High Hole Mobility of GaSb Relaxed Epilayer Grown on GaAs Substrate by MOCVD through Interfacial Misfit Dislocations Array

The structural property of GaSb epilayers grown on semi-insulator GaAs (001) substrate by metalorganic chemical vapor deposition (MOCVD) using Triethylgallium (TEGa) and trimethylantimony (TMSb),was investigated by variation of the Sb:Ga (V/III) ratio.An optimum V/III ratio of 1.4 was determined in our growth conditions.Using transmission electron microscopy (TEM),we found that there was an interfacial misfit dislocations (IMF) growth mode in our experiment,in which the large misfit strain between epilayer and substrate is relaxed by periodic 90 deg.IMF array at the hetero-epitaxial interface.The rms roughness of a 300 nm-thick GaSb layer is only 2.7 nm in a 10 μm×10 μm scan from atomic force microscopy (AFM) result.The best hole density and mobility of 300 nm GaSb epilayer are 5.27×10 6 cm 3 (1.20×10 6) and 553 cm 2 ·V 1 ·s 1 (2340) at RT (77 K) from Hall measurement,respectively.These results indicate that the IMF growth mode can be used in MOCVD epitaxial technology similar to molecular beam epitaxy (MBE) technology to produce the thinner GaSb layer with low density of dislocations and other defects on GaAs substrate for the application of devices.     

河北某难选银矿选冶工艺试验研究

河北省某难选银矿中银矿物种类多且嵌布特征复杂,在工艺矿物学研究基础上,通过选矿方案对比,采用浮选—浮选尾矿氰化联合工艺流程。浮选试验研究了磨矿细度、矿浆PH值、组合捕收剂丁基黄药和FZ-9538用量等条件对银回收率的影响,确定了最佳工艺条件,闭路试验可获得银品位3145g/t、回收率82.52%的银精矿;浮选尾矿含银42g/t,经氰化浸出24小时后,银浸出率为65.48%,对原矿回收率11.45%,浮选加氰化总回收率93.97%。     

Effectiveness of some diquaternary ammonium surfactants as corrosion inhibitors for carbon steel in 0.5 M HCl solution

Four Gemini surfactants were synthesized and characterized using elemental analysis, FTIR and ¹H NMR spectroscopy. The synthesized compounds were evaluated as corrosion inhibitors for carbon steel in 0.5 M HCl solution. The inhibition efficiencies of the tested inhibitors were depended on the hydrophobic chain length and the used doses of the inhibitors. The polarization measurements showed that these inhibitors are acting as mixed inhibitors for both anodic and cathodic reactions. The results showed that the inhibition efficiencies were increased by increasing the inhibitor doses and the hydrophobic chain length and reached the maximum at 500 ppm by weight for stearyl derivative. The efficiencies obtained from the impedance measurements were in good agreement with those obtained from the gravimetrical and polarization techniques which prove the validity of these tolls in the measurements of the tested inhibitors.     

Interfacial bonding of Flax fibre/Poly(l-lactide) bio-composites

The use of glass fibre reinforced polyester composites raises many health and safety and environmental questions. One alternative is the development of high performance bio-based bio-composites with low environmental impact. Improved understanding of interfacial properties is essential to optimise the mechanical properties and durability of these materials, but so far few data are available. The present work describes the interfacial characterization of Flax fibre/Poly(lactic) acid (PLLA) system at the micro-scale using the microbond test. Different thermal treatments have been carried out (cooling rate and annealing) in order to evaluate the influence of matrix and interfacial morphologies as well as residual stress on interfacial properties. Micromechanical models have been used to determine the interfacial shear strength. When cooling rate is slow, improved interfacial properties are observed.     

A Comprehensive Overview on the Latest Progress in the Additive Manufacturing of Metal Matrix Composites: Potential,Challenges, and Feasible Solutions

Nowadays, as an emerging technology, additive manufacturing(AM) has received numerous attentions from researchers around the world. The method comprises layer-by-layer manufacturing of products according to the 3D CAD models of the objects. Among other things, AM is capable of producing metal matrix composites(MMCs). Hence, plenty of works in the literature are dedicated to developing different types of MMCs through AM processes. Hence, this paper provides a comprehensive overview on the latest research that has been carried out on the development of the powder-based AM manufactured MMCs from a scientific and technological viewpoint, aimed at highlighting the opportunities and challenges of this innovative manufacturing process. For instance, it is documented that AM is not only able to resolve the reinforcement/matrix bonding issues usually faced with during conventional manufacturing of MMCs, but also it is capable of producing functionally graded composites and geometrically complex objects. Furthermore, it provides the opportunity for a uniform distribution of the reinforcing phase in the metallic matrix and is able to produce composites using refractory metals thanks to the local heat source employed in the method. Despite the aforementioned advantages, there are still some challenges needing more attention from the researchers. Rapid cooling nature of the process, significantly different coe fficient of expansion of the matrix and reinforcement, processability, and the lack of suitable parameters and standards for the production of defect-free AM MMCs seem to be among the most important issues to deal with in future works.     

