Optimum Calcination Research Articles

Analysis of Optimum Temperature and Calcination Time in the Production of CaO Using Seashells Waste as CaCO<sub>3</sub> Source

Analysis of Optimum Temperature and Calcination Time in the Production of CaO Using Seashells Waste as CaCO<sub>3</sub> Source

Improved thermal and mechanical properties of CdBa2-x SrxCa2Cu3O8+δ superconducting compounds

The aim of this paper is to study the possibility of improvement thermal and mechanical properties of CdBa2-x SrxCa2Cu3O8+δ superconducting compounds by particle replacement the Barium by strontium. We have used a three-steps of solid state reaction method to preparation the homogeneous compound CdBa2-x SrxCa2Cu3O8+δ by the partial substitution of Sr+2 into the Ba+2 sites. The substitutions for this compound were taken as with the x=0. 0.4. 0.5 and 0.6. The optimum calcinations was 800 C0 and for sintering was within 845-850 C0. The structural were studied by using X-ray powder diffraction (XRD). X-ray diffraction (XRD) analysis showed a tetragonal structure with an increase of the c-axis lattice constant for the samples doped with Sr as compared with those have no Sr content. The XRD data collected from various samples were polycrystalline. It was found that the change of the Sr concentrations of all our samples produce a change in lattice parameters (a, c), the ratio of lattice parameters c/a, mass density ρm and the volume fraction (Vphase). The thermal and mechanical proprieties were studied. It was found that the change in Sr concentration of all our samples produce increasing thermal and mechanical proprieties.

The Effect of Oxygen Flow on the Transition Temperature of Hg0.75Pb0.25Sr2-yBayCa2Cu3O8+ δ Superconductors

In this paper, there are three different high temperature superconductors which are Hg0.75Pb0.25Sr2-y BayCa2Cu3O8+δ with deferent weight fractions y = 0.10, 0.20 and 0.25 that have been prepared successfully by solid state reaction and the samples have been equipped with/without O2 flow. The optimum calcinations is 1073 K and the sintering process that has been achieved within 1128-1133 K. Transition temperature Tc has been found by using four probe technique through electrical resistivity measurements. The greatest Tc that has been found for Hg0.75Pb0.25Sr1.75 Ba0.25Ca2Cu3O8.31 is 115 oK. Oxygen content (O2) flow exhibits high-phased superconductors that is similar to the samples prepared without O2. Investigation of X-ray diffraction (XRD) is revealed (tetragonal structure) by the c-axis lattice parameter increasing of the samples substituted with Ba. It has been established, from the calculated results, that the Ba variation concentrations of all samples products a modification in the density (ρm), (c/a) and volume fraction (VPh(2223)).

Preparation and Physical Properties of Doped CdBa2-x SrxCa2Cu3O8+δ Compound

In the present paper, two-steps of solid state reaction method have used to prepare the homogeneous compound CdBa2-x SrxCa2Cu3O8+δ by substitution of strontium (Sr+2) into the barium (Br+2) sites, this substitutions were taken as x = 0.0, 0.20 and 0.30. The optimum calcinations were 800 C0 and for sintering within 845-850 C0.The structural was studied by using X-ray powder diffraction (XRD) and scanning electron microscope (SEM).The XRD analysis showed the structures a polycrystalline with tetragonal diagram and the change of the strontium concentrations produce a change in lattice parameters(a, b and c-axis). c/a, density of mass (ρm ), volume fraction (Vphase) and shore hardness for all our samples. It has been found that the optimum Tc(offset) = 113 K has been found for the composition CdBa2-x SrxCa2Cu3O8+δ with x = 0.30.The A.C electrical conductivity as a function of frequency is used to find the dielectric constant. It was found that changing in dielectric constant; dielectric loss factor and tangent loss were produced by increasing the Sr concentration.

