In additive manufacturing, the flowability of feedstock particles determines the quality of the parts that are affected by different parameters, including the chemistry and morphology of the powders and particle size distribution. In this study, the microstructures and flowabilities of gas-atomized heat-resistant alloys for additive manufacturing applications are investigated. A KHR45A alloy powder with a composition of Fe-30Cr-40Mn-1.8Nb (wt.%) is fabricated using gas atomization process. The microstructure and effect of powder chemistry and morphology on the flow behavior are investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and revolution powder analysis. The results reveal the formation of spherical particles composed of single-phase FCC dendritic structures after gas atomization. SEM observations show variations in the microstructures of the powder particles with different size distributions. Elemental distribution maps, line scans, and high-resolution XPS results indicate the presence of a Si-rich oxide accompanied by Fe, Cr, and Nb metal oxides in the outer layer of the powders. The flowability behavior is found to be induced by the particle size distribution, which can be attributed to the interparticle interactions and friction of particles with different sizes.

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• Al-based amorphous coatings by warm spraying: Numerical simulation and experimental validation
  Deming Wang, Nianchu Wu, Peng Cao
  Journal of Alloys and Compounds.2024; 1008: 176674.     CrossRef

Ni wires with a diameter and length of 0.4 and 100 mm, respectively, and a purity of 99.9% are electrically exploded at 25 cycles per minute. The Ni nanopowders are successfully synthesized by a pulsed wire evaporation (PWE) method, in which Ar gas is used as the ambient gas. The characterization of the nanopowders is carried out using X-ray diffraction (XRD) and a high-resolution transmission electronmicroscope (HRTEM). The Ni nanopowders are classified for a multilayer ceramic condenser (MLCC) application using a type two Air-Centrifugal classifier (model: CNI, MP-250). The characterization of the classified Ni nanopowders are carried out using a scanning electron microscope (SEM) and particle size analysis (PSA) to observe the distribution and minimum classification point (minimum cutting point) of the nanopowders.

In this study, Bi-Sb-Te thermoelectric materials are produced by mechanical alloying (MA) and spark plasma sintering (SPS). To examine the influence of the milling atmosphere on the microstructure and thermo-electric (TE) properties, a p-type Bi-Sb-Te composite powder is mechanically alloyed in the presence of argon and air atmospheres. The oxygen content increases to 55% when the powder is milled in the air atmosphere, compared with argon. All grains are similar in size and uniformly, distributed in both atmospheric sintered samples. The Seebeck coefficient is higher, while the electrical conductivity is lower in the MA (Air) sample due to a low carrier concentration compared to the MA (Ar) sintered sample. The maximum figure of merit (ZT) is 0.91 and 0.82 at 350 K for the MA (Ar) and MA (Air) sintered samples, respectively. The slight enhancement in the ZT value is due to the decrease in the oxygen content during the MA (Ar) process. Moreover, the combination of mechanical alloying and SPS process shows a higher hardness and density values for the sintered samples.

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• Revealing the improved thermoelectric performances of (BiSb)2Te3 alloy through rapid solidification of cold-water assisted water atomization approach
  Eun-Ha Go, Rathinam Vasudevan, Ji-Won Ha, Sung-Jae Jo, GeonWoo Baek, Soon-Jik Hong
  Journal of Alloys and Compounds.2025; 1010: 177548.     CrossRef
• Grain Size‐Dependent Thermoelectric Performances of Al2O3 Addition into BiSbTe Alloy During Heat Treatment Fabricated by Mechanical Alloying
  Ji‐Won Ha, Vasudevan Rathinam, Eun‐Ha Go, Soon‐Jik Hong
  Advanced Engineering Materials.2024;[Epub]     CrossRef
• Advancement of thermoelectric performances through the dispersion of expanded graphene on p-type BiSbTe alloys
  Eun-Ha Go, Rathinam Vasudevan, Babu Madavali, Peyala Dharmaiah, Min-Woo Shin, Sung Ho Song, Soon-Jik Hong
  Powder Metallurgy.2023; 66(5): 722.     CrossRef
• Influence of milling atmosphere on the structure and magnetic properties of mechanically alloyed Fe40Co30Ni30
  Alex Abraham Paul, Anuj Rathi, Ganesh Varma Thotakura, Tanjore V. Jayaraman
  Materials Chemistry and Physics.2021; 258: 123897.     CrossRef
• Enhancement of mechanical properties and thermoelectric performance of spark plasma sintered P-type Bismuth Telluride by powder surface oxide reduction
  Ahmed A. Abdelnabi, Vickram Lakhian, Joseph R. McDermid, Yu-Chih Tseng, James S. Cotton
  Journal of Alloys and Compounds.2021; 858: 157657.     CrossRef
• Solid solution evolution during mechanical alloying in Cu-Nb-Al compounds
  Kaouther Zaara, Mahmoud Chemingui, Virgil Optasanu, Mohamed Khitouni
  International Journal of Minerals, Metallurgy, and Materials.2019; 26(9): 1129.     CrossRef

