Influence of corrosive solutions on microhardness and chemistry of magnesium oxide /001/ surfaces

Science.gov (United States)

Ishigaki, H.; Miyoshi, K.; Buckley, D. H.

1982-01-01

X-ray photoelectron spectroscopy analyses and hardness experiments were conducted on cleaved magnesium oxide /001/ surfaces. The magnesium oxide bulk crystals were cleaved to specimen size along the /001/ surface, and indentations were made on the cleaved surface in corrosive solutions containing HCl, NaOH, or HNO3 and in water without exposing the specimen to any other environment. The results indicated that chloride (such as MgCl2) and sodium films are formed on the magnesium oxide surface as a result of interactions between an HCl-containing solution and a cleaved magnesium oxide surface. The chloride films soften the magnesium oxide surface. In this case microhardness is strongly influenced by the pH value of the solution. The lower the pH, the lower the microhardness. Sodium films, which are formed on the magnesium oxide surface exposed to an NaOH containing solution, do not soften the magnesium oxide surface.

On the effect of interaction of molybdenum trioxide and magnesium oxide in water

International Nuclear Information System (INIS)

Bunin, V.M.; Karelin, A.I.; Solov'eva, L.N.

1992-01-01

Interaction of molybdenum trioxide and magnesium oxide in water was studied. It is shown that molybdenum trioxide forms consecutively magnesium molybdate, dimolybdate and magnesium polymolybdates with magnesium oxide

Effect of magnesium aluminum silicate glass on the thermal shock resistance of BN matrix composite ceramics

NARCIS (Netherlands)

Cai, Delong; Jia, Dechang; Yang, Zhihua; Zhu, Qishuai; Ocelik, Vaclav; Vainchtein, Ilia D.; De Hosson, Jeff Th M.; Zhou, Yu

The effects of magnesium aluminum silicate (MAS) glass on the thermal shock resistance and the oxidation behavior of h-BN matrix composites were systematically investigated at temperature differences from 600 degrees C up to 1400 degrees C. The retained strength rate of the composites rose with the

Composites of aluminum alloy and magnesium alloy with graphite showing low thermal expansion and high specific thermal conductivity

Science.gov (United States)

Oddone, Valerio; Boerner, Benji; Reich, Stephanie

2017-12-01

High thermal conductivity, low thermal expansion and low density are three important features in novel materials for high performance electronics, mobile applications and aerospace. Spark plasma sintering was used to produce light metal-graphite composites with an excellent combination of these three properties. By adding up to 50 vol.% of macroscopic graphite flakes, the thermal expansion coefficient of magnesium and aluminum alloys was tuned down to zero or negative values, while the specific thermal conductivity was over four times higher than in copper. No degradation of the samples was observed after thermal stress tests and thermal cycling. Tensile strength and hardness measurements proved sufficient mechanical stability for most thermal management applications. For the production of the alloys, both prealloyed powders and elemental mixtures were used; the addition of trace elements to cope with the oxidation of the powders was studied.

A Raman spectroscopic study of thermally treated glushinskite--the natural magnesium oxalate dihydrate.

Science.gov (United States)

Frost, Ray L; Adebajo, Moses; Weier, Matt L

2004-02-01

Raman spectroscopy has been used to study the thermal transformations of natural magnesium oxalate dihydrate known in mineralogy as glushinskite. The data obtained by Raman spectroscopy was supplemented with that of infrared emission spectroscopy. The vibrational spectroscopic data was complimented with high resolution thermogravimetric analysis combined with evolved gas mass spectrometry. TG-MS identified two mass loss steps at 146 and 397 degrees C. In the first mass loss step water is evolved only, in the second step carbon dioxide is evolved. The combination of Raman microscopy and a thermal stage clearly identifies the changes in the molecular structure with thermal treatment. Glushinskite is the dihydrate phase in the temperature range up to the pre-dehydration temperature of 146 degrees C. Above 397 degrees C, magnesium oxide is formed. Infrared emission spectroscopy shows that this mineral decomposes at around 400 degrees C. Changes in the position and intensity of the CO and CC stretching vibrations in the Raman spectra indicate the temperature range at which these phase changes occur.

Nuclear reactor shield including magnesium oxide

International Nuclear Information System (INIS)

Rouse, C.A.; Simnad, M.T.

1981-01-01

An improvement is described for nuclear reactor shielding of a type used in reactor applications involving significant amounts of fast neutron flux. The reactor shielding includes means providing structural support, neutron moderator material, neutron absorber material and other components, 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

Modeling of thermal expansion coefficient of perovskite oxide for solid oxide fuel cell cathode

Science.gov (United States)

Heydari, F.; Maghsoudipour, A.; Alizadeh, M.; Khakpour, Z.; Javaheri, M.

2015-09-01

Artificial intelligence models have the capacity to eliminate the need for expensive experimental investigation in various areas of manufacturing processes, including the material science. This study investigates the applicability of adaptive neuro-fuzzy inference system (ANFIS) approach for modeling the performance parameters of thermal expansion coefficient (TEC) of perovskite oxide for solid oxide fuel cell cathode. Oxides (Ln = La, Nd, Sm and M = Fe, Ni, Mn) have been prepared and characterized to study the influence of the different cations on TEC. Experimental results have shown TEC decreases favorably with substitution of Nd3+ and Mn3+ ions in the lattice. Structural parameters of compounds have been determined by X-ray diffraction, and field emission scanning electron microscopy has been used for the morphological study. Comparison results indicated that the ANFIS technique could be employed successfully in modeling thermal expansion coefficient of perovskite oxide for solid oxide fuel cell cathode, and considerable savings in terms of cost and time could be obtained by using ANFIS technique.

Precipitation of plutonium from acidic solutions using magnesium oxide

International Nuclear Information System (INIS)

Jones, S.A.

1994-01-01

Magnesium oxide will be used as a neutralizing agent for acidic plutonium-containing solutions. It is expected that as the magnesium oxide dissolves, the pH of the solution will rise, and plutonium will precipitate. The resulting solid will be tested for suitability to storage. The liquid is expected to contain plutonium levels that meet disposal limit requirements

Ultrathin Oxide Passivation Layer by Rapid Thermal Oxidation for the Silicon Heterojunction Solar Cell Applications

Directory of Open Access Journals (Sweden)

Youngseok Lee

2012-01-01

Full Text Available It is difficult to deposit extremely thin a-Si:H layer in heterojunction with intrinsic thin layer (HIT solar cell due to thermal damage and tough process control. This study aims to understand oxide passivation mechanism of silicon surface using rapid thermal oxidation (RTO process by examining surface effective lifetime and surface recombination velocity. The presence of thin insulating a-Si:H layer is the key to get high Voc by lowering the leakage current (I0 which improves the efficiency of HIT solar cell. The ultrathin thermal passivation silicon oxide (SiO2 layer was deposited by RTO system in the temperature range 500–950°C for 2 to 6 minutes. The thickness of the silicon oxide layer was affected by RTO annealing temperature and treatment time. The best value of surface recombination velocity was recorded for the sample treated at a temperature of 850°C for 6 minutes at O2 flow rate of 3 Lpm. A surface recombination velocity below 25 cm/s was obtained for the silicon oxide layer of 4 nm thickness. This ultrathin SiO2 layer was employed for the fabrication of HIT solar cell structure instead of a-Si:H, (i layer and the passivation and tunneling effects of the silicon oxide layer were exploited. The photocurrent was decreased with the increase of illumination intensity and SiO2 thickness.

Determination of thermal conductivity of magnesium-alloys

Institute of Scientific and Technical Information of China (English)

无

2001-01-01

An indirect method, Angstroms method was adopted and an instrument was designed to determine the thermal conductivity of magnesium metal and alloys. Angstroms method is an axial periodic heat flow technique by which the thermal diffusivity can be measured directly. Then thermal conductivity can be obtained with relation to thermal diffusivity. Compared with the recommended data from the literature the fitted values of the thermal diffiusivity correspond with 3%, and the credible probability of the thermal conductivity in the range of 0-450 ℃ is about 95%. The method is applicable in the given temperature range.

Effect of Magnesium Oxide Nanoparticles on Water Glass Structure

Directory of Open Access Journals (Sweden)

Bobrowski A.

2012-09-01

Full Text Available An attempt has been made to determine the effect of an addition of colloidal suspensions of the nanoparticles of magnesium oxide on the structure of water glass, which is a binder for moulding and core sands. Nanoparticles of magnesium oxide MgO in propanol and ethanol were introduced in the same mass content (5wt.% and structural changes were determined by measurement of the FT-IR absorption spectra.

Nanostructured magnesium increases bone cell density.

Science.gov (United States)

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.

Ultrathin Oxide Passivation Layer by Rapid Thermal Oxidation for the Silicon Heterojunction Solar Cell Applications

OpenAIRE

Lee, Youngseok; Oh, Woongkyo; Dao, Vinh Ai; Hussain, Shahzada Qamar; Yi, Junsin

2012-01-01

It is difficult to deposit extremely thin a-Si:H layer in heterojunction with intrinsic thin layer (HIT) solar cell due to thermal damage and tough process control. This study aims to understand oxide passivation mechanism of silicon surface using rapid thermal oxidation (RTO) process by examining surface effective lifetime and surface recombination velocity. The presence of thin insulating a-Si:H layer is the key to get high Voc by lowering the leakage current (I0) which improves the efficie...

Performance, carcass and meat quality of ewes supplemented with magnesium oxide

Directory of Open Access Journals (Sweden)

Camila Constantino

2014-01-01

Full Text Available The objective of this study was to evaluate the performance, the carcass and meat characteristics of ewes supplemented with magnesium oxide. Eighteen 6-year-old Santa Ines ewes were used in a completely randomized experimental design, where three levels of supplementation (0.0, 0.1 and 0.2% magnesium oxide in the concentrate were tested, with six replicates. Final weight, weight gain, feed intake and feed conversion were not affected by levels of magnesium supplementation. Hot and cold carcass weights showed linear increasing and quadratic responses, respectively, according to supplementation with magnesium. Carcass measurements such as length, depth, and measures of arm and leg were not affected by supplementation. Depth and width of the longissimus muscle and rib-eye area were not affected; however, marbling and ether extract increased linearly with supplementation. Water loss and color were not affected. Lipid oxidation and shear force were not affected by supplementation, while the myofibrillar fragmentation index showed a quadratic regression. There was a linear decrease in pH with magnesium supplementation. Supplementation with magnesium can improve carcass and meat pH, but can act negatively by increasing the amount of marbling and ether extract of meat.

Solidification of aqueous radioactive waste using insoluble compounds of magnesium oxide

International Nuclear Information System (INIS)

Carlson, J.E.

1986-01-01

A process is described for the treatment of radioactive waste which comprises: (a) first adding, under continuous agitation, a sufficient amount of a powdered magnesium oxide or magnesium hydroxide to an aqueous radioactive waste solution containing boric acid, the temperature of the water solution being 55-95 degrees C. to produce a magnesium borate derivative; (b) adding cement, under continuous agitation, to the magnesium borate derivative; and (c) then adding, under continuous agitation, after the cement has been dispersed, a sufficient amount of a compound selected from the group consisting of calcium oxide and calcium hydroxide to (b) to produce a gel matrix structure

Special metallurgy - the electrical butt-welding by flashing of sintered magnesium-magnesium oxide composites (1963)

International Nuclear Information System (INIS)

Charleux, J.

1963-01-01

Electrical resistance welding has become quite important since World War II because of the need of a high yield in aeronautical production. Progress has been due in particular to the improvements made in electronically controlled apparatus making possible the automatic control of welding. For the butt-welding of sections requiring either a high production rate or a high quality weld, the flash butt-welding system has been very much developed these last few years. The use of this welding method is of great importance in the field of the bonding of oxidisable metals such as magnesium or aluminium and its alloys, because the welded joint is free from oxides. This study consists of general considerations on the flash-welding process with regard to temperature distribution in the parts during welding, and to electrical phenomena connected with flashing. Besides this general or theoretical section, we have applied the welding process to the bonding of sintered magnesium, a magnesium-magnesium oxide composite, whose use as a structural element in nuclear reactors is considered. (author) [fr

Nanostructured magnesium increases bone cell density

International Nuclear Information System (INIS)

Weng, Lucy; Webster, Thomas J

2012-01-01

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. (paper)

Problems of magnesium oxide wallboard usage in construction

Science.gov (United States)

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.

[Effect of food thickener on disintegration and dissolution of magnesium oxide tablets].

Science.gov (United States)

Tomita, Takashi; Goto, Hidekazu; Yoshimura, Yuya; Tsubouchi, Yoshiko; Nakanishi, Rie; Kojima, Chikako; Yoneshima, Mihoko; Yoshida, Tadashi; Tanaka, Katsuya; Sumiya, Kenji; Kohda, Yukinao

2015-01-01

It has been reported that magnesium oxide tablets are excreted in a non-disintegrated state in the stool of patients when the tablets are administered after being immersed in a food thickener. Therefore we examined whether immersion in a food thickener affects the pharmacological effect in patients taking magnesium oxide tablets, and whether immersion affects its disintegration and solubility. The mean dosage (1705 mg/d) was higher for patients who took tablets after immersion in a food thickener than for those who took non-immersed tablets (1380 mg/d). The disintegration time and dissolution rate of the immersed tablets were lower than those of non-immersed tablets in vitro. Furthermore, components that constitute the food thickener and differences in composition concentrations differentially affect the disintegration and solubility of magnesium oxide tablets. This suggests that commercially available food thickeners are likely to be associated with changes in the degradation of magnesium oxide tablets, and they therefore should be carefully used in certain clinical situations.

The effect of adding magnesium oxide on the mechanical properties of the tricalcium phosphate-zirconia composites

Energy Technology Data Exchange (ETDEWEB)

Sallemi, Imen, E-mail: imen.sallemi@hotmail.com; Bouaziz, Jamel; Ben Ayed, Foued

2015-02-01

The effect of magnesium oxide on the mechanical properties of the tricalcium phosphate – 50 wt.% zirconia composites was investigated during a sintering process between 1300 °C and 1400 °C. The characteristics of the samples before and after the sintering process were realized by using the differential thermal analysis, dilatometry, X-ray diffraction, the {sup 31}P magic angle scanning nuclear magnetic resonance, the scanning electron microscope and by considering such mechanical properties as the rupture strength and Vickers hardness. The mechanical performances of the tricalcium phosphate-50 wt.% zirconia composites increased with both the percentage of magnesium oxide and the sintering temperature. At 1400 °C, the mechanical properties of the composites sintered with 10 wt.% magnesium oxide reached their maximum value. Thus, Vickers hardness increased from 554 to 6350 MPa and the rupture strength of the corresponding composites varied from 5.2 to 25 MPa. The increase of the mechanical properties of the samples is due to the formation of both the tetragonal zirconia phase and the liquid phase which helps to fill the pores. The microstructure of needle form is most probably phosphate precipitates which are formed from this liquid phase. Furthermore, the presence of magnesium oxide in the composites prevented the inverse allotropic transformation of zirconia. - Highlights: • We measure the rupture strength and Vickers hardness of bioceramics. • We characterize the effect of MgO on the mechanical properties of the tricalcium phosphate – 50 wt% zirconia composites. • MgO increase the mechanical properties of the composites.

Preparation and characterization of the micro-arc oxidation composite coatings on magnesium alloys

Directory of Open Access Journals (Sweden)

Yanfeng Ge

2014-12-01

Full Text Available The magnesium alloys attract the light-weight manufacture due to its high strength to weight ratio, however the poor corrosion resistance limits the application in automobile industry. The Micro-arc Composite Ceramic (MCC coatings on AZ91D magnesium alloys were prepared by Micro-arc Oxidation (MAO and electrophoresis technologies. The microstructure, corrosion resistance, abrasion resistance, stone impact resistance and adhesion of MCC coatings were studied respectively. The cross section morphologies showed that the outer organic coating was filled into the hole on surface of MAO coating, and it acted as a shelter against corrosive products. The copper-accelerated acetic acid salt spray Test, abrasion resistance test, stone impact resistance test, thermal shock resistance test and adhesion test were used to evaluate the protective characterization by the third testing organization which approved by GM. The test results showed the composite coatings meet all the requirements. The MCC coating on Mg presents excellent properties, and it is a promising surface treatment technology on magnesium alloys for production vehicles.

d° Ferromagnetism of Magnesium Oxide

Directory of Open Access Journals (Sweden)

Jitendra Pal Singh

2017-11-01

Full Text Available Magnetism without d-orbital electrons seems to be unrealistic; however, recent observations of magnetism in non-magnetic oxides, such as ZnO, HfO2, and MgO, have opened new avenues in the field of magnetism. Magnetism exhibited by these oxides is known as d° ferromagnetism, as these oxides either have completely filled or unfilled d-/f-orbitals. This magnetism is believed to occur due to polarization induced by p-orbitals. Magnetic polarization in these oxides arises due to vacancies, the excitation of trapped spin in the triplet state. The presence of vacancies at the surface and subsurface also affects the magnetic behavior of these oxides. In the present review, origins of magnetism in magnesium oxide are discussed to obtain understanding of d° ferromagnetism.

Capture of negative muons in magnesium oxides and crystalline modifications of phosphorus

International Nuclear Information System (INIS)

Zinov, V.G.; Kachalkin, A.K.; Nikityuk, L.N.; Pokrovskij, V.N.; Rybakov, V.N.; Yutlandov, I.A.

1977-01-01

The paper is aimed at comparing the structure of mesic K X-ray patterns of phosphorus in its crystalline modifications, comparing the structure of mesic X-ray patterns of magnesium and oxygen in compounds of MgO, MgO 2 , H 2 O and metallic magnesium, as well as comparison of propabilities of μ - atomic capture in magnesium oxides. By analyzing the mesic K X-ray patterns of red and white phosphorus it is concluded that the phosphorus crystalline modification produces the effect on the line structure, the higher series number being somewhat larger for the allotrope of phosphorus with polymeric structure. A comparison is made of the mesic X-ray series of the magnesium in oxide and metal, of the oxygen in oxide and water with the analogous data for aluminium and silicon. The data confirm the supposition that chemical bond (valence electrons) plays a substantial role in meson capture

Effect of Dissolved Silica on Immobilization of Boron by Magnesium Oxide

Directory of Open Access Journals (Sweden)

Shoko Nozawa

2018-02-01

Full Text Available The effect of silica on the immobilization reaction of boron by magnesium oxide was investigated by laboratory experiments. In the absence of silica, due to dissolution of the magnesium oxide, boron was removed from solutions by the precipitation of multiple magnesium borates. In the presence of silica, magnesium silica hydrate (M-S-H was formed as a secondary mineral, which takes up boron. Here 11B magic-angle spinning nuclear magnetic resonance (MAS-NMR and Fourier transform infrared spectrometer (FT-IR data show that a part of the boron would be incorporated into M-S-H structures by isomorphic substitution of silicon. Another experiment where magnesium oxide and amorphous silica were reacted beforehand and boron was added later showed that the shorter the reaction time of the preceding reaction, the higher the sorption ratio of boron. That is, boron was incorporated into the M-S-H mainly by coprecipitation. The experiments in the study here show that the sorption of boron in the presence of silica is mainly due to the incorporation of boron during the formation of the M-S-H structure, which suggests that boron would not readily leach out, and that stable immobilization of boron can be expected.

Moisture damage with magnesium oxide boards in Danish facade structures

DEFF Research Database (Denmark)

Rode, Carsten; Bunch-Nielsen, Tommy; Hansen, Kurt Kielsgaard

2017-01-01

Magnesium oxide boards have been widely used on facades in Denmark during 2010-2015. However, the magnesium salts absorb humidity from the ambient, and they begin to leak salty water, which is highly corrosive, and leads to moisture and mould problems in wooden members of the structures. Mg...

Mosaic-shaped cathode for highly durable solid oxide fuel cell under thermal stress

Science.gov (United States)

Joo, Jong Hoon; Jeong, Jaewon; Kim, Se Young; Yoo, Chung-Yul; Jung, Doh Won; Park, Hee Jung; Kwak, Chan; Yu, Ji Haeng

2014-02-01

In this study, we propose a novel "mosaic structure" for a SOFC (solid oxide fuel cell) cathode with high thermal expansion to improve the stability against thermal stress. Self-organizing mosaic-shaped cathode has been successfully achieved by controlling the amount of binder in the dip-coating solution. The anode-supported cell with mosaic-shaped cathode shows itself to be highly durable performance for rapid thermal cycles, however, the performance of the cell with a non-mosaic cathode exhibits severe deterioration originated from the delamination at the cathode/electrolyte interface after 7 thermal cycles. The thermal stability of an SOFC cathode can be evidently improved by controlling the surface morphology. In view of the importance of the thermal expansion properties of the cathode, the effects of cathode morphology on the thermal stress stability are discussed.

Thermal imaging of solid oxide fuel cell anode processes

Energy Technology Data Exchange (ETDEWEB)

Pomfret, Michael B.; Kidwell, David A.; Owrutsky, Jeffrey C. [Chemistry Division, U.S. Naval Research Laboratory, Washington, DC 20375 (United States); Steinhurst, Daniel A. [Nova Research Inc., Alexandria, VA 22308 (United States)

2010-01-01

A Si-charge-coupled device (CCD), camera-based, near-infrared imaging system is demonstrated on Ni/yttria-stabilized zirconia (YSZ) fragments and the anodes of working solid oxide fuel cells (SOFCs). NiO reduction to Ni by H{sub 2} and carbon deposition lead to the fragment cooling by 5 {+-} 2 C and 16 {+-} 1 C, respectively. When air is flowed over the fragments, the temperature rises 24 {+-} 1 C as carbon and Ni are oxidized. In an operational SOFC, the decrease in temperature with carbon deposition is only 4.0 {+-} 0.1 C as the process is moderated by the presence of oxides and water. Electrochemical oxidation of carbon deposits results in a {delta}T of +2.2 {+-} 0.2 C, demonstrating that electrochemical oxidation is less vigorous than atmospheric oxidation. While the high temperatures of SOFCs are challenging in many respects, they facilitate thermal imaging because their emission overlaps the spectral response of inexpensive Si-CCD cameras. Using Si-CCD cameras has advantages in terms of cost, resolution, and convenience compared to mid-infrared thermal cameras. High spatial ({proportional_to}0.1 mm) and temperature ({proportional_to}0.1 C) resolutions are achieved in this system. This approach provides a convenient and effective analytical technique for investigating the effects of anode chemistry in operating SOFCs. (author)

Thermal imaging of solid oxide fuel cell anode processes

Science.gov (United States)

Pomfret, Michael B.; Steinhurst, Daniel A.; Kidwell, David A.; Owrutsky, Jeffrey C.

A Si-charge-coupled device (CCD), camera-based, near-infrared imaging system is demonstrated on Ni/yttria-stabilized zirconia (YSZ) fragments and the anodes of working solid oxide fuel cells (SOFCs). NiO reduction to Ni by H 2 and carbon deposition lead to the fragment cooling by 5 ± 2 °C and 16 ± 1 °C, respectively. When air is flowed over the fragments, the temperature rises 24 ± 1 °C as carbon and Ni are oxidized. In an operational SOFC, the decrease in temperature with carbon deposition is only 4.0 ± 0.1 °C as the process is moderated by the presence of oxides and water. Electrochemical oxidation of carbon deposits results in a Δ T of +2.2 ± 0.2 °C, demonstrating that electrochemical oxidation is less vigorous than atmospheric oxidation. While the high temperatures of SOFCs are challenging in many respects, they facilitate thermal imaging because their emission overlaps the spectral response of inexpensive Si-CCD cameras. Using Si-CCD cameras has advantages in terms of cost, resolution, and convenience compared to mid-infrared thermal cameras. High spatial (∼0.1 mm) and temperature (∼0.1 °C) resolutions are achieved in this system. This approach provides a convenient and effective analytical technique for investigating the effects of anode chemistry in operating SOFCs.

Recovery of Chromium from Waste Taning Liquors by Magnesium Oxide

Directory of Open Access Journals (Sweden)

Mahmood M. Barbooti

2010-10-01

Full Text Available This is a case study of AL-Za’afaraniya tanning factory, 15 km to the south of Baghdad, to spot light on simple chemical treatment of the discharged water to solve the environmental problems associated with its chromium content management. The treatment was extended to the recovery and reuse of chromium. Chromium was precipitated by the addition of magnesium oxide which also aid as a neutralizer for the acidic effluent. The laboratory treatment was carried out to find the optimum conditions. The wastewater samples were taken from the outline area of the tannery. Box-Wilson method was adopted to find useful relationships between the operating variables (temperature, mixing period and magnesium oxide dose and the pH and chromium content of effluent. The experimental data were successfully fitted to second order polynomial mathematical models for the treatment. The most favorable operating conditions for the treatment were: temperature, 30 ºC; mixing period, 50 min and magnesium oxide concentration, 3000 mg/L. On using the optimum conditions a mathematical model simulating the operation for the treatment was obtained as follows:Cr = 6.0848 – 0.001839 X11 – 0.105334 X12 – 0.041038 X13pH = 10.29086 – 0.001223 X11 – 0.140043 X12 – 0.00953 X13Experimentally Cr concentration was decreased to about (0.5 mg/L in wastewater after raising the pH value to (7.35 by adding magnesium oxide.

Electrolytes for magnesium electrochemical cells

Science.gov (United States)

Burrell, Anthony K.; Sa, Niya; Proffit, Danielle Lee; Lipson, Albert; Liao, Chen; Vaughey, John T.; Ingram, Brian J.

2017-07-04

An electrochemical cell includes a high voltage cathode configured to operate at 1.5 volts or greater; an anode including Mg.sup.0; and an electrolyte including an ether solvent and a magnesium salt; wherein: a concentration of the magnesium salt in the ether is 1 M or greater.

Laboratory evaluation of PAH oxidation by magnesium peroxides and iron oxides mixtures as reactive material for groundwater remediation

International Nuclear Information System (INIS)

Valderrama, C.; Gamisans, X.; Cortina, J.L.; Farran, A.; Marti, V.

2005-01-01

contaminant(s) of concern; 2) the total oxidant requirements, pH dependence and relative reaction rate, and 3) the reaction by-products formed. The main goal of this work the evaluation of mixtures of magnesium peroxide and iron oxides as reactive materials for Poly-aromatic Hydrocarbons (PAH) degradation reagents in permeable reactive barriers or zones. One goal of this study is to examine and determine the release rate of hydrogen peroxide from magnesium peroxide by means of laboratory experiments. The magnesium peroxide from two different sources (i.e. Regenesis and Solvay) will be compared. Another objective is to study how a catalyst such as iron speeds up the degradation of PAHs. Not only the release rate will be studied, but also the dissolution process of magnesium peroxide. The experiments mentioned above will be carried out in both batch and continuous reactors. The results of this study showed that the magnesium peroxide from Solvay can release more hydrogen peroxide than the magnesium peroxide from Regenesis. The oxidation factors for the two preparations are quite similar, even though the release of hydrogen peroxide differs greatly. Another point, which ought to be considered, is the minor effect of iron oxides in the degradation of PAHs. The dissolution process of magnesium peroxide is a complex process with magnesium hydroxide as the main reaction by product. So, magnesium peroxides can be used as a hydrogen peroxide releasing compound. Further studies on the removal mechanisms should be performed to identify the oxidation products as well as the sorption properties of magnesium hydroxide. The heterogeneous oxidation of a family of poly-aromatic hydrocarbons (anthracene, pyrene, fluorene and naphthalene) proceeds with a highly efficiency ratio and following a first order kinetic

Oxidation behavior of molten magnesium in atmospheres containing SO2

International Nuclear Information System (INIS)

Wang Xianfei; Xiong Shoumei

2011-01-01

Graphical abstract: Highlights: → We found the film formed on molten magnesium had a two or three layers structure. → The formation mechanism of film was investigated and a growth model was proposed. → We found the formation of MgSO 4 was critical and promoted the growth of the film. - Abstract: The microchemistry and morphology of the oxide layer formed on molten magnesium in atmospheres containing SO 2 were examined. Based on the results and the thermodynamic and kinetic calculations of oxide-growth process, a schematic oxidation mechanism is presented. The results showed that the oxide scales with network structure were generally composed of MgO, MgS, and MgSO 4 with different layers, depending on the SO 2 content, the time and the temperature. The formation of MgSO 4 was important for the formation of the protective oxide scales. The growth of the oxide scales followed the parabolic law at 973 K and was controlled by diffusion.

Effect of antimony oxide on magnesium vanadates for the selective oxidation of hydrogen sulfide to sulfur

Energy Technology Data Exchange (ETDEWEB)

Li, K.T.; Chi, Z.H. [Department of Chemical Engineering, Tunghai University, ROC Taichung (Taiwan)

2001-05-17

The effect of antimony oxide addition to MgV{sub 2}O{sub 6} and Mg{sub 3}V{sub 2}O{sub 8} was studied in the selective oxidation of hydrogen sulfide to sulfur. Significant improvements in sulfur selectivity and yield were observed for the uncalcined mechanical mixtures of magnesium vanadates with {alpha}-Sb{sub 2}O{sub 4}. Calcination of the mechanical mixtures resulted in the much stronger synergy in catalytic activity and sulfur selectivity. For the uncalcined samples, XRD, TPR and XPS studies indicated that antimony reduction behaviors in the mechanical mixtures differed very much from those in {alpha}-Sb{sub 2}O{sub 4} alone, suggested that their selectivity improvements might be due to the interactions (probably oxygen transfer) between {alpha}-Sb{sub 2}O{sub 4} and magnesium vanadates. For the calcined samples, XRD results indicated that their better catalytic performances in H{sub 2}S oxidation were primarily attributed to the formation of VSbO{sub 4} compound from antimony oxide and magnesium vanadates.

Magnesium stannide as a high-capacity anode for magnesium-ion batteries

Science.gov (United States)

Nguyen, Dan-Thien; Song, Seung-Wan

2017-11-01

Driven by the limited global resources of lithium, magnesium metal batteries are considered as potential energy storage systems. The battery chemistry of magnesium metal anode, however, limits the selection of electrolytes, cathode materials and working temperature, making the realization of magnesium metal batteries complicated. Herein, we report the development of a new magnesium-insertion anode, magnesium stannide (Mg2Sn), and demonstrate reversible electrochemical Mg2+-extraction and insertion of Mg2Sn anode at 0.2 V versus Mg, delivering discharge capacity of 270 mAhg-1 in a half-cell with the electrolyte of PhMgCl/THF and enabling of room temperature magnesium-ion batteries with Mg2Sn anode combined with Mg-free oxide cathode and conventional-type electrolyte of Mg(TFSI)2/diglyme. The combination of Mg2Sn anode with various cathodes and electrolytes holds great promise for enabling room temperature magnesium-ion batteries.

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

Science.gov (United States)

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.

Statistical optimization of microencapsulation process for coating of magnesium particles with Viton polymer

Energy Technology Data Exchange (ETDEWEB)

Pourmortazavi, Seied Mahdi, E-mail: pourmortazavi@yahoo.com [Faculty of Material and Manufacturing Technologies, Malek Ashtar University of Technology, P.O. Box 16765-3454, Tehran (Iran, Islamic Republic of); Babaee, Saeed; Ashtiani, Fatemeh Shamsi [Faculty of Chemistry & Chemical Engineering, Malek Ashtar University of Technology, Tehran (Iran, Islamic Republic of)

2015-09-15

Graphical abstract: - Highlights: • Surface of magnesium particles was modified with Viton via solvent/non-solvent method. • FT-IR, SEM, EDX, Map analysis, and TG/DSC techniques were employed to characterize the coated particles. • Coating process factors were optimized by Taguchi robust design. • The importance of coating conditions on resistance of coated magnesium against oxidation was studied. - Abstract: The surface of magnesium particles was modified by coating with Viton as an energetic polymer using solvent/non-solvent technique. Taguchi robust method was utilized as a statistical experiment design to evaluate the role of coating process parameters. The coated magnesium particles were characterized by various techniques, i.e., Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and thermogravimetry (TG), and differential scanning calorimetry (DSC). The results showed that the coating of magnesium powder with the Viton leads to a higher resistance of metal against oxidation in the presence of air atmosphere. Meanwhile, tuning of the coating process parameters (i.e., percent of Viton, flow rate of non-solvent addition, and type of solvent) influences on the resistance of the metal particles against thermal oxidation. Coating of magnesium particles yields Viton coated particles with higher thermal stability (632 °C); in comparison with the pure magnesium powder, which commences oxidation in the presence of air atmosphere at a lower temperature of 260 °C.

Arsenic adsorption in pre-treatment natural zeolite with magnesium oxides

International Nuclear Information System (INIS)

Mejia Z, F.; Valenzuela G, J. L.; Aguayo S, S.; Meza F, D.

2009-01-01

A methodology was developed to modify a natural zeolite (chabazite) with magnesium oxide in order to remove arsenic (As +5 ) from water for human consumption. It is proposed a magnesium oxide while regarded as an efficient adsorbent for removing metals in water. X-ray diffraction analyses show significant changes in the chabazite due to the presence of oxides and amorphous hydroxides incorporated during the pre-treatment. Experimental design results show an efficiency greater than 90% of As +5 adsorbed in five minutes. The results indicate that the most significant variables affecting the adsorption of As +5 are the initial concentration of As and the solid/liquid ratio. Experimental data fitted better to Freundlich isotherm with a 20.17 mg/g adsorption capability. (Author)

Synthesis of Binary Magnesium-Transition Metal Oxides via Inverse Coprecipitation

Science.gov (United States)

Yagi, Shunsuke; Ichikawa, Yuya; Yamada, Ikuya; Doi, Takayuki; Ichitsubo, Tetsu; Matsubara, Eiichiro

2013-02-01

Synthesis of binary magnesium-transition metal oxides, MgM2O4 (M: Cr, Mn, Fe, Co) and MgNiO2, was performed by calcination at relatively low temperatures of 500 and 750 °C for 24 h through inverse coprecipitation of carbonate hydroxide precursors. The important roles of the precipitation agent, sodium carbonate, were clarified by considering equilibria in an aqueous solution. The structure parameters of the obtained binary magnesium-transition metal oxide powders, specifically the occupancy of atomic sites, were evaluated from synchrotron X-ray diffraction (XRD) profiles by Rietveld refinement in addition to the magnetic properties at room temperature. The present work provides general guidelines for low-cost and high-volume synthesis of complex oxides, which are easily decomposed at high temperatures.

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

Energy Technology Data Exchange (ETDEWEB)

Tang, Xiaojia; Guo, Lin; Chen, Chen; Liu, Quan; Li, Tie; Zhu, Yimin, E-mail: ntp@dlmu.edu.cn

2014-05-01

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-phase 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.

Aging of magnesium stearate under high doses gamma irradiation and oxidative conditions

Energy Technology Data Exchange (ETDEWEB)

Lebeau, D.; Beuvier, L.; Cornaton, M. [CEA, DEN, DPC, SECR, LRMO, F-91191 Gif-sur-Yvette (France); Miserque, F. [CEA, DEN, DPC, SCCME, LECA, F-91191 Gif-sur-Yvette (France); Tabarant, M. [CEA, DEN, DPC, SEARS, LISL, F-91191 Gif-sur-Yvette (France); Esnouf, S. [CEA, DEN, DPC, SECR, LRMO, F-91191 Gif-sur-Yvette (France); Ferry, M., E-mail: muriel.ferry@cea.fr [CEA, DEN, DPC, SECR, LRMO, F-91191 Gif-sur-Yvette (France)

2015-05-15

Highlights: • Magnesium stearate was radio-oxidized at very high doses using gamma-rays. • H{sub 2} emission was estimated as a function of the integrated dose. • Modifications in the organic solid were followed as a function of the integrated dose. • A non-exhaustive degradation mechanism of magnesium stearate was proposed. - Abstract: In nuclear waste packages conditioning processes, magnesium stearate is widely used because of its high lubricating properties. For safety purposes, the radiolytic degradation of these organic materials has to be better understood to be able to predict their aging in repository conditions. This study reports the radiolytic degradation of magnesium stearate, using gamma-rays at room temperature and under air. Modifications were followed using different analytical tools (XPS, ATR-FTIR, ICP-AES, ATG and mass spectrometry). It has been observed that molecules mainly formed up to 1000 kGy of gamma irradiation dose under radio-oxidation are alkanes, hydroperoxides, double bonds in the aliphatic chain, carboxylates with aliphatic chain shorter than the one of stearate and ketones. At a dose of 4000 kGy, dicarboxylic acids are observed: the formation of these molecules needs a dose of at least 1000 kGy to be created under radio-oxidation. These observations allow us to propose a non-exhaustive degradation mechanism of magnesium stearate under gamma-irradiation at room temperature and under air.

Synthesis of nanocrystalline magnesium nitride (Mg3N2) powder using thermal plasma

International Nuclear Information System (INIS)

Kim, Dong-Wook; Kim, Tae-Hee; Park, Hyun-Woo; Park, Dong-Wha

2011-01-01

Nanocrystalline magnesium nitride (Mg 3 N 2 ) powder was synthesized from bulk magnesium by thermal plasma at atmospheric pressure. Magnesium vapor was generated through heating the bulk magnesium by DC plasma jet and reacted with ammonia gas. Injecting position and flow rates of ammonia gas were controlled to investigate an ideal condition for Mg 3 N 2 synthesis. The synthesized Mg 3 N 2 was cooled and collected on the chamber wall. Characteristics of the synthesized powders for each experimental condition were analyzed by X-ray diffractometer (XRD), scanning electron microscopy (SEM) and thermogravity analysis (TGA). In absence of NH 3 , magnesium metal powder was formed. The synthesis with NH 3 injection in low temperature region resulted in a formation of crystalline magnesium nitride with trigonal morphology, whereas the mixture of magnesium metal and amorphous Mg 3 N 2 was formed when NH 3 was injected in high temperature region. Also, vaporization process of magnesium was discussed.

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

Science.gov (United States)

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.

Evolution of thermal stress and failure probability during reduction and re-oxidation of solid oxide fuel cell

Science.gov (United States)

Wang, Yu; Jiang, Wenchun; Luo, Yun; Zhang, Yucai; Tu, Shan-Tung

2017-12-01

The reduction and re-oxidation of anode have significant effects on the integrity of the solid oxide fuel cell (SOFC) sealed by the glass-ceramic (GC). The mechanical failure is mainly controlled by the stress distribution. Therefore, a three dimensional model of SOFC is established to investigate the stress evolution during the reduction and re-oxidation by finite element method (FEM) in this paper, and the failure probability is calculated using the Weibull method. The results demonstrate that the reduction of anode can decrease the thermal stresses and reduce the failure probability due to the volumetric contraction and porosity increasing. The re-oxidation can result in a remarkable increase of the thermal stresses, and the failure probabilities of anode, cathode, electrolyte and GC all increase to 1, which is mainly due to the large linear strain rather than the porosity decreasing. The cathode and electrolyte fail as soon as the linear strains are about 0.03% and 0.07%. Therefore, the re-oxidation should be controlled to ensure the integrity, and a lower re-oxidation temperature can decrease the stress and failure probability.

Thermoelectric Properties of Hot-Pressed and PECS-Sintered Magnesium-Doped Copper Aluminum Oxide

Science.gov (United States)

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.

Atomization of magnesium, strontium, barium and lead nitrates on surface of graphite atomizers

International Nuclear Information System (INIS)

Nagdaev, V.K.; Pupyshev, A.A.

1982-01-01

Modelling of the processes on graphite surface using differential-thermal analysis and graphite core with identification of decomposition products of magnesium, strontium, barium and lead nitrates by X-ray analysis has shown that carbon promotes the formation of strontium, barium and lead carbonates. The obtained temperatures of strontium and barium carbonate decomposition to oxides agree satisfactorily with calculation ones. Magnesium nitrate does not react with carbon. Formation of strontium and barium carbonates results in considerable slowing down of the process of gaseous oxide dissociation. Lead carbonate is unstable and rapidly decomposes to oxide with subsequent reduction to free metal. Formation of magnesium, strontium and barium free atoms is connected with appearance of gaseous oxides in analytical zone. Oxide and free metal lead are present on graphite surface simultaneously

Thermal stress analysis of sulfur deactivated solid oxide fuel cells

Science.gov (United States)

Zeng, Shumao; Parbey, Joseph; Yu, Guangsen; Xu, Min; Li, Tingshuai; Andersson, Martin

2018-03-01

Hydrogen sulfide in fuels can deactivate catalyst for solid oxide fuel cells, which has become one of the most critical challenges to stability. The reactions between sulfur and catalyst will cause phase changes, leading to increase in cell polarization and mechanical mismatch. A three-dimensional computational fluid dynamics (CFD) approach based on the finite element method (FEM) is thus used to investigate the polarization, temperature and thermal stress in a sulfur deactivated SOFC by coupling equations for gas-phase species, heat, momentum, ion and electron transport. The results indicate that sulfur in fuels can strongly affect the cell polarization and thermal stresses, which shows a sharp decrease in the vicinity of electrolyte when 10% nickel in the functional layer is poisoned, but they remain almost unchanged even when the poisoned Ni content was increased to 90%. This investigation is helpful to deeply understand the sulfur poisoning effects and also benefit the material design and optimization of electrode structure to enhance cell performance and lifetimes in various hydrocarbon fuels containing impurities.

Formation of a Spinel Coating on AZ31 Magnesium Alloy by Plasma Electrolytic Oxidation

Science.gov (United States)

Sieber, Maximilian; Simchen, Frank; Scharf, Ingolf; Lampke, Thomas

2016-03-01

Plasma electrolytic oxidation (PEO) is a common means for the surface modification of light metals. However, PEO of magnesium substrates in dilute electrolytes generally leads to the formation of coatings consisting of unfavorable MgO magnesium oxide. By incorporation of electrolyte components, the phase constitution of the oxide coatings can be modified. Coatings consisting exclusively of MgAl2O4 magnesium-aluminum spinel are produced by PEO in an electrolyte containing hydroxide, aluminate, and phosphate anions. The hardness of the coatings is 3.5 GPa on Martens scale on average. Compared to the bare substrate, the coatings reduce the corrosion current density in dilute sodium chloride solution by approx. one order of magnitude and slightly shift the corrosion potential toward more noble values.

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

Science.gov (United States)

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.

Synthesis of magnesium aluminate spinel by periclase and alumina chlorination

International Nuclear Information System (INIS)

Orosco, Pablo; Barbosa, Lucía; Ruiz, María del Carmen

2014-01-01

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 2 –N 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 2 O 3 (alumina) in chlorine atmosphere was developed and the results were compared with those 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 2 atmosphere of the MgO–Al 2 O 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

Concentration-dependent behaviors of bone marrow derived mesenchymal stem cells and infectious bacteria toward magnesium oxide nanoparticles.

Science.gov (United States)

Wetteland, Cheyann Lee; Nguyen, Nhu-Y Thi; Liu, Huinan

2016-04-15

This article reports the quantitative relationship between the concentration of magnesium oxide (MgO) nanoparticles and its distinct biological activities towards mammalian cells and infectious bacteria for the first time. The effects of MgO nanoparticles on the viability of bone marrow derived mesenchymal stem cells (BMSCs) and infectious bacteria (both gram-negative Escherichia coli and gram-positive Staphylococcus epidermidis) showed a concentration-dependent behavior in vitro. The critical concentrations of MgO nanoparticles identified in this study provided valuable guidelines for biomaterial design toward potential clinical translation. BMSCs density increased significantly when cultured in 200μg/mL of MgO in comparison to the Cells Only control without MgO. The density of BMSCs decreased significantly after culture in the media with 500μg/mL or more of MgO. Concentrations at or above 1000μg/mL of MgO resulted in complete BMSCs death. Quantification of colony forming units (CFU) revealed that the minimum bactericidal concentration (MBC) of MgO for E. coli and S. epidermidis was 1200μg/mL. The addition of MgO nanoparticles into the cultures increased the pH and Mg(2+) ion concentration in the respective culture media, which might have played a role in the observed cell responses but not the main factors. E. coli and S. epidermidis still proliferated significantly at alkaline pH up to 10 or with supplemental Mg(2+) dosages up to 50mM, indicating bactericidal properties of MgO are beyond the effects of increased media pH and Mg(2+) ion concentrations. MgO nanoparticles at a concentration of 200μg/mL provided dual benefits of promoting BMSC proliferation while reducing bacterial adhesion, which should be further studied for potential medical implant applications. The use of free MgO nanoparticles yielded detrimental effects to BMSCs in concentrations above 300μg/mL. We recommend further study into MgO nanoparticle as a coating material or as a part of a

In-depth investigation on physicochemical and thermal properties of magnesium (II gluconate using spectroscopic and thermoanalytical techniques

Directory of Open Access Journals (Sweden)

Mahendra Kumar Trivedi

2017-10-01

Full Text Available Magnesium gluconate is a classical organometallic pharmaceutical compound used for the prevention and treatment of hypomagnesemia as a source of magnesium ion. The present research described the in-depth study on solid state properties viz. physicochemical and thermal properties of magnesium gluconate using sophisticated analytical techniques like PXRD, PSA, FT-IR, UV–Vis spectroscopy, TGA/DTG, and DSC. Magnesium gluconate was found to be crystalline in nature along with the crystallite size ranging from 14.10 to 47.35 nm. The particle size distribution was at d(0.1=6.552 µm, d(0.5=38.299 µm, d(0.9=173.712 µm and D(4,3=67.122 µm along with the specific surface area of 0.372 m2/g. The wavelength for the maximum absorbance was at 198.0 nm. Magnesium gluconate exhibited 88.51% weight loss with three stages of thermal degradation process up to 895.18 °C from room temperature. The TGA/DTG thermograms of the analyte indicated that magnesium gluconate was thermally stable up to around 165 °C. Consequently, the melting temperature of magnesium gluconate was found to be 169.90 °C along with the enthalpy of fusion of 308.7 J/g. Thus, the authors conclude that the achieved results from this study are very useful in pharmaceutical and nutraceutical industries for the identification, characterization and qualitative analysis of magnesium gluconate for preformulation studies and also for developing magnesium gluconate based novel formulation.

In-depth investigation of spin-on doped solar cells with thermally grown oxide passivation

Directory of Open Access Journals (Sweden)

Samir Mahmmod Ahmad

Full Text Available Solar cell industrial manufacturing, based largely on proven semiconductor processing technologies supported by significant advancements in automation, has reached a plateau in terms of cost and efficiency. However, solar cell manufacturing cost (dollar/watt is still substantially higher than fossil fuels. The route to lowering cost may not lie with continuing automation and economies of scale. Alternate fabrication processes with lower cost and environmental-sustainability coupled with self-reliance, simplicity, and affordability may lead to price compatibility with carbon-based fuels. In this paper, a custom-designed formulation of phosphoric acid has been investigated, for n-type doping in p-type substrates, as a function of concentration and drive-in temperature. For post-diffusion surface passivation and anti-reflection, thermally-grown oxide films in 50–150-nm thickness were grown. These fabrication methods facilitate process simplicity, reduced costs, and environmental sustainability by elimination of poisonous chemicals and toxic gases (POCl3, SiH4, NH3. Simultaneous fire-through contact formation process based on screen-printed front surface Ag and back surface through thermally grown oxide films was optimized as a function of the peak temperature in conveyor belt furnace. Highest efficiency solar cells fabricated exhibited efficiency of ∼13%. Analysis of results based on internal quantum efficiency and minority carried measurements reveals three contributing factors: high front surface recombination, low minority carrier lifetime, and higher reflection. Solar cell simulations based on PC1D showed that, with improved passivation, lower reflection, and high lifetimes, efficiency can be enhanced to match with commercially-produced PECVD SiN-coated solar cells. Keywords: Crystalline Si solar cells, Phosphoric acid spin-on doping, Screen printing, Thermal oxide passivation

Selective Aerobic Oxidation of 5-Hydroxymethylfurfural in Water Over Solid Ruthenium Hydroxide Catalysts with Magnesium-Based Supports

DEFF Research Database (Denmark)

Gorbanev, Yury; Kegnæs, Søren; Riisager, Anders

2011-01-01

Solid catalyst systems comprised of ruthenium hydroxide supported on magnesium-based carrier materials (spinel, magnesium oxide and hydrotalcite) were investigated for the selective, aqueous aerobic oxidation of the biomass-derived chemical 5-hydroxymethylfurfural into 2,5-furandicarboxylic acid...

Influence of Magnesium Alloy Degradation on Undifferentiated Human Cells.

Science.gov (United States)

Cecchinato, Francesca; Agha, Nezha Ahmad; Martinez-Sanchez, Adela Helvia; Luthringer, Berengere Julie Christine; Feyerabend, Frank; Jimbo, Ryo; Willumeit-Römer, Regine; Wennerberg, Ann

2015-01-01

Magnesium alloys are of particular interest in medical science since they provide compatible mechanical properties with those of the cortical bone and, depending on the alloying elements, they have the capability to tailor the degradation rate in physiological conditions, providing alternative bioresorbable materials for bone applications. The present study investigates the in vitro short-term response of human undifferentiated cells on three magnesium alloys and high-purity magnesium (Mg). The degradation parameters of magnesium-silver (Mg2Ag), magnesium-gadolinium (Mg10Gd) and magnesium-rare-earth (Mg4Y3RE) alloys were analysed after 1, 2, and 3 days of incubation in cell culture medium under cell culture condition. Changes in cell viability and cell adhesion were evaluated by culturing human umbilical cord perivascular cells on corroded Mg materials to examine how the degradation influences the cellular development. The pH and osmolality of the medium increased with increasing degradation rate and it was found to be most pronounced for Mg4Y3RE alloy. The biological observations showed that HUCPV exhibited a more homogeneous cell growth on Mg alloys compared to high-purity Mg, where they showed a clustered morphology. Moreover, cells exhibited a slightly higher density on Mg2Ag and Mg10Gd in comparison to Mg4Y3RE, due to the lower alkalinisation and osmolality of the incubation medium. However, cells grown on Mg10Gd and Mg4Y3RE generated more developed and healthy cellular structures that allowed them to better adhere to the surface. This can be attributable to a more stable and homogeneous degradation of the outer surface with respect to the incubation time.

