Increase In Magnesium Content Research Articles

Effects of Magnesium on Inclusions in Consumable Electrode of H13 Die Steel

Consumable electrodes of H13 die steel with different magnesium contents were produced by medium frequency induction furnace. Effects of magnesium on deoxidation rate and inclusions in consumable electrode were studied. Results show that the deoxidization ability of Fe-Al-Mg alloy is better than that of aluminum and the dissolved oxygen content is decreased with the increase of magnesium content in liquid steel. The deoxidation rate is less than 15 % for steel without magnesium and more than 24 % for steel with 20 × 10-4wt% magnesium content. The number of inclusions is decreased with the increase of the magnesium content in steel. Because tiny MgO·Al2O3inclusions are generated in the steel containing magnesium, the number of inclusions with size less than 2 μm is increased obviously and the number of inclusions with size larger than 5 μm is decreased. Some VN and VN-TiN inclusions with size less than 10 μm are precipitated taking MgO·Al2O3, MgO, MgS as cores in the steel containing magnesium.

The influence of chromium on the structure and superplasticity of Al–Mg–Mn alloys

The structure and superplasticity of Al–Mg–Mn–Cr alloys that have different Mg contents are studied. An increase in magnesium content provides finer grains and improves the superplasticity of the chromium alloys. Transmission electron microscopy analyses indicate that there are differences in alloy particle fragmentation processes during mechanical and heat treatment when chromium is present. Fine particles (<60nm) and fine grains (5μm) are formed prior to the superplastic deformation when chromium is present. The Al–6.3Mg–0.7Mn alloy with Cr (0.3wt.%) demonstrates good superplasticity. Specifically, the strain rate sensitivity index, m,is0.6, and the elongation is over 400% at a constant strain rate of 5×10−3s−1.

Synthesis, Characterization, and Chemical Vapor Transport of Solid Solutions in the MgMoO4‐NiMoO4 System

AbstractTwo solid solution series exist in the system MgMoO4‐NiMoO4. The α‐Ni1–yMgyMoO4 solution series, isostructural to α‐NiMoO4, is thermodynamically stable at ambient conditions for compositions between 0 % and about 75 % magnesium content. The solution series β‐Mg1–xNixMoO4, isostructural to MgMoO4 and the high temperature β modification of NiMoO4, is thermodynamically stable at ambient conditions for compositions with &lt; 25 % nickel content. A complete solid solution series β‐Mg1–xNixMoO4 exists at higher temperatures (&gt; 823 K). The transition temperature for the α → β transition decreases with increasing magnesium content. The coexistence of both polymorphs at room temperature in samples with a wide range of composition is a result of the kinetic inhibition of the phase transition β → α. The chemical vapor transport of β‐Mg1–xNixMoO4 solid solutions with chlorine was investigated. Crystals with a nickel content up to 25 % were synthesized in temperature gradients 1273 K → 1223 K or 1273 K → 1173 K. Deposited nickel richer crystals are destroyed during cooling down to room temperature due to the phase transition. The observed distinctive nickel enrichment during the transport process is in good agreement with predictions by thermodynamic modeling.

Electrochemical evaluation of zinc and magnesium alloy coatings deposited on electrogalvanized steel by PVD

Zinc alloy coating attracted much attention due to its high anti-corrosive properties. Particularly, zinc alloy coatings containing magnesium was considered a promising metallic alloy due to a remarkable improvement of corrosion resistance. The proper magnesium content for Zn–Mg alloy coatings was studied. The samples were prepared using thermal evaporation method. The influence of Zn–Mg alloy coating on corrosion resistance was evaluated using immersion test, potentiodynamic test, and galvanic test in 3% NaCl solution at room temperature. The results show that the corrosion resistance of Zn–Mg alloy coatings is strongly dependent on magnesium content. Corrosion potential decreases with increasing magnesium content, whereas current density increases up to 15% magnesium content, and passivity region was found only in Zn–Mg coatings.

