Microhardness studies on as-grown faces of NaClO sub(3) and NaBrO sub(3) crystals

• Published in: Bulletin of materials science Vol. 25; no. 7; pp. 641 - 646
• Main Authors: Rao, KKishan, Surender, V, Rani, BSaritha
• Format: Journal Article
• Language: English
• Published: 01.12.2002
• Subjects: Corners; Cracks; Crystals; Evaporation; Hardness; Mathematical analysis; Microcracks; Microhardness
• ISSN: 0250-4707; 0973-7669
• DOI: 10.1007/BF02707897

Single crystals of NaClO sub(3) and NaBrO sub(3) are grown from their aqueous solutions at a constant temperature of 35 degree C by slow evaporation by using good quality seed crystals. Systematic microhardness studies are made on as-grown faces of these crystals at various loads. Typical cracks are observed at the corners of the impressions in NaClO sub(3) whereas in addition to the cracks at the corners microcracks also appeared in NaBrO sub(3) crystals around the impressions. The impressions formed in NaBrO sub(3) are not very clear as in NaClO sub(3), a possible mechanism for it is discussed. The work hardening index number(n) for both these crystals is around 1.6 suggesting that these are moderately harder samples. The hardness studies point out that NaBrO sub(3) is harder than NaClO sub(3) ( Delta H approximately 100 kg/mm super(2),this could be due to strong inter ionic forces acting between Na-Br in NaBrO sub(3) crystals. Using Gilman's empirical relation, hardness values are calculated from the values of elastic constants (C sub(44)) and are found to be close to the experimental results.