共查询到20条相似文献,搜索用时 15 毫秒
1.
New dielectric-constant gas-thermometry (DCGT) measurements were performed at PTB from 2.4 K to 26 K in order to establish
a temperature scale with reduced uncertainty. The progress concerning the measurement of capacitance changes, temperature,
and pressure compared with the results published in 1996 is described. This is the first step on the way to determine the
Boltzmann constant at the triple point of water. At more than 20 temperatures, isotherms were measured and evaluated performing
both single- and multi-isotherm fits. Based on this evaluation, a more accurate DCGT scale has been established that is compared
with the constant-volume gas-thermometry scale NPL-75, being one basis of the International Temperature Scale of 1990. Coincidence
has been found within only a few tenths of a millikelvin above 3.3 K. This gives, together with literature data, confidence
with respect to thermodynamic temperature at this level. Emphasis is also given to the results obtained for the virial coefficients,
especially below 3.3 K, where the 1996 DCGT results show strong deviations from the expected behavior. The new experimental
data for the second virial coefficient are compared with ab initio calculations. 相似文献
2.
Standard capsule-type platinum–cobalt (PtCo) resistance thermometers represent one of the few types of resistance thermometers that have been developed for precise thermometry in the cryogenic temperature range. These thermometers remain sensitive even at 0.65 K, which is the lower limit of the ITS-90. Standard capsule-type rhodium–iron (RhFe) resistance thermometers are another type of resistance thermometer intended for use in this temperature range and have been well characterized and are the de facto standard worldwide. Existing data show RhFe resistance thermometers are more reproducible than the corresponding PtCo resistance thermometer. However, it has become difficult to obtain brand-new standard capsule-type RhFe resistance thermometers since their production was discontinued in the early 2000s. Unfortunately, information regarding the characteristics of standard capsule-type PtCo resistance thermometers is limited compared to that available for RhFe resistance thermometers. In this study, the characteristics of two standard capsule-type PtCo resistance thermometers between 0.65 K and 25 K were investigated. Because the resistance versus temperature curves for these thermometers over this temperature range exhibit two inflection points, setting break points near each of the inflection points was found to be beneficial during polynomial curve fitting to obtain mK-level precision. Special attention was paid to the reproducibility of these thermometers, and it was observed that the reproducibility of one of the thermometers within the cryogenic temperature range was ±0.5 mK over 6 years, while the second thermometer showed a larger variation. Similar trends in the resistance characteristics of the two thermometers were observed at the triple point of water. 相似文献
3.
4.
The densities, ρ, and speeds of sound, u, have been measured as a function of composition for binary liquid mixtures of dipropylene glycol monopropyl ether (DPGMPE)
with n-butylamine (BA), dibutylamine (DBA), and tributylamine (TBA) at (288.15, 293.15, 298.15, 303.15, and 308.15) K and atmospheric
pressure using an Anton Paar DSA-5000 instrument. The ρ and u values were used to calculate excess molar volumes, V
E, deviations from the ideal behavior of the thermal expansion coefficient, α
E, and the isentropic compressibilities, Δκ
S
. Moreover, the apparent molar volume , and apparent molar compressibility , of the components have been calculated at infinite dilution. The Jouyban–Acree model is used to correlate the experimental
values of density and ultrasonic speed at different temperatures. 相似文献
5.
The thermal conductivity of Manganin (Cu 86 %, Ni 2 %, Mn 12 %) in the range 10–50 mK was measured by means of a new method that uses a metal–insulator junction (M-I.J) of known characteristics to read temperatures at one end of the sample. The same power P that crosses the sample to measure its thermal resistance flows through the M-I.J. A suitable choice of the M-I.J allows the temperature T of the upper end of the sample to rise above 20 mK. T was measured by a small size Ruthenium thermometer. 相似文献
6.
The specific heat capacity and electrical resistivity of titanium were measured by a subsecond pulse-heating method. Specimens were in the form of a 1.6-mm-diameter-wire. Experiments covered the range between 300 and 1900K; thermometry was provided by Pt10%Rh/Pt and W5%Re/W25%Re thermocouples. The maximum uncertainties in the specific heat capacity and electrical resistivity determinations were less than 3 and 1%, respectively. Results are reported and discussed for both the bcc and hcp structures and the transformation between the two phases. 相似文献
7.
