共查询到20条相似文献,搜索用时 564 毫秒
1.
Banjong Boonchom Chanaiporn Danvirutai 《Journal of Thermal Analysis and Calorimetry》2009,98(3):717-723
The non-isothermal kinetics of dehydration of AlPO4·2H2O was studied in dynamic air atmosphere by TG–DTG–DTA at different heating rates. The result implies an important theoretical
support for preparing AlPO4. The AlPO4·2H2O decomposes in two step reactions occurring in the range of 80–150 °C. The activation energy of the second dehydration reaction
of AlPO4·2H2O as calculated by Kissinger method was found to be 69.68 kJ mol−1, while the Avrami exponent value was 1.49. The results confirmed the elimination of water of crystallization, which related
with the crystal growth mechanism. The thermodynamic functions (ΔH*, ΔG* and ΔS*) of the dehydration reaction are calculated
by the activated complex theory. These values in the dehydration step showed that it is directly related to the introduction
of heat and is non-spontaneous process. 相似文献
2.
Magnetic chitosan microspheres were prepared by the emulsification cross-linking technique in the presence of glutaraldehyde as cross-linking agent, liquid paraffin as dispersant, and Span-80 as emulsifier. The optimal cross-linking time and Co0.5Ni0.5Fe2O4: chitosan ratio were determined. The morphology of particles was studied by different techniques. The adsorption characteristics were studied and the effect exerted by the initial concentration of methyl orange, the time of cross-linking, and the amount of the adsorbent was determined. It is found that the product obtained at the Co0.5Ni0.5Fe2O4: chitosan ratio 1: 4 and the crosslinking time 5 h has the uniform morphology. At room temperature, the Co0.5Ni0.5Fe2O4–chitosan magnetic composite has maximal adsorption for methyl orange at the dosage 20 mg. 相似文献
3.
The Ba0.5Sr0.5Co0.8–xWxFe0.2O3–δ (х = 0–0.1) materials prepaMIECred by partial substitution of cobalt in BSCF with tungsten were studied. The tungsten solubility limit in the structure of cubic perovskite BSCF was shown to be ~2%. The doping with the highly charged W6+ (2%) cation improved the functional properties of BSCF: it increased the oxygen permeability and membrane stability in the CO2-containing atmosphere and suppressed the cubic–hexagonal perovskite polymorphic transition. This stabilizes high oxygen fluxes during long-term stability tests. 相似文献
4.
(BiFeO3)1−x
–(BaTiO3)
x
solid solution thin films are grown on Pt/Ti/SiO2/Si substrates by chemical solution deposition method. Films with x = 0.00, 0.05 and 0.10 were prepared by annealing at 500°C. X-ray diffraction patterns indicate that the pure BiFeO3 film adopts random orientation while the solid solution films are highly (100) preferentially oriented. Improved electric
property at room temperature was observed in the BaTiO3 incorporated BiFeO3 films. The remanent polarization of the film with x = 0.0, 0.05 and 0.10 are 76.6, 51.9 and 19.7 μC/cm2 respectively under a measuring electric field of 0.94 MV/cm. The BaTiO3 incorporated BiFeO3 films show improved fatigue endurance. By the solid solution with BaTiO3, the leakage current density is reduced effectively. 相似文献
5.
T. G. Aminov E. V. Busheva G. G. Shabunina V. M. Novotortsev 《Russian Journal of Inorganic Chemistry》2018,63(4):519-529
The magnetic phase diagram of solid solutions in the CoCr2S4–Cu0.5Ga0.5Cr2S4 system was constructed. The widest concentration range (0.38 < x < 1) in the diagram represents solid solutions based on the ferrimagnetic semiconductor CoCr2S4 (TC = 223 K), which exhibits unusual properties in the magnetic ordering region while measuring the temperature dependence of the dynamic susceptibility. The magnetic properties were studied with a Quantum Design PPMS-9 platform within the temperature range 5–300 K in a 100-Oe constant magnetic field and/or a varying (100-, 500-, and 1000-Hz) magnetic field with an amplitude of 1 Oe. 相似文献
6.
