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Sample records for magnesium aluminum spinel

  1. Thermoluminescence of magnesium aluminum spinel

    NASA Astrophysics Data System (ADS)

    Kim, Taekyu; Whang, Chungnam; Sakurai, Takao

    Three-dimensional thermoluminescence (TL) spectra of MgAl2O4 spinel exposed to UV light showed a TL peak with a 710nm emission band at 472K and another peak with 520nm around 490K. The algorithm of the numerical analysis based on the model of 2 recombination centers had been developed for TL glow curves of MgAl2O4. The best-fit activation energy and frequency factor were determined as 0.61 eV and 3.75 × 104s-1, respectively, with the chi squared value of 0.010073. On the contrary, the parameters fitted by the conventional theory were the activation energy of 0.66 eV and the frequency factor of 1.25 × 105s-1 with the chi squared value of 0.01358. For TL of MgAl2O4, the model of 2 recombination centers gave a better fit than the conventional theory.

  2. Photoelectric effects in magnesium aluminum spinel

    NASA Astrophysics Data System (ADS)

    Woosley, J. D.; Wood, C.; Sonder, E.; Weeks, R. A.

    1980-07-01

    The electronic and transport properties of magnesium aluminum spinel have been investigated photoelectrically. Photoemission of holes and electrons into spinel from metal contacts (Pt, Au, Ta, Mo, and Cu) has been used to determine barrier heights. From this information, as well as vacuum-uv photoconductivity data, we have obtained the following energy-band parameters: The Fermi level lies ~3 eV below the bottom of the conduction band, which in turn is located ~ 2 eV below the vacuum level, and the band gap is ~ 9 eV. Photoemission was not observed from graphite electrodes which form Ohmic contacts. Electron, neutron, or gamma irradiation produced three photoconductivity bands of half-width ~0.5 eV, with peaks at 4.5, 5.0, and 5.5 eV. The three bands, equally spaced in energy, may be associated with the same center. The optical absorption band of the F center is in the same region of the spectrum; however, its shape did not correspond to the observed photoconductivity spectrum. A lower limit of 10-6 cm2/V has been calculated for the μτ product of the photogenerated charge carriers.

  3. First-principle Simulation of Magnesium-aluminum Spinel (MgAl2O4)

    NASA Astrophysics Data System (ADS)

    Zhang, W.; Seagle, C. T.; Zhou, H.; Heinz, D. L.

    2008-12-01

    11033768 First-principle Simulation of Magnesium-aluminum Spinel (MgAl2O4) Materials with the spinel crystal structure, AB2O4 are believed to be an important component of Earth's mantle and may be related to density and seismic wave velocity discontinuities at the transition zone from 400km to 660km depth. Using Ab-initio calculations, five phases are predicted to have a stability range at zero temperature: magnesium-aluminum spinel (MgAl2O4), two of its polymorphs, which are of Pbnm and Cmcm space groups, periclase (MgO) and corundum (Al2O3). Pbnm-MgAl2O4 has the calcium-ferrite structure and Cmcm-MgAl2O4 takes the calcium-titanate structure. Calculations are preformed using the PWSCF (Plane-Wave Self-Consistent Field) codes. The free energy of the compressed volume was calculated directly for each of the phases above. Based on the energy-volume results from the calculations, dissolution of MgAl2O4 into MgO + Al2O3 occurs at 12GPa and the mixture (MgO + Al2O3) is expected to recombine to form the calcium-ferrite type phase at about 27GPa. The two phase transition pressures are consistent with experimental results. Cell parameters of the five phases simulated and their bulk modulus derived from the energy-volume curve are also in good agreement with experimental work. But unlike the conclusions drawn from some previous experimental work, the calcium-ferrite type structure (Pbnm-MgAl2O4) did not transform to the calcium-titanate type structure (Cmcm-MgAl2O4) at around 40GPa, which provides the possibility that calcium-ferrite type phase may be stable to even higher pressures (up to100GPa). Derived parameters, bulk modulus and density of each phase are in good agreement with experimental results. The differences are within 4%. Compared to seismic velocity profiles of the earth, these phase transitions pressures match the discontinuity pressures at transition zone 400km (Fd3m- MgAl2O4 -> MgO + Al2O3) and 660km (MgO + Al2O3 -> Pbnm-MgAl2O4) respectively, suggesting

  4. In vitro biological and tribological properties of transparent magnesium aluminate (Spinel) and aluminum oxynitride (ALON®).

    PubMed

    Bodhak, Subhadip; Balla, Vamsi Krishna; Bose, Susmita; Bandyopadhyay, Amit; Kashalikar, Uday; Jha, Santosh K; Sastri, Suri

    2011-06-01

    The purpose of this first generation investigation is to evaluate the in vitro cytotoxicity, cell-materials interactions and tribological performance of Spinel and ALON® transparent ceramics for potential wear resistant load bearing implant applications. Besides their non-toxicity, the high surface energy of these ceramics significantly enhanced in vitro cell-materials interactions compared to bioinert commercially pure Ti as control. These transparent ceramics with high hardness in the range of 1334 and 1543 HV showed in vitro wear rate of the order of 10⁻⁶ mm³ Nm⁻¹ against Al₂O₃ ball at a normal load of 20 N. PMID:21562889

  5. Aluminum Hydroxide and Magnesium Hydroxide

    MedlinePlus

    Aluminum Hydroxide, Magnesium Hydroxide are antacids used together to relieve heartburn, acid indigestion, and upset stomach. They ... They combine with stomach acid and neutralize it. Aluminum Hydroxide, Magnesium Hydroxide are available without a prescription. ...

  6. Mobility of cations in magnesium aluminate spinel

    NASA Astrophysics Data System (ADS)

    Martinelli, J. R.; Sonder, E.; Weeks, R. A.; Zuhr, R. A.

    1986-04-01

    Transport of cations in magnesium aluminate spinel due to an applied electric field at approximately 1000 °C has been measured by observing changes in elemental concentrations near the cathode and anode surfaces using ion backscattering techniques. The results indicate that magnesium ions are the mobile species at 1000 °C and that these ions combine with ambient oxygen at the cathode surface to form a MgO layer. Quantitative interpretation of the data leads to the conclusion that the ionic transference number of spinel becomes approximately 0.5 after treatment in an electric field.

  7. Synthesis of magnesium aluminate spinel by periclase and alumina chlorination

    SciTech Connect

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

    2014-11-15

    Highlights: • Use of chlorination for the synthesis of magnesium aluminate spinel. • The reagents used were alumina, periclase and chlorine. • Isothermal and non-isothermal assays were performed in air and Cl{sub 2}–N{sub 2} flows. • The chlorination produced magnesium aluminate spinel at 700 °C. • Selectivity of the chlorination reaction to obtain spinel is very high. - Abstract: A pyrometallurgical route for the synthesis of magnesium aluminate spinel by thermal treatment of a mechanical mixture containing 29 wt% MgO (periclase) and 71 wt% Al{sub 2}O{sub 3} (alumina) in chlorine atmosphere was developed and the results were compared with 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{sub 2} atmosphere of the MgO–Al{sub 2}O{sub 3} mixture produces magnesium aluminate spinel at 700 °C, while in air, magnesium spinel is generated at 930 °C. The synthesis reaction of magnesium aluminate spinel was complete at 800 °C.

  8. Electrodeposition of magnesium and magnesium/aluminum alloys

    DOEpatents

    Mayer, A.

    1988-01-21

    Electrolytes and plating solutions for use in processes for electroplating and electroforming pure magnesium and alloys of aluminum and magnesium and also electrodeposition processes. An electrolyte of this invention is comprised of an alkali metal fluoride or a quaternary ammonium halide, dimethyl magnesium and/or diethyl magnesium, and triethyl aluminum and/or triisobutyl aluminum. An electrolyte may be dissolved in an aromatic hydrocarbon solvent to form a plating solution. The proportions of the component compounds in the electrolyte are varied to produce essentially pure magnesium or magnesium/aluminum alloys having varying selected compositions.

  9. Electrodeposition of magnesium and magnesium/aluminum alloys

    DOEpatents

    Mayer, Anton

    1988-01-01

    Electrolytes and plating solutions for use in processes for electroplating and electroforming pure magnesium and alloys of aluminum and magnesium and also electrodeposition processes. An electrolyte of this invention is comprised of an alkali metal fluoride or a quaternary ammonium halide, dimethyl magnesium and/or diethyl magnesium, and triethyl aluminum and/or triisobutyl aluminum. An electrolyte may be dissolved in an aromatic hydrocarbon solvent to form a plating solution. The proportions of the component compounds in the electrolyte are varied to produce essentially pure magnesium or magnesium/aluminum alloys having varying selected compositions.

  10. Electrodeposition of magnesium and magnesium/aluminum alloys

    SciTech Connect

    Mayer, A.

    1988-10-18

    Electrolytes and plating solutions for use in processes for electroplating and electroforming pure magnesium and alloys of aluminum and magnesium and also electrodeposition processes. An electrolyte of this invention is comprised of an alkali metal fluoride or a quaternary ammonium halide, dimethyl magnesium and/or diethyl magnesium, and triethyl aluminum and/or triisobutyl aluminum. An electrolyte may be dissolved in an aromatic hydrocarbon solvent to form a plating solution. The proportions of the component compounds in the electrolyte are varied to produce essentially pure magnesium or magnesium/alumnum alloys having varying selected compositions.

  11. Shock-induced cation disorder in magnesium aluminate spinel

    NASA Astrophysics Data System (ADS)

    Chen, Q. Y.; Meng, C. M.; Lu, T. C.; Xu, M.; Qi, J. Q.; Tan, J. J.

    2010-12-01

    An increase in lattice constants and an order-disorder phase transition were observed in the magnesium aluminate spinel (MgAl2O4) powders after shock compression. Theoretical calculations on the basis of density functional theory confirm that the remarkable volume expansion in shocked MgAl2O4 powders is closely related to the substantial site disorder in the MgAl2O4 lattice. The calculations also show that the partially inverse MgAl2O4 spinel with an inversion index of 0.7 represents the greatest disordered metastable phase and the most unstable structure.

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

    NASA Astrophysics Data System (ADS)

    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.

  13. Neutron irradiation influence on magnesium aluminium spinel inversion

    NASA Astrophysics Data System (ADS)

    Skvortsova, V.; Mironova-Ulmane, N.; Ulmanis, U.

    2002-05-01

    Grown by the Verneuil method MgO · nAl 2O 3 single crystals and natural spinel crystal have been studied using X-ray diffraction and photoluminescence spectra. The fast neutron irradiation of magnesium aluminium spinel leads to the lattice parameter decrease. The bond lengths of Mg-O and Al-O vary with the u-parameter and the lattice parameter. On the other hand, the bond lengths are related with the inversion parameter. Using changes of the lattice parameter during irradiation we have calculated the inversion parameter, which is 15-20%. In the luminescence spectra, the fast neutron radiation (fluence 10 16 cm -2) produces an increase in the intensity ratio of the N- to R-lines by 5-20%. Taking into account that intensity of the N-lines is closely associated with the inversion parameter, it is possible to state that the neutron irradiation causes the increasing of the spinel inversion.

  14. On the Compressive and Tensile Strength of Magnesium Aluminate Spinel

    NASA Astrophysics Data System (ADS)

    Paris, V.; Hayun, S.; Dariel, M. P.; Frage, N.; Zaretsky, E.

    2009-12-01

    Magnesium aluminate spinel is a strong polycrystalline transparent ceramic. Spinel is an attractive material for armor applications and its behavior under shock wave loading is of obvious interest. The purpose of the present study was to determine the Hugoniot elastic limit (HEL) of this material, its Hugoniot response above the HEL, and its spall strength. Planar impact experiments were performed over the 2 to 40 GPa stress range using the Velocity Interferometer System for Any Reflector (VISAR) as a principal diagnostics tool. According to these tests, spinel has a HEL of about 11.3 GPa. The spall strength of the material was found to be close to zero at low, about 2 GPa, impact stress.

  15. Hard transparent domes and windows from magnesium aluminate spinel

    NASA Astrophysics Data System (ADS)

    DiGiovanni, Anthony A.; Fehrenbacher, Larry; Roy, Don W.

    2005-05-01

    Transparent magnesium aluminate spinel is an attractive material for use in a wide range of optical applications including windows, domes, armor, and lenses, which require excellent transmission from the visible through to the mid IR. Theoretical transmission is very uniform and approaches 87% between 0.3 to 5 microns. Transmission characteristics rival that of ALON and sapphire in the mid-wave IR, making it especially attractive for the everincreasing performance requirements of current and next-generation IR imaging systems. Future designs in missile technology will require materials that can meet stringent performance demands in both optical and RF wavelengths. Loss characteristics for spinel are being investigated to meet those demands. Technology Assessment and Transfer Inc. (TA&T), have established a 9000 ft2 production facility for optical quality spinel based on the traditional hot-pressing followed by hot isostatic pressing (HIPing) route. Additionally, TA&T is developing pressureless sintering - a highly scalable, near net shape processing method based on traditional ceramic processing technology - to fabricate optical components. These two main processing approaches allow the widest variety of applications to be addressed using a range of optical components and configurations. The polycrystalline nature of spinel facilitates near net shape processing, which provides the potential to fabricate physically larger optical parts or larger quantities of parts at significantly lower costs compared to single crystal materials such as sapphire. Current research is focused at optimizing the processing parameters for both synthesis routes to maximize strength and transparency while minimizing the cost of fabrication.

  16. Luminescence and photoconductivity in magnesium aluminum spinel

    NASA Astrophysics Data System (ADS)

    Bandyopadhyay, Pradip K.; Summers, G. P.

    1985-02-01

    Ultraviolet-light excitation of thermochemically reduced MgAl2O4 single crystals below room temperature produces a luminescence band with a peak at 2.69 eV. The excitation spectrum of the 2.69-eV band coincides with the broad F-center absorption band at 5.30 eV. The 2.69-eV band is also emitted in uv-stimulated glow peaks which occur at 95 and 265 K. A photoconductivity maximum is observed at 5.39 eV at temperatures above 160 K, but the band is readily bleached by uv light.

  17. Production of Magnesium by Vacuum Aluminothermic Reduction with Magnesium Aluminate Spinel as a By-Product

    NASA Astrophysics Data System (ADS)

    Wang, Yaowu; You, Jing; Peng, Jianping; Di, Yuezhong

    2016-03-01

    The Pidgeon process currently accounts for 85% of the world's magnesium production. Although the Pidgeon process has been greatly improved over the past 10 years, such production still consumes much energy and material and creates much pollution. The present study investigates the process of producing magnesium by employing vacuum aluminothermic reduction and by using magnesite as material and obtaining magnesium aluminate spinel as a by-product. The results show that compared with the Pidgeon process, producing magnesium by vacuum aluminothermic reduction can save materials by as much as 50%, increase productivity up to 100%, and save energy by more than 50%. It can also reduce CO2 emission by up to 60% and realize zero discharge of waste residue. Vacuum aluminothermic reduction is a highly efficient, low-energy-consumption, and environmentally friendly method of producing magnesium.

  18. Production of Magnesium by Vacuum Aluminothermic Reduction with Magnesium Aluminate Spinel as a By-Product

    NASA Astrophysics Data System (ADS)

    Wang, Yaowu; You, Jing; Peng, Jianping; Di, Yuezhong

    2016-06-01

    The Pidgeon process currently accounts for 85% of the world's magnesium production. Although the Pidgeon process has been greatly improved over the past 10 years, such production still consumes much energy and material and creates much pollution. The present study investigates the process of producing magnesium by employing vacuum aluminothermic reduction and by using magnesite as material and obtaining magnesium aluminate spinel as a by-product. The results show that compared with the Pidgeon process, producing magnesium by vacuum aluminothermic reduction can save materials by as much as 50%, increase productivity up to 100%, and save energy by more than 50%. It can also reduce CO2 emission by up to 60% and realize zero discharge of waste residue. Vacuum aluminothermic reduction is a highly efficient, low-energy-consumption, and environmentally friendly method of producing magnesium.

  19. Lattice site of helium implanted in magnesium aluminate spinel

    NASA Astrophysics Data System (ADS)

    Alien, W. R.

    1993-01-01

    The lattice site of helium implanted at 60 keV in magnesium aluminate spinel (MgAl 2O 4) has been investigated with channeling effect measurements that apply the ion-induced 3He(d, p) 4He nuclear reaction. Within the spinel crystal structure, numerous interstices characterized by octahedral anion coordination are intrinsically unfilled by cations. For implantation at 300 K, a typical helium atom locates centrally in one of these vacant octahedral interstices with a probability of approximately 95%. Significant occupation of other lattice sites of either high or low symmetry was rejected. In particular, helium neither clusters in defect complexes nor locates in tetrahedral interstices or substitutional sites.

  20. Structure and mechanical properties of irradiated magnesium aluminate spinel

    NASA Astrophysics Data System (ADS)

    Devanathan, R.; Yu, N.; Sickafus, K. E.; Nastasi, M.

    1996-09-01

    The relationship between structure and mechanical properties of MgAl 2O 4 spinel single crystals following 400 keV Xe 2+ irradiation at 100 K to doses up to 1 × 10 20 ions/m 2 was examined. The structural changes in the irradiated layer were studied using electron diffraction from cross-sectional samples. The nano-indentation technique was used to determine the mechanical properties. At low doses, the material transformed into a metastable crystalline phase characterized by the rearrangement of cations. At the onset of this transformation, the Young's modulus and hardness rose to values about 10 and 15% higher, respectively, than those of the unirradiated crystal. Upon further irradiation, the metastable crystal became amorphous. The Young's modulus and hardness of the amorphous state were about 30 and 60% less, respectively, than the corresponding values of unirradiated spinel. These results, in conjunction with the findings of a recent computer simulation study, provide important insights into the exceptional radiation resistance of magnesium aluminate spinel.

  1. Lithium-aluminum-magnesium electrode composition

    DOEpatents

    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.

  2. Method for removing magnesium from aluminum-magnesium alloys with engineered scavenger compound

    SciTech Connect

    Riley, W.D.; Jong, B.W.

    1994-12-31

    The invention relates to a method for removal and production of high purity magnesium from aluminum-magnesium alloys using an engineered scanvenger compound. In particular, the invention relates to a method for removal and production of high purity magnesium from aluminum-magnesium alloys using the engineered scanvenger compound (ESC) lithium titanate (Li2O3TiO2). The removal of magnesium from the aluminum-magnesium alloys is performed at about 600-750 C in a molten salt bath of KCl or KCl-MgCl2 using lithium titanate (Li2O3TiO2) as the engineered scavenger compound (ESC). Electrode deposition of magnesium from the loaded ESC onto a stainless steel electrode is accomplished in a second step, and provides a clean magnesium electrode deposit for recycling. The second step also prepares the ESC for reuse.

  3. Exchange of sodium by magnesium in aluminum hydroxycarbonate gel.

    PubMed

    Scholtz, E C; Feldkamp, J R; White, J L; Hem, S L

    1984-07-01

    Approximately 90% of the sodium present in a washed aluminum hydroxycarbonate gel was removed by exchange with magnesium. This behavior supports recent structural studies which have suggested that cations such as sodium serve as counterions in aluminum hydroxycarbonate gel. However, sodium could not be removed from dihydroxyaluminum sodium carbonate by exchange with magnesium because sodium is part of the crystal structure. It is hypothesized that aluminum hydroxycarbonate gels which resist removal of sodium are actually mixtures containing dihydroxyaluminum sodium carbonate in addition to aluminum hydroxycarbonate. PMID:6470941

  4. Magnesium, aluminum and lead in various brain areas

    SciTech Connect

    Zumkley, H.; Bertram, H.P.; Brandt, M.; Roedig, M.; Spieker, C.

    1986-01-01

    Whereas the lead concentrations were increased in brain tissue of patients with chronic alcoholism, the aluminum concentrations remained within the normal range. The magnesium concentrations were found decreased in patients with chronic alcoholism compared to normal controls. The sources for the elevated lead levels seem to be the increased intake of alcohol. The decreased magnesium levels are probably caused by an increased loss of magnesium with the urine, malnutrition, malabsorption, hormonal factors and drugs. Various neurological disorders which often accompanied chronic alcoholism may be caused or aggravated by lead encephalopathy and hypomagnesemia. Therapeutical implications may be the early substitution of magnesium deficiency in chronic alcoholism. 10 references, 5 figures.

  5. The viability of aluminum Zintl anion moieties within magnesium-aluminum clusters

    SciTech Connect

    Wang, Haopeng; Jae Ko, Yeon; Zhang, Xinxing; Gantefoer, Gerd; Bowen, Kit H. E-mail: akandalam@wcupa.edu; Schnoeckel, Hansgeorg; Eichhorn, Bryan W.; Jena, Puru; Kiran, Boggavarapu E-mail: akandalam@wcupa.edu; Kandalam, Anil K. E-mail: akandalam@wcupa.edu

    2014-03-28

    Through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations, we have investigated the extent to which the aluminum moieties within selected magnesium-aluminum clusters are Zintl anions. Magnesium-aluminum cluster anions were generated in a pulsed arc discharge source. After mass selection, photoelectron spectra of Mg{sub m}Al{sub n}{sup −} (m, n = 1,6; 2,5; 2,12; and 3,11) were measured by a magnetic bottle, electron energy analyzer. Calculations on these four stoichiometries provided geometric structures and full charge analyses for the cluster anions and their neutral cluster counterparts, as well as photodetachment transition energies (stick spectra). Calculations revealed that, unlike the cases of recently reported sodium-aluminum clusters, the formation of aluminum Zintl anion moieties within magnesium-aluminum clusters was limited in most cases by weak charge transfer between the magnesium atoms and their aluminum cluster moieties. Only in cases of high magnesium content, e.g., in Mg{sub 3}Al{sub 11} and Mg{sub 2}Al{sub 12}{sup −}, did the aluminum moieties exhibit Zintl anion-like characteristics.

  6. The viability of aluminum Zintl anion moieties within magnesium-aluminum clusters.

    PubMed

    Wang, Haopeng; Ko, Yeon Jae; Zhang, Xinxing; Gantefoer, Gerd; Schnoeckel, Hansgeorg; Eichhorn, Bryan W; Jena, Puru; Kiran, Boggavarapu; Kandalam, Anil K; Bowen, Kit H

    2014-03-28

    Through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations, we have investigated the extent to which the aluminum moieties within selected magnesium-aluminum clusters are Zintl anions. Magnesium-aluminum cluster anions were generated in a pulsed arc discharge source. After mass selection, photoelectron spectra of MgmAln (-) (m, n = 1,6; 2,5; 2,12; and 3,11) were measured by a magnetic bottle, electron energy analyzer. Calculations on these four stoichiometries provided geometric structures and full charge analyses for the cluster anions and their neutral cluster counterparts, as well as photodetachment transition energies (stick spectra). Calculations revealed that, unlike the cases of recently reported sodium-aluminum clusters, the formation of aluminum Zintl anion moieties within magnesium-aluminum clusters was limited in most cases by weak charge transfer between the magnesium atoms and their aluminum cluster moieties. Only in cases of high magnesium content, e.g., in Mg3Al11 and Mg2Al12 (-), did the aluminum moieties exhibit Zintl anion-like characteristics. PMID:24697443

  7. The viability of aluminum Zintl anion moieties within magnesium-aluminum clusters

    NASA Astrophysics Data System (ADS)

    Wang, Haopeng; Jae Ko, Yeon; Zhang, Xinxing; Gantefoer, Gerd; Schnoeckel, Hansgeorg; Eichhorn, Bryan W.; Jena, Puru; Kiran, Boggavarapu; Kandalam, Anil K.; Bowen, Kit H.

    2014-03-01

    Through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations, we have investigated the extent to which the aluminum moieties within selected magnesium-aluminum clusters are Zintl anions. Magnesium-aluminum cluster anions were generated in a pulsed arc discharge source. After mass selection, photoelectron spectra of MgmAln- (m, n = 1,6; 2,5; 2,12; and 3,11) were measured by a magnetic bottle, electron energy analyzer. Calculations on these four stoichiometries provided geometric structures and full charge analyses for the cluster anions and their neutral cluster counterparts, as well as photodetachment transition energies (stick spectra). Calculations revealed that, unlike the cases of recently reported sodium-aluminum clusters, the formation of aluminum Zintl anion moieties within magnesium-aluminum clusters was limited in most cases by weak charge transfer between the magnesium atoms and their aluminum cluster moieties. Only in cases of high magnesium content, e.g., in Mg3Al11 and Mg2Al12-, did the aluminum moieties exhibit Zintl anion-like characteristics.

  8. Atomistic structures of metastable and amorphous phases in ion-irradiated magnesium aluminate spinel

    NASA Astrophysics Data System (ADS)

    Ishimaru, Manabu; Hirotsu, Yoshihiko; Afanasyev-Charkin, Ivan V.; Sickafus, Kurt E.

    2002-02-01

    Ion-beam-induced microstructures in magnesium aluminate (MgAl2O4) spinel have been examined using transmission electron microscopy (TEM). Irradiations were performed at cryogenic temperature (~120 K) on MgAl2O4 spinel single-crystal surfaces with (111) orientation, using 180 keV neon (Ne+) ions to ion fluences ranging from 1016 to 1017 Ne+ cm-2. Cross-sectional TEM observations indicated that the MgAl2O4 spinel transforms first into a metastable crystalline phase and then into an amorphous phase under these irradiation conditions. On the basis of selected-area electron diffraction and high-resolution TEM, we concluded that Ne-ion-beam irradiation induces an ordered spinel-to-disordered rock-salt-like structural phase transformation. Atomistic structures of amorphous MgAl2O4 were also examined on the basis of atomic pair distribution functions. We compared the experimentally obtained results with previous theoretically calculated results for the metastable and amorphous phases of MgAl2O4, and discussed the validity of the proposed ion-beam-induced structural changes in MgAl2O4 spinel.

  9. Transparent magnesium aluminate spinel: a prospective biomaterial for esthetic orthodontic brackets.

    PubMed

    Krishnan, Manu; Tiwari, Brijesh; Seema, Saraswathy; Kalra, Namitha; Biswas, Papiya; Rajeswari, Kotikalapudi; Suresh, Madireddy Buchi; Johnson, Roy; Gokhale, Nitin M; Iyer, Satish R; Londhe, Sanjay; Arora, Vimal; Tripathi, Rajendra P

    2014-11-01

    Adult orthodontics is recently gaining popularity due to its importance in esthetics, oral and general health. However, none of the currently available alumina or zirconia based ceramic orthodontic brackets meet the esthetic demands of adult patients. Inherent hexagonal lattice structure and associated birefringence limits the visible light transmission in polycrystalline alumina and make them appear white and non transparent. Hence focus of the present study was to assess the feasibility of using magnesium aluminate (MgAl2O4) spinel; a member of the transparent ceramic family for esthetic orthodontic brackets. Transparent spinel specimens were developed from commercially available white spinel powder through colloidal shaping followed by pressureless sintering and hot isostatic pressing at optimum conditions of temperature and pressure. Samples were characterized for chemical composition, phases, density, hardness, flexural strength, fracture toughness and optical transmission. Biocompatibility was evaluated with in-vitro cell line experiments for cytotoxicity, apoptosis and genotoxicity. Results showed that transparent spinel samples had requisite physico-chemical, mechanical, optical and excellent biocompatibility for fabricating orthodontic brackets. Transparent spinel developed through this method demonstrated its possibility as a prospective biomaterial for developing esthetic orthodontic brackets. PMID:25027301

  10. Mechanical properties of several magnesium and aluminum composites. Final report

    SciTech Connect

    Tsangarakis, N.; Taleghani, B.

    1992-12-01

    Several composites of magnesium and aluminum alloys were tested in order to assess and evaluate their mechanical properties. The magnesium alloys were AZ91 C, ZE41 A, and commercially pure magnesium, reinforced with 40% by volume continuous graphite fiber. The tensile properties of these composites were not superior to those of unreinforced magnesium and estimates of their fracture toughness were low. The matrices of the aluminum composites were 2124-T6, 6061-T4, 2124-T4, and 2219-T4. The reinforcements were either particulate or whiskers of silicon carbide or boron carbide and their volume content was 15% to 30%. The aluminum composites which were reinforced with silicon carbide particulate exhibited improved yield and ultimate tensile stresses, as well as tensile elastic modulus over the unreinforced aluminum alloys. The 2124-T4/B4C/25p composite exhibited the highest ultimate tensile strength which was 511 MPa. The composite which was reinforced with whiskers of silicon carbide exhibited an endurance limit which was 20% higher than that of the matrix alloy. The compressive properties and fracture toughness of some of these aluminum composites were not improved over those of the unreinforced matrix alloy.... Composites, Mechanical properties.

  11. Czochralski growth and optical properties of magnesium-aluminium spinel doped with nickel

    NASA Astrophysics Data System (ADS)

    Wyon, C.; Aubert, J. J.; Auzel, F.

    1986-12-01

    Blue single crystals of magnesium aluminium spinel doped with nickel have been pulled from the melt, by the Czochralski technique. The transmission spectrum of doped samples show three broad absorption bands. According to the absorption map and the chemical analysis of these crystals, the effective segregation coefficient of Ni 2+ in MgAl 20 4 seems to be roughly 1. At T= 80 K. the expected tuning range of the stimulated emission lies from 1.2 to 1.4 μm.

  12. Mechanical properties and microstructure of α-alumina and magnesium aluminate spinel irradiated with He ions

    NASA Astrophysics Data System (ADS)

    Izumi, Koichiro; Yasuda, Kazuhiro; Kinoshita, Chiken; Kutsuwada, Masanori

    1998-10-01

    Mechanical properties of α-alumina, stoichiometric- and nonstoichiometric-magnesium aluminate spinel single crystals were examined by using ultra-microhardness technique. The samples were irradiated with 100 keV He + ions at temperatures of 300-870 K and to fluences up to 2 × 10 20 He +/m 2. Apparent hardness, Δ H, in α-alumina increases with fluence in three stages, while that of spinel crystals increases monotonically with fluence. We have also evaluated elastic modulus, plastic and elastic energies, and plastic and elastic indentation depths through the analysis of load-displacement curves. These analyses showed that plastic and elastic hardening are responsible for the variation of Δ H of α-alumina, and that plastic hardening is the main cause of hardening in spinel crystals. Corresponding TEM observations suggested the importance of point defects and/or `invisible' defect clusters for radiation hardening compared to `visible' dislocation loops. The relationship between microstructure and mechanical properties is given for various ceramics.

  13. Processing method and process modeling of large aperture transparent magnesium aluminate spinel domes

    NASA Astrophysics Data System (ADS)

    Yu, Jian; McWilliams, Brandon; Kilczewski, Steven; Gilde, Gary; Lidie, Ashley; Sands, James

    2009-05-01

    Polycrystalline spinel serves as an alternative to materials such as sapphire and magnesium fluoride that are currently being used in electromagnetic window applications such as missile domes, where high strength, high hardness and high transmittance in the visible and infrared spectra are required. The cubic crystal lattice of spinel imparts an isotropy to the bulk optical property, which eliminates optical distortion due to birefringence that occurs in sapphire and other non-cubic materials. The current study is to find a reliable manufacturing process to produce large magnesium aluminate spinel domes from powder consolidation efficiently. A binder-less dry ball milling process was used to deflocculate the spinel powder to increase its fluidity in an effort to ease the shape-forming. Dry ball milling time trials were conducted at several intervals to determine the appropriate level of time required to break up both the hard and soft agglomerates associated with the virgin spinel powder. The common problems encountered in dry powder shape-forming are crack growth and delamination of the green body during cold isostatic pressing (CIPing). The cracking and the delamination are due to the buildup of stress gradients on the green body that are created by the frictional force between the powder and the die wall or mold wall. To understand the stresses during the CIPing process, a finite element analysis of stresses on the green body was conducted. The simulation was used to evaluate the effect of die tooling and process characteristics on the development of stress gradients in the green body dome. Additionally, the effect of friction between the die wall and powder was examined by the simulation. It was found that by mitigating the frictional forces, cracking and delamination on the green body could be eliminated. A stepped-pressure CIPing technique was developed to reduce stress gradient build-up during CIPing. Also, oleic acid lubricant was applied to the die wall to

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

    SciTech Connect

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

    2012-01-01

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

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

    SciTech Connect

    Guan, Xiaofei; Zink, Peter; Pal, Uday

    2012-03-11

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

  16. Warm formability of aluminum-magnesium alloys

    SciTech Connect

    Taleff, E.M.; Henshall, G.A.; Lesuer, D.R.; Nieh, T.G.

    1994-05-27

    Manufacturers have become increasingly interested in near-net-shape forming of aluminum alloys as a means to reduce production costs and the weight of aircraft and automotive structures. To achieve the ductilities required for this process, we have examined extended ductility of Al-Mg alloys in the warm forming, or Class I creep, regime. We have studied a high-purity, binary alloy of Al-2.8Mg and ternary alloys of Al-xMg-0.5Mn with Mg concentrations from 1.0 to 6.6 wt. %. Tensile tests, including strain rates-change tests, have been performed with these materials at temperatures of 300 and 400C over a range 10{sup {minus}4} to 2 {times} 10{sup {minus}2} s{sup {minus}1}. A maximum tensile failure strain of 325% for the binary alloy and a maximum of 125% in the ternary alloys have been measured. The experimental results have been used to evaluate the effects of solute concentration, microstructure, temperature, and strain rate on flow stress ({sigma}), elongation to failure (e{sub f}), and strain-rate sensitivity (m) of these alloys.

