SiC (Optical) SSIC
Grade
SSIC = pressureless sintered α-SiC
Pick pressureless sintered α-phase blanks for medium and large lightweighted mirrors — no free silicon, high strength and chemical resistance — but clad with CVD or Si before polishing to close residual micropores.
Values for the SSIC condition
Other SiC (Optical) tempers and conditions
SiC (Optical) is listed in 3 conditions; see the grade overview at SiC (Optical).
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
RB-SiC / SiSiC | Choose the reaction-bonded, silicon-infiltrated blank for large near-net-shape mirrors with complex lightweighting ribs: low firing shrinkage and cost, but 8–15 % free silicon cuts conductivity and alkali resistance. | — | — | — | 2,000 HV | 160 W/m·K |
SSICThis page Pressureless sintered α-SiC | Pick pressureless sintered α-phase blanks for medium and large lightweighted mirrors — no free silicon, high strength and chemical resistance — but clad with CVD or Si before polishing to close residual micropores. | — | — | — | 2,400 HV | 130 W/m·K |
hot pressed / HIPed SiC (highest strength optical grade) | Use the hot-pressed or HIPed grade for small-aperture, highly stressed or high-power laser mirrors: fully dense with the highest strength and fracture toughness, but simple shapes only and costly. | — | — | — | 2,600 HV | 110 W/m·K |
What is SiC (Optical) SSIC?
SiC (Optical) SSIC is SiC (Optical) in the SSIC grade — pick pressureless sintered α-phase blanks for medium and large lightweighted mirrors — no free silicon, high strength and chemical resistance — but clad with CVD or Si before polishing to close residual micropores. SiC (Optical) SSIC has a tensile strength of 300 MPa (43.5 ksi), stronger than 89% of glass grades. Elongation at break is 0% and the elastic modulus is 410 GPa (59.5 Msi). SiC (Optical) SSIC has a density of 3.13 g/cm³ (0.113 lb/in³), heavier than 58% of glass grades. It melts at 2,730°C (4,946 °F).
Advantages
- Tough — resists crack growth — 3.2 MPa·√m (2.91 ksi·√in), better than 100% of glass grades
- Stiff — 410 GPa (59.5 Msi), better than 98% of glass grades
- High service temperature — 1,600°C (2,912 °F), better than 98% of glass grades
- Conducts heat well — 130 W/m·K (75.1 BTU/hr·ft·°F), better than 97% of glass grades
- Good corrosion resistance — 94/100, better than 88% of glass grades
Limitations
- Difficult to machine — 3/100, worse than 97% of glass grades
- High embodied carbon — 18 kg CO₂/kg, worse than 76% of glass grades
SiC (Optical) SSIC properties
Typical room-temperature values for SiC (Optical) SSIC; 17 are specific to this condition. Other listed values are SiC (Optical) reference data and may not represent this condition. Bars are the position among glass grades.
Physical4
SiC (Optical) SSIC has a density of 3.13 g/cm³ (0.113 lb/in³), heavier than 58% of glass grades. It melts at 2,730°C (4,946 °F).
Mechanical12
SiC (Optical) SSIC has a tensile strength of 300 MPa (43.5 ksi), stronger than 89% of glass grades. Elongation at break is 0% and the elastic modulus is 410 GPa (59.5 Msi).
Thermal5
SiC (Optical) SSIC is rated for continuous service to 1,600°C (2,912 °F). It conducts heat at 130 W/m·K (75.1 BTU/hr·ft·°F), better than 97% of glass grades. Thermal expansion is 4 µm/m·K (2.22 µin/in·°F).
Electrical3
SiC (Optical) SSIC has an electrical resistivity of 100 Ω·m.
Chemical & Environmental2
Corrosion resistance is excellent (94/100), better than 88% of glass grades.
Sustainability4
Producing a kilogram of SiC (Optical) SSIC takes about 250 MJ of energy and emits 18 kg of CO₂ — more than 76% of glass grades. Typical recycled content is 0%.
