用低纯碳化硅微粉烧结碳化硅陶瓷

用工业尾料低纯W3.5 μm SiC微粉为原料,在N2保护下烧结碳化硅(SiC)陶瓷.研究了低纯SiC微粉中杂质对SiC陶瓷力学性能的影响,对比了微粉提纯后材料的性能与结构.通过扫描电镜、金相显微镜分析材料的显微结构.结果表明:微粉杂质中SiO2、金属氧化物在SiC烧结温度下的放气反应是影响陶瓷材料力学性能的主要因素.由低纯SiC粉制得的材料的烧结密度达到(3.15±0.01)g/cm3,抗折强度达到(441±10)MPa.     

预分解系统用多功能浇注料的研究

以陶瓷废料、SiC、纯铝酸钙水泥、SiO2微粉和矾土粉为主要原料研制成回转窑预分解系统用多功能浇注料,通过对SiC含量的调节,研究SiC对耐火浇注料力学性能、耐碱性能、抗结皮性能的影响。结果表明,以铝酸钙水泥为结合相的浇注料系统,SiC含量越高,其成型性能变差,但其耐碱性能、抗结皮性能更加优异,SiC含量为15％、30％和55％的三种材料的综合性能均可以满足预分解系统用耐火材料要求。     

用于太阳能储热的粘土结合SiC复相陶瓷结构分析

采用SiC粉、高岭土、苏州土为主要原料制备了太阳能储热用粘土结合SiC复相陶瓷.对烧结样品进行了XRD、SEM、EPMA测试分析,同时测试了样品的抗弯强度和热导率.研究结果表明,在1 400℃烧结温度下保温2 h获得了性能优良的粘土结合SiC复相陶瓷样品,主晶相由SiC、莫来石、刚玉和方石英组成,其抗弯强度为65.5 MPa,热导率为8.9W/(m·K),该复相陶瓷具有优良的抗热震性能,有望应用于太阳能热发电中的储热材料.     

碱性锌酸盐电镀锌–碳化硅复合镀层工艺优化

以Q235钢板为基体,在由70.0 g/L氧化锌、180.0 g/L氢氧化钠、2.8 g/L香草醛、1 m L/L甲醛、1.0 g/L硫脲和1.0 g/L三乙烯四胺组成的普通碱性镀锌液中加入SiC微粒电镀得到Zn–SiC复合镀层。研究了电流密度、温度、SiC用量和搅拌速率对Zn–SiC复合镀层耐蚀性的影响,得到较佳工艺条件为:SiC用量8 g/L,电流密度2.5~4.0 A/dm~2,温度20~25°C,搅拌速率120 r/min。SiC的存在有利于生成晶粒细小、致密且显微硬度较高的镀层。在较佳工艺下,Zn–SiC复合镀层中SiC的质量分数为1.51%,其耐蚀性优于纯锌镀层。     

碳化硅-线性低密度聚乙烯导热复合材料的制备与性能

用粉末共混-模压成型法制备碳化硅/线性低密度聚乙烯(SiC/LLDPE)导热复合材料,探讨了SiC和偶联剂处理对复合材料导热性能和力学性能的影响.结果表明复合材料的导热系数随SiC用量的增加而增加,当SiC的体积分数为30.4%时,复合材料的导热系数为0.8233 W/(m·K),为纯LLDPE的2倍多;拉伸强度则随SiC填充量的增加而显著下降.当SiC填充量为一定值时,表面改性使SiC在LLDPE基体中的分散状态得到改善,拉伸强度和导热性能得到进一步提高,当NDZ-105用量为3%质量分数时,复合材料性能最佳.SiC的加人使LLDPE材料由韧性断裂转变为脆性断裂,SiC的加入影响了LLDPE的熔融温度和结晶度.     