  17. Defects and radiation induced electronic processes in magnesium aluminate spinel of different compositions

    NASA Astrophysics Data System (ADS)

    Gritsyna, V. T.; Kazarinov, Y. G.; Kobyakov, V. A.; Sickafus, K. E.

    The time dependence of the formation and decay of irradiation-induced optical absorption centers in magnesium aluminate spinel single crystals of different compositions (MgO.1.0Al(2)O(3) and MgO.2.5Al(2)O(3)) was investigated. The kinetics of accumulation of X-ray irradiation-induced absorption bands is consistent with the mechanism of trap filling with free charge carriers through the conduction band. The model includes Coulomb blocking effects on spatially correlated defects. The observed two-stage decay of absorption bands after termination of X-ray irradiation is explained by electron hole recombination between centers of two different distances and/or different potential barriers. UV-irradiation confirms the existence of charge exchange between complex spatially correlated defects.

  18. On the Compressive and Tensile Dynamic Strength of Magnesium Aluminate Spinel

    NASA Astrophysics Data System (ADS)

    Hayun, Shmuel; Paris, Vitaly; Dariel, Moshe; Zaretsky, Eugene; Frage, Nahum

    2009-06-01

    Polycrystalline transparent Magnesium Aluminate Spinel (MAS) is an attractive material for a wide range of optical, electronic, structural and armor applications. Transparent MAS samples of 20-30 mm diameter and 3-5 mm thickness has been successfully fabricated by means of Field Assisted Sintering Technology. The dynamic response of MAS was investigated by plate impact experiments. The values of the Hugoniot Elastic Limit (HEL) and the spall strength were derived from the VISAR records of the velocities of the free sample surface or of the sample/window (PMMA) interface. The dependence of the HEL and the spall strength on the impact stress, as well as, correlation between the spall strength and the width of the loading pulse are discussed.

  19. Radiation-induced disordering in magnesium aluminate spinel subjected to ionizing radiation

    NASA Astrophysics Data System (ADS)

    Shimada, M.; Matsumura, S.; Yasuda, K.; Kinoshita, C.; Chimi, Y.; Ishikawa, N.; Iwase, A.

    2004-08-01

    An analytical electron microscope study was carried out on single crystal specimens of magnesium aluminate spinel irradiated with 200 MeV Xe 14+ ions up to 5.0 × 10 15 and 2.0 × 10 16 ions/m 2 at ambient temperature. Bright-field images showed structurally disordered columns of about 4-5 nm in diameter along ion tracks. Tiny pits were observed on the incident surface of the columns. Quantitative HARECXS analysis of atomic configurations revealed that disordering proceeds in more extended regions over 10 nm in diameter. The configurations of Al 3+ ions are more disordered than that of Mg 2+ ions. The disordered areas are appeared to overlap each other in the specimen irradiated with 2.0 × 10 16 ions/m 2.

  20. Optical transitions in magnesium aluminate spinel crystals of different compositions exposed to irradiation

    NASA Astrophysics Data System (ADS)

    Gritsyna, V. T.; Afanasyev-Charkin, I. V.; Kazarinov, Yu. G.; Sickafus, K. E.

    2004-06-01

    Optical absorption of magnesium aluminate spinel single crystals of different compositions MgO · nAl 2O 3 ( n=1.0 and 2.5) were investigated after irradiation with neutrons, X-rays and the UV-light to elucidate existence of specific absorption bands related to lattice defects. The radiation induced absorption envelope is shifted to higher energy and is larger in intensity in non-stoichiometric spinel in comparison with stoichiometric one at the same irradiation conditions. Deconvolution of difference optical spectra of irradiated crystals shows the shift of the F-type centers from 4.75 and 5.3 eV in stoichiometric crystals to 5.08 and 5.63 eV in MgO · 2.5Al 2O 3 for F +- and F-centers, respectively. The absorption bands at 3.1 and 3.78 eV are present in both stoichiometric and non-stoichiometric crystals and are identified as V-type centers. By changing the irradiation time and using isochronal annealing it was revealed that additional bands appear in optical absorption spectra at 4.15 eV for MgO · 1.0Al 2O 3 crystals and at 4.46 eV for MgO · 2.5Al 2O 3 crystals. From the shift of the band energy position and the high intensity of this band in non-stoichiometric spinel crystals, it could be identified with electronic centers related to lattice defects.

  1. Microstructure and atomic disordering of magnesium aluminate spinel irradiated with swift heavy ions

    NASA Astrophysics Data System (ADS)

    Yamamoto, T.; Shimada, M.; Yasuda, K.; Matsumura, S.; Chimi, Y.; Ishikawa, N.

    2006-04-01

    We have investigated the microstructure and atomic disordering of nearly stoichiometric magnesium aluminate spinel (MgO · 1.1Al2O3), irradiated with 200 MeV Xe14+ ions (Se = 25 keV/nm). Transmission electron microscopy techniques of bright-field (BF) and high-resolution (HR) imaging, as well as high angular resolution electron channeling X-ray spectroscopy (HARECXS) were employed for quantitative analysis of radiation-induced structural change. BF images of ion tracks show columnar dark contrast of ∼4 nm in diameter accompanying distinct black or white dots at the incident surface. Clear lattice fringes are observed in HR images even inside the ion tracks, indicating that the spinel crystals are not amorphized but partially disordered along the ion tracks. HARECXS analysis showed that cation disordering progresses successively with ion fluence, and the disordered regions are found to extend over 12.8 ± 0.9 nm in diameter for Al ions and 9.6 ± 0.6 nm for Mg ions along the ion tracks. This chemically disordered region is much larger than the strained volume detected by BF and HR images.

  2. Cation disordering in magnesium aluminate spinel crystals induced by electron or ion irradiation

    NASA Astrophysics Data System (ADS)

    Soeda, Takeshi; Matsumura, Syo; Kinoshita, Chiken; Zaluzec, Nestor J.

    2000-12-01

    Structural changes in magnesium aluminate spinel (MgO · nAl 2O 3) single crystals, which were irradiated with 900 keV electrons or 1 MeV Ne + ions at 873 K, were examined by electron channeling enhanced X-ray microanalysis. Unirradiated MgO · Al 2O 3 has a tendency to form the normal spinel configuration, where Mg 2+ ions and Al 3+ ions occupy mainly the tetrahedral and the octahedral sites, respectively. Electron irradiation induces simple cation disordering between the tetrahedral sites and the octahedral sites in MgO · Al 2O 3. In addition to cation disordering, slight evacuation of cations from the tetrahedral sites to the octahedral sites occurs in a peak-damaged area in MgO · Al 2O 3 irradiated with Ne + ions. In contrast, cation disordering is suppressed in MgO · 2.4Al 2O 3 irradiated with electrons. The structural vacancies, present in the non-stoichiometric compound, appear to be effective in promoting irradiation damage recovery through interstitial-vacancy recombination.

  3. EFFECTS OF XE ION IRRADIATION AND SUBSEQUENT ANNEALING ON THE PROPERTIES OF MAGNESIUM-ALUMINATE SPINEL

    SciTech Connect

    I. AFANASYEV; ET AL

    2000-04-01

    Single crystals of magnesium-aluminate spinel MgAl{sub 2}O{sub 4} were irradiated with 340 keV Xe{sup 2} ions at {minus}173 C ({approximately} 100 K). A fluence of 1 x 10{sup 20} Xe/m{sup 2} created an amorphous layer at the surface of the samples. The samples were annealed for 1 h at different temperatures ranging from 130 C to 880 C. Recrystallization took place in the temperature interval between 610 C and 855 C. Transmission electron microscopy (TEM) images show two distinct layers near the surface: (1) a polycrystalline layer with columnar grain structure; and (2) a buried damaged layer epitaxial with the substrate. After annealing at 1100 C for 52 days, the profile of implanted Xe ions did not change, which means that Xe ions are not mobile in the spinel structure up to 1100 C. The thickness of the buried damaged layer decreased significantly in the 1100 C annealed sample comparing to the sample annealed for 1 h at 855 C.

  4. The Corrosion of Magnesium and of the Magnesium Aluminum Alloys Containing Manganese

    NASA Technical Reports Server (NTRS)

    Boyer, J A

    1927-01-01

    The extensive use of magnesium and its alloys in aircraft has been seriously handicapped by the uncertainties surrounding their resistance to corrosion. This problem has been given intense study by the American Magnesium Corporation and at the request of the Subcommittee on Materials for Aircraft of the National Advisory Committee for Aeronautics this report was prepared on the corrosion of magnesium. The tentative conclusions drawn from the experimental facts of this investigation are as follows: the overvoltage of pure magnesium is quite high. On immersion in salt water the metal corrodes with the liberation of hydrogen until the film of corrosion product lowers the potential to a critical value. When the potential reaches this value it no longer exceeds the theoretical hydrogen potential plus the overvoltage of the metal. Rapid corrosion consequently ceases. When aluminum is added, especially when in large amounts, the overvoltage is decreased and hydrogen plates out at a much lower potential than with pure magnesium. The addition of small amount of manganese raises the overvoltage back to practically that of pure metal, and the film is again negative.

  5. Final report on the safety assessment of aluminum silicate, calcium silicate, magnesium aluminum silicate, magnesium silicate, magnesium trisilicate, sodium magnesium silicate, zirconium silicate, attapulgite, bentonite, Fuller's earth, hectorite, kaolin, lithium magnesium silicate, lithium magnesium sodium silicate, montmorillonite, pyrophyllite, and zeolite.

    PubMed

    Elmore, Amy R

    2003-01-01

    This report reviews the safety of Aluminum, Calcium, Lithium Magnesium, Lithium Magnesium Sodium, Magnesium Aluminum, Magnesium, Sodium Magnesium, and Zirconium Silicates, Magnesium Trisilicate, Attapulgite, Bentonite, Fuller's Earth, Hectorite, Kaolin, Montmorillonite, Pyrophyllite, and Zeolite as used in cosmetic formulations. The common aspect of all these claylike ingredients is that they contain silicon, oxygen, and one or more metals. Many silicates occur naturally and are mined; yet others are produced synthetically. Typical cosmetic uses of silicates include abrasive, opacifying agent, viscosity-increasing agent, anticaking agent, emulsion stabilizer, binder, and suspending agent. Clay silicates (silicates containing water in their structure) primarily function as adsorbents, opacifiers, and viscosity-increasing agents. Pyrophyllite is also used as a colorant. The International Agency for Research on Cancer has ruled Attapulgite fibers >5 microm as possibly carcinogenic to humans, but fibers <5 microm were not classified as to their carcinogenicity to humans. Likewise, Clinoptilolite, Phillipsite, Mordenite, Nonfibrous Japanese Zeolite, and synthetic Zeolites were not classified as to their carcinogenicity to humans. These ingredients are not significantly toxic in oral acute or short-term oral or parenteral toxicity studies in animals. Inhalation toxicity, however, is readily demonstrated in animals. Particle size, fibrogenicity, concentration, and mineral composition had the greatest effect on toxicity. Larger particle size and longer and wider fibers cause more adverse effects. Magnesium Aluminum Silicate was a weak primary skin irritant in rabbits and had no cumulative skin irritation in guinea pigs. No gross effects were reported in any of these studies. Sodium Magnesium Silicate had no primary skin irritation in rabbits and had no cumulative skin irritation in guinea pigs. Hectorite was nonirritating to the skin of rabbits in a Draize primary skin

  6. An Aluminum Magnesium Hydroxide Stearate-based Skin Barrier Protection Cream Used for the Management of Eczematous Dermatitis

    PubMed Central

    Bhambri, Sanjay; Michaels, Brent

    2008-01-01

    Eczematous dermatoses can often be very difficult to treat. An aluminum magnesium hydroxide stearate-based cream has recently become available for clinical use. Aluminum magnesium hydroxide stearate-based cream provides an alternative option in treating these dermatoses while providing barrier protection against external allergens and irritants. This article reviews various studies evaluating aluminum magnesium hydroxide stearate-based cream. PMID:21212843

  7. Ionic conductivity measurement in magnesium aluminate spinel and solid state galvanic cell with magnesium aluminate electrolyte

    NASA Astrophysics Data System (ADS)

    Lee, Myongjai

    This thesis work is about the experimental measurement of electronic and ionic conductivities in the MgAl2O4 spinel at 500˜600°C range and exploring the fundamental origin of solid-state galvanic cell behavior in the cell of Al|MgAl2O4|Mg, Al|MgAl2O 4|C, and Mg|MgAl2O4|C, in which at least one metal electrode in common with the composition of the electrolyte. For the electronic conductivity measurement, we have used the ion-blocking Gold and Carbon electrodes which are inert with both Mg and Al ions to suppress the ionic conduction from the total conduction. DC polarization method was used to measure the conduction through Au|MgAl2O4|Au and C|MgAl2O4|C specimens. The measured electrical conductivity using Au|MgAl2O4|Au and C|MgAl2O4|C specimens showed 10-9.3 ˜ 10-8.4 (O·cm) -1 at 600˜720°C range following the Arrhenius-type relation. These conductivity data are in agreement with reported data obtained from Pt and Ag ion-blocking electrodes deposited on MgAl2O4 specimens. For the ionic conductivity measurement, we have used the non-blocking Al and Mg electrodes for Al and Mg ionic conductivities, respectively. Ionic conductivity measurement of Al and Mg in separate manner has not been reported yet. In both Al|MgAl2O4|Al and Mg|MgAl2O 4|Mg specimens, gradual increase of conduction was observed once at the initial period before it reaches the steady state conduction. By DC method on the range of 580˜650°C, steady state Al ionic conductivity was measured from Al|MgAl2O4|Al specimen showing 10 -7.7 ˜ 10-6.8 (O·cm)-1 with the activation energy of 1.9eV in sigma = sigma0 exp-QRT formula. There was no difference in the conductivity by the change of the atmosphere from 5%H2 + 95%N2 mixed gas to pure Ar gas. So it was confirmed that the oxygen defect chemistry did not play a role. For Mg ionic conductivity Mg|MgAl2O4|Mg specimen was used and the measured conductivity shows 10-6.7 ˜ 10-4.4 (O·cm)-1 at 400˜550°C with the activation energy of 1.44eV at Ar gas

  8. Formation of magnesium aluminate (spinel) in cast SiC particulate-reinforced Al(A356) metal matrix composites

    NASA Astrophysics Data System (ADS)

    Wang, Ning; Wang, Zhirui; Weatherly, George C.

    1992-05-01

    Transmission (TEM) and scanning electron microscopy (SEM) are employed to study the SiC/Al-alloy interface in a cast SiCp/Al(A356) metal matrix composite (MMC). Magnesium aluminate (spinel), MgAl2O4, was found at the interface as a reaction product after material processing. Comparisons of the crystal structure, structure factor, and interface reaction ther-modynamics between MgAl2O4 and MgO have been carried out. The results from these com-parisons confirm the experimental observation; i.e., the favored interface phase is magnesium aluminate (spinel). Based on the thermodynamic analysis, the presence of oxygen in various forms in the system during processing, such as SiO2, A12O3, and MgO, is believed to be the source which supplies the oxygen for the formation of MgAl2O4.

  9. Color-Center Production and Formation in Electron-Irradiated Magnesium Aluminate Spinel and Ceria

    DOE PAGESBeta

    Costantini, Jean-Marc; Lelong, Gerald; Guillaumet, Maxime; Weber, William J.; Takaki, Seiya; Yasuda, Kazuhiro

    2016-06-20

    Single crystals of magnesium aluminate spinel (MgAl2O4) with (100) or (110) orientations and cerium dioxide or ceria (CeO2) were irradiated by 1.0-MeV and 2.5-MeV electrons in a high fluence range. Point-defect production was studied by off-line UV-visible optical spectroscopy after irradiation. For spinel, regardless of both crystal orientation and electron energy, two characteristic broad bands centered at photon energies of 5.4 eV and 4.9 eV were assigned to F and F+ centers (neutral and singly-ionized oxygen vacancies), respectively, on the basis of available literature data. No clear differences in colour-centre formation were observed for the two crystal orientations. Using calculationsmore » of displacement cross sections by elastic collisions, these results are consistent with a very large threshold displacement energy (200 eV) for oxygen atoms at RT. A third very broad band centered at 3.7 eV might be attributed either to an oxygen hole center (V-type center) or an F2 dimer center (oxygen di-vacancy). The onset of recovery of these color centers took place at 200°C with almost full bleaching at 600°C. Activation energies (~0.3-0.4 eV) for defect recovery were deduced from the isochronal annealing data by using a first-order kinetics analysis. For ceria, a sub band-gap absorption feature peaked at ~3.1 eV was recorded for 2.5-MeV electron irradiation only. Assuming a ballistic process, we suggest that the latter defect might result from cerium atom displacement on the basis of computed cross sections.« less

  10. Color-center production and recovery in electron-irradiated magnesium aluminate spinel and ceria.

    PubMed

    Costantini, Jean-Marc; Lelong, Gérald; Guillaumet, Maxime; Weber, William J; Takaki, Seiya; Yasuda, Kazuhiro

    2016-08-17

    Single crystals of magnesium aluminate spinel (MgAl2O4) with (1 0 0) or (1 1 0) orientations and cerium dioxide or ceria (CeO2) were irradiated by 1.0 MeV and 2.5 MeV electrons in a high-fluence range. Point-defect production was studied by off-line UV-visible optical spectroscopy after irradiation. For spinel, regardless of both crystal orientation and electron energy, two characteristic broad bands centered at photon energies of 5.4 eV and 4.9 eV were assigned to F and F(+) centers (neutral and singly ionized oxygen vacancies), respectively, on the basis of available literature data. No clear differences in color-center formation were observed for the two crystal orientations. Using calculations from displacement cross sections by elastic collisions, these results are consistent with a very large threshold displacement energy (200 eV) for oxygen atoms at room temperature. A third very broad band centered at 3.7 eV might be attributed either to an oxygen hole center (V-type center) or an F2 dimer center (oxygen di-vacancy). The onset of recovery of these color centers took place at 200 °C with almost full bleaching at 600 °C. Activation energies (~0.3-0.4 eV) for defect recovery were deduced from the isochronal annealing data by using a first-order kinetics analysis. For ceria, a sub-band-gap absorption feature, which peaked at ~3.1 eV, was recorded for 2.5 MeV electron irradiation only. Assuming a ballistic process, we suggest that the latter defect might result from cerium atom displacement on the basis of computed cross sections. PMID:27319289

  11. Color-center production and recovery in electron-irradiated magnesium aluminate spinel and ceria

    NASA Astrophysics Data System (ADS)

    Costantini, Jean-Marc; Lelong, Gérald; Guillaumet, Maxime; Weber, William J.; Takaki, Seiya; Yasuda, Kazuhiro

    2016-08-01

    Single crystals of magnesium aluminate spinel (MgAl2O4) with (1 0 0) or (1 1 0) orientations and cerium dioxide or ceria (CeO2) were irradiated by 1.0 MeV and 2.5 MeV electrons in a high-fluence range. Point-defect production was studied by off-line UV–visible optical spectroscopy after irradiation. For spinel, regardless of both crystal orientation and electron energy, two characteristic broad bands centered at photon energies of 5.4 eV and 4.9 eV were assigned to F and F+ centers (neutral and singly ionized oxygen vacancies), respectively, on the basis of available literature data. No clear differences in color-center formation were observed for the two crystal orientations. Using calculations from displacement cross sections by elastic collisions, these results are consistent with a very large threshold displacement energy (200 eV) for oxygen atoms at room temperature. A third very broad band centered at 3.7 eV might be attributed either to an oxygen hole center (V-type center) or an F2 dimer center (oxygen di-vacancy). The onset of recovery of these color centers took place at 200 °C with almost full bleaching at 600 °C. Activation energies (~0.3–0.4 eV) for defect recovery were deduced from the isochronal annealing data by using a first-order kinetics analysis. For ceria, a sub-band-gap absorption feature, which peaked at ~3.1 eV, was recorded for 2.5 MeV electron irradiation only. Assuming a ballistic process, we suggest that the latter defect might result from cerium atom displacement on the basis of computed cross sections.

  12. An investigation of aluminum titanate-spinel composites behavior in radiation

    SciTech Connect

    Cevikbas, G.; Tugrul, A. B.; Boyraz, T.; Buyuk, B.; Onen, U.

    2015-03-30

    In the present work, the radiation attenuation properties of Aluminum titanate (Al{sub 2}TiO{sub 5})-Spinel (MgAl{sub 2}O{sub 4}) ceramics composites were investigated. Al{sub 2}TiO{sub 5}-MgAl{sub 2}O{sub 4} ceramics composites which have different Al{sub 2}TiO{sub 5} percentages (0%, 5% and 10%) were produced and performed against gamma sources. Cs-137 and Co-60 were used as gamma radiation sources. Transmission technique was used in the experiments. The linear and mass attenuation coefficients of the samples were carried out for gamma radiation sources. The experimental results were compared with the theoretical mass attenuation coefficients which were calculated by using XCOM computer code. Increasing Al{sub 2}TiO{sub 5} percentage in the Aluminum titanate/ Spinel ceramics composites causes the higher linear and mass attenuation coefficients of the composites against Cs-137 and Co-60 gamma radioisotopes. Therefore Also theoretical mass attenuation coefficients are compatible with the experimental results. In conclusion, increasing the Aluminum titanate ratio in the Al{sub 2}TiO{sub 5}-MgAl{sub 2}O{sub 4} ceramics composites increases the gamma shielding property of the Al{sub 2}TiO{sub 5}-MgAl{sub 2}O{sub 4} ceramics for nuclear shielding applications.

  13. An investigation of aluminum titanate-spinel composites behavior in radiation

    NASA Astrophysics Data System (ADS)

    Cevikbas, G.; Tugrul, A. B.; Onen, U.; Boyraz, T.; Buyuk, B.

    2015-03-01

    In the present work, the radiation attenuation properties of Aluminum titanate (Al2TiO5)-Spinel (MgAl2O4) ceramics composites were investigated. Al2TiO5-MgAl2O4 ceramics composites which have different Al2TiO5 percentages (0%, 5% and 10%) were produced and performed against gamma sources. Cs-137 and Co-60 were used as gamma radiation sources. Transmission technique was used in the experiments. The linear and mass attenuation coefficients of the samples were carried out for gamma radiation sources. The experimental results were compared with the theoretical mass attenuation coefficients which were calculated by using XCOM computer code. Increasing Al2TiO5 percentage in the Aluminum titanate/ Spinel ceramics composites causes the higher linear and mass attenuation coefficients of the composites against Cs-137 and Co-60 gamma radioisotopes. Therefore Also theoretical mass attenuation coefficients are compatible with the experimental results. In conclusion, increasing the Aluminum titanate ratio in the Al2TiO5-MgAl2O4 ceramics composites increases the gamma shielding property of the Al2TiO5-MgAl2O4 ceramics for nuclear shielding applications.

  14. Coprecipitation Synthesis of Superplastic 3 Mol. % Yttria -- Stabilized Tetragonal Zirconia Polycrystalline / Magnesium Aluminate Spinel Nanocomposite

    NASA Astrophysics Data System (ADS)

    Opoku, Michael

    3 mole % Yttria-stabilized tetragonal zirconia polycrystalline/Magnesium aluminate spinel (3Y-TZP/MgAl2O4) nanocomposite have exhibited high strain rate superplasticity at 1.7x10--2 --3.3x10--1 s --1. Low strain rate superplasticity (10--5--10 --3 s--1) has been the main drawback of using superplastic ceramics in industries. Microstructural design of 3Y-TZP/MgAl2O4 composite is a key in obtaining high strain rate superplasticity within the range of 10 --2--100 s--1 ). 3Y-TZP/MgAl2O4 may experience a surge in its application at high temperature if the microstructure is designed to exhibit high strain rates at low temperatures. In the present study, the reverse coprecipitation synthesis technique was adopted to synthesize nanocomposite powders containing 70%3Y-TZP/30%MgAl 2O4 and 60%3Y-TZP/40%MgAl2O4 with microstructural characteristics suitable for superplastic application. It was expected that the coprecipitation synthesis technique route will yield highly homogeneous nanocrystalline composite powders, which could be sintered into a dense component with high thermal stability of the small grains. Microstructual features observed after processing powders of 3Y-TZP/MgAl2O4 revealed that the coprecipitation synthesis is a suitable technique for processing nanocomposite powders for superplastic application.

  15. Neutron irradiation of polycrystalline yttrium aluminate garnet, magnesium aluminate spinel and α-alumina.

    NASA Astrophysics Data System (ADS)

    Neeft, E. A. C.; Konings, R. J. M.; Bakker, K.; Boshoven, J. G.; Hein, H.; Schram, R. P. C.; van Veen, A.; Conrad, R.

    1999-08-01

    Polycrystalline pellets of yttrium aluminate garnet (Y 3Al 5O 12), magnesium aluminate spinel (MgAl 2O 4) and α-alumina (α-Al 2O 3) have been irradiated in the high flux reactor (HFR) at Petten to a neutron fluence of 1.7 × 10 26 m -2 ( E>0.1 MeV) at a temperature of about 815 K. Volume changes smaller than 1% have been measured for Y 3Al 5O 12 and MgAl 2O 4. Transmission electron microscopy (TEM) results of Y 3Al 5O 12 show no difference between the unirradiated TEM samples and neutron-irradiated samples. For MgAl 2O 4, dislocation loops in some grains are found in the irradiated samples. TEM results of Al 2O 3 show a dense network of dislocation loops after neutron irradiation. The increase in volume is 4.2% for a neutron fluence of 1.7 × 10 26 m -2.

  16. A theoretical study of intrinsic point defects and defect clusters in magnesium aluminate spinel.

    PubMed

    Gilbert, C A; Smith, R; Kenny, S D; Murphy, S T; Grimes, R W; Ball, J A

    2009-07-01

    Point and small cluster defects in magnesium aluminate spinel have been studied from a first principles viewpoint. Typical point defects that occur during collision cascade simulations are cation anti-site defects, which have a small formation energy and are very stable, O and Mg split interstitials and vacancies. Isolated Al interstitials were found to be energetically unfavourable but could occur as part of a split Mg-Al pair or as a three atom-three vacancy Al 'ring' defect, previously observed in collision cascades using empirical potentials. The structure and energetics of the defects were investigated using density functional theory (DFT) and the results compared to simulations using empirical fixed charge potentials. Each point defect was studied in a variety of supercell sizes in order to ensure convergence. It was found that empirical potential simulations significantly overestimate formation energies, but that the type and relative stability of the defects are well predicted by the empirical potentials both for point defects and small defect clusters. PMID:21828490

  17. A theoretical study of intrinsic point defects and defect clusters in magnesium aluminate spinel

    NASA Astrophysics Data System (ADS)

    Gilbert, C. A.; Smith, R.; Kenny, S. D.; Murphy, S. T.; Grimes, R. W.; Ball, J. A.

    2009-07-01

    Point and small cluster defects in magnesium aluminate spinel have been studied from a first principles viewpoint. Typical point defects that occur during collision cascade simulations are cation anti-site defects, which have a small formation energy and are very stable, O and Mg split interstitials and vacancies. Isolated Al interstitials were found to be energetically unfavourable but could occur as part of a split Mg-Al pair or as a three atom-three vacancy Al 'ring' defect, previously observed in collision cascades using empirical potentials. The structure and energetics of the defects were investigated using density functional theory (DFT) and the results compared to simulations using empirical fixed charge potentials. Each point defect was studied in a variety of supercell sizes in order to ensure convergence. It was found that empirical potential simulations significantly overestimate formation energies, but that the type and relative stability of the defects are well predicted by the empirical potentials both for point defects and small defect clusters.

  18. Minimum quantity lubrication machining of aluminum and magnesium alloys

    NASA Astrophysics Data System (ADS)

    Bhowmick, Sukanta

    2011-12-01

    The use of minimum quantity lubrication (MQL) machining, i.e. drilling and tapping of aluminum and magnesium alloys using very low quantities of cutting fluids was studied and the MQL machining performance was compared to dry and conventional flooded conditions. An experimental drilling station with an MQL system was built to measure torque and thrust force responses. Uncoated and diamond-like carbon (DLC) coated HSS drills were tested against 319 Al and AZ91 alloys using 10--50 ml/h of distilled water (H 2O-MQL) and a fatty acid based MQL agent (FA-MQL). The results indicated that H2O-MQL used in conjunction with non-hydrogenated DLC (NH-DLC) coatings reduced the average torque and thrust-force compared to dry cutting and achieved a performance comparable with conventional flooded drilling. At least 103 holes could be drilled using NH-DLC in H2O-MQL and uncoated HSS in FA-MQL in drilling of both 319 Al and AZ91. MQL drilling and tapping provided a stable machining performance, which was evident from the uniform torque and force patterns and also resulted in desirable hole surface, thread quality and chip segments. The maximum temperature generated in the workpiece during MQL machining was lower than that observed in dry drilling and tapping, and comparable to flooded conditions. The mechanical properties of the material adjacent to drilled holes, as evaluated through plastic strain and hardness measurements, revealed a notable softening in case of dry drilling, with magnesium alloys exhibiting a recrystallized grain zone, but not for MQL drilling. Softened aluminum and magnesium promoted adhesion to the tools resulted built-up edge formation and consequently high torques and thrust-forces were generated. NH-DLC coatings' low COF in H 2O-MQL against 319 Al (0.10) and AZ91 (0.12) compared to uncoated HSS (0.63 and 0.65) limited the temperature increase during NH-DLC in H2 O-MQL drilling and hence both torques and thrust forces were effectively reduced.

  19. Textures, microstructures, anisotropy and formability of aluminum-manganese-magnesium and aluminum-magnesium alloys

    NASA Astrophysics Data System (ADS)

    Liu, Jiantao

    In this dissertation work, the microstructure and texture evolution of continuous cast (CC) and direct chill (DC) cast Al-Mn-Mg (AA 3105 and AA 3015) and Al-Mg (AA 5052) alloys during cold rolling and annealing are systematically investigated. Macrotexture analyses were based on three-dimensional orientation distribution functions (ODFs) calculated from incomplete pole figures from X-ray diffraction by using arbitrarily defined cell (ADC) and series expansion methods. A new technique, electron backscatter diffraction (EBSD), was adopted for microtexture and mesotexture investigation. The anisotropy and formability of Al-Mn-Mg and Al-Mg alloys are correlated to the texture results. For aluminum alloys studied in this work, a stronger Cube orientation is observed in DC hot band than in CC hot band after complete recrystallization. alpha and beta fibers become well developed beyond 50% cold rolling in both CC and DC aluminum alloys. The highest intensity along the beta fiber (skeleton line) is located between the Copper and the S orientations in both materials after high cold rolling reductions. In both CC and DC aluminum alloys, a cell structure develops with the indication of increasing CSL Sigma1 boundaries during the early stages of cold rolling. There is no evidence of the development of twin boundaries (Sigma3, Sigma9, Sigma27a & 27b) in either CC or DC aluminum alloys when the cold rolling reductions are less than 40%. The R and Cube textures are dominant recrystallization texture components in CC and DC AA 5052 alloys. The volume fraction of the Cube component is increased by increasing cold rolling reduction and annealing temperature but not by increasing annealing time while the volume fraction of the R component is only increased by increasing cold rolling reduction. Stronger Cube and R orientations are found at the surface layer than at half-thickness layer of cold rolled hot bands after annealing. The Cube and P textures are dominant recrystallization

  20. Spinel: where did it go?

    NASA Astrophysics Data System (ADS)

    Roy, Donald W.

    1997-11-01

    Polycrystalline magnesium aluminum oxide, transparent from 200 nanometers to 6 microns, offers a unique combination of optical and physical properties. A superior dome and window material in respect to rain and particle erosion, solar radiation, high temperatures and humidity; it is resistant to attack by strong acids, sea water, and jet fuels. Although it had been qualified for, and designed into several advanced UV/visible/IR optical systems, production of hot-pressed Spinel was stopped at Alpha Optical Systems in 1993 by the parent company Coors Ceramics. Development efforts on cold-pressed/sinter/HIP Spinel at RCS Technologies are reportedly stalemated at the present time. Therefore, there is no known significant effort directed toward the development of polycrystalline Spinel. however, the author is in contact with both domestic and foreign laboratories which have expressed a desire to develop the technology for transparent Spinel. Renewed development may begin during calendar year 1997. Because of the apparent continuing significant interest in Spinel this paper will review the properties of Spinel and will compare the most significant properties of Spinel with sapphire and aluminum oxynitride. The limitations of competing manufacturing processes, will be mentioned. Grinding and polishing considerations will be reviewed in respect to maximizing optical and structural properties.

  1. Disordering and annealing effects of magnesium aluminate spinel implanted with high-flux 60 keV Cu -

    NASA Astrophysics Data System (ADS)

    Lee, C. G.; Takeda, Y.; Kishimoto, N.

