It has been required to change the industrial production processes to low waste emission ones from a view point of environmental issue. In the production of aluminum building materials, large amount of sludge is emitted as industrial waste. If we can change the waste to valuable products, we can respond to the request. Synthesis technology of kaolinitic particles from various starting raw materials had been established at National Industrial Research Institute of Nagoya (NIRIN, present: AIST Chubu). Hydro-thermal treatment is applied to the technology and obtained particles show various shapes such as plate, shell and so on. Collaborative research work between NIRIN and YKK corporation to develop high performance alumina powder form aluminum sludge, a by-product from surface treatment process in the manufacturing of aluminum building materials, had been done by using the fruits from the research project on kaolinite synthesis at NIRIN. As the result, high performance platy alumina powder was developed by using hydro-thermal synthesis technology.