Observation of sublimation of ice using terahertz spectroscopy

Although many studies have investigated the phase change of water, few have focused on the sublimation of ice. This study revealed that ice sublimation can be observed using terahertz (THz) spectroscopy. From measurements in the range of 210–270 K, the sublimation was observed over the entire temperature range and the rate of sublimation was increased proportionally with temperature. Particularly on a time scale of a few hundred minutes, the sublimation progresses visibly above 250 K. Above a certain temperature, the absorption coefficient increased during sublimation. These findings suggest that an interesting phenomenon may occur in the phase change of water at sub-zero temperatures, indicating that THz spectroscopy would be useful for measuring water and ice.

New formula for predication thermal conductivity for homologous alkanes series function of carbon number

The main aim of this paper is to establish a correlation for prediction the thermal conductivity of n-alkanes within a give temperature range for homologous n-alkanes series from CH4 to C30H62. The predicted thermal conductivity values depend on the temperature and carbon number for each alkanes component. This paper describes a method of predicting the thermal conductivity of any alkanes between the temperature range, based on a measurement of the thermal conductivity. Where prediction are based on lower temperature measurements, where the accuracy is generally better then 3.1% for 178 data points. Useful predictions can also be made from any temperature measurements for most alkanes, but with reduced accuracy. This method permits alkanes to be used in situations where the thermal conductivity is important without having to make (or find) direct measurements over the entire temperature range of interest. Recommended thermal conductivity values are presented for 30 components.

Hot-salt corrosion of alloys PT-7M, 42ХНМ, Inconel 690, Incoloy 800

The Article contains the results of the study performed for the samples made from alloys PT-7М, 42ХНМ, Inconel 690, Incoloy 800 for resistance against hot salt corrosion in the mixture of crystallized NaCl and KBr salts, in ratio 300:1 by weight, and in the temperature range from 150 °С to 300 °С, both in contact with the air and in a leak-tight autoclave in the atmosphere of saturated water steam. Regularities of hot salt corrosion behavior in the alloys under the study were detected under testing conditions. The atmosphere of saturated water steam inhibits development of halt salt corrosion of alloy ПТ-7М in the entire temperature range of the testing.

Thermally Robust Non-Wetting Ni-PTFE Electrodeposited Nanocomposite

The effect of high temperature exposure on the water wetting properties of co-electrodeposited superhydrophobic nickel-polytetrafluoroethylene (Ni-PTFE) nanocomposite coating on copper substrates was studied. This was accomplished by comparing the performance with a commercial superhydrophobic spray treatment (CSHST). The Ni-PTFE and CSHST coatings were both subjected to heating at temperatures up to 400 °C. Results showed that the Ni-PTFE was able to maintain its superhydrophobicity throughout the entire temperature range, whereas the CSHST became more wettable at 300 °C. Furthermore, additional abrasive wear tests were conducted on both materials that were subjected to heating at 400 °C. The Ni-PTFE remained highly non-wettable even after 60 m of abrasion length on 800 grit silicon carbide paper, whereas the CSHST coating was hydrophilic after 15 m.

Анизотропия эффекта Холла в квазидвумерном электронно-легированном сверхпроводнике Nd-=SUB=-2-x-=/SUB=-Ce-=SUB=-x-=/SUB=-CuO-=SUB=-4+delta-=/SUB=-

—The temperature dependences of the Hall effect of an electron-doped Nd_2 – _ x Ce_ x CuO_4 + δ superconductor have been studied at the antiferromagnet–superconductor quantum phase transition boundary (0.135 ≤ x ≤ 0.15) in conducting CuO_2 planes and in the direction perpendicular to the CuO_2 plane. The hall coefficient between the conducting planes has been found be two orders higher than that in the conducting planes over entire temperature range, which is due to the incoherent character of the charge carrier transfer in the direction of axis c .

Thermoelectric Properties of n-Type AgPbSbTe Composites Containing Nanoscaled Phases

The effects of nanophase additions on the thermoelectric properties of n-type AgPb18SbTe20 fabricated by combining fast melting and hot pressing were investigated. The presence of sovelthermally syntheszied AgPb18SbTe20 nanospheres or nanorods in the bulk yields remarkably improved thermoelectric properties. Nanophase additions produce a reduction in the Seebeck coefficent at about 300~550 K and the maximum Seebeck coefficient absolute values are, respectively, 378 and 380 μV·K-1 for LAST-18 with nanospheres and nanorods samples. The κ values of two samples with nanophases show a lower value in the entire temperature range compared to that of LAST-18 matrix. A maximum figure of merit, ZT=0.92 at 673K for the nanorod-containing composite is achieved mainly due to the reduced thermal conductivity. Furthermore, the temperature of ZT peak shift to a higher range originated from the enlarged energy gap.

Theory of Heat Capacity of Liquid Helium-4 for Temperatures above the Critical Point

We analyze numerically the behavior of the heat capacity of liquid 4He for the entire temperature range with the corresponding formula for the internal energy obtained in Ref. [I.O. Vakarchuk, R.O. Prytula, A.A. Rovenchak, J. Phys. Stud. 11, 259 (2007)] combined with a simple calculation of the effective mass of interacting Bose particles. The results agree quite well with experimental data.

Bipolar Integrated OR-NOR Gate in 4H-SiC

An integrated bipolar OR-NOR gate based on emitter coupled logic (ECL) is demonstrated in 4H-SiC. Operated from 27 up to 300 °C on –15 V supply voltage the logic gate exhibits stable noise margins (NMs) of about 1 V in the entire temperature range.

CHARACTERIZATION OF LAYERED Na2-x-yLixKyTi3O7 CERAMICS BY DIELECTRIC-SPECTROSCOPIC INVESTIGATIONS

In this paper, we present detailed investigations on the dielectric properties of Lithium (x = 0.10) and Potassium (y = 0.01, 0.02, 0.04, 0.05) mixed Sodium tri-titanate, Na 2-x-y Li x K y Ti 3 O 7 polycrystalline materials synthesized by solid-state reaction. The characteristics of the pelletized samples have been studied in the temperature range from 350 to 725 K and on the frequency in the range from 10 kHz to 1 MHz. The studies reveal that the chain structured Na 2-x-y Li x K y Ti 3 O 7 layered compound possesses electronic, ionic, dipolar, and space charge polarization mechanisms over the respective temperature regions in the entire temperature range of study.

1700V, 20A 4H-SiC DMOSFETs Optimized for High Temperature Operation

DMOSFETs fabricated in 4H-SiC with capabilities for blocking in excess of 1700V and conducting 20A continuous current in the on-state are presented. These SiC DMOSFETs remain functional to temperatures in excess of 225°C, with leakage current at 1700V at 225°C of less than 5 A with VGS = 0V. The DMOSFETs show excellent switching characteristics, with total switching energy of 1.8 to 1.95 mJ over the entire temperature range of testing (25°C to 200°C), when switched from the blocking state at 1200V to conducting at 20A in a clamped inductive load switching circuit. The electrical characteristics are compared to commercially available Si IGBTs rated to 1700V with similar current ratings as the SiC DMOSFET described herein.