Ce0.6Zr0.4O2 solid solution ultrafine particle was prepared in the cyclohexane/water/OP-10/n-hexanol reversed microemulsion. The quasi-ternary phase diagram investigations showed that the system has narrow W/O type mi...Ce0.6Zr0.4O2 solid solution ultrafine particle was prepared in the cyclohexane/water/OP-10/n-hexanol reversed microemulsion. The quasi-ternary phase diagram investigations showed that the system has narrow W/O type microemulison region, so it is the proper system to prepare Ce0.6Zr0.4O2 solid solution ultrafine particle. Some physical-chemical techniques such as TG/DTA, XRD, BET, and HRTEM are used to characterize the resultant powders. The results show that the fluorite cubic Ce0.6Zr0.4O2 solid solution is obtained at 400 ℃. The surface area is （146.7 m^2·g^-1）, which is higher than the surface area for sol-gel prepared sample （59.5m^2·g^-1）. HRTEM images indicated that the Ce0.6Zr0.4O2 solid solution ultrafine particle is well-crystallized, narrow size distribution, less agglomeration, within mean size of 5 -7 nm.展开更多
The influence of different nanoparticle sizes on the elastic modulus and the fatigue properties of epoxy/SiO_(2) nanocomposite is studied in this paper.Here,the cross-linked epoxy resins formed by the combination of D...The influence of different nanoparticle sizes on the elastic modulus and the fatigue properties of epoxy/SiO_(2) nanocomposite is studied in this paper.Here,the cross-linked epoxy resins formed by the combination of DGEBA and 1,3-phenylenediamine are used as the matrix phase,and spherical SiO_(2) particles are used as the reinforcement phase.In order to simulate the elastic modulus and long-term performance of the composite material at room temperature,the simulated temperature is set to 298 K and the mass fraction of SiO_(2) particles is set to 28.9%.The applied strain rate is 109/s during the simulation of the elastic modulus.The results show that the elastic modulus of the material increases with the increase in particle size.Furthermore,fatigue simulation under strain control is performed on the model with SiO_(2) nanoparticle radius of 12˚A.The results indicate that the influence trend of variable frequencies on the fatigue mechanical response is similar,and the mean stress decreases with the increase in number of cycles.In addition,the smaller the loading period and the more the number of cycles,the greater the mean stress reduction.Finally,the change in energy and free volume fraction are evaluated under fatigue loading condition.展开更多
The SiO_2 particle material has weak electrorheological (ER) activity. The ER performance of the SiO_2 particles can be ameliorated after adsorbing Y_2(CO_3)_3. In this paper, the effect of Y_2(CO_3)_3 and different s...The SiO_2 particle material has weak electrorheological (ER) activity. The ER performance of the SiO_2 particles can be ameliorated after adsorbing Y_2(CO_3)_3. In this paper, the effect of Y_2(CO_3)_3 and different surfactants on the ER performance of the SiO_2 particle materials is investigated. The results show that anionic or cationic surfactants maybe enhance the ER activity of SiO_2 material, and nonionic surfactants cannot when surfactants are added during the process of the SiO_2 particle preparation, only the anionic surfactant, AES, can enhance markedly the ER performance of the material. The surface area, pore volume and pore diameter of the particles were measured. The effect of Y_2(CO_3)_3 and the surfactants on the microstructure of SiO_2 materials and the relationship between ER effect and the microstructure are described.展开更多
Y_2O_3 ultrafine particles have been prepared by means of precipitation in Japan and U.S.A., and ultrafine particles of rare earth oxide have been prepared with dicarboxyl precipitate by Wang Zenglin et al. It has not...Y_2O_3 ultrafine particles have been prepared by means of precipitation in Japan and U.S.A., and ultrafine particles of rare earth oxide have been prepared with dicarboxyl precipitate by Wang Zenglin et al. It has not been reported, however, to prepare La_2O_3 ultrafine particles with urea as the hydrolytic agent. This method is easy to operate, and the materials are cheap and easily available, besides, it is easy to obtain homogeneous spherical precursors of ultrafine particles. The present, paper describes the preparation of La_2O_3 ultrafine particles with urea as hydrolytic agent, and observes some of its characteristics.展开更多
文摘Ce0.6Zr0.4O2 solid solution ultrafine particle was prepared in the cyclohexane/water/OP-10/n-hexanol reversed microemulsion. The quasi-ternary phase diagram investigations showed that the system has narrow W/O type microemulison region, so it is the proper system to prepare Ce0.6Zr0.4O2 solid solution ultrafine particle. Some physical-chemical techniques such as TG/DTA, XRD, BET, and HRTEM are used to characterize the resultant powders. The results show that the fluorite cubic Ce0.6Zr0.4O2 solid solution is obtained at 400 ℃. The surface area is （146.7 m^2·g^-1）, which is higher than the surface area for sol-gel prepared sample （59.5m^2·g^-1）. HRTEM images indicated that the Ce0.6Zr0.4O2 solid solution ultrafine particle is well-crystallized, narrow size distribution, less agglomeration, within mean size of 5 -7 nm.
