共查询到20条相似文献,搜索用时 31 毫秒
1.
Marcela Stoia Costica Caizer Mircea Ştefănescu Paul Barvinschi Lucian Barbu-Tudoran 《Journal of Sol-Gel Science and Technology》2011,58(1):126-134
The paper presents a study regarding the structure, morphology and magnetic behaviour of x% (Ni0.65Zn0.35Fe2O4)/(100 − x)% SiO2 ferrimagnetic nanocomposites for low Ni–Zn ferrite concentration (x = 5, 10, 15, 20 and 30 mass percent) obtained by an improved
modified sol–gel method. The obtained gels and nanocomposites have been characterized by fast Fourier transform-infrared (FT-IR)
spectrometry, X-ray diffraction (XRD), transmission electron microscopy (TEM) and magnetic measurements (MM). The addition
of a supplementary quantity of diol in the synthesis, corresponding to a molar ratio EG : TEOS = 1:1, and the control of the
thermal treatment applied to the precursor xerogels tetraethylortosilicate (TEOS)–metal nitrates (MN)–ethylene glycol (EG)
leads to fine (~2–9 nm), almost spherical Ni–Zn ferrite nanoparticles homogenously dispersed inside the amorphous SiO2 matrix. TEM images reveal the fine nature and the narrow size distribution of the ferrite nanoparticles. Nanoparticles diameter
increases with the ferrite concentration and with the annealing temperature. For all concentrations of ferrite in SiO2 and all annealing temperature, we have obtained Ni0.65Zn0.35Fe2O4 ferrite as single phase (proven by XRD) in the amorphous silica matrix, only after a pre-treatment of synthesized gels, at
573 K, for 3 h. The magnetic behaviour of ferrite nanoparticles in quasi-static magnetic fields is very particular, depending
on the annealing temperature and the ferrite content in silica matrix. We have obtained superparamagnetic behaviour for the
nanocomposites, for a concentration of 30% ferrite in SiO2 at high annealing temperature, of 1,273 K. 相似文献
2.
Large-scale Li1+x
V3O8 nanobelts were successfully fabricated using filter paper as deposition substrate through a simple surface sol–gel method.
The nanobelts were as long as tens of micrometers with widths of 0.4–1.0 μm and thickness of 50–100 nm. The nanobelts were
characterized by X-ray diffration (XRD), Fourier infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), transmission
electron microscopy (TEM). The formation mechanism of the nanobelts was investigated, showing that the morphology of the nanobelts
is mainly determined by the calcination temperature. Electrochemical properties of the Li1+x
V3O8 nanobelts were characterized by charge–discharge experiments, and the results demonstrate that the Li1+x
V3O8 nanobelts exhibit a high discharge capacity (278 mAh g−1) and excellent cycling stability. 相似文献
3.
Sara Goñi Francisca Puertas María Soledad Hernández Marta Palacios Ana Guerrero Jorge S. Dolado Bruno Zanga Fulvio Baroni 《Journal of Thermal Analysis and Calorimetry》2010,102(3):965-973
This research is part of a European project (namely, CODICE project), main objective of which is modelling, at a multi-scale,
the evolution of the mechanical performance of non-degraded and degraded cementitious matrices. For that, a series of experiments
were planned with pure synthetic tri-calcium silicate (C3S) and bi-calcium silicate (C2S) (main components of the Portland cement clinker) to obtain different calcium–silicate–hydrate (C–S–H) gel structures during
their hydration. The characterization of those C–S–H gels and matrices will provide experimental parameters for the validation
of the multi-scale modelling scheme proposed. In this article, a quantitative method, based on thermal analyses, has been
used for the determination of the chemical composition of the C–S–H gel together with the degree of hydration and quantitative
evolution of all the components of the pastes. Besides, the microstructure and type of silicate tetrahedron and mean chain
length (MCL) were studied by scanning electron microscopy (SEM) and 29Si magic-angle-spinning (MAS) NMR, respectively. The main results showed that the chemical compositions for the C–S–H gels
have a CaO/SiO2 M ratio almost constant of 1.7 for both C3S and C2S compounds. Small differences were found in the gel water content: the H2O/SiO2 M ratio ranged from 2.9 ± 0.2 to 2.6 ± 0.2 for the C3S (decrease) and from 2.4 ± 0.2 to 3.2 ± 0.2 for the C2S (increase). The MCL values of the C–S–H gels, determined from 29Si MAS NMR, were 3.5 and 4 silicate tetrahedron, for the hydrated C3S and C2S, respectively, remaining almost constant at all hydration periods. 相似文献
4.
