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Journal of Thermal Analysis and Calorimetry
Authors: Márcia Silva, Lydianne de O. Miranda, Maria Cassia-Santos, S. Lima, L. Soledade, E. Longo, C. Paskocimas, A. Souza, and Iêda Santos

Abstract  

Undoped and/or doped with 1 mol% of Co2+ Mg2TiO4 andMg2SnO4 powders were synthesized by the polymeric precursor method. The influence of the network former (Sn4+ or Ti4+) on the thermal, structural and optical properties was investigated. The recorded mass losses are due to the escape of water and adsorbed gases and to the elimination of the organic matter. Mg2TiO4 crystallizes at lower temperatures and also presents more ordered structure with a smaller unit call and having more intense green color than Mg2SnO4 has.

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Abstract  

A series of LiMn2O4 samples with nominal Li/Mn molar ratio=1/2 has been synthesized at 700 and 750C by the ceramic procedure from Mn2O3 and several lithium sources. Lattice parameters determined from X-ray diffraction patterns are within a narrow range, from a c=8.238(1) to a c=8.245(1) , Da c/a c<0.1%. The study by differential scanning calorimetry (DSC) shows that the temperatures of the cubic (Fd3m)↔orthorhombic (Fddd) phase transition are spread off in a wide range, from -30 to -2C for the exothermic C→O phase transition, and from -21 to +13C for the endothermic O→C transformation. Relationships between the lattice parameter values, the temperature of the phase transformation, and the stoichiometry of the LiMn2O4 samples are pointed out. The DSC technique, which reveals more sensitive than X-ray diffraction to very small variations of composition, is put forward as an essential technique to characterize LiMn2O4 samples.

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Abstract  

The enthalpy of formation for LiMyMn2–yO4 (M=Co, Cr, Li, Mg, Ni) was measured by a Tian-Calvet type high temperature isothermal microcalorimeter. The standard enthalpy of formation for LiMn2O4 at 876 K was evaluated to be H f 0=–1404.2±6.4 kJ mol–1. The partial substitution of Co and Ni for Mn decreased the absolute H f 0 value, while that of Cr and Mg for Mn increased the absolute H f 0 value. In the case of the partial substitution of Li for Mn, no marked change in H f 0 could be observed.

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Chemistry of chromian spinel in volcanic rocks as a potential guide to magma chemistry Mineralogical Magazine 56 173 184 . S

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discussion Figure 1 shows T and RT XRD patterns of the synthesized samples with the indicated zinc contents in the mixture. After RT annealing, reflections of only spinel phases were detected for all structures. After T annealing, the XRD

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Introduction Magnetic nanoparticles continue to evoke interest largely due to their prospective applicability. The spinel ferrite is a widely studied class of materials having remarkable magnetic and electric properties which

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ferrite components (Fe, Zn and Mn) in them was determined by ICP-AES. In both cases, the obtained material contains about 21 mol% less Zn than the assumed amount, but spinel phase occurs in a wide range of composition. The detected lower Zn content may be

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–3, 3–5 mm) and CAC as hydraulic binder (15 wt%). A spinel, MgO·Al 2 O 3 , was used as an additive in concrete mixture. A chemical composition of starting raw materials obtained by atomic absorption spectrophotometer, AAS Analyst 300, is given in Table

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