共查询到18条相似文献,搜索用时 171 毫秒
1.
对传统的以高价钛卤盐(TiI4)热裂解制备高纯钛的实验方法进行了改进,使用了低价钛卤盐(TiI2)的热裂解法制备4N高纯钛,使得卤化源区温度、热裂解区(又称沉积区)温度更为优越。并对卤化源区及沉积区温度、高价卤化物的生成、原料中杂质行为以及沉积区低价碘化物的蒸汽压等影响钛沉积速率的因素进行了分析。结果表明:炉内两区温度更易于控制,且可使钛卤盐保持较高的蒸汽压与转移速度,可以有效抑制部分杂质卤化物的转移分解,从而得到制备高纯钛较为理想的沉积速率。 相似文献
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结合实验情况对通过基底材料的电流密度、原料中杂质行为、高价卤化物的生成以及卤化物的蒸汽压等影响钛沉积速率的主要因素进行了系统分析。以自制的卤化剂和粗钛为原料,采用特殊的工艺设备,首先使粗钛与卤化剂反应制得钛卤盐,然后控制反应条件,使该钛卤盐在适宜条件下发生热裂解制备高纯钛。结果发现:控制适宜的电流密度和操作温度,可使钛卤盐保持较高的蒸汽压与转移速度,并且可以抑制杂质碘化物的转移分解,从而使得纯钛有较为满意的沉积速率和纯度。 相似文献
3.
以粗钛和自制的卤化剂为原料,采用化学气相沉积法(CVD)制得高纯钛。结合热力学和晶体形核-长大理论对CVD高纯钛的反应热力学和成核热力学因素进行了分析,并依据热力学分析结果,重点归纳了温度对CVD高纯钛沉积速率的影响,并结合实验对分析结果作出优化,得出了CVD法生产高纯钛的最佳温度控制条件:碘化源区温度应控制在750~850 K,沉积区温度应控制在1350~1450 K。 相似文献
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《稀有金属》2016,(9)
在碘化法提纯金属锆过程中,影响沉积速率的因素较多,其中温度是影响反应十分重要的一个因素,温度决定着反应是否能够发生以及反应快慢。本文研究分析了高温区与低温区发生的主要反应,研究了低温区温度、高温区温度和加碘量等3个主要因素对碘化法提纯金属锆沉积速率的影响。实验结果表明:低温区保持在250℃时,生产效率高、沉积速率稳定、持续时间长;高温区温度显著影响着沉积速率,在反应中K值保持在90时沉积速率较快,而且相对节约能源;随着加碘量的增多,反应的时间变长,其沉积速率变化不大,加碘量的增多有利于提高生产效率,并且采用多次加碘可以使碘的利用率升高。通过实验可得出每一种影响因素对沉积速率的影响特点,从而可以根据影响反应的因素去指导实际生产。 相似文献
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在氢气保护下,通过机械合金化制备2LiNH_2/MgH_2+5%M(M=0,AlCl_3,MgCl_2,TiCl_3)复合材料,研究添加金属卤化物对2LiNH_2/MgH_2复合材料相结构及储氢性能的影响。结果表明,复合材料的相结构主要由MgH_2和LiNH_2组成,且添加MgCl_2和TiCl_3后复合材料的粒度相对较小;2LiNH_2/MgH_2复合材料在添加金属卤化物后表观活化能增大,但在相同的温度下吸氢速率明显增大,并在升温速率为8K/min时添加这些金属卤化物后都能使复合材料的氢化反应温度降低。 相似文献
11.
对化学蒸汽沉积法(CVD法)制备高纯钛及制备过程中锆的行为进行热力学分析。结果表明,在钛卤化温度条件下,杂质元素Zr能够在卤化区生成ZrI2、ZrI3和ZrI4,且更倾向于生成ZrI3和ZrI4。ZrI2、ZrI3和ZrI4不能在沉积区温度下分解,高纯钛中的锆不是通过卤化裂解而是由其它途径携入的。 相似文献
12.
