Behavior Of MgO Research Articles

Deformation behavior of high-entropy oxide (Mg,Co,Ni,Cu,Zn)O under extreme compression

Following the discovery of high-entropy alloys, high-entropy oxides have gained considerable interest due to their unconventional structural characteristics and versatile functional properties for promising applications. Via synchrotron radial x-ray diffraction in a diamond anvil cell, the mechanical strength and deformation behavior of a typic high-entropy oxide (Mg,Co,Ni,Cu,Zn)O with a rock-salt structure under extreme compression has been investigated in situ. This compound in a polycrystalline state shows a large elastic anisotropy at the initial compression stage and then gradually becomes isotropic at around 21.4 GPa, similar with the behavior of MgO. Based on the lattice strain order conversion and texture evolution under compression, a dominant slip system transition from {100}<011> to {110}<1–10> is proposed in this high-entropy oxide. This work deepens our understanding on the role of chemical disorder in the mechanical properties of entropy-stabilized oxides, which would be indispensable to the design of advanced structural ceramics with optimal strength-to-ductility ratio.

Influence of Cr Content in Steel on the Behavior of MgO·Al2O3 Spinel Inclusions During Ladle Treatment by Using Kinetic Reaction Model

Influence of Cr Content in Steel on the Behavior of MgO·Al2O3 Spinel Inclusions During Ladle Treatment by Using Kinetic Reaction Model

Behavior of MgO Based Ceramics under Electron Irradiation

MgO is one of environment friendly ceramic material under harsh environment such as electron irradiation. Different response of MgO ceramics under the irradiation was reviewed. The response was in the appearance of surface breakdown/flashover on the surface of MgO after a certain time under irradiation exposure. The different response was shown for small addition of CaO, ZrO2and SiO2into high purity of MgO. Addition of CaO resulted in the appearance of flashover could be 30% earlier of that of pure MgO. Moreover, addition of ZrO2 resulted in 70% earlier. On the other hand, small addition of SiO2 revealed that the MgO based ceramics could withstand the appearance of flashover underthe same energetic electron irradiation.

Immobilization of arsenate in kaolinite by the addition of magnesium oxide: An experimental and modeling investigation

MgO was chosen as an As(V) immobilization agent and a series of immobilization experiments was performed to obtain insights into the behavior of As(V) and MgO during leaching tests. Our experimental and modeling results demonstrated that As(V) immobilization by MgO consists of the following steps: (i) an increase in sample pH, (ii) desorption of As(V) from the samples, and (iii) the re-immobilization of As(V) by MgO/Mg(OH)2 particles. Regarding the behavior of MgO, the modeling results showed that when the MgO dosage was 25mgMgO/4g-drysample or less, the majority of MgO was used to increase pH, and less than 1% of MgO was used to sorb As(V), which was consistent with the result of leaching tests showing that a high level of As(V) was leached at the MgO dosages. On the other hand, when the MgO dosage was above 25mgMgO/4g-drysample, the percentage of MgO used for As(V) sorption increased up to 35%, and correspondingly, the As(V) leaching level decreased to below 0.01mgAs/L at an MgO dosage of 75mgMgO/4g-drysample. Additionally, when the MgO dosage was 50mgMgO/4g-drysample or more, it was found that more than 40% of MgO remained as fresh MgO without undergoing chemical reactions.

Pressure-induced phase transition and structural behavior of MgO at high temperatures: a model study

A realistic interaction potential model approach by including temperature effects is developed to study phase transition, elastic properties and thermo-physical properties at very high pressures and temperatures. This approach is effectively able to explain the inter-atomic interaction involved at high temperature and high pressure as it includes the three-body interactions. Earlier works overlooked the three-body interactions at high temperature and pressures. Moreover, the phase-transition pressures of MgO crystal at high temperatures including the three-body interaction are computed for the first time. Elastic behavior, anisotropic factor and Debye temperature of MgO at high pressures and temperatures are also reported.

Pinning behavior of glycine-doped MgB2 bulks with excellent critical current density by Cu-activated low-temperature sintering

Abstract Mg–B system with single glycine addition was composed of MgO phase rather than MgB 2 when sintered at 600 °C for 2 to 5 h. Cu was further introduced into Mg–B–glycine system to active the low-temperature sintering efficiency, and more than 80% MgB 2 superconducting phase was successfully obtained in Cu and glycine co-doped samples sintered at 600 °C for 8 h, 12 h, and 15 h, respectively. The sample sintered for 8 h showed uncompetitive critical current density ( J c ) because of the uncompleted MgB 2 phase and the unreacted Mg phase, while the 15-h sample showed the best J c of 1.5 × 10 4 A cm −2 at 3 T and 20 K. The pinning behavior of MgO (∼20 nm) and MgCu 2 (∼10 nm), which should be responsible for the exciting current-carrying capability that the J c performance was improved over the entire field in contrast with pure MgB 2 , was systematically investigated. According to the phase identification and the microstructure observation, both the pre-generated MgO involved in the MgB 2 grains and the MgCu 2 precipitated along the steps of the screw dislocation growth mechanism could serve as effective pinning centers. Finally, we illustrated the whole sintering process of the sample sintered at 600 °C for 15 h.

