反应烧结碳化硼/碳化硅坯体和烧结体的性能测试及分析

以聚乙烯吡咯烷酮作碳化硼和炭黑分散剂;四甲基氢氧化铵作碳化硅分散剂,分别以丙烯酰胺、N,N'-亚甲基双丙烯酰胺为单体和交联剂,采用凝胶注模工艺制备碳化硼/碳化硅坯体,再经过高温烧结,制备碳化硼/碳化硅烧结体试样.通过对凝胶注模成型反应烧结碳化硼/碳化硅坯体及烧结试样的性能研究表明:坯体的弯曲强度随着固含量的增加而增大,当固含量为55vol％时强度达到24.3 MPa.烧结体的断裂韧性随碳化硼含量的增加先提高后降低.最佳碳化硼含量为10wt％,此时断裂韧性可达到最大值5.07 MPa·m1/2.烧结体的硬度随着碳化硼含量的增加而增加,当碳化硼含量达20wt％时,硬度达到94.5HRA.     

SiC陶瓷凝胶注模成形研究

采用丙烯酰胺单体及合适的外加剂，可较好地实现SiC陶瓷的凝胶注模成型，SiC浆料注模成形合适的pH值为10，热固化温度为60℃，脱模时间为6小时。每100克SiC中加入8克丙烯酰胺时，坯体强度可达7.42MPa。     

氧化铝陶瓷凝胶注模成形工艺研究

本文以氧化铝陶瓷为例,研究探讨了凝胶注模成形工艺中制备低粘度、高固相含量浓悬浮体的关键技术;讨论分散剂等因素对粘度的影响;不同固相含量对坯体的强度的影响;以及不同固相含量坯体烧结后的SEM分析。     

碳化硼-铝复合材料凝胶注模成型工艺研究

研究分散剂用量、固相体积含量对碳化硼-铝浆料粘度的影响,采用扫描电子显微镜(SEM)对素坯和烧结体形貌和组成进行了表征。实验结果表明:以正辛醇为分散介质,当分散剂CH-10S用量为3%(质量分数)时,可以制得固相体积分数为55%的碳化硼-铝浆料。素坯的抗弯强度为38MPa,且素坯中颗粒堆积紧密、颗粒均匀分散。     

氧化铝凝胶注模成形的研究

研究了Al2O3凝胶注模成形中浆料的流变性,素坯的强度、密度等随有机单体丙烯酰胺和Al2O3固含量的变化特性。实验采用L8(27)正交试验,并对各分散剂对屈服应力有显著影响,球磨时间主要影响流变指数。在120℃干燥后,凝胶注模后的素坯的强度可达到28—45MPa。随着有机单体丙烯酰胺的含量的增加,素坯强度上升,而随着Al2O3固含量的增加,素坯强度下降。在600℃热处理后,坯体相对密度为57—60%。随着有机单体含量和Al2O3固含量的增加,坯体密度表现为先上升后下降的趋势。     

凝胶注模成形工艺制备高强度的氧化铝陶瓷

本文以氧化铝陶瓷为例,研究探讨了凝胶注模成形工艺中制备低粘度、高固相含量浓悬浮体的关键技术,讨论了分散剂因素对粘度的影响和不同固相含量对坯体强度的影响。     

ZTA复相陶瓷凝胶注模成形工艺的研究

本文研究了ＺｒＯ２（３Ｙ）－Ａｌ２Ｏ３复相陶瓷的凝胶注模成形工艺,着重研究了低粘度高固相体积分数浓悬浮体的制备。     

碳化硅材料凝胶注模成型工艺的研究

系统研究了碳化硅材料凝胶注模成型过程,研究了固相体积含量、分散剂、有机单体、交联剂和引发剂对碳化硅凝胶注模成型工艺的影响.实验结果表明:固相体积分数为50%,加入0.05%的分散剂,1%有机单体,0.05%交联剂,0.07%引发剂可以得到强度大,显微结构均匀的素坯.     

凝胶注模成形技术的研究与发展

凝胶注模成形是一种近净尺寸成形工艺，是制备形状复杂、成分均匀和可靠性高的陶瓷材料的理想成形工艺。笔者阐述了凝胶注模成形工艺过程和成形原理，以及国内外的研究现状，指出了凝胶注模成形技术的未来发展方向。     

通过凝胶注模成型和无压烧结制备碳化硅陶瓷

以四甲基氢氧化铵为分散剂,糊精为碳源,通过静电稳定作用,制备了高固相含量、分散良好的碳化硅陶瓷浆料。以水溶性N,N–二甲基丙烯酰胺为单体,N,N’–亚甲基双丙烯酰胺为交联剂,采用实验室开发的偶氮[2–(2–咪唑啉–2–基)]丙烷HCl引发体系,在45～50℃引发单体聚合,制备出水基凝胶注模碳化硅素坯,素坯的相对密度达58%,抗弯强度大于40MPa。进一步通过无压烧结制备相对密度高于98%,硬度达28GPa,强度达530 MPa的SiC陶瓷。对素坯和SiC陶瓷的微结构和力学性能进行了测试和表征。结果表明:采用糊精作为碳源可以提高凝胶注模浆料的分散性,避免凝胶过程中的碳阻聚问题,有利于制备出高性能的碳化硅陶瓷材料。     

中国卫生陶瓷行业的发展与努力方向

经过30多年的迅猛发展,中国卫生陶瓷产量已多年位居世界第一,成为名符其实的世界卫生陶瓷生产大国。笔者介绍了中国卫生陶瓷行业由最初引进国外先进技术和设备到消化吸收,科技创新,逐步形成完整的工业体系的发展历程;指出了中国卫生陶瓷目前尚存在的不足;提出了中国卫生陶瓷行业会今后努力的方向。     

