Point defect agglomeration

In addition to these defects di-vacancies, agglomerations of interstitials and extended clusters of point defects are well known. 

Because boron carbide can be used as the control rod material in a nuclear reactor, in order to interpret its performance it is necessary to establish nature of grown-in and neutron-radiation-induced lattice defects in boron carbide. It was found that the dose received by the irradiated specimen corresponds to transmutation of about eight B nuclei per unit cell in equal number of both Li and " He nuclei (Ashbee 1971). It is believed that the formation of the partial dislocation loops resulting from the agglomeration of point defects are introduced during neutron irradiation. 

Geng, L. and Yang, W. (2006) Agglomeration of point defects in ferroelectric ceramics under cyclic electric field. Moded. Simul. Mater. Sci. Eng., 14, 137-155. 

With irradiation, point defects are formed and agglomerated one with another in each crystallite, causing its remarkable growth in the c-axis direction and a little shrink in the other two directions [XXX-35] such changes cause the material distortion. The lifetime of the material is determined by failure criterion and decreased by the radiation-induced degradation of thermal conductivity. 

Order or disorder of defects is a matter of a fine balance between the configurational entropy of the defects and the exothermic enthalpy gained in association of certain point defects to form various t) es of larger defect agglomerations. Systems with relatively small defect concentrations are entropy controlled and consist of randomly distributed point defects. As concentration increases the enthalpy takes control and leads successively to formation of larger defect entities randomised associated defects or defect clusters, point defects assimilated into randomised stmcture elements of a new phase, superlattice ordering and extended defects, shear planes, and discrete intermediate phases. 

Nucleation occurs by agglomeration of point defects on the surface of solids. This nucleation will require two stages the creation of point defects and their agglomeration. 

On the other hand, from much research work and aforementioned studies, the Cu" species stabilized by a certain structure must be the active center for methanol synthesis. The structure stabilizing the active site is considered to exist due to the contiguity between Cu and ZnO. Relatively small clusters of ZnO on the Cu surface and/or small clusters of Cu on the ZnO surface must make up the specific chemical and physical structure, such as amorphous Cu, two-dimensional layer, small Cu clusters, partially oxidized alloy, lattice defect structure, etc., which cannot significantly be formed at the contact points between large agglomerates. 

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