Nano-sized MgO Research Articles

A Facile Microwave-Assisted Solution Combustion Synthesis of Highly Stable Magnesium Oxide for Multicomponent Mannich Reaction

A green and robust solid base MgO has been synthesized by a rapid microwave-assisted solution combustion synthesis method and evaluated for multicomponent Mannich reaction under solvent-free conditions at ambient temperature in the liquid phase. The synthesized catalyst was characterized by various techniques to ascertain its phase composition and thermal stability. Catalyst characterization studies revealed that magnesium oxide synthesized by microwaveassisted solution combustion synthesis method offers stable nanosized MgO crystallites. Good to excellent yields of β-amino carbonyl compounds were achieved with aromatic aldehydes bearing an electron withdrawing group.

Microwave Assisted Sol-Gel Synthesis of MgO Nanoparticles and Their Catalytic Activity in the Synthesis of Hantzsch 1,4-Dihydropyridines

A microwave-assisted sol-gel method was employed for the preparetion of nano-sized MgO particles using Mg(NO3)2·6H2O as precursor and deionized water as solvent. The sample calcined at 500 °C had a high specific surface area of 243.2 m2/g and particles sizes from 9.5 to 10.5 nm. For comparison, MgO nanoparticles were also synthesized without microwave irradiation. X-ray diffraction (XRD) characterization showed the formation of smaller particles after microwave irradiation. The structure and morphology of the MgO particles were analyzed by N2 adsorption-desorption, XRD, scanning electron microscopy, and transmission electron microscopy. Their catalytic behavior was studied with the one-pot synthesis of Hantzsch 1,4-dihydropyridines from the reaction of aromatic aldehydes, ethyl acetoacetate, and ammonium acetate. The MgO nanoparticles have high catalytic activity and gave the desired products in good to high yields. The catalyst can be easily recovered by filtration and was used at least three times with only a slight reduction in its catalytic activity.

Enhancing the Sinterability of Chemically-Derived Tl1212 Superconducting Powders Using Nano-Sized MgO as Sintering Aid

The superconducting Tl0.8Bi0.2Sr2Ca0.8Y0.2Cu2O7 powder prepared from chemical route was mixed with varying amounts of nano-sized MgO powders (x=0 to 0.50 wt. %) to form bulk superconducting composites. XRD results show that the addition of 0.15 wt.% nano-MgO is accompanied by an increase in 1212-phase and the disappearance of SrCO3 impurity. SEM investigations revealed more regular-shaped and smaller grains microstructure for MgO added samples in contrast to MgO-free sample which revealed irregular shaped grains. EDS showed homogenous distribution of Mg for all MgO-added samples with the exception of x=0.50 where agglomeration of MgO particles were observed. However, MgO added samples exhibit lower zero-resistance critical temperature, Tc zero than the MgO-free sample.

Coal tar pitch-based porous carbon by one dimensional nano-sized MgO template

Porous carbons are derived by carbonizing coal tar pitch with one dimension non-silica template (needle-like nano-sized MgO). The samples are characterized by nitrogen adsorption at 77K and XRD analysis. The electrochemical performances for supercapacitor are evaluated in a 6M KOH aqueous solution. The results show that the as-prepared porous carbons possess abundant mesopores of 3.7–6.5nm. With air stabilization process, the samples possess more micropores, contributing nearly 50% of surface areas. The porous carbon with large template content through air stabilization possess a high surface area of 864m2g−1. For supercapacitors electrode material, the porous carbon shows a high capacity and excellent power performance, retaining 100Fg−1 even at a current density of 30Ag−1.

