Surface energy bond fine

Fine structure extending several hundred eV in kinetic energy below a CEELS peak, analogous to EXAFS, have been observed in REELS. Bond lengths of adsorbed species can be determined from Surface Electron Energy-Loss Fine Structure (SEELFS) using a modified EXAFS formalism. 

M. De Crescenzi. Phys. Rev. Letts. 30,1949,1987. Use of surface electron energy-loss fine structure (SEELFS) to determine oxygen-nickel bond length changes for oxygen absorbed on Ni (100) on a function of coverage from 0 to 1.0 monolayer. 

The starting powders firstly reacted with each other to form TijSiC -SiC composites. Then the synthesized fine particles in contact with each other wiU preferably form necks and bond together. The driving force for the reduction in the free surface energy of the particles in neck formation was be provided by the extra mechanical pressure as well as the generated heat by the passed current. Hence with the adoption of spark plasma sintering system, the FGMs can be synthesized and densified quickly in one step. 

Local surface structure and coordination numbers of neighbouring atoms can be extracted from the analysis of extended X-ray absorption fine structures (EXAFS). The essential feature of the method22 is the excitation of a core-hole by monoenergetic photons modulation of the absorption cross-section with energy above the excitation threshold provides information on the distances between neighbouring atoms. A more surface-sensitive version (SEXAFS) monitors the photoemitted or Auger electrons, where the electron escape depth is small ( 1 nm) and discriminates in favour of surface atoms over those within the bulk solid. Model compounds, where bond distances and atomic environments are known, are required as standards. 

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