DTA studies on the liquidus temperatures of Cr complex with the addition of an anhydrous Ni complex P. Antony Premkumar a , K.S. Nagaraja a , R. Pankajavalli b , C. Mallika b , O.M. Sreedharan b, * a Department of Chemistry, Loyola Institute of Frontier Energy (LIFE), Loyola College, Chennai TN-600 034, India b Materials Characterization Group, Thermodynamics and Kinetics Division, Indira Gandhi Centre for Atomic Research, Kalpakkam TN-603 102, India Received 23 January 2003; received in revised form 16 June 2003; accepted 25 June 2003 Abstract Determination of T – X Cr diagram for a binary system of tris(2,4-pentanedionato)Cr(III) and anhydrous bis(2,4-pentanedionato)Ni(II) over the range of 1.000 – 0.506 for the mole fraction (X Cr ) of the Cr complex by employing DTA revealed the system to behave as an ideal eutectic exhibiting lowering of the melting point of the former complex with the addition of the latter one. The thermodynamic correlation between T and X Cr yielded an average value of 109.9 F 0.4 kJ mol  1 for the standard enthalpy of fusion of the Cr complex. D 2003 Elsevier B.V. All rights reserved. Keywords: Phase diagram; Thermal properties; Materials processing; Cr– Ni complexes; Vapourisation; Fusion enthalpy 1. Introduction The standard enthalpy of sublimation ( DHj sub ) of tris(2,4-pentanedionato)Cr(III) (commonly referred to as Cr(acac) 3 ) was recently reported by Mallika et al. [1] owing to its potential application as a precursor for plasma assisted CVD [2] for hard facing (chrome nitriding) of stainless steel substrates. These authors employed a TG-based transpira- tion technique and compared their results with those reported in the literature by employing diverse techniques namely isoteniscopic [3], effusion/sublimation bulb [4,5], TG and DSC [6,7]. Due to the high volatility of Cr(acac) 3 , the maximum temperature of its volatilization for CVD purposes seemed to be restricted to its melting point (488 K), beyond which it was reported to sublime rapidly without leaving any residue. Hence, there is no report in the literature on its standard enthalpy of fusion DH fus j that has to be de- termined indirectly by a cryoscopic technique employing a non-volatile solute. The results of its determination using such a technique employing an anhydrous nickel complex namely, bis(2,4-pentanedionato)Ni(II) (Ni(acac) 2 ) as the solute, are presented here. 2. Experimental 2.1. Materials The synthesis and characterization of Cr(acac) 3 were the same as described elsewhere [1,8] while the phase analysis was carried out by powder X-ray diffraction (XRD) within its 5 mass% threshold of detection of impurity phases. Chemical purity was established by determination of its melting point to be 488 K besides elemental analysis and estimation of chromium as lead chromate [9]. Crystals of Ni(acac) 2 4H 2 O were synthe- sized from reagent grade NiCl 2 6H 2 O (Loba Chemie, India) of purity >99.9% and acetylacetone (Merck, Ger- many) of purity >99.99% as per the procedure adapted by Charles and Pawlikowski [10] and was likewise characterized using powder XRD and by elemental anal- ysis including gravimetric analysis of nickel as its di- methyl glyoxime complex [9]. No purity determination by melting point was resorted to owing to its decompo- sition without melting. The mixtures of Cr(acac) 3 and 0167-577X/$ - see front matter D 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0167-577X(03)00528-7 * Corresponding author. Tel.: +91-4114-280116; fax: +91-4114- 280301. E-mail address: oms@igcar.ernet.in (O.M. Sreedharan). www.elsevier.com/locate/matlet Materials Letters 58 (2004) 474 – 477