溶胶—凝胶法制备SiC—AlN复合超细粉末的研究

用溶胶－凝胶碳热氮化法在１５５０－１６５０℃，５０ｍｉｎ下制得平均粒径为０．２μｍ左右的ＳｉＣ－ＡｌＮ复合超细粉末，粉末烧结性能良好，在较低合成温度下（１５５０－１６００℃），粉末中出现晶须。本研究还探讨了粉末氮化合成条件对粉末颗粒及物相的影响。     

氮化硅粉末制备新技术

本文介绍了氮化硅陶瓷对氮化硅粉末烧结原料的特性要求，述评了SiO2还系氮化法，硅亚胺热分解法、高温气相反应法，激光气相反应法和等离子体气相反应法等五种氮化硅粉末的制备新技术。     

高频等离子体化学气相淀积制备氮化硅超细粒子

利用高频等离子本化学气相淀积方法以四氯化硅及氨为原料，合成了粒度小、粒径分布均匀、氮含量为３６．３％的无定形氮化硅粉末，研究了放置环境，合成及热处理环境，进料位置，ＮＨ３与ＳｉＣｌ４配比等不同的工艺条件对产物氮化硅氮含量的影响。推究了高温下四氯化硅与氨反应合成氮化硅的过程机理。     

铝源对碳热还原氮化法制备AIN粉末的合成工艺及粉末性能的影响

本文从比较不同铝对碳热还原氮化法制备ALN粉末的影响入手，用溶胶－凝胶法制得了一种铝碳良好结合、均匀、无（或弱）团聚的混合凝胶细粉（文中简称“均质混料”）；进而合成了纯度达98％的超细AIN粉末。文中着重分析了均质混料对降低合成条件、提高粉末性能的作用机制；探讨了影响合成过程的诸因素；认为：使用均质混料是改进碳热还原氮化工艺的有效途径。     

AIN粉末的制备方法

本文论述了ＡＩＮ陶恣粉末的三种典型制备方法－铝粉氮化法，还原氮化法和化学气相淀积法，总结了ＡＩＮ粉末的生成机理以及影响ＡＩＮ末质量的主要因素，理论分析了ＡＩＮ粉末制备过程中的有关实验现象，评述了ＡＩＮ粉末制备方法的优缺点，给出大量工艺参数。     

AlN陶瓷粉末的主要制备方法及展望

论述了国内外氮化铝陶瓷粉末的主要制备方法：铝粉直接氮化法、Al2O3碳热还原法、化学气相沉积法、溶胶-凝胶法、自蔓延高温合成法和等离子化学合成法，分析了这几种制备方法的特点和研究进展，为氮化铝粉末的制备指明了方向。     

氮化铝纳米末的氧化特性研究

采用直流电弧等离子体蒸发－凝聚法制备了高纯氮化铝纳米粉末，粉末的平均晶粒度为５０ｎｍ，纯度大于９８％。借助Ｘ射线光电子能谱、化学分析和差热失重等测试手段，探索了ＡＩＮ纳米粉末的表面化学组成和氧化特性，研究结果表明，ＡＩＮ纳米粉末易吸湿氧化，大大降低了其纯度。ＡＩＮ纳米粉末表面的氧是以两种状态即物理吸附态和化合态存在。     

添加MgO对碳热还原法合成尖晶石型氮氧化铝粉末的影响

研究了碳热还原氧化铝合成尖晶石型氮氧化铝（γ－ＡｌＯＮ）粉末，结果表明：氮氧化铝相是碳热还原法合成了ＡｌＮ粉末的过渡相，受其稳定性的影响，很难在低于１６５０℃下制备出纯氮氧化铝相的粉末，但引入一定的氧化镁可以在低于此温度下合成纯氮氧化铝相粉末，用ＸＲＤ，ＳＥＭ及ＥＭＰＡ分析了其相成分，形貌以及氮氧化铝相的晶格常数与外加剂引入量的关系，用Ｍａｌｖｅｒｎ激光粒度仪分析了合成的氮氧化铝粉末，其具有粒度小     

BaB6陶瓷粉末的反应合成

研究了利用BaCO3,B4C粉和活性炭粉制备BaB6陶瓷粉末的反应合成工艺。利用X－射线衍射分析了不同反应温度和保温时间条件下所生成粉末的相组成，利用扫描电镜分析了所生成BaB6粉末的颗粒尺寸及形貌。实验结果表明，BaCO3-B4C-C系制备BaB6粉末是一固相反应过程，其间要经过Ba2B2O5,BaB2O4等过渡相的生成过程。反应合成BaB6粉末的优化为：在10^-2Pa的真空条件下，1673K保温2小时，所合成的BaB6粉末形状主要由原材料B4C粉的形状决定，其颗粒由多边形集合体构成，通过改善原材料颗粒形貌可优化BaB6粉末形貌及性能。     

