共查询到19条相似文献,搜索用时 171 毫秒
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针对炭/炭埚帮在单晶硅拉晶过程中不断受到硅蒸气的腐蚀以及硅料与石英坩埚的共同挤压等,使得埚帮出现破损报废问题,根据埚帮在热场中的破坏机理,从CVD设备规格、预制体的编织方式、热解炭涂层、产品密度、高温处理温度、加工次数等几个方面研究了对埚帮使用寿命的影响。结果表明,采用小炉型沉积,轴向采用无纬布,环向采用炭纤维缠绕,斜向±45°采用长纤维缠绕,以炭纤维体积比为1∶3∶1的比例,分别与炭纤维网胎针刺成型的预制体,经高温热解炭涂层,产品密度为1.55 g/cm^3以上,机械加工2次,并且在1850℃高温处理下,所制得埚帮达到了的设计寿命。 相似文献
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《Diamond and Related Materials》2006,15(1):117-120
Effects of graphite crucible on mass transport and crystal growth process has been investigated in the fabrication of SiC single crystal by the seeded sublimation growth method. Different graphitization degrees of the crucibles were obtained by heat treatment at various temperatures between 2100 and 2300 °C. The crucibles were subjected to SEM and XRD in which the graphitization degree was determined quantitatively. The experimental results indicate that the graphite crucible plays an important role in the SiC crystal growth by providing carbon. High crystal growth is obtained by using the untreated crucibles (corresponding to low graphitization degree), which contributes to the reaction activity between Si and graphite of the crucible. Increasing the graphitization degree results in degradation in crystal growth, even in the graphitization of the SiC seed crystal. 相似文献
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P. S. Mamykin I. D. Kashcheev V. A. Perepelitsyn T. P. Karzhavina 《Refractories and Industrial Ceramics》1969,10(5-6):284-287
Conclusions We prepared and tested in service crucibles of fused magnesium oxide with special additions, having a considerably higher resistance in induction-furnace conditions at temperatures of about 2000°C. The additives guaranteed the necessary sintering of the working zone in the crucible, and helped to form a direct bond between the crystals of periclase.The structure of the used crucibles is described. The formation of the zone structure is connected with the temperature gradient, and in the hot zones is accompanied by intensive recrystallization and growth of periclase crystals.Translated from Ogneupory, No. 5, pp. 19–23, May, 1969. 相似文献
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Sung Ho Lee Choon Ho Cho Yoon Sang Lee Han Soo Lee Jeong-Guk Kim 《Korean Journal of Chemical Engineering》2010,27(6):1786-1790
A graphite crucible is used for the manufacturing of uranium ingots in the uranium casting equipment of the electrorefining
process. Uranium and uranium alloys are typically induction melted in graphite crucibles under a vacuum condition; however,
due to the chemical reactivity of uranium and most alloying elements with carbon, a protective ceramic coating is generally
applied to the graphite crucibles. To investigate the most suitable ceramic coating material for application to graphite melting
crucibles used for the melting uranium in uranium casting equipment, firstly, a thermodynamic analysis using HSC software
was performed to examine the chemical reactivity of ceramic oxide materials with uranium and uranium trichloride, and also,
experiments concerning the reactivity of molten uranium in some ceramic coated crucibles were performed at 1,300 °C. From
the results, yttria was finally selected as the most suitable ceramic coating material for application to graphite crucibles
for melting the uranium. 相似文献
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P. G. Frenkel' N. I. Fomin V. I. Krizental' N. V. Bol'shakova A. M. Il'in V. N. Davydov D. D. Gorshenin V. V. Fedorov M. M. Gol'dberg 《Refractories and Industrial Ceramics》1985,26(5-6):229-233
Conclusions We observed significant differences in the magnitude of the electrical resistivity of the (crucible) material in the zones of the diametric section of the graphite-bearing crucibles having unidirectionally oriented natural-graphite flakes, but differing in their location with respect to the direction of pressing.In order to obtain a more uniform distribution of the (t) values along the walls of a crucible designed for working in the medium frequency furnaces, its production technology must provide for a more isotropic structure, a more uniform densification in the wall along its entire height, and an identical material composition. It is desirable to carry out the melting process in the crucible under an atmosphere avoiding oxidation of graphite, or taking into account its possible burnup and the consequent increase in the electrical resistance of the crucible and its destruction during service.The obtained data permit one to evaluate the order of magnitude of the electrical resistivity in the crucible zones which are of particular interest during induction heating: side walls close to the inductor and the outer corners of the top and the bottom parts. However, the specific features of the crucible texture give a basis to propose that the results of the electrical resistivity measurements carried out on the crucible material using the contact method (in particular, the dc measurements) must be specified more accurately for the calculations concerning heating of the metal-filled crucibles under medium frequencies. It is necessary to determine the effective electrical resistivity of the crucible material developed under these conditions using a special noncontact method under the most commonly used frequencies for the induction furnaces working with conducting crucibles.Translated from Ogneupory, No. 5, pp. 22–24, May, 1985. 相似文献
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Melt flow phenomena of magnetic Czochralski processes are simulated numerically. A model is established for the system that
can grow a 5 inch diameter single crystal from the melt in a 14 inch diameter cylindrical crucible. Effective conditions to
suppress convection adequately are studied by varying rotation rates of the crucible and the crystal for given magnetic fields.
