Thermoelectric effects induced dendrite branching dynamics in pure substances: An insight from morphological theory

AbstractThe contact problem for thermoelectric materials with functionally graded properties is considered. The material properties, such as the electric conductivity, the thermal conductivity, the shear modulus, and the thermal expansion coefficient, vary in an exponential function. Using the Fourier transform technique, the electro-thermo-elastic problems are transformed into three sets of singular integral equations which are solved numerically in terms of the unknown normal electric current density, the normal energy flux, and the contact pressure. Meanwhile, the complex homogeneous solutions of the displacement fields caused by the gradient parameters are simplified with the help of Euler’s formula. After addressing the non-linearity excited by thermoelectric effects, the particular solutions of the displacement fields can be assessed. The effects of various combinations of material gradient parameters and thermoelectric loads on the contact behaviors of thermoelectric materials are presented. The results give a deep insight into the contact damage mechanism of functionally graded thermoelectric materials (FGTEMs).

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Heterogeneity of the Dendrite Array Created in the Root of Cored SX Turbine Blades during Initial Stage of Crystallization

Materials ◽

10.3390/ma14010080 ◽

2020 ◽

Vol 14 (1) ◽

pp. 80

Author(s):

Robert Paszkowski ◽

Jacek Krawczyk ◽

Włodzimierz Bogdanowicz ◽

Dariusz Szeliga ◽

Jan Sieniawski

Keyword(s):

Transverse Section ◽

Turbine Blades ◽

Lateral Growth ◽

X Ray Diffraction ◽

Dendrite Branching ◽

X Ray ◽

Initial Stage ◽

Vertical Bridgman ◽

Lateral Dendrite ◽

Root Connection

The roots of cored single-crystalline turbine blades made of a nickel-based CMSX-4 superalloy were studied. The casts were solidified by the vertical Bridgman method in an industrial ALD furnace using the spiral selector and selector continuer situated asymmetrically in the blade root transverse section. Scanning electron microscopy, the Laue diffraction and X-ray diffraction topography were used to visualize the dendrite array and the local crystal misorientation of the roots. It has been stated that heterogeneity of the dendrite array and creation of low-angle boundaries (LABs) are mostly related to the lateral dendrite branching and rapid growth of the secondary and tertiary dendrites near the surface of the continuer–root connection. These processes have an unsteady character. Additionally, the influence of the mould walls on the dendrite array heterogeneity was studied. The processes of the lateral growth of the secondary dendrites and competitive longitudinal growth of the tertiary dendrites are discussed and a method of reducing the heterogeneity of the root dendrite array is proposed.

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Giant Magnetoresistance and Magneto-Thermopower in 3D Interconnected NixFe1−x/Cu Multilayered Nanowire Networks

Nanomaterials ◽

10.3390/nano11051133 ◽

2021 ◽

Vol 11 (5) ◽

pp. 1133

Author(s):

Nicolas Marchal ◽

Tristan da Câmara Santa Clara Gomes ◽

Flavio Abreu Araujo ◽

Luc Piraux

Keyword(s):

Giant Magnetoresistance ◽

Nanowire Array ◽

Three Dimensional ◽

Strong Increase ◽

Thermoelectric Effect ◽

Heat Management ◽

Thermoelectric Effects ◽

Nanowire Network ◽

Potential Applications ◽

Nanowire Networks

The versatility of the template-assisted electrodeposition technique to fabricate complex three-dimensional networks made of interconnected nanowires allows one to easily stack ferromagnetic and non-magnetic metallic layers along the nanowire axis. This leads to the fabrication of unique multilayered nanowire network films showing giant magnetoresistance effect in the current-perpendicular-to-plane configuration that can be reliably measured along the macroscopic in-plane direction of the films. Moreover, the system also enables reliable measurements of the analogous magneto-thermoelectric properties of the multilayered nanowire networks. Here, three-dimensional interconnected NixFe1−x/Cu multilayered nanowire networks (with 0.60≤x≤0.97) are fabricated and characterized, leading to large magnetoresistance and magneto-thermopower ratios up to 17% and −25% in Ni80Fe20/Cu, respectively. A strong contrast is observed between the amplitudes of magnetoresistance and magneto-thermoelectric effects depending on the Ni content of the NiFe alloys. In particular, for the highest Ni concentrations, a strong increase in the magneto-thermoelectric effect is observed, more than a factor of 7 larger than the magnetoresistive effect for Ni97Fe3/Cu multilayers. This sharp increase is mainly due to an increase in the spin-dependent Seebeck coefficient from −7 µV/K for the Ni60Fe40/Cu and Ni70Fe30/Cu nanowire arrays to −21 µV/K for the Ni97Fe3/Cu nanowire array. The enhancement of the magneto-thermoelectric effect for multilayered nanowire networks based on dilute Ni alloys is promising for obtaining a flexible magnetic switch for thermoelectric generation for potential applications in heat management or logic devices using thermal energy.

