MgO Materials Research Articles

Preparation and high-temperature oxidation behaviors of MgAl2O4-MgAlON composites by in-situ nitriding

In this study, MgAl2O4-MgAlON composites with Al, α-Al2O3, MgO and MgAl2O4 raw materials were fabricated through in-situ nitriding and reaction sintering, with a tunable MgAlON composition from 10 wt% to 25 wt%. Subsequently, the sintered samples were calcined at 1500 ℃ for 3 h in an oxidation atmosphere. The densification, mechanical properties, phase assemblage, microstructures, and oxidation behaviors of MgAl2O4-MgAlON composites were investigated. Results reveal that the MgAlON grains were well-crystallized and exhibited a spinel structure in sintered body. The mechanical properties were markedly improved with the increase of MgAlON mass fraction and reached the maximum at 25 wt%. After oxidation, the densification and mechanical properties have both declined, despite the composites were oxidized to a core-shell structure. Additionally, the weight gain rate and linear expansion rate of oxidized samples simultaneously exhibited a gradual rise with the increase in MgAlON contents. More specifically, the MgAlON grains were transformed into many submicron MgAl2O4 and α-Al2O3 grains with particle sizes< 1 µm after oxidation, while the oxidation reaction was carried out along the particle gaps created by MgAlON grains oxidized from surface to interior. Our findings provide some scientific guidance for enhancing the oxidation resistance and application potentials of MgAlON composites in high-temperature.

Effect of magnesia-calcium hexaaluminate refractories on the quality of low-carbon alloy steel

High-performance alloy steel is distinguished by its purity. Inclusion contamination and oxygen addition to the steel due to long contact between the refractories of the tundish and the steel should be avoided. In this study, the static crucible method was used in the interaction experiments between MgO–CA6 composite and low carbon alloy steel. The effects of different proportions of MgO–CA6 on the content of alloying elements in steel were analyzed. Morphology, quantity, size, and distribution of inclusions were also examined. The results indicated that more inclusions (e.g., MnO, FeO, and MnS) were generated between the MgO material and alloy elements (e.g., Fe and Mn) in molten steel. The oxygen content in molten steel of CA6, MgO–0.28CA6, and MgO–0.70CA6 materials, as well as the number of inclusions, were sharply reduced. The particle size was smaller, resulting in good molten steel purification ability. The oxygen content of the steel in contact with the MgO–0.28CA6 material was relatively low, characterized by a reduction in the proportion of inclusion area and particle.

First-Principle Study on Electronic Structure and Magnetism in Doped MgO Materials

First-Principle Study on Electronic Structure and Magnetism in Doped MgO Materials

Magnesium-Modified Co3O4 Catalyst with Remarkable Performance for Toluene Low Temperature Deep Oxidation

Co3O4, MgCo2O4 and MgO materials have been synthesized using a simple co-precipitation approach and systematically characterized. The total conversion of toluene to CO2 and H2O over spinel MgCo2O4 with wormlike morphology has been investigated. Compared with single metal oxides (Co3O4 and MgO), MgCo2O4 with the highest activity has exhibited almost 100% oxidation of toluene at 255 °C. The obtained results are analogous to typical precious metal supported catalysts. The activation energy of toluene over MgCo2O4 (38.5 kJ/mol) is found to be much lower than that of Co3O4 (68.9 kJ/mol) and MgO ((87.8 kJ/mol)). Compared with the single Co and Mg metal oxide, the as-prepared spinel MgCo2O4 exhibits a larger surface area, highest absorbed oxygen and more oxygen vacancies, thus highest mobility of oxygen species due to its good redox capability. Furthermore, the samples specific surface area, low-temperature reducibility and surface adsorbed oxygenated species ratio decreased as follows: MgCo2O4 &gt; Co3O4 &gt; MgO; which is completely in line with the catalytic performance trends and constitute the reasons for MgCo2O4 high excellent activity towards toluene total oxidation. The overall finding supported by ab initio molecular dynamics simulations of toluene oxidation on the Co3O4 and MgCo2O4 suggest that the catalytic process follows a Mars–van Krevelen mechanism.

