共查询到20条相似文献,搜索用时 15 毫秒
1.
I. A. Zvereva I. V. Otrepina V. G. Semenov E. A. Tugova V. F. Popova V. V. Gusarov 《Russian Journal of General Chemistry》2007,77(6):973-978
The mechanism of formation of the perovskite-like layered structure of the oxide Gd2SrFe2O7 was studied. The limiting stages are those of formation of phases with perovskite (GdFeO3, SrFeO3?x ) and K2NiF4 (GdSrFeO4) structures. The Mössbauer study has shown that iron atoms exist in a heterovalent state (Fe3+ and Fe4+) only in the structure of SrFeO3?x ). 相似文献
2.
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
3.
L. T. Denisova A. D. Izotov L. A. Irtyugo Yu. F. Kargin V. V. Beletskii V. M. Denisov 《Doklady Physical Chemistry》2017,472(1):10-12
Erbium stannate Er2Sn2O7 and thulium stannate Tm2Sn2O7 with a pyrochlore-type structure were produced by solid-phase synthesis by calcining stoichiometric mixtures of the respective oxides in air at 1473 K for 240 and 200 h. The high-temperature heat capacity of Er2Sn2O7 and Tm2Sn2O7 was studied by differential thermal calorimetry at 353–1000 K. From the experimental dependences C P = f(T), the thermodynamic functions (enthalpy change, entropy change, and reduced Gibbs free energy) of oxide compounds were calculated. 相似文献
4.
Y. Akishige H. Shigematsu T. Tojo H. Kawaji T. Atake 《Journal of Thermal Analysis and Calorimetry》2005,81(3):537-540
Summary Specific heats on the single crystals of Sr2Nb2O7, Sr2Ta2O7 and (Sr1-xBax)2Nb2O7 were measured in a wide temperature range of 2-600 K. Heat anomalies of a λ-type were observed at the incommensurate phase transition of TINC (=495 K) on Sr2Nb2O7 and at the super-lattice phase transition of TSL (=443 K) on Sr2Ta2O7; the transition enthalpies and the transition entropies were estimated. Furthermore, a small heat anomaly was observed at the low temperature ferroelectric phase transition of TLOW (=95 K) on Sr2Nb2O7. The transition temperature TLOW decreases with increasing Ba content x and it vanishes for samples of x>2%. 相似文献
5.
A. V. Mikhailov N. A. Gribchenkova E. N. Kolosov A. R. Kaul’ A. S. Alikhanyan 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2011,85(1):26-30
The thermodynamics of vaporization in the Bi2O3-Fe2O3 quasibinary system was studied by high-temperature mass-spectrometry. The partial pressures of the constituents of a saturated
vapor over the system at 1100 K were determined. Based on the experimental data, the following parameters were calculated:
the activities of the components of the Bi2O3-Fe2O3 system condensed phase, the standard enthalpies of some heterogeneous reactions, and standard enthalpies of formation and
enthalpies of formation for crystalline BiFeO3 and Bi2Fe4O9 from individual oxides. An optimal temperature for the solid-phase synthesis of bismuth ferrites from simple oxides is recommended. 相似文献
6.
A. V. Egorysheva V. D. Volodin T. Milenov P. Rafailov V. M. Skorikov T. D. Dudkina 《Russian Journal of Inorganic Chemistry》2010,55(11):1810-1817
A physicochemical study of glasses based on the MO-Bi2O3-B2O3 and SrO-Bi2O3-B2O3 systems was performed. Glass formation regions were found. The structural and optical properties, as well as the thermal
behavior of the glasses, were studied. 相似文献
7.
