Small Amount Of Mg Research Articles

Synthesis of a non-stoichiometric pyroxene under ambient pressure.

Crystallization experiments were carried out on powdered glasses having the composition Di23Es53An24 at temperatures of 1250, 1275, 1300, 1325 and 1350°C. The resulting crystalline phases are clinopyroxenes and a trace of unknown oxide crystals. The pyroxenes grown at 1325 and 1350°C are stoichiometric clinopyroxenes rich in Al and Fe. Those grown at the lower three temperatures are non-stoichiometric clinopyroxenes which are extremely rich in Al and contain only negligibly small amounts of Mg. Non-stoichiometric clinopyroxenes are shown not to be characteristic products of high pressure conditions.

石炭液化用高活性リモナイト触媒の開発 ２ インドネシア産Ｎｉ含有リモナイトの性状と液化活性

Properties and liquefaction activities of Ni containing Soroako limonite ores, deposited in the upper layers of nickel mine, Sulawesi Island in Indonesia, were examined by comparing with those of Yandi Yellow limonite in Australia. It was found that Soroako limonite consisted of mainly a -FeOOH and Al (OH) 3, containing 1.0-2.0wt‰ of Ni, Cr, Si and a small amount of Mg and Co on the dry basis. Results of the wet pulverization test with a process solvent by using an agitated mill showed that Soroako limonite could be easily pulverized to sub-micron particle size as well as Yandi Yellow. The finely pulverized Soroako limonite catalyst exhibited a high liquefaction activity in the liquefaction of Indonesian Banko coal, compared to Yandi Yellow catalyst. It appeared that Soroako limonite could be transformed into smaller crystallite size of pyrrhotites (Fe1-XS) by the addition of elemental sulfur, leading to high catalytic activity. The agglomeration or crystal growth of pyrrotites may be suppressed by Al-O-Fe strong interaction between FeOOH and Al (OH) 3. Results of TEM-EDX analysis indicated that Ni could be coexisted with Fe and S in the used catalyst. It suggested that Ni could be located near the Fel_xS structure, leading to the promotion effect on the liquefaction activity. Soroako limonite can be used advantageously in a commercial plant as a cata-lyst raw material for the liquefaction of brown coal in Indonesia.

Monitoring the Precipitation Reactions in a Cold Rolled Al-Mn-Mg-Cu Alloy using Thermoelectric Power and Resistivity Measurements

Precipitation processes in an industrial Al-Mn-Mg-Cu alloy have been monitored using thermoelectric power and resistivity measurements. Using both techniques it is possible to separate effects due to Mg/Cu and Mn/Fe precipitation, and to calculate the weight percentage precipitated during each process. It is found that Al 2 MgCu precipitates form at annealing temperatures below 225°C. At these temperatures a maximum of 0.25 wt% of each element precipitates. For this type of precipitation the dislocation density prior to annealing has no significant effect on the precipitation kinetics. Precipitation of Mn occurs at temperatures above 225°C and a maximum of 0.48 wt% precipitates. In contrast to Mg/Cu precipitation, the dislocation density and annealing temperature both exert a significant influence on the Mn/Fe precipitation kinetics. Only a very small amount of Mg 2 Si phase was found to precipitate. Based on the experimental evidence it is likely that Al 2 MgCu precipitation on dislocations is favored by annealing at temperatures below 300°C whilst Mn bearing precipitates form at dislocations after short annealing times at 500°C.

Preparation of spherical apatite particles by the homogeneous precipitation method in the presence of magnesium ions and their ion-exchange properties

Spherical apatite particles were prepared by the homogeneous precipitation method in the presence of magnesium ions. The starting solutions were prepared by mixing 0.167 mol·L −1 of Ca(NO 3) 2, 0.100 mol·L −1 of (NH 4) 2HPO 4, 1.00 mol·L −1 of (NH 2) 2CO, 0.10 mol·L −1 of HNO 3, and a small amount of Mg(NO 3) 2. The carbonate-containing apatite powders were obtained by heating these solutions at 80∼95°C for 48∼192 h. Although fibrous particles with long-axis lengths of 30 to 60 μm were obtained from the magnesium-free solution, spherical agglomerates with diameters of ∼10 μm, which contained minute plate-like particles, were present in the apatite powders derived from the solutions with 5 mass% of magnesium ions. The ion-exchange test for the harmful ions (Pb 2+, Cd 2+, and Ni 2+) showed that the ion-exchange abilities of the apatite powders containing magnesium ions were much better than the ability of the magnesium-free apatite powder. The ion-exchanged amounts of the apatite powder containing magnesium ions were arranged in the following order: Pb 2+ >> Cd 2+ > Ni 2+.

