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1.
Shichong Xu Zhihe Wang Rui Su Na Han Ailing Xie Li Wang Haibo Li 《Ceramics International》2018,44(8):9377-9383
Multi-morphological CoFe2O4/CoFe nanocomposites have been synthesized using a facile hydrothermal process. The effects of hydrazine hydrate amount during hydrothermal reaction on the structure and magnetic property of the specimens were studied. With increasing hydrazine hydrate amount, the CoFe2O4 transformed to CoFe and the morphology of the specimen changed from granular particles to faceted particles. The saturation magnetization monotonically increased and the coercivity monotonically decreased with increasing hydrazine hydrate amount. The magnetic interactions, determining the magnetic properties of the composites, result from the dominant dipole coupling and relative weak exchange coupling between CoFe2O4 and CoFe nanoparticles. The CoFe2O4/CoFe nanocomposite prepared with 2?mL hydrazine hydrate exhibited the optimal magnetic properties, with the saturation magnetization of 81?emu/g and coercivity of 636?Oe. 相似文献
2.
T. Karpova V. VassilievE. Vladimirova V. OsotovM. Ronkin A. Nosov 《Ceramics International》2012,38(1):373-379
Peculiarities of synthesis of nanocrystalline NiFe2O4 powders by thermal decomposition of citrate precursors were investigated. It was found that the parameters of nanopowders are determined by the decomposition temperature and pH of the precursor media. The temperature and duration of the process of precursor decomposition are limiting factors for decrease of the grain size. An optimum relation between the limiting factors can be determined experimentally by variation of pH. Correlation between the synthesis parameters, particle size, and magnetic properties is discussed. It is shown that optimum magnetic and magnetostrictive properties were found for the bulk polycrystalline samples sintered using the powders obtained for pH 2. 相似文献
3.
NiFe2O4 powders were prepared by combustion synthesis, polyol-mediated and sol–gel methods. Morphological characterization of sintered disks was carried out using scanning electron microscopy (SEM). Dielectric properties of NiFe2O4 synthesized by different routes were investigated over the frequency range of 100 Hz–5 MHz at room temperature. A difference in dielectric constant (εr) and dissipation factor (tan δ) of NiFe2O4 samples obtained by different synthesis methods has been observed. The observed dissimilarity in the behavior originates from the variation in the microstructure of the samples that is evident in the Cole–Cole plot results. 相似文献
4.
Uniform MoS2 nanosheets/C hybrid microspheres with mean diameter of 320 nm have been successfully synthesized via a facile one-pot hydrothermal route by sodium molybdate reacting with sulfocarbamide in d-glucose solutions. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). XRD patterns showed that the MoS2 was kept as a two-dimensional nanosheet crystal and C was retained as amorphous even after their annealing treatment at 800 °C. TEM and SEM images indicated that the MoS2 nanosheets were uniformly dispersed in the amorphous carbon. The experiment results also revealed that the appropriate amount of d-glucose had an obvious effect on the formation of uniform MoS2 nanosheets/C hybrid microspheres. A possible formation process of MoS2 nanosheets/C hybrid microspheres was preliminarily presented. 相似文献
5.
Jinhui Dai Chao ZhangLeiyan Shi Wenwen SongPingwei Wu Xiang Huang 《Ceramics International》2012,38(2):1211-1214
ZnNb2O6 powder was successfully synthesized via hydrothermal method with Nb2O5 and Zn(NO3)2·6H2O as raw materials and cyclohexane as solvent. Phase composition, morphology, and chemical composition were determined via a combination of XRD, SEM, TEM and EDS techniques. The effects of synthesis temperature and reaction time on phase composition and particle morphology were investigated in this paper. The results showed that fine ZnNb2O6 powders could be obtained at a hydrothermal temperature of 190 °C or above under different reaction time. 相似文献
6.
D.A. Permin S.S. Balabanov A.V. Novikova I.L. Snetkov O.V. Palashov A.A. Sorokin M.G. Ivanov 《Ceramics International》2019,45(1):522-529
A comparative analysis of sintering and grain growth processes of lutetium oxide and lutetium-yttrium-lanthanum oxides solid solutions, as well as optical properties, luminescence and laser generation of (LuxY0.9-xLa0.05Yb0.05)2O3 transparent ceramics are reported. Fabrication of highly dispersed initial powders of these compounds was performed via nitrate-glycine self-propagating high-temperature synthesis (SHS) method. The powders were compacted at 300?MPa and vacuum sintered at temperatures up to 1750?°С. Optical ceramics of (Lu0.65Y0.25La0.05Yb0.05)2O3 elemental composition were shown to have the highest in-line transmittance, which achieved 78% at the wavelength of 800?nm. Generation of laser radiation at a wavelength of 1032?nm with the differential efficiency of 20% was demonstrated in the (Lu0.65Y0.25La0.05Yb0.05)2O3 ceramics. 相似文献
7.
