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1.
难熔金属氧化物直接制备难熔金属的研究现状   总被引:1,自引:0,他引:1  
综述了难熔金属的概况,包括资源现状、特性及应用。重点阐述了难熔金属氧化物直接制备难熔金属的新工艺研究,主要介绍了5种工艺方法:传统熔盐电解法、新熔盐电解法、金属热还原法、气体还原法和熔盐电沉积法。同时,对它们的研究现状,优、缺点以及相互之间的区别进行分析,并展望了难熔金属的发展趋势和应用前景。  相似文献   

2.
金属镁生产方法及其评价   总被引:2,自引:0,他引:2  
概述介绍了金属镁工业生产方法;熔盐电解法与金属热还原法的原料制备和生产原理;从环境保护和能量消耗对两种生产方法进行比较;通过对镁生产方法的发展趋势进行探讨认为,用CO气体作还原剂氯化煅烧菱镁矿炉料和研究开发一种新的单级电解槽电解氯化镁是电解法主要发展趋势;采用内热法与半连续硅热法技术,应用水煤浆高效能源作为燃料可提高金属镁的还原效率。  相似文献   

3.
随着锂电池市场需求的不断扩大,锂资源的提取与回收成为研究的热点。介绍了盐湖卤水提锂工艺中沉淀法和萃取法的研究进展。重点阐述了废旧锂离子电池正极材料回收锂资源的研究现状。介绍了金属锂的制备工艺,包括熔盐电解法和真空热还原法,其中真空热还原法包括硅热还原法、铝热还原法和铁热还原法。目前盐湖卤水萃取法提锂的工业化是需要解决的重点问题;废旧锂离子电池锂资源的绿色回收是当前研究的热点,在保证锂回收效率的同时尽量选用有机酸以减少污染,同时废旧锂离子电池的工业化回收前景广阔;真空热还原制备锂单质目前仍处于实验室研究阶段,连续化生产是研究的主要方向。  相似文献   

4.
太阳能级硅因其在光伏产业的巨大市场,而具有十分重要的研究价值.对几种太阳能级硅的制备方法,如改良的西门子法、熔盐电解法、冶金法、合金精炼法,进行了介绍.概述了各方法的制备原理和研究现状,并说明了各方法的优点和不足.  相似文献   

5.
为回收利用硅灰,将硅灰通过碳热还原法制备了SiC粉体。研究不添加切割废料时温度(1 550、1 650、1 750、1 850℃)对冶炼效果的影响。在较优冶炼温度基础上,研究了切割废料添加质量(分别为硅灰添加质量的5%、15%、25%、35%、50%)对制备碳化硅粉体的影响。结果表明:最佳冶炼温度为1 750℃,此时产物中SiC含量为92.47%(w);切割废料最优加入量为硅灰添加质量的25%,得到的产物中SiC含量为95.36%(w)。切割废料加入量为硅灰添加质量的25%时,显著提高了产物中SiC的纯度,对实现两种固废共同回收利用,环境保护以及解决资源浪费问题具有重要的意义。  相似文献   

6.
为了在较低温度和较短时间内合成h-BN粉体,以硼砂和镁粉为原料,以n(NaCl)n(MgCl_2)分别为1:3、1:1和3:1的3种NaCl-MgCl_2和n(KCl)n(MgCl_2)为1:1的KCl-MgCl_2为熔盐介质,在氮气气氛中分别于800、1 000和1 200℃保温3 h,采用镁热还原法合成h-BN,经5%(w)的盐酸溶液浸泡、抽滤、洗涤、干燥、研磨后得到产物粉体,并进行XRD和SEM分析,研究了不同种类和配比的熔盐介质及合成温度对合成产物的物相组成和显微结构的影响。结果表明:1)在本试验的不同熔盐介质和不同温度下合成的产物粉体均由纯相h-BN组成,但h-BN的结晶度随合成温度的升高而逐渐提高:在NaCl-MgCl_2熔盐介质中于1 000℃制备的产物中有片状h-BN,在1 200℃出现层叠层片状h-BN,而在KCl-MgCl_2熔盐介质中于1 200℃才有片状h-BN。2)在NaCl-MgCl_2熔盐中通过镁热还原法合成h-BN粉体,不仅克服了其他方法合成温度高的缺陷,同时还有效地控制了h-BN晶粒的尺寸和形貌。  相似文献   

