Experimental analysis of friction stir forming for dissimilar material joining application

Mass reduction of automotive body structures is a critical part of achieving reduced CO₂ emissions in the automotive industry. There has been significant work on the application of ultra high strength steels and aluminum alloys. However, the next paradigm is the integrated use of both materials, which poses a challenge of how to join the dissimilar materials. Friction stir forming is a new manufacturing process for joining dissimilar materials. The concept of this process is stir heating one material and forming it into a mechanical interlocking joint with the second material. In this research the process was experimentally analyzed in a position controlled robotic friction stir welding machine between aluminum and steel workpieces. New tool geometries were evaluated toward the goal of optimizing joint strength. The significant process parameters were identified and their optimized settings for the current experimental conditions defined using a design of experiments methodology. A scanning electron microscope was used to characterize the bonding and joint structure for single and multi-pin configurations. Two failure modes, aluminum sheet peeling and bonding delamination, i.e. braze fracture, were identified. It was found that the presence of zinc coating on the steel and overall joint geometry greatly affected the joint strength. The aluminum–zinc braze joint appears to be the largest contributor to joint strength for the single-pin joint configuration. The multi-pin geometry enabled a distribution of load to the four pins following fracture of the braze for increased joint toughness and ductility. Thus, the FSF method has been shown to exhibit potential for joining of aluminum to steel.     

La-EDTA coated Fe3O4 nanomaterial: Preparation and application in removal of phosphate from water

La-EDTA-Fe3O4 was prepared by a chemical co-precipitation method. The magnetic composite was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Furthermore, the adsorption properties of La-EDTA-Fe3O4 toward phosphate in water were investigated. The uptake rate of phosphate in water by La-EDTA-Fe3O4 was 3-1000 times than that of EDTA-Fe3O4 , and reached 97.8% at 7 hr. The adsorption process agreed well with the Freundlich model and kinetics studies showed that the adsorption of phosphate proceeds according to pseudo second-order adsorption kinetics. The maximum removal rate was achieved at pH 6.0-7.0. The La-EDTA-Fe3O4 had good adsorption properties and could be separated well from aqueous solution by a permanent magnet. Therefore, this nanomaterial has potential application for the removal of phosphate from large water bodies.     

NGO/PDA-DAG改性膜制备及抗污染性能研究

以多巴胺（DA）、1,3-二氨基胍盐酸盐（DAG）、氨基化氧化石墨烯（NGO）为改性剂,将氧化沉积和表面接枝法联用于聚偏氟乙烯（PVDF）原膜表面改性,得到NGO/PDA-DAG改性膜,研究改性膜的制备条件及其抗污染性能.结果表明：①改性膜最佳制备条件为DA浓度1.5mg/mL,DA氧化沉积时间4h,DAG质量浓度1wt%,NGO浓度2mg/mL,NGO接枝时间1h;②改性膜的亲水性能改善明显.改性剂向膜面引入了-NH₂、C=N、-OH、C=O等亲水性官能团,使静态接触角由68.7°（原膜）下降到38.7°（改性膜）;③改性膜比原膜具有更高的机械强度.改性层改善了原膜表面应力传递盲区,使改性膜表面粗糙度由原膜的46.5nm下降到18.3nm.改性膜的拉伸强度和杨氏模量分别为22.83和376.25Mpa,比原膜提高了39.72%和13.57%;④改性膜的选择透过性和抗有机污染性能显著提高.与原膜相比,改性膜对牛血清白蛋白（BSA）的截留率提高18.64%、纯水通量恢复率提高34.08%、膜总污染率下降20.67%（可逆污染率提高13.41%、不可逆污染率下降34.08%）;⑤改性膜抗菌性能强,且抗菌效果稳定持久.改性膜连续4次抗菌测试（38℃下接触2h）的平均抗菌率分别为92.3%、88.5%、87.9%、85.6%,能有效防止生物膜污染发生,而原膜无任何抗菌特性.     

哈密地区建筑材料氡发射系数测定

本文用FD-125型氡钍分析仪以α-射气闪烁法测定了哈密地区建材氡发射系数,其范围值为0～18.7％.氡发射平均系数的高低顺序是土块>普通水泥>花岗石材>红砖>预制构件>沙>石灰.结果表明,建材氡发射系数的高低不仅取决于建材~(226)Ra含量,很大程度上也取决于建材氡发射系数.测定该系数对评价建材所致居民室内氡浓度有一定意义.     

The effects of arm posture and holding time on holding capability and muscle activity

The aim of this study was to examine the effects of arm posture and holding time on human holding capability and resulting muscle activity. Fifteen healthy young males were recruited as participants. Maximum holding capacity was examined at 0 (degrees of shoulder forward flexion angle)/90 (degrees of elbow angle), 30/120 and 90/180 arm postures. Maximum acceptable weight of holding was evaluated in three arm postures (0/90, 30/120, 90/180) by three holding times (10?s, 20?s, 30?s). The greatest and lowest maximum holding capacity or maximum acceptable weight of holding occurred at 0/90 and 90/180 arm postures, respectively. Maximum acceptable weight of holding decreased with increasing holding time. While holding maximum acceptable weights, the % of maximum voluntary contraction of brachioradialis, biceps brachii and erector spinae ranged from 14 to 44%, from 14 to 53% and from 25 to 36%, respectively.     

