自蔓延高温合成锰锌铁氧体粉料

采用内氧化剂KClO₃,在常压空气中自蔓延高温合成锰锌铁氧体粉料.粉料性能用XRD、SEM、VSM等表征,讨论了燃烧合成的影响因素.结果表明:当反应放热供氧系数m为0.54、反应控制放热系数k为0.6、燃烧合成速度为1.93mm·s^-1、燃烧温度为1593K时,可制备性能优良的锰锌铁氧体粉料,其比饱和磁化强度为64.44A·m²·kg^-1,比剩磁强度为1.349A·m²·kg^-1,矫顽力为0.24kA·m^-1,平均粒径为1.42μm.     

Self-propagating high-temperature synthesis of promising ceramic materials for deposition technologies of functional nanostructured coatings

Taking into account the demand for composite targets or precursors for ion-plasma technologies for the deposition of functional nanostructured coatings, this work is a review of recently obtained and previously unpublished results of synthesis in the combustion mode of a series of chemical classes of systems differing in regards to the mechanisms of combustion and structure formation. The experimental results for self-propagating high-temperature synthesis are presented for the following systems: Ti-Al-C, Cr-Al-C, Ti-Cr-Al-C, Cr-B, Ti-Cr-B, Ti-Ta-C, and Ti-Si₃N₄-Al-C. The compositions of reaction mixtures and conditions of obtaining the most interesting and needed materials with high mechanical properties and resistance to high-temperature oxidation are found.     

自蔓延高温合成二硅化钨粉末

利用自蔓延高温合成法成功制备了WSi2粉末。计算了各相合成时的绝热温度,探讨了各相生成的先后顺序及转化关系,利用XRD及SEM分析了合成产物中相组成及组织形貌等。     

层状可加工陶瓷Ti3SiC2自蔓延高温合成反应机理的研究

采用燃烧波淬熄法,以Ti粉、Si粉和C粉为原料研究了层状可加工陶瓷Ti3SiC2在自蔓延高温合成(SHS)中的反应机理.淬熄试样中保留未反应区、反应区和已反应区,用扫描电子显微镜观察燃烧反应中显微组织的转变过程,用能谱仪分析各微区的成分变化,并通过差热分析(DSC-TGA)和XRD分析考察了从600℃到1500℃ Ti-C-Si系统的反应合成过程和相形成规律.结果表明:层状可加工陶瓷Ti3SiC2自蔓延高温合成的机理为溶解-析出机制,Ti粉与Si粉的固态扩散导致低熔点Ti-Si溶液形成,Ti、Si、C粉粒逐渐向Ti-Si溶液中溶解,当溶液中的Ti、Si、C浓度饱和时,从中析出TiC、SiC颗粒,最后形成最终产物Ti3SiC2.     

Self-propagating high-temperature synthesis in the production of functional coatings

The direct synthesis of refractory compounds and the reduction of metal oxides by self-propagating high-temperature synthesis are subjected to thermodynamic analysis. The laws of self-propagating high-temperature synthesis are investigated, and the possibility of creating functional metal-oxide coatings of specified composition by that means is considered.     

自蔓延高温合成金属钒的热力学研究

对自蔓延高温合成金属钒的吉布斯自由能、单位热效应及绝热燃烧温度进行热力学计算和分析。结果表明,自蔓延高温合成金属钒能自发进行,且反应剧烈;绝热燃烧温度为3 021K,单位热效应为4 988J/g;高纯V2O5和铝粉的反应在943K左右发生,为液—固反应。     

反应火焰喷涂TiC/Fe金属陶瓷复合涂层的组织结构

采用钛铁矿粉、石墨粉和铁粉为主要原料,利用反应火焰喷涂技术成功制备了TiC/Fe金属陶瓷复合涂层.采用X射线衍射仪、扫描电镜、透射电镜等手段,研究了涂层的显微组织结构.结果表明,反应火焰喷涂TiC/Fe复合涂层主要由TiC和Fe两相组成.涂层具有多层多相的结构,即由TiC含量不同的片层交替叠加而成;在富TiC片层中,大量的、比较细小的(粒度小于0.5μm)、大致呈球形的TiC颗粒弥散分布在Fe基体上.这种显微组织结构有利于改善金属陶瓷涂层的耐磨性能.     

TiC-TiB2复相陶瓷的自蔓延高温合成研究

以Ti、B和C粉末为原料,采用SHS/PHIP工艺制备了不同组份的TiC-TiB2复相陶瓷,通过试验研究了复相陶瓷的微观结构特征和力学性能.结果表明,SHS反应产物纯净,TiC-TiB2复相陶瓷中只有TiC和TiB2两相存在;随着TiB2含量的增加,复相陶瓷中TiC颗粒尺寸变小,而TiB2颗粒有异常长大现象;TiC-TiB2复相陶瓷的相对密度、硬度和横向断裂强度均随TiB2含量的增加呈先增后减趋势;当TiB2与TiC的重量比为60%时,该复相陶瓷的横向断裂强度和断裂韧度分别为576MPa和5.45MPa·m1/2,而相对密度达到99.4%.     

