Mixture Of Mg Research Articles

Synthesis and characterization of magnesium–carbon compounds for hydrogen storage

Magnesium (Mg) and carbon (C) compounds were synthesized by ball-milling a mixture of Mg and different graphites with different crystallinities. The materials were characterized by X-ray diffraction, X-ray absorption spectroscopy, and X-ray total scattering techniques. Hydrogen storage properties were also investigated. In the case of the material using low-crystalline graphite, a Mg and C compound was formed as main phase, and its chemical bonding state was similar to that of magnesium carbide (Mg2C3). The hydrogen absorption reaction of the Mg–C compound occurred at around 400°C under 3MPa of hydrogen pressure to form magnesium hydride (MgH2) and the C–H bonds in the carbon material. The hydrogenated Mg–C material desorbed about 3.7mass% of hydrogen below 420°C with two processes, which were the decomposition of MgH2 and the subsequent reaction of the generated Mg and the C–H bonds. From the results, it is concluded that the Mg–C compound absorb and desorb about 3.7mass% of hydrogen below 420°C.

Synthesis, Microstructural and Thermal analysis of inverse spinel compound Mg2TiO4

In the present work, the influence of mechanical activation on Mg2TiO4 has been studied. High-energy wet ball-mill and post-anneal processing were applied to synthesize Mg2TiO4 single phase crystalline material. The mixture of Mg(NO3)2.6H2O and TiO2 were mechanically activated for 10, 15, 24 and 48 hours in a planetary ball mill and sintered at 1300 ºC for 72 hours. Phase composition, morphological changes and thermal stability of the sample have been analyzed. The thermal analysis of Magnesium Ortho Titanate reveals the exothermic reaction to the abrupt change in two steps.

Effect of H2O on Diamond Crystal Growth in Metal–Carbon Systems

In this paper, we report on the influence of the H2O additive in the metal melt on the growth processes, morphology, and defect-and-impurity structure of diamond crystals. As a source of water, a mixture of Mg(OH)2 and SiO2 was used, which reacted under the experimental conditions following the reaction 2Mg(OH)2 + SiO2 = Mg2SiO4 + 2H2O. The main experiments were performed in the Ni0.7Fe0.3–C system at a pressure of 6 GPa, a temperature of 1370 °C, a duration of 15 h, and a H2O concentration (CH2O) ranging from 0 to 0.5 wt %. It is found that, as the H2O content increases from 0 to 0.2 wt %, the diamond morphology changes from bulky octahedra to {111} platelike crystals and then to {111} dendrites. Further increases in CH2O in the range of 0.22–0.4 wt % result in crystallization of bulky rhombic dodecahedra and then {110} dendrites. At a CH2O higher than approximately 0.43 wt %, nucleation and growth of diamond are completely terminated and only graphite crystallizes. The systematic changes in diamond growth and morphology are accompanied by a decrease in nitrogen impurity concentration in diamond from 220–230 to 40–50 ppm, an increase in the density of microinclusions, and the appearance in the IR spectra of a peak at 2840 cm–1, related to hydrocarbons.

Synthesis of biodiesel using potassium fluoride (KF) supported by hydrotalcite and process optimization by Box–Behnken design

Biodiesel has been developed using a heterogeneous catalyst potassium fluoride (KF) supported on hydrotalcite (HT) and waste frying oil (WFO) as feedstock. Hydrotalcite was synthesized by co-precipitation method using mixture of Mg(NO3)2·6H2O and Al(NO3)2·9H2O slowly added to a solution containing NaOH and Na2CO3 and calcined at 500 °C. KF was impregnated on hydrotalcite at KF/HT load ratio of 80:100 by addition of a small amount of water. Biodiesel was developed using KF/HT as heterogeneous catalyst by transesterification. Box–Behnken Design using Minitab 15.1 Statistical Software and Design-Expert (Demo version 8.0.6.1) software were used as statistical tool for design of experiments and optimization of fatty acid methyl ester yield. A high yield and conversion of biodiesel was obtained by optimization of variables affecting the reaction. The variables affected the reaction in the priority order of: catalyst amount >> molar ratio (methanol to oil) > reaction time. A 12:1 methanol to WFO molar ratio, 2.5 wt.% of catalyst at 60 °C in 1 h reaction time gave a high fatty acid methyl ester yield of >98 %. The quantitative analysis of the product (i.e., biodiesel) was done on a Fourier-transform-nuclear magnetic resonance spectrometer.