The influence of B4C and MgB2 additions on the behavior of MgO–C bricks

Carbon-containing refractory materials have received great attention over the last years due to their importance in the steelmaking process. The oxidation of carbon present in refractory materials at temperatures above 500°C is usually accompanied by the decrease of their mechanical strength and chemical resistance. Aiming to improve the oxidation resistance of carbon-oxide refractories, the use of materials known as antioxidants has been extensively studied. In this work we evaluated the performance of MgB2 and B4C antioxidants when incorporated into MgO–C bricks. We observed that the co-addition of metallic antioxidants and B4C or MgB2 leads to refractory bricks with enhanced hot modulus of rupture and resistance against oxidation and slag corrosion. However, the excessive addition of these antioxidants could impair the performance of the obtained bricks. Thus, when determining the optimum concentration of MgB2 and B4C to be added into MgO–C refractories, one must take into consideration this behavior.

Behavior of MgO • Al 2O 3 Based Inclusions in Alloy Steel During Refining Process

The transformation of MgO • Al 2O 3 based inclusions in alloy steel during refining has been studied by industrial trials. Besides Factsage software is used to study the formation and modification of spinel inclusions in alloy steel using calcium treatment during refining process. The results show that the transformation sequence of inclusions is: MgO • Al 2O 3→CaO-Al 2O 3-MgO complex inclusions→MgO • Al 2O 3, and under present experimental condition, in order to avoid forming MgO • Al 2O 3 inclusions the content of dissolved Ca in the molten steel has to reach 1×10 −6. Also the results show that when more calcium was added to molten steel, the content of Al 2O 3 and MgO will be lower. Besides, increasing the content of CaO in the inclusions will increase even if the content of SiO 2 changes little.

On the adsorption of hydrogen by supported transition-metal catalysts and MgO

Many industrial catalysts consist of fine particles of transition metals bonded to substrates such as silica or alumina. These particles may be as few as 6 to 12 atoms (in fact some sources believe that the essential catalytic unit may be as few as two transition-metal atoms) in number. Such systems may catalyze a wide variety of reactions. The simplest reaction possible is the dissociation of H/sub 2/. In this paper the interaction of hydrogen with supported transition-metal catalysts is examined. Another system which dissociates H/sub 2/ is MgO when properly prepared. The active site for H/sub 2/ dissociation on an MgO surface is also examined and the behavior of MgO with that of a support transition metal for H/sub 2/ dissociation is contrasted. All calculations are performed using a molecular cluster approach. The computational methods employed are the restricted Hartree-Fock method, the unrestricted Hartree-Fock method, and the generalized valence bond method in the perfect pairing limit.

Behavior of MgO as a CO2 Scavenger at the Waste Isolation Pilot Plant (WIPP), Carlsbad, New Mexico

Behavior of MgO as a CO2 Scavenger at the Waste Isolation Pilot Plant (WIPP), Carlsbad, New Mexico

A simulation study of induced failure and recrystallization of a perfect MgO crystal under non-hydrostatic compression; application to melting in the diamond-anvil cell

Recent experimental studies revealed that the thermal pressure in a diamond-anvil cell with laser heating can be large. Accounting for this pressure is therefore important for treatment of experimental results. In earlier studies, we developed an MgO model that was demonstrated to perform very well for calculations of thermoelastic properties. Here, we study the effect of thermal stress on the behavior of MgO under high pressure and temperature conditions using molecular dynamics and the earlier developed interatomic potential. The simulations show that thermal stress can produce such effects as dynamic recrystallization, which may be interpreted as onset of convective-like motion and which may cause a change in the slope of laser power-temperature curve. Because these two criteria are used for the identification of melting, it is possible that what was interpreted as melting in previous experiments with MgO was in reality recrystallization.

Epitaxial Oxide Films

AbstractSome perspective concerning the capabilities and potential of epitaxial oxide films is gained by comparison with the field of semiconductor epitaxy. The specific epitaxial behavior of MgO, (ZrY)O2, and the layered cuprates is discussed. A suggestion is given for a method of searching for higher temperature superconductors by the use of epitaxial indusions in layered structures.

