urna Am,Cem.Sox,8615830-37(2003) Thermal Response and Oxidation of TyrannotM-Fiber-Reinforced Si-Ti-C-O Matrix Composites for a Thermal Protection System in High-Enthalpy Dissociated Air Toshio Ogasawara, Takashi Ishikawa, and Takashi Matsuzaki National Aerospace Laboratory of Japan, Mitaka, Tokyo, 181-0015, Japan The thermal response and oxidation of Tyranno no Lox-M Il. Experimental Procedure fiber-reinforced Si-Ti-C-O matrix composites in high-enthalpy dissociated air was investigated in an are jet facility (an are ()Materials wind tunnel). The maximum surface temperature reached The composites under investigation contained TyrannoTM 1310-1670C. Catalytic recombination of oxygen and nitrogen Lox-M fibers woven into an orthogonal 3-D fabric (Z-PlusTM on the composite surface under dissociated air was not signif- SCL, Shikibo, Ltd, Shiga, Japan), or a stitched 2-D plain weave icant. Surface recession was insignificant below 1600.C sur fabric(Z-PlusTM Netshape). The composite constituents are face temperatures and above 5 kPa of oxygen partial pressure summarized in Table I. The optical micrographs in Figs. 1(a) at the stagnation point. Passive-to-active oxidation transition nd(b)illustrate the fiber architecture of the present compos- of the composite agreed with Balat's theory for monolithic ites. Polytitanocarbosilane was used as the matrix precursor silicon carbide. a glass sealant prevented active oxidation of with eight impregnation and pyrolysis cycles being required to the composite for short-time exposures. chieve satisfactory densification. Glass-sealed and unsealed composites were prepared to investigate the effect of glass sealant. The glass-sealed composite specimens were subject to I. Introduction an antioxidation procedure in which a SiO2-Na, O-based glas was repeatedly impregnated into the composite open porosity C ONTINUOUS-CERAMIC- FIBER-REINFORCED ceramIc-matnix com posites exhibit excellent damage tolerance required for aero- chosen because of low viscosity above 1000C. Thermal space applications. The National Aerospace Laboratory of Japan properties are listed in Table IL. Thermal diffusivity and pecific heat were measured by a laser flash method and a DSC te, for use as a structural material in a future reentry space method, respectively. Emissivity of sealed and unsealed com- vehicle, The composite is referred to as NUSK-CMC from the posites was measured using a blackbody furnace(Emissiom- initials of the collaborators. The composite has been developed eter, ThermogageTM, Vatell Corp, VA)at 900 and 1100C in over several years and the present incarnation contains Tyrannoonp N2 gas flow. For direct comparison, commercial graphite Lox-M fibers that have been surface-modified in a carbon mon and a fiber -be oxide atmosphere to produce a 10 nm surface layer rich in Sio matrix composite (Tyrannohex M, Ube Industries, Ltd, Ube, surrounding an inner 40 nm layer rich in carbon. The rationale apan) were tested under similar conditions. behind the surface modification is to promote crack deflection and fiber/matrix debonding at the carbon-rich layer within the fiber (2) Arc Jet Testing ites, orthogonal 3-D woven fabric or stitched two-dimensional This test series was conducted in a 750 kW arc wind tunnel (2-D)fabric preform was used for reinforcement. Matrix densifi- (AWT: Sumitomo Heavy Industries, Ltd, Tokyo, Japan). I cation was achieved through the repeated impregnation and pyrol. Figure 2(a) shows a schematic drawing of a plasma generator of sis of a polymer precursor. The composites exhibit excellent the AWT. In the plasma generator, air is heated by electrical discharge in a water-cooled constrictor arc column. Then, the To apply the composites to the thermal protection system(TPS) gas (air) is supersonically expanded through a converging- of a future reusable space vehicle, thermal response and oxidation under atmospheric reentry conditions