共查询到20条相似文献,搜索用时 15 毫秒
1.
B. S. Shirke P. V. Korake P. P. Hankare S. R. Bamane K. M. Garadkar 《Journal of Materials Science: Materials in Electronics》2011,22(7):821-824
Pure anatase TiO2 nanoparticles were synthesized by microwave assisted sol–gel method and further characterized by powder X-ray diffraction
(XRD), energy dispersive x-ray analysis (EDAX), scanning electron microscopy (SEM), transmission electron microscopy (TEM),
and UV–Visible spectrophotometer, SEM images showed that TiO2 nanoparticles were porous structure. The XRD patterns indicated that TiO2 after annealed at 300 °C for 3 h was mainly pure anatase phase. The crystallite size was in the range of 20–25 nm, which
is consistent with the results obtained from TEM images. Microwave heating offers several potential advantages over conventional
heating for inducing or enhancing chemical reactions. 相似文献
2.
Koji Nakane Naoki Shimada Takashi Ogihara Nobuo Ogata Shinji Yamaguchi 《Journal of Materials Science》2007,42(11):4031-4035
Anatase type TiO2 nanotubes were formed by calcination of poly(vinyl alcohol)-Ti alkoxide hybrid precursor nanofibers in air. The outer and
inner diameters of the TiO2 nanotubes calcined at 500 °C for 5 h were ca. 440 nm and ca. 270 nm, respectively. The specific surface area of the TiO2 nanotubes was 38.8 m2/g, and the existence of mesopores (average pore diameter, 14.8 nm) on the nanotube wall was indicated by the nitrogen adsorption
isotherm (−196 °C). The photocatalysis of the TiO2 nanotubes was superior to that of commercially available anatase type TiO2 nanoparticles. 相似文献
3.
Synthesis of nano-MoS<Subscript>2</Subscript>/TiO<Subscript>2</Subscript> composite and its catalytic degradation effect on methyl orange 总被引:1,自引:0,他引:1
A nano-MoS2/TiO2 composite was synthesized in H2 atmosphere by calcining a MoS3/TiO2 precursor, which was obtained via a quick deposition of MoS3 on anatase nano-TiO2 under a strong acidic condition. The obtained nano-MoS2/TiO2 composite was characterized by X-ray diffraction spectroscopy, Brunauer–Emmett–Teller (BET) surface area, scanning electron
microscopy, high-resolution transmission electron microscopy, energy-dispersive spectrometry, ultraviolet–visible spectroscopy,
and Fourier transform infrared spectroscopy. The results show that the composite had a high BET surface area because of its
small size and irregularly layered structure. MoS2 in the composite was composed of typical layered structures with thicknesses of 2–8 nm and lengths of 10–40 nm. The composite
contained a wide and intensive absorption at 400–700 nm, which is in the visible light region, and presented a positive catalytic
effect on removing methyl orange from the aqueous solution. The catalytic activity of the composite was influenced by the
initial concentration of methyl orange, the amount of the catalyst, the pH value, and the degradation temperature. In addition,
the composite catalyst could be regenerated and repeatedly used via filtration three times. The deactivating catalyst could
be reactivated after catalytic reaction by heating at 450 °C for 30 min in H2. 相似文献
4.
Cong-Ju Li Jiao-Na Wang Xiu-Yan Li Lian-Lian Zhang 《Journal of Materials Science》2011,46(7):2058-2063
Magnetically separable TiO2-coated SrFe12O19 electrospun nanofibers were obtained successfully by means of sol–gel, electrospinning, and coating technology, followed
by heat treatment at 550–650 °C for 3 h. The average diameter of the electrospun fibers was 500–600 nm. The fibers were characterized
by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), and vibrating sample
magnetometer (VSM). The optimized calcining temperature was determined by XRD and the analysis of decolorizing efficiency
of methylene blue (MB) under UV–vis irradiation. The photocatalytic activity of the TiO2-coated SrFe12O19 fibers was investigated using ultraviolet–visible absorbance by following the photooxidative decomposition of a model pollutant
dye solution, MB in a photochemical reactor. In contrast to pure TiO2 fibers, the TiO2-coated SrFe12O19 fibers have higher absorption in 250–750 nm wavelength regions. The presence of SrFe12O19 not only broadened the response region of visible-light, but also enhanced the absorbance for UV light. The decolorizing
efficiency of MB under UV–vis irradiation was up to 98.19%, which was a little higher than that of Degussa P25 (97.68%). Furthermore,
these fibers could be recollected easily with a magnet in a photocatalytic process and had effectively avoided secondary pollution
of treated water. 相似文献
5.
