Shock Consolidation of Coarse Sic Powder

Sic compacts with 98.6% of theoretical density were obtained from coarse powder by a shock compaction technique. Microhardness values for the compacts obtained at 8 and 13 GPa ranged from 15.7 to 22.5 GPa and from 21.6 to 28.2 GPa, respectively. Scanning electron microscopy suggested that small amounts of molten material participated in the shock consolidation process.     

Appropriate thickness of pyrolytic carbon coating on SiC fiber reinforcement to secure reasonable quasi-ductility on NITE SiC/SiC composites

Pyrolytic carbon (PyC) coating of silicon carbide (SiC) fibers is an important technology that creates quasi-ductility to SiC/SiC composites. Nano-infiltration and transient eutectic-phase (NITE) process is appealing for the fabrication of SiC/SiC composites for use in high temperature system structures. However, the appropriate conditions for the PyC coating of the composites have not been sufficiently tested. In this research, SiC fibers, with several thick PyC coatings prepared using a chemical vapor infiltration continuous furnace, were used in the fabrication of NITE SiC/SiC composites. Three point bending tests of the composites revealed that the thickness of the PyC coating affected the quasi-ductility of the composites. The composites reinforced by 300?nm thick coated SiC fibers showed a brittle fracture behavior; the composites reinforced 500 and 1200?nm thick PyC coated SiC fibers exhibited a better quasi-ductility. Transmission electron microscope research revealed that the surface of the as-coated PyC coating on a SiC fiber was almost smooth, but the interface between the PyC coating and SiC matrix in a NITE SiC/SiC composite was very rough. The thickness of the PyC coating was considered to be reduced maximum 400?nm during the composite fabrication procedure. The interface was possibly damaged during the composite fabrication procedure, and therefore, the thickness of the PyC coating on the SiC fibers should be thicker than 500?nm to ensure quasi-ductility of the NITE SiC/SiC composites.     

铝在硫酸溶液中的复合阳极氧化研究Ⅳ. 添加SiC粉体硫酸溶液中铝的阳极氧化工艺

采用常规阳极氧化法，研究电解液中各成分和电解规范对复合阳极氧化膜层性能的影响后，提出了添加SiC粉体硫酸溶液中铝的复合阳极氧化工艺。实验结果表明：该工艺具有操作容易、设备简单、成本低等特点，与常规阳极氧化比较，其氧化速度、操作温度上限和膜层性能均有显著提高。     

Composite ceramic materials with SiC fiber

The technology and mechanical characteristics of composite ceramic materials strengthened by discrete and continuous fibers of silicon carbide are described. The introduction of an 8% volume fraction of continuous SiC fibers into cordierite increases its strength by almost a factor of 2. Among composites strengthened by SiC whisker the highest density is exhibited by materials with a matrix of Al₂O₃ - ZrO₂ (580 MPa). Materials with matrices of Al₂O₃ and synthetic mullite have mean ultimate bending strengths of 460 and 420 MPa, respectively. The microstructures of the materials are described.Translated from Ogneupory, No. 8, pp. 3 – 6, August, 1995.     

Evaluation of SiC/SiC minicomposites with yttrium disilicate fiber coating

Hi‐Nicalon‐S/α‐Y₂Si₂O₇/SiC minicomposites were formed by polymer infiltration pyrolysis (PIP) and characterized by TEM, SEM fractography, tensile testing, and fiber push‐in testing. All minicomposites with α‐Y₂Si₂O₇ fiber coatings had strengths significantly higher than the control samples without fiber coatings. Extensive fiber pullout with debonding at the coating‐fiber interface or within the coating itself was observed in minicomposites with Y₂Si₂O₇ fiber coatings, but no debonding was observed in minicomposites without fiber coatings. Debond energies of 4.5 ± 3, 4.6 ± 3 J/m² and average sliding stresses of 91 ± 40, 94 ± 40 MPa were measured by fiber push‐in tests.     

