• Title/Summary/Keyword: Plasma spheroidization

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Spheroidization of Pure-vanadium Powder using Radio Frequency Thermal Plasma Process (RF 플라즈마를 이용한 순수 바나늄 분말의 구상화 거동 연구)

  • Adomako, Nana Kwabena;Yang, Seungmin;Lee, Min Gyu;Reddy, N.S.;Kim, Jeoung-Han
    • Journal of Powder Materials
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    • v.26 no.4
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    • pp.305-310
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    • 2019
  • In the present work, spheroidization of angular vanadium powders using a radio frequency (RF) thermal plasma process is investigated. Initially, angular vanadium powders are spheroidized successfully at an average particle size of $100{\mu}m$ using the RF-plasma process. It is difficult to avoid oxide layer formation on the surface of vanadium powder during the RF-plasma process. Titanium/vanadium/stainless steel functionally graded materials are manufactured with vanadium as the interlayer. Vanadium intermediate layers are deposited using both angular and spheroidized vanadium powders. Then, 17-4PH stainless steel is successfully deposited on the vanadium interlayer made from the angular powder. However, on the surface of the vanadium interlayer made from the spheroidized powder, delamination of 17-4PH occurs during deposition. The main cause of this phenomenon is presumed to be the high thickness of the vanadium interlayer and the relatively high level of surface oxidation of the interlayer.

Spheroidization of Enamel Powders by Radio Frequency Plasma Treatment and Application to Additive Manufacturing (RF 플라즈마 처리를 이용한 칠보 유약 분말의 구상화 및 적층 제조 공정 적용)

  • Kim, Ki-Bong;Yang, Dong-Yeol;Kim, Yong-Jin;Choe, Jungho;Kwak, Ji-Na;Jung, Woo-Hyung
    • Journal of Powder Materials
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    • v.27 no.5
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    • pp.388-393
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    • 2020
  • The enamel powders used traditionally in Korea are produced by a ball-milling process. Because of their irregular shapes, enamel powders exhibit poor flowability. Therefore, polygonal enamel powders are only used for handmade cloisonné crafts. In order to industrialize or automate the process of cloisonné crafts, it is essential to control the size and shape of the powder. In this study, the flowability of the enamel powders was improved using the spheroidization process, which employs the RF plasma treatment. In addition, a simple grid structure and logo were successfully produced using the additive manufacturing process (powder bed fusion), which utilizes spherical enamel powders. The additive manufacturing technology of spherical enamel powders is expected to be widely used in the field of cloisonné crafting in the future.

Manufacturing and Properties of Low Vacuum Plasma Sprayed W-Carbide Hybrid Coating Layer (진공 플라즈마 스프레이 공정을 이용한 W계 복합 코팅층의 제조 및 특성 연구)

  • Cho, Jin-Hyeon;Jin, Young-Min;Ahn, Jee-Hoon;Lee, Kee-Ahn
    • Journal of Powder Materials
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    • v.18 no.3
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    • pp.226-237
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    • 2011
  • W-ZrC and W-HfC composite powders were fabricated by the Plasma Alloying & Spheroidization (PAS) method and the powders were sprayed into hybrid coating layers by using Low Vacuum Plasma Spray (LVPS) process, respectively. Microstructure, mechanical properties, and ablation characteristics of the fabricated coating layers were investigated. The LVPS process led to successful production of W-Carbide hybrid coatings, approximately 400 ${\mu}M$ or above in thickness. As the substrate preheating temperature increased from $870^{\circ}C$ to $917^{\circ}C$, the hardness of the W-ZrC coating layer increased due to decreased porosity. Vickers hardness showed higher value (about 108.4 HV) in W-ZrC hybrid coating material compared to that of W-HfC while adhesive strength was found to be similar in both coating layers. The plasma torch test revealed good ablation resistance of the W-Carbide hybrid coating layers. The relatively high performance W-ZrC coating layer at the elevated temperature is thought to be attributed to both the strengthening effect of ZrC particle remained in the layer and the formation of ZrO2 phase with high temperature stability.

Plasma Engineering for Nano-Materials

  • Kim, Seong-In;Shin, Myoung-Sun;Son, Byung-Koo;Song, Seok-Kyun;Choi, Sun-Yong
    • Proceedings of the Korean Vacuum Society Conference
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    • 2012.08a
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    • pp.79-79
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    • 2012
  • A high temperature and a low temperature plasma process technologies were developed and demonstrated for synthesis, hybrid formation, surface treatment and CVD engineering of nano powder. RF thermal plasma is used for synthesis of spherical nano particles in a diameter ranged from 10 nm to 100 nm. A variety of nano particules such as Si, Ni, has been synthesized. The diameter of the nano-particles can be controlled by RF plasma power, pressure, gas flow rate and raw material feed rate. A modified RF thermal plasma also produces nano hybrid materials with graphene. Hemispherical nano-materials such as Ag, Ni, Si, SiO2, Al2O3, size ranged from 30 to 100 nm, has been grown on graphene nanoplatelet surface. The coverage ranged from 0.1 to 0.7 has been achieved uniformly over the graphene surface. Low temperature AC plasma is developed for surface modification of nano-powder. In order to have a three dimensional and lengthy plasma treatment, a spiral type of reactor has been developed. A similar plasma reactor has been modfied for nano plasma CVD process. The reactor can be heated with halogen lamp.