용융법과 기계적 합금화에 의한 열전재료 Mg3Sb2의 제조

Mg와 Sb 분말을 사용하여 1173 K에서 결정성이 좋은 단일상의 <TEX>$Mg_3Sb_2$</TEX> 합금을 제조하였다. 이 합금의 열전성능지수 zT는 온도상승에 따라 크게 증가하였고 593 K에서 <TEX>$2.39{\times}10^{-2}$</TEX>의 값을 나타내었다. 얻어진 <TEX>$Mg_3Sb_2$</TEX> 합금을 planetary ball mill에서 12~48시간 볼밀링할 경우 주 결정상 <TEX>$Mg_3Sb_2$</TEX>는 유지가 되었으나 결정성이 나빠졌고 금속원소 Sb상이 나타났다. Mg와 Sb를 섞고 24시간 볼밀링에 의한 합금화 방법으로 합성할 경우 원소금속 Sb가 나타나지 않은 <TEX>$Mg_3Sb_2$</TEX> 결정상을 얻을 수 있었다. A single phase <TEX>$Mg_3Sb_2$</TEX> alloy was synthesized by melting the mixture of Mg and Sb metal powders at 1173 K. The figure of merit of the <TEX>$Mg_3Sb_2$</TEX> prepared by melting method increased with temperature and showed a value of <TEX>$2.39{\times}10^{-2}$</TEX> at 593 K. When the <TEX>$Mg_3Sb_2$</TEX> powders were milled at high speed in a planetary ball mill for 12~48 h, Zintle phase (<TEX>$Mg_3Sb_2$</TEX>) was maintained as a main phase, but its crystallinity became deteriorated and elemental Sb phase appeared. Sb phase free <TEX>$Mg_3Sb_2$</TEX> could be obtained by the mechanical alloying of high speed ball milling for 24 h using elemental Mg and Sb powder mixtures.

ChemInform Abstract: A New Ammine Dual‐Cation (Li, Mg) Borohydride: Synthesis, Structure, and Dehydrogenation Enhancement.

AbstractLiMg(BH4)3(NH3)2 is synthesized by ball‐milling of a 1:2 mixture of Mg(BH4)2 and LiBH4·NH3 (argon atmosphere, 350 rpm, 6 h).

Modulation of the hepatocyte rough endoplasmic reticulum single chloride channel by nucleotide–Mg2+ interaction

The effect of nucleotides on single chloride channels derived from rat hepatocyte rough endoplasmic reticulum vesicles incorporated into bilayer lipid membrane was investigated. The single chloride channel currents were measured in 200/50mmol/l KCl cis/trans solutions. Adding 2.5mM adenosine triphosphate (ATP) and adenosine diphosphate (ADP) did not influence channel activity. However, MgATP addition inhibited the chloride channels by decreasing the channel open probability (Po) and current amplitude, whereas mixture of Mg(2+) and ADP activated the chloride channel by increasing the Po and unitary current amplitude. According to the results, there is a novel regulation mechanism for rough endoplasmic reticulum (RER) Cl(-) channel activity by intracellular MgATP and mixture of Mg(2+) and ADP that would result in significant inhibition by MgATP and activation by mixture of Mg(2+) and ADP. These modulatory effects of nucleotide-Mg(2+) complexes on chloride channels may be dependent on their chemical structure configuration. It seems that Mg-nucleotide-ion channel interactions are involved to produce a regulatory response for RER chloride channels.

