C/C HTC
Grade
also Carbon-Carbon
HTC = high thermal conductivity, mesophase-pitch fiber C/C
Mesophase-pitch fiber reinforcement gives in-plane conductivity several times that of copper per unit mass — for spacecraft radiators, heat spreaders and leading edges.
Values for the HTC condition
Other C/C grades and fills
C/C is listed in 7 conditions; see the grade overview at C/C.
Compare all 7 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Needled felt (quasi-3D) C/C, thermal-field grade | Low-cost needled non-woven preform densified to medium density — the standard for PV/semiconductor furnace crucibles, guide cylinders and insulation hardware. | — | 60 | 0.4 | — |
High-purity (halogen-purified) C/C, ash < 20 ppm | Halogen-gas purified grade for silicon single-crystal pulling, SiC epitaxy and semiconductor furnaces where metal contamination is unacceptable. | — | 70 | 0.4 | — |
HTCThis page High thermal conductivity, mesophase-pitch fiber C/C | Mesophase-pitch fiber reinforcement gives in-plane conductivity several times that of copper per unit mass — for spacecraft radiators, heat spreaders and leading edges. | — | 80 | 0.25 | — |
Friction (aircraft/racing brake disc) grade C/C | Densified needled/CVI disc stock tuned for stable friction coefficient and huge heat-sink capacity in aircraft and motorsport brakes. | — | 80 | 0.4 | — |
Resin/pitch impregnation and carbonization matrix | Cheaper, faster route to medium-density C/C for tooling, fixtures and non-critical thermal-field parts; more residual porosity and lower conductivity than CVI. | — | 90 | 0.4 | — |
Multi-directional (3D/4D) woven or braided C/C preform | Choose when through-thickness strength and delamination resistance matter — rocket nozzle throats, nose tips, thick structural parts. | — | 130 | 0.7 | — |
Chemical vapor infiltration (pyrolytic carbon) matrix | Highest matrix quality and thermal conductivity, cleanest chemistry — pick for brakes, thermal management and high-purity furnace parts, at the cost of long densification cycles. | — | 140 | 0.6 | — |
What is C/C HTC?
C/C HTC is C/C in the HTC grade — mesophase-pitch fiber reinforcement gives in-plane conductivity several times that of copper per unit mass — for spacecraft radiators, heat spreaders and leading edges. C/C HTC has a tensile strength of 80 MPa (11.6 ksi), weaker than 77% of composite grades. Elongation at break is 0.25% and the elastic modulus is 110 GPa (16 Msi). C/C HTC has a density of 1.9 g/cm³ (0.0686 lb/in³), heavier than 72% of composite grades.
Advantages
- Conducts heat well — 250 W/m·K (144.4 BTU/hr·ft·°F), better than 97% of composite grades
- Good UV / weathering resistance — 100/100, better than 93% of composite grades
- High service temperature — 450°C (842 °F), better than 85% of composite grades
Limitations
- Limited ductility — 0.25%, worse than 97% of composite grades
- High embodied carbon — 60 kg CO₂/kg, worse than 96% of composite grades
- Hard to polish — 25/100, worse than 76% of composite grades
C/C HTC properties
Typical room-temperature values for C/C HTC; 15 are specific to this condition. Other listed values are C/C reference data and may not represent this condition. Bars are the position among composite grades.
Physical1
C/C HTC has a density of 1.9 g/cm³ (0.0686 lb/in³), heavier than 72% of composite grades.
Mechanical11
C/C HTC has a tensile strength of 80 MPa (11.6 ksi), weaker than 77% of composite grades. Elongation at break is 0.25% and the elastic modulus is 110 GPa (16 Msi).
Thermal6
C/C HTC is rated for continuous service to 450°C (842 °F). It conducts heat at 250 W/m·K (144.4 BTU/hr·ft·°F), better than 97% of composite grades. Thermal expansion is -0.2 µm/m·K (-0.111 µin/in·°F).
Electrical2
C/C HTC has an electrical resistivity of 4×10⁻⁶ Ω·m.
Chemical & Environmental3
Corrosion resistance is very good (80/100), better than 54% of composite grades. UV resistance is excellent.
