SITALL ÑÎ-115Ì is a crystalline glass ceramic material with ultra low Coefficient of thermal expansion.
SITALL ÑÎ-115Ì is an ideal material to be used for manufacturing of astr6onomical telescopes mirrors and other optical parts that require linear dimensions and surface figure stability at significant temperature changes.
Thermal stability of SITALL ÑÎ-115Ì material enables the fabrication of high precision mirrors within quicker time of treatment process since testing measurements are able to be conducted not waiting until thermal equilibrium is achieved.
sitall blanks with various forms of lightweightening
| THERMAL PROPERTIES | ||
| mean linear coefficient of thermal expansion (CTE) within temperature range -60 to 60 oÑ | 10-7 oC-1 | 0±1.5 |
| CTE homogeneity | 10-7 oC-1 | <= 0.2 |
| specific heat capacity | kilocalorie kg-1 oC-1 | 0.22 |
| heat conductivity | kilocalorie h-1 m-1 oC-1 | 1.71 |
| thermal resistance | oC | 550 |
| MECHANICAL PROPERTIES | ||
| density | g cm-3 | 2.46 |
| micro hardness | 10-7Pa | 860 |
| lapping relative hardness (with reference to glass, K-8 type) | - | 1.78 |
| modulus of elasticity (Young’s) | GPa | 92 |
| bending strength | 10-7Pa | 16.6 |
| Poisson’s coefficient | - | 0.28 |
| OPTICAL PROPERTIES | ||
| refractive index ne | - | 1.538 |
| refractive index nd | - | 1.536 |
| average variance nF - nC | - | 0.0102 |
| quality | - | as per requirements |
| bubbles and striae | - | as per requirements |
| stress birefringence | nm/cm | up to 15 |
Sitall material shapes and forms of supply:
Sitall is made in form of flat round and rectangular plates, with maximum dimensions up to 3000mm. More detailed information about sitall material is submitted in reply to your request.