Solubility Of Magnesium Research Articles

Insights into alkali and acid-activated volcanic ash-based materials: A review

This review provides a comprehensive study of the fundamentals of the alkaline and acid activation of volcanic ashes (VA), for mainstreaming their use as a conventional feedstock for developing geopolymers and their applications. The low reactivity in an alkaline environment is driven by the low content of the amorphous phase and the low solubility of iron, calcium and magnesium at pH > 12. Nevertheless, techniques such as mechanochemical activation has significantly improved the reactivity and the properties of the resulting products. In the acid phosphate medium, the high solubility of iron, calcium and magnesium ensures good reactivity and a high reaction rate at room temperature. As a result, the engineering properties of acid-phosphate-activated volcanic ash are superior to those of alkali-activated volcanic ash. The resulting materials have great potential for use as binders in concrete design, for the stabilization of compressed earth bricks and for the rapid repair of deteriorated concrete structures. However, significant research is required to fully understand their durability performances, life cycle and techno-economic viability for large-scale utilisation. Further, the limited availability of phosphate resources makes acid activation not a viable route to activate volcanic ash for building purposes. The acid-activated volcanic ash has potential in waste management applications such as nuclear waste or heavy metal encapsulation. Finally, volcanic ash emerges as a promising raw material for developing sustainable building materials through alkali and acid activation. This holds as its exploitation is non-disruptive, and processing requires less energy compared to calcined clay or fly ash.

Polymorphism of the Tb2Ni7 binary compound solubility of lithium and magnesium in α-phase

The solubility of lithium and magnesium in the binary intermetallic compound Tb 2 Ni 7 and its polymorphism were investigated by X-ray powder diffraction, X-ray fluorescent spectroscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy. The alloys for investigation were synthesized by arc melting of pure components taken in stoichiometric composition with the exception of Li and Mg which were taken in excess of 5 wt. % under purified argon atmosphere and further annealing at 400 °C for two months in sealed evacuated silica tubes. Morphology of the alloys surfaces was studied using scanning electron microscope TESCAN Vega3 LMU. Quantitative compositions of the powders were established using Oxford Instruments energy-dispersive X-ray analyser (Aztec ONE system). X-ray fluorescent spectroscopy (spectrometer ElvaX Pro) was used for investigation of the integral composition of the alloys. X-ray phase analysis was carried out on powder data obtained on diffractometer DRON-2.0M (Fe K α -radiation). We confirmed that the Tb 2 Ni 7 binary compound exists in two polymorphic modifications: low-temperature α -Tb 2 Ni 7 (structure type Ce 2 Ni 7 , space group P 6 3 / mmc ) and high-temperature β -Tb 2 Ni 7 (structure type Gd 2 Co 7 , space group R -3 m ). The phase transition α -Tb 2 Ni 7 <=> β -Tb 2 Ni 7 according to the results of differential thermal analysis occurs at 931 °C. The solubility of lithium and magnesium is observed in both modifications however it is larger in α -phase. Substitution of Ni-atoms by the statistical mixture of Li and Mg in α -Tb 2 Ni 7 and formation of the solid solution α -Tb 2 Ni 7- 2 х Li х Mg x ( х = 0–0.5) causes an increase of the unit cell parameters. This solid solution is in equilibrium with the CaCu 5 -type (space group P 6/ mmm ) and PuNi 3 -type (space group R -3 m ) phases. Keywords: polymorphism, solid solution, X-ray diffraction, energy-dispersive X-ray spectroscopy.

Solubility of magnesium in silicon

The solubility of impurity magnesium, which was introduced by diffusion in the temperature range of 1100-1300oC in silicon, is studied by secondary-ion mass spectrometry. It is demonstrated that, with the electrically inactive impurity component taken into account, the maximum solubility of magnesium in silicon is 1-2 orders of magnitude lower (and the diffusion coefficient is higher) than the values reported earlier. Keywords: silicon, doping, magnesium impurity, solubility.

