Vickers Microhardness Studies Research Articles

Growth and characterization of 4-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) single crystals

Experimental determination of metastable zonewidth and induction period for 4-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) is reported. The interfacial tension for different supersaturation conditions has been estimated for the DAST solution at 30°C. The solubility of DAST in methanol has been determined and bulk crystals of dimensions 6×5×2 mm 3 have been grown by spontaneous nucleation technique with the optimized growth parameters. XRD and FTIR studies confirm the structure and presence of functional groups in the grown crystals. Vicker's microhardness studies carried out on {0 0 1} face of DAST crystals reveal that these crystals possess higher hardness values than other organic crystals.

Microhardness and slip systems of solution grown MHB crystals

Today nonlinear optical organic materials are widely used for a variety of photonic technologies. Many NLO organic single crystals have been identified as potential candidates in optical and electro-optical devices. In this paper, we report the mechanical anisotropic hardness behaviour of the organic NLO molecular crystal methyl parahydroxybenzoate (MHB). MHB compound was synthesized and the crystals were grown by solution growth technique. Single crystal X-ray diffraction studies were carried out to determine the lattice parameters of the grown crystal and SHG measurements reveal SHG efficiency 15 times higher than Urea. MHB is an aromatic crystal with noncentrosymmetric structure, and exhibits anisotropy in mechanical behaviour. The Vickers microhardness studies were carried out on all the visible planes using Vickers microhardness tester and the microhardness owing to plastic deformation is discussed in terms of various slip systems. A suitable combination of acetone and methanol as etchant was identified for visualizing the slips.

The study of impurities effect on the growth and nucleation kinetics of potassium dihydrogen phosphate

Potassium dihydrogen phosphate is a well-known non-linear optical material and has immense uses in solid state laser source devices. In the search for suitable materials with higher non-linear responses and good optical, thermal, mechanical properties as well as fast growth rate, an attempt has been made to grow potassium dihydrogen phosphate separately doped with urea and KCl in different molar ratios. The effect of impurities on the growth, nucleation kinetics, surface morphology, structural, optical and mechanical properties have been investigated. With increasing impurity concentration (viz. 1–10 mol%) the growth rate was found to increase. Vicker's microhardness study shows higher mechanical stability in urea doped KDP crystals than KCl. Moreover, the addition of KCl improves the quality of the crystal surface and yields highly transparent crystals with well defined features.

Vicker's Microhardness Studies of L-arginine Hydrobromide Monohydrate Crystals (LAHBr)

Vicker's microhardness study of (100), (010) and (001) faces of a non-linear optical crystal, L-arginine hydrobromide monohydrate (LAHBr)have been reported.(100) plane is found to be the weakest plane. It has been observed that the microhardness decreases with increasing load for the three crystal planes. The microhardness behaviour have been explained successfully with the help of the PSR model proposed by Li and Bradt. Work hardening index n for the three planes are found to be greater than 1.6 which indicates that LAHBr is a soft crystal.

Observations made during the growth of trihalides of group Vb elements

Single crystals of antimony triiodide (SbI 3), bismuth triiodide (BiI 3), antimony tribromide (SbBr 3) and arsenic triiodide (AsI 3) have been grown from the vapour. Experiments have been carried out both by oscillating and without oscillating the source-zone temperature. In the case of crystals grown without oscillation, it has been found that dendritic growth favours the growth of platelets. When the temperature is oscillated, the surfaće morphology is found to depend upon the supersaturation. Etching studies and Vickers microhardness studies have also been made.

Microhardness of nanocrystalline palladium and copper produced by inert-gas condensation

This report describes the major results of a Vickers microhardness study of nanocrystalline palladium and copper produced by the inert-gas condensation method. Small grain size is known to have a strong influence on mechanical properties at low and intermediate temperatures, as observed in the Hall--Petch effect, Coble creep, and superplasticity. Until recently, the mechanical properties of nanocrystalline materials with mean grain diameters of 5 to 50 nm have not been explored. A microhardness study on conventional compacted tungsten powder indicated that the Hall--Petch effect extends to the 150 nm range; and effects of nanocrystalline grain size on mechanical properties of TiO{sub 2} have been investigated.

An Investigation on the Growth and Characterization of Thiourea Single Crystal Grown from Aqueous Solutions

Thiourea single crystals have been grown from aqueous solution by slow cooling technique. The stability of the saturated solutions of different pH values has been assessed by measuring the metastable zone width (MSZW) by a nucleation method. MSZW has been enhanced by the influence of pH of thiourea solution. The growth rate of the thiourea crystal along the c-direction [001] was found faster for the higher pH value of the solution. The structural, optical and mechanical properties of the grown crystals were characterized by FT-IR spectroscopy, UV-Vis spectroscopy and powder X-ray diffraction. FT-IR and UV-Vis spectra provide information about the presence of functional groups. The Vicker's micro-hardness study has been performed on the grown crystals and the results reveal the softening nature according to Onistch concept. The growth features of the thiourea crystals were observed by etching study. A hexagonal spiral growth was observed on the [001] faces of thiourea crystals. DOI: 10.3329/jbas.v33i1.2951 Journal of Bangladesh Academy of Sciences, Vol. 33, No. 1, 63-70, 2009