Effect of Oxygen Treatment on the Structural and Electrical Properties of Tl0.85Cd0.15Sr2CuO5−δ , Tl0.85Cd0.15Sr2Ca2Cu2 O 7−δ and Tl0.85Cd0.15Sr3Ca2Cu3 O 9−δ Superconductors

The solid-state reaction was used to prepare three different high-temperature superconductors, namely Tl0.85Cd0.15Sr2CuO5−δ, Tl0.85Cd0.15Sr2Ca2Cu2O7−δ and Tl0.85Cd0.15Sr2Ca2Cu3O9−δ. The optimum calcinations were performed at 800∘C, and the sintering was performed within 855–860∘C. The samples were tested before and after oxygen treatment. It has been found that the oxygen flow on samples during preparation produces high-phase superconductors as compared with the samples prepared without oxygen flow. The four-probe techniques were used to measure the electrical resistivity to know the transition temperature (Tc). It was found that the samples which were prepared with oxygen flow have the highest zero-transition temperatures (Tc(offset)) of 85, 106 and 121 K for the samples Tl0.85Cd0.15Sr2CuO5−δ, Tl0.85Cd0.15Sr2Ca2Cu2O7−δ and Tl0.85Cd0.15Sr2Ca2Cu3O9−δ, respectively. X-ray diffraction spectrum showed all samples are polycrystalline with a tetragonal structure and also showed an increase of the c-axis and lattice constant with the increase of CuO layers and oxygen content. It was noticed that the change of CuO layers of all samples produced a modification in the transition temperature, mass density (ρm) and c/a parameter.

Assessment of soda ash calcination treatment of Turkish trona ore

Trona is relatively rare, non-metallic mineral, Na2 CO3 · NaHCO3 · 2H2 O. The pure material contains 70.3% sodium carbonate and by calcination the excess CO2 and water can be driven off, yielding natural soda ash. The terms soda ash and sodium carbonate are used interchangeably. Trona calcining is a key process step in production of soda ash (sodium carbonate anhydrate) from the relatively cheap trona ore. The calcination reaction may proceeds in a sequence of steps. Depending on the conditions, it may result in formation of either sodium carbonate monohydrate (Na2 CO3 · H2 O), sodium sesquicarbonate or weigschederite (Na2 CO3 · 3NaHCO3 ). The Beypazari Turkish trona deposit is the second largest deposit in the world with the content of 84% trona. The decomposition of trona appeared to be a single stage process across the temperature range studied (150-200 °C) with the representative samples of different size fractions in the draught up metallurgical furnace. The optimum particle size and calcination time were −6.35 mm and 30 minutes, respectively, at calcination temperature of 175 °C in a metallurgical furnace. Microwave-induced dry calcination of trona was possible and 5 minutes of calcination time at a power level of 900 was sufficient for complete calcination of −6.35 mm feed. This includes short time calcinations with the goal of improving economics and simplifying the thermal process.

Local Nanoelectromechanical Properties of Multiferroics Gd-Doped BiFeO3–BaTiO3 Solid Solution

Bi(1-x-y)GdxBayFe(1-y)TiyO3 (x = 0.1 and y = 0.1, 0.2, 0.3) solid solutions have been prepared via solid state reaction method with the aim to obtaining magnetoelectric coupling (i.e., linear relation between magnetization and electric field) at room temperature. Optimum calcination and sintering strategies for obtaining pure perovskite phase, high density ceramics and homogeneous microstructures have been determined. The maximum ferroelectric transition temperature (Tc) of this system was 150-170 degrees C with the dielectric constant peak of 2300 at 100 kHz for y = 0.1. Well saturated piezoelectric loops were observed for all composition indicating room temperature ferroelectricity. Hardness and Young's modulus decrease with depth and with increasing concentration y.

Enhancement of Magnetic and Dielectric Properties in Chemically Modified Multiferroic (0.90)BiFe1−x Cr x O3–(0.10)BaTiO3 Nanocomposite