Sustainability4
Producing a kilogram of C/C HTC takes about 1,000 MJ of energy and emits 60 kg of CO₂ — more than 97% of composite grades. Typical recycled content is 0%.
Manufacturability2
C/C HTC's machinability is poor (30/100, worse than 54% of composite grades).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with C/C HTC
Is C/C easy to machine?
Machine dry with diamond-coated or PCD tools at high speed/low feed and full dust extraction; support laminates to avoid edge delamination, and re-coat any surface where an antioxidation layer is cut through.
Can C/C be welded?
Not weldable — join by carbon/graphite cement, brazing to metals with active Ti/Zr-bearing fillers, or mechanical carbon-composite bolts and pins.
Can C/C be formed, bent or molded?
Net-shape is set at the preform stage (cloth layup, filament winding, braiding or needled felt) followed by CVI and/or resin/pitch impregnation–carbonization cycles and 2000–2800 °C graphitization; expect weeks of densification and only minor final machining allowance.
What surface finishes work on C/C?
Common finishes are CVD SiC conversion coating with phosphate/borosilicate glass sealer for oxidation protection, halogen purification for semiconductor use, and pyrolytic-carbon sealing for particle-free surfaces; no plating or anodizing applies.
C/C chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| carbon fiber (PAN or mesophase pitch)volume fraction of reinforcement; woven cloth, needled felt or multi-directional preform | 30 – 60 | 45 |
| Ctotal carbon content | 99 – 100 | 99.9 |
| ash (metallic impurities)< 20 ppm in halogen-purified HP grade | 0 – 0.3 | 0.05 |
| SiC (coating only)0.05–0.5 mm CVD/pack-cementation layer on oxidation-protected variants | ≈ 0 | 0 |
| carbon matrix (pyrolytic carbon / resin-CVI, LPI or hybrid densification; residual open porosity typically 5–15 % | balance | — |
C/C HTC — frequently asked
What is C/C HTC used for?
C/C HTC is typically used for rocket nozzle throats and exit cones, aircraft brake discs, re-entry vehicle nose tips, hot-pressing dies and high-temperature furnace fixtures. In short: lowest-density CMC; highest conductivity in family; 450 °C uncoated air limit.
What is the tensile strength of C/C HTC?
C/C HTC has a typical tensile strength of 80 MPa (11.6 ksi) — weaker than 77% of composite grades. Strength varies by condition: see the 7 listed tempers.
Is C/C HTC easy to machine?
Not especially — machinability is rated poor (30/100, worse than 54% of composite grades). Machine dry with diamond-coated or PCD tools at high speed/low feed and full dust extraction; support laminates to avoid edge delamination, and re-coat any surface where an antioxidation layer is cut through.
Can C/C HTC be welded?
Not weldable — join by carbon/graphite cement, brazing to metals with active Ti/Zr-bearing fillers, or mechanical carbon-composite bolts and pins.
What surface finishes work on C/C HTC?
Common finishes are CVD SiC conversion coating with phosphate/borosilicate glass sealer for oxidation protection, halogen purification for semiconductor use, and pyrolytic-carbon sealing for particle-free surfaces; no plating or anodizing applies.
Can C/C HTC be formed, bent or molded?
Net-shape is set at the preform stage (cloth layup, filament winding, braiding or needled felt) followed by CVI and/or resin/pitch impregnation–carbonization cycles and 2000–2800 °C graphitization; expect weeks of densification and only minor final machining allowance.
What is the maximum service temperature of C/C HTC?
C/C HTC is rated for continuous use to about 450°C (842 °F), and briefly to 2,500°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- ASM Handbook Vol. 21: Composites — Carbon-Carbon Composites — ASM International (2001)
- Carbon-Carbon Materials and Composites (Buckley & Edie) — Noyes Publications / NASA RP-1254 (1993)
- SIGRABOND carbon fiber reinforced carbon — SGL Carbon (2022)
- Carbon-fiber reinforced carbon (CFC) product data — Schunk Carbon Technology (2021)
- C/C composite CX series data — Toyo Tanso (2020)
- ASTM C1341 — Flexural Properties of Continuous Fiber-Reinforced Advanced Ceramic Composites — ASTM (2013)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.