无压烧结制备表面微孔碳化硅陶瓷

以碳化硅（SiC）微粉为骨料,Al2O3-Y2O3为烧结助剂,氯化钙（CaCl2）作为造孔剂,采用无压液相烧结制备了表面微孔SiC陶瓷,分析了不同CaCl2含量对SiC陶瓷的烧结性能、显微结构和摩擦性能的影响。结果表明：加CaCl2会降低SiC陶瓷的体积密度、硬度和抗弯强度;可以有效地细化SiC陶瓷晶粒;能在SiC陶瓷...     

常压烧结莫来石／氧化锆／碳化硅复相陶瓷的研究

本文对莫来石／氧化锆／碳化硅复相陶瓷进行了Ｎ２气氛中常压烧结的研究。实验结果表明：ＳｉＣ粒子添加量≤２０ｖｏｌ％，材料均可致密烧结并可获得均匀的微观结构。ＳｉＣ粒子的加入使材料人力学性能较莫来石／氧化锆陶瓷有明显的提高，并在ＳｉＣ含量为１０ｖｏｌ％时达到峰值，室温强度和断裂韧性分别为６０１ＭＰａ和５．８ＭＰａ＾Ｃ２，接近热压材料。     

常压烧结碳化硅陶瓷的制备及导电性能

采用常压烧结法制备碳化硅陶瓷．对其显微结构和导电性能进行了分析。研究发现，常压法可获得致密的碳化硅烧结体，具有较低的电阻率，在300～600℃温度范围内表现出明显的负电阻率温度系数。     

碳化硅泡沫陶瓷中烧结助剂对莫来石生成的影响

添加几种烧结助剂如硅溶胶、氧化铝、黏土、苏州土和石英的不同组合,研究了烧结助剂对碳化硅泡沫陶瓷中莫来石相生成的影响.实验结果表明：在1 400℃烧结1 h的过程中,氧化铝、黏土和硅溶胶的组合会显著促进莫来石的生成,从而提高碳化硅泡沫陶瓷的高温强度和耐火度.莫来石相在较低温度下的大量生成主要归功于黏土产生液相,以及硅溶胶中非晶态氧化硅对氧化铝颗粒的包裹作用,从而降低了扩散距离.     

常压烧结SiC陶瓷的研究

研究了以Y2O3、Al2O3为添加剂的SiC陶瓷的常压烧结性能,讨论了烧成温度、添加剂配比对烧结性能的影响,认为添加氧化物的SiC陶瓷烧结属于液相参与下的烧结,烧成失重对致密化的影响十分重要。采用合理的配方组成和工艺制度,可以在1950℃获得相对密度97%以下的致密SiC陶瓷。     

碳化硅陶瓷的热等静压烧结

系统地研究了不同添加剂（如Ａｌ２Ｏ３，ＡｌＮ和Ｂ４Ｃ等）在热等静压（ＨＩＰ）烧结条件下对ＳｉＣ陶瓷之致密机理，显微结构以及力学性能的影响，结果表明：在ＨＩＰ烧结过程中，Ａｌ２Ｏ３可以与ＳｉＣ颗粒表面的ＳｉＯ２生成低共熔的铝硅酸盐玻璃相，并有效地促进ＳｉＣ陶瓷的致密化，当添加３％（以质量计）Ａｌ２Ｏ３时，采用ＨＩＰ烧结工艺，在１８５０℃温度和２００ＭＰａ压力下降结１ｈ，就可获得相对密度和抗弯强度分别     

氧化物结合碳化硅复合材料的粒度级配对其性能的影响

通过分析氧化物结合碳化硅复合材料中加入的不同氧化物，以及碳化硅粗、中、细颗粒间的粒度级配，对该材料的组成进行合理的设计，使其既保证一定的抗弯强度，又具有良好的抗氧化性能，得出氧化钙的加入有利于材料强度的提高；粗粉质量分数一定，细粉质量分数不超过45％时,材料的强度随细粉含量的增加而提高；粗粉、细粉质量比为1：1，中粉质量分数不超过35％时，强度随中粉质量分数增加而提高。     

