共查询到20条相似文献,搜索用时 750 毫秒
1.
Yu. N. Ivanov I. P. Aleksandrova A. A. Sukhovsky A. I. Baranov 《Physics of the Solid State》2007,49(6):1142-1148
A crystal of the Cs5H3(SO4)4 · xH2O (x ≈ 0.5) (PCHS) compound, which belongs to the family of proton conductors with a complex system of hydrogen bonds, is investigated by 2H NMR spectroscopy. The temperature and orientation dependences of the 2H NMR spectra are measured and analyzed. It is established that, upon transition to the glassy phase at the temperature T g = 260 K, the parameters characterizing the proton exchange between positions in hydrogen bonds remain unchanged to within the limits of experimental error. The protons in the two-dimensional network of hydrogen bonds in the (001) plane are dynamically disordered over possible positions down to temperatures considerably lower than the glass transition point T g . However, water molecules are fixed at particular structural positions in the phase transition range. In PCHS crystals with a nonstoichiometric water content, this circumstance can be responsible for the frustration that leads to the formation of the glassy state. 相似文献
2.
Organic–inorganic hybrid sample [N(C4H9)4]2Cu2Cl6 was prepared via the reaction between copper chloride and tetrabutylammonium chloride. The compound was characterized by
X-ray powder diffraction, IR, Raman, differential scanning calorimetry (DSC), DTA-TGA analysis and electrical impedance spectroscopy.
DSC studies indicate a presence of one-phase transition at 343 K. The complex impedance of compound [N(C4H9)4]2Cu2Cl6 have been investigated in temperature and frequency ranges 300–380 K and 200 Hz–5 MHz, respectively. The Z′ and Z″ versus frequency plots are well fitted to an equivalent circuit model. The circuits consist of the parallel combination
of bulk resistance R
p and constant phase elements CPE. The frequency dependence of the conductivity is interpreted in term of Jonscher's law: s(w) = sdc + Awn \sigma (\omega ){ } = {\sigma_{\rm{dc}}} + { }A{\omega^n} . The conductivity follows the Arrhenius relation. The variation of the value of these elements with temperatures confirmed
the availability of the phase transition at 343 K detected by DSC and electrical measurements. 相似文献
3.
The heat capacity of the [[N(C2H5)4]2CdBr4 crystal is measured by the calorimetric method in the temperature range from 80 to 300 K. It is revealed for the first time that the temperature dependence of the heat capacity C p (T) exhibits an anomaly associated with the first-order phase transition occurring at the temperature T 1 = 226.5 K. A long relaxation of the temperature of the crystal is observed in the temperature range 150–165 K. 相似文献
4.
X-ray structural and polarization optical investigations have been performed, and birefringence and rotation angles of the
optical indicatrix φ
b
and φ
c
of the K2WO2F4 · H2O crystal have been measured in the temperature range of 100–600 K. The structure and symmetry of compounds at room temperature
have been refined. It has been established that the layered crystal K2WO2F4 · H2O can exist in two states (A and B) depending on the atmospheric humidity and undergoes the sequence of reversible and irreversible
phase transformations G
3 ↔ G
2 → G
1 → G
0. The sequences of changes in the phase symmetry P
[`1]\bar 1 ↔ C2/m → P4/nmm for samples A and m ↔ C2/m → P4/nmm for samples B have been found. The second-order proper ferroelastic phase transition (P
[`1]\bar 1 ↔ C2/m) at T
03 = 270–290 K (G
3 ↔ G
2) is accompanied by twinning and appearance of the shift deformation x
6. The crystal system of the substance for the B crystals remains invariable after the second-order phase transition G
3 ↔ G
2. The irreversible first-order phase transition G
2 → G
1 occurs in a temperature range T
02 ≈ 350–380 K; it is accompanied by the loss of the crystallization water, which then is reduced easily from the atmosphere for a day.
The substance decomposes at T
01 ≈ 510 K (G
1 → G
0). The distinction between the A and B crystals has been explained by the presence or absence of free water in interlayer spacings. 相似文献
5.
Composite cathode material LiFePO4–Li3V2(PO4)3 is synthesized through a chemical reduction and lithiation using FeVO4·xH2O as both iron and vanadium sources. The structural properties of LiFePO4–Li3V2(PO4)3 are investigated. X-ray diffraction results show the composite material containing olivine type LiFePO4 and monoclinic Li3V2(PO4)3 phases. High-resolution transmission electron microscopy and energy-dispersive X-ray spectrometry results indicate that mutual
doping effects take place between the LiFePO4 and Li3V2(PO4)3 particles with V3+ doping the LiFePO4 while Fe2+ dopes the Li3V2(PO4)3. LiFePO4–Li3V2(PO4)3 nanocomposites are formed in the carbon webs. There is no structural compatibility between monoclinic (Li3V2(PO4)3) and olivine (LiFePO4) domains in composite material LiFePO4–Li3V2(PO4)3. 相似文献
6.