We fabricate fine (<20 μm) powders of Bi_0.5Sb_1.5Te₃ alloys using a large-scale production method and subsequently consolidate them at temperatures of 573, 623, and 673 K using a spark plasma sintering process. The microstructure, mechanical properties, and thermoelectric properties are investigated for each sintering temperature. The microstructural features of both the powders and bulks are characterized by scanning electron microscopy, and the crystal structures are analyzed by X-ray diffraction analysis. The grain size increases with increasing sintering temperature from 573 to 673 K. In addition, the mechanical properties increase significantly with decreasing sintering temperature owing to an increase in grain boundaries. The results indicate that the electrical conductivity and Seebeck coefficient (217 μV/K) of the sample sintered at 673 K increase simultaneously owing to decreased carrier concentration and increased mobility. As a result, a high ZT value of 0.92 at 300 K is achieved. According to the results, a sintering temperature of 673 K is preferable for consolidation of fine (<20 μm) powders.

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• Complex microstructure induced high thermoelectric performances of p-type Bi–Sb–Te alloys
  Eun-Ha Go, Babu Madavali, Min-Woo Shin, Sung Ho Song, Soon-Jik Hong
  Materials Chemistry and Physics.2023; 307: 128156.     CrossRef
• Role of sintering temperature on electronic and mechanical properties of thermoelectric material: A theoretical and experimental study of TiCoSb half-Heusler alloy
  Ajay Kumar Verma, Kishor Kumar Johari, Kriti Tyagi, Durgesh Kumar Sharma, Pawan Kumar, Sudhir Kumar, Sivaiah Bathula, S.R. Dhakate, Bhasker Gahtori
  Materials Chemistry and Physics.2022; 281: 125854.     CrossRef
• Enhanced thermoelectric properties of Li and Mg co−substituted Bi2Sr2Co2O fabricated by combined conventional sintering and spark plasma sintering
  K. Park, H.Y. Hong, S.Y. Gwon
  Inorganic Chemistry Communications.2022; 145: 110005.     CrossRef

In this work, p-type Bi−Sb−Te alloys powders are prepared using gas atomization, a mass production powder preparation method involving rapid solidification. To study the effect of the sintering temperature on the microstructure and thermoelectric properties, gas-atomized powders are consolidated at different temperatures (623, 703, and 743 K) using spark plasma sintering. The crystal structures of the gas-atomized powders and sintered bulks are identified using an X-ray diffraction technique. Texture analysis by electron backscatter diffraction reveals that the grains are randomly oriented in the entire matrix, and no preferred orientation in any unique direction is observed. The hardness values decrease with increasing sintering temperature owing to a decrease in grain size. The conductivity increases gradually with increasing sintering temperature, whereas the Seebeck coefficient decreases owing to increases in the carrier mobility with grain size. The lowest thermal conductivity is obtained for the bulk sintered at a low temperature (603 K), mainly because of its fine-grained microstructure. A peak ZT of 1.06 is achieved for the sample sintered at 703 K owing to its moderate electrical conductivity and sustainable thermal conductivity.

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• Influence of the SPS heating rate on the optical and mechanical properties of Y2O3-MgO nanocomposites
  Seok-Min Yong
  Journal of Ceramic Processing Research.2019; 20(1): 59.     CrossRef

P-type ternary Bi_0.5Sb_1.5Te₃ alloys are fabricated via mechanical alloying (MA) and spark plasma sintering (SPS). Different ball sizes are used in the MA process, and their effect on the microstructure; hardness, and thermoelectric properties of the p-type BiSbTe alloys are investigated. The phases of milled powders and bulks are identified using an X-ray diffraction technique. The morphology of milled powders and fracture surface of compacted samples are examined using scanning electron microscopy. The morphology, phase, and grain structures of the samples are not altered by the use of different ball sizes in the MA process. Measurements of the thermoelectric (TE) transport properties including the electrical conductivity, Seebeck coefficient, and power factor are measured at temperatures of 300- 400 K for samples treated by SPS. The TE properties do not depend on the ball size used in the MA process.

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• Investigation of Spark Plasma Sintering Temperature on Microstructure and Thermoelectric Properties of p-type Bi-Sb-Te alloys
  Jin-Koo Han, Dong-won Shin, Babu Madavali, Soon-Jik Hong
  Journal of Korean Powder Metallurgy Institute.2017; 24(2): 115.     CrossRef
• Flexible Thermoelectric Device Using Thick Films for Energy Harvesting from the Human Body
  Han Ki Cho, Da Hye Kim, Hye Sun Sin, Churl-Hee Cho, Seungwoo Han
  Journal of the Korean Ceramic Society.2017; 54(6): 518.     CrossRef
• Investigation of the Microstructure and Thermoelectric Properties of P-Type BiSbTe Alloys by Usage of Different Revolutions Per Minute (RPM) During Mechanical Milling
  S.-M. Yoon, B. Madavali, Y.-N. Yoon, S.-J. Hong
  Archives of Metallurgy and Materials.2017; 62(2): 1167.     CrossRef
• Mechanical and thermoelectric properties of Bi2−xSbxTe3 prepared by using encapsulated melting and hot pressing
  Woo-Jin Jung, Il-Ho Kim
  Journal of the Korean Physical Society.2016; 69(8): 1328.     CrossRef

