Diffusion Of Mg Research Articles

Revealing the intergranular corrosion mechanism of AA5083 alloys through experiments and atomic-scale computation

Continuously exposure to elevated temperature, known as sensitization, can accelerate the precipitation of the electrochemically active β phase (Al3Mg2) at grain boundaries (GBs) in Al-Mg alloys. This results in intergranular corrosion (IGC), which seriously affects the application of Al-Mg alloys in marine environments. Low-angle GBs (< 15°) are considered to restrict the nucleation and growth of the β phase, while high-angle GBs (> 15°) can promote these processes. However, the quantitative relationship between GB misorientation and IGC sensitivity at atomic scale is unknown. Herein, the underlying mechanism of IGC in AA5083 alloys with β phase and GB misorientation is investigated by experiments and simulation. The experimental results show that after sensitization when the misorientation angle exceeded 22.6°, the density of the β phase at GBs reaches up to 50 %–60 %. The hybrid molecular dynamics/Monte Carlo algorithm was utilized to simulate the diffusion of Mg and cluster formation in Al-5Mg alloy with 11 different GB models at 300 and 425 K. The maximum GB misorientation angle insensitive to IGC is about 18.9° to 22.6°. However, at 425 K, this angle decreases to 16.3°, increasing the IGC risk of Al-5Mg alloys. The calculation results provide valuable quantitative guidance for the corrosion resistance design of Al-Mg alloys.

Microstructure and mechanical properties of Mg/Al laminated composite: The effect of transition layer thickness

This study successfully prepared Mg/Al laminated composites with various thicknesses of pure Cu transition layer via extrusion, overcoming the challenge of forming of Mg/Al composite plates through stacked extrusion technology. The effects of varying Cu layer thicknesses on the microstructure, mechanical properties, and fracture behaviors were systematically investigated. Microstructure analysis showed an uneven Cu layer distribution at the interface of the composite plate, characterized by alternating thicker and thinner layers, which stemmed from the low fluidity of pure Cu during extrusion. Although the thicker Cu layer significantly inhibited the diffusion of Mg and Al elements, there was still a significant enrichment of Mg-Al intermetallic compounds (IMCs) in the thinner Cu layer. There hard and brittle IMCs caused cracking during the deformation process. Increasing Cu layer thickness did not significantly affect the microstructure but contributed to the decrease of strength owing to increased stress concentration. Moreover, the thicker Cu layer exacerbated its uneven distribution and Mg-Al IMCs enrichment at the interface, resulting in a pattern of first decreasing and then increasing elongation and shear strength of the laminated composite.

An innovative approach for overcoming challenges in the stacked extrusion forming of Mg/Al composite plates

This study successfully produced Mg/Al composite plates with Cu transition layer, thus overcoming the limitations of traditional stacked extrusion methods in achieving satisfactory bonding of Mg/Al laminates. The relationship between the microstructure and mechanical properties of composite plates under three extrusion temperatures was revealed, and the deformation process and failure modes of composite plates were investigated. Microstructure observations revealed that the Cu layer exhibited a discontinuous distribution characteristic, and its thicker area effectively impeded the diffusion of Mg and Al elements, thus inhibiting the formation of Mg-Al intermetallic compounds (IMCs). The extrusion temperature did not significantly affect the distribution of the precipitates and texture in the Mg/Al layers. The grain size of the Mg layer showed a growing tendency with rising extrusion temperature, while that of the Al layer remained relatively constant. Mechanical results indicated that the strength of the composite plates decreased as the extrusion temperature increased, which was attributed to the weakening of fine grain strengthening in the Mg layer and dislocation strengthening in the Al layer. Additionally, higher extrusion temperature markedly reduced the elongation of the composite plate, potentially due to accelerated element diffusion at the interface and the discontinuous distribution of the Cu layer, resulting in significant enrichment of IMCs. The Mg-Cu IMCs accumulated and formed in the thicker Cu layer areas, along with Mg-Al IMCs formed in the weaker Cu layer areas, served as crack sources, resulting in cracking of the composite plate during the tensile and eventual failure.