    2002-05-01

    Magnesium aluminate spinel of single crystal MgO n(Al 2O 3) was implanted with 60 keV Cu - at a flux up to 100 μA/cm 2, and effects of damage accumulation on the lattice were studied by Rutherford backscattering spectrometry (RBS)/channeling measurements. No complete amorphization was observed in the spinel over the flux range examined in this study, although the crystalline lattice was significantly damaged. The damaged region on the Al sublattice extended to a deeper region with increasing flux. Fluence- and flux dependence of Al damage peak is greatly influenced by the stoichiometry n of spinel. The Al damage peak of MgO1.0(Al 2O 3) is smaller for higher flux and fluence. It is understood that recombination of radiation-induced interstitials with structural vacancies effectively reduces damage of the Al sublattice. In the case of MgO2.4(Al 2O 3), the Al damage peak, however, increases with increasing fluence and flux. The results of RBS/channeling indicate that the recombination mechanism is more effective in the stoichiometric spinel than the nonstoichiometric one.

  2. The role of impurities, LIF, and processing on the sintering, microstructure, and optical properties of transparent polycrystalline magnesium aluminate (MgAl2O4) spinel

    NASA Astrophysics Data System (ADS)

    Rubat du Merac, Marc

    Transparent polycrystalline magnesium aluminate (MgAl2O4) spinel has an exceptional combination of properties that is well-suited to fulfill demanding optical applications that few other materials can satisfy. However, spinel is inherently difficult to densify due to high defect formation energies, variable stoichiometry, and extreme sensitivity to powder and processing parameters. In addition, the LiF sintering additive typically required to impart transparency degrades optical and mechanical properties, precluding wider application. Furthermore, there remains a fundamental lack of understanding of the processing-structure-property relationships required to obtain high transparency and good mechanical properties. In this work, hot-press experiments were designed to determine the role of impurities and LiF and the key variables required to obtain transparent spinel. Hot-pressed compacts were characterized with electron microscopy, chemical spectroscopy, and spectrophotometry, and impurities present in parts-per-million in starting powders were found to cause restricted grain size and opacity. LiF addition was found to reduce the content of some impurities by one order of magnitude, counteract absorption, and impart transparency, but also to cause grain coarsening, grain-boundary embrittlement, and scatter. Thermal analysis and residual gas analysis of prepared powders in combination with thermodynamic modeling demonstrated for the first time the specific mechanism by which LiF acts as a cleanser. LiF reacts with impurities to form volatile fluorides, and the temperature at which pressure is applied during hot-pressing determines the extent to which compact-scale differential sintering either traps LiF and volatile fluorides or allows their removal, the latter enabling transparency. The main cause of absorption in hot-pressed spinel compacts was found to be carbon contamination from graphitic hot-press components and it could be completely eliminated with proper

  3. Electrochemical corrosion of iron-magnesium-alumina spinel (FMAS) in molten potassium salts and coal slag

    SciTech Connect

    Marchant, D.D.; Griffin, C.W.; Bates, J.L.

    1981-01-01

    Iron, magnesium-alumina spinel (FMAS) (0.25 Fe/sub 3/O/sub 4/ . 0.75 MgAl/sub 2/O/sub 4/) has been considered for use as an electrode in magnetohydrodynamic (MHD) generator channels. Predominantly an electronic conductor, FMAS has adequate electrical conductivity (>1 S/m) above 520/sup 0/K. In addition, FMAS can be easily fabricated into a form and sintered in air to >90% theoretical density and has a melting point of 2124 +- 20/sup 0/K. Laboratory tests to measure both the electrochemical and chemical corrosion of FMAS in molten K/sub 2/CO/sub 3/, K/sub 2/SO/sub 4/ and coal slags were developed at the Pacific Northwest Laboratory to evaluate the relative corrosion of FMAS. Under isothermal conditions, a direct electric current was passed between an anode and a cathode through a molten electrolyte. The molten coal slags were synthetic high-calcium, low-iron Montana Rosebud and low-calcium, high-iron Illinois No. 6. Evaluations of electrochemical corrosion were made as functions of current density, temperature, and slag composition. These results were compared to those of FMAS tested without electric current. The corrosion rates and reaction products were investigated by optical microscopy and scanning electron microscopy. Overall, FMAS has too-high an electrochemical corrosion rate to be considered as MHD electrodes in Montana Rosebud coal slag or in systems where only molten potassium salts are present. However, FMAS may be considered for use in high-iron coal slags although the corrosion rates are still quite high even in these slags.

  4. Optical properties of laser spinel

    NASA Astrophysics Data System (ADS)

    Mironova-Ulmane, Nina; Skvortsova, Vera; Smirnovs, Andrejs; Riekstinya, Daina; Litvinov, L.; Sildos, Ilmo; Osvet, Andris

    1997-02-01

    The present work summarizes the results of absorption and luminescence spectra investigation of natural and synthetic magnesium aluminum spinels (MgO*nAl2O3) containing chromium and manganese ions. The spectra have been analyzed with an aim to determine the effect of stoichiometry 'n' on distribution of emitting ions. The Mn2+ is observed in both tetrahedral and octahedral coordinations providing green or orange emission. Absorption bands have been explained in terms of the Mn2+ configuration model. Laser excitation of chromium-comprising magnesium aluminum spinel crystals has been carried out at 7 K with the purpose to detect the nearest neighbors of Cr3+ ions. Luminescence emission spectra have been obtained for natural sample and three synthetic samples (MgO*nAl2O3, n equals 1, 2, 2.8). Decay time has been measured at different wavelengths and compared for crystals of different stoichiometry. In case n equals 2 or 2.8, computer simulation has been used to decompose smeared luminescence spectra in the 680 - 700 nm region. Gaussian curves corresponding to R- and N-lines of natural spinel spectrum have been applied as components in the calculations of nonstoichiometric spinel spectra. This suggests that there aren't normally arranged Cr-occupied octahedral positions in nonstoichiometric spinel (n equals 2.8, e.g.).

  5. Evaluation of magnesium-aluminum eutectic to improve combustion efficiency in low burning rate propellants

    NASA Technical Reports Server (NTRS)

    Northam, B. G.; Sullivan, E. M.

    1973-01-01

    A previous investigation indicated that combustion efficiency of low burning-rate propellants could be improved if the aluminum fuel was replaced by aluminum particles coated with a magnesium-aluminum eutectic alloy (ALCAL). The purpose of the present investigation was to evaluate the possibility of improving the combustion efficiency of these propellants by admixing the eutectic with the aluminum rather than coating the aluminum. Tests of three propellants similar in every respect except for the metal fuel were conducted in test motors with 4.54 kg (10 lbm) of propellant. The first propellant used aluminum fuel; the second contained aluminum admixed with magnesium-aluminum eutectic; the third used ALCAL. The test results show the the admixed fuel gave better low burning-rate combustion efficiency than the other two. The test results also showed that the ALCAL was deficient in that much, if not all, of the coating material could be found as the fine particles in a bimodal mix of aluminum and eutectic. The combustion efficiency of low burning-rate aluminized propellants can be significantly improved by mixing a small amount of magnesium-aluminum alloy with the aluminum fuel.

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

    NASA Astrophysics Data System (ADS)

    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.

  7. Cordierite-spinel troctolite, a new magnesium-rich lithology from the lunar highlands.

    PubMed

    Marvin, U B; Carey, J W; Lindstrom, M M

    1989-02-17

    A clast of spinel troctolite containing 8 percent cordierite (Mg(2)Al(4)Si(5)O(18)) has been identified among the constituents of Apollo 15 regolith breccia 15295. The cordierite and associated anorthite, forsteritic olivine, and pleonaste spinel represent a new, Mg-rich lunar highlands lithology that formed by metamorphism of an igneous spinel cumulate. The cordierite-forsterite pair in the assemblage is stable at a maximum pressure of 2.5 kilobars, equivalent to a depth of 50 kilometers, or 10 kilometers above the lunar crust-mantle boundary. The occurrence of the clast indicates that spinel cumulates are a more important constituent of the lower lunar crust than has been recognized. The rarity of cordierite-spinel troctolite among lunar rock samples suggests that it is excavated only by large impact events, such as the one that formed the adjacent Imbrium Basin. PMID:17783768

  8. Cordierite-spinel troctolite, a new magnesium-rich lithology from the lunar highlands

    SciTech Connect

    Marvin, U.B. ); Carey, J.W. ); Lindstrom, M.M. )

    1989-02-17

    A clast of spinel troctolite containing 8% cordierite (Mg{sub 2}Al{sub 4}Si{sub 5}O{sub 18}) has been identified among the constituents of Apollo 15 regolith breccia 15295. The cordierite and associated anorthite, forsteritic olivine, and pleonaste spinel represent a new, Mg-rich lunar highlands lithology that formed by metamorphism of an igneous spinel cumulate. The cordierite-forsterite pair in the assemblage is stable at a maximum pressure of 2.5 kilobars, equivalent to a depth of 50 kilometers, or 10 kilometers above the lunar crust-mantle boundary. The occurrence of the clast indicates that spinel cumulates are a more important constituent of the lower lunar crust than has been recognized. The rarity of cordierite-spinel troctolite among lunar rock samples suggests that it is excavated only by large impact events, such as the one that formed the adjacent Imbrium Basin. 15 refs., 2 figs., 4 tabs.

  9. Neutron irradiation effects in magnesium-aluminate spinel doped with transition metals

    NASA Astrophysics Data System (ADS)

    Gritsyna, V. T.; Afanasyev-Charkin, I. V.; Kobyakov, V. A.; Sickafus, K. E.

    2000-12-01

    We present data on optical properties for stoichiometric (MgO · Al 2O 3) and non-stoichiometric (MgO · 2Al 2O 3) spinel crystals: (1) nominally pure; (2) doped with transition metals Mn, Cr, and Fe to a concentration of 0.01 wt%; (3) irradiated with neutrons to a fluence of 1.8×10 21 m -2; (4) post-annealed at 650 K. The temperature during neutron irradiation was 350 K. Optical absorption and thermoluminescence measurements were performed on irradiated and annealed samples at room temperature. Results of absorption measurements show spectra with the following features: (1) a prominent band at 2.33 eV (for stoichiometric spinel); (2) overlapping bands attributed to hole centers (3.17 eV); (3) optical centers on antisite defects (3.78 and 4.14 eV); (4) F +- and F-centers (4.75 and 5.3 eV); (5) bands related to defect complexes. For nominally pure samples, the efficiency of optical center formation in stoichiometric spinel is half that in non-stoichiometric spinel. Doped crystals exhibit high efficiencies for defect creation, independent of spinel composition. All dopants enhance the efficiency of defect creation in spinel. Doping with Mn has the least effect on increasing the number of radiation-induced stable defects. Apparently, impurities in spinel serve as centers for stabilization of irradiation-induced interstitials or vacancies.

  10. Radiation-induced swelling and softening in magnesium aluminate spinel irradiated with high-flux Cu - ions

    NASA Astrophysics Data System (ADS)

    Lee, C. G.; Ohmura, T.; Takeda, Y.; Matsuoka, S.; Kishimoto, N.

    2004-03-01

    Magnesium aluminate spinel of single crystal was irradiated with 60 keV Cu - at a flux up to 6.2 × 10 18 ions/m 2 s, to a total fluence of 3 × 10 20 ions/m 2, in order to study changes in hardness and step-height swelling by high-flux implantation. Hardness determined by nano-indentation measurements steeply decreased with implantation. There is a strong negative correlation between flux dependences of the hardness and the step-height swelling: the former decreases as the latter increases. The Rutherford backscattering spectrometry (RBS)/channeling measurements showed that the spinel is not completely amorphized over the flux range in this study, and the radiation-induced softening observed is not due to amorphization. Results of optical absorbance suggested that radiation-induced point defects and their clusters on the anion sublattices of the spinel played an important role in the radiation-induced swelling under high-flux ion implantation.

  11. Cordierite-spinel troctolite, a new magnesium-rich lithology from the lunar highlands

    NASA Astrophysics Data System (ADS)

    Marvin, U. B.; Carey, J. W.; Lindstrom, M. M.

    1989-02-01

    A clast of spineltroctolite containing 8 percent cordierite (Mg2,Al4Si5O18) has been identified among the constituents of Apollo 15 regolith breccia 15295. The cordierite and associated anorthite, forsteritic olivine, and pleonaste spinel represent a new, Mg-rich lunar highlands lithology that formed by metamorphism of an igneous spinel cumulate. The cordierite-forsterite pair in the assemblage is stable at a maximum pressure of 2.5 kilobars, equivalent to a depth of 50 kilometers, or 10 kilometers above the lunar crust-mantle boundary. The occurrence of the clast indicates that spinel cumulates are a more important constituent of the lower lunar crust than has been recognized. The rarity of cordierite-spinel troctolite among lunar rock samples suggests that it is excavated only by large impact events, such as the one that formed the adjacent Imbrium Basin.

  12. Cordierite-spinel troctolite, a new magnesium-rich lithology from the lunar highlands

    NASA Technical Reports Server (NTRS)

    Marvin, Ursula B.; Carey, J. William; Lindstrom, Marilyn M.

    1989-01-01

    A clast of spineltroctolite containing 8 percent cordierite (Mg2,Al4Si5O18) has been identified among the constituents of Apollo 15 regolith breccia 15295. The cordierite and associated anorthite, forsteritic olivine, and pleonaste spinel represent a new, Mg-rich lunar highlands lithology that formed by metamorphism of an igneous spinel cumulate. The cordierite-forsterite pair in the assemblage is stable at a maximum pressure of 2.5 kilobars, equivalent to a depth of 50 kilometers, or 10 kilometers above the lunar crust-mantle boundary. The occurrence of the clast indicates that spinel cumulates are a more important constituent of the lower lunar crust than has been recognized. The rarity of cordierite-spinel troctolite among lunar rock samples suggests that it is excavated only by large impact events, such as the one that formed the adjacent Imbrium Basin.

  13. Direct Observation of Reversible Magnesium Ion Intercalation into a Spinel Oxide Host

    SciTech Connect

    Kim, Chunjoong; Phillips, Patrick J.; Key, Baris; Yi, Tanghong; Nordlund, Dennis; Yu, Young-Sang; Bayliss, Ryan D.; Han, Sang-Don; He, Meinan; Zhang, Zhengcheng; Burrell, Anthony K.; Klie, Robert F.; Cabana, Jordi

    2015-04-17

    Direct evidence of Mg2+ intercalation into a spinel-type Mn2O4 is provided. By com­bining tools with different sensitivities, from atomic-resolution X-ray spectro­scopy to bulk X-ray diffraction, it is demonstrated that Mg2+ reversibly occupies the tetrahedral sites of the spinel structure through the reduction of Mn when the electrochemical reaction is performed.

  14. Electrolytic conditioning of a magnesium aluminum chloride complex for reversible magnesium deposition

    SciTech Connect

    Barile, Christopher J.; Barile, Elizabeth C.; Zavadil, Kevin R.; Nuzzo, Ralph G.; Gewirth, Andrew A.

    2014-12-04

    We describe in this report the electrochemistry of Mg deposition and dissolution from the magnesium aluminum chloride complex (MACC). The results define the requirements for reversible Mg deposition and definitively establish that voltammetric cycling of the electrolyte significantly alters its composition and performance. Elemental analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy (SEM-EDS) results demonstrate that irreversible Mg and Al deposits form during early cycles. Electrospray ionization-mass spectrometry (ESI-MS) data show that inhibitory oligomers develop in THF-based solutions. These oligomers form via the well-established mechanism of a cationic ring-opening polymerization of THF during the initial synthesis of the MACC and under resting conditions. In contrast, MACC solutions in 1,2-dimethoxyethane (DME), an acyclic solvent, do not evolve as dramatically at open circuit potential. Furthermore, we propose a mechanism describing how the conditioning process of the MACC in THF improves its performance by both tuning the Mg:Al stoichiometry and eliminating oligomers.

  15. Electrolytic conditioning of a magnesium aluminum chloride complex for reversible magnesium deposition

    DOE PAGESBeta

    Barile, Christopher J.; Barile, Elizabeth C.; Zavadil, Kevin R.; Nuzzo, Ralph G.; Gewirth, Andrew A.

    2014-12-04

    We describe in this report the electrochemistry of Mg deposition and dissolution from the magnesium aluminum chloride complex (MACC). The results define the requirements for reversible Mg deposition and definitively establish that voltammetric cycling of the electrolyte significantly alters its composition and performance. Elemental analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy (SEM-EDS) results demonstrate that irreversible Mg and Al deposits form during early cycles. Electrospray ionization-mass spectrometry (ESI-MS) data show that inhibitory oligomers develop in THF-based solutions. These oligomers form via the well-established mechanism of a cationic ring-opening polymerization of THF during the initial synthesis of the MACC andmore » under resting conditions. In contrast, MACC solutions in 1,2-dimethoxyethane (DME), an acyclic solvent, do not evolve as dramatically at open circuit potential. Furthermore, we propose a mechanism describing how the conditioning process of the MACC in THF improves its performance by both tuning the Mg:Al stoichiometry and eliminating oligomers.« less

  16. Impurity control and corrosion resistance of magnesium-aluminum alloy

    SciTech Connect

    Liu, M.; Song, GuangLing

    2013-01-01

    The corrosion resistance of magnesium alloys is very sensitive to the contents of impurity elements such as iron. In this study, a series of diecast AXJ530 magnesium alloy samples were prepared with additions of Mn and Fe. Through a comprehensive phase diagram calculation and corrosion evaluation, the mechanisms for the tolerance limit of Fe in magnesium alloy are discussed. This adds a new dimension to control the alloying impurity in terms of alloying composition design and casting conditions.

  17. Formation of hydrotalcite in mixtures of aluminum hydroxycarbonate and magnesium hydroxide gels.

    PubMed

    Vanderlaan, R K; White, J L; Hem, S L

    1982-07-01

    IR and X-ray analysis demonstrate that hydrotalcite forms during the aging of aluminum hydroxycarbonate gel and magnesium hydroxide gel mixtures. The formation of hydrotalcite produces a change in the pH-stat titrigram and a sharp increase in the pH of the mixture. Hydrotalcite was noted earlier in mixtures having a high molar ratio of magnesium to aluminum, a high total gel concentration, a high initial pH, or in mixtures stored at elevated temperatures. The addition of sorbitol to the mixtures substantially delayed the appearance of hydrotalcite. Nonacid-reactive hydrotalcite formed when mixtures of chloride-containing aluminum hydroxide gel and magnesium hydroxide gel were aged. PMID:7120062

  18. Post irradiation examination of irradiated americium oxide and uranium dioxide in magnesium aluminate spinel

    NASA Astrophysics Data System (ADS)

    Klaassen, F. C.; Bakker, K.; Schram, R. P. C.; Klein Meulekamp, R.; Conrad, R.; Somers, J.; Konings, R. J. M.

    2003-06-01

    To study MgAl 2O 4 spinel as inert matrix material for the transmutation of minor actinides, two capsules were irradiated at the high flux reactor in Petten, containing 12.5 wt% micro-dispersed 241AmO x in spinel and 25 wt% micro-dispersed enriched UO 2 in spinel. During irradiation, the initially present 241Am was converted for 99.8% to fission products (50%), plutonium (30%), curium (16%) and 243Am (4%). The UO 2 spinel target experienced a burn-up of 32% fission per initial metal atom. The post irradiation examination of the AmO x inert matrix target showed swelling of 27 vol.%, and a gas release of 48% for He and 16% for Xe and Kr. The UO 2 inert matrix target also showed a large volumetric swelling of 11%, directed mainly radially. Ceramography on the UO 2 inert matrix target revealed a complete restructuring of the spinel grains upon irradiation and the absence of porosity, suggesting that amorphisation is the main cause of the swelling.

  19. Eddy Current Defectoscope for Monitoring the Duralumin and Aluminum-Magnesium Alloys

    NASA Astrophysics Data System (ADS)

    Dmitriev, S.; Dmitrieva, L.; Malikov, V.; Sagalakov, A.

    2016-02-01

    The system developed is based on an eddy-current transducer of the transformer type, and is capable of inspecting plates made of duralumin and aluminum-magnesium alloys for defects. The measurement system supports absolute and differential control modes. The system was tested on a number of duralumin and aluminum-magnesium plates with internal flaws located as deep as 5 mm under the surface. The article provides data that demonstrates a link between the response time and the presence of defects in similar structures at a signal frequency of 1000 Hz.

  20. Corrosion resistance of aluminum-magnesium alloys in glacial acetic acid

    SciTech Connect

    Zaitseva, L.V.; Romaniv, V.I.

    1984-05-01

    Vessels for the storage and conveyance of glacial acetic acid are produced from ADO and AD1 aluminum, which are distinguished by corrosion resistance, weldability and workability in the hot and cold conditions but have low tensile strength. Aluminum-magnesium alloys are stronger materials close in corrosion resistance to technical purity aluminum. An investigation was made of the basic alloying components on the corrosion resistance of these alloys in glacial acetic acid. Both the base metal and the weld joints were tested. With an increase in temperature the corrosion rate of all of the tested materials increases by tens of times. The metals with higher magnesium content show more pitting damage. The relationship of the corrosion resistance of the alloys to magnesium content is confirmed by the similar intensity of failure of the joint metal of all of the investigated alloys and by electrochemical investigations. The data shows that AMg3 alloy is close to technically pure ADO aluminum. However, the susceptibility of even this material to local corrosion eliminates the possibility of the use of aluminum-magnesium alloys as reliable constructional materials in glacial acetic acid.

  1. Effects of Xe ion irradiation and subsequent annealing on the structural properties of magnesium-aluminate spinel

    NASA Astrophysics Data System (ADS)

    Afanasyev-Charkin, Ivan V.; Dickerson, Robert M.; Wayne Cooke, D.; Bennett, Bryan L.; Gritsyna, Vasily T.; Sickafus, Kurt E.

    2001-02-01

    Single crystals of magnesium-aluminate spinel MgAl 2O 4 were irradiated with 340 keV Xe ++ ions at -173°C (˜100 K). A fluence of 1×10 20 Xe/m 2 created an amorphous layer at the surface of the samples. The samples were annealed for 1 h at different temperatures ranging from 130°C to 880°C. Recrystallization took place in the temperature interval between 610°C and 855°C. Transmission electron microscopy (TEM) images show two distinct layers near the surface: (1) a polycrystalline layer with columnar grain structure; and (2) a buried damaged layer epitaxial with the substrate. After annealing at 1100°C for 52 days, the profile of implanted Xe ions did not change, which means that Xe ions are not mobile in the spinel structure up to 1100°C. The thickness of the buried damaged layer decreased significantly in the 1100°C annealed sample comparing to the sample annealed for 1 h at 855°C.

  2. In vivo stimulation of bone formation by aluminum and oxygen plasma surface-modified magnesium implants.

    PubMed

    Wong, Hoi Man; Zhao, Ying; Tam, Vivian; Wu, Shuilin; Chu, Paul K; Zheng, Yufeng; To, Michael Kai Tsun; Leung, Frankie K L; Luk, Keith D K; Cheung, Kenneth M C; Yeung, Kelvin W K

    2013-12-01

    A newly developed magnesium implant is used to stimulate bone formation in vivo. The magnesium implant after undergoing dual aluminum and oxygen plasma implantation is able to suppress rapid corrosion, leaching of magnesium ions, as well as hydrogen gas release from the biodegradable alloy in simulated body fluid (SBF). No released aluminum is detected from the SBF extract and enhanced corrosion resistance properties are confirmed by electrochemical tests. In vitro studies reveal enhanced growth of GFP mouse osteoblasts on the aluminum oxide coated sample, but not on the untreated sample. In addition to that a small amount (50 ppm) of magnesium ions can enhance osteogenic differentiation as reported previously, our present data show a low concentration of hydrogen can give rise to the same effect. To compare the bone volume change between the plasma-treated magnesium implant and untreated control, micro-computed tomography is performed and the plasma-treated implant is found to induce significant new bone formation adjacent to the implant from day 1 until the end of the animal study. On the contrary, bone loss is observed during the first week post-operation from the untreated magnesium sample. Owing to the protection offered by the Al2O3 layer, the plasma-treated implant degrades more slowly and the small amount of released magnesium ions stimulate new bone formation locally as revealed by histological analyses. Scanning electron microscopy discloses that the Al2O3 layer at the bone-implant interface is still present two months after implantation. In addition, no inflammation or tissue necrosis is observed from both treated and untreated implants. These promising results suggest that the plasma-treated magnesium implant can stimulate bone formation in vivo in a minimal invasive way and without causing post-operative complications. PMID:24060425

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  4. Advanced hybrid battery with a magnesium metal anode and a spinel LiMn2O4 cathode.

    PubMed

    Pan, Baofei; Feng, Zhenxing; Sa, Niya; Han, Sang-Don; Ma, Qing; Fenter, Paul; Vaughey, John T; Zhang, Zhengcheng; Liao, Chen

    2016-08-01

    Two Mg-Li dual salt hybrid electrolytes are developed, which exhibit excellent oxidative stability up to around 3.8 V (vs. Mg/Mg(2+)) on an aluminum current collector, enabling the successful coupling of several state-of-the-art lithium-ion intercalation cathodes (LiMn2O4, LiCoO2 and LiNi1/3Mn1/3Co1/3O2) with magnesium metal anodes. The Mg-LiMn2O4 battery delivers an initial discharge capacity of about 106 mA h g(-1) with a working voltage of around 2.8 V (vs. Mg/Mg(2+)), highlighting the highest working voltage of rechargeable batteries with magnesium metal anodes to date. PMID:27439946

  5. Method for thermal processing alumina-enriched spinel single crystals

    DOEpatents

    Jantzen, C.M.

    1995-05-09

    A process for age-hardening alumina-rich magnesium aluminum spinel to obtain the desired combination of characteristics of hardness, clarity, flexural strength and toughness comprises selection of the time-temperature pair for isothermal heating followed by quenching. The time-temperature pair is selected from the region wherein the precipitate groups have the characteristics sought. The single crystal spinel is isothermally heated and will, if heated long enough pass from its single phase through two pre-precipitates and two metastable precipitates to a stable secondary phase precipitate within the spinel matrix. Quenching is done slowly at first to avoid thermal shock, then rapidly. 12 figs.

  6. Method for thermal processing alumina-enriched spinel single crystals

    DOEpatents

    Jantzen, Carol M.

    1995-01-01

    A process for age-hardening alumina-rich magnesium aluminum spinel to obtain the desired combination of characteristics of hardness, clarity, flexural strength and toughness comprises selection of the time-temperature pair for isothermal heating followed by quenching. The time-temperature pair is selected from the region wherein the precipitate groups have the characteristics sought. The single crystal spinel is isothermally heated and will, if heated long enough pass from its single phase through two pre-precipitates and two metastable precipitates to a stable secondary phase precipitate within the spinel matrix. Quenching is done slowly at first to avoid thermal shock, then rapidly.

  7. Distribution of manganese ions in magnesium-aluminium spinels of different stoichiometries

    NASA Astrophysics Data System (ADS)

    Mironova, Nina; Skvortsova, Vera; Smirnovs, Andrejs; Čugunov, Leonid

    1996-09-01

    Cathodoluminescence (CL), photoluminescence (PL) and EPR spectra of natural and synthetic spinels have been measured. CL spectra reveal two emission bands caused by transitions within Mn 2+ ion. Relative intensities of green and red emission of Mn 2+ have been compared during simultaneous excitation of tetra- and octa-coordinated manganese ions under electron beam. Growth of relative intensity of Mn 2+ CL in tetrahedral sites has been found in common with decrease of manganese relative concentration. A peculiar Mn-associated PL, which is typical for 3d 3 ions, has been observed in lilac natural spinel. Proceeding from position of optical band, the corresponding coordination has been chosen. Simulating EPR spectra have been used to estimate the degree and kind of disorder of nearest neighbours of Mn 2+ ions.

  8. Metal nanocrystal formation in magnesium aluminate spinel and silicon dioxide with high-flux Cu - ions

    NASA Astrophysics Data System (ADS)

    Kishimoto, N.; Takeda, Y.; Umeda, N.; Gritsyna, V. T.; Lee, C. G.; Saito, T.

    2000-05-01

    Intense Cu- ions of 60 keV spontaneously grow nanospheres embedded within a shallow depth in insulators, which exhibit optical nonlinearity. The in-beam growth of nanoparticles is preferred but subjected to phase instability. Spinel oxides may be a candidate substrate to realize the phase stability, because of good radiation resistance and sufficient transparency. Spinel of MgAl2O4 and amorphous(a-) SiO2 were irradiated with Cu- at dose rates up to 100 μA/cm2, at a total dose of 3.0 × 1016 ions/cm2. Nanocrystal morphology and optical absorption (hν=0.5 - 5 eV) varied depending on dose rate. At high dose rates, a-SiO2 showed a strong tendency of depth-dependent rearrangement and particle coarsening. The MgAl2O4 also showed spontaneous precipitation of nanoparticles but, in contrast, neither long-range rearrangement of implants nor particle coarsening, up to high dose rates. Therefore, the MgAl2O4 spinel is a promising substrate to realize fine and stable nanostructures.

  9. Effect of copper and magnesium on the structure and the phase composition of boron/aluminum composite ingots

    NASA Astrophysics Data System (ADS)

    Belov, N. A.; Samoshina, M. E.; Alabin, A. N.; Chervyakova, K. Yu.

    2016-01-01

    The phase composition of aluminum Al-B-Cu-Mg alloys has been studied using calculations and experimental methods. Unlike copper, magnesium is shown to substitute aluminum in the AlB2 phase substantially. The use of Al-Cu-Mg alloys (duraluminums) as the matrix of boron/aluminum composite prepared by liquid-phase technologies is substantiated.

  10. Extractive separation of sodium 22 and aluminum 26 from cyclotron-irradiated magnesium targets

    SciTech Connect

    Iofa, B.Z.; Dzhigirkhanov, M.S.A.; Maklachkov, A.G.; Ovcharenko, V.P.; Sevast'yanov, Yu.G.; Silant'ev, A.I.

    1988-05-01

    An extraction procedure has been developed for the successive isolation of carrier-free sodium 22 and aluminum 26 from deuteron- (proton-) irradiated magnesium targets. The irradiated magnesium metal or alloy target is dissolved in sulfuric acid and the pH adjusted to 1.0-1.5 with ammonia. Sodium 22 is extracted with a chloroform solution of 15-crown-5 and picric acid and back-extracted with water in the presence of tetraphenylphosphonium chloride or a tetraalkylammonium chloride. Then aluminum 26 is extracted by trioctyl-ammonium oxalate in benzene (toluene) containing chloroform and back-extracted with 6M hydrochloric acid. The yields of sodium 22 and aluminum 26 are better than 95%.

  11. On the Utility of Spinel Oxide Hosts for Magnesium-Ion Batteries.

    PubMed

    Knight, James C; Therese, Soosairaj; Manthiram, Arumugam

    2015-10-21

    There is immense interest to develop Mg-ion batteries, but finding suitable cathode materials has been a challenge. The spinel structure has many advantages for ion insertion and has been successfully used in Li-ion batteries. We present here findings on the attempts to extract Mg from MgMn2O4-based spinels with acid (H2SO4) and with NO2BF4. The acid treatment was able to fully remove all Mg from MgMn2O4 by following a mechanism involving the disproportionation of Mn(3+), and the extraction rate decreased with increasing cation disorder. Samples with additional Mg(2+) ions in the octahedral sites (e.g., Mg1.1Mn1.9O4 and Mg1.5Mn1.5O4) also exhibit complete or near complete demagnesiation due to an additional mechanism involving ion exchange of Mg(2+) by H(+), but no Mg could be extracted from MgMnAlO4 due to the disruption of Mn-Mn interaction/contact across shared octahedral edges. In contrast, no Mg could be extracted with the oxidizing agent NO2BF4 from MgMn2O4 or Mg1.5Mn1.5O4 as the electrostatic repulsion between the divalent Mg(2+) ions prevents Mg(2+) diffusion through the 16c octahedral sites, unlike Li(+) diffusion, suggesting that spinels may not serve as potential hosts for Mg-ion batteries. The ability to extract Mg with acid in contrast to that with NO2BF4 is attributed to Mn dissolution from the lattice and the consequent reduction in electrostatic repulsion. The findings could provide insights toward the design of Mg hosts for Mg-ion batteries. PMID:26436429

  12. Copper stabilization via spinel formation during the sintering of simulated copper-laden sludge with aluminum-rich ceramic precursors.

