Increase Of Mg Content Research Articles

Crystallization Process, Structure and Hydrogen Absorption and Desorption Properties of MgxNi10 (x = 20.5-26.5) Alloys with Hypereutectic Composition

We have analyzed crystallization process of the MgxNi10 (x = 20.5 – 26.5) alloys using phase diagram of Mg-Ni system. Their structure, atomic arrangement and crystal defects were tested by XRD, SEM and HRTEM, respectively. Hydrogenation and dehydrogenation behaviors were measured by pressure-composition-isotherm measurement. The results show that the crystallization processes of the MgxNi10 (x = 20.5 and 22.5) alloys are unlike those of the MgxNi10 (x = 24.5 and 26.5) alloys, but their room temperature microstructure all contain Mg2Ni and eutectic structure of Mg2Ni + α-Mg. The alloys are composed of Mg2Ni phase and α-Mg phase. The addition of Mg is beneficial to the formation of eutectic structure. The alloys have all good activation property. At a lower temperature, such as 200 and 250 °C, the hydrogen absorption rate and hydrogen saturation ratio are significantly lower than those of the alloy at the higher temperatures, such as 300 and 350 °C. At 350 °C, the hydrogen absorption capacity of the alloy increase and the hydrogen release efficiency of the alloy decreases with the increase of Mg content. The time of 90% of the amount of saturated hydrogen absorption and desorption of the alloys is not more than 10 and 2 minutes, respectively. The hydrogen desorption rate of the Mg22.5Ni10 alloy in the four investigated alloys is relatively large and up to 7.170 wt.%.min-1.

Effect of magnesium content and growth temperature on structural and optical properties of USCVD-grown MgZnO films

Magnesium zinc oxide (MgxZn1-xO) films (x < 0.4) have been grown by ultrasonic spray chemical vapor deposition on soda-lime glass substrates for different growth temperature and different Mg mole fractions (x). Effects of Mg content in the liquid solution and the effect of growth temperature on optical and structural properties of MgZnO films have been investigated with X-ray diffraction, atomic force microscope, and UV–visible spectrophotometry measurements. The growth temperature has a significant effect on determining the Mg mole fractions of MgZnO films. There is a linear correlation between the measured Mg mole fraction in the resulted grown structures and Mg content in the solution. The peak of (0002) diffraction for the grown samples has been shifted to the higher diffraction angles with increase in Mg content in the liquid solution and has also become stronger. The growth temperature and Mg content in a liquid solution are crucial parameters in the controlling Mg mole fraction of samples.

Synthesis and Characterization of Undoped and Magnesium Doped Zinc Oxide Nanoparticles

Undoped and Mg-doped ZnO nanoparticles were synthesized by co-precipitation method. The synthesized nanoparticles are successfully characterized by XRD, SEM, and UV-visible analysis. The Structure, Morphology, and Optical activity of the synthesized nanoparticle were studied with respect to ZnxMg1-xO (where x= 0, 2.5%M and 7.5%M). The XRD patterns revealed the wurtzite structure for all the nano samples. XRD studies confirmed that the crystalline size increased with increase in Mg content. The surface morphology of the prepared pure and Mg doped ZnO nanoparticles are investigated by SEM analysis. Optical characterization reveals that band gap energy decreases from 3.24 to 3.13 eV with Mg doping. UV-Visible results revealed that absorption underwent a red shift with Mg into ZnO as compared to pure ZnO.

Effect of Mg content on electronic structure, optical and structural properties of amorphous ZnO nanoparticles: A DFTB study

In this work, we perform a theoretical analysis of structural, electronic, and optical properties of pure and Mg-doped amorphous ZnO nanoparticles (a-ZnO NPs) using DFTB method. Our results show that Zn atoms are more preferential for Mg atoms than for O atoms because the number of MgZn bonds is greater than that of MgO. The rise in the content of Mg in a-ZnO NPs leads to an increase of Mg–Zn and MgO interactions. Mg atoms prefer to locate near the center of a-ZnO NP, but Zn and O atoms nearly preserve their positions which is compatible with radial distribution function peaks. The orbital energies display a decrease in the energy gap from 3.592 to 3.546 eV while increasing Mg content. The LUMO level is also significantly shifted to higher energies. The results also reveal that the performance of pure a-ZnO NP can be enhanced with a subsequent increase in Mg content.

