Surface contribution to the specific heat of he II films

The surface contribution to the specific heat of saturated and unsaturated He II films has been considered. The temperature dependence of the surface-contributed specific heat is found to depend on the range of temperatures as well as the film thickness under consideration. A comparison with earlier results is made, and it is found that those results are not consistent with the specific heat contributed by the capillary wave modes of the free surface.     

Superconductors with crystalline-field split impurities: Upper critical field and specific heat

We continue the investigation of crystalline-field effects on the properties of superconductors containing rare-earth impurities. Attention is focused on impurities with a nonmagnetic ground state. We calculate the upper critical fieldH _{c 2} and the jump of the specific heat at the phase transition.     

The specific heat and critical magnetic field of superconducting PdH(D)

From the solution of the Eliashberg equations on the imaginary axis, the thermodynamic properties, specific heat, and critical magnetic field of PdH(D) have been calculated. The Eliashberg kernels ²()F() were constructed using a published value of ²(), and F() was obtained from inelastic neutron scattering data. The results for the specific heat are in good agreement with published experimental data. The critical magnetic field shows a nearly parabolic behavior as a function of temperature, in disagreement with the linear experimental behavior. The deviation function D(t) and the ratios C(T _c)/T _c and [T _c/H _c(0)]² indicate that the PdH(D) system is BCS-like. The functional derivative of T _c with respect to changes in the kernel is also calculated.On sabbatical leave from the Instituto de Investigaciones en Materiales, UNAM, Mexico.     

Isochoric specific heat in the methane-ethane system around the liquid-gas critical line

Experimental and theoretical studies have been made on the behavior of the isochoric specific heat for binary methane-ethane mixtures in the critical region.     

Free energy functional and Bogolubov equations

By using a functional integral formulation of the theory of superconductivity, we derive a generalization of the Ginsburg-Landau free energy functional valid at all temperatures. It reduces to it near the critical temperature. By minimization of this new functional we get the usual Bogolubov self-consistent equations for superconductors.     

Nuclear specific heat of thallium

We have measured the nuclear specific heat of a 0.79 mole thallium sample of 5 N+ purity in the temperature range 70 µKT20 mK and in magnetic fields from 20 mTB228 mT. The experimental results agree with the theoretical expectation for the specific heat of a nuclear paramagnet with the properties of Tl. Our results for the nuclear specific heat imply that the static properties of bulk Tl seem to differ from the dynamic, surface-sensitive properties of Tl samples investigated in former nuclear magnetic resonance experiments.     

The specific heat of solid oxygen

Measurements have been made in the temperature range from 1.3° K to about 71°K with particular attention to the behavior at very low temperatures, and in the neighborhood of the - transition at about 23.89° K. Assuming that near 0° K each molecule moves as a single mass point with the passage of lattice waves, the effective Debye temperature at 0° K is extrapolated to be 104±2° K. As the temperature rises above 10° K, the specific heat rises more rapidly than a reasonable Debye model would predict, suggesting the appearance of additional degrees of freedom, which are thought to be the superposition of a librational motion of the molecules superposed on the longitudinal and transverse lattice waves controlling the motion of a molecule's center of mass. The specific heat shows a very sharp high spike at the - transition with an entropy change of aboutR ln 1.65; there is no evidence for a latent heat associated with this transition.     

Very-low temperature specific heat of Torlon

The specific heat of Torlon has been measured in the 0.15-4.2 K temperature range. Data below 1 K can be represented by c(T) = P₁T^1+δ + P₂T³, with P₁ = (5.41 ± 0.08)·10⁻⁶J K^−(2+δ) g⁻¹, P₂ = (2.82 ± 0.03) ·10⁻⁵JK⁻⁴g⁻¹ and δ = 0.28 ± 0.01, as predicted by the tunnelling theory. Above 1 K, the behaviour of c(T) is similar to that of other amorphous materials and can be expressed as: c(T) = P · T^Ω with P = (2.68 ± 0.07)·10⁻⁵JK^Ω+1g⁻¹ and Ω = 3.32 ± 0.02.     

Constant-volume specific heat of solid xenon

Specific heats of solid xenon were measured between 110 and 223 K in a closed pressure vessel. In this temperature interval the pressure increased from the vapor pressure of the solid at 110 K to about 1.7 kbar at the melting point. After a small correction for the nonrigidity of the container, we find that c_v increases from 2.9R at 110 K to the classical Dulong-Petit value of 3R at 200 K. The behavior of the specific heat in the vicinity of the melting point depended on the treatment of the samples.Research supported by the National Science Foundation. This paper is based on a thesis submitted to the Graduate Faculty of Rutgers University in partial fulfillment of the requirements for the PhD degree.     

Low-temperature specific heat of high-purity calcium

Low-temperature specific heat of high-purity calcium has been measured with an adiabatic calorimeter with a mechanical heat switch to avoid helium exchange gas errors, over the temperature range 1.1–4.2 K. The values obtained for the electronic coefficient of specific heat and the Debye temperature _D are =1.99±0.05 mJ/moleK ² and _D=250±4K.     

