激光烧结纳米A12O3陶瓷的研究

纳米陶瓷材料具有许多优异的功能和特性，但在烧结过程中纳米颗粒容易长大，从而失去纳米特性。对激光烧结纳米陶瓷进行的理论和试验分析证明：利用激光烧结的方法，可使烧结陶瓷的晶粒保持在纳米尺度，从而为纳米材料在功能部件和结构部件等方面的应用提供了基础。     

激光烧结纳米Al2O3陶瓷的研究

纳米陶瓷材料具有许多优异的功能和特性,但在烧结过程中纳米颗粒容易长大,从而失去纳米特性.对激光烧结纳米陶瓷进行的理论和试验分析证明:利用激光烧结的方法,可使烧结陶瓷的晶粒保持在纳米尺度,从而为纳米材料在功能部件和结构部件等方面的应用提供了基础.     

选择性激光烧结成形温度场的研究进展

选择性激光烧结技术与传统铸造工艺相结合,为快速制造某些难以用传统方法获得的铸件提供了有利途径.对于各种粉末材料在选择性激光烧结成形过程中温度场的模拟与预测,是合理选择其烧结工艺参数的基础.本文中综述了聚合物粉末、聚合物覆膜金属/陶瓷粉末和金属粉末在选择性激光烧结过程中的热物性参数变化规律及其相应的成形温度场分布,以利于激光选择性烧结各类粉末材料而精确成形零部件.     

基于选择性激光烧结覆膜金属纳米复合粉末材料的研究进展

综述了选择性激光烧结金属粉末材料和纳米粉末材料的研究进展。介绍了选择性激光烧结覆膜Al-Fe-Ni合金系金属纳米复合粉末材料的开发思路。提出了选择性激光烧结覆膜Al-Fe-Ni合金系金腻纳米复合粉末材料的主要成分与制备方法，并对前景进行了展望。     

塑料粉末选择性激光烧结收缩实验研究

针对塑料粉末材料激光烧结过程中成形质量不高的问题,设计实验,分析了收缩对成形精度的影响,得到了制件的收缩规律,给出了改善选择性激光烧结制件精度的具体方式.     

激光选择性烧结金属粉末快速成形的研究

描述了激光选择性烧结金属粉末快速成形设备的粉末供给和铺平压实系统及动作，探讨了烧结过程参数对烧结质量的影响，粘结剂含量、孔隙率和缺陷尺寸与烧结件压缩强度之间的关系，并指出影响激光选择性烧结的重要因素是烧结粉末的特性、激光参数的设置等。     

青铜-镍粉末直接选择性激光烧结的研究

简要分析了选择性激光烧结的成形机制及其工艺和材料影响因素。详细分析了青铜一镍粉末直接选择性激光烧结的材料组分以及磷元素对烧结成形质量的影响。具体讨论了粉床温度、粉层厚度、激光功率以及激光扫描速率和方向等工艺参数对烧结件致密度和强度等机械性能的影响     

HAP／ZrO2纳米复相生物陶瓷的制备

采用化学反应法制备了纳米羟基磷灰石（HAP）粉体，并采用醇．水溶液加热法制备了纳米ZrO2粉体，通过对制备工艺的研究，同时结合TEM等分析测试手段对获得的纳米粉体进行了成分、颗粒尺度分布和微观形态分析。控制HAP和ZrO2的不同配比，分别选择40％和60％含量的HAP，采用热压烧结技术制备了HAP／ZrO2纳米复相生物陶瓷材料。分析了烧结温度、烧结时间及HAP含量等因素对HAP／ZrO2陶瓷材料的影响。确定了烧结工艺参数，即烧结温度1300℃，烧结压力30MPa及烧结时间1h，并对纳米生物陶瓷的微观组织和性能进行了分析测试，并采用模拟体液研究了该材料的体外生物相容性。结果表明：在短时烧结过程中HAP与ZrO2颗粒间没有反应发生，且该生物陶瓷材料具有无毒、无过敏等特点。     

