石墨烯在金属防护中的应用与展望

石墨烯(类)材料作为明星材料,是诸多应用领域的研究热点。主要从两个方面综述了石墨烯材料在金属腐蚀防护中的应用研究现状,简要概述了单纯的石墨烯薄膜用于金属防护的发展历程,并对该防护手段的弊端进行了分析与讨论,得出石墨烯薄膜不适合直接覆于金属表面用于防腐蚀的结论。详细介绍了石墨烯复合防护涂层的制备方法与性能,针对将石墨烯类材料作为填料改性防护涂层的研究现状,概括了该防护手段的缺点与改进策略,即通过在氧化石墨烯表面进行分子(硅烷偶联剂、聚合物单体等)修饰和表面覆盖纳米粒子(纳米Si O2、Al2O3、Ti O2颗粒等),达到增强石墨烯材料与防护涂层之间的相容性的目的。在此基础上,提出了"主动防护"的概念,构想出一种以石墨烯材料为基础的新型缓蚀剂纳米存储器,同时提出石墨烯材料的深层防护机制仍亟待解决。最后,立足于整个石墨烯行业,从工业化应用的角度出发,对石墨烯防护技术进行了展望。     

Recovery of valuable metals from zinc leaching residue by sulfate roasting and water leaching

Zinc leaching residue (ZLR), produced from traditional zinc hydrometallurgy process, is not only a hazardous waste but also a potential valuable solid. The combination of sulfate roasting and water leaching was employed to recover the valuable metals from ZLR. The ZLR was initially roasted with ferric sulfate at 640 °C for 1 h with ferric sulfate/zinc ferrite mole ratio of 1.2. In this process, the valuable metals were efficiently transformed into water soluble sulfate, while iron remains as ferric oxide. Thereafter, water leaching was conducted to extract the valuable metals sulfate for recovery. The recovery rates of zinc, manganese, copper, cadmium and iron were 92.4%, 93.3%, 99.3%, 91.4% and 1.1%, respectively. A leaching toxicity test for ZLR was performed after water leaching. The results indicated that the final residue was effectively detoxified and all of the heavy metal leaching concentrations were under the allowable limit.     

Volatility forecasting in Chinese nonferrous metals futures market

This paper seeks to model and forecast the Chinese nonferrous metals futures market volatility and allows new insights into the time-varying volatility of realized volatility and leverage effects using high-frequency data. The LHAR-CJ model is extended and the empirical research on copper and aluminum futures in Shanghai Futures Exchange suggests the dynamic dependencies and time-varying volatility of realized volatility, which are captured by long memory HAR-GARCH model. Besides, the findings also show the significant weekly leverage effects in Chinese nonferrous metals futures market volatility. Finally, in-sample and out-of-sample forecasts are investigated, and the results show that the LHAR-CJ-G model, considering time-varying volatility of realized volatility and leverage effects, effectively improves the explanatory power as well as out-of sample predictive performance.     

生物吸附法回收溶液中铂族金属的研究进展

铂族金属具有诸多优良的物化特性,广泛应用于制药行业、催化领域、微电子材料和饰品投资等。全球铂族金属储量少,研究铂族金属资源二次回收利用意义重大。微生物吸附机理主要包括静电吸附、离子交换、表面络合和氧化还原作用等,该法具有工艺简单、经济环保、选择性强等优点,因此,在金属离子回收领域有较大的发展前景,代表着未来技术的发展方向。     

Nanoporous copper fabricated from Zr65Cu17.5Fe10Al7.5 amorphous alloy and its electrocatalytic oxidation performance

A series of bi-continuous and uniform nanoporous structures were fabricated successfully through chemical dealloying from quaternary Zr₆₅Cu_17.5Fe₁₀Al_7.5 amorphous ribbons in hydrofluoric acid (HF) solutions under a free corrosion condition. Nanoporous structures obtained from dealloying amorphous ribbons for 5 h in 0.02 M,0.035 M and 0.05 M HF solutions have mean pore sizes of 30–40 nm. A three-dimensional bi-continuous nanoporous copper (NPC) structure formed on Zr₆₅Cu_17.5Fe₁₀Al_7.5 ribbon alloys has pore sizes of 44.91 nm,52.60 nm and 57.37 nm, respectively, after immersion in 0.02 M HF solution for 15 h, 20 h, and 25 h. It shows that the pore size of NPC structure increases with increasing the dealloying time. The cyclic voltammetry (CV) results reveal that all NPC structures have the obvious electrocatalytic ability to the oxidation of (CH₂OH)₂ solution, compared with the initial amorphous ribbon without oxidation peak on CV curve. Zr-Cu-Fe-Al amorphous alloys can be new candidates for fabricating NPC structures.     