A study is made of the electrolytic deposition of titanium boride powders from halide melts. The conditions required for the deposition of different phases are determined. On the whole, the synthesis process is controlled by interrelated factors: electrolyte composition, current density, and the temperature and duration of the electrolysis operation. 相似文献
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R. L. Axelbaum S. M. L. Sastry D. P. Dufaux C. A. Frey 《Metallurgical and Materials Transactions B》1997,28(6):1199-1211
A gas-phase flame process for synthesizing unagglomerated nanoparticles of metals, intermetallics, ceramics, and composites
is described. Employing this process, titanium and titanium boride have been synthesized by the vapor-phase reaction of sodium
with titanium tetrachloride and a 1:2 mixture of titanium tetrachloride and boron trichloride, respectively. To minimize agglomeration
and protect the particles from postflame oxidation, the NaCl by-product is allowed to condense onto the particles in situ, yielding NaCl-encapsulated particles. In this way, stable, unagglomerated Ti and TiB2 nanoparticles have been produced and the encapsulated powders have been handled in air without oxidation. Particle size has
also been varied with the encapsulation process, and titanium particles with mean sizes of 10 and 60 nm have been produced
by varying operating conditions. The NaCl has been removed by water washing as well as vacuum annealing. Thermodynamic results
show that the sodium/halide process is applicable for synthesis of many materials, with yields approaching 100 pct under a
wide range of operating conditions. Similarly, the encapsulation process is generally applicable, making the sodium/halide
flame and encapsulation process a viable one for large-scale synthesis of environmentally insensitive nanopowders. 相似文献
14.
Reduction of titania using methane-containing gas was investigated in a laboratory fixed-bed reactor in the temperature range
1373 to 1773 K. The reduction product is titanium oxycarbide, which is a solid solution of TiC and TiO. At 1373 K, the formation
rate of TiC is very slow. The rate and extent of reaction increase with increasing temperature to 1723 K. A further increase
in temperature to 1773 K does not affect the reaction rate and extent. An increase in methane concentration to 8 vol pct favors
the reduction process. A further increase in methane concentration above 8 vol pct causes excessive carbon deposition, which
has a negative effect on the reaction rate. Hydrogen partial pressure should be maintained above 35 vol pct to depress the
cracking of methane. Addition of water vapor to the reducing gas strongly retards the reduction reaction, even at low concentrations
of 1 to 2 vol pct. Carbon monoxide also depresses the reduction process, but its effect is significant only at higher concentrations,
above 10 vol pct. 相似文献
15.
采用水热法,以氢氧化钠为分离剂,从含钛电炉熔分渣中成功制备出纳米片状结构二氧化钛光催化剂,并探讨了水热反应时间、水热温度以及碱液浓度对分离提取纳米片状结构二氧化钛的影响.随着水热反应时间的延长,水热温度以及氢氧化钠溶液浓度的提高,从含钛电炉熔分渣中分离提取的二氧化钛结晶度越好,微观形貌更趋近于纳米片状结构.水热法处理含钛电炉熔分渣的最佳反应条件是:水热温度高于180℃,水热反应时间大于24 h,碱液浓度达到12 mol·L-1.以制备得到的纳米片状结构二氧化钛为光催化剂,在氙灯光照90 min后,甲基蓝降解率可达81.1%. 相似文献
16.
Analysis of multicomponent evaporation in electron beam melting and refining of titanium alloys 总被引:3,自引:0,他引:3
A. Powell U. Pal J. van den Avyle B. Damkroger J. Szekely 《Metallurgical and Materials Transactions B》1997,28(6):1227-1239
Experimental evidence and a mathematical model are presented to evaluate the effect of beam-scan frequency on composition
change in electron-beam melting of titanium alloys. Experiments characterized the evaporation rate of commercially pure (CP)
titanium and vapor composition over titanium alloy with up to 6 wt pct aluminum and 4.5 wt pct vanadium, as a function of
beam power, scan frequency, and background pressure. These data and thermal mapping of the hearth melt surface are used to
estimate activity coefficients of aluminum and vanadium in the hearth. The model describes transient heat transfer in the
surface of the melt and provides a means of estimating enhancement of pure titanium evaporation and change in final aluminum
composition due to local heating at moderate beam-scan frequencies. 相似文献
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甲烷部分氧化制备合成气对于提高天然气的利用价值具有重要的意义。甲烷部分氧化反应是一个非常复杂的反应体系。反应涉及部分氧化(主反应)、燃烧、重整、水煤气变换、积炭等。使用Aspen Plus和HSC Chemistry软件对甲烷部分氧化制备合成气过程进行热力学模拟计算。考察了温度、压力和CH4/O2比对CH4转化率、氢和CO选择性的影响。同时对甲烷部分氧化反应热力学平衡产物组成和积炭副反应进行了热力学计算分析。研究结果表明,随反应温度的升高,压力的减小,CH4的转化率和CO与H2的选择性均呈上升趋势。反应温度在300℃时就有相当多的积炭生成,在550℃积炭量达到最大,随后又随温度上升,积炭量逐渐减少,在900℃以上无积炭产生。 相似文献