青铜-镍粉末直接选择性激光烧结的研究

简要分析了选择性激光烧结的成形机制及其工艺和材料影响因素。详细分析了青铜-镍粉末直接选择性激光烧结的材料组分以及磷元素对烧结成形质量的影响。具体讨论了粉床温度、粉层厚度、激光功率以及激光扫描速率和方向等工艺参数对烧结件致密度和强度等机械性能的影响。     

纳米块体材料烧结技术进展

综述了压力烧结、微波烧结、场辅助烧结、激光烧结、锻造烧结、热挤压、冲击波烧结等纳米块体材料烧结新技术以及每种技术的特点和应用。     

Grain growth during the early stage of sintering of nanosized WC–Co powder

Rapid grain growth during the early stage of sintering has been found in many nano material systems including cemented tungsten carbide WC–Co. To date, however, there have been few reported studies in the literature that deal directly with the kinetics or the mechanisms of this part of grain growth. In this work, the grain growth of nanosized WC during the early stages of sintering was studied as a function of temperature and time. The effects of other influencing factors, such as the initial grain size, cobalt content, and the grain growth inhibitor VC, were investigated. The kinetics of the grain growth process was analyzed and the evolution of the morphology of WC grains during heating-up was studied using high resolution scanning electron microscopy. The results showed that the grain growth process consists of an initial stage rapid growth process which typically takes place during heat-up and the normal grain growth during isothermal holding. The initial rapid grain growth is at least partially attributed to the process of coalescence of grains via elimination common grain boundary. The preferred orientation between WC grains within the aggregates is considered a favorable condition for coalescence of grains, hence rapid grain growth. The solution–reprecipitation process is considered a mechanism of coalescence.     

纳米材料在硬质合金中的应用

WC晶粒不断细化是硬质合金发展的一个重要特征。从硬质合金的纳米原料、纳米硬质合金、纳米材料助长或增强超粗晶硬质合金以及硬质合金的纳米涂层材料等4个方面论述了纳米材料在硬质合金中的应用,着重报道了中国在这些方面的优势。纳米粒径原料的制备是首要难题,1997年发明的“紫钨原位还原”技术利用传统工艺制备纳米、超细碳化钨粉末,碳化钨粉的粒径可小于20 nm。纳米硬质合金技术利用低压热等静压或热等静压,克服了烧结过程中 WC异常长大的难题,制备100～200 nm纳米硬质合金,抗弯强度在5000 MPa以上,使用性能优于亚微或超细晶硬质合金,已用于生产。利用“纳米颗粒溶解法”制备的超粗晶硬质合金晶粒度可达12μm;而含有纳米Co2 W4 C增强相的超粗晶硬质合金产品,使用寿命比普通合金产品提高了2～3倍。涂层材料纳米化,是硬质合金工具的一个发展方向,在耐磨性、硬度和抗裂纹扩展方面有明显优势,加工工件表面质量更好,工具使用寿命更长。     

Nanophase materials in solid freeform fabrication

Solid freeform fabrication (SFF) is a manufacturing technology that produces parts directly from computer-aided design databases. Examples of the SFF approach are selective laser sintering (SLS) and selective laser reactive sintering (SLRS), both of which have the potential to directly produce structurally sound metallic or ceramic parts. The development of suitable materials systems that can optimize the SLS or SLRS processes are critical to this technology. For instance, nanocomposites, in which the constituents are mixed on a nanometer scale, have the potential to provide important advantages in the SLS and SLRS processes. One strategy is to design and develop nanocomposites in which one nanosize component has a lower melting point than the other nanosize component, either of which can serve as the matrix phase. The nanoscale dispersion of the low-melting component can aid the sintering process during SLS or SLRS. In this article, the philosophical basis for SLS and SLRS of nanocomposites is discussed. Conceptual design of nanocomposite systems and the SLS/SLRS results of a few exploratory systems are presented.     

