0000000000022952
AUTHOR
Arnaud Fabre
Effects of temperature and pressure on microcantilever resonance response.
Abstract The variation in resonance response of microcantilevers was investigated as a function of pressure (10 −2 –10 6 Pa) and temperature (290–390 K) in atmospheres of helium (He) and dry nitrogen (N 2 ). Our results for a silicon cantilever under vacuum show that the frequency varies in direct proportion to the temperature. The linear response is explained by the decrease in Young's modulus with increasing the temperature. However, when the cantilever is bimaterial, the response is nonlinear due to differential thermal expansion. Resonance response as a function of pressure shows three different regions, which correspond to molecular flow regime, transition regime, and viscous regime. …
Activation process of reversible Pd thin film hydrogen sensors
Abstract Microcantilever-based thin film palladium hydrogen sensors have high selectivity and sensitivity. Reproducibility and accuracy of the sensor performance depend on the activation process of the polycrystalline palladium film deposited on the cantilever. When the hydrogen is in solid solution ( α -phase), the cantilever bending is mostly governed by the residual film stress induced by the swelling at the grain boundaries in the film. When the palladium hydride ( β -phase) starts to be formed, the cantilever undergoes a large deflection due to hydrogen absorption-induced film swelling (10% change in volume). Differences in the phase diagrams of the palladium hydride for two film thick…
In situ measurement of elastic properties of PdH , PdD , and PdT
Abstract The Young’s modulus E of palladium hydride PdH x , deuteride PdD x and tritide PdT x were measured for studying the effect of both hydrogen stoichiometry x and isotope nature. A special technique based on optical detection of flexural modes of a palladium cylindrical microcantilever was adapted to in situ measurements to guarantee the sample homogeneity during the hydriding process. A 10% decrease in E was found between pure polycrystalline palladium and hydride phases. The non linear dependence observed with the H content was discussed in terms of lattice expansion, phonons and electronic properties. Sensitivity of the technique enables to distinguish an isotope effect on E .
Monitoring the chemical changes in Pd induced by hydrogen absorption using microcantilevers.
Abstract The reactivity of the palladium shaped as a microcantilever is investigated as a function of the hydrogen stoichiometry. A small cell holding the microcantilever is designed to monitor the deflection and the flexural resonance response from high vacuum to a hydrogen gas pressure of several bars. The measurements show that the Young's modulus is accurate if the cantilever is thick enough to be described by a continuum mechanics approach. The orientation distribution function of the palladium grains determined by X-ray diffraction enables to correlate Young's modulus measured using microcantilevers with the elastic constant tensor issued from the literature. The surface stress induce…