Radiation-Thermal Processes at the Surface of Pyrogenic γ-Alumina

The effects of ⁶⁰Co -radiation, 75-keV electrons, and thermal history (295–973 K) on the surface properties of pyrogenic -Al₂O₃ were studied by thermal desorption mass spectrometry. It was found that the state of a hydroxyl cover and the concentrations of surface acid–base sites and chlorine impurity atoms can be regulated by changing the conditions of oxide irradiation.     

Quantum-chemical investigation of influence of solvation on structure and energy characteristics of lithium borohydride and aluminohydride

Institute of New Chemical Problems, Academy of Sciences of the USSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 31, No. 6, pp. 9–19, November–December, 1990.     

Structured water in partially dehydrated yeast cells and at partially hydrophobized fumed silica surface

Nonfreezable water structured due to interaction with endocellular objects in yeast cells (endocellular water) or with partially hydrophobic fumed silica (interfacial water) was studied by means of (1)H NMR spectroscopy with layer-by-layer freezing-out of bulk water and quantum chemical methods applied to water clusters in the gas and liquid (chloroform and cyclohexene) phases and adsorbed on silylated silica. Variation in cell hydration as well as in amount of water adsorbed on modified fumed silica leads to changes in the ratio between contributions of two water states characterized by NMR chemical shifts at delta(H)=1.1-1.7 and 4-5 ppm. Lowering of hydration and temperature results in an enhancement of the first signal, and the opposite result is observed for the second signal. These effects may be explained by structured water distribution in the form of relatively large nanodroplets (delta(H)=4-5 ppm is close to that for bulk water) and small clusters of the 2D structure, in which the fraction of hydrogen atoms out of the hydrogen bonds (delta(H)=1.1-1.7 ppm) is larger than that in nanodroplets.     

Hydrogen adsorption on silicalite in the presence of water and benzene

¹H NMR techniques in the temperature range 200–280 K under isobaric conditions are used to investigate concurrent adsorption of hydrogen and water in the pores of silicalite, a microporous silica. The possibility for a small (up to a few weight percent) quantity of water to exist in the pores is demonstrated. Water is found to exist in the form of two types of cluster structures differing in the degree of water association. A conclusion about the stabilization of the weakly associated form by weakly polar organic molecules is made. Water is shown to promote the hydrogen adsorption process; when its concentration is c _H2O = 2 wt %, adsorption increases more than twofold. A suggestion that this effect is caused by the formation of water-hydrogen cluster structures in the pores is made.     

Heat effects upon the immersional wetting of silica gel and yeast cells during formation of aqueous suspensions

Heat effects that accompany the formation of water⦌ilica gel and water3yeast cells suspensions are studied by differential microcalorimetry. The analysis of kinetic dependences obtained for mineral adsorbent and yeast cells in the context of quasi-chemical first-order reactions demonstrates that the change in the character of interaction between the cell and water corresponds to the transition from the wetting of external and intracellular membrane surfaces of the cell to the stage of enzyme activity at the expense of reserve polysaccharides. Adsorption ability and rate constants of wetting process are determined for both systems; the thickness of interfacial layer is calculated for silica gel.