Effect of MgO/ZnO ratio on the formation process of MgxZn1-xO ceramics

The structural characteristics, chemical composition, and element spatial distribution in MgxZn1-xO ceramics were investigated using X-ray diffraction, scanning electron microscopy, Auger electron spectroscopy, energy-dispersive X-ray spectroscopy, and cathodoluminescence techniques. The study revealed that the morphology of the ceramic samples, as well as the mechanism of solid solution formation, depend on the relative contribution of both oxides in the charge. It was discovered that hexagonal and cubic phases of the solid solution were found to form simultaneously. An increase in the MgO content in the charge results in the magnesium content rise in the hexagonal grains continuously, reaching approximately 13 at.%. It was discovered an enrichment of grain boundaries with zinc and magnesium playing a significant role in doping ZnO and MgO grains. Obtained results allowed to propose two mechanisms involved in the formation of solid solution ceramics: i) diffusion of Mg and Zn along grain boundaries, followed by their incorporation into ZnO or MgO grains, respectively, and ii) interdiffusion of Mg into ZnO and Zn into MgO due to direct contact of ZnO and MgO grains. The second mechanism appears to dominate when both ZnO and MgO contribute comparably, increasing the probability of their direct contact. This study significantly advances the understanding of the process of the formation of MgxZn1-xO ceramics under thermodynamic conditions. These insights are crucial for optimizing the doping process and improving the material properties, thereby promoting innovations in the ceramics industry.

Physical and chemical properties of CaF2−CaO−Al2O3−MgO slag for electroslag remelting of Mg-containing GH3128 superalloy

During electroslag remelting, Mg in the electrode reacts with some components in the slag, resulting in its serve oxidation loss. The CaF2−CaO−Al2O3−MgO slags with high MgO content are generally used for remelting Mg-containing Fe- and Ni-based alloys. However, there is a scarcity of foundational data available on the physical and chemical properties of the slags, posing a challenge in developing a suitable slag for remelting Mg-containing GH3128 superalloy. Hence, this paper conducted a comprehensive study on the melting temperature, viscosity, and reactivity of four known slags. The results show that D2 slag (50%CaF2–20%CaO–20%Al2O3–10%MgO) has the lowest melting temperature of 1588 K due to containing fewer high-melting-point phases and possesses lower viscosity because of simpler aluminate structures. Additionally, the D2 slag has the highest activity ratio, enabling the superalloy to achieve the highest equilibrium Mg content of 0.0174%. The D2 slag exhibits a heightened MgO activity and facilitates the release of more Mg2+ ions, thereby exerting a pronounced inhibitory effect on the diffusion of Mg2+ ions from the slag–metal interface to the slag. The superalloy attains a highest Mg yield of about 30%. Therefore, the D2 slag emerges as the most suitable choice for remelting the Mg-containing GH3128 superalloy.

Olivine in ultramafic rocks from the Polaris Alaskan-type intrusion: A geochemical record of open-system crystallization, diffusional re-equilibration, mantle source, and redox conditions in primitive arc magmas

