| 氮化铝（AlN）陶瓷常见的坯体成型与烧结方法概述 |
| 添加时间：2017/11/20 14:04:39 浏览次数： |
| 氮化铝（AlN）是一种六方纤锌矿结构的共价键化合物，晶体结构和微观组织如图1所示。室温强度高、热膨胀系数小、抗熔融金属侵蚀的能力强、介电性能良好，这些得天独厚的优点使其成为高导热材料而引起国内外的普遍关注。作为高性能的介电陶瓷，氮化铝可以取代碳化硅，甚至部分取代氧化铝，被视为新一代很有发展前途的优良的基片材料 Aluminum nitride (AlN) is a covalent bond compound of six wurtzite structure. The crystal structure and microstructure are shown in figure 1. High strength at room temperature, small thermal expansion coefficient, strong resistance to molten metal, good dielectric properties, these unique advantages make it become a high thermal conductivity material and caused widespread concern at home and abroad. As high performance dielectric ceramics, aluminum nitride can replace silicon carbide and even partially replace alumina, and is considered as a new generation of promising substrate materials 1 One 常见的AlN坯体成型方法 Common forming method of AlN body 由氮化铝粉末制备氮化铝陶瓷坯体，需要利用成型工艺把粉体制备成坯体，然后再进行烧结工作。氮化铝成型工艺主要有干压成型、等静压成型、流延法成型和注射成型等。 The aluminum nitride ceramic body is prepared from AlN powder, and the powder is prepared into a green body by using the forming process, and then the sintering process is carried out. The forming processes of aluminum nitride mainly include dry pressing, isostatic pressing, tape casting and injection molding. 1 One 干压成型 Dry pressing molding 图2为干压成型机。干压成型（轴向压制成型）是将经表面活性剂改性等预处理的 AlN 粉体加入至金属模具中，缓慢施加压力使其成为致密的坯体成型工艺。实质是借助外部施压，依靠AlN粉末颗粒之间的相互作用力使坯体保持一定的形状和致密度高致密坯体，其有利于陶瓷烧结，可以降低烧结温度，提高陶瓷致密度。由于AlN粉末易水解，干压成型中常用的水-聚乙烯醇（PVA）不能用于AlN粉末的压制，可选用石蜡与有机溶剂代替。 Figure 2 is a dry press machine. Dry pressing (axial pressing forming) is to add AlN powder, such as surfactant modification, into the metal mold, and slowly apply pressure to make it become a compact body forming process. The essence is to use the external pressure to rely on the interaction between AlN powder particles, so that the body to maintain a certain shape and density dense body, which is conducive to ceramic sintering, can reduce the sintering temperature, improve the ceramic density. Because the AlN powder is easy to hydrolyze, the water polyvinyl alcohol (PVA) used in the dry pressing process can not be used to suppress the AlN powder, and paraffin wax and organic solvent can be used instead. 优点： Advantage： 干压成型法操作简单，工艺环节少，效率高。 Dry pressing method is simple in operation, less in process and high in efficiency. 缺点： Shortcoming: 不能压制复杂几何形状的坯体；需严格控制压力大小，过大或过小均不利于得到高致密度AlN陶瓷烧结件。 It is not necessary to control the size of the complex geometry. It is very difficult to obtain high density AlN ceramic sintered parts by strictly controlling the size of the pressure. [undefined] [undefined] 2 Two 等静压成型 Isostatic pressing 等静压成型是传统干压法的改进方法，将AlN 粉体置于高压容器中，利用液体的不可压缩性和液体对压力传导的特性，将粉体置于弹性材料制造的成型模具中，从不同的方向对待压粉体进行均匀施压，以液体对模具进行加压而使坯体成型的方法。 Isostatic pressing is method to improve the traditional dry pressing method, AlN powder is put into the high pressure container, the liquid can not be compressed and the characteristics of the liquid pressure transmission, the mold manufacturing powder in elastic materials, from different directions to treat pressure powder uniform pressure, to die the method of forming pressure in liquid. 优点： Advantage： 坯体的致密度较高，密度分布均一，可以近净尺寸成型。 The density of the body is high, and the density distribution is uniform, which can be formed by near net size. 缺点： Shortcoming: 成型设备昂贵，且存在脱模问题，限制了将其应用于大规模的工业生产。 The molding equipment is expensive and has the problem of demoulding, which limits its application in large-scale industrial production. 3 Three 流延成型 Tape casting 流延成型法是一种十分重要的陶瓷基片的成型工艺。将AlN 粉体与复合粘合剂（分散剂、溶剂、粘结剂和增塑剂组成）混合均匀后得到 AlN 流延料浆，除气等过程处理后的浆料倒入料斗，经刮刀口后，形成厚度均匀、表面光滑附着于光滑带上的薄层，再经干燥后制备成具有良好韧性的坯体；排胶烧结之后得到 AlN 基片材料。 Tape casting is a very important process for forming ceramic substrates. AlN powder and composite binder (solvent, dispersant, binder and plasticizer composition) after blending AlN slurry casting, in addition to gas process after poured into the hopper, the scraping knife, the formation of uniform thickness and smooth surface attached to the smooth thin belt, after drying prepare the body has good toughness; after discharging the sintered AlN substrate material. 