Effect Of MgO Content Research Articles

Effects of MgO Content on Dielectric Properties of Ba0.94Bi0.04Sn0.06Ti0.94O3/MgO Composite Ceramics

The composite ceramics of Ba0.94Bi0.04Sn0.06Ti0.94O3 (BBST) with x wt.% MgO (0 ≤ x ≤ 30) were prepared by solid-state sintering. The effects of MgO content on the microstructure and dielectric properties of the composite ceramics have been investigated. The results show that MgO is uniformly distributed in BBST matrix and enhances the relative density of composite ceramics remarkably, which effectively optimizes the performances of dielectric loss, alternating current (AC) breakdown strength (BDS) and insulation. With the content of MgO increasing from 0 wt.% to 30 wt.%, the dielectric constant decreases from 2900 to 920, dielectric loss decreases from 0.011 to 0.0065, BDS is improved from 26 kV/cm to 53.6 kV/cm and leakage current density decreases from 2.96 × 10−7 A/cm2 to 9.55 × 10−8 A/cm2. The ceramic added with 30 wt.% MgO exhibits the best comprehensive dielectric properties, which is a superior dielectric used in high-voltage ceramic capacitors.

Effects of MgO content and CaO/Al2O3 ratio on surface tension of calcium aluminate refining slag

Surface tension of calcium aluminate refining slag was measured by the Slide method at 1823 K. Based on different levels of the MgO content and the mass ratio of CaO to Al2O3, the effects of MgO content and the mass ratio of CaO to Al2O3 on surface tension were investigated. The results indicate that surface tension decreased with increasing MgO content (from 0 to 4.86%), followed by an increase with further increasing MgO content up to 11.33%. The trend that surface tension changed with the mass ratio of CaO to Al2O3 was the same as the trend that surface tension changed with the MgO content. The surface tension was varied from 0.617 N/m to 0.710 N/m, for the mass ratio of CaO to Al2O3 varying between 0.60 and 1.28. An attempt was made to estimate surface tension of CaO−Al2O3−MgO slag and its sub-system, and the application showed that the model worked well.

Bimodal Mesoporous Carbon-Coated MgO Nanoparticles for CO2 Capture at Moderate Temperature Conditions

Bimodal mesoporous carbon supported MgO (MgOMC) materials were prepared to provide a candidate for trapping CO2 in flue gas at high temperature by an impregnation method. Textural properties of MgOMC were characterized by X-ray diffraction, N2 adsorption/desorption isotherm, scanning electron microscopy, transmission electron microscopy and an element mapping method, and their CO2 adsorption behaviors in both pure CO2 and 10 vol % CO2 simulated flue gas were evaluated by a thermal gravimetric method at ambient temperature. Effects of MgO content in composite and calcination temperature on CO2 adsorption capacity were studied. Results showed that MgOMC samples with high content of basic MgO sites and well-developed porous structure exhibit high CO2 uptakes at 75 °C, rapid adsorption kinetics, excellent CO2 selectivity in flue gas and good regenerability under mild temperature below 300 °C, indicating their potential application in the CO2 capture from flue gas.

Visible light activated photocatalytic degradation of tetracycline by a magnetically separable composite photocatalyst: Graphene oxide/magnetite/cerium-doped titania

In this study, magnetic graphene oxide-loaded Ce-doped titania (MGO–Ce–TiO2) hybridized composite was prepared by a facile method. The as-prepared samples exhibited good adsorption capacity, high visible-light photoactive and magnetic separability as a novel photocatalyst in the degradation of tetracyclines (TC). The intermediate products and photocatalytic route of TC were proposed based on the analysis results of LC–MS. Moreover, the repeatability of the photoactivity with the use of MGO–Ce–TiO2 was investigated in the multi-round experiments with the assistance of an applied magnetic field. Therefore, the prepared composite photocatalysts were considered as a kind of promising photocatalyst in a suspension reaction system, in which they can offer effectively recovery ability. The effect of MGO content on the photocatalytic performance was also studied, and an optimum content was obtained.