When the axial magnetic force is used, the method of co-rotation of the crystal and the crucible is found more effective to
suppress meridional circulation than the conventional counter-rotation operation. 相似文献
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A Fe–Si (FeSi2 + Si)/C composite was prepared by mechanical ball milling and investigated as a new inserting anode for use in Li-ion batteries. The composite so prepared has a sandwich structure with the alloy particles as middle cores and the graphite layer as outer shells. The charge-discharge measurements revealed that the Fe–Si/C composite not only had a quite high initial capacity of approximately 680 mAh g−1, but also exhibited greatly improved capacity retention with a reversible capacity of approximately 500 mAh g−1 after 15 cycles in comparison with pure Si and Fe–Si alloy. Based on XRD, XPS, SEM, Raman and EIS analysis of the composite electrode in different lithiated states, the mechanism for improved cycleability is found to be due to the effective buffering of the volumetric changes of the Fe–Si particles by the graphite shell. 相似文献
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Ze Yu Wang Man Ni Li Jin Ba Qiang Ma Zeng Qi Fan Jing Huang Lin Zheng Xiang Zhong Jun Lei Qi Jian Cao Ji Cai Feng 《Journal of the European Ceramic Society》2018,38(4):1059-1068
Brazing C/C composite to Nb is often associated with the problem of high residual stress, resulting in low-strength joints. To overcome these problems, here we carried out a simple polymer carbonization process to acquire uniform carbon-covered Cu foam composite interlayer, which was subsequently used for soundly brazing C/C composite and Nb with the assembly of C/C composite/Ag-Cu-Ti foil/C-Cu foam/Ag-Cu-Ti foil/Nb. Microstructure and mechanical properties of the joints were well investigated. The carbonization reacted with Ti elements, forming uniformly distributed in-situ TiC nano-flakes in the joint seam by virtue of the porous Cu foam skeleton. Results present that the in-situ TiC nano-flakes not only greatly reduced the thermal expansion coefficient but also effectively impeded the Cu solid solutions agglomeration. The average shear strength of the joint brazed with 3% C-Cu (wt.%) foam interlayer reached ~52.8 MPa with the brazing temperature of 880 °C for 10 min. 相似文献
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N. V. Bol'shakova A. M. Il'in P. G. Frenkel' 《Refractories and Industrial Ceramics》1987,28(5-6):242-247
Conclusions A study of the thermal conductivity and the electrical resistivity of the specimens of the graphite-containing TGN, TGG, and TKG type crucibles shows that the characteristics of these properties significantly differ depending on the type of the crucibles and the zones in different parts of a given crucible.It is expected that the properties of a given type of crucibles can vary from product to product because of the differences in the compositions and the size fractions of the original raw materials, the postfiring differences in the material, and the structural nonuniformities resulting from compaction.We established the differences in the properties of the graphite-containing crucibles (that depend on the nature of the atmosphere) as a function of temperature.Heating the crucibles in an oxidizing atmosphere leads to partial burning-off (depletion) of their main component (graphite) and to a reduction of the thermal and electrical conductivity of the material of the crucibles.It must be considered that the thermal conductivity of the crucibles working in carbon dioxide atmosphte is 5–10% less than that of the crucibles working in argon atmosphere.Translated from Ogneupory, No. 5, pp. 10–14, May, 1987. 相似文献