Effect of talcum powder in alumina ceramics
Because of its high mechanical strength, high hardness, wear resistance, high temperature resistance, corrosion resistance, and excellent thermal conductivity, alumina ceramics are widely used in the fields of machinery, construction, electronics, electricity, biology, medicine, and chemical engineering. It has been increasingly favored by high-tech fields such as aerospace and has become the most widely used oxide ceramic on the market.
Alumina has a very large lattice energy, with a melting point as high as 2050°C. Correspondingly, the sintering temperature of alumina ceramics is very high (solid phase sintering of pure alumina ceramics, the sintering temperature is as high as 1650~1990 ℃), which has brought huge energy consumption and equipment loss to the current alumina ceramic production industry. In order to save energy and reduce emissions and improve the economic benefits of producing alumina ceramics, it is particularly important to reduce the sintering temperature of alumina ceramics.
At present, there are generally three ways to achieve low-temperature sintering of alumina ceramics: one is to reduce the particle size of alumina particles through chemical or mechanical methods, and to increase the reactivity of Al2O3 particles; second, through the use of special sintering methods ( Such as hot pressing sintering technology, hot isostatic pressing sintering technology, spark plasma sintering technology, etc.), using different oxidation principles to improve process conditions; third, mixing appropriate additives to reduce the reaction temperature.
The first method has high production cost, low powder yield, difficult to control the shape and size of the particles, and the smaller the particle size, the more serious the particle agglomeration, which has become an unavoidable problem; the second method has high energy consumption and impairs equipment , The technical requirements are strict and the practicability is low; in contrast, the method of using additives for low-temperature sintering of alumina ceramics has become the closest approach to industrialization for low-temperature sintering of alumina ceramics due to its low cost and strong operability. For example, some researchers used cheap materials such as talc, kaolin, calcium carbonate, silica, and alkaline earth metal oxides as additives, and fired qualified 95 porcelain at 1520~1540°C and successfully put them into actual production.
Adding a series of sintering aids such as talc powder can not only effectively reduce the sintering temperature of alumina ceramics, but also some researchers have found that when the firing temperature is 1330℃, when the amount of talc added is 15wt.%, talc is in the alumina ceramics. During the firing process, it not only plays a good fluxing role, but also reacts with the green body at high temperature to form evenly distributed protoenstatite fine particles, which play a role of dispersion and reinforcement on the porcelain body and contribute to the mechanics of alumina ceramics. Performance improvement.
According to research, adding a small amount of talc to Al2O3 ceramics can inhibit the abnormal growth of Al2O3 crystal grains, ensure that the crystal grains are small, the ceramic structure is dense, and the ceramics have a higher smoothness and have a better effect. To obtain alumina ceramic substrates with good performance, it is of great significance to prepare alumina ceramic suspension slurry containing talc with good fluidity, low viscosity and good dispersibility.