Cohesion of solid

We have now completed our reviews of the four principal types of interatomic force responsible for the cohesion of solids, and have illustrated by examples some characteristic properties of simple crystal structures in which these different types of force operate. These properties, and also some additional physical properties which we shall not discuss in detail, are summarized in table 6.03. 

States of Matter.—Matter exists in one of three states solid, liquid, and gaseous. In the solid form the Yvorticles of matter ore comparatively close together, and are separated with more difficulty than are those of liquid or gaseous matter or, in other words, the cohesion of solid matter is greater tlian that of the other two forms. In the liquid the particles are less firmly bound together and are capable of freer motion about one another. In the gas the mutual attraction of the particles disappears entirely, and their distance from each other depends upon the pressure to which the gas is subjected. 

This glue can be strong, which gives rise to primary bonds, which can be ionic, covalent, or metallic. Usually van der Waals and hydrogen bonds are referred to as. secondary bonds and are weaker. In all cases, however, it is the attractive electrostatic interaction between the positive charges of the nuclei and the negative charges of the electrons that is responsible for the cohesion of solids. 

The main factors that affect the particle passage through sieve aperture are the method of sieve shaking, the ratio of open area of sieve to total area, particle size distribution, the number of particles on the sieve (sieve loading), and the dimension and shape of the particle. Friability and cohesiveness of solid particles can also affect the sieving operation. Difficulty can also arise with high aspect ratio particles (i.e., needle-shaped or flaky particles). 

The cellular method is of little direct practical importance today. Its significance is historical (as a precursor of the APW and related methods) and conceptual (as a convenient framework for the understanding of the cohesion of solids). 

Cortona P 1992 Direct determination of self-consistent total energies and charge densities of solids A study of the cohesive properties of the alkali halides Phys. Rev. B 46 2008... 

Orowan (1949) suggested a method for estimating the theoretical tensile fracture strength based on a simple model for the intermolecular potential of a solid. These calculations indicate that the theoretical tensile strength of solids is an appreciable fraction of the elastic modulus of the material. Following these ideas, a theoretical spall strength of Bq/ti, where Bq is the bulk modulus of the material, is derived through an application of the Orowan approach based on a sinusoidal representation of the cohesive force (Lawn and Wilshaw, 1975). 

The simplest model is the lattice-gas or Ising model. The whole space is divided into a lattice of N sites, and on each site two different states are possible a crystalline state denoted by the variable 5, = 1 and a gaseous state by Sj = -. The variable s denotes the degree of crystalline order. The cohesion of nearest-neighboring solid atoms leads to the following interaction energy... 

Vijh, A. K., The Influence of Solid State Cohesion of Metals on Their Pitting Potentials , Corros. Sci., 12, 935 (1972)... 

Lowdin, P.-O., Advances in Phys. 5, 1, Quantum theory of cohesive properties of solids/ ... 

A surface is that part of an object which is in direct contact with its environment and hence, is most affected by it. The surface properties of solid organic polymers have a strong impact on many, if not most, of their apphcations. The properties and structure of these surfaces are, therefore, of utmost importance. The chemical stmcture and thermodynamic state of polymer surfaces are important factors that determine many of their practical characteristics. Examples of properties affected by polymer surface stmcture include adhesion, wettability, friction, coatability, permeability, dyeabil-ity, gloss, corrosion, surface electrostatic charging, cellular recognition, and biocompatibility. Interfacial characteristics of polymer systems control the domain size and the stability of polymer-polymer dispersions, adhesive strength of laminates and composites, cohesive strength of polymer blends, mechanical properties of adhesive joints, etc. 

Philipsen, P.H.T. and Baerends, E.J. (2000) Relativistic calculations to assess the ability of the generalized gradient approximation to reproduce trends in cohesive properties of solids. Physical Review B - Condensed Matter, 61, 1773-1778. 

If, when a liquid drop is placed on a smooth surface, the forces of adhesion between the solid and the liquid are greater than the forces of cohesion of the liquid, then the liquid will spread and will perfectly wet the surface spontaneously. If the forces reach an intermediate balance determined by the interfacial energies ylv, ysj and ysv, then the liquid drop will form a definite contact angle (0) with the solid surface (Figure 4.12). 

Apparently, the first reference to 7S or superficial cohesion of a solid is found in an Essay by Thomas Young1). The original does not contain illustrations, but Fig. 1 here represents the author s idea. A solid wall (S) is partly wetted by liquid L... 

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