Effects of γ-Irradiation and Ageing on Surface and Catalytic Properties of Nano-sized CuO/MgO System

CuO/MgO system prepared by impregnation method was calcined at 350 and 450 oC. The effects of γ-rays (0.2-1.6 MGy) on its structure, surface and catalytic properties were investigated by using XRD, N2-adsorption at -196 oC and catalytic conversion of iso- propanol at 150-275 oC using a flow technique. The results revealed that the investigated solids consisted of nano-sized MgO as a major phase besides CuO and trace amount of Cu2O. γ-Irradiation of the solids investigated exerted measurable changes on their surface and catalytic properties dependent on the calcination temperature and dose of irradiation. The catalysts investigated acted as active dehydrogena- tion solids. The five years-ageing of different solids showed limited changes of their surface and catalytic properties indicating a good catalytic stability of the irradiated prepared solids.

Electrochemical stability of lithium bis(oxatlato) borate containing solid polymer electrolyte for lithium ion batteries

The electrochemical stability of lithium bis(oxatlato) borate (LiBOB) containing solid polymer electrolyte has been evaluated both by inert electrode and real cathodes. Enhanced intrinsic anodic stability and decreased interface impedance, are obtained by addition of nano-sized MgO to PEO 20–LiBOB. It is also found that the LiBOB-containing SPEs exhibit prominent kinetic stability between 3.0 and 4.5 V. For cells using SPEs as the separators, good cycling performance is obtained for real 4 V class cathodes material LiNi 1/3Co 1/3Mn 1/3O 2 and LiCoO 2. The Li|PEO 20–LiBOB|LiNi 1/3Co 1/3Mn 1/3O 2 cell takes an initial capacity of 156.8 mAh g −1, with retention of 142.5 mAh g −1 after 20 cycles at 0.2 C-rate. The cell also works well up to 1 C-rate. The addition of nano-sized MgO into PEO 20–LiBOB readily reduces the irreversible capacity per cycle, both for LiNi 1/3Co 1/3Mn 1/3O 2 and LiCoO 2 cathodes. In addition, the critical role of LiBOB in obtaining kinetic stability and passivating ability towards cathodes are specially discussed.

Preparation of Mesoporous Carbon–Carbon Nanotube Composites Using the Template Method

Reported herein is a simple template method for preparing mesoporous carbons (MPCs) from a mesophase pitch, using homemade nano-sized MgOs and MgO-carbon nanotube (CNT) composites as templates. Nano-sized MgO particles containing iron-molybdenum were synthesized through the heat treatment of the precursor ash, and the MgO-CNT composites were prepared via catalytic chemical vapor deposition of CH4 over the MgO-based particles. MPCs with a high surface area of 443-578 m2/g were obtained through the heat treatment of well-mixed mesophase pitch-MgO (or MgO-CNT), followed by mild-acid treatment to remove the MgO and other catalyst components. All the materials (the precursors, nano-particles, and MPCs) were analyzed via powder X-ray diffraction, N2 adsorption-desorption isotherms, scanning electron microscopy, and high resolution transmission electron microscopy. The formation of the pore structure in the MPCs is discussed, and the potential application of the MPC-CNT composite is demonstrated through cyclic voltammetry.

Formation and Magnetic Characterization of Magnesium Oxide / Iron Nano Composite Particles

Nano-sized composite magnetic particles MgO /Fe were in-situ combustion synthesized at 620°Cfor the Mg-70.9wt%Fe3O4 system. In this paper, we discussed the reactant ratio on the influence of micro-morphology and the magnetic properties of nanoparticles. It was indentified that: Mg(29.1wt%) was the suitable reactant ratio, the sintered composite spherical particles with mean diameter 40nm distributed evenly, particles had good soft magnetic properties, and it was the future drug carriers materials.

Removal of phosphate from aqueous solution by biochar derived from anaerobically digested sugar beet tailings

