AlN陶瓷作为新型材料，具有众多优异的性能：如优异的热导率、较低的介电损耗和介电常数以及可靠的电绝缘性能，同时具有与Si相接近的热膨胀系数等一些列优异的特性，被认为是高集成度半导体基片和电子器件封装的理想材料。因此关于AlN功能陶瓷材料的研究受到了广泛关注。AlN是Ⅲ-Ⅴ族半导体化合物，其晶体是以[AlN4]四面体为结构单位的共价键化合物，晶体结构如下图所示。25℃时晶格常数α0 = 3.1172，c0=4.9816，属六方晶系。

As a new material, AlN ceramics have many excellent properties, such as excellent thermal conductivity, low dielectric loss and dielectric constant, reliable electrical insulation property, and excellent properties such as thermal expansion coefficient close to Si. It is considered as the ideal material for high integration semi conductor substrate and electronic device package. Material. Therefore, the research on AlN functional ceramics has attracted wide attention. AlN is a third - V family semiconductor compound whose crystal is a covalent bond with [AlN4] tetrahedron as the structural unit. The crystal structure is shown in the following figure. At 25 C, the lattice constant 0 is 3.1172, c0=4.9816, belonging to six square crystal system.

图 AlN晶体结构

Figure AlN crystal structure

对于AlN陶瓷材料而言，原始AlN粉末的技术指标，如粒径、纯度以及颗粒形貌等因素直接影响AlN陶瓷材料的综合性能。为了制备出高品质的AlN陶瓷材料，必须制备出纯度高、颗粒细小且均匀的氮化铝粉末。本文主要对氮化铝粉体的制备工艺进行总结和归纳，氮化铝粉末的常见制备方法主要有：铝粉直接氮化法、碳热还原法、自蔓延高温合成法和溶胶凝胶法等。

For AlN ceramic materials, the technical indexes of original AlN powder, such as particle size, purity and particle morphology, have a direct influence on the comprehensive properties of AlN ceramics. In order to prepare high quality AlN ceramics, AlN powder with high purity and fine particle size must be prepared. In this paper, the preparation process of aluminum nitride powder is summarized and summarized. The main preparation methods of aluminum nitride powder include aluminum powder direct nitriding, carbon thermal reduction, self propagating high temperature synthesis and sol-gel method.

1.AlN粉体制备方法

Preparation of 1.AlN powder system

1.1 铝粉直接氮化法

Direct nitriding of 1.1 aluminum powder

铝粉直接氮化法就是在持续的流动N2（或NH3）气氛条件下（或密闭的氮气气氛容器内），铝粉与N2（或NH3）在较高温度下直接发生化学反应生成AlN粉末团块或粉末颗粒。该反应温度一般控制在800~1200℃。该方法是最早用来制备AlN粉体的方法，该方法所需原料丰富，工艺简单，目前已用于大规模生产。铝粉直接氮化法涉及的化学反应为：

The direct nitriding of aluminum powder is under the continuous flow of N2 (or NH3) atmosphere (or in a closed nitrogen atmosphere container), and the aluminum powder and N2 (or NH3) directly react at higher temperatures to produce AlN powder pellets or powder particles. The reaction temperature is generally controlled at 800~1200 C. This method is the earliest method used to prepare AlN powder. The method requires abundant raw materials and simple process, and has been used in mass production at present. The chemical reactions involved in the direct nitriding of aluminum powder are as follows:

Al(s)+N2(g)→AlN(s)

Al (s) +N2 (g) - AlN (s)

优点：成本低廉，设备成本低且制备工艺简单；

Advantages: low cost, low equipment cost and simple preparation process.

缺点：反应初期铝粉表面被氮化生成氮化铝层，进而阻止了N2或NH3进一步向铝粉颗粒中心扩散，导致制备的氮化铝产率较低；铝粉与N2或NH3反应会释放大量热量，释放的热量导致生成的氮化铝粉体出现自烧结而形成团聚体，最终导致粉体颗粒粗化。

Defects: the aluminum powder surface was nitridated to produce aluminum nitride layer at the beginning of the reaction, which prevented N2 or NH3 from spreading further into the center of aluminum powder particles, resulting in the low yield of aluminum nitride; the reaction of aluminum powder with N2 or NH3 would release a large amount of heat, and the release of heat caused the formation of aluminum nitride powder to form aggregates and finally formed aggregates. It causes the coarse-grained particles of the powder.

目前的直接氮化法的研究热点主要集中于：如何提高氮化速率、产物氮含量以及消除产物团聚等方面。为了提高反应速率和锅粉的转化率目前所做的改进主要集中于两个方面：一方面对传统直接氮化法的设备和工艺进行改进；另一方面在原材料锅粉中加入各类添加剂促进培粉的转化率和减少产物团聚。

At present, the research focus of direct nitriding mainly focuses on how to improve nitriding rate, nitrogen content of products and the agglomeration of products. In order to improve the rate of reaction and the conversion rate of the pan powder, the improvements are mainly concentrated in two aspects: on the one hand, the equipment and technology of the traditional direct nitriding are improved; on the other hand, the addition of various additives in the raw material of the raw material can promote the conversion rate of the powder and reduce the reunion of the product.