Hot Compression Behavior of New Al-6Mg and Al-8Mg Alloy with Improved Hot Workability Fabricated by Direct Chill Casting Method

A hot compression test of new Al-6Mg and Al-8Mg alloys was conducted to understand the dynamic recrystallization (DRX) behavior by Mg contents. To investigate the hot workability of Al-Mg with high Mg contents, the hot deformation behavior of Al-6Mg and Al-8Mg alloys was analyzed by a hot compression test in the temperature range of 300–450 °C, and the strain rate range of 10−3–100/s. Subsequently, high-temperature deformation behavior was investigated through the processing map and microstructure observation. In this study, the results have shown that, as the Mg contents increase, the maximum and yield strength increase while rapid flow softening after the peak strain has been observed due to accelerated dynamic recrystallization (DRX). Finally, the increase of Mg contents affects an increase of heat dissipation efficiency to be an indicator of regular deformation.

Formation of Phases and Microstructures in Al-8Si Alloys with Different Mg Content.

Mg-containing high-silicon aluminum alloy is a heat-treatable aluminum alloy that is now widely used in the aerospace and automotive industries because of its high specific strength, high wear resistance and corrosion resistance, low thermal expansion coefficient, and low cost. More attention has been paid to optimizing the microstructure to increase the performance of this type of aluminum alloy. In the present work, the solidification processes of Mg-free and Mg-containing (0.33–1.32%) Al-8Si alloys were analyzed by the experimental results combined with the thermodynamic calculation. The results showed that α-Al, Si, and Al5FeSi were in the Mg-free Al-8Si alloy ingots, while the Al5FeSi phases in alloys with Mg additions were transformed into π phases (Al8Mg3FeSi6) by the reaction L+Al5FeSi→α-Al+Si+Al8Mg3FeSi6. There was a binary eutectic reaction of L→α-Al+Al5FeSi when the Mg content exceeded 0.51% and the Fe content was higher than 0.17%. With the increase of Mg content, the volume of Mg2Si was gradually increased while the divorced eutectic phenomenon of the quaternary eutectic structure (α-Al+Si+Mg2Si+Al8Mg3FeSi6) was weakened and the eutectic structure was significantly refined.

Effect of Mg content on microstructure and properties of Zn-Al-Cu Alloy

Zn-Cu-Al-xMg (x=0,0.25,0.5) zinc alloy was prepared by metal mould casting. The effects of Mg addition on the structure, electrical conductivity and mechanical properties of Zn-Al-Cu alloy were studied. The results show that without Mg addition, the alloy consists of Zn solid solution(ƞ phase) containing of Cu and Al and layered α+η eutectic structure. With the addition of Mg, the η phase grains were refined, the layered eutectic structure disappeared, and the intermetallic compound Mg2Zn11 appeared, and its content increased with the increase of Mg content. The hardness of the alloy increases with the increase of Mg content. When the content of Mg is 0.5wt.%, the hardness reaches the maximum value of 151HV. Tensile strength and electrical conductivity first increase and then decrease. When the addition of Mg is 0.25wt.%, the maximum tensile strength and electrical conductivity are 270 MPa and 26.4% IACS, respectively. The wear mechanism of zinc alloy is a mixture of adhesive wear and abrasive wear, and the adhesive wear is dominant.

Effects of mg content and heat treatment on the microstructure and mechanical properties of rolled Al–Zn–Sc alloy

The effects of Mg content and heat treatment on the microstructure and mechanical properties of an Al–15Zn–0.5Sc alloy were investigated to improve the mechanical properties of high-Zn-content Al alloys. Results show that the Mg content did not significantly affect the mechanical properties of hot-rolled alloys, and the alloys exhibited high ductility but low strength. Increase in Mg content improved the strength of heat-treated alloys by enhancing the precipitation strengthening effect. The ZnMg phases in the high-Mg-content alloy consumed a large number of Zn solution atoms, inhibited the formation of Zn phases during aging, and deteriorated the ductility of heat-treated alloys. The Al–15Zn–0.5Sc–0.5 Mg alloy after solution treatment and natural aging exhibited the best comprehensive mechanical properties, including high ductility and reasonable strength.