Insight into the role and mechanism of polysaccharide in polymorphous magnesium oxide nanoparticle synthesis for arsenate removal

The low cost and non-toxic of magnesium oxides make it a potential eco-friendly material for arsenic removal. Polysaccharide is a kind of green modifier to obtain nanoscale MgO particles with a higher adsorption affinity. In this study, the impact of chain structures of polysaccharides on the morphology features and arsenate removal efficiency of MgO-NPs were investigated. Pullulan and starch facilitated the synthesis of flower-like MgO-NPs, and pectin facilitated the synthesis of plate-like ones. Although the two kinds of flower-like MgO-NPs undergone similar time to reach equilibrium, the one obtained from the starch-synthesis route showed a higher arsenate adsorption capacity (98 mg g−1), due to that their bushy and smaller petals on the surface provide more active sites for arsenic adsorption. The pectin-synthesis route also produced MgO-NPs with higher arsenate adsorption capacity (101 mg g−1), ascribed to stacking of nano-plates on their surfaces facilitated to form defect surfaces. However, due to their lower BET area, the plate-like MgO-NPs took twice times to reach equilibrium for arsenic adsorption compared with the others. In the stage for the hydrolysis of MgO, hydroxyl groups on the polymer chain provide active sites to physically trap or bond with MgO particles and then to produce hydrolyzed precursors. The poly chain containing inter- and intra-hydroxyl groups directed MgO molecular growing into hydroxide crystals with 3D frameworks during their nucleation and growth. However, pectin only provides inter-hydroxyl groups and directs to form hydroxides with 2D frameworks. Furthermore, the rapid-nucleation vs. slow-growth model in the stage of pyrolysis of hydroxide crystals successfully interprets the thinner petals and complex chemical phases of the final nanoparticles obtained from the pullulan-synthesis route. This work may provide direction and perspectives for the rational design of well-performing MgO materials for arsenate removal.

Corrosion Resistance of MgO and Cr2O3-Based Refractory Raw Materials to PbO-Rich Cu Slag Determined by Hot-Stage Microscopy and Pellet Corrosion Test.

Chemical resistance of commercial refractory raw materials against Cu slag is critical to consider them as candidates for the production of refractories used in Cu metallurgy. In this study, we show the comparative results for the corrosion resistance of four commercial refractory raw materials—magnesia chromite co-clinkers FMC 45 and FMC 57, PAK, and fused spinel SP AM 70—against aggressive, low-melting PbO-rich Cu slag (Z1) determined by hot-stage microscopy (up to 1450 °C) and pellet test (1100 and 1400 °C). Samples were characterized after the pellet test by XRD, SEM/EDS, and examination of their physicochemical properties to explore the corrosion reactions and then assess comparatively their chemical resistance. Since many works have focused on corrosion resistance of refractory products, the individual refractory raw materials have not been investigated so far. In this work, we show that magnesia chromite co-clinker FMC 45 exhibits the most beneficial properties considering its application in the production of refractories for the Cu industry. Forsterite (Mg2SiO4) and güggenite (Cu2MgO3) solid solutions constitute corrosion products in FMC 45, and its mixture with slag shows moderate dimensional stability at high temperatures. On the other hand, the fused spinel SP AM 70 is the least resistant to PbO-rich Cu slag (Z1); it starts to sinter at 970 °C, followed by a fast 8%-shrinkage caused by the formation of güggenite solid solution in significant amounts.

MgO-Based Board Materials for Dry Construction Are a Tool for More Sustainable Constructions—Literature Study and Thermal Analysis of Different Wall Compositions

Growing global environmental problems force us to think about their impact and search for ways to protect the environment. While the construction industry and the production of construction materials contribute to environmental pollution, they also offer great potential for addressing many environmental problems. Important opportunities exist in the use and processing of a whole host of industrial and construction waste and in the use of mineral resources. Among such mineral resources is magnesite, whose deposits in Slovakia are abundant. The current sustainability trends impose strict requirements on construction materials and products, favoring solutions with sufficient ecological and efficiency performance characteristics. With this focus on efficient and sustainable solutions in mind, the objective of this research was to analyze magnesium oxide construction boards, as they are the most commonly used construction product based on MgO. The specific MgO-based boards that were studied were applied in selected constructions built using the so-called dry method of construction and were compared with traditional material solutions. The research methodology is based on an analysis of computational models of the proposed variants to determine selected thermal-technical parameters. The analyses of external and interior structures presented in this work suggest that when boards based on MgO and traditional materials are used for coating constructions built using the dry method of construction, the former provide certain benefits in terms of energy accumulation, improving living comfort, and in terms of the fire resistance of constructions, improving overall safety. The conclusion of the presented article is devoted to discussions with works that addressed various perspectives on the application of MgO in the field of materials research. The findings from this analysis are beneficial especially in terms of expanding the knowledge in the area.

