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Vapor Power Cycles and Alternative Power Systems
Published in Irving Granet, Jorge Luis Alvarado, Maurice Bluestein, Thermodynamics and Heat Power, 2020
Irving Granet, Jorge Luis Alvarado, Maurice Bluestein
The most suitable materials are the semiconductors, such as lead telluride, germanium–silicon alloys, and germanium telluride. The thermoelectric converter is basically a form of heat engine receiving heat from a source, rejecting heat to a sink, and converting heat to electrical work. Thus, it has as its theoretical upper limit the Carnot cycle efficiency. Because of losses, the Carnot cycle limit is not even approached, and although in theory the thermoelectric converter is capable of operating at efficiencies greater than 15%, most of the devices built to date have shown efficiencies much lower than this figure. With development of new materials and using semiconductors, a thermal efficiency approaching 25% is a reasonable objective. Because of their reliability and lack of moving parts, they have been used in such diverse applications as converting waste heat from kerosene lamps to power radio receivers in rural areas and in conjunction with radioisotope heat sources to power long-life, unattended ocean buoys.
Space Applications
Published in D.M. Rowe, CRC Handbook of Thermoelectrics, 2018
Each Viking SNAP-19 thermoelectric converter, like those on Nimbus III and Pioneers 10 and 11, had six thermoelectric modules, each consisting of 15 thermoelectric couples (for a total of 90 couples per generator), Johns-Manville Type 1301 Min-K thermal insulation, interconnecting electrical straps, and associated cold end hardware. The cold-end hardware, which consisted of springs, pistons, alignment buttons, and heat sink bar, was located between the modules and the cylindrical generator housing where it could provide a compressive load on each thermoelectric element to maintain adequate electrical and thermal paths in the converter. The thermoelectric couples were fabricated from Teledyne Energy Systems TAGS-85 material (with a thin SnTe segment at the hot side) for the p-leg and from 3M Company 3M-TEGS 2N(M) material for the n-leg. (The acronym TAGS is derived from the names of its major constituents: tellurium, antimony, germanium, and silver. TAGS is a solid solution of silver antimony telluride in germanium telluride. TAGS is an undoped inherent "p" material. TAGS thermoelectric elements were designed to provide higher
Superconductivity in Low-Carrier-Density Systems: Degenerate Semiconductors
Published in R. D. Parks, Superconductivity, 2018
The degenerate semiconductors which exhibit superconducting properties are germanium telluride (7), strontium titanate (8), and tin telluride (9). All these materials are superconducting in 0.1 °K range, all are type II superconductors, and the transition temperatures of these materials are sensitive to changes in carrier concentration. Strain data are not available as yet for these materials.
Unraveling Mg 〈c + a〉 slip using neural network potential
Published in Philosophical Magazine, 2022
Mashroor S. Nitol, Sungkwang Mun, Doyl E. Dickel, Christopher D. Barrett
We developed a new rapid atomistic neural network (RANN) potential for Mg. Machine learning based interatomic potentials show outstanding performance in DFT accuracy for pure Mg [33], Al-Mg-Si alloys [34], TiO [35], carbon [36], sodium [37], zinc oxide [38], germanium telluride [39], copper [40], gold [41] and Ti [42]. Physically motivated features based on the MEAM formalism have been introduced [42] and successfully show DFT quality result for Mg as well as Ti, Zr [43, 44] and Zn [45]. Here, we used the same methodology to create our structural fingerprints and used a feed-forward artificial neural network (RANN), as in [43]. The RANN potential formulation has been incorporated into Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) [46] software by Dickel et al. [33] which shows it can run near the speed of MEAM for lightweight RANN potentials. (This particular potential is approximately one quarter as fast as MEAM.) More recently, by the authors, the calibration software has been parallelised using OpenMP, an Application Program Interface (API) enabling shared-memory multiprocessing programming, in C++ to speed up the calibration process. The code is available on the https://github.com/ranndip/ RANN Github repository page.
Recent advances in two-dimensional ferromagnetism: strain-, doping-, structural- and electric field-engineering toward spintronic applications
Published in Science and Technology of Advanced Materials, 2022
Sheng Yu, Junyu Tang, Yu Wang, Feixiang Xu, Xiaoguang Li, Xinzhong Wang
Xu and Zhang et al. independently reported the ferromagnetic behavior in atomically thin layers of chromium germanium telluride (Cr2Ge2Te6) [1] and chromium triiodide (CrI3) [2] in 2017, using a polar magneto-optical Kerr effect microscopy technique. Subsequently, a wide variety of emerging two-dimensional (2D) materials with intrinsic magnetic ground states of ferromagnetism (FM) or anti-ferromagnetism (AFM) down to atomic-layer thicknesses have been discovered and predicted [3,4], as summarized in Table 1, for listing the values of their transition temperatures and coercive fields. Two-dimensional ferromagnetism was discovered in 2D materials with stable long-range magnetic ordering, exhibiting the ferromagnetic behavior at magnetic ground state. In comparison to the conventional bulk magnetic materials, the magnetic anisotropy plays a vital role for the stable magnetic order in 2D magnets. This can break the limitation of the Mermin–Wagner theorem that long-range magnetic order could not be induced in low dimensional isotropic systems with continuous symmetry at finite temperatures [5]. The magnetic exchange mechanisms in conventional 3D bulk magnets, including direct exchange interaction, superexchange interaction, Stoner-magnetism, and Ruderman–Kittel–Kasuya–Yosida (RKKY) mechanisms, can be found in various 2D magnets [6,7]. Also, some interesting exchange mechanisms, knows as super-spuerexchange, extended superexchange, and multi-intermediate double exchange, are newly discovered in 2D magnetic systems [7]. Meanwhile, distinct from their bulk materials, 2D magnets have an interesting thickness-dependent magnetism. For example, VSe2 and CrI3 monolayers demonstrated a ferromagnetic behavior, while their bilayer counterparts show interlayer-antiferromagnetism at low temperature [8,9]. The special attributes of 2D magnetism as compared to their bulk counterparts are briefly summarized below: (1) they show strong quantum confinement [10]; (2) they can be artificially integrated into heterostructure with arbitrary and flexible choices [11,12]; (3) their properties are thickness-dependent and highly anisotropic [13,14]; (4) they are the naturally perfect structure for magnetic and electronic tunneling effect [15,16], (5) they have large deformation and great endurance under external strain [17,18] and (6) they exhibit full tunability by external electric field, indicating a great potential for practical applications in voltage-controlled spintronic devices [19,20].