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1.
We performed measurements of positron lifetimes and the lineshape parameter on molybdenum samples irradiated with neutrons at temperatures from 350° to 1000° C. The results show that the correlation between swelling and positron characteristics depends strongly on irradiation temperature. From 350° to 500° C, ΔS, and notI 2, correlates with sweelling; from 500° to 800° C, both ΔS andI 2 correlate with swelling; and at higher temperatures, none of them correlates with swelling. 相似文献
2.
The dielectric constant (ɛ′) and dielectric loss (ɛ″) for dilute solutions of sulfolane in carbon tetrachloride solution have been measured at 9.885 GHz at different temperatures
viz. 25°C, 30°C, 35°C and 40°C by using standard microwave techniques. Following the single frequency concentration variational
method, the dielectric relaxation time (τ) and dipole moment (μ) have been calculated. It is found that dielectric relaxation process can be treated as the rate process,
just like the viscous flow. Based on the above studies, monomer structure of sulfolane in carbon tetrachloride has been inferred.
Energy parameters (ΔH
g
, ΔF
g
, ΔS
g
) for dielectric relaxation process of sulfolane in carbon tetrachloride at 25°C, 30°C, 35°C and 40°C have been calculated
and compared with the corresponding energy parameters (ΔH
η
, ΔF
η
, ΔS
η
) for the viscous flow. 相似文献
3.
This investigation is a contribution to the research on alternative cathode materials with much more promising performances
for lithium batteries. It deals with the electrochemical properties of iron phosphate compound FePO4, chemically prepared through the so-called sol–gel Pechini process, terminated by a calcination of the product precursor
at temperatures (T
c) ranging between 350°C and 650°C. A crystalline phase was obtained for temperatures ≥400°C. The particle size decreased with
the decrease in T
c, giving rise to a Brunauer–Emmett–Teller (BET)-specific surface area, S
BET, as high as 28 m2 g−1 for the sample annealed at 400°C. The electrochemical properties of FePO4-based composite cathodes were characterized on three-electrode laboratory cells. Charge–discharge cycling determined a maximum
reversible capacity of 132 mAh g−1, which fell with the increase in T
c. A direct correlation was established between the activity of the material and its active surface area. 相似文献
4.
The amplitudes of the nonstationary Josephson current I
1, the interference current I
2, and the quasiparticle current J through symmetric and asymmetric tunnel junctions, including superconductors with charge density waves, are calculated. In
the symmetric (s) case the dependence of the Josephson current I
s
1
on the voltage V on the junction has a logarithmic singularity at |eV|=2Δ, Δ+D, and 2D, where
, Δ and Σ are the superconducting and dielectric order parameters, and e is the unit charge. At temperatures T≠0 jumps appear in the current-voltage characteristics I
s
1
(V) at |eV|=D−Δ. Jumps and singularities are observed in the currents I
s
2
and J
s at the same voltages at which singularities and jumps appear in I
s
1
, respectively. In the nonsymmetric (ns) junctions which include an ordinary superconductor, singularities and jumps occur at |eV|=D+ΔBCS, Δ+ΔBCS, and (for T≠0) |D−ΔBCS| and |Δ−ΔBCS|, where ΔBCS is the order parameter of an ordinary superconductor. The quasiparticle current J
ns is an asymmetric function of the voltage V and does not depend on the sign of Σ. The results are compared with experiment.
Fiz. Tverd. Tela (St. Petersburg) 39, 991–999 (June 1997) 相似文献
5.
Osamu Yamashita Hirotaka Odahara Takahiro Ochi Kouji Satou 《Applied Physics A: Materials Science & Processing》2009,94(1):57-64
The resultant local Seebeck coefficient α
R (=α
S−α
T) at the interface of a thermoelement has not yet been measured, although it is an important factor governing the thermoelectric
efficiency, where α
S is the local Seebeck coefficient and α
T is the one caused by the Thomson effect. It is shown in this paper that α
S, α
T, and α
R of the p- and n-type Cu/Bi–Te/Cu composites are obtained analytically and experimentally on the assumption that the local temperature of
the composite on which the temperature difference ΔT is imposed varies linearly with changes in position along the composite. They were indeed estimated as a function of position
from the local experimental data of R,ΔI,ΔT, and V generated by applying an additional current of ±I to the composite, where R is the electrical resistance and ΔI is a current generated by the composite. As a result, it was found that the absolute values of α
S at the hot interface of the p- and n-type composites are approximately 1.5 and 1.4 times higher than their lowest values in the middle region of the composite,
respectively, while those of α
T are less than 8% of α
S all over the composite and are so small that the relation α
R≈α
S can be held. We thus succeeded in measuring α
R at the interfaces of the composite. 相似文献
6.
