Ceramic tubes protect, isolate and carry. They serve as thermocouple sheaths, furnace muffles, insulating bushes and fluid paths where metal would corrode, creep or conduct.
Fused silica tubes are the standard for rapid thermal cycling and for UV transmission. Expansion of 0.5 ×10⁻⁶/K means a tube can be pulled from a 1000°C furnace and quenched without cracking, which no other ceramic here will survive.
Fused silica expands by only 0.5 ×10⁻⁶/K, so it can go from red heat to cold water without cracking. It is an excellent electrical insulator, transmits UV, and its amorphous structure gives a very smooth non-porous surface.
Strength is low for a ceramic at 50-70 MPa and the material is relatively soft. Above 1000°C it starts to devitrify, losing both transparency and thermal shock resistance.
Specifications
| Outer diameter | 3-150 mm |
| Inner diameter | 1-120 mm |
| Length | up to 600 mm |
| Minimum wall thickness | 0.5 mm |
| Concentricity | 0.02 mm |
| Bore finish | Ra 0.4 µm, honed Ra 0.2 µm |
| Ends | square cut, chamfered, flanged or closed one end |
Fused Silica Properties
| Composition | Amorphous silicon dioxide |
| Density | 2.20 g/cm³ |
| Vickers hardness | 600-800 HV |
| Flexural strength | 50-70 MPa |
| Fracture toughness | 0.7-1.0 MPa·m½ |
| Max. service temperature | 1000°C (1200°C short term) |
| Thermal conductivity | 1.4 W/m·K |
| Thermal expansion (20-1000°C) | 0.5 ×10⁻⁶/K |
Machining and Tolerances
Tubes are extruded, isostatically pressed or slip cast depending on size and quantity, then ground on the outside and honed internally. Long thin-wall tubes are the most distortion-prone parts we make, so we rough grind, allow the part to relax, then finish grind.
Where It Is Used
- Thermocouple protection sheaths and furnace muffles
- Insulating bushes through heated panels and vacuum chambers
- Fluid and slurry transport in corrosive or abrasive service
- Lamp, laser and UV equipment bodies
- High-voltage insulators and standoffs
Frequently Asked Questions
What is the thinnest wall you can produce?
0.5 mm is the practical floor for most materials and lengths. Below that, yield drops sharply during firing and grinding, so we review the drawing and usually suggest thickening the wall or shortening the tube.
Can you supply closed-end tubes?
Yes. Closed one end, hemispherical closed ends and reduced-tip ends for thermocouple sheaths are all produced, either formed during shaping or ground after firing.
