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1.
自蔓延冶金法制备硼粉 总被引:2,自引:0,他引:2
提出了自蔓延冶金法制备硼粉的新工艺,由计算可知,B2O3-Mg反应体系的绝热温度为2 604 K,大于自蔓延判据温度1 800 K,故采用自蔓延反应是可行的.分析了添加剂MgO和预热温度对反应体系绝热温度的影响,并对B2O3-Mg体系的相关反应热力学数据进行了分析.由DTA分析可知,B2O3-Mg反应体系在1 123~1 203 K时的放热峰表观活化能为903.75 kJ/mol,反应级数为1.由XRD分析确定了燃烧产物以及各个阶段的浸出产物相组成,证实了三步浸出方案的可行性.考察了自蔓延反应初始条件对硼粉纯度的影响,硼粉纯度可达92.43%,平均粒度为0.5~0.8μm. 相似文献
2.
《中国有色金属学会会刊》2022,32(10):3469-3477
An effective method was reported to prepare low-oxygen Ti powder, which included two experimental steps: the fast conversion of TiO2 to TiOx<1 powder by self-propagating high-temperature synthesis (SHS) process and the generation of low-oxygen Ti powder by electrodeoxidizing TiOx<1 powder at the cathode in molten CaCl2. The key intermediate steps were analyzed by XRD, SEM and electrochemical testing techniques. The results demonstrated that TiOx<1 powder (TiO0.325 and TiO0.97) was generated after acid leaching MgO in SHS products with TiO2/Mg molar ratio of 1:2, and the TiOx<1 powder with 16.3 wt.% oxygen could be transformed into pure titanium powder with 0.121 wt.% oxygen by electrodeoxidation at a constant potential of -3.3 V for 10 h. The electrodeoxidation of TiOx<1 powder in CaCl2 molten salt follows the step-by-step deoxidation mode, and the lattice of TiOx<1 powder after electrodeoxidation shrinks. 相似文献
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Plasma sprayed Ni-Cr-40vol%TiC coatings produced from powders obtained by self-propagating hightemperature synthesis (SHS)
and plasma densification (PD) processes are characterized. Chemical composition, microstructure, and mechanical properties,
such as microhardness and wear resistance, are evaluated and compared. SHS coatings exhibit good sliding wear performance.
The exact stoichiometry of titanium carbide inclusions in the metallic matrix affects the dimension of the crystal lattice
parameter and was investigated by examining the shift of x-ray diffraction (XRD) peaks of the TiC. A value of the combined
carbon/titanium ratio of about 0.6 was calculated for both powders, thus excluding the influence of the stoichiometry of the
carbide inclusions on the wear properties of the coatings. 相似文献
5.
采用自蔓延高温合成技术实现了TiAl合金的连接。在连接过程中采用了具有很高放热量的Ti-Al-C中间层以及外加电磁场辅助连接。连接接头包括3个典型的反应区域,靠近TiAl母材界面处发现了深灰色的TiAl,反应层,在中间层内观察到了TiC颗粒以及Ti-Al系化合物。直接连接时由于产物和反应物之间的比热差,杂质的气化和孔隙中束缚气体的释放而导致孔隙无法避免。为了提高致密度,在粉末压坯和TiAl母材之间添加了Ag-Cu钎料箔。在SHS反应过程中熔化的钎料改善了中间层对TiAl母材的润湿同时填充到了中间层反应产物的孔隙中,采用这种方法能够提高反应产物的致密度和连接质量。 相似文献
6.
Effect of inner oxidant on self-propagating high-temperature synthesis of MnZn-ferrite powder 总被引:1,自引:0,他引:1
Using KClO3 as an inner oxidant, MnZn-ferrite powder was synthesized by a self-propagating high-temperature synthesis (SHS) process in normal air atmosphere. The effects of the inner oxidant on combustion temperature, combustion velocity, microstructure and the phase of the product were investigated by XRD and SEM,respectively. The results show that a highly ferritized powder can be obtained as well as the highest combustion temperature and the highest combustion velocity when the inner oxidant content m equals 5/4( k -1/6). 相似文献
7.