Olivine in cumulates from the Early Jurassic Polaris Alaskan-type ultramafic-mafic intrusion in the North American Cordillera displays a wide range of textures and compositions produced in a dynamic crystallization environment as part of a transcrustal arc magmatic system. Major, minor, and trace element analyses of olivine were determined using combined electron probe microanalysis (EPMA) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) to assess the utility of olivine as a petrogenetic indicator in ultramafic intrusions. High forsterite contents (>Fo87) of olivine from dunite, olivine wehrlite, and wehrlite indicate that the parent melts were primitive in composition and that they may represent intrusive analogues to extrusive arc picrites found elsewhere in the Cordillera. Forsterite-Ni systematics (Fo92–80, Ni = 3000–300 ppm) show fractional crystallization-controlled evolution from dunite to olivine wehrlite to wehrlite through olivine clinopyroxenite. Low-Ni olivine (Fo84–80, 500–300 ppm) in magnetite-olivine clinopyroxenite indicates the effects of sulfide melt saturation and Ni-depletion of the residual magma. Entrainment of high-Fo olivine in evolved melts and mixing between fractionated and primitive magmas explains olivine compositions with Ni concentrations (1000–3000 ppm) in excess of those predicted by fractional crystallization models. Extensive subsolidus diffusion of Mg, Fe, Ni, Mn, Ca, Cr, Al, and Li occurred during crystallization and cooling of olivine. Uniform concentrations of Mg, Fe, Ni, and Mn in individual samples and across crystals of olivine indicate complete equilibration in the consolidating cumulate pile. Calcium, Cr, and Al from Polaris olivine (e.g., typically <1000 ppm Ca, <100 ppm Cr and Al), and from plutonic olivine in general, are depleted relative to volcanic olivine as the result of diffusional re-equilibration with interstitial melt and other co-crystallizing phases (Cr-spinel, clinopyroxene). Ratios of first-row transition elements (Mn, Zn, Fe, Co, Ni) in olivine were modified during intracrustal processes (e.g., fractional crystallization, diffusion), however, ratios from the most primitive olivine are indicative of primary mantle signals. Lithium concentrations in olivine (2–12 ppm) show evidence for subsolidus diffusive re-equilibration with Li-enriched melts. Ratios of V/Sc (0.03–0.5) are consistent with relatively oxidized parent magmas and arc mantle sources to Polaris and Alaskan-type intrusions. The Polaris parent magmas ascended through the uppermost mantle and lowermost crust on sufficiently short timescales to avoid significant magmatic differentiation prior to emplacement at a depth of ≤15 km. The findings of this microanalytical study highlight the utility of olivine as a petrogenetic recorder of primary magmatic and high-temperature diffusional processes in ultramafic plutonic rocks and contribute to our understanding of the evolution of primitive arc magmas.

Effect of Cooling Conditions on the Size and Morphology Evolution of MgAl2O4 Inclusions in Al‐Deoxidized Steel Coupling with Mg Treatment

The experiment of Al‐deoxidized steel coupling with Mg treatment is conducted under three cooling methods to observe the size and morphology of MgAl2O4. Most of MgAl2O4 in the water‐cooled steel are sphere or ellipsoid‐like shape, in the furnace‐cooled steel are cubic or octahedral‐like shape, and in the air‐cooled steel are irregular shape. The quantity of inclusions in the size of 1–3 μm increases with the increasing cooling rate, whereas the quantity of the other size decreases with the increasing cooling rate. The result shows that the changing of cooling methods has little effect on the critical size and the nucleation rate of MgAl2O4. The growth of MgAl2O4 is effected by diffusion, Ostwald, and collision growth, and the increasing cooling rate leads to the decreasing growth time. The size of MgAl2O4 is decided by the diffusion of Mg and the growth time of MgAl2O4. Four possible morphological transformation paths of MgAl2O4 in steel are found, and the shape of MgAl2O4 can evolve from sphere or ellipsoid to octahedron via truncated octahedron or cubic‐like shape. The final morphology of MgAl2O4 is controlled by the transformation path which has a close relationship with the cooling rate.

Microstructure, Hardness and Corrosion Resistance of Al-TiC MMC Prepared by Laser Cladding on AZ31B Magnesium Alloy

Magnesium alloy is extensively used in aircraft, automobiles, and electronic industries due to its low density, high specific strength, and enhanced machinability. However, low hardness and poor corrosion resistance limit its application. In this work, an Al-TiC metal matrix composite (MMC) was prepared on AZ31B magnesium alloy via laser cladding. The effects of laser power and TiC content on the microstructure, hardness, and corrosion resistance of the MMC were investigated. The results showed that the MMC with 10% TiC had a hardness of 184 HV0.1, which was 3.5 times higher than 52 HV0.1 of the substrate. The current density of MMC with 10% TiC was 3.90 × 10−7 A/cm2, which was three orders of magnitude lower than 5.45 × 10−4 A/cm2 of the substrate. Due to more intermetallic compounds (IMCs) and TiC particles, the MMC with 30% TiC had higher hardness. The increased laser power would not change the phase composition, but it contributed to the formation of a concave crescent shape, promoted the diffusion of Mg, and induced the formation of a thicker Al3Mg2 transition layer. Modifications in the TiC concentration markedly influenced the coating’s microstructural characteristics.