Preservative effectiveness of essential oils in vapor phase combined with modified atmosphere packaging against spoilage bacteria on fresh cabbage

This study was conducted to investigate the antibacterial effects of various essential oils (EOs) against pathogens using the disc volatilization method. Also, combined effects of EOs in vapor phase and MAP were evaluated for reducing levels of total mesophilic microorganisms on fresh cabbage. The vapor phase activities of EOs (thyme-1, oregano-1, lemongrass-1, and lemongrass-2 oils) observed strong inhibitory effects. The MAP results showed that 100% CO₂ gas packaging reduced significantly levels of total mesophilic microorganisms on cabbage and radish sprouts, and their reduction level was 1.55 and 2.26 log₁₀ CFU/g compared to control after 21 days of storage (p ≤ 0.05). Based on previous results, combined effects of EOs in vapor phase and MAP (100% CO₂) showed that lemongrass-2 oil with 20 discs showed complete inactivation by <1.0 log₁₀ CFU/g after 14 days of storage. These results could provide useful information for developing alternative preservation method to improve the freshness and shelf-life of fresh produce using natural antimicrobials.     

A Mixture Toxicity Study Employing Binary Combinations Of Dinitrobenzene And Trinitrobenzene Using The Bioluminescent Marine Bacterium Vibrio Harveyi As The Test Organism

A combination mixture study was conducted with two organic compounds, dinitrobenzene and trinitrobenzene, using the marine bioluminescent bacterium Vibrio harveyi . This assay employs the photogenic properties of this organism for determination of toxicity in a direct procedure. Evaluation of toxicity was performed using an additive index methodology, mixture toxicity index and graphic representations. Graphic representations employed were isobole plot and isobologram, both isopleths. The additive index procedure employed both chemicals at their estimated median effective concentration (EC 50 ) for determination of a toxicity value. Isopleths employed combinations of both chemicals, using an equitoxic concentration, at 20% intervals of their EC 50 . An additive index value for this mixture was statistically antagonistic. Mixture toxicity index suggests that these chemical in various combinations are antagonistic. Combinations for both isopleths were similar and exhibited additivity for three mixture values and statistical synergism for one mixture. Statistical analysis of combinations using the z test found some mixtures to be statistically different. This analysis, in part, supports findings for isopleths. These results suggest that different mixtures of the two chemicals may have different interaction outcomes.     

黑钨矿捕收剂的应用及其使用后水中残留物的去除

通过分析黑钨矿浮选药剂应用现状,总结近年来黑钨矿浮选捕收剂应用实践。其中含胂和膦的脂肪酸类捕收剂含有有害金属,对环境中土壤以及水有极大的污染;螯合剂使用前需预先处理,不仅增加了成本和流程复杂,同时也危害环境;组合药剂的使用提高了药剂效率,节约资源,通过减少使用对环境有污染的药剂,保护了环境。并采用PAC、PFS及其组合絮凝剂对捕收剂使用后废水进行处理,结果表明:PAC及PAC+PFS处理后废水排放达到《污水综合排放标准》(GB8978-1996)的一级标准,而PFS处理则没有达到一级标准。     

促进天然气水合物形成的影响因素分析

天然气水合物(NGH)工业化生产中面临的主要问题是天然气水合物的合成速率较低。天然气水合物的生成反应为相间界面反应,任何影响气液相之间传质或传热的操作均可以增加天然气水合物的生成速率。结合影响天然气水合物形成的特点,从改善相平衡条件、增加气水接触面积和增加天然气的溶解度三方面介绍了促进天然气水合物形成的办法,并分析了各自的优缺点。     

喷涂机器人路径组合优化中喷枪新模型

针对当前已有的喷炬二维和三维模型,由于在解决喷枪路径组合优化时涂层均匀性仍出现的不足,提出了一种考虑喷枪喷射高度的涂层生长速率新模型。该模型以路径组合优化中常见的交界线平行和不平行两种情况为研究对象,并基于面片交界处喷枪轨迹为PA-PA时涂层厚度均匀性较好的原则,分别采用修正喷枪速率法和变偏距变速率法来提高喷涂的均匀性,最后通过应用实例与仿真,证明了该模型的有效性。