The recent rise in applications of thermoelectric materials has attracted interest in studies toward the fabrication of thermoelectric materials using mass production techniques. In this study, we successfully fabricate n-type Bi₂Te_2.7Se_0.3 material by a combination of mass production powder metallurgy techniques, gas atomization, and spark plasma sintering. In addition, to examine the effects of hydrogen reduction in the microstructure, the thermoelectric and mechanical properties are measured and analyzed. Here, almost 60% of the oxygen content of the powder are eliminated after hydrogen reduction for 4 h at 360°C. Micrographs of the powder show that the reduced powder had a comparatively clean surface and larger grain sizes than unreduced powder. The density of the consolidated bulk using as-atomized powder and reduced atomized powder exceeds 99%. The thermoelectric power factor of the sample prepared by reduction of powder is 20% better than that of the sample prepared using unreduced powder.

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• Tuning of power factor in bismuth selenide through Sn/Te co doping for low temperature thermoelectric applications
  Ganesh Shridhar Hegde, Ashwatha Narayana Prabhu, Ramakrishna Nayak, C. F. Yang, Y. K. Kuo
  Applied Physics A.2024;[Epub]     CrossRef
• Enhancing thermoelectric performance of K-doped polycrystalline SnSe through band engineering tuning and hydrogen reduction
  Nan Xin, Yifei Li, Guihua Tang, Longyun Shen
  Journal of Alloys and Compounds.2022; 899: 163358.     CrossRef
• The effect of powder pre-treatment on the mechanical and thermoelectric properties of spark plasma sintered N-type bismuth telluride
  Ahmed A. Abdelnabi, Vickram Lakhian, Joseph R. McDermid, James S. Cotton
  Journal of Alloys and Compounds.2021; 874: 159782.     CrossRef
• Investigation of Spark Plasma Sintering Temperature on Microstructure and Thermoelectric Properties of p-type Bi-Sb-Te alloys
  Jin-Koo Han, Dong-won Shin, Babu Madavali, Soon-Jik Hong
  Journal of Korean Powder Metallurgy Institute.2017; 24(2): 115.     CrossRef
• The Preparation and Growth Mechanism of the Recovered Bi2Te3 Particles with Respect to Surfactants
  Hyeongsub So, Eunpil Song, Yong-Ho Choa, Kun-Jae Lee
  Journal of Korean Powder Metallurgy Institute.2017; 24(2): 141.     CrossRef
• Enhanced thermoelectric cooling properties of Bi2Te3−xSex alloys fabricated by combining casting, milling and spark plasma sintering
  Seung Tek Han, Pradip Rimal, Chul Hee Lee, Hyo-Seob Kim, Yongho Sohn, Soon-Jik Hong
  Intermetallics.2016; 78: 42.     CrossRef

Electronic products are a major part of evolving industry and human life style; however most of them are known to emit electromagnetic waves that have severe health hazards. Therefore, different materials and fabrication techniques are understudy to control or limit transfer of such waves to human body. In this study, nanocomposite powder is dispersed into epoxy resin and shielding effects such as absorption, reflection, penetration and multiple reflections are investigated. In addition, nano size powder (Ni, Fe₂O₃, Fe-85Ni, C-Ni) is fabricated by pulsed wire evaporation method and dispersed manually into epoxy. Characterization techniques such as X-ray diffraction, Scanning electron microscopy and Transmission electron microscopy are used to investigate the phase analysis, size and shape as well as dispersion trend of a nano powder on epoxy matrix. Shielding effect is measured by standard test method to investigate the electromagnetic shielding effectiveness of planar materials, ASTM D4935. At lower frequency, sample consisting nano-powder of Fe-85%Wt Ni shows better electromagnetic shielding effect compared to only epoxy, only Ni, Fe₂O₃ and C-Ni samples.

As recognized by all scientific and industrial groups, carbon dioxide(CO₂) capture and storage(CCS) could play an important role in reducing greenhouse gas emissions. Especially carbon capture technology by dry sorbent is considered as a most energy-efficient method among the existing CCS technologies. Patent analysis has been considered to be a necessary step for identifying technological trend and planning technology strategies. This paper is aimed at identifying evolving technology trend and key indicators of dry sorbent from the objective information of patents. And technology map of key patents is also presented. In this study the patents applied in korea, japan, china, canada, US, EU from 1993 to 2013 are analyzed. The result of patent analysis could be used for R&D and policy making of domestic CCS industry.