SiC (Optical)
SiC (Optical) is polycrystalline silicon carbide supplied as CVD, pressureless-sintered (SSiC), reaction-bonded (RBSiC) and hot-pressed (HPSiC) grades for mirror substrates and optical structures.
Reference datasheet — SiC (Optical) is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
SiC (Optical) tempers and conditions
SiC (Optical) is supplied in 3 conditions, soft to hard.
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 | |||
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 |
Supply forms, finishes and certifications
Ways SiC (Optical) is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
CVDDefault | CVD-SiC | Coating |
What is SiC (Optical)?
SiC (Optical) is polycrystalline silicon carbide supplied as CVD, pressureless-sintered (SSiC), reaction-bonded (RBSiC) and hot-pressed (HPSiC) grades for mirror substrates and optical structures. It is chosen for a 466 GPa modulus, 300 W/m·K thermal conductivity, 3.21 g/cm3 density and near-inert chemistry (corrosion score 95), giving high specific stiffness and thermal stability to 1500 °C in lightweighted mirrors and benches. It cannot be melt-welded and post-sinter machining is diamond-only (machinability 3), so blanks are near-net formed; porous sintered bodies need a CVD SiC or Si cladding before polishing. SiC (Optical) has a density of 3.21 g/cm³ (0.116 lb/in³), heavier than 63% of glass grades. It melts at 2,730°C (4,946 °F). SiC (Optical) 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 466 GPa (67.6 Msi).
What is SiC (Optical) used for?
- space telescope mirrors
- high-power laser mirror substrates
- precision optical benches
Advantages
- Stiff — 466 GPa (67.6 Msi), better than 98% of glass grades
- Tough — resists crack growth — 3 MPa·√m (2.73 ksi·√in), better than 98% of glass grades
- Conducts heat well — 300 W/m·K (173.3 BTU/hr·ft·°F), better than 98% of glass grades
- High service temperature — 1,500°C (2,732 °F), better than 97% of glass grades
- Good corrosion resistance — 92/100, better than 81% 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) properties
Typical room-temperature values; bars are the position among glass grades.
Physical4
SiC (Optical) has a density of 3.21 g/cm³ (0.116 lb/in³), heavier than 63% of glass grades. It melts at 2,730°C (4,946 °F).
Mechanical12
SiC (Optical) 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 466 GPa (67.6 Msi).
Thermal5
SiC (Optical) is rated for continuous service to 1,500°C (2,732 °F). It conducts heat at 300 W/m·K (173.3 BTU/hr·ft·°F), better than 98% of glass grades. Thermal expansion is 2.2 µm/m·K (1.22 µin/in·°F).
Electrical3
SiC (Optical) has an electrical resistivity of 1,000 Ω·m.
Chemical & Environmental2
Corrosion resistance is excellent (92/100), better than 81% of glass grades.
Sustainability4
Producing a kilogram of SiC (Optical) 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)'s machinability is not recommended (3/100, worse than 97% of glass grades).
Common Calculations4
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the glass family
Yield strength against density for every glass grade FabDigit runs. SiC (Optical) is highlighted; hover a dot for its name, or open the interactive family chart.
Working with SiC (Optical)
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.
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 |
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.
Equivalent designations
Standards and trade names that resolve to SiC (Optical) in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Also called
- SiC
How much does SiC (Optical) cost?
SiC (Optical) is a high-cost glass ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
SiC (Optical) — frequently asked
What is SiC (Optical) used for?
SiC (Optical) 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)?
SiC (Optical) 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) 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) 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)?
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) 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)?
SiC (Optical) is rated for continuous use to about 1,500°C (2,732 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does SiC (Optical) cost?
SiC (Optical) is a high-cost glass ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
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; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.