    PubMed

    Tang, Yuanyuan; Chui, Stephen Sin-Yin; Shih, Kaimin; Zhang, Lingru

    2011-04-15

    The feasibility of incorporating copper-laden sludge into low-cost ceramic products, such as construction ceramics, was investigated by sintering simulated copper-laden sludge with four aluminum-rich ceramic precursors. The results indicated that all of these precursors (γ-Al(2)O(3), corundum, kaolinite, mullite) could crystallochemically stabilize the hazardous copper in the more durable copper aluminate spinel (CuAl(2)O(4)) structure. To simulate the process of copper transformation into a spinel structure, CuO was mixed with the four aluminum-rich precursors, and fired at 650-1150 °C for 3 h. The products were examined using powder X-ray diffraction (XRD) and scanning electron microscopic techniques. The efficiency of copper transformation among crystalline phases was quantitatively determined through Rietveld refinement analysis of the XRD data. The sintering experiment revealed that the optimal sintering temperature for CuAl(2)O(4) formation was around 1000 °C and that the efficiency of copper incorporation into the crystalline CuAl(2)O(4) structure after 3 h of sintering ranged from 40 to 95%, depending on the type of aluminum precursor used. Prolonged leaching tests were carried out by using acetic acid with an initial pH value of 2.9 to leach CuO and CuAl(2)O(4) samples for 22 d. The sample leachability analysis revealed that the CuAl(2)O(4) spinel structure was more superior to stabilize copper, and suggested a promising and reliable technique for incorporating copper-laden sludge or its incineration ash into usable ceramic products. Such results also demonstrated the potential of a waste-to-resource strategy by using waste materials as part of the raw materials with the attainable temperature range used in the production of ceramics. PMID:21428386

  13. Radiation-induced luminescence in magnesium aluminate spinel crystals and ceramics

    NASA Astrophysics Data System (ADS)

    Gritsyna, V. T.; Kazarinov, Yu. G.; Kobyakov, V. A.; Reimanis, I. E.

    2006-09-01

    Radioluminescence (RL) and thermoluminescence (TL) in spinel crystals and ceramics were investigated to elucidate the radiation-induced electronic processes in single crystals grown by Verneuil and Czochralski methods as well as transparent and translucent ceramics. Both RL and TL spectra demonstrate a UV-band related to electron-hole recombination luminescence at intrinsic defects; green and red luminescence are identified with emission of Mn 2+- and Cr 3+-ions, respectively. The kinetics of growth of different RL luminescence bands depending on dose at the prolonged X-irradiation shows the competitive character of charge and energy transfer between defects and impurity ions. The dependence of RL intensity on the temperature of the sample was measured in the range of 300-750 K and compared with TL for different emission bands. The variety of maxima in the temperature dependence of RL and in the glow curves of TL measured for different luminescence bands in spinels of different origins and crystalline forms is used to show that charge carrier traps and luminescence centers are not isolated defects but are complexes of defects and impurities. The formation, structure and properties of these complexes depend on the processing conditions.

  14. Growth and characterization of Mn 2+-activated magnesium aluminate spinel single crystals

    NASA Astrophysics Data System (ADS)

    Jouini, Anis; Yoshikawa, Akira; Fukuda, Tsuguo; Boulon, Georges

    2006-08-01

    Several concentrations of Mn 2+-doped MgAl 2O 4 single crystals have been successfully grown using the micro-pulling-down (μ-PD) method. Due to their high melting temperature, the use of special Ir-Re crucibles was necessary. Because of the wide solubility range, the dependence of the behavior of the solid-liquid interface on the growth parameters was carefully studied to establish the growth conditions of stoichiometric MgAl 2O 4 spinel. Rod shaped <1 0 0> oriented single crystals of undoped and manganese doped MgAl 2O 4 spinel with 3 mm in diameter and a few centimeters in length were obtained in reducing argon atmosphere. The composition of Mn ions along the growth a-axis was controlled by the electron probe micro-analysis (EPMA). The optical transmission, crystallinity and thermal expansion of the grown crystals are investigated as well the annealing effect under oxidizing atmosphere will be detailed.

  15. In-pile studies of inert matrices with emphasis on magnesia and magnesium aluminate spinel

    NASA Astrophysics Data System (ADS)

    Chauvin, N.; Albiol, T.; Mazoyer, R.; Noirot, J.; Lespiaux, D.; Dumas, J. C.; Weinberg, C.; Ménard, J. C.; Ottaviani, J. P.

    1999-08-01

    Various inert matrices - oxide, nitride and metallic - were irradiated in the French Phénix reactor in order to study their behaviour under a fast neutron fluence ( E > 0.1 MeV). This paper summarises the material selection criteria and the irradiation conditions of the MATrices for INcineration of Actinides (MATINA) 1 experiment. Emphasis is given on non-destructive examinations of the pins and on more complete examinations performed on (MgO + UO 2) and (MgAl 2O 4 + UO 2) pellets which were irradiated up to a fast neutron fluence of 2 × 10 26 m -2. For these pellets, dimensional examinations, scanning electronic microscopy pictures and electron-probe microanalyses, were performed before and after irradiation. Fission gas release was also studied. These preliminary results show a good behaviour of both magnesia and spinel under irradiation.

  16. An EBSP investigation of alternate microstructures for superplasticity in aluminum-magnesium alloys

    SciTech Connect

    McNelley, T.R.; McMahon, M.E.; Hales, S.J.

    1997-02-15

    This study proposes to provide insight into alternative grain boundary structures in two aluminum-magnesium alloys processed to achieve superplastic behavior. A commercially processes superplastic 5083 aluminum alloy, SKY5083, and a laboratory processed, non-commercial superplastic Al-10Mg-0.1Zr alloy have been selected for examination. Although alloy content, processing routes, and deformation conditions vary for each material, a comparison of results may provide evidence that alternate grain structures and boundary misorientation distributions may support superplasticity in the GBS regime, depending on the TMP processing and alloy system chosen.

  17. Laser Surface Alloying of Copper, Manganese, and Magnesium with Pure Aluminum Substrate

    NASA Astrophysics Data System (ADS)

    Jiru, Woldetinsay G.; Sankar, M. Ravi; Dixit, Uday S.

    2016-03-01

    Laser surface alloying is one of the recent technologies used in the manufacturing sector for improving the surface properties of the metals. Light weight materials like aluminum alloys, titanium alloys, and magnesium alloys are used in the locomotive, aerospace, and structural applications. In the present work, an experimental study was conducted to improve the surface hardness of commercially pure aluminum plate. CO2 laser is used to melt pre-placed powders of pure copper, manganese, and magnesium. Microstructure of alloyed surface was analyzed using optical microscope. The best surface alloying was obtained at the optimum values of laser parameters, viz., laser power, scan speed, and laser beam diameter. In the alloyed region, microhardness increased from 30 HV0.5 to 430 HV0.5, while it was 60 HV0.5 in the heat-affected region. Tensile tests revealed some reduction in the strength and total elongation due to alloying. On the other hand, corrosion resistance improved.

  18. Expansion during the formation of the magnesium aluminate spinel (MgAl(2)O(4)) from its basic oxide (MgO and Al(2)O(3)) powders

    NASA Astrophysics Data System (ADS)

    Duncan, Flavia Cunha

    The extraordinary expansion during the reaction sintering of the magnesium aluminate spinel (MgAl2O4) from its basic oxide (MgO and Al2O3) powders was studied. Experimental series of different size fractions of the reacting materials were formulated to produce the Mg-Al spinel. After batches were prepared, specimens were compacted and fired in air from 1200° to 1700°C for a fixed firing time. A separate set of specimens was fired as a function of time to determine the reaction kinetic parameters. Dimensional changes confirmed that extraordinary expansions of three to four times greater than the prediction from the reaction of solids occur. The solid-state reactions were monitored by X-ray diffraction. The activation energy of the spinel reaction formation was determined to be 280 +/- 20 kJ/mol. It is believed to be associated with the diffusivity of Mg 2+ in either magnesia or spinel during the development of the final spinel structure. New porosity developed in the compacts during the reaction formation of spinel. Scanning electron microscopy confirmed that the magnesia evaporated leaving behind porous magnesia grains, condensed on the alumina particles and reacted to form a shell of spinel. Hollow spinel particles resulted from the original particles of alumina. These porosities generated within the reacting materials influenced the expansions. Final volumetric expansion could potentially reach 56% as a result of the reaction of solids and the porosity generation within MgO and Al2O3. Models of a single alumina particle with and without development of internal porosity were developed. 3-D arrangements of particles showed additional porosity, influencing on the expansions. The decrease in porosity of some specimens fired at higher temperatures indicated that sintering and densification occur simultaneously with the reaction formation of spinel. The decrease in the interparticle porosity limits the full expansion of the particulates to levels lower than the

  19. Ion-induced photon emission of magnesium aluminate spinel during 60 keV Cu - implantation

    NASA Astrophysics Data System (ADS)

    Bandourko, V.; Lay, T. T.; Takeda, Y.; Lee, C. G.; Kishimoto, N.

    2001-04-01

    The beam-solid interaction during high flux heavy-ion implantation has been studied by the in situ detection of photon emission. A spinel of MgO· n(Al 2O 3) with n=2.4 was irradiated with 60 keV Cu - at dose rates of 10, 50 or 100 μA/cm 2 to a dose of 1.5×10 17 ions/cm2. Under the implantation, photon emission ranging from 1.4 to 6.2 eV was detected by a time-resolved optical device based on a fast-response CCD (Princeton Instruments: IMAX-512). Emission lines of sputtered Mg, Al and Cu atoms were observed. A comparison of the dose and dose rate dependence of the Cu I line intensity from MgO· n(Al 2O 3) with those obtained for amorphous (a-)SiO 2 substrate revealed the good correlation of Cu I line intensity with nanoparticle formation detected by optical absorbance measurement.

  20. Neutron irradiation effect on site distribution of cations in non-stoichiometric magnesium aluminate spinel

    NASA Astrophysics Data System (ADS)

    Sawabe, Takashi; Yano, Toyohiko

    2008-02-01

    Neutron irradiation effects on cation distribution in non-stoichiometric Mg-Al spinel were examined by ALCHEMI (Atom Location by Channeling Enhanced Microanalysis) method. Parameter n, or non-stoichiometry of MgO · nAl 2O 3 of the specimens, were n = 1.00, 1.01, 1.10, 1.48. These specimens were neutron-irradiated up to a fluence of 2.3 × 10 24 n/m 2 ( E > 0.1 MeV) at 500-530 °C in JMTR. Some specimens contracted by the irradiation and the arrangement of cations became more disorder. The other specimens showed very small swelling by the irradiation and the cation distribution became slightly ordered. The cation distribution of the contracted specimen returned stepwise to the pre-irradiated condition after the annealing at 700 °C. The cation distribution of the slightly swollen specimens did not change after the annealing up to 700 °C. Cation distribution in the T-site was more sensitively influenced by the irradiation.

  1. Crystal structure of complex natural aluminum magnesium calcium iron oxide

    SciTech Connect

    Rastsvetaeva, R. K. Aksenov, S. M.; Verin, I. A.

    2010-07-15

    The structure of a new natural oxide found near the Tashelga River (Eastern Siberia) was studied by X-ray diffraction. The pseudo-orthorhombic unit cell parameters are a = 5.6973(1) A, b = 17.1823(4) A, c = 23.5718(5) A, {beta} = 90{sup o}, sp. gr. Pc. The structure was refined to R = 0.0516 based on 4773 reflections with vertical bar F vertical bar > 7{sigma}(F) taking into account the twin plane perpendicular to the z axis (the twin components are 0.47 and 0.53). The crystal-chemical formula (Z = 4) is Ca{sub 2}Mg{sub 2}{sup IV}Fe{sub 2}{sup (2+)IV}[Al{sub 14}{sup VI}O{sub 31}(OH)][Al{sub 2}{sup IV}O][Al{sup IV}]AL{sup IV}(OH)], where the Roman numerals designate the coordination of the atoms. The structure of the mineral is based on wide ribbons of edge-sharing Al octahedra (an integral part of the spinel layer). The ribbons run along the shortest x axis and are inclined to the y and z axes. The adjacent ribbons are shifted with respect to each other along the y axis, resulting in the formation of step-like layers in which the two-ribbon thickness alternates with the three-ribbon thickness. Additional Al octahedra and Mg and Fe{sup 2+} tetrahedra are located between the ribbons. The layers are linked together to form a three-dimensional framework by Al tetrahedra, Ca polyhedra, and hydrogen bonds with the participation of OH groups.

  2. Studies on densification, mechanical, micro-structural and structure–properties relationship of magnesium aluminate spinel refractory aggregates prepared from Indian magnesite

    SciTech Connect

    Ghosh, Chandrima; Ghosh, Arup; Haldar, Manas Kamal

    2015-01-15

    The present work intends to study the development of magnesium aluminate spinel aggregates from Indian magnesite in a single firing stage. The raw magnesite has been evaluated in terms of chemical analysis, differential thermal analysis, thermogravimetric analysis, infrared spectroscopy, and X-ray diffraction. The experimental batch containing Indian magnesite and calcined alumina has been sintered in the temperature range of 1550 °C–1700 °C. The sintered material has been characterized in terms of physico-chemical properties like bulk density, apparent porosity, true density, relative density and thermo-mechanical/mechanical properties like hot modulus of rupture, thermal shock resistance, cold modulus of rupture and structural properties by X-ray diffraction in terms of phase identification and evaluation of crystal structure parameters of corresponding phases by Rietveld analysis. The microstructures developed at different temperatures have been analyzed by field emission scanning electron microscope study and compositional analysis of the developed phase has been carried out by energy dispersive X-ray study. - Highlights: • The studies have been done to characterize the developed magnesium aluminate spinel. • The studies reveal correlation between refractory behavior of spinel and developed microstructures. • The studies show the values of lattice parameters of developed phases.

  3. X-ray structural study of chrome-aluminum lunar spinel from the Sea of Fertility

    NASA Technical Reports Server (NTRS)

    Nozik, Y. Z.; Tovbis, A. B.

    1974-01-01

    An X-ray structural study was made of a lunar spinel sample from the Sea of Fertility. The chemical composition and distribution of cations in the structure were characterized. Interpretation of the experimental data by the least squares method yielded the oxygen parameter u = 0.261 and the isotropic temperature factor 1.09 AU squared.

  4. Magnesium

    MedlinePlus

    ... supplements are available? Magnesium is available in multivitamin-mineral supplements and other dietary supplements . Forms of magnesium ... higher intakes of magnesium have a higher bone mineral density , which is important in reducing the risk ...

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

    SciTech Connect

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

    1983-05-01

    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.

  6. Microstructural characterization of ultrasonic impact treated aluminum-magnesium alloy

    NASA Astrophysics Data System (ADS)

    Tran, Kim Ngoc Thi

    Aluminum 5456-H116 has high as-welded strength, is formable, and highly corrosion resistant, however, it can become sensitized when exposed to elevated temperatures for a prolonged time. Sensitization results in the formation of a continuous β phase at the grain boundaries that is anodic to the matrix. Thus the grain boundaries become susceptible to stress corrosion cracking (SCC) and intergranular corrosion cracking (IGC). Cracking issues on aluminum superstructures have prompted the use of a severe plastic deformation processes, such as ultrasonic impact treatment (UIT), to improve SCC resistance. This study correlated the effects of UIT on the properties of 5456-H116 alloy to the microstructural evolution of the alloy and helped develop a fundamental understanding of the mechanisms that cause the microstructural evolution. Ultrasonic impact treatment produces a deformed layer at the surface ˜ 10 to 18 µm thick that is characterized by micro-cracks, tears, and voids. Ultrasonic impact treatment results in grain refinement within the deformation layer and extending below the deformed layer. The microstructure exhibits weak crystallographic texture with larger fraction of high angle grain boundaries. Nanocrystalline grains within the deformation layer vary in size from 2 to 200 nm in diameter and exhibit curved or wavy grain boundaries. The nanocrystalline grains are thermally stable up to 300°C. Above 300°C, grain growth occurs with an activation energy of ˜ 32 kJ/mol. Below the deformation layer, the microstructure is characterized by submicron grains, complex structure of dislocations, sub-boundaries, and Moiré fringes depicting overlapping grains. The deformation layer does not exhibit the presence of a continuous β phase, however below the deformation layer; a continuous β phase along the grain boundaries is present. In general the highest hardness and yield strength is at the UIT surface which is attributed to the formation of nanocrystalline grains

  7. Characteristics of aluminum and magnesium based nanocomposites processed using hybrid microwave sintering.

    PubMed

    Eugene, Wong Wai Leong; Gupta, Manoj

    2010-01-01

    Powder metallurgy is one of the highly established methods to synthesize metals, alloys and composites. Sintering is one of the important steps in powder metallurgy methodology and is usually realized through conventional resistance furnaces. The sintering usually takes a few hours to realize density in excess of 90%. The present study highlights the use of energy efficient and environment friendly microwave sintering route to synthesize pure aluminum, magnesium and magnesium based nanocomposites. Three reinforcements were targeted: a) silicon carbide, a microwave susceptor, b) alumina, a microwave transparent material and c) copper, a conducting material. Composites were prepared using blend - compact - microwave sintering - extrusion methodology. Process evaluation revealed that microwave assisted sintering can lead to a reduction of 86% in sintering time and energy savings of 96% when compared to conventional sintering. Moreover, microwave assisted sintering of metal compacts in this study was carried out in air, in the absence of any protective atmosphere, without compromising the mechanical properties of the materials. Results revealed that properties of magnesium can be convincingly enhanced using the said processing methodology and the materials formulations selected. Most importantly, the study established the viability of microwave sintering approach used in place of conventional sintering for magnesium based formulations. PMID:21721326

  8. The influence of stepwise deformation of aluminum-magnesium alloy upon its electrical conduction

    NASA Astrophysics Data System (ADS)

    Shibkov, A. A.; Zolotov, A. E.; Gasanov, M. F.; Zheltov, M. A.; Greben'kov, O. V.

    2016-04-01

    The influence of stepwise deformation upon the electrical conduction of the AlMg6 aluminum-magnesium alloy is investigated experimentally. It is found that the nucleation and development of single deformation bands causing stepwise deformation increase the specific electric resistance of the alloy on average by 2-3%. It is supposed that the main mechanism of an increase in the electric resistance in the deformation band is growth of the deformation vacancy concentration, which is connected with intensive dislocation multiplication in the deformation band front.

  9. Optimization of chlorine fluxing process for magnesium removal from molten aluminum

    NASA Astrophysics Data System (ADS)

    Fu, Qian

    High-throughput and low operational cost are the keys to a successful industrial process. Much aluminum is now recycled in the form of used beverage cans and this aluminum is of alloys that contain high levels of magnesium. It is common practice to "demag" the metal by injecting chlorine that preferentially reacts with the magnesium. In the conventional chlorine fluxing processes, low reaction efficiency results in excessive reactive gas emissions. In this study, through an experimental investigation of the reaction kinetics involved in this process, a mathematical model is set up for the purpose of process optimization. A feedback controlled chlorine reduction process strategy is suggested for demagging the molten aluminum to the desired magnesium level without significant gas emissions. This strategy also needs the least modification of the existing process facility. The suggested process time will only be slightly longer than conventional methods and chlorine usage and emissions will be reduced. In order to achieve process optimization through novel designs in any fluxing process, a system is necessary for measuring the bubble distribution in liquid metals. An electro-resistivity probe described in the literature has low accuracy and its capability to measure bubble distribution has not yet been fully demonstrated. A capacitance bubble probe was designed for bubble measurements in molten metals. The probe signal was collected and processed digitally. Higher accuracy was obtained by higher discrimination against corrupted signals. A single-size bubble experiment in Belmont metal was designed to reveal the characteristic response of the capacitance probe. This characteristic response fits well with a theoretical model. It is suggested that using a properly designed deconvolution process, the actual bubble size distribution can be calculated. The capacitance probe was used to study some practical bubble generation devices. Preliminary results on bubble distribution

  10. Cryomilled Aluminum with Diamantane: Thermal Characterization by DSC and Effects of Magnesium

    NASA Astrophysics Data System (ADS)

    Arnold, Michael Colin

    Many structural applications require a material that is both lightweight and corrosion resistant, for which aluminum and its alloys may be considered for use if not for their relatively low strength. By improving strength of aluminum through the Hall-Petch mechanism, it could become a more suitable choice for many structural applications. Cryomilling is used as a production technique to strengthen aluminum by reduction of grain size to the 20-50 nm range. Although the powders produced by cryomilling are well within the nanocrystalline regime, the powders experience significant grain growth during consolidation to a solid body. Cryomilled powders have been shown to remain nanocrystalline by introducing a nano-diamond, diamantane to the grain boundaries. To better characterize the thermal stability of the cryomilled powder with diamantane, Differential Scanning Calorimetry (DSC) was used to measure the isothermal heat flow in the 0.6Tm to 0.9Tm range. A model was developed to correlate the isothermal DSC signal to a grain growth curve and grain growth parameters were elucidated by assuming variable boundary mobility with a sigmoidal form. The model revealed a tendency for boundary mobility to transition from an athermal grain growth mechanism to standard thermally activated grain growth. Grain growth parameters were compared to shed light on possible mechanisms of aluminum-diamantane involvement during grain growth. Powders and consolidated samples with very low concentrations of diamantane and with magnesium were observed by TEM, SEM and XRD, and compared both separately and together to characterize the how thermal stability is affected by diamantane concentration and the presence of magnesium.

  11. SO 2 adsorption and thermal stability and reducibility of sulfates formed on the magnesium-aluminate spinel sulfur-transfer catalyst

    NASA Astrophysics Data System (ADS)

    Wang, Jin-an; Li, Cheng-lie

    2000-07-01

    Magnesium-aluminate spinel used as a sulfur-transfer catalyst in the fluid catalytic cracking units for SO x emission control was prepared by the precipitation method. The crystalline structure, textural property, and surface dehydroxylation of the sample were characterized by thermogravimetry-derivative thermogravimetry (TG-DTG), differential thermal analysis (DTA), X-ray diffraction (XRD), liquid N 2 adsorption-desorption and infrared spectroscopy (IR) measurements. The behavior of SO 2 adsorption and oxidation on the surface of catalyst was evaluated with IR from 50°C to 600°C. Particularly, the thermal stability and H 2-reducibility of the formed sulfite or sulfate during SO 2 adsorption or oxidation were tested under various conditions. In the absence of oxygen in the feed mixture, weak physically adsorbed SO 2 species and surface sulfite were identified. In the case of SO 2 oxidative adsorption, both surface sulfate and bulk-like sulfate were formed. When the sulfated sample was reduced with hydrogen, the surface sulfite and sulfates were completely removed below 550°C in vacuum. The bulk-like sulfate, however, showed a high ability to resist H 2-reduction, which indicates that the reducibility of bulk-like sulfate formed on magnesium-aluminate spinel must be enhanced when it is used as a sulfur-transfer catalyst.

  12. Experimental determination of equilibrium magnesium isotope fractionation between spinel, forsterite, and magnesite from 600 °C to 800 °C

    NASA Astrophysics Data System (ADS)

    Macris, C. A.; Young, E. D.; Manning, C. E.

    2012-12-01

    Magnesium isotopes are potentially powerful tools for high-temperature geochemistry if relevant fractionation factors are known. However, experimental data for Mg isotope fractionation are lacking at high temperatures. We performed piston-cylinder experiments at 600, 700, and 800 °C at 1 GPa to establish the equilibrium magnesium isotope partitioning between forsterite (Mg2SiO4) and magnesite (MgCO3) and between spinel (MgAl2O4) and magnesite, making use of the well-established advantages of using carbonates as an isotope exchange medium (e.g. Clayton et al., 1989). In these experiments we implemented the three-isotope method with forsterite and magnesite, and with spinel and magnesite, at three different temperatures in high-pressure piston cylinder apparatus for varying lengths of time. The present study extends the applicability of the three-isotope method to experiments involving simple isotope exchange rather than exchange by heterogeneous reaction (Shahar et al., 2008). We used magnesite as the exchange medium (and exchange partner) to overcome the sluggish diffusion-limited exchange between spinel and forsterite alone. The carbonate medium evidently facilitates chemical and isotopic exchange by promoting annealing and re-crystallization of minerals during the experiment. Results are as follows: 600 °C and 1 GPa 26ΔSp-Mgs = 1.73 ± 0.38‰ and 26ΔFo-Mgs = 0.44 ± 0.10‰; 700 °C 26ΔSp-Mgs = 1.10 ± 0.27‰ and 26ΔFo-Mgs = -0.13 ± 0.13‰; 800 °C 26ΔSp-Mgs = 0.90 ± 0.28‰ and 26ΔFo-Mgs = 0.04 ± 0.04‰. From these experimentally determined equilibrium fractionation values, we derive the temperature-dependent equilibrium fractionation between spinel and forsterite by difference, yielding 26ΔSp-Fo = 1.29 ± 0.39‰, 26ΔSp-Fo = 1.22 ± 0.30‰, and 26ΔSp-Fo = 0.86 ± 0.29‰ for 600, 700, and 800 °C respectively. These results agree within error with first- principles estimates of equilibrium magnesium isotope fractionation between spinel and

  13. Development and compatibility of magnesium matrix fuel plates clad with 6061 aluminum alloy.

    SciTech Connect

    Wiencek, T. C.

    1998-10-22

    Aluminum (Al) is a commonly used matrix for research reactor fuel plates. It has been found that a reaction between the fuel and the aluminum matrix may reduce or increase the irradiation stability of the fuel. To further understand the contribution of the reaction to the irradiation stability, experiments to develop a non-reacting matrix were performed. The work focused on magnesium (Mg), which is an excellent non-reacting matrix candidate and has a neutron absorption coefficient similar to Al. To avoid the formation of a liquid Al/Mg phase, improvements were made to the roll bonding process to achieve acceptable bonding at 415 C. After these methods were developed, fuel plates were produced with two fuels, uranium (U)-2 w/o molybdenum (Mo) and U-10-w/o Mo with two matrices, Al and Mg. A reaction between the magnesium and the 6061 Al cladding was discovered to take place during the processing at 415 C. To minimize the amount of reaction, methods were successfully developed to roll bond the fuel plates at 275 C. No reaction zone was observed in fuel plates processed at 275 C. Using this method, fuel plates with a Mg matrix are planned to be fabricated and included in the next irradiation matrix for the RERTR high density fuel development program.

  14. Effects of Cation Disordering in Magnesium Aluminate Spinel on the Rectangular Parallelepiped Resonance and Raman Measurements of Vibrational Spectra

    NASA Astrophysics Data System (ADS)

    Cynn, Hyunchae

    The effects of cation disordering of a natural MgAl_2O_4^inel on acoustic and optic vibration were measured for the first time using the rectangular parallelepiped resonance method and Raman measurements. In the resonant frequency measurements of a natural spinel at high temperatures over the temperature range 298 to 1068 K, a discontinuous increase in the measured acoustic resonant vibrations of the lower harmonic modes and a discontinuous decrease in the measured acoustic resonant vibrations of the higher harmonic modes were observed at around 1000 K. Similar differences among the resonant frequencies were also observed at ambient conditions between a less disordered spinel and the highly disordered states of a natural spinel. In the Raman measurements of the same natural spinel over the temperature range 298 to 1424 K, plots of the Raman vibrational frequencies of the external and internal vibrational modes versus temperature change slopes at around 1000 K. These two measurements clearly indicate that a major change occurred at 1000 K, which I label as a transition temperature. I interpret the change that occurred around 1000 K as the onset of cation disordering in the natural spinel. The interpretation is consistent with the following observations: (1) an abrupt decrease in oxygen positional parameter in an x-ray single crystal structure analysis of a synthetic spinel between 873 and 973 K; (2) a discontinuous decrease of linear thermal expansion coefficients in a synthetic spinel at 933 K by dilatometry, and (3) a discontinuous decrease of the unit cell parameter of a natural spinel at around 1073 K by x-ray diffraction. The adiabatic elastic moduli found here for the natural spinel are different from results which have been previously reported by others, however, the moduli of a disordered natural spinel are similar to those previously reported for synthetic spinels. These observations demonstrate that cation disordering of a spinel clearly affects the

  15. Experimental determination of equilibrium magnesium isotope fractionation between spinel, forsterite, and magnesite by the three-isotope method at 700 °C and 1 GPa

    NASA Astrophysics Data System (ADS)

    Macris, C. A.; Young, E. D.; Manning, C. E.; Schauble, E. A.

    2011-12-01

    Magnesium isotopes are potentially powerful tools for high-temperature geochemistry if relevant fractionation factors are known. However, experimental data for Mg isotope fractionation are lacking at high temperatures. We performed piston-cylinder experiments at 700 °C and 1 GPa to establish the equilibrium magnesium isotope partitioning between forsterite (Mg2SiO4) and magnesite (MgCO3), and between spinel (MgAl2O4) and magnesite, making use of the well-established advantages of using carbonates as an isotope exchange medium (e.g. Clayton et al., 1989). Our results provide the first experimental calibration of the equilibrium 26Mg/24Mg fractionation between minerals at high temperature. For these experiments we used a high-pressure piston cylinder apparatus and a three-isotope spike technique. The present study extends the applicability of the three-isotope method to experiments involving simple isotope exchange rather than exchange by heterogeneous reaction (Shahar et al., 2008). In these experiments we used magnesite as the exchange medium (and exchange partner) to overcome the sluggish diffusion-limited exchange between spinel and forsterite alone. The carbonate media facilitates chemical and isotopic exchange by promoting annealing and re-crystallization of minerals during the experiment. The combination of a three-isotope method with the use of carbonate as exchange media, used for the first time in this study, allows the experimentalist to determine the partitioning of Mg isotopes between two solid phases without requiring heterogeneous reaction. Results show that at 700 °C and 1 GPa 26ΔFo-Mgs = -0.16 ± 0.13% and 26ΔSp-Mgs = 0.93 ± 0.28%. From these two experimentally-determined equilibrium fractionation values, we can derive the equilibrium fractionation between spinel and forsterite by difference, yielding 26ΔSp-Fo = 1.09 ± 0.31%. This agrees within error with a first- principles estimate of equilibrium magnesium isotope fractionation of 26

  16. Thermoelectric properties of hot-pressed and PECS-sintered magnesium-doped copper aluminum oxide

    SciTech Connect

    Liu, Chang; Morelli, Donald T

    2011-02-03

    Copper aluminum oxide (CuAlO{sub 2}) is considered as a potential candidate for thermoelectric applications. Partially magnesium-doped CuAlO{sub 2} 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.

  17. Overview of DOE'S programs on aluminum and magnesium for automotive application

    SciTech Connect

    Carpenter, J.; Diamond, S.; Dillich, S.; Fitzsimmons, T.; Milliken, J.; Sklad, P.

    1999-02-28

    The U.S. Department of Energy will present an update and review of its programs in aluminum and magnesium for automotive and heavy-duty vehicle applications. While the main programs focused on vehicle materials are in the Office of Transportation Technologies, contributing efforts will be described in the DOE Office of Industrial Technologies and the DOE Office of Energy Research. The presentation will discuss materials for body/chassis and power train, and will highlight the considerable synergy among the efforts. The bulk of the effort is on castings, sheet, and alloys with a smaller focus on metal matrix composites. Cost reduction and energy savings are the overriding themes of the programs.

  18. Investigation on the Explosive Welding of 1100 Aluminum Alloy and AZ31 Magnesium Alloy

    NASA Astrophysics Data System (ADS)

    Chen, Pengwan; Feng, Jianrui; Zhou, Qiang; An, Erfeng; Li, Jingbo; Yuan, Yuan; Ou, Sanli

    2016-07-01

    The undesirable properties of magnesium alloys include easy embrittlement, low oxidation resistance, and difficulty in welding with other materials. Their application in industry is, therefore, restricted. In this paper, plates of 1100 aluminum alloy and AZ31 magnesium alloy were successfully welded together using the explosive welding technique. The influences of the welding parameters on the weld quality were investigated. The surface morphology and microstructure near the weld interface were examined by optical microscopy, scanning electron microscopy (equipped with energy-dispersive x-ray spectroscopy), and transmission electron microscopy. The experimental results demonstrated the typical wavy bonding interface. In addition, elemental diffusion with a thickness of approximately 3 μm occurred near the bonding interface. The two plates were joined together well at the atomic scale. Nanograins with a size of approximately 5 nm were observed in the diffusion layer. The microhardness and shear strength were measured to evaluate the mechanical properties, which confirmed that a high quality of bonding was acquired.

  19. Cells with sodium hypochlorite or chlorite and anodes of magnesium or aluminum

    SciTech Connect

    Brenner, A.

    1996-10-01

    A cell composed of a chlorine oxy-ion salt, acting as the battery positive, and anodes of magnesium or aluminum was found to be capable of producing potentials and currents comparable to those of conventional batteries. However, its use would have to be limited to that of a reserve type of battery with a short service-life because of the chemical interaction of the anodes with the electrolyte. This rate of reaction was considerably reduced by the presence of nitrate ion in the electrolyte. The rate of decomposition of hypochlorite solutions on aging was found not to be significant for their use in a reserve type of battery. The utilization of the reactants in the magnesium-chlorine oxy-ion cells was about 60% on a continuous discharge. Since these cells after being discharged would contain only a solution of common salt and a slurry of a metal hydroxide, they were innocuous with respect to the environment. Since this characteristic might make the battery of possible interest for a green motor vehicles, a battery was evaluated with respect to the adaptations that would be necessary for such an application.

