Semiconductor CdS nanoparticles were synthesized by the sonochemical reduction of a mixed aqueous solution of CdCl2, Na2S2O3 and (CH3)CHOH in Ar atmosphere at room temperature. The results of a detailed investigation ...Semiconductor CdS nanoparticles were synthesized by the sonochemical reduction of a mixed aqueous solution of CdCl2, Na2S2O3 and (CH3)CHOH in Ar atmosphere at room temperature. The results of a detailed investigation with X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectrum and optical absorption spec-troscopy are reported. A clearly red shift of the absorption edge and a broad absorption band related to the surface states of nanoparticles have been observed in the optical absorption spectra with the increasing of CdS particle size. The mechanisms of the CdS nanoparticle formation and size growth during sonochemical irradiation were discussed. This convenient method is found to be an efficient way to produce other chalcogenides as well.展开更多
Homogeneous Ni2+-doped titania gel was synthesized by a sol-gel process, and the xerogel was then ob-tained through aging and drying, leading to the formation of Ni/TiO2 nanocomposite after heat treatment under a suit...Homogeneous Ni2+-doped titania gel was synthesized by a sol-gel process, and the xerogel was then ob-tained through aging and drying, leading to the formation of Ni/TiO2 nanocomposite after heat treatment under a suitable reducing atmosphere. The resulting nanocomposite was characterized by TGA-DSC, TEM, XRD and BET methods. The results show that the structure and grain size of the nanocomposites could be manipulated by altering the heat-treatment conditions, and that the nanocomposite possesses a mesoporous structure with a pore radius of ca. 28 nm and a specific surface area of 49.1 m2.g-1. It is demonstrated that the nanosized Ni dispersion in the titania matrix significantly affects the anatase-rutile phase transformation.展开更多
Nanosized palladium particles were incorporated into mesoporous silica matrix to obtain nanocomposites using the sol-gel technique. Effects of the finely dispersed metallic palladium on the microstructure and properti...Nanosized palladium particles were incorporated into mesoporous silica matrix to obtain nanocomposites using the sol-gel technique. Effects of the finely dispersed metallic palladium on the microstructure and properties of the nanocomposites were investigated. By means of X-ray diffraction and optical absorption, it was found that palladium particles were 5~9 nm in diameter and their uniform dispersion in the mesoporous silica depended on both the content of the palladium and the structural features of the silica matrix. The results showed that the mixing method of preparation led to wider size distribution of the nanosized particles as compared to the immersion method, but dispersed degree was reduced. Although the incorporation of nanosized palladium particles could not substantially induce significant structural changes of the matrix, the apparent red-shifted optical absorptions for the nanocomposites were observed as compared to the parent monolithic silica, particularly with increase in palladium loading and calcination temperature.展开更多
This paper presents the preparation of ultrafine powders of Fe3O4 and Ni by a chemical method, followed by mixing the prepared powders with mica and other ultrafine powders for synthesizing microwave absorption coatin...This paper presents the preparation of ultrafine powders of Fe3O4 and Ni by a chemical method, followed by mixing the prepared powders with mica and other ultrafine powders for synthesizing microwave absorption coatings. The microwave attenuation rate of the coatings was measured by the Microwave Network Analyzer in the frequency range of 8-12 GHz at room temperature. The results indicate that microwave could be absorbed by the coatings with an effectiveness strongly dependent on the powder sort and content and the coating thickness.展开更多
基金This work was supported by the National Key Basic Research Project(G1999064501)the Natural Science Foundation of Anhui Province(No.01044903).
文摘Semiconductor CdS nanoparticles were synthesized by the sonochemical reduction of a mixed aqueous solution of CdCl2, Na2S2O3 and (CH3)CHOH in Ar atmosphere at room temperature. The results of a detailed investigation with X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectrum and optical absorption spec-troscopy are reported. A clearly red shift of the absorption edge and a broad absorption band related to the surface states of nanoparticles have been observed in the optical absorption spectra with the increasing of CdS particle size. The mechanisms of the CdS nanoparticle formation and size growth during sonochemical irradiation were discussed. This convenient method is found to be an efficient way to produce other chalcogenides as well.
基金support from Anhui Natural Science Foundation(Grant No.00046403)“973”Key Project of the National Fundamental Research of China,Nanomaterials and Nanostructure(Grant No.G19990645)Creative Program of Chinese Academy of Sciences in Nano—structured Materials Field
文摘Homogeneous Ni2+-doped titania gel was synthesized by a sol-gel process, and the xerogel was then ob-tained through aging and drying, leading to the formation of Ni/TiO2 nanocomposite after heat treatment under a suitable reducing atmosphere. The resulting nanocomposite was characterized by TGA-DSC, TEM, XRD and BET methods. The results show that the structure and grain size of the nanocomposites could be manipulated by altering the heat-treatment conditions, and that the nanocomposite possesses a mesoporous structure with a pore radius of ca. 28 nm and a specific surface area of 49.1 m2.g-1. It is demonstrated that the nanosized Ni dispersion in the titania matrix significantly affects the anatase-rutile phase transformation.
文摘Nanosized palladium particles were incorporated into mesoporous silica matrix to obtain nanocomposites using the sol-gel technique. Effects of the finely dispersed metallic palladium on the microstructure and properties of the nanocomposites were investigated. By means of X-ray diffraction and optical absorption, it was found that palladium particles were 5~9 nm in diameter and their uniform dispersion in the mesoporous silica depended on both the content of the palladium and the structural features of the silica matrix. The results showed that the mixing method of preparation led to wider size distribution of the nanosized particles as compared to the immersion method, but dispersed degree was reduced. Although the incorporation of nanosized palladium particles could not substantially induce significant structural changes of the matrix, the apparent red-shifted optical absorptions for the nanocomposites were observed as compared to the parent monolithic silica, particularly with increase in palladium loading and calcination temperature.
文摘This paper presents the preparation of ultrafine powders of Fe3O4 and Ni by a chemical method, followed by mixing the prepared powders with mica and other ultrafine powders for synthesizing microwave absorption coatings. The microwave attenuation rate of the coatings was measured by the Microwave Network Analyzer in the frequency range of 8-12 GHz at room temperature. The results indicate that microwave could be absorbed by the coatings with an effectiveness strongly dependent on the powder sort and content and the coating thickness.
