Jerzy Ranachowski

Acoustic emission to accompany the superconducting transition of YBa2Cu3Ox

Abstract The acoustic emission was measured during the superconductor-normal state transition. The transition was carried out by increasing the temperature of YBa2Cu3Ox samples. Acoustic signals were observed in the case of no current flow as well as for currents of 1, 10, and 100 mA.

Surface Acoustic Wave Probe for Nondestructive Testing

We propose a new ultrasonic probe for investigation of mechanical properties of material surfaces. This probe was used to measure velocity of Rayleigh waves on various heat treated steel surfaces. Results show linear dependence between Vickers hardness number and velocity.

THE COMPARATIVE STUDY OF THE APPEARANCE OF ACOUSTIC EMISSION (AE) SIGNALS

Simultaneous AE and electric conductivity measurements of ceramic materials in three-point bending are presented. A coefficient Q, which binds changes of conductivity, AE, and mechanical strength has been introduced. AE activity in reaction of H2O2 decomposition with liberation of gas bubbles is shown.

Acoustic emission signals from the sol–gel transition of tetraethoxysilan (TEOS) and sodium silicate solutions

Sol–gel processes have been used extensively to prepare oxide materials (glasses and ceramics). The acoustic emission (AE) method with broadband piezoelectric transducer (up to 500 kHz) was used to control the evolution of slow gel formation from organic TEOS and fast formations from sodium silicate as the precursors of silica. The obtained dependencies of the AE count rate and rms values versus time characterize the dynamic of the cross‐linking and desolvation processes under ambient conditions. The frequency distribution analysis of individual power spectra provides an activity estimation of integral parts of processes. In sodium silicate solutions the spectra of low frequency (17–70 kHz) were mainly observed. On the other hand, the most representative spectra from the gelation of TEOS display at three basic ranges; 16–20 kHz, 200–230 kHz, and 400–470 kHz. The relative intensities of spectra in these ranges were changed considerably during the gel formation. [Work partly supported by KBN Grant No. T 07B...

Photoacoustic cells for liquids and solids investigation

The photoacoustic (PA) cell containing the sample of material under investigation is considered as one among the most important parts of the photoacoustic spectroscope. Examples of newly designed cells for liquids and solids investigation are presented. The special photoacoustic cell for laser beam intensity measurement, together with its preliminary test results, is described.

Investigations of the luminescence of N-alkenylcarbazoles and their charge-transfer complexes with 2,4,7-trinitro-9-fluore-none and 7,7,8,8-tetracyanoquinodimethane

Abstract The efficiency of flourescence quenching of N-alkenylcarbazoles was higher for TCNO than for TNF and increased with the carbon chain lenght. The flourescence of CT complexes of N-alkenylcarbazoles consisted of two superimposed bands corresponding to two orientational isomers. The energy distribution in the CT band depended on the excitation wavelenth.