Abstract Magnesium Research Articles

Comparison of the Thermal Conductivity of Sm-Containing AZ31 and ZK30 Alloys

Magnesium alloys with different Sm contents, with research focus on ZK30 and AZ31, were prepared and their microstructures and thermal conductivities were investigated. Results of microstructure analysis showed that Sm element in the as-cast ZK series of magnesium alloys was mainly distributed along the grain boundaries in the form of (Mg, Zn)3Sm rare-earth phase. However, Sm element in AZ series of magnesium alloys was distributed over the grains and at grain boundaries in form of Al2Sm phase. The Al2Sm phase at the core acted as a nucleus to refine the grain of AZ series of magnesium alloys. The grain size of the as-extruded magnesium alloys was obviously smaller than that of the as-cast magnesium alloys. Moreover, the crushed secondary phases were arranged along the direction of extrusion. Results showed that thermal conductivity of magnesium alloys could be improved by increasing Sm content. Thermal conductivities of ZK series of magnesium alloys were obviously higher than those of AZ series of magnesium alloys. This was mainly attributed to the significantly smaller lattice distortion of ZK series of magnesium alloys compared to that of AZ series of magnesium alloys.

Optimization of tribological behavior of magnesium metal-metal composite using pattern search and simulated annealing techniques

Abstract Magnesium based metal-metal composite was synthesized through the disintegrated melt deposition technique with the inclusion of aluminium and titanium powders. To examine the metallurgical features of the metal-metal composite the samples of the produced composite was subjected to x-ray diffraction analysis and scanning electron microscopy analysis. To study the tribology of the metal-metal composite, pins of composites were subjected to dry sliding wear test as per standards and the specific wear and the coefficient of friction was taken as response variables. Two different computational techniques such as pattern search and simulated annealing was used to identify the optimal values of specific wear and coefficient of friction along with the identification of optimal parameter combinations. The optimum values of specific wear and coefficient of friction obtained from the pattern search technique is found to be closer to the calculated values compared to the simulated annealing technique.

Water Resistance Modification of Magnesium Oxychloride Cement with H<sub>3</sub>PO<sub>4</sub>/Na<sub>2</sub>O·xSiO<sub>2</sub>·nH<sub>2</sub>O

Magnesium oxychloride cement (MOC) possesses rapid hardening, high mechanical strength, abrasion resistance, low alkali and low corrosive performances. However, its disadvantages of poor water resistance, easily deformation, moisture absorption and halogenations limit the application. A low cost-effective modifier H3PO4/Na2O·xSiO2·nH2O was designed for MOC system. The results showed that the softening coefficient of the modified MOC reaches 0.988 by adding appropriate dosage of the modifier. Gelatinous substances in the modified MOC was produced after soaking in water, which effectively inhibit the hydrolysis of phase 5 (5Mg (OH)2·MgCl2·8H2O) and the formation of Mg (OH)2, thus improving the water resistance of MOC system. Keywords: Magnesium oxychloride cement; Water resistance; Phosphoric acid

Laser Surface Modification of Rare Earth Containing Magnesium Alloy Through Simulated Body Fluid and Its Impact on Cell Viability

Magnesium alloys have a good potential as structural biomaterials for temporary implant applications because of their self-degradation properties and biocompatibility. The surface condition is important for such applications, and lasers are often used to modify the surface characteristics of such components. In this context, the media through which the laser beam passes before reaching the surface to be irradiated is also of interest. In particular, laser irradiation in liquids affects the thermal energy delivery to the surface of the material, which in turns influences the formation of surface structures. In this work, rare earth containing WE54 Mg alloy has been irradiated under air and through a simulated body fluid (SBF) layer using a 500 watt pulsed Nd: YAG laser. As compared to direct laser surface treatment through air, laser irradiation through SBF generates new surface structures and deposition of ions issued from the SBF solution. Scanning electron microscope combined with energy dispersive spectroscopy (EDS) was used for the examination of surface structures formation and determination of elemental composition. Mesenchymal stem cells (MSC) culture was performed on laser modified WE54 alloy surface, and the MSC cytocompatibility on SBF-treated substrates was evaluated by the PrestoBlue™ assay test method. Cell reproducibility was observed on the SBF laser-treated surface which indicated that cell viability was improved by the surface treatment. The deposition of calcium and phosphorus ions on the WE54 surface was beneficial for cell viability. These results motivate the potential use of SBF-based films for biomedical purposes.