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Microstructural Evolution of Aluminum Nitride - Yttrium Aluminum Garnet Composite Coatings by Plasma Spraying from Different Feedstock Powders (Aluminum Nitride - Yttrium Aluminum Garnet 분말 특성과 플라즈마 용사 코팅층의 미세조직)

  • So, Woong-Sub;Baik, Kyeong-Ho
    • Korean Journal of Materials Research
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    • v.21 no.2
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    • pp.106-110
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    • 2011
  • A high thermal conductive AlN composite coating is attractive in thermal management applications. In this study, AlN-YAG composite coatings were manufactured by atmospheric plasma spraying from two different powders: spray-dried and plasma-treated. The mixture of both AlN and YAG was first mechanically alloyed and then spray-dried to obtain an agglomerated powder. The spray-dried powder was primarily spherical in shape and composed of an agglomerate of primary particles. The decomposition of AlN was pronounced at elevated temperatures due to the porous nature of the spray-dried powder, and was completely eliminated in nitrogen environment. A highly spherical, dense AlN-YAG composite powder was synthesized by plasma alloying and spheroidization (PAS) in an inert gas environment. The AlN-YAG coatings consisted of irregular-shaped, crystalline AlN particles embedded in amorphous YAG phase, indicating solid deposition of AlN and liquid deposition of YAG. The PAS-processed powder produced a lower-porosity and higher-hardness AlN-YAG coating due to a greater degree of melting in the plasma jet, compared to that of the spray-dried powder. The amorphization of the YAG matrix was evidence of melting degree of feedstock powder in flight because a fully molten YAG droplet formed an amorphous phase during splat quenching.

The Effect of Uni-nanoadditive Manufactured Using RF Plasma Processing on Core-shell Structure in MLCC

  • Song, Soon-Mo;Kim, Hyo-Sub;Park, Kum-Jin;Sohn, Sung-Bum;Kim, Young-Tae;Hur, Kang-Heon
    • Journal of the Korean Ceramic Society
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    • v.46 no.2
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    • pp.131-136
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    • 2009
  • Radio frequency (RF) plasma treatment is studied for the size reduction and the spheroidization of coarse particles to change them into nano-sized powders of spherical shape in MLCC fields. The uni-nanoadditives manufactured by RF plasma processing for high dispersion have been investigated for the effect on core-shell structure in dielectrics of MLCC. Microstructures have been characterized using scanning electron microscope (SEM), transmission electron microscope (TEM) and Electron Probe Micro Analyzer (EPMA). We compared the distribution of core-shell grains between specimens manufactured using uni-nanoadditive and using mixed additive. In addition, the uniformity of rare earth elements in the core-shell structured grains was analyzed. It was shown, from TEM observations, that the sintered specimen manufactured using uni-nanoadditives had more dense small grains with well-developed core-shell structure than the specimen using mixed additives, which had a homogeneous microstructure without abnormal grain growth and shows broad temperature coefficient of capacitance (TCC) curves in all temperature ranges because of well dispersed additives.

Preparation of Metal Injection Molded Dental Components using Spheroidized Ti Powders by Plasma Process (플라즈마 공정으로 구상화된 티타늄 분말과 금속사출성형 공정을 이용한 치과용 부품 제조)

  • Gwak, Ji-Na;Yang, Sangsun;Yun, Jung-Yeul;Kim, Ju-Yong;Park, Seongjin;Kim, Hyun-Seung;Kim, Yong-Jin;Park, Yong-Ho
    • Journal of Powder Materials
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    • v.20 no.6
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    • pp.467-473
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    • 2013
  • This research presents a preparation method of dental components by metal injection molding process (MIM process) using titanium scrap. About $20{\mu}m$ sized spherical titanium powders for MIM process were successfully prepared by a novel dehydrogenation and spheroidization method using in-situ radio frequency thermal plasma treatment. The effects of MIM process parameters on the mechanical and biological properties of dental components were investigated and the optimum condition was obtained. After sintering at $1250^{\circ}C$ for 1 hour in vacuum, the hardness and the tensile strength of MIMed titanium components were 289 Hv and 584 MPa, respectively. Prepared titanium dental components were not cytotoxic and they showed a good cell proliferation property.