Piezoelectric Behavior of Wood Treated with Liquid Ammonia

Abstract

The effects of wood treated with liquid ammonia on piezoelectric, dielectric and elastic relaxation were studied by using x-ray diffraction and measuring the piezoelectric, dielectric and elastic constants at the frequencies of 10, 30 and 100Hz. The relative crystallinity of wood after treatment was improved, so that the intensity of diffraction increased remarkably and the peaks appeared at about 20 and 12 degree.
The piezoelectric relaxation of shinanoki showed that the real part of piezoelectric constant d decreased with increasing temperature against control, but that of hinoki was different from shinanoki. It was supposed that the crystallinity of hinoki was not improved, because the micro-structure of hinoki was more complicated than that of shinanoki so that liquid ammonia was not effective enough to permeate into cell wall.
The piezoelectric relaxation was calculated using the two-phase system model, which consists of piezoelectric and non-piezoelectric phases. The piezoelectric dispersion of the piezoelectric phase appeared at the same temperature as the observed piezoelectric dispersion, and the dispersions of local coefficients L_T and L_E appeared at the same temperature as the observed dielectric and elastic dispersions. The piezoelectric relaxation existed in the piezoelectric phase and a part of non-piezoelectric phase; ie. piezoelectric relaxation was not only in the crystalline region but also in the amorphous region, especially that of oriented molecules.