Shiming Liu Xiaoliang Qian Jianzhong Xiao 《Journal of Sol-Gel Science and Technology》2007,44(3):187-193
Nano-crystalline La0.8Sr0.2Co0.5Fe0.5O3±δ powder has been successfully synthesized by microwave assisted sol–gel (MWSG) method. The decomposition and crystallization
behavior of the gel-precursor was studied by Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) analysis.
From the result of FT-IR and X-ray diffraction patterns, it is found that a perovskite La0.8Sr0.2Co0.5Fe0.5O3±δ was formed by irradiating the precursor at 700 W for 3 min, but the well-crystalline perovskite La0.8Sr0.2Co0.5Fe0.5O3±δ was obtained at 700 W for 35 min. Morphological and specific area analysis of the powder were done by transmission electron
microscopy (TEM), scanning electron microscope (SEM) and Brunauer–Emmett–Teller (BET). The surface areas measured was 38.9 m2/g and the grain size was ∼23 nm. Electrochemical properties of pure LSCF cathode on YSZ electrolyte at intermediate temperatures
were investigated by using AC impedance analyzer, which shows a low area specific resistance (0.077 Ω cm2 at 1073 K and 0.672 Ω cm2 at 953 K). Moreover, the synthesis period of 20 h usually observed for conventional heating mode is reduced to a few minutes.
Thus, the MWSG method is proved to be a novel, extremely facile, time-saving and energy-efficient route to synthesize LSCF
powders. 相似文献
5.
A. Ananthanarayanan A. Dixit R. K. Lenka R. D. Purohit V. K. Shrikhande G. P. Kothiyal 《Journal of Thermal Analysis and Calorimetry》2011,106(3):839-844
Lithium aluminum silicate (LAS) glasses of compositions (wt%) 10.6Li2O–71.7SiO2–7.1Al2O3–4.9K2O–3.2B2O3–1.25P2O5–1.25TiO2 were prepared by the melt quench technique. Crystallization kinetics was investigated by the method of Kissinger and Augis–Bennett
using differential thermal analysis (DTA). Based on the DTA data, glass ceramics were prepared by single-, two-, and three-step
heat treatment schedules. The interdependence of different phases formed, microstructure, thermal expansion coefficient (TEC)
and microhardness (MH) was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermo-mechanical
analysis (TMA), and microhardness (MH) measurements. Crystallization kinetics revealed that Li2SiO3 is the kinetically favored phase with activation energy of 91.10 kJ/mol. An Avrami exponent of n = 3.33 indicated the dominance of bulk crystallization. Based upon the formation of phases, it was observed that the two-stage
heat treatment results in highest TEC glass ceramics. The single-step heat treatment yielded glass ceramics with the highest
MH. 相似文献
6.
N. N. Gedam P. R. Padole S. K. Rithe G. N. Chaudhari 《Journal of Sol-Gel Science and Technology》2009,50(3):296-300
Thick film of nanocrystalline Co0.8Ni0.2Fe2O4 was obtained by sol–gel citrate method for gas sensing application. The synthesized powder was characterized by X-ray diffraction
(XRD) and transmission electron microscopy. The XRD pattern shows spinel type structure of Co0.8Ni0.2Fe2O4. XRD of Co0.8Ni0.2Fe2O4 revels formation of solid solution with average grain size of about 30 nm. From gas sensing properties it observed that nickel
doping improves the sensor response and selectivity towards ammonia gas and very low response to LPG, CO, and H2S at 280 °C. Furthermore, incorporation of Pd improves the sensor response and stability of ammonia gas and reduced the operating
temperature upto 210 °C. The sensor is a promising candidate for practical detector of ammonia. 相似文献
7.
Shanxia Luo Fumin Wang Zhansheng Shi Feng Xin 《Journal of Sol-Gel Science and Technology》2009,52(1):1-7
TiO2 nanocrystals with diameters 8–10 nm have been prepared through sol–gel method using a mixed template of polyethylene glycol
(PEG) and cetytrimethylammonium bromide (CTAB) at low temperature. The samples were characterized by X-ray diffraction (XRD),
transmission electron microscopy (TEM), high-resolution (HR) TEM and fourier transform infrared spectroscopy (FT-IR) etc.
XRD analysis showed the TiO2 photocatalysts prepared with mixed template are pure anatase. FTIR spectrum revealed that the cationic surfactant provides
CTA+ molecules and bonds to Ti–O to prevent the condensation reaction. PEG plays a dispersant role in controlling the structure
of nano-TiO2 particles. CTAB and PEG incorporated with each other to restrain the growth of crystal nucleus and control the size of grain.
