Thermogravimetry and X-ray diffraction study of the thermal decomposition processes in Li2CO3-MnCO3 mixtures

The thermal decomposition processes taking place in solid state mixtures Li2CO3–MnCO3 (xLi=0.10–0.50, xLi=lithium cathionic fraction) have been studied (both in air and nitrogen flow) by thermogravimetric analysis (TGA), in order to get a better understanding of the different possible by-products, and by X-ray powder diffractometry (XRD) to assess the equilibrium compounds. As concerns the measurements performed in air, LiMn2O4 and excess Mn2O3 are the equilibrium products obtained for xLi up to 0.33. By 0.33xLi0.50 a mixture of LiMn2O4 and Li2MnO3 is obtained. In this case the TGA data show that an excess lithiated spinel phase (Li1+xMn2O4) is obtained as an intermediate phase. The measurements performed in nitrogen (xLi up to 0.33) show, when examined by TGA, the formation reaction of LiMn2O4 and Mn3O4 which is completed within about 720°C. At higher temperatures a rather complex reaction takes place between LiMn2O4 and the excess Li2O present at 720°C, leading to the formation of the compounds Li2Mn2O4 and LiMnO2 again with excess of Mn3O4. At higher mixture lithium content (0.33xLi0.50) LiMn2O4, Li2MnO3 and Mn3O4 form up to about 720°C. At higher temperatures LiMnO2 is by far the majority phase present which is formed by solid state reactions occurring between LiMn2O4 and Li2MnO3 and between Li2MnO3 and Mn3O4

TG/FT-IR: An Analysis of the Conditions Affecting the Combined TG/Spectral Response

The results of TG/FT-IR measurements performed on hydrated beta-cyclodextrin at different heating rates and with different carrier gas fluxes are reported. It is shown that the shape of the spectral curve and the its degree of matching with the DTG curves depend on both the TG heating rate and the carrier gas flow rate

Effect of extended ball milling on graphite

Graphite has been milled for up to 1000 h in a laboratory scale tumbling ball mill under vacuum. Raman spectroscopy of the powders indicated the increasing dominance of D-type graphitic sp bonding over G-type bonding with increasing milling time. Diamond-like sp bonding and possibly fullerene-like bonding also became evident after milling. TEM of the 100 h sample showed the presence of ribbons which were composed of sheets showing defects, delamination, translation, warping and curvature. Interplanar spacings of 0.40–0.50 nm were measured with the spacing increasing towards the edge of the ribbons where delamination was evident. Thermogravimetric analysis in argon of the powder after exposure to air showed an increasing mass loss with milling time indicating the presence of chemisorbed gas. Using TG–FTIR the gas was found to be a mixture of CO and an unidentified gas (probably oxygen). BET surface area measurements showed a maximum in the surface area; however, this was shown to be massively in error for the longer milling times due to the presence of the chemisorbed gas

Oxidation Behaviour of Mechanically Activated Mn3O4 by TGA/DSC/XRPD

The effect of high energy milling on the solid-state reactions taking place in Mn3O4 has been studied. Thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC) have been employed to study the solid-state reaction occurring under air in the temperature range between room temperature (rt) and 1100 °C. X-ray Powder Diffractometry (XRPD) has been used to ascertain the chemical nature of the transformations brought into evidence by thermo-analysis

Solid State Synthesis of Strontium Oxoferrates from the Mechanically Activated System SrCO3-Fe2O3

The solid state reactions occurring in the SrCO3 - Fe2O3 system have been studied by DSC, TGA and XRPD techniques. The enthalpies of reactions have been determined

Kinetics of BaBr2·2H2O Dehydration: Comparison Between Isothermal and non-Isothermal Methods

For the reaction of dehydration of BaBr2 with a different content of water molecules, a comparison was made between the experimental non-isothermal alpha vs time curves and those calculated on the basis of a isothermal study. For low heating rates, the two data sets are in good agreement