Effect of MgO content in sinter on the softening–melting behavior of mixed burden made from chromium-bearing vanadium–titanium magnetite

The effect of sinter with different MgO contents on the softening–melting behavior of mixed burden made from chromium- bearing vanadium–titanium magnetite was investigated. The results show that with increasing MgO content in the sinter, the softening interval and melting interval increased and the location of the cohesive zone shifted downward slightly and became moderately thicker. The softening–melting characteristic value was less pronounced when the MgO content in the sinter was 2.98wt%–3.40wt%. Increasing MgO content in the sinter reduced the content and recovery of V and Cr in the dripped iron. In addition, greater MgO contents in the sinter resulted in the generation of greater amounts of high-melting-point components, which adversely affected the permeability of the mixed burden. When the softening–melting behavior of the mixed burden and the recovery of valuable elements were taken into account, proper MgO contents in the sinter and slag ranged from 2.98wt% to 3.40wt% and from 11.46wt% to 12.72wt%, respectively, for the smelting of burden made from chromium-bearing vanadium–titanium magnetite in a blast furnace.

Microstructure, in vitro bioactivity and degradability of various magnesia-containing wollastonite

Wollastonite (CaSiO3) ceramics with various magnesia contents (0, 5, 10, 15 and 20mol%) were successfully prepared by sintering sol–gel derived precursors. The effects of MgO content on microstructure, in vitro bioactivity and degradability of wollastonite were reported. The ceramics are composed of β-CaSiO3. When adding 5mol% MgO, the new phase of Ca3Mg(SiO4)2 forms. With increasing MgO content, CaMgSi2O6 and Ca2MgSi2O7 form. All ceramics possess apatite formation ability in simulated body fluid. The TEM results indicated that the ceramic structure is polycrystal. MgO decreases the total pore volume of wollastonite and the degradation rate is decreased gradually with increasing MgO content.

Preparation and properties of Al2O3–MgAl2O4 ceramic foams

In this work, a series of alumina (Al2O3)–magnesium aluminate (MgAl2O4) ceramic foams (AMCFs) were fabricated from powders of fused white corundum and magnesia (MgO) by a polymeric foam replication method combined with a reaction sintering process. The effects of MgO content and sintering temperature on the sintering properties and post-sintering properties of the AMCFs such as phase composition, appearance, microstructure, cold compressive strength and thermal shock resistance have been investigated. During the sintering process, MgO reacted with Al2O3 to form MgAl2O4 ceramic phase, which contributed to the improvement in sintering properties, cold compressive strength and thermal shock resistance of the AMCFs. The AMCFs doped with 8wt% MgO and sintered at 1450°C for 2h displayed high cold compressive strength of 0.89MPa, good sintering properties and thermal shock resistance. Although their apparent porosities were about 87%, the cold compressive strength of as-prepared foam was about 1.3 times higher than that of commercial Al2O3 foam.

Effect of MgO content in slag on dephosphorisation in converter steelmaking

In this study, the effect of MgO content in slag on the phosphorus distribution ratios, and the equilibrium solubility of MgO in slag during converter steelmaking were analysed using the modified Kozheurov regular solution model and the thermodynamic package FactSage. Thermodynamic analysis shows that the MgO content in the final slag should be greater than 5% to saturate the slag with MgO and minimise the chemical wear of the refractory lining. However, the phosphorus distribution ratio decreases dramatically with increasing MgO. Industrial tests were performed using an 80-t top-and-bottom combined blown converter showed that the average phosphorus distribution ratio reduces significantly from 120.7 to 75.7 when the average MgO content in the final slag increases from 7.0 to 9.8%, due to thermodynamics and kinetics reasons. By optimizing the MgO content between 6 and 8% dephosphorisation and refractory wear are optimised.

