Cu与三元层状化合物复合材料研究现状

现代工业的需求,迫使铜为克服自身缺点而向合金化和弥散增强化发展。铜基复合材料我们早已不陌生,但是各种弥散增强相制成的复合材料有其自身缺点。本文回顾了常见的Cu基增强相以及他们的优缺点比较,简要介绍三元层状化合物Mn+1AXn的组成与结构以及其优异性能,并分别介绍了Ti3SiC2、Ti3AlC2、Ti2AlN Ti2AlC和Ti2SnC它们分别与Cu复合材料的研究进展和展望未来应用前景。     

无压烧结制备Ti–Al–C系三元层状陶瓷

以TiC粉、Al粉、Ti粉为原料,采用无压烧结工艺制备高纯Ti–Al–C三元层状陶瓷,探究了烧结温度、烧结时间、烧结助剂等对Ti–Al–C系三元层状陶瓷制备的影响。结果表明:在一定范围内提高烧结温度和烧结时间能减少杂质相的产生,不添加助剂情况下在1 400℃下保温3 h能得到80%(质量分数)以上的Ti–Al–C系三元层状陶瓷,该条件下掺入少量Si粉或Sn粉能得到高纯Ti–Al–C系三元层状陶瓷。TiC、Al、Ti和Si质量比为2.0:1.2:1.0:0.1的原料粉末在1 400℃保温3 h能得到纯度99%以上的Ti_3AlC_2陶瓷,TiC、Al、Ti和Sn质量比为2.0:1.2:1.0:0.1与TiC、Al、Ti和Sn质量比为1.0:1.2:1.0:0.1的原料粉末在1 400℃保温3 h均能制备出纯度99%的以Ti_3AlC_2为主晶相的Ti_3AlC_2/Ti_2AlC复相陶瓷。     

中国近10年耕地总量变化评价

文章依据国家统计年鉴数据,通过单指标趋势法,分析了全国近10年耕地数量、粮食产能、农业结构产值变化情况,同时分析了全国各省(区、市)3个指标综合变化趋势。通过两个层次的分析,引出耕地总量的概念,提出科学理解1.2亿hm2耕地红线的内涵:既要综合考虑耕地数量、粮食产能、农业结构产值3个指标,又要用发展的观点去理解他们之间的动态变化,统筹好它们之间的内在关系,使之向着良好的方向发展。     

以铝为助剂结合放电等离子烧结制备Ti3SiC2

以铝为助剂结合放电等离子烧结工艺，在较低温度下快速制备出高纯致密Ti3SiC2块体材料．掺加适量铝能加快Ti3SiC2的反应合成，提高制备材料的纯度，并促进Ti3SiC2晶体的生长和材料的快速烧结致密．在升温速率为80℃／min，z轴压力为30MPa时，材料制备的最佳温度为1200-1250℃．所制备材料经XBD、SEM和EDS分析表明不含TiC和SiC等杂质相，Ti3SiC2为5-25μm的板状结晶．     

柔性陶瓷三元层状碳化物Ti3SiC2的金属特性

Ti3SiC2兼有金属和陶瓷材料的优异性能，是新一代高性能高温结构材料、电工材料、自润滑轴承的理想侯选对象。重点介绍制备Ti3SiC2的主要方法：气相沉积法、自蔓延高温合成法、热压和热等静压法、放电等离子烧结法，并论述了Ti3SiC2的未来研究方向和潜在的应用前景。     

Synthesis of Ti3SiC2 by spark plasma sintering(SPS)of elemental powders

Ti3SiC2 materials have been fabricated by spark plasma sintering of the elemental powders with the addition of Al.At the heating rate of 80℃/min and under the pressure of 30MPa,the ideal synthesis temperature of Ti3SiC2 is in the range of 1150-1250℃.The addition of Al is in favor of the formation of Ti3SiC2.The synthesized compound has the molecular of Ti3Si0.8Al0.2C2 and lattice parameters of α=0.3069nm,c=1.7670nm.Its grain is plane-shape with a size of about 50μm in the elongated dimension.The prepared material has Vickers hardness of 3.5-5.5GPa(at 1N and 15s) and is as readily machinable as graphite‘s.     

填充剂对NBR/PVC共混物力学性能等的影响

考察了填充剂(高耐磨炭黑、白炭黑、轻质碳酸钙)对丁腈橡胶/聚氯乙烯(NBR/PVC)热塑性弹性体(TPE)的力学性能和耐热老化、耐油性能的影响。     

多孔陶瓷的制备和性能研究

选用普通陶瓷原料粉为主要原料，适当添加造孔剂(有机细粉碳黑)和高温活性剂，制备出一种性能优良的多孔陶瓷。通过扫描电镜及性能测试分析，探讨了多孔陶瓷的微观结构及性能的影响因数。     

Electrical,Thermal, and Mechanical Properties of Cu/Ti_3AlC_2 Functional Gradient Materials Prepared by Low-temperature Spark Plasma Sintering

Cu/Ti_3AlC_2 composite and functional-gradient materials with excellent electrical conductivity and thermal conductivity as well as good flexural properties were prepared by low-temperature spark plasma sintering of Cu and Ti_3AlC_2 powder mixtures. The phase compositions of the materials were analyzed by X-ray diffraction, and their microstructure was characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy. Further, the electrical conductivity, thermal conductivity, and flexural properties of the materials were tested. Results show that, for the composite materials, the resistivity rises from 0.75 × 10~(-7) Ω·m only to 1.32 × 10~(-7) Ω·m and the thermal diffusivity reduces from 82.5 mm~2/s simply to 39.8 mm~2/s, while the flexural strength improves from 412.9 MPa to 471.3 MPa, as the content of Ti_3AlC_2 is increased from 5 wt%to 25 wt%. Additionally, the functional-gradient materials sintered without interface between the layers exhibit good designability, and their overall electrical conductivity, thermal conductivity, and flexural strength are all higher than those of the corresponding uniform composite material.