Cobalt Phthalocyanine/Iron (CoPc/Fe) nanocomposite particles were prepared using mehods of organic inorganic composite in situ with cobalt phthalocyanine(CoPc) and carbonyl iron. The structure of composite particles w...Cobalt Phthalocyanine/Iron (CoPc/Fe) nanocomposite particles were prepared using mehods of organic inorganic composite in situ with cobalt phthalocyanine(CoPc) and carbonyl iron. The structure of composite particles was characterized by density measurement, XRD, SEM and TEM. The results show that CoPc/Fe nanocomposites with density of 3.99 g· cm－ 3 were almost micro sized regular spheroids consisting ofα Fe nanoparticles with average diameter 20 nm in inner and CoPc layer on the surface of spheroids. Further, microwave electromagnetic parameters of CoPc/Fe nanocomposite particles was measured, and the dependences ofε r andμ r on frequency were investigated. Compared with carbonyl iron powders, the composite permittivityε r significantly decreases while composite permabilityμ r changes slightly, which may increases the width of microwave absorbing frequency.展开更多
Abstract： Maghemite-silica particulate nanocomposites were prepared by modified 2-step sol-gel process. Superparamagnetic maghemite nanoparticles were successfully produced using Massart＇s procedure. Nanocomposites ...Abstract： Maghemite-silica particulate nanocomposites were prepared by modified 2-step sol-gel process. Superparamagnetic maghemite nanoparticles were successfully produced using Massart＇s procedure. Nanocomposites consisting of synthesized maghemite nanoparticles and silica were produced by dispersing the as-synthesized maghemite nanoparticles into the silica particulate form. The system was then heated at 140 ℃for 3 d. A variety of mass ratios of Fe2O3/SiO2 was investigated. Moreover, no surfactant or other unnecessary precursor was involved. The nanocomposites were characterized using XRD, BET and AGM. The XRD diffraction patterns show the reflection corresponding to maghemite nanoparticles and a visible wide band at 20 from 20° to 35° which are the characteristics of the amorphous phase of the silica gel. The patterns also exhibit the presence of only maghemite and SiO2 amorphous phase, which indicates that there is no chemical reaction between the silica particulate gel and maghemite nanoparticles to form other compounds. The calculated crystallite size for encapsulated maghemite nanoparticles is smaller than the as-synthesized maghemite nanoparticles indicating the dissolution of the nanoparticles. Very high surface area is attained for the produced nanocomposites （360-390 m^2/g）. This enhances the sensitivity and the reactivity of the nanocomposites. The shapes of the magnetization curves for nanocomposites are very similar to the as-synthesized maghemite nanoparticles. Superparamagnetic behaviour is exhibited by all samples, indicating that the size of the maghemite nanoparticles is always within the nanometre range. The increase in iron content gives rise to a small particle growth.展开更多
文摘Cobalt Phthalocyanine/Iron (CoPc/Fe) nanocomposite particles were prepared using mehods of organic inorganic composite in situ with cobalt phthalocyanine(CoPc) and carbonyl iron. The structure of composite particles was characterized by density measurement, XRD, SEM and TEM. The results show that CoPc/Fe nanocomposites with density of 3.99 g· cm－ 3 were almost micro sized regular spheroids consisting ofα Fe nanoparticles with average diameter 20 nm in inner and CoPc layer on the surface of spheroids. Further, microwave electromagnetic parameters of CoPc/Fe nanocomposite particles was measured, and the dependences ofε r andμ r on frequency were investigated. Compared with carbonyl iron powders, the composite permittivityε r significantly decreases while composite permabilityμ r changes slightly, which may increases the width of microwave absorbing frequency.
基金Project(RP021-2012C)supported by University of Malaya under the UMRG Fund,Malaysia
文摘Abstract： Maghemite-silica particulate nanocomposites were prepared by modified 2-step sol-gel process. Superparamagnetic maghemite nanoparticles were successfully produced using Massart＇s procedure. Nanocomposites consisting of synthesized maghemite nanoparticles and silica were produced by dispersing the as-synthesized maghemite nanoparticles into the silica particulate form. The system was then heated at 140 ℃for 3 d. A variety of mass ratios of Fe2O3/SiO2 was investigated. Moreover, no surfactant or other unnecessary precursor was involved. The nanocomposites were characterized using XRD, BET and AGM. The XRD diffraction patterns show the reflection corresponding to maghemite nanoparticles and a visible wide band at 20 from 20° to 35° which are the characteristics of the amorphous phase of the silica gel. The patterns also exhibit the presence of only maghemite and SiO2 amorphous phase, which indicates that there is no chemical reaction between the silica particulate gel and maghemite nanoparticles to form other compounds. The calculated crystallite size for encapsulated maghemite nanoparticles is smaller than the as-synthesized maghemite nanoparticles indicating the dissolution of the nanoparticles. Very high surface area is attained for the produced nanocomposites （360-390 m^2/g）. This enhances the sensitivity and the reactivity of the nanocomposites. The shapes of the magnetization curves for nanocomposites are very similar to the as-synthesized maghemite nanoparticles. Superparamagnetic behaviour is exhibited by all samples, indicating that the size of the maghemite nanoparticles is always within the nanometre range. The increase in iron content gives rise to a small particle growth.
