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Mechanical activation leads to the creation of new surfaces and decrease in particle size of the initial powder particles, which affects the crystallization of PVDF matrix. In addition, prolonged mechanical activation leads to agglomeration of nanoparticles agglomerates of different sizes. Microstructural changes due to mechanical activation in ZnO, BaTiO3, SrTiO3 and TiO2 powders were investigated using electron microscopy (TEM and SEM), x-ray diffraction (XRD) and particle size analysis (PSA). These were correlated with molecular simulations of mechanical properties of PVDF-nanocluster composites with different oxide nanocluster sizes (1, 1.5 and 2 nm) Each system was simulated using a periodic system of metal oxide nanocrystal inside β-PVDF matrix. β-PVDF was chosen for its superior properties over α- and γ- phases. Geometry of each system was optimized prior to the calculation of mechanical properties using GULP v4.3 software package. Molecular simulations show that, in general, mechanical properties (Young modulus as an indication of elasticity, Shear modulus as an indication of hardness) for all systems improve with decrease in nanocluster size. This suggests that mechanical activation of fillers in PVDF-metal oxide nanoparticle composites should have a positive effect on the mechanical properties of composite systems. This suggests mechanical activation as an easy an inexpensive method of improving mechanical properties of polymer-nanocrystal composite materials. Conference abstract: [https://hdl.handle.net/21.15107/rcub_dais_882]

Mechanically activated powders (0, 10, 40, 80 and 160 minutes) were formed by isostatic pressure 300 MPa to cylindrical green bodies (φ 12 mm). First set of samples was sintered at 1300°C for 30 min in air (heating rate 10 °C/min, cooling rate 5 oC/min). These samples were re-sintered at 1200 oC for 20 h in air (heating rate 20 °C/min, cooling rate 10 oC/min). Samples reached almost 90 % TD. The second set of samples was sintered at 1400 °C for 30 in air (heating rate 10 oC/min, cooling rate 5 °C/min). Relative densities increased up to 93 % TD. The samples of absence of open porosity (MTO-10, 40, 80 and 160) were post-sintered by pressure assisted technique Hot Isostatic Pressing (HIP) at 1200 °C for 2 h in argon atmosphere with pressure 200 MPa. The samples increased densities up to 96 % TD for sample MT-160. Electrical measurements were performed in the microwave field of frequency. IV Serbian Ceramic Society Conference - Advanced Ceramics and Application : new frontiers in multifunctional material science and processing : program and the book of abstracts; September 21-23, 2015; Belgrade

The structure and lattice dynamics of mechanically activated nanocrystalline Fe/BaTiO3 is investigated in this work. The powder mixture of 60%Fe and 40% BaTiO3 was mechanically activated up to 240 min in 500 cm3 zirconium oxide beakers together with balls of 10 mm in diameter (the ratio of powder and balls was 1:20). The microstructure development has been studied by scanning electron microscope equipped with energy dispersive x-ray analysis spectrometer. Room temperature Raman spectra of the samples were obtained in the spectral range from 100 to 1650 cm-1, in the backscattering geometry, using 633 nm line of a He-Ne laser. Raman spectroscopy was employed to investigate the laser power dependence of the spectra of the activated samples as wells. Microstructural investigations showed that mechanical activation has led to the creation of new surfaces and the comminution of the initial powder particles. Raman spectroscopy analysis pointed out that activation had a pronounced influence on Fe/BaTiO3 lattice spectra, thus affecting both the stability of the crystal structure and the phase transition phenomena.

Powder mixture of 60 mass % of iron (Fe) and 40 mass % of barium titanate (BaTiO3) has been activated in planetary mill for 100, 120, 150, 180, 210 and 240 min in the air. During the activation the iron powder transits into iron oxides FeO, Fe2O3 and Fe3O4. Depending on the activation time the percentage of iron oxides varies. Simultaneously, with the content change of the activated system, magnetic properties change as well. The thermomagnetic measurements in the temperature interval from 200C up to 6200C have shown that the powder activated for 120 minutes exhibits maximum magnetization prior to annealing. After multiple annealings of the same sample it has been shown that the maximum magnetization of the cooled sample is obtained upon annealing at 5600C during 10 min for all activation times of as-cast powder sample. The sample obtained from pressed powder mixture activated for 120 min has the maximum magnetization, upon isothermal sintering of samples at 12000C during 2h, being M = 2,9 Am2/kg. With additional annealing of the same sample up to Curie temperature (TC = 4300C) and subsequent cooling of the sample in the magnetic field of H = 20 kA/m, the sample is permanently magnetized. The magnetization of sample cooled in the magnetic field with intensity of 20 kA/m being M = 10,15 Am2/kg.