Bismuth zinc niobate posses a cubic pyrochlore structure and normally is obtained by the conventional solid-state reaction. The great disadvantage of this method is the lack of chemical homogeneity, requiring high synthesis and sintering temperatures (higher than 1000 °C), which is an impeditive for BZN application in LTCC with silver as the internal electrode. The aim of this paper is to compare, from synthesis to sintering, BZN ceramics, derived either from chemically or conventionally synthesized powders, sintered either in both conventional oven for 2 h or microwave oven for 15 min. The results showed that chemically synthesized BZN ceramics sintered in microwave oven at 900 °C for 15 min presented a relative density of 97%, while those obtained by conventional method required 1000 °C to reach the same density. Despite the short period for thermal treatment in microwave oven, the electrical properties of BZN ceramics are compatible with those sintered in conventional oven for 2 h. 相似文献
8.
Robert Ianoş Radu LazăuRoxana Băbuƫă Silvana BorcănescuCristian Renato Boruntea 《Ceramics International》2013
In order to achieve BaAl2O4 formation via combustion synthesis, two types of recipes were designed: single fuel recipes (urea, glycine, β-alanine or hexamethylenetetramine) and innovative fuel mixture recipes (urea+glycine, urea+β-alanine and urea+hexamethylenetetramine respectively). No combustion reactions were noticed in the case of single fuel recipes based on urea or hexamethylenetetramine. The only crystalline phase present in the case of the powders obtained in such a way was unreacted Ba(NO3)2. Glycine and β-alanine generated smoldering reactions, leading to the formation of black powders, which consist of Ba(NO3)2, BaCO3 and traces of BaAl2O4 (in the case of β-alanine). Fuel mixture recipes proved to be better than single fuel recipes, yielding BaAl2O4 as main crystalline phase. The specific surface area of the resulted powders ranges between 2.0 and 3.9 m2/g. The urea and glycine fuel mixture was the most efficient yielding BaAl2O4 with an average crystallite size of 60 nm. 相似文献
9.
Dana Gingasu Ioana Mindru Luminita Patron Gabriela Marinescu Floriana Tuna Silviu Preda Jose Maria Calderon-Moreno Cristian Andronescu 《Ceramics International》2012
Copper gallate spinels, CuGa2O4, have been synthesized by two wet chemical routes: precursor method and self-propagating combustion involving a glycine-nitrate system. All complex precursors have been characterized by chemical analysis, infrared spectroscopy (IR), ultraviolet visible spectroscopy (UV–vis), electron paramagnetic resonance spectroscopy (EPR), thermal analysis and scanning electron microscopy (SEM). The copper gallate spinel oxides have been further investigated by X-ray diffraction (XRD), SEM, IR, UV–vis, magnetic measurements and EPR. The crystallite size of the copper gallate was found about 280 Å. 相似文献
10.
Seung Ho Han Kyoung Sun Kim Ho Gi Kim Hyeung-Gyu Lee Hyung-Won Kang Jeong Seog Kim Chae Il Cheon 《Ceramics International》2010
The influence of processing parameters on phase formation and particle size of hydrothermally synthesized BiFeO3 powders was investigated. BiFeO3 powder was synthesized by dissolving bismuth nitrate and iron nitrate in KOH solution at temperatures ranging from 150 to 225 °C. X-ray diffraction patterns and scanning electron microscopy observation indicated that rod-like α-Bi2O3 phase was formed at initial stage of reaction and dissolved into ions to form thermodynamically stable BiFeO3 phase. Single-phase perovskite BiFeO3 has been formed using a KOH concentration of 8 M at a temperature of ≥175 °C in a 6 h reaction period. BiFeO3 particle growth was promoted by lowering the KOH concentration, or increasing the duration time or reaction temperature. The effects of processing conditions on the formation of crystalline BiFeO3 powders were discussed in terms of a dissolution–precipitation mechanism. The magnetization of the BiFeO3 powders at room temperature showed a weak a ferromagnetic nature. 相似文献
11.
《Ceramics International》2017,43(12):8585-8589
In the work, we explored an efficient synthetic platform to purposefully fabricate different morphologies of NiCo2O4 by controlling the hydrothermal temperature. All the obtained samples were characterized by means of X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy. With the increase of hydrothermal temperature, the morphology of obtained samples transformed from spongy nanosphere to ellipse-like, then to peanut-like structure and an effective blue shifting of Raman spectroscopy occurred. The magnetic measurements indicated that the materials transform from paramagnetic to weak ferromagnetic with the increase of hydrothermal temperature. 相似文献
12.
