Rate of elapsed polymerization of hydroxyethylacrylate gel induced by gamma irradiation

The rate of elapsed polymerization of polyhydroxyethylacrylate in gelatin has been studied to investigate the effect of co-monomers consumption at a given dose.The polymer gel dosimeters consisted of 2%～4%N,N-methyelene-bis-acrylamJde cross-linker,2%-4% 2-hydroxyethylaerylate monomer and gelatin at 3% and 5%,The dosimeters were irradiated by using 60Co teletherapy Y-ray source up to 20 Gy at a constant dose rate.The relaxation rate of water proton in the dosimeters at different doses and co-monomer concentrations were measured using a nuclear magnetic resonance spectroscopy.The rate of elapsed polymerization decreases with increasing the dose and the initial concentration of co-monomers.The rate of consumption of co-monomers increases with an increase of the polymerization and the gelatin content of the polymer gel.     

Mechanics Model to Determine Swelling Potential of Expansive Soils

The factors influencing on soil expansion are reviewed in the paper. A mechanics model to determine swelling potential of expansive soils is presented. The mechanics model is based on the softening of expansivesoil following absorption of water. The constitutive relationships of the mechanics model include the relationshipamong swelling under free load, swelling under load, and vertical pressure, and the relationship of swelling under free loading and swellingpressure. A concept of additional compression modulus is introduced and the method determining the modulus is proposed. Finally, the predicted results of swelling potential using the mechanics model compare well with the measured data.     

Material Loss and High Temperature Phase Transition in Lithium Ferrite

The morphology and kinetics of the phase transformations accompanying oxygen and lithium loss in LiFe₅O₈ were studied at 1200°C in air, in oxygen ( P O₂ = 760 torr), and in vacuum ( P = 5×10⁻⁵torr), using high-voltage electron microscopy. LiFeO₂ nucleated and grew in the LiFe₅O₈ matrix and finally transformed to spinel in all three atmospheres; however, the kinetics of the transformation depended on the atmobphere. The dependence of these phase transformations on material loss is discussed.