We have generated planar blast waves over the large area using carbon nanotubes(CNT)-poly-dimethylsiloxane(PDMS) optoacoustic transducer. Pulse laser is absorbed by CNT and converted to heat, and the heat is transferred to PDMS inducing its thermal expansion and blast wave generation. To theoretically describe the planar blast wave generation, we build one-dimensional simulation model and find analytical solutions for temperature and pressure distributions. The analytical solution validated by the experimental data sheds light on how to improve the performance of the new transducer. Resonance of acoustic waves inside the transducer is also discussed. The new optoacoustic transducer optimized based on the fundamental understandings will be useful in generating high quality blast waves for research and industrial applications.
Polycrystalline and nanocrystalline samples of the CuCr 2 Se 4 ferromagnetic spinel are synthesized. The mean size of nanocrystals is 50 nm. The Curie temperature of spinel nanocrystals (465 K) is higher than that of spinel polycrystals (435 K). Laser irradiation at a wavelength of 1.5 µ m (in an external magnetic field) increases the magnetization of the noncrystalline powder. Most likely, this can be explained by the change in the orientation of magnetic moments of single-domain nanoparticles. The observed effect reaches a maximum in magnetic fields with a strength lower than that of the saturation field.
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