共查询到20条相似文献,搜索用时 31 毫秒
1.
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
2.
Mesoporous titania nanoparticles (denoted as MTN) with high surface area (e.g., 252 m2 g−1) were prepared using tetrapropyl orthotitanate (TPOT) as a titania precursor and 10–20 nm or 20–30 nm silica colloids as
templates. Co-assembly of TPOT and silica colloids in an aerosol-assisted process and immediate calcination at 450 °C resulted
in anatase/silica composite nanoparticles. Subsequent removal of the silica colloids from the composite by NaOH solution created
mesopores in the TiO2 nanoparticles with pore size corresponding to that of silica colloids. Effects of silica colloids’ contents on MTN porosity
and crystallites’ growth at a higher calcination temperature (e.g., 1000 °C) were investigated. Silica colloids suppressed
the growth of TiO2 crystallites during calcination at a higher calcination temperature and controllable contents of the silica colloids in precursor
solution resulted in various atomic ratios of anatase to rutile in the calcinated materials. The mesostructure and crystalline
structure of these titania materials were characterized by transmission electron microscope (TEM), scanning electron microscope
(SEM), X-ray diffraction (XRD), differential thermal analysis (DTA)-thermo-gravimetric analysis (TGA), and N2 sorption. 相似文献
3.
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
4.
Xiangqian Shen Zhi Zhou Fuzhan Song Xianfeng Meng 《Journal of Sol-Gel Science and Technology》2010,53(2):405-411
Nanocomposites of ferrite and ferroelectric phases are attractive functional ceramic materials. In this work, the nanocomposite
Ni1−x
Co
x
Fe2O4–BaTiO3(x = 0.2, 0.3, 0.4, 0.5) fibers with fine diameters of 3 ~ 7 μm and high aspect ratios were synthesized by the organic gel-thermal
decomposition process from the raw materials of citric acid and metal salts. The structure, thermal decomposition process
and morphologies of the gel precursors and the resultant fibers derived from thermal decomposition of the gel precursors were
characterized by Fourier transform infrared spectroscopy, thermogravimetric differential thermal analysis, X-ray diffraction
and scanning electron microscopy. The magnetic properties of the nanocomposite fibers were measured by vibrating sample magnetometer.
The nanocomposite fibers of ferrite Ni1−x
Co
x
Fe2O4 and perovskite BaTiO3 are formed at the calcination temperature of 900 °C for 2 h. The average grain sizes of Ni1−x
Co
x
Fe2O4 and BaTiO3 in the nanocomposite fibers increase from about 15 nm to approximately 67 nm with the increasing calcination temperatures
from 900 to 1,180 °C. The saturation magnetization of the nanocomposite Ni1−x
Co
x
Fe2O4–BaTiO3(x = 0.2, 0.3, 0.4, 0.5) fibers increases with the increase of grain sizes of Ni1−x
Co
x
Fe2O4 and Co content, while the coercivity reaches a maximum value at the single-domain size of about 65 nm of Ni0.5Co0.5Fe2O4 obtained at the calcination temperature of 1,100 °C. 相似文献
5.
Mingquan Liu Fuzhan Song Xiangqian Shen Yongwei Zhu 《Journal of Sol-Gel Science and Technology》2010,56(1):39-46
The composite nanofibers of xSrSiO3/(100 − x)SrFe12O19 (x = 0–13 wt%) with diameters around 110 nm have been prepared by calcination of the electrospun SrSiO3/SrFe12O19/poly (vinyl pyrrolidone) (PVP) composite fibers at 800–900 °C. The composite nanofibers were characterized by Fourier transform
infrared spectroscopy, X-ray diffraction, scanning electron microscopy and vibrating sample magnetometer. After calcined at
800° the M-type strontium ferrite is formed and the strontium silicate exists as an amorphous state when the calcination temperature
below about 950 °C. The addition of SrSiO3 has an obvious suppression effect on the strontium ferrite grain growth and the ferrite grain size decreases from 66.9 to
33.5 nm corresponding SrSiO3 content from 0 to 9 wt% in the composite. The specific saturation magnetization (Ms) of the xSrSiO3/(100 − x)SrFe12O19 composite nanofibers exhibits a continuous reduction from 58.0 to 45.6 A m2 kg−1 with the increase of SrSiO3 content from 0 to 13 wt%. With addition of SrSiO3 from 0 to 13 wt%, the coercivity of the composite nanofibers obtained at 900 °C initially increases, reaching a maximum value
501.1 kA m−1 at the silicate content 7 wt%, and then shows a reduction tendency with the strontium silicate content increase further up
to 13 wt%. This influence on the coercivity by strontium silicate can be attributed mainly to the ferrite grain growth suppression
and the non-magnetic phase barrier for the domains misalignment. 相似文献
6.
