ZrB2系陶瓷材料的研究进展

主要对硼化锆的基本性质、粉体的制备、致密体的烧结及其复合陶瓷材料等方面做了较为详细的概述,并对当前硼化锆陶瓷的研究所存在的问题,如高温氧化、强度等提出几点可能的解决办法.     

ZrB2粉体制备的研究进展

随着高温技术的快速发展,高温材料的需求日益增大,同时对高温材料的性能也提出了更高的要求.ZrB2作为一种重要的高温结构材料,具有较高的化学稳定性、高的电导率和热导率、良好的阻燃性及高的耐腐蚀性等优点,因此应用前景广阔,逐渐引起了科研工作者的关注.主要介绍了ZrB2粉体的制备技术,综述了ZrB2陶瓷的主要应用,详细分析了各种制备方法的特点,最后展望了ZrB2粉体的应用前景.     

Influence of the microstructure evolution of ZrO2 fiber on the fracture toughness of ZrB2–SiC nanocomposite ceramics

ZrB₂–SiC nanocomposite ceramics toughened by ZrO₂ fiber were fabricated by spark plasma sintering (SPS) at 1700 °C. The content of ZrO₂ fiber incorporated into the ZrB₂–SiC nanocomposites ranged from 5 mass% to 20 mass%. The content, microstructure, and phase transformation of ZrO₂ fiber exhibited remarkable effects on the fracture toughness of the ZrO_2(f)/ZrB₂–SiC composites. Fracture toughness of the composites greatly improved to a maximum value of 6.56 MPa m^1/2 ± 0.3 MPa m^1/2 by the addition of 15 mass% of ZrO₂ fiber. The microstructure of the ZrO₂ fiber exhibited certain alterations after the SPS process, which enhanced crack deflection and crack bridging and affected fracture toughness. Some microcracks were induced by the phase transformation from t-ZrO₂ to m-ZrO₂, which was also an important reason behind the improvement in toughness.     

Toughening effect of short carbon fibers in the ZrB2–ZrSi2 ceramic composites

The toughening effect of the short carbon fibers in the ZrB₂–ZrSi₂ ceramic composites were investigated, where the ZrB₂–ZrSi₂ ceramics without carbon fibers were used as the reference. The mechanical properties were evaluated by means of flexural and SENB tests, respectively. The microstructure was characterized by SEM equipped with EDS. The results found that the short carbon fibers were uniformly incorporated in the ZrB₂–ZrSi₂ matrix and the relative density was about 97.92%. The flexural strength of short carbon fiber-reinforced ZrB₂–ZrSi₂ composites is 437 MPa; the fracture toughness and the work of fracture are 6.89 MPa m^1/2 and 259 J/m², respectively, which increased significantly in comparing with composites without fibers. The microstructure analysis revealed that the improved fracture toughness could be attributed to the fiber bridging, the fiber–matrix interface debonding and the fiber pullout, which consumed more fracture energy during the fracture process.     

反应烧结ZrB2基多孔陶瓷

利用碳还原法,研究了在放电等离子烧结(SPS)技术下反应制得孔隙率较高的多孔ZrB2基陶瓷的烧结制度,制备了不同孔隙率的ZrB2基多孔陶瓷.并对其孔隙率、物相组成、微观结构和力学性能进行了分析和评价.结果表明:得到高孔隙率的ZrB2基多孔陶瓷的烧结工艺为,室温～1400℃升温速率100℃/min,1400～1750℃之间50℃/min,中间保温温度1700℃,最终烧结温度1800℃,保温3min.用该烧结制度通过调节反应得到的ZrB2的量在0.11到0.35范围内可达到孔隙可控,微观结构较均匀,随着孔隙率的增加,热导率显著降低.     

