Coalescence of grains

For coalescence of grains and for reactions between sohds that do not comprise any gas as principal component, the study of the influence of partial pressures of gas is very recent and is very profitable to describe mechanisms. 

We studied [PIJ 94] the reduction in porosity and the coalescence of grains of ceria and the influences of partial pressures of gas and concentrations of some foreign cations on the speed. 

Use of curves of variations of the specific area in the study of coalescence of grains. 

This order A suggests the existence in the reactional mechanism of the coalescence of grain, the presence of an elementary step in the dissociation of water molecules. 

The third part (Chapters 12 to 16) is devoted to the application of the general concepts of modeling to a certain number of families of transformations such as the transformations of coalescence of grains (Chapter 12), decompositions of solids (Chapter 13), reactions between solids (Chapter 14), and reactions between gases and solids (Chapter 15). Finally, we approach the treatment of transformations involving solid solutions, a field still largely in the waste land (Chapter 16). Essentially, this part is concerned with the function reactivity. 

Suspension Polymerization. Suspension polymerization is carried out in small droplets of monomer suspended in water. The monomer is first finely dispersed in water by vigorous agitation. Suspension stabiUzers act to minimize coalescence of droplets by forming a coating at the monomer—water interface. The hydrophobic—hydrophilic properties of the suspension stabiLizers ate key to resin properties and grain agglomeration (89). 

At the time of the discovery of radio-activity, about seventy-five substances were called elements in other words, about seventy-five different substances were known to chemists, none of which had been separated into unlike parts, none of which had been made by the coalescence of unlike substances. Compounds of only two of these substances, uranium and thorium, are radio-active. Radio-activity is a very remarkable phenomenon. So far as we know at present, radio-activity is not a property of the substances which form almost the whole of the rocks, the waters, and the atmosphere of the earth it is not a property of the materials which constitute living organisms. It is a property of some thirty substances—of course, the number may be increased—a few of which are found widely distributed in rocks and waters, but none of which is found anywhere except in extraordinarily minute quantity. Radium is the most abundant of these substances but only a very few grains of radium chloride can be obtained from a couple of tons of pitchblende. 

Gases and grains in interstellar clouds probably experienced many shock events during the formation of planetesimals and meteorites. These events are as follows 1) coagulation of dust into clumps, which settle to the equatorial plane of the nebula 2) breakup of the gravitationally unstable dust disk into clusters of dust clumps 3) coalescence of the clusters into 1 km planetesimals ... 

Further increase in the deposition time increases still further a number of grains deposited and nickel grains coalesce to threads as shown in Fig. 4. However, single grains are distinguishable in the thread structure. 

The nickel electrodeposition into pores of mesoporous silicon begins from the metal grain formation randomly all over the surface of the silicon skeleton. The size of grains increases up to 100 nm with the deposition time and further nickel deposition is accompanied by the increase in the number of grains, which finally coalesce to threads. The moment of complete pore filling with nickel is controlled by the surface potential of the sample. 

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