Weiqian Zhuo

Helium Permeability Measurement of SiC Ceramic Composites for Advanced Reactor Application

Permeability of helium gas of Silicon carbide ceramic composites material, which is one of the most important properties in application of SiC composite for advanced reactors, is studied by using a simple, low-cost test system. The test system can not only qualitatively determine whether the sample is permeable or not, but also quantitatively measure the permeability for the permeable ones by water displacement. The tests are conducted with low pressure in room temperature. The permeability of the SiSiC composite depends on the preparation method. In four flat-plate materials prepared by different processes for the test, the splint based SiSiC and cordierite coated fiber reinforced SiSiC are hermetic, the permeability of uncoated fiber reinforced SiSiC and CVD carbon coated fiber reinforced SiSiC are 0.216cm2/s and 0.109cm2/s, which imply that the permeability is cut in half with the coating. The samples are scanned under SEM to analyze their microscopic structures and verified that the difference of permeability is related to their coatings as well as the pores and cracks.Copyright

Young’s Modulus and Gas Tightness Measurement of Ceramic Matrix Composite-SiC for Advanced Reactor Application

Considering the core outlet temperature of high temperature gas-cooled reactor (HTGR) is above 1000 °C and in the accident conditions, a new type of heat-resistant silicon carbide (SiC) ceramic matrix composites needs to be developed. Analysis of the Young’s modulus and gas tightness of ceramic matrix composite-SiC should be paid attention to due to the inherent brittleness and large porosity of SiC ceramics and also the high temperature and high pressure environment where the fuel cladding works. In this paper, a set of measuring device is designed, which is capable of measuring both Young’s modulus and gas tightness of sic ceramic materials. In order to avoid the shatter of ceramic matrix composite-SiC due to excessive deformation in the measurement process of Young’s modulus, Wheatstone bridge principle is used in the experiment to convert the changes of resistance which generated by the micro-deformation of resistance strain gage adhesive on the surface of the specimen into voltage signal, then the relationship between the amplified voltage signal and the strain of specimen can be established, thereby the Young’s modulus of the specimen can be calculated. The measuring method used in this experiment is more rapid, accurate and economic than previous methods. Besides, there is no need for extra measuring device to measure gas tightness of specimen for it has been taken into account in designing process.Copyright