Influence of synthesis parameters and thermal treatment on functional properties of Fe3O4-BaTiO3 multiferroics obtained by mechanical activation

Mechanical activation of a mixture of polycrystalline powders Fe3O4 (50% wt.) and BaTiO3 (50% wt.) was performed in a planetary ball-mill, with different milling times (3 h, 6 h and 12 h). Average crystallite size determined by XRD analysis ranges from 12 to 30 nm, depending on the milling time. The activated powders were pressed into disc-shaped samples, 8 mm in diameter and 1.5 mm thick, applying the pressure of 500 MPa,. Thermoelectric measurements conducted in the temperature range from room temperature to 350 °C revealed that the electrical resistivity of the sample depends on temperature and activation time. At room temperature, the maximum value of specific electrical resistivity (ρ0 = 1 MΩm) was observed for the sample obtained by pressing the powder activated for 6 h. Magnetic properties of pressed powder samples were studied using a modified Faraday method. At room temperature, the pressed powder activated for 3 h exhibited the maximum value of magnetization, M0= 0.86 Am2/kg. Multiple heating of the pressed samples, for 10 min, was performed in a magnetic field of 20 KA/m. After cooling, the highest magnetization values were observed for the samples previously heated at 380 °C, while the maximum one (M’= 1.04 Am2/kg) corresponds to the sample activated for 3 h

Static-dynamic model for endpoint control used in Smederevo's BOF shop

This paper describes the computer model for BOF control that was in use at Smederevo, Serbia, during the period 1994-2006. The model was developed at the Institute of Metallurgy of the Smederevo Steelwork in mid-1994 and was motivated by the fact that the plant in Smederevo, by that time, had many years of experience in endpoint control using Intermediate Stop Practice (ISP). The vision for the model was to continuously improve and adapt to the working conditions of production through self-learning and adjustments. The model belongs to the well-known family of Static-Dynamic models (SDMs). It is aimed to reduce the "oxygen off-to-start tap" time and thus increase productivity and reduce production costs. The paper briefly describes the metallurgical software, operator operations and provides some information on the model's effectiveness

Effect of temperature on the physical changes and drying kinetics in plum (Prunus domestica L.) Požegača variety

In this study, drying kinetics of autochthonous variety Požegača plum was examined in a laboratory dryer at three temperatures. The whole plum fruits, together with the kernels were subjected to the drying process. The effect of drying has been examined at temperatures of 55, 60 and 75 °C, with a constant air velocity of 1.1 m s-1. The corresponding experimental results were tested using six nonlinear regression models. Coefficient of determination (R2), standard regression error (SSE), model correlation coeficient (Vy), as well as the maximum absolute error (ΔY) showed that the logaritmic model was in good agreement with the experimental data obtained. During drying of plums, the effective diffusivity was found to be between 5.6×10-9 for 55 °C and 8.9×10-9 m2 s-1 at 75 °C, respectively. The physical characteristics of fresh (length 39.64 mm and width 29.15 mm) and dried (length 37.52 mm and width 22.85 mm) plum fruit were determined. Finally, by chemical analysis, the contents of micro- and macro-elements (Fe, Mn, Cu, B and N, F, K, Ca, Mg and S) in the skin and flesh of the dried product, prunes, has been established

Microstructure evolution and sintering kinetics of ZnO

The aim of this work was to analyse the kinetics and microstructure evolution of ZnO sintering process. ZnO powder was isothermally sintered (15, 30, 60, 90 and 120 min) in the temperature range from 8000C to 12000C. The values of Lenel parameter were calculated and used for the analysis of the densification and mass transport processes. Using scanning electron microscopy the analysis of the microstructure evolution and dependence of the average grain size with temperature and time of sintering was obtained. The results of this research could enable development of a new phenomenological equations in the analyses of ZnO-based materials sintering kinetics

