碳热还原法制备氮化铝陶瓷粉末的研究

从原料的准备，合成，二次除碳工艺三个部分介绍了碳热还原法合成氮化铝粉末的工艺过程，详细总结了该工艺几个关键步预的研究状况，包括铝源的选择，碳源的选择，添加剂的选择，碳铝摩尔比的确定，原料的分散与混合，煅烧，氮气的流速和压力的确定，二次除碳，指 碳热还原法合成氮化铝粉末的主要研究方向。     

低温碳热还原法合成氮化铝陶瓷超细粉末

采用硝酸盐-有机物低温燃烧反应溶胶-凝胶工艺,以硝酸铝（Al（NO3）3·9H2O）、葡萄糖（C6H12O6·H2O）、尿素（CO（NH2）2）为原料,制备出粒度细小、混合均匀的铝源和碳源的混合前驱物,然后以该前驱物为原料进行碳热还原反应制备氮化铝粉末.研究表明,该前驱物具有较高的反应活性,氮化反应速率快,1550℃时仅用90min即可实现完全转化,SEM分析结果表明合成粉末为粒度分布均匀的纳米级（～100nm）粉末.     

碳热还原氮化法结合泡沫前驱体制备超细氮化铝粉体

本研究使用改良的碳热还原氮化法合成超细氮化铝粉体。以γ氧化铝和蔗糖作为铝源和碳源, 先预处理制备成多孔泡沫, 再通过碳热还原氮化法合成氮化铝粉体。反应过程和产物通过X射线衍射分析、SEM和TEM确定。X射线衍射分析表明整个反应过程不存在氧化铝的相转变。高分辨透射电子显微镜显示γ-Al₂O₃颗粒被无定型碳包裹, 从而抑制了γ-Al₂O₃到α-Al₂O₃的相转变。泡沫的多孔结构促进了氮气的扩散和反应副产物的释放, 使得最低反应温度降低至1450 ℃。SEM结果表明得到的氮化铝颗粒粒径大约为50 nm。本研究合成的氮化铝粉体可用于制备高热导氮化铝陶瓷。     

几种碳源对碳热还原氮化法制备Ti(C,N)粉末的影响

以纳米TiO2和不同碳源为原料,采用碳热还原氮化法,制备了Ti(C,N)粉末.通过X射线衍射分析、热分析、扫描电镜、化学成分分析等手段研究了TiO2碳热还原氮化过程的反应机理和不同碳源对制备碳氮化钛粉末的影响.结果表明,在TiO2碳热还原氮化过程中,前期主要为TiO2/C固-固反应,后期CO参与的气-固反应变为主要反应...     

碳热还原氮化法制备β-Sialon的影响因素

综述了采用碳热还原氮化法制备β-Sialon的影响因素.详细分析了各种因素,如反应温度、恒温时间、N2流量和分压、配C量、碳源、添加剂以及原料组成和粒度对反应速率、反应氮化率、产物相组成和粒度等的影响.     

湿化学法合成纳米AlN粉末

采用醇盐水解工艺结合碳热氮化还原法进行纳米Al N粉末的制备。以异丙醇铝、果糖、无水乙醇为原料,制备出透明的凝胶,干燥后得到分子水平混合的前驱体,在1 450℃经碳热氮化还原法制备出单相Al N纳米粉末。系统研究了前躯体形成机制,以及碳热氮化还原的温度和时间、C/Al摩尔比、凝胶温度等因素对合成粉体的影响。采用XRD、TG-DSC和SEM对合成产物的特性进行了分析和表征。通过优化工艺,制得类球形的Al N粉末颗粒,其颗粒大小为30~90 nm。     

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。     

尿素对以硝酸铝和葡萄糖为原料合成氮化铝粉末反应过程中相变及反应速率的影响

以硝酸铝(Al(NO3)3·9H2O)和葡萄糖(C6H12O6·H2O)为原料,利用碳热还原法制备氮化铝粉末,研究了尿素对前驱物的制备及前驱物氮化反应的影响,研究发现添加尿素合成的前驱物和未添加尿素合成的前驱物在氮化反应过程中相变和反应速率存在较大差异。在没有添加尿素合成的前驱物的氮化反应过程中,出现了γ-Al2O3、α-Al2O3、AlON和AIN相,该前驱物的反应速率慢,完全氮化需要在1600℃下才能完成。对于添加尿素合成的前驱物而言,在其氮化反应过程中仅出现了γ-Al2O3和AIN相,没有α-Al2O3和AlON的生成,AIN直接由γ-Al2O3氮化生成,该前驱物的氮化反应速率快,氮化反应温度低,在1400℃下即可实现完全氮化。分析讨论了两种前驱物的氮化反应速率不同的主要原因,并利用XRD、SEM等分析方法对粉末进行了表征。     

工艺因素对碳热还原法合成SiC的影响

介绍了碳热还原法合成SiC的反应机理,综述了影响碳热还原法合成SiC的工艺因素,分析并比较了反应温度、碳源及配C量、原料组成和粒度、Ar流量和CO分压以及添加剂等因素对反应速率、产率及相组成的影响.     

碳化硅微粉的低温合成与制备

以硅溶胶为硅源,淀粉为碳源,采用低温碳热还原法合成了SiC微粉.实验结果表明:淀粉热解得到的碳颗粒和硅溶胶中的SiO2能形成较好的包覆,增大了接触面积,促进了反应的进行.在1700℃下反应1h,反应前驱体全部转化为β-SiC,产物为SiC颗粒和纳米棒的混合物.升高反应温度和延长反应时间都能显著增加转化率.但温度过高会导致晶粒长大.     