should be evaluated in addition to the mechanical properties. An are jet facility(are win Table L. Composite Constituents of N MC tunnel) is often used to simulate the aerodynamic heating condi- tions experienced by space vehicles during reentry. In a high- Tyranno M Lox-M(Si-Ti-C-O) enthalpy convective environment, the catalytic recombination (Ube Industries Ltd )(Si, 54%: Ti, 2%: C reaction of dissociated oxygen and nitrogen on the material 32%;0.12%(mass%) surfaces affects the thermal response of the materials. b-In this Fabric Orthogonal 3-D woven fabric (Z-plusTM SCL study, the thermal response and oxidation behavior of various Shikibo Ltd ) 20 vol%, 20 vol%, and 2 vol% NUSK-CMCs were investigated using an are jet facility. in the x, y, and z directions Stitched 2-D plain fabric (Z-plusTM Netshape. Shikibo Ltd. ) 22 vol%, 22 vol%, and 1 vol% in the x, y, and z directions S6 Treatment(10 nm SiO, -rich layer surrounding R. J. Kerans--contributing editor an inner 40 nm carbon-rich layer at the fiber surface, Ube Industries Ltd Matrix Si-Ti-C-O derived from polytitanocarbosilane 8 PIP cycles(Ube Industries Ltd) eoManuscript No. 187186 Received January 28, 2002: approved December 16. Glass sealant SiO -Na, O-based glass sealant(Kawasaki Heavy stne fember, American Ceramic Society. 830
May 2003 Thermal Response and Oxidation of Tyrannoan-Fiber-Reinforced Si-Ti-C-O Matrix Composites Z fibers Stitching fibers Z ∠mm 2mm Fig 1. Optical microphotographs of Tyrannot Lox-M fiber reinforced Si-Ti-C-O matrix composites(NUSK-CMC): (a)orthogonal 3-D woven fabric (Z-Plust SCL),(b)stitched 2-D plain woven fabric (Z-Plus t Netshape) diverging nozzle into an evacuated test chamber. In the test interlacing loops shown in Fig. I were not present in the final chamber, a sample assembly was mounted onto a mechanical amples. The sample was mounted in a reusable Sic-coated swing arm, and it was positioned 100 mm from a nozzle exit as aphite holder by using three alumina pins with Ni alloy shown in Fig. 2(b). A sample assembly was exposed to the prings. Figure 4 shows a typical test in progress; a shock wave dissociated gas stream, and taken out immediately after the around the sample can be seen. Cold-wall heat flux 4w was desired exposure time measured using a Gardon-type calorimeter (Thermogageo, 3. Samples were 20 mm in diameter and 5 mm thick with a 30 two-color optical pyrometer(IR-CQS21C, Chino, Japan)was taper angle. The tested geometry was that appropriate for the used to determine the surface temperature of the samples. Type leading edge of a blunt body during reentry. The sample R thermocouples were used to measure the internal thermal surfaces were also ground to a flat finish such that the response of the samples during arc jet testing. It is known that Table ll. Thermal Properties of NUSK-CMC, Graphite(IG-110), and Tyrannohex NUSK-CMC G-110 Tyranno Fabric Orthogonal 3-D Orthogonal 3-D Plain weave 2-D Satin weave 2-D Glass sealant Unsealed Sealed Bulk density(g/cm 252.21 1.772.4 Specific heat(/g K) 0.70 0.71 0.320.65 Thermal conductivity (W/mk) 1.74 1062.74 3.03 193 Emissivity 9000.90 0.95 1100 0.89 0.94 0.91 0.900.88
832 Journal of the American Ceramic Sociery-Ogasawara et al Vo.86.No.5 Converger Modular Packs of Diverger Section Anode Cathode Supply (750kW) Plasma generator Test chamber (a) Fig. 2. Schematic drawing of an arc jet facility (arc wind tunnel)used for the experiment (NASDA/NAL 750 kW AWT):(a) segmented constrictor-type plasma generator, (b) plasma generator and test chamber configuration some oxides selectively emit at wavelengths used for optical Ill. Results and Discussion pyrometry at high temperatures. Therefore, the surface temper ature of the composite placed in a blackbody furnace wa (1) Thermal Response easured using both a pyrometer and thermocouples. As a The maximum surface temperatures during arc jet testing are result, it was confirmed