Biochar converted from agricultural residues or other carbon-rich wastes may provide new methods and materials for environmental management, particularly with respect to carbon sequestration and contaminant remediation. In this study, laboratory experiments were conducted to investigate the removal of phosphate from aqueous solution by biochar derived from anaerobically digested sugar beet tailings (DSTC). Batch adsorption kinetic and equilibrium isotherm experiments and post-adsorption characterizations using SEM–EDS, XRD, and FTIR suggested that colloidal and nano-sized MgO (periclase) particles on the biochar surface were the main adsorption sites for aqueous phosphate. Batch adsorption experiments also showed that both initial solution pH and coexisting anions could affect the adsorption of phosphate onto the DSTC biochar. Of the mathematical models used to describe the adsorption kinetics of phosphate removal by the biochar, the Ritchie N_th-order ( N = 1.14) model showed the best fit. Two heterogeneous isotherm models (Freundlich and Langmuir–Freundlich) fitted the experimental isotherm of phosphate adsorption onto the biochar better than the Langmuir adsorption model. Our results suggest that biochar converted from anaerobically digested sugar beet tailings is a promising alternative adsorbent, which can be used to reclaim phosphate from water or reduce phosphate leaching from fertilized soils. In addition, there is no need to regenerate the exhausted biochar because the phosphate-laden biochar contains abundance of valuable nutrients, which may be used as a slow-release fertilizer to enhance soil fertility and to sequester carbon.

Filament Temperature Dependence of the Nano-size MgO Particles Prepared by the HWCVD Technique

Metal oxide nanoparticles play an important role in many nanotechnical applications. Among these, magnesium oxide has attracted great attention in different applications. Here, hot wire chemical vapor deposition (HWCVD) method was employed for the deposition of magnesium oxide nanoparticles on pre-ultrasonically cleaned P type Si (111) substrates of 1 cm × 1 cm. High purity magnesium ribbon was heated up to high temperatures in the vicinity of tungsten filament in oxygen surrounding medium at a constant working pressure. The samples were deposited by the proposed method and their properties were studied by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Energy Dispersive X-Ray spectroscopy (EDAX). The key parameters of our experiments including results of changes in filament temperature on the properties of Magnesium oxide nanoparticles are presented here. The mean size of the nano MgO Particles was between 80–120 nm.

Mixed oxide (MgO–Y _2O_3) coatings fabricated on glasses from nitrate solutions

This article describes the formation of nanosize MgO–Y 2O3 protective coatings (10–15 nm thick) on the surface of glasses, using aqueous and water–alcohol solutions of magnesium and yttrium nitrates. Based on the results of electron-microscopic and X-ray-phase analyses, the influence of the thickness of the coating on its structure and morphology has been investigated. It is shown that interaction with the glass substrate plays an important role in stabilizing the amorphous structure of coatings consisting of nanoparticles of metal oxides.

Effect of MgO particle size on the microstructure, mechanical properties and wear performance of ZTA–MgO ceramic cutting inserts

The mechanical properties, microstructure and wear performance of zirconia-toughened alumina (ZTA) cutting inserts with Magnesia (MgO) in different particle sizes as additives was investigated. The MgO particle sizes were varied from 80 nm to 7000 nm. The alumina (Al 2O 3), yittria stabilized zirconia (YSZ) and MgO powders were mixed, compacted and sintered at 1600 °C using the solid-state sintering method. The mechanical and physical properties of the samples such as wear resistance, Vickers hardness, fracture toughness, microstructure and density were analyzed. Commercially available stainless steel (316L) was used as the workpiece for the wear resistance study. It was observed that smaller MgO particle sizes induce better wear performance and mechanical properties for the cutting inserts. Wear resistance analysis showed that the cutting insert with nano-sized MgO (particle size 80 nm) had the lowest wear area of 0.019 mm². The same cutting insert also possessed the highest Vickers hardness value of 1740 Hv compared to the other samples. Furthermore, microstructural observations show that the Al 2O 3 grain size depends on the particle size of MgO, and is directly related to its hardness property.

