RH Jones et al. Journal of Nuclear Materials 307-311(2002)1057-1072 Hi-Nicalon Type-S/PyC/FCVI-SiC icalon/PyC/FCV-Sie O-SAP\C/FCVI-SiC o Monolithic CVD-sic 5 1:500C·HFIR 6: 300C: HFIR 740C HFIR 5:430-5 Fig. 6. Relative strength, irradiated/unirradiated, for SiC/SiC composites These results show that it is possible to achieve signifi cant bend ultimate strengths for unirradiated SiCr/SiC CVD SI composites with either multilayer and pseudo-porous interfaces but that the radiation stability for a composite matrix with Hi-Nicalon is better with the multilayer than the pseudo-porous interface 6.1.2. New SiC /SiC composites by transient liquid phase sIntering process iC-interlayer The LPS process, which has been a common tech nique in producing monolithic silicon carbide and other C-interlayer at relatively low costs, was successfully applied to matrix densification for SiCr/SiC composites for the first time. The lab-grade materials with uni-directiona reinforcement exhibits typically 700 MPa in three-point 0.5 flexural strength and pseudo-ductile fracture mode with a good fiber pull-out. Tensile strength tests, both toughness evaluation are in progress. The composites are almost fully-dense, with very minor porosity within Hi-Nicalon fib intra-fiber-bundles. Thermal conductivity and herme ticity data will soon be available. Larger scale pro- ig. 7. Multilayer SiC interphase with thin pyrolitic layer ap duction and complex shaping are presently being plied followed by SiC interlayers. n other non-radiation environments where components 6.2. Thermal conductivity: modeling based guidance to or structures are subjected to a high heat flux, is the performance improvements expected in-service behavior of its effective transverse hermal conductivity, Ke. Knowledge about the ex- jor issue to be considered when using SiCr/Sic pected range of Kef is necessary to optimize Sic/Sic temperature neutron radiation environment, orThese results show that it is possible to achieve signifi- cant bend ultimate strengths for unirradiated SiCf /SiC composites with either multilayer and pseudo-porous interfaces but that the radiation stability for a composite with Hi-Nicalon is better with the multilayer than the pseudo-porous interface. 6.1.2. New SiCf /SiC composites by transient liquidphase sintering process The LPS process, which has been a common tech￾nique in producing monolithic silicon carbide and other ceramics at relatively low costs, was successfully applied to matrix densification for SiCf /SiC composites for the first time. The lab-grade materials with uni-directional reinforcement exhibits typically 700 MPa in three-point flexural strength and pseudo-ductile fracture mode with a good fiber pull-out. Tensile strength tests, both at room and at elevated temperature, and fracture toughness evaluation are in progress. The composites are almost fully-dense, with very minor porosity within intra-fiber-bundles. Thermal conductivity and herme￾ticity data will soon be available. Larger scale pro￾duction and complex shaping are presently being attempted. 6.2. Thermal conductivity: modeling based guidance to performance improvements A major issue to be considered when using SiCf /SiC in a high-temperature neutron radiation environment, or in other non-radiation environments where components or structures are subjected to a high heat flux, is the expected in-service behavior of its effective transverse thermal conductivity, Keff . Knowledge about the ex￾pected range of Keff is necessary to optimize SiCf /SiC configurations for their intended uses. Several modeling Fig. 7. Multilayer SiC interphase with thin pyrolitic layer ap￾plied followed by SiC interlayers. Fig. 6. Relative strength, irradiated/unirradiated, for SiCf /SiC composites versus radiation dose. R.H. Jones et al. / Journal of Nuclear Materials 307–311 (2002) 1057–1072 1063