Global anthropogenic tellurium cycles for 1940–2010

Tellurium is increasingly used in solar photovoltaics in the form of cadmium–telluride (CdTe) thin films. There are concerns regarding whether tellurium availability could be a constraint on large-scale deployment of CdTe photovoltaics. The present work brings a new perspective to the discussion of tellurium availability by providing the first extant global tellurium cycles constructed with material flow analysis principles. The tellurium cycles, for 1940–2010, present information on the production, fabrication and manufacturing, use, and resource management stages during this period. The results of the analysis show that during 1940–2010 approximately 11 Gg of refined tellurium was produced. This represents about 4.5% of the tellurium that was extracted from the ground during copper mining. Almost 80% of the refined tellurium, 8.5 Gg, was dissipated into end-uses such as metallurgical additives to iron, steel, and nonferrous metals, and thereby lost to potential reuse. As of 2010, the in-use tellurium stock is estimated at 1.1 Gg, which mainly accumulated after 1990s with the increasing tellurium use in electronics, specifically photovoltaic and thermoelectric devices. Because tellurium is a byproduct of copper ores, its supply can be enhanced by more attention to recovery during processing of the copper parent. Tellurium can also, in principle, be recovered from end-of-life electronics; the increasing in-use stock indicates the potential for significant end-of-life recycling in the coming decades.     

A hybrid approach using AHP–TOPSIS–entropy methods for sustainable ranking of structural materials

Nowadays, many countries are looking towards sustainability as a goal because our world has limited resources and serious environmental impacts. In the construction industry, the process of sustainable selection of structural material is considered one of the keys to achieve more sustainable construction. In this paper, the theories of decision making are utilised to develop an approach for evaluation and ranking the structural materials over their total life based on sustainability criteria using multi-attribute decision-making methods. One of them is Analytical Hierarchy Process which is utilised to build the problem hierarchical structure and assign weights of the predetermined sustainable factors. The other is Technique for Order Preference by Similarity to the Ideal Solution which is utilised to rank the structural materials within both each material life cycle phase and the complete material life cycle phases. The third is the concept of entropy by Shannon to evaluate the weight factor for each phase of material life cycle. The proposed approach presents an objective, systematic and comprehensive method for the sustainable ranking of materials that links between the structural element design and the sustainable selection of materials.     

Interfacial mechanisms of heterogeneous Fenton reactions catalyzed by iron-based materials: A review

The heterogeneous Fenton reaction can generate highly reactive hydroxyl radicals(·OH)from reactions between recyclable solid catalysts and H_2O_2 at acidic or even circumneutral pH.Hence,it can effectively oxidize refractory organics in water or soils and has become a promising environmentally friendly treatment technology.Due to the complex reaction system,the mechanism behind heterogeneous Fenton reactions remains unresolved but fascinating,and is crucial for understanding Fenton chemistry and the development and application of efficient heterogeneous Fenton technologies.Iron-based materials usually possess high catalytic activity,low cost,negligible toxicity and easy recovery,and are a superior type of heterogeneous Fenton catalysts.Therefore,this article reviews the fundamental but important interfacial mechanisms of heterogeneous Fenton reactions catalyzed by iron-based materials..OH,hydroperoxyl radicals/superoxide anions(HO_2./O_2~-.)and high-valent iron are the three main types of reactive oxygen species(ROS),with different oxidation reactivity and selectivity.Based on the mechanisms of ROS generation,the interfacial mechanisms of heterogeneous Fenton systems can be classified as the homogeneous Fenton mechanism induced by surface-leached iron,the heterogeneous catalysis mechanism,and the heterogeneous reaction-induced homogeneous mechanism.Different heterogeneous Fenton systems catalyzed by characteristic iron-based materials are comprehensively reviewed.Finally,related future research directions are also suggested.     

南京市化学原料及化学制品制造业能源消耗预测

化学原料及化学制品制造业作为南京市高能耗、高污染产业,对其能源消耗总量及能源消耗结构进行预测,对节能减排具有重要意义。以2002—2012年能源消耗量弱化之后的数据为原始数据,运用灰色GM(1,1)模型对2013—2020年南京市化学原料及化学制品制造业能源消耗总量以及主要能耗进行了预测。由于部分原始数据序列光滑性较差,所建预测模型的精度较低,使用平均弱化缓冲算子对其进行处理。结果表明,处理之后建模精度提高,预测的结果更加准确。     

饮用水消毒中茶多酚抑菌机理的研究进展

饮用水消毒关系着人类的身体健康,茶多酚作为绿色消毒剂具有良好的消毒作用及消毒持续性,无毒副作用。对茶多酚的抑菌机理进行系统的综述,介绍了茶多酚对菌体正常生理形态的改变、对细胞壁膜的破坏、对蛋白质合成和表达的阻碍以及对遗传物质的作用,并阐述了酚羟基与金属离子、蛋白质的络合作用,以及酯官能团、聚合度对儿茶素抑菌效能的影响,为茶多酚在饮用水消毒中的应用提供理论基础。