The sol-gel transition process of PMMA/SiO2 hybrid materials was first studied by means of the dynamic torsional vibration method. The different stages of the transition can be described by the change of torque. The t...The sol-gel transition process of PMMA/SiO2 hybrid materials was first studied by means of the dynamic torsional vibration method. The different stages of the transition can be described by the change of torque. The temperature-dependent measurement of the gel time（ tg ） gives the possibility to determine the apparent activation energy.（ Ea ） of this transition according to Flory＇s gelation theory. The non-equilibrium thermodynamic fluctuation theory was used to predict the transition behavior. The isothermal transition experiments on hybrid sols with different TEOS（tetraethyl orthosilicate） contents were carried out. The results show that the Ea of a hybrid sol is higher than that of a non- hybrid sol of a TEOS-water-ethanol system. The increasing of TEOS content in a hybrid sol has no obvious effect on the Ea value, but it can enhance the sol-gel .reaction rate.展开更多
A step index-type Nd^(3+) -doped polymer optical fiber(POF)was prepared by using bulk polymerization of solution of Nd^(3+) -octanoate(NOA)and methyl and methacrylate.A method of wide-angle x-ray diffraction was used ...A step index-type Nd^(3+) -doped polymer optical fiber(POF)was prepared by using bulk polymerization of solution of Nd^(3+) -octanoate(NOA)and methyl and methacrylate.A method of wide-angle x-ray diffraction was used to measure the solubility of NOA.In a high concentration Nd^(3+) doped POF,a residual absorption at 810nm could not be saturated,which is attributed to the high clustered ion rate in the Nd^(3+) POF.A model based on the rate equations to infer the clustered ion rate by the measurement of transmission is presented.展开更多
基金Supported by the National Natural Science Foundation of China(Nos.50025309 and 90201016).
文摘The sol-gel transition process of PMMA/SiO2 hybrid materials was first studied by means of the dynamic torsional vibration method. The different stages of the transition can be described by the change of torque. The temperature-dependent measurement of the gel time（ tg ） gives the possibility to determine the apparent activation energy.（ Ea ） of this transition according to Flory＇s gelation theory. The non-equilibrium thermodynamic fluctuation theory was used to predict the transition behavior. The isothermal transition experiments on hybrid sols with different TEOS（tetraethyl orthosilicate） contents were carried out. The results show that the Ea of a hybrid sol is higher than that of a non- hybrid sol of a TEOS-water-ethanol system. The increasing of TEOS content in a hybrid sol has no obvious effect on the Ea value, but it can enhance the sol-gel .reaction rate.
基金Supported by the National Natural Science Foundation of China under Grant No.19674053。
文摘A step index-type Nd^(3+) -doped polymer optical fiber(POF)was prepared by using bulk polymerization of solution of Nd^(3+) -octanoate(NOA)and methyl and methacrylate.A method of wide-angle x-ray diffraction was used to measure the solubility of NOA.In a high concentration Nd^(3+) doped POF,a residual absorption at 810nm could not be saturated,which is attributed to the high clustered ion rate in the Nd^(3+) POF.A model based on the rate equations to infer the clustered ion rate by the measurement of transmission is presented.