G. M. Kuzmicheva A. V. Eremin V. B. Rybakov K. A. Subbotin E. V. Zharikov 《Russian Journal of Inorganic Chemistry》2009,54(6):854-863
The structural data for single crystals of (Na0.5R0.5)MO4 and (Na0.5R0.5)MO4:R′ (R = La, Gd; R′ = Er, Tm, Yb; M = W, Mo) grown by the Czochralski method were studied by X-ray diffraction and analyzed. The structural characteristics of these compounds depend on the sort of cations M and R. The formation of superstructures was found in the scheelite structure, and distortion of the scheelite structure depending on the composition and preparation conditions was established (with unit cell rotation by 45° and triclinic distortion of the scheelite structure for (Na0.5Gd0.5)WO4:Tm, with doubled unit cell compared to the scheelite type structure for (Na0.5Gd0.5)WO4 and (Na0.5Gd0.5)WO4:Yb). In the case of overstoichiometric oxygen content in the crystal, the unit cell symmetry increases to space group I41/amd or (Na0.5Gd0.5)WO4:Yb without considerable change in the cell parameters. On the basis of experimental data, a transformation scheme for the structures in the system Na 2 + M6+O4?-“R3+M5+O4” was proposed. 相似文献
7.
A new composite, Li2MnO3·LiNi0.5Co0.45Fe0.05O2, can be synthesized by a solid-state method and preconditioned with 5 wt% HCl, H2SO4, or H3PO4 solution to achieve H+/Li+ exchange. The effects of acid treatment on the structure, morphology, and electrochemical properties of Li2MnO3·LiNi0.5Co0.45Fe0.05O2 cathode materials are analyzed. The X-ray powder diffraction patterns imply that the hexagonal α-NaFeO2 structure (space group R\(\bar{3}\)m) of the materials is not changed by the acid treatment. The scanning electron microscope images show that particles become spherical with smooth surfaces after acid treatment, and the Brunauer–Emmett–Teller analysis reveals that the specific surface area increases. The charge–discharge test demonstrates that acid-treated Li2MnO3·LiNi0.5Co0.45Fe0.05O2 cathode materials deliver higher initial coulombic efficiencies than untreated material, owing to the improvement of the catalytic reduction activity of oxygen released during the initial charge process. Furthermore, Li2MnO3·LiNi0.5Co0.45Fe0.05O2 treated with HCl displays the best electrochemical performance, with the acid treatment improving the initial coulombic efficiency from 66.0 to 82.2%. Thus, acid treatment can effectively improve the electrochemical performance of electrode materials in Li-ion batteries. 相似文献
8.
Chiwon Kang Jung-Hyun Park Dongna Shen Hosang Ahn Minseo Park Dong-Joo Kim 《Journal of Sol-Gel Science and Technology》2011,58(1):85-90
(K0.5 Na0.5)NbO3 (KNN) perovskite materials have been developed as a promising lead-free piezoelectric material for environmentally benign
piezoelectric devices. KNN films with about 320 nm thickness were fabricated on Pt(111)/SiO2/Si(100) substrates by a sol–gel method from stoichiometric and A-site ion excess precursor solutions. Two different annealing
methods were also used to investigate the crystallographic evolution of the films. A layer-by-layer annealing process results
in highly (001) oriented KNN from the annealing temperature of 550 °C, while the final annealing method leads to weaker crystalline
peaks with a random orientation. The KNN films from the K and Na excess precursor solutions show similar crystallization behavior.
However, the ferroelectric hysteresis loops of the films were greatly improved by compensating for an A-site vacancy. In particular,
the KNN films from K-excess precursor solutions show better ferroelectric properties compared to the films prepared from Na
excess solutions. 相似文献
9.
Martin Tsvetkov Maria Milanova Laura C. J. Pereira Jaão C. Waerenbourgh Zara Cherkezova-Zheleva Joana Zaharieva Ivan Mitov 《Chemical Papers》2016,70(12):1600-1610
The spinel-type ferrites NiFe2O4 and Zn0.5Ni0.5Fe2O4 modified by lanthanide ions Eu3+ and Tb3+ were prepared by a sol—gel process with propylene oxide as a gelating agent. The phase homogeneity of the samples was tested by XRD and Mössbauer spectroscopy. Transmission electronic microscopy used for characterisation of the morphology of the samples revealed nanosized powdered samples with a narrow distribution of particle sizes. It was noted that the presence of Ln3+ ions influenced the magnetic properties of nanosized NiFe2O4 and Ni0.5Zn0.5Fe2O4 ferrites. The dependence of the magnetic properties of the samples on the rare-earth doping may be explained by the different grain sizes. The saturation magnetisation tends to decrease with increasing rare-earth doping and decreasing crystallite size. A similar trend was observed for the coercive field, with the exception of the Tb3+-doped Zn0.5Ni0.5Fe2O4 where it remained the same as in the pure ferrite. 相似文献
10.
