摘要
随着电子产品朝着轻型化，高度集成化，热电损耗低，稳定性高且能适应各种工作环境的方向发展，以氮化铝（AlN）、氮化镓（GaN）为代表的宽禁带半导体逐渐成为工业上研究与应用的热点。作为第三代半导体材料，氮化铝（AlN）产品热导率高达100~260 W/(m·K)，室温电阻率大于1014Ω·cm，绝缘耐压为15kV/mm。因此AlN以其高热导率、优异的绝缘性、介电常数高、线膨胀系数小以及稳定性较好而吸引了广大科研工作者的关注，在基体材料、电子封装材料、薄膜材料以及结构材料等领域应用广泛。但是目前工业上制备AlN粉体的方法普遍存在着粉体纯度不高、粒径分布不均匀和成本高等问题。而且在烧结过程中容易引入杂质，且烧结致密度不高，导致获得的AlN陶瓷性能达不到预期要求。本文研究了AlN粉体的新型制备工艺，共探讨了各工艺参数对实验结果的影响。
本文以Al4C3作为中间体，通过与NH3反应来制备AlN粉体。在制备中间体粉末Al4C3过程中。我们以微米级的Al粉与石墨粉为原料，取一定量的Al粉与C粉真空球磨8h进行充分混匀，置于电炉中在氩气气氛的保护下加热至一定温度下反应3h。文中通过添加不同石墨含量并在不同温度条件下反应，通过对实验结果进行分析表征，发现石墨含量的增加有助于促进Al4C3的生成，同时温度的升高也有助于增加C在熔融Al 中的溶解度，也可有效促进Al4C3的生成。在Al4C3与NH3反应来制备AlN粉体过程中，文章系统研
dap究了温度、水分与气流量对实验结果的影响。实验结果表明温度的升高有助于提高NH3的扩散速度与固相反应速度，因此升高温度有助于AlN的生成。而从实验结果并结合热力学分析表明实验条件中存在水分的情况下，Al4C3更容易与水反应生成Al2O3，因此为了制备出高纯AlN粉体，必须对实验中的NH3进行充分干燥处理。氨气气流量主要是通过自身的分解与影响反应区的温度来影响实验结果。当气流量较低时，大部分氨气发生了分解，没有没有足够的处于激活态的NH3分子与Al4C3发生反应，造成反应不能充分进行；而当氨气气流量过大时，处于或者低于室温的氨气会带走中心反应区大部分热量，导致中心反应区温度降低，影响氨气的扩散速度与反应速率。
关键词:AlN粉体，Al4C3粉体，氨气，石墨
Abstract
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As electronic products develop toward lightweight, highly integrated, low thermoelectric loss, high stability and good adaptability to various work environments,a wide bandgap miconductor reprented by aluminum nitride(AlN) and gallium nitride(GaN) has become a hot topic in industrial rearch and application. As a third generation of miconductor materials, the thermal conductivity of AlN can reaches up to 100~260 W/(m·K), and the room temperature resistivity is as higher as 101
4Ω·cm, and theinsulation withstandvoltage is 15kV / mm. With its high thermal conductivity, excellent insulation, high dielectric constant,small linear expansion coefficient and good stability, AlN has attracted the attention of scientific rearch workers and has been widely ud in matrix materials, electronic packaging materials, film materials and structural materials. However, there still existes problem in the method of preparing AlN powders at prent, such as the low purity of the powder, the ununiform particle size distribution and the high cost. It is also easy to introduce impurities during the sintering process,and the sintered density is not high, resulting in the performance of AlN ceramicsdoes not meet the expected requirements.In this paper, the new preparation technology of AlN powder was studied, and the influence of each process parameter on the experimental results was also discusd.
In this paper,Al4C3is ud as an intermediate to prepare AlN powder by reacting with NH3. During the preparation of the intermediate powder Al4C3,we u micron-sized Al powder and graphite powder as raw material, and a certain amount of Al powder and C powder are ball milled for 8h under vacuum conditions for full mixing, then ball-milled powders are placed in the electric furnace under the protection of argon atmosphere and heated to a certain temperature for 3h. In this paper, different graphite contents are added and reactions are completed under different temperature condit
ions, and it can be conclued that the increa of graphite content can promote the formation of Al4C3, furthermore the increa of temperature also contributes to increasing the solubility of C in molten Al,resulting in the effective formation of Al4C3.In the process of reaction between Al4C3 and NH3 to prepare AlN powder, the effects of temperature, moisture and gas flow on the experimental results are studied.The experimental results show that the increa of temperature can improve the diffusion rate of NH3and the reaction speed of solid pha. Therefore, the increa of
temperature contributes to the formation of AlN. Al4C3 is more likely to react with water to produce Al2O3from the experimental results and the thermodynamic analysis. So it is necessary to dry the NH3 in the experiment in order to prepare the high purity AlN powder. Ammonia gas flow mainly affect the experimental results through its own decomposition and affecting the temperature of the reaction zone. When the gas flow is low, most of the ammonia has decompod, so there is not enough NH3 moleculesin the active state to react with Al4C3 to form AlN, resulting in the reaction can not be fully completed; when the ammonia gas flow is too large, ammonia gas at or below the room temperature will take away most of the heat of the the central reaction zone, resulting in the decrea of the central reaction zone temperature, affecting the ammonia diffusion rate and reaction cotton什么意思
rate.
Key words: AlN powder , Al4C3 powder，ammonia gas，graphite
目录
摘要.......................................................................................................................II 第一章绪论1 1.1引言 .. (1)
1.2氮化铝的结构与性能 (3)
1.2.1 氮化铝的结构 (3)
1.2.2氮化铝的性能 (4)
1.3 氮化铝的应用 (6)
等腰三角形有几条对称轴1.3.1基体材料和组件封装材料 (7)
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1.3.2 耐热冲和热交换材料 (8)abdomen
1.3.3 氮化铝薄膜材料 (8)
1.3.4其他应用 (9)
1.4 氮化铝粉体的制备 (10)
1.4.1 铝粉直接氮化法 (10)
1.4.2 碳热还原法 (11)
1.4.3 高温自蔓延法 (13)
1.4.4化学气相沉积法 (14)
1.4.5等离子体法 (14)
海口翻译1.5 本论文的设计思路与主要内容.................................... 错误!未定义书签。第二章热力学分析
火龙果的英文2.1绪论 (17)
2.2碳化铝制备过程中的热力学分析 (18)
2.3氮化铝制备过程中的热力学分析 (19)
2.4本章小结 (21)
第三章碳化铝粉体的制备
3.1引言 (22)
3.2 实验部分 (23)
3.2.1实验中采用的试剂及设备 (23)
3.2.2碳化铝粉体的备制 (24)
3.3结果与讨论 (25)
3.3.1石墨含量对合成碳化铝粉体的影响 (27)
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3.3.2温度对合成碳化铝粉体的影响 (28)
3.4 本章小结 (32)
第四章氮化化铝粉体的制备
4.1引言 (34)
4.2 实验部分 (35)
陕西二级建造师报名时间4.2.1实验中采用的试剂及设备 (35)
4.2.2 氮化铝粉体的制备 (35)
4.3 结果与讨论 (35)
4.3.1温度对合成氮化铝粉体的影响 (35)
4.3.2 水分对合成氮化铝粉体的影响 (39)
4.3.3氨气流量对合成氮化铝粉体的影响 (42)
4.4 本章小结 (43)
