Ultrasonic imaging, particle detection, and V(z) measurements have been performed using focused clad buffer rods in molten zinc at temperature more than 600 °C. The focused ultrasonic waves are generated by a spherical or cylindrical acoustic lens which is fabricated at the end of the clad buffer rod. In order to evaluate its focusing ability, several experiments are carried out at 10 MHz in a pulse-echo mode. The lateral resolution at the focus of the spherical acoustic lens in molten zinc is quantitatively examined and compared with that in water using a thin stainless wire with a diameter of 380 μm. High resolution ultrasonic imaging is carried out by the common C-scan technique. The signal-to-noise ratio of the reflected signals from the flat sample surface at the focus is better than 35 dB. Ultrasonic images are obtained from the amplitude and time delay variations of the reflected signals. An attempt has also been made to detect particles suspended in molten zinc. Backscattered signals from particles are clearly visible at the focal region of the lens. For quantitative materials evaluation, V(z) curve measurements are performed using both spherical and cylindrical surface lenses and the leaky surface acoustic wave velocity of a ceramic (SiC) plate immersed in molten zinc is successfully determined.

An all-optical technique was developed to determine the in-plane and out-of-plane Young's modulus, E, and Poisson's ratio, σ, in silicon wafers through excitation and detection of vibration modes. The technique is remote, non-destructive and works on-line, making it an attractive inspection tool for use in semiconductor foundries. Vibration modes were generated by a pulse from a frequency-doubled Q-switched Nd:YAG laser and detected by a commercial heterodyne Michelson interferometer. Because of their importance as component substrates in the electronic and MEMS industries, both the ⟨100⟩ and ⟨111⟩ silicon wafers were investigated. It was found that the resonance frequencies of the first pure torsional and of the first hybrid (torsional and flexural) modes varied continuously and symmetrically with respect to a 90° rotation of the wafer around the centre, while the resonance frequencies of the first and second pure flexural modes remained constant. On the basis of this experimental observation, we could correlate the resonance frequencies of the two former and two latter modes with the in-plane and out-of-plane mechanical parameters E and σ, respectively. A novel inverse method for circular anisotropic plates was then derived to extract the in-plane and out-of-plane parameters from the resonance frequency measurements. The results obtained by this approach were in good agreement with the standard values calculated by the theory of elasticity.

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The cure of a set of polyester resin samples having different styrene contents has been monitored by means of Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), rheometry, and ultrasonic measurements. ETIR and DSC experimental data were used to calculate the cure kinetics using a freeradical polymerization model (multiple steps) and also an empirical model that considers the curing to involve only a single step. The dependence of viscosity on the degree of curing has been investigated at different shear rates. Finally, correlations among the results from the different techniques have been established and discussed in terms of the curing mechanism.

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