定向金属氮化法制备AlN/Al陶瓷基复合材料研究进展

介绍了氮化铝的结构和性能,并回顾了国内外采用定向金属氮化法制备AlN/Al陶瓷基复合材料的研究成果,详细探讨了合金成分和预形体对AlN/Al陶瓷基复合材料显微结构和生长的影响.指出工艺和显微结构优化、新型复合材料开发是定向金属氮化法制备AlN陶瓷材料的发展方向.     

AlN陶瓷粉末制备方法特点和进展

本文就国内外AlN粉开合成的研究情况,综述了直接氮化法、Al2O3碳热还原法、自蔓延高温合成法、等离子体法、气溶胶法等主要的几种AlN粉末制备方法的特点和研究进展,分析了制备AlN粉末的主要发展方向。     

热压烧结工艺对AlN陶瓷显微结构及性能的影响

以直接氮化法制备的AlN粉体为原材料,添加质量分数为5％ 的Y2O3做烧结助剂,采用热压烧结工艺制备AlN陶瓷.研究烧结温度和压力对AlN陶瓷显微结构、相对密度和热导率的影响.结果表明:随着烧结温度的升高,AlN陶瓷的晶粒长大,第二相逐渐增多,热导率和相对密度均为先增大后减小;随着压力的增大,AlN陶瓷的晶粒逐渐细小,气孔率减少,热导率和相对密度都显著增大.确定AlN陶瓷的最优烧结条件如下:温度为1800℃,压力为50 MPa.     

AlN粉体制备技术研究进展

直接氮化法和碳热还原法是现代规模化制备AlN陶瓷粉体的主要方法。本文结合最新研究成果,分析了这两大类A1N粉体制备方法的优缺点,探讨了今后A1N粉体制备技术发展需要解决的关键问题。     

直接氮化法制备氮化铝粉末的结构特性

用金属镁（Mg）作催化剂,氮气和铝块为反应物,采用直接氮化法制备出氮化铝（AlN）粉末样品。运用X射线衍射仪（XRD）、扫描电子显微镜（SEM）和拉曼光谱仪（Raman）对样品进行结构特性分析发现,AlN样品为纯六方相结构,呈现纳米线堆积形貌,纳米线直径约60nm,且尺寸均匀。拉曼散射光谱峰值较单晶AlN向低波数方向移动,表明此方法制备的AlN纳米线存在表面拉应力。     

纯铝材电解液微弧氮化工艺探讨

电解液微弧氮化工艺简单,过去未见用其制备AlN膜的报道。采用电解液微弧氮化工艺在纯铝基片上制备了AlN陶瓷膜,利用正交试验优化工艺,研究了最优工艺制备的膜层的物相、形貌,并探讨了占空比、放电频率对膜层硬度、绝缘电阻、耐压值的影响。结果表明：正交试验优化的工艺为100mL超纯水中CO（NH2）235．0g,EDTA-2N...     

温度对高压烧结氮化铝陶瓷热导率的影响

以直接氮化法合成的AlN微米粉为原料,添加3%(质量分数)的CaC2为烧结助剂,在5GPa的压力下烧结30min,考察不同烧结温度对AlN陶瓷热导率的影响。用阿基米德排水法、XRD、SEM等技术手段对AlN烧结体进行性能检测。研究表明,在1500～1800℃范围内,温度的升高能促使AlN陶瓷内部晶粒长大,晶型饱满,尺寸均一,晶界相减少,实现烧结致密化,利于热导率的提高。     

直接氮化法制备氮化铝纳米线

在氮、氢混合气气流中(氢气10%,体积比),以铝和氯化铵混合粉体为原料,在水平管式炉中采用直接氮化法合成了氮化铝纳米线。使用扫描电子显微镜(SEM)、X射线衍射仪(XRD)和透射电子显微镜(TEM)对纳米线的形貌和结构进行了检测与分析;研究了铝和氯化铵的比例(质量比)、反应温度、升温速度等因素对生成物的种类、形貌和氮化铝纳米线产量的影响。研究发现,所获得的AlN纳米线为单晶六方纤锌矿结构,表面不光滑且有非晶层,而AlN纳米线依照Vapor-Solid(VS,气-固)生长机制生长。获得了较为优化的制备氮化铝纳米线的工艺条件,利用VS生长机制和气相过饱和度概念对上述影响氮化铝纳米线生长的条件进行了初步的机理分析。     