that the experimental error of the plotted in Fig. 5 as a function of cold-wall heat flux measured with pyrometer was insignificant up to 1500C a calorimeter, The cold-wall heat fluxes reflected a finite catalytic The electrical power input and the air mass flow rate were surface, because the surface of the calorimeter was made of changed for each arc jet test condition. Typical arc jet test constantan( Cu-Ni alloy). Therefore, it should be noticed that the old-wall heat fluxes are not actual values for the sample surfaces conditions are summarized in Table Ill. Cold-wall heat fluxes because of differences in the catalytic efficiency between the measured with the calorimeter ranged form 0.9 to 2. 1 MW/m and stagnation pressures varied from 13. 1 to 30.7 kPa. The the composites reached 1310-1670C, which was much lower gas enthalpy was estimated by energy balance of the are jet than that of graphite. The difference in observed surface temper- facility, which ranged form 13. 4 to 20.3 MJ/kg. The test atures between glass-sealed and unsealed composites was not chamber pressure before testing was-180-240 Pa Exposure significant. time was 300 s for each sample, which was chosen because Numerical analyses based on the one-dimensional(1-D) finite this is a severe heat flux time for a typical reentry space difference method(FDM) were conducted to evaluate the surface hicle temperature during arc jet testing. In general. the heat transfer After arc jet testing, the mass loss and the surface recession of equation is as follows: each sample were measured. The surface and the cross section of each sample were observed using a scanning electron microscope (SEM, S-4700, Hitachi, Japan). X-ray diffraction(XRD) analysis 0()-a: was conducted using a CuKa source with an X-ray diffractometer (RINT2500, Rigaku, Japan) to investigate the chemical composi where, p, Cn, and K are the density, the specific heat, and the tion of the composite surface. thermal conductivity, respectively, Based on the control volume Ceramic Insulator 5.0 44 号 Graphite holder umina pin Ni alloy Spring Fig. 3. Geometry and dimensions of sample and sample holder assembly used for are jet testing
May 2003 Thermal Response and Oxidation of Tyrannoa-Fiber-Reinforced Si-Ti-C-O Matrix Composites Sample(中20×t5 Radiation equilibrium 2 2000 FCalc.(NUSK-CMC) 1500 ·· 100 aled 3-D sealed 2-D Nozzle Sample assembly 0.5 1.0 2.0 Fig. 4. Typical test in progress. The shock wave around the sample can Measured cold wall heat flux(MW/m tween calculated and experimental results during are jet testing as a function of cold-wall heat chnique the following finite difference equations are obtained: 2 Gardon-type calorimeter. The nominal exposure time s Predicted curves were calculated using the 1-D finite difference aT=ar-T-+ ak+Tk-1+b (2a) (2b) potentials across the boundary layer for the hot and cold walls as a+1-(6x)k ch-hewi pC (2d) where h, hew, and hhw are the gas enthalpies at the boundary layer dge, at a cold wall, and at the surface temperature of the test b=apT?+Q (2e) model, respect/vely. If the gas composition at a hot wall is mainly air, the gas enthalpy at the wall can be obtained by integrating the at=ak-1+ ar+ta specific heat of air from a reference temperature to the hot-wall temperature, where k is the number of divided element air is the distance from an adjacent element, and Q is the heat generation. The boundary h CadT condition at the front surface of the sample can be illustrated by writing a general surface energy balance equation 9=ghw+OET+ r,(h,-hs where cmo (/(g K ))= Co DoT, with Co = 0.979 J/(g K) and Do-15X 10 J/(g K), is the specific heat of air, and Tw and Tref are the hot-wall temperature and the reference temperature where ghw is the hot-wall heat flux at the stagnation point, or is the (300 K), respective me 2-D effect on the heat transfer, a 2-D Stefan-Boltzmann constant, E is the