Study On The Interface And Propertis Of Al₂O₃-SrFe₁₂O₁₉

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.