler content up to certain content. A comparison was also made between the current-voltage (I-V) performances of fabricated composite bipolar plates and commercial graphite bipolar plate. The I-V characteristic in single cell test exhibited more uniform power density at both higher and lower current density and single cell performance increased with increasing the electrical conductivity.

Abstract: Gradient permeable metallic substrate material consisting of two layers of NiAl alloy was developed for the SOFC design. The open-cell foam layer (thickness 1-2 mm, cell density 60 ppi) provides the structure robustness, while a thin (100-200 μm) mesoporous layer facilitates supporting functional layers. Cathode layers (LSM, LSFN and their nanocomposites with GDC or YSZ) and anode layers (NiO/YSZ, NiO/YSZ +Ru/Ln-Sr-Mn-Cr-O nanocomposite catalyst) were deposited by slip casting, electrophoretic deposition or air brushing. Thin (5-10 μm) YSZ layer was deposited by MO CVD. Power density up to 550 mW/cm2 at 700oC was obtained on button-size cells using wet H2-air feeds.

Abstract: In this work, poly(amide imide) (PAI) fibers containing various silicon content ratios were prepared for the precursor of carbon fibers by electrospinning method from 25 wt.% PAI in dimethylformamide (DMF) solution. The fibers were stabilized and then subsequently carbonized in a flow of nitrogen to obtain porous Si/carbon fibers. The morphologies and the crystalline structures of the Si/CFs were characterized by scanning electron microscopy (SEM) and X-ray diffractometer (XRD). The electrochemical behaviors of the Si/CFs were observed by cyclic voltammetry tests. The experimental results indicated that the Si/CFs exhibited convoluted structure and wrinkled surface morphology. The silicon particles had a uniform diameter of approximately 1 μm. And the electrochemical activity of the Si/CFs was gradually improved due to the buffering effect of the large Si volume expansion and shrinkage. In addition, the fibers exhibited large accessible surface area, high reversible capacity, and relatively good cycling performance at high current densities. Consequently, it was found that the introduction of silica could affect the electrochemical properties of the CFs, and the Si/CFs might have potential applications for various fields of electrochemical materials.

Abstract: As the demand for radiation grafted Proton Exchange Membranes (PEMs) is intensifying, interest in new materials for preparing PEM is rapidly increasing. This study aims to develop sustainable low-cost highly conductive PEM. In our work we have prepared linear low density polyethylene (LLDPE) based PEM and investigated the membrane characteristics. Simultaneous radiation grafting technique has been applied to introduce the styrene monomer onto the LLDPE films by UV radiation under atmospheric circumstances. It has been observed that grafting yield gradually changes depending on the irradiation time and monomer molar ratio. We have performed experiments to assess certain membrane properties, such as water uptake, ion exchange capacity with respect to their applicability in fuel cells. Our experimental results demonstrate the effectiveness of LLDPE based PEM as a cation exchange membrane.

Abstract: Acid doped polybenzimidazole membrane has been prepared for proton exchange membrane fuel cell. The present work aims at improving the proton conductivity without losing mechanical properties at high doping level by modifying poly (2,5-benzimidazole) (ABPBI). The nitration of ABPBI has been carried out with acid mixture of HNO3 and H2SO4 at 30oC. This nitro compound has been reduced successfully by stannous chloride/dimethylacetamide in presence of hydrochloric acid. Fourier transform infrared (FT-IR) spectra confirm the presence of primary amine groups in the ABPBI structure. The primary amine functionalized ABPBI has been cross-linked by hexamethylene diisocyanate and casted onto glass Petridis using dimethyl sulfoxide as solvent. Membrane doped with phosphoric acid shows comparatively higher proton conductivity, but lower tensile strength.

Abstract: Recently core/shell nanostructures including nanotubes, nanowires, and nanofibers have a considerable attension because multiple or enhanced functionality can be obtained by the synergistic effect of different materials in the formation of a core/shell structure. In this work, porous carbon/carbon core/shell carbon electrode (P-C/C-CE) composed of core graphene and disordered shells were prepared to obtain a new type of carbon electrode materials. The disordered carbon shells were prepared by coating of polyaniline onto the graphene by in-situ polymerization in the presence of nano-sized silica and subsequent carbonization at 850°C. After carbonization, P-C/C-CE showed the hollow structure and crystallinity. In addition, P-C/C-CE exhibited superior electrochemical performance compared to graphene and graphene/PANI composites, which was attributed to the high surface area of P-C/C-CE and the presence of nitrogen groups formed onto carbon electrode after the carbonization of shell polyaniline.