Amorphous phase, definition

The electronic microscopy method on the EM-125 (fig. 1) for definition of ZnCFO particles size and characteristic of its surface was applied. Known zinc oxide was chosen as the object of comparison. The electronic photos of powders testify, that new composite and zinc oxide have external similarity under the form of particles, wide range on dispersiveness (0,4-6,0 microns for zinc oxide, fig. la 0,3-6,0 microns for ZnCFO, fig. lb) also contain as crystal as amorphous phases in their structure. 

It is generally accepted that the reaction chemistry is the same as in the melt and that the chemical reactions take place in the amorphous phase. This, by definition, implies that the polymer end groups, monomers, catalyst and by-products are present only in the amorphous phase [11], The most important reactions occurring in the melt have been identified as follows [12] ... 

Another aspect of diffraction experiments that is often overlooked is the presence of amorphous materials, the amount of which cannot be easily quantified from a diffraction experiment. As pointed out above, there is no consensus on whether amorphous solids should be considered a form of the substance under investigation. On the one hand, the amorphous component of a given substance is the same chemical as the crystalline material. When melted or dissolved in a solvent the amorphous phase of a molecular material will yield the same molecules as those in crystals, thus falling within McCrone s definition, but will behave as a different solid. On the other hand, an amorphous material may be several different systems. After all, the only difference between a microcrystalline powder and an amorphous powder is the failure to obey the restrictions of Bragg s law. 

An allotrope of a chemical element is defined as a solid phase (of the pure element) which differs by its crystal structure and therefore by its X-ray diffraction pattern from the other allotropes of that element. This definition can be extended to microcrystalline and amorphous phases which may be characterized either by their diffraction pattern or by suitable molecular spectra. 

Figure 2.5 shows also the concentration dependence of the inverse Kauzmann temperature T (entropy catastrophe temperature). For the pure metal, T is much higher than the temperature T0 as discussed. The 77-line should also decrease with increasing concentration and end in the triple point(C, 7 )[2.21] as follows from its definition (AS = 0). It is interesting to note that at this point the real Kauzmann temperature and the inverse Kauzmann temperature meet. But in real systems, the amorphous phase has an excess entropy (small fraction of the entropy of fusion) when compared to the corresponding crystal, the exact amount determined from the kinetics and timescale of the glass transformation. Therefore, another glass transition temperature line with finite excess entropy must be considered, which will be parallel to the Tg-line (above it) and cross the T0- and 77-lines not exactly in the triple point. 

The crystalline and noncrystalline phases in polyamide fibers do not appear to be governed by what may be defined as thermodynamie equilibria, nor is there evidenee for definite boundaries between a phase, characterized by a simple or complex state of order and an essentially amorphous phase. It is therefore quite obvious that the morphological structure of nylons cannot be described adequately in terms of a simple two-phase model according to which ideally ordered crystallites exist together with eompletely amorphous domains. This model constitutes merely one of the two limiting cases the other is that of a paracrystal according to which all deviations from the ideal crystal are ascribed to defects and distortions of the crystal lattice [275-277]. 

Ceramics are inorganic, nonmetallic materials. The structure of ceramics may be crystalline or partly crystalline (having intergranular amorphous phases). The definition of ceramic is often restricted to inorganic crystalline materials. 

Additionally, the a value of PEO declines when blended with PAc, contrary to an increase in a value when ENR is added to PEO in the absence or presence of LiClO,. The T values, as discussed earlier, show diat die salt is more soluble in PAc as compared to ENR. Therefore, with a fixed salt content, the amount of salt dissociated in the PEO amorphous phase is definitely higher for the PEO/ ENR blend compared to the PEO/PAc blend. Besides, the T values of PAc in the presence of salt is raised to a range of 29-37 °C which means the PAc is in its glassy state when ion conductivity of the blend is measured leading to restricted ion mobility in the PEO amorphous phase which forms the predominant percolating pathway of the blend electrolyte. It can be concluded that the ion conductivity of miscible or immiscible PEO-based blend electrolyte is governed by the charge... 

A concise review of the relative order, mobility, density, and possible types of phase transitions of one-component systems is presented by the schematic of Fig. 2.115, along with the dictionary definition of the word transition. This schematic is discussed in Sect. 2.5 in connection with an initial description of phases and their transitions. More details of the structure and properties of crystals, mesophases, and amorphous phases are given in Chap. 5. Some characteristics of the three types of mesophases are given in Fig. 2.107. Quantitative information on the thermodynamic parameters of the transitions between the condensed phases is summarized in Fig. 2.103 and described in more detail in Sect. 5.5. The dilute phases in Fig. 2.115, the gases, are of lesser interest for the present description, although the ideal gas law in Figs. 2.8 and... 

The principal experimental result consists of the fact that in liquid crystals the blurred interference rings of which we have learned in the discussion of normal liquids split up in the magnetic field into a pair of crescents, whereas in the amorphous phase the influence of the magnetic field is inappreciable. Diagrams, which show this effect on exposure of the allyl ester of phenetol azoxybenzoic acid in the magnetic field have been taken by Hermann and Krummacher with Cu radiation a very definite accumulation of the interference intensity in the region of the equator is evident. 

Degree of ciystallinity of polymer films (a volume fraction of the crystal ordered areas in a material) in this research was defined by diffractograms Fig. 5.3 for a series of samples only semiquantitative (more/less). The essence of the method of crystallinity definition consists in analytical division of a diffractogram profile on the Bragg peaks from crystal areas and diffusion peak of an amorphous phase [20], as is shown in Fig. 5.4. 

Dealing with nomenclature issues, it is worthwhile to call attention to an incorrect practice in the composite community the use of the term phase instead of fcomponent . The term phase is very well defined in thermodynamics. Phase is frequently used in polymer physics to describe the various phases in one-component systems. Let us mention only poly(vinylidene fluoride) (PVDF) exhibiting five crystalhne polymorphic modifications (phases) and one amorphous phase, but PVDF is still a one-component system. The misuse of the term phase instead of component would require the definition of another term to describe the phase in the sense of thermodynamics. In this book, and particularly in the present chapter, care was taken to avoid such misuse. 

Polymer crystallization and melting are typically first-order phase transitions between the amorphous phase and the crystalline phase. When these two phases are in thermodynamic equilibrium, two phase transitions are thermodynamically reversible under a certain temperature. This temperature is referred to the equilibrium melting point of polymer crystallization. The free energy changes of amorphous phase and crystalline phase under various temperatures are depicted in Fig. 4.1, illustrating the definition of the equilibrium melting point 7. ... 

In Fig. 3.4, the comparison of experimental and calculated according to the Eq. (3.13) values tp j and respectively, is adduced, which shows their good correspondence. This means, that at impact loading of HOPE with de-vitrificated amorphous phase a its definite part mechanical vitrification occurs, the fraction of which increases at testing temporal scale reduction [21 ]. 

Hence, the stated above results demonstrate nonzero contribution of noncrystalline regions in yield stress even for such semicrystalline polymers, which have devitrificated amorphous phase in testing conditions. At definite conditions noncrystalline regions contribution can be prevailed. Polymers yield stress and elastic constants proportionality is not a general rule and is fulfilled only at definite conditions. 

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