共查询到20条相似文献,搜索用时 31 毫秒
1.
M. Donaldson Rebecca Stevens B. E. Lang Juliana Boerio-Goates B. F. Woodfielda R. L. Putnam Alexandra Navrotsky 《Journal of Thermal Analysis and Calorimetry》2005,81(3):617-625
Summary As part of a larger study of the physical properties of potential ceramic hosts for nuclear wastes, we report the molar heat capacity of brannerite (UTi2O6) and its cerium analog (CeTi2O6) from 10 to 400 K using an adiabatic calorimeter. At 298.15 K the standard molar heat capacities are (179.46±0.18) J K-1 mol-1 for UTi2O6 and (172.78±0.17) J K-1 mol-1 for CeTi2O6. Entropies were calculated from smooth fits of the experimental data and were found to be (175.56±0.35) J K-1 mol-1 and (171.63±0.34) J K-1 mol-1 for UTi2O6 and CeTi2O6, respectively. Using these entropies and enthalpy of formation data reported in the literature, Gibb’s free energies of formation from the elements and constituent oxides were calculated. Standard free energies of formation from the elements are (-2814.7±5.6) kJ mol-1 for UTi2O6 and (-2786.3±5.6) kJ mol-1 for CeTi2O6. The free energy of formation from the oxides at T=298.15 K are (-5.31±0.01) kJ mol-1 and (15.88±0.03) kJ mol-1 for UTi2O6 and CeTi2O6, respectively. 相似文献
2.
L. P. Ogorodova I. A. Kiseleva E. N. Korytkova T. P. Maslennikova V. V. Gusarov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(1):44-47
Nanotubular (Mg,Fe2+,Fe3+)3Si2O5(OH)4 hydrosilicates with a chrysotile structure were synthesized under hydrothermal conditions. The phases prepared were studied
thermochemically on a high-temperature Tian-Calvet microcalorimeter by solution calorimetry. The standard enthalpies of formation
of magnesium-iron nanotubular hydrosilicates were determined. The formation of iron-containing nanotubes was shown to be lass
favorable energetically than the formation of magnesium nanotubes. 相似文献
3.
Yu. V. Kokunov Yu. E. Gorbunova V. V. Kovalev 《Russian Journal of Coordination Chemistry》2009,35(9):643-647
The complex [Co(2-Me-Pyz)2(H2O)4](NO3)2 is synthesized and its structure is determined. The crystals are monoclinic: space group P21/n, a = 10.685(2) Å, b = 6.837(1), c = 12.515(3) Å, β = 91.84(3)°, V = 913.8(3) Å3, ρcalcd = 1.042 g/cm 3, Z = 2. The Co2+ ion (in the inversion center) is coordinated at the vertices of the distorted octahedron by two nitrogen atoms of methylpyrazine and four oxygen atoms of the water molecules (Co(1)–N(1) 2.180(3), average Co(1)–O(w) 2.079(3) Å, angles at the Co atom 87.9(1)–92.1(1)°). Supramolecular pseudometallocycles are formed in the structure through the O(w)–H…N(1) hydrogen bonds between the coordinated H2O molecules and the terminal nitrogen atoms of the 2-methylpyrazine molecules. Their interaction results in the formation of supramolecular layers joined by the NO3 groups into a three-dimensional framework. 相似文献
4.
Marcela Stoia C. Caizer M. Stefanescu P. Barvinschi I. Julean 《Journal of Thermal Analysis and Calorimetry》2007,88(1):193-200
This article presents the results
of our investigation on the obtaining of Ni0.65Zn0.35Fe2O4 ferrite nanoparticles embedded in a SiO2 matrix using
a modified sol–gel synthesis method, starting from tetraethylorthosilicate
(TEOS), metal (FeIII,NiII,ZnII)
nitrates and ethylene glycol (EG). This method consists in the formation of
carboxylate type complexes, inside the silica matrix, used as forerunners
for the ferrite/silica nanocomposites. We prepared gels with different compositions,
in order to obtain, through a suitable thermal treatment, the nanocomposites
(Ni0.65Zn0.35Fe2O4)x–(SiO2)100–x (where x=10,
20, 30, 40, 50, 60 mass%). The synthesized gels were studied by differential
thermal analysis (DTA), thermogravimetry (TG) and FTIR spectroscopy.
