The Study Of Alumina Ceramic Filtering Material

With the improvement of industrial technology, discharge of waste water is growing and the species of waster water is increasing. How to efficiently deal with polluted water are all world puzzles to be settled. The development of new type filter material for sewage disposal is very important.Excellent and controllable pore size and density filtering ceramic balls which can be applied to sewage disposal were made from α-Al₂O₃ diatomite, and added pore-forming agent and flux to improve performance. Factors that influence ceramic pore feature and density were discussed. Coal powder was added as pore-forming agent to increase porosity in this study. The porosity of filtering ceramic balls is 40 % ⁶0%.The density is 0.7g/cm3².0g/cm3. The crushing strength is 5MPa 31MPa.The acid and alkaline resistance are above 96.75% and 97.62%, respectively.These performances were djusted by modifying the quantity of pore-forming agent and diatomite, grain size of coal powder, firing temperature and temperature holding time.The results show that with the increasing of addition quantity of pore-forming agent and diatomite, the porosity increases and density and strength decrease. With the increasing of grain size of coal powder, the porosity decreases and density and strength increase. With the increasing of sintering temperature and temperature holding time, the porosity increases and density and strength decrease. XRD analysis shows that the main phases in specimens are α-Al₂O₃, SiO₂ and mullite. SEM analysis shows that there are large quantities of three-dimensional pores whose diameters are about 100μm. The micro pores whose diameters are between several hundreds run and several μm breakthrough the macro pores.Furthermore, In-situ mullite whisker which was made from xingzi-kaoline, diatomite and industrial aluminum hydroxide was prepared to improve the strength of alumina ceramics . Properties of samples such as phase and microstructure have been tested by advanced testing methods such as XRD, SEM and EPMA.The study showsfactors that influence in-situ mullite whisker are the addition quantity and atmosphere of AIF3, the temperature and temperature holding time of nucleation and crystallization, the addition quantity of V₂O₅ and the species of flux. Mullite whisker whose slenderness ratio is 15⁵0 has been prepared by meliorating the growing condition and the bending strength has been increased to 70MPa in the condition of that porosity is 70%.