Role of heat treatment on machining characteristics and surface roughness of AZ91 Mg alloy

AZ91 Mg alloy is one of the widely used materials in commercial Mg alloys. Presence of different phases and their relative amounts influence the bulk behavior of metals and alloys. Hence, AZ91 Mg alloy has been subjected to solution treatment at 440 °C with an aim to understand the effect of heat treatment on the machining characteristics. After heat treatment, it was noticed that the solubility of aluminium in AZ91 Mg alloy has been elevated, and observed that the amount of β-phase that has appeared before heat treatment was significantly reduced. Because of more amount of aluminium solubility in magnesium, α-phase grains have become supersaturated. Increased hardness due to solid solution strengthening was observed in heat treated alloy. The cutting forces were measured by conducting turning experiments and were found to be increased after heat treatment due to increased hardness. Roughness of the machined surfaces was measured in contact mode and observed as decreased for the heat treated AZ91 Mg alloy. From the results, it can be concluded that decreasing secondary phase by heat treatment has a profound effect on machining behavior and the roughness of the machined surface of AZ91 Mg alloy.

Qualitative Portrayal of Esomeprazole Magnesium by Exploring Diverse Analytical and Investigative Approaches

Purpose: The present study was intended to qualitatively analyze and drive meaningful statistics for Esomeprazole magnesium; to establish its inherent properties qualitatively & quantitatively.
 Methods: Esomeprazole magnesium was analyzed using various traditional & modern analytical and investigative tools viz FTIR, HPLC, UV spectroscopy, X-ray diffraction, zetasizer.
 Results: The absorption maxima were found at 301 nm with UV Spectrophotometric and HPLC analysis. The particle size of the drug was analyzed through Malvern zetasizer employing water as diluent and found to be 11.818 µm. The quantitative solubility of Esomeprazole magnesium was predicted in various solvents at 25 0C and found that it was most soluble in methanol and was least soluble in distilled water. Solubility was also found to be pH-dependent. Solubility increases with an increase in pH. The order of solubility determined was; Methanol (1.214 mg/ml) > Phosphate buffer pH- 7.4 (0.521 mg/ml) > Simulated Intestinal fluid pH-6.8 (0.475 mg/ml) > Phosphate buffer pH- 6.8 (0.466 mg/ml) > Simulated Gastric fluid pH-1.2 (0.147 mg/ml) > 0.1 N HCl (0.131 mg/ml) > Distilled water (0.017 mg/ml). The predicted log P value was found to be 2.39.
 Conclusion: Esomeprazole magnesium was qualitatively analyzed using various analytical techniques to establish its inherent properties quantitatively. It is an off-white amorphous powder with a characteristic obnoxious odor and slightly bitter taste. The drug was identified through FTIR, using the classification of characteristic peaks of functional groups in the spectrum and also additionally through analytical methods viz HPLC, UV spectroscopy and found the absorption maxima at 301 nm. The linear regression analyses of a standard plot from UV spectrophotometric analysis demonstrate an unswerving relationship in the concentration range of 5-30μg/ml. The log P value indicates that the drug is significantly lipophilic. Various Micromeritic parameters like the Angle of repose, compressibility index, and Hausner's ratio predict the inherent flow properties of Esomeprazole magnesium as Fair (aid not needed). The present study will be an asset in the development of a modified released quick action formulation (Tablet-in-Tablet), to offer quick and protracted relief in gastritis and allied disorders.

