Young-Min Kong | University of Ulsan (original) (raw)
Papers by Young-Min Kong
Journal of materials science. Materials in medicine, 2002
The effect of calcinations of starting powder on the mechanical properties of hydroxyapatite (HA)... more The effect of calcinations of starting powder on the mechanical properties of hydroxyapatite (HA)-based bioceramic composite was investigated. The calcinations of HA powder in air at 900 degrees C increased the crystallinity as well as the size of the powder. Ball milling after the calcinations was effective in eliminating large agglomerates in the powder. When the powder was mixed with reinforcing Al(2)O(3) powder, the mixture became fine and homogeneous. The flexural strength of HA-Al(2)O(3) composite was increased by the calcinations processes at all the Al(2)O(3) concentration. However, the fracture toughness was not much influenced by the calcinations. These results lead to the conclusion that the calcinations process effectively reduced the critical flaw size in the body by removing the agglomerates in the HA powder.
We investigated the effects of internal electrode composition on the reliability of low-firing mu... more We investigated the effects of internal electrode composition on the reliability of low-firing multilayer ceramic actuators using Ag internal electrodes. Ag–ceramic composite pastes were prepared by adding Pb(Mg1/3Nb2/3)O3–Pb(Zr0.475,Ti0.525)O3 (PMNZT) ceramic powders to a commercial Ag paste at concentraccepted 12 June 2009 vailable online 21 June 2009
Journal of the Korean Society of Manufacturing Technology Engineers
Journal of Asian Ceramic Societies
Films fabricated by aerosol deposition (AD) can be coated through interactions between the partic... more Films fabricated by aerosol deposition (AD) can be coated through interactions between the particles and substrate. Accelerated particles collide with the substrate, generating impact energy at the contact point. These interactions depend on the hardness of the substrate. This study examined the effects of the hardness of the substrate on the deposition behavior of thick glass films by AD. Substrates with different hardness, Al 2 O 3 , glass, and STS304, were used, and the film formation behavior was observed. The coating thickness of the initial layer was inversely proportional to the hardness of the substrate. The STS304 substrate exhibited a phase transition after the coating process that was induced by the strong impact energy. The film formation mechanism depending on the substrate hardness was proposed based on the microstructure of the interface between the film and substrate.
Journal of the Korean Ceramic Society
In this study, the dielectric and polarization properties of manganese (Mn% = 0.0, 0.1, 0.2, 0.5)... more In this study, the dielectric and polarization properties of manganese (Mn% = 0.0, 0.1, 0.2, 0.5) doped (Pb 0.93 La 0.07)(Zr 0.82 Ti 0.18)O 3 (PLZT 7/82/18) anti-ferroelectric ceramics were studied for energy storage capacitor and pyroelectric applications. A systematic investigation demonstrated that the electric properties of PLZT 7/82/18 ceramics are affected significantly by the Mn-doping content. A maximum dielectric constant of ~2,128 at 1 kHz was found for 0.1% Mn-doped PLZT ceramics with a low dielectric loss of 0.018. The bipolar polarization versus electric field (P-E) hysteresis loops were traced for all compositions showing a typical anti-ferroelectric nature. The breakdown field was found to decrease with Mn-doping. The energy storage density and efficiency were found to be 460 J/cm 3 and ~63%, respectively, for 0.2% Mn-doped PLZT ceramics. The pyroelectric coefficient of PLZT ceramics shows an increase based on the amount of Mn-doping.
Korean Journal of Metals and Materials
ZnO/Ag/SnO 2 (ZAS) tri-layer films were prepared on glass substrates via RF and DC magnetron sput... more ZnO/Ag/SnO 2 (ZAS) tri-layer films were prepared on glass substrates via RF and DC magnetron sputtering, and then the influence of the thickness of the ZnO and SnO 2 layers on the optical and electrical properties of the ZAS films was investigated. As deposited ZnO 50 nm/Ag 10 nm/SnO 2 50 nm films showed a higher figure of merit, 1.08 × 10-2 Ω-1 , than the other films due to a high visible transmittance of 80.8% and a low resistivity of 1.21 × 10 −4 Ωcm. From the observed results, it can be concluded that the ZnO 50 nm/Ag 10 nm/SnO 2 50 nm tri-layer films can be used as a substitute for conventional transparent conducting oxide films in various opto-electrical applications.