Synthesis of BaFe12O19-BaTiO3 multiferroics by mechanical activation

A mixture of polycrystalline powders of Fe (70 % wt.) and BaTiO3 (30 % wt.) was ball-milled in a planetary mill under air atmosphere, for different time intervals: 60, 120, 180, 240, 300 and 360 min. During the mechanical activation, the powder was exposed to oxygen from the air, resulting in formation of iron oxides: FeO and then Fe2O3 and Fe3O4. XRD and SEM analyses of the activated powders revealed that the weight fraction of the iron oxides in the mixture and microcrystal size depend on the activation time. For the powders activated for different time intervals, average crystallite size (Dhkl), dislocation density (ρn) and average microcrystal size of BaTiO3 and Fe were determined. In order to investigate the influence of thermally induced structural changes on magnetic properties, the change of magnetic properties of the pressed activated powders during multiple heating in a magnetic field of 10KA/m was measured. Maximum magnetization of the samples was reached after heating at 620 K. Pressed powder samples were sintered at temperatures of 1100 oC and 1200 °C for 2h giving the different phase diagrams. The samples sintered at 1100 oC include BaTiO3, BaFe12O19 and BaFeO2,67 as the dominant components. The samples sintered at 1200 °C containing only two components, BaTiO3 and BaFe12O19, exhibited pronounced ferromagnetic and ferroelectric propertie

Spektroskopski studij sintetskog forsterita dobivenog iz zeolitnih prekursora

Important ceramics materials are prepared from aluminosilicate based precursors using novel methods, offering at the same time a better control over many important properties. Forsterite, due to its good refractoriness with melting point at 2163 K, excellent electrical insulation properties even at high temperatures, low dielectric permittivity, thermal expansion and chemical stability, is a material of interest to engineers and designers especially as an active medium for tuneable laser and is also a material of interest to SOFC (Solid oxide fuel cells) manufacturers. The aim of this study is to investigate the synthesis of crystalline forsterite using different zeolite precursors previously activated by ball milling. Synthetic forsterite was synthesized from different zeolite precursors and MgO combining highenergy ball milling and thermal treatment of the mixture under determined conditions of time and temperature for each operation. In this research are studied the solid-state phase transformations taking place at temperatures below 1273 K. The obtained products were characterized using different spectroscopy techniques in comparison with surface analysis method and X-ray diffraction.Važni keramički materijali pripremljeni su iz alumosilikatnih prekursora, pri čemu su primijenjene novije metode, koje istodobno daju mogućnost intervencije u procese nastajanja i kontrolu nad mnogim svojstvima. Forsterit je silikatni materijal posebno interesantan inženjerima i konstruktorima procesne opreme, osobito u laserskoj tehnici i području gorivih čvrstih oksidnih ćelija (SOFC), zbog svoje kemijske stabilnosti, dobrih vatrostalnih karakteristika, tališta od 2163 K, izvrsnih električkih izolacijskih svojstava, male električne permitivnosti i slabog termičkog širenja. Cilj ovog rada je istraživanje na području sinteze kristalnog forsterita uz upotrebu različitih zeolitnih prekursora koji su prethodno aktivirani mljevenjem kugličnim mlinom. Sintetski forsterit dobiven je iz smjese MgO i različitih zeolitnih prekursora, kombinirajući visoko energijsko mljevenje i termičku obradu u kontroliranim vremenskim i temperaturnin uvjetima. U ovom istraživanju studirane su fazne transformacije čvrstog stanja koje se odvijaju na temperaturama ispod 1273 K. Dobiveni proizvod je opisan pomoću različitih spektroskopskih tehnika, analizom specifične površine i rendgenskom difrakcijom

