Effects of Al in different added condition on pores shape and mullite configuration were investigated. Three sorts of hole were got by using Al as foaming agent in mullite composites. It was concluded that isolated holes could be formed by Al changing to Al2Ol3 with acidity condition in green state, open holes could be formed by Al changing to Al2O3 directly in sintering process, and mixed hole of isolated and open ones could be formed by Al changing to Al(OH)3 with alkalescence condition in green state followed changing to Al2O3 in sintering process. These holes could supply a position for growth of mullite as well.
Effects of SiO2 and Fe2O3 on morphological of mullite were investigated for a special use related to mullite containing SiO2 and Fe2O3. It was concluded that, when Al2O3/SiO2 ratio near the theoretical component of mullite, the composites cannot been sintered at 1600°C. The normal morphology of mullite presents granule form with Fe2O3 addition, while takes a long column shape with the condition of excessive. SiO2 presenting. Fe2O3 can promote sintering of mullite, as well as growing in needle-like morphology.
A new technique of flyash utilization was presented and high-purity silica was prepared by alkali leaching. The flyash was added into sodium hydroxide solution, and then the suspension was heated to 115 °C for 30 min. After filtrated, the filtrate was collected and carbon dioxide was imported into the solution. Finally, the silica would precipitate from the solution. The silica was characterized by scanning electron microscopy, X-ray diffraction and X-ray fluorescence spectrometer. The high-purity silica prepared from flyash was qualified for the rubber reinforcing agent used in shoemaking.
At present, the hypersonic vehicles cannot be adapted to all the flight phases perfectly, and the aerodynamic heating and lift - to - drag ratio are contradictory to the shape of the vehicles. From the perspective of aerodynamic heating, a blunt shaped body is desired to reduce the heat flow of the hypersonic vehicles. However, the lift - to - drag ratio demands a sharp leading edge. In this paper, a scheme of variable leading edge which could satisfy with both the requirements of aerodynamic heating and lift-to-drag ratio was investigated, and an adaptive thermal barrier was proposed based on the features of the variable leading edge hot structure. According to the heat flux calculated from a certain trajectory by computational fluid dynamics, the heat transfer behaviour of the variable leading edge with adaptive thermal barriers was analyzed by the finite element method. The results indicated that the temperature peak of the panel reached 1428.2 K at 400 s, temperature of the adaptive thermal barriers approached 1418.4 K at 420 s, and the temperature of the internal insulation increased to 667.86 K finally. At the end of trajectory, temperature distribution in the thermal barrier and internal insulation tended to be balanced respectively, which exhibited an excellent thermal property and a promising prospect in complex environment..
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.