Nanostructured Strain-Hardened Aluminum–Magnesium Alloys Modified by C60 Fullerene Obtained by Powder Metallurgy: Part 1. The Effect of the Magnesium Concentration on the Structure and Phase Composition of Powders

This paper provides the first part of a study on the effect of magnesium on the structural phase composition and physical and mechanical properties of nanostructured aluminum–magnesium composite materials with the composition AlxMgy + 0.3 wt % C60 fullerene. Composite powders are obtained by the simultaneous mechanical activation of the initial materials in a planetary ball mill in an argon atmosphere. It is found that the powders have a complex hierarchical structure made up of 50–200 μm aggregates consisting of 5–10 μm strong high-density agglomerates, which in turn are a combination of nanoscale (30–60 nm) crystallites. It is found that the increase in magnesium concentration in the composite up to 18 wt % makes it possible to obtain crystallites with an average size of less than 30 nm during mechanical activation, while the size of aggregates is less than 50 μm. The maximum solubility of magnesium in aluminum with a crystallite size of 30–70 nm during mechanical activation is 15 wt % (17 at %). Using the differential scanning calorimetry method, it is found that nanostructured composites undergo irreversible structural phase transformations during heat treatment in a temperature range of 250–400°C: recrystallization, decomposition of the α-solid solution of magnesium in aluminum, and the formation of intermetallic β-(Al3Mg2), γ-(Al12Mg17) and carbide (Al4C3) phases. In addition, the Raman spectra contain peaks that, according to some sources, correspond to covalent compounds of aluminum with C60 fullerene—aluminum–fullerene complexes. The data that have been obtained will be used in further research to determine the parameters for the thermobaric treatment of nanocomposite powder mixtures in order to obtain and test bulk samples.

Extraction of polyoxotantalate by Mg-Fe layered double hydroxides: elucidation of sorption mechanisms.

The extraction of Ta(v) as polyoxometallate species (HxTa6O19(8−x)−) using Mg–Fe based Layered Double Hydroxide (LDH) was evaluated using pristine material or after different pre-treatments. Thus, the uptake increased from 100 ± 5 mg g−1 to 604 ± 30 mg g−1, for respectively the carbonated LDH and after calcination at 400 °C. The uptake with calcined solid after its reconstruction with Cl− or NO3− anions has also been studied. However, the expected exchange mechanism was not found by X-ray Diffraction analysis. On the contrary, an adsorption mechanism of Ta(v) on LDH was consistent with measurements of zeta potential, characterized by very negative values for a wide pH range. Moreover, another mechanism was identified as the main contributor to the uptake by calcinated LDH, even after its reconstruction with Cl− or NO3−: the precipitation of Ta(v) with magnesium cations released from MgO formed by calcination of the LDH. This latter reaction has been confirmed by the comparison of the uptake of Ta(v) in dedicated experiments with solids characterized by a higher magnesium solubility (MgO and MgCl2). The obtained precipitate has been analyzed by X-ray diffraction (XRD) and would correspond to a magnesium (polyoxo)tantalate phase not yet referenced in the powder diffraction databases.

Nanostructured strain hardened aluminum-magnesium alloys modified by C<sub>60</sub> fullerene obtained by powder metallurgy. Part 1. Effect of magnesium concentration on the structure and phase composition of powders

This paper provides the first part of the study on the magnesium effect on the structural phase composition, physical and mechanical properties of nanostructured aluminum-magnesium composite materials with the composition AlxMgy + 0.3 wt.% C60 fullerene. Composite powders were obtained by the simultaneous mechanical activation of initial materials in a planetary ball mill in an argon atmosphere. It was found that the obtained powders have a complex hierarchical structure made up of 50–200 μm aggregates consisting of 5–10 μm strong high-density agglomerates, which in turn are a combination of nanoscale (30–60 nm) crystallites. It was found that the increase in magnesium concentration in the composite up to 18 wt.% makes it possible to obtain crystallites with an average size of less than 30 nm during mechanical activation, while the size of aggregates is less than 50 μm. The maximum solubility of magnesium in aluminum with a crystallite size of 30–70 nm during mechanical activation was 15 wt.% (17 at.%). Using the differential scanning calorimetry method, it was found that nanostructured composites undergo irreversible structural phase transformations during heat treatment in a temperature range of 250–400 °C: recrystallization, decomposition of the α-solid solution of magnesium in aluminum and formation of intermetallic β-(Al3Mg2), γ-(Al12Mg17) and carbide (Al4C3) phases. In addition, the Raman spectra contain peaks that, according to some sources, correspond to covalent compounds of aluminum with C60 fullerene – aluminum-fullerene complexes. The data obtained will be used in further research to determine parameters for the thermobaric treatment of nanocmposite powder mixtures in order to obtain and test bulk samples.