Microstructural and optical properties of high-quality Mg–Zn oxide thin films

The microstructural and optical properties of Mg–Zn oxide thin films deposited by aerosol assisted chemical vapor deposition onto fused silica substrates were studied as a function of the Mg concentration in the precursor solution, which was varied from 0 to 100 mol %. The thickness of all the samples was around 150 ± 20 nm. Scanning electron microscopy and grazing incidence x-ray diffraction were used for the analysis of the morphology, composition, and crystalline structure. Outcomes showed a gradual evolution of the microstructural and optical properties of the films as the Mg content increased. The systematic increase of the lattice parameter a, and the decrease of parameter c were observed with the increase of Mg concentration, nevertheless, the unit cell volume remained nearly constant, around 0.0471 ± 0.0007 nm3. Energy dispersive x-ray microanalysis results indicated that Mg /(Zn + Mg) atomic ratio (x) up to 0.59 was found for a single-phase hexagonal MgxZn1-xO film. This value is higher than most of the reported Mg content in wurtzite ZnO. At higher Mg loadings (>70 mol % in solution), the segregation of periclase MgO phases occurred. X-ray photoelectron spectroscopy confirmed the composition of selected Mg doped ZnO films and the substitution of Zn+2 by Mg+2 atoms. The Williamson-Hall analysis of diffracted peaks was employed to determine the micro-strain in the films, it was found ∈ = 0.2 ± 0.1 % with a slight tendency to decrease ∈ as x increases. For single-phase hexagonal MgxZn1-xO films, the computation of the dispersion relations of the optical constants was achieved using direct transmittance and near-normal absolute reflectance. For this objective, TFcalc software was used to fix the Sellmeier dispersion relation parameters by fitting the modeled transmittance and reflectance spectra of the stack film-substrate with corresponding experimental spectra. A detailed analysis of the optical band gap energy and its correlation with the microstructural characteristics of the films was performed, in particular with lattice parameters. The modification of optical band gap energy and lattice parameters with the inclusion of Mg in the wurtzite structure can be explained because the MgO4 unit has a compressed tetrahedral geometry with a much shorter height than those of ZnO4 tetrahedra, and due to the change in electronegativities and ionic radius between Mg and Zn, the bonding character becomes more ionic, and the increased localization of Zn 3d and O 2p orbitals. The optical band gap energy was tuned by changing the Mg content, from about 3.3 eV of undoped ZnO up to 4.3 eV of hexagonal MgxZn1−xO (x ~ 0.59). Moss relation was used to analyze the relationship of optical band gap energy and refractive index.

Mechanical Properties of High Mg-Content Al-Mg-Sc-Zr Alloy Fabricated by Selective Laser Melting

The effects of process parameters and aging treatment on the microstructure and mechanical properties of selective laser melting (SLM) fabricated high Mg-content Al-Mg-Sc-Zr aluminum alloy were systematically studied. Our experiment results show that the samples exhibit good processability with porosity less than 1%. The increase of Mg content in Al-Mg-Sc-Zr is beneficial to reduce the texture of the alloy. The laser scanning speed has a large influence on the Vickers hardness of as-fabricated samples. The maximum microhardness of as-fabricated sample reaches 148 ± 2 HV with a compression yield strength of 342 ± 7 MPa. After aging treatment, the distinction in microhardness of the samples obtained under different laser scanning speed is obviously reduced, and the mechanical properties of the samples are further improved with a maximum microhardness of 175 ± 5 HV and a maximum compressive yield strength of 476 ± 10 MPa, which are superior to the known Al-Mg-Sc-Zr alloy with same Sc and Zr content fabricated by SLM. In this study, a novel high Mg-content Al-Mg-Sc-Zr aluminum alloy specifically for SLM with good processability and mechanical properties was reported.

