基于焊点载荷的焊接工艺参数优化

通过建立基于多物理场耦合的焊点模型,得到焊接参数与焊点力学性能之间的窗口关系;对焊点进行车身综合工况下的受力分析,将焊点所受到的拉、剪力以及装配节拍要求的焊接时间作为约束条件,以最低焊接能耗为优化目标,提出了基于焊点“质量—能耗”均衡模型的焊接参数优化方法. 通过该优化方法,可以得到焊点力学性能及工业能耗的均衡优点. 结果表明,以某车型安全带固定座结构为算例,相比传统方法,优选的焊接参数在保证焊点性能要求的同时,还能使生产能耗降低超55%,这对保证质量及降低企业生产成本具有重要意义.     

B93пч合金挤压棒材在固溶及双级时效过程中的组织转变

通过扫描、透射电镜进行显微组织观察和能谱分析、力学性能测试、电导率测量等途径,研究了B93пч合金在固溶及双级时效处理过程中的组织转变规律,探讨了组织转变和性能变化之间的联系。结果表明,B93пч合金棒材中的条状η和T相在固溶过程中明显溶入基体,而大块状和圆片状η和T相也部分溶入基体,变为小块状和小圆片状。Al6(CuFe)相未能溶入基体,仍呈较大块状。经过逐步提高二级时效温度的双级时效后,合金强度降低,主要原因是基体析出相发生η′相向η相的转变,析出相长大粗化,密度降低。双级时效后还出现了晶间无沉淀析出带,并且随时效温度的升高而宽化。     

烧成工艺对莫来石陶瓷相组成和显微结构的影响

以煤矸石、石英粉、氧化铝微粉和碳酸钡微粉为原料,采用常压烧结法制备了莫来石陶瓷材料,研究了烧成工艺对莫来石陶瓷材料相组成及显微结构的影响.结果表明:在高温下,石英和刚玉反应生成二次莫来石,试样主要由莫来石、钡长石及刚玉三相组成.由于一次莫来石与二次莫来石的生成温度差异较大,可以通过控制烧成制度,控制它们的生长和晶粒大小,得到两者长径比对比明显的显微结构.     

Transient measurements of lattice oxygen in photocatalytic decomposition of formic acid on TiO2

In the absence of gas-phase O₂, formic acid extracted lattice oxygen from TiO₂ during photocatalytic decomposition (PCD) at room temperature. The amount of oxygen extracted was determined by interrupting PCD of a monolayer of formic acid after various reaction times and measuring O₂ uptake in the dark. After surface oxygen was depleted by PCD, oxygen diffused from the bulk to replenish the surface oxygen vacancies. The rate of oxygen diffusion to the surface was determined by measuring O₂ uptake after various dark times. A small fraction of the CO₂ that formed during PCD remained on the reduced sites of the TiO₂ surface, but this CO₂ was displaced by O₂ adsorption at room temperature.     

Effects of surface area on electrochemical performance of Li[Ni<Subscript>0.2</Subscript>Li<Subscript>0.2</Subscript>Mn<Subscript>0.6</Subscript>]O<Subscript>2</Subscript> cathode material

The effect of surface area on the electrochemical properties and thermal stability of Li[Ni_0.2Li_0.2Mn_0.6]O₂ powders was characterized using a charge/discharge cycler and DSC (Differential Scanning Calorimeter). The surface area of the samples was successfully controlled from ~4.0 to ~11.7 m² g⁻¹ by changing the molar ratio of the nitrate/acetate sources and adding an organic solvent such as acetic acid or glucose. The discharge capacity and rate capability was almost linearly increased with increase in surface area of the sample powder. A sample with a large surface area of 9.6–11.7 m² g⁻¹ delivered a high discharge capacity of ~250 mAh g⁻¹ at a 0.2 C rate and maintained 62–63% of its capacity at a 6 C rate versus a 0.2 C rate. According to the DSC analysis, heat generation by thermal reaction between the charged electrode and electrolyte was not critically dependent on the surface area. Instead, it was closely related to the type of organic solvent employed in the fabrication process of the powder.     

Determination of hydroxyl radical rate constants in a continuous flow system using competition kinetics

It is important to determine reaction kinetics of the hydroxyl radical (OH) with various water pollutants for understanding advanced oxidation processes (AOPs). Hence, a simple competition kinetics in a continuous flow system was employed to determine the second-order rate constants of OH with 14 organic and inorganic solutes selected in this study. In this method, p-nitrosodimethylaniline (PNDA) was specifically employed as a well-known reference probe for OH, which gave a competitive relationship between the PNDA and each solute over OH radicals. PNDA decay with OH radicals obeyed reaction kinetics in a first-order as long as the initial concentrations of H₂O₂ and PNDA were less than 30 μM and 2 μM, respectively. The second-order rate constants of OH radical with 14 solutes obtained in this study were found to be consistent with literature values using pulse radiolysis method.     

Performance of Au/M x Oy/TiO2 Catalysts in Water-Gas Shift Reaction

Our group recently developed a series of Au/M _x O _y /TiO₂ catalysts for CO oxidation, and demonstrated that some of these catalysts are still active after high-temperature treatment whereas Au/TiO₂ deactivates significantly due to the sintering of gold nanoparticles at elevated temperatures (Ma Z, Overbury SH, Dai S (2007) J Mol Catal A 273:97). In the current work, the performance of Au/M _x O _y /TiO₂ (M = Al, Ca, Fe, Zn, Ga, Y, Zr, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Yb) catalysts in water-gas shift (WGS) reaction was evaluated. The influences of different metal oxide (M _x O _y ) additives and pretreatment temperatures were investigated, and the catalyst stability as a function of reaction time on stream was tested. Some of these novel gold catalysts, with high activity and stability in water-gas shift, furnish new possibilities for further fundamental research and industrial development.     

薄板焊接变形分析

通过建立的薄板焊接有限元模型,对薄板结构件焊接变形进行有限元模拟,并对获得的薄板焊接温度场分布、应力场分布和变形规律进行了分析.结果显示,在整个焊接过程中,焊接薄板的平均温度在逐渐升高,直至准稳态状态;焊缝区域产生了拉应力,焊缝区域周边的母材金属则产生压应力,远离焊缝区域其残余应力较小;焊接变形成“马鞍”型.     

微生物清蜡降粘技术在采油工艺中的应用

介绍了微生物技术在油田清蜡降粘方面的应用最新成果.通过油田油水的现场实施和应用,在生产过程中见到了明显增油增注效果,并取得了较大的经济效益.     

Metal Phosphates as a New Class of Supports for Gold Nanocatalysts

Oxides and carbon are commonly used as supports for gold nanoparticles, but metal salts are barely considered as suitable supports. Our group recently communicated that gold nanoparticles supported on nanosized LaPO₄ (6–8 nm) are active for CO oxidation (Yan et al., Angew Chem Int Ed 45:3614, 2006). In the current work, we systematically developed an array of Au/M–P–O catalysts and tested them for catalytic activity and stability. It was found that 200 °C-pretreated Au/M–P–O (M = Ca, Fe, Co, Y, La, Pr, Nd, Sm, Eu, Ho, Er) show high CO conversions below 50 °C, and 500 °C-pretreated Au/M–P–O (M = Ca, Y, La, Pr, Nd, Sm, Eu, Ho, Er) show high CO conversions below 100 °C. These samples were characterized by ICP-OES, BET, XRD, TEM, SEM, and H₂-TPR. The stability of selected catalysts was studied as a function of time on stream. This work furnishes a new catalyst system for further fundamental and applied research.