Sifang Kong Jiang Cheng Yangsheng Liu Xiufang Wen Pihui Pi Zhuoru Yang 《Central European Journal of Chemistry》2008,6(4):627-633
In this study, a novel and effective suspension polymerization has been employed to prepare functional magnetic porous SrFe12O19/P(St-DVB-MAA) microspheres in the presence of bilayer surfactants (sodium dodecyl benzene sulfonate (SDBS) and oleic acid
(OA)) coated on micro-size magnetic SrFe12O19. This was achieved by pre-polymerizing the organic phase, which contained co-monomers, porogens and treated magnetic particles,
at 65°C for 0.5 h under ultrasound conditions. Aqueous solutions containing a dispersion agent were then added to effect suspension
polymerization. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD),
thermogravimetric analysis (TGA) and magnetic property measurement system (MPMS) were used to characterize the functional
magnetic porous microspheres. The results show that the microparticles are well shaped with a uniform size distribution of
about 0.5 ∼ 0.7 mm and the surfaces of the microspheres have many micro-pores with an average diameter of 0.533 μm. There
are carboxyl groups (−COOH) on the surface of the microspheres to the extent of 0.65 mmol g−1, as determined by conductometric titration. According to the XRD spectra, iron oxide consists mainly of SrFe12O19 which reveals hexahedral structure. The content of magnetic SrFe12O19 reaches 17.81% (by mass), and the microspheres have good heat resistance. The magnetic porous microspheres are ferromagnetic
with high residual magnetization and coercivity, 21.59 emu g−1 and 4.13 kOe, respectively. The saturation magnetisation is around 42.85 emu g−1.
相似文献
8.
Yu. F. Kargin S. N. Ivicheva L. I. Shvorneva M. G. Komova V. A. Krut’ko 《Russian Journal of Inorganic Chemistry》2008,53(9):1512-1516
Phase relations in the CaO-Bi2O3-B2O3 system have been investigated by X-ray powder diffraction and differential thermal analyses, and the isothermal section at 600°C has been constructed. The formation of ternary compounds at the component ratios 1CaO: 1Bi2O3: 1B2O3 (CaBi2B2O7) and 1CaO: 1Bi2O3: 2B2O3 (CaBi2B4O10) has been established X-ray diffraction characteristics of these phases are presented. 相似文献
9.
Sheng-Li Chen Haitao Wang Guimei Yuan Zhiqing Wang Zhi Cai 《Transition Metal Chemistry》2011,36(4):441-445
Macro-/mesoporous Al2O3 supports were prepared by using monodisperse polystyrene (PS) microspheres as a template. The pore volume and BET surface
area of the Al2O3 supports increased considerably with increasing amounts of the PS microspheres; further investigation showed that PS template
only increased the volume of macro-pores but did not change the volume of meso-pores or micro-pores. Macro-/mesoporous Re2O7/Al2O3 metathesis catalysts were prepared through loading Re2O7 onto the as-prepared macro-/mesoporous Al2O3 supports, and their catalytic performance was tested in a fixed-bed tubular reactor using the metathesis of normal butylenes
as a probe reaction. The results showed that the prepared macro-/mesoporous Re2O7/Al2O3 catalyst had high activity with consistent selectivity; propylene and pentene accounted for more than 90 wt% of the metathesis
products, while the amount of ethylene plus hexane was less than 10 wt%, the majority of which was hexane. These Re2O7/Al2O3 catalysts had not only higher activity, but also longer working life span and higher tolerance to carbon residues than conventional
Re2O7/Al2O3 catalysts. 相似文献
10.
Chun-Liang Hang Li-Xia Yang Chang-Mei Sun Ying Liang 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2018,92(3):496-501
Monodisperse and porous nonstoichiometric Zn ferrite can be prepared by a solvothermal method. Such non-Zn ferrite was used to be the precursor for synthesis of ZnFe2O4/Fe2O3 composite via calcination at 600°C for 3 h in air. X-ray powder diffractometer (XRD) and Energy Dispersive Spectrometer (EDS) proved the nonstoichiometry of Zn ferrite synthesized by solvothermal method and the formation of ZnFe2O4/Fe2O3 composite via calcination. TEM image showed that non-Zn ferrite spheres with wormlike nanopore structure were made of primary nanocrystals. BET surface area of non-Zn ferrite was much higher than that of ZnFe2O4/Fe2O3 composite. Saturation magnetization of non-Zn ferrites was significantly higher than that of ZnFe2O4/Fe2O3 composites. Calcination of non-Zn ferrite resulted in the formation of large amount of non-magnetic Fe2O3,which caused a low magnetization of composite. Because of higher BET surface area and higher saturation magnetization, non-Zn ferrite presented better Cr6+ adsorption property than ZnFe2O4/Fe2O3 composites. 相似文献
11.
