Magnesium Precursors Research Articles

Synthesis, characterization, and application of sol gel derived Mg2SiO4 powder

This paper reports a successful preparation of a pure forsterite Mg2SiO4 using the sol–gel approach and its application for the removal of impurities from a Tunisian frying oil. Magnesium nitrate hexahydrate and tetraethylortho-silicate were used as magnesium and silicon precursors, respectively. The synthesis was held at different calcination temperatures for 30 min. The annealed samples were characterized by X-ray diffraction, Fourier transform infrared, scanning electron microscopy, and laser diffraction. The results revealed that the sample calcined at 500 °C was forsterite with unimodal particle size distribution (PSD) centered at 122.8 ± 0.3 μm. The dispersion index I (indicator of particle size uniformity) was 1.84. With the temperature increase, well crystallized compounds were obtained. Their PSDs remain unimodal and shift towards smaller particles. A decrease of the dispersion index was also noted, indicating the formation of Mg2SiO4 with more uniform particle size. This study showed that 900 °C could be selected as energy saving temperature suitable for the preparation of a pure and well crystallized Mg2SiO4 within just 30 min of annealing time. The obtained silicate exhibited promoting results for the purification of waste frying oils.

Formation of magnesium silicate hydrate in the Mg(OH)2-SiO2 suspensions and its influence on the properties of magnesia castables

Brucite is an alternative magnesium precursor for magnesia castables. The hydration process of brucite-microsilica suspensions at 50 °C was firstly studied to identify the magnesium-silicate-hydrate (M-S-H) formation. The existence of M-S-H was dependent on the characteristics of brucite. The brucite with smaller grain size exhibited higher reactivity and favored the formation of M-S-H. The early strength of magnesia castables with addition of the 1 wt% reactive brucite powder was increased, which was related to the modified microstructure via filling effect of brucite fine particles and the formation of M-S-H. Explosion resistance of castables was improved as well attributed to the enhanced early strength and the M-S-H phase in the presence of reactive brucite. Besides, the facilitated formation of forsterite bonding phase in the brucite containing castables during firing process and the thermal-mechanical strength such as hot modulus of rupture and refractoriness under load were significantly increased.

Conformal MgO film grown at high rate at low temperature by forward-directed chemical vapor deposition

MgO thin films are deposited by chemical vapor deposition from the precursor magnesium N,N-dimethylaminodiboranate, Mg(H3BNMe2BH3)2, and water at a substrate temperature of 270–350 °C. Highly conformal coatings with 98% step coverage in trenches of aspect ratio 9 are obtained at a substrate temperature of 270 °C and a growth rate of 7.5 nm/min, most notably through the use of a forward-directed flux, in which some of the precursor molecules travel ballistically down the recessed feature, strike the bottom, and are scattered there to create a virtual source. The deposition conditions can also be adjusted to afford a growth rate up to 200 nm/min with reduced conformality. Most of the films have a dense and column-free microstructure with low surface roughness; the film density, measured by a combination of Rutherford backscattering spectrometry and scanning electron microscopy, is 82%–86% of bulk. Films grown on Si substrates have good adhesion and a low coefficient of friction (∼0.1) in nanoscratch measurements. The refractive index of the films is slightly lower than that of bulk MgO, consistent with the reduced physical densities. Depending on the growth conditions, the C content in the films varies between 0.7 and 6 at. %, and the B content ranges from 1 to 16 at. %. B in the film is present in the B2O3 chemical state; after subtracting the O content in B2O3, the O/Mg ratio = 1.02 in the MgO matrix. A film grown at a temperature of 270 °C and a growth rate of 6 nm/min has a dielectric constant of 9.5 and a breakdown strength of 6 MV/cm.