  20. Investigation on the Explosive Welding of 1100 Aluminum Alloy and AZ31 Magnesium Alloy

    NASA Astrophysics Data System (ADS)

    Chen, Pengwan; Feng, Jianrui; Zhou, Qiang; An, Erfeng; Li, Jingbo; Yuan, Yuan; Ou, Sanli

    2016-06-01

    The undesirable properties of magnesium alloys include easy embrittlement, low oxidation resistance, and difficulty in welding with other materials. Their application in industry is, therefore, restricted. In this paper, plates of 1100 aluminum alloy and AZ31 magnesium alloy were successfully welded together using the explosive welding technique. The influences of the welding parameters on the weld quality were investigated. The surface morphology and microstructure near the weld interface were examined by optical microscopy, scanning electron microscopy (equipped with energy-dispersive x-ray spectroscopy), and transmission electron microscopy. The experimental results demonstrated the typical wavy bonding interface. In addition, elemental diffusion with a thickness of approximately 3 μm occurred near the bonding interface. The two plates were joined together well at the atomic scale. Nanograins with a size of approximately 5 nm were observed in the diffusion layer. The microhardness and shear strength were measured to evaluate the mechanical properties, which confirmed that a high quality of bonding was acquired.

  1. Self-diffusion of magnesium in spinel and in equilibrium melts - Constraints on flash heating of silicates

    NASA Technical Reports Server (NTRS)

    Sheng, Y. J.; Wasserburg, G. J.; Hutcheon, I. D.

    1992-01-01

    An isotopic tracer is used to measure Mg self-diffusion in spinel and coexisting melt at bulk chemical equilibrium. The diffusion coefficients were calculated from the measured isotope profiles using a model that includes the complementary diffusion of Mg-24, Mg-25, and Mg-26 in both phases with the constraint that the Mg content of each phase is constant. The activation energy and preexponential factor for Mg self-diffusion in spinel are, respectively, 384 +/- 7 kJ and 74.6 +/- 1.1 sq cm/s. These data indicate Mg diffusion in spinel is much slower than previous estimates. The activation energy for Mg self-diffusion in coexisting melt is 343 +/- 25 kJ and the preexponential factor is 7791.9 +/- 1.3 sq cm/s. These results are used to evaluate cooling rates of plagioclase-olivine inclusions (POIs) in the Allende meteorite. Given a maximum melting temperature for POIs of about 1500 C, these results show that a 1-micron radius spinel would equilibrate isotopically with a melt within about 60 min.

  2. Comparative analysis of the friction stir welded aluminum-magnesium alloy joint grain structure

    NASA Astrophysics Data System (ADS)

    Zaikina, A. A.; Sizova, O. V.; Novitskaya, O. S.

    2015-10-01

    A comparative test of the friction stir welded aluminum-magnesium alloy joint microstructure for plates of a different thickness was carried out. Finding out the structuring regularities in the weld nugget zone, that is the strongest zone of the weld, the effects of temperature-deformational conditions on the promotion of a metal structure refinement mechanism under friction stir welding can be determined. In this research friction stir welded rolled plates of an AMg5M alloy; 5 and 8 mm thick were investigated. Material fine structure pictures of the nugget zone were used to identify and measure subgrain and to define a second phase location. By means of optical microscopy it was shown that the fine-grained structure developed in the nugget zone. The grain size was 5 flm despite the thickness of the plates. In the sample 5.0 mm thick grains were coaxial, while in the sample 8.0 mm thick grains were elongate at a certain angle to the tool travel direction.

  3. Lysozyme-magnesium aluminum silicate microparticles: Molecular interaction, bioactivity and release studies.

    PubMed

    Kanjanakawinkul, Watchara; Medlicott, Natalie J; Rades, Thomas; Puttipipatkhachorn, Satit; Pongjanyakul, Thaned

    2015-09-01

    The objectives of this study were to investigate the adsorption behavior of lysozyme (LSZ) onto magnesium aluminum silicate (MAS) at various pHs and to characterize the LSZ-MAS microparticles obtained from the molecular interaction between LSZ and MAS. The results showed that LSZ could be bound onto the MAS layers at different pHs, leading to the formation of LSZ-MAS microparticles. The higher preparation pH permitted greater adsorption affinity but a lower adsorption capacity of LSZ onto MAS. LSZ could interact with MAS via hydrogen bonds and electrostatic forces, resulting in the formation of intercalated nanocomposites. The particle size, %LSZ adsorbed, and LSZ release rate of LSZ-MAS microparticles increased when the LSZ-MAS ratio was increased. The secondary structure of LSZ bound onto the MAS layers in microparticles prepared at various pHs was altered compared with that of native LSZ. Moreover, the LSZ extracted from microparticles prepared at pH 4 showed an obvious change in the tertiary structure, leading to a decrease in the biological activity of the LSZ released. These findings suggested that LSZ can strongly interact with MAS to form microparticles that may potentially be used as delivery systems for sustained protein release. PMID:26193680

  4. Quaternary polymethacrylate-magnesium aluminum silicate films: molecular interactions, mechanical properties and tackiness.

    PubMed

    Rongthong, Thitiphorn; Sungthongjeen, Srisagul; Siepmann, Juergen; Pongjanyakul, Thaned

    2013-12-15

    The aim of this study was to investigate the impact of the addition of magnesium aluminum silicate (MAS), a natural clay, on the properties of polymeric films based on quaternary polymethacrylates (QPMs). Two commercially available aqueous QPM dispersions were studied: Eudragit(®) RS 30D and Eudragit(®) RL 30D (the dry copolymers containing 5 and 10% quaternary ammonium groups, respectively). The composite QPM-MAS films were prepared by casting. Importantly, QPM interacted with MAS and formed small flocculates prior to film formation. Continuous films were obtained up to MAS contents of 19% (referred to the QPM dry mass). ATR-FTIR and PXRD revealed that the positively charged quaternary ammonium groups of QPM interacted with negatively charged SiO(-) groups of MAS, creating nanocomposite materials. This interaction led to improved thermal stability of the composite films. The puncture strength and elongation at break of dry systems decreased with increasing MAS content. In contrast, the puncture strength of the wet QPM-MAS films (upon exposure to acidic or neutral media) increased with increasing MAS content. Furthermore, incorporation of MAS into QPM films significantly decreased the latter's tackiness in the dry and wet state. These findings suggest that nanocomposite formation between QPM and MAS in the systems can enhance the strength of wet films and decrease their tackiness. Thus, MAS offers an interesting potential as novel anti-tacking agent for QPM coatings. PMID:24144950

  5. Mechanism of freeze-thaw instability of aluminum hydroxycarbonate and magnesium hydroxide gels.

    PubMed

    Zapata, M I; Feldkamp, J R; Peck, G E; White, J L; Hem, S L

    1984-01-01

    The effect of freeze-thaw cycles on the physical stability of aluminum hydroxycarbonate and magnesium hydroxide gels was studied. Coagulation following a freeze-thaw cycle, leading to the formation of visible aggregates, affected the content uniformity of both gels. The freeze-thaw cycles did not affect the crystal form or surface characteristics of the gels as determined by X-ray powder diffraction and point of zero charge, but caused a slight reduction in the rate of acid neutralization and a large increase in the rate of sedimentation. The greatest effect was observed after the first freeze-thaw cycle. While the duration of freezing was not a factor, the rate of freezing was important and was inversely related to the aggregate size. The aggregates which formed following a freeze-thaw cycle were not redispersed by shaking, but were reversed by ultrasonic treatment or homogenization. The adsorption of polymers or surface-active agents prior to freezing reduced and, in some cases, prevented the formation of aggregates. The physical instability produced by a freeze-thaw cycle was explained by the modified DLVO theory. The force exerted on the particles by the growing ice crystals forced the particles into the primary minimum, producing strong interparticle attraction. On thawing, simple agitation did not provide enough force to overcome the attractive force of the primary minimum. Adsorption of polymers or surface-active agents increased the steric repulsive force and prevented the particles from reaching the primary minimum. PMID:6694078

  6. Fabrication of nanocrystalline aluminum-magnesium alloy powders by electrodeposition and their characterization

    NASA Astrophysics Data System (ADS)

    Tatiparti, Sankara Sarma V.

    Aluminum-magnesium alloy powders can potentially be used as hydrogen storage materials. In order to enhance the kinetics of hydrogenation it is desirable to have agglomerates of fine powders with very small grain size. In this study, nanocrystalline Al-Mg alloys in the form of powders were successfully fabricated by the electrodeposition technique using an organometallic based electrolyte. Mg was introduced into the electrolyte by a process called "pre-electrodeposition". The mechanism for Mg accumulation can be explained considering the electrode reactions as well as the chemical changes in the electrolyte. Using a copper cathode, the effects of the electrolyte composition and current density on composition of the deposit, its constituent phases and morphology were investigated. The magnesium content of the deposits improved with increasing Mg concentration in the electrolyte, temperature and current density. Depending on the composition, the deposits consisted of FCC-Al(Mg) and HCP-Mg(Al) phases and no intermetallic phase was found except for long deposition times. Generally, the deposits formed initially on the copper substrate with three dendritic morphologies namely, rod-like, feather-like and small globular, which eventually evolved into the large globular morphology. This observation is attributed to the establishment of spherical diffusion conditions at the sharp dendrite tips. Potentiostatic studies suggested that the appearance of different morphologies is associated with differing rates of deposition. While the initial dendrites consisted of the FCC Al-rich phase, the large globular morphology manifested as both FCC Al-rich and HCP Mg-rich phases, with the latter always forming over the former. The observation of formation of only the FCC phase implies that the nucleation barrier for the HCP phase on the copper substrate is quite high. The investigation of the effect of substrate, namely, Cu, graphite and Mg, revealed that the HCP phase can directly

  7. Comparative study of radiation-induced damage in magnesium aluminate spinel by means of IL, CL and RBS/C techniques

    NASA Astrophysics Data System (ADS)

    Jozwik, Iwona; Jagielski, Jacek; Gawlik, Grzegorz; Jozwik, Przemyslaw; Ratajczak, Renata; Panczer, Gerard; Moncoffre, Nathalie; Wajler, Anna; Sidorowicz, Agata; Thomé, Lionel

    2016-03-01

    A comparative study of damage accumulation in magnesium aluminate spinel (MgAl2O4) has been conducted using ionoluminescence (IL), cathodoluminescence (CL) and Rutherford Backscattering Spectrometry/channeling (RBS/C) techniques. MgAl2O4 single crystal and polycrystalline samples were irradiated with 320 keV Ar+ ions at fluencies ranging from 1 × 1012 to 2 × 1016 cm-2 in order to create various levels of radiation damage. RBS/C measurements provided quantitative data about damage concentration in the samples. These values were then compared to the luminescence measurements. The results obtained by IL and RBS/C methods demonstrate a two-step character of damage buildup process. The CL data analysis points to the three-step damage accumulation mechanism involving the first defect transformation at fluencies of about 1013 cm-2 and second at about 1015 cm-2. The rate of changes resulting from the formation of nonluminescent recombination centers is clearly nonlinear and cannot be described in terms of continuous accumulation of point defects. Both, IL and CL techniques, appear as new, complementary tools bringing new possibilities in the damage accumulation studies in single- and polycrystalline materials.

  8. Comparative study of radiation-induced damage in magnesium aluminate spinel by means of IL, CL and RBS/C techniques

    NASA Astrophysics Data System (ADS)

    Jozwik, Iwona; Jagielski, Jacek; Gawlik, Grzegorz; Jozwik, Przemyslaw; Ratajczak, Renata; Panczer, Gerard; Moncoffre, Nathalie; Wajler, Anna; Sidorowicz, Agata; Thomé, Lionel

    2016-06-01

    A comparative study of damage accumulation in magnesium aluminate spinel (MgAl2O4) has been conducted using ionoluminescence (IL), cathodoluminescence (CL) and Rutherford Backscattering Spectrometry/channeling (RBS/C) techniques. MgAl2O4 single crystal and polycrystalline samples were irradiated with 320 keV Ar+ ions at fluencies ranging from 1 × 1012 to 2 × 1016 cm-2 in order to create various levels of radiation damage. RBS/C measurements provided quantitative data about damage concentration in the samples. These values were then compared to the luminescence measurements. The results obtained by IL and RBS/C methods demonstrate a two-step character of damage buildup process. The CL data analysis points to the three-step damage accumulation mechanism involving the first defect transformation at fluencies of about 1013 cm-2 and second at about 1015 cm-2. The rate of changes resulting from the formation of nonluminescent recombination centers is clearly nonlinear and cannot be described in terms of continuous accumulation of point defects. Both, IL and CL techniques, appear as new, complementary tools bringing new possibilities in the damage accumulation studies in single- and polycrystalline materials.

  9. Quaternary polymethacrylate-magnesium aluminum silicate films: Water uptake kinetics and film permeability.

    PubMed

    Rongthong, Thitiphorn; Sungthongjeen, Srisagul; Siepmann, Florence; Siepmann, Juergen; Pongjanyakul, Thaned

    2015-07-25

    The aim of this study was to investigate the impact of the addition of different amounts of magnesium aluminum silicate (MAS) to polymeric films based on quaternary polymethacrylates (QPMs, here Eudragit RS and RL). MAS contains negatively charged SiO(-) groups, while QPM contains positively charged quaternary ammonium groups. The basic idea is to be able to provide desired water and drug permeability by simply varying the amount of added MAS. Thin, free films of varying composition were prepared by casting and exposed to 0.1M HCl and pH 6.8 phosphate buffer. The water uptake kinetics and water vapor permeability of the systems were determined gravimetrically. The transport of propranolol HCl, acetaminophen, methyl-, ethyl- and propylparaben across thin films was studied using side-by-side diffusion cells. A numerical solution of Fick's second law of diffusion was applied to determine the apparent compound diffusion coefficients, partition coefficients between the bulk fluids and the films as well as the apparent film permeability for these compounds. The addition of MAS resulted in denser inner film structures, at least partially due to ionic interactions between the positively charged quaternary ammonium groups and the negatively charged SiO(-) groups. This resulted in lower water uptake, reduced water vapor permeability and decreasing apparent compound diffusivities. In contrast, the affinity of the investigated drugs and parabens to the films substantially increased upon MAS addition. The obtained new knowledge can be helpful for the development of novel coating materials (based on QPM-MAS blends) for controlled-release dosage forms. PMID:26004005

  10. Forge Welding of Magnesium Alloy to Aluminum Alloy Using a Cu, Ni, or Ti Interlayer

    NASA Astrophysics Data System (ADS)

    Yamagishi, Hideki; Sumioka, Junji; Kakiuchi, Shigeki; Tomida, Shogo; Takeda, Kouichi; Shimazaki, Kouichi

    2015-08-01

    The forge-welding process was examined to develop a high-strength bonding application of magnesium (Mg) alloy to aluminum (Al) alloy under high-productivity conditions. The effect of the insert material on the tensile strength of the joints, under various preheat temperatures and pressures, was investigated by analyzing the reaction layers of the bonded interface. The tensile strengths resulting from direct bonding, using pure copper (Cu), pure nickel (Ni), and pure titanium (Ti) inserts were 56, 100, 119, and 151 MPa, respectively. The maximum joint strength reached 93 pct with respect to the Mg cast billet. During high-pressure bonding, a microscopic plastic flow occurred that contributed to an anchor effect and the generation of a newly formed surface at the interface, particularly prominent with the Ti insert in the form of an oxide layer. The bonded interfaces of the maximum-strength inserts were investigated using scanning electron microscopy-energy-dispersive spectroscopy and electron probe microanalysis. The diffusion reaction layer at the bonded interface consisted of brittle Al-Mg intermetallics having a thickness of approximately 30 μm. In contrast, for the three inserts, the thicknesses of the diffusion reaction layer were infinitely thin. For the pure Ti insert, exhibiting the maximum tensile strength value among the inserts tested, focused ion beam-transmission electron microscopy-EDS analysis revealed a 60-nm-thick Al-Ti reaction layer, which had formed at the bonded interface on the Mg alloy side. Thus, a high-strength Al-Mg bonding method in air was demonstrated, suitable for mass production.

  11. The Effectiveness of Surface Coatings on Preventing Interfacial Reaction During Ultrasonic Welding of Aluminum to Magnesium

    NASA Astrophysics Data System (ADS)

    Panteli, Alexandria; Robson, Joseph D.; Chen, Ying-Chun; Prangnell, Philip B.

    2013-12-01

    High power ultrasonic spot welding (USW) is a solid-state joining process that is advantageous for welding difficult dissimilar material couples, like magnesium to aluminum. USW is also a useful technique for testing methods of controlling interfacial reaction in welding as the interface is not greatly displaced by the process. However, the high strain rate deformation in USW has been found to accelerate intermetallic compound (IMC) formation and a thick Al12Mg17 and Al3Mg2 reaction layer forms after relatively short welding times. In this work, we have investigated the potential of two approaches for reducing the IMC reaction rate in dissimilar Al-Mg ultrasonic welds, both involving coatings on the Mg sheet surface to (i) separate the join line from the weld interface, using a 100- μm-thick Al cold spray coating, and (ii) provide a diffusion barrier layer, using a thin manganese physical vapor deposition (PVD) coating. Both methods were found to reduce the level of reaction and increase the failure energy of the welds, but their effectiveness was limited due to issues with coating attachment and survivability during the welding cycle. The effect of the coatings on the joint's interface microstructure, and the fracture behavior have been investigated in detail. Kinetic modeling has been used to show that the benefit of the cold spray coating can be attributed to the reaction rate reverting to that expected under static conditions. This reduces the IMC growth rate by over 50 pct because at the weld line, the high strain rate dynamic deformation in USW normally enhances diffusion through the IMC layer. In comparison, the thin PVD barrier coating was found to rapidly break up early in USW and become dispersed throughout the deformation layer reducing its effectiveness.

  12. Alginate-magnesium aluminum silicate composite films: effect of film thickness on physical characteristics and permeability.

    PubMed

    Pongjanyakul, Thaned; Puttipipatkhachorn, Satit

    2008-01-01

    The different film thicknesses of the sodium alginate-magnesium aluminum silicate (SA-MAS) microcomposite films were prepared by varying volumes of the composite dispersion for casting. Effect of film thickness on thermal behavior, solid-state crystallinity, mechanical properties, water uptake and erosion, and water vapor and drug permeability of the microcomposite films were investigated. The film thickness caused a small change in thermal behavior of the films when tested using DSC and TGA. The crystallinity of the thin films seemed to increase when compared with the thick films. The thin films gave higher tensile strength than the thick films, whereas % elongation of the films was on the contrary resulted in the lower Young's modulus of the films when the film thickness was increased. This was due to the weaker of the film bulk, suggesting that the microscopic matrix structure of the thick films was looser than that of the thin films. Consequently, water uptake and erosion, water vapor permeation and drug diffusion coefficient of the thick films were higher than those of the thin films. The different types of drug on permeability of the films also showed that a positive charge and large molecule of drug, propranolol HCl, had higher lag time and lower diffusion coefficient that acetaminophen, a non-electrolyte and small molecule. This was because of a higher affinity of positive charge drug on MAS in the films. The findings suggest that the evaporation rate of solvent in different volumes of the composite dispersion used in the preparation method could affect crystallinity and strength of the film surface and film bulk of the microcomposite films. This led to a change in water vapor and drug permeability of the films. PMID:17611056

  13. Effect of geometrical stress concentrators on the band formation and the serrated deformation in aluminum-magnesium alloys

    NASA Astrophysics Data System (ADS)

    Shibkov, A. A.; Zolotov, A. E.; Zheltov, M. A.; Denisov, A. A.; Gasanov, M. F.; Kochegarov, S. S.

    2016-05-01

    The effect of holes on the band formation and the serrated deformation in planar specimens of aluminum-magnesium alloys AlMg5 and AlMg6 is studied by high-speed video filming of moving deformation bands. It is found that the concentration of an elastic field near a hole causes early nucleation of macrolocalized deformation bands and decreases the critical deformation of the first stress drop. Differences between the spatial-temporal patterns of deformation bands near holes under various deformation conditions are revealed.

  14. Magnesium

    NASA Astrophysics Data System (ADS)

    Bechtel, H.; Bulian, W.; Bungardt, K.; Gürs, K.; Gürs, U.; Helling, W.; Kyri, H.; Laue, H. J.; Mahler, W.; Matting, A.; Meyer, F. R.; Mialki, W.; Ritter, F.; Ruge, J.; Saur, G.; Simon, W.; Strnat, K.; Weber, R.; Weigand, H. H.; Weik, H.; Ziesler, H.; Borchers, Heinz; Schmidt, Ernst

    Magnesium wird überwiegend durch Schmelzflußelektrolyse hergestellt. Das dabei anfallende Reinmagnesium hat einen Mg-Gehalt von etwa 99,9%. Hauptbeimengung ist das Eisen; Silizium und Aluminium sind nur in Spuren vorhanden. Der Anwendungsumfang des Reinmagnesiums ist gering; dagegen werden Magnesiumlegierungen zunehmend, insbesondere für den Druckguß verwendet. Neben den bis etwa zum Jahre 1950 allein gebräuchlichen Mg-Mn-, Mg-Al- und Mg-Al-Zn-Legierungen werden heute mehr und mehr die besonders warmfesten Legierungen mit Zusätzen von Zirkon, Thorium und Seltenen Erden hergestellt (siehe dazu auch Abschnitt Seltene Erden). Als Umhüllungsmaterial für Uranstäbe dient die Legierung Magnox A 12, die nach [H 3] neben 1 % Al noch geringe Mengen an Ca und Ba enthält. In den in Deutschland üblichen Kurzzeichen (DIN 1729) werden die chemischen Symbole und der ungefähre Gehalt der wichtigsten Legierungselemente angegeben. Gußlegierungen werden zusätzlich durch ein G (Sandguß oder Kokillenguß) oder ein D (Druckguß) gekennzeichnet (siehe Tab. 5).

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

    NASA Astrophysics Data System (ADS)

    Wang, Duhua

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

  16. A study of aluminum-lithium alloys: Strength profile in 2090 aluminum-lithium-copper-magnesium-zirconium alloy

    SciTech Connect

    Soepriyanto, S.

    1991-01-01

    Aluminum-containing lithium alloys are undergoing intensive development as replacements for conventional aluminum alloys 2024 and 7075 in aircraft structural applications. Lithium is a very reactive metal so that an elevated temperature heat treatments can cause lithium diffusion to the surface and reaction with the atmosphere. Solid state diffusion of lithium within the 2090 alloy and subsequent surface oxidation during solution heat treatment were investigated. Thermodynamic and kinetic analyses were used to evaluate the alloy's thermal oxidation behavior. A mathematical model based on simultaneous diffusion and surface oxidation of lithium was developed to predict lithium concentration profiles across the specimen. Agreement was obtained between the predicted lithium concentration profiles and their corresponding experimental results. Microhardness and yield strength profiles were found also to follow the corresponding lithium concentration profiles. Various heat treatment procedures were studied on this 2090 alloy to give a greater understanding of precipitate strengthening.

  17. Thermodynamic investigation of the effect of alkali metal impuries on the processing of aluminum and magnesium alloys

    NASA Astrophysics Data System (ADS)

    Zhang, Shengjun

    2006-12-01

    Aluminum and magnesium alloys are widely used in the automobile and aerospace industries as structural materials due to their light weight, high specific strength and good formability. However, they suffer from the poor hot rolling characteristics due to undesired impurities like calcium, potassium, lithium and sodium. They increase the hydrogen solubility in the melt and promote the formation of porosity in aluminum castings. During fabrication of aluminum alloys, they cause the hot-shortness and embrittlement due to cracking. They also led to "blue haze" corrosion which promotes the discoloration of aluminum under humid condition. The removal of these elements increases overall melt loss of aluminum alloys when aluminum products are remelted and recast. Na is one of the common impurities in the Al and Mg alloys. In industry, primary Al is produced by the Hall-Heroult process, through the electrolysis of the mixture of molten alumina and cryolite (Al2O3+Na 3AlF6), the latter being added to lower the melting point. Therefore, Al inevitably contains some Na (>0.002%) without further treatment. The Na content in Al is influenced by the thermodynamics and kinetics of the electrolysis. Similarly, in the electrolytic production and subsequent processing of Mg, Mg is commonly in contact with molten salt mixtures of NaCl and MgCl 2. Consequently, 2--20 wt. ppm Na is often found in Mg alloys. Besides originating from the industrial production process, Na can be introduced in laboratory experiments from alumina crucibles by the reaction between the molten Al-Mg alloys and the Na2O impurity in the alumina crucible. The trace element K plays a similar role in Al alloys although it is seldom discussed. No systematic theoretic research has been carried out to investigate the behavior of these impurities during the processing of aluminum alloys. The thermodynamic description of the Al-Ca-K-Li-Mg-Na system is needed to understand the effects of Ca, K, Li and Na on phase stability

  18. Explosion bonding: aluminum-magnesium alloys bonded to austenitic stainless steel

    SciTech Connect

    Patterson, R.A.

    1982-01-01

    The explosion bonding of 5000 series aluminum alloys to 300 series stainless steel alloys is summarized. The process technique involves a parallel gap arrangement with copper or aluminum bonding aids. Successful bonds have been achieved using either a single shot process for joining the trilayer clad or a sequential shot technique for each metal component. Bond success is monitored through a combined metallographic and tensile strength evaluation. Tensile properties are shown to be strongly dependent upon process parameters and the amount of intermetallic formation at the aluminum bond interface. Empirical data has been compared with experimental and destructive test results to determine the optimum procedures.

  19. Burning time and size of aluminum, magnesium, zirconium, tantalum, and pyrofuze particles burning in steam. Contractor's report, November 1984-March 1985

    SciTech Connect

    Kol, J.; Chozev, Y.

    1985-07-01

    The energy released by metals burning in steam has several important applications including torpedo propulsion, nuclear reactor safety, underwater vehicles, underwater ordnance, etc. This report continues the studies that were performed by Hallenbeck and Kol, Fuhs and Berger which are related to underwater shaped-charge investigations. Wires of various metals were exploded in a steam atmosphere. The metals investigated were aluminum, magnesium, tantalum, zirconium, and pyrofuze. Exploding wires generated numerous hot, small particles. Using photography, the burning time and particle sizes were measured. Typical results are as follows: 125 + or - 25 micron diameter aluminum burns in 3.8 + or - .75 ms; 175 + or - 35 micron diameter magnesium burns in 3.8 + or - .75 ms; 125 + or - 25 micron diameter zirconium in 25 to 31 ms; 125 + or - 25 micron diameter tantalum in 24 to 50 ms; and 125 + or - 25 micron pyrofuze in 30 to 50 ms. The atmosphere was pure saturated steam at approximately 20 psig.

  20. Optical absorption and luminescence study of cobalt-doped magnesium aluminosilicate glass ceramics

    NASA Astrophysics Data System (ADS)

    Malyarevich, A. M.; Denisov, I. A.; Yumashev, K. V.; Dymshits, O. S.; Zhilin, A. A.

    2002-08-01

    Linear and nonlinear optical properties of cobalt-doped magnesium aluminosilicate transparent glass ceramics that were prepared under different conditions have been studied. It has been shown that absorption and luminescence spectra and absorption bleaching of these glass ceramics are defined mainly by tetrahedrally coordinated Co 2+ ions located in magnesium aluminum spinel nanocrystals. The lifetimes of the 4 T 1 ( 4 F) and 4 T 2 ( 4 F) excited states of the tetrahedral Co 2+ ions were found to be in the ranges 2540 and 120450 ns, respectively, depending on the Co concentration. 2002 Optical Society of America

  1. DEGRADATION OF SM2ZR2O7 THERMAL BARRIER COATING CAUSED BY CALCIUM-MAGNESIUM-ALUMINUM-SILICON OXIDE (CMAS) DEPOSITION

    SciTech Connect

    Wang, Honglong; Sheng, Zhizhi; Tarwater, Emily; Zhang, Xingxing; Dasgupta, Sudip; Fergus, Jeffrey

    2015-03-16

    Rare earth zirconates are promising materials for use as thermal barrier coatings in gas turbine engines. Among the lanthanide zirconate materials, Sm2Zr2O7 with the pyrochlore structure has lower thermal conductivity and better corrosion resistance against calcium-magnesium-aluminum-silicon oxide (CMAS). In this work, after reaction with CMAS, the pyrochlore structure transforms to the cubic fluorite structure and Ca2Sm8(SiO4)6O2 forms in elongated grain.

  2. Chromium and yttrium-doped magnesium aluminum oxides prepared from layered double hydroxides

    NASA Astrophysics Data System (ADS)

    García-García, J. M.; Pérez-Bernal, M. E.; Ruano-Casero, R. J.; Rives, V.

    2007-12-01

    Layered double hydroxides with the hydrotalcite-like structures, containing Mg 2+ and Al 3+, doped with Cr 3+ and Y 3+, have been prepared by precipitation at constant pH. The weight percentages of Cr 3+ and Y 3+ were 1, 2, or 3%, and 0.5 or 1%, respectively. Single phases were obtained in all cases, whose crystallinity decreased as the content in Cr and Y was increased. The solids have been characterised by element chemical analysis, powder X-ray diffraction, thermal analyses (differential, thermogravimetric and programmed reduction), FT-IR and UV-vis spectroscopies; the specific surface areas have been determined from nitrogen adsorption isotherms at -196 °C. Upon calcination at 1200 °C for 5 h in air all solids display a mixed structure (spinel and rock salt for MgO); these solids have also been characterised by these techniques and their chromatic coordinates (CIE - L∗a∗b∗) have been determined. Their pink colour makes these solids suitable for being used as ceramic pigments.

  3. Modulus, strength and thermal exposure studies of FP-Al2O3/aluminum and FP-Al2O3/magnesium composites

    NASA Technical Reports Server (NTRS)

    Bhatt, R. T.

    1981-01-01

    The mechanical properties of FP-Al2O3 fiber reinforced composites prepared by liquid infiltration techniques are improved. A strengthening addition, magnesium, was incorporated with the aluminum-lithium matrix alloy usually selected for these composites because of its good wetting characteristics. This ternary composite, FP-Al2O3/Al-(2-3)Li-(3-5)Mg, showed improved transverse strength compared with FP-Al2O3/Al-(2-3)Li composites. The lower axial strengths found for the FP-Al2O3/Al-(2-3)Li-(3-5)Mg composites were attributed to fabrication related defects. Another technique was the use of Ti/B coated FP-Al2O3 fibers in the composites. This coating is readily wet by molten aluminum and permitted the use of more conventional aluminum alloys in the composites. However, the anticipated improvements in the axial and transverse strengths were not obtained due to poor bonding between the fiber coating and the matrix. A third approach studied to improve the strengths of FP-Al2O3 reinforced composites was the use of magnesium alloys as matrix materials. While these alloys wet fibers satisfactorily, the result indicated that the magnesium alloy composites used offered no axial strength or modulus advantage over FP-Al2O3/Al-(2-3)Li composites.

  4. Analytical electron microscopy of precipitates in ion-implanted MgAl{sub 2}O{sub 4} spinel

    SciTech Connect

    Evans, N.D.; Zinkle, S.J.; Bentley, J.

    1994-12-31

    Magnesium aluminate spinel (MgAl{sub 2}O{sub 4}) is being considered as an insulator material within proposed fusion reactors where considerable radiation fields are anticipated. Analytical electron microscopy (AEM) has been used to investigate precipitates within MgAl{sub 2}O{sub 4} spinel following implantation of Al{sup +}, Mg{sup +}, or Fe{sup 2+} ions. Combined diffraction experiments, energy dispersive X-ray spectrometry (EDS), electron energy-loss spectrometry (EELS), and energy-filtered imaging were employed to identify and characterize precipitates observed in the implanted ion region. Diffraction studies suggested these are metallic aluminum colloids, although EELS and energy-filtered images revealed this to be the case only for the Al{sup +} and Mg{sup +} implantations, and not for Fe{sup 2+} ion implantations. Multiple-least-squares (MLS) fitting of EELS spectra was employed to quantify the volume fraction of metallic aluminum when present in the implanted ion region. Energy-filtered images of the implanted ion region clearly show the colloid distribution in the Al{sup +} and Mg{sup +} implanted spinel. Energy-filtered images from the Fe {sup 2+} ion implanted spinel indicate that the features visible in diffraction contrast cannot be associated with either metallic aluminum or iron-rich precipitates.

  5. Influence of Aluminum Content on Grain Refinement and Strength of AZ31 Magnesium GTA Weld Metal

    SciTech Connect

    Babu, N. Kishore; Cross, Carl E.

    2012-06-28

    The goal is to characterize the effect of Al content on AZ31 weld metal, the grain size and strength, and examine role of Al on grain refinement. The approach is to systematically vary the aluminum content of AZ31 weld metal, Measure average grain size in weld metal, and Measure cross-weld tensile properties and hardness. Conclusions are that: (1) increased Al content in AZ31 weld metal results in grain refinement Reason: higher undercooling during solidification; (2) weld metal grain refinement resulted in increased strength & hardness Reason: grain boundary strengthening; and (3) weld metal strength can be raised to wrought base metal levels.

