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Abstract  

The crystallization behaviour and the physical characterization of supramolecular complexes formed between permethylated-α-cyclodextrin (TMα-CD) and the enantiomers of phenylethanol (PE) are investigated. According to crystal structure analyses, complexes containing the pure guest enantiomers are almost isomorphous, indicating that the host presents a poor ability to distinguish PE enantiomers at a molecular level. Nevertheless, crystallizations from racemic PE in water induce an efficient chiral discrimination and allow the enantio-separation of the guests despite the existence of a solid solution revealed by XRPD and coupled TG-DSC analyses. The enantiodifferentiation is explained by solubility differences between the two diastereomeric complexes in the studied temperature range. Moreover, it is shown that the diastereomeric complex TMα-CD/(S)-PE crystallizes in two distinct phases: a monohydrate and an anhydrous form, with a transition temperature close to 37C. The insertion of a water molecule in the crystals grown below 37C does not involve any other change of the crystal packing nor of the molecular conformation, but leads to different crystal growth mechanisms inducing different morphologies and distinct thermal behaviours.

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Abstract  

Diamagnetic muon yields (P D) in (AlxCo1−x)(acac)3 and (GaxCo1−x)(acac)3 systems were investigated. Both in (AlxCo1−x)(acac)3 and (GaxCo1−x)(acac)3, Co(acac)3 was more influential on diamagnetic muon yield than Al(acac)3 and Ga(acac)3. Zerofield muon spin relaxation rate suggests that the diamagnetic muon resides in the vicinity of Co(acac)3 molecules.

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Differential thermal and phase X-ray analyses have shown that MoO3 and Fe2V4O13 form a solid substitution solution, in which Mo6+ ions are incorporate into the crystal lattice of Fe2V4O13 in place of V5+ ions. The solubility limit of MoO3 in Fe2V4O13 at ambient temperature is 18 mole % of MoO3. The phase equilibria in the system Fe2V4O13-FeVMoO7, were also studied. Results are presented in the form of a phase diagram.

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Abstract  

The thermal dehydration-decomposition of Ln2(SeO4)3·nH2O (wheren=12 forLn=Pr, Nd andn=8 forLn=Sm) and PrxLn2−x(SeO4)3·nH2O (wheren=12 forx=1.0 andLn=Nd;n=8 forx=0.2 and 1.0 in case ofLn=Sm) have been reported.

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Abstract  

Dynamic and controlled rate thermal analysis has been used to characterise synthesised jarosites of formula [M(Fe)3(SO4)2(OH)6] where M is Pb, Ag or Pb–Ag mixtures. Thermal decomposition occurs in a series of steps. (a) dehydration, (b) well defined dehydroxylation and (c) desulphation. CRTA offers a better resolution and a more detailed interpretation of water formation processes via approaching equilibrium conditions of decomposition through the elimination of the slow transfer of heat to the sample as a controlling parameter on the process of decomposition. Constant-rate decomposition processes of water formation reveal the subtle nature of dehydration and dehydroxylation. CRTA offers a better resolution and a more detailed interpretation of the decomposition processes via approaching equilibrium conditions of decomposition through the elimination of the slow transfer of heat to the sample as a controlling parameter on the process of decomposition. Constant-rate decomposition processes of non-isothermal nature reveal separation of the dehydroxylation steps, since in these cases a higher energy (higher temperature) is needed to drive out gaseous decomposition products through a decreasing space at a constant, pre-set rate.

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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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Abstract  

The research concerns the influence of a substantial range of sodium ion concentrations on the structure of the calcium aluminates C3A*, C12A7 and CA until CaO is emitted. The research also shows the influence of sodium ions of the cell parameters of each calcium aluminate and what reaction occur in mixtures of Na2O and calcium aluminates at elevated temperatures.

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