The formation of Ni–Zn ferrite in the silica matrix and the behavior
in an external magnetic field were studied by X-ray diffraction (XRD) and
quasi-static magnetic measurements (50 Hz). 相似文献
5.
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
6.
CaAl2O4:Eu2+, Nd3+@TiO2 composite powders were synthesized by a sol–gel method under mild conditions (i.e. low temperature and ambient pressure).
The as-prepared powders were characterized by transmission electron microscopy (TEM) and analyzed by X-ray diffraction (XRD).
The photocatalytic behavior of the TiO2-base surfaces was evaluated by the degradation of nitrogen monoxide gas. It suggested that CaAl2O4:Eu2+, Nd3+@TiO2 composite powders were composed of anatase titania and that CaAl2O4:Eu2+, Nd3+. TiO2 particles were deposited on the surface of CaAl2O4:Eu2+, Nd3+ to form uniform film. CaAl2O4:Eu2+, Nd3+@TiO2 composite powders exhibited higher photocatalytic activity compared with pure TiO2 under visible light. And the result also clearly indicated that the long afterglow phosphor absorbed and stored lights for
the TiO2 to remain photocatalytic activity in the dark. 相似文献
7.
M. Yu. Shilova A. V. Vologzhanina L. B. Serezhkina V. N. Serezhkin 《Russian Journal of Coordination Chemistry》2009,35(2):153-156
The single crystals of [UO2(C2O4){CONH2N(CH3)2}2] were synthesized and studied by X-ray diffraction. The crystals are monoclinic, a = 7.461(2) Å, b = 8.828(2) Å, c = 11.756(2) Å, β = 107.21(3)°, space group Pc, Z = 2, R = 2.94%. The structure comprises infinite chains [UO2(C2O4){CONH2N(CH3)2}2] extended along [001] and corresponding to the AT11M 2 1 crystallochemical group (A = UO 2 2+ , T11 = C2O 4 2? , M1 = N,N-CONH2N(CH3)2) of uranyl complexes. The chains are connected into a three-dimensional framework by hydrogen bonds involving the oxygen atoms of oxalate and uranyl ions and the N,N-dimethylcarbamide methyl groups. 相似文献
8.
The energies of formation of platinum complexes with borohydrides B10H14 and B10H
14
2-
or carboranes B8C2H14 and B8C2H
14
2-
were considered in terms of the structure—thermodynamics model. The thermodynamic stability of these complexes was substantiated.Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 2, 2005, pp. 149–152. Original Russian Text Copyright © 2005 by Ionov, Kuznetsov. 相似文献
9.
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
10.
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
11.
A new electrical conductive crystal PyEt[Ni(dmit)2]2 (dmit = 4,5-dimercapto-1,3-dithiole-2-thione) has been synthesized and its X-ray structure has been determined to be in monoclinic
system, C2/c space group. In PyEt[Ni(dmit)2]2 crystal, the conducting component [Ni(dmit)2]0.5- is face-to-face packed forming molecular column along the c-direction, and these molecular columns are then side-by-side
extended along the a-direction forming a kind of two-dimensional conducting sheet on (010). The measured conductivity at room
temperature along a certain direction on (010) plane is 10 S · cm-1. From 282 to 269 K, the crystal shows metallic behavior but changes to semiconductor below 269 K. Based on the measured crystal
structure and calculated band structure, this conductor-semiconductor phase transformation can be primarily interpreted: The
metallic conductivity is corresponding to the uniform molecular column and the atomic-lattice-chain structure of Ni chain,
while the semi-conductive behavior to staggered molecular column and the atomic-zigzag-chain structure of Ni chain. 相似文献
12.
