Journal of Powder Materials

Kyung-Ja Kim

4 Articles

The Effect of Sintering Processes and Additives on the Microstructures and Mechanical Properties of ZrB₂-SiC Composite Ceramics: Chang-Sup Kwon, Jung-Min Chae, Hyung-Tae Kim, Kyung-Ja Kim, Seong-Won Kim; J Korean Powder Metall Inst. 2011;18(6):562-567.; DOI: https://doi.org/10.4150/KPMI.2011.18.6.562

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This paper reports the effect of sintering processes and additives on the microstructures and mechanical properties of ZrB_2-SiC composite ceramics. We fabricated sintered bodies of ZrB_2-20 vol.% SiC with or without sintering additive, such as C or B_4C, densified by spark plasma sintering as well as hot pressing. While almost full densification was achieved regardless of sintering processes or sintering additives, significant grain growth was observed in the case of spark plasma sintering, especially with B_4C. With sintered bodies, mechanical properties, such as flexural strength and Vickers hardness, were also examined.

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Effect of the Size and Amount of SiC on the Microstructures and Thermal Conductivities of ZrB2-SiC Composite Ceramics
Seong-Won Kim, Chang-Sup Kwon, Yoon-Suk Oh, Sung-Min Lee, Hyung-Tae Kim
Journal of Korean Powder Metallurgy Institute.2012; 19(5): 379. CrossRef

Effect of MgO and NH₄OH on Formation of 5Mg(OH)₂·MgSO₄·3H₂O Whiskers: Ri Yu, Jae-Hwan Pee, Hyung-Tae Kim, Kyung-Ja Kim, Young-Woong Kim, Woong Kim, Yoo-Jin Kim; J Korean Powder Metall Inst. 2011;18(3):283-289.; DOI: https://doi.org/10.4150/KPMI.2011.18.3.283

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Magnesium hydroxide sulfate hydrate whiskers (5Mg(OH)_2cdotMgSO_4cdot3H_2O, abbreviated 513 MHSH) were prepared using hydrothermal reaction with magnesium oxide (MgO) and magnesium sulfate (MgSO_4cdot7H_2O) as the starting materials. The effects of the molar ratio of MgSO_4/MgO and amount of NH_4OH were studied. As a result, 513 MHSH whiskers co-existed with hexagonal plate Mg(OH)_2 at low concentration of SO_42-. The molar ratio of MgSO_4cdot7H_2O/MgO was 7:1, uniform 513 MHSH whiskers were formed without impurity such as Mg(OH)_2. Appropriate amount of NH_4OH has affected to formation of high quality MHSH. Their morphologies and structures were determined by powder X-ray diffraction (XRD) scanning electron microscopy (SEM) and thermo-gravimetric analyzer (TGA).

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Effect of sulfate ion on synthesis of 5 Mg(OH)2·MgSO4·3H2O whiskers using non-hydrothermal method with acid catalyst
Areum Choi, Nuri Oh, YooJin Kim
Journal of the Korean Ceramic Society.2022; 59(2): 224. CrossRef
Effect of H₂SO₄ and Reaction Time on Synthesis of 5Mg(OH)₂∙MgSO₄∙3H₂O Whiskers using Hydrothermal Reaction
Areum Choi, Nuri Oh, YooJin Kim
Journal of Korean Powder Metallurgy Institute.2020; 27(5): 401. CrossRef
Study of Fabrication and Improvement of Mechanical Properties of Mg-based Inorganic Fiber using Reflux Process and Silica Coating
Ri Yu, YooJin Kim
Journal of Korean Powder Metallurgy Institute.2019; 26(3): 195. CrossRef
Effect of MgSO4/MgO on the Synthesis of 5Mg(OH)2·MgSO4·3H2O Whiskers using One-step Ambient Pressure
Ri Yu, Jae-Hwan Pee, Hyung Tae Kim, YooJin Kim
Journal of the Korean Ceramic Society.2013; 50(3): 201. CrossRef

Thickness Control of Core Shell type Nano CoFe₂O₄@SiO₂ Structure: Ri Yu, Yoo-Jin Kim, Jae-Hwan Pee, Kyung-Ja Kim; J Korean Powder Metall Inst. 2010;17(3):230-234.; DOI: https://doi.org/10.4150/KPMI.2010.17.3.230

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Abstract PDF: Homogenous silica-coated CoFe_2O_4 samples with controlled silica thickness were synthesized by the reverse microemulsion method. First, 7 nm size cobalt ferrite nanoparticles were prepared by thermal decomposition methods. Hydrophobic cobalt ferrites were coated with controlled SiO_2 using polyoxyethylene(5)nonylphenylether (Igepal) as a surfactant, NH_4OH and tetraethyl orthosilicate (TEOS). The well controlled thickness of the silica shell was found to depend on the reaction time and the amount of surfactant used during production. Thick shell was prepared by increasing reaction time and small amount of surfactant.

Fabrication of Ag doped Hydroxyapatite and its Antimicrobial Effects with the Particle Size: Kyung-Sik Oh, Kyung-Ja Kim, Young-Keun Jeong; J Korean Powder Metall Inst. 2001;8(3):192-196.

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Abstract PDF: Ag doped Hydroxyapatite powder in nano-scale was successfully synthesized either by co-precipitation or by ion exchange route. The fabricated powder was successfully dispersed through freeze drying due to the prevention of secondary particles. The antimicrobial effects of nano-HAp against E.coli was superior to micron ones not only in its strength but also in duration.

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