Retardation of surface corrosion of biodegradable magnesium-based materials by aluminum ion implantation

NASA Astrophysics Data System (ADS)

Wu, Guosong; Xu, Ruizhen; Feng, Kai; Wu, Shuilin; Wu, Zhengwei; Sun, Guangyong; Zheng, Gang; Li, Guangyao; Chu, Paul K.

2012-07-01

Aluminum ion implantation is employed to modify pure Mg as well as AZ31 and AZ91 magnesium alloys and their surface degradation behavior in simulated body fluids is studied. Polarization tests performed in conjunction with scanning electron microscopy (SEM) reveal that the surface corrosion resistance after Al ion implantation is improved appreciably. This enhancement can be attributed to the formation of a gradient surface structure with a gradual transition from an Al-rich oxide layer to Al-rich metal layer. Compared to the high Al-content magnesium alloy (AZ91), a larger reduction in the degradation rate is achieved from pure magnesium and AZ31. Our results reveal that the surface corrosion resistance of Mg alloys with no or low Al content can be improved by Al ion implantation.

Ultrasound-assisted activation of zero-valent magnesium for nitrate denitrification: identification of reaction by-products and pathways.

PubMed

Ileri, Burcu; Ayyildiz, Onder; Apaydin, Omer

2015-07-15

Zero-valent magnesium (Mg(0)) was activated by ultrasound (US) in an aim to promote its potential use in water treatment without pH control. In this context, nitrate reduction was studied at batch conditions using various doses of magnesium powder and ultrasound power. While neither ultrasound nor zero-valent magnesium alone was effective for reducing nitrate in water, their combination removed up to 90% of 50 mg/L NO3-N within 60 min. The rate of nitrate reduction by US/Mg(0) enhanced with increasing ultrasonic power and magnesium dose. Nitrogen gas (N2) and nitrite (NO2(-)) were detected as the major reduction by-products, while magnesium hydroxide Mg(OH)2 and hydroxide ions (OH(-)) were identified as the main oxidation products. The results from SEM-EDS measurements revealed that the surface oxide level decreased significantly when the samples of Mg(0) particles were exposed to ultrasonic treatment. The surface passivation of magnesium particles was successfully minimized by mechanical forces of ultrasound, which in turn paved the way to sustain the catalyst activity toward nitrate reduction. Copyright © 2015 Elsevier B.V. All rights reserved.

Surface properties of calcium and magnesium oxide nanopowders grafted with unsaturated carboxylic acids studied with inverse gas chromatography.

PubMed

Maciejewska, Magdalena; Krzywania-Kaliszewska, Alicja; Zaborski, Marian

2012-09-28

Inverse gas chromatography (IGC) was applied at infinite dilution to evaluate the surface properties of calcium and magnesium oxide nanoparticles and the effect of surface grafted unsaturated carboxylic acid on the nanopowder donor-acceptor characteristics. The dispersive components (γ(s)(D)) of the free energy of the nanopowders were determined by Gray's method, whereas their tendency to undergo specific interactions was estimated based on the electron donor-acceptor approach presented by Papirer. The calcium and magnesium oxide nanoparticles exhibited high surface energies (79 mJ/m² and 74 mJ/m², respectively). Modification of nanopowders with unsaturated carboxylic acids decreased their specific adsorption energy. The lowest value of γ(s)(D) was determined for nanopowders grafted with undecylenic acid, approximately 55 mJ/m². The specific interactions were characterised by the molar free energy (ΔG(A)(SP)) and molar enthalpy (ΔH(A)(SP)) of adsorption as well as the donor and acceptor interaction parameters (K(A), K(D)). Copyright © 2012 Elsevier B.V. All rights reserved.

Growth, stability and decomposition of Mg2Si ultra-thin films on Si (100)

NASA Astrophysics Data System (ADS)

Sarpi, B.; Zirmi, R.; Putero, M.; Bouslama, M.; Hemeryck, A.; Vizzini, S.

2018-01-01

Using Auger Electron Spectroscopy (AES), Scanning Tunneling Microscopy/Spectroscopy (STM/STS) and Low Energy Electron Diffraction (LEED), we report an in-situ study of amorphous magnesium silicide (Mg2Si) ultra-thin films grown by thermally enhanced solid-phase reaction of few Mg monolayers deposited at room temperature (RT) on a Si(100) surface. Silicidation of magnesium films can be achieved in the nanometric thickness range with high chemical purity and a high thermal stability after annealing at 150 °C, before reaching a regime of magnesium desorption for temperatures higher than 350 °C. The thermally enhanced reaction of one Mg monolayer (ML) results in the appearance of Mg2Si nanometric crystallites leaving the silicon surface partially uncovered. For thicker Mg deposition nevertheless, continuous 2D silicide films are formed with a volcano shape surface topography characteristic up to 4 Mg MLs. Due to high reactivity between magnesium and oxygen species, the thermal oxidation process in which a thin Mg2Si film is fully decomposed (0.75 eV band gap) into a magnesium oxide layer (6-8 eV band gap) is also reported.

Defects in oxide surfaces studied by atomic force and scanning tunneling microscopy

PubMed Central

König, Thomas; Simon, Georg H; Heinke, Lars; Lichtenstein, Leonid

2011-01-01

Summary Surfaces of thin oxide films were investigated by means of a dual mode NC-AFM/STM. Apart from imaging the surface termination by NC-AFM with atomic resolution, point defects in magnesium oxide on Ag(001) and line defects in aluminum oxide on NiAl(110), respectively, were thoroughly studied. The contact potential was determined by Kelvin probe force microscopy (KPFM) and the electronic structure by scanning tunneling spectroscopy (STS). On magnesium oxide, different color centers, i.e., F0, F+, F2+ and divacancies, have different effects on the contact potential. These differences enabled classification and unambiguous differentiation by KPFM. True atomic resolution shows the topography at line defects in aluminum oxide. At these domain boundaries, STS and KPFM verify F2+-like centers, which have been predicted by density functional theory calculations. Thus, by determining the contact potential and the electronic structure with a spatial resolution in the nanometer range, NC-AFM and STM can be successfully applied on thin oxide films beyond imaging the topography of the surface atoms. PMID:21977410

Improved biological performance of magnesium by micro-arc oxidation

PubMed Central

Ma, W.H.; Liu, Y.J.; Wang, W.; Zhang, Y.Z.

2014-01-01

Magnesium and its alloys have recently been used in the development of lightweight, biodegradable implant materials. However, the corrosion properties of magnesium limit its clinical application. The purpose of this study was to comprehensively evaluate the degradation behavior and biomechanical properties of magnesium materials treated with micro-arc oxidation (MAO), which is a new promising surface treatment for developing corrosion resistance in magnesium, and to provide a theoretical basis for its further optimization and clinical application. The degradation behavior of MAO-treated magnesium was studied systematically by immersion and electrochemical tests, and its biomechanical performance when exposed to simulated body fluids was evaluated by tensile tests. In addition, the cell toxicity of MAO-treated magnesium samples during the corrosion process was evaluated, and its biocompatibility was investigated under in vivo conditions. The results of this study showed that the oxide coating layers could elevate the corrosion potential of magnesium and reduce its degradation rate. In addition, the MAO-coated sample showed no cytotoxicity and more new bone was formed around it during in vivo degradation. MAO treatment could effectively enhance the corrosion resistance of the magnesium specimen and help to keep its original mechanical properties. The MAO-coated magnesium material had good cytocompatibility and biocompatibility. This technique has an advantage for developing novel implant materials and may potentially be used for future clinical applications. PMID:25517917

Phenolic Modified Ceramic Coating on Biodegradable Mg Alloy: The Improved Corrosion Resistance and Osteoblast-Like Cell Activity.

PubMed

Lee, Hung-Pang; Lin, Da-Jun; Yeh, Ming-Long

2017-06-25

Magnesium alloys have great potential for developing orthopedic implants due to their biodegradability and mechanical properties, but the rapid corrosion rate of the currently-available alloys limits their clinical applications. To increase the corrosion resistance of the substrate, a protective ceramic coating is constructed by a micro-arc oxidation (MAO) process on ZK60 magnesium alloy. The porous ceramic coating is mainly composed of magnesium oxide and magnesium silicate, and the results from cell cultures show it can stimulate osteoblastic cell growth and proliferation. Moreover, gallic acid, a phenolic compound, was successfully introduced onto the MAO coating by grafting on hydrated oxide and chelating with magnesium ions. The gallic acid and rough surface of MAO altered the cell attachment behavior, making it difficult for fibroblasts to adhere to the MAO coating. The viability tests showed that gallic acid could suppress fibroblast growth and stimulate osteoblastic cell proliferation. Overall, the porous MAO coating combined with gallic acid offered a novel strategy for increasing osteocompatibility.

Phenolic Modified Ceramic Coating on Biodegradable Mg Alloy: The Improved Corrosion Resistance and Osteoblast-Like Cell Activity

PubMed Central

Lee, Hung-Pang; Lin, Da-Jun; Yeh, Ming-Long

2017-01-01

Magnesium alloys have great potential for developing orthopedic implants due to their biodegradability and mechanical properties, but the rapid corrosion rate of the currently-available alloys limits their clinical applications. To increase the corrosion resistance of the substrate, a protective ceramic coating is constructed by a micro-arc oxidation (MAO) process on ZK60 magnesium alloy. The porous ceramic coating is mainly composed of magnesium oxide and magnesium silicate, and the results from cell cultures show it can stimulate osteoblastic cell growth and proliferation. Moreover, gallic acid, a phenolic compound, was successfully introduced onto the MAO coating by grafting on hydrated oxide and chelating with magnesium ions. The gallic acid and rough surface of MAO altered the cell attachment behavior, making it difficult for fibroblasts to adhere to the MAO coating. The viability tests showed that gallic acid could suppress fibroblast growth and stimulate osteoblastic cell proliferation. Overall, the porous MAO coating combined with gallic acid offered a novel strategy for increasing osteocompatibility. PMID:28773055

Understanding growth mechanisms and tribocorrosion behaviour of porous TiO2 anodic films containing calcium, phosphorous and magnesium

NASA Astrophysics Data System (ADS)

Oliveira, Fernando G.; Ribeiro, Ana R.; Perez, Geronimo; Archanjo, Bráulio S.; Gouvea, Cristol P.; Araújo, Joyce R.; Campos, Andrea P. C.; Kuznetsov, Alexei; Almeida, Clara M.; Maru, Márcia M.; Achete, Carlos A.; Ponthiaux, Pierre; Celis, Jean-Pierre; Rocha, Luis A.

2015-06-01

The growth of the dental implant market increases the concern regarding the quality, efficiency, and lifetime of dental implants. Titanium and its alloys are dominant materials in this field thanks to their high biocompatibility and corrosion resistance, but they possess a very low wear resistance. Besides problems related to osteointegration and bacterial infections, tribocorrosion phenomena being the simultaneous action between corrosion and wear, are likely to occur during the lifetime of the implant. Therefore, tribocorrosion resistant surfaces are needed to guarantee the preservation of dental implants. This work focused on the incorporation of magnesium, together with calcium and phosphorous, in the structure of titanium oxide films produced by micro-arc oxidation (MAO). The characterization of morphology, chemical composition, and crystalline structure of the surfaces provided important insights leading to (1) a better understanding of the oxide film growth mechanisms during the MAO treatment; and (2) a better awareness on the degradation process during tribocorrosion tests. The addition of magnesium was shown to support the formation of rutile which improves the tribocorrosion properties of the surfaces.

The fabrication and hydrophobic property of micro-nano patterned surface on magnesium alloy using combined sparking sculpture and etching route

NASA Astrophysics Data System (ADS)

Wu, Yunfeng; Wang, Yaming; Liu, Hao; Liu, Yan; Guo, Lixin; Jia, Dechang; Ouyang, Jiahu; Zhou, Yu

2016-12-01

Magnesium alloy with micro-nano structure roughness surface, can serve as the loading reservoirs of medicine capsule and industrial lubricating oil, or mimic 'lotus leaf' hydrophobic surface, having the potential applications in medical implants, automobile, aerospace and electronic products, etc. Herein, we propose a novel strategy to design a micro-nano structure roughness surface on magnesium alloy using combined microarc sparking sculpture and etching in CrO3 aqueous solution. A hydrophobic surface (as an applied example) was further fabricated by chemical decorating on the obtained patterned magnesium alloy surface to enhance the corrosion resistance. The results show that the combined micro-nano structure of 7-9 μm diameter big pores insetting with nano-scale fine pores was duplicated after etched the sparking sculptured 'over growth' oxide regions towards the magnesium substrate. The micro-nano structure surface was chemically decorated using AgNO3 and stearic acid, which enables the contact angle increased from 60° to 146.8°. The increasing contact angle is mainly attributed to the micro-nano structure and the chemical composition. The hydrophobic surface of magnesium alloy improved the corrosion potential from -1.521 V of the bare magnesium to -1.274 V. Generally, the sparking sculpture and then etching route demonstrates a low-cost, high-efficacy method to fabricate a micro-nano structure hydrophobic surface on magnesium alloy. Furthermore, our research on the creating of micro-nano structure roughness surface and the hydrophobic treatment can be easily extended to the other metal materials.

Problems of magnesium oxide wallboard usage in construction

NASA Astrophysics Data System (ADS)

Gravit, Marina; Zybina, Olga; Vaititckii, Artem; Kopytova, Anna

2017-10-01

Magnesium oxide wallboard is the building and finishing material, which has a reputation of new generational ecological constructing material. It has a wide range of uses: as a revetment in ventilated facades’ production, as a decorative material, as different types of formworks for a foundation filling and as a protector against a fire threat. During the study it was considered that magnesium oxide wallboards have some defects, such as moisture formation as a concentrated brine on the surface under special climatic conditions and absence of clear distinguishing between different types of magnesia boards. Usage of this material can become a cause of frame’s corrosion and origin of mold on wooden details. Authors provide the information from a foreign data source about negative consequences of SML usage. In conclusion researchers state that it is necessary to provide a clear magnesium wallboards classification and define technical requirements, which will, in their opinion, lead to Russian standard formulation.

Activation of Magnesium Lignosulfonate and Kraft Lignin: Influence on the Properties of Phenolic Resin-Based Composites for Potential Applications in Abrasive Materials

PubMed Central

Klapiszewski, Lukasz; Jamrozik, Artur; Strzemiecka, Beata; Matykiewicz, Danuta; Voelkel, Adam; Jesionowski, Teofil

2017-01-01

Magnesium lignosulfonate and kraft lignin were activated by different oxidizing agents for use in phenolic resin composites used for the production of abrasive components. The physicochemical properties of the oxidized materials were analyzed by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), dynamic mechanical-thermal analysis (DMTA) and inverse gas chromatography (IGC). The homogeneity of the model abrasive composites containing the studied products was assessed based on observations obtained using a scanning electron microscope (SEM). FTIR and XPS analysis of the oxidized products indicated that the activation process leads mainly to the formation of carbonyl groups. The IGC technique was used to assess changes in the surface energy and the acid–base properties of the studied biopolymers. The changes in the acid–base properties suggest that more groups acting as electron donors appear on the oxidized surface of the materials. DMTA studies showed that the model composites with 5% magnesium lignosulfonate oxidized by H2O2 had the best thermomechanical properties. Based on the results it was possible to propose a hypothetical mechanism of the oxidation of the natural polymers. The use of such oxidized products may improve the thermomechanical properties of abrasive articles. PMID:28594358

Plastic deformation of a magnesium oxide 001-plane surface produced by cavitation

NASA Technical Reports Server (NTRS)

Hattori, S.; Miyoshi, K.; Buckley, D. H.; Okada, T.

1986-01-01

An investigation was conducted to examine plastic deformation of a cleaved single-crystal magnesium oxide 001-plane surface exposed to cavitation. Cavitation damage experiments were carried out in distilled water at 25 C by using a magnetostrictive oscillator in close proximity (2 mm) to the surface of the cleaved specimen. The dislocation-etch-pit patterns induced by cavitation were examined and compared with that of microhardness indentations. The results revealed that dislocation-etch-pit patterns around hardness indentations contain both screw and edge dislocations, while the etch-pit patterns on the surface exposed to cavitation contain only screw dislocations. During cavitation, deformation occurred in a thin surface layer, accompanied by work-hardening of the ceramic. The row of screw dislocations underwent a stable growth, which was analyzed crystallographically.

Effect of Adding SiO2-Al2O3 Sol into Anodizing Bath on Corrosion Resistance of Oxidation Film on Magnesium Alloy

NASA Astrophysics Data System (ADS)

Liu, Huicong; Zhu, Liqun; Li, Weiping

Due to the widely use in automobile and construction field, AZ91D magnesium alloy need to be protected more effectively for its high chemical activity. In this paper, three kinds of films were formed on magnesium alloy. The first kind of film, named as anodic oxidation film, was prepared by anodic oxidation in the alkaline solution. The processes for preparing the second kind of film, named as multiple film, involved coating sol-gel on the samples and heat-treating before anodic oxidation. The third kind of film was prepared by anodic oxidation in the alkaline oxidation solution containning 5% (vol) SiO2-Al2O3 sol, named as modified oxidation film. The corrosion resistance of the three different films was investigated. The results showed that the modified oxidation film had the highest corrosion resistance due to the largest thickness and most dense surface morphology. Sol was discussed to react during the film forming process, which leaded to the difference between modified oxidation film and anodic oxidation film.

Adsorption of Atoms of 3 d Metals on the Surfaces of Aluminum and Magnesium Oxide Films

NASA Astrophysics Data System (ADS)

Ramonova, A. G.; Kibizov, D. D.; Kozyrev, E. N.; Zaalishvili, V. B.; Grigorkina, G. S.; Fukutani, K.; Magkoev, T. T.

2018-01-01

The adsorption and formation of submonolayer structures of Ti, Cr, Fe, Ni, Cu on the surfaces of aluminum and magnesium oxide films formed on Mo(110) under ultrahigh vacuum conditions are studied via X-ray, ultraviolet photo-, and Auger electron spectroscopy (XPS, UVES, AES); spectroscopy of energy losses of high-resolution electrons (SELHRE); spectroscopy of the backscattering of low-energy ions (SBSLEI); infrared absorption spectroscopy (IAS); and the diffraction of slow electrons (DSE). Individual atoms and small clusters of all the investigated metals deposited on oxides acquire a positive charge, due presumably to interaction with surface defects. As the concentration of adatoms increases when the adsorption centers caused by defects are filled, charge transfer from adatoms to substrates is reduced. This is accompanied by further depolarization caused by the lateral interaction of adatoms.

Single Crystal Membranes

NASA Technical Reports Server (NTRS)

Stormont, R. W.; Morrison, A.

1974-01-01

Single crystal a- and c-axis tubes and ribbons of sodium beta-alumina and sodium magnesium beta-alumina were grown from sodium oxide rich melts. Additional experiments grew ribbon crystals containing sodium magnesium beta, beta double prime, beta triple prime, and beta quadruple prime. A high pressure crystal growth chamber, sodium oxide rich melts, and iridium for all surfaces in contact with the melt were combined with the edge-defined, film-fed growth technique to grow the single crystal beta-alumina tubes and ribbons. The crystals were characterized using metallographic and X-ray diffraction techniques, and wet chemical analysis was used to determine the sodium, magnesium, and aluminum content of the grown crystals.

Systematic understanding of corrosion behavior of plasma electrolytic oxidation treated AZ31 magnesium alloy using a mouse model of subcutaneous implant.

PubMed

Jang, Yongseok; Tan, Zongqing; Jurey, Chris; Collins, Boyce; Badve, Aditya; Dong, Zhongyun; Park, Chanhee; Kim, Cheol Sang; Sankar, Jagannathan; Yun, Yeoheung

2014-12-01

This study was conducted to identify the differences between corrosion rates, corrosion types, and corrosion products in different physiological environments for AZ31 magnesium alloy and plasma electrolytic oxidation (PEO) treated AZ31 magnesium alloy. In vitro and in vivo tests were performed in Hank's Balanced Salt Solution (HBSS) and mice for 12 weeks, respectively. The corrosion rates of both AZ31 magnesium alloy and PEO treated AZ31 magnesium alloy were calculated based on DC polarization curves, volume of hydrogen evolution, and the thickness of corrosion products formed on the surface. Micro X-ray computed tomography (Micro-CT), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) were used to analyze morphological and chemical characterizations of corrosion products. The results show that there is more severe localized corrosion after in vitro test in HBSS; however, the thicknesses of corrosion products formed on the surface for AZ31 magnesium alloy and PEO treated AZ31 magnesium alloy in vivo were about 40% thicker than the thickness of corrosion products generated in vitro. The ratio of Ca and P (Ca/P) in the corrosion products also differed. The Ca deficient region and higher content of Al in corrosion product than AZ31 magnesium alloy were identified after in vivo test in contrast with the result of in vitro test. Copyright © 2014 Elsevier B.V. All rights reserved.

Effect of Native Oxide Film on Commercial Magnesium Alloys Substrates and Carbonate Conversion Coating Growth and Corrosion Resistance

PubMed Central

Feliu, Sebastián; Samaniego, Alejandro; Bermudez, Elkin Alejandro; El-Hadad, Amir Abdelsami; Llorente, Irene; Galván, Juan Carlos

2014-01-01

Possible relations between the native oxide film formed spontaneously on the AZ31 and AZ61 magnesium alloy substrates with different surface finish, the chemistry of the outer surface of the conversion coatings that grows after their subsequent immersion on saturated aqueous NaHCO3 solution treatment and the enhancement of corrosion resistance have been studied. The significant increase in the amount of aluminum and carbonate compounds on the surface of the conversion coating formed on the AZ61 substrate in polished condition seems to improve the corrosion resistance in low chloride ion concentration solutions. In contrast, the conversion coatings formed on the AZ31 substrates in polished condition has little effect on their protective properties compared to the respective as-received surface. PMID:28788582

Effect of Native Oxide Film on Commercial Magnesium Alloys Substrates and Carbonate Conversion Coating Growth and Corrosion Resistance.

PubMed

Feliu, Sebastián; Samaniego, Alejandro; Bermudez, Elkin Alejandro; El-Hadad, Amir Abdelsami; Llorente, Irene; Galván, Juan Carlos

2014-03-28

Possible relations between the native oxide film formed spontaneously on the AZ31 and AZ61 magnesium alloy substrates with different surface finish, the chemistry of the outer surface of the conversion coatings that grows after their subsequent immersion on saturated aqueous NaHCO₃ solution treatment and the enhancement of corrosion resistance have been studied. The significant increase in the amount of aluminum and carbonate compounds on the surface of the conversion coating formed on the AZ61 substrate in polished condition seems to improve the corrosion resistance in low chloride ion concentration solutions. In contrast, the conversion coatings formed on the AZ31 substrates in polished condition has little effect on their protective properties compared to the respective as-received surface.

Detection of defects in laser welding of AZ31B magnesium alloy in zero-gap lap joint configuration by a real-time spectroscopic analysis

NASA Astrophysics Data System (ADS)

Harooni, Masoud; Carlson, Blair; Kovacevic, Radovan

2014-05-01

The effect of surface oxide layer existing at the lap-joint faying surface of magnesium sheets is investigated on the keyhole dynamics of the weld pool and weld bead qualities. It is observed that by removing the oxide layer from the faying surface of the lap joint, a high quality weld can be achieved in the laser welding process. However, the presence of an oxide layer deteriorates the quality of the weld by forming pores at the interface of the two overlapped sheets. The purpose of this paper is to identify the correlation between the integrity of the weld and the interaction between the laser and material. A spectroscopy sensor was applied to detect the spectra emitted from a plasma plume during the laser welding of AZ31B magnesium alloy in a zero-gap lap joint configuration. The electron temperature was calculated by applying a Boltzmann plot method based on the detected spectra, and the correlation between the pore formation and the spectral signals was studied. The laser molten pool and the keyhole condition were monitored in real-time by a high speed charge-coupled device (CCD) camera. A green laser was used as an illumination source in order to detect the influence of the oxide layer on the dynamic behavior of the molten pool. Results revealed that the detected spectrum and weld defects had a meaningful correlation for real-time monitoring of the weld quality during laser welding of magnesium alloys.

The impact of LDEF results on the space application of metal matrix composites

NASA Technical Reports Server (NTRS)

Steckel, Gary L.; Le, Tuyen D.

1993-01-01

Over 200 graphite/aluminum and graphite/magnesium composites were flown on the leading and trailing edges of LDEF on the Advanced Composites Experiment. The performance of these composites was evaluated by performing scanning electron microscopy and x-ray photoelectron spectroscopy of exposed surfaces, optical microscopy of cross sections, and on-orbit and postflight thermal expansion measurements. Graphite/aluminum and graphite/magnesium were found to be superior to graphite/polymer matrix composites in that they are inherently resistant to atomic oxygen and are less susceptible to thermal cycling induced microcracking. The surface foils on graphite/aluminum and graphite/magnesium protect the graphite fibers from atomic oxygen and from impact damage from small micrometeoroid or space debris particles. However, the surface foils were found to be susceptible to thermal fatigue cracking arising from contamination embrittlement, surface oxidation, or stress risers. Thus, the experiment reinforced requirements for carefully protecting these composites from prelaunch oxidation or corrosion, avoiding spacecraft contamination, and designing composite structures to minimize stress concentrations. On-orbit strain measurements demonstrated the importance of through-thickness thermal conductivity in composites to minimize thermal distortions arising from thermal gradients. Because of the high thermal conductivity of aluminum, thermal distortions were greatly reduced in the LDEF thermal environment for graphite/aluminum as compared to graphite/magnesium and graphite/polymer composites. The thermal expansion behavior of graphite/aluminum and graphite/magnesium was stabilized by on-orbit thermal cycling in the same manner as observed in laboratory tests.

Effects of environment on microhardness of magnesium oxide

NASA Technical Reports Server (NTRS)

Ishigaki, H.; Buckley, D. H.

1982-01-01

Micro-Vickers hardness measurements of magnesium oxide single crystals were conducted in various environments. These environments included air, nitrogen gas, water, mineral oil with or without various additives, and aqueous solutions with various pH values. Indentations were made on the (100) plane with the diagonals of the indentation in the (100) direction. The results indicate that a sulfur containing additve in mineral oil increased hardness, a chlorine containing additive in mineral oil decreased hardness, and aqueous solutions of hydrogen chloride decreased hardness. Other environments were found to have little effect on hardness. Mechanically polished surfaces showed larger indentation creep than did as-cleaved surfaces.

In situ loading of well-dispersed silver nanoparticles on nanocrystalline magnesium oxide for real-time monitoring of catalytic reactions by surface enhanced Raman spectroscopy.

PubMed

Zhang, Kaige; Li, Gongke; Hu, Yuling

2015-10-28

The surface-enhanced Raman spectroscopy (SERS) technique is of great importance for insight into the transient reaction intermediates and mechanistic pathways involved in heterogeneously catalyzed chemical reactions under actual reaction conditions, especially in water. Herein, we demonstrate a facile method for in situ synthesis of nanocrystalline magnesium oxide-Ag(0) (nano MgO-Ag(0)) hybrid nanomaterials with dispersed Ag nanoparticles (Ag NPs) on the surface of nanocrystalline magnesium oxide (nano MgO) via Sn(2+) linkage and reduction. As a benefit from the synergy effect of nano MgO and Ag NPs, the nano MgO-Ag(0) exhibited both excellent SERS and catalytic activities for the reduction of 4-nitrothiophenol in the presence of NaBH4. The nano MgO-Ag(0) was used for real-time monitoring of the catalytic reaction process of 4-nitrothiophenol to 4-aminothiophenol in an aqueous medium by observing the SERS signals of the reactant, intermediate and final products. The intrinsic reaction kinetics and reaction mechanism of this reaction were also investigated. This SERS-based synergy technique provides a novel approach for quantitative in situ monitoring of catalytic chemical reaction processes.

Structure and in vitro bioactivity of ceramic coatings on magnesium alloys by microarc oxidation

NASA Astrophysics Data System (ADS)

Yu, Huijun; Dong, Qing; Dou, Jinhe; Pan, Yaokun; Chen, Chuanzhong

2016-12-01

Magnesium and its alloys have the potential to serve as lightweight, degradable, biocompatible and bioactive orthopedic implants for load-bearing applications. However, severe local corrosion attack and high corrosion rate have prevented their further clinical use. Micro-arc oxidation (MAO) is proved to be a simple, controllable and efficient electrochemistry technique that can prepare protective ceramic coatings on magnesium alloys. In this paper, electrolyte containing silicate salts was used for microarc oxidation to form ceramic bioactive coatings on the ZK61 alloy substrate. The structure characteristics and element distributions of the coating were investigated by XRD, TEM, SEM and EPMA. The MAO samples were immersed in simulated body fluid (SBF) for 7 and 14 days, respectively. The surface characteristic of the immersed coatings was investigated by Fourier-transform infrared (FTIR) spectroscopy. The results show that these MAO coatings have low crystallinity and are mainly composed of MgO, Mg2SiO4 and Mg2Si2O6. The coating surface is porous. During the SBF immersion period, the nucleation and precipitation of bone-like apatites occur on the MAO coating surface. The corrosion resistance of the substrate is improved by the MAO coatings.

Magnesium Recycling of Partially Oxidized, Mixed Magnesium-Aluminum Scrap through Combined Refining and Solid Oxide Membrane Electrolysis Processes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiaofei Guan; Peter A. Zink; Uday B. Pal

2012-01-01

Pure magnesium (Mg) is recycled from 19g of partially oxidized 50.5wt.% Mg-Aluminum (Al) alloy. During the refining process, potentiodynamic scans (PDS) were performed to determine the electrorefining potential for magnesium. The PDS show that the electrorefining potential increases over time as the magnesium content inside the Mg-Al scrap decreases. Up to 100% percent of magnesium is refined from the Mg-Al scrap by a novel refining process of dissolving magnesium and its oxide into a flux followed by vapor phase removal of dissolved magnesium and subsequently condensing the magnesium vapor. The solid oxide membrane (SOM) electrolysis process is employed in themore » refining system to enable additional recycling of magnesium from magnesium oxide (MgO) in the partially oxidized Mg-Al scrap. The combination of the refining and SOM processes yields 7.4g of pure magnesium.« less

Growth Kinetics of the S Sub H Center on Magnesium Oxide Using Electron Paramagnetic Resonance

NASA Technical Reports Server (NTRS)

Jayne, J. P.

1971-01-01

Electron paramagnetic resonance spectroscopy was used to study the growth of S sub H centers on magnesium oxide powder which had hydrogen adsorbed on its surface. The centers were produced by ultraviolet radiation. The effects of both radiation intensity and hydrogen pressure were also studied. At constant hydrogen pressure and radiation dose, the initial S sub H center growth rate was found to be zero order. Beyond the initial region the growth rate deviated from zero order and finally approached saturation. The results are interpreted in terms of a model which assumes that the S sub H center is a hydrogen atom associated with a surface vacancy. Saturation appears to result from a limited supply of surface vacancies.

Magnesium Recycling of Partially Oxidized, Mixed Magnesium-Aluminum Scrap Through Combined Refining and Solid Oxide Membrane (SOM) Electrolysis Processes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guan, Xiaofei; Zink, Peter; Pal, Uday

2012-03-11

Pure magnesium (Mg) is recycled from 19g of partially oxidized 50.5wt.%Mg-Aluminum (Al) alloy. During the refining process, potentiodynamic scans (PDS) were performed to determine the electrorefining potential for magnesium. The PDS show that the electrorefining potential increases over time as the Mg content inside the Mg-Al scrap decreases. Up to 100% percent of magnesium is refined from the Mg-Al scrap by a novel refining process of dissolving magnesium and its oxide into a flux followed by vapor phase removal of dissolved magnesium and subsequently condensing the magnesium vapors in a separate condenser. The solid oxide membrane (SOM) electrolysis process ismore » employed in the refining system to enable additional recycling of magnesium from magnesium oxide (MgO) in the partially oxidized Mg-Al scrap. The combination of the refining and SOM processes yields 7.4g of pure magnesium; could not collect and weigh all of the magnesium recovered.« less

The analysis of magnesium oxide hydration in three-phase reaction system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Xiaojia; Guo, Lin; Chen, Chen

In order to investigate the magnesium oxide hydration process in gas–liquid–solid (three-phase) reaction system, magnesium hydroxide was prepared by magnesium oxide hydration in liquid–solid (two-phase) and three-phase reaction systems. A semi-empirical model and the classical shrinking core model were used to fit the experimental data. The fitting result shows that both models describe well the hydration process of three-phase system, while only the semi-empirical model right for the hydration process of two-phase system. The characterization of the hydration product using X-Ray diffraction (XRD) and scanning electron microscope (SEM) was performed. The XRD and SEM show hydration process in the two-phasemore » system follows common dissolution/precipitation mechanism. While in the three-phase system, the hydration process undergo MgO dissolution, Mg(OH){sub 2} precipitation, Mg(OH){sub 2} peeling off from MgO particle and leaving behind fresh MgO surface. - Graphical abstract: There was existence of a peeling-off process in the gas–liquid–solid (three-phase) MgO hydration system. - Highlights: • Magnesium oxide hydration in gas–liquid–solid system was investigated. • The experimental data in three-phase system could be fitted well by two models. • The morphology analysis suggested that there was existence of a peel-off process.« less

In vitro biocompatibility of magnesium-incorporated submicro-porous titanium oxide surface produced by hydrothermal treatment

NASA Astrophysics Data System (ADS)

Park, Jin-Woo; Kim, Youn-Jeong; Jang, Je-Hee; An, Chang-Hyeon

2010-11-01

This study investigated the surface characteristics and in vitro biocompatibility of titanium (Ti) oxide surface incorporating magnesium ions (Mg), produced by hydrothermal treatment using an alkaline Mg-containing solution, for future biomedical applications. The surface characteristics were evaluated by scanning electron microscopy, thin-film X-ray diffractometry, X-ray photoelectron spectroscopy, inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and optical profilometry. Mouse calvaria-derived osteoblastic cell (MC3T3-E1) attachment, spreading, proliferation, alkaline phosphatase (ALP) activity, and osteoblastic gene expression on Mg-containing surfaces were compared with untreated Ti surfaces. Hydrothermal treatment resulted in Mg-incorporated Ti oxide layer with submicro-porous surface structures approximately 2 μm in thickness. ICP-AES analysis revealed Mg ions release from treated surfaces into the solution. The Mg-incorporated surface displayed significantly increased cellular attachment and ALP activity compared with untreated surface ( p < 0.05), and supported better cell spreading. Real-time polymerase chain reaction analysis showed notably higher mRNA expression of the osteoblast transcription factor genes (Dlx5, Runx2) and the osteoblast phenotype genes (ALP, bone sialoprotein and osteocalcin) in cells grown on the Mg-incorporated surfaces than untreated surfaces. These results demonstrate that the Mg-incorporated submicro-porous Ti oxide surface produced by hydrothermal treatment may improve implant osseointegration by enhancing the attachment, spreading and differentiation of osteoblastic cells.

Magnesium-phosphate-glass cements with ceramic-type properties

DOEpatents

Sugama, T.; Kukacka, L.E.

1982-09-23

Rapid setting magnesium phosphate (Mg glass) cementitious materials consisting of magnesium phosphate cement paste, polyborax and water-saturated aggregate, exhibits rapid setting and high early strength characteristics. The magnesium glass cement is prepared from a cation-leachable powder and a bivalent metallic ion-accepting liquid such as an aqueous solution of diammonium phosphate and ammonium polyphosphate. The cation-leachable powder includes a mixture of two different magnesium oxide powders processed and sized differently which when mixed with the bivalent metallic ion-accepting liquid provides the magnesium glass cement consisting primarily of magnesium ortho phosphate tetrahydrate, with magnesium hydroxide and magnesium ammonium phosphate hexahydrate also present. The polyborax serves as a set-retarder. The resulting magnesium mono- and polyphosphate cements are particularly suitable for use as a cementing matrix in rapid repair systems for deteriorated concrete structures as well as construction materials and surface coatings for fireproof structures.

Magnesium phosphate glass cements with ceramic-type properties

DOEpatents

Sugama, Toshifumi; Kukacka, Lawrence E.

1984-03-13

Rapid setting magnesium phosphate (Mg glass) cementitious materials consisting of magnesium phosphate cement paste, polyborax and water-saturated aggregate exhibiting rapid setting and high early strength characteristics. The magnesium glass cement is prepared from a cation-leachable powder and a bivalent metallic ion-accepting liquid such as an aqueous solution of diammonium phosphate and ammonium polyphosphate. The cation-leachable powder includes a mixture of two different magnesium oxide powders processed and sized differently which when mixed with the bivalent metallic ion-accepting liquid provides the magnesium glass cement consisting primarily of magnesium ortho phosphate tetrahydrate, with magnesium hydroxide and magnesium ammonium phosphate hexahydrate also present. The polyborax serves as a set-retarder. The resulting magnesium mono- and polyphosphate cements are particularly suitable for use as a cementing matrix in rapid repair systems for deteriorated concrete structures as well as construction materials and surface coatings for fireproof structures.

21 CFR 184.1431 - Magnesium oxide.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Magnesium oxide. 184.1431 Section 184.1431 Food... Specific Substances Affirmed as GRAS § 184.1431 Magnesium oxide. (a) Magnesium oxide (MgO, CAS Reg. No... light magnesium oxide. Heating the salts under more rigorous conditions (1200 °C for 12 hours) produces...

Detection of the adsorption of water monolayers through the ion oscillation frequency in the magnesium oxide lattice by means of low energy electron diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guevara-Bertsch, M.; Avendaño, E.; Centro de Investigación en Ciencia e Ingeniería de Materiales, Universidad de Costa Rica, 2060 San Pedro, San José

We investigate the variation of the oscillation frequency of the Mg{sup 2+} and O{sup 2−} ions in the magnesium oxide lattice due to the interactions of the surface with water monolayers by means of Low Energy Electron Diffraction. Our key result is a new technique to determine the adsorbate vibrations produced by the water monolayers on the surface lattice as a consequence of their change in the surface Debye temperature and its chemical shift. The latter was systematically investigated for different annealing times and for a constant external thermal perturbation in the range of 110–300 K in order to accomplish adsorptionmore » or desorption of water monolayers in the surface lattice.« less

21 CFR 184.1431 - Magnesium oxide.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Magnesium oxide. 184.1431 Section 184.1431 Food and... Substances Affirmed as GRAS § 184.1431 Magnesium oxide. (a) Magnesium oxide (MgO, CAS Reg. No. 1309-48-4... magnesium oxide. Heating the salts under more rigorous conditions (1200 °C for 12 hours) produces heavy...

Periodic disruptions induced by high repetition rate femtosecond pulses on magnesium-oxide-doped lithium niobate surfaces

NASA Astrophysics Data System (ADS)

Zhang, Shuanggen; Kan, Hongli; Zhai, Kaili; Ma, Xiurong; Luo, Yiming; Hu, Minglie; Wang, Qingyue

2017-02-01

In this paper, we demonstrate the periodic disruption formation on magnesium-oxide-doped lithium niobate surfaces by a femtosecond fiber laser system with wavelength and repetition rate of 1040 nm and 52 MHz, respectively. Three main experimental conditions, laser average power, scanning speed, and orientation of sample were systematically studied. In particular, the ablation morphologies of periodic disruptions under different crystal orientations were specifically researched. The result shows that such disruptions consisting of a bamboo-like inner structure appears periodically for focusing on the surface of X-, Y- and Z-cut wafers, which are formed by a rapid quenching of the material. Meanwhile, due to the anisotropic property, the bamboo-like inner structures consist of a cavity only arise from X- and Z-cut orientation.

Magnesium oxide prepared via metal-chitosan complexation method: Application as catalyst for transesterification of soybean oil and catalyst deactivation studies

NASA Astrophysics Data System (ADS)

Almerindo, Gizelle I.; Probst, Luiz F. D.; Campos, Carlos E. M.; de Almeida, Rusiene M.; Meneghetti, Simoni M. P.; Meneghetti, Mario R.; Clacens, Jean-Marc; Fajardo, Humberto V.

2011-10-01

A simple method to prepare magnesium oxide catalysts for biodiesel production by transesterification reaction of soybean oil with ethanol is proposed. The method was developed using a metal-chitosan complex. Compared to the commercial oxide, the proposed catalysts displayed higher surface area and basicity values, leading to higher yield in terms of fatty acid ethyl esters (biodiesel). The deactivation of the catalyst due to contact with CO2 and H2O present in the ambient air was verified. It was confirmed that the active catalytic site is a hydrogenocarbonate adsorption site.

21 CFR 184.1431 - Magnesium oxide.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Magnesium oxide. 184.1431 Section 184.1431 Food... Specific Substances Affirmed as GRAS § 184.1431 Magnesium oxide. (a) Magnesium oxide (MgO, CAS Reg. No... bulky white powder (light) or a relatively dense white powder (heavy) by heating magnesium hydroxide or...

21 CFR 184.1431 - Magnesium oxide.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Magnesium oxide. 184.1431 Section 184.1431 Food... GRAS § 184.1431 Magnesium oxide. (a) Magnesium oxide (MgO, CAS Reg. No. 1309-48-4) occurs naturally as... a relatively dense white powder (heavy) by heating magnesium hydroxide or carbonate. Heating these...

21 CFR 184.1431 - Magnesium oxide.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Magnesium oxide. 184.1431 Section 184.1431 Food... Specific Substances Affirmed as GRAS § 184.1431 Magnesium oxide. (a) Magnesium oxide (MgO, CAS Reg. No... bulky white powder (light) or a relatively dense white powder (heavy) by heating magnesium hydroxide or...

Composition of highly concentrated silicate electrolytes and ultrasound influencing the plasma electrolytic oxidation of magnesium

NASA Astrophysics Data System (ADS)

Simchen, F.; Rymer, L.-M.; Sieber, M.; Lampke, T.

2017-03-01

Magnesium and its alloys are increasingly in use as lightweight construction materials. However, their inappropriate corrosion and wear resistance often prevent their direct practical use. The plasma electrolytic oxidation (PEO) is a promising, environmentally friendly method to improve the surface characteristics of magnesium materials by the formation of oxide coatings. These PEO layers contain components of the applied electrolyte and can be shifted in their composition by increasing the concentration of the electrolyte constituents. Therefore, in contrast to the use of conventional low concentrated electrolytes, the process results in more stable protective coatings, in which electrolyte species are the dominating constitutes. In the present work, the influence of the composition of highly concentrated alkaline silicate electrolytes with additives of phosphate and glycerol on the quality of PEO layers on the magnesium alloy AZ31 was examined. The effect of ultrasound coupled into the electrolyte bath was also considered. The process was monitored by recording the electrical process variables with a transient recorder and by observation of the discharge phenomena on the sample surface with a camera. The study was conducted on the basis of a design of experiments. The effects of the process parameter variation are considered with regard to the coatings thickness, hardness and corrosion resistance. Information about the statistical significance of the effects of the parameters on the considered properties is obtained by an analysis of variance (ANOVA).

Recycling of Magnesium Alloy Employing Refining and Solid Oxide Membrane (SOM) Electrolysis

NASA Astrophysics Data System (ADS)

Guan, Xiaofei; Zink, Peter A.; Pal, Uday B.; Powell, Adam C.

2013-04-01

Pure magnesium was recycled from partially oxidized 50.5 wt pct Mg-Al scrap alloy and AZ91 Mg alloy (9 wt pct Al, 1 wt pct Zn). Refining experiments were performed using a eutectic mixture of MgF2-CaF2 molten salt (flux). During the experiments, potentiodynamic scans were performed to determine the electrorefining potentials for magnesium dissolution and magnesium bubble nucleation in the flux. The measured electrorefining potential for magnesium bubble nucleation increased over time as the magnesium content inside the magnesium alloy decreased. Potentiostatic holds and electrochemical impedance spectroscopy were employed to measure the electronic and ionic resistances of the flux. The electronic resistivity of the flux varied inversely with the magnesium solubility. Up to 100 pct of the magnesium was refined from the Mg-Al scrap alloy by dissolving magnesium and its oxide into the flux followed by argon-assisted evaporation of dissolved magnesium and subsequently condensing the magnesium vapor. Solid oxide membrane electrolysis was also employed in the system to enable additional magnesium recovery from magnesium oxide in the partially oxidized Mg-Al scrap. In an experiment employing AZ91 Mg alloy, only the refining step was carried out. The calculated refining yield of magnesium from the AZ91 alloy was near 100 pct.

Synthesis and properties of hydroxyapatite-containing coating on AZ31 magnesium alloy by micro-arc oxidation

NASA Astrophysics Data System (ADS)

Tang, Hui; Han, Yu; Wu, Tao; Tao, Wei; Jian, Xian; Wu, Yunfeng; Xu, Fangjun

2017-04-01

In this study, hydroxyapatite-containing coatings were prepared by microarc oxidation on AZ31 magnesium alloy surface to improve its biodegradation performance. Five applied voltages were chosen to prepare the MAO coatings. The results demonstrate that the number of micropores in the films increases but their dimensions decrease after higher voltage is applied. As the surface roughness of the MAO coatings increases with the applied voltage, the wettability of the coatings improves continuously. The MAO coatings were mainly composed of magnesium oxide (MgO) and hydroxyapatite. The amount of hydroxyapatite phase increased with increasing voltage that was applied. The bonding strength became slightly weaker after a higher voltage was applied. But the bonding strengths of all the coatings were consistently higher than 37 MPa, which met the requirement of implant biomaterials. All coatings exhibited higher corrosion resistances and lower hydrogen evolution rate than the bare AZ31 Mg substrate, implying that the degradation rate of the AZ31 Mg alloy was enhanced by the hydroxyapatite-containing coatings. The results indicate that the present treatment of applying hydroxyapatite-containing coatings is a promising technique for the degradable Mg-based biomaterials for orthopedic applications.

Solid-state rechargeable magnesium battery

DOEpatents

Shao, Yuyan; Liu, Jun; Liu, Tianbiao; Li, Guosheng

2016-09-06

Embodiments of a solid-state electrolyte comprising magnesium borohydride, polyethylene oxide, and optionally a Group IIA or transition metal oxide are disclosed. The solid-state electrolyte may be a thin film comprising a dispersion of magnesium borohydride and magnesium oxide nanoparticles in polyethylene oxide. Rechargeable magnesium batteries including the disclosed solid-state electrolyte may have a coulombic efficiency .gtoreq.95% and exhibit cycling stability for at least 50 cycles.

21 CFR 582.1431 - Magnesium oxide.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Magnesium oxide. 582.1431 Section 582.1431 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1431 Magnesium oxide. (a) Product. Magnesium oxide. (b) Conditions of use. This substance is...

21 CFR 582.1431 - Magnesium oxide.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Magnesium oxide. 582.1431 Section 582.1431 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1431 Magnesium oxide. (a) Product. Magnesium oxide. (b) Conditions of use. This substance is...

21 CFR 582.1431 - Magnesium oxide.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Magnesium oxide. 582.1431 Section 582.1431 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1431 Magnesium oxide. (a) Product. Magnesium oxide. (b) Conditions of use. This substance is...

21 CFR 582.1431 - Magnesium oxide.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Magnesium oxide. 582.1431 Section 582.1431 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1431 Magnesium oxide. (a) Product. Magnesium oxide. (b) Conditions of use. This substance is...

21 CFR 582.1431 - Magnesium oxide.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Magnesium oxide. 582.1431 Section 582.1431 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1431 Magnesium oxide. (a) Product. Magnesium oxide. (b) Conditions of use. This substance is...

Nanostructured magnesium oxide biosensing platform for cholera detection

NASA Astrophysics Data System (ADS)

Patel, Manoj K.; Azahar Ali, Md.; Agrawal, Ved V.; Ansari, Z. A.; Ansari, S. G.; Malhotra, B. D.

2013-04-01

We report fabrication of highly crystalline nanostructured magnesium oxide (NanoMgO, size >30 nm) film electrophoretically deposited onto indium-tin-oxide (ITO) glass substrate for Vibrio cholerae detection. The single stranded deoxyribonucleic acid (ssDNA) probe, consisting of 23 bases (O1 gene sequence) immobilized onto NanoMgO/ITO electrode surface, has been characterized using electrochemical, Fourier Transform-Infra Red, and UltraViolet-visible spectroscopic techniques. The hybridization studies of ssDNA/NanoMgO/ITO bioelectrode with fragmented target DNA conducted using differential pulse voltammetry reveal sensitivity as 16.80 nA/ng/cm2, response time of 3 s, linearity as 100-500 ng/μL, and stability of about 120 days.

Color stable phosphors for LED lamps and methods for preparing them

DOEpatents

Murphy, James Edward; Setlur, Anant Achyut; Camardello, Samuel Joseph

2013-11-26

An LED lamp includes a light source configured to emit radiation with a peak intensity at a wavelength between about 250 nm and about 550 nm; and a phosphor composition configured to be radiationally coupled to the light source. The phosphor composition includes particles of a phosphor of formula I, said particles having a coating composition disposed on surfaces thereof; ((Sr.sub.1-zM.sub.z).sub.1-(x+w)A.sub.wCe.sub.x).sub.3(Al.sub.1-ySi.sub.y-)O.sub.4+y+3(x-w)F.sub.1-y-3(x-w) I wherein the coating composition comprises a material selected from aluminum oxide, magnesium oxide, calcium oxide, barium oxide, strontium oxide, zinc oxide, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, barium hydroxide, strontium hydroxide, zinc hydroxide, aluminum phosphate, magnesium phosphate, calcium phosphate, barium phosphate, strontium phosphate, and combinations thereof; and A is Li, NA, K, or Rb, or a combination thereof; M is Ca, Ba, Mg, Zn, or a combination thereof; and 0

Preparation and characterization of HA microflowers coating on AZ31 magnesium alloy by micro-arc oxidation and a solution treatment

NASA Astrophysics Data System (ADS)

Tang, Hui; Yu, Dezhen; Luo, Yan; Wang, Fuping

2013-01-01

Magnesium and its alloys are potential biodegradable implant materials due to their attractive biological properties. But the use of magnesium is still hampered by its poor corrosion resistance in physiological fluids. In this work, hydroxyapatite microflowers coating is fabricated by micro-arc oxidation and a solution treatment on AZ31 magnesium alloy. The microstructure and composition are analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The potentiodynamic polarization and electrochemical impedance spectroscopy are studied in simulated body fluid (SBF) solution, and the apatite-forming ability is studied also. The results show that the corrosion resistance of the magnesium alloy has been enhanced by MAO coating. And the solution treatment can improve the corrosion resistance of the MAO sample, by forming a barrier layer on the surface of the MAO coating, and by penetrating into the outer layer of the MAO film, sealing the micropores and micro-cracks existed in the MAO coating. In addition, the MAO-ST coating also exhibits a high ability to form apatite.

Method for production of magnesium

DOEpatents

Diaz, Alexander F.; Howard, Jack B.; Modestino, Anthony J.; Peters, William A.

1998-01-01

A continuous process for the production of elemental magnesium is described. Magnesium is made from magnesium oxide and a light hydrocarbon gas. In the process, a feed stream of the magnesium oxide and gas is continuously fed into a reaction zone. There the magnesium oxide and gas are reacted at a temperature of about 1400.degree. C. or greater in the reaction zone to provide a continuous product stream of reaction products, which include elemental magnesium. The product stream is continuously quenched after leaving the reaction zone, and the elemental magnesium is separated from other reaction products.

Method for production of magnesium

DOEpatents

Diaz, A.F.; Howard, J.B.; Modestino, A.J.; Peters, W.A.

1998-07-21

A continuous process for the production of elemental magnesium is described. Magnesium is made from magnesium oxide and a light hydrocarbon gas. In the process, a feed stream of the magnesium oxide and gas is continuously fed into a reaction zone. There the magnesium oxide and gas are reacted at a temperature of about 1400 C or greater in the reaction zone to provide a continuous product stream of reaction products, which include elemental magnesium. The product stream is continuously quenched after leaving the reaction zone, and the elemental magnesium is separated from other reaction products. 12 figs.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ayala, Alicia; Corral, Erica L.; Loehman, Ronald E.

A tape casting procedure for fabricating ceramic magnesium oxide tapes has been developed as a method to produce flat sheets of sintered MgO that are thin and porous. Thickness of single layer tapes is in the range of 200-400 {micro}m with corresponding surface roughness values in the range of 10-20 {micro}m as measured by laser profilometry. Development of the tape casting technique required optimization of pretreatment for the starting magnesium oxide (MgO) powder as well as a detailed study of the casting slurry preparation and subsequent heat treatments for sintering and final tape flattening. Milling time of the ceramic powder,more » plasticizer, and binder mixture was identified as a primary factor affecting surface morphology of the tapes. In general, longer milling times resulted in green tapes with a noticeably smoother surface. This work demonstrates that meticulous control of the entire tape casting operation is necessary to obtain high-quality MgO tapes.« less

40 CFR 721.10021 - Magnesium potassium titanium oxide.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Magnesium potassium titanium oxide... Specific Chemical Substances § 721.10021 Magnesium potassium titanium oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as magnesium potassium...

40 CFR 721.10021 - Magnesium potassium titanium oxide.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Magnesium potassium titanium oxide... Specific Chemical Substances § 721.10021 Magnesium potassium titanium oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as magnesium potassium...

40 CFR 721.10021 - Magnesium potassium titanium oxide.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Magnesium potassium titanium oxide... Specific Chemical Substances § 721.10021 Magnesium potassium titanium oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as magnesium potassium...

40 CFR 721.10021 - Magnesium potassium titanium oxide.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Magnesium potassium titanium oxide... Specific Chemical Substances § 721.10021 Magnesium potassium titanium oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as magnesium potassium...

Micro-mechanisms of Surface Defects Induced on Aluminum Alloys during Plastic Deformation at Elevated Temperatures

NASA Astrophysics Data System (ADS)

Gali, Olufisayo A.

Near-surface deformed layers developed on aluminum alloys significantly influence the corrosion and tribological behavior as well as reduce the surface quality of the rolled aluminum. The evolution of the near-surface microstructures induced on magnesium containing aluminum alloys during thermomechanical processing has been investigated with the aim generating an understanding of the influence of individual forming parameters on its evolution and examine the microstructure of the roll coating induced on the mating steel roll through material transfer during rolling. The micro-mechanisms related to the various features of near-surface microstructure developed during tribological conditions of the simulated hot rolling process were identified. Thermomechanical processing experiments were performed with the aid of hot rolling (operating temperature: 550 to 460 °C, 4, 10 and 20 rolling pass schedules) and hot forming (operating temperature: 350 to 545 °C, strain rate: 4 x 10-2 s-1) tribo-simulators. The surface, near-surface features and material transfer induced during the elevated temperature plastic deformation were examined and characterized employing optical interferometry, SEM/EDS, FIB and TEM. Near-surface features characterized on the rolled aluminum alloys included; cracks, fractured intermetallic particles, aluminum nano-particles, oxide decorated grain boundaries, rolled-in oxides, shingles and blisters. These features were related to various individual rolling parameters which included, the work roll roughness, which induced the formation of shingles, rolling marks and were responsible for the redistribution of surface oxide and the enhancements of the depth of the near-surface damage. The enhanced stresses and strains experienced during rolling were related to the formation and propagation of cracks, the nanocrystalline structure of the near-surface layers and aluminum nano-particles. The mechanism of the evolution of the near-surface microstructure were determined to include grain boundary sliding which induced the cracks at the surface and subsurface of the alloy, magnesium diffusion to free surfaces, crack propagation from shear stresses and the shear strains inducing the nanocrystalline grain structure, the formation of shingles by the shear deformation of micro-wedges induced by the work roll grooves, and the deformation of this oxide covered micro-wedges inducing the rolled-in oxides. Magnesium diffusion to free surfaces was identified as inducing crack healing due to the formation of MgO within cracks and was responsible for the oxide decorated grain boundaries. An examination of the roll coating revealed a complex layered microstructure that was induced through tribo-chemical and mechanical entrapment mechanisms. The microstructure of the roll coating suggested that the work roll material and the rolled aluminum alloy were essential in determining its composition and structure. Subsequent hot forming processes revealed the rich oxide-layer of the near-surface microstructure was beneficial for reducing the coefficient of friction during tribological contact with the steel die. Damage to the microstructure include cracks induced from grain boundary sliding of near-surface grains and the formation of oxide fibres within cracks of the near-surface deformed layers.

Finite-element analysis of scattering parameters of surface acoustic wave bandpass filter formed on barium titanate thin film

NASA Astrophysics Data System (ADS)

Timoshenko; Kalinchuk; Shirokov

2018-04-01

The frequency dependence of scattering parameters of interdigital surface acoustic wave transducers placed on ferroelectric barium titanate (BaTiO3) epitaxial film in c-phase coated over magnesium oxide has been studied using the finite-element method (FEM) approach along with the perfectly matched layer (PML) technique. The interdigital transducer which has a comb-like structure with aluminum electrodes excites the mechanical wave. The distance between the fingers allows tuning the frequency properties of the wave propagation. The magnesium oxide is taken as the substrate. The two-dimensional model of two-port surface acoustic wave filter is created to calculate scattering parameters and to show how to design the fixture in COMSOLTM. Some practical computational challenges of finite element modeling of SAW devices in COMSOLTM are shown. The effect of lattice misfit strain on acoustic properties of heterostructures of BaTiO3 epitaxial film in c-phase at room temperature is discussed in present article for two low-frequency surface acoustic resonances.

Heat Treatment of Tantalum and Niobium Powders Prepared by Magnesium-Thermic Reduction

NASA Astrophysics Data System (ADS)

Orlov, V. M.; Prokhorova, T. Yu.

2017-11-01

Changes in the specific surface area and porous structure of tantalum and niobium powders, which were prepared by magnesium-thermic reduction of Ta2O5, Mg4Ta2O9, and Mg4Nb2O9 oxide compounds and subjected to heat treatments at temperatures of 600-1500°C, have been studied. It is noted that, owing to the mesoporous structure of the magnesium-thermic powders, the decrease in the surface area during heat treatment, first of all, is related to a decrease in the amount of pores less than 10 nm in size. The heat treatment of a reacting mass is shown to allow us to correct the specific surface area of the powder without any increase in the oxygen content in it. Data on the effect of heat treatment conditions on the specific charge of capacitor anodes are reported.

21 CFR 582.5431 - Magnesium oxide.

Code of Federal Regulations, 2014 CFR

2014-04-01

... DRUGS, FEEDS, AND RELATED PRODUCTS SUBSTANCES GENERALLY RECOGNIZED AS SAFE Nutrients and/or Dietary Supplements 1 § 582.5431 Magnesium oxide. (a) Product. Magnesium oxide. (b) Conditions of use. This substance...

21 CFR 582.5431 - Magnesium oxide.

Code of Federal Regulations, 2013 CFR

2013-04-01

... DRUGS, FEEDS, AND RELATED PRODUCTS SUBSTANCES GENERALLY RECOGNIZED AS SAFE Nutrients and/or Dietary Supplements 1 § 582.5431 Magnesium oxide. (a) Product. Magnesium oxide. (b) Conditions of use. This substance...

21 CFR 582.5431 - Magnesium oxide.

Code of Federal Regulations, 2011 CFR

2011-04-01

... DRUGS, FEEDS, AND RELATED PRODUCTS SUBSTANCES GENERALLY RECOGNIZED AS SAFE Nutrients and/or Dietary Supplements 1 § 582.5431 Magnesium oxide. (a) Product. Magnesium oxide. (b) Conditions of use. This substance...

21 CFR 582.5431 - Magnesium oxide.

Code of Federal Regulations, 2012 CFR

2012-04-01

... DRUGS, FEEDS, AND RELATED PRODUCTS SUBSTANCES GENERALLY RECOGNIZED AS SAFE Nutrients and/or Dietary Supplements 1 § 582.5431 Magnesium oxide. (a) Product. Magnesium oxide. (b) Conditions of use. This substance...

21 CFR 582.5431 - Magnesium oxide.

Code of Federal Regulations, 2010 CFR

2010-04-01

... DRUGS, FEEDS, AND RELATED PRODUCTS SUBSTANCES GENERALLY RECOGNIZED AS SAFE Nutrients and/or Dietary Supplements 1 § 582.5431 Magnesium oxide. (a) Product. Magnesium oxide. (b) Conditions of use. This substance...

Characterizations of Ca- and Mg-incorporating micro/nano-structured surfaces on titanium fabricated by microarc oxidation and hydrothermal treatments

NASA Astrophysics Data System (ADS)

Ko, Sang-Hoon; Hwang, Moon-Jin; Moon, Won-Jin; Park, Yeong-Joon; Song, Ho-Jun

2015-12-01

The micro/nano-surface characteristics of magnesium- and calcium-incorporating titanium oxide layers fabricated on titanium metal using microarc oxidation (MAO) and hydrothermal (HT) treatments were investigated. Calcium acetate monohydrate (CA), magnesium acetate monohydrate (MA), and β-glycerophosphoric acid disodium salt pentahydrate were used as electrolytes for MAO treatment of titanium disks. CA/MA electrolyte concentrations (all in M) were 0.2/0.0 (CA20-MAO), 0.15/0.05 (CA15MA5-MAO), 0.1/0.1 (CA10MA10-MAO), 0.05/0.15 (CA5MA15-MAO), and 0.0/0.2 (MA20-MAO). MAO-HT groups were prepared by hydrothermal treatment of MAO groups. The porous surface morphology was consistent even after HT treatment. The incorporation of Mg ions in the oxide layer during MAO treatment was more favorable than incorporation of Ca ions. However, Mg ions were released more rapidly than Ca ions after HT treatment. The anatase TiO2 structure was dominant for all the groups and an increase in the rutile TiO2 structure was observed with an increase in MA concentration. Nano-sized crystallites were observed on the porous surface for all MAO-HT groups. Nano-needle-like crystallites were observed on the surface of CA20-MAO-HT. The crystallites exhibited shorter and thicker characteristics with an increase in Mg concentration.

Characterization and Properties of Micro-arc Composite Ceramic Coatings on Magnesium Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Long; Jiang, Bailing; Ge, Yanfeng

2013-05-21

Magnesium alloys are of growing interest for many industrial applications due to their favorable strength-to-weight ratio and excellent cast ability. However, one of the limiting factors in the use of magnesium on production vehicles is its poor corrosion resistance. Micro-arc Composite Ceramic (MCC) coatings on AZ91D magnesium alloys were prepared in combination with Micro-arc Oxidation (MAO) and electrophoresis technologies. The microstructure, corrosion resistance, abrasion resistance, stone impact resistance, thermal shock resistance and adhesion of MCC coating were studied, respectively. The surface and cross-section morphologies of MAO and MCC coating showed that the outer organic coating filled the holes on themore » surface of the MAO coating. It acted as a shelter on the MAO coating surface when the MCC coatings were exposed to corrosive environments. The corrosion resistance of the MCC coating was characterized by a copper-accelerated acetic acid salt spray test. The testing results showed that the creep back from scribe lines was less than 1mm and completely fit the evaluation standard. The composite structure of the MCC coating vastly improved the corrosion resistance of Mg alloys. According to testing standards, the resistance to abrasion, stone impact resistance, thermal shock resistance and adhesion of MCC coatings completely met the evaluation standard requirements. The MCC coated AZ91D magnesium alloys possessed excellent properties; this is a promising corrosion and wear resistance surface treatment technology on magnesium alloys for production vehicles.« less

Parallel nano-assembling of a multifunctional GO/HapNP coating on ultrahigh-purity magnesium for biodegradable implants

NASA Astrophysics Data System (ADS)

Santos, C.; Piedade, C.; Uggowitzer, P. J.; Montemor, M. F.; Carmezim, M. J.

2015-08-01

This work reports the one-step fabrication of a novel coating on ultra high purity magnesium using a parallel nano assembling process. The multifunctional biodegradable surface was obtained by adding hydroxyapatite nanoparticles (HapNP) plus graphene oxide (GO). The coating was characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffractometer (XRD), micro-Raman spectroscopy. The thin phosphate coating (thickness of 1 μm) reveals a uniform coverage with cypress like structures. The incorporation of HapNP and GO promotes the hydrophilic behavior of the coating surface. The results revealed that the proposed coating can be used to tailor the surface properties such as wettability by adjusting the contents of HapNP and GO. The in vitro degradation rate of the coated magnesium suggests that the presence of HapNP and GO/HapNP in the phosphate coating decreased the current density compared to the single phosphate coating and uncoated magnesium. This study also reveals the HapNP/GO/phosphate coating induces apatite formation, showing suitable degradability that makes it a promising coating candidate for enhanced bone regeneration.

Isotopically pure magnesium isotope-24 is prepared from magnesium-24 oxide

NASA Technical Reports Server (NTRS)

Chellew, N. R.; Schilb, J. D.; Steunenberg, R. K.

1968-01-01

Apparatus is used to prepare isotopically pure magnesium isotope-24, suitable for use in neutron scattering and polarization experiments. The apparatus permits thermal reduction of magnesium-24 oxide with aluminum and calcium oxide, and subsequent vaporization of the product metal in vacuum. It uses a resistance-heated furnace tube and cap assembly.

Ramp compression of magnesium oxide to 234 GPa

DOE PAGES

Wang, Jue; Smith, R. F.; Coppari, F.; ...

2014-05-07

Single-crystal magnesium oxide (MgO) samples were ramp compressed to above 200 GPa pressure at the Omega laser facility. Multi-stepped MgO targets were prepared using lithography and wet etching techniques. Free surface velocities of ramp-compressed MgO were measured with a VISAR. The sound velocity and stress-density response were determined using an iterative Lagrangian analysis. The measured equation of state is consistent with expectations from previous shock and static data as well as with a recent X-ray diffraction measurement under ramp loading. The peak elastic stresses observed in our samples had amplitudes of 3-5.5 GPa, decreasing with propagation distance.

