高能球磨制备氮化铝粉体的研究进展

综述了应用高能球磨技术制备氮化铝粉体的研究进展。高能球磨机械力活化效应可以降低后续合成氮化铝的碳热还原反应温度,其主要机制是球磨导致氧化铝粉体的细化以及晶格畸变的积累,进而降低了反应的热力学能垒。而球磨使得原料粉体均匀混合,增加动力学扩散通道并不是低温合成氮化铝的主要原因。利用等离子体辅助高能球磨技术可以高效活化氧化铝粉体,显著降低后续反应的激活能,这有望成为制备氮化铝粉体的一条新途径。     

高能球磨Al2O3相变及其反应活性研究

本文研究了高能球磨以及碳热还原反应加热过程中AlO3相结构的变化,及其对碳热还原反应活性的影响.不同相结构Al2O3碳热还原反应活性差别很大,γ-Al2O3是其中反应活性最好的.随着球磨时间的延长和加热温度的提高,粉末中发生了γ-Al2O3→α-Al2O3的转变,这一点对于降低碳热还原反应激活能是不利的.高能球磨20小时,Al2O3部分非晶化,而且有立方结构AlN生成,这两个现象属于首次报道.碳热还原反应加入的活性炭粉,能够抑制加热过程中的γ-Al2O3→α-Al2O3相变,有效地保证了粉末的反应活性.     

高能球磨固态扩散反应研究

从扩散理论出发,结合结合Ａｌ－Ｃｕ合金高能球磨实验结果,分析了高能球磨过程中的扩散特点,提出了固态合成反应模型并进行了分析计算,结果表明,高能球磨过程中固态反应能否发生取决于体系在球磨过程中能量升高程度,而反应完成与否则受体系中的扩散过程控制,即受制于晶粒细化攻粉末碰撞温度。     

机械合金化过程中Fe70B30粉末晶粒尺寸和微观应变的研究

用Ｘ射线和电镜研究了Ｆｅ＿（７０）Ｂ＿（３０）粉末经不同时间高能球磨后晶粒尺寸和微观应力的变化。在机械合金化过程中，粉末的Ｘ射线衍射谱的宽度随球磨时间的增加逐渐加宽，这是晶粒细化和内部微观应力共同作用的结果。Ｘ射线衍射结果表明：随着机械合金化的进行，粉末的晶粒尺寸逐渐减小，球磨初期晶粒尺寸下降较快，经１５ｈ球磨，晶粒尺寸为２５ｎｍ，机械合金化进行到一定时间后晶粒尺寸下降缓慢，８０ｈ球磨后晶粒尺寸可达５ｎｍ。在机械合金化过程中球磨所造成的微观应变不大，球磨初期粉末的内应力随球磨时间增加而增加，当粉末粒子尺寸很小时，随球磨的进行粉末中的微观应变显著下降。     

高能球磨制备立方A1N及其高温相变

研究了高能球磨过程中Al2O3的相变，随着球磨时间的延长，粉末中发生了γ-Al2O3向α—Al2O3的转变、高能球磨20h，Al2O3部分非晶化，同时，有立方A1N生成．增加球磨强度，立方A1N生成量增加，650r／min高能球磨40h，A1N生成量达到72％．随后的氮气气氛退火实验发现，在500℃以上，立方氮化铝与氧化铝反应，生成AION相．AION相的生成，有效地降低了碳热还原氮化反应激活能．     

高能球磨制备立方AlN及其高温相变

研究了高能球磨过程中Al₂O₃的相变, 随着球磨时间的延长, 粉末中发生了γ -Al₂O₃向α -Al₂O₃3的转变. 高能球磨20h, Al₂O₃部分非晶化, 同时, 有立方AlN生成. 增加球磨强度, 立方AlN生成量增加, 650r/min高能球磨40h, AlN生成量达到72%. 随后的氮气气氛退火实验发现, 在500℃以上, 立方氮化铝与氧化铝反应, 生成AlON相. AlON相的生成, 有效地降低了碳热还原氮化反应激活能.     

