Glass - Back to the Future!

Presenting Author:
Shirley K. Fong

article posted 21 March 2016

Shirley K. Fong

Development of high CTE glass-ceramics for sealing

Shirley K. Fong* and Phillip M. Mallinson
AWE, Aldermaston, Reading, RG7 4PR

High CTE glass-ceramics are required for sealing applications. The crystallisation and nucleation behaviour for two candidate lithium silicate based glasses, AZS2 and AS13, have been optimised for high CTE values using the method developed by Marotta et al. The ideal nucleation time and temperature was determined as 475oC for 120 mins for AZS2. This gave the crystalline phases cristobalite, tridymite and a Li2ZnSiO4, yielding a glass ceramic of CTE 18-18.5 x 10-6 K-1. For AS13 nucleation parameters were 512 oC for 90 mins, giving Li2SiO3 and Li3PO4 as the main phases and yielding a glass-ceramic with a CTE of 14.0 x 10-6 K-1. Examination of the AZS glass-ceramics also indicates that areas of inhomogeniety were present where very little crystallisation occurred. These areas, when adjacent to pores, appeared to act as crack initiation points; however cracks were significantly reduced when the particle size of the glass was reduced to below 355 Ám.