ZrB2-SiC和Csf／ZrB2-SiC超高温陶瓷基复合材料烧蚀机理的研究

通过真空热压工艺制备了ZrB2-SiC材料和Csf(碳短纤维)/ZrB2-SiC超高温陶瓷基复合材料.采用氧乙炔火焰在4186.8kW/m2的热流下分别喷吹烧蚀两种材料180s.ZrB2-SiC材料表而最高温度达到2406°C,烧蚀后质量烧蚀率为-0.14%,线烧蚀率为1×10-3mm/s,Csf/ZrB2-SiC材料表面最高温度达到1883°C,烧蚀后质量烧蚀率为-0.19%,线烧蚀率为-4×10-4mm/s.对两种材料烧蚀表面和剖面的分析发现,ZrB2-SiC材料烧蚀后由表及里依次形成了疏松ZrO2氧化层、SiC富集层和未反应层的三层结构,其中SiC富集层能够起到抗氧化的作用. Csf/ZrB2-SiC材料烧蚀后由外到内分别形成了ZrO2-SiO2氧化层、SiC耗尽层和末反应层的三层结构,其中最外层以ZrO2为骨架,SiO2弥合其中的结构有效地阻挡了烧蚀中氧的侵入.     

Effects of (TiB2 + ZrB2) nanoparticles on microstructure and properties of 7055Al matrix composites

The in situ (TiB₂?+?ZrB₂)/7055Al composites were successfully fabricated from the 7055Al-K₂TiF₆-K₂ZrF₆-KBF₄ system by a direct melt reaction method. Microstructural observations revealed that the nanoparticles were distributed relatively uniformly in the aluminium matrix, and that these nanoparticles exhibit various shapes such as spherical, hexagonal and cubic, with an average size of about 80?nm. Mechanical property testing showed that the strength and Young’s modulus of the composites increased significantly in comparison to the 7055 matrix alloy. The maximum ultimate tensile strength was approximately 361?MPa, with a yield strength of 323?MPa and an elongation of 3.6%, which constitute increases of 31.3%, 28.7% and 44% when compared to the 7055Al alloy, respectively. The strengthening mechanisms of the fabricated composites were also discussed.     

恒温环境中ZrB2氧化行为模拟

二硼化锆(ZrB₂)是一种应用于高超声速飞行器的新型防热材料, 近年来受到广泛关注。本研究根据ZrB₂在不同温度下的氧化产物二氧化锆(ZrO₂)与三氧化二硼(B₂O₃)的微观结构和形貌, 改进了原有的ZrB₂氧化唯象模型, 研究了ZrB₂的氧化行为, 提出了中等温度区间液态B₂O₃的生成、蒸发、填充的动态平衡关系, 并考虑了孔隙出口处的B₂O₃蒸气浓度。研究结果表明: 改进后的模型能够预测低流速准静态条件下ZrB₂的氧化行为, 与加热炉中的样品恒温氧化测试结果吻合良好; 孔隙对氧化过程有较大影响, 在相同的温度、氧分压下, 孔隙率越大, 被氧化程度越高; 在基材表面存在B₂O₃液态膜的情况下, 扩散过程对氧化速率的控制被极大地降低, 材料表现出最强的抗氧化性能。     

Effects of high-temperature annealing on the microstructure and properties of C/SiC–ZrB2 composites

C/SiC–ZrB₂ composites prepared via precursor infiltration and pyrolysis (PIP) were treated at high temperatures ranging from 1200 °C to 1800 °C. The mass loss rate of the composites increased with increasing annealing temperature and the flexural properties of the composites increased initially and then decreased reversely. Out of the four samples, the flexural strength and the modulus of the specimen treated at 1400 °C are maximal at 216.9 MPa and 35.5 GPa, suggesting the optimal annealing temperature for mechanical properties is 1400 °C. The fiber microstructure evolution during high-temperature annealing would not cause the decrease of fiber strength, and moderate annealing temperature enhanced the thermal stress whereas weakened the interface bonding, thus boosting the mechanical properties. However, once the annealing temperature exceeded 1600 °C, element diffusion and carbothermal reduction between ZrO₂ impurity and carbon fibers led to fiber erosion and a strong interface, jeopardizing the mechanical properties of the composites. The mass loss rate and linear recession rate of composites treated at 1800 °C are merely 0.0141 g/s and 0.0161 mm/s, respectively.     

