Bi
Te
thermoelectric materials are utilized for refrigeration for decades, while their application of energy harvesting requires stable thermoelectric and mechanical performances at elevated ...temperatures. This work reveals that a steady
of ≈0.85 at 200 to 300 °C can be achieved by doping small amounts of copper iodide (CuI) in Bi
Te
Se
-silicon carbide (SiC) composites, where SiC nanodispersion enhances the flexural strength. It is found that CuI plays two important roles with atomic Cu/I dopants and CuI precipitates. The Cu/I dopants show a self-tuning behavior due to increasing solubility with increasing temperatures. The increased doping concentration increases electrical conductivity at high temperatures and effectively suppresses the intrinsic excitation. In addition, a large reduction of lattice thermal conductivity is achieved due to the "in situ" CuI nanoprecipitates acting as phonon-scattering centers. Over 60% reduction of bipolar thermal conductivity is achieved, raising the maximum useful temperature of Bi
Te
for substantially higher efficiency. For module applications, the reported materials are suitable for segmentation with a conventional ingot. This leads to high device
values of ≈0.9-1.0 and high efficiency up to 9.2% from 300 to 573 K, which can be of great significance for power generation from waste heat.
碩士
臺北市立大學
中國語文學系碩士在職專班
106
The Study of Su-Shi’s Dietary Writing
Abstract
Su-shi was well-known as a multitalented schloar in Chinese history. Excpet for a large number of poetry and articles, he had ...outstanding achievements in politics, calligraphy, and the art of painting. It could be said Su-shi was a all-around atrist. From a quantity of literature dedication, it could be found that dietary writing took up most of proportion. Therefore, daily diet not only played a significant part in Su-shi’s entire life, but recorded the way he lived and the experience he created. The study was arranged by Su-shi’s route, divided into four areas, in his political life. In order to research the way how he implement hand-made cuisine and the art of vegetarianism. Regardless of living in the capital or out-of-the-way, in his dietary philosophy, Su-shi constantly insisted in executing personal diet plans by doing on his own.Additionally, he loved to write down what he experienced to shared with people. Through dietary writi
Spall fracture induced by interaction of multiple shockwaves in shock-loaded material is a key issue for both basic science and practical application. Here, shock induced spall and subsequent ...recompression process of polycrystalline copper are investigated using molecular dynamics simulations. Two significant velocity peaks are observed from the velocity history of free surface, which is explained through the complex propagation of waves and dynamic damage processes. The overshoot feature is also noted in the free-surface velocities on account of the shock response of the damaged region. Recrystallization occurs after secondary shock passes through the spall region. Meanwhile, the differences in recrystallization processes are observed for the different shock response states of the spall region induced by secondary shock waves. What's more, the reduction of grain sizes in the spall region is also revealed in our simulation, which is consistent with experiments.
•The two typical velocity peaks of free surface velocities and the internal dynamic processes were revealed in simulations.•The overshoot feature observed from the free surface velocities was resulted by the shock response of shock damaged region.•Different secondary shock response resulted in different recrystallization processes in spall damaged region.
Fine-grained and nanostructured composites have long been known for their superiority in enhancing thermoelectric performance; however, exploring these structures based on Cu12Sb4S13 tetrahedrites is ...difficult due to the methods of synthesis. This study reports Nb2O5 nanoparticles-dispersed Cu11.5Ni0.5Sb4S13-δ composites synthesized by a facile method combining mechanical alloying (MA) and spark plasma sintering (SPS). The enhanced electrical conductivity and the high power factor were obtained over the entire temperature ranges, likely derived from the fine-grained nanostructures through the repeated MA and SPS process. The uniformly distributed Nb2O5 nanoparticles and nanopores indicate the effectiveness of reducing the lattice thermal conductivity, below 0.6 W m−1 K−1, due to strong low-mid frequency phonon scattering. A small quantity of Nb2O5 addition (0.3 vol%) led to a high ZT ~1.2 at 723 K, which increased by ~50% compared to the matrix sample. These nanocomposites also possessed high average ZT, thermoelectric conversion efficiency, and fracture toughness.