M. R. Barati 《Journal of Sol-Gel Science and Technology》2009,52(2):171-178
Nanocrystalline Mg–Cu–Zn ferrite powders were successfully synthesized through nitrate–citrate gel auto-combustion method.
Characterization of the nitrate–citrate gel, as-burnt powder and calcined powders at different calcination conditions were
investigated by using XRD, DTA/TG, IR spectra, EDX, VSM, SEM and TEM techniques. IR spectra and DTA/TGA studies revealed that
the combustion process is an oxidation–reduction reaction in which the NO3
− ion is oxidant and the carboxyl group is reductant. The results of XRD show that the decomposition of the gel indicated a
gradual transition from an amorphous material to a crystalline phase. In addition, increasing the calcination temperature
resulted in increasing the crystallite size of Mg–Cu–Zn ferrite powders. VSM measurement also indicated that the maximum saturation
magnetization (64.1 emu/g) appears for sample calcined at 800 °C while there is not much further increase in M
s at higher calcination temperature. The value of coercivity field (H
c) presents a maximum value of 182.7 Oe at calcination temperature 700 °C. TEM micrograph of the sample calcined at 800 °C
showed spherical nanocrystalline ferrite powders with mean size of 36 nm. The toroidal sample sintered at 900 °C for 4 h presents
the initial permeability (μ
i) of 405 at 1 MHz and electrical resistivity (ρ) of 1.02 × 108 Ω cm. 相似文献
7.
A. L. M. de Oliveira J. M. Ferreira Márcia R. S. Silva Soraia C. de Souza F. T. G. Vieira E. Longo A. G. Souza Iêda M. G. Santos 《Journal of Thermal Analysis and Calorimetry》2009,97(1):167-172
NiWO4 and ZnWO4 were synthesized by the polymeric precursor method at low temperatures with zinc or nickel carbonate as secondary phase.
The materials were characterized by thermal analysis (TG/DTA), infrared spectroscopy, UV–Vis spectroscopy and X-ray diffraction.
NiWO4 was crystalline after calcination at 350 °C/12 h while ZnWO4 only crystallized after calcination at 400 °C for 2 h. Thermal decomposition of the powder precursor of NiWO4 heat treated for 12 h had one exothermic transition, while the precursor heat treated for 24 h had one more step between
600 and 800 °C with a small mass gain. Powder precursor of ZnWO4 presented three exothermic transitions, with peak temperatures and mass losses higher than NiWO4 has indicating that nickel made carbon elimination easier. 相似文献
8.
Xiangqian Shen Mingquan Liu Fuzhan Song Xianfeng Meng 《Journal of Sol-Gel Science and Technology》2010,53(2):448-453
The SrFe12O19/poly (vinyl pyrrolidone) (PVP) composite fiber precursors were prepared by the sol-gel assisted electrospinning with ferric
nitrate, strontium nitrate and PVP as starting reagents. Subsequently, the M-type strontium ferrite (SrFe12O19) nanofibers were derived from calcination of these precursors at 750–1,000 °C.The composite precursors and strontium ferrite
nanofibers were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy
and vibrating sample magnetometer. The structural evolution process of strontium ferrite consists of the thermal decomposition
and M-type strontium ferrite formation. After calcined at 750 °C for 2 h the single M-type strontium ferrite phase is formed
by reactions of iron oxide and strontium oxide produced during the precursor decomposition process. The nanofiber morphology,
diameter, crystallite size and grain morphology are mainly influenced by the calcination temperature and holding time. The
SrFe12O19 nanofibers characterized with diameters of around 100 nm and a necklace-like structure obtained at 900 °C for 2 h, which
is fabricated by nanosized particles about 60 nm with the plate-like morphology elongated in the preferred direction perpendicular
to the c-axis, show the optimized magnetic property with saturation magnetization 59 A m2 kg−1 and coercivity 521 kA m−1. It is found that the single domain critical size for these M-type strontium ferrite nanofibers is around 60 nm. 相似文献
9.