SiC颗粒增强不饱和聚酯树脂复合材料的力学性能

采用万能试验机和硬度计测试研究了SiC颗粒含量和粒径对不饱和聚酯树脂基复合材料力学性能的影响,通过扫描电子显微镜观察了拉伸试样的端口形貌。结果表明,填充的SiC质量分数为10%时,其不饱和聚酯树脂复合材料拉伸强度达到最大,8000目、1000目SiC填充体系拉伸强度分别为53.2MPa,44.8MPa,较纯树脂体系提高68.1%,41.5%。当SiC质量分数为30%时,SiC填充体系的弹性模量较纯树脂体系提高25.8%以上,硬度提高2.3%以上,SiC颗粒尺寸对复合材料的弹性模量和硬度影响不大。SiC/不饱和聚酯树脂复合材料的断裂属脆性断裂。     

Ni-Co-P/SiC纳米复合粉体化学镀机理及其电磁性能

以SiC为原材料,以KNaC4H4O6为络合剂、(C2H3O2)2Pb为稳定剂,用化学镀方法,在Ph 9～10,65℃条件下,将纳米SiC表面处理制得Ni-Co-P/SiC纳米复合粉体.用X射线衍射及能谱分析了镀层的组成并提出了其化学镀机理.用波导法测定了Ni-Co-P/SiC复合粉体的电磁参数,用振动样品磁强计测试了样品的磁性能.结果表明:Ni-Co-P/SiC颗粒表面的Ni-Co-P镀层由非晶态Ni-Co-P及微晶态α-Co,500℃热处理后该表面镀层转化为晶态的Ni3P,Ni和β-Co.当Ni2 与Co2 的摩尔比为0.88,H2PO2-与(Ni2 Co2 )的摩尔比为0.95时,镀液有足够的还原能力和良好的稳定性,Ni-Co-P镀层有较高矫顽力和较好的电磁参数,此时SiC颗粒表面Ni和Co的质量分数分别为9.4%和11.5%.     

水泥窑分解系统用含SiC的铝硅质浇注料研究

以矾土熟料、碳化硅、纯铝酸钙水泥、SiO2微粉和矾土粉为主要原料,铝酸钙水泥为结合剂,制备了水泥窑分解系统用含SiC的铝硅质浇注料,通过调整SiC的加入量(其质量分数分别为15%、30%、50%)及加入形式(分别以15%的颗粒和15%的细粉形式加入),研究SiC对铝硅质耐火浇注料性能的影响.结果表明:铝酸钙水泥结合铝硅质浇注料,随SiC加入量的增加,其流动性、体积密度以及强度总体呈下降趋势,但引入SiC可以提高材料的耐碱性和抗结皮性,且SiC以细粉形式加入时,更有助于提高材料的耐碱性能.     

纳米SiC及其与石墨、二硫化钼填充PTFE基复合材料摩擦磨损性能研究

用摩擦磨损试验机对纳米碳化硅（SiC）及其与石墨、二硫化钼（MoS2）混合填充聚四氟乙烯（PTFE）复合材料在干摩擦条件下与45#钢对磨时摩擦磨损性能进行了研究,用洛氏硬度计对PTFE及其复合材料的硬度进行了测量,用扫描电子显微镜对PTFE复合材料磨损表面进行了观察。结果表明,纳米SiC的加入能提高PTFE复合材料的硬度和耐磨性,纳米SiC与MoS2混合填充会使PTFE复合材料的耐磨性提高更多,特别是在载荷增大时其耐磨效果更好。纳米SiC填充PTFE复合材料的摩擦因数比纯PTFE大,且随载荷增加有所减小, MoS2、石墨的加入可降低PTFE的摩擦因数。     

SiC部件泥浆浇注工艺

本文论述了影响SiC泥浆性能的几个主要因素,运用SiC粉料Zeta电位随PH值变化曲线作指导,通过PH值调整和改变分散介质,着重研究了SiC泥浆稳定性、泥浆浇注样品的性能和显微结构,获得了浇注性能好、长时间稳定不沉淀的泥浆。分析了浇注过程中的各种影响因素,讨论了泥浆性状对浇注性能及样品烧结后力学性能的影响,最终浇注出大尺寸SiC陶瓷部件。     

