A theoretical model is presented for combining parameters of 1-3 ultrasonic composite materials in order to predict ultrasonic characteristics such as velocity, acoustic impedance, electromechanical coupling factor, and piezoelectric coefficients. Hence, the model allows the estimation of resonance frequencies of 1-3 composite transducers. This model has been extended to cover more material parameters, and they are compared to experimental results up to PZT volume fraction nu of 0.8. The model covers calculation of piezoelectric charge constants d(33) and d(31). Values are found to be in good agreement with experimental results obtained for PZT 7A/Araldite D 1-3 composites. The acoustic velocity, acoustic impedance, and electromechanical coupling factor are predicted and found to be close to the values determined experimentally.

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The fabrication and sensor properties of polyaniline-platinum oxide chemoresistors in the presence of combustible gases such as hydrogen, methane, ethylene, acetylene and carbon monoxide is reported. Prior conditioning of the sensors in a hydrogen atmosphere resulted in increased selectivity and sensitivity for hydrogen in air at concentrations between 1000 and 5400 ppm. The conditioned sensors showed negligible response to hydrocarbons and carbon monoxide.

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