【作者】 张魁宝；

【导师】 傅正义； 张金咏；

【作者基本信息】 武汉理工大学 ， 材料学， 2008， 硕士

【摘要】 TiB₂陶瓷具有优良的物理化学性能和机械力学性能,它除了具有非常高的硬度和弹性模量外,还表现出一系列良好的特性——导电性、高熔点、耐磨损、重量轻以及高的化学稳定性,其应用前景十分广阔。但是TiB₂材料较高的制作成本以及较差的烧结性为制备带来了困难,同时TiB₂的常温脆性阻碍了它的实际应用。制备复相陶瓷、添加烧结助剂以及应用先进的成型和烧结技术被认为是提高TiB₂材料的力学性能、改善其烧结性能和降低制备成本的重要方法。本文采用OxideⅠ为第二相,以OxideⅡ为烧结助剂,热压烧结制备TiB₂-OxideⅠ复相陶瓷材料,研究了OxideⅠ含量、OxideⅡ含量和烧结工艺对材料结构和性能的影响,分析了材料显微结构和力学性能的关系,同时研究了助烧剂OxideⅡ的加入对材料烧结过程的影响,探讨了烧结过程中一些现象的产生原因。添加OxideⅠ作为第二相能显著改善材料的烧结性能,在OxideⅠ含量在为0～20%变化时,材料的相对密度都达到96%以上,同时获得材料力学性能优良,可以发现当OxideⅠ含量为15%时,材料的综合力学性能最佳。添加OxideⅡ作为烧结助剂时,OxideⅡ与OxideⅠ发生反应,生成SolideSolutionⅠ（SⅠ）,在高温条件下会扩散到TiB₂与TiB₂或者TiB₂与OxideⅠ颗粒之间的孔隙处,在一定程度上提高了材料的致密度。通过OxideⅡ添加量对材料结构和性能影响的研究,发现当OxideⅡ添加量为3%时,获得材料的综合力学性能最佳。OxideⅡ的含量继续增加时,材料的力学性能反而逐渐下降。在不同的烧结温度条件下,对添加3%OxideⅡ的TiB₂-15%OxideⅠ复相陶瓷进行烧结,结果发现1600℃烧结获得材料结构均匀,抗弯强度最高。而当烧结温度继续升高时,材料的性能反而下降,出现明显的晶粒生长。添加4%OxideⅡ的TiB₂-15%OxideⅠ复相陶瓷,在1600℃进行烧结不同的时间,发现当烧结时间仅为10min时,获得材料性能优良,致密度较高,表明第二相和助烧剂的加入能显著改善材料的烧结性能,能够在较低的温度下快速烧结得到致密材料。当OxideⅡ含量较低时,OxideⅡ没有完全参与反应生成SⅠ相;而当其含量达到6%时,OxideⅡ全部参与反应生成SⅠ。反应过程中存在液相流出和粘模现象,分析可能时TiB₂原始粉中存在氧化物杂质和表面吸附氧,在烧结过程中形成的氧化物造成低熔点的共熔相,从而造成了低温的液相流出。更多还原

【Abstract】 TiB₂ exhibits high electrical conductivity,melting temperature and wear resistance,low specific weight and relatively good chemical stability,besides its extremely high hardness and elastic modulus.TiB₂ ceramics are very promising in modern industry.The main problems that limit the application of TiB₂ ceramics include:high fabrication cost,low sintering activity and inherent brittleness.Adding second ceramic phase,using sintering aids and optimizing fabrication technologies are believed important ways to improve its mechanical properties,sinterability of ceramics and cut down on costing.In this paper,TiB₂ ceramics were prepared by hot pressing technology,using OxideⅠas the second phase,OxideⅡas the sintering additive.The effects of OxideⅠcontents,OxideⅡcontents,sintering temperature and sintering parameter on structure and mechanical properties of TiB₂ ceramics were studied.The relationship between microstructure and mechanical properties was analyzed.The effects of OxideⅡadditive on the sintering process was also investigated.The factors of some phenomena in the sintering process were discussed as well.The sinter ability of TiB₂ ceramics were greatly improved when OxideⅠwas added as the second phase.The relative density of TiB₂- OxideⅠmultiphase ceramics reached above 96%with OxideⅠcontent between 0%and 20%.These materials can also maintain eminent mechanical properties.In our research we can see that best integrated properties can be obtained with 15%OxideⅠ.Solide SolutionⅠ（S I）can be obtained from reaction of OxideⅠand OxideⅡwhen OxideⅡwas added as the sintering additive.This phase can diffuse to holes between granules of TiB₂ and TiB₂ or TiB₂ and OxideⅠunder high temperature,which is good for densification of materials at some extent.The multiphase materials achieved most imaginable proerties with 3%OxideⅡin our research.The mechanical properties was going to decrease when continuously increasing OxideⅡcontents.TiB₂- 15%OxideⅠmultiphase ceramics with 3%OxideⅡwas sintered under different temperature.The results showed that best mechanical properties can be acheved when the samles was sintered under 1600℃.When increasing the sintering temperature,properties of materials declined reversely,with grains grow obviously. The effects of hold time on microstructure and mechanical properties were studied at the same system.With 10 minutes of holding time,materials got high relative density and excellent mechanical properties.These means that the addition of second phase and sintering additive can greatly improve the sintering ability of TiB₂ ceramics.It can be densified quicky under relatively lower temperature.It was discovered in our research that OxideⅡdidn’t react with OxideⅠcompletely in forming S I when additive content was low.While 6%OxideⅡwas added,OxideⅡcompletely reacted to form S I.We also found outflow of liquid phase and agglutination of sintering mould during sintering process.These phenomena should be attributed to oxide impurities and surface adsorption of oxygen,which can form eutectic phases with low melting points.They would flow out under temperature as low as 1600℃.更多还原