共查询到20条相似文献,搜索用时 31 毫秒
1.
Mary C. F. Alves Soraia C. Souza Márcia R. S. Silva Elaine C. Paris S. J. G. Lima R. M. Gomes E. Longo A. G. de Souza Iêda M. Garcia dos Santos 《Journal of Thermal Analysis and Calorimetry》2009,97(1):179-183
SrSnO3 was synthesized by the polymeric precursor method with elimination of carbon in oxygen atmosphere at 250 °C for 24 h. The
powder precursors were characterized by TG/DTA and high temperature X-ray diffraction (HTXRD). After calcination at 500, 600
and 700 °C for 2 h, samples were evaluated by X-ray diffraction (XRD), infrared spectroscopy (IR) and Rietveld refinement
of the XRD patterns for samples calcined at 900, 1,000 and 1,100 °C. During thermal treatment of the powder precursor ester
combustion was followed by carbonate decomposition and perovskite crystallization. No phase transition was observed as usually
presented in literature for SrSnO3 that had only a rearrangement of SnO6 polyhedra. 相似文献
2.
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
3.
Lingli Li Xiangqian Shen Lei Li Xianfeng Meng 《Journal of Sol-Gel Science and Technology》2011,57(2):198-203
Li0.25Sr0.5(MoO4):Eu0.253+ red-emitting phosphors were prepared by the organic gel-thermal decomposition process with metal salts and citric acid as
starting reagents. X-ray diffraction, scanning electron microscopy and photoluminescent spectroscopy were used to characterize
the as-prepared phosphors. The Li0.25Sr0.5(MoO4):Eu0.253+ phase consisting of nanosized crystallites is formed at 400 °C and the nanosized crystallites with a tetragonal-dipyramid
morphology increase with the calcination temperature and time. During the early period at 650 °C, the microstructure of the
Li0.25Sr0.5(MoO4):Eu0.253+ crystallites are unstable and the re-crystallization for some particles takes place with a particle morphological modification.
The optimized calcination conditions for the Li0.25Sr0.5(MoO4):Eu0.253+ phosphors are 650 °C for 13 h. The Li0.25Sr0.5(MoO4):Eu0.253+ phosphors with particle sizes about 0.5 to 2.0 μm obtained under the optimized conditions can be excited by the ultraviolet
light 395 nm and blue light 466 nm, which are well met with the requirements for the current commercial near-UV and blue LEDs,
and exhibit a high emission performance. 相似文献
4.
Xu Zhao 《Journal of solid state chemistry》2006,179(8):2562-2570
Porous ZnWO4 films have been fabricated on Indium-tin oxide (ITO) glass and its photoelectrochemical properties and high photocatalytic activities towards degradation of rhodamine B (RhB) has been investigated. Using amorphous heteronuclear complex as precursor and with the addition of polyethylene glycol (PEG, molecular weight=400), the porous ZnWO4 films have been achieved at the temperature of 500 °C via dip-coating method. It is composed of approximately 70 nm-sized particles and exhibits substantial porosity. The textures and porosity of ZnWO4 films are dependent on preparation factors, such as the ratio of precursor/PEG and the annealing conditions. The formation mechanism of porous ZnWO4 films was proposed. The porous ZnWO4 films exhibited high photocatalytic activities towards degrading RhB. The top of valence band and the bottom of the conduction band was estimated to be −0.56 and 3.45 eV (vs. saturated calomel electrode (SCE)), respectively. 相似文献
5.
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
6.
Juan M. Quintana-Melgoza Antonio Gómez-cortés Miguel Avalos-Borja 《Reaction Kinetics and Catalysis Letters》2002,76(1):131-140
We present a comparative study of NiWO4, NiO, and WO3 catalysts for simultaneous conversion of NO and CO. Samples were synthesized by reacting ammonium metatungstate and/or nickel nitrate at high temperature (773 K to 903 K) under an oxygen stream. Catalysts were characterized by X-ray diffraction, surface area measurements, energy dispersive spectroscopy and scanning electron microscopy. The catalytic reduction of NO by CO took place in the temperature range (523 to 973) K under highly reductive conditions (NO:CO= 1:5) over NiWO4NiO, and WO3, respectively. The 100 % NO conversion at GHSV of 11460 h-1 was achieved at 773 K over NiWO4 and at 848 K over NiO. The WO3 was deactivated at 898 K. However, in the range (523 to 723) K NiO was more active than NiWO4 and WO3 catalysts. 相似文献
7.