Shenmin Zhu Di Zhang Jiajun Gu Jiaqiang Xu Junping Dong Jinlong Li 《Journal of nanoparticle research》2010,12(4):1389-1400
A sonochemical method is developed to fabricate SnO2 nanotubular materials from biological substances (here, it is cotton). The cotton fibers in SnCl2 solution were first treated with ultrasonic waves in air, followed by calcinations to give nanotubular materials that faithfully
retain the initial cotton morphology. The microstructure and morphology of the obtained SnO2 nanotubules were characterized by the combination of field-emission scanning electron microscope (FE-SEM), transmission electron
microscopy (TEM), Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and N2 adsorption/desorption measurements. The thermal behavior and crystalline properties were examined in the temperature range
of 450–700 °C. The nanocrystals composing of SnO2 nanotubules were estimated about 8.5, 13.2, and 14.2 nm corresponding to calcination temperatures of 450, 550, and 700 °C,
respectively. The sensor performance of biomorphic SnO2 nanotubules calcined at 700 °C was investigated in the atmosphere of ethanol, formaldehyde, carbinol, carbon monoxide, hydrogen,
ammonia, and acetone, respectively, which exhibited a good selectivity for acetone at a working temperature of 350 °C. The
sensitivity to 20 ppm acetone, S, was 6.4 at 350 °C with rapid response and recovery (around 10–9 s). These behaviors were well explained in relation to the
morphology of the nanotubules thus produced. 相似文献
7.
We have studied the magnetic aftereffects in the Ni
x
Fe3−x−ΔO4 system, for 0≦x≦1 and 10−5≦Δ≦2×10−1, between 80 and 500 K. The samples were obtained by sintering at 1400°C in an appropriate gas atmosphere. The measurements
are based on the deviation from equilibrium that is produced in a Maxwell-Wien bridge when the self-induction of a coil with
ferrite core varies because of the phenomenon of magnetic aftereffects. The numerical analysis of the results shows the presence
of relaxation processes at 300 K (III), 330 K (IIa), and above 500 K (I). The Processes III and IIa are related to the concentration
of nickel,x, and of vacancy, Δ. It is seen that the IIa peak can be attributed to a process of diffusion of Ni ions in the spinel lattice
by means of vacancies on octahedral sites. 相似文献
8.
Approximating the shape of the magneto-thermoelectric power (TEP) ΔS(T,H) measured in Bi2Sr2CaCu2Oy by an asymmetric linear triangle of the form ΔS(T,H)≃S
p
(H)±B
±(H)(T
c
−T) with positive B
−(H) and B
+(H) defined below and above T
c
, we observe that B
+(H) ≃2B
−(H). To account for this asymmetry, we explicitly introduce the field-dependent chemical potential μ(H) of holes into the Ginzburg-Landau theory and calculate both an average ΔS
av(T,H) and fluctuation contribution ΔS
fl(T,H) to the total magneto-TEP ΔS(T,H). As a result, we find a rather simple relationship between the field-induced variation of the chemical potential in this
material and the above-mentioned magneto-TEP data around T
c
, viz. Δ μ(H)∝S
p
(H).
Zh. éksp. Teor. Fiz. 116, 257–262 (July 1999)
Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor. 相似文献
9.
H.Y. Wang Z.W. Ma E.Y. Jiang Y.J. He H.S. Huang 《Applied Physics A: Materials Science & Processing》1999,68(5):559-562
The structure and magnetic properties of Fe-N and Fe-Ti-N films have been studied as a function of annealing temperature Ta with a transmission electron microscope and a vibrating sample magnetometer. The as-prepared Fe-N films consist of the γ′-Fe4N and α′′-Fe16N2 phases, and the Fe-Ti-N films are composed of the γ′-Fe4N, α′′-Fe16N2, and TiN phases. The structural changes with annealing temperature in the Fe-N films are distinct. The α′′-Fe16N2 decomposes into α+γ′ phases in the Fe-N film annealed at about 300 °C, and it disappears in the film annealed at 350 °C. Annealing of the Fe-Ti-N
films shows no structural changes between room temperature (RT) and 500 °C. The saturation magnetization 4πMS and coercivity Hc of the Fe-N films change drastically with the annealing temperature Ta, whereas those of the Fe-Ti-N films do not change with Ta up to 500 °C. These results indicate that the additon of Ti may improve the thermal stability of Fe-N films.
Recieved: 6 Juli 1998 / Accepted: 19 Oktober 1998 / Published online: 10 March 1999 相似文献
10.
B. A. Strukov E. P. Ragula S. Yu. Stefanovich I. V. Shnaidshtein S. V. Arkhangel’skaya A. Onodera 《Physics of the Solid State》1998,40(7):1193-1195
The specific heat of the ceramic and the permittivity of a single-crystal sample of LaBSiO5, a new ferroelectric in the stilwellite family, were measured in a temperature range which includes the phase transition
point (T
C=140 °C). The excess entropy of the phase transition ΔS=1.05 J/mol · K and the Curie-Weiss constant C
C-W=3.2×103 K were determined. The results indicate that the phase transition in this crystal is of a “mixed” nature and exhibits features
of a displacement-type transition and an order-disorder transition.
Fiz. Tverd. Tela (St. Petersburg) 40, 1310–1312 (July 1998) 相似文献