Magnesium Oxide Nanoparticles: Effective Agricultural Antibacterial Agent Against Ralstonia solanacearum

Directory of Open Access Journals (Sweden)

Lin Cai

2018-04-01

Full Text Available Magnesium (Mg is an essential mineral element for plants and is nontoxic to organisms. In this study, we took advantage of nanotechnologies to systematically investigate the antibacterial mechanisms of magnesium oxide nanoparticles (MgONPs against the phytopathogen Ralstonia solanacearum (R. solanacearum in vitro and in vivo for the first time. R. solanacearum has contributed to catastrophic bacterial wilt, which has resulted in the world-wide reduction of tobacco production. The results demonstrated that MgONPs possessed statistically significant concentration-dependent antibacterial activity, and the minimum inhibitory concentration (MIC and minimum bactericidal concentration (MBC were measured as 200 and 250 μg/mL, respectively. Additional studies, aimed at understanding the toxicity mechanism of MgONPs, indicated that physical injury occurred to the cell membranes, along with decreased motility and biofilm formation ability of R. solanacearum, due to the direct attachment of MgONPs to the surfaces of the bacterial cells, which was observed by scanning electron microscopy (SEM and transmission electron microscopy (TEM. Reactive oxygen species (ROS accumulation could also be an important reason for the antibacterial action, inducing DNA damage. The toxicity assessment assay under greenhouse conditions demonstrated that the MgONPs had exerted a large effect on tobacco bacterial wilt, reducing the bacterial wilt index. Altogether, the results suggest that the development of MgONPs as alternative antibacterial agents will become a new research subject.

Behavior of 32P, 35S, 36Cl and 42K in magnesium oxide

International Nuclear Information System (INIS)

Santos, C.N.T. dos.

1979-01-01

A separation method of 32 P from 35 S using magnesium oxide as adsorbent of radiophosphorus is described. The behaviour of 32 P and 35 S, both carrier-free, on magnesium oxide, individually, in dependence of the amount of the adsorbent, of mixing time, of the pH of the loading solution and of potassium chloride concentration, is studied. The separation of the mentioned radioisotopes, using a misture of them, is also analysed. In order to apply this method to the routine production of carrier-free 35 S by potassium chloride irradiation, the adsorption behaviour of the chloride and potassium on magnesium oxide using radioactive tracers of these elements, is studied. The separation of 35 S from 32 P is analyzed by the maximum range of β - particles in aluminum. The absorption curves are presented and compared. (Author) [pt

Oxidation of an aluminium-magnesium alloy in liquid state. Methodology of determination of mechanisms from not necessarily repeatable experiments

International Nuclear Information System (INIS)

Surla, Karine

1998-01-01

This research thesis reports the study of the oxidation of an aluminium-5 pc magnesium alloy in its liquid state in an oxygen environment, using thermogravimetric analysis and that of magnesium in its solid state. In a first part, the author reports a thermodynamic and bibliographical study on magnesium transformation in its solid state (Mg/O 2 and Mg/H 2 O systems, transformation with dry and humid synthetic air, oxidation inhibitors) and on Al-Mg alloy transformation in presence of oxygen (thermodynamic properties of aluminium-rich Al-Mg alloys, Al-Mg/O 2 /N 2 and Al-Mg/O 2 /N 2 /H 2 O systems). The next parts address the selection of reaction systems for the different cases (oxidation of solid magnesium in oxygen, oxidation of the Al-Mg alloy in oxygen), the modelling of the formation of magnesia from solid magnesium and from the Al-Mg alloy, and the modelling of the liquid Al-Mg A5182 alloy oxidation in oxygen [fr

The initial oxidation of magnesium

Energy Technology Data Exchange (ETDEWEB)

Kurth, M.

2004-07-01

Pure Magnesium samples have been oxidised in an UHV chamber under controlled conditions. Pressure range was 10{sup -10} Torr to 10{sup -7} Torr, temperature range was 273 K to 435 K. The samples have then been investigated with XPS, Ellipsometry and HERDA. Additionally, furnace oxidations at 750 Torr and 673 K have been carried out and investigated with XPS. From the XPS measurements data concerning layer thickness, composition, oxidation state and binding state have been gained. The ellipsometrie measurements yielded additional data concerning layer thickness as well as the size of the band gap of the developing oxide. With the HERDA measurements, the oxygen content within the oxide layer has been determined yielding additional information about composition and layer thickness. The layer thickness as a function of time have then been modelled with a kinetic growth model of Fromhold and Cook. For the refinement of the XPS data concerning layer thickness and composition, the pronounced plasmon excitations that occur in magnesium have been determined with two different procedures which have been developed in the methodical part of this work. The layer thickness and composition values have thus been corrected. Results: Two oxidation stages could be identified: a strong increase for the first few Langmuirs (1L = 1s x 10{sup -6} Torr), followed by a saturation'' region which was about 1.2 nm to 1.5 nm in magnitude. XPS and ellipsometry results have thereby been in very good agreement. The composition of the developing oxide showed a clear deviation from stoichiometric MgO, mainly caused by an oxygen deficiency; this deficiency has also been confirmed with the HERDA measurements. The Mg/O ratio as a function of layer thickness showed a continous decay starting from very high values for the thinnest layers (>{proportional_to}2.5) down to a saturation value of about 1.4, even for larger layer thicknesses gained with the furnace oxidations. The determination of

#%In-depth investigation on physicochemical and thermal properties of magnesium (II) gluconate using spectroscopic and thermoanalytical techniques

Institute of Scientific and Technical Information of China (English)

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2017-01-01

Magnesium gluconate is a classical organometallic pharmaceutical compound used for the prevention and treatment of hypomagnesemia as a source of magnesium ion. The present research described the in-depth study on solid state properties viz. physicochemical and thermal properties of magnesium gluconate using sophisticated analytical techniques like Powder X-ray diffraction (PXRD), particle size analysis ( PSA), Fourier transform infrared (FT-IR) spectrometry, ultraviolet–visible (UV–Vis) spectroscopy, thermogravimetric analysis (TGA)/differential thermogravimetric analysis (DTG), and differential scanning calorimetry (DSC). Magnesium gluconate was found to be crystalline in nature along with the crystallite size ranging from 14.10 to 47.35 nm. The particle size distribution was at d(0.1)=6.552 μm, d(0.5)=38.299 μm, d(0.9)=173.712 μm and D(4,3)=67.122 μm along with the specific surface area of 0.372 m2/g. The wavelength for the maximum absorbance was at 198.0 nm. Magnesium gluconate exhibited 88.51% weight loss with three stages of thermal degradation process up to 895.18 ℃ from room temperature. The TGA/DTG thermograms of the analyte indicated that magnesium gluconate was thermally stable up to around 165 ℃. Consequently, the melting temperature of magnesium gluconate was found to be 169.90 ℃ along with the enthalpy of fusion of 308.7 J/g. Thus, the authors conclude that the achieved results from this study are very useful in pharmaceutical and nutraceutical industries for the identification, characterization and qualitative analysis of magnesium gluconate for preformulation studies and also for developing magnesium gluconate based novel formulation.

Influence of Magnesium Alloy Degradation on Undifferentiated Human Cells.

Directory of Open Access Journals (Sweden)

Francesca Cecchinato

Full Text Available Magnesium alloys are of particular interest in medical science since they provide compatible mechanical properties with those of the cortical bone and, depending on the alloying elements, they have the capability to tailor the degradation rate in physiological conditions, providing alternative bioresorbable materials for bone applications. The present study investigates the in vitro short-term response of human undifferentiated cells on three magnesium alloys and high-purity magnesium (Mg.The degradation parameters of magnesium-silver (Mg2Ag, magnesium-gadolinium (Mg10Gd and magnesium-rare-earth (Mg4Y3RE alloys were analysed after 1, 2, and 3 days of incubation in cell culture medium under cell culture condition. Changes in cell viability and cell adhesion were evaluated by culturing human umbilical cord perivascular cells on corroded Mg materials to examine how the degradation influences the cellular development.The pH and osmolality of the medium increased with increasing degradation rate and it was found to be most pronounced for Mg4Y3RE alloy. The biological observations showed that HUCPV exhibited a more homogeneous cell growth on Mg alloys compared to high-purity Mg, where they showed a clustered morphology. Moreover, cells exhibited a slightly higher density on Mg2Ag and Mg10Gd in comparison to Mg4Y3RE, due to the lower alkalinisation and osmolality of the incubation medium. However, cells grown on Mg10Gd and Mg4Y3RE generated more developed and healthy cellular structures that allowed them to better adhere to the surface. This can be attributable to a more stable and homogeneous degradation of the outer surface with respect to the incubation time.

Porous ceramics out of oxides

International Nuclear Information System (INIS)

Bakunov, V.S.; Balkevich, V.L.; Vlasov, A.S.; Guzman, I.Ya.; Lukin, E.S.; Poluboyarinov, D.N.; Poliskij, R.Ya.

1977-01-01

A review is made of manufacturing procedures and properties of oxide ceramics intended for high-temperature thermal insulation and thermal protection applications. Presented are structural characteristics of porous oxide refractories and their properties. Strength and thermal conductivity was shown to depend upon porosity. Described is a procedure for manufacturing porous ceramic materials from aluminium oxide, zirconium dioxide, magnesium oxide, beryllium oxide. The thermal resistance of porous ceramics from BeO is considerably greater than that of other high-refractoriness oxides. Listed are areas of application for porous materials based on oxides

Magnesium deficiency and increased inflammation: current perspectives

Directory of Open Access Journals (Sweden)

Nielsen FH

2018-01-01

Full Text Available Forrest H Nielsen Research Nutritionist Consultant, Grand Forks, ND, USA Abstract: Animal studies have shown that magnesium deficiency induces an inflammatory response that results in leukocyte and macrophage activation, release of inflammatory cytokines and acute-phase proteins, and excessive production of free radicals. Animal and in vitro studies indicate that the primary mechanism through which magnesium deficiency has this effect is through increasing cellular Ca2+, which is the signal that results in the priming of cells to give the inflammatory response. Primary pro-inflammatory cytokines such as tumor necrosis factor-α and interleukin (IL-1; the messenger cytokine IL-6; cytokine responders E-selectin, intracellular adhesion molecule-1 and vascular cell adhesion molecule-1; and acute-phase reactants C-reactive protein and fibrinogen have been determined to associate magnesium deficiency with chronic low-grade inflammation (inflammatory stress. When magnesium dietary intake, supplementation, and/or serum concentration suggest/s the presence of magnesium deficiency, it often is associated with low-grade inflammation and/or with pathological conditions for which inflammatory stress is considered a risk factor. When magnesium intake, supplementation, and/or serum concentration suggest/s an adequate status, magnesium generally has not been found to significantly affect markers of chronic low-grade inflammation or chronic disease. The consistency of these findings can be modified by other nutritional and metabolic factors that affect inflammatory and oxidative stress. In spite of this, findings to date provide convincing evidence that magnesium deficiency is a significant contributor to chronic low-grade inflammation that is a risk factor for a variety of pathological conditions such as cardiovascular disease, hypertension, and diabetes. Because magnesium deficiency commonly occurs in countries where foods rich in magnesium are not consumed in

AC plasma electrolytic oxidation of magnesium with zirconia nanoparticles

International Nuclear Information System (INIS)

Arrabal, R.; Matykina, E.; Viejo, F.; Skeldon, P.; Thompson, G.E.; Merino, M.C.

2008-01-01

The incorporation of monoclinic zirconia nanoparticles and their subsequent transformation is examined for coatings formed on magnesium by plasma electrolytic oxidation under AC conditions in silicate electrolyte. The coatings are shown to comprise two main layers, with nanoparticles entering the coating at the coating surface and through short-circuit paths to the region of the interface between the inner and outer coating layers. Under local heating of microdischarges, the zirconia reacts with magnesium species to form Mg 2 Zr 5 O 12 in the outer coating layer. Relatively little zirconium is present in the inner coating layer. In contrast, silicon species are present in both coating layers, with reduced amounts in the inner layer

Characterization and mechanical properties of coatings on magnesium by micro arc oxidation

International Nuclear Information System (INIS)

Durdu, Salih; Usta, Metin

2012-01-01

Highlights: ► The commercial pure magnesium was coated by MAO in sodium silicate and sodium phosphate. ► Coatings produced in the phosphate electrolyte are thicker than ones in the silicate electrolyte. ► Coatings in the silicate electrolyte are harder than ones in the phosphate electrolyte. ► Adhesion strength of coatings increases with increasing coating thickness. ► The wear resistance of the coated commercial pure magnesium is improved. - Abstracts: The commercial pure magnesium was coated by micro arc oxidation method in different aqueous solution, containing sodium silicate and sodium phosphate. Micro arc oxidation process was carried out at 0.060 A/cm 2 , 0.085 A/cm 2 and 0.140 A/cm 2 current densities for 30 min. The thickness, phase composition, morphology, hardness, adhesion strength and wear resistance of coatings were analyzed by eddy current, X-ray diffraction (XRD), scanning electron microscope (SEM), micro hardness tester, scratch tester and ball-on disk tribometer, respectively. The average thicknesses of the micro arc oxidized coatings ranged from 27 to 48 μm for sodium silicate solution and from 45 to 75 μm for sodium phosphate solution. The dominant phases formed on the pure magnesium were found to be a mixture of spinel Mg 2 SiO 4 (Forsterite) and MgO (Periclase) for sodium silicate solution and Mg 3 (PO 4 ) 2 (Farringtonite) and MgO (Periclase) for sodium phosphate solution. The average hardnesses of the micro arc oxidized coatings were between 260 HV and 470 HV for sodium silicate solution and between 175 HV and 260 HV for sodium phosphate solution. Adhesion strengths and wear resistances of coatings produced in sodium silicate solution were higher than those of the ones in sodium phosphate solution due to high hardness of coatings produced in sodium silicate solution.

Simulation of thermal stresses in anode-supported solid oxide fuel cell stacks. Part II: Loss of gas-tightness, electrical contact and thermal buckling

Science.gov (United States)

Nakajo, Arata; Wuillemin, Zacharie; Van herle, Jan; Favrat, Daniel

Structural stability issues in planar solid oxide fuel cells arise from the mismatch between the coefficients of thermal expansion of the components. The stress state at operating temperature is the superposition of several contributions, which differ depending on the component. First, the cells accumulate residual stresses due to the sintering phase during the manufacturing process. Further, the load applied during assembly of the stack to ensure electric contact and flatten the cells prevents a completely stress-free expansion of each component during the heat-up. Finally, thermal gradients cause additional stresses in operation. The temperature profile generated by a thermo-electrochemical model implemented in an equation-oriented process modelling tool (gPROMS) was imported into finite-element software (ABAQUS) to calculate the distribution of stress and contact pressure on all components of a standard solid oxide fuel cell repeat unit. The different layers of the cell in exception of the cathode, i.e. anode, electrolyte and compensating layer were considered in the analysis to account for the cell curvature. Both steady-state and dynamic simulations were performed, with an emphasis on the cycling of the electrical load. The study includes two different types of cell, operation under both thermal partial oxidation and internal steam-methane reforming and two different initial thicknesses of the air and fuel compressive sealing gaskets. The results generated by the models are presented in two papers: Part I focuses on cell cracking. In the present paper, Part II, the occurrences of loss of gas-tightness in the compressive gaskets and/or electrical contact in the gas diffusion layer were identified. In addition, the dependence on temperature of both coefficients of thermal expansion and Young's modulus of the metallic interconnect (MIC) were implemented in the finite-element model to compute the plastic deformation, while the possibilities of thermal buckling

Gas sensing behaviour of cerium oxide and magnesium aluminate

Indian Academy of Sciences (India)

Gas sensing behaviour of cerium oxide and magnesium aluminate composites ... A lone pairof the electron state was identified from the electro paramagnetic ... carbon monoxide (CO) (at 0.5, 1.0 and 1.5 bar) and ethanol (at 50 and 100 ppm) was ... The magnitude of the temperature varied linearly regardless of the gas ...

Electrophoretic deposition of magnesium silicates on titanium implants: Ion migration and silicide interfaces

Energy Technology Data Exchange (ETDEWEB)

Afshar-Mohajer, M. [Center for Advanced Manufacturing and Material Processing, Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603 (Malaysia); Yaghoubi, A., E-mail: yaghoubi@siswa.um.edu.my [Center for High Impact Research, University of Malaya, Kuala Lumpur 50603 (Malaysia); Ramesh, S., E-mail: ramesh79@um.edu.my [Center for Advanced Manufacturing and Material Processing, Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603 (Malaysia); Bushroa, A.R.; Chin, K.M.C.; Tin, C.C. [Center for Advanced Manufacturing and Material Processing, Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603 (Malaysia); Chiu, W.S. [Low Dimensional Materials Research Center, Department of Physics, University of Malaya, Kuala Lumpur 50603 (Malaysia)

2014-07-01

Magnesium silicates (Mg{sub x}SiO{sub y}) and in particular forsterite (Mg{sub 2}SiO{sub 4}) owing to their low thermal expansion mismatch with metals are promising materials for bioactive coating of implants. Here, we report the electrophoretic deposition (EPD) of forsterite onto titanium substrates using different precursors. Unlike bulk samples which achieve full stoichiometry only beyond 1400 °C, non-stoichiometric magnesium silicate rapidly decomposes into magnesium oxide nanowires during sintering. Elemental mapping and X-ray diffraction suggest that oxygen diffusion followed by ion exchange near the substrate leads to formation of an interfacial Ti{sub 5}Si{sub 3} layer. Pre-annealed forsterite powder on the other hand shows a comparatively lower diffusion rate. Overall, magnesium silicate coatings do not exhibit thermally induced microcracks upon sintering as opposed to calcium phosphate bioceramics which are currently in use.

Enhancing the Heat Transfer Efficiency in Graphene-Epoxy Nanocomposites Using a Magnesium Oxide-Graphene Hybrid Structure.

Science.gov (United States)

Du, Fei-Peng; Yang, Wen; Zhang, Fang; Tang, Chak-Yin; Liu, Sheng-Peng; Yin, Le; Law, Wing-Cheung

2015-07-08

Composite materials, such as organic matrices doped with inorganic fillers, can generate new properties that exhibit multiple functionalities. In this paper, an epoxy-based nanocomposite that has a high thermal conductivity and a low electrical conductivity, which are required for the use of a material as electronic packaging and insulation, was prepared. The performance of the epoxy was improved by incorporating a magnesium oxide-coated graphene (MgO@GR) nanomaterial into the epoxy matrix. We found that the addition of a MgO coating not only improved the dispersion of the graphene in the matrix and the interfacial bonding between the graphene and epoxy but also enhanced the thermal conductivity of the epoxy while preserving the electrical insulation. By adding 7 wt % MgO@GR, the thermal conductivity of the epoxy nanocomposites was enhanced by 76% compared with that of the neat epoxy, and the electrical resistivity was maintained at 8.66 × 10(14) Ω m.

A lumped model of venting during thermal runaway in a cylindrical lithium cobalt oxide lithium-ion cell

DEFF Research Database (Denmark)

Coman, Paul Tiberiu; Rayman, Sean; White, Ralph

2016-01-01

This paper presents a mathematical model built for analyzing the intricate thermal behavior of a 18650 LCO (Lithium Cobalt Oxide) battery cell during thermal runaway when venting of the electrolyte and contents of the jelly roll (ejecta) is considered. The model consists of different ODEs (Ordinary...

Ceramic coated Y1 magnesium alloy surfaces by microarc oxidation

Indian Academy of Sciences (India)

The magnesium alloys occupy an important place in marine applications, but their poor corrosion resistance, wear resistance, hardness and so on, have limited their application. To meet these defects, some techniques are developed. Microarc oxidation is a one such recently developed surface treatment technology under ...

Precipitation of iron (III) using magnesium oxide in fluidized bed

International Nuclear Information System (INIS)

Esteban-Bocardo, P. A.; Ferreira-Rocha, S. D.

2006-01-01

A process for iron (III) removal by hydroxide precipitation from and acid synthetic inorganic effluent using magnesium oxide as an alternative precipitant agent in a fluidized bed was developed. An acid synthetic inorganic effluent containing 100 and 200 mg/l of ferric ions (pH=1.0) was continuously fed up to the acrylic column (30 cm high and 2 cm diameter) during 180 minutes. Magnesium oxide pulp (3% v/v) was injected at the beginning of the experiment in order to allow the iron hydroxides precipitation. The concentration and pH profiles agreed in their curves, while the pH profile rose,the concentration profile decreased and a high percentage of iron removal /higher to 99%) was reached. Extremely low iron concentrations have been reached, thus permitting to attend to the environmental standard of 10.0 mg/l for discharge of effluent containing ferric ions established by the law DN 10/86 of COPAM (Conselho de Politica Ambiental do Estado de Minas Gerais-Brazil). (Author)

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

Science.gov (United States)

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.

Preparation and characterization of the micro-arc oxidation composite coatings on magnesium alloys

OpenAIRE

Yanfeng Ge; Bailing Jiang; Ming Liu; Congjie Wang; Wenning Shen

2014-01-01

The magnesium alloys attract the light-weight manufacture due to its high strength to weight ratio, however the poor corrosion resistance limits the application in automobile industry. The Micro-arc Composite Ceramic (MCC) coatings on AZ91D magnesium alloys were prepared by Micro-arc Oxidation (MAO) and electrophoresis technologies. The microstructure, corrosion resistance, abrasion resistance, stone impact resistance and adhesion of MCC coatings were studied respectively. The cross section m...

Characteristics of thermally reduced graphene oxide and applied for dye-sensitized solar cell counter electrode

Energy Technology Data Exchange (ETDEWEB)

Ho, Ching-Yuan, E-mail: cyho@cycu.edu.tw [Department of Mechanical Engineering, Chung Yuan Christian University, Chung-Li, Taiwan (China); Department of Chemistry, Center for Nanotechnology and Institute of Biomedical Technology, Chung Yuan Christian University, Chung-Li, Taiwan (China); Wang, Hong-Wen [Department of Chemistry, Center for Nanotechnology and Institute of Biomedical Technology, Chung Yuan Christian University, Chung-Li, Taiwan (China); Department of Chemistry, Chung Yuan Christian University, Chung-Li, Taiwan (China)

2015-12-01

Graphical abstract: Experimental process: (1) graphite oxidized to graphene oxide; (2) thermal reduction from graphene oxide to graphene; (3) applying to DSSC counter electrode. - Highlights: • Intercalated defects were eliminated by increasing reduction temperature of GO. • High reduction temperature of tGP has lower resistance, high the electron lifetime. • Higher thermal reduction of GO proposes electrocatalytic properties. • DSSC using tGP{sub 250} as counter electrode has energy conversion efficiency of 3.4%. - Abstract: Graphene oxide (GO) was synthesized from a flake-type of graphite powder, which was then reduced to a few layers of graphene sheets using the thermal reduction method. The surface morphology, phase crystallization, and defect states of the reduced graphene were determined from an electron microscope equipped with an energy dispersion spectrometer, X-ray diffraction, Raman spectroscopy, and infrared spectra. After graphene formation, the intercalated defects that existed in the GO were removed, and it became crystalline by observing impurity changes and d-spacing. Dye-sensitized solar cells, using reduced graphene as the counter electrode, were fabricated to evaluate the electrolyte activity and charge transport performance. The electrochemical impedance spectra showed that increasing the thermal reduction temperature could achieve faster electron transport and longer electron lifetime, and result in an energy conversion efficiency of approximately 3.4%. Compared to the Pt counter electrode, the low cost of the thermal reduction method suggests that graphene will enjoy a wide range of potential applications in the field of electronic devices.

Characteristics of thermally reduced graphene oxide and applied for dye-sensitized solar cell counter electrode

International Nuclear Information System (INIS)

Ho, Ching-Yuan; Wang, Hong-Wen

2015-01-01

Graphical abstract: Experimental process: (1) graphite oxidized to graphene oxide; (2) thermal reduction from graphene oxide to graphene; (3) applying to DSSC counter electrode. - Highlights: • Intercalated defects were eliminated by increasing reduction temperature of GO. • High reduction temperature of tGP has lower resistance, high the electron lifetime. • Higher thermal reduction of GO proposes electrocatalytic properties. • DSSC using tGP 250 as counter electrode has energy conversion efficiency of 3.4%. - Abstract: Graphene oxide (GO) was synthesized from a flake-type of graphite powder, which was then reduced to a few layers of graphene sheets using the thermal reduction method. The surface morphology, phase crystallization, and defect states of the reduced graphene were determined from an electron microscope equipped with an energy dispersion spectrometer, X-ray diffraction, Raman spectroscopy, and infrared spectra. After graphene formation, the intercalated defects that existed in the GO were removed, and it became crystalline by observing impurity changes and d-spacing. Dye-sensitized solar cells, using reduced graphene as the counter electrode, were fabricated to evaluate the electrolyte activity and charge transport performance. The electrochemical impedance spectra showed that increasing the thermal reduction temperature could achieve faster electron transport and longer electron lifetime, and result in an energy conversion efficiency of approximately 3.4%. Compared to the Pt counter electrode, the low cost of the thermal reduction method suggests that graphene will enjoy a wide range of potential applications in the field of electronic devices.

Nanostructured magnesium oxide biosensing platform for cholera detection

Science.gov (United States)

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.

Hydrogenation properties of pure magnesium and magnesium-aluminium thin films

Energy Technology Data Exchange (ETDEWEB)

Domenech-Ferrer, Roger; Gurusamy Sridharan, Madana; Garcia, Gemma; Pi, Francesc; Rodriguez-Viejo, Javier [Departament de Fisica, Universitat Autonoma de Barcelona, 08193 Bellaterra (Spain)

2007-06-10

We have studied the hydrogenation/dehydrogenation behaviour of multilayered stacks of Pd/Mg/Pd and Pd-Fe(Ti)-Mg-Al-Mg-Fe(Ti)-Pd grown by electron beam physical vapour deposition. The palladium coating was deposited at both sides of the structure to ensure a fast dissociation rate and good transport properties for hydrogen as well as to avoid oxidation of magnesium either from atmosphere as from the substrate surface. Fe and Ti layers were included in the stack composition in order to assess their possible catalyst effect as well as to prevent the formation of Mg{sub x}Pd{sub y} intermetallics during the thermal treatments. We have studied the structure evolution after thermal treatments as well as after the hydrogenation and dehydrogenation processes using XRD. We have also followed the reactions kinetics by resistometry and differential scanning calorimetry. The nanostructured Mg films have been hydrogenated at temperature as low as 50 C in few minutes. Adding aluminium to magnesium has improved its hydrogenation capacity. We have also observed that the formation of an Mg{sub x}Al{sub y} intermetallic before hydrogenation improves the storage capacity. We have confirmed that titanium is a better catalyst for the hydrogenation/dehydrogenation of the Mg films. (author)

Resistance of WE43 and ZRE1 Magnesium Alloys to Gas Corrosion

Directory of Open Access Journals (Sweden)

Przeliorz R.

2017-06-01

Full Text Available In spite of the fact that in most applications, magnesium alloys are intended for operation in environments with room temperature, these alloys are subject to elevated temperature and oxidizing atmosphere in various stages of preparation (casting, welding, thermal treatment. At present, the studies focus on development of alloys with magnesium matrix, intended for plastic forming. The paper presents results of studies on oxidation rate of WE43 and ZRE1 magnesium foundry alloys in dry and humidified atmosphere of N2+1%O2. Measurements of the oxidation rate were carried out using a Setaram thermobalance in the temperature range of 350-480°C. Corrosion products were analyzed by SEM-SEI, BSE and EDS. It was found that the oxide layer on the WE43 alloy has a very good resistance to oxidation. The high protective properties of the layer should be attributed to the presence of yttrium in this alloy. On the other hand, a porous, two-layer scale with a low adhesion to the substrate forms on the ZRE1 alloy. The increase in the sample mass in dry gas is lower than that in humidified gas.

Thermally exfoliated graphite oxide

Science.gov (United States)

Prud'Homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor); Abdala, Ahmed (Inventor)

2011-01-01

A modified graphite oxide material contains a thermally exfoliated graphite oxide with a surface area of from about 300 sq m/g to 2600 sq m/g, wherein the thermally exfoliated graphite oxide displays no signature of the original graphite and/or graphite oxide, as determined by X-ray diffraction.

Influence of temperature on oxidation behaviour of ZE41 magnesium alloy

International Nuclear Information System (INIS)

Lopez, M.D.; Munez, C.J.; Carboneras, M.; Rodrigo, P.; Escalera, M.D.; Otero, E.

2010-01-01

The influence of temperature on the oxidation behaviour of commercial ZE41 magnesium alloy has been studied. Thermogravimetric tests were carried out to determine the oxidation kinetics in the 350-500 o C range. Morphology and growth of the oxidation films were analysed by Scanning Electronic Microscopy (SEM), Energy Dispersive X-Ray Spectrometry (EDS) and X-Ray Diffraction (XRD). It was found that the oxidation kinetics initially follow a parabolic law, following a linear law for higher exposure times. Results also showed that the protective nature of the oxide layer depends on the oxidation temperature. At temperatures in the range of 350-450 o C the ZE41 alloy is covered by a protective oxide layer, very thin and compact, whereas the oxide layer formed at 500 o C exhibits a non-protective nature, showing an 'oxide sponges' morphology.

Low Temperature Synthesis of Magnesium Aluminate Spinel

International Nuclear Information System (INIS)

Lebedovskaya, E.G.; Gabelkov, S.V.; Litvinenko, L.M.; Logvinkov, D.S.; Mironova, A.G.; Odejchuk, M.A.; Poltavtsev, N.S.; Tarasov, R.V.

2006-01-01

The low-temperature synthesis of magnesium-aluminum spinel is carried out by a method of thermal decomposition in combined precipitated hydrates. The fine material of magnesium-aluminium spinel with average size of coherent dispersion's area 4...5 nanometers is obtained. Magnesium-aluminum spinel and initial hydrates were investigated by methods of the differential thermal analysis, the x-ray phase analysis and measurements of weight loss during the dehydration and thermal decomposition. It is established that synthesis of magnesium-aluminum spinel occurs at temperature 300 degree C by method of the x-ray phase analysis

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

Science.gov (United States)

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

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

Energy Technology Data Exchange (ETDEWEB)

Tang Hui [School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin 150001 (China); Yu Dezhen [School of Material Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Luo Yan [Department of Chemistry, Harbin Institute of Technology, Harbin 150001 (China); Wang Fuping, E-mail: hitth001@yahoo.cn [School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin 150001 (China)

2013-01-01

Highlights: Black-Right-Pointing-Pointer Hydroxyapatite microflowers coating is fabricated by micro-arc oxidation and a solution treatment on AZ31 magnesium alloy. Black-Right-Pointing-Pointer The corrosion resistance of the magnesium alloy has been enhanced by micro-arc oxidation and solution treatment. Black-Right-Pointing-Pointer The coating fabricated by micro-arc oxidation and solution treatment exhibits a high ability to form apatite. - Abstract: 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.

Special metallurgy - the electrical butt-welding by flashing of sintered magnesium-magnesium oxide composites (1963); Metallurgie speciale - le soudage electrique en bout par etincelage du composite fritte magnesium-magnesie (1963)

Energy Technology Data Exchange (ETDEWEB)

Charleux, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1963-07-01

Electrical resistance welding has become quite important since World War II because of the need of a high yield in aeronautical production. Progress has been due in particular to the improvements made in electronically controlled apparatus making possible the automatic control of welding. For the butt-welding of sections requiring either a high production rate or a high quality weld, the flash butt-welding system has been very much developed these last few years. The use of this welding method is of great importance in the field of the bonding of oxidisable metals such as magnesium or aluminium and its alloys, because the welded joint is free from oxides. This study consists of general considerations on the flash-welding process with regard to temperature distribution in the parts during welding, and to electrical phenomena connected with flashing. Besides this general or theoretical section, we have applied the welding process to the bonding of sintered magnesium, a magnesium-magnesium oxide composite, whose use as a structural element in nuclear reactors is considered. (author) [French] Le soudage electrique par resistance a pris un essor important depuis la derniere guerre mondiale a cause du besoin de haut rendement pour la production aeronautique. Les progres ont ete possibles surtout par l'amelioration des appareils de commande electronique qui permettent un controle automatique de la soudure. Pour le soudage bout a bout de profiles, demandant soit un haut debit de fabrication, soit une haute qualite du joint soude, le procede de soudage en bout par etincelage a ete tres developpe ces dernieres annees. Ce mode de soudage a un domaine d'utilisation important dans la liaison des metaux oxydables tels le magnesium ou l'aluminium et ses alliages, du fait de la proprete du joint soude exempt d'oxydes. Cette etude comporte une consideration generale du processus de l'etincelage, quant a la repartition de la temperature dans les pieces pendant le soudage et aux

Special metallurgy - the electrical butt-welding by flashing of sintered magnesium-magnesium oxide composites (1963); Metallurgie speciale - le soudage electrique en bout par etincelage du composite fritte magnesium-magnesie (1963)

Energy Technology Data Exchange (ETDEWEB)

Charleux, J. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1963-07-01

Electrical resistance welding has become quite important since World War II because of the need of a high yield in aeronautical production. Progress has been due in particular to the improvements made in electronically controlled apparatus making possible the automatic control of welding. For the butt-welding of sections requiring either a high production rate or a high quality weld, the flash butt-welding system has been very much developed these last few years. The use of this welding method is of great importance in the field of the bonding of oxidisable metals such as magnesium or aluminium and its alloys, because the welded joint is free from oxides. This study consists of general considerations on the flash-welding process with regard to temperature distribution in the parts during welding, and to electrical phenomena connected with flashing. Besides this general or theoretical section, we have applied the welding process to the bonding of sintered magnesium, a magnesium-magnesium oxide composite, whose use as a structural element in nuclear reactors is considered. (author) [French] Le soudage electrique par resistance a pris un essor important depuis la derniere guerre mondiale a cause du besoin de haut rendement pour la production aeronautique. Les progres ont ete possibles surtout par l'amelioration des appareils de commande electronique qui permettent un controle automatique de la soudure. Pour le soudage bout a bout de profiles, demandant soit un haut debit de fabrication, soit une haute qualite du joint soude, le procede de soudage en bout par etincelage a ete tres developpe ces dernieres annees. Ce mode de soudage a un domaine d'utilisation important dans la liaison des metaux oxydables tels le magnesium ou l'aluminium et ses alliages, du fait de la proprete du joint soude exempt d'oxydes. Cette etude comporte une consideration generale du processus de l'etincelage, quant a la repartition de la temperature dans les pieces

In-depth investigation of spin-on doped solar cells with thermally grown oxide passivation

Science.gov (United States)

Ahmad, Samir Mahmmod; Cheow, Siu Leong; Ludin, Norasikin A.; Sopian, K.; Zaidi, Saleem H.

Solar cell industrial manufacturing, based largely on proven semiconductor processing technologies supported by significant advancements in automation, has reached a plateau in terms of cost and efficiency. However, solar cell manufacturing cost (dollar/watt) is still substantially higher than fossil fuels. The route to lowering cost may not lie with continuing automation and economies of scale. Alternate fabrication processes with lower cost and environmental-sustainability coupled with self-reliance, simplicity, and affordability may lead to price compatibility with carbon-based fuels. In this paper, a custom-designed formulation of phosphoric acid has been investigated, for n-type doping in p-type substrates, as a function of concentration and drive-in temperature. For post-diffusion surface passivation and anti-reflection, thermally-grown oxide films in 50-150-nm thickness were grown. These fabrication methods facilitate process simplicity, reduced costs, and environmental sustainability by elimination of poisonous chemicals and toxic gases (POCl3, SiH4, NH3). Simultaneous fire-through contact formation process based on screen-printed front surface Ag and back surface through thermally grown oxide films was optimized as a function of the peak temperature in conveyor belt furnace. Highest efficiency solar cells fabricated exhibited efficiency of ∼13%. Analysis of results based on internal quantum efficiency and minority carried measurements reveals three contributing factors: high front surface recombination, low minority carrier lifetime, and higher reflection. Solar cell simulations based on PC1D showed that, with improved passivation, lower reflection, and high lifetimes, efficiency can be enhanced to match with commercially-produced PECVD SiN-coated solar cells.

Effects of thermal aging on thermo-mechanical behavior of a glass sealant for solid oxide cell applications

DEFF Research Database (Denmark)

Abdoli, Hamid; Alizadeh, Parvin; Boccaccini, Dino

2014-01-01

Thermo-mechanical properties of a silicate based glass and its potential use for sealing application in intermediate temperature solid oxide cell (SOC) are presented in this paper. Effects of thermal aging are discussed on structural and microstructural evolution, thermal expansion, viscosity......'s modulus in which a transition between a slow softening (elastic) regime and a rapid softening one was observed. Crystallization induced by thermal aging led to higher creep resistance, but lower capability of crack healing when inspected by electron microscopy. However, potential of stress relaxation...

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

Energy Technology Data Exchange (ETDEWEB)

Lips, Irene M., E-mail: i.m.lips@umcutrecht.nl [Department of Radiation Oncology, University Medical Center Utrecht, Utrecht (Netherlands); Gils, Carla H. van [Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht (Netherlands); Kotte, Alexis N.T.J. [Department of Radiation Oncology, University Medical Center Utrecht, Utrecht (Netherlands); Leerdam, Monique E. van [Department of Gastroenterology and Hepatology, Erasmus University Medical Center, Rotterdam (Netherlands); Franken, Stefan P.G.; Heide, Uulke A. van der; Vulpen, Marco van [Department of Radiation Oncology, University Medical Center Utrecht, Utrecht (Netherlands)

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. Secondary 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.

Investigation of Mechanical Properties and Metallurical Characteristics of a Metallic Chromium and Magnesium Oxide Composite

National Research Council Canada - National Science Library

Manning, Charles

1963-01-01

An experimental investigation has been made to evaluate an uncoated thin composite sheet material containing metallic chromium and magnesium oxide for aerospace applications in the temperature range...

Cell Adhesion on Surface-Functionalized Magnesium.

Science.gov (United States)

Wagener, Victoria; Schilling, Achim; Mainka, Astrid; Hennig, Diana; Gerum, Richard; Kelch, Marie-Luise; Keim, Simon; Fabry, Ben; Virtanen, Sannakaisa

2016-05-18

The biocompatibility of commercially pure magnesium-based (cp Mg) biodegradable implants is compromised of strong hydrogen evolution and surface alkalization due to high initial corrosion rates of cp Mg in the physiological environment. To mitigate this problem, the addition of corrosion-retarding alloying elements or coating of implant surfaces has been suggested. In the following work, we explored the effect of organic coatings on long-term cell growth. cp Mg was coated with aminopropyltriehtoxysilane + vitamin C (AV), carbonyldiimidazole (CDI), or stearic acid (SA). All three coatings have been previously suggested to reduce initial corrosion and to enhance protein adsorption and hence cell adhesion on magnesium surfaces. Endothelial cells (DH1+/+) and osteosarcoma cells (MG63) were cultured on coated samples for up to 20 days. To quantify Mg corrosion, electrochemical impedance spectroscopy (EIS) was measured after 1, 3, and 5 days of cell culture. We also investigated the speed of initial cell spreading after seeding using fluorescently labeled fibroblasts (NIH/3T3). Hydrogen evolution after contact with cell culture medium was markedly decreased on AV- and SA-coated Mg compared to uncoated Mg. These coatings also showed improved cell adhesion and spreading after 24 h of culture comparable to tissue-treated plastic surfaces. On AV-coated cp Mg, a confluent layer of endothelial cells formed after 5 days and remained intact for up to 20 days. Together, these data demonstrate that surface coating with AV is a viable strategy for improving long-term biocompatibility of cp Mg-based implants. EIS measurements confirmed that the presence of a confluent cell layer increased the corrosion resistance.

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

Energy Technology Data Exchange (ETDEWEB)

Lin, Xiao [Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China); Yang, Xiaoming [Panyu Hospital of Chinese Medicine, 65 Qiaodong Road, Guangzhou 511400 (China); Tan, Lili, E-mail: lltan@imr.ac.cn [Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China); Li, Mei [Hospital of Orthopedics, Guangzhou General Hospital of Guangzhou Military Command, 111 Liuhua Road, Guangzhou 510010 (China); Wang, Xin [College of Chemistry, Liaoning University, 66 Chongshanzhong Road, Shenyang 110036 (China); Zhang, Yu, E-mail: luck_2001@126.com [Hospital of Orthopedics, Guangzhou General Hospital of Guangzhou Military Command, 111 Liuhua Road, Guangzhou 510010 (China); Yang, Ke, E-mail: kyang@imr.ac.cn [Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China); Hu, Zhuangqi [Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China); Qiu, Jianhong [Trauson Medical Instrument Co., Ltd., Changzhou 213163 (China)

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.

Effect of oxygen on the hydrogenation properties of magnesium films

DEFF Research Database (Denmark)

Ostenfeld, Christopher Worsøe; Chorkendorff, Ib

2006-01-01

The effect of magnesium oxide on the magnesium and hydrogen desorption properties of magnesium films have been investigated. We find that by capping metallic magnesium films with oxide overlayers the apparent desorption energy of magnesium is increased from 146 kJ/mol to 314 kJ/mol. The results...... are discussed in light of previous investigations of ball-milled magnesium powders....

Room temperature and thermal decomposition of magnesium hydride/deuteride thin films

Energy Technology Data Exchange (ETDEWEB)

Ares, J.R.; Leardini, F.; Bodega, J.; Macia, M.D.; Diaz-Chao, P.; Ferrer, I.J.; Fernandez, J.F.; Sanchez, C. [Universidad Autonoma de Madrid (Spain). Lab. de Materiales de Interes en Energias Renovables

2010-07-01

Magnesium hydride (MgH{sub 2}) can be considered an interesting material to store hydrogen as long as two main drawbacks were solved: (i) its high stability and (ii) slow (de)hydriding kinetics. In that context, magnesium hydride films are an excellent model system to investigate the influence of structure, morphology and dimensionality on kinetic and thermodynamic properties. In the present work, we show that desorption mechanism of Pd-capped MgH{sub 2} at room temperature is controlled by a bidimensional interphase mechanism and a similar rate step limiting mechanism is observed during thermal decomposition of MgH{sub 2}. This mechanism is different to that occurring in bulk MgH{sub 2} (nucleation and growth) and obtained activation energies are lower than those reported in bulk MgH{sub 2}. We also investigated the Pd-capping properties upon H-absorption/desorption by means of RBS and isotope experiments. (orig.)

Calcium and magnesium determination

International Nuclear Information System (INIS)

Bhattacharya, S.K.

1982-01-01

The roles of calcium and magnesium in human health and disease have been extensively studied. Calcium and magnesium have been determined in biological specimens by atomic absorption spectroscopy using stiochiometric nitrous oxide-acetylene flame

Investigation of magnesium oxychloride cement at the initial hardening stage

Directory of Open Access Journals (Sweden)

Averina Galina

2018-01-01

Full Text Available The paper investigates the process of variation of magnesium oxychloride cement deformations at the initial hardening stage depending on the activity of magnesium oxide powder which is determined by the parameters of the source material burning. Investigation is focused on magnesium cements obtained from pure magnesium hydroxide. Source materials were burnt at various temperatures with the purpose to obtain magnesium oxide powder with different activity. Regular content of hydrated phases was determined in hardened magnesium cement prepared on the basis of binders with different activity. The study reveals the influence of magnesium oxide powder activity on the process of deformation occurrence in hardened magnesium cement and its tendency to crack formation.

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

Science.gov (United States)

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.

Thermal Analysis On The Kinetics Of Magnesium-Aluminum Layered Double Hydroxides In Different Heating Rates

Directory of Open Access Journals (Sweden)

Hongbo Y.

2015-06-01

Full Text Available The thermal decomposition of magnesium-aluminum layered double hydroxides (LDHs was investigated by thermogravimetry analysis and differential scanning calorimetry (DSC methods in argon environment. The influence of heating rates (including 2.5, 5, 10, 15 and 20K/min on the thermal behavior of LDHs was revealed. By the methods of Kissinger and Flynn-Wall-Ozawa, the thermal kinetic parameters of activation energy and pre-exponential factor for the exothermic processes under non-isothermal conditions were calculated using the analysis of corresponding DSC curves.

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

Science.gov (United States)

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.

Octahedral magnesium manganese oxide molecular sieves as the cathode material of aqueous rechargeable magnesium-ion battery

International Nuclear Information System (INIS)

Zhang, Hongyu; Ye, Ke; Shao, Shuangxi; Wang, Xin; Cheng, Kui; Xiao, Xue; Wang, Guiling; Cao, Dianxue

2017-01-01

Highlights: • The mico-sheet Mg-OMS-1 is synthesized by a simple hydrothermal method. • The mechanism of Mg 2+ insertion/deinsertion from Mg-OMS-1 is explored. • The electrode exhibits a good electrochemical performance in MgCl 2 electrolyte. - Abstract: Aqueous magnesium-ion batteries have shown the desired properties of high safety characteristics, similar electrochemical properties to lithium and low cost for energy storage applications. The micro-sheet morphology of todorokite-type magnesium manganese oxide molecular sieve (Mg-OMS-1) material, which applies as a novel cathode material for magnesium-ion battery, is obtained by the simple hydrothermal method. The structure and morphology of the particles are confirmed by X-ray power diffraction, X-ray photoelectron spectroscopy, inductively coupled plasma, scanning and transmission electron microscopy. The electrochemical performance of Mg-OMS-1 is researched by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and constant current charge-discharge measurement. Mg-OMS-1 shows a good battery behavior for Mg 2+ insertion and deinsertion in the aqueous electrolyte. When discharging at 10 mA g −1 in 0.2 mol dm −3 MgCl 2 aqueous electrolyte, the initial discharge capacity reaches 300 mAh g −1 . The specific capacity retention rate is 83.7% after cycling 300 times at 100 mA g −1 in 0.5 mol dm −3 MgCl 2 electrolyte with a columbic efficiency of nearly 100%.

Structural and surface properties of highly ordered mesoporous magnesium-aluminium composite oxides derived from facile synthesis

Energy Technology Data Exchange (ETDEWEB)

Pan, Dahai, E-mail: pandahai@foxmail.com; Dong, Zhaoyang; He, Min; Chen, Wei; Chen, Shuwei; Yu, Feng; Fan, Binbin; Cui, Xingyu; Li, Ruifeng, E-mail: rfli@tyut.edu.cn

2017-01-15

Highly ordered mesoporous magnesium-aluminium composite oxides (denoted as OMMA-x) with a variety of n{sub Al}/n{sub Mg} ratios have been successfully synthesized via a facile strategy, and a salt effect was proposed to explain the formation mechanism. The incorporation of Mg can significantly improve the structural and surface properties of ordered mesoporous alumina (OMA) material. The resultant OMMA-x exhibited a much more ordered 2-D hexagonal mesostructure, a narrower pore size distribution, a higher specific surface area and pore volume, and a stronger basicity than those of OMA. More importantly, the highly homogeneous incorporation of Mg at the atomic level and the formation of framework Mg−O−Al bonds could effectively suppress the formation of crystalline alumina during the calcination process. As a result, OMMA-x demonstrated a superior thermal stability. For example, the ordered mesostructure of OMMA-8 could be well maintained with a high surface area of 182 m{sup 2}/g even after thermal treatment at 1000 °C. - Graphical abstract: A schematic procedure to illustrate the preparation of highly ordered mesoporous Mg-Al composite oxides (OMMA-x) with highly homogeneously dispersed Mg species and enhanced structural stability. - Highlights: • Mesoporous Mg-Al composite oxides with excellent structural and surface properties. • A highly homogeneous incorporation of Mg into the mesoporous framework of alumina. • A superior structural stability up to 1000 °C coupled with a large surface area. • A salt effect from the addition of Mg(NO{sub 3}){sub 2}·6H{sub 2}O to explain the formation mechanism.

The oxidation resistance and ignition temperature of AZ31 magnesium alloy with additions of La2O3 and La

International Nuclear Information System (INIS)

Zhao, Shizhe; Zhou, Hong; Zhou, Ti; Zhang, Zhihui; Lin, Pengyu; Ren, Luquan

2013-01-01

Highlights: ► Using lanthanum and lanthanum oxide (La 2 O 3 ) can improve oxidation resistance of magnesium alloy. ► La 2 O 3 is as effective as La in affecting both alloy microstructure and oxidation resistance. ► The optimum La concentration in alloy is ∼0.7 wt.%. ► We analyzed the oxidation kinetics of AZ31 alloy with both additions. - Abstract: We investigate the oxidation resistance of AZ31 magnesium alloy with additions of La and La oxide (La 2 O 3 ). The contributor is the practical La content in alloy. Both La and La 2 O 3 are effective in improving the oxidation resistance of Mg alloys. The samples with La content of ∼ 0.7 wt.% possess the best resistance to oxidation of all. Oxide scale, ignition temperature and oxidation kinetics are analyzed. However, higher La content is detrimental to the oxidation resistance.