Crystal structure and thermal expansion of LaCr1−xMgxO3, 0 < x ≤ 0.25

Solid solution LaCr1−xMgxO3, 0<х≤0.25 was prepared by heating stoichiometric amounts of appropriate oxides in air at 1400°C, 48h. At room temperature it crystallizes in orthorhombically distorted GdFeO3-type structure (a≈√2×aper; b≈√2×ape; c≈2×aper, where aper – perovskite subcell parameter). High-temperature X-ray powder diffraction (HT XRPD) and dilatometry revealed first order phase transition to rhombohedral perovskite phase (R-3c, a≈√2×aper, c≈2√3×aper) at 260–311°C (OR phase transition). Crystal structures of room-temperature orthorhombic and high-temperature rhombohedral phases for LaCr0.75Mg0.25O3 were refined using HT XRPD data. Temperature of OR phase transition increases gradually with increasing of magnesium content. Low-temperature orthorhombic phase exhibits TEC lower in comparison with high-temperature rhombohedral one (e.g. for LaCr0.85Mg0.15O3 TEC(O)=8.8ppmK−1; TEC(R)=11.6ppmK−1). TEC for rhombohedral phase increases with increasing magnesium content from 10.4ppmK−1 for LaCr0.95Mg0.05O3 to 12.1ppmK−1 for LaCr0.75Mg0.25O3.

Study on microstructure and mechanical properties of Al–Mg–Si–Cu alloy with high manganese content

The microstructure and mechanical properties of Al–Mg–Si–Cu alloy with high manganese content were studied in the present work to develop a new alloy. The microstructure features were quantificationally determined by a combination of scanning electron microscope and high resolution transmission electron microscopy. The dominant strengthening precipitates comprising the needle-shaped pre-β″(or β″) and lath-shaped Q′ phases were identified in the T6 temper. With the increase of magnesium content, S phase was promoted to precipitate to give an enhancement in strength. The yield strength of the examined alloys with high manganese content was found to be about 52–65% higher than that of commercial 6061 alloy. It was considered that, in addition to the strengthening precipitates, Mn dispersoids generating the dispersion hardening effect and the homogeneous deformation contributed a lot to the favorable mechanical properties.

CRYSTAL ANALYSIS OF MULTI PHASE CALCIUM PHOSPHATE NANOPARTICLES CONTAINING DIFFERENT AMOUNT OF MAGNESIUM

In this study, Mg doped hydroxyapatite [( Ca , Mg )10( PO 4)6( OH )2] and β-tricalcium phosphate nanoparticles were synthesized via sol gel method. Triethyl phosphite, calcium nitrate tetrahydrate and magnesium nitrate hexahydrate were used as P , Ca and Mg precursors. The ratio of ( Ca + Mg )/ P and the amount of magnesium ( x ) were kept constant at 1.67 and ranging x = 0 up to 3 in molecular formula of Ca 10- x Mg x ( PO 4)6( OH )2, respectively. Phase composition and chemical structure were performed using X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR). Phase percentages, crystallite size, degree of crystallinity and lattice parameters were investigated. The presence of magnesium led to form the Mg doped tricalcium phosphate (β-TCMP) and Mg doped hydroxyapatite ( Mg - HA ). Based on the results of this study, lattice parameters, degree of crystallinity and crystallite size decreased with magnesium content. In addition, with increasing magnesium content, the amount of CaO phase decreased whereas the amount of MgO phase increased significantly. Obtained results can be used for new biomaterials design.

Effect of essential inorganic metals on primary thermal degradation of lignocellulosic biomass

This study employed thermogravimetric analysis (TGA) and analytical Py-GC/MS in order to examine the catalytic effect of main inorganic metals (K, Mg and Ca) on the thermal degradation and the formation of pyrolytic products in lignocellulosic biomass. In addition, potential mechanisms of the primary pyrolysis in presence of the inorganic metals were derived. TG analysis showed that when potassium content increased in the biomass, char formation increased from 10.5wt.% to 19.6wt.% at 550°C, and temperatures at which the maximum degradation rate was achieved shifted from 367°C to 333°C. With increasing magnesium content, the maximum degradation rate increased from 1.21wt.%/°C to 1.43wt.%/°C. Analytical Py-GC/MS revealed that potassium had a distinguished catalytic effect promoting the formation of low molecular weight compounds and suppressing the formation of levoglucosan. An increase in the yield of C6 and C2C6 lignin derivatives with increasing potassium content was also observed.

