Effects of particle packing on the sintered microstructure

The sintering process is shown to be critically dependent on particle-packing density and porosity uniformity. Sintering experiments were conducted on compacts consisting of monodisperse, spherical TiO₂ particles. Densification kinetics and microstructure evolution for two initial packing densities, 55% and 69% of theoretical, were investigated. The lower-density compacts sintered rapidly to theoretical density, yet improved particle-packing density and uniformity significantly enhanced densification.     

Perturbation calculation of correlation energies for polyatomic molecules I. Initial results

The calculation of correlation energies for polyatomic molecules is discussed. Four second-order perturbation expressions are considered; only the simplest, a Rayleigh-Schroedinger expansion with the Moller-Plesset partitioning of the Hamiltonian is invariant to an arbitrary mixing of degenerate orbitals and has the correct dependence on the number of particles. In the absence of degeneracies an iterative Brillouin-Wigner method is proposed. Calculations predict that correlation effects favor the non-classical form of carbonium ions.     

Chemical ionization mass spectrometry. i-Butane reactant gas modified by ethanolamine or ethylenediamine

1,2-Diaminoethane and 2-aminoethanol-1 were added to the isobutane plasma of a chemical ionization mass spectrometer. The resulting reactant gas mixture did not react with additives containing a single oxygen functional group. Addition reactions were observed with some additives containing multiple oxygen functions. Additives containing nitrogen functions were protonated by the reactant mixture. The relative proportion of protonation to addition depended on the ability of the additive to chelate the reactant ion and on the basicity of the additive. This use of 1,2-diaminoethane and 2-aminoethanol-1 provides a convenient method of varying the reactivity of the plasma in a chemical ionization source.