  6. Diffusion and growth of nickel, iron and magnesium adatoms on the aluminum truncated octahedron: A molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Yang, Jianyu; Hu, Wangyu; Wu, Yurong; Dai, Xiongying

    2012-06-01

    The structure of nickel (Ni), iron (Fe), and magnesium (Mg) adatoms on the aluminum (Al) truncated octahedron is studied using molecular dynamics and the analytic embedded atom method. First, the energy barriers of several typical diffusion processes of Ni, Fe, and Mg adatoms on the Al truncated octahedral cluster were calculated using the nudged elastic band method. The calculated energy barriers were found to be related to the surface energy and atomic radius of the adatom and substrate atom. The result shows that the incorporation of Ni and Fe atoms into Al core easily occurs, and the Mg atom should segregate at the surface of the Al cluster. Thus, the growth of Ni, Fe and Mg on the Al truncated octahedron with 1289 atoms was simulated at several temperatures. In the Ni-Al and Fe-Al cases, the core-shell structure was not obtained. For the Mg-Al system, a good Mg shell on the Al core was found at lower temperatures, and an almost perfect truncated octahedron with more Al shells emerged with an increase in temperature.

  7. The deformation and acoustic emission of aluminum-magnesium alloy under non-isothermal thermo-mechanical loading

    SciTech Connect

    Makarov, S. V.; Plotnikov, V. A. Lysikov, M. V.; Kolubaev, E. A.

    2015-10-27

    The following study investigates the deformation behavior and acoustic emission in aluminum-magnesium alloy under conditions of non-isothermal thermo-mechanical loading. The accumulation of deformation in the alloy, in conditions of change from room temperature to 500°C, occurs in two temperature intervals (I, II), characterized by different rates of deformation. The rate of deformation accumulation is correlated with acoustic emission. With load increasing in cycles from 40 to 200 MPa, the value of the boundary temperature (T{sub b}) between intervals I and II changes non-monotonically. In cycles with load up to 90 MPa, the T{sub b} value increases, while an increase up to 200 MPa makes T{sub b} shift toward lower temperatures. This suggests that the shift of boundaries in the region of low temperatures and the appearance of high-amplitude pulses of acoustic emission characterize the decrease of the magnitude of thermal fluctuations with increasing mechanical load, leading to the rupture of interatomic bonds in an elementary deformation act.

  8. Solidification, growth mechanisms, and associated properties of aluminum-silicon and magnesium lightweight casting alloys

    NASA Astrophysics Data System (ADS)

    Hosch, Timothy Al

    Continually rising energy prices have inspired increased interest in weight reduction in the automotive and aerospace industries, opening the door for the widespread use and development of lightweight structural materials. Chief among these materials are cast Al-Si and magnesium-based alloys. Utilization of Al-Si alloys depends on obtaining a modified fibrous microstructure in lieu of the intrinsic flake structure, a process which is incompletely understood. The local solidification conditions, mechanisms, and tensile properties associated with the flake to fiber growth mode transition in Al-Si eutectic alloys are investigated here using bridgman type gradient-zone directional solidification. Resulting microstructures are examined through quantitative image analysis of two-dimensional sections and observation of deep-etched sections showing three-dimensional microstructural features. The transition was found to occur in two stages: an initial stage dominated by in-plane plate breakup and rod formation within the plane of the plate, and a second stage where the onset of out-of-plane silicon rod growth leads to the formation of an irregular fibrous structure. Several microstructural parameters were investigated in an attempt to quantify this transition, and it was found that the particle aspect ratio is effective in objectively identifying the onset and completion velocity of the flake to fiber transition. The appearance of intricate out-of-plane silicon instability formations was investigated by adapting a perturbed-interface stability analysis to the Al-Si system. Measurements of silicon equilibrium shape particles provided an estimate of the anisotropy of the solid Si/liquid Al-Si system and incorporation of this silicon anisotropy into the model was found to improve prediction of the instability length scale. Magnesium alloys share many of the benefits of Al-Si alloys, with the added benefit of a 1/3 lower density and increased machinability. Magnesium castings

  9. Plutonium and americium recovery from spent molten-salt-extraction salts with aluminum-magnesium alloys

    SciTech Connect

    Cusick, M.J.; Sherwood, W.G.; Fitzpatrick, R.F.

    1984-04-23

    Development work was performed to determine the feasibility of removing plutonium and americium from spent molten-salt-extraction (MSE) salts using Al-Mg alloys. If the product buttons from this process are compatible with subsequent aqueous processing, the complex chloride-to-nitrate aqueous conversion step which is presently required for these salts may be eliminated. The optimum alloy composition used to treat spent 8 wt % MSE salts in the past yielded poor phase-disengagement characteristics when applied to 30 mol % salts. After a limited investigation of other alloy compositions in the Al-Mg-Pu-Am system, it was determined that the Al-Pu-Am system could yield a compatible alloy. In this system, experiments were performed to investigate the effects of plutonium loading in the alloy, excess magnesium, age of the spent salt on actinide recovery, phase disengagement, and button homogeneity. Experimental results indicate that 95 percent plutonium recoveries can be attained for fresh salts. Further development is required for backlog salts generated prior to 1981. A homogeneous product alloy, as required for aqueous processing, could not be produced.

  10. Modeling and experimental study on heat transfer in squeeze casting of magnesium alloy AM60 and aluminum alloy A443

    NASA Astrophysics Data System (ADS)

    Sun, Zhizhong

    This study developed a solution algorithm based on the function specification method to solve the inverse heat conduction equations. By this solution, the casting-die interfacial heat transfer coefficients (IHTC) in light metal squeeze castings were determined accurately and the pressurized solidification was simulated precisely. This goal was accomplished in the four stages. First, a model was developed to simulate fluid flow in forced convection and heat transfer in pressurized solidification of a cylindrical simple shape squeeze casting. Pressure-dependent heat transfer coefficients (HTC) and non-equilibrium solidification temperatures were determined by experimental measurements. With the measured HTC and temperatures under the different pressures, the temperature distributions and the cooling behaviours of squeeze cast were simulated. In the second stage, a different wall-thickness 5-step casting mould was designed, and squeeze casting of magnesium alloy AM60 was performed under an applied pressure 30, 60 and 90 MPa in a hydraulic press. With measured temperatures, heat fluxes and IHTCs were evaluated using the polynomial curve fitting method and numerical inverse method. The accuracy of these curves was analyzed by the direct modeling calculation. The results indicated that heat flux and IHTCs determined by the inverse method were more accurately than those from the extrapolated fitting method. In the third stage, the inverse method was applied to an aluminum alloy A443 and magnesium alloy AM60. As the applied hydraulic pressure increased, the IHTC peak value of each step was increased accordingly. Compared to the thin steps at the upper cavity, the relatively thick steps attained higher peak IHTCs and heat fluxes values due to high local pressures and high melt temperature. The empirical equations relating IHTC to the local pressures and solidification temperature at the casting surface were derived and summarized. Finally, the IHTC values calculated by

  11. Chemistry between magnesium and multiple molecules in tris(8-hydroxyquinoline) aluminum films.

    PubMed

    Meloni, Simone; Palma, Amedeo; Schwartz, Jeffrey; Kahn, Antoine; Car, Roberto

    2003-07-01

    Metal organic contacts are at the basis of devices such as organic light emitting diodes (OLEDs). Here, we report a theoretical investigation of the chemical interaction between a Mg atom and an organic film made of tris(8-hydroxyquinoline)aluminum (Alq3) molecules. The latter is modeled either by an isolated molecule or by a bulk crystal. Using first-principles molecular dynamics for structural optimization, we find that an isolated Alq3 molecule and a Mg atom form an ion-pair. However, when the metal atom interacts with molecules in a bulk crystalline environment, we find that an organometallic complex is energetically preferred over the ion-pair. The complex formation is an effect of the environment which makes possible the interaction of the metal atom with several adjacent molecules. Here, our calculated O(1s) and N(1s) core level shifts agree well with recent experimental data on Alq3 films exposed to Mg. Our results resolve the apparent contradiction between experiment and predictions made in previous calculations in which a single Alq3 molecule was used to model a thin film. PMID:12822992

  12. Microstructure and creep behavior of magnesium-aluminum alloys containing alkaline and rare earth additions

    NASA Astrophysics Data System (ADS)

    Saddock, Nicholas David

    In the past few decades governmental regulation and consumer demands have lead the automotive companies towards vehicle lightweighting. Powertrain components offer significant potential for vehicle weight reductions. Recently, magnesium alloys have shown promise for use in powertrain applications where creep has been a limiting factor. These systems are Mg-Al based, with alkaline earth or rare earth additions. The solidification, microstructure, and creep behavior of a series of Mg-4 Al- 4 X:(Ca, Ce, La, and Sr) alloys and a commercially developed AXJ530 (Mg--5 Al--3 Ca--0.15 Sr) alloy (by wt%) have been investigated. The order of decreasing freezing range of the five alloys was: AX44, AXJ530, AJ44, ALa44 and ACe44. All alloys exhibited a solid solution primary alpha-Mg phase surrounded by an interdendritic region of Mg and intermetallic(s). The primary phase was composed of grains approximately an order of magnitude larger than the cellular structure. All alloys were permanent mold cast directly to creep specimens and AXJ530 specimens were provided in die-cast form. The tensile creep behavior was investigated at 175 °C for stresses ranging from 40 to 100 MPa. The order of decreasing creep resistance was: die-cast AXJ530 and permanent mold cast AXJ530, AX44, AJ44, ALa44 and ACe44. Grain size, solute concentration, and matrix precipitates were the most significant microstructural features that influenced the creep resistance. Decreases in grain size or increases in solute concentration, both Al and the ternary addition, lowered the minimum creep rate. In the Mg-Al-Ca alloys, finely distributed Al2Ca precipitates in the matrix also improved the creep resistance by a factor of ten over the same alloy with coarse precipitates. The morphology of the eutectic region was distinct between alloys but did not contribute to difference in creep behavior. Creep strain distribution for the Mg-Al-Ca alloys developed heterogeneously on the scale of the alpha-Mg grains. As

  13. Beryllium aerosol characteristics in the magnesium and aluminum transformation industry in Quebec: a comparison of four different sampling methodologies.

    PubMed

    Dufresne, A; Dion, C; Viau, S; Cloutier, Y; Perrault, G

    2009-11-01

    To examine the influence of the sampling method on beryllium (Be) exposure assessment, a study was conducted in foundries and smelters to contrast the performance of five different dust sampling devices. Six sampling surveys were conducted in four different settings, and both personal and fixed station samples were collected using the following sampling heads: IOM samplers (inhalable dust), 35-mm plastic cassettes (total dust), aluminum SKC cyclones (respirable dust), 8-stage Sierra cascade impactors, and 12-stage MOUDI impactors. In total, beryllium concentrations were determined for 66/68 inhalable dust samples, 62/62 total dust samples, 56/57 respirable dust samples, 54/64 8-stage Sierra samples, and 19/25 12-stage MOUDI samples. In the magnesium foundry and aluminum smelters, the concentrations obtained during specific tasks could exceed the actual permissible exposure limit of the province of Quebec (0.15 microg/m(3)) or of the ACGIH threshold limit value (TLV) (0.05 microg/m(3)). The median of median dust concentration ratios computed from the sampling heads at the fixed station decreased as follows: IOM (1.00) > Sierra (0.76) > 37-mm cassette (0.61) > MOUDI (0.48) > respirable (0.12). The same trends were observed with the ratios of the median of median Be concentrations at the fixed station but with a larger scattering within sampling heads as follows: IOM (1.00) > Sierra (0.69) > 37-mm cassette (0.64) > MOUDI (0.54) > respirable (0.19). The median of median ratios of dust (IOM (1.00) > Sierra (0.56) > 37-mm cassette (0.35) > respirable (0.06)) and Be (IOM (1.00) > Sierra (0.66) > 37-mm cassette (0.48) > respirable (0.11)) in dust were lower, and there was less scattering for the 37-mm cassette and SKC cyclone used during breathing zone sampling than for the same sampling heads at the fixed station. Inhalable aerosol measurements should remain the tool for estimating the risk of exposure to beryllium in these settings until a clear dose response is

  14. The development and characterization of a novel aluminum-copper-magnesium P/M alloy

    NASA Astrophysics Data System (ADS)

    Boland, Christopher Daniel

    Powder metallurgy (P/M) is a metal fabrication process that is characterized by high yield and ability to be automated, as well as the resultant part complexity and reproducibility. This press and sinter process is favoured by the automotive industry. Aluminum alloy P/M parts are particularly attractive because they have a high strength to weight ratio and they can be made to have high corrosion and wear resistance. There are few commercial Al P/M alloys currently in use and they occupy a small portion of the market. To expand the use of aluminum in the industry a new alloy was created, modeled after the wrought AC2024 family of alloys. P/M 2324, with a nominal composition of Al-4.4Cu-1.5Mg, was assessed using physical, chemical and mechanical methods to help maximize alloy properties through processing. The objective of this work was to develop a viable industrial alloy. The investigation of 2324 included the evaluation of starting powders, starting composition, processing methods, secondary treatments, and industrial response. All blending and compacting was completed at Dalhousie University, while sintering was undertaken at Dalhousie and GKN Sinter Metals. The green alloy was assessed for best compaction pressure using green density and strength. The sintered alloy was assessed to determine the best press and sinter variables, using dimensional change, sintered density, apparent hardness, tensile properties and microscopy. These same sintered properties were tested to determine if sintering done on a laboratory scale could be replicated industrially. The viability of heat treatment was tested using differential scanning calorimetry, hardness and tensile properties. The alloy was also subject to modifications of Cu and Mg amounts, as well as to the addition of tin to the base composition. It was determined that compaction at 400MPa and sintering at 600°C for 20min produced the best properties for the sintered bodies. The resultant mechanical properties were

  15. Effect of geometrical stress concentrators on the current-induced suppression of the serrated deformation in an aluminum-magnesium AlMg5 alloy

    NASA Astrophysics Data System (ADS)

    Shibkov, A. A.; Zolotov, A. E.; Zheltov, M. A.; Denisov, A. A.; Gasanov, M. F.; Kochegarov, S. S.

    2016-05-01

    The effect of an electric current on the band formation and the serrated deformation of planar specimens made of an aluminum-magnesium AlMg5 alloy and weakened by holes is experimentally studied. It is found that the concentration of elastic stress fields and the self-localized unstable plastic deformation field near a hole decreases the critical strain of appearance of the first stress drop and hinders the currentinduced suppression of band formation and the serrated Portevin-Le Chatelier deformation. These results are shown not to be related to the concentration of Joule heat near a hole.

  16. Accelerated Bonding of Magnesium and Aluminum with a CuNi/Ag/CuNi Sandwich Interlayer by Plasma-Activated Sintering

    NASA Astrophysics Data System (ADS)

    Wang, Yiyu; Rao, Mei; Li, Leijun; Luo, Guoqiang; Shen, Qiang; Zhang, Lianmeng

    2016-02-01

    Plasma-activated sintering (PAS) has been applied, for the first time, to join magnesium and aluminum using a CuNi/Ag/CuNi sandwich structural interlayer. A cleaning effect and high efficient plasma heating mode in PAS have contributed to forming a strong interfacial diffusion bond under low temperature 673 K (400 °C) and short dwell time (0.6 ks). The designed interlayer provides a diffusion barrier effect and an enhanced physical contact between the interfaces. Strong bonding has been achieved without forming the brittle Mg-Al intermetallics.

  17. Preparation and controlled-release studies of a protocatechuic acid-magnesium/aluminum-layered double hydroxide nanocomposite

    PubMed Central

    Barahuie, Farahnaz; Hussein, Mohd Zobir; Hussein-Al-Ali, Samer Hasan; Arulselvan, Palanisamy; Fakurazi, Sharida; Zainal, Zulkarnain

    2013-01-01

    In the study reported here, magnesium/aluminum (Mg/Al)-layered double hydroxide (LDH) was intercalated with an anticancer drug, protocatechuic acid, using ion-exchange and direct coprecipitation methods, with the resultant products labeled according to the method used to produce them: “PANE” (ie, protocatechuic acid-Mg/Al nanocomposite synthesized using the ion-exchange method) and “PAND” (ie, protocatechuic acid-Mg/Al nanocomposite synthesized using the direct method), respectively. Powder X-ray diffraction and Fourier transform infrared spectroscopy confirmed the intercalation of protocatechuic acid into the inter-galleries of Mg/Al-LDH. The protocatechuic acid between the interlayers of PANE and PAND was found to be a monolayer, with an angle from the z-axis of 8° for PANE and 15° for PAND. Thermogravimetric and differential thermogravimetric analysis results revealed that the thermal stability of protocatechuic acid was markedly enhanced upon intercalation. The loading of protocatechuic acid in PANE and PAND was estimated to be about 24.5% and 27.5% (w/w), respectively. The in vitro release study of protocatechuic acid from PANE and PAND in phosphate-buffered saline at pH 7.4, 5.3, and 4.8 revealed that the nanocomposites had a sustained release property. After 72 hours incubation of PANE and PAND with MCF-7 human breast cancer and HeLa human cervical cancer cell lines, it was found that the nanocomposites had suppressed the growth of these cancer cells, with a half maximal inhibitory concentration of 35.6 μg/mL for PANE and 36.0 μg/mL for PAND for MCF-7 cells, and 19.8 μg/mL for PANE and 30.3 μg/mL for PAND for HeLa cells. No half maximal inhibitory concentration for either nanocomposite was found for 3T3 cells. PMID:23737666

  18. Spark Plasma Sintering of Aluminum-Magnesium-Matrix Composites with Boron Carbide and Tungsten Nano-powder Inclusions: Modeling and Experimentation

    NASA Astrophysics Data System (ADS)

    Dvilis, E. S.; Khasanov, O. L.; Gulbin, V. N.; Petyukevich, M. S.; Khasanov, A. O.; Olevsky, E. A.

    2016-03-01

    Spark-plasma sintering (SPS) is used to fabricate fully-dense metal-matrix (Al/Mg) composites containing hard ceramic (boron carbide) and refractory metal (tungsten) inclusions. The study objectives include the modeling (and its experimental verification) of the process of the consolidation of the composites consisted of aluminum-magnesium alloy AMg6 (65 wt.%), B4C powder (15 wt.%), and W nano-powder (20 wt.%), as well as the optimization of the composite content and of the SPS conditions to achieve higher density. Discrete element modeling of the composite particles packing based on the particle size distribution functions of real powders is utilized for the determination of the powder compositions rendering maximum mixture packing densities. Two models: a power-law creep model of the high temperature deformation of powder materials, and an empirical logarithmic pressure-temperature-relative density relationship are successfully applied for the description of the densification of the aluminum-magnesium metal matrix powder composite subjected to spark-plasma sintering. The elastoplastic properties of the sintered composite samples are assessed by nanoindentation.

  19. Energy-Saving Melting and Revert Reduction Technology (E-SMARRT): Lost Foam Thin Wall - Feasibility of Producing Lost Foam Castings in Aluminum and Magnesium Based Alloys

    SciTech Connect

    Fasoyinu, Yemi; Griffin, John A.

    2014-03-31

    With the increased emphasis on vehicle weight reduction, production of near-net shape components by lost foam casting will make significant inroad into the next-generation of engineering component designs. The lost foam casting process is a cost effective method for producing complex castings using an expandable polystyrene pattern and un-bonded sand. The use of un-bonded molding media in the lost foam process will impose less constraint on the solidifying casting, making hot tearing less prevalent. This is especially true in Al-Mg and Al-Cu alloy systems that are prone to hot tearing when poured in rigid molds partially due to their long freezing range. Some of the unique advantages of using the lost foam casting process are closer dimensional tolerance, higher casting yield, and the elimination of sand cores and binders. Most of the aluminum alloys poured using the lost foam process are based on the Al-Si system. Very limited research work has been performed with Al-Mg and Al-Cu type alloys. With the increased emphasis on vehicle weight reduction, and given the high-strength-to-weight-ratio of magnesium, significant weight savings can be achieved by casting thin-wall (≤ 3 mm) engineering components from both aluminum- and magnesium-base alloys.

  20. Magnesium for automotive applications

    SciTech Connect

    VanFleteren, R.

    1996-05-01

    Die cast magnesium parts are rapidly replacing steel and aluminum structural components in automotive applications, as design engineers seek to reduce assembly costs, raise fuel efficiency, and improve safety. Dozens of automotive components are now die cast from magnesium alloys, including seat stanchions, valve covers, steering wheels, and a variety of steering column components. Because of their excellent castability, complex magnesium die castings can sometimes consolidate several components and eliminate assembly steps. Highly ductile magnesium alloys such as AM60B (6% aluminum) and AM50A (5% aluminum) are important in helping to meet automotive industry crash-energy requirements for car seating and steering components. AZ91D (9% aluminum, 1% zinc) alloys are making removable rear seats in new minivans much easier to handle.

  1. Low-pH and aluminum resistance in arabidopsis correlates with high cytosolic magnesium content and increased magnesium uptake by plant roots.

    PubMed

    Bose, Jayakumar; Babourina, Olga; Shabala, Sergey; Rengel, Zed

    2013-07-01

    Low-pH stress and Al(3+) toxicity affect root growth in acid soils. It was hypothesized that the capacity of genotypes to maintain Mg(2+) uptake in acidic environments may contribute to low-pH and Al resistance, but explicit evidence is lacking. In this work, an Al-resistant alr104 mutant and two Al-sensitive mutants (als5 and als3) of Arabidopsis thaliana were compared with the wild type (Col-0) for Mg(2+) uptake and intracellular Mg(2+) concentration under low-pH and combined low-pH/Al stresses. Magnesium accumulation in roots was measured in long-term (7 d) experiments. The Mg(2+) fluxes were measured using ion-sensitive microelectrodes at the distal elongation and the mature root zones in short-term (0-60 min) experiments. Intracellular Mg(2+) concentrations were measured in intact root cells at the distal elongation zone using magnesium-specific fluorescent dye and fluorescent lifetime imaging (FLIM) analysis. Under low-pH stress, Arabidopsis mutants als5 and alr104 maintained a higher Mg concentration in roots, and had greater Mg(2+) influx than the wild type and the als3 mutant. Under combined low-pH/Al treatment, Al-resistant genotypes (wild type and alr104) maintained a higher Mg(2+) accumulation, and had a higher Mg(2+) influx and higher intracellular Mg(2+) concentration than Al-sensitive genotypes (als3 and als5). Overall, these results show that increased Mg(2+) uptake correlates with an enhanced capacity of Arabidopsis genotypes to cope with low-pH and combined low-pH/Al stresses. PMID:23620479

  2. Double-blind clinical, endoscopic and histological comparison of hydrotalcite/dimethicone suspension and magnesium hydroxide/aluminum hydroxide suspension in the treatment of symptomatic gastritis.

    PubMed

    Cobden, I; McMahon, M J; Dixon, M F; Axon, A T

    1981-01-01

    A double-blind, randomized trial was undertaken to compare the clinical, endoscopic and histological response to 6-weeks' treatment with hydrotalcite/dimethicone suspension or magnesium hydroxide/aluminum hydroxide suspension in 36 patients with symptomatic gastritis. Significantly more patients (P less than 0.05) showed symptomatic improvement in the antacid-treated group than in the hydrotalcite/dimethicone-treated group and more had a reduction in histological inflammatory scores (P less than 0.01), although there was little correlation between histology and symptoms. There was no evidence from this study that the bile acid binding and anti-foaming properties of hydrotalcite/dimethicone suspension were of any benefit in the treatment of patients with symptomatic gastritis. PMID:7267678

  3. Native defects as sources of optical transitions in MgAl2O4 spinel

    NASA Astrophysics Data System (ADS)

    Borges, P. D.; Cott, J.; Pinto, F. G.; Tronto, J.; Scolfaro, L.

    2016-07-01

    The outstanding physical and chemical properties of the magnesium aluminate (MgAl2O4) spinel makes it an important material for novel technological applications. Considering that a presence of native defects can promote important changes in those properties, in this work we present a study of the structural, electronic and thermodynamic properties of the MgAl2O4 spinel. The calculated formation energy for isolated defects, such as the vacancies of magnesium (V Mg), aluminum (V Al) and oxygen (V O), oxygen interstitial (Oi), magnesium and aluminum antisites (MgAl, AlMg), as well as some complex defects (V O + Oi, V O + AlMg, V O + MgAl, MgAl + AlMg) in the most stable charge states are shown. Through experimental data, we obtained that complex defects centers, such as V O , V O + Oi, V O + AlMg and VO + MgAl at different charge states are good candidates for the observed optical transitions at 4.75, 5.3, and 6.4 eV. Our findings were obtained from ab initio electronic structure calculations performed by using density functional theory. The Perdew–Burke–Ernzerhof generalized gradient approximation was used for the exchange-correlation potential. Furthermore, a modified Becke-Johnson exchange potential (GGA-mBJ) correction to the exchange potential were used to obtain a suitable value for the band gap energy, 7.40 eV, in accordance with the experimental one of 7.8 eV.

  4. Chromian spinels from Apollo 14 rocks.

    NASA Technical Reports Server (NTRS)

    Steele, I. M.

    1972-01-01

    Results of electron microprobe analysis of 13 pink, isotropic, high-relief grains from Apollo 14 elastic rock 14063,14 and a lithic fragment from the 1 to 2 mm fines, 14002,7, identifying them as spinel minerals dominated by the spinel component MgAl2O4 associated with a moderate content of chromite and hercynite. The spinel is thought to have crystallized from a magma high in aluminum and low in iron, with possible crystal separation, followed by incorporation in clastic rocks by impacts. Many bulk compositions of the elastic fragments fall near the field of primary spinel in the model system An-Fo-SiO2. Experimental syntheses of Apollo 14 rocks are needed to test the suggested primary origin.

  5. Effect of iron-intermetallics and porosity on tensile and impact properties of aluminum-silicon-copper and aluminum-silicon-magnesium cast alloys

    NASA Astrophysics Data System (ADS)

    Ma, Zheyuan

    Aluminum-silicon (Al-Si) alloys are an important class of materials that constitute the majority of aluminum cast parts produced, due to their superior properties and excellent casting characteristics. Within this family of alloys, Al-Si-Cu and Al-Si-Mg cast alloys are frequently employed in automotive applications. The commercially popular 319 and 356 alloys, representing these two alloy systems, were selected for study in the present work, with the aim of investigating the effect of iron intermetallics and porosity on the alloy performance. This was carried out through a study of the tensile and impact properties, these being two of the important mechanical properties used in design calculations. Iron, through the precipitation of second phase intermetallic constituents, in particular the platelike beta-Al5FeSi phase, is harmful to the alloy properties. Likewise, gas- or shrinkage porosity in castings is also detrimental to the mechanical properties. By determining the optimum alloying, melt processing and solidification parameters (viz., Fe content, Sr modification and cooling rate) required to minimize the harmful effects of porosity and iron intermetallics, and studying their role on the fracture behavior, the fracture mechanism in the alloys could be determined. Castings were prepared from both industrial and experimental 319.2, B319.2 and A356.2 alloy melts, containing Fe levels of 0.2--1.0 wt%. Sr-modified (˜200 ppm) melts were also prepared for each alloy Fe level. The end-chilled refractory mold used provided directional solidification and a range of cooling rates (or dendrite arm spacings, DAS) within the same casting. Tensile and impact test samples machined from specimen blanks sectioned from the castings at various heights above the chill end provided DASs of 23--85mum. All samples were T6-heat-treated before testing. Tests were carried out employing Instron Universal and Instrumented Charpy testing machines. Optical microscopy, image analysis, SEM

  6. Modeling the Break-up of Nano-particle Clusters in Aluminum- and Magnesium-Based Metal Matrix Nano-composites

    NASA Astrophysics Data System (ADS)

    Manoylov, Anton; Bojarevics, Valdis; Pericleous, Koulis

    2015-07-01

    Aluminum- and magnesium-based metal matrix nano-composites with ceramic nano-reinforcements promise low weight with high durability and superior strength, desirable properties in aerospace, automobile, and other applications. However, nano-particle agglomerations lead to adverse effects on final properties: large-size clusters no longer act as dislocation anchors, but instead become defects; the resulting particle distribution will be uneven, leading to inconsistent properties. To prevent agglomeration and to break-up clusters, ultrasonic processing is used via an immersed sonotrode, or alternatively via electromagnetic vibration. A study of the interaction forces holding the nano-particles together shows that the choice of adhesion model significantly affects estimates of break-up force and that simple Stokes drag due to stirring is insufficient to break-up the clusters. The complex interaction of flow and co-joint particles under a high frequency external field (ultrasonic, electromagnetic) is addressed in detail using a discrete-element method code to demonstrate the effect of these fields on de-agglomeration.

  7. Physicochemical properties of magnesium aluminum silicate (smectone) gels prepared using electrolytic-reduction ion water (2): Effects of various salts on the phase diagram.

    PubMed

    Okajima, Masahiro; Shimokawa, Ken-ichi; Ishii, Fumiyoshi

    2009-09-01

    We produced gels using electrolytic-reduction ion water and magnesium aluminum silicates (smectone), and evaluated in detail gel properties in the presence of various types of salt (NaCl, KCl, CaCl(2), MgCl(2), and AlCl(3)). Each salt was added to deionized-distilled water or electrolytic-reduction ion water, and phase diagrams for the smectone concentration (2.0-4.0%) were produced. The areas of the three phases of smectone (gel, sol, and separation) at each salt concentration were expressed as percentages of the total area. As a result, uni- and polyvalent cations (excluding Ca(2+) ions) affected the stability of gels produced using electrolytic-reduction ion water, and, particularly, univalent cations (Na(+), K(+)) markedly improved gel stability. Using electrolytic-reduction ion water as a dispersal medium, drug delivery systems (DDS) that can maintain the gelling state can be prepared. Thus, gel preparations with maintained functions or controlled-release transdermal drugs can be obtained. PMID:19477104

  8. Bulky metallocavitands with a chiral cavity constructed by aluminum and magnesium atrane-likes: enantioselective recognition and separation of racemic alcohols.

    PubMed

    Li, Yingguo; Yu, Dawei; Dai, Zhongran; Zhang, Jinjin; Shao, Yongliang; Tang, Ning; Wu, Jincai

    2015-03-28

    Seven new type metallocavitand complexes 1–7 were synthesized via the self-assembly of aluminum and magnesium atrane-likes. The recognition of R-2-butanol from racemic 2-butanol can be achieved in the chiral cavity of metallocavitand complex 5. The crystal structure of complex 5 showed that the enantioselectivity of the center cavity for the inclusion of two 2-butanol molecules is higher than that of the groups at the outer rim, which indicates that the size-limited cavity is more sensitive to the chirality of 2-butanol. Furthermore, desorption of R-2-butanol is successful through vacuumization which afforded complex 6 and gives R-2-butanol with an enantiomeric excess (ee) value of 53(±1)%. The reaction of enantiopure H3L2, MgnBu2, and racemic 1-phenylethanol afforded complex 7. The structure of complex 7 showed that the center cavity was occupied by three H2O molecules and one molecular R-1-phenylethanol suspended in the outer rim of the metallocavitand via a hydrogen bond, which indicated that 1-phenylethanol is too bulky for the size-limited cavity. Because a certain amount of racemic 1-phenylethanol is also co-crystallized in the unit cell, the final separated 1-phenylethanol has an ee value of 33(±1)%. The host–guest mechanism for the separation is clearly determined through X-ray crystal structural analysis. PMID:25710446

  9. Magnesium Gluconate

    MedlinePlus

    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 ...

  10. The crystallisation trends of spinels in tertiary basalts from Rhum and Muck and their petrogenetic significance. [chemical composition changes during crystal formation

    NASA Technical Reports Server (NTRS)

    Ridley, W. I.

    1977-01-01

    Spinels found in transitional olivine basalts from the Islands of Rhum and Muck in the British Tertiary Province are analyzed to determine their chemical variability and their relationship to silicate phases. Chemical zoning of the cores of spinels which spilled into the basaltic liquid may be due to a reaction between the spinel and the liquid resulting in more Fe- and Ti-rich spinels. In addition, a peritectic-type reaction seems to have occurred, causing the transformation of aluminum spinel to chrome spinel with precipitation of plagioclase. Changes in the basaltic liquid are reflected by these transformations in the spinel composition.

  11. A comparison of microstructure, texture and formability of direct chill cast versus continuous cast aluminum-magnesium alloys

    NASA Astrophysics Data System (ADS)

    Zhao, Yumin

    cold rolling and isothermal annealing was quantitatively analyzed by Johnson-Mehl-Avrami-Kolmogorov (JMAK) type equations, which allow the precise prediction of texture of cold rolled and annealed aluminum sheets. CC materials show good mechanical isotropy, while DC materials possess superior bendability and stretchability at O-temper condition.

  12. Luna 24 - Systematics in spinel mineral chemistry in the context of an intrusive petrogenetic grid

    NASA Technical Reports Server (NTRS)

    Haggerty, S. E.

    1978-01-01

    Spinels in the Luna 24 gabbroic fragments have a restricted bimodal distribution of aluminum chromite and ulvospinel, whereas those in the Luna 24 basalts form a continuous sequence which defines a compositional variation from Al-Mg-chromites to ulvospinels containing 1 wt% Al2O3. A comparison of these spinel mineral chemistries with basaltic spinels from other mare regions and with spinels from other lunar intrusive rocks suggest that the Luna 24 gabbroic spinels lie at the low pressure end of a P-T spinel grid, and that titanium enrichment trends on Mg-Al-Cr rich spinel cores are related to extrusion and formed at the terminal stages of magmatic crystallization.