Reaction of boron-containing materials with titanium during self-propagating high-temperature synthesis

We have studied the contact reaction of titanium, chromium, and tungsten borides with titanium. We have established that the materials react according to an exothermic solid-phase reaction mechanism with formation of titanium monoboride and diboride. The reaction is limited by diffusion of boron atoms through the layer of titanium monoboride formed. This makes it possible to successfully use reaction to effectively control the process for obtaining composite materials in the Ti-B₄C system under selfpropagating high-temperature synthesis conditions. __________ Translated from Poroshkovaya Metallurgiya, Nos. 3–4(448), pp. 67–72, March–April, 2006.     

A new class of electric-spark coatings for articles made of titanium alloys for use in extreme conditions

The formation, structure, composition, and properties of electric-spark coatings on titanium alloys (VT 6, VT 20) obtained with the use of hard-alloy electrode materials (EM) on the basis of titanium carbide and boride, as well as nanodispersed tungsten carbide are considered. The peculiarities of the mass transfer of EM on VT 20 grade titanium alloy when the parameters (current strength, frequency, and duration) of the pulsed current discharge vary are investigated. The optimum power mode of the electric-spark treatment of the Ti alloy by new EMs (I = 175 A, f = 800 Hz, and = τ μs) are determined. Investigations of the structure, phase composition, and properties (such as continuity; thickness; microhardness; friction coefficient; and wear-, heat-, and fretting resistance) of formed electric-spark coatings are carried out. Their phase composition and topography are investigated after high-temperature treatment (at 600°C for 100 h). It is shown that electric-spark treatment by new hard-alloy EMs improves the properties of electric-spark coatings on VT 20 titanium alloy compared to similar coatings obtained with the use of widely spread electrodes VK8, T15K6, and relit.     

钛酸钡陶瓷粉末的低温燃烧合成

以Ba (NO₃)₂-TiO₂-C₆H₇O₈·H₂O为体系,在600℃加热进行低温燃烧合成实验,制得粒度为1.2~.4 μm的四方相BaTiO₃陶瓷粉体.结果表明燃烧的均匀程度对燃烧产物的相组成和微观结构有很大的影响.通过热力学分析,提出低温燃烧合成BaTiO₃陶瓷粉末的形成机理.     

原位合成Mo5SiB2的热力学分析

计算了Mo-Si-B三元系中各化合物不同温度下标准生成自由焓和合成Mo₅SiB₂(T2相)反应在不同开始温度下的绝热温度及反应产物的熔化比.结果表明:用Mo、Si和B三种元素粉末混合物来原位合成Mo₅SiB₂在热力学上是完全可行的;合成Mo₅SiB₂不宜用燃烧合成的自蔓延模式,宜采用燃烧合成的热爆模式(原位反应热压工艺);反应的绝热温度及反应产物的熔化比与开始温度有关.     

基于自蔓延高温合成(SHS)的涂层技术

综述了几种利用自蔓延高温合成(SHS)反应制备涂层的技术,包括反应热喷涂、SHS离心铸造涂层、SHS熔铸涂层以及反应铸渗涂层.介绍了它们的工艺过程、工艺特点、适应的反应体系以及涂层性能.这些基于SHS反应,用于制备耐磨耐蚀陶瓷或金属陶瓷涂层的涂层技术,充分利用SHS技术本身具有的节能、工艺简单、产物纯度高等优点,显示出了很强的竞争优势.     

Self-propagating high-temperature synthesis of composite targets based on titanium carbonitride,silicide, and aluminide for ion-plasma deposition of multifunctional coatings

The macrokinetic features of combustion of the mixtures in the Ti-Al-Si₃N₄-C system calculated for the formation of compact ceramic materials (CCMs), the composition of which is described by the general formula X(TiAl₃) + (100 − X)(0.448TiC_0.5 + 0.552(Ti₅Si₃ + 4AlN) with mixture parameter X = 10–50%, are investigated. Compact CCM samples with the main structural components in the form of TiC _x N _y grains and binding phases TiAl3 and Ti5Si3 are fabricated by the technology of forced self-propagating high-temperature synthesis (SHS) compaction. An increase in X promotes the formation of the M _n +1AX _n phase with the composition Ti₃SiC₂ in the synthesis products. Complex investigations into the physicomechanical properties of the obtained ceramics are performed. Based on their results, the inverse dependence of the density and hardness of compact materials on parameter X is established. Tests of the samples for oxidation resistance showed that the obtained CCMs based on titanium carbonitride, silicide, and aluminide possess excellent resistance to high-temperature oxidation, and their oxidation rate in air at t = 900°C for 30 h does not exceed 7.8 × 10⁻⁵ g/(m² s).     