Carbon coated magnesium oxide based amperometric glucose biosensor

Energy Technology Data Exchange (ETDEWEB)

Silva, L.L.; Mello, J.M.M.; Fiori, M.A.; Duarte, G.W. [Universidade Comunitaria Regional de Chapeco (UNICHAPECO), SC (Brazil); Fernandes, S.C. [Instituto Federal Catarinense (IFC), Blumenau, SC (Brazil); Riella, H.G. [Centro Universitario Barriga Verde (UNIBAVE), Orleans, SC (Brazil); Anzolin, C.; Figueiro, A.; Grando, M.C. [Universidade Federal de Santa Catarina (UFSC), SC (Brazil)

2016-07-01

Full text: Diabetes is a serious disease that is harmful to human health since it is related to cardiovascular and stroke events. Since the first glucose oxidase (GOx) sensor, different approaches have been explored. Carbon was used to cover nano-magnesium oxide (MgO-C) forming a core-shell which was used to improve its biocompatibility and chemical stability for the preparation of GOx biosensor. MgO nanostructures have been prepared by calcination of the gel formed by the reaction of magnesium acetate tetrahydrate dissolved in cetyltrimethylammonium with the addition of tartaric acid solution. MgO-C nanostructures were obtained by heating MgO nanoparticles previously prepared together with glucose and PEG dissolved in an aqueous suspension. Reaction conditions such as concentration of magnesium precursor, temperature and aging time show important roles in the size, morphology and growth process of the final products. The core-shell structure was evidenced by SEM/FEG and XRD and showed that the product appeared to have morphological forms of nanowires. GOx was spread onto the surface of a modified carbon paste electrode (CPE) doped with MgO-C and the effect on the biosensing properties investigated by comparing the electrochemical properties of the proposed biosensor with bare and modified CPEs by cyclic voltammetry. The amount of modifier in CPE (5-75 weight% with respect to graphite) influences the peak current and the influence of different experimental parameters (enzyme percentage, pH solution and amperometric methods) was also investigated. The results demonstrate that the GOx retains its biocatalytic activity and that the bioelectrode modified can be a possible use for other nanotechnological purposes including biomedical ones. (author)

Carbon coated magnesium oxide based amperometric glucose biosensor

International Nuclear Information System (INIS)

Silva, L.L.; Mello, J.M.M.; Fiori, M.A.; Duarte, G.W.; Fernandes, S.C.; Riella, H.G.; Anzolin, C.; Figueiro, A.; Grando, M.C.

2016-01-01

Full text: Diabetes is a serious disease that is harmful to human health since it is related to cardiovascular and stroke events. Since the first glucose oxidase (GOx) sensor, different approaches have been explored. Carbon was used to cover nano-magnesium oxide (MgO-C) forming a core-shell which was used to improve its biocompatibility and chemical stability for the preparation of GOx biosensor. MgO nanostructures have been prepared by calcination of the gel formed by the reaction of magnesium acetate tetrahydrate dissolved in cetyltrimethylammonium with the addition of tartaric acid solution. MgO-C nanostructures were obtained by heating MgO nanoparticles previously prepared together with glucose and PEG dissolved in an aqueous suspension. Reaction conditions such as concentration of magnesium precursor, temperature and aging time show important roles in the size, morphology and growth process of the final products. The core-shell structure was evidenced by SEM/FEG and XRD and showed that the product appeared to have morphological forms of nanowires. GOx was spread onto the surface of a modified carbon paste electrode (CPE) doped with MgO-C and the effect on the biosensing properties investigated by comparing the electrochemical properties of the proposed biosensor with bare and modified CPEs by cyclic voltammetry. The amount of modifier in CPE (5-75 weight% with respect to graphite) influences the peak current and the influence of different experimental parameters (enzyme percentage, pH solution and amperometric methods) was also investigated. The results demonstrate that the GOx retains its biocatalytic activity and that the bioelectrode modified can be a possible use for other nanotechnological purposes including biomedical ones. (author)

Spectroscopic study of plasma during electrolytic oxidation of magnesium- and aluminium-alloy

International Nuclear Information System (INIS)

Jovović, J.; Stojadinović, S.; Šišović, N.M.; Konjević, N.

2012-01-01

We present the results of an optical emission spectroscopy study of Plasma during Electrolytic Oxidation (PEO) of magnesium- and aluminum-alloy. Plasma electron number density N e diagnostics is performed either from the H β line shape or from the width or shift of non-hydrogenic ion lines of aluminum and magnesium. The line profile analysis of the H β suggests presence of two PEO processes characterized by relatively low electron number densities N e ≈1.2×10 15 cm −3 and N e ≈2.3×10 16 cm −3 . Apart from these two low N e processes, there is the third one related to the ejection of evaporated anode material through micro-discharge channels. This process is characterized by larger electron density N e =(1.2–1.6)10 17 cm −3 , which is detected from the shape and shift of aluminum and magnesium singly charged ion lines. Two low N e values detected from the H β and large N e measured from the widths and shift of ion lines suggest presence of three types of discharges during PEO with aluminum- and magnesium-alloy anode. On the basis of present and earlier results one can conclude that low N e processes do not depend upon anode material or electrolyte composition. The electron temperature of 4000 K and 33,000 K are determined from relative intensities of Mg I and O II lines, respectively. The attention is drawn to the possibility of N e application for T e evaluation using Saha equation what is of importance for PEO metal plasma characterization. During the course of this study, difficulties in the analysis of spectral line shapes are encountered and the ways to overcome some of the obstacles are demonstrated. -- Highlights: ► Optical emission spectroscopy of plasma during electrolytic oxidation. ► Spectral line profiles of the H-beta and non-hydrogenic singly charged ion lines of aluminum and magnesium. ► Experimental line profiles with complex structure. ► Three plasma processes involved. ► The application of Saha equation for the process

Toxicity of magnesium alloy biodegradation products in experiment

Directory of Open Access Journals (Sweden)

Yu. M. Neryanov

2013-08-01

Full Text Available The article presents information on the study of possible toxic effects of biodegradation products of original magnesium-based alloy on laboratory rats. The used laboratory methods of investigation are described. Author has examined biochemical parameters of plasma on the base of which endogenous intoxication in rats was studied. It was found out that products of alloy biological resorption don’t cause toxic effects on tissues and don’t enhance cell destruction, that is evidenced by the absence of signs of endogenous intoxication and oxidative damage of functional macromolecules. Materials and methods. We used white mongrel male rats weighing 220-270 g (n = 20. Fixator consisting of a modified magnesium alloy ML-10 was implanted into the femur muscle mass of the animals of the experimental group (n = 14. The control group consisted of white mongrel male rats weighing 230-250 g (n = 6, which were not subjected to surgery (intact group. The degree of oxidative damage to proteins, the content of the average molecular weight, nucleic acids and the stable metabolites of nitric oxide were evaluated in plasma. Results and discussion. The studies revealed the reliable (relative to the intact group increase in the content of all fractions of middle molecules in the plasma of the experimental group of rats, the increase shows only that the immune system of animals with magnesium implants is in a reactive state and responds with minor release of biologically active substances into the bloodstream. At this rate of endogenous intoxication this exponent usually increases tenfold, but we have not seen that. Levels of stable metabolites of nitric oxide increase insignificantly(1,4 times, that likely indicates more on the start of adaptive signaling processes than a pathological condition. The experimental data concerning the content of nucleic acids in the plasma of animals with magnesium implants testifies in support of this hypothesis. There were no

21 CFR 184.1443 - Magnesium sulfate.

Science.gov (United States)

2010-04-01

... 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... magnesium oxide, hydroxide, or carbonate with sulfuric acid and evaporating the solution to crystallization...

Stabilization of Cs/Re trapping filters using magnesium phosphate ceramics

International Nuclear Information System (INIS)

Jae Hwan Yang; Jin Myeong Shin; Chang Hwa Lee; Chul Min Heo; Min Ku Jeon; Kweon Ho Kang

2013-01-01

The present study a promising method for stabilizing spent filters trapping cesium and technetium by using magnesium phosphate ceramics. Simulated spent filters were fabricated by vaporizing nonradioactive cesium and rhenium (a surrogate of Tc) through the voloxidizer. In order to reveal the characteristics of spent filters, phase structures and thermal stability were analyzed by using X-ray diffraction (XRD), X-ray photoelectron spectroscopy, and thermogravimetric analysis techniques. Waste forms were fabricated by crushing spent filters and mixing them with magnesium oxide and potassium phosphate. Characterizations of the waste forms were performed by the analyses of compressive strength, apparent porosity, XRD, and scanning electron microscopy. The waste forms showed the excellent mechanical property compared with that of ordinary Portland cement, with the highest compressive strength of 38.1 MPa in the sample with 30 wt% of Cs-filter. Microstructural analysis suggests that waste materials are encapsulated by the binding matrix composed of magnesium potassium phosphate. The results of characterization suggest that fabricating a sound and durable waste form is possible with magnesium phosphate ceramics. (author)

Plasma electrolytic oxidation of magnesium and its alloys: Mechanism, properties and applications

Directory of Open Access Journals (Sweden)

Gh. Barati Darband

2017-03-01

Full Text Available Plasma Electrolyte Oxidation (PEO process has increasingly been employed to improve magnesium surface properties by fabrication of an MgO-based coating. Originating from conventional anodizing procedures, this high-voltage process produces an adhesive ceramic film on the surface. The present article provides a comprehensive review around mechanisms of PEO coatings fabrication and their different properties. Due to complexity of PEO coatings formation, a complete explanation regarding fabrication mechanisms of PEO coatings has not yet been proposed; however, the most important advancements in the field of fabrication mechanisms of PEO coatings were gathered in this work. Mechanisms of PEO coatings fabrication on magnesium were reviewed considering voltage–time plots, optical spectrometry, acoustic emission spectrometry and electronic properties of the ceramic film. Afterwards, the coatings properties, affecting parameters and improvement strategies were discussed. In addition, corrosion resistance of coatings, important factors in corrosion resistance and methods for corrosion resistance improvement were considered. Tribological properties (important factors and improvement methods of coatings were also studied. Since magnesium and its alloys are broadly used in biological applications, the biological properties of PEO coatings, important factors in their biological performance and existing methods for improvement of coatings were explained. Addition of ceramic based nanoparticles and formation of nanocomposite coatings may considerably influence properties of plasma electrolyte oxidation coatings. Nanocomposite coatings properties and nanoparticles adsorption mechanisms were included in a separate sector. Another method to improve coatings properties is formation of hybrid coatings on PEO coatings which was discussed in the end.

Corrosion of magnesium and some magnesium alloys in gas cooled reactors

International Nuclear Information System (INIS)

Caillat, R.; Darras, R.

1958-01-01

The results of corrosion tests on magnesium and some magnesium alloys (Mg-Zr and Mg-Zr-Zn) in moist air (like G1 reactor) and in CO 2 : (like G2, G3, EDF1 reactors) are reported. The maximum temperature for exposure of magnesium to moist air without any risk of corrosion is 350 deg. C. Indeed, the oxidation rate follows a linear law above 350 deg. C although it reaches a constant level and keeps on very low under 350 deg. C. However, as far as corrosion is concerned this temperature limit can be raised up to 500 deg. C if moist air is very slightly charged with fluorinated compounds. Under pressure of CO 2 , these three materials oxidate much more slowly even if 500 deg. C is reached. The higher is the temperature, the higher is the constant level of the weight increase and the quicker is reached this one. However, Mg-Zr alloy behaves quite better than pure magnesium and especially than Mg-Zr-Zn alloy. (author) [fr

Thermal properties of graphite oxide, thermally reduced graphene and chemically reduced graphene

Science.gov (United States)

Jankovský, Ondřej; Sedmidubský, David; Lojka, Michal; Sofer, Zdeněk

2017-07-01

We compared thermal behavior and other properties of graphite oxide, thermally reduced graphene and chemically reduced graphene. Graphite was oxidized according to the Hofmann method using potassium chlorate as oxidizing agent in strongly acidic environment. In the next step, the formed graphite oxide was chemically or thermally reduced yielding graphene. The mechanism of thermal reduction was studied using STA-MS. Graphite oxide and both thermally and chemically reduced graphenes were analysed by SEM, EDS, elemental combustion analysis, XPS, Raman spectroscopy, XRD and BET. These findings will help for the large scale production of graphene with appropriate chemical composition.

DT fusion neutron irradiation of ORNL magnesium oxide crystals and BNL--LASL superconductor wires

International Nuclear Information System (INIS)

MacLean, S.C.

1978-01-01

The DT fusion neutron irradiation of two ORNL magnesium oxide crystals and eleven BNL-LASL superconductor wires is described. The sample position and neutron dose record are given. The maximum neutron fluence on any sample was 2.16 x 10 16 neutrons/cm 2

Imparting passivity to vapor deposited magnesium alloys

Science.gov (United States)

Wolfe, Ryan C.

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

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

Energy Technology Data Exchange (ETDEWEB)

Jang, Yongseok [Engineering Research Center for Revolutionizing Metallic Biomaterials (ERC-RMB), North Carolina A and T State University, Greensboro, NC, 27411 (United States); Tan, Zongqing [Internal Medicine, College of Medicine, University of Cincinnati, OH 45211 (United States); Jurey, Chris [Luke Engineering, Wadsworth, OH 44282 (United States); Collins, Boyce [Engineering Research Center for Revolutionizing Metallic Biomaterials (ERC-RMB), North Carolina A and T State University, Greensboro, NC, 27411 (United States); Badve, Aditya [Business and Biology, The University of North Carolina at Chapel Hill, NC 27514 (United States); Dong, Zhongyun [Internal Medicine, College of Medicine, University of Cincinnati, OH 45211 (United States); Park, Chanhee; Kim, Cheol Sang [Department of Bio-nano System Engineering, Chonbuk National University, Jeonju, Jeonbuk 561-756 (Korea, Republic of); Sankar, Jagannathan [Engineering Research Center for Revolutionizing Metallic Biomaterials (ERC-RMB), North Carolina A and T State University, Greensboro, NC, 27411 (United States); Yun, Yeoheung, E-mail: yyun@ncat.edu [Engineering Research Center for Revolutionizing Metallic Biomaterials (ERC-RMB), North Carolina A and T State University, Greensboro, NC, 27411 (United States)

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. - Highlights: • Effects of plasma electrolytic oxidation on AZ31 in vitro and in vivo • Retardation of degradation via plasma electrolytic oxidation in vitro and in vivo • Differentiation of in vitro and in vivo corrosion types and products.

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

International Nuclear Information System (INIS)

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

2014-01-01

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. - Highlights: • Effects of plasma electrolytic oxidation on AZ31 in vitro and in vivo • Retardation of degradation via plasma electrolytic oxidation in vitro and in vivo • Differentiation of in vitro and in vivo corrosion types and products

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

Science.gov (United States)

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

2013-12-15

Nanostructured magnesium oxide (sizeEIS) 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.

Behavior of bone cells in contact with magnesium implant material.

Science.gov (United States)

Burmester, Anna; Willumeit-Römer, Regine; Feyerabend, Frank

2017-01-01

Magnesium-based implants exhibit several advantages, such as biodegradability and possible osteoinductive properties. Whether the degradation may induce cell type-specific changes in metabolism still remains unclear. To examine the osteoinductivity mechanisms, the reaction of bone-derived cells (MG63, U2OS, SaoS2, and primary human osteoblasts (OB)) to magnesium (Mg) was determined. Mg-based extracts were used to mimic more realistic Mg degradation conditions. Moreover, the influence of cells having direct contact with the degrading Mg metal was investigated. In exposure to extracts and in direct contact, the cells decreased pH and osmolality due to metabolic activity. Proliferating cells showed no significant reaction to extracts, whereas differentiating cells were negatively influenced. In contrast to extract exposure, where cell size increased, in direct contact to magnesium, cell size was stable or even decreased. The amount of focal adhesions decreased over time on all materials. Genes involved in bone formation were significantly upregulated, especially for primary human osteoblasts. Some osteoinductive indicators were observed for OB: (i) an increased cell count after extract addition indicated a higher proliferation potential; (ii) increased cell sizes after extract supplementation in combination with augmented adhesion behavior of these cells suggest an early switch to differentiation; and (iii) bone-inducing gene expression patterns were determined for all analyzed conditions. The results from the cell lines were inhomogeneous and showed no specific stimulus of Mg. The comparison of the different cell types showed that primary cells of the investigated tissue should be used as an in vitro model if Mg is analyzed. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 165-179, 2017. © 2015 Wiley Periodicals, Inc.

Blockage of both the extrinsic and intrinsic pathways of diazinon-induced apoptosis in PaTu cells by magnesium oxide and selenium nanoparticles

Directory of Open Access Journals (Sweden)

Shiri M

2016-11-01

Full Text Available Mahdi Shiri,1,2,* Mona Navaei-Nigjeh,1,3,* Maryam Baeeri,1 Mahban Rahimifard,1 Hossein Mahboudi,4 Ahmad Reza Shahverdi,5 Abbas Kebriaeezadeh,1 Mohammad Abdollahi1,6,7 1Department of Toxicology and Pharmacology, Faculty of Pharmacy and Pharmaceutical Sciences Research Center, Tehran University of Medical Sciences, 2School of Medicine, Artesh University of Medical Sciences, 3Department of Tissue Engineering, School of Advanced Technologies in Medicine, Tehran University of Medical Sciences, Tehran, Iran; 4Department of Biotechnology, Faculty of Advanced Technologies in Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran; 5Department of Biotechnology, Faculty of Pharmacy and Biotechnology Research Center, 6Toxicology Interest Group, USERN, 7Endocrinology & Metabolism Research Institute, Tehran University of Medical Sciences, Tehran, Iran *These authors contributed equally to this work Abstract: Diazinon (DZ is an organophosphorus insecticide that acts as an acetylcholinesterase inhibitor. It is important to note that it can induce oxidative stress, lipid peroxidation, diabetic disorders, and cytotoxicity. Magnesium oxide (MgO and selenium nanoparticles (Se NPs showed promising protection against oxidative stress, lipid peroxidation, cytotoxicity, and diabetic disorders. Therefore, this study was conducted to explore the possible protective mechanisms of MgO and Se NPs against DZ-induced cytotoxicity in PaTu cell line. Cytotoxicity of DZ, in the presence or absence of effective doses of MgO and Se NPs, was determined in human pancreatic cancer cell line (PaTu cells after 24 hours of exposure by using mitochondrial activity and mitochondrial membrane potential assays. Then, the insulin, proinsulin, and C-peptide release; caspase-3 and -9 activities; and total thiol molecule levels were assessed. Determination of cell viability, including apoptotic and necrotic cells, was assessed via acridine orange/ethidium bromide double

The protective effect of magnesium lithospermate B against glucose-induced intracellular oxidative damage

Energy Technology Data Exchange (ETDEWEB)

Qu, Jian [Institute of Clinical Pharmacology, Hunan Key Laboratory of Pharmacogenetics, Central South University, Xiangya School of Medicine, Changsha 410078 (China); Ren, Xian [Shanghai Green Valley Pharmaceutical Co., Ltd., Shanghai 201304 (China); Hou, Rui-ying; Dai, Xing-ping [Institute of Clinical Pharmacology, Hunan Key Laboratory of Pharmacogenetics, Central South University, Xiangya School of Medicine, Changsha 410078 (China); Zhao, Ying-chun [Laboratories of Functional Genomics and Proteomics, Creighton University Medical Center, Omaha, NE 68131 (United States); Xu, Xiao-jing; Zhang, Wei; Zhou, Gan; Zhou, Hong-hao [Institute of Clinical Pharmacology, Hunan Key Laboratory of Pharmacogenetics, Central South University, Xiangya School of Medicine, Changsha 410078 (China); Liu, Zhao-qian, E-mail: liuzhaoqian63@126.com [Institute of Clinical Pharmacology, Hunan Key Laboratory of Pharmacogenetics, Central South University, Xiangya School of Medicine, Changsha 410078 (China)

2011-07-22

Highlights: {yields} LAB reduced the ROS production in HEK293T cells cultured under oxidative stress. High dose of glucose enhanced the expression of HO-1 mRNA and HO-1 protein in a time-dependent manner. {yields} LAB enhanced the expression of HO-1 mRNA and HO-1 protein in a dose-dependent manner treated with high dose of glucose. {yields} LAB plays an important role against glucose-induced intracellular oxidative damage. {yields} The enhanced expression of HO-1 mRNA and HO-1 protein caused by LAB is regulated via Nrf2 signal pathway. -- Abstract: Objectives: To investigate the effects of magnesium lithospermate B (LAB) on intracellular reactive oxygen species (ROS) production induced by high dose of glucose or H{sub 2}O{sub 2}, we explored the influences of LAB on the expression of heme oxygenase-1 (HO-1) and nuclear factor E2-related factor-2 (Nrf2) in HEK293T cells after treatment with high dose of glucose. Materials and methods: The total nuclear proteins in HEK293T cells were extracted with Cytoplasmic Protein Extraction Kit. The ROS level was determined by flow cytometry. The mRNA and protein expression of HO-1 and Nrf2 were determined by quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western blot. Results: LAB reduced the ROS production in HEK293T cells cultured under oxidative stress. High dose of glucose enhanced the expression of HO-1 mRNA and HO-1 protein in a time-dependent manner. LAB enhanced the expression of HO-1 mRNA and HO-1 protein in a dose-dependent manner treated with high dose of glucose. The amount of Nrf2 translocation was enhanced after cells were pretreated with 50 {mu}mol/L or 100 {mu}mol/L LAB. Silencing of Nrf2 gene eliminated the enhanced expression of HO-1 protein induced by high dose of glucose plus LAB. Conclusions: LAB plays an important role against glucose-induced intracellular oxidative damage. The enhanced expression of HO-1 mRNA and HO-1 protein caused by LAB is regulated via Nrf2 signal pathway.

Effect of the laxative magnesium oxide on gastrointestinal functional recovery in fast-track colonic resection: a double-blind, placebo-controlled randomized study

DEFF Research Database (Denmark)

Andersen, J; Christensen, H; Pachler, J H

2012-01-01

Aim: A double-blind randomised controlled study was conducted to compare the effect of magnesium oxide (1 g 12-hourly) with placebo given within an evidence-based multimodal rehabilitation programme on gastrointestinal recovery, pain, mobilisation and hospital stay after open colonic resection....... Method: Of sixty two potentially eligible patients, thirteen were excluded leaving 22 in the magnesium oxide group and 27 in the placebo group. The main outcome measure was time to normalization of bowel function. Secondary outcome measures included post operative nausea, vomiting, pain, fatigue...... were similar in the groups (p>0.3). The median postoperative hospital stay was three days in both groups (p>0.65). Conclusion: Magnesium oxide does not enhance the recovery of gastrointestinal function within the context of an evidence-based multimodal rehabilitation programme after open colonic...

Yttrium ion implantation on the surface properties of magnesium

International Nuclear Information System (INIS)

Wang, X.M.; Zeng, X.Q.; Wu, G.S.; Yao, S.S.

2006-01-01

Owing to their excellent physical and mechanical properties, magnesium and its alloys are receiving more attention. However, their application has been limited to the high reactivity and the poor corrosion resistance. The aim of the study was to investigate the beneficial effects of ion-implanted yttrium using a MEVVA ion implanter on the surface properties of pure magnesium. Isothermal oxidation tests in pure O 2 at 673 and 773 K up to 90 min indicated that the oxidation resistance of magnesium had been significantly improved. Surface morphology of the oxide scale was analyzed using scanning electron microscope (SEM). Auger electron spectroscopy (AES) and X-ray diffraction (XRD) analyses indicated that the implanted layer was mainly composed of MgO and Y 2 O 3 , and the implanted layer with a duplex structure could decrease the inward diffusion of oxygen and reduce the outward diffusion of Mg 2+ , which led to improving the oxidation resistance of magnesium. Potentiodynamic polarization curves were used to evaluate the corrosion resistance of the implanted magnesium. The results show yttrium implantation could enhance the corrosion resistance of implanted magnesium compared with that of pure magnesium

Sol-gel synthesis of magnesium oxide-silicon dioxide glass compositions

Science.gov (United States)

Bansal, Narottam P.

1988-01-01

MgO-SiO2 glasses containing up to 15 mol pct MgO, which could not have been prepared by the conventional glass melting method due to the presence of stable liquid-liquid immiscibility, were synthesized by the sol-gel technique. Clear and transparent gels were obtained from the hydrolysis and polycondensation of silicon tetraethoxide (TEOS) and magnesium nitrate hexahydrate when the water/TEOS mole ratio was four or more. The gelling time decreased with increase in magnesium content, water/TEOS ratio, and reaction temperature. Magnesium nitrate hexahydrate crystallized out of the gels containing 15 and 20 mol pct MgO on slow drying. This problem was partially alleviated by drying the gels quickly at higher temperatures. Monolithic gel samples were prepared using glycerol as the drying control additive. The gels were subjected to various thermal treatments and characterized by several methods. No organic groups could be detected in the glasses after heat treatments to approx. 800 C, but trace amounts of hydroxyl groups were still present. No crystalline phase was found from X-ray diffraction in the gel samples to approx. 890 C. At higher temperatures, alpha quartz precipitated out as the crystalline phase in gels containing up to 10 mol pct MgO. The overall activation energy for gel formation in 10MgO-90SiO2 (mol pct) system for water/TEOS mole ratio of 7.5 was calculated to be 58.7 kJ/mol.

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

Science.gov (United States)

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.

Effects of Lithium Dopant on Size and Morphology of Magnesium Oxide Nano powders

International Nuclear Information System (INIS)

Mohd Sufri Mastuli; Siti Nur Hazlinda Hasbu; Noraziahwati Ibrahim; Mohd Azizi Nawawi; Mohd Sufri Mastuli

2014-01-01

Lithium doped of magnesium oxide powders have been synthesized using the sol-gel method with magnesium acetate tetrahydrate, oxalic acid dihydrate and lithium acetate dihydrate used as the starting materials. The dried sol-gel products were calcined at 950 degree Celsius for 36 h to form the Li doped-MgO samples. The calcined samples were characterized using X-Ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The present work is investigated the effect of lithium ion on the band gap energy of studied samples. The band gap energies were obtained from a Tauc plot that drawn based on absorption edge of each sample that measured using a UV-Vis spectrophotometer. It is found that the doped and undoped MgO samples showed a slightly different in their band gap energies. The lithium ion that present in the MgO as a dopant affects the crystallite size and morphology of the final products. Our study shows that the lithium dopant can modified optical properties of the metal oxide which to be beneficial in some industrial applications. (author)

Thermal Stability of Li-Ion Cells

International Nuclear Information System (INIS)

ROTH, EMANUEL P.

1999-01-01

The thermal stability of Li-ion cells with intercalating carbon anodes and metal oxide cathodes was measured as a function of state of charge and temperature for two advanced cell chemistries. Cells of the 18650 design with Li(sub x)CoO(sub 2) cathodes (commercial SONY cells) and Li(sub x)Ni(sub 0.8)Co(sub 0.2)O(sub 2) cathodes were measured for thermal reactivity in the open circuit cell condition. Accelerating rate calorimetry (ARC) was used to measure cell thermal runaway as a function of state of charge (SOC). Microcalorimetry was used to measure the time dependence of heat generating side reactions also as a function of SOC. Components of cells were measured using differential scanning calorimetry (DSC) to study the thermal reactivity of the individual electrodes to determine the temperature regimes and conditions of the major thermal reactions. Thermal decomposition of the SEI layer at the anodes was identified as the initiating source for thermal runaway. The cells with Li(sub x)CoO(sub 2) cathodes showed greater sensitivity to SOC and higher accelerating heating rates than seen for the cells with Li(sub x)Ni(sub 0.8)Co(sub 0.2)O(sub 2)cathodes. Lower temperature reactions starting as low as 40 C were also observed that were SOC dependent but not accelerating. These reactions were also measured in the microcalorimeter and observed to decay over time with a power-law dependence and are believed to result in irreversible capacity loss in the cells

Effect of magnesium ions on the initial oxidation stages of carbon steel

International Nuclear Information System (INIS)

Subramanian, H.; Subramanian, Veena; Rangarajan, S.; Narasimhan, S.V.; Velmurugan, S.

2012-09-01

Metal Ion Passivation (MIP) is a technique in which passivating ions get into the oxide of structural materials and modifies the oxide in such a way as to reduce the corrosion and corrosion release rates. Magnesium ions are found to be efficient in passivating carbon steel. This study is an attempt to understand the role of magnesium ions during the early stage of film growth on carbon steel. The study reveals that in the presence of Mg, the initial oxide film formed by the application of potential had a different electrochemical property. The microstructure of the parent alloy of steel also interacted differently with Mg during the film formation. The ferrite film was grown on carbon steel by applying 0.1 V (vs SCE) in borate buffer (pH=9, 85 deg. C). The formation and coverage of film on the surface was ascertained by measuring the steady state current density as a function of time. The steady state current density was achieved faster when Mg was present in the solution. The thin film formed was characterized by both by electrochemical impedance spectroscopy and atomic force microscopy. The formation of a passive film (at 0.1 V vs SCE) was evident in both with and without Mg cases, with total impedance of the system increasing by an order of magnitude compared to the film formed at OCP (∼ - 0.825 V vs SCE). The data was fitted to an equivalent circuit representing a metal covered with a porous film. The fit parameters were significantly different for Mg containing system and the charge transfer resistance at oxide/solution interface was observed to be two times higher. The capacitance of the film was also higher in presence of Mg indicating a thinner film. The thin films on carbon steel were characterized by AFM in semi contact mode. The surfaces were found to be covered with fine oxide. Two morphologically different regions could be identified on the surface and they were assigned as pearlite and ferrite regions. One of the most notable observations was the

A comparative study of the ignition and burning characteristics of after burning aluminum and magnesium particles

International Nuclear Information System (INIS)

Lim, Ji Hwan; Lee, Sang Hyup; Yoon, Woong Sup

2014-01-01

Ignition and the burning of air-born single aluminum and magnesium particles are experimentally investigated. Particles of 30 to 106 μm-diameters were electrodynamically levitated, ignited, and burnt in atmospheric air. The particle combustion evolution was recorded by high-speed cinematography. Instant temperature and thermal radiation intensity were measured using two-wavelength pyrometry and photomultiplier tube methods. Ignition of the magnesium particle is prompt and substantially advances the aluminum particle by 10 ms. Burning time of the aluminum particles is extended 3 to 5 times longer than the magnesium particles. Exponents of a power-law fit of the burning rates are 1.55 and 1.24 for aluminum and magnesium particles, respectively. Flame temperature is slightly lower than the oxide melting temperature. For the aluminum, dimensionless flame diameter is inert to the initial particle size, but for the magnesium inversely proportional to the initial diameter.

A comparative study of the ignition and burning characteristics of after burning aluminum and magnesium particles

Energy Technology Data Exchange (ETDEWEB)

Lim, Ji Hwan; Lee, Sang Hyup; Yoon, Woong Sup [Yonsei University, Seoul (Korea, Republic of)

2014-10-15

Ignition and the burning of air-born single aluminum and magnesium particles are experimentally investigated. Particles of 30 to 106 μm-diameters were electrodynamically levitated, ignited, and burnt in atmospheric air. The particle combustion evolution was recorded by high-speed cinematography. Instant temperature and thermal radiation intensity were measured using two-wavelength pyrometry and photomultiplier tube methods. Ignition of the magnesium particle is prompt and substantially advances the aluminum particle by 10 ms. Burning time of the aluminum particles is extended 3 to 5 times longer than the magnesium particles. Exponents of a power-law fit of the burning rates are 1.55 and 1.24 for aluminum and magnesium particles, respectively. Flame temperature is slightly lower than the oxide melting temperature. For the aluminum, dimensionless flame diameter is inert to the initial particle size, but for the magnesium inversely proportional to the initial diameter.

Structural and Optical Studies of Magnesium Doped Zinc Oxide Thin Films

OpenAIRE

Arpana Agrawal; Tanveer Ahmad Dar; Pratima Sen

2013-01-01

The paper describes the structural and optical properties of Magnesium doped Zinc Oxide (Mg  3.5 %, 6 %, 9 %, 12 % by weight) thin films prepared by pulsed laser deposition technique. The samples are characterized by X-ray diffraction technique, Ultra-violet visible absorption spectroscopy, X-ray photoelectron spectroscopy. X-ray diffraction results reveal the polycrystalline nature of samples with no impurity or secondary phase formation. Ultra-violet visible absorption spectroscopy studies...

Physical, mechanical and electrochemical characterization of all-perovskite intermediate temperature solid oxide fuel cells

Science.gov (United States)

Mohammadi, Alidad

Strontium- and magnesium-doped lanthanum gallate (LSGM) has been considered as a promising electrolyte for solid oxide fuel cell (SOFC) systems in recent years due to its high ionic conductivity and chemical stability over a wide range of oxygen partial pressures and temperatures. This research describes synthesis, physical and mechanical behavior, electrochemical properties, phase evolution, and microstructure of components of an all-perovskite anode-supported intermediate temperature solid oxide fuel cell (ITSOFC), based on porous La 0.75Sr0.25Cr0.5Mn0.5O3 (LSCM) anode, La0.8Sr0.2Ga0.8Mg0.2O 2.8 (LSGM) electrolyte, and porous La0.6Sr0.4Fe 0.8Co0.2O3 (LSCF) cathode. The phase evolution of synthesized LSGM and LSCM powders has been investigated, and it has been confirmed that there is no reaction between LSGM and LSCM at sintering temperature. Using different amounts of poreformers and binders as well as controlling firing temperature, porosity of the anode was optimized while still retaining good mechanical integrity. The effect of cell operation conditions under dry hydrogen fuel on the SOFC open circuit voltage (OCV) and cell performance were also investigated. Characterization study of the synthesized LSGM indicates that sintering at 1500°C obtains higher electrical conductivity compared to the currently published results, while conductivity of pellets sintered at 1400°C and 1450°C would be slightly lower. The effect of sintering temperature on bulk and grain boundary resistivities was also discussed. The mechanical properties, such as hardness, Young's modulus, fracture toughness and modulus of rupture of the electrolyte were determined and correlated with scanning electron microscopy (SEM) morphological characterization. Linear thermal expansion and thermal expansion coefficient of LSGM were also measured.

Compressive Deformation Behavior of Closed-Cell Micro-Pore Magnesium Composite Foam

Directory of Open Access Journals (Sweden)

Jing Wang

2018-05-01

Full Text Available The closed-cell micro-pore magnesium composite foam with hollow ceramic microspheres (CMs was fabricated by a modified melt foaming method. The effect of CMs on the compressive deformation behavior of CM-containing magnesium composite foam was investigated. Optical microscopy and scanning electron microscopy were used for observation of the microstructure. Finite element modeling of the magnesium composite foam was established to predict localized stress, fracture of CMs, and the compressive deformation behavior of the foam. The results showed that CMs and pores directly affected the compressive deformation behavior of the magnesium composite foam by sharing a part of load applied on the foam. Meanwhile, the presence of Mg2Si phase influenced the mechanical properties of the foam by acting as the crack source during the compression process.

Effect of magnesium oxide on interfraction prostate motion and rectal filling in prostate cancer radiotherapy. Analysis of a randomized clinical trial

International Nuclear Information System (INIS)

Harder, Annemarie M. den; Kotte, Alexis N.T.J.; Vulpen, Marco van; Lips, Irene M.; Gils, Carla H. van

2014-01-01

To investigate whether magnesium oxide reduces the interfraction motion of the prostate and the amount of rectal filling and rectal gas, which influences prostate position during radiotherapy for prostate cancer. From December 2008 to February 2010, 92 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. In a previous study, we investigated the effect on intrafraction motion and did not find a difference between the treatment arms. Here, we compared the interfraction prostate motion between the two treatment arms as well as the amount of rectal filling and rectal air pockets using pretreatment planning computed tomography and magnetic resonance imaging scans. There was no statistically significant difference between the treatment arms in translation and rotation of the prostate between treatment fractions, except for the rotation around the cranial caudal axis. However, the difference was less than 1 and therefore considered not clinically relevant. There was no significant difference in the amount of rectal filling and rectal air pockets between the treatment arms. Magnesium oxide is not effective in reducing the interfraction prostate motion or the amount of rectal filling and rectal gas during external-beam radiotherapy. Therefore, magnesium oxide is not recommended in clinical practice for these purposes. (orig.) [de

The effect of Y2O3 addition on thermal shock behavior of magnesium aluminate spinel

Directory of Open Access Journals (Sweden)

Pošarac Milica

2009-01-01

Full Text Available The effect of yttria additive on the thermal shock behavior of magnesium aluminate spinel has been investigated. As a starting material we used spinel (MgAl2O4 obtained by the modified glycine nitrate procedure (MGNP. Sintered products were characterized in terms of phase analysis, densities, thermal shock, monitoring the damaged surface area in the refractory specimen during thermal shock and ultrasonic determination of the Dynamic Young modulus of elasticity. It was found that a new phase between yttria and alumina is formed, which improved thermal shock properties of the spinel refractories. Also densification of samples is enhanced by yttria addition.

Thermal conductivity of bulk GaN—Effects of oxygen, magnesium doping, and strain field compensation

International Nuclear Information System (INIS)

Simon, Roland B.; Anaya, Julian; Kuball, Martin

2014-01-01

The effect of oxygen doping (n-type) and oxygen (O)-magnesium (Mg) co-doping (semi-insulating) on the thermal conductivity of ammonothermal bulk GaN was studied via 3-omega measurements and a modified Callaway model. Oxygen doping was shown to significantly reduce thermal conductivity, whereas O-Mg co-doped GaN exhibited a thermal conductivity close to that of undoped GaN. The latter was attributed to a decreased phonon scattering rate due the compensation of impurity-generated strain fields as a result of dopant-complex formation. The results have great implications for GaN electronic and optoelectronic device applications on bulk GaN substrates

Niobium nitride Josephson tunnel junctions with magnesium oxide barriers

International Nuclear Information System (INIS)

Shoji, A.; Aoyagi, M.; Kosaka, S.; Shinoki, F.; Hayakawa, H.

1985-01-01

Niobium nitride-niobium nitride Josephson tunnel junctions have been fabricated using amorphous magnesium oxide (a-MgO) films as barriers. These junctions have excellent tunneling characteristics. For example, a large gap voltage (V/sub g/ = 5.1 mV), a large product of the maximum critical current and the normal tunneling resistance (I/sub c/R/sub n/ = 3.25 mV), and a small subgap leakage current (V/sub m/ = 45 mV, measured at 3 mV) have been obtained for a NbN/a-MgO/NbN junction. The critical current of this junction remains finite up to 14.5 K

In vivo study of nanostructured diopside (CaMgSi2O6) coating on magnesium alloy as biodegradable orthopedic implants

International Nuclear Information System (INIS)

Razavi, Mehdi; Fathi, Mohammadhossein; Savabi, Omid; Razavi, Seyed Mohammad; Heidari, Fariba; Manshaei, Maziar; Vashaee, Daryoosh; Tayebi, Lobat

2014-01-01

Highlights: • In vitro biocompatibility of biodegradable Mg alloy was improved by diopside coating. • In vivo biocompatibility of biodegradable Mg alloy was improved by diopside coating. • Degradation behavior of biodegradable Mg alloy was improved by diopside coating. - Abstract: In order to improve the corrosion resistance and bioactivity of a biodegradable magnesium alloy, we have recently prepared a nanostructured diopside (CaMgSi 2 O 6 ) coating on AZ91 magnesium alloy through a combined micro-arc oxidation (MAO) and electrophoretic deposition (EPD) method (reported elsewhere). In this work, we performed a detailed biocompatibility analysis of the implants made by this material and compared their performance with those of the uncoated and micro arc oxidized magnesium implants. The biocompatibility evaluation of samples was performed by culturing L-929 cells and in vivo animal study, including implantation of samples in greater trochanter of rabbits, radiography and histological examinations. The results from both the in vitro and in vivo studies indicated that the diopside/MAO coated magnesium implant significantly enhanced cell viability, biodegradation resistance and new bone formation compared with both the uncoated and the micro-arc oxidized magnesium implants. Our data provides an example of how the proper surface treatment of magnesium implants can overcome their drawbacks in terms of high degradation rate and gas bubble formation under physiological conditions

Electrode Kinetics and Gas Conversion in Solid Oxide Cells

DEFF Research Database (Denmark)

Njodzefon, Jean-Claude

The solid oxide fuel cell (SOFC) converts hydrogen, carbon monoxide and hydrocarbon fuels (directly) into electricity with very high efficiencies and has demonstrated almost comparable performance when operated in reverse mode as a solid oxide electrolysis cell (SOEC). In this case electrical (and...... thermal) energy is stored as chemical energy of reaction products. To this end, the cells are fed with steam (H2O electrolysis), carbon dioxide (CO2 electrolysis) or a mixture of both (H2O/CO2 co-electrolysis) and of course electrical (ΔG) and thermal (TΔS) energies for the splitting of reactant compounds...... of the solid oxide cell (SOC) and independent of polarization mode (fuel cell mode or electrolysis mode), the current flowing through the cell is limited by processes such as adsorption and desorption of reactants or products, diffusion through the porous electrodes, activation or charge transfer...

Exposure to titanium dioxide and other metallic oxide nanoparticles induces cytotoxicity on human neural cells and fibroblasts

Directory of Open Access Journals (Sweden)

James C K Lai

2008-12-01

Full Text Available James C K Lai1, Maria B Lai1, Sirisha Jandhyam1, Vikas V Dukhande1, Alok Bhushan1, Christopher K Daniels1, Solomon W Leung21Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, and Biomedical Research Institute; 2Department of Civil and Environmental Engineering, College of Engineering and Biomedical Research Institute, Idaho State University, Pocatello, ID, USAAbstract: The use of titanium dioxide (TiO2 in various industrial applications (eg, production of paper, plastics, cosmetics, and paints has been expanding thereby increasing the occupational and other environmental exposure of these nanoparticles to humans and other species. However, the health effects of exposure to TiO2 nanoparticles have not been systematically assessed even though recent studies suggest that such exposure induces inflammatory responses in lung tissue and cells. Because the effects of such nanoparticles on human neural cells are unknown, we have determined the putative cytotoxic effects of these nanoparticles on human astrocytes-like astrocytoma U87 cells and compared their effects on normal human fibroblasts. We found that TiO2 micro- and nanoparticles induced cell death on both human cell types in a concentration-related manner. We further noted that zinc oxide (ZnO nanoparticles were the most effective, TiO2 nanoparticles the second most effective, and magnesium oxide (MgO nanoparticles the least effective in inducing cell death in U87 cells. The cell death mechanisms underlying the effects of TiO2 micro- and nanoparticles on U87 cells include apoptosis, necrosis, and possibly apoptosis-like and necrosis-like cell death types. Thus, our findings may have toxicological and other pathophysiological implications on exposure of humans and other mammalian species to metallic oxide nanoparticles.Keywords: cytotoxicity of titanium dioxide micro- and nanoparticles, cytotoxicity of zinc oxide and magnesium oxide nanoparticles, human neural cells

Precipitation of plutonium from acidic solutions using magnesium oxide

International Nuclear Information System (INIS)

Jones, S.A.

1994-01-01

Plutonium (IV) is only marginally soluble in alkaline solution. Precipitation of plutonium using sodium or potassium hydroxide to neutralize acidic solutions produces a gelatinous solid that is difficult to filter and an endpoint that is difficult to control. If the pH of the solution is too high, additional species precipitate producing an increased volume of solids separated. The use of magnesium oxide as a reagent has advantages. It is added as a solid (volume of liquid waste produced is minimized), the pH is self-limiting (pH does not exceed about 8.5), and the solids precipitated are more granular (larger particle size) than those produced using KOH or NaOH. Following precipitation, the raffinate is expected to meet criteria for disposal to tank farms. The solid will be heated in a furnace to dry it and convert any hydroxide salts to the oxide form. The material will be cooled in a desiccator. The material is expected to meet vault storage criteria

Thermal oxidation for air toxics control

International Nuclear Information System (INIS)

Pennington, R.L.

1991-01-01

The Administration projects annual expenditures of $1.1 billion by 1995, increasing to $6.7 billion by 2005, in order to comply with the new Clean Air Act Title III hazardous air pollutant requirements. The Title III requirements include 189 hazardous air pollutants which must be reduced or eliminated by 2003. Twenty of the 189 listed pollutants account for approximately 75 percent of all hazardous air pollutant emissions. Ninety percent of these 20 pollutants can be effectively controlled through one or mote of the thermal oxidation technologies. This paper reports that the advantages and disadvantages of each thermal oxidation technology vary substantially and must be reviewed for each application in order to establish the most effective thermal oxidation solution. Effective thermal oxidation will meet MACT (maximum achievable control technology) emission standards

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

Science.gov (United States)

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.

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

Science.gov (United States)

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.

A novel magnesium-vanadium hydride synthesized by a gigapascal-high-pressure technique

Energy Technology Data Exchange (ETDEWEB)

Kyoi, Daisuke; Sato, Toyoto; Roennebro, Ewa; Tsuji, Yasufumi; Kitamura, Naoyuki; Ueda, Atsushi; Ito, Mikio; Katsuyama, Shigeru; Hara, Shigeta; Noreus, Dag; Sakai, Tetsuo

2004-07-28

A magnesium-based vanadium-doped hydride was prepared in a high-pressure anvil cell by reacting a MgH{sub 2}-25%V molar mixture at 8 GPa and 873 K. The new magnesium-vanadium hydride has a cubic F-centred substructure (a=4.721(1) Angst), with an additional superstructure, which could be described by a doubling of the cubic cell axis and a magnesium atom framework, including an ordered arrangement of both vanadium atoms and vacancies (a=9.437(3) Angst, space group Fm3-bar m (no. 225), Z=4, V=840.55 Angst{sup 3}). The metal atom structure is related to the Ca{sub 7}Ge type structure but the refined metal atom composition with vacancies on one of the magnesium sites corresponding to Mg{sub 6}V nearly in line with EDX analysis. The thermal properties of the new compound were also studied by TPD analysis and TG-DTA. The onset of the hydrogen desorption for the new Mg{sub 6}V hydride occurred at a 160 K lower temperature when compared to magnesium hydride at a heating rate of 10 K/min.

TiO2 on magnesium silicate monolith: effects of different preparation techniques on the photocatalytic oxidation of chlorinated hydrocarbons

International Nuclear Information System (INIS)

Cardona, Ana I.; Candal, Roberto; Sanchez, Benigno; Avila, Pedro; Rebollar, Moises

2004-01-01

In this article, the comparative results of the photocatalytic oxidation of trichloroethylene (TCE) alone and a mixture of chlorinated hydrocarbons (trichloroethylene, perchloroethylene and chloroform) in gas phase, obtained with three different monolithic catalysts in a flat reactor frontally illuminated with a Xenon lamp are presented. The three catalysts incorporate titanium dioxide (TiO 2 ) as active phase on a magnesium silicate support, by means of different procedures: (i) incorporation of commercial TiO 2 powder into the silicate matrix ('massic monolith'); (ii) sol-gel coating of the silicate support; (iii) impregnation with a commercial TiO 2 aqueous suspension of the same silicate support. In the first case, the massic monolith was made from a 50:50 w/w mixture of magnesium silicate and 'Titafrance G5' TiO 2 powder. In the second case, a magnesium silicate monolith was coated with several layers of an aqueous TiO 2 sol prepared from hydrolysis and condensation of titanium tetra-isopropoxide (Ti(OC 3 H 7 ) 4 ) in excess of acidified water (acid catalysis). The third catalyst was prepared by impregnating the same silicate support with several layers of 'Titafrance G5' TiO 2 powder water suspension. All the catalysts were thermal treated under comparable conditions in order to fix the TiO 2 active phase to the silicate support. Although the performance of the massic monolith was better than the sol-gel monolith, the latter is of great interest because this technique allows the chemical composition of the active films to be easily modified

Magnesium Inhibits Wnt/β-Catenin Activity and Reverses the Osteogenic Transformation of Vascular Smooth Muscle Cells

Science.gov (United States)

Montes de Oca, Addy; Guerrero, Fatima; Martinez-Moreno, Julio M.; Madueño, Juan A.; Herencia, Carmen; Peralta, Alan; Almaden, Yolanda; Lopez, Ignacio; Aguilera-Tejero, Escolastico; Gundlach, Kristina; Büchel, Janine; Peter, Mirjam E.; Passlick-Deetjen, Jutta; Rodriguez, Mariano; Muñoz-Castañeda, Juan R.

2014-01-01

Magnesium reduces vascular smooth muscle cell (VSMC) calcification in vitro but the mechanism has not been revealed so far. This work used only slightly increased magnesium levels and aimed at determining: a) whether inhibition of magnesium transport into the cell influences VSMC calcification, b) whether Wnt/β-catenin signaling, a key mediator of osteogenic differentiation, is modified by magnesium and c) whether magnesium can influence already established vascular calcification. Human VSMC incubated with high phosphate (3.3 mM) and moderately elevated magnesium (1.4 mM) significantly reduced VSMC calcification and expression of the osteogenic transcription factors Cbfa-1 and osterix, and up-regulated expression of the natural calcification inhibitors matrix Gla protein (MGP) and osteoprotegerin (OPG). The protective effects of magnesium on calcification and expression of osteogenic markers were no longer observed in VSMC cultured with an inhibitor of cellular magnesium transport (2-aminoethoxy-diphenylborate [2-APB]). High phosphate induced activation of Wnt/β-catenin pathway as demonstrated by the translocation of β-catenin into the nucleus, increased expression of the frizzled-3 gene, and downregulation of Dkk-1 gene, a specific antagonist of the Wnt/β-catenin signaling pathway. The addition of magnesium however inhibited phosphate-induced activation of Wnt/β-catenin signaling pathway. Furthermore, TRPM7 silencing using siRNA resulted in activation of Wnt/β-catenin signaling pathway. Additional experiments were performed to test the ability of magnesium to halt the progression of already established VSMC calcification in vitro. The delayed addition of magnesium decreased calcium content, down-regulated Cbfa-1 and osterix and up-regulated MGP and OPG, when compared with a control group. This effect was not observed when 2-APB was added. In conclusion, magnesium transport through the cell membrane is important to inhibit VSMC calcification in vitro

Continuous synthesis of magnesium-hydroxide, zinc-oxide, and silver nanoparticles by microwave plasma in water

International Nuclear Information System (INIS)

Hattori, Yoshiaki; Mukasa, Shinobu; Toyota, Hiromichi; Inoue, Toru; Nomura, Shinfuku

2011-01-01

Nanoparticles are continuously synthesized from submerged magnesium, zinc, and silver rods 1–2 mm in diameter by microwave plasma in pure water at 20 kPa. Magnesium-hydroxide nanoplates shaped as triangles, truncated triangles or hexagons with 25–125 nm in size are synthesized with a production rate of 60 g h −1 . Zinc-oxide nanoparticles formed as sharp sticks with diameters of 50 nm and lengths of 150–200 nm are synthesized with a production rate of 14 g h −1 . Silver nanoparticles with a diameter of approximately 6 nm are synthesized with a production rate of 0.8 g h −1 . The excitation temperature is estimated by applying the Boltzmann plot method in assumption of local thermodynamic equilibrium. The excitation temperatures obtained from hydrogen, magnesium, and zinc lines are 3300 ± 100 K, 4000 ± 500 K, and 3200 ± 500 K, respectively.

