【作者】 冷先锋；

【导师】 刘艳改；

【作者基本信息】 中国地质大学（北京） ， 材料科学与工程， 2010， 硕士

【摘要】 针对Al₂O₃陶瓷的韧化,本论文把不同晶粒大小的LiTaO₃粉体作为第二相引入到Al₂O₃结构陶瓷,研究了LiTaO₃晶粒大小对LiTaO₃/Al₂O₃复相陶瓷（简称LTA）微观结构和力学性能的影响,探讨了LiTaO₃/Al₂O₃复相陶瓷中LiTaO₃晶粒内电畴结构的形成机理和复相陶瓷的韧化机理。研究工作对发展陶瓷材料的组织结构设计和陶瓷材料韧化技术具有重要的科学意义。采用溶胶-凝胶法,以Ta₂O₅和Li₂CO₃为原料,以柠檬酸（CA）为络合剂,乙二醇为酯化剂,聚乙二醇（PEG）为分散剂制备前躯体,分别在650℃、750℃、800℃、850℃、900℃温度下煅烧制备了平均粒径为91nm、125nm、310nm、324nm、386nm的LiTaO₃粉体。通过热压烧结,在1350℃保温90min条件下制备了含有不同晶粒尺寸LiTaO₃的Al₂O₃复相陶瓷,致密度均在96%以上。研究得到随着第二相LiTaO₃晶粒尺寸的减小LiTaO₃/Al₂O₃复相陶瓷的力学性能有所提高。添加15vol%的平均粒径为91nmLiTaO₃的LTA复相陶瓷的平均抗弯强度和平均断裂韧性分别达到511MPa和6.13MPa·m^1/2。LiTaO₃晶粒尺寸在100nm左右时其力学性能递减趋势较为明显,呈现较典型的“第二相颗粒尺寸阈值效应”。研究发现LiTaO₃/Al₂O₃复相陶瓷中LiTaO₃晶粒内的电畴结构特征为“尖劈状”、“板条状”和“薄片状”的90°电畴,阐明90°电畴的形成机制为“应力诱发机制”。研究揭示LiTaO₃第二相对LiTaO₃/Al₂O₃复相陶瓷的韧化机理为“裂纹偏转”和“电畴翻转能量消耗”的协同作用机制。更多还原

【Abstract】 For toughening Al₂O₃ ceramics,the paper introduced LiTaO₃ powders of different grain sizes into Al₂O₃ structural ceramics as the second phase,investigate the influence of the LiTaO₃ grain size on the microstructure and mechanical properties of LiTaO₃/Al₂O₃ composite ceramics（the LTA）,explore formation mechanism of domain structures in the LiTaO₃ grain also,research work has important scientific significance for development of ceramic materials structure design and Toughening technology.Research shows LiTaO₃ powders with 91nm,125nm,310nm,324nm,386nm grain sizes are synthesized by sol-gel precursor calcined at 650℃,750℃,800℃,850℃, 900℃for 2h,the precursor prepared,using Ta₂O₅ and Li₂CO₃ as raw materials,citric acid（CA） as chelating agent,ethylene glycol（EG）as esterification agent and polyethylene glycol（PEG） as dispersant agent by the sol-gel technique.Al₂O₃ ceramics with LiTaO₃ of different grain sizes prepared at 1350℃for 90min by hot-pressed sintering,the relative density is above 96%.Study shows that with decrease initial grain size of LiTaO₃,the flexural strength and fracture strength increased, when 15vol%LiTaO₃ powders of 91nm introduced Al₂O₃ ceramics,the LTA composite ceramics’ flexural strength and fracture strength values reached 511MPa and 6.13MPa·m^1/2 respectively.When LiTaO₃ grain size is about 100nm decreasing trend of the mechanical properties is Obvious,showing typical "threshold effect of second phase particle size".Research found the domain structure Characteristics are "wedge-shaped","banded", "Lamellar" 90°domain in the LiTaO₃ grains of LTA composite ceramics,clarify the formation mechanism 90°ferroelectric domain is the "stress-induced mechanism".The study reveals the second phase of LiTaO₃ toughening mechanisms are "crack deflection" and "energy consumption toughening of domain switching" synergy mechanism in LiTaO₃/Al₂O₃ composite ceramics.更多还原