化学激励燃烧合成Si3N4/SiC复合粉体的研究

研究了利用聚四氟乙烯作活化剂时Si／C混合粉末在氮气中燃烧合成Si3N4／SiC复合粉体。结果表明：当聚四氟乙烯的加入量为10％(质量分数)时可有效激励Si-C弱放热反应，使之以燃烧合成方式生成Si3N4／SiC复相粉。在埋粉条件下Si／C／SiC混合粉末也可以实现燃烧合成Si3N4／SiC复相粉。氮气参与反应时可进一步提高燃烧反应温度，并且首先以气相-晶体生长机制生成Si3N4，然后在高温贫氮的反应前沿Si3N4分解，再与C反应生成SiC。在Si3N4／SiC复合粉中Si3N,形貌以晶须为主。综合X射线衍射分析、扫描电镜观察及原子力显微镜观察对实验结果进行了讨论，解释了Si3N4晶须的形成原理。     

Synthesis and characterization of Fe-Ti nanoparticles by nitrogen plasma metal reaction

The plasma state and nanoparticle formation of Ti-Fe alloys were studied by nitrogen plasma metal reaction. The nitrogen plasma state is dependent on the nitrogen partial pressure and the master alloy composition. Synthesis of Ti-Fe nanoparticles can be carried out only when the nitrogen partial pressure is smaller than 10% or the Ti composition is larger than 50 at.%. The as-received nanoparticles are composed of TiN and Fe phases with the mean particle diameters ranging from 25 to 40 nm; the TiN and Fe nanoparticles have quadrangular and spherical appearance, respectively. The nitrogen plasma promotes Fe evaporation more strongly than Ti, and as a result the as-received nanoparticles are Fe-rich. Compared with the hydrogen plasma, the nitrogen plasma has a smaller effect on evaporation enhancement, but stronger reactivity.     

氮化铝纳米粉末的氧化特性研究

采用直流电弧等离子体蒸发－凝聚法制备了高纯氮化铝（ＡＩＮ）纳米粉末。粉末的平均晶粒度为５０ｎｍ，纯度大于９８％。借助Ｘ射线光电子能谱、化学分析和差热失重等测试手段，探索了ＡＩＮ纳米粉末的表面化学组成和氧化特性。研究结果表明，ＡＩＮ纳米粉末易吸湿氧化，大大降低了其纯度。ＡＩＮ纳米粉末表面的氧是以两种状态即物理吸附态和化合态存在。     

硅粉氮化输送床内气固反应过程数值模拟

以单个硅颗粒氮化反应缩核模型为基础,本文建立了硅颗粒在输送床内反应、辐射与对流传热耦合的数学模型,并借助CFD软件FLUENT对输送床内能质传输过程进行了数值模拟,分析了输送床壁面温度、氮气流量、预热温度、硅粉粒径等因素对输送床内温度场和硅粉氮化率的影响。在数值计算域内将单个颗粒反应过程转化为颗粒群整体反应过程,实时监测颗粒粒径及未反应硅颗粒粒径,为数值模拟颗粒流反应提供一种新思路。当壁面温度高于1723K时,输送床内会出现一高温区加速硅粉氮化反应;反应温度越高、颗粒粒径越小,氮化过程越剧烈,硅粉到达完全氮化所需时间越短。模型表明为使粒径为2.5μm的硅粉达到完全氮化且输送床内最高温度不超过氮化硅的分解温度2173K,应控制输送床壁面温度在1773K,氮化时间在170s以上,预热温度在1273K,粉气质量比为0.2,稀释剂比例为0.5~1。     

Consolidation of Nano-Sized TiN Powders by Spark Plasma Sintering

Nano-sized TiN powders with an average particle size of 19 nm were synthesized via a new method, reduction–nitridation reaction in liquid ammonia. A consolidation procedure using spark plasma sintering (SPS) was used, and a dense TiN ceramic (>98% of theoretical) with mean grain size of 100–150 nm was obtained at 1380°C. The influence of sintering temperature on grain growth and microstructural evolution was also discussed.     