The effect of milling conditions on the magnetic and topological properties of MgB2 synthesized by high-energy ball mill and sintered at low temperature

Magnesium diboride, MgB2, is known to be an important high-temperature superconductor material. High-energy ball milling with subsequent low-temperature sintering remains an attractive solid-state method for its synthesis. One main optimization parameter of this method is to ensure a balance between cold welding and fracturing at the milling stages. Therefore, in many cases, the use of a process control agent at the milling stage is considered to be the preferred solution in the prevention of particle size enlargement. The aim of this paper is to determine the effect of dry and toluene-assisted milling on the magnetic and surface topology properties of obtained MgB2. The calculated critical current density of 2.89 × 105 A/cm2 at 10 K 0.3 T for a toluene-assisted sample, compared with the 2.37 × 105 A/cm2 for a dry-milled sample as well as the relatively higher mean surface roughness, clearly indicated a notable positive contribution of surfactant use on the true alloying of MgB2 by mechanical activation.

Ionized and Total Magnesium Levels Change during Repeated Exercise in Older Adults.

Magnesium is essential for health and performance. Sub-optimal levels have been reported for older persons. In addition, physical exercise is known to temporally decrease magnesium blood concentrations. To investigate these observations in conjunction we assessed total (tMg) and ionized magnesium (iMg) concentrations in plasma and whole blood, respectively, during 4 consecutive days of exercise in very old vital adults. 68 participants (age 83.7±1.9 years) were monitored on 4 consecutive days at which they walked 30-40km (average ~8 hours) per day at a self-determined pace. Blood samples were collected one or two days prior to the start of exercise (baseline) and every walking day immediately post-exercise. Samples were analysed for tMg and iMg levels. Baseline tMg and iMg levels were 0.85±0.07 and 0.47±0.07 mmol/L, respectively. iMg decreased after the first walking day (-0.10±0.09 mmol/L, p<.001), increased after the second (+0.11±0.07 mmol/L, p<.001), was unchanged after the third and decreased on the final walking day, all compared to the previous day. tMg was only higher after the third walking day compared to the second walking day (p=.012). In 88% of the participants, iMg levels reached values considered to be sub-optimal at day 1, in 16% of the participants values were sub-optimal for tMg at day 2. Prolonged moderate intensity exercise caused acute effects on iMg levels in a degree comparable to that after a bout of intensive exercise. These effects were not associated with drop-out or health problems. After the second consecutive day of exercise, levels were returned to baseline values, suggesting rapid adaptation/resilience in this population.

Plasma preparation method and tribological properties of diamond-like carbon coating on magnesium alloy AZ31 substrate

Magnesium alloys are light weight and exhibit good recyclability but suffer from low hardness and wear resistance. In this study, the hardness and wear resistance of AZ31 magnesium alloy were improved by depositing diamond-like carbon (DLC) films as hard protective coatings using ion-beam-enhanced deposition with various CH4/H2 ratio, gas flow rates and accelerating voltages. The supporting effect of the magnesium alloy was enhanced by the production of a graded interfacial layer which is composed of film atoms and substrate atoms. The composition and mechanical properties of the DLC coatings were characterized using scanning electron microscopy (SEM), Raman spectroscopy, Rockwell test and nano-indentor. The tribological properties of the coating were also investigated using a frictional surface microscope with an in situ observation system and friction force measurements. The DLC films were characterized by a lower intensity ratio of the D-peak to G-peak (ID/IG), higher hardness, and improved tribological properties when deposited at a lower accelerating voltage (6 kV). At the CH4/H2 ratio of 1:99 and 6 sccm/6 kV, minimum ID/IG values of 0.62, relatively low friction force value of 0.12 N, and a maximum hardness of 4056HV were attained respectively. In addition, the DLC film exhibited improved wear resistance and a shallower wear track at this condition.

Solid State Characterization of the Consciousness Energy Healing Treated Magnesium

Magnesium (Mg) is abundantly present in the human body, which functions for many metabolic activities, normal functioning of cells, muscles, heart, bones, etc.

No Difference in Magnesium Intake between Obese Women and Healthy Controls.

Magnesium is a predominantly intracellular ion and plays an important role in energy metabolism and in the maintenance of energy homeostasis. This study aimed to estimate the dietary intake of magnesium and its association with adiposity parameters in obese women. This cross-sectional study included 125 women, aged between 20 and 50years, who were divided into two groups: obese group (n=62) and control group (n=63). The control group was age-matched. Adiposity parameters determined were weight, body mass index and waist circumference as well as the intake of calories, macronutrients, and magnesium were calculated. The cut-off for obesity was body mass index between 30.0 and 39.9kg/m2 and for control group was between 18.5 and 24.9kg/m2 Food intake was calculated using 3-day food records, and energy consumption as well as the intake of macronutrients and magnesium was calculated using the NutWin software version 1.5. The reference values used were the Acceptable Macronutrient Distribution Range for macronutrients and the Estimated Average Requirement (EAR) for magnesium. The average levels of magnesium found in the diet were lower than those recommended (169.1±64.5mgMg/day and 158.5±42.9mgMg/day, for obese women and control group, respectively) and the differences between the groups were not statistically different (p>0.05). The correlation analysis indicated that the association between the dietary intake of magnesium and adiposity was not significant. The results of this study indicate that dietary magnesium does not influence the adiposity parameters in obese women.

