自蔓延高温合成法制备WC—Al2O3得合陶瓷材料的研究

研究了ＷＣ－Ａｌ２Ｏ３复合陶瓷材料的自蔓延高温合成过程中，稀释剂含量、反应和类型、金属还原剂粒度，以及碳的配比含量对燃烧反应的速率、温度和燃烧含成物相组成的影响。结果表明，采用自蔓延高温合成技术制备ＣＷ－Ａｌ２Ｏ３复合陶瓷材料时，气相产物的生成及挥发是影响反应参数和合成物相组成的重要因素。通过改变反应物的配比含量，可以有效地调整合成产物中ＣＷ，Ｗ２Ｃ以及Ｗ的相对含量。     

自蔓延高温合成Al2O3＋ZrO2＋Cr复合材料

自蔓延高温合成是制备材料的一种新工艺。通过热力学和显微结构分析研究了Ａｌ－Ｃｒ２Ｏ３－ＺｒＯ２系统，结果表明：在Ａｌ：Ｃｒ２Ｏ３：ＺｒＯ２＝１：２．８：１．４３（ｗｔ）时，可以自蔓延高温合成Ａｌ２Ｏ３－ＺｒＯ２－Ｃｒ复合材料，ＺｒＯ２不与Ａｌ发生反应，产物孔隙度达３５％－４５％。     

自蔓燃高温合成CrB2

以铝粉、氧化铬、氧化硼为主要原料，采用自蔓燃高温合成工艺制取硼化铬ＣｒＢ２。实验证明，合成反应Ｃｒ２Ｏ３＋６Ａｌ＋２Ｂ２Ｏ３＝２ＣｒＢ２＋３Ａｌ２Ｏ３可顺利进行，经化学分析及Ｘ线衍射分析证实产物的主要物相为ＣｒＢ２，并研究了各种因素对结果的影响。     

相图计算技术在复相陶瓷燃烧合成热力学分析中的应用

应用相图计算技术（ＣＡＬＰＨＡＤ）对燃烧合成复相陶瓷的绝热燃烧温度，平衡相组成等进行了热力学分析。讨论了铝热型自蔓延高温合成反应中副产物相的成因及可能的消除途径。根据稀释剂对绝热温度的影响方式提出了稀释作用的两种模式。对反应热压中采用的硼，碳和Ａｌ２Ｏ３体系的绝热温度进行了计算，并对其放热能力进行了评价。     

添加剂对Cr2O3—Al系SHS反应的影响

研究了添加ＣｒＯ３－Ａｌ、Ｆｅ２Ｏ３－Ａｌ＋ＭｇＯ及Ｔｉ－Ｃ的Ｃｒ２Ｏ３－Ａｌ系的燃烧特性。实验发现，添加ＣｒＯ３－Ａｌ、Ｆｅ２Ｏ３－Ａｌ＋ＭｇＯ时，自蔓燃反应易于引发；体系中混入Ｔｉ－Ｃ添加剂对反应引发不利，但在用纯Ｔｉ－Ｃ作引火剂情况下可以引发。随着ＣｒＯ３－Ａｌ添加量的增加，燃烧温度升高，但添加量大于２０％时，燃烧温度反而下降。燃烧温度随Ｆｅ２Ｏ３－Ａｌ＋ＭｇＯ添加量的增加而升高。Ｔｉ－Ｃ添加量的增大对燃烧温度影响不大。燃烧速度随以上添加剂量的增大而增大     

CaO—SiO2—MgO—Al2O3精炼渣的脱硫性能

在实验室用模拟装置研究了ＣａＯ－ＳｉＯ２－ＭｇＯ－Ａｌ２Ｏ３精炼渣脱硫的性能。碱度和助溶剂ＣａＦ２含量对硫分配比Ｌｓ影响较为显著，并分析了ＭｇＯ、Ａｌ２Ｏ３对脱硫反应的作用。     