渗硅碳化硅材料结构与性能关系的研究

采用低廉石油焦碳分为原料制造全碳粉生坯，通过有机添加剂来调配生坯中碳的比例，以控制烧结体中游离硅（fsi）、游离碳（fC）含量（其中fs,fc为烧结中未反应的硅和碳），研究了全碳粉反应硅碳化硅（PCRSC）材料的结构与力学性能的关系，分析了渗硅碳化硅材料中游离硅、游了碳含量对抗弯强度的影响。结果表明：渗硅碳化硅材料中随游离硅含量的增加，其抗弯速度下降，并且二者呈直线关系，符合线性复合规则，另一方面，游离碳含量较高的渗硅碳化硅材料，尽管游离硅含量低，但其抗弯强度低于等量或较多游了硅含量的渗硅碳化硅材料的抗弯强度。     

Synthesis of multi-walled carbon nanotube-tungsten carbide composites by the reduction and carbonization process

Multi-walled carbon nanotube-tungsten carbide composites were prepared by the reduction and carbonization process using multi-walled carbon nanotubes (MWCNTs) and WO₃ precursor by molecular level mixing and calcination. The pre-prepared MWCNT-tungsten carbide composites were characterized by scanning electron microscope and transmission electron microscope. Furthermore, the crystal phase was identified by X-ray diffraction. The results showed that the one-dimensional (1D) nanostructure of the MWCNTs was destroyed by the direct carbonization reaction between the MWCNTs and the WO₃ precursor without an additional carbon source. Moreover, pure MWCNT-tungsten carbide composites were difficult to obtain. With the additional carbon source CH₄, pure MWCNT-tungsten carbide composites were prepared, and the 1D nanostructure of the MWCNTs was retained.     

Early stages of carbon film growth: carbide interface formation on molybdenum

In this study we present an investigation of the carbide formation and early stages of carbon film growth using a low energy carbon beam to supply the growth species. Carbon is supplied through electron beam evaporation of graphite and between 0.1 and 40 ML are deposited on a molybdenum substrate (substrate temperature 400 °C). Photoelectron spectroscopy in the ultraviolet and X-ray regime was employed to characterize the surface and observe the carbide and carbon film formation. Two regimes, with respect to the surface composition, can be identified: firstly, the carbide formation, and, secondly the growth of a pure carbon overlayer. A carbide interface with Mo₂C stoichiometry is created, and the formation of a pure amorphous carbon layer is observed for carbon coverages exceeding about 3.4 ML. But even after the onset of carbon film growth, the carbide interface growth is not terminated, and the extension of the carbide region into the bulk continues to increase. Diffusion through the carbide interface is still present and a dynamic rather than static interfacial layer exists. The diffusion of carbon through the metal carbide dominates the interface formation, which is also evidenced by a delayed onset of carbon film formation at 600 °C. Apart from the observation of interface formation, this experiment also enabled us to observe the valence band spectrum of molybdenum carbide (Mo₂C) for the first time. The sequential deposition of carbon was shown to be a suitable method to produce clean carbide surfaces.     

纯B4C和掺碳B4C的烧结机制

研究了中位粒径为0．42μm的纯B4C和掺碳B4C的烧结致密化过程。根据烧结温度和保温时间对线收缩率的影响。得出了它们的烧结动力学方程;由特征指数n值对比研究了它们的烧结致密机制。纯B4C的烧结致密机制为体扩散和晶界扩散,而掺碳B4C的烧结机制主要为晶界扩散,因此,掺碳对B4C起到了活化烧结的作用,在2160℃烧结45min,掺碳B4C烧结后相对密度大于90％,掺入的碳除了固溶于B4C晶格中之外,其它均以游离石墨形式存在,不形成新相。掺碳还导致B4C晶粒尺寸大大减小。     