Zh. V. Akhmerkina E. V. Peresypkina A. V. Virovets L. B. Serezhkina 《Russian Journal of Inorganic Chemistry》2008,53(9):1396-1400
Single crystals of Ba3[UO2(C2O4)2(NCS)]2 · 9H2O are synthesized and studied by X-ray diffraction. The crystals are orthorhombic, space group Fddd, Z = 16, and the unit cell parameters are a = 16.253(3) Å, b = 22.245(3) Å, c = 39.031(6) Å. The main crystal structural units are mononuclear complex groups [UO2(C2O4)2NCS]3? of the crystal-chemical family (AB 2 01 M1 (A = UO 2 2+ , B01 = C2O 4 2? , M1 = NCS?) of the uranyl complexes linked into a three-dimensional framework by electrostatic interactions and hydrogen bonds involving oxalate ions and water molecules. 相似文献
11.
I. A. Baidina V. D. Il’yashevich V. F. Malakhov A. V. Belyaev 《Journal of Structural Chemistry》2007,48(5):973-976
The complex Na3(NH4)2[Ir(SO3)2Cl4]·4H2O was examined with single crystal X-ray diffraction and IR spectroscopy. Crystal data: a = 7.3144(4) Å, b = 10.0698(5) Å, c = 12.3748(6) Å, β = 106.203(1)°, V = 875.26(8) Å3, space group P21/c, Z = 2, d calc = 2.547 g/cm3. In the complex anion two trans SO 3 2? groups are coordinated to iridium through the S atom. The splitting of O-H bending vibrations of crystallization water molecules and N-H ones of the ammonium cation is considered in the context of different types of interactions with the closest neighbors in the structure. 相似文献
12.
Stefan Götzendörfer Robert Bywalez Peer Löbmann 《Journal of Sol-Gel Science and Technology》2009,52(1):113-119
CuCrO2 and CuAl0.5Cr0.5O2 thin films were prepared by sol–gel processing and subsequent two-step annealing in air and inert gas atmosphere. Phase pure
films with delafossite structure were obtained by adjusting the respective temperatures. The related phase development strongly
affects the optical and electrical performance, giving leeway for optimization. The resulting CuCrO2 (16 Ωcm, transmittance 21%) and CuAl0.5Cr0.5O2 (11 Ωcm, transmittance 49%) films showed p-type conductivity by their positive Seebeck coefficients. The microstructure of the systems was characterized by scanning
and transmission electron microscopy and correlated to the growth of different crystalline phases during the annealing steps.
Thereby, crystal thermodynamics also affects the respective film performance, alleviating delafossite formation from the amorphous
phase. 相似文献
13.
L. B. Serezhkina E. V. Peresypkina A. V. Virovets I. V. Medrish D. V. Pushkin 《Russian Journal of Inorganic Chemistry》2009,54(10):1577-1580
Single crystals of Cs[(UO2)2(C2O4)2(OH)] · H2O were synthesized and structurally studied using X-ray diffraction. The compound crystallizes in monoclinic space group P21/m, Z = 2, with the unit cell parameters a = 5.5032(4) Å, b = 13.5577(8) Å, c = 9.5859(8) Å, β = 97.012(3)°, V = 709.86(9) Å3, R = 0.0444. The main building units of crystals are [(UO2)2(C2O4)2(OH)]? layers of the A2K 2 02 M2 (A = UO 2 2+ , K02 = C2O 4 2? , and M2 = OH?) crystal-chemical family. Uranium-containing layers are linked into a three-dimensional framework via electrostatic interactions with outer-sphere cations and hydrogen bonds with water molecules. 相似文献
14.
I. V. Fedorova M. G. Kiselev L. P. Safonova 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(12):2103-2109
The molecular dynamics simulation method was for the first time used to study the structural and energy parameters of H3PO4, H2PO4−, and (DMFA)H+ (protonated dimethylformamide) in liquid N,N-dimethylformamide. The predominant orientation of the nearest neighbors of H3PO4, H2PO4−, DMFA, and (DMFA)H+ was determined from ranked distribution functions. The most probable structure of H-bonded complexes was obtained. It was
shown that H3PO4 formed H-bonds with two DMFA molecules, and and (DMFA)H+ formed H-bonds with one molecule. The dependence of Coulomb interaction energies on the distance between H3PO4, H2PO4−, (DMFA)H+, and DMFA had the form of damped oscillations, as is characteristic of intermolecular interactions in pure DMFA. The molecular
dynamics simulation of the H2PO4−-(DMFA)H+-DMFA ternary system showed a high probability of the formation of contact ion pairs. 相似文献
15.