Nondestructive tests on the effect of Mg content on the corrosion and mechanical properties of 5000 series aluminum alloys

Using the nondestructive testing techniques conductivity measurement and ultrasonic testing, we explored the importance of the effect of Mg content (3–6 wt%) on the corrosion and mechanical properties of 5000 series chill-rolled Al–Mg alloys. The results indicate that all of alloys showed no β-phase precipitation before sensitization and that their conductivity and sound wave velocity decreased with increasing Mg content. After sensitization of the alloys, their grain boundaries showed significant β-phase precipitation and corrosion. The alloy conductivity and sound wave velocity increased with the increase in Mg content. Precipitates became more obvious and continuous, and the change in rate of conductivity was greater, while the change in rate of sound wave velocity had a less-significant trend.Addition of Mg atoms not only increased the strengthening effect on the solid solution of Al–Mg alloys, but it also reduced the stacking-fault energy of the alloys. During tensile deformation, the alloys exhibited high work-hardening rate, effectively suppressing the occurrence of necking. Thus, when the Mg content was higher, the strength and elongation of the alloy increased. In contrast, the strength of sensitized high-Mg alloys declined within a larger range. The conductivity, sound wave velocity, corrosion properties, and mechanical properties were linearly correlated. We thus demonstrated that nondestructive testing techniques can be effective methods for evaluating the effect of Mg content on the corrosion and mechanical properties of chill-rolled Al–Mg alloys. Moreover, the conductivity measurement was more sensitive than was ultrasonic testing in detecting precipitation of the strengthening phase.

Effect of Ag on aging precipitation behavior and mechanical properties of aluminum alloy 7075

Effects of Ag addition on the age hardening and precipitation behavior of aluminum alloy 7075 were investigated. The transmission electron microscopy (TEM) and atom probe tomography (APT) were used to study the aggregate distribution and identify the role of Ag in precipitation hardening of the alloy. The hardness and strength of the Ag–containing alloy were increased by more than 10% due to a higher number density of fine aggregates, which was 2.5 times that of the Ag–free alloy 7075. Both T–type and η–type precipitates existed in the alloys, and two precipitation sequences occurred simultaneously as: SSS → η–type cluster → GP zone → η′ → η → T, and SSS → T–type cluster → GP zone→ T′ → T. Particularly, Ag promoted the formation of T–type clusters due to the interaction among Ag, Mg and Zn atoms as well as vacancies at the early stage of aging. The Mg–Ag, Zn–Ag, and vacancy–Ag co–clusters acted as nucleation sites for the subsequent precipitates (η′, T′, etc.). This also caused the increase of Mg concentration in T–type clusters at the beginning of aging and the narrowing of the precipitation free zone (PFZ) near grain boundaries at the peak aging.

Effect of magnesium doping on thermoelectric and magnetic properties of copper chromite ceramic samples

We investigated thermoelectric and magnetic properties of polycrystalline CuCr 1-x Mg x O 2 (x = 0; 0.002; 0.008; 0.015; 0.030) ceramic samples, synthesized by a special chemical homogenization method (nitrate synthesis). Temperature dependencies of magnetization were measured in magnetic field H = 1000 G. Transition temperature do not noticeably shift with variation of Mg content. Seebeck coefficient S increases with temperature for all investigated samples. At room temperature S decreases from nearly 700 mV/K in pristine material to about 250 mV/K for the copper chromite with 3at.% Mg. Heat conductivity k of all investigated samples is close to the heat conductivity of undoped CuCrO 2 crystals. Resistivity of investigated samples decreases several orders of magnitude with increase of Mg content up to 3%. Temperature dependence of resistivity and Seebeck coefficient was interpreted by hopping conductivity in the presence of the Coulomb (parabolic) gap in the density of states.

A high magnesium concentration in citrate dialysate prevents oxidative stress and damage in human monocytes in vitro.

BackgroundThe use of dialysis fluids (DFs) during haemodialysis has been associated with increased oxidative stress and reduced serum magnesium (Mg) levels, contributing to chronic inflammation. Since the role of Mg in modulating immune function and reducing oxidative stress has been demonstrated, the aim of this study was to characterize in vitro whether increasing the Mg concentration in DFs could protect immune cells from oxidative stress and damage.MethodsThe effect of citrate [citrate dialysis fluid (CDF), 1 mM] or acetate [acetate dialysis fluid (ADF), 3 mM] dialysates with low (0.5 mM; routinely used) or high (1 mM, 1.25 mM and 2 mM) Mg concentrations was assessed in THP-1 human monocytes. The levels of reactive oxygen species (ROS), malondialdehyde (MDA) and oxidized/reduced (GSSG/GSH) glutathione were quantified under basal and inflammatory conditions (stimulation with lipopolysaccharide, LPS).ResultsThe increase of Mg in CDF resulted in a significant reduction of ROS production under basal and inflammatory conditions (extremely marked in 2 mM Mg; P < 0.001). These effects were not observed in ADF. Interestingly, in a dose-dependent manner, high Mg doses in CDF reduced oxidative stress in monocytes under both basal and inflammatory conditions. In fact, 2 mM Mg significantly decreased the levels of GSH, GSSG and MDA and the GSSG/GSH ratio in relation to 0.5 mM Mg.ConclusionsCDF produces lower oxidative stress than ADF. The increase of Mg content in DFs, especially in CDF, could have a positive and protective effect in reducing oxidative stress and damage in immune cells, especially under inflammatory conditions.