Effect of various rare-earth metals in magnesium alloys on their strength properties

Based on the results of previously published studies, the main laws of the effect of various rare earth metals on the properties of magnesium alloys used as light structural materials are formulated. It is noted that the properties of magnesium alloys containing rare-earth metals are largely determined by their solubility in solid magnesium, which changes successively with an increase in the atomic number of these elements, as well as the tendency to harden during the decomposition of magnesium solid solutions. The possibility of improving the properties of magnesium alloys when doped with various rare-earth metals in a certain ratio is reported, and the examples of such new alloys are provided.

Solubilities of Magnesium and Cadmium Sulfates in Water at High Temperatures and Pressures

The solubilities of salts in the MgSO4–H2O and CdSO4–H2O systems are studied at 276–500°C using various methods (visual examination of phase transformations in water–salt mixtures in sealed quartz ampoules, collecting solution samples and performing chemical analysis, and measuring p–V–T dependences in an autoclave) to determine temperature dependence and classify the compounds as one the of two types (type 1 or type 2) according to the classification of inorganic salts. In the studied temperature range, the solubility of these salts is very low at pressures below 157 MPa and decreases when approaching the critical point of water. The systems under study are found to be classified as type 2 water–salt systems having the critical point (G = L – S) lying near the critical point of water. No separation of fluid into two liquid phases was detected at temperatures below 500°C and pressures below 157 MPa, thus indicating that the second critical point (L1 = L2 – S) has very high parameters. The resulting data can be used for elaborating methods for raw material processing.

Magnesium Solubility in Primary α-Al and Heat Treatment Response of Cast Al-7Si-Mg

Magnesium and silicon concentrations in the interior of primary α-Al of Al-7Si-Mg alloys were studied at temperatures in the liquid-solid range and just after solidification was completed. Analysis of the results showed that the magnesium concentration in the interior of primary α-Al is very low in the temperatures range from the liquidus to the start of the Al-Si eutectic reaction. Formation of silicon-rich phases during eutectic reactions, such as eutectic silicon and β-Al5FeSi, phases trigger a significant increase in the magnesium concentration in the interior of primary α-Al, when sufficient time is allowed for solid-state diffusion to occur. When fast cooling rates are applied during the Al-Si eutectic reaction, most of the magnesium is retained in π-Al8FeMg3Si6 and Mg2Si phases formed during solidification. Semi-solid Al-7Si-Mg castings were produced with varying magnesium contents, and the mechanical properties were evaluated in the as-cast, T5 and T6 conditions. It was found that the 0.2% offset yield strength of the semi-solid Al-7Si-Mg castings in the T5 and T6 conditions increases linearly with the square root of the magnesium concentration in the interior of the α-Al globules formed during the slurry preparation process.

Setting and hardening behavior of volcanic ash phosphate cement

This study aims at determining the setting and hardening behavior of volcanic ash-phosphate cement (VAPC) at room temperature using various concentrations of phosphoric acid. The properties of the fresh and hardened pastes of the VAPCs were assessed. The results reveal that iron is the main element taking part in the hardening reaction followed by aluminum, calcium, and magnesium, while silicon remained inert in phosphoric acid. The initial setting time is delayed when the concentration of phosphoric acid is increased (low pH). The low solubility of calcium and magnesium at high pH fostered the rapid formation of the binder, which hinders the further dissolution of the remaining particles. Whilst the high solubility of iron and aluminum at low pH slows down the rate of reaction but is beneficial for the extensive dissolution of reactive elements leading to the formation of a binder with high compressive strength. The microstructural analyses revealed that the binder is X-ray amorphous with a homogeneous distribution of all elements except silicon which is present in very few amounts.