Synthesis of Ru nanoparticles confined in magnesium oxide-modified mesoporous alumina and their enhanced catalytic performance during ammonia decomposition

KAUST Repository

Tan, Hua

2012-09-01

In this work, Ru nanoparticles confined in the channels of ordered mesoporous alumina (MA) and magnesium oxide-modified ordered MA are prepared for the first time via a two-solvent technique, combined with the amorphous citrate route. Structural characterizations reveal that uniform 2-3 nm Ru nanoparticles are highly dispersed in the blockage-free channels of mesoporous supports. The Ru nanoparticles confined in MA modified with 20% molar ratio magnesium oxide exhibited a high catalytic activity and stability during ammonia decomposition due to the optimized particle size, basic support, lack of chlorine, and confined space provided by the channels of the mesoporous supports. © 2012 Elsevier B.V. All rights reserved.

Synthesis of Ru nanoparticles confined in magnesium oxide-modified mesoporous alumina and their enhanced catalytic performance during ammonia decomposition

KAUST Repository

Tan, Hua; Li, Kun; Sioud, Salim; Cha, Dong Kyu; Amad, Maan H.; Hedhili, Mohamed N.; Al-Talla, Zeyad

2012-01-01

In this work, Ru nanoparticles confined in the channels of ordered mesoporous alumina (MA) and magnesium oxide-modified ordered MA are prepared for the first time via a two-solvent technique, combined with the amorphous citrate route. Structural characterizations reveal that uniform 2-3 nm Ru nanoparticles are highly dispersed in the blockage-free channels of mesoporous supports. The Ru nanoparticles confined in MA modified with 20% molar ratio magnesium oxide exhibited a high catalytic activity and stability during ammonia decomposition due to the optimized particle size, basic support, lack of chlorine, and confined space provided by the channels of the mesoporous supports. © 2012 Elsevier B.V. All rights reserved.

The role of magnesium in the electrochemical behaviour of 5XXX aluminium-magnesium alloys

NARCIS (Netherlands)

Flores Ramirez, J.R.

2006-01-01

An investigation concerning the effects of magnesium on the intergranular corrosion susceptibility of AA5XXX aluminium alloys was carried out. In the present work, magnesium is found to be highly mobile in the bulk metal as well as in the aluminium oxide. This mobility is also found to be dependent

Behaviour of magnesium and two magnesium alloys heated in a carbon dioxide flow

International Nuclear Information System (INIS)

Boussion, M.-L.; Darras, R.; Leclercq, D.

1959-01-01

Magnesium is a particularly attractive material for sheathing uranium fuel elements in nuclear reactors in order to avoid uranium hot temperature oxidation by the cooling fluid. As this cooling fluid will be carbon dioxide at the (future) Marcoule plants, a thorough study of magnesium and magnesium alloys behaviour when heated by carbon dioxide at a 400 C temperature, have been completed. Tests on three materials (Mg, Mg-Zr and Mg-Zr-Zn) have been performed with CO 2 up to a temperature of 550 C, at atmospheric pressure in the presence of a certain amount of oxygen and nitrogen (in order to study the influence of these impurities), and at a pressure of 15 kg / cm 2 . Oxidation results are detailed. Reprint of a paper published in 'Revue de Metallurgie', LVI, n. 1, 1959, p. 61-67

Factors Influencing Plasma Electrolytic Oxidation(PEO) Coatings on Magnesium Alloys: A Review

Energy Technology Data Exchange (ETDEWEB)

Shim, Gunchoo [KISTI ReSEAT Program, Daejon (Korea, Republic of)

2017-05-15

Magnesium alloys, which possess excellent specific strength and castability, are highly susceptible to corrosion. Although anodizing is widely used to resolve this problem, it requires toxic electrolytes and produces relatively thin and weak surface coatings. Recently, plasma electrolytic oxidation (PEO) has emerged as an alternative to anodizing. Although it is derived from conventional anodizing, it uses eco-friendly electrolytes and forms thicker, denser, and harder coatings on the surface of magnesium alloys. However, PEO is a complex process involving physical, chemical, and electrochemical reactions, and it is influenced by various factors such as the alloy substrate composition, electrolyte/additive composition, and the electrical variables including the mode of power supply, applied voltage/current density, frequency, and duty cycle. In this article, the detailed effects of these parameters on the microstructure and properties of the PEO coatings are reviewed, and methods of improving the coatings are proposed.

Lithium/magnesium oxide catalyst and method of making

Energy Technology Data Exchange (ETDEWEB)

Lunsford, J.H.; Hinson, P.G.

1991-07-16

This patent describes a method for preparing a catalyst which is effective for converting methane to ethane and ethylene. It comprises mixing a solution of a magnesium alkoxide in an alcohol with a solution containing a source of lithium in an alcohol, to obtain a ratio of magnesium metal to lithium metal; hydrolyzing the magnesium alkoxide in the solution to form a gel; and calcining the gel to form a catalyst which is effective for converting methane to ethane and ethylene.

Calcium-Magnesium-Aluminosilicate (CMAS) Infiltration and Cyclic Degradations of Thermal and Environmental Barrier Coatings in Thermal Gradients

Science.gov (United States)

Zhu, Dongming; Harder, Bryan; Smialek, Jim; Miller, Robert A.

2014-01-01

In a continuing effort to develop higher temperature capable turbine thermal barrier and environmental barrier coating systems, Calcium-Magnesium-Aluminosilicate (CMAS) resistance of the advanced coating systems needs to be evaluated and improved. This paper highlights some of NASA past high heat flux testing approaches for turbine thermal and environmental barrier coatings assessments in CMAS environments. One of our current emphases has been focused on the thermal barrier - environmental barrier coating composition and testing developments. The effort has included the CMAS infiltrations in high temperature and high heat flux turbine engine like conditions using advanced laser high heat flux rigs, and subsequently degradation studies in laser heat flux thermal gradient cyclic and isothermal furnace cyclic testing conditions. These heat flux CMAS infiltration and related coating durability testing are essential where appropriate CMAS melting, infiltration and coating-substrate temperature exposure temperature controls can be achieved, thus helping quantify the CMAS-coating interaction and degradation mechanisms. The CMAS work is also playing a critical role in advanced coating developments, by developing laboratory coating durability assessment methodologies in simulated turbine engine conditions and helping establish CMAS test standards in laboratory environments.

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

Science.gov (United States)

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).

Magnesium bicarbonate as an in situ uranium lixiviant

International Nuclear Information System (INIS)

Sibert, J.W.

1984-01-01

In the subsurface solution mining of mineral values, especially uranium, in situ, magnesium bicarbonate leaching solution is used instead of sodium, potassium and ammonium carbonate and bicarbonates. The magnesium bicarbonate solution is formed by combining carbon dioxide with magnesium oxide and water. The magnesium bicarbonate lixivant has four major advantages over prior art sodium, potassium and ammonium bicarbonates

Metal-Carbon Interactions on Reduced Graphene Oxide under Facile Thermal Treatment: Microbiological and Cell Assay

Directory of Open Access Journals (Sweden)

N. L. V. Carreño

2017-01-01

Full Text Available Silver-functionalized reduced graphene oxide (Ag-rGO nanosheets were prepared by single chemical and thermal processes, with very low concentration of silver. The resulting carbon framework consists of reduced graphene oxide (rGO sheets or 3D networks, decorated with anchored silver nanoparticles. The Ag-rGO nanosheets were dispersed into a polymer matrix and the composites evaluated for use as biological scaffolds. The rGO material in poly(dimethylsiloxane (PDMS has been tested for antimicrobial activity against Gram-positive Staphylococcus aureus (S. Aureus bacteria, after exposure times of 24 and 120 hours, as well as in the determination of cell viability on cultures of fibroblast cells (NIH/3T3. Using 1 mL of Ag-rGO in PDMS the antibacterial effectiveness against Staphylococcus aureus was limited, showing an increased amount of Colony Forming Units (CFU, after 24 hours of contact. In the cell viability assay, after 48 hours of contact, the group of 1 mL of Ag-rGO with PDMS was the only group that increased cell viability when compared to the control group. In this context, it is believed these behaviors are due to the increase in cell adhesion capacity promoted by the rGO. Thus, the Ag-rGO/PDMS hybrid nanocomposite films can be used as scaffolds for tissue engineering, as they limit antimicrobial activity.

Magnesium Cermets and Magnesium-Beryllium Alloys; Cermets au magnesium et au magnesium-beryllium; Metallokeramicheskie magnievye i magnievo-berillievye splavy; Cermets de magnesio y aleaciones de magnesio y berillio

Energy Technology Data Exchange (ETDEWEB)

Ivanov, V. E.; Zelenskij, V. F.; Fajfer, S. I.; Zhdanov, S. M.; Maksimenko, V. I.; Savchenko, V. I. [Fiziko-Tekhnicheskij Institut an USSR, Khar' kov, SSSR (Russian Federation)

1963-11-15

The paper describes some results of work on the development of magnesium-magnesium oxide cermets and of super heat-resistant magnesiumberyllium alloys produced by powder metallurgical methods. The introduction of even a minute quantity of finely dispersed magnesium oxide into magnesium results in a strengthening of the material, the degree of which increases with increased magnesium oxide concentration, although variation of this concentration within the limits of 0.3 to 5 wt.% has a comparatively slight effect on the corresponding variation in the short-term strength over the whole range of temperatures investigated. At 20{sup o}C, in the case of the cermets, {sigma}{sub {beta}} = 28 to 31 kg/mm{sup 2} and {delta} = 3 .5 to 4.5%; at 500{sup o}C {sigma}{sub {beta}} = 2.6 to 3.2 kg/mm{sup 2} and {delta} =30 to 40%. The positive effect of the finely dispersed oxide phase is particularly evident in protracted tests. For magnesium cermets, {sigma} (300)/100 = 2.2 kg/mm{sup 2}. Characteristic of the mixtures is the high thermal stability of the strength properties, linked chiefly with the thermodynamic stability of the strength-giving oxide phase in the metal matrix. The use of powder metallurgical methods has yielded super heat-resistant magnesium-beryllium alloys containing heightened concentrations of beryllium (PMB alloys). In their strength characteristics PMB alloys are close to Mg-MgO cermets, but the magnesium-beryllium alloys have a degree and duration of resistance to high temperature oxidation which exceeds the corresponding qualities of the magnesium alloys at present known. Thus, in air of 580{sup o}C, PMB alloys with 2 to 5% beryllium maintain a high resistance to oxidation for a period of over 12000 to 14000 h. This long-term heat resistance is chiefly a result of the amount of beryllium in the alloy, and increases with increasing beryllium content. PMB alloys are also marked by high resistance to short bursts of overheating. Magnesium cermets and

In vivo study of nanostructured diopside (CaMgSi{sub 2}O{sub 6}) coating on magnesium alloy as biodegradable orthopedic implants

Energy Technology Data Exchange (ETDEWEB)

Razavi, Mehdi, E-mail: mrzavi2659@gmail.com [Biomaterials Research Group, Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Torabinejad Dental Research Center, School of Dentistry, Isfahan University of Medical Sciences, Isfahan 81746-73461 (Iran, Islamic Republic of); School of Materials Science and Engineering, Helmerich Advanced Technology Research Center, Oklahoma State University, Tulsa, OK 74106 (United States); School of Electrical and Computer Engineering, Helmerich Advanced Technology Research Center, Oklahoma State University, Tulsa, OK 74106 (United States); Fathi, Mohammadhossein [Biomaterials Research Group, Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Dental Materials Research Center, Isfahan University of Medical Sciences, Isfahan (Iran, Islamic Republic of); Savabi, Omid [Torabinejad Dental Research Center, School of Dentistry, Isfahan University of Medical Sciences, Isfahan 81746-73461 (Iran, Islamic Republic of); Razavi, Seyed Mohammad [School of Dentistry, Isfahan University of Medical Sciences, Isfahan 81746-73461 (Iran, Islamic Republic of); Heidari, Fariba; Manshaei, Maziar [Torabinejad Dental Research Center, School of Dentistry, Isfahan University of Medical Sciences, Isfahan 81746-73461 (Iran, Islamic Republic of); Vashaee, Daryoosh [School of Electrical and Computer Engineering, Helmerich Advanced Technology Research Center, Oklahoma State University, Tulsa, OK 74106 (United States); Tayebi, Lobat, E-mail: lobat.tayebi@okstate.edu [School of Materials Science and Engineering, Helmerich Advanced Technology Research Center, Oklahoma State University, Tulsa, OK 74106 (United States); School of Chemical Engineering, Oklahoma State University, Stillwater, OK 74078 (United States)

2014-09-15

Highlights: • In vitro biocompatibility of biodegradable Mg alloy was improved by diopside coating. • In vivo biocompatibility of biodegradable Mg alloy was improved by diopside coating. • Degradation behavior of biodegradable Mg alloy was improved by diopside coating. - Abstract: In order to improve the corrosion resistance and bioactivity of a biodegradable magnesium alloy, we have recently prepared a nanostructured diopside (CaMgSi{sub 2}O{sub 6}) coating on AZ91 magnesium alloy through a combined micro-arc oxidation (MAO) and electrophoretic deposition (EPD) method (reported elsewhere). In this work, we performed a detailed biocompatibility analysis of the implants made by this material and compared their performance with those of the uncoated and micro arc oxidized magnesium implants. The biocompatibility evaluation of samples was performed by culturing L-929 cells and in vivo animal study, including implantation of samples in greater trochanter of rabbits, radiography and histological examinations. The results from both the in vitro and in vivo studies indicated that the diopside/MAO coated magnesium implant significantly enhanced cell viability, biodegradation resistance and new bone formation compared with both the uncoated and the micro-arc oxidized magnesium implants. Our data provides an example of how the proper surface treatment of magnesium implants can overcome their drawbacks in terms of high degradation rate and gas bubble formation under physiological conditions.

Lightweight Heat Pipes Made from Magnesium

Science.gov (United States)

Rosenfeld, John N.; Zarembo, Sergei N.; Eastman, G. Yale

2010-01-01

Magnesium has shown promise as a lighter-weight alternative to the aluminum alloys now used to make the main structural components of axially grooved heat pipes that contain ammonia as the working fluid. Magnesium heat-pipe structures can be fabricated by conventional processes that include extrusion, machining, welding, and bending. The thermal performances of magnesium heat pipes are the same as those of equal-sized aluminum heat pipes. However, by virtue of the lower mass density of magnesium, the magnesium heat pipes weigh 35 percent less. Conceived for use aboard spacecraft, magnesium heat pipes could also be attractive as heat-transfer devices in terrestrial applications in which minimization of weight is sought: examples include radio-communication equipment and laptop computers.

Growth of ceramic coatings on AZ91D magnesium alloys by micro-arc oxidation in aluminate-fluoride solutions and evaluation of corrosion resistance

International Nuclear Information System (INIS)

Guo, H.F.; An, M.Z.

2005-01-01

Micro-arc oxidization of AZ91D magnesium alloys was studied in solutions containing sodium aluminate and potassium fluoride at constant applied current densities. The influence of applied current densities, concentration and constituents of the electrolyte as well as treatment time on micro-arc oxidization process was investigated, respectively; surface morphology and phase structure were analyzed using scanning electron microscope (SEM) and X-ray powder diffraction (XRD). Potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) were used to evaluate the corrosion resistance of ceramic coatings formed on magnesium alloys. XRD analyses indicate that the ceramic coatings fabricated on the surface of magnesium alloys by micro-arc oxidization are composed of spinel phase MgAl 2 O 4 and intermetallic phase Al 2 Mg; variation of treatment time arises no obvious difference to phase structure of the ceramic coatings. A few circular pores and micro-cracks are also observed to remain on the ceramic coating surface; the number of the pores is decreasing, while the diameter of the pores is apparently increasing with prolonging of treatment time. The corrosion resistance of ceramic coatings is improved more than 100 times compared with magnesium alloy substrate

Magnesium and Osteoporosis

Directory of Open Access Journals (Sweden)

Ferda Özdemir

2004-03-01

Full Text Available Osteoporosis (OP is a condition of bone fragility resulting from micro-architectural deterioration and decreased bone mass. OP depends on the interaction of genetic, hormonal, environmental and nutritional factors. Chronic low intakes of vitamin D and possibly magnesium, zinc, fluoride and vitamins K, B12, B6 and folic acid may predispose to osteoporosis. Magnesium is a mineral needed by every cell of your body. It helps maintain normal muscle and nerve function, keeps heart rhythm steady, and bones strong. Mg serves as co-factors for enzymes that help build bone matrix. Magnesium deficiency occurs due to excessive loss of magnesium in urine, gastrointestinal system disorders that cause a loss of magnesium or limit magnesium absorption, or a chronic low intake of magnesium. Signs of magnesium deficiency include confusion, disorientation, loss of appetite, depression, muscle contractions and cramps, tingling, numbness, abnormal heart rhythms, coronary spasm, and seizures. Magnesium deficiency alters calcium metabolism and the hormones that regulates calcium. Several studies have suggested that magnesium supplementation may improve bone mineral density and prevent fractures.

Thermal Oxidation of Structured Silicon Dioxide

DEFF Research Database (Denmark)

Christiansen, Thomas Lehrmann; Hansen, Ole; Jensen, Jørgen Arendt

2014-01-01

The topography of thermally oxidized, structured silicon dioxide is investigated through simulations, atomic force microscopy, and a proposed analytical model. A 357 nm thick oxide is structured by removing regions of the oxide in a masked etch with either reactive ion etching or hydrofluoric acid....... Subsequent thermal oxidation is performed in both dry and wet ambients in the temperature range 950◦C to 1100◦C growing a 205 ± 12 nm thick oxide in the etched mask windows. Lifting of the original oxide near the edge of the mask in the range 6 nm to 37 nm is seen with increased lifting for increasing...

Performance of planar single cell lanthanum gallate based solid oxide fuel cells

Energy Technology Data Exchange (ETDEWEB)

Maffei, N.; Kuriakose, A.K. [Materials Technology Labs., CANMET, Natural Resources Canada, Ottawa, ON (Canada)

1998-09-01

A novel synthesis of high purity, single phase strontium-magnesium doped lanthanum gallate through a nitrate route is described. The prepared powder is formed into planar monolithic elements by uniaxial pressing followed by isostatic pressing and sintering. XRD analysis of the sintered elements reveal no detectable secondary phases. The performance of the electrolyte in solid oxide fuel cells (SOFC) with three different anode/cathode combinations tested at 700 C with respect to the J-V and power density is reported. The data show that the characteristics of this SOFC are strongly dependent on the particular anode/cathode system chosen. (orig.)

Performance of planar single cell lanthanum gallate based solid oxide fuel cells

Science.gov (United States)

Maffei, N.; Kuriakose, A. K.

A novel synthesis of high purity, single phase strontium-magnesium doped lanthanum gallate through a nitrate route is described. The prepared powder is formed into planar monolithic elements by uniaxial pressing followed by isostatic pressing and sintering. XRD analysis of the sintered elements reveal no detectable secondary phases. The performance of the electrolyte in solid oxide fuel cells (SOFC) with three different anode/cathode combinations tested at 700°C with respect to the J- V and power density is reported. The data show that the characteristics of this SOFC are strongly dependent on the particular anode/cathode system chosen.

Role of magnesium oxide and strontium oxide as modifiers in silicate-based bioactive glasses: Effects on thermal behaviour, mechanical properties and in-vitro bioactivity

International Nuclear Information System (INIS)

Bellucci, Devis; Sola, Antonella; Salvatori, Roberta; Anesi, Alexandre; Chiarini, Luigi; Cannillo, Valeria

2017-01-01

The composition of a CaO-rich silicate bioglass (BG-Ca-Mix, in mol%: 2.3 Na 2 O; 2.3 K 2 O; 45.6 CaO; 2.6 P 2 O 5 ; 47.2 SiO 2 ) was modified by replacing a fixed 10 mol% of CaO with MgO or SrO or fifty-fifty MgO-SrO. The thermal behaviour of the modified glasses was accurately evaluated via differential thermal analysis (DTA), heating microscopy and direct sintering tests. The presence of MgO and/or SrO didn't interfere with the thermal stability of the parent glass, since all the new glasses remained completely amorphous after sintering (treatment performed at 753 °C for the glass with MgO; at 750 °C with SrO; at 759 °C with MgO and SrO). The sintered samples achieved good mechanical properties, with a Young's modulus ranging between 57.9 ± 6.7 for the MgO-SrO modified composition and 112.6 ± 8.0 GPa for the MgO-modified one. If immersed in a simulated body fluid (SBF), the modified glasses after sintering retained the strong apatite forming ability of the parent glass, in spite of the presence of MgO and/or SrO. Moreover, the sintered glasses, tested with MLO-Y4 osteocytes by means of a multi-parametrical approach, showed a good bioactivity in vitro, since neither the glasses nor their extracts caused any negative effect on cell viability or any inhibition on cell growth. The best results were achieved by the MgO-modified glasses, both BGMIX-Mg and BGMIX-MgSr, which were able to exert a strong stimulating effect on the cell growth, thus confirming the beneficial effect of MgO on the glass bioactivity. - Highlights: • The composition of a CaO-rich, K 2 O-containing silicate bioglass was modified: • A fixed 10 mol% of CaO was replaced with MgO or SrO or fifty-fifty MgO-SrO. • The sintered glasses showed a strong volume shrinkage with low residual porosity. • The samples showed good mechanical performance and apatite-forming ability in vitro. • The presence of such oxides, especially MgO, improves the samples' bioactivity.

Role of magnesium oxide and strontium oxide as modifiers in silicate-based bioactive glasses: Effects on thermal behaviour, mechanical properties and in-vitro bioactivity

Energy Technology Data Exchange (ETDEWEB)

Bellucci, Devis, E-mail: devis.bellucci@unimore.it [Department of Engineering “E. Ferrari”, University of Modena and Reggio Emilia, Via P. Vivarelli 10, 41125 Modena (Italy); Sola, Antonella [Department of Engineering “E. Ferrari”, University of Modena and Reggio Emilia, Via P. Vivarelli 10, 41125 Modena (Italy); Salvatori, Roberta; Anesi, Alexandre; Chiarini, Luigi [Lab. Biomaterials, Department of Medical and Surgical Sciences of Children & Adults, University of Modena and Reggio Emilia, Via Campi 213/A, 41125 Modena (Italy); Cannillo, Valeria [Department of Engineering “E. Ferrari”, University of Modena and Reggio Emilia, Via P. Vivarelli 10, 41125 Modena (Italy)

2017-03-01

The composition of a CaO-rich silicate bioglass (BG-Ca-Mix, in mol%: 2.3 Na{sub 2}O; 2.3 K{sub 2}O; 45.6 CaO; 2.6 P{sub 2}O{sub 5}; 47.2 SiO{sub 2}) was modified by replacing a fixed 10 mol% of CaO with MgO or SrO or fifty-fifty MgO-SrO. The thermal behaviour of the modified glasses was accurately evaluated via differential thermal analysis (DTA), heating microscopy and direct sintering tests. The presence of MgO and/or SrO didn't interfere with the thermal stability of the parent glass, since all the new glasses remained completely amorphous after sintering (treatment performed at 753 °C for the glass with MgO; at 750 °C with SrO; at 759 °C with MgO and SrO). The sintered samples achieved good mechanical properties, with a Young's modulus ranging between 57.9 ± 6.7 for the MgO-SrO modified composition and 112.6 ± 8.0 GPa for the MgO-modified one. If immersed in a simulated body fluid (SBF), the modified glasses after sintering retained the strong apatite forming ability of the parent glass, in spite of the presence of MgO and/or SrO. Moreover, the sintered glasses, tested with MLO-Y4 osteocytes by means of a multi-parametrical approach, showed a good bioactivity in vitro, since neither the glasses nor their extracts caused any negative effect on cell viability or any inhibition on cell growth. The best results were achieved by the MgO-modified glasses, both BGMIX-Mg and BGMIX-MgSr, which were able to exert a strong stimulating effect on the cell growth, thus confirming the beneficial effect of MgO on the glass bioactivity. - Highlights: • The composition of a CaO-rich, K{sub 2}O-containing silicate bioglass was modified: • A fixed 10 mol% of CaO was replaced with MgO or SrO or fifty-fifty MgO-SrO. • The sintered glasses showed a strong volume shrinkage with low residual porosity. • The samples showed good mechanical performance and apatite-forming ability in vitro. • The presence of such oxides, especially MgO, improves the samples

Al₂O₃ Coatings on Magnesium Alloy Deposited by the Fluidized Bed (FB) Technique.

Science.gov (United States)

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.

Structural evolution of tunneling oxide passivating contact upon thermal annealing.

Science.gov (United States)

Choi, Sungjin; Min, Kwan Hong; Jeong, Myeong Sang; Lee, Jeong In; Kang, Min Gu; Song, Hee-Eun; Kang, Yoonmook; Lee, Hae-Seok; Kim, Donghwan; Kim, Ka-Hyun

2017-10-16

We report on the structural evolution of tunneling oxide passivating contact (TOPCon) for high efficient solar cells upon thermal annealing. The evolution of doped hydrogenated amorphous silicon (a-Si:H) into polycrystalline-silicon (poly-Si) by thermal annealing was accompanied with significant structural changes. Annealing at 600 °C for one minute introduced an increase in the implied open circuit voltage (V oc ) due to the hydrogen motion, but the implied V oc decreased again at 600 °C for five minutes. At annealing temperature above 800 °C, a-Si:H crystallized and formed poly-Si and thickness of tunneling oxide slightly decreased. The thickness of the interface tunneling oxide gradually decreased and the pinholes are formed through the tunneling oxide at a higher annealing temperature up to 1000 °C, which introduced the deteriorated carrier selectivity of the TOPCon structure. Our results indicate a correlation between the structural evolution of the TOPCon passivating contact and its passivation property at different stages of structural transition from the a-Si:H to the poly-Si as well as changes in the thickness profile of the tunneling oxide upon thermal annealing. Our result suggests that there is an optimum thickness of the tunneling oxide for passivating electron contact, in a range between 1.2 to 1.5 nm.

The Degradation Interface of Magnesium Based Alloys in Direct Contact with Human Primary Osteoblast Cells.

Science.gov (United States)

Ahmad Agha, Nezha; Willumeit-Römer, Regine; Laipple, Daniel; Luthringer, Bérengère; Feyerabend, Frank

2016-01-01

Magnesium alloys have been identified as a new generation material of orthopaedic implants. In vitro setups mimicking physiological conditions are promising for material / degradation analysis prior to in vivo studies however the direct influence of cell on the degradation mechanism has never been investigated. For the first time, the direct, active, influence of human primary osteoblasts on magnesium-based materials (pure magnesium, Mg-2Ag and Mg-10Gd alloys) is studied for up to 14 days. Several parameters such as composition of the degradation interface (directly beneath the cells) are analysed with a scanning electron microscope equipped with energy dispersive X-ray and focused ion beam. Furthermore, influence of the materials on cell metabolism is examined via different parameters like active mineralisation process. The results are highlighting the influences of the selected alloying element on the initial cells metabolic activity.

Oxidation and thermal behavior of Jatropha curcas biodiesel ...

African Journals Online (AJOL)

The thermal and oxidation behavior is also affected adversely by the container metal. The present paper is dealing with the study of oxidation and thermal behavior of JCB with respect to different metal contents. It was found that influence of metal was detrimental to thermal and oxidation stability. Even small concentrations ...

Arsenic adsorption in pre-treatment natural zeolite with magnesium oxides; Adsorcion de arsenico en zeolita natural pretratada con oxidos de magnesio

Energy Technology Data Exchange (ETDEWEB)

Mejia Z, F. [Universidad Autonoma de Baja California, Instituto de Ingenieria, Blvd. Benito Juarez s/n, 21900 Mexicali, Baja California (Mexico); Valenzuela G, J. L.; Aguayo S, S.; Meza F, D., E-mail: fleridam@iq.uson.m [Universidad de Sonora, Departamentos de Geologia e Ingenieria Quimica y Metalurgia, Blvd. Luis Encinas y Rosales s/n, Col. Centro, 83000 Hermosillo, Sonora (Mexico)

2009-07-01

A methodology was developed to modify a natural zeolite (chabazite) with magnesium oxide in order to remove arsenic (As{sup +5}) from water for human consumption. It is proposed a magnesium oxide while regarded as an efficient adsorbent for removing metals in water. X-ray diffraction analyses show significant changes in the chabazite due to the presence of oxides and amorphous hydroxides incorporated during the pre-treatment. Experimental design results show an efficiency greater than 90% of As{sup +5} adsorbed in five minutes. The results indicate that the most significant variables affecting the adsorption of As{sup +5} are the initial concentration of As and the solid/liquid ratio. Experimental data fitted better to Freundlich isotherm with a 20.17 mg/g adsorption capability. (Author)

Measurement of airborne droplets by the magnesium oxide method

Energy Technology Data Exchange (ETDEWEB)

May, K R

1950-01-01

A complete calibration has been made for the first time of the method of detecting and measuring airborne droplets whereby the permanent impressions made when they strike a layer of magnesium oxide smoked on a glass slide are measured microscopically. A size range of 200 to 10 microns and a wide range of liquids and impact velocities were investigated, and it was found that the ratio of true drop size to impression size is constant at 0.86 for droplets greater than 20 microns of any liquid. The method fails below 10 microns. The calibration was made against an absolute method of droplet measurement, also against the so-called focal-length method. Droplets of any desired size were generated by a uniform spray apparatus.

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

Science.gov (United States)

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%.

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

Science.gov (United States)

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.

SOFC seal and cell thermal management

Science.gov (United States)

Potnis, Shailesh Vijay [Neenah, WI; Rehg, Timothy Joseph [Huntington Beach, CA

2011-05-17

The solid oxide fuel cell module includes a manifold, a plate, a cathode electrode, a fuel cell and an anode electrode. The manifold includes an air or oxygen inlet in communication with divergent passages above the periphery of the cell which combine to flow the air or oxygen radially or inwardly for reception in the center of the cathode flow field. The latter has interconnects providing circuitous cooling passages in a generally radial outward direction cooling the fuel cell and which interconnects are formed of different thermal conductivity materials for a preferential cooling.

Mechanistic Study of Magnesium Carbonate Semibatch Reactive Crystallization with Magnesium Hydroxide and CO2

DEFF Research Database (Denmark)

Han, B.; Qu, H. Y.; Niemi, H.

2014-01-01

This work investigates semibatch precipitation of magnesium carbonate at ambient temperature and pressure using Mg(OH)(2) and CO2 as starting materials. A thermal analysis method was developed that reflects the dissolution rate of Mg(OH)(2) and the formation of magnesium carbonate. The method...... the liquid and solid phases. A stirring rate of 650 rpm was found to be the optimum speed as the flow rate of CO2 was 1 L/min. Precipitation rate increased with gas flow rate, which indicates that mass transfer of CO2 plays a critical role in this precipitation case. Magnesium carbonate trihydrate...

Synthesis of graphene oxide through different oxidation degrees for solar cells

Science.gov (United States)

Zhang, Xiaoshan; Wang, Huan; Huang, Tianjiao; Wen, Lingling; Zhou, Liya

2018-03-01

Graphene is known as an electro-chemical material and widely used in electro-chemical devices, especially in solar cell. Decreasing the thickness of the layer is a critical way to improve the electrochemical property of solar cells as far as possible. Among the various oxidation approaches, presented herein is a facile approach, which is easier, less cost and more effective, environmental benign with the greener processing and without any requirement for post purification, towards the synthesis of graphene oxide (GO) with different oxidation degrees by potassium ferrate (K2FeO4). A modified method using less amount of oxidizing agent is reported herein. It is the pretreatment of the synthesis of graphite, which maintains the thermal cycle of the system. This novel reports to compound GO with controlled oxidation degrees can not only increase the quantity of oxygen-containing functional groups on GO surface, increase space between graphene oxide layer and facilitate the dispersion of graphene in aqueous solution. Thus, the modified method shows prospect for large-scale production of graphene oxide and its novel application, in addition to its derivative and market potential for solar cells.

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

Science.gov (United States)

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...

The Degradation Interface of Magnesium Based Alloys in Direct Contact with Human Primary Osteoblast Cells.

Directory of Open Access Journals (Sweden)

Nezha Ahmad Agha

Full Text Available Magnesium alloys have been identified as a new generation material of orthopaedic implants. In vitro setups mimicking physiological conditions are promising for material / degradation analysis prior to in vivo studies however the direct influence of cell on the degradation mechanism has never been investigated. For the first time, the direct, active, influence of human primary osteoblasts on magnesium-based materials (pure magnesium, Mg-2Ag and Mg-10Gd alloys is studied for up to 14 days. Several parameters such as composition of the degradation interface (directly beneath the cells are analysed with a scanning electron microscope equipped with energy dispersive X-ray and focused ion beam. Furthermore, influence of the materials on cell metabolism is examined via different parameters like active mineralisation process. The results are highlighting the influences of the selected alloying element on the initial cells metabolic activity.

Magnesium analysis. Spectrophotometric determination of chromium

International Nuclear Information System (INIS)

Anon.

Chromium determination in magnesium used in uranium fabrication by magnesiothermics, applicable for chromium content between 2 to 10 ppm. Magnesium is dissolved in sulfuric acid, oxidized by potassium permanganate, the excess of permanganate is eliminated by sodium nitride. Spectrophotometry at 540 nm of the chromium (VI)-diphenylcarbazide complex [fr

Separation medium containing thermally exfoliated graphite oxide

Science.gov (United States)

Prud'homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor); Herrera-Alonso, Margarita (Inventor)

2012-01-01

A separation medium, such as a chromatography filling or packing, containing a modified graphite oxide material, which is a thermally exfoliated graphite oxide with a surface area of from about 300 m.sup.2/g to 2600 m.sup.2/g, wherein the thermally exfoliated graphite oxide has a surface that has been at least partially functionalized.

Layered materials with improved magnesium intercalation for rechargeable magnesium ion cells

Energy Technology Data Exchange (ETDEWEB)

Doe, Robert Ellis; Downie, Craig Michael; Fischer, Christopher; Lane, George Hamilton; Morgan, Dane; Nevin, Josh; Ceder, Gerbrand; Persson, Kristin Aslaug; Eaglesham, David

2016-07-26

Electrochemical devices which incorporate cathode materials that include layered crystalline compounds for which a structural modification has been achieved which increases the diffusion rate of multi-valent ions into and out of the cathode materials. Examples in which the layer spacing of the layered electrode materials is modified to have a specific spacing range such that the spacing is optimal for diffusion of magnesium ions are presented. An electrochemical cell comprised of a positive intercalation electrode, a negative metal electrode, and a separator impregnated with a nonaqueous electrolyte solution containing multi-valent ions and arranged between the positive electrode and the negative electrode active material is described.

Effect of electrolyte additives on performance of plasma electrolytic oxidation films formed on magnesium alloy AZ91D

International Nuclear Information System (INIS)

Duan, Hongping; Yan, Chuanwei; Wang, Fuhui

2007-01-01

Various plasma electrolytic oxidation (PEO) films were prepared on magnesium alloy AZ91D in a silicate bath with different additives such as phosphate, fluoride and borate. Effects of the additives on chemical composition and corrosion resistance of the PEO films were examined by means of scanning electron microscopy (SEM), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in 3.5% NaCl solution. The results showed that the PEO films obtained in solutions with both borate and fluoride had better corrosion resistance. In order to understand the corrosion mechanism of PEO films on magnesium alloy AZ91D, electronic property of the magnesium electrode with PEO films was studied by Mott-Schottky approach in a solution containing borate and chloride. The results indicated that magnesium electrodes with and without PEO films all exhibited n-type semiconducting property. However, in comparison with the magnesium electrode treated in solutions containing phosphate or borate, the electrode treated in solutions containing both borate and fluoride (M-film) had lower donor concentration and much negative flat band potential; therefore, the M-film had lower reactivity and higher corrosion resistance

Oxidation phase growth diagram of vanadium oxides film fabricated by rapid thermal annealing

Institute of Scientific and Technical Information of China (English)

Tamura KOZO; Zheng-cao LI; Yu-quan WANG; Jie NI; Yin HU; Zheng-jun ZHANG

2009-01-01

Thermal evaporation deposited vanadium oxide films were annealed in air by rapid thermal annealing (RTP). By adjusting the annealing temperature and time, a series of vanadium oxide films with various oxidation phases and surface morphologies were fabricated, and an oxidation phase growth diagram was established. It was observed that different oxidation phases appear at a limited and continuous annealing condition range, and the morphologic changes are related to the oxidation process.

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

Directory of Open Access Journals (Sweden)

M. Guevara-Bertsch

2016-03-01

Full Text Available We investigate the variation of the oscillation frequency of the Mg2+ and O2− 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 adsorption or desorption of water monolayers in the surface lattice.

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

Energy Technology Data Exchange (ETDEWEB)

Guevara-Bertsch, M.; Avendaño, E. [Escuela de Física, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Centro de Investigación en Ciencia e Ingeniería de Materiales, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Ramírez-Hidalgo, G. [Centro de Investigación en Ciencia e Ingeniería de Materiales, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Sección de Física Teórica, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Chavarría-Sibaja, A.; Araya-Pochet, J. A. [Centro de Investigación en Ciencia e Ingeniería de Materiales, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Herrera-Sancho, O. A., E-mail: oscar-andrey.herrera@uibk.ac.at [Escuela de Física, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Centro de Investigación en Ciencia e Ingeniería de Materiales, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, Technikerstr. 21a, 6020 Innsbruck (Austria)

2016-03-15

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 adsorption or desorption of water monolayers in the surface lattice.

Removal of Oil Spills from Salt Water by Magnesium, Calcium ...

African Journals Online (AJOL)

Magnesium, calcium carbonates and oxides that are widely used in cement industries were employed in studying sorption of petroleum oil spills from salt water at different condition parameters such as temperature, loading weight, degree of salinity. Treatment of magnesium, calcium carbonates and oxides by dodecyl ...

Enhanced regeneration of degraded polymer solar cells by thermal annealing

Energy Technology Data Exchange (ETDEWEB)

Kumar, Pankaj, E-mail: pankaj@mail.nplindia.ernet.in [CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012 (India); Centre for Organic Electronics, Physics, University of Newcastle, Callaghan NSW-2308 (Australia); Bilen, Chhinder; Zhou, Xiaojing; Belcher, Warwick J.; Dastoor, Paul C., E-mail: Paul.Dastoor@newcastle.edu.au [Centre for Organic Electronics, Physics, University of Newcastle, Callaghan NSW-2308 (Australia); Feron, Krishna [Centre for Organic Electronics, Physics, University of Newcastle, Callaghan NSW-2308 (Australia); CSIRO Energy Technology, P. O. Box 330, Newcastle NSW 2300 (Australia)

2014-05-12

The degradation and thermal regeneration of poly(3-hexylethiophene) (P3HT):[6,6]-phenyl-C{sub 61}-butyric acid methyl ester (PCBM) and P3HT:indene-C{sub 60} bisadduct (ICBA) polymer solar cells, with Ca/Al and Ca/Ag cathodes and indium tin oxide/poly(ethylene-dioxythiophene):polystyrene sulfonate anode have been investigated. Degradation occurs via a combination of three primary pathways: (1) cathodic oxidation, (2) active layer phase segregation, and (3) anodic diffusion. Fully degraded devices were subjected to thermal annealing under inert atmosphere. Degraded solar cells possessing Ca/Ag electrodes were observed to regenerate their performance, whereas solar cells having Ca/Al electrodes exhibited no significant regeneration of device characteristics after thermal annealing. Moreover, the solar cells with a P3HT:ICBA active layer exhibited enhanced regeneration compared to P3HT:PCBM active layer devices as a result of reduced changes to the active layer morphology. Devices combining a Ca/Ag cathode and P3HT:ICBA active layer demonstrated ∼50% performance restoration over several degradation/regeneration cycles.

Enhanced regeneration of degraded polymer solar cells by thermal annealing

International Nuclear Information System (INIS)

Kumar, Pankaj; Bilen, Chhinder; Zhou, Xiaojing; Belcher, Warwick J.; Dastoor, Paul C.; Feron, Krishna

2014-01-01

The degradation and thermal regeneration of poly(3-hexylethiophene) (P3HT):[6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM) and P3HT:indene-C 60 bisadduct (ICBA) polymer solar cells, with Ca/Al and Ca/Ag cathodes and indium tin oxide/poly(ethylene-dioxythiophene):polystyrene sulfonate anode have been investigated. Degradation occurs via a combination of three primary pathways: (1) cathodic oxidation, (2) active layer phase segregation, and (3) anodic diffusion. Fully degraded devices were subjected to thermal annealing under inert atmosphere. Degraded solar cells possessing Ca/Ag electrodes were observed to regenerate their performance, whereas solar cells having Ca/Al electrodes exhibited no significant regeneration of device characteristics after thermal annealing. Moreover, the solar cells with a P3HT:ICBA active layer exhibited enhanced regeneration compared to P3HT:PCBM active layer devices as a result of reduced changes to the active layer morphology. Devices combining a Ca/Ag cathode and P3HT:ICBA active layer demonstrated ∼50% performance restoration over several degradation/regeneration cycles

Thermal Protection Performance of Carbon Aerogels Filled with Magnesium Chloride Hexahydrate as a Phase Change Material

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Ali Kazemi

2014-02-01

Full Text Available Carbon aerogels are comprised of a class of low density open-cell foams with large void space, nanometer pore size and composed of sparsely semi-colloidal nanometer sized particles forming an open porous structure. Phase change materials are those with high heat of fusion that could absorb and release a large amount of energy at the time of phase transition. These materials are mostly used as thermal energy storage materials but in addition they could serve as an obstacle for passage of heat during phase changes and this has led to their use in thermal protection systems. In this study, the effect of magnesium chloride hexahydrate, as a phase change material (melting point 115°C, on thermal properties of carbon aerogels is investigated. Thermal performance tests are designed and used for comparing the temperature-time behavior of the samples. DSC is applied to obtain the latent heat of melting of the phase change materials and the SEM tests are used to analyze the microstructure and morphology of carbon aerogels. The results show that the low percentage of phase change materials in carbon aerogels does not have any significant positive effect on carbon aerogels thermal properties. However, these properties are improved by increasing the percentage of phase change materials. With high percentage of phase change materials, a sample surface at 300°C would display an opposite surface with a significant drop in temperature increases, while at 115-200°C, with carbon aerogels, having no phase change materials, there is a severe reduction in the rate of temperature increase of the sample.

TiO{sub 2} on magnesium silicate monolith: effects of different preparation techniques on the photocatalytic oxidation of chlorinated hydrocarbons

Energy Technology Data Exchange (ETDEWEB)

Cardona, Ana I.; Candal, Roberto; Sanchez, Benigno; Avila, Pedro; Rebollar, Moises

2004-05-01

In this article, the comparative results of the photocatalytic oxidation of trichloroethylene (TCE) alone and a mixture of chlorinated hydrocarbons (trichloroethylene, perchloroethylene and chloroform) in gas phase, obtained with three different monolithic catalysts in a flat reactor frontally illuminated with a Xenon lamp are presented. The three catalysts incorporate titanium dioxide (TiO{sub 2}) as active phase on a magnesium silicate support, by means of different procedures: (i) incorporation of commercial TiO{sub 2} powder into the silicate matrix ('massic monolith'); (ii) sol-gel coating of the silicate support; (iii) impregnation with a commercial TiO{sub 2} aqueous suspension of the same silicate support. In the first case, the massic monolith was made from a 50:50 w/w mixture of magnesium silicate and 'Titafrance G5' TiO{sub 2} powder. In the second case, a magnesium silicate monolith was coated with several layers of an aqueous TiO{sub 2} sol prepared from hydrolysis and condensation of titanium tetra-isopropoxide (Ti(OC{sub 3}H{sub 7}){sub 4}) in excess of acidified water (acid catalysis). The third catalyst was prepared by impregnating the same silicate support with several layers of 'Titafrance G5' TiO{sub 2} powder water suspension. All the catalysts were thermal treated under comparable conditions in order to fix the TiO{sub 2} active phase to the silicate support. Although the performance of the massic monolith was better than the sol-gel monolith, the latter is of great interest because this technique allows the chemical composition of the active films to be easily modified.

A multidisciplinary study on magnesium

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Radić-Perić Jelena

2012-01-01

Full Text Available During plasma electrolytic oxidation of a magnesium alloy (96% Mg, 3% Al, 1% Zn we obtained a luminescence spectrum in the wave number range between 19 950 and 20 400 cm-1. The broad peak with clearly pronounced structure was assigned to the v’-v” = 0 sequence of the B 1Σ+ → X 1Σ+ electronic transition of MgO. Quantum-mechanical perturbative approach was applied to extract the form of the potential energy curves for the electronic states involved in the observed spectrum, from the positions of spectral bands. These potential curves, combined with the results of quantum-chemical calculations of the electric transition moment, were employed in subsequent variational calculations to obtain the Franck-Condon factors and transition moments for the vibrational transitions observed. Comparing the results of these calculations with the measured intensity distribution within the spectrum we derived relative population of the upper electronic state vibration levels. This enabled us to estimate the plasma temperature. Additionally, the temperature was determined by analysis of the recorded A 2Σ+ (v’ = 0 - X 2П (v” = 0 emission spectrum of OH. The composition of plasma containing magnesium, oxygen, and hydrogen under assumption of local thermal equilibrium was calculated in the temperature range up to 12 000 K and for pressures of 105, 106, 107, and 108 Pa, in order to explain the appearance of the observed spectral features and to contribute to elucidation of processes taking place during the electrolytic oxidation of Mg. [Projekat Ministarstva nauke Republike Srbije, br. 172040

Convenient method of simultaneously analyzing aluminum and magnesium in pharmaceutical dosage forms using californium-252 thermal neutron activation

International Nuclear Information System (INIS)

Landolt, R.R.; Hem, S.L.

1983-01-01

A commercial antacid suspension containing aluminum hydroxide and magnesium hydroxide products was used as a model sample to study the use of a californium-252 thermal neutron activation as a method for quantifying aluminum content as well as for the simultaneous assay of aluminum and magnesium. A 3.5-micrograms californium-252 source was used for the activation, and the induced aluminum-28 and magnesium-27 activity was simultaneously measured by sodium iodide crystal gamma-ray spectrometry using dual single-channel analyzers and scalers. The antacid suspension was contained in a chamber designed with the unique capability of serving as the container for counting the induced radioactivity in addition to being the irradiation chamber itself. This pilot study demonstrated that use of more intense californium-252 sources, which are commonly available, would provide a method that is competitive with the ethylenediaminetetraacetic acid titration method in precision and in other aspects as well

Improving thermal stability and efficacy of BCNU in treating glioma cells using PAA-functionalized graphene oxide

Directory of Open Access Journals (Sweden)

Lu YJ

2012-03-01

Full Text Available Yu-Jen Lu1,2,#, Hung-Wei Yang1,#, Sheng-Che Hung3, Chiung-Yin Huang2, Shin-Ming Li4, Chen-Chi M Ma4, Pin-Yuan Chen2, Hong-Chieh Tsai2, Kuo-Chen Wei2, Jyh-Ping Chen1 1Department of Chemical and Materials Engineering, Chang Gung University, Kwei-San, Taoyuan, Taiwan; 2Department of Neurosurgery, Chang Gung Memorial Hospital, Kwei-San, Taoyuan, Taiwan; 3Department of Radiology, Taipei Veterans General Hospital, Taipei, Taiwan; 4Department of Chemical Engineering, National Tsing Hua University, Hsinchu, Taiwan#These authors contributed equally to this workBackground: 1,3-bis(2-chloroethyl-1-nitrosourea (BCNU, a commercial chemotherapeutic drug for treating malignant brain tumors, has poor thermal stability and a short half-life. Immobilization of BCNU on a nanocarrier might increase the thermal stability of BCNU and extend its half-life.Methods: Nanosized graphene oxide (GO could be modified by polyacrylic acid (PAA to improve the aqueous solubility and increase the cell penetration efficacy of the nanocarrier. PAA–GO intended as a drug carrier for BCNU was prepared and characterized in this study. The size and thickness of PAA–GO was investigated by transmission electron microscopy and atomic force microscopy, and the presence of PAA functional groups was confirmed by electron spectroscopy for chemical analysis and thermogravimetric analysis. BCNU was conjugated to PAA–GO by covalent binding for specific killing of cancer cells, which could also enhance the thermal stability of the drug.Results: Single layer PAA–GO (about 1.9 nm with a lateral width as small as 36 nm was successfully prepared. The optimum drug immobilization condition was by reacting 0.5 mg PAA–GO with 0.4 mg BCNU, and the drug-loading capacity and residual drug activity were 198 µg BCNU/mg PAA–GO and 70%, respectively. This nanocarrier significantly prolonged the half-life of bound BCNU from 19 to 43 hours compared with free drug and showed efficient intracellular

Novel magnesium alloy Mg–2La caused no cytotoxic effects on cells in physiological conditions

Energy Technology Data Exchange (ETDEWEB)

Weizbauer, Andreas, E-mail: weizbauer.andreas@mh-hannover.de [Laboratory for Biomechanics and Biomaterials, Department of Orthopedic Surgery, Hannover Medical School, Anna-von-Borries-Straße 1-7, 30625 Hannover (Germany); CrossBIT, Center for Biocompatibility and Implant-Immunology, Department of Orthopedic Surgery, Hannover Medical School, Feodor-Lynen-Str. 31, 30625 Hannover (Germany); Seitz, Jan-Marten [Institute of Materials Science, Leibniz Universität Hannover, An der Universität 2, 30823 Garbsen (Germany); Werle, Peter [ABB AG, Trafoweg 4, 06112 Halle (Germany); Hegermann, Jan [Institute of Functional and Applied Anatomy, Hannover Medical School, Carl-Neuberg-Straße 1, 30625 Hannover (Germany); Willbold, Elmar [Laboratory for Biomechanics and Biomaterials, Department of Orthopedic Surgery, Hannover Medical School, Anna-von-Borries-Straße 1-7, 30625 Hannover (Germany); CrossBIT, Center for Biocompatibility and Implant-Immunology, Department of Orthopedic Surgery, Hannover Medical School, Feodor-Lynen-Str. 31, 30625 Hannover (Germany); Eifler, Rainer [Institute of Materials Science, Leibniz Universität Hannover, An der Universität 2, 30823 Garbsen (Germany); Windhagen, Henning [Laboratory for Biomechanics and Biomaterials, Department of Orthopedic Surgery, Hannover Medical School, Anna-von-Borries-Straße 1-7, 30625 Hannover (Germany); Reifenrath, Janin [Small Animal Clinic, University of Veterinary Medicine Hannover, Bünteweg 9, 30559 Hannover (Germany); Waizy, Hazibullah [Laboratory for Biomechanics and Biomaterials, Department of Orthopedic Surgery, Hannover Medical School, Anna-von-Borries-Straße 1-7, 30625 Hannover (Germany)

2014-08-01

Using several different in vitro assays, a new biodegradable magnesium alloy Mg–2La, composed of 98% magnesium and 2% lanthanum, was investigated as a possible implant material for biomedical applications. An in vitro cytotoxicity test, according to EN ISO 10993-5/12, with L929 and human osteoblastic cells identified no toxic effects on cell viability at physiological concentrations (at 50% dilutions and higher). The metabolic activity of human osteoblasts in the 100% extract was decreased to < 70% and was therefore rated as cytotoxic. The degradation rates of Mg–2La were evaluated in phosphate buffered saline and four different cell culture media. The degradation rates were shown to be influenced by the composition of the solution, and the addition of fetal bovine serum slightly accelerated the corrosive process. The results of these in vitro experiments suggest that Mg–2La is a promising candidate for use as an orthopedic implant material. - Highlights: • A new magnesium alloy (Mg–2La) has been developed. • Magnesium alloy Mg–2La revealed no toxic effect in physiological concentrations. • Degradation rates were influenced by the corrosion media. • The addition of fetal bovine serum increased the corrosive process slightly.

