关键词： Nanocomposites   Biomedical   Mechanical alloying   SiC   Mechanical properties  

摘要： In this study, SiC/Ti-Cu nanocomposite was fabricated by mechanical alloying and sintering process. Effects of SiC nano-reinforcement on phase transformation, microstructure and tribological and antibacterial properties Ti-Cu intermetallic alloy were studied. The microstructure of the powders and sintered materials was investigated using X-ray diffraction, and scanning/transmission electron microscopy. The results exhibited the formation of major TiCu and TiCu4, and minor Ti2Cu and Ti2Cu3 nanocrystalline phases in the sintered Ti-Cu and SiC/Ti-Cu samples. With the addition of the nanoparticles, the amount of TiCu4 phase increased. Reinforcing Ti-Cu intermetallic alloy by SiC nanoparticles resulted in a considerable improvement in antibacterial activity, hardness, wear resistance, and reduction in friction coefficient. The excellent wear resistance of SiC/Ti-Cu nanocomposite is attributed to the formation of hard TiCu and TiCu4 phases with a homogeneous distribution of the phases in the nanocomposite as a result of SiC addition.

关键词： Heat treatment process   WC-binderless   WC-Co   Mechanical property   Microstructure  

摘要： In this study, the heat treatment process was performed to improve the mechanical properties of WC-binderless and WC-Co hard materials pre-fabricated by PCAS process. The microstructural and mechanical properties were varied significantly by the heat treatment process with the treatment time. To increase the fracture toughness value, the heat-treatment process of the WC-binderless, WC-5 wt.% Co and WC-10 wt% Co hard materials were performed at (1,300, 1,150, and 950) degrees C under (5 and 48) h, respectively. Enhancement of fracture toughness that focused on the major reasons was estimated for four mechanisms. Firstly, the microstructure formation of a mechanism was investigated to demonstrate the grain coarsening behavior for variation of heat treatment time. Secondly, the fraction of the coherent interface at WC/Co to the existing in the specific plane orientation was investigated. In particular, the texture distribution of WC (0001)(hcp) plane and Co (111)(fcc) plane were discussed in the EBSD micrograph. Thirdly, the increase of the mean free path by the Co content was exhibited in relation to the variation of mechanical properties. Finally, the mechanism of the decarburization effect of WC, which occurs during the heat treatment process under specific condition were demonstrated in the XRD peaks and FE-SEM analysis. In this chemical reaction, the separated W phases were locally precipitated, resulting in an increase in fracture toughness. (C) 2019 Elsevier B.V. All rights reserved.

关键词： 电化学法   聚苯胺   石墨烯   超级电容器  

摘要： 采用电化学方法制备出聚苯胺/石墨烯复合材料,并通过扫描电子显微镜(SEM)、傅里叶红外光谱仪(FT-IR)、紫外-可见分光光度计(UV-Vis)对氧化石墨烯、聚苯胺和聚苯胺/石墨烯复合材料的结构进行表征。结果表明,聚苯胺纳米颗粒均匀分布在石墨烯片层间。聚苯胺/石墨烯复合材料的比电容最大为238 F/g。循环1 000次以后,聚苯胺的电容衰减24. 5%,而复合材料的电容衰减15%。与聚苯胺相比,聚苯胺/石墨烯复合材料的电容量高、循环稳定性好,电导率从5 S/cm提高到10 S/cm。

关键词： 柔性应变传感器   碳纳米管   微结构   可穿戴   运动监测  

摘要： 设计了一种具有双层微结构的柔性压阻式应变传感器,并进行了制备方法研究。通过在半固化的环氧树脂基底(Ecoflex~? 00-30)表面制备形成碳纳米管(MCNTs)/环氧树脂(Ecoflex~? 00-30)复合薄膜,用毛刷制备微结构。通过测试分析可得,该柔性应变传感器具有高度可拉伸性能,可承受200%的应变,在0～80%,80%～170%,170%～195%的应变区间,GF值分别为10.5,40.5,190.5。将传感器进行可穿戴运动监测测试,可验证本传感器既可以实现手指和手腕运动等大动作应变的监测,输出电阻值相对变化达到7.5倍;也可以监测肌肉形变弯曲等小应变,输出电阻值相对变化达到1.4倍。

关键词： 微孔注塑   微观结构   聚丙烯   退火   冲击强度  

摘要： 通过二次开模微孔发泡注塑工艺制备不同聚四氟乙烯(PTFE)含量的聚丙烯(PP)微孔发泡材料,对比常规注塑成型的 PP 未发泡材料,研究不同退火温度对材料微结构及冲击强度的影响规律。结果表明,经二次开模微孔发泡注塑成型,再经退火处理能有效提高微孔发泡材料的冲击强度,达到退火前材料的 1.45 倍,而退火工艺对微孔发泡材料的微结构影响与对未发泡材料的影响基本相似。退火处理时PP材料结构中软无定型区的分子链进一步松弛,使材料更易于塑性变形,而其它软无定型区分子链易于规整重排,转变为硬无定型区,原硬无定型区的分子链同样进一步规整重排,甚至转变为结晶区,变得更硬,从而提高材料软硬兼具的抗冲击性能。

关键词： Intermetallic compound   Corrosion   EBSD   Dissimilar material joining   TEM   Friction stir welding  

