Microhardness study of the nonlinear optical crystal L-arginine hydrochloride monohydrate
- PDF / 148,468 Bytes
- 4 Pages / 612 x 792 pts (letter) Page_size
- 97 Downloads / 177 Views
I. INTRODUCTION
L-ARGININE hydrochloride monohydrate (LAHCl), with the chemical formula (H2N)+CNH(CH2)3CH(NH3)+ COO2?Cl2?H2O, is one of the new semiorganic nonlinear optical (NLO) materials discovered by Monaco et al.[1] Various physical and NLO properties, as well as the growth mechanism of different faces of the single crystal of LAHCl, have been reported.[1–5] As a part of our project work, we have studied the growth, thermal behavior, vibrational spectroscopy, and chemical etching behavior of LAHCl in different solvents and have published reports in international journals.[6,7] Thus, extensive studies have been carried out on different aspects of LAHCl. But, to our knowledge, the study of the hardness of the LAHCl crystal, which is important as far as the fabrication of devices is concerned, has not been done yet. The present article is devoted to this particular aspect of LAHCl. The hardness of a material is defined as the resistance it offers to the motion of dislocations, deformation, or damage under an applied stress.[8] The general definition of indentation hardness, which relates to the various forms of indenters, is the ratio of the applied load to the projected area of indentation. Generally, the apparent hardness of the material varies with applied load. The decrease of microhardness with applied test load is known as the indentation-size effect (ISE) and has been reported by various authors.[9–15] Kotru et al.[16] described the ISE with the help of a modified law of Hays and Kendall.[17] Recently, Li et al.[18] developed a proportional specimen-resistance (PSR) model to explain the ISE. In this model, the two contributing factors to the ISE are the friction between the indenter facets and the test specimen and the elastic resistance of the test specimen. We applied the PSR model to describe the variation of hardness with applied load in the case of LAHCl. II. EXPERIMENTAL Single crystals of LAHCl were grown by slow evaporation (at 28 8C) as well as by a slow cooling method. The detailed SUDESHNA MUKERJI, PDF, is with the Department of Electrochemistry, Technion Israel Institute of Technology, Israel. TANUSREE KAR, Senior Lecturer, is with the Department of Materials Science, Indian Association for the Cultivation of Science, Calcutta - 700 032, India. Manuscript submitted April 19, 1999. METALLURGICAL AND MATERIALS TRANSACTIONS A
studies of the growth of LAHCl were described in our previous work.[6] The LAHCl crystal belongs to the monoclinic system; the typical growth habit is shown in Figure 1. For hardness measurement, transparent crystals grown by the slow evaporation method, which are free from visible inclusions or cracks, were selected. The crystals were 3 mm in thickness and had a surface area of 8 3 10 mm2. The microhardness of the LAHCl crystal was determined using a mhp160 microhardness tester fitted with a Vickers diamond indenter and attached to a Carl–Zeiss (Jenavert) microscope. The Vickers microhardness (Hv) was measured on the (100), (001), and (010) faces for applied loads ranging
Data Loading...
