In situ aqueous synthesis of silver nanoparticles supported on titanium as active electrocatalyst for the hydrogen evolution reaction

Dispersed silver nanoparticles (AgNPs) were successfully assembled on titanium (Ti) substrates by electroless deposition without using reducing agents, stabilizers, or any chemical pre-treatments. The substrate was immersed in aqueous solutions of AgNO₃ of various concentrations (0.001–0.5 M) for different durations (5 s–2 h) at room temperature. Subsequently, Ti substrates with various AgNP densities (number of AgNPs per unit surface area) were obtained. Nitrate anions in solution were found to destabilize the passivity of Ti proportionally to C_nitrate. This in turn activated the reducing ability of Ti, and hence resulted in an obvious increase in the population of AgNPs on Ti. This study was complemented with SEM/EDS, TEM, XPS and XRD examinations. The mechanism by which Ag ions are reduced to metallic Ag and the catalytic influence of destabilizing the passivity of Ti in enhancing its reducing ability are discussed. The electrocatalytic properties of as-prepared Ti-AgNPs catalysts for the hydrogen evolution reaction (HER) were investigated in 0.1 M HCl solution by means of cathodic polarization and impedance studies as a function of various experimental parameters. The results show that the Ti substrate loaded with the highest population of AgNPs exhibits the most effective electrocatalytic activity towards the HER, even better than platinum. Hence, the as-prepared Ti-AgNPs catalysts look promising in catalyzing the HER.     

倾斜板浓缩机结构参数的分析及优化

介绍了倾斜板浓缩机的工作原理,分析了影响其沉降效果的各个结构参数,为优化设计倾斜板浓缩机提供了参考依据。     

Phase-field simulation of lamellar growth for a binary eutectic alloy

Using general multi-phase-field model,detailed microstructures corresponding to different initial lamellar sets were simulated in a binary eutectic alloy with an asymmetric phase diagram.The simulation results show that regular or unstable oscillating lamellar structures depend on the initial lamellar widths of two solid phases.A lamellar morphology map associating with the initial widths has been derived,which is capable of showing the condition of forming various lamella structures.For instance,a regular ...     

弹性约束高墩的稳定性分析

实际工程中桥梁上部结构的约束对桥墩的稳定计算具有不可忽略的作用,从能量原理出发,推导出了考虑墩顶受桥梁弹性约束的高墩失稳临界力的计算公式,并建立有限元模型验证了公式的正确性,同时分析了墩顶约束刚度、墩高和桥墩直径对高墩稳定性的影响。该公式计算简单,精确度高,能满足工程需要,可为设计人员提供参考。     

气喷旋冲吸收塔整体结构应力计算分析

气喷旋冲吸收塔整体结构复杂,脱硫过程中受烟气压力、自重以及浆液压力等外载的作用,对塔体结构进行应力分析和强度校核是吸收塔结构设计的重要步骤。针对某实际的气喷旋冲吸收塔结构,考虑了两种常规的最不利工况,采用有限元法对塔整体结构进行了应力计算分析。分析中,用梁单元和壳单元建立了完整的吸收塔模型。基于计算结果和相关结构规范,对关键结构应力强度和塔壁失稳进行了校核。分析结果表明,吸收塔结构设计满足实际应用需求,设计中的塔壁厚度偏于安全。     

Oxygen electrode degradation in solid oxide cells operating in electrolysis and fuel cell modes: LSCF destabilization and interdiffusion at the electrode/electrolyte interface

Three long-term experiments have been performed in SOEC and SOFC modes at different operating temperatures. The durability tests confirm a higher degradation in electrolysis mode with respect to fuel cell operation. In addition, a larger increase of the ohmic resistance is observed for the cell operated at higher temperature in electrolysis mode. The oxygen electrodes of the pristine and tested cells have been characterized by synchrotron X-ray micro-diffraction and micro-fluorescence to assess the relation between the material destabilization and the formation of insulating phases due to interlayer diffusion. The analyses of the pristine cell confirm the presence after the electrode sintering of strontium zirconate and a Gd-rich interdiffusional layer in the electrolyte just below the zirconates. Moreover, evolutions in the LSCF unit cell volume reveal strontium segregation after aging. The associated material destabilization is linked to the accumulation of SrZrO₃ at the barrier layer/interdiffusional layer interface in operation and both phenomena are found to be thermally-activated and promoted in electrolysis mode. Finally, the crystallographic evolution of the interdiffusional layer in electrolysis mode has been investigated by X-ray diffraction. A slight increase of the phase peaks intensity detected at the highest temperature is correlated to the largest formation of SrZrO₃ observed in this condition. Based on these preliminary results, it is proposed that the loss of Zr⁴⁺ from the electrolyte due to the zirconates formation could facilitate the interdiffusion of Gd, reducing the local ionic conductivity and thus significantly contributing to the largest increase in the ohmic resistance observed in this case.     

大型"H"型钢压力矫直塑性变形失稳区域及侧压力的估算

针对国内首次研制的大型"H"型钢矫直机,提出了塑性变形区域及侧压力估算方法,并进行了分析与讨论,以供本行业科技人员参考与借鉴.     

脱稳-脱水处理含油污泥试验研究

对含油污泥的主要处理方法进行了简要分析。以含油污泥的脱水为研究重点,根据污泥稳定性高的特点,提出了采用化学方法脱除油泥稳定性,然后再进行絮凝脱水的技术路线。实验过程中采用了YN-3高效油泥脱稳剂,其主要成份是固体酸和强电解质,对油泥具有较好的脱稳效果。对脱稳剂YN-3加量对油泥脱稳效果影响以及PAM加量对固液分离的影响进行了重点考查,结果发现,YN-3和PAM的加量分别为2.0%～3.0%和400mg/L～500mg/L,对油泥脱稳和脱水效果最佳,经脱水处理后的污泥中原油含量提高到24.0%,体积降到原来的三分之一左右;脱稳脱水后的油泥无粘性,可掺和到煤粉中燃烧。同时提出了现场处理工艺,并进行了处理量为2.5m3/h的现场中试,处理结果略优于室内实验,脱水油泥中油含量为26.3%。对提高处理后油泥中的油含量和降低水含量的方法进行了讨论。     

Catastrophic destabilization of tunnel under rocks slipping in faultage

The model of catastrophic destabilization of tunnel under rock slipping in fault zone based on catastrophic theory and the potential function of fault movement were presented. On the basis of the results above, through Taylor series expansion of the equation of equilibrium surface, its standard form was obtained. Analysis show that catastrophic destabilization of tunnel will occur only when stiffness ratio between elastic sector and strain weakening sector of soft rocks was larger than or equal to 1. On the other hand, sliding behavior and evolution path of fault were directly affected by exogenous process, and it was a major extraneous factor which leads to catastrophic destabilization of tunnel. In the condition of system catastrophe could be generated, if external forces vary from smaller to larger, firstly, fault sticks or creeps, and secondly, when external force equal to or larger than critical value, fault turns to slip suddenly. Inverse, if external forces vary from larger to smaller, fault smoothly slips firstly, when external force equal to or smaller than critical value, and fault turns to stick or creep suddenly. Supported by the National Natural Science Foundation of China(50678079)