Novel magnesium alloy Mg–2La caused no cytotoxic effects on cells in physiological conditions

International Nuclear Information System (INIS)

Weizbauer, Andreas; Seitz, Jan-Marten; Werle, Peter; Hegermann, Jan; Willbold, Elmar; Eifler, Rainer; Windhagen, Henning; Reifenrath, Janin; Waizy, Hazibullah

2014-01-01

Using several different in vitro assays, a new biodegradable magnesium alloy Mg–2La, composed of 98% magnesium and 2% lanthanum, was investigated as a possible implant material for biomedical applications. An in vitro cytotoxicity test, according to EN ISO 10993-5/12, with L929 and human osteoblastic cells identified no toxic effects on cell viability at physiological concentrations (at 50% dilutions and higher). The metabolic activity of human osteoblasts in the 100% extract was decreased to < 70% and was therefore rated as cytotoxic. The degradation rates of Mg–2La were evaluated in phosphate buffered saline and four different cell culture media. The degradation rates were shown to be influenced by the composition of the solution, and the addition of fetal bovine serum slightly accelerated the corrosive process. The results of these in vitro experiments suggest that Mg–2La is a promising candidate for use as an orthopedic implant material. - Highlights: • A new magnesium alloy (Mg–2La) has been developed. • Magnesium alloy Mg–2La revealed no toxic effect in physiological concentrations. • Degradation rates were influenced by the corrosion media. • The addition of fetal bovine serum increased the corrosive process slightly

Effect of Nano-Magnesium Hydride on the Thermal Decomposition Behaviors of RDX

International Nuclear Information System (INIS)

Yao, M.; Chen, L.; Rao, G.; Peng, J.; Zou, J.; Zeng, X.

2013-01-01

In order to improve the detonation performance of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) explosive, addictive with high heat values were used, and magnesium hydride (MgH 2 ) is one of the candidates. However, it is important to see whether MgH 2 is a safe addictive. In this paper, the thermal and kinetic properties of RDX and mixture of RDX/MgH 2 were investigated by differential scanning calorimeter (DSC) and accelerating rate calorimeter (ARC), respectively. The apparent activation energy (E) and frequency factor (A) of thermal explosion were calculated based on the data of DSC experiments using the Kissinger and Ozawa approaches. The results show that the addition of MgH 2 decreases both E and A of RDX, which means that the mixture of RDX/MgH 2 has a lower thermal stability than RDX, and the calculation results obtained from the ARC experiments data support this too. Besides, the most probable mechanism functions about the decomposition of RDX and RDX/MgH 2 were given in this paper which confirmed the change of the decomposition mechanism.

Stability of solid oxide fuel cell materials

Energy Technology Data Exchange (ETDEWEB)

Armstrong, T.R.; Bates, J.L.; Chick, L.A. [Pacific Northwest Lab., Richland, WA (United States)

1996-04-01

Interconnection materials in a solid oxide fuel cell are exposed to both highly oxidizing conditions at the cathode and to highly reducing conditions at the anode. The thermal expansion characteristics of substituted lanthanum and yttrium chromite interconnect materials were evaluated by dilatometry as a function of oxygen partial pressures from 1 atm to 10{sup -18} atm, controlled using a carbon dioxide/hydrogen buffer.

Al2O3 Coatings on Magnesium Alloy Deposited by the Fluidized Bed (FB Technique

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Gabriele Baiocco

2018-01-01

Full Text Available 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.

Osteogenic potential of human adipose-derived stromal cells on 3-dimensional mesoporous TiO2 coating with magnesium impregnation

International Nuclear Information System (INIS)

Cecchinato, Francesca; Karlsson, Johan; Ferroni, Letizia; Gardin, Chiara; Galli, Silvia; Wennerberg, Ann; Zavan, Barbara; Andersson, Martin; Jimbo, Ryo

2015-01-01

The aim of this study was to evaluate the osteogenic response of human adipose-derived stromal cells (ADScs) to mesoporous titania (TiO 2 ) coatings produced with evaporation-induced self-assembly method (EISA) and loaded with magnesium. Our emphasis with the magnesium release functionality was to modulate progenitor cell osteogenic differentiation under standard culture conditions. Osteogenic properties of the coatings were assessed for stromal cells by means of scanning electron microscopy (SEM) imaging, colorimetric mitochondrial viability assay (MTT), colorimetric alkaline phosphates activity (ALP) assay and real time RT-polymerase chain reaction (PCR). Using atomic force microscopy (AFM) it was shown that the surface expansion area (S dr ) was strongly enhanced by the presence of magnesium. From MTT results it was shown that ADSc viability was significantly increased on mesoporous surfaces compared to the non-porous one at a longer cell culture time. However, no differences were observed between the magnesium impregnated and non-impregnated surfaces. The alkaline phosphatase activity confirmed that ADSc started to differentiate into the osteogenic phenotype after 2 weeks of culturing. The gene expression profile at 2 weeks of cell growth showed that such coatings were capable to incorporate specific osteogenic markers inside their interconnected nano-pores and, at 3 weeks, ADSc differentiated into osteoblasts. Interestingly, magnesium significantly promoted the osteopontin gene expression, which is an essential gene for the early biomaterial–cell osteogenic interaction. - Highlights: • The magnesium loading presents a transitory effect on mesoporous TiO 2 surface topography • The mesoporous structure promotes cellular attachment and spreading • The mesoporous structure activates osteogenesis of mesenchymal stem cells in absence of osteogenic promoters • The physical adsorbed magnesium is suggested to be involved in the expression of osteopontin

Magnesium doping of boron nitride nanotubes

Science.gov (United States)

Legg, Robert; Jordan, Kevin

2015-06-16

A method to fabricate boron nitride nanotubes incorporating magnesium diboride in their structure. In a first embodiment, magnesium wire is introduced into a reaction feed bundle during a BNNT fabrication process. In a second embodiment, magnesium in powder form is mixed into a nitrogen gas flow during the BNNT fabrication process. MgB.sub.2 yarn may be used for superconducting applications and, in that capacity, has considerably less susceptibility to stress and has considerably better thermal conductivity than these conventional materials when compared to both conventional low and high temperature superconducting materials.

Magnesium in pregnancy.

Science.gov (United States)

Dalton, Lynne M; Ní Fhloinn, Deirdre M; Gaydadzhieva, Gergana T; Mazurkiewicz, Ola M; Leeson, Heather; Wright, Ciara P

2016-09-01

Magnesium deficiency is prevalent in women of childbearing age in both developing and developed countries. The need for magnesium increases during pregnancy, and the majority of pregnant women likely do not meet this increased need. Magnesium deficiency or insufficiency during pregnancy may pose a health risk for both the mother and the newborn, with implications that may extend into adulthood of the offspring. The measurement of serum magnesium is the most widely used method for determining magnesium levels, but it has significant limitations that have both hindered the assessment of deficiency and affected the reliability of studies in pregnant women. Thus far, limited studies have suggested links between magnesium inadequacy and certain conditions in pregnancy associated with high mortality and morbidity, such as gestational diabetes, preterm labor, preeclampsia, and small for gestational age or intrauterine growth restriction. This review provides recommendations for further study and improved testing using measurement of red cell magnesium. Pregnant women should be counseled to increase their intake of magnesium-rich foods such as nuts, seeds, beans, and leafy greens and/or to supplement with magnesium at a safe level. © The Author(s) 2016. Published by Oxford University Press on behalf of the International Life Sciences Institute. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Cermet cathodes for strontium and magnesium-doped LaGaO3-based solid oxide fuel cells

International Nuclear Information System (INIS)

Datta, Pradyot; Bronin, D.I.; Majewski, P.; Aldinger, F.

2009-01-01

To check the suitability of La 0.9 Sr 0.1 Ga 0.85 Mg 0.15 O 3-δ -Ag cermets as cathode material for solid oxide fuel cell (SOFC) with Sr- and Mg-doped LaGaO 3 electrolyte a series of cermets with different Ag contents were prepared by conventional sintering process. The chemical compatibility between La 0.9 Sr 0.1 Ga 0.85 Mg 0.15 O 3-δ (LSGM) and Ag was investigated by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. Thermal expansion coefficient of the cermets was measured as a function of Ag content and was found to increase with increasing metallic content. Oxygen adsorption at the surface of the cermets could be detected but no reaction or solid solubility between LSGM and Ag was found. It was noticed that a minimum of 30 wt.% Ag is needed to form a cermet with percolating network. From impedance spectroscopy measurement activation energy for the polarization conductance was found to be around 110 kJ mol -1

Controlling the ignition and flammability of magnesium for aerospace applications

International Nuclear Information System (INIS)

Czerwinski, Frank

2014-01-01

The perceived easy ignition and flammability of magnesium alloys create a detrimental safety feature that overshadows their high strength-to-weight ratio and hinders the aerospace application opportunities. To overcome the existing barriers a progress in understanding and controlling the reactivity of magnesium at high temperatures is required. This report describes fundamentals of magnesium ignition and flammability along with laboratory testing procedures and correlations with full scale fire scenarios, related in particular to the aircraft cabin. The influence of alloying elements on high temperature reactivity of magnesium and global efforts to develop ignition resistant and non-flammable magnesium alloys are reviewed. Although ignition and flammability represent quite different quantities, both are controlled by an oxidation resistance of the alloy and its capability to form a dense and protective surface oxide after exposures to an open flame or other heat source. Since surface oxide, composed of pure MgO, does not offer a sufficient protection, the research strategy is focused on modification of its chemistry and microstructure by micro-alloying the substrate with rare earths and other elements having high affinity to oxygen

Thermal stress management of a solid oxide fuel cell using neural network predictive control

International Nuclear Information System (INIS)

Hajimolana, S.A.; Tonekabonimoghadam, S.M.; Hussain, M.A.; Chakrabarti, M.H.; Jayakumar, N.S.; Hashim, M.A.

2013-01-01

In SOFC (solid oxide fuel cell) systems operating at high temperatures, temperature fluctuation induces a thermal stress in the electrodes and electrolyte ceramics; therefore, the cell temperature distribution is recommended to be kept as constant as possible. In the present work, a mathematical model based on first principles is presented to avert such temperature fluctuations. The fuel cell running on ammonia is divided into five subsystems and factors such as mass/energy/momentum transfer, diffusion through porous media, electrochemical reactions, and polarization losses inside the subsystems are presented. Dynamic cell-tube temperature responses of the cell to step changes in conditions of the feed streams is investigated. The results of simulation indicate that the transient response of the SOFC is mainly influenced by the temperature dynamics. It is also shown that the inlet stream temperatures are associated with the highest long term start-up time (467 s) among other parameters in terms of step changes. In contrast the step change in fuel velocity has the lowest influence on the start-up time (about 190 s from initial steady state to the new steady state) among other parameters. A NNPC (neural network predictive controller) is then implemented for thermal stress management by controlling the cell tube temperature to avoid performance degradation by manipulating the temperature of the inlet air stream. The regulatory performance of the NNPC is compared with a PI (proportional–integral) controller. The performance of the control system confirms that NNPC is a non-linear-model-based strategy which can assure less oscillating control responses with shorter settling times in comparison to the PI controller. - Highlights: • Effect of the operating parameters on the fuel cell temperature is analysed. • A neural network predictive controller (NNPC) is implemented. • The performance of NNPC is compared with the PI controller. • A detailed model is used for

Thermal expansion of beryllium oxide

International Nuclear Information System (INIS)

Solodukhin, A.V.; Kruzhalov, A.V.; Mazurenko, V.G.; Maslov, V.A.; Medvedev, V.A.; Polupanova, T.I.

1987-01-01

Precise measurements of temperature dependence of the coefficient of linear expansion in the 22-320 K temperature range on beryllium oxide monocrystals are conducted. A model of thermal expansion is suggested; the range of temperature dependence minimum of the coefficient of thermal expansion is well described within the frames of this model. The results of the experiment may be used for investigation of thermal stresses in crystals

The modeling and simulation of thermal based modified solid oxide fuel cell (SOFC for grid-connected systems

Directory of Open Access Journals (Sweden)

Ayetül Gelen

2015-05-01

Full Text Available This paper presents a thermal based modified dynamic model of a Solid Oxide Fuel Cell (SOFC for grid-connected systems. The proposed fuel cell model involves ohmic, activation and concentration voltage losses, thermal dynamics, methanol reformer, fuel utilization factor and power limiting module. A power conditioning unit (PCU, which consists of a DC-DC boost converter and a DC-AC voltage-source inverter (VSI, their controller, transformer and filter, is designed for grid-connected systems. The voltage-source inverter with six Insulated Gate Bipolar Transistor (IGBT switches inverts the DC voltage that comes from the converter into a sinusoidal voltage synchronized with the grid. The simulations and modeling of the system are developed on Matlab/Simulink environment. The performance of SOFC with converter is examined under step and random load conditions. The simulation results show that the designed boost converter for the proposed thermal based modified SOFC model has fairly followed different DC load variations. Finally, the AC bus of 400 Volt and 50 Hz is connected to a single-machine infinite bus (SMIB through a transmission line. The real and reactive power managements of the inverter are analyzed by an infinite bus system. Thus, the desired nominal values are properly obtained by means of the inverter controller.

Thermal oxidation of silicon with two oxidizing species

International Nuclear Information System (INIS)

Vild-Maior, A.A.; Filimon, S.

1979-01-01

A theoretical model for the thermal oxidation of silicon in wet oxygen is presented. It is shown that the presence of oxygen in the oxidation furnace has an important effect when the water temperature is not too high (less than about 65 deg C). The model is in good agreement with the experimental data. (author)

Magnesium growth in magnesium deuteride thin films during deuterium desorption

Energy Technology Data Exchange (ETDEWEB)

Checchetto, R., E-mail: riccardo.checchetto@unitn.it [Dipartimento di Fisica and CNISM, Università di Trento, Via Sommarive 14, I-38123 Trento (Italy); Miotello, A. [Dipartimento di Fisica and CNISM, Università di Trento, Via Sommarive 14, I-38123 Trento (Italy); Mengucci, P.; Barucca, G. [Dipartimento di Fisica e Ingegneria dei Materiali e del Territorio, Università Politecnica delle Marche, I-60131 Ancona (Italy)

2013-12-15

Highlights: ► Highly oriented Pd-capped magnesium deuteride thin films. ► The MgD{sub 2} dissociation was studied at temperatures not exceeding 100 °C. ► The structure of the film samples was analyzed by XRD and TEM. ► The transformation is controlled by the re-growth velocity of the Mg layers. ► The transformation is thermally activated, activation energy value of 1.3 ± 0.1 eV. -- Abstract: Pd- capped nanocrystalline magnesium thin films having columnar structure were deposited on Si substrate by e-gun deposition and submitted to thermal annealing in D{sub 2} atmosphere to promote the metal to deuteride phase transformation. The kinetics of the reverse deuteride to metal transformation was studied by Thermal Desorption Spectroscopy (TDS) while the structure of the as deposited and transformed samples was analyzed by X-rays diffraction and Transmission Electron Microscopy (TEM). In Pd- capped MgD{sub 2} thin films the deuteride to metal transformation begins at the interface between un-reacted Mg and transformed MgD{sub 2} layers. The D{sub 2} desorption kinetics is controlled by MgD{sub 2}/Mg interface effects, specifically the re-growth velocity of the Mg layers. The Mg re-growth has thermally activated character and shows an activation energy value of 1.3 ± 0.1 eV.

Magnesium-phosphate-glass cements with ceramic-type properties

Science.gov (United States)

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

Science.gov (United States)

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.

Direct-reading spectrochemical analysis of magnesium alloys

International Nuclear Information System (INIS)

Roca Adell, M.

1964-01-01

A Quantometer has been applied to the determination of aluminum, berylium, calcium, iron, silicon and zinc in magnesium alloys Magnox, after the conversion of the samples to the oxide. For the aluminum, whose concentration is relatively high, the conducting briquets technique with an interrupted discharge is employed, using the magnesium as the internal standard. For the other elements a total burning method with direct current arc is employed, using also the magnesium as the internal standard. (Author) 7 refs

Potential Health Implications of the Consumption of Thermally-Oxidized Cooking Oils – a Review

Directory of Open Access Journals (Sweden)

Falade Ayodeji Osmund

2017-06-01

Full Text Available Cooking oils are an integral part of a human diet as they are used in almost all types of culinary practices. They serve as sources of lipids with a significant nutritive value and health benefits which can be attributed to their fatty acid compositions and biological antioxidants. However, cooking oils are usually subjected to thermal oxidation which occurs when fresh cooking oil is heated at high temperatures during various food preparations. Repeated use of cooking oils in the commercial food industry is also common to maximize profit. Thermal oxidation of edible oils had since attracted great attention of nutritionist and researchers given the deteriorative effect such as generation of very cytotoxic compounds, loss of carotenoid, phenolics and vitamins thus reducing the overall antioxidant properties of the oils. Furthermore, several in vivo studies had suggested that consumption of thermally-oxidized cooking oils might not be healthy as it might negatively influence the lipid profile (increased low density lipoprotein (LDL, decreased high density lipoprotein (HDL and elevated cholesterol level, haematological system (alteration in concentration of heamoglobin (Hb, packed cell volume (PCV, white blood cell (WBC count, neutrophil and lymphocyte counts, kidney function, and induce lipid peroxidation and oxidative stress which have been associated with the pathogenesis of various degenerative diseases. Therefore, thermal oxidation seems not to provide any health benefit, as it deteriorates cooking oils and the consumption of the oils may predispose consumers to various disease conditions that may ensue from free radical generation, thereby having deleterious effect on human health.

Exoelectron emission from magnesium borate glass ceramics

International Nuclear Information System (INIS)

Kawamoto, Takamichi; Yanagisawa, Hideo; Nakamichi, Hiroshi; Kikuchi, Riichi; Kawanishi, Masaharu.

1986-01-01

Thermally stimulated exoelectron emission (TSEE) of a magnesium borate glass ceramics was investigated for its application to dosemetric use. It has been found that the TSEE glow patterns of the magnesium borate glass ceramics as well as a Li 2 B 4 O 7 glass ceramics depend on the kind of the radiation used and that the heat resistance of the magnesium borate glass ceramics is higher than that of the Li 2 B 4 O 7 glass ceramics. Therefore, the TSEE glow patterns of the magnesium borate glass ceramics indicate a possibility to be used as the dose measurement for each kind of radiation in the mixed radiation field. (author)

Biodegradable magnesium nanoparticle-enhanced laser hyperthermia therapy

Directory of Open Access Journals (Sweden)

Wang Q

2012-08-01

Full Text Available Qian Wang,1 Liping Xie,1 Zhizhu He,2 Derui Di,2 Jing Liu1,21Department of Biomedical Engineering, School of Medicine, Tsinghua University, 2Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, People's Republic of ChinaBackground: Recently, nanoparticles have been demonstrated to have tremendous merit in terms of improving the treatment specificity and thermal ablation effect on tumors. However, the potential toxicity and long-term side effects caused by the introduced nanoparticles and by expelling them out of the body following surgery remain a significant challenge. Here, we propose for the first time to directly adopt magnesium nanoparticles as the heating enhancer in laser thermal ablation to avoid these problems by making full use of the perfect biodegradable properties of this specific material.Methods: To better understand the new nano “green” hyperthermia modality, we evaluated the effects of magnesium nanoparticles on the temperature transients inside the human body subject to laser interstitial heating. Further, we experimentally investigated the heating enhancement effects of magnesium nanoparticles on a group of biological samples: oil, egg white, egg yolk, in vitro pig tissues, and the in vivo hind leg of rabbit when subjected to laser irradiation.Results: Both the theoretical simulations and experimental measurements demonstrated that the target tissues injected with magnesium nanoparticles reached much higher temperatures than tissues without magnesium nanoparticles. This revealed the enhancing behavior of the new nanohyperthermia method.Conclusion: Given the unique features of magnesium nanoparticles – their complete biological safety and ability to enhance heating – which most other advanced metal nanoparticles do not possess, the use of magnesium nanoparticles in hyperthermia therapy offers an important “green” nanomedicine modality for treating tumors

Two-dimensional zeolites: Adsorption of carbon dioxide on pristine materials and on materials modified by magnesium oxide

Czech Academy of Sciences Publication Activity Database

Zukal, Arnošt; Kubů, Martin; Pastva, Jakub

2017-01-01

Roč. 21, OCT 2017 (2017), s. 9-16 ISSN 2212-9820 R&D Projects: GA ČR(CZ) GAP106/12/0189 Institutional support: RVO:61388955 Keywords : Carbon dioxide adsorption * Two-dimensional zeolites * Magnesium oxide incorporation Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 4.292, year: 2016

Thermal Design for Extra-Terrestrial Regenerative Fuel Cell System

Science.gov (United States)

Gilligan, R.; Guzik, M.; Jakupca, I.; Bennett, W.; Smith, P.; Fincannon, J.

2017-01-01

The Advanced Exploration Systems (AES) Advanced Modular Power Systems (AMPS) Project is investigating different power systems for various lunar and Martian mission concepts. The AMPS Fuel Cell (FC) team has created two system-level models to evaluate the performance of regenerative fuel cell (RFC) systems employing different fuel cell chemistries. Proton Exchange Membrane fuel cells PEMFCs contain a polymer electrolyte membrane that separates the hydrogen and oxygen cavities and conducts hydrogen cations (protons) across the cell. Solid Oxide fuel cells (SOFCs) operate at high temperatures, using a zirconia-based solid ceramic electrolyte to conduct oxygen anions across the cell. The purpose of the modeling effort is to down select one fuel cell chemistry for a more detailed design effort. Figures of merit include the system mass, volume, round trip efficiency, and electrolyzer charge power required. PEMFCs operate at around 60 C versus SOFCs which operate at temperatures greater than 700 C. Due to the drastically different operating temperatures of the two chemistries the thermal control systems (TCS) differ. The PEM TCS is less complex and is characterized by a single pump cooling loop that uses deionized water coolant and rejects heat generated by the system to the environment via a radiator. The solid oxide TCS has its own unique challenges including the requirement to reject high quality heat and to condense the steam produced in the reaction. This paper discusses the modeling of thermal control systems for an extraterrestrial RFC that utilizes either a PEM or solid oxide fuel cell.

Osteogenic potential of human adipose-derived stromal cells on 3-dimensional mesoporous TiO{sub 2} coating with magnesium impregnation

Energy Technology Data Exchange (ETDEWEB)

Cecchinato, Francesca, E-mail: francesca.cecchinato@mah.se [Department of Prosthodontics, Faculty of Odontology, Malmö University, Malmö (Sweden); Karlsson, Johan [Department of Chemical and Biological Engineering, Applied Surface Chemistry, Chalmers University of Technology, Gothenburg (Sweden); Ferroni, Letizia; Gardin, Chiara [Department of Histology, Microbiology, and Medical Biotechnologies, University of Padova, Padova (Italy); Galli, Silvia; Wennerberg, Ann [Department of Prosthodontics, Faculty of Odontology, Malmö University, Malmö (Sweden); Zavan, Barbara [Department of Histology, Microbiology, and Medical Biotechnologies, University of Padova, Padova (Italy); Andersson, Martin [Department of Chemical and Biological Engineering, Applied Surface Chemistry, Chalmers University of Technology, Gothenburg (Sweden); Jimbo, Ryo [Department of Prosthodontics, Faculty of Odontology, Malmö University, Malmö (Sweden); Department of Applied Prosthodontics, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki (Japan)

2015-07-01

The aim of this study was to evaluate the osteogenic response of human adipose-derived stromal cells (ADScs) to mesoporous titania (TiO{sub 2}) coatings produced with evaporation-induced self-assembly method (EISA) and loaded with magnesium. Our emphasis with the magnesium release functionality was to modulate progenitor cell osteogenic differentiation under standard culture conditions. Osteogenic properties of the coatings were assessed for stromal cells by means of scanning electron microscopy (SEM) imaging, colorimetric mitochondrial viability assay (MTT), colorimetric alkaline phosphates activity (ALP) assay and real time RT-polymerase chain reaction (PCR). Using atomic force microscopy (AFM) it was shown that the surface expansion area (S{sub dr}) was strongly enhanced by the presence of magnesium. From MTT results it was shown that ADSc viability was significantly increased on mesoporous surfaces compared to the non-porous one at a longer cell culture time. However, no differences were observed between the magnesium impregnated and non-impregnated surfaces. The alkaline phosphatase activity confirmed that ADSc started to differentiate into the osteogenic phenotype after 2 weeks of culturing. The gene expression profile at 2 weeks of cell growth showed that such coatings were capable to incorporate specific osteogenic markers inside their interconnected nano-pores and, at 3 weeks, ADSc differentiated into osteoblasts. Interestingly, magnesium significantly promoted the osteopontin gene expression, which is an essential gene for the early biomaterial–cell osteogenic interaction. - Highlights: • The magnesium loading presents a transitory effect on mesoporous TiO{sub 2} surface topography • The mesoporous structure promotes cellular attachment and spreading • The mesoporous structure activates osteogenesis of mesenchymal stem cells in absence of osteogenic promoters • The physical adsorbed magnesium is suggested to be involved in the expression of

Characterization and corrosion behavior of ceramic coating on magnesium by micro-arc oxidation

International Nuclear Information System (INIS)

Durdu, Salih; Aytac, Aylin; Usta, Metin

2011-01-01

Highlights: · The commercial pure magnesium was coated by micro-arc oxidation method. · The coating is composed of two layers, a porous outer layer and a dense inner layer. · A super corrosion resistance was achieved with MAO coatings. · Coating with Mg 2 SiO 4 is more resistant to corrosion than that containing Mg 3 (PO 4 ) 2 . - Abstract: In this study, the commercial pure magnesium was coated in different aqueous solutions of Na 2 SiO 3 and Na 3 PO 4 by the micro-arc oxidation method (MAO). Coating thickness, phase composition, surface and cross sectional morphology and corrosion resistance of coatings were analyzed by eddy current method, X-ray diffraction (XRD), scanning electron microscope (SEM) and tafel extrapolation method, respectively. The average thickness of the coatings ranged from 52 to 74 μm for sodium silicate solution and from 64 to 88 μm for sodium phosphate solution. The dominant phases on the coatings were detected as spinal Mg 2 SiO 4 (Forsterite) and MgO (Periclase) for sodium silicate solution and Mg 3 (PO 4 ) 2 (Farringtonite) and MgO (Periclase) for sodium phosphate solution. SEM images reveal that the coating is composed of two layers as of a porous outer layer and a dense inner layer. The corrosion results show the coating consisting Mg 2 SiO 4 is more resistant to corrosion than that containing Mg 3 (PO 4 ) 2 .

Nano-Structured Magnesium Oxide Coated Iron Ore: Its Application to the Remediation of Wastewater Containing Lead.

Science.gov (United States)

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.

Chemopreventive Effects of Magnesium Chloride Supplementation on Hormone Independent Prostate Cancer Cells

Directory of Open Access Journals (Sweden)

Elsa Quiroz

2016-01-01

Full Text Available Background: Lifestyle significantly impacts the risk factors associated with prostate cancer, out of which diet appears to be the most influential. An emerging chemopreventive approach, which involves the adequate intake of dietary constituents, has shown great potential in preventing the occurrence or progression of cancer. Magnesium is known to be an essential cofactor for more than 300 enzymatic processes, and is responsible for the regulation of various cellular reactions in the body. A plethora of studies have shown evidence that changes in the intracellular levels of magnesium could contribute to cell proliferation and apoptosis in some normal and malignant cells. The aim of the study was to investigate the effects of magnesium chloride (MgCl2 in DU-145 prostate cancer cells. Methodology: Cultured DU-145 cells were subjected to graded concentrations or doses (50-500 µM of MgCl2 for 48 hours. The cell viability was assessed using MTT and Resazurin reduction assays. NBT assay was also used to assess the treatment-induced intracellular ROS levels. Acridine Orange/Ethidium Bromide (AcrO/EtBr and Rh123/EtBr fluorescent stains were used to assess the cell death type and mitochondrial membrane potential (Δψm respectively. Results: The results revealed a dose-dependent decrease (P < 0.05 in cell viability in treated DU-145 cells after 48 hours. The NBT assay also revealed a dose dependent biphasic response (P < 0.05 in intracellular levels of ROS. There was a drop (P < 0.05 in ROS levels in all groups except at 100 µM, where ROS level was higher than the control. Apoptosis was the primary mode of cell death as observed in the fluorescence analysis. Conclusion: Our finding suggests that MgCl2 may be potentially chemopreventive for prostate cancer. This justifies further studies into its mechanism of action in DU-145 and other prostate cancer cell types.

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

Directory of Open Access Journals (Sweden)

Hung-Pang Lee

2017-06-01

Full Text Available 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.

Characterization of Porous Phosphate Coatings Enriched with Magnesium or Zinc on CP Titanium Grade 2 under DC Plasma Electrolytic Oxidation

Directory of Open Access Journals (Sweden)

Krzysztof Rokosz

2018-02-01

Full Text Available The aim of the paper is to study and determine the effect of voltage increasing from 500 up to 650 VDC on chemical and electrochemical properties of the obtained porous coatings with plasma electrolytic oxidation (PEO processes, known also as micro arc oxidation (MAO. In the present paper, the chemical and electrochemical characterization of porous phosphate coatings enriched with magnesium or zinc on commercially pure (CP Titanium Grade 2 under DC-PEO obtained in electrolytes based on concentrated 85% analytically pure H3PO4 (98 g/mole acid with additions of 500 g·L−1 of zinc nitrate Zn(NO32∙6H2O or magnesium nitrate Mg(NO32∙6H2O, are described. These materials were characterized using scanning electron microscope (SEM with energy-dispersive X-ray spectroscopy (EDS, X-ray photoelectron spectroscopy (XPS and glow discharge optical emission spectroscopy (GDOES. It was found that the voltage of PEO process has influence on the chemical composition and thickness of the obtained porous coatings as well as on their electrochemical behavior. The higher the potential of PEO treatment, the higher the amount of zinc-to-phosphorus ratio for zinc enriched coatings was obtained, whereas in magnesium enriched coatings, the average amount of magnesium detected in PEO coating is approximately independent of the PEO voltages. Based on XPS studies, it was found out that most likely the top 10 nm of porous coatings is constructed of titanium (Ti4+, magnesium (Mg2+, zinc (Zn2+, and phosphates PO43− and/or HPO42− and/or H2PO4− and/or P2O74−. On the basis of GDOES studies, a four-sub-layer model of PEO coatings is proposed. Analysis of the potentiodynamic corrosion curves allowed to conclude that the best electrochemical repeatability was noted for magnesium and zinc enriched coatings obtained at 575 VDC.

Magnesium and Space Flight

Science.gov (United States)

Smith, Scott M.; Zwart, Sara R.

2015-01-01

Magnesium is an essential nutrient for muscle, cardiovascular, and bone health on Earth, and during space flight. We sought to evaluate magnesium status in 43 astronauts (34 male, 9 female; 47 ± 5 years old, mean ± SD) before, during, and after 4–6-month space missions. We also studied individuals participating in a ground analog of space flight (head-down-tilt bed rest; n = 27 (17 male, 10 female), 35 ± 7 years old). We evaluated serum concentration and 24-h urinary excretion of magnesium, along with estimates of tissue magnesium status from sublingual cells. Serum magnesium increased late in flight, while urinary magnesium excretion was higher over the course of 180-day space missions. Urinary magnesium increased during flight but decreased significantly at landing. Neither serum nor urinary magnesium changed during bed rest. For flight and bed rest, significant correlations existed between the area under the curve of serum and urinary magnesium and the change in total body bone mineral content. Tissue magnesium concentration was unchanged after flight and bed rest. Increased excretion of magnesium is likely partially from bone and partially from diet, but importantly, it does not come at the expense of muscle tissue stores. While further study is needed to better understand the implications of these findings for longer space exploration missions, magnesium homeostasis and tissue status seem well maintained during 4–6-month space missions. PMID:26670248

Magnesium and Space Flight

Directory of Open Access Journals (Sweden)

Scott M. Smith

2015-12-01

Full Text Available Magnesium is an essential nutrient for muscle, cardiovascular, and bone health on Earth, and during space flight. We sought to evaluate magnesium status in 43 astronauts (34 male, 9 female; 47 ± 5 years old, mean ± SD before, during, and after 4–6-month space missions. We also studied individuals participating in a ground analog of space flight (head-down-tilt bed rest; n = 27 (17 male, 10 female, 35 ± 7 years old. We evaluated serum concentration and 24-h urinary excretion of magnesium, along with estimates of tissue magnesium status from sublingual cells. Serum magnesium increased late in flight, while urinary magnesium excretion was higher over the course of 180-day space missions. Urinary magnesium increased during flight but decreased significantly at landing. Neither serum nor urinary magnesium changed during bed rest. For flight and bed rest, significant correlations existed between the area under the curve of serum and urinary magnesium and the change in total body bone mineral content. Tissue magnesium concentration was unchanged after flight and bed rest. Increased excretion of magnesium is likely partially from bone and partially from diet, but importantly, it does not come at the expense of muscle tissue stores. While further study is needed to better understand the implications of these findings for longer space exploration missions, magnesium homeostasis and tissue status seem well maintained during 4–6-month space missions.

Oxide growth and damage evolution in thermal barrier coatings

NARCIS (Netherlands)

Hille, T.S.; Turteltaub, S.R.; Suiker, A.S.J.

2011-01-01

Cracking in thermal barrier coatings (TBC) is triggered by the development of a thermally-grown oxide (TGO) layer that develops during thermal cycling from the oxidation of aluminum present in the bond coat (BC). In the present communication a numerical model is presented that describes the

Stability of solid oxide fuel cell materials

Energy Technology Data Exchange (ETDEWEB)

Armstrong, T.R.; Bates, J.L.; Coffey, G.W.; Pederson, L.R. [Pacific Northwest National Lab., Richland, WA (United States)] [and others

1996-08-01

Chromite interconnection materials in an SOFC are exposed to both highly oxidizing conditions at the cathode and to highly reducing conditions at the anode. Because such conditions could lead to component failure, the authors have evaluated thermal, electrical, chemical, and structural stabilities of these materials as a function of temperature and oxygen partial pressure. The crystal lattice of the chromites was shown to expand for oxygen partial pressures smaller than 10{sup {minus}10} atm, which could lead to cracking and debonding in an SOFC. Highly substituted lanthanum chromite compositions were the most susceptible to lattice expansion; yttrium chromites showed better dimensional stability by more than a factor of two. New chromite compositions were developed that showed little tendency for lattice expansion under strongly reducing conditions, yet provided a good thermal expansion match to other fuel cell components. Use of these new chromite interconnect compositions should improve long-term SOFC performance, particularly for planar cell configurations. Thermodynamic properties of substituted lanthanum manganite cathode compositions have been determined through measurement of electromotive force as a function of temperature. Critical oxygen decomposition pressures for Sr and Ca-substituted lanthanum manganites were established using cells based on a zirconia electrolyte. Strontium oxide and calcium oxide activities in a lanthanum manganite matrix were determined using cells based on strontium fluoride and calcium fluoride electrolytes, respectively. The compositional range of single-phase behavior of these ABO{sub 3}-type perovskites was established as a function of A/B cation ratios and the extent of acceptor doping. Before this work, very little thermodynamic information was in existence for substituted manganite compositions. Such information is needed to predict the long-term stability of solid oxide fuel cell assemblies.

A lumped model of venting during thermal runaway in a cylindrical Lithium Cobalt Oxide lithium-ion cell

Science.gov (United States)

Coman, Paul T.; Rayman, Sean; White, Ralph E.

2016-03-01

This paper presents a mathematical model built for analyzing the intricate thermal behavior of a 18650 LCO (Lithium Cobalt Oxide) battery cell during thermal runaway when venting of the electrolyte and contents of the jelly roll (ejecta) is considered. The model consists of different ODEs (Ordinary Differential Equations) describing reaction rates and electrochemical reactions, as well as the isentropic flow equations for describing electrolyte venting. The results are validated against experimental findings from Golubkov et al. [1] [Andrey W. Golubkov, David Fuchs, Julian Wagner, Helmar Wiltsche, Christoph Stangl, Gisela Fauler, Gernot Voitice Alexander Thaler and Viktor Hacker, RSC Advances, 4:3633-3642, 2014] for two cases - with flow and without flow. The results show that if the isentropic flow equations are not included in the model, the thermal runaway is triggered prematurely at the point where venting should occur. This shows that the heat dissipation due to ejection of electrolyte and jelly roll contents has a significant contribution. When the flow equations are included, the model shows good agreement with the experiment and therefore proving the importance of including venting.

Photoluminescence of magnesium-associated color centers in LiF crystals implanted with magnesium ions

Science.gov (United States)

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.

Evaluation of short-term effects of rare earth and other elements used in magnesium alloys on primary cells and cell lines.

Science.gov (United States)

Feyerabend, Frank; Fischer, Janine; Holtz, Jakob; Witte, Frank; Willumeit, Regine; Drücker, Heiko; Vogt, Carla; Hort, Norbert

2010-05-01

Degradable magnesium alloys for biomedical application are on the verge of being used clinically. Rare earth elements (REEs) are used to improve the mechanical properties of the alloys, but in more or less undefined mixtures. For some elements of this group, data on toxicity and influence on cells are sparse. Therefore in this study the in vitro cytotoxicity of the elements yttrium (Y), neodymium (Nd), dysprosium (Dy), praseodymium (Pr), gadolinium (Gd), lanthanum (La), cerium (Ce), europium (Eu), lithium (Li) and zirconium (Zr) was evaluated by incubation with the chlorides (10-2000 microM); magnesium (Mg) and calcium (Ca) were tested at higher concentrations (200 and 50mM, respectively). The influence on viability of human osteosarcoma cell line MG63, human umbilical cord perivascular (HUCPV) cells and mouse macrophages (RAW 264.7) was determined, as well as the induction of apoptosis and the expression of inflammatory factors (TNF-alpha, IL-1alpha). Significant differences between the applied cells could be observed. RAW exhibited the highest and HUCPV the lowest sensitivity. La and Ce showed the highest cytotoxicity of the analysed elements. Of the elements with high solubility in magnesium alloys, Gd and Dy seem to be more suitable than Y. The focus of magnesium alloy development for biomedical applications should include most defined alloy compositions with well-known tissue-specific and systemic effects. Copyright (c) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Thermal Oxidation Resistance of Rare Earth-Containing Composite Elastomer

Institute of Scientific and Technical Information of China (English)

邱关明; 张明; 周兰香; 中北里志; 井上真一; 冈本弘

2001-01-01

The rare earth-containing composite elastomer was obtained by the reaction of vinyl pyridine-SBR (PSBR) latex with rare earth alkoxides, and its thermal oxidation resistance was studied. After aging test, it is found that its retention rate of mechanical properties is far higher than that of the control sample. The results of thermogravimetric analysis show that its thermal-decomposing temperature rises largely. The analysis of oxidation mechanisms indicates that the main reasons for thermal oxidation resistance are that rare earth elements are of the utility to discontinue autoxidation chain reaction and that the formed complex structure has steric hindrance effect on oxidation.

Structural design considerations for micromachined solid-oxide fuel cells

Science.gov (United States)

Srikar, V. T.; Turner, Kevin T.; Andrew Ie, Tze Yung; Spearing, S. Mark

Micromachined solid-oxide fuel cells (μSOFCs) are among a class of devices being investigated for portable power generation. Optimization of the performance and reliability of such devices requires robust, scale-dependent, design methodologies. In this first analysis, we consider the structural design of planar, electrolyte-supported, μSOFCs from the viewpoints of electrochemical performance, mechanical stability and reliability, and thermal behavior. The effect of electrolyte thickness on fuel cell performance is evaluated using a simple analytical model. Design diagrams that account explicitly for thermal and intrinsic residual stresses are presented to identify geometries that are resistant to fracture and buckling. Analysis of energy loss due to in-plane heat conduction highlights the importance of efficient thermal isolation in microscale fuel cell design.

Improved corrosion resistance on biodegradable magnesium by zinc and aluminum ion implantation

Science.gov (United States)

Xu, Ruizhen; Yang, Xiongbo; Suen, Kai Wong; Wu, Guosong; Li, Penghui; Chu, Paul K.

2012-12-01

Magnesium and its alloys have promising applications as biodegradable materials, and plasma ion implantation can enhance the corrosion resistance by modifying the surface composition. In this study, suitable amounts of zinc and aluminum are plasma-implanted into pure magnesium. The surface composition, phases, and chemical states are determined, and electrochemical tests and electrochemical impedance spectroscopy (EIS) are conducted to investigate the surface corrosion behavior and elucidate the mechanism. The corrosion resistance enhancement after ion implantation is believed to stem from the more compact oxide film composed of magnesium oxide and aluminum oxide as well as the appearance of the β-Mg17Al12 phase.

Effect of CaO Addition on the High-Temperature Oxidation of AM30 Magnesium Alloys

International Nuclear Information System (INIS)

Won, Sung-Bin; Lee, Dong Bok

2014-01-01

AM30 + (0, 0.5, 1, 1.5) wt%CaO magnesium alloys were cast and oxidized at 625 ℃ and 650 ℃ in atmospheric air. The CaO particles that were added during casting allowed casting the AM30 alloys in air without using environmentally hazardous SF_6 or SO_2 gases. They decomposed to dissolve in the α-Mg matrix and also to precipitate along the matrix grain boundaries as Al_2Ca during casting. The ignition temperatures were 584.6 ℃ for AM30, 604.5 ℃ for AM30 + 0.5 wt%CaO, and 691.7 ℃ for AM30 + 1 wt%CaO. No ignition occurred for AM30 + 1.5 wt%CaO up to 700 ℃. During oxidation, CaO-rich oxide scales formed on the alloy surface, which prevented direct contact of the alloy with air and fast oxidation of the alloy in air

Effect of CaO Addition on the High-Temperature Oxidation of AM30 Magnesium Alloys

Energy Technology Data Exchange (ETDEWEB)

Won, Sung-Bin; Lee, Dong Bok [Sungkyunkwan University, Suwon (Korea, Republic of)

2014-03-15

AM30 + (0, 0.5, 1, 1.5) wt%CaO magnesium alloys were cast and oxidized at 625 ℃ and 650 ℃ in atmospheric air. The CaO particles that were added during casting allowed casting the AM30 alloys in air without using environmentally hazardous SF{sub 6} or SO{sub 2} gases. They decomposed to dissolve in the α-Mg matrix and also to precipitate along the matrix grain boundaries as Al{sub 2}Ca during casting. The ignition temperatures were 584.6 ℃ for AM30, 604.5 ℃ for AM30 + 0.5 wt%CaO, and 691.7 ℃ for AM30 + 1 wt%CaO. No ignition occurred for AM30 + 1.5 wt%CaO up to 700 ℃. During oxidation, CaO-rich oxide scales formed on the alloy surface, which prevented direct contact of the alloy with air and fast oxidation of the alloy in air.

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

Science.gov (United States)

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.

Cytotoxic effect of galvanically coupled magnesium-titanium particles.

Science.gov (United States)

Kim, Jua; Gilbert, Jeremy L

2016-01-01

Recent work has shown that reduction reactions at metallic biomaterial surfaces can induce significant killing of cells in proximity to the surface. To exploit this phenomenon for therapeutic purposes, for example, for cancer tumor killing or antibacterial effects (amongst other applications), magnesium metal particles, galvanically coupled to titanium by sputtering, have been evaluated for their cell-killing capability (i.e. cytotoxicity). Magnesium (Mg) particles large enough to prevent particle phagocytosis were investigated, so that only electrochemical reactions, and not particle toxicity per se, caused cytotoxic effects. Titanium (Ti) coated magnesium particles, as well as magnesium-only particles were introduced into MC3T3-E1 mouse pre-osteoblast cell cultures over a range of particle concentrations, and cells were observed to die in a dosage-dependent manner. Ti-coated magnesium particles killed more cells at lower particle concentration than magnesium alone (Pmagnesium and magnesium-titanium had no significant difference at similar particle concentrations. Complete cell killing occurred at 750μg/ml and 1500μg/ml for Mg-Ti and Mg, respectively. Thus, this work demonstrates that galvanically coupled Mg-Ti particles have a significant cell killing capability greater than Mg alone. In addition, when the pH associated with complete killing with particles was created using NaOH only (no particles), then the percentage of cells killed was significantly less (Pmagnesium-titanium microparticles kill cells more effectively than magnesium particles alone. The killing effect was shown to not be due to pH shifts since no differences were seen for different particle types and pH adjusted medium without particles did not exhibit the same level of killing. The significance of this work is the recognition of this killing effect with Mg particles and the potential therapeutic applications in infection control and cancer treatment that this process may provide. Copyright �

Magnesium fluoride recovery method

International Nuclear Information System (INIS)

Gay, R.L.; McKenzie, D.E.

1989-01-01

A method of obtaining magnesium fluoride substantially free from radioactive uranium from a slag formed in the production of metallic uranium by the reduction of depleted uranium tetrafluoride with metallic magnesium in a retort wherein the slag contains the free metals magnesium and uranium and also oxides and fluorides of the metals. The slag having a radioactivity level of at least about 7,000 rhoCi/gm. The method comprises the steps of: grinding the slag to a median particle size of about 200 microns; contacting the ground slag in a reaction zone with an acid having a strength of from about 0.5 to 1.5 N for a time of from about 4 to about 20 hours in the presence of a catalytic amount of iron; removing the liquid product; treating the particulate solid product; repeating the last two steps at least one more time to produce a solid residue consisting essentially of magnesium fluoride substantially free of uranium and having a residual radioactivity level of less than about 1000 rhoCi/gm

Effect of Ca and Y additions on oxidation behavior of magnesium alloys at high temperatures

Institute of Scientific and Technical Information of China (English)

FAN Jianfeng; YANG Changlin; XU Bingshe

2012-01-01

Oxidation and ignition of magnesium alloys at elevated temperature were successfully retarded by additions of Y and Ca.which could be melted at 1173 K in air without any protection.Thermogravimetric measurements in dry air revealed that the oxidation dynamics curves of Mg-2.5Ca alloy and Mg-3.5Y-0.79Ca alloy at high temperatures followed the parabolic-line law or the ubic-line law.X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis indicated that the oxide film on the surface of Mg-3.5Y-0.79Ca and Mg-2.5Ca alloys exhibited a duplex structure.which agreed with the results of thermodynamic analysis.By comparison,the ignition-proof effect of the combination addition of Y and Ca was better than that of the single addition of Ca.

Polymer Photovoltaic Cells with Rhenium Oxide as Anode Interlayer.

Science.gov (United States)

Wei, Jinyu; Bai, Dongdong; Yang, Liying

2015-01-01

The effect of a new transition metal oxide, rhenium oxide (ReO3), on the performance of polymer solar cells based on regioregular poly(3-hexylthiophene) (P3HT) and methanofullerene [6,6]-phenyl C61-butyric acid methyl ester (PCBM) blend as buffer layer was investigated. The effect of the thickness of ReO3 layer on electrical characteristics of the polymer solar cells was studied. It is found that insertion of ReO3 interfacial layer results in the decreased performance for P3HT: PCBM based solar cells. In order to further explore the mechanism of the decreasing of the open-circuit voltage (Voc), the X-ray photoelectron spectroscopy (XPS) is used to investigate the ReO3 oxidation states. Kelvin Probe method showed that the work function of the ReO3 is estimated to be 5.13eV after thermal evaporation. The results indicated the fact that a portion of ReO3 decomposed during thermal evaporation process, resulting in the formation of a buffer layer with a lower work function. As a consequence, a higher energy barrier was generated between the ITO and the active layer.

