Advanced Materials Research Vols. 197-198

Abstract: The microstructure and mechanical properties of ferrite-bainite dual-phase pipeline steels respectively produced by thermomechanical control process (TMCP) and intercritical annealing were studied using optical microscope, scanning electron microscope (SEM), Vickers hardness tester and MTS 810 servo-hydraulic machine. The results show that these two processes obtain different morphology and distribution of microstructure, but the mechanical properties of them are similar and superior, especially the yield ratios are low. It is found that for TMCP steel, the grains of ferrite are large and the average ferrite grain size is approximately 6.1µm. The bainite structures are lump-shaped with concentrated distribution in the ferrite matrix and the band structure is obvious. For steels produced by intercritical annealing process, the grains are finer and the distribution of bainite is uniform on the ferrite grain boundaries. From the rolling plane to the centre, the grain sizes of ferrite in these two microstructures increase obviously, and the volume fraction of bainite first increases significantly, then decreases slightly in the TMCP steel and the average volume fraction is approximately 60.1%. However, the bainite volume fraction in the intercritical annealing steel decreases gradually and the average volume fraction is approximately 35.4%. Moreover, hardness values in through-thickness direction are uniform in the TMCP steel and these values are also similar in the intercritical annealing steel except the values in the region near the rolling plane are much larger.

Abstract: An integration platform assembling with methanol reformer and high-temperature proton exchange membrane fuel cell (PEMFC) was constructed in this present. The methanol micro reformer combines with catalytic reaction section and reforming section. Catalytic reaction section with Pt calalysis maintains the constant temperature envoriment for reforming process. SRM reforming results show the 74%~74.9% hydrogen and 23.5%~25.7% of carbon dioxide in the mixture product. Less than 2% of carbon monoxide was produced. Using the reforming product of low carbon monoxide concentration and the highest methanol conversion rate, a micro reformer links with fuel cell integration experiment was performed. Results show the high temperature PEMFC with 3 ~ 4W power output under methaol flow rate 15ml/hr. Due to the lower of hydrogen pressure supplying from the micro reformer, may cause the fuel cell power output become unstable.

Abstract: Based on dynamic instability theory, by incremental dynamic analysis method, large-scale parameters-analysis is carried on double-layer Kiewitt shell under harmonic loading，with weight effects and double non-linear effect calculated and Failure-amplitude is determined. Further exploring on the relationship between excitation frequency changes and failure-amplitude and between initial imperfection effect and load reduction are also conducted.

Abstract: The long term stability and durability of gaskets made of silicone rubber in proton exchange membrane fuel cell (PEMFC) has important effect on the sealing and the electric-chemical performance of the fuel cell. In present paper, the time-dependent chemical degradation of a silicone rubber was studied in three simulated PEMFC environments. The test temperature was selected and used at 90°C in this study according to the actual PEM fuel cell operation. Optical microscopy was used to show the topographical changes on the sample surface. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy was employed to study the surface chemistry of the gasket material before and after exposure to the simulated PEM fuel cell environments over time. The results show that the weight loss increased with the exposure time for the samples. Optical microscopy reveals that the surface conditions of the samples changed over time from initially smooth to rough, crack appearance and finally crack propagation. The ATR-FTIR results show that the surface chemistry changed significantly via de-crosslinking and chain scission in the backbone for the material over time.

Abstract: The Mg₂NiH₄ hydrogen storage material was successfully prepared by controlled hydriding combustion synthesis (CHCS) from Mg and Ni powders in a high magnetic field. The effects of magnetic intensity on the structure, phase compositions and the hydriding/dehydriding (A/D) properties of the composite are investigated. As a result, a high magnetic field promotes the formation of Mg₂NiH₄. The PCT results show that the maximal hydrogen capacity at 573 K is 3.59 wt.%. The comparison of the hydrogen A/D results under the different conditions suggested that 4 T is the optimal magnetic intensity in our trial.

Abstract: Bipolar plate of stack in polymer electrolyte membrane fuel cell (PEMFC) has high cost and heavy weight. In this study, low carbon steel was used as a base metal of bipolar plate for the lower cost than stainless steels, which are widely researched as bipolar plate. Low carbon steel has not a good corrosion resistance. In order to improve the corrosion resistance and electrolytic conductivity, low carbon Steel needs to be surface modified. We made chromium electroplated layer of 5㎛ and 10㎛ thickness on the surface of low carbon steel, and it was thermally nitrided for 3hours at 1173K in a furnace with 50torr nitrogen gas pressure. Cross-section and surface microstructures of surface treated low carbon steel were investigated using OM and SEM. Also crystal structures are observed by XRD. Interfacial contact resistance and corrosion test were considered to simulate the internal operating conditions of PEMFC stack. The corrosion test was performed in 0.1N H₂SO₄ + 2ppm F- solution at 80°C. The results show that the surface modified steel plates have good corrosion resistance and relatively low interfacial contact resistance, and it should be candidate material as a bipolar plate of PEMFC.

