AbstractAcrylate rubber molecules contain sterically hindered and highly polar ester groups, which can generate a large amount of internal friction energy under external alternating stress and ...exhibit high internal friction for energy dissipation. Based on previous studies on the formulation of acrylate viscoelastic materials, the optimal formulation was prepared and made into acrylate viscoelastic dampers and the mechanical properties of the corresponding damper specimens were tested. The acrylate viscoelastic dampers at different ambient temperatures, excitation frequencies, and displacement amplitudes were systematically investigated. The experimental results indicate an excellent damping capacity of the acrylate viscoelastic dampers, where the dynamic properties are affected by the ambient temperature and excitation frequency, and the single-loop energy dissipation capacity is significantly affected by the displacement amplitude. To accurately represent the effects of the temperature, frequency, and amplitude on the dynamic properties of the damper, a modified fractional-derivative equivalent model is introduced, where the internal variable theory and temperature-frequency equivalent principle are introduced to reflect the amplitude effect and temperature effect, respectively. Finally, the results calculated by the proposed model were compared with the experimental data, which verified the correctness of the mathematical model.
Given that more than two thirds of all energy is lost, mostly as waste heat, in utilization processes worldwide, thermoelectric materials, which can directly convert waste heat to electricity, ...provide an alternative option for optimizing energy utilization processes. After the prediction that superlattices may show high thermoelectric performance, various methods based on quantum effects and superlattice theory have been adopted to analyze bulk materials, leading to the rapid development of thermoelectric materials. Bulk materials with two‐dimensional (2D) structures show outstanding properties, and their high performance originates from both their low thermal conductivity and high Seebeck coefficient due to their strong anisotropic features. Here, the advantages of superlattices for enhancing the thermoelectric performance, the transport mechanism in bulk materials with 2D structures, and optimization methods are discussed. The phenomenological transport mechanism in these materials indicates that thermal conductivities are reduced in 2D materials with intrinsically short mean free paths. Recent progress in the transport mechanisms of Bi2Te3‐, SnSe‐, and BiCuSeO‐based systems is summarized. Finally, possible research directions to enhance the thermoelectric performance of bulk materials with 2D structures are briefly considered.
Thermoelectric bulk materials with 2D structures possess natural structures similar to artificial superlattices, hence enabling the utilization of enhancement methods for superlattices. General optimization methods for Bi2Te3 are reviewed; meanwhile, the progress of advanced research into SnSe and BiCuSeO as promising thermoelectric materials is summarized.
Moving fast makes for better cooling Qin, Bingchao; Zhao, Li-Dong
Science (American Association for the Advancement of Science),
11/2022, Letnik:
378, Številka:
6622
Journal Article
Recenzirano
Optimizing carrier mobility with composition and processing is key for thermoelectric coolers
Thermoelectric technology enables direct and reversible conversion between thermal and electrical ...energies, which includes waste heat recovery and solid-state cooling (
1
). Compared with power generation, because of the Peltier effect, thermoelectric cooling has application advantages in precise temperature control, fast response, and size controllability. Because it is mainly used around ambient temperature with a small temperature difference, the issue of device failure under large temperature differences is no longer a problem (
2
). In addition to use in civil and industrial areas, thermoelectric cooling has an important role for precise temperature control in key areas such as 5G communications and electronic devices. The development of highly integrated and miniaturized communication technologies and circuit systems and the urgent demand for lower power dissipations have put forward higher requirements for the development of thermoelectric cooling.
There has been a renaissance of interest in exploring highly efficient thermoelectric materials as a possible route to address the worldwide energy generation, utilization, and management. This ...review describes the recent advances in designing high-performance bulk thermoelectric materials. We begin with the fundamental stratagem of achieving the greatest thermoelectric figure of merit ZT of a given material by carrier concentration engineering, including Fermi level regulation and optimum carrier density stabilization. We proceed to discuss ways of maximizing ZT at a constant doping level, such as increase of band degeneracy (crystal structure symmetry, band convergence), enhancement of band effective mass (resonant levels, band flattening), improvement of carrier mobility (modulation doping, texturing), and decrease of lattice thermal conductivity (synergistic alloying, second-phase nanostructuring, mesostructuring, and all-length-scale hierarchical architectures). We then highlight the decoupling of the electron and phonon transport through coherent interface, matrix/precipitate electronic bands alignment, and compositionally alloyed nanostructures. Finally, recent discoveries of new compounds with intrinsically low thermal conductivity are summarized, where SnSe, BiCuSeO, MgAgSb, complex copper and bismuth chalcogenides, pnicogen-group chalcogenides with lone-pair electrons, and tetrahedrites are given particular emphasis. Future possible strategies for further enhancing ZT are considered at the end of this review.
Abstract
PbTe is a typical intermediate-temperature thermoelectric material, which has undergone extensive developments and achieved excellent high thermoelectric performance. In this perspective we ...summarized several strategies that were successfully applied in PbTe-based thermoelectric materials through manipulating charge and phonon transports, such as optimizing carrier density to tune Fermi level, tailoring band structure to enhance effective mass, and designing all-scale hierarchical architectures to suppress phonon propagation. Meanwhile, due to the different features of conduction and valence bands, we separately introduced the approaches to enhance performance of p-type and n-type PbTe. In p-type PbTe, the strategies of band convergence, band alignment and density of state (DOS) distortion are more effective to achieve high electrical transport properties. By contrast, flattening conduction bands and introducing deep impurity level are more suitable for n-type PbTe. Lastly, several potential strategies were proposed to further improve the thermoelectric performance of PbTe-based materials, which might be extended to other thermoelectric systems.
