Research About Microstructure and Wear Resistance of Hardfacing Layer on Cast Iron

It's simple technology to manufacture big trimming die by hardfacing on the base metal of cast iron. The chemical composition, microstructure, hardness, wear resistance and wear mechanism of the hardfacing layer were studied.The experimental results indicate that the hardfacing technology has much more advantages and cheaper than that of traditional process. The chemical composition, microstructure, hardness of the hardfacing metal are all satisfied for manufacturing the big trimming die by welding on cast iron. The wear resistant test of hardfacing layers were carried out by using two different electrodes. The wear resistance of new electrode hardfacing layer is higher than that of normal hardfacing electrode D322. The wear mechanism of hardfacing layer is belongs to abrasive wear model.     

Corrosion Resistance of an electrodeposited Zinc Coating Containing CeO2 Nanoparticles

A Zinc coating containing CeO2 nanoparticles has been deposited by electrodeposition in a zinc plating bath.The content of CeO2 in the coating is 0.22 mass%. The results of weight loss experiments and electrochemistry tests show that corrosion resistance of the Zinc coating containing CeO2 nanoparticles is remarkably improved in contrast to the pure zinc coating in 0.5 M MgSO4 solution. The effects of CeO2 microparticles on the corrosion resistance of the zinc coating have been studied, the results show that CeO2 microparticles have no effect on the corrosion resistance of the zinc coating. SEM and XRD experiments suggest that the presence of CeO2 nanoparticles in the coating causes the modification of the surface morphology and preferential orientation of the crystal planes; therefore, the reason for the enhancement of corrosion resistance is mainly related to improvement of the structure of the coating.     

Study on the thermo-effect of nugget growing in single-phase AC resistance spot welding based on the calculation of dynamic resistance

According to the welding current and electrode voltage detected in resistance spot welding, the dynamic resistance was calculated and the nugget growing thermo-effect in process of nugget forming was studied. The results showed that the process of nugget growth in resistance spot welding can be divided into three stages, which were initial stage, growing stage and stable stage. The welding current provided energy for nugget growth, which showed a high linear relationship with mean dynamic resistance and more prominent polynomial relationship with dynamic resistance heat. The dynamic resistance heat was an important evaluating indicator to the nugget growing thermo-effect, which was closely related to the characteristics of nugget forming. As the dynamic resistance heat was increased, the nugget diameter and tensile shear strength of spot weld were raised and showed a more prominent polynomial relationship. According to the calculation of dynamic resistance heat, these relationships provided a method for the nondestructive test of nugget quality features.     

The role of surface roughness in the measurement of slipperiness

Surface roughness has been shown to have substantial effects on the slip resistance between shoe heels and floor surfaces under various types of walking environments. This paper summarizes comprehensive views of the current understanding on the roles of surface roughness on the shoe and floor surfaces in the measurement of slipperiness and discusses promising directions for future research. Various techniques and instruments for surface roughness measurements and related roughness parameters are reviewed in depth. It is suggested that a stylus-type profilometer and a laser scanning confocal microscope are the preferred instruments for surface roughness measurements in the field and laboratory, respectively. The need for developing enhanced methods for reliably characterizing the slip resistance properties is highlighted. This could be based on the principal understanding of the nature of shoe and floor interface and surface analysis techniques for characterizing both surfaces of shoe and floor. Therefore, surface roughness on both shoe and floor surfaces should be measured and combined to arrive at the final assessment of slipperiness. While controversies around the friction measurement for slipperiness assessment still remain, surface roughness measurement may provide an objective alternative to overcoming the limitations of friction measurements.     

Assessment of resistance spot welding quality based on ultrasonic testing and tree-based techniques

Classification and regression tree (CART) and random forest techniques were proposed as pattern recognition tools for classification of ultrasonic oscillograms of resistance spot welding (RSW) joints. The results showed that CART models produced an acceptable error rate with high interpretability. These features may be used to understand and control the decision processes, instruct other human operators, compare margins of safety or modify them depending on the criticality of the industrial process. Compared with CART trees, random forests reduced the error rate at the cost of decreasing decision interpretability. The use of the agreement of the forest was proposed as a measure to reduce the workload of human operators, who would only have to focus on the analysis of ultrasonic oscillograms that are difficult to interpret.     