Coalescence of Al2O3/Al, MgO/Mg, and MgO/Al two nanoparticles during combustion

Metal and metal oxide aggregates are easily sintered by migration–diffusion in combustion, and the aggregates hold a complex morphological and structural variability that increases with temperature. The underlying thermomechanical response remains a challenging mystery for active nanoparticles. Here, a computational strategy based on ReaxFF molecular dynamics were performed to shed much light on the coalescence behavior of Al2O3/Al, MgO/Mg, and MgO/Al nanoparticles – a doublet of two spheres. The complex sintering phenomenon was further quantitatively described in terms of coordination number, charge distribution, density distribution, atomic displacement, radius ratio, shrinkage, and sintering time, etc. Results showed that the Al2O3/Al and MgO/Mg two nanoparticles undergo collision and coalescence, and the two were connected through the neck. MgO/Al aggregates are unstable at higher temperatures (T > 1200 K) and segregate at junctions, followed by re-coalescence in the simulation box. A stable neck structure can be formed when enough O atoms are dissolved in MgO nanoparticles or at a lower temperature. The diffusion of Mg, Al, and O atoms in aggregates is driven by concentration gradients and self-generated electromotive forces. The Al2O3 passivation layer forms and hinders the diffusion of O atoms, and the oxygen-rich regions are distributed in the neck (Al2O3/Al) or the contact surface on the side of the Al nanoparticles (MgO1.5/Al) during sintering. In MgO/Al aggregates, Mg atoms tend to wrap Al nanoparticles by surface diffusion.

Interface Polarization Effects Enhancing Mn2O3@TiO2@MXene Heterostructures for Aqueous Magnesium Ion Capacitors: Guided Charge Distribution and Transportation via Built‐in Electric Fields

The electrochemical performances of aqueous magnesium ion energy storage devices rely on the transmission capacity of magnesium ions (Mg2+) at the electrode/electrolyte interface. However, the diffusion of Mg2+ is hindered by the strong electrostatic attraction of doubly charged magnesium cations. Herein, novel Mn2O3@TiO2@MXene three‐phase heterostructures with rich phase boundaries and synergistic effects is successfully designed. As expected, the mesoporous Mn2O3/TiO2@MXene can deliver a relatively high specific capacity of 241.5 mAh g−1 at 0.1 A g−1. Moreover, the energy density of the device using mesoporous Mn2O3@TiO2@MXene as cathode can reach 146.62 Wh kg−1. The unique construction of extensive interfaces between different phases creates a polarization effect. This polarization effect leads to intrinsic electric fields that guide charge distribution and promote fast migration of Mg2+ ions. Additionally, the in‐situ growth of TiO2 nanoparticles derived from MXene on Mn2O3 helps mitigate the volume expansion of host material, resulting in enhanced cycle stability. By strategically implementing the interface polarization effect and carefully engineering the heterostructure interfaces, we demonstrate a promising electrode synthesis approach with potential commercial viability and robust performance. This research aims to advance the field of materials science by exploring interface engineering and the multifunctional applications of MXene‐related materials.

First-Principles Dynamics Investigation of Germanium as an Anode Material in Multivalent-Ion Batteries