V. K. Duplyakin O. N. Baklanova O. A. Chirkova N. V. Antonicheva A. B. Arbuzov N. N. Voitenko V. A. Drozdov V. A. Likholobov 《Kinetics and Catalysis》2010,51(1):126-130
The interaction of nickel hydroxocarbonate, ammonium paramolybdate, and ammonium metatungstate (Ni: Mo: W = 3: 1: 1) is reported.
Under mechanical activation conditions, nickel hydroxocarbonate particles undergo comminution and ammonium paramolybdate and
ammonium metatungstate particles soften and aggregate. It is demonstrated by DTA, X-ray diffraction, and IR spectroscopy that
heat treatment of the mechanically activated mixture at 400–450°C yields the salts NiMoO4 and NiWO4. 相似文献
8.
9.
The formation ofβ-phase Bi2Mo2O9 catalyst from a precursor precipitate has been studied using thein situ combined XRD/QuEXAFS technique and DSC during calcination. Accordingly the precursor was observed to undergo a number of
changes in both the molybdenum (VI) coordination and long-range ordering during this heating. Initially the two other forms
of bismuth molybdate (α-andγ-phases) were observed to form from the poorly crystalline precursor at about 230°C, however, theβ-phase eventually crystallised after prolonged heating at 560°C.
Dedicated to Professor C N R Rao on his 70th birthday 相似文献
10.
Zhan-Hui Zhang Hong-Juan Wang Xiao-Qian Ren Yan-Yan Zhang 《Monatshefte für Chemie / Chemical Monthly》2009,7(1):1481-1483
Abstract
HBF4/SiO2 was used as an efficient, green, and inexpensive catalytic system for synthesis of 12-aryl or 12-alkyl-8,9,10,12-tetrahydro-11H-benzo[a]xanthen-11-one derivatives via a one-pot three-component reaction of aldehydes, 2-naphthol, and cyclic 1,3-dicarbonyl compounds. The reactions proceeded rapidly at 80 °C under solvent-free conditions and the desired products were obtained in good to excellent yields. 相似文献11.
Rong Li Qiang Zhen Xionggang Lu Michel Drache Rose-No?lle Vannier 《Journal of Solid State Electrochemistry》2011,15(9):1919-1926
Nanopowders of Bi0.75Er0.25O1.5 and Bi0.75Er0.125Y0.125O1.5 were prepared by a reverse titration chemical coprecipitation method under controlled pH conditions. After calcination at
500 °C for 3 h, powders with grain size in the order of 10 nm were obtained. In order to keep the nanosize of grains, these
powders were densified by spark plasma sintering. Samples with relative density higher than 96% were prepared in only 10 min
up to 500 °C with an average grain size of 15 and 11 nm for Bi0.75Er0.25O1.5 and Bi0.75Er0.125Y0.125O1.5, respectively. Impedance spectroscopy revealed slightly higher conductivity for the Bi0.75Er0.125Y0.125O1.5 composition compared to Bi0.75Er0.25O1.5 nanoceramic, but performances remained lower than the corresponding Bi0.75Er0.25O1.5 microcrystalline sample. However, mechanical properties of both nanocrystalline ceramics are improved when compared to microcrystalline
samples. 相似文献
12.
Yutaka Sawada Junji Yamaguchi Osamu Sakurai Keizo Uematsu Nobuyasu Mizutani Masanori Kato 《Thermochimica Acta》1979,34(2):233-237
An exothermic phenomenon and a simultaneous rapid evolution of a small amount of carbon dioxide at ?500°C during thermal decomposition of hydromagnesite 4 MgCO3 · Mg(OH)2 · 4 H2O was studied by isothermal DSCTG in a carbon dioxide atmosphere. It was quantitatively confirmed that the exothermic phenomenon was due to crystallization of MgCO3 from the amorphous phase and that the evolution of carbon dioxide was due to decomposition of the MgCO3 by the heat of crystallization (?3.4 kcal mole?1. 相似文献
13.