F. Ancilotto M. Barranco E. S. Hernández M. Pi 《Journal of Low Temperature Physics》2009,157(3-4):174-205
This paper reviews the most recent research of adsorption of finite helium systems, performed in the frame of Density Functional theory. These comprehend the deposition and spreading of helium droplets on flat alkali metal surfaces, the determination of isotherms, the construction of the phase diagram of helium on such substrates, the adsorption of helium on spherical and cylindrical surfaces, the filling of wedges and of infinite polygonal pores, and the adsorption on planar surfaces structured with an array of parabolic nanocavities. 相似文献
8.
The thermal conductivities of carbon dioxide and three mixtures of carbon dioxide and methane at six nominal temperatures between 300 and 425 K have been measured as a function of pressure up to 12 MPa. The measurements were made with a transient hot-wire apparatus. The relative uncertainty of the reported thermal conductivities at a 95% confidence level is estimated to be ±1.2%. Results of the low-density analysis of the obtained data were used to test expressions for predicting the thermal conductivity of nonpolar mixtures in a dilute-gas limit developed by Schreiber, Vesovic, and Wakeham. The scheme was found to underestimate the experimental thermal conductivity with deviations not exceeding 5%. The dependence of the thermal conductivity on density was used to test the predictive scheme for the thermal conductivity of gas mixtures under pressure suggested by Mason et al. and improved by Vesovic and Wakeham. Comparisons reveal a pronounced critical enhancement on isotherms at 300 and 325 K for mixtures with methane mole fractions of 0.25 and 0.50. For other states, comparisons of the experimental and predicted excess thermal conductivity contributions showed a smaller increase of the experimental data with deviations approaching 3% within the examined range of densities. 相似文献
9.
O. Tkachenko A. Morawski A. J. Zaleski P. Przyslupski T. Dietl R. Diduszko A. Presz K. Werner-Malento 《Journal of Superconductivity and Novel Magnetism》2009,22(6):599-602
The FeSe material was prepared from pure components under inert gas atmosphere. Typically, synthesized material was HIP-ed
under pressure of 0.45 GPa of 5N purity argon with use of the High Gas Pressure Trap System (HGPTS). The thin films were obtained
by epitaxial process performed on substrates. Thin layers were manufactured by mixed procedures with the use of DC sputtering
on the substrate from various types of targets. The FeSe0.88 material has T
c
from 8 to 12 K. It was synthesized at high Se vapor pressure at equilibrium conditions of pressure and temperature.
The used HGPTS assure the full separation of the active inner volume for synthesis or crystal growth of material and the outside
gas medium. The material has been investigated by SEM, EDX, XRD, magnetic susceptibility and resistivity measurements. 相似文献
10.
D. Shaltiel H.-A. Krug von Nidda B. Y. Shapiro B. Rosenstein A. Loidl B. Bogoslavsky I. Shapiro T. Fujii T. Watanabe T. Tamegai 《Journal of Superconductivity and Novel Magnetism》2009,22(4):387-399
The Josephson Vortex dynamics in high anisotropy superconductors Bi2212 and Bi2223 induced by AC magnetic field collinear
to DC magnetic field and parallel to the layers is studied via their interaction with microwave field. Experimental results
as function of DC magnetic field, AC magnetic field and temperature are presented. The AC induced microwave dissipation is
larger than dissipation without AC field. The results are explained by the theoretical interpretation reported recently due
to shaking by the AC field that depins the JV (Shaltiel et al., Phys. Rev. B 77, 014508, 2008). Similar behavior in these two compounds as a function of the variables involved discloses that the shaking effect should
be observed in any high anisotropy superconductors. It shows that the AC field interacting with JV has an active and not the
usual passive modulating role of the DC field in EPR dissipation experiments. The technique can be used to investigate JV
dynamics and JV phase diagram. 相似文献
11.
Divya Shukla Shashi Singh Shahla Parveen Manisha Gupta J.P. Shukla 《International Journal of Thermophysics》2008,29(4):1376-1384
Densities and viscosities have been measured for the binary mixtures of methanol with chlorobenzene and with bromobenzene
from 293 K to 313 K over the complete composition range. Densities were used to compute the excess molar volume ( , for these binary systems. The results have been discussed in terms of molecular interactions. Furthermore, viscosity results
were compared with a corresponding-states model. The average absolute deviation was found to be 1.9 %. 相似文献
12.
