Structural, Electrical and Optical Properties for (Polyvinyl Alcohol–Polyethylene Oxide–Magnesium Oxide) Nanocomposites for Optoelectronics Applications

Qayssar M. Jebur,Ahmed Hashim,Majeed A. Habeeb 한국전기전자재료학회 2019 Transactions on Electrical and Electronic Material Vol.20 No.4

Preparation of polyvinyl alcohol (PVA)–polyethylene oxide (PEO)–magnesium oxide (MgO) nanocomposites and studying their structural, AC electrical and optical properties for dielectric and optoelectronic applications have been investigated. The nanocomposites have been fabricated with diff erent concentrations of (PVA–PEO) blend and MgO nanoparticles. The experimental results showed that the dielectric constant, dielectric loss and AC electrical conductivity of (PVA–PEO) blend are increased with the increase in MgO nanoparticles concentrations. The dielectric constant and dielectric loss of (PVA–PEO) blend are decreased while the AC electrical conductivity increases with the increase in frequency. The optical measurements are showed that the absorbance of (PVA–PEO–MgO) nanocomposites is increased with increasing of the magnesium oxide nanoparticles concentrations. The indirect energy gap (E g ) of (PVA–PEO) blend decreases with an increase inconcentrations of magnesium oxide nanoparticles. The optical constants as absorption coeffi cient, extinction coeffi cient, refractive index, real and imaginary dielectric constants of nanocomposites are variation with increasing of the magnesium oxide nanoparticles weight percentages.

Enhanced Chemical Stability of D-Cycloserine via Tablet Form Containing Magnesium Oxide as an Alkali Stabilizer

Jung Suk Kim,이상민,김동식,김동욱,김경수,조관형,Dong Xun Li,진성규,최한곤 대한화학회 2020 Bulletin of the Korean Chemical Society Vol.41 No.1

The purpose of this study was to improve the chemical stability of D-cycloserine via tablet form containing an alkali stabilizer. The influence of alkalizing agents on the stability of D-cycloserine was investigated at 60 °C/75% RH for 2?days. The drug stability was evaluated with the D-cycloserine-loaded tablets prepared with various amounts of magnesium oxide using direct compression method. Compared to D-cycloserine powder and a commercial D-cycloserine-loaded product, the long-term drug stability on the chosen tablet was assessed at 40, 60, and 40 °C/75% RH during 6?months. Amongst the stabilizers investigated, magnesium oxide most improved the stability of D-cycloserine at the accelerated stress condition. The magnesium oxide/drug ratio of 1 and 2 showed higher remaining drug concentrations than those less than 0.5; however, two formers gave no significant difference in the remaining drug concentrations. Amongst the tablets tested, the formulation composed of D-cycloserine, magnesium oxide, and talc at the weight ratio of 250/250/5 most increased the stability of D-cycloserine. Additionally, due to the alkali and water-proofing property of magnesium oxide, this tablet improved the stability of D-cycloserine compared to the drug powder and commercial product. Hence, this novel tablet with enhanced drug stability would be a candidate for oral pharmaceutical product of D-cycloserine.

Sulfur removal from municipal gas using magnesium oxides and a magnesium oxide/silicon dioxide composite

Kim, Y.H.,Tuan, V.A.,Park, M.K.,Lee, C.H. Elsevier 2014 Microporous and mesoporous materials Vol.197 No.-

<P>Magnesium oxides (MgOs) were synthesized by polyol-meditation thermolysis, hydrothermal, and aerogel methods and utilized to remove sulfur compounds from municipal gas. The capacity to remove methyl mercaptan (291 mu mol/mol) from methane was evaluated by using an adsorption breakthrough method at different temperatures. Then, to improve the sulfur removal capacity, a MgO-SiO2 composite was developed using the aerogel method and its breakthrough capacity was compared to those of the MgOs. The synthesized MgOs and MgO-SiO2 composite were characterized by XRD, BET, TGA, and HR-TEM. The MgO prepared by the aerogel method had the highest surface area and sorptioh capacity among the as-synthesized MgOs. Furthermore, the sulfur sorption capacity of the MgO-SiO2 composite prepared by the same aerogel method as MgO was three times higher than the aerogel MgO even though the sorption capacity of SiO2 was negligible. (C) 2014 Elsevier Inc. All rights reserved.</P>