Coke-resistance enhancement of mesoporous γ-Al2O3 and MgO-supported Ni-based catalysts for sustainable hydrogen generation via steam reforming of acetic acid

Highly ordered mesoporous γ-Al2O3 particles and MgO materials were synthesized by evaporation induced self-assembly (EISA) and template-free hydrothermal co-precipitation routes, respectively. Ni, Ni–MgO, and Ni–La2O3-containing catalysts were prepared using a wet-impregnation method. The synthesized catalysts were characterized by N2 adsorption–desorption, XRD, SEM-EDS, DRIFTS, XPS, TGA-DTA, and Raman spectroscopy analysis. The mesoporous γ-Al2O3 catalyst support exhibited a high surface area of 245 m2/g and average pore volume of 0.481 cm3/g. The DRIFTS results indicate the existence of large Lewis's acid regions in the pure γ-Al2O3 and metal-containing catalysts. Catalytic activity tests of pure materials and metal-containing catalysts were carried out at the reaction temperature of 750 °C and a feed molar ratio of AA/H2O/Ar:1/2.5/2 over 3 h. Complete conversion of acetic acid and 81.75% hydrogen selectivity were obtained over the catalyst 5Ni@γ-Al2O3. The temperature and feed molar ratio had a noticeable impact on H2 selectivity and acetic acid conversion. Increasing the water proportion in the feed composition from 2.5 to 10 considerably improved the catalytic activity by increasing hydrogen selectivity from 81.75% to 91%. Although the Ni-based γ-Al2O3-supported catalysts exhibited higher activity performance compared to the Ni-based MgO-supported catalysts, they were not as resistant to coke formation as were MgO-supported catalysts. The introduction of MgO and La2O3 into the Ni@γ-Al2O3 and Ni@MgO catalysts' structures played a significant role in lowering the carbon formation (from 37.15% to 17.6%–12.44% and 12.17%, respectively) and improving the thermal stability of the catalysts by decreasing the agglomeration of acidic sites and reinforcing the adsorption of CO2 on the catalysts' surfaces. Therefore, coke deposition was reduced, and catalyst lifetime was improved.

Hydration properties of alkali-activated fly ash/slag binders modified by MgO with different reactivity

The roles of MgO in alkali-activated materials have attracted much attention in recent decades. The effects of the reactivity of MgO on the compressive strengths and hydration properties of alkali-activated materials consisting of a blend of fly ash, slag, and MgO were studied here. The alkalinity of the activator, vital to the dissolution and hydration mechanisms of MgO, was investigated as well. It was found that MgO reactivity had little influence on the crystallization of C–S–H type gels, while increasing the MgO reactivity prompted incorporation of Na and Mg atoms into amorphous binding chains within the binders. A higher hydration degree of MgO and alkali-activated materials can be achieved by using highly reactive MgO, as revealed by crystallinity and hydration analyses. The hydration mechanism of reactive MgO in the alkali-activated fly ash and slag blended materials is discussed.

High-Index (Ni,Mg)O Crystallization during Molten Salt Synthesis

Heterogeneous NiO–MgO materials and (Ni,Mg)O solid solutions have found application in catalysis owing to the combined redox properties of NiO and basic properties of MgO. Examples include the use of (Ni,Mg)O to tune the surface reducibility of Ni(II), which determines the Ni cluster size and the tendency of catalysts to form coke and deactivate in dry reforming and partial oxidation of methane. To this end, control of the metal oxide structure and surface properties, both in terms of composition and faceting, are of paramount importance. In this article, we show that both compositional and morphological control can be achieved by selecting an appropriate molten salt synthesis (MSS) to obtain a solid solution of (Ni,Mg)O or segregated NiO–MgO crystals at low temperature (≤550 °C). Our findings reveal that nitrate precursors in a medium with excess NaCl/KCl (1:1) putatively results in the formation of a reaction intermediate comprised of molten K3Na(Mg,Ni)Cl6. In the presence of exchanged nitrate ions acting as Lux-Flood bases, this molten intermediate forms solid oxide solutions whose morphology is dictated by the composition of the medium, shifting from an octahedral to icositetrahedral (trapezohedral) habit with increasing Ni(II) content. Conversely, when using NaNO3/KNO3 (1:1) as a growth medium, solid solutions are inhibited and we observe segregation of the oxide phases. Under these conditions, the morphologies of the heterogeneous products are predominantly octahedral for MgO and truncated cubic-to-octahedral for NiO, depending on the Ni(II) content. Systematic examination of Ni/Mg mixed metal oxide crystallization highlights the strikingly different pathways followed in nitrate and chloride salt media. Overall, this study highlights the importance of molten intermediates in solid solution synthesis and reveals that the judicious selection of ions in MSS plays a major role in achieving well-defined crystals with high-index facets.

