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排序方式: 共有1455条查询结果,搜索用时 156 毫秒
1.
Sol-gel method has been used for the synthesis of biocompatible superparamagnetic nanoferrites of AFeO2 (A = Li, Na, K, Ca). Structural study of the nanoferrites reveals that LiFeO2 exhibits cubic phase on the other hand NaFeO2, KFeO2, CaFeO2 nanoparticles possess orthorhombic phase. Transmission electron microscopy (TEM) suggests that synthesized nanoferrites are nano-sized with spherical morphology. Optical properties confirm that nanoferrites emit and absorb light in a visible range of the electromagnetic spectrum. International Commission on Illumination (CIE) study discloses that the nanoparticles can be used to produce light of various colors. Magnetic study reveals that the nanoferrites exhibit superparamagnetic nature with high values of saturation magnetization 40.26 emu/g, 41.69 emu/g, 57.16 emu/g, and 43.66 emu/g, respectively for LiFeO2, NaFeO2, KFeO2, and CaFeO2. Biocompatibility study of the nanoferrites has been performed using Sulforhodamine B (SRB) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The reason behind the observed properties and behavior has been discussed. 相似文献
2.
Dielectric and nonohmic properties of CaCu3Ti4O12 (CCTO) ceramics can be modified by addition of SrTiO3 (STO) in different molar proportions which were fabricated by a modified sol-gel method. XRD results indicated that all modified ceramics showed mixed phase consisting of both CCTO and STO. SEM images and grain size distribution probability also presented the change of microstructure with the addition of STO. The dielectric loss of the CCTO/0.4STO ceramics sintered at 1000 °C can be lower than 0.02 in a wide frequency (1 kHz–10 kHz), especially at 1 kHz, the dielectric loss of this sample is as low as 0.012. Furthermore, excellent nonlinear I–V electrical characteristic (high breakdown voltage to 54.15 kV/cm for CCTO/0.4STO sintered at 1000 °C) was observed as well. All the results indicated that the addition of STO does improve the dielectric properties and nonohmic characteristics of CCTO ceramics dramatically. 相似文献
3.
《Current Applied Physics》2020,20(1):82-88
A detailed investigation about the effect of Sc2O3: 1 mol%Ho3+/5 mol%Yb3+ co-doped with Ce4+ ions prepared by sol-gel methods was performed systematically. Under the excitation of 980 nm laser diode, both green emission (553 nm, 5F4/5S2→5I8) and red emission (672 nm, 5F5→5I8) were both observed in the emission spectra of the samples, which were found to be two-photon process and sensitized by Yb3+ ions. With the increasing of Ce4+ ions, the up-conversion green emission intensity are increased by 6.52, 8.69, 10.85, 13.92 and 16.66 fold, corresponding to the Ce4+ ions concentrations from 5 mol% to 13 mol%, respectively. The number of photons are necessary to populate the upper emitting state decreases to 2 and the infrared absorption coefficient is reduced, when the Ce4+ ions concentration increase to 13 mol%. Ce4+ ions play an important role in tailoring the local crystal field around Ho3+ ions, lowering the highest phonon cut-off energy of matrix and reducing the infrared absorption coefficient, thus hindering the non-radiative processes, which contribute to the increased emission intensity. The excellent enhancement makes it a promising multifunctional optical luminescence material. 相似文献
4.
《Current Applied Physics》2020,20(3):462-469
Transparent heat-insulating SnO2 films were prepared on the glass substrate with sol-gel. The effects of Sb doping on the structure and photoelectric properties of the films were investigated. The films were characterized by scanning electron microscope (SEM), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), Ultraviolet–Visible-Near Infrared Spectrometer (UV-VIS-NIR) and Hall Effect tester. The results show that the doping of Sb did not change the basic crystal structure of the SnO2 film, but reduced the crystallinity of the film. With the increase of Sb doping, the grain size decreases first and then maintains basically invariable. The sheet resistance of the film decreases first and then increases. The transmittance of the substrate glass coated with this film (hereinafter referred to as the film's transmittance) in the near-infrared region (780–2500 nm) decreases from 92.55% to 60.48%, and increases a little when the doping amount exceeded 11 mol%. And its transmittance of visible light (380–780 nm) fluctuated slightly between about 81% and 86%. 相似文献
5.
《Arabian Journal of Chemistry》2023,16(5):104700
The bright blue nano crystallite cobalt aluminate (CoAl2O4) was synthesized by sol–gel method using a mixture of chelating agent of glycerol and citric acid. The effects of changing (0.05, 0.075, 0.10, 0.25, 0.50, and 0.75 mol/L) metal ion concentration on the structural, morphological and color properties of synthesized CoAl2O4 were characterized by using X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), Nanoparticle size analyzer, Simultaneous Thermal Analyzer (STA), UV–vis absorption spectroscopy, and CIE-LAB colorimetric analysis. From the X-ray peak profile analysis, the crystallite size was measured by Debye-Scherrer (D-S) equation, and three different models presenting average crystallite sizes between 88.3 and 125.4 nm.The average lattice strain, dislocation density, lattice constant, cell volume, and zeta potential were between 0.00021 and 0.0058, (1.73 to 12.8) × 1014 (lines/m2), 8.10658 to 8.11181 Å, 533.60 to 533.81 Å3, ?56.4 to ? 63.5 mV, respectively. Using UV–vis absorption spectroscopy, the band gap was calculated from Kubelka-Munk method, and the values of band gap increasing from 1.82 to 1.84 eV, respectively. The reflectance spectra and the CIE-L*a*b* values of cobalt aluminate is also measured which confirmed the formation of blue nano crystallite cobalt aluminate. 相似文献
6.
