Structural phase diagrams of animal communities in assessment of freshwater ecosystem conditions

Hydrobiologia ◽  
1996 ◽  
Vol 322 (1-3) ◽  
pp. 277-282 ◽  
Author(s):  
Vladimir B. Verbitskii ◽  
Vladimir G. Tereshchenko
Keyword(s):  
Phase Diagrams ◽  
Structural Phase ◽  
Freshwater Ecosystem ◽  
Animal Communities

T-O, OII-OIII and OIII-OI Phase Boundary in Oxygen-Chain-Equalised and Order-Stabilised Polycrystalline Pair Samples of YBa2Cu3O6+x

1999 ◽  
Vol 13 (09n10) ◽  
pp. 1073-1078 ◽  
Author(s):  
G. Calestani ◽  
P. Manca ◽  
S. Sanna ◽  
A. Migliori
Keyword(s):  
Electron Diffraction ◽  
Symmetry Breaking ◽  
Phase Diagrams ◽  
Structural Phase ◽  
Comparative Investigation ◽  
Oxygen Stoichiometry ◽  
Antiferromagnetic Ordering ◽  
Critical Oxygen ◽  
Oxygen Chain ◽  
First Time

A comparative investigation, performed on Oxygen-Chain-equalised(k) Deintercalated [ OCD ] k and Intercalated [ OCD ] k pair-samples ( k -pairs) of YBa 2 Cu 3 O 6+x by resistive T c and electron diffraction (ED) at steps Δk=0.02-0.03, revealed that equivalent or non-equivalent microscopic oxygen-chain arrangements are produced, at the same oxygen content k, by intercalation and deintercalation of oxygen in the Cu(1)Ox chains. These arrangements manifest in Tc -singularities or Tc -splittings of the k -pairs, whose occurrence can be straightforwardly explained by taking into account the non equivalence of the structural phase diagrams of YBCO, pointed out by electron diffraction, when produced by intercalation of oxygen in the tetragonal T structure or by deintercalation from the orthorhombic OI structure. Tc -singularities are produced in the k ranges for which a superimposition of the phase diagrams occurs, whereas Tc -splitting are pointed out in correspondence of splitted structural regions. The maximum Tc -splitting is observed in proximity of the semiconductor-metal transition with the appearing of superconductivity related to an anti-OIII (OIII*) superstructure in intercalated samples at k =0.30, where the corresponding deintercalated samples are tetragonal and semiconductor. This result confirms that the vanishing of the antiferromagnetic ordering, the emergence of hole doped superconductivity and the symmetry breaking at the T-O transition are nearly coincident phenomena in YBCO. However the related critical oxygen stoichiometry is strictly dependent on the ordering parameter in the Cu(1) plane, i.e. on the formation of extended chains. The OIII* structure, for the first time observed in a systematic way at the T-O transition in intercalated samples, seems to exhibit in analogy with OII and OIII a characteristic Tc .

On the Physics of Enhanced Fickian Diffusion and Structural-Phase Changes in Intensively Deforming Metallic Materials

2006 ◽  
Vol 251-252 ◽  
pp. 123-126 ◽  
Author(s):  
Yuriy S. Nechaev
Keyword(s):  
Mass Transport ◽  
Phase Diagrams ◽  
Structural Phase ◽  
Cold Deformation ◽  
Phase Changes ◽  
Fickian Diffusion ◽  
Metallic Materials ◽  
Open Questions ◽  
Diffusion Mass

Urgent open questions and their solution ways are considered of the thermodynamic stimuli and mechanisms of the enhanced Fickian diffusion mass-transport providing the unusual structuralphase transformations in metallic materials undergoing the intensive cold deformation, those can not be described in the framework of the conventional phase diagrams.

scholarly journals Pressure-Temperature Phase Relations in Complex Hydrides

2009 ◽  
Vol 150 ◽  
pp. 175-195 ◽  
Author(s):  
Bertil Sundqvist
Keyword(s):  
High Pressure ◽  
Phase Diagrams ◽  
Structural Properties ◽  
High Pressures ◽  
Structural Phase ◽  
Experimental Studies ◽  
Strong Increase ◽  
Temperature Phase ◽  
Complex Hydrides ◽  
Theoretical Predictions

Interest in hydrogen as a future energy carrier in mobile applications has led to a strong increase in research on the structural properties of complex alkali metal and alkaline earth hydrides, with the aim to find structural phases with higher hydrogen densities. This contribution reviews recent work on the structural properties and phase diagrams of these complex hydrides under elevated pressures, an area where rapid progress has been made over the last few years. The materials discussed in greatest detail are LiAlH4, NaAlH4, Li3AlH6, Na3AlH6, LiBH4, NaBH4, and KBH4. All of these have been studied under high pressure by various methods such as X-ray or neutron scattering, Raman spectroscopy, differential thermal analysis or thermal conductivity measurements in order to find information on their structural phase diagrams. Based mainly on experimental studies, preliminary or partial phase diagrams are also given for six of these materials. In addition to this information, data are provided also on experimental results for a number of other complex hydrides, and theoretical predictions of new phases and structures under high pressures are reviewed for several materials not yet studied experimentally under high pressure.

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