NANO-SCALE METAL OXIDE PARTICLES/CLUSTERS AS CHEMICAL REAGENTS: SYNTHESIS AND PROPERTIES OF ULTRA-HIGH SURFACE AREA MAGNESIUM OXIDE. (R825549C015)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

IMPROVED MAGNESIUM OXIDE SLIP CASTING METHOD

DOEpatents

Stoddard, S.D.; Nuckolls, D.E.

1963-12-31

A process for making an aqueous magnesium oxide slip casting slurry comprising the steps of mixing finely ground fused magnesium oxide with water, milling the slurry for at least 30 hours at a temperature of 2-10 deg C (the low temperature during milling inhibiting the formation of hydrated magnesium oxide), discharging the slurry from the mill, adding hydrochloric acid as a deflocculent, and adding a scum inhibitor is presented. (AEC)

A study of degradation resistance and cytocompatibility of super-hydrophobic coating on magnesium.

PubMed

Zhang, Yufen; Feyerabend, Frank; Tang, Shawei; Hu, Jin; Lu, Xiaopeng; Blawert, Carsten; Lin, Tiegui

2017-09-01

Calcium stearate based super-hydrophobic coating was deposited on plasma electrolytic oxidation (PEO) pre-treated magnesium substrate. The pre-treated magnesium and super-hydrophobic coating covered sample were characterized by scanning electron microscopy, X-ray diffraction and electrochemical corrosion measurements. The cytocompatibility and degradation resistance of magnesium, pre-treated magnesium and super-hydrophobic coating were analysed in terms of cell adhesion and osteoblast differentiation. The results indicate that the calcium stearate top coating shows super-hydrophobicity and that the surface is composed of micro/nanostructure. The super-hydrophobic coating covered sample shows higher barrier properties compared with the PEO pre-treated magnesium and bare magnesium. Human osteoblast proliferation, but not differentiation is enhanced by the PEO coating. Contrary, the super-hydrophobic coating reduces proliferation, but enhances differentiation of osteoblast, observable by the formation of hydroxyapatite. The combination of corrosion protection and cell reaction indicates that this system could be interesting for biomedical applications. Copyright © 2017 Elsevier B.V. All rights reserved.

Biodegradation behavior of micro-arc oxidized AZ31 magnesium alloys formed in two different electrolytes

NASA Astrophysics Data System (ADS)

Seyfoori, A.; Mirdamadi, Sh.; Khavandi, A.; Raufi, Z. Seyed

2012-11-01

Degradation behavior of coated magnesium alloys is among most prominent factors for their biomedical applications. In this study, bio-corrosion behavior of micro-arc oxidized magnesium AZ31 alloys formed in silicate and phosphate baths was investigated in r-SBF medium. For this purpose polarization behavior and open circuit profile of the coated samples were achieved by electrochemical and immersion tests, respectively. Moreover, the morphology and composition of the coatings were evaluated before and after immersion test using scanning electron microscopy, X-ray diffraction and energy dispersive spectroscopy. The results showed that the phosphate film had better corrosion resistance and greater thickness than silicate film and, in turn, the lesser degradability in SBF solution, so that Ca2+ and PO43- containing compounds were more abundant on silicate film than phosphate film. Moreover phosphate film had greater surface roughness and lesser hydrophilic nature.

PRODUCTION OF ACTINIDE METAL

DOEpatents

Knighton, J.B.

1963-11-01

A process of reducing actinide oxide to the metal with magnesium-zinc alloy in a flux of 5 mole% of magnesium fluoride and 95 mole% of magnesium chloride plus lithium, sodium, potassium, calcium, strontium, or barium chloride is presented. The flux contains at least 14 mole% of magnesium cation at 600-- 900 deg C in air. The formed magnesium-zinc-actinide alloy is separated from the magnesium-oxide-containing flux. (AEC)

A Case of a Magnesium Oxide Bezoar.

PubMed

Iwamuro, Masaya; Saito, Shunsuke; Yoshioka, Masao; Urata, Haruo; Ueda, Kumiko; Yamamoto, Kazuhide; Okada, Hiroyuki

2018-06-06

A 75-year-old Japanese woman presented with nausea and appetite loss. Computed tomography showed a radiopaque substance in the stomach. Esophagogastroduodenoscopy revealed bezoars in the stomach, which were endoscopically retrieved. The bezoars were mainly composed of magnesium and oxide. Although bezoar formation associated with magnesium oxide consumption is infrequently encountered, the present case indicates that pharmacobezoar should be considered among the differential diagnoses in patients who demonstrate a radiopaque mass in the digestive tract and have a history of magnesium oxide use.

Enhanced mechanical properties and increased corrosion resistance of a biodegradable magnesium alloy by plasma electrolytic oxidation (PEO).

PubMed

White, Leon; Koo, Youngmi; Neralla, Sudheer; Sankar, Jagannathan; Yun, Yeoheung

2016-06-01

We report the enhanced mechanical properties of AZ31 magnesium alloys by plasma electrolytic oxidation (PEO) coating in NaOH, Na 2 SiO 3 , KF and NaH 2 PO 4 ·2H 2 O containing electrolytes. Mechanical properties including wear resistance, surface hardness and elastic modulus were increased for PEO-coated AZ31 Mg alloys (PEO-AZ31). DC polarization in Hank's solution indicating that the corrosion resistance significantly increased for PEO-coating in KF-contained electrolyte. Based on these results, the PEO coating method shows promising potential for use in biodegradable implant applications where tunable corrosion and mechanical properties are needed.

Improved Interfacial Bonding in Magnesium/Aluminum Overcasting Systems by Aluminum Surface Treatments

NASA Astrophysics Data System (ADS)

Zhang, Hui; Chen, Yiqing; Luo, Alan A.

2014-12-01

"Overcasting" technique is used to produce bimetallic magnesium/aluminum (Mg/Al) structures where lightweight Mg can be cast onto solid Al substrates. An inherent difficulty in creating strong Mg/Al interfacial bonding is the natural oxide film on the solid Al surfaces, which reduces the wettability between molten Mg and Al substrates during the casting process. In the paper, an "electropolishing + anodizing" surface treatment has been developed to disrupt the oxide film on a dilute Al-0.08 wt pct Ga alloy, improving the metallurgical bonding between molten Mg and Al substrates in the bimetallic experiments carried out in a high-vacuum test apparatus. The test results provided valuable information of the interfacial phenomena of the Mg/Al bimetallic samples. The results show significantly improved metallurgical bonding in the bimetallic samples with "electropolishing + anodizing" surface treatment and Ga alloying. It is recommended to adjust the pre-heating temperature and time of the Al substrates and the Mg melt temperature to control the interfacial reactions for optimum interfacial properties in the actual overcasting processes.

Inelastic vibrational bulk and surface losses of swift electrons in ionic nanostructures

NASA Astrophysics Data System (ADS)

Hohenester, Ulrich; Trügler, Andreas; Batson, Philip E.; Lagos, Maureen J.

2018-04-01

In a recent paper [Lagos et al., Nature (London) 543, 533 (2017), 10.1038/nature21699] we have used electron energy loss spectroscopy with sub-10 meV energy and atomic spatial resolution to map optical and acoustic, bulk and surface vibrational modes in magnesium oxide nanocubes. We found that a local dielectric description works well for the simulation of aloof geometries, similar to related work for surface plasmons and surface plasmon polaritons, while for intersecting geometries such a description fails to reproduce the rich spectral features associated with excitation of bulk acoustic and optical phonons. To account for scatterings with a finite momentum exchange, in this paper we investigate molecular and lattice dynamics simulations of bulk losses in magnesium-oxide nanocubes using a rigid-ion description and investigate the loss spectra for intersecting electron beams. From our analysis we can evaluate the capability of electron energy loss spectroscopy for the investigation of phonon modes at the nanoscale, and we discuss shortcomings of our simplified approach as well as directions for future investigations.

Tribological Behaviors of Graphene and Graphene Oxide as Water-Based Lubricant Additives for Magnesium Alloy/Steel Contacts.

PubMed

Xie, Hongmei; Jiang, Bin; Dai, Jiahong; Peng, Cheng; Li, Chunxia; Li, Quan; Pan, Fusheng

2018-01-29

The tribological behaviors of graphene and graphene oxide (GO) as water-based lubricant additives were evaluated by use of a reciprocating ball-on-plate tribometer for magnesium alloy-steel contacts. Three sets of test conditions were examined to investigate the effect of concentration, the capacity of carrying load and the endurance of the lubrication film, respectively. The results showed that the tribological behaviors of water can be improved by adding the appropriate graphene or GO. Compared with pure deionized water, 0.5 wt.% graphene nanofluids can offer reduction of friction coefficient by 21.9% and reduction of wear rate by 13.5%. Meanwhile, 0.5 wt.% GO nanofluids were found to reduce the friction coefficient and wear rate up to 77.5% and 90%, respectively. Besides this, the positive effect of the GO nanofluids was also more pronounced in terms of the load-carrying capacity and the lubrication film endurance. The wear mechanisms have been tentatively proposed according to the observation of the worn surfaces by field emission scanning electron microscope-energy dispersive spectrometer (FESEM-EDS) and Raman spectrum as well as the wettability of the nanofluids on the magnesium alloy surface by goniometer.

Tribological Behaviors of Graphene and Graphene Oxide as Water-Based Lubricant Additives for Magnesium Alloy/Steel Contacts

PubMed Central

Xie, Hongmei; Jiang, Bin; Dai, Jiahong; Peng, Cheng; Li, Chunxia; Li, Quan; Pan, Fusheng

2018-01-01

The tribological behaviors of graphene and graphene oxide (GO) as water-based lubricant additives were evaluated by use of a reciprocating ball-on-plate tribometer for magnesium alloy-steel contacts. Three sets of test conditions were examined to investigate the effect of concentration, the capacity of carrying load and the endurance of the lubrication film, respectively. The results showed that the tribological behaviors of water can be improved by adding the appropriate graphene or GO. Compared with pure deionized water, 0.5 wt.% graphene nanofluids can offer reduction of friction coefficient by 21.9% and reduction of wear rate by 13.5%. Meanwhile, 0.5 wt.% GO nanofluids were found to reduce the friction coefficient and wear rate up to 77.5% and 90%, respectively. Besides this, the positive effect of the GO nanofluids was also more pronounced in terms of the load-carrying capacity and the lubrication film endurance. The wear mechanisms have been tentatively proposed according to the observation of the worn surfaces by field emission scanning electron microscope-energy dispersive spectrometer (FESEM-EDS) and Raman spectrum as well as the wettability of the nanofluids on the magnesium alloy surface by goniometer. PMID:29382160

40 CFR 98.193 - Calculating GHG emissions.

Code of Federal Regulations, 2011 CFR

2011-07-01

.... Calcium oxide and magnesium oxide content must be analyzed monthly for each lime product type that is...). MgOi,n = Magnesium oxide content for lime type i, for month n, determined according to § 98.194(c... type i sold, for month n (metric tons CaO/metric ton lime). MgOLKD,i,n = Magnesium oxide content for...

A facile method to fabricate a superhydrophobic surface with biomimetic structure on magnesium alloy

NASA Astrophysics Data System (ADS)

Bai, Zigang; Zhu, Jiyuan

2018-06-01

Superhydrophobic surface was obtained via a convenient two-step method in this paper on magnesium alloy. The microstructured oxide or hydroxide layers were constructed on the Mg alloy though hydrothermal process. The treated sample was modified with low-energy surface material. After modification, the contact angle of water droplet on the surface is higher than 150° which indicates superhydrophobicity. With scanning electron microscope(SEM), mammillaria-herrerae-like rough structure was obtained. The composition of the superhydrophobic film was analyzed by using x-ray Diffraction instrument and Fourier-transform infrared spectrometer. Moreover, the superhydrophobic surface has good stability. The potentiodynamic polarization test shows that the corrosion current density of superhydrophobic surface was 1–2 order of magnitudes smaller than the bare substrate, which means the anti-corrosion performance has been improved significantly. This route offers an environmentally-benign and effective way to fabricate superhydrophobic surface without using complicated equipment and dangerous chemicals.

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

NASA Astrophysics Data System (ADS)

Guan, Xiaofei; Pal, Uday B.; Powell, Adam C.

2013-10-01

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.

Selective radiative cooling with MgO and/or LiF layers

DOEpatents

Berdahl, P.H.

1984-09-14

A selective radiation cooling material which is absorptive only in the 8 to 13 microns wavelength range is accomplished by placing ceramic magnesium oxide and/or polycrystalline lithium fluoride on an infrared-reflective substrate. The reflecting substrate may be a metallic coating, foil or sheet, such as aluminum, which reflects all atmospheric radiation from 0.3 to 8 microns, the magnesium oxide and lithium fluoride being nonabsorptive at those wavelengths. <10% of submicron voids in the material is permissible in which case the MgO and/or LiF layer is diffusely scattering, but still nonabsorbing, in the wavelength range of 0.3 to 8 microns. At wavelengths from 8 to 13 microns, the magnesium oxide and lithium fluoride radiate power through the ''window'' in the atmosphere, and thus remove heat from the reflecting sheet of material and the attached object to be cooled. At wavelengths longer than 13 microns, the magnesium oxide and lithium fluoride reflects the atmospheric radiation back into the atmosphere. This high reflectance is only obtained if the surface is sufficiently smooth: roughness on a scale of 1 micron is permissible but roughness on a scale of 10 microns is not. An infrared-transmitting cover or shield is mounted in spaced relationship to the material to reduce convective heat transfer. If this is utilized in direct sunlight, the infrared transmitting cover or shield should be opaque in the solar spectrum of 0.3 to 3 microns.

Regeneration of Waste Edible Oil by the Use of Virgin and Calcined Magnesium Hydroxide as Adsorbents.

PubMed

Ogata, Fumihiko; Kawasaki, Naohito

2016-01-01

In this study, we prepared virgin (S, L) and calcined (S-380, S-1000, L-380, L-1000) magnesium hydroxide for regeneration of waste edible oil. Deterioration of soybean oil, rapeseed oil, and olive oil was achieved by heat and aeration treatment. The properties of the different adsorbents were investigated using specific surface area measurements, scanning electron microscopy, X-ray diffraction analysis, thermogravimetric-differential thermal analysis, and surface pH measurement. Moreover, the relationship between the changes in acid value (AV) and carbonyl value (CV) and the adsorbent properties were evaluated. The specific surface areas of S-380 and L-380 were greater than that of other adsorbents. In addition, the XRD results show that S-380 and L-380 contain both magnesium hydroxide and magnesium oxide structures. The decreases in AV and CV using S-380 and L-380 were greater than achieved using other adsorbents. The correlation coefficients between the decrease in AV and CV and specific surface area were 0.947 for soybean oil, 0.649 for rapeseed oil, and 0.773 for olive oil, respectively. The results obtained in this study suggest that a physical property of the adsorbent, namely specific surface area, was primarily responsible for the observed decreases in AV and CV. Overall, the results suggest that S-380 and L-380 are useful for the regeneration of waste edible oil.

Surface plasmon coupled chemiluminescence during adsorption of oxygen on magnesium surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hagemann, Ulrich; Nienhaus, Hermann, E-mail: hermann.nienhaus@uni-due.de

The dissociative adsorption of oxygen molecules on magnesium surfaces represents a non-adiabatic reaction exhibiting exoelectron emission, chemicurrent generation, and weak chemiluminescence. Using thin film Mg/Ag/p-Si(111) Schottky diodes with 1 nm Mg on a 10-60 nm thick Ag layer as 2π-photodetectors, the chemiluminescence is internally detected with a much larger efficiency than external methods. The chemically induced photoyield shows a maximum for a Ag film thickness of 45 nm. The enhancement is explained by surface plasmon coupled chemiluminescence, i.e., surface plasmon polaritons are effectively excited in the Ag layer by the oxidation reaction and decay radiatively leading to the observed photocurrent.more » Model calculations of the maximum absorption in attenuated total reflection geometry support the interpretation. The study demonstrates the extreme sensitivity and the practical usage of internal detection schemes for investigating surface chemiluminescence.« less

Remanufacture of Zirconium-Based Conversion Coatings on the Surface of Magnesium Alloy

NASA Astrophysics Data System (ADS)

Liu, Zhe; Jin, Guo; Song, Jiahui; Cui, Xiufang; Cai, Zhaobing

2017-04-01

Brush plating provides an effective method for creating a coating on substrates of various shapes. A corroded zirconium-based conversion coating was removed from the surface of a magnesium alloy and then replaced with new coatings prepared via brush plating. The structure and composition of the remanufactured coating were determined via x-ray photoelectron spectroscopy, x-ray diffraction, and Fourier transform infrared spectroscopy. The results revealed that the coatings consist of oxide, fluoride, and tannin-related organics. The composition of the coatings varied with the voltage. Furthermore, as revealed via potentiodynamic polarization spectroscopy, these coatings yielded a significant increase in the corrosion resistance of the magnesium alloy. The friction coefficient remained constant for almost 300s during wear resistance measurements performed under a 1-N load and dry sliding conditions, indicating that the remanufactured coatings provide effective inhibition to corrosion.

Preparation and characterization of nanostructured metal oxides for application to biomass upgrading Polar (111) metal oxide surfaces for pyrolysis oil upgrading and lignin depolymerization

NASA Astrophysics Data System (ADS)

Finch, Kenneth

2013-01-01

Pyrolysis oil, or bio-oil, is one of the most promising methods to upgrade a variety of biomass to transportation fuels. Moving toward a more "green" catalytic process requires heterogeneous catalysis over homogeneous catalysis to avoid extraction solvent waste. Nanoscale catalysts are showing great promise due to their high surface area and unusual surfaces. Base catalyzed condensation reactions occur much quicker than acid catalyzed condensation reactions. However, MgO is slightly soluble in water and is susceptible to degradation by acidic environments, similar to those found in fast-pyrolysis oil. Magnesium oxide (111) has a highly active Lewis base surface, which can catalyze Claisen-Schmidt condensation reactions in the organic phase. It has been shown previously that carbon coating a catalyst, such as a metal oxide, provides integrity while leaving the catalytic activity intact. Here, carbon-coated MgO(111) will be discussed with regards to synthesis, characterization and application to bio-oil upgrading through model compounds. Raman spectroscopy and HR-TEM are used to characterize the thickness and carbon-bonding environment of the carbon coating. Propanal self-condensation reactions have been conducted in the aqueous phase with varying amounts of acetic acid present. Quantitative analysis by gas chromatography was completed to determine the catalytic activity of CC-MgO(111). ICP-OES analysis has been conducted to measure the magnesium concentration in the product solution and give insight into the leaching of the catalyst into the reaction solution.

Dual-beam laser welding of AZ31B magnesium alloy in zero-gap lap joint configuration

NASA Astrophysics Data System (ADS)

Harooni, Masoud; Carlson, Blair; Kovacevic, Radovan

2014-03-01

Porosity within laser welds of magnesium alloys is one of the main roadblocks to achieving high quality joints. One of the causes of pore formation is the presence of pre-existing coatings on the surface of magnesium alloy such as oxide or chromate layers. In this study, single-beam and dual-beam laser heat sources are investigated in relation to mitigation of pores resulting from the presence of the as-received oxide layer on the surface of AZ31B-H24 magnesium alloy during the laser welding process. A fiber laser with a power of up to 4 kW is used to weld samples in a zero-gap lap joint configuration. The effect of dual-beam laser welding with different beam energy ratios is studied on the quality of the weld bead. The purpose of this paper is to identify the beam ratio that best mitigates pore formation in the weld bead. The laser molten pool and the keyhole condition, as well as laser-induced plasma plume are monitored in real-time by use of a high speed charge-coupled device (CCD) camera assisted with a green laser as an illumination source. Tensile and microhardness tests were used to measure the mechanical properties of the laser welded samples. Results showed that a dual-beam laser configuration can effectively mitigate pore formation in the weld bead by a preheating-welding mechanism.

Experiments On Transparent Conductive Films For Spacecraft

NASA Technical Reports Server (NTRS)

Perez-Davis, Marla E.; Rutledge, Sharon K.; De Groh, Kim K.; Hung, Ching-Cheh; Malave-Sanabria, Tania; Hambourger, Paul; Roig, David

1995-01-01

Report describes experiments on thin, transparent, electrically conductive films made, variously, of indium tin oxide covered by magnesium fluoride (ITO/MgF2), aluminum-doped zinc oxide (AZO), or pure zinc oxide (ZnO). Films are candidates for application to such spacecraft components, including various optoelectronic devices and window surfaces that must be protected against buildup of static electric charge. On Earth, such films useful on heat mirrors, optoelectronic devices, gas sensors, and automotive and aircraft windows.

Porous Aluminum Oxide and Magnesium Oxide Films Using Organic Hydrogels as Structure Matrices

PubMed Central

Chen, Zimei

2018-01-01

We describe the synthesis of mesoporous Al2O3 and MgO layers on silicon wafer substrates by using poly(dimethylacrylamide) hydrogels as porogenic matrices. Hydrogel films are prepared by spreading the polymer through spin-coating, followed by photo-cross-linking and anchoring to the substrate surface. The metal oxides are obtained by swelling the hydrogels in the respective metal nitrate solutions and subsequent thermal conversion. Combustion of the hydrogel results in mesoporous metal oxide layers with thicknesses in the μm range and high specific surface areas up to 558 m2∙g−1. Materials are characterized by SEM, FIB ablation, EDX, and Kr physisorption porosimetry. PMID:29565802

Electrodeposition of r-GO/SiC nano-composites on Magnesium and its Corrosion Behavior in Aqueous Electrolyte

NASA Astrophysics Data System (ADS)

Kavimani, V.; K, Soorya Prakash; R, Rajesh; Rammasamy, Devaraj; Selvaraj, Nivas Babu; Yang, Tao; Prabakaran, Balasubramanian; Jothi, Sathiskumar

2017-12-01

In this paper a detailed investigation for corrosion behavior of magnesium substrate electrodeposited differently by nanoparticles like Reduced Graphene Oxide (r-GO synthesized through Modified Hummer's Method), Silicon Carbide (SiCsbnd mechanically alloyed) and also r-GO/SiC nanocomposites (dispersed through ultrasonication process) as coating materials for varying time period was done. Synthesized nanocomposite was characterized through various physio-chemical techniques and confirmation of the same was carried out. Surface morphology of the developed set of specimens was scrutinized through SEM and EDAX which establishes a clean surface coating with minimal defects attainment through electro deposition technique. Electrochemical corrosion behavior for the magnesium substrates coated with r-GO, SiC, r-GO/SiC for 5 and 10 min coating time period was conceded over in 0.1 M of NaCl and Na2SO4 aqueous solution using Tafel polarization and then compared with a pure magnesium substrate. r-GO/SiC nanocomposite coated magnesium substrate showcased a drastic breakthrough in corrosion resistance when compared with other set of specimens in aqueous medium. Delamination behavior for the same set of specimens was carried and the r-GO/SiC nanocomposite coated magnesium exposed a minimum delamination area accounting to the hydrophobic property of graphene and the binding effect of SiC nano particles.

Corrosion prevention of magnesium surfaces via surface conversion treatments using ionic liquids

DOEpatents

Qu, Jun; Luo, Huimin

2016-09-06

A method for conversion coating a magnesium-containing surface, the method comprising contacting the magnesium-containing surface with an ionic liquid compound under conditions that result in decomposition of the ionic liquid compound to produce a conversion coated magnesium-containing surface having a substantially improved corrosion resistance relative to the magnesium-containing surface before said conversion coating. Also described are the resulting conversion-coated magnesium-containing surface, as well as mechanical components and devices containing the conversion-coated magnesium-containing surface.

Ignition Temperatures of Metals in Oxygen Atmospheres

NASA Technical Reports Server (NTRS)

Laurendeau, N. M.; Glassman, I.

1971-01-01

The ignition temperature of ten common non-toxic metals has been determined experimentally in an oxygen environment. In this investigation a induction furnace facility that emphasized the preignition surface.oxidation effects upon the ignition temperature was used. The bulk ignition temperatures of barium, bismuth, calcium, iron, lead, magnesium, molybdenum, strontium, tin, and zinc were found and compared to the previous results of Grosse and Conway. The differences in the results are attributed to how the heating cycle is carried out and how the cycle affects the surface oxide coat.

21 CFR 331.11 - Listing of specific active ingredients.

Code of Federal Regulations, 2010 CFR

2010-04-01

... aluminosilicates. (4) Magnesium carbonate. (5) Magnesium glycinate. (6) Magnesium hydroxide. (7) Magnesium oxide..., aluminum hydroxide-magnesium carbonate codried gel, aluminum hydroxide-magnesium trisilicate codried gel... or salt; maximum daily dosage limit 8 grams. (f) Glycine (aminoacetic acid). (g) Magnesium-containing...

21 CFR 331.11 - Listing of specific active ingredients.

Code of Federal Regulations, 2011 CFR

2011-04-01

... aluminosilicates. (4) Magnesium carbonate. (5) Magnesium glycinate. (6) Magnesium hydroxide. (7) Magnesium oxide..., aluminum hydroxide-magnesium carbonate codried gel, aluminum hydroxide-magnesium trisilicate codried gel... or salt; maximum daily dosage limit 8 grams. (f) Glycine (aminoacetic acid). (g) Magnesium-containing...

Evaluation of magnesium ions release, biocorrosion, and hemocompatibility of MAO/PLLA-modified magnesium alloy WE42.

PubMed

Lu, Ping; Cao, Lu; Liu, Yin; Xu, Xinhua; Wu, Xiangfeng

2011-01-01

Magnesium alloys may potentially be applied as biodegradable metallic materials in cardiovascular stent. However, the high corrosion rate hinders its clinical application. In this study, a new approach was adopted to control the corrosion rate by fabricating a biocompatible micro-arc oxidation/poly-L-lactic acid (MAO/PLLA) composite coating on the magnesium alloy WE42 substrate and the biocompatibility of the modified samples was investigated. The scanning electronic microscope (SEM) images were used to demonstrate the morphology of the samples before and after being submerged in hanks solution for 4 weeks. The degradation was evaluated through the magnesium ions release rate and electrochemical impedance spectroscopy (EIS) test. The biocompatibility of the samples was demonstrated by coagulation time and hemolysis behavior. The result shows that the poly-L-lactic acid (PLLA) effectively improved the corrosion resistance by sealing the microcracks and microholes on the surface of the MAO coating. The modified samples had good compatibility. © 2010 Wiley Periodicals, Inc.

Role of Magnesium in Oxidative Stress in Individuals with Obesity.

PubMed

Morais, Jennifer Beatriz Silva; Severo, Juliana Soares; Santos, Loanne Rocha Dos; de Sousa Melo, Stéfany Rodrigues; de Oliveira Santos, Raisa; de Oliveira, Ana Raquel Soares; Cruz, Kyria Jayanne Clímaco; do Nascimento Marreiro, Dilina

2017-03-01

Adipose tissue is considered an endocrine organ that promotes excessive production of reactive oxygen species when in excess, thus contributing to lipid peroxidation. Magnesium deficiency contributes to the development of oxidative stress in obese individuals, as this mineral plays a role as an antioxidant, participates as a cofactor of several enzymes, maintains cell membrane stability and mitigates the effects of oxidative stress. The objective of this review is to bring together updated information on the participation of magnesium in the oxidative stress present in obesity. We conducted a search of articles published in the PubMed, SciELO and LILACS databases, using the keywords 'magnesium', 'oxidative stress', 'malondialdehyde', 'superoxide dismutase', 'glutathione peroxidase', 'reactive oxygen species', 'inflammation' and 'obesity'. The studies show that obese subjects have low serum concentrations of magnesium, as well as high concentrations of oxidative stress marker in these individuals. Furthermore, it is evident that the adequate intake of magnesium contributes to its appropriate homeostasis in the body. Thus, this review of current research can help define the need for intervention with supplementation of this mineral for the prevention and treatment of disorders associated with this chronic disease.

Quantifying the degradation of degradable implants and bone formation in the femoral condyle using micro-CT 3D reconstruction

PubMed Central

Xu, Yichi; Meng, Haoye; Yin, Heyong; Sun, Zhen; Peng, Jiang; Xu, Xiaolong; Guo, Quanyi; Xu, Wenjing; Yu, Xiaoming; Yuan, Zhiguo; Xiao, Bo; Wang, Cheng; Wang, Yu; Liu, Shuyun; Lu, Shibi; Wang, Zhaoxu; Wang, Aiyuan

2018-01-01

Degradation limits the application of magnesium alloys, and evaluation methods for non-traumatic in vivo quantification of implant degradation and bone formation are imperfect. In the present study, a micro-arc-oxidized AZ31 magnesium alloy was used to evaluate the degradation of implants and new bone formation in 60 male New Zealand white rabbits. Degradation was monitored by weighing the implants prior to and following implantation, and by performing micro-computed tomography (CT) scans and histological analysis after 1, 4, 12, 24, 36, and 48 weeks of implantation. The results indicated that the implants underwent slow degradation in the first 4 weeks, with negligible degradation in the first week, followed by significantly increased degradation during weeks 12–24 (P<0.05), and continued degradation until the end of the 48-week experimental period. The magnesium content decreased as the implant degraded (P<0.05); however, the density of the material exhibited almost no change. Micro-CT results also demonstrated that pin volume, pin mineral density, mean ‘pin thickness’, bone surface/bone volume and trabecular separation decreased over time (P<0.05), and that the pin surface area/pin volume, bone volume fraction, trabecular thickness, trabecular number and tissue mineral density increased over time (P<0.05), indicating that the number of bones and density of new bone increased as magnesium degraded. These results support the positive effect of magnesium on osteogenesis. However, from the maximum inner diameter of the new bone loop and diameter of the pin in the same position, the magnesium alloy was not capable of creating sufficient bridges between the bones and biomaterials when there were preexisting gaps. Histological analyses indicated that there were no inflammatory responses around the implants. The results of the present study indicate that a micro-arc-oxidized AZ31 magnesium alloy is safe in vivo and efficiently degraded. Furthermore, the novel bone formation increased as the implant degraded. The findings concluded that micro-CT, which is useful for providing non-traumatic, in vivo, quantitative and precise data, has great value for exploring the degradation of implants and novel bone formation. PMID:29375677

Quantifying the degradation of degradable implants and bone formation in the femoral condyle using micro-CT 3D reconstruction.

PubMed

Xu, Yichi; Meng, Haoye; Yin, Heyong; Sun, Zhen; Peng, Jiang; Xu, Xiaolong; Guo, Quanyi; Xu, Wenjing; Yu, Xiaoming; Yuan, Zhiguo; Xiao, Bo; Wang, Cheng; Wang, Yu; Liu, Shuyun; Lu, Shibi; Wang, Zhaoxu; Wang, Aiyuan

2018-01-01

Degradation limits the application of magnesium alloys, and evaluation methods for non-traumatic in vivo quantification of implant degradation and bone formation are imperfect. In the present study, a micro-arc-oxidized AZ31 magnesium alloy was used to evaluate the degradation of implants and new bone formation in 60 male New Zealand white rabbits. Degradation was monitored by weighing the implants prior to and following implantation, and by performing micro-computed tomography (CT) scans and histological analysis after 1, 4, 12, 24, 36, and 48 weeks of implantation. The results indicated that the implants underwent slow degradation in the first 4 weeks, with negligible degradation in the first week, followed by significantly increased degradation during weeks 12-24 (P<0.05), and continued degradation until the end of the 48-week experimental period. The magnesium content decreased as the implant degraded (P<0.05); however, the density of the material exhibited almost no change. Micro-CT results also demonstrated that pin volume, pin mineral density, mean 'pin thickness', bone surface/bone volume and trabecular separation decreased over time (P<0.05), and that the pin surface area/pin volume, bone volume fraction, trabecular thickness, trabecular number and tissue mineral density increased over time (P<0.05), indicating that the number of bones and density of new bone increased as magnesium degraded. These results support the positive effect of magnesium on osteogenesis. However, from the maximum inner diameter of the new bone loop and diameter of the pin in the same position, the magnesium alloy was not capable of creating sufficient bridges between the bones and biomaterials when there were preexisting gaps. Histological analyses indicated that there were no inflammatory responses around the implants. The results of the present study indicate that a micro-arc-oxidized AZ31 magnesium alloy is safe in vivo and efficiently degraded. Furthermore, the novel bone formation increased as the implant degraded. The findings concluded that micro-CT, which is useful for providing non-traumatic, in vivo , quantitative and precise data, has great value for exploring the degradation of implants and novel bone formation.

Osteoblast response to magnesium ion-incorporated nanoporous titanium oxide surfaces.

PubMed

Park, Jin-Woo; Kim, Youn-Jeong; Jang, Je-Hee; Song, Hwangjun

2010-11-01

This study investigated the surface characteristics and in vitro osteoconductivity of a titanium (Ti) surface incorporated with the magnesium ions (Mg) produced by hydrothermal treatment for future application as an endosseous implant surface. Mg-incorporated Ti oxide surfaces were produced by hydrothermal treatment using Mg-containing solution on two different microstructured surfaces--abraded minimally rough (Ma) or grit-blasted moderately rough (RBM) samples. The surface characteristics were evaluated using scanning electron microscopy, thin-film X-ray diffractometry, X-ray photoelectron spectroscopy, optical profilometry, and inductively coupled plasma atomic emission spectroscopy (ICP-AES). MC3T3-E1 pre-osteoblast cell attachment, proliferation, alkaline phosphatase (ALP) activity, and quantitative analysis of osteoblastic gene expression on Ma, RBM, Mg-incorporated Ma (Mg), and Mg-incorporated grit-blasted (RBM/Mg) Ti surfaces were evaluated. Hydrothermal treatment produced an Mg-incorporated Ti oxide layer with nanoporous surface structures. Mg-incorporated surfaces showed surface morphologies and surface roughness values almost identical to those of untreated smooth or micro-rough surfaces at the micron scale. ICP-AES analysis showed Mg ions released from treated surfaces into the solution. Mg incorporation significantly increased cellular attachment (P=0 at 0.5 h, P=0.01 at 1 h) on smooth surfaces, but no differences were found on micro-rough surfaces. Mg incorporation further increased ALP activity in cells grown on both smooth and micro-rough surfaces at 7 and 14 days of culture (P=0). Real-time polymerase chain reaction analysis showed higher mRNA expressions of the osteoblast transcription factor gene (Dlx5), various integrins, and the osteoblast phenotype genes (ALP, bone sialoprotein and osteocalcin) in cells grown on micro-rough (RBM) and Mg-incorporated (Mg and RBM/Mg) surfaces than those on Ma surfaces. Mg incorporation further increased the mRNA expressions of key osteoblast genes and integrins (α1, α2, α5, and β1) in cells grown on both the smooth and the micro-rough surfaces. These results indicate that an Mg-incorporated nanoporous Ti oxide surface produced by hydrothermal treatment may improve implant bone healing by enhancing the attachment and differentiation of osteoblastic cells. © 2010 John Wiley & Sons A/S.

High-compactness coating grown by plasma electrolytic oxidation on AZ31 magnesium alloy in the solution of silicate-borax

NASA Astrophysics Data System (ADS)

Shen, M. J.; Wang, X. J.; Zhang, M. F.

2012-10-01

A ceramic coating was formed on the surface of AZ31 magnesium alloy by plasma electrolytic oxidation (PEO) in the silicate solution with and without borax doped. The composition, morphology, elements and roughness as well as mechanical property of the coating were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and reciprocal-sliding tribometer. The results show that the PEO coating is mainly composed of magnesia. When using borax dope, boron element is permeating into the coating and the boron containing phase exist in the form of amorphous. In addition, the microhardness and compactness of the PEO coating are improved significantly due to doped borax.

Effect of increased magnesium intake on plasma cholesterol, triglyceride and oxidative stress in alloxan-diabetic rats.

PubMed

Olatunji, L A; Soladoye, A O

2007-06-01

Cardiovascular disorders are the primary causes of morbidity and mortality in patients with diabetes mellitus (DM). Agents that improve lipid profile and reduce oxidative stress have been shown to reduce the ensuing risk factors. In the present study, we investigated whether increased magnesium intake could improve hyperglycaemia, dyslipidaemia, and reduce oxidative stress in alloxan-induced diabetic rats. Male Wistar rats were divided into non-diabetic (ND), diabetic (DM) and diabetic fed on a high magnesium diet (DM-Mg) groups. Plasma concentrations of thiobarbituric acid reactive substances (TBARS) were used as markers of oxidative stress. Plasma levels of ascorbic acid, magnesium and calcium were also determined. Diabetes was induced by injecting alloxan (100 mg/kg B.W). The fasting blood glucose levels were significantly lower in the DM-Mg rats than in the DM rats. Plasma total cholesterol, triglyceride, TBARS levels were significantly higher while plasma HDL-cholesterol, HDL-cholesterol/total cholesterol ratio, ascorbic acid levels were significantly lowered in DM rats compared with the ND rats. Increased intake of magnesium significantly abrogated these alterations. There were no significant differences in the plasma levels of magnesium and calcium between the DM and ND groups. However, plasma levels of magnesium but not calcium were significantly elevated in DM-Mg rats when compared with other groups. In conclusion, these results suggest that diet rich in magnesium could exert cardioprotective effect through reduced plasma total cholesterol, triglyceride, oxidative stress and ameliorated HDL-cholesterol/total cholesterol ratio as well as increased plasma ascorbic acid and magnesium in diabetic rats.

Method to decrease loss of aluminum and magnesium melts

DOEpatents

Hryn, John N.; Pellin, Michael J.; Calaway, Jr., Wallis F.; Moore, Jerry F.; Krumdick, Gregory K.

2002-01-01

A method to minimize oxidation of metal during melting processes is provided, the method comprising placing solid phase metal into a furnace environ-ment, transforming the solid-phase metal into molten metal phase having a molten metal surface, and creating a barrier between the surface and the environment. Also provided is a method for isolating the surface of molten metal from its environment, the method comprising confining the molten metal to a controlled atmos-phere, and imposing a floating substrate between the surface and the atmosphere.

Scaling-Up Solid Oxide Membrane Electrolysis Technology for Magnesium Production

NASA Astrophysics Data System (ADS)

Pati, Soobhankar; Powell, Adam; Tucker, Steve; Derezinski, Steve

Metal Oxygen Separation Technologies, Inc. (MOxST) is actively developing Solid Oxide Membrane (SOM) electrolysis technology for production of magnesium directly from its oxide. The vital component of this technology is the oxygen ion-conducting solid zirconia electrolyte separating the molten flux (a mixture of salts and oxide) and the inert anode. The zirconia not only protects the anode from the flux but also prevents anode gas back-reaction, increasing the efficiency. This makes it possible to produce low-cost high-purity magnesium and high-purity oxygen as a byproduct with no direct greenhouse gas emissions. In this paper we discuss the design modifications made to address the scaling-up challenges, particularly for producing magnesium in liquid form. The key accomplishment to date is the successful development of a prototype capable of producing few kilograms of magnesium per day. We will also describe the prerequisite properties of an inert anode and suitable materials for the same.

Fabrication and Tribological Behavior of Stir Cast Mg/B4C Metal Matrix Composites

NASA Astrophysics Data System (ADS)

Singh, Amandeep; Bala, Niraj

2017-10-01

Magnesium-based metal matrix composites (MMMCs) have emerged as good alternative material to conventional materials due to their promising advanced properties. In the present work, magnesium-based metal matrix composites (MMMCs) reinforced with B4C particles were successfully fabricated by cost-effective conventional stir casting technique. MMMCs with an average particle size of 63 µm and different weight percent (wt pct) of B4C between 3 and 12 were fabricated. Wear tests were carried out using a pin-on-disk against a steel disk under dry sliding condition at loads that varied between 1 and 5 kg at fixed sliding velocity of 1 m/s. The wear data clearly showed that wear resistance of cast composites is better than that of unreinforced magnesium, which is attributed to dispersion hardening caused by carbide particles. An increase in wt pct of B4C showed the wear resistance and hardness to increase significantly. The wear rate and coefficient of friction increased with an increase in applied load. The SEM and EDS analysis of the worn surfaces delineated the dominant wear mechanisms to be abrasion, adhesion, and oxidation under the different sliding conditions. At lower loads, the wear mechanism transformed from severe abrasive wear in pure magnesium (Mg) to mild abrasion, slight delamination, and oxidation in the Mg/12 wt pct B4C fabricated composite. At higher loads, severe abrasion, adhesion, delamination, and oxidation were found to be the major wear mechanisms in pure Mg, whereas in the Mg/12 wt pct B4C fabricated composites the corresponding mechanisms were mild abrasion, mild adhesion, slight delamination, and oxidation.

Synthesis and characterization of magnesium doped cerium oxide for the fuel cell application

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Amit; Kumari, Monika; Kumar, Mintu

2016-05-06

Cerium oxide has attained much attentions in global nanotechnology market due to valuable application for catalytic, fuel additive, and widely as electrolyte in solid oxide fuel cell. Doped cerium oxide has large oxygen vacancies that allow for greater reactivity and faster ion transport. These properties make cerium oxide suitable material for SOFCs application. Cerium oxide electrolyte requires lower operation temperature which shows improvement in processing and the fabrication technique. In our work, we synthesized magnesium doped cerium oxide by the co-precipitation method. With the magnesium doping catalytic reactivity of CeO{sub 2} was increased. Synthesized nanoparticle were characterized by the XRDmore » and UV absorption techniques.« less

21 CFR 82.3 - Definitions.

Code of Federal Regulations, 2011 CFR

2011-04-01

...) The term mixed oxides means the sum of the quantities of aluminum, iron, calcium, and magnesium (in whatever combination they may exist in a coal-tar color) calculated as aluminum trioxide, ferric oxide, calcium oxide, and magnesium oxide. (k)-(m) [Reserved] (n) The term externally applied drugs and cosmetics...

21 CFR 82.3 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-04-01

...) The term mixed oxides means the sum of the quantities of aluminum, iron, calcium, and magnesium (in whatever combination they may exist in a coal-tar color) calculated as aluminum trioxide, ferric oxide, calcium oxide, and magnesium oxide. (k)-(m) [Reserved] (n) The term externally applied drugs and cosmetics...

In vitro degradation and biocompatibility of a strontium-containing micro-arc oxidation coating on the biodegradable ZK60 magnesium alloy

NASA Astrophysics Data System (ADS)

Lin, Xiao; Yang, Xiaoming; Tan, Lili; Li, Mei; Wang, Xin; Zhang, Yu; Yang, Ke; Hu, Zhuangqi; Qiu, Jianhong

2014-01-01

Magnesium alloys are promising biodegradable implant candidates for orthopedic application. In the present study, a phosphate-based micro-arc oxidation (MAO) coating was applied on the ZK60 alloy to decrease its initial degradation rate. Strontium (Sr) was incorporated into the coating in order to improve the bioactivity of the coating. The in vitro degradation studies showed that the MAO coating containing Sr owned a better initial corrosion resistance, which was mainly attributed to the superior inner barrier layer, and a better long-term protective ability, probably owning to its larger thickness, superior inner barrier layer and the superior apatite formation ability. The degradation of MAO coating was accompanied by the formation of degradation layer and Ca-P deposition layer. The in vitro cell tests demonstrated that the incorporation of Sr into the MAO coating enhanced both the proliferation of preosteoblast cells and the alkaline phosphatase activity of the murine bone marrow stromal cells. In conclusion, the MAO coating with Sr is a promising surface treatment for the biodegradable magnesium alloys.

Influence of Applied Voltage and Film-Formation Time on Microstructure and Corrosion Resistance of Coatings Formed on Mg-Zn-Zr-Ca Bio-magnesium Alloy

NASA Astrophysics Data System (ADS)

Yandong, Yu; Shuzhen, Kuang; Jie, Li

2015-09-01

The influence of applied voltage and film-formation time on the microstructure and corrosion resistance of coatings formed on a Mg-Zn-Zr-Ca novel bio-magnesium alloy has been investigated by micro-arc oxidation (MAO) treatment. Phase composition and microstructure of as-coated samples were analyzed by the x-ray diffraction, energy dispersive x-ray spectroscopy and scanning electron microscopy. And the porosity and average of micro-pore aperture of the surface on ceramic coatings were analyzed by general image software. Corrosion microstructure of as-coated samples was caught by a microscope digital camera. The long-term corrosion resistance of as-coated samples was tested in simulated body fluid for 30 days. The results showed that the milky white smooth ceramic coating formed on the Mg-Zn-Zr-Ca novel bio-magnesium alloy was a compound of MgO, Mg2SiO4 and MgSiO3, and its corrosion resistance was significantly improved compared with that of the magnesium substrate. In addition, when the MAO applied voltage were 450 V and 500 V and film-formation time were 9 min and 11 min, the surface micro-morphology and the corrosion resistance of as-coated samples were relatively improved. The results provided a theoretical foundation for the application of the Mg-Zn-Zr-Ca novel bio-magnesium alloy in biomedicine.

Magnesium Status and Its Association with Oxidative Stress in Obese Women.

PubMed

Morais, Jennifer Beatriz Silva; Severo, Juliana Soares; de Oliveira, Ana Raquel Soares; Cruz, Kyria Jayanne Clímaco; da Silva Dias, Thaline Milany; de Assis, Régina Célia; Colli, Célia; do Nascimento Marreiro, Dilina

2017-02-01

The aim of this study was to assess the relationship between magnesium status and oxidative stress in obese and nonobese women. This cross-sectional study included 83 women, aged between 20 and 50 years, who were divided into two groups: the obese group (n = 31) and the control group (n = 52). The control group was age-matched with the obese group. Magnesium intake was monitored using 3-day food records and NutWin software version 1.5. The plasma and erythrocyte magnesium concentrations were determined by flame atomic absorption spectrophotometry. Plasma levels of thiobarbituric acid reactive substances (TBARS) were determined as biomarkers for lipid peroxidation and therefore of oxidative stress. The mean values of the magnesium content in the diet were found to be lower than those recommended, though there was no significant difference between groups (p > 0.05). The mean concentrations of plasma and erythrocyte magnesium were within the normal range, with no significant difference between groups (p > 0.05). The mean concentration of plasma TBARS was higher in obese woman, and the difference between the groups was statistically different (p < 0.05). There was a positive correlation between erythrocyte magnesium and plasma TBARS in the obese group (p = 0.021). Obese patients ingest low dietary magnesium content, which does not seem to affect the plasma and erythrocyte concentrations of the mineral. The study showed a negative correlation between erythrocyte magnesium concentrations and plasma TBARS, suggesting the influence of magnesium status on the parameters of oxidative stress in obese women.

Balancing surface adsorption and diffusion of lithium-polysulfides on nonconductive oxides for lithium–sulfur battery design

DOE PAGES

Tao, Xinyong; Wang, Jianguo; Liu, Chong; ...

2016-04-05

Lithium–sulfur batteries have attracted attention due to their six-fold specific energy compared with conventional lithium-ion batteries. Dissolution of lithium polysulfides, volume expansion of sulfur and uncontrollable deposition of lithium sulfide are three of the main challenges for this technology. State-of-the-art sulfur cathodes based on metal-oxide nanostructures can suppress the shuttle-effect and enable controlled lithium sulfide deposition. However, a clear mechanistic understanding and corresponding selection criteria for the oxides are still lacking. Herein, various nonconductive metal-oxide nanoparticle-decorated carbon flakes are synthesized via a facile biotemplating method. The cathodes based on magnesium oxide, cerium oxide and lanthanum oxide show enhanced cycling performance.more » Adsorption experiments and theoretical calculations reveal that polysulfide capture by the oxides is via monolayered chemisorption. Moreover, we show that better surface diffusion leads to higher deposition efficiency of sulfide species on electrodes. Lastly, oxide selection is proposed to balance optimization between sulfide-adsorption and diffusion on the oxides.« less

Balancing surface adsorption and diffusion of lithium-polysulfides on nonconductive oxides for lithium-sulfur battery design

NASA Astrophysics Data System (ADS)

Tao, Xinyong; Wang, Jianguo; Liu, Chong; Wang, Haotian; Yao, Hongbin; Zheng, Guangyuan; Seh, Zhi Wei; Cai, Qiuxia; Li, Weiyang; Zhou, Guangmin; Zu, Chenxi; Cui, Yi

2016-04-01

Lithium-sulfur batteries have attracted attention due to their six-fold specific energy compared with conventional lithium-ion batteries. Dissolution of lithium polysulfides, volume expansion of sulfur and uncontrollable deposition of lithium sulfide are three of the main challenges for this technology. State-of-the-art sulfur cathodes based on metal-oxide nanostructures can suppress the shuttle-effect and enable controlled lithium sulfide deposition. However, a clear mechanistic understanding and corresponding selection criteria for the oxides are still lacking. Herein, various nonconductive metal-oxide nanoparticle-decorated carbon flakes are synthesized via a facile biotemplating method. The cathodes based on magnesium oxide, cerium oxide and lanthanum oxide show enhanced cycling performance. Adsorption experiments and theoretical calculations reveal that polysulfide capture by the oxides is via monolayered chemisorption. Moreover, we show that better surface diffusion leads to higher deposition efficiency of sulfide species on electrodes. Hence, oxide selection is proposed to balance optimization between sulfide-adsorption and diffusion on the oxides.

Balancing surface adsorption and diffusion of lithium-polysulfides on nonconductive oxides for lithium-sulfur battery design.

PubMed

Tao, Xinyong; Wang, Jianguo; Liu, Chong; Wang, Haotian; Yao, Hongbin; Zheng, Guangyuan; Seh, Zhi Wei; Cai, Qiuxia; Li, Weiyang; Zhou, Guangmin; Zu, Chenxi; Cui, Yi

2016-04-05

Lithium-sulfur batteries have attracted attention due to their six-fold specific energy compared with conventional lithium-ion batteries. Dissolution of lithium polysulfides, volume expansion of sulfur and uncontrollable deposition of lithium sulfide are three of the main challenges for this technology. State-of-the-art sulfur cathodes based on metal-oxide nanostructures can suppress the shuttle-effect and enable controlled lithium sulfide deposition. However, a clear mechanistic understanding and corresponding selection criteria for the oxides are still lacking. Herein, various nonconductive metal-oxide nanoparticle-decorated carbon flakes are synthesized via a facile biotemplating method. The cathodes based on magnesium oxide, cerium oxide and lanthanum oxide show enhanced cycling performance. Adsorption experiments and theoretical calculations reveal that polysulfide capture by the oxides is via monolayered chemisorption. Moreover, we show that better surface diffusion leads to higher deposition efficiency of sulfide species on electrodes. Hence, oxide selection is proposed to balance optimization between sulfide-adsorption and diffusion on the oxides.

Balancing surface adsorption and diffusion of lithium-polysulfides on nonconductive oxides for lithium–sulfur battery design

PubMed Central

Tao, Xinyong; Wang, Jianguo; Liu, Chong; Wang, Haotian; Yao, Hongbin; Zheng, Guangyuan; Seh, Zhi Wei; Cai, Qiuxia; Li, Weiyang; Zhou, Guangmin; Zu, Chenxi; Cui, Yi

2016-01-01

Lithium–sulfur batteries have attracted attention due to their six-fold specific energy compared with conventional lithium-ion batteries. Dissolution of lithium polysulfides, volume expansion of sulfur and uncontrollable deposition of lithium sulfide are three of the main challenges for this technology. State-of-the-art sulfur cathodes based on metal-oxide nanostructures can suppress the shuttle-effect and enable controlled lithium sulfide deposition. However, a clear mechanistic understanding and corresponding selection criteria for the oxides are still lacking. Herein, various nonconductive metal-oxide nanoparticle-decorated carbon flakes are synthesized via a facile biotemplating method. The cathodes based on magnesium oxide, cerium oxide and lanthanum oxide show enhanced cycling performance. Adsorption experiments and theoretical calculations reveal that polysulfide capture by the oxides is via monolayered chemisorption. Moreover, we show that better surface diffusion leads to higher deposition efficiency of sulfide species on electrodes. Hence, oxide selection is proposed to balance optimization between sulfide-adsorption and diffusion on the oxides. PMID:27046216

Effect of sintering conditions on the microstructural and mechanical characteristics of porous magnesium materials prepared by powder metallurgy.

PubMed

Čapek, Jaroslav; Vojtěch, Dalibor

2014-02-01

There has recently been an increased demand for porous magnesium materials in many applications, especially in the medical field. Powder metallurgy appears to be a promising approach for the preparation of such materials. Many works have dealt with the preparation of porous magnesium; however, the effect of sintering conditions on material properties has rarely been investigated. In this work, we investigated porous magnesium samples that were prepared by powder metallurgy using ammonium bicarbonate spacer particles. The effects of the purity of the argon atmosphere and sintering time on the microstructure (SEM, EDX and XRD) and mechanical behaviour (universal loading machine and Vickers hardness tester) of porous magnesium were studied. The porosities of the prepared samples ranged from 24 to 29 vol.% depending on the sintering conditions. The purity of atmosphere played a significant role when the sintering time exceeded 6h. Under a gettered argon atmosphere, a prolonged sintering time enhanced diffusion connections between magnesium particles and improved the mechanical properties of the samples, whereas under a technical argon atmosphere, oxidation at the particle surfaces caused deterioration in the mechanical properties of the samples. These results suggest that a refined atmosphere is required to improve the mechanical properties of porous magnesium. © 2013.

Preparation of Composite Coating on AZ91D Magnesium Alloy by Silica Sol-Micro Oxidation

NASA Astrophysics Data System (ADS)

Shao, Zhongcai; Zhang, Feifei; Zhao, Ruiqiang; Shen, Xiaoyi

2016-03-01

Composite coating was prepared on AZ91D magnesium alloy with a new method which combined silica sol with micro-arc oxidation (MAO). The MAO coating was prepared on the basis of MAO solution, and then coated by sol-gel process. The composite coating was obtained after second MAO treatment. Scanning electron microscopy coupled with X-ray diffraction (XRD), energy spectrum analysis and electrochemical testing was applied to characterize the properties of MAO coating and composite coating. The experimental test results indicated that the Si element derived from SiO2 gel particle embedded into the MAO coating by second MAO treatment. The surface of composite coating became dense and the holes were smaller with silica sol sealing process. The corrosion resistance of composite coating was improved than the MAO coating.

Nanostructured magnesium has fewer detrimental effects on osteoblast function.

PubMed

Weng, Lucy; Webster, Thomas J

2013-01-01

Efforts have been made recently to implement nanoscale surface features on magnesium, a biodegradable metal, to increase bone formation. Compared with normal magnesium, nanostructured magnesium has unique characteristics, including increased grain boundary properties, surface to volume ratio, surface roughness, and surface energy, which may influence the initial adsorption of proteins known to promote the function of osteoblasts (bone-forming cells). Previous studies have shown that one way to increase nanosurface roughness on magnesium is to soak the metal in NaOH. However, it has not been determined if degradation of magnesium is altered by creating nanoscale features on its surface to influence osteoblast density. The aim of the present in vitro study was to determine the influence of degradation of nanostructured magnesium, created by soaking in NaOH, on osteoblast density. Our results showed a less detrimental effect of magnesium degradation on osteoblast density when magnesium was treated with NaOH to create nanoscale surface features. The detrimental degradation products of magnesium are of significant concern when considering use of magnesium as an orthopedic implant material, and this study identified a surface treatment, ie, soaking in NaOH to create nanoscale features for magnesium that can improve its use in numerous orthopedic applications.

Nanostructured magnesium has fewer detrimental effects on osteoblast function

PubMed Central

Weng, Lucy; Webster, Thomas J

2013-01-01

Efforts have been made recently to implement nanoscale surface features on magnesium, a biodegradable metal, to increase bone formation. Compared with normal magnesium, nanostructured magnesium has unique characteristics, including increased grain boundary properties, surface to volume ratio, surface roughness, and surface energy, which may influence the initial adsorption of proteins known to promote the function of osteoblasts (bone-forming cells). Previous studies have shown that one way to increase nanosurface roughness on magnesium is to soak the metal in NaOH. However, it has not been determined if degradation of magnesium is altered by creating nanoscale features on its surface to influence osteoblast density. The aim of the present in vitro study was to determine the influence of degradation of nanostructured magnesium, created by soaking in NaOH, on osteoblast density. Our results showed a less detrimental effect of magnesium degradation on osteoblast density when magnesium was treated with NaOH to create nanoscale surface features. The detrimental degradation products of magnesium are of significant concern when considering use of magnesium as an orthopedic implant material, and this study identified a surface treatment, ie, soaking in NaOH to create nanoscale features for magnesium that can improve its use in numerous orthopedic applications. PMID:23674891

Template-free magnesium oxide hollow sphere inclusion in organic-inorganic hybrid films via sol-gel reaction.

PubMed

Kang, Eun-Seok; Takahashi, Masahide; Tokuda, Yomei; Yoko, Toshinobu

2006-06-06

Magnesium oxide hollow spheres without a template core were conveniently prepared by stabilized bubble formation in a hybrid solution containing a magnesium acetate precursor, thus avoiding the complicated preparation process using a template. The hollow sphere could be aligned along the radial striation by spin coating, and its diameter from a micrometer to submicrometer dimension could be easily modified by the solution composition. It was also possible to control the open or closed hollow sphere by changing the solvent. Thus, the produced magnesium oxide hollow sphere is envisioned to have applications in many areas such as medicine, analysis, optics, and so on.

Synthesis of sintering-resistant sorbents for CO2 capture.

PubMed

Liu, Wenqiang; Feng, Bo; Wu, Yueqin; Wang, Guoxiong; Barry, John; da Costa, João C Diniz

2010-04-15

Sorbents for high temperature CO2 capture are under intensive development owing to their potential applications in advanced zero emission power, sorption-enhanced steam methane reforming for hydrogen production and energy storage systems in chemical heat pumps. One of the challenges in the development is the prevention of sintering of the sorbent (normally a calcium oxide derivative) which causes the CO2 capture capacity of the material to deteriorate rapidly after a few cycles of utilization. Here we show that a simple wet mixing method can produce sintering-resistant sorbents from calcium and magnesium salts of d-gluconic acid. It was found that calcium oxide was well distributed in the sorbents with metal oxide nanoparticles on the surface acting as physical barriers, and the CO2 capture capacity of the sorbents was largely maintained over multiple cycles of utilization. This method was also applied to other organometallic salts of calcium and magnesium/aluminum and the produced sorbents showed similarly high reversibility.

Surface-interface exploration of Mg deposited on Si(100) and oxidation effect on interfacial layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sarpi, B.; Daineche, R.; Girardeaux, C.

Using scanning tunneling microscopy and spectroscopy, Auger electron spectroscopy, and low energy electron diffraction, we have studied the growth of Mg deposited on Si(100)-(2 × 1). Coverage from 0.05 monolayer (ML) to 3 ML was investigated at room temperature. The growth mode of the magnesium is a two steps process. At very low coverage, there is formation of an amorphous ultrathin silicide layer with a band gap of 0.74 eV, followed by a layer-by-layer growth of Mg on top of this silicide layer. Topographic images reveal that each metallic Mg layer is formed by 2D islands coalescence process on top of the silicidemore » interfacial layer. During oxidation of the Mg monolayer, the interfacial silicide layer acts as diffusion barrier for the oxygen atoms with a decomposition of the silicide film to a magnesium oxide as function of O{sub 2} exposure.« less

Magnesium Oxide

MedlinePlus

... used for different reasons. Some people use it as an antacid to relieve heartburn, sour stomach, or acid indigestion. Magnesium oxide also may be used as a laxative for short-term, rapid emptying of ...

Corrosion resistant thermal barrier coating. [protecting gas turbines and other engine parts

NASA Technical Reports Server (NTRS)

Levine, S. R.; Miller, R. A.; Hodge, P. E. (Inventor)

1981-01-01

A thermal barrier coating system for protecting metal surfaces at high temperature in normally corrosive environments is described. The thermal barrier coating system includes a metal alloy bond coating, the alloy containing nickel, cobalt, iron, or a combination of these metals. The system further includes a corrosion resistant thermal barrier oxide coating containing at least one alkaline earth silicate. The preferred oxides are calcium silicate, barium silicate, magnesium silicate, or combinations of these silicates.

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

NASA Astrophysics Data System (ADS)

Guan, Xiaofei; Pal, Uday B.; Powell, Adam C.

2014-06-01

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.

Preparation of porous magnesium oxide foam and study on its enrichment of uranium

NASA Astrophysics Data System (ADS)

Wang, Yunsheng; Chen, Yuantao; Liu, Chen; Yu, Fang

2018-06-01

Herein, we prepared porous magnesium oxide (MP-MgO) by in situ carbonization and using Mg(NO3)2 as precursor along with P123 as soft template. The BET surface area, and total pore volume of MP-MgO were found to be 14.76 m2 g, 0.15 cm3 g-1, respectively. The adsorption behavior of U (Ⅵ) by the porous MgO was studied by static adsorption experiments, and also the effects of adsorption time, pH of wastewater and U (Ⅵ) concentration were discussed. The results indicated that the optimum pH for MP-MgO was 3.0-4.5, the removal of uranium in this case was mainly due to surface complexation. Through the study, we found that the adsorption capacity of MP-MgO for uranium was more than 2500 mg g-1, the adsorption equilibrium time was about 150 min. Moreover, the kinetic study showed that the process followed the pseudo-first-order model, and the adsorption process was spontaneous and endothermic.

Surface properties of AZ91 magnesium alloy after PEO treatment using molybdate salts and low current densities

NASA Astrophysics Data System (ADS)

Pezzato, Luca; Brunelli, Katya; Napolitani, Enrico; Magrini, Maurizio; Dabalà, Manuele

2015-12-01

Plasma electrolytic oxidation (PEO) process is a recently developed electrochemical method used to produce on the surface of various metals oxide ceramic coatings that improve corrosion and wear properties of the substrate. In this work, PEO process was applied on AZ91 magnesium alloy using low current densities (0.05 A/cm2) and an alkaline solution of silicates with different concentrations of sodium molybdate (0.3-3 g/l). The effect of the low current densities of process and of molybdate salts on the corrosion resistance of the coatings was studied with potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) in chloride and sulfate environment. The morphology, the phases and the chemical composition of the coatings were examined using a scanning electron microscope equipped with EDS, X-ray diffraction, secondary ion mass spectrometry and X-ray photoelectron spectroscopy. The corrosion properties of the PEO coated samples were remarkably improved if compared with the uncoated samples. The addition of sodium molybdate, in determinate conditions, had a positive effect on the characteristics of the coatings in terms of corrosion resistance.

Improvement of Cycling Performance of Lithium-Sulfur Batteries by Using Magnesium Oxide as a Functional Additive for Trapping Lithium Polysulfide.

PubMed

Ponraj, Rubha; Kannan, Aravindaraj G; Ahn, Jun Hwan; Kim, Dong-Won

2016-02-17

Trapping lithium polysulfides formed in the sulfur positive electrode of lithium-sulfur batteries is one of the promising approaches to overcome the issues related to polysulfide dissolution. In this work, we demonstrate that intrinsically hydrophilic magnesium oxide (MgO) nanoparticles having surface hydroxyl groups can be used as effective additives to trap lithium polysulfides in the positive electrode. MgO nanoparticles were uniformly distributed on the surface of the active sulfur, and the addition of MgO into the sulfur electrode resulted in an increase in capacity retention of the lithium-sulfur cell compared to a cell with pristine sulfur electrode. The improvement in cycling stability was attributed to the strong chemical interactions between MgO and lithium polysulfide species, which suppressed the shuttling effect of lithium polysulfides and enhanced the utilization of the sulfur active material. To the best of our knowledge, this report is the first demonstration of MgO as an effective functional additive to trap lithium polysulfides in lithium-sulfur cells.

In vivo assessments of bioabsorbable AZ91 magnesium implants coated with nanostructured fluoridated hydroxyapatite by MAO/EPD technique for biomedical applications.

PubMed

Razavi, Mehdi; Fathi, Mohammadhossein; Savabi, Omid; Vashaee, Daryoosh; Tayebi, Lobat

2015-03-01

Although magnesium (Mg) is a unique biodegradable metal which possesses mechanical property similar to that of the natural bone and can be an attractive material to be used as orthopedic implants, its quick corrosion rate restricts its actual clinical applications. To control its rapid degradation, we have modified the surface of magnesium implant using fluoridated hydroxyapatite (FHA: Ca10(PO4)6OH2-xFx) through the combined micro-arc oxidation (MAO) and electrophoretic deposition (EPD) techniques, which was presented in our previous paper. In this article, the biocompatibility examinations were conducted on the coated AZ91 magnesium alloy by implanting it into the greater trochanter area of rabbits. The results of the in vivo animal test revealed a significant enhancement in the biocompatibility of FHA/MAO coated implant compared to the uncoated one. By applying the FHA/MAO coating on the AZ91 implant, the amount of weight loss and magnesium ion release in blood plasma decreased. According to the histological results, the formation of the new bone increased and the inflammation decreased around the implant. In addition, the implantation of the uncoated AZ91 alloy accompanied by the release of hydrogen gas around the implant; this release was suppressed by applying the coated implant. Our study exemplifies that the surface coating of magnesium implant using a bioactive ceramic such as fluoridated hydroxyapatite may improve the biocompatibility of the implant to make it suitable as a commercialized biomedical product. Published by Elsevier B.V.

The simultaneous removal of calcium, magnesium and chloride ions from industrial wastewater using magnesium-aluminum oxide.

PubMed

Hamidi, Roya; Kahforoushan, Davood; Fatehifar, Esmaeil

2013-01-01

In this article, a method for simultaneous removal of calcium, magnesium and chloride by using Mg0.80Al0.20O1.10 as a Magnesium-Aluminum oxide (Mg‒Al oxide) was investigated. Mg‒Al oxide obtained by thermal decomposition of the Mg-Al layered double hydroxide (Mg-Al LDH). The synthesized Mg‒Al oxide were characterized with respect to nitrogen physicosorption, X-ray diffraction (XRD) and field emission scan electron microscopy (FESEM) morphology. Due to high anion-exchange capacity of Mg‒Al oxide, it was employed in simultaneously removal of Cl(-), Mg(+2) and Ca(+2) from distiller waste of a sodium carbonate production factory. For this purpose, experiments were designed to evaluate the effects of quantity of Mg‒Al oxide, temperature and time on the removal process. The removal of Cl(-), Mg(+2) and Ca(+2) from wastewater was found 93.9%, 93.74% and 93.25% at 60°C after 0.5 h, respectively. Results showed that the removal of Cl(-), Mg(+2) and Ca(+2) by Mg‒Al oxide increased with increasing temperature, time and Mg‒Al oxide quantity.