Preparation of MgO-Templated N-Doped Mesoporous Carbons from Polyvinylpyrrolidone: Effect of Heating Temperature on Pore Size Distribution

Magnesium oxide (MgO)-templated nitrogen (N)-doped mesoporous carbons were prepared by using polyvinylpyrrolidone (PVP) as a raw material and magnesium lactate (Mglac) as a precursor for the MgO template to examine the influence of heating temperature and MgO precursor (magnesium acetate was used in similar previous studies) on the pore size and nitrogen content. The MgO-templated carbon was obtained by heating the PVP/Mglac mixture in an inert atmosphere followed by an acid treatment for MgO removal. The mesopore size of the carbons was approximately 4 nm regardless of heating temperature, corresponding to the crystallite size of the MgO template estimated via X-ray diffraction. This indicates that the mesopore of approximately 4 nm was generated using the MgO template. However, larger pores were also found to exist. This result indicates that the larger pores generated through processes other than the MgO templating, likely the thermal decomposition of PVP, are contained in the templated carbon. The volume of the larger pores and the specific surface area increased with increasing heating temperature. The nitrogen content of the carbon decreased as the heating temperature was increased, but it was found to be irrelevant to the MgO precursor.

Study of magnesium precipitation based on biocementation

Magnesium carbonate has a cementing character like calcium carbonate, and the addition of magnesium ion enables the microbe cementitious material to have the denser microstructure with the lower porosity. The effects of various factors, such as the concentration of Ca2+ and Mg2+, on the urease activity were studied. Comparison of the productive rates for calcium carbonate and magnesium carbonate were carried out, as well as productive rates for magnesium carbonate with adding different amount of urea to medium. Calcium acetate and magnesium acetate were, respectively, used for sands solidification. Results showed that the increase in urea concentration and magnesium ion enhanced urease activity, while calcium ion significantly impaired urease activity. Sodium chloride and acetate ion had little influence on it. Productive rates for magnesium carbonate were dramatically smaller than its calcium counterpart. However, adding urea to medium allowed for more magnesium precipitation, and the higher the urea concentration, the more the magnesium precipitation. The sand columns with adding urea to medium can have a high strength despite using magnesium acetate. Therefore, the method could solve the problem of insufficient magnesium precipitation. The results will act as a guide for the application of biocementation technology with magnesium carbonate.

Study of the Total Serum Concentration of Serrum Ionized Magnesium in Children and Adolescents from Sibiu Area

Magnesium is an essential nutrient for the living organisms and plays an important part in the prevention and treatment of many diseases. It is an enzymatic cofactor for more than 300 reactions. Magnesium is essential for regulating blood pressure, muscle contraction, cardiac excitability, insulin metabolism, vasomotor tonus. Studying the way in which serum magnesium concentration varies in children and adolescents in the Sibiu area according to the reference intervals we especially set for this area. The study is a retrospective one, using approximately 4900 data from the archives of the Medical Analysis Laboratory within the Sibiu Pediatric Clinical Hospital. Serum magnesium was dosed using the Konelab Prime 30i analyser. The data from the literature was used to compare the results. The reference ranges obtained in the current study were similar to the literature studied. The percentage of patients with magnesium concentration outside the reference ranges was roughly equal for all age groups. The difference was between 1 month and 2 year-old children with very few deviations from the reference range. The results of our study reflect more accurately the real reference range for the population in the Sibiu area, helping clinicians to establish a diagnosis as quickly and accurate as possible. These results were not significantly different from the literature studied.

Optimization of current parameters during variable polarity GMAW of magnesium alloy

Magnesium alloy welding suffers from problems such as burn through and loss of alloying elements during conventional welding process due to high heat input. Variable polarity gas metal arc welding (VP-GMAW) features low heat input. Therefore, it is an attractive method for welding of magnesium alloy. However, the principles governing the correlations among welding current parameters, metal transfer modes, and bead formation are not well understood. Identifying optimal welding current parameters by trial and error is unrealistic. Therefore, peak current, base current, and negative current were selected as independent variables. Their impact mechanism on metal transfer and bead formation were investigated by experiments with high-speed photographs. Then, weld quality evaluation was conducted by a fuzzy comprehensive evaluation. A mathematical method was proposed to calculate optimal current parameters for VP-GMAW of magnesium alloy. In addition, a significant sequence of current parameters is obtained. The results indicate that almost defect-free weld joint is produced by the optimal welding current parameters. The significance sequence of current parameters on weld quality is negative current, peak current, and base current.

