• Resources Recycling
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• v.25 no.3
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• pp.63-73
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• 2016

With the purpose of concentrating the magnesium from seawater, in this study, we have conducted experiments to precipitate the magnesium using three precipitants (NaOH, cement kiln dust, and paper sludge ash), and then extract it using sulfuric acid. Results show that the precipitation and extraction performance does not depend so significantly on the kind of precipitant: for all the precipitants used, the precipitation efficiency is measured almost 100% and the extraction efficiency is in the short range of 77 - 89%. The magnesium concentration in the extract is measured 4975 - 5775 mg/L, implying that the magnesium in seawater should be 3.8 - 4.4 times concentrated through the precipitation and extraction reactions. The reaction efficiency of the industrial by-product used as a precipitant in this study is almost 100% similar to those of the other existing expensive precipitants.

• Resources Recycling
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• v.14 no.1
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• pp.33-38
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• 2005

Worldwide magnesium market has been considerably growing recently due to adoption as light materials for automobile engines and electronic devices such as mobile phones. In this study, it is to prepare magnesium oxide, which is the first-step product in smelting of magnesium from the ore, using magnesite of Yongyanag mines in North Korea as raw ores. MgO grade of the magnesite was about 45 wt%, and SiO$_2$, CaO, Al$_2O_3$ and Fe$_2O_3$ were contained as impurities. The sample ore was crushed, classified and thermally analyzed to determine its calcination temperature. The sample of 45-75 ${\mu}m$ size was calcined at 600-900$^{\circ}C$, and effect of temperature on calcination and change of the particle shape was investigated. Optimum temperature of the calcination was about 750$^{\circ}C$, and 30 minutes was sufficient to obtain over 99% conversion. The purity of the calcined MgO was about 95 wt%.

• Journal of the Korean institute of surface engineering
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• v.44 no.3
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• pp.82-88
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• 2011

A uniform chromium-free conversion coating treated with an alkaline phosphate- permanganate solution was formed on the AZ 31 magnesium alloy. The effect of acid pickling on the morphology and on the corrosion resistance of the alkaline phosphate-permanganate conversion coating was investigated. The chemical composition and phase structure of conversion coating layer were determined via optical microscopy, SEM, EDS, XPS and XRD. Results show that the conversion coatings are relatively uniform and continuous, with thickness 1.8 to $2.4\;{\mu}m$. The alkaline phosphate-permanganate conversion coating was mainly composed of elements Mg, O, P, Al and Mn. The conversion-coated layers were stable compounds of magnesium oxide and spinel ($MgAl_2O_4$). These compounds were excellent inhibitors to corrosion. The electrochemical corrosion behaviors of coatings in 3.5 wt.% NaCl solutions were evaluated by electrochemical impedance spectroscopy, potentiodynamic polarization technique. EIS results showed a polarization resistance of $0.1\;k{\Omega}$ for the untreated Mg and $16\;k{\Omega}$ for the alkaline phosphate-permanganate conversion treatment sample, giving an improvement of about 160 times. The results of the electrochemical measurements demonstrated that the corrosion resistance of the AZ 31 magnesium alloy was improved by the alkaline phosphate-permanganate conversion treatment.

• Korean Journal of Metals and Materials
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• v.46 no.5
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• pp.304-309
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• 2008

Magnesium alloys containing $Mg_2Si$ particles, as a promising cheap heat-resistant magnesium alloy for automobile power train parts applications, are attracting more attention of both material scientists and design engineers. Modification of the Chinese script shape $Mg_2Si$ particle is a key for using this alloy in sand or permanent mould casting. In the present work, the modification effect of Sr and Sb on the corrosion properties of the Mg-5Al-2Si alloy was investigated. Sr or Sb addition promoted the formation of fine polygonal shape $Mg_2Si$ particles by providing the nucleation sites. Sr was more effective element than Sb for shape modification of Chinese script shape $Mg_2Si$. Such improved microstructure of the modified alloy resulted in large improvement in corrosion resistance as compared to unmodified Mg-5Al-2Si alloy.

• Progress in Superconductivity and Cryogenics
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• v.10 no.1
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• pp.19-23
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• 2008

Spherical $MgB_2$ powders was synthesized with the ultrasonic spray pyrolysis(USP) process using aqueous solutions of boron and magnesium ion. The properties of synthesized $MgB_2$ powder were characterized by XRD, SEM and EDS. A small amount of MgO was detected as the secondary phase out of the synthesized powder and the ratios of $MgB_2$ to MgO increased with increasing furnace temperature. The particle size and morphology of $MgB_2$ powder were investigated with varying molar concentration of the boron and magnesium solution and furnace temperature between $600^{\circ}C$ and $1000^{\circ}C$ in $Ar/H_2$. The average particle size of $MgB_2$ showed narrow distribution ranging from 300nm to 400nm. The morphology of particles exhibited mostly spherical shapes and uniform distribution.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.31 no.1
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• pp.41-45
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• 2020