Manufacturability3
SiC (Optical) SSIC's machinability is not recommended (3/100, worse than 97% of glass grades).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SiC (Optical) SSIC
Is SiC (Optical) easy to machine?
Rough machine in the green or preform state with carbide tooling to cut lightweighting back ribs. After sintering only diamond grinding and ultrasonic or laser-assisted machining are practical, so keep stock removal to a minimum.
Can SiC (Optical) be welded?
Not fusion weldable; sections are joined by reaction bonding (silicon infiltration), active-metal brazing or epoxy bonding, and a CVD SiC layer can be deposited over the joint.
Can SiC (Optical) be formed, bent or molded?
Near-net shapes are produced by gel casting, slip casting, dry pressing or 3D printing of carbon/SiC preforms. RB-SiC fires with near-zero shrinkage, while SSiC shrinks about 17-20% and needs compensation.
What surface finishes work on SiC (Optical)?
Work through rough grinding, fine grinding, diamond lapping and then CMP or ion-beam figuring. Porous sintered bodies are usually clad with CVD SiC or Si before polishing, then coated with Al or Ag plus a protective overcoat to form the reflective surface.
SiC (Optical) 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 |
|---|---|---|
| SiSi in stoichiometric SiC; RB-SiC also has 8–15% free Si | 69 – 70.5 | 70 |
| CRB-SiC/SSiC may contain <1% free carbon | 29 – 30.5 | 29.9 |
| BSSiC sintering aid (B+C); absent in CVD grade | 0 – 0.5 | 0.3 |
| SiCbalance is the SiC phase | balance | — |
SiC (Optical) SSIC — frequently asked
What is SiC (Optical) SSIC used for?
SiC (Optical) SSIC is typically used for space telescope mirrors, high-power laser mirror substrates and precision optical benches. In short: high specific stiffness mirror material; 300 W/m·K thermal stability; near-net formed, diamond finished.
What is the tensile strength of SiC (Optical) SSIC?
SiC (Optical) SSIC has a typical tensile strength of 300 MPa (43.5 ksi) — stronger than 89% of glass grades. Strength varies by condition: see the 3 listed tempers.
Is SiC (Optical) SSIC easy to machine?
Not especially — machinability is rated not recommended (3/100, worse than 97% of glass grades). Rough machine in the green or preform state with carbide tooling to cut lightweighting back ribs. After sintering only diamond grinding and ultrasonic or laser-assisted machining are practical, so keep stock removal to a minimum.
Can SiC (Optical) SSIC be welded?
Not fusion weldable; sections are joined by reaction bonding (silicon infiltration), active-metal brazing or epoxy bonding, and a CVD SiC layer can be deposited over the joint.
What surface finishes work on SiC (Optical) SSIC?
Work through rough grinding, fine grinding, diamond lapping and then CMP or ion-beam figuring. Porous sintered bodies are usually clad with CVD SiC or Si before polishing, then coated with Al or Ag plus a protective overcoat to form the reflective surface.
Can SiC (Optical) SSIC be formed, bent or molded?
Near-net shapes are produced by gel casting, slip casting, dry pressing or 3D printing of carbon/SiC preforms. RB-SiC fires with near-zero shrinkage, while SSiC shrinks about 17-20% and needs compensation.
What is the maximum service temperature of SiC (Optical) SSIC?
SiC (Optical) SSIC is rated for continuous use to about 1,600°C (2,912 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- CVD Silicon Carbide for Optics and Semiconductor Applications — Rohm and Haas / DuPont Electronic Solutions (2019)
- Silicon Carbide Material Properties (SSiC / SiSiC) — CoorsTek (2021)
- SiC Lightweight Mirror Substrates — Kyocera / Schott (Cesic-class SiC optics) (2020)
- ASM Engineered Materials Handbook Vol.4: Ceramics and Glasses — ASM International (1991)
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.