Distinctive features of diffusion-controlled radiation defect recombination in stoichiometric magnesium aluminate spinel single crystals and transparent polycrystalline ceramics

MgAl2O4 spinel is important optical material for harsh radiation environment and other important applications. The kinetics of thermal annealing of the basic electron (F, F+) and hole (V) centers in stoichiometric MgAl2O4 spinel irradiated by fast neutrons and protons is analyzed in terms of diffusion-controlled bimolecular reactions. Properties of MgAl2O4 single crystals and optical polycrystalline ceramics are compared. It is demonstrated that both transparent ceramics and single crystals, as well as different types of irradiation show qualitatively similar kinetics, but the effective migration energy Ea and pre-exponent D0 are strongly correlated. Such correlation is discussed in terms of the so-called Meyer-Neldel rule known in chemical kinetics of condensed matter. The results for the irradiated spinel are compared with those for sapphire, MgO and other radiation-resistant materials.

Effect of plasmon–phonon interaction on the infrared reflection spectra of MgxZn1-xO/Al2O3 structures

The effect of plasmon–phonon interaction on the vibrational properties of the MgxZn1-xO films on anisotropic substrate is studied versus Mg content (x), film thickness (0.5–20 μm), free carrier concentration (1×1016–5×1018 cm−3) and damping coefficients using infrared reflection spectroscopy. The mathematical model with additive and phenomenological contribution of several oscillators to dielectric permittivity of MgxZn1-xO material was developed. The infrared reflection spectra were simulated in the range of “residual rays” of the film and the substrate for MgxZn1-xO/Al2O3 structures using self-consisted parameters of bulk ZnO, MgO and Al2O3 materials. Based on the Kramers–Kronig relationship, the frequency range where film reflectivity is sensitive to the variation of film doping and thickness was determined. The frequencies and damping coefficients of TO and LO modes of the oscillators, static and high-frequency dielectric permittivity for orientation E⊥c were obtained with high accuracy. Main attention was paid to the compositions which were in hexagonal structure. Experimental infrared reflection spectra were recorded for the films with x = 0.25 additionally doped with manganese and their simulation was performed based on the model developed. The free carrier concentration and mobility as well as film conductivity were determined. The results obtained showed the utility of infrared reflection spectroscopy for the investigation of textured alloy films. This non-destructive and contactless method can be implemented for the determination of optical properties of other semiconductor films.

Microstructure, optical and photocatalytic properties of MgO nanoparticles

The present work is focused on the synthesize of MgO nanoparticles using combustion method. The magnesium nitrate is used as a precursor with urea as a fuel. The precursor material is dissolved in 50 ml DI water along with the fuel and the solution is heated at 80 °C for 2 h. Then, the solution is transferred to crucible and kept it in the temperature of 500 °C. The as-synthesized MgO nanopowders are analyzed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM), photoluminescence (PL) and photocatalytic studies. The XRD results of MgO nanoparticles indicated the cubic structure with the crystallite size of 27 nm. The FESEM studies indicated the formation of MgO crystallites in spherical shape. In addition, MgO nanoparticles are porous and agglomerated. PL spectrum of MgO materials exhibit emission peaks, which indicates the occurrence of band to band transition with the bandgap of 2.9 eV. The photocatalytic degradation of methylene blue dye is evaluated using the as-prepared MgO nanoparticles under UV light. The photocatalytic studies indicate the 75% degradation efficiency of the catalyst after 120 min irradiation. Hence, the MgO Nanoparticles (NPs) can be used for the treatment of effluents from the dye industries.

Facile synthesis of MCM-41/MgO for highly efficient adsorption of organic dye

Recently, MgO has been demonstrated to be a promising adsorption material for dye removal from wastewater due to its unique characteristics. However, the low surface area and recyclability have seriously limited its practical application in water treatment. Herein, MgO was introduced to mesoporous MCM-41 to improve its surface properties. A series of MCM-41/MgO nanocomposites with high surface areas (˜1000 m2/g) and mesostructures were synthesized by a facile in situ method. Compared with pure MgO and MCM-41, the mesoporous MCM-41/MgO exhibited enhanced adsorption capacity and superior recycling stability for fast removal of an organic dye from water. The maximum adsorption capacity for crystal violet (CV) can reach 1861.38 mg/g, which is several times higher than that of MgO itself and of most other adsorbents. Even after five consecutive cycles, the removal efficiency is still up to 90%. It is expected that the mesoporous MCM-41/MgO materials will have a considerable potential in wastewater treatment.

