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1.
We investigate the spectroscopic properties of the 1.5-μm emission from the 4I13/2 → 4I15/2 transition of Er3+ ions in PbO–Bi2O3–Ga2O3–GeO2 glasses for applications in broadband fiber amplifiers. The measured emission peak locates at 1,532 nm with a full width
at half-maximum of ∼45 nm. The glasses exhibit a large stimulated emission cross-section of 0.89 × 10−20 cm2 and a large product of 40.0. Infrared-to-green upconversion occurs simultaneously upon excitation of the 1.5-μm emission with a commercially
available 980 nm laser diode. The green-upconversion intensity has a quadratic dependence on incident pump laser power, indicating
a two-photon process. Energy transfer processes and nonradiative phonon-assisted decays could account for the population of
the 2H11/2 of Er3+. The results indicate the possibility towards the development of lead–bismuth–gallate–germanate based glasses as photonics
devices. 相似文献
2.
Equilibrium between synthetic ion exchangers and solutions of cations has been the subject of this investigation. Competitive
ion exchange reactions were studied for two cation exchange membranes (CMX and CRP) involving K+, Na+, and Ca2+ ions. The ionic strength of the equilibrating solutions was maintained constant, but the molar fraction varied; all experiments
were conduced with nitrate as nonexchanging anions at 25 °C. Adsorption isotherm for the three binaries systems: K+/Na+, K+/Ca2+, and Na+/Ca2+ were studied. The obtained results show that potassium was the most strongly sorbed and the selectivity order for CMX and
CRP membranes is K+>Ca2+>Na+ at 0.1 M, under the experimental conditions. Selectivity coefficients , , and for the three binaries and for the two membranes were determined at an ionic strength of 0.1 M and at a constant temperature
of 25 °C. We remark that all the selectivity coefficient values are quite different from the unit. Ternary equilibrium was
taken for the Ca2+/K+/Na+ system. It was found that binary selectivity data could be successfully used to predict the ternary ion exchange equilibrium. 相似文献
3.
A modification of the Pechini method was applied to obtain luminescent rare earth orthophosphates. The developed synthetic
route is based on the ability of the tripolyphosphate anion () to act both as a complexing agent and as an orthophosphate precursor. Heating of aqueous solutions containing RE3+, Eu3+, , citric acid, and ethylene glycol led to polymeric resins. The ignition of these resins at different temperatures yielded
luminescent orthophosphates. The produced nanosized phosphors (YPO4:Eu3+, (Y,Gd)PO4:Eu3+, and LaPO4:Eu3+) were analyzed by infrared and luminescence spectroscopies, X-ray diffractometry, and scanning electron microscopy. 相似文献
4.
The phenomenon of the diffusion of proton and deuteron in a single crystal of magnesium aluminate spinel was studied by infrared
absorption. The chemical diffusion coefficient of proton was determined by the relaxation time of the absorption intensity
upon the substitution of deuteron with proton. The temperature dependence of the chemical diffusion coefficient of proton
for was expressed as . The chemical diffusion coefficient of proton was found to be independent of the composition of spinel and of the atmosphere.
Paper presented at the 11th Euro Conference on the Science and Technology of Ionics, Batz-sur-Mer, Sept. 9–15 2007. 相似文献
5.
We report the electrochemical Li reactivity of the cubic NiP3 phase, a candidate for anode applications for Li-ion batteries. NiP3 reacts with nine lithium per formula unit leading to a first cycle reversible capacity of 1,475 mAh/g at an average potential
of 0.9 V vs. Li+/Li°. Electrochemical measurements and complementary X-ray diffraction showed that NiP3 presents a conversion process competing with an insertion process. A good cycleability may only be obtained on a limited potential window, excluding the
low-potential region.
This paper was presented at the 11th EuroConference on the Science and Technology of Ionics, Batz-sur-Mer, Sept. 9–15, 2007. 相似文献
6.
