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SITALL

Sitall CO-115M (Astrositall)

SITALL __115_ is a crystalline glass ceramic material with ultra low Coefficient of thermal expansion.
SITALL __115_ is an ideal material to be used for manufacturing of astronomical telescopes mirrors and other optical parts that require linear dimensions and surface figure stability at significant temperature changes.Thermal stability of SITALL 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.

 

THERMAL PROPERTIES


Mean linear coefficient of thermal expansion
(CTE) within temperature range -60 to 60oC
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
PoissonÕs 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