Spectral–directional emittance measurements of aluminum oxide (99.5% pure), in air, were performed at 823 K using an apparatus
comprised of a Fourier Transform Infrared (FTIR) spectrometer, a blackbody radiating cavity (hohlraum), and a sample holder
which allows directional measurements. The data cover a wide spectral range between 2 and 25 μm, and a directional range from
a surface normal to a 72° polar angle. The aluminum oxide sample used in the experiment had a nominal surface roughness of
1 μm determined by a profilometer. Directional emittance shows no departure from dielectric behavior. 相似文献
13.
Cai Hong Dai Boris Khlevnoy Zhi Feng Wu Yan Fei Wang Maxim Solodilov Svetlana Kolesnikova Irina Grigoryeva Yan Dong Lin Ling Li 《Mapan》2017,32(3):243-250
With the new spectral irradiance measurement facility based on blackbody BB3500M of National Institute of Metrology (NIM), a bilateral spectral irradiance comparison was carried out between NIM and VNIIOFI (All Russian Research Institute for Optical and Physical Measurements) in the spectral wavelength from 250 to 2500 nm for the period of January 2015 to June 2016. The temperature measurement of the high temperature blackbodies were traced to the Pt–C and Re–C fixed point blackbodies and checked against the WC–C fixed-point blackbody for the two institutes respectively. The consistency of the temperature at 3021 K is better than 70 mK. The comparison result shows that the average relative deviation of spectral irradiance at 44 designated wavelengths is 0.45%. The consistency is better than 0.9% except the maximum deviation 1.1% at the wavelength of 2000 nm. The spectral irradiance units measured by NIM and VNIIOFI in this comparison are in agreement within the combined standard uncertainties of the laboratories over the wavelength range compared. 相似文献
14.
S. M. Mosameh A. S. Sandouqa H. B. Ghassib B. R. Joudeh 《Journal of Low Temperature Physics》2014,175(3-4):523-542
The thermodynamic properties of $^{4}$ He gas are investigated in the temperature-range 4.2–10 K, with special emphasis on the second virial coefficient in both the classical and quantum regimes. The main input in computing the quantum coefficient is the ‘effective’ phase shifts. These are calculated within the framework of the Galitskii–Migdal–Feynman (GMF) formalism, using the HFDHE2 and Sposito potentials. The virial equation of state is constructed. Extensive calculations are carried out for the pressure–volume–temperature (P–V–T) behavior, as well as chemical potential, and nonideality of the system. The following results are obtained. First, the validity of the GMF formalism for the present system is demonstrated beyond any doubt. Second, the boiling point (phase-transition point) of $^{4}$ He gas is determined from the P–V behavior using the virial equation of state, its value being closest than all previous results to the experimental value. Third, the chemical potential $\upmu $ is evaluated from the quantum second virial coefficient. It is found that $\upmu $ increases (becomes less negative) as the temperature decreases or the number density n increases. Further, $\upmu $ shows no sensitivity to the differences between the potentials used up to n = 10 $^{27}$ m $^{-3}$ . Finally, the compressibility Z is computed and discussed as a measure of the nonideality of the system. 相似文献
15.
Dawei Fan Wenge Zhou Chongqiang Liu Yonggang Liu Xi Jiang Fang Wan Jing Liu Xiaodong Li Hongsen Xie 《Journal of Materials Science》2008,43(16):5546-5550
A pressure–volume–temperature data set has been obtained for natural chromium spinel, using synchrotron X-ray diffraction
with a resistance heated diamond-anvil cell (RHDAC). The unit cell parameter of the chromium spinel was measured by energy
dispersive X-ray diffraction up to pressures of 26.8 GPa and temperatures of 628 K. No phase change has been observed. The
observed P–V–T data were fit to the high-temperature Birch-Murnaghan equation of state, with V
0 fixed at its experimental value, yields K
0 = 209 ± 9 GPa, (∂K/∂T)P = −0.056 ± 0.035 GPa K−1, and α0 = 7±1 × 10−5 K−1. The temperature derivative of the bulk modulus (∂K/∂T)P of chromium spinel is determined here for the first time. The obtained K
0 is slightly higher than the previous results of synthetic spinel. We suggest that Fe2+–Mg2+ substitution is responsible for the high bulk modulus of chromium spinel. 相似文献
16.