Huiming Ji Guijiu Xie Ying Lv Huixiang Lu 《Journal of Sol-Gel Science and Technology》2007,44(2):133-137
The flower-like phosphors of Sr2MgSi2O7: Eu2+, Dy3+ with high brightness and long afterglow were obtained by sol–gel method. X-ray diffraction pattern (XRD) shows that single-phased
Sr2MgSi2O7 phosphor is prepared by sol–gel method under 1250 °C. Scanning electron microscope (SEM) indicates that the phosphor consists
of nano-sized whiskers which are detected for the first time in Eu2+ and Dy3+ co-doped long-lasting phosphorescence silicates. Furthermore, the investigation on the mechanism indicates that the internal
structure and gas, liquid and solid phase effect play important roles in the formation of flower-like Sr2MgSi2O7: Eu2+, Dy3+ nanostructure. Finally, the optical properties of flower-like Sr2MgSi2O7 nanostructure have been characterized by photoluminescence (PL) spectra. 相似文献
13.
M. Yu. Shilova A. V. Vologzhanina L. B. Serezhkina S. A. Novikov V. N. Serezhkin 《Russian Journal of Inorganic Chemistry》2011,56(10):1555-1560
A new complex [UO2CrO4{CH3CON(CH3)2}2] (I) was studied by thermal analysis, IR spectroscopy, and X-ray crystallography. The crystals are monoclinic: a = 13.8108(11) Å, b = 8.6804(7) Å, c = 13.0989(10) Å, β = 104.777(1)°, V = 1518.4(2) Å3, space group P21/c, Z = 4, R = 2.39%. The structure of I contains infinite chains of the [UO2CrO4{CH3CON(CH3)2}2] composition running along [001]; the complex belongs to the AT11M1 2 crystal-chemical group (A = UO 2 2+ , T11 = CrO 4 2? , M1 = CH3CON(CH3)2) of uranyl complexes. The chains are linked into a three-dimensional framework due to hydrogen bonds between oxygen atoms of chromate ions and hydrogen atoms of methyl groups of the dimethylacetamide. 相似文献
14.
S. N. Eliseeva K. A. Vorob’eva E. V. Shkreba R. V. Apraksin V. V. Kondrat’ev 《Russian Journal of Applied Chemistry》2017,90(8):1230-1233
Lithium-ion battery based on LiMn2O4/Li4Ti5O12 materials was assembled for the first time. The cathode and anode of this battery are prepared with the aqueous combined binder poly-3,4-ethylenedioxythiophene: polystyrene sulfonate/carboxymethylcellulose (without polyvinylidene fluoride). The capacity of the LiMn2O4/Li4Ti5O12 battery was found to be 75 mA h g–1 at 0.1 C and 55 mA h g–1 at 1 C. A 95% capacity was retained after 100 charge-discharge cycles. The batteries demonstrated a high Coulombic efficiency close to 100%. Scanning electron microscopy demonstrated that using the conducting binder poly-3,4-ethylenedioxythiophene: polystyrene sulfonate/carboxymethylcellulose provides formation of dense compact layers of electrode materials with good adhesion to the substrate. The electrode structure remains maintained after 100 charge-discharge cycles. 相似文献
15.
16.
M. M. Godneva D. L. Motov M. P. Rys’kina 《Russian Journal of Inorganic Chemistry》2011,56(9):1363-1369
The ZrO(NO3)2-H3PO4-CsF-H2O system was studied at 20°C along the section at a molar ratio of PO43−/Zr = 0.5 (which is of the greatest interest in the context of phase formation) at ZrO2 concentrations in the initial solutions of 2–14 wt % and molar ratios of CsF: Zr = 1−6. The following compounds were isolated
for the first time: crystalline fluorophosphates CsZrF2PO4 · H2O, amorphous oxofluorophosphate Cs2Zr3O2F4(PO4)2 · 3H2O, and amorphous oxofluorophosphate nitrate CsZr3O1.25F4(PO4)2(NO3)0.5 · 4.5H2O. The compound Cs3Zr3O1.5F6(PO4)2 · 3H2O was also isolated, which forms in a crystalline or glassy form, depending on conditions. The formation of the following
new compounds was established: Cs2Zr3O1.5F5(PO4)2 · 2H2O, Cs2Zr3F2(PO4)4 · 4.5H2O, and Zr3O4(PO4)1.33 · 6H2O, which crystallize only in a mixture with known phases. All the compounds were studied by X-ray powder diffraction, crystal-optical,
thermal, and IR spectroscopic analyses. 相似文献
17.