Spektroskopski studij sintetskog forsterita dobivenog iz zeolitnih prekursora

Important ceramics materials are prepared from aluminosilicate based precursors using novel methods, offering at the same time a better control over many important properties. Forsterite, due to its good refractoriness with melting point at 2163 K, excellent electrical insulation properties even at high temperatures, low dielectric permittivity, thermal expansion and chemical stability, is a material of interest to engineers and designers especially as an active medium for tuneable laser and is also a material of interest to SOFC (Solid oxide fuel cells) manufacturers. The aim of this study is to investigate the synthesis of crystalline forsterite using different zeolite precursors previously activated by ball milling. Synthetic forsterite was synthesized from different zeolite precursors and MgO combining highenergy ball milling and thermal treatment of the mixture under determined conditions of time and temperature for each operation. In this research are studied the solid-state phase transformations taking place at temperatures below 1273 K. The obtained products were characterized using different spectroscopy techniques in comparison with surface analysis method and X-ray diffraction.Važni keramički materijali pripremljeni su iz alumosilikatnih prekursora, pri čemu su primijenjene novije metode, koje istodobno daju mogućnost intervencije u procese nastajanja i kontrolu nad mnogim svojstvima. Forsterit je silikatni materijal posebno interesantan inženjerima i konstruktorima procesne opreme, osobito u laserskoj tehnici i području gorivih čvrstih oksidnih ćelija (SOFC), zbog svoje kemijske stabilnosti, dobrih vatrostalnih karakteristika, tališta od 2163 K, izvrsnih električkih izolacijskih svojstava, male električne permitivnosti i slabog termičkog širenja. Cilj ovog rada je istraživanje na području sinteze kristalnog forsterita uz upotrebu različitih zeolitnih prekursora koji su prethodno aktivirani mljevenjem kugličnim mlinom. Sintetski forsterit dobiven je iz smjese MgO i različitih zeolitnih prekursora, kombinirajući visoko energijsko mljevenje i termičku obradu u kontroliranim vremenskim i temperaturnin uvjetima. U ovom istraživanju studirane su fazne transformacije čvrstog stanja koje se odvijaju na temperaturama ispod 1273 K. Dobiveni proizvod je opisan pomoću različitih spektroskopskih tehnika, analizom specifične površine i rendgenskom difrakcijom

Rhinoplasty: The Nasal Bones - Anatomy and Analysis

Background: The analysis of nasal anatomy, and especially the nasal bones including the osseocartilaginous vault, is significant for functional and aesthetic reasons. Objectives: The objective was to understand the anatomy of the nasal bones by establishing new descriptions, terms, and definitions because the existing parameters were insufficient. Adequate terminology was employed to harmonize the anthropometric and clinical measurements. Methods: A two-part harvest technique consisting of resecting the specimen and then creating a replica of the skull was performed on 44 cadavers to obtain specific measurements. Results: The nasal bones have an irregular, variable shape, and three distinct angles can be found along the dorsal profile line beginning with the nasion angle (NA), the dorsal profile angulation (DPA) and the kyphion angulation (KA). In 12% of cases, the caudal portion of the nasal bones was straight and without angulation resulting in a "V-shape" configuration. In 88% of cases, the caudal portion of the bone was angulated, which resulted in an "S-shape" nasal bone configuration. The intervening cephalic bone, nasion to sellion (N-S), represents the radix while the caudal bone, sellion to r (S-R), represents the bony dorsum. Conclusions: By standardizing and measuring existing nasal landmarks and understanding the different anatomic configurations of the nasal bones, rhinoplasty surgeons can better plan their operations within the radix and bony and osseocartilaginous vaults

Microstructure evolution and sintering kinetics of ZnO

The aim of this paper was to analyse the sintering kinetics and microstructure evolution of ZnO. Powder was isothermally sintered (15, 30, 60, 90 and 120 minutes) in the temperature range from 800 to 1200oC. The values of Lenel parameter were used to analyze both densification and mass transport processes. Scanning electron microscopy was performed in order to determine the microstructure evolution and dependence of average grain size on temperature and time of sintering. These results will enable development of new phenomenological equations that can be applied in analyses of sintering kinetics