The self-assembling process has been confirmed by HRTEM. PEG played different role in mixed template from the single template.
The photocatalytic activity of samples was determined by using as a model reaction. The results showed that TiO2 photocatalysts with mixed template have higher photocatalytic activity than P25. 相似文献
8.
Microwave-induced combustion with glycine, CTAB-assisted hydrothermal process with NaOH and NH3, EDTA assisted-hydrothermal
methods have been applied to prepare NiFe2O4 nanoparticles for the first time. Structural and magnetic properties of the products were investigated by X-ray powder diffraction
(XRD), scanning electron microscopy (SEM), transmison electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR),
and electron spin resonance spectrometry (EPR). TEM measurements showed that morphology of the product depends on the synthesis
method employed. The average cystallite size of NiFe2O4 nanoparticles was in the range of 14–59 nm as measured by XRD. The uncoated sample (Method A) had an EPR linewidth of 1973
Oe, the coated samples reached lower values. The magnetic dipolar interactions existing among the Ni ferrite nanoparticles
are reduced by the coatings, which could cause the decrease in the linewidth of the EPR signals. Additionally, the linewidth
increases with an increase in the size and the size distribution of nanoparticles. 相似文献
9.
Xiangzhong Ren Yingkai Jiang Peixin Zhang Jianhong Liu Qianling Zhang 《Journal of Sol-Gel Science and Technology》2009,51(2):133-138
One-dimensional (1D) submicron-belts of V2O5 have been prepared by a sol–gel route using V2O5, H2O2 and aniline as starting materials. Thermogravimetric and differential thermal analysis, X-ray diffraction, Fourier transform
infrared spectroscopy and scanning electron microscopy were employed to characterize the samples. Electrochemical behaviors
as cathode material in rechargeable lithium-ion batteries were investigated by galvanostatic charge–discharge measurement
and cyclic voltammeter. The results showed that the synthesized V2O5 appeared to be submicron-belts and orthorhombic structure. The V2O5 submicron-belts exhibited a high initial discharge capacity of 346 mAh/g and stayed 240 mAh/g after 20 cycles at 0.1 C discharge
rate in the potential region 1.8–4.0 V. 相似文献
10.
R. Sathiyamoorthi P. Santhosh P. Shakkthivel T. Vasudevan 《Journal of Solid State Electrochemistry》2007,11(12):1665-1669
Layered Ti-doped lithiated nickel cobaltate, LiNi0.8Co0.2 − xTixO2 (where x = 0.01, 0.03, and 0.05) nanopowders were prepared by wet-chemistry technique. The structural properties of synthesized materials
were characterized by X-ray diffraction (XRD) and thermo-gravimetric/differential thermal analysis (TG/DTA). The morphological
changes brought about by the changes in composition of LiNi0.8Co0.2 − xTixO2 particles were examined through surface examination techniques such as scanning electron microscopy (SEM) and transmission
electron microscopy (TEM) analyses. Electrochemical studies were carried out using 2016-type coin cell in the voltage range
of 3.0–4.5 V (vs carbon) using 1 M LiClO4 in ethylene carbonate and diethyl carbonate as the electrolyte. Among the various concentrations of Ti-doped lithiated nickel
cobaltate materials, C/LiNi0.8Co0.17Ti0.03O2 cell gives stable charge–discharge features. 相似文献
11.
Nanocrystalline single-phase neodymium monoaluminate (NdAlO3) has been prepared from neodymium oxide and aluminium nitrate by modified Pechini’s method. Malic acid has been used for
the first time as a new complexing agent in the sol–gel process. It has facilitated, without adding 1,2-ethanediol, a low-temperature
synthesis at 1,050 °C compared to the temperature of 1,630 °C needed for the solid-state preparation. The characterisation
of the nanoparticles has been carried out by X-ray diffraction, scanning electron microscopy, transmission electron microscopy,
X-ray photoelectron spectroscopy, and infrared spectroscopy in the range 75–4,000 cm−1. The smallest particles have size of 30 nm and are anisometric; agglomerates of particles have been also observed. The material
has pyknometric density of 3.956 g/cm3 at T = 293.15 K and specific surface area 5.2 m2/g. The binding energies of O 1s, Al 2p, Nd 3d, and Nd 4d electrons have been found chemically shifted in NdAlO3 compared to the values for the respective elements. 相似文献
12.
Ultra-long and uniform CuAlO2 nanowires were successfully synthesized within a porous anodic aluminum oxide template by means of sol–gel method at 900 °C.
