- Thermoelectric Performance Enhancement of Sintered Bi-Te Pellets by Rotary-type Atomic Layer Deposition
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Myeong Jun Jung, Ji Young Park, Su Min Eun, Byung Joon Choi
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J Powder Mater. 2023;30(2):130-139. Published online April 1, 2023
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DOI: https://doi.org/10.4150/KPMI.2023.30.2.130
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Thermoelectric materials and devices are energy-harvesting devices that can effectively recycle waste heat into electricity. Thermoelectric power generation is widely used in factories, engines, and even in human bodies as they continuously generate heat. However, thermoelectric elements exhibit poor performance and low energy efficiency; research is being conducted to find new materials or improve the thermoelectric performance of existing materials, that is, by ensuring a high figure-of-merit (zT) value. For increasing zT, higher σ (electrical conductivity) and S (Seebeck coefficient) and a lower к (thermal conductivity) are required. Here, interface engineering by atomic layer deposition (ALD) is used to increase zT of n-type BiTeSe (BTS) thermoelectric powders. ALD of the BTS powders is performed in a rotary-type ALD reactor, and 40 to 100 ALD cycles of ZnO thin films are conducted at 100°C. The physical and chemical properties and thermoelectric performance of the ALD-coated BTS powders and pellets are characterized. It is revealed that electrical conductivity and thermal conductivity are decoupled, and thus, zT of ALD-coated BTS pellets is increased by more than 60% compared to that of the uncoated BTS pellets. This result can be utilized in a novel method for improving the thermoelectric efficiency in materials processing.
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- Enhancing Electrical Properties of N-type Bismuth Telluride Alloys through Graphene Oxide Incorporation in Extrusion 3D Printing
Jinhee Bae, Seungki Jo, Kyung Tae Kim journal of Korean Powder Metallurgy Institute.2023; 30(4): 318. CrossRef
- The Effect of Surface Defects on the Optical Properties of ZnSe:Eu Quantum Dots
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Da-Woon Jeong, Ji Young Park, Han Wook Seo, Kyoung-Mook Lim, Tae-Yeon Seong, Bum Sung Kim
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J Powder Mater. 2016;23(5):348-352. Published online October 1, 2016
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DOI: https://doi.org/10.4150/KPMI.2016.23.5.348
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244
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Quantum dots (QDs) are capable of controlling the typical emission and absorption wavelengths because of the bandgap widening effect of nanometer-sized particles. These phosphor particles have been used in optical devices, photovoltaic devices, advanced display devices, and several biomedical complexes. In this study, we synthesize ZnSe QDs with controlled surface defects by a heating-up method. The optical properties of the synthesized particles are analyzed using UV-visible and photoluminescence (PL) measurements. Calculations indicate nearly monodisperse particles with a size of about 5.1 nm at 260°C (full width at half maximum = 27.7 nm). Furthermore, the study results confirm that successful doping is achieved by adding Eu3+ preparing the growth phase of the ZnSe:Eu QDs when heating-up method. Further, we investigate the correlation between the surface defects and the luminescent properties of the QDs.
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- An investigation into the effective surface passivation of quantum dots by a photo-assisted chemical method
So-Yeong Joo, Hyun-Su Park, Do-yeon Kim, Bum-Sung Kim, Chan Gi Lee, Woo-Byoung Kim AIP Advances.2018;[Epub] CrossRef - Multimodal luminescence properties of surface-treated ZnSe quantum dots by Eu
Ji Young Park, Da-Woon Jeong, Kyoung-Mook Lim, Yong-Ho Choa, Woo-Byoung Kim, Bum Sung Kim Applied Surface Science.2017; 415: 8. CrossRef
- Optical Characteristics of CdSe/ZnS Quantum Dot with Precursor Flow Rate Synthesized by using Microreactor
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Ji Young Park, Da-Woon Jeong, Won Ju, Han Wook Seo, Yong-Ho Choa, Bum Sung Kim
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J Powder Mater. 2016;23(2):91-94. Published online April 1, 2016
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DOI: https://doi.org/10.4150/KPMI.2016.23.2.91
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High-quality colloidal CdSe/ZnS (core/shell) is synthesized using a continuous microreactor. The particle size of the synthesized quantum dots (QDs) is a function of the precursor flow rate; as the precursor flow rate increases, the size of the QDs decreases and the band gap energy increases. The photoluminescence properties are found to depend strongly on the flow rate of the CdSe precursor owing to the change in the core size. In addition, a gradual shift in the maximum luminescent wave (λmax) to shorter wavelengths (blue shift) is found owing to the decrease in the QD size in accordance with the quantum confinement effect. The ZnS shell decreases the surface defect concentration of CdSe. It also lowers the thermal energy dissipation by increasing the concentration of recombination. Thus, a relatively high emission and quantum yield occur because of an increase in the optical energy emitted at equal concentration. In addition, the maximum quantum yield is derived for process conditions of 0.35 ml/min and is related to the optimum thickness of the shell material.
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- Quantum materials made in microfluidics - critical review and perspective
M. Wojnicki, V. Hessel Chemical Engineering Journal.2022; 438: 135616. CrossRef - Poly(methylmethacrylate) coating on quantum dot surfaces via photo-chemical reaction for defect passivation
Doyeon Kim, So-Yeong Joo, Chan Gi Lee, Bum-Sung Kim, Woo-Byoung Kim Journal of Photochemistry and Photobiology A: Chemistry.2019; 376: 206. CrossRef - Multimodal luminescence properties of surface-treated ZnSe quantum dots by Eu
Ji Young Park, Da-Woon Jeong, Kyoung-Mook Lim, Yong-Ho Choa, Woo-Byoung Kim, Bum Sung Kim Applied Surface Science.2017; 415: 8. CrossRef
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