Germanium, a promising electrode material for high-capacity lithium ion batteries (LIBs) anodes, attracted much attention because of its large capacity and remarkably fast charge/discharge kinetics. Multivalent-ion batteries are of interest as potential alternatives to LIBs because they have a higher energy density and are less prone to safety hazards. In this study, we probed the potential of amorphous Ge anodes for use in multivalent-ion batteries. Although alloying Al and Zn in Ge anodes is thermodynamically unstable, Mg and Ca alloys with Ge form stable compounds, Mg2.3Ge and Ca2.4Ge that exhibit higher capacities than those obtained by alloying Li, Na, or K with Ge, corresponding to 1697 and 1771 mA·h·g–1, respectively. Despite having a slightly lower capacity than Ca–Ge, Mg–Ge shows an approximately 150% smaller volume expansion ratio (231% vs. 389%) and three orders of magnitude higher ion diffusivity (3.0 × 10−8 vs. 1.1 × 10−11 cm2 s−1) than Ca–Ge. Furthermore, ion diffusion in Mg–Ge occurs at a rate comparable to that of monovalent ions, such as Li+, Na+, and K+. The outstanding performance of the Mg–Ge system may originate from the coordination number of the Ge host atoms and the smaller atomic size of Mg. Therefore, Ge anodes could be applied in multivalent-ion batteries using Mg2+ as the carrier ion because its properties can compete with or surpass monovalent ions. Here, we report that the maximum capacity, volume expansion ratio, and ion diffusivities of the alloying electrode materials can be understood using atomic-scale structural properties, such as the host–host and host–ion coordination numbers, as valuable indicators.

Preventing formation of intermetallic compounds in ultrasonic-assisted Sn soldering of Mg/Al alloys through pre-plating a Ni coating layer on the Mg substrate

Magnesium and aluminum alloys are widely used in various industries because of their excellent properties, and their reliable connection may increase application of materials. Intermetallic compounds (IMCs) affect the joint performance of Mg/Al. In this study, AZ31 Mg alloy with/without a nickel (Ni) coating layer and 6061 Al alloy were joined by ultrasonic-assisted soldering with Sn-3.0Ag-0.5Cu (SAC) filler. The effects of the Ni coating layer on the microstructure and mechanical properties of Mg/Al joints were systematically investigated. The Ni coating layer had a significant effect on formation of the Mg2Sn IMC and the mechanical properties of Mg/Al joints. The blocky Mg2Sn IMC formed in the Mg/SAC/Al joints without a Ni coating layer. The content of the Mg2Sn IMC increased with increasing soldering temperature, but the joint strength decreased. The joint without a Ni coating layer fractured at the blocky Mg2Sn IMC in the solder, and the maximum shear strength was 32.2 MPa. By pre-plating Ni on the Mg substrate, formation of the blocky Mg2Sn IMC was inhibited in the soldering temperature range 240–280 °C and the joint strength increased. However, when the soldering temperature increased to 310 °C, the blocky Mg2Sn IMC precipitated again in the solder. Transmission electron microscopy showed that some nano-sized Mg2Sn IMC and the (Cu, Ni)6Sn5 phase formed in the Mg(Ni)/SAC/Al joint soldered at 280 °C, indicating that the Ni coating layer could no longer prevent diffusion of Mg into the solder when the soldering temperature was higher than 280 °C. The maximum shear strength of the Mg(Ni)/SAC/Al joint was 58.2 MPa for a soldering temperature of 280 °C, which was 80.7% higher than that of the Mg/SAC/Al joint, and the joint was broken at the Mg(Ni)/SAC interface. Pre-plating Ni is a feasible way to inhibit formation of IMCs when joining dissimilar metals.

Thermal Conductivity and Thermal Diffusivity of Mg–Ca Eutectic Alloys in Solid State

Thermal Conductivity and Thermal Diffusivity of Mg–Ca Eutectic Alloys in Solid State

Elemental diffusion, atomic substitution mechanisms and interfacial fracture behavior in laser welded–brazed Al/Ti

Interfacial microstructure, fracture behavior, elemental diffusion, and Si atom substitution behavior were investigated in laser-welded–brazed Al/Ti joints. The results indicated that discontinuous intermetallic composite (IMC) and thick Ti(Al, Si) + Ti(Al, Si)2 + Ti(Al, Si)3 were generated under extremely low and high heat inputs, damaging joint strength. Interfaces with 1.02–3.20 μm Ti(Al, Si)3 was fractured at heat affected zone of Al and exhibited the highest strength of 252.0 MPa. Thermodynamic calculations indicated that elemental Mg and Si possessed lower chemical potentials at interface. This resulted in their aggregation at interface and formation of Mg2Si. Notably, the formation of Ti(Al, Si)3 acted as a barrier for further diffusion of Mg to IMCs. Density functional theory calculations were employed to clarify Si substitution behavior of Al. The calculated results indicated that smaller formation enthalpies and binding energies were obtained when Al atoms were substituted with Si atoms. Furthermore, the introduction of AlSi covalent bonds, lower total density of state (TDOS) values at EF level, and wider and negatively shifted pseudo-gaps contributed to a more stable structure and favored this substituted behavior. In addition, Si substitution would release charge accumulation level around the Ti atoms, resulting in a softening effect on the IMCs.