Sulfate resistance of carbonated ternary mortar blends: Portland cement, reactive MgO and supplementary cementitious materials

Abstract: Reactive MgO (rMgO) and supplementary cementitious materials are promising to formulate sustainable construction binders. This study compares the effect of GGBFS and FA on the properties of mortar systems containing both r-MgO and Portland cement (rMgO-PC) as binder. The experimental results reveal that the incorporation of 10% GGBFS or 10% FA increases the carbonation degree of the rMgO-PC system at rMgO replacement levels of 0%, 30%, 50% and 70%. The incorporation of 10% GGBFS or 10% FA reduces the expansion of mortars with the 0% and 30% rMgO replacement levels during the sulfate exposure. Sulfate exposure not only leads to the formation of ettringite and gypsum in the mortars with the 0% and 30% rMgO replacement levels, but also accelerates the formation of protodolomite in the 50% and 70% rMgO replacement levels. However, only the ettringite and gypsum were found to jeopardize the volume stability of carbonated mortars.

New Study of Mgo Nps in Drilling Fluid to Reduce Stick-Slip Vibration in Drilling System

Stick-slip is kind of vibration which associated with drilling operation in around the bottom hole assembly (BHA) due to the small clearance between drill string &amp; the open hole and due to the eccentric rotating of string. This research presents results of specific experimental study that was run by using two types of drilling mud (Fresh water Bentonite &amp; Polymer), with/without Nanoparticle size materials of MgO in various ratios and computes the rheological properties of mud for each concentration [Yield point, plastic viscosity, Av, PH, filter loss (30 min), filter cake, Mud Cake Friction, Friction Factor]. These results then were used to find a clear effects of Nanoparticle drilling mud rheology on stick - slip strength by several perspectives through a special “Torque and Drag” software which simulate the torque amount expected on BHA during drilling a vertical well in different conditions using real drilling string design that usually used in Iraqi oil fields. Thus to mitigate or to prevent stick–slip and cure the sequence events that could happen to both of drilling string and the well, i.e. Bit/BHA wear, pipe sticking, borehole instability and low Rate of penetration. Our study concluded that there are good reduction in the torque from (2031lb-ft) to (1823lb-ft) using polymer mud and torque reduction from (4000lb-ft) to (3450lb-ft) using Fresh Water Bentonite, these results do not include any breaking in the satisfactory range of other mud rheology.

Synthesis of Highly Dispersed Al2O3–ZrO2–MgO Materials Using Electrogenerated Reagents

We have studied the morphology and phase composition of precursors for the preparation of highly dispersed alumina-based Al2O3–ZrO2–MgO materials. The precursors were synthesized in a coaxial diaphragmless electrolyzer with a soluble anode. Zr(IV) and Mg(II) ions were added during the synthesis process. It has been shown that varying electrolysis conditions allows the particle size and phase composition of the precipitate to be controlled. Synthesis in the Al2O3–ZrO2–MgO system is accompanied by Al2MgO4 spinel formation. Increasing the spinel concentration helps the metastable phase θ-Al2O3 to persist.

Controlled synthesis of Mg(OH)2 thin films by chemical solution deposition and their thermal transformation to MgO thin films

The chemical solution deposition of Mg(OH)2 thin films on glass substrates and their transformation to MgO by annealing in air is presented. The chemical solution deposition consists of a chemical reaction employing an aqueous solution composed of magnesium sulfate, triethanolamine, ammonium hydroxide, and ammonium chloride. The as-deposited films were annealed at different temperatures ranging from 325 to 500 °C to identify the Mg(OH)2-to-MgO transition temperature, which resulted to be around 375 °C. Annealing the as-deposited Mg(OH)2 films at 500 °C results in homogeneous MgO thin films. The properties of the Mg(OH)2 and MgO thin films were analyzed by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, UV–Vis spectroscopy, and by circular transmission line model. Results by X-ray diffraction show that the as-deposited thin films have a brucite structure (Mg(OH)2), that transforms into the periclase phase (MgO) after annealing at 500 °C. For the as-deposited Mg(OH)2 thin film, a nanowall surface morphology is found; this morphology is maintained after the annealing to obtain MgO, which occurred with the evident formation of pores on the nanowall surface. The assessed chemical composition from X-ray photoelectron spectroscopy yields Mg0.36O0.64 (O/Mg ratio of 1.8) for the as-deposited Mg(OH)2 film, where the expected stoichiometric composition is Mg0.33O0.67 (O/Mg ratio of 2.0); the same assessment yields Mg0.60O0.40 (O/Mg ratio of 0.7) for the annealed thin film, which indicates the obtainment of a MgO material with oxygen vacancies, given the deviation from the stoichiometric composition of Mg0.50O0.50 (O/Mg ratio of 1.0). These results confirm the deposition of Mg(OH)2 films and the obtainment of MgO after the heat-treatment. The energy band gap of the films is found to be 4.64 and 5.10 eV for the as-deposited and the film annealed at 500 °C, respectively. The resistivity of both Mg(OH)2 and MgO thin films lies around 108 Ω·cm.