The authors investigated the morphological characteristics of mechanically activated ZnO powder. ZnO powder was mechanically activated for 2, 5, 10 and 30 minutes in a planetary ball mill. Mechanical activation introduces lattice disorder and defects into ZnO hexagonal wurtzite structure. In order to determine specific surface area and pore volume, we performed N2 porosimetry and SEM in order to investigate the microstructure of non-activated and mechanically activated ZnO powders. Using Kubelka-Munk function, UV-Vis spectra showed the reducing in band gap with activation time. ZnO powder activated for 5 minutes has the narrowest band gap.

Cordierite, 2MgO•2Al2O3•5SiO2 (MAS), is high-temperature ceramic material. Cordierite is commonly used material because of outstanding electrical properties, low temperature expansion coefficient and low dielectric constant. In order to accelerate the process of sintering, 5.00 mass% MoO3 has been added to the starting mixtures. The mechanical activation of the starting mixtures was performed in a high energy ball mill during 0-160 minutes. All starting mixtures were sintered at 1100°C, 1200°C and 1300°C for 2h. The particle size analysis (PSA) was employed in order to determine the changes in the particle size of the mechanically treated powders. The phase composition of the starting powders was analyzed by the X-ray diffraction method. Differential thermal (DTA) and thermogravimetric (TG) analysis were used in order to determine characteristic temperatures within the system during heating. Based on the obtained DTA results, it was established that mechanical activation with additive MoO3, has influence on decreasing sintering temperatures for about 150°C. III Serbian Ceramic Society Conference - Advanced Ceramics and Application : new frontiers in multifunctional material science and processing : program and the book of abstracts; September 29 - October 1, 2014; Belgrade

Materials based on ZnO structure have more frequently application as fillers in polymer ceramics nanocompozites. Performances of these materials depends on fillers morphology, surfaces texture and particles size. According to this, in this paper, the authors investigated the influence of mechanical activation of ZnO powder on crystal and micro structure. Commercially available ZnO powder was activated in a planetary ball mill for 2, 5, 10 and 30 minutes. Characterization of such obtained powders was performed using XRD, SEM and Raman spectroscopy. XRD patterns indicated at lowering of peak intensities along with its broadening wich is realted to partical fragmentation and amorphyzation. Micrographs show irregularly shaped particles at the beginning and with prolonged milling time, particles gained uniformed distibution, while after 30 minutes of activation agglomerates started forming. The results we got by investigation of dynamical structure by Raman spectroscopy are in correlation with the other results of structures analysis. Results presented here enable further optimization of, polymer nanocompozite based on ZnO and PVDF, making process. II Serbian Ceramic Society Conference - Advanced Ceramics and Application : new frontiers in multifunctional material science and processing : program and the book of abstracts; September 30 - October 1, 2013; Belgrade

In this article the influence of ball miling process on structure of MgO-TiO2 system was investigated. The mixtures of MgO-TiO2 powders were mechanically activated in a planetary ball mill for the time period from 0 to 120 minutes. The influence of mechanical activation on the lattice vibrational spectra was studied by Raman spectroscopy at room temperature. Structural investigations have been performed on produced powders. Nitrogen adsorption method was used to determine the BET specific surface area and pore size distribution. Unusual results have been obtained: specific surface area continuously decreased up to 40 minutes of activation and increased after that, reaching its minimun value of 5.5 m2/g. The Raman spectra of activated powders have shown that anatase modes have been decreasing in intensity and broadening as the time of activation extended. Also, the additional modes attributed to TiO2 II, srilankite and rutile phases started to appear as a consequence of activation.

Mechanical activation is widely used and relatively inexpensive procedure for sintering process sample preparation. However, the influence of pressure, which is used for compaction, has not been completely investigated. Cordierite, 2MgO⋅2Al2O3⋅5SiO2, is a very actual hightemperature ceramic material, due to its characteristics. Based on our previous investigation, the mechanical activation of the starting mixtures with 5.00 mass% TiO2 was performed in a high energy ball mill during 10 minutes. Compaction pressure varied from 0.5 to 6t/cm2 (49 MPa - 588 MPa). Sintering process was performed at 1350oC for 4h in air atmosphere. The phase composition of activated and sintered samples was analyzed by the X-ray diffraction method. Scanning electron microscopy was performed to analyze the microstructure of both compacted and sintered sample. Non-isothermal sintering up to 1400oC, with a constant heating rate, was investigated by thermal shrinkage change with dilatometer. In this paper we research green bodies and sintered samples compaction pressure influence electrical properties. II Serbian Ceramic Society Conference - Advanced Ceramics and Application : new frontiers in multifunctional material science and processing : program and the book of abstracts; September 30 - October 1, 2013; Belgrade

