Effects of Ytterbium Oxide Nanopowder Particle Size on the Acoustic Properties of Silicone Rubber Lens for Medical Echo Array Probe

概要

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The effects of Yb2O3 powder particle size, namely, 2000, 16, and 8 nm, on the physical and acoustic properties of a high-temperature-vulcanization (HTV) silicone (Q) rubber have been investigated in order to develop an acoustic lens material with a low sound velocity ($c$) and acoustic attenuation coefficient ($\alpha$). The Yb2O3-doped HTV Q rubber with the large particle size of 2000 nm showed a density ($\rho$) of $1.6\times 10^{3}$ kg/m3, with $c = 828$ m/s, characteristic acoustic impedance $(Z) = 1.32\times 10^{6}$ kg$\cdot$m-2$\cdot$s-1, $\alpha = 1.32$ dB$\cdot$mm-1$\cdot$MHz-1, and an $\alpha$-figure of merit (FOM) ($\alpha\times c$) of 1090 at 5 MHz at 37 °C. For the Yb2O3-doped Q rubber with the small particle size of 8 nm, $\rho = 1.57\times 10^{3}$ kg/m3, $c = 864$ m/s, $Z = 1.36\times 10^{6}$ kg$\cdot$m-2$\cdot$s-1, $\alpha = 0.68$ dB$\cdot$mm-1$\cdot$MHz-1, and $\alpha$-FOM = 590. The 16 nm Yb2O3-doped Q rubber had intermediate values of $\alpha = 0.88$ dB$\cdot$mm-1$\cdot$MHz-1 and $\alpha$-FOM = 760. These results show that there is a clear dopant particle size dependence on the acoustic properties of Yb2O3-doped HTV Q rubbers. The 8-nm-doped HTV Q rubber also showed an excellent mechanical properties for practical application. Microstructure observation revealed that the low-$\alpha$ rubber shows a uniform Yb2O3 nanopowder distribution in the HTV Q rubber matrix.
2008-05-25