【作者】 钟润牙；

【导师】 王皓； 张金咏；

【作者基本信息】 武汉理工大学 ， 材料学， 2004， 硕士

【摘要】 结构陶瓷具有耐高温、高硬度、耐磨损、抗腐蚀等诸多特点，是结构材料的重要组成部分。然而由于陶瓷材料存在较大的脆性，至今仍仅能用于静态环境下的结构件。为了提高陶瓷材料的韧性，人们开展了大量的研究工作。归纳起来可分为两类：即通过在裂纹尖端周围长生非弹性区域来增加材料的固有韧性和采用补强剂来引起裂纹桥联。上述两类增韧原理分别在ZrO₂应力诱导的相变增韧和纤维、晶须或二相粒子的补强增韧中得到以成功的应用。 在几乎所有的磁性材料中，材料磁化强度的变化与应力或应变等力学量之间均存在着密切的联系。如对铁磁材料施加应力时，往往会导致磁畴、自发磁化方向和强度发生变化，这一现象称之为压磁效应，由于得益于压磁效应的作用，不论是磁畴重新排列还是自发磁化方向发生变化都会引起材料额外的形变，因此在一定应力的作用下铁磁材料能产生非弹性变形。另外，作用在铁磁材料上的应力能使其自发磁化强度发生变化，为检测材料中的应力分布提供了依据。基于铁磁材料的上述特性，我们认为在结构陶瓷中引入铁磁体作为二相粒子，能够提高复合材料的力学性能并且使结构陶瓷兼具结构和功能的特性。这是因为当结构陶瓷中裂纹尖端的应力作用在弥散于基体内的铁磁体二相粒子上时，铁磁粒子不仅在裂纹尖端周围产生的非弹性区域使复合材料的韧性提高；而且还能利用铁磁材料在外应力作用下自发磁化强度发生变化的性质，通过测量复合材料在应力作用下磁场强度的变化，探测出结构陶瓷中的应力分布情况。 本文首先采用自蔓延高温合成技术合成了SrFe₁₂O₁₉，然后通过改变烧结工艺条件及参数，分别用热压烧结工艺（HP）和脉冲放电等离子烧结技术（SPS）来制备致密Al₂O₃-SrFe₁₂O₁₉复合陶瓷。试图通过控制工艺条件使Al₂O₃与SrFe₁₂O₁₉铁氧体粒子在界面上形成部分固溶的复合材料。建立Al₂O₃-SrFe₁₂O₁₉复合材料的晶体结构、界面结构与材料力学性能、磁性能之间的关系。从界面结构变化的角度来预测和控制材料的性能，在此基础上发展陶瓷材料的界面结构设计理论，并为最终研制出高性能的结构陶瓷-硬磁铁氧体结构-功能一体化复合材料打下基础。采用XRD技术鉴定复合材料的物相，利用SEM，TEM来分析SrFe12O19及其复合材料的结构形貌，颗粒大小及结合情况，使用伺服材料实验机、洛氏硬度计及振动样品磁强计（VSM）测试了复合陶瓷的抗弯强度、硬度及其磁性能，并探讨它们之间关系。更多还原

【Abstract】 Structure ceramics are becoming the key materials in many kinds of industrial fields due to its bearing-high temperature, anti-abrasion, anti-erosion and possessing high hardness. But it has been constrained on only the static condition because of its bad toughness. Recently many efforts to improve toughness of ceramic materials have been made by controlling their microstructure. Sum them up to two parts: develop non-elastic area around crack tip to improve nature toughness of the composites and induce bridge between crack by supplement. The principles have been successfully applied in those that ZrO2 stress inducement change phase and fiber, crystal beard or the second particles improve the toughness.There is close relation between magnetization change and stress in almost magnetic material. For example, when magnetic material being pressed, magnetic domain, direction and strength of spontaneous magnetization will vary. This phenomenon is called effect of pressing magnet. Whichever rearrangement of magnetic domain or direction change of spontaneous magnetization will induces extra shape change of material. So magnetic material will produce non-elastic shape change when it is pressed or drawn. Additionally the strength changes of spontaneous magnetization benefits to detect distribution of stress. Due to those properties of the M-type ferrite, we consider that the mechanical properties of structural materials which the M-type ferrite as a second particles is dispersed in will be improved, and at the same time they will possess magnetism. When the stress at the tip of crack is inflicted on the M-type ferrite particle dispersed in matrix as a second particle, not only the toughness of composites will be proved because of the non-elastic area produced by the particle but also the strength change of magnetic field and the stress distribution in the structural ceramics will be detected by the strength of spontaneous magnetization varying while magnetic materials being pressed or drawn.The synthesis of SrFe12O19 by self-propagating high-temperature synthesis (SHS) was firstly reported in this paper. Then using hot pressing (HP) and spark plasma sintering (SPS) prepare dense Al2O3-SrFe12O19 composites respectively by controlling the sintering conditions. And try to make the particle of Al2O3 and SrFe12O19 solidly dissolve each other to form new composites. Then Construct relation between crystal structure, interface structure and mechanical, magnetic properties of composites and predict and control the properties of material from the interface structure varying, on the basis of that developing the principle of design of interface structure. Finally build the foundation to prepare the composites of structure and M-type ferrite with structure and function properties. The constituent phases, microstructure and crystal dimension and crystal coalescence, mechanical properties, magnetic properties of the composites were investigated by means of X-ray diffraction (XRD), scanning electron micrograph (SEM) and transmission electron micrograph (TEM), mechanical testing instrument, vibrating sample magnetometer (VSM) respectively.更多还原