Effect of temperature and time on solvothermal synthesis of tetragonal BaTiO<Subscript>3</Subscript>
Tetragonal BaTiO3 nanoparticles are synthesized via solvothermal route in an ethanol water mixture. Ba(OH)2·8H2O is used as Ba precursor and TiO2 (P25 Degussa ∼25 nm, 30% anatase, 70% rutile) is used as Ti precursor in the Ba : Ti molar ratio 2 : 1. Effect of temperature
and time study on solvothermal synthesis of BaTiO3 revealed that a moderate reaction temperature i.e. 185°C and longer reaction time favour tetragonal phase stabilization.
Dissolution–precipitation appears to be the transformation mechanism for the crystallization of BaTiO3 from particulate TiO2 precursor. 相似文献
6.
A. Turgut I. Tavman M. Chirtoc H. P. Schuchmann C. Sauter S. Tavman 《International Journal of Thermophysics》2009,30(4):1213-1226
In this study, the thermal conductivity and viscosity of TiO2 nanoparticles in deionized water were investigated up to a volume fraction of 3% of particles. The nanofluid was prepared
by dispersing TiO2 nanoparticles in deionized water by using ultrasonic equipment. The mean diameter of TiO2 nanoparticles was 21 nm. While the thermal conductivity of nanofluids has been measured in general using conventional techniques
such as the transient hot-wire method, this work presents the application of the 3ω method for measuring the thermal conductivity. The 3ω method was validated by measuring the thermal conductivity of pure fluids (water, methanol, ethanol, and ethylene glycol),
yielding accurate values within 2%. Following this validation, the effective thermal conductivity of TiO2 nanoparticles in deionized water was measured at temperatures of 13 °C, 23 °C, 40 °C, and 55 °C. The experimental results
showed that the thermal conductivity increases with an increase of particle volume fraction, and the enhancement was observed
to be 7.4% over the base fluid for a nanofluid with 3% volume fraction of TiO2 nanoparticles at 13 °C. The increase in viscosity with the increase of particle volume fraction was much more than predicted
by the Einstein model. From this research, it seems that the increase in the nanofluid viscosity is larger than the enhancement
in the thermal conductivity. 相似文献
7.
A. Sadeghzadeh Attar M. Sasani Ghamsari F. Hajiesmaeilbaigi Sh. Mirdamadi K. Katagiri K. Koumoto 《Journal of Materials Science》2008,43(17):5924-5929
Well-aligned anatase and rutile TiO2 nanorods and nanotubes with a diameter of about 80–130 nm have successfully been fabricated via sol-gel template method.
The prepared samples were characterized by using thermogravimetric (TG) and differential thermal analysis (DTA), X-ray diffraction
(XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy
(EDS). The XRD results indicated that the TiO2 nanorods were crystallized in the anatase and rutile phases, after annealing at 400–800 °C for different periods of time
from 0.2 to 10 h. 相似文献
8.
The precipitation behavior of niobium component out of niobium-doped anatase-type TiO2 and structural change in the course of heating were investigated. The samples were directly formed under hydrothermal conditions
at 240 °C for 5 h in the presence of aqueous ammonia via crystallization from co-precipitates that were obtained from precursor
solutions of TiOSO4 and NbCl5. The as-prepared niobium-doped anatase-type titania nanoparticles showed bluish color and absorption in the visible region,
which was confirmed to be due to the presence of Ti(III) in the solid solutions using electron paramagnetic resonance measurement.