Nanostructured MgO Sorbents Derived from Organometallic Magnesium Precursors for Post-combustion CO2 Capture

Nanostructured MgO sorbents show promise for intermediate-temperature CO2 capture from post-combustion flue gas stream. However, their CO2 capture behaviors can be affected by the magnesium precursors applied for sorbent synthesis. To screen potential precursors for fabricating excellent CO2 trappers, MgO nanoparticles (NPs) were synthesized by calcining several organometallic precursors, including magnesium ethoxide, magnesium acetate tetrahydrate, magnesium oxalate dehydrate, magnesium lactate dihydrate, magnesium citrate nonahydrate, and magnesium gluconate hydrate. The precursors and MgO NPs were characterized by thermogravimetric analysis, X-ray diffraction, N2 adsorption–desorption, field emission scanning electron microscopy, and CO2 temperature-programmed desorption. A fixed-bed reactor was used to evaluate the CO2 capture performances of the MgO NPs in a simulated flue gas stream. The effect of organometallic precursors on CO2 capture behaviors of the sorbents was further demonstrated. Results in...

Preparation of a Ni-MgO-Al2O3 catalyst with high activity and resistance to potassium poisoning during direct internal reforming of methane in molten carbonate fuel cells

Steam reforming of methane (SRM) is conducted using a series of Ni-MgO-Al2O3 catalysts for direct internal reforming (DIR) in molten carbonate fuel cells (MCFCs). Ni-MgO-Al2O3 catalysts are prepared by the homogeneous precipitation method with a variety of MgO loading amounts ranging from 3 to 15 wt%. In addition, each precursor concentrations are systemically changed (Ni: 1.2–4.8 mol L−1; Mg: 0.3–1.2 mol L−1; Al: 0.4–1.6 mol L−1) at the optimized composition (10 wt% MgO). The effects of MgO loading and precursor concentration on the catalytic performance and resistance against poisoning of the catalyst by potassium (K) are investigated. The Ni-MgO-Al2O3 catalyst with 10 wt% MgO and the original precursor concentration (Ni: 1.2 mol L−1; Mg: 0.3 mol L−1; Al: 0.4 mol L−1) exhibits the highest CH4 conversion and resistance against K poisoning even at the extremely high gas space velocity (GHSV) of 1,512,000 h−1. Excellent SRM performance of the Ni-MgO-Al2O3 catalyst is attributed to strong metal (Ni) to alumina support interaction (SMSI) when magnesium oxide (MgO) is co-precipitated with the Ni-Al2O3. The enhanced interaction of the Ni with MgO-Al2O3 support is found to protect the active Ni species against K poisoning.

Effects of water vapor on the crystallization and microstructure manipulation of MgO ceramic fibers

Magnesium oxide (MgO) ceramic fibers are a promising candidate material in high temperature insulating area, supporting area, adsorption area and catalytic area, and most of the properties are determined by the microstructure. In the present work, MgO precursor fibers were fabricated by the centrifugal-spinning combined with sol-gel method. The thermal decomposition and crystallization process of the ceramic fibers were fully characterized. Different atmosphere preheat treatment results suggested that water vapor promoted the thermal decomposition and crystallization of precursor fibers at a lower temperature. Three kinds of particles, including round particles, polyhedron particles to plate particles in the microstructure of the fibers could be manipulated by adjusting the water vapor preheat treatment. The change in textural properties (BET surface area, pore size and pore volume) of the MgO fibers, heated at different temperatures in air after pre-heated treatment in water vapor, was analyzed. Furthermore, the formation mechanisms of the microstructures of the fibers were also presented. The easy manipulation of the microstructures of MgO ceramic fibers may make it a promising material in various areas.

Photocatalytic activity of electrospun MgO nanofibres: Synthesis, characterization and applications

One dimensional MgO nanofibres with high photocatalytic activity were fabricated using the electrospinning method via a polyvinyl alcohol (PVA)/magnesium precursor based system and the dye degradation efficacy of MgO nanofibres was compared with MgO nanospheres. Optimum electrospinning parameters including suitable magnesium precursors were investigated and the formation of MgO nanofibres were confirmed with scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) mapping. Furthermore, the crystalline lattice structure and surface roughness of fabricated nanofibres were evaluated using transmission electron microscopic-electron diffraction mode (TEM-SAED) and atomic force microscopy (AFM), respectively. Fabricated MgO nanofibres exhibited excellent photocatalytic degradation activity against widely used model reactive dye, Reactive Yellow (RY). In contrast to MgO nanospheres, electrospun MgO nanofibres completely degraded the reactive dye under UV irradiation. These photocatalytic MgO nanofibres show a great potential to be used in efficient treatment of industrial dye effluents.