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Magnetic field amplification in newly-born neutron stars

International Astronomical Union Colloquium ◽

10.1017/s0252921100042056 ◽

1996 ◽

Vol 160 ◽

pp. 435-436

Author(s):

H.-J. Wiebicke ◽

U. Geppert

Keyword(s):

Magnetic Field ◽

Neutron Stars ◽

Gravitational Collapse ◽

Dipole Field ◽

Numerical Calculations ◽

Selection Effects ◽

Thermoelectric Effects ◽

Field Amplification ◽

Seed Field ◽

Flux Conservation

AbstractWe present a scenario of magnetic field (MF) evolution of newly-born neutron stars (NSs). Numerical calculations show that in the hot phase of young NSs the MF can be amplified by thermoelectric effects, starting from a moderately strong seed-field. Therefore, there is no need to assume a 1012G dipole field immediately after the gravitational collapse of the supernova (SN) event. The widely accepted scenario for such a field to be produced by flux conservation during the collapse is critically discussed. Instead, it can be generated by amplification and selection effects in the first 104yrs, and by the subsequent fast ohmic decay of higher multipole components, when the NS cools down.

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Perceptual salience and analogical change: evidence from vowel lengthening in modern Swiss German dialects

Journal of Linguistics ◽

10.1017/s0022226700000542 ◽

1995 ◽

Vol 31 (1) ◽

pp. 1-13 ◽

Cited By ~ 8

Author(s):

Carol Chapman

Keyword(s):

Semantic Relation ◽

Short Vowel ◽

Swiss German ◽

Perceptual Salience ◽

German Dialects ◽

Morphological Theory ◽

Vowel Lengthening

In the light of current morphological theory, this paper examines the analogical levelling of long/short vowel oppositions in certain inflectional and derivational alternations in a number of modern Swiss German dialects. The regular occurrence of levelling is shown to depend on the extent to which the alternation in question is ‘perceptually salient’ (Chapman 1994). That is, if the semantic relation between base and derivative is transparent and the derivative is uniformly marked, analogical levelling occurs regularly. On the basis of this evidence it is argued that all morphological alternations, both inflectional and derivational, are listed in the lexicon and that each one is assigned a different status according to its degree of perceptual salience.

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Correlation of Melting Results for Both Pure Substances and Impure Substances

Journal of Heat Transfer ◽

10.1115/1.3246985 ◽

1986 ◽

Vol 108 (3) ◽

pp. 649-653 ◽

Cited By ~ 15

Author(s):

E. M. Sparrow ◽

G. A. Gurtcheff ◽

T. A. Myrum

Keyword(s):

Solid Phase ◽

Equilibrium Phase ◽

Equilibrium Phase Diagram ◽

Vertical Tube ◽

Step Change ◽

Pure Substance ◽

Characteristic Temperatures ◽

Pure Substances ◽

T Values ◽

Melting Experiments

Melting experiments were performed encompassing both pure and impure substances. The pure substances included n-octadecane paraffin and n-eicosane paraffin, while the impure substances were mixtures synthesized from the pure paraffins. The experiments were carried out in a closed vertical tube whose wall was subjected to a step-change increase in temperature to initiate the melting. For each impure substance, supplementary measurements were made of two characteristic temperatures: the temperature T** at which melting of the solid phase first begins and the lowest temperature T* at which the melting can go to completion. For a pure substance, T** = T*. The time-dependent melting results for all the investigated substances, both pure and impure, were well correlated as a function of FoSte**(Gr**)1/8 alone, where the ** signifies the presence of T** in the temperature difference which appears in Ste and Gr. This correlation enables melting rates for impure substances to be determined from melting rates for pure substances. The T** values needed for the implementation of the correlation can be obtained from simple experiments, obviating the need for the complete equilibrium phase diagram.

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Thermoelectric effects in the superconducting state

Soviet Physics Uspekhi ◽

10.1070/pu1991v034n02abeh002338 ◽

1991 ◽

Vol 34 (2) ◽

pp. 101-107 ◽

Cited By ~ 19

Author(s):

Vitalii L Ginzburg

Keyword(s):

Superconducting State ◽

Thermoelectric Effects

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Boron nitride zigzag nanoribbons: optimal thermoelectric systems

Physical Chemistry Chemical Physics ◽

10.1039/c5cp03570h ◽

2015 ◽

Vol 17 (34) ◽

pp. 22448-22454 ◽

Cited By ~ 8

Author(s):

K. Zberecki ◽

R. Swirkowicz ◽

J. Barnaś

Keyword(s):

Density Functional Theory ◽

Boron Nitride ◽

Density Functional ◽

Thermoelectric Effects ◽

Functional Theory ◽

Thermoelectric Systems ◽

The Density Functional Theory ◽

Boron Nitride Nanoribbons

Conventional and spin related thermoelectric effects in zigzag boron nitride nanoribbons are studied theoretically within the Density Functional Theory (DFT) approach.

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Spatial Profile of Thermoelectric Effects During Peltier Pulsing in Bi and Bi/MnBi Eutectic

MRS Proceedings ◽

10.1557/proc-87-129 ◽

1986 ◽

Vol 87 ◽

Cited By ~ 4

Author(s):

R. P. Silberstein ◽

D. J. Larson

Keyword(s):

Directional Solidification ◽

Joule Heating ◽

Current Density ◽

Peltier Effect ◽

Thomson Effect ◽

Thermoelectric Effects ◽

Spatial Profile ◽

Thermal Transients ◽

Solid Liquid Interface ◽

Solid Liquid

AbstractWe have studied the spatial profile of the thermal transients that occur during and following the current pulsing associated with Peltier Interface Demarcation during directional solidification. Results for pure Bi are presented in detail and compared with corresponding results for the Bi/MnBi eutectic. Significant thermal transients occur throughout the sample that can be accounted for by the Peltier effect, the Thomson effect, and Joule heating. We have separated these effects and studied their behavior as a function of time, current density, and position with respect to the solid/liquid interface.

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