Soraia Carvalho de Souza Mary Cristina Ferreira Alves A. Luiz M. de Oliveira E. Longo F. Ticiano Gomes Vieira Rodinei Medeiros Gomes L. E. B. Soledade A. G. de Souza Iêda M. Garcia dos Santos 《Journal of Thermal Analysis and Calorimetry》2009,97(1):185-190
In this work, the synthesis of Nd-doped SrSnO3 by the polymeric precursor method, with calcination between 250 and 700 °C is reported. The powder precursors were characterized
by TG/DTA and high temperature X-ray diffraction (HTXRD). After heat treatment, the material was characterized by XRD and
infrared spectroscopy. Ester and carbonate amounts were strictly related to Nd-doping. According to XRD patterns, the orthorhombic
perovskite was obtained at 700 °C for SrSnO3 and SrSn0.99Nd0.01O3. For Sr0.99Nd0.01SnO3, the kinetics displayed an important hole in the crystallization process, as no peak was observed in HTXRD up to 700 °C,
while a XRD patterns showed a crystalline material after calcination at 250 °C. 相似文献
14.
Hou-Yin Zhao Yan Cao Quentin Lineberry Wei-Ping Pan 《Journal of Thermal Analysis and Calorimetry》2011,106(1):199-205
The CO2 adsorption capacity of the low-cost solid sorbents of waste tire char (TC) and chicken waste char (CW) was compared with
commercial active carbon (AC) and 5 ? zeolite (ZA) using thermogravimetric analysis (TG), pressurized TG, and differential
scanning calorimetry (DSC). The sorbents were degassed in a TG up to 150 °C to release all gases on the surface of the sample,
then cooled down to the designed temperature for adsorption. TG results indicated that the CO2 adsorption capacity of TC was higher than that of CW, but lower than those of AC and ZA. The maximum adsorption rate of TC
at 50 °C was 0.61% min−1, lower than that of AC, but higher than that of CW, 0.44% min−1. The maximum adsorption rate of ZA at 50 °C was 3.1% min−1. When the pressure was over 4 bar, the adsorption rate of ZA was lower than that of TC and AC. At 30 bar, the total CO2 uptake of TC was 20 wt%, higher than that of CW and ZA but lower than that of AC. The temperature, nitrogen concentration,
and water content also influenced the CO2 adsorption capacity of sorbents to some extent. DSC results showed that adsorption was an exothermic process. The heat of
CO2 adsorption per mole of CO2 of TC at 50 °C was 24 kJ mol−1 while the ZA had the largest heat of adsorption at 38 kJ mol−1. Comparing the characteristics of TC and CW, TC may be a promising sorbent for removal of CO2. 相似文献
15.
Han Lin Guo-Qiang Tan Wei Zhang Yu-Qin Zheng Ao Xia Hui-Jun Ren 《Journal of Cluster Science》2013,24(1):315-325
A novel chrysanthemum-shaped monocline ZnWO4 photocatalyst was synthesized by microwave-assisted hydrothermal method with Na2WO4·2H2O and Zn(NO3)2·6H2O as raw materials at different reaction temperatures. The prepared ZnWO4 photocatalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Field emission scanning electron microscopy (FE-SEM), Transmission electron microscopy, Photoluminescence spectrum (PL) and UV–Vis absorption spectrum (UV–Vis). The photocatalytic property of the prepared chrysanthemum-shaped monocline ZnWO4 photocatalyst was evaluated by the degradation of Rhodamine B (RhB) in aqueous solution. The effects of reaction temperature on the photocatalytic degradation efficiency of RhB were investigated. The results indicated that the chrysanthemum-shaped monocline ZnWO4 photocatalyst is prepared by foliated powders with the sizes of about 30 nm and 500 nm respectively at 160 and 220 °C. The PL relative intensity of prepared ZnWO4 photocatalyst is apparently intensifying with increasing temperature. The photocatalytic property decreases with the increasing recombination probability of the excited electrons and holes. The chrysanthemum-shaped monocline ZnWO4 photocatalyst prepared at 160 °C possesses the best photocatalytic property, and the degradation efficiency of RhB at 180 min UV-light irradiation is achieved 75 %. The ZnWO4 has good reusability property on degradation of RhB and the degradation rate is still higher than 65 % after three cycles. 相似文献
16.