Protective conversion coating on mixed-metal substrates and methods thereof

DOEpatents

O'Keefe, Matthew J.; Maddela, Surender

2016-09-06

Mixed-metal automotive vehicle bodies-in-white comprising ferrous metal surfaces, zinc surfaces, aluminum alloy surfaces, and magnesium alloy surfaces are cleaned and immersed in an aqueous bath comprising an adhesion promoter and an aqueous electrocoat bath (the adhesion promoter may be in the electrocoat bath. The adhesion promoter, which may be a cerium salt, is selected to react with each metal in the body surfaces to form an oxide layer that provides corrosion resistance for the surface and adherence for the deposited polymeric paint coating. The body is cathodic in the electrocoat deposition.

Stabilization of arsenic and lead by magnesium oxide (MgO) in different seawater concentrations.

PubMed

Kameda, Kentaro; Hashimoto, Yohey; Ok, Yong Sik

2018-02-01

Ongoing sea level rise will have a major impact on mobility and migration of contaminants by changing a number of natural phenomena that alter geochemistry and hydrology of subsurface environment. In-situ immobilization techniques may be a promising remediation strategy for mitigating contaminant mobility induced by sea level rise. This study investigated the reaction mechanisms of magnesium oxide (MgO) with aqueous Pb and As under freshwater and seawater using XAFS spectroscopy. Initial concentrations of Pb and As in freshwater strongly controlled the characteristics of the reaction product of MgO. Our study revealed that i) the removal of aqueous Pb and As by MgO was increased by the elevation of seawater concentration, and ii) the removal of As was attributed primarily to (inner-sphere) surface adsorption on MgO, independent on seawater concentrations, and iii) the retention mechanism of Pb was dependent on seawater concentrations where formations of Pb oxides and adsorption on the MgO surface were predominant in solutions with low and high salinity, respectively. The release of As fixed with MgO significantly increased in seawater compared to freshwater, although the amount of As desorbed accounted for <0.2% of total As. Copyright © 2017 Elsevier Ltd. All rights reserved.

Synthesis and characterization of magnesium oxide nanocrystallites and probing the vacancy-type defects through positron annihilation studies

NASA Astrophysics Data System (ADS)

Das, Anjan; Mandal, Atis Chandra; Roy, Soma; Prashanth, Pendem; Ahamed, Sk Izaz; Kar, Subhrasmita; Prasad, Mithun S.; Nambissan, P. M. G.

2016-09-01

Magnesium oxide nanocrystallites exhibit certain abnormal characteristics when compared to those of other wide band gap oxide semiconductors in the sense they are most prone to water absorption and formation of a hydroxide layer on the surface. The problem can be rectified by heating and pure nanocrystallites can be synthesized with controllable sizes. Inevitably the defect properties are distinctly divided between two stages, the one with the hydroxide layer (region I) and the other after the removal of the layer by annealing (region II). The lattice parameters, the optical band gap and even the positron annihilation characteristics are conspicuous by their distinct behavior in the two stages of the surface configurations of nanoparticles. While region I was specific with the formation of positronium-hydrogen complexes that drastically altered the defect-specific positron lifetimes, pick-off annihilation of orthopositronium atoms marked region II. The vacancy clusters within the nanocrystallites also trapped positrons. They agglomerated due to the effect of the higher temperatures and resulted in the growth of the nanocrystallites. The coincidence Doppler broadening spectroscopic measurements supported these findings and all the more indicated the trapping of positrons additionally into the neutral divacancies and negatively charged trivacancies. This is apart from the Mg2+ monovacancies which acted as the dominant trapping centers for positrons.

21 CFR 184.1428 - Magnesium hydroxide.

Code of Federal Regulations, 2011 CFR

2011-04-01

... salt or by hydration of reactive grades of magnesium oxide. (b) The ingredient meets the specifications... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Magnesium hydroxide. 184.1428 Section 184.1428... Listing of Specific Substances Affirmed as GRAS § 184.1428 Magnesium hydroxide. (a) Magnesium hydroxide...

21 CFR 184.1428 - Magnesium hydroxide.

Code of Federal Regulations, 2010 CFR

2010-04-01

... hydration of reactive grades of magnesium oxide. (b) The ingredient meets the specifications of the Food... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Magnesium hydroxide. 184.1428 Section 184.1428 Food... Specific Substances Affirmed as GRAS § 184.1428 Magnesium hydroxide. (a) Magnesium hydroxide (Mg(OH)2, CAS...

Synthesis, characterization, and hydrogen uptake studies of magnesium nanoparticles by solution reduction method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rather, Sami ullah, E-mail: rathersami@gmail.com

2014-12-15

Graphical abstract: X-ray diffraction (XRD) pattern of magnesium nanoparticles synthesized by solution reduction method with and without TOPO. - Highlights: • Simple and convenient method of preparing Mg nanoparticles. • Characterized by XRD, SEM, FESEM and TEM. • Trioctylphosphine oxide offers a greater control over the size of the particles. • Hydrogen uptake of samples at different temperatures and pressure of 4.5 MPa. - Abstract: Facile and simple, surfactant-mediated solution reduction method was used to synthesize monodisperse magnesium nanoparticles. Little amount of magnesium oxide nanoparticles were also formed due to the presence of TOPO and easy oxidation of magnesium, eventhough,more » all precautions were taken to avoid oxidation of the sample. Precise size control of particles was achieved by carefully varying the concentration ratio of two different types of surfactants, – trioctylphosphine oxide and hexadecylamine. Recrystallized magnesium nanoparticle samples with and without TOPO were analyzed by X-ray diffraction, scanning electron microscope, field emission scanning electron microscope, and transmission electron microscope. The peak diameters of particles were estimated from size distribution analysis of the morphological data. The particles synthesized in the presence and absence of TOPO found to have diameters 46.5 and 34.8 nm, respectively. This observed dependence of particle size on the presence of TOPO offers a convenient method to control the particle size by simply using appropriate surfactant concentrations. Exceptional enhancement in hydrogen uptake and kinetics in synthesized magnesium nanoparticles as compared to commercial magnesium sample was due to the smaller particle size and improved morphology. Overall hydrogen uptake not affected by the little variation in particle size with and without TOPO.« less

A Double-Blind Placebo-Controlled Randomized Clinical Trial With Magnesium Oxide to Reduce Intrafraction Prostate Motion for Prostate Cancer Radiotherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lips, Irene M., E-mail: i.m.lips@umcutrecht.nl; Gils, Carla H. van; Kotte, Alexis N.T.J.

2012-06-01

Purpose: To investigate whether magnesium oxide during external-beam radiotherapy for prostate cancer reduces intrafraction prostate motion in a double-blind, placebo-controlled randomized trial. Methods and Materials: At the Department of Radiotherapy, prostate cancer patients scheduled for intensity-modulated radiotherapy (77 Gy in 35 fractions) using fiducial marker-based position verification were randomly assigned to receive magnesium oxide (500 mg twice a day) or placebo during radiotherapy. The primary outcome was the proportion of patients with clinically relevant intrafraction prostate motion, defined as the proportion of patients who demonstrated in {>=}50% of the fractions an intrafraction motion outside a range of 2 mm. Secondarymore » outcome measures included quality of life and acute toxicity. Results: In total, 46 patients per treatment arm were enrolled. The primary endpoint did not show a statistically significant difference between the treatment arms with a percentage of patients with clinically relevant intrafraction motion of 83% in the magnesium oxide arm as compared with 80% in the placebo arm (p = 1.00). Concerning the secondary endpoints, exploratory analyses demonstrated a trend towards worsened quality of life and slightly more toxicity in the magnesium oxide arm than in the placebo arm; however, these differences were not statistically significant. Conclusions: Magnesium oxide is not effective in reducing the intrafraction prostate motion during external-beam radiotherapy, and therefore there is no indication to use it in clinical practice for this purpose.« less

40 CFR 721.10504 - Surface modified magnesium hydroxide (generic).

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Surface modified magnesium hydroxide... Specific Chemical Substances § 721.10504 Surface modified magnesium hydroxide (generic). (a) Chemical... as surface modified magnesium hydroxide (PMN P-06-682) is subject to reporting under this section for...

40 CFR 721.10573 - Magnesium hydroxide surface treated with substituted alkoxysilanes (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Magnesium hydroxide surface treated... SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10573 Magnesium hydroxide surface... to reporting. (1) The chemical substance identified generically as magnesium hydroxide surface...

40 CFR 721.10504 - Surface modified magnesium hydroxide (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Surface modified magnesium hydroxide... Specific Chemical Substances § 721.10504 Surface modified magnesium hydroxide (generic). (a) Chemical... as surface modified magnesium hydroxide (PMN P-06-682) is subject to reporting under this section for...

40 CFR 721.10573 - Magnesium hydroxide surface treated with substituted alkoxysilanes (generic).

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Magnesium hydroxide surface treated... SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10573 Magnesium hydroxide surface... to reporting. (1) The chemical substance identified generically as magnesium hydroxide surface...

Radio frequency surface resistance of Tl-Ba-Ca-Cu-O films on metal and single-crystal substrates

NASA Astrophysics Data System (ADS)

Arendt, P. N.; Reeves, G. A.; Elliott, N. E.; Cooke, D. W.; Gray, E. R.; Houlton, R. J.; Brown, D. R.

1990-01-01

Films of Tl-Ba-Ca-Cu were dc magnetron sputtered from a single multielement target. The films were deposited onto substrates of: (1) magnesium oxide, (2) a silver based alloy (Consil 995), (3) a nickel based alloy (Haynes 230), and (4) buffer layers of barium fluoride or copper oxide on Consil. To form superconducting phases, post-deposition anneals were made on these films using an alumina crucible with an over pressure of thallium and flowing oxygen. After annealing, the film phases were determined using x-ray diffraction. The film surface resistances (Rs) were measured at 22 GHz in a TE011 cavity.

Timeline (Bioavailability) of Magnesium Compounds in Hours: Which Magnesium Compound Works Best?

PubMed

Uysal, Nazan; Kizildag, Servet; Yuce, Zeynep; Guvendi, Guven; Kandis, Sevim; Koc, Basar; Karakilic, Aslı; Camsari, Ulas M; Ates, Mehmet

2018-04-21

Magnesium is an element of great importance functioning because of its association with many cellular physiological functions. The magnesium content of foods is gradually decreasing due to food processing, and magnesium supplementation for healthy living has become increasingly popular. However, data is very limited on the bioavailability of various magnesium preparations. The aim of this study is to investigate the bioavailability of five different magnesium compounds (magnesium sulfate, magnesium oxide, magnesium acetyl taurate, magnesium citrate, and magnesium malate) in different tissues. Following a single dose 400 mg/70 kg magnesium administration to Sprague Dawley rats, bioavailability was evaluated by examining time-dependent absorption, tissue penetration, and the effects on the behavior of the animals. Pharmacokinetically, the area under the curve calculation is highest in the magnesium malate. The magnesium acetyl taurate was found to have the second highest area under the curve calculation. Magnesium acetyl taurate was rapidly absorbed, able to pass through to the brain easily, had the highest tissue concentration level in the brain, and was found to be associated with decreased anxiety indicators. Magnesium malate levels remained high for an extended period of time in the serum. The commonly prescribed dietary supplements magnesium oxide and magnesium citrate had the lowest bioavailability when compared to our control group. More research is needed to investigate the bioavailability of magnesium malate and acetyl taurate compounds and their effects in specific tissues and on behavior.

Surface Charge at the Oxide/Electrolyte Interface: Toward Optimization of Electrolyte Composition for Treatment of Aluminum and Magnesium by Plasma Electrolytic Oxidation.

PubMed

Nominé, Alexandre; Martin, Julien; Noël, Cédric; Henrion, Gérard; Belmonte, Thierry; Bardin, Ilya V; Lukeš, Petr

2016-02-09

Controlling microdischarges in plasma electrolytic oxidation is of great importance in order to optimize coating quality. The present study highlights the relationship between the polarity at which breakdown occurs and the electrolyte pH as compared with the isoelectric point (IEP). It is found that working at a pH higher than the IEP of the grown oxide prevents the buildup of detrimental cathodic discharges. The addition of phosphates results in a shift in the IEP to a lower value and therefore promotes anodic discharges at the expense of cathodic ones.

Magnesium supplementation through seaweed calcium extract rather than synthetic magnesium oxide improves femur bone mineral density and strength in ovariectomized rats.

PubMed

Bae, Yun Jung; Bu, So Young; Kim, Jae Young; Yeon, Jee-Young; Sohn, Eun-Wha; Jang, Ki-Hyo; Lee, Jae-Cheol; Kim, Mi-Hyun

2011-12-01

Commercially available seaweed calcium extract can supply high amounts of calcium as well as significant amounts of magnesium and other microminerals. The purpose of this study was to investigate the degree to which the high levels of magnesium in seaweed calcium extract affects the calcium balance and the bone status in ovariectomized rats in comparison to rats supplemented with calcium carbonate and magnesium oxide. A total of 40 Sprague-Dawley female rats (7 weeks) were divided into four groups and bred for 12 weeks: sham-operated group (Sham), ovariectomized group (OVX), ovariectomized with inorganic calcium and magnesium supplementation group (OVX-Mg), and ovariectomized with seaweed calcium and magnesium supplementation group (OVX-SCa). All experimental diets contained 0.5% calcium. The magnesium content in the experimental diet was 0.05% of the diet in the Sham and OVX groups and 0.1% of the diet in the OVX-Mg and OVX-SCa groups. In the calcium balance study, the OVX-Mg and OVX-SCa groups were not significantly different in calcium absorption compared to the OVX group. However, the femoral bone mineral density and strength of the OVX-SCa group were higher than those of the OVX-Mg and OVX groups. Seaweed calcium with magnesium supplementation or magnesium supplementation alone did not affect the serum ALP and CTx levels in ovariectomized rats. In summary, consumption of seaweed calcium extract or inorganic calcium carbonate with magnesium oxide demonstrated the same degree of intestinal calcium absorption, but only the consumption of seaweed calcium extract resulted in increased femoral bone mineral density and strength in ovariectomized rats. Our results suggest that seaweed calcium extract is an effective calcium and magnesium source for improving bone health compared to synthetic calcium and magnesium supplementation.

Electrophoretic deposition of nanostructured hydroxyapatite coating on AZ91 magnesium alloy implants with different surface treatments

NASA Astrophysics Data System (ADS)

Rojaee, Ramin; Fathi, Mohammadhossein; Raeissi, Keyvan

2013-11-01

Bio-absorbable magnesium (Mg) based alloys have been introduced as innovative orthopedic implants during recent years. It has been specified that rapid degradation of Mg based alloys in physiological environment should be restrained in order to be utilized in orthopedic trauma fixation and vascular intervention. In this developing field of healthcare materials, micro-arc oxidation (MAO), and MgF2 conversion coating were exploited as surface pre-treatment of AZ91 magnesium alloy to generate a nanostructured hydroxyapatite (n-HAp) coating via electrophoretic deposition (EPD) method. X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and transmission electron microscopy (TEM) techniques were used to characterize the obtained powder and coatings. The potentiodynamic polarization tests were carried out to evaluate the corrosion behavior of the coated and uncoated specimens, and in vitro bioactivity evaluation were performed in simulated body fluid. Results revealed that the MAO/n-HAp coated AZ91 Mg alloy samples with a rough topography and lower corrosion current density leads to a lower Mg degradation rate accompanied by high bioactivity.

Activated Metal Oxide Surfaces as Highly Basic and Reducing Environments.

DTIC Science & Technology

1987-05-21

were formed, as illustrated by [Mg iO] and 93 12[Mg9AI301 2] . Unique reaction properties were described. 2. Spin Traps Organic nitroso and nitrone ...J. V. Ortiz, R. Basu and Y. Ohrn, Chem. Phys. Lett. 103, 29 (1983). 39. K. J. Klabunde and A. Whetten, J. Am. Chem. Soc., 108, 6529 (1986). 40 . G. H...editor, Elsevier, in press. 40 . F. Mousa and K. J. Klabunde, "Base Condensation of Carbonyl Compounds on Thermally Activated Magnesium Oxide

In Vitro Analysis of Electrophoretic Deposited Fluoridated Hydroxyapatite Coating on Micro-arc Oxidized AZ91 Magnesium Alloy for Biomaterials Applications

NASA Astrophysics Data System (ADS)

Razavi, Mehdi; Fathi, Mohammadhossein; Savabi, Omid; Vashaee, Daryoosh; Tayebi, Lobat

2015-03-01

Magnesium (Mg) alloys have been recently introduced as a biodegradable implant for orthopedic applications. However, their fast corrosion, low bioactivity, and mechanical integrity have limited their clinical applications. The main aim of this research was to improve such properties of the AZ91 Mg alloy through surface modifications. For this purpose, nanostructured fluoridated hydroxyapatite (FHA) was coated on AZ91 Mg alloy by micro-arc oxidation and electrophoretic deposition method. The coated alloy was characterized through scanning electron microscopy, transmission electron microscopy, X-ray diffraction, in vitro corrosion tests, mechanical tests, and cytocompatibility evaluation. The results confirmed the improvement of the corrosion resistance, in vitro bioactivity, mechanical integrity, and the cytocompatibility of the coated Mg alloy. Therefore, the nanostructured FHA coating can offer a promising way to improve the properties of the Mg alloy for orthopedic applications.

Degradation and biological properties of Ca-P contained micro-arc oxidation self-sealing coating on pure magnesium for bone fixation

PubMed Central

Wang, Weidan; Wan, Peng; Liu, Chen; Tan, Lili; Li, Weirong; Li, Lugee; Yang, Ke

2015-01-01

Poor corrosion resistance is one of the main disadvantages for biodegradable magnesium-based metals, especially applied for bone fixation, where there is a high demand of bio-mechanical strength and stability. Surface coating has been proved as an effective method to control the in vivo degradation. In this study a Ca-P self-sealing micro-arc oxidation (MAO) coating was studied to verify its efficacy and biological properties by in vitro and in vivo tests. It was found that the MAO coating could effectively retard the degradation according to immersion and electrochemical tests as well as 3D reconstruction by X-ray tomography after implantation. The MAO coating exhibited no toxicity and could stimulate the new bone formation. Therefore, the Ca-P self-sealing MAO coating could be a potential candidate for application of biodegradable Mg-based implant in bone fixations. PMID:26816635

Corrosion behaviors and effects of corrosion products of plasma electrolytic oxidation coated AZ31 magnesium alloy under the salt spray corrosion test

NASA Astrophysics Data System (ADS)

Wang, Yan; Huang, Zhiquan; Yan, Qin; Liu, Chen; Liu, Peng; Zhang, Yi; Guo, Changhong; Jiang, Guirong; Shen, Dejiu

2016-08-01

The effects of corrosion products on corrosion behaviors of AZ31 magnesium alloy with a plasma electrolytic oxidation (PEO) coating were investigated under the salt spray corrosion test (SSCT). The surface morphology, cross-sectional microstructure, chemical and phase compositions of the PEO coating were determined using scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction analysis (XRD), respectively. Further, the corrosion process of the samples under the SSCT was examined in a non-aqueous electrolyte (methanol) using electrochemical impedance spectroscopy (EIS) coupled with equivalent circuit. The results show that the inner layer of the coating was destroyed firstly and the corrosion products have significant effects on the corrosion behaviors of the coating. The results above are discussed and an electrochemical corrosion model is proposed in the paper.

Sodium Picosulfate, Magnesium Oxide, and Anhydrous Citric Acid

MedlinePlus

Sodium picosulfate, magnesium oxide, and anhydrous citric acid combination powder is used to empty the colon (large ... clear view of the walls of the colon. Sodium picosulfate is in a class of medications called ...

Organosilane self-assembled layers (SAMs) and hybrid silicate magnesium-rich primers for the corrosion protection of aluminum alloy 2024 T3

NASA Astrophysics Data System (ADS)

Wang, Duhua

Although current chromate coatings function very well in corrosion protection for aircraft alloys, such as aluminum alloy 2024 T3, the U.S. Environmental Protection Agency is planning to totally ban the use of chromates as coating materials in the next decade or so because of their extremely toxic effect. For this purpose, both self-assembled layers and silicate magnesium-rich primers were tested to provide the corrosion protection for aluminum alloy. The long-term goal of this research is to develop a coating system to replace the current chromate coating for aircraft corrosion protection. Aluminum alloy 2024 T3 substrates were modified with self-assembled monolayer or multilayer thin films from different alkylsilane compounds. Mono-functional silanes, such as octadecyltrichlorosilane (C18SiCl3), can form a mixed hydrophobic monolayer or multilayer thin film on the aluminum oxide surface to provide a barrier to water and other electrolytes, so the corrosion resistance of the SAMs modified surface was increased significantly. On the other hand, the bi-functional silane self-assembly could attach the aluminum surface through the silicon headgroup while using its functional tailgroup to chemically bond the polymer coating, thus improving the adhesion between the aluminum substrate and coating substantially, and seems to contribute more to corrosion protection of aluminum substrate. Organosilanes were also combined with tetraethyl orthosilicate (TEOS) in propel ratios to form a sol-gel binder to make silicate magnesium-rich primers. Analogue to the inorganic zinc-rich coatings, the silicate magnesium-rich primers also showed excellent adhesion and solvent resistance. The sacrificial magnesium pigments and the chemically inert silicate binder both contribute to the anti-corrosion properties. Future studies will be focused on the formula optimization for better toughness, chemical resistance and anticorrosion performance.

21 CFR 184.1426 - Magnesium chloride.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Magnesium chloride. 184.1426 Section 184.1426 Food... Specific Substances Affirmed as GRAS § 184.1426 Magnesium chloride. (a) Magnesium chloride (MgC12·6H2O, CAS... mineral bischofite. It is prepared by dissolving magnesium oxide, hydroxide, or carbonate in aqueous...

21 CFR 184.1426 - Magnesium chloride.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Magnesium chloride. 184.1426 Section 184.1426 Food... Specific Substances Affirmed as GRAS § 184.1426 Magnesium chloride. (a) Magnesium chloride (MgC12·6H2O, CAS... mineral bischofite. It is prepared by dissolving magnesium oxide, hydroxide, or carbonate in aqueous...

21 CFR 184.1426 - Magnesium chloride.

Code of Federal Regulations, 2011 CFR

2011-04-01

... mineral bischofite. It is prepared by dissolving magnesium oxide, hydroxide, or carbonate in aqueous... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Magnesium chloride. 184.1426 Section 184.1426 Food... Specific Substances Affirmed as GRAS § 184.1426 Magnesium chloride. (a) Magnesium chloride (MgC12·6H2O, CAS...

21 CFR 184.1426 - Magnesium chloride.

Code of Federal Regulations, 2010 CFR

2010-04-01

... mineral bischofite. It is prepared by dissolving magnesium oxide, hydroxide, or carbonate in aqueous... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Magnesium chloride. 184.1426 Section 184.1426 Food... Specific Substances Affirmed as GRAS § 184.1426 Magnesium chloride. (a) Magnesium chloride (MgC12·6H2O, CAS...

21 CFR 184.1443 - Magnesium sulfate.

Code of Federal Regulations, 2011 CFR

2011-04-01

... magnesium oxide, hydroxide, or carbonate with sulfuric acid and evaporating the solution to crystallization... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Magnesium sulfate. 184.1443 Section 184.1443 Food... Specific Substances Affirmed as GRAS § 184.1443 Magnesium sulfate. (a) Magnesium sulfate (MgSO4·7H2O, CAS...

21 CFR 184.1443 - Magnesium sulfate.

Code of Federal Regulations, 2010 CFR

2010-04-01

... magnesium oxide, hydroxide, or carbonate with sulfuric acid and evaporating the solution to crystallization... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Magnesium sulfate. 184.1443 Section 184.1443 Food... Specific Substances Affirmed as GRAS § 184.1443 Magnesium sulfate. (a) Magnesium sulfate (MgSO4·7H2O, CAS...

Aerosol chemical vapor deposition of metal oxide films

DOEpatents

Ott, K.C.; Kodas, T.T.

1994-01-11

A process of preparing a film of a multicomponent metal oxide including: forming an aerosol from a solution comprised of a suitable solvent and at least two precursor compounds capable of volatilizing at temperatures lower than the decomposition temperature of said precursor compounds; passing said aerosol in combination with a suitable oxygen-containing carrier gas into a heated zone, said heated zone having a temperature sufficient to evaporate the solvent and volatilize said precursor compounds; and passing said volatilized precursor compounds against the surface of a substrate, said substrate having a sufficient temperature to decompose said volatilized precursor compounds whereby metal atoms contained within said volatilized precursor compounds are deposited as a metal oxide film upon the substrate is disclosed. In addition, a coated article comprising a multicomponent metal oxide film conforming to the surface of a substrate selected from the group consisting of silicon, magnesium oxide, yttrium-stabilized zirconium oxide, sapphire, or lanthanum gallate, said multicomponent metal oxide film characterized as having a substantially uniform thickness upon said substrate.

Imparting passivity to vapor deposited magnesium alloys

NASA Astrophysics Data System (ADS)

Wolfe, Ryan C.

Magnesium has the lowest density of all structural metals. Utilization of low density materials is advantageous from a design standpoint, because lower weight translates into improved performance of engineered products (i.e., notebook computers are more portable, vehicles achieve better gas mileage, and aircraft can carry more payload). Despite their low density and high strength to weight ratio, however, the widespread implementation of magnesium alloys is currently hindered by their relatively poor corrosion resistance. The objective of this research dissertation is to develop a scientific basis for the creation of a corrosion resistant magnesium alloy. The corrosion resistance of magnesium alloys is affected by several interrelated factors. Among these are alloying, microstructure, impurities, galvanic corrosion effects, and service conditions, among others. Alloying and modification of the microstructure are primary approaches to controlling corrosion. Furthermore, nonequilibrium alloying of magnesium via physical vapor deposition allows for the formation of single-phase magnesium alloys with supersaturated concentrations of passivity-enhancing elements. The microstructure and surface morphology is also modifiable during physical vapor deposition through the variation of evaporation power, pressure, temperature, ion bombardment, and the source-to-substrate distance. Aluminum, titanium, yttrium, and zirconium were initially chosen as candidates likely to impart passivity on vapor deposited magnesium alloys. Prior to this research, alloys of this type have never before been produced, much less studied. All of these metals were observed to afford some degree of corrosion resistance to magnesium. Due to the especially promising results from nonequilibrium alloying of magnesium with yttrium and titanium, the ternary magnesium-yttrium-titanium system was investigated in depth. While all of the alloys are lustrous, surface morphology is observed under the scanning electron microscope. The corrosion rate of the nonequilibrium sputtered alloys, as determined by polarization resistance, is significantly reduced compared to the most corrosion resistant commercial magnesium alloys. The open circuit potentials of the sputter deposited alloys are significantly more noble compared to commercial, equilibrium phase magnesium alloys. Galvanic corrosion susceptibility has also been considerably reduced. Nonequilibrium magnesium-yttrium-titanium alloys have been shown to achieve passivity autonomously by alteration of the composition chemistry of the surface oxide/hydroxide layer. Self-healing properties are also evident, as corrosion propagation can be arrested after initial pitting of the material. A clear relationship exists between the corrosion resistance of sputter vapor deposited magnesium alloys and the amount of ion bombardment incurred by the alloy during deposition. Argon pressure, the distance between the source and the substrate, and alloy morphology play important roles in determining the ability of the alloy to develop a passive film. Thermal effects, both during and after alloy deposition, alter the stress state of the alloys, precipitation of second phases, and the mechanical stability of the passive film. An optimal thermal treatment has been developed in order to maximize the corrosion resistance of the magnesium-yttrium-titanium alloys. The significance of the results includes the acquisition of electrochemical data for these novel materials, as well as expanding the utilization of magnesium alloys by the improvement in their corrosion resistance. The magnesium alloys developed in this work are more corrosion resistant than any commercial magnesium alloy. Structural components comprised of these alloys would therefore exhibit unprecedented corrosion performance. Coatings of these alloys on magnesium components would provide a corrosion resistant yet galvanically-compatible coating. The broad impact of these contributions is that these new low-density, corrosion resistant magnesium alloys can be used to produce engineering components for vehicles that have greater acceleration, longer range, heavier payloads, lower life cycle costs, and longer inspection intervals.

Nanoparticle Addition to Enhance the Mechanical Response of Magnesium Alloys Including Nanoscale Deformation Mechanisms

NASA Astrophysics Data System (ADS)

Paramsothy, Muralidharan; Gupta, Manoj

In this study, various magnesium alloy nanocomposites derived from AZ (Aluminium-Zinc) or ZK (Zinc-Zirconium) series matrices and containing Al2O3, Si3N4, TiC or carbon nanotube (CNT) nanoparticle reinforcement (representative oxide, nitride, carbide or carbon nanoparticle reinforcement, respectively) were fabricated using solidification processing followed by hot extrusion. The main aim here was to simultaneously enhance tensile strength and ductility of each alloy using nanoparticles. The magnesium-oxygen strong affinity and magnesium-carbon weak affinity (comparison of extremes in affinity) are both well known in the context of magnesium composite processing. However, an approach to possibly quantify this affinity in magnesium nanocomposite processing is not clear. In this study accordingly, Nanoscale Electro Negative Interface Density or NENID quantifies the nanoparticle-alloy matrix interfacial area per unit volume in the magnesium alloy nanocomposite taking into consideration the electronegativity of the nanoparticle reinforcement. The beneficial (as well as comparative) effect of the nanoparticles on each alloy is discussed in this article. Regarding the mechanical performance of the nanocomposites, it is important to understand the experimentally observed nanoparticle-matrix interactions during plastic deformation (nanoscale deformation mechanisms). Little is known in this area based on direct observations for metal matrix nanocomposites. Here, relevant multiple nanoscale phenomena includes the emanation of high strain zones (HSZs) from nanoparticle surfaces.

A SEARCH FOR MAGNESIUM IN EUROPA'S ATMOSPHERE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoerst, S. M.; Brown, M. E., E-mail: sarah.horst@colorado.edu

Europa's tenuous atmosphere results from sputtering of the surface. The trace element composition of its atmosphere is therefore related to the composition of Europa's surface. Magnesium salts are often invoked to explain Galileo Near Infrared Mapping Spectrometer spectra of Europa's surface, thus magnesium may be present in Europa's atmosphere. We have searched for magnesium emission in the Hubble Space Telescope Faint Object Spectrograph archival spectra of Europa's atmosphere. Magnesium was not detected and we calculate an upper limit on the magnesium column abundance. This upper limit indicates that either Europa's surface is depleted in magnesium relative to sodium and potassium,more » or magnesium is not sputtered as efficiently resulting in a relative depletion in its atmosphere.« less

Efficient One-Step Electrolytic Recycling of Low-Grade and Post-Consumer Magnesium Scrap

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adam C. Powell, IV

2012-07-19

Metal Oxygen Separation Technologies, Inc. (abbreviated MOxST, pronounced most) and Boston University (BU) have developed a new low-cost process for recycling post-consumer co-mingled and heavily-oxidized magnesium scrap, and discovered a new chemical mechanism for magnesium separations in the process. The new process, designated MagReGenTM, is very effective in laboratory experiments, and on scale-up promises to be the lowest-cost lowest-energy lowest-impact method for separating magnesium metal from aluminum while recovering oxidized magnesium. MagReGenTM uses as little as one-eighth as much energy as today's methods for recycling magnesium metal from comingled scrap. As such, this technology could play a vital role inmore » recycling automotive non-ferrous metals, particularly as motor vehicle magnesium/aluminum ratios increase in order to reduce vehicle weight and increase efficiency.« less

Nuclear reactor shield including magnesium oxide

DOEpatents

Rouse, Carl A.; Simnad, Massoud T.

1981-01-01

An improvement in nuclear reactor shielding of a type used in reactor applications involving significant amounts of fast neutron flux, the reactor shielding including means providing structural support, neutron moderator material, neutron absorber material and other components as described below, wherein at least a portion of the neutron moderator material is magnesium in the form of magnesium oxide either alone or in combination with other moderator materials such as graphite and iron.

Formation of chemically bonded ceramics with magnesium dihydrogen phosphate binder

DOEpatents

Wagh, Arun S.; Jeong, Seung-Young

2004-08-17

A new method for combining magnesium oxide, MgO, and magnesium dihydrogen phosphate to form an inexpensive compactible ceramic to stabilize very low solubility metal oxides, ashes, swarfs, and other iron or metal-based additives, to create products and waste forms which can be poured or dye cast, and to reinforce and strengthen the ceramics formed by the addition of fibers to the initial ceramic mixture.

21 CFR 184.1426 - Magnesium chloride.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Magnesium chloride. 184.1426 Section 184.1426 Food... GRAS § 184.1426 Magnesium chloride. (a) Magnesium chloride (MgC12·6H2O, CAS Reg. No. 7786-30-3) is a... prepared by dissolving magnesium oxide, hydroxide, or carbonate in aqueous hydrochloric acid solution and...

Magnesium ion implantation on a micro/nanostructured titanium surface promotes its bioactivity and osteogenic differentiation function

PubMed Central

Wang, Guifang; Li, Jinhua; Zhang, Wenjie; Xu, Lianyi; Pan, Hongya; Wen, Jin; Wu, Qianju; She, Wenjun; Jiao, Ting; Liu, Xuanyong; Jiang, Xinquan

2014-01-01

As one of the important ions associated with bone osseointegration, magnesium was incorporated into a micro/nanostructured titanium surface using a magnesium plasma immersion ion-implantation method. Hierarchical hybrid micro/nanostructured titanium surfaces followed by magnesium ion implantation for 30 minutes (Mg30) and hierarchical hybrid micro/nanostructured titanium surfaces followed by magnesium ion implantation for 60 minutes (Mg60) were used as test groups. The surface morphology, chemical properties, and amount of magnesium ions released were evaluated by field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy, field-emission transmission electron microscopy, and inductively coupled plasma-optical emission spectrometry. Rat bone marrow mesenchymal stem cells (rBMMSCs) were used to evaluate cell responses, including proliferation, spreading, and osteogenic differentiation on the surface of the material or in their medium extraction. Greater increases in the spreading and proliferation ability of rBMMSCs were observed on the surfaces of magnesium-implanted micro/nanostructures compared with the control plates. Furthermore, the osteocalcin (OCN), osteopontin (OPN), and alkaline phosphatase (ALP) genes were upregulated on both surfaces and in their medium extractions. The enhanced cell responses were correlated with increasing concentrations of magnesium ions, indicating that the osteoblastic differentiation of rBMMSCs was stimulated through the magnesium ion function. The magnesium ion-implanted micro/nanostructured titanium surfaces could enhance the proliferation, spreading, and osteogenic differentiation activity of rBMMSCs, suggesting they have potential application in improving bone-titanium integration. PMID:24940056

Effect of surface treatment on the corrosion properties of magnesium-based fibre metal laminate

NASA Astrophysics Data System (ADS)

Zhang, X.; Zhang, Y.; Ma, Q. Y.; Dai, Y.; Hu, F. P.; Wei, G. B.; Xu, T. C.; Zeng, Q. W.; Wang, S. Z.; Xie, W. D.

2017-02-01

The surface roughness, weight of phosphating film and wettability of magnesium alloy substrates after abrasion and phosphating treatment were investigated in this work. The interfacial bonding and corrosion properties of a magnesium-based fibre metal laminate (MgFML) were analysed. The results showed that the wettability of the magnesium alloy was greatly influenced by the surface roughness, and the rough surface possessed a larger surface energy and better wettability. The surface energy and wettability of the magnesium alloy were significantly improved by the phosphating treatment. After phosphating for 5 min, a phosphating film with a double-layer structure was formed on the magnesium substrate, and the weight of the phosphating film and the surface energy reached their maximum values. The surface energies of the phosphated substrate after abrasion with #120 and #3000 grit abrasive papers were 84.31 mJ/m2 and 83.65 mJ/m2, respectively. The wettability of the phosphated magnesium was significantly better than the abraded magnesium. The phosphated AZ31B sheet had a better corrosion resistance than the abraded AZ31B sheet within short times. The corrosion resistance of the magnesium alloy was greatly increased by being composited with glass fibre/epoxy prepregs.

Highly mobile oxygen holes in magnesium oxide

NASA Technical Reports Server (NTRS)

Freund, Minoru M.; Freund, Friedemann; Batllo, Francois

1989-01-01

High-purity MgO exhibits an unexpected giant anomaly of the apparent static dielectric constant and a positive surface charge of the order of 5 x 10 to the 21st/cu cm in the top 15 nm. It is postulated that the MgO matrix contains traces of peroxy defects, O2(2-), associated with Mg(2+) vacancies. Above approximately 400 C the O2(2-) dissociates to vacancy bound O(-) and highly mobile O(-) states, which diffuse to the surface, giving rise to a high surface conductivity.

Two-Dimensional Fluorescence Difference Spectroscopy of ZnO and Mg Composites in the Detection of Physiological Protein and RNA Interactions

PubMed Central

Hoffman, Amanda; Wu, Xiaotong; Wang, Jianjie; Brodeur, Amanda; Thomas, Rintu; Thakkar, Ravindra; Hadi, Halena; Glaspell, Garry P.; Duszynski, Molly; Wanekaya, Adam; DeLong, Robert K.

2017-01-01

Two-dimensional fluorescence difference spectroscopy (2-D FDS) was used to determine the unique spectral signatures of zinc oxide (ZnO), magnesium oxide (MgO), and 5% magnesium zinc oxide nanocomposite (5% Mg/ZnO) and was then used to demonstrate the change in spectral signature that occurs when physiologically important proteins, such as angiotensin-converting enzyme (ACE) and ribonuclease A (RNase A), interact with ZnO nanoparticles (NPs). When RNase A is bound to 5% Mg/ZnO, the intensity is quenched, while the intensity is magnified and a significant shift is seen when torula yeast RNA (TYRNA) is bound to RNase A and 5% Mg/ZnO. The intensity of 5% Mg/ZnO is quenched also when thrombin and thrombin aptamer are bound to the nanocomposite. These data indicate that RNA–protein interaction can occur unimpeded on the surface of NPs, which was confirmed by gel electrophoresis, and importantly that the change in fluorescence excitation, emission, and intensity shown by 2-D FDS may indicate specificity of biomolecular interactions. PMID:29244716

Preparation of aluminum-magnesium alloy from magnesium oxide in RECl3-KCl-MgCl2 electrolyte by molten salts electrolysis method

NASA Astrophysics Data System (ADS)

Yang, Shaohua; Wu, Lin; Yang, Fengli; Li, Mingzhou; Hu, Xianwei; Wang, Zhaowen; Shi, Zhongning; Gao, Bingliang

Aluminum-magnesium alloys were prepared from magnesium oxide by molten salt electrolysis method. 10w%RECl3-63.5w%KCl-23.5w%MgCl2-3w%MgO was taken as electrolyte. The results showed that RE could be attained in aluminum-magnesium alloy, and it was proved that the RE was reduced directly by aluminum. Magnesium in the alloy was produced by electrolysis on cathode. The content of RE in the alloy was about 0.8wt %-1.2wt%, and the content of Mg in the alloy was lwt%˜6wt% with electrolytic times. The highest current efficiency was 81.3% with 0.8A/cm2 current density. The process of electrolysis was controlled together by electrochemical polarization and concentration polarization.

Single-Step Electrophoretic Deposition of Non-noble Metal Catalyst Layer with Low Onset Voltage for Ethanol Electro-oxidation.

PubMed

Ahmadi Daryakenari, Ahmad; Hosseini, Davood; Ho, Ya-Lun; Saito, Takumi; Apostoluk, Aleksandra; Müller, Christoph R; Delaunay, Jean-Jacques

2016-06-29

A single-step electrophoretic deposition (EPD) process is used to fabricate catalyst layers which consist of nickel oxide nanoparticles attached on the surface of nanographitic flakes. Magnesium ions present in the colloid charge positively the flake's surface as they attach on it and are also used to bind nanographitic flakes together. The fabricated catalyst layers showed a very low onset voltage (-0.2 V vs Ag/AgCl) in the electro-oxidation of ethanol. To clarify the occurring catalytic mechanism, we performed annealing treatment to produce samples having a different electrochemical behavior with a large onset voltage. Temperature dependence measurements of the layer conductivity pointed toward a charge transport mechanism based on hopping for the nonannealed layers, while the drift transport is observed in the annealed layers. The hopping charge transport is responsible for the appearance of the low onset voltage in ethanol electro-oxidation.

Process for the manufacture of an attrition resistant sorbent used for gas desulfurization

DOEpatents

Venkataramani, Venkat S.; Ayala, Raul E.

2003-09-16

This process produces a sorbent for use in desulfurization of coal gas. A zinc titanate compound and a metal oxide are mixed by milling the compounds in an aqueous medium, the resulting mixture is dried and then calcined, crushed, sleved and formed into pellets for use in a moving-bed reactor. Metal oxides suitable for use as an additive in this process include: magnesium oxide, magnesium oxide plus molybdenum oxide, calcium oxide, yttrium oxide, hafnium oxide, zirconium oxide, cupric oxide, and tin oxide. The resulting sorbent has a percentage of the original zinc or titanium ions substituted for the oxide metal of the chosen additive.

76 FR 57021 - Magnesium Metal From the People's Republic of China: Rescission of Antidumping Duty...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-15

... metals/mischmetal, cryolite, silica/fly ash, magnesium oxide, periclase, ferroalloys, dolomite lime, and... DEPARTMENT OF COMMERCE International Trade Administration [A-570-896] Magnesium Metal From the... initiation of an administrative review of the antidumping duty order on magnesium metal from the People's...

Oxidation characteristics of MgF2 in air at high temperature

NASA Astrophysics Data System (ADS)

Chen, H. K.; Jie, Y. Y.; Chang, L.

2017-02-01

High temperature oxidation properties of MgF2 in air were studied. The changes of phase composition, macro surface morphology, weight and elemental composition of MgF2 samples with temperature were investigated by using XRD, EDS and gravimetric analyses. The results show that the oxidation reaction of MgF2 converted to MgO occurred at high temperature, and the reaction was accelerated by the increase of temperature and the presence of impurities. This result clarifies the understanding of the high temperature oxidation behavior of MgF2 in air, and provides a theoretical basis for the reasonable application of MgF2 in optical coating materials, electronic ceramic materials and magnesium melt protection.

Thermal oxidation behavior of an Al-Li-Cu-Mg-Zr alloy

NASA Astrophysics Data System (ADS)

Ahmad, Maqsood

1987-04-01

The chemical composition of oxide films formed during thermal treatments of an Al-Li-Cu-Mg-Zr alloy has been studied by means of Auger electron spectroscopy and X-ray photoelectron spectroscopy. The oxide layers formed after oxidation of 2.5 minutes to 30 minutes at 530 °C in lab air have been characterized. In the early stages of oxidation the surface is composed of both the lithium rich oxides and magnesium rich oxides. However, after longer oxidation times the oxidation of lithium becomes predominant and the air/oxide interface is completely covered by lithium compounds. Oxidation products formed on the alloy surface have been studied by X-ray diffraction analysis. The following three phases, namely, Li2CO3, α-Li5AlO4, and γ-LiAlO2, were identified. During heat treatment in lab air at 530 °C and at atmospheric pressure the dominating reaction product is Li2CO3. Due to the selective oxidation of lithium a soft surface layer is developed. The width of the soft layer formed during solution heat treatments carried out in lab air and in salt bath environments has been determined by microhardness measurements. The lithium concentration profiles were calculated from a diffusion equation. The depletion of alloying elements from the near surface region during heat treatments has been investigated using energy dispersive X-ray analysis. The oxide morphology was examined using scanning electron microscopy and optical microscopy.

Thermal oxidation behavior of an Al-Li-Cu-Mg-Zr alloy

NASA Astrophysics Data System (ADS)

Ahmad, Maqsood

1987-05-01

The chemical composition of oxide films formed during thermal treatments of an Al-Li-Cu-Mg-Zr alloy has been studied by means of Auger electron spectroscopy and X-ray photoelectron spectroscopy. The oxide layers formed after oxidation of 2.5 minutes to 30 minutes at 530 °C in lab air have been characterized. In the early stages of oxidation the surface is composed of both the lithium rich oxides and magnesium rich oxides. However, after longer oxidation times the oxidation of lithium becomes predominant and the air/oxide interface is completely covered by lithium compounds. Oxidation products formed on the alloy surface have been studied by X-ray diffraction analysis. The following three phases, namely, Li2CO3, α-Li5AlO4, and γ-LiAlO2, were identified. During heat treatment in lab air at 530 °C and at atmospheric pressure the dominating reaction product is Li2CO3. Due to the selective oxidation of lithium a soft surface layer is developed. The width of the soft layer formed during solution heat treatments carried out in lab air and in salt bath environments has been determined by microhardness measurements. The lithium concentration profiles were calculated from a diffusion equation. The depletion of alloying elements from the near surface region during heat treatments has been investigated using energy dispersive X-ray analysis. The oxide morphology was examined using scanning electron microscopy and optical microscopy.

Spontaneous Cracking in Unfired Magnesia Compacts Upon Standing in Air

NASA Technical Reports Server (NTRS)

Davies, Myron O.; Grimes, Hubert H.; May, Charles E.

1961-01-01

Analytical-grade magnesium oxide powder without binder was compressed hydrostatically to 50,000 lb. per sq. in. to form compacts. When exposed to moist air immediately after pressing, these compacts developed irregularly shaped cracks. Controlled tests, in which these compacts were exposed for various lengths of time to various atmospheres, indicated that in general water vapor, carbon dioxide, and residual stresses had to be present if cracking was to occur. The probable cause of the cracking was the formation of a less dense and mechanically weak basic carbonate of magnesium at crystallite surface points of high stress concentration which developed during the compacting. The adsorption of dry CO2 at such sites prevented subsequent delayed fracture.

Magnesium oxide grafted carbon nanotubes based impedimetric genosensor for biomedical application.

PubMed

Patel, Manoj Kumar; Ali, Md Azahar; Srivastava, Saurabh; Agrawal, Ved Varun; Ansari, S G; Malhotra, Bansi D

2013-12-15

Nanostructured magnesium oxide (size<10nm) grafted carboxyl (COOH) functionalized multi-walled carbon nanotubes (nMgO-cMWCNTs) deposited electrophoretically onto indium tin oxide (ITO) coated glass electrode and have been utilized for Vibrio cholerae detection. Aminated 23 bases single stranded DNA (NH2-ssDNA) probe sequence (O1 gene) of V. cholerae has been covalently functionalized onto nMgO-cMWCNTs/ITO electrode surface using EDC-NHS chemistry. This DNA functionalized MgO grafted cMWCNTs electrode has been characterized using X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical techniques. The results of XPS studies reveal that sufficient O-C=O groups present at the nMgO-cMWCNTs surface are utilized for DNA binding. The results of hybridization studies conducted with fragmented target DNA (ftDNA) of V. cholerae using electrochemical impedance spectroscopy (EIS) reveal sensitivity as 3.87 Ω ng(-1) cm(-2), detection limit of ~21.70 ng µL(-1) in the linear range of 100-500 ng µL(-1) and stability of about 120 days. The proposed DNA functionalized nMgO-cMWCNTs nanomatrix provides a novel impedimetric platform for the fabrication of a compact genosensor device for biomedical application. © 2013 Elsevier B.V. All rights reserved.

Peculiarities of physical and chemical processes of clinker formation in raw mixes with increased content of magnesium oxide in presence of barite waste

NASA Astrophysics Data System (ADS)

Novoselova, I. N.; Novosyolov, A. G.

2018-03-01

The article considers the influence of barite waste on clinker formation processes in raw mixes with the increased content of magnesium oxide. A by-product of the barite concentrate manufacture of Tolcheinskoye deposit has been used as a barite waste, its predominant content of barium sulphate BaSO4 amounts to 76,11%. The impact of BaO and SO3 has been revealed, particularly the impact of barium oxide on clinker formation processes in raw mixes with the increased content of magnesium oxide. It has been clarified that the addition of barite waste into a raw mix causes the formation of dicalcium silicate in two modifications, reduces the amount of alite and influences on the composition of tricalcium aluminate. Barium mono-alluminate is formed in the composition of the intermediate material. Solid solutions with barium oxide are formed in clinker phases. The authors have determined the saturation speed of calcium oxide in magnesium-bearing raw mixes with saturation coefficient (SC) 0,91 and 0,80 in the presence of 2 and 3% barite waste in the temperature range 1300-1450°C.

Nanostructured magnesium oxide as cure activator for polychloroprene rubber.

PubMed

Kar, Sritama; Bhowmick, Anil K

2009-05-01

The aim of this research was to synthesize magnesium oxide nanoparticles and to use them as cure activator for polychloroprene rubber (CR). The effects of counterions of magnesium salts on the homogeneous phase precipitation reaction to control size, monodispersity, crystallinity, and morphology of Mg(OH)2 nanoparticles were also investigated. Magnesium oxide nanoparticles were synthesized by optimizing the calcination temperature of Mg(OH)2 nanoparticles. Finally, the MgO nanoparticles were dispersed in polychloroprene rubber (CR) solution along with zinc oxide (ZnO) powder. The influence of MgO nanoparticles on the mechanical, dynamic mechanical and thermal properties of the resulting nanocomposites was quantified. The modulus and strength of ZnO-cured polychloroprene rubber with 4% MgO nanoparticles appeared to be superior to those with ZnO particles or ZnO with rubber grade MgO particles. These composites were further characterized by transmission electron microscopy and infrared spectroscopy in order to understand the morphology of the resulting system and the load transfer mechanism.

Magnesium supplementation improves indicators of low magnesium status and inflammatory stress in adults older than 51 years with poor quality sleep

USDA-ARS?s Scientific Manuscript database

Low magnesium status has been associated with numerous conditions characterized as having a chronic inflammatory stress component. Some animal findings indicate that a moderate magnesium deficiency, similar to which apparently commonly occurs in humans, may enhance inflammatory or oxidative stress i...

Arsenic removal from water

DOEpatents

Moore, Robert C [Edgewood, NM; Anderson, D Richard [Albuquerque, NM

2007-07-24

Methods for removing arsenic from water by addition of inexpensive and commonly available magnesium oxide, magnesium hydroxide, calcium oxide, or calcium hydroxide to the water. The hydroxide has a strong chemical affinity for arsenic and rapidly adsorbs arsenic, even in the presence of carbonate in the water. Simple and commercially available mechanical methods for removal of magnesium hydroxide particles with adsorbed arsenic from drinking water can be used, including filtration, dissolved air flotation, vortex separation, or centrifugal separation. A method for continuous removal of arsenic from water is provided. Also provided is a method for concentrating arsenic in a water sample to facilitate quantification of arsenic, by means of magnesium or calcium hydroxide adsorption.

Effects of binders on the electrochemical performance of rechargeable magnesium batteries

NASA Astrophysics Data System (ADS)

Wang, Nan; NuLi, Yanna; Su, Shuojian; Yang, Jun; Wang, Jiulin

2017-02-01

A comparative study on the effects of different binders on the electrochemical performance of rechargeable magnesium batteries with Mo6S8 cathode is conducted for the first time. The selected binders are commercial organic-soluble polyvinylidene fluoride (PVDF), water-soluble poly(acrylic acid) (PAA), poly(vinyl alcohol) (PVA), gelatin, sodium alginate (SA) and Beta-cyclodextrin (β-CD). The binders significantly affect the physical properties, thus the electrochemical performance of Mo6S8 cathode. Compared with those using traditional PVDF binder, Mo6S8 electrodes with PAA and PVA exhibit enhanced cycling stabilities and rate capabilities, which are attributed to the improved cohesion among the electrode constituents and adhesion between the electrode laminate and the current collector. In addition, the anodic stability of these binders is not only related to the chemical structure of binders, but also to the uniformity of electrode surface. SA binder shows low anodic stability duo to containing easily oxidized groups. Non-uniform electrode surface decreases the anodic stability of PVDF based Mo6S8 electrode. Gelatin can be used as a binder in the formulation of high voltage cathodes for rechargeable magnesium batteries.

Magnesium sulfate provides neuroprotection in lipopolysaccharide-activated primary microglia by inhibiting NF-κB pathway.

PubMed

Gao, Feng; Ding, Baozhong; Zhou, Longan; Gao, Xueshan; Guo, Huiguang; Xu, Hong

2013-10-01

Magnesium sulfate has been used as an anticonvulsant in severe preeclamptic or eclamptic women prior to surgical trauma, but its effects on neuroinflammation is not well defined. In the present study, we investigated the neuroprotective effects of magnesium sulfate in lipopolysaccharide (LPS)-induced microglia and explored the underlying mechanism. Microglia was incubated with LPS in the presence or absence of various concentrations of magnesium sulfate, or L-type calcium channel activator BAY-K8644. The levels of inflammatory mediators, such as nitric oxide, prostaglandin E2, interleukin 1β, and tumor necrosis factor α, were measured using enzyme-linked immunosorbent assay. The expression of inducible nitric oxide synthase mRNA was detected by reverse-transcription polymerase chain reaction. Nuclear factor κB (NF-κB) activity in the nuclear extract of microglia was detected by NF-κB p50/p65 transcription factor assay kit. Magnesium sulfate at 5 and 10 mmol/L significantly inhibited the release of nitric oxide, prostaglandin E2, interleukin 1β, and tumor necrosis factor α, and the expression of inducible nitric oxide synthase mRNA in LPS-activated microglia. Furthermore, magnesium sulfate inhibited the translocation of NF-κB from the cytoplasm to the nucleus in a dose-dependent manner. Notably, these effects were significantly reversed by L-type calcium channel activator BAY-K8644. Magnesium sulfate protects microglia against LPS-induced release of inflammatory mediators, and these effects may be mediated by inhibiting L-type calcium channels and NF-κB signaling. Crown Copyright © 2013. Published by Elsevier Inc. All rights reserved.

Biocompatibility enhancement of rare earth magnesium alloy by laser surface processing

NASA Astrophysics Data System (ADS)

Nie, Shilin; Wang, Yuqing; Liu, Haifeng; Guan, Yingchun

2018-01-01

Although magnesium and magnesium alloys are considered biocompatible and biodegradable, insufficient biocompatibility in body fluid environment is still the major drawback of magnesium alloys for their successful applications as biodegradable orthopaedic implants. In this work, magnesium alloy surface with both enhanced corrosion resistance and better cell adhesion property was directly fabricated by laser surface processing. Laser surface melting was used to improve corrosion resistance of Mg-6Gd-0.6Ca alloy. After laser surface melting, laser surface texturing was utilized on melted surface for better cell adhesion property. The corrosion resistance of laser-treated and as-received samples were evaluated using electrochemical technique. The effect of laser surface treatment on phase and microstructure evolution was evaluated using scanning electron microscopy, optical microscopy and X-ray diffraction. This work investigated the effect of laser treatment on cell distribution across the surface of magnesium alloy substrates. Osteoblast was cultured on the laser-treated surface and as-received surface. Cell morphology was observed with a scanning electron microscopy, and cell viability was evaluated by optical density measurement.

Using Demonstrations Involving Combustion and Acid-Base Chemistry to Show Hydration of Carbon Dioxide, Sulfur Dioxide, and Magnesium Oxide and Their Relevance for Environmental Climate Science

ERIC Educational Resources Information Center

Shaw, C. Frank, III; Webb, James W.; Rothenberger, Otis

2016-01-01

The nature of acidic and basic (alkaline) oxides can be easily illustrated via a series of three straightforward classroom demonstrations for high school and general chemistry courses. Properties of carbon dioxide, sulfur dioxide, and magnesium oxide are revealed inexpensively and safely. Additionally, the very different kinetics of hydration of…

A Comparison of the Greenhouse Impacts of Magnesium Produced By Electrolytic and Pidgeon Processes

NASA Astrophysics Data System (ADS)

Ramakrishnan, Subramania; Koltun, Paul

With a focus on the global warming impact, this paper deals with the cradle-to-gate life cycle study of the following two practical production systems for producing magnesium ingots: (i) Magnesite ore is processed using the Australian Magnesium process to produce anhydrous magnesium chloride, which is then electrolysed to produce magnesium; and (ii) Dolomite ore is calcined to produce magnesium oxide, which is then thermally reduced with ferrosilicon using the Pidgeon process, based on the current practice used in China for magnesium production

Factors Affecting the Plasticity of Sodium Chloride, Lithium Fluoride, and Magnesium Oxide Single Crystals. 1

NASA Technical Reports Server (NTRS)

Stearns, Carl A.; Pack, Ann E.; Lad, Robert A.

1959-01-01

A study was made of the relative magnitude of the effects of various factors on the ductility of single crystals of sodium chloride (NaCl), lithium fluoride (LiF), and magnesium oxide (MgO). Specimen treatments included water-polishing, varying cleavage rate, annealing, quenching, X-irradiation, surface coating, aging, and combinations of some of these treatments. The mechanical behavior of the crystals was studied in flexure and in compression, the latter study being performed at both constant strain rate and constant load. Etch-pit studies were carried out to provide some pertinent information on the results of pretreatment on the dislocation concentration and distribution in the vicinity of the surface. The load deformation curves for these ionic single crystals show an initial region of very low slope which proved to be due to anelastic deformation. The extent of initial anelastic deformation is modified by specimen pretreatment in a way that suggests that this deformation is the result of expansion of cleaved-in dislocation loops, which can contract on the removal of the stress. The effects of the various pretreatments on the load and deflection at fracture are in accord with the prediction one might make with regard to their effect on the nucleation of fatal surface cracks. For NaCl, increases in ductility are always accompanied by increases in strength. The creep constants for NaCl are a function of treatments which affect the bulk structure but are not a function of treatments which only affect the surface.

Investigation of organic solvents assisted nano magnesium oxide nanoparticles and their structural, morphological, optical and antimicrobial performance

NASA Astrophysics Data System (ADS)

Deepa, B.; Rajendran, V.

2018-01-01

Investigation on the structural, morphological, optical studies and antimicrobial performance of organic solvent assisted magnesium oxide (MgO) nanoparticles. Nanoparticles are in 16-18 nm of grain size prepared by sol-gel method. The XRD studies shows as synthesized products are in cubic phase with periclase structurer. The well disperesd spherical morphology were obtained in SEM and TEM. The organic solvent methanol had profound effects on the size of the nano particles. The optical absorption edge energy was present in UV region and the corresponding band gap energy values are 4.5 and 4.9 eV for water with ethanol and methanol mediated MgO sample respectively. The PL emission spectrum has a emission peak at 340 and 353 nm which is due to surface defects. The obtained MgO nanoparticles showed superior antimicrobial activities for the gram positive, gram negative and fungus strains using the ELISA reader at 450 nm.

An artificial interphase enables reversible magnesium chemistry in carbonate electrolytes.

PubMed

Son, Seoung-Bum; Gao, Tao; Harvey, Steve P; Steirer, K Xerxes; Stokes, Adam; Norman, Andrew; Wang, Chunsheng; Cresce, Arthur; Xu, Kang; Ban, Chunmei

2018-05-01

Magnesium-based batteries possess potential advantages over their lithium counterparts. However, reversible Mg chemistry requires a thermodynamically stable electrolyte at low potential, which is usually achieved with corrosive components and at the expense of stability against oxidation. In lithium-ion batteries the conflict between the cathodic and anodic stabilities of the electrolytes is resolved by forming an anode interphase that shields the electrolyte from being reduced. This strategy cannot be applied to Mg batteries because divalent Mg 2+ cannot penetrate such interphases. Here, we engineer an artificial Mg 2+ -conductive interphase on the Mg anode surface, which successfully decouples the anodic and cathodic requirements for electrolytes and demonstrate highly reversible Mg chemistry in oxidation-resistant electrolytes. The artificial interphase enables the reversible cycling of a Mg/V 2 O 5 full-cell in the water-containing, carbonate-based electrolyte. This approach provides a new avenue not only for Mg but also for other multivalent-cation batteries facing the same problems, taking a step towards their use in energy-storage applications.

Layer-by-Layer Assembly of a Self-Healing Anticorrosion Coating on Magnesium Alloys.

PubMed

Fan, Fan; Zhou, Chunyu; Wang, Xu; Szpunar, Jerzy

2015-12-16

Fabrication of self-healing anticorrosion coatings has attracted attention as it has the ability to extend the service life and prevent the substrate from corrosive attack. However, a coating system with a rapid self-healing ability and an improved corrosion resistance is rarely reported. In this work, we developed a self-healing anticorrosion coating on a magnesium alloy (AZ31). The coating comprises a cerium-based conversion layer, a graphene oxide layer, and a branched poly(ethylene imine) (PEI)/poly(acrylic acid) (PAA) multilayer. We incorporated the graphene oxide as corrosion inhibitors and used the PEI/PAA multilayers to provide the self-healing ability to the coating systems. X-ray diffraction (XRD) and Raman spectroscopy were used to characterize the composition of the multilayers, and scanning electron microscopy (SEM) was used to analyze the surface morphology. The electrochemical impedance spectroscopy (EIS) results illustrate the improved corrosion resistance of the coating. The proposed coating also has a rapid self-healing ability in the presence of water.

Mg-Enriched Engineered Carbon from Lithium-Ion Battery Anode for Phosphate Removal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Yan; Guo, Xingming; Yao, Ying

2016-02-10

Three Mg-enriched engineered carbons (mesocarbon microbeads, MCMB) were produced from lithium-ion battery anode using concentrated nitric acid oxidization and magnesium nitrate pretreatment. The obtained 15%Mg-MCMB, 30%Mg-MCMB, and 40%Mg-MCMB have magnesium level of 10.19, 19.13, and 19.96%, respectively. FTIR spectrum shows the functional groups present on the oxidized MCMB including OH, C=O, C–H, and C–O. XRD, SEM-EDX, and XPS analyses show that nanoscale Mg(OH) 2 and MgO particles were presented on the surface of the Mg-MCMB samples, which could serve as the main adsorption mechanism as to precipitate phosphate from aqueous solutions. The sorption experiments indicate that Mg modification dramatically promotesmore » MCMB’s phosphate removal ability and phosphate removal rates reach as high as 95%. Thus, modification of the spent LIBs anode could provide a novel direction of preparing wastewater adsorbent and develop an innovative way to achieve sustainable development.« less

An artificial interphase enables reversible magnesium chemistry in carbonate electrolytes

NASA Astrophysics Data System (ADS)

Son, Seoung-Bum; Gao, Tao; Harvey, Steve P.; Steirer, K. Xerxes; Stokes, Adam; Norman, Andrew; Wang, Chunsheng; Cresce, Arthur; Xu, Kang; Ban, Chunmei

2018-05-01

Magnesium-based batteries possess potential advantages over their lithium counterparts. However, reversible Mg chemistry requires a thermodynamically stable electrolyte at low potential, which is usually achieved with corrosive components and at the expense of stability against oxidation. In lithium-ion batteries the conflict between the cathodic and anodic stabilities of the electrolytes is resolved by forming an anode interphase that shields the electrolyte from being reduced. This strategy cannot be applied to Mg batteries because divalent Mg2+ cannot penetrate such interphases. Here, we engineer an artificial Mg2+-conductive interphase on the Mg anode surface, which successfully decouples the anodic and cathodic requirements for electrolytes and demonstrate highly reversible Mg chemistry in oxidation-resistant electrolytes. The artificial interphase enables the reversible cycling of a Mg/V2O5 full-cell in the water-containing, carbonate-based electrolyte. This approach provides a new avenue not only for Mg but also for other multivalent-cation batteries facing the same problems, taking a step towards their use in energy-storage applications.

Study on the mechanism of antibacterial action of magnesium oxide nanoparticles against foodborne pathogens

USDA-ARS?s Scientific Manuscript database

Magnesium oxide nanoparticles (MgO nanoparticles, with average size of 20 nm) have strong antibacterial activities against several important foodborne pathogens. Resazurin (a redox sensitive dye) microplate assay was used for measuring growth inhibition of bacteria treated with MgO nanoparticles. Th...

40 CFR 721.10021 - Magnesium potassium titanium oxide.

Code of Federal Regulations, 2010 CFR

2010-07-01

... or tight-fitting facepiece (either half- or full-face). As an alternative to the respiratory... significant new uses subject to reporting. (1) The chemical substance identified as magnesium potassium titanium oxide (PMN P-01-764; CAS No. 39290-90-9) is subject to reporting under this section for the...

Magnesium oxide doping reduces acoustic wave attenuation in lithium metatantalate and lithium metaniobate crystals

NASA Technical Reports Server (NTRS)

Croft, W.; Damon, R.; Kedzie, R.; Kestigian, M.; Smith, A.; Worley, J.

1970-01-01

Single crystals of lithium metatantalate and lithium metaniobate, grown from melts having different stoichiometries and different amounts of magnesium oxide, show that doping lowers temperature-independent portion of attenuation of acoustic waves. Doped crystals possess optical properties well suited for electro-optical and photoelastic applications.

21 CFR 178.1010 - Sanitizing solutions.

Code of Federal Regulations, 2010 CFR

2010-04-01

... permanganate (CAS Reg. No. 7722-64-7). Magnesium oxide (CAS Reg. No. 1309-48-4) and potassium bromide (CAS Reg... permanganate. (ii) The solution identified in paragraph (b)(37) of this section with potassium bromide shall... potassium permanganate. (iii) Magnesium oxide when used in paragraph (c)(32) (i) or (ii) of this section...

NANOSIZED MAGNESIUM OXIDE AS CATALYST FOR THE RAPID AND GREEN SYNTHESIS OF SUBSTITUTED 2-AMINO-2-CHROMENES

EPA Science Inventory

A nanosized magnesium oxide catalyzed three-component condensation reaction of aldehyde, malononitrile and ¿-naphthol proceeded rapidly in water/PEG to afford corresponding 2-amino-2-chromenes in high yields at room temperature. The greener protocol was found to be fairly general...

