Why Recycle Alumina Ceramics Waste
Alumina ceramics are the most extensively used material in advanced ceramics, and a certain number of scrap products are unavoidably produced during the manufacturing process. The implementation of large-scale production has resulted in a large production quantity, so the number of wastes is relatively high, resulting in a high overall value after direct scrapping. Currently, refractory material manufacturers recycle the majority of the alumina ceramics' production waste; however, their practice has a low utilization rate and minimal added value.
By using the existing recycling method, the performance of the recycled alumina foam ceramics is subpar, or the recycling rate is low and the recycled alumina ceramics display poor electrical performance. In order to overcome the shortcomings of the traditional technique, this article presents a method to recycle alumina ceramic wastes with straightforward operation and high recycling rate, and the recycled alumina ceramics can have good performance.
Steps to Recycle Alumina Ceramics Waste
The recycling process makes advantage of the properties of the ceramic waste itself and modifies the alumina ceramic waste with nano-scale calcined kaolin, nano-scale silica, and nano-scale calcined talc. On the premise of ensuring ceramic qualities, it is utilized for the molding conditions in the production of new alumina ceramic goods, thereby increasing their electrical and mechanical properties, lowering the sintering temperature, lowering processing costs, and lowering waste emissions. The specific steps of the procedure are as follows:
Recycling, Sorting and Crushing Ceramic Waste
Recycle the used alumina ceramic material, sort it by color, and then add it in batches to the ball mill for milling;
Physical and Chemical Testing and Modification of Ceramic Waste
Quantitative sampling is done in proportion from separate batches of pulverized ceramic waste powder, and samples from the same batch are mixed together before being physically and chemically detected and analyzed. The modifier is applied at a rate of 6-8% of the weight of the ceramic waste powder, according to the test findings. The modifier is made up of a combination of nanoscale calcined talc, silica, and kaolin.
The nano-scale calcined kaolin in the modifier can effectively prevent flaws such product fractures by reducing the shrinkage of alumina ceramic waste during the sintering process in addition to meeting composition and slurry performance requirements. In order to create mullite crystal phase, nano-scale silica and alumina are combined in a high temperature liquid phase. This increases the product's high-temperature strength. In the sintering process of alumina ceramic waste powder, nano-scale calcined talc can effectively prevent the formation of alumina grains, resulting in fine and uniform ceramic grain size and a dense structure that guarantees the ceramic's high performance and smoothness while cutting molding time and increasing productivity.
During sintering, modifiers can close lattice gaps to create oxides with low melting points. New ecological nano-sized stable solid particles with good activity, uniform distribution, and high dispersibility are generated during the sintering process from the low melting point oxide's liquid phase, which has significant penetration capacity. In the course of secondary sintering, it prevents grain growth. The sintering activation energy of the waste alumina ceramic powder is significantly decreased by the liquid phase created by the modifier during the sintering stage, which encourages the transfer of substances during sintering and the densification of the product, increasing its bulk density and lowering its sintering temperature.
Different batches of ceramic waste powder are added the same amount of modifier, and the sintering aid is added and combined for a second ball milling for more than 24 hours. The ceramic waste powder and sintering aids (such MgO-Al2O3-S12, potassium feldspar), which are added simultaneously with the weight of the ceramic waste powder, are combined in a mass ratio of 100:5-8 during the secondary ball milling. Vegetable oleic acid is used as a surfactant and grinding aid at 0.4-0.6%.
The high temperature at which the alumina ceramic waste is sintered gives it a strong mechanical strength but a weak impact toughness and a rather basic structure. It uses the ball milling technique to create a favorable particle size ratio and then has exceptional fluidity, which is useful for creating the green body in further procedures. The waste alumina ceramic has a very low alkali metal concentration and a stable composition, allowing for precise size control and an increase in insulating performance during secondary sintering.
Sifting Ceramic Waste Powder
As a raw material for the molding of ceramic products, the ball milled ceramic waste powder is sieved.
Conclusion
The alumina ceramics recycled through the above method have good physical and chemical characteristics and can be used as new raw materials for the manufacture of alumina ceramics. The necessary sintering temperature is low when the raw material is utilized to create a new alumina ceramic product, considerably shortening the processing cycle. Additionally, the final product has a high bulk density and requires low processing cost.