Effect Of MgO Content Research Articles

Correction: Effect of MgO Content on the Microstructure and Properties of Zirconia-Toughened Alumina (ZTA) Ceramics by Hot Pressure Sintering

Correction: Effect of MgO Content on the Microstructure and Properties of Zirconia-Toughened Alumina (ZTA) Ceramics by Hot Pressure Sintering

Effect of MgO Content on the Microstructure and Properties of Zirconia-Toughened Alumina (ZTA) Ceramics by Hot Pressure Sintering

Effect of MgO Content on the Microstructure and Properties of Zirconia-Toughened Alumina (ZTA) Ceramics by Hot Pressure Sintering

Effect of MgO Content and CaO/Al2O3 Ratio of CaF2–CaO–Al2O3–MgO Slag on the Oxidation Behavior of Mg in Mg-Containing GH3128 Alloy

Effect of MgO Content and CaO/Al2O3 Ratio of CaF2–CaO–Al2O3–MgO Slag on the Oxidation Behavior of Mg in Mg-Containing GH3128 Alloy

Preparation and Magnetic Properties of Low-Loss Soft Magnetic Composites Using MgO-Phenolic Resin Coating.

Optimizing the interface between a magnetic powder matrix and an oxide-insulating layer is an effective method to improve the permeability and lower eddy current loss of iron-based soft magnetic composites. In this study, in order to improve the bonding strength of the substrate and insulation layer, soft magnetic composites were prepared by pressing and heat treating with reduced iron powder as a magnetic matrix, high-temperature MgO nanoparticles as insulating coating, and phenolic resin as an adhesive. The effects of MgO content on the microstructure and magnetic properties of the composites were investigated. The results of a scanning electron microscopy and an energy-dispersive spectrometer analysis corroborate that the results obtained regarding the frequency characteristics and the resistivity of the iron powder agree with the scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) analysis and confirm their improvement by the presence of an insulating layer of MgO. The resistivity of the sample coated with 4 wt.% MgO is nearly 45 times higher than that of the uncoated sample under the same conditions. The MgO-insulating film formed on the surface of iron powder makes the coated sample have low effective grain size, high resistivity, and low magnetic loss at a high frequency. At 1 kHz, the magnetic loss of the 4 wt.% MgO-coated sample is reduced by 77.3%, and the magnetic loss is only 5.8% compared with the uncoated sample at 50 kHz. This magnetic loss separation study shows that the addition of MgO insulation material can effectively reduce the eddy current loss of the magnetic powder core. The 4 wt.% MgO-coated sample has the lowest hysteresis loss factor and relatively low eddy current loss factor, so it can be determined that the addition of 4 wt.% MgO is the optimum content to attain a low magnetic loss.

Effect of MgO content in refining slag on the non-metallic inclusions in tire cord steel

In order to weaken the corrosion of refractory during the refining process of tire cord steel, the MgO content in the low basicity (w(CaO)/w(SiO2)≈1.0) slags was increased from 7.9% to 12.6% in industrial experiments. The evolution and removal of inclusions during the refining process were investigated, and the slag properties were also measured in laboratory. It is found that during the refining process, the contents of Al2O3 and CaO generally climb in the inclusions, and SiO2 and MnO contents drop accordingly. Even though, the increase of MgO contents in the refining slag has no obvious effect on the evolution trend and the final composition of inclusions. Therefore, the plasticity of inclusions would not be evidently influenced. On the other hand, with the increase of MgO content in slags, the viscosity and surface tension of the refining slags decrease, while the melting point and the melting rate increase. Due to the lower viscosity and surface tension, a higher MgO content in the slag is beneficial for the removal of inclusions in steel. So, a suitable increase of MgO content in the refining slags is suggested considering the melting point of the slag.