Effect of MgO on microstructure and microwave dielectric properties of 0.84CaTiO3–0.16Sm0.9Nd0.1AlO3 ceramics

The effect of MgO content on the microstructure and microwave dielectric properties of MgO-doped 0.84CaTiO3–0.16Sm0.9Nd0.1AlO3 ceramics, prepared by solid-state reaction method, was investigated. The permittivity, ϵr, of the MgO-doped 0.84CaTiO3–0.16Sm0.9Nd0.1AlO3 ceramics was about 65, and it decreased slightly with increasing MgO content. And the temperature coefficient of resonant frequency, τf was tuned from +53.3ppm/°C to +26.4ppm/°C as the MgO addition increasing. In addition, it is found that a small amount of MgO could effectively promote the uniformity of the grain morphology, which is beneficial for the improvement of Q×f value. However, grain growth was restrained, and secondary phase MgAl2O4 was observed as MgO content increasing to 0.8wt%; thus, Q×f value deteriorated seriously. Considering these three parameters of the microwave dielectric properties, the 0.4wt% MgO-doped 0.84CaTiO3–0.16Sm0.9Nd0.1AlO3 ceramics exhibited the best performance of ϵr=64.21, Q×f=30867GHz, and τf=26.4ppm/°C sintered at 1375°C for 3h.

The Effects of MgO Content on the Mechanical Properties and Microstructures of Al<sub>2</sub>O<sub>3</sub>-TiN-TiC Ceramic Materials

Al2O3-TiN-TiC ceramic materials with different MgO content were fabricated by hot-pressing technique. The MgO volume percent was varied from 0vol% to 5vol%. The mechanical properties such as flexural strength, Vickers hardness and fracture toughness were tested. The phase composition of the sintered body was analyzed by XRD while the microstures of the sintering body were observed by OM (Optical Microscope) and SEM. The effects of MgO content on the mechanical properties and microstructures of Al2O3-TiN-TiC were investigated. The results shows that the addition of MgO can change the phase composition of the sintered ceramic materials which displayed with diverse solid solutions and intermetallic compounds. Meanwhile the new sintering products changed the the microstructure morphology which made the crack path complex and affected the mechanical properties.

Iridium supported on MgF 2–MgO as catalyst for CO oxidation

A combination of iridium catalytic phase and a new MgF 2–MgO support, obtained by the sol–gel method, has been shown to be an active catalyst for CO oxidation reaction. A series of catalysts containing 1 wt.% Ir were obtained by impregnation of MgF 2–MgO and pure MgF 2 or MgO supports with different precursors, i.e. H 2IrCl 6, Ir(acac) 3 and Ir 4(CO) 12. The surface areas and pore size distributions of the catalysts obtained were determined by the BET and BJH methods, respectively. Dispersion of iridium and the mean size of the crystallites were evaluated on the basis of hydrogen chemisorption. The activity of the catalysts in the CO oxidation reaction was measured. The effect of MgO content in the support and the influence of iridium precursor on the structure and activity of the iridium catalysts in the CO oxidation reaction were studied. The results show that the use of MgF 2–MgO support with 60 mol % content of MgO and the use of Ir(acac) 3 precursor lead to the catalyst with high surface area, high iridium dispersion and the best catalytic performance in CO oxidation.

Effect of MgO content on the microstructure and mechanical properties of Fe–Cr–Ni/MgO composites produced by reactive hot pressing

Fe–Cr–Ni/MgO (17.0–34.9wt.%) composites were produced by reactive hot pressing at 600°C/30MPa/2h. The composites comprised predominantly of Cr0.7Fe0.36Ni2.9, CrFe and MgO phases. The Fe–Cr–Ni/MgO (17.0wt.%) composite had the optimal mechanical properties: 5.09GPa for Vickers hardness, 412MPa for bending strength and 11.6MPam1/2 for fracture toughness, respectively.