1.2 碳热还原法

1.2 carbon thermal reduction method

碳热还原法是将一定量的Al2O3粉末和过量C粉的混合粉末（或通过各种制备方法制备的前驱体粉末）在一定温度下（1200~2000℃）的流动N2气氛条件下进行氮化还原反应制备AlN粉末。该制备方法涉及的化学反应方程式为：

The carbothermal reduction method is the preparation of AlN powder by the reduction reaction of a certain amount of Al2O3 powder and excess C powder (or precursor powder prepared by various preparation methods) under a flow N2 atmosphere at a certain temperature (1200~2000 C). The preparation method involves the chemical reaction equation as follows:

Al2O3(s)+3C(s)+N2(g)→2AlN(s)+3CO(g)

Al2O3 (s) +3C (s) +N2 (g) - 2AlN (s) +3CO (g)

从该化学式可以看出：碳热还原法中Al2O3/C的摩尔比要求为3，实际操作中为了加快反应速率、提高氮化铝的转化率以及获得颗粒均匀和粒径适中的粉体，会加入过量的碳粉，因此合成反应完成后因对粉体进行除碳处理以提高所制备的氮化铝纯度。此外，反应的另一影响因素是原料球磨混合的均匀程度，所使用的原料能均匀分散与充分混合时，可有效降低碳粉的用量，减少二次除碳工艺所需的时间，降低制造成本。

It can be seen from the chemical formula that the mole ratio of Al2O3/C in the carbon thermal reduction method is 3. In practice, in order to speed up the reaction rate, improve the conversion rate of aluminum nitride, and obtain the powder with uniform particle size and moderate particle size, the excess carbon powder will be added, so the synthesis reaction is completed because of the removal of carbon to the powder to improve the system. The purity of aluminum nitride prepared. In addition, the other factor of the reaction is the uniformity of the mixing of material ball milling. When the raw materials are evenly dispersed and mixed fully, the amount of carbon powder can be reduced effectively, the time required for the two carbon removal process is reduced and the manufacturing cost is reduced.

优点：原料丰富工艺过程简单等特点，合成的粉体纯度高粒径小且分布均匀；

Advantages: rich raw materials, simple process and so on. The synthesized powder has high purity and small particle size distribution.

缺点：合成时间较长氮化温度较高，而且反应后还需对过量的碳进行除碳处理，导致生产成本较高。

Disadvantages: longer synthesis time, higher nitriding temperature, and carbon removal for excess carbon after reaction, resulting in higher production cost.

目前，碳热还原法的研究热点主要集中在：

At present, the research focus of carbothermal reduction is mainly focused on:

（1）寻找合适的碳源，从而减少碳粉的使用量，避免除碳处理；

(1) search for suitable carbon sources, thereby reducing carbon consumption and avoiding carbon removal.

（2）通过多种方法制备合适的前驱体粉末，从而降低反应的活化能和反应温度。

(2) preparation of suitable precursor powders by various methods, thereby reducing the activation energy and reaction temperature.

1.3 自蔓延高温合成法

1.3 self propagating high temperature synthesis

自蔓延高温合成法合成氮化铝，是指用外加热源点燃反应物，利用铝粉氮化过程中放出的高化学反应热自加热自传导合成氮化铝材料的一种方法，又称燃烧合成法。该法的实质就是铝粉的直接氮化，只是不需要将铝粉加热至1000℃以上长时间氮化，只需将铝粉于氮气中点燃。自蔓延高温合成法制备AlN粉体涉及的化学反应方程为：

The synthesis of aluminum nitride by self propagating high temperature synthesis is a method of synthesizing aluminum nitride by self heating Autobiography of high chemical reaction heat released in the process of nitriding of aluminum powder, also known as combustion synthesis. The essence of the method is direct nitridation of aluminum powder, but it does not need to heat the aluminum powder to more than 1000 C for long time. The chemical reaction equation of AlN powder prepared by SHS is:

2Al(s)+N2(g)+X→2AlN(s)

2Al (s) +N2 (g) +X to 2AlN (s)

自蔓延高温合成法一般需要加入一定量的合成产物作为稀释剂来降低反应温度，控制反应速度，减少产物团聚现象。在铝粉中混入一定量的氮化铝粉末后，可以有效减少合成产物的团聚，提高合成产物的氮含量。

A certain amount of synthetic products should be added as diluents to reduce the reaction temperature, control the reaction speed and reduce the agglomeration of products. The incorporation of a certain amount of AlN powder into aluminum powder can effectively reduce the agglomeration of synthetic products and improve the nitrogen content of synthetic products.

优点：该工艺反应速度很快，不需要外部加热，成本低廉，适应于大批量工业化生产；

Advantages: the reaction speed is very fast, no external heating is required, the cost is low, and it is suitable for mass industrial production.