Thermal shock resistant 3D printed ceramics reinforced with MgAl2O4 shell structure

The demand for the swirl nozzle with enhanced temperature resistance and lightweight properties is increasing as the thrust-to-weight ratio of aero-engines rises. The Al2O3 ceramic swirl nozzle can maintain high strength in a hostile environment of high temperature and severe corrosion, while also meeting the requirements of aircraft to enhance efficiency and decrease weight. However, Al2O3 ceramics are limited in their application for aerospace components due to their poor thermal shock resistance (TSR) stemming from their inherent brittleness. This work reported an innovative design and fabrication strategy based on photopolymerization 3D printing technology to realize the three-dimensional shell structure through element interdiffusion and nanoscale stacking of the reinforced phase. With this strategy, a novel type of the new dual-structure Al2O3 ceramic composed of MgAl2O4 shell structure and matrix could be constructed in situ. The nano-sized MgAl2O4 caused a crack passivation effect after the thermal shock, which could improve the strength and TSR of 3D-printed Al2O3 ceramic. In addition, the effects of MgO content and sintering temperature on sintering behavior, flexural strength, porosity, and TSR of Al2O3 ceramics manufactured by digital light processing (DLP) processing were systematically studied. The optimum overall performance of Al2O3 ceramics was obtained at the sintering temperature of 1550 °C and the MgO content of 1.0 wt.%, with a maximum flexural strength of 111.929 MPa and a critical temperature difference of 374.24 °C for TSR. Based on the above research, an aero-engine swirl nozzle with high thermal shock resistance has been successfully prepared by ceramic 3D printing technology, which enhances high-temperature resistance and promotes lightweight design in aero-engine.

Effect of MgO on wetting and corrosion behaviour of corundum substrate by CaO–SiO2–MgO (–Al2O3) slags

ABSTRACT Effect of MgO content on wetting and corrosion behaviour of corundum substrate by CaO–SiO2–MgO (−15%Al2O3) molten slags was investigated at 1450°C via joint application of a sessile drop technique, SEM–EDS detection and FactSage thermodynamic software. All slags exhibit good wettability on the substrate, and the contact angle values are small. Increasing MgO content from 7% to 9% in CaO-SiO2-MgO slags can increase the contact angle between the droplet and the substrate, while the substrate dissolution thickness and the slag penetration depth tend to decrease. Increasing MgO content from 8% to 15% in CaO-SiO2-MgO-15% Al2O3 slags can also increase the contact angle, but significantly decrease the slag penetration depth. The indirect dissolution thickness increases instead due to the formation of a large amount of MgAl2O4 by the interface reaction. The wettability can give an indication of the slag penetration depth in the substrate but not the dissolution thickness of the substrate.

Controlling the microstructure and properties of lithium disilicate glass-ceramics by adjusting the content of MgO

In order to obtain lithium disilicate glass-ceramics for dental restoration with both high strength and high translucency, lithium disilicate glass-ceramics with different MgO contents were prepared by melt-casting and heat treatment method. The effects of MgO content on the crystallization temperature, microstructure and flexural strength of lithium disilicate glass-ceramics were investigated. The results indicate that Mg2+ exists in the form of [MgO4] in the network of lithium disilicate glass-ceramics when the MgO content is 0.56 mol% (M0.56), which is beneficial to increasing the homogeneity and thermal stability of the glass system, and short rod-like lithium disilicate crystals can be formed after heat treatment at 840°C. Thus, the obtained lithium disilicate glass-ceramics exhibit excellent comprehensive performance, with the flexural strength being 312 ± 23 MPa, and the average transmittance of visible light being 37.3% (d = 1.62 mm). Especially, the glass-ceramic sample shows better translucency than the commercially available products. The research results are of great significance for developing high performance lithium disilicate glass ceramics and promoting its broad application in the field of dental restoration.

Effect of MgO content on the quantitative role of hydrotalcite-like phase in a cement-slag system during carbonation

This paper reports the carbonation characteristics of a cement-slag system exposed to accelerated carbonation testing, and its improved carbonation resistance with the increasing MgO content in blast furnace slag, in which hydrotalcite-like phase plays a key role.Our research showed that the hydrotalcite-like phase started to carbonate upon contacting with the carbonate ions and bound more than 15 wt% CO2−3 in the mildly carbonated and transition areas. This value was positively associated with the magnesia content of slag. Additionally, the proportion shared by hydrotalcite-like phase decreased in the fully carbonated area, and more CO2 was fixed in the form of calcium carbonate. Consistent with the thermodynamic modelling, the ratio of CO2 bound in carbonated hydrotalcite-like phase to the total CaCO3 continued to decrease as the CO2 ingress progressed. On the other hand, the reaction between hydrotalcite-like phase and CO2 was found to be volumetrically stable due to binding CO2 in the interlayer space, and Mg was still distributed within the original slag grain region. Mg/Al atomic ratio of hydrotalcite-like phase remained nearly the same before and after carbonation. Results of this study quantitatively emphasized the favorable effect of hydrotalcite-like phase to improve the carbonation resistance of slag-rich cementitious systems.