Halide Substitution in Magnesium Borohydride

The synthesis of halide-substituted Mg(BH4)2 by ball-milling, and characterization with respect to thermodynamics and crystal structure, has been addressed. The ball-milled mixture of Mg(BH4)2 and MgX2 (X = Cl, Br) has been investigated by in situ/ex situ synchrotron powder X-ray diffraction (SR-PXD), differential scanning calorimetry (DSC), and infrared and Raman spectroscopy. High resolution SR-PXD patterns reveal that the unit cell volume of β-Mg(BH4)2 in milled and annealed mixtures of Mg(BH4)2 with MgCl2/MgBr2 is smaller than that of pure β-Mg(BH4)2. This is due to substitution of BH4– by Cl–/Br– ions which have ionic radii smaller than that of BH4–. For comparison, ab initio calculations were run to simulate Cl substitution in α-Mg(BH4)2. The α-polymorph was used rather than the β-polymorph because the size of the unit cell was more manageable. Electronic energy data and thermodynamic considerations confirm the miscibility of MgCl2 and Mg(BH4)2, both in α- and β-polymorphs.

Mechanochemical synthesis of Fe3O4@(Mg-Al-OH LDH) magnetic composite

A magnetic composite of a meixnerite (Mg-Al-OH) type layered double hydroxide (LDH) and magnetite (Fe3O4), abbreviated as Fe3O4@(Mg-Al-OH LDH), was successfully synthesized by a mechanochemical route with a two-step milling operation. In the first step, the mixture of Mg(OH)2, Al(OH)3 and Fe3O4 as the starting materials was milled without water for 1h, and then with addition water for another 5h in the second step. The so-synthesized composite has the structure of Fe3O4 cores homogeneously dispersed in the LDH matrix and demonstrates super-paramagnetic behavior. This mechanochemical process provides a facile and environmentally safe method for synthesizing magnetic composites based on LDHs.

Development of High Performance MgB2Tapes and Wires

MgB 2 shows no weak coupling of grains, indicating that grain alignment is not essential to obtain large current transfer from one grain to adjacent grain. This is a very big advantage because a simple process, such as powder-in-tube (PIT) method, can be applied for the fabrication of wires and tapes. Here, we report the recent progress of our MgB 2 tapes and wires. There are two PIT methods. One is an in situ method, in which a powder mixture of Mg and B is used as a starting material. The other is an ex situ method, in which reacted MgB 2 powder is used. Superconducting properties are much sensitive to the quality of the starting powder, the porosity of the MgB 2 core and the heat-treatment conditions. Impurity addition to the mixture of starting powder is an effective method to improve J c of MgB 2 tapes and wires. Among the impurities nano-SiC powder is the most popular additive. SiC addition introduces C substitution for B site in MgB 2 and enhances H c2 , thus leading to the increase of J c in high ...

Influence of Bi, Se and Te additions on the formation temperature ofMgB2

The formation of the MgB2 superconducting compound from a mixture of Mg and amorphous B powderswith various low melting point metals (Bi, Se and Te) was studied in situ bymeans of high-energy (synchrotron) x-ray diffraction in wires with a compositeCu/Nb sheath. In comparison with an undoped sample, it was found that theaddition of Bi results in a clear lowering of the formation temperature ofMgB2, whereas Se and Te have no significant influence.Tc is slightly higher in the Bi-doped sample than in the others but thejc in this case is lowerthan in the pure MgB2 sample, probably due to the presence of remainingMg3Bi2 particles that formed as an intermediate compound during reaction. Likewise,in the Se-and Te-doped samples, MgSe and MgTe respectively form below450 °C. Whereasjc is also depressed in the Se-doped sample, the MgTe particles do not appear to affect theperformance of the Te-doped wire.