Mechanical and superconducting properties of nanosize MgO added dip-coated Bi<sub>2</sub>Sr<sub>2</sub>CaCu<sub>2</sub>O<sub>8</sub> superconducting tape

In this work, 3% to 8% (in weight) of nanosize MgO particles was added to Bi2Sr2CaCu2O8 (Bi- 2212) high-temperature superconductor to fab-ricate Bi-2212 superconducting material with superior mechanical properties. The mechanical strength of the samples was studied by con-ducting the compression test at room tempera-ture, and the addition of 5% nanosize MgO par-ticles produced the highest strength when com- pared with other samples. The sample with 5% MgO addition also exhibited superior super-conducting properties. The Bi-2212 powder with 5% nanosize MgO addition was used to fabricate Bi-2212 tapes through the dip-coating-then- stacking method. The fully processed tapes were investigated via dc electrical resistance measurements, XRD patterns, SEM micrographs, transport critical current density and tensile tests. The tensile tests were conducted at room and cryogenic (77 K) temperatures. Results of tensile tests and Young’s modulus for the tapes showed that the Bi-2212 tapes with nanosize MgO addition recorded better mechanical prop-erty compared to the non-added samples both at room and cryogenic temperatures. The double- core tape with 5% MgO addition recorded the highest failure point at 160 MPa. In addition to the strengthening effect that was observed in the nanosize MgO added Bi-2212 superconduc-tor tapes, the superconducting properties re-mained intact in the tapes.

A New Xenon Plasma Flat Fluorescent Lamp Enhanced with MgO Nano-Crystals for Liquid Crystal Display Applications

Nano-sized MgO single crystal powders have recently been reported to emit ultraviolet by stimulation of electrons in a vacuum. In this study, nanocrystalline MgO powders were applied to a xenon plasma flat fluorescent lamp (FFL) for a liquid crystal display backlight to improve its emission efficiency through the extra ultraviolet from the nano-MgO crystals. For comparison, a MgO nano-thin film was applied directly on the phosphors inside a lamp panel through e-beam evaporation. Adding MgO nano-crystal powders to the phosphors improved the luminance and efficiency of FFLs by around 20% and MgO nano-crystal coverage of 40% of the phosphor provided the best FFL emission characteristics; however, application of MgO thin film to the phosphors degraded the emission characteristics, even compared to FFLs without MgO. This was due to insufficient ultraviolet stimulation of the phosphors and the crystallinity and low secondary electron coefficient of the MgO.

Porous carbons prepared from deoiled asphalt and their electrochemical properties for supercapacitors

Porous carbon was prepared from deoiled asphalt by conventional NaOH activation process and by the combination of nano-sized MgO template method and NaOH activation process. The electrochemical properties used as supercapacitors electrode material were evaluated in 7 M KOH aqueous solution. Porous carbon sample obtained by NaOH activation possessed more micropores and higher specific surface area, resulting in a higher specific capacitance of 235 F g − 1 at low charge–discharge current of 50 mA g − 1 . For the combination method, the resultant carbons possessed higher capacitance and good capacitance maintaining at high current, with a capacitance of nearly twice as that of the former at current density of 10 A g − 1 , due to their abundant mesopores.

Electrical and electrochemical properties of magnesium ion conducting composite gel polymer electrolytes

The effect of micro- and nano-sized MgO and nano-sized SiO2 dispersion on the electrical and electrochemical properties of poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) based Mg2+ ion conducting gel polymer electrolyte has been investigated. The gel electrolytes have been characterized using electrical conductivity, cationic transport number (t+) measurements and cyclic voltammetry. A two-maxima feature has been observed in the ‘conductivity versus composition’ curve at ∼3 wt% and 10–15 wt% of the filler contents. The highest conductivity has been obtained for the SiO2 dispersed gel electrolyte of ∼1 × 10−2 S cm−1 for 3 wt% and ∼9 × 10−3 S cm−1 at 15 wt% content. The value of ‘t+’ is found to be enhanced substantially with increasing amount of MgO (both micro- and nanoparticles), whereas in the case of SiO2 dispersion the value does not increase substantially. The highest ‘t+’ value of ∼0.44 has been obtained for the addition of 10 wt% MgO nanoparticles. The enhancement in ‘t+’ is explained on the basis of the formation of space-charge regions due to the presence of MgO : Mg2+-like species, which supports Mg2+ ion motion. A substantial increase in the amount of anodic and cathodic peak currents is observed due to the addition of nano-sized MgO particles in the gel polymer electrolyte, whereas in the cases of micrometre-sized MgO and nano-sized SiO2 the enhancement is not significant. The enhancement in conductivity in SiO2 dispersed nanocomposite gel electrolyte is predominantly due to anionic motion.