In the present work, the results of the influence of diamagnetic additives on the defects level of ferrite ceramics, its microstructure and magnetic properties are presented. A method based on a mathematical analysis of the experimental temperature dependences of the initial permeability was used for estimation of the defects level in the samples. Model samples containing a controlled amount of the diamagnetic additive Al2O3 served to test the possibility of monitoring this method of nonmagnetic phases of ferrite ceramics. It was shown that with an increase in the concentration of the Al2O3 additive in the range of (0–0.5) wt%, a significant increase in the defects level was observed almost 6-fold. The data from SEM micrographs showed that the addition of Al2O3 affects the type of grains of ferrite ceramics, but does not affect their grain size. Grains are highly agglomerated and show large grain size dispersion and also pore. Obtained data were compared to hysteresis loop parameters. It is shown that with an increase in the concentration of the Al2O3 addition, there is a regular decrease in the residual induction and an increase in the coercive force. However, such changes in hysteresis loop parameters are small in comparison to defects level. Investigations of the true physical broadening of the diffraction reflections were performed for the same model samples in order to compare the change in the defects level to the direct X-ray diffraction measurements of micro deformations. The defects level as a characteristic of the elastic stress of a ferrite ceramics is proposed. This assumption follows from a linear relationship between the defects level and the width of the diffraction reflections. The consistency of the obtained results made it possible to evaluate the high efficiency and sensitivity of the method for defects level estimating. 相似文献
13.
Eu-based vanadate Ca9Eu(VO4)7 phosphor was synthesized by the solid state reaction method and was characterized by X-ray powder diffraction (XRD). The photoluminescence excitation and emission spectra, fluorescence decay curves and the dependence of luminescence intensity on temperature were investigated. The phosphor can be efficiently excited by near UV light to realize an intense red luminescence (614 nm) corresponding to the electric dipole transition 5D0 → 7F2 of Eu3+ ions. The crystallographic site-occupations of the Eu3+ ions in Ca9Eu(VO4)7 were investigated by the site-selective excitation and emission spectra, and the fluorescence decay curves in the 5D0 → 7F0 region using a pulsed, tunable, narrowband dye laser. The red luminescence together with the thermal stability was discussed on the base of the Eu3+ site-distribution in Ca9Eu(VO4)7 host. 相似文献
14.
Dielectric (εr′) studies of phase pure T′-type Eu2CuO4 ceramics of two markedly different grain sizes (D), prepared by (i) conventional powder mixing and (ii) citrate complexation-Pechini process, have been carried out in the frequency range 0.1 Hz to 1 MHz, and at temperatures −100 °C to 150 °C. εr′ is found to be highly grain size dependent. For the sample with coarse bar-like grains (D2~17×6 μm2) εr′ is >103, and for the finer grain size sample with bimodal distribution (D1~1 μm, D2~3 μm) εr′ is ~105; for both the samples, high εr′ value is nearly frequency independent over 500 Hz≤f<100 kHz and T≥30 °C. The impedance spectroscopy (IS) study has clearly shown that both, the coarse- and the fine-grained samples consist of semiconducting grains and insulating grain boundaries that primarily lead to an internal barrier layer capacitance (IBLC) effect. And thus, manifest colossal dielectric constant (εr′>103) in Eu2CuO4 ceramics. The smaller grain size (Pechini) sample, with over an order higher number of grains and grain boundary network, showing over an order higher εr′ (~105) compared to the coarse grained one, further endorses the IBLC effect. 相似文献
15.
The red-emitting (Y1−xGdx)0.94Eu0.06VO4 (0 ≤ x ≤ 1.0) phosphors were synthesized by ultrasonic spray pyrolysis. The (Y1−xGdx)0.94Eu0.06VO4 (0 ≤ x ≤ 1.0) phosphors had the tetragonal xenotime structure with a space group of I41/amd (1 4 1). The calculated crystallite sizes of the annealed phosphors ranged from 58 to 68 nm. In this study, we discussed the photoluminescence properties of the (Y1−xGdx)0.94Eu0.06VO4 phosphors under VUV excitation, depending on Gd content. The emission intensity of the (Y1−xGdx)0.94Eu0.06VO4 phosphors increased with increasing Gd content up to x = 0.5, and then decreased with a further increase in Gd content. The purest red color was obtained for the (Y0.5Gd0.5)0.94Eu0.06VO4 phosphors. 相似文献
16.
