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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• Influence of milling atmosphere on the structure and magnetic properties of mechanically alloyed Fe40Co30Ni30
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• Enhancement of mechanical properties and thermoelectric performance of spark plasma sintered P-type Bismuth Telluride by powder surface oxide reduction
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  Journal of Alloys and Compounds.2021; 858: 157657.     CrossRef
• Solid solution evolution during mechanical alloying in Cu-Nb-Al compounds
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  International Journal of Minerals, Metallurgy, and Materials.2019; 26(9): 1129.     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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• The effect of powder pre-treatment on the mechanical and thermoelectric properties of spark plasma sintered N-type bismuth telluride
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  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.