Crack Healing Behavior of Silicon Carbide Ceramics

This study focuses on the crack healing behavior of three kinds of commercial SiC ceramics. Specimens with and without cracks were subjected to thermal treatment at different temperatures, and their strengths were measured by a three-point bending test in accordance with JIS standards. The tests were performed in air at both room temperature and elevated temperatures between 600° and 1500°C. The healed specimens showed a complete recovery of strength at room temperature for the investigated crack sizes of 2 c ≅ 100 μm and 2 c ≅ 200 μm, and their strength increased in accordance with the healing temperature. The behavior of the healed specimens at elevated temperatures was influenced by the material used and the test temperature. Generally, the strength decreased at a high temperature, but the degree of strength reduction was determined by the kind of ceramic. The most important difference between the healed and smooth specimens was exhibited in material A. It was observed that at 1400°C, the bending strength of the healed specimens made from this ceramic was about 37% of the value for specimens in an as-received state. Static fatigue tests were also performed for ceramic B at 900° and 1000°C. The experiment demonstrated that the static fatigue limit of a healed specimen is about 75% of the monotonic bending strength at the same temperature.     

SiC纳米线增强反应烧结碳化硅陶瓷的性能研究

以单晶SiC纳米线作为增强体,碳化硅-碳为陶瓷基体,在1550℃下,采用反应烧结制备碳化硅基陶瓷复合材料(SiCnf/SiC).结合X射线衍射、万能试验机和扫描电镜等检测和分析,研究SiC纳米线对复合材料的微结构和力学性能的影响.研究表明:与未加入SiC纳米线的反应烧结碳化硅陶瓷相比,添加SiC纳米线的复合陶瓷的抗弯强度和断裂韧性都得到显著的提高,抗弯强度提高了52％,达到320 MPa(SiC纳米线含量为12wt％),断裂韧性提高了40.6％,达到4.5 MPa· m1/2(SiC纳米线含量为15wt％);反应后的SiC纳米线仍然可以保持原有的竹节状结构,且随着SiC纳米线的加入,复合陶瓷的断口可以观察到SiC纳米线拔出现象.但由于SiC纳米线“架桥”的现象,添加过量的纳米线会降低复合陶瓷的密度和限制复合陶瓷力学性能的提高.同时还讨论了SiCnf/SiC的增强机理.     

碳化硅陶瓷的冲蚀磨损机理

采用自主研发的冲蚀磨损试验机,以碳素钢为参照,对碳化硅陶瓷进行冲蚀磨损实验.通过控制冲蚀角度、冲蚀时间和粒子冲蚀速度,测定碳化硅陶瓷的冲蚀磨损量,并借助于SEM对冲蚀磨损后试样的显微结构进行观察.实验结果表明:碳化硅陶瓷体积冲蚀率随角度增大而增大,在90°下达到最大;碳化硅陶瓷的冲蚀磨损机理为:在小角度下主要以切削磨损为主,在大角度下主要以脆性断裂为主.     

Process and Mechanical Properties of in Situ Silicon Carbide-Nanowire-Reinforced Chemical Vapor Infiltrated Silicon Carbide/Silicon Carbide Composite

A SiC nanowire/Tyranno-SA fiber-reinforced SiC/SiC composite was fabricated via simple in situ growth of SiC nanowires directly in the fibrous preform before CVI matrix densification; the purpose of the SiC nanowires was to markedly improve strength and toughness. The nanowires consisted of single-crystal β-phase SiC with a uniform ∼5 nm carbon shell; the nanowires had diameters of several tens to one hundred nanometers. The volume fraction of the nanowires in the fabricated composite was ∼5%. However, the composite did not show significant increase in strength and toughness, likely because of strong bonding between the nanowires and the matrix caused by the very thin carbon coating on the nanowires. Little debonding and pullout of SiC nanowires from the matrix were observed at the fracture surfaces of the composite.     