Ge Yu Hailong Zhang Bo-Ping Zhang Jiamin Zhang 《Journal of Sol-Gel Science and Technology》2012,61(2):403-410
Sol–gel processing of Cu-particle-dispersed (K0.5Na0.5)NbO3 (Cu/KNN) thin films was studied in an attempt to develop a method producing piezoelectric composite films with good mechanical
performance. The Cu/KNN films were prepared via crystallization annealing at 650–750 °C for 1 min in air, followed by reduction
annealing at 400–500 °C for 1–2 h in a 5% H2 and 95% Ar gas mixture. The resultant composite films consisted of perovskite KNN, metallic Cu, and Cu4O3. This suggests that the decomposition of Cu sources takes two different ways in this study. The Cu/KNN composite films containing
Cu4O3 phases were produced by the crystallization annealing at 700 °C for 1 min followed by the reduction annealing at 500 °C for
1 h. Surface morphology observations reveal that these films have dense KNN matrix with a grain size of ~200 nm and uniformly
dispersed Cu or Cu4O3 particles with a size of <500 nm. 相似文献
10.
Zhanyong Wang Wenjun Fei Huichun Qian Min Jin Hui Shen Minglin Jin Jiayue Xu Weirong Zhang Qin Bai 《Journal of Sol-Gel Science and Technology》2012,61(2):289-295
CoFe2O4 ferrites were synthesized sol–gel with cobalt chloride, ferric chloride and citric acid as the main raw material. X-ray diffraction,
vibrating sample magnetometer and simultaneous thermal analysis were applied to character the structure and magnetic properties
of traditional and microwave calcined samples. The samples with pH 5 and molar ratio of citric acid to metal nitrate 1–1.2
showed the optimal structure and magnetic properties. Microwave calcination reduces the synthesis time from 2 h for conventional
calcination to 15–30 min. The saturation magnetization (σ
s
) for sample microwave-calcined at 550 °C for 30 min reaches to 75.89 emu/g, much higher than that of conventional-calcined
samples. 相似文献
11.
T. Zaremba A. Krząkała J. Piotrowski D. Garczorz 《Journal of Thermal Analysis and Calorimetry》2010,101(2):479-485
This article reports the possibility of detoxification of chrysotile asbestos through a low temperature heating and grinding
treatment. The effect of thermal treatment at different temperatures in the range from 500 to 725 °C for 3 h on raw natural
asbestos was characterized by thermal analysis, X-ray diffraction, and scanning electron microscopy. It was found that an
isothermal treatment at 650 °C caused the complete dehydroxylation of chrysotile Mg3Si2O5(OH)4. Transformation of the dehydroxylated phase to forsterite Mg2SiO4 was obtained by heat treatment in the range 650–725 °C. The study of microstructure changes of heated asbestos show the destruction
of characteristic fibers of chrysotile and formation of strips of forsterite. It is easily milled to pulverulent-shape material
by mechanical milling in vibratory mill. 相似文献
12.
Hua Ke Wen Wang Lin Chen Jiahuan Xu Dechang Jia Zhe Lu Yu Zhou 《Journal of Sol-Gel Science and Technology》2010,53(1):135-140
We present a facile sol–gel route to synthesize lanthanum-substituted bismuth titanate (BLT). The chemical reactions and crystallization
process of this method using the initial materials of bismuth subnitrate [4BiNO3(OH)2·BiO(OH)], lanthanum nitrate [La(NO3)3·6H2O] and tetrabutyl titanate [Ti(C4H9O)4] were investigated by thermogravimetric and differential thermal analysis, IR spectroscopy, gas chromatography/mass spectrometry,
Raman spectroscopy and XRD. The evaporation of the dissolved CO2 in the amorphous BLT matrix is associated with the crystallization of BLT. The BLT gel is pure BLT perovskite when calcination
temperature is higher than 500 °C. The grain size of the obtained nanoparticles ranges from 15 to 82 nm. The Arrhenius curve
is obtained from the representation of the reduced sizes with respect to the calcination temperature. The activation energy
of grain growth in BLT nanoparticles is 0.36 eV, which shows a rapidly growth process in the temperature range of 500–850 °C. 相似文献
13.
