Mullite/Mullite
Mullite/Mullite is an all-oxide ceramic-matrix composite with mullite (aluminosilicate) fibers in a mullite matrix, so there is no oxidation or fiber-degradation concern in air up to a maximum service temperature of 1200 °C.
Reference datasheet — Mullite/Mullite 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.
Values for the 2D-WOVEN condition
Mullite/Mullite grades and fills
Mullite/Mullite is supplied in 4 conditions, soft to hard. 2D-WOVEN is the default FabDigit quotes; the values on this page are for it.
Compare all 4 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Chopped / short mullite fiber reinforced mullite | Use chopped short-fibre reinforcement for low-cost complex shapes such as insulation blocks, tooling and seals; it is quasi-isotropic but only 45 MPa, far below continuous-fibre strength and toughness. | 45 | 0.15 | ||
Filament-wound highly porous oxide CMC | Pick the filament-wound form with 25–35 % matrix porosity for bodies of revolution such as liners, nozzles and combustor shells; thermal shock and damage tolerance are excellent, strength and gas tightness low. | 100 | 0.4 | ||
2D-WOVENDefault 2D woven mullite fabric / porous mullite matrix laminate | Use for plate and shell parts: Nextel 550/720 plain- or satin-weave layup, slurry infiltrated and sintered, gives balanced in-plane properties at 130 MPa and service to 1200 °C. | 130 | 0.35 | ||
Monolithic (unreinforced) sintered mullite | Pick the unreinforced sintered baseline when only high-temperature dimensional stability and insulation to 1500 °C are needed; strength is higher but it is brittle with no thermal-shock tolerance. |
Supply forms, finishes and certifications
Ways Mullite/Mullite is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
SEALED | Sealcoated / dense surface layer | Surface finish |
What is Mullite/Mullite?
Mullite/Mullite is an all-oxide ceramic-matrix composite with mullite (aluminosilicate) fibers in a mullite matrix, so there is no oxidation or fiber-degradation concern in air up to a maximum service temperature of 1200 °C. It is chosen for hot-gas hardware that must survive thermal cycling at low weight (density 2.7 g/cm³, thermal conductivity 2 W/m·K), and is supplied as 2D woven laminates, WHIPOX-type wound structures, chopped-fiber and sealed grades, and monolithic sections. Mechanical capability is modest — 130 MPa tensile strength, 70 GPa modulus, 0.35 % elongation — and the porous matrix can absorb moisture unless surface-sealed. Where higher strength or service above 1200 °C is needed, SiC/SiC is the nearest alternative. Mullite/Mullite has a density of 2.7 g/cm³ (0.0975 lb/in³), heavier than 85% of composite grades. Mullite/Mullite has a tensile strength of 130 MPa (18.9 ksi), weaker than 59% of composite grades. Elongation at break is 0.35% and the elastic modulus is 70 GPa (10.2 Msi).
What is Mullite/Mullite used for?
- gas turbine combustor liners
- industrial kiln furniture
- burner nozzles
- exhaust components
Advantages
- High service temperature — 1,200°C (2,192 °F), better than 94% of composite grades
- Good UV / weathering resistance — 100/100, better than 93% of composite grades
- Good corrosion resistance — 90/100, better than 85% of composite grades
Limitations
- Absorbs moisture — dry before molding — 8%, worse than 99% of composite grades
- Limited ductility — 0.35%, worse than 92% of composite grades
- High embodied carbon — 40 kg CO₂/kg, worse than 87% of composite grades
- Heavy — 2.7 g/cm³ (0.0975 lb/in³), worse than 85% of composite grades
- Difficult to machine — 15/100, worse than 84% of composite grades
Mullite/Mullite properties
Typical room-temperature values for Mullite/Mullite-2D-WOVEN; bars are the position among composite grades.
Physical2
Mullite/Mullite has a density of 2.7 g/cm³ (0.0975 lb/in³), heavier than 85% of composite grades.
Mechanical11
Mullite/Mullite has a tensile strength of 130 MPa (18.9 ksi), weaker than 59% of composite grades. Elongation at break is 0.35% and the elastic modulus is 70 GPa (10.2 Msi).
Thermal6
Mullite/Mullite is rated for continuous service to 1,200°C (2,192 °F). It conducts heat at 2 W/m·K (1.16 BTU/hr·ft·°F), better than 58% of composite grades. Thermal expansion is 5.3 µm/m·K (2.94 µin/in·°F).
Electrical5
Mullite/Mullite is an electrical insulator with a dielectric strength of 8 kV/mm (203.2 V/mil) and a resistivity of 1×10¹⁰ Ω·m.