  13. S-asteroids 387 Aquitania and 980 Anacostia - Possible fragments of the breakup of a spinel-bearing parent body with CO3/CV3 affinities

    NASA Technical Reports Server (NTRS)

    Burbine, Thomas H.; Gaffey, Michael J.; Bell, Jeffrey F.

    1992-01-01

    Asteroids 387 Aquitania and 980 Anacostia are anomalous members of the S-class. Their reflectance spectra exhibit a strong broad absorption feature longwards of 1.5 micron and no significant feature near 1 micron. Their spectra indicate the presence of spinel, an aluminum-magnesium oxide mineral commonly present in inclusions in CV3 and CO3 meteorites. Spinel probably makes up only a small percentage of the surface assemblages of these asteroids, but its spectral effect may be enhanced by its presence in fine-grained white inclusions in immature asteroid regoliths. It is speculated that Aquitania and Anacostia represent material formed in the same nebular zone as the CV3 and CO3 chondrites but either: (A) at an earlier time in the nebula when such inclusions might have been a relatively larger fraction of the nebular grain population; or (B) in local regions where nebular processes (e.g., settling to the midplane) had concentrated such inclusions. The close similarity of two orbital elements (a, i) suggests that Aquitania and Anacostia may be members of a partially dispersed asteroid family produced by the early disruption of a spinel-bearing parent body.

  14. Slow crack growth in spinel in water

    NASA Technical Reports Server (NTRS)

    Schwantes, S.; Elber, W.

    1983-01-01

    Magnesium aluminate spinel was tested in a water environment at room temperature to establish its slow crack-growth behavior. Ring specimens with artificial flaws on the outside surface were loaded hydraulically on the inside surface. The time to failure was measured. Various precracking techniques were evaluated and multiple precracks were used to minimize the scatter in the static fatigue tests. Statistical analysis techniques were developed to determine the strength and crack velocities for a single flaw. Slow crack-growth rupture was observed at stress intensities as low as 70 percent of K sub c. A strengthening effect was observed in specimens that had survived long-time static fatigue tests.

  15. Structure of spinel

    SciTech Connect

    Sickafus, K.E.; Wills, J.M.; Grimes, N.W.

    1999-12-01

    This paper reviews the crystal structure of compounds with the general formula AB{sub 2}X{sub 4}, which crystallize with the same atomic structure as the mineral spinel, MgAl{sub 2}O{sub 4}. Three degrees of freedom associated with the detailed atomic arrangements of spinels are considered here: (i) the lattice parameter, a; (ii) the anion parameter, u; and (iii) the cation inversion parameter, i. Oxide spinels are used as examples to explore the interrelationships between these parameters.

  16. Aluminum Hydroxide and Magnesium Hydroxide

    MedlinePlus

    ... Talk to your pharmacist or contact your local garbage/recycling department to learn about take-back programs in your community. See the FDA's Safe Disposal of Medicines website (http://goo.gl/c4Rm4p) for ...

  17. ALUMINUM IMPURITY DIFFUSION IN MAGNESIUM

    SciTech Connect

    Brennan, Sarah; Warren, Andrew; Coffey, Kevin; Kulkarni, Nagraj S; Todd, Peter J; Sohn, Yong Ho; Klimov, Mikhail

    2012-01-01

    The Al impurity diffusion in polycrystalline Mg (99.9%) via depth profiling with secondary ion mass spectrometry was studied in the temperature range of 673-573K, utilizing the thin film method and thin film solution to the diffusion equation. Multiple samples were utilized and multiple profiles were obtained to determine statistically confident coefficient with maximum standard deviation of 16%. Activation energy and pre-exponential factor of Al impurity diffusion in Mg was determined as 155 kJ/mole and 3.9 x 10-3 m2/sec.

  18. Magnesium basics

    PubMed Central

    Ketteler, Markus

    2012-01-01

    As a cofactor in numerous enzymatic reactions, magnesium fulfils various intracellular physiological functions. Thus, imbalance in magnesium status—primarily hypomagnesaemia as it is seen more often than hypermagnesaemia—might result in unwanted neuromuscular, cardiac or nervous disorders. Measuring total serum magnesium is a feasible and affordable way to monitor changes in magnesium status, although it does not necessarily reflect total body magnesium content. The following review focuses on the natural occurrence of magnesium and its physiological function. The absorption and excretion of magnesium as well as hypo- and hypermagnesaemia will be addressed. PMID:26069819

  19. Lightweight Heat Pipes Made from Magnesium

    NASA Technical Reports Server (NTRS)

    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.

  20. Magnesium Hydroxide

    MedlinePlus

    Magnesium hydroxide is used on a short-term basis to treat constipation.This medication is sometimes prescribed ... Magnesium hydroxide come as a tablet and liquid to take by mouth. It usually is taken as ...

  1. Magnesium Oxide

    MedlinePlus

    ... repeatedly. Magnesium oxide also is used as a dietary supplement when the amount of magnesium in the diet ... any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each ...

  2. Surface Analytical Methods Applied to Magnesium Corrosion.

    PubMed

    Dauphin-Ducharme, Philippe; Mauzeroll, Janine

    2015-08-01

    Understanding magnesium alloy corrosion is of primary concern, and scanning probe techniques are becoming key analytical characterization methods for that purpose. This Feature presents recent trends in this field as the progressive substitution of steel and aluminum car components by magnesium alloys to reduce the overall weight of vehicles is an irreversible trend. PMID:25826577

  3. Thermoelectric Properties of Selenides Spinels

    NASA Technical Reports Server (NTRS)

    Snyder, G.; Caillat, T.; Fleurial, J-P.

    2000-01-01

    Many compounds with the spinel structure type have been analyzed for their thermoelectric properties. Published data was used to augment experimental results presented here to select promising thermoelectric spinels.

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

    NASA Technical Reports Server (NTRS)

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

    1968-01-01

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

  5. Aluminum battery alloys

    DOEpatents

    Thompson, D.S.; Scott, D.H.

    1984-09-28

    Aluminum alloys suitable for use as anode structures in electrochemical cells are disclosed. These alloys include iron levels higher than previously felt possible, due to the presence of controlled amounts of manganese, with possible additions of magnesium and controlled amounts of gallium.

  6. Aluminum battery alloys

    DOEpatents

    Thompson, David S.; Scott, Darwin H.

    1985-01-01

    Aluminum alloys suitable for use as anode structures in electrochemical cs are disclosed. These alloys include iron levels higher than previously felt possible, due to the presence of controlled amounts of manganese, with possible additions of magnesium and controlled amounts of gallium.

  7. A study of the composition and microstructure of aluminum matrix composites reinforced with alumina fibers

    NASA Astrophysics Data System (ADS)

    Zolotova, D.; Serpova, V.; Prokofiev, M.; Rabinskiy, L.; Shavnev, A.

    2016-04-01

    This article presents the results of a study of the microstructure and the composition of aluminum-based metal matrix composites (MMC) reinforced with continuous alumina fibers. An Al-Mg-Cu alloy similar to that of AA 2024 was used. X-ray diffraction and X-ray fluorescence analyses were used for investigation of a probable volume fraction of a spinel phase in MMC. Scanning electron microscopy and an X-ray microanalysis were used to study a change of the elemental composition of the composites microstructure on the polished cross sections. The constant mass fractions of magnesium (0.65 wt. %) and copper (1.25 wt. %) were found in the interphase area within radius of 1 μm around fibers.

  8. Compositional variations in lunar spinels.

    NASA Technical Reports Server (NTRS)

    Haggerty, S. E.

    1971-01-01

    Electron probe data for spinels from Apollo 11, 12, and 14 are presented and analyzed. A modified Johnstone spinel prism showing the data distribution is given. Three projections of this prism are then presented which illustrate the variations of simple ratios that are present in the prism and permit three different perspectives of the data. The results are summarized as fO2 isobars on the spinel prism.

  9. Ultrasound Nondestructive Characterization of Transparent Spinel

    NASA Astrophysics Data System (ADS)

    Bottiglieri, S.; Portune, A. R.; Haber, R. A.

    2011-06-01

    Ceramic materials have attractive attributes for applications that experience high stresses or strain rates. Compared to metal-based systems, ceramics offer a lower areal density which reduces weight, but do not depreciate the integrity of other properties. The ability to tailor the microstructure of ceramics used in armor systems is a common way to increase specific mechanical properties or obtain certain material characteristics. Properties such as elastic modulus, hardness, and density are those that are typically desired to be enhanced. By modifying the microstructure one can obtain a ceramic with these enhanced properties as well as high optical transmission across a wide range of the electromagnetic spectrum. The testing of these properties and ballistic performance is usually destructive, expensive, and time consuming. Common assessments using ultrasonic NDE usually include spatially locating large flaws, sonic velocity measurements, and elastic property measurements. The use of acoustic spectroscopy to go beyond typical ultrasonic NDE in structural ceramics and allow for the use of a microstructural characterization tool is investigated in this paper. Ultrasound absorption by lithium fluoride precipitates in aluminate spinel (MgAl2O4) present as defined spectral peaks. Average heterogeneity size determination in magnesium aluminate spinel MgAl2O4 by method of acoustic spectroscopy is shown.

  10. Ultrasound nondestructive characterization of transparent spinel

    SciTech Connect

    Bottiglieri, S.; Portune, A. R.; Haber, R. A.

    2011-06-23

    Ceramic materials have attractive attributes for applications that experience high stresses or strain rates. Compared to metal-based systems, ceramics offer a lower areal density which reduces weight, but do not depreciate the integrity of other properties. The ability to tailor the microstructure of ceramics used in armor systems is a common way to increase specific mechanical properties or obtain certain material characteristics. Properties such as elastic modulus, hardness, and density are those that are typically desired to be enhanced. By modifying the microstructure one can obtain a ceramic with these enhanced properties as well as high optical transmission across a wide range of the electromagnetic spectrum. The testing of these properties and ballistic performance is usually destructive, expensive, and time consuming. Common assessments using ultrasonic NDE usually include spatially locating large flaws, sonic velocity measurements, and elastic property measurements. The use of acoustic spectroscopy to go beyond typical ultrasonic NDE in structural ceramics and allow for the use of a microstructural characterization tool is investigated in this paper. Ultrasound absorption by lithium fluoride precipitates in aluminate spinel (MgAl{sub 2}O{sub 4}) present as defined spectral peaks. Average heterogeneity size determination in magnesium aluminate spinel MgAl{sub 2}O{sub 4} by method of acoustic spectroscopy is shown.

  11. Polishing-assisted galvanic corrosion in the dissimilar friction stir welded joint of AZ31 magnesium alloy to 2024 aluminum alloy

    SciTech Connect

    Liu, C.; Chen, D.L. Bhole, S.; Cao, X.; Jahazi, M.

    2009-05-15

    Galvanic corrosion of a dissimilar friction stir welded 2024-T3 Al/AZ31B-H24 Mg joint prepared using a water-based and a non-water-based polishing solution was characterized. Microstructure and the distribution of chemical elements were analyzed using optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. The stir zone polished using water-based solution was observed to be much more susceptible to galvanic corrosion attack than that obtained using non-water-based polishing solution. The location of corrosion attack was observed in the narrow regions of AZ31 Mg alloy adjacent to Al2024 regions in the stir zone. The occurrence of galvanic corrosion was due to the formation of Mg/Al galvanic couples with a small ratio of anode-to-cathode surface area. The corrosion product was primarily the porous magnesium hydroxide with characteristic microcracks and exhibited a low microhardness value.

  12. [The corrosion resistance of aluminum and aluminum-based alloys studied in artificial model media].

    PubMed

    Zhakhangirov, A Zh; Doĭnikov, A I; Aboev, V G; Iankovskaia, T A; Karamnova, V S; Sharipov, S M

    1991-01-01

    Samples of aluminum and its alloys, designed for orthodontic employment, were exposed to 4 media simulating the properties of biologic media. The corrosion resistance of the tested alloys was assessed from the degree of aluminum migration to simulation media solutions, which was measured by the neutron activation technique. Aluminum alloy with magnesium and titanium has shown the best corrosion resistance. PMID:1799002

  13. Thermodynamic equilibrium analyses of the uptake of aromatic compounds from an aqueous solution by magnesium-aluminum (Mg-Al) layered double hydroxide intercalated with 1-naphthol-3,8-disulfonate

    NASA Astrophysics Data System (ADS)

    Kameda, Tomohito; Uchiyama, Tomomi; Yoshioka, Toshiaki

    2013-06-01

    Magnesium-aluminum layered double hydroxide (Mg-Al LDH) intercalated with 1-naphthol-3,8-disulfonate (1-N-3,8-DS2-) was prepared by coprecipitation. Thermodynamically, the prepared Mg-Al LDH showed greater preferential uptake of 1,3-dinitrobenzene (DNB) than of 1,2-dimethoxybenzene (DMB). This preferential uptake of aromatic compounds, which is adequately expressed by the Dubinin-Radushkevich adsorption isotherm, was attributed to the π-π stacking interactions between the benzene ring of the aromatic compounds and the naphthalene core of 1-N-3,8-DS2- intercalated in the interlayer spaces of Mg-Al LDH. Negative values of ΔG for DNB and DMB indicate that the adsorption process is spontaneous at all temperatures. The value of ΔS for DNB was much lower than that for DMB. This implies that DNB was far more strongly adsorbed to 1-N-3,8-DS2- than was DMB, resulting in a lower degree of freedom for and higher uptake of DNB than those in the case DMB. The absolute values of |ΔH| for DNB and DMB were less than 20 kJ mol-1, indicating that the uptake of DNB or DMB by 1-N-3,8-DS·Mg-Al LDH can be considered a physical adsorption process caused by π-π stacking interactions.

  14. Magnesium compounds

    USGS Publications Warehouse

    Kramer, D.A.

    2010-01-01

    Seawater and natural brines accounted for about 40 percent of U.S. magnesium compounds production in 2009. Dead-burned magnesia was produced by Martin Marietta Magnesia Specialties from well brines in Michigan. Caustic-calcined magnesia was recovered from seawater by Premier Chemicals in Florida, from well brines in Michigan by Martin Marietta and from magnesite in Nevada by Premier Chemicals. Intrepid Potash-Wendover, and Great Salt Lake Minerals Corp. recovered magnesium chloride brines from the Great Salt Lake in Utah. Magnesium hydroxide was produced from seawater by SPI Pharma in Delaware and Premier Chemicals in Florida, and by Martin Marietta from its operation mentioned above.

  15. Magnesium compounds

    USGS Publications Warehouse

    Kramer, D.A.

    2011-01-01

    Seawater and natural brines accounted for about 54 percent of U.S. magnesium compounds production in 2010. Dead-burned magnesia was produced by Martin Marietta Magnesia Specialties from well brines in Michigan. Caustic-calcined magnesia was recovered from seawater by Premier Magnesia in Florida, from well brines in Michigan by Martin Marietta and from magnesite in Nevada by Premier Magnesia. Intrepid Potash-Wendover and Great Salt Lake Minerals Corp. recovered magnesium chloride brines from the Great Salt Lake in Utah. Magnesium hydroxide was produced from seawater by SPI Pharma in Delaware and Premier Magnesia in Florida, and by Martin Marietta from its operation mentioned above.

  16. Magnesium Test

    MedlinePlus

    ... Mg; Mag Formal name: Magnesium Related tests: Calcium , Potassium , Phosphorus , PTH , Vitamin D At a Glance Test ... can, over time, cause persistently low calcium and potassium levels, it may be checked to help diagnose ...

  17. Studies of hydrogen embrittlement and stress-corrosion cracking in an aluminum-zinc-magnesium alloy. [5. 6 Zn - 2. 6 Mg

    SciTech Connect

    Ciaraldi, S.W.; Nelson, J.L.; Yeske, R.A.; Pugh, E.N.

    1980-01-01

    Tensile tests have been carried out on a high-purity A1-5.6 Zn-2.6 Mg alloy hydrogenated by exposure to moist air. Results indicate that internal hydrogen embrittlement occurs by the formation and rupture of a stress-induced hydride at the grain boundaries. The hydride, identified by electron diffraction as A1H/sub 3/, is shown to be unstable in laboratory air, reverting to aluminum. The hydride phase was not detected in specimens failed by SCC, despite evidence that hydrogen is transported ahead of advancing stress-corrosion cracks, and this leads to the possibility that a basically different mechanism may be responsible for SCC in this alloy.

  18. A Processing Map for Hot Deformation of an Ultrafine-Grained Aluminum-Magnesium-Silicon Alloy Prepared by Mechanical Milling and Hot Extrusion

    NASA Astrophysics Data System (ADS)

    Asgharzadeh, Hamed; Rahbar Niazi, Masoud; Simchi, Abdolreza

    2015-12-01

    Uniaxial compression test at different temperatures [573 K to 723 K (300 °C to 450 °C)] and strain rates (0.01 to 1 s-1) was employed to study the hot deformation behavior of an ultrafine-grained (UFG) Al6063 alloy prepared by the powder metallurgy route. The UFG alloy with an average grain size of ~0.3 µm was prepared by mechanical milling of a gas-atomized aluminum alloy powder for 20 hours followed by hot powder extrusion at 723 K (450 °C). To elaborate the effect of grain size, the aluminum alloy powder was extruded without mechanical milling to attain a coarse-grained (CG) structure with an average grain size of about 2.2 µm. By employing the dynamic materials model, processing maps for the hot deformation of the UFG and CG Al alloy were constructed. For investigation of microstructural evolutions and deformation instability occurring upon hot working, optical microscopy, scanning electron microscopy coupled with electron backscattered diffraction and transmission electron microscopy were utilized. It is shown that the grain refinement increases the deformation flow stress while reducing the strain hardening and power dissipation efficiency during the deformation process at the elevated temperatures. Restoration mechanisms, including dynamic recovery and recrystallization are demonstrated to control microstructural evolutions and thus the deformation behavior. Coarsening of the grain structure in the UFG alloy is illustrated, particularly when the deformation is performed at high temperatures and low strain rates. The manifestations of instability are observed in the form of cracking and void formation.

  19. Production of magnesium metal

    DOEpatents

    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.

  20. Photoinduced radical processes on the spinel (MgAl2O4) surface involving methane, ammonia, and methane/ammonia.

    PubMed

    Emeline, A V; Abramkin, D A; Zonov, I S; Sheremetyeva, N V; Rudakova, A V; Ryabchuk, V K; Serpone, N

    2012-05-15

    The present study explored photoinduced radical processes caused by interaction of CH(4) and NH(3) with a photoexcited surface of a complex metal oxide: magnesium-aluminum spinel (MgAl(2)O(4); MAS). UV irradiation of MAS in vacuo yielded V-type color centers as evidenced by the 360 nm band in difference diffuse reflectance spectra. Interaction of these H-bearing molecules with photogenerated surface-active hole states (O(S)(-)•) yielded radical species which on recombination produced more complex molecules (including heteroatomic species) relative to the initial molecules. For the MAS/CH(4) system, photoinduced dissociative adsorption of CH(4) on surface-active hole centers produced •CH(3) radicals that recombined to yield CH(3)CH(3). For MAS/NH(3), a similar dissociative adsorption process led to formation of •NH(2) radicals with formation of NH(2)NH(2) as an intermediate product; continued UV irradiation ultimately yielded N(2). For the mixed MAS/CH(4)/NH(3) system, however, interaction of adsorbed NH(3) and CH(4) on the UV-activated surface of MAS yielded •NH(2) and •CH(3) radicals, respectively, which produced CH(3)-NH(2) followed by loss of the remaining hydrogens to form a surface-adsorbed cyanide, CN(S), species. Recombination of photochemically produced radicals released sufficient energy to re-excite the solid spinel, generating new surface-active sites and a flash luminescence (emission decay time at 520 nm, τ ~ 6 s for the MAS/NH(3) case) referred to as the PhICL effect. PMID:22497296

  1. Integrated thick-film nanostructures based on spinel ceramics

    PubMed Central

    2014-01-01

    Integrated temperature-humidity-sensitive thick-film structures based on spinel-type semiconducting ceramics of different chemical compositions and magnesium aluminate ceramics were prepared and studied. It is shown that temperature-sensitive thick-film structures possess good electrophysical characteristics in the region from 298 to 358 K. The change of electrical resistance in integrated thick-film structures is 1 order, but these elements are stable in time and can be successfully used for sensor applications. PMID:24670141

  2. Integrated thick-film nanostructures based on spinel ceramics.

    PubMed

    Klym, Halyna; Hadzaman, Ivan; Shpotyuk, Oleh; Brunner, Michael

    2014-01-01

    Integrated temperature-humidity-sensitive thick-film structures based on spinel-type semiconducting ceramics of different chemical compositions and magnesium aluminate ceramics were prepared and studied. It is shown that temperature-sensitive thick-film structures possess good electrophysical characteristics in the region from 298 to 358 K. The change of electrical resistance in integrated thick-film structures is 1 order, but these elements are stable in time and can be successfully used for sensor applications. PMID:24670141

  3. Phosphorylation and Interaction with the 14-3-3 Protein of the Plasma Membrane H+-ATPase are Involved in the Regulation of Magnesium-Mediated Increases in Aluminum-Induced Citrate Exudation in Broad Bean (Vicia faba. L).

    PubMed

    Chen, Qi; Kan, Qi; Wang, Ping; Yu, Wenqian; Yu, Yuzhen; Zhao, Yan; Yu, Yongxiong; Li, Kunzhi; Chen, Limei

    2015-06-01

    Several studies have shown that external application of micromolar magnesium (Mg) can increase the resistance of legumes to aluminum (Al) stress by enhancing Al-induced citrate exudation. However, the exact mechanism underlying this regulation remains unknown. In this study, the physiological and molecular mechanisms by which Mg enhances Al-induced citrate exudation to alleviate Al toxicity were investigated in broad bean. Micromolar concentrations of Mg that alleviated Al toxicity paralleled the stimulation of Al-induced citrate exudation and increased the activity of the plasma membrane (PM) H(+)-ATPase. Northern blot analysis shows that a putative MATE-like gene (multidrug and toxic compound extrusion) was induced after treatment with Al for 4, 8 and 12 h, whereas the mRNA abundance of the MATE-like gene showed no significant difference between Al plus Mg and Al-only treatments during the entire treatment period. Real-time reverse transcription-PCR (RT-PCR) and Western blot analyses suggest that the transcription and translation of the PM H(+)-ATPase were induced by Al but not by Mg. In contrast, immunoprecipitation suggests that Mg enhanced the phosphorylation levels of VHA2 and its interaction with the vf14-3-3b protein under Al stress. Taken together, our results suggest that micromolar concentrations of Mg can alleviate the Al rhizotoxicity by increasing PM H(+)-ATPase activity and Al-induced citrate exudation in YD roots. This enhancement is likely to be attributable to Al-induced increases in the expression of the MATE-like gene and vha2 and Mg-induced changes in the phosphorylation levels of VHA2, thus changing its interaction with the vf14-3-3b protein. PMID:25745032

  4. Magnesium uptake of Arabidopsis transporters, AtMRS2-10 and AtMRS2-11, expressed in Escherichia coli mutants: Complementation and growth inhibition by aluminum.

    PubMed

    Ishijima, Sumio; Uda, Misaki; Hirata, Tomohiro; Shibata, Makiko; Kitagawa, Nozomi; Sagami, Ikuko

    2015-06-01

    Magnesium (Mg2+) plays a critical role in many physiological processes. Mg2+ transport systems in Salmonella have been well documented, but those in Escherichia coli have not been fully elucidated. We examined the effects of corA, mgtA, yhiD and corC gene deletion on Mg2+ transport in E. coli. We obtained every combination of double, triple and quadruple mutants. The corA and mgtA double mutant required addition of 10 mM Mg2+ to Luria-Bertani (LB) medium for growth, and the corA, mgtA and yhiD triple mutant TM2 required a higher Mg2+ concentration. The Mg2+ requirement of the quadruple mutant was similar to that of TM2. The results demonstrated that either CorA or MgtA is necessary for normal E. coli growth in LB medium and that YhiD plays a role in Mg2+ transport under high Mg2+ growth conditions in E. coli. The Arabidopsis Mg2+ transporters, AtMRS2-10 and AtMRS2-11, were heterologously expressed in TM2 cells. TM2 cells expressing AtMRS2-10 and AtMRS2-11 could grow in LB medium that had been supplemented with 1 mM Mg2+ and without Mg2+ supplementation, respectively, and cell growth was inhibited by 2 mM AlCl3. The results indicated that the growth of TM2 expressing AtMRS2-10 and AtMRS2-11 reflected these AtMRS2 function for Mg2+ and aluminum. The E. coli TM2 cells are useful for functional analysis of Arabidopsis MRS2 proteins. PMID:25772503

  5. Elevated temperature aluminum alloys

    NASA Technical Reports Server (NTRS)

    Meschter, Peter (Inventor); Lederich, Richard J. (Inventor); O'Neal, James E. (Inventor)

    1989-01-01

    Three aluminum-lithium alloys are provided for high performance aircraft structures and engines. All three alloys contain 3 wt % copper, 2 wt % lithium, 1 wt % magnesium, and 0.2 wt % zirconium. Alloy 1 has no further alloying elements. Alloy 2 has the addition of 1 wt % iron and 1 wt % nickel. Alloy 3 has the addition of 1.6 wt % chromium to the shared alloy composition of the three alloys. The balance of the three alloys, except for incidentql impurities, is aluminum. These alloys have low densities and improved strengths at temperatures up to 260.degree. C. for long periods of time.

  6. Production of magnesium metal

    DOEpatents

    Blencoe, James G.; Anovitz, Lawrence M.; Palmer, Donald A.; Beard, James S.

    2012-04-10

    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 also relates to the magnesium metal produced by the processes described herein.

  7. Magnesium compounds

    USGS Publications Warehouse

    Kramer, D.A.

    2012-01-01

    Seawater and natural brines accounted for about 57 percent of magnesium compounds produced in the United States in 2011. Dead-burned magnesia was produced by Martin Marietta Magnesia Specialties LLC from well brines in Michigan. Caustic-calcined magnesia was recovered from seawater by Premier Magnesia LLC in Florida, from well brines in Michigan by Martin Marietta and from magnesite in Nevada by Premier Magnesia. Intrepid Potash Wendover LLC and Great Salt Lake Minerals Corp. recovered magnesium chloride brines from the Great Salt Lake in Utah. Magnesium hydroxide was produced from seawater by SPI Pharma Inc. in Delaware and Premier Magnesia in Florida, and by Martin Marietta from its brine operation in Michigan.

  8. Laser sintering of magnesia with nanoparticles of iron oxide and aluminum oxide

    NASA Astrophysics Data System (ADS)

    García, L. V.; Mendivil, M. I.; Roy, T. K. Das; Castillo, G. A.; Shaji, S.

    2015-05-01

    Nanoparticles of iron oxide (Fe2O3, 20-40 nm) and aluminum oxide (Al2O3, 50 nm) were mixed in different concentrations (3, 5 and 7 wt%) in a magnesium oxide (MgO) matrix. The mixture pellet was irradiated with 532 nm output from a Q-switched Nd:YAG laser using different laser fluence and translation speed for sintering. The refractory samples obtained were analyzed using X-ray diffraction technique, scanning electron microscopy and X-ray photoelectron spectroscopy. The results showed that the samples irradiated at translation speed of 110 μm/s and energy fluence of 1.7 J/cm2 with a concentration of 5 and 7 wt% of Fe2O3 presented the MgFe2O4 spinel-type phase. With the addition of Al2O3 nanoparticles, at a translation speed of 110 μm/s and energy fluence of 1.7 J/cm2, there were the formations of MgAl2O4 spinel phase. The changes in morphologies and microstructure due to laser irradiation were analyzed.

  9. Magnesium compounds

    USGS Publications Warehouse

    Kramer, D.A.

    2002-01-01

    Seawater and natural brines accounted for about 60% of US magnesium compounds production in 2001. Dead-burned and caustic-calcined magnesias were recovered from seawater in Florida by Premier Chemicals. They were also recovered from Michigan well brines by Dow Chemical, Martin Marietta Magnesia Specialties and Rohm & Haas. And Premier Chemicals recovered dead-burned and caustic-calcined magnesias from magnesite in Nevada. Reilly Industries and Great Salt Lake Minerals recovered magnesium chloride brines from the Great Salt Lake in Utah.

  10. Magnetostructural coupling in spinel oxides

    NASA Astrophysics Data System (ADS)

    Kemei, Moureen

    2015-03-01

    Spinels oxides are of great interest functionally as multiferroic, battery, and magnetic materials as well as fundamentally because they exhibit novel spin, structural, and orbital ground states. Competing interactions are at the heart of novel functional behavior in spinels. Here, we explore the intricate landscape of spin, lattice, and orbital interactions in magnetic spinels by employing variable-temperature high-resolution synchrotron x-ray powder diffraction, total neutron scattering, magnetic susceptibility, dielectric, and heat capacity measurements. We show that the onset of long-range magnetic interactions often gives rise to lattice distortions. Our work illustrates that the spinels NiCr2O4, CuCr2O4,andMn3O4, which are tetragonal at room temperature due to Jahn-Teller ordering, undergo further spin-driven structural distortions at the onset of long-range ferrimagnetic order. We have also studied the complete structural description of the ground states of several spinels including the geometrically frustrated spinels ZnCr2O4andMgCr2O4. The detailed spin-lattice studies of spinel oxides presented here illustrate the prevalence of structural phase coexistence when magnetostructural changes occur below 50 K. The new understanding of structural ground states in spinel oxides will guide the design of structure-property relationships in these materials. Broadly, this work highlights the importance of variable-temperature high-resolution synchrotron x-ray diffraction in understanding phase transitions in functional materials. Schlumberger Foundation Faculty for the Future fellowship, MRL Facilities funded by the NSF under Award No. DMR 1121053, and the Advanced Photon Source supported by the DOE, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.

  11. Magnesium compounds

    USGS Publications Warehouse

    Kramer, D.A.

    2004-01-01

    Dead-burned and caustic-calcined magnesias were recovered from seawater by Premier Chemicals in Florida; from well brines in Michigan by Dow Chemical, Martin Marietta Magnesia Specialties, and Rohm & Haas; and from magnesite in Nevada by Premier Chemicals. Reilly Industries and Great Salt Lake Minerals recovered magnesium chloride brines from the Great Salt Lake in Utah.

  12. Magnesium compounds

    USGS Publications Warehouse

    Kramer, D.A.

    2007-01-01

    Seawater and natural brines accounted for about 52 percent of U.S. magnesium compounds production in 2006. Dead-burned magnesia was produced by Martin Marietta Magnesia Specialties from well brines in Michigan. Caustic-calcined magnesia was recovered from sea-water by Premier Chemicals in Florida; from well brines in Michigan by Martin Marietta and Rohm and Haas; and from magnesite in Nevada by Premier Chemicals. Intrepid Potash-Wendover and Great Salt Lake Minerals recovered magnesium chloride brines from the Great Salt Lake in Utah. Magnesium hydroxide was produced from brucite by Applied Chemical Magnesias in Texas, from seawater by SPI Pharma in Delaware and Premier Chemicals in Florida, and by Martin Marietta and Rohm and Haas from their operations mentioned above. About 59 percent of the magnesium compounds consumed in the United States was used for refractories that are used mainly to line steelmaking furnaces. The remaining 41 percent was consumed in agricultural, chemical, construction, environmental and industrial applications.

  13. Magnesium compounds

    USGS Publications Warehouse

    Kramer, D.A.

    2001-01-01

    Seawater and natural brines accounted for about 63% of US magnesium compounds production during 2000. Premier Services in Florida, Dow Chemical in Michigan, Martin Marietta Magnesia Specialties, and Rohm & Haas recovered dead-burned and caustic-calcined magnesias from seawater. And Premier Services' recoveries, in Nevada, were from magnasite.

  14. Assessment of the magnesium primary production technology. Final report

    SciTech Connect

    Flemings, M.C.; Kenney, G.B.; Sadoway, D.R.; Clark, J.P.; Szekely, J.

    1981-02-01

    At current production levels, direct energy savings achievable in primary magnesium production are 1.2 milliquads of energy per annum. Were magnesium to penetrate the automotive market to an average level of 50 pounds per vehicle, the resultant energy savings at the production stage would be somewhat larger, but the resulting savings in gasoline would conserve an estimated 325 milliquads of energy per year. The principal barrier to more widespread use of magnesium in the immediate future is its price. A price reduction of magnesium of 10% would lead to widespread conversion of aluminum die and permanent mold castings to magnesium. This report addresses the technology of electrolytic and thermic magnesium production and the economics of expanded magnesium production and use.

  15. First principles pseudopotential calculations on aluminum and aluminum alloys

    SciTech Connect

    Davenport, J.W.; Chetty, N.; Marr, R.B.; Narasimhan, S.; Pasciak, J.E.; Peierls, R.F.; Weinert, M.

    1993-12-31

    Recent advances in computational techniques have led to the possibility of performing first principles calculations of the energetics of alloy formation on systems involving several hundred atoms. This includes impurity concentrations in the 1% range as well as realistic models of disordered materials (including liquids), vacancies, and grain boundaries. The new techniques involve the use of soft, fully nonlocal pseudopotentials, iterative diagonalization, and parallel computing algorithms. This approach has been pioneered by Car and Parrinello. Here the authors give a review of recent results using parallel and serial algorithms on metallic systems including liquid aluminum and liquid sodium, and also new results on vacancies in aluminum and on aluminum-magnesium alloys.

