976 MATERIALS CHARACTERIZATION 59(2008)975-978 polymer pyrolysis(AFCOP)by the incorporation of active filler into the preceramic polymer has been raised [6]. The volume expansion caused by nitridation and carburization of the active filler on polymer pyrolysis can compensate for the volume shrinkage of the polymer to some extent, decreasing the density of microcracks formed in the matrix The present research work involved the fabrication of 2D CySic composites by a modified PIP process, using Sic as inert filler and Al as active filler. Single and multilayered Pyc interphases were deposited to investigate the effect on the Experimental Procedure E0LSEI28.0V×1,8818m1m 2.1. Composite Manufacturing 2D 0/90 woven C fiber fabrics(Xinka Carbon Co., Shanghai, China) were stacked to prepare the fiber preforms which were Pyc interphase used for composite fabrication. The fiber volume fraction was controlled at about 30% The preforms were PyC and then Sic coated by isothermal chemical vapor infiltration(ICVT). More details about the apparatus used for PyC and Sic deposition can be found in [1]. Two kinds of Pyc interphases were deposited. The first type consisted of a single Pyc interphase of 200 nm. The Sic interphase econd type was made out of four layers of Pyc interphases, the thickness of each layer being about 50 nm. The curve of deposition temperature and time for multilayered PyC inter COMPO 100kv x10,000 1gm WD 8 0mm phase is shown in Fig. 1. Hexamethyldisilazane(HMDS)was employed as precursor for deposition of Sic coating around PyC interphase. The thickness was about 200 nm. The polymer precursor employed for the matrix was polycarbosilane(PCS). Sic powders(Germany)with an average grain size of 0.5 um and Al powders(Liaoning, China) with an average grain size of 4 um were utilized as the filler material. The coated preforms were first dipped into a slurry containing 20 wt% Sic powders, 20 wt% Al powders and 10 wt% polycarbosilane(PCS)in vacuum. After drying, the samples underwent a high-temperature pyrolysis process in nitrogen atmosphere. Subsequently, the samples underwent PIP process using PCS as precursor. The pyrolysis process was conducted at SICCA SEI 20 0kV x600 10um WD12m Fig 2- SEM micrographs of the polished cross sections 9eE 1200C to convert the polymer to ceramic matrix. The above process was repeated six times in order to increase the final density of the material. 2.2. Characterization The fabricated composites were cut and ground into 2.5 mmx4 mmx36 mm samples for density, open porosity and Time(min) three-point bending test. The density and open porosity of each sample were measured by the Archimedes method. Three- Fig. 1-Curve of deposition temperature versus time point bending test was performed on the Instron 5566 universalpolymer pyrolysis (AFCOP) by the incorporation of active filler into the preceramic polymer has been raised [6]. The volume expansion caused by nitridation and carburization of the active filler on polymer pyrolysis can compensate for the volume shrinkage of the polymer to some extent, decreasing the density of microcracks formed in the matrix. The present research work involved the fabrication of 2D Cf/SiC composites by a modified PIP process, using SiC as inert filler and Al as active filler. Single and multilayered PyC interphases were deposited to investigate the effect on the mechanical properties of the composites. 2. Experimental Procedure 2.1. Composite Manufacturing 2D 0°/90° woven C fiber fabrics (Xinka Carbon Co., Shanghai, China) were stacked to prepare the fiber preforms which were used for composite fabrication. The fiber volume fraction was controlled at about 30%. The preforms were PyC and then SiC coated by isothermal chemical vapor infiltration (ICVI). More details about the apparatus used for PyC and SiC deposition can be found in [1]. Two kinds of PyC interphases were deposited. The first type consisted of a single PyC interphase of 200 nm. The second type was made out of four layers of PyC interphases, the thickness of each layer being about 50 nm. The curve of deposition temperature and time for multilayered PyC inter￾phase is shown in Fig. 1. Hexamethyldisilazane (HMDS) was employed as precursor for deposition of SiC coating around PyC interphase. The thickness was about 200 nm. The polymer precursor employed for the matrix was polycarbosilane (PCS). SiC powders (Germany) with an average grain size of 0.5 μm and Al powders (Liaoning, China) with an average grain size of 4 μm were utilized as the filler material. The coated preforms were first dipped into a slurry containing 20 wt.% SiC powders, 20 wt.% Al powders and 10 wt.% polycarbosilane (PCS) in vacuum. After drying, the samples underwent a high-temperature pyrolysis process in nitrogen atmosphere. Subsequently, the samples underwent PIP process using PCS as precursor. The pyrolysis process was conducted at 1200 °C to convert the polymer to ceramic matrix. The above process was repeated six times in order to increase the final density of the material. 2.2. Characterization The fabricated composites were cut and ground into 2.5 mm×4 mm×36 mm samples for density, open porosity and three-point bending test. The density and open porosity of each sample were measured by the Archimedes method. Three￾Fig. 1 – Curve of deposition temperature versus time. point bending test was performed on the Instron 5566 universal Fig. 2 – SEM micrographs of the polished cross sections. 976 MATERIALS CHARACTERIZATION 59 (2008) 975 – 978