Glass-alumina functionally graded materials: their preparation and compositional profile evaluation

Surface acoustic wave depth profiling of a functionally graded material

“…The values are similar to the ones in Ref. 18 for similar samples. When comparing the simulated dispersion curve to the experimental results, it becomes clear that the high frequency limit ͑100 MHz͒ of the experimental dispersion curve on the graded glass-coated ceramic samples ͑3500 m s −1 ͒, tends to a 200 m s −1 higher value than the Rayleigh velocity of pure glass ͑3260 m s −1 ͒, the assumed top layer material in the simulation.…”

“…The situation was thus different than the one for the similar materials investigated in Ref. 18, where a gradual composition transition was found. Interestingly, the experimental dispersion curve for sample II was found equal within the error bar with the one of sample I, suggesting that for our samples the additional duration of the heat treatment did not induce additional glass diffusion, so that the sample structure remained unchanged.…”

“…The purpose of putting a glass graded coating on a ceramic body is to improve the resistance to thermomechanical loading in daily use conditions and to protect the substrate against surface damage. 18 The adhesion between glass and ceramic is in general quite good because of glass-ceramic interdiffusion during the production stage achieved by fusion of diffusing molten glass with the top layer of the slightly porous ceramic substrate. The quality of glass-coated ceramic samples is determined by the ͑uni-formity of the͒ thickness of the top layer, and its adhesion to ͑and thus interdiffusion with͒ the ceramic substrate.…”

“…Two different heat treatments were applied: 2 h at 1873 K for sample I and 4 h at the same temperature for sample II. 18 The small amount of residual glass that remained on the top surface was then polished away and the remaining surface was chromium coated by physical vapor deposition to ensure optimum conditions for absorbing the pump laser beam and to achieve specular reflection conditions for the probe laser beam during the SAW excitation and detection experiments. Care was taken during these after treatments not to change the sample characteristics by removing too much glass or even ceramic, or by heating the sample too much due to friction.…”

Microstructure-based modelling and experimental investigation of crack propagation in glass–alumina functionally graded materials

“…In the present study, a CaO-ZrO 2 -SiO 2 glass was used, since the glasses belonging to this ternary system usually show interesting mechanical properties, such as a high Young's modulus and a relatively good fracture toughness (K IC ). [12][13][14] Moreover, the absence of Al 2 O 3 in the glass composition was helpful to characterize the resulting functionally graded materials, since it was easier to distinguish the glass domains and the alumina grains, for example, by scanning electron microscope-X-ray energy dispersion spectroscopy (SEM-EDS) analysis. Finally, in order to reduce the mismatch in thermal properties, the glass composition was carefully formulated thus achieving a coefficient of thermal expansion similar to that of the alumina.…”