Carbothermal reduction synthesis of aluminium oxynitride spinel powders at low temperatures

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

The fatigue life and plastic deformation character of copper at low temperatures

The fatigue life of polycrystalline copper has been determined in the temperature range 293 K - 12 K in vacuum at constant strain amplitude and the plastic deformation of the samples followed. The fatigue life is found to increase with decreasing temperature down to 100 K, it then decreases as the temperature is further reduced. This behaviour is explained in terms of the change in plastic deformation of the sample with temperature.     

The melting pressure of helium-3 at very low temperatures

The melting pressure of³ He at very low temperatures was shown earlier to be determined overwhelmingly by the solid phase. Using an extended solid³He model based on isotropic effective first-neighbor-pair antiferromagnetic and second-neighbor-pair ferromagnetic exchange interactions, the melting process is reinvestigated here. One of its motivating aspects may be said to be tied to its possible use, suggested by us earlier, for the establishment of a thermodynamic temperature scale at very low temperatures. As a consequence of the assumed multineighbor interactions, spin ordering is accelerated and, at the same temperature, the extended-model solid entropy falls below that of the simpler nearest-neighbor-pair interaction model. Equivalently, the spinordering critical transition temperature is raised over that associated with the simpler interaction scheme. The overall result is a decrease in the melting pressure variations at very low temperatures below those arising from the simple solid model. In the absence of a reliable experimental temperature scale at very low temperatures, only a qualified and cursory comparison is justified with recent experimentally estimated melting pressures. Discrepancies arise between theory and preliminary data on the temperature derivatives of the melting pressure or the entropy of the solid at melting. They might be due in part to the tentative experimental temperatures, which appear shifted toward too low temperatures when compared with the theoretical temperature scale implicit in the treatment of the generalized solid model. However, from the viewpoint which accepts the rather preliminary, scarce, very low temperature melting pressure data at face value, failure of the extended exchange model of solid³He at those temperatures must be kept in mind.Work performed under the auspices of the U.S. Atomic Energy Commission.     

Thermal properties of Zerodur at low temperatures

The linear thermal expansion of Zerodur has been measured from 20 to 300 K and the thermal conductivity from 2 to 100 K. For each property the temperature dependence appears to reflect the composite nature of the ceramic-glass.     

Cerium (IV) oxide nanotubes prepared by low temperature deposition at normal pressure

This paper reports the synthesis of cerium dioxide nanotubes (CeNTs) by electroless deposition using ion-track-etched polycarbonate templates. To achieve nanotubes with thin walls and small surface roughness the tubes were generated by a several-step-containing procedure under aqueous conditions. The approach reported below will process open end nanotubes with well-defined outer diameter and wall thickness.     

不同沉积温度下V掺杂的TiN薄膜的结构和性能

利用常压化学气相沉积法(APCVD)在玻璃基板上沉积制备了钒(V)掺杂的氮化钛(TiN)薄膜.利用X射线衍射仪(XRD)、光电子能谱仪(XPS)、扫描电子显微镜(SEM)、四探针电阻仪和分光光度计等对TiN薄膜的结构、形貌、以及光电性能进行了分析.结果表明,薄膜呈典型的粒状结构.随着沉积温度的升高,薄膜的结晶强度不断增...     

Synthesis and characterization of the manganese cobaltite spinel prepared using two “soft chemical” methods

Using the coprecipitation method and EDTA gel processes, manganese cobaltite (Mn_1.5Co_1.5O₄) powders were successfully synthesized. The thermal decomposition behavior of the gel precursors, phase formation and morphology of the Mn_1.5Co_1.5O₄ powders were characterized by means of DTA/TGA and MS analyses, X-ray diffraction (XRD), and scanning electron microscopy (SEM), respectively. Well-crystallized dual-phase manganese cobaltite spinel, containing both the cubic and tetragonal phases, was obtained at room temperature for both types of powders calcinated at 800 °C for 10 h in static air, without formation of any intermediate phase. SEM investigations show that the Mn_1.5Co_1.5O₄ powders prepared using two “soft chemical” methods were agglomerates composed of approximately micron-sized particles. The structure and morphology of the bulk samples, as well as their electrical conductivity, were investigated using XRD, SEM, and EIS, respectively. Mn_1.5Co_1.5O₄ spinels with different microstructure exhibited excellent electrical conductivity and structural stability. Major emphasis was placed on structural transformations of the spinel solid solutions with temperature and their effect on the electrical properties of these solutions.     