The niobium-doped anatase-type titania existed stably without an appearance of any other phases after heating up to 500 °C
for 1 h. In the course of heating at 500–800 °C, continual and clear decrease in the lattice parameters a
0 and c
0 of the anatase was observed, which was followed by the precipitation of Nb2O5 and TiNb2O7 out of the niobium-doped anatase, but the anatase phase was maintained without anatase-to-rutile phase transformation up
to 850–1,000 °C. The anatase-to-rutile phase transformation was gradually retarded when the niobium content increased. 相似文献
9.
Pellets of ceramic Na1−xKxNbO3 (x = 0, 0.2 and 0.5), were prepared by conventional solid-state reaction method. Prepared samples were characterized using
XRD and SEM. The frequency and temperature variation of dielectric constant, loss tangent and dielectric conductivity of prepared
samples were measured in the frequency range from 10 KHz-1 MHz, and in the temperature range from 50–250°C for x = 0.2 and
0.5, and between 50 and 480°C for x = 0 compositions. It was observed that the dielectric constant and loss tangent decrease,
and conductivity increases with increasing frequency. Near the transition temperature the material shows anomalous behaviour
for the observed properties, and the peaks of dielectric constant and loss tangent were observed shifting towards lower temperature
with increasing frequency. 相似文献
10.
Hemisphere-like F-doped anatase TiO2 has been synthesized by hydrothermal treatment of TiF4 aqueous solution in the presence of starch at 130 °C for 10 h, and then calcined at 450 °C for 2.5 h in air. The as-synthesized
product has been investigated by photocatalytic reaction test and characterized by powder X-ray diffraction (XRD), scanning
electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray photoelectron
spectroscopy (XPS), and UV–Vis diffuse reflectance spectra (DRS). The results showed that fluorine was successfully doped
into the TiO2 hemispheres. The F-doped TiO2 hemispheres showed high visible light activity in degradation of acid orange II, which could be attributed to the creation
of oxygen vacancies and good crystallinity. 相似文献
11.
TiO2 nanotube arrays were synthesized by anodization of Ti metal sheets followed by thermal annealing at elevated temperatures
from 400 to 600 °C. Scanning electron microscopic measurements showed that dense arrays of nanotubes were produced with the
inner diameter about 100 nm, wall thickness 35 nm, and length about 10 μm. X-ray diffraction measurements showed that the
as-prepared nanotubes were largely amorphous, whereas thermal annealing led to the formation of well-defined anatase crystalline
phase. More interestingly, at 470 °C, the brookite crystalline phase also started to emerge, which became better defined at
500 °C and disappeared eventually at higher temperatures, a phenomenon that has not been observed previously in TiO2 nanotube arrays prepared by anodization. The impacts of the TiO2 nanocrystalline structure on the photocatalytic activity were then examined by using the reduction of methylene blue in water
as an illustrating example. Upon exposure to UV lights, the visible absorption profiles of methylene blue exhibited apparent
diminishment. Based on these spectrophotometric measurements, the corresponding pseudo-first-order rate constant was estimated,
and the sample thermally annealed at 500 °C was found to exhibit the highest activity. The strong correlation between the
TiO2 crystalline characteristics and photocatalytic performance suggests that the synergistic coupling of the anatase and brookite
crystalline domains led to effective charge separation upon photoirradiation and hence improved photocatalytic activity, most
probably as a consequence of the vectorial displacement at the nanoscale junctions between these crystalline grains that impeded
the dynamics of electron–hole recombination. These results demonstrate the significance of nanoscale engineering in the manipulation
of oxide photocatalytic performance. 相似文献
12.
The anatase-rutile phase transition in fine-particle TiO2-NiO oxides has been studied using physicochemical characterization techniques (X-ray diffraction, differential thermal analysis,
and mass spectrometry). The results demonstrate that NiO additions considerably increase the rate of the anataserutile polymorphic
transformation. Nickel titanate formation depends on the procedures used to prepare both titanium dioxide and nickel oxide.
In the temperature range 700–850°C, the anatase to rutile phase transition prevents nickel titanate formation. 相似文献
13.