Plasma assists titanium nitride and surface modified titanium nitride nanoparticles from titanium scraps for magnetic properties and supercapacitor applications

Plasma methods are efficient processing for metal recovery from metal scrap, bearing minerals, electronic waste, etc. In this work, pure titanium nitride nanoparticles (TiN NPs) were synthesized from titanium scraps by the thermal plasma arc discharge (TPAD) method. TPAD synthesized TiN NPs have a highly crystalline nature with cubic and spherical morphologies with average particle sizes of 30–100 nm. Further, prepared TiN NPs involving surface modification (SM) or etching processes were investigated by using the non-thermal DC glow discharge plasma technique with air atmosphere at different processing times. SM@TiN NPs have a comparatively low crystalline, which was confirmed from the powder X-ray diffraction technique. SM@TiN NPs have very interesting core shell morphologies, which are due to the surface interactions of ionized air molecules. TiN and SM@TiN NPs have room-temperature ferromagnetic properties with high saturation magnetization (Ms) up to 2.6 and 3.0 emu/g and very high coercivity (Hc) of 235.5 Oe, respectively. TiN and SM@TiN NPs have superior energy storage performance with an outstanding specific capacitance of 192.8 and 435.1 F/g at a current density of 2 A/g with pseudocapacitive behavior. These results reveal that TiN and SM@TiN NPs have highly promising electrodes for supercapacitor applications.     

铝源孔容和焙烧升温过程对碳热还原法制备氮化铝粉体的影响

碳热还原氮化法是大规模制备高纯度氮化铝（AlN）粉体的主要方法,通过微反应器制备不同孔容的铝源,系统探究了前体孔容和微观形貌对AlN粉体产物的影响,并通过动力学模拟验证了筛选出的前体的活性。同时对氮化反应升温过程的影响也做了探究,最终通过对前体和焙烧升温过程的优化,得到纯度99%以上的AlN粉体,其平均粒径约为150 nm,O元素含量为0.55%。     

流化床化学气相沉积法制备近化学计量比的TiN粉体

传统气-固反应工艺制备TiN粉体存在难以逾越的内扩散控制过程,导致制备高纯、正化学计量比的TiN粉体至今存在巨大困难。提出了流态化化学气相沉积工艺(FBCVD)制备高质量TiN粉体,即基于TiCl₄-N₂-H₂体系,在往复运动的TiN种子粉体上沉积新生高质量TiN粉体的新方法。实验发现,当TiN种子粉体粒径大于52.95 μm时,即使在1000℃沉积2 h也不会失流,同时在TiN种子粉体上获得了亚微米级的结节状新生TiN颗粒。通过氧氮分析仪和XRD分析发现,新方法显著提升了粉体的氮含量,获得了近化学计量比的TiN_0.96,且氧含量下降了约40%。此外,流化床中气相沉积TiN的生长模式为岛状生长模式,为工业中制备高质量TiN粉体提供了一种新的方法。     

Composite powders for fabricating ceramics with pseudoeutectic structure in the ain-tin system

A new process is suggested for manufacturing a composite powder material in the A1N — TiN system with submicron distribution of TiN grains. Parallel processes of physical breakup of liquid drops of metallic aluminum upon wetting the surface of titanium oxide grains, carbothermal reduction of titanium oxide to metallic titanium, and nitriding of aluminum and titanium particles in high-frequency heating are envisaged. The mean grain size of TiN is 0.54 μm.     

Wear and corrosion studies of duplex surface-treated AISI-304 steel by a combination of cathodic cage plasma nitriding and PVD-TiN coating

This work aims to improve the surface properties of AISI-304 austenite stainless steel by using duplex treatment of cathodic cage plasma nitriding (CCPN) and PVD-TiN, and the results are compared with individual treated samples. This combination of treatments is used to improve the inherent drawbacks of individual PVD deposited TiN, such as voids, cracks, and detachment of hard layer from steel due to significant differences in the hardness of steel and hard layer. The hardness of steel (1.9 GPa) is improved to 17 GPa, 12 GPa, and 22 GPa by using only TiN, CCPN, and duplex treatment. The only TiN deposited sample shows the formation of layer with intense diffraction peaks along (311) and (400) orientation, and its orientation changed with intense peaks along (111), (200), and (220) by using duplex treatment, which increases the hardness. Furthermore, the wear resistance is improved by all treatments, specifically by using duplex treatment. While using a ball-on-disc wear tester, the TiN layer is not detached from the substrate in the duplex treated sample, in contrast with the only TiN sample. Furthermore, the corrosion rates are reduced by using the duplex treatment and the appliance of plasma nitriding before the TiN fills the voids and cracks in layer, and thus, the duplex layer effectively prevents steel against corrosive environment. This study suggests that combining these treatments improves surface hardness, wear resistance, and corrosion resistance.     

Nitride formation during combustion of Ti-TiO2 and Ti-Al powder mixtures in air under SHS conditions

Nitride formation during SHS combustion of a micron-size titanium powder and its mixtures with additives in air was studied. It was shown that the yield of TiN Ti powder was higher for SHS combustion in air than for SHS combustion of powders of the same degree of dispersion in nitrogen. The mechanism of formation of TiN is probably determined by the reaction of the intermediate product TiO with atmospheric nitrogen. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 5, pp. 131–135, September–October, 2008.