钎焊技术在金刚石工具中的应用

简要介绍了金刚石工具、工具分类及其制造过程中用到的钎焊技术,分析了金刚石颗粒与基体的连接原理与形式,就金刚石工具行业国内外发展状况评述了钎焊技术的相应发展,阐述了预合金粉末的扩散钎焊现象及有益作用,探讨了钎焊材料、钎焊工艺和钎焊设备的协同规律,提出了金刚石工具行业钎焊技术的发展方向,为国内金刚石工具和焊接行业发展研究提供参考。     

TIG电弧预热辅助铝-铜超声波缝焊工艺研究

对1 mm厚铝-铜TIG电弧预热辅助超声波缝焊试验进行了研究,通过金相显微镜、扫描电子显微镜、能谱分析等技术分析了不同TIG电流对焊缝成形、界面温升、界面形貌以及力学性能的影响。结果表明,TIG电弧预热可以软化板材,有助于高频振动能量的传递,为得到良好的缝焊接头提供条件。在TIG电弧预热和纯铝夹层的共同作用下,界面处温度最高可达446℃。当TIG电流较小时,电弧预热不充分,焊接界面处起伏比较平缓,局部区域出现未连接现象,拉剪试件在铝铜界面处断裂;当TIG电流增大到30 A时,在电弧热和高利用率的高频振动能的作用下,界面塑性流动程度提高,界面处出现"嵌合"、"连续凸起"等典型形貌,EDS分析显示界面未出现金属间化合物,拉剪试件断裂在紫铜母材上,最大拉剪力为2.58 kN。     

Identifying pathways of exposure to highway pollutants in great crested newt (Triturus cristatus) road mitigation tunnels

Road mitigation tunnels are increasingly deployed for amphibians but very little is known about chemical pollution in such schemes. We assessed pollution pressures associated with road runoff at a major great crested newt mitigation scheme in England. Sediments and waters in the mitigation system were analysed for major physico‐chemical parameters, trace metals and total petroleum hydrocarbons and compared to a nearby reference site. Seven out of eight tested metals including copper, zinc, lead and iron were in significantly greater concentrations in the tunnels than at a reference site and at environmentally significant concentrations. Water samples also exhibited elevated concentrations of aluminium and chromium and occasionally extreme alkaline pH associated with leaching of portlandite in tunnel cements. High conductivity values in waters and sediments corresponding with seasonal de‐icing salt application were also apparent. The study highlights the potential pollutant pressures for amphibians associated with large‐scale urban development and road mitigation schemes.     

Preparation of growth substrate to improve runoff quality from green roofs: physico-chemical characterization,sorption and plant-support experiments

Growth substrate plays an important role in determining the quality of runoff from green roofs. However, no systematic research has been conducted to design a substrate to improve runoff quality. Hence, the present study aimed at designing and developing a green roof substrate using low-cost and environmentally-benign materials. The inorganic fraction of the substrate includes purosil, vermiculite, sand and light-weight clay aggregates (LECA); whereas the organic fraction includes coco-peat and Sargassum wightii. Through factorial design, 13 different substrate mixes were prepared and the optimum mix (20% purosil, 30% vermiculite, 10% sand, 20% LECA, 10% coco-peat and 10% S. wightii) was found to have high water holding capacity (67.6%), air filled porosity (21%), hydraulic conductivity (5524 mm/h) and low bulk density (495 kg/m³). The substrate also provided maximum support for the growth of Portulaca oleracea. Experiments with metal-contaminated influent from the down-flow of a packed reactor revealed that the green roof substrate possesses a high sorption capacity towards various metal ions.     

东洞庭湖鲢鱼和鳙鱼中重金属富集差异分析

为分析东洞庭湖水体中重金属污染情况以及鲢鳙鱼间重金属富集存在的差异性,测定东洞庭湖沉积物以及鲢鱼和鳙鱼不同组织中5种重金属(Cr、Cu、Cd、Pb和Hg)的含量。结果显示,沉积物中Cr的含量低于国家一级土壤标准限值,Cu、Pb和Hg低于二级土壤标准限值,Cd的含量是国家三级土壤环境标准值的6倍;鲢鱼和鳙鱼中重金属的分布排序均为Cr:鳃肝脑肉,Cu:肝脑鳃肉,Cd:肝鳃脑肉,Pb:鳃肝肉脑,Hg:肉肝脑鳃;根据鱼类的生物-沉积物富集因子,相比Cr和Pb,鲢鱼和鳙鱼都更易富集Cu、Cd和Hg,而鲢鱼比鳙鱼更易富集Cd,鳙鱼比鲢鱼更易富集Hg;另外,鲢鱼和鳙鱼肝脏中Cd的含量超出行业标准限量,其它组织中重金属均未超标。表明东洞庭湖中Cd的污染最为严重;不同鱼类对重金属的富集确实存在差异性,不同组织对同一重金属的富集能力也存在显著差异;相比较鱼鳃和肝脏,鱼肉和鱼脑对重金属的亲和能力较弱。