Plasma electrolytic oxidation coating of synthetic Al–Mg binary alloys

Abstract The binary Al–Mg synthetic alloys were prepared in a vacuum/atmosphere controlled furnace with the addition of 0.5, 1, 2, 4, 7, and 15 wt.% pure Mg into pure aluminum as substrate material. The surfaces of the Al–Mg alloys and pure aluminum were coated for 120 min by plasma electrolytic oxidation in the same electrolyte of 12 g/L sodium silicate and 2 g/L KOH in distilled water. The coating was characterized by X-ray diffraction, scanning electron microscopy, profilometry and Vickers microhardness measurements. There regions of loose outer layer, dense inner layer with precipitate like particles of α-Al 2 O 3 and a thin transition layer were identified for the coated samples. The coating thickness increases from 85 to 150 μm with Mg contents in the alloys. The surface morphology becomes more porous and consequently surface roughness tends to increase with plasma electrolytic oxidation treatment and further with Mg content. The increase in magnesium content reduces the formation of α-Al 2 O 3 and crystalline mullite phases in the coating and decreases microhardness of coating. The Mg concentration is constant throughout the other loose and dense regions of coating though it gradually decreases in the thin inner region.

Mg xMn (1−x)(BH 4) 2 ( x = 0–0.8), a cation solid solution in a bimetallic borohydride

A solid solution of magnesium and manganese borohydrides was studied by in situ synchrotron radiation X-ray powder diffraction and infrared spectroscopy. A combination of thermogravimetry, mass and infrared spectroscopy, and atomic emission spectroscopy were applied to clarify the thermal gas desorption of pure Mn(BH 4) 2 and a solid solution of composition Mg 0.5Mn 0.5(BH 4) 2. Mg x Mn (1− x )(BH 4) 2 ( x = 0–0.8) conserves the trigonal structure of Mn(BH 4) 2 at room temperature. Manganese is dissolved in the hexagonal structure of α-Mg(BH 4) 2, with the upper solubility limit not exceeding 10 mol.% at room temperature. There exists a two-phase region of trigonal and hexagonal borohydrides within the compositional range x = 0.8–0.9 at room temperature. Infrared spectra show splitting of various vibrational modes, indicating the presence of two cations in the trigonal Mg x Mn (1− x )(BH 4) 2 solid solutions, as well as the appearance of a second phase, hexagonal α-Mg(BH 4) 2, at higher magnesium contents. All vibrational frequencies are shifted to higher values with increasing magnesium content. The decomposition temperature of the trigonal Mg x Mn (1− x )(BH 4) 2 ( x = 0–0.8) does not vary significantly as a function of the magnesium content (433–453 K). The desorbed gas contains mostly hydrogen and 3–7.5 mol.% diborane B 2H 6, as determined from analyses of the Mn(BH 4) 2 and Mg 0.5Mn 0.5(BH 4) 2 samples. An eutectic relation between α-Mg(BH 4) 2 and LiBH 4 is observed. The solid solution Mg x Mn (1− x )(BH 4) 2 is a promising material for hydrogen storage as it decomposes at a similar temperature to Mn(BH 4) 2, i.e. at a much lower temperature than pure Mg(BH 4) 2 without significantly losing hydrogen weight capacity thanks to substitution of Mn by Mg up to 80 mol.%. The questions of diborane release and reversibility remain to be addressed.

Highly Controlled Wet and Dry Etching of Gallium Doped (Mg, Zn) O Epilayers Grown Using Metalorganic Vapor Phase Epitaxy

The wet and dry etch rates of Ga-doped ZnO and MgxZn1-xO deposited on r-plane sapphire by metalorganic vapor phase epitaxy (MOVPE) were studied for magnesium content 0 ≤ x ≤ 0.3 using dilute phosphoric acid and halogen–based inductively coupled plasma reactive ion etching (ICP-RIE) respectively. A decrease in the dry etch rates with increasing magnesium content was observed along with relatively low thermal activation energies of 21, 25, and 55 meV corresponding to n-ZnO, n-Mg0.1Zn0.9O, and n-Mg0.3Zn0.7O films respectively. Conversely, wet etch rates increased with increasing magnesium content with corresponding thermal activation energies of 8.4, 5.5, and 4.3 kCal/mol for n-ZnO, n-Mg0.05Zn0.95O, and n-Mg0.1Zn0.9O epilayers respectively. The dominant rate-limiting step was determined to be ion-assisted desorption of the etch products including (Mg, Zn) Cl2 during ICP-RIE etching and the wet etch process transitioned from reaction rate-limited to diffusion rate-limited etching with increasing magnesium content.

