Phase transitions irreversible

The high electrical resistivity and the magnitude of the optical bandgap of Cfio can be reduced by the application of high pressure, with decreases in resistivity of about one order of magnitude observed per 10 GPa pressure [117]. However, at a pressure of 20 GPa, an irreversible phase transition to a more insulating phase has been reported [117]. 

FIG. 4 Qualitative phase diagram close to a first-order irreversible phase transition. The solid line shows the dependence of the coverage of A species ( a) on the partial pressure (Ta). Just at the critical point F2a one has a discontinuity in (dashed line) which indicates coexistence between a reactive state with no large A clusters and an A rich phase (hkely a large A cluster). The dotted fine shows a metastability loop where Fas and F s are the upper and lower spinodal points, respectively. Between F2A and Fas the reactive state is unstable and is displaced by the A rich phase. In contrast, between F s and F2A the reactive state displaces the A rich phase. 

E. V. Albano. Irreversible phase transitions in the dimer-monomer surface reaction process on fractal media. Phys Lett A 765 55-58, 1992. 

E. V. Albano. Critical behavior of the irreversible phase transitions of a dimer-monomer process on fractal media. J Phys A (Math Gen) 27 431-436, 1994. 

E. V. Albano. Branching annihilating Levy flights Irreversible phase transitions with long-range exchanges. Europhys Lett 54 97-102, 1996. 

A convenient illustration of an irreversible phase transition is the crystallization of water at — 10°C and constant pressure ... 

One of the remarkable features of alkali metal adsorption on A1 surfaces is the occurrence of phase transitions involving ordered phases. These phase transitions occur at or below room temperature. Perhaps most remarkable are the order-preserving, irreversible phase transitions involving the Al(lll)—(. 3 x 3)/ 30°—K and Rb phases, and the Al(lOO)—c(2 x 2)—Na phases. For these systems, the surface unit cell, and hence the symmetry of the associated LEED... 

As described in Sec. 4.2, adsorption of 0.2 ML Na on Al(lOO) at room temperatures followed by cooling to 240 K leads to a disorder-order phase transition from a phase with a (1 x 1) LEED pattern to a 5 x. y5)/ 26.6°—Na phase [62], with Na atoms adsorbed in substitutional sites. Once the substitutional structure has been formed, the order-disorder phase transition is completely reversible. However, if 0.2 ML Na is first adsorbed at low temperature, islands of c(2 X 2) structure are formed in which Na atoms are adsorbed in four-fold hollow sites [79, 80]. Annealing this phase to room temperature leads to an irreversible phase transition to a phase with a (1 x 1) LEED pattern, with Na atoms adsorbed in substitutional sites. At this point the reversible, disorder-order phase transition between (1x1) and 5 x y/5)R26.6° phases can be performed by cooling to 240 K as before. 

In this paper, we discuss an irreversible phase transition occuring in the TCNQ salt which diethylcyclohexylammonium cation DECA (TCNQlz, when heated above 350 K. The transition,... 

However, despite its widespread popularity in material science, PNIPAM has inherent disadvantages such as an irreversible phase transition and, for short polymers, a significant influence of end-groups on the thermal behavior. Moreover, strictly speaking, PNIPAM is not a bio-inert polymer. Indeed, the presence of multiple secondary amide functions in the molecular stracture of PNIPAM may lead to the formation of cooperative H-bonding interactions with other amide polymers, in particular with proteins. Thus, the design of new types of thermoresponsive polymers is a cracial topic in contemporary polymer chemistry. 

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