自蔓延烧结在金刚石制品中的应用 总被引:1,自引:1,他引:0
本文主要介绍了自蔓延高温合成技术的发展和特点,阐述了自蔓延高温合成技术在金刚石制品工业中应用的必要性和意义,分析了自蔓延高温合成技术在金刚石制品工业中应用的可行性,并介绍了国内外的应用研究现状,提出了自蔓延高温合成技术在超硬材料制品中的应用需要进一步研究解决的问题。 相似文献
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The success in synthesizing high purity SnO2 nanobelts via self-propagating high temperature synthesis was achieved.According to the experimental results,a rela... 相似文献
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The success in synthesizing high purity SnO 2 nanobelts via self-propagating high temperature synthesis was achieved. According to the experimental results, a relationship between the residual heat of the reaction system at 2848 K and SnO 2 nanobelts yield was identified. The most appropriate formula for this self-propagating high temperature synthesis method is turned out to be composed of Sn powder and thermite with weight ratio of 1:1. 相似文献
10.
以Ti、Al、C粉、立方氮化硼磨料为原料,采用自蔓延高温合成法制备Ti3AlC2陶瓷结合剂立方氮化硼复合材料。研究Al的摩尔量、CBN浓度对复合材料制备的影响。通过XRD、SEM、EDS表征方法,对制备的复合材料进行物相及组织结构分析。研究结果表明:添加CBN浓度25%的3Ti/1.2Al/2C的试样,自蔓延反应生成的Ti3AlC2较多,且晶体发育良好。CBN参与Ti-Al-C体系的反应,在CBN表面与基体之间形成了硼化物、氮化物的过渡层,实现了磨料与结合剂的化学键合,提高了基体对磨料的把持力。 相似文献
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FENG Peizhong QU Xuanhui Akhtar Farid S.H. Islam 《稀有金属(英文版)》2006,25(3):225-230
MoSi2 is presently regarded as the most important material for electrical heating and as one with huge potential for high temperature structural uses. MoSi2 and MoSi2 matrix composites were prepared by self-propagating high temperature synthesis (SHS). Pure MoSi2 was obtained and a compound of MoSi2 and WSi2was synthesized in the form of predominant solid solution (Mo,W)Si2. By adding aluminum of 5.5 at.% to Mo-Si, the crystal structure of MoSi2 changed into a mixture of tetragonal Cllb MoSi2and hexagonal C40 Mo(Si,Al)2. The (Mo,W)Si2-Mo(Si,Al)2-W(Si,Al)2 composite materials were synthesized by adding aluminum of 5.5 at.% to Mo-W-Si. However, if the amount of the added aluminum was not larger than 2.5 at.%, it did not have any significant effect. SHS is an effective technology for synthesis of MoSi2 and MoSi2 matrix composites. 相似文献
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B.Y. Tay C.W. Goh Y.W. Gu C.S. Lim M.S. Yong M.K. Ho M.H. Myint 《Journal of Materials Processing Technology》2008,202(1-3):359-364
Porous NiTi shape memory alloy has been an active area of research for medical application due to their similar microstructure to human bone. In this study, porous product was obtained by self-propagating high-temperature synthesis (SHS) of compacts prepared from elemental nickel and titanium powders and the effects of the green porosity and preheating temperature were examined. The porosity in the synthesised products was in the range of 45–59 vol.%, with the green porosity being the primary source of final porosity. NiTi was present as the dominant phase in the porous product with other secondary intermetallic compounds and element powders. The effect of green porosity and preheating temperature was found to have an effect on the pore morphology and microstructure. 相似文献
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工业纯钛高温拉伸断裂极限 总被引:1,自引:0,他引:1
拉伸断裂极限值是预测零件高温裂纹的主要依据。为了研究工业纯钛在高温拉伸下的断裂极限,采用理论模型和试验相结合的方法,通过GFL(Gleeble fracture limit)试验测得工业纯钛在不同温度下的真应力-应变曲线,并利用真应力-应变曲线求得工业纯钛的断裂极限值,分析了温度和应变速率对断裂极限值的影响。结果表明,温度和应变速率对断裂极限值有较大影响。温度升高使断裂极限增加,在应变速率为0.1 s-1下随着温度从800℃升高到1000℃,断裂极限值从1.798增加到2.343;在900℃相同温度下,随着应变速率从0.01 s-1的提高到1 s-1,断裂极限值从2.496降低到1.745。 相似文献
15.