Ferroelectric ceramic barium strontium titanate (Ba0.77Sr0.23TiO3), BST, was prepared by solid-state reactions using starting powders of barium carbonate (BaCO3), strontium carbonate (SrCO3) and titanium dioxide (TiO2-anatase). Non-activated and mechanically activated mixtures with high-energy planetary ball mill (0, 5, 10, 20, 80 and 120 minutes) were sintered at 1100, 1200, 1300 and 1400 °C for two hours in air. The maximum value of ceramic density is about 86.20% TG. X-ray diffraction analysis was used to obtain information on the phase composition, as well as determining the influence of mechanical activation on the half height width of the diffraction lines (111) BST isothermally sintered samples at 1400 °C during two hours. Defects and the beginning process of sintering on the microstructure were investigated by scanning electron microscopy (SEM). Electrical measurements (loss tangent of the angle, Nyquist diagrams and influence the activation time dependence of XC = f (log ν)) are made of ceramics sintered at 1400 °C for two hours.

Cordierite, 2MgO⋅2Al2O3⋅5SiO2, is a very attractive high-temperature ceramic material, due to its outstanding electrical characteristics, such as the low temperature expansion coefficient, low dielectric constant and good mechanical properties. In order to accelerate the process of sintering, 5.00 mass% MoO3 has been added to the starting mixtures. The mechanical activation of the starting mixtures was performed in a high energy ball mill during 0-80 minutes. The particle size analysis (PSA) was employed in order to determine the changes in the particle size of the mechanically treated powders. The phase composition of the starting powders and sintered samples was analyzed by the X-ray diffraction method. Furthermore, differential thermal analysis (DTA) was used in order to determine characteristic temperatures within the system during heating. Based on the obtained DTA results, it was established that mechanical activation has some influence on temperatures of phase transitions. Sintering process was performed in air at 1200oC for 2h. II Serbian Ceramic Society Conference - Advanced Ceramics and Application : new frontiers in multifunctional material science and processing : program and the book of abstracts; September 30 - October 1, 2013; Belgrade

Strontium-titanate powder was mechanically activated in a planetary ball mill for 0, 5, 10, 30, 60, 90 and 120 minutes. Non-isothermal sintering of non-activated and activated SrTiO3 powder samples in the temperature interval from 50 to 1300 0C with three different heating rates (10, 15 and 20 0C/min) was investigated on a dilatometer. X-ray powder diffraction and scanning electron microscopy (SEM) were used to determine the phase composition, lattice microstrains and microstructure morphology of the samples. XRD results showed the presence of new phases: SrCO3 (strontuim-carbonate) and TiO2 (anatase) after 30 minutes of mechanical activation. II Serbian Ceramic Society Conference - Advanced Ceramics and Application : new frontiers in multifunctional material science and processing : program and the book of abstracts; September 30 - October 1, 2013; Belgrade

In this article the influence of mechanical activation on sintering process of barium-strontiumtitanate ceramics has been investigated. Both non-activated and mixtures treated in planetary ball mill for 5, 10, 20, 40, 80 and 120 minutes were sintered at 1100-1400 °C for 2 hours in 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 to low to induce final sintering stage for the system. Electrical measurements have been conducted for the densest ceramics sintered at 1400 °C for 2 hours. I Serbian Ceramic Society Conference - Advanced Ceramics and Application : program and the book of abstracts; May 10-11, 2012; Belgrade

Mixtures of MgO and TiO2 were mechanically activated in a planetary ball mill for different time intervals. Thus obtained powders were sintered in a furnace for 2 h at temperature of 1300 °C in air atmosphere. Raman scattering spectroscopy at room temperature has been used for characterization of sintered samples. Very similar spectra for all samples were observed, which indicate that there has been structure recovery during treatment at higher temperature. SEM analyses were performed in order to investigate effect of activation and sintering process on microstructure. Electrical measurements showed difference in dielectric constant (εr), loss tangent (tgδ) and specific resistance (ρ) as a function of time of mechanical treatment. The aim of this paper was to determine optimal parameters for materials preparation with a goal to obtain dense ceramic with appropriate characteristic.