The theory of the thermal conductivity of metals and alloys is reviewed. There are two components: electronic and lattice. The electronic component is related to the electrical conductivity by the Lorenz ratio. Deviations from the Sommerfeld value of the Lorentz ratio are discussed. At high temperature deviations are due to incomplete degeneracy of the electron gas (Fermi smearing), at low temperatures deviations are due to the inelastic nature of the electron-phonon interactions and to the electron-electron interactions. The lattice conductivity is discussed as a function of temperature, point defects, and electron density. The predictions of the theory are compared with measured thermal conductivities. For the elements, the effects of the lattice component can be distinguished from deviations of the electronic component from the Lorenz ratio. Three representative alloy systems are discussed. In aluminium alloys the lattice component is small, and the electronic component well behaved. In titaniu...

Thermal conductivity of metals and alloys

A simple scheme is presented for remotely maneuvering individual microscopic swimmers by means of on-demand photo-induced actuation, where a laser gently and intermittently pushed the swimmer along its body axis (photon nudging) through a combination of radiation-pressure force and photophoretic pull. The proposed strategy utilized rotational random walks to reorient the micro-swimmer and turned on its propulsion only when the swimmer was aligned with the target location (adaptive control). A Langevin-type equation of motion was formulated, integrating these two ideas to describe the dynamics of the stochastically controlled swimmer. The strategy was examined using computer simulations and illustrated in a proof-of-principle experiment steering a gold-coated Janus micro-sphere moving in three dimensions. The physical parameters relevant to the two actuating forces under the experimental conditions were investigated theoretically and experimentally, revealing that a ∼7 K temperature differential on the micro-swimmer surface could generate a propelling photophoretic strength of ∼0.1 pN. The controllability and positioning error were discussed using both experimental data and Langevin dynamics simulations, where the latter was further used to identify two key unitless control parameters for manipulation accuracy and efficiency; they were the number of random-walk turns the swimmer experienced on the experimental timescale (the revolution number) and the photon-nudge distance within the rotational diffusion time (the propulsion number). A comparison of simulation and experiment indicated that a near-optimal micron-precision motion control was achieved.

Harnessing thermal fluctuations for purposeful activities: the manipulation of single micro-swimmers by adaptive photon nudging

We present a numerical model for calculating the temperature distribution inside resistance-heated high-pressure solid-medium axi-symmetric cell assemblies that incorporates both composition- and temperature-dependent thermal conductivity. The code was validated using both analytic solutions of simplified thermal diffusion problems and comparisons to actual laboratory experiments and was found to be reliable in matching the temperature characteristics of multi-anvil experiments. Calculations for various cell assembly designs resulted in temperature fields that are consistent with experimental measurements of thermal gradients. These calculations also illustrated the influence of temperature-dependence of thermal conductivity, an important and often-overlooked property, on the thermal profiles. This model may be used to fine-tune the design of cell assemblies, either to minimize thermal gradients or to produce a desired temperature distribution. The four "typical" multi-anvil cells that we used to demonstrate this technique have temperature profiles across the sample that range from 25 to 75 °C when the thermocouple temperature is 1200 °C. The thermocouple in all four is in a region where the temperature gradient is on the order of 100 °C per millimeter, which could lead to experimental temperature uncertainties that are correlated with the thermocouple location.

/pdf/a-numerical-model-for-steady-state-temperature-distributions-1cby2qu171.pdf

A numerical model for steady-state temperature distributions in solid-medium high-pressure cell assemblies

The absolute Seebeck coefficient of platinum was determined from 80 to 340 K by direct comparsion to lead. Results of this comparison disagree with previous results which have been used for the calculation of absolute values for other materials. The thermal conductivity λ and electrical resistivity ρ of the lead standard were also determined. The electrical resistivity could be described with a modified Gruneisen‐Bloch equation which allows for the effect of thermal expansion on the Debye temperature ΘD. The ratio λρ/T was within 1% of the Sommerfeld value of 2.443×10−8 (V/K)2 from 1.0 to 5.0 ΘD.

Absolute Seebeck coefficient of platinum from 80 to 340 K and the thermal and electrical conductivities of lead from 80 to 400 K

We present the first coplanar waveguide transmission line resonator patterned from a perovskite high Tc superconducting film at 9 GHz. At 77 K the unloaded quality factor Q0 of the resonator patterned from a YBa2Cu3O7−x film on a MgO substrate is 1300, that is, 14 times higher than that of the copper resonator and 17 times higher than that of the gold resonator at the same temperature. At 4.2 K a Q0 factor of 3300 was measured for the YBa2Cu3O7−x /MgO resonator. Simple calculations of the quality factor show that values of 10 000 at 77 K should be possible using better substrates, films, and etching techniques. This resonator could form the basic structure of more complex microwave filter systems operating at liquid‐nitrogen temperatures.

High Q coplanar transmission line resonator of YBa2Cu3O7−x on MgO

We present data on the electrical and thermal resistivities and the thermopower of three pure Na specimens from 40 to 360 K. The measurements were made using a guarded longitudinal heat flow apparatus that had previously been calibrated with Au and Al. The specimens were placed in a vacuum environment using no solid inert liner.The electrical resistivity data indicate ΘR = 194 K. The thermal conductivity data show a 4% minimum near 70 K and an ice point value of 1.420 W/cm K. The reduced Lorenz function L/L0 agrees with published data at low temperatures but above 300 K levels off at approximately 0.91. On the basis of published data for liquid Na, L/L0 does not change by more than 3% at the melting point.The minimum in the thermal conductivity and a part of the high temperature deviations of L from L0 are tentatively ascribed to inelastic electron–phonon collisions having a characteristic temperature near that of longitudinal phonons. The possibility that electron–electron collisions further depress L at...

Thermal and Electrical Conductivities of Sodium from 40 to 360 K

The electrical resistivity and thermal conductivity of a sample of pure gold has been measured from 80 to 340 K, using apparatus designed for the simultaneous measurement of these properties. The r...

The thermal conductivity and electrical resistivity of gold from 80 to 340 K

The thermal conductivity of high-purity platinum was measured between 300 and 1 000 °K. The results obtained agree very well with the previously reported work of Bode and of Martin and Sidles, but ...

The thermal conductivity of platinum between 300 and 1 000 °k

Data are presented for the thermal and electrical resistivity and thermoelectric power of two samples of Ca (having residual resistance ratios of 10 and 70) between 30 and 300 K. Large deviations from both Matthiessen's rule and the Wiedemann–Franz relationship are observed. The former are tentatively attributed to the presence of two distinct groups of carriers in Ca, and analyzed using the two band model. The latter deviations are interpreted as the effects of band structure. The thermoelectric power of Ca is large. In many respects the transport properties of Ca appear to be similar to those of the transition metals.

The electrical resistivity, thermal-conductivity, and thermoelectric power of calcium from 30 K to 300 K

Equipment to perform low-level thermocouple thermometry using a computer, a digital voltmeter, and very low thermal offset switching has been used to measure the thermal conductivity, electrical resistivity, and thermoelectric power of Rb from its melting point, near 313 K, to 650 K. The data obtained, which are accurate to the percent level, may be explained by combining the effect of the elastic scattering of electrons by ionic density fluctuations, and the effect of electron–electron scattering.

Measurement of the transport properties of liquid Rb using automated equipment

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