凝固过程钢中氧化物成分对氧化物和硫反应的影响

为了阐明钢在凝固过程中氧化物和硫之间的反应，观察分析了连铸钢氧化物成分对它的影响，结果如下：在低Ａｌ含量钢中（Ａｌ＝０．００５％）观察到ＣａＯ－ＳｉＯ２－Ａｌ２Ｏ３和ＣａＯ－ＳｉＯ２氧化物，在高Ａｌ含量钢中（Ａｌ＝０．０３１％）看到ＣａＯ－Ａｌ２Ｏ３氧化物。ＣａＯ－ＳｉＯ２＿Ａｌ２Ｏ３和ＣａＯ－Ａｌ２Ｏ３氧化物比ＣａＯ－ＳｉＯ２氧化物具有较高的硫含量。氧化物中的Ｓ含量随钢在凝固温度下的液相率和硫容     

用SHS工艺合成TiAl,TiNi,Nial金属间化合物

用自蔓延高温合成技术的热爆模式制备了ＴｉＡｌ、ＴｉＮｉ和ＮｉＡｌ金属间化合物。研究了合成产物的形态及相组成，ＴｉＡｌ和ＮｉＡｌ系得到了铸态的组织，相组成为单一的ＴｉＮｉ相和ＮｉＡｌ相。ＴｉＡｌ系的产物形态为疏松的多孔体，由ＴｉＡｌ３、ＴｉＡｌ和Ｔｉ３Ａｌ三种相组成，获得的合成粉末颗粒尺寸比原料粉末小一个数量级。     

SiC陶瓷常压烧结研究

研究了ＳｉＣ粉末粒度、助剂Ａｌ２Ｏ３＋Ｙ２Ｏ３加入量和Ａｌ２Ｏ３与Ｙ２Ｏ３的配比等因素对ＳｉＣ陶瓷材料性能的影响。结果表明，添加Ａｌ２Ｏ３＋Ｙ２Ｏ３助剂可实现ＳｉＣ陶瓷的低温（１８５０℃）常压烧结。ＳｉＣ粉末粒度是影响可烧结性的重要因素之一，助剂加入量为２０％，Ａｌ２Ｏ３与Ｙ２Ｏ３之比为１：１时材料性能较好。     

非调质塑料模具钢中易切削相的分析

运用光学显微镜、扫描电镜、电子探针以及图像分析仪，分析了Ｓ、Ｓ－ＲＥ、Ｓ－Ｃａ－ＲＥ非调质塑料模具钢中易切削相的形貌、分布、组成及其对力学性能的影响。结果表明，经Ｃａ、ＲＥ处理的钢中，出现以ｍＣａＯ·ｎＡｌ２Ｏ３为核心的ＭｎＳ和ＣａＯ·Ａｌ２Ｏ３·ＴｉＮ·（Ｍｎ，Ｃａ）Ｓ·ＲＥ２Ｓ３组成的复合硫化物，多呈纺锤形，提高了钢的横向冲击韧性，另外采用适量的铝和微量的钛也有利于改善易切削相形态     

自蔓燃高温合成碳化物陶瓷

介绍了自蔓延高温合成（SHS）制备碳化物粉体。单晶、多孔材料和致密材料。重点讨论了通过控制反应参数,控制合成材料的组织结构和性能的一些措施。以催化剂载体、泡沫陶瓷过滤器、粗TiC磨料以及Si-SiC复合材料为例,介绍了SHS在材料合成中的应用和控制方法。参考Ti3SiC2陶瓷的合成,讨论了多元SHS体系中产物相的控制问题。另外,文中还介绍了提高烧结助剂BxC在SiC中的分散性,从而提高SHSSiC烧结性的实例。     

碳/氮源对碳热还原(Ti,W)(C,N,B)固溶体粉末合成的影响

采用"前驱体+碳热还原"的方法,利用XRD、SEM研究了不同碳源和氮源对合成(Ti,W)(C,N,B)固溶体粉末的物相组成和微观形貌的影响。结果表明:以木糖和氮气分别作为碳源和氮源,能在1 200℃下合成相成分单一的纳米晶(Ti,W)(C,N,B)固溶体粉末,且操作工艺简单、易控;选用炭黑和大分子量的酚醛树脂作为碳源,尿素作为氮源时,碳热还原反应和固溶反应难以充分进行,反应产物存在大量钛氧化物的中间相(如Ti_3O_5、Ti_2O_3等)和单质W等杂质相。     