使用木糖醇合成纳米ZrB2粉末的研究

以正丙醇锆、乙酸、硼酸和木糖醇为原料, 采用溶胶-凝胶法, 通过碳热还原反应制备了纳米ZrB₂粉末。在反应体系中, 木糖醇既提供反应所需的碳, 又与硼酸形成了配位化合物。通过对凝胶前驱体粉末进行傅里叶红外光谱以及热重分析, 探讨了溶胶-凝胶反应过程对碳热还原反应温度以及凝胶陈化时间的影响。结果表明, 引入木糖醇促进了反应过程的进行, 湿凝胶无需陈化处理, 并且降低了碳热还原温度。当木糖醇与正丙醇锆的摩尔配比为1.4时, 使用未经陈化的凝胶前驱体, 经1450℃碳热还原即可获得平均直径约50 nm的等轴状ZrB₂纳米颗粒, 粉体氧含量为1.36wt%。     

等离子喷涂制备ZrB2-MoSi2复合涂层及其抗氧化性能

采用喷雾干燥与真空烧结技术制备出不同MoSi₂含量的ZrB₂-MoSi₂球形团聚粉末, 并以平均粒径为30 μm的ZrB₂-MoSi₂团聚粉末为原料, 利用大气等离子喷涂法在C/C复合材料表面制备包覆完整的ZrB₂-MoSi₂复合涂层, 借助XRD、SEM等对涂层的组织结构以及涂层的抗氧化性能进行了研究。结果表明: ZrB₂-MoSi₂涂层结构均匀致密, 结合强度达到7.2 MPa。适当含量的MoSi₂, 可以提高涂层的抗高温氧化性能; ZrB₂-40wt%MoSi₂涂层C/C复合材料试样在1500℃静态空气中氧化9 h, 失重率仅为1.7%, 涂层具有良好的自愈合能力, 表现出优异的抗高温氧化性能。     

Transparency Effect in Zr−B−N Coatings Obtained by Magnetron Sputtering of ZrB2 Target

Technical Physics Letters - Thin fims in the Zr−B−N system possessing optical transparency have been studied. It is established that increase in the volume fraction of nitrogen in the...     

凝胶陈化对ZrB2粉末制备的影响

以正丙醇锆、硼酸、醋酸和D-果糖为原料, 采用溶胶-凝胶法, 结合高温碳热还原反应制备得到了长柱状单相ZrB₂粉末。反应体系中, D-果糖不仅提供碳热还原反应的碳源, 同时作为化学修饰剂, 起到抑制正丙醇锆快速水解的作用。通过对比未陈化和陈化的凝胶制备得到的产物, 探讨了陈化过程对于ZrB₂粉末制备的影响。结果表明, 凝胶陈化有利于ZrO₂向ZrB₂的完全转化。当起始原料满足n(B)/n(Zr) = 3.5~4, n(C)/n(Zr)= 7时, 采用室温陈化7 d的凝胶在1550℃保温2 h可获得长度为4~7 μm, 横截面等效直径约为1 μm, 长径比约为4~7, 比表面积为2.53 m²/g, D₅₀ = 6.46 μm的单相长柱状ZrB₂粉末。     

Microstructure and Mechanical Properties of C/(ZrB2–SiC) Composites Produced from Ceramic Ribbons

Inorganic Materials - We have studied the morphology, texture, and bending strength of Cf/(ZrB2–SiC) continuous carbon fiber-reinforced ceramic composite materials prepared by a new method...     

ZrB2颗粒增韧B4C陶瓷的原位合成

采用机械混合法无压烧结原位合成ZrB2/B4C陶瓷复合材料,研究了ZrB2含量对复相陶瓷主要性能的影响,分析了复相陶瓷的增韧机理.结果表明,当ZrB2的体积分数为16%时,相对密度最大约为94%,维氏硬度为39.5 GPa,抗折强度为320 MPa,断裂韧性为3.10 MPa·m1/2.由B4C基体和ZrB2颗粒热膨胀系数不匹配引起的裂纹偏转是ZrB2/B4C复相陶瓷增韧的主要原因.     