Barium titanate powders differing in particle size (110–740 nm) were prepared by calcining barium titanyl oxalate precipitated
by the Merker method. The powders were sintered to produce PTCR ceramics with the composition 100(Ba0.89Ca0.08Pb0.03)TiO3 + 0.8TiO2 + 0.7Y + 0.1Mn + 2.5SiO2 and electrical properties of the ceramics were studied. The results demonstrate that improving the crystallinity of the barium
titanate powder suppresses recrystallization of the ceramics and has a significant effect on their resistance ratio and electric
strength. We found the optimal range of calcination temperatures (950–1000°C) for barium titanyl oxalate which ensures the
highest electric strength of thermistors with a resistance of 31 Ω. The average crystallite size of the parent barium titanate
powder is ∼250–320 nm. 相似文献
14.
A. B. Bodade Minaz Alvi A. V. Kadu G. N. Chaudhari 《Journal of Materials Science》2010,45(19):5264-5270
Nanocrystalline La1−x
Co
x
Mn1−y
Ni
y
O3 (x = 0.2 and 0.4; y = 0.1, 0.3, and 0.5) thick films sensors prepared by sol–gel method were studied for their H2S gas sensitivity. The structural and morphological properties have been carried out by X-ray diffraction (XRD) and transmission
electron microscopy (TEM). Average particle size estimated from XRD and TEM analyses was observed to be 30–35 nm. The gas
response characteristics were found to depend on the dopants concentration and operating temperature. The maximum H2S gas response of pure LaMnO3 was found to be at 300 °C. In order to improve the gas response, material doped with transition metals Co and Ni on A- and
B-site, respectively. The La0.6Co0.4Mn0.5Ni0.5O3 shows high response towards H2S gas at an operating temperature 250 °C. The Pd-doped La0.6Co0.4Mn0.5Ni0.5O3 sensor was found to be highly sensitive to H2S at an operating temperature 200 °C. The gas response, selectivity, response time and recovery time were studied and discussed. 相似文献
15.
T. Joseph S. Uma J. Philip M. T. Sebastian 《Journal of Materials Science: Materials in Electronics》2011,22(8):1000-1009
A new polymer-ceramic composite was prepared using PTFE and low loss Sr2ZnSi2O7. The dielectric properties of the composite were studied in the microwave and radiofrequency ranges. The relative permittivity
(εr) and dielectric loss (tan δ) increased with the filler loading from 0.10 to 0.50 volume fractions (vf). The observed values of εr, thermal conductivity and coefficient of thermal expansion (CTE) were compared with the corresponding theoretical predictions.
The ability of the composite towards moisture absorption resistance was studied as a function of filler loading. It was also
found that the variation of εr was less than 2% in the temperature range 25–90 °C, at 1 MHz. For a filler content of 0.50 vf, the PTFE/Sr2ZnSi2O7 composite exhibited εr = 4.4, tan δ = 0.003 (at 4–6 GHz), CTE = 38.3 ppm/°C, thermal conductivity = 2.1 W/mK and moisture absorption = 0.09 wt%. 相似文献
16.
Based on the principle of stability of geopolymer gel as refractory binder, a geopolymeric paste in the K2O–Al2O3–SiO2 system was developed and used to produce refractory concretes by adding various amount of α-quartz sand (grain size in the
range 0.1 μm to 1 mm) and fine powder alumina (grain size in the range 0.1–100 μm). The consolidated samples were characterized
before and after sintering using optical dilatometer, DSC, XRD and SEM. The total shrinkage in the range of 25–900 °C was
less than 3%, reduced with respect to the most diffused potassium or sodium based geopolymer systems, which generally records
a >5% shrinkage. The maximum shrinkage of the basic geopolymer composition was recorded at 1000 °C with a 17% shrinkage which
is reduced to 12% by alumina addition. The temperature of maximum densification was shifted from 1000 °C to 1150 or 1200 °C
by adding 75 wt% α-quartz sand or fine powder alumina respectively. The sequences of sintering of geopolymer concretes could
be resumed as dehydration, dehydroxylation, densification and finally plastic deformation due to the importance of liquid
phase. The geopolymer formulations developed in this study appeared as promising candidates for high-temperature applications:
refractory, fire resistant or insulating materials. 相似文献
17.