《印度化学会志》2021,98(4):100052
Zirconia (ZrO2) coating was developed on mild steel surface through an aqueous sol-gel route followed by heat treatment. The coating quality was optimized by varying dipping time, curing time, and drying temperature. ZrO2 coating was competent to prevent a substantial corrosion loss in 0.5 M–2 M hydrochloric acid with more than 90% efficiency. The morphology of coated surface has revealed the formation of a fine ZrO2 network on the metal surface at optimum conditions. This network is found to be effective to control steel deterioration in hydrochloric acid and the same appeared to be either cracked or irregular for less efficient formulations. 相似文献
7.
以环氧丙烷为凝胶剂,采用简便低廉的无表面活性剂的溶胶-凝胶法制备了一系列不同Cu/Fe摩尔比的高比表面积介孔Fe-Cu复合氧化物纳米粉末。运用微反应器-色谱体系考察了它们在低温CO氧化反应中的催化性能。采用X射线衍射、N2吸附-脱附、热重-差热分析、程序升温还原、傅里叶变换红外光谱和透射电镜对所制样品进行了表征。结果表明,这些介孔Fe-Cu复合氧化物催化剂具有纳米晶结构、窄的孔径分布和高的比表面积,在低温CO氧化反应中表现出高的活性和稳定性。 CuO的添加影响了Fe2O3的结构和催化性能。当CuO含量为15 mol%时,催化剂具有最高的比表面积和催化活性,在低温CO氧化反应中表现出较高的催化稳定性。 相似文献
8.
以氢氧化锂、乙酸锰、硝酸镁和钛酸丁酯为原料, 以柠檬酸为螯合剂, 采用溶胶-凝胶法制备了二价镁离子与四价钛离子等摩尔共掺杂的尖晶石型锂离子电池正极材料LiMn1.9Mg0.05Ti0.05O4. 采用热重分析(TGA), X射线衍射(XRD), 扫描电子显微镜(SEM), 透射电子显微镜(TEM)和电化学性能测试(包括循环伏安(CV)和电化学交流阻抗谱(EIS)测试)对所得样品的结构、形貌及电化学性能进行了表征. 结果表明: 780℃下煅烧12 h 得到了颗粒均匀细小的尖晶石型结构的LiMn1.9Mg0.05Ti0.05O4材料, 该材料具有良好的电化学性能, 在室温下以0.5C倍率充放电, 在4.35-3.30 V电位范围内放电比容量达到126.8 mAh·g-1, 循环50 次后放电比容量仍为118.5mAh·g-1, 容量保持率为93.5%. 在55℃高温下循环30次后的放电比容量为111.9 mAh·g-1, 容量保持率达到91.9%, 远远高于未掺杂的LiMn2O4的容量保存率. 二价镁离子与四价钛离子等摩尔共掺杂LiMn2O4, 改善了尖晶石锰酸锂的电子导电和离子导电性能, 使其倍率性能和高温性能都得到了明显的提高. 相似文献
9.
Xiao-Fei. SUN You-Long. XU Xiao-Yu. ZHENG Xiang-Fei. MENG Peng. DING Hang. REN Long. LI 《物理化学学报》2015,31(8):1513-1520
Li3V2(PO4)3 and its triple-cation-doped counterpart Li2.85Na0.15V1.9Al0.1(PO4)2.9F0.1 were prepared by a conventional sol-gel method. The effect of Na-Al-F co-doping on the physicochemical properties, especially the electrochemical performance of Li3V2(PO4)3, were investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS), Raman spectroscopy, scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS), galvanostatic charge/discharge, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). It was found that combined with surface coating from residual carbon, this triple-cation co-doping stabilizes the crystalline structure of Li3V2(PO4)3, suppresses secondary particle agglomeration, and improves the electric conductivity. Moreover, reversible deinsertion/insertion of the third lithium ion at deeper charge/discharge is enabled by such doping. As a consequence, the practical electrochemical performance of Li3V2(PO4)3 is significantly improved. The specific capacity of the doped material at a low rate of 1/9C is 172 mAh·g-1 and it maintains 115 mAh·g-1 at a rate of 14C, while the specific capacities of the undoped sample at 1/9C and 6C are only 141 and 98 mAh·g-1, respectively. After 300 cycles at 1C rate, the doped material has a capacity of 118 mAh·g-1, which is 32.6% higher than that of the undoped counterpart. It is also noteworthy that the multiplateau discharge curve of Li3V2(PO4)3 transforms to a slope-like curve, indicating the possibility of a different lithium intercalation mechanism after this co-doping. 相似文献
10.
The gelation of a ceramic precursor, zirconium alkoxide, has been studied using dynamic oscillatory measurements. The gelation time is controlled by varying the concentrations of zirconium propoxide, hydrolysis with water, and acetylacetone concentration which acts as a chelating ligand. Gelation times were varied from minutes to months. The gelation time varied with zirconium concentration to the –10 power, hydrolysis to the –7 power, and ligand concentration of the –17 power. The sol-gel transition was monitored using the criteria of Winter in which GG
n
and tan () = tan
. It is shown that the use of multiple superimposed sinusoidal waves to simultaneously measure the moduli at several frequencies is faster than using individual frequency sweep experiments. The selection of rate and strain criteria for brittle network gels is discussed in detail. 相似文献