Zhao Biying

Monolayer dispersion of oxide additives on SnO2 and their promoting effects on thermal stability of SnO2 ultrafine particles

The dispersion behavior of some oxides on the surface of SnO2 and the effects on the thermal stability of SnO2 have been studied. The results show that many oxides such as NiO, CuO, ZnO, Bi2O3, MoO3, Cr2O3 and Sb2O3 can disperse onto the surface of SnO2 by impregnation method or dry method—mixing a compound with the support thoroughly, followed by calcination at an appropriate temperature. The utmost dispersion capacities of these oxides on the surface of SnO2 are measured and they are all in good agreement with those estimated by a close-packed monolayer model. These oxides dispersed on the surface of SnO2 can retard the decrease in the specific surface areas of the samples and the increase in the crystallite size of SnO2 during calcination. In numerous effect factors, the surface coverage is a key factor. It is easy to stabilize the size of SnO2 grains to be 6 nm by this means, and the higher the valence of the cation of oxide, the stronger the stabilizing effects.

Synthesis of high surface area nanometer magnesia by solid-state chemical reaction

Nanometer MgO samples with high surface area, small crystal size and mesoporous texture were synthesized by thermal decomposition of MgC2O4 · 2H2O prepared from solid-state chemical reaction between H2C2O4 · 2H2O and Mg (CH3COO)2 · 4H2O. Steam produced during the decomposition process accelerated the sintering of MgO, and MgO with surface area as high as 412 m2 · g−1 was obtained through calcining its precursor in flowing dry nitrogen at 520°C for 4 h. The samples were characterized by X-ray diffraction, N2 adsorption, transmission electron microscopy, thermogravimetry, and differential thermal analysis. The as-prepared MgO was composed of nanocrystals with a size of about 4–5 nm and formed a wormhole-like porous structure. The MgO also had good thermal stability, and its surface areas remained at 357 and 153 m2·g−1 after calcination at 600 and 800°C for 2 h, respectively. Compared with the MgO sample prepared by the precipitation method, MgO prepared by solid-state chemical reaction has uniform pore size distribution, surface area, and crystal size. The solid-state chemical method has the advantages of low cost, low pollution, and high yield, therefore it appears to be a promising method in the industrial manufacture of nanometer MgO.

Application of ion scattering spectroscopy to investigations of the interaction between the active component and carrier in supported catalysts

In this article we will show, however, that the electronic effect is measurable for Cu, Zn, and Na by the ISS technique, and we will use the concept of «effective mass» based upon a binary collision approach to develop a method for the determination of the chemical shift in solid-solid surface interactions in catalyst systems. A series of Cu, Na, and Zn compounds, Al foil, and supported Cu and Zn catalysts have been investigated, and the 4 He + scattering energy from the different atoms in the different compounds or catalysts has been determined. The «mass increments» in these samples are calculated from scattering peak shifts in the ion scattering spectra and the «mass increment» is used as a means to characterize interaction between surface atoms

DISPERSION STATE OF ZINC OXIDE ON SURFACE OF SILICA GEL AND SURFACE ACIDITY OF ZnO/SiO 2

units emerge as a result of interaction between dispersed ZnO and the carrier, which are responsible for the acidity of the surfaces of samples.

Solid/Solid Adsorption

We have found experimentally that many solids can disperse spontaneously onto supports to form a monolayer or submonolayer. This is a quite widespread phenomenon) which has not been recognized before. We call it solid/solid adsorption. This phenomenom may be attributed to the formation of strong surface bonds between the atoms, ions or molecules of these solids and the surface of the supports. Another driving force for this phenomenon is the entropy increase associated with the changing from an ordered three-dimensional crystalline phase to a less ordered two-dimensional phase. In addition, the diffusion of atoms along the surface is much easier than that into the bulk of a support, so under suitable conditions the monolayer dispersion may be a stable state.