Structural investigation of mechanically activated ZnO powder

Commercially available ZnO powder was mechanically activated in a planetary ball mill. In order to investigate the specific surface area, pore volume and microstructure of non-activated and mechanically activated ZnO powders the authors performed N-2 physisorption, SEM and TEM. Crystallite size and lattice microstrain were analyzed by X-ray diffraction method. XRD patterns indicate that peak intensities are getting lower and expend with activation time. The reduction in crystallite size and increasing of lattice microstrain with prolonged milling time were determined applying the Rietveld's method. The difference between non-activated and the activated powder has been also observed by X-ray photoelectron spectroscopy (XPS). XPS is used for investigating the chemical bonding of ZnO powder by analyzing the energy of photoelectrons. The lattice vibration spectra were obtained using Raman spectroscopy. In Raman spectra some changes along with atypical resonant scattering were noticed, which were caused by mechanical activation

Application of the master sintering curve theory to non-isothermal sintering of BaTiO3 ceramics

In this paper a practical approach to the analysis of sintering of BaTiO3 using the Master Sintering Curve concept has been presented. Non-isothermal sintering of high-purity non-doped BaTiO3 ceramics was monitored using a sensitive dilatometer at three different heating rates (10, 20 and 30 degrees C/min) up to 1380 degrees C. Densification. of BaTiO3 during sintering was analyzed using the Master Curve Sintering Theory. A MSC was defined characterizing the sintering behavior of barium-titanate regardless of the heating rate. Construction of the MSC enabled estimation of the process activation energy. Using defined MSC, densification behavior of BaTiO3 ceramics during sintering can be predicted for arbitrary temperature-time excursions and these predictions can be used in controlling and planning the sintering process of this material

The influence of mechanical activation on sintering process of BaCO3-SrCO3-TiO2 system

In this article the influence of mechanical activation on sintering process of bariumstrontium-titanate ceramics has been investigated. Both non-activated and mixtures treated in a planetary ball mill for 5, 10, 20, 40, 80 and 120 minutes were sintered at 1100-1400°C for 2 hours in presence of air atmosphere. The influence of mechanical activation on phase composition and crystal structure has been analyzed by XRD, while the effect of activation and sintering process on microstructure was investigated by scanning electron microscopy. It has been established that temperature of 1100°C was too low to induce final sintering stage for this system. Electrical measurements have been conducted for the densest ceramics sintered at 1400°C for 2 hours. [Projekat Ministarstva nauke Republike Srbije, br. OI172057

Sintering of cordierite in the presence of MoO3 and crystallization analysis

Cordierite (MAS) is difficult to sinter because of the very narrow sintering temperature range (1300-1400ºC). Because a low temperature process is desirable, it is necessary to find functional ads which can allow easier sintering process at lower temperature. The influence of MoO3 on the preparation process of cordierite ceramics was investigated. 2MgO-2Al2O3-5SiO2 was researched by sintering followed binary systems: MgO/MoO3, Al2O3/MoO3 and SiO2/MoO3 (all sintered at 850ºC and 1100ºC, sintering time 2h). Composition of these systems was 80 mass% of oxide and 20 mass% MoO3. The effects of sintering, the composition and morphology were followed by X-ray diffraction and SEM microscopy. It has been found that MoO3, beside liquid phase, forms intermediary unstable compounds with MgO and Al2O3, which is the significance information for further research. MAS ceramics were sintered with 20 mass% MoO3 at 1100ºC, 1200ºC and 1300ºC, during 2h. [Projekat Ministarstva nauke Republike Srbije, br. OI 172057

The influence of tribophysical activation on non-isothermal sintering of BaTiO3 ceramics

In this paper the influence of tribophysical activation on non-isothermal sintering of barium titanate has been investigated. BaTiO3 powders were tribophysically activated in a planetary ball mill for 0, 60 and 120 min., pressed and non-isothermally sintered up to 1380°C. Dilatometric analysis was performed in air in the temperature range from room temperature to 1380°C with heating rates of 10, 20 and 30°C/min. The samples were analyzed by the X-ray powder diffraction method. Investigation of the morphology of microstructure constituents was performed using the scanning electron microsocopy method. With the purpose of optimizing technological parameters the results obtained by microstructure analysis were correlated with the results of quantitative dilatometric analysis

The influence of mechanical activation on the morphological changes of Fe/BaTiO3 powder

Crystal structure and morphology of mechanically activated nanocrystalline Fe/BaTiO3 was investigated using a combination of spectroscopic and microscopic methods. These show that mechanical activation led to the creation of new surfaces and the comminution of the initial powder particles. Prolonged milling resulted in formation of larger agglomerates of BaTiO3 and bimodal particle size distribution, where BaTiO3 particles were significantly larger than those of iron-containing phases. Milling times of 210 min and above lead to a significant decrease in temperature of the oxidation of iron in the sample, indicating abrupt change in reactivity. Raman spectroscopy analysis has revealed that activation had a pronounced influence on Fe/BaTiO3 lattice, thereby affecting both the stability of the crystal structure and the phase transition phenomena