Rod-like ZnO nanoparticles were prepared by the hydrolysis of zinc acetate under heating in diethylene glycol (DEG). Structural
characterization of the synthesized powders was investigated by XRD, FT-IR, electron paramagnetic resonance (EPR) and transmission
electron microscopy (TEM). The size of the particles increased as the amount of H2O added increased in the nano size range. The average crystallite size calculated from the XRD patterns varied from 6 to 64 nm
corresponding to the amount of H2O added. The ZnO nanopartilces possess the wurtzite type crystallographic structure. It was found that these ZnO nanoparticles
had singly ionized oxygen vacancy defect () and superoxide ions from the EPR investigations. A strong near UV emission of the ZnO nanoparticles at about 380 nm was observed
and its intensity decreased as the amount of H2O increased. This emission of ZnO nanoparticles is found to be particles size dependent due to the confinement effect. A green
emission at about 540 nm due to the recombination of electrons trapped at singly ionized oxygen vacancies defect () appeared when the amount of H2O increased. The intensity of the green emission increases as the concentration of increases. 相似文献
7.
A dense (BCSO) membrane was fabricated by a modified suspension spraying on porous NiO–BCSO anode support. In the process, the suspension
was directly prepared by ball-milling the BaCO3, CeO2, and Sm2O3 powders in ethanol. A dense and uniform electrolyte layer in the thickness of 10 μm was successfully prepared on porous anode
support by suspension spray process after co-sintering at 1,400 °C for 5 h. With (NSMO) cathode, a single cell was assembled and tested with hydrogen and ammonia as fuels, respectively. The hydrogen-fueled
cell exhibits 1.01 V for open circuit voltage (OCV) and 560 mW/cm2 for peak power density at 700 °C. In comparison, the cell in ammonia displays a similar performance (1.02 V for OCV and 530 mW/cm2 for output), which indicates the liquid ammonia is a promising substitute for hydrogen. Moreover, the fuel cell displays
good interface contacts. To sum up, ammonia-fueled solid oxide fuel cells prepared by this simple suspension spray is an alternative
way to promote the commercialization. 相似文献
8.
The activities of bacterial consortia enable organisms to maximize their metabolic capabilities. This article assesses the synergetic relationship between iron reducing bacteria (IRB), Shewanella putrefaciens and sulphate reducing bacteria (SRB) Desulfovibrio alaskensis. Thus, the aim of this study was first to form a biogenic hydroxy-sulpahte green rust GR2( $ {\text{SO}}_{{\text{4}}} ^{{2 - }} The activities of bacterial consortia enable organisms to maximize their metabolic capabilities. This article assesses the
synergetic relationship between iron reducing bacteria (IRB), Shewanella putrefaciens and sulphate reducing bacteria (SRB) Desulfovibrio alaskensis. Thus, the aim of this study was first to form a biogenic hydroxy-sulpahte green rust GR2() through the bioreduction of lepidocrocite by S. putrefaciens and secondly to investigate if sulfate anions intercalated in the biogenic GR2() could serve as final electron acceptor for a sulfate reducing bacterium, D. alaskensis. The results indicate that the IRB lead to the formation of GR2() and this mineral serve as an electron acceptor for SRB. GR2() precipitation and its transformation was demonstrated by using X-ray diffraction (DRX), M?ssbauer spectroscopy (TMS) and
transmission electron spectroscopy (TEM). These observations point out the possible acceleration of steel corrosion in marine
environment in presence of IRB/SRB consortia. 相似文献
9.
The small polarons in LiFePO4 are associated with the presence of Fe3+ ions introduced by the native defects in relative concentration in the samples known to be optimized with respect to their electrochemical properties. The nearest iron neighbours around
the central polaron site are spin-polarized by the indirect exchange mediated by the electronic charge in excess. These small
magnetic polarons are responsible for the interplay between electronic and magnetic properties that are quantitatively and
self-consistently analysed. Comparison is made with other magnetic polaron effects in other members of the family of magnetic
semiconductors to which this material belongs.
Paper presented at the 11th Euro-Conference on Science and Technology of Ionics, Batz-sur-Mer, France, 9–15 September 2007. 相似文献
10.
C. Ruby A. Géhin R. Aissa J. Ghanbaja M. Abdelmoula J.-M. R. Génin 《Hyperfine Interactions》2006,167(1-3):803-807
Hydroxysulphate green rust species were precipitated in the presence of various anions. is stable at ∼pH 7 and is transformed into a mixture of magnetite and ferrous hydroxide when the pH raised at ∼12. In the
presence of carbonate species, is partially transformed into a mixture of magnetite and siderite at ∼pH 8.5. This transformation is stopped when silicate
anions are present in the solution. As already observed for phosphate anions, the adsorption of silicate anions on the lateral
faces of the crystals may explain this stabilization effect. Sulphate anions are easily exchanged by carbonate species at ∼pH 10.5. In
contrast, anionic exchange between sulphate and phosphate anions was not observed. 相似文献
11.