Self-propagating high-temperature synthesis of ceramic materials based on the M<Subscript><Emphasis Type="Italic">n</Emphasis> + 1</Subscript>AX<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> phases in the Ti-Cr-Al-C system

Compact ceramic materials based on the M_{n + 1}AX _n phases in the Ti-Cr-Al-C system are produced by forced self-propagating high-temperature synthesis (SHS) compaction. The mechanisms of the structure and phase formation in synthetic products, as well as the combustion macrokinetics of the SHS mixture, are studied. Complex investigations of the structure, phase composition, and physical and mechanical properties of new Ti_{2 ? x} Cr _x AlC ceramic materials synthesized at different charging parameters (x = 0, 0.5, 1, 1.5, and 2) are performed. The highest content (96–98%) of the M_{n + 1}AX _n phase in the composition of synthetic products is found to be in samples where just one of the host elements (titanium (x = 0) or chromium (x = 2)) is present. The produced materials have a high heat resistance, and the increase in the chromium concentration is favorable to an appreciable growth in resistance to high-temperature oxidation.     

SHS Metallurgy of Cr<Subscript>2</Subscript>AlC MAX Phase-Based Cast Materials

A review of publications on the structure, properties, fabrication methods, and application fields of materials based on the Cr₂AlC MAX phase is given. It is noted that the most promising method of formation of such materials is self-propagating high-temperature synthesis (SHS), one of the directions of which is SHS metallurgy. A powder mixture of chromium III and chromium VI oxides of the analytical grade, aluminum of ASD-1 grade, and carbon is used as the base charge in investigations. The adiabatic combustion temperature and composition of final products is calculated using the THERMO special program. Experiments were performed in an SHS reactor with volume V = 3 dm³ under the initial pressure of inert gas (Ar) P₀ = 5 MPa. The influence of the ratio of initial reagents on SHS parameters (the combustion rate, pressure increment, and yield of the target product), composition, and microstructure of target products is investigated experimentally. A scientific approach of the formation of cast materials in the Cr–Al–C system consisting of the Cr₂AlC MAX phase and phases Cr₃C₂ and Cr₅Al₈ by the SHS metallurgy method is developed. The structural-phase states of target products are studied. It is established experimentally that, varying the content of initial reagents (aluminum and carbon) in the charge, it is possible to substantially affect the synthesis regularities, composition, and microstructure of final products. An increase in the content of the Cr₂AlC MAX phase in the final product and a decrease in the Cr₅Al₈ content occur with an increase in the carbon content (above stoichiometric) in the initial mixture. An increase in the aluminum content (above stoichiometric) in the initial mixture leads to an increase in the content of the Cr₂AlC MAX phase in the final product and a decrease in the content of the Cr₃C₂ phase.     

Ti-W-C体系的自蔓延高温合成与反应机理

研究了Ti-W-C体系自蔓延高温合成(SHS)的燃烧温度和燃烧速度与W含量、Ti粉粒度及预热温度的关系。分析了不同W含量和预热温度时SHS产物的相组成,并对体系的SHS反应机理进行了研究。结果表明:W/(Ti+W)≤ 0.3时,基本能合成单相(W/Ti)C;而预热可促进(W,Ti) C的SHS合成;体系的SHS反应过程中存在两种反应机制,即溶解-析出机制和扩散-固溶机制     

Preparation of CeB6 nano-powders by self-propagating high-temperature synthesis （SHS）

CeB6 powders were prepared by high-temperature self-propagating synthesis(SHS) in which CeO2,B2O3 and Mg were taken asreactants.The adiabatic temperature and dynamics of SHS reactions were investigated.The SHS reaction products and leached products werecharacterized by X-ray diffraction(XRD) and scanning electron microscopy(SEM).The results indicated that the adiabatic temperature ofMg-B2O3-CeO2 reaction system was rather higher than 1800 K to make the reaction propagate by itself,and the apparent activation energy(Ea)and reaction order(n) of exothermic peak on Mg-B2O3-CeO2 differential scanning calorimetry(DSC) curve were 23.03 kJ/mol and 1.31,respectively.The apparent activation energy was lower,so the reaction occurred easily.The SHS products consisted of MgO,CeB6 and littleMg3B2O6.The leached products consisted of single CeB6 phase and its purity was higher than 99.0%,and the average particle sizes of CeB6were smaller than 150 nm.     