Synthesis of ordered mesoporous MgO/carbon composites by a one-pot assembly of amphiphilic triblock copolymers

Ordered mesoporous MgO/carbon composites have been synthesized for the first time via a “one-pot” assembly strategy associated with a direct carbonization process by using phenolic resol as a carbon source, inorganic salt magnesium nitrate as a precursor and amphiphilic triblock copolymer Pluronic F127 as a template. The obtained mesoporous MgO/carbon composites exhibit uniform pore sizes (3.9–4.9 nm), high specific surface areas (510–780 m2 g−1), and high pore volumes (0.30– 0.53 cm3 g−1). In addition, a phase transformation from hexagonal (p6m) to body-centred cubic mesostructure (Imm) occurs as the magnesium content increases. To the best of our knowledge, this is the first time the synthesis of ordered mesoporous carbon nanocomposites with cubic symmetry has been reported. With this facile “one-pot” assembly approach, one can incorporate as high as 37 wt % of MgO in the composites. Especially, the increased magnesium content induces the enlarged particle sizes of the MgO nanocrystals, which can be tuned in the size range from more than 4 nm to around 13 nm, together with a high dispersion in the amorphous carbon framework. When the MgO particles have sizes larger than the mesopore wall thickness, they can extend from the carbon walls into mesopore channels, and hence bring a rougher pore surface and a lower degree of mesostructure regularity. For the application test, such mesoporous MgO/carbon nanocomposites show excellent solid base property as proved by CO2 adsorption.

The Solid Solutions Gd2Cu2In1–xMgx – Drastic Increase of the Curie Temperature upon In/Mg Substitution

The Mo2B2Fe-type intermetallic compounds Gd2Cu2In and Gd2Cu2Mg form a complete set of solid solutions Gd2Cu2In1−xMgx. The a lattice parameter, the Weiss constant and the Curie temperature increase with increasing magnesium content in an almost Vegard-like manner, while the c parameter remains almost constant. All members of the solid solutions show ferromagnetism with TCs between 114 and 80 K.

Effect of Magnesium Content on the Corrosion Behaviors of Grf/Al Composite

Graphite-fiber-reinforced aluminum composites (Grf/Al) with different magnesium content were fabricated with the pressure infiltration method. Their corrosion behaviors were investigated by potentiodynamic polarization measurements, immersion tests, electrochemical impedance spectroscopy (EIS) analysis, and scanning electron microscopy (SEM). Both the corrosion potential (Ecorr) and the pitting potential (Epit) decreased with the increase of magnesium content, whereas the corrosion current density (icorr) decreased sharply at first and then increased slightly. The icorr of Grf/Al-3.2Mg was the lowest among the four composites with different magnesium contents, which indicated that Grf/Al-3.2Mg had the best corrosion resistance. EIS showed that the capacitive reactance of Grf/Al-8.5Mg was 1682 Ω × cm−2, which was the worst, whereas that of Grf/Al-3.2Mg was 3498 Ω × cm−2, which was the best. SEM results revealed that magnesium and silicon formed the Mg2Si phase in Grf/Al-3.2Mg, which hindered the extension of corrosion crack and improved the corrosion resistance.

Effect of composition on structural and magnetic properties of nanocrystalline Ni 0.8−xZn 0.2Mg xFe 2O 4 ferrite

Nanocrystalline magnetic particles of Ni 0.8− x Zn 0.2Mg x Fe 2O 4 ferrites with x lying between 0.0 and 0.8 were synthesized using metal nitrates and freshly extracted egg-white. The synthesized powders were characterized using X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and transmission electron microscopy (TEM). With increasing magnesium concentration, the lattice constant increases while X-ray density decreases. The average crystallite size determined from XRD data using Scherrer formula lie in the range of 35–59 nm. TEM image shows spherically agglomerated particles with average crystallite size agreed well with that obtained from XRD. Magnetic properties measured at room temperature by vibrating sample magnetometer (VSM) reveal a decrease in saturation magnetization up to Mg content of 0.6. In agreement with FT-IR results, the unexpected increase in the magnetization at Mg content of 0.8 can be attributed to the tendency of Mg 2+ ions to occupy the tetrahedral site. The decrease in the value of coercivity with increasing magnesium content can be explained based on the magneto-crystalline anisotropy.

Hot Cracking Susceptibility of Twin Roll Cast Al-Mg Alloy Welds

The hot cracking susceptibility of two different Al-Mg alloys during welding at various applied strains was investigated. At each strain value, the amount of hot cracking susceptibility increased with increasing magnesium content. Thermal analysis results verified that hot cracking susceptibility indeed can be related to the solidification range. As suggested in the solidification range approach, the results of the present study confirm that the extent of solidification and liquation cracking depend on the magnitude of solidification range and the strain imposed during welding. The fracture surfaces of liquation and solidification cracks were investigated with EDS. Liquation crack surfaces were found to have high Mg content whereas solidification crack surfaces revealed iron rich phases. A quench test was designed to observe the effect of mid-plane segregation zone. It was observed that high segregation at the mid-section of the alloy having higher magnesium can increase the liquation cracking susceptibility during welding since it decreases the solidus temperature of the intergranular liquid.