Thermophysical properties of epoxy compounds at low temperatures

Thermophysical properties of epoxy resin and its compounds are studied experimentally in the temperature range of 4.2–400 K. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 1, pp. 14–18, January–February, 1997.     

Transport properties of cold-worked aluminum at low temperatures

The electrical resistivity and thermoelectric power in annealed and cold-worked samples of Al and Al-Mg alloy have been measured between1.5 and8.5 K. The deviation from Matthiessen's rule is found to decrease with cold work, while the residual resistivity increases. The lattice imperfections also have strong effects on the thermoelectric power. A critical discussion focuses on the relation of and discrimination among these effects.     

Dielectric properties of glasses at ultra low temperatures

A temperature dependence in the dielectric constant of vitreous silica has been measured down to a few hundred microkelvin at frequencies between 110Hz and 10kHz. Homosil glass shows a logarithmic increase below 10 mK down to the lowest temperature of 0.61 mK. On the other hand, Suprasil glass exibits a saturation behavior following a logarithmic increase above 3 mK. These phenomena are discussed on the basis of the two level system.     

Thermal expansion of copper,silver, and gold at low temperatures

Improvements have been made in a differential dilatometer using the three-terminal capacitance detector. The dilatometer is of copper and has been calibrated from 1.5–34 K in an extended series of observations using silicon and lithium fluoride as low-expansion reference materials. The expansion of silver and gold samples has been measured relative to the dilatometer, while the calibrations themselves have been used to determine the expansion of copper relative to the reference materials. Analyses of six sets of observations indicate that below 12 K the linear expansion coefficient α of copper is represented by $$10^{10} \alpha = (2.1_5 \pm 0.1){\rm T} + (0.284 \mp 0.005){\rm T}^3 + (5 \pm 3) \times 10^{ - 5} T^5 K^{ - 1} $$ corresponding to respective electronic and lattice Grüneisen parameters γ _e =0.9 ₃ and γ ₀ =γ ₁ =1.78. Measurements on oxygen-free silver yield $$10^{10} \alpha = (1.9 \pm 0.2){\rm T} + (1.14 \mp 0.03){\rm T}^3 + (2 \pm 2) \times 10^{ - 4} T^5 K^{ - 1} $$ below 7 K, whence γ _e ? 0.9 ₇ , γ ₀ =γ ₁ =2.23. By contrast, silver containing ca. 0.02 at. % oxygen showed a much larger expansion at the lowest temperatures: below 7 K, 10 ¹⁰ α ～ 7T+1.19T ³ . We have not been able to obtain an unambiguous representation for gold, but find a reasonable fit below 7 K to be $$10^{10} \alpha \simeq (1 \pm 0.5){\rm T} + (2.44 \mp 0.05){\rm T}^3 - (5 \pm 1) \times 10^{ - 3} T^5 K^{ - 1} $$ with γ ₁ ? 2.94 and γ _e ? 0.7 (free-electron value).     

Longitudinal ultrasonic attenuation in normal and superconducting lead at low temperatures

We have measured longitudinal ultrasonic attenuation along the [110] direction in normal and superconducting states in two single crystals of lead, one made from high-purity lead and the other made with high-purity lead doped with 0.1 at % gold. In both specimens an amplitude-dependent effect in the superconducting state has been observed. The data have been taken in the frequency range from 12 to 108 MHz. In high-purity lead the amplitude-independent ratio α_s/α_n shows the frequency dependence observed by Randorff and Marshall, whereas in the doped specimen this ratio shows a very small spread with frequency. In both specimens deformation does not change the α_s/α_n ratio appreciably.     

Dielectric and thermal properties of a machinable glass—ceramic at low temperatures

Measurements of the dielectric properties (2–300 K), specific heat (2–20 K), and thermal conductivity (2–22 K) are reported for a mica-containing glass-ceramic which has a machinability in the range from brass to low-carbon steel. The dielectric constant increases with increasing temperature and is field independent for field strengths up to at least 70 kV cm^?1 at low temperatures. Power-supply-limited attempts to measure the dielectric breakdown strength at low temperatures are consistent with the reported strength at room temperature (1.4 MV cm^?1). The thermal properties are similar to fused SiO₂ with two exceptions: the thermal conductivity does not show the ‘knee’ at ～ 10 K typical of amorphous materials, and the specific heat deviates strongly from a T³ law below 3.5 K