Multiferroic BiFeO3 and Cr-doped (0.90)BiFe1−x Cr x O3–(0.10)BaTiO3 (x=0.00, 0.03, and 0.05) nanocomposites were prepared by sol–gel method. Optimum calcination and sintering strategies for obtaining pure perovskite phase have been determined. X-ray diffraction and transmission electron microscope (TEM) were used for the structural and particle size analysis, whereas LCR and SQUID magnetometer was used for dielectric and magnetic measurements. TEM measurements show that the average particle sizes of all the samples were ∼19 nm. The dielectric constant was found to be increased twofold in low frequency region with the Cr-doping for x=0.05 in (0.90)BiFe1−x Cr x O3–(0.10)BaTiO3. The hysteresis curve (M–H) exhibits ferromagnetic nature for all the samples (x=0.0, 0.03, and 0.05) and the spontaneous magnetization at room temperature was found to be 0.63 emu/gm in pure BiFeO3, which increased to 0.99 emu/gm for x=0.05. Zero-field-cooled (ZFC) and field-cooled (FC) magnetization curves show large discrepancy suggesting spin glass behavior.

Ferroelectric and ferromagnetic properties of Gd-doped BiFeO 3–BaTiO 3 solid solution

The solid solutions of Bi 1− x− y Gd x Ba y Fe 1− y Ti y O 3 have been prepared via solid-state reaction method with the aim to obtain magnetoelectric coupling (i.e., linear relation between magnetization and electric field) at room temperature. Optimum calcination and sintering strategies for obtaining pure perovskite phase, high density ceramics and homogeneous microstructures have been determined. All the samples of the composition Bi 1− x− y Gd x Ba y Fe 1− y Ti y O 3 ( x = 0.1 and y = 0.1, 0.2, and 0.3) reported in the present work are tetragonal at room temperature. The maximum ferroelectric transition temperature ( T c) of this system was 150–170 °C with the dielectric constant peak of 2300 at 100 kHz for y = 0.1. Above T c the dielectric constant is decreasing up to a certain temperature and then increasing with temperature similar to that observed in other perovskites due to chemical inhomogeneities in both A and B sites of the ABO 3 cell. The variation of ferroelectric and magnetic properties was followed by piezoresponse force microscopy and vibrating sample magnetometer, respectively. Well-saturated piezoelectric loops were observed for all composition indicating room temperature ferroelectricity.

The Effect of Simultaneous Substitution of Strontium at the Barium site of Tl0.6Pb0.4Ba2−x Sr x Ca2Cu3O9−δ Superconductors

High temperature superconductors, namely Tl0.6⋅ Pb0.4Ba2−xSrxCa2Cu3O9−δ, have successfully been prepared by the solid state reaction method. The substitutions for this compound were taken as x=0.0, 0.10, 0.20, 0.30, 0.40 and 0.50. The optimum calcination was at 1073 K and for sintering was within 1128–1133 K. Electrical resistivity, using the four-probe technique, was used to find the transition temperature Tc. The highest Tc(offset) was 113 K for Tl0.6Pb0.4Ba1.5Sr0.5Ca2Cu3O8.76. All samples were prepared by using O2 flow. X-ray diffraction (XRD) analysis have shown a pseudotetragonal structure with an increase of the c-axis lattice constant for the samples which were doped with Sr as compared to those which have no Sr content.

Preparation and characterisation of the magneto-electric xBiFeO 3–(1 − x)BaTiO 3 ceramics

The solid solutions of BiFeO 3–BaTiO 3 have been prepared via solid state with a view to obtaining magnetoelectric properties, i.e. ferroelectric and magnetic activity in the same range of temperatures. Optimum calcination and sintering strategy for obtaining pure perovskite phase, dense ceramics (>97% relative density) and homogeneous microstructures have been determined. The sample of composition 0.7BiFeO 3–0.3BaTiO 3 reported in the present work is pseudo-cubic at room temperature. The permittivity is ɛ r ≈ 150 at the room temperature and shows a broad ferro-para phase transition at around 175 °C where ɛ r ≈ 1600. This diffuse maximum of the permittivity, similar to that in relaxors, is due to the chemical inhomogeneity in both A and B sites of the perovskite unit cell ABO 3. Higher losses, tan δ > 1, appear above 200 °C and other different conduction mechanisms start to be active particularly at temperatures higher than 400 °C, when the ceramic becomes conductive. The magnetic properties show a succession of transitions from weak ferro/ferrimagnetism-to-antiferromagnetism and antiferromagnetism-to-paramagnetism at T N1 ≈ 10 K and T N2 ≈ 265 K. Below T N2 the ceramic 0.7BiFeO 3–0.3BaTiO 3 can present magnetoelectric coupling, due to the fact that is simultaneously ferroelectric and antiferromagnetic.

