A modified polyacrylamide gel route was used to prepare SrFe12O19 magnetic nanoparticles; ethylenediaminetetraacetic acid (EDTA) was used as a carboxyl chelating agent. The phase purity, morphology and magnetic properties of as-prepared samples were analyzed via X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating sample magnetometery (VSM). XRD analysis indicates that high-purity SrFe12O19 magnetic nanoparticles can be synthesized at 700°C in air. The characteristic peaks of as-prepared sample at 210, 283, 321, 340, 381, 411, 432, 475, 532, 618, 686, and 726 cm–1 were observed in Raman spectra. SEM and TEM show that the synthesized SrFe12O19 magnetic nanoparticles are uniform with the mean particle size of ~60 nm. VSM measurement shows that the maximum magnetic energy product (BH)max of sample prepared using EDTA as a chelating agent is higher than that of sample prepared using citric acid as a chelating agent.
A one-pot, three-component reaction of aromatic aldehydes, 2-hydroxy-1,4-naphthoquinone, and 3,4-methylenedioxyphenol has been reported for the synthesis of novel 7-aryl-6H-benzo[h][1,3]dioxolo[4,5-b]xanthene-5,6(7H)-diones using environmentally benevolent para-toluene sulfonic acid (p-TSA) as the catalyst. This methodology provides a mild and fast route to diverse pyran derivatives in moderate to good yields. 相似文献
A metal-free protocol for the selective cleavage of unstrained C–C single bonds was developed. Under the catalysis of KI and in the presence of NaHCO3, the readily available α-chloro-β-hydroxy ketones underwent bond breaking and sulfonylation smoothly to afford β-ketosulfones with high efficiency and broad substrate scope. Mechanism investigations, both experimental and theoretical, showed that a retro-aldol cleavage/nucleophilic substitution sequence might be involved. 相似文献
In this work,the effect of dioctadecyl dimethyl ammonium chloride(DDAC,a kind of alkyl ammonium salt) on polar β phase content and the diameter of electrospun PVDF nanofibers was investigated for the first time.Our experimental results show that the diameter of the electrospun PVDF nanofiber could be largely reduced and the content of polar β phase also become dominant immediately by just adding a little amount of DDAC.When the mass fraction of DDAC reached 4%,the content of polar β phase increased by about 39.1% compared with PVDF nanofibers without DDAC.Besides,the crystallinity of PVDF nanofibers also increased with the addition of DDAC.Based on the results,the possible mechanism of cooperative effect between electrospinning and DDAC on fiber diameter and formation of β phase in PVDF was discussed. 相似文献
The neonicotinoid imidacloprid is a very important insecticide in maize cultivation in China. A laboratory experiment was conducted to investigate its absorption, transportation and distribution in maize plants. Plants were exposed to an aqueous solution of imidacloprid at five concentrations (10, 20, 50, 100 and 200 μg/mL). The residues of imidacloprid in different plant parts were determined by using a quick and effective method of high-performance liquid chromatography. Results showed that the average recoveries ranged from 85.16% to 102.23%, with relative standard deviations of 1.82–4.40% at three different spiking levels in each different matrix. The half-lives of imidacloprid in hydroponic maize water were from 5.33 to 11.55 days. The concentrations in roots, stems and leaves were from 5.61 to 7.48, 1.03 to 4.03 and 0 to 30.57 μg/mL after 6 h–7 days exposed in 10 μg/mL imidacloprid aqueous solutions, respectively. Our study showed that imidacloprid was strongly absorbed by roots and mainly accumulated in leaves. Quantity ratio and bioconcentration factors (BCFs) were also used to estimate the distribution and accumulation in maize. The values of quantity ratios were the highest in the leaves while lowest in the root after 7 days treatments, with the ranking of leaves > stem > root. The BCFs were 0.63–1.66, 0.52–0.92 and 3.20–6.78 in root, stem and leaves, respectively. These results demonstrated that the exposed time and imidacloprid application concentrations were also the main factors influencing the absorption. This study enhances our understandings of the uptake and distribution of imidacloprid in maize plants. 相似文献
Analytical studies on electromagnetoelastic behaviors are
presented for the functionally graded piezoelectric material (FGPM) solid
cylinder and sphere placed in a uniform magnetic field and subjected to the
external pressure and electric loading. When the mechanical, electric and
magnetic properties of the material obey an identical power law in the
radial direction, the exact displacements, stresses, electric potentials and
perturbations of magnetic field vector in the FGPM solid cylinder and sphere
are obtained by using the infinitesimal theory of electromagnetoelasticity.
Numerical examples also show the significant influence of material
inhomogeneity. It is interesting to note that selecting a specific value of
inhomogeneity parameter can optimize the electromagnetoelastic
responses, which will be of particular importance in modern engineering
designs. 相似文献