铸渗法制备金属基表面复合材料的研究现状与进展

铸渗技术是近年来发展起来的一种制备金属基表面复合材料的新技术。对铸渗金属基表面复合材料的形成机理，铸渗成型工艺、铸渗技术的研究和应用现状进行了综述，指出了该项技术目前还存在的若干问题，并对其今后的发展方向进行了展望。     

Corrosion mechanism of micro-arc oxidation treated biocompatible AZ31 magnesium alloy in simulated body fluid

The rapid degradation of magnesium(Mg) based alloys has prevented their further use in orthopedic trauma fixation and vascular intervention,and therefore it is essential to investigate the corrosion mechanism for improving the corrosion resistance of these alloys. In this work, the effect of applied voltage on the surface morphology and the corrosion behavior of micro-arc oxidation(MAO) with different voltages were carried out to obtain biocompatible ceramic coatings on AZ31 Mg alloy. The effects of applied voltage on the surface morphology and the corrosion behavior of MAO samples in the simulated body fluid(SBF) were studied systematically. Scanning electron microscope(SEM) and X-ray diffractometer(XRD)were employed to characterize the morphologies and phase compositions of coating before and after corrosion. The results showed that corrosion resistance of the MAO coating obtained at 250 V was better than the others in SBF. The dense layer of MAO coating and the corrosion precipitation were the key factors for corrosion behavior. The corrosion of precipitation Mg(OH)2and the calcium phosphate(Ca–P) minerals on the surface of MAO coatings could enhance their corrosion resistance effectively. In addition, the mechanism of MAO coated Mg alloys was proposed.     

高速冲击下2519A-T87铝合金微观组织研究

用金相显微镜(OM)和透射电子显微镜(TEM)对2519A-T87铝合金靶材弹坑周围的高速冲击特征组织进行了观察分析。在OM下观察分析发现弹坑周围形成了变形带和绝热剪切带,裂纹在绝热剪切带内萌发和扩展。TEM下观察分析发现变形带内为微带组织,绝热剪切带内是动态再结晶组织。位错在微观组织演化过程中起到了重要作用。显微硬度测试结果表明,绝热剪切带的硬度值远远低于基体。     

昆虫滞育的研究进展

滞育是昆虫度过不良环境条件的一种重要行为，通过识别周围环境，昆虫可调节自身内分泌机制，进而决定其是否进入滞育。笔者介绍了近年来有关昆虫滞育的研究现状，阐述了昆虫滞育与环境因素的关系、昆虫滞育的生理生化基础及昆虫滞育这一生态适应的神经内分泌调节机理。     

超声波清洗工艺在汽车清洗中的应用

对汽车清洗技术中传统的机械清洗法、湿法化学清洗法的应用现状进行了分析,介绍了超声波清洗技术的工艺特点以及与传统清洗技术相比具有的优势.通过对超声波清洗设备结构、清洗机理和清洗过程的介绍,进一步阐述了超声波清洗技术在汽车上的具体应用和广阔的发展前景.     

高价金属离子与聚丙烯酰胺的交联机理

对Zr(Ⅳ),Al(Ⅲ),Fe(Ⅲ),Cr(Ⅲ)和Ti(Ⅳ)等高价金属离子在水溶液中的化学机理进行了研究.结果表明,高价金属离子通过水解聚合可生成多核羟桥络离子.试验证实,高价金属离子与聚丙烯酰胺(PAM)的交联体系具有最高成冻酸度,此酸度主要由体系中高价金属离子的性质所决定.PAM水解度对交联有一定影响,水解度太大或太小的PAM都不能形成冻胶,高价金属离子是以其多核羟桥络离子与PAM的羧基形成极性键和配位键产生交联的.     

Depositing Ag3PO4 on WO3 hollow microspheres at room temperature for rapid photocatalytic degradation of Rhodamine B

A series of WO₃ hollow microspheres decorated with Ag₃PO₄ nanoparticles (APW) composites with Ag₃PO₄:WO₃ mass percentage of 20% (20APW), 30%(30APW), 40%(40APW) and 50% (APW) were successfully synthesized, characterized and tested for the degradation of the Rhodamine B(RhB) under 300 ?W xenon lamp radiation. The photocatalytic results showed that the photocatalytic degradation performances of WO₃ hollow microspheres decorated with Ag₃PO₄ nanoparticles on RhB were significantly enhanced, which were much higher than that of individual Ag₃PO₄ and WO₃. Especially for 40APW, RhB can be completely degraded within 10 ?min. The order of degradation efficiency is 20APW<50APW< 30APW<40APW. The rate constant of 40APW (0.3902 min^?1) is about 81.3 times that of WO₃ (0.0048 min^?1). The diffuse reflection, photoluminescence and electrochemical impedance tests showed that the formation of Ag₃PO₄/WO₃ composite structure broadened the light absorption range, reduced the recombination rate of photogenerated electrons and holes, and decreased the resistance to charge transfer, which are beneficial to the improvement of photocatalytic performance. The capture agent experiments were carried out with 40APW, which specified the primary role of h⁺ and ?O₂^? in the degradation of RhB. The formation of heterojunction between Ag₃PO₄ and WO₃ that effectively separates photogenerated electrons and holes are contributed to the enhancement of photocatalytic properties of APW composites.     

中老年太极拳练习者膝关节损伤机理及预防措施

中老年太极拳练习者中常发生膝关节损伤,本文根据中老年人膝关节解剖生理特点,分析了太极拳练习中膝关节损伤机理,提出了预防损伤的措施。