Zirconia bricks for special grade refractory materials
By using industrial zirconia and alumina as raw materials, ultrafine grinding, strict particle size control, and conventional processes, high-strength and high toughness zirconia alumina composite ceramics can be produced. This zirconia brick is a special grade refractory material.
The research results indicate that adding alumina to the zirconia matrix can effectively inhibit the growth of zirconia grains, which is beneficial for the existence of metastable tetragonal zirconia grains, thereby improving the strength and fracture toughness of the material. When the mass fraction of alumina is 20%, the flexural strength of the composite ceramic reaches 676.7MPa, and the fracture toughness reaches 10MPa/m ². The combination of phase transformation toughening and particle dispersion toughening enhances the mechanical properties of composite ceramic materials.
Preparation of alumina micro powder by thermal decomposition method, preparation of zirconia ultrafine powder by chemical co precipitation method, and preparation of zirconia/alumina composite ceramics through appropriate processes. It is believed that adding alumina can inhibit the growth of zirconia grains and improve the strength and toughness of the matrix. When the mass fraction of alumina reaches 30%, the flexural strength of yesterday phase ceramics fired at 1600 ℃ is 968MPa, and the fracture toughness is 13.7MPa/cm ².
Adding zirconia to corundum refractory materials to produce jade zirconia composite materials is an example of the application of phase transformation strengthening, toughening, and microcrack toughening theories in refractory materials. During the cooling process of the corundum zirconia sample, the zirconia undergoes a phase transition, forming a certain number of microcracks inside the material, which is beneficial for improving the mechanical strength and toughness of the material. When the amount of zirconia added is small, the number of microcracks in the material is not significant, which has little effect on the strength of corundum refractory materials; When the external amount is too high (such as reaching a mass fraction of 9% or more), due to the large number of microcracks in the material, the flexural strength of the material decreases.
Using corundum, synthetic mullite, and monoclinic zirconia as raw materials, the mixture is formed by isostatic pressing and fired at 1650-1700 ℃. The law of temperature variation of the flexural strength of the sample is that the strength first increases with temperature until the transition temperature, and then decreases with increasing temperature. This is due to the thermal expansion mismatch between different crystal phases and the local bridging of microcracks. The transition temperature is between 800-900 ℃, and due to the martensitic transformation of zirconia, there is a "valley" characteristic at 1000-1200 ℃, with the valley bottom at 1100 ℃.