Nanoscale Multilayered ZrAlN/ZrB2 Coatings Synthesized by Magnetron Sputtering

Multilayered ZrAlN/ZrB2 coatings containing alternating bilayer periods were synthesized by dc magnetron sputtering technique. The intensities of ZrN （111） or ZrN （200） textures in the structure of the nanolayers depended on the bilayer period as well as N2 gas partial pressure during deposition. Nanoindentation testing showed that hardness and internal stress of the nanolayers varied with the bilayer period and crystallographic orientation in the coatings. The hardness of the nanolayers with bilayer periods of 3-6 nm was enhanced （-27%） over the rule-of-mixture value. A low percent of N2 in processing gas was proved to be benefitial to the synthesis of high hard nanoscale multilayered coatings.     

ZrB2对浸入式水口用ZrO2-C材料性能的影响

浸入式水口渣线材料性能的优劣决定着连铸安全和效率的高低,为提高浸入式水口渣线的性能,本研究在ZrO2-C材料中加入ZrB2,探讨ZrB2对ZrO2-C材料性能尤其是抗侵蚀性的影响.结果表明:ZrB2添加到ZrO2-C材料中后,会显著提高材料的抗氧化性,其机理是高温下ZrB2生成B2O3,B2O3在高温下为液相,堵塞气孔,大幅度减缓氧化.适量ZrB2添加到ZrO2-C材料中后,可以提高材料的抗侵蚀性.但ZrB2容易在CO气氛下生成B2O3,B2O3易使氧化锆脱溶、分解,加速ZrO2-C材料的侵蚀.     

ZrB2-SiC陶瓷的注浆成型与无压烧结

研究了以聚乙烯亚胺 (PEI) 为分散剂,ZrB₂粉体在水相中的分散性能. 结果显示ZrB₂的等电点在pH为5.7,加入PEI后的等电点移到pH为11.5. 以PEI为分散剂,在pH为8.0处制备了固含量达45vol%的ZrB₂-20vol%SiC陶瓷浆料. 采用注浆成型方法制备了相对密度为53%的ZrB₂-SiC陶瓷坯体,并对其进行了无压烧结,同时研究了硼粉为烧结助剂对其致密化及性能的影响. 结果表明：硼粉为烧结助剂,实现了ZrB₂-SiC陶瓷的完全致密化的同时,也降低了ZrB₂-SiC陶瓷的烧结温度,2100℃烧结3h后的陶瓷维氏硬度为(17.5±0.5)GPa,弯曲强度为(406±41)MPa,断裂韧性为(4.6±0.4)MPa·m^1/2.     

无机盐溶胶-凝胶法制备超细ZrB2-ZrC复合粉体

利用ZrO2-B2O3-C体系中碳热还原的基本原理,分别采用氧氯化锆、硼酸和酚醛树脂作为ZrO2,B2O3和C的来源,利用溶胶-凝胶法制备出超细ZrB2-ZrC复合粉体.采用热分析仪,X射线衍射和透射电镜对前驱粉体煅烧中的热力学过程,复合粉体的物相以及粒径和形貌进行了分析和表征.结果表明,ZrB2、ZrC相在1300°C开始生成,1500°C煅烧1h后碳热还原反应基本完成.复合粉体的平均粒径在200nm左右,比表面积达87m2g-1,加入1.0wt%的聚乙二醇作为分散剂时,粉体的团聚现象得到很大的改善.     

碳短纤维对ZrB2-SiC基超高温陶瓷力学性能的影响

ZrB2-SiC基材料具有高熔点,高热导率,高电导率和良好的化学稳定性,可以在高超声速的极端条件下工作.但是这种材料的主要问题是低的断裂韧性,为了改善这一性能,将碳短纤维加入到ZrB2-20%(体积分数)SiC中热压烧结,得到了断裂韧性明显提高的试样,从2.0MPa·m 1/2提高到 6.56MPa·m 1/2,同时弯曲强度略有降低,从502MPa降至445MPa,弹性模量也有所降低,从414GPa降至322GPa.为了深入理解这种变化,建立了模型来计算纤维造成的影响,计算结果与实验结果比较接近,证明对于本实验的材料体系,用该模型来解释是合理的.