Effect of Mg content on microstructure, texture and strength of severely equal channel angular pressed aluminium-magnesium alloys

Equal channel angular pressing was carried out on Al–Mg alloys to study the effect of Mg addition on the microstructure, texture and strength after severe plastic deformation by 8 passes of equal channel angular pressing (ECAP) through route Bc. The increase in Mg content enhanced the propensity of continuous dynamic recrystallization and simultaneously decreased the average grain size of the alloy. The microstructure and local texture was heterogeneous across the billet thickness for all the samples, irrespective of composition. All the samples showed a shear-type bulk texture generally observed in face-centred cubic metals with strong BE/‾BE components. The weakening of the texture with increase in Mg content is attributed to the substructure evolution during the ECAP process. The grain size and dislocation density have been determined by X-ray diffraction line profile analysis. The experimentally determined yield strength of the ultrafine grained samples can be explained by a combination of solid solution, dislocation and grain size strengthening, the latter being predominant.

Effects of magnesium on the microstructure and properties of Al–Si alloy deposited by wire and arc-based additive manufacturing

ABSTRACT The effects of Mg on microstructure, defects and properties of Al–Si alloy deposited by Wire and Arc-based Additive Manufacturing (WAAM) were investigated. The WAAM alloys were characterised by the metallographic microscope, X-ray diffraction, scanning electron microscope, computed tomography and electronic universal testing machine. The results show that the secondary dendrite arm spacing (SDAS) and hydrogen content of as-deposited WAAM alloy increase, and the tendency of pore formation increases with an increase in Mg content. The impurity Fe in the WAAM alloy with low Mg content is mainly in β-Fe phase, while with high Mg content is mainly in the π-Fe phase. After solution treating and ageing treatment (T6 heat-treat), the microstructure of WAAM alloy tends to be uniform. With the increase of Mg content, the size of eutectic silicon particles increases gradually. Furthermore, the UTS and YS of the alloys increased, and the elongation decreased.

Electrospun Mg/poly(lactic-co-glycolic acid) composite scaffold for urethral reconstruction

Hypospadias is a common congenital malformation of the male urogenital system. As a recently arisen reconstruction method for hypospadias, polymer tissue engineering urethral scaffold often results in necrosis and other complications due to the lack of bioactivity. To improve the bioactivity of polymer, in this work, we prepared biodegradable Mg/poly(lactic-co-glycolic acid) (PLGA) composite nanofiber scaffolds by electrospun with 3, 6, and 9 wt.% of micron-scale Mg particles. The mechanical properties of the PLGA scaffold gradually decrease with the addition of Mg particles but still at an acceptable level. On the other hand, these composite scaffolds show very good biocompatibility and promotional bioactivity, namely non-cytotoxicity, gradual proliferation enhancement, and good adhesion state of human adipose stem cells (HADSCs) on the scaffold surface. Besides, through quantitative real-time polymerase chain reaction (qRT-PCR) test, different genes expression levels of human umbilical vein endothelial cells (HUVECs) were also gradually up-regulated with the increase in Mg content. The present results indicate that Mg containing PLGA scaffolds might not only have the potential to promote tissue regeneration related to urethral repair, but also stimulate endothelial cells to achieve vascularization and anti-inflammatory functions. Consequently, considering both the mechanical properties and bioactivity for clinical demand, the Mg/PLGA composite scaffolds with suitable Mg contents are promising for the regeneration of defective urethral tissues.

