Characterization and control of the fiber-matrix interface in ceramic ...

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140 Table 10.9. Thermochemical evaluation of the system containing molybdenum-coated Nicalon fibers. Molybdenum coating 1125K 1. Sic + Si02 + C + MoF6 + 10 H2 L 0.6 Si02 0.7 C + 3.3KPa 0.5 M02C 9.4 H2 + 1.4 SiF4 + 0.6 CO + 0.5 HF + 0.1 CH4 + 0.1 H20 1473K 2. SIC + Si02 + C + MO - 0.4 SIC + Si02 + 1.6 C + 3. Si02 + MOF6 + 10 H2 - lOOKPa 0.2 MogSig 1125K 3.3KPa 1473K 4. Si02 + Mo Si02 + MO lOOKPa 5. Mo + CH3SiCl-j + 10H2 - 6. Sic + Mo - 147 3K lOOKPa 1473K lOOKPa 0.4 Mo + 0.6 Moo2 + SiF4 + 8.2 H2 + 2 HF + 0.8 H20- 0.3 SIC + 0.7 C + 0.2 MogSi3 + 10.1 H2 + 2.8 HC1 + 0.1 SIC1, 0.4 Sic + 0.6 C + 0.2 M05Si3 Nicalon fibers in an HF containing environment 1125K SIC + Si02 + C + HF- 0.75 SIC + Si02 + 1.25 C + 0.5 H2 + 3.3KPa 0.25 SiF4
141 infiltration by the preferred production of Ho5Si3. This also can lead to a carbon enrichment of the fiber surface-intermediate coating boundary. The reactions exacerbate fiber-degradation mechanisms. Molybdenum was not as evident as expected in the Auger spectral analyses (Figure 10.24). The three Mo peaks that occur at 160, 186, and 217 eV were extremely weak compared with those for carbon, silicon, and oxygen (Appendix A). Molybdenum could be found in some areas of the matrix and fibers of a specimen but not in all regions of the same specimen. As predicted by the thermochemical calculations, carbon- enrichment was observed at fiber surfaces and in pull-out grooves. 10.5 Framented CoatinPs on Individual Filaments 10.5.1 -re e-diameter filaments Initial tests were performed on AVCO SCS-6 filaments with only a silicon carbide coating and with a modifying interlayer of pyrolytic carbon. The critical lengths were measured to be 1.67 f 0.58 mm and 7.46 2 0.61 mm, respectively. Using a coating fracture strength of 500 MPa, extrapolated from matrix fracture results recorded during flexure testing, the interfacial shear strengths were calculated to be 3.98 f 0.37 MPa and 0.89 f 0.04 MPa. Figure 10.25 shows fractures as observed through a stereoscopic microscope at 70X. 10.5.2 Nicalon fibers Tensile testing of the Nicalon fibers to determine interfacial frictional stresses was more complex and tedious than for the AVCO filaments. Segmented fracturing was observed on a limited portion of the filaments in each fiber bundle. The lengths of the fragments for
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ORNL/TM-11039 Metals and Ceramics D
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Page 9.3 Composite Fabrication . .
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LIST OF TABLES Table Page 5,l. Prop
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Figure 8.3. 9.1.. 9.2. 9.3. 9.4. 9.
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Figure 10.18. 10.19. 10.20. 10. 21.
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ACKNOWLEDGMENTS The author wishes t
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CWCTERIZATION AND CONTROL OF THE FI
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1. INTRODUCTION During the last sev
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The development of low-density, hig
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3. FABRICATION TECHNIQUES 3.1 Intro
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11 isostatic pressing (HIP), can be
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13 utilizing the comparatively low-
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16 ORN L- DWG 85- 4 i 4 18RS HEAT1
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5. COMPOSITE DESIGN 5.1 Introductio
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21 5,2 Mechanical Considerations Th
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23 GRNL-DWG 88-74 26 Figure 5.1. Th
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25 Equation (6) shows that the stre
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27 of reinforcement. There are two
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29 in strength. Conversely, the fib
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-I_- Table 5.2. Thermally induced a
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33 1.2 ID 0.8 ;.r 1 e fi v 0.6 a4 Q
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35 will affect the interface and, t
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38 fiber-matrix bonding; thus, a fu
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40 In the analysis of the mechanica
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42 1.2 I .o .6 - E f aa '3 0.6 cn 3
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44 will result in the matrix being
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I I MATRIX MATRIX Figure 7.1. Schem
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48 F = 2a2H, where H is the hardnes
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50 OWL-PHOTO 6866-86 i d c I 20pm F
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52 where Af is the surface area of
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54 Figure 7.4. Tensile and shear st
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56 I I I / -c rc -c / . Om / / I /
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58 ORNL-OWG 87-i 8234 F Figure 7.7.