Objective: The objective of this study was to assess serum, hair, and urinary magnesium (Mg) levels in children with attention-deficit/hyperactivity disorder (ADHD), autism spectrum disorder (ASD), and both ASD and ADHD to reveal potential interactive effects. Methods: A total of 148 boys aged 4-9 years old were enrolled in this study, including 44 children with ADHD, 40 pediatric patients with ASD, 32 patients with both ADHD and ASD, as well as 32 healthy neurotypical children. Hair, serum, and urinary Mg levels were assessed using inductively-coupled plasma mass spectrometry (ICP-MS). Laboratory quality control was performed using certified reference materials of human hair, plasma, and urine. Results: No significant group difference in serum Mg levels was observed. Mg content in hair was found to be reduced in children with ADHD and ADHD+ASD compared to that in healthy controls by 11% and 15%, respectively. Urinary Mg levels in children with ADHD+ASD exceeded the control, ADHD, and ASD values by 51, 76, and 65%, respectively. Factorial analysis revealed significant contribution of ADHD to hair and urinary Mg levels. Multiple regression analysis demonstrated that hair and urinary Mg levels were considered as significant predictors of neurodevelopmental disorder complexity. Conclusion: We propose that impaired Mg status may provide a link between ADHD and ASD.

• Nutrition Research and Practice
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• v.6 no.6
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• pp.527-533
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• 2012

It is thought that calcium (Ca) and magnesium (Mg) may be related to mental disorders such as depression; however, there have been few studies investigating the association between Ca and Mg nutrition status with depression in middle-aged female adults. Study subjects in this study included 105 women between the ages of 41 and 57 years. The subjects were divided into three groups according to the Zung Self-rating Depression Scale (SDS) score: Group I (SDS score < 33 percentile; n = 32), Group II (33 percentile ${\leq}$ SDS score < 67 percentile; n = 37), and Group III (67 percentile ${\leq}$ SDS score; n = 36). Anthropometric measurements, dietary intake survey using 3-day dietary records, SDS questionnaire and measurement of serum Ca and Mg were obtained and analyzed. No differences were observed in Ca, plant Ca, and Mg intake among the three groups. However, animal Ca intake by Group III was 141.3 mg, which was significantly lower than 207.6 mg by Group I and 198.3 mg by Group II (P = 0.0345). There were no significant differences in serum levels of Ca, and Mg among the three groups. Correlation analysis indicated that the SDS score had negative correlations with Ca intake (r = -0.2927, P<0.01) and animal Ca (r = -0.3411, P<0.001) after adjusting for age, menopause and energy intake. In conclusion, dietary Ca and animal Ca had negative associations with SDS score among middle-aged Korean female adults. Additional analysis of factors related to the association of calcium and magnesium nutritional status and depression is necessary.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.22 no.3
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• pp.270-281
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• 2019

Purpose: To compare the effectiveness of the magnesium (Mg)-enriched formula vs. control formula in constipated infants. Methods: An open-label, interventional, and the comparator-controlled study was conducted to evaluate the effectiveness of the Mg-enriched formula in formula-fed infants ${\leq}6$ months old presenting with functional constipation according to modified Rome IV criteria. Infants were randomized 1:1 to intervention or control formula for 30 days. Parents recorded stool consistency (hard, normal, or watery) and frequency on days 1-7 and 23-29. Physicians recorded patient baseline characteristics and performed the clinical examination at the time of three patient visits (baseline, day 8, and 30). Results: Of the 286 recruited infants, 143 received the Mg-rich formula and 142 received the control formula. After 7 days, significantly more infants had stools with normal consistency with the Mg-rich formula compared to the infants fed with the control formula (81.8% vs. 41.1%; p<0.001). The number of infants passing one or more stools per day was increased at day 7 in the Mg-rich formula group (86.7% vs. 68.2%; p<0.001). At days 7 and 29, >25% of infants responded completely to the Mg-rich formula compared to <5% of infants fed with the control formula (p<0.001). Parents of infants in the Mg-rich formula group were very satisfied with the treatment (80.8% vs. 10.2%), with the majority willing to continue treatment after 30 days (97.9% vs. 52.6%; p<0.001). Conclusion: The Mg-rich formula significantly improved stool consistency and frequency compared to the control formula in constipated infants.

• Journal of Korea Foundry Society
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• v.22 no.4
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• pp.155-159
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• 2002

Magnesium alloys have high strength to weight ratio and are extremely attractive for applications in transport industry. Most of structural magnesium alloys are manufactured by die casting process. The tensile properties of AZ91HP magnesium alloy were investigated after die casting under various die casting conditions. After die casting by using cold chamber machine, the volume porosity of specimens was examined with density method. With the increase of the volume porosity of specimens, both the tensile strength and elongation were significantly decreased, however the 0.2% offset strength was almost independent of the amount of porosity. With the increase of crystal pressure from 500 to 900 bar during die casting, the volume porosity was decreased, which resulted in the increase of the tensile strength. The mould temperature within the range of $150{\sim}250^{\circ}C$ has not influenced the microstructure with the eutectic phase and tensile properties of specimens. The tensile strength was the highest at 90m/sec of gate speed.

• Transactions of Materials Processing
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• v.16 no.6
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• pp.447-451
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• 2007

The springback characteristics of AZ31B magnesium alloy sheet was investigated in OSU draw/bend test Springback is the elastically-driven change of shape of a part after forming and it should be estimated and controlled to manufacture more precise products in sheet forming. Magnesium alloy sheets have unique mechanical properties such as high in-plane anisotropy/asymmetry of yield stress and hardening response. So, there will be a difference in the prediction of springback with symmetric mechanical properties for magnesium alloy sheets. In this work, the Strip draw/bend tests were conducted with various conditions - die radius, sheet thickness and controlled tensile force and the tendency of springback angle was observed from the tests.