Under a 980 nm laser pumping, quenching of green upconversion (UC) emission accompanied with enhancement of red UC emission
observed was dominated by the energy back-transfer (EBT) process in Er3+ and Yb3+ co-doped PbTiO3, BaTiO3, and SrTiO3 polycrystalline powders. The efficiency of the EBT process depends not only on Yb3+ concentration but also on level match of the doped Er3+ and Yb3+ ions caused by the crystal fields with different symmetries. Our UC emission spectra and X-ray diffraction confirm that the
centrosymmetric crystal field arising from reducing tetragonality causes level match of transition of Er3+ and of Yb3+. This level match is responsible for enhancing red UC emission. 相似文献
12.
For weakly non ergodic systems, the probability density function of a time average observable
is
where
is the value of the observable when the system is in state j=1,…L. p
j
eq is the probability that a member of an ensemble of systems occupies state j in equilibrium. For a particle undergoing a fractional diffusion process in a binding force field, with thermal detailed
balance conditions, p
j
eq is Boltzmann’s canonical probability. Within the unbiased sub-diffusive continuous time random walk model, the exponent 0<α<1 is the anomalous diffusion exponent 〈x
2〉∼t
α
found for free boundary conditions. When α→1 ergodic statistical mechanics is recovered
. We briefly discuss possible physical applications in single particle experiments. 相似文献
13.
J. Nowotny M. Rekas W. Weppner 《Applied Physics A: Materials Science & Processing》1988,47(2):205-208
Thermoelectric power (TP) and electrical conductivity (EC) measurements were performed for YEa2Cu3Ox at 1128 K under controlled oxygen partial pressure varying between 50 and 105 Pa. Three regimes are observed for the electrical properties. At low
both TP and EC remain constant with
. In the medium range
sharp changes of both electrical parameters occur; TP changes sign from positive above 4×102 Pa to negative below this
value. In the high
region (>7.6×103 Pa) TP vs log
exhibits two slopes; 5.1 below 1.5×104 Pa and 8.4 above this
value. The slopes can be discussed in terms of the defect structure involving singly and doubly ionized oxygen vacancies below and above 7.6×103 Pa, respectively. 相似文献
14.
Al, F-doped new perovskite lithium ion conductors (x=0.11) have been prepared by solid state reaction. It is found that a pure perovskite-structured phase with space group of P4mm(99) exits in the composition range of 0<y≤0.10. The sample with y=0.02 possesses the highest ionic conductivity of 1.06×10−3 S/cm at room temperature, and its decomposing voltage is 2.3 V. The factors affecting the conductivity of this system are discussed. 相似文献
15.
Borisevich NA Raichyonok TF Sukhodola AA Tolstorozhev GB 《Journal of fluorescence》2006,16(5):649-653
The delayed fluorescence spectrum for 8-aza-d-homogonane in the gas phase consists of a band of E-type delayed fluorescence of M-centers and a band of P-type delayed fluorescence of L-centers being the products of photo- and thermotransformations of a basic steroid. Triplet-triplet energy transfer from the M-centers to the L-centers is established and its efficiency is determined. For 8-aza-d-homogonane in frozen hexane solutions at T=77 K only the phosphorescence of the M- and L-centers is revealed. The phosphorescence of the basic steroid itself ( nm) as well as that of the M- and L-centers ( and 532 nm, respectively) is seen in a mixture of frozen tetrahydrofuran and toluene solutions. This is evident of the fact that the basic steroid has the products of its transformations, whose amount grows due to irradiation and heating. The M- and L-centers are stable molecules. 相似文献
16.
J. P. Wesley 《Foundations of Physics Letters》1992,5(6):597-604
The Weber potential energy U for charges q and q' separated by the distance R is U = (qq'/R)[1 – (dR/dt)2/2c2]. If this potential arises from a finite velocity c of energy transfer Q', where the retarded rate of transfer from q' to q is dQ(t-R/c)/dt = Q'[1 – (dR/dt)/c] and where the advanced rate from q to q' is dQ(t+R/c)/dt = Q'[1 + (dR/dt)/c], then the resultant time-average root-mean-square action is given by
. Identifying Q' with the Coulomb potential energy qq'/R, the Weber potential is obtained. Using the same argument, Newtonian gravitation yields a corresponding Weber potential energy, qq'/R being replaced by ( - Gmm'/R). 相似文献
17.
