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19 results on '"Cha, Hyun‐Ae"'

10. Nanocrystalline Composite Layer Realized by Simple Sintering Without Surface Treatment, Reducing Hydrophilicity and Increasing Thermal Conductivity.

Author

Cha, Hyun‐Ae, Ha, Su‐Jin, Jang, Hye‐Jeong, Ahn, Byeong‐Min, Moon, Young Kook, Kim, Jung‐Hwan, Choi, Jong‐Jin, Hahn, Byung‐Dong, Han, Sang‐Ho, Lim, Jun, Ahn, Do‐Cheon, Jung, In Chul, Cho, Kyung‐Hoon, Kim, Do Kyung, Kim, Jae Chul, and Ahn, Cheol‐Woo

Subjects
*THERMAL conductivity, *SURFACE preparation, *THERMAL interface materials, *SINTERING, *SURFACE morphology
Abstract

The surface treatment for a polymer‐ceramic composite is additionally performed in advanced material industries. To prepare the composite without a surface treatment, the simplest way to manufacture an advanced ceramic‐particle is devised. The method is the formation of a nanocrystalline composite layer through the simple liquid‐phase sintering. Using magnesia (MgO) which shows hydrophilicity, a nanocrystalline surface layer is realized by liquid‐phase sintering. The amorphous matrix of nanocrystalline composite layer makes MgO hydrophobic and ensures miscibility with polymers, and the nanocrystalline MgO ensures high thermal conductivity. In addition, the liquid phase removes the open pores and makes the surface morphology smooth MgO with smooth surface (MgO‐SM). Thermal interface materials (TIM) prepared with MgO‐SM and epoxy show a high thermal conductivity of ≈7.5 W m−1K−1, which is significantly higher than 4.5 W m−1K−1 of pure MgO TIM. Consequently, the formation process of a nanocrystalline surface layer utilizing simple liquid‐phase sintering is proposed as a fabrication method for a next‐generation ceramic‐filler. In addition, it is fundamentally identified that the thermal conductivity of MgO depends on the Mg deficiency, and therefore a poly‐crystal MgO‐SM (produced at a low temperature) has a higher thermal conductivity than a single‐crystal MgO (produced at a high temperature). [ABSTRACT FROM AUTHOR]

Published
2024
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16. Low thermal conductivity and high durability porous thermal insulation coating via room–temperature spray coating process

Author

Yun, Sae-Jung, Kim, Jung-Hwan, Cha, Hyun-Ae, Ahn, Cheol-Woo, Moon, Young Kook, Jang, Jongmoon, Yoon, Woon-Ha, Choi, Jong-Jin, and Hahn, Byung-Dong

Abstract

Herein, an efficient approach using aerosol deposition (AD) is proposed to fabricate a porous ceramic film with high thermal insulating and adhesive properties. Polyethylene powder (PE) is incorporated to regulate the kinetic energy of the ZrSiO4powder, which hinders the formation of structurally stable film layers. During the high-energy milling process, the ZrSiO4-PE composite powder agglomerates suitably and exhibits adequate kinetic energy to produce a porous film. Despite its exceptional thermally insulating characteristics, the ZrSiO4-PE composite film demonstrates relatively poor adhesion properties. Consequently, an optimized quantity of Y2O3powder is blended to modulate the thermal insulating and mechanical adhesion properties of the porous coating films. The Y2O3-(ZrSiO4-PE) composite film (approximately 60 μm) exhibits low density (2.2 g/cm3), low thermal conductivity (at ambient temperature, approximately 0.64 W/m∙K), and excellent adhesion strength (37 MPa) attributes. This research offers valuable guidance for fabricating composite porous ceramic films with low thermal conductivity and high adhesion at room temperatures using AD.

Published
2023
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17. Stabilities and piezoelectric properties of morphotropic phase boundary composition 0.2Pb(Mg1/3Nb2/3)O3-0.38PbZrO3-0.42PbTiO3 ternary piezoceramics.

Author

Upadhyay, Ashutosh, Cha, Hyun Ae, and Jeon, Jae-Ho

Subjects
*ELECTRIC properties of piezoelectric ceramics, *PIEZOELECTRIC ceramics, *SINTERING, *PIEZOELECTRICITY, *MORPHOTROPIC phase boundaries, *PIEZOELECTRIC materials, *LEAD zirconate titanate, *LEAD magnesium niobate, *TERNARY forms
Abstract

The phase stabilities and piezoelectric properties of morphotropic phase boundary ternary piezoceramics (0.2Pb(Mg1/3Nb2/3)O3-0.38PbZrO3-0.42PbTiO3) are investigated as a function of sintering conditions. The tetragonality (c/a) of the morphotropic phase boundary, where the rhombohedral and tetragonal phases coexist (space groups R3m and P4mm, respectively), is affected by the sintering temperature and time. This tetragonality affects the piezoelectric properties. The results demonstrate that a large tetragonality is undesirable for the piezoelectric properties. The structure and properties of morphotropic phase boundary piezoelectric materials are strongly correlated. [ABSTRACT FROM AUTHOR]

Published
2019
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