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

Science.gov (United States)

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.

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

Science.gov (United States)

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.

Multi-functional magnesium alloys containing interstitial oxygen atoms.

Science.gov (United States)

Kang, H; Choi, H J; Kang, S W; Shin, S E; Choi, G S; Bae, D H

2016-03-15

A new class of magnesium alloys has been developed by dissolving large amounts of oxygen atoms into a magnesium lattice (Mg-O alloys). The oxygen atoms are supplied by decomposing titanium dioxide nanoparticles in a magnesium melt at 720 °C; the titanium is then completely separated out from the magnesium melt after solidification. The dissolved oxygen atoms are located at the octahedral sites of magnesium, which expand the magnesium lattice. These alloys possess ionic and metallic bonding characteristics, providing outstanding mechanical and functional properties. A Mg-O-Al casting alloy made in this fashion shows superior mechanical performance, chemical resistance to corrosion, and thermal conductivity. Furthermore, a similar Mg-O-Zn wrought alloy shows high elongation to failure (>50%) at room temperature, because the alloy plastically deforms with only multiple slips in the sub-micrometer grains (alloys are expected to open a new paradigm in commercial alloy design.

Magnesium for Hydrogen Storage

DEFF Research Database (Denmark)

Vigeholm, B.; Kjøller, John; Larsen, Bent

1980-01-01

The reaction of hydrogen with commercially pure magnesium powder (above 99.7%) was investigated in the temperature range 250–400 °C. Hydrogen is readily sorbed above the dissociation pressure. During the initial exposure the magnesium powder sorbs hydrogen slowly below 400 °C but during the second...... that the particles do not disintegrate is explained by a sintering process at the working temperatures. Exposure to air does not impair the sorption ability; on the contrary, it appears that surface oxidation plays an important role in the reaction. Some handling problems, e.g. the reaction of the hydride with water...

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

International Nuclear Information System (INIS)

Rather, Sami ullah

2014-01-01

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, 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

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

Energy Technology Data Exchange (ETDEWEB)

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 in recycling automotive non-ferrous metals, particularly as motor vehicle magnesium/aluminum ratios increase in order to reduce vehicle weight and increase efficiency.

Hydrogenations of alloys and intermetallic compounds of magnesium

International Nuclear Information System (INIS)

Gavra, Z.

1981-08-01

A kinetic and thermodynamic study of the hydrogenation of alloys and intermetallic compounds of magnesium is presented. It was established that the addition of elements of the IIIA group (Al, Ga, In) to magnesium catalyses its hydrogenation. This is explained by the mechanism of diffusion of magnesium cation vacancies. The hydride Mg 2 NiH 4 was characterized by thermal analysis, x-ray diffraction and NMR measurements. The possibility of forming pseudo-binary compounds of Mg 2 Ni by the substitution of nickel or magnesium was examined. The hydrogenation of the inter-metallic compounds of the Mg-Al system was investigated. It was found that the addition of indium and nickel affected the hydrogenation kinetics. A preliminary study of the hydrogenation of various binary and ternary alloys of magnesium was carried out. (Author)

Corrosion resistance of titanium ion implanted AZ91 magnesium alloy

International Nuclear Information System (INIS)

Liu Chenglong; Xin Yunchang; Tian Xiubo; Zhao, J.; Chu, Paul K.

2007-01-01

Degradable metal alloys constitute a new class of materials for load-bearing biomedical implants. Owing to their good mechanical properties and biocompatibility, magnesium alloys are promising in degradable prosthetic implants. The objective of this study is to improve the corrosion behavior of surgical AZ91 magnesium alloy by titanium ion implantation. The surface characteristics of the ion implanted layer in the magnesium alloys are examined. The authors' results disclose that an intermixed layer is produced and the surface oxidized films are mainly composed of titanium oxide with a lesser amount of magnesium oxide. X-ray photoelectron spectroscopy reveals that the oxide has three layers. The outer layer which is 10 nm thick is mainly composed of MgO and TiO 2 with some Mg(OH) 2 . The middle layer that is 50 nm thick comprises predominantly TiO 2 and MgO with minor contributions from MgAl 2 O 4 and TiO. The third layer from the surface is rich in metallic Mg, Ti, Al, and Ti 3 Al. The effects of Ti ion implantation on the corrosion resistance and electrochemical behavior of the magnesium alloys are investigated in simulated body fluids at 37±1 deg. C using electrochemical impedance spectroscopy and open circuit potential techniques. Compared to the unimplanted AZ91 alloy, titanium ion implantation significantly shifts the open circuit potential (OCP) to a more positive potential and improves the corrosion resistance at OCP. This phenomenon can be ascribed to the more compact surface oxide film, enhanced reoxidation on the implanted surface, as well as the increased β-Mg 12 Al 17 phase

Electronic properties of thermally formed thin iron oxide films

International Nuclear Information System (INIS)

Wielant, J.; Goossens, V.; Hausbrand, R.; Terryn, H.

2007-01-01

The oxide layer, present between an organic coating and the substrate, guarantees adhesion of the coating and plays a determinating role in the delamination rate of the organic coating. The purpose of this study is to compare the resistive and semiconducting properties of thermal oxides formed on steel in two different atmospheres at 250 deg. C: an oxygen rich atmosphere, air, and an oxygen deficient atmosphere, N 2 . In N 2 , a magnetite layer grows while in air a duplex oxide film forms composed by an inner magnetite layer and a thin outer hematite scale. The heat treatment for different amounts of time at high temperature was used as method to sample the thickness variation and change in electronic and semiconducting properties of the thermal oxide layers. Firstly, linear voltammetric measurements were performed to have a first insight in the electrochemical behavior of the thermal oxides in a borate buffer solution. Electrochemical impedance spectroscopy in the same buffer combined with the Mott-Schottky analysis were used to determine the semiconducting properties of the thermal oxides. By spectroscopic ellipsometry (SE) and atomic force microscopy (AFM), respectively, the thickness and roughness of the oxide layers were determined supporting the physical interpretation of the voltammetric and EIS data. These measurements clearly showed that oxide layers with different constitution, oxide resistance, flatband potential and doping concentration can be grown by changing the atmosphere

Magnesium and manganese content of halophilic bacteria

International Nuclear Information System (INIS)

de Medicis, E.; Paquette, J.; Gauthier, J.J.; Shapcott, D.

1986-01-01

Magnesium and manganese contents were measured by atomic absorption spectrophotometry in bacteria of several halophilic levels, in Vibrio costicola, a moderately halophilic eubacterium growing in 1 M NaCl, Halobacterium volcanii, a halophilic archaebacterium growing in 2.5 NaCl, Halobacterium cutirubrum, an extremely halophilic archaebacterium growing in 4 M NaCl, and Escherichia coli, a nonhalophilic eubacterium growing in 0.17 M NaCl. Magnesium and manganese contents varied with the growth phase, being maximal at the early log phase. Magnesium and manganese molalities in cell water were shown to increase with the halophilic character of the logarithmically growing bacteria, from 30 mmol of Mg per kg of cell water and 0.37 mmol of Mn per kg of cell water for E. coli to 102 mmol of Mg per kg of cell water and 1.6 mmol of Mn per kg of cell water for H cutirubrum. The intracellular concentrations of manganese were determined independently by a radioactive tracer technique in V. costicola and H. volcanii. The values obtained by 54 Mn loading represented about 70% of the values obtained by atomic absorption. The increase of magnesium and manganese contents associated with the halophilic character of the bacteria suggests that manganese and magnesium play a role in haloadaptation

X-linked immunodeficiency with magnesium defect, Epstein-Barr virus infection, and neoplasia disease: a combined immune deficiency with magnesium defect.

Science.gov (United States)

Ravell, Juan; Chaigne-Delalande, Benjamin; Lenardo, Michael

2014-12-01

To describe the role of the magnesium transporter 1 (MAGT1) in the pathogenesis of 'X-linked immunodeficiency with magnesium defect, Epstein-Barr virus (EBV) infection, and neoplasia' (XMEN) disease and its clinical implications. The magnesium transporter protein MAGT1 participates in the intracellular magnesium ion (Mg) homeostasis and facilitates a transient Mg influx induced by the activation of the T-cell receptor. Loss-of-function mutations in MAGT1 cause an immunodeficiency named 'XMEN syndrome', characterized by CD4 lymphopenia, chronic EBV infection, and EBV-related lymphoproliferative disorders. Patients with XMEN disease have impaired T-cell activation and decreased cytolytic function of natural killer (NK) and CD8 T cells because of decreased expression of the NK stimulatory receptor 'natural-killer group 2, member D' (NKG2D). Patients may have defective specific antibody responses secondary to T cell dysfunction, but B cells have not been shown to be directly affected by mutations in MAGT1. XMEN disease has revealed a novel role for free intracellular magnesium in the immune system. Further understanding of the MAGT1 signaling pathway may lead to new diagnostic and therapeutic approaches.

Influence of creep and cyclic oxidation in thermal barrier coatings

Energy Technology Data Exchange (ETDEWEB)

Seiler, Philipp; Baeker, Martin; Roesler, Joachim [Technische Univ. Braunschweig (Germany). Inst. fuer Werkstoffe

2012-01-15

The lifetime of thermal barrier coating systems is limited by cracks close to the interfaces, causing delamination. To study the failure mechanisms, a simplified model system is analysed which consists of a bond-coat bulk material, a thermally grown oxide, and an yttria-stabilised zirconia topcoat. The stresses in the model system are calculated using a finite element model which covers the simulation of full thermal cycles, creep in all layers, and the anisotropic oxidation during dwelling. Creep in the oxide and the thermal barrier coating is varied with the use of different creep parameter sets. The influence of creep in the bondcoat is analysed by using two different bond-coat materials: fast creeping Fecralloy and slow creeping oxide dispersion strengthened MA956. It is shown that creep in the bondcoat influences the lifetime of the coatings. Furthermore, a fast creeping thermally grown oxide benefits the lifetime of the coating system. (orig.)

A hydrous Ca-bearing magnesium carbonate from playa lake sediments, Salines Lake, Spain

Science.gov (United States)

Queralt, I.; Julia, R.; Plana, F.; Bischoff, J.L.

1997-01-01

Sediments of playa Lake Salines, SE, Spain, contain a carbonate mineral characterized by X-ray diffraction peaks very similar to, but systematically shifted from those of pure magnesite. Analyses (SEM, IR and Raman spectroscopy, DTA, TGA, and ICP) indicate the mineral is a hydrous Ca-bearing magnesium carbonate with the chemical formula (Mg0.92,Ca0.08)CO3??3H2O. Thermal characteristics of the mineral are similar to those of other known hydrated magnesium carbonates. X-ray and electron diffraction data suggests a monoclinic system (P21/n space group) with unit-cell parameters of a = 6.063(6), b = 10.668(5), and c = 6.014(4) A?? and ?? = 107.28??.

On the hydrogenation mechanism in magnesium I

DEFF Research Database (Denmark)

Pedersen, A.S.; Kjøller, John; Larsen, Bent

1985-01-01

The first time hydriding of spherical magnesium particles covered by a thin oxide layer and sieve-fractionated into narrow size distributions within the range 40–90 μm was followed by microgravimetry. The size distributions of the fractions were determined by semiautomatic image analysis....... The hydridings were run at 402°C and 3 MPa hydrogen pressure after heating in helium. A dependence of the rate of hydriding on the heat treatment prior to reaction was observed and it is proposed that the heat treatment causes oxygen atoms to diffuse into the bulk metal and thereby break up the protective oxide...... generalizing results from the hydriding of magnesium powders....

HPLC Separation of Vitamin E and Its Oxidation Products and Effects of Oxidized Tocotrienols on the Viability of MCF-7 Breast Cancer Cells in Vitro.

Science.gov (United States)

Drotleff, Astrid M; Büsing, Anne; Willenberg, Ina; Empl, Michael T; Steinberg, Pablo; Ternes, Waldemar

2015-10-14

Tocotrienols, a vitamin E subgroup, exert potent anticancer effects, but easily degrade due to oxidation. Eight vitamin E reference compounds, α-, β-, γ-, or δ-tocopherols or -tocotrienols, were thermally oxidized in n-hexane. The corresponding predominantly dimeric oxidation products were separated from the parent compounds by diol-modified normal-phase HPLC-UV and characterized by mass spectroscopy. The composition of test compounds, that is, α-tocotrienol, γ-tocotrienol, or palm tocotrienol-rich fraction (TRF), before and after thermal oxidation was determined by HPLC-DAD, and MCF-7 cells were treated with both nonoxidized and oxidized test compounds for 72 h. Whereas all nonoxidized test compounds (0-100 μM) led to dose-dependent decreases in cell viability, equimolar oxidized α-tocotrienol had a weaker effect, and oxidized TRF had no such effect. However, the IC50 value of oxidized γ-tocotrienol was lower (85 μM) than that of nonoxidized γ-tocotrienol (134 μM), thereby suggesting that γ-tocotrienol oxidation products are able to reduce tumor cell viability in vitro.

Direct oxide reducing method

International Nuclear Information System (INIS)

Tokiwai, Moriyasu.

1995-01-01

Calcium oxides and magnetic oxides as wastes generated upon direct reduction are subjected to molten salt electrolysis, and reduced metallic calcium and magnesium are separated and recovered. Then calcium and magnesium are used recyclically as the reducing agent upon conducting direct oxide reduction. Even calcium oxides and magnesium oxides, which have high melting points and difficult to be melted usually, can be melted in molten salts of mixed fluorides or chlorides by molten-salt electrolysis. Oxides are decomposed by electrolysis, and oxygen is removed in the form of carbon monoxide, while the reduced metallic calcium and magnesium rise above the molten salts on the side of a cathode, and then separated. Since only carbon monoxide is generated as radioactive wastes upon molten salt electrolysis, the amount of radioactive wastes can be greatly reduced, and the amount of the reducing agent used can also be decreased remarkably. (N.H.)

Tire containing thermally exfoliated graphite oxide

Science.gov (United States)

Prud'homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor)

2011-01-01

A tire, tire lining or inner tube, containing a polymer composite, made of at least one rubber and/or at least one elastomer and a modified graphite oxide material, which is a thermally exfoliated graphite oxide with a surface area of from about 300 sq m/g to 2600 sq m/g.

Cermet cathodes for strontium and magnesium-doped LaGaO{sub 3}-based solid oxide fuel cells

Energy Technology Data Exchange (ETDEWEB)

Datta, Pradyot [Technische Universitaet Clausthal, Institut fuer Metallurgie, 42 Robert-Koch Strasse, 38678 Clausthal-Zellerfeld (Germany); Max-Planck-Institut fuer Metallforschung and Institut fuer Nichtmetallische and Anorganische Materialien, Universitaet Stuttgart, Pulvermetallurgisches Laboratorium, Heisenbergstrasse 3, Stuttgart 70569 (Germany)], E-mail: pradyot.datta@gmail.com; Bronin, D.I. [Institute of High-Temperature Electrochemistry of Russian Academy of Sciences, Ekaterinburg 620219, S. Kovalevskoz 22 (Russian Federation); Majewski, P. [University of South Australia, School of Advanced Manufacturing and Mechanical Engineering, Mawson Institute, Mawson Lakes, South Australia 5095 (Australia); Aldinger, F. [Max-Planck-Institut fuer Metallforschung and Institut fuer Nichtmetallische and Anorganische Materialien, Universitaet Stuttgart, Pulvermetallurgisches Laboratorium, Heisenbergstrasse 3, Stuttgart 70569 (Germany)

2009-03-15

To check the suitability of La{sub 0.9}Sr{sub 0.1}Ga{sub 0.85}Mg{sub 0.15}O{sub 3-{delta}}-Ag cermets as cathode material for solid oxide fuel cell (SOFC) with Sr- and Mg-doped LaGaO{sub 3} electrolyte a series of cermets with different Ag contents were prepared by conventional sintering process. The chemical compatibility between La{sub 0.9}Sr{sub 0.1}Ga{sub 0.85}Mg{sub 0.15}O{sub 3-{delta}} (LSGM) and Ag was investigated by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. Thermal expansion coefficient of the cermets was measured as a function of Ag content and was found to increase with increasing metallic content. Oxygen adsorption at the surface of the cermets could be detected but no reaction or solid solubility between LSGM and Ag was found. It was noticed that a minimum of 30 wt.% Ag is needed to form a cermet with percolating network. From impedance spectroscopy measurement activation energy for the polarization conductance was found to be around 110 kJ mol{sup -1}.

Thermal radiation modelling in a tubular solid oxide fuel cell

International Nuclear Information System (INIS)

Austin, M.E.; Pharoah, J.G.; Vandersteen, J.D.J.

2004-01-01

Solid Oxide Fuel Cells (SOFCs) are becoming the fuel cell of choice among companies and research groups interested in small power generation units. Questions still exist, however, about the operating characteristics of these devices; in particular the temperature distribution in the fuel cell. Using computational fluid dynamics (CFD) a model is proposed that incorporates conduction, convection and radiation. Both surface-to-surface and participating media are considered. It is hoped that a more accurate account of the temperature field in the various flow channels and cell components will be made to assist work on design of fuel cell components and reaction mechanisms. The model, when incorporating radiative heat transfer with participating media, predicts substantially lower operating temperatures and smaller temperature gradients than it does without these equations. It also shows the importance of the cathode air channel in cell cooling. (author)

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

Science.gov (United States)

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.

Magnesium, magnesium alloys, and magnesium composites

National Research Council Canada - National Science Library

Gupta, M; Sharon, Nai Mui Ling

2011-01-01

"Properties of Magnesium Composites for Material Scientists, Engineers and Selectors is the first book-length reference to provide an insight into current and future magnesium-based materials in terms...

TiO2 Deposition on AZ31 Magnesium Alloy Using Plasma Electrolytic Oxidation

Directory of Open Access Journals (Sweden)

Leon White

2013-01-01

Full Text Available Plasma electrolytic oxidation (PEO has been used in the past as a useful surface treatment technique to improve the anticorrosion properties of Mg alloys by forming protective layer. Coatings were prepared on AZ31 magnesium alloy in phosphate electrolyte with the addition of TiO2 nanoparticles using plasma electrolytic oxidation (PEO. This present work focuses on developing a TiO2 functional coating to create a novel electrophotocatalyst while observing the surface morphology, structure, composition, and corrosion resistance of the PEO coating. Microstructural characterization of the coating was investigated by X-ray diffraction (XRD and scanning electron microscopy (SEM followed by image analysis and energy dispersive spectroscopy (EDX. The corrosion resistance of the PEO treated samples was evaluated with electrochemical impedance spectroscopy (EIS and DC polarization tests in 3.5 wt.% NaCl. The XRD pattern shows that the components of the oxide film include Mg from the substrate as well as MgO and Mg2TiO4 due to the TiO2 nanoparticle addition. The results show that the PEO coating with TiO2 nanoparticles did improve the corrosion resistance when compared to the AZ31 substrate alloy.

Corrosion resistance and durability of superhydrophobic surface formed on magnesium alloy coated with nanostructured cerium oxide film and fluoroalkylsilane molecules in corrosive NaCl aqueous solution.

Science.gov (United States)

Ishizaki, Takahiro; Masuda, Yoshitake; Sakamoto, Michiru

2011-04-19

The corrosion resistant performance and durability of the superhydrophobic surface on magnesium alloy coated with nanostructured cerium oxide film and fluoroalkylsilane molecules in corrosive NaCl aqueous solution were investigated using electrochemical and contact angle measurements. The durability of the superhydrophobic surface in corrosive 5 wt% NaCl aqueous solution was elucidated. The corrosion resistant performance of the superhydrophobic surface formed on magnesium alloy was estimated by electrochemical impedance spectroscopy (EIS) measurements. The EIS measurements and appropriate equivalent circuit models revealed that the superhydrophobic surface considerably improved the corrosion resistant performance of magnesium alloy AZ31. American Society for Testing and Materials (ASTM) standard D 3359-02 cross cut tape test was performed to investigate the adhesion of the superhydrophobic film to the magnesium alloy surface. The corrosion formation mechanism of the superhydrophobic surface formed on the magnesium alloy was also proposed. © 2011 American Chemical Society

Effects of extracellular magnesium on the differentiation and function of human osteoclasts.

Science.gov (United States)

Wu, Lili; Luthringer, Bérengère J C; Feyerabend, Frank; Schilling, Arndt F; Willumeit, Regine

2014-06-01

Magnesium-based implants have been shown to influence the surrounding bone structure. In an attempt to partially reveal the cellular mechanisms involved in the remodelling of magnesium-based implants, the influence of increased extracellular magnesium content on human osteoclasts was studied. Peripheral blood mononuclear cells were driven towards an osteoclastogenesis pathway via stimulation with receptor activator of nuclear factor kappa-B ligand and macrophage colony-stimulating factor for 28 days. Concomitantly, the cultures were exposed to variable magnesium concentrations (from either magnesium chloride or magnesium extracts). Osteoclast proliferation and differentiation were evaluated based on cell metabolic activity, total protein content, tartrate-resistant acid phosphatase activity, cathepsin K and calcitonin receptor immunocytochemistry, and cellular ability to form resorption pits. While magnesium chloride first enhanced and then opposed cell proliferation and differentiation in a concentration-dependent manner (peaking between 10 and 15mM magnesium chloride), magnesium extracts (with lower magnesium contents) appeared to decrease cell metabolic activity (≈50% decrease at day 28) while increasing osteoclast activity at a lower concentration (twofold higher). Together, the results indicated that (i) variations in the in vitro extracellular magnesium concentration affect osteoclast metabolism and (ii) magnesium extracts should be used preferentially in vitro to more closely mimic the in vivo environment. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Metal Injection Molding (MIM of Magnesium and Its Alloys

Directory of Open Access Journals (Sweden)

Martin Wolff

2016-05-01

Full Text Available Current research has highlighted that magnesium and its alloys as biodegradable material are highly suitable for biomedical applications. The new material fully degrades into nontoxic elements and offers material properties matching those of human bone tissue. As biomedical implants are rather small and complex in shape, the metal injection molding (MIM technique seems to be well suited for the near net shape mass production of such parts. Furthermore, MIM of Mg-alloys is of high interest in further technical fields. This study focusses on the performance of MIM-processing of magnesium alloy powders. It includes Mg-specific development of powder blending, feedstock preparation, injection molding, solvent and thermal debinding and final sintering. Even though Mg is a highly oxygen-affine material forming a stable oxide layer on each particle surface, the material can be sintered to nearly dense parts, providing mechanical properties matching those of as cast material. An ultimate tensile strength of 142 MPa, yield strength of 67 MPa, elastic modulus of 40 GPa and 8% elongation at fracture could be achieved using novel organic polymer binders for the feedstock preparation. Thus, first implant demonstrator parts could be successfully produced by the MIM technique.

Hydration of Magnesium Carbonate in a Thermal Energy Storage Process and Its Heating Application Design

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Rickard Erlund

2018-01-01

Full Text Available First ideas of applications design using magnesium (hydro carbonates mixed with silica gel for day/night and seasonal thermal energy storage are presented. The application implies using solar (or another heat source for heating up the thermal energy storage (dehydration unit during daytime or summertime, of which energy can be discharged (hydration during night-time or winter. The applications can be used in small houses or bigger buildings. Experimental data are presented, determining and analysing kinetics and operating temperatures for the applications. In this paper the focus is on the hydration part of the process, which is the more challenging part, considering conversion and kinetics. Various operating temperatures for both the reactor and the water (storage tank are tested and the favourable temperatures are presented and discussed. Applications both using ground heat for water vapour generation and using water vapour from indoor air are presented. The thermal energy storage system with mixed nesquehonite (NQ and silica gel (SG can use both low (25–50% and high (75% relative humidity (RH air for hydration. The hydration at 40% RH gives a thermal storage capacity of 0.32 MJ/kg while 75% RH gives a capacity of 0.68 MJ/kg.

Studies of physicochemical properties of graphite oxide and thermally exfoliated/reduced graphene oxide

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Drewniak Sabina Elżbieta

2015-12-01

Full Text Available The aim of the experimental research studies was to determine some electrical properties of graphite oxide and thermally exfoliated/reduced graphene oxide. The authors tried to interpret the obtained physicochemical results. For that purpose, both resistance measurements and investigation studies were carried out in order to characterize the samples. The resistance was measured at various temperatures in the course of composition changes of gas atmospheres (which surround the samples. The studies were also supported by such methods as: scanning electron microscopy (SEM, Raman spectroscopy (RS, atomic force microscopy (AFM and thermogravimetry (TG. Moreover, during the experiments also the elemental analyses (EA of the tested samples (graphite oxide and thermally exfoliated/reduced graphene oxide were performed.

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

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Zimei Chen

2018-03-01

Full Text Available 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.

Role of high-temperature creep stress in thermally grown oxide growth of thermal barrier coatings

Energy Technology Data Exchange (ETDEWEB)

Ogawa, K.; Nakao, Y.; Seo, D.; Miura, H.; Shoji, T. [Tohoku Univ., Sendai (Japan)

2008-07-01

Thermally grown oxide (TGO) grows at the top / bond coating interface of the thermal barrier coating (TBC) in service. It is supposed that the failures of the TBC occur due to thermal stress and the decrease of adhesive strength caused by the TGO growth. Recently, large local stress has been found to change both the diffusion constant of oxygen through an existing oxide and the rate of chemical reaction at the oxide / oxidized material interface. Since high thermal stress occurs in the TBC, the volume expansion of the newly grown oxide, and centrifugal force, the growth rate of the TGO may change depending on not only temperature but also the stress. The aim of this study is to make clear the influence of stress on the growth rate of the TGO quantitatively. As a result, the thickness of the TGO clearly increases with increase of the amplitude of the applied stress and temperature. The increase rate of the TGO thickness is approximately 23% when the applied stress is increased from 0 to 205 MPa at 900 C, and approximately 29% when the stress is increased from 0 to 150 MPa at 950 C. (orig.)

Composite Materials for Thermal Energy Storage: Enhancing Performance through Microstructures

Science.gov (United States)

Ge, Zhiwei; Ye, Feng; Ding, Yulong

2014-01-01

Chemical incompatibility and low thermal conductivity issues of molten-salt-based thermal energy storage materials can be addressed by using microstructured composites. Using a eutectic mixture of lithium and sodium carbonates as molten salt, magnesium oxide as supporting material, and graphite as thermal conductivity enhancer, the microstructural development, chemical compatibility, thermal stability, thermal conductivity, and thermal energy storage performance of composite materials are investigated. The ceramic supporting material is essential for preventing salt leakage and hence provides a solution to the chemical incompatibility issue. The use of graphite gives a significant enhancement on the thermal conductivity of the composite. Analyses suggest that the experimentally observed microstructural development of the composite is associated with the wettability of the salt on the ceramic substrate and that on the thermal conduction enhancer. PMID:24591286

Precipitation of iron (III) using magnesium oxide in fluidized bed; Precipitacion de hierro (III) utilizando oxido de magnesio en lecho fluidizado

Energy Technology Data Exchange (ETDEWEB)

Esteban-Bocardo, P. A.; Ferreira-Rocha, S. D.

2006-07-01

A process for iron (III) removal by hydroxide precipitation from and acid synthetic inorganic effluent using magnesium oxide as an alternative precipitant agent in a fluidized bed was developed. An acid synthetic inorganic effluent containing 100 and 200 mg/l of ferric ions (pH=1.0) was continuously fed up to the acrylic column (30 cm high and 2 cm diameter) during 180 minutes. Magnesium oxide pulp (3% v/v) was injected at the beginning of the experiment in order to allow the iron hydroxides precipitation. The concentration and pH profiles agreed in their curves, while the pH profile rose,the concentration profile decreased and a high percentage of iron removal (higher to 99%) was reached. Extremely low iron concentrations have been reached, thus permitting to attend to the environmental standard of 10.0 mg/l for discharge of effluent containing ferric ions established by the law DN 10/86 of COPAM (Conselho de Politica Ambiental do Estado de Minas Gerais-Brazil). (Author)

Energy density enhancement of chemical heat storage material for magnesium oxide/water chemical heat pump

International Nuclear Information System (INIS)

Myagmarjav, Odtsetseg; Zamengo, Massimiliano; Ryu, Junichi; Kato, Yukitaka

2015-01-01

A novel candidate chemical heat storage material having higher reaction performance and higher thermal conductivity used for magnesium oxide/water chemical heat pump was developed in this study. The material, called EML, was obtained by mixing pure Mg(OH)_2 with expanded graphite (EG) and lithium bromide (LiBr), which offer higher thermal conductivity and reactivity, respectively. With the aim to achieve a high energy density, the EML composite was compressed into figure of the EML tablet (ϕ7.1 mm × thickness 3.5 mm). The compression force did not degrade the reaction conversion, and furthermore it enabled us to achieve best heat storage and output performances. The EML tablet could store heat of 815.4 MJ m_t_a_b"−"3 at 300 °C within 120 min, which corresponded to almost 4.4 times higher the heat output of the EML composite, and therefore, the EML tablet is the solution which releases more heat in a shorter time. A relatively larger volumetric gross heat output was also recorded for the EML tablet, which was greater than one attained for the EML composite at certain temperatures. As a consequence, it is expected that the EML tablet could respond more quickly to sudden demand of heat from users. It was concluded that the EML tablet demonstrated superior performances. - Highlights: • A new chemical heat storage material, donated as EML, was developed. • EML composite made from pure Mg(OH)_2, expanded graphite and lithium bromide. • EML tablet was demonstrated by compressing the EML composite. • Compression force did not degrade the conversion in dehydration and hydration. • EML tablet demonstrated superior heat storage and output performances.

Magnesium Borate Synthesis by Microwave Energy: A New Method

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Azmi Seyhun Kipcak

2013-01-01

Full Text Available Magnesium borates are one of the major groups of boron minerals that have important properties such as high heat and corrosion resistances and high coefficients of elasticity. In this study, magnesium borate minerals are synthesized using boric acid and magnesium oxide with a new method of microwave, and the synthesized minerals are characterized by various analysis techniques. The results show that pure, “magnesium borate hydrate” minerals are obtained at the end of various steps. The characterization of the products is determined with the techniques of X-Ray Diffraction (XRD, Fourier Transform Infrared Spectroscopy (FT-IR, Raman Spectroscopy, and Scanning Electron Microscopy (SEM. Additionally, overall “magnesium borate hydrate” yields are calculated and found about 67% at 270 W, 8 minutes and 360 W, 3 minutes of reaction times, respectively.

Corrosion and protection of magnesium alloys

Energy Technology Data Exchange (ETDEWEB)

Ghali, E. [Laval Univ., Quebec City, PQ (Canada). Dept. of Mining and Metallurgy

2000-07-01

The oxide film on magnesium offers considerable surface protection in rural and some industrial environments and the corrosion rate lies between that of aluminum and low carbon steels. Galvanic coupling of magnesium alloys, high impurity content such as Ni, Fe, Cu and surface contamination are detrimental for corrosion resistance of magnesium alloys. Alloying elements can form secondary particles which are noble to the Mg matrix, thereby facilitating corrosion, or enrich the corrosion product thereby possibly inhibiting the corrosion rate. Bimetallic corrosion resistance can be increased by fluxless melt protection, choice of compatible alloys, insulating materials, and new high-purity alloys. Magnesium is relatively insensible to oxygen concentration. Pitting, corrosion in the crevices, filiform corrosion are observed. Granular corrosion of magnesium alloys is possible due to the cathodic grain-boundary constituent. More homogeneous microstructures tend to improve corrosion resistance. Under fatigue loading conditions, microcrack initiation in Mg alloys is related to slip in preferentially oriented grains. Coating that exclude the corrosive environments can provide the primary defense against corrosion fatigue. Magnesium alloys that contain neither aluminum nor zinc are the most SCC resistant. Compressive surface residual stresses as that created by short peening increase SCC resistance. Cathodic polarization or cladding with a SCC resistant sheet alloy are good alternatives. Effective corrosion prevention for magnesium alloy components and assemblies should start at the design stage. Selective surface preparation, chemical treatment and coatings are recommended. Oil application, wax coating, anodizing, electroplating, and painting are possible alternatives. Recently, it is found that a magnesium hydride layer, created on the magnesium surface by cathodic charging in aqueous solution is a good base for painting. (orig.)

Hydrophilic Graphene Preparation from Gallic Acid Modified Graphene Oxide in Magnesium Self-Propagating High Temperature Synthesis Process

Science.gov (United States)

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 Magnesium Borates on the Fire-Retarding Properties of Zinc Borates

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Azmi Seyhun Kipcak

2014-01-01

Full Text Available Magnesium borate (MB is a technical ceramic exhibiting high heat resistance, corrosion resistance, great mechanical strength, great insulation properties, lightweightness, high strength, and a high coefficient of elasticity. Zinc borate (ZB can be used as a multifunctional synergistic additive in addition to flame retardant additives in polymers. In this study, the raw materials of zinc oxide (ZnO, magnesium oxide (MgO, and boric acid (H3BO3 were used in the mole ratio of 1 : 1 : 9, which was obtained from preexperiments. Using the starting materials, hydrothermal synthesis was applied, and characterisation of the products was performed using X-Ray diffraction (XRD and Fourier transform infrared (FT-IR and Raman spectroscopies. The forms of Zn3B6O12·3.5H2O, MgO(B2O33·7(H2O, and Mg2(B6O7(OH62·9(H2O were synthesised successfully. Moreover, the surface morphology was investigated using scanning electron microscopy (SEM, and the B2O3 content was determined. In addition, the reaction yields were calculated. The results of the B2O3 content analysis were in compliance with the literature values. Examination of the SEM images indicated that the obtained nanoscale minerals had a reaction efficiency ranging between 63–74% for MB and 87–98% for ZB. Finally, the fire-retarding properties of the synthesised pure MBs, pure ZBs, and mixtures of MB and ZB were determined using differential thermal analysis and thermal gravimetry (DTA-TG and differential scanning calorimetry (DSC.

Interdiffusion of the aluminum magnesium system. Quantitative analysis and numerical model; Interdiffusion des Aluminium-Magnesium-Systems. Quantitative Analyse und numerische Modellierung

Energy Technology Data Exchange (ETDEWEB)

Seperant, Florian

2012-03-21

Aluminum coatings are a promising approach to protect magnesium alloys against corrosion and thereby making them accessible to a variety of technical applications. Thermal treatment enhances the adhesion of the aluminium coating on magnesium by interdiffusion. For a deeper understanding of the diffusion process at the interface, a quantitative description of the Al-Mg system is necessary. On the basis of diffusion experiments with infinite reservoirs of aluminum and magnesium, the interdiffusion coefficients of the intermetallic phases of the Al-Mg-system are calculated with the Sauer-Freise method for the first time. To solve contradictions in the literature concerning the intrinsic diffusion coefficients, the possibility of a bifurcation of the Kirkendall plane is considered. Furthermore, a physico-chemical description of interdiffusion is provided to interpret the observed phase transitions. The developed numerical model is based on a temporally varied discretization of the space coordinate. It exhibits excellent quantitative agreement with the experimentally measured concentration profile. This confirms the validity of the obtained diffusion coefficients. Moreover, the Kirkendall shift in the Al-Mg system is simulated for the first time. Systems with thin aluminum coatings on magnesium also exhibit a good correlation between simulated and experimental concentration profiles. Thus, the diffusion coefficients are also valid for Al-coated systems. Hence, it is possible to derive parameters for a thermal treatment by simulation, resulting in an optimized modification of the magnesium surface for technical applications.

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

Science.gov (United States)

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 poly(lactide) stereocomplex structure with modified magnesium oxide and its effects in enhancing the mechanical properties and suppressing inflammation.

Science.gov (United States)

Kum, Chang Hun; Cho, Youngjin; Seo, Seong Ho; Joung, Yoon Ki; Ahn, Dong June; Han, Dong Keun

2014-09-24

Biodegradable polymers such as poly(L-lactide) (PLLA) have been widely utilized as materials for biomedical applications. However, the relatively poor mechanical properties of PLLA and its acid-induced cell inflammation brought about by the acidic byproducts during biodegradation pose severe problems. In this study, these drawbacks of PLLA are addressed using a stereocomplex structure, where oligo-D-lactide-grafted magnesium hydroxide (MgO-ODLA) is synthesized by grafting d-lactide onto the surface of magnesium hydroxide, which is then blended with a PLLA film. The structure, morphology, pH change, thermal and mechanical properties, in-vitro cytotoxicity, and inflammation effect of the MgO-ODLAs and their PLLA composites are evaluated through various analyses. The PLLA/MgO70-ODLA30 (0-20 wt%) composite with a stereocomplex structure shows a 20% increase in its tensile strength and an improvement in the modulus compared to its oligo-L-lactide (PLLA/MgO70-OLLA30) counterpart. The interfacial interaction parameter of PLLA/MgO70-ODLA30 (5.459) has superior properties to those of PLLA/MgO70-OLLA30 (4.013) and PLLA/Mg(OH)2 (1.774). The cell cytotoxicity and acid-induced inflammatory response are suppressed by the neutralizing effect of the MgO-ODLAs. In addition, the inflammatory problem caused by the rapid acidification of the stereocomplex structure is also addressed. As a result, the stereocomplex structure of the MgO-ODLA/PLLA composite can be used to overcome the problems associated with the biomedical applications of PLLA films. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of oral magnesium supplementation on inflammatory markers in middle-aged overweight women

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Nazanin Moslehi

2012-01-01

Full Text Available Background: This study aimed to investigate whether magnesium supplementation might affect serum magnesium, high sensitive C-reactive protein (hs-CRP, plasma fibrinogen, and interleukin 6 (IL-6 levels in healthy middle-aged overweight women. The relationships, if any, between serum magnesium and the inflammatory markers were also examined cross-sectionally in the entire participants at the beginning of the study. Materials and Methods: This double-blinded, placebo-controlled, randomized trial included 74 middle-aged overweight women. Participants were randomly assigned to receive either 250 mg magnesium as magnesium oxide or placebo daily for 8 weeks. Serum magnesium, hs-CRP, fibrinogen and IL-6 concentrations were measured before and after the intervention. Results: Serum magnesium was found to be inversely correlated with hs-CRP (r s =−0.22, P=0.05 in the entire participants at baseline. Serum hs-CRP declined significantly in both groups as compared with baseline values (median change=0.8 mg/L; P Magnesium= 0.03, P Placebo 0.001. Plasma fibrinogen decreased significantly, by 9%, in the magnesium group at the end of week 8 compared to baseline (P=0.001. Mean concentration of IL-6 was significantly increased in the magnesium group comparing the baseline value(P=0.001. However hs-CRP, fibrinogen and IL-6 levels at week 8 or any changes during the study were not statistically different between the two groups. Serum magnesium showed no significant changes in any groups. Conclusions: Serum magnesium had a significant inverse correlation with hs-CRP. In the present study, magnesium as magnesium oxide, 250 mg/day, for 8 weeks did not significantly attenuate inflammatory markers in the magnesium group as compared to the placebo.

Interfacial Reaction Characteristics and Mechanical Properties of Welding-brazing Bonding Between AZ31B Magnesium Alloy and PRO500 Ultra-high Strength Steel

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CHEN Jian-hua

2017-11-01

Full Text Available Experiments were carried out with TIG welding-brazing of AZ31B magnesium alloy to PRO500 steel using TIG arc as heat source. The interfacial reaction characteristics and mechanical properties of the welding-brazing bonding were investigated. The results show that an effective bonding is achieved between AZ31B magnesium alloy and PRO500 steel by using TIG welding-brazing method. Some spontaneous oxidation reactions result in the formation of a transition zone containing AlFe3 phase with rich oxide. The micro-hardness value of the interfacial transition zone is between that of the AZ31B and the PRO500. Temper softening zone appears due to the welding thermal cycle nearby the bonding position in the interface. A higher heat input makes an increase of the brittle phases and leads to an obvious decrease of the bonding strength.

Method of manufacturing a thermally insulating body

Energy Technology Data Exchange (ETDEWEB)

McWilliams, J.A.; Morgan, D.E.; Jackson, J.D.

1988-10-11

A method of manufacturing a microporous thermally insulating body comprises mixing together a finely divided microporous insulating material such as silica aerogel or pyrogenic silica and a solid ammonia-generating compound in particulate form, and compressing the mixture to form a thermally insulating body. The ammonia-generating compound is dispersed evenly throughout the insulating material and may comprise, for example, ammonium carbonate, ammonium acetate or urea. Preferably, the ammonia-generating compound comprises a mixture of about one third by weight of ammonium carbonate and about two thirds by weight of ammonium bicarbonate together with a small proportion of magnesium oxide. Experiments are described which illustrate the manufacturing process. 6 tabs.

Thermal System Modeling for Lunar and Martian Surface Regenerative Fuel Cell Systems

Science.gov (United States)

Gilligan, Ryan Patrick; Smith, Phillip James; Jakupca, Ian Joseph; Bennett, William Raymond; Guzik, Monica Christine; Fincannon, Homer J.

2017-01-01

The Advanced Exploration Systems (AES) Advanced Modular Power Systems (AMPS) Project is investigating different power systems for various lunar and Martian mission concepts. The AMPS Fuel Cell (FC) team has created two system-level models to evaluate the performance of regenerative fuel cell (RFC) systems employing different fuel cell chemistries. Proton Exchange Membrane fuel cells PEMFCs contain a polymer electrolyte membrane that separates the hydrogen and oxygen cavities and conducts hydrogen cations (protons) across the cell. Solid Oxide fuel cells (SOFCs) operate at high temperatures, using a zirconia-based solid ceramic electrolyte to conduct oxygen anions across the cell. The purpose of the modeling effort is to down select one fuel cell chemistry for a more detailed design effort. Figures of merit include the system mass, volume, round trip efficiency, and electrolyzer charge power required. PEMFCs operate at around 60 degrees Celsius versus SOFCs which operate at temperatures greater than 700 degrees Celsius. Due to the drastically different operating temperatures of the two chemistries the thermal control systems (TCS) differ. The PEM TCS is less complex and is characterized by a single pump cooling loop that uses deionized water coolant and rejects heat generated by the system to the environment via a radiator. The solid oxide TCS has its own unique challenges including the requirement to reject high quality heat and to condense the steam produced in the reaction. This paper discusses the modeling of thermal control systems for an extraterrestrial RFC that utilizes either a PEM or solid oxide fuel cell.

Multidimensional flow, thermal, and chemical behavior in solid-oxide fuel cell button cells

Energy Technology Data Exchange (ETDEWEB)

Goldin, Graham M. [Ansys Incorporated, 10 Cavendish Ct., Centerra Resource Park, Lebanon, NH 03766 (United States); Zhu, Huayang; Kee, Robert J. [Engineering Division, Colorado School of Mines, Golden, CO 80401 (United States); Bierschenk, David; Barnett, Scott A. [Materials Science, Northwestern University, Evanston, IL 60208 (United States)

2009-02-01

The quantitative analysis and interpretation of button-cell experiments usually depends upon assuming isothermal conditions together with uniform and known gas composition within the gas compartments. An objective of the present effort is to develop computational tools to study the validity of such assumptions. A three-dimensional computational fluid dynamics (CFD) model is developed and applied to a particular SOFC button cell, characterizing the fluid flow, chemistry, and thermal transport. Results show that when inlet flow rates are sufficiently high, button-cell data can be interpreted using the commonly used assumptions. However, when flow rates are not sufficient, the assumptions of uniform composition can be significantly violated. Additionally, depending on operating conditions there can be significant temperature variations within the gas compartments and the membrane-electrode assembly. (author)

Thermal oxidation of III-V compounds

International Nuclear Information System (INIS)

Monteiro, O.R.; Evans, J.W.

1988-01-01

The thermal oxidation of two important III-V compound semiconductor materials, namely GaAs and InP, has been studied between 300 and 600 0 C. In-situ TEM, cross-sectional TEM (XTEM) and SIMS analyses were used to characterize the reaction products. The first technique allows us to access the reactions at the very moment they are occurring. XTEM provides a clearer picture of the distribution of phases in the oxidized samples. SIMS gives us information on the dopant redistribution after oxidation as well as enrichment of group V element at the oxide semiconductor interface. Based on those results, the reaction products were characterized and reaction mechanisms proposed

Impurity characterization of magnesium diuranate using simultaneous TG–DTA–FTIR measurements

Energy Technology Data Exchange (ETDEWEB)

Raje, Naina, E-mail: nraje@barc.gov.in [Analytical Chemistry Division, B.A.R.C., Mumbai 400 085 (India); Ghonge, Darshana K. [Analytical Chemistry Division, B.A.R.C., Mumbai 400 085 (India); Hemantha Rao, G.V.S. [NFC, ECIL Post, Hyderabad (India); Reddy, A.V.R. [Analytical Chemistry Division, B.A.R.C., Mumbai 400 085 (India)

2013-05-15

Current studies describe the application of simultaneous thermogravimetry–differential thermal analysis – evolved gas analysis techniques for the compositional characterization of magnesium diuranate (MDU) with respect to the impurities present in the matrix. The stoichiometric composition of MDU was identified as MgU{sub 2}O{sub 7}⋅3H{sub 2}O. Presence of carbonate and sulphate as impurities in the matrix was confirmed through the evolved gas analysis using Fourier Transformation Infrared Spectrometry detection. Carbon and magnesium hydroxide content present as impurities in magnesium diuranate have been determined quantitatively using TG and FTIR techniques and the results are in good agreement. Powder X-ray diffraction analysis of magnesium diuranate suggests the presence of magnesium hydroxide as impurity in the matrix. Also these studies confirm the formation of magnesium uranate, uranium sesquioxide and uranium dioxide above 1000 °C, due to the decomposition of magnesium diuranate.

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

International Nuclear Information System (INIS)

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

2012-01-01

Highlights: ► The MgO ceramic coating has been prepared on the surface of AZ31 magnesium alloy by plasma electrolytic oxidation in the borax-doped silicate system. ► Boron element exists in the PEO films in the form of noncrystal. ► The microhardness and compactness of doped ceramic coating are much higher than that of the substrate and undoped ceramic coating, and this doped coated sample shows better wear-resisting property. - Abstract: 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.

Improved cytotoxicity testing of magnesium materials

Energy Technology Data Exchange (ETDEWEB)

Fischer, Janine [Helmholtz-Zentrum Geesthacht, Institute of Materials Research, Department for Structural Research on Macromolecules, Max-Planck Str. 1, D - 21502 Geesthacht (Germany); Proefrock, Daniel [Helmholtz-Zentrum Geesthacht, Institute for Coastal Research, Department for Marine Bioanalytical Chemistry, Max-Planck Str. 1, D - 21502 Geesthacht (Germany); Hort, Norbert [Helmholtz-Zentrum Geesthacht, Institute of Materials Research, Department for Magnesium Processing, Max-Planck Str. 1, D - 21502 Geesthacht (Germany); Willumeit, Regine; Feyerabend, Frank [Helmholtz-Zentrum Geesthacht, Institute of Materials Research, Department for Structural Research on Macromolecules, Max-Planck Str. 1, D - 21502 Geesthacht (Germany)

2011-06-25

Metallic magnesium (Mg) and its alloys are highly suitable for medical applications as biocompatible and biodegradable implant materials. Magnesium has mechanical properties similar to bone, stimulates bone regeneration, is an essential non-toxic element for the human body and degrades completely within the body environment. In consequence, magnesium is a promising candidate as implant material for orthopaedic applications. Protocols using the guideline of current ISO standards should be carefully evaluated when applying them for the characterization of the cytotoxic potential of degradable magnesium materials. For as-cast material we recommend using 10 times more extraction medium than recommended by the ISO standards to obtain reasonable results for reliable cytotoxicity rankings of degradable materials in vitro. In addition primary isolated human osteoblasts or mesenchymal stem cells should be used to test magnesium materials.

Improved cytotoxicity testing of magnesium materials

International Nuclear Information System (INIS)

Fischer, Janine; Proefrock, Daniel; Hort, Norbert; Willumeit, Regine; Feyerabend, Frank

2011-01-01

Metallic magnesium (Mg) and its alloys are highly suitable for medical applications as biocompatible and biodegradable implant materials. Magnesium has mechanical properties similar to bone, stimulates bone regeneration, is an essential non-toxic element for the human body and degrades completely within the body environment. In consequence, magnesium is a promising candidate as implant material for orthopaedic applications. Protocols using the guideline of current ISO standards should be carefully evaluated when applying them for the characterization of the cytotoxic potential of degradable magnesium materials. For as-cast material we recommend using 10 times more extraction medium than recommended by the ISO standards to obtain reasonable results for reliable cytotoxicity rankings of degradable materials in vitro. In addition primary isolated human osteoblasts or mesenchymal stem cells should be used to test magnesium materials.

Investigation of Combination Effect of Magnesium Oxide and Iron Oxide Nanoparticles on the Growth And Morphology of the Bacteria Staphylococcus Aureus and Escherichia Coli in Juice

Directory of Open Access Journals (Sweden)

mahdi torabi zarchi

2017-02-01

Full Text Available Introduction: Nanoparticles (NPs are one of the antibacterial substances, among them nanoparticles type MgO and Fe2O3 are less toxic to mammalian cells. So, the aim of this study was investigation of combination effects of iron oxide and magnesium oxide nanoparticles on the growth of Staphylococcus aureus and Escherichia coli (E.coli to achieve the optimum combination of nanoparticles inhibit the growth of Staphylococcus aureus and Escherichia coli in food (juice. Methods: In this experimental research, the effect of MgO and Fe2O3 Nanoparticles compound on Staphylococcus aureus and Escherichia coli bacteria in liquid environment was investigated, and then their effect was investigated separately in juices of carrot, pomegranate and apple via colony count approach. Also, scanning electron microscopy was used to characterize the morphological changes of Staphylococcus aureus and Escherichia coli after antimicrobial treatments. The results of the research were analyzed using one way ANNOVA. Results: The results of the research indicated that in liquid medium, these nanoparticles lead to reduce the growth of both bacteria. compound of 1.5Mg+0.5Fe2O3 was introduced as the most appropriate antibacterial compounds; Staphylococcus aureus sensitivity to Escherichia coli was higher against nanoparticles. The findings of research about the juices revealed that the combined effect of nanoparticles reduced the growth of both bacteria. the combined effect of Fe2o3 and MgO nanoparticles treatments distorted and damaged the cell membrane, resulting in a leakage of intracellular contents and eventually the death of bacterial cells. Conclusion: Nanoparticles in the allowed concentrations have significant effect on Staphylococcus aureus and Escherichia coli bacteria.

