Low-cost Preparation And Performance Study Of α-Al₂O₃Powder

In this thesis, using the by-product of aluminum-water hydrogen generation as mainstarting material, superfine α-Al₂O₃powders were prepared, Powders were analyzed andstudied the applied research. Chemical analysis, phase analysis and comprehensive thermalanalysis were carried out to investigate the structure and property of by-product. Influences ofdrying methods, different kinds of mineralizer, calcining heat and temperature-holding time onthe phase and grain size of the powder were investigated. Using TEM, X-ray diffract meter,TG-DSC and BET.etc, the characterizations of the powders were conducted. The normalproperties and high temperature properties of samples prepared by powders were studied. Themain conclusions were listed below:1. The by-product after drying main is bayerite, crystal type is monoclinic, purity as highas99.58%. few impurity content, large specific surface area, narrow space distribution, fineparticle size, after fired at1300℃for3h, it is completely transformed to α-Al₂O₃, so thisby-product can be used as starting material to prepare α-Al₂O₃.2. SDBS is used as dispersing agent,0.45wt%SDBS can disperse well when200ml waterscattered100g by-product. Comparing with oven drying technology, microwave drying methodcan effectively control the reunion of dry produces in the process.3. With1%ZnF₂as phase-transition additives,1%crystal seed, the by-product can becompletely transformed to α-Al₂O₃at1200℃, best temperature-holding time is3h. Thepowder’s surface area is6.17m²/g, average particle size is244nm, apertures mainly distributein between10to100nm.4. With1%AlF₃as phase-transition additives,1%crystal seed, the by-product cancompletely transformed to α-Al₂O₃at1200℃, best temperature-holding time is1h. D₅₀is5.575μm, particle size is well-distributed, good dispersion, and grain appearance is plate.5.Using the control powder and the powder added ZnF₂, SDBS, seed crystal as rawmaterial, made φ20cylinder samples in230MPa, after fired an different temperatures, it can befind that the appearance of the sample with none additive is round in sintering process, but theone with additives is plate. Two groups of samples have significant densification phenomenononly when the temperature above par1700℃. Calcining temperature and holding time affectthe densification degree and particle size distribution.