文摘The influence of different nanoparticle sizes on the elastic modulus and the fatigue properties of epoxy/SiO_(2) nanocomposite is studied in this paper.Here,the cross-linked epoxy resins formed by the combination of DGEBA and 1,3-phenylenediamine are used as the matrix phase,and spherical SiO_(2) particles are used as the reinforcement phase.In order to simulate the elastic modulus and long-term performance of the composite material at room temperature,the simulated temperature is set to 298 K and the mass fraction of SiO_(2) particles is set to 28.9%.The applied strain rate is 109/s during the simulation of the elastic modulus.The results show that the elastic modulus of the material increases with the increase in particle size.Furthermore,fatigue simulation under strain control is performed on the model with SiO_(2) nanoparticle radius of 12˚A.The results indicate that the influence trend of variable frequencies on the fatigue mechanical response is similar,and the mean stress decreases with the increase in number of cycles.In addition,the smaller the loading period and the more the number of cycles,the greater the mean stress reduction.Finally,the change in energy and free volume fraction are evaluated under fatigue loading condition.
文摘The SiO_2 particle material has weak electrorheological (ER) activity. The ER performance of the SiO_2 particles can be ameliorated after adsorbing Y_2(CO_3)_3. In this paper, the effect of Y_2(CO_3)_3 and different surfactants on the ER performance of the SiO_2 particle materials is investigated. The results show that anionic or cationic surfactants maybe enhance the ER activity of SiO_2 material, and nonionic surfactants cannot when surfactants are added during the process of the SiO_2 particle preparation, only the anionic surfactant, AES, can enhance markedly the ER performance of the material. The surface area, pore volume and pore diameter of the particles were measured. The effect of Y_2(CO_3)_3 and the surfactants on the microstructure of SiO_2 materials and the relationship between ER effect and the microstructure are described.
文摘Y_2O_3 ultrafine particles have been prepared by means of precipitation in Japan and U.S.A., and ultrafine particles of rare earth oxide have been prepared with dicarboxyl precipitate by Wang Zenglin et al. It has not been reported, however, to prepare La_2O_3 ultrafine particles with urea as the hydrolytic agent. This method is easy to operate, and the materials are cheap and easily available, besides, it is easy to obtain homogeneous spherical precursors of ultrafine particles. The present, paper describes the preparation of La_2O_3 ultrafine particles with urea as hydrolytic agent, and observes some of its characteristics.
文摘采用“两步法”分别将50 nm、500 nm粒径的SiO_(2)纳米颗粒加入去离子水中制备纳米悬浮液,采用稳定性分析仪测试SiO_(2)-H_(2)O纳米悬浮液的分散稳定性。结果显示:SiO_(2)-H_(2)O纳米悬浮液的不稳定性指数低于0.37,说明SiO_(2)纳米颗粒在去离子水中分散稳定。在此基础上,采用Hotdisk导热系数仪分别测试SiO_(2)-H_(2)O纳米悬浮液在25℃、-20℃下的导热系数,就颗粒浓度和粒径的影响进行研究。结果显示:SiO_(2)-H_(2)O纳米悬浮液在25℃下的液相导热系数随颗粒浓度的增大、粒径的减小而上升;在-20℃下由于冰的导热系数比SiO_(2)纳米颗粒大,SiO_(2)-H_(2)O纳米悬浮液的固相导热系数转而下降。采用Maxwell、Bruggeman、Yu and Choi和Xie提出的导热系数模型计算SiO_(2)-H_(2)O纳米悬浮液的液相和固相导热系数,与测试结果对比发现:导热系数模型能相对较好地预测SiO_(2)-H_(2)O纳米悬浮液的固相导热系数,但对悬浮液液相导热系数的预测存在很大偏差。分析认为,在纳米颗粒自身导热性能和其微观布朗运动对SiO_(2)-H_(2)O纳米悬浮液的导热强化中,纳米颗粒的微观布朗运动起到主要作用。
