Search

Mg2TiO4was synthesized by the polymeric precursor method, was doped with 1 mol% of Mn2+, Fe2+or Co2+. The powder precursors were characterized by TG/DTA methods. The mass loss took place in three steps. In the first one water and adsorbed gases were released while the second and third step were representative to the decomposition of the organic substance. The DTA experiments indicated the combustion as well as the decomposition and recrystallization of Mg2TiO4between 800 and 1200°C. XRD results indicated that spinel (AB2O4) which have been observed at 600°C transformed to ilmenite (MgTiO3) over 800°C. [ABSTRACT FROM AUTHOR]

In the recent years, the interest concerning to the synthesis of complex oxides, to be applied as electronic ceramics is continuously increasing. One good example is strontium titanate, displaying a perovskite structure, which favors the occurrence of important electronic properties. In the present study, SrxCo1-xTiO3powders, in which 0≤;x≤;0.3, were synthesized by the polymeric precursor method, achieving good a stoichiometric control and presented a crystalline structure at temperatures as low as 600°C. These systems were thermally and structurally characterized using thermogravimetric analysis (TG/DTA), X-ray diffraction (XRD) and infrared spectroscopy (IR). The TG results of the powder precursors show that the mass loss process observed for the undoped and Co-doped SrTiO3takes place in four well-defined stages. These stages are related to the evaporation of water and to the combustion of the organic matter present in the powder precursors (pyrolysis process). The addition of cobalt to the SrTiO3promotes a decrease in the mass loss and also decreases the final decomposition temperature of the organic matter. The XRD analysis showed a single phase when 10% of Sr2+was replaced by Co2+. When the extent of cobalt substitution was higher than 10 mol% and the substance was heat treated over 900°C, a CoTiO3secondary phase appeared. By means of IR, it was possible to observe the vibration bands related to the Ti-O bonds and to carbonates. [ABSTRACT FROM AUTHOR]

In this work, the thermodynamic activation and kinetic study of mineral lubricant oils was accomplished using isothermal and non-isothermal thermogravimetry based on mass loss as a function of time and temperature. The thermodynamic and kinetic behavior of the mineral lubricant oils depends on the atmosphere and heating rates used in TG analysis. The kinetic and thermodynamic results were satisfactory, presenting good correlation, with a linear correlation coefficient close to unit with a low standard deviation. [ABSTRACT FROM AUTHOR]

The objective of this work was to obtain ceramic pigments starting from Zn2TiO4and containing chromophore ions (Co, Ni and Mn in 1-20 mol%), using the polymeric precursor method. Zn2TiO4displays an inverse spinel structure and can accommodate different chromophores in its lattice. The characterization was carried out by means of TG, DTA and XRD. From the TG curves, it can be stated that the pigments are stable above 600°C. X-ray diffraction patterns of the materials containing Co are single phase, whereas the addition of Ni and Mn leads to second phases from 1 and 20% of substitution, respectively. [ABSTRACT FROM AUTHOR]

A series of AlMCM-41 molecular sieves were synthesized starting from a hydrogel keeping the following molar composition: 1CTMABr:4.58SiO2:(0.437+X)Na2O:XAl2O3:200H2O. Tetramethylammonium silicate (TMAS) was used as silicon source and cethyltrimethylammonium bromide (CTMABr) was used as structure template. The obtained materials were characterized by nitrogen adsorption, XRD and TG/DTG. Acid properties were determined by pyridine thermodesorption. Model-free and Flynn-Wall kinetic models were used in order to correlate the total acidity with the apparent activation energy of pyridine desorption. [ABSTRACT FROM AUTHOR]