Deposit Formation in a Coal-Fired Rotary Kiln for Fluxed Iron Ore Pellet Production: Effect of MgO Content

During the roasting process of fluxed pellets in a coal-fired rotary kiln, the incomplete combustion of pulverized coal injection accelerates deposit formation, which further limits the production efficiency of fluxed pellets. In order to eliminate the above problem, this study investigated the influence of MgO on deposit formation mechanism. The thermodynamic analysis revealed that MgO could increase the melting temperature of silicates in fluxed pellets with 0.8–1.2 basicity (CaO/SiO2) when roasted at 1200–1250 °C, thereby decreasing the amount of liquid phase that formed initial deposits. XRD and SEM analyses of deposit simulants demonstrated that the addition of MgO was conducive to form magnesium magnetite and ferri-diopside, thereby avoiding the formation of hedenbergite with lower melting temperature. Moreover, the softening-melting performance and adhesivity tests confirmed that MgO had a positive effect on reducing liquid-phase deposition and inhibiting the adhesion of deposits on refractory bricks below 1250 °C. The above studies indicated that the addition of MgO helped to slow down the deposit formation of fluxed pellets prepared by coal-fired rotary kiln.

Structural, Optical, Mechanical and Antibacterial Properties of MgO/Poly(Vinyl Acetate)/Poly(Vinyl Chloride) Nanocomposites

Polymeric blends and nanocomposites with improved functional properties have attracted attention worldwide for industrial applications. For food packaging applications and carrying purposes, the materials to be used should have UV blocking ability, antibacterial activity, and good mechanical properties. In this study, polyvinyl acetate (PVAc)/polyvinyl chloride (PVC) blends with optimized properties and MgO/PVAc/PVC polymer nanocomposites (PNCs) were prepared by solution casting and evaporation. Fourier transform infrared (FTIR) spectroscopy confirmed the complexation and miscibility between PVAc and PVC and their interaction with MgO nanoparticles (NP). X-ray diffraction and HR-TEM analyses showed the phase purity of MgO NP with a crystallite size of ~ 18.8 nm and their dispersion in the amorphous regions of the blend without affecting the structure of each other. UV–vis-NIR spectroscopy revealed that the band gap of the blend can be tuned by changing the added ratio of each polymer, and loading MgO NP increased the semiconducting behavior of the blend. Various optical constants such as the refractive index, absorption index, and optical dispersion parameters have been evaluated. The blend composition and effects of MgO content on the stress–strain behavior were studied. The addition of MgO to the blend enhanced the tensile modulus and strength. However, there was a corresponding decline in toughness and elongation at break. These results reflect the reinforcing effect of MgO NP, which reduces the flexibility of the polymer chains. The antibacterial activities of MgO/PVAc/PVC PNCs against Staphylococcus aureus, Escherichia coli, and Candida albicans fungi are studied. The improvements in optical, mechanical, and anitmicrobial properties make these nanocomposites suitable for some optical devices and in food packaging applications.

In vitro evaluation and mechanical studies of MgO added borophosphate glasses for biomedical applications

The objective of current research is to evaluate the bioactive and tribological properties of the MgO doped borophosphate glass system. The glass system constituted of 40% B2O3 - (20-x) % CaO – 25% Li2O – 15% P2O5 – x % MgO (mol%), x = 0, 0.5, 01, 02, 03 and synthesized using the melt quench technique. In-vitro bioactivity was determined using simulated body fluid (SBF) at 37 °C with time intervals of 7, 14 and 21 days. Hydroxyapatite (HA) layer formation was assessed using characterization techniques like XRD, FTIR and FESEM-EDS for structural, functional and morphological analysis respectively. The effect of MgO content on microhardness and tribological properties was studied by making cylindrical shaped glass samples. MTT assay was performed for various doses (62.5–1000 μg/ml) of glass dilutions using MG-63 cell line. In-vitro bioactivity showed higher Ca/P ratio with increase in MgO content after 21 days of immersion. MgO content seemed to promote degradation of glass due to formation of open structure in glass network. Borophosphate glass having 3% MgO exhibited the highest hardness value of 5.79(±0.08) GPa with minimum specific wear rate of 1.86 × 10−11 and 1.38 × 10−11 m3/Nm at a load of 15 N and 20 N respectively. MTT assay demonstrated the non-toxic behaviour of glass samples even at a higher dose level of 1000 μg/ml which confirmed its biocompatible behaviour. The study suggests that produced MgO doped borophosphate glass exhibits essential characteristics of bioactive materials and hence could be effective in bone filling and wound healing applications.

