Journal of Powder Materials

Volume 31(2); April 2024

Research Articles

Exploring Thermoelectric Transport Properties and Band Parameters of n-Type Bi_2-xSb_xTe₃ Compounds Using the Single Parabolic Band Model: Linh Ba Vu, Soo-ho Jung, Jinhee Bae, Jong Min Park, Kyung Tae Kim, Injoon Son, Seungki Jo; J Powder Mater. 2024;31(2):119-125. Published online April 30, 2024; DOI: https://doi.org/10.4150/jpm.2024.00045

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Abstract PDF: The n-type Bi2-xSbxTe3 compounds have been of great interest due to its potential to achieve a high thermoelectric performance, comparable to that of p-type Bi2-xSbxTe3. However, a comprehensive understanding on the thermoelectric properties remains lacking. Here, we investigate the thermoelectric transport properties and band characteristics of n-type Bi2-xSbxTe3 (x = 0.1 – 1.1) based on experimental and theoretical considerations. We find that the higher power factor at lower Sb content results from the optimized balance between the density of state effective mass and nondegenerate mobility. Additionally, a higher carrier concentration at lower x suppresses bipolar conduction, thereby reducing thermal conductivity at elevated temperatures. Consequently, the highest zT of ~ 0.5 is observed at 450 K for x = 0.1 and, according to the single parabolic band model, it could be further improved by ~70 % through carrier concentration tuning.

Inorganic Compound and Cycloserine Composite Particles for Improved Stability: Dongwon Kim, Heeseo Kim, Hongjun Yoon, Hyuk Jun Cho, Sung Giu Jin; J Powder Mater. 2024;31(2):126-131. Published online April 30, 2024; DOI: https://doi.org/10.4150/jpm.2024.00002

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Abstract PDF: The aim of this study was to improve the chemical stability of cycloserine containing organic and inorganic compounds. Composite particles were manufactured with a 1:1 weight ratio of organic/inorganic compounds and cycloserine. The influence of organic/inorganic compounds on the stability of cycloserine was investigated under accelerated stress conditions at 60°C/75% RH for 24 hours. In addition, the properties of the composite particles were evaluated using differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and the dissolution of the drug was assessed by preparing it as a hard capsule. Among the organic and inorganic compounds investigated, calcium hydroxide most improved the stability of cycloserine under accelerated stress conditions (53.3 ± 2.2% vs 1.7 ± 0.2%). DSC results confirmed the compatibility between calcium hydroxide and the cycloserine, and SEM results confirmed that it was evenly distributed around the cycloserine. Calcium hydroxide also showed more than 90% cycloserine dissolution within 15 minutes. Therefore, the calcium hydroxide and cycloserine composite particles may be candidates for cycloserine oral pharmaceuticals with enhanced drug stability.

Effect of Ball Milling Conditions on the Microstructure and Dehydrogenation Behavior of TiH₂ Powder: Ji Young Kim, Eui Seon Lee, Ji Won Choi, Youngmin Kim, Sung-Tag Oh; J Powder Mater. 2024;31(2):132-136. Published online April 30, 2024; DOI: https://doi.org/10.4150/jpm.2024.00001

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Abstract PDF: This study investigated the effects of revolution speed and ball size in planetary milling on the microstructure and dehydrogenation behavior of TiH2 powder. The particle size analysis showed that the large particles present in the raw powder were effectively refined as the revolution speed increased, and when milled at 500 rpm, the median particle size was 1.47 m. Milling with a mixture of balls of two or three sizes was more effective in refining the raw powder than milling with balls of a single size. A mixture of 3-mm and 5-mm-diameter balls was the optimal condition for particle refinement, and the measured median particle size was 0.71 m. The dependence of particle size on revolution speed and ball size was explained by changes in input energy and the number of contact points of the balls. In the milled powder, the endothermic peak measured using differential thermal analysis was observed at a relatively low temperature. This finding was interpreted as the activation of a dehydrogenation reaction, mainly due to the increase in the specific surface area and the concentration of lattice defects.

Data-driven Approach to Explore the Contribution of Process Parameters for Laser Powder Bed Fusion of a Ti-6Al-4V Alloy: Jeong Min Park, Jaimyun Jung, Seungyeon Lee, Haeum Park, Yeon Woo Kim, Ji-Hun Yu; J Powder Mater. 2024;31(2):137-145. Published online April 30, 2024; DOI: https://doi.org/10.4150/jpm.2024.00038

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Abstract PDF: In order to predict the process window of laser powder bed fusion (LPBF) for printing metallic components, the calculation of volumetric energy density (VED) has been widely calculated for controlling process parameters. However, because it is assumed that the process parameters contribute equally to heat input, the VED still has limitation for predicting the process window of LPBF-processed materials. In this study, an explainable machine learning (xML) approach was adopted to predict and understand the contribution of each process parameter to defect evolution in Ti alloys in the LPBF process. Various ML models were trained, and the Shapley additive explanation method was adopted to quantify the importance of each process parameter. This study can offer effective guidelines for fine-tuning process parameters to fabricate high-quality products using LPBF.