丙烯酸树脂/LDH纳米复合材料的合成及其耐老化性研究

主要采用成核/晶化隔离法制备纳米双羟基复合金属氧化物(LDH)并改性,再用乳液聚合法合成丙烯酸树脂/LDH纳米复合乳液。利用FTIR、SEM和材料试验机对其进行结构和力学性能表征。结果表明:最佳反应温度为80℃,反应时间为2.5 h,催化剂的用量为0.2 g。并在该条件下成功地合成了丙烯酸树脂/LDH纳米复合材料;并随着LDH含量的增加其成膜速度,膜的透明度,耐老化性都有所提高;但当LDH的含量超过一定值时,其各项性能呈下降趋势。当LDH的含量为3%时,复合材料的各项性能均达到了最佳状态。     

Investigating fuel-cell transport limitations using hydrogen limiting current

Reducing mass-transport losses in polymer-electrolyte fuel cells (PEFCs) is essential to increase their power density and reduce overall stack cost. At the same time, cost also motivates the reduction in expensive precious-metal catalysts, which results in higher local transport losses in the catalyst layers. In this paper, we use a hydrogen-pump limiting-current setup to explore the gas-phase transport losses through PEFC catalyst layers and various gas-diffusion and microporous layers. It is shown that the effective diffusivity in the gas-diffusion layers is a strong function of liquid saturation. In addition, it is shown how the catalyst layer unexpectedly contributes significantly to the overall measured transport resistance. This is especially true for low catalyst loadings. It is also shown how the various losses can be separated into different mechanisms including diffusional processes and mass-dependent and independent ones, where the data suggests that a large part of the transport resistance in catalyst layers cannot be attributed to a gas-phase diffusional process. The technique is promising for deconvoluting transport losses in PEFCs.     

The impact of porosity,pH2 and pH2O on the polarisation resistance of Ni–BaZr0.85Y0.15O3−δ cermet anodes for Protonic Ceramic Fuel Cells (PCFCs)

The effect of porosity and atmosphere on the polarisation resistance of Ni-BZY cermet anodes for protonic ceramic fuel cells (PCFCs) was investigated using electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The level of porosity was adjusted by the use of differing amounts of starch porogen. The total polarisation resistance of the cermet anode (Rp) generally showed an increase with increasing porosity. The high frequency polarisation resistance (R2) was shown to have low atmosphere dependence but presented a strong correlation to microstructural variations. In contrast, the low frequency polarisation resistance (R3) was shown to have a low dependence on humidity but demonstrated a strong negative dependence on pH₂ with a value of unity. Subsequent discussion relates the lower frequency response to the dissociative adsorption of H₂ on the anode surface. The present study highlights that porogens are not required for peak performance in PCFC anodes under standard operating conditions, a result contrary to that of their oxide-ion conducting cermet counterparts.     

Primary and secondary metabolite compounds in cowpea seeds resistant to the cowpea bruchid [Callosobruchus maculatus (F.)] in postharvest storage

Cowpea is a one important legume crop in Sub-Saharan Africa due to its high content of protein and other nutrients. However, seeds of cowpea varieties are destroyed by Callosobruchus maculatus in storage. This study investigated various biochemical compounds of susceptible and resistant cowpea genotypes, to determine the biochemical compounds underlying cowpea resistance to bruchid. Six cowpea genotypes were analyzed in three replicates. One-way analysis of variance, Pearson correlation and path analysis were used to determine the influence of the biochemical compounds on the cowpea status. Amongst the cowpea genotypes assayed the biochemical compounds analyzed (Vicilin; α-amylase Inhibitor; Phenols; Condensed Tannin; Tannin; Carbohydrate; Flavonoid and Protein), were present in amounts. Resistant genotypes exhibited higher contents of Phenols (22.29 mg/g for WC66*5T and 19.74 mg/g for WC36); Tannin (2.45CEmg/g for WC36 and 2.52CEmg/g for TVU13677); and Carbohydrate (72.82% for TVU13677 and 71.09% for WC36). The most susceptible genotypes had the lowest content of Phenols (13.5 mg/g for TVU946 and 12.72 mg/g for Glessissaffodo); Tannin (0.74CEmg/g for Akounado and 0.97CEmg/g for Glessissaffodo) and Carbohydrate (60.95% for Akounado and 61.39% for TVU946), while Condensed Tannin was associated to their seed coat colour but not to their resistance status against bruchid. The resistant genotypes TVU13677; WC36 and WC66*5T were found to contain a higher amount of a subset of biochemical compounds as defensive compounds against cowpea bruchid. The susceptible cowpea genotypes (Akounado; Glessissaffodo; TVU946) screened for their biochemical content presented low amounts of these defensive compounds. The path analysis implemented highlighted the existence of causal relationships among biochemical compounds analyzed and resistance parameters, thus revealing the resistance basis of cowpea seed biochemical compounds. These latter results point out the possibilities to consider the presence of these biochemical compounds underlying the resistance of cowpea to bruchid in the breeding program toward the resistance to bruchid.