ORAL BIOLOGY RESEARCH : Original Article ; Osteoblast responses of thermally oxidized magnesium-calciummanganese alloy

( Young Tae Kim ),( Jun Young Cha ),( Xing Hui Piao ),( Young Joon Kim ) 조선대학교 구강생물학연구소 2016 Oral Biology Research (Oral Biol Res) Vol.40 No.1

Magnesium alloys are considered as potential biomedical materials due to their mechanical properties, which approximate cortical bone, as well as their biocompatibility. Thermal oxidation is one surface modification method used to increase the corrosion resistance of biomaterial surfaces. Thus, the aim of this study is to assess physical and biological differences of Mg-Ca-Mn alloy depending on oxidation heat treatment methods. The sample were divided into 3 groups: Group II: pure magnesium as a control group; Group II: untreated Mg-Ca-Mn alloy; Group III: Mg-Ca-Mn alloy treated at 500℃ for 2 hours. Scanning electron microscope assessment, immersion test, roughness test, and MTT assay were used to evaluate surface characteristics and physical and biologic properties of each sample. Oxide-treated Mg-Ca-Mn alloy treated thermally (Group III) showed an oxidized layer and precipitate with granular structure on the surface. During the immersion test, no significant difference was shown in pH values between the groups. The roughness measurements in Group I and Group III were significantly higher than the value in Group II, while there was no meaningful difference between Group I and Group III. The cell viability of Group III was higher than that of Group II, and statistically significant differences were observed on the third and fifth days. Also, significant differences were confirmed in Group III on the third and fifth days. Consequently, oxidation heat treatment, among various methods of surface treatment, can be considered as one method to improve properties in biocompatible materials by creating an oxidation layer on Mg-Ca-Mn alloys.

Mental Change, Cardiovascular Depression and QT Prolongation Caused by Severe Hypermagnesemia

최형오,이성근,이필형,임성남,손병석,정윤희,남기병 대한중환자의학회 2008 Acute and Critical Care Vol.23 No.2

A 50-year-old woman was referred to our hospital for evaluation of mental change and general weakness accompanied by an irregular and weak pulse. She had previously been diagnosed with Bartter`s syndrome and had taken potassium-sparing diuretics. She had developed constipation that had led to abdominal pain and had taken excessive magnesium oxide over a long time. On admission, she was lethargic. Her blood pressure (BP) was 130/74 mmHg, with a heart rate varying from 30 to 78 beats/min. An electrocardiogram (ECG) revealed several abnormalities, including first degree AV block, QT prolongation, sinus pause with a junctional rhythm, and paroxysmal tachycardia alternating with sinus pause. Her serum concentration of magnesium was markedly elevated to 16.19 mg/dl. Hemodialysis and a calcium gluconate infusion was attempted to reduce magnesium levels and to counteract the cardiovascular effect of magnesium. As magnesium levels declined, her general medical condition improved and her ECG changes were normalized. Severe hypermagnesemia should be suspected as the cause of mental change, cardiovascular dysfunction, and variable ECG changes.