先驱体转化法制备AlN粉体的研究现状

有机先驱体裂解工艺制备的AlN粉体因具有低氧含量和高烧结活性而被广泛关注。AlN先驱体的组成与结构对陶瓷产率及陶瓷粉体的性能有着重要影响,因此先驱体的合成对AlN陶瓷起至关重要的作用。选择不同的合成原料直接决定了先驱体的分子组成与结构。重点介绍了以三烷基铝化合物、无机铝化合物及氢化铝锂3种铝源制备AlN先驱体的工艺方法与反应机制。     

泡沫前驱体碳热还原氮化法合成氮化铝粉体

本研究采用碳热还原氮化法(CRN)合成AlN粉体。以γ-Al₂O₃和炭黑为原料, 采用直接发泡工艺与注凝成型相结合的方法制备出Al₂O₃/C泡沫, 作为合成AlN粉体的前驱体。泡沫孔隙尺寸从几十微米到几百微米, 总孔隙率56%~90%。具有通孔结构的泡沫前驱体实现了原料内部各处的均匀的固-气反应, 泡沫总孔隙率≥80%可显著提高CRN反应的速率。XRD分析结果显示: CRN过程中存在γ-Al₂O₃到α-Al₂O₃的相转变, 反应起始温度在1300℃以上, 并在1550℃反应完全。在1650℃合成得到的AlN颗粒平均粒径不超过1 µm, 氮含量为32.9wt%。     

Nitridation reactions of molten Al-(Mg,Si) alloys

The isothermal nitridation of magnesium- and silicon-doped aluminium melt at 1273 K was investigated. With increasing Mg/Si ratio and decreasing oxygen content in the nitriding atmosphere, four major reaction mechanisms may be separated: (i) a passivating surface nitridation, (ii) a volume nitridation with precipitation of isolated AlN in the aluminium matrix, (iii) a volume nitridation resulting in a three-dimensionally interconnected AlN/Al composite microstructure, and (iv) a break-away nitridation with complete conversion of aluminium to AlN. The behavioural transition of the nitridation mechanism is reflected by the growth direction and the crystal morphology of AlN which change from inward (mechanisms i, ii) to outward (mechanisms iii, iv) growth of the reaction product with [0 0 0 1] as the dominating growth direction. Attempts are made to define the critical magnesium and silicon contents for the regime of controlled AlN/Al composite growth (mechanism iii) at 1273 K, in order to develop novel AlN/Al composite materials.     

Aluminium nitride: review of synthesis methods

Abstract

Several technologies have been reported for the synthesis of AlN. These are reviewed and described in detail. The processes are classified according to the principle of synthesis, and the AlN product characteristics for each method of synthesis are identified. Only two of the methods reported, direct nitridation and carbothermal reduction, are currently used industrially. Due to the requirement for higher quality AlN powders, several other methods are being developed. The level of development, the principle of synthesis, the raw materials used, the reaction products, and the powder characteristics of the synthesis methods are discussed. Where appropriate, environmental or safety concerns are identified. Process flowcharts for each of the technologies were developed on the basis of information available.

MST/1794     

Review of the Synthesis Methods for AIN

The different routes for the synthesis of aluminum nitride (AIN) powders are reviewed: the different industrial techniques from both the direct nitridation of aluminum metal and the carbothermal nitridation of alumina, and also other synthesis routes not industrially developed up to now. This paper presents a comprehensive presentation of the different chemical systems analyzed from the compilation of more than 70 publications and analysis of 91 patents.     