Supported MgO–V2O5/Al2O3 catalysts for oxidative propane dehydration: Effect of the molar Mg : V ratio on the phase composition and catalytic properties of samples

The physicochemical properties of V2O5/Al2O3 and MgO–V2O5/Al2O3 supported catalysts (Mg : V = 1 : 1, 2 : 1, and 3 : 2) obtained by consecutive impregnation of the support with solutions of vanadium and magnesium precursors are studied using a complex of mutually complementary methods (XRD, Raman spectroscopy, UV–Vis spectrometry, and TPR-H2). The effect of the formation of surface magnesium vanadates of various composition and structure on the catalytic properties of the supported vanadium oxide catalysts in the oxidative dehydrogenation of propane is studied. The introduction of magnesium in the samples and an increase in its content, accompanied by a change in the structure of the surface vanadium oxide phases from polymeric VO6/VO5 species to surface metavanadate species, magnesium metavanadate, and further to magnesium divanadate, significantly affects their catalytic properties in the reaction of the oxidative dehydrogenation of propane to propylene.

Physicochemical and adsorptive characteristics of activated carbons from waste polyester textiles utilizing MgO template method.

Activated carbons with high specific surface areas were produced, utilizing waste polyester textiles as carbon precursor by magnesium oxide (MgO) template method. Magnesium chloride (MgCl2), magnesium citrate (MgCi), and MgO were employed as MgO precursors to prepare activated carbons (AC-MgCl2, AC-MgCi, and AC-MgO). Thermogravimetry-differential scanning calorimetry was conducted to investigate the pore-forming mechanism, and N2 adsorption/desorption isotherms, XRD, SEM-EDS, TEM, FTIR and pHpzc were achieved to analyze physicochemical characteristics of the samples. The specific surface areas of AC-MgCl2 (1173m2/g) and AC-MgCi (1336m2/g) were much higher than that of AC-MgO (450m2/g), and the pores sizes of which were micro-mesoporous, mesoporous, and macropores, respectively, due to the formation of MgO crystal with different sizes. All activated carbons had abundant acidic oxygen groups. In addition, batch adsorption experiments were carried out to investigate the adsorptive characteristics of the prepared activated carbons toward Cr(VI). The adsorption kinetics fitted well with the pseudo-second order, and the adsorptive capacity of AC-MgCl2 (42.55mg/g) was higher than those of AC-MgCi (40.93mg/g) and AC-MgO (35.87mg/g).

Deactivation studies of bimetallic AuPd nanoparticles supported on MgO during selective aerobic oxidation of alcohols

Here we report the synthesis and characterisation of high surface area MgO prepared via the thermal decomposition of various magnesium precursors (MgCO3, Mg(OH)2 and MgC2O4). Bimetallic gold-palladium nanoalloy particles were supported on these MgO materials and were tested as catalysts for the solvent-free selective aerobic oxidation of benzyl alcohol to benzaldehyde. All these catalysts were found to be active and very selective (>97%) to the desired product (benzaldehyde). However, MgO prepared via the thermal decomposition of magnesium oxalate displayed the highest activity among all the magnesium oxide supports tested. Attempts were made to unravel the reasons for the deactivation of these catalysts using different characterisation techniques namely in situ XRD, XPS, ICP-MS, TEM, and TGA-MS. From the data obtained, it is clear that MgO undergoes phase changes from MgO to Mg(OH)2 and MgCO3 during catalyst preparation as well as during the catalytic reaction. Besides phase changes, strong adsorption of reactants and products on the catalyst surface, during the reaction, were also observed and washing the catalyst with organic solvents did not completely remove them. The phase change and catalyst poisoning were reversed through high temperature heat treatments. However, these processes led to the sintering of the metal nanoparticles. Moreover, substantial leaching of the support material (MgO) was also observed during the reaction. These latter two processes led to the irreversible deactivation of AuPd nanoparticles supported on MgO catalyst during the solvent-free selective aerobic oxidation of alcohols. Among the three different MgO supports studied in this article, an inverse correlation between the catalytic activity and Mg leaching has been observed. This article reports a deeper understanding of the mode of deactivation observed in metal nanoparticles supported on MgO during liquid phase reactions.