The Effect of TiO₂ Addition on Low-temperature Sintering Behaviors in a SnO₂-CoO-CuO System: Jae-Sang Lee, Kyung-Sik Oh, Yeong-Kyeun Paek; J Powder Mater. 2024;31(2):146-151. Published online April 30, 2024; DOI: https://doi.org/10.4150/jpm.2024.00024

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Abstract PDF: Pure SnO2 has proven very difficult to densify. This poor densification can be useful for the fabrication of SnO2 with a porous microstructure, which is used in electronic devices such as gas sensors. Most electronic devices based on SnO2 have a porous microstructure, with a porosity of > 40%. In pure SnO2, a high sintering temperature of approximately 1300C is required to obtain > 40% porosity. In an attempt to reduce the required sintering temperature, the present study investigated the low-temperature sinterability of a current system. With the addition of TiO2, the compositions of the samples were Sn1-xTixO2-CoO(0.3wt%)-CuO(2wt%) in the range of x ≤ 0.04. Compared to the samples without added TiO2, densification was shown to be improved when the samples were sintered at 950C. The dominant mass transport mechanism appears to be grain-boundary diffusion during heat treatment at 950C.

Effect of Hot Isostatic Pressing on the Stellite 6 Alloy prepared by Directed Energy Deposition: Joowon Suh, Jae Hyeon Koh, Young-Bum Chun, Young Do Kim, Jinsung Jang, Suk Hoon Kang, Heung Nam Han; J Powder Mater. 2024;31(2):152-162. Published online April 30, 2024; DOI: https://doi.org/10.4150/jpm.2024.00066

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Abstract PDF: The directed energy deposited (DED) alloys show higher hardness values than the welded alloys due to the finer microstructure following the high cooling rate. However, defects such as microcracks, pores, and the residual stress are remained within the DED alloy. These defects deteriorate the wear behavior so post-processing such as heat treatment and hot isostatic pressing (HIP) are applied to DED alloys to reduce the defects. HIP was chosen in this study because the high pressure and temperature uniformly reduced the defects. The HIP is processed at 1150oC under 100 MPa for 4 hours. After HIP, microcracks are disappeared and porosity is reduced by 86.9%. Carbides are spherodized due to the interdiffusion of Cr and C between the dendrite and interdendrite region. After HIP, the nanohardness (GPa) of carbides increased from 11.1 to 12, and the Co matrix decreased from 8.8 to 7.9. Vickers hardness (HV) decreased by 18.9 % after HIP. The dislocation density (10-2/m2) decreased from 7.34 to 0.34 and the residual stress (MPa) changed from tensile 79 to a compressive -246 by HIP. This study indicates that HIP is effective in reducing defects, and the HIP DED Stellite 6 exhibits a higher HV than welded Stellite 6.

Hydrogen Reduction Behavior of NCM-based Lithium-ion Battery Cathode Materials: So-Yeong Lee, So-Yeon Lee, Dae-Hyeon Lee, Ho-Sang Sohn; J Powder Mater. 2024;31(2):163-168. Published online April 30, 2024; DOI: https://doi.org/10.4150/jpm.2024.00017

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Abstract PDF: As the demand for lithium-ion batteries for electric vehicles is increasing, it is important to recover valuable metals from waste lithium-ion batteries. In this study, the effects of gas flow rate and hydrogen partial pressure on hydrogen reduction of NCM-based lithium-ion battery cathode materials were investigated. As the gas flow rate and hydrogen partial pressure increased, the weight loss rate increased significantly from the beginning of the reaction due to the reduction of NiO and CoO by hydrogen. At 700 °C and hydrogen partial pressure above 0.5 atm, Ni and Li2O were produced by hydrogen reduction. From the reduction product and Li recovery rate, the hydrogen reduction of NCM-based cathode materials was significantly affected by hydrogen partial pressure. The Li compounds recovered from the solution after water leaching of the reduction products were LiOH, LiOH·H2O, and Li2CO3, with about 0.02 wt% Al as an impurity.

Critical Review

Recent Developments in Quantum Dot Patterning Technology for Quantum Dot Display: Yeong Jun Jin, Kyung Jun Jung, Jaehan Jung; J Powder Mater. 2024;31(2):169-179. Published online April 30, 2024; DOI: https://doi.org/10.4150/jpm.2024.00073

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Abstract PDF: Colloidal quantum dot (QDs) have emerged as a crucial building block for LEDs due to their size-tunable emission wavelength, narrow spectral line width, and high quantum efficiency. Tremendous efforts have been dedicated to improving the performance of quantum dot light-emitting diodes (QLEDs) in the past decade, primarily focusing on optimization of device architectures and synthetic procedures for high quality QDs. However, despite these efforts, the commercialization of QLEDs has yet to be realized due to the absence of suitable large-scale patterning technologies for high-resolution devices., This review will focus on the development trends associated with transfer printing, photolithography, and inkjet printing, and aims to provide a brief overview of the fabricated QLED devices. The advancement of various quantum dot patterning methods will lead to the development of not only QLED devices but also solar cells, quantum communication, and quantum computers.

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