Abstract: SPV490Q steel is a low alloy high strength structural steel plate used in the manufacture of oil storage tank. To improve the comprehensive performance of SPV490Q steel plate and reduce manufacturing costs, direct quenching technology has been developed as revolutionary plate manufacturing technologies in recent years. Effect of direct quenching on microstructure and mechanical properties of high performance SPV490Q steel plate has been studied. The direct quenched (DQ) steel plates are rolled at different finish rolling temperatures, and their microstructures and mechanical properties are compared with those of reheat quenched (RQ) steel plate. The optical microstructure of the DQ steel shows deformed grains elongated parallel to the rolling direction, while complete equiaxed grains are visible in RQ steel. The transmission electron microscope (TEM) microstructure of the DQ steel shows refined lath martensite with high density of dislocations. The findings indicate that the application of the direct quenching process to low-carbon alloy steels contributes to the production of steel plates with excellent strength and toughness.

Abstract: Multi-walled carbon nanotubes ( MWCNTs) was used, as a catalyst carrier, to load cerous sulfate for catalyzing the synthesis of n-butyl propionate. The effects of nitric acid concentration, reaction time and reaction temperature on the purification of MWCNTs were investigated. The effects of molar ratio of butyl alcohol to propionic acid, the cerous sulfate load and the reaction time on the conversion of butyl acid were studied by single factor experiment method and orthogonal experiment method, respectively. The results show that the optimal conditions for purifying MWCNTs are: nitric acid concentration of 4 M, reaction time of 8 h and reaction temperature of 103°С and the optimal conditions for synthesizing n-butyl propionate are: molar ratio of butyl alcohol to propionic acid of 1.5:1, use level of loaded cerous sulfate of 0.15 g and reaction time of 70 min. The conversion of butyl acid for the MWCNTs loaded cerous sulfate reaches 96.7% which is higher than that for the unloaded cerous sulfate and the use level of cerous sulfate for the former is much less than that for the latter under same operation conditions.

Abstract: The composites of expanded ghaphite with ZnO (EG/ZnO) have been prepared in the method of impregnation, and their degradation performance for crude oil have been investigated by the means of UV-Vis and FT-IR. The morphology and crystal structure of the EG/ZnO composites have been characterized by the means of SEM and XRD. The results are shown as follows: the EG/ZnO composites keep the laminated and microporous network structure of EG. ZnO particles in the composites are hexagonal crystal system, and they widely distribute in the cavities and the network pores of EG. In the UV-Vis spectra, there is a blue shift about 13 nm, which is from 255 nm to 242 nm at the biggest absorption peak. That indicates the component of the crude oil has already changed. Meanwhile, the results of FT-IR spectra show that a degradation reaction occurs obviously in the crude oil after irradiated by ultraviolet ray, and the degradation products possibly include alkone, aldehyde, alcohol, and so on. Thus, it can be inferred that the prepared EG/ZnO composites would be a new kind of functional material integrated strong adsorption property and degradation property into itself.

Abstract: The nano-TiO₂ photocatalyst was prepared via sol-gel method, and the crystal structure and surface morphology were characterized by XRD and SEM. The photocatalytic degradation of ammonia-N in aquaculture wastewater was investigated by using nano-TiO₂ under UV irradiation. In the experiment, the effect of nano-TiO₂ dosage, ammonia-N initial concentration, pH value, H₂O₂ volume concentration, and reaction time, respectively, on the removal of ammonia-N was investigated. On the basis of the results of these experimental data, an orthogonal array experimental design was used to select more efficient degradation condition. The optimal experimental conditions for photocatalytic degradation of ammonia-N can be stated as follows: when the concentration of ammonia-N was 20 mg/L, nano-TiO₂ catalyst dosage was 1.2 g/L, the pH value of solution was 5, H₂O₂ volume fraction was 4 %, respectively, if the reaction time may last 3 h, the removal rate of ammonia-N was expected to reach 92.10 %.