The influence of mechanochemical activation and thermal treatment on magnetic properties of the BaTiO3 -FexOy powder mixture

Powder mixture of 50 mass % of barium titanate (BaTiO3) and 50 mass % of iron (Fe) was prepared by solid-state reaction technique, i.e. ball milled in air for 60 min, 80 min, 100 min, 120 min and 150 min. During mechanochemical activation it was observed the iron powder transitsion to iron oxides. Depending on the activation time the content of iron oxides FeO, Fe2 O3 and Fe3O4 varies. Simultaneously, with the content change of the activated system, magnetic properties change as well. The XRD analysis of milled samples shown that as the activation time increase, the iron oxide percentage increases to, whereby the percentage of BaTiO3 in a total sample mass decreases. The percentage of iron oxides and BaTiO3 in annealed samples changes depending on annealing temperature. The thermomagnetic measurements performed by Faraday method shown that the powder mixture milled for 100 minutes exhibit maximum magnetization prior to annealing. The increase of magnetization maximum was observed after annealing at 540 oC with all milled samples, and at room temperature it has enhancement from 10 % to 22 % depending on the activation time. The samples milled for 100 min and 150 min and then sintered at 1200 oC exhibit magnetoelectric properties. © 2015 International Institute for the Science of Sintering (IISS). All rights reserved

Characterization of Barium Titanate Ceramic Powders by Raman Spectroscopy

Barium titanate, BaTiO3 ceramic powders were prepared by mechanochemical synthesis and by the Pechini method. A powder mixture of BaO and TiO2 was treated in a planetary ball mill in an air atmosphere for Lip to 1 h, using zirconium oxide vial and zirconium oxide balls as the milling medium. After 60 min BaTiO3 phase was formed. In both ways BaTiO3 ceramics were sintered after 2 h on 1300 degrees C without pre-calcinations step. The heating rate was 10 degrees C min(-1). The formation of phase and crystal structure of BaTiO3 was approved by X-ray diffraction analysis and the Raman spectroscopy. The morphology and microstructure of obtained powders were examined by scanning electron microscopy method. Sharp phase transition from ferroelectric to paraelectric state was observed. The hysteresis loop is very well performed with regular sharp characteristic of ferroelectric materials

The Prevalence of Spinal Deformities in Children of the Early School Age in the Republic of Srpska

Due to the acceleration of biological and lifestyle changes, scientific and technological revolution, disproportionate growth and development, and the impact of endogenous and exogenous factors, postural disorders in the early school age children from the Republic of Srpska and the countries of the region have been increasingly on the rise. A research of a transversal character was conducted in order to analyse the presence of spinal deformities in children of early school age in the Republic of Srpska (Bosnia and Herzegovina). The sample included the population of children in the lower grades of elementary schools from Bijeljina and Foča (Republic of Srpska) and consisted of 90 boys and girls who were divided into two subgroups. One sub-sample consisted of 45 boys, while the other consisted of 45 girls. The measurement was conducted during the 2014/15 school year, when all pupils included in the sample attended the second grade of either “Jovan Dučić” elementary school in Bijeljina or “St. Sava” school in Foča. One of the most state-of-the-art 3D computer methods, Spine Win Pointer Zebris Medical, was used in the analysis of the spinal column. The results of the measurement showed an increased percentage of spinal deformity in the population of the school children in the lower grades of elementary school

THE EFFECTS OF APPLYING A FIVE-MONTH TREATMENT OF PHYSICAL EXERCISE ON PRESCHOOL CHILDREN

The aim of this paperis to determine whether significant effects can be achieved on the kinanthropological space of preschool children compared to the initial state, by applying a five-month treatment of physical exercise with dominantly applied natural forms of movement. The sample consisted of 114 boys (5.89 ± .64 decimal years) from the city of Uţice. A battery of 10 motor tests was applied: Running 20 m, Polygon behind, Tapping with hand, Bending in a sitting position, Long jump from a place, Endurance in a push-up, Raising the body, Darts, Standing on one leg on the ground and Speed of hand movement. The structure of the activity was four-part (introductory, preparatory, main and final), with clearly defined tasks. The biggest and statistically significant differences were found in the variables Running 20 m, Endurance in the push-up, Lifting the trunk and Darts. Applying an experimental program of natural forms of movement in preschool age can have the effect of qualitatively improving motor skills, but it should be borne in mind that not all motor skills are equally sensitive and susceptible to influence.Publishe

Effects of unsymmetrical voltage sags on industrial adjustable speed drives

This paper researches unsymmetrical voltage sag influence on torque ripple in scalar controlled (V/Hz), rotor field oriented (RFO) and direct torque controlled (DTC) drives. Electric drives performance degradation during voltage sag mainly depends on the used control algorithm. Industrial drives with all three types control methods are experimentally tested. Experiments with digital observer's application confirm the proposed solution.

Study on bi-layered ceramics powders prepared by the mechanochemical synthesis

Bi-layered structured ferroelectric materials-bismuth titanate, Bi4Ti3O12 (BIT) and barium-bismuth titanate, BaBi4Ti4O15 (BBT) powders were prepared by homogenization and sintering of mixture of stehiometric quantities of bismuth titanate and barium titanate obtained via mechanochemical synthesis. The Bi4Ti3O12 ceramic was obtained at 1000 degrees C for 4 h and BaBi4Ti4O15 ceramic at 1100 degrees C for 4 h. The phase formation and properties of Bi4Ti3O12 and BaBi4Ti4O15 were studied using XRD, Raman spectroscopy, EDS and SEM. Microstructure of Bi4Ti3O12 and BaBi4Ti4O15 exhibits plate-like grains typical for the bi-layered structured material. The Ba2+ addition leads to the change in the microstructure development, particularly in the change of the average grain size. Crow

The characterization of the barium titanate ceramic powders prepared by the Pechini type reaction route and mechanically assisted synthesis

BaTiO3 ceramic powders were prepared by a complex method based on the Pechini type reaction route and mechanically assisted synthesis. In both ways BaTiO3 ceramics were sintered after 120 min on 1300 degrees C without pre-calcination steps. The crystal structure was investigated by the XRD, IR and Raman spectroscopy. The particle size and morphology of BaTiO3 were examined by XRD and SEM. The XRD results of powders indicate the formation of cubic phase of BaTiO3. It can be observed that in the case of Pechini process BaTiO3 powder is well crystallized but in the case of mechanochemistry process, significant amount of amorphous phase was detected. The sintered BaTiO3 ceramic sample prepared by Pechini process, shows the formation of tetragonal phase. However, IR and Raman spectrum showed a mixture of cubic and tetragonal for BaTiO3 obtained by Pechini process and tetragonal for BaTiO3 obtained by mechanically assisted synthesis

Characterization of Barium Titanate Ceramic Powders by Raman Spectroscopy

Barium titanate, BaTiO3 ceramic powders were prepared by mechanochemical synthesis and by the Pechini method. A powder mixture of BaO and TiO2 was treated in a planetary ball mill in an air atmosphere for Lip to 1 h, using zirconium oxide vial and zirconium oxide balls as the milling medium. After 60 min BaTiO3 phase was formed. In both ways BaTiO3 ceramics were sintered after 2 h on 1300 degrees C without pre-calcinations step. The heating rate was 10 degrees C min(-1). The formation of phase and crystal structure of BaTiO3 was approved by X-ray diffraction analysis and the Raman spectroscopy. The morphology and microstructure of obtained powders were examined by scanning electron microscopy method. Sharp phase transition from ferroelectric to paraelectric state was observed. The hysteresis loop is very well performed with regular sharp characteristic of ferroelectric materials