X. H. Zheng J. Xiao X. Huang D. P. Tang X. L. Liu 《Journal of Materials Science: Materials in Electronics》2011,22(8):1116-1119
The formation behavior of CaCu3Ti4O12 (CCTO) had been investigated via solid state reaction from CaTiO3, CuO and TiO2 powders. In the temperature range from 750 to 1,200 °C, the reaction sequence was traced by XRD, and the microstructure evolution
of calcined powders was also investigated by SEM. CCTO began to form owing to the reaction between CaTiO3, CuO and TiO2 at around 850 °C, and became the major phase at 1,000 °C. Finally, the single phase CCTO was obtained at 1,150 °C. However,
CCTO was decomposed at CaTiO3, CuO and TiO2 when the temperature increased to 1,200 °C. In addition, no other intermediate phases occurred in the synthesized process.
The formation behaviors indicated that CaTiO3 prevented the formation and growth of CCTO. 相似文献
18.
Akitoshi Hayashi Keiichi Minami Fuminori Mizuno Masahiro Tatsumisago 《Journal of Materials Science》2008,43(6):1885-1889
The 70Li2S·30P2S5 (mol%) glass was prepared by the melt quenching method and the glass–ceramic electrolytes were obtained by heating the prepared
glass over crystallization temperatures. The superionic metastable Li7P3S11 crystal was formed by heating the glass in the temperature range from 280 and 360 °C. The conductivity of the glass–ceramics
was enhanced by the precipitation and growth of the Li7P3S11 crystal, and the highest conductivity of 4.1 × 10−3 S cm−1 at room temperature was achieved in the glass–ceramic heated at 360 °C for 1 h. The Li7P3S11 crystal changed into the thermodynamically stable phase such as the Li4P2S6 crystal with further increasing heat treatment temperature and holding time, resulting in lowering conductivities of the
glass–ceramics. 相似文献
19.
Prasanta Dhak Debasis Dhak Manasmita Das Panchanan Pramanik 《Journal of Materials Science: Materials in Electronics》2011,22(12):1750-1760
Nanocrystalline ceramic powder of Ba0.8Bi2.133Nb1.6Ta0.4O9 was synthesized by chemical precursor decomposition method. The single-phase formation of the compound was confirmed using
an X-ray diffraction technique and was found to be a tetragonal phase at room temperature. Average crystallite size and particle
size were found to be 41 and 48.5 nm, which were analyzed through XRD and TEM respectively. The dielectric constant and tangent
loss were measured in the frequency range 1 kHz–1 MHz after sintering the sample at 900 °C for 4 h. The polarization behavior
was studied at an applied voltage of 6.2 kV/cm. Electrical properties of the material were investigated using complex impedance
spectroscopy (CIS) technique, which revealed the presence of both grain and grain-boundary effects in the materials, which
is also evidenced from the scanning electron microscope image. Grain conductivity indicated Arrhenius-type thermally activated
process. AC conductivity spectrum obeys Jonscher’s universal power law. The electric modulus analysis suggests the possibility
of hopping mechanism for electrical processes in the system with a non-debye type relaxation, which is supported by the impedance
data. 相似文献
20.
The regular and homogeneous single-crystal CoMoO4·3/4H2O nanorods, with the diameters ca. 100–300 nm and lengths ca. 8–15 μm, have been successfully prepared by a simple and facile
precipitation method. Their morphology conversion from broom-like to cage-like structure has been firstly reported through
controlling the reaction temperature. The broom-like microbunches were obtained at 50 °C while at 80 °C, dispersive nanorods
can be prepared. As the temperature reached 90 °C, the morphology of the products converted to cage-like microspheres. SEM
results show that the reaction temperature has a critical role in both the formation of the products and their morphologies.
The UV–visible diffuse reflectance absorbance spectra of the products display two intense, broad absorbance bands cover almost
the whole ultraviolet and visible region except for a narrow region around 450 nm, which is in the region for purple light.
Based on the experimental results, a possible formation mechanism was also proposed. The synthesis strategy is simple, facile,
mild, and has a good reproducibility. The as-prepared products may have potential applications in optics, catalysis, and grating
materials. 相似文献