聚甲基丙烯酸甲酯对碳化硅表面改性的研究

制备了低分子量的聚甲基丙烯酸甲酯,用其对碳化硅粉进行表面处理。改善了粉体的流动性,为制备高固相含量浆料奠定了基础。     

硅烷偶联剂对碳化硅粉体的表面改性

采用KH-550硅烷偶联剂对SiC粉体表面进行改性,得到了改性最佳工艺参数,分析了表面改性对SiC浆料分散稳定性的影响.结果表明:SiC微粉经硅烷偶联剂处理后没有改变原始SiC微粉的物相结构,只改变了其在水中的胶体性质;减少了微粉团聚现象.与原始SiC微粉相比,改性SiC微粉表面特性发生了明显变化,Zeta电位绝对值提...     

SiC fiber reinforced geopolymer composites,part 1: Short SiC fiber

In this paper, short SiC fiber (SiC_sf) reinforced geopolymer composites (SiC_sf/geopolymer) were prepared and effects of fiber contents and lengths on the microstructure and mechanical properties of the composites were investigated. In-situ crack growth was carried out to study the fracture behavior and toughening mechanism of the composites. The results showed that SiC_sf/geopolymer composite developed weak interfacial bonding state through mechanical interlocking rather than chemical interfacial reaction. The presence of SiC_sf not only enhanced both flexural strength and work of fracture, but also prevented the catastrophic failure as seen in neat geopolymer. When fiber content was 2.0 vol% with length of 5 mm, the composite obtained the highest flexural strength and work of fracture, which were 5.6 and 63 times as high as those of neat geopolymer, respectively. In-situ crack growth together with fractographs showed that toughening mechanisms of the composite included formation and propagation of microcracks, crack deflection, fiber debonding and significant pulling-out.     

SiC fiber reinforced geopolymer composites,part 2: Continuous SiC fiber

In this paper, unidirectional SiC fiber (SiC_f) reinforced geopolymer composites (SiC_f/geopolymer) were prepared and effects of fiber contents on the microstructure and mechanical properties of the composites in different directions were investigated. The XRD results showed that addition of SiC_f retarded geopolymerization process of geopolymer matrix by weakening the typical amorphous hump. SiC_f in all the composites were well infiltrated by geopolymer matrix, but microcracks which were perpendicular to the fiber axial direction were noted in the interface area due to the thermal shrinkage of matrix during the curing process. With the increases in fiber contents, although Young's modulus of the composites increased continuously, flexural strength, fracture toughness and work of fracture increased at first, reached their peak values and then decreased. And when fiber content was 20 vol%, the composites showed the highest flexural strength, fracture toughness and work of fracture, which were 14.2, 15.2 and 81.6 times as high as those of pristine geopolymer, respectively, indicating significant strengthening and toughening effects from SiC_f. Meanwhile, SiC_f/geopolymer composites failed in different failure modes in the different directions, i.e., tensile failure mode in the x direction (in-plane and perpendicular to the fiber axial direction) and shear failure mode in the z direction (laminate lay-up direction).     

微粉级氢氧化铝的干燥方法的研究

通过半工业扩大实验 ,验证了一种将桨叶式干燥与旋转闪蒸干燥相结合用于干燥微粉级氢氧化铝的新方法。     

水性氟碳铝粉漆的研制

通过对铝粉、树脂和助剂等种类及用量的选择,合成了铝粉贮存稳定性、定向排列性及分散性均好的水性氟碳铝粉漆.     

SiC/SiC mini-composites with yttrium disilicate fiber coatings: Oxidation in steam

Solutions of YPO₄ were used to precipitate YPO₄ on pre-oxidized Hi-Nicalon-S SiC fibers. Tows of the coated fibers were then infiltrated with a preceramic polymer loaded with SiC particles to form mini-composites. During pyrolysis of the matrix, SiO₂ and YPO₄ on the fibers reacted and formed a Y₂Si₂O₇ fiber matrix interphase. Mini-composites were exposed to steam at 1000 °C for 10, 50, and 100 h, tensile tested, and the effect of oxidation in steam on the functionality of the Y₂Si₂O₇ fiber coating was investigated. The minicomposites oxidized at 1000 °C for 10 h retained 100 % of their unoxidized strength, and those oxidized for 50 and 100 h retained 92 % and 90 % of unoxidized strength, respectively. Strength retention and fiber pullout in both unoxidized and oxidized minicomposites suggests that the Y₂Si₂O₇ interphase was effective in maintaining a weak fiber-matrix interface.     

