炭/炭复合材料在半导体制造行业的应用

综述了传统炭/炭复合材料和膨胀石墨基低密度炭/炭复合材料在半导体制造业直拉(CZ)法单晶硅炉中的应用。指出了在CZ单晶炉内炭/炭复合材料比石墨材料热场零部件的优势所在,并认为随着硅单晶直径的增大,炭/炭复合材料取代石墨材料将成为硅晶体生长炉热场系统的首选材料。     

单晶硅直拉炉用炭/炭埚帮的侵蚀机理探讨

埚帮是单晶硅直拉炉中最重要的结构损耗件,随着直拉法热场尺寸的不断增大,主流单晶硅制造企业已经大批量采用炭/炭复合材料埚帮替代石墨埚帮。采用针刺法制备毛坯预制体,经化学气相沉积、树脂浸渍炭化增密和高温纯化处理后制成炭/炭复合材料埚帮。根据热场温度及元素分析炭/炭埚帮侵蚀破坏的机理,对使用后的炭/炭埚帮断口进行观察分析,结合反应机理进而推断影响埚帮使用寿命的主要因素,为提高炭/炭埚帮寿命的设计提供参考。     

炭/炭复合材料分体坩埚的研制开发

研制了一种单晶硅炉用炭/炭复合材料分体坩埚,重点讨论了炭/炭复合材料坩埚帮的设计制造、石墨底托的设计、底托与坩埚帮的结合等问题。通过试制品在客户单晶硅拉制过程中的应用,满足了成本低、寿命长的要求,达到了研制的目的。     

碳化硅涂层在单晶硅用炭/炭热场材料中的应用及研究进展北大核心

碳化硅涂层是目前解决单晶硅生产用炭/炭热场材料高温侵蚀的有效手段之一,本文介绍了碳化硅涂层的制备技术及优缺点,综述了碳化硅涂层在炭/炭热场材料领域的应用及研究进展,对炭/炭热场材料高温抗侵蚀涂层的发展提出了建议和方向。     

炭／炭U型加热器的制备与性能

研究了炭布与薄网胎交替叠层针刺制成准三向结构U型加热体预制体,经糠酮树脂浸渍／炭化致密工艺,并通过真空高温处理制备了炭／炭复合材料U型加热器。结果表明,其弯曲强度为122MPa,压缩强度182MPa,层间剪切强度为14．9MPa。其电阻值可达到0．10～0．21Ω。在多晶硅氢化炉中应用寿命达到6个月～9个月,凸显出高电阻值和长使用寿命的两大特色。     

炭/炭复合材料埚帮使用寿命的影响研究

针对单晶硅拉晶过程不断受硅化侵蚀造成炭/炭埚帮使用寿命短的问题,从炭/炭埚帮的破坏模式出发,分析了埚帮在单晶硅炉热场中受侵蚀破坏的机理。采用准三维针刺法制备预制体,经化学气相沉积、树脂浸渍炭化、高温处理及热解碳涂层处理后制成炭/炭复合材料埚帮。研究了不同密度、炭纤维含量以及涂层对炭/炭埚帮使用寿命的影响。结果表明随着密度、环向炭纤维含量的提升,炭/炭埚帮的使用寿命明显提升,而炭/炭埚帮表面热解碳涂层能在一定程度上提升其使用寿命,但提升效果有限。     

单晶硅炉用炭/炭复合材料埚帮使用寿命的影响因素研究北大核心

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。     

毡体热处理对炭/炭复合材料氧化行为的影响

将炭纤维毡体进行两组不同温度的高温热处理，然后采用化学气相沉积工艺制备炭／炭复合材料，考察了两组材料在不同温度、时间下的氧化失重率，利用X射线衍射技术分析了炭纤维的石墨化度，采用扫描电子显微镜观察了氧化前、后炭／炭复合材料的形貌，探讨了两组材料的氧化反应过程及其氧化行为差异的原因。     

炭材料的制法

炭材料制备工艺的特点是通过汽相沉积法在炭／炭复合材料表面涂覆第一层炭，然后，在此表面上用化学汽相沉积法，用陶瓷或用陶瓷和炭的混合物制成第二层涂履层，至少使第一层涂覆层的炭的热物理性能或者是机械物理性能两者中之一发生连续的或阶式的变化。     

炭/炭复合材料的热物理性能

综述了炭／炭复合材料的热物理性能及其影响因素。炭／炭复合材料热导率的大小由炭纤维的类型、取向、体积分数以及基体的结构类型决定，热处理工艺也对它有很大的影响。炭／炭复合材料的热导率随温度升高一般先升高后降低。炭／炭复合材料在低温时具有负热膨胀系数，影响其这一性能的因素除了坯体结构和基体     

Effects of graphitization degree of crucible on SiC single crystal growth process

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.     

Service of rammed crucibles for melting noble metals in induction furnaces

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.     

Chemical reactivity of oxide materials with uranium and uranium trichloride

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.     

Evaluating the service parameters of crucible induction furnaces with graphite-bearing crucibles

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.     

Computational simulation of melt flow in magnetic Czochralski growth process

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.     

加压焙烧法制备短纤维增强C/C复合材料

采用加压焙烧工艺制备了短纤维增强C／C复合材料，研究了基体材料配比及纤维含量对其力学性能的影响，结果发现，基体材料中粘接剂沥青的最佳含量为30w%，当炭纤维含量小于8．3vol%时，随着炭纤维含量的增加，复合材料的抗折强度逐渐升高，之后，随着炭纤维的体积含量的增加，复合材料的抗折强度有所下降。     

Structural and electrochemical characterization of Fe–Si/C composite anodes for Li-ion batteries synthesized by mechanical alloying

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.     

In-Situ synthesized TiC nano-flakes reinforced C/C composite-Nb brazed joint

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.     

Properties of graphite-containing crucibles

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.