纳米陶瓷的研究进展

纳米陶瓷是指晶界宽度、晶粒尺寸、缺陷尺寸和第二相分布都在纳米量级上的陶瓷材料,因其克服了传统陶瓷脆性较大的致命缺点,并在超塑性、铁电性能和力学性能等方面具有特殊的性能,而受到人们的广泛关注。综述了纳米陶瓷粉体的制备方法,包括物理合成与化学合成两种方式。物理合成方法消耗较大的能量且设备投资较大,因此纳米陶瓷粉体的制备以化学合成为主。在制备粉体的后期,还需通过加入分散剂和超声等方法来解决其团聚的问题。成型与烧结过程直接影响纳米陶瓷的性能。成型过程包括干法与湿法成型。干法成型简单易行,成体均匀,但容易引入杂质;而湿法成型能最大程度地减少杂质与团聚,但其工艺复杂、条件苛刻。烧结方法分无压烧结和压力烧结。在烧结过程中,如何将颗粒限制在纳米级别上成为各种技术需要攻克的难点。最后,阐述了纳米陶瓷的力学性能、铁电性能和超塑性,并简要介绍其在防护与涂层、生物医学材料和器具等方面的应用与创新。     

Tungsten carbide platelet-containing cemented carbide with yttrium containing dispersed phase

A fine and platelet tungsten carbide patterned structure with fine yttrium containing dispersed phase was observed in liquid phase sintered WC-20% Co-1%Y2O3 cemented carbide with ultrafine tungsten carbide and nano yttrium oxide as starting materials. By comparing the microstructures of the alloy prepared by hot-press at the temperature below the eutectic melting temperature and by conventional liquid phase sintering, it is shown that hexagonal and truncated trigonal plate-like WC grains are formed through the mechanism of dissolution-precipitation （recrystallization） at the stage of liquid phase sintering. Yttrium in the addition form of oxide exhibits good ability in inhibiting the discontinuous or inhomogeneous WC grain growth in the alloy at the stage of solid phase sintering.     

准一维纳米材料的合成及其研究进展

准一维纳米材料(纳米管、纳米线、纳米电缆、纳米带等)具有特异的物理、化学性质，并在未来纳米器件中具有潜在的应用价值，因此成为纳米材料领域中的研究热点。着重介绍了准一维纳米材料的合成方法：气相法、液相法和模板法。介绍了各种不同方法的生长条件和形成机制，并展望了准一维纳米材料的研究趋势。     

Progress on grain growth dynamics in sintering of nano-powders

Nanostructured materials, characterized by an ultrafine grain size, have stimulated much research interest by virtue of their unusual mechanical, electrical, optical, and magnetic properties. In this paper, the sintering process of nano-powders were reviewed, to which sintering of the traditional materials compared. The microstructural development, i.e., grain growth and densification during sintering as well as the mechanism of crystal surface diffusion and boundary migration were analyzed, and the dynamic models on sintering process were summarized by the relationship of grain growth and pores size, interface diffusion, densification rate, and sintering temperature. Finally, the research tendency of this major on the basis of above models was discussed.     

EFFECTS OF SIZE COMBINATION AND CONTACTING STATE OF RAW POWDER PARTICLES ON SPARK PLASMA SINTERED ULTRAFINE CEMENTED CARBIDES

本文采用亚微米WC粉和纳米Co粉、亚微米WC粉和高能球磨后具有纳米晶组织的微米级Co粉这两种具有不同粒径匹配的混合粉末作为原料粉末，利用放电等离子烧结（SPS）技术制备超细晶WC-10Co硬质合金。对不同原料粉末的SPS过程及烧结试样的显微组织和性能进行了系统的对比分析。实验结果表明，以两种混合粉末为原料均获得了平均晶粒尺寸在200nm以下的超细硬质合金材料，其中，采用亚微米WC粉和高能球磨的微米级Co粉利用SPS技术制备的材料相对密度达到98%以上，硬度达到HRA94.5，断裂韧性达到13.50MPa•m1/2，表明具有优良的综合性能。而采用亚微米WC粉和纳米Co粉利用SPS技术制备出的超细晶硬质合金的组织均匀性和性能较差。根据SPS技术的特殊烧结机理，对采用不同粒径匹配和结合状态的WC和Co混合粉末的SPS致密化机制进行了分析。