摘要
二硼化锆(ZrB_(2))陶瓷的优异性能使其作为航空航天推进系统结构材料的潜力巨大。然而,其分子中的强共价键和低晶界扩散速率使ZrB_(2)烧结致密化困难,且ZrB_(2)陶瓷固有脆性大、对裂纹较为敏感、服役可靠性不高,限制了ZrB_(2)的应用。通过合成性质优良的粉体促进ZrB_(2)陶瓷烧结致密化、改善其固有脆性具有重要现实意义。减小粉体粒径、降低氧杂质含量是促进ZrB_(2)烧结致密化的关键。此外,高长径比一维粉体可有效提高基体的强韧性。因此,超细、低氧含量和一维ZrB_(2)粉体合成是近年来ZrB_(2)粉体合成领域的研究热点。合成反应原理及制备工艺决定了ZrB_(2)粉体的性质。超细粉体的合成关键在于降低反应温度,优化现有反应体系具有一定成效但限制较大,通过新反应体系可在低温下合成粒径为25~35 nm的超细粉体;ZrB_(2)中氧杂质主要是未完全反应的ZrO_(2),使反应物适度过量可有效提高反应进行程度,氧杂质含量可降至0.14%(质量分数);原位合成的一维ZrB_(2)粉体长径比不高,高长径比纤维仍主要通过静电纺丝工艺制备,但纤维产率较低,因此原位合成高长径比ZrB_(2)粉体仍是一大挑战。本文分析了元素合成、碳热还原、硼热还原、硼/碳热还原、镁热还原及铝热还原合成ZrB_(2)粉体的反应过程与原理;总结了自蔓延高温合成法、熔盐法、机械合金化、溶胶凝胶法和静电纺丝法等制备工艺的优缺点;综述了ZrB_(2)在超细、低氧含量及一维粉体合成三个方向的最新进展;分析了在ZrB_(2)粉体合成过程中影响粒径、氧杂质含量的因素及晶体生长机制,并对未来ZrB_(2)粉体合成研究进行了展望。
Zirconium diboride(ZrB_(2))ceramics have been proved to be a promising structural material in aerospace propulsion system owing to its remarkable properties.However,the application of ZrB_(2)is hindered to a great extent due to the difficulty to be densified,sensitivity to cracks and poor service reliability because of its strong covalent bonds in the molecules and low grain boundary diffusion rate.Hence,it is important to synthesize high-quality ZrB_(2)powders with excellent properties to promote its sintering densification and overcome its inherent brittleness.The activity of ZrB_(2)powders is influenced by the particle size and oxygen impurity content.In addition,with the incorporation of powders with high aspect ratio,a higher strength and toughness can be achieved for ZrB_(2)ceramics.Thus,the synthesis of ultra-fine,low-oxygen content and one-dimensional ZrB_(2)powders has attracted plenty of interest.Thermodynamic and kinetic principles in synthesis as well as preparation technologies have great effects on the quality of ZrB_(2)powders.It is essential to lower the reaction temperature in the synthesis of ultra-fine ZrB_(2)powders.Optimization of existing reaction systems is effective but there are many limitations.Nano ZrB_(2)powders with particle size 25—35 nm can be obtained under a lower temperature in a new system.The oxygen impurity in ZrB_(2)powders is mainly the unreacted ZrO_(2) and it can be effectively reduced to 0.14%(mass fraction)by introducing excessive reactants appropriately.In-situ synthesizing ZrB_(2)powders with high aspect ratio is still a challenge and continuous fibers are still mainly prepared by electrospinning.The processes and reaction mechanisms of ZrB_(2)powders synthesis were reviewed,including element synthesis,carbothermal reduction,borothermal reduction,boro/carbothermal reduction,magnesiothermic reduction and aluminothermic reduction.The advantages and disadvantages of self-propagating high temperature synthesis,molten salt method,mechanical alloying,sol-gel method and electrospinning were overviewed.The latest developments of ZrB_(2)powders synthesis were introduced from the aspects of ultra-fine,low-oxygen content and one-dimensional powders preparation.The factors affecting the particle size and oxygen content as well as the crystal growth mechanism were analyzed.Finally,the studies on the synthesis of ZrB_(2)powders were prospected.
作者
骆吉源
肖国庆
丁冬海
种小川
任金翠
LUO Jiyuan;XIAO Guoqing;DING Donghai;CHONG Xiaochuan;REN Jincui(College of Materials Science and Engineering,Xi'an University of Architecture and Technology,Xi'an 710055,China)
出处
《材料导报》
EI
CAS
CSCD
北大核心
2021年第21期21159-21168,共10页
Materials Reports
基金
国家自然科学基金(51502236,51572212,51772236)
陕西省重点研发计划项目(2018ZDXM-GY-128)。
关键词
二硼化锆
合成原理
制备工艺
发展方向
zirconium diboride
synthesis mechanism
preparation technology
development direction