Chemical & Environmental3
Corrosion resistance is excellent (90/100), better than 85% of composite grades. UV resistance is excellent.
Sustainability3
Producing a kilogram of Mullite/Mullite takes about 550 MJ of energy and emits 40 kg of CO₂ — more than 86% of composite grades. Typical recycled content is 0%.
Manufacturability2
Mullite/Mullite's machinability is poor (15/100, worse than 84% of composite 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 composite family
Yield strength against density for every composite grade FabDigit runs. Mullite/Mullite is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Mullite/Mullite
Is Mullite/Mullite easy to machine?
After sintering, only diamond grinding, ultrasonic machining or abrasive waterjet cutting are practical. Avoid high feed rates, which cause delamination and fiber pull-out; chamfer all hole edges.
Can Mullite/Mullite be welded?
Not weldable; join by mechanical fastening (ceramic or superalloy bolts with compliant spacers), oxide ceramic adhesive, or co-firing as a single integral part.
Can Mullite/Mullite be formed, bent or molded?
Fabric layup with slurry impregnation and vacuum bagging, filament winding, or slip casting, followed by air sintering at 1100–1300 °C. Parts are near-net shape, so sintering shrinkage must be compensated in the tooling.
Mullite/Mullite 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 |
|---|---|---|
| Al2O3Combined fiber (Nextel 550 ~73%, 720 ~85%) and matrix value | 70 – 85 | 75 |
| B2O3Sintering aid in some alumina-aluminosilicate fibers | 0 – 1 | 0.2 |
| Fe2O3+Na2O+K2OImpurities; affect high-temperature creep | 0 – 0.5 | 0.2 |
| SiO2Mullite stoichiometry 3Al2O3.2SiO2 is 71.8/28.2 | ≥ 15 (balance) |
What surface finishes work on Mullite/Mullite?
An alumina or mullite sealing coat, or an FGI-type coating, can be applied to improve erosion resistance and limit moisture pickup. Surfaces normally retain the fabric texture and are not polished.
How much does Mullite/Mullite cost?
Mullite/Mullite is a high-cost composite ($$$$), 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.
Mullite/Mullite — frequently asked
What is Mullite/Mullite used for?
Mullite/Mullite is typically used for gas turbine combustor liners, industrial kiln furniture, burner nozzles and exhaust components. In short: oxidation-immune oxide CMC; low thermal conductivity, 1200 °C; lower cost than SiC/SiC.
What is the tensile strength of Mullite/Mullite?
Mullite/Mullite has a typical tensile strength of 130 MPa (18.9 ksi) — weaker than 59% of composite grades. Strength varies by condition: see the 4 listed tempers.
Is Mullite/Mullite easy to machine?
Not especially — machinability is rated poor (15/100, worse than 84% of composite grades). After sintering, only diamond grinding, ultrasonic machining or abrasive waterjet cutting are practical. Avoid high feed rates, which cause delamination and fiber pull-out; chamfer all hole edges.
Can Mullite/Mullite be welded?
Not weldable; join by mechanical fastening (ceramic or superalloy bolts with compliant spacers), oxide ceramic adhesive, or co-firing as a single integral part.
What surface finishes work on Mullite/Mullite?
An alumina or mullite sealing coat, or an FGI-type coating, can be applied to improve erosion resistance and limit moisture pickup. Surfaces normally retain the fabric texture and are not polished.
Can Mullite/Mullite be formed, bent or molded?
Fabric layup with slurry impregnation and vacuum bagging, filament winding, or slip casting, followed by air sintering at 1100–1300 °C. Parts are near-net shape, so sintering shrinkage must be compensated in the tooling.
What is the maximum service temperature of Mullite/Mullite?
Mullite/Mullite is rated for continuous use to about 1,200°C (2,192 °F), and briefly to 1,300°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does Mullite/Mullite cost?
Mullite/Mullite is a high-cost composite ($$$$), 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
- ASM Handbook Vol.21: Composites — Oxide/Oxide Ceramic Matrix Composites — ASM International (2001)
- 3M Nextel Ceramic Textiles Technical Notebook (550/610/720 fibers) — 3M (2018)
- COI Ceramics / ATK Oxide-Oxide CMC (AS-N720) property sheet — COI Ceramics (2015)
- WHIPOX all-oxide CMC property publications — DLR Institute of Materials Research (2012)
- Mullite ceramic technical data (density, MOR, CTE, thermal conductivity) — CoorsTek / Kyocera (2020)
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.