마그네슘합금내 개재물 함유량에 따른 파단면의 명도변화

김현식 ( Hyun Sik Kim ),예대희 ( Dea Hee Ye ),강민철 ( Min Cheol Kang ),김정대 ( Jung Dae Kim ),정해용 ( Hae Yong Jeong ) 한국주조공학회 2014 한국주조공학회지 Vol.34 No.6

Pure magnesium and magnesium alloys have been applied to various kinds of industrial fields, especially automotive and electronic parts. These parts are manufactured mainly through a diecasting process. These days, magnesium ingots are used as raw material, and recycled ingots are often used for commercial purposes. But the quality of virgin magnesium and recycled ingots is not secure. Therefore, massive casting defects can occur, and some things manufactured can be damaged by these defects. This study evaluated the inclusions of virgin magnesium and recycled ingot. It also included composition analysis by spectrometer, measuring inclusion contents by SEM & EDS, and performing a brightness test on fractured surfaces. The brightness test is generally very easy and obtains results quickly, so its results have been compared with the results obtained from various test methods. From the test results, we obtained a satisfactory result in evaluating inclusion and oxide. The brightness values are lower as the inclusion contents are higher. When the brightness value is over 47 in AM50A and 44 in AZ91D, the mechanical properties are expected to be good.

High-Temperature Oxidation of AZ91-0.3%Ca-0.1%Y Alloy in Air

이동복,Muhammad Ali Abro,유봉선 대한금속·재료학회 2017 METALS AND MATERIALS International Vol.23 No.4

AZ91 magnesium alloys containing 0.3% Ca and 0.1% Y were cast, and their oxidation behavior was investigatedbetween 425 and 600 °C in atmospheric air to examine roles of Ca and Y during oxidation. During casting, Caformed Al2Ca particles intergranularly, and reduced the amount of Al12Mg17 particles, while most of yttriumexisted as Al2Y particles inter- and intra-granularly in the alloy. The AZ91 alloy oxidized fast above 425 °C, leadingto complete ignition. By contrast, AZ91-0.3Ca-0.1Y alloy oxidized very slowly up to 550 °C. Calcium, whichis more active than Mg, preferentially oxidized to CaO at the surface of the MgO-rich oxide to suppress the oxidation,evaporation and diffusion of Mg during the initial oxidation stage. Such suppression was due to the quitelow vapor pressure and high stoichiometry of CaO. Calcium also suppressed the formation of less oxidation-resistantAl12Mg17 through forming oxidation-resistant Al2Ca in the alloy from the initial oxidation stage.

탄탈륨 산화물의 마그네슘 가스환원에 의한 탄탈륨 금속분말 제조

이동원,Lee, Dong-Won 한국분말야금학회 2018 한국분말재료학회지 (KPMI) Vol.25 No.5

Metallic tantalum powder is manufactured by reducing tantalum oxide ($Ta_2O_5$) with magnesium gas at 1,073-1,223 K in a reactor under argon gas. The high thermodynamic stability of magnesium oxide makes the reduction reaction from tantalum oxide into tantalum powder possible. The microstructure after the reduction reaction has the form of a mixture of tantalum and magnesium oxide, and the latter could be entirely eliminated by dissolving in weak hydrochloric acid. The powder size in SEM microstructure for the tantalum powder increases after acid leaching in the range of 50-300 nm, and its internal crystallite sizes are observed to be 11.5 to 24.7 nm with increasing reduction temperatures. Moreover, the optimized reduction temperature is found to be 1,173 K as the minimum oxygen concentration is approximately 1.3 wt.%.