Forming nanosize MgO coatings on a glass surface

This article shows that nanosize (10-15nm thick) MgO protective coatings can be formed on glass surfaces, using aqueous and water-alcohol solutions of magnesium nitrate. The effect of the concentration and pH of the solutions on the coating structure is investigated.

Superconductivity and enhancement of critical current density of Ta-substituted TlSr1212 with addition of nanosize MgO

In this paper, the authors report the effect of nanosize MgO particles addition on superconducting and transport critical current density Jc of TlSr1212 superconductors prepared from Tl0·9Bi0·1Sr1·95Ta0·05Ca0·9Y0·1Cu2O7 starting composition using conventional solid state synthesis. X-ray diffraction analyses of Tl0·9Bi0·1Sr1·95Ta0·05Ca0·9Y0·1Cu2O7+xMgO (x=0 to 0·8 wt-%) showed formation of dominant 1212 phase (>90 vol.-%) together with minor 1201 phases. Undoped TlSr1212(x=0) was observed to superconduct with a zero-resistance critical temperature Tc zero of 65 K. The x=0·2 sample recorded the highest Tc zero (80 K) but for higher x, Tc zero was gradually suppressed. The effect of the MgO addition also caused Jc enhancement in zero field with highest value at x=0·2. Using the self-field approximation model, the variation of Jc with temperature for x=0 to 0·4 samples indicate that MgO addition reduces the characteristics length Lc associated with the pinning force. Jc measurements in external magnetic field of 0–0·8 T showed smallest drop in Jc at x=0·2. The Jc enhancements in self-field and in the external fields are suggested to be due to increased flux pinning of the samples as a result of the MgO addition.

Enhanced heterogeneous nucleation in AZ91D alloy by intensive melt shearing

Intensive melt shearing was applied to the commercial AZ91D alloy melt to investigate its effects on grain refinement. Alloy melts with and without melt shearing were also filtered using a pressurized filtration technique to concentrate the potential nucleating particles for electron microscopic examination. The results showed that intensive melt shearing resulted in significant refinement of both the Al 8Mn 5 intermetallics and the primary α-Mg phase in the as-cast AZ91D alloy, and that this grain-refining effect is insensitive to the superheat and can persist even after prolonged isothermal holding. The pressurized filtration experiments showed for the first time that oxide films and skins consist of nano-sized MgO particles populated densely in a liquid matrix. Intensive melt shearing can effectively disperse such MgO particles throughout the alloy melt. The HRTEM investigation and detailed crystallographic analysis confirmed that dispersed MgO particles act as potent heterogeneous nucleation sites for both the Al 8Mn 5 and α-Mg phase.

Influence of precursor of MgO and preparation conditions on the catalytic dehydrogenation of iso-propanol over CuO/MgO catalysts

0.2CuO/MgO solids prepared by impregnation method and calcined at 450 °C. The effects of preparation conditions and precursor of the support on the structure, surface and catalytic properties of the catalysts were investigated by using XRD, N 2-adsorption at −196 °C and catalytic conversion of isopropyl alcohol at 75–275 °C using a flow technique. The results revealed that the investigated solids consisted of nano-sized MgO as a major phase besides CuO and trace amount of Cu 2O. The precursor of MgO (hydroxide or carbonate) affects the thermal properties of CuO/MgO system. The S BET of CuO/MgO system calcined at 450 °C increases with using carbonate precursor of MgO or using proper preparation method of magnesium hydroxide. Different investigated solids behave mainly as a dehydrogenation catalyst yielding acetone. Methyl iso-butyl ketone (MIBK) product was detected in catalytic conversion of isopropyl alcohol via aldol condensation mechanism. Various catalytic activities, selectivities and stabilities are affected by method of preparation and the precursor of the support.