Glass fabrics self-cracking catalytic growth of boron nitride nanotubes

Glass fabrics were used to fabricate boron nitride nanotubes (BNNTs) with a broad diameter range through a combined chemical vapor deposition and self-propagation high-temperature synthesis (CVD-SHS) method at different holding times (0min, 30min, 90min, 180min and 360min). SEM characterization has been employed to investigate the macro and micro structure/morphology changes of the glass fabrics and BNNTs in detail. SEM image analysis has provided direct experimental evidences for the rationality of the optimized self-cracking catalyst VLS growth mechanism, including the transformation situations of the glass fabrics and the BNNTs growth processes respectively. This paper was the further research and compensation for the theory and experiment deficiencies in the new preparation method of BNNTs reported in our previous work. In addition, it is likely that the distinctive self-cracking catalyst VLS growth mechanism could provide a new idea to preparation of other inorganic functional nano-materials using similar one-dimensional raw materials as growth templates and catalysts.     

Ti-C-Ni-Mo系的自蔓燃-加压致密化

本工作基于对自蔓燃过程的分析,提出了自蔓燃-加压致密化过程中的可压制温度下限T_p和与之相应的可压制时间上限t_p的概念,并建立了温度-时间-状态图。t_p与燃烧持续时间t_c之差为该工艺的控制参量-压制延迟时间t的上限值。据此时Ti-C-Ni-Mo系进行了研究.确定了最佳工艺参数,获得了近于完全致密的TiC-Ni-Mo合金。     

自蔓延焊条的焊接工艺性研究

研究了焊药密实度、焊前预热、焊接速度、试板厚度和后热等对自蔓延焊条的焊接工艺性影响规律.结果发现,当药粉密度在2.60~2.80g/cm3时,自蔓延焊条燃烧速度为10.5mm/s,焊接可控性好.焊前350℃预热可以增加焊接熔深,实现单面焊双面成形效果.焊接速度取决于试板厚度,提高焊接速度明显降低较厚试板的焊透性和焊接效果.后热对自蔓延焊条工艺性能没有显著影响.     

挤压铸造制备三维连续网络结构增强金属基复合材料

基于真空反压浸渍多孔陶瓷获得一种新型三维连续网络结构增强的金属基复合材料的基础上,采用挤压铸造的方法对这种新型结构金属基复合材料的制备方法作进一步研究．以Ａｌ－ＴｉＯ２－Ｃ系为例,对利用自蔓延高温合成方法（ＳＨＳ）制备的Ａｌ２Ｏ３－ＴｉＣ多孔连通网络陶瓷骨架进行挤压铸造Ｌｙ１２Ａｌ合金液获得这种复合材料,并利用扫描电镜、光学显微镜和透射电镜对Ａｌ２Ｏ３－ＴｉＣ多孔陶瓷材料,以及得到的三维连续网络结构增强金属基复合材料的微观形貌特征进行了观察和分析     

TiC-xAl复合材料的SHS过程与制备

研究了Al含量对自蔓延高温合成(SHS)TiC-xAl金属陶瓷过程的绝热温度、燃烧温度和燃烧波速度的影响,并采用SHS QP技术制备了密实的TiC-xAl金属陶瓷复合材料,对密实材料进行．XRD和SEM分析和密度测试．结果表明,随Al含量的增加,体系的燃烧温度逐渐下降,而燃烧波速度先增加而后又减小,在Al含量为33mol％时出现一个极大值;对密实材料而言,在其它参数不变的情况下,控制加压延迟时间是制得高密度材料的关键．     

Ti-C-Al-Fe_2O_3反应体系的热力学及形成产物的分析

针对Ti-C-Al-Fe2O3体系进行了热力学计算,并结合DSC及XRD分析,为研究该体系反应合成TiC,Al2O3提供了理论依据.计算结果表明:该体系在发生SHS反应时,可以生成TiC,Al2O3,Fe2Ti,TiAl3,Fe3C和Al4C3等产物,但TiC,Al2O3的热力学稳定性要远远大于Fe2Ti,TiAl3,Fe3C和Al4C3等相,因此,在1600℃的钢液引燃的SHS反应过程中,只能生成TiC,Al2O3两种产物.通过XRD分析也证明了在反应产物中只有TiC,Al2O3两种物质形成.     

SHS-离心法制备W—C—Fe金属陶瓷内衬复合钢管

以Fe2O3、WO3、Al和C为反应原料,采用SHS-离心法制备W-C-Fe内衬复合钢管.利用X射线衍射分析内衬层的相组成,扫描电镜观察金属陶瓷涂层的组织,利用能谱仪分析涂层与基体结合处的元素分布,显微硬度仪测量内衬层硬度.结果表明:涂层与基体之间形成良好的冶金结合,涂层主要由Fe3W3C组成,还有少量的WC、W2C、Fe3C和Fe;涂层组织呈梯度分布,靠近基体处晶粒细小,远离基体处晶粒呈粗大树枝状;涂层显微硬度为13.5±1.6 GPa,是基体的7~8倍.     

包容核废物的钛酸锶人造岩石SHS-致密化的影响因素

采用自蔓延高温合成(SHS)与加压致密一体化技术制备了包容锶核素(Sr2+)的钛酸锶(SrTiO3)人造岩石固化体. 通过实验分析SHS产物致密化的影响因素,确定了钛酸锶反应体系自蔓延高温合成时的最佳工艺参数:预制块相对密度为54%左右;预压力为10MPa,加压时间为4s;致密化时高压压力为300MPa,高压保压时间为8s.     

甘氨盐燃烧法制备BaFe12O19纳米粉末及其磁性能

以硝酸铁[Fe(NO3)39H2O]、乙酸钡[Ba(CH3COO)2]和甘氨酸[C2H5NO2]为原料,采用甘氨酸溶胶凝胶-自蔓延燃烧法成功制备成BaFe12O19纳米粉末;用XRD、SEM和VSM等测试方法研究了不同条件下产物的微观形貌、晶体结构及磁学性能。研究表明,煅烧温度和甘氨酸与金属盐的摩尔比会影响单相六角BaFe12O19的形成;甘氨酸与金属盐摩尔比为3∶1的前驱体在800℃下,煅烧2 h后可得到六角片状、粒度40~50 nm的单相BaFe12O19粉末;当温度升高到900℃时,钡铁氧体颗粒长大到100 nm以上,矫顽力下降。     

Combustion characteristics of aluminium-iron oxidein SHS-gravitational process

In order to get high quality of products, the combustion of aluminium-iron oxide thermite in SHS-gravitational process must be under control. The effects of thermite filling density, hole in thermite and inclined angle of pipe on combustion rate were studied. It shows that the combustion rate decreases with the decrease of filling density. The thermite combusts downwards the pipe much more quickly if there are holes in the thermite. And the combustion rate increases with the increase of the inclined angle of pipe. The experiment results show that the combustion of thermite is predominantly controlled by gas phase reaction, which is attributed to the high temperature of the thermite combustion.