Compositional characterization of Cu-rich phase particles present in as-cast Al-Cu-Mg(-Li) alloys containing Ag

The effects of small additions of Ag on the aging of wrought Al-Cu-Mg(-Li) alloys, involving widespread nucleation of Cu-rich Ω (and T1) phase precipitates, are known. This article examines the influence of small additions of Ag on the nature of Cu-rich θ-Al2Cu, S-Al2CuMg, and T1-Al2CuLi phases present in appropriate as-cast Al-Cu, Al-Cu-Mg, and Al-Cu-Li-Mg alloys. Using a combination of light microscopy, scanning electron microscopy (SEM), and electron probe microanalysis (EPMA), it is shown that neither independent nor combined additions of Ag and Mg to the binary Al-Cu alloy alter the composition of the θ phase; however, there are differences in the ways the θ phase is evolved in Al-Cu-Mg alloys with and without Ag. Ag additions to the Al-Cu-Mg alloy result in the formation of an Al-Cu-Mg-based ternary phase, having a Cu content similar to that of the θ phase and containing small amounts of Mg; rapid rates of cooling cause the retention of this phase in the as-cast alloy. Relatively large amounts of both Ag and Mg are always located in the peripheral regions of such a phase. This phase is readily replaced by θ phase upon annealing at 450 °C. The S phase of the ternary Al-Cu-Mg system is identified in this alloy and is found to dissolve small amounts of Ag. In the case of the Al-Cu-Li-Mg-Ag alloy, two major changes are observed: both Ag and Mg are always present in relatively large amounts in the peripheral regions of the T1 phase, and the S-phase particles are once again found to dissolve small amounts of Ag. These results are discussed in light of the known compositional features of the precipitates formed in the artificially aged Al-Cu-Mg(-Li)-Ag alloys, to reveal that examination of phases present in the as-cast microstructure is a contributory step toward determining the locations of trace alloy additions in the phase precipitates of interest.

Response of field-grown maize to applied magnesium in acidic soils in north-eastern Australia

Split-plot field experiments, with main plots consisting of various rates of calcitic lime and single rates of dolomite, gypsum, and calcium silicate, were conducted at each of 4 sites to determine the effect of band-applied magnesium (Mg) on maize yield. The sites were acidic with pH values of 4.5, 4.9, 5.0, and 6.1 and exchangeable Mg levels of 0.16, 0.10, 6.0, and 2.0 cmol(+)/kg, respectively. Magnesium significantly (P < 0.05) increased grain yield at the 2 low-Mg sites, both of which were strongly acidic and responsive to lime application, but the nature of the Mg × lime interaction was different at each of the 2 responsive sites. The absence of a response to Mg at lime rates ≥1 t/ha at one responsive site was attributed to the presence of small amounts of Mg in the calcitic lime and/or an improved root environment enabling better exploitation of the soil Mg. Supplying a readily soluble source of Mg in the fertiliser band also resulted in increased grain yield in the gypsum, dolomite, and calcium silicate treatments at the 2 Mg-responsive sites. When the initial soil pH was strongly acidic, exchangeable Mg levels increased with increasing lime rate, suggesting that the small quantities of Mg that occur in the majority of liming materials may be of importance with respect to Mg nutrition. In contrast, gypsum application exacerbated the Mg deficiency at one site. The relationship between grain yield response and soil Mg level across all sites indicated that above an exchangeable Mg level of 0.27 cmol(+)/kg there would be little likelihood of a response to applied Mg.