The results of X-Ray diffraction indicate that the obtained CuAlO2 nanowires have a single delafossite structure. The scanning electron microscopy and transmission electron microscopy show
that the CuAlO2 nanowires have a uniform diameter with about 50 nm and a length up to 10 μm. Room-temperature photoluminescence measurement
of nanowires exhibits an ultraviolet near-band-edge emission around 350 nm (3.54 eV). 相似文献
13.
Cornelia Marinescu Ancuta Sofronia Cristina Rusti Roxana Piticescu Viorel Badilita Eugeniu Vasile Radu Baies Speranta Tanasescu 《Journal of Thermal Analysis and Calorimetry》2011,103(1):49-57
The aim of the article is to investigate the influence of particle size on titanium dioxide phase transformations. Nanocrystalline
titanium dioxide powder was obtained through a hydrothermal procedure in an aqueous media at high pressure (in the range 25–100 atm)
and low temperature (≤200 °C). The as-prepared samples were characterized with respect to their composition by ICP (inductive
coupled plasma), structure and morphology by XRD (X-ray diffraction), and TEM (transmission electron microscopy), thermal
behavior by TG (thermogravimetry) coupled with DSC (differential scanning calorimetry). Thermal behavior of nanostructured
TiO2 was compared with three commercial TiO2 samples. The sequence of brookite–anatase–rutile phase transformation in TiO2 samples was investigated. The heat capacity of anatase and rutile in a large temperature range are reported. 相似文献
14.
Powders of composition Ni3(XO4)2 with X = P and V were synthesized by both the ceramic conventional and the Pechini-type in situ polymerizable complex (IPC)
method. The Pechini-type IPC technique produces these materials as single phases at reduced temperatures (750–810 °C) as opposed
to the conventional solid-state reaction methods in which processing temperatures higher than 800 °C are usually required
to obtain a single-phase of these materials. Reflections peaks of the samples obtained in both cases can be indexed well with
the standard patterns for Ni3(PO4)2 and Ni3(VO4)2 compounds. The lattice parameters of these materials were calculated by the Rietveld refinement method from X-ray diffraction
data (XRD). The average crystal size as well as the crystallinity and morphology of the powder samples were characterized
by scanning electron microscopy (SEM). The results show a clearly minor particle size by using the Pechini-IPC method than
the ceramic one. Moreover, the magnetic behaviour was studied on powered samples by using magnetic susceptibility data. 相似文献
15.
Xiaochang Qiao Jiandong Yang Yaobin Wang Quanqi Chen Tingting Zhang Li Liu Xianyou Wang 《Journal of Solid State Electrochemistry》2012,16(3):1211-1217
LiVPO4F/C composites with better electrochemical performance were prepared by calcination of LiF and amorphous vanadium phosphorus
oxide (VPO) intermediate synthesized by a sol–gel method using H3PO4, V2O5 and citric acid as raw materials. The properties of LiVPO4F/C composites were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical tests.
The analysis of XRD patterns and Fourier transform infrared spectra (FTIR) reveal that VPO intermediate prepared by sol–gel
method is amorphous and VPO4 may exist in VPO intermediate. The compositions of LiVPO4F/C composites are related to the calcination temperature for preparation of amorphous VPO/C intermediate and LiVPO4F/C composite prepared by VPO/C synthesized at 700°C consists of a single crystal phase of LiVPO4F. The electrochemical tests show that LiVPO4F/C composite prepared by VPO/C synthesized at 700°C exhibits higher discharge capacity and excellent cycle performance. This
LiVPO4F/C composite displays discharge capacity of 133 mAh g−1 at 0.5 C (78 mA g−1) and remains capacity retention of 96.8% after 30 cycles, even at a high rate of 5 C, the composite exhibits high discharge
capacity of 115 mAh g−1 and capacity retention of 97% after 100 cycles. 相似文献
16.
Tatiana Nedoseykina Pavel Plyusnin Yuri Shubin Sergey Korenev 《Journal of Thermal Analysis and Calorimetry》2010,102(2):703-708
Thermolysis of double complex salt [Pd(NH3)4][AuCl4]2 has been studied in helium atmosphere from ambient to 350 °C. The XAFS of Pd K and Au L3 edges and thermogravimetry measurements have been carried out to characterize the intermediates and the final product. In
the temperature range 115–160 °C the complex is decomposed to form Pd(NH3)2Cl2 and AuCl4−x
N
x
species with x ranging from 2 to 3. Subsequent heating of the intermediate up to 300 °C leads to the total loss of NH3. The Au–Cl and Au–Au bonds form the local environment of Au at the stage of decomposition while only four chlorine atoms
are around Pd. At the temperature of 330 °C the Au and Pd nanoparticles as well as residues of palladium chloride are detected.