Advanced materials (Deerfield Beach, Fla.), Jan 7, 2018
Following the celebrated discovery of graphene, considerable attention has been directed toward t... more Following the celebrated discovery of graphene, considerable attention has been directed toward the rich spectrum of properties offered by van der Waals crystals. However, studies have been largely limited to their 2D properties due to lack of 1D structures. Here, the growth of high-yield, single-crystalline 1D nanobelts composed of transition metal ditellurides at low temperatures (T ≤ 500 °C) and in short reaction times (t ≤ 10 min) via the use of tellurium-rich eutectic metal alloys is reported. The synthesized semimetallic 1D products are highly pure, stoichiometric, structurally uniform, and free of defects, resulting in high electrical performances. Furthermore, complete compositional tuning of the ternary ditelluride nanobelts is achieved with suppressed phase separation, applicable to the creation of unprecedented low-dimensional materials/devices. This approach may inspire new growth/fabrication strategies of 1D layered nanostructures, which may offer unique properties that...
Journal of the Korean Ceramic Society
As a case study on yttria stabilized zirconia ceramics, the sintering characteristics of submicro... more As a case study on yttria stabilized zirconia ceramics, the sintering characteristics of submicron powders and the granulation prepared by two-fluid spray drying of submicron particles were investigated. As-received powders of yttria stabilized zirconia particles were reduced to a uniform size of less than about 200 nm by repeated milling. Granulation size obtained by the two-fluid spray drying was affected by the organic matter and the primary particle size. Sintering behavior such as porosity, water absorption ratio, density, and transparency was influenced by processing conditions of the powder, and the discontinuous interfaces in a green body were reduced.
Journal of the Korean Ceramic Society
Bi 1/2 Na 1/2) 0.94 Ba 0.06 (Ti 1-x Nb x)O 3 (BNBTxNb) ceramics were investigated in terms of the... more Bi 1/2 Na 1/2) 0.94 Ba 0.06 (Ti 1-x Nb x)O 3 (BNBTxNb) ceramics were investigated in terms of the crystal structure as well as the ferroelectric, dielectric, and piezoelectric properties. While little change was observed in the microstructure except for a slight decrease in the average grain size, a significant change was noticed in the temperature dependence of dielectric and piezoelectric properties. It was shown that the property changes are closely related to the downward shift in the position of the ferroelectric-to-relaxor transition temperature with increasing amount of Nb doping. A special emphasis is put on the fact that Nb doping is so effective at decreasing the ferroelectric-to-relaxor transition temperature that even at no more than 2 at.% Nb addition, the transition temperature was already brought down slightly below room temperature, resulting in the birth of a large strain at 0.46 %, equivalent to S max /E max = 767 pm/V.
Korean Journal of Materials Research
In this study, nitrogen ions were implanted into STS 316L austenitic stainless steel by plasma im... more In this study, nitrogen ions were implanted into STS 316L austenitic stainless steel by plasma immersion ion implantation (PIII) to improve the corrosion resistance. The implantation of nitrogen ions was performed with bias voltages of −5, −10, −15, and −20 kV. The implantation time was 240 min and the implantation temperature was kept at room temperature. With nitrogen implantation, the corrosion resistance of 316 L improved in comparison with that of the bare steel. The effects of nitrogen ion implantation on the electrochemical corrosion behavior of the specimen were investigated by the potentiodynamic polarization test, which was conducted in a 0.5 M H 2 SO 4 solution at 70 o C. The phase evolution and texture caused by the nitrogen ion implantation were analyzed by an X-ray diffractometer. It was demonstrated that the samples implanted at lower bias voltages, i.e., 5 kV and 10 kV, showed an expanded austenite phase, γ N , and strong (111) texture morphology. Those samples exhibited a better corrosion resistance.