Longlong Yang Ping Shen Xiaoshuang Cong Qichuan Jiang 《Journal of Materials Science》2013,48(2):960-966
Wetting of poly- and mono-crystalline MgO substrates by molten La was investigated at 1323 K in a high vacuum using a modified sessile drop method. The wettability seems to depend mildly on the substrate orientation but strongly on the surface roughness. The initial contact angles on the smooth (100), (110), and (111) surfaces are 63° ± 1°, 69° ± 1°, and 69° ± 1°, respectively, while on the rough polycrystalline surfaces they are much larger (104° ± 3°). The wetting behavior is dictated by the disruption of the oxide film covering the La surface, the extent of the interfacial reaction and the evolution of the reaction product. A thick layer of La2O3 phase formed at the interface and then enwrapped the liquid surface, leading to the recession and warping of the triple line and finally the deterioration in the wettability. On the other hand, magnesium was displaced by the reaction and its evaporation provided additional impetus for the movement of the triple line. Due to different reaction intensities, the wetting behavior of La on the different orientations of the MgO surfaces also showed some discrepancies. 相似文献
17.
Pingjun Zheng Xianyang Meng Jiangtao Wu Zhigang Liu 《International Journal of Thermophysics》2008,29(4):1244-1256
Measurements of the density and viscosity of dimethoxymethane and 1,2-dimethoxyethane are reported over the temperature range
from 243 K to 373 K and at pressures up to 20 MPa. The measurements were performed simultaneously using a vibrating-wire instrument
operated in the forced mode of oscillation. The overall uncertainties of these results are 2.0% in viscosity and 0.2% in density.
The measurements were correlated with a Tait-type equation for density and a hard-sphere model for viscosity. The maximum
absolute deviation and the average absolute deviation (AAD) of the density measurements from the correlation for dimethoxymethane
are 0.065% and 0.012%, respectively, and for 1,2-dimethoxyethane, are 0.16% and 0.044%. With regard to viscosity, the maximum
absolute deviation and the AAD of the present results from the correlation for dimethoxymethane are 1.55% and 0.40%, respectively,
and for 1,2-dimethoxyethane, are 1.05% and 0.26%. Comparisons of the experimental data and measurements from the literature
with values calculated by the correlations at different temperatures and pressures are presented. 相似文献
18.
The thermodynamic properties of liquid 3He-4He mixtures at pressures of up to 10 bar and temperatures below 1.5 K are determined. The calculations are based on previously determined thermodynamic properties of 3He-4He mixtures at saturated (zero) pressure, and available experimental measurements of the molar volume, which are used to determine an expression for the molar volume. Since available experimental data for mixtures at higher pressures are restricted to low temperatures (below about 0.7 K), the calculated molar volumes at high pressure and high temperature are largely based on pure 3He and pure 4He data. 相似文献
19.
A newly designed experimental apparatus has been used to measure the speed of sound u in high-purity water on nine isotherms between 274 and 394 K and at pressures up to 90 MPa. The measurement technique is
based on a traditional double-reflector pulse-echo method with a single piezoceramic transducer placed at unequal distances
from two stainless steel reflectors. The transit times of an acoustic pulse are measured at a high sampling rate by a digital
oscilloscope. The distances between the transducer and the reflectors were obtained at ambient temperature and pressure by
direct measurements with a coordinate measuring machine. The speeds of sound are subject to an overall estimated uncertainty
of 0.05 %. The acoustic data were combined with available values of density ρ and isobaric heat capacity cp along one isobar at atmospheric pressure to calculate the same quantities over the whole temperature and pressure range by
means of a numerical integration technique. These results were compared with those calculated from the IAPWS-95 formulation
with corresponding relative deviations which are within 0.1%.
Paper presented at the Fifteenth Symposium on Thermophysical Properties, June 22–27, 2003, Boulder, Colorado, U.S.A. 相似文献
20.
Thermal conductivity measurements have been taken between 20 and 300 K on composites prepared from polyethylene glycol (PEG) containing various amounts of superconducting (Bi,Pb)2223 powder. The nature of temperature variation of thermal conductivity (C) of the composites and its magnitude depend strongly on the volume concentration of the high-temperature superconductor (HTSC) filler present in the material. The results have been discussed in the light of models known for polymer–metal powder composites. It is shown that for composites with 2223 powder content <44 vol. %, the measured data can be accounted well with Hamilton–Crosser model, taking the sphericity factor into consideration. Failure of Hamilton–Crosser expression for composites with higher filler concentration is thought to be associated with direct contact between the superconducting grains, which shortcircuits the acoustic mismatch resistance in the composites. 相似文献