研究了温度对3555和471硬质合金抗弯强度的影响.结果表明,3555和471硬质合金的抗弯强度在室温至300℃的范围内基本保持不变,在300~400℃开始下降,在400~500℃范围内剧烈下降,在500~600℃范围内下降变缓,在600~700℃时,抗弯强度值出现一个平台,比室温时强度降低30%左右.这是由于高温下合金的软化,hcp γ→fcc γ相变,W、C在粘结相中的固溶以及热应力共同作用的结果.3540和3475合金高温下断面的粗糙度降低,孔洞增多,沿晶断裂比例增加.高温下合金表面发生氧化,形成疏松的垂直于表面生长的柱状晶氧化层,3555抗氧化能力比471合金高. 相似文献
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陶瓷以优良的性能正成为极具潜力的新型结构材料,在其应用过程中往往需与金属连接,但因两者间的组织结构及物化性质相差悬殊,往往得不到满意的连接结果.在陶瓷与金属间用一定厚度的成分和结构呈梯度变化的梯度过渡层作为连接二者的焊缝层,是解决陶瓷与金属连接时所存在问题的较好措施之一.本文将自蔓延高温合成技术引入焊接领域,探索了陶瓷-金属焊接时接头中梯度过渡层的制备工艺.试验结果表明,采用自蔓延高温合成技术可成功地制取陶瓷-金属的梯度过渡层,这种过渡层可以有效地缓和因线膨胀系数差在陶瓷-金属焊接时界面处所产生的热应力,为获得综合性能良好的异种材料焊接接头开辟了一条新途径. 相似文献
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高温高压下金刚石/碳化硅体系烧结反应机理研究 总被引:1,自引:1,他引:0
本文研究了微米级金刚石与硅粉在高温(800~1 200℃)高压(5.1 GPa)下的反应机理。通过对金刚石与硅粉反应过程的研究,发现微米级金刚石与硅粉在硅熔点以下发生了反应;并指出高温高压下微米金刚石与硅粉的反应分为两个阶段:硅未熔化前的金刚石与硅的反应,硅熔化后的金刚石与硅、石墨与硅的反应。最后提出了一种新的合成金刚石/碳化硅复合材料的工艺,即采用高压熔渗法合成金刚石/碳化硅复合材料时,在温度略高于硅熔点之后保温一段时间,再升温到合成材料的设定温度,可以合成出结构更加均匀的、高质量的金刚石/碳化硅复合材料。 相似文献
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自蔓延还原合成BN反应机理 总被引:3,自引:1,他引:3
结合差热分析,通过研究B2O3和Al在不同温度下的反应以及在不同氮气压力中的自蔓延实验,搪塞了B2O3-Al-N2体系自蔓延还原合成BN的反应机理。结果表明:铝热还原B2O3的反应是一个分步过程,低于820℃时,B2O3与Al2缓慢反应生成Al4B2O3;高于820℃时,B2O3与Al剧烈反应生成Al4B2O9;高于1050℃时,Al与在低温生成的Al4B2O9反应生成Al18B4O33;在更高的 相似文献
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Influence of Fe addition on products of self-propagating high-temperature synthesis (SHS) reaction in 3Ti-Si-2C system was investigated in the present study. Without Fe addition, Ti5Si3 and TiC are the dominant phases along with a small amount of Ti3SiC2 phase and unreacted C left in the final products. As Fe content ranges from 10% to 30%, the products consist of TiC, Ti5Si3, Fe2Ti and unreacted C, but no trace of Ti3SiC2 phase is detected. Furthermore, the amounts of both Fe2Ti and C phases increase with ... 相似文献
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1 INTRODUCTIONSelf propagatinghigh temperaturesynthesis(SHS)orcombustionsynthesis ,wasdevelopedbyMezhanovetalinthe 196 0’s .Comparedtotradition almethods,itsadvantagesincludehigh purityofproducts ,lowenergyrequirement ,rapidreactionandsimplicityofprocess[1] .Beca… 相似文献