System for removal of arsenic from water

DOEpatents

Moore, Robert C.; Anderson, D. Richard

2004-11-23

Systems for removing arsenic from water by addition of inexpensive and commonly available magnesium oxide, magnesium hydroxide, calcium oxide, or calcium hydroxide to the water. The hydroxide has a strong chemical affinity for arsenic and rapidly adsorbs arsenic, even in the presence of carbonate in the water. Simple and commercially available mechanical systems for removal of magnesium hydroxide particles with adsorbed arsenic from drinking water can be used, including filtration, dissolved air flotation, vortex separation, or centrifugal separation. A system for continuous removal of arsenic from water is provided. Also provided is a system for concentrating arsenic in a water sample to facilitate quantification of arsenic, by means of magnesium or calcium hydroxide adsorption.

Effect of magnesium supplementation on depression status in depressed patients with magnesium deficiency: A randomized, double-blind, placebo-controlled trial.

PubMed

Rajizadeh, Afsaneh; Mozaffari-Khosravi, Hassan; Yassini-Ardakani, Mojtaba; Dehghani, Ali

2017-03-01

The aim of this study was to determine the effect of magnesium supplementation on the depression status of depressed patients suffering from magnesium deficiency. Sixty depressed people suffering from hypomagnesemia participated in this trial. The individuals were randomly categorized into two groups of 30 members; one receiving two 250-mg tablets of magnesium oxide (MG) daily and the other receiving placebo (PG) for 8 wk. The Beck Depression Inventory-II was conducted and the concentration of serum magnesium was measured. At the end of intervention, 88.5% of the MG and 48.1% of the PG (P = 0.002) had a normal level of magnesium. The mean changes of serum magnesium were significantly different across the two groups. After the intervention, the mean Beck score significantly declined. However, in the MG, this reduction was more significant than in the PG (P = 0.02), so that the mean changes in this group experienced 15.65 ± 8.9 reduction, but in the PG, it declined by 10.40 ± 7.9. Daily consumption of 500 mg magnesium oxide tablets for ≥8 wk by depressed patients suffering from magnesium deficiency leads to improvements in depression status and magnesium levels. Therefore, assessment of the magnesium serum and resolving this deficiency positively influence the treatment of depressed patients. Copyright © 2016 Elsevier Inc. All rights reserved.

Micro-arc oxidation treatment to improve the hard-tissue compatibility of Ti-29Nb-13Ta-4.6Zr alloy

NASA Astrophysics Data System (ADS)

Tsutsumi, Yusuke; Niinomi, Mitsuo; Nakai, Masaaki; Tsutsumi, Harumi; Doi, Hisashi; Nomura, Naoyuki; Hanawa, Takao

2012-12-01

Micro-arc oxidation (MAO) was performed on a β-type Ti-29Nb-13Ta-4.6Zr alloy (TNTZ) in this study to improve its bioactivity in a body fluid and its hard-tissue compatibility. The surface oxide layer formed on TNTZ by MAO treatment in a mixture of calcium glycerophosphate and magnesium acetate was characterized using various surface analyses. The oxide layer was mainly composed of two types of TiO2 (rutile and anatase), and it also contained Ca, P, and Mg, which were incorporated from the electrolyte during the treatment. The calcium phosphate formation on the surface of the specimens after immersion in Hanks' solution was evaluated to determine the bioactivity of TNTZ with and without MAO treatment. As a result, thick calcium phosphate layers formed on the TNTZ specimen that underwent MAO treatment, whereas only a small amount of precipitate was observed on TNTZ without treatment. Thus, the MAO treatment is a promising method to improve the bioactivity and hard-tissue compatibility of TNTZ.

In vivo study of microarc oxidation coated biodegradable magnesium plate to heal bone fracture defect of 3mm width.

PubMed

Wu, Y F; Wang, Y M; Jing, Y B; Zhuang, J P; Yan, J L; Shao, Z K; Jin, M S; Wu, C J; Zhou, Y

2017-10-01

Microarc oxidation (MAO) coated magnesium (Mg) with improved corrosion resistance appeal increasing interests as a revolutionary biodegradable metal for fractured bone fixing implants application. However, the in vivo corrosion degradation of the implants and bone healing response are not well understood, which is highly required in clinic. In the present work, 10μm and 20μm thick biocompatible MAO coatings mainly composed of MgO, Mg 2 SiO 4 , CaSiO 3 and Mg 3 (PO 4 ) 2 phases were fabricated on AZ31 magnesium alloy. The electrochemical tests indicated an improved corrosion resistance of magnesium by the MAO coatings. The 10μm and 20μm coated and uncoated magnesium plates were separately implanted into the radius bone fracture site of adult New Zealand white rabbits using a 3mm width bone fracture defect model to investigate the magnesium implants degradation and uninhibited bone healing. Taking advantage of the good biocompatibility of the MAO coatings, no adverse effects were detected through the blood test and histological examination. The implantation groups of coated and uncoated magnesium plates were both observed the promoting effect of bone fracture healing compared with the simple fracture group without implant. The releasing Mg 2+ by the degradation of implants into the fracture site improved the bone fracture healing, which is attributed to the magnesium promoting CGRP-mediated osteogenic differentiation. Mg degradation and bone fracture healing promoting must be tailored by microarc oxidation coating with different thickness for potential clinic application. Copyright © 2017. Published by Elsevier B.V.

X-ray photoelectron spectroscopy (XPS) investigation of the surface film on magnesium powders.

PubMed

Burke, Paul J; Bayindir, Zeynel; Kipouros, Georges J

2012-05-01

Magnesium (Mg) and its alloys are attractive for use in automotive and aerospace applications because of their low density and good mechanical properties. However, difficulty in forming magnesium and the limited number of available commercial alloys limit their use. Powder metallurgy may be a suitable solution for forming near-net-shape parts. However, sintering pure magnesium presents difficulties due to surface film that forms on the magnesium powder particles. The present work investigates the composition of the surface film that forms on the surface of pure magnesium powders exposed to atmospheric conditions and on pure magnesium powders after compaction under uniaxial pressing at a pressure of 500 MPa and sintering under argon at 600 °C for 40 minutes. Initially, focused ion beam microscopy was utilized to determine the thickness of the surface layer of the magnesium powder and found it to be ~10 nm. The X-ray photoelectron analysis of the green magnesium sample prior to sintering confirmed the presence of MgO, MgCO(3)·3H(2)O, and Mg(OH)(2) in the surface layer of the powder with a core of pure magnesium. The outer portion of the surface layer was found to contain MgCO(3)·3H(2)O and Mg(OH)(2), while the inner portion of the layer is primarily MgO. After sintering, the MgCO(3)·3H(2)O was found to be almost completely absent, and the amount of Mg(OH)(2) was also decreased significantly. This is postulated to occur by decomposition of the compounds to MgO and gases during the high temperature of sintering. An increase in the MgO content after sintering supports this theory.

Effects of surface treatments and bonding types on the interfacial behavior of fiber metal laminate based on magnesium alloy

NASA Astrophysics Data System (ADS)

Zhang, Xi; Ma, Quanyang; Dai, Yu; Hu, Faping; Liu, Gang; Xu, Zouyuan; Wei, Guobing; Xu, Tiancai; Zeng, Qingwen; Xie, Weidong

2018-01-01

Fiber metal laminates based on magnesium alloys (MgFML) with different surface treatments and different bonding types were tested and analyzed. By using dynamic contact angle measurement and scanning electron microscopy (SEM), it was found that phosphating treatment can significantly improve the surface energy and wettability of magnesium alloy, and the surface energy of phosphated magnesium alloy was approximately 50% higher than that of abraded-only magnesium alloy. The single cantilever beam (SCB) test showed that the interfacial fracture energies of directly bonded MgFMLs based on abraded-only magnesium and abraded + phosphated magnesium were 650 J/m2 and 1030 J/m2, respectively, whereas the interfacial fracture energies of indirectly bonded MgFMLs were 1650 J/m2 and 2260 J/m2, respectively. Phosphating treatment and modified polypropylene interleaf were observed to improve the tensile strength and interfacial fracture toughness of MgFML. In addition, the rougher surface was more conducive to enhance the bonding strength and interfacial fracture toughness of MgFML.

Effect of Graphite Powder Amount on Surface Films Formed on Molten AZ91D Alloy

NASA Astrophysics Data System (ADS)

Li, Weihong; Zhou, Jixue; Ma, Baichang; Wang, Jinwei; Wu, Jianhua; Yang, Yuansheng

2017-10-01

Graphite powder was adopted to prevent AZ91D magnesium alloy from oxidizing during the melting and casting process. The microstructure of the resultant surface films formed on the molten alloy protected by 0, 2.7, 5.4, 8.1, and 10.8 g dm-2 graphite powder at 973 K (700 °C) for holding time of 30 minutes was investigated by scanning electron microscopy, energy dispersive spectrometer, X-ray diffraction, and the thermodynamic method. The results indicated that the surface films were composed of a protective layer and the underneath MgF2 particles with different morphology. The protective layer was continuous with a thickness range from 200 to 550 nm consisting of magnesium, oxygen, fluorine, carbon, and a small amount of aluminium, possibly existing in the form of MgO, MgF2, C, and MgAl2O4. The surface films were the result of the interaction between the graphite powder, the melt, and the ambient atmosphere. The unevenness of the micro surface morphology and the number and size of the underneath MgF2 particles increased with graphite powder amount. The mechanism of the effect of graphite powder amount on the resultant surface films was also discussed.

Effects of self-assembly of 3-phosphonopropionic acid, 3-aminopropyltrimethoxysilane and dopamine on the corrosion behaviors and biocompatibility of a magnesium alloy.

PubMed

Pan, Chang-Jiang; Hou, Yu; Wang, Ya-Nan; Gao, Fei; Liu, Tao; Hou, Yan-Hua; Zhu, Yu-Fu; Ye, Wei; Wang, Ling-Ren

2016-10-01

Magnesium based alloys are attracting tremendous interests as the novel biodegradable metallic biomaterials. However, the rapid in vivo degradation and the limited surface biocompatibility restrict their clinical applications. Surface modification represents one of the important approaches to control the corrosion rate of Mg based alloys and to enhance the biocompatibility. In the present study, in order to improve the corrosion resistance and surface biocompatibility, magnesium alloy (AZ31B) was modified by the alkali heating treatment followed by the self-assembly of 3-phosphonopropionic acid, 3-aminopropyltrimethoxysilane (APTMS) and dopamine, respectively. The results of attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectra (XPS) indicated that the molecules were successfully immobilized on the magnesium alloy surface by the self-assembly. An excellent hydrophilic surface was obtained after the alkali heating treatment and the water contact angle increased to some degree after the self-assembly of dopamine, APTMS and 3-phosphonopropionic acid, however, the hydrophilicity of the modified samples was better than that of the pristine magnesium substrate. Due to the formation of the passivation layer after the alkali heating treatment, the corrosion resistance of the magnesium alloy was obviously improved. The corrosion rate further decreased to varying degrees after the self-assembly surface modification. The blood compatibility of the pristine magnesium was significantly improved after the surface modification. The hemolysis rate was reduced from 56% of the blank magnesium alloy to 18% of the alkali heating treated sample and the values were further reduced to about 10% of dopamine-modified sample and 7% of APTMS-modified sample. The hemolysis rate was below 5% for the 3-phosphonopropionic acid modified sample. As compared to the pristine magnesium alloy, fewer platelets were attached and activated on the modified surfaces and the activated partial thromboplastin times (APTT) were prolonged to some degree. Furthermore, the modified samples showed good cytocompatibility. Endothelial cells exhibited the improved proliferative profiles in terms of CCK-8 assay as compared to those on the pristine magnesium alloy. The modified samples showed better endothelial cell adhesion and spreading than the pristine magnesium alloy. Taking all these results into consideration, the method of this study can be used to modify the magnesium alloy surface to improve the corrosion resistance and biocompatibility simultaneously. Copyright © 2016 Elsevier B.V. All rights reserved.

Surface modification of biodegradable magnesium and its alloys for biomedical applications

PubMed Central

Tian, Peng; Liu, Xuanyong

2015-01-01

Magnesium and its alloys are being paid much attention recently as temporary implants, such as orthopedic implants and cardiovascular stents. However, the rapid degradation of them in physiological environment is a major obstacle preventing their wide applications to date, which will result in rapid mechanical integrity loss or even collapse of magnesium-based implants before injured tissues heal. Moreover, rapid degradation of the magnesium-based implants will also cause some adverse effects to their surrounding environment, such as local gas cavity around the implant, local alkalization and magnesium ion enrichment, which will reduce the integration between implant and tissue. So, in order to obtain better performance of magnesium-based implants in clinical trials, special alloy designs and surface modifications are prerequisite. Actually, when a magnesium-based implant is inserted in vivo, corrosion firstly happens at the implant-tissue interface and the biological response to implant is also determined by the interaction at this interface. So the surface properties, such as corrosion resistance, hemocompatibility and cytocompatibility of the implant, are critical for their in vivo performance. Compared with alloy designs, surface modification is less costly, flexible to construct multi-functional surface and can prevent addition of toxic alloying elements. In this review, we would like to summarize the current investigations of surface modifications of magnesium and its alloys for biomedical application. The advantages/disadvantages of different surface modification methods are also discussed as a suggestion for their utilization. PMID:26816637

Improving the corrosion properties of magnesium AZ31 alloy GTA weld metal using microarc oxidation process

NASA Astrophysics Data System (ADS)

Siva Prasad, M.; Ashfaq, M.; Kishore Babu, N.; Sreekanth, A.; Sivaprasad, K.; Muthupandi, V.

2017-05-01

In this work, the morphology, phase composition, and corrosion properties of microarc oxidized (MAO) gas tungsten arc (GTA) weldments of AZ31 alloy were investigated. Autogenous gas tungsten arc welds were made as full penetration bead-on-plate welding under the alternating-current mode. A uniform oxide layer was developed on the surface of the specimens with MAO treatment in silicate-based alkaline electrolytes for different oxidation times. The corrosion behavior of the samples was evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy. The oxide film improved the corrosion resistance substantially compared to the uncoated specimens. The sample coated for 10 min exhibited better corrosion properties. The corrosion resistance of the coatings was concluded to strongly depend on the morphology, whereas the phase composition and thickness were concluded to only slightly affect the corrosion resistance.

Development of the Electromagnetic Continuous Casting Technology for of Magnesium Alloys

NASA Astrophysics Data System (ADS)

Park, Joon-Pyo; Kim, Myoung-Gyun; Kim, Jong-Ho; Lee, Gyu-Chang

Currently, magnesium billets produced by ingot casting or direct chill casting process, result in low-quality surfaces and low productivity, Continuous casting technology to solve these problem has not only high-quality surface billets with fine-grained and homogeneous microstructure but also cost down. The latent heat of fusion per weight (J/g) of magnesium is similar to other metals, however, considering the heat emitted to the mold surface during continuous casting in meniscus region and converting it to the latent heat of fusion per volume, magnesium will be rapidly solidified in the mold during continuous casting, which induces subsequent surface defect formation. In this study, electromagnetic casting and stirring (EMC and EMS) techniques are proposed to control solidification process conveniently by compensating the low latent heat of solidification by volume and to fabricate magnesium billet with high-quality surface. This technique was extended to large scale billets up to 300 mm diameter and continuous casting was successfully conducted. Then magnesium billet was used for the fabrication of prototype automobile pulley.

Fabrication of Nanocomposites of SnO2 and MgAl2O4 for Gas Sensing Applications

NASA Astrophysics Data System (ADS)

Nithyavathy, N.; Arunmetha, S.; Vinoth, M.; Sriram, G.; Rajendran, V.

2016-04-01

Simple solid-state and sol-gel routes have been used to synthesize nanocomposites of tin oxide and magnesium aluminate at calcination temperature of 900 K for gas sensing applications. The effects of the surface structure of magnesium aluminate on the gas response for different concentrations of tin oxide addition were investigated for potential use in gas sensors. (SnO2) x doped in small amounts x into magnesium aluminate resulted in three nanocomposite samples MAS0.25, MAS0.50, and MAS0.75 for x = 0.25, 0.50, and 0.75, respectively, plus MgAl2O4 (MA) for x = 0. The response to different pressures of gases such as oxygen (O2), carbon monoxide (CO), and ethanol (C2H5OH) was quantitatively analyzed for all samples at different operating temperatures. The temperature was varied linearly by increasing the supply to a heating pad mounted below the sensor sample, regardless of the gas pressure inside the chamber. All the sample materials showed good response at different gas pressures (1 bar to 2 bar) and operating temperatures (300 K to 600 K). It was noted that the composite samples showed enhanced and fast response to gases, at both lower and higher operating temperatures, with detection of even the smallest change in gas pressure.

Synthesis and effectiveness of overbased magnesium and calcium petroleum sulfonates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fialkovskii, R.V.; Romanyutina, L.V.; Korbut, L.F.

Overbased sulfonate additives are widely used to improve the service properties of motor oils. This paper describes the preparation of an overbased magnesium sulfonate additive from MSG-8 oil and an investigation of its functional properties. In experiments, the solution of ammonium sulfate, fat diluted with I-20A oil to a 38% concentration, was heated and stirred continuously in the presence of water and excess magnesium oxide for a period of 4 h at 80-120/degree/C while stripping out the liberated ammonia with nitrogen. The resulting oil solution of magnesium sulfonate was dissolved in toluene. The toluene solution after cleanup was held undermore » vacuum to remove the solvent; the residue was an oil solution of overbased magnesium sulfonate. Their properties are tabulated. Comparative data are shown in Table 1 for a calcium sulfonate additive synthesized from the same intermediate (ammonium sulfate), using calcium hydroxide as the base. Test results on M-11 oil containing 5% of the magnesium or calcium additive are listed. It is shown that the magnesium additive gave better results from the calcium additive at the same concentration in terms of oxidation stability, corrosion properties, detergency, and dispersancy. 9 refs.« less

Effect of magnesium oxide content on oxidation behavior of some superalloy-base cermets

NASA Technical Reports Server (NTRS)

Zaplatynsky, I.

1975-01-01

The effect of increasing magnesium oxide (MgO) content on the cyclic oxidation resistance of hot-pressed cermets of MgO in NiCrAlY, MgO in Hoskins-875, MgO in Inconel-702, and MgO in Hastelloy-X was investigated. The cermets with magnesium oxide levels of 5, 10, 20, and 40 vol percent were examined. The cyclic oxidation behavior of these cermets at 1100 and 1200 C in still air was determined by a thermogravimetric method supplemented by X-ray diffraction analysis and light and electron microscopy. In all instances, MgO prevented grain growth in the metallic phase. No evidence of oxidation along interphase boundaries was detected. Cermets of MgO in NiCrAlY and MgO in Hoskins-875 were superior to cermets of MgO in Inconel-702 and MgO in Hastelloy-X. Their oxidation resistance was degraded only when the MgO content was 40 vol percent. The oxidation behavior of MgO-in-Inconel-702 powder cermets containing 5- and 10-vol percent MgO was approximately similar to that of pure Inconel-702 compacts. The 20- and 40-vol percent MgO content reduced the oxidation resistance of MgO-in-Inconel-702 powder cermets relative to that of pure Inconel-702.

Development of high-efficiency solar cells on silicon web

NASA Technical Reports Server (NTRS)

Rohatgi, A.; Meier, D. L.; Campbell, R. B.; Seidensticker, R. G.; Rai-Choudhury, P.

1985-01-01

High-efficiency dendritic cells were discussed. The influence of twin planes and heat treatment on the location and effect of trace impurities was of particular interest. Proper heat treatment often increases efficiency by causing impurities to pile up at twin planes. Oxide passivation had a beneficial effect on efficiency. A very efficient antireflective (AR) coating of zinc selenide and magnesium fluoride was designed and fabricated. An aluminum back-surface reflector was also effective.

Cerium Addition Improved the Dry Sliding Wear Resistance of Surface Welding AZ91 Alloy

PubMed Central

Zhao, Zhihao; Zhu, Qingfeng; Wang, Gaosong; Tao, Kai

2018-01-01

In this study, the effects of cerium (Ce) addition on the friction and wear properties of surface welding AZ91 magnesium alloys were evaluated by pin-on-disk dry sliding friction and wear tests at normal temperature. The results show that both the friction coefficient and wear rate of surfacing magnesium alloys decreased with the decrease in load and increase in sliding speed. The surfacing AZ91 alloy with 1.5% Ce had the lowest friction coefficient and wear rate. The alloy without Ce had the worst wear resistance, mainly because it contained a lot of irregularly shaped and coarse β-Mg17Al12 phases. During friction, the β phase readily caused stress concentration and thus formed cracks at the interface between β phase and α-Mg matrix. The addition of Ce reduced the size and amount of Mg17Al12, while generating Al4Ce phase with a higher thermal stability. The Al-Ce phase could hinder the grain-boundary sliding and migration and reduced the degree of plastic deformation of subsurface metal. Scanning electron microscopy observation showed that the surfacing AZ91 alloy with 1.5% Ce had a total of four types of wear mechanism: abrasion, oxidation, and severe plastic deformation were the primary mechanisms; delamination was the secondary mechanism. PMID:29415492

Cross-linked gelatin/nanoparticles composite coating on micro-arc oxidation film for corrosion and drug release

NASA Astrophysics Data System (ADS)

Xu, Xinhua; Lu, Ping; Guo, Meiqing; Fang, Mingzhong

2010-02-01

A composite coating which could control drug release and biocorrosion of magnesium alloy stent materials WE42 was prepared. This composite coating was fabricated on the surface of the micro-arc oxidation (MAO) film of the magnesium alloy, WE42, by mixing different degrees of cross-linked gelatin with well-dispersed poly( DL-lactide-co-glycolide) (PLGA) nanoparticles. The PLGA nanoparticles were prepared by emulsion solvent evaporation/extraction technique. Nano ZS laser diffraction particle size analyzer detected that the size of the nanoparticles to be 150-300 nm. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) was used to analyze the morphology of the nanoparticles and the composite coating. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were used to evaluate the corrosion behavior of the composite coating. Drug release was determined by ultraviolet-visible (UV-vis) spectrophotometer. The corrosion resistance of the composite coating was improved by preventing the corrosive ions from diffusing to the MAO films. The drug release rate of paclitaxel (PTX) exhibited a nearly linear sustained-release profile with no significant burst releases.

Effect of current density on electron beam induced charging in MgO

NASA Astrophysics Data System (ADS)

Boughariou, Aicha; Hachicha, Olfa; Kallel, Ali; Blaise, Guy

2005-11-01

It is well known that the presence of space charge in an insulator is correlated with an electric breakdown. Many studies have been carried out on the experimental characterization of space charges. In this paper, we outline the dependence on the current density of the charge-trapping phenomenon in magnesium oxide. Our study was performed with a dedicated scanning electron microscope (SEM) on the electrical property evolution of surface of magnesium oxide (1 0 0) (MgO) single crystal, during a 1.1, 5 and 30 keV electron irradiation. The types of charges trapped on the irradiated areas and the charging kinetics are determined by measuring the total secondary electron emission (SEE) σ during the injection process by means of two complementary detectors. At low energies 1.1 and 5 keV, two different kinds of self-regulated regime (σ = 1) were observed as a function of current density. At 30 keV energy, the electron emission appears to be stimulated by the current density, due to the Poole-Frenkel effect.

An artificial interphase enables reversible magnesium chemistry in carbonate electrolytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Son, Seoung-Bum; Gao, Tao; Harvey, Steve P.

Magnesium-based batteries possess potential advantages over their lithium counterparts. However, reversible Mg chemistry requires a thermodynamically stable electrolyte at low potential, which is usually achieved with corrosive components and at the expense of stability against oxidation. In lithium-ion batteries the conflict between the cathodic and anodic stabilities of the electrolytes is resolved by forming an anode interphase that shields the electrolyte from being reduced. This strategy cannot be applied to Mg batteries because divalent Mg2+ cannot penetrate such interphases. Here, we engineer an artificial Mg2+-conductive interphase on the Mg anode surface, which successfully decouples the anodic and cathodic requirements formore » electrolytes and demonstrate highly reversible Mg chemistry in oxidation-resistant electrolytes. The artificial interphase enables the reversible cycling of a Mg/V2O5 full-cell in the water-containing, carbonate-based electrolyte. This approach provides a new avenue not only for Mg but also for other multivalent-cation batteries facing the same problems, taking a step towards their use in energy-storage applications.« less

Incipient plasticity and indentation response of MgO surfaces using molecular dynamics

NASA Astrophysics Data System (ADS)

Tran, Anh-Son; Hong, Zheng-Han; Chen, Ming-Yuan; Fang, Te-Hua

2018-05-01

The mechanical characteristics of magnesium oxide (MgO) based on nanoindentation are studied using molecular dynamics (MD) simulation. The effects of indenting speed and temperature on the structural deformation and loading-unloading curve are investigated. Results show that the strained surface of the MgO expands to produce a greater relaxation of atoms in the surroundings of the indent. The dislocation propagation and pile-up for MgO occur more significantly with the increasing temperature from 300 K to 973 K. In addition, with increasing temperature, the high strained atoms with a great perturbation appearing at the groove location.

Magnesium Supplementation Diminishes Peripheral Blood Lymphocyte DNA Oxidative Damage in Athletes and Sedentary Young Man

PubMed Central

Petrović, Jelena; Stanić, Dušanka; Dmitrašinović, Gordana; Plećaš-Solarović, Bosiljka; Ignjatović, Svetlana; Batinić, Bojan; Popović, Dejana

2016-01-01

Sedentary lifestyle is highly associated with increased risk of cardiovascular disease, obesity, and type 2 diabetes. It is known that regular physical activity has positive effects on health; however several studies have shown that acute and strenuous exercise can induce oxidative stress and lead to DNA damage. As magnesium is essential in maintaining DNA integrity, the aim of this study was to determine whether four-week-long magnesium supplementation in students with sedentary lifestyle and rugby players could prevent or diminish impairment of DNA. By using the comet assay, our study demonstrated that the number of peripheral blood lymphocytes (PBL) with basal endogenous DNA damage is significantly higher in rugby players compared to students with sedentary lifestyle. On the other hand, magnesium supplementation significantly decreased the number of cells with high DNA damage, in the presence of exogenous H2O2, in PBL from both students and rugby players, and markedly reduced the number of cells with medium DNA damage in rugby players compared to corresponding control nonsupplemented group. Accordingly, the results of our study suggest that four-week-long magnesium supplementation has marked effects in protecting the DNA from oxidative damage in both rugby players and in young men with sedentary lifestyle. Clinical trial is registered at ANZCTR Trial Id: ACTRN12615001237572. PMID:27042258

Cognitive and hippocampus biochemical changes following sleep deprivation in the adult male rat.

PubMed

Nabaee, Ebrahim; Kesmati, Mahnaz; Shahriari, Ali; Khajehpour, Lotfollah; Torabi, Mozhgan

2018-05-14

Sleep deprivation (SD) influences physiological processes such as cognitive function. The balance of oxidant and antioxidant markers, neurotrophic factors and magnesium are affected by sleep deprivation but there is no difference between pre and post training sleep deprivation. This study was designed to investigate memory retrieval and biochemical factors such as oxidant and antioxidant enzyme, brain-derived neurotrophic factor (BDNF) and magnesium levels in the hippocampus following pre and post-training sleep deprivation. Male Wistar rats (weighing 200 ± 20 g) in below groups were used: control 1, 24, 48 and 72 h SD before training groups, control2, 24 h SD1 after training (being evaluated 24 h after training) and SD2 24 after training (being evaluated 48 h after training). Memory was evaluated 90 min, 24 h or 48 h after training by step-through passive avoidance apparatus. Multiple platforms method was used to induce SD. Oxidant and antioxidant markers including glutathione (GSH), glutathione reductase (GPx), malonedialdehyde (MDA), Total antioxidant concentration, catalase, superoxide dismutase (SOD), magnesium and BDNF were assessed in the hippocampus or/and brain. 72 h pre-training SD impaired short and long-term memory significantly. There was no significant difference in hippocampus oxidant and antioxidant markers compared to control. Hippocampal BDNF and magnesium did not show any changes in all SD groups. Lack of correlation between memory impairment and levels of BDNF, magnesium and/or oxidant and antioxidant balance in the hippocampus is likely to be related to animal locomotor activity in the multiple platforms method. More research is needed to clarify the role of neurochemical systems. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

Influence of albumin and inorganic ions on electrochemical corrosion behavior of plasma electrolytic oxidation coated magnesium for surgical implants

NASA Astrophysics Data System (ADS)

Wan, Peng; Lin, Xiao; Tan, LiLi; Li, Lugee; Li, WeiRong; Yang, Ke

2013-10-01

Magnesium and its alloys are of great interest for biodegradable metallic devices. However, the degradation behavior and mechanisms of magnesium treated with coating in physiological environment in the presence of organic compound such as albumin have not been elucidated. In this study, the plasma electrolytic oxidation coated magnesium immersed in four different simulated body fluids: NaCl, PBS and with the addition of albumin to investigate the influence of protein and inorganic ions on degradation behavior by electrochemical methods. The results of electrochemical tests showed that aggressive corrosion took place in 0.9 wt.% NaCl solution; whereas albumin can act as an inhibitor, its adsorption impeded further dissolution of the coating. The mechanism was attributed to the synergistic effect of protein adsorption and precipitation of insoluble salts.

A Comparison of University Lecturers' and Pre-service Teachers' Understanding of a Chemical Reaction at the Particulate Level

NASA Astrophysics Data System (ADS)

Lee, Kam-Wah Lucille

1999-07-01

This study identified a number of views prevalent among two groups of teachers about a single chemical reaction. Teachers' views were identified on the basis of the diagrammatic representations of particles that they made about the combustion of magnesium in air. Two major differences were identified between the university lecturers' and student teachers' views. According to university lecturers, in general, intermediates form between the reactants of magnesium and oxygen gas, whereas in the view of half of the pre-service teachers, the reactants form free particles before forming magnesium oxide. Many pre-service teachers held a view of loosely packed magnesium oxide, a scientifically invalid position. While training future teachers, more attention should be paid to the "atomic" level of chemical description and its associations with the macro and symbolic levels.

Monomolecular Silane Coatings on Magnesium/Aluminium Fuels

DTIC Science & Technology

1991-07-01

iii SUMMARY The aim of this project was to investigate the curing reaction between CTBN and magnesium/aluminium ailoy surfaces. A dispersion of...performing rheoloqacai experiments with these coated magnesium particles and CTBN . Surface analysis ot the alloys show a nigh percentage of magnesium...Rheoloq’cai analysis of these alloys dispersed 40% w/w in CTBN show increasing rates of change in viscosity with time for each alloy with increasing nominal

Aerosol chemical vapor deposition of metal oxide films

DOEpatents

Ott, Kevin C.; Kodas, Toivo T.

1994-01-01

A process of preparing a film of a multicomponent metal oxide including: forming an aerosol from a solution comprised of a suitable solvent and at least two precursor compounds capable of volatilizing at temperatures lower than the decomposition temperature of said precursor compounds; passing said aerosol in combination with a suitable oxygen-containing carrier gas into a heated zone, said heated zone having a temperature sufficient to evaporate the solvent and volatilize said precursor compounds; and passing said volatilized precursor compounds against the surface of a substrate, said substrate having a sufficient temperature to decompose said volatilized precursor compounds whereby metal atoms contained within said volatilized precursor compounds are deposited as a metal oxide film upon the substrate is disclosed. In addition, a coated article comprising a multicomponent metal oxide film conforming to the surface of a substrate selected from the group consisting of silicon, magnesium oxide, yttrium-stabilized zirconium oxide, sapphire, or lanthanum gallate, said multicomponent metal oxide film characterized as having a substantially uniform thickness upon said FIELD OF THE INVENTION The present invention relates to the field of film coating deposition techniques, and more particularly to the deposition of multicomponent metal oxide films by aerosol chemical vapor deposition. This invention is the result of a contract with the Department of Energy (Contract No. W-7405-ENG-36).

Multi-Physics Modeling of Molten Salt Transport in Solid Oxide Membrane (SOM) Electrolysis and Recycling of Magnesium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Powell, Adam; Pati, Soobhankar

2012-03-11

Solid Oxide Membrane (SOM) Electrolysis is a new energy-efficient zero-emissions process for producing high-purity magnesium and high-purity oxygen directly from industrial-grade MgO. SOM Recycling combines SOM electrolysis with electrorefining, continuously and efficiently producing high-purity magnesium from low-purity partially oxidized scrap. In both processes, electrolysis and/or electrorefining take place in the crucible, where raw material is continuously fed into the molten salt electrolyte, producing magnesium vapor at the cathode and oxygen at the inert anode inside the SOM. This paper describes a three-dimensional multi-physics finite-element model of ionic current, fluid flow driven by argon bubbling and thermal buoyancy, and heat andmore » mass transport in the crucible. The model predicts the effects of stirring on the anode boundary layer and its time scale of formation, and the effect of natural convection at the outer wall. MOxST has developed this model as a tool for scale-up design of these closely-related processes.« less

Experimental and theoretical study of hydrogen thiocarbonate for heterogeneous reaction of carbonyl sulfide on magnesium oxide.

PubMed

Liu, Yongchun; He, Hong

2009-04-09

In situ diffuse reflectance infrared Fourier transform spectroscopy combined with derivative spectroscopy analysis, two-dimensional correlation spectroscopy analysis, and quantum chemical calculations were used to investigate the infrared absorbance assignment and the molecular structure of hydrogen thiocarbonate on magnesium oxide. The bands at 1283 and 1257 cm(-1), which had the typical characteristic of intermediate, were observed in experiments for the heterogeneous reaction of COS on MgO. On the basis of two-dimensional correlation spectroscopy analysis and quantum chemical calculations, the band at 1283 cm(-1) was assigned to the v(s) band of bridged thiocarbonate which formed on the two neighboring Mg atoms in the (100) face of MgO crystal, and the band at 1257 cm(-1) was the v(s) band of monodentate thiocarbonate on MgO. The v(as)(OCO) band of thiocarbonates was invisible in the experiment due to their weak absorbance and the interruption of surface carbonate. The formation mechanism of thiocarbonates is proposed, which occurred through a nucleophilic attack of preadsorbed COS by surface -OH groups followed by hydrogen atom transfer from the -OH group to the sulfur atom of preadsorbed COS. The activation energy for the intramolecular proton-transfer reaction of bridged thiocarbonate was calculated to be 18.52 kcal x mol(-1) at the B3LYP/6-31+G(d,p) level of theory.

Facile formation of biomimetic color-tuned superhydrophobic magnesium alloy with corrosion resistance.

PubMed

Ishizaki, Takahiro; Sakamoto, Michiru

2011-03-15

The design of color-tuned magnesium alloy with anticorrosive properties and damping capacity was created by means of a simple and inexpensive method. The vertically self-aligned nano- and microsheets were formed on magnesium alloy AZ31 by a chemical-free immersion process in ultrapure water at a temperature of 120 °C, resulting in the color expression. The color changed from silver with metallic luster to some specific colors such as orange, green, and orchid, depending on the immersion time. The color-tuned magnesium alloy showed anticorrosive performance and damping capacity. In addition, the colored surface with minute surface textures was modified with n-octadecyltrimethoxysilane (ODS), leading to the formation of color-tuned superhydrophobic surfaces. The corrosion resistance of the color-tuned superhydrophobic magnesium alloy was also investigated using electrochemical potentiodynamic measurements. Moreover, the color-tuned superhydrophobic magnesium alloy showed high hydrophobicity not just for pure water but also for corrosive liquids, such as acidic, basic, and some aqueous salt solutions. In addition, the American Society for Testing and Materials (ASTM) standard D 3359-02 cross cut tape test was performed to investigate the adhesion of the color-tuned superhydrophobic film to the magnesium alloy surface.

Improved performance of Mg-Y alloy thin film switchable mirrors after coating with a superhydrophobic surface

NASA Astrophysics Data System (ADS)

La, Mao; Zhou, Huaijuan; Li, Ning; Xin, Yunchuan; Sha, Ren; Bao, Shanhu; Jin, Ping

2017-05-01

The magnesium based switchable mirrors can reversibly change their optical properties between the transparent and the reflective state as a result of hydrogenation and dehydrogenation. These films can potentially be applied as new energy-saving windows, by controlling the transmittance of solar radiation through the regulation of their reflective state. In this study, magnesium-yttrium (Mg-Y) alloy thin films were prepared using a DC magnetron sputtering method. However, the luminous transmittance in the transparent state and the switching durability of switchable mirrors are too poor to satisfy practical demands. In order to improve the films switching durability, luminous transmittance and the surface functionalization, polytetrafluoroethylene (PTFE) was coated with thermal vacuum deposition for use as the top layer of Mg-Y/Pd switchable mirrors. The PTFE layer had a porous network structure and exhibited a superhydrophobic surface with a water contact angle of approximately 152°. By characterization, PTFE thin films shows the excellent protection role against the oxidization of Mg, the switching durability of the films were improved 3 times, and also shows the antireflection role the luminous transmission of films was enhanced by 7% through the top covered with PTFE.

Solid solution lithium alloy cermet anodes

DOEpatents

Richardson, Thomas J.

2013-07-09

A metal-ceramic composite ("cermet") has been produced by a chemical reaction between a lithium compound and another metal. The cermet has advantageous physical properties, high surface area relative to lithium metal or its alloys, and is easily formed into a desired shape. An example is the formation of a lithium-magnesium nitride cermet by reaction of lithium nitride with magnesium. The reaction results in magnesium nitride grains coated with a layer of lithium. The nitride is inert when used in a battery. It supports the metal in a high surface area form, while stabilizing the electrode with respect to dendrite formation. By using an excess of magnesium metal in the reaction process, a cermet of magnesium nitride is produced, coated with a lithium-magnesium alloy of any desired composition. This alloy inhibits dendrite formation by causing lithium deposited on its surface to diffuse under a chemical potential into the bulk of the alloy.

Dissolution profile of dolomite in chloric acid solution: The effect of chloric acid concentration and pulp density

NASA Astrophysics Data System (ADS)

Solihin, Indriani, Mubarok, M. Zaki

2018-05-01

Dolomite is one of carbonate minerals that contain magnesium. Magnesium is important element used in many aspects of life such as cofactor of many enzymes in human body, nutrient for plants, and raw material in automotive industry. Dolomite can be processed through low temperature process to obtain magnesium and calcium oxide that is needed in important applications such as base material for making drugs, raw material in the synthesize slow release fertilizer, materials for fire retardant, component for catalyst, etc. One of the important step of this low temperature process is dissolution of dolomite. Optimizing the dissolution process determines the % extraction of magnesium and calcium oxide from dolomite. The dissolution of dolomite from Gresik, East Java Provence Indonesia, in chloric acid solution has been conducted. Chloric acid concentration and pulp density are the variables that were observed. The dissolution of magnesium and calcium from Gresik dolomite was found to be very fast. The stable stage of dissolution can be reached for 5-10 seconds. The % extraction is mainly determined by the molar ratio of chloric acid / dolomite. At molar ratio of chloric acid / dolomite equal or above stoichiometric of dolomite dissolution, % extraction of magnesium is almost 100 %.

Physicochemical and adsorptive characteristics of activated carbons from waste polyester textiles utilizing MgO template method.

PubMed

Xu, Zhihua; Zhang, Daofang; Yuan, Zhihang; Chen, Weifang; Zhang, Tianqi; Tian, Danqi; Deng, Haixuan

2017-10-01

Activated carbons with high specific surface areas were produced, utilizing waste polyester textiles as carbon precursor by magnesium oxide (MgO) template method. Magnesium chloride (MgCl 2 ), magnesium citrate (MgCi), and MgO were employed as MgO precursors to prepare activated carbons (AC-MgCl 2 , AC-MgCi, and AC-MgO). Thermogravimetry-differential scanning calorimetry was conducted to investigate the pore-forming mechanism, and N 2 adsorption/desorption isotherms, XRD, SEM-EDS, TEM, FTIR and pH pzc were achieved to analyze physicochemical characteristics of the samples. The specific surface areas of AC-MgCl 2 (1173 m 2 /g) and AC-MgCi (1336 m 2 /g) were much higher than that of AC-MgO (450 m 2 /g), and the pores sizes of which were micro-mesoporous, mesoporous, and macropores, respectively, due to the formation of MgO crystal with different sizes. All activated carbons had abundant acidic oxygen groups. In addition, batch adsorption experiments were carried out to investigate the adsorptive characteristics of the prepared activated carbons toward Cr(VI). The adsorption kinetics fitted well with the pseudo-second order, and the adsorptive capacity of AC-MgCl 2 (42.55 mg/g) was higher than those of AC-MgCi (40.93 mg/g) and AC-MgO (35.87 mg/g).

Quasi-isentropic Compression of Iron and Magnesium Oxide to 3 Mbar at the Omega Laser Facility

NASA Astrophysics Data System (ADS)

Wang, J.; Smith, R. F.; Coppari, F.; Eggert, J. H.; Boehly, T.; Collins, G.; Duffy, T. S.

2011-12-01

Developing a high-pressure, modest temperature ramp compression drive permits exploration of new regions of thermodynamic space, inaccessible through traditional methods of shock or static compression, and of particular relevance to material conditions found in planetary interiors both within and outside our solar system. Ramp compression is a developing technique that allows materials to be compressed along a quasi-isentropic path and provides the ability to study materials in the solid state to higher pressures than can be achieved with diamond anvil cell or shock wave methods. Iron and magnesium oxide are geologically important materials each representative of one of the two major interior regions (core and mantle) of terrestrial planets. An experimental platform for ramp loading of iron (Fe) and magnesium oxide (MgO), has been established and tested in experiments at the Omega Laser Facility, University of Rochester. Omega is a 60-beam ultraviolet (352 nm) neodymium glass laser which is capable of delivery kilojoules of energy in ~10 ns pulses onto targets of a few mm in dimension. In the current experiments, we used a composite ramped laser pulse involving typically 15 beams with total energy of 2.6-3.3 kJ. The laser beams were used to launch spatially planar ramp compression waves into Fe and MgO targets. Each target had four steps that were approximately 5-7 μm thick. Detection of the ramp wave arrival and its velocity at the free surface of each step was made using a VISAR velocity interferometer. Through the use of Lagrangian analysis on the measured wave profiles, stress-density states in iron and magnesium oxide have been determined to pressures of 291 GPa and 260 GPa respectively. For Fe, the α-ɛ transition of iron is overdriven by an initial shock pulse of ~90.1 GPa followed by ramp compression to the peak pressure. The results will be compared with shock compression and diamond anvil cell data for both materials.

We acknowledge the Omega staff at LLE for their assistance, Micro/Nano fabrication laboratory staff at Princeton University and the Target Engineering Team at LLNL for fabrication and metrology of the targets used in these experiments. The research was supported by DOE under DE-FG52-09NA29037.

Ignition and Combustion of Bulk Metals in a Microgravity Environment

NASA Technical Reports Server (NTRS)

Branch, M. C.; Daily, J. W.; Abbud-Madrid, A.

1996-01-01

This annual report summarizes the latest results obtained in a NASA-supported project to investigate the effect of gravity on the ignition and combustion of bulk metals. The experimental arrangement used for this purpose consists of a 1000-W xenon lamp that irradiates the top surface of cylindrical titanium and magnesium specimens, 4 mm in diameter and 4 mm in height, in a quiescent, pure-oxygen environment at 1 atm. Reduced gravity is obtained from the NASA LeRC DC-9 aircraft flying parabolic trajectories. Values of critical and ignition temperatures are obtained from thermocouple records. Qualitative observations and propagation rates are extracted from high-speed cinematography. Emission spectra of gas-phase reactions are obtained with an imaging spectrograph/diode array system. It was found that high applied heating rates and large internal conduction losses generate critical and ignition temperatures that are several hundred degrees above the values obtained from isothermal experiments. Because of high conduction and radiation heat losses, no appreciable effect on ignition temperatures with reduced convection in low gravity is detected. Lower propagation rates of the molten interface on titanium and of ignition waves on magnesium are obtained at reduced gravity. These rates are compared to theoretical results from heat conduction analyses with a diffusion/convection controlled reaction. The close agreement found between experimental and theoretical values indicates the importance of the influence of natural convection-enhanced oxygen transport on combustion rates. Lower oxygen flux and lack of oxide product removal in the absence of convective currents appear to be responsible for longer burning times of magnesium diffusion flames at reduced gravity. The accumulation of condensed oxide particles in the flame front at low gravity produces a previously unreported unsteady explosion phenomenon in bulk magnesium flames. This spherically symmetric explosion phenomenon seems to be driven by increased radiation heat transfer from the flame front to an evaporating metal core covered by a porous, flexible oxide coating. These important results have revealed the significant role of gravity on the burning of metals, and are now being used as the database for future experiments to be conducted with different metals at various pressures, oxygen concentrations and gravity levels.

Handbook of the optical, thermal and mechanical properties of six polycrystalline dielectric materials

NASA Technical Reports Server (NTRS)

Dewitt, D. P.

1972-01-01

The design data for six polycrystalline dielectric materials are presented to describe the optical, thermal, and mechanical properties. The materials are aluminum oxide, calcium fluoride, magnesium fluoride, magnesium oxide, silicon dioxide, and titanium dioxide. The primary interest is in the polycrystalline state, although single crystal data are included when appropriate. The temperature range is room temperature to melting point. The wavelength range is from near ultraviolet to near infrared.

Experimental and DFT studies of gold nanoparticles supported on MgO(111) nano-sheets and their catalytic activity.

PubMed

Li, Zhi; Ciobanu, Cristian V; Hu, Juncheng; Palomares-Báez, Juan-Pedro; Rodríguez-López, José-Luis; Richards, Ryan

2011-02-21

A wet chemical preparation of MgO with the (111) facet as the primary surface has recently been reported and with alternating layers of oxygen anions and magnesium cations, this material shows unique chemical and physical properties. The potential to utilize the MgO(111) surface for the immobilization of metal particles is intriguing because the surface itself offers a very different environment for the metal particle with an all oxygen interface, as opposed to the typical (100) facet that possesses alternating oxygen anion and magnesium cation sites on the surface. Gold nanoparticles have demonstrated a broad range of interesting catalytic properties, but are often susceptible to aggregation at high temperatures and are very sensitive to substrate effects. Here, we investigate gold-supported on MgO(111) nanosheets as a catalyst system for the aerobic oxidation of benzyl alcohol. Gold nanoparticles deposited on MgO(111) show an increased level of activity in the solvent-free benzyl alcohol aerobic oxidation as compared to gold nanoparticles deposited on a typical MgO aerogel. TEM studies reveal that the gold nanoparticles have a hemispherical shape while sitting on the main surface of MgO(111) nanosheets, with a large Au-MgO interface. Given that the gold nanoparticles deposited on the two types of MgO have similar size, and that the two types of unmodified MgO show almost the same activities in the blank reaction, we infer that the high activity of Au/MgO(111) is due to the properties of the (111) support and/or those of the gold-support interface. To understand the binding of Au on low-index MgO surfaces and the charge distribution at the surface of the support, we have performed density functional theory (DFT) calculations on all low-index MgO substrates (with and without gold), using a model Au(10) cluster. Due to similar lattice constants of Au(111) and MgO(111) planes, the Au cluster retains its structural integrity and binds strongly on MgO(111) with either oxygen or magnesium termination. Furthermore, we have found that for the (001) and (110) substrates the charges of the ions in the top surface layer have similar values as in bulk MgO, but that on (111) surfaces these charges are significantly different. This difference in surface charge determines the direction of the electronic transfer upon adsorption of gold, such transfer occurring so as to restore the bulk MgO charge values. Using the results from theoretical calculations, we provide an explanation of our observations of increased catalytic activity in the case of the Au/MgO(111) system.

Influences of die channel angles on microstructures and wear behaviors of AZ61 wrought magnesium alloy fabricated by extrusion-shear process

NASA Astrophysics Data System (ADS)

Hu, Hong-J.; Sun, Z.; Ou, Z.-W.

2016-12-01

Extrusion-shear (ES) process for magnesium alloy is a newly developed plastic deformation process, and ES process combines direct extrusion and two steps of ECAE (equal channel angular extrusion). To investigate the effects of the die channel angles on the microstructures and wear behaviors of AZ61 wrought magnesium alloy, the samples used in this study were fabricated by ES process with different die channel angles (120° and 135°). The microstructures of the samples were characterized by optical microscopy (OM), X-ray diffraction (XRD) and (SEM). The cumulative strains in the ES process were predicted by approaches of numerical simulation and theoretical calculation. To characterize the wear resistance of the samples, pin-on-disk tests under dry sliding conditions with various normal loads and reciprocating frequencies were conducted. To define the wear mechanisms of AZ61 magnesium alloy, the worn surfaces after wear tests were analyzed by SEM and energy-dispersive X-ray spectrometer (EDS). Based on the results obtained, die channel angles have significant influences on the grain refinements and wear behaviors of the samples. Decreasing channel angles of the ES die will not only refine the microstructures of magnesium alloys effectively and improve their harnesses, but also improve their wear resistance as decreasing channel angles results in higher friction coefficients and wear rates. With the increase in applied loads and frequencies, wear mechanisms change from mild wear (adhesion, abrasion and oxidation) to severe wear (delamination, plastic deformation and melting). In summary, the wear resistance of ES-processed AZ61 magnesium alloy could be improved by decreasing channel angles of ES dies.

Positive holes in magnesium oxide - Correlation between magnetic, electric, and dielectric anomalies

NASA Technical Reports Server (NTRS)

Batllo, F.; Leroy, R. C.; Parvin, K.; Freund, F.; Freund, M. M.

1991-01-01

The present magnetic susceptibility investigation of high purity MgO single crystals notes an anomally at 800 K which is associated with increasing electrical conductivity, a rise in static dielectric constant from 9 to 150, and the appearance of a pronounced positive surface charge. These phenomena can be accounted for in terms of peroxy defects which represent self-trapped, spin-paired positive holes at Mg(2+) vacancy sites. The holes begin to decouple their spins above 600 K.

Surface microstructure and in vitro analysis of nanostructured akermanite (Ca2MgSi2O7) coating on biodegradable magnesium alloy for biomedical applications.

PubMed

Razavi, Mehdi; Fathi, Mohammadhossein; Savabi, Omid; Hashemi Beni, Batoul; Vashaee, Daryoosh; Tayebi, Lobat

2014-05-01

Magnesium (Mg) alloys, owing to their biodegradability and good mechanical properties, have potential applications as biodegradable orthopedic implants. However, several poor properties including low corrosion resistance, mechanical stability and cytocompatibility have prevented their clinical application, as these properties may result in the sudden failure of the implants during the bone healing. In this research, nanostructured akermanite (Ca2MgSi2O7) powder was coated on the AZ91 Mg alloy through electrophoretic deposition (EPD) assisted micro arc oxidation (MAO) method to modify the properties of the alloy. The surface microstructure of coating, corrosion resistance, mechanical stability and cytocompatibility of the samples were characterized with different techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), electrochemical corrosion test, immersion test, compression test and cell culture test. The results showed that the nanostructured akermanite coating can improve the corrosion resistance, mechanical stability and cytocompatibility of the biodegradable Mg alloy making it a promising material to be used as biodegradable bone implants for orthopedic applications. Published by Elsevier B.V.

Preparation of Si-containing oxide coating and biomimetic apatite induction on magnesium alloy

NASA Astrophysics Data System (ADS)

Yu, Huijun; Dong, Qing; Dou, Jinhe; Pan, Yaokun; Chen, Chuanzhong

2016-12-01

Magnesium and its alloys are recently found important in the field of bone repairing for their ideal mechanical performance and excellent biocompatibility. Micro-arc oxidation (MAO) is a simple, controllable and efficient electrochemistry method that can prepare protective ceramic coatings on magnesium alloys. The properties of the MAO coating, such as thickness, microstructure, roughness and composition, can easily be controlled by adjusting the voltage, current density, duration or the electrolyte concentration. In this work, MAO coatings are prepared on ZK61 magnesium alloy at different voltages. The structure characteristics and element distributions of the coating are investigated by XRD, TEM, SEM and EPMA. The MAO samples are immersed in SBF for 7, 14 and 28 days respectively. The corrosion behaviors of the samples in SBF were also investigated by potentiodynamic polarization curves. The corrosion products were characterized by EDS and FT-IR. The MAO coated ZK61 alloy samples showed excellent corrosion resistance and bioactivity. The MAO method demonstrates a great potential in the preparation of degradable and bioactive orthopedic magnesium-based implants.

77 FR 33165 - Pure Magnesium in Granular Form From the People's Republic of China: Final Results of Expedited...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-05

... Department is aware used to make such excluded reagents are: lime, calcium metal, calcium silicon, calcium.../mischmetal, cryolite, silica/fly ash, magnesium oxide, periclase, ferroalloys, dolomitic lime, and colemanite...

Microwave-induced electrostatic etching: generation of highly reactive magnesium for application in Grignard reagent formation.

PubMed

van de Kruijs, Bastiaan H P; Dressen, Mark H C L; Meuldijk, Jan; Vekemans, Jef A J M; Hulshof, Lumbertus A

2010-04-07

A detailed study regarding the influence of microwave irradiation on the formation of a series of Grignard reagents in terms of rates and selectivities has revealed that these heterogeneous reactions may display a beneficial microwave effect. The interaction between microwaves and magnesium turnings generates violent electrostatic discharges. These discharges on magnesium lead to melting of the magnesium surface, thus generating highly active magnesium particles. As compared to conventional operation the microwave-induced discharges on the magnesium surface lead to considerably shorter initiation times for the insertion of magnesium in selected substrates (i.e. halothiophenes, halopyridines, octyl halides, and halobenzenes). Thermographic imaging and surface characterization by scanning electron microscopy showed that neither selective heating nor a "specific" microwave effect was causing the reduction in initiation times. This novel and straightforward initiation method eliminates the use of toxic and environmentally adverse initiators. Thus, this initiation method limits the formation of by-products. We clearly demonstrated that microwave irradiation enables fast Grignard reagent formation. Therefore, microwave technology is promising for process intensification of Grignard based coupling reactions.

Rapid recipe formulation for plasma etching of new materials

NASA Astrophysics Data System (ADS)

Chopra, Meghali; Zhang, Zizhuo; Ekerdt, John; Bonnecaze, Roger T.

2016-03-01

A fast and inexpensive scheme for etch rate prediction using flexible continuum models and Bayesian statistics is demonstrated. Bulk etch rates of MgO are predicted using a steady-state model with volume-averaged plasma parameters and classical Langmuir surface kinetics. Plasma particle and surface kinetics are modeled within a global plasma framework using single component Metropolis Hastings methods and limited data. The accuracy of these predictions is evaluated with synthetic and experimental etch rate data for magnesium oxide in an ICP-RIE system. This approach is compared and superior to factorial models generated from JMP, a software package frequently employed for recipe creation and optimization.

Fabrication of solid oxide fuel cell by electrochemical vapor deposition

DOEpatents

Brian, Riley; Szreders, Bernard E.

1989-01-01

In a high temperature solid oxide fuel cell (SOFC), the deposition of an impervious high density thin layer of electrically conductive interconnector material, such as magnesium doped lanthanum chromite, and of an electrolyte material, such as yttria stabilized zirconia, onto a porous support/air electrode substrate surface is carried out at high temperatures (approximately 1100.degree.-1300.degree. C.) by a process of electrochemical vapor deposition. In this process, the mixed chlorides of the specific metals involved react in the gaseous state with water vapor resulting in the deposit of an impervious thin oxide layer on the support tube/air electrode substrate of between 20-50 microns in thickness. An internal heater, such as a heat pipe, is placed within the support tube/air electrode substrate and induces a uniform temperature profile therein so as to afford precise and uniform oxide deposition kinetics in an arrangement which is particularly adapted for large scale, commercial fabrication of SOFCs.

Chemical Composition of Ceramic Tile Glazes

NASA Astrophysics Data System (ADS)

Anufrik, S. S.; Kurian, N. N.; Zhukova, I. I.; Znosko, K. F.; Belkov, M. V.

2016-11-01

We have carried out laser emission and x-ray fluorescence spectral analysis of glaze before and after its application to ceramic tile produced by Keramin JSC (Belarus). We have studied the internal microstructure of the ceramic samples. It was established that on the surface and within the bulk interior of all the samples, there are micropores of sizes ranging from a few micrometers to tens of micrometers and microcracks as long as several hundred micrometers. The presence of micropores on the surface of the ceramic tile leads to an increase in the water absorption level and a decrease in frost resistance. It was found that a decrease in the surface tension of ceramic tile coatings is promoted by substitution of sodium by potassium, silica by boric anhydride, magnesium and barium by calcium, CaO by sodium oxide, and SiO2 by chromium oxide. We carried out a comparative analysis of the chemical composition of glaze samples using S4 Pioneer and ElvaX x-ray fluorescence spectrometers and also an LIBS laser emission analyzer.

Molecular Beam Epitaxial Growth of Iron Nitrides on Zinc-Blende Gallium Nitride(001)

NASA Astrophysics Data System (ADS)

Pak, Jeongihm; Lin, Wenzhi; Chinchore, Abhijit; Wang, Kangkang; Smith, Arthur R.

2008-03-01

Iron nitrides are attractive materials for their high magnetic moments, corrosion, and oxidation resistance. We present the successful epitaxial growth of iron nitride on zinc-blende gallium nitride (c-GaN) in order to develop a novel magnetic transition metal nitride/semiconductor system. First, GaN is grown on magnesium oxide (MgO) substrates having (001) orientation using rf N2-plasma molecular beam epitaxy. Then we grow FeN at substrate temperature of ˜ 210 ^oC up to a thickness of ˜ 10.5 nm. In-situ reflection high-energy electron diffraction (RHEED) is used to monitor the surface during growth. Initial results suggest that the epitaxial relationship is FeN[001] || GaN[001] and FeN[100] || GaN[100]. Work in progress is to investigate the surface using in-situ scanning tunneling microscopy (STM) to reveal the surface structure at atomic scale, as well as to explore more Fe-rich magnetic phases.

Development and evaluation of magnesium oxide-based ceramics for chamber parts in mass-production plasma etching equipment

NASA Astrophysics Data System (ADS)

Kasashima, Yuji; Tsutsumi, Kota; Mitomi, Shinzo; Uesugi, Fumihiko

2017-06-01

In mass-production plasma etching equipment, the corrosion of ceramic chamber parts reduces the production yield of LSI and overall equipment effectiveness (OEE) owing to contamination, short useful life, and particle generation. Novel ceramics that can improve the production yield and OEE are highly required. We develop magnesium oxide (MgO)-based ceramics and evaluate them under mass-production plasma etching conditions. The results of this study indicate that the developed MgO-based ceramics with high mechanical properties and low electric resistivity have a higher resistance to corrosion in plasma etching using CF4 gas than Si and conventional ceramic materials such as aluminum oxide and yttrium oxide.

Process for converting magnesium fluoride to calcium fluoride

DOEpatents

Kreuzmann, A.B.; Palmer, D.A.

1984-12-21

This invention is a process for the conversion of magnesium fluoride to calcium fluoride whereby magnesium fluoride is decomposed by heating in the presence of calcium carbonate, calcium oxide or calcium hydroxide. Magnesium fluoride is a by-product of the reduction of uranium tetrafluoride to form uranium metal and has no known commercial use, thus its production creates a significant storage problem. The advantage of this invention is that the quality of calcium fluoride produced is sufficient to be used in the industrial manufacture of anhydrous hydrogen fluoride, steel mill flux or ceramic applications.

Selective radiative cooling with MgO and/or LiF layers

DOEpatents

Berdahl, Paul H.

1986-01-01

A material for a wavelength-selective radiative cooling system, the material comprising an infrared-reflective substrate coated with magnesium oxide and/or lithium fluoride in a polycrystalline form. The material is non-absorptive for short wavelengths, absorptive from 8 to 13 microns, and reflective at longer wavelengths. The infrared-reflective substrate inhibits absorption at wavelengths shorter than 8 microns, and the magnesium oxide and/or lithium fluoride layers reflect radiation at wavelengths longer than 13 microns.

Operating mechanisms of electrolytes in magnesium ion batteries: chemical equilibrium, magnesium deposition, and electrolyte oxidation.

PubMed

Kim, Dong Young; Lim, Younhee; Roy, Basab; Ryu, Young-Gyoon; Lee, Seok-Soo

2014-12-21

Since the early nineties there have been a number of reports on the experimental development of Mg electrolytes based on organo/amide-magnesium chlorides and their transmetalations. However, there are no theoretical papers describing the underlying operating mechanisms of Mg electrolytes, and there is no clear understanding of these mechanisms. We have therefore attempted to clarify the operating mechanisms of Mg electrolytes by studying the characteristics of Mg complexes, solvation, chemical equilibrium, Mg-deposition processes, electrolyte-oxidation processes, and oxidative degradation mechanism of RMgCl-based electrolytes, using ab initio calculations. The formation and solvation energies of Mg complexes highly depend on the characteristics of R groups. Thus, changes in R groups of RMgCl lead to changes in the equilibrium position and the electrochemical reduction and oxidation pathways and energies. We first provide a methodological scheme for calculating Mg reduction potential values in non-aqueous electrolytes and electrochemical windows. We also describe a strategy for designing Mg electrolytes to maximize the electrochemical windows and oxidative stabilities. These results will be useful not only for designing improved Mg electrolytes, but also for developing new electrolytes in the future.

Kinetic-limited etching of magnesium doping nitrogen polar GaN in potassium hydroxide solution

NASA Astrophysics Data System (ADS)

Jiang, Junyan; Zhang, Yuantao; Chi, Chen; Yang, Fan; Li, Pengchong; Zhao, Degang; Zhang, Baolin; Du, Guotong

2016-01-01

KOH based wet etchings were performed on both undoped and Mg-doped N-polar GaN films grown by metal-organic chemical vapor deposition. It is found that the etching rate for Mg-doped N-polar GaN gets slow obviously compared with undoped N-polar GaN. X-ray photoelectron spectroscopy analysis proved that Mg oxide formed on N-polar GaN surface is insoluble in KOH solution so that kinetic-limited etching occurs as the etching process goes on. The etching process model of Mg-doped N-polar GaN in KOH solution is tentatively purposed using a simplified ideal atomic configuration. Raman spectroscopy analysis reveals that Mg doping can induce tensile strain in N-polar GaN films. Meanwhile, p-type N-polar GaN film with a hole concentration of 2.4 ÿ 1017 cm⿿3 was obtained by optimizing bis-cyclopentadienyl magnesium flow rates.

Method of enhancing the wettability of boron nitride for use as an electrochemical cell separator

DOEpatents

McCoy, L.R.

1981-01-23

A felt or other fabric of boron nitride suitable for use as an interelectrode separator within an electrochemical cell is wetted with a solution containing a thermally decomposable organic salt of an alkaline earth metal. An aqueous solution of magnesium acetate is the preferred solution for this purpose. After wetting the boron nitride, the solution is dried by heating at a sufficiently low temperature to prevent rapid boiling and the creation of voids within the separator. The dried material is then calcined at an elevated temperature in excess of 400/sup 0/C to provide a coating of an oxide of magnesium on the surface of the boron nitride fibers. A fabric or felt of boron nitride treated in this manner is easily wetted by molten electrolytic salts, such as the alkali metal halides or alkaline earth metal halides, that are used in high temperature, secondary electrochemical cells.

Method of enhancing the wettability of boron nitride for use as an electrochemical cell separator

DOEpatents

McCoy, Lowell R.

1982-01-01

A felt or other fabric of boron nitride suitable for use as an interelecte separator within an electrochemical cell is wetted with a solution containing a thermally decomposable organic salt of an alkaline earth metal. An aqueous solution of magnesium acetate is the preferred solution for this purpose. After wetting the boron nitride, the solution is dried by heating at a sufficiently low temperature to prevent rapid boiling and the creation of voids within the separator. The dried material is then calcined at an elevated temperature in excess of 400.degree. C. to provide a coating of an oxide of magnesium on the surface of the boron nitride fibers. A fabric or felt of boron nitride treated in this manner is easily wetted by molten electrolytic salts, such as the alkali metal halides or alkaline earth metal halides, that are used in high temperature, secondary electrochemical cells.

Laboratory Annealing Experiments Of Refractory Silicate Grain Analogs Using Differential Scanning Calorimetry

NASA Technical Reports Server (NTRS)

Kimura, Yuki; Nuth, Joseph A., III; Tsukamota, Katsuo; Kaito, Chihiro

2010-01-01

Exothermic reactions during the annealing of laboratory synthesized amorphous magnesium-bearing silicate particles used as grain analogs of cosmic dust were detected by differential scanning calorimetry (DSC) in air. With infrared spectroscopy and transmission electron microscopy, we show that cosmic dust could possibly undergo fusion to larger particles, with oxidation of magnesium silicide and crystallization of forsterite as exothermic reactions in the early solar system. The reactions begin at approximately 425, approximately 625, and approximately 1000 K, respectively, and the reaction energies (enthalpies) are at least 727, 4151, and 160.22 J per gram, respectively. During the crystallization of forsterite particles, the spectral evolution of the 10 micrometer feature from amorphous to crystalline was observed to begin at lower temperature than the crystallization temperature of 1003 K. During spectral evolution at lower temperature, nucleation and/or the formation of nanocrystallites of forsterite at the surface of the grain analogs was observed.

Biocompatible nanostructured magnesium oxide-chitosan platform for genosensing application.