7.
A new polyanionic cathode material, Li3V2(PO4)3·LiMn0.33Fe0.67PO4/C for lithium-ion batteries, was synthesized using a sol-gel method and with N,N-dimethyl formamide as a dispersion agent. The analysis of electron transmission spectroscopy and X-ray diffraction revealed that the composite contained two phases. The material has high crystallinity with a grain size of 20–50 nm. The valence states of Mn, V, and Fe in the composite were analyzed by X-ray photoelectron spectroscopy. The electrochemical kinetics in Li3V2(PO4)3 is effectively enhanced by the incorporation of LiMnPO4 and LiFePO4, via structure modification and reduced Li diffusion length. The Li3V2(PO4)3·LiMn0.33Fe0.67PO4/C materials displayed high rate capacity and steady cycle performance with discharge capacity remained 148 mAh g?1 after 50 cycles at the rate of 0.2C. In particular, the composite exhibited excellent reversible capacities, with the values of 157, 134, 120, 102, and 94 mAh g?1 at charge/discharge 0.2, 0.5, 1, 2, and 5C rates, respectively. 相似文献
8.
The heat capacity of [(C2H5)2NH2]2CuCl4 crystals, both nonirradiated and γ-irradiated to a dose of 107R, was studied in the temperature interval 90–330 K by adiabatic calorimetry. The temperature dependence of Cp(T) was found to have a peak-shaped anomaly in the region of the thermochromic phase transition (PT) at T = 322.7 K. Smoothened experimental heat capacity data were used to calculate the changes in the thermodynamic functions. The changes in the entropy and enthalpy of the thermochromic PT were determined to be ΔS = 42 J K?1 mol?1 and ΔH = 13653 J mol?1 for the nonirradiated crystals and ΔS = 39 J K?1 mol?1 and ΔH = 12120 J mol?1 for the irradiated crystals, respectively. Irradiation of a [(C2H5)2NH2]2CuCl4 crystal by γ rays to a dose of 107 R was shown to shift the PT point toward lower temperatures by ΔT ≈ 1.7 K. 相似文献
9.
H. Rauscher J. Braun R.J. Behm 《Applied Physics A: Materials Science & Processing》2003,76(5):711-719
We report the results of a study on ultrahigh-vacuum chemical vapor deposition of SixGe1-x layers on Si(111)(7×7) with GeH4 and Si2H6 mixtures. Using combined scanning tunneling microscopy and X-ray photoelectron spectroscopy, structural properties, the growth
kinetics and the composition of the deposited alloys are analyzed as a function of the growth temperature for two different
GeH4:Si2H6 mixture ratios. The mutual influence of the precursors is shown by comparing the structures formed during deposition and
the sticking coefficients of Si2H6 and GeH4 with results obtained from exposure of Si(111) to the pure gases.
Received: 28 July 2002 / Accepted: 2 October 2002 / Published online: 5 February 2003
RID="*"
ID="*"Corresponding author. Fax: +49-731/502-5452, E-mail: hubert.rauscher@chemie.uni-ulm.de 相似文献
10.
O. S. Volkova I. V. Morozov E. A. Lapsheva V. V. Shutov A. N. Vasil’ev R. Klingeler B. Büchner 《JETP Letters》2009,89(2):88-91
The magnetic phase diagram of copper nitrate monohydrate Cu(NO3)2 · H2O and the basic parameters of its magnetic subsystem have been determined by measuring the thermodynamic properties of this compound. This compound becomes antiferromagnetically ordered at T N = 3.6 K, undergoes the spin-flop and spin-flip transitions at H C1 ~ 0.06 T and H C2 ~ 1.1 T, respectively, at low temperatures. The magnetization of Cu(NO3)2 · H2O at T SR = 2.7 K exhibits an additional anomaly, which is likely attributed to the spin-reorientation transition. 相似文献
11.
