Damage localization in piezo-ceramic using ultrasonic waves excited by dual point contact excitation and detection scheme

A novel experimental technique based on point contact and Coulomb coupling is devised and optimized for ultrasonic imaging of bulk and guided waves propagation in piezo-ceramics. The Coulomb coupling technique exploits the coupling and transfer of electric field to mechanical vibrations by excitation of phonons. The point contact excitation and detection technique facilitates the spatial-temporal imaging of ultrasonic waves. The motivation of this research is the diagnosis and localization of surface cracks in the piezoelectric sensors and actuators. The underlying principle of the detection scheme is that any discontinuity on the surface causes high localization of electric gradient. The localized electric field at the defect boundaries enables then to behave as secondary passive ultrasonic sources resulting in strong back reflections. However, due to the interference between transmitted and reflected wave components from rigid boundaries and defect, the resolution on the localization of the damage is challenging. Therefore, an algorithm based on the two-dimensional spectral decomposition is utilized for selective suppression of the transmitted wave. The algorithm includes data transformation and vectorization in polar coordinates for efficient spectral decomposition. In the spectral domain, the complex wave component (phase and amplitude) are suppressed for the transmitted wave field. The reflected wave component in the spectral domain is retained and retrieved back using inverse spectral transformation. The algorithm is successful in retaining and exemplifying only the reflected wave sources arising from the strong scattering of ultrasonic waves from the surface and sub-surface defects. In summary, a novel experimental technique based on Coulomb coupling and spectral decomposition technique has been implemented for localization of surface defect in piezo-ceramic structures.

Novel antibacterial application of photovoltaic Cu2SnS3 (CTS) nanoparticles

In the present work, Cu₂SnS₃ (CTS) nanoparticles were synthesized using the hot injection method.

Advanced 3D-Sonographic Imaging as a Precise Technique to Evaluate Tumor Volume

Determination of tumor volume in subcutaneously inoculated xenograft models is a standard procedure for clinical and preclinical evaluation of tumor response to treatment. Practitioners frequently use a hands-on caliper method in conjunction with a simplified formula to assess tumor volume. Non-invasive and more precise techniques as investigation by MR or (μ)CT exist but come with various adverse effects in terms of radiation, complex setup or elevated cost of investigations. Therefore, we propose an advanced three-dimensional sonographic imaging technique to determine small tumor volumes in xenografts with high precision and minimized observer variability. We present a study on xenograft carcinoma tumors from which volumes and shapes were calculated with the standard caliper method as well as with a clinically available three-dimensional ultrasound scanner and subsequent processing software. Statistical analysis reveals the suitability of this non-invasive approach for the purpose of a quick and precise calculation of tumor volume in small rodents.

Mechanical characterization of sintered piezo-electric ceramic material using scanning acoustic microscope

Lead Zirconate Titanate (PZT) is a piezo-electric ceramic material that needs to be characterized for its potential use in microelectronics. Energy dispersive X-ray analysis (EDX) is conducted to determine the chemical composition of the PZT ceramics. The scanning electron microscope (SEM) is performed to study the surface morphology, grain structure and grain boundaries. The SEM image helps us to understand the surface wave propagation and scattering phenomena by the PZT and the reason for its anisotropy and inhomogeneity due to the grain structure. In this paper scanning acoustic microscopy at 100 MHz excitation frequency is conducted for determining mechanical properties of PZT. Earlier works reported only the longitudinal wave speed in PZT while in this paper longitudinal, shear and surface acoustic wave speeds of sintered PZT are measured from its acoustic material signature (AMS) curves, also known as V(z) curves. AMS or V(z) curve is the variation of the output voltage as a function of the distance between the acoustic lens focal point and the reflecting surface. The average velocities of longitudinal, shear and surface acoustic waves in a PZT specimen are determined from its V(z) curve generated at 100 MHz excitation frequency and found to be over 5000 m/s, over 3000 m/s and between 2500 and 3000 m/s, respectively. From these velocities all elastic constants of the specimen are obtained.