급속 보수용 마그네슘 인산염 모르타르의 경화 및 강도특성

오홍섭,이인희 한국구조물진단유지관리공학회 2019 한국구조물진단유지관리공학회 논문집 Vol.23 No.3

Damage to the pavement system due to various causes will be required rapid repair work for reopening the vehicle traffic. The magnesium oxide phosphate composite(MPC) has a short curing time and is capable of early compressive strength development, is suitable for rapid repair materials. The aim of this study was to evaluate the hardening and compressive strength characteristics of MPC according to the water-binder (W / B) ratio and magnesium-phosphate(M / P) ratio in order to develop repair materials consisted with light burned magnesia and potassium dihydrogen phosphate. In order to ensure the workability in the field application, the difference of mechanical properties according to standard sand and ordinary sand and performance of retards were evaluated. The mix proportion with W/B ratio was about 35% and the M/P ratio was about 1.0 ~ 1.2 has a superior perfomance with strength and hardening condition. Especially, the strength of composite at only 1 day curing with W/B ratio of 0.35 and the M/P ratio of 1.2 was shown the higher than 25.0 MPa. Boric acid as a retarder was found to be suitable for ensuring the working time, and the purity of magnesium oxide was about 90 ~ 95%, which is effective for ensuring curing time and strength. 다양한 원인에 의한 포장체에 손상이 발생하면 신속한 통행재개를 위한 급속보수가 필요하게 된다. 산화마그네슘인산염복합체의 는 경화시간이 짧고, 조기 강도발현이 가능하여 급속보수재료로 적합한 특성을 갖고 있다. 연구에서는 경소마그네시아와 제1인산칼륨을 결합하여 보수재료로 개발하기 위하여 물-결합재(W/B)비, 마그네슘-인산염(M/P)비 등의 배합비를 조정하면서 경화와 강도특성을 평가하고자 하였다. 그리고 현장 적용시의 작업성을 확보하기 위하여 표준사와 일반모래에 따른 거동차이와 지연제별 특성을 평가하였다. 실험결과 물-결합재비는 35%내외와 마그네슘-인산염비는 1.0~1.2 내외가 강도측면에서 가장 적합한 것으로 분석되었다. W/B비 0.35, M/P비 1.2 변수에서 1일강도 25.0MPa 이상 발현되어 조기 보수재료로서 활용가능성이 충분한 것으로 분석되었다. 작업시간 확보를 위해서는 붕산을 지연제로 사용하는 것이 적합한 것으로 나타났으며, 산화마그네슘의 순도는 90~95%내외가 경화시간 확보를 위해 효과적인 것으로 나타났다.

마그네슘 합금 안경테의 Plasma Electrolytic Oxidation표면처리 효과 연구

김기홍 한국안광학회 2010 한국안광학회지 Vol.15 No.4

Purpose: The purpose of this study was to investigate the surface characteristics of plasma electrolytic oxidation (PEO) surface treatment on AZ31 magnesium alloy eyeglass frames. Methods: The plasma electrolytic oxidation (PEO) surface was created by varying the DC voltage. The oxidation layer of coating was measured using phase analysis by X-ray diffraction. The microstructural morphology was observed using a scanning electron microscopy. Coating layer and the concentration of elements were investigated using the energy dispersive X-ray spectra. Results: The MgO XRD peak was increased as the voltage increased, and the density of the surface oxide film was also increased. The changes in the composition of the EDS also showed a good agreement. Conclusions: The compound oxide crystallization of PEO oxide film layer was done by increasing formation of MgO as the voltage increased. The treatment at 65V and 60 sec showed the best results at surface state, contact angles and salt spray test. 목적: 이 연구 목적은 가공한 마그네슘 합금 AZ31 안경테를 plasma electrolytic oxidation(PEO) 표면 처리 후 표 면특성에 대하여 조사하는 것이다. 방법: Plasma electrolytic oxidation(PEO) 표면 처리는 DC 전압을 변화시키며 처 리하였고, 피막의 상 분석은 X-ray 회절기로 측정하였고, 형태학적 미세구조는 주사전자현미경로 관찰하였다. 그리 고 피막층에 존재하는 원소의 농도를 에너지 분산 X-선 스펙트럼으로 조사하였다. 결과: PEO 처리시 전압이 증가 함에 따라 XRD 측정 결과 MgO 피크가 증가하였으며, SEM 사진에서는 표면의 산화피막이 조밀하게 생기는 것을 확인 할 수 있었다. 그리고 EDS에서 성분의 변화도 일치함을 보여주었다. 결론: PEO 산화피막층은 전압이 증가 할 수록 MgO 화합물의 형성이 점점 증가하기 때문에 산화막의 결정화가 진행되며, 65V에 60초 처리 시 표면상태, 접 촉각, 내식성 시험에서 가장 좋은 결과를 보여 주었다.