Effect of MgO Content on Properties of Bahariya Iron Ore Sinter under the Conditions of Egyptian Iron & Steel Company (EISCO)

Effect of MgO Content on Properties of Bahariya Iron Ore Sinter under the Conditions of Egyptian Iron & Steel Company (EISCO)

Effect of MgO Content on Heat Capacity of Synthetic BF Slag and Heat Release Behavior during Cooling Process

The differential scanning calorimetry (DSC) sapphire analysis was used to measure the specific heat capacity of the BF (BF) slag and observe the CaO-SiO2-MgO-Al2O3-TiO2 5-element slag system with the binary basicity fixed at 1.17. The specific heat capacity of the BF slag and the cooling heat distribution were obtained during the cooling process when the MgO content changing from 7% to 11%. The results showed that the heat released of BF slag was more than 1.2 GJ/ton during the cooling process from 1400 °C to 35 °C, of which the sensible heat was dominant. At MgO content of 9%, the latent heat of crystallization is maximum. The cooling and heat release law of BF slag is directly associated with the phase precipitated in slag cooling and micromorphology.

Microstructure, mechanical and biological properties of laser cladding derived CaO-SiO2-MgO system ceramic coatings on titanium alloys

To improve the bioactivity of titanium alloy (Ti-6Al-4V), laser cladding derived CaO-SiO2-MgO system ceramic coatings were successfully fabricated on the surface of titanium alloy. The effect of MgO content on microstructure, mechanical and biological properties of laser cladding coatings was analyzed. The mechanism of the formation of apatite on the cladding layer in simulated body fluid (SBF) was discussed. The laser cladding derived CaO-SiO2 ceramic layer is mainly composed of CaTiO3, CaO, α-Ca2(SiO4), SiO2 and TiO2. The main phases of the ceramic layer contained different MgO content are all CaTiO3. MgO refines the microstructure of the ceramic layer, and slightly reduces the average hardness of the ceramic layer. The wear resistance decreases with the increase of MgO content. The compounds containing Si in the cladding layer are the main components that induced apatite formation. After soaking in simulated body fluid (SBF) for 21 days, the apatite layer is formed on the coating surface. The hemolysis test, in vitro cytotoxicity test and systemic toxicity test demonstrate that the cladding coating not cause hemolysis reaction, and have no toxicity to cell and living animal, which shows the cladding coating has good biocompatibility.

Simultaneous enhancement of tunability and reduction of permittivity in P(VDF-TrFE)-MgO ferroelectric-dielectric composite films

Ferroelectric-dielectric composite has the potential to combine low dielectric constant of the dielectrics with the high tunability of ferroelectrics. However, one significant drawback of the composites is that the decreased dielectric constant is at the expense of tunability. Here, we eliminate the doping effect through organic-inorganic compositing and redistribute electric field to let the tunability increases while dielectric constant decreases. Poly(vinylidene fluoride-trifluoroethylene) copolymers based ferroelectric-dielectric composite films were prepared through spinning-coating method and the effect of MgO content on the dielectric tunable properties was studied. With increasing MgO content up to 30 wt%, the tunability of composite films increased while the dielectric constant decreased. The tunability of P(VDF-TrFE)-MgO composite films with 30 wt% MgO at 10 kHz under 32.5 kV/mm can reach to 25.6%, 1.22 times that of pure P(VDF-TrFE) (20.9%). This research paves a new pathway to increase the tunability and decrease the dielectric constant of ferroelectric materials simultaneously.