高能球磨中促进粉体细化的主要因素研究

高能球磨技术作为一种制备包括纳米粉体在内的多种亚稳相材料的有效方法,已获得广泛应用.通常可以添加过程处理剂或在低温下球磨来抑制球磨过程中的冷焊,促使粉末细化.利用外加物理能场辅助高能球磨,使物理能与机械能协同作用到粉末,也是提高高能球磨效率的一种有效途径.根据不同条件下Fe粉的球磨细化结果,分析了高能球磨中过程处理剂、低温和外加能场辅助等主要促进粉体细化的因素及其作用.研究表明,采用等离子体辅助球磨仅仅10h,铁粉颗粒就被细化到了100nm.这种高的细化效率是因为等离子体辅助球磨中,等离子体对粉体产生的热爆效应和热应力的协同作用使粉体更易细化.     

球磨氧化铝晶粒尺寸与显微应变的关系

研究了高能球磨氧化铝的晶粒尺寸和显微应变。发现球磨后氧化铝的显微应变（ε）与晶粒尺寸（Ｄ）符合逆变关系,即晶粒尺寸越小,显微应变越大。显微应变与晶粒尺寸的倒数成线性关系,在ε～１／Ｄ图上出现双斜率。表明球磨不同阶段,显微应变增加的机制不同。     

碳热还原法生成AlN晶须的形貌及结晶方向

在用碳热还原法制备ＡｌＮ粉未过程中，发现大量白色ＡｌＮ晶须存在于ＡｌＮ粉末坯体表面某形貌有直板状、锯齿状及抿曲状，电子衍射花斑显示结晶方向均为（０００２），其生长机理可能为ＶＳ机制。     

机械合金化制备纳米Cu-Zn-Al2O3复合粉末的研究

采用X射线衍射仪、电子扫描电镜和透射电镜等研究了Ar气氛保护下Cu-Zn-Al2O3复合粉末在高能球磨过程中发生的机械合金化反应,分析了不同球磨时间对a-Cu(Zn)的晶格常数、晶粒尺寸以及复合粉末粉体形貌、颗粒尺寸的影响.结果表明,球磨初期,Cu的晶格常数增大,但75h后由于γ相的析出,a-Cu(Zn)晶格常数减小;高能球磨120h后,可获得氧化铝颗粒弥散分布的纳米级Cu(Zn)复合粉末.     

Preparation and characterization of morph-genetic aluminum nitride/carbon composites from filter paper

Morph-genetic aluminum nitride/carbon composites with cablelike structure were prepared from filter paper template through the surface sol-gel process and carbothermal nitridation reaction. The resulting materials have a hierarchical structure originating from the morphology of cellulose paper. The aluminum nitride/carbon composites have the core-shell microstructure, the core is graphitic carbon, and the shell is aluminum nitride nanocoating formed by carbothermal nitridation reduction of alumina with the interfacial carbon in nitrogen atmosphere. Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and transmission electron microscope were employed to characterize the structural morphology and phase compositions of the final products.     

Synthesis of Vanadium Nitride by a One Step Method

Vanadium nitrides were prepared via one step method of carbothermal reduction and nitridation of vanadium trioxide. Thermalgravimetric analysis （TGA） and X-ray diffraction were used to determine the reaction paths of vanadium carbide, namely the following sequential reaction： V2O3→V8C7 in higher temperature stage, the rule of vanadium nitride synthesized was established, and defined conditions of temperature for the production of the carbides and nitrides were determined. Vanadium oxycarbide may consist in the front process of carbothermal reduction of vanadium trioxide. In one step method for vanadium nitride by carbothermal reduction and nitridation of vanadium trioxide, the nitridation process is simultaneous with the carbothermal reduction. A one-step mechanism of the carbothermal reduction with simultaneous nitridation leaded to a lower terminal temperature in nitridation process for vanadium nitride produced, compared with that of carbothermal reduction process without nitridation. The grain size and shape of vanadium nitride were uniform, and had the shape of a cube. The one step method combined vacuum carborization and nitridation （namely two step method） into one process. It simplified the technological process and decreased the costs.     

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。     

Review of the Synthesis Methods for AIN

The different routes for the synthesis of aluminum nitride (AIN) powders are reviewed: the different industrial techniques from both the direct nitridation of aluminum metal and the carbothermal nitridation of alumina, and also other synthesis routes not industrially developed up to now. This paper presents a comprehensive presentation of the different chemical systems analyzed from the compilation of more than 70 publications and analysis of 91 patents.     