CrCN涂层在不同沉积温度下的摩擦学性能研究

利用多弧离子镀技术,在乙炔和氮气环境下,设定不同沉积温度(150℃、250℃、350℃、450℃),在316L不锈钢及单晶硅片上沉积CrCN涂层,通过XRD、XPS、SEM、纳米压痕仪和UMT-3多功能摩擦磨损试验机等涂层的微观结构、力学性能和摩擦学性能进行表征.结果表明:随着沉积温度的升高,CrCN涂层的硬度和模量呈现出递增的趋势,在沉积温度为450℃时达到最高,分别为24 GPa和354 GPa;摩擦系数和磨损率则呈现出先递减后递增的趋势,在沉积温度为350℃时达到最低,摩擦系数在大气和水环境下分别为0.38和0.23,磨损率在大气和水环境下则分别为1.717 1×10-6mm3/N·m和9.529 7×10-7mm3/N·m.同时,涂层在水环境中的摩擦系数和磨损率均低于大气环境中,说明水分子在摩擦过程中起到了较好的润滑作用.     

Magnetic properties of La-Zn substituted Sr-hexaferrites by self-propagation high-temperature synthesis

The La-Zn substituted SrM-type ferrites with the composition of Sr1-xLaxFe12-xZnxO19 （x=0-0.4） were prepared by self-propagating high-temperature synthesis （SHS）. The single SrM phase was detected by XRD in the as-received samples by controlling the Fe contents in the reagents. The substitution of La^3＋and Zn^2＋ obviously increased the magnetic properties of the as-prepared samples. The maximum improvements of Br, Hcb and （BH）m were 14.4%, 15.3% and 30.7%, respectively compared with that of the samples without La-Zn substitution. Microstructure observation by SEM showed that the SHS method benefited forming the better particle features and achieving the higher Hcj in comparison with the traditional firing method.     

电沉积Ni-W-WC复合镀层摩擦磨损性能

为了提高Ni-W合金镀层的硬度,改善其耐磨性,在镀层中添加WC颗粒作为硬质相,采用乙醇作为分散剂,利用超声波分散和机械搅拌相结合使WC颗粒均匀地分散于镀液中. 初步探究WC的添加量对镀层硬度及耐磨性能的影响. 结果表明:其他工艺条件不变的情况下,在一定范围内添加WC颗粒,可以较大幅度地提高镀层的硬度及耐磨性;WC添加量为1 g/L时,镀层的综合力学性能最好.      

Microstructure and high-temperature properties of Fe-Ti-Cr-Mo-B-C-Y_2O_3 laser cladding coating

Fe-based composite coatings were fabricated on 5 CrNiMo die steel by laser beam melting a precursor mixture of ferrotitanium,ferrochromium,ferromolybdenum,B4 C and Y_2 O_3 powders.Micro structure and properties of the coatings were studied by X-ray diffraction(XRD),scanning electron microscopy(SEM),energy-dispersive spectrometer(EDS),resistance furnace and high-temperature tribometer.The results show that(Ti,Mo)C particles with flower-like and(Ti,Mo)B_2 with block-like shapes are in situ formed during laser cladding.Volume faction of multiple ceramic particles increases with the increasing of Y_2 O_3.The cumulative oxidation mass of the coating with 2 wt% Y_2 O_3 is decreased by one-third than that of the coating without Y_2 O_3.The oxidation layer of the coating with Y_2 O_3 is getting smooth.Meanwhile,high temperature wear volume loss of the coating with 2 wt% Y_2 O_3 is about 40% that of the coating without Y_2 O_3.The coating with 2 wt% Y_2 O_3 shows a smoother wear scar and few flat grooves are observed after high temperature wear test.     

Self-propagating high-temperature synthesis of titanium carbide nanopowder from the granulated charge

Parameters and combustion products of the Ti + C + cellulose nitrate porous granulated batch with added KCl, NaCl, or K₂CO₃ salts and/or C₆H₈Cl₁₄ perchlorovinyl resin allowing for the evolved impurity gas filtration are investigated. The influence of these additives is shown and the formation conditions of nanostructured titanium carbide powder are found.     

Some Characteristic Features of Formation of Ceramics Based on Composite Powders SiC ― Si3N4 ― Si2N2O

We have studied the characteristic features of synthesis of composite powders SiC Si₃N₄ Si₂N₂O. We have investigated processes involving hot pressing of these powders without activating additives and a protective atmosphere. We consider the mechanical properties of ceramics obtained on the basis of these composite powders.