Characterization of Mg 2+ transport in brush border membrane vesicles of rabbit ileum studied with mag-fura-2

Mg 2+ transport in rabbit ileal brush border membrane vesicles (BBMV) was characterized by means of a modified mag-fura-2 technique. In the presence of an i> o Na + gradient, BBMV showed a saturable Mg 2+ uptake with a K m of 1.64 mmol l −1. There was no evidence of an overshoot. K +, Li +, and choline + were as effective as Na + in stimulating Mg 2+ transport. In contrast, only a small amount of Mg 2+ transport was observed in the presence either of an o> i Na + gradient, or in an Na + equilibrium or in the absence of Na +. Moreover, the findings that Na + efflux was not stimulated but inhibited by outside Mg 2+ and that the nonfluorescent amiloride-analogues DMA and EIPA did not affect Mg 2+ transport do not favour the idea of an Mg 2+/Na + antiport system. At Cl − equilibrium, independent of the Na + gradient, the rate of Mg 2+ transport was markedly suppressed compared with the transport rate noted in the presence of an i> o Cl − gradient. The stimulating effect of inside anions could be enhanced by SCN − and decreased by SO 2− 4. Furthermore, nonfluorescent anion transport antagonist H 2-DIDS stimulated Mg 2+ transport. These findings indicate that Mg 2+ transport can be modulated by inside anions. Mg 2+ transport appeared to be electroneutral because it was not dependent on membrane potential. Mg 2+ transport was neither stimulated by Bay K8644, a Ca 2+ channel agonist, nor inhibited by verapamil, diltiazem, nifedipine and imipramine, the Ca 2+ channel antagonists. It, therefore, seems unlikely that Mg 2+ uses the Ca 2+ transport system.

Effects of Mg addition on the kinetics of low-temperature precipitation in Al–Li–Cu–Ag–Zr alloys

The thermal stability at around 343 K is one important problem of Al–Li alloys related to the microstructural changes during the low temperature exposure. The present work aims to investigate the effects of Mg addition on the age-hardening behavior and precipitation kinetics of an Al–Li–Cu–Mg–Ag–Zr alloy in the low temperature range from 278 to 373 K. The microstructures observed with transmission electron microscopy (TEM) and the hardness changes indicate that a small amount of Mg markedly accelerates the formation of GP(1) zones, not the δ′ (Al 3Li) phase, resulting in an enhanced age- hardening. Quantitative analysis of the precipitation kinetics determined by the electrical resistivity changes also elucidates the more detailed effects of Mg addition on the characteristic precipitation phenomena in the Al–Li–Cu alloys, i.e. a decreased activation energy for the GP(1) zone nucleation and a suppressed growth of both GP(1) zones and the δ′ phase (and/or its precursory structures). The complicated effects of Mg addition are well explained in terms of both the enhanced nucleation rate of GP(1) zones with the aid of Mg/Cu/Vacancy complexes and the pronounced decrease in free-vacancies available for Cu and Li diffusion due to the preferential vacancy trapping by Mg atoms.

Crystal Structure of the Product of Mg2+Insertion into V2O5Single Crystals

Chemical (by interaction with a dibutylmagnesium solution) and electrochemical (in acetonitrile solution of magnesium perchlorate) insertion of Mg2+into the single crystals of V2O5was performed. The morphology change of V2O5crystals as a result of the Mg2+insertion was studied by scanning electron microscopy. The wavelength dispersive electron probe microanalysis clearly showed the presence of Mg (at least) at the surface of intercalated V2O5. Based on the single crystal X-ray diffraction study of intercalated V2O5(orthorhombic,Pmn21,a= 11.544(6),b= 4.383(3),c= 3.574(2) Å,Z= 4) the location of a small amount of Mg (∼1%) in the bulk V2O5may be suggested, with [6 + 4] oxygen atoms surrounding Mg. The resulting Mg–O separations essentially exceed the accepted values for the Mg–O distances in crystals with hexacoordinated Mg atoms, which may be correlated with the structural and electrochemical properties of Mg2+-inserted V2O5.

Stress effects in thermal cycling of copper (magnesium) thin films

The stress in the thin films of pure Cu and Cu (Mg) alloy deposited on oxidized silicon substrates has been measured in the range of room temperature to 500 °C by the use of an in situ laser based curvature measuring tool. Results indicate that small amounts of Mg (∼2–3 at. %) in copper changes the stress-temperature behavior significantly when compared with that of pure copper. The alloy, after the first annealing cycle which apparently equilibrates the film, shows a predominantly elastic stress-temperature behavior up to ∼400 °C compared to pure Cu, which shows a departure from linearity at ∼200 °C. Rutherford backscattering and x-ray diffraction studies were also carried out to elucidate the role of Mg in strengthening the copper film. The results indicate that additions of Mg to Cu increase the mechanical strength of the film and that such behavior is retained in several (subsequent) thermal cycles to 400 °C.

