HF acid attack of SiO2 and Si3N4 substrates is analyzed to improve the sensitivity of a sensor based on microcantilever. Ex situ analysis of the etching using XPS, SIMS and AFM show significant changes in the anisotropy and the rate of the etching of the oxides on SiO2 and Si3N4 surface. Those differences influence the kinetic evolution of the plastic bending deflection of the cantilever coated with SiO2 and Si3N4 layer, respectively. The linear dependence between the HF concentration and the Si3N4 cantilever bending corresponds to a deep attack of the layer whereas the non-linear behavior observed for SiO2 layer can be explained by a combination of deep and lateral etching. The cantilever bending is discussed in terms of free surface energy, layer thickness and grain size.

HF acid attack of SiO2 and Si3N4 substrates is analyzed to improve the sensitivity of a sensor based on microcantilever. Ex situ analysis of the etching using XPS, SIMS and AFM show significant changes in the anisotropy and the rate of the etching of the oxides on SiO2 and Si3N4 surface. Those differences influence the kinetic evolution of the plastic bending deflection of the cantilever coated with SiO2 and Si3N4 layer, respectively. The linear dependence between the HF concentration and the Si3N4 cantilever bending corresponds to a deep attack of the layer whereas the non-linear behavior observed for SiO2 layer can be explained by a combination of deep and lateral etching. The cantilever bending is discussed in terms of free surface energy, layer thickness and grain size.

Ti-6Al-4V (TA6V) titanium alloy is widely used in industrial applications such as aeronautic and aerospace due to its good mechanical properties at high temperatures. Experiments on two different resistive pulse heating devices (CEA Valduc and TU-Graz) have been carried out in order to study thermophysical properties (such as electrical resistivity, volume expansion, heat of fusion, heat capacity, normal spectral emissivity, thermal diffusivity, and thermal conductivity) of both solid and liquid Ti-6Al-4V Fast time-resolved measurements of current, voltage, and surface radiation and shadowgraphs of the volume have been undertaken. At TU-Graz, a fast laser polarimeter has been used for determining the emissivity of liquid Ti-6Al-4V at 684.5 nm and a differential scanning calorimeter (DSC) for measuring the heat capacity of solid Ti-6Al-4V. This study deals with the specific behavior of the different solid phase transitions (effect of heating rate) and the melting region, and emphasizes the liquid state (T>2000 K).

Microcantilevers have been used as a gas sensor in order to detect Hydrofluoric acid (HF) in the concentration range of 0.26–13ppm. Silicon derived elements (Si3N4, SiOx) were chosen to serve as chemical sensitive layer. Cantilever deflection and frequency shift were analyzed and compared as a function of the flow rate and the concentration of the HF molecules. The stoichiometry and roughness of the sensitive layer were found to be of major importance. Results show that the most appropriate signal at the lowest concentration (<10ppm) is the cantilever deflection that is particularly sensitive to the change in surface stress induced by the lateral attack of SiOx surface by HF. The frequency shift that is mainly governed by the loss in cantilever mass can be used at higher concentration.

The variation in resonance response of microcantilevers was investigated as a function of pressure (10(-2)-10(6)Pa) and temperature (290-390K) 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. The deflection in flow transition regime resulting from thermal variation has minimal effect on frequency. The frequency variation of the cantilever is caused mainly by changes in the mean free path of gas molecules.

This research concentrates on the sensitivity of semiconductor tin dioxide-based gas sensors to hydrogen fluoride in air. After evaluating the characteristic detection temperature, the sensor's signals were studied for different HF concentrations. Despite the corrosive effects of hydrogen fluoride, a reproducibility of the signal was found. Likewise, we did not observe any long-term degradation to the sensor. For the experiment, the sensor was exposed to a gas mixture formed by HF, O 2 , N 2 with a constant flow rate of 150 ml min −1 . The semiconductor gas sensor reached maximum sensitivity near 380 °C, and a minimum concentration was detected approximately 50 ppb. Moreover, the detection phenomenon appears to be reversible when considering the electrical response under a constant air flow.

This paper presents theoretical and experimental developments for the implementation of SAW sensors able to detect small concentration of anhydride HF acid in air. Solutions based on the used of surface transverse waves (STW) on quartz (YXlt)/36°/90° have been analysed to evaluate their potential sensitivity to HF. Devices have been first tested in a BHF solution to identify the kinetics of the reaction. Measurements have been then performed under various gaseous conditions to characterise their actual behaviour when submitted to controlled concentrations of HF. STW as well as love wave resonators have been successfully tested, with capabilities to detect HF concentration much smaller than 1 ppm.

This paper presents theoretical and experimental developments for the implementation of SAW sensors able to detect small concentration of anhydride HF acid in air. Solutions based on the used of Surface Transverse Waves (STW) on Quartz (YXlt)/36/spl deg//90/spl deg/ have been analysed to evaluate their potential sensitivity to HF. Devices have been first tested in a BHF solution to identify the kinetics of the reaction. Another set of tests have been then performed under various gaseous conditions to characterise their actual behaviour when submitted to controlled combinations of HF and other well identified chemical compounds.

All the microstructural parameters involved in metallurgical processes are difficult to determine directly on a shaped material. The aim of this paper is to use an impulse line-focus acoustic microscope (LFAM) as a non-destructive alternative to X-ray diffraction for measuring texture of slightly anisotropic materials. We apply it to characterize the rolling and annealing texture for tantalum sheets.

In recent years, several studies have proposed a variety of ultrasonic techniques for a non-destructive determination of texture in materials shaped by rolling or embossing. In this paper, we proposed to use as ultrasonic method an impulse line-focus acoustic microscope operating in the MHz range for the material characterization by means of measuring the Rayleigh waves velocity versus their propagation direction. The goal of this study is to evaluate the accessible coefficients W1mn of the Crystallite Orientation Distribution Function (C.O.D.F.) in the case of rolled tantalum sheets exhibiting an induced texture

Deals with the theoretical prediction of the impulse response of materials achieved by a special surface acoustic microscope operating in the MHz frequency range. This is applied to a lensless transducer with a line focus (cylindrical shape) in order to characterize anisotropic materials. A one dimensional (1 D) modelling is developed and then validated by comparison between experiments and theoretical predictions. By means of an optimization technique, this modelling tends to solve the inverse problem of the elastic constant evaluation applied to rolled materials