Imre Miklós Szilágyi Eero Santala Mikko Heikkilä Marianna Kemell Timur Nikitin Leonid Khriachtchev Markku Räsänen Mikko Ritala Markku Leskelä 《Journal of Thermal Analysis and Calorimetry》2011,105(1):73-81
This article demonstrates how important it is to find the optimal heating conditions when electrospun organic/inorganic composite
fibers are annealed to get ceramic nanofibers in appropriate quality (crystal structure, composition, and morphology) and
to avoid their disintegration. Polyvinylpyrrolidone [PVP, (C6H9NO)
n
] and ammonium metatungstate [AMT, (NH4)6[H2W12O40]·nH2O] nanofibers were prepared by electrospinning aqueous solutions of PVP and AMT. The as-spun fibers and their annealing were
characterized by TG/DTA-MS, XRD, SEM, Raman, and FTIR measurements. The 400–600 nm thick and tens of micrometer long PVP/AMT
fibers decomposed thermally in air in four steps, and pure monoclinic WO3 nanofibers formed between 500 and 600 °C. When a too high heating rate and heating temperature (10 °C min−1, 600 °C) were used, the WO3 nanofibers completely disintegrated. At lower heating rate but too high temperature (1 °C min−1, 600 °C), the fibers broke into rods. If the heating rate was adequate, but the annealing temperature was too low (1 °C min−1, 500 °C), the nanofiber morphology was excellent, but the sample was less crystalline. When the optimal heating rate and
temperature (1 °C min−1, 550 °C) were applied, WO3 nanofibers with excellent morphology (250 nm thick and tens of micrometer long nanofibers, which consisted of 20–80 nm particles)
and crystallinity (monoclinic WO3) were obtained. The FTIR and Raman measurements confirmed that with these heating parameters the organic matter was effectively
removed from the nanofibers and monoclinic WO3 was present in a highly crystalline and ordered form. 相似文献
14.
Yabin Zhang Yaping Ding Yong Li Jiqiang Gao Jianfeng Yang 《Journal of Sol-Gel Science and Technology》2009,49(3):385-390
The polyvinyl butyral–Al(NO3)3 composite sol used for alumina based fibers was synthesized by the sol–gel process in an aqueous solution using the polyvinyl
butyral (PVB) and Al(NO3)3 · 9H2O (AN). The alumina fibers with smooth surface and uniform diameter were prepared. PVB, AN, PVB–AN composite sol and alumina
fibers have been studied by X-ray diffraction (XRD), derivative thermo-gravimetric/differential scanning calorimetry (DTG/DSC),
Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). The interaction between PVB and AN
was reported. The presence of a new weak peak at low angle and deviation of diffraction angle in XRD patterns implied that
the reaction between PVB and AN took place. DTG/DSC curves showed the decomposition temperatures of AN increased and that
of PVB decreased in the PVB–AN composite sol, which was considered to be caused by the interaction between PVB and AN. FTIR
spectroscopy of PVB–AN gel showed a new absorption peak due to the COOH group, which implied the presence of new reaction
product. The schematic reaction formula was shown in this paper. The XRD pattern of fibers sintered at 1,200 °C showed the
formation of α-alumina and the fibers showed smooth surface and uniform diameter. 相似文献
15.
Lifeng Cao Lingxia Li Ping Zhang Haitao Wu 《Journal of Sol-Gel Science and Technology》2009,51(2):251-254
Perovskite-type Ag(Nb0.6Ta0.4)O3 nanopowder was prepared by the sol–gel process from the AgNO3, Ta2O5 and Nb2O5, with help of K2CO3, avoiding use of strong corrosive acid or expensive niobium ethoxide and tantalum ethoxide. The results suggested that thermal
decomposition of the xerogel took place when the xerogel was heated at 450 °C. Well-crystallized single-phased powder was
obtained at low temperature about 680 °C. With the heat-treatment temperature increasing (680–1,100 °C), the intensity of
the diffraction peaks increased. The crystallite size determined by Scherer formula and the result suggested that higher temperature
lead to larger crystallite size. Moreover, the average grain size 30–50 nm was estimated by a field emission scanning electron
microscope. The influence of holding time on microstructures indicated that the homogeneous and small grains were obtained
at 800 °C for 2–4 h while larger ones for 8–16 h. 相似文献
16.