Influence of bending and heat treatment under high isostatic pressure on synthesis reaction and transport critical current density in isotopic IMD Mg11B2 'wind and react' coils

We show for the first time the results for small coils, which were wound with unreacted magnesium diboride (MgB2) wires with nano-amorphous isotopic boron (11B) by using combined internal magnesium (Mg) diffusion (IMD) and hot isostatic pressing (HIP) techniques. The small coils with a diameter of 20 mm or 10 mm were annealed under low (0.1 MPa) and high (1.1 GPa) isostatic pressure. The 10 mm coils annealed under high isostatic pressure of 1.1 GPa had significantly increased critical temperature (Tc), irreversible magnetic field (Birr) and transport critical current density (Jtc), with significantly accelerated Mg diffusion and improved homogeneity of the Mg11B2 material. Moreover, our findings show for the first time that the bending of the unreacted IMD Mg11B2 wires significantly affects the synthesis reaction under the low and high isostatic pressure. Our findings also show for the first time that diffusion of Mg during heat treatment under high isostatic pressure is completely different than during heating under low isostatic pressure. Mg diffusion under low isostatic pressure annealing is mainly dependent on the heat treatment temperature, bending diameter and 11B layer density. This Mg diffusion is related to the simultaneous formation of the superconducting phase. However, the diffusion of Mg under high isostatic pressure heat treatment is mainly dependent on the isostatic pressure, 11B layer density and Mg state (liquid or solid). Our results indicate that liquid Mg is first pushed into the 11B layer by high isostatic pressure and then a superconducting phase is formed.

Irradiation-enhanced Interactions at UO2/Al2O3/Al Interfaces

Combustion synthesis is used to prepare thin UO2 films on aluminum alloy substrates. This simple preparation method involves electrospraying uranyl nitrate + acetylacetone + 2-methoxyethanol solution on the substrate, followed by a short annealing at 350 or 550 °C. The irradiation of films with a 40Ar2+ ion beam (energy of 1.7 MeV and fluences of 7.7 × 1016 and 1.3 × 1017 ions/cm2) is conducted to investigate irradiation-induced restructuring processes. High-resolution transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) investigations show that the annealing temperature significantly influences the crystallinity and stability of materials during irradiation. A small amount of Mg in the alloy substrate diffuses into the amorphous Al2O3 interfacial layer between the film and the substrate. Local thermal spikes from the incoming ions facilitate the irradiation-induced mixing of immiscible Al2O3 and UO2 for the materials prepared at 350 °C. This mass diffusion produces relatively large cavities at the interface. Selective diffusion of a more significant amount of Mg for the materials prepared at 550 °C suppresses the mixing of the Al2O3 interlayer with the film but forms MgyU1–yO2±x solid solutions during irradiation. Local thermal heating triggers the precipitation of a discontinuous crystalline MgO layer close to the film surface. The enhanced and selective diffusion of Mg into the film makes the materials prepared at 550 °C more robust and mechanically stable than those prepared at 350 °C.