Achieving excellent thermal stability and very high activation energy in an ultrafine-grained magnesium silver rare earth alloy prepared by friction stir processing

Energy Technology Data Exchange (ETDEWEB)

Khan MD, F. [Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600036 (India); Panigrahi, S.K., E-mail: skpanigrahi@iitm.ac.in [Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600036 (India)

2016-10-15

Ultrafine-grained microstructure of a QE22 alloy prepared by Friction Stir processing (FSP) is isochronally annealed to study the thermal stability and grain growth kinetics. The FSPed microstructure of QE22 alloy is thermally stable under ultrafine-grained regime up to 300 °C and the activation energy required for grain growth is found to be exceptionally high as compared to conventional ultrafine-grained magnesium alloys. The high thermal stability and activation energy of the FSPed QE22 alloy is due to Zener pinning effect from thermally stable eutectic Mg{sub 12}Nd and fine precipitates Mg{sub 12}Nd{sub 2}Ag and solute drag effect from segregation of Neodymium (Nd) solute atoms at grain boundaries.

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

Science.gov (United States)

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.

Composite materials for thermal energy storage: enhancing performance through microstructures.

Science.gov (United States)

Ge, Zhiwei; Ye, Feng; Ding, Yulong

2014-05-01

Chemical incompatibility and low thermal conductivity issues of molten-salt-based thermal energy storage materials can be addressed by using microstructured composites. Using a eutectic mixture of lithium and sodium carbonates as molten salt, magnesium oxide as supporting material, and graphite as thermal conductivity enhancer, the microstructural development, chemical compatibility, thermal stability, thermal conductivity, and thermal energy storage performance of composite materials are investigated. The ceramic supporting material is essential for preventing salt leakage and hence provides a solution to the chemical incompatibility issue. The use of graphite gives a significant enhancement on the thermal conductivity of the composite. Analyses suggest that the experimentally observed microstructural development of the composite is associated with the wettability of the salt on the ceramic substrate and that on the thermal conduction enhancer. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Corrosion of magnesium and some magnesium alloys in gas cooled reactors; Corrosion du magnesium et de certains de ses alliages dans les piles refroidies par gaz

Energy Technology Data Exchange (ETDEWEB)

Caillat, R; Darras, R [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1958-07-01

The results of corrosion tests on magnesium and some magnesium alloys (Mg-Zr and Mg-Zr-Zn) in moist air (like G1 reactor) and in CO{sub 2}: (like G2, G3, EDF1 reactors) are reported. The maximum temperature for exposure of magnesium to moist air without any risk of corrosion is 350 deg. C. Indeed, the oxidation rate follows a linear law above 350 deg. C although it reaches a constant level and keeps on very low under 350 deg. C. However, as far as corrosion is concerned this temperature limit can be raised up to 500 deg. C if moist air is very slightly charged with fluorinated compounds. Under pressure of CO{sub 2}, these three materials oxidate much more slowly even if 500 deg. C is reached. The higher is the temperature, the higher is the constant level of the weight increase and the quicker is reached this one. However, Mg-Zr alloy behaves quite better than pure magnesium and especially than Mg-Zr-Zn alloy. (author)Fren. [French] On expose essentiellement les resultats d'etudes sur la corrosion du magnesium et de certains de ses alliages (Mg-Zr et Mg-Zr-Zn) dans l'air humide (cas de la pile G1) et dans le gaz carbonique (cas des piles G2, G3, EDF1, etc...). La temperature limite d'exposition du magnesium dans l'air humide sans risque de corrosion se situe a 350 deg. C; en effet l'oxydation a un caractere lineaire au-dessus de cette temperature, alors qu'elle atteint un palier et reste tres limitee au-dessous de 350 deg. C. Du point de vue de la corrosion, cette temperature limite d'emploi peut cependant etre elevee jusqu'a 500 deg. C si l'on introduit dans l'air humide de tres faibles teneurs de composes fluores. Dans le gaz carbonique sous pression, l'oxydation est beaucoup plus faible, meme jusqu'a 50g. C pour les trois materiaux: l'augmentation de poids atteint un palier d'autant plus eleve et ceci d'autant plus rapidement que la temperature est elle-meme plus elevee. Cependant, l'alliage Mg-Zr se comporte nettement mieux que le magnesium pur et surtout que l

Corrosion of magnesium and some magnesium alloys in gas cooled reactors; Corrosion du magnesium et de certains de ses alliages dans les piles refroidies par gaz

Energy Technology Data Exchange (ETDEWEB)

Caillat, R.; Darras, R. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1958-07-01

The results of corrosion tests on magnesium and some magnesium alloys (Mg-Zr and Mg-Zr-Zn) in moist air (like G1 reactor) and in CO{sub 2}: (like G2, G3, EDF1 reactors) are reported. The maximum temperature for exposure of magnesium to moist air without any risk of corrosion is 350 deg. C. Indeed, the oxidation rate follows a linear law above 350 deg. C although it reaches a constant level and keeps on very low under 350 deg. C. However, as far as corrosion is concerned this temperature limit can be raised up to 500 deg. C if moist air is very slightly charged with fluorinated compounds. Under pressure of CO{sub 2}, these three materials oxidate much more slowly even if 500 deg. C is reached. The higher is the temperature, the higher is the constant level of the weight increase and the quicker is reached this one. However, Mg-Zr alloy behaves quite better than pure magnesium and especially than Mg-Zr-Zn alloy. (author)Fren. [French] On expose essentiellement les resultats d'etudes sur la corrosion du magnesium et de certains de ses alliages (Mg-Zr et Mg-Zr-Zn) dans l'air humide (cas de la pile G1) et dans le gaz carbonique (cas des piles G2, G3, EDF1, etc...). La temperature limite d'exposition du magnesium dans l'air humide sans risque de corrosion se situe a 350 deg. C; en effet l'oxydation a un caractere lineaire au-dessus de cette temperature, alors qu'elle atteint un palier et reste tres limitee au-dessous de 350 deg. C. Du point de vue de la corrosion, cette temperature limite d'emploi peut cependant etre elevee jusqu'a 500 deg. C si l'on introduit dans l'air humide de tres faibles teneurs de composes fluores. Dans le gaz carbonique sous pression, l'oxydation est beaucoup plus faible, meme jusqu'a 50g. C pour les trois materiaux: l'augmentation de poids atteint un palier d'autant plus eleve et ceci d'autant plus rapidement que la temperature est elle-meme plus elevee. Cependant, l

The potential for ionic liquid electrolytes to stabilise the magnesium interface for magnesium/air batteries

International Nuclear Information System (INIS)

Khoo, Timothy; Howlett, Patrick C.; Tsagouria, Maureen; MacFarlane, Douglas R.; Forsyth, Maria

2011-01-01

Magnesium/air batteries are a possible high-energy density power source that, to date, have not received strong commercial interest due to issues with the corrosion of the magnesium and evaporation of the electrolyte. In this work we report on the use of ionic liquid based electrolytes to stabilise the metal/electrolyte interface and their impact on the electrochemical performance. Galvanostatic measurements indicate that the water content of the ionic liquid electrolyte plays an important role in the cell discharge characteristics. Surface characterisation using EIS, ATR-FTIR and powder diffraction examined the unique properties of the surface film formed on the magnesium anode.

Tribological Behaviour of the Ceramic Coating Formed on Magnesium Alloy

International Nuclear Information System (INIS)

Chen Fei; Zhou Hai; Chen Qiang; Ge Yuanjing; Lv Fanxiu

2007-01-01

Micro-arc oxidation is a recently developed surface treatment technology under anodic oxidation. Through micro-arc oxidation, a ceramic coating is directly formed on the surface of magnesium alloy, by which its surface property is significantly improved. In this paper, a dense ceramic oxide coating was prepared on an AZ31 magnesium alloy by micro-arc oxidation in a NaOH-Na 2 SiO 3 -NaB 4 O 7 -(NaPO 3 ) 6 electrolytic solution. Micro-structure, surface morphology and phase composition were analysed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The tribological behavior of the micro-arc oxidation ceramic coating under dry sliding against GCr15 steel was evaluated on a ball-on-disc test rig. The results showed that the AZ31 alloy was characterized by adhesion wear and scuffing under dry sliding against the steel, while the surface micro-arc oxidation ceramic coating experienced much abated adhesion wear and scuffing under the same testing conditions. The micro-arc oxidation ceramic coating showed good friction-reducing and fair antiwear ability in dry sliding against the steel

Influence of 8-hydroxyquinoline on properties of anodic coatings obtained by micro arc oxidation on AZ91 magnesium alloys

Energy Technology Data Exchange (ETDEWEB)

Zhang, R.F. [Jiangxi Key Laboratory of Surface Engineering, Jiangxi Science and Technology Normal University, Nanchang 330013 (China); School of Material Science and Engineering, Jiangxi Science and Technology Normal University, Nanchang 330013 (China); Zhang, S.F., E-mail: zhangshufang790314@sina.com [Jiangxi Key Laboratory of Surface Engineering, Jiangxi Science and Technology Normal University, Nanchang 330013 (China); School of Material Science and Engineering, Jiangxi Science and Technology Normal University, Nanchang 330013 (China); Yang, N.; Yao, L.J.; He, F.X.; Zhou, Y.P.; Xu, X.; Chang, L.; Bai, S.J. [School of Material Science and Engineering, Jiangxi Science and Technology Normal University, Nanchang 330013 (China)

2012-10-25

Highlights: Black-Right-Pointing-Pointer 8-HQ can promote the coating formation and change the coating color. Black-Right-Pointing-Pointer 8-HQ can increase the coating thickness and decrease the pore size. Black-Right-Pointing-Pointer Insoluble Mg(HQ){sub 2} is formed in anodic coatings in an alkaline solution with 8-HQ. Black-Right-Pointing-Pointer 8-HQ improves the corrosion resistance of the anodized magnesium alloys. - Abstract: The influence of 8-hydroxyquinoline (8-HQ) on formation and properties of anodic coatings obtained by micro arc oxidation (MAO) on AZ91 magnesium alloys was studied by scanning electron microscope (SEM), energy dispersive spectrometry (EDS), Fourier transform infrared (FT-IR) spectroscopy and potentiodynamic polarization tests. The results demonstrate that 8-HQ can decrease the solution conductivity, take part in the coating formation and change the coating color. By developing anodic coatings with increasing thickness, insoluble Mg(HQ){sub 2} and small pore size, 8-HQ improves the corrosion resistance of the anodized magnesium alloys. The coating shows the best corrosion resistance in the solution of 10 g/L NaOH and 18 g/L Na{sub 2}SiO{sub 3} with 2 g/L 8-HQ.

Magnesium Counteracts Vascular Calcification: Passive Interference or Active Modulation?

Science.gov (United States)

Ter Braake, Anique D; Shanahan, Catherine M; de Baaij, Jeroen H F

2017-08-01

Over the last decade, an increasing number of studies report a close relationship between serum magnesium concentration and cardiovascular disease risk in the general population. In end-stage renal disease, an association was found between serum magnesium and survival. Hypomagnesemia was identified as a strong predictor for cardiovascular disease in these patients. A substantial body of in vitro and in vivo studies has identified a protective role for magnesium in vascular calcification. However, the precise mechanisms and its contribution to cardiovascular protection remain unclear. There are currently 2 leading hypotheses: first, magnesium may bind phosphate and delay calcium phosphate crystal growth in the circulation, thereby passively interfering with calcium phosphate deposition in the vessel wall. Second, magnesium may regulate vascular smooth muscle cell transdifferentiation toward an osteogenic phenotype by active cellular modulation of factors associated with calcification. Here, the data supporting these major hypotheses are reviewed. The literature supports both a passive inorganic phosphate-buffering role reducing hydroxyapatite formation and an active cell-mediated role, directly targeting vascular smooth muscle transdifferentiation. However, current evidence relies on basic experimental designs that are often insufficient to delineate the underlying mechanisms. The field requires more advanced experimental design, including determination of intracellular magnesium concentrations and the identification of the molecular players that regulate magnesium concentrations in vascular smooth muscle cells. © 2017 American Heart Association, Inc.

Corrosion resistance and calcium–phosphorus precipitation of micro-arc oxidized magnesium for biomedical applications

Energy Technology Data Exchange (ETDEWEB)

Zhao, Lichen; Cui, Chunxiang, E-mail: hutcui@hebut.edu.cn; Wang, Xin; Liu, Shuangjin; Bu, Shaojing; Wang, Qingzhou; Qi, Yumin

2015-03-01

Highlights: • Hydroxyapatite (HA) powders were added to the electrolyte. • The HA powders have participated in the formation reactions of MAO coating. • The growth efficiency of MAO coating was greatly enhanced owing to the HA addition. • The specimen anodized in the HA-containing electrolyte has a better corrosion resistance. • The specimen anodized in the HA-containing electrolyte can more efficiently induce Ca–P precipitation. - Abstract: To improve the corrosion resistance of magnesium, micro-arc oxidation (MAO) coatings were prepared on magnesium substrates in an aqueous solution with and without hydroxyapatite (HA) powders addition. The micrographs of scanning electron microscopy (SEM), the energy dispersive spectrometer (EDS) spectra, and X-ray diffraction (XRD) analysis show that the HA powders added into the electrolyte have participated in the formation reactions of MAO coating and the growth efficiency of MAO coating is greatly enhanced. Potentiodynamic polarization tests and immersion tests in simulated body fluid (SBF) confirm that the specimen anodized in the HA-containing electrolyte has a better corrosion resistance than the specimen anodized in the HA-free electrolyte. Immersion tests also indicate that the specimen anodized in the HA-containing electrolyte can more efficiently induce Ca–P precipitation compared with the specimen anodized in the HA-free electrolyte.

Detection of thermally grown oxides in thermal barrier coatings by nondestructive evaluation

Science.gov (United States)

Fahr, A.; Rogé, B.; Thornton, J.

2006-03-01

The thermal-barrier coatings (TBC) sprayed on hot-section components of aircraft turbine engines commonly consist of a partially stabilized zirconia top-coat and an intermediate bond-coat applied on the metallic substrate. The bond-coat is made of an aluminide alloy that at high engine temperatures forms thermally grown oxides (TGO). Although formation of a thin layer of aluminum oxide at the interface between the ceramic top-coat and the bond-coat has the beneficial effect of protecting the metallic substrate from hot gases, oxide formation at splat boundaries or pores within the bond-coat is a source of weakness. In this study, plasma-sprayed TBC specimens are manufactured from two types of bond-coat powders and exposed to elevated temperatures to form oxides at the ceramic-bond-coat boundary and within the bond-coat. The specimens are then tested using nondestructive evaluation (NDE) and destructive metallography and compared with the as-manufactured samples. The objective is to determine if NDE can identify the oxidation within the bond-coat and give indication of its severity. While ultrasonic testing can provide some indication of the degree of bond-coat oxidation, the eddy current (EC) technique clearly identifies severe oxide formation within the bond-coat. Imaging of the EC signals as the function of probe location provides information on the spatial variations in the degree of oxidation, and thereby identifies which components or areas are prone to premature damage.

Behavior of strontium- and magnesium-doped gallate electrolyte in direct carbon solid oxide fuel cells

International Nuclear Information System (INIS)

Zhang, Li; Xiao, Jie; Xie, Yongmin; Tang, Yubao; Liu, Jiang; Liu, Meilin

2014-01-01

Highlights: • La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3−δ (LSGM) can be used as electrolyte of direct carbon SOFCs. • DC-SOFC with LSGM electrolyte gives higher performance than that with YSZ. • LSGM-electrolyte DC-SOFC gives maximum power density of 383 mW cm −2 at 850 °C. • Operation of LSGM-DC-SOFC at 210 mA cm −2 lasts 72 min, with fuel utilization of 60%. - Abstract: Perovskite-type La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3−δ (LSGM) is synthesized by conventional solid state reaction. Its phase composition, microstructure, relative density, and oxygen-ionic conductivity are investigated. Tubular electrolyte-supported solid oxide fuel cells (SOFCs) are prepared with the LSGM as electrolyte and gadolinia doped ceria (GDC) mixed with silver as anode. The SOFCs are operated with Fe-loaded activated carbon as fuel and ambient air as oxidant. A typical single cell gives a maximum power density of 383 mW cm −2 at 850 °C, which is nearly 1.3 times higher than that of the similar cell with YSZ as electrolyte. A stability test of 72 min is carried out at a constant current density of 210 mA cm −2 , with a fuel utilization of 60%, indicating that LaGaO 3 -based electrolyte is promising to be applied in direct carbon SOFCs (DC-SOFCs)

Evaluation of magnesium alloys with alternative surface finishing for the proliferation and chondro-differentiation of human mesenchymal stem cells

International Nuclear Information System (INIS)

Trinidad, J; Arruebarrena, G; De Argandona, E Saenz; De Eguino, G Ruiz; Infante, A; RodrIguez, C I

2010-01-01

Articular cartilage has little capacity for self-repair. As a result, continuous mechanical stress can lead to the degradation of articular cartilage, culminating in progressive damage and joint degeneration. Tissue engineering has arisen as a promising therapeutic approach to cartilage repair. Magnesium alloys are one of the most important metallic biomaterials emerging in this area due to their biocompatibility, bio-absorbability and especially to their mechanical properties. These properties make magnesium alloys a promising biomaterial in the regeneration of cartilage tissue. Objective. This study was undertaken to analyze the influence of surface characteristics of magnesium alloys in the adhesion, proliferation and differentiation of human mesenchymal stem cells (MSCs). Methods. Two commercial magnesium alloys (AZ31B and ZM21) were subjected to different treatments in order to obtain four different surfaces in each alloy. Human MSCs were seeded into the magnesium alloys and analyzed for their proliferation and chondrogenesis differentiation ability. Results. Human MSCs showed a greater proliferation and chondro-differentiation when cultured in the ZM21 magnesium alloy with a surface finishing of fine sanding, polishing, and etching.

Enzymatic, urease-mediated mineralization of gellan gum hydrogel with calcium carbonate, magnesium-enriched calcium carbonate and magnesium carbonate for bone regeneration applications.

Science.gov (United States)

Douglas, Timothy E L; Łapa, Agata; Samal, Sangram Keshari; Declercq, Heidi A; Schaubroeck, David; Mendes, Ana C; der Voort, Pascal Van; Dokupil, Agnieszka; Plis, Agnieszka; De Schamphelaere, Karel; Chronakis, Ioannis S; Pamuła, Elżbieta; Skirtach, Andre G

2017-12-01

Mineralization of hydrogel biomaterials is considered desirable to improve their suitability as materials for bone regeneration. Calcium carbonate (CaCO 3 ) has been successfully applied as a bone regeneration material, but hydrogel-CaCO 3 composites have received less attention. Magnesium (Mg) has been used as a component of calcium phosphate biomaterials to stimulate bone-forming cell adhesion and proliferation and bone regeneration in vivo, but its effect as a component of carbonate-based biomaterials remains uninvestigated. In the present study, gellan gum (GG) hydrogels were mineralized enzymatically with CaCO 3 , Mg-enriched CaCO 3 and magnesium carbonate to generate composite biomaterials for bone regeneration. Hydrogels loaded with the enzyme urease were mineralized by incubation in mineralization media containing urea and different ratios of calcium and magnesium ions. Increasing the magnesium concentration decreased mineral crystallinity. At low magnesium concentrations calcite was formed, while at higher concentrations magnesian calcite was formed. Hydromagnesite (Mg 5 (CO 3 ) 4 (OH) 2 .4H 2 O) formed at high magnesium concentration in the absence of calcium. The amount of mineral formed and compressive strength decreased with increasing magnesium concentration in the mineralization medium. The calcium:magnesium elemental ratio in the mineral formed was higher than in the respective mineralization media. Mineralization of hydrogels with calcite or magnesian calcite promoted adhesion and growth of osteoblast-like cells. Hydrogels mineralized with hydromagnesite displayed higher cytotoxicity. In conclusion, enzymatic mineralization of GG hydrogels with CaCO 3 in the form of calcite successfully reinforced hydrogels and promoted osteoblast-like cell adhesion and growth, but magnesium enrichment had no definitive positive effect. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Mechanism of antioxidant interaction on polymer oxidation by thermal and radiation ageing

International Nuclear Information System (INIS)

Seguchi, Tadao; Tamura, Kiyotoshi; Shimada, Akihiko; Sugimoto, Masaki; Kudoh, Hisaaki

2012-01-01

The mechanism of polymer oxidation by radiation and thermal ageing was investigated for the life evaluation of cables installed in radiation environments. The antioxidant as a stabilizer was very effective for thermal oxidation with a small content in polymers, but was not effective for radiation oxidation. The ionizing radiation induced the oxidation to result in chain scission even at low temperature, because the free radicals were produced and the antioxidant could not stop the oxidation of radicals with the chain scission. A new mechanism of antioxidant effect for polymer oxidation was proposed. The effect of antioxidant was not the termination of free radicals in polymer chains such as peroxy radicals, but was the depression of initial radical formation in polymer chains by thermal activation. The antioxidant molecule was assumed to delocalize the activated energy in polymer chains by the Boltzmann statics (distribution) to result in decrease in the probability of radical formation at a given temperature. The interaction distance (delocalization volume) by one antioxidant molecule was estimated to be 5–10 nm by the radius of sphere in polymer matrix, though the value would depend on the chemical structure of antioxidant. - Highlights: ► Interaction of antioxidant on polymer oxidation is discussed for thermal and radiation ageings. ► Antioxidant is very effective for thermal oxidation, but not for radiation induced oxidation. ► Interaction of antioxidant is not the termination reaction of radicals on polymers. ► Antioxidant is supposed to reduce the provability of polymer radical formation by thermal activation. ► Mechanism of polymer oxidation may not be chain reaction via peroxy radical and hydro-peroxide.

Operation strategy for solid oxide fuel cell systems for small-scale stationary applications

DEFF Research Database (Denmark)

Liso, Vincenzo; Nielsen, Mads Pagh; Kær, Søren Knudsen

2009-01-01

Solid oxide fuel cell micro cogeneration systems have the potential to reduce domestic energy consumption by providing both heat and power on site without transmission losses. The high grade heat produced during the operation of the power causes high thermal transients during startup/shutdown pha......Solid oxide fuel cell micro cogeneration systems have the potential to reduce domestic energy consumption by providing both heat and power on site without transmission losses. The high grade heat produced during the operation of the power causes high thermal transients during startup....../shutdown phases and degrades the fuel cells. To counteract the degradation, the system has not to be stressed with rapid load variation during the operation. The analysis will consider an average profile for heat and power demand of a family house. Finally data analysis and power system limitations will be used...

Feasibility of solid oxide fuel cell dynamic hydrogen coproduction to meet building demand

Science.gov (United States)

Shaffer, Brendan; Brouwer, Jacob

2014-02-01

A dynamic internal reforming-solid oxide fuel cell system model is developed and used to simulate the coproduction of electricity and hydrogen while meeting the measured dynamic load of a typical southern California commercial building. The simulated direct internal reforming-solid oxide fuel cell (DIR-SOFC) system is controlled to become an electrical load following device that well follows the measured building load data (3-s resolution). The feasibility of the DIR-SOFC system to meet the dynamic building demand while co-producing hydrogen is demonstrated. The resulting thermal responses of the system to the electrical load dynamics as well as those dynamics associated with the filling of a hydrogen collection tank are investigated. The DIR-SOFC system model also allows for resolution of the fuel cell species and temperature distributions during these dynamics since thermal gradients are a concern for DIR-SOFC.

Fabrication and Optoelectrical Properties of IZO/Cu2O Heterostructure Solar Cells by Thermal Oxidation

Directory of Open Access Journals (Sweden)

Cheng-Chiang Chen

2012-01-01

Full Text Available Indium zinc oxide (IZO/cupper oxide (Cu2O is a nontoxic nature and an attractive all-oxide candidate for low-cost photovoltaic (PV applications. The present paper reports on the fabrication of IZO/Cu2O heterostructure solar cells which the Cu2O layers were prepared by oxidation of Cu thin films deposited on glass substrate. The measured parameters of cells were the short-circuit current (Isc, the open-circuit voltage (Voc, the maximum output power (Pm, the fill factor (FF, and the efficiency (η, which had values of 0.11 mA, 0.136 V, 5.05 μW, 0.338, and 0.56%, respectively, under AM 1.5 illumination.

Probing the thermal stability and the decomposition mechanism of a magnesium-fullerene polymer via X-ray Raman spectroscopy, X-ray diffraction and molecular dynamics simulations.

Science.gov (United States)

Aramini, Matteo; Niskanen, Johannes; Cavallari, Chiara; Pontiroli, Daniele; Musazay, Abdurrahman; Krisch, Michael; Hakala, Mikko; Huotari, Simo

2016-02-21

We report the microscopic view of the thermal structural stability of the magnesium intercalated fullerene polymer Mg2C60. With the application of X-ray Raman spectroscopy and X-ray diffraction, we study in detail the decomposition pathways of the polymer system upon annealing at temperatures between 300 and 700 °C. We show that there are at least two energy scales involved in the decomposition reaction. Intermolecular carbon bonds, which are responsible for the formation of a 2D fullerene polymer, are broken with a relatively modest thermal energy, while the long-range order of the original polymer remains intact. With an increased thermal energy, the crystal structure in turn is found to undergo a transition to a novel intercalated cubic phase that is stable up to the highest temperature studied here. The local structure surrounding magnesium ions gets severely modified close to, possibly at, the phase transition. We used density functional theory based calculations to study the thermodynamic and kinetic aspects of the collapse of the fullerene network, and to explain the intermediate steps as well as the reaction pathways in the break-up of this peculiar C60 intermolecular bonding architecture.

Curvature and Strength of Ni-YSZ Solid Oxide Half-Cells After Redox Treatments

DEFF Research Database (Denmark)

Faes, Antonin; Frandsen, Henrik Lund; Pihlatie, Mikko

2010-01-01

One of the main drawbacks of anode-supported solid oxide fuel cell technology is the limited capability to withstand reduction and oxidation (“RedOx”) of the Ni phase. This study compares the effect of RedOx cycles on curvature and strength of half-cells, composed of a nickel-yttria-stabilized-zi......One of the main drawbacks of anode-supported solid oxide fuel cell technology is the limited capability to withstand reduction and oxidation (“RedOx”) of the Ni phase. This study compares the effect of RedOx cycles on curvature and strength of half-cells, composed of a nickel...... it is calculated analytically from the force. In this calculation the thermal stresses are estimated from the curvature of the half-cell. For each treatment, more than 30 samples are tested. About 20 ball-on-ring samples are laser cut from one original 12×12 cm2 half-cell. Curvature and porosity are measured...

Non-Parametric Kinetic (NPK Analysis of Thermal Oxidation of Carbon Aerogels

Directory of Open Access Journals (Sweden)

Azadeh Seifi

2017-05-01

Full Text Available In recent years, much attention has been paid to aerogel materials (especially carbon aerogels due to their potential uses in energy-related applications, such as thermal energy storage and thermal protection systems. These open cell carbon-based porous materials (carbon aerogels can strongly react with oxygen at relatively low temperatures (~ 400°C. Therefore, it is necessary to evaluate the thermal performance of carbon aerogels in view of their energy-related applications at high temperatures and under thermal oxidation conditions. The objective of this paper is to study theoretically and experimentally the oxidation reaction kinetics of carbon aerogel using the non-parametric kinetic (NPK as a powerful method. For this purpose, a non-isothermal thermogravimetric analysis, at three different heating rates, was performed on three samples each with its specific pore structure, density and specific surface area. The most significant feature of this method, in comparison with the model-free isoconversional methods, is its ability to separate the functionality of the reaction rate with the degree of conversion and temperature by the direct use of thermogravimetric data. Using this method, it was observed that the Nomen-Sempere model could provide the best fit to the data, while the temperature dependence of the rate constant was best explained by a Vogel-Fulcher relationship, where the reference temperature was the onset temperature of oxidation. Moreover, it was found from the results of this work that the assumption of the Arrhenius relation for the temperature dependence of the rate constant led to over-estimation of the apparent activation energy (up to 160 kJ/mol that was considerably different from the values (up to 3.5 kJ/mol predicted by the Vogel-Fulcher relationship in isoconversional methods

Hydrogen determination in magnesium, zirconium, sodium and lithium using installation, C2532

International Nuclear Information System (INIS)

Malikova, E.D.; Velyukhanov, V.P.; Makhinova, L.O.; Kunin, L.L.

1980-01-01

Techniques of hydrogen determination in magnesium, lithium, sodium and zirconium using the S 2532 installation are developed. The method of oxidizing melting using lead borate has been used for hydrogen determination in lithium and sodium and the method of vacuum extraction - for hydrogen determination in zirconium and magnesium. Zr and Mg extraction has been carried out in steel reactor at the temperatures of 1000 and 650 deg C, the time of extraction being 30 and 10 minutes respectively. A quartz reactor, temperatures of oxidizing melting of 700-800 deg C, the time of analysis 10 and 20 minutes have been used for sodium and lithium. A possibility to determine volumetric content of hydrogen in magnesium at the existing surface contaminations with hydrogen-containing compounds is shown [ru

Fire performance, microstructure and thermal degradation of an epoxy based nano intumescent fire retardant coating for structural applications

Energy Technology Data Exchange (ETDEWEB)

Aziz, Hammad, E-mail: engr.hammad.aziz03@gmail.com; Ahmad, Faiz, E-mail: faizahmad@petronas.com.my; Yusoff, P. S. M. Megat; Zia-ul-Mustafa, M. [Department of Mechanical Engineering, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, Tronoh 31750, Perak (Malaysia)

2015-07-22

Intumescent fire retardant coating (IFRC) is a passive fire protection system which swells upon heating to form expanded multi-cellular char layer that protects the substrate from fire. In this research work, IFRC’s were developed using different flame retardants such as ammonium polyphosphate, expandable graphite, melamine and boric acid. These flame retardants were bound together with the help of epoxy binder and cured together using curing agent. IFRC was then reinforced with nano magnesium oxide and nano alumina as inorganic fillers to study their effect towards fire performance, microstructure and thermal degradation. Small scale fire test was conducted to investigate the thermal insulation of coating whereas fire performance was calculated using thermal margin value. Field emission scanning electron microscopy was used to examine the microstructure of char obtained after fire test. Thermogravimetric analysis was conducted to investigate the residual weight of coating. Results showed that the performance of the coating was enhanced by reinforcement with nano size fillers as compared to non-filler based coating. Comparing both nano size magnesium oxide and nano size alumina; nano size alumina gave better fire performance with improved microstructure of char and high residual weight.

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

Science.gov (United States)

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.

Characterization and Neutron Shielding Behavior of Dehydrated Magnesium Borate Minerals Synthesized via Solid-State Method

Directory of Open Access Journals (Sweden)

Azmi Seyhun Kipcak

2013-01-01

Full Text Available Magnesium borates are one of the major groups of boron minerals that have good neutron shielding performance. In this study, dehydrated magnesium borates were synthesized by solid-state method using magnesium oxide (MgO and boron oxide (B2O3, in order to test their ability of neutron shielding. After synthesizing the dehydrated magnesium borates, characterizations were done by X-ray Diffraction (XRD, fourier transform infrared (FT-IR, Raman spectroscopy, and scanning electron microscopy (SEM. Also boron oxide (B2O3 contents and reaction yields (% were calculated. XRD results showed that seven different types of dehydrated magnesium borates were synthesized. 1000°C reaction temperature, 240 minutes of reaction time, and 3 : 2, 1 : 1 mole ratios of products were selected and tested for neutron transmission. Also reaction yields were calculated between 84 and 88% for the 3 : 2 mole ratio products. The neutron transmission experiments revealed that the 3 : 2 mole ratio of MgO to B2O3 neutron transmission results (0.618–0.655 was better than the ratio of 1 : 1 (0.772–0.843.

Electrochemical corrosion behavior of composite MAO/sol-gel coatings on magnesium alloy AZ91D using combined micro-arc oxidation and sol-gel technique

International Nuclear Information System (INIS)

Shang Wei; Chen Baizhen; Shi Xichang; Chen Ya; Xiao Xiang

2009-01-01

Protective composite coatings were obtained on a magnesium alloy by micro-arc oxidation (MAO) and sol-gel technique. The coatings consisted of a MAO layer and a sol-gel layer. The microstructure and composition of the MAO coating and the composite coatings were analyzed by scanning electron microscopy (SEM) and energy dispersive X-rays (EDX). Potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and total immersion tests were used to evaluate the corrosion behavior of these coatings in a 3.5 wt.% NaCl solution. The results show that the sol-gel layer provides corrosion protection by physically sealing the pores in the MAO coating and acting as a barrier. The composite coatings can suppress the corrosion process by preventing the corrosive ions from transferring or diffusing to the magnesium alloy substrate. This enhances the corrosion resistance of the magnesium alloy AZ91D significantly

Automotive body panel containing thermally exfoliated graphite oxide

Science.gov (United States)

Prud'Homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor); Adamson, Douglas (Inventor); Abdala, Ahmed (Inventor)

2011-01-01

An automotive body panel containing a polymer composite formed of at least one polymer and a modified graphite oxide material, which is a thermally exfoliated graphite oxide with a surface area of from about 300 m.sup.2/g to 2600 m.sup.2/g.

Complex anticorrosion coating for ZK30 magnesium alloy

International Nuclear Information System (INIS)

Lamaka, S.V.; Knoernschild, G.; Snihirova, D.V.; Taryba, M.G.; Zheludkevich, M.L.; Ferreira, M.G.S.

2009-01-01

This work aims at developing a new complex anticorrosion protection system for ZK30 magnesium alloy. This protective coating is based on an anodic oxide layer loaded with corrosion inhibitors in its pores, which is then sealed with a sol-gel hybrid polymer. The porous oxide layer is produced by spark anodizing. The sol-gel film shows good adhesion to the oxide layer as it penetrates through the pores of the anodized layer forming an additional transient oxide-sol-gel interlayer. The thickness of this complex protective coating is about 3.7-7.0 μm. A blank oxide-sol-gel coating system or one doped with Ce 3+ ions proved to be effective corrosion protection for the magnesium alloy preventing corrosion attack after exposure for a relatively long duration in an aggressive NaCl solution. The structure and the thickness of the anodized layer and the sol-gel film were characterized by scanning electron microscopy (SEM). The corrosion behaviour of the ZK30 substrates pre-treated with the complex coating was tested by electrochemical impedance spectroscopy (EIS), scanning vibrating electrode technique (SVET), and scanning ion-selective electrode techniques (SIET).

Iodine doping effects on the lattice thermal conductivity of oxidized polyacetylene nanofibers

Energy Technology Data Exchange (ETDEWEB)

Bi, Kedong, E-mail: lishi@mail.utexas.edu, E-mail: kedongbi@seu.edu.cn [Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, School of Mechanical Engineering, Southeast University, Nanjing 211189 (China); Department of Mechanical Engineering, University of Texas at Austin, Austin, Texas 78712 (United States); Weathers, Annie; Pettes, Michael T.; Shi, Li, E-mail: lishi@mail.utexas.edu, E-mail: kedongbi@seu.edu.cn [Department of Mechanical Engineering, University of Texas at Austin, Austin, Texas 78712 (United States); Matsushita, Satoshi; Akagi, Kazuo [Department of Polymer Chemistry, Kyoto University, Kyoto 615-8510 (Japan); Goh, Munju [Department of Polymer Chemistry, Kyoto University, Kyoto 615-8510 (Japan); Institute of Advanced Composite Materials, Korea Institute of Science and Technology (KIST), Eunha-ri san 101, Bondong-eup, Wanju-gun, Jeolabuk-do 565-905 (Korea, Republic of)

2013-11-21

Thermal transport in oxidized polyacetylene (PA) nanofibers with diameters in the range between 74 and 126 nm is measured with the use of a suspended micro heater device. With the error due to both radiation and contact thermal resistance corrected via a differential measurement procedure, the obtained thermal conductivity of oxidized PA nanofibers varies in the range between 0.84 and 1.24 W m{sup −1} K{sup −1} near room temperature, and decreases by 40%–70% after iodine doping. It is also found that the thermal conductivity of oxidized PA nanofibers increases with temperature between 100 and 350 K. Because of exposure to oxygen during sample preparation, the PA nanofibers are oxidized to be electrically insulating before and after iodine doping. The measurement results reveal that iodine doping can result in enhanced lattice disorder and reduced lattice thermal conductivity of PA nanofibers. If the oxidation issue can be addressed via further research to increase the electrical conductivity via doping, the observed suppressed lattice thermal conductivity in doped polymer nanofibers can be useful for the development of such conducting polymer nanostructures for thermoelectric energy conversion.

Iodine doping effects on the lattice thermal conductivity of oxidized polyacetylene nanofibers

International Nuclear Information System (INIS)

Bi, Kedong; Weathers, Annie; Pettes, Michael T.; Shi, Li; Matsushita, Satoshi; Akagi, Kazuo; Goh, Munju

2013-01-01

Thermal transport in oxidized polyacetylene (PA) nanofibers with diameters in the range between 74 and 126 nm is measured with the use of a suspended micro heater device. With the error due to both radiation and contact thermal resistance corrected via a differential measurement procedure, the obtained thermal conductivity of oxidized PA nanofibers varies in the range between 0.84 and 1.24 W m −1  K −1 near room temperature, and decreases by 40%–70% after iodine doping. It is also found that the thermal conductivity of oxidized PA nanofibers increases with temperature between 100 and 350 K. Because of exposure to oxygen during sample preparation, the PA nanofibers are oxidized to be electrically insulating before and after iodine doping. The measurement results reveal that iodine doping can result in enhanced lattice disorder and reduced lattice thermal conductivity of PA nanofibers. If the oxidation issue can be addressed via further research to increase the electrical conductivity via doping, the observed suppressed lattice thermal conductivity in doped polymer nanofibers can be useful for the development of such conducting polymer nanostructures for thermoelectric energy conversion

Effect of magnesium oxide on interfraction prostate motion and rectal filling in prostate cancer radiotherapy. Analysis of a randomized clinical trial

Energy Technology Data Exchange (ETDEWEB)

Harder, Annemarie M. den; Kotte, Alexis N.T.J.; Vulpen, Marco van; Lips, Irene M. [University Medical Center Utrecht, Department of Radiation Oncology, Utrecht (Netherlands); Gils, Carla H. van [University Medical Center Utrecht, Julius Center for Health Sciences and Primary Care, Utrecht (Netherlands)

2014-08-15

To investigate whether magnesium oxide reduces the interfraction motion of the prostate and the amount of rectal filling and rectal gas, which influences prostate position during radiotherapy for prostate cancer. From December 2008 to February 2010, 92 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. In a previous study, we investigated the effect on intrafraction motion and did not find a difference between the treatment arms. Here, we compared the interfraction prostate motion between the two treatment arms as well as the amount of rectal filling and rectal air pockets using pretreatment planning computed tomography and magnetic resonance imaging scans. There was no statistically significant difference between the treatment arms in translation and rotation of the prostate between treatment fractions, except for the rotation around the cranial caudal axis. However, the difference was less than 1 and therefore considered not clinically relevant. There was no significant difference in the amount of rectal filling and rectal air pockets between the treatment arms. Magnesium oxide is not effective in reducing the interfraction prostate motion or the amount of rectal filling and rectal gas during external-beam radiotherapy. Therefore, magnesium oxide is not recommended in clinical practice for these purposes. (orig.) [German] Ziel der Studie war es, zu untersuchen, ob Magnesiumoxid die interfraktionaere Bewegung und die rektale Fuellung sowie rektales Gas reduziert, was die Position der Prostata waehrend der Strahlentherapie bei Prostatakrebs beeinflusst. Von Dezember 2008 bis Februar 2010 haben 92 Prostatakrebspatienten die intensitaetsmodulierte Strahlentherapie (IMRT) mit bezugsmarkenbasierter Positionsverifikation erhalten (77 Gy in 35 Fraktionen). Sie wurden waehrend

Oxide, interface, and border traps in thermal, N2O, and N2O-nitrided oxides

International Nuclear Information System (INIS)

Fleetwood, D.M.; Saks, N.S.

1996-01-01

We have combined thermally stimulated-current (TSC) and capacitance endash voltage (C endash V) measurements to estimate oxide, interface, and effective border trap densities in 6 endash 23 nm thermal, N 2 O, and N 2 O-nitrided oxides exposed to ionizing radiation or high-field electron injection. Defect densities depend strongly on oxide processing, but radiation exposure and moderate high-field stress lead to similar trapped hole peak thermal energy distributions (between ∼1.7 and ∼2.0 eV) for all processes. This suggests that similar defects dominate the oxide charge trapping properties in these devices. Radiation-induced hole and interface trap generation efficiencies (0.1%endash 1%) in the best N 2 O and N 2 O-nitrided oxides are comparable to the best radiation hardened oxides in the literature. After ∼10 Mrad(SiO 2 ) x-ray irradiation or ∼10 mC/cm 2 constant current Fowler endash Nordheim injection, effective border trap densities as high as ∼5x10 11 cm -2 are inferred from C endash V hysteresis. These measurements suggest irradiation and high-field stress cause similar border trap energy distributions. In each case, even higher densities of compensating trapped electrons in the oxides (up to 2x10 12 cm -2 ) are inferred from combined TSC and C endash V measurements. These trapped electrons prevent conventional C endash V methods from providing accurate estimates of the total oxide trap charge density in many irradiation or high-field stress studies. Fewer compensating electrons per trapped hole (∼26%±5%) are found for irradiation of N 2 O and N 2 O-nitrided oxides than for thermal oxides (∼46%±7%). (Abstract Truncated)

Role of magnesium on the biomimetic deposition of calcium phosphate

Science.gov (United States)

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.

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

Science.gov (United States)

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.

Non-thermal Plasma and Oxidative Stress

Science.gov (United States)

Toyokuni, Shinya

2015-09-01

Thermal plasmas and lasers have been used in medicine to cut and ablate tissues and for coagulation. Non-equilibrium atmospheric pressure plasma (NEAPP; non-thermal plasma) is a recently developed, non-thermal technique with possible biomedical applications. Although NEAPP reportedly generates reactive oxygen/nitrogen species, electrons, positive ions, and ultraviolet radiation, few research projects have been conducted to merge this technique with conventional free radical biology. Recently, Prof. Masaru Hori's group (Plasma Nanotechnology Research Center, Nagoya University) developed a NEAPP device with high electron density. Here electron spin resonance revealed hydroxyl radicals as a major product. To merge non-thermal plasma biology with the preexisting free radical biology, we evaluated lipid peroxidation and DNA modifications in various in vitro and ex vivo experiments. Conjugated dienes increased after exposure to linoleic and alfa-linolenic acids. An increase in 2-thiobarbituric acid-reactive substances was also increased after exposure to phosphatidylcholine, liposomes or liver homogenate. Direct exposure to rat liver in medium produced immunohistochemical evidence of 4-hydroxy-2-nonenal- and acrolein-modified proteins. Exposure to plasmid DNA induced dose-dependent single/double strand breaks and increased the amounts of 8-hydroxy-2'-deoxyguanosine and cyclobutane pyrimidine dimers. These results indicate that oxidative biomolecular damage by NEAPP is dose-dependent and thus can be controlled in a site-specific manner. Simultaneous oxidative and UV-specific DNA damage may be useful in cancer treatment. Other recent advancements in the related studies of non-thermal plasma in Nagoya University Graduate School of Medicine will also be discussed.

Current Status and Future Prospects of Copper Oxide Heterojunction Solar Cells.

Science.gov (United States)

Wong, Terence K S; Zhuk, Siarhei; Masudy-Panah, Saeid; Dalapati, Goutam K

2016-04-07

The current state of thin film heterojunction solar cells based on cuprous oxide (Cu₂O), cupric oxide (CuO) and copper (III) oxide (Cu₄O₃) is reviewed. These p-type semiconducting oxides prepared by Cu oxidation, sputtering or electrochemical deposition are non-toxic, sustainable photovoltaic materials with application potential for solar electricity. However, defects at the copper oxide heterojunction and film quality are still major constraining factors for achieving high power conversion efficiency, η. Amongst the Cu₂O heterojunction devices, a maximum η of 6.1% has been obtained by using pulsed laser deposition (PLD) of Al x Ga 1- x O onto thermal Cu₂O doped with Na. The performance of CuO/n-Si heterojunction solar cells formed by magnetron sputtering of CuO is presently limited by both native oxide and Cu rich copper oxide layers at the heterointerface. These interfacial layers can be reduced by using a two-step sputtering process. A high η of 2.88% for CuO heterojunction solar cells has been achieved by incorporation of mixed phase CuO/Cu₂O nanopowder. CuO/Cu₂O heterojunction solar cells fabricated by electrodeposition and electrochemical doping has a maximum efficiency of 0.64% after surface defect passivation and annealing. Finally, early stage study of Cu₄O₃/GaN deposited on sapphire substrate has shown a photovoltaic effect and an η of ~10 -2 %.

Behavior of strontium- and magnesium-doped gallate electrolyte in direct carbon solid oxide fuel cells

Energy Technology Data Exchange (ETDEWEB)

Zhang, Li; Xiao, Jie; Xie, Yongmin [The Key Laboratory of Fuel Cell Technology of Guangdong Province, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510641 (China); Tang, Yubao [Key Laboratory of Sensor Analysis of Tumor Marker Ministry of Education, College of Chemistry and Molecular Engineering, Qingdao University of Science and Technology, Qingdao o 266042 (China); Liu, Jiang, E-mail: jiangliu@scut.edu.cn [The Key Laboratory of Fuel Cell Technology of Guangdong Province, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510641 (China); New Energy Research Institute, College of Environment and Energy, South China University of Technology, Guangzhou 510006 (China); Liu, Meilin [New Energy Research Institute, College of Environment and Energy, South China University of Technology, Guangzhou 510006 (China); School of Materials Science and Engineering, Georgia Institute of Technology, 771 Ferst Drive, Atlanta, GA 30332-0245 (United States)

2014-09-01

Highlights: • La{sub 0.9}Sr{sub 0.1}Ga{sub 0.8}Mg{sub 0.2}O{sub 3−δ} (LSGM) can be used as electrolyte of direct carbon SOFCs. • DC-SOFC with LSGM electrolyte gives higher performance than that with YSZ. • LSGM-electrolyte DC-SOFC gives maximum power density of 383 mW cm{sup −2} at 850 °C. • Operation of LSGM-DC-SOFC at 210 mA cm{sup −2} lasts 72 min, with fuel utilization of 60%. - Abstract: Perovskite-type La{sub 0.9}Sr{sub 0.1}Ga{sub 0.8}Mg{sub 0.2}O{sub 3−δ} (LSGM) is synthesized by conventional solid state reaction. Its phase composition, microstructure, relative density, and oxygen-ionic conductivity are investigated. Tubular electrolyte-supported solid oxide fuel cells (SOFCs) are prepared with the LSGM as electrolyte and gadolinia doped ceria (GDC) mixed with silver as anode. The SOFCs are operated with Fe-loaded activated carbon as fuel and ambient air as oxidant. A typical single cell gives a maximum power density of 383 mW cm{sup −2} at 850 °C, which is nearly 1.3 times higher than that of the similar cell with YSZ as electrolyte. A stability test of 72 min is carried out at a constant current density of 210 mA cm{sup −2}, with a fuel utilization of 60%, indicating that LaGaO{sub 3}-based electrolyte is promising to be applied in direct carbon SOFCs (DC-SOFCs)

Lithium-aluminum-magnesium electrode composition

Science.gov (United States)

Melendres, Carlos A.; Siegel, Stanley

1978-01-01

A negative electrode composition is presented for use in a secondary, high-temperature electrochemical cell. The cell also includes a molten salt electrolyte of alkali metal halides or alkaline earth metal halides and a positive electrode including a chalcogen or a metal chalcogenide as the active electrode material. The negative electrode composition includes up to 50 atom percent lithium as the active electrode constituent and a magnesium-aluminum alloy as a structural matrix. Various binary and ternary intermetallic phases of lithium, magnesium, and aluminum are formed but the electrode composition in both its charged and discharged state remains substantially free of the alpha lithium-aluminum phase and exhibits good structural integrity.

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

Science.gov (United States)

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.

Compatibility of various magnesium alloys with pressurized carbon dioxide at high temperatures; Compatibilite de divers alliages de magnesium avec le gaz carbonique sous pression aux temperatures elevees

Energy Technology Data Exchange (ETDEWEB)

Dewanckel, B; David, R; Hulin, C; Leclercq, D [Commissariat a l' Energie Atomique, 38 - Grenoble (France). Centre d' Etudes Nucleaires

1968-07-01

This work on the compatibility of magnesium alloys with pressurized carbon dioxide has been carried out along three lines: - testing of special alloys containing additions of zirconium, manganese, cerium, zinc, beryllium and yttrium. The results are satisfactory, generally speaking, and the corrosion kinetics are often comparable to those of conventional magnesium-zirconium alloy; - influence of the quality of the carbon dioxide, in particular the presence of water vapour or of carbon monoxide in this gas. It appears that oxidation is reduced if the carbon dioxide contains traces of water vapour, but is more pronounced if carbon monoxide is also present; - study of certain phenomena related to corrosion: size changes in the samples during tests, structural modifications in the alloys (grain-size changes, formation of a cortical zone in the case of alloys containing zirconium). The influence of thermal cycling has also been studied in a few specific tests. The results obtained make it possible to compare the behaviour of various alloys under varying conditions of long-term use, and to choose, if required, the best composition for a given application. (authors) [French] Ce travail sur la compatibilite des alliages de magnesium avec le gaz carbonique sous pression a ete particulierement oriente dans trois directions: - epreuve, d'alliages speciaux comportant des additions de zirconium, manganese, cerium, zinc, beryllium et yttrium. Les resultats sont generalement satisfaisants et les cinetiques de corrosion souvent comparables a celles de l'alliage magnesium-zirconium classique; - influence de la qualite du gaz carbonique, et notamment de la presence de vapeur d'eau ou d'oxyde de carbone dans ce gaz. Il est apparu que l'oxydation est reduite si le gaz carbonique contient des traces d'eau, mais accrue si l'oxyde de carbone est egalement present; - etude de certains phenomenes lies a la corrosion: variations dimensionnelles des echantillons au cours des essais

Preparation and investigations of thermal properties of copper oxide ...