The “CNAS-NPs-CNAS hamburger” nanostructure is introduced into the Cu11.5Ni0.5Sb4S13-δ tetrahedrite using a facile ball-milling process, which significantly improves the power factor and simultaneously reduces the thermal conductivity, and then leads to a state-of-the-art ZT ~1.2 at 723 K for thermoelectric nanocomposite. Display omitted
•Grain boundary-distributed Nb2O5 nanoparticles are firstly introduced into Cu12Sb4S13 tetrahedrite.•A state-of-the-art ZT value ~1.2 is achieved for CNAS-0.3NPs nanocomposite at 723 K.•Nb2O5-dispersed nanocomposites present excellent thermoelectric conversion efficiency and fracture toughness.
Last two decades have witnessed significant progress in thermoelectric research, to which materials processing has crucial contributions. Compared with traditional zone-melting method used for ...fabricating bismuth telluride alloys, new powder-based processes have more freedom for manipulating nanostructnres and nanocomposites. Thermoelectric performance enhancement is realized in most thermoelectric materials by introducing fine-grained and nano-composite structures with accurately controlled compositions. This review gives a comprehensive summary on the processing aspects of thermoelectric materials with three focuses on the powder synthesis, advanced sintering process and the formation of nanostructures in bulk materials.
Swelling and constituent redistribution of uranium-zirconium (U-Zr) alloys under irradiation will hinder their further application as feasible nuclear fuels. It is necessary to explore the primary ...irradiation damage induced by collision cascades in U-Zr alloys due to its profound effect on subsequent swelling and constituent redistribution. Herein, we perform molecular dynamic simulations to investigate the irradiation characteristic in the collision cascade of U-10Zr (U with 10 wt% Zr). It is found that, compared with pure U, the addition of Zr can reduce the peak number and increase the surviving number of Frenkel pairs, which should be attributed to the huge atomic mass difference between U and Zr. In U-10Zr alloy, the formation of Zr interstitials is found to be suppressed by analyzing the solute interstitial production efficiency, which is caused by the higher formation energy of Zr interstitials than that of U interstitials in a U matrix. Our simulations also indicate that the solute separation phenomenon actually happens in the collision cascade of U-10Zr. In addition, secondary peaks appear in the curves of defect number, which is induced by the interaction between shock waves and periodic boundaries. The present simulation data and insights would be significant for understanding the irradiation damage behavior of U-Zr alloy in collision cascades.
•Zr with light atomic mass inhibits the thermal spike in U-10Zr.•The suppressed formation of Zr interstitial is found in U-10Zr.•Segregation is detected after collision cascades in U-10Zr.•Shock waves caused by collision cascades are captured in U-10Zr.
Under the environment of high radiation, materials used in fission and fusion reactors will internally accumulate numerous lattice defects and bubbles. With extensive studies focused on bubble ...resolution under irradiation, the mutually effects between helium bubbles and displacement cascades in irradiated materials remain unaddressed. Therefore, the defects production and microstructure evolution under self-irradiation events in vicinity of helium bubbles are investigated by preforming large scale molecular dynamics simulations in single-crystal copper. When subjected to displacement cascades, distinguished bubble resolution categories dependent on bubble size are observed. With the existence of bubbles, radiation damage is aggravated with the increasing bubble size, represented as the promotion of point defects and dislocations. The atomic mechanisms of heterogeneous dislocation structures are attributed to different helium-vacancy cluster modes, transforming from the resolved gas trapped with vacancies to the biased absorption of vacancies by the over-pressured bubble. In both cases, helium impedes the recombination of point defects, leading to the accelerated formation of interstitial loops. The results and insight obtained here might contribute to understand the underlying mechanism of transmutant solute on the long-term evolution of irradiated materials.
To understand the role of helium on self-irradiation effects in δ-plutonium, microstructure evolutions due to α-decay events near pre-existing helium bubbles in gallium-stabilized δ-plutonium are ...investigated using molecular dynamics simulations. Bubble promoting effect plays a dominating role in point defects production, resulting in increasing number of point defects. When lightweight helium atoms act as media, energy transfer discrepancy and altered spatial morphology of point defects induced by mass effect are revealed. The evolution of stacking faults surrounding the disordered core is studied and their binding effect on the propagation of point defects are presented. The cascade-induced bubble coalescence, resolution and re-nucleation driven by internal pressure are obtained in the investigation on helium behaviors. The intrinsic tendency in our simulated self-irradiation with helium bubbles is significant for understanding the underlying mechanism of aging in plutonium and its alloys.
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