Synthesis of magnesium-beta-alumina composite electrolytes via a vapour phase method

γ-Al2O3, Na2CO3, MgCO3 and Li2CO3 were employed to synthesise MgO-doped Na-β″-Al2O3 composite electrolytes via a vapour phase method. The effects of MgO content on the β″-Al2O3 content, microstructure and electrical properties of each of the composite electrolytes were investigated by using X-ray diffraction, scanning electron microscopy and AC impedance spectroscopy, respectively. The bulk density and bending strength of the samples were also measured in this study. The results demonstrate that the composite electrolyte with an appropriate amount of MgO increased the β″-Al2O3 content of the solid electrolytes and accelerated their densification. The spinel phase resulting from MgO doping not only assisted the conversion process, but also facilitated the formation of Na1.67Mg0.67Al10.33O17. Lastly, the Na-β″-Al2O3 composite electrolyte doped with 0.4 wt% MgO was found to exhibit the best ionic conductivity and bending strength among all of the electrolytes.

Real-time indices focus on slag flowability and coke strength for blast furnace operation

It was well known that abnormal burden quality has a significant impact on the blast furnace (BF) permeability resulting in bad slag flowability and HM tapping, and the coke fines inside BF become much finer to reduce HM production and BF life when the coke strength is weak. Therefore, it is necessary to develop the real-time operation indices of the slag flowability and coke strength after reaction (CSR) in a lower part of BF. BF slag flowability was determined with liquidus temperature and viscosity from measured semi-synthetic slags (SiO2-Al2O3-CaO-MgO-TiO2), and the effects of MgO content, Al2O3 content and CaO/SiO2 on slag flowability are investigated according to the model equations derived from above measured data by using multiple-regression method. A real-time index combined with viscosity and liquidus temperature has been also designed to indicate appropriate slag flowability. In addition, a coke sampler was used to collect the coke samples at tuyere level to analyze the strength of BF bosh coke at various HM productivities. CSR quantitative target and its online index were obtained from the data of sampling coke properties, BF operation conditions and BF permeability to provide real-time reference for coke and HM production.

Investigation on the effect of MgO content on the crystallization behavior of synthetic BF slag

ABSTRACTThe crystallization of molten blast furnace (BF) slag can increase its viscosity and reduce its liquidity; it can also affect the quality of slag fibers following their manufacture. The crystallization behavior of BF slag is influenced by its chemical composition. In this study, four synthetic BF slags with various MgO contents, ranging from 6 to 12%, were investigated. FactSage simulations were performed to predict the types of crystallized phases as well as their mass fractions that are developed within the synthetic BF slags during the cooling process. To verify the validity of FactSage simulation, X-ray diffraction and scanning electron microscope–backscattered electron imaging, where the equipment was coupled to an energy-dispersive spectrometer, were performed to explore the mineralogical compositions and morphologies of the synthetic BF slags. Experiments using the hot thermocouple technique were performed to identify the initial crystallization temperatures of the synthetic BF slags. The results indicate that the observed phases of the synthetic BF slags were primarily composed of akermanite (2CaO · MgO · 2SiO2) and gehlenite (2CaO · Al2O3 · SiO2), which could form a solid solution, melilite, and control the initial crystallization temperature. The initial crystallization temperature increased as the MgO content of the slag increased. A low initial crystallization temperature was achieved in the cases of the synthetic BF slag samples with MgO contents of 6–8%; these slags were considered suitable for the manufacture of slag fiber.

Effect of MgO loading over zeolite-supported Ni catalysts in methane reforming with carbon dioxide for synthesis gas production

Dry reforming of methane (DRM) was investigated for synthesis gas production over zeolite-supported Ni catalysts, and the effect of MgO content was explained. The results revealed that nickel nanoparticles have strong interaction with MgO-zeolite. Adding MgO on beta zeolite increases the conversion of methane and carbon dioxide, and also provides better catalytic stability. The catalyst with Ni/Mg (1:1 wt) on beta zeolite showed the best catalytic activity, with 95% conversion and 97% for CH4 and CO2, respectively. This catalyst also showed higher catalytic stability in the dry reforming of methane and there was low coke formation (2.0 mg/gcat h). Ni catalysts supported on MgO-beta have shown great promise for use in DRM.