emissivity, Tw is the surface mperature, i, is the mass flux from the sample, hw is the total enthalpy of the vapor species, and hws is the enthalpy of the numerical analysis was also performed using a commercial finite material lement method (FEM) code, ABAQUS 5.8(Hibbitt, Karlsson, For the numerical analyses, the radiation boundary condition and Sorensen, Inc, Pawtucket, RI), Figure 6(a) shows the temper- was given for both front and backside surfaces. Mass flux from the ature distribution of a sample and a sample holder under the cold-wall heat flux of 1 MW/m", which was calculated by 2-D temperature difference on the heat transfer (namely, the"hot-wall analysis results is shown in Fig. 6(b). The 1-D FDM numerical ffect")from the cold-wall heat flux measured with the calorim- results are in good agreement with the 2-D FEM results eter. This correction factor is a function of the ratio of the enthal Numerical results based on 1-D FDM are superimposed on Fig 5: the estimated curve for graphite agrees with the experimental results, On the other hand. the estimated curve for NUSK-CMC is much higher than the experimental results. This is due to the Table Ill. Typical Are Jet Test Condition composite surfaces. -9 From the numerical results, actual heat Air mass flow Gas enthalpy Cold-wall heat Impact pressure Current(A) fluxes for the composites were estimated as shown in Fig. 7. It was predicted that the actual heat fluxes would be about 52% of the 13.4 cold-wall heat fluxes measured with the calorimeter. It was 12.9 1.0 15 reported that SiO, surfaces produced very low catalytic efficien- 16.9 cies compared with metallic materials such as Ni, Pt, Cr, and Cr: 4.5 the heat transfer rate to SiO, was reduced to a minimum value of 18 1.8 only one-third of the value obtained on relatively active NI surfaces,which agrees with the experimental results in this study When the surface temperature exceeded 1650C for the un- sealed composite, the surface temperature increased rapidly above
Journal of the American Ceramic Society--Ogasawara et aL. VoL. 86. No. 5 Surface Heat flux (IMW/m2) 2500 Back side Surface temperature 2000 Te emperature 1500 h11 +1,700+03 @@自@@@ 51000 +2.500e+03 1.300+0 8 O 2-D FEM(ABAQUS) +:00+0 Holder E500● ●2-DHM( ABAQUS) I-D FDM +5.000e+0 200 CL Time(sec) Numerical analysis results based on the 1-D finite difference method(FDM) and the 2-D finite element method(2-D FEM) under a hot-wall heat MW/m2: (a) temperature distribution calculated by 2-D FEM program, ABAQUS 5.8:(b) comparison of temperature profiles between 1-D FDM FEM at the center of the sample surface. 1900 C as shown in Fig. 8. In these samples, significant mass loss Furthermore, the hot air through these pores might hay and surface recession were also observed, which was due to active the internal temperature of the samples. On the other oxidation. However, this was not observed in the glass-sealed pposed that the effect of z-fibers on the thermal through thickness was insignificant because of the low volume The effect of fiber configuration on the thermal response was fraction of z-fibers(2 vol% for the 3-D composite also investigated under the same are jet testing conditions. Figures 9(a) and (b)show the temperature profile of a 3-D woven composite and a stitched 2-D plain weave composite. The surface 2) Mass Loss and Surface Recession ind internal temperatures in the 3-D composite were higher than A summary of the mean mass loss rate of the materials tested in those in the 2-D composite, which was caused by differences in the the arc jet is shown Fig. I l as a function of cold-wall heat fluxes urface roughness. The 3-D composite had large pores(pocket The mean mass loss rate is defined by gion) derived from the orthogonal 3-D woven architecture as thmean=(mo-m)Tr shown in Fi The aerodynamic heating conditions were severe around the pores because of turbulent flow; therefore, the surface