Effect of MgO content in the support of Au/MgF2–MgO catalysts on CO oxidation

Novel magnesium oxo-fluoride supports containing different amounts of MgO, prepared by the sol–gel method have been proposed for the synthesis of gold catalysts. The MgF2–MgO supports have mesoporous structure and their surface area is a few times larger than those of pure MgF2 or pure MgO. Gold catalysts have been prepared by impregnation of the MgF2–MgO supports with HAuCl4 in the amount corresponding to 1 wt.% Au. The gold catalysts has been characterized by XRD, TEM measurements and the catalytic activity in CO oxidation at temperatures 30–300 °C have been performed. The Au/MgF2–MgO catalysts show higher activities (depending on the content of MgO in the support) as compared to Au/MgF2 and Au/MgO prepared under the same conditions. Their activities fall into the upper range of gold catalysts supported on other carrier reported in literature.

Hydrocarbon production from decarboxylation of fatty acid without hydrogen

Decarboxylation of oleic acid without hydrogen was carried out using hydrotalcites with three different MgO contents (30, 63 and 70 wt%). Effect of MgO content in hydrotalcites and reaction temperatures on the decarboxylation performance in terms of oleic acid conversion and product distribution were investigated. Also, the stability of hydrotalcites in the decarboxylation reaction was examined by XRD analysis. It was found that MgO content in hydrotalcites and reaction temperature played key roles in decarboxylation reaction. At lower reaction temperature and MgO concentration in hydrotalcite, the conversion of oleic acid scarcely occurred. On the other hand, oleic acid conversions were more than 98% and the oxygen content in the reaction product was less than 1 wt% in the case of decarboxylation with MG63 (63% of MgO) and MG70 (70% of MgO) at 673 K. Solid-like products were formed in the reaction at 623 K, resulting from saponification of oleic acid and MgO. Considering conversion and the stability of catalysts, higher temperature, 673 K, is preferred to prevail decarboxylation over saponification. It was confirmed that most of the oxygen molecules in oleic acid were removed in the form of CO 2 from the elemental and FT-IR analysis of the liquid products. Pure hydrocarbons such as octane, nonane and heptadecene were produced in the case of MG63 and MG70 at 673 K while decanoic acid was additionally observed in case of blank test and MG30 catalyst at 673 K.

Effect of Magnesia Addition on Physical Properties and Slag Attack Resistance of Ultra-Low Cement Castables (ULC)

In this study, tabular alumina and seawater magnesia were used to synthesize in situ Al2O3-MgO spinel castables. Secar® 71 cement was used as a binder. In order to produce in situ formation of Al2O3-MgO spinel castables, the effect of MgO content on refractory properties was investigated by adding to the mixture at the proportions of 3, 4, 5, 6, 7 wt%. Using 5 wt% content of MgO decreased the bulk density of castables to 3.03 g/cm3 and increased the porosity to about 17.43%. In situ spinel formation in samples led to the expansion in its lattice as well as an increase in the porosity. On the other hand, 5 wt% MgO had a positive effect on Cold Crushing Strength (CCS) of the castable. SEM investigations of fired samples were carried out to compare the effect of MgO addition and in situ phase formation on the physico-mechanical properties of castables. The effect of MgO content on the mechanism of slag penetration of ultra-low cement castables (ULC) for steel ladles was examined and the penetration layer was chemically analyzed.

