Internal Residual Stresses in Sintered and Commercial Low Expansion Li2O-Al2O3-SiO2 Glass-Ceramics

Abstract

We performed Synchrotron X‐ray diffraction (XRD) analyses of internal residual stresses in monolithic samples of a newly developed Li2O–Al2O3–SiO2 (LAS) glass–ceramic produced by sintering and in a commercial LAS glass–ceramic, CERAN®, produced by the traditional crystal nucleation and growth treatments. The elastic constants were measured by instrumented indentation and a pulse‐echo technique. The thermal expansion coefficient of virgilite was determined by high temperature XRD and dilatometry. The c‐axis contracts with the increasing temperature whereas the a‐axis does not vary significantly. Microcracking of the microstructure affects the thermal expansion coefficients measured by dilatometry and thermal expansion hysteresis is observed for the sintered glass–ceramic as well as for CERAN®. The measured internal stress is quite low for both glass–ceramics and can be explained by theoretical modeling if the high volume fraction of the crystalline phase (virgilite) is considered. Using a modified Green model, the calculated critical (glass) island diameter for spontaneous cracking agreed with experimental observations. The experimental data collected also allowed the calculation of the critical crystal grain diameters for grain‐boundary microcracking due to the anisotropy of thermal expansion of virgilite and for microcracking in the residual glass phase surrounding the virgilite particles. All these parameters are important for the successful microstructural design of sintered glass–ceramics.

Ceramic ChemCam Calibration Targets on Mars Science Laboratory

“…There is a bit of serendipity in the formation of virgilite within these ceramics, for the virgilite type locality is Macusani, Peru (French et al 1978), where it was discovered within Macusani volcanic glass that happens to be used as the sole natural volcanic glass calibration target on ChemCam (Fabre et al 2011). Virgilite also occurs synthetically in other lithium aluminum silicate glass-ceramics that are sintered at low temperature (e.g., Serbena et al 2011).…”

Internal residual stresses in glass-ceramics: A review

“…Using the Eshelby model of transformation strains, expressions are obtained for the thermal residual stresses. For example, in a crystal phase with a hexagonal unit cell, the residual stresses are given by the following equations [28][29][30]:…”

“…Residual stresses in low expansion Li 2 O-Al 2 O 3 -SiO 2 (LAS) glassceramics produced by sintering and in a commercial LAS glass-ceramic, CERAN®, were measured by Serbena et al [30] using synchrotron radiation. The crystallized phase is virgilite (Li x Al x Si 3 − x O 6 ).…”

“…6. The critical radius, as a function of the crystallized volume fraction, was estimated by Todd and Derby [29] based on Green's model [35] and is given by [30]:…”

Resistencia al desgaste de recubrimientos sol-gel de SiO₂ y SiO₂ - ZrO₂ sobre materiales vitrocerámicos obtenidos por sinterización

“…La Tabla 1 resume las relaciones molares TEOS/MTES, HCl/TEOS+MTES y H 2 O/TEOS+MTES, junto con el porcentaje que no pueden obtenerse a partir de un material monolítico [7,8].…”