I. S. Ignat’ev T. A. Kochina D. V. Vrazhnov 《Russian Journal of General Chemistry》2007,77(4):575-580
The potential energy surfaces of the (CH3)nH3?n M+ ions, where n = 1, 2; M = Si, Ge, were scanned using the B3LYP method with 6–31G* and aug-cc-pVDZ basis sets. The major attention was given to isomeric species having the form of complexes of the HM+ and CH3M+ ions with hydrogen, methane, and ethane molecules. These species were characterized previously neither by experimental nor by theoretical methods. It was found that these species become more stable in going from Si to Ge; the complex [CH3Ge+CH4] is the second isomer in the energy after (CH3)2HGe+. However, the heights of the activation barriers to formation of these complexes from the most stable isomer, though decreasing in going from Si to Ge, remain relatively high and, what is particularly important, somewhat exceed the activation barrier to formation of the complex [H3Ge+·C2H4]. 相似文献
18.
Hermi F. Brito Jukka Hassinen Jorma Hölsä Högne Jungner Taneli Laamanen Mika Lastusaari Marja Malkamäki Janne Niittykoski Pavel Novák Lucas C. V. Rodrigues 《Journal of Thermal Analysis and Calorimetry》2011,105(2):657-662
The details of the mechanism of persistent luminescence were probed by investigating the trap level structure of Sr2MgSi2O7:Eu2+,R3+ materials (R: Y, La-Lu, excluding Pm and Eu) with thermoluminescence (TL) measurements and Density Functional Theory (DFT)
calculations. The TL results indicated that the shallowest traps for each Sr2MgSi2O7:Eu2+,R3+ material above room temperature were always ca. 0.7 eV corresponding to a strong TL maximum at ca. 90 °C. This main trap
energy was only slightly modified by the different co-dopants, which, in contrast, had a significant effect on the depths
of the deeper traps. The combined results of the trap level energies obtained from the experimental data and DFT calculations
suggest that the main trap responsible for the persistent luminescence of the Sr2MgSi2O7:Eu2+,R3+ materials is created by charge compensation lattice defects, identified tentatively as oxygen vacancies, induced by the R3+ co-dopants. 相似文献
19.
E. A. Tugova V. F. Popova I. A. Zvereva V. V. Gusarov 《Russian Journal of General Chemistry》2007,77(6):979-981
Phase formation processes in the systems Ln2O3-SrO-Fe2O3 (Ln = La, Nd) in air in the temperature range 1200–1500°C were studied. The synthesis of the complex ferrites La2SrFe2O7 and Nb2SrFe2O7 involves the formation of the intermediate compounds LnFeO3 and LnSrFeO4 and occurs by the same mechanism as the synthesis of the corresponding aluminates, but much faster. 相似文献
20.
P. Schwendt D. Dudášová J. Chrappová M. Drábik J. Marek 《Journal of Thermal Analysis and Calorimetry》2008,91(1):293-297
The compound [Ni(NH3)6][VO(O2)2(NH3)]2 was prepared and characterized by elemental analysis and vibrational spectra. The single crystal X-ray study revealed that
the structure consists of [Ni(NH3)6]2+ and [VO(O2)2(NH3)]− ions. As a result of weak interionic interactions V′···Op (Op-peroxo oxygen), ([VO(O2)2(NH3)]−)2 dimers are formed in the solid-state. The thermal decomposition of [Ni(NH3)6][VO(O2)2(NH3)]2 is a multi-step process with overlapped individual steps; no defined intermediates were obtained. The final solid products
of thermal decomposition up to 600°C were Ni2V2O7 and V2O5. 相似文献