碳化硅材料中游离硅及游离碳对性能的影响

研究了全碳粉反应渗硅碳化硅（PCRBSC）材料的结构与力学性能的关系。分析了渗硅碳化硅材料中游离硅（fsi),游离碳（fc)含量对抗折强度的影响。结果表明：参硅碳化硅材料中随游离硅（fsi)含量的增加,其抗折强度下降,并且二者呈直线关系,符合线性复合规划,另一方面,游离碳（fc)含量较高的渗硅碳化硅材料,尽管游离硅（fsi)含量低,但其抗折强度低于等量或较多游离硅（fsi)含量的渗硅碳化硅材料的抗折强度。     

Silicon Carbide Based Nanotubes as a Sensing Material for Gaseous H2SiCl2

Silicon - The ability of carbon- and silicon-based nanotubes, including pure carbon, silicon carbide, and Ge-doped silicon carbide nanotubes (CNT, SiCNT, SiCGeNT, respectively), for sensing highly...     

Microstructure and ablation properties of zirconium carbide doped carbon/carbon composites

Carbon/carbon composites doped with zirconium carbide were prepared by a three-step process. Carbon fiber felts were first immersed in a zirconium oxychloride solution, followed by rapid densification using thermal gradient chemical vapor infiltration. The densified carbon/carbon composites were then graphitized at 2500 °C. The phase composition and morphology of the composites were investigated by X-ray diffraction and scanning electron microscopy. The ablation properties were tested in an oxyacetylene torch. The results show that the linear and mass ablation rates of the composites after doping with 4.14 wt.% zirconium carbide decreased by 83.0% and 77.0%, respectively. The ablated surface of the carbon matrix for pure carbon/carbon composites was very smooth and glossy, while that for doped carbon/carbon composites was honeycombed and dim. The bonding between carbon fibers and matrix decreased because of the formation of more zirconium dioxide, resulting in carbon fibers peeling off the matrix and the ablation resistance of carbon fibers could not be brought into play when the zirconium carbide contents achieved 4.14 wt.%. Although mechanical denudation does not seem to play a dominant role, the ablation was mainly controlled by heterogeneous mass transfer.     

Synthesis and characterisation of medium surface area silicon carbide nanotubes

Silicon carbide nanotubes with medium surface area (30-60 m²/g) were successfully prepared by reaction between carbon nanotubes and SiO vapor according to the shape memory synthesis (SMS). The gross morphology of the carbon nanotubes was maintained during the carburization process. A calcination in air at 600 °C was performed to remove unreacted carbon domains in order to obtain pure carbon-free SiC nanotubes. The synthesized SiC nanotubes had a mean outer diameter of 100 nm and lengths up to several tens of micrometres.     

Microstructure evolution process of porous silicon carbide ceramics prepared through coat-mix method

Porous silicon carbide ceramics were prepared through the coat-mix method and molding, carbonization and sintering process with silicon powders and phenolic resin as raw materials. The crystalline phase, microstructure, and porosity of samples treated at different stages were characterized. Results showed that the fabricated porous silicon carbide ceramics consist of pure β-SiC phase with a homogeneous structure and porosity of above 60%. Each of the processing stages, including coat-mix, molding, carbonization, and sintering, has certain contribution to the porosity of the final porous silicon carbide ceramics, in which the mole ratio of resin carbon to silicon and the molding temperature are the main factors to affect the porosity. A porosity evolution process of porous silicon carbide ceramics during fabrication process was also proposed.     

The synthesis of microporous carbon by the fluorination of titanium carbide

Fluorination of titanium carbide with pure fluorine gas leads to the formation of a nanoporous carbon with a monodisperse pore size distribution centered at 0.59 nm. As with chlorination, a selective etching of titanium atoms from the carbide matrix occurs but at lowers temperatures (130–300 °C) than chlorination.Complementary physico-chemical characterizations such as quantitative XRD, Raman spectroscopy, solid state ¹³C nuclear magnetic resonance have been performed to determine accurately the amount and hybridization state of carbon in the studied samples. Textural analysis by scanning electron microscopy and N₂ sorption at 77 K shows that titanium trifluoride acts as a protective layer which limits the transformation of the new carbon formed into carbon fluorides.