Thermodynamic Modeling of the Processes of Interaction of Calcium, Magnesium, Aluminum and Boron with Oxygen in Metallic Melts

A method for calculation of the diagrams of steel deoxidation and modification by calcium, magnesium, aluminum and boron was developed. The coordinates of the liquidus surfaces of the oxide systems B2O3–Al2O3–MgO, B2O3–Al2O3–CaO, B2O3–MgO–CaO were found at 1873 K. The energy parameters were determined for the theory of subregular ionic solutions of the studied oxide systems. The coordinates of the solubility surfaces for the systems Fe–Mg–Al–B–O, Fe–Ca–Al–B–O, Fe–Mg–Ca–Al–B–O were calculated. The effect of the total pressure on solubility of magnesium and calcium in liquid iron was studied. The activity of the components of the metallic melt was calculated using the first-order interaction parameters (Wagner's theory). The activities of the components of solid solutions (oxides and spinels) were equated with their molar fractions. It was shown that during extensive refining of metal from the oxygen, only a small fraction of boron oxidizes and these oxides form fraction of the oxide melts. The major non-metallic oxide inclusions were magnesia spinel, calcium bialuminate and liquid oxide formations. The "free" boron was dissolved in liquid metal in amounts which were in equilibrium with oxide phases.

Strengthening and ductilizing of magnesium alloying with heavy rare earth elements

Among all alloying elements the rare earth elements (RE) play a key role in improving the ductility, high temperature strength and corrosion resistance effectively for magnesium and its alloys. The present work investigated the influences of single alloying or multi heavy REs (Gd, Dy and Y) alloying on the strengthening and ductilizing of magnesium. These heavy REs have a higher solid solubility in magnesium than that the light REs such as Nd and Ce. It is found that the solid solution strengthening caused by Gd follows the linear relationship with the exponent n value of 1/2 or 2/3. When adding two or more heavy REs in Mg, owing to their interactions and resultant synergetic effects, the effectiveness of strengthening and ductilizing caused by multiple RE addition is much better than that by single RE addition.

Preparation and solubility of magnesium substituted HA films using a sputtering method

Preparation and solubility of magnesium substituted HA films using a sputtering method

Effect of growth temperature of GaN:Mg layer on internal quantum efficiency of LED structures with InGaN/GaN quantum wells

The results of studies of quantum efficiencies for photoluminescence and electroluminescence regimes of blue light-emitting diode structures with InGaN/GaN quantum wells are presented. Experimental samples differed in growth temperature of p-GaN emitter layer. It is shown that increasing of growth temperature of p-GaN layer in temperature range 940-1060 °C leads to decreasing of internal quantum efficiency due to diffusion of magnesium atoms from p-GaN into quantum wells. At the electroluminescence regime quantum efficiency of samples with low temperature p-GaN is limited by insufficient crystal quality or low solubility of magnesium in emitter layer.

Ligand-promoted dissolution of serpentine in ultramafic nickel ores

The ligands catechol, citrate, EDTA, oxalate and tiron were investigated for their ability to improve the dissolution of serpentine in ultramafic nickel ores at neutral to alkaline pH to enhance mineral carbon sequestration. It is desirable to leach magnesium from serpentine in ores at neutral to alkaline pH so that leaching and carbonation can be conducted at the same pH value, and ultimately so that the reagent requirements of mineral carbon sequestration can be reduced. Both solution modeling and experimental work were conducted. The solution modeling revealed that each of the ligands studied is able to enhance the solubility of magnesium at the desired pH, with the order of effectiveness being EDTA>tiron>citrate>catechol>oxalate. Experimentally it was shown that the ligands studied could improve both the total amount and rate of magnesium leaching from ultramafic nickel ores. The order of ligand effectiveness based on the experimental work for the Pipe ore was EDTA⩾tiron>catechol>oxalate⩾citrate. For the OK ore, the order was tiron>EDTA=catechol>oxalate>citrate. Overall, the ligands studied in this work, particularly EDTA, tiron, and catechol, appear promising for enhancing the dissolution of serpentine in ultramafic nickel ores at neutral to alkaline pH.

