高压氮气中自蔓延燃烧合成氮化铝

高压氮气下，自蔓延燃烧合成（SHS）氨化铝实验中，研究了稀释剂含量、添加剂含量、氮气压力、反应物的相对密度、反应物厚度对燃烧波最高温度、燃烧波蔓延速率的影响，并制备了含氮量较高（33.4Wt％）的氨化铝.     

铝粉在高压氮气中自蔓延燃烧合成氮化铝

利用铝粉在高压氮气中的自蔓延燃烧合成（SHS）方法,制备了氮含量较高（33．5wt％）的AIN,研究了稀释剂含量、添加剂含量、氮气压力、反应物的相对密度、反应物厚度对燃烧产物氮含量的影响,并对后燃烧现象进行了分析,产物中发现氮化铝晶须和棒晶．     

高压氮气中自蔓延燃烧合成氮化钛

利用钛粉在高压氮气中的自蔓延燃烧合成（ＳＨＳ），制备了含氮量较高的ＴｉＮ，研究了反应物的松装密度、氮气压的改变与稀释剂的加入对燃烧波蔓延速率和产物转化率的影响，还观察到燃烧方式的改变。     

自蔓延燃烧合成氮化铝的产物特征及表面处理

利用铝粉在高压氮气中的自蔓延燃烧合成（ＳＨＳ）合成了较高氮含量（３３．５ｗｔ％）的氮化铝粉末，考察了ＡｌＮ晶须和ＡｌＮ棒晶，提出了它们的形成机理，研究了Ａ１Ｎ粉末的表面处理。     

高压氮气中燃烧合成氮化铝的机理研究(1)

基于实验结果,提出了燃烧合成AiN的反应机理,合成反应是由气相反应和液相反应组成的,结合燃烧波曲线,反应分为4个区,即预热区、反应区、后燃烧区、冷却区,不同的区域中出现不同的反应.     

高压氮气中燃烧合成氮化铝的机理研究(2)

基于实验结果,提出了燃烧合成AiN的反应机理,合成反应是由气相反应和液相反应组成的,结合燃烧波曲线,反应分为4个区,即预热区、反应区、后燃烧区、冷却区,不同的区域中出现不同的反应.     

硅粉在高压氮气中自蔓延燃烧合成氮化硅的反应机理

本文对Ｓｉ粉在高压氮气中自蔓延燃烧合成（ＳＨＳ）Ｓｉ３Ｎ４的反应机理进行了研究。燃烧反应中Ｓｉ以蒸汽形式与Ｎ２在Ｓｉ３Ｎ４晶种表面反应，反应分为两个主要阶段：（１）动力学反应阶段：Ｓｉ蒸汽不需经过扩散直接与Ｎ２进行反应，反应速度快；（２）扩散控制反应阶段：Ｓｉ蒸汽经过Ｎ２气层扩散到Ｓｉ３Ｎ４晶种表面与Ｎ２反应，反应受扩散控制，速度较慢。     

规则结晶形态氮化铝颗粒的自蔓延高温合成

以铝粉和AlN粉末为原料，按重量比60／40的比例进行混合，加入3wt％NH4F和3wt％碳黑，在8MPa的氮气气氛条件下进行高温自蔓延合成，合成产物为具有良好结晶形态的规则AlN颗粒．采用扫描电子显微镜(SEM)和X射线衍射仪(XRD)研究了加入NH4F和碳黑后合成产物形态和物相的变化情况．研究结果表明同时加入NH4F和碳黑使得燃烧过程出现了后烧现象，即样品可以维持在高温阶段较长的时间，促进了AlN气相的传输，最终使得AlN颗粒以较为规则的外形生长．     

氮气压对自蔓延高温合成A1N后烧的影响

研究了氮气压力对自蔓延高温合成A1N的影响和后烧机理，结果表明，自蔓延高温合成A1N的生长机制为气相－晶体（Vapor-Crystal,VC)机制，气相沉积的台阶平面为A1N的基面（0001面）为了降低表面能，生长台阶必须以六棱柱形态形核，在后烧阶段，A1N颗粒中心的小台阶被重新“蒸发”，井沉积到远离中心的大台阶上，使A1N颗粒棱角分明，形状规则，随着氮气压力的增加，燃烧温度逐渐提高，后烧的时间缩短。     

氮气压对自蔓延高温合成AlN后烧的影响

研究了氮气压力对自蔓延高温合成AlN的影响和后烧机理.结果表明,自蔓延高温合成AlN的生长机制为气相-晶体(Vapor-Crystal,VC)机制.气相沉积的台阶平面为AlN的基面({0001)面).为了降低表面能,生长台阶必须以六棱柱形态形核.在后烧阶段,AlN颗粒中心的小台阶被重新"蒸发",并沉积到远离中心的大台阶上,使AlN颗粒棱角分明,形状规则.随着氮气压力的增加,燃烧温度逐渐提高,后烧的时间缩短.     