Korean Journal of Metals and Materials
Korean Journal of Materials Research, 2015
A simulation method to estimate microstructure dependent material properties and their influence ... more A simulation method to estimate microstructure dependent material properties and their influence on performance for a honeycomb structured SiC heating element has been established. Electrical and thermal conductivities of a porous SiC sample were calculated by solving a current continuity equation. ...
Journal of the European Ceramic Society, Sep 1, 2000
The eects of chromia (Cr 2 O 3) additions on the microstructural evolution and the mechanical pro... more The eects of chromia (Cr 2 O 3) additions on the microstructural evolution and the mechanical properties of alumina (Al 2 O 3) were investigated. When small amounts (<5 mol%) of Cr 2 O 3 were added in samples hot pressed at 1500 C, the grain size distribution became bimodal; large platelike grains were dispersed in a relatively small grained matrix. The large grains were composed of a core region that is free of Cr and a surrounding shell region rich in Cr. The interface between the core and the shell was composed of mis®t dislocations. The high diusion rate of Cr ions through the surface of alumina was attributed to this microstructural evolution. The mechanical properties of the specimens were strongly in¯uenced by this microstructural change. The fracture toughness and the¯aw tolerance (R-curve behavior) of Al 2 O 3 were improved markedly by the formation of the large platelike grains. The hardness and the elastic modulus also increased, however, the fracture strength decreased by the addition of Cr 2 O 3 .
Journal of the Korean Physical Society, 2015
ABSTRACT
Journal of Korean Powder Metallurgy Institute, 2012
Journal of Korean Powder Metallurgy Institute, 2011
Journal of the Korean institute of surface engineering, 2011
Journal of materials science. Materials in medicine, 2002
The effect of calcinations of starting powder on the mechanical properties of hydroxyapatite (HA)... more The effect of calcinations of starting powder on the mechanical properties of hydroxyapatite (HA)-based bioceramic composite was investigated. The calcinations of HA powder in air at 900 degrees C increased the crystallinity as well as the size of the powder. Ball milling after the calcinations was effective in eliminating large agglomerates in the powder. When the powder was mixed with reinforcing Al(2)O(3) powder, the mixture became fine and homogeneous. The flexural strength of HA-Al(2)O(3) composite was increased by the calcinations processes at all the Al(2)O(3) concentration. However, the fracture toughness was not much influenced by the calcinations. These results lead to the conclusion that the calcinations process effectively reduced the critical flaw size in the body by removing the agglomerates in the HA powder.
We investigated the effects of internal electrode composition on the reliability of low-firing mu... more We investigated the effects of internal electrode composition on the reliability of low-firing multilayer ceramic actuators using Ag internal electrodes. Ag–ceramic composite pastes were prepared by adding Pb(Mg1/3Nb2/3)O3–Pb(Zr0.475,Ti0.525)O3 (PMNZT) ceramic powders to a commercial Ag paste at concentraccepted 12 June 2009 vailable online 21 June 2009
Journal of the Korean Society of Manufacturing Technology Engineers
Journal of Asian Ceramic Societies
Films fabricated by aerosol deposition (AD) can be coated through interactions between the partic... more Films fabricated by aerosol deposition (AD) can be coated through interactions between the particles and substrate. Accelerated particles collide with the substrate, generating impact energy at the contact point. These interactions depend on the hardness of the substrate. This study examined the effects of the hardness of the substrate on the deposition behavior of thick glass films by AD. Substrates with different hardness, Al 2 O 3 , glass, and STS304, were used, and the film formation behavior was observed. The coating thickness of the initial layer was inversely proportional to the hardness of the substrate. The STS304 substrate exhibited a phase transition after the coating process that was induced by the strong impact energy. The film formation mechanism depending on the substrate hardness was proposed based on the microstructure of the interface between the film and substrate.
Journal of