Effects of Mg addition on the phase formation, morphology, and mechanical and tribological properties of Ti-Nb-Mg immiscible alloy coatings produced by magnetron co-sputtering

The addition of Mg to Ti-based alloys is a promising method for improving bioactivity in this type of alloys because Mg is absorbed by the body and can biologically activate the implant material, facilitating its adaptation. However, the fabrication of Ti-Nb-Mg alloys by conventional processes is extremely difficult due to the very low solubility of Mg in Ti and the very large difference in their melting points. Therefore, non-equilibrium processing methods such as magnetron sputtering can be used to produce metastable supersaturated Ti-Mg alloys with low density and attractive mechanical properties. In the present study, Ti85-xNb15Mgx (x = 5, 8, 16, 25 at.%) coatings were successfully produced by magnetron co-sputtering deposition on AISI 316L SS substrates. The effects of Mg content on the phase formation, morphology, and mechanical and tribological properties of the Ti-Nb-Mg coatings were investigated. The coatings with lower Mg contents (5 and 8 at.%) presented a predominance of the α (hexagonal close packed - HCP) phase (near α-Ti), the coating with 16 at.% Mg had near equal relative quantity of the α and the β phases (α + β type), and the coating with 25 at.% Mg had almost only the β phase (β-Ti type). A greater stabilization of the β-Ti phase with the increase of Mg content yielded a decrease in both the elastic modulus (102 to 88 GPa) and the hardness values (2.7 to 2.1 GPa). Tribological tests did not detect any detachment of the coatings, due to the high plastic joint strain of the coating/substrate systems, that ensures integrity and good adhesion. Failure was observed only on the coating and depended on α and β relative amounts in the coating.

Mg/Ag ratios induced in vitro cell adhesion and preliminary antibacterial properties of TiN on medical Ti-6Al-4V alloy by Mg and Ag implantation

Titanium alloy (Ti-6Al-4V) has been extensively applied in joint replacements, orthopedic prostheses, dental implants, and so on, because of their good biocompatibilities and mechanical properties. However, the inferior antibacterial activity and biological inert of titanium alloy limit its application in the field of hard tissue repair. Therefore, the surface modification to Ti-6Al-4V is well method. In this paper, titanium nitride (TiN) was first deposited on the surface of Ti-6Al-4V alloy. Then magnesium (Mg) and silver (Ag) ions with different ratios (Mg:Ag = 0.5:1; 1:1; 3:1) were implanted into TiN via a plasma immersion ion implantation (PIII) system to explore the effects of Mg/Ag ratios on the cell adhesion and the preliminary antibacterial properties. Structure characteristics and compositions of Mg/Ag implanted TiN were analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD). X-ray photoelectron spectrometer (XPS) proved the presence of Mg and Ag on the surface of Mg/Ag-TiN. The results of water contact angle and protein adsorption proved that the wettability and protein adsorption energy of the materials increased significantly with the increase of Mg content. Moreover, in vitro investigations indicated that Mg/Ag (1/1)-TiN exhibited the best cell adhesion and spreading activity, and ideal proliferation, as well as preliminary antibacterial activities, which made it has a good application prospect in orthopedic material.

Bandgap tuning and optimization of green-emitting Zn2SnO4-Mg2SnO4:Mn2+ using combinatorial pulsed laser deposition

We investigated a compositional spread Mn2+-doped Zn2SnO4-Mg2SnO4 (Mn-ZMTO) film prepared by combinatorial pulsed laser deposition. The composition of the prepared film gradually changed from Zn2SnO4 (ZTO) to Mg2SnO4 (MTO). Moreover, the lattice constant decreased with an increase in MTO composition. Under ultraviolet irradiation, the film exhibited bright green luminescence attributable to the transition from 4T1 to 6A1 of Mn2+. This is the report of the observation of green luminescence from Mn-ZMTO on the ZTO-rich side. In addition, the most intense luminescence was located at the center of the sample. The emission intensity and the most intense position were changed by irradiation at various excitation wavelengths. This was clarified by the positional dependence of PLE spectra. The bandgap of the prepared film, which corresponded to the PLE peak wavelength, was larger than that of the bulk material and increased with an increase in Mg concentration. Since emission cannot usually be observed from Mn-doped ZTO, we suggest that the luminescence from the prepared film was caused by an increase in the bandgap attributable to the 1-dimentional thin film size effect along thickness direction. Thus, using the thin film technique we revealed that bandgap tuning is important in phosphor material.