Effect of Mg doping on the properties of combustion synthesized LiCoO2 powders

The LiCo1-xMgxO2 (x = 0–0.1) cathode materials for rechargeable lithium ion batteries were synthesized by starch assisted combustion route method. The structural characterization was carried out by X-ray powder diffraction and Laser Raman Spectroscopy. The sample exhibited a well-defined rhombohedral structure and the lattice parameters varied with the increasing magnesium contents. Surface morphology of the synthesized materials was determined by Scanning electron microscope. The cathode materials consist of highly-ordered single crystalline particles with spherical shape. The electrical resistivities of the samples were studied by Hall Effect. Electrical resistivities decrease with increase in magnesium content. Electrochemical properties were characterized by the assembled test cells using Galvanostatic discharge studies that were carried out at a current rate of 0.1 C. Magnesium doped LiCo0.95Mg0.05O2 show improved structural stability, high reversible capacity and excellent electrochemical performance.

Synthesis of MgAPO-5 molecular sieves and their kinetic behavior for n-hexane cracking

Five magnesium substituted aluminophosphate molecular sieves (denoted as MgAPO-5 (a–e), AFI topology) with different magnesium contents were synthesized hydrothermally and characterized by XRD, ICP-AES, IR, and NH3-TPD techniques. The characterization data show that the isomorphous substitution of magnesium for aluminum in the pure AFI framework results in MgAPO-5 (a–e) with weak and strong acid sites and that the number of strong acid sites linearly increases with increasing magnesium content (correlation coefficient: 0.9960). n-Hexane catalytic cracking over MgAPO-5 (a–e) was investigated at low conversions (≤5%) in a microflow fixed bed reactor. Under controlled conditions, the reaction was first order in both the n-hexane concentration and the magnesium content. The analysis of the kinetic parameters and the product selectivities suggests that the cracking transformation is effected by strong Mg(II)-related acid sites rather than weak ones and predominantly undergoes the monomolecular protolytic mechanism, which is consistently explained by a proposed kinetic model.

Effect of Mg substitution on the magnetic properties of NiCuZn ferrite nanoparticles prepared through a novel method using egg white

Nanocrystalline Mg-substituted NiCuZn ferrites were successfully synthesized, for the first time, by using metal nitrates and freshly extracted egg white. The thermal decomposition process of the nitrate–egg white precursors was investigated by thermogravimetric (TG) technique. X-ray diffraction (XRD) revealed that, single-phase cubic ferrites with average particle size of 23.9–35.1 nm were directly formed after ignition at 500 °C. No noticeable variation of lattice parameters with increasing magnesium content was observed, while X-ray densities were found to decrease. This can be explained on the basis of ionic radii and atomic masses of the substituted cation. Transmission electron microscope (TEM) shows that, particles are permanently magnetized and get agglomerated. The saturation magnetization ( M s ) and coercivity ( H c ) as a function of Mg content were investigated using vibrating sample magnetometer (VSM). It has been found that the M s increases firstly up to x=0.2 and then decreases, while H c continuously decreases. Magnetic susceptibility measurements give results which agree well with those obtained by VSM. The obvious decrease in the Curie temperature ( T C ) with increasing Mg indicates that the ferrimagnetic grains are widely separated and enclosed by non-magnetic magnesium ions.

Chemical, microstructural and strength development of calcium and magnesium carbonate binders

The influence of magnesium on the chemistry of calcium carbonate formation has been studied. It was found that the type of carbonate formed by subjecting compacts of Ca(OH) 2 and Mg(OH) 2 to carbon dioxide (up to 20 atm CO 2 pressure) for variable periods of time is largely controlled by the molar proportion of calcium to magnesium in the initial mixture. Increasing magnesium content in the initial mixture favours the formation of nesquehonite and other carbonates containing both calcium and magnesium. The compressive strength of the carbonate is improved with the presence of nesquehonite and/or other magnesium-containing phases. Curing time and CO 2 exposure influence the strength differently, depending on the initial Ca/Mg ratio of the initial mixture. The formation of magnesium-containing carbonate phases is particularly favoured at higher CO 2 pressures combined with prolonged exposure times.