H. Assaridis I. Panagiotopoulos A. Moukarika V. Papaefthymiou T. Bakas 《Hyperfine Interactions》2006,169(1-3):1331-1336
The magnetic critical behavior of the manganese perovskite series $ {\text{La}}_{{0.67 - y}} {\left( {{\text{Sr,}}\,\,{\text{Ba,}}\,\,{\text{Ca}}} \right)}_{{0.33 + y}} {\text{Mn}}_{{1 - x}} {\text{Sn}}_{x} {\text{O}}_{3} The magnetic critical behavior of the manganese perovskite series (x = 0.01, 0.02, y = 0, 0.07) is studied by means of dc magnetic measurements and 119Sn M?ssbauer spectroscopy. The structure can be described by a rhombohedral unit cell (space group R–3C) for the samples where
the A-site is occupied by La and Sr or La and Ba ions and orthorhombic unit cell (space group Pnma) for the samples where
the A-site is occupied by La and Ca ions. Arrott and scaling plots show that the samples, where the A-site is occupied by
La and Sr or La and Ba ions, follow the behavior of a conventional second-order ferromagnetic transition. In contrast, the
samples that contain La and Ca ions in the A-site show anomalous behavior around Curie point. M?ssbauer measurements show
two magnetic phases below T
c. One of them exhibits stronger exchange interactions with more rapid electron transfer between Mn3+/Mn4+, compared to the other. 相似文献
18.
Rhodamine derivatives are popular, photostable fluorophores that are used in a number of fluorescent based techniques, including
fluorescence correlation spectroscopy (FCS). Indeed, in FCS, both rhodamine 6G (R6G) and rhodamine 110 (R110) are used as
calibration standards to determine the dimensions of the instrument confocal volume. In spite of a requirement for precise
values of the diffusion coefficients, literature values are scarce and vary over an order of magnitude. In this paper, the
diffusion coefficients of four rhodamine fluorophores (rhodamine 6G (R6G), rhodamine B (RB), rhodamine 123 (R123), rhodamine
110 (R110)) were determined by pulsed field gradient nuclear magnetic resonance (PFG-NMR) spectrometry and then validated
by comparison with fluorescence correlation spectroscopy. With the objective of validating the FCS calibration, diffusion
coefficients of several dextrans and a polystyrene nanoparticle were also determined and compared with literature values or
theoretical values that were based upon the Stoke–Einstein equation. The work presented here lead us to conclude that the
diffusion coefficients for R6G and R110 have generally been underestimated in the literature. We propose revised values of
4.4 × 10−10 m2 s−1 for R110 and 4.0 × 10−10 m2 s−1 for R6G. Using the revised D value for R110 to calibrate the FCS instrument, diffusion coefficients have then been systematically determined for different
conditions of pH, ionic strength and concentration. To correct for differences due to solvent effects (D2O vs. H2O), an isotopic correction factor, of 1.23, was determined from both FCS and from the solvent auto-diffusion coefficients obtained by NMR. 相似文献
19.
We present the main ingredients of twistor theory leading up to and including the Penrose-Ward transform in a coordinate algebra
form which we can then ‘quantise’ by means of a functorial cocycle twist. The quantum algebras for the conformal group, twistor
space , compactified Minkowski space and the twistor correspondence space are obtained along with their canonical quantum differential calculi, both in a local
form and in a global *-algebra formulation which even in the classical commutative case provides a useful alternative to the
formulation in terms of projective varieties. We outline how the Penrose-Ward transform then quantises. As an example, we
show that the pull-back of the tautological bundle on pulls back to the basic instanton on and that this observation quantises to obtain the Connes-Landi instanton on θ-deformed S
4 as the pull-back of the tautological bundle on our θ-deformed . We likewise quantise the fibration and use it to construct the bundle on θ-deformed that maps over under the transform to the θ-deformed instanton.
The work was mainly completed while S.M. was visiting July-December 2006 at the Isaac Newton Institute, Cambridge, which both
authors thank for support. 相似文献
20.
We find that the Laplace sequences of surfaces of period n in projective space P
n–1 have two types, while type II occurs only for even n. The integrability condition of the fundamental equations of these two types have the same form
When all
i
= 1, the above equations become two-dimensional Toda equations. Darboux transformations are used to obtain explicit solutions to the above equations and the Laplace sequences of surfaces. Two examples in P
3 of types I and II are constructed. 相似文献