Silicate and direct bonding of low thermal expansion materials

Joining of materials becomes an issue, when high stability at large temperature variation is required. Stress from thermal mismatch of auxiliary materials and corresponding distortions are often unavoidable. We describe the use of two inorganic bonding technologies for joining low thermal expansion glasses. The techniques of silicate and direct bonding were applied to join ultra-low thermal expansion glass elements of 150 mm diameter to from light-weight and high precision opto-mechanical compounds. Related bond strengths were investigated on separate reference specimen. Dimensional stability of the bonded systems during thermal cycling in vacuum was investigated by Fizeau interferometry at temperatures between 78 K and 335 K with high accuracy. The results illustrate the great potential of both bonding technologies for glass based precision engineering applications to be used under highly demanding environmental conditions, like in space.