Temperature programmed decomposition of cobalt ethylene diamine complexes

The cobalt co-ordination complexes, [Co(en)(2)Cl-2]Cl and [Co(en)(2)CO3]Cl, synthesised through literature procedures, were characterised by FTIR. Tra ce metallic impurities were determined by ICP-MS. Crystallinity of the samp les were ascertained by preliminary X-ray powder diffraction analysis. Dark field polarised optical microscopy (OM) was used to observe particle size distribution. These compounds were subjected to temperature programmed deco mposition (TPD) in thermogravimetric analyser (TGA). TPD was also carried o ut in a home built mass spectrometry based evolved gas analyser (EGA-MS). T he complex TGA weight loss profile could be successfully explained through EGA data. Complimentary information received from both the above techniques indicated sequential decomposition, prevalence of steric effect and functi onal group ejection. The non-isothermal kinetic analysis of TGA and EGA dat a showed dominance of kinetic control mechanisms based on sigmoidal rate la ws like Avarami-Erofeev (AE) and random nucleation (RN). The fraction relea se alpha similar to T plots were used to evaluate integral model function g (alpha) of non-isothermal kinetic rate expressions. From log[g(alpha)/T-2] similar to 1/T plots of well correlated model functions, Arrhenius paramete rs like activation energy and pre-exponential factors were evaluated for va rious decomposition steps. (C) 1999 Elsevier Science B.V. All rights reserv ed.