Controlled stepwise synthesis of a Cu-MOF: Transmetallation of a magnesium precursor to a three-dimensional framework with very high solvent content

Abstract A copper metal-organic framework (MOF) was synthesized by transmetalation. The ditopic ligand 3-(3,5-dimethyl-pyrazol-4-yl)pentane-2,4-dione is introduced via its Mg precursor complex in which it is oxygen-coordinated. After transmetallation, the ligand acts as N,O,O′ linker between dinuclear, sulfato-bridged Cu(II) nodes. The resulting three-dimensional solid crystallizes in the chiral space group I213, with more than half of its cell volume occupied by disordered methanol and dichloromethane molecules: the coordination framework encloses a large solvent-filled region along [1 1 1] which coounts for 54.8% of the crystal volume. The structure collapses upon removal of the clathrated solvent. Sulfate-O atoms are exposed towards the solvent region and facilitate trapping of polar guest molecules. The framework topology corresponds to a lcv net with Vertex symbol 3·3·102·102·103·103.

Growth of high purity N-polar (In,Ga)N films

In this work, secondary ion mass spectroscopy was used to study carbon and oxygen impurity incorporation in N-polar [000–1] GaN films grown by MOCVD. The effects of growth temperature, V/III ratio, and precursor flows were studied within a regime relevant to low temperature (In,Ga)N:Mg growth for device structures containing high indium concentrations. For films grown without magnesium, oxygen levels were between 3 and 8×1016cm−3 and did not depend strongly on the growth conditions. Mg-doped films yielded higher oxygen concentrations ranging from 8×1016 to 4×1017cm−3 depending on the gallium and magnesium precursor flow rates. The carbon concentration in the films varied significantly with different growth conditions, and was most affected by the growth temperature and the V/III ratio. With careful tuning of the growth parameters carbon and oxygen concentrations of 2 and 4×1016cm−3, respectively, were achievable under a wide range of conditions.

Superior transport Jc obtained in in-situ MgB2 wires by tailoring the starting materials and using a combined cold high pressure densification and hot isostatic pressure treatment

The best Jc performance (8×104A·cm−2 at 10T, 4.2K) has been obtained in our work among all the in-situ powder-in-tube (PIT) MgB2 wires reported so far by tailoring their boron and magnesium precursors, as well as employing appropriate high pressure during the manufacturing process. Moreover, the second stage densification using the special HIP has been applied to commercial long-length wire. Our work suggests that the economical starting precursors and the combination of cold and hot densification techniques could represent a promising alternative for industrial and economical production of practical MgB2 wires with excellent Jc.

Controlled stepwise synthesis of a Cu MOF: from magnesium precursor to mesoporous material

Controlled stepwise synthesis of a Cu MOF: from magnesium precursor to mesoporous material

Preparation of active magnesium oxide with caustic calcined magnesia by ammonia circulation method

Magnesium oxide (MgO) with different morphology were prepared by calcining precursors (magnesium hydroxide MH). The precursors were synthesized from industry lightly calcined powder (MgO content of 80–93%) by ammonia circulation method. The structures of MH and MgO were characterized by scanning electron microscope and laser particle size analyzer. The crystal growth mechanism of MgO precursors were simulated by materials studio. The experimental results showed that the MgO had the same morphology with their precursors. The adsorption of SO42− can significantly increase the particle size of precursors, and its D50 reached 2.05μm. After adsorping Cl−, the exposure proportion of planes (001) and (101) was reduced, and the morphology of MH more easily grow to be uniform bulk crystal. The activity of MgO (CAA) produced with MgCl2 was 15″85 by the citric acid method, which was higher than other MgO produced with Mg(NO3)2 and MgSO4.

