正在加载图片...
P. Bansal, J.A. Setlock/Composites: Part A 32(2001)1021-1029 A- BaAl2O4 2500 B-Ba2SiO4 C-Ba Sr2 A207 500 B BAcA 20, deg Fig 3. Powder XRD pattern of the mixed 0.75BaCO3-0 25SrCO3 -Al2O3-2Sio powder calcined at 915'C for 20 h in air. grinding. A small part of the calcined powder was loaded dual surface layer of BN overcoated with Sic were used in into a graphite die and hot pressed at 1300C for 2-3 h the present study. The fiber coatings were applied by a under 27. 5 MPa (4 ksi) pressure. commercial vendor using a continuous chemical vapor Polymer derived Hi-Nicalon fiber tows(1800 denier, 500 deposition(CVD)reactor. The Bn coating was deposited filaments/tow) with low oxygen content produced by at -1000C utilizing a proprietary precursor and was amor- Nippon Carbon Co were used as the reinforcement. These phous to partly turbostratic in nature. A thin overcoating of fibers have an average diameter of -14 um; a report Sic was also deposited by CVD onto the BN-coated fibers 14, 15] chemical composition(wt %)of 62.4% Si, 37 The SiC layer was crystalline. The nominal coating thick- C, and 0.5%O; and C/Si atomic ratio of -1.39. The Hi- nesses were 0. 4 um for BN and 0.3 um for SiC. The BN Nicalon fibers mainly consist of Sic microcrystals with an interfacial layer acts as a weak, crack-deflecting phase average grain size of 4 nm and amorphous carbon. These while the Sic overcoat acts as a barrier to diffusion of fibers have a density of 2.7 g/cm, room temperature tensile boron from bn into the oxide matrix and also prevents strength of -2.8 GPa, elastic modulus of 270 GPa, and an diffusion of matrix elements into the fiber. average coefficient of thermal expansion of 3.5 x 10 /C A sketch of the set-up used for infiltration of the matrix from room temperature to 500"C. Hi-Nicalon fibers having a slurry into the fiber tows is shown in Fig. 1. This is similar to 1000 25 eg Fig. 4. XRD spectra from the surface of a hot pressed plate of Bao.7sSro25Al2Si2Os. All the diffraction peaks match with the monoclinic celsian phase.& & ! ! & 5/))' .-/ .*+ 4 >1 ? # $ ! >5A)) +)) %!? ! ! #& # ' ' ! ( & 51 @ B515+C >!2? 7.12 /*52 ' )+2 ,@ '% 5/6 ( $ # ' # ! & & 0 1 ( # .* &%/ & .A : .*) : & /+ 5)7 %' +))' $ & # ! ' ! # ( & ! # & >'3D? ( & ! 5)))' 0 & # ! # & ' ! # '3D ( ' # ! # ( & ! )1 )/ ' ( # ! L & ! ' # ! ! & 5 ( / 0 1 2 . / 3 43** 5 *3 6 *3! 5)./ & / ! GJD )*+',/-).+ ',/-.,/-. ,. ! 65+' .) & 1 GJD )*+ ).+. .,A !