High frequency wideband underwater acoustic transducer for ring shaped composite material

A kind of circular ring high frequency wideband underwater acoustic transducer is developed by using the Low Q value and broadband characteristics of the piezoelectricity composite material,and the dual mode coupling is used to broaden the bandwidth of the transducer by double ring stacking along the axial direction.Through theoretical analysis and simulation calculation,the geometric dimensions of the sensitive components are determined.The piezoelectric composite rings are processed and then the stack sensitive element can be made by stacking two piezoelectric composite rings with the same outer diameter and different thickness in axial direction by cutting piezoelectric ceramicsfilling the flexible polymer-coating electrode.Finally,the transducer can be made by pouring waterproof sound-permeable layer.The performances of transducer have also been tested in the water and the test results show that the resonant frequency is 410 kHz,the maximum transmit voltage response is 150 dB,the-3 dB bandwidth can reaches 60 kHz,the horizontal directivity（-5 dB） is 360°,and the vertical directivity（-3 dB） is 20°.It is also shown that the bandwidth of the transducer can be enlarged remarkably by using the method of stacking two different thickness piezoelectric composite rings along the axial direction,and the horizontal omnidirectional emission of acoustic wave can be realized

Corrosion mechanism of ceramic glaze from the Yangtze EstuaryⅡ

Ancient lead-glazed ceramics frequently corrode physically,chemically,and biologically when buried in soil,submerged in water,or exposed to air.In comparison to the other two environments,relatively little research has been conducted on how leadglazed ceramics deteriorate in the water environment.Four lead-glazed ceramic samples from the Yangtze EstuaryⅡwere examined for their micromorphology and structural composition using scanning electron microscopy-energy spectrum analysis,micro-area X-ray diffraction analysis,fluorescence microanalysis,and Fourier infrared spectroscopy analysis.The results demonstrate the formation of deposits of PbCO_(3),Pb(OH)Cl,and Cu FeS_(2)and corrosion pits and fractures on the glaze layer surfaces.According to the corrosion phenomenon,the lead glaze layers of ceramics mainly underwent chemical and microbial corrosion in water,and the corrosion process of the lead glaze was expounded and modeled.The research results deepen the understanding of the corrosion mechanism of lead-glazed ceramics,which is of great significance for the study of the conservation of lead-glazed ceramics and other types of ceramic relics and can also provide a reference for the long-term preservation of contemporary silicate products.