Formation of the structure and phase composition of the Ti–Al–Ta-based materials

The experiments on the fabrication of materials based on the Ti–3Al–0.5Ta and 3Ti–2Al–Ta systems by self-propagating high-temperature synthesis (SHS) are performed. The influence of the composition of the initial mixture, dispersity of powders, and preliminary mechanical activation on the phase composition and structure of the SHS product is investigated. The optimal ratio between the mechanically activated and initial powder in a mixture for the synthesis of materials is determined. The dependence of the structure of final products on the structure of initial powders is established. The use of porous tantalum leads to the formation of the intermetallic matrix based on titanium aluminide with the uniform distribution of Ta particles. It is noteworthy that tantalum powders of both studied series (which differ by dispersity and morphology) partially reacted already at the stage of mechanical activation with the formation of the Al₂Ta phase. It is shown that aluminum plays the leading role in processes of mechanical activation in Ti–Al–Ta reaction mixtures. Indeed, a considerable rise of unreacted tantalum particles in the microstructure of sintered samples is observed with a decrease in the amount of aluminum in the reaction mixture.     

Effect of Yb2O3 Additive on Transformation Behavior of Anatase for TiO2/( O'' + β'' )-Sialon Multi phase Ceramics

TiO2/(O' β')-Sialon multiphase ceramics were prepared with nano Ti O2 (anatase) powder and (O' β')-Sialon powder as raw materials. Effect of Yb2O3 additive on transformation behavior of anatase for TiO2/(O' β')-Sialon multi phase ceramic was investigated and its influence mechanism was discussed. XRD was employed for the analysis of phase composition and lattice parameters. The results show that even though Yb2O3 has no obvious influence on starting temperature of phase transformation, it significantly accelerates the transformation process, which displays a weakened effect with more Yb2O3 addition. There exist two forms of the added Yb2O3: some enters TiO2 lattice and the other deposits on the surface of TiO2. The function of Yb2O3 on phase transformation of anatase can be attributed to the coaction of active and negative influence mechanisms as follows: some Ybn enter TiO2 lattice and replace Ti4 , as well as the redox reaction between Yb3 and TiO2, which promote the transformation, whereas other Yb2O3 deposits on the surface of TiO2, and TiO-Yb bond is formed by the coaction of Yb3 and TiO2, which inhibit the process.     

自蔓延法制备氮化铬铁的实验研究

以Cr_2O_3、Fe_2O_3和Al为实验原料,尿素作为渗氮剂,NaNO_3作为发热剂,采用自蔓延法制备氮化铬铁。通过热力学计算和实验研究,证明了自蔓延法制备氮化铬铁的可行性,并计算出了NaNO_3的加入量。采用XRD进行物相分析,用XRF检测主要金属元素的含量,其中Cr、Fe的质量分数分别为62.70%和33.25%;用定氮仪检测N元素的质量分数为3.42%,达到了氮化铬铁的生产标准。     

高岭石-C体系高温碳热反应过程

以高岭石和无机碳为原料合成SiCw/A12O3复相陶瓷粉末,借助X射线衍射(XRD)、扫描电镜(SEM)等手段对该陶瓷粉体进行测试表征,研究合成温度和保温时间对合成产物的影响,并初步探明高岭石碳热还原反应过程和机理。结果表明:高岭石与碳在高温下反应过程由2段组成,第1段是高岭石的低温分解,第2段是高岭石分解产物SiO2和莫来石的碳化还原。其中第2段反应又由SiO2的碳化还原和莫来石的碳化还原组成,二者是先后发生而不是并列发生。在高岭石碳热还原过程中,气-固(V-S)反应机制和固-固(S-S)反应机制均有可能发生,SiC晶须的形成由占主导地位的反应机制决定。