Energy-Efficient and Environmentally Friendly Solid Oxide Membrane Electrolysis Process for Magnesium Oxide Reduction: Experiment and Modeling

This paper reports a solid oxide membrane (SOM) electrolysis experiment using an LSM(La0.8Sr0.2MnO3-δ)-Inconel inert anode current collector for production of magnesium and oxygen directly from magnesium oxide at 1423 K (1150 °C). The electrochemical performance of the SOM cell was evaluated by means of various electrochemical techniques including electrochemical impedance spectroscopy, potentiodynamic scan, and electrolysis. Electronic transference numbers of the flux were measured to assess the magnesium dissolution in the flux during SOM electrolysis. The effects of magnesium solubility in the flux on the current efficiency and the SOM stability during electrolysis are discussed. An inverse correlation between the electronic transference number of the flux and the current efficiency of the SOM electrolysis was observed. Based on the experimental results, a new equivalent circuit of the SOM electrolysis process is presented. A general electrochemical polarization model of SOM process for magnesium and oxygen gas production is developed, and the maximum allowable applied potential to avoid zirconia dissociation is calculated as well. The modeling results suggest that a high electronic resistance of the flux and a relatively low electronic resistance of SOM are required to achieve membrane stability, high current efficiency, and high production rates of magnesium and oxygen.

Bioavailability of Magnesium Salts – A Review

Background: Magnesium supplementation is of value in several different medical disorders. Several kinds of Mg-salts are commercially available.Purpose: This review evaluates their bioavailability criteria such as solubility, urinary excretion, and plasma levels of magnesium from studies of different Mg-salts.Conclusion: Although methodology differences were large, the results consistently demonstrate a better bioavailability for Mg-citrate.

An Environmentally Friendly Process Involving Refining and Membrane-Based Electrolysis for Magnesium Recovery from Partially Oxidized Scrap Alloy

Magnesium is recovered from partially oxidized scrap alloy by combining refining and solid oxide membrane (SOM) electrolysis. In this combined process, a molten salt eutectic flux (45 wt.% MgF2–55 wt.% CaF2) containing 10 wt.% MgO and 2 wt.% YF3 was used as the medium for magnesium recovery. During refining, magnesium and its oxide are dissolved from the scrap into the molten flux. Forming gas is bubbled through the flux and the dissolved magnesium is removed via the gas phase and condensed in a separate condenser at a lower temperature. The molten flux has a finite solubility for magnesium and acts as a selective medium for magnesium dissolution, but not aluminum or iron, and therefore the magnesium recovered has high purity. After refining, SOM electrolysis is performed in the same reactor to enable electrolysis of the dissolved magnesium oxide in the molten flux producing magnesium at the cathode and oxygen at the SOM anode. During SOM electrolysis, it is necessary to decrease the concentration of the dissolved magnesium in the flux to improve the faradaic current efficiency and prevent degradation of the SOM. Thus, for both refining and SOM electrolysis, it is very important to measure and control the magnesium solubility in the molten flux. High magnesium solubility facilitates refining whereas lower solubility benefits the SOM electrolysis process. Computational fluid dynamics modeling was employed to simulate the flow behavior of the flux stirred by the forming gas. Based on the modeling results, an optimized design of the stirring tubes and its placement in the flux are determined for efficiently removing the dissolved magnesium and also increasing the efficiency of the SOM electrolysis process.