• KSBB Journal
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• v.13 no.5
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• pp.477-482
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• 1998

A biosensor with PZT piezoelectric ceramic crystal was developed for the detection of formaldehyde gas. Poled PZT piezoelectric ceramic disk was made from ZrO2, TiO2 and Nb2O5, together with the addition of PbO and polyvinyl alcohol, through various processes of mixing, calcination drying, crushing, forming, sintering, polishing, ion coating and poling. Oscillator circuit of sensor was made of operational amplifier(AD811AN). Formaldehyde dehydrogenase was immobilized onto a piezoelectic ceramic crystal, together with the cofactors, reduced glutathione and nicotinamide adenine dinucleotide. The effect of flow rate on the sensitivity was determined by varing the flow rate of carrier gas from 24.7mL/min to 111.7mL/min through detector cell. The results indicated that as the flow rate was increased, the recovery rate was increased. And a significant increase in the sensitivity was observed in enhanced flow rate of carrier gas. Frequency difference(ΔF) of immobilized PZT piezoelectic disk increased proportionally to the concentration gas and reproduced to repeated exposures of formaldehyde gas(28ppm, Δ68Hz).

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.1
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• pp.14-19
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• 2013

Nonlinearity parameter is an inherent property of materials measuring fundamental acoustic amplitude($A_1$) and second harmonic amplitude($A_2$). However, measurement of $A_1$ and $A_2$ has complex calibration procedure, many researchers prefer to measure relative nonlinearity parameter rather than absolute nonlinearity parameter. But, relative nonlinearity parameter is only detect materials degradation with various degradation samples, it is limited application in determining third order elastic constants of materials. Therefore, in this study, the piezoelectric detection method is adopted to measure absolute nonlinearity parameter due to experimental simplicity compare to capacitive detector. Linearity of measurement system is verified by $A_1^2vsA_2$ plot, and we measured ultrasonic nonlinearity parameters of fused silica and Al2024-T4.