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coating and the distribution of she
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62 O m PHOTO 6676-87 i SIC FIBERS -
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the composite, therefore an interme
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methane as the reactant and is, thu
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9. EXPERIMENTAL PROCEDURES 9.1 Depo
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71 furnace. The furnace is, therefo
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73 further protection. A 6.5-cm-dia
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76 of the specimen slowly decreased
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78 The programmer is also equipped
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80 graphite holders through multipl
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82 temperature by simply switching
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84 ORNk DWG 87- 4494 3 METAL LOGR A
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86 9.5 Fracture Surface Analvsis Th
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88 treated and untreated halves wer
Page 108 and 109: 90 9.8.2 Tensile testinq In an init
Page 110 and 111: 92 ORNL-DUG 85-11767R.2 ? ! 2 f CEN
Page 112 and 113: 94 fracture of individual Nicalon f
Page 114: 96 Figure 10.1. SiC-infiltrated Nic
Page 117 and 118: 99 compared with the dimensions acq
Page 119 and 120: 101 Table 10.3. Strength and modulu
Page 121 and 122: 100 ORNL- DWG 87-1 6292 R CVI-I73 7
Page 123 and 124: BULK FIBER SAMPLE NO. 173: FIBER SU
Page 125 and 126: 107 similar samples show the film o
Page 127 and 128: Figure 10.7. SEM micrographs showin
Page 129 and 130: 111 Table 10.4. Thermochemical eval
Page 131 and 132: 100 ORNL-DUG 87-15969R CVI- 170 75
Page 133 and 134: 115 Analysis conversion of of the m
Page 135 and 136: 117 A 1 I S N 31 N I I'd I LN 3H 3
Page 137 and 138: 119 n 0 W n 9 v P n w- n v
Page 139 and 140: 121 s m f c I m z - Ir 2 a 0 9 In u
Page 141 and 142: Figure 10.14. SEM micrographs of in
Page 143 and 144: J ORNL-DWC 88-6289 z cF u) w I- z O
Page 145 and 146: 127 300 I CVI-480 I I 1 0 R N L-DWG
Page 147 and 148: io0 I I I I CVI- 172 75 - - 0 z v -
Page 149 and 150: 131 RAL 033021 RAL 033023 Figure 10
Page 151: 133 include: the reaction of boron
Page 154 and 155: 136 that BN coatings react with the
Page 156 and 157: 75 7 ORNL-DWG 87-48234 50 - - c5 z
Page 160 and 161: OANL-bwo 88-9025 ORNL-DWG 66-9027 I
Page 162 and 163: 144 uncoated tows were 14 k 2 pm; t
Page 165 and 166: 11. DISCUSSION 11.1 Constituent Pro
Page 167 and 168: 149 The properties of CVD Sic have
Page 169 and 170: 151 11.2.1 Matrix cracking In the N
Page 171 and 172: 153 OWL-DWG 88-10677 CVI- (78 22 I
Page 173 and 174: 155 Table 11.3. Property comparison
Page 175 and 176: 157 a f ““f f- L c I Figure 11.
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Page 179 and 180: 161 The equations demonstrate that
Page 181 and 182: 163 calculations of the matrix depo
Page 183 and 184: 165 In four of the samples, the fib
Page 185 and 186: 167 Table 11.4. Properties of glass
Page 187 and 188: 169 rare-earth magnets and coils to
Page 189 and 190: 171 stress fields along the fiber i
Page 191 and 192: 173 11.3.2 Tensile testinp, The use
Page 193 and 194: 17 5 contraction have been ignored,
Page 195: 177 the system, and when the result
Page 198 and 199: 180 reduces fiber strength. The str
Page 200 and 201: 182 15. R. A. J. Sambell, D. H. Bow
Page 202 and 203: 184 41. A. J. Caputo et al., "Fiber
Page 204 and 205: 186 71, N. F. DOW, Study of Stresse
Page 206 and 207: 188 98. M. H. Rawlins et al., "Inte
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190 125. R. Warren and C-H. Anderss
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192 155. M. F. Doerner and W, D. Ni
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APPENDIX A. AUGER ELECTRON SPECTROS
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APPENDIX B DETAILS OF THE FIBER-SHE
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200 Those for the fiber (primed) ar
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202 89-92. 93. 94. 95" 96. 97. 98-9
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204 130-133. E. I. DUPONT DE NEMOUR
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206 173. NATIONAL ACADEMY OF SCIENC
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208 203 - 204. 20s. 206 - 207. 208.
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