Yan-Fang Zhao Yong-Liang Zhao Feng Bai Xiao-yan Wei Yong-sheng Zhou Mei-na Shan Huan-huan Li Rui-jun Ma Xiao-tao Fu Yan Du 《Journal of fluorescence》2010,20(3):763-770
The complex of Tb(TPTZ)Cl3·3H2O was synthesized by adding the ethyl alcohol solution of TbCl3 (1 mmol) to the solution of 2,4,6-tris-(2-pyridyl)-s-triazine(TPTZ,1 mmol) with constant stirring. The solution which had
been filtered was kept at the room temperature for 4 weeks, and then a kind of transparent crystal was formed. Besides, nine
kinds of solid complexes in the different molar proportion of terbium to gadolinium had been synthesized by adopting the similar
method mentioned above. It was inferred from the elemental analysis and rare earth complexometry that the composition of these
complexes is (TbxGdy)(TPTZ)Cl3·3H2O (x : y = 0.9 : 0.1, 0.8 : 0.2, 0.7 : 0.3, 0.6 : 0.4, 0.5 : 0.5, 0.4 : 0.6, 0.3 : 0.7, 0.2 : 0.8, 0.1 : 0.9). The absorption
spectra and photoluminescence of the complexes were determined in dimethylsulfoxide (DMF), which showed that the excitation
of the complexes is mostly ligand based. The triplet state energy level of TPTZ was measured, indicating that the lowest excitation
state energy level of Tb(III) and the triplet state energy level of TPTZ match well each other. The fluorescent data indicated
that the fluorescent emission intensity of Tb3+ ions would be enhanced in the complexes after terbium was doped with Gd3+ ion. When x : y was 0.5 : 0.5, the fluorescent emission intensity was the largest. The result obtained by testing the X-ray
diffraction of the monocrystal revealed that the molecular formula of the mono-crystal complex is [Tb(TPTZ)(H2O)6]Cl3·3H2O. The number of metal ion coordinates is nine, and the tridentate TPTZ and six water molecules are bonded with terbium respectively.
Besides, it also revealed that the monocrystal belongs to the monoclinic system, and space group Cc with the following unit
cell parameters is a = 1.4785 (3) nm, b = 1.0547 (2) nm, c = 1.7385 (4) nm, β = 94.42 (3)°, V = 2.7028 (9) nm3 and Z = 4. 相似文献
12.
A novel artificial anion chemosensor 1 based on 2, 2′-di (4-nitrophenylurea-β-N-yl) -1, 1′-binaphthyl is designed and synthesized for sensing anions including halide ions and oxoanions. The fluorescent
emission of the binaphthyl of receptor 1, forming the hydrogen bonding with anions as the sensing mechanism, is monitored in DMSO for detecting anions. In brief,
while most of the anion chemosensors are switch-off fluorescent chemosensor, or non-fluorescent sensor, receptor 1 exhibits obviously the switch-on emission during the complexation with H2PO4−. 相似文献
13.
Kiichirou?Koyasu Wilko?Westh?user Marco?Niemietz Jan?Heinen Gerd?Gantef?r 《Applied Physics A: Materials Science & Processing》2009,96(3):679-684
Using time-resolved photoelectron spectroscopy, the decay channels of AuO2− and Au2O2− following photoexcitation with 3.1-eV photons have been studied. For AuO2−, a state with a rather long lifetime of 30 ps has been identified. Its decay path could not be determined but photodesorption
can be excluded. For Au2O2−, the spectra indicate O2 desorption after 3.1-eV photoexcitation on a time scale of 1 ps. While comparing these results on Au
n
O2− with analogous data on Ag
n
O2− clusters, a discernible pattern emerges: for dissociatively bound O2(AuO2−, Ag3O2−), there are long-living excited states which do not decay by oxygen desorption, while for molecular chemisorption (Au2O2−, Ag2O2−, Ag4O2−, Ag8O2−), the 3.1-eV photoexcitation triggers fast O2 desorption with a high quantum yield. 相似文献
14.
B. I. Kidyarov 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(9):1255-1256
The growth conditions of perfect acentric aluminum iodate octahydrate (Al(IO3)3 · 8H2O) crystals from aqueous solutions was experimentally studied. The properties of the crystals grown are reported. 相似文献
15.
We have studied the magnetic structure of Fe[Fe(CN)6]·4H2O, prepared by precipitation method, using neutron diffraction technique. Temperature dependent DC magnetization study down
to 4.2 K shows that the compound undergoes from a high temperature disordered (paramagnetic) to an ordered magnetic phase
transition at 22.6 K. Rietveld analysis of neutron diffraction pattern at 60 K (in its paramagnetic phase) revealed a face
centred cubic structure with space group Fm3m. The structure contains three-dimensional network of straight Fe3+-C≡N-Fe3+ chains along the edges of the unit cell cube. Fe3+ ions occupy 4a (0, 0, 0) and 4b (1/2, 1/2, 1/2) positions. Fe3+(0, 0, 0) is surrounded octahedrally by six nitrogen atoms and Fe3+ (1/2, 1/2, 1/2) is surrounded octahedrally by six carbon atoms. Magnetic Rietveld refinement of neutron diffraction data
at 11 K shows a ferromagnetic coupling between the two inequivalent Fe3+ sites. Refinement yielded an ordered moment of 4.4(6) and 0.8(6) μB per Fe ion located at (0, 0, 0) and (1/2, 1/2, 1/2), respectively. Ordered moments are found to align along the face diagonal.