Effect of Magnesia Addition on Physical Properties and Slag Attack Resistance of Ultra-Low Cement Castables (ULC)

In this study, tabular alumina and seawater magnesia were used to synthesize in situ Al2O3-MgO spinel castables. Secar® 71 cement was used as a binder. In order to produce in situ formation of Al2O3-MgO spinel castables, the effect of MgO content on refractory properties was investigated by adding to the mixture at the proportions of 3, 4, 5, 6, 7 wt%. Using 5 wt% content of MgO decreased the bulk density of castables to 3.03 g/cm3 and increased the porosity to about 17.43%. In situ spinel formation in samples led to the expansion in its lattice as well as an increase in the porosity. On the other hand, 5 wt% MgO had a positive effect on Cold Crushing Strength (CCS) of the castable. SEM investigations of fired samples were carried out to compare the effect of MgO addition and in situ phase formation on the physico-mechanical properties of castables. The effect of MgO content on the mechanism of slag penetration of ultra-low cement castables (ULC) for steel ladles was examined and the penetration layer was chemically analyzed.

Influence of magnesia on the structure and properties of MgO-Al 2O 3-SiO 2-F − glass-ceramics

Effects of MgO content (13.4–31.4 mol%) on the structure and properties of MgO-Al 2O 3-SiO 2-F − glass-ceramics were investigated by differential scanning calorimetry (DSC), X-ray diffractometry (XRD), infrared spectrophotometry (IR) and scanning electron microscopy (SEM). Results show that the main units of glass network structure are [SiO 4] and [AlO 4]. MgO contributes to the weakening of silica network and reduce the stability of glass structure. The main crystals of the MgO-Al 2O 3-SiO 2-F − glass-ceramics are phlogopite, spinel, flur-pargrasite and forsterite. The increase of reheating temperature and MgO content are beneficial to the separation of phlogopite crystal, and cause an higher aspect ratio of the phlogopite phase, which improves the machinability of the glass-ceramics. Excellent machinability is obtained when MgO content is 31.4 mol% at the processing temperature of 1100 °C for 2 h.

The Effect of MgO Content on the Preparation of Porous Hydroxyapaite Scaffolds by Polymer Sponge Method

Porous hydroxyapatite (HAp) scaffolds have been prepared by using the slurry including HAp and magnesia based on the replication of polymer sponge substrate. The influence of MgO content in slurry on the pore morphology and size, density, porosity, and mechanical strength of porous HAp scaffolds was investigated. The obtained scaffolds with average pore sizes ranging 150 to 300 mm had open, relatively uniform, and interconnected porous structure regardless of MgO content. As the MgO content increased, the pore network frame of scaffolds became to be relatively stronger, even though the pore size was not much changed. The compressive strength of the scaffolds increased rapidly with the increase of MgO content because of increasing the pore wall thickness and density of the scaffolds. As a result, the porosity, density, and compressive strength of the porous HAp scaffolds prepared by the sponge method were significantly affected by the addition of MgO.

Effect of MgO content on the formation and superconducting properties of (Bi,Pb)-2223 phase in the partial-melting and sintering process

The bulk samples with the composition Bi 1.8Pb 0.4Sr 1.9Ca 2.1Cu 3.5O y + x wt.% MgO ( x=0, 0.5, 2, 5, 10 and 15) were prepared by sintering at 840°C for 240 h after partial-melting at 875°C for 1 h. The sample with 0.5 wt.% MgO addition shows the lowest melting temperature of Bi-2212 phase and the highest conversion of Bi-2212 phase to Bi-2223 phase. With increasing MgO content, the width of hysteresis loop ΔM of the bulk samples at 77 K increases (0⩽ x⩽5), and then decreases (5⩽ x⩽15). The largest ΔM appears in the sample with 5 wt.% MgO addition. It is suggested that an amount (∼5 wt.%) of MgO addition in the (Bi,Pb)-2223 superconductors can increase J c due to improving the flux pinning. In contrast, MgO overdoping (>5 wt.%) decreases J c due to decreasing the conversion of Bi-2212 phase to Bi-2223 phase.

OH-related capacitance-voltage recovery effect in MOS capacitors passivated by PbO-B2O3-SiO2-MgO glasses VII, the effects of MgO content

OH-related capacitance-voltage recovery effect in MOS capacitors passivated by PbO-B2O3-SiO2-MgO glasses VII, the effects of MgO content