  16. Electrodeposition of aluminium, aluminium/magnesium alloys, and magnesium from organometallic electrolytes

    SciTech Connect

    Mayer, A.

    1988-01-01

    The electrodeposition of aluminum, magnesium, and the combination of these metals from nonaqueous media is discussed. Plating baths for depositing Al/Mg alloys or for plating essentially pure Mg were developed. These solutions contain alkali meal fluoride or quaternary ammonium halide/aluminium alkyl complexes and dialkyl magnesium dissolved in aromatic hydrocarbons. Alloy deposits over the whole composition range can be plated from these solutions by varying the relative quantities of the aluminium and magnesium alkyls and by changing the bath-operating parameters. 18 refs., 4 figs.

  17. Orbital Superstructures in Spinels

    NASA Astrophysics Data System (ADS)

    Khomskii, Daniel

    2006-03-01

    Orbital degrees of freedom often lead to specific types of orbital and spin ordering. Complicated and interesting superstructures are observed in B-sublattice of spinels. This is connected with the geometric frustration of this lattice and with the interconnection of edge-sharing MO6 octahedra, which is especially important for transition metals with partially-filled t2g levels. In some such systems (MgTi2O4, CuIr2S4, AlV2O4) there appears strange superstructures with the formation of spin gap states. In other cases (ZnV2O4) structural transitions, apparently connected with orbital ordering, are followed by long-range magnetic ordering. Last but not least, the famous Verwey transition in magnetite Fe3O4 leads to a very complicated structural pattern, accompanied by the appearance of ferroelectricity. In this talk I will discuss all these examples, paying main attention to an interplay of charge, spin and orbital degrees of freedom. In particular, for MgTi2O4, and CuIr2S4 we proposed the picture of orbitally-driven Peierls state [1]. Similar phenomenon can also explain situation in ZnV2O4 [2], although the corresponding superstructure has not yet been observed experimentally. Finally, I propose the model of charge and orbital ordering in magnetite [3], which uses the idea of an interplay of site- and bond-centered ordering [4] and which seems to explain both the structural data and the presence of ferroelectricity in Fe3O4 below Verwey transition. [1] D.I.Khomskii and T.Mizokawa, Phys.Rev.Lett. 94, 156402 (2005); [2] Hua Wu, T.Mizokawa and D.I.Khomskii, unpublished; [3] D.I.Khomskii, unpublished; [4] D.V.Efremov, J.van den Brink and D.I.Khomskii, Nature Mater. 3, 853 (2004)

  18. Magnesium compounds

    USGS Publications Warehouse

    Kramer, D.A.

    2003-01-01

    Seawater and natural brines accounted for about 60 percent of U.S. magnesium compounds production during 2002. Dead-burned and caustic-calcined magnesias were recovered from seawater by Premier Chemicals in Florida. They were also recovered from well brines in Michigan by Dow Chemical, Martin Marietta Magnesia Specialties and Rohm & Haas. And they were recovered from magnesite in Nevada by Premier Chemicals.

  19. Magnesium compounds

    USGS Publications Warehouse

    Kramer, D.A.

    2006-01-01

    In 2005, seawater and natural brines accounted for 51% of US magnesium compounds production. World magnesia production was estimated to be 14.5 Mt. Most of the production came from China, North Korea, Russia and Turkey. Although no specific production figures are available, Japan and the United States are estimated to account for almost one-half of the world's capacity from seawater and brines.

  20. Dissolution and Separation of Aluminum and Aluminosilicates

    DOE PAGESBeta

    McFarlane, Joanna; Benker, Dennis; DePaoli, David W.; Felker, Leslie Kevin; Mattus, Catherine H.

    2015-12-19

    The selection of an aluminum alloy for target irradiation affects post-irradiation target dissolution and separations. Recent tests with aluminum alloy 6061 yielded greater than expected precipitation in the dissolver, forming up to 10 wt.% solids of aluminum hydroxides and aluminosilicates. Aluminosilicate dissolution presents challenges in a number of different areas, metals extraction from minerals, flyash treatment, and separations from aluminum alloys. We present experimental work that attempts to maximize dissolution of aluminum metal, along with silicon, magnesium, and copper impurities, through control of temperature, the rate of reagent addition, and incubation time. Aluminum phase transformations have been identified as amore » function of time and temperature, using X-ray diffraction. Solutions have been analyzed using wet chemical methods and X-ray fluorescence. Our data have been compared with published calculations of aluminum phase diagrams. Approaches are given to enhance the dissolution of aluminum and aluminosilicate phases in caustic solution.« less

  1. Dissolution and Separation of Aluminum and Aluminosilicates

    SciTech Connect

    McFarlane, Joanna; Benker, Dennis; DePaoli, David W.; Felker, Leslie Kevin; Mattus, Catherine H.

    2015-12-19

    The selection of an aluminum alloy for target irradiation affects post-irradiation target dissolution and separations. Recent tests with aluminum alloy 6061 yielded greater than expected precipitation in the dissolver, forming up to 10 wt.% solids of aluminum hydroxides and aluminosilicates. Aluminosilicate dissolution presents challenges in a number of different areas, metals extraction from minerals, flyash treatment, and separations from aluminum alloys. We present experimental work that attempts to maximize dissolution of aluminum metal, along with silicon, magnesium, and copper impurities, through control of temperature, the rate of reagent addition, and incubation time. Aluminum phase transformations have been identified as a function of time and temperature, using X-ray diffraction. Solutions have been analyzed using wet chemical methods and X-ray fluorescence. Our data have been compared with published calculations of aluminum phase diagrams. Approaches are given to enhance the dissolution of aluminum and aluminosilicate phases in caustic solution.

  2. Magnesium in diet

    MedlinePlus

    Diet - magnesium ... Magnesium is needed for more than 300 biochemical reactions in the body. It helps to maintain normal ... There is ongoing research into the role of magnesium in preventing and managing disorders such as high ...

  3. Low magnesium level

    MedlinePlus

    Low magnesium level is a condition in which the amount of magnesium in the blood is lower than normal. The medical ... that convert or use energy ( metabolism ). When the level of magnesium in the body drops below normal, ...

  4. Selective Adsorption of Sodium Aluminum Fluoride Salts from Molten Aluminum

    SciTech Connect

    Leonard S. Aubrey; Christine A. Boyle; Eddie M. Williams; David H. DeYoung; Dawid D. Smith; Feng Chi

    2007-08-16

    Aluminum is produced in electrolytic reduction cells where alumina feedstock is dissolved in molten cryolite (sodium aluminum fluoride) along with aluminum and calcium fluorides. The dissolved alumina is then reduced by electrolysis and the molten aluminum separates to the bottom of the cell. The reduction cell is periodically tapped to remove the molten aluminum. During the tapping process, some of the molten electrolyte (commonly referred as “bath” in the aluminum industry) is carried over with the molten aluminum and into the transfer crucible. The carryover of molten bath into the holding furnace can create significant operational problems in aluminum cast houses. Bath carryover can result in several problems. The most troublesome problem is sodium and calcium pickup in magnesium-bearing alloys. Magnesium alloying additions can result in Mg-Na and Mg-Ca exchange reactions with the molten bath, which results in the undesirable pickup of elemental sodium and calcium. This final report presents the findings of a project to evaluate removal of molten bath using a new and novel micro-porous filter media. The theory of selective adsorption or removal is based on interfacial surface energy differences of molten aluminum and bath on the micro-porous filter structure. This report describes the theory of the selective adsorption-filtration process, the development of suitable micro-porous filter media, and the operational results obtained with a micro-porous bed filtration system. The micro-porous filter media was found to very effectively remove molten sodium aluminum fluoride bath by the selective adsorption-filtration mechanism.

  5. Life-Cycle Assessment of the Recycling of Magnesium Vehicle Components

    NASA Astrophysics Data System (ADS)

    Ehrenberger, Simone; Friedrich, Horst E.

    2013-10-01

    Life-cycle assessment is basically the assessment of a product from the cradle to the grave. Ideally, a product is recycled after its useful life is complete and the end-of-life of the first life cycle leads to the beginning of a new product system. For the end-of-life of magnesium vehicle parts, there are various possible paths to a second life cycle. When magnesium parts are dismantled or magnesium is separated after shredding, the resulting magnesium alloys can be used for secondary, noncritical applications. However, the typical case for magnesium components is that the magnesium postconsumer scrap ends up in the nonferrous metals fraction that consists primarily of aluminum, magnesium, and heavy metals. Today, aluminum is typically fed into a second life cycle as a secondary alloy, and magnesium becomes part of the aluminum cycle as an alloy addition. In this article, we evaluate the environmental effects of using magnesium in the aluminum cycle. We also assess the influence of end-of-life scenarios on the overall environmental impact of a component's life cycle. The primary focus of our analysis is the evaluation of the effects of magnesium vehicle components on greenhouse gas emissions.

  6. Limited subsolidus diffusion in type B1 CAI: Evidence from Ti distribution in spinel

    NASA Technical Reports Server (NTRS)

    Meeker, G. P.; Quick, J. E.; Paque, Julie M.

    1993-01-01

    Most models of calcium aluminum-rich inclusions (CAI) have focused on early stages of formation by equilibrium crystallization of a homogeneous liquid. Less is known about the subsolidus cooling history of CAI. Chemical and isotopic heterogeneties on a scale of tens to hundreds of micrometers (e.g. MacPherson et al. (1989) and Podosek, et al. (1991)) suggest fairly rapid cooling with a minimum of subsolidus diffusion. However, transmission electron microscopy indicates that solid state diffusion may have been an important process at a smaller scale (Barber et al. 1984). If so, chemical evidence for diffusion could provide constraints on cooling times and temperatures. With this in mind, we have begun an investigation of the Ti distribution in spinels from two type B1 CAI from Allende to determine if post-crystallization diffusion was a significant process. The type B1 CAIs, 3529Z and 5241 have been described by Podosek et al. (1991) and by El Goresy et al. (1985) and MacPherson et al. (1989). We have analyzed spinels in these inclusions using the electron microprobe. These spinels are generally euhedral, range in size from less than 10 to 15 micron and are poikilitically enclosed by millimeter-sized pyroxene, melilite, and anorthite. Analyses were obtained from both the mantles and cores of the inclusions. Compositions of pyroxene in the vicinity of individual spinel grains were obtained by analyzing at least two points on opposite sides of the spinel and averaging the compositions. The pyroxene analyses were obtained within 15 microns of the spinel-pyroxene interface. No compositional gradients were observed within single spinel crystals. Ti concentrations in spinels included within pyroxene, melilite, and anorthite are presented.

  7. Chemical vapour deposition of undoped and spinel-doped cubic zirconia film using organometallic process

    NASA Astrophysics Data System (ADS)

    Takahashi, Yasutaka; Kawae, Takayuki; Nasu, Mineji

    1986-03-01

    Growth of undoped and spinel-doped ZrO 2 films on glass substrates by the vapour phase decomposition of zirconium t-butoxide (ZTB) was investigated. Undoped tetragonal and monoclinic ZrO 2 films were formed below and above 400°C, respectively. Cubic ZrO 2 films were grown when the ZrO 2 was doped with more than 5 mol% of spinel MgAl 2O 4. Magnesium aluminium isopropoxide MgAl 2 (O-i-Pr) 8 (MAI) was used as the dopant source of the spinel. The cubic films have a higher Vickers hardness than the monoclinic films by about 200-250 kg/mm 2, and are stable up to 800°C, above which they were transformed to the monoclinic phase. This is in contrast to the higher temperature stability of the spinel-doped zirconia powder with spinel content 6 mol% formed by hydrolysis of a isopropanol solution of mixed zirconium n-butoxide and MAI, where the tetragonal form of ZrO 2 was kept unchanged by annealing it up to about 1000°C. The difference is attributed to effect of surface energy control in the tetragonal powders which is absent in the cubic films produced by CVD.

  8. Imparting passivity to vapor deposited magnesium alloys

    NASA Astrophysics Data System (ADS)

    Wolfe, Ryan C.

    Magnesium has the lowest density of all structural metals. Utilization of low density materials is advantageous from a design standpoint, because lower weight translates into improved performance of engineered products (i.e., notebook computers are more portable, vehicles achieve better gas mileage, and aircraft can carry more payload). Despite their low density and high strength to weight ratio, however, the widespread implementation of magnesium alloys is currently hindered by their relatively poor corrosion resistance. The objective of this research dissertation is to develop a scientific basis for the creation of a corrosion resistant magnesium alloy. The corrosion resistance of magnesium alloys is affected by several interrelated factors. Among these are alloying, microstructure, impurities, galvanic corrosion effects, and service conditions, among others. Alloying and modification of the microstructure are primary approaches to controlling corrosion. Furthermore, nonequilibrium alloying of magnesium via physical vapor deposition allows for the formation of single-phase magnesium alloys with supersaturated concentrations of passivity-enhancing elements. The microstructure and surface morphology is also modifiable during physical vapor deposition through the variation of evaporation power, pressure, temperature, ion bombardment, and the source-to-substrate distance. Aluminum, titanium, yttrium, and zirconium were initially chosen as candidates likely to impart passivity on vapor deposited magnesium alloys. Prior to this research, alloys of this type have never before been produced, much less studied. All of these metals were observed to afford some degree of corrosion resistance to magnesium. Due to the especially promising results from nonequilibrium alloying of magnesium with yttrium and titanium, the ternary magnesium-yttrium-titanium system was investigated in depth. While all of the alloys are lustrous, surface morphology is observed under the scanning

  9. Imparting passivity to vapor deposited magnesium alloys

    NASA Astrophysics Data System (ADS)

    Wolfe, Ryan C.

    Magnesium has the lowest density of all structural metals. Utilization of low density materials is advantageous from a design standpoint, because lower weight translates into improved performance of engineered products (i.e., notebook computers are more portable, vehicles achieve better gas mileage, and aircraft can carry more payload). Despite their low density and high strength to weight ratio, however, the widespread implementation of magnesium alloys is currently hindered by their relatively poor corrosion resistance. The objective of this research dissertation is to develop a scientific basis for the creation of a corrosion resistant magnesium alloy. The corrosion resistance of magnesium alloys is affected by several interrelated factors. Among these are alloying, microstructure, impurities, galvanic corrosion effects, and service conditions, among others. Alloying and modification of the microstructure are primary approaches to controlling corrosion. Furthermore, nonequilibrium alloying of magnesium via physical vapor deposition allows for the formation of single-phase magnesium alloys with supersaturated concentrations of passivity-enhancing elements. The microstructure and surface morphology is also modifiable during physical vapor deposition through the variation of evaporation power, pressure, temperature, ion bombardment, and the source-to-substrate distance. Aluminum, titanium, yttrium, and zirconium were initially chosen as candidates likely to impart passivity on vapor deposited magnesium alloys. Prior to this research, alloys of this type have never before been produced, much less studied. All of these metals were observed to afford some degree of corrosion resistance to magnesium. Due to the especially promising results from nonequilibrium alloying of magnesium with yttrium and titanium, the ternary magnesium-yttrium-titanium system was investigated in depth. While all of the alloys are lustrous, surface morphology is observed under the scanning

  10. Spinel electrodes for rechargeable lithium batteries.

    SciTech Connect

    Thackeray, M. M.

    1999-11-10

    This paper gives a historical account of the development of spinel electrodes for rechargeable lithium batteries. Research in the late 1970's and early 1980's on high-temperature . Li/Fe{sub 3}O{sub 4} cells led to the evaluation of lithium spinels Li[B{sub 2}]X{sub 4} at room temperature (B = metal cation). This work highlighted the importance of the [B{sub 2}]X{sub 4}spinel framework as a host electrode structure and the ability to tailor the cell voltage by selection of different B cations. Examples of lithium-ion cells that operate with spinel anode/spinel cathode couples are provided. Particular attention is paid to spinels within the solid solution system Li{sub 1+x}Mn{sub 2-x}O{sub 4} (0 {le} x {le} 0.33).

  11. Al-TiH2 Composite Foams Magnesium Alloy

    NASA Astrophysics Data System (ADS)

    Prasada Rao, A. K.; Oh, Y. S.; Ain, W. Q.; A, Azhari; Basri, S. N.; Kim, N. J.

    2016-02-01

    The work presented here in describes the synthesis of aluminum based titanium-hydride particulate composite by casting method and its foaming behavior of magnesium alloy. Results obtained indicate that the Al-10TiH2 composite can be synthesized successfully by casting method. Further, results also reveal that closed-cell magnesium alloy foam can be synthesized by using Al-10TiH2 composite as a foaming agent.

  12. Esthetic improvements and in vitro testing of In-Ceram Alumina and Spinell ceramic.

    PubMed

    Magne, P; Belser, U

    1997-01-01

    The original In-Ceram material (In-Ceram Alumina), composed of sintered aluminum oxide subsequently infused with a glass, features interesting mechanical properties. In-Ceram Spinell was marketed more recently to improve the esthetic potential. This study compared the flexural strength of various combinations of sintered alumina and spinel infiltrated with the associated glasses. In addition, the influence of vacuum during the infusion process was investigated using density measurements. The characteristic strength (load at which 63% of the specimens had failed) was 530 MPa for the original material, 523.7 MPa when the same material was infiltrated under vacuum, 481.4 MPa when sintered alumina was infused under vacuum with the glass originally marketed for the spinel, and 283.1 MPa for the sintered spinel infiltrated under vacuum with the associated glass. A significant increase in density was observed when the infiltration firing of sintered alumina was performed under vacuum. Furthermore, the in vivo evaluation of specific esthetic parameters inherent to different types of cores was made and revealed the relative opacity of alumina; spinel was found to have the ability to blend in with the underlying substrate. Both materials demonstrated a general lack of fluorescence. PMID:9495165

  13. Magnesium and sudden death.

    PubMed

    Leary, W P; Reyes, A J

    1983-10-22

    Magnesium deficiency may result from reduced dietary intake of the ion or increased losses in sweat, urine or faeces. Stress potentiates magnesium deficiency, and an increased incidence of sudden death associated with ischaemic heart disease is found in some areas in which soil and drinking water lack magnesium. Furthermore, it has been demonstrated experimentally that reduction of the plasma magnesium level is associated with arterial spasm. Careful studies are required to assess the clinical importance of magnesium and the benefits of magnesium supplementation in man. PMID:6353622

  14. Corrosion and hydrogen permeation of A216 Grade WCA steel in hydrothermal magnesium-containing brines

    SciTech Connect

    Haberman, J.H.; Frydrych, D.J.; Westerman, R.E.

    1988-03-01

    Corrosion rates determined at 1 month in 150/degree/C brine increased with magnesium concentration. The structure of the corrosion product, as determined by x-ray diffraction, depended upon the magnesium concentration. In brines with less than 10,000 ppM magnesium, the primary corrosion product had a spinel structure characteristic of magnetite or magnesioferrite. In brines containing magnesium concentrations greater than 20,000 ppM, the primary corrosion product had the amakinite structure characteristic of a complex iron-magnesium hydroxide. The high corrosion rates observed in brines containing high magnesium concentrations suggest that the corrosion products having the amakinite structure is less protective than corrosion products having the spinel structure. Corrosion rates in high-magnesium (inclusion) brine determined over a 6-month test duration were essentially constant. Hydrogen permeation rates observed in exposing mild steel to high-Mg/sup 2/plus// brine at 150/degree/C could be potentially damaging to a mild steel waste package container. The rate of hydrogen permeation was proportional to the brine flow rate in the autoclave. Thiourea additions to the brine increased the hydrogen permeation rate; sulfate and bromide ion additions did not. The maximum gaseous hydrogen pressure attainable is not known (based on 3Fe /plus/ 4H/sub 2/O /plus/ Fe(sub 3)O /plus/ 4H/sub 2/, would be /approximately/900 atmospheres), and the dependence of permeation rate on temperature is not known. 8 refs., 13 figs., 3 tabs.

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

    SciTech Connect

    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.

  16. Synthesis and characterization of nanocrystalline MgAl{sub 2}O{sub 4} spinel via sucrose process

    SciTech Connect

    Alinejad, Babak Sarpoolaky, Hosein; Beitollahi, Ali; Saberi, Ali; Afshar, Shahrara

    2008-05-06

    Nanocrystalline MgAl{sub 2}O{sub 4} spinel powder was synthesized using metal nitrates and a polymer matrix precursor composed of sucrose and polyvinyl alcohol (PVA). The precursor and the calcined powders were characterized by simultaneous thermal analysis (STA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). According to XRD results, the inceptive formation temperature of spinel via this technique was between 600 and 700 deg. C. The calcined powder at 800 deg. C for 2 h has faced shaped morphology and its crystallite size is in the range of 8-12 nm. Further studies also showed that the amount of polymeric matrix to metal ions has significant influence on the crystallite size of synthesized magnesium aluminate spinel powder.

  17. Aluminum Hydroxide

    MedlinePlus

    Aluminum hydroxide is used for the relief of heartburn, sour stomach, and peptic ulcer pain and to ... Aluminum hydroxide comes as a capsule, a tablet, and an oral liquid and suspension. The dose and ...

  18. Choline Magnesium Trisalicylate

    MedlinePlus

    Choline magnesium trisalicylate is used to relieve the pain, tenderness, inflammation (swelling), and stiffness caused by arthritis and painful ... used to relieve pain and lower fever. Choline magnesium trisalicylate is in a class of nonsteroidal anti- ...

  19. Magnesium and Space Flight.

    PubMed

    Smith, Scott M; Zwart, Sara R

    2015-12-01

    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

  20. Magnesium and Space Flight

    PubMed Central

    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

  1. Magnesium and Space Flight

    NASA Technical Reports Server (NTRS)

    Smith, Scott M.; Zwart, Sara R.

    2016-01-01

    Magnesium is an essential nutrient for muscle, cardiovascular, and bone health on Earth, and during space flight. We sought to evaluate magnesium status in astronauts before, during, and after space missions, in 43 astronauts (34 male, 9 female) on 4-6 month space flight missions. We also studied individuals participating in a ground analog of space flight, (head-down tilt bed rest, n=27, 35 +/- 7 y). We evaluated serum concentration and 24-hour 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-d 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- to 6-month space missions.

  2. Surface electrical conductivity of single crystal spinel in cesium vapor. Final report

    SciTech Connect

    Agnew, P.; Ing, J.L.

    1995-04-02

    The operation of a thermionic fuel element (TFE) requires the maintenance of good electrical resistance between the anode and cathode, and between the electrodes and the TFE body. A program of research was established as part of the TOPAZ International Program (TIP) with the purpose of investigating the degradation of TFE electrical insulators. The major emphasis of this research has been on the interactions of oxide ceramics with cesium (Cs) vapor, and the resurfacing decrease of surface resistivity. Previous work has studied the surface electrical conductivity of sapphire exposed to Cs. In this report the authors describe the results of an experimental investigation of the surface electrical conductivity of single crystal magnesium aluminate spinel at temperatures ranging from 573K to 923K, in the presence of cesium vapor at pressures up to 1 Torr. The interest in spinel has arisen in view of its apparent resistance to radiation damage.

  3. First principles pseudopotential calculations on aluminum and aluminum alloys

    SciTech Connect

    Davenport, J.W.; Chetty, N.; Marr, R.B.; Narasimhan, S.; Pasciak, J.E.; Peierls, R.F.; Weinert, M.; Rahman, T.S.

    1994-12-31

    Recent advances in computational techniques have led to the possibility of performing first principles calculations of the energetics of alloy formation on systems involving several hundred atoms. This includes impurity concentrations in the 1% range as well as realistic models of disordered materials (including liquids), vacancies, and grain boundaries. The new techniques involve the use of soft, fully nonlocal pseudopotentials, iterative diagonalization, and parallel computing algorithms. This approach has been pioneered by Car and Parrinello. Here the authors give a review of recent results using parallel and serial algorithms by their group on metallic systems including liquid aluminum and liquid sodium, and also new results on vacancies in aluminum and on aluminum-magnesium alloys.

  4. Magnesium industry overview

    SciTech Connect

    Clow, B.B.

    1996-10-01

    Magnesium products provide an excellent strength-to-weight ratio, good fatigue strength, high impact strength, good corrosion resistance, high-speed machinability, and good thermal and electrical conductivities. As a result, applications are expanding in almost every industry. Dozens of automotive components are now made of magnesium, including steering wheels, valve covers, and seat frames. Magnesium alloys are also used in computer housings, in-line roller skates, golf clubs, tennis racquets, and baseball bats. Good strength and stiffness at both room and elevated temperatures make magnesium alloys especially valuable for aerospace applications. This article presents an overview of magnesium technology, world production, increasing demand, and recycling.

  5. Enhancements in Magnesium Die Casting Impact Properties

    SciTech Connect

    David Schwam; John F. Wallace; Yulong Zhu; Srinath Viswanathan; Shafik Iskander

    2000-06-30

    The need to produce lighter components in transportation equipment is the main driver in the increasing demand for magnesium castings. In many automotive applications, components can be made of magnesium or aluminum. While being lighter, often times the magnesium parts have lower impact and fatigue properties than the aluminum. The main objective of this study was to identify potential improvements in the impact resistance of magnesium alloys. The most common magnesium alloys in automotive applications are AZ91D, AM50 and AM60. Accordingly, these alloys were selected as the main candidates for the study. Experimental quantities of these alloys were melted in an electrical furnace under a protective atmosphere comprising sulfur hexafluoride, carbon dioxide and dry air. The alloys were cast both in a permanent mold and in a UBE 315 Ton squeeze caster. Extensive evaluation of tensile, impact and fatigue properties was conducted at CWRU on permanent mold and squeeze cast test bars of AZ91, AM60 and AM50. Ultimate tensile strength values between 20ksi and 30ksi were obtained. The respective elongations varied between 25 and 115. the Charpy V-notch impact strength varied between 1.6 ft-lb and 5 ft-lb depending on the alloy and processing conditions. Preliminary bending fatigue evaluation indicates a fatigue limit of 11-12 ksi for AM50 and AM60. This is about 0.4 of the UTS, typical for these alloys. The microstructures of the cast specimens were investigated with optical and scanning electron microscopy. Concomitantly, a study of the fracture toughness in AM60 was conducted at ORNL as part of the study. The results are in line with values published in the literature and are representative of current state of the art in casting magnesium alloys. The experimental results confirm the strong relationship between aluminum content of the alloys and the mechanical properties, in particular the impact strength and the elongation. As the aluminum content increases from about 5

  6. Production of Magnesium and Aluminum-Magnesium Alloys from Recycled Secondary Aluminum Scrap Melts

    NASA Astrophysics Data System (ADS)

    Gesing, Adam J.; Das, Subodh K.; Loutfy, Raouf O.

    2016-02-01

    An experimental proof of concept was demonstrated for a patent-pending and trademark-pending RE12™ process for extracting a desired amount of Mg from recycled scrap secondary Al melts. Mg was extracted by electrorefining, producing a Mg product suitable as a Mg alloying hardener additive to primary-grade Al alloys. This efficient electrorefining process operates at high current efficiency, high Mg recovery and low energy consumption. The Mg electrorefining product can meet all the impurity specifications with subsequent melt treatment for removing alkali contaminants. All technical results obtained in the RE12™ project indicate that the electrorefining process for extraction of Mg from Al melt is technically feasible. A techno-economic analysis indicates high potential profitability for applications in Al foundry alloys as well as beverage—can and automotive—sheet alloys. The combination of technical feasibility and potential market profitability completes a successful proof of concept. This economical, environmentally-friendly and chlorine-free RE12™ process could be disruptive and transformational for the Mg production industry by enabling the recycling of 30,000 tonnes of primary-quality Mg annually.

  7. Investigation of Synthetic Mg(1.3)V(1.7)O4 Spinel with MgO Inclusions: Case Study of a Spinel with an Apparently occupied Interstitial Site

    NASA Technical Reports Server (NTRS)

    Uchida, Hinako; Righter, Kevin; Lavina, Barbara; Nowell, Matthew M.; Wright, Stuart I.; Downs, Robert T.; Yang, Hexiong

    2007-01-01

    A magnesium vanadate spinel crystal, ideally MgV2O4, synthesized at 1 bar, 1200 C and equilibrated under FMQ + 1.3 log f(sub o2) condition, was investigated using single-crystal X-ray diffraction, electron microprobe, and electron backscatter (EBSD). The initial X-ray structure refinements gave tetrahedral and octahedral site occupancies, along with the presence of 0.053 apfu Mg at an interstitial octahedral site . Back-scattered electron (BSE) images and electron microprobe analyses revealed the existence of an Mg-rich phase in the spinel matrix, which was too small (less than or equal to 3microns) for an accurate chemical determination. The EBSD analysis combined with X-ray energy dispersive spectroscop[y (XEDS) suggested that the Mg-rich inclusions are periclase oriented coherently with the spinel matrix. The final structure refinements were optimized by subtracting the X-ray intensity contributions (approx. 9%) of periclase reflections, which eliminated the interstitial Mg. This study provides insight into possible origins of refined interstitial cations reported in the the literature for spinel, and points to the difficulty of using only X-ray diffraction data to distinguish a spinel with interstitial cations from one with coherently oriented MgO inclusions.

  8. Magnesium and the Athlete.

    PubMed

    Volpe, Stella Lucia

    2015-01-01

    Magnesium is the fourth most abundant mineral and the second most abundant intracellular divalent cation in the body. It is a required mineral that is involved in more than 300 metabolic reactions in the body. Magnesium helps maintain normal nerve and muscle function, heart rhythm (cardiac excitability), vasomotor tone, blood pressure, immune system, bone integrity, and blood glucose levels and promotes calcium absorption. Because of magnesium's role in energy production and storage, normal muscle function, and maintenance of blood glucose levels, it has been studied as an ergogenic aid for athletes. This article will cover the general roles of magnesium, magnesium requirements, and assessment of magnesium status as well as the dietary intake of magnesium and its effects on exercise performance. The research articles cited were limited from those published in 2003 through 2014. PMID:26166051

  9. The Spinel Explorer--Interactive Visual Analysis of Spinel Group Minerals.

    PubMed

    Luján Ganuza, María; Ferracutti, Gabriela; Gargiulo, María Florencia; Castro, Silvia Mabel; Bjerg, Ernesto; Gröller, Eduard; Matković, Krešimir

    2014-12-01

    Geologists usually deal with rocks that are up to several thousand million years old. They try to reconstruct the tectonic settings where these rocks were formed and the history of events that affected them through the geological time. The spinel group minerals provide useful information regarding the geological environment in which the host rocks were formed. They constitute excellent indicators of geological environments (tectonic settings) and are of invaluable help in the search for mineral deposits of economic interest. The current workflow requires the scientists to work with different applications to analyze spine data. They do use specific diagrams, but these are usually not interactive. The current workflow hinders domain experts to fully exploit the potentials of tediously and expensively collected data. In this paper, we introduce the Spinel Explorer-an interactive visual analysis application for spinel group minerals. The design of the Spinel Explorer and of the newly introduced interactions is a result of a careful study of geologists' tasks. The Spinel Explorer includes most of the diagrams commonly used for analyzing spinel group minerals, including 2D binary plots, ternary plots, and 3D Spinel prism plots. Besides specific plots, conventional information visualization views are also integrated in the Spinel Explorer. All views are interactive and linked. The Spinel Explorer supports conventional statistics commonly used in spinel minerals exploration. The statistics views and different data derivation techniques are fully integrated in the system. Besides the Spinel Explorer as newly proposed interactive exploration system, we also describe the identified analysis tasks, and propose a new workflow. We evaluate the Spinel Explorer using real-life data from two locations in Argentina: the Frontal Cordillera in Central Andes and Patagonia. We describe the new findings of the geologists which would have been much more difficult to achieve using the

  10. Grosnaja ABCs: Magnesium isotope compositions

    NASA Technical Reports Server (NTRS)

    Goswami, J. N.; Srinivasan, G.; Ulyanov, A. A.

    1993-01-01

    Three CAI's from the Grosnaja CV3 chondrite were analyzed for their magnesium isotopic compositions by the ion microprobe. The selected CAI's represent three distinct types: GR4(compact Type A), GR7(Type B) and GR2(Type C). Petrographic studies indicate that all three Grosnaja inclusions were subjected to secondary alterations. The Type A CAI GR4 is primarily composed of melilite with spinel and pyroxene occurring as minor phases. The rim of the inclusion does not exhibit distinct layered structure and secondary alteration products (garnet, Fe-rich olivine and Na-rich plagioclase) are present in some localized areas near the rim region. The average major element compositions of different mineral phases in GR4 are given. Preliminary REE data suggest a depletion of HREE relative to LREE by about a factor of 3 without any clear indication of interelement fractionation. The CAI GR7 has textural and minerological characteristics similar to Type B inclusions. The REE data show a pattern that is similar to Group 6 with enrichment in Eu and Yb. In addition, a depletion of HREE compared to LREE is also evident in this object. Melilite composition shows a broad range of akermanite content (Ak(sub 15-55)). Detailed petrographic study is in progress. GR2 is a anorthite-rich Type C inclusion with large plagioclase laths intergrown with Ti-rich pyroxene. The average plagioclase composition is close to pure anorthite (An99).