The synthesis of new compounds based on Bi2O3
is investigated because they can be used as new environmentally friendly inorganic
pigments. Chemical compounds of the (Bi2O3)1–x(Er2O3)x type were synthetized.
The host lattice of these pigments is Bi2O3 that is doped by Er3+
ions. The incorporation of doped ions provides interesting colours and contributes
to an increase in the thermal stability of these compounds. The simultaneous
TG-DTA measurements were used for determination of the temperature region
of the pigment formation and thermal stability of pigments. 相似文献
12.
L. T. Denisova L. A. Irtyugo Yu. F. Kargin V. V. Beletskii V. M. Denisov 《Russian Journal of Inorganic Chemistry》2018,63(3):361-363
Yttrium germanate Y2Ge2O7 was prepared by solid-phase synthesis from a stoichiometric Y2O3–GeO2 mixture under multistage calcination in air within a temperature range of 1273–1473 K. The molar heat capacity of polycrystalline samples was measured by differential scanning calorimetry (DSC), and the C P = f(T) dependence was used to calculate the thermodynamic properties of yttrium digermanates, such as the enthalpy and entropy changes and the reduced Gibbs energy. 相似文献
13.
M. Boča V. Danielik Z. Ivanová E. Mikšíková B. Kubíková 《Journal of Thermal Analysis and Calorimetry》2007,90(1):159-165
The phase diagrams of the systems KF-K2TaF7 and KF-Ta2O5 were determined using the thermal analysis method. The phase diagrams were described by suitable thermodynamic model. In
the system KF-K2TaF7 eutectic points at x
KF=0.716 and t=725.4°C and at x
KF=0.214 and t=712.2°C has been calculated. It was suggested that K2TaF7 melts incongruently at around 743°C forming two immiscible liquids. The system KF-Ta2O5 have been measured up to 8 mol% of Ta2O5. The eutectic point was estimated to be at x
KF∼0.9 and t∼816°C. The formation of KTaO3 and K3TaO2F4 compounds has been observed in the solidified samples. 相似文献
14.
T. I. Krasnenko M. V. Rotermel’ S. A. Petrova R. G. Zakharov O. V. Sivtsova A. N. Chvanova 《Russian Journal of Inorganic Chemistry》2008,53(10):1641-1647
Phase relations in the Zn2V2O7-Cu2V2O7 system were studied by high-temperature X-ray diffraction and differential thermal analysis. The major phase constituents
of the system are solid solutions based on Zn2V2O7 and Cu2V2O7 polymorphs and their coexistence regions. The generation of α-Zn2 − 2x
Cu2x
V2O7 solid solution, where 0 ≤ x ≤ 0.30, leaves almost unchanged the stabilization temperature of the high-temperature zinc pyrovanadate phase. The α-Cu2 − 2x
Zn2x
V2O7 homogeneity range is 5 mol % Zn2V2O7. In the range 0.050 ≤ x ≤ 0.09 from 20 to ∼ 620°C, there is the two-phase field of α-Cu2V2O7 and β-Cu2V2O7 base solid solutions. At still higher temperatures, β-Zn2 − 2x
Cu2x
V2O7 and α-Cu2 − 2x
Zn2x
V2O7 coexist in the mixed-phase region. β-Zn2 − 2x
Cu2x
V2O7 solid solution, where 0 ≤ x ≤ 0.30, exists above 610 ± 5°C. The extent of the β′-Cu2V2O7-base solid solution is 9 to 65 mol % Zn2V2O7 at 615 ± 5°C, expanding to 0 mol % Zn2V2O7 with rising temperature.
Original Russian Text ¢ T.I. Krasnenko, M.V. Rotermel’, S.A. Petrova, R.G. Zakharov, O.V. Sivtsova, A.N. Chvanova, 2008, published
in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 10, pp. 1755–1762. 相似文献
15.