Herein, we report a facile homogeneous urea – assisted hydrothermal approach for the design of CoFe2O4/Co3O4 nano hetrostructure. A variation in Co concentration leads to smartly designed composite material namely CFC-11 and CFC-12 where CFC-12 appreciates the benefits of both CoFe2O4 and Co3O4 nanoparticles. The physico – chemical properties of as developed materials were investigated by X-ray diffraction (XRD), field emission electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), X-ray photoelectron microscopy (XPS) and Raman spectroscopy. The specific surface area and pore size distribution was determined by Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halendo (BJH) respectively. Magnetic measurements via. vibrating sample magnetometer (VSM) demonstrate that saturation magnetization decreases with the incorporation of Co3O4 antiferromagnetic nanoparticles. To explore the utility of as designed nano-hetrostructures as supercapacitor electrodes, we employed cyclic voltammetry (CV) and electrochemical impedence spectroscopy (EIS) measurements. A high specific capacitance of 761.1?F?g?1 at 10?mV?s?1, admirable cyclic durability of 92.2% and a low resistance value obtained from impedence measurements was observed for CFC-12. The favorable performance demonstrates the synergistic effect of CoFe2O4 and Co3O4 nanoparticles and thus promise an excellent material for energy storage devices. 相似文献
17.
Ce2(WO4)3 ceramics have been synthesized by the conventional solid-state ceramic route. Ce2(WO4)3 ceramics sintered at 1000 °C exhibited ?r = 12.4, Qxf = 10,500 GHz (at 4.8 GHz) and τf = −39 ppm/°C. The effects of B2O3, ZnO–B2O3, BaO–B2O3–SiO2, ZnO–B2O3–SiO2 and PbO–B2O3–SiO2 glasses on the sintering temperature and microwave dielectric properties of Ce2(WO4)3 were investigated. The Ce2(WO4)3 + 0.2 wt% ZBS sintered at 900 °C/4 h has ?r = 13.7, Qxf = 20,200 GHz and τf = −25 ppm/°C. 相似文献
18.
Guihua Yang Yuebing Xu Xintai Su Yahong Xie Chao Yang Zejuan Dong Jide Wang 《Ceramics International》2014
CuO/Bi2O3 (CuO/Bi2O3/MCM-41) nanoparticles supported on MCM-41 were synthesized by a facile impregnation method. The products were characterized by nitrogen adsorption/desorption, X-ray diffraction (XRD), H2 temperature programmed reduction (H2-TPR) and scanning electron microscopy (SEM). XRD patterns indicated the presence of crystalline CuO and Bi2O3 phase for CuO/Bi2O3/MCM-41 catalyst. TPR results revealed CuO nanoparticles were dispersed well on MCM-41. SEM results showed that the nanoparticles were located on the MCM-41. The activity of the catalysts towards ethynylation of formaldehyde for 1,4-butynediol synthesis was evaluated at atmospheric pressure. Compared with unsupported CuO/Bi2O3 and commercial Cu/Bi-based catalyst, CuO/Bi2O3/MCM-41 catalyst showed maximum conversion (51%) and selectivity (94%) towards 1,4-butynediol. The results show that CuO/Bi2O3 catalysts supported on MCM-41 have potential for 1,4-butynediol synthesis in industrial application. 相似文献
19.
Bojana Mojić Konstantinos P. Giannakopoulos Željka Cvejić Vladimir V. Srdić 《Ceramics International》2012
In this paper, magnetic nanoparticles (Fe3O4 and NiFe2O4) were coated with a biocompatible silica shell via hydrolysis and condensation of tetraethyl orthosilicate (TEOS) by the Stöber process. Magnetic nanoparticles, prepared by chemical co-precipitation from iron and nickel salts, were functionalized with citric acid, in order to provide their deagglomeration and to enable their coating with silica. The parameters of the functionalization procedure were varied (concentration–pH and type of treatment), in order to examine if and how this particular step of preparation affects the final morphology of the core-shell particles. Transmission electron microscopy, zeta potential and particle size measurements revealed that the morphology and the size of obtained core shell particles depend significantly on the core particle size, and thus on the parameters of the functionalization step. 相似文献
20.
《Ceramics International》2016,42(4):5195-5202
Reduced graphene oxide/cryptomelane (RGO/KMn8O16) composites are successfully synthesized from α-MnO2 nanorods and GO using a water-bathing precipitation method. The unique structure of KMn8O16 nanorods, with a length of 2–4 μm, dispersed on the surface of RGO leads to a much enhanced electrical conductivity and ionic transport, finally achieving composites with an improved electrochemical performance. Electrochemical measurement results show a specific capacitance of 222.3 F/g at a current density of 0.2 A/g, much higher than that of the original α-MnO2. After 500 cycles at 2.0 A/g, the RGO/KMn8O16 composite electrode still retains 92.6% of its initial specific capacitance. The excellent electrochemical performance and durability observed for this composite electrode suggest its potential application for electrochemical capacitors. 相似文献