摘要： The use of aluminum in conjunction of steel can reduce the weight of structures but dissimilar materials welded structure results in the formation of intermetallic compounds and inhomogeneous distribution of grains. Since aluminum is more active than the steel, the structures made from such dissimilar materials can be affected from corrosion medium which needs to be investigated. In the present work, friction stir welding has been used to join AA6061-T6 and AISI304 in lap configuration, each having a thickness of 1mm under varied process parameters. The detailed investigations have been made which includes understanding the effect of process variables on microstructures, intermetallic compounds and their phases, and thereby on corrosion of the aluminum-steel welded joint. SEM with integrated EBSD detector and XRD analyses have been carried out to characterize the weld interface that revealed the evolution of grain boundaries and existence of phases such as Fe2Al5 and AlCrFe2. The grain size of the weld zone has been found to be decreasing with increase in weld speed and plunge depth. The temperature profiles have shown a faster rate of heating and cooling with increase in welding speed and plunge depth which led to the refinement of microstructure. The evolution precipitates mainly comprised of Al, Mg and Si as the major elements. The corrosion rate was found to be increasing with decrease in grain size. Samples were corroded by pitting corrosion, inter-granular corrosion, and environmental corrosion. Severity of pits have been found to be non-uniform in the along weld cross-section.

关键词： Voronoi   多晶集合体   晶体塑性有限元   晶体取向   各向异性  

摘要： 材料的力学性能,尤其是在有限变形下所呈现的宏观各向异性,是材料结构设计和服役寿命考虑的关键因素。由于宏观模型不能较好地反映材料微观结构(晶粒的形貌和取向等)对宏观塑性各向异性的影响,因此,本文建立了能实际反映晶粒形貌的三维Voronoi模型,并基于晶体塑性理论对铝合金在有限变形下的响应进行计算。首先,建立反映材料微结构的代表性体积单元RVE模型进行计算,并与实验结果进行对比验证。然后,以单向拉伸为例,分析了有限变形过程中试件的晶粒形貌和取向分布等微观因素对宏观各向异性演化的影响,并从材料和结构两个层面讨论了微观结构对宏观力学性能的影响。结果表明,本文模型能够反映微观结构对宏观力学性能的影响,为实际生产制造领域构件的力学性能提供可靠的预测。

关键词： 方镁石   镁铝尖晶石   氧化铈   氧化钐   烧结致密化  

摘要： 为了研究稀土氧化物掺杂方镁石-尖晶石复相材料的烧结性能及显微结构,以富镁尖晶石细粉与烧结镁砂细粉为主要原料,分别外加质量分数为1%、2%和3%的CeO_2和Sm_2O_3,于1 600、1 650、1 700和1 750℃保温3 h烧成分别测定烧后试样的线收缩率、体积密度、显气孔率,并通过XRD、SEM、EDS等对其物相组成及显微结构进行分析。结果表明:1)引入稀土氧化物CeO_2与Sm_2O_3均有利于镁砂与尖晶石烧结致密化,引入CeO_2未参与反应,呈孤立形态分布于晶粒间;引入Sm_2O_3与原料中杂质反应形成稀土硅酸盐相分布于晶粒间。2)材料的体积密度和线收缩率随稀土氧化物加入量的增加而增加。在加入量相同的情况下,引入CeO_2的材料致密化程度相对较高。添加3%(w) CeO_2的材料体积密度达到3. 29 g·cm-3,显气孔率为10. 3%,烧后线收缩率为7. 79%。3)引入CeO_2和Sm_2O_3都有部分固溶于尖晶石与方镁石晶体内,活化晶格,促进晶粒发育。

关键词： Ag2CO3   形貌调控   异质结   抗光腐蚀性   电子空穴对  

摘要： Ag_2CO_3是近年来发现的一种新型的可见光响应光催化剂,对甲基橙(MO)、罗丹明B(RhB)和亚甲基蓝(MB)等染料和苯酚等有机物都具有较高的光催化降解能力.然而,在光催化反应过程中,Ag_2CO_3晶体中的Ag+会被自身的光生电子(e-)还原形成金属Ag单质,随着反应的进行,样品的稳定性和光催化效果迅速降低.贵金属沉积、非金属掺杂和形成异质结等方法,可以使Ag_2CO_3的光吸收得到扩展,同时促进光生电子空穴对的分离,从而提升Ag_2CO_3的抗光腐蚀性能和对污染物的降解效率.通过不同的物理和化学方法调控Ag_2CO_3催化材料的形貌、晶粒尺寸和晶体缺陷等,可以提升其比表面积和光生电子空穴的传输效率,进而提高其光催化活性.文中归纳了近年来Ag_2CO_3光催化材料的研究进展,分析了Ag_2CO_3光催化的特点,阐述了一系列提升Ag_2CO_3光催化性能的方法,并对Ag_2CO_3光催化材料的研究进行了总结与展望.

关键词： 生物材料   超快激光   微纳结构   细胞行为  

摘要： 提高医疗植入材料的生物相容性,对提升植入医疗器械的安全性有重要意义。通过超快激光制造出微纳米级别尺寸的材料结构以改善材料的生物相容性,近年来已被广泛应用于生物医学领域。本文简单介绍了细胞与生物材料相互作用原理,从生物材料表面微结构对其生物相容性能的影响出发,综述了超快激光加工不同材料表面形貌特征对细胞粘附、迁移、增殖、分化的影响,并进一步指出超快激光制备微纳结构在生物材料领域的局限和发展趋势。