P. Šulcová 《Journal of Thermal Analysis and Calorimetry》2005,82(1):51-54
Summary The synthesis of new compounds based on the CeO2-PrO2-Nd2O3system, which can be used as pigments for colouring of ceramic glazes, is investigated in our laboratory. The optimum conditions
for the syntheses of these compounds have been estimated. The methods of thermal analysis provided first information about
the temperature region of the formation of the pigments investigated. The synthesis of these compounds was followed by thermal
analysis using STA 449/C Jupiter (Netzsch, Germany). 相似文献
16.
Wenzhang Fang Li Zhou Bin Shen Yi Zhou Qiuying Yi Mingyang Xing Jinlong Zhang 《Research on Chemical Intermediates》2018,44(8):4609-4618
Bi2O2.7/Bi2Ti2O7 composite photocatalyst films are synthesized by sol–gel dip-coating. The ratio of adding Bi and Ti precursors can be controlled during the preparation process. The phase structure is confirmed by X-ray diffraction. The UV–visible diffuse reflectance spectrum shows that the composite catalysts present light absorption in the visible region. The obtained Bi2O2.7/Bi2Ti2O7 composite films possess superior photocatalytic degradation of rhodamine B, owing to the visible light response of Bi2O2.7 and the separation of photogenerated electrons and holes between the two components. As a result, the Bi2O2.7/Bi2Ti2O7 (Bi/Ti = 1:1) displays the highest photocatalytic activity under visible light or UV light irradiation for the degradation of different organic dyes, including methyl blue, methyl orange and acid orange 7. 相似文献
17.
The results concerning the synthesis, structure and thermal properties of V2O5-MoO3-Ag2O samples in the vanadium rich region of ternary system are presented in the form of quasi-binary phase diagrams in which
at constant V2O5/MoO3 molar ratios, equal 9:1, 7:3 and 1:1, the content of Ag2O was variable. A new ternary phase isostructural with NaVMoO6 has been detected in the investigated system. 相似文献
18.
The solid-phase interaction in the V2O5-Nb2O5-MoO3 system has been investigated, and the formation of a solid solution bounded by the compositions MoNb2V4O18 ? δ, Mo2NbV5O21 ? δ, Mo2Nb3V3O21 ? δ, and Mo4Nb9V9O57 ? δ has been found (δ is nonstoichiometry). In the V2O5?Nb2O5 system, the formation of three compounds is verified, namely, VNbO5 (tetragonal structure), VNb9O25, and V2Nb23O62.5. The first two compounds are isostructural and form a continuous solid solution with tetragonal symmetry. A new compound of the composition Mo3NbVO14 ? δ has been synthesized. This compound is isostructural to the Mo3Nb2O14 compound described in the literature and forms a tetragonal solid solution with it. The phase equilibria in the V2O5-Nb2O5-MoO3 system in the subsolidus region have been determined. 相似文献
19.
A. M. Yankin O. M. Fedorova V. F. Balakirev Yu. V. Golikov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2007,81(1):139-142
Measurements on a circulation static setup with subsequent XRD analysis of quenched solid phases were used to study phase equilibria implicated in the thermal dissociation of SmMn2O5over the temperature and pressure ranges from 973 to 1123 K and from 10?3 to 10?16 Pa, respectively. The thermal dissociation of SmMn2O5 results in the sequential formation of constant-composition phases: SmMn2O5 → SmMnO3 + Mn3O4 + O2 → SmMnO3 + MnO + O2 → Sm2O3 + MnO + O2. The temperature dependence of the equilibrium oxygen pressure for the observed monovariant phase equilibria was used to calculate the thermodynamic characteristics of dissociation and formation of SmMn2O5 and SmMnO3 from the elements. 相似文献
20.
The results concerning the synthesis, structure and thermal properties of V2O5-MoO3-Ag2O samples in the molybdenum rich region of ternary system are presented in the form of quasi-binary systems: β-AgVO3-β-Ag2MoO4, AgVMoO6-MoO3, AgVMoO6-Ag2Mo4O13, AgVMoO6-Ag2Mo2O7, AgVMoO6-β-Ag2MoO4 and also of the system in which at V2O5/MoO3 molar ratio 3:7 the content of Ag2O was variable. The ternary phase AgVMoO6 was not described earlier in the literature. 相似文献