Defect-mediated diffusion of implanted Mg in GaN: Suppressing dopant redistribution by sequential thermal and microwave annealing

The diffusion behavior of Mg in Mg/N co-implanted GaN is investigated in response to a set of annealing conditions and methodologies, namely, 1000 °C/30 min thermal anneal, by high-temperature pulsed gyrotron microwave annealing at 1420 or 1500 °C, or by thermal and microwave annealing, sequentially. After 1000 °C annealing, the diffusion of Mg in GaN is found to be negligible, as measured by secondary ion mass spectrometry. Annealing by gyrotron microwave annealing alone induces the diffusion of Mg at a rate on the order of 10−12 cm2/s. However, the use of a thermal anneal before microwave gyrotron annealing reduces this rate by an order of magnitude to 10−13 cm2/s. We find that a model that considers Mg diffusion from an inhomogeneous medium that contains a defect-rich implanted region near-surface to a relatively pristine region below the implant range better explains the observed diffusion behavior than a conventional model that assumes a homogeneous medium. By analyzing the diffusion behavior using the Boltzmann–Matano method, we present a discussion of reduction in [VGa] by thermal annealing at 1000 °C, leading to a suppressed diffusion coefficient during subsequent high-temperature annealing relative to diffusion after 1420/1500 °C annealing alone. This effect holds potential for improvement in the precision of selectively doped regions for future applications based on the (Al)GaN material system. An improved field profile control in real devices can increase the breakdown and current-handling capabilities in power electronic applications.

High-Capacity Ion Batteries Based on Ti2C MXene and Borophene First Principles Calculations

In this paper, we report an ab initio study of a composite material based on Ti2C and borophene B12 as an anode material for magnesium-ion batteries. The adsorption energy of Mg, specific capacitance, electrical conductivity, diffusion barriers, and open-circuit voltage for composite materials are calculated as functions of Mg concentration. It is found that the use of Ti2C as a substrate for borophene B12 is energetically favorable; the binding energy of Ti2C with borophene is −1.87 eV/atom. The translation vectors of Ti2C and borophene B12 differ by no more than 4% for in the X direction, and no more than 0.5% in the Y direction. The adsorption energy of Mg significantly exceeds the cohesive energy for bulk Mg. The energy barrier for the diffusion of Mg on the surface of borophene B12 is ~262 meV. When the composite surface is completely covered with Mg ions, the specific capacity is 662.6 mAh g−1 at an average open-circuit voltage of 0.55 V (relative to Mg/Mg+). The effect of reducing the resistance of borophene B12 upon its binding to Ti2C is established. The resulting electrical conductivity of the composite Ti16C8B40 is 3.7 × 105 S/m, which is three times higher than the electrical conductivity of graphite. Thus, a composite material based on Ti2C and borophene B12 is a promising anode material for magnesium-ion batteries.

P-ZnO/n-ZnMgO Nanoparticle-Based Heterojunction UV Light-Emitting Diodes.

Heterojunction light-emitting diodes (LEDs), based on p-type ZnO and n-type ZnMgO nanoparticles, have been demonstrated. ZnMgO nanoparticles were prepared by the thermal diffusion of Mg onto ZnO nanoparticles. p-ZnO/GZO homostructure LEDs and p-ZnO/n-ZnMgO/GZO heterostructure LEDs have been fabricated using ZnO and ZnMgO nanoparticles. By comparing the characteristic results of these diodes, it can be seen that LEDs with the p-ZnO/n-ZnMgO/GZO structure showed better I-V characteristics with a lower current density leakage than those with the p-ZnO/GZO LED structure. Moreover, the emission intensity was improved by adding the ZnMgO NP layer to the LEDs. These results show that the ZnMgO NP layer acts as a hetero-barrier layer that suppresses the diffusion of holes into the n-type layer and confines holes to the p-type layer.

Substitutional diffusion of Mg into GaN from GaN/Mg mixture

We evaluated Mg-diffusion into GaN from GaN/Mg mixture. The diffusion depth of Mg increased with diffusion temperature from 1100 °C to 1300 °C, whereas the Mg concentration remained constant at 2–3 × 1018 cm−3 independent of temperature. The estimated activation energy for Mg diffusion was 2.8 eV, from which the substitutional diffusion mechanism was predicted. Mg-diffused GaN samples showed p-type conductivity with a maximum hole mobility of 27.7 cm2 V−1 s−1, suggesting that substitutional diffusion contributes to Mg activation. This diffusion technique can be used to easily form p-type GaN and has potential as a p-type selective doping technique.