PubMed

Patel, Manoj Kumar; Ali, Md Azahar; Zafaryab, Md; Agrawal, Ved Varun; Rizvi, M Moshahid Alam; Ansari, Z A; Ansari, S G; Malhotra, Bansi D

2013-07-15

A novel organic-inorganic platform comprising of chitosan (CH) modified nanostructured magnesium oxide (nanoMgO) has been electrophoretically deposited on the indium-tin-oxide (ITO) substrate. The single stranded probe DNA (ssDNA) sequence of Vibrio cholerae has been covalently functionalized onto CH-nanoMgO/ITO surface. The cytotoxicity assay of nanoMgO particles, examined using human intestinal cell line (INT 407), reveals no significant cytotoxicity at the given doses in the range of 50-350 μg/mL. The X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and various microscopic techniques have been employed for the structural and morphological analysis of the fabricated electrodes. The electrochemical response studies of ssDNA and fragmented genomic DNA hybridized electrode (dsGDNA/CH-nanoMgO/ITO) have been carried out using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The dsGDNA/CH-nanoMgO/ITO bioelectrode exhibits a linear response in the range 100-500 ng/μL with improved sensitivity of 36.72 nA/ng/cm(2), faster response time of 3s and high stability of 3-4 months under refrigerated condition. The lower detection limit of fabricated genosensor has been estimated as 35.20 ng/μL and it shows good reproducibility/repeatability. Copyright © 2013 Elsevier B.V. All rights reserved.

Coating of tips for electrochemical scanning tunneling microscopy by means of silicon, magnesium, and tungsten oxides

NASA Astrophysics Data System (ADS)

Salerno, Marco

2010-09-01

Different combinations of metal tips and oxide coatings have been tested for possible operation in electrochemical scanning tunneling microscopy. Silicon and magnesium oxides have been thermally evaporated onto gold and platinum-iridium tips, respectively. Two different thickness values have been explored for both materials, namely, 40 and 120 nm for silicon oxide and 20 and 60 nm for magnesium oxide. Alternatively, tungsten oxide has been grown on tungsten tips via electrochemical anodization. In the latter case, to seek optimal results we have varied the pH of the anodizing electrolyte between one and four. The oxide coated tips have been first inspected by means of scanning electron microscopy equipped with microanalysis to determine the morphological results of the coating. Second, the coated tips have been electrically characterized ex situ for stability in time by means of cyclic voltammetry in 1 M aqueous KCl supporting electrolyte, both bare and supplemented with K3[Fe(CN)6] complex at 10 mM concentration in milliQ water as an analyte. Only the tungsten oxide coated tungsten tips have shown stable electrical behavior in the electrolyte. For these tips, the uncoated metal area has been estimated from the electrical current levels, and they have been successfully tested by imaging a gold grating in situ, which provided stable results for several hours. The successful tungsten oxide coating obtained at pH=4 has been assigned to the WO3 form.

Coating of tips for electrochemical scanning tunneling microscopy by means of silicon, magnesium, and tungsten oxides.

PubMed

Salerno, Marco

2010-09-01

Different combinations of metal tips and oxide coatings have been tested for possible operation in electrochemical scanning tunneling microscopy. Silicon and magnesium oxides have been thermally evaporated onto gold and platinum-iridium tips, respectively. Two different thickness values have been explored for both materials, namely, 40 and 120 nm for silicon oxide and 20 and 60 nm for magnesium oxide. Alternatively, tungsten oxide has been grown on tungsten tips via electrochemical anodization. In the latter case, to seek optimal results we have varied the pH of the anodizing electrolyte between one and four. The oxide coated tips have been first inspected by means of scanning electron microscopy equipped with microanalysis to determine the morphological results of the coating. Second, the coated tips have been electrically characterized ex situ for stability in time by means of cyclic voltammetry in 1 M aqueous KCl supporting electrolyte, both bare and supplemented with K(3)[Fe(CN)(6)] complex at 10 mM concentration in milliQ water as an analyte. Only the tungsten oxide coated tungsten tips have shown stable electrical behavior in the electrolyte. For these tips, the uncoated metal area has been estimated from the electrical current levels, and they have been successfully tested by imaging a gold grating in situ, which provided stable results for several hours. The successful tungsten oxide coating obtained at pH=4 has been assigned to the WO(3) form.

In vitro toxicity test of nano-sized magnesium oxide synthesized via solid-phase transformation

NASA Astrophysics Data System (ADS)

Zheng, Jun; Zhou, Wei

2018-04-01

Nano-sized magnesium oxide (MgO) has been a promising potential material for biomedical pharmaceuticals. In the present investigation, MgO nanoparticles synthesized through in-situ solid-phase transformation based on the previous work (nano-Mg(OH)2 prepared by precipitation technique) using magnesium nitrate and sodium hydroxide. The phase structure and morphology of the MgO nanoparticles are characterized by X-ray powder diffraction (XRD), selected area electronic diffraction (SAED) and transmission electron microscopy (TEM) respectively. In vitro hemolysis tests are adopted to evaluate the toxicity of the synthesized nano-MgO. The results evident that nano-MgO with lower concentration is slightly hemolytic, and with concentration increasing nano-MgO exhibit dose-responsive hemolysis.

Magnesium Oxide Embedded Nitrogen Self-Doped Biochar Composites: Fast and High-Efficiency Adsorption of Heavy Metals in an Aqueous Solution.

PubMed

Ling, Li-Li; Liu, Wu-Jun; Zhang, Shun; Jiang, Hong

2017-09-05

Lead (Pb) pollution in natural water bodies is an environmental concern due to toxic effects on aquatic ecosystems and human health, while adsorption is an effective approach to remove Pb from the water. Surface interactions between adsorbents and adsorbates play a dominant role in the adsorption process, and properly engineering a material's surface property is critical to the improvement of adsorption performance. In this study, the magnesium oxide (MgO) nanoparticles stabilized on the N-doped biochar (MgO@N-biochar) were synthesized by one-pot fast pyrolysis of an MgCl 2 -loaded N-enriched hydrophyte biomass as a way to increase the exchangeable ions and N-containing functional groups and facilitate the adsorption of Pb 2+ . The as-synthesized MgO@N-biochar has a high performance with Pb in an aqueous solution with a large adsorption capacity (893 mg/g), a very short equilibrium time (<10 min), and a large throughput (∼4450 BV). Results show that this excellent adsorption performance can be maintained with various environmentally relevant interferences including pH, natural organic matter, and other metal ions, suggesting that the material may be suitable for the treatment of wastewater, natural bodies of water, and even drinking water. In addition, MgO@N-biochar quickly and efficiently removed Cd 2+ and tetracycline. Multiple characterizations and comparative tests have been performed to demonstrate the surface adsorption and ion exchange contributed to partial Pb adsorption, and it can be inferred from these results that the high performance of MgO@N-biochar is mainly due to the surface coordination of Pb 2+ and C═O or O═C-O, pyridinic, pyridonic, and pyrrolic N. This work suggests that engineering surface functional groups of biochar may be crucial for the development of high performance heavy metal adsorbents.

An improved soft-chemistry approach to the preparation of spinel powders

NASA Astrophysics Data System (ADS)

Cook, Ronald

2007-04-01

Spinel powders for the production of transparent polycrystalline ceramic windows have been produced using a number of traditional ceramic and sol-gel methods. We have demonstrated that magnesium aluminate spinel powders produced from the reaction of organo-magnesium compounds with surface modified boehmite precursors can be used to produce high quality transparent spinel parts. In previous work, the spinel powders were prepared by the reaction of surface-modified boehmite nanoparticles with magnesium acetylacetonate. While the magnesium acetylacetonate can produce small quantities of high quality spinel powders, it use for large scale production of spinel powders is problematic. Through a thermodynamic analysis we have identified a new high-purity, low-cost, low-toxicity organomagnesium compound that reacts the with surface modified boehmite nanoparticles to produce a spinel precursor. The magnesium doped precursor readily transforms into pure phase spinel at temperature between 900°C and 1200°C.

Effect upon biocompatibility and biocorrosion properties of plasma electrolytic oxidation in trisodium phosphate electrolytes.

PubMed

Kim, Yu-Kyoung; Park, Il-Song; Lee, Kwang-Bok; Bae, Tae-Sung; Jang, Yong-Seok; Oh, Young-Min; Lee, Min-Ho

2016-03-01

Surface modification to improve the corrosion resistance and biocompatibility of the Mg-Al-Zn-Ca alloy was conducted via plasma electrolytic oxidation (PEO) in an electrolyte that included phosphate. Calcium phosphate can be easily induced on the surface of a PEO coating that includes phosphate in a physiological environment because Ca(2+) ions in body fluids can be combined with PO4 (3-). Cytotoxicity of the PEO coating formed in electrolytes with various amounts of Na3PO4 was identified. In particular, the effects that PEO films have upon oxidative stress and differentiation of osteoblast activity were studied. As the concentration of Na3PO4 in the electrolyte increased, the oxide layer was found to become thicker, which increased corrosion resistance. However, the PEO coating formed in electrolytes with over 0.2 M of added Na3PO4 exhibited more microcracks and larger pores than those formed in smaller Na3PO4 concentrations owing to a large spark discharge. A nonuniform oxide film that included more phosphate caused more cytotoxicity and oxidative stress, and overabundant phosphate content in the oxide layer interrupted the differentiation of osteoblasts. The corrosion resistance of the magnesium alloy and the thickness of the oxide layer were increased by the addition of Na3PO4 in the electrolyte for PEO treatment. However, excessive phosphate content in the oxide layer led to oxidative stress, which resulted in reduced cell viability and activity.

Method for the production of mineral wool and iron from serpentine ore

DOEpatents

O'Connor, William K [Albany, OR; Rush, Gilbert E [Scio, OR; Soltau, Glen F [Lebanon, OR

2011-10-11

Magnesium silicate mineral wools having a relatively high liquidus temperature of at least about 1400.degree. C. and to methods for the production thereof are provided. The methods of the present invention comprise melting a magnesium silicate feedstock (e.g., comprising a serpentine or olivine ore) having a liquidus temperature of at least about 1400.degree. C. to form a molten magnesium silicate, and subsequently fiberizing the molten magnesium silicate to produce a magnesium silicate mineral wool. In one embodiment, the magnesium silicate feedstock contains iron oxide (e.g., up to about 12% by weight). Preferably, the melting is performed in the presence of a reducing agent to produce an iron alloy, which can be separated from the molten ore. Useful magnesium silicate feedstocks include, without limitation, serpentine and olivine ores. Optionally, silicon dioxide can be added to the feedstock to lower the liquidus temperature thereof.

High performance YBCO films. Report for 1 August-31 October 1992

DOE Office of Scientific and Technical Information (OSTI.GOV)

Denlinger, E.J.; Fathy, A.; Kalokitis, D.

1992-10-31

The objective of this program is to identify suitable low loss, low dielectric constant substrates and develop and optimize deposition processes for high quality YBCO films including the necessary buffer layers. Ultimate goals are large area substrates having double-sided HTS coating with a surface resistance ten times lower than copper at 40 GHz. High quality HTS films on low dielectric constant substrates are expected to find widespread use in advanced millimeter wave components, in extending the power handling capability of microwave and millimeter wave circuitry, and in facilitating high speed computer interconnects. Sample demonstration circuits will be built toward themore » end of the program. We have successfully deposited a high quality YBCO film on a good low loss and low dielectric constant substrate, magnesium fluoride (e=5). With the use of two buffer layers (magnesium oxide and strontium titanate) between the YBCO and the substrate, transition temperatures of 89 deg K and transition widths of about 0.5 deg K were achieved. The critical current density Jc of 4 x 10 6 A/cm2 at 77K in zero field is among the highest reported for YBCO films. The magnesium fluoride (MgF2) substrate has a tetragonal structure with a dielectric constant of 5.2 in the plane of the substrate and 4.6 perpendicular to the substrate surface. It has a good harness (-575 Knoop) and a linear thermal expansion coefficient that closely matches YBCO and the buffer layers.« less

Communication—Sol-Gel Synthesized Magnesium Vanadium Oxide, Mg x V 2 O 5 · nH 2 O: The Role of Structural Mg 2+ on Battery Performance

DOE PAGES

Yin, Jiefu; Pelliccione, Christopher J.; Lee, Shu Han; ...

2016-07-12

Magnesium intercalated vanadium oxide xerogels, Mg 0.1V 2O 5 · 2.35H 2O and Mg 0.2V 2O 5 · 2.46H 2O were synthesized using an ion removal sol gel strategy. X-ray diffraction indicated lamellar ordering with turbostratic character. X-ray absorption spectroscopy indicated greater distortion of the vanadium-oxygen coordination environment in Mg 0.2V 2O 5 · 2.46H 2O. Elemental analysis after cycling in Li + or Mg 2+ based electrolytes revealed that the magnesium content was unchanged, indicating structural Mg 2+ are retained. Furthermore, the Mg 0.1V 2O 5 · 2.35H 2O material displayed high voltage, energy density, and discharge/charge efficiency, indicatingmore » promise as a cathode material for future magnesium based batteries.« less

One-step electrodeposition process to fabricate corrosion-resistant superhydrophobic surface on magnesium alloy.

PubMed

Liu, Qin; Chen, Dexin; Kang, Zhixin

2015-01-28

A simple, one-step method has been developed to construct a superhydrophobic surface by electrodepositing Mg-Mn-Ce magnesium plate in an ethanol solution containing cerium nitrate hexahydrate and myristic acid. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy were employed to characterize the surfaces. The shortest electrodeposition time to obtain a superhydrophobic surface was about 1 min, and the as-prepared superhydrophobic surfaces had a maximum contact angle of 159.8° and a sliding angle of less than 2°. Potentiodynamic polarization and electrochemical impedance spectroscopy measurements demonstrated that the superhydrophobic surface greatly improved the corrosion properties of magnesium alloy in 3.5 wt % aqueous solutions of NaCl, Na2SO4, NaClO3, and NaNO3. Besides, the chemical stability and mechanical durability of the as-prepared superhydrophobic surface were also examined. The presented method is rapid, low-cost, and environmentally friendly and thus should be of significant value for the industrial fabrication of anticorrosive superhydrophobic surfaces and should have a promising future in expanding the applications of magnesium alloys.

Corrosion resistant properties of polyaniline acrylic coating on magnesium alloy

NASA Astrophysics Data System (ADS)

Sathiyanarayanan, S.; Azim, S. Syed; Venkatachari, G.

2006-12-01

The performance of the paint coating based on acrylic-polyaniline on magnesium alloy ZM 21 has been studied by electrochemical impedance spectroscopy in 0.5% NaCl solution. The polyaniline was prepared by chemical oxidative method of aniline with ammonium persulphate in phosphoric acid medium. The phosphate-doped polyaniline was characterized by FTIR and XRD methods. Acrylic paint containing the phosphate-doped polyaniline was prepared and coated on magnesium ZM 21 alloy. The coating was able to protect the magnesium alloy and no base metal dissolution was noted even after 75 days exposure to sodium chloride solution.

Biodegradable Magnesium Alloys: A Review of Material Development and Applications

PubMed Central

Persaud-Sharma, Dharam; McGoron, Anthony

2012-01-01

Magnesium based alloys possess a natural ability to biodegrade due to corrosion when placed within aqueous substances, which is promising for cardiovascular and orthopedic medical device applications. These materials can serve as a temporary scaffold when placed in vivo, which is desirable for treatments when temporary supportive structures are required to assist in the wound healing process. The nature of these materials to degrade is attributed to the high oxidative corrosion rates of magnesium. In this review, a summary is presented for magnesium material development, biocorrosion characteristics, as well as a biological translation for these results. PMID:22408600

Characterization of crystalline structures in Opuntia ficus-indica.

PubMed

Contreras-Padilla, Margarita; Rivera-Muñoz, Eric M; Gutiérrez-Cortez, Elsa; del López, Alicia Real; Rodríguez-García, Mario Enrique

2015-01-01

This research studies the crystalline compounds present in nopal (Opuntia ficus-indica) cladodes. The identification of the crystalline structures was performed using X-ray diffraction, scanning electron microscopy, mass spectrometry, and Fourier transform infrared spectroscopy. The crystalline structures identified were calcium carbonate (calcite) [CaCO3], calcium-magnesium bicarbonate [CaMg(CO3)2], magnesium oxide [MgO], calcium oxalate monohydrate [Ca(C2O4)•(H2O)], potassium peroxydiphosphate [K4P2O8] and potassium chloride [KCl]. The SEM images indicate that calcite crystals grow to dipyramidal, octahedral-like, prismatic, and flower-like structures; meanwhile, calcium-magnesium bicarbonate structures show rhombohedral exfoliation and calcium oxalate monohydrate is present in a drusenoid morphology. These calcium carbonate compounds have a great importance for humans because their bioavailability. This is the first report about the identification and structural analysis of calcium carbonate and calcium-magnesium bicarbonate in nopal cladodes, as well as the presence of magnesium oxide, potassium peroxydiphosphate and potassium chloride in these plants. The significance of the study of the inorganic components of these cactus plants is related with the increasing interest in the potential use of Opuntia as a raw material of products for the food, pharmaceutical, and cosmetic industries.

Dealloying, Microstructure and the Corrosion/Protection of Cast Magnesium Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sieradzki, Karl; Aiello, Ashlee; McCue, Ian

The purpose of this project was to develop a greater understanding of micro-galvanic corrosion effects in cast magnesium alloys using both experimental and computational methods. Experimental accomplishments have been made in the following areas of interest: characterization, aqueous free-corrosion, atmospheric corrosion, ionic liquid dissolution, rate kinetics of oxide dissolution, and coating investigation. Commercial alloys (AZ91D, AM60, and AZ31B), binary-phase alloys (αMg-2at.%Al, αMg-5at.%Al, and Mg-8at.%Al), and component phases (Mg, Al, β-Mg, β-1%Zn, MnAl3) were obtained and characterized using energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Full immersion in aqueous chloride was used to characterize the corrosionmore » behavior of alloys. Rotating disc electrodes (RDEs) were used to observe accelerated long-term corrosion behavior. Al surface redistribution for freely corroded samples was analyzed using SEM, EDS, and lithium underpotential deposition (Li UPD). Atmospheric corrosion was observed using contact angle evolution, overnight pH monitoring, and surface pH evolution studies. Ionic liquid corrosion characterization was performed using linear sweep voltammetry and potentiostatic dissolution in 150° choline chloride-urea (cc-urea). Two surface coatings were investigated: (1) Li-carbonate and (2) cc-urea. Li-carbonate coatings were characterized using X-ray photoelectron spectroscopy (XPS), SEM, and aqueous free corrosion potential monitoring. Hydrophobic cc-urea coatings were characterized using contact angle measurements and electrochemical impedance spectroscopy. Oxide dissolution rate kinetics were studied using inductively coupled plasma mass spectroscopy (ICP-MS). Computational accomplishments have been made through the development of Kinetic Monte Carlo (KMC) simulations which model time- and composition-dependent effects on the microstructure due to spatial redistribution of alloying elements during corrosion.« less

Sulfates on Mars: A systematic Raman spectroscopic study of hydration states of magnesium sulfates

USGS Publications Warehouse

Wang, A.; Freeman, J.J.; Jolliff, B.L.; Chou, I.-Ming

2006-01-01

The martian orbital and landed surface missions, OMEGA on Mar Express and the two Mars Explorations Rovers, respectively, have yielded evidence pointing to the presence of magnesium sulfates on the martian surface. In situ identification of the hydration states of magnesium sulfates, as well as the hydration states of other Ca- and Fe- sulfates, will be crucial in future landed missions on Mars in order to advance our knowledge of the hydrologic history of Mars as well as the potential for hosting life on Mars. Raman spectroscopy is a technique well-suited for landed missions on the martian surface. In this paper, we report a systematic study of the Raman spectra of the hydrates of magnesium sulfate. Characteristic and distinct Raman spectral patterns were observed for each of the 11 distinct hydrates of magnesium sulfates, crystalline and non-crystalline. The unique Raman spectral features along with the general tendency of the shift of the position of the sulfate ??1 band towards higher wavenumbers with a decrease in the degree of hydration allow in situ identification of these hydrated magnesium sulfates from the raw Raman spectra of mixtures. Using these Raman spectral features, we have started the study of the stability field of hydrated magnesium sulfates and the pathways of their transformations at various temperature and relative humidity conditions. In particular we report on the Raman spectrum of an amorphous hydrate of magnesium sulfate (MgSO4??2H2O) that may have specific relevance for the martian surface. ?? 2006 Elsevier Inc. All rights reserved.

Magnesium degradation products: effects on tissue and human metabolism.

PubMed

Seitz, J-M; Eifler, R; Bach, Fr-W; Maier, H J

2014-10-01

Owing to their mechanical properties, metallic materials present a promising solution in the field of resorbable implants. The magnesium metabolism in humans differs depending on its introduction. The natural, oral administration of magnesium via, for example, food, essentially leads to an intracellular enrichment of Mg(2+) . In contrast, introducing magnesium-rich substances or implants into the tissue results in a different decomposition behavior. Here, exposing magnesium to artificial body electrolytes resulted in the formation of the following products: magnesium hydroxide, magnesium oxide, and magnesium chloride, as well as calcium and magnesium apatites. Moreover, it can be assumed that Mg(2+) , OH(-) ions, and gaseous hydrogen are also present and result from the reaction for magnesium in an aqueous environment. With the aid of physiological metabolic processes, the organism succeeds in either excreting the above mentioned products or integrating them into the natural metabolic process. Only a burst release of these products is to be considered a problem. A multitude of general tissue effects and responses from the Mg's degradation products is considered within this review, which is not targeting specific implant classes. Furthermore, common alloying elements of magnesium and their hazardous potential in vivo are taken into account. © 2013 Wiley Periodicals, Inc.

Bioactive Ca-P coating with self-sealing structure on pure magnesium.

PubMed

Gan, Junjie; Tan, Lili; Yang, Ke; Hu, Zhuangqi; Zhang, Qiang; Fan, Xinmin; Li, Yangde; Li, Weirong

2013-04-01

Bioactive coatings containing Ca and P with self-sealing structures were fabricated on the surface of pure magnesium using micro-arc oxidation technique (MAO) in a specific calcium hydroxide based electrolyte system. Coatings were prepared at three applied voltages, i.e. 360, 410 and 450 V, and the morphology, chemical composition, corrosion resistance and the degradation properties in Hank's solution of the MAO-coated samples with three different applied voltages were investigated. It was found that all the three coatings showed similar surface morphologies that the majority of micro-pores were filled with compound particles. Both the porous structures and the compound particles were found to contain consistent chemical compositions which were mainly composed of O, Mg, F, Ca and P. Electrochemical tests showed a significant increase in corrosion resistance for the three coatings, meanwhile the coating obtained at 450 V exhibited the superior corrosion resistance owing to the largest coating thickness. The long term immersion tests in Hank's solution also revealed an effective reduction in corrosion rate for the MAO coated samples, and the pH values of the coated samples always maintained a lower level. Besides, all the three coatings were subjected to a mild and uniform degradation, while the coating obtained at 360 V showed a relatively obvious degradation characteristic and appreciable Ca and P contents on the surfaces of the three coatings were observed after immersion in Hank's solution. The results of the present study confirmed that the MAO coatings containing bioactive Ca and P elements with self-sealing structures could significantly enhance the corrosion resistance of magnesium substrate in Hanks' solution with great potential for medical application.

Characterization of coatings formed on AZX magnesium alloys by plasma electrolytic oxidation

NASA Astrophysics Data System (ADS)

Anawati, Anawati; Gumelar, Muhammad Dikdik

2018-05-01

Plasma Electrolytic Oxidation (PEO) is an electrochemical anodization process which involves the application of a high voltage to create intense plasma on a metal surface to form a ceramic type of oxide. The resulted coating exhibits high wear resistance and good corrosion barrier which are suitable to enhance the performance of biodegradable Mg alloys. In this work, the role of alloying element Ca in modifying the characteristics of PEO layer formed on AZ61 series magnesium alloys was investigated. PEO treatment was conducted on AZ61, AZX611, and AZX612 alloys in 0.5 M Na3PO4 solution at a constant current of 200 A/m2 at 25°C for 8 min. The resulted coatings were characterized by field emission-scanning electron microscope (FESEM), X-ray diffraction spectroscopy (XRD), and X-ray fluorescence spectroscopy (XRF), as well as hardness test. The presence of alloying element Ca in the AZ61 alloys accelerated the PEO coatings formation without altering the coating properties significantly. The coating formed on AZX specimen was slightly thicker ( 14-17 µm) than that of formed onthe AZ specimens ( 13 µm). Longer exposure time to plasma discharge was the reason for faster thickening of the coating layer on AZX specimen. XRD detected a similar crystalline oxide phase of Mg3(PO4)2 in the oxide formed on all of the specimens. Zn was highly incorporated in the coatings with a concentration in the range 24-30 wt%, as analyzed by XRF. Zn compound might exist in amorphous phases. The microhardness test on the coatings revealed similar average hardness 124 HVon all of the specimens.

The microstructure of the surface layer of magnesium laser alloyed with aluminum and silicon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dziadoń, Andrzej

2016-08-15

The surface layer under analysis was formed as a result of diffusion bonding of a thin AlSi20 plate to a magnesium substrate followed by laser melting. Depending on the process parameters, the laser beam melted the AlSi20 plate only or the AlSi20 plate and a layer of the magnesium surface adjacent to it. Two types of microstructure of the remelted layer were thus analyzed. If the melting zone was limited to the AlSi20 plate, the microstructure of the surface layer was typical of a rapidly solidified hypereutectic Al–Si alloy. Since, however, the liquid AlSi20 reacted with the magnesium substrate, themore » following intermetallic phases formed: Al{sub 3}Mg{sub 2}, Mg{sub 17}Al{sub 12} and Mg{sub 2}Si. The microstructure of the modified surface layer of magnesium was examined using optical, scanning electron and transmission electron microscopy. The analysis of the surface properties of the laser modified magnesium revealed that the thin layer has a microstructure of a rapidly solidified Al–Si alloy offering good protection against corrosion. By contrast, the surface layer containing particles of intermetallic phases was more resistant to abrasion but had lower corrosion resistance than the silumin type layer. - Highlights: •A CO{sub 2} laser was used for surface alloying of Mg with AlSi20. •Before alloying, an AlSi20 plate was diffusion bonded with the Mg substrate. •The process parameters affected the alloyed layer microstructure and properties. •With melting limited to AlSi20, the layer had a structure of rapidly solidified AlSi20. •Mg–Al and Mg–Si phases were present when both the substrate and the plate were melted.« less

NADH fluorescence lifetime analysis of the effect of magnesium ions on ALDH2

USDA-ARS?s Scientific Manuscript database

ALDH2 catalyzes oxidation of toxic aldehydes to their corresponding carboxylic acids. Magnesium ions influence enzyme activity in part by increasing NADH binding affinity. Traditional fluorescence measurements have monitored the blue shift of the NADH fluorescence spectrum to elucidate the extent of...

Chrome-free Samarium-based Protective Coatings for Magnesium Alloys

NASA Astrophysics Data System (ADS)

Hou, Legan; Cui, Xiufang; Yang, Yuyun; Lin, Lili; Xiao, Qiang; Jin, Guo

The microstructure of chrome-free samarium-based conversion coating on magnesium alloy was investigated and the corrosion resistance was evaluated as well. The micro-morphology, transverse section, crystal structure and composition of the coating were observed by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) and X- ray photoelectron spectroscopy (XPS), respectively. The corrosion resistance was evaluated by potentiodynamic polarization curve and electrochemical impedance spectroscopy (EIS). The results reveal that the morphology of samarium conversion coating is of crack-mud structure. Tiny cracks distribute in the compact coating deposited by samarium oxides. XRD, EDS and XPS results characterize that the coating is made of amorphous and trivalent-samarium oxides. The potentiodynamic polarization curve, EIS and OCP indicate that the samarium conversion coating can improve the corrosion resistance of magnesium alloys.

Tunneling rates in electron transport through double-barrier molecular junctions in a scanning tunneling microscope

PubMed Central

Nazin, G. V.; Wu, S. W.; Ho, W.

2005-01-01

The scanning tunneling microscope enables atomic-scale measurements of electron transport through individual molecules. Copper phthalocyanine and magnesium porphine molecules adsorbed on a thin oxide film grown on the NiAl(110) surface were probed. The single-molecule junctions contained two tunneling barriers, vacuum gap, and oxide film. Differential conductance spectroscopy shows that electron transport occurs via vibronic states of the molecules. The intensity of spectral peaks corresponding to the individual vibronic states depends on the relative electron tunneling rates through the two barriers of the junction, as found by varying the vacuum gap tunneling rate by changing the height of the scanning tunneling microscope tip above the molecule. A simple, sequential tunneling model explains the observed trends. PMID:15956189

Tunneling rates in electron transport through double-barrier molecular junctions in a scanning tunneling microscope.

PubMed

Nazin, G V; Wu, S W; Ho, W

2005-06-21

The scanning tunneling microscope enables atomic-scale measurements of electron transport through individual molecules. Copper phthalocyanine and magnesium porphine molecules adsorbed on a thin oxide film grown on the NiAl(110) surface were probed. The single-molecule junctions contained two tunneling barriers, vacuum gap, and oxide film. Differential conductance spectroscopy shows that electron transport occurs via vibronic states of the molecules. The intensity of spectral peaks corresponding to the individual vibronic states depends on the relative electron tunneling rates through the two barriers of the junction, as found by varying the vacuum gap tunneling rate by changing the height of the scanning tunneling microscope tip above the molecule. A simple, sequential tunneling model explains the observed trends.

Magnesium Isoglycyrrhizinate attenuates lipopolysaccharide-induced depressive-like behavior in mice.

PubMed

Jiang, Wenjiao; Chen, Qianying; Li, Peijin; Lu, Qianfeng; Pei, Xue; Sun, Yilin; Wang, Guangji; Hao, Kun

2017-02-01

Magnesium Isoglycyrrhizinate (MI) is a magnesium salt of 18α-GA stereoisomer which has been reported to exert hepatoprotective activity. The aim of the present study was to ascertain the underlying mechanisms behind the action of Magnesium Isoglycyrrhizinate on neuroinflammatation and oxidative stress in LPS-stimulated mice. Mice were pretreated with Magnesium Isoglycyrrhizinate (MI, 25, 50mg/kg) as well as fluoxetine (Flu, positive control, 20mg/kg) once daily for one week before intraperitoneal injection of LPS (0.83mg/kg). Pretreatments with MI and Flu significantly improved immobility time in tail suspension test (TST) and forced swim test (FST) as well as locomotor activity in open-field test (OFT). In addition, the levels of pro-inflammatory cytokines and oxidative stress in serum and hippocampus were also suppressed effectively by MI and Flu administrations. Western blot analysis showed the up-regulated levels of p-Jak3, p-STAT3, p-NF-κBp65, and p-IκBα in mice exposed to LPS, while different degrees of down-regulation in these expression were observed in MI (25, 50mg/kg) and Flu (20mg/kg) groups respectively. Taken together, our obtained results demonstrated that Magnesium Isoglycyrrhizinate (MI) exhibited an antidepressant-like effect in LPS-induced mice, which might be mediated by JAK/STAT/NF-κB signaling pathway. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Nanostructured magnesium increases bone cell density.

PubMed

Weng, Lucy; Webster, Thomas J

2012-12-07

Magnesium has attracted some attention in orthopedics due to its biodegradability and mechanical properties. Since magnesium is an essential natural mineral for bone growth, it can be expected that as a biomaterial, it would support bone formation. However, upon degradation in the body, magnesium releases OH(-) which results in an alkaline pH that can be detrimental to cell density (for example, osteoblasts or bone forming cells). For this reason, modification of magnesium may be necessary to compensate for such detrimental effects to cells. This study created biologically inspired nanoscale surface features on magnesium by soaking magnesium in various concentrations of NaOH (from 1 to 10 N) and for various periods of time (from 10 to 30 min). The results provided the first evidence of increased roughness, surface energy, and consequently greater osteoblast adhesion, after 4 h as well as density up to 7 days on magnesium treated with any concentration of NaOH for any length of time compared to untreated controls. For these reasons, this study suggests that soaking magnesium in NaOH could be an inexpensive, simple and effective manner to promote osteoblast functions for numerous orthopedic applications and, thus, should be further studied.

Mechanism of sodium chloride in promoting reduction of high-magnesium low-nickel oxide ore

PubMed Central

Zhou, Shiwei; Wei, Yonggang; Li, Bo; Wang, Hua; Ma, Baozhong; Wang, Chengyan

2016-01-01

Sodium chloride has been proved that it is an effective promoter for the reduction of high-magnesium, low-nickel oxide ore. The aim of current work is to clarify the promotion behavior of sodium chloride in the roasting reduction process. The influence of moisture on the reduction of ore in the presence of sodium chloride is studied to get clear comprehension of promotion process. In the presence of moisture, the HCl is produced by pyrohydrolysis of sodium chloride for chlorinating nickel and iron oxides, moreover, interactions between metallic oxides and sodium chloride are also a way for chlorination at high temperature (>802 °C); subsequently, the metal chloride would be reduced by reductant. In the absence of moisture, the magnetic separation results show that the recoveries of iron and nickel have a significant increase; moreover, olivine structure would be destroyed gradually with the increase of roasting temperature in the action of sodium chloride, and the sodium chloride existed in high-magnesium, low-nickel oxide ore could make the NiO isolate from NiO-bearing minerals. The NiO reacts with Fe2O3 at high temperature to form NiFe2O4, which is conductive to the formation of Ni-Fe alloy during the reduction process. PMID:27374991

Mechanism of sodium chloride in promoting reduction of high-magnesium low-nickel oxide ore.

PubMed

Zhou, Shiwei; Wei, Yonggang; Li, Bo; Wang, Hua; Ma, Baozhong; Wang, Chengyan

2016-07-04

Sodium chloride has been proved that it is an effective promoter for the reduction of high-magnesium, low-nickel oxide ore. The aim of current work is to clarify the promotion behavior of sodium chloride in the roasting reduction process. The influence of moisture on the reduction of ore in the presence of sodium chloride is studied to get clear comprehension of promotion process. In the presence of moisture, the HCl is produced by pyrohydrolysis of sodium chloride for chlorinating nickel and iron oxides, moreover, interactions between metallic oxides and sodium chloride are also a way for chlorination at high temperature (>802 °C); subsequently, the metal chloride would be reduced by reductant. In the absence of moisture, the magnetic separation results show that the recoveries of iron and nickel have a significant increase; moreover, olivine structure would be destroyed gradually with the increase of roasting temperature in the action of sodium chloride, and the sodium chloride existed in high-magnesium, low-nickel oxide ore could make the NiO isolate from NiO-bearing minerals. The NiO reacts with Fe2O3 at high temperature to form NiFe2O4, which is conductive to the formation of Ni-Fe alloy during the reduction process.

Self-healing effect of the protective inhibitor-containing coatings on Mg alloys

NASA Astrophysics Data System (ADS)

Gnedenkov, A. S.; Sinebryukhov, S. L.; Mashtalyar, D. V.; Gnedenkov, S. V.

2017-09-01

The method of self-healing coating formation on the surface of magnesium alloys on the base of plasma electrolytic oxidation (PEO) with subsequent impregnation of the obtained layer with inhibitor has been suggested. The protective and electrochemical properties of such coatings have been described. Localised Scanning Electrochemical Methods were used for determining the kinetics and mechanism of the self-healing process. The treatment with the solution containing inhibitor enables us to increase the protective properties of the PEO-coating in 30 times in the corrosion-active environment.

Mechanical properties of PEO-coatings on the surface of magnesium alloy MA8 modified by TiN nanoparticles

NASA Astrophysics Data System (ADS)

Imshinetsky, Igor M.; Mashtalyar, Dmitriy V.; Sunebryukhov, Sergey L.; Gnedenkov, Sergey V.

2017-09-01

The methods to form protective coatings by the plasma electrolytic oxidation method (PEO) in the electrolytic system containing nanosized particles of titanium nitride has been develoted. Tribological and morfological studies of the composite coatings have been carried out. It has been established that the microhardness of the coating with nanoparticles concentration of 3 g/l increases by 2 folds, while the wear resistance - by 2.2 fold, as compared to respective values for the PEO-coating formed in the electrolyte without nanoparticles.

PRECIPITATION CHEMISTRY OF MAGNESIUM SULFITE HYDRATES IN MAGNESIUM OXIDE SCRUBBING

EPA Science Inventory

The report gives results of laboratory studies defining the precipitation chemistry of MgSO3 hydrates. The results apply to the design of Mg-based scrubbing processes for SO2 removal from combustion flue gas. In Mg-based scrubbing processes, MgSO3 precipitates as either trihydrat...

Electrochemical Performance Estimation of Anodized AZ31B Magnesium Alloy as Function of Change in the Current Density

NASA Astrophysics Data System (ADS)

Girón, L.; Aperador, W.; Tirado, L.; Franco, F.; Caicedo, J. C.

2017-08-01

The anodized AZ31B magnesium alloys were synthesized via electrodeposition processes. The aim of this work was to determine the electrochemical behavior of magnesium alloys by using anodized alloys as a protective coating. The anodized alloys were characterized by x-ray diffraction, exhibiting the crystallography orientation for Mg and MgO phases. The x-ray photoelectron spectroscopy was used to determine the chemical composition of anodized magnesium alloys. By using electrochemical impedance spectroscopy and Tafel curves, it was possible to estimate the electrochemical behavior of anodized AZ31B magnesium alloys in Hank's balanced salt solution (HBSS). Scanning electron microscopy was performed to analyze chemical changes and morphological surface changes on anodized Mg alloys due to the reaction in HBSS/anodized magnesium surface interface. Electrochemical behavior in HBSS indicates that the coatings may be a promising material for biomedical industry.

The Role of Magnesium in the Pathogenesis and Treatment of Glaucoma

PubMed Central

Korkmaz, Şafak; Sül, Sabahattin; Tufan, Hasan Ali; Aydın, Bahri; Dileköz, Ergin

2014-01-01

Glaucoma is characterized by chronic optic neuropathy resulting in progressive vision loss. Not only is glaucoma considered as a condition of elevated intraocular pressure (IOP), but also other risk factors may play a role in the pathogenesis of glaucomatous optic nerve damage. Vascular dysregulation in ocular blood flow and oxidative stress are currently suggested as important risk factors for glaucomatous retinal ganglion cell loss. New treatment modalities that improve ocular blood flow and reduce oxidative stress have been investigated in many studies. Magnesium (Mg) is thought to be one of the molecules that has a treatment potential in glaucoma. Mg has been shown to improve blood flow by modifying endothelial function via endothelin-1 (ET-1) and endothelial nitric oxide (NO) pathways. Mg also exhibits neuroprotective role by blocking N-methyl-D-aspartate (NMDA) receptor-related calcium influx and by inhibiting the release of glutamate, and hence protects the cell against oxidative stress and apoptosis. Both improvement in ocular blood flow and prevention of ganglion cell loss would make magnesium a good candidate for glaucoma management. Further studies on the effect of Mg may open a new therapeutic era in glaucoma. PMID:27433524

Exoelectron emission from a clean, annealed magnesium single crystal during oxygen adsorption

NASA Technical Reports Server (NTRS)

Ferrante, J.

1976-01-01

Exoelectron emission was observed from a clean, annealed Mg (0001) surface during oxygen and chlorine adsorption at pressures of 6.5x10 0.00001- N/sq m and lower. the studies were performed in an ultrahigh vacuum system. The crystals were cleaned by argon ion bombardment and annealed at 300 C. Auger electron spectroscopy was used to verify surface cleanliness, and low energy electron diffraction was used to verify that the surface was annealed. The emission was found to be oxygen arrival rate dependent. Two peaks were observed in the electron emission with exposure. Evidence is presented that the formation of the second peak corresponds to oxidation of the Mg surface. No emission was observed from clean aluminum during adsorption. Results verify that electron emission occurs from a strain free surface simply upon adsorption of oxygen. A qualitative explanation for the mechanisms of emission in terms of chemical effects is presented.

Steel refining with an electrochemical cell

DOEpatents

Blander, M.; Cook, G.M.

1988-05-17

Apparatus is described for processing a metallic fluid containing iron oxide, container for a molten metal including an electrically conductive refractory disposed for contact with the molten metal which contains iron oxide, an electrolyte in the form of a basic slag on top of the molten metal, an electrode in the container in contact with the slag electrically separated from the refractory, and means for establishing a voltage across the refractory and the electrode to reduce iron oxide to iron at the surface of the refractory in contact with the iron oxide containing fluid. A process is disclosed for refining an iron product containing not more than about 10% by weight oxygen and not more than about 10% by weight sulfur, comprising providing an electrolyte of a slag containing one or more of calcium oxide, magnesium oxide, silica or alumina, providing a cathode of the iron product in contact with the electrolyte, providing an anode in contact with the electrolyte electrically separated from the cathode, and operating an electrochemical cell formed by the anode, the cathode and the electrolyte to separate oxygen or sulfur present in the iron product therefrom. 2 figs.

Steel refining with an electrochemical cell

DOEpatents

Blander, M.; Cook, G.M.

1985-05-21

Disclosed is an apparatus for processing a metallic fluid containing iron oxide, container for a molten metal including an electrically conductive refractory disposed for contact with the molten metal which contains iron oxide, an electrolyte in the form of a basic slag on top of the molten metal, an electrode in the container in contact with the slag electrically separated from the refractory, and means for establishing a voltage across the refractory and the electrode to reduce iron oxide to iron at the surface of the refractory in contact with the iron oxide containing fluid. A process is disclosed for refining an iron product containing not more than about 10% by weight sulfur, comprising providing an electrolyte of a slag containing one or more of calcium oxide, magnesium oxide, silica or alumina, providing a cathode of the iron product in contact with the electrolyte, providing an anode in contact with the electrolyte electrically separated from the cathode, and operating an electrochemical cell formed by the anode, the cathode and the electrolyte to separate oxygen or sulfur present in the iron product therefrom.

Steel refining with an electrochemical cell

DOEpatents

Blander, Milton; Cook, Glenn M.

1988-01-01

Apparatus for processing a metallic fluid containing iron oxide, container for a molten metal including an electrically conductive refractory disposed for contact with the molten metal which contains iron oxide, an electrolyte in the form of a basic slag on top of the molten metal, an electrode in the container in contact with the slag electrically separated from the refractory, and means for establishing a voltage across the refractory and the electrode to reduce iron oxide to iron at the surface of the refractory in contact with the iron oxide containing fluid. A process is disclosed for refining an iron product containing not more than about 10% by weight oxygen and not more than about 10% by weight sulfur, comprising providing an electrolyte of a slag containing one or more of calcium oxide, magnesium oxide, silica or alumina, providing a cathode of the iron product in contact with the electrolyte, providing an anode in contact with the electrolyte electrically separated from the cathode, and operating an electrochemical cell formed by the anode, the cathode and the electrolyte to separate oxygen or sulfur present in the iron product therefrom.

Refractory lining for electrochemical cell

DOEpatents

Blander, Milton; Cook, Glenn M.

1987-01-01

Apparatus for processing a metallic fluid containing iron oxide, container for a molten metal including an electrically conductive refractory disposed for contact with the molten metal which contains iron oxide, an electrolyte in the form of a basic slag on top of the molten metal, an electrode in the container in contcat with the slag electrically separated from the refractory, and means for establishing a voltage across the refractory and the electrode to reduce iron oxide to iron at the surface of the refractory in contact with the iron oxide containing fluid. A process is disclosed for refining an iron product containing not more than about 10% by weight oxygen and not more than about 10% by weight sulfur, comprising providing an electrolyte of a slag containing one or more of calcium oxide, magnesium oxide, silica or alumina, providing a cathode of the iron product in contact with the electrolyte, providing an anode in contact with the electrolyte electrically separated from the cathode, and operating an electrochemical cell formed by the anode, the cathode and the electrolyte to separate oxygen or sulfur present in the iron product therefrom.

High-quantum efficiency, long-lived luminescing refractory oxides

DOEpatents

Chen, Yok; Gonzalez, Roberto; Summers, Geoffrey P.

1984-01-01

A crystal having a high-quantum efficiency and a long period of luminescence is formed of an oxide selected from the group consisting of magnesium oxide and calcium oxide and possessing a concentration ratio of H.sup.- ions to F centers in the range of about 0.05 to about 10.

Preparation of magnesium metal matrix composites by powder metallurgy process

NASA Astrophysics Data System (ADS)

Satish, J.; Satish, K. G., Dr.

2018-02-01

Magnesium is the lightest metal used as the source for constructional alloys. Today Magnesium based metal matrix composites are widely used in aerospace, structural, oceanic and automobile applications for its light weight, low density(two thirds that of aluminium), good high temperature mechanical properties and good to excellent corrosion resistance. The reason of designing metal matrix composite is to put in the attractive attributes of metals and ceramics to the base metal. In this study magnesium metal matrix hybrid composite are developed by reinforcing pure magnesium with silicon carbide (SiC) and aluminium oxide by method of powder metallurgy. This method is less expensive and very efficient. The Hardness test was performed on the specimens prepared by powder metallurgy method. The results revealed that the micro hardness of composites was increased with the addition of silicon carbide and alumina particles in magnesium metal matrix composites.

Neutral Endopeptidase Inhibition Enhances Substance P Mediated Inflammation Due to Hypomagnesemia

PubMed Central

Weglicki, William B.; Chmielinska, Joanna J.; Tejero-Taldo, M. Isabel; Kramer, Jay H.; Spurney, Christopher; Viswalingham, Kandan; Lu, Bao; Mak, I. Tong

2013-01-01

During dietary deficiency of magnesium neurogenic inflammation is mediated, primarily, by elevated levels of substance P (SP). The enzyme most specific for degrading this neuropeptide is neutral endopeptidase (NEP). In recent studies we found that pharmacological inhibition of NEP by phosphoramidon resulted in elevated plasma levels of SP and greater oxidative stress. We also observed that hypomagnesemia reduced cardiac and intestinal expression of NEP. In these magnesium deficient rats increased intestinal permeability and impaired cardiac contractility occurred. In our colony of genetically-engineered NEP knockout mice that have reduced ability to degrade SP, we found increased oxidative stress that was prevented by SP (neurokinin-1) receptor blockade. Thus, we submit that inhibition of NEP by pharmacological, genetic and dietary approaches (magnesium restriction), causes greater neurogenic inflammation that may result in increased intestinal and cardiac dysfunction. PMID:19780404

Neutral endopeptidase inhibition enhances substance P mediated inflammation due to hypomagnesemia.

PubMed

Weglicki, William B; Chmielinska, Joanna J; Tejero-Taldo, Isabel; Kramer, Jay H; Spurney, Christopher F; Viswalingham, Kandan; Lu, Bao; Mak, I Tong

2009-09-01

During dietary deficiency of magnesium neurogenic inflammation is mediated, primarily, by elevated levels of substance P (SP). The enzyme most specific for degrading this neuropeptide is neutral endopeptidase (NEP). In recent studies we found that pharmacological inhibition of NEP by phosphoramidon resulted in elevated plasma levels of SP and greater oxidative stress. We also observed that hypomagnesemia reduced cardiac and intestinal expression of NEP. In these magnesium-deficient rats increased intestinal permeability and impaired cardiac contractility occurred. In our colony of genetically-engineered NEP knockout mice that have reduced ability to degrade SP, we found increased oxidative stress that was prevented by SP (neurokinin-1) receptor blockade. Thus, we submit that inhibition of NEP by pharmacological, genetic and dietary approaches (magnesium restriction), causes greater neurogenic inflammation that may result in increased intestinal and cardiac dysfunction.

Fabrication of solid oxide fuel cell by electrochemical vapor deposition

DOEpatents

Riley, B.; Szreders, B.E.

1988-04-26

In a high temperature solid oxide fuel cell (SOFC), the deposition of an impervious high density thin layer of electrically conductive interconnector material, such as magnesium doped lanthanum chromite, and of an electrolyte material, such as yttria stabilized zirconia, onto a porous support/air electrode substrate surface is carried out at high temperatures (/approximately/1100/degree/ /minus/ 1300/degree/C) by a process of electrochemical vapor deposition. In this process, the mixed chlorides of the specific metals involved react in the gaseous state with water vapor resulting in the deposit of an impervious thin oxide layer on the support tube/air electrode substrate of between 20--50 microns in thickness. An internal heater, such as a heat pipe, is placed within the support tube/air electrode substrate and induces a uniform temperature profile therein so as to afford precise and uniform oxide deposition kinetics in an arrangement which is particularly adapted for large scale, commercial fabrication of SOFCs.

Utilization and recycling of industrial magnesite refractory waste material for removal of certain radionuclides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morcos, T.N.; Tadrous, N.A.; Borai, E.H.

2007-07-01

Increased industrialization over the last years in Egypt has resulted in an increased and uncontrolled generation of industrial hazardous waste. The current lack of management of the solid waste in Egypt has created a situation where large parts of the land (especially industrial areas) are covered by un-planned dumps of industrial wastes. Consequently, in the present work, industrial magnesite waste produced in large quantities after production process of magnesium sulfate in Zinc Misr factory, Egypt, was tried to be recycled. Firstly, this material has been characterized applying different analytical techniques such as infrared spectroscopy (IR), surface analyzer (BET), particle sizemore » distribution (PSD), elemental analysis by X-ray fluorescence (XRF) and X-ray diffraction (XRD). The magnesite material has been used as a source of producing aluminum, chromium, and magnesium oxides that has better chemical stability than conventional metal oxides. Secondly, utilization of magnesite material for removal of certain radionuclides was applied. Different factors affecting the removal capability such as pH, contacting time, metal concentration, particle size were systematically investigated. The overall objective was aimed at determining feasible and economic solution to the environmental problems related to re-use of the industrial solid waste for radioactive waste management. (authors)« less

In situ synthesis of magnesium-substituted biphasic calcium phosphate and in vitro biodegradation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Tae-Wan; Lee, Hyeong-Shin; Kim, Dong-Hyun

Highlights: ► Mg–BCP were successfully prepared through in situ aqueous co-precipitation method. ► The amount of β-TCP phase was changed with the magnesium substitution level. ► The substitution of magnesium led to a decrease in the unit cell volume. ► Mg–BCP could be able to develop a new apatite phase on the surface faster than BCP. -- Abstract: In situ preparation of magnesium (Mg) substituted biphasic calcium phosphate (BCP) of hydroxyapatite (HAp)/β-tricalcium phosphate (β-TCP) were carried out through aqueous co-precipitation method. The concentrations of added magnesium were varied with the calcium in order to obtain constant (Ca + Mg)/P ratiosmore » of 1.602. X-ray diffraction (XRD) and Fourier transformed infrared (FTIR) spectroscopy were used to characterize the structure of synthesized magnesium substituted BCP powders. The results have shown that substitution of magnesium in the calcium deficient apatites revealed the formation of biphasic mixtures of different HAp/β-TCP ratios after heating at 1000 °C. The ratios of the formation of phase mixtures were dependent on the content of magnesium. After immersing in Hanks’ balanced salt solution (HBSS) for 1 week, 1 wt% magnesium substituted BCP powders were degraded and precipitation started to be formed with small granules consisting of number of flake-like crystal onto the surface of synthesized powders. On the other hand, in the case of pure BCP powders, the formation of new precipitates was detected after immersion in HBSS for 2 weeks. On the basis of these results, magnesium substituted BCP could be able to develop a new apatite phase on the surface in contact with physiological fluids faster than BCP does. In addition, the retention time to produce the new apatite phase in implantation operation for the BCP powder could be controlled by the amount of magnesium substitution.« less

Coating Systems for Magnesium-Based Biomaterials — State of the Art

NASA Astrophysics Data System (ADS)

Waterman, J.; Staiger, M. P.

Magnesium and its alloys have the potential to be used for biodegradable orthopedic implants. However, the corrosion rate in physiological conditions is too high for most applications. For this reason, surface modification to slow the corrosion rate is of great interest. Such modifications must remain biologically compatible as well as protective in corrosive environments. What follows is a brief review of recent research in inorganic coatings and surface modifications to create coatings for magnesium-based biomaterials.

The in vitro digestibility and absorption of magnesium in some edible seaweeds.

PubMed

Nakamura, Eri; Yokota, Hiroki; Matsui, Tohru

2012-08-30

Many edible seaweeds are rich in magnesium (Mg). However, Mg absorption is low in some seaweeds because fibers in these seaweeds suppress Mg absorption. We hypothesize that Mg absorption from some other seaweeds is not low because of the diversity of fibers. We measured Mg concentration and Mg solubility after in vitro digestion in edible seaweeds, Aosa (Ulvaceae pertusa), Kombu (Laminaria japonica) and Funori (Gloiopeltis furcata). Then we determined Mg absorption in rats given diets containing these seaweeds or magnesium oxide as the major source of Mg, and calculated Mg absorption from seaweeds. The fractional apparent absorption of Mg in seaweeds was Kombu = magnesium oxide > Aosa = Funori. Mg concentration was Aosa > Kombu and Funori had an intermediate amount of Mg, while Mg solubility after in vitro digestion was Funori = Kombu > Aosa. Consequently, the absorbable Mg concentration was Aosa = Kombu > Funori. The absorption of Mg from different seaweeds differs and is not affected by the Mg solubility alone. The absorbable Mg concentration was high in Aosa and in Kombu, indicating that Aosa and Kombu are good sources of Mg. Copyright © 2012 Society of Chemical Industry.

Nondestructive spot test method for magnesium and magnesium alloys

NASA Technical Reports Server (NTRS)

Wilson, M. L. (Inventor)

1973-01-01

A method for spot test identification of magnesium and various magnesium alloys commonly used in aerospace applications is described. The spot test identification involves color codes obtained when several drops of 3 M hydrochloric acid are placed on the surface to be tested. After approximately thirty seconds, two drops of this reacted acid is transferred to each of two depressions in a spot plate for additions of other chemicals with subsequent color changes indicating magnesium or its alloy.

Thermodynamic criteria for the removal of impurities from end-of-life magnesium alloys by evaporation and flux treatment

NASA Astrophysics Data System (ADS)

Hiraki, Takehito; Takeda, Osamu; Nakajima, Kenichi; Matsubae, Kazuyo; Nakamura, Shinichiro; Nagasaka, Tetsuya

2011-06-01

In this paper, the possibility of removing impurities during magnesium recycling with pyrometallurgical techniques has been evaluated by using a thermodynamic analysis. For 25 different elements that are likely to be contained in industrial magnesium alloys, the equilibrium distribution ratios between the metal, slag and gas phases in the magnesium remelting process were calculated assuming binary systems of magnesium and an impurity element. It was found that calcium, gadolinium, lithium, ytterbium and yttrium can be removed from the remelted end-of-life (EoL) magnesium products by oxidization. Calcium, cerium, gadolinium, lanthanum, lithium, plutonium, sodium, strontium and yttrium can be removed by chlorination with a salt flux. However, the other elements contained in magnesium alloy scrap are scarcely removed and this may contribute toward future contamination problems. The third technological option for the recycling of EoL magnesium products is magnesium recovery by a distillation process. Based on thermodynamic considerations, it is predicted that high-purity magnesium can be recovered through distillation because of its high vapor pressure, yet there is a limit on recoverability that depends on the equilibrium vapor pressure of the alloying elements and the large energy consumption. Therefore, the sustainable recycling of EoL magnesium products should be an important consideration in the design of advanced magnesium alloys or the development of new refining processes.

Thermodynamic criteria for the removal of impurities from end-of-life magnesium alloys by evaporation and flux treatment

PubMed Central

Hiraki, Takehito; Takeda, Osamu; Nakajima, Kenichi; Matsubae, Kazuyo; Nakamura, Shinichiro; Nagasaka, Tetsuya

2011-01-01

In this paper, the possibility of removing impurities during magnesium recycling with pyrometallurgical techniques has been evaluated by using a thermodynamic analysis. For 25 different elements that are likely to be contained in industrial magnesium alloys, the equilibrium distribution ratios between the metal, slag and gas phases in the magnesium remelting process were calculated assuming binary systems of magnesium and an impurity element. It was found that calcium, gadolinium, lithium, ytterbium and yttrium can be removed from the remelted end-of-life (EoL) magnesium products by oxidization. Calcium, cerium, gadolinium, lanthanum, lithium, plutonium, sodium, strontium and yttrium can be removed by chlorination with a salt flux. However, the other elements contained in magnesium alloy scrap are scarcely removed and this may contribute toward future contamination problems. The third technological option for the recycling of EoL magnesium products is magnesium recovery by a distillation process. Based on thermodynamic considerations, it is predicted that high-purity magnesium can be recovered through distillation because of its high vapor pressure, yet there is a limit on recoverability that depends on the equilibrium vapor pressure of the alloying elements and the large energy consumption. Therefore, the sustainable recycling of EoL magnesium products should be an important consideration in the design of advanced magnesium alloys or the development of new refining processes. PMID:27877407

Influence of biocompatible metal ions (Ag, Fe, Y) on the surface chemistry, corrosion behavior and cytocompatibility of Mg-1Ca alloy treated with MEVVA.

PubMed

Liu, Yang; Bian, Dong; Wu, Yuanhao; Li, Nan; Qiu, Kejin; Zheng, Yufeng; Han, Yong

2015-09-01

Mg-1Ca samples were implanted with biocompatible alloy ions Ag, Fe and Y respectively with a dose of 2×10(17)ionscm(-2) by metal vapor vacuum arc technique (MEVVA). The surface morphologies and surface chemistry were investigated by SEM, AES and XPS. Surface changes were observed after all three kinds of elemental ion implantation. The results revealed that the modified layer was composed of two sublayers, including an outer oxidized layer with mixture of oxides and an inner implanted layer, after Ag and Fe ion implantation. Y ion implantation induced an Mg/Ca-deficient outer oxidized layer and the distribution of Y along with depth was more homogeneous. Both electrochemical test and immersion test revealed accelerated corrosion rate of Ag-implanted Mg-1Ca and Fe-implanted Mg-1Ca, whereas Y ion implantation showed a short period of protection since enhanced corrosion resistance was obtained by electrochemical test, but accelerated corrosion rate was found by long period immersion test. Indirect cytotoxicity assay indicated good cytocompatibility of Y-implanted Mg-1Ca. Moreover, the corresponding corrosion mechanisms involving implanting ions into magnesium alloys were proposed, which might provide guidance for further application of plasma ion implantation to biodegradable Mg alloys. Copyright © 2015 Elsevier B.V. All rights reserved.

Influence of aggressive ions on the degradation behavior of biomedical magnesium alloy in physiological environment.

PubMed

Xin, Yunchang; Huo, Kaifu; Tao, Hu; Tang, Guoyi; Chu, Paul K

2008-11-01

Various electrochemical approaches, including potentiodynamic polarization, open circuit potential evolution and electrochemical impedance spectroscopy (EIS), are employed to investigate the degradation behavior of biomedical magnesium alloy under the influence of aggressive ions, such as chloride, phosphate, carbonate and sulfate, in a physiological environment. The synergetic effects and mutual influence of these ions on the degradation behavior of Mg are revealed. Our results demonstrate that chloride ions can induce porous pitting corrosion. In the presence of phosphates, the corrosion rate decreases and the formation of pitting corrosion is significantly delayed due to precipitation of magnesium phosphate. Hydrogen carbonate ions are observed to stimulate the corrosion of magnesium alloy during the early immersion stage but they can also induce rapid passivation on the surface. This surface passivation behavior mainly results from the fast precipitation of magnesium carbonate in the corrosion product layer that can subsequently inhibit pitting corrosion completely. Sulfate ions are also found to stimulate magnesium dissolution. These results improve our understanding on the degradation mechanism of surgical magnesium in the physiological environment.

Ferromagnetic tunnel contacts to graphene: Contact resistance and spin signal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cubukcu, M.; Laczkowski, P.; Vergnaud, C.

2015-02-28

We report spin transport in CVD graphene-based lateral spin valves using different magnetic contacts. We compared the spin signal amplitude measured on devices where the cobalt layer is directly in contact with the graphene to the one obtained using tunnel contacts. Although a sizeable spin signal (up to ∼2 Ω) is obtained with direct contacts, the signal is strongly enhanced (∼400 Ω) by inserting a tunnel barrier. In addition, we studied the resistance-area product (R.A) of a variety of contacts on CVD graphene. In particular, we compared the R.A products of alumina and magnesium oxide tunnel barriers grown by sputteringmore » deposition of aluminum or magnesium and subsequent natural oxidation under pure oxygen atmosphere or by plasma. When using an alumina tunnel barrier on CVD graphene, the R.A product is high and exhibits a large dispersion. This dispersion can be highly reduced by using a magnesium oxide tunnel barrier, as for the R.A value. This study gives insight in the material quest for reproducible and efficient spin injection in CVD graphene.« less

Phase Transformations and Metallization of Magnesium Oxide at High Pressure and Temperature

NASA Astrophysics Data System (ADS)

McWilliams, R. Stewart; Spaulding, Dylan K.; Eggert, Jon H.; Celliers, Peter M.; Hicks, Damien G.; Smith, Raymond F.; Collins, Gilbert W.; Jeanloz, Raymond

2012-12-01

Magnesium oxide (MgO) is representative of the rocky materials comprising the mantles of terrestrial planets, such that its properties at high temperatures and pressures reflect the nature of planetary interiors. Shock-compression experiments on MgO to pressures of 1.4 terapascals (TPa) reveal a sequence of two phase transformations: from B1 (sodium chloride) to B2 (cesium chloride) crystal structures above 0.36 TPa, and from electrically insulating solid to metallic liquid above 0.60 TPa. The transitions exhibit large latent heats that are likely to affect the structure and evolution of super-Earths. Together with data on other oxide liquids, we conclude that magmas deep inside terrestrial planets can be electrically conductive, enabling magnetic field-producing dynamo action within oxide-rich regions and blurring the distinction between planetary mantles and cores.

Thermal Mechanical Stability of Single-Crystal-Oxide Refractive Concentrators Evaluated for High-Temperature Solar-Thermal Propulsion

NASA Technical Reports Server (NTRS)

Jacobson, Nathan S.; Jacobson, Nathan S.; Miller, Robert A.

1999-01-01

Recently, refractive secondary solar concentrator systems were developed for solar thermal power and propulsion (ref. 1). Single-crystal oxides-such as yttria-stabilized zirconia (Y2O3-ZrO2), yttrium aluminum garnet (Y3Al5O12, or YAG), magnesium oxide (MgO), and sapphire (Al2O3)-are candidate refractive secondary concentrator materials. However, the refractive concentrator system will experience high-temperature thermal cycling in the solar thermal engine during the sun/shade transition of a space mission. The thermal mechanical reliability of these components in severe thermal environments is of great concern. Simulated mission tests are important for evaluating these candidate oxide materials under a variety of transient and steady-state heat flux conditions. In this research at the NASA Lewis Research Center, a controlled heat flux test approach was developed for investigating the thermal mechanical stability of the candidate oxide. This approach used a 3.0-kW continuous-wave (wavelength, 10.6 mm) carbon dioxide (CO2) laser (ref. 2). The CO2 laser is especially well-suited for single-crystal thermal shock tests because it can directly deliver well-characterized heat energy to the oxide surfaces. Since the oxides are opaque at the 10.6-mm wavelength of the laser beam, the light energy is absorbed at the surfaces rather than transmitting into the crystals, and thus generates the required temperature gradients within the specimens. The following figure is a schematic diagram of the test rig.

Role of magnesium on the biomimetic deposition of calcium phosphate

NASA Astrophysics Data System (ADS)

Sarma, Bimal K.; Sarma, Bikash

2016-10-01

Biomimetic depositions of calcium phosphate (CaP) are carried out using simulated body fluid (SBF), calcifying solution and newly developed magnesium containing calcifying solution. Calcium phosphate has a rich phase diagram and is well known for its excellent biocompatibility and bioactivity. The most common phase is hydroxyapatite (HAp), an integral component of human bone and tooth, widely used in orthopedic and dental applications. In addition, calcium phosphate nanoparticles show promise for the targeted drug delivery. The doping of calcium phosphate by magnesium, zinc, strontium etc. can change the protein uptake by CaP nanocrystals. This work describes the role of magnesium on the nucleation and growth of CaP on Ti and its oxide substrates. X-ray diffraction studies confirm formation of HAp nanocrystals which closely resemble the structure of bone apatite when grown using SBF and calcifying solution. It has been observed that magnesium plays crucial role in the nucleation and growth of calcium phosphate. A low magnesium level enhances the crystallinity of HAp while higher magnesium content leads to the formation of amorphous calcium phosphate (ACP) phase. Interestingly, the deposition of ACP phase is rapid when magnesium ion concentration in the solution is 40% of calcium plus magnesium ions concentration. Moreover, high magnesium content alters the morphology of CaP films.

Purifying arsenic and fluoride-contaminated water by a novel graphene-based nanocomposite membrane of enhanced selectivity and sustained flux.

PubMed

Pal, Madhubonti; Mondal, Mrinal Kanti; Paine, Tapan Kanti; Pal, Parimal

2018-06-01

A novel graphene-based nanocomposite membrane was synthesized by interfacial polymerization (IP) through chemical bonding of the graphene oxide (GO) layer to polyethersulfone surface. Detailed characterization of the composite membrane through AFM, SEM, ATR-FTIR, XRD analysis, and Raman spectroscopy indicates strong potential of the membrane in highly selective removal of the toxic contaminants like arsenic and fluoride while permeating the essential minerals like calcium and magnesium. This makes the membrane suitable for production of safe drinking water from contaminated water. The membrane applied in a flat-sheet cross-flow module succeeded in removal of more than 98% arsenic and around 80% fluoride from contaminated water while selectively retaining the useful calcium and magnesium minerals in drinking water. A sustained pure water flux of around 150 LMH (liter per square meter per hour) during operation over long hours (> 150 h) with only 3-5% drop in flux indicates antifouling character of the membrane module.

Multifunctional MgO Layer in Perovskite Solar Cells.

