Quenched phase

Spin-Singlets in the Cubic Quenched Phase of CsC60.179... 

Fig. 10 133Cs spectra in the cubic quenched phase of CsQ, as a function of temperature... 

Fig. 12. Pair distribution functions j hhM and ft (/) for the plastic and annealed (A) and quenched phases (Q) of methane. Only the orientational degrees of freedom were considered in the calculation.

Apparently the (2x1) phase cannot be attributed to the equilibrium structure at room temperature, but may be described as a quenched phase probably due a limited surface diffusion parameter. Aside of finding the ordered surface by LEED, the (4x1) structure has been imaged for the first time in real space by scanning tunneling microscopy [76] which is presented in Fig. 5 a. 

Fig. 11.13 INS spectra (IN6, ILL) obtained in neutron energy gain of the low energy region of (a) Qo at 300K, (b) Cao dimers in the quenched phase of RbCeo. (c) linear chains in pressure polymerized and (d) two-dimensional polymer sheets in pressure polymerized Cso (the material is a mixture of rhombohedral and tetragonal networks). Reproduced from [39] with permission from Gordon and Breach.

Kinetic Evolution of Thermal CO2 Dissociation Products During Quenching Phase... 

Experiments of this type have been carried out on partially deuterated polystyrenes (using quenched phases from the melt) by J. P. G>tton and co-workers. These experiments give us precise information oil the local correlations between chains in a polymer melt. Also, because of the simplicity introduced by the Flory theorem, this is one of the few cases where the scattering diagrams can be computed accurately. The method is described in Chapter X. Here we present the results only, in qualitative terms. 

As an example, fig. 44 shows the thermograms of an amorphous Als4Ce6Ni o alloy. The Cp value of the as-quenched phase is 22.8 J/molK near room temperature. As the temperature rises, the Cp value gradually increases initially and then begins to decrease at about 365 K, indicating an irreversible structural relaxation at about 365 K. With a further increase in temperature, the Cp value shows a minimum at about 500 K, then increases rapidly in the region of glass transition at about 515 K and reaches 32.4 J/mol K for the supercooled liquid around 535 K. With a further increase of the temperature, the... 

Figure 105 summarizes the changes in the as-quenched phase and the atomic diameter in the Zn55Mg4oRs alloys with the R elements. We note a systematic change dependent on the atomic size of the R elements. The as-quenched structure exhibits the amorphous phase when it contains La, Ce, Pr or Eu, and the icosahedral phase wdien it contains Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu or Y. It seems that the atomic size of the R element is an important factor for the formation of amorphous and icosahedral phases. The alloys containing an R element with an atomic diameter larger than 0.366 nm, except Yb, form... 

Fig. 105. Change in the as-quenched phase with atomic number of R elements for the melt-spun ZnssMg jRj alloys. The values listed below each element are the atomic radii.

The change of the specific heat of the transition from amorphous solid to supereooled liquid as well as the temperature dependence of the specific heat in the amorphous solid and supercooled liquid has been examined for the La-Al-Ni amorphous alloys through detailed differential scanning calorimetric measurements (Inoue et al. 1989f). As an example, fig. 115 shows the thermograms of the amorphous La5sAl25Ni2o alloy with the widest supercooled liquid region. The Cp value of the as-quenched phase is 24 J/mol K... 

Fluorescence measurements and detection can either be made under steady-state or time-resolved conditions. Some of the commonly used measurement techniques focus on changes in optical properties such as fluorescence intensity quenching, phase fluorometry (lifetime), polarization, surface plasmon resonance (SPR), and evanescent waves. Here, we will present detector systems based for (a) fluorescence intensity quenching and (b) phase fluorometry in detail. A few example references of integrated optical sensor systems based on the various optical measurement techniques are given in Table 1 and the reader is encourage to review those papers if more details are desired. 

Figure 6.39. Temperature dependence of the magnetic susceptibilities obtained by ESR for both the orthorhombic polymer (slow cooling) and the metastable (rapid quenching) phases in AjC o- (Reproduced by permission from ref 198.)...

In view of this, some reference state for the cation distribution needs to be defined to serve as a bench mark to which observed low-temperature states can be referred. Summerville (1973) has coined the phrase operational equilibrium to describe the state achieved after a low-temperature anneal when the anion sub-lattice adjusts to a random cation distribution this should be reproducible. Operational equilibrium will be achieved in principle with samples that have been melted initially, or in practice perhaps with those which have been heated above, say, 2000°C. Any tendency for changes in the random cation distribution thus achieved, which might stem from the stable existence below, say, 1600 C of some intermediate compound of defined composition, would only be revealed if the sample were annealed at close to this temperature for sufficient time for the diffusion-controlled reaction to take place. So it is that for the Zr02-Sc203 system, arc-nlelted samples of compositions between those of the y- and S-phases appear optically, to X-rays, but not to electrons as monophasic. However, after a week s annealing at 1600°C and subsequent quenching, phase separation does occur on a sub-microscopic scale, and is clearly shown in X-ray diffraction. 

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