Synthesis and application of amorphous magnesium silicate in sample preparation for analysis

Magnesium silicate, one of silicate materials, is widely used as adsorbent for sample cleanup in solid phase extraction as well as color reducing agent in the industry of sugar, paint, paper, ... In this research, magnesium silicate is synthesized by precipitation method. The synthesis process was optimized by experimental design with quadratic orthogonal experimental method. The optimal reaction conditions are as follows: the mole ratio of sodium silicate/magnesium chloride = 1:1, the speed of stirring sodium silicate solution: 177 rpm, the added flow rate of magnesium chloride solution: 3.86 mL/min, drying temperature: 98oC. In addition, it takes at least 6 hours to eliminate water adsorption at this temperature. The product has amorphous structure with average particle size of 116 m, surface area of 454 m2/g, and trioleate glyceryl absorption capacity of 110 mg/g. The efficiency in the removal of esters of glyceryl and fatty acids in hydrocarbons determination and the removal of matrix in the analysis of organochlorides are as good as that of commercial Florisil.&#x0D;

Spectrophotometric determination of magnesium oxide content in supplements of magnesium

Magnesium is an essential element and the intracellular divalent cation involved in many biochemical functions. People with magnesium deficiency must increase their intake of magnesium, usually in the form of various supplements. A common form of magnesium supplement widely available in pharmacies is magnesium oxide (MgO). In this work, the content of MgO was determined in pharmaceutical supplementations using spectrophotometry, based on the reaction between magnesium ions and eriochrome black T at a wavelength of 535 nm. The analysed content of MgO ranged from 360.5 to 386.5 mg MgO, which corresponds to the daily Mg recommended values (300 to 400 mg).

Возрастные различия морфофункционального состояния поджелудочной железы крыс после введения хлорида магния

Magnesium is directly involved in the regulation of exo- and endocrine function of the pancreas. However, the efficacy of different magnesium agents in activating the pancreas function is uncertain. One possible reason for that is the age differences in the structural and functional response of the pancreas to magnesium administration. The aim of this study was to investigate the age-related patterns of changes in the morphofunctional state of the pancreas following prolonged magnesium chloride administration. The experiments were performed on 48 male Wistar rats aged 3 and 15 months. The animals in the experimental group received magnesium chloride (50 mg/kg body weight) in addition to the normal feeding ration. At the end of the experiment the histo-morphological evidence of lowered functional activity of both exocrine (reduced size of the acini and the exocrinocytes) and endocrine (reduced relative area, number and size of the Langerhans islets) was observed in 3 month old rats. In contrast, the administration of magnesium chloride to 15 month old rats moderately increased the activity of the exocrine part of the pancreas (increased size of the exocrinocytes). The significant increase of the relative exocrine part area, linear size of the pancreatic islets, number and density of the endocrinocytes in the islets, suggests that the endocrine activity of the pancreas is increased in adult rats. The tendency for the increased relative stroma area and stromal-parenchymal index was observed in 3 month old rats in the experimental group. These values were decreased in 15 month old rats. The results of the study indicate the age-related differences in the changes for exocrine and endocrine parts of the pancreas following the prolonged magnesium chloride administration. The nature and prominence of these changes suggest that the magnesium lowered the activity of the exo- and endocrine parts of the pancreas in 3 month old rats, and increased it in 15 month old animals.

Numerical investigation of one-dimensional steady detonation wave characteristics for magnesium particle-air mixture