On the performance of a highly loaded Co/SiO 2 catalyst in the gas phase hydrogenation of crotonaldehyde : Thermal treatments—catalyst structure–selectivity relationship

This paper reports on the performance and its relation with the structure of a highly loaded (41 wt.%) Co/SiO 2 catalyst in the gas phase hydrogenation of crotonaldehyde when varying the thermal treatments to which the catalyst precursor has been subjected. The optimum calcination and reduction temperatures were identified where the highest selectivity to crotyl alcohol (around 90%) was obtained with the catalyst calcined at 400 °C and reduced at 350 °C even at conversions as high as 60%. Higher temperature of calcination was found to lower the crotyl alcohol selectivity. Both, lower and higher reduction temperatures will not favour the crotyl alcohol formation. These results were interpreted and correlated with the surface structure of the catalyst which was shown by temperature programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS) analysis. Depending on the thermal conditions imposed, the surface consisted of either Co metal, or coexisting metal and its oxide; structure which favours the high crotyl alcohol selectivity. By TEM analysis, large particles (diameter exceeding 50 nm) were identified after reduction at 350 °C. A global activation energy of 44 kJ/mol was obtained with this catalyst. In the light of the obtained results a discussion on the reaction mechanism involving metal, metal-oxide double sites has been put forward. It was emphasised that, for selective hydrogenation of crotonaldehyde into unsaturated alcohol, Co catalysts compete favourably with platinum based catalysts.

Propylene Epoxidation Over Silver Supported on Titanium Silicalite Zeolite

Epoxidation of propylene to propylene oxide over Ag/TS-1 in the presence of oxygen and hydrogen was carried out in a fixed-bed, quartz flow reactor. The effects of Ag loading, Si/Ti ratio of TS-1 and calcination temperature and calcination method of Ag/TS-1 on the propylene epoxidation were investigated. The results show that Ag loading, the calcination temperature and calcination method of Ag/TS-1 as well as the Si/Ti ratio of TS-1 have a great effect on the catalytic properties. The optimum Ag loading, calcination temperature and calcination method of Ag/TS-1 and Si/Ti ratio of TS-1 are 2 wt%, 450 °C in air and 64 respectively. Over 2.0 wt% Ag/TS-1(nSi/nTi = 64) catalyst, at a space velocity of 3000 h-1, 0.92% propylene conversion with 91.21% selectivity to propylene oxide is obtained at 150 °C. The deactivation of Ag/TS-1 catalyst is not due to the changes of active species, but because of the coke of the catalyst, which can be easily regenerated by calcination at 450 °C in air.

Thermal Activation of a Clayzic Catalyst Useful for Friedel–Crafts Reactions: HCl Evolved with Creation of Active Sites in Different Thermal Treatments to ZnCl 2 /Mont-K10

Thermal activation of clayzic catalyst has been thoroughly investigated by calcining anhydrous ZnCl2 impregnated on Mont-K10 with different ZnCl2 loadings (0.5-2.0 mmol g-1) under static or flowing air at 270 °C and also under N2 flow at different temperatures (150-400 °C). Depending upon the ZnCl2 loading and calcination temperatures, an appreciable amount of HCl is evolved in the thermal activation, indicating an occurrence of reaction between the ZnCl2 and the surface hydroxyl groups of the clay (- OH + ZnCl2→ - O - Zn - Cl + HCl), leading to formation of new Lewis acid sites (- O - Zn -Cl). The Cl/Zn ratio, surface area and catalytic activity (in the benzene benzylation by benzyl chloride at 80 °C) of the clayzic formed in the thermal activation are influenced markedly by the ZnCl2 loading and calcination conditions (temperature and gas atmosphere). The maximum catalytic activity for the clayzic is observed at the optimum ZnCl2 loading (about 1.0 mmol g-1) and calcination temperature (about 270 °C). The thermal activation at 270 °C under flowing N2 led to a most active clayzic catalyst for the benzene benzylation. A temperature-programmed evolution of HCl in the calcination of ZnCl2/Mont-K10 with different ZnCl2 loadings from 25 to 400 °C at a linear heating rate of 2 °C min-1 has also been investigated.