7.
以硅灰、白炭黑、硅溶胶为硅源,炭黑为碳源,采用碳热还原法合成碳化硅晶须,通过XRD及SEM对合成产物的物相及形貌进行分析,探讨了合成温度(分别为1 400、1 450、1 500、1 550℃)、硅源、n(C)∶n(SiO2)对合成碳化硅晶须的影响.结果表明:n(C)∶n(SiO2)为2.4~3.6,合成温度为1 500 ℃,保温3 h时,硅溶胶与炭黑反应没有生成碳化硅晶须,硅灰、白炭黑与炭黑反应均生成碳化硅晶须;以硅灰为硅源合成碳化硅晶须的质量及数量明显优于以白发黑为硅源合成碳化硅晶须;合成碳化硅晶须的最佳n(C)∶n(SiO2)为3.3.  相似文献   

8.
采用由氯化钠、氯化钾、氟化钠和二氧化硅(摩尔比为1∶1∶3∶0.3)组成的熔盐,分别以直流、单脉冲、换向脉冲的电沉积方式在纯铌表面渗硅。对比研究了不同电沉积方式下所得渗硅层的厚度、成分、组织、相结构和抗氧化性。结果表明,渗硅层厚度按照单脉冲、换向脉冲、直流电沉积的方式依次降低。与直流和单脉冲电沉积相比,换向脉冲方式所得渗硅层的组织更加致密、平整。电沉积方式对渗硅层的相结构无影响,所得渗硅层均由单相Nb Si2组成,并在(110)和(200)晶面上择优生长。换向脉冲方式制备的渗硅层抗高温氧化性能最好。  相似文献   

9.
美国斯坦福大学(加利福尼亚州)的科学家,最近申请了一项以硅藻土为原料电解制硅的专利。迄今,还原法制硅一直是用砂作原料。  相似文献   

10.
戈明亮  陈萌 《化工进展》2014,(12):3309-3312
水羟硅钠石(kenyaite)以其良好的离子交换性、吸附性和热稳定性而被广泛应用于催化和吸附等领域。本文以高纯度且价格低廉的沉淀白炭黑为硅源、以碳酸钠(分析纯)和氢氧化钠(分析纯)为碱源,水热法制备了高纯度的单一晶相的水羟硅钠石,考察了反应时间和反应温度对制备的影响。利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、红外光谱仪(IR)、X射线荧光光谱仪(XRF)和同步热分析仪等对样品进行了测试表征。实验结果表明,温度是影响kenyaite制备的主要因素,单一晶相水羟硅钠石的最佳晶化合成条件为晶化温度为180℃,晶化时间为24h,所制备的水羟硅钠石形态为玫瑰花形且其热稳定性在350℃以下。  相似文献   

11.
SiC-monofilament-reinforced SiC or Si3N4 matrix composites were fabricated by hot-pressing, and their mechanical properties and effects of filaments and filament coating layers were studied. Relationships between frictional stress of filament/matrix interface and fracture toughness of SiC monofilament/Si3N4 matrix composites were also investigated. As a result, it was confirmed experimentally that in the case of composites fractured with filament pullout, the fracture toughness increased as the frictional stress increased. On the other hand, when frictional stress was too large (>about 80 MPa) for the filament to be pulled out, fracture toughnesses of the composites were almost the same and not so much improved over that of Si3N4 monolithic ceramics. The filament coating layers were found to have a significant effect on the frictional stress of the SiC monofilament/Si3N4 matrix interface and consequently the fracture toughness of the composites. Also the crack propagation behavior in the SiC monofilament/Si3N4 matrix composites was observed during flexural loading and cyclic loading tests by an in situ observation apparatus consisting of an SEM and a bending machine. The filament effect which obstructed crack propagation was clearly observed. Fatigue crack growth was not detected after 300 cyclic load applications.  相似文献   

12.
Composites of SiC/Si and SiC/SiC were prepared from single yarns of SiC. The use of carbon coatings on SiC yarn prevented the degradation normally observed when chemically vapor deposited Si is applied to SiC yarn. The strength, however, was not retained when the composite was heated at elevated temperatures in air. In contrast, the strength of a SiC/C/SiC composite was not reduced after this composite was heated at elevated temperatures, even when the fiber ends were exposed.  相似文献   

13.
α-silicon carbide platelet/β-silicon carbide composites have been produced in which the individual platelets were coated with an aluminum oxide layer. Hot-pressed composites showed a fracture toughness as high as 7.2 MPa·m1/2. The experiments indicated that the significant increase in fracture toughness is mainly the result of crack deflection and accompanying platelet pullout. The coating on the platelets also served to prevent the platelets from acting as nucleation sites for the α- to β-phase transformation, so that the advantageous microstructure remains preserved during high-temperature processing.  相似文献   