A new compound containing the tetraphenylphosphonium cation and the nickel(III) bisdicarbollyl anion, [(C6H5)4P][Ni(B9C2H11)2]·CCl4, was synthesized and investigated by XRD at room temperature (295 K). Crystal data: C29H42B18PCl4Ni, M = 816.69, monoclinic, space group P2/c; unit cell parameters a = 13.5873(6) Å, b = 7.1475(2) Å, c = 20.7829(8) Å, β = 94.4595(13)°, V = 2012.2(2) Å3, Z = 2, d calc = 1.348 g/cm3. The structure was solved by direct and Fourier methods and refined by the full-matrix least squares method in an anisotropic (isotropic for H) approximation to the final R 1 = 0.0466 for 3055 I hkl ≥ 2σ I of 23,655 reflections collected and 5618 independent I hkl (Bruker X8 APEX diffractometer, λMoK α). 相似文献
16.
New caprolactam dodecamolybdosilicate of the composition (C6H11NO)4.5Н4[SiМо12O40] (I) is synthesized. Chemical and crystallographic analyses, NMR and IR spectroscopic studies are performed. Compound I is found to crystallize in the monoclinic system with the space group P21/n. Unit cell parameters are: a = 19.945(4) Å, b = 13.340(3) Å, c = 28.110(6) Å, β = 110.75(3)°, ρcalc = 2.232 g/cm3, М = 2350.63, Z = 4, V = 6994(3) Å3. 相似文献
17.
Gligor Jovanovski Branko Kaitner Orhideja Grupce Pance Naumov 《Central European Journal of Chemistry》2004,2(1):254-275
The crystal structure of tripotassium trisaccharinate dihydrate, K3(C7H4NO3S)3·2H2O, is triclic, space group\(P \bar 1, Z = 2\). It consists of three crystallographically independent potassium and saccharinato ions as well as two structurally different water molecules. Potassium coordination polyhedra are irregular, with K1 and K3 six-coordinated and the third one K2 seven-coordinated. The K?O distances range from 2.652(9) to 3.100(2) Å(mean: 2.790 Å) whereas the K?N distance is 3.025(3) Å. The water molecules W2 is disordered over three positions with occupancies of approximately 0.6, 0.2 and 0.2. The hydrogen atom (H1W1) of the ordered water molecule (O1W) is hydrogen bonded to the sulfonyl oxygen atom (O11) (R(O...O)=2.976(3) Å), whereas the other hydrogen atom (H2W1) is bifurcated to the carbonyl oxygen atom (O13) (R(O...O)=2.851(3) Å) and the disordered water molecules (O23W) (R(O...O)=3.067(12) Å). The carbonyl oxygens (O13, O23 and O33) and one of the disordered water molecules (O22W) are involved in C?H...O hydrogen bonds (R(C?H...O)=3.027(4)–3.304(9) Å). Structural characteristics of the studied compound are compared with the analogous trisodium trisaccharinate dihydrate and dipotassium sodium trisaccharinate monohydrate. Infrared and Raman spectra of the title compound have been analyzed in relation to the structure, and compared with the spectra of trisodium trisaccharinate dihydrate. 相似文献
18.
The concentration space of homogeneous garnet in the system Ga2O3–(Y, Bi)3(Fe, Ga)5O12–Fe2O3 was determined by X-ray powder diffraction analysis. The obtained results expand the knowledge of the possible variations of cation ratios Y : Bi : Fe : Ga in garnet, which can be used for searching for and creating new stable magneto-optical materials. 相似文献
19.
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
20.
A. A. Kashaev I. V. Rozhdestvenskaya I. I. Bannova A. N. Sapozhnikov O. D. Glebova 《Journal of Structural Chemistry》2008,49(4):708-711
Four structural models of volborthite Cu3(OH)2(V2O7)·2H2O (a = 10.646(2) Å, b = 5.867(1) Å, c = 14.432(2) Å, β = 95.19(1)°, V = 897.7(5) Å3, Z = 4, R/R w = 0.038/0.046) calculated in the space groups determined from the systematic absences are compared. Based on the structure balance and the similarity of constituting polyhedra, values of the R factor, and isotropic thermal parameters, the space group Ia is found to be preferable, which is the only possible asymmetric and uniform variant. Hydrogen atoms of OH-groups, oxygen atoms and, partially, hydrogen atoms of water are localized. 相似文献