Combined effect of partial calcination and sintering condition on low loss Mn-Zn ferrite

In order to achieve highly densified lower loss Mn-Zn ferrite materials, various powder processing routes have been under investigation. In this report, a lower sintering temperature with lower oxygen partial pressure and proper attrition milling duration are suggested. From the previous study, a partial calcination procedure was studied and an optimum partial calcination level was found. Accordingly, Mn0.71Zn0.22Fe2.07O4 ferrite was prepared by \({\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 2}}\right.\kern-\nulldelimiterspace}\!\lower0.7ex\hbox{$2$}}\) calcination with small amounts of CaCO3, SiO2, Nb2O5 and SnO2. The partially calcined ferrites were made by calcining the mixture of the whole amount of ZnO and \({\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 2}}\right.\kern-\nulldelimiterspace}\!\lower0.7ex\hbox{$2$}}\) amount of Fe2O3 and Mn3O4 and sintering the mixture of the calcined powders and the remaining \({\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 2}}\right.\kern-\nulldelimiterspace}\!\lower0.7ex\hbox{$2$}}\) of Fe2O3 and Mn3O4. Initially, from the 40 min secondary milling and the \({\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 2}}\right.\kern-\nulldelimiterspace}\!\lower0.7ex\hbox{$2$}}\) partial calcination, lower temperature (1300°C) sintered samples showed a power loss of ∼340 mW cm−3 at 90°C. Secondly, several milling durations showed secondary milling had a more profound effect on magnetic properties than primary milling. The 20 min primary and 90 min secondary milling showed lower core loss around 320 mW cm−3 at 1300°C and 1250°C, suggesting the sintering temperature could be reduced to 1250°C. Thus, the proper sintering condition of lower oxygen partial pressure at 1250°C was studied. As a result, lower loss with higher density was realized.

Metallurgical studies and optimization of sintering for the Bi-Sr-Ca-Cu-O superconductors

Metallurgical studies and optimization of sintering condition to obtain the maximum volume fraction of the high Tc phase (∼110 K) have been made for the Bi-Sr-Ca-Cu-O system. In the differential thermal analysis, double peaks of endothermic reaction at ∼870 and ∼910 °C were observed during the increase of temperature, and a weight loss accompanied each endothermic reaction. Optimum calcining and sintering conditions to obtain a large volume fraction of the high Tc phase were 820 °C×14 h+840 °C×6 h and 875 °C×100 to 200 h in air, respectively. As for the variation of Cu concentration, nominal composition of Bi1Sr1Ca1Cu2Ox gave the maximum volume fraction of the high Tc phase. (For these specimens, sintering time was varied up to 20 days.) Post annealing at 400 °C for 20 h in an oxygen atmosphere after the sintering at 875 °C for 100 to 470 h in air had little effect on the improvement of volume fraction of the high Tc phase. As for the specimen to which Pb is added, however, the post annealing at 400 °C for 20 h increased the volume fraction of the high Tc phase. Scanning electron microscopy showed that the Bi1Sr1Ca1Cu2Ox (nominal composition) specimens sintered at 875 °C for 100 to 470 h consist mostly of well-grown thin layers, while the specimen sintered at 875 °C for 14 h consists mostly of fine pieces of thin layers piling up at random. Electron probe microanalysis revealed that microstructure of the specimen sintered at 875 °C consists of Bi-poor regions and the matrix surrounding them, and that these Bi-poor regions are classified into Cu-rich regions and Ca-rich regions. The superconducting phases of this material are considered to exist in the matrix region. We identified the Cu-rich regions and Ca-rich regions as (Sr0.45, Ca0.55 )3 Cu5 Ox and (Sr0.08, Ca0.92 )2 CuOx, respectively. The average size of these regions increased with increasing time of sintering, although total volume fraction of these regions did not increase.