The transparent TiO2 thin films coated on fused-SiO2 substrates were prepared by the sol–gel method and spin-coating technique. Effects of calcination temperature on crystal
structure, grain size, surface texture, and light transmittance of the films were investigated. After calcining at 600–1,200 °C,
the thicknesses of the TiO2 films were all around 80 nm and the molecular structures of the films were anatase, even at 1,200 °C. The calcined TiO2 films had the ultraviolet light (wavelength 200–400 nm) transmittances of ≤29% and the visible light (wavelength 400–800 nm)
transmittance of ≥72%. By photocatalytically decomposing the methylene blue (MB) in water, the photocatalytic activities of
the TiO2 thin films were measured and represented using the characteristic time constant (τ) for the MB degradation. While the films
prepared at 1,000 and 1,200 °C photodecomposed about 54 mol% of the MB in water (the corresponding τ ≈ 14.8 h) after exposing to 365-nm UV light for 12 h, the films prepared at 600 and 800 °C had smaller τ (≈9.0 h) and photodecomposed
about 74 mol% of the MB in water at the same testing conditions. 相似文献
17.
Shinji Sakai Tetsu Yamaguchi Ryan Anugrah Putra Rie Watanabe Masaaki Kawabe Masahito Taya Koei Kawakami 《Journal of Sol-Gel Science and Technology》2012,61(2):374-380
Electrospun ultrafine silica fibers were calcined at 150–800 °C. The relation of calcination temperature to the ability to
form biomimetic apatite in a simulated body fluid solution (SBF) was evaluated. The largest apatite particles, formed on non-calcined
fibers after 1 week of soaking in SBF, were 10 μm in diameter, had a narrow size distribution (coefficient of variation 9%),
and were similar to pearls on string. The particles size decreased with increasing calcination temperature below 250 °C and
the particles formed on the fibers calcined at 250 °C were 4.5 μm in diameter. No particles were found on those calcined above
500 °C. By using a concentrated SBF at 1.5-times higher ionic concentrations than SBF, the size of apatite microparticles
increased about 50%. The fibrous substrate covered with apatite particles was effective for osteoblastic differentiation of
pre-osteoblastic cells. 相似文献
18.
Andrei Rotaru 《Journal of Thermal Analysis and Calorimetry》2012,108(1):9-17
Thermal decomposition of an agrowaste, namely banana trunk fibers (BTF) were investigated by thermogravimetry (TG) and derivative
thermogravimetry (DTG) up to 900 °C at different heating rates (from 5 to 100 °C/min). The BTF was subjected to modification
by means of various known chemical methods (mercerization, acetylation, peroxide treatment, esterification, and sulfuric acid
treatment). Various degradation models, such as the Kissinger, Friedman, and Flynn–Wall–Ozawa were used to determine the apparent
activation energy. The obtained apparent activation energy values (149–210 kJ/mol) allow in developing a simplified approach
to understand the thermal decomposition behavior of natural fibers as a function of polymer composite processing. 相似文献
19.
Marlene Rodríguez-Reyes Héctor J. Dorantes-Rosales 《Journal of Sol-Gel Science and Technology》2011,59(3):658-661
In this work, titanium dioxide (TiO2) nanowires were synthesized by the sol–gel method, without using any kind of templates, instead of that acetic acid was used
as morphological modifier. In order to control crystalline phases and crystal size, TiO2 was calcinated at 400, 500 and 600 °C during 1 h. The resulting morphology was nanowires, which diameter was maintained constant
after calcination at different temperature (about 76 nm). Moreover, crystalline phases in order of predominance were anatase,
anatase–rutile and rutile–anatase at 400, 500 and 600 °C, respectively. Additionally, the crystallite size increases with
respect to temperature from 13 to 75 nm. 相似文献
20.
Fabiane Alexsandra Andrade de Jesus Ronaldo Santos da Silva Zélia Soares Macedo 《Journal of Thermal Analysis and Calorimetry》2010,100(2):537-541
Bismuth germanate ceramic powders were synthesized for the first time by the polymeric precursor method (Pechini’s method).
Differential thermal analysis and thermogravimetric techniques were used to study the decomposition of the resin precursor,
which indicated a suitable calcination temperature at 600 °C. It was observed that the mass loss occurs in two main stages
that are associated with two exothermic reactions. The crystalline phases of the powders were inspected by the X-ray diffraction
technique after thermal treatment between 300 and 600 °C. Single phase Bi4Ge3O12 ceramic bodies were obtained after sintering at 840 °C for 10 h. The sintered ceramics presented a luminescence band emission
centred at around 530 nm when excited with X-rays and UV radiation. 相似文献