Theoretical study on the hydrogen storage properties of (MgO)&lt;sub&gt;4&lt;/sub&gt; under external electric field

MgO is a typical ionic compound with strong polarity. Hydrogen absorbed by MgO materials subjected to an external electric field is a potential method to store hydrogen. However, the method requires an extremely high intensity of electric field, which is difficult to achieve. Therefore, reducing field intensity has become a key problem in the field of hydrogen storage. In this paper, the hydrogen storage properties of an (MgO)&lt;sub&gt;4&lt;/sub&gt; cluster under an external electric field are investigated. The results show that under the external electric field, (MgO)&lt;sub&gt;4&lt;/sub&gt; keeps the frame of cube structure but with little distortion, which implies that (MgO)&lt;sub&gt;4&lt;/sub&gt; cluster can sustain the strong electric field. The (MgO)&lt;sub&gt;4&lt;/sub&gt; is also polarized by the external electric field and its dipole momentum increases to 1.67 and 3.33 Debye when the field intensity is 0.005 and 0.010 a.u., respectively. H&lt;sub&gt;2&lt;/sub&gt; can be adsorbed on a single Mg/O atom: H&lt;sub&gt;2&lt;/sub&gt; is adsorbed at lateral position of Mg atom, while at the top of O atom. The adsorption strength is substantially enhanced under an external electric field. Under only 0.010 a. u. of electric field, the adsorption energy of H&lt;sub&gt;2&lt;/sub&gt; on the Mg or O atoms increases from –0.118 eV to –0.225 eV or from –0.060 eV to –0.150 eV, respectively. The electric field required is significantly lower than that of a large (MgO)&lt;sub&gt;9&lt;/sub&gt; cluster. This result suggests that reducing the size of material is a possible method toreduce the electric field for hydrogen storage in polarizable materials. The weak interaction between H&lt;sub&gt;2&lt;/sub&gt; and (MgO)&lt;sub&gt;4&lt;/sub&gt; is analyzed by the quantum theory of atoms in molecules. The results indicate that under an electric field, (MgO)&lt;sub&gt;4&lt;/sub&gt; and H&lt;sub&gt;2&lt;/sub&gt; are effectively polarized, and the electrostatic interaction between them is subsequently enhanced. Meanwhile, the small cluster is easily polarized because most of the atoms are in the surface and have low coordination. Therefore, the electric field required can be substantially reduced. Moreover, (MgO)&lt;sub&gt;4&lt;/sub&gt; adsorbs 16 H&lt;sub&gt;2&lt;/sub&gt; molecules at most. The corresponding mass density of hydrogen storage reaches 16.7 wt%, indicating that (MgO)&lt;sub&gt;4&lt;/sub&gt; can be used as a hydrogen storage material under an electric field.

Isomerization of Glucose into Fructose over Natural and Synthetic MgO Catalysts

Fructose is one of the most important aldoses and has been gaining attention as the starting material for the synthesis of biobased platform and high-added value chemicals such as 5-hydroxymethylfurfural (5-HMF), levulinic acid and lactic acid. However, due to its low natural occurrence, fructose is produced from glucose, an abundant hexose, via isomerization. Currently, the conventional industrial process utilizes glucose isomerase as a catalyst and is therefore subjected to the limitations of enzymatic reactions. Consequently, an alternative efficient solid catalyst is required that will exhibit high activity, selectivity and stability/reusability. Toward this end, we have demonstrated the effectiveness of using natural MgO, derived from simple calcination of magnesite ores, as a low cost catalyst with increased basicity. A series of industrial and laboratory prepared natural MgO materials with different morphology, porosity and basicity were investigated and the optimum catalyst afforded 44.1 wt % gluc...