有机前驱体浸渍法制备碳化硅泡沫陶瓷的性能改进

本文对有机前驱体浸渍法制备的碳化硅泡沫陶瓷进行渗硅处理,使碳化硅泡沫陶瓷的孔筋结构致密,20%体积分数陶瓷体的抗压强度达到32MPa,抗热震性能优良,导电特性发生变化。     

碳化硅/堇青石复相多孔陶瓷的制备及性能研究

采用碳化硅、烧高岭土、氢氧化铝、滑石为主要原料,石墨为造孔剂制备了碳化硅/堇青石复相多孔陶瓷.研究了烧结温度和烧结助剂二氧化铈对碳化硅/堇青石复相多孔陶瓷气孔率和强度的影响,并分别用XRD和SEM分析晶相组成和断面显微结构表明:制备出的SiC多孔陶瓷的主相是SiC,结合相是堇青石与方石英,多孔陶瓷具有相互连通的开孔结构;在1350℃烧结,并保温3h,当造孔剂含量为15％时,碳化硅/堇青石复合多孔陶瓷性能最佳,其气孔率31.80％,相应的弯曲强度为63.74 MPa.在1200℃下,添加不同含量的CeO2,对烧结样品的相组成有影响,能够降低生成堇青石的温度,在CeO2含量为3％的样品中,堇青石的峰最明显,但是过量的氧化铈会抑制了堇青石的生成;随着CeO2加入量的增加,其气孔率和弯曲强度也会随之变化,1200℃下,在CeO2加入量为4％时其弯曲强度最优.但随着CeO2的含量的增加,其气孔率逐渐下降.     

Tensile Rupture Strength and Fracture Defects of Sintered Silicon Carbide

The tensile strength distribution of sintered silicon carbide was measured at room temperature and 1300°C in air and fracture defects were characterized. The measured strength was compared with strength obtained from flaw characteristics and fracture toughness assuming a peripherally cracked spherical void model.     

纳米碳颗粒/碳化硅陶瓷基复合材料的氧化行为

以微米硅(Si)和纳米碳黑(Cp)粉体为主要原料,采用经机械化学法合成的碳化硅(SiC)和15%和25%的纳米碳颗粒与碳化硅(Cp-SiC)的复合粉体,并经无压烧结得到了Cp/SiC陶瓷基复合材料,分析了在不同温度条件下Cp/SiC烧结体的氧化行为。结果表明:当温度小于700℃时,Cp/SiC复合陶瓷在空气中的氧化受C—O2反应控制,致使其为均匀氧化;700℃时,氧化后的复合材料显气孔率最大,弯曲强度达极小值;大于700℃,氧化过程受O2的气相扩散控制,呈非均匀氧化;700~900℃之间,O2通过微裂纹的扩散控制着Cp/SiC的氧化过程;900~1 100℃之间,O2通过SiC缺陷的扩散控制着Cp/SiC的氧化过程,并在1 000℃时的最初的2 h内,复合材料弯曲强度增大,且达到了极大值。同时表明,纳米碳含量是影响复合材料强度及氧化行为的关键因素,添加纳米碳质量分数为15%的Cp/SiC复合陶瓷可以作为一种抗氧化性能优良的玻璃夹具材料。     

氧化反应结合SiC基陶瓷的制备与性能

本文采用反应结合制备方法,通过对坯体进行预氧化使ＳｉＣ颗凿表面氧化形成ＳｉＯ２,而后在烧成中与添中剂ＡＩ２Ｏ３－Ｙ２Ｏ３反应,使坯体气化率减少,制备了多孔ＳｉＣ基陶瓷。文章探讨了坯体中ＳｉＣ的氧化特征、反应结合过程和相变化以及它们对烧结体性能的影响。