1,444 research outputs found

    Magnetoresistance, specific heat and magnetocaloric effect of equiatomic rare-earth transition-metal magnesium compounds

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    We present a study of the magnetoresistance, the specific heat and the magnetocaloric effect of equiatomic RETRETMg intermetallics with RE=LaRE = {\rm La}, Eu, Gd, Yb and T=AgT = {\rm Ag}, Au and of GdAuIn. Depending on the composition these compounds are paramagnetic (RE=LaRE = {\rm La}, Yb) or they order either ferro- or antiferromagnetically with transition temperatures ranging from about 13 to 81 K. All of them are metallic, but the resistivity varies over 3 orders of magnitude. The magnetic order causes a strong decrease of the resistivity and around the ordering temperature we find pronounced magnetoresistance effects. The magnetic ordering also leads to well-defined anomalies in the specific heat. An analysis of the entropy change leads to the conclusions that generally the magnetic transition can be described by an ordering of localized S=7/2S=7/2 moments arising from the half-filled 4f74f^7 shells of Eu2+^{2+} or Gd3+^{3+}. However, for GdAgMg we find clear evidence for two phase transitions indicating that the magnetic ordering sets in partially below about 125 K and is completed via an almost first-order transition at 39 K. The magnetocaloric effect is weak for the antiferromagnets and rather pronounced for the ferromagnets for low magnetic fields around the zero-field Curie temperature.Comment: 12 pages, 7 figures include

    Epsomite as flame retardant treatment for wood: Preliminary study

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    The effect of epsomite as flame retardant for wood has been investigated and compared with a commercial boron salt. Both flame retardants have been introduced into wood samples by vacuum impregnation. Epsomite is a hydrated sulphate salt with a water solubility of 731 g L-1 at room temperature. Thanks to this high solubility it was possible to obtain elevated epsomite loadings in comparison with the borax salt. Flame retardancy was evaluated by means of the limiting oxygen index, the dripping test and the exposition to a direct flame (Bunsen test). The results showed that the addition of epsomite increases the limiting oxygen index, delays the time to ignition and the evolution of the temperatures trough the wood. © 2016 Elsevier LtdPeer ReviewedPostprint (author's final draft

    Water for thirsty industry

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    Quantum chemical study of the properties of grignard reagents

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    Master of Science

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    thesisTitanium is often referred to as "wonder metal" due to its superior properties. At present, titanium is predominantly produced through Kroll's process which is complex, expensive, and needs much higher specific energy than the thermodynamic requirement and that restricts titanium's widespread use. Direct reduction of titanium slag (DRTS) is an alternative process to produce titanium from titanium hydride at a lower projected cost and energy expense. In DRTS, a two-step leaching process is used to lower the aluminum, magnesium, and silicon content in titanium to meet the ASTM International (ASTM) specifications. Magnesium was leached in a mildly acidic condition while aluminum, and silicon impurities were leached under alkaline condition. The effect of varying temperature, concentration of acid or alkali, and adding certain additives to the lixiviants have been investigated for aluminum and silicon removal. Leaching at 140¬įC for 3 h using a solution of 2 M NaOH and 2.5 g/l of sodium gluconate, and a solid-liquid ratio of 1g to 100 ml, produced titanium hydride with the desired aluminum and silicon contents. The effect of varying temperature, concentration of acid, and solid to liquid ratio have been investigated for magnesium removal. Magnesium content in titanium hydride was lowered below specification requirements by leaching with 0.05 M hydrochloric acid at 50¬įC for 15 min using solid-liquid ratio of 1 g to 400 ml. Another process for separating titanium from dissolved ilmenite using dihydroxybenzene (catechol) as a metal-organic precipitate was demonstrated. Titanium (IV) was chemically bonded with catechol at a pH of 5.5 to form a precipitate containing 98.7% Ti. The results from density functional theory simulations predicted a gap of 2.914 eV between the two frontier orbital lobes (highest occupied molecular orbital and lowest unoccupied molecular orbital) suggesting stability of the metal complex. This precipitate can be reduced in a hydrogen atmosphere to form titanium hydride which again can be dehydrogenated to form titanium

    Cleavage by Organic Magnesium Compounds.

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