Synthesis kinetics of Mg2Si and solid-state formation of Mg–Mg2Si composite

The synthesis kinetics of Mg2Si intermetallic compounds (IMC) from the elemental mixture of Mg–Si powders was studied by using differential thermal analysis (DTA). The exothermic peaks were at 818K, which indicated the synthesis reaction of 2Mg+Si→Mg2Si. The synthesis kinetics of Mg2Si was evaluated by the Ozawa method and KAS method, and its activation energy was calculated as 377.53KJ/mol. Based on the data from DTA curves, the bulky materials of Mg–Mg2Si composite were prepared through solid-state reaction by using SPS consolidation process. From the results of XRD and SEM-EDS analysis on the composite materials, it was clarified that at low temperatures of 813K and 833K, Mg and Si powders never react completely, and the suitable temperature of solid-state synthesis by SPS should be about 853K.

Effect of raw materials on microstructure and bending strength of porous in situ MgO/Fe–Cr–Ni composites

Abstract Porous in situ MgO (17.0–34.9 wt.%)/Fe–Cr–Ni composites were prepared from the mixtures of Mg and the powder compositions, such as nano-Fe 2 O 3 + Cr + Ni, micro-Fe 2 O 3 + Cr + Ni, micro-Cr 2 O 3 + Fe + Ni or micro-Ni 2 O 3 + Fe + Cr, via pressureless reactive sintering at 600–800 °C for 2 h. The influence of raw materials on microstructure and bending strength of the resultant porous composites were studied. The results showed that the porous composites, fabricated at 700 °C for 2 h, consisted of MgO, Cr 0.7 Fe 0.36 Ni 2.9 and CrFe phases generally. The porous composite fabricated from the mixture of nano-Fe 2 O 3 , Mg, Cr and Ni, whose fracture mode was a mainly ductile manner, had uniform pore size and possessed higher bending strength than other resultant porous composites.

Effects of processing parameters on properties of selective laser melting Mg–9%Al powder mixture

In the present study, selective laser melting (SLM) was used to sinter a powder mixture of Mg–9%Al. Both densification mechanism and microstructure evolution of laser sintered powder mixture were established. The effect of laser processing parameter on Mg–9%Al powder using SLM was also investigated. It can be found that a maximum relative density was 82% with preferable process parameters of v = 0.02 m/s, P = 15 W. An overlapped structure can be obtained when decreasing the laser energy density due to an incomplete melt. On the other hand, a severe particulate agglomeration appeared as the increase of the laser energy due to a balling effect. A critical scanning speed of 0.02 m/s can ensure that the particulates were well melted and not evaporated during the experiment. Moreover, the Mg and Al elements were dispersed uniformly in the samples. The microstructure and composition phase were studied through scanning electron microscopy (SEM) and X-ray elemental mapping (XRD) respectively.

Textures and mechanical properties in rare-earth free quasicrystal reinforced Mg–Zn–Zr alloys prepared by extrusion

Microstructure and mechanical properties of quasicrystals dispersed Mg alloys prepared by warm extrusion of the mixtures of Mg and Zn–Mg–Zr quasicrystalline (Qc) powders have been studied. Strong texture oriented along a 1 0 1 ¯ 0 direction observed in pure Mg was reduced in Qc-dispersed samples, as verified by pole figure method and electron back scattering diffraction. The ultimate tensile strengths at 150 °C for Qc-dispersed extrusions were much higher than 110 MPa for pure Mg, which drastically reached 156 MPa for 15 wt.% Qc by preventing the motion of dislocations. Elongation was improved by the randomization of grain orientation: from 5.7% for pure Mg to 12.9% for 10 wt.% Qc at room temperature; from 15% for pure Mg to 37.1% for 5 wt.% Qc at 150 °C.