Low-temperature specific heat of Ti-Hf alloys

The effect of alloying on the specific heat of Ti-Hf alloys has been investigated in the temperature range 1.2–4.5 K. A maximum is observed in the electronic specific heat coefficient γ around 35 at % Ti and the Debye temperature θ _D decreases from titanium to hafnium. No superconductivity is found down to the lowest temperature studied.     

Low-temperature specific heat of layered compounds

Specific heat measurements in the temperature range from 1 to 10 K and in magnetic fields up to 1.2 T have been made on a number of layered transition metal dichalcogenide crystal complexes. The thermodynamic critical fieldH _c and the Ginzburg-Landau coherence length and penetration depth have been calculated. For TaS₂ (pyridine)_1/2 and TaS_1.6Se_0.4 (pyridine)_1/2, the coherence length perpendicular to the layers is slightly less than the interlayer separation.Research at Stanford supported by Air Force Office of Scientific Research, Air Force Systems Command, USAF, under grant AFOSR 73-2435B.     

Constant-volume specific heat of solid argon

Specific heats of solid argon were measured between 25 K and 120 K in a closed pressure vessel. Between 60 K and the melting point of 120 K the solid filled the vessel, and at the m.p. the pressure was 1.6 kbar. After correction for the nonrigidity of the container, we find thatC _v increases by 7.3% between 60 K and 120 K, reaching 2.8 R. Comparison with recent calculations based on self-consistent phonon theory reveals substantial discrepancies from the data, indicating the necessity of including higher-order terms in the theory.Research supported by the National Science Foundation and the Rutgers University Research Council.     

Specific heat of quench-condensed hydrogen films

The specific heatC(X, T) of quench-condensed films of H₂ has been measured as a function of ortho concentration X with 0.28–2 at temperatures between 0.4 and 3.0 K. The films were condensed on evaporated gold substrates held at several temperaturesT. _cond between 1.0 and 3.5 K. The observed specific heat is attributed to orientational ordering of the ortho-H₂ molecules. For the films withX = 0.74 condensed atT _cond>2.5 K, there is a peak which indicates a bulk-like ordering transition. At temperatures below the peak, there is a large contribution toC, which is not present in bulk H₂, and which we attribute to short-range ordering size effects. AsT _cond is decreased below 2.5 K, the shape of the specific heat curve changes, and the peak at 1.5 K is replaced by a gradual rise with a sharp drop above 2.6 K. Despite this strong dependence ofC onT _cond, the entropy per molecule at 3 K is only weakly dependent onT _cond and comparable to that for bulk H₂. Film annealing at 3.4 K produces a change in the specific heat curve, and a study of this effect is presented. The ortho-para conversion rate of the films condensed at the various temperatures is found to be same as in bulk, well-annealed H₂. As in bulk H₂, the transition temperature inferred from the location of the specific heat peak or anomaly decreases withX. Unlike in bulk H₂, there is no temperature hysteresis inC for any of the quench-condensed films. This implies that the ordering transitions are not accompanied by a martensitic transformation.     

New instrument for commercial metering of heat carriers and heat energy

This article discusses distinguishing features of the functioning and specifications of new meter SPT960 in relation to previous meters made by the company LOGIKA. It examines one of the techniques used to improve instrument accuracy and make monitoring of the consumption of heat energy and heat carriers more reliable. In this case, the heat carrier is water in the form of superheated and saturated steam — including wet steam (two-phase medium).Translated from Izmeritel'naya Tekhnika, No. 10, pp. 41–43, October, 1995.     

Free-energy landscape and the critical velocity of superfluid films

We briefly review some important properties of superfluid flow, especially the problem of critical velocity. We then present new numerical simulation results for a mesoscopic model of superfluids shedding light on the free-energy landscape, the critical velocity and the formation of vortices, which destroy the superflow when the velocity is high.     

Determination of effective specific heat of nanofluids

The effective specific heat of several types of nanofluids are measured by transient double hot-wire technique. Sample nanofluids are prepared by suspending 1–5 volume percentages of titanium dioxide (TiO₂), aluminium oxide (A1₂O₃) and aluminium (Al) nanoparticles in various base fluids, such as deionised water, ethylene glycol and engine oil. The effective specific heats of these nanofluids were found to decrease substantially with increased volume fraction of nanoparticles. Besides particle volume fraction, particle materials and base fluids also have influence on the effective specific heat of nanofluids. Except Al/engine oil-based nanofluid, predictions of the effective specific heat of nanofluids by the volume fraction mixture rule-based model showed reasonably good agreement with the experimental results. Based on the calibration results obtained for the base fluids, the measurement error is estimated to be within 2.77%.     

Low temperature specific heat of cry-con grease

The specific heat of Cry-Con grease, a copper loaded electrically insulating grease, was measured between 0.5 and 20 K. The low specific heat and high thermal conductivity of Cry-Con grease render it a useful thermal bonding material for calorimetric measurements on samples with low thermal conductivity.     

Low temperature specific heat of propylene glycol

The specific heat of propylene glycol has been measured at temperatures from 0.1 K to 6 K. The magnitude and the temperature dependence of the specific heat are similar to that found in other fragile glasses.