优点： Advantage： 设备简单，可以连续操作，生产率高，自动化程度高等。 The equipment is simple, continuous operation, high productivity, high degree of automation. 缺点： Shortcoming: 要求较为严格，料浆就工艺参数的变化十分敏感，成型坯体表面粗糙且结合不充分，强度较低，干燥过程中易出现起泡开裂、弯曲变形等现象；同时流延成型只能用于片状材料的生产。 Requirements are more strict, slurry is very sensitive to changes in process parameters, forming rough surface of the body and inadequate combination, low strength, drying process prone to foaming, cracking, bending deformation and other phenomena; at the same time, tape casting can only be used for sheet material production. 4 Four 注射成型 injection molding AlN陶瓷注射成形是粉末注射成形应用于陶瓷粉末成型的一种方法，以塑料注射成形工艺为基础，经过技术改进而产生的成型技术。其基本过程为先在AlN粉末中加入粘结剂并使其混合均匀，形成具有粘塑性的喂料，在加热状态下，利用注射成型机将喂料注入模具模腔内冷凝成型，经过加热去除粘结剂后，便可用于烧结，如图3所示。喂料的流变性是影响注射成型成品质量的一个重要因素，通常我们希望喂料粘度较低，这就要求原料粉末与粘结剂相容性要好，而且混合均匀。 AlN ceramic injection molding is a method of powder injection molding applied to ceramic powder molding. It is based on the plastic injection molding process and has been formed by technical improvement. The basic process is first in the AlN powder with binder and the mixing, form a viscoplastic feeding in a heated state, the injection molding machine will feed into the mold cavity condensation forming, after heating to remove the binder, can be used for sintering, as shown in figure 3. The rheological property of the feedstock is an important factor affecting the quality of the finished product. Generally, we hope that the feedstock viscosity is low, which requires the compatibility of the raw powder and binder is better, and the mixture is even. 优点： Advantage： 致密度高，密度分布均匀，可用于复杂形态坯体成型，且成型精度高，无需后期机械加工。 With high density and uniform density distribution, it can be used for complex shape body forming, with high precision and no late mechanical processing. 缺点： Shortcoming: 易出现欠注、飞边、熔接痕、气穴等缺陷影响AlN陶瓷烧结。 AlN ceramic sintering is easy to occur due to defects such as under injection, edge, weld line, cavitation and so on. 制备好的坯体需要经过高温烧结，才能获得高致密度和优良性能的AlN陶瓷，从而在各个领域得到广泛应用。AlN作为高熔点的强共价键化合物，原子自扩散系数小，烧结出致密零件难度大，必须选择合适的烧结方法，并严格控制烧结条件，才能制得具有高致密度和所需优良性能的AlN陶瓷。 In order to obtain high density and excellent properties of AlN ceramics, the prepared compacts need to be sintered at high temperature so as to be widely used in various fields. AlN is a kind of strong covalent bond compound with high melting point. It is difficult to sinter dense parts because of its small self diffusion coefficient. It is necessary to choose the proper sintering method and strictly control the sintering conditions so as to obtain AlN ceramics with high density and excellent properties. 2 Two 常见的AlN烧结方法 Common AlN sintering methods 烧结是指陶瓷粉体经压力压制后形成的素坯在高温下的致密化过程,在烧结温度下陶瓷粉末颗粒相互键联，晶粒长大，晶界和坯体内空隙逐渐减少，坯体体积收缩，致密度增大，直至形成具有一定强度的多晶烧结体。 Refers to the sintering ceramic powders by pressing after the formation of the blank densification process at high temperature, the sintering temperature of ceramic powder particles are bonded, grain growth, grain boundaries and voids in billet billet decreased, volume shrinkage, density increase, until the formation of polycrystalline sintered body has a certain strength. 氮化铝作为共价键化合物，难以进行固相烧结。通常采用液相烧结机制，即向氮化铝原料粉末中加入能够生成液相的烧结助剂，并通过溶解产生液相，促进烧结。 AlN is difficult to be sintered by solid phase as covalent bond compound. Liquid sintering mechanism is usually adopted, that is, adding sintering agent which can produce liquid phase into aluminum nitride powder, and producing liquid phase by dissolving to promote sintering. AlN烧结动力：粉末的比表面能、晶格缺陷、固液相之间的毛细力等。要制备高热导率的AlN陶瓷，在烧结工艺中必须解决两个问题：第一是要提高材料的致密度，第二是在高温烧结时，要尽量避免氧原子溶入的晶格中。常见的烧结方法如下： AlN sintering power: specific surface energy of powders, lattice defects, capillary force between solid and liquid phases, etc.. In order to prepare AlN ceramics with high thermal conductivity, two problems must be solved in the sintering process: the first is to improve the density of materials; second, in the sintering process at high temperature, it is necessary to avoid the oxygen atoms dissolved into the lattice. The common sintering methods are as follows: 1 One 常压烧结 pressureless sintering 常压烧结是AlN Pressureless sintering is AlN |
| 上一页 氮化铝晶体的制备及应用简介 |
| 下一页 没有了 |
Copyright © 技术支持：遨游网络