Preparation of nano-TiN powders by Ni-catalysed carbothermal reduction nitridation

TiN nanoparticles were prepared at 900–1100 °C by Ni-catalysed carbothermal reduction nitridation from sol-gel using tetrabutyl titanate, citric acid monohydrate and nickel chloride hexahydrate as starting materials. The catalytic effects of nickel on the carbothermal reduction nitridation of xerogels were investigated. Ni has a crucial promoting effect on the carbothermal reduction reaction of the xerogels and visibly enhanced carbothermal reduction and nitridation reactions. The dry gel with 5% NiCl₂ was added to obtain nano-TiN at 900 °C. The transmission electron microscopy analysis and Materials Studio simulation results showed that the facilitating effect of Ni on carbothermal reduction nitridation reaction was ascribed to the provision of heterogeneous nucleation sites for amorphous titania, promoting crystallisation and adsorption of N₂, resulting in its smooth dissociation into highly active N atoms and consequently enhancing the carbothermal reduction nitridation.     

Fabrication of silicon nitride nanoceramics—Powder preparation and sintering: A review

Fine-grained silicon nitride ceramics were investigated mainly for their high-strain-rate plasticity. The preparation and densification of fine silicon nitride powder were reviewed. Commercial sub-micrometer powder was used as raw powder in the “as-received” state and then used after being ground and undergoing classification operation. Chemical vapor deposition and plasma processes were used for fabricating nanopowder because a further reduction in grain size caused by grinding had limitations. More recently, nanopowder has also been obtained by high-energy milling. This process in principle is the same as conventional planetary milling. For densification, primarily hot pressing was performed, although a similar process known as spark plasma sintering (SPS) has also recently been used. One of the advantages of SPS is its high heating rate. The high heating rate is advantageous because it reduces sintering time, achieving densification without grain growth. We prepared silicon nitride nanopowder by high-energy milling and then obtained nanoceramics by densifying the nanopowder by SPS.     

高能机械化学法制备超微氮化钼粉体

利用自行设计的高能机械化学球磨机,在室温下通过使钼粉在NH3气氛下高能球磨得到了超微氮化钼粉体。XRD和SEM分析表明,在球料比仅为8:1的情况下,经过30 h球磨,粉体平均粒度在100nm以内。机械化学反应过程中,氨气分子在钼金属清洁表面的化学吸附起着重要的作用,球磨过程中介质球碰撞储存于钼粉中的能量则提供了Mo-N化学吸附向氮化钼转变所需的激活能。在Mo与NH3的高能机械化学反应过程中,球磨转速的高低对整个反应的速度很大的影响。     

Preparation of aluminum nitride granules by a two-step heat treatment method

The sintered aluminum nitride granules were prepared in a continuous process through a two-step heat treatment at 1600?°C for 5?h and 1850?°C for 5?h using the spherical γ-alumina/phenol-resin precursor obtained by spray granulation as the starting material. In the first step of heat treatment, the alumina powders were nitrided to form porous aluminum nitride granules via a carbothermal reduction reaction and then were continuously heated in the second step of heat treatment to produce dense spherical aluminum nitride granules without using sintering aids. The obtained porous and sintered aluminum nitride granules were characterized by XRD, SEM and BET measurements and exhibited an average grain size of about 1 and 3?µm, respectively. Furthermore, the specific surface area of the obtained porous and sintered aluminum nitride granules dramatically decreased from 2.49 to 0.16?m²/g showing that the low-porosity, dense, polycrystalline aluminum nitride granules were successfully prepared.     

Effect of filler load and high-energy ball milling process on properties of plasticized wheat gluten/olive pomace biocomposite

The increase of particles surface area can optimize the dispersion state of biocomposite components and enhance their properties. First in this paper, we aimed to elaborate a novel biocomposite without any treatments. Plasticized wheat gluten (WG), was filled with 0–20% of olive pomace (OP) powder. The second objective was the improvement of biocomposite properties using physical treatment. High-energy ball milling process was applied on the blend of wheat gluten and olive pomace powders (MPs). The grinding effect of particle shape, size and distribution in biocomposite was characterised by particle size distribution using a laser-light diffraction and by SEM analysis. The cryo-fractured surface of selected films, mechanical properties, moisture absorption and thermal properties of both biocomposites were described in details. It was found that the sensitivity of biocomposites to moisture absorption was reduced with the increase of filler content after the applying of high-energy ball milling process. The thermal stability of OP biocomposite decreased with the increase of loading, while that of MPs was unaffected by high-energy ball milling process. This process affects the physical and morphological characteristics of the powders. The mechanical properties were improved by grinding process at filler content lower than15%.