Development of a drug delivery system for the treatment of periodontal disease based on bioerodible poly(ortho esters)

Poly(ortho esters) prepared by the condensation of 1,2,6-hexanetriol and an alkyl orthoacetate are viscous, semisolid materials at room temperature that can be injected using a blunt needle. When tetracycline was incorporated into these materials, complete release occurred within about 24 hours, but when small amounts of Mg(OH) 2 were incorporated into the polymer release could be extended to many weeks, and a loading of 0.5wt% resulted in sustained release of about 10 days. When adhesion was tested using bovine teeth, cohesive failure of the pure polymer occurred at a force of about 392 mNcm −2 and cohesive failure of a polymer incorporating 10wt% tetracycline and 1 wt% (Mg(OH) 2 occurred at about 118 mNcm −2. The combination of injectability, dentoadhesiveness and ability to control accurately the release of incorporated antibiotics makes these materials promising candidates for bioerodible delivery systems useful in the treatment of periodontitis. Toxicological studies are currently in progress.

Transmission Electron Microscopic Observation of Glass-Ceramic A-W and Apatite Layer Formed on Its Surface in a Simulated Body Fluid

In the interior of glass-ceramic A-W, both the apatite and β-wollastonite were homogeneously dispersed in a glassy matrix, taking a form of rice grain 50 nm in width and 100 nm in length. The apatite layer formed on the glass-ceramic in the simulated body fluid consisted of fine needle-like apatite crystals about 10 nm in thickness and 100 nm in length, which are elongated along c-axis and randomly oriented. The apatite crystals in the surface layer were in direct contact with those within the glassceramic without intervention of such silica gel layer as observed for Bioglass®-type glasses. No crystallographic relation was observed between them. The apatite crystals in the surface layer were calciumdeficient, and contained small amounts of Mg and Si.

Characterization of PrBa 2Cu 3O 7-δ single crystals grown by crystal pulling method using MgO crucible

Single crystals of PrBa 2Cu 3O 7-δ containing small amounts of Mg were successfully fabricated by the improved crystal pulling method (SRL-CP method) using MgO crucibles. The melt temperature was between 965°C and 970°C. No MgO inclusion was observed by electron probe micro analysis (EPMA). The lattice constants of the grown crystal are a=3.907(1) A ̊ , b=11.768(1) A ̊ , V=176.6(1) A ̊ 3 . The Mg contamination from MgO crucible was relatively small with a composition of Pr 1.00Ba 2.00Cu 2.94O 6.72Mg 0.06. analyzed by 4-circle single crystal diffractometer.

The Mg/Ca ratio determination by high resolution PIXE

Small amounts of Mg in the presence of much Ca can be measured with a PIXE system, using a plane crystal X-ray spectrometer. The dolomitization grade of limestones can be measured with this method. Some possibilities for improving the method are given.

イオンアシスト蒸着窒化鉄薄膜の磁気特性に及ぼす添加元素の影響

Iron nitride films prepared by the ion-assisted vapor deposition method are promising for high density recording media because of their high coercivity. Their structure and magnetic properties were studied as a function of the contents of additive elements which were insoluble with iron such as Cu, Ag or Mg. Prepared films were characterized by VSM, XPS and Mössbauer spectroscopy. The coercivity of FeMgN films showed drastic decrease with the addition of only a small amount of Mg, while that of FeCuN and FeAgN remained nearly unchaged until the concentration of the additive elements reached a certain amount. XPS and Mössbauer studies showed that the nitrization of iron was suppressed only when Mg was chosen as the additive element, this is due to the selective nitrization of Mg in FeMgN films. It was concluded that the decrease in the coercivity of FeMgN was attributable to the decrease in the magnetic separation effect by the paramagnetic iron nitride phase, which presumably segregated along the column in FeN, FeCuN and FeAgN films.

The effects of small amounts of Mg on the creep performance of a Ni-base superalloy

AbstractSmall amounts of magnesium (Mg) have been shown to increase the creep life and fracture elonga.twn of GH698, a mckel-base superalloy. The minimum creep rate, however, remained unaffected. This mechanism is due to Mg segregation which reduces the surface tenswn and surface diffusion coefficient, thus decreasing the growth rate of cavities. Mg may also react with sulphur (S), reducing S segregation.

The effects of magnesium additions in two nickel-base superalloys on the stress rupture properties and grain boundary microstructure

The effects of adding small amounts ofMg to Ni- Cr-Mo-Ti-Nb and Ni-Cr- W-Mo-Al-Ti Ni-base superalloys on the stress rupture lives have been studied. The features ofvarious precipitates at the grain...