temperature was higher compared with a stitched 2-D composite 1900C (over range 2000 1650cT 0.8 1500 0.6 Q52 1000 urface temperature 500 Internal temperature (3.5mm) 0.0 0 50 1.52.0 100 Measured heat flux(MW/m") Time(sec) ig. 8. Temperature profiles of the unsealed orthogonal 3-D c d cold-wall heat fluxes versus measured heat fluxes for under high heat flux condition (measured cold-wall heat flux 2.06 the glass composite(stitched 2-D plain fabric version). The estimate MW/m). The surface temperature exceeded the upper limited values heat fluxes are calculated by I-D FDM, and they are normalized by (1900 C)of the pyrometer, and the thermocouples embedded in the sample
May 2003 Thermal Response and Oxidation of Tyrannot-Fiber-Reinforced Si-Ti-C-O Matrix Composites 835 00 Surface temperature 2000 Surface temperature 1500 1500 1000 日1000 Internal temperature (3.5mm) 500 -o--3-D fabric 500 -o--3-D fabric 2-D fabric D fabr Time(sec) (a) (a)1.,/ erature profiles for the orthogonal 3-D composites and the stitched 2-D composites. Cold-wall heat fluxes measured with the calorimeter were Fig 9, Tem where mo and m are the sample mass before and after testing, r is composite surface before and after arc jet testing. The surfaces of the nominal sample radius(10 mm), and tmax is the heating time. the glass-sealed composites were uniformly covered with a silica Most of the composite samples were exposed in a dissociated air layer formed by crystallization of the glass sealant material during tream for 300 s except for a couple of unsealed composite an are jet test. However, evaporation of silicon oxide could be samples tested under high heat flux. when the surface bserved at 1640.C, which suggests that active oxidation of a as below 1600%C, no surface recession was observed silica layer occurred under the experimental conditions. On the Although mass loss in the composites was not considerable other hand, only titanium oxides were detected for the unsealed below 1650%C. a small amount of mass loss was observed above composite surfaces above 1670%C, which is evidence of active 1500 C. The mass loss rate increased slightly with temperature for oxidation, as described in the next section. the sealed composites. This was due to evaporation of sodium in the glass sealant, and decomposition of the Tyranno fiber and the PIP matrix. Both Tyranno fiber and PIP matrix are unstable at ( Passive-to-Active Oxidation Transition elevated temperature; thus, the following decomposition occurs at NUSK-CMC consists of Si-Ti-C-O fiber, a Si-Ti-C-0 elevated temperature and Na,O-SiO, glass sealant. It is known that Si-Ti-C-O has a complicated structure with nanoscale Sic particles SiTion CL3Oou(s)-0.94SiC +0.02TiC +0.065SiO bon. and silicon oxide, Therefore, to understand oxidation of +0.375C0 NUSK-CMC. oxidation of Sic should be considered At high SiC exhibits two types of oxidation The sample surfaces were analyzed by X-ray diffraction(XRD) havior, active"and"passive"depending on the ambient oxygen analysis Figures 12(a) and(b) show the XRD patterns from the potential and the temperature. At high oxygen pressures, "passive Pocket regi 2 21 mm Fig. 10. Optical micrographs of the unsealed composite surfaces: (a) orthogonal 3-D composite, (b) stitched 2-D plain composite
836 Journal of the American Ceramic Society-Ogasawara et al Vol. 86, No 5 30.0 035 Graphite (IG-110 104 画 Unsealed 2-D 103 1032 Balat mode 10.0 10 Singhal model.oxidation o Active oxidation 1200 1600 1800 2000 1400 1600 1800 Maximum surface temperature('C) Temperature(K) Fig. ll. Mean mass loss rate of graphite, sealed and unsealed composites a function of cold-wall heat fluxes measured with a Gardon-type calorimeter. The nominal exposure time was 300 s for the passive oxidation for the active-to-passive oxidation transition of silicon carbi.temperature gaseous species at the solid/gas interface, based on the free-energy oxidation