Magnesium particles have broad application prospects as fuel or additive for detonation combustion power systems due to their high energy density, ignition characteristics and combustion efficiency. In this paper, a one-dimensional steady-state model is established for the magnesium particle-air mixture. The distribution of the flow field and the influences of factors such as phase transition process, inlet velocity, particle radius and initial particle density on the structure of detonation wave are analyzed numerically under different working conditions. The studies have shown that the process accelerating to the sound speed due to the expansion of the gas phase mainly occurs in the pure evaporation reaction stage of the magnesium particles. The duration of magnesium and magnesium oxide melting accounts for a small proportion of the entire combustion process. Under the initial conditions of normal temperature and pressure, the theoretical maximum temperature in the detonation wave during self-sustaining propagation is lower than the dissociation temperature of the magnesium oxide. The heat absorbed in the magnesium melting process is released into the gas phase for expansion work as the reaction progresses, leading to a small effect of magnesium melting on the structure of the detonation wave. The amount of exothermic heat absorbed in the magnesium oxide melting process is so large that the process of expansion of the gaseous working fluid is almost stopped. Moreover, the absorbed heat cannot be used for gas phase expansion work. Therefore, the melting process of magnesium oxide has a great influence on the structure of the detonation wave. The detonation wave of the magnesium particle-air mixture can be stabilized and self-sustained only at the eigenvalue velocity. Below this value, a singular point appears in the flow field. Above this value, the wave cannot be accelerated to the speed of sound, and the downstream flow field disturbance can pass through the reaction combustion zone and weaken the intensity of the detonation wave. When the end of the detonation wave is in the melting process, the detonation wave can still stabilize the self-sustaining propagation when a certain inflow velocity and a magnesium particle density are satisfied. Otherwise, the detonation wave can propagate only at an average speed with oscillation. The initial particle concentration corresponding to the peak of the eigenvalue velocity is smaller than the stoichiometric one corresponding to the peaks of the density, pressure and temperature, indicating that the eigenvalue velocity is not dependent solely on the heat release of the reaction because the interaction between the two phases also affects the conversion efficiency of thermal energy into gas phase kinetic energy. Under the premise of uniform distribution of internal temperature of magnesium particles, the particle size mainly affects the size of the detonation wave, but has little effect on the characteristic value of the eigenvalue velocity and the Chapman-Jouguet parameters. The model in this paper comprehensively reflects the influence of the phase transition process in the combustion process on the structure of the detonation wave and the self-sustaining propagation mechanism. It has a certain guiding significance for designing the detonation power device using powder fuel.

Effect of Nano-SiC on Microstructure and Mechanical Properties of AZ91 Magnesium Alloy Processed by Thixomolding

Magnesium injection molding technology was used to produce Mg based nanocomposites. AZ91 chips were mixed with 5 wt.% of β-SiC nanoparticles in solid state and fed to pre-heated cylinder of prototype injection molding machine. Using screw rotation, granules were transferred to nozzle area at simultaneous intensive shearing and mixing of slurry containing reinforcement phases. Injection process was conducted at 595 °C, which corresponded to about 90% liquid phase and cast to steel die preheated to 150 °C. Detailed characterization of microstructure was performed using SEM and TEM microscopes. Composite microstructure consisted of α(Mg) globular grains with size of about 60 μm and volume of 7-10% surrounded by mixture of proeutectic magnesium solid solution with irregular shape and average size of 12 μm as well as fine eutectic mixture (α(Mg) + β-Mg17Al12). Additionally, TEM-BF image showed β-SiC nanoparticles with size of 20-50 nm in the area of eutectic. Hardness and compression strength of AZ91 nanocomposites increased from 58 to 75 HV and from 200 to 235 MPa, respectively.

Photocatalytic properties of magnesium aluminate spinel nanoparticles prepared by chemical precipitation method

Magnesium aluminate spinel nanoparticles were synthesised via chemical precipitation method using ammonia as precipitating agent. The effects of calcination temperature on the phase constitution, morphologies, specific surface area and photocatalytic properties were investigated. Single phase cubic MgAl2O4 formed by calcining the precursors at the temperature ranges from 700°C to 1,000°C for 90 min. The mean crystallite size of the MgAl2O4 powder increases slightly with the increase in calcination temperature. Increasing the calcination temperature leads to decrease in the specific surface area and the decline of the photocatalytic properties. The methylene blue removal ratio reaches 96.3% within 240 min using MgAl2O4 spinel powder calcined at 700°C.

Supply Chain Quality Management of Magnesium Components: Concept, Examples and Recommendations

Magnesium components offer an enormous potential to achieve considerable weight savings in the automotive industry. As with any innovative construction material, (e.g. carbon-fiber-reinforced polymer, ultra-high-strength steel) a rigid quality management system needs to be established along the supply chain. For this purpose, the concept of the supply chain quality management is to be introduced for the special case of magnesium components, using the example of the magnesium strip production. By the implementation of the widespread ISO 9001 norm, opportunities can be leveraged by both the creation of upstream, downstream linkages and the defined internal processes to achieve the required and stable quality for the automotive industry. The paper suggests procedures and instructions for process control during the magnesium strip production according to the twin-roll casting technology, giving feedback to the respective production system to avoid insufficient quality. The results serve as a basis for the development of all stages up to the assembly of magnesium components. The individual process stages dependent on the manufacturer should be considered during the procedure.