Self-terminated electrodeposition of platinum on titanium nitride for methanol oxidation reaction in acidic electrolyte

The development of high-performance electrocatalysts for methanol oxidation is an urgent task to enhance the efficiency of direct methanol fuel cells. We report a simple and controllable method to fabricate Pt-decorated TiN electrocatalysts using self-terminated electrodeposition at room temperature and ambient pressure. Under optimized deposition parameters such as electrolyte pH, TiN substrate pretreatment, and pulsed deposition potential, quenching of the Pt electrodeposition facilitates obtaining an extremely low Pt mass loading (0.93 μg/cm²) on the TiN substrate. Repeated deposition potential pulses enable a gradual increase in Pt loading, with a precise control of the loaded Pt mass. Maximum intrinsic and mass activities for the methanol oxidation reaction are achieved for the catalyst with a Pt loading mass of 55.0 μg/cm², prepared by 20 deposition pulses. The maximum intrinsic activity achieved with the Pt-decorated TiN electrocatalyst is five times higher than that obtained with bulk Pt. The present results thus provide a facile method for the fabrication of cost-effective electrocatalysts.     

Photocatalytic evolution of hydrogen over mesoporous TiO2 supported NiO photocatalyst prepared by single-step sol–gel process with surfactant template

Photocatalytic activity of mesoporous titania supported nickel oxide photocatalyst synthesized by single-step sol–gel (SSSG) process combined with surfactant-assisted template method was investigated for hydrogen evolution from an aqueous methanol solution, in comparison with one prepared by conventional incipient wetness impregnation (IWI) method. In single-step sol–gel process, nickel precursor was introduced into the titania sol prepared with the aid of a surfactant template behaving as pore-controlling agent to attain meso-scaled pore. The single-step sol–gel photocatalyst was experimentally found to enhance the photocatalytic evolution of hydrogen rather than the impregnated one. The optimum level of nickel loading in photocatalytic activity test for single-step sol–gel method was slightly higher than that for incipient wetness impregnation method. Characterization results demonstrated the significant modification of physical characteristics of the single-step sol–gel photocatalyst, anticipated to relating to the observation of higher photocatalytic hydrogen evolution activity.     

A New Role of M1 Type Dopant for Nd-Rich Nd-Fe-Co-B Nanocrystalline Ribbons

In this work, our attempts focused on Ge effects on magnetic-microstructural relationships in Nd-Fe-Co-B nanocrystalline ribbons. Based on Transmission Electron Microscopy (TEM) and three dimensional atom probe (3DAP) analysis, it was observed that Ge containing alloys have a new behavior that was not observed yet. The increase of Ge content up to 0.36at% caused the increase of B_r and (BH)_max due to increase of Co content of Nd₂Fe₁₄B phase. However, the magnetic properties deteriorated for Ge bearing samples beyond 0.36at% due to the decrease of volume fraction of Nd₂Fe₁₄B phase. The comparison of Ge and Ga (another M1 dopant) effects on coercivity was reported and microstructural studies (using TEM and 3DAP) were shown the Nd-rich phase morphology and its alloying elements distribution in the nanometer sized intergranular phase.     

加工助剂对炭黑填充丁腈橡胶性能的影响

在填充50份(质量,下同)高耐磨炭黑(HAF)且用过氧化物硫化的丁腈橡胶(NBR)中使用一种新型加工助剂M(一种具有特定相对分子质量的含醚键和羟基等多种官能团的氟硅化合物),测定了炭黑填充NBR胶料的门尼黏度、硫化特性和硫化胶的物理机械性能,用橡胶加工分析仪和扫描电子显微镜对其进行了分析,并与加入硅烷偶联剂Si69及常用的以脂肪酸酯和不饱和脂肪酸锌皂为主要成分的2种分散剂进行了比较。结果表明,使用上述加工助剂均有利于炭黑在NBR胶料中的分散,胶料的加工性能和硫化胶的物理机械性能均得到不同程度的改善;以脂肪酸酯和不饱和脂肪酸锌皂为主要成分的分散剂能延缓炭黑填充NBR胶料的过氧化物硫化和降低硫化胶的交联密度;随着Si69的用量在2.0～6.0份范围内增加,胶料的正硫化时间减小,硫化胶的交联密度和定伸应力增加,而硫化胶的撕裂强度、耐热空气老化性、耐热油性、耐压缩永久变形性能和溶胀指数有下降的趋势;在Si69用量2.0～6.0份内及用量相同时,与无加工助剂和使用其他加工助剂相比,加工助剂M对胶料的硫化无明显影响,能够改善其加工性能,硫化胶的综合性能较好,其中耐热和压缩永久变形性能的改善最为明显。     

基于Web的大型注射模报价系统研究

介绍了模具价格的基本构成和大型注射模报价特点,设计了基于Web的大型注射模报价系统。报价系统以工时技术参数法和材料比价法为基础,在MS S QL上借助Delphi编程软件,能准确快速地估算出模具制造成本,对模具给出合理报价,有助于企业快速响应客户,在竞争中占得先机。     

IM-UFF: Extending the universal force field for interactive molecular modeling

The universal force field (UFF) is a broadly applicable classical force field that contains parameters for almost every atom type of the periodic table. This force field is non-reactive, i.e. the topology of the system under study is considered as fixed and no creation or breaking of covalent bonds is possible. This paper introduces interactive modeling-UFF (IM-UFF), an extension of UFF that combines the possibility to significantly modify molecular structures (as with reactive force fields) with a broad diversity of supported systems thanks to the universality of UFF. Such an extension lets the user easily build and edit molecular systems interactively while being guided by physics based inter-atomic forces. This approach introduces weighted atom types and weighted bonds, used to update topologies and atom parameterizations at every time step of a simulation. IM-UFF has been evaluated on a large set of benchmarks and is proposed as a self-contained implementation integrated in a new module for the SAMSON software platform for computational nanoscience available at http://www.samson-connect.net.     