PubMed

Guo, Xudong; Dong, Haopeng; Li, Wenzhe; Li, Nan; Wang, Liduo

2015-06-08

A multifunctional magnesium oxide (MgO) layer was successfully introduced into perovskite solar cells (PSCs) to enhance their performance. MgO was coated onto the surface of mesoporous TiO(2) by the decomposition of magnesium acetate and, therefore, could block contact between the perovskite and TiO(2). X-ray photoelectron spectroscopy and infrared spectroscopy showed that the amount of H(2)O/hydroxyl absorbed on the TiO(2) decreased after MgO modification. The UV/Vis absorption spectra of the perovskite with MgO modification revealed an enhanced photoelectric performance compared with that of unmodified perovskite after UV illumination. In addition to the photocurrent, the photovoltage and fill factor also showed an enhancement after modification, which resulted in an increase in the overall efficiency of the cell from 9.6 to 13.9 %. Electrochemical impedance spectroscopy (EIS) confirmed that MgO acts as an insulating layer to reduce charge recombination. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Threshold to N-methyl-D-aspartate-induced seizures in mice undergoing chronic nutritional magnesium deprivation is lowered in a way partly responsive to acute magnesium and antioxidant administrations.

PubMed

Maurois, Pierre; Pages, Nicole; Bac, Pierre; German-Fattal, Michèle; Agnani, Geneviève; Delplanque, Bernadette; Durlach, Jean; Poupaert, Jacques; Vamecq, Joseph

2009-02-01

Magnesium deficiency may be induced by a diet impoverished in magnesium. This nutritional deficit promotes chronic inflammatory and oxidative stresses, hyperexcitability and, in mice, susceptibility to audiogenic seizures. Potentiation by low-magnesium concentrations of the opening of N-methyl-D-aspartate (NMDA) receptor/calcium channel in in vitro and ex vivo studies, and responsiveness to magnesium of in vivo brain injury states are now well established. By contrast, little or no specific attention has been, however, paid to the in vivo NMDA receptor function/excitability in magnesium deficiency. The present work reports for the first time that, in mice undergoing chronic nutritional deprivation in magnesium (35 v. 930 parts per million for 27 d in OF1 mice), NMDA-induced seizure threshold is significantly decreased (38 % of normal values). The attenuation in the drop of NMDA seizure threshold (percentage of reversal) was 58 and 20 % upon acute intraperitoneal administrations of magnesium chloride hexahydrate (28 mg magnesium/kg) and the antioxidant ebselen (20 mg/kg), respectively. In nutritionally magnesium-deprived animals, audiogenic seizures are completely prevented by these compound doses. Taken as a whole, our data emphasise that chronic magnesium deprivation in mice is a nutritional in vivo model for a lowered NMDA receptor activation threshold. This nutritional model responds remarkably to acute magnesium supply and moderately to acute antioxidant administration.

Preparation and corrosion resistance of magnesium phytic acid/hydroxyapatite composite coatings on biodegradable AZ31 magnesium alloy.

PubMed

Zhang, Min; Cai, Shu; Zhang, Feiyang; Xu, Guohua; Wang, Fengwu; Yu, Nian; Wu, Xiaodong

2017-06-01

In this work, a magnesium phytic acid/hydroxyapatite composite coating was successfully prepared on AZ31 magnesium alloy substrate by chemical conversion deposition technology with the aim of improving its corrosion resistance and bioactivity. The influence of hydroxyapatite (HA) content on the microstructure and corrosion resistance of the coatings was investigated. The results showed that with the increase of HA content in phytic acid solution, the cracks on the surface of the coatings gradually reduced, which subsequently improved the corrosion resistance of these coated magnesium alloy. Electrochemical measurements in simulated body fluid (SBF) revealed that the composite coating with 45 wt.% HA addition exhibited superior surface integrity and significantly improved corrosion resistance compared with the single phytic acid conversion coating. The results of the immersion test in SBF showed that the composite coating could provide more effective protection for magnesium alloy substrate than that of the single phytic acid coating and showed good bioactivity. Magnesium phytic acid/hydroxyapatite composite, with the desired bioactivity, can be synthesized through chemical conversion deposition technology as protective coatings for surface modification of the biodegradable magnesium alloy implants. The design idea of the new type of biomaterial is belong to the concept of "third generation biomaterial". Corrosion behavior and bioactivity of coated magnesium alloy are the key issues during implantation. In this study, preparation and corrosion behavior of magnesium phytic acid/hydroxyapatite composite coatings on magnesium alloy were studied. The basic findings and significance of this paper are as follows: 1. A novel environmentally friendly, homogenous and crack-free magnesium phytic acid/hydroxyapatite composite coating was fabricated on AZ31 magnesium alloy via chemical conversion deposition technology with the aim of enhancing its corrosion resistance and bioactivity. The chemical conversion coatings, which are formed through the reaction between the substrate and the environment, have attracted increasing attention owing to the relative low treatment temperature, favorable bonding to substrate and simple implementation process. 2. With the increasing of hydroxyapatite (HA) content, the crack width in the composite coatings and the thickness of the coatings exhibit obviously decreased. The reason is probably that when adding HA into the phytic acid solution, the amount of active hydroxyl groups in the phytic acid are reduced via forming the coordination bond between P-OH groups from phytic acid and P-OH groups from the surface of HA, thus decreasing the coating thickness and hydrogen formation, as well as avoiding coating cracking. 3. By adjusting the HA content to 45 wt.%, a dense and relatively smooth composite coating with ~1.4 μm thickness is obtained on magnesium alloy, and exhibits high corrosion resistance and good bioactivity when compared with the single phytic acid conversion coating.

Biomimetic hydrophobic surface fabricated by chemical etching method from hierarchically structured magnesium alloy substrate

NASA Astrophysics Data System (ADS)

Liu, Yan; Yin, Xiaoming; Zhang, Jijia; Wang, Yaming; Han, Zhiwu; Ren, Luquan

2013-09-01

As one of the lightest metal materials, magnesium alloy plays an important role in industry such as automobile, airplane and electronic product. However, magnesium alloy is hindered due to its high chemical activity and easily corroded. Here, inspired by typical plant surfaces such as lotus leaves and petals of red rose with super-hydrophobic character, the new hydrophobic surface is fabricated on magnesium alloy to improve anti-corrosion by two-step methodology. The procedure is that the samples are processed by laser first and then immersed and etched in the aqueous AgNO3 solution concentrations of 0.1 mol/L, 0.3 mol/L and 0.5 mol/L for different times of 15 s, 40 s and 60 s, respectively, finally modified by DTS (CH3(CH2)11Si(OCH3)3). The microstructure, chemical composition, wettability and anti-corrosion are characterized by means of SEM, XPS, water contact angle measurement and electrochemical method. The hydrophobic surfaces with microscale crater-like and nanoscale flower-like binary structure are obtained. The low-energy material is contained in surface after DTS treatment. The contact angles could reach up to 138.4 ± 2°, which hydrophobic property is both related to the micro-nano binary structure and chemical composition. The results of electrochemical measurements show that anti-corrosion property of magnesium alloy is improved. Furthermore, our research is expected to create some ideas from natural enlightenment to improve anti-corrosion property of magnesium alloy while this method can be easily extended to other metal materials.

Catalyst for the methanation of carbon monoxide in sour gas

DOEpatents

Kustes, William A.; Hausberger, Arthur L.

1985-01-01

The invention involves the synergistic effect of the specific catalytic constituents on a specific series of carriers for the methanation of carbon monoxide in the presence of sulfur at relatively high temperatures and at low steam to gas ratios in the range of 0.2:1 or less. This effect was obtained with catalysts comprising the mixed sulfides and oxides of nickel and chromium supported on carriers comprising magnesium aluminate and magnesium silicate. Conversion of carbon monoxide to methane was in the range of from 40 to 80%. Tests of this combination of metal oxides and sulfides on other carriers and tests of other metal oxides and sulfides on the same carrier produced a much lower level of conversion.

Raman chemical mapping of magnesium stearate delivered by a punch-face lubrication system on the surface of placebo and active tablets.

PubMed

Šašiċ, Slobodan; Ojakovo, Peter; Warman, Martin; Sanghvi, Tapan

2013-09-01

Raman chemical mapping was used to determine the distribution of magnesium stearate, a lubricant, on the surface of tablets. The lubrication was carried out via a punch-face lubrication system with different spraying rates applied on placebo and active-containing tablets. Principal component analysis was used for decomposing the matrix of Raman mapping spectra. Some of the loadings associated with minuscule variation in the data significantly overlap with the Raman spectrum of magnesium stearate in placebo tablets and allow for imaging the domains of magnesium stearate via corresponding scores. Despite the negligible variation accounted for by respective principal components, the score images seem reliable as demonstrated through thresholding the one-dimensional representation and the spectra of the hot pixels that show a weak but perceivable magnesium stearate band at 1295 cm(-1). The same approach was applied on the active formulation, but no magnesium stearate was identified, presumably due to overwhelming concentration and spectral contribution of the active pharmaceutical ingredient.

Corrosion resistance and biocompatibility of magnesium alloy modified by alkali heating treatment followed by the immobilization of poly (ethylene glycol), fibronectin and heparin.

PubMed

Pan, Changjiang; Hu, Youdong; Hou, Yu; Liu, Tao; Lin, Yuebin; Ye, Wei; Hou, Yanhua; Gong, Tao

2017-01-01

In recent years, magnesium alloys are attracting more and more attention as a kind of biodegradable metallic biomaterials, however, their uncontrollable biodegradation speed in vivo and the limited surface biocompatibility hinder their clinical applications. In the present study, with the aim of improving the corrosion resistance and biocompatibility, the magnesium alloy (AZ31B) surface was modified by alkali heating treatment followed by the self-assembly of 3-aminopropyltrimethoxysilane (APTMS). Subsequently, poly (ethylene glycol) (PEG) and fibronectin or fibronectin/heparin complex were sequentially immobilized on the modified surface. The results of attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) confirmed that the above molecules were successfully immobilized on the magnesium alloy surface. An excellent hydrophilic surface was obtained after the alkali heating treatment while the hydrophilicity decreased to some degree after the self-assembly of APTMS, the surface hydrophilicity was gradually improved again after the immobilization of PEG, fibronectin or fibronectin/heparin complex. The corrosion resistance of the control magnesium alloy was significantly improved by the alkali heating treatment. The self-assembly of APTMS and the following immobilization of PEG further enhanced the corrosion resistance of the substrates, however, the grafting of fibronectin or fibronectin/heparin complex slightly lowered the corrosion resistance. As compared to the pristine magnesium alloy, the samples modified by the immobilization of PEG and fibronectin/heparin complex presented better blood compatibility according to the results of hemolysis assay and platelet adhesion as well as the activated partial thromboplastin time (APTT). In addition, the modified substrates had better cytocompatibility to endothelial cells due to the improved anticorrosion and the introduction of fibronectin. The substrates modified by fibronectin or fibronectin/heparin complex can significantly promote endothelial cell adhesion and proliferation. Taking all these results into consideration, the method of the present study can be used for the surface modification of the magnesium alloy to simultaneously impart it better corrosion resistance, favorable blood compatibility and good cytocompatibility to endothelial cells. Copyright © 2016 Elsevier B.V. All rights reserved.

Attrition resistant, zinc titanate-containing, reduced sulfur sorbents and methods of use thereof

DOEpatents

Vierheilig, Albert A.; Gupta, Raghubir P.; Turk, Brian S.

2006-06-27

Reduced sulfur gas species (e.g., H.sub.2S, COS and CS.sub.2) are removed from a gas stream by compositions wherein a zinc titanate ingredient is associated with a metal oxide-aluminate phase material in the same particle species. Nonlimiting examples of metal oxides comprising the compositions include magnesium oxide, zinc oxide, calcium oxide, nickel oxide, etc.

Defect and adsorbate induced ferromagnetic spin-order in magnesium oxide nanocrystallites

NASA Astrophysics Data System (ADS)

Kumar, Ashok; Kumar, Jitendra; Priya, Shashank

2012-05-01

We report the correlation between d0 ferromagnetism, photoluminescence (PL), and adsorbed hydrogen (H-) species in magnesium oxide (MgO) nanocrystallites. Our study suggests that the oxygen vacancies, namely singly ionized anionic vacancies (F+) and dimers (F22+) induce characteristic photoluminescence and the room-temperature ferromagnetic spin-order. Nanocrystallites with low population of oxygen vacancies have revealed diamagnetic behavior. Intriguingly, on adsorption of hydrogen (H-) species in the MgO nanocrystallites, ferromagnetic behavior was either enhanced (in the case of highly oxygen deficient nanocrystallites) or begun to percolate (in the case of nanocrystallite with low population density of oxygen vacancies).

Stable dimeric magnesium(I) compounds: from chemical landmarks to versatile reagents.

PubMed

Stasch, Andreas; Jones, Cameron

2011-06-07

The chemistry of the s-block metals is dominated by the +1 oxidation state for the Alkali metals (group 1) and the +2 oxidation state for the Alkaline Earth metals (group 2). In recent years, a series of stable dimeric magnesium(I) compounds has been prepared and their chemistry has started to develop. These complexes feature "deformable" Mg-Mg single bonds and are stabilised by sterically demanding and chelating anionic N-ligands that prevent their disproportionation. They have rapidly proven useful in organic and organometallic/inorganic reduction reactions as hydrocarbon soluble, stoichiometric, selective and safe reducing agents. The scope of this perspective focuses on stable molecular compounds of the general type LMgMgL and describes their synthesis, structures, theoretical and spectroscopic studies as well as their further chemistry. Also, comparisons are drawn with related complexes including magnesium(II) hydrides and dimeric zinc(I) compounds.

46 CFR 153.530 - Special requirements for alkylene oxides.

Code of Federal Regulations, 2011 CFR

2011-10-01

... Equipment Special Requirements § 153.530 Special requirements for alkylene oxides. When Table 1 refers to... materials, and gasket materials. (3) Materials containing oxides of magnesium, such as mineral wools. (e... this section must have continuous monitoring of oxygen concentration or have an arrangement to enable...

Zirconia-molybdenum disilicide composites

DOEpatents

Petrovic, John J.; Honnell, Richard E.

1991-01-01

Compositions of matter comprised of molybdenum disilicide and zirconium oxide in one of three forms: pure, partially stabilized, or fully stabilized and methods of making the compositions. The stabilized zirconia is crystallographically stabilized by mixing it with yttrium oxide, calcium oxide, cerium oxide, or magnesium oxide and it may be partially stabilized or fully stabilized depending on the amount of stabilizing agent in the mixture.

High rate buffer layer for IBAD MgO coated conductors

DOEpatents

Foltyn, Stephen R [Los Alamos, NM; Jia, Quanxi [Los Alamos, NM; Arendt, Paul N [Los Alamos, NM

2007-08-21

Articles are provided including a base substrate having a layer of an oriented material thereon, and, a layer of hafnium oxide upon the layer of an oriented material. The layer of hafnium oxide can further include a secondary oxide such as cerium oxide, yttrium oxide, lanthanum oxide, scandium oxide, calcium oxide and magnesium oxide. Such articles can further include thin films of high temperature superconductive oxides such as YBCO upon the layer of hafnium oxide or layer of hafnium oxide and secondary oxide.

Mechanism and Microstructure of Oxide Fluxes for Gas Tungsten Arc Welding of Magnesium Alloy

NASA Astrophysics Data System (ADS)

Liu, L. M.; Zhang, Z. D.; Song, G.; Wang, L.

2007-03-01

Five single oxide fluxes—MgO, CaO, TiO2, MnO2, and Cr2O3—were used to investigate the effect of active flux on the depth/width ratio in AZ31B magnesium alloy. The microstructure and mechanical property of the tungsten inert gas (TIG) welding seam were studied. The oxygen content in the weld seam and the arc images during the TIG welding process were analyzed. A series of emission spectroscopy of weld arc for TIG welding for magnesium with and without flux were developed. The results showed that for the five single oxide fluxes, all can increase the weld penetration effectively and grain size in the weld seam of alternating current tungsten inert gas (ACTIG) welding of the Mg alloy. The oxygen content of the welds made without flux is not very different from those produced with oxide fluxes not considering trapped oxide. However, welds that have the best penetration have a relatively higher oxygen content among those produced with flux. It was found that the arc images with the oxide fluxes were only the enlarged form of the arc images without flux; the arc constriction was not observed. The detection of arc spectroscopy showed that the metal elements in the oxides exist as the neutral atom or the first cation in the weld arc. This finding would influence the arc properties. When TIG simulation was carried out on a plate with flux applied only on one side, the arc image video showed an asymmetric arc, which deviated toward the flux free side. The thermal stability, the dissociation energy, and the electrical conductivity of oxide should be considered when studying the mechanism for increased TIG flux weld penetration.

Time-of-flight spectroscopy of positronium emission from quartz and magnesium oxide

NASA Astrophysics Data System (ADS)

Sferlazzo, P.; Berko, S.; Canter, K. F.

1987-04-01

The energy distribution of Ps emitted from SiO2 and MgO single crystals bombarded by 500-900-eV positrons was measured. For SiO2 a nearly monoenergetic component at 3.27(4) is observed and is consistent with a bulk excitonlike Ps emitted from the surface. A broader component of ~1.5 eV full width at half maximum is also observed. For MgO the Ps spectrum is characterized by a high-energy tail extending up to 6-7 eV. Possible models which would explain the MgO results are discussed.

Surface structures of L10-MnGa (001) by scanning tunneling microscopy and first-principles theory

NASA Astrophysics Data System (ADS)

Corbett, J. P.; Guerrero-Sanchez, J.; Richard, A. L.; Ingram, D. C.; Takeuchi, N.; Smith, A. R.

2017-11-01

We report on the surface reconstructions of L10-ordered MnGa (001) thin films grown by molecular beam epitaxy on a 50 nm Mn3N2 (001) layer freshly grown on a magnesium oxide (001) substrate. Scanning tunneling microscopy, Auger electron spectroscopy, and reflection high energy electron diffraction are combined with first-principles density functional theory calculations to determine the reconstructions of the L10-ordered MnGa (001) surface. We find two lowest energy reconstructions of the MnGa (001) face: a 1 × 1 Ga-terminated structure and a 1 × 2 structure with a Mn replacing a Ga in the 1 × 1 Ga-terminated surface. The 1 × 2 reconstruction forms a row structure along [100]. The manganese:gallium stoichiometry within the surface based on theoretical modeling is in good agreement with experiment. Magnetic moment calculations for the two lowest energy structures reveal important surface and bulk effects leading to oscillatory total magnetization for ultra-thin MnGa (001) films.

Research on super-hydrophobic surface of biodegradable magnesium alloys used for vascular stents.

PubMed

Wan, Peng; Wu, Jingyao; Tan, LiLi; Zhang, Bingchun; Yang, Ke

2013-07-01

Micro-nanometer scale structure of nubby clusters overlay was constructed on the surface of an AZ31 magnesium alloy by a wet chemical method. The super-hydrophobicity was achieved with a water contact angle of 142° and a sliding angle of about 5°. The microstructure and composition of the super-hydrophobic surface were characterized by SEM and FTIR. Potentiodynamic polarization and electrochemical impedance spectroscopy were used to evaluate the corrosion behavior, and the hemocompatibility of the super-hydrophobic surface was investigated by means of hemolytic and platelet adhesion tests. Results showed that the super-hydrophobic treatment could improve the corrosion resistance of magnesium alloys in PBS and inhibit blood platelet adhesion on the surface, which implied excellent hemocompatibility with controlled degradation. Copyright © 2013 Elsevier B.V. All rights reserved.

Two-dimensional magnesium oxide nanosheets reinforced epoxy nanocomposites for enhanced fracture toughness

NASA Astrophysics Data System (ADS)

Balguri, Praveen Kumar; Harris Samuel, D. G.; Guruvishnu, T.; Aditya, D. B.; Mahadevan, S. M.; Thumu, Udayabhaskararao

2018-01-01

Metal oxide nanoparticles have been used as excellent reinforcements to enhance mechanical properties of polymers, natural composites, and ceramics. To date, a major portion of metal oxides used as nanofillers is three dimensional spherical nanoparticles. In the last decade, two-dimensional (2D) materials such as graphene have been widely investigated to improve the mechanical and electrical properties of polymer materials. In this paper, 2D Magnesium oxide (MgO) nanosheets reinforced epoxy composites (0.1, 0.2 and 0.4 wt%) are fabricated and studied for their ability to resist the propagation of preexisting flaw by conducting fracture toughness test for K IC, critical stress intensity factor. This property is an important mechanical property for designing applications in various engineering technologies. Our results show that the MgO with 0.2 wt% is the optimized level to improve the fracture toughness of the epoxy polymer by 47%.

Adsorptive removal of an anionic dye Congo red by flower-like hierarchical magnesium oxide (MgO)-graphene oxide composite microspheres

NASA Astrophysics Data System (ADS)

Xu, Jing; Xu, Difa; Zhu, Bicheng; Cheng, Bei; Jiang, Chuanjia

2018-03-01

Flower-like magnesium oxide (MgO) microspheres and MgO-graphene oxide (GO) composites with an average diameter of 500 nm and hierarchical structure were synthesized through an ethylene glycol-mediated self-assembly process. The adsorption of Congo red (CR) by the prepared samples was evaluated in water under ambient conditions. The equilibrium adsorption isotherms of CR on the as-prepared samples could be described by the Langmuir model. The MgO-GO microspheres prepared with 0.5 wt% GO showed higher adsorption capacity (237.0 mg/g) than the MgO microspheres (227.7 mg/g). Adsorption kinetics results of CR indicated that pseudo-second-order kinetic equation could well explain the adsorption kinetics behaviors of CR. These findings indicate that the MgO-GO composite microspheres are potential adsorbents for effective removal of Congo red from wastewater.

Coating of biodegradable magnesium alloy bone implants using nanostructured diopside (CaMgSi2O6)

NASA Astrophysics Data System (ADS)

Razavi, Mehdi; Fathi, Mohammadhossein; Savabi, Omid; Beni, Batoul Hashemi; Razavi, Seyed Mohammad; Vashaee, Daryoosh; Tayebi, Lobat

2014-01-01

Magnesium alloys with their biodegradable characteristic can be a very good candidate to be used in orthopedic implants. However, magnesium alloys may corrode and degrade too fast for applications in the bone healing procedure. In order to enhance the corrosion resistance and the in vitro bioactivity of a magnesium alloy, a nanostructured diopside (CaMgSi2O6) film was coated on AZ91 magnesium alloy through combined micro-arc oxidation (MAO) and electrophoretic deposition (EPD) methods. The crystalline structures, morphologies and compositions of the coated and uncoated substrates were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy. Polarization, electrochemical impedance spectroscopy, and immersion test in simulated body fluid (SBF) were employed to evaluate the corrosion resistance and the in vitro bioactivity of the samples. The results of our investigation showed that the nanostructured diopside coating deposited on the MAO layer increases the corrosion resistance and improves the in vitro bioactivity of the biodegradable magnesium alloy.

Converting chemical energy into electricity through a functionally cooperating device with diving-surfacing cycles.

PubMed

Song, Mengmeng; Cheng, Mengjiao; Ju, Guannan; Zhang, Yajun; Shi, Feng

2014-11-05

A smart device that can dive or surface in aqueous medium has been developed by combining a pH-responsive surface with acid-responsive magnesium. The diving-surfacing cycles can be used to convert chemical energy into electricity. During the diving-surfacing motion, the smart device cuts magnetic flux lines and produces a current, demonstrating that motional energy can be realized by consuming chemical energy of magnesium, thus producing electricity. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Elucidating the role of the TRPM7 alpha-kinase: TRPM7 kinase inactivation leads to magnesium deprivation resistance phenotype in mice

PubMed Central

Ryazanova, Lillia V.; Hu, Zhixian; Suzuki, Sayuri; Chubanov, Vladimir; Fleig, Andrea; Ryazanov, Alexey G.

2014-01-01

TRPM7 is an unusual bi-functional protein containing an ion channel covalently linked to a protein kinase domain. TRPM7 is implicated in regulating cellular and systemic magnesium homeostasis. While the biophysical properties of TRPM7 ion channel and its function are relatively well characterized, the function of the TRPM7 enzymatically active kinase domain is not understood yet. To investigate the physiological role of TRPM7 kinase activity, we constructed mice carrying an inactive TRPM7 kinase. We found that these mice were resistant to dietary magnesium deprivation, surviving three times longer than wild type mice; also they displayed decreased chemically induced allergic reaction. Interestingly, mutant mice have lower magnesium bone content compared to wild type mice when fed regular diet; unlike wild type mice, mutant mice placed on magnesium-depleted diet did not alter their bone magnesium content. Furthermore, mouse embryonic fibroblasts isolated from TRPM7 kinase-dead animals exhibited increased resistance to magnesium deprivation and oxidative stress. Finally, electrophysiological data revealed that the activity of the kinase-dead TRPM7 channel was not significantly altered. Together, our results suggest that TRPM7 kinase is a sensor of magnesium status and provides coordination of cellular and systemic responses to magnesium deprivation. PMID:25534891

Controllable degradation of medical magnesium by electrodeposited composite films of mussel adhesive protein (Mefp-1) and chitosan.

PubMed

Jiang, Ping-Li; Hou, Rui-Qing; Chen, Cheng-Dong; Sun, Lan; Dong, Shi-Gang; Pan, Jin-Shan; Lin, Chang-Jian

2016-09-15

To control the degradation rate of medical magnesium in body fluid environment, biocompatible films composed of Mussel Adhesive Protein (Mefp-1) and chitosan were electrodeposited on magnesium surface in cathodic constant current mode. The compositions and structures of the films were characterized by atomic force microscope (AFM), scanning electron microscope (SEM) and infrared reflection absorption spectroscopy (IRAS). And the corrosion protection performance was investigated using electrochemical measurements and immersion tests in simulated body fluid (Hanks' solution). The results revealed that Mefp-1 and chitosan successfully adhered on the magnesium surface and formed a protective film. Compared with either single Mefp-1 or single chitosan film, the composite film of chitosan/Mefp-1/chitosan (CPC (chitosan/Mefp-1/chitosan)) exhibited lower corrosion current density, higher polarization resistance and more homogenous corrosion morphology and thus was able to effectively control the degradation rate of magnesium in simulated body environment. In addition, the active attachment and spreading of MC3T3-E1 cells on the CPC film coated magnesium indicated that the CPC film was significantly able to improve the biocompatibility of the medical magnesium. Copyright © 2016 Elsevier Inc. All rights reserved.

WATER COOLED RETORT COVER

DOEpatents

Ash, W.J.; Pozzi, J.F.

1962-05-01

A retort cover is designed for use in the production of magnesium metal by the condensation of vaporized metal on a collecting surface. The cover includes a condensing surface, insulating means adjacent to the condensing surface, ind a water-cooled means for the insulating means. The irrangement of insulation and the cooling means permits the magnesium to be condensed at a high temperature and in massive nonpyrophoric form. (AEC)

Total control of chromium in tanneries - thermal decomposition of filtration cake from enzymatic hydrolysis of chrome shavings.

PubMed

Kocurek, P; Kolomazník, K; Bařinová, M; Hendrych, J

2017-04-01

This paper deals with the problem of chromium recovery from chrome-tanned waste and thus with reducing the environmental impact of the leather industry. Chrome-tanned waste was transformed by alkaline enzymatic hydrolysis promoted by magnesium oxide into practically chromium-free, commercially applicable collagen hydrolysate and filtration cake containing a high portion of chromium. The crude and magnesium-deprived chromium cakes were subjected to a process of thermal decomposition at 650°C under oxygen-free conditions to reduce the amount of this waste and to study the effect of magnesium removal on the resulting products. Oxygen-free conditions were applied in order to prevent the oxidation of trivalent chromium into the hazardous hexavalent form. Thermal decomposition products from both crude and magnesium-deprived chrome cakes were characterized by high chromium content over 50%, which occurred as eskolaite (Cr 2 O 3 ) and magnesiochromite (MgCr 2 O 4 ) crystal phases, respectively. Thermal decomposition decreased the amount of chrome cake dry feed by 90%. Based on the performed experiments, a scheme for the total control of chromium in the leather industry was designed.

Recovery of phosphorous from industrial waste water by oxidation and precipitation.

PubMed

Ylmén, Rikard; Gustafsson, Anna M K; Camerani-Pinzani, Caterina; Steenari, Britt-Marie

2017-07-03

This paper describes the development of a method for recovery of phosphorous from one of the waste waters at an Akzo Nobel chemical plant in Ale close to Göteborg. It was found that it is possible to transform the phosphorous in the waste water to a saleable product, i.e. a slowly dissolving fertilizer. The developed process includes oxidation of phosphite to phosphate with hydrogen peroxide and heat. The phosphate is then precipitated as crystalline struvite (ammonium magnesium phosphate) by the addition of magnesium chloride. The environmental impacts of the new method were compared with those of the current method using life cycle assessment. It was found that the methodology developed in this project was an improvement compared with the current practice regarding element resource depletion and eutrophication. However, the effect on global warming would be greater with the new method. There could however be several ways to decrease the global warming effect. Since most of the carbon dioxide emissions come from the production of magnesium chloride from carbonates, changing to utilization of a magnesium chloride from desalination of seawater or from recycling of PVC would decrease the carbon footprint significantly.

Machining-induced surface transformations of magnesium alloys to enhance corrosion resistance in human-like environment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bruschi, Stefania; Bertolini, Rachele; Ghiotti, Andrea

We report that magnesium alloys are becoming increasingly attractive for producing temporary prosthetic devices thanks to their bioresorbable characteristics in human body. However, their poor corrosion resistance to body fluids seriously limits their applicability. In this work, machining-induced surface transformations are explored as means to enhance corrosion resistance of AZ31 magnesium alloy. Surface characteristics including topography, residual stresses, wettability, microstructures and depth of transformed layer, were analysed and correlated to in-vitro corrosion resistance. Results showed that cryogenic machining at low feed provided the most promising corrosion reduction. Finally, thorough physical characterizations gave fundamental insights into possible drivers for this enhancedmore » resistance.« less

Machining-induced surface transformations of magnesium alloys to enhance corrosion resistance in human-like environment

DOE PAGES

Bruschi, Stefania; Bertolini, Rachele; Ghiotti, Andrea; ...

2018-04-22

We report that magnesium alloys are becoming increasingly attractive for producing temporary prosthetic devices thanks to their bioresorbable characteristics in human body. However, their poor corrosion resistance to body fluids seriously limits their applicability. In this work, machining-induced surface transformations are explored as means to enhance corrosion resistance of AZ31 magnesium alloy. Surface characteristics including topography, residual stresses, wettability, microstructures and depth of transformed layer, were analysed and correlated to in-vitro corrosion resistance. Results showed that cryogenic machining at low feed provided the most promising corrosion reduction. Finally, thorough physical characterizations gave fundamental insights into possible drivers for this enhancedmore » resistance.« less

In vitro degradation of pure Mg in response to glucose

NASA Astrophysics Data System (ADS)

Zeng, Rong-Chang; Li, Xiao-Ting; Li, Shuo-Qi; Zhang, Fen; Han, En-Hou

2015-08-01

Magnesium and its alloys are promising biodegradable biomaterials but are still challenging to be used in person with high levels of blood glucose or diabetes. To date, the influence of glucose on magnesium degradation has not yet been elucidated, this issue requires more attention. Herein, we present pure Mg exhibiting different corrosion responses to saline and Hank’s solutions with different glucose contents, and the degradation mechanism of pure Mg in the saline solution with glucose in comparison with mannitol as a control. On one hand, the corrosion rate of pure Mg increases with the glucose concentration in saline solutions. Glucose rapidly transforms into gluconic acid, which attacks the oxides of the metal and decreases the pH of the solution; it also promotes the absorption of chloride ions on the Mg surface and consequently accelerates corrosion. On the other hand, better corrosion resistance is obtained with increasing glucose content in Hank’s solution due to the fact that glucose coordinates Ca2+ ions in Hank’s solution and thus improves the formation of Ca-P compounds on the pure Mg surface. This finding will open up new avenues for research on the biodegradation of bio-Mg materials in general, which could yield many new and interesting results.

Influence of sealing post-treatments on the corrosion resistance of PEO coated AZ91 magnesium alloy

NASA Astrophysics Data System (ADS)

Mingo, B.; Arrabal, R.; Mohedano, M.; Llamazares, Y.; Matykina, E.; Yerokhin, A.; Pardo, A.

2018-03-01

The effect of three different post-treatments carried out on Plasma Electrolytic Oxidation (PEO) coated magnesium alloys are evaluated in terms of characterisation and corrosion resistance. Special interest is given to the role of a common additive (NaF) to the coating properties. The post-treatments are based on immersion sealing processes in aqueous solutions of inorganic salts (cerium and stannate based salts) and alcoholic solution of an organic acid (octodecylphosphate acid, ODP). Sealing mechanisms for each post-treatment are proposed. Cerium and stannate sealings are based on filling of the pores with the products of dissolution/precipitation reactions, while the ODP acid sealing is based on the formation of a thin layer of ODP over the coating through specific interactions between the polar part of the organic acid and the coating surface. All coatings are evaluated by salt fog test and analysed by electrochemical impedance spectroscopy. All sealings show a slight increase in the corrosion resistance of the coatings formed in the NaF-free electrolyte, but their positive influence is boosted in case of the coatings obtained in the NaF-containing electrolyte. This is related to the chemical and morphological changes at the coating surface induced by the presence of NaF in the electrolyte.

In vitro degradation of pure Mg in response to glucose

PubMed Central

Zeng, Rong-Chang; Li, Xiao-Ting; Li, Shuo-Qi; Zhang, Fen; Han, En-Hou

2015-01-01

Magnesium and its alloys are promising biodegradable biomaterials but are still challenging to be used in person with high levels of blood glucose or diabetes. To date, the influence of glucose on magnesium degradation has not yet been elucidated, this issue requires more attention. Herein, we present pure Mg exhibiting different corrosion responses to saline and Hank’s solutions with different glucose contents, and the degradation mechanism of pure Mg in the saline solution with glucose in comparison with mannitol as a control. On one hand, the corrosion rate of pure Mg increases with the glucose concentration in saline solutions. Glucose rapidly transforms into gluconic acid, which attacks the oxides of the metal and decreases the pH of the solution; it also promotes the absorption of chloride ions on the Mg surface and consequently accelerates corrosion. On the other hand, better corrosion resistance is obtained with increasing glucose content in Hank’s solution due to the fact that glucose coordinates Ca2+ ions in Hank’s solution and thus improves the formation of Ca-P compounds on the pure Mg surface. This finding will open up new avenues for research on the biodegradation of bio-Mg materials in general, which could yield many new and interesting results. PMID:26264413

40 CFR 98.194 - Monitoring and QA/QC requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

... Association (incorporated by reference—see § 98.7). (d) You must use the analysis of calcium oxide and magnesium oxide content of each lime product that is produced and that is collected during the same month as...

Darkening effect on AZ31B magnesium alloy surface induced by nanosecond pulse Nd:YAG laser

NASA Astrophysics Data System (ADS)

Guan, Y. C.; Zhou, W.; Zheng, H. Y.; Li, Z. L.

2013-09-01

Permanent darkening effect was achieved on surface of AZ31B Mg alloy irradiated with nanosecond pulse Nd:YAG laser, and special attention was made to examine how surface structure as well as oxidation affect the darkening effect. Experiments were carried out to characterize morphological evolution and chemical composition of the irradiated areas by optical reflection spectrometer, Talysurf surface profiler, SEM, EDS, and XPS. The darkening effect was found to be occurred at the surface under high laser energy. Optical spectra showed that the induced darkening surface was uniform over the spectral range from 200 nm to 1100 nm. SEM and surface profiler showed that surface morphology of darkening areas consisted of large number of micron scale cauliflower-like clusters and protruding particles. EDS and XPS showed that compared to non-irradiated area, oxygen content at the darkening areas increased significantly. It was proposed a mechanism that involved trapping of light in the surface morphology and chemistry variation of irradiated areas to explain the laser-induced darkening effect on AZ31B Mg alloy.

Stabilizing contact resistance of isotropically conductive adhesives on various metal surfaces by incorporating sacrificial anode materials

NASA Astrophysics Data System (ADS)

Moon, Kyoung-Sik; Liong, Silvia; Li, Haiying; Wong, C. P.

2004-11-01

The contact resistance stability of isotropically conductive adhesives (ICAs) on non-noble metal surfaces under the 85°C/85% relative humidity (RH) aging test was investigated. Previously, we demonstrated that galvanic corrosion has been shown as the main mechanism of the unstable contact resistance of ICAs on non-noble metal surfaces. A sacrificial anode was introduced into the ICA joint for cathodic protection. Zinc, chromium, and magnesium were employed in the ICA formulations as sacrificial anode materials that have much lower electrode-potential values than the metal pad surface, such as tin or tin-based alloys. The effect of particle sizes and loading levels of sacrificial anode materials were studied. Chromium was not as effective in suppressing corrosion as magnesium or zinc because of its strong tendency to self-passivate. The corrosion potential of ICAs was reduced by half with the addition of zinc and magnesium into the ICA formulation. The addition of zinc and magnesium was very effective in controlling galvanic corrosion that takes place in the ICA joints, resulting in stabilized contact resistance of ICAs on Sn, SnPb, and SnAgCu surfaces during the 85°C/85% RH aging test.

Photoluminescence of magnesium-associated color centers in LiF crystals implanted with magnesium ions

NASA Astrophysics Data System (ADS)

Nebogin, S. A.; Ivanov, N. A.; Bryukvina, L. I.; V. Shipitsin, N.; E. Rzhechitskii, A.; Papernyi, V. L.

2018-05-01

In the present paper, the effect of magnesium nanoparticles implanted in a LiF crystal on the optical properties of color centers is studied. The transmittance spectra and AFM images demonstrate effective formation of the color centers and magnesium nanoparticles in an implanted layer of ∼ 60-100 nm in thickness. Under thermal annealing, a periodical structure is formed on the surface of the crystal and in the implanted layer due to self-organization of the magnesium nanoparticles. Upon excitation by argon laser with a wavelength of 488 nm at 5 K, in a LiF crystal, implanted with magnesium ions as well as in heavily γ-irradiated LiF: Mg crystals, luminescence of the color centers at λmax = 640 nm with a zero-phonon line at 601.5 nm is observed. The interaction of magnesium nanoparticles and luminescing color centers in a layer implanted with magnesium ions has been revealed. It is shown that the luminescence intensity of the implanted layer at a wavelength of 640 nm is by more than two thousand times higher than that of a heavily γ-irradiated LiF: Mg crystal. The broadening of the zero-phonon line at 601.5 nm in the spectrum of the implanted layer indicates the interaction of the emitting quantum system with local field of the surface plasmons of magnesium nanoparticles. The focus of this work is to further optimize the processing parameters in a way to result in luminescence great enhancement of color centers by magnesium nanoparticles in LiF.

SOLID-STATE SYNTHESIS AND SOME PROPERTIES OF MAGNESIUM-DOPED COPPER ALUMINUM OXIDES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Chang; Ren, Fei; Wang, Hsin

2010-01-01

Copper aluminum oxide (CuAlO2) with delafossite structure is a promising candidate for high temperature thermoelectric applications because of its modest band gap, high stability and low cost. We investigate magnesium doping on the aluminum site as a means of producing higher electrical conductivity and optimized Seebeck coefficient. Powder samples were synthesized using solid-state reaction and bulk samples were prepared using both cold-pressing and hot-pressing techniques. Composition analysis, microstructural examination and transport property measurements were performed, and the results suggest that while hot-pressing can achieve high density samples, secondary phases tend to form and lower the performance of the materials.

Magnesium Oxide (MgO) pH-sensitive Sensing Membrane in Electrolyte-Insulator-Semiconductor Structures with CF4 Plasma Treatment.

PubMed

Kao, Chyuan-Haur; Chang, Chia Lung; Su, Wei Ming; Chen, Yu Tzu; Lu, Chien Cheng; Lee, Yu Shan; Hong, Chen Hao; Lin, Chan-Yu; Chen, Hsiang

2017-08-03

Magnesium oxide (MgO) sensing membranes in pH-sensitive electrolyte-insulator-semiconductor structures were fabricated on silicon substrate. To optimize the sensing capability of the membrane, CF 4 plasma was incorporated to improve the material quality of MgO films. Multiple material analyses including FESEM, XRD, AFM, and SIMS indicate that plasma treatment might enhance the crystallization and increase the grain size. Therefore, the sensing behaviors in terms of sensitivity, linearity, hysteresis effects, and drift rates might be improved. MgO-based EIS membranes with CF 4 plasma treatment show promise for future industrial biosensing applications.

Soft-Templating Synthesis of Mesoporous Silica-Based Materials for Environmental Applications

NASA Astrophysics Data System (ADS)

Gunathilake, Chamila Asanka

Dissertation research is mainly focus on: 1) the development of mesoporous silica materials with organic pendant and bridging groups (isocyanurate, amidoxime, benzene) and incorporated metal (aluminum, zirconium, calcium, and magnesium) species for high temperature carbon dioxide (CO2) sorption, 2) phosphorous-hydroxy functionalized mesoporous silica materials for water treatment, and 3) amidoxime-modified ordered mesoporous silica materials for uranium sorption under seawater conditions. The goal is to design composite materials for environmental applications with desired porosity, surface area, and functionality by selecting proper metal oxide precursors, organosilanes, tetraethylorthosilicate, (TEOS), and block copolymer templates and by adjusting synthesis conditions. The first part of dissertation presents experimental studies on the merge of aluminum, zirconium, calcium, and magnesium oxides with mesoporous silica materials containing organic pendant (amidoxime) and bridging groups (isocyanurate, benzene) to obtain composite sorbents for CO2 sorption at ambient (0-25 °C) and elevated (60-120 °C) temperatures. These studies indicate that the aforementioned composite sorbents are fairly good for CO2 capture at 25 °C via physisorption mechanism and show a remarkably high affinity toward CO2 chemisorption at 60-120 °C. The second part of dissertation is devoted to silica-based materials with organic functionalities for removal of heavy metal ions such as lead from contaminated water and for recovery of metal ions such as uranium from seawater. First, ordered mesoporous organosilica (OMO) materials with diethylphosphatoethyl and hydroxyphosphatoethyl surface groups were examined for Pb2+ adsorption and showed unprecedented adsorption capacities up to 272 mg/g and 202 mg/g, respectively However, the amidoxime-modified OMO materials were explored for uranium extraction under seawater conditions and showed remarkable capacities reaching 57 mg of uranium per gram of adsorbent.

Bonding and vibrations of CO molecules adsorbed at transition metal impurity sites on the MgO (001) surface. A density functional model cluster study

NASA Astrophysics Data System (ADS)

Neyman, K. M.; Rösch, N.

1993-11-01

First principles density functional cluster investigations of adsorption at the (001) surface of pure and doped magnesium oxide are carried out to characterize and compare the interaction of CO molecules with main group (Mg 2+) and d metal (Co 2+, Ni 2+, Cu 2+) surface cationic centers of the ionic substrate. The geometry of the adsorption complexes, the binding mechanism and spectroscopic manifestations of the surface species are analyzed. Special attention is payed to vibrational frequencies and intensities. The calculations qualitatively reproduce observed trends in the adsorption-induced frequency shifts for the series of the surface aggregates Mg 5cCO→Ni 5cCO→CO 5cCO and the corresponding change of the infrared intensities of the CO vibrational mode. For the transition metal impurity sites these results are rationalized in terms of a small, but notable Md πCOπ interaction.

40 CFR 63.7081 - Am I subject to this subpart?

Code of Federal Regulations, 2010 CFR

2010-07-01

...) National Emission Standards for Hazardous Air Pollutants for Lime Manufacturing Plants What This Subpart... a lime manufacturing plant (LMP) that is a major source, or that is located at, or is part of, a... manufacture of lime product (calcium oxide, calcium oxide with magnesium oxide, or dead burned dolomite) by...

Influence of shot peening on corrosion properties of biocompatible magnesium alloy AZ31 coated by dicalcium phosphate dihydrate (DCPD).

PubMed

Mhaede, Mansour; Pastorek, Filip; Hadzima, Branislav

2014-06-01

Magnesium alloys are promising materials for biomedical applications because of many outstanding properties like biodegradation, bioactivity and their specific density and Young's modulus are closer to bone than the commonly used metallic implant materials. Unfortunately their fatigue properties and low corrosion resistance negatively influenced their application possibilities in the field of biomedicine. These problems could be diminished through appropriate surface treatments. This study evaluates the influence of a surface pre-treatment by shot peening and shot peening+coating on the corrosion properties of magnesium alloy AZ31. The dicalcium phosphate dihydrate coating (DCPD) was electrochemically deposited in a solution containing 0.1M Ca(NO3)2, 0.06M NH4H2PO4 and 10mL/L of H2O2. The effect of shot peening on the surface properties of magnesium alloy was evaluated by microhardness and surface roughness measurements. The influence of the shot peening and dicalcium phosphate dihydrate layer on the electrochemical characteristics of AZ31 magnesium alloy was evaluated by potentiodynamic measurements and electrochemical impedance spectroscopy in 0.9% NaCl solution at a temperature of 22±1°C. The obtained results were analyzed by the Tafel-extrapolation method and equivalent circuit method. The results showed that the application of shot peening process followed by DCPD coating improves the properties of the AZ31 surface from corrosion and mechanical point of view. Copyright © 2014 Elsevier B.V. All rights reserved.

A case of osteomalacia due to deranged mineral balance caused by saccharated ferric oxide and short-bowel syndrome: A case report.

PubMed

Nomoto, Hiroshi; Miyoshi, Hideaki; Nakamura, Akinobu; Nagai, So; Kitao, Naoyuki; Shimizu, Chikara; Atsumi, Tatsuya

2017-09-01

Saccharated ferric oxide has been shown to lead to elevation of fibroblast growth factor 23, hypophosphatemia, and, consequently, osteomalacia. Moreover, mineral imbalance is often observed in patients with short-bowel syndrome to some degree. A 62-year-old woman with short-bowel syndrome related with multiple resections of small intestines due to Crohn disease received regular intravenous administration of saccharated ferric oxide. Over the course of treatment, she was diagnosed with tetany, which was attributed to hypocalcemia. Additional assessments of the patient revealed not only hypocalcemia, but also hypophosphatemia, hypomagnesemia, osteomalacia, and a high concentration of fibroblast growth factor 23 (314 pg/mL). We diagnosed her with mineral imbalance-induced osteomalacia due to saccharated ferric oxide and short-bowel syndrome. Magnesium replacement therapy and discontinuation of saccharated ferric oxide alone. These treatments were able to normalize her serum mineral levels and increase her bone mineral density. This case suggests that adequate evaluation of serum minerals, including phosphate and magnesium, during saccharated ferric oxide administration may be necessary, especially in patients with short-bowel syndrome.

Electrochemical characteristics of calcium-phosphatized AZ31 magnesium alloy in 0.9 % NaCl solution.

PubMed

Hadzima, Branislav; Mhaede, Mansour; Pastorek, Filip

2014-05-01

Magnesium alloys suffer from their high reactivity in common environments. Protective layers are widely created on the surface of magnesium alloys to improve their corrosion resistance. This article evaluates the influence of a calcium-phosphate layer on the electrochemical characteristics of AZ31 magnesium alloy in 0.9 % NaCl solution. The calcium phosphate (CaP) layer was electrochemically deposited in a solution containing 0.1 M Ca(NO3)2, 0.06 M NH4H2PO4 and 10 ml l(-1) of H2O2. The formed surface layer was composed mainly of brushite [(dicalcium phosphate dihidrate (DCPD)] as proved by energy-dispersive X-ray analysis. The surface morphology was observed by scanning electron microscopy. Immersion test was performed in order to observe degradation of the calcium phosphatized surfaces. The influence of the phosphate layer on the electrochemical characteristics of AZ31, in 0.9 % NaCl solution, was evaluated by potentiodynamic measurements and electrochemical impedance spectroscopy. The obtained results were analysed by the Tafel-extrapolation method and equivalent circuits method. The results showed that the polarization resistance of the DCPD-coated surface is about 25 times higher than that of non-coated surface. The CaP electro-deposition process increased the activation energy of corrosion process.

Co-Registered In Situ Secondary Electron and Mass Spectral Imaging on the Helium Ion Microscope Demonstrated Using Lithium Titanate and Magnesium Oxide Nanoparticles.

PubMed

Dowsett, D; Wirtz, T

2017-09-05

The development of a high resolution elemental imaging platform combining coregistered secondary ion mass spectrometry and high resolution secondary electron imaging is reported. The basic instrument setup and operation are discussed and in situ image correlation is demonstrated on a lithium titanate and magnesium oxide nanoparticle mixture. The instrument uses both helium and neon ion beams generated by a gas field ion source to irradiate the sample. Both secondary electrons and secondary ions may be detected. Secondary ion mass spectrometry (SIMS) is performed using an in-house developed double focusing magnetic sector spectrometer with parallel detection. Spatial resolutions of 10 nm have been obtained in SIMS mode. Both the secondary electron and SIMS image data are very surface sensitive and have approximately the same information depth. While the spatial resolutions are approximately a factor of 10 different, switching between the different images modes may be done in situ and extremely rapidly, allowing for simple imaging of the same region of interest and excellent coregistration of data sets. The ability to correlate mass spectral images on the 10 nm scale with secondary electron images on the nanometer scale in situ has the potential to provide a step change in our understanding of nanoscale phenomena in fields from materials science to life science.

Effects of phosphates on microstructure and bioactivity of micro-arc oxidized calcium phosphate coatings on Mg-Zn-Zr magnesium alloy.

PubMed

Pan, Y K; Chen, C Z; Wang, D G; Zhao, T G

2013-09-01

Calcium phosphate (CaP) coatings were prepared on Mg-Zn-Zr magnesium alloy by micro-arc oxidation (MAO) in electrolyte containing calcium acetate monohydrate (CH3COO)2Ca·H2O) and different phosphates (i.e. disodium hydrogen phosphate dodecahydrate (Na2HPO4·12H2O), sodium phosphate (Na3PO4·H2O) and sodium hexametaphosphate((NaPO3)6)). Scanning electron microscope (SEM), energy-dispersive X-ray spectrometry (EDS) and X-ray diffractometer (XRD) were employed to characterize the microstructure, elemental distribution and phase composition of the CaP coatings. Simulated body fluid (SBF) immersion test was used to evaluate the coating bioactivity and degradability. Systemic toxicity test was used to evaluate the coating biocompatibility. Fluoride ion selective electrode (ISE) was used to measure F(-) ions concentration during 30 days SBF immersion. The CaP coatings effectively reduced the corrosion rate and the surfaces of CaP coatings were covered by a new layer formed of numerous needle-like and scale-like apatites. The formation of these calcium phosphate apatites indicates that the coatings have excellent bioactivity. The coatings formed in (NaPO3)6-containging electrolyte exhibit thicker thickness, higher adhesive strength, slower degradation rate, better apatite-inducing ability and biocompatibility. Copyright © 2013 Elsevier B.V. All rights reserved.

A Study of the Electrostatic Interaction Between Insulators and Martian/Lunar Soil Simulants

NASA Technical Reports Server (NTRS)

Mantovani, James G.

2001-01-01

Using our previous experience with the Mars Environmental Compatibility Assessment (MECA) electrometer, we have designed a new type of aerodynamic electrometer. The goal of the research was to measure the buildup of electrostatic surface charge on a stationary cylindrical insulator after windborne granular particles have collided with the insulator surface in a simulated dust storm. The experiments are performed inside a vacuum chamber. This allows the atmospheric composition and pressure to be controlled in order to simulate the atmospheric conditions near the equator on the Martian surface. An impeller fan was used to propel the dust particles at a cylindrically shaped insulator under low vacuum conditions. We tested the new electrometer in a 10 mbar CO2 atmosphere by exposing two types of cylindrical insulators, Teflon (1.9 cm diameter) and Fiberglass (2.5 cm diameter), to a variety of windborne granular particulate materials. The granular materials tested were JSC Mars-1 simulant, which is a mixture of coarse and fine (<5microns diameter) particle sizes, and some of the major mineral constituents of the Martian soil. The minerals included Ottawa sand (SiO2), iron oxide (Fe2O3), aluminum oxide (Al2O3) and magnesium oxide (MgO). We also constructed a MECA-like electrometer that contained an insulator capped planar electrode for measuring the amount of electrostatic charge produced by rubbing an insulator surface over Martian and lunar soil simulants. The results of this study indicate that it is possible to detect triboelectric charging of insulator surfaces by windborne Martian soil simulant, and by individual mineral constituents of the soil simulant. We have also found that Teflon and Fiberglass insulator surfaces respond in different ways by developing opposite polarity surface charge, which decays at different rates after the particle impacts cease.

Chemistry Notes

ERIC Educational Resources Information Center

School Science Review, 1976

1976-01-01

Describes several chemistry projects, including solubility, formula for magnesium oxide, dissociation of dinitrogen tetroxide, use of 1-chloro-2, 4-dinitrobenzene, migration of ions, heats of neutralizations, use of pocket calculators, sonic cleaning, oxidation states of manganese, and cell potentials. Includes an extract from Chemical Age on…

High Temperature Solar Reflector, Its Preparation and Use

NASA Technical Reports Server (NTRS)

Jaworske, Donald A. (Inventor)

1999-01-01

A coating-substrate combination having high specular reflectivity at high temperatures reaching 8000 C in a vacuum is described. The substrate comprises pure nickel metal or a nickel-containing metal alloy such as stainless steel having a highly polished reflective surface. The coating is a layer of silver deposited on the substrate to a thickness of 300 A to 3000 A. A 300 A to 5000 A protective coating of silica, alumina or magnesium fluoride is used to cover the silver and to protect it from oxidation. The combination is useful as a parabolic shaped secondary concentrator for collecting solar radiation for generating power or thermal energy for satellite uses. The reflective layer and protective coating preferably are applied to the reflective surface of the substrate by electron beam evaporation or by ion sputtering.

Effect of co-doping process on topography, optical and electrical properties of ZnO nanostructured

NASA Astrophysics Data System (ADS)

Mohamed, R.; Mamat, M. H.; Malek, M. F.; Ismail, A. S.; Yusoff, M. M.; Syamsir, S. A.; Khusaimi, Z.; Rusop, M.

2018-05-01

We investigated of Undoped ZnO and Magnesium (Mg)-Aluminium (Al) co-doped Zinc Oxide (MAZO) nanostructured films were prepared by sol gel spin coating technique. The surface topography was analyzed using Atomic Force Microscopy (AFM). Based on the AFM results, Root Mean Square (RMS) of MAZO films have rougher surface compared to pure ZnO films. The optical and electrical properties of thin film samples were characterized using Uv-Vis spectroscopy and two point probes, current-voltage (I-V) measurements. The transmittance spectra for both thin samples was above 80% in the visible wavelength. The MAZO film shows the highest conductivity compared to pure ZnO films. This result indicates that the improvement of carrier mobility throughout doping process and possibly contribute by extra ion charge.

Magnesium, zinc, and chromium levels in children, adolescents, and young adults with type 1 diabetes.

PubMed

Lin, Ching-Chiang; Tsweng, Guey-Ju; Lee, Cheng-Fa; Chen, Bai-Hsiun; Huang, Yeou-Lih

2016-08-01

Several trace elements are involved in insulin signal transduction and glucose metabolism. Our aim for this present study was to determine the levels of three important elements-magnesium, chromium, and zinc-as well as one oxidative stress marker-malondialdehyde (MDA)-in young type 1 diabetic patients at different periods of their growth, and to realize the relationships between trace elements, oxidative stress, and growth stages. A total of 88 patients with type 1 diabetes mellitus in different growth stages and 76 gender- and age-matched healthy subjects were included in this study. The levels of MDA were measured through HPLC using a C-18 column. Zinc, magnesium, and chromium concentrations in serum were assessed using atomic absorption spectrophotometry. We found higher levels of blood malondialdehyde (MDA; p < 0.001), significantly lower levels of magnesium (p < 0.001), and no differences in zinc and chromium levels (p = 0.153 and 0.515, respectively) in younger type 1 diabetic subjects relative to those of control subjects. Only 3.4% (3/88) of younger diabetic subjects exhibited hypomagnesemia; similar results were obtained when comparing different subgroups: children, adolescents, and adults. We also observed no differences in the levels of the three elements between the genders and among the growth stages (p > 0.05) of the diabetic subjects. There were no correlations between the three trace elements and HbA1C, diabetes duration, and insulin dose/BMI (all p > 0.05), but there was a significant difference between zinc levels and insulin dose/BMI (p = 0.043) in the diabetic patients. We found elevated blood MDA, decreased magnesium, and no changes in zinc and chromium levels in younger type 1 diabetic subjects relative to those of control subjects. Only 3.4% of younger diabetic subjects exhibited hypomagnesemia. Whether magnesium supplementation is suitable for improving insulin sensitivity and decreasing oxidative stress and inflammation will require confirmation through additional studies. Copyright © 2015 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.

Cardiac effects of magnesium sulfate pretreatment on acute dichlorvos-induced organophosphate poisoning: an experimental study in rats.

PubMed

Gunay, Nurullah; Kekec, Zeynep; Demiryurek, Seniz; Kose, Ataman; Namiduru, Emine S; Gunay, Nahide E; Sari, Ibrahim; Demiryurek, Abdullah T

2010-02-01

Although atropine and oximes are traditionally used in the management of organophosphate poisoning, investigations have been directed to finding additional therapeutic approaches. Thus, the aim of this study was to evaluate the cardiac effects of magnesium sulfate pretreatment on dichlorvos intoxication in rats. Rats were randomly divided into three groups as control, dichlorvos, and magnesium sulfate groups. After 6 h of dichlorvos or corn oil (as a vehicle) injection, venous blood samples were collected, and cardiac tissue samples were obtained. Biochemical analyses were performed to measure some parameters on serum and cardiac tissue. Immunohistochemical analyses of apoptosis and inducible nitric oxide (NO) synthase showed no change in cardiac tissue. Serum cholinesterase levels were markedly depressed with dichlorvos, and further suppressed markedly with magnesium sulfate pretreatment. Although we have demonstrated that serum NO levels in dichlorvos and magnesium sulfate groups were lower than the control group, cardiac tissue NO levels in magnesium sulfate group were higher than the other two groups. Mortality was not significantly affected with magnesium sulfate pretreatment. Uncertainty still persists on the right strategies for the treatment of organophosphate acute poisoning; however, it was concluded that our results do not suggest that magnesium sulfate therapy is beneficial in the management of acute dichlorvos-induced organophosphate poisoning, and also further studies are required.

Development of magnesium calcium phosphate biocement for bone regeneration.

PubMed

Jia, Junfeng; Zhou, Huanjun; Wei, Jie; Jiang, Xin; Hua, Hong; Chen, Fangping; Wei, Shicheng; Shin, Jung-Woog; Liu, Changsheng

2010-08-06

Magnesium calcium phosphate biocement (MCPB) with rapid-setting characteristics was fabricated by using the mixed powders of magnesium oxide (MgO) and calcium dihydrogen phosphate (Ca(H(2)PO(4))(2).H(2)O). The results revealed that the MCPB hardened after mixing the powders with water for about 7 min, and the compressive strength reached 43 MPa after setting for 1 h, indicating that the MCPB had a short setting time and high initial mechanical strength. After the acid-base reaction of MCPB containing MgO and Ca(H(2)PO(4))(2).H(2)O in a molar ratio of 2 : 1, the final hydrated products were Mg(3)(PO(4))(2) and Ca(3)(PO(4))(2). The MCPB was degradable in Tris-HCl solution and the degradation ratio was obviously higher than calcium phosphate biocement (CPB) because of its fast dissolution. The attachment and proliferation of the MG(63) cells on the MCPB were significantly enhanced in comparison with CPB, and the alkaline phosphatase activity of MG(63) cells on the MCPB was significantly higher than on the CPB at 7 and 14 days. The MG(63) cells with normal phenotype spread well on the MCPB surfaces, and were attached in close proximity to the substrate, as seen by scanning electron microscopy (SEM). The results demonstrated that the MCPB had a good ability to support cell attachment, proliferation and differentiation, and exhibited good cytocompatibility.

Co-administration of water containing magnesium ion prevents loxoprofen-induced lesions in gastric mucosa of adjuvant-induced arthritis rat.

PubMed

Nagai, Noriaki; Takeda, Atsushi; Itanami, Yuri; Ito, Yoshimasa

2012-01-01

Non-steroidal anti-inflammatory drugs (NSAIDs) comprise one of the most frequently used classes of medicines in the world; however, NSAIDs have significant side effects, such as gastroenteropathy, and rheumatoid arthritis patients taking NSAIDs are more susceptible to NSAID-induced gastric lesions as compared to patients with other diseases. In Asian countries, loxoprofen has been used clinically for many years as a standard NSAID. We demonstrate the preventive effect of the co-administration of water containing magnesium ion (magnesium water, 1-200 µg/kg) on the ulcerogenic response to loxoprofen in adjuvant-induced arthritis (AA) rats. Oral administration of loxoprofen (100 mg/kg) caused hemorrhagic lesions in the gastric mucosa of AA rats 14 d after adjuvant injection, and, following loxoprofen administration, the lesion score of AA rats was significantly higher than that of normal rats. The expression of inducible nitric oxide synthase (iNOS) mRNA and nitric oxide (NO) production in the gastric mucosa of AA rats were also increased by the administration of loxoprofen, and the increase in lesions and NO were prevented by the administration of aminoguanidine, an iNOS inhibitor. The co-administration of magnesium water decreased the ulcerogenic response to loxoprofen in AA rats. In addition, the co-administration of magnesium water attenuated the increase in iNOS mRNA expression and NO production in AA rats receiving loxoprofen. These results suggest that the oral co-administration of magnesium water to AA rats has a potent preventive effect on the ulcerogenic response to loxoprofen, probably by inhibiting the rise in iNOS and NO levels in the gastric mucosa.

Crucible cast from beryllium oxide and refractory cement is impervious to flux and molten metal

NASA Technical Reports Server (NTRS)

Jastrzebski, Z. D.

1966-01-01

Crucible from a mixture of a beryllium oxide aggregate and hydraulic refractory cement, and coated with an impervious refractory oxide will not deteriorate in the presence of fused salt- molten metal mixtures such as uranium- magnesium-zinc-halide salt systems. Vessels cast by this process are used in the flux reduction of oxides of thorium and uranium.

Ignition and Combustion of Bulk Metals in a Microgravity Environment

NASA Technical Reports Server (NTRS)

Branch, Melvyn C.; Daily, John W.; Abbud-Madrid, Angel

1999-01-01

Results of a study of heterogeneous and homogeneous combustion of metals in reduced gravity are presented. Cylindrical titanium and magnesium samples are radiatively ignited in pure-oxygen at 1 atm. Qualitative observations, propagation rates, and burning times are extracted from high-speed cinematography. Time-resolved emission spectra of gas-phase reactions are acquired with an imaging spectrograph. Lower propagation rates of the reacting mass on titanium and of ignition waves on magnesium are obtained at reduced gravity. These rates are compared to theoretical results from fire-spread analyses with a diffusion/convection controlled reaction. The close agreement found between experimental and theoretical propagation rates indicates the strong influence of natural-convection-enhanced oxygen transp6rt on burning rates. Lower oxygen flux and lack of condensed product removal appear to be responsible for longer burning times of magnesium gas-phase diffusion flames in reduced gravity. Spherically symmetric explosions in magnesium flames at reduced gravity (termed radiation-induced metal explosions, or RIME) may be driven by increased radiation heat transfer from accumulated condensed products to an evaporating metal core covered by a porous, flexible oxide coating. In titanium specimens, predominantly heterogeneous burning characterizes the initial steady propagation of the molten mass, while homogeneous gas-phase reactions are detected around particles ejected from the molten mixture. In magnesium specimens, band and line reversal of all the UV spectral systems of Mg and MgO are attributed to the interaction between small oxide particles and the principal gaseous emitters.

Laser Surface Alloying of Copper, Manganese, and Magnesium with Pure Aluminum Substrate

NASA Astrophysics Data System (ADS)

Jiru, Woldetinsay G.; Sankar, M. Ravi; Dixit, Uday S.

2016-03-01

Laser surface alloying is one of the recent technologies used in the manufacturing sector for improving the surface properties of the metals. Light weight materials like aluminum alloys, titanium alloys, and magnesium alloys are used in the locomotive, aerospace, and structural applications. In the present work, an experimental study was conducted to improve the surface hardness of commercially pure aluminum plate. CO2 laser is used to melt pre-placed powders of pure copper, manganese, and magnesium. Microstructure of alloyed surface was analyzed using optical microscope. The best surface alloying was obtained at the optimum values of laser parameters, viz., laser power, scan speed, and laser beam diameter. In the alloyed region, microhardness increased from 30 HV0.5 to 430 HV0.5, while it was 60 HV0.5 in the heat-affected region. Tensile tests revealed some reduction in the strength and total elongation due to alloying. On the other hand, corrosion resistance improved.

Removal of phosphate from eutrophic lakes through adsorption by in situ formation of magnesium hydroxide from diatomite.

PubMed

Xie, Fazhi; Wu, Fengchang; Liu, Guijian; Mu, Yunsong; Feng, Chenglian; Wang, Huanhua; Giesy, John P

2014-01-01

Since in situ formation of Mg(OH)2 can efficiently sorb phosphate (PO4) from low concentrations in the environment, a novel dispersed magnesium oxide nanoflake-modified diatomite adsorbent (MOD) was developed for use in restoration of eutrophic lakes by removal of excess PO4. Various adsorption conditions, such as pH, temperature and contact time were investigated. Overall, sorption capacities increased with increasing temperature and contact time, and decreased with increasing pH. Adsorption of PO4 was well described by both the Langmuir isotherm and pseudo second-order models. Theoretical maximum sorption capacity of MOD for PO4 was 44.44-52.08 mg/g at experimental conditions. Characterization of PO4 adsorbed to MOD by use of X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and solid state (31)P nuclear magnetic resonance revealed that electrostatic attraction, surface complexation and chemical conversion in situ were the major forces in adsorption of PO4. Mg(OH)2 formed in situ had a net positive charge on the surface of the MOD that could adsorb PO4(3-) and HPO4(2-) anion to form surface complex and gradually convert to Mg3(PO4)2 and MgHPO4. Efficiency of removal of PO4 was 90% when 300 mg MOD/L was added to eutrophic lake water. Results presented here demonstrated the potential use of the MOD for restoration of eutrophic lakes by removal of excess PO4.