Behavior of MgO and NiO in Molten Slags

Behavior of MgO and NiO in Molten Slags

Behavior of MgO and NiO in Molten Slags

Abstract The measurement of electrical conductivity and viscosity of slag containing MgO and/or NiO has been carried out together with spectroscopic investigation of quenched glasses. In the CaO–SiO2–MgO system these measurements revealed that MgO showed the same effect as CaO, whereas MgO was regarded as acidic oxide in more basic melts like Na2O–SiO2 system. In the CaO–SiO2–NiO system, NiO exhibits more basic property than CaO in the lower content region of NiO. As the content of NiO increases, however, this basic property tends to decrease. ESCA spectra of quenched samples revealed the existence of Ni3+ ion in the lower content region of NiO. Far-infrared absorption spectra showed the existence of undissociated NiO in higher NiO content region. The interaction of MgO and NiO in the melt has been studied, and the results indicate that presence of MgO in NiO-bearing slags helps the dissociation of NiO to Ni2+ and O2−.

High‐Temperature Stress‐Strain Behavior of MgO in Compression

Compressive stress‐strain curves for several types of polycrystalline MgO specimens were correlated with those for single crystals and analyzed as a function of grain size and grain‐boundary character at 1200° and 1400°C for several strain rates. The results for fully dense specimens were explained in terms of grain‐boundary sliding and intergranular separation in addition to slip. The modification of grain‐boundary nature concurrent with heat treatment for grain growth, caused by residual LUF, was associated with enhanced grain‐boundary sliding and intergranular separation. For grain sizes &lt;30 μm, it was concluded that the von Miss criteria for ductility could be relaxed by the Occurrence of dislocation climb and, to a limited extent, by intergranular separation. Yield drop corresponding to dislocation multiplication occurred when grain‐boundary sliding was initially promoted. Specimens with a liquid phase of adequate viscosity also indicated plasticity accompanied by high strength. Specimens with clean grain boundaries exhibited ductility and normal strain hardening with no intergranular separation.

Na&lt;SUB&gt;2&lt;/SUB&gt;O-SiO&lt;SUB&gt;2&lt;/SUB&gt;-MgO系およびCaO-SiO&lt;SUB&gt;2&lt;/SUB&gt;-MgO系融体の電気伝導度

The measurements on the electrical conductivity of Na2O-SiO2-MgO and CaO-SiO2-MgO melts have been conducted to find out the behavior of MgO in these systems.The electrical conductivity decreased with increasing MgO content in the Na2O-SiO2 system, but it slightly increased in the CaO-SiO2 system. The electrical conductivity gave a good linear relationship with Na atomic % in the Na2O-SiO2-MgO system and Ca+Mg atomic % in the CaO-SiO2-MgO system. Mg2+ ions contributed to the electrical conductivity in the CaO-SiO2 system to such a degree as shown by Ca2+ ions, whereas it will give no contribution in the Na2O-SiO2 system, probably due to the formation of complex anions. Compared with the viscosity data in the previous paper, the SiO2 equivalent to MgO was calculated, and the structural aspects of Mg2+ in the melt were estimated.

Ionization-stimulated annealing effects on displacement damage in magnesium oxide

The effects of ion bombardment into MgO were investigated by measuring resulting volume changes with a cantilever beam technique and by monitoring the F band absorption induced in the uv region of the spectrum. Single crystals of MgO were bombarded near 〈100〉 with 500-keV argon, which resulted in an expansion of the implanted near-surface layer due to the ion-induced lattice damage. Under subsequent 100-keV proton irradiation, however, a large fraction of this expansion is relieved since the material compacts. This seems to indicate that defects with different charge states are produced in MgO by heavy-ion bombardment and that electronic processes account for the volume changes observed during subsequent irradiation with the primarily ionizing radiation from the 100-keV H+ implantation. Identical behavior was found earlier for the highly ionic Al2O3 while no such effect was observed in the predominantly covalent SiO2. The present results thus corroborate our model of the existence of defects with different charge states in ionic materials. This behavior of MgO and Al2O3 is of considerable interest since both materials are candidates for first-wall application in CTR environments.

Mechanism for Environmental Control of Drilling in MgO and CaF2 Monocrystals

The effects of certain liquid environments on the penetration of a carbide spade drill and on the mobility of near-surface edge dislocations in freshly cleaved MgO and CaF2 monocrystals were determined at room temperature. The environments were water, toluene, DMF, DMSO, DMF-DMSO solutions, n-alkanes ranging from heptane to hexadecane, and aqueous solutions of AlCl3. Drilling efficiency and near-surface dislocation mobility are directly related, and “softening” environments facilitate crack initiation in MgO. The n-alkanes are extremely surface-active with respect to MgO and CaF2. It is proposed that adsorbed surface-active species control the drilling behavior of MgO and CaF2 (and perhaps of other notch-sensitive nonmetallic solids (minerals) also) as a consequence of their influence on the flow and flow-dependent fracture properties of the near-surface regions of these solids. Possible effects of adsorption-induced reductions in surface free energy are of minor importance.