Metallic Superconductors [7] - MgB2 Wires -

Since the discovery in 2001, MgB2 has gained much interests as a new hope of superconductors for its applicability at temperatures of liquid H2 (~20 K) or liquid Ne (~27 K). Then large efforts have been dedicated to the processing of MgB2 wires. Ex situ and in situ techniques are two major techniques for the fabrication of MgB2 wires. The ex situ process uses previously reacted MgB2 powders filled into appropriate sheath tubes which are then fabricated into a wire. In the in situ process a mixture of Mg and B powders is encased in a sheath tube, and after the wire fabrication, the MgB2 core is synthesized in situ by the heat treatment. C or SiC nano-powders are effective dopants to enhance the high-field performance of MgB2 wires. Wires a few kilometers long have been produced via both processes. The diffusion process starting from a composite of Mg rod or pipe and B powder is another promising process in MgB2 wire fabrication. The connectivity of MgB2 grains is still poor due to the insufficient packing factor of powders, voids caused by the volume contraction during MgB2 formation, and the envelope of MgO and other insulating phase around MgB2 grains. This poor connectivity reduces the critical current density of MgB2 wires. Improved powder quality, fabrication techniques, and dopants may appreciably improve the performance of MgB2 wires. Presently, the main target of MgB2 wire application is direct-current use at 20 K, such as for MRI magnets. In this article, material aspects, fabrication process, superconducting performance and future possibilities of MgB2 wires are briefly surveyed.

Laser-induced Mg production from magnesium oxide using Si-based agents and Si-based agents recycling

We succeeded in laser-induced magnesium (Mg) production from magnesium oxide (MgO) using Si-based agents, silicon (Si) and silicon monoxide (SiO). In these experiments, a cw CO2 laser irradiated a mixture of Mg and Si-based agents. Both experimental studies and theoretical analysis help not only understand the function of reducing agents but also optimize Mg extraction in laser-induced Mg production. The optimal energy efficiencies 12.1 mg/kJ and 4.5 mg/kJ of Mg production were achieved using Si and SiO, respectively. Besides, the possibility of recycling Si and SiO was preliminarily investigated without reducing agents but only with laser-irradiation. As for the Si-based agents recycling, we succeed in removing 36 mol % of oxygen fraction from SiO2, obtaining 0.7 mg/kJ of Si production efficiency as well as 15.6 mg/kJ of SiO one at the same time. In addition, the laser irradiation to MgO-SiO mixture produced 24 mg/kJ of Si with more than 99% purity.

ChemInform Abstract: Preparation and Characterization of Nanocrystalline Mg2FeH6.

AbstractNanocrystalline Mg2FeH6 is synthesized by ball milling of 3:1 mixtures of Mg and Fe powders under a hydrogen pressure of 5.5 bar at room temperature for 110 h.

ChemInform Abstract: Synthesis, Structure and Dehydrogenation of Magnesium Amidoborane Monoammoniate.

AbstractMg(NH2BH3)2·NH3 is prepared by ball milling of a mixture of Mg(NH2)2 and 2 equiv.

Local atomic structure of Ca-Mg-Zn metallic glasses

The amorphous structure of four ${\text{Ca}}_{60}{\text{Mg}}_{X}{\text{Zn}}_{40\ensuremath{-}X}$ ($X=10$, 15, 20, and $25\text{ }\text{at}\text{.}\text{ }\mathrm{%}$) ternary metallic glasses (MGs) has been investigated by neutron and x-ray diffraction, using Reverse Monte Carlo modeling to simulate the results. A critical analysis of the resultant models, corroborated by ab initio molecular-dynamics simulations, indicate that the glass structure for this system can be described as a mixture of Mg- and Zn-centered clusters, with Ca dominating in the first coordination shell of these clusters. A coordination number (CN) of 10 [with about 7 Ca and 3 $(\text{Mg}+\text{Zn})$ atoms] is most common for the Zn-centered clusters. $\text{CN}=11$ and 12 [with about 7--8 Ca and 4 $(\text{Mg}+\text{Zn})$ atoms] are most common for Mg-centered clusters. Fivefold bond configurations (pentagonal pyramids) dominate $(\ensuremath{\sim}60\mathrm{%})$ in the first coordination shell of the clusters, suggesting dense atomic packing. Bond-angle distributions suggest near-equilateral triangles and pentagonal bipyramids to be the most common nearest atom configurations. This is the systematic characterization of the structure of Ca-Mg-Zn MGs, a category of bulk MGs with interesting properties and intriguing applications. It is also the experimental verification of the principle of efficient packing of solute-centered clusters in ternary MGs.