Indian Academy of Sciences (India)

The effects of copper oxide, aluminium oxide and graphite on the thermal and structural properties of the organic ... solar energy, and heat regulation of electronics, biomedical ..... We gratefully acknowledge the financial support provided by.

Magnesium borate radiothermoluminescent detectors

International Nuclear Information System (INIS)

Kazanskaya, V.A.; Kuzmin, V.V.; Minaeva, E.E.; Sokolov, A.D.

1974-01-01

In the report the technology of obtaining polycrystalline magnesium borate activated by dysprosium is described briefly and the method of preparing the tabletted detectors from it is presented. The dependence of the light sum of the samples on the proportion of the components and on the sintering regime has shown that the most sensitive material is obtained at the proportion of boric anhydride and magnesium oxide 2.2-2.4 and at the dysprosium concentration about 1 milligram-atom per gram molecule of the base. The glow curve of such a material has a simple form with one peak the maximum of which is located at 190-200 0 C. The measurement of the main dosimetric characteristics of the magnesium borate tabletted detectors and the comparison with similar parmaeters of the lithium fluoride tabletted detectors have shown that at practically identical effective number the former detectors have the following substantial advantages: the sensitivity is ten-twenty times as large, they are substantially more technological on synthesis of the radiothermoluminophor and during the production of the tabletted detectors, they have a simple glow curve, they do not require the utilization of the thermocycling during the use. (author)

Oxidation and thermal shock behavior of thermal barrier coated 18/10CrNi alloy with coating modifications

Energy Technology Data Exchange (ETDEWEB)

Guergen, Selim [Vocational School of Transportation, Anadolu University, Eskisehir (Turkmenistan); Diltemiz, Seyid Fehmi [Turkish Air Force1st Air Supply and Maintenance Center Command, Eskisehir (Turkmenistan); Kushan, Melih Cemal [Dept. of Mechanical Engineering, Eskisehir Osmangazi University, Eskisehir (Turkmenistan)

2017-01-15

In this study, substrates of 18/10CrNi alloy plates were initially sprayed with a Ni-21Cr-10Al-1Y bond coat and then with an yttria stabilized zirconia top coat by plasma spraying. Subsequently, plasma-sprayed Thermal barrier coatings (TBCs) were treated with two different modification methods, namely, vacuum heat treatment and laser glazing. The effects of modifications on the oxidation and thermal shock behavior of the coatings were evaluated. The effect of coat thickness on the bond strength of the coats was also investigated. Results showed enhancement of the oxidation resistance and thermal shock resistance of TBCs following modifications. Although vacuum heat treatment and laser glazing exhibited comparable results as per oxidation resistance, the former generated the best improvement in the thermal shock resistance of the TBCs. Bond strength also decreased as coat thickness increased.

Sol – Gel synthesis and characterization of magnesium peroxide nanoparticles

International Nuclear Information System (INIS)

Jaison, J; Chan, Y S; Ashok raja, C; Balakumar, S

2015-01-01

Magnesium peroxide is an excellent source of oxygen in agriculture applications, for instance it is used in waste management as a material for soil bioremediation to remove contaminants from polluted underground water, biological wastes treatment to break down hydrocarbon, etc. In the present study, sol-gel synthesis of magnesium peroxide (MgO 2 ) nanoparticles is reported. Magnesium peroxide is odourless; fine peroxide which releases oxygen when reacts with water. During the sol-gel synthesis, the magnesium malonate intermediate is formed which was then calcinated to obtain MgO 2 nanoparticles. The synthesized nanoparticles were characterized using Thermo gravimetric -Differential Thermal Analysis (TG- DTA), X-Ray Diffraction studies (XRD) and High Resolution Transmission Electron Microscope (HRTEM). Our study provides a clear insight that the formation of magnesium malonate during the synthesis was due to the reaction between magnesium acetate, oxalic acid and ethanol. In our study, we can conclude that the calcination temperature has a strong influence on particle size, morphology, monodispersity and the chemistry of the particles. (paper)

Materials system for intermediate temperature solid oxide fuel cells based on doped lanthanum-gallate electrolyte

Science.gov (United States)

Gong, Wenquan

2005-07-01

The objective of this work was to identify a materials system for intermediate temperature solid oxide fuel cells (IT-SOFCs). Towards this goal, alternating current complex impedance spectroscopy was employed as a tool to study electrode polarization effects in symmetrical cells employing strontium and magnesium doped lanthanum gallate (LSGM) electrolyte. Several cathode materials were investigated including strontium doped lanthanum manganite (LSM), Strontium and iron doped lanthanum cobaltate (LSCF), LSM-LSGM, and LSCF-LSGM composites. Investigated Anode materials included nickel-gadolinium or lanthanum doped cerium oxide (Ni-GDC, or Ni-LDC) composites. The ohmic and the polarization resistances of the symmetrical cells were obtained as a function of temperature, time, thickness, and the composition of the electrodes. Based on these studies, the single phase LSM electrode had the highest polarization resistance among the cathode materials. The mixed-conducting LSCF electrode had polarization resistance orders of magnitude lower than that of the LSM-LSGM composite electrodes. Although incorporating LSGM in the LSCF electrode did not reduce the cell polarization resistance significantly, it could reduce the thermal expansion coefficient mismatch between the LSCF electrodes and LSGM electrolyte. Moreover, the polarization resistance of the LSCF electrode decreased asymptotically as the electrode thickness was increased thus suggesting that the electrode thickness needed not be thicker than this asymptotic limit. On the anode side of the IT-SOFC, Ni reacted with LSGM electrolyte, and lanthanum diffusion occurred from the LSGM electrolyte to the GDC barrier layer, which was between the LSGM electrolyte and the Ni-composite anode. However, LDC served as an effective barrier layer. Ni-LDC (70 v% Ni) anode had the largest polarization resistance, while all other anode materials, i.e. Ni-LDC (50 v% Ni), Ni-GDC (70 v% NO, and Ni-GDC (50 v% Ni), had similar polarization

Fabrication and thermal oxidation of ZnO nano fibers prepared via electro spinning technique

International Nuclear Information System (INIS)

Baek, Jeongha; Park, Juyun; Kim, Don; Kang, Yongcheol; Koh, Sungwi; Kang, Jisoo

2012-01-01

Materials on the scale of nano scale have widely been used as research topics because of their interesting characteristics and aspects they bring into the field. Out of the many metal oxides, zinc oxide (ZnO) was chosen to be fabricated as nano fibers using the electro spinning method for potential uses of solar cells and sensors. After ZnO nano fibers were obtained, calcination temperature effects on the ZnO nano fibers were studied and reported here. The results of scanning electron microscopy (SEM) revealed that the aggregation of the ZnO nano fibers progressed by calcination. X-ray diffraction (XRD) study showed the hcp ZnO structure was enhanced by calcination at 873 and 1173 K. Transmission electron microscopy (TEM) confirmed the crystallinity of the calcined ZnO nano fibers. X-ray photoelectron spectroscopy (XPS) verified the thermal oxidation of Zn species by calcination in the nano fibers. These techniques have helped US deduce the facts that the diameter of ZnO increases as the calcination temperature was raised; the process of calcination affects the crystallinity of ZnO nano fibers, and the thermal oxidation of Zn species was observed as the calcination temperature was raised

Biodegradable Magnesium Alloys: A Review of Material Development and Applications

Science.gov (United States)

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

Influence of chloride ion concentration on the electrochemical corrosion behaviour of plasma electrolytic oxidation coated AM50 magnesium alloy

International Nuclear Information System (INIS)

Liang, J.; Srinivasan, P. Bala; Blawert, C.; Dietzel, W.

2010-01-01

The electrochemical degradation of a silicate- and a phosphate-based plasma electrolytic oxidation (PEO) coated AM50 magnesium alloy obtained using a pulsed DC power supply was investigated using potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) in NaCl solutions of different chloride ion concentrations viz., 0.01 M, 0.1 M, 0.5 M and 1 M. The surface of the PEO coated specimens after 50 h of immersion/EIS testing was examined by optical microscopy and scanning electron microscopy. The results showed that the corrosion deterioration of PEO coated magnesium alloy in NaCl solutions was significantly influenced by chloride ion concentration. The silicate-based coating was found to offer a superior corrosion resistance to the magnesium substrate than the phosphate-based coatings in lower chloride ion concentration NaCl solutions (0.01 M and 0.1 M NaCl). On the other hand both these PEO coatings were found to be highly susceptible to localized damage, and could not provide an effective corrosion protection to Mg alloy substrate in solutions containing higher chloride concentrations (0.5 M and 1 M). The extent of localized damage was observed to be more with increase in chloride concentration in both the cases.

Economic Evaluation of the Production Magnesium Oxide Nanoparticles via Liquid-Phase Route

Science.gov (United States)

Nandiyanto, A. B. D.; Fariansyah, R.; Ramadhan, M. F.; Abdullah, A. G.; Widiaty, I.

2018-02-01

The purpose of this study was to evaluate the production of magnesium oxide (MgO) nanoparticles. The evaluation was done in two perspectives: engineering and economic evaluation. The engineering perspective concerned about the analysis of the production rate based on the available apparatuses and raw materials, completed with mass balance calculation. The economic analysis was conducted based on several economic parameters: gross profit margin (GPM), internal return rate (IRR), payback period (PBP), cumulative net present value (CNPV), break even point (BEP), and profit to investment (PI). The engineering perspective showed that the production of MgO is feasibly done in small scale industry. This is verified by the potential production using current available apparatuses and raw materials in the market. Economic analysis obtained that the present project is profitable. But, for some cases, further studies must be done to get the present production process is attractive for investor.

Effect of current density on the microstructure and corrosion resistance of microarc oxidized ZK60 magnesium alloy.

Science.gov (United States)

You, Qiongya; Yu, Huijun; Wang, Hui; Pan, Yaokun; Chen, Chuanzhong

2014-09-01

The application of magnesium alloys as biomaterials is limited by their poor corrosion behavior. Microarc oxidation (MAO) treatment was used to prepare ceramic coatings on ZK60 magnesium alloys in order to overcome the poor corrosion resistance. The process was conducted at different current densities (3.5 and 9.0 A/dm(2)), and the effect of current density on the process was studied. The microstructure, elemental distribution, and phase composition of the MAO coatings were characterized by scanning electron microscopy, energy-dispersive x-ray spectrometry, and x-ray diffraction, respectively. The increment of current density contributes to the increase of thickness. A new phase Mg2SiO4 was detected as the current density increased to 9.0 A/dm(2). A homogeneous distribution of micropores could be observed in the coating produced at 3.5 A/dm(2), while the surface morphology of the coating formed at 9.0 A/dm(2) was more rough and apparent microcracks could be observed. The coating obtained at 3.5 A/dm(2) possessed a better anticorrosion behavior.

Preparation of magnesium metal matrix composites by powder metallurgy process

Science.gov (United States)

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.

Thermal diffusivity and conductivity of thorium- uranium mixed oxides

Science.gov (United States)

Saoudi, M.; Staicu, D.; Mouris, J.; Bergeron, A.; Hamilton, H.; Naji, M.; Freis, D.; Cologna, M.

2018-03-01

Thorium-uranium oxide pellets with high densities were prepared at the Canadian Nuclear Laboratories (CNL) by co-milling, pressing, and sintering at 2023 K, with UO2 mass contents of 0, 1.5, 3, 8, 13, 30, 60 and 100%. At the Joint Research Centre, Karlsruhe (JRC-Karlsruhe), thorium-uranium oxide pellets were prepared using the spark plasma sintering (SPS) technique with 79 and 93 wt. % UO2. The thermal diffusivity of (Th1-xUx)O2 (0 ≤ x ≤ 1) was measured at CNL and at JRC-Karlsruhe using the laser flash technique. ThO2 and (Th,U)O2 with 1.5, 3, 8 and 13 wt. % UO2 were found to be semi-transparent to the infrared wavelength of the laser and were coated with graphite for the thermal diffusivity measurements. This semi-transparency decreased with the addition of UO2 and was lost at about 30 wt. % of UO2 in ThO2. The thermal conductivity was deduced using the measured density and literature data for the specific heat capacity. The thermal conductivity for ThO2 is significantly higher than for UO2. The thermal conductivity of (Th,U)O2 decreases rapidly with increasing UO2 content, and for UO2 contents of 60% and higher, the conductivity of the thorium-uranium oxide fuel is close to UO2. As the mass difference between the Th and U atoms is small, the thermal conductivity decrease is attributed to the phonon scattering enhanced by lattice strain due to the introduction of uranium in ThO2 lattice. The new results were compared to the data available in the literature and were evaluated using the classical phonon transport model for oxide systems.

Corrosion Monitoring of PEO-Pretreated Magnesium Alloys

Energy Technology Data Exchange (ETDEWEB)

Gnedenkov, A. S.; Sinebryukhov, S. L.; Mashtalyar, D. V.; Gnedenkov, S. V.; Sergienko, V. I. [Institute of Chemistry, Vladivostok (Russian Federation)

2017-06-15

The MA8 alloy (formula Mg-Mn-Ce) has been shown to have greater corrosion stability than the VMD10 magnesium alloy (formula Mg-Zn-Zr-Y) in chloride-containing solutions by Scanning Vibrating Electrode Technique (SVET) and by optical microscopy, gravimetry, and volumetry. It has been established that the crucial factor for the corrosion activity of these samples is the occurrence of microgalvanic coupling at the sample surface. The peculiarities of the kinetics and mechanism of the corrosion in the local heterogeneous regions of the magnesium alloy surface were investigated by localized electrochemical techniques. The stages of the corrosion process in artificial defects in the coating obtained by plasma electrolytic oxidation (PEO) at the surface of the MA8 magnesium alloy were also studied. The analysis of the experimental data enabled us to determine that the corrosion process in the defect zone develops predominantly at the magnesium/coating interface. Based on the measurements of the corrosion rate of the samples with PEO and composite polymer-containing coatings, the best anticorrosion properties were displayed by the composite polymer-containing coatings.

Magnesium Gluconate

Science.gov (United States)

Magnesium gluconate is used to treat low blood magnesium. Low blood magnesium is caused by gastrointestinal disorders, prolonged vomiting or ... disease, or certain other conditions. Certain drugs lower magnesium levels as well.This medication is sometimes prescribed ...

Graphene oxide as a sulfur immobilizer in high performance lithium/sulfur cells

Science.gov (United States)

Zhang, Yuegang; Cairns, Elton J.; Ji, Liwen; Rao, Mumin

2017-06-06

The loss of sulfur cathode material as a result of polysulfide dissolution causes significant capacity fading in rechargeable lithium/sulfur cells. Embodiments of the invention use a chemical approach to immobilize sulfur and lithium polysulfides via the reactive functional groups on graphene oxide. This approach obtains a uniform and thin (.about.tens of nanometers) sulfur coating on graphene oxide sheets by a chemical reaction-deposition strategy and a subsequent low temperature thermal treatment process. Strong interaction between graphene oxide and sulfur or polysulfides demonstrate lithium/sulfur cells with a high reversible capacity of 950-1400 mAh g.sup.-1, and stable cycling for more than 50 deep cycles at 0.1 C.

Graphene oxide as a sulfur immobilizer in high performance lithium/sulfur cells

Energy Technology Data Exchange (ETDEWEB)

Zhang, Yuegang; Cairns, Elton J.; Ji, Liwen; Rao, Mumin

2017-12-26

The loss of sulfur cathode material as a result of polysulfide dissolution causes significant capacity fading in rechargeable lithium/sulfur cells. Embodiments of the invention use a chemical approach to immobilize sulfur and lithium polysulfides via the reactive functional groups on graphene oxide. This approach obtains a uniform and thin (.about.tens of nanometers) sulfur coating on graphene oxide sheets by a chemical reaction-deposition strategy and a subsequent low temperature thermal treatment process. Strong interaction between graphene oxide and sulfur or polysulfides demonstrate lithium/sulfur cells with a high reversible capacity of 950-1400 mAh g.sup.-1, and stable cycling for more than 50 deep cycles at 0.1 C.

Cathodoluminescence study of vickers indentations in magnesium ...

African Journals Online (AJOL)

Vickers diamond pyramid indentations made in single crystal of magnesium oxide (MgO) were examined in an environmental scanning electron microscope interfaced with an AVS-2000 spectrophotometer for luminescence. Three distinct zones around the indentations were identified to exhibit cathodoluminescence, which ...

Intrinsic Conductivity in Magnesium-Oxygen Battery Discharge Products: MgO and MgO2

DEFF Research Database (Denmark)

Smith, Jeffrey G.; Naruse, Junichi; Hiramatsu, Hidehiko

2017-01-01

Nonaqueous magnesium–oxygen (or “Mg-air”) batteries are attractive next generation energy storage devices due to their high theoretical energy densities, projected low cost, and potential for rechargeability. Prior experiments identified magnesium oxide, MgO, and magnesium peroxide, MgO2...

Effect of the top coat on the phase transformation of thermally grown oxide in thermal barrier coatings

Energy Technology Data Exchange (ETDEWEB)

Zhao, X. [Materials Science Centre, School of Materials, University of Manchester, Manchester M1 7HS (United Kingdom); Hashimoto, T. [Materials Science Centre, School of Materials, University of Manchester, Manchester M1 7HS (United Kingdom); Xiao, P. [Materials Science Centre, School of Materials, University of Manchester, Manchester M1 7HS (United Kingdom)]. E-mail: ping.xiao@manchester.ac.uk

2006-12-15

The phase transformation of the thermally grown oxide (TGO) formed on a Pt enriched {gamma} + {gamma}' bond coat in electron beam physical vapour deposited thermal barrier coatings (TBCs) was studied by photo-stimulaluminescence spectroscopy. The presence of the TBC retards the {theta} to {alpha} transformation of the TGO and leads to a higher oxidation rate. The reasons for these phenomena are discussed.

Current Status and Future Prospects of Copper Oxide Heterojunction Solar Cells

Directory of Open Access Journals (Sweden)

Terence K. S. Wong

2016-04-01

Full Text Available The current state of thin film heterojunction solar cells based on cuprous oxide (Cu2O, cupric oxide (CuO and copper (III oxide (Cu4O3 is reviewed. These p-type semiconducting oxides prepared by Cu oxidation, sputtering or electrochemical deposition are non-toxic, sustainable photovoltaic materials with application potential for solar electricity. However, defects at the copper oxide heterojunction and film quality are still major constraining factors for achieving high power conversion efficiency, η. Amongst the Cu2O heterojunction devices, a maximum η of 6.1% has been obtained by using pulsed laser deposition (PLD of AlxGa1−xO onto thermal Cu2O doped with Na. The performance of CuO/n-Si heterojunction solar cells formed by magnetron sputtering of CuO is presently limited by both native oxide and Cu rich copper oxide layers at the heterointerface. These interfacial layers can be reduced by using a two-step sputtering process. A high η of 2.88% for CuO heterojunction solar cells has been achieved by incorporation of mixed phase CuO/Cu2O nanopowder. CuO/Cu2O heterojunction solar cells fabricated by electrodeposition and electrochemical doping has a maximum efficiency of 0.64% after surface defect passivation and annealing. Finally, early stage study of Cu4O3/GaN deposited on sapphire substrate has shown a photovoltaic effect and an η of ~10−2%.

Current Status and Future Prospects of Copper Oxide Heterojunction Solar Cells

Science.gov (United States)

Wong, Terence K. S.; Zhuk, Siarhei; Masudy-Panah, Saeid; Dalapati, Goutam K.

2016-01-01

The current state of thin film heterojunction solar cells based on cuprous oxide (Cu2O), cupric oxide (CuO) and copper (III) oxide (Cu4O3) is reviewed. These p-type semiconducting oxides prepared by Cu oxidation, sputtering or electrochemical deposition are non-toxic, sustainable photovoltaic materials with application potential for solar electricity. However, defects at the copper oxide heterojunction and film quality are still major constraining factors for achieving high power conversion efficiency, η. Amongst the Cu2O heterojunction devices, a maximum η of 6.1% has been obtained by using pulsed laser deposition (PLD) of AlxGa1−xO onto thermal Cu2O doped with Na. The performance of CuO/n-Si heterojunction solar cells formed by magnetron sputtering of CuO is presently limited by both native oxide and Cu rich copper oxide layers at the heterointerface. These interfacial layers can be reduced by using a two-step sputtering process. A high η of 2.88% for CuO heterojunction solar cells has been achieved by incorporation of mixed phase CuO/Cu2O nanopowder. CuO/Cu2O heterojunction solar cells fabricated by electrodeposition and electrochemical doping has a maximum efficiency of 0.64% after surface defect passivation and annealing. Finally, early stage study of Cu4O3/GaN deposited on sapphire substrate has shown a photovoltaic effect and an η of ~10−2%. PMID:28773398

Synthesis and characterization of magnesium gluconate contained poly(lactic-co-glycolic acid)/chitosan microspheres

Energy Technology Data Exchange (ETDEWEB)

Rahman, Shekh M. [Department of Chemical, Biological and Bioengineering, North Carolina A& T State University, 1601 East Market Street, Greensboro, NC 27411 (United States); NSF Engineering Research Center for Revolutionizing Metallic Biomaterials, North Carolina A& T State University, Greensboro, NC 27411 (United States); Mahoney, Christopher [Department of Bioengineering, University of Pittsburgh, 4200 Fifth Avenue, Pittsburgh, PA 15250 (United States); Sankar, Jagannathan [NSF Engineering Research Center for Revolutionizing Metallic Biomaterials, North Carolina A& T State University, Greensboro, NC 27411 (United States); Department of Mechanical Engineering, North Carolina A& T State University, 1601 East Market Street, Greensboro, NC 27411 (United States); Marra, Kacey G. [NSF Engineering Research Center for Revolutionizing Metallic Biomaterials, North Carolina A& T State University, Greensboro, NC 27411 (United States); Department of Bioengineering, University of Pittsburgh, 4200 Fifth Avenue, Pittsburgh, PA 15250 (United States); Department of Plastic Surgery, University of Pittsburgh, 200 Lothrop Street, Pittsburgh, PA 15250 (United States); McGowan Institute for Regenerative Medicine, University of Pittsburgh, 450 Technology Drive, Pittsburgh, PA 15250 (United States); Bhattarai, Narayan, E-mail: nbhattar@ncat.edu [Department of Chemical, Biological and Bioengineering, North Carolina A& T State University, 1601 East Market Street, Greensboro, NC 27411 (United States); NSF Engineering Research Center for Revolutionizing Metallic Biomaterials, North Carolina A& T State University, Greensboro, NC 27411 (United States)

2016-01-15

Graphical abstract: - Highlights: • Magnesium gluconate contained PLGA/chitosan microspheres were fabricated. • In vitro release of magnesium ions was performed using Xylidyl Blue assay. • Chitosan coated PLGA can significantly control the release of magnesium ions. • Cellular compatibility was tested using adipose-derived stem cells and PC12 cells. • The cells encounter acceptably low levels of damage in contact with microspheres. - Abstract: The goal of this study was to fabricate and investigate the chitosan coated poly(lactic-co-glycolic acid) (PLGA) microspheres for the development of controlled release magnesium delivery system. PLGA based microspheres are ideal vehicles for many controlled release drug delivery applications. Chitosan is a naturally occurring biodegradable and biocompatible polysaccharide, which can coat the surface of PLGA to alter the release of drugs. Magnesium gluconate (MgG) was encapsulated in the PLGA and PLGA/chitosan microspheres by utilizing the double emulsion solvent evaporation technique for controlled release study. The microspheres were tested with respect to several physicochemical and biological properties, including morphology, chemical structure, chitosan adsorption efficiency, magnesium encapsulation efficiency, in vitro release of magnesium ions, and cellular compatibility using both human adipose-derived stem cells (ASCs) and PC12 cells. Chitosan coated PLGA microspheres can significantly control the release of magnesium ions compared to uncoated PLGA microspheres. Both coated and uncoated microspheres showed good cellular compatibility.

Effects of Thermal Annealing Conditions on Cupric Oxide Thin Film

Energy Technology Data Exchange (ETDEWEB)

Kim, Hyo Seon; Oh, Hee-bong; Ryu, Hyukhyun [Inje University, Gimhae (Korea, Republic of); Lee, Won-Jae [Dong-Eui University, Busan (Korea, Republic of)

2015-07-15

In this study, cupric oxide (CuO) thin films were grown on fluorine doped tin oxide(FTO) substrate by using spin coating method. We investigated the effects of thermal annealing temperature and thermal annealing duration on the morphological, structural, optical and photoelectrochemical properties of the CuO film. From the results, we could find that the morphologies, grain sizes, crystallinity and photoelectrochemical properties were dependent on the annealing conditions. As a result, the maximum photocurrent density of -1.47 mA/cm{sup 2} (vs. SCE) was obtained from the sample with the thermal annealing conditions of 500 ℃ and 40 min.

Hydrogen production through high-temperature electrolysis in a solid oxide cell

International Nuclear Information System (INIS)

Herring, J.St.; Lessing, P.; O'Brien, J.E.; Stoots, C.; Hartvigsen, J.; Elangovan, S.

2004-01-01

An experimental research programme is being conducted by the INEEL and Ceramatec, Inc., to test the high-temperature, electrolytic production of hydrogen from steam using a solid oxide cell. The research team is designing and testing solid oxide cells for operation in the electrolysis mode, producing hydrogen rising a high-temperature heat and electrical energy. The high-temperature heat and the electrical power would be supplied simultaneously by a high-temperature nuclear reactor. Operation at high temperature reduces the electrical energy requirement for electrolysis and also increases the thermal efficiency of the power-generating cycle. The high-temperature electrolysis process will utilize heat from a specialized secondary loop carrying a steam/hydrogen mixture. It is expected that, through the combination of a high-temperature reactor and high-temperature electrolysis, the process will achieve an overall thermal conversion efficiency of 40 to 50%o while avoiding the challenging chemistry and corrosion issues associated with the thermochemical processes. Planar solid oxide cell technology is being utilised because it has the best potential for high efficiency due to minimized voltage and current losses. These losses also decrease with increasing temperature. Initial testing has determined the performance of single 'button' cells. Subsequent testing will investigate the performance of multiple-cell stacks operating in the electrolysis mode. Testing is being performed both at Ceramatec and at INEEL. The first cells to be tested were single cells based on existing materials and fabrication technology developed at Ceramatec for production of solid oxide fuel cells. These cells use a relatively thick (∼ 175 μm) electrolyte of yttria- or scandia-stabilised zirconia, with nickel-zirconia cermet anodes and strontium-doped lanthanum manganite cathodes. Additional custom cells with lanthanum gallate electrolyte have been developed and tested. Results to date have

Effects of solid fission products forming dissolved oxide (Nd) and metallic precipitate (Ru) on the thermal conductivity of uranium base oxide fuel

International Nuclear Information System (INIS)

Kim, Dong-Joo; Yang, Jae-Ho; Kim, Jong-Hun; Rhee, Young-Woo; Kang, Ki-Won; Kim, Keon-Sik; Song, Kun-Woo

2007-01-01

The effects of solid fission products on the thermal conductivity of uranium base oxide nuclear fuel were experimentally investigated. Neodymium (Nd) and ruthenium (Ru) were added to represent the physical states of solid fission products such as 'dissolved oxide' and 'metallic precipitate', respectively. Thermal conductivity was determined on the basis of the thermal diffusivity, density and specific heat values. The effects of the additives on the thermal conductivity were quantified in the form of the thermal resistivity equation - the reciprocal of the phonon conduction equation - which was determined from the measured data. It is concluded that the thermal conductivity of the irradiated nuclear fuel is affected by both the 'dissolved oxide' and the 'metallic precipitate', however, the effects are in the opposite direction and the 'dissolved oxide' influences the thermal conductivity more significantly than that of the 'metallic precipitate'

Interstitial pressure dependence of the thermal conductivity of some rare earth oxide powders

International Nuclear Information System (INIS)

Pradeep, P.

1997-01-01

Thermal transport properties of powdered materials depend upon interstitial gas pressure. The present study reports the experimental results for the effective thermal conductivity of three rare earth oxide powders viz. yttrium oxide, samarium oxide, and gadolinium oxide, at various interstitial pressures by using transient plane source (TPS) method. A theoretical model is also proposed for the interpretation of the variation of the effective thermal conductivity with interstitial gas pressure. Its validity is found to be good in low pressure range of 45 mm Hg to normal pressure when compared with the experimental results. Also an attempt has been made to calculate the variation of thermal conductivity with interstitial pressure in the high pressure range up to 2 kbar using the proposed model. (author)

Microstructure of oxides in thermal barrier coatings grown under dry/humid atmosphere

International Nuclear Information System (INIS)

Zhou Zhaohui; Guo Hongbo; Wang Juan; Abbas, Musharaf; Gong Shengkai

2011-01-01

Graphical abstract: The presence of water vapor promoted the formation of spinels in the TBC. Highlights: → Thermal barrier coatings are produced by electron beam physical vapour deposition. → Oxidation behaviour of the coatings at 1100 deg. C has been investigated in dry/humid O 2 . → Thermally grown oxides formed in the coatings are characterized. → The presence of water vapour promotes the formation of spinel in the TBCs. - Abstract: The microstructure of thermally grown oxide (TGO) in thermal barrier coatings (TBCs) oxidized under dry/humid atmosphere at 1100 deg. C has been characterized by transmission electron microscopy. A thin and continuous oxide layer is formed in the as-deposited TBCs produced by electron beam physical vapor deposition. The TGO formed in dry atmosphere consists of an outer layer of fine α-alumina, zirconia grains and an inner layer of columnar α-alumina grains. However, a small amount of spinel is observed in the TGO under humid atmosphere. The presence of water vapour promotes the formation of spinel.

Evaluation of Anticonvulsive ٍEffect of Magnesium Oxide Nanoparticles in Comparison with Conventional MgO in Diabetic and Non-diabetic Male Mice

Directory of Open Access Journals (Sweden)

Leila Jahangiri

2014-05-01

Full Text Available Introduction: Some studies show magnesium has anticonvulsive effect in some animal models. Despite of the availability of well-studied anticonvulsant drugs, this evaluation was not carried on new kind of magnesium supplement, magnesium oxide nanoparticles (nMgO. According to the interaction between magnesium and convulsion, this study was designed to evaluate the effect of nMgO on strychnine-induced convulsive model in compared to its conventional in diabetic and normal mice. Methods: Healthy male albino mice were divided to 10 groups. Diabete mellitus was induced by streptozocin in 5 groups. Conventional and nanoparticle MgO (5&10mg/kg in presence and absence diabetes injected to mice, then strychnine injected and onset of convulsions and time of death were measured after strychnine administration. Results: Convulsive parameters did not change in normal and diabetic mice. cMgO pretreatment did not have anticonvulsant effect in strychnine-induced convulsion in normal and diabetic mice. But nMgO significantly changed convulsion onset and death time after strychnine administration in normal and diabetic status. Discussion: According to our results It seems that nMgO may be important in prevention or treatment of epilepsy and has more efficacy than its conventional form to showing anticonvulsive effect that probably is related to the physicochemical properties of nMgO, specially in diabetic subjects, a point that need to further investigation.

Mechanical and oxidation properties of some B2 rare earth–magnesium intermetallic

Energy Technology Data Exchange (ETDEWEB)

Stumphy, Brad [Iowa State Univ., Ames, IA (United States)

2006-12-15

The remainder of Chapter 1 provides background information on three main topics. First is a discussion about the basic structure and composition of binary B2 intermetallic compounds. Second, the mechanical properties of intermetallics are examined, starting with the cause for the typically inherent brittleness observed in B2 intermetallics. A number of B2 compounds have been found to possess an abnormal level of ductility compared to other intermetallics in this class, including a handful of other rare earth–non-rare earth (RM) B2 line compounds, and these findings are also discussed. Finally, oxidation studies of rare earth metals, focusing on yttrium and cerium, as well as magnesium and some B2 materials are discussed. Chapter 2 is an in-depth look into certain aspects of the laboratory work done during this study. The many challenges and difficulties encountered required that a variety of laboratory techniques be attempted in the making, processing, and testing of these two intermetallic materials. The results and ensuing discussion for the mechanical testing that was performed are found in Chapter 3. Tensile and compression testing results for YMg are shown first, followed by those for CeMg. Some samples were made using electrical discharge machining (EDM) while others were polished into the desired shape. A scanning electron microscope (SEM) was utilized to inspect surfaces of the tensile and compression samples. Hardness values and attempts to determine fracture toughness are also recorded before beginning the discussion. Chapter 4 follows the same basic format for the oxidation study portion of the research. Oxidation curves for CeMg are followed by a qualitative chemical analysis using energy dispersive spectroscopy (EDS). The YMg oxidation curves are shown next followed by an x-ray diffraction (XRD) analysis of the oxidation process for this material and a discussion of the results. Chapter 5 is a summary of the research performed in the mechanical and

Reprint of: Improved cytotoxicity testing of magnesium materials

International Nuclear Information System (INIS)

Fischer, Janine; Pröfrock, Daniel; Hort, Norbert; Willumeit, Regine; Feyerabend, Frank

2011-01-01

Metallic magnesium (Mg) and its alloys are highly suitable for medical applications as biocompatible and biodegradable implant materials. Magnesium has mechanical properties similar to bone, stimulates bone regeneration, is an essential non-toxic element for the human body and degrades completely within the body environment. In consequence, magnesium is a promising candidate as implant material for orthopaedic applications. Protocols using the guideline of current ISO standards should be carefully evaluated when applying them for the characterization of the cytotoxic potential of degradable magnesium materials. For as-cast material we recommend using 10 times more extraction medium than recommended by the ISO standards to obtain reasonable results for reliable cytotoxicity rankings of degradable materials in vitro. In addition primary isolated human osteoblasts or mesenchymal stem cells should be used to test magnesium materials.

Reprint of: Improved cytotoxicity testing of magnesium materials

Energy Technology Data Exchange (ETDEWEB)

Fischer, Janine [Helmholtz-Zentrum Geesthacht, Institute of Materials Research, Department for Structural Research on Macromolecules, Max-Planck Str. 1, D - 21502 Geesthacht (Germany); Proefrock, Daniel [Helmholtz-Zentrum Geesthacht, Institute for Coastal Research, Department for Marine Bioanalytical Chemistry, Max-Planck Str. 1, D - 21502 Geesthacht (Germany); Hort, Norbert [Helmholtz-Zentrum Geesthacht, Institute of Materials Research, Department for Magnesium Processing, Max-Planck Str. 1, D - 21502 Geesthacht (Germany); Willumeit, Regine; Feyerabend, Frank [Helmholtz-Zentrum Geesthacht, Institute of Materials Research, Department for Structural Research on Macromolecules, Max-Planck Str. 1, D - 21502 Geesthacht (Germany)

2011-12-15

Metallic magnesium (Mg) and its alloys are highly suitable for medical applications as biocompatible and biodegradable implant materials. Magnesium has mechanical properties similar to bone, stimulates bone regeneration, is an essential non-toxic element for the human body and degrades completely within the body environment. In consequence, magnesium is a promising candidate as implant material for orthopaedic applications. Protocols using the guideline of current ISO standards should be carefully evaluated when applying them for the characterization of the cytotoxic potential of degradable magnesium materials. For as-cast material we recommend using 10 times more extraction medium than recommended by the ISO standards to obtain reasonable results for reliable cytotoxicity rankings of degradable materials in vitro. In addition primary isolated human osteoblasts or mesenchymal stem cells should be used to test magnesium materials.

Solid oxide fuel cells fueled with reducible oxides

Science.gov (United States)

Chuang, Steven S.; Fan, Liang Shih

2018-01-09

A direct-electrochemical-oxidation fuel cell for generating electrical energy includes a cathode provided with an electrochemical-reduction catalyst that promotes formation of oxygen ions from an oxygen-containing source at the cathode, a solid-state reduced metal, a solid-state anode provided with an electrochemical-oxidation catalyst that promotes direct electrochemical oxidation of the solid-state reduced metal in the presence of the oxygen ions to produce electrical energy, and an electrolyte disposed to transmit the oxygen ions from the cathode to the solid-state anode. A method of operating a solid oxide fuel cell includes providing a direct-electrochemical-oxidation fuel cell comprising a solid-state reduced metal, oxidizing the solid-state reduced metal in the presence of oxygen ions through direct-electrochemical-oxidation to obtain a solid-state reducible metal oxide, and reducing the solid-state reducible metal oxide to obtain the solid-state reduced metal.

Lightweight, High Strength Nano-Composite Magnesium for Radiators, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — In this Phase I SBIR, Terves will develop processing routes to produce high thermal conductivity magnesium composites for use in heat transfer applications such as...

Thermoluminescence of magnesium doped zirconium oxide (ZrO2:Mg) UV irradiated

International Nuclear Information System (INIS)

Rivera Montalvo, Teodoro; Furetta, Claudio

2008-01-01

Full text: The monitoring of ultraviolet radiation (UVR) different thermoluminescent (TL) materials have been used to measure UVR. UV dosimetry using thermoluminescence phenomena has been suggested in the past by several authors. This technique has an advantage over others methods due to the readout of the samples. Other advantages of these phosphors are their small size, portability, lack of any power requirements, linear response to increasing radiation dose and high sensitivity. Zirconium oxide, recently received full attention in view of their possible use as thermoluminescent dosimeter (TLD), if doped with suitable activators, in radiation dosimetry. In the present investigation thermoluminescent (TL) properties of magnesium doped zirconium oxide (ZrO 2 :Mg) under ultraviolet radiation (UVR) were studied. The ZrO 2 :Mg powder of size 30-40 nm, having mono clinical structure, exhibit a thermoluminescent glow curve with one peak centered at 180 C degrees. The TL response of ZrO 2 :Mg as a function ultraviolet radiation exhibits four maxima centered at 230, 260, 310 and 350 nmn. TL response of ZrO 2 :Mg as a function of spectral irradiance of UV Light was linear in a wide range. Fading and reusability of the phosphor were also studied. The results showed that ZrO 2 :Mg nano powder has the potential to be used as a UV dosemeter in UVR dosimetry. (author)

Embedded Si/Graphene Composite Fabricated by Magnesium-Thermal Reduction as Anode Material for Lithium-Ion Batteries

Science.gov (United States)

Zhu, Jiangliu; Ren, Yurong; Yang, Bo; Chen, Wenkai; Ding, Jianning

2017-12-01

Embedded Si/graphene composite was fabricated by a novel method, which was in situ generated SiO2 particles on graphene sheets followed by magnesium-thermal reduction. The tetraethyl orthosilicate (TEOS) and flake graphite was used as original materials. On the one hand, the unique structure of as-obtained composite accommodated the large volume change to some extent. Simultaneously, it enhanced electronic conductivity during Li-ion insertion/extraction. The MR-Si/G composite is used as the anode material for lithium ion batteries, which shows high reversible capacity and ascendant cycling stability reach to 950 mAh·g-1 at a current density of 50 mA·g-1 after 60 cycles. These may be conducive to the further advancement of Si-based composite anode design.

The reactions of magnesium and its alloys with moist gases at high temperatures

International Nuclear Information System (INIS)

Darras, R.

1963-02-01

The kinetics and mechanisms of the reaction of pure or low alloyed magnesium with various gas saturated by water vapor: oxygen, argon, nitrogen, air, carbon dioxide, have been studied and compared in the temperature range 350-600 deg C. After picturing the large chemical reactivity of magnesium surface, the more or less properties of the oxide film, always made of magnesia, have been shown depending on the nature of the gas carrying water vapor; in fact, metal sublimation occurs the more easily as the surrounding atmosphere is less oxidizing. Moreover, an activation energy change is systematic, but at a temperature which depends also on the latter. In the case of the alloys, the linear oxidation rate is generally obtained only after short induction periods, parabolic in nature. Two possibilities of corrosion inhibition of magnesium by water vapor are then demonstrated and explained: either by a partial superficial fluoridation, or when the carrier gas is carbon dioxide. Also, the extreme conditions of oxidation were studied, that is the ignition processes that occur at a particular temperature in every gas mixture. Finally, it is tried to evolve the fundamental and practical significance of all the results. (author) [fr

Research of growth mechanism of ceramic coatings fabricated by micro-arc oxidation on magnesium alloys at high current mode

OpenAIRE

Wei-wei Chen; Ze-xin Wang; Lei Sun; Sheng Lu

2015-01-01

Micro-arc oxidation (MAO) coatings of ZK60 magnesium alloys were formed in a self-developed dual electrolyte composed of sodium silicate and phosphate at the high constant current of 1.8 A (15 A/dm2). The MAO process and growth mechanism were investigated by scanning electron microscopy (SEM) coupled with an energy dispersive spectrometer (EDS), confocal laser scanning microscopy and X-ray diffraction (XRD). The results indicate that the growth process of MAO coating mainly goes through “form...

Nanostructured calcium phosphate coatings on magnesium alloys: characterization and cytocompatibility with mesenchymal stem cells.

Science.gov (United States)

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.

Nanostructured magnesium has fewer detrimental effects on osteoblast function

Science.gov (United States)

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

Nanostructured magnesium has fewer detrimental effects on osteoblast function.

Science.gov (United States)

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.

Growth and thermal oxidation of Ru and ZrO2 thin films as oxidation protective layers

NARCIS (Netherlands)

Coloma Ribera, R.

2017-01-01

This thesis focuses on the study of physical and chemical processes occurring during growth and thermal oxidation of Ru and ZrO2 thin films. Acting as oxidation resistant capping materials to prevent oxidation of layers underneath, these films have several applications, i.e., in microelectronics

Blood compatibility of magnesium and its alloys.

Science.gov (United States)

Feyerabend, Frank; Wendel, Hans-Peter; Mihailova, Boriana; Heidrich, Stefanie; Agha, Nezha Ahmad; Bismayer, Ulrich; Willumeit-Römer, Regine

2015-10-01

Blood compatibility analysis in the field of biomaterials is a highly controversial topic. Especially for degradable materials like magnesium and its alloys no established test methods are available. The purpose of this study was to apply advanced test methodology for the analysis of degrading materials to get a mechanistic insight into the corrosion process in contact with human blood and plasma. Pure magnesium and two magnesium alloys were analysed in a modified Chandler-Loop setup. Standard clinical parameters were determined, and a thorough analysis of the resulting implant surface chemistry was performed. The contact of the materials to blood evoked an accelerated inflammatory and cell-induced osteoconductive reaction. Corrosion products formed indicate a more realistic, in vivo like situation. The active regulation of corrosion mechanisms of magnesium alloys by different cell types should be more in the focus of research to bridge the gap between in vitro and in vivo observations and to understand the mechanism of action. This in turn could lead to a better acceptance of these materials for implant applications. The presented study deals with the first mechanistic insights during whole human blood contact and its influence on a degrading magnesium-based biomaterial. The combination of clinical parameters and corrosion layer analysis has been performed for the first time. It could be of interest due to the intended use of magnesium-based stents and for orthopaedic applications for clinical applications. An interest for the readers of Acta Biomaterialia may be given, as one of the first clinically approved magnesium-based devices is a wound-closure device, which is in direct contact with blood. Moreover, for orthopaedic applications also blood contact is of high interest. Although this is not the focus of the manuscript, it could help to rise awareness for potential future applications. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All

The Role of Magnesium in Neurological Disorders

Directory of Open Access Journals (Sweden)

Anna E. Kirkland

2018-06-01

Full Text Available Magnesium is well known for its diverse actions within the human body. From a neurological standpoint, magnesium plays an essential role in nerve transmission and neuromuscular conduction. It also functions in a protective role against excessive excitation that can lead to neuronal cell death (excitotoxicity, and has been implicated in multiple neurological disorders. Due to these important functions within the nervous system, magnesium is a mineral of intense interest for the potential prevention and treatment of neurological disorders. Current literature is reviewed for migraine, chronic pain, epilepsy, Alzheimer’s, Parkinson’s, and stroke, as well as the commonly comorbid conditions of anxiety and depression. Previous reviews and meta-analyses are used to set the scene for magnesium research across neurological conditions, while current research is reviewed in greater detail to update the literature and demonstrate the progress (or lack thereof in the field. There is strong data to suggest a role for magnesium in migraine and depression, and emerging data to suggest a protective effect of magnesium for chronic pain, anxiety, and stroke. More research is needed on magnesium as an adjunct treatment in epilepsy, and to further clarify its role in Alzheimer’s and Parkinson’s. Overall, the mechanistic attributes of magnesium in neurological diseases connote the macromineral as a potential target for neurological disease prevention and treatment.

Revisiting the effects of organic solvents on the thermal reduction of graphite oxide

International Nuclear Information System (INIS)

Barroso-Bujans, Fabienne; Fierro, José Luis G.; Alegría, Angel; Colmenero, Juan

2011-01-01

Highlights: ► Retention of organic solvent on graphite oxide interlayer space. ► Decreasing exfoliation temperature. ► Close link between structure and thermal behavior of solvent treated graphite oxide. ► Restacking inhibition of thermally reduced graphite oxide sheets. ► Changes in kinetic mechanisms of thermal reduction. - Abstract: Treatment of graphite oxide (GO) with organic solvents via sorption from either liquid or gas phase, and subsequent desorption, induces profound changes in the layered GO structure: loss of stacking order, retention of trace amounts of solvents and decreasing decomposition temperature. This study presents new evidences of the effect of organic solvents on the thermal reduction of GO by means of thermogravimetric analysis, X-ray diffraction and X-ray photoelectron spectroscopy. The results reveal a relative higher decrease of the oxygen amounts in solvent-treated GO as compared to untreated GO and the restacking inhibition of the thermally reduced GO sheets upon slow heating. The kinetic experiments evidence changes occurring in the reduction mechanisms of the solvent-treated GO, which support the close link between GO structure and thermal properties.

Production of magnesium metal

Science.gov (United States)

Blencoe, James G [Harriman, TN; Anovitz, Lawrence M [Knoxville, TN; Palmer, Donald A [Oliver Springs, TN; Beard, James S [Martinsville, VA

2010-02-23

A process of producing magnesium metal includes providing magnesium carbonate, and reacting the magnesium carbonate to produce a magnesium-containing compound and carbon dioxide. The magnesium-containing compound is reacted to produce magnesium metal. The carbon dioxide is used as a reactant in a second process. In another embodiment of the process, a magnesium silicate is reacted with a caustic material to produce magnesium hydroxide. The magnesium hydroxide is reacted with a source of carbon dioxide to produce magnesium carbonate. The magnesium carbonate is reacted to produce a magnesium-containing compound and carbon dioxide. The magnesium-containing compound is reacted to produce magnesium metal. The invention further relates to a process for production of magnesium metal or a magnesium compound where an external source of carbon dioxide is not used in any of the reactions of the process. The invention also relates to the magnesium metal produced by the processes described herein.

Study of Seal Glass for Solid Oxide Fuel/Electrolyzer Cells

OpenAIRE

Mahapatra, Manoj Kumar

2009-01-01

Seal glass is essential and plays a crucial role in solid oxide fuel/electrolyzer cell performance and durability. A seal glass should have a combination of thermal, chemical, mechanical, and electrical properties in order to seal different cell components and stacks and prevent gas leakage. All the desired properties can simultaneously be obtained in a seal glass by suitable compositional design. In this dissertation, SrO-La₂O₃-A₂O₃-B₂O₃3-SiO₂ based seal glasses have been developed and compo...

Comparison of radiation-induced and thermal oxidative aging of polyethylene in the presence of inhibitors

International Nuclear Information System (INIS)

Dalinkevich, A.A.; Piskarev, I.M.

1996-01-01

Thermal oxidative and radiation-induced oxidative aging of inhibited polyethylene of commercial brands with known properties was studied at 60, 80 and 140 deg C. Radiation-induced oxidative aging was carried out under X-ray radiation with E max = 25 keV at dose rates providing specimen oxidation in kinetic conditions. The value of activation energy of thermal oxidative destruction of inhibited polyethylene under natural conditions of its employment at 60-140 deg C (E a = 60 kJ/mol) was obtained by comparison of data for radiation-induced and thermal oxidative destruction

Strategies for Lowering Solid Oxide Fuel Cells Operating Temperature

Directory of Open Access Journals (Sweden)

Albert Tarancón

2009-11-01

Full Text Available Lowering the operating temperature of solid oxide fuel cells (SOFCs to the intermediate range (500–700 ºC has become one of the main SOFC research goals. High operating temperatures put numerous requirements on materials selection and on secondary units, limiting the commercial development of SOFCs. The present review first focuses on the main effects of reducing the operating temperature in terms of materials stability, thermo-mechanical mismatch, thermal management and efficiency. After a brief survey of the state-of-the-art materials for SOFCs, attention is focused on emerging oxide-ionic conductors with high conductivity in the intermediate range of temperatures with an introductory section on materials technology for reducing the electrolyte thickness. Finally, recent advances in cathode materials based on layered mixed ionic-electronic conductors are highlighted because the decreasing temperature converts the cathode into the major source of electrical losses for the whole SOFC system. It is concluded that the introduction of alternative materials that would enable solid oxide fuel cells to operate in the intermediate range of temperatures would have a major impact on the commercialization of fuel cell technology.