Hamdi Ben Yahia Ute Ch. Rodewald Rainer P?ttgen 《Monatshefte für Chemie / Chemical Monthly》2010,37(12):495-499
Abstract
The titanyl arsenate NaTiO[AsO4] was synthesized in the form of colourless lath-shaped crystals from arsenic and titanium dioxide in a NaCl/KCl flux at 850 °C. NaTiO[AsO4] crystallizes with the monoclinic low-temperature form LT-CaTiO[SiO4], space group P21/c. The structure was refined from single crystal diffractometer data: a = 6.7170(9), b = 8.7707(12), c = 7.2447(10) ?, β = 114.77(1)°, wR2 = 0.0559, 789 F 2 values, and 74 variables. NaTiO[AsO4] is characterized by a topology common to a wide range of oxide structures of stoichiometry AMOXO4. It consists of parallel chains of trans-corner-sharing TiO6 octahedra, cross-linked by isolated AsO4 tetrahedra. 相似文献17.
A facile synthesis of NaNbO3 powders was performed by solid-state reaction at low temperature. Stoichiometric ammonium niobium oxalate and Na2CO3 were mixed in water and then calcined at different temperatures for various times after drying. A combination of X-ray diffraction
(XRD), scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectroscopy and thermogravimetric (TG) analysis
was used to characterize the product and precursor compound. The XRD patterns show that single-phase NaNbO3 powders with high crystallinity can be synthesized at 425 °C for 15 min. The particle size from XRD data is found to be about
40 nm for NaNbO3 powders calcined at 500 °C for 3 h, which is in good agreement with SEM data. The SEM photograph shows that NaNbO3 powders are cuboid-like and well crystallized when calcination at 800 °C for 3 h. The product compositions prepared using
other sodium reactants, such as HCOONa and NaNO3, are also discussed. 相似文献
18.
V. V. Sidorchuk S. V. Khalameida N. S. Litvin V. A. Zazhigalov 《Russian Journal of Inorganic Chemistry》2010,55(6):848-856
X-ray powder diffraction, DTA, FT-IR spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), nitrogen
adsorption, and mercury porometry were used to characterize samples prepared as a result of mechanochemical treatment (MCT)
of a V2O5/(NH4)2Mo2O7 (V/Mo = 0.7/0.3) composition in water, ethanol, and air, as well as after calcining them at temperatures from the range 300–700°C.
The MCT of nonporous powders in water yields porous materials with definite meso- and macropore sizes. Heat treatment in air
at 300–450°C enhances the formation of a molybdenum substitutional solid solution in V2O5 and conserves rather high values of specific surface areas and pore volumes. An increase in heat treatment temperature is
accompanied by the degradation of the solid solution and the formation of a V2MoO8 phase. 相似文献
19.
G. Ya. Popova A. A. Budneva T. V. Andrushkevich 《Reaction Kinetics and Catalysis Letters》1997,62(1):97-103
Effect of the H3PMo12O40/SiO2(P-Mo-HPA) thermal treatment on adsorbed forms of HCOOH and H2CO has been studied by IR spectroscopy. On the sample pretreated at 150°C, HCOOH adsorbed mainly as hydrogen-bonded complexes.
The HPA calcination at 350°C resulted in the formation of surface formates along with hydrogen-bonded complexes. This proves
the formation of coordinatively unsaturated surface cations (Lewis acid sites) during HPA dehydration. Alteration of the surface
composition due to dehydration was found to have a major influence on the H2CO adsorbed forms. 相似文献
20.
《Solid State Sciences》2012,14(4):451-455
Three-dimensional chrysanthemum-like Co3O4 was prepared via a facile hydrothermal route without any template, and a subsequent calcination process. With a controlled concentration of the homogeneous precipitation agent, urea, a chrysanthemum-like precursor was hydrothermally obtained at 120 °C for 20 h, and the morphology was kept for Co3O4 after a subsequent calcination at 300 °C for 2 h. Co3O4 chrysanthemum-like architectures are assemblies of nanorods radiating from a common centre, and the nanorods consisted of interconnected nanoparticles with the size of about 30 nm. When tested as an anode material of Li-ion batteries, chrysanthemum-like Co3O4 presented a discharge capacity of ∼450 mA h/g after 50 discharge/charge cycles. 相似文献