Growth, structural and optical properties of ZnO/ZnMgO core‐shell heterostructures

AbstractZnO nanowires have been grown by metalorganic chemical vapor deposition on sapphire substrates. The use of N2O and DEZn as oxygen and zinc precursors combined with high temperature leads to the spontaneous growth of vertical ZnO nanowires (NWs) on underlying three dimensional islands present at the bottom of each nanowire. These nanowires are grown along the c axis of the wurtzite structure, exhibit well defined m‐plane facets and are free of extended defects. This configuration is favorable to band‐gap engineering studies. Based on this, we have grown a series of radial ZnO/ZnMgO shells and quantum wells with different thicknesses and Mg concentrations. ZnxMg1‐xO alloys have been grown using O2, (MCp)2Mg and DEZn as oxygen, magnesium and zinc precursors. Low temperature photoluminescence spectroscopy and transmission electron microscopy have assessed Mg concentrations in the shell up to 20%. Electron diffraction reveals that the ZnMgO alloyed structure is, at least partially, ordered. Micro‐photoluminescence performed on a single ZnO/ZnMgO coreshell nanowire including a quantum well exhibits luminescence properties, with a lateral quantum confined emission. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Steam gasification of oat with conversion of tars on clay catalyst and gas cleaning by condensation of steam

Abstract Gasification of oat grains with steam at normal pressure has been performed in a laboratory scale. Experiments were carried out in a vertical quartz reactor, with a steady flow of the steam and immediate tars conversion at 900ºC on the catalytic bed prepared from local clay with simple additives. Condensation of steam excess enabled essential elimination of non-volatile components of the gas stream. Condensates were analyzed with GC-MS. The highest level of organic compounds was detected in experiment with non-catalytic bed of small quartz pieces (90.2 mg/15 g of oat grains) and successful decreased by 86% for original clay without additives (precursors), 94% for clay with magnesium precursor, 97% with iron and more than 99% with calcium one.

Mg-MOF-74 nanostructures: facile synthesis and characterization with aid of 2,6-pyridinedicarboxylic acid ammonium

In this study, MgOF-74 was successfully synthesized through the microwave method with the aid of 2,6-pyridinedicarboxylic acid ammonium as an organic ligand and Mg(NO3)2·2H2O as a magnesium precursor at various conditions. Furthermore, the effect of microwave irradiation time and power on morphology, particle size, and structure of final products were investigated. It was found that the size and morphology of the products could be greatly influenced by the aforementioned parameters. The morphology and microstructure of the obtained products were characterized by X-ray diffraction, Fourier transformed infrared spectrum, scanning electron microscopy, transition electron microscopy, thermo-gravimetric analysis, differential scanning calorimetry, and BET techniques.

New heteroleptic magnesium complexes for MgO thin film application.

Novel heteroleptic magnesium complexes, [Mg(dmamp)(acac)]2 (), [Mg(dmamp)(tmhd)]2 (), [Mg(dmamp)(tfac)]2 (), and [Mg(dmamp)(hfac)]2 (), were successfully synthesized using dmamp and β-diketonate as ligands. The thermogravimetric analyses and volatile studies of the complexes showed that the complexes and display high volatility and thermal stability. The single crystal X-ray study of the complexes reveals that both the complexes and were crystalized in the triclinic space group and as dimers, where magnesium atoms are in the pentacoordinate state with distorted trigonal bipyramidal geometry.

The effects of solvent and microwave on the preparation of Magnesium Oxide Precursor

Four methods including hydrothermal method, glycol‐hydrothermal method, microwave‐hydrothermal method and glycol‐microwave‐hydrothermal method were used to prepare magnesium oxide precursor by the reaction of MgSO4·7H2O with (NH4)2CO3. The composition, crystallinity, morphology, aspect ratio, yield, functional groups, atom distribution, and interplanar spacing of the sample were investigated by X‐ray diffraction (XRD), Scan Electron Microscope (SEM), Fourier Transform Infrared Spectroscopy (FT‐IR), and High Resolution Transmission Electron Microscope (HRTEM). The properties of Magnesium Oxide precursor were compared with each other. The results of FT‐IR and XRD showed that the crystals were all nesquehonite. However, it was shown by FT‐IR results that the crystals prepared by glycol‐microwave‐hydrothermal method contained OH− and HCO3− groups, which indicated that the Mg(OH)(HCO3)·2H2O type crystals would be facilitated by this method. The glycol‐hydrothermal method can create high quality Magnesium Oxide precursor with a high degree of crystallinity, high purity, high aspect ratio, smooth surface, and good dispersibility.