Solid State Research, 1973:2.

DTIC Science & Technology

MERCURY COMPOUNDS, CADMIUM COMPOUNDS, TELLURIDES, NEODYMIUM COMPOUNDS, PHOSPHATES , ELECTRON TRANSITIONS, INFRARED OPTICAL MATERIALS, CRYSTAL GROWTH, MAGNESIUM OXIDES, PHOSPHORESCENT MATERIALS, SEMICONDUCTOR DIODES, MICROELECTRONICS

The role of magnesium as an adjuvant during general anaesthesia.

PubMed

Gupta, K; Vohra, V; Sood, J

2006-11-01

Magnesium sulphate is used extensively in the treatment of eclampsia, and is also used to treat refractory arrhythmias, asthma, myocardial ischaemia and acute respiratory failure. We studied the interaction between magnesium sulphate and the anaesthetic agents propofol, rocuronium bromide and fentanyl citrate. This randomised, double blind study was conducted in 50 patients. The magnesium group A (n = 25) received 30 mg x kg(-1) magnesium sulphate before induction of anaesthesia and 10 mg x kg(-1) continuously intra-operatively until the end of surgery. Group B (n = 25) received the same volume of isotonic saline. Propofol, rocuronium and fentanyl infusions were started and the patients lungs' were ventilated with 33% oxygen in nitrous oxide. Anaesthetic depth was maintained at a bispectral index value of between 40 and 60. Muscle relaxation was maintained at a train-of-four count of 1 throughout surgery using neuromuscular monitoring. The fentanyl infusion was titrated to haemodynamic variables: heart rate and blood pressure. We concluded that magnesium sulphate has anaesthetic, analgesic and muscle relaxation effects and significantly reduces the drug requirements of propofol, rocuronium and fentanyl during anaesthesia.

Preparation and characterization of magnesium borate for special glass

NASA Astrophysics Data System (ADS)

Dou, Lishuang; Zhong, Jianchu; Wang, Hongzhi

2010-05-01

Magnesium borate with a variety of B2O3/MgO molar ratios, which can be applied for special glass, has been prepared through the reaction of light-burned magnesia with boric acid by a hydrothermal method. The effects of the B2O3/MgO molar ratio of raw materials, reaction time, temperature and liquid to solid ratio (ml g-1) on the synthetic product are investigated. The XRD and TG-DTG analyses indicate that the prepared magnesium borate is a mixture of magnesium hexaborate hydrate and ascharite. The results show that high B2O3/MgO molar ratios of raw materials and low reaction liquid-solid ratios favour the product with a high B2O3/MgO molar ratio and vice versa. There exists free MgO in the product when the reaction temperature is below 140 °C or the reaction time is not enough, because of the incomplete reaction of magnesium oxide with boric acid. The process of fractional crystallization for the magnesium borate mixture is also discussed.

The Effect of Continuous Weathering on Light Metal Alloys Used in Aircraft

NASA Technical Reports Server (NTRS)

Mutchler, Willard

1939-01-01

An investigation of the corrosion of light metal alloys used in aircraft was begun at the National Bureau of Standards in 1925 and has for its purpose causes of corrosion in aluminum-rich and magnesium-rich alloys together with the development of methods for its prevention. The results, obtained in an extensive series of laboratory and weather-exposure tests, reveal the relative durability of a number of commercially available materials and the extent to which the application of various surface coatings of oxide alone and with paint coatings afforded additional protection. The paper may be considered as a supplement to NACA report 490.

Recovery of phosphate from aqueous solution by magnesium oxide decorated magnetic biochar and its potential as phosphate-based fertilizer substitute.

PubMed

Li, Ronghua; Wang, Jim J; Zhou, Baoyue; Awasthi, Mukesh Kumar; Ali, Amjad; Zhang, Zengqiang; Lahori, Altaf Hussain; Mahar, Amanullah

2016-09-01

The present study deals with the preparation of a novel MgO-impregnated magnetic biochar (MMSB) for phosphate recovery from aqueous solution. The MMSB was evaluated against sugarcane harvest residue biochar (SB) and magnetic biochar without Mg (MSB). The results showed that increasing Mg content in MMSB greatly improved the phosphate adsorption compared to SB and MSB, with 20% Mg-impregnated MMSB (20MMSB) recovering more than 99.5% phosphate from aqueous solution. Phosphate adsorption capacity of 20MMSB was 121.25mgP/g at pH 4 and only 37.53% of recovered phosphate was desorbed by 0.01mol/L HCl solutions. XRD and FTIR analysis showed that phosphate sorption mechanisms involved predominately with surface electrostatic attraction and precipitation with impregnated MgO and surface inner-sphere complexation with Fe oxide. The 20MMSB exhibited both maximum phosphate sorption and strong magnetic separation ability. Overall, phosphate-loaded 20MMSB significantly enhanced plant growth and could be used as a potential substitute for phosphate-based fertilizer. Copyright © 2016 Elsevier Ltd. All rights reserved.

Nano-Structured Magnesium Oxide Coated Iron Ore: Its Application to the Remediation of Wastewater Containing Lead.

PubMed

Nagarajah, Ranjini; Jang, Min; Pichiah, Saravanan; Cho, Jongman; Snyder, Shane A

2015-12-01

Magnetically separable nano-structured magnesium oxide coated iron ore (IO(MgO)) was prepared using environmentally benign chemicals, such as iron ore (IO), magnesium(II) nitrate hexahydrate [Mg(NO3)2 x 6H2O] and urea; via an easy and fast preparation method. The lO(MgO) was characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS) and alternating gradient magnetometer (AGM) analyses. The isotherm and kinetic studies indicated that lO(MgO) has a comparably higher Langmuir constant (K(L), 1.69 L mg(-1)) and maximum sorption capacity (33.9 mg g(-1)) for lead (Pb) than other inorganic media. Based on MgO amount, the removal capacity of Pb by IO(MgO) was 2,724 mg Pb (g MgO)(-1), which was higher than that (1,980 mg g(-1)) for flowerlike magnesium oxide nanostructures reported by Cao et al. The kinetics, FE-SEM, elemental mapping and XRD results revealed that the substitution followed by precipitation was identified as the mechanism of Pb removal and plumbophyllite (Pb2Si4O10 x H2O) was the precipitated phase of Pb. A leaching test revealed that IOMgO) had negligible concentrations of leached Fe at pH 4-9. Since the base material, IO, is cheap and easily available, lO(MgO) could be produced in massive amounts and used for remediation of wastewater containing heavy metals, applying simple and fast magnetic separation.

Magnesium Sulfate as a Key Mineral for the Detection of Organic Molecules on Mars Using Pyrolysis

NASA Technical Reports Server (NTRS)

Francois, P.; Szopa, C.; Buch, A.; Coll, P.; McAdam, A. C.; Mahaffy, P. R.; Freissinet, C.; Glavin, D. P.; Navarro-Gonzalez, R.; Cabane, M.

2016-01-01

Pyrolysis of soil or rock samples is the preferred preparation technique used on Mars to search for organic molecules up today. During pyrolysis, oxichlorines present in the soil of Mars release oxidant species that alter the organic molecules potentially contained in the samples collected by the space probes.This process can explain the difficulty experienced by in situ exploration probes to detect organic materials in Mars soil samples until recently. Within a few months, the Curiosity rover should reach and analyze for the first time soils rich in sulfates which could induce a different behavior of the organics during the pyrolysis compared with the types of soils analyzed up today. For this reason, we systematically studied the pyrolysis of organic molecules trapped in magnesium sulfate, in the presence or absence of calcium perchlorate. Our results show that organics trapped in magnesium sulfate can undergo some oxidation and sulfuration during the pyrolysis. But these sulfates are also shown to protect organics trapped inside the crystal lattice and/or present in fluid inclusions from the oxidation induced by the decomposition of calcium perchlorate and probably other oxychlorine phases currently detected on Mars. Trapped organics may also be protected from degradation processes induced by other minerals present in the sample, at least until these organics are released from the pyrolyzed sulfate mineral (700C in our experiment). Hence, we suggest magnesium sulfate as one of the minerals to target in priority for the search of organic molecules by the Curiosity and ExoMars 2018 rovers.

Therapeutic effect of magnesium sulphate on carbon monoxide toxicity-mediated brain lipid peroxidation.

PubMed

Yavuz, Y; Mollaoglu, H; Yürümez, Y; Ucok, K; Duran, L; Tünay, K; Akgün, L

2013-02-01

Carbon monoxide (CO) toxicity primarily results from cellular hypoxia caused by impedance of oxygen delivery. Studies show that CO may cause brain lipid peroxidation and leukocyte-mediated inflammatory changes in the brain. The aim of this study was to investigate whether magnesium sulphate could prevent or diminish brain lipid peroxidation caused by carbon monoxide toxicity in rats. Fourty rats were divided into five groups of 8 rats each. Group l was not received any agent during the experiment. Group 2 was inhaled CO gas followed by intraperitoneally normal saline 30 minutes (min) later. Group 3 was inhaled CO gas followed by 100 mg/kg magnesium sulphate intraperitoneally 30 min later. Group 2 and Group 3 rats was undergone laparotomy and craniotomy while still under anesthesia at 6 hour, and tissue sample was obtained from the cerebrum. Group 4 was inhaled CO gas followed by intraperitoneally normal saline 30 min later. Group 5 was inhaled CO gas followed by 100 mg/kg magnesium sulphate intraperitoneally 30 min later. Group 4 and Group 5 rats was undergone laparotomy and craniotomy while still under anesthesia at 24 hour, and tissue sample was obtained from the cerebrum. Nitric oxide levels were no significantly different between all groups. Malonyldialdehyde levels increased in intoxication group (group 2) and decreased in treatment group (group 3). Activities of superoxide dismutase decreased in intoxication group (group 2) and increased in treatment group (group 3). Activities of catalase increased in intoxication group (group 2) and decreased in treatment group (group 3). Activities of glutathione peroxidase (GSH-Px) decreased in intoxication group (group 4) and increased in treatment group (group 5). CO poisoning caused significant damage, detected within the first 6 hours. Due to antioxidant enzymes, especially GSH-Px activity reaching the top level within 24th hours, significant oxidative damage was not observed. The protective effect against oxidative damage of magnesium sulfate has been identified within the first 6 hours.

Inhibitory effect of phosphates on magnesium lactate efflorescence formation in dry-fermented sausages.

PubMed

Walz, Felix H; Gibis, Monika; Schrey, Pia; Herrmann, Kurt; Reichert, Corina L; Hinrichs, Jörg; Weiss, Jochen

2017-10-01

This study aimed to prevent the phenomena of efflorescence formation on the surface of dry fermented sausages due to the complexation of efflorescence forming cations with phosphates. Efflorescence formation is a critical issue constituting a major quality defect, especially of dry fermented sausages. Different phosphates (di- and hexametaphosphate) were added (3.0g/kg) to the sausage batter. As a hypothesis, these additives should complex with one of the main efflorescence-causing substances such as magnesium. The formation of efflorescences was determined for dry fermented sausages without phosphate addition, with diphosphate, or hexametaphosphate addition during 8weeks of storage under modified atmosphere. The visual analyses of the sausage surface revealed high amounts of efflorescences for the control (42.2%) and for the sausages with added diphosphate (40.9%), whereas the sausages containing hexametaphosphate had significantly reduced amounts of efflorescence formation, showing only 11.9% efflorescences after 8weeks of storage. This inhibition was a result of strong complexation of hexametaphosphate with magnesium ions, thus preventing the diffusion of magnesium towards the sausage surface. This can be explained by the magnesium content on the sausage surface that increased by 163.9, 127.8, and 52.8% for the sausages without phosphate, diphosphate, and hexametaphosphate addition, respectively. The mass transport of lactate and creatine was not affected by phosphate addition. Isothermal titration calorimetry confirmed that, theoretically, 4.5g/kg of diphosphate or 2.8g/kg hexametaphosphate are required to complex 0.2g/kg magnesium ions naturally occurring in dry fermented sausages and, thus, the chosen overall phosphate concentration of 3.0g/kg was enough when adding hexametaphosphate, but not for diphosphate, to inhibit the efflorescence formation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effect of surface roughness on the in vitro degradation behaviour of a biodegradable magnesium-based alloy

NASA Astrophysics Data System (ADS)

Walter, R.; Kannan, M. Bobby; He, Y.; Sandham, A.

2013-08-01

In this study, the in vitro degradation behaviour of AZ91 magnesium alloy with two different surface finishes was investigated using electrochemical impedance spectroscopy (EIS) in simulated body fluid (SBF). The polarisation resistance (Rp) of the rough surface alloy immersed in SBF for 3 h was ~30% lower as compared to that of the smooth surface alloy. After 12 h immersion in SBF, the Rp values for both the surface finishes decreased and were also similar. However, localised degradation occurred sooner, and to a noticeably higher severity in the rough surface alloy as compared to the smooth surface alloy.

Mechanism of the anticataract effect of liposomal magnesium taurate in galactose-fed rats

PubMed Central

Iezhitsa, Igor; Saad, Sarah Diyana Bt; Zakaria, Fatin Kamilah Bt; Agarwal, Puneet; Krasilnikova, Anna; Rahman, Thuhairah Hasrah Abdul; Rozali, Khairul Nizam Bin; Spasov, Alexander; Ozerov, Alexander; Alyautdin, Renad; Ismail, Nafeeza Mohd

2016-01-01

Purpose Increased lenticular oxidative stress and altered calcium/magnesium (Ca/Mg) homeostasis underlie cataractogenesis. We developed a liposomal formulation of magnesium taurate (MgT) and studied its effects on Ca/Mg homeostasis and lenticular oxidative and nitrosative stress in galactose-fed rats. Methods The galactose-fed rats were topically treated with liposomal MgT (LMgT), liposomal taurine (LTau), or corresponding vehicles twice daily for 28 days with weekly anterior segment imaging. At the end of the experimental period, the lenses were removed and subjected to analysis for oxidative and nitrosative stress, Ca and Mg levels, ATP content, Ca2+-ATPase, Na+,K+-ATPase, and calpain II activities. Results The LTau and LMgT groups showed significantly lower opacity index values at all time points compared to the corresponding vehicle groups (p<0.001). However, the opacity index in the LMgT group was lower than that in the LTau group (p<0.05). Significantly reduced oxidative and nitrosative stress was observed in the LTau and LMgT groups. The lens Ca/Mg ratio in LMgT group was decreased by 1.15 times compared to that in the LVh group. Calpain II activity in the LMgT group was decreased by 13% compared to the LVh group. The ATP level and Na+,K+-ATPase and Ca2+-ATPase activities were significantly increased in the LMgT group compared to the LVh group (p<0.05). Conclusions Topical liposomal MgT delays cataractogenesis in galactose-fed rats by maintaining the lens mineral homeostasis and reducing lenticular oxidative and nitrosative stress. PMID:27440992

Evolution processes of the corrosion behavior and structural characteristics of plasma electrolytic oxidation coatings on AZ31 magnesium alloy

NASA Astrophysics Data System (ADS)

Chen, Dong; Wang, Ruiqiang; Huang, Zhiquan; Wu, Yekang; Zhang, Yi; Wu, Guorui; Li, Dalong; Guo, Changhong; Jiang, Guirong; Yu, Shengxue; Shen, Dejiu; Nash, Philip

2018-03-01

Evolution processes of the corrosion behavior and structural characteristics of the plasma electrolytic oxidation (PEO) coated AZ31 magnesium alloy were investigated by using scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), potentio-dynamic polarization curves and electrochemical impedance spectroscopy (EIS) measurements. Detached coating samples were fabricated by an electrochemical method and more details of the internal micro-structure of coatings were clearly observed on the fractured cross-section morphologies of the samples compared to general polished cross-section morphologies. Evolution mechanisms of the coating corrosion behavior in relation to the evolution of micro-structural characteristics were discussed in detail.

Cardiovascular and intestinal responses to oxidative and nitrosative stress during prolonged magnesium deficiency.

PubMed

Weglicki, William B; Chmielinska, Joanna J; Kramer, Jay H; Mak, I Tong

2011-08-01

In rodents with dietary magnesium deficiency (Mg deficiency), hypomagnesemia, occurs leading to a rise in circulating substance P from neuronal tissues to trigger systemic inflammatory stress in cardiac and intestinal tissues. Sustained elevations of substance P may result from impaired neutral endopeptidase (NEP) activity due to reactive oxygen and reactive nitrogen species. Associated increase in intestinal permeability includes infiltration of WBC and endotoxemia, which can further amplify the systemic inflammatory response that leads to impaired contractile function associated with up-regulation of the cardiac CD14 endotoxin receptor. The neurogenic signal transduction pathways that we have identified in the pro-oxidant/pro-inflammatory processes found with prolonged hypomagnesemia are described in this report.

Thermoelectric Properties of Hot-Pressed and PECS-Sintered Magnesium-Doped Copper Aluminum Oxide

NASA Astrophysics Data System (ADS)

Liu, Chang; Morelli, Donald T.

2011-05-01

Copper aluminum oxide (CuAlO2) is considered as a potential candidate for thermoelectric applications. Partially magnesium-doped CuAlO2 bulk pellets were fabricated using solid-state reactions, hot-pressing, and pulsed electric current sintering (PECS) techniques. X-ray diffraction and scanning electron microscopy were adopted for structural analysis. High-temperature transport property measurements were performed on hot-pressed samples. Electrical conductivity increased with Mg doping before secondary phases became significant, while the Seebeck coefficient displayed the opposite trend. Thermal conductivity was consistently reduced as the Mg concentration increased. Effects of Mg doping, preparation conditions, and future modification on this material's properties are discussed.

Study of Some Dielectric Properties of Suspensions of Magnesium Particles in Mineral Oil

NASA Technical Reports Server (NTRS)

Altshuller, Aubrey P

1954-01-01

The variation of dielectric constant has been measured as a function of the concentration of magnesium particles; the shape, size, and degree of oxidation of the particles; the temperature; and the frequency of oscillation. The variation of dielectric constant and settling rate was investigated as a function of time. Also investigated were the effects of particle concentration, shape and time on dielectric losses.

REFRACTORY DIE FOR EXTRUDING URANIUM

DOEpatents

Creutz, E.C.

1959-08-11

A die is presented for the extrusion of metals, said die being formed of a refractory complex oxide having the composition M/sub n/O/sub m/R/sub x/O/sub y/ where M is magnesium, zinc, manganese, or iron, R is aluminum, chromic chromium, ferric iron, or manganic manganese, and m, n, x, and y are whole numbers. Specific examples are spinel, magnesium aluminate, magnetite, magnesioferrite, chromite, and franklinite.

Hydrophilic Graphene Preparation from Gallic Acid Modified Graphene Oxide in Magnesium Self-Propagating High Temperature Synthesis Process

NASA Astrophysics Data System (ADS)

Cao, Lei; Li, Zhenhuan; Su, Kunmei; Cheng, Bowen

2016-10-01

Hydrophilic graphene sheets were synthesized from a mixture of magnesium and gallic acid (GA) modified graphene oxide (GO) in a self-propagating high-temperature synthesis (SHS) process, and hydrophilic graphene sheets displayed the higher C/O ratio (16.36), outstanding conductivity (~88900 S/m) and excellent water-solubility. GO sheets were connected together by GA, and GA was captured to darn GO structure defects through the formation of hydrogen bonds and ester bonds. In SHS process, the most oxygen ions of GO reacted with magnesium to prevent the escape of carbon dioxide and carbon monoxide to from the structure defects associated with vacancies, and GA could take place the high-temperature carbonization, during which a large-area graphene sheets formed with a part of the structure defects being repaired. When only GO was reduced by magnesium in SHS process, and the reduced GO (rGO) exhibited the smaller sheets, the lower C/O ratio (15.26), the weaker conductivity (4200 S/m) and the poor water-solubility because rGO inevitably left behind carbon vacancies and topological defects. Therefore, the larger sheet, less edge defects and free structure defects associated with vacancies play a key role for graphene sheets good dispersion in water.

Effect of Melt Temperature on Surface Films Formed on Molten AZ91D Alloy Protected by Graphite Powder

NASA Astrophysics Data System (ADS)

Li, Weihong; Zhou, Jixue; Ma, Baichang; Wang, Jinwei; Wu, Jianhua; Yang, Yuansheng

2017-12-01

Graphite powder was adopted to prevent AZ91D alloy from oxidizing during melting and casting. The microstructure of the resultant surface films, formed at 933 K, 973 K, 1013 K, and 1053 K (660 °C, 700 °C, 740 °C, and 780 °C) for 30 minutes, was investigated by scanning electron microscopy, energy dispersive spectrometer, and X-ray diffraction, and the phase composition of the surface films was analyzed by the standard Gibbs free energy change of the reactions between the graphite powder, the alloy melt, and the ambient atmosphere. The effect and mechanism of melt temperature on the resultant surface films were also discussed. The results indicated that the surface films, of which the surface morphology comprised folds and wrinkles, were composed of a protective layer and MgF2 particles. The protective layer was contributive to the prevention of the molten alloy from oxidizing, and consisted of magnesium, oxygen, fluorine, carbon, and a small amount of aluminium existing in the form of MgO, MgF2, C, and MgAl2O4. The layer thickness was 200 to 900 nm. The melt temperature may affect the surface films through the increased interaction between the graphite powder, the melt, and the ambient atmosphere. The oxygen content and thickness of the protective layer decreased and then increased, while the height of the folds increased with melt temperature.

Formation of a hydrophobic and corrosion resistant coating on magnesium alloy via a one-step hydrothermal method.

PubMed

Zheng, Tianxu; Hu, Yaobo; Zhang, Yuxin; Pan, Fusheng

2017-11-01

A hydrophobic coating was fabricated on the surface of magnesium alloy using a simple one-step hydrothermal method with the use of environmentally friendly agent. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and contact angle test were used to characterize the surfaces. Corrosion behavior in a 3.5wt.% NaCl solution was evaluated using OCP time curves test, potentiodynamic polarization test and EIS analysis. The findings show that the substrate is covered by the coating of magnesium hydroxide and magnesium stearate, reaching a contact angle of around 146°. Corrosion behavior show huge improvement, the progress with increase of treatment time could be related to the increased growth rate of coating. Copyright © 2017 Elsevier Inc. All rights reserved.

Concrete with steel furnace slag and fractionated reclaimed asphalt pavement.

DOT National Transportation Integrated Search

2014-09-01

Steel furnace slag (SFS) is an industrial by-product material that can contain free calcium oxide (CaO) and free magnesium oxide (MgO), both : of which can cause significant expansion when hydrated. SFS aggregates are therefore not commonly used in c...

Comparative study on the biodegradation and biocompatibility of silicate bioceramic coatings on biodegradable magnesium alloy as biodegradable biomaterial

NASA Astrophysics Data System (ADS)

Razavi, M.; Fathi, M. H.; Savabi, O.; Razavi, S. M.; Hashemibeni, B.; Yazdimamaghani, M.; Vashaee, D.; Tayebi, L.

2014-03-01

Many clinical cases as well as in vivo and in vitro assessments have demonstrated that magnesium alloys possess good biocompatibility. Unfortunately, magnesium and its alloys degrade too quickly in physiological media. In order to improve the biodegradation resistance and biocompatibility of a biodegradable magnesium alloy, we have prepared three types of coating include diopside (CaMgSi2O6), akermanite (Ca2MgSi2O6) and bredigite (Ca7MgSi4O16) coating on AZ91 magnesium alloy through a micro-arc oxidation (MAO) and electrophoretic deposition (EPD) method. In this research, the biodegradation and biocompatibility behavior of samples were evaluated in vitro and in vivo. The in vitro analysis was performed by cytocompatibility and MTT-assay and the in vivo test was conducted on the implantation of samples in the greater trochanter of adult rabbits. The results showed that diopside coating has the best bone regeneration and bredigite has the best biodegradation resistance compared to others.

Rapid recovery from major depression using magnesium treatment.

PubMed

Eby, George A; Eby, Karen L

2006-01-01

Major depression is a mood disorder characterized by a sense of inadequacy, despondency, decreased activity, pessimism, anhedonia and sadness where these symptoms severely disrupt and adversely affect the person's life, sometimes to such an extent that suicide is attempted or results. Antidepressant drugs are not always effective and some have been accused of causing an increased number of suicides particularly in young people. Magnesium deficiency is well known to produce neuropathologies. Only 16% of the magnesium found in whole wheat remains in refined flour, and magnesium has been removed from most drinking water supplies, setting a stage for human magnesium deficiency. Magnesium ions regulate calcium ion flow in neuronal calcium channels, helping to regulate neuronal nitric oxide production. In magnesium deficiency, neuronal requirements for magnesium may not be met, causing neuronal damage which could manifest as depression. Magnesium treatment is hypothesized to be effective in treating major depression resulting from intraneuronal magnesium deficits. These magnesium ion neuronal deficits may be induced by stress hormones, excessive dietary calcium as well as dietary deficiencies of magnesium. Case histories are presented showing rapid recovery (less than 7 days) from major depression using 125-300 mg of magnesium (as glycinate and taurinate) with each meal and at bedtime. Magnesium was found usually effective for treatment of depression in general use. Related and accompanying mental illnesses in these case histories including traumatic brain injury, headache, suicidal ideation, anxiety, irritability, insomnia, postpartum depression, cocaine, alcohol and tobacco abuse, hypersensitivity to calcium, short-term memory loss and IQ loss were also benefited. Dietary deficiencies of magnesium, coupled with excess calcium and stress may cause many cases of other related symptoms including agitation, anxiety, irritability, confusion, asthenia, sleeplessness, headache, delirium, hallucinations and hyperexcitability, with each of these having been previously documented. The possibility that magnesium deficiency is the cause of most major depression and related mental health problems including IQ loss and addiction is enormously important to public health and is recommended for immediate further study. Fortifying refined grain and drinking water with biologically available magnesium to pre-twentieth century levels is recommended.

A new powder production route for transparent spinel windows: powder synthesis and window properties

NASA Astrophysics Data System (ADS)

Cook, Ronald; Kochis, Michael; Reimanis, Ivar; Kleebe, Hans-Joachim

2005-05-01

Spinel powders for the production of transparent polycrystalline ceramic windows have been produced using a number of traditional ceramic and sol-gel methods. We have demonstrated that magnesium aluminate spinel powders produced from the reaction of organo-magnesium compounds with surface modified boehmite precursors can be used to produce high quality transparent spinel parts. The new powder production method allows fine control over the starting particle size, size distribution, purity and stoichiometry. The new process involves formation of a boehmite sol-gel from the hydrolysis of aluminum alkoxides followed by surface modification of the boehmite nanoparticles using carboxylic acids. The resulting surface modified boehmite nanoparticles can then be metal exchanged at room temperature with magnesium acetylacetonate to make a precursor powder that is readily transformed into pure phase spinel.

Efficacy of a simethicone, activated charcoal and magnesium oxide combination (Carbosymag®) in functional dyspepsia: results of a general practice-based randomized trial.

PubMed

Coffin, Benoit; Bortolloti, Claude; Bourgeois, Odile; Denicourt, Luc

2011-06-01

A simethicone, activated charcoal and magnesium oxide combination (Carbosymag(®)) has been used for almost 20 years in functional dyspepsia, but there is limited scientific evidence of efficacy. We evaluated the efficacy of Carbosymag(®) in 18- to 49-year-old patients with functional dyspepsia. A total of 276 dyspeptic patients consulting a general practitioner and meeting the Rome III criteria were included in this prospective placebo-controlled study. Variations in overall and individual dyspeptic symptoms were evaluated after 1 month of treatment. At the end of the treatment period, overall dyspeptic symptom intensity was significantly lower in the Carbosymag(®) group (P=0.01). The intensity of post-prandial fullness, epigastric pain, epigastric burning and abdominal bloating was significantly reduced in the Carbosymag(®) group relative to the placebo group (P<0.05). The number need to treat to induce a 70-% decrease in overall dyspeptic symptoms by Carbosymag(®) was 7 (IC 95%: 4-32). A simethicone, activated charcoal and magnesium oxide combination (Carbosymag(®)) was significantly more effective than a placebo on overall symptom intensity in dyspeptic patients consulting a general practitioner. Copyright © 2011 Elsevier Masson SAS. All rights reserved.

A case of osteomalacia due to deranged mineral balance caused by saccharated ferric oxide and short-bowel syndrome

PubMed Central

Nomoto, Hiroshi; Miyoshi, Hideaki; Nakamura, Akinobu; Nagai, So; Kitao, Naoyuki; Shimizu, Chikara; Atsumi, Tatsuya

2017-01-01

Abstract Rationale: Saccharated ferric oxide has been shown to lead to elevation of fibroblast growth factor 23, hypophosphatemia, and, consequently, osteomalacia. Moreover, mineral imbalance is often observed in patients with short-bowel syndrome to some degree. Patient concerns: A 62-year-old woman with short-bowel syndrome related with multiple resections of small intestines due to Crohn disease received regular intravenous administration of saccharated ferric oxide. Over the course of treatment, she was diagnosed with tetany, which was attributed to hypocalcemia. Additional assessments of the patient revealed not only hypocalcemia, but also hypophosphatemia, hypomagnesemia, osteomalacia, and a high concentration of fibroblast growth factor 23 (314 pg/mL). Diagnoses: We diagnosed her with mineral imbalance-induced osteomalacia due to saccharated ferric oxide and short-bowel syndrome. Interventions: Magnesium replacement therapy and discontinuation of saccharated ferric oxide alone. Outcomes: These treatments were able to normalize her serum mineral levels and increase her bone mineral density. Lessons: This case suggests that adequate evaluation of serum minerals, including phosphate and magnesium, during saccharated ferric oxide administration may be necessary, especially in patients with short-bowel syndrome. PMID:28953654

Method and product for phosphosilicate slurry for use in dentistry and related bone cements

DOEpatents

Wagh, Arun S.; Primus, Carolyn

2006-08-01

The present invention is directed to magnesium phosphate ceramics and their methods of manufacture. The composition of the invention is produced by combining a mixture of a substantially dry powder component with a liquid component. The substantially dry powder component comprises a sparsely soluble oxide powder, an alkali metal phosphate powder, a sparsely soluble silicate powder, with the balance of the substantially dry powder component comprising at least one powder selected from the group consisting of bioactive powders, biocompatible powders, fluorescent powders, fluoride releasing powders, and radiopaque powders. The liquid component comprises a pH modifying agent, a monovalent alkali metal phosphate in aqueous solution, the balance of the liquid component being water. The use of calcined magnesium oxide as the oxide powder and hydroxylapatite as the bioactive powder produces a self-setting ceramic that is particularly suited for use in dental and orthopedic applications.

Influence of defect luminescence and structural modification on the electrical properties of Magnesium Doped Zinc Oxide Nanorods

NASA Astrophysics Data System (ADS)

Santoshkumar, B.; Biswas, Amrita; Kalyanaraman, S.; Thangavel, R.; Udayabhanu, G.; Annadurai, G.; Velumani, S.

2017-06-01

Magnesium doped zinc oxide nanorod arrays on zinc oxide seed layers were grown by hydrothermal method. X-ray diffraction (XRD) patterns revealed the growth orientation along the preferential (002) direction. The hexagonal morphology was revealed from the field emission scanning electron microscope (FESEM) images. The elemental composition of the samples was confirmed by energy dispersive x-ray analysis spectra (EDS) and mapping dots. Carrier concentration, resistivity and mobility of the samples were obtained by Hall measurements. I-V characteristic curve confirmed the increase in resistivity upon doping. Photoluminescence (PL) spectra exposed the characteristic of UV emission along with defect mediated visible emission in the samples. Electrochemical impedance spectroscopy and cyclic voltammetry were undertaken to study the charge transport property. Owing to the change in the structural parameters and defect concentration the electrical properties of the doped samples were altered.

Charge induced enhancement of adsorption for hydrogen storage materials

NASA Astrophysics Data System (ADS)

Sun, Xiang

2009-12-01

The rising concerns about environmental pollution and global warming have facilitated research interest in hydrogen energy as an alternative energy source. To apply hydrogen for transportations, several issues have to be solved, within which hydrogen storage is the most critical problem. Lots of materials and devices have been developed; however, none is able to meet the DOE storage target. The primary issue for hydrogen physisorption is a weak interaction between hydrogen and the surface of solid materials, resulting negligible adsorption at room temperature. To solve this issue, there is a need to increase the interaction between the hydrogen molecules and adsorbent surface. In this study, intrinsic electric dipole is investigated to enhance the adsorption energy. The results from the computer simulation of single ionic compounds with hydrogen molecules to form hydrogen clusters showed that electrical charge of substances plays an important role in generation of attractive interaction with hydrogen molecules. In order to further examine the effects of static interaction on hydrogen adsorption, activated carbon with a large surface area was impregnated with various ionic salts including LiCl, NaCl, KCl, KBr, and NiCl2 and their performance for hydrogen storage was evaluated by using a volumetric method. Corresponding computer simulations have been carried out by using DFT (Density Functional Theory) method combined with point charge arrays. Both experimental and computational results prove that the adsorption capacity of hydrogen and its interaction with the solid materials increased with electrical dipole moment. Besides the intrinsic dipole, an externally applied electric field could be another means to enhance hydrogen adsorption. Hydrogen adsorption under an applied electric field was examined by using porous nickel foil as electrodes. Electrical signals showed that adsorption capacity increased with the increasing of gas pressure and external electric voltage. Direct measurement of the amount of hydrogen adsorption was also carried out with porous nickel oxides and magnesium oxides using the piezoelectric material PMN-PT as the charge supplier due to the pressure. The adsorption enhancement from the PMN-PT generated charges is obvious at hydrogen pressure between 0 and 60 bars, where the hydrogen uptake is increased at about 35% for nickel oxide and 25% for magnesium oxide. Computer simulation reveals that under the external electric field, the electron cloud of hydrogen molecules is pulled over to the adsorbent site and can overlap with the adsorbent electrons, which in turn enhances the adsorption energy. Experiments were also carried out to examine the effects of hydrogen spillover with charge induced enhancement. The results show that the overall storage capacity in nickel oxide increased remarkably by a factor of 4.

Synthesis of magnesium aluminate spinel by periclase and alumina chlorination

DOE Office of Scientific and Technical Information (OSTI.GOV)

Orosco, Pablo, E-mail: porosco@unsl.edu.ar; Facultad de Química, Bioquímica y Farmacia, Universidad Nacional de San Luis Chacabuco y Pedernera, San Luis; Barbosa, Lucía

2014-11-15

Highlights: • Use of chlorination for the synthesis of magnesium aluminate spinel. • The reagents used were alumina, periclase and chlorine. • Isothermal and non-isothermal assays were performed in air and Cl{sub 2}–N{sub 2} flows. • The chlorination produced magnesium aluminate spinel at 700 °C. • Selectivity of the chlorination reaction to obtain spinel is very high. - Abstract: A pyrometallurgical route for the synthesis of magnesium aluminate spinel by thermal treatment of a mechanical mixture containing 29 wt% MgO (periclase) and 71 wt% Al{sub 2}O{sub 3} (alumina) in chlorine atmosphere was developed and the results were compared with thosemore » obtained by calcining the same mixture of oxides in air atmosphere. Isothermal and non-isothermal assays were performed in an experimental piece of equipment adapted to work in corrosive atmospheres. Both reagents and products were analyzed by differential thermal analysis (DTA), X-ray diffraction (XRD) and X-ray fluorescence (XRF). Thermal treatment in Cl{sub 2} atmosphere of the MgO–Al{sub 2}O{sub 3} mixture produces magnesium aluminate spinel at 700 °C, while in air, magnesium spinel is generated at 930 °C. The synthesis reaction of magnesium aluminate spinel was complete at 800 °C.« less

Magnesium-containing mixed coatings on zirconia for dental implants: mechanical characterization and in vitro behavior.

PubMed

Pardun, Karoline; Treccani, Laura; Volkmann, Eike; Streckbein, Philipp; Heiss, Christian; Gerlach, Juergen W; Maendl, Stephan; Rezwan, Kurosch

2015-07-01

An important challenge in the field of dental and orthopedic implantology is the preparation of implant coatings with bioactive functions that feature a high mechanical stability and at the same time mimic structural and compositional properties of native bone for a better bone ingrowth. This study investigates the influence of magnesium addition to zirconia-calcium phosphate coatings. The mixed coatings were prepared with varying additions of either magnesium oxide or magnesium fluoride to yttria-stabilized zirconia and hydroxyapatite. The coatings were deposited on zirconia discs and screw implants by wet powder spraying. Microstructure studies confirm a porous coating with similar roughness and firm adhesion not hampered by the coating composition. The coating morphology, mechanical flexural strength and calcium dissolution showed a magnesium content-dependent effect. Moreover, the in vitro results obtained with human osteoblasts reveal an improved biological performance caused by the presence of Mg(2+) ions. The magnesium-containing coatings exhibited better cell proliferation and differentiation in comparison to pure zirconia-calcium phosphate coatings. In conclusion, these results demonstrate that magnesium addition increases the bioactivity potential of zirconia-calcium phosphate coatings and is thus a highly suitable candidate for bone implant coatings. © The Author(s) 2015 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

Hyperfine Interactions in the Electron Paramagnetic Resonance Spectra of Point Defects in Wide-Band-Gap Semiconductors

DTIC Science & Technology

2014-09-18

compensation) during growth due to their preferred trivalent charge states. The electron paramagnetic resonance spectrum of the singly ionized chromium ...neutral nitrogen acceptor in ZnO . . . . . . . . . . . . . . . . . . 45 16 Spectrum of the singly ionized chromium acceptor in TiO2 . . . . . . . . . 49...is a single crystal of magnesium oxide that has been doped with chromium . Chromium Cr3+ substitutes for magnesium Mg2+ and creates a paramagnetic

Magnesium Nanoparticles for Hydrogen Storage: Structure, Kinetics and Thermodynamics

NASA Astrophysics Data System (ADS)

Pasquini, L.; Brighi, M.; Montone, A.; Vittori Antisari, M.; Dam, B.; Palmisano, V.; Bonetti, E.

2012-08-01

Magnesium nanoparticles coated by a native oxide shell and decorated by palladium clusters were synthesized by the inert gas condensation technique. The kinetics and thermodynamics of hydrogen sorption were investigated by Sieverts measurements at high temperature and by optical hydrogenography close to ambient temperature. The structure and morphology of the nanoparticles were studied by electron microscopy and X-ray diffraction both in the as-prepared state and after hydrogen sorption cycles.

Magnesiothermic conversion of the silica-mineralizing golden algae Mallomonas caudata and Synura petersenii to elemental silicon with high geometric precision

PubMed Central

Petrack, Janina; Jost, Steffen; Boenigk, Jens

2014-01-01

Summary Chrysophyceae, also known as golden algae, contain characteristic, three-dimensional biomineralized silica structures. Their chemical composition and microscopic structure was studied. By high-temperature conversion of the skeleton of Mallomonas caudata and Synura petersenii into elementary silicon by magnesium vapour, nanostructured defined replicates were produced which were clearly seen after removal of the formed magnesium oxide with acid. PMID:24991491

Laser surface modification of Ti and TiC coatings on magnesium alloy

NASA Astrophysics Data System (ADS)

Kim, J. M.; Lee, S. G.; Park, J. S.; Kim, H. G.

2014-12-01

In order to enhance the surface properties of magnesium alloy, a highly intense laser surface melting process following plasma spraying of Ti or TiC on AZ31 alloy were employed. When laser surface melting was applied to Ti coated magnesium alloy, the formation of fine Ti particle dispersed surface layer on the substrate occurred. The corrosion potential of the AZ31 alloy with Ti dispersed surface was significantly increased in 3.5 wt % NaCl solution. Additionally, an improved hardness was observed for the laser treated specimens as compared to the untreated AZ31 alloy. Laser melting process following plasma thermal deposition was also applied for obtaining in situ TiC coating layer on AZ31 alloy. The TiC coating layer could be successfully formed via in situ reaction between pure titanium and carbon powders. Incomplete TiC formation was observed in the plasma sprayed specimen, while completely transformed TiC layer was found after post laser melting process. It was also confirmed that the laser post treatment induced enhanced adhesion strength between the coating and the substrate.

Controlling corrosion rate of Magnesium alloy using powder mixed electrical discharge machining

NASA Astrophysics Data System (ADS)

Razak, M. A.; Rani, A. M. A.; Saad, N. M.; Littlefair, G.; Aliyu, A. A.

2018-04-01

Biomedical implant can be divided into permanent and temporary employment. The duration of a temporary implant applied to children and adult is different due to different bone healing rate among the children and adult. Magnesium and its alloys are compatible for the biodegradable implanting application. Nevertheless, it is difficult to control the degradation rate of magnesium alloy to suit the application on both the children and adult. Powder mixed electrical discharge machining (PM-EDM) method, a modified EDM process, has high capability to improve the EDM process efficiency and machined surface quality. The objective of this paper is to establish a formula to control the degradation rate of magnesium alloy using the PM-EDM method. The different corrosion rate of machined surface is hypothesized to be obtained by having different combinations of PM-EDM operation inputs. PM-EDM experiments are conducted using an opened-loop PM-EDM system and the in-vitro corrosion tests are carried out on the machined surface of each specimen. There are four operation inputs investigated in this study which are zinc powder concentration, peak current, pulse on-time and pulse off-time. The results indicate that zinc powder concentration is significantly affecting the response with 2 g/l of zinc powder concentration obtaining the lowest corrosion rate. The high localized temperature at the cutting zone in spark erosion process causes some of the zinc particles get deposited on the machined surface, hence improving the surface characteristics. The suspended zinc particles in the dielectric fluid have also improve the sparking efficiency and the uniformity of sparks distribution. From the statistical analysis, a formula was developed to control the corrosion rate of magnesium alloy within the range from 0.000183 mm/year to 0.001528 mm/year.

Thermal-Mechanical Stability of Single Crystal Oxide Refractive Concentrators for High-Temperature Solar Thermal Propulsion

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Jacobson, Nathan S.; Miller, Robert A.

1999-01-01

Single crystal oxides such as yttria-stabilized zirconia (Y2O3-ZrO2), yttrium aluminum garnet (Y3Al5O12, or YAG), magnesium oxide (MgO) and sapphire (Al2O3) are candidate refractive secondary concentrator materials for high temperature solar propulsion applications. However, thermo-mechanical reliability of these components in severe thermal environments during the space mission sun/shade transition is of great concern. Simulated mission tests are important for evaluating these candidate oxide materials under a variety of transient and steady-state heat flux conditions, and thus provide vital information for the component design. In this paper, a controlled heat flux thermal shock test approach is established for the single crystal oxide materials using a 3.0 kW continuous wave CO2 laser, with a wavelength 10.6 micron. Thermal fracture behavior and failure mechanisms of these oxide materials are investigated and critical temperature gradients are determined under various temperature and heating conditions. The test results show that single crystal sapphire is able to sustain the highest temperature gradient and heating-cooling rate, and thus exhibit the best thermal shock resistance, as compared to the yttria-stabilized zirconia, yttrium aluminum garnet and magnesium oxide.

Thermal-Mechanical Stability of Single Crystal Oxide Refractive Concentrators for High-Temperature Solar Thermal Propulsion

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Jacobson, Nathan S.; Miller, Robert A.

1999-01-01

Single crystal oxides such as yttria-stabilized zirconia (Y2O3-ZrO2), yttrium aluminum garnet (Y3Al5O12, or YAG), magnesium oxide (MgO) and sapphire (Al2O3) are candidate refractive secondary concentrator materials for high temperature solar propulsion applications. However, thermo-mechanical reliability of these components in severe thermal environments during the space mission sun/shade transition is of great concern. Simulated mission tests are important for evaluating these candidate oxide materials under a variety of transient and steady-state heat flux conditions, and thus provide vital information for the component design. In this paper, a controlled heat flux thermal shock test approach is established for the single crystal oxide materials using a 3.0 kW continuous wave CO2 laser, with a wavelength 10.6 micron. Thermal fracture behavior and failure mechanisms of these oxide materials are investigated and critical temperature gradients are determined under various temperature and heating conditions. The test results show that single crystal sapphire is able to sustain the highest temperature gradient and heating-cooling rate, and thus exhibit the best thermal shock resistance, as compared to the yttria-stabilized zirconia, yttrium aluminum garnet, and magnesium oxide.

Degradation of Adenine on the Martian Surface in the Presence of Perchlorates and Ionizing Radiation: A Reflectron Time-of-flight Mass Spectrometric Study

NASA Astrophysics Data System (ADS)

Góbi, Sándor; Bergantini, Alexandre; Kaiser, Ralf I.

2017-04-01

The aim of the present work is to unravel the radiolytic decomposition of adenine (C5H5N5) under conditions relevant to the Martian surface. Being the fundamental building block of (deoxy)ribonucleic acids, the possibility of survival of this biomolecule on the Martian surface is of primary importance to the astrobiology community. Here, neat adenine and adenine-magnesium perchlorate mixtures were prepared and irradiated with energetic electrons that simulate the secondary electrons originating from the interaction of the galactic cosmic rays with the Martian surface. Perchlorates were added to the samples since they are abundant—and therefore relevant oxidizers on the surface of Mars—and they have been previously shown to facilitate the radiolysis of organics such as glycine. The degradation of the samples were monitored in situ via Fourier transformation infrared spectroscopy and the electron ionization quadruple mass spectrometric method; temperature-programmed desorption profiles were then collected by means of the state-of-the-art single photon photoionization reflectron time-of-flight mass spectrometry (PI-ReTOF-MS), allowing for the detection of the species subliming from the sample. The results showed that perchlorates do increase the destruction rate of adenine by opening alternative reaction channels, including the concurrent radiolysis/oxidation of the sample. This new pathway provides a plethora of different radiolysis products that were identified for the first time. These are carbon dioxide (CO2), isocyanic acid (HNCO), isocyanate (OCN-), carbon monoxide (CO), and nitrogen monoxide (NO); an oxidation product containing carbonyl groups (R1R2-C=O) with a constrained five-membered cyclic structure could also be observed. Cyanamide (H2N-C≡N) was detected in both irradiated samples as well.

Magnetic multi-metal co-doped magnesium ferrite nanoparticles: An efficient visible light-assisted heterogeneous Fenton-like catalyst synthesized from saprolite laterite ore.

PubMed

Diao, Yifei; Yan, Zhikai; Guo, Min; Wang, Xidong

2018-02-15

Magnetic nanoparticles of multi-metal co-doped magnesium ferrite (MgFe 2 O 4 ) were synthesized from saprolite laterite ore by a hydrothermal method, and firstly proposed as a heterogeneous photon-Fenton-like catalyst for degradation of Rhodamine B (RhB). The factors that influence the degradation reaction including pH value, the concentration of H 2 O 2 and the amount of catalyst, were systematically investigated. The doped MgFe 2 O 4 exhibited a degradation efficiency up to 96.8%, and the chemical oxygen demand (COD) and total organic carbon (TOC) removal efficiencies about 85.6% and 68.3%, respectively, under visible light illumination for 180min. The high activity is mainly attributed to the high specific surface area of the catalyst and the synergistic interaction between photo-catalytic oxidation and Fenton-like oxidation. Moreover, the catalyst also showed good stability and recycling performance for degrading RhB. After five consecutive degradation cycles, the activity decayed no more than 10%. Compared to other catalysts prepared from pure chemical agents, the multi-metal co-doped MgFe 2 O 4 is more competitive due to its high activity, good stability, ease of recollection, and especially the use of saprolite laterite ore as precursor. This work may provide a new avenue to synthesize efficient ferrite catalysts for degrading organic pollutants in wastewater by using natural minerals. Copyright © 2017 Elsevier B.V. All rights reserved.

Effects of Coating Materials and Processing Conditions on Flow Enhancement of Cohesive Acetaminophen Powders by High-Shear Processing With Pharmaceutical Lubricants.

PubMed

Wei, Guoguang; Mangal, Sharad; Denman, John; Gengenbach, Thomas; Lee Bonar, Kevin; Khan, Rubayat I; Qu, Li; Li, Tonglei; Zhou, Qi Tony

2017-10-01

This study has investigated the surface coating efficiency and powder flow improvement of a model cohesive acetaminophen powder by high-shear processing with pharmaceutical lubricants through 2 common equipment, conical comil and high-shear mixer. Effects of coating materials and processing parameters on powder flow and surface coating coverage were evaluated. Both Carr's index and shear cell data indicated that processing with the lubricants using comil or high-shear mixer substantially improved the flow of the cohesive acetaminophen powder. Flow improvement was most pronounced for those processed with 1% wt/wt magnesium stearate, from "cohesive" for the V-blended sample to "easy flowing" for the optimally coated sample. Qualitative and quantitative characterizations demonstrated a greater degree of surface coverage for high-shear mixing compared with comilling; nevertheless, flow properties of the samples at the corresponding optimized conditions were comparable between 2 techniques. Scanning electron microscopy images demonstrated different coating mechanisms with magnesium stearate or l-leucine (magnesium stearate forms a coating layer and leucine coating increases surface roughness). Furthermore, surface coating with hydrophobic magnesium stearate did not retard the dissolution kinetics of acetaminophen. Future studies are warranted to evaluate tableting behavior of such dry-coated pharmaceutical powders. Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Preparation of Calcium Carbonate (from Shellfish)/Magnesium Oxide Composites as an Antibacterial Agent

NASA Astrophysics Data System (ADS)

Jannah, Z.; Mubarok, H.; Syamsiyah, F.; Putri, A. A. H.; Rohmawati, L.

2018-05-01

We have performed research on antibacterial substance from a natural substance, one of them is calcite from shellfish (Anadara granosa) in Kenjeran Beach Surabaya. This calcite is composed of magnesium oxide using PEG 4000 (Polyethylene glycol) as a solvent and then heated at 800 °C for 30 minutes. Weight variety of calcite used was 80% wt, 85% wt, and 90 wt%. Subsequently, that composites characterized using XRD, antibacterial activity test (Escherichia coli and Staphylococcus aureus), and SEM. The result of antibacterial assay shows that composite of CaCO3/MgO with 80% wt composition have the best activity inhibitory of 31,96 mm for Escherichia coli bacteria and 32.26 mm for Staphylococcus aureus bacteria.

Glancing-angle-deposited magnesium oxide films for high-fluence applications

DOE PAGES

Oliver, J. B.; Smith, C.; Spaulding, J.; ...

2016-06-15

Here, Birefringent magnesium oxide thin films are formed by glancing angle deposition to perform as quarter-wave plates at a wavelength of 351 nm. These films are being developed to fabricate a large aperture distributed-polarization rotator for use in vacuum, with an ultimate laser-damage–threshold goal of up to 12 J/cm 2 for a 5-ns flat-in-time pulse. The laser-damage threshold, ease of deposition, and optical film properties are evaluated. While the measured large-area laser-damage threshold is limited to ~4 J/cm 2 in vacuum, initial results based on small-spot testing in air (>20 J/cm 2) suggest MgO may be suitable with further processmore » development.« less

Method of preparing porous, rigid ceramic separators for an electrochemical cell

DOEpatents

Bandyopadhyay, Gautam; Dusek, Joseph T.

1981-01-01

Porous, rigid separators for electrochemical cells are prepared by first calcining particles of ceramic material at temperatures above about 1200.degree. C. for a sufficient period of time to reduce the sinterability of the particles. A ceramic powder that has not been calcined is blended with the original powder to control the porosity of the completed separator. The ceramic blend is then pressed into a sheet of the desired shape and sintered at a temperature somewhat lower than the calcination temperature. Separator sheets of about 1 to 2.5 mm thickness and 30 to 70% porosity can be prepared by this technique. Ceramics such as yttria, magnesium oxide and magnesium-aluminum oxide have advantageously been used to form separators by this method.

Biosynthesis and characterization of zinc, magnesium and titanium nanoparticles: an eco-friendly approach

NASA Astrophysics Data System (ADS)

Raliya, Ramesh; Tarafdar, J. C.

2014-02-01

In the present study, zinc (Zn), magnesium (Mg) and titanium (Ti) nanoparticles synthesized using fungus by employing various precursor salts of sulfate salts, nitrate salts, chloride salts and oxide salts. To access the nanoparticle production potential, over a hundreds of fungi were isolated from the soil and tested with precursor salts of the Zn, Mg and Ti. Out of which, only 14 fungal isolates were identified, having potential to reduce metal salt into metal nanoparticles. Upon molecular identification, six were identified as Aspergillus flavus, two each as Aspergillus terreus and Aspergillus tubingensis and one each as Aspergillus niger, Rhizoctonia bataticola, Aspergillus fumigatus, and Aspergillus oryzae. Factors responsible for more production of monodispersed Zn, Mg and Ti nanoparticles were optimized. It was concluded that 0.01 mM precursor salt concentration, 72 h of incubation at pH 5.5 and temperature 28 °C resulted smaller nanoparticles obtained. The biosynthesized functional Zn and Ti nanoparticles can be stored up to 90 days and Mg nanoparticles up to 105 days in its nanoform. Bio-transformed products were analyzed using valid characterization technique i.e. dynamic light scattering, transmission electron microscopy, atomic force microscopy, energy dispersive X-ray spectroscopy to confirm size, shape, surface morphology and elemental composition. It was found that the average size of developed nano Zn was 8.2 nm, with surface charge of -5.70 mV and 98 % particles were of Zn metal only. Similarly, the average size of Mg nanoparticles was 6.4 nm with surface charge of -6.66 and 97.4 % Mg metal yield, whereas, Ti nanoparticles size were found in the ranges between 1.5 and 30 nm with surface charge of -6.25 mV and 98.6 % Ti metal yield.

Composite polymer-containing coatings on Mg alloys perspective for industry and implant surgery

NASA Astrophysics Data System (ADS)

Gnedenkov, S. V.; Sinebryukhov, S. L.; Mashtalyar, D. V.; Imshinetskiy, I. M.; Gnedenkov, A. S.; Minaev, A. N.

2017-09-01

In order to improve the corrosion resistance of magnesium alloys the ways of composite protective coating formation were developed by means of plasma electrolytic oxidation (PEO) as well as electrophoretic deposition methods. Electrochemical, corrosion, tribological, and morphological properties of the MAS magnesium alloy composite coatings were studied. The composite polymer-containing coating decrease the corrosion current density values by three orders of magnitude (Ic = 2.0 . 10-10 A/cm2), in comparison with the base PEO-layer. These polymer-containing layers enable one to expand the practical usage area of Mg alloys. The application of such coatings provides the increasing the bioactivity and regulate the corrosion rate of resorbable magnesium implants.

Sol-gel preparation of lead magnesium niobate (PMN) powders and thin films

DOEpatents

Boyle, T.J.

1999-01-12

A method of preparing a lead magnesium niobium oxide (PMN), Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}, precursor solution by a solvent method wherein a liquid solution of a lead-complex PMN precursor is combined with a liquid solution of a niobium-complex PMN precursor, the combined lead- and niobium-complex liquid solutions are reacted with a magnesium-alkyl solution, forming a PMN precursor solution and a lead-based precipitate, and the precipitate is separated from the reacted liquid PMN precursor solution to form a precipitate-free PMN precursor solution. This precursor solution can be processed to form both ferroelectric powders and thin films. 3 figs.

Sol-Gel Preparation Of Lead Magnesium Ni Obate (Pmn) Powdersand Thin Films

DOEpatents

Boyle, Timothy J.

1999-01-12

A method of preparing a lead magnesium niobium oxide (PMN), Pb(Mg.sub.1/3 Nb.sub.2/3)O.sub.3, precursor solution by a solvent method wherein a liquid solution of a lead-complex PMN precursor is combined with a liquid solution of a niobium-complex PMN precursor, the combined lead- and niobium-complex liquid solutions are reacted with a magnesium-alkyl solution, forming a PMN precursor solution and a lead-based precipitate, and the precipitate is separated from the reacted liquid PMN precursor solution to form a precipitate-free PMN precursor solution. This precursor solution can be processed to form both ferroelectric powders and thin films.

Shot peening influence on corrosion resistance of AE21 magnesium alloy.

DOT National Transportation Integrated Search

2010-12-15

"Evaluation of the electrochemical characteristics of the AE21 magnesium alloy is presented in the article. : The surfaces of tested alloys were treated by grinding and grinding followed by sodium bicarbonate shotpeening. : The specimens were evaluat...

Direct Observation of Charge Transfer at a MgO(111) Surface

NASA Astrophysics Data System (ADS)

Subramanian, A.; Marks, L. D.; Warschkow, O.; Ellis, D. E.

2004-01-01

Transmission electron diffraction (TED) combined with direct methods have been used to study the √(3)×√(3)R30° reconstruction on the polar (111) surface of MgO and refine the valence charge distribution. The surface is nonstoichiometric and is terminated by a single magnesium atom. A charge-compensating electron hole is localized in the next oxygen layer and there is a nominal charge transfer from the oxygen atoms to the top magnesium atom. The partial charges that we obtain for the surface atoms are in reasonable agreement with empirical bond-valence estimations.

Superconducting magnesium diboride films with Tc≈24 K grown by pulsed laser deposition with in situ anneal

NASA Astrophysics Data System (ADS)

Christen, H. M.; Zhai, H. Y.; Cantoni, C.; Paranthaman, M.; Sales, B. C.; Rouleau, C.; Norton, D. P.; Christen, D. K.; Lowndes, D. H.

2001-05-01

Thin superconducting films of magnesium diboride (MgB 2) with T c≈24 K were prepared on various oxide substrates by pulsed laser deposition followed by an in situ anneal. A systematic study of the influence of various in situ annealing parameters shows an optimum temperature of about 600°C in a background of 0.7 atm of Ar/4%H 2 for layers consisting of a mixture of magnesium and boron. Contrary to ex situ approaches (e.g. reacting boron films with magnesium vapor at ≈900°C), these films are processed at a temperature at which MgB 2 does not decompose rapidly even in vacuum. This may prove enabling in the formation of multilayers, junctions, and epitaxial films in future work. Issues related to the improvement of these films and to the possible in situ growth of MgB 2 at elevated temperature are discussed.

MESSENGER observations of Mercury's exosphere: detection of magnesium and distribution of constituents.

PubMed

McClintock, William E; Vervack, Ronald J; Bradley, E Todd; Killen, Rosemary M; Mouawad, Nelly; Sprague, Ann L; Burger, Matthew H; Solomon, Sean C; Izenberg, Noam R

2009-05-01

Mercury is surrounded by a tenuous exosphere that is supplied primarily by the planet's surface materials and is known to contain sodium, potassium, and calcium. Observations by the Mercury Atmospheric and Surface Composition Spectrometer during MESSENGER's second Mercury flyby revealed the presence of neutral magnesium in the tail (anti-sunward) region of the exosphere, as well as differing spatial distributions of magnesium, calcium, and sodium atoms in both the tail and the nightside, near-planet exosphere. Analysis of these observations, supplemented by observations during the first Mercury flyby, as well as those by other MESSENGER instruments, suggests that the distinct spatial distributions arise from a combination of differences in source, transfer, and loss processes.

Enhanced cell attachment and hemocompatibility of titanium by nanoscale surface modification through severe plastic integration of magnesium-rich islands and porosification.

PubMed

Rezaei, Masoud; Tamjid, Elnaz; Dinari, Ali

2017-10-11

Besides the wide applications of titanium and its alloys for orthopedic and biomedical implants, the biocompatible nature of titanium has emerged various surface modification techniques to enhance its bioactivity and osteointegration with living tissues. In this work, we present a new procedure for nanoscale surface modification of titanium implants by integration of magnesium-rich islands combined with controlled formation of pores and refinement of the surface grain structure. Through severe plastic deformation of the titanium surface with fine magnesium hydride powder, Mg-rich islands with varying sizes ranging from 100 nm to 1000 nm can be integrated inside a thin surface layer (100-500 µm) of the implant. Selective etching of the surface forms a fine structure of surface pores which their average size varies in the range of 200-500 nm depending on the processing condition. In vitro biocompatibility and hemocompatibility assays show that the Mg-rich islands and the induced surface pores significantly enhance cell attachment and biocompatibility without an adverse effect on the cell viability. Therefore, severe plastic integration of Mg-rich islands on titanium surface accompanying with porosification is a new and promising procedure with high potential for nanoscale modification of biomedical implants.

Formation of Microcracks During Micro-Arc Oxidation in a Phytic Acid-Containing Solution on Two-Phase AZ91HP

NASA Astrophysics Data System (ADS)

Zhang, R. F.; Chang, W. H.; Jiang, L. F.; Qu, B.; Zhang, S. F.; Qiao, L. P.; Xiang, J. H.

2016-04-01

Micro-arc oxidation (MAO) is an effective method to produce ceramic coatings on magnesium alloys and can considerably improve their corrosion resistance. The coating properties are closely related with microcracks, which are always inevitably developed on the coating surface. In order to find out the formation and development regularity of microcracks, anodic coatings developed on two-phase AZ91HP after different anodizing times were fabricated in a solution containing environmentally friendly organic electrolyte phytic acid. The results show that anodic film is initially developed on the α phase. At 50 s, anodic coatings begin to develop on the β phase, evidencing the formation of a rough area. Due to the coating successive development, the microcracks initially appear at the boundary between the initially formed coating on the α phase and the subsequently developed coating on the β phase. With the prolonging treatment time, the microcracks near the β phase become evident. After treating for 3 min, the originally rough area on the β phase disappears and the coatings become almost uniform with microcracks randomly distributed on the sample surface. Inorganic phosphates are found in MAO coatings, suggesting that phytate salts are decomposed due to the high instantaneous temperature on the sample surface resulted from spark discharge.

Effect of temperature on the anodizing process of aluminum alloy AA 5052

NASA Astrophysics Data System (ADS)

Theohari, S.; Kontogeorgou, Ch.

2013-11-01

The effect of temperature (10-40 °C) during the anodizing process of AA 5052 for 40 min in 175 g/L sulfuric acid solution at constant voltage (15 V) was studied in comparison with pure aluminum. The incorporated magnesium species in the barrier layer result in the further increase of the minimum current density passed during anodizing, as the temperature increases, by about 42% up to 30 °C and then by 12% up to 40 °C. Then during the anodizing process for 40 min a blocking effect on oxide film growth was gradually observed as the temperature increased until 30 °C. The results of EDAX analysis on thick films reveal that the mean amount of the magnesium species inside the film is about 50-70% less than that in the bulk alloy, while it is higher at certain locations adjacent to the film surface at 30 °C. The increase of anodizing temperature does not influence the porosity of thin films (formed for short times) on pure aluminum, while it reduces it on the alloy. At 40 °C the above mentioned blocking effects disappear. It means that the presence of magnesium species causes an impediment to the effect of temperature on iss, on the film thickness and on the porosity of thin films, only under conditions where film growth takes place without significant loss of the anodizing charge to side reactions.

Biodegradable metals for cardiovascular stents: from clinical concerns to recent Zn - alloys

PubMed Central

Bowen, Patrick K.; Shearier, Emily R.; Zhao, Shan; Guillory, Roger J.; Zhao, Feng; Goldman, Jeremy; Drelich, Jaroslaw W.

2016-01-01

Metallic stents are commonly used to promote revascularization and maintain patency of plaqued or damaged arteries following balloon angioplasty. To mitigate the long-term side effects associated with corrosion-resistant stents (i.e. chronic inflammation and late stage thrombosis), a new generation of so-called “bioabsorbable” stents is currently being developed. The bioabsorbable coronary stents will corrode and be absorbed by the artery after completing their task as vascular scaffolding. Research spanning the last two decades has focused on biodegradable polymeric, iron-based, and magnesium-based stent materials. The inherent mechanical and surface properties of metals make them more attractive stent material candidates than their polymeric counterparts. Unfortunately, iron produces a voluminous, retained oxide product in the arterial wall, whereas magnesium and its alloys corrode too rapidly. A third class of metallic bioabsorbable materials that are based on zinc has been introduced in the last few years. As summarized in this contribution, this new zinc-based class of materials demonstrates the potential for an absorbable metallic stent with the mechanical and biodegradation characteristics required for optimal stent performance. They appear to be free of flaws that limit the application of iron- and magnesium-based alloys, and polymers. This review compares bioabsorbable materials and summarizes progress towards bioabsorbable stents. It emphasizes on current understanding of physiological and biological benefits of zinc and its biocompatibility. Finally, the review provides an outlook on challenges in designing zinc-based stents of optimal mechanical properties and biodegradation rate. PMID:27094868

Effect of sorbent attrition on utilization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Keener, T.C.; Khang, S.J.; Lee, S.K.

1992-10-01

During this period, the project has focused on two aspects of attrition; (1) mechanical attrition which is responsible for particle fracture whenever particles are moving with respect to a fixed reference frame, and (2) chemical attrition which can be responsible for particle fracture whenever particles undergo reactions. The experiments were conducted with calcium based sorbent materials. Two specific project objectives were identified and studied. The first of these was to determine the effect of temperature, particle velocity, and particle surface area on the extent of attrition in a circulating fluidized reactor. The second was to investigate if attrition could improvemore » sorbent utilization of typical calcium based sorbents of small size (<20 [mu]m). A sample of sulfated calcium hydroxide sorbent was obtained for attrition tests in a circulating fluidized bed reactor. Attempts at attriting this material in the fluidized bed were not successful, and no improvements in sorbent utilization were measured in subsequent TGA tests with the solids. However, an analysis of the other constituents in the particles revealed that a major portion of the hydroxide had been converted to calcium carbonate. This gave rise to the possibility that dolomitic hydroxide may have characteristics which may be beneficial and that improvements in utilization could be realized by means of chemical attrition. This is due to the thermal instability of magnesium carbonate at temperatures above 650[degree]F which means that magnesium oxide will be the major unreacted magnesium species in spent sorbent.« less

Effect of sorbent attrition on utilization. Final report, August 1, 1991--August 31, 1992

DOE Office of Scientific and Technical Information (OSTI.GOV)

Keener, T.C.; Khang, S.J.; Lee, S.K.

