Advanced Materials Research Vols. 197-198

Abstract: By reactions of indium chloride tetrahydrate with three bis-Schiff bases ligands (N, N’-bis (3-methoxy-salicylidene)benzidine = L¹; N, N’-bis (3-methoxysalicylidene)-2, 2’-dimethyl- benzidine =L²; N, N’-bis (3-methoxysalicylidene)-o- dianisidine = L³), respectively, three novel corresponding complexes 1~3 were obtained. The complexes were characterized by infrared spectrum, molar conductance, elemental analysis and thermal gravimetric analysis. The chemical formulae of the complexes 1~3 were determined as (InCl₃)₂Lⁿ (1, n = 1; 2, n = 2; 3, n = 3). All the complexes are constructed with binuclear indium ions. Every complex consists of two central In (III) ions, one corresponding bis-Schiff base ligand and six Cl^-.

Abstract: Cellulose treated with fire retardant was studied by thermogravimetry (TG), differential thermal analysis (DTA) and limiting oxygen index (LOI). The kinetic parameters for the thermal degradation are obtained following the method of Broido. For the fire retardant cellulose, the activation energy and decomposition temperature were much decreased while char yield and LOI were increased. The main thermal decomposition of the samples with higher LOI occurs at lower temperatures, while that with lower LOI occurs at higher temperatures.

Abstract: The sinter ore samples with different content of silica were prepared by the mini-sintering method so as to study the micro-mechanism of sinter. The fractal theory was also applied to analyze quantitatively the grain distribution in the samples’ two-dimensional microstructure. The study found that the grain distribution of the sinter shows the fractal characteristic, its fractal dimension is about 1.95, and the fractal dimension can be used to characterize uniformity of the grain distribution. With the increase of silica content, the fractal dimension of the samples shows a linear decreasing trend and it is the same trend in the comparing sintering-cup experiment when the fractal dimension of particle size distribution reduces, the silica content increases. In addition, the compressive strength of mini-sintering sinter sample was also measured. It shows that the compressive strength is the highest when the silica content is 3.8 wt%, which is correlative with the porosity, the content of calcium ferrite and glassiness in the sinter ore besides the fractal dimension.

Abstract: The hydrogen embrittlement of a low carbon HSLA steel has been investigated by means of slow strain rate test (SSRT) on circumferentially notched specimens. Hydrogen was introduced into specimens by electrochemical charging and the diffusible hydrogen content was measured by thermal desorption spectrometry (TDS) analysis. The activation energy of hydrogen desorption in the present steel was calculated to be 12.75 kJ/mol after TDS analysis. The peak stress and displacement during notch tensile tests had been found to decrease simultaneously with diffusible hydrogen content, which could be expressed by two power law relationships, respectively. Fracture surface was a cleavage type indicating that the steel had high susceptibility of hydrogen embrittlement.

Abstract: Electrode structure plays an important role on performance of the proton exchange membrane (PEM) fuel cell. A two-dimensional, two-phase flow model is presented to simulate the performance of PEM fuel cell with direct flow fields and its mass transfer in cathode in this paper. Effects of depth and width of channel and depth of gas diffusion layer on the performance of PEM fuel cell and mass transfer in its cathode are analyzed. The results show that electrode structure affects strongly the performance of fuel cell and mass transfer in its electrode; when depth of channel is 0.75mm, there are the worst performance and mass transfer; decreases of the width of the channel and depth of the gas diffusion layer are beneficial to improving mass transfer and increase performance of PEM fuel cell. These results are very helpful for optimization of PEM fuel cells.

Abstract: PEM fuel cell is an ideal power for modern automobile. Characteristics distribution of PEM fuel cell is one of key parameters for its application. Reactant gas stoic ratio, current density and charge capacity are measured by the current distribution measurement system, and their distribution and the influence of load on them are analyzed in this paper. Experimental results show that the reactant stoic ratio and charge capacity decrease along the gas channel; the optimal humidification temperature decreases with the increase of external load. These results are very helpful for the optimization of operating parameters of PEM fuel cell and its application.

Abstract: We investigate the influence of grain size on mechanical properties in a Fe-9Ni-12Mn-2.5Si-1.0C TWIP steel by unidirectional tensile. Meanwhile the microstructures of the TWIP steel were observed and analyzed by optical microscope (OM) and transmission electron microscope (TEM). The experimental results show that the TWIP steel’s yield strength and tensile strength decrease with the increasing of grain size, whereas the plasticity increases with it. When the average grain size reaches to 27μm, the tensile strength is 1080MPa, the elongation percentage is 77%, and the strength-plasticity product achieves the 83160MPa•%. Steel’s strain hardening rate can be changed from three-stage to four-stage with the increasing of grain sizes, the areas of strain hardening by twin deformation mechanism are expanded. Through the microstructure observation we found that, coarse-grained TWIP steel conducts to twinning formation, the high density twins can increase the alloy’s ductility by splitting the grain.

Abstract: The pore in the sinter is an important character. Because of multiphase and asymmetry in the sinter, the structure of the pore is very complex. To study the character of the pore effectively, the method of mercury intrusion porosimetry is applied to measure the pore in the sinter, and the results are dealt with by the fractal theory. The results prove that the pores in the sinter are actually fractal structure when the size of the pores is more than 204.5 nm because their curves in the log-log plot are linear, and some curves qualified with the linearity obviously possess of the segment linearity character. According to the calculation of the fractal D, the relationship of the strength and fractal D will be established.

Abstract: Reduced graphene sheets (RGSs) were prepared via hydrazine reduction of exfoliated graphite oxide and their morphology was characterized by atomic force microscopy. The electrocatalytic reduction of oxygen (O₂) with RGSs was studied by cyclic and rotating risk electrode voltammetry using RGSs-modified glassy carbon electrodes in alkaline media. The results show that this modification with RGSs makes the peak potential shift in the positive direction and increases the peak current. The kinetics study shows that the numbers of electrons transferred for the oxygen reduction reaction are ca. 3 at potentials of the first reduction wave, indicating the peroxide produced can transfer into OH^–.

Abstract: Micro-tubular solid oxide fuel cell (SOFC) has been fabricated with NiO-YSZ hollow fiber as anode support and La_0.6Sr_0.4Co_0.8Cu_0.2O_3−δ-Sm_0.2Ce_0.8O_1.9 (LSCCu-SDC) composite cathode. The NiO-YSZ hollow fiber anode was prepared by the immersion-induced phase inversion technique and shows a special asymmetrical structure with porous sponge-like structure in the middle and finger-like structure on the inner and outer side of the hollow fiber. A thin and dense electrolyte membrane (about 12μm) was deposited on the anode by a vacuum-assisted dip-coating process. The performance of the as-prepared hollow fiber SOFC (HF-SOFC) was tested at 600-800°C with humidified H₂ as fuel and ambient air as the oxidant. The peak power densities of 531.1, 362.5 and 214.6mWcm^-2 can be obtained at 800, 700 and 600°C, respectively. The good performance at intermediate temperature (IT) indicates promising applications as power sources for portable devices for the prepared YSZ-based micro-tubular SOFCs with LSCCu-SDC composite cathode.