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At least 1,189 records · Page 66

The growth of benzophenone crystals by Sankaranarayanan-Ramasamy (SR) method and slow evaporation solution technique (SEST): A comparative investigation

Highlights: Black-Right-Pointing-Pointer Benzophenone single crystal was grown by Sankaranarayanan-Ramasamy method which has the sizes of 1060 mm length and 55 mm diameter for the first time. Black-Right-Pointing-Pointer The conventional and SR-grown benzophenone crystals were characterized and compared using HRXRD, etching, laser damage threshold, microhardness, UV-transmittance, birefringence and dielectric analysis. Black-Right-Pointing-Pointer The SR-grown benzophenone crystal has higher LDT, microhardness, transparency, dielectric permittivity, birefringence and lower FWHM, EPD, dielectric loss than the crystal grown by conventional method. Black-Right-Pointing-Pointer The probable reason for higher crystalline perfection in SR-grown crystal was discussed. -- Abstract: Longest unidirectional Left-Pointing-Angle-Bracket 1 0 0 Right-Pointing-Angle-Bracket benzophenone (BP) crystal having dimension of 1060 mm length and 55 mm diameter was grown by Sankaranarayanan-Ramasamy method. The growth rate was measured by monitoring the elevation of the crystal-solution interface at different temperatures. The high resolution X-ray diffraction and etching measurements indicate that the unidirectional grown benzophenone crystal has good crystalline perfection and less density of defects. The optical damage threshold of SEST and SR grown BP crystals has been investigated and found that the SR grown benzophenone crystal has higher laser damage threshold value than the conventional method grown crystal. Microhardness measurement shows that crystals grown by SR method have a higher mechanical stability than the crystals grown by SEST method. Dielectric permittivity and birefringence are high in SR grown crystal compared to SEST grown BP crystal. The UV-vis-NIR results show that SR method grown crystal exhibits 7% higher transmittance as against crystals grown by conventional method.

36 MATERIALS SCIENCE↗

Carbyne fiber synthesis within evaporating metallic liquid carbon

Carbyne (e.g., linear chains of sp-bonded carbon) has been the subject of intense research focus due to its presence in astrophysical bodies, as well as its potential for use as a nanoelectronic device and superhard material. In this work, we discuss the formation of carbyne fiber bundles over a nanosecond time scale in laser pulse melting studies, using a previously determined density functional tight binding model for carbon coupled with a new correction for the dispersion energy. We determine our dispersion energy model by optimizing a modified Lennard-Jones potential to an experimentally determined equation of state for graphite, yielding excellent results for the bulk modulus and density under ambient conditions. We then simulate previous experiments by heating graphite to high temperature, followed by expanding the ensuing liquid phase to low density. Our results indicate that the initial, hot liquid phase mainly consists of sp2-bonded carbon atoms, which form a system of sp-bonded strands bound together via dispersion interactions upon achieving low density and temperature. Lastly, the high computational efficiency of our approach allows for direct comparison with experiments that span a wide range of thermodynamic conditions and can help determine parameters for synthesis of carbon-based materials with potentially exotic properties.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