The lanthanum aluminum mesoporous materials were synthesized using sodium dodecyl sulfate as a template agent by ultrasonic hydrothermal method.The resulting samples were characterized by low angle X-ray diffraction（...The lanthanum aluminum mesoporous materials were synthesized using sodium dodecyl sulfate as a template agent by ultrasonic hydrothermal method.The resulting samples were characterized by low angle X-ray diffraction（XRD）,N2 adsorption-desorption studies,transmission electron microscopy（TEM）and surface morphology analysis（SEM）,surface acid（NH3-TPD）,reducibility properties（TPR）,X-ray energy dispersive spectrometer（EDS）and thermogravimetric analysis（TG/DTG）.A l/La composite mesoporous material were synthesized with n（Al）︰n（La）=70︰1.0,80°C of reaction temperature,20 h of reaction time,12 h of crystallization time,650°C of calcination temperature.The specific surface area of the sample is 273.90 m 2 ·g ？1 ,with the average diameter 5.642 nm and pore volume 0.2354 cm 3 ·g ？1 .The samples have mesoporous structure and its particles are similar to a worm-shaped tubular structure.The influence of calcination temperature on the surface physical and chemical properties of Al/La composited mesoporous materials was examined,and the results showed that the acid strength was increased but the amount of acidic sites is decreased as the calcination temperature increased.It was found that the sample calcined at 650°C had appropriate acid content,acid strength and better reducibility.展开更多
Polyvinyl Pyrrolidone（PVP）/（Lanthanum nitrate and Manganese acetate） composite microfibres were fabricated by electrospinning technique. SEM micrographs indicated that the surface of the composite microfibres was ...Polyvinyl Pyrrolidone（PVP）/（Lanthanum nitrate and Manganese acetate） composite microfibres were fabricated by electrospinning technique. SEM micrographs indicated that the surface of the composite microfibres was smooth, and the diameter of the microfibres was in the range of 1-2μm. XRD analysis revealed that the composite microfibres were amorphous in structure. LaMnO3 ultrafine fibres were fabricated by calcination of the PVP/[La（NO3）3＋Mn（CH3COO）2] composite microfibres, The diameters of LaMnO3 ultrafine fibres were smaller than those of the PVP/[La（NO3）3＋Mn（CH3COO）2] composite microfibres. The surface of the LaMnO3 ultrafine fibres became coarse with the increase of calcination temperatures. LaMnO3 hollow-centered and porous ultrafine fibres formed by nanoparticles were acquired when firing temperature was 600-900℃. SEM analysis indicated that the diameters of the synthesized LaMnO3 ultrafine fibres were in the range of 500-800 nm with the mean wall thickness of 100 nm, and their lengths were greater than 100 ~tm. XRD analysis revealed that the crystal structure of LaMnO3 ultrafine fibres was orthorhombic with space group Pbnm. Possible formation mechanism for LaMnO3 ultrafine fibres was preliminarily proposed.展开更多
Porous Fe3O4 sub-micro particles with sphere-like, cube-like and walnut-like morphologies were obtained by a two-step process, and the electromagnetic properties of the Fe3O4 particle/wax composites were investigated....Porous Fe3O4 sub-micro particles with sphere-like, cube-like and walnut-like morphologies were obtained by a two-step process, and the electromagnetic properties of the Fe3O4 particle/wax composites were investigated. The reflect loss was less than -20 dB for all of the composites in different frequency ranges. The cube-like and walnut-like Fe3O4 composites exhibit improved complex permittivity and permeability and dual-frequency and wide bandwidth absorption characteristics, which is mainly attributed to the larger shape anisotropy. Such a high absorption property indicates that these porous Fe3O4 particles with various morphologies are very promising for electromagnetic wave absorptive materials.展开更多
文摘The lanthanum aluminum mesoporous materials were synthesized using sodium dodecyl sulfate as a template agent by ultrasonic hydrothermal method.The resulting samples were characterized by low angle X-ray diffraction（XRD）,N2 adsorption-desorption studies,transmission electron microscopy（TEM）and surface morphology analysis（SEM）,surface acid（NH3-TPD）,reducibility properties（TPR）,X-ray energy dispersive spectrometer（EDS）and thermogravimetric analysis（TG/DTG）.A l/La composite mesoporous material were synthesized with n（Al）︰n（La）=70︰1.0,80°C of reaction temperature,20 h of reaction time,12 h of crystallization time,650°C of calcination temperature.The specific surface area of the sample is 273.90 m 2 ·g ？1 ,with the average diameter 5.642 nm and pore volume 0.2354 cm 3 ·g ？1 .The samples have mesoporous structure and its particles are similar to a worm-shaped tubular structure.The influence of calcination temperature on the surface physical and chemical properties of Al/La composited mesoporous materials was examined,and the results showed that the acid strength was increased but the amount of acidic sites is decreased as the calcination temperature increased.It was found that the sample calcined at 650°C had appropriate acid content,acid strength and better reducibility.
文摘Polyvinyl Pyrrolidone（PVP）/（Lanthanum nitrate and Manganese acetate） composite microfibres were fabricated by electrospinning technique. SEM micrographs indicated that the surface of the composite microfibres was smooth, and the diameter of the microfibres was in the range of 1-2μm. XRD analysis revealed that the composite microfibres were amorphous in structure. LaMnO3 ultrafine fibres were fabricated by calcination of the PVP/[La（NO3）3＋Mn（CH3COO）2] composite microfibres, The diameters of LaMnO3 ultrafine fibres were smaller than those of the PVP/[La（NO3）3＋Mn（CH3COO）2] composite microfibres. The surface of the LaMnO3 ultrafine fibres became coarse with the increase of calcination temperatures. LaMnO3 hollow-centered and porous ultrafine fibres formed by nanoparticles were acquired when firing temperature was 600-900℃. SEM analysis indicated that the diameters of the synthesized LaMnO3 ultrafine fibres were in the range of 500-800 nm with the mean wall thickness of 100 nm, and their lengths were greater than 100 ~tm. XRD analysis revealed that the crystal structure of LaMnO3 ultrafine fibres was orthorhombic with space group Pbnm. Possible formation mechanism for LaMnO3 ultrafine fibres was preliminarily proposed.
基金supported by the National Natural Science Foundation of China (Grant Nos. 51072038, 50772025 and 21001035)NECT, Outstanding Youth Foundation of Heilongjiang Province (Grant No. JC201008)+4 种基金the Natural Science Foundation of Heilongjiang Province, China (Grant No. F200828)the Ministry of Science and Technology of China (Grant No. 2008DFR20420)the Fundamental Research Funds for the Central Universities (Grant Nos. HEUCFT1010, HEUCF101016, HEUCF20111124 and HEUCF101016)the National Basic Research Program of China (Grant No. 2007CB310500)Harbin Key Sci-Tech Project (Grant No. 2010AA4BG004)
文摘Porous Fe3O4 sub-micro particles with sphere-like, cube-like and walnut-like morphologies were obtained by a two-step process, and the electromagnetic properties of the Fe3O4 particle/wax composites were investigated. The reflect loss was less than -20 dB for all of the composites in different frequency ranges. The cube-like and walnut-like Fe3O4 composites exhibit improved complex permittivity and permeability and dual-frequency and wide bandwidth absorption characteristics, which is mainly attributed to the larger shape anisotropy. Such a high absorption property indicates that these porous Fe3O4 particles with various morphologies are very promising for electromagnetic wave absorptive materials.