Pressureless Sintering of Boron Carbide

B₄C powder compacts were sintered using a graphite dilatometer in flowing He under constant heating rates. Densification started at 1800°C. The rate of densification increased rapidly in the range 1870°–2010°C, which was attributed to direct B₄C–B₄C contact between particles permitted via volatilization of B₂O₃ particle coatings. Limited particle coarsening, attributed to the presence or evolution of the oxide coatings, occurred in the range 1870°–1950°C. In the temperature range 2010°–2140°C, densification continued at a slower rate while particles simultaneously coarsened by evaporation–condensation of B₄C. Above 2140°C, rapid densification ensued, which was interpreted to be the result of the formation of a eutectic grain boundary liquid, or activated sintering facilitated by nonstoichiometric volatilization of B₄C, leaving carbon behind. Rapid heating through temperature ranges in which coarsening occurred fostered increased densities. Carbon doping (3 wt%) in the form of phenolic resin resulted in more dense sintered compacts. Carbon reacted with B₂O₃ to form B₄C and CO gas, thereby extracting the B₂O₃ coatings, permitting sintering to start at ∼1350°C.     

烧结温度对原位反应TiB2/B4C复合材料的组织与力学性能的影响

为了降低B_4C的烧结温度,提高B_4C断裂韧性,本文以B_4C、TiO_2、活性炭为原料,采用原位反应法热压烧结制备了TiB_2体积分数为10％的TiB_2/B_4C复合材料。探索了烧结温度对复合材料组织和力学性能的影响规律。结果表明,随烧结温度的提高,复合材料的抗弯强度和断裂韧性先增大后减小,在2050℃时有最大值,分别为544MPa和6.3MPa·m~(1/2),弹性模量和断裂韧性变化不大。随烧结温度的升高,基体和第二相晶粒逐渐长大。采用2050℃/1h/35MPa为最佳烧结工艺。     

Experimental Design Applied to Silicon Carbide Sintering

Silicon carbide is a promising structural ceramic used as abrasives and applied in metallurgical components, due to its low density, high hardness, and excellent mechanical properties. The composition and content of the additive can control liquid-phase sintering of SiC. Compositions based on the SiO₂–Al₂O₃–RE₂O₃ system (RE = rare earth) have been largely used to promote silicon carbide densification, but most studies are not systematically presented. The aim of this work is to study the effect of several oxide additives in the SiO₂–Al₂O₃–Y₂O₃ system on the densification of silicon carbide using experimental design. This technique seems to be effective in optimizing the values of maximum density with minimum weight loss.     

成型方式对反应烧结碳化硼基复合材料性能的影响

本文针对干压成型结合冷等静压成型对反应烧结碳化硼基复合材料样品性能的影响进行研究.考察了成型压力、保压时间、加压方式对压坯密度和强度的影响.结果表明:采用100 MPa干压2 min,再经过150 MPa冷等静压保压1 min,压坯密度由干压压制时最大密度1.86 g/cm3升高到1.96 g/cm3,压坯强度可达到2.0 MPa.保压时间和加压方式对压坯的密度、强度的影响不大.干压结合冷等静压相对于干压成型,在相同的烧结温度下样品性能有明显的提高,烧结后样品密度为2.44 g/cm3,显微硬度为2394 kg/cm2,三点抗弯强度为241 MPa.     

连续碳纤维增韧碳化硅基复合材料数据库

连续碳纤维增韧碳化硅基复合材料(C/SiC)数据库为C/SiC复合材料的研究和应用提供了一个高效的数据存储、管理和访问的平台,实现了从材料制备、试样加工到性能试验的全过程的信息管理,包含了物理性能、力学性能、热物理化学性能等多种类型的数据,并提供了数据管理功能和一些应用工具.系统采用了最先进的软硬件平台以延长系统的生命周期,应用了一些新的数据库技术,如对像数据类型、统一建模语言(UML)等,简化了数据库的逻辑结构.制定了数据规范、约束、触发器等保证数据的完整性和一致性,并建立了严格的安全机制.     

碳化硅陶瓷的液相烧结及其研究进展

本文对碳化硅液相烧结添加系统及其烧结机理作了论述。有氧化物参与的碳化硅的液相烧结可以降低碳化硅的烧结温度，促进碳化硅的致密化，提高碳化硅陶瓷的性能。沿晶断裂和穿晶断裂混合断裂机理是液相烧结碳化硅陶瓷强度和韧性提高的原因，表面强化和韧化可以进一步提高碳化硅陶瓷材料的性能。     

Role of Carbon in the Sintering of Boron-Doped Silicon Carbide

The effect of carbon on the sintering of boron-doped SiC was studied. The free carbon present in the green compact was found to react with the SiO₂ covering the surfaces of the SiC particles; however, even if no carbon was added, the surface SiO₂ reacted with the SiC itself at a slightly higher temperature. This latter reaction was associated with the onset of substantial pore growth in the shrinking green body, which, as the pores continued to grow at higher temperatures, prevented complete densification. Therefore, the reaction of the SiC with the SiO₂ may have led to the fracture of interparticle contacts, resulting in the onset of coarsening. Thus, the role of the carbon was to prevent reaction between the SiC and the surface SiO₂, by removing the SiO₂ at a temperature below that at which this reaction could occur.     

Fabrication of Dense Nanostructured Silicon Carbide Ceramics through Two-Step Sintering

SiC powder compacts were prepared with Al₂O₃, Y₂O₃, and CaO powders. By two-step sintering, fully dense nanostructured SiC ceramics with a grain sizes of ∼40 nm were obtained. The grain size–density trajectories are compared with those of conventional sintering processes.