40TH ANNIVERSARY TABLE III Details of manufacture, elemental composition and approximate cost of all three generations of SiC based fibres maximum Cross linki Elemental composition Trade mark Manufacture temperature (wt%) (g/cm)(um)(US S/g First Gen. Nicalon 200 Nippon Carbon Oxygen 1200°C 56si+32C+120 2.5514 2000 Tyranno LOX-M Ube Ind. 1200°C 54Si+32C+120+2T24811 Second Hi-Nicalon Electron °C 1300° 625Si+37C+0502.7412 8000 Gen irradiation Tyranno LOX-E Ube Ind Electron 1300°C 55Si+37.5+5.50+2T2.3911 radiation Tyranno ZM Ube Ind Oxygen 1300°C 57Si+345C+7.50+248 11 1500 Tyranno ZE Ube Ind Electron 1300°C 585Si+38.5C+20+2.5511 Third Gen. Tyranno SA 68Si+32C+0.6Al Tyranno SA 3 Ind 68Si+32C+06Al Sylramic COI ceramics 67Si+29c+0.80+3.0 23B+04N+2.1T Sylramic iB COI Ceramics Oxygen >1700°CN/A 3.05 002 Hi-Nicalon Type-S Nippon Carbon Electron 1500°C 69Si+31C+0.20 3.05 3000 irradiation TABLE IV Details of mechanical and thermal properties of all three generations of SiC based fibres Thermal expansion Room om temperature coefficient, ppm/C(to emal conductivity W/m tempera gs modulus Trade mark Manufacturer 1000°C)[1 K[15 rength(GPa)(GPa) First gen Nicalon 200 Nippon Carbon 3.2 Second Gen. Hi-Nicalon Nippon Carbon 3.5 Tyranno LOX-E Ube Ind Tyranno ZM Third gen Tyranno SA3 Sylramic iBN Hi-Nicalon Type-s Nippon Carbon NA 3. Mechanical behaviour of first generation Sic The behaviour of the first generation fibres remains lin- fibres early elastic up to 1250C but short term strength begins to At room temperature the fibres show linearly elastic be- fall around 1000oC. There is a difference, particularly for haviour. The variation in fibre diameter along individual the Tyranno LOX-M fibre, when tested in air or in argon, fibres makes the measurement of stress and modulus in- with an earlier onset of strength reduction being observed herently difficult which explains some discrepancies in the when the fibres are tested in air indicating a higher sen- published data for these fibres which in any case have been sitivity to carbon oxidation of the surfaces. However the improved since their introduction. Some typical property oxidation of the Nicalon 100 series fibres could be bene- data for first generation SiC fibres can be found in Tables ficial particularly under long term loading conditions as it II and IV. It should be noted that the Tyranno LOX-M, al- slowed internal decomposition of the fibres [17]. Growth nerally available. Fig. 5 shows of silica is observed on the surfaces of both fibre the fracture morphology of a first generation Nicalon fi- they are heated in air at 1200C and above in air. This bre broken in tension [15]. It can be seen that the fracture layer can have an irregular thickness along the fibre and suggests a glassy structure of the fibre. A critical stress pores are formed at the silica/SiC fibre interface and pores intensity factor K lc of 2 MPa.m was determined for the can be formed at 1450C which induce local decohesion Nicalon NLM-202 fibre which is more characteristic of of the silica layer from the fibre. These pores are pro glass than bulk Sic [16] duced by the outgassing of carbon monoxide from the40TH ANNIVERSARY T A B L E I I I Details of manufacture, elemental composition and approximate cost of all three generations of SiC based fibres Trade mark Manufacturer Cross linking method Approximate maximum production temperature Elemental composition (wt%) Density (g/cm3) Average diameter (µm) Cost (US $/kg) First Gen. Nicalon 