加入纳米铝粉以可塑成型法合成堇青石

研究了采用含水的可塑性泥料成型时纳米铝粉对堇青石陶瓷的合成及烧结的影响。查明了此类加入剂的活化作用对堇青石相合成的效应。加入预先合成的含有氮化铝的加入剂时会提高材料的总气孔率，并保持其连通式开口气孔率。所取得的材料可以用于制造催化剂的载体。     

Plasma Spray Deposition of Fine SiC Powder

Plasma powder deposition of SiC has been investigated to develop a suitable process for making a dense body of covalent bond ceramics without additives. Several kinds of β-and α-SiC powders under 10 μm were fed into Ar + H₂ dc plasma jet generated at 1 × 10⁴ Pa to 1.3 × 10⁴ Pa and were deposited on a heated graphite substrate. Dense SiC specimens of 5 mm × 5 mm × 2 mm or 16-mm dia × 0.5 mm could be obtained within a deposition time of 120 s. They bonded to the substrate well, and the hardness reached about 24–30 GPa. Surface activation effects caused by the interaction between plasma and particles are considered to play an important role in enhancing the dense deposition.     

浮型铝银粉的生产工艺技术研究

针对国内浮型铝银粉的分散性和贮存稳定性差等缺点,对浮型铝银粉工业生产的关键技术进行了研究,通过对溶剂置换用溶剂和表面处理助剂种类及用量、搅拌时间以及分散处理时间的选择性研究,确定了最佳的生产工艺条件。选择芳烃类溶剂用于溶剂置换,用量与浮铝型银浆质量比为2∶1;选择磷酸酯类助剂为表面处理助剂,用量为滤饼中所含铝的质量的5%;搅拌3 h,分散处理时间为16 h,所制得的浮型铝银粉分散性和贮存稳定性好。     

铝型材粉末涂装的成本控制

本文主要介绍铝型材粉末涂装成本控制的因素,包括前处理液、粉末消耗、能源消耗等方面做了详细的阐述。并且给了一些重要的参考数据。     

铝型材粉末涂装中的问题分析

本文对铝型材粉末涂装过程中出现的种种问题做了分析和归纳,分析产生的原因,以及如何改善。     

锦纶纤维特性及纤维骨架材料的发展

一、锦纶骨架材料世界应用概况 锦纶66的合成及纺丝技术于1935～1937年由美国杜邦公司的Carothers发明，并于1938年实现了中试规模，第二次世界大战期间美国开始使用锦纶66帘布制造军用飞机轮胎，1947年后用于载重胎，到50年代后期，美国的载重胎用骨架材料几乎完全由锦纶66取代了人造丝。德国于1941年实现锦纶66工业化生产。日本1958年发明用锦纶6做轮胎骨架材料制造轮胎。     

Porous Si3N4/SiC Ceramics Prepared via Nitridation of Si Powder with SiC Addition

Porous Si₃N₄/SiC ceramics with high porosity were prepared via nitridation of Si powder, using SiC as the second phase and Y₂O₃ as sintering additive. With increasing SiC addition, porous Si₃N₄/SiC ceramics showed high porosity, low flexural strength, and decreased grain size. However, the sample with 20wt% SiC addition showed highest flexural strength and lowest porosity. Porous Si₃N₄/SiC ceramics with a porosity of 36–45% and a flexural strength of 107‐46MPa were obtained. The linear shrinkage of all porous Si₃N₄/SiC ceramics is below 0.42%. This study reveals that the nitridation route is a promising way to prepare porous Si₃N₄/SiC ceramics with favorable flexural strength, high porosity, and low linear shrinkage.