5083-H321铝合金板材搅拌摩擦焊缝组织演变

采用搅拌摩擦焊接法焊接了5083-H321铝合金板材,借助光学显微镜、扫描电镜、背散射电子衍射分析仪及取向显微成像分析技术对焊缝与母材的组织进行了对比性研究.结果表明,该合金板材的焊缝无宏观缺陷,焊缝成形区呈现出与母材明显不同的组织特征;搅拌摩擦焊使该合金板材中大量的小角度晶界转化为大角度晶界,母材和焊核区的晶粒尺寸分布范围分别为6-55 μm及15-30 μm,晶粒纵横比分布范围分别为2~8和15-3,焊核区呈现均匀化与等轴化的动态再结晶特征.     

Efficiency of acetic acid and formic acid as a catalyst in catalytical and mechanocatalytical pretreatment of barley straw

In this study, the potential of organic acids (formic acid, acetic acid) in a catalytical and mechanocatalytic conversion of lignocellulosic barley straw to valuable sugars is explored using sulfuric acid as a reference. Acid-catalyzed hydrolysis has been carried out with acid-impregnated samples as well as unmodified barley straw. In the mechanocatalytical approach, pretreatment consists of impregnation with the acid catalyst and mechanical treatment by ball milling following chemical hydrolysis. Straw samples and residues were analyzed by Fourier transform infrared spectrometry (FT-IR) whereas hydrolysate analysis was based on total reducing sugar (TRS) determination following the DNS method and capillary electrophoresis (CE) analysis. The results indicated that acetic acid and formic acid are rather mild acids yielding low TRS levels compared to the reference acid. Mechanocatalytical pretreatment slightly increased TRS yields, but not significantly. Strikingly, sulfuric acid showed an efficient conversion efficiency yielding almost 45% of TRS. Furthermore, this study provided evidence for the acetylation of straw components when acetic acid was used as catalyst. Alkali hydrolysis induced the de-esterification, but revealed no significant increase of TRS yields.     

An intelligent θ-Modified Bat Algorithm to solve the non-convex economic dispatch problem considering practical constraints

This paper proposes a practical formulation for the non-convex economic dispatch problem to consider multi-fuel options, ramp rate limits, valve loading effect, prohibited operating zones and spinning reserve. A new optimization algorithm based on the θ-bat algorithm (θ-BA) is suggested to solve the problem. The θ-BA converts the Cartesian search space into the polar coordinates such that more search ability would be achieved. According to the complex, nonlinear, and constrained nature of the problem, a new self-adaptive modification method is proposed. The proposed modified θ-BA (θ-MBA) is constructed based on the roulette wheel mechanism to effectively increase the convergence of the algorithm. The high ability and satisfying performance of the proposed optimization method is examined on IEEE 15-unit, 40-unit and 100-unit test systems.     

Experimental and thermodynamic investigations regarding the effect of chromium on the carbides population in cast {Ni(bal.)-0.4C-6Ta-xCr} alloys with x varying from 0 to 50 wt%

Involving a particularly strong carbide-former metallic element, the tantalum carbides are potentially very stable at elevated temperatures in term of volume fraction and morphology. The TaC phase represents a major strengthening way to allow cast chromium-rich superalloys resisting mechanical stresses at elevated temperatures. They are exploited in recent high performance cobalt-based superalloys but seemingly not in nickel-chromium refractory alloys. Earlier studies showed that the stability of TaC in Ni-Cr alloys is not so good as in the Co-Cr ones, and they evidenced that chromium carbides may compete with TaC in the formation of the carbides population. A possible way to optimize the presence of TaC in Ni-Cr alloy may consist in rating the chromium content to an ideal value but preliminary knowledge about the TaC dependence on the Cr content is compulsory. The aim of this work is precisely the investigation of the effect of the content in chromium on the appearance and stability of the TaC phase in Ni-Cr alloys, by the means of thermodynamic calculations and real experiments in parallel. A global system Ni(bal.)-xCr-0.4C-6Ta compositions (with x varying from 0 to 50 wt%) was chosen. Thermodynamic calculations were performed to know the theoretic metallurgical states inside the considered x range. These theoretic results being dependent on the suitability of the used database, real experiments of verifications were also carried out for a selection of six alloys (x = 0, 10, 20, 30, 40 and 50 wt%). The alloys prepared by respecting these compositions were cast and isothermally exposed at high temperature (1400 and 1510 K), then subjected to metallographic characterization. For the used database the calculated results showed that no TaC should never appear whatever their Cr content, while TaC were really observed in the as-cast and aged versions of the alloys containing 20 wt%Cr and more, but never alone since chromium carbides were systematically also present. When the Cr content in the alloy is too low, the TaC are rare or even no present. This allowed concluding first that the database used for the calculations needs serious improvements, followed by tests with, as first criteria of quality, a good correspondence with the present experimental results. Second, the presence of Cr in quantity high enough is surprisingly compulsory to obtain TaC carbides in quantity high enough, but it is no possible to avoid the appearance of chromium carbides. Obviously, other ways than Cr adjustments must be found to obtain TaC in nickel-based alloys as the single carbide phase and in quantity high enough to achieve high mechanical properties at high temperature.