球磨促进碳热还原反应合成氮化铝研究

研究了高能球磨氧化铝和细化和机械力化学作用及球磨对碳热还原反应合成氮化铝（ＡｌＮ）的影响。结果表明：经高能球磨细化后的氧化铝（Ａｌ２Ｏ３）,相对于原始粉末,反应生成的ＡｌＮ 较大提高,且随着球磨时间增加,ＡｌＮ生成量增大。用灰色关联分析方法比较了几种球磨效应对碳热还原反应的作用,发现粉末的晶粒尺雨与反应的关联度最大,表明球磨晶粒细化作用是球磨促进碳热还原反应的最主要原因。     

Preparation and characterization of morph-genetic aluminum nitride/carbon composites from filter paper

Morph-genetic aluminum nitride/carbon composites with cablelike structure were prepared from filter paper template through the surface sol-gel process and carbothermal nitridation reaction. The resulting materials have a hierarchical structure originating from the morphology of cellulose paper. The aluminum nitride/carbon composites have the core-shell microstructure, the core is graphitic carbon, and the shell is aluminum nitride nanocoating formed by carbothermal nitridation reduction of alumina with the interfacial carbon in nitrogen atmosphere. Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and transmission electron microscope were employed to characterize the structural morphology and phase compositions of the final products.     

Synthesis of Vanadium Nitride by a One Step Method

Vanadium nitrides were prepared via one step method of carbothermal reduction and nitridation of vanadium trioxide. Thermalgravimetric analysis （TGA） and X-ray diffraction were used to determine the reaction paths of vanadium carbide, namely the following sequential reaction： V2O3→V8C7 in higher temperature stage, the rule of vanadium nitride synthesized was established, and defined conditions of temperature for the production of the carbides and nitrides were determined. Vanadium oxycarbide may consist in the front process of carbothermal reduction of vanadium trioxide. In one step method for vanadium nitride by carbothermal reduction and nitridation of vanadium trioxide, the nitridation process is simultaneous with the carbothermal reduction. A one-step mechanism of the carbothermal reduction with simultaneous nitridation leaded to a lower terminal temperature in nitridation process for vanadium nitride produced, compared with that of carbothermal reduction process without nitridation. The grain size and shape of vanadium nitride were uniform, and had the shape of a cube. The one step method combined vacuum carborization and nitridation （namely two step method） into one process. It simplified the technological process and decreased the costs.     

Preparation of nano-TiN powders by Ni-catalysed carbothermal reduction nitridation

TiN nanoparticles were prepared at 900–1100 °C by Ni-catalysed carbothermal reduction nitridation from sol-gel using tetrabutyl titanate, citric acid monohydrate and nickel chloride hexahydrate as starting materials. The catalytic effects of nickel on the carbothermal reduction nitridation of xerogels were investigated. Ni has a crucial promoting effect on the carbothermal reduction reaction of the xerogels and visibly enhanced carbothermal reduction and nitridation reactions. The dry gel with 5% NiCl₂ was added to obtain nano-TiN at 900 °C. The transmission electron microscopy analysis and Materials Studio simulation results showed that the facilitating effect of Ni on carbothermal reduction nitridation reaction was ascribed to the provision of heterogeneous nucleation sites for amorphous titania, promoting crystallisation and adsorption of N₂, resulting in its smooth dissociation into highly active N atoms and consequently enhancing the carbothermal reduction nitridation.     

微波碳热还原法制备氮化铝粉末的工艺研究

采用微波碳热还原法制备了氮化铝粉末,研究了铝源、碳源和添加剂对制备氮化铝粉末的影响. 通过对所合成的产物进行XRD检测分析表明,氢氧化铝和乙炔黑是最合适的铝源和碳源、单质添加剂的氮化催化效果最明显. 以氢氧化铝和乙炔黑为原料,加入单质添加剂,在氮气气氛下反应温度为1300℃、反应时间为1h时能获得完全氮化的氮化铝粉末,可见微波碳热还原工艺能够大大降低碳热还原法制备氮化铝粉末的反应温度,并缩短反应时间.     

Lanxide技术合成含烧结助剂的复合AIN粉体

高纯度的氮气中，以Al-Mg-Y合金为母合金，利用Lanxide技术合成了含烧结助剂Y2O3的复合AlN粉体。通过扫描电镜、X射线衍射、粒径分析及化学成分分析等检测手段对氮化产物进行表征。实验结果表明，合金氮化反应完全，氮化产物疏松易于粉化，粉化后获得的复合AlN粉体具有纯度高，氧杂质含量低，粒度细小等优点。