Mechanisms of the Combustion Synthesis of Aluminum Nitride in High Pressure Nitrogen Atmosphere (2)

The self-propagating high-temperature synthesis of aluminum nitride by combustion of aluminum in pressurized nitrogen atmosphere is investigated and a mechanism proposed. According to the experimental phenomena, the SHS process is considered as composed of a gaseous- and a liquid-phase reaction. For the combustion of Al with an appropriate amount of diluent AlN, the dominant reaction is between the Al vapor and nitrogen. The primary structure of the combustion wave in the nitridation of Al is proposed. The combustion reaction process is divided into four stages: (1) kinetic stage: Al vapor and Al liquid drops react with nitrogen directly (without diffusion); (2) thermal explosion stage: Al particle produces many small Al liquid drops; (3) transition stage: Al liquid drops evaporate; Al vapor reacts with nitrogen and AlN is synthesized; (4) diffusion-controlled reaction stage: as the reaction proceeds, the amount of nitrogen becomes scarce and, thus, the reaction is controlled by diffusion of nitrogen. For different reactant compositions and reaction regions, the reactions are controlled by different mechanisms. Thermodynamic phase-stability calculations and experiment characterization of combustion products support the proposed mechanism.     

Mechanisms of the Combustion Synthesis of Aluminum Nitride in High Pressure Nitrogen Atmosphere (2)

Based on calculating the free energy _r G _m of reactions, the reaction mechanism of combustion synthesis of AlN is possibly the reactions between N₂ and Al vapor and/or liquid Al. Other oxides of Al, such as Al₂O, AlO, can also react with N₂ to form AlN. However, the reaction between liquid Al and N₂ as well as the reactions between other oxides of Al and N₂ are not the main reaction mechanism.     

材料合成新技术──自蔓延高温合成

自蔓延高温合成（ＳＨＳ）是目前被广泛开发用于工业陶瓷和其它先进材料制备的一种独特的先进工艺技术。本文对生产高科技材料的自蔓延高温合成技术方法进行了介绍，并分析了该工艺的特点及其理论基础，同时还讨论了影响材料合成的因素。     

Preparation of Ultrafine Boron Nitride Powders by Self-propagating High-Temperature Synthesis

The possibility of preparing ultrafine boron nitride powders by self-propagating high-temperature synthesis (SHS) is examined. The results demonstrate that, by varying SHS conditions (starting-mixture composition, combustion rate, cooling rate, and intermediate grinding time), one can control the morphology and particle size of the resultant hexagonal BN powder. Systematic data are presented on the chemical dispersion of SHS products for separating nanometer-sized particles. The effect of chemical dispersion (composition of the dispersion medium, process temperature, and dispersion time) on the particle size, morphology, and chemical and phase compositions of boron nitride powders is analyzed. Hexagonal boron nitride powders are obtained with a purity of 99.5+%, particle size of 0.1–0.2 m, and specific surface of up to 65 m²/g.     

Preparation of Submicron Silicon Nitride Powders via Self-propagating High-Temperature Synthesis

Nitridation of commercial ferrosilicon via self-propagating high-temperature synthesis is described. The nitrogen pressure is shown to influence the conversion and the combustion rate of the alloy. Dilution of the starting alloy with the final product or an ammonium salt influences the nitrogen content of the nitrided material. The high nitrogen content of the reaction products made it possible to isolate a sufficient amount of silicon nitride with a particle size of 0.43 μm by acid enrichment in an HCl solution. The microstructure of silicon nitride prepared under different conditions is studied by electron microscopy. Electron diffraction results indicate that the final product contains, in addition to the well-known α and β phases (hexagonal structure), tetragonal and orthorhombic Si₃N₄ polymorphs. __________ Translated from Neorganicheskie Materialy, Vol. 41, No. 12, 2005, pp. 1468–1473. Original Russian Text Copyright ? 2005 by Chukhlomina, Ivanov, Maksimov, Akhunova, Krivosheeva.     

氮化铝粉末制备工艺的研究

本文介绍了氮化铝(AlN)陶瓷的特性,并以金属铝直接氮化法和氧化物高温碳还原氮化法为重点,阐述了AlN粉末的各种制备工艺及反应机理、主要工艺参数的影响,对各种方法的优缺点进行了评述。提出:还原法和直接氮化法是目前较成熟的方法,而气相反应法具有较好的推广应用前景。     

自蔓延高温合成过程中的非平衡问题

自蔓延高温合成(SHS)技术是一门新兴的学科，因其独特的优越性而备受材料科学家的关注。在简要介绍自蔓延高温合成技术的基础上，系统地阐述了SHS过程中的非平衡现象，重点分析了非平衡现象的影响因素及SHS非平衡理论的研究进展，并对SHS非平衡研究作了简要评价，提出了目前存在的问题和未来SHS的研究方向。