Determination of x-ray elastic constants using an in situ pressing device

The experimental determination of x-ray elastic constants are performed by in situ measurements of the dependence of the strain state in selected crystallites for different applied external compressive stresses. The use of compressive applied stresses instead of tensile applied stresses is of interest for x-ray elastic constant determinations for materials which exhibit brittle crack-like behavior, which cannot be loaded to high tensile stresses in, for example, four-point bending devices. The x-ray elastic constants for {146} α–Al2O3 are determined with the pressing device and compared to calculated as well as experimentally determined values which were tested in tensile loading devices.

Residual stress fields in sol-gel-derived thin TiO2 layers

This paper discusses the induction of residual stresses during the curing process of thin titania layers, which are derived using a sol-gel process. During this process, stresses may build up in the spinning stage, the drying stage, and the consolidation stage. The magnitude and character of these stresses depend heavily on the morphology of the layers in the various stages and the processing conditions. Dried layers are densified using two different processes, conventional furnace heating and laser heating. X-ray analysis and scanning electron microscopy are used as tools to study crystallization, grain growth, phase transformation, and the evolution of residual stress fields in the thin titania layers. Through an extensive study of the residual stress state in the layers, more insight is gained in the evolution of stresses during the curing process of sol-gel-derived thin titania layers.