共查询到19条相似文献,搜索用时 156 毫秒
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磷肥副产物氟硅酸钠热解可制备四氟化硅气体,该方法无废弃物产生,生产成本较低,具有广阔的发展前景。对影响氟硅酸钠热解的各种因素进行了一系列静态实验研究,实验发现,氟硅酸钠热解的最佳反应温度应保持在中温区(500~700 ℃),反应压力维持在常压或微负压状态。利用该法生产四氟化硅气体具有气体纯度高和无副产物产生的特点。 相似文献
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面对中国战略资源萤石日益匮乏的现状,开发了以磷肥副产氟硅酸为原料合成氟硅酸钠,经动态分解得到四氟化硅,四氟化硅纯化后和无水氯化铝发生气相沉积反应、提纯制备高纯氟化铝工艺路线,并对反应原理、工艺流程、关键点控制及产品质量和原料成本等进行研究。结果表明:氟硅酸钠软膏采用两级干燥方式进行干燥,干燥后水分≤0.05%(质量分数);氟硅酸钠热解采用动态分解方式,分解率>99%。粗四氟化硅气体采用浓硫酸洗涤、分子筛吸附、精馏提纯后纯度>99.5%;无水氯化铝以气体状态和提纯的四氟化硅反应,反应后产品纯度>99.5%,符合高端领域市场需求。该研究可为磷肥副产低品位氟资源的高效高值利用提供参考和借鉴。 相似文献
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介绍了用氢氟酸重量法直接测定工业硅中硅含量的方法。试样用硝酸和氢氟酸分解,使硅生成四氟化硅除去。然后进入高温炉中灼烧。根据氢氟酸处理前后的质量差,扣除铁氧化成三氧化二铁的增量,计算硅的质量百分数。本方法的相对标准偏差小于0.20%。 相似文献
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High temperature annealing reduces the residual microstress in the silicon phase and silicon carbide phase in monolithic reaction bonded silicon carbide and in the matrix of melt-infitrated composites of silicon carbide reinforced with silicon carbide fibers. Stress relaxation is related to creep of the silicon carbide with power-law creep exponents similar to tensile creep in reaction bonded silicon carbide. 相似文献
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Silicon carbide nanotubes were found to grow in straight as well as curved configurations by treating silicon carbide grains in an arc plasma reactor/furnace followed by 3 h of cooling (in air). By increasing the plasma treatment time from 16 min to 20 min, multi-wall tubes were found to change to single wall tubes with reduction in diameter from few nm to sub-nm. Typical in situ grown nanotubes were characterized by XRD, TEM, SAED, HRTEM, EDS and micro Raman spectroscopy, and it is established from these evaluations that the nanotubes are made up of silicon carbide and not carbon. A possible mechanism, involving reaction between the plasma dissociated carbon (solid) forming carbon nanotube and the left-out silicon (existing in vapour state) during the cooling period (3000–2680 °C), is suggested to be responsible for silicon carbide nanotube formation in the plasma assisted process. 相似文献
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A novel three-step process is used to fabricate submicron silicon carbide powders in this paper. The commercially available silicon powders and phenolic resin are used as raw materials. In the first step, precursor powders are produced by coating each silicon powder with phenolic resin shell. Then, precursor powders are converted into carbonized powders by decomposing the phenolic resin shell. The submicron silicon carbide powders are formed in the reaction of silicon with carbon during the third step of thermal treatment. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and thermogravimetric (TG) analyses are employed to characterize the microstructure, phase composition and free carbon content. It is found that the sintered powders consist of β-SiC with less than 0.2 wt.% of free carbon. The particle size of the obtained silicon carbide powders varies from 0.1 to 0.4 μm and the mean particle size is 0.2 μm. The silicon carbide formation mechanism of this method is based on the liquid-solid reaction between liquid silicon and carbon derived from phenolic resin. The heat generated during the reaction leads to great thermal stress in silicon carbide shell, which plays an important role in its fragmenting into submicron powders. 相似文献
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为加快磷肥副产氟资源的综合利用,同时解决电石灰堆放占用大量土地、污染水资源等问题,采用磷肥副产氟硅酸与电石灰反应制备四氟化硅同时副产氟化钙,制备出高附加值、高品质的氟化物。重点研究了氯化钙与氟硅酸的配料比、反应温度、氯化钙溶液浓度、母液循环等因素对氟硅酸钙收率的影响,同时也分析了氟硅酸钙热解温度对四氟化硅产品质量的影响。研究结果表明,在氯化钙溶液浓缩至质量分数为60%、反应温度为55 ℃、氯化钙与氟硅酸质量比为2∶1条件下,氟硅酸钙的单批收率可达到86%;氟硅酸钙在350 ℃静态分解1 h,分解率达到99%,所得四氟化硅产品质量符合硅烷制备和无水氟化氢制备对原料的要求,所得副产物氟化钙产品质量满足行业标准(YB/T 5217—2019《萤石》)的要求。该方法氟、硅资源能够充分利用,且工艺简单、便于操作、易于工业化生产,为磷肥副产氟硅酸的综合利用提供了一定的指导方向。 相似文献
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Cyril Sarrieu Elizabeth Bauer-GrosseSilvère Barrat 《Diamond and Related Materials》2011,20(8):1246-1249
In order to improve the crystalline quality of diamond films produced by microwave plasma assisted chemical vapour deposition (MPCVD), the structural evolution of the silicon carbide interlayer during the bias nucleation step has been investigated by reflection high energy electron diffraction (RHEED). Here we highlight the fact that the carbonisation pre-treatment induces a strong extension of the silicon carbide lattice in the direction perpendicular to the surface. This extension gives a lattice constant close to that of silicon. Then, during bias enhanced nucleation, the carbide lattice relaxes. At the same time, this modification is accompanied by an increase of the surface roughness and by a progressive polar misorientation of the silicon carbide. All these transformations could be responsible for the observed drop of the diamond epitaxial ratio when the duration of the bias step is extended. Finally, we found that a lower methane concentration in the plasma slows down this carbide transformation, allowing us to obtain a promising 37% epitaxial ratio. 相似文献