Synthesis of aluminum nitride fibres from aluminum silicate fibres by carbothermal reduction method

Aluminum nitride (AlN) fibres were synthesized by carbothermal reduction of aluminum silicate fibres and carbon black in a flowing nitrogen atmosphere. XRD and SEM were employed to study the phase structure, chemical composition and morphologies of the products. It is suggested that aluminum silicate fibres can be converted into AlN fibres by carbothermal reduction. SEM confirmed that the fibres maintained the morphologies of aluminum silicate fibres during reduction, but their details of surface have been altered. A carbothermal nitriding model of the aluminum silicate fibres has been developed.     

Effects of Cation Impurities on Thermal Conductivity of Yttria-Doped Aluminum Nitride

Effects of cation impurities such as Fe and Si on thermal conductivity of yttria-doped aluminum nitride were investigated. Two types of aluminum nitride powders, Tokuyama F-grade and Denka AP-10, were compared. The powders have similar contents of oxygen but different levels of cation impurities. Since the thermal conductivity of sintered aluminum nitride is virtually affected by the residual oxygen contents in the grains, effects of yttria additions and prolonged firing time are also investigated. The resultant thermal conductivity is thought to be influenced by the sample size of sintering bodies because extracting oxygen from the aluminum nitride lattice in larger samples requires longer time resulting from a longer diffusion path. In comparing the AlN powders, impurity contents of Fe and Si are somewhat higher in Denka powder than Tokuyama powder. These impurity elements degrade the thermal conductivity of sintered aluminum nitride. Degradation effects in thermal conductivity due to presence of Fe and Si are evaluated by artificially introducing these elements to Tokuyama AlN powder. The difference in the thermal conductivity resulting from the two types of powders is discussed.     

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。     

Mechanochemical synthesis and shock wave consolidation of TiN(Al) nanostructure solid solution

This paper aims to report the study of the synthesis of a titanium nitride nanostructure solid solution through the reduction of aluminum nitride with titanium based on the stoichiometric reaction of 2Ti + AlN by mechanical alloying (MA) process at a ball-to-powder weight ratio of 15:1. A nanostructure solid solution of in-situ titanium nitride was formed through exchange reaction between Ti and AlN at the initial time of MA. XRD, SEM, EPMA, TEM, and particle size analysis (PSA) were used to characterize the products. It was found that the amount of Al resulting from decomposition of aluminum nitride dissolved in the TiN lattice increased in accordance with milling time, leading to the formation of TiN(Al) solid solution and a reduction of the TiN lattice interplanar distance. The milled powder displayed equiaxed morphology and a narrow size distribution of about 1 μm at the end of the milling process. In-situ TiN(Al) crystallites were of an average size of 6 ± 2 nm. Subsequent to MA, an underwater shock compaction method was applied to the prolonged milled powders to obtain bulk sample. The effect of this shock compaction on the selected sample resulted in the preservation of its nanostructure characteristics with no additional phase transformation which are considered advantageous in the use of high dynamic compaction method for ceramic materials.     

AlN-CNTs/聚酰亚胺复合材料的制备与性能

为了研究氮化铝(AlN)和碳纳米管(CNTs)对聚酰亚胺(PI)的导热、热学、力学性能的协同效应,采用湿法球磨和热压成型法制备了AlN/PI和CNTs-AlN/PI复合材料。利用X射线衍射仪、扫描电子显微镜对复合材料进行了物相分析和断面形貌表征,分别考察了AlN及其与CNTs协同对PI复合材料的导热、热学、力学性能的影响。结果表明,AlN和CNTs在PI基体中分散均匀且接触界面良好,AlN的加入可以显著地提高复合材料的导热性能,且对复合材料的热稳定性和力学性能有一定的提高;固定AlN的含量为10%,加入少量的CNTs可以提高复合材料的导热性能,但对复合材料的力学性能有一定的负面影响。     

AlN陶瓷的薄膜金属化及其与金属的焊接研究

针对AlN陶瓷在微波管中的应用特点 ,采用磁控溅射镀膜方法对AlN陶瓷进行表面金属化 ,并与无氧铜焊接 ,测试焊接体的抗拉强度并对陶瓷 金属接合界面进行了微观分析。     

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．     

液晶聚酯/氮化铝复合基板材料制备中偶联剂的应用

本文研究了在液晶聚酯/氮化铝复合基板材料的制备中偶联剂(KH-550和NDZ-101) 对复合材料的加工性能和复合材料的强度, 导热系数和介电性能的影响。     

固相反应法合成碳化硼纳米粉体

以六方氮化硼和炭黑(或石墨)为原料, 采用固相反应法合成了碳化硼粉体. 碳源、反应气氛和温度对粉体合成产生重要影响. 以炭黑为碳源, 在1900℃真空下保温5 h, 得到了平均粒径约为100 nm的碳化硼纳米粉体. 与商业粉体相比, 合成的粉体具有较好的烧结活性. 在2000℃/30 MPa/1 h条件下烧结, 样品的相对密度达到97.9%(商业粉体样品为93.1%), 这可归结于合成的粉体具有细小的粒径、低的氧含量和一定程度的孪晶结构.     

Synthesis of boron carbide powder from hexagonal boron nitride

We report the synthesis of boron carbide powder via the reaction of hexagonal boron nitride with carbon black. The reaction between hexagonal boron nitride and carbon black completed at 1900 °C for 5 h in vacuum. The particle sizes of the synthesized boron carbide powder were about 100 nm from transmission electron microscopy. The possible reaction mechanism was that hexagonal boron nitride decomposed into elemental boron and nitrogen even when there was no carbon at a relatively low rate, and introduction of carbon into hexagonal boron nitride powder facilitated the decomposition process; the boron from the decomposition of boron nitride reacted with carbon to form boron carbide.