Thermoelectric materials offer an alternative opportunity to tackle the energy crisis and environmental problems by enabling the direct solid-state energy conversion. As a promising candidate with ...full potentials for the next generation thermoelectrics, tin selenide (SnSe) and its associated thermoelectric materials have been attracted extensive attentions due to their ultralow thermal conductivity and high electrical transport performance (power factor). To provide a thorough overview of recent advances in SnSe-based thermoelectric materials that have been revealed as promising thermoelectric materials since 2014, here, we first focus on the inherent relationship between the structural characteristics and the supreme thermoelectric performance of SnSe, including the thermodynamics, crystal structures, and electronic structures. The effects of phonon scattering, pressure or strain, and oxidation behavior on the thermoelectric performance of SnSe are discussed in detail. Besides, we summarize the current theoretical calculations to predict and understand the thermoelectric performance of SnSe, and provide a comprehensive summary on the current synthesis, characterization, and thermoelectric performance of both SnSe crystals and polycrystals, and their associated materials. In the end, we point out the controversies, challenges and strategies toward future enhancements of the SnSe thermoelectric materials.
Thermoelectric technology, harvesting electric power directly from heat, is a promising environmentally friendly means of energy savings and power generation. The thermoelectric efficiency is ...determined by the device dimensionless figure of merit ZTdev, and optimizing this efficiency requires maximizing ZT values over a broad temperature range. Here, we report a record high ZTdev ~1.34, with ZT ranging from 0.7 to 2.0 at 300 to 773 kelvin, realized in hole-doped tin selenide (SnSe) crystals. The exceptional performance arises from the ultrahigh power factor, which comes from a high electrical conductivity and a strongly enhanced Seebeck coefficient enabled by the contribution of multiple electronic valence bands present in SnSe. SnSe is a robust thermoelectric candidate for energy conversion applications in the low and moderate temperature range.
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•Process structure of SHI irradiation damage in FLG are studied.•Effect of stacking on structural damage is analysed with a fixed θ of incident ion.•Damage of the two surface layers ...is not significantly affected.•Dynamic process of damage generation is constructed with atomic images.
The molecular dynamics simulation has been utilized to investigate the structural damage via heavy ion irradiation in graphene. The effects of stacking and incident angle of ion on the structural damage are mainly explored. The growth of stacking layers makes structural damage of overall and surface layer more and more serious. The damage of each layer shows obvious differences, the damage becomes weaker toward the centre. The effect of incident angle on damage is discussed in 3-layer graphene. The two surface layers are not affected while the damage of intermediate layer is weak with the decrease of incident angle. The driving force for structural damage is the stress wave propagating from the energy deposition region to the surrounding.
The Dachang Sn-polymetallic ore district in South China is the second largest tin district in the world with a tin reserve of over one million tonnes. Zn-Cu skarn and stratiform, massive, and vein ...Sn-Pb-Zn ores are all present in this district. This has led to a debate as to whether the Sn orebodies were formed by Cretaceous magmatic-hydrothermal replacement or Devonian submarine exhalative-hydrothermal sedimentation. Here, we present a systematic investigation of the major, trace element, and boron isotopic compositions of different types of tourmaline in the Dachang ore district. Tourmaline disseminated in the Longxianggai granite and pegmatite veins belongs to the schorl series and has high contents of Li, Zn, and Ga. The δ
11
B value of primary magma of the Longxianggai granite is estimated to be about −13‰, close to the global average δ
11
B value (−11‰) for S-type granites. Tourmaline from quartz-tourmaline veins in the Longxianggai granite has similar chemical composition to the magmatic tourmaline and likely formed from hydrothermal fluids exsolved from the evolved granitic melt. The δ
11
B value of the initial hydrothermal fluids is also calculated to be about −13‰. Tourmalines from the skarn and sulfide ores in the Lamo deposit have higher Mg/(Mg+Fe) and lower Na/(Na+Ca) ratios and higher contents of Be, Ge, Sr, and Sn than magmatic tourmaline. These patterns likely reflect input of elements derived from the host Devonian limestone. The δ
11
B values of the hydrothermal fluids are estimated to be between −13 and −10‰, suggesting evolved magmatic-hydrothermal fluids related to the Longxianggai granite. Tourmalines from the stratiform and vein ores in the Changpo-Tongkeng deposit are extremely Mg-rich and mostly belong to the dravite series. They have high contents of Sc, V, Cr, Sr, and Sn and show positive Eu anomalies. The δ
11
B values of these B- and Sn-rich fluids are estimated to be between −15 and −10‰, suggesting that the fluids also have a magmatic-hydrothermal origin. These fluids are most likely derived from the same granitic magma source, but may have interacted with the Devonian volcanic rocks.
Thermoelectric technology enables direct conversion between heat and electricity. The conversion efficiency of a thermoelectric device is determined by the average dimensionless figure of merit ...ZTave. Here, a record high ZTave of ≈1.34 in the range of 300–723 K in n‐type SnSe based crystals is reported. The remarkable thermoelectric performance derives from the high power factor and the reduced thermal conductivity in the whole temperature range. The high power factor is realized by promoting the continuous phase transition in SnSe crystals through alloying PbSe, which results in a higher symmetry of the crystal structure and the correspondingly modified electronic band structure. Moreover, PbSe alloying induces mass and strain fluctuations, which enables the suppression of thermal transport. These findings provide a new strategy to enhance the thermoelectric performance for the continuous phase transition materials.
SnSe–xPbSe crystals with a record high ZTave of ≈1.34 in the range of 300–723 K are presented. The outstanding thermoelectric performance derives from the countinous phase transition, which results in the significant crystal symmetry enhancement and the corresponding band structures modification. Our findings provide a new strategy to enhance the thermoelectric performance for the continuous phase transition materials.
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