14.
采用硅钼蓝分光光度法测定氮化钒铁中的硅含量,研究了氮化钒铁溶样方法,通过溶样效果,选择确定溶样酸。结果表明,该方法准确度高、重复性好,操作简便,可广泛运用于氮化钒铁中硅的检测。  相似文献   

15.
Dense Si/SiC composites were fabricated via a conventional reaction-bonding process, using oak charcoal that exhibited a honeycomb structure. The silicon melt was infiltrated into the porous oak charcoal (density of ~0.6 g/cm3) while the sample was heated to 1700°C under vacuum (10-3 torr (~0.133 Pa)), which resulted in in situ silicon-fiber/SiC composites. The reaction product had an average density of 2.8 g/cm3 and showed three-point flexural strengths of 330 MPa at room temperature and 280 MPa at 1300°C. Good oxidation resistance also was observed at temperatures up to 1300°C in flowing air. This process provided excellent shape-making capability, because the charcoal that was used as a preform was readily machinable.  相似文献   

16.
Nonaqueous Processing of Silicon for Reaction-Bonded Silicon Nitride   总被引:1,自引:0,他引:1  
Ethanolic silicon suspensions, with and without a polyethoxylated amine of low molecular weight, were studied by rheological, adsorption, electrophoretic, and sedimentation methods. Pellets were pressure-cast and nitrided to form reaction-bonded silicon nitride. Density and binding strength in the green state relate well to rheological behavior and other collodial aspects of the suspensions used, particularly the additive's role and distribution. Density and degree of nitridation in the final state are not importantly affected by the additive's use. Its greatest benefit is to modify the binding strength in the green state. The mode by which this small molecule affects the processing of silicon consists of adsorption, combined with an increased electrostatic interparticle repulsion which increases the suspension viscosity and that of undried pellets. Although the improved binding strength is accompanied by decreased green and nitrided densities, high degrees of conversion to silicon nitride are still achieved.  相似文献   

17.
Oxidation of {111} single-crystal silicon and dense, chemically-vapor-deposited silicon nitride was done in clean silica tubes at temperatures of 1000° to woo°C. The oxidation rates of silicon nitride under various atmospheres (dry O2, wet O2, wet inert gas, and steam) were several orders of magnitude slower than those of silicon under the identical conditions. The activation energy for the oxidation of silicon nitride decreased from 330 to 259 kJ/mol in going from dry O2 to steam while that for Si decreased from 120 to 94 kJ/mol. The parabolic rate constant for Si increased linearly as the water vapor pressure increased. However, the parabolic rate constant for silicon nitride showed nonlinear dependency on the water vapor pressure in the presence of oxygen. The oxidation kinetics of silicon nitride is explained by the formation of nitrogen compounds (NO and NH3) at the reaction interface and the counterpermeation of these reaction products.  相似文献   

18.
ICP—AES法测定高硅钢中的硅   总被引:1,自引:0,他引:1  
孙晓天  王玲  张振禹  于欣 《当代化工》2007,36(6):663-664,668
研究了用ICP-AES法快速测定高硅钢中的硅,确定了最佳测定条件.在此条件下测定,获得满意结果.实验结果表明,该方法简便、快速、灵敏,检出限为0.000 9 μg/mL;RSD<0.5 %;回收率为99 %~101 %,结果令人满意.  相似文献   

19.
SiC was synthesized via the gas-phase reaction between SiO and CH4 at 1500° and 1560°C in a tubular flow reactor. SiO vapor was generated from equimolar powder mixtures of Si and SiO2 in the reactor while CH4 was externally supplied. Products of different morphologies were collected at different longitudinal locations: whiskers, crystal aggregates, scale, and powder. The total yield of SiC, based on the amount of SiO generated, reached as high as 99%, of which 25–46% by mass was fine powder with sizes ranging from 60 to 300 nm.  相似文献   

20.
四氯化硅为原料制备二氧化硅粉体的研究   总被引:1,自引:0,他引:1  
以多晶硅生产中的副产物四氯化硅为原料,在碱性溶液中制备了二氧化硅.研究了碱性溶液种类、浓度以及后处理、表面活性剂对于二氧化硅性能的影响.结果表明,采用氢氧化钠质量分数为5%的氢氧化钠水溶液时,二氧化硅邻苯二甲酸二丁酯(DBP)的吸附值为2.92 mL/g,一次粒子直径在20 nm左右,BET比表面积为260.382 m2/g;不论采用何种碱液,随着碱液浓度的增大,二氧化硅的DBP吸附值都减小,相应的粒子直径也都增大;正丁醇恒沸蒸馏处理可较大幅度提高二氧化硅的DBP吸附值;制备过程中表面活性剂的加入只能一定程度上提高产品二氧化硅的DBP吸附值.  相似文献   

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