The observed net moment from low temperature neutron diffraction study is consistent with DC magnetization results. 相似文献
16.
Crystals of [Rb0.7(NH4)0.3]2SO4 solid solutions are studied using x-ray diffractometry in the temperature range 4.2–300 K. No anomalies are revealed in the temperature dependences of the lattice parameters and the volume of the host unit cell. A series of superstructure reflections observed along the basis axes corresponds to the guest lattice formed in the matrix of the host structure. From analyzing the axial ratio of these structures and their temperature dependences, it is concluded that the structure of the crystal has the form of an incommensurate composite. The guest structure of the composite at room temperature can be considered a set of chains that are not correlated along the b direction. In the plane perpendicular to the chain axes, these chains form a regular framework that is also incommensurate to the host lattice. 相似文献
17.
The specific heat of [NH2(CH3)2]2ZnCl4 was measured calorimetrically in the temperature region 80–300 K. As the temperature T decreases, the C p (T) dependence indicates a phase transition sequence, with the phase transition at T6=151 K observed for the first time. The thermodynamic characteristics of the crystal were refined. The transformation occurring at T2=298.3 K is shown to be an incommensurate-commensurate phase transition. 相似文献
18.
D. M. Shukurova A. S. Orekhov B. Z. Sharipov V. V. Klechkovskaya T. S. Kamilov 《Technical Physics》2011,56(10):1423-1428
The current-voltage characteristics of Mn4Si7-Si〈Mn〉-Mn4Si7 and Mn4Si7-Si〈Mn〉-M photodiodes are studied experimentally. The current passage mechanism under illumination with hν ≥ E
g
is considered. The role of a contact to Mn4Si7 in the provision of high photosensitivity under illumination of the base by light with hν ≥ 1.14 eV at low temperatures, 77–220 K, is analyzed. From electrical measurements, electron microscopic data for the Mn4Si7-Si〈Mn〉 interface, and photocurrent-voltage characteristics, a band diagram under the conditions of photocurrent passage is
constructed. The high low-temperature photosensitivity of the diodes (I
ph/I
d ≥ 109) is explained by the impact-ionization-induced modulation of the base conductivity and injection amplification of holes in
the transition layer. 相似文献
19.
V. V. Zelenov E. V. Aparina A. V. Chudinov S. A. Kashtanov 《Russian Journal of Physical Chemistry B, Focus on Physics》2010,4(3):399-407
The reactive uptake of NO3 radicals on the surface of wetted individual X salts and of wetted X-NaCl salts (X = MgCl2 · 6H2O and MgBr2 · 6H2O) at [H2O] = 2 × 1012−2 × 1015 cm−3 and NO3 (4.8 × 1012 cm−3) was studied using a reactor with a movable insert covered with a salt coating in combination with a mass spectrometer for
monitoring the initial reactant and products. The probabilities of NO3 uptake γ on X-NaCl binary salts as functions of the content of doping salt were determined. A parametric approximation of
the experimental data was proposed, which makes it possible to quantitatively predict the extent of surface enrichment of
a wetted binary salt coating in doping salt and its dependence on the humidity and the content of this salt in the binary
mixture. It was established that the relative surface density σX of X doping salt depends on its mole fraction μX in the X-NaCl binary salt as σX = aμX (a = 2.2 for MgBr2 and 13.1 for MgCl2) over the entire humidity range covered. The contributions of the X salts to the overall uptake of NO3 at NO3 concentration typical of the tropospheric conditions ([NO3] ∼ 107 cm−3 and relative humidities of RH ≤ 20%) were estimated. 相似文献
20.
O. V. Kravchina A. I. Kaplienko E. P. Nikolova A. G. Anders D. V. Ziolkovskii A. Orendachova M. Kajnakova 《Russian Journal of Physical Chemistry B, Focus on Physics》2011,5(2):209-214
The influence of the replacement of hydrogen with deuterium in molecules of water of crystallization in the structure of the
(CuSO4)(en) · 2H2O and (CuSO4)(en)·2D2O organometallic compound molecules on exchange interaction between copper ions was studied. The X-ray structural data and
the data on angular anisotropy of the effective g-factor of Cu2+ ions in both compounds show that distortions of the initial structure caused by deuteration are minimum. A comparative analysis
of the width of the exchange coupled EPR lines of the two compounds is indicative of a decrease in the exchange parameter
in the deuterated sample, which substantiates the participation of H-bonds in exchange interactions in the systems studied. 相似文献