occurs and a protective oxide film is formed on the minimization method. For the calculation, computer program surface by the following reaction Solgasmixs was used. And then, Wagners model was applied to SiC(s)+20, (8)-Sio, (s)+Co(8 take the mass-transfer constraints(open system) at the e bound nto consideration. The disparity between the two estimated curves is due to the method of calculation of the diffusion coefficients and At low oxygen potentials, severe"active"oxidation occurs due to the formation of gaseous products according to the following the thermodynamic data (JANAF Tables 1971 and 1985).The reaction: xperimental results in this study agree with Balat's model(Fig SiC(s)+0(g)-Sio(g)+co(g) On the other hand, for the glass-sealed composite, significant mass loss was not observed above 1650 C. The surface of the In the case of active oxidation, rapid surface recession glass-sealed composite was covered with the glass, and the glass loss are observed. Many researchers have worked on the decomposed into silica during are jet testing because of sodium nation of the active-to-passive transition using both ex evaporation, as shown in Fig. 12(b). For silica-covered compos and analytical approaches; however, the results differ. tes, weight losses do not occur until much lower oxygen partial In this study, the maximum surface temperature reached 1310 pressure or much higher temperature because now the reaction 1670C, and the oxygen partial pressure at the stagnation point occurring is the decomposition of the silica: 27.23 was30-7.I kPa. The passive and active oxidation data are indicated by solid circles and open circles in Fig. 13, respectivel SiO2→SiO(g)+O4(g) Passive-to-active transition curves estimated by Singhal's and Balat's model are also plotted in Fig. 13. 8-2 Both Singhal's and The diffraction peak intensities of cristobalite significantly de- Balat's models are based on the Eriksson"and Wagner models2 creased at 1640 C surface temperature, as shown in Fig. 12(b):this with JANAF thermochemical tables. For these models, passive- suggests the evaporation of the silica layer. Therefore, for long- to-active transition curves were estimated by the following proce- time exposure, active oxidation of the composite may occur even dure. First, Eriksson's model was used to estimate the dominant for glass-sealed CMC T10 SiO( Cristobalite Sio,Tridymite) 1670° 1640℃C 人M~A1570°℃C 1450°C A NEW 80> NEW 2 (b) Fig. 12. X-ray diffraction patterns from te surface before and after arc re:(a) unsealed 3-D com b) glass-sealed 3-D
May 2003 Thermal Response and Oxidation of Tyrannoao-Fiber-Reinforced Si-Ti-C-0 Matrix Composite 837 For the unsealed composites, rapid temperature rises were L. A. Anderson. "Effect of Surface Catalytic Activity on Stagnation Heat-Transfer observed during active oxidation. We supposed that rapid temper- tes,"AAJ,1l1S649-56(1973 SiO, and the bare SiC surface. The low catalytic efficiency of Sic High-Temperature Reusable Surface Insulation,"J. Thermophys, Heat Transfer, 7 I11 ature rises were due to differences in catalytic efficiency betweer R. J. Willey, " Comparison of Kinetic Models for Atom Recombination on can be attributed to a thin surface oxide layer(SiO,). Once the E. J. Jumper and w. A. Seward, "Model for Oxygen Recombination on surface oxide layer is removed by active oxidation, substrate Sic is exposed directly to dissociated air. If the catalytic efficiency of "T. Stockle, S. Fasoulas. and M. Auwerter-Kurtz, Heterogeneous Catalytic bare SiC is much greater than that of silicon oxide, a rapid rise in Recombination Reactions Including Energy Accommodation Considerations in High Enthalpy Gas Flows, "AlAA Pap, AlAA97-2591(1997) emperature might occur. However, Balat et al. reported that the loT. Ishikawa, S Kaji. K. Matsunaga, T. Hogami, and Y. Kohtoku, "Structure and catalytic efficiency of SiC in atomic oxygen was nearly equal