Domain Segregation in Ni-Fe-Mg-Smectites

AbstractThe first stage of lateritic weathering of pyroxenes in the Niquelandia area, Brazil, leads either to Fe-rich products or to a phyllosilicate clay. In relatively unfractured parent rock the phyllosilicate clay contains Ni-rich smectites, the atomic ratio of Ni: octahedral cations ranging from 0.3 to 0.5. These smectites were studied by polarized light microscopy, X-ray powder diffraction (XRD), transmission electron microscopy, and electron microprobe, and infrared, optical absorption, Mössbauer, and extended X-ray absorption fine-structure (EXAFS) spectroscopy. The chemical composition of the smectite is constant on the optical microscope scale even to the smallest analyzed particles (3000 A in diameter and about 75 Å thick). From XRD data the mineral is principally a swelling, trioctahedral smectite; however, some kerolite-pimelite-like layers are present, and a weak 06,33 reflection indicates the presence of a small amount of a dioctahedral phase. Mössbauer results show that all Fe cations are Fe3+ in octahedral sites. The structural formula of the smectite is: (Ca0.01K0.05)(Al0.17Fe0.5Mg0.48Ni1.47Cr0.02)(Si3.92Al0.08)O10(OH)2The results obtained from all the above methods suggest that in the smectites Ni, and, perhaps, a small amount of Mg are clustered in pimelite-like domains (or layers), whereas Fe and some Al are clustered in nontronite-like domains (or layers). Most selected-area electron diffraction patterns exhibit continuous or punctuated (hk) rings, indicating that particles contain several stacked layers. The patterns of some thin particles, however, suggest dioctahedral layers having trans-octahedral vacancies, such as in the Garfield, Washington, nontronite. Thus, the Ni-Fe-Mg-smectite, which seemingly is homogeneous, actually consists of mixed trioctahedral and dioctahedral layers or domains.

Kinetics of intracrystalline order-disorder reactions in tremolite

The temperature dependent Fe-Mg distribution in tremolite from Zillertal, Austria was investigated using Mossbauer spectroscopy. The standard free energy change for the exchange reaction Fe2+(M4)+Mg(M2)=Mg(M4)+Fe2+(M2) decreases with increasing temperature, corresponding to an enthalpy term of 9.2±1.5 kcal/mole and an entropy term of 1.9±1.7 cal/mole K. Kinetic experiments performed as hydrothermal runs, yield an activation energy of 70±7 kcal/mole for the disordering reaction. Difficulties in analysing the very small amount of Mg(M4) in the natural sample introduce large errors in the calculation of cooling rates for the natural rock. The estimated error in the Mg(M4) site occupancy results in a shift of the obtained cooling rate of about three orders of magnitude, making tremolite less useful for estimations of rock cooling rates.

Tight divalent metal binding to Escherichia coli F1-adenosinetriphosphatase. Complete substitution of intrinsic magnesium by manganese or cobalt and studies of metal binding sites.

Tight divalent metal binding sites in Escherichia coli F1-adenosinetriphosphatase (F1-ATPase) were studied. Native enzyme contained two Mg per F1, confirming previous results. All of the Mg may be replaced by Co or Mn using a dissociation-repolymerization procedure. The substituted enzymes are homogeneous and contain two Mn per F1 or two Co per F1. They are fully active as ATPases, they rebind to F1-depleted membranes, and they catalyze ATP-driven proton pumping. N,N'-Dicyclohexylcarbodiimide-(DCCD) inactivated F1 retains all the intrinsic tightly bound Mg. Evidence is presented that DCCD affects at least two beta subunits in E. coli F1, and therefore, the tightly bound metals appear not to be bound at the DCCD-reactive glutamate residue on the beta subunit. However, the nature of the tightly bound metal (Mg, Mn, or Co) as well as the presence of added (2 mM) MgSO4, MnSO4, or CoSO4 affected the rate of DCCD inactivation, showing that metal binding changes the beta-subunit conformation. Isolated F1 alpha subunit bound Mg, Mn, or Co stoichiometrically and independently of ATP binding. Isolated F1 beta subunit bound only small amounts of Mg, and no Co or Mn. Therefore, it is possible, although not conclusively shown, that the alpha subunit is the site of tight metal binding in the intact F1.