Acoustic emission from phase transition of some chemicals

An Analytical Perspective on ACOUSTIC EMISSION

“…Recent chemical AE studies have focused on general investigation of the AE phenomenon (9,(28)(29)(30), thermosonimetry (16,31,32), instrument development (19,33), analysis of frequency domain information (14,15), Figure 3. AE signal and five parameters used by materials scientists to describe its waveform.…”

Acoustic Emission from Organic Martensites

“…Despite the potentials that these materials could have for fast transduction of heat directly into motion or work, the short time scales of their transitions and frequent disintegration with explosive outcome have precluded elucidation of the underlying mechanisms and quantification of their kinetics. [38][39][40][41][42] However,unlike the continuous acoustic emission that occurs during plastic deformation with slow progression of dislocations,the response from the martensitic transitions is discontinuous.T he intensity of the acoustic bursts is several orders of magnitude higher than that of the continuous emission, and is akin to the acoustic emission generated by an avalanche or the seismic waves that precede an earthquake.H erein, we provide direct evidence that, in addition to only one brief previously reported case, [5] the phase transitions in thermosalient crystals are generally associated with outbursts of elastic energy that translate into acoustic waves.T he energy,i ntensity,a nd time scale of the thermoacoustic response is scrutinized with the mechanism of the thermosalient transition. [16][17][18][19][20][21][22][23][24][25][26][27][28] We hypothesized that the sudden release of the accrued elastic strain in thermosalient crystals,reflected in extraordinarily high velocities of the progressing habit plane,c ould generate detectable acoustic waves.I na ddition to sudden release of accumulated strain, [29,30] elastic waves can evolve by dislocations in plastic deformation, [31][32][33][34] crack formation, [35] anisotropic thermal expansion, [36,37] and rapid molecular rearrangement.…”

“…[16][17][18][19][20][21][22][23][24][25][26][27][28] We hypothesized that the sudden release of the accrued elastic strain in thermosalient crystals,reflected in extraordinarily high velocities of the progressing habit plane,c ould generate detectable acoustic waves.I na ddition to sudden release of accumulated strain, [29,30] elastic waves can evolve by dislocations in plastic deformation, [31][32][33][34] crack formation, [35] anisotropic thermal expansion, [36,37] and rapid molecular rearrangement. [38][39][40][41][42] However,unlike the continuous acoustic emission that occurs during plastic deformation with slow progression of dislocations,the response from the martensitic transitions is discontinuous.T he intensity of the acoustic bursts is several orders of magnitude higher than that of the continuous emission, and is akin to the acoustic emission generated by an avalanche or the seismic waves that precede an earthquake.H erein, we provide direct evidence that, in addition to only one brief previously reported case, [5] the phase transitions in thermosalient crystals are generally associated with outbursts of elastic energy that translate into acoustic waves.T he energy,i ntensity,a nd time scale of the thermoacoustic response is scrutinized with the mechanism of the thermosalient transition. Thea ssociated strong waves carry important information on the dynamics and mechanism of transformation; [43] not only do the results provide deeper understanding of the mechanistic and kinetic profile of the thermosalient phenomenon, but in addition to the previous conclusions,they confirm that the thermosalient materials are molecular analogues of the inorganic martensites and that the molecular solids can behave in am anner similar to metals and alloys.…”

Acoustic emission sensor for identification of chemical reactions

“…A block diagram of the AEC sensor shown in Figure 1 consists of the following sections: the measurement cell with ultrasonic transducer (1); the signal conditioning unit (2); the time domain data acquisition unit which includes digital (3) and analog (4) oscilloscopes. a mixer (5).…”

“…They found a correlation between chemical and acoustic events, although some acoustic responses were difficult to interpret. Sawada and co-workers [3] indicated that AE signals were influenced by changes of volume, heat balance, and reaction rate. Wentzel and Wade [4] analyzed the frequency spectra of AE signals from several chemical systems.…”