1992-10-01

During this period, the project has focused on two aspects of attrition; (1) mechanical attrition which is responsible for particle fracture whenever particles are moving with respect to a fixed reference frame, and (2) chemical attrition which can be responsible for particle fracture whenever particles undergo reactions. The experiments were conducted with calcium based sorbent materials. Two specific project objectives were identified and studied. The first of these was to determine the effect of temperature, particle velocity, and particle surface area on the extent of attrition in a circulating fluidized reactor. The second was to investigate if attrition could improvemore » sorbent utilization of typical calcium based sorbents of small size (<20 {mu}m). A sample of sulfated calcium hydroxide sorbent was obtained for attrition tests in a circulating fluidized bed reactor. Attempts at attriting this material in the fluidized bed were not successful, and no improvements in sorbent utilization were measured in subsequent TGA tests with the solids. However, an analysis of the other constituents in the particles revealed that a major portion of the hydroxide had been converted to calcium carbonate. This gave rise to the possibility that dolomitic hydroxide may have characteristics which may be beneficial and that improvements in utilization could be realized by means of chemical attrition. This is due to the thermal instability of magnesium carbonate at temperatures above 650{degree}F which means that magnesium oxide will be the major unreacted magnesium species in spent sorbent.« less

Lunar and Planetary Science XXXV: Weird Martian Minerals: Complex Mars Surface Processes

NASA Technical Reports Server (NTRS)

2004-01-01

The session "Complex Mars Surface" included the following reports:A Reappraisal of Adsorbed Superoxide Ion as the Cause Behind the Reactivity of the Martian Soils; Sub-Surface Deposits of Hydrous Silicates or Hydrated Magnesium Sulfates as Hydrogen Reservoirs near the Martian Equator: Plausible or Not?; Thermal and Evolved Gas Analysis of Smectites: The Search for Water on Mars; Aqueous Alteration Pathways for K, Th, and U on Mars; Temperature Dependence of the Moessbauer Fraction in Mars-Analog Minerals; Acid-Sulfate Vapor Reactions with Basaltic Tephra: An Analog for Martian Surface Processes; Iron Oxide Weathering in Sulfuric Acid: Implications for Mars; P/Fe as an Aquamarker for Mars; Stable Isotope Composition of Carbonates Formed in Low-Temperature Terrestrial Environments as Martian Analogs; Can the Phosphate Sorption and Occlusion Properties Help to Elucidate the Genesis of Specular Hematite on the Mars Surface?; Sulfate Salts, Regolith Interactions, and Water Storage in Equatorial Martian Regolith; Potential Pathways to Maghemite in Mars Soils: The Key Role of Phosphate; and Mineralogy, Abundance, and Hydration State of Sulfates and Chlorides at the Mars Pathfinder Landing Site.

78 FR 12763 - Pediatric Advisory Committee; Notice of Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2013-02-25

... [Immune Globulin Subcutaneous (Human), 20% Liquid], INOMAX (nitric oxide), INVEGA (paliperidone), KEDBUMIN... (moxifloxacin ophthalmic solution 0.5%), NATROBA (spinosad), NEXIUM (esomeprazole magnesium), NEXIUM IV...

An investigation into the impact of magnesium stearate on powder feeding during roller compaction.

PubMed

Dawes, Jason; Gamble, John F; Greenwood, Richard; Robbins, Phil; Tobyn, Mike

2012-01-01

A systematic evaluation on the effect of magnesium stearate on the transmission of a placebo formulation from the hopper to the rolls during screw fed roller compaction has been carried out. It is demonstrated that, for a system with two 'knurled' rollers, addition of 0.5% w/w magnesium stearate can lead to a significant increase in ribbon mass throughput, with a consequential increase in roll gap, compared to an unlubricated formulation (manufactured at equivalent process conditions). However, this effect is reduced if one of the rollers is smooth. Roller compaction of a lubricated formulation using two smooth rollers was found to be ineffective due to a reduction in friction at the powder/roll interface, i.e. powder was not drawn through the rollers leading to a blockage in the feeding system. An increase in ribbon mass throughput could also be achieved if the equipment surfaces were pre-lubricated. However this increase was found to be temporary suggesting that the residual magnesium stearate layer was removed from the equipment surfaces. Powder sticking to the equipment surfaces, which is common during pharmaceutical manufacturing, was prevented if magnesium stearate was present either in the blend, or at the roll surface. It is further demonstrated that the influence of the hopper stirrer, which is primarily used to prevent bridge formation in the hopper and help draw powder more evenly into the auger chamber, can lead to further mixing of the formulation, and could therefore affect a change in the lubricity of the carefully blended input material.

Effect of low additives of calcium on corrosion resistance of alloys of the Mg - Al - Zn - Mn system

NASA Astrophysics Data System (ADS)

Koltygin, A. V.; Bazlova, T. A.

2012-03-01

The effect of calcium (0.2 - 0.5 wt.%) on the resistance of a liquid and solid magnesium alloy to oxidation is investigated. It is shown that calcium may be used as a microalloying additive raising the corrosion resistance of magnesium alloys not only at a high temperature but also at the operating temperature of parts produced from them for both cast and heat treated conditions.

A Double-Blind Randomized Placebo Controlled Trial of Magnesium Oxide for Alleviation of Chronic Low Back Pain

DTIC Science & Technology

1999-10-01

analgesics has also been extensively researched. Miranda and Paeile (1989) reported a minireview of the interactions between calcium channel blockers and...1990). Interactions between analgesics and calcium channel blockers. General Pharmacology, 21, 171-174. Peikert, A., Wilimzig, C., & Kohne-Volland, R...important actions of magnesium that relates to this study is the regulation of calcium access into the cell and the actions of calcium inside the cell

Nitrogen recovery from a stabilized municipal landfill leachate.

PubMed

Di Iaconi, Claudio; Pagano, Michele; Ramadori, Roberto; Lopez, Antonio

2010-03-01

The present paper reports the results of an investigation aimed at evaluating the effectiveness of magnesium ammonium phosphate precipitation (MAP), commonly called struvite, for removing ammonia from a mature municipal landfill leachate. MAP precipitation was carried out at laboratory scale by adding phosphoric acid and magnesium oxide as external sources of phosphorus and magnesium, respectively, and regulating the pH at 9.0. The effect of Mg:NH(4):PO(3) ratio was studied. Due to the low solubility of MgO, a low ammonia removal efficiency (i.e. 67%), with a rather high residual concentration, was obtained when the stoichiometric molar ratio was applied. However, by doubling the amount of magnesium oxide (i.e. by using a molar ratio of 2:1:1), ammonia removal efficiency increased up to 95% with a residual concentration compatible with a successive biological treatment. The struvite produced in the present study showed a composition close to the theoretical one. Furthermore, the precipitate was characterized by a heavy metal content much lower than that of typical raw soil, excluding any concern about heavy metal contamination in the case of its use as a fertilizer. The economic analysis of the process showed that ammonia can be removed at a cost of 9.6 euro/kg NH(4)-N(removed). This value can be greatly reduced, however, if the value of the struvite produced is considered. Copyright (c) 2009 Elsevier Ltd. All rights reserved.

Heated Hydro-Mechanical Deep Drawing of Magnesium Sheet Metal

NASA Astrophysics Data System (ADS)

Kurz, Gerrit

In order to reduce fuel consumption efforts have been made to decrease the weight of automobile constructions by increasing the use of lightweight materials. In this field of application magnesium alloys are important because of their low density. A promising alternative to large surfaced and thin die casting parts has been found in construction parts that are manufactured by sheet metal forming of magnesium. Magnesium alloys show a limited formability at room temperature. A considerable improvement of formability can be achieved by heating the material. Formability increases above a temperature of approximately T = 225 °C.

Method for cleaning bomb-reduced uranium derbies

DOEpatents

Banker, John G.; Wigginton, Hubert L.; Beck, David E.; Holcombe, Cressie E.

1981-01-01

The concentration of carbon in uranium metal ingots induction cast from derbies prepared by the bomb-reduction of uranium tetrafluoride in the presence of magnesium is effectively reduced to less than 100 ppm by removing residual magnesium fluoride from the surface of the derbies prior to casting. This magnesium fluoride is removed from the derbies by immersing them in an alkali metal salt bath which reacts with and decomposes the magnesium fluoride. A water quenching operation followed by a warm nitric acid bath and a water rinse removes the residual salt and reaction products from the derbies.

Method for cleaning bomb-reduced uranium derbies

DOEpatents

Banker, J.G.; Wigginton, H.L.; Beck, D.E.; Holcombe, C.E.

The concentration of carbon in uranium metal ingots induction cast from derbies prepared by the bomb-reduction of uranium tetrafluoride in the presence of magnesium is effectively reduced to less than 100 ppM by removing residual magnesium fluoride from the surface of the derbies prior to casting. This magnesium fluoride is removed from the derbies by immersing them in an alkali metal salt bath which reacts with and decomposes the magnesium fluoride. A water quenching operation followed by a warm nitric acid bath and a water rinse removes the residual salt and reaction products from the derbies.

A combination of genistein and magnesium enhances the vasodilatory effect via an eNOS pathway and BK(Ca) current amplification.

PubMed

Sun, Lina; Hou, Yunlong; Zhao, Tingting; Zhou, Shanshan; Wang, Xiaoran; Zhang, Liming; Yu, Guichun

2015-04-01

The phytoestrogen genistein (GST) and magnesium have been independently shown to regulate vascular tone; however, their individual vasodilatory effects are limited. The aim of this study was to examine the combined effects of GST plus magnesium on vascular tone in mesenteric arteries. The effects of pretreatment with GST (0-200 μmol/L), MgCl2 (0-4.8 mmol/L) and GST plus MgCl2 on 10 μmol/L phenylephrine (PE) precontracted mesenteric arteries in rats were assessed by measuring isometric force. BK(Ca) currents were detected by the patch clamp method. GST caused concentration- and partial endothelium-dependent relaxation. Magnesium resulted in dual adjustment of vascular tone. Magnesium-free solution eliminated the vasodilatation of GST in both endothelium-intact and denuded rings. GST (50 μmol/L) plus magnesium (4.8 mmol/L) caused stronger relaxation in both endothelium-intact and denuded rings. Pretreatment with the nitric oxide synthase (NOS) inhibitor L-N-nitroarginine methyl ester (L-NAME, 100 μmol/L) significantly inhibited the effects of GST, high magnesium, and the combination of GST and magnesium. BK(Ca) currents were amplified to a greater extent when GST (50 μmol/L) was combined with 4.8 versus 1.2 mmol/L Mg(2+). Our data suggest that GST plus magnesium provides enhanced vasodilatory effects in rat mesenteric arteries compared with that observed when either is used separately, which was related to an eNOS pathway and BK(Ca) current amplification.

Magnesium-Aluminum-Zirconium Oxide Amorphous Ternary Composite: A Dense and Stable Optical Coating

NASA Technical Reports Server (NTRS)

Sahoo, N. K.; Shapiro, A. P.

1998-01-01

In the present work, the process parameter dependent optical and structural properties of MgO-Al(2)O(3)-ZrO(2) ternary mixed-composite material have been investigated. Optical properties were derived from spectrophotometric measurements. The surface morphology, grain size distributions, crystallographic phases and process dependent material composition of films have been investigated through the use of Atomic Force Microscopy (AFM), X-ray diffraction analysis and Energy Dispersive X- ray (EDX) analysis. EDX analysis made evident the correlation between the optical constants and the process dependent compositions in the films. It is possible to achieve environmentally stable amorphous films with high packing density under certain optimized process conditions.

Recycling of aluminium scrap for secondary Al-Si alloys.

PubMed

Velasco, Eulogio; Nino, Jose

2011-07-01

An increasing amount of recycled aluminium is going into the production of aluminium alloy used for automotive applications. In these applications, it is necessary to control and remove alloy impurities and inclusions. Cleaning and fluxing processes are widely used during processing of the alloys for removal of inclusions, hydrogen and excess of magnesium. These processes use salt fluxes based in the system NaCl-KCl, injection of chlorine or mixture of chlorine with an inert gas. The new systems include a graphite wand and a circulation device to force convection in the melt and permit the bubbling and dispersion of reactive and cleaning agents. This paper discusses the recycling of aluminium alloys in rotary and reverberatory industrial furnaces. It focuses on the removal of magnesium during the melting process. In rotary furnaces, the magnesium lost is mainly due to the oxidation process at high temperatures. The magnesium removal is carried out by the reaction between chlorine and magnesium, with its efficiency associated to kinetic factors such as concentration of magnesium, mixing, and temperature. These factors are also related to emissions generated during the demagging process. Improvements in the metallic yield can be reached in rotary furnaces if the process starts with a proper salt, with limits of addition, and avoiding long holding times. To improve throughput in reverberatories, start the charging with high magnesium content material and inject chlorine gas if the molten metal is at the right temperature. Removal of magnesium through modern technologies can be efficiently performed to prevent environmental problems.

Theoretical evaluation on selective adsorption characteristics of alkali metal-based sorbents for gaseous oxidized mercury.

PubMed

Tang, Hongjian; Duan, Yufeng; Zhu, Chun; Cai, Tianyi; Li, Chunfeng; Cai, Liang

2017-10-01

Alkali metal-based sorbents are potential for oxidized mercury (Hg 2+ ) selective adsorption but show hardly effect to elemental mercury (Hg 0 ) in flue gas. Density functional theory (DFT) was employed to investigate the Hg 0 and HgCl 2 adsorption mechanism over alkali metal-based sorbents, including calcium oxide (CaO), magnesium oxide (MgO), potassium chloride (KCl) and sodium chloride (NaCl). Hg 0 was found to weakly interact with CaO (001), MgO (001), KCl (001) and NaCl (001) surfaces while HgCl 2 was effectively adsorbed on top-O and top-Cl sites. Charge transfer and bond population were calculated to discuss the covalency and ionicity of HgCl 2 bonding with the adsorption sites. The partial density of states (PDOS) analysis manifests that HgCl 2 strongly interacts with surface sites through the orbital hybridizations between Hg and top O or Cl. Frontier molecular orbital (FMO) energy and Mulliken electronegativity are introduced as the quantitative criteria to evaluate the reactivity of mercury species and alkali metal-based sorbents. HgCl 2 is identified as a Lewis acid and more reactive than Hg 0 . The Lewis basicity of the four alkali metal-based sorbents is predicted as the increasing order: NaCl < MgO < KCl < CaO, in consistence with the trend of HgCl 2 adsorption energies. Copyright © 2017 Elsevier Ltd. All rights reserved.

Numerical reproduction and explanation of road surface mirages under grazing-angle scattering.

PubMed

Lu, Jia; Zhou, Huaichun

2017-07-01

The mirror-like reflection image of the road surface under grazing-angle scattering can be easily observed in daily life. It was suggested that road surface mirages may occur due to a light-enhancing effect of the rough surface under grazing-angle scattering. The main purpose of this work is to explain the light-enhancing mechanism of rough surfaces under grazing-angle scattering. The off-specular reflection from a random rough magnesium oxide ceramic surface is analyzed by using the geometric optics approximation method. Then, the geometric optics approximation method is employed to develop a theoretical model to predict the observation effect of the grazing-angle scattering phenomenon of the road surface. The rough surface is assumed to consist of small-scale rough surface facets. The road surface mirage is reproduced from a large number of small-scale rough surface facets within the eye's resolution limit at grazing scattering angles, as the average bidirectional reflectance distribution function value at the bright location is about twice that of the surface in front of the mirage. It is suggested that the light-enhancing effect of the rough surface under grazing-angle scattering is not proper to be termed as "off-specular reflection," since it has nothing to do with the "specular" direction with respect to the incident direction.

Organic-inorganic nanosystems designed for multiple metal corrosion inhibition

NASA Astrophysics Data System (ADS)

Stockley, Robert

This research focuses on the refinement and discovery of environmentally friendly coatings of metals with increased durability and longer lifetimes as the goal. In the pursuit of an ideal, such as environmentally friendly coatings or "green chemistry," there are many obstacles that must be overcome. This is particularly true in the case of protecting magnesium and its alloys. The relatively low open circuit potential of magnesium makes it highly susceptible to galvanic corrosion when in contact with other metals. It is also easily oxidized when exposed to air or humid conditions and forms a loose hydroxide/oxide layer (Mg(OH)2/MgO). However, for all of its problems, the advantages to using magnesium far outweigh the disadvantages; if and only if, its natural tendency to corrode can be adequately controlled. Magnesium has a high strength to weight ratio, similar to that of glass, making it ideal for a vast array of commercial applications. Magnesium has a high electromagnetic shielding effect (-52.34 dB at 2.45/ GHz for AZ31), making it applicable not only to aircraft instrumentation, but structure as well, due to its low density (d = 1.48 g/cm3). The list of applications for magnesium and its alloys is extensive. Our research has provided insights into the prevention of magnesium corrosion and the applications of "green chemistry" to a metal used across a multitude of industries. Specifically, excellent results were obtained for the electrochemical impedance spectroscopy of LZ91 (magnesium alloy) which demonstrated an impedance of 1.0 x 1010 Ohms to 1.0 x 1011 Ohms. These results suggest our coatings display a pure capacitance behavior in the Bode plot. According to ASTM B117 testing (salt fog testing) the coating on LZ91 panels reached 120 hours, a period considered to be the equivalent of five years of real world conditions, without appreciable corrosion. The possible mechanism for this corrosion protection will also be discussed. These advancements are compelling evidence that our coating is ready for use by industry. From the development of sol-gels and in situ phosphatizing reagents (ISPRs) to their utilization in long lasting, durable coatings, we hope our achievements will help to provide the stepping stones of future scientific advancement in the field of environmentally friendly coating formulations.

Effect of parylene C coating on the antibiocorrosive and mechanical properties of different magnesium alloys

NASA Astrophysics Data System (ADS)

Surmeneva, M. A.; Vladescu, A.; Cotrut, C. M.; Tyurin, A. I.; Pirozhkova, T. S.; Shuvarin, I. A.; Elkin, B.; Oehr, C.; Surmenev, R. A.

2018-01-01

In this paper, parylene C coating with the thickness of 2 μm was deposited on different magnesium alloy substrates (AZ31, WE43 and AZ91). The structure and phase composition of parylene C coating was analysed by Fourier transformed infrared (FTIR) spectroscopy and X-ray diffraction (XRD). In addition, extensive surface characterization was done using atomic force microscopy. The corrosion performance of polymer-coated magnesium alloys was investigated by electrochemical measurements in Hanks' balanced salts solution that simulates bodily fluids at 37 ± 0.5 °C. The depth-dependent mechanical properties including Young's modulus and nanohardness of parylene C films were investigated using nanoindentation technique. The effect of the penetration depth on the properties on nano- and microscale level have been described in detail. The percentage of elastic recovery was used to characterize the elastic properties of the polymeric coatings. The results of XRD showed (020) preferred orientation of the monoclinic unit cell of the alpha phase of parylene C. The parylene C revealed a semicrystalline structure with nanocrystalline blocks of 4.9 nm. The parylene C film shows a uniform surface morphology with a higher roughness level at micro and nanoscales compared to magnesium alloy surfaces. All of the uncoated substrates exhibited a low corrosion resistance compared to the coated samples, indicating that the corrosion resistance of the magnesium alloys could be improved by parylene C coating. The resulting average nanohardness and Young's modulus of the parylene C coatings deposited onto different substrates were in the range of 0.18-0.25 GPa and 4.19-5.14 GPa, respectively. Furthermore, a higher percentage of elastic recovery of the polymer coating indicated a higher elasticity as compared to the magnesium alloy surface. The polymer coating has revealed the ability to recover elastically. Therefore, parylene C coating can not only improve corrosion resistance, but also provide the ability to recover elastically, expanding the potential applications of this material to include various biointerface platforms.

Thin magnesium layer confirmed as an antibacterial and biocompatible implant coating in a co-culture model

PubMed Central

Zaatreh, Sarah; Haffner, David; Strauss, Madlen; Dauben, Thomas; Zamponi, Christiane; Mittelmeier, Wolfram; Quandt, Eckhard; Kreikemeyer, Bernd; Bader, Rainer

2017-01-01

Implant-associated infections commonly result from biofilm-forming bacteria and present severe complications in total joint arthroplasty. Therefore, there is a requirement for the development of biocompatible implant surfaces that prevent bacterial biofilm formation. The present study coated titanium samples with a thin, rapidly corroding layer of magnesium, which were subsequently investigated with respect to their antibacterial and cytotoxic surface properties using a Staphylococcus epidermidis (S. epidermidis) and human osteoblast (hOB) co-culture model. Primary hOBs and S. epidermidis were co-cultured on cylindrical titanium samples (Ti6Al4V) coated with pure magnesium via magnetron sputtering (5 µm thickness) for 7 days. Uncoated titanium test samples served as controls. Vital hOBs were identified by trypan blue staining at days 2 and 7. Planktonic S. epidermidis were quantified by counting the number of colony forming units (CFU). The quantification of biofilm-bound S. epidermidis on the surfaces of test samples was performed by ultrasonic treatment and CFU counting at days 2 and 7. The number of planktonic and biofilm-bound S. epidermidis on the magnesium-coated samples decreased by four orders of magnitude when compared with the titanium control following 7 days of co-culture. The number of vital hOBs on the magnesium-coated samples was observed to increase (40,000 cells/ml) when compared with the controls (20,000 cells/ml). The results of the present study indicate that rapidly corroding magnesium-coated titanium may be a viable coating material that possesses antibacterial and biocompatible properties. A co-culture test is more rigorous than a monoculture study, as it accounts for confounding effects and assesses additional interactions that are more representative of in vivo situations. These results provide a foundation for the future testing of this type of surface in animals. PMID:28260022

Concentration of Nitrate near the Surface of Frozen Salt Solutions

NASA Astrophysics Data System (ADS)

Michelsen, R. R. H.; Marrocco, H. A.

2017-12-01

The photolysis of nitrate near the surface of snow and ice in Earth's environment results in the emission of nitrogen oxides (NO, NO2 and, in acidic snow, HONO) and OH radicals. As a result, nitrate photolysis affects the composition and oxidative capacity of the overlying atmosphere. Photolysis yields depend in part on how much nitrate is close enough to the surface to be photolyzed. These concentrations are assumed to be higher than the concentrations of nitrate that are measured in melted snow and ice samples. However, near-surface concentrations of nitrate have not been directly measured. In this work, laboratory studies of the concentration of nitrate in frozen aqueous solutions are described. Individual aqueous solutions of nitric acid, sodium nitrate, and magnesium nitrate were mixed. Attenuated total reflection infrared spectroscopy was utilized to measure the nitrate and liquid water signals within 200 - 400 nm of the lower surface of frozen samples. Temperature was varied from -18°C to -2°C. In addition to the amount of nitrate observed, changes to the frozen samples' morphology with annealing are discussed. Nitrate concentrations near the lower surface of these frozen solutions are high: close to 1 M at warmer temperatures and almost 4 M at the coldest temperature. Known freezing point depression data describe the observed concentrations better than ideal solution thermodynamics, which overestimate concentration significantly at colder temperatures. The implications for modeling the chemistry of snow are discussed. Extending and relating this work to the interaction of gas-phase nitric acid with the surfaces of vapor-deposited ice will also be explored.

Al₂O₃ Coatings on Magnesium Alloy Deposited by the Fluidized Bed (FB) Technique.

PubMed

Baiocco, Gabriele; Rubino, Gianluca; Tagliaferri, Vincenzo; Ucciardello, Nadia

2018-01-09

Magnesium alloys are widely employed in several industrial domains for their outstanding properties. They have a high strength-weight ratio, with a density that is lower than aluminum (33% less), and feature good thermal properties, dimensional stability, and damping characteristics. However, they are vulnerable to oxidation and erosion-corrosion phenomena when applied in harsh service conditions. To avoid the degradation of magnesium, several coating methods have been presented in the literature; however, all of them deal with drawbacks that limit their application in an industrial environment, such as environmental pollution, toxicity of the coating materials, and high cost of the necessary machinery. In this work, a plating of Al₂O₃ film on a magnesium alloy realized by the fluidized bed (FB) technique and using alumina powder is proposed. The film growth obtained through this cold deposition process is analyzed, investigating the morphology as well as tribological and mechanical features and corrosion behavior of the plated samples. The resulting Al₂O₃ coatings show consistent improvement of the tribological and anti-corrosive performance of the magnesium alloy.

Al2O3 Coatings on Magnesium Alloy Deposited by the Fluidized Bed (FB) Technique

PubMed Central

Rubino, Gianluca; Ucciardello, Nadia

2018-01-01

Magnesium alloys are widely employed in several industrial domains for their outstanding properties. They have a high strength-weight ratio, with a density that is lower than aluminum (33% less), and feature good thermal properties, dimensional stability, and damping characteristics. However, they are vulnerable to oxidation and erosion-corrosion phenomena when applied in harsh service conditions. To avoid the degradation of magnesium, several coating methods have been presented in the literature; however, all of them deal with drawbacks that limit their application in an industrial environment, such as environmental pollution, toxicity of the coating materials, and high cost of the necessary machinery. In this work, a plating of Al2O3 film on a magnesium alloy realized by the fluidized bed (FB) technique and using alumina powder is proposed. The film growth obtained through this cold deposition process is analyzed, investigating the morphology as well as tribological and mechanical features and corrosion behavior of the plated samples. The resulting Al2O3 coatings show consistent improvement of the tribological and anti-corrosive performance of the magnesium alloy. PMID:29315222

Facile synthesis and unique physicochemical properties of three-dimensionally ordered macroporous magnesium oxide, gamma-alumina, and ceria-zirconia solid solutions with crystalline mesoporous walls.

PubMed

Li, Huining; Zhang, Lei; Dai, Hongxing; He, Hong

2009-05-18

Three-dimensionally (3D) ordered macroporous (3DOM) MgO, gamma-Al(2)O(3), Ce(0.6)Zr(0.4)O(2), and Ce(0.7)Zr(0.3)O(2) with polycrystalline mesoporous walls have been successfully fabricated with the triblock copolymer EO(106)PO(70)EO(106) (Pluronic F127) and regularly packed monodispersive polymethyl methacrylate (PMMA) microspheres as the template and magnesium, aluminum, cerium and zirconium nitrate(s), or aluminum isopropoxide as the metal source. The as-synthesized metal oxides were characterized by means of techniques such as X-ray diffraction (XRD), thermogravimetric analysis/differential scanning calorimetry (TGA/DSC), Fourier transform infrared (FT-IR), high-resolution scanning electron microscopy (HRSEM), high-resolution transmission electron microscopy/selected area electron diffraction (HRTEM/SAED), BET, carbon dioxide temperature-programmed desorption (CO(2)-TPD), and hydrogen temperature-programmed reduction (H(2)-TPR). It is shown that the as-fabricated MgO, gamma-Al(2)O(3), Ce(0.6)Zr(0.4)O(2), and Ce(0.7)Zr(0.3)O(2) samples possessed single-phase polycrystalline structures and displayed a 3DOM architecture; the MgO, Ce(0.6)Zr(0.4)O(2), and Ce(0.7)Zr(0.3)O(2) samples exhibited worm-hole-like mesoporous walls, whereas the gamma-Al(2)O(3) samples exhibited 3D ordered mesoporous walls. The solvent (ethanol or water) nature and concentration, metal precursor, surfactant, and drying condition have an important impact on the pore structure and surface area of the final product. The introduction of surfactant F127 to the synthesis system could significantly enhance the surface areas of the 3DOM metal oxides. With PMMA and F127 in a 40% ethanol solution, one can generate well-arrayed 3DOM MgO with a surface area of 243 m(2)/g and 3DOM Ce(0.6)Zr(0.4)O(2) with a surface area of 100 m(2)/g; with PMMA and F127 in an ethanol-HNO(3) solution, one can obtain 3DOM gamma-Al(2)O(3)with a surface area of 145 m(2)/g. The 3DOM MgO and 3DOM gamma-Al(2)O(3) samples showed excellent CO(2) adsorption behaviors, whereas the 3DOM Ce(0.6)Zr(0.4)O(2) sample exhibited exceptional low-temperature reducibility. The unique physicochemical properties associated with the copresence of 3DOM and mesoporous walls make these porous materials ideal candidates for applications in heterogeneous catalysis and CO(2) adsorption.

Zinc and magnesium ions synergistically inhibit superoxide generation by cultured human neutrophils--a promising candidate formulation for amnioinfusion fluid.

PubMed

Uchida, Toshiyuki; Itoh, Hiroaki; Nakamura, Yuki; Kobayashi, Yukiko; Hirai, Kyuya; Suzuki, Kazunao; Sugihara, Kazuhiro; Kanayama, Naohiro; Hiramatsu, Mitsuo

2010-06-01

Oligohydramnios is often caused by the premature rupturing of membranes and subsequent intrauterine infections, such as chorioamnionitis, in which event oxidative stress is hypothesized to be closely associated with the damage to the fetal organs. The clinical efficiency of amnioinfusion using warmed saline in cases of premature rupture of membranes is still controversial, especially concerning the prognosis for the fetus. In the present study, we found that human amniotic fluid per se suppresses the release of superoxide from cultured human neutrophils, suggesting an acute or chronic shortage of amniotic fluid in cases of premature rupture of membranes can affect the shielding of intrauterine organs from oxidative stress. The aim of this study was to propose a formula of zinc and magnesium ions in saline for amnioinfusion, by assessing antioxidative activities. A combination of 5 microM zinc and 5mM magnesium in saline synergistically inhibited superoxide production by cultured human neutrophils, equivalent to human amniotic fluid. The intraperitoneal administration of this formula significantly improved the survival rate in a rat model of peritonitis compared to the saline control (46.7% vs. 10%). The combination of these metals with saline may thus be a promising formula for an amnioinfusion fluid with the capacity to protect fetal organs from oxidative stress. Copyright (c) 2010 Elsevier Ireland Ltd. All rights reserved.

Improving halide-containing magnesium-ion electrolyte performance via sterically hindered alkoxide ligands

NASA Astrophysics Data System (ADS)

Nist-Lund, Carl A.; Herb, Jake T.; Arnold, Craig B.

2017-09-01

While homoleptic magnesium dialkoxides (MgR2, R = alkoxide) have shown promise as precursors for magnesium-ion electrolytes, the effect of ligand steric bulk on the performance of electrolytes based on these compounds is not fully understood. Increasing steric hindrance, studied via R groups with additional phenyl moieties, produces electrolytes with sequentially lower deposition overpotentials (less than -90 mV), higher purity Mg deposits (ca. 100% Mg), and lower overall cell impedances. The two largest alkoxide ligands show consistent cycling behavior and low stripping and plating overpotentials over 200 constant-current plating/stripping cycles. A deep-red visual change and the presence of large solubilized magnesium particulates above 450 nm in size is observed in an electrolyte containing magnesium bis(triphenylmethoxide) and aluminum chloride in contact with an abraded magnesium anode. Further morphological and impedance characterization show that this electrolyte system rapidly activates the magnesium metal anode surface to produce low overpotentials and, as such, is a candidate for further investigation.

The Volumetric Imaging System for the Ionosphere (VISION)

DTIC Science & Technology

2011-01-01

telescope mirror is an 80 mm focal length, 50 mm diameter, first surface mirror with magnesium fluoride over aluminum coating on a zerodur blank...will be either a wedge–and–strip anode or a codacon. The telescope mirror is an 80 mm focal length, 2.5 cm diameter, first surface mirror with...magnesium fluoride over aluminum coating on a zerodur blank. The filters are the three reflection bandpass filters developed for and flown on

The one-step electroposition of superhydrophobic surface on AZ31 magnesium alloy and its time-dependence corrosion resistance in NaCl solution

NASA Astrophysics Data System (ADS)

Zhong, Yuxing; Hu, Jin; Zhang, Yufen; Tang, Shawei

2018-01-01

A calcium myristic superhydrophobicity coating with a hierarchical micro-nanostructure was fabricated on AZ31 magnesium alloy by one-step electroposition. The effects of deposition time on the coating structure, such as morphology, thickness, wettability and phase composition of the coating were studied. The corrosion behavior of the coated samples in 3.5% NaCl solution was also investigated and the corrosion mechanism was discussed. It was found that the deposition time has a visible effect on the morphology, thickness and wettability, which distinctly affects the corrosion resistance of coatings. The corrosion resistance of the coating gradually decreases with the increase in the immersion time due to the disappearance of the air layer which exists on the coating surface. The superhydrophobic surfaces present the temporal limitations to the corrosion resistance of AZ31 magnesium alloy.

Degradation of paraoxon (VX chemical agent simulant) and bacteria by magnesium oxide depends on the crystalline structure of magnesium oxide.

PubMed

Sellik, A; Pollet, T; Ouvry, L; Briançon, S; Fessi, H; Hartmann, D J; Renaud, F N R

2017-04-01

In this work, our goal was to study the capability of a single metallic oxide to neutralize a chemical agent and to exhibit an antibacterial effect. We tested two types of magnesium oxides, MgO. The first MgO sample tested, which commercial data size characteristic was -325 mesh (MgO-1) destroyed in 3 h, 89.7% of paraoxon and 93.2% of 4-nitrophenol, the first degradation product. The second MgO sample, which commercial data size was <50 nm (MgO-2) neutralized in the same time, 19.5% of paraoxon and 10.9% of 4-nitrophenol. For MgO-1 no degradation products could be detected by GC-MS. MgO-1 had a bactericidal activity on Escherichia coli (6 log in 1 h), and showed a decrease of almost 3 log on a Staphylococcus aureus population in 3 h. MgO-2 caused a decrease of 2 log of a E.coli culture but had no activity against S. aureus. Neither of these two products had an activity on Bacillus subtilis spores. Analytical investigations showed that the real sizes of MgO nanoparticles were 11 nm for MgO-1 and 25 nm for MgO-2. Moreover, their crystalline structures were different. These results highlighted the importance of the size of the nanoparticles and their microscopic arrangements to detoxify chemical products and to inhibit or kill microbial strains. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Magnesium Content of the Core: an Experimental Study

NASA Astrophysics Data System (ADS)

Fiquet, G.; Badro, J.; Auzende, A.; Siebert, J.; Gregoryanz, E.; Guignot, N.

2006-12-01

There is still a considerable debate about which light element among sulfur, silicon, oxygen, carbon or hydrogen should be in the core [Poirier, Phys. Earth Planet. Int., 85, 319, 1994]. The nature and distribution of these elements is a standing problem of prime importance, since it controls the freezing point depression at the inner core boundary. In addition to these candidates, new elements have been recently proposed as iron alloying constituants for the core, such as magnesium [Dubrovinskaia et al., Phys. Rev. Lett., 95, 245502, 2005]. We present series of experiments carried out on hot-pressed samples of iron and periclase in a laser-heated diamond-anvil cell, combined with in situ X-ray diffraction analysis and ATEM examination of recovered samples. We show that even at megabar pressures the amount of magnesium released in iron from the equilibrium with magnesium oxide is marginal. This finding is at odds with the 10 at% of magnesium found by Dubrovinskaia et al. [2005] in an iron alloy made from the reaction between iron and a metallic magnesium foil. Our observations suggest that magnesium is unlikely to be an important light element in the Earth's core. In addition, we provide structural data for iron to 130 GPa in excess of 3000 K with reliable pressure and temperature measurements, which enable us to propose a new thermal equation of state for iron at megabar pressures.

In-situ upgrading of biomass pyrolysis vapors: catalyst screening on a fixed bed reactor.

PubMed

Stefanidis, S D; Kalogiannis, K G; Iliopoulou, E F; Lappas, A A; Pilavachi, P A

2011-09-01

In-situ catalytic upgrading of biomass fast pyrolysis vapors was performed in a fixed bed bench-scale reactor at 500°C, for catalyst screening purposes. The catalytic materials tested include a commercial equilibrium FCC catalyst (E-cat), various commercial ZSM-5 formulations, magnesium oxide and alumina materials with varying specific surface areas, nickel monoxide, zirconia/titania, tetragonal zirconia, titania and silica alumina. The bio-oil was characterized measuring its water content, the carbon-hydrogen-oxygen (by difference) content and the chemical composition of its organic fraction. Each catalytic material displayed different catalytic effects. High surface area alumina catalysts displayed the highest selectivity towards hydrocarbons, yielding however low organic liquid products. Zirconia/titania exhibited good selectivity towards desired compounds, yielding higher organic liquid product than the alumina catalysts. The ZSM-5 formulation with the highest surface area displayed the most balanced performance having a moderate selectivity towards hydrocarbons, reducing undesirable compounds and producing organic liquid products at acceptable yields. Copyright © 2011 Elsevier Ltd. All rights reserved.

Corrosion in Magnesium and a Magnesium Alloy

NASA Astrophysics Data System (ADS)

Akavipat, Sanay

Magnesium and a magnesium alloy (AZ91C) have been ion implanted over a range of ions energies (50 to 150 keV) and doses (1 x 10('16) to 2 x 10('17) ions/cm('2)) to modify the corrosion properties of the metals. The corrosion tests were done by anodic polarization in chloride -free and chloride-containing aqueous solutions of a borated -boric acid with a pH of 9.3. Anodic polarization measurements showed that some implantations could greatly reduce the corrosion current densities at all impressed voltages and also increased slightly the pitting potential, which indicated the onset of the chloride attack. These improvements in corrosion resistance were caused by boron implantations into both types of samples. However, iron implantations were found to improve only the magnesium alloy. To study the corrosion in more detail, Scanning Auger Microprobe Spectrometer (SAM), Scanning Electron Microscope (SEM) with an X-ray Energy Spectrometry (XES) attachment, and Transmission Electron Microscope (TEM) measurements were used to analyze samples before, after, and at various corrosion stages. In both the unimplanted pure magnesium and AZ91C samples, anodic polarization results revealed that there were three active corrosion stages (Stages A, C, and E) and two passivating stages (Stages B and D). Examination of Stages A and B in both types of samples showed that only a mild, generalized corrosion had occurred. In Stage C of the TD samples, a pitting breakdown in the initial oxide film was observed. In Stage C of the AZ91C samples, galvanic and intergranular attack around the Mg(,17)Al(,12) intermetallic islands and along the matrix grain boundaries was observed. Stage D of both samples showed the formation of a thick, passivating oxygen containing, probably Mg(OH)(,2) film. In Stage E, this film was broken down by pits, which formed due to the presence of the chloride ions in both types of samples. Stages A through D of the unimplanted samples were not seen in the boron or iron implanted samples. Instead one low current density passivating stage was formed, which was ultimately broken down by the chloride attack. It is believed that the implantation of boron modified the initial surface film to inhibit corrosion, whereas the iron implantation modified the intermetallic (Mg(,17)Al(,12)) islands to act as sacrificial anodes.

Deposition of magnesium nitride thin films on stainless steel-304 substrates by using a plasma focus device

NASA Astrophysics Data System (ADS)

Ramezani, Amir Hoshang; Habibi, Maryam; Ghoranneviss, Mahmood

2014-08-01

In this research, for the first time, we synthesize magnesium nitride thin films on 304-type stainless steel substrates using a Mather-type (2 kJ) plasma focus (PF) device. The films of magnesium nitride are coated with different number of focus shots (like 15, 25 and 35) at a distance of 8 cm from the anode tip and at 0° angular position with respect to the anode axis. For investigation of the structural properties and surface morphology of magnesium nitride films, we utilized the X-ray diffractometer (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM) analysis, respectively. Also, the elemental composition is characterized by energy-dispersive X-ray (EDX) analysis. Furthermore, Vicker's microhardness is used to study the mechanical properties of the deposited films. The results show that the degree of crystallinity of deposited thin films (from XRD), the average size of particles and surface roughness (from AFM), crystalline growth of structures (from SEM) and the hardness values of the films depend on the number of focus shots. The EDX analysis demonstrates the existence of the elemental composition of magnesium in the deposited samples.

Making MgO/SiO2 Glasses By The Sol-Gel Process

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.

1989-01-01

Silicon dioxide glasses containing 15 mole percent magnesium oxide prepared by sol-gel process. Not made by conventional melting because ingredients immiscible liquids. Synthesis of MgO/SiO2 glass starts with mixing of magnesium nitrate hexahydrate with silicon tetraethoxide, both in alcohol. Water added, and transparent gel forms. Subsequent processing converts gel into glass. Besides producing glasses of new composition at lower processing temperatures, sol-gel method leads to improved homogeneity and higher purity.

First Principles Modeling of Structure and Transport in Solid Polymer Electrolytes, Ionic Liquids, and Methanol/Water Mixtures

DTIC Science & Technology

2016-02-10

potential in making high- performance solid state lithium ion batteries [1,2]. Among them, the polyethylene oxide-alkali salts systems PEO6:XPF6 (X = H...electrolytes for magnesium batteries incorporating chloro- or iodo- ionic liquids. Much of this work was done in collaboration with the experimental group...magnesium batteries incorporating chloro- or iodo- ionic liquids. Much of this work was done in collaboration with the experimental group of Prof. Vito Di

The machined surface of magnesium AZ31 after rotary turning at air cooling condition

NASA Astrophysics Data System (ADS)

Akhyar, G.; Purnomo, B.; Hamni, A.; Harun, S.; Burhanuddin, Y.

2018-04-01

Magnesium is a lightweight metal that is widely used as an alternative to iron and steel. Magnesium has been applied in the automotive industry to reduce the weight of a component, but the machining process has the disadvantage that magnesium is highly flammable because it has a low flash point. High temperature can cause the cutting tool wear and contributes to the quality of the surface roughness. The purpose of this study is to obtain the value of surface roughness and implement methods of rotary cutting tool and air cooling output vortex tube cooler to minimize the surface roughness values. Machining parameters that is turning using rotary cutting tool at speed the workpiece of (Vw) 50, 120, 160 m/min, cutting speed of rotary tool of (Vt) 25, 50, 75 m/min, feed rate of (f) 0.1, 0.15, 0.2 mm/rev, and depth of cut of 0.3 mm. Type of tool used is a carbide tool diameter of 16 mm and air cooling pressure of 6 bar. The results show the average value of the lowest surface roughness on the speed the workpiece of 80 m/min, cutting speed of rotary tool of 50 m/min, feed rate of 0.2 mm/rev, and depth of cut of 0.3 mm. While the average value of the highest surface roughness on the speed the workpiece of 160 m/min, cutting speed of rotary tool of 50 m/min, feed rate of 0.2 mm/rev, and depth of cut of 0.3 mm. The influence of machining parameters concluded the higher the speed of the workpiece the surface roughness value higher. Otherwise the higher cutting speed of rotary tool then the lower the surface roughness value. The observation on the surface of the rotary tool, it was found that no uniform tool wear which causes non-uniform surface roughness. The use of rotary cutting tool contributing to lower surface roughness values generated.

21 CFR 163.112 - Breakfast cocoa.

Code of Federal Regulations, 2011 CFR

2011-04-01

... ingredients. Ammonium, potassium, or sodium bicarbonate, carbonate, or hydroxide, or magnesium carbonate or oxide, used as such, or in aqueous solution; (2) Neutralizing agents. Phosphoric acid, citric acid and L...

Method of preparing porous, rigid ceramic separators for an electrochemical cell. [Patent application

DOEpatents

Bandyopadhyay, G.; Dusek, J.T.

Porous, rigid separators for electrochemical cells are prepared by first calcining particles of ceramic material at temperatures above about 1200/sup 0/C for a sufficient period of time to reduce the sinterability of the particles. A ceramic powder that has not been calcined is blended with the original powder to control the porosity of the completed separator. The ceramic blend is then pressed into a sheet of the desired shape and sintered at a temperature somewhat lower than the calcination temperature. Separator sheets of about 1 to 2.5 mm thickness and 30 to 70% porosity can be prepared by this technique. Ceramics such as yttria, magnesium oxide, and magnesium-aluminium oxide have advantageously been used to form separators by this method.

Nanostructured calcium phosphate coatings on magnesium alloys: characterization and cytocompatibility with mesenchymal stem cells.

PubMed

Iskandar, Maria Emil; Aslani, Arash; Tian, Qiaomu; Liu, Huinan

2015-05-01

This article reports the deposition and characterization of nanostructured calcium phosphate (nCaP) on magnesium-yttrium alloy substrates and their cytocompatibility with bone marrow derived mesenchymal stem cells (BMSCs). The nCaP coatings were deposited on magnesium and magnesium-yttrium alloy substrates using proprietary transonic particle acceleration process for the dual purposes of modulating substrate degradation and BMSC adhesion. Surface morphology and feature size were analyzed using scanning electron microscopy and quantitative image analysis tools. Surface elemental compositions and phases were analyzed using energy dispersive X-ray spectroscopy and X-ray diffraction, respectively. The deposited nCaP coatings showed a homogeneous particulate surface with the dominant feature size of 200-500 nm in the long axis and 100-300 nm in the short axis, and a Ca/P atomic ratio of 1.5-1.6. Hydroxyapatite was the major phase identified in the nCaP coatings. The modulatory effects of nCaP coatings on the sample degradation and BMSC behaviors were dependent on the substrate composition and surface conditions. The direct culture of BMSCs in vitro indicated that multiple factors, including surface composition and topography, and the degradation-induced changes in media composition, influenced cell adhesion directly on the sample surface, and indirect adhesion surrounding the sample in the same culture. The alkaline pH, the indicator of Mg degradation, played a role in BMSC adhesion and morphology, but not the sole factor. Additional studies are necessary to elucidate BMSC responses to each contributing factor.

Magnesium ferrite nanoparticles: a rapid gas sensor for alcohol

NASA Astrophysics Data System (ADS)

Godbole, Rhushikesh; Rao, Pratibha; Bhagwat, Sunita

2017-02-01

Highly porous spinel MgFe2O4 nanoparticles with a high specific surface area have been successfully synthesized by a sintering free auto-combustion technique and characterized for their structural and surface morphological properties using XRD, BET, TEM and SEM techniques. Their sensing properties to alcohol vapors viz. ethanol and methanol were investigated. The site occupation of metal ions was investigated by VSM. The as-synthesized sample shows the formation of sponge-like porous material which is necessary for gas adsorption. The gas sensing characteristics were obtained by measuring the gas response as a function of operating temperature, concentration of the gas, and the response-recovery time. The response of magnesium ferrite to ethanol and methanol vapors was compared and it was revealed that magnesium ferrite is more sensitive and selective to ethanol vapor. The sensor operates at a substantially low vapor concentration of about 1 ppm of alcohol vapors, exhibits fantastic response reproducibility, long term reliability and a very fast response and recovery property. Thus the present study explored the possibility of making rapidly responding alcohol vapor sensor based on magnesium ferrite. The sensing mechanism has been discussed in co-relation with magnetic and morphological properties. The role of occupancy of Mg2+ ions in magnesium ferrite on its gas sensing properties has also been studied and is found to influence the response of magnesium ferrite ethanol sensor.

Corrosion behavior of mesoporous bioglass-ceramic coated magnesium alloy under applied forces.

PubMed

Zhang, Feiyang; Cai, Shu; Xu, Guohua; Shen, Sibo; Li, Yan; Zhang, Min; Wu, Xiaodong

2016-03-01

In order to research the corrosion behavior of bioglass-ceramic coated magnesium alloys under applied forces, mesoporous 45S5 bioactive glass-ceramic (45S5 MBGC) coatings were successfully prepared on AZ31 substrates using a sol-gel dip-coating technique followed by a heat treatment at the temperature of 400°C. In this work, corrosion behavior of the coated samples under applied forces was characterized by electrochemical tests and immersion tests in simulated body fluid. Results showed that the glass-ceramic coatings lost the protective effects to the magnesium substrate in a short time when the applied compressive stress was greater than 25MPa, and no crystallized apatite was formed on the surface due to the high Mg(2+) releasing and the peeling off of the coatings. Whereas, under low applied forces, apatite deposition and crystallization on the coating surface repaired cracks to some extent, thus improving the corrosion resistance of the coated magnesium during the long-term immersion period. Copyright © 2015 Elsevier Ltd. All rights reserved.

Influence of Magnesium Ion Substitution on Structural and Thermal Behavior of Nanodimensional Hydroxyapatite

NASA Astrophysics Data System (ADS)

Batra, Uma; Kapoor, Seema; Sharma, Sonia

2013-06-01

Hydroxyapatite (HA), incorporating small amount of magnesium, shows attractive biological performance in terms of improved bone metabolism, osteoblast and osteoclast activity, and bone in-growth. This article reports a systematic investigation on the influence of magnesium (Mg) substitution on structural and thermal behavior of nanodimensional HA. HA and Mg-substituted HA nanopowders were synthesized through sol-gel route. The morphology and size of nanopowders were characterized by transmission electron microscopy. The BET surface area was evaluated from N2 adsorption isotherms. Structural analysis and thermal behavior were investigated by means of Fourier transform infrared spectroscopy, x-ray diffraction, thermogravimetry, and differential thermal analysis. As-synthesized powders consisted of flake-like agglomerates of HA and calcium-deficient HA. The incorporation of magnesium in HA resulted in decrease of crystallite size, crystallinity, and lattice parameters a and c and increase in BET surface area. β-tricalcium phosphate formation occured at lower calcination temperature in Mg-substituted HA than HA.

Geochemistry and hydrology of a calcareous fen within the Savage Fen wetlands complex, Minnesota, USA

USGS Publications Warehouse

Komor, S.C.

1994-01-01

Savage Fen is a wetlands complex at the base of north-facing bluffs in the Minnesota River Valley. The complex includes 27.8 hectares of calcareous fen that host rare calciphile plants whose populations are declining in Minnesota. Water and sediment compositions in the calcareous fen were studied to gain a better understanding of the hydrologie System that sustains the rare vegetation. Groundwater in the fen is a calcium-magnesium-bicarbonate type with circumneutral pH values. The groundwater composition is the resuit of interactions among water, dissolved and gaseous carbon species, carbonates, and ion exchangers. Shallow groundwater is distinguished from deep groundwater by smaller concentrations of chloride, sulfate, magnesium, and sodium, and larger concentrations of calcium, bicarbonate, hydrogen sulfide, and ammonium. Magnesian calcite is the prevalent carbonate in unconsolidated sedimentary fill beneath the fen and is an important source and sink for dissolved calcium, magnesium, and inorganic carbon. Calcite concentrations just below the water table are small because aerobic and anaerobic oxidation of organic matter increase the partial pressure of carbon dioxide (PCO2), decrease pH, and cause calcite to dissolve. Thick calcite accumulations just above the water table, in the root zone of calciphile plants, result from water table fluctuations and attendant changes in PCO2. Groundwater beneath Savage Fen recharges in lakes and ponds south of the fen and upwells to the surface within the fen. Water at the water table is a mixture of upwelling groundwater and water near the surface that flows downslope from higher elevations in the fen. Changes in oxygen and hydrogen isotope compositions of shallow groundwater indicate that the proportion of upwelling groundwater in shallow groundwater decreases downgradient in the calcareous fen. Encroachment of reed grasses into the calcareous fen may reflect human-caused disturbances in the recharge area.

Ignition and Combustion Characteristics of Pure Bulk Metals: Normal-Gravity Test Results

NASA Technical Reports Server (NTRS)

Abbud-Madrid, A.; Fiechtner, G. J.; Branch, M. C.; Daily, J. W.

1994-01-01

An experimental apparatus has been designed for the study of bulk metal ignition under elevated, normal and reduced gravity environments. The present work describes the technical characteristics of the system, the analytical techniques employed, the results obtained from the ignition of a variety of metals subjected to normal gravity conditions and the first results obtained from experiments under elevated gravity. A 1000 W xenon short-arc lamp is used to irradiate the top surface of a cylindrical metal specimen 4 mm in diameter and 4 mm high in a quiescent pure-oxygen environment at 0.1 MPa. Iron, titanium, zirconium, magnesium, zinc, tin, and copper specimens are investigated. All these metals exhibit ignition and combustion behavior varying in strength and speed. Values of ignition temperatures below, above or in the range of the metal melting point are obtained from the temperature records. The emission spectra from the magnesium-oxygen gas-phase reaction reveals the dynamic evolution of the ignition event. Scanning electron microscope and x-ray spectroscopic analysis provide the sequence of oxide formation on the burning of copper samples. Preliminary results on the effect of higher-than-normal gravity levels on the ignition of titanium specimens is presented.

Media calcification, low erythrocyte magnesium, altered plasma magnesium, and calcium homeostasis following grafting of the thoracic aorta to the infrarenal aorta in the rat--differential preventive effects of long-term oral magnesium supplementation alone and in combination with alkali.

PubMed

Schwille, P O; Schmiedl, A; Schwille, R; Brunner, P; Kissler, H; Cesnjevar, R; Gepp, H

2003-03-01

Calcifications in arterial media are clinically well documented, but the role played by magnesium in pathophysiology and therapy is uncertain. To clarify this, an animal model in which the juxtacardial aorta was grafted to the infrarenal aorta, and the subsequent calcifications in the media of the graft and their response to oral supplementation with three magnesium-containing and alkalinizing preparations was investigated. Groups of highly inbred rats were formed as follows: sham-operation (Sham, n = 12), aorta transplantation (ATx, n = 12), ATx + magnesium citrate (MgC, n = 12), ATx + MgC + potassium citrate (MgCPC, n = 12), ATx + MgC + MgCPC (MgCPCSB, n = 12). At 84 (+/-2) days after ATx with or without treatment the following observations were made: (1) weight gain and general status were normal; (2) ATx rats developed massive media calcification, mineral accumulation in the graft, decreased erythrocyte magnesium and plasma parathyroid hormone, and increased plasma ionized magnesium and calcium, and uric acid; (3) Mg-treated rats developed variable degrees of metabolic alkalosis, but only MgCPCSB supplementation prevented calcifications. Additional findings after ATx alone were: imbalance in endothelin and nitric oxide production, the mineral deposited in media was poorly crystallized calcium phosphate, calcium exchange between plasma and graft, and bone resorption were unchanged. The superior anti-calcification effect of MgCPCSB was characterized by complete restoration of normal extracellular mineral homeostasis and uric acid, but sub-optimal normalization of erythrocyte magnesium. It was concluded that in the rat: (1) ATx causes loss of cellular magnesium, excess of extracellular magnesium and calcium in the presence of apparently unchanged bone resorption, and increased uricemia; (2) ATx facilitates enhanced influx of calcium into vascular tissue, leading to calcium phosphate deposition in the media; (3) ATx-induced calcification is prevented by dietary supplementation with a combination of magnesium, alkali citrate and bases. Although the described circulatory model of media calcification in the rat requires further investigation, the data allow ascribing a fundamental role to magnesium and acid-base metabolism.

Light-weight titanium magnesium alloys by vapor deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ward-Close, C.M.; Lu, G.; Bagnall, K.E.

A novel range of Ti-Mg alloys were produced by a high rate evaporation and vapor quenching route. Magnesium is virtually insoluble in titanium under equilibrium conditions, and this alloy combination is not possible by conventional ingot metallurgy due to the high vapor pressure of magnesium, which boils at atmospheric pressure below the melting point of titanium. X-ray diffraction data showed that at least 27 wt% magnesium was retained in solid solution. Each 1 wt% addition of magnesium reduced the alloy density by approximately 1%. For the more dilute alloys (< 10 wt%) heat treatment in air or in vacuum upmore » to 700 C was accompanied by a very substantial increase in hardness, which could not be explained in terms of oxygen absorption by the titanium lattice. A Ti-9Mg alloy has been studied by transmission electron microscopy using electron energy loss (PEELS) and energy dispersive X-ray techniques. After hot-pressing, particles in the 2--20 nm range, and others at about 100 nm diameter were found within the grains and in the grain boundaries respectively. These particles were identified as magnesium. Controlled oxidation led to the formation of MgO particles, and an increase in hardness by a factor of 2.3.« less

Effects of grain size on the corrosion resistance of pure magnesium by cooling rate-controlled solidification

NASA Astrophysics Data System (ADS)

Liu, Yichi; Liu, Debao; You, Chen; Chen, Minfang

2015-09-01

The aim of this study was to investigate the effect of grain size on the corrosion resistance of pure magnesium developed for biomedical applications. High-purity magnesium samples with different grain size were prepared by the cooling rate-controlled solidification. Electrochemical and immersion tests were employed to measure the corrosion resistance of pure magnesium with different grain size. The electrochemical polarization curves indicated that the corrosion susceptibility increased as the grain size decrease. However, the electrochemical impedance spectroscopy (EIS) and immersion tests indicated that the corrosion resistance of pure magnesium is improved as the grain size decreases. The improvement in the corrosion resistance is attributed to refine grain can produce more uniform and density film on the surface of sample.

A comparison between the electrochemical behavior of reversible magnesium and lithium electrodes

NASA Astrophysics Data System (ADS)

Aurbach, D.; Gofer, Y.; Schechter, A.; Chusid, O.; Gizbar, H.; Cohen, Y.; Moshkovich, M.; Turgeman, R.

This paper describes briefly the difference between reversible lithium and magnesium electrodes. In the case of lithium, the active metal is always covered by surface films. Li dissolution-deposition is reversible only when the surface films contain elastomers and are flexible. Hence, they can accommodate the morphological changes of the electrode during the electrochemical processes without breaking down. In an ideal situation, lithium is deposited beneath the surface films, while being constantly protected in a way that prevents reactions between freshly deposited lithium and solution species. In contrast to lithium, magnesium electrodes are reversible only in solutions where surface film free conditions exist. Mg does not react with ethers, and thus, in ethereal solutions of Grignard reagents (RMgX, where R=alkyl, aryl, X=halide) and complexes of the following type: Mg(AlX 4- nR n' R n″ ') 2, R and R'=alkyl groups, X=halide, A=Al, 0< n<4 and n'+ n''= n, magnesium electrodes behave reversibly. However, it should be noted that the above stoichiometry of the Mg salts does not reflect the true structure of the active ions in solutions. Mg deposition does not occur via electron transfer to simply solvated Mg 2+ ions. The behavior of Mg electrodes in these solutions is discussed in light of studies by EQCM, EIS, FTIR, XPS, STM and standard electrochemical techniques.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ejiofor, J.U.; Reddy, R.G.

The influence of microporous particulate carbon char on the mechanical, thermal, and tribological properties of wear-resistant Al-13.5Si-2.5Mg alloy composites was studied. Large increases in surface area due to the formation of micropores in coconut shell chars were achieved by high-temperature activation under CO{sub 2} gas flow. Activated char particles at 0.02 V{sub f} were used to reinforce the alloy. The composites were fabricated via a double-compaction reaction sintering technique under vacuum at a compaction pressure of 250 MPa and sintering temperature of 600 C. At more than 35% burn-off of the carbon chars at the temperature of activation, 915 C,more » the total surface area remained virtually unaffected. The ultimate tensile strength and hardness decreased by 23% and 6%, respectively; with increasing surface area of the reinforcement from 123 to 821 m{sup 2} g{sup {minus}1}. The yield strength and the percentage of elongation decreased by a factor of 2 and 5, respectively. No significant change in sliding wear rate was observed but the coefficient of friction increased by 13% (0.61 to 0.69). The coefficient of linear thermal expansion was reduced by 16% (11.7 {times} 10{sup {minus}6} to 9.8 {times} 10{sup {minus}6} C{sup {minus}1}), and remained unaffected at more than 35% burn-off. Energy-dispersive spectrometry of the particles of the activated chars showed that oxides of potassium and copper coated the open surfaces. Failure at the matrix-char interface was observed, and this was attributed to localized presence of oxides at the interfaces as identified by electron probe microanalysis. Poor wetting of the oxides by magnesium at the sintering conditions resulted in formation of weak matrix-char interface bonds.« less

Late diagenetic indicators of buried oil and gas

USGS Publications Warehouse

Donovan, Terrence J.; Dalziel, Mary C.

1977-01-01

At least three hydrocarbon seepage mechanisms are interpreted to operate over oil and gas fields. These are: (1) effusion ofh ydrocarbons through inadequate caprocks and along faults and fractures, (2) low-molecular-weight hydrocarbons dissolved in water moving vertically through capping shales as a result of a hydrodynamic or chemical potential drive, and (3) diffusion of gases dissolved in water. Combinations of these mechanisms may also occur. Seeping hydrocarbons are oxidized near the earth's surface, and the resulting carbon dioxide reacts with water producing bicarbonate ions, which combine with calcium and magnesium dissolved in ground waters to yield isotopically distinctive pore-filling carbonate cements and surface rocks. The passage of hydrocarbons and associated compounds such as hydrogen sulfide through surface rocks causes a reducing environment and consequent reduction, mobilization, and loss of iron from iron-bearing minerals commonly resulting in a discoloration. Other metals such as manganese are also mobilized and redistributed. These changes in the physical and chemical properties of surface rocks correlate with the subsurface distribution of petroleum, and potentially can be detected from both airborne and spaceborne platforms.

77 FR 11390 - Delegation of National Emission Standards for Hazardous Air Pollutants for Source Categories; Nevada

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-27

... Tanks. O Ethylene Oxide X X X Sterilization Facilities. Q Industrial Process Cooling X X Towers. R... Organic-Water Separators. WW Storage Vessels (Tanks)-- X X Control Level 2. XX Ethylene Manufacturing X X... Refractory Products X X Manufacturing. TTTTT Primary Magnesium Refining. X WWWWW Hospital Ethylene Oxide X X...

Effect of Holding Time on Surface Films Formed on Molten AZ91D Alloy Protected by Graphite Powder

NASA Astrophysics Data System (ADS)

Li, Weihong; Zhou, Jixue; Ma, Baichang; Wang, Jinwei; Wu, Jianhua; Yang, Yuansheng

2017-10-01

Graphite powder was adopted to prevent the AZ91D magnesium alloy from oxidizing during the melting and casting process. The microstructure of the resultant surface films formed at 973 K (700 °C) holding for 0, 15, 30, 45, and 60 minutes was investigated by scanning electron microscopy, energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) after mechanical polishing and chemical etching. The results indicated that the surface films were composed of a protective layer and the underneath particles with different morphology. The protective layer was continuous with a thickness of 200 to 1000 nm mainly consisting of MgO, MgF2, and C, while the underneath particles mainly consisted of MgF2 and MgAl2O4. The surface films were the result of the interaction between the graphite powder, the melt, and the ambient atmosphere. The number and the size of the underneath particles, determining the thickness uniformity of the surface films, and the unevenness of the microsurface morphology increased with holding time. The mechanism of holding time on the resultant surface films was also discussed.

Mineral Plot from Esperance Target

NASA Image and Video Library

2014-01-23

This plot segregates various minerals examined by NASA Mars Exploration Rover Opportunity according to their different compositions; for example, those with more iron and magnesium oxides are located in the lower right corner.

Defect states at organic-inorganic interfaces: Insight from first principles calculations for pentaerythritol tetranitrate on MgO surface

NASA Astrophysics Data System (ADS)

Tsyshevsky, Roman V.; Rashkeev, Sergey N.; Kuklja, Maija M.

2015-07-01

Light-responsive organic-inorganic interfaces offer experimental opportunities that are otherwise difficult to achieve. Since laser light can be manipulated very precisely, it becomes possible to engineer selective, predictive, and highly controlled interface properties. Photochemistry of organic-inorganic energetic interfaces is a rapidly emerging research field in which energy absorption and interface stability mechanisms have yet to be established. To explore the interaction of the laser irradiation with molecular materials, we performed first principle calculations of a prototype organic-inorganic interface between a nitroester (pentaerythritol tetranitrate, PETN, C5H8N4O12) and a magnesium oxide (MgO) surface. We found that the light absorption is defined by the band alignment between interface components and interfacial charge transfer coupled with electronic states in the band gap, generated by oxide surface defects. Hence the choice of an oxide substrate and its morphology makes the optical absorption tunable and governs both the energy accumulation and energy release at the interface. The obtained results offer a possible consistent interpretation of experiments on selective laser initiation of energetic materials, which reported that the presence of metal oxide additives triggered the photoinitiation by excitation energy much lower than the band gap. We suggest that PETN photodecomposition is catalyzed by oxygen vacancies (F0 centers) at the MgO surface. Our conclusions predict ways for a complete separation of thermo- and photo-stimulated interface chemistry of molecular materials, which is imperative for highly controllable fast decomposition and was not attainable before. The methodology described here can be applied to any type of molecular material/wide band gap dielectric interfaces. It provides a solid basis for novel design and targeted improvements of organic-inorganic interfaces with desired properties that promise to enable vastly new concepts of energy storage and conversion, photocatalysis, and molecular electronics.

Gas-phase spectra of MgO molecules: a possible connection from gas-phase molecules to planet formation

NASA Astrophysics Data System (ADS)

Kloska, Katherine A.; Fortenberry, Ryan C.

2018-02-01

A more fine-tuned method for probing planet-forming regions, such as protoplanetary discs, could be rovibrational molecular spectroscopy observation of particular premineral molecules instead of more common but ultimately less related volatile organic compounds. Planets are created when grains aggregate, but how molecules form grains is an ongoing topic of discussion in astrophysics and planetary science. Using the spectroscopic data of molecules specifically involved in mineral formation could help to map regions where planet formation is believed to be occurring in order to examine the interplay between gas and dust. Four atoms are frequently associated with planetary formation: Fe, Si, Mg and O. Magnesium, in particular, has been shown to be in higher relative abundance in planet-hosting stars. Magnesium oxide crystals comprise the mineral periclase making it the chemically simplest magnesium-bearing mineral and a natural choice for analysis. The monomer, dimer and trimer forms of (MgO)n with n = 1-3 are analysed in this work using high-level quantum chemical computations known to produce accurate results. Strong vibrational transitions at 12.5, 15.0 and 16.5 μm are indicative of magnesium oxide monomer, dimer and trimer making these wavelengths of particular interest for the observation of protoplanetary discs and even potentially planet-forming regions around stars. If such transitions are observed in emission from the accretion discs or absorptions from stellar spectra, the beginning stages of mineral and, subsequently, rocky body formation could be indicated.