Papers by Author: Ji Guo Sun

Abstract: The application and the transpirational behavior of oriented porous SiC as transpiration cooling materials in a simulating test were studied. The test sample was shaped by freeze-casting process and reaction sintered. The testing device was composed by an electric arc combustor and a hydrogen coolant providing system. It was found that the permeability, the amount of coolant required and the uniformity of coolant infiltration were all effected by the microstructure of porous SiC, which furthermore influced the cooling efficiency of the testing system. In this test, the inner face temperature of the combustion chamber was maintained less than 400K throughout the thermal testing period contrasting with the fire temperature up to 3600K by the utilization of oriented porous SiC transpiration cooling materials.

Abstract: This paper describes the fabrication of porous reaction-bonded SiC ceramics with radial directed pores and the application of these materials to transpiration cooling system of rocket engines. A special mold is designed for freeze-casting process to prepare SiC cylinders with radial directed pores. Green bodies with well-oriented pore structure are obtained from slurry with solid loading up to 47vol%. The pore size is in the level of several tens micron. Green bodies with various porosities are infiltrated with different amount of liquid Si. The intrinsic permeability of each sample is measured with air as flowing media. It is concluded that permeability has relationship with not only the porosity but also the pore structure of samples.

Abstract: Low-activation Fe-Cr-Mn alloy and 316L stainless steel were irradiated with 92 MeV Ar ions at about 500°C, to fluences of 0.8~1.7×1021 ions m-2 .After irradiation, cross-sectional specimens were investigated with transmission electron microscopy.Cavities with high number density were observed in the peak dose regions. The cavity number density reaches maximum at Ar concentration peak, while cavity mean size is consistent with displacement damage profile. It is indicated that Ar atoms can enhance cavity formation in a manner similar to helium. There are thresholds of dose and dose rate for the bi-modal size distribution of cavities. The significant growth of a small portion of cavities in the peak damage region at the highest ion-fluence is ascribed to the effect of interactive sink strength of cavities.