to Properties of Si-Ti-C-O Fiber-Bonded Ceramic Material, "J Mater. Sci. 30, 6218 that of Sio,, which contradicts the above hypothesis. To confirm (995 the reason for the phenomenon, additional experiments and anal- IY. Watanabe. T. Matsuzaki, H. Itagaki, K. Yudate, T. Yoshinaka, T. T: ysis of the effect of dissociated nitrogen are required Y. Shouda, and S, Hasegawa,"A mmm千14 isphere Publishing Ⅳ. Conclusion K. Tran. D. J Rasky, and L. Esfahani,"Thermal Response and Ablation nd oxidation of Tyranno Lox-M Characteristics of Lightweight Ceramic Ablators,J. Spacecr. Rockets, 31 [6]993-98 reinforced Si-Ti-C-O ceramic-matrix composites (NUSK under supersonic dissociated air was investigated using an IR. L. Potts, "Application of Integral Methods to Ablation Charring Erosion. A facility. The following results were found Review, "J. Spacer, Rockets, 32 [2] 200-209(199 ndard Test Method for Heat of Ablation, ASTM E458-72(reapproved 1990) (1) The catalytic efficiency of the composite surface under a IoK. Kakimoto, T. Shimon, and K. Okamura. "Microstructural Stal dissociated air stream was not significant Si-Ti-C-O Fibers at High Temperatures. "J, Ceram. Soc. Jpr., 105 [6] 504-508 (2) Surface recession was insignificant below (199 surface temperature, and above 5 kPa in oxygen parti ITH Ichikawa and T. Ishikawa, "Silicon Carbide Fibers(Organometallic Pyroly sure at sis)": Pp. 107-44 in Comprehensive Composite Materials, Vol. 1. Edited by A. Kelly. the stagnation point C. Zweben. and T-w. Chou, Elsevier Science LId, Oxford, U. K. 2000 (3) Passive-to-active oxidation transition of the composites iS. C. Singhal, Oxidation Kinetics of Hot-Pressed Silicon Carbide. "J.Mater agreed with Balat's theory for silicon carbide. (4) A glass sealant prevented active oxidation of the compos- S. C. Singhal, "Thermodynamic Analysis of the High- Temperature Stability of ite for a short time the Oxidation of Silicon Carbide at High Temperature and Low Pressure in Molecular and Atomic Oxygen. "J. Mater. Sci. 27. 697-703(1992) Silicon Carbide in Standard and Microwave-Excited Air, J. Eur Ceram. Soc. 16 We gratefully thank J. Nagai and S Kobayashi of AES Co, Ltd. K Ishida and D 55-62(1996 Ltd, T. Hirokawa and T. Tanamura of Shikibu, Ltd, and J Gotoh of Kawasaki Heavy Industries, Ltd for their dedication in the development of NUSK-CMC 2T. Narushima, T, Goto, Y, Iguchi, and T, Hirai, "High-Temperature Active 2G. Eriksson,"Thermodynamic Studies of High Temperature Equilibria XIl Solgasmix, " Chem. Scr, 8, 100-103(1973) T. Ishikawa, K. Bansaku, N. Watanabe, Y. Nomura, M. Shibuya. and T C. Wagner. "Passivity during the Oxidation of Silicon at Elevated Temperature, C-Matrix Composites of Matrix App. Phys,29.1295-97(1958) ci. Technol,58.51-63(1998) The latest version is J, Physical and Chemical Reference Data, Monog 9,"NIST-JANAF Thermochemical Tables, 4th Ed. Edited by M. w. Ch Composite to the Thermal Protection Sy merican Chemical Society and the American Institute of Physics for the Vehicle. Ceram. Sci. Eng. Proc. 22 3]23-30(2001) PL. J Davies, T. Ishikawa, M. Shibuya, T. Hirokawa, and J Gotoh,"Fibre and E J. Opila and N. S. Jacobson, ""Corrosion of Ceramic Materials": pp. 327-88 in es Measured In Situ for a 3D Woven SiC/SiC-Based Composite Material Science and Technology, Corrasion and Environmental Degradation. Vol with Glass Sealant, " Composites: Part A. 30. 587-91(1999 2. Edited by M. Schutze. Wiley-VCH, Weinheim, Germany, 200 J. Davies, " Multiple 2N. S. Jacobson and E J. Opila, "Nonoxide Ceramics" pp. 311-50 in Environ- Microcracking and Tensile Behavior for an Orthogonal 3-D Woven Si-T1-C-O mental Effects on Engineered Materials. Edited by R H Jones. Marcel Dekker. New Fiber/Si-Ti-C-O Matrix Composite. "J. Am. Ceram. Soc., 84 [71 1565-74(2001) York. 2001 Composite with Glass Sealant, J, Mater. Sci, 38, 1-9 (2000) 3621273-7901999
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