200 Nippon Carbon Oxygen 1200◦C 56Si + 32C + 12O 2.55 14 2000 Tyranno LOX-M Ube Ind. Oxygen 1200◦C 54Si + 32C +12O + 2Ti 2.48 11 1250 Second Gen. Hi-Nicalon Nippon Carbon Electron irradiation 1300◦C 62.5Si + 37C +O.5O 2.74 12 8000 Tyranno LOX-E Ube Ind. Electron irradiation 1300◦C 55Si + 37.5 +5.5O + 2Ti 2.39 11 N/A Tyranno ZM Ube Ind. Oxygen 1300◦C 57Si + 34.5C + 7.5O + 1Zr 2.48 11 1500 Tyranno ZE Ube Ind. Electron irradiation 1300◦C 58.5Si + 38.5C + 2O + 1Zr 2.55 11 N/A Third Gen. Tyranno SA 1 Ube Ind. Oxygen >1700◦C 68Si + 32C +0.6Al 3.02 11 N/A Tyranno SA 3 Ube Ind. Oxygen >1700◦C 68Si + 32C +0.6Al 3.1 7.5 5000 Sylramic COI ceramics Oxygen >1700◦C 67Si + 29C +0.8O + 2.3B +0.4N +2.1Ti 3.05 10 10000 Sylramic iBN COI Ceramics Oxygen >1700◦C N/A 3.05 10 >10000 Hi-Nicalon Type-S Nippon Carbon Electron irradiation >1500◦C 69Si + 31C + 0.2O 3.05 12 13000 T A B L E I V Details of mechanical and thermal properties of all three generations of SiC based fibres Trade mark Manufacturer Thermal expansion coefficient, ppm/◦C (to 1000◦C) [15] Room temperature axial thermal conductivity W/m K [15] Room temperature strength (GPa) Room temperature Young’s modulus (GPa) First Gen. Nicalon 200 Nippon Carbon 3.2 3 3 200 Tyranno LOX-M Ube Ind. 3.1 1.5 3.3 185 Second Gen. Hi-Nicalon Nippon Carbon 3.5 8 2.8 270 Tyranno LOX-E Ube Ind. NA NA 2.9 200 Tyranno ZM Ube Ind. NA 2.5 3.4 200 Tyranno ZE Ube Ind. NA NA 3.5 233 Third Gen. Tyranno SA1 Ube Ind. NA 65 2.8 375 Tyranno SA3 Ube Ind. NA 65 2.9 375 Sylramic COI Ceramics 5.4 46 3.2 400 Sylramic iBN COI Ceramics 5.4 >46 3.5 400 Hi-Nicalon Type-S Nippon Carbon NA 18 2.5 400 3. Mechanical behaviour of first generation SiC fibres At room temperature the fibres show linearly elastic be￾haviour. The variation in fibre diameter along individual fibres makes the measurement of stress and modulus in￾herently difficult which explains some discrepancies in the published data for these fibres which in any case have been improved since their introduction. Some typical property data for first generation SiC fibres can be found in Tables III and IV. It should be noted that the Tyranno LOX-M, al￾though still made, is not generally available. Fig. 5 shows the fracture morphology of a first generation Nicalon fi- bre broken in tension [15]. It can be seen that the fracture suggests a glassy structure of the fibre. A critical stress intensity factor K1c of 2 MPa.m1/2 was determined for the Nicalon NLM-202 fibre which is more characteristic of glass than bulk SiC [16]. The behaviour of the first generation fibres remains lin￾early elastic up to 1250◦C but short term strength begins to fall around 1000◦C. There is a difference, particularly for the Tyranno LOX-M fibre, when tested in air or in argon, with an earlier onset of strength reduction being observed when the fibres are tested in air indicating a higher sen￾sitivity to carbon oxidation of the surfaces. However the oxidation of the Nicalon 100 series fibres could be bene- ficial particularly under long term loading conditions as it slowed internal decomposition of the fibres [17]. Growth of silica is observed on the surfaces of both fibres when they are heated in air at 1200◦C and above in air. This layer can have an irregular thickness along the fibre and pores are formed at the silica/SiC fibre interface and pores can be formed at 1450◦C which induce local decohesion of the silica layer from the fibre. These pores are pro￾duced by the outgassing of carbon monoxide from the 826