The final product consists of separated Au and Pd nanoparticles. 相似文献
17.
Deuk Yong Lee Kyong-Ho Lee Myung-Hyun Lee Nam-Ihn Cho Bae-Yeon Kim 《Journal of Sol-Gel Science and Technology》2010,53(1):43-49
Ba1−x
Sr
x
TiO3(x = 0–0.5, BST) nanofibers with diameters of 150–210 nm were prepared by using electrospun BST/polyvinylpyrrolidone (PVP) composite
fibers by calcination for 2 h at temperatures in the range of 650–800 °C in air. The morphology and crystal structure of calcined
BST/PVP nanofibers were characterized as functions of calcination temperature and Sr content with an aid of XRD, FT-IR, and
TEM. Although several unknown XRD peaks were detected when the fibers were calcined at temperatures less than 750 °C, they
disappeared with increasing the temperature (above 750 °C) due to its thermal decomposition and complete reaction in the formation
of BST. In addition, the FT-IR studies of BST/PVP fibers revealed that the intensities of the O–H stretching vibration bands
(at 3430 and 1425 cm−1) became weaker with increasing the calcination temperature and a broad band at 540 cm−1, Ti–O vibration, appeared sharper and narrower after calcination above 750 °C due to the formation of metal oxide bonds.
However, no effect of Sr content on the crystal structure of the composites was detected. 相似文献
18.
B. Machura M. Wolff A. Świtlicka R. Kruszynski J. Mroziński 《Structural chemistry》2010,21(4):761-769
The reaction of [ReOBr3(PPh3)2] with 5,6-diphenyl-3-(2-pyridyl)-1,2,4-trazine (dppt) has been examined and [ReBr3(dppt)(OPPh3)] has been obtained. It was characterised by IR, UV–Vis spectroscopy, magnetic measurements, and X-ray crystallography. The
electronic structure of [ReBr3(dppt)(OPPh3)] has been studied by DFT/B3LYP level calculations, and TDDFT calculations were employed for discussion of its electronic
spectrum in more detail. The magnetic behavior is characteristic of mononuclear complexes with d4 low-spin octahedral Re(III) complexes (3T1g ground state) and arise because of the large spin–orbit coupling (ζ = 2500 cm−1), which gives diamagnetic ground state. 相似文献
19.
Mingquan Liu Xiangqian Shen Fuzhan Song Jun Xiang Ruijiang Liu 《Journal of Sol-Gel Science and Technology》2011,59(3):553-560
Sr0.8La0.2Zn0.2Fe11.8O19/poly(vinyl pyrrolidone) (PVP) composite fiber precursors were prepared by the sol–gel assisted electrospinning. Subsequently,
the M-type ferrite Sr0.8La0.2Zn0.2Fe11.8O19 nanofibers with diameters about 120 nm were obtained by calcination of these precursors at different heat treatment conditions.
The precursor and resultant Sr0.8La0.2Zn0.2Fe11.8O19 nanofibers were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy-dispersive
X-ray spectrometer and vibrating sample magnetometer. With the calcination temperature increased up to 1,000 °C for 2 h or
the holding time prolonged to 12 h at 900 °C, the Sr0.8La0.2Zn0.2Fe11.8O19 particles gradually grow into a hexagonal elongated plate-like morphology due to the dimensional control along the nanofiber
length. These elongated plate-like particles will be linked one by one to form the nanofiber with a necklace-like morphology.
The magnetic properties of the Sr0.8La0.2Zn0.2Fe11.8O19 nanofibers are closely related to grain sizes, impurities and defects in the ferrite, which are influenced by the calcination
temperature, holding time and heating rate. After calcined at 900 °C for 12 h with a heating rate of 3 °C/min, the optimized
magnetic properties are achieved with the specific saturation magnetization 75.0 A m2 kg−1 and coercivity 426.3 kA m−1 for the Sr0.8La0.2Zn0.2Fe11.8O19 nanofibers. 相似文献
20.
A. Katelnikovas J. M. Ogiegło H. Winkler A. Kareiva T. Jüstel 《Journal of Sol-Gel Science and Technology》2011,59(2):311-314
Y3−xLuxAl3MgSiO12 (x = 0–3) garnet powders were synthesized by an aqueous sol–gel method based on metal chelates with 1,2-ethanediol in aqueous
media. Target samples were characterized by powder X-ray diffraction (XRD), scanning electron microscopy and reflection spectra.
XRD analysis revealed that sintering of polycrystalline Y3−xLuxAl3MgSiO12 powders at 1,600 °C results in single-phase garnet materials. 相似文献