Comparative investigations of structural, mechanical, optical and conductivity measurements of L-arginine 4-nitrophenol 4-nitrophenolate dihydrate (LAPP) single crystals grown by conventional and unidirectional method
V. Sivasubramani, Muthu Senthil Pandian*, P. Ramasamy
SSN Research Centre, SSN College of Engineering, Kalavakkam-603 110, Chennai, Tamilnadu
Good quality and optically transparent uniaxial L-arginine 4-nitrophenolate 4-nitrophenol dihydrate (LAPP) single crystal having dimension of 15 mm diameter and 40 mm length was grown by Sankaranarayanan-Ramasamy (SR) method with an average growth rate of 1 mm per day. Using an identical solution the conventional crystal grown to a dimension of 12×10×5…show more content… A homogeneous solution was made with the help of magnetic stirrer at room temperature. The prepared solution was filtered by using WhatMan filter paper to remove the suspended impurities and then evaporated to dryness. The dried crystalline sample was collected and used for the further growth of LAPP conventional crystal. The synthesized crystalline sample was purified by the repeated recrystallization process. The solubility of LAPP is 2.5 gm for 100 ml with room temperature. Single crystals of LAPP were grown from the super saturation solution at room temperature. Well defined morphology of LAPP single crystal of size 12×10×5 mm3 was harvested in a growth period of 20 days and as grown crystal shown in (Fig.1 (a)). The grown LAPP single crystals are chemically…show more content… Fig.4 shows the hardness number of SEST and SR method grown LAPP crystal was 44 kg/mm2 and 52 kg/mm2 respectively. For an indentation load of 25 g, cracks were initiated on the SEST and SR grown crystal’s on the surface in around the indenter. This may be due to the release of internal stress generated by indentation (3). Low hardness of conventional solution grown crystals may be due to entrapment of solvent inclusion during the growth (4). The work hardening co efficient was calculated from Meyer’s index plot. The obtained values are 2.1 and 2.2 for SEST and SR method grown crystals respectively. According to Onitsch microhardness values LAPP crystals have work hardening co efficient value higher than 1.6. So that LAPP crystal belongs to soft material category. The higher hardness value of SR method grown crystal having fewer dislocations due to very less growth fluctuation during the growth process and less impurities compare to the SEST crystals. So the SR had grown crystals mechanically good for compare to the conventional crystal.
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