Crystal-originated particle

The presence of second-phase particles in as-grown crystals named COPs (crystal-originated particles), markedly affecting the optical and electronic bulk quality but also the surface perfection of epiready substrates, is one of the most-studied harmful defect types in compound semiconductor crystals. They are present in II-VIs (e.g. [35, 91]), III-Vs (e.g. [92, 93]) and IV-VIs (e.g. [94]). As is explained... 

It should be recognized that a seemingly completed precipitation process can be subject to secondary reactions, designated in the overall scheme as aging, which may involve dehydration, crystallization, recrystallization, ripening, etc. of the original particles. 

From these data one can estimate the change in enthalpy when finely dispersed crystalline goethite converts to macrocrystals. If it is assumed that the original particles (seed crystals) were of the order of 100 A in size, then crystallization of such sediment to form crystals 10-50 fim in size would be accompanied by liberation of about 3 kcal/mol of heat by FeOOH. 

Nuclei As a solute becomes insoluble, the formation of a new phase has its origin in the formation of clusters of solute molecules, termed germs, that increase in size to form small crystals or particles, termed nuclei. One means of preparing colloidal dispersions involves precipitation from solution onto nuclei, which may be of the same or different chemical species. See also Condensation Methods. 

In clinkers and cements, expansive hydration of free lime produces popcorn or cauliflowerlike crystals of calcium hydroxide, called epezite, surrounding the original particle of free lime (see Brown and Swayze, 1938). Formation of epezite via air slaking normally causes clinker disintegration. 

The crystallization behavior of a dispersed melt phase, for example, discrete melt droplets, in an amorphous matrix can be dramatically affected compared to that of the bulk polymer. It has been reported by several authors that crystaUizable dispersed droplets can exhibit the phenomenon of fractionated crystallization originating from the primary nucleation of isolated melt particles by species with different nucleating activities (heterogeneities, local chain ordering)... 

Figure 13. Average mean square particle displacement and Debye Waller factor of interfacial and crystal core atomic motion of a Ni nanoparticle. Filled circles denote the interfacial particles and the circles in the lower corner of the figure denote the crystal core particles. The size of the particle corresponds to N= 2899 atoms or a NP radius = 2.0 nm. Figure 13 was originally published in [71], ...

In order to cause bridging between crystals and particles, one needs to apply external compressive forces. In the laboratory studies, these forces were introduced by applying suitable compression. However, in the course of hydration hardening, such forces are originated in the system internally. One is thus faced with the need to answer a number of questions. Specifically, what is the origin of those forces in the process of structure formation What are the nature, magnitude, and... 

Diamond cells are about 4 mm in aperture and depending on the area of the spot of the spread sample it is possible to utilize a beam condenser or a microscope. Despite the absorption of diamond in the mid infrared, the wavenumber reproducibility that FT-IR is able to achieve makes it possible to subtract the diamond spectrum and to obtain clean spectra of the sample. In forensic analysis this technique is applied to paints, varnishes, inks, fibres, crystals and particles in general, which can be put under pressure and suffer a deformation. To avoid excess of absorption, one of the cells can be removed. In the case of samples such as cork, tobacco and some polymers, which recover their original size after decompression of the cell, the alternative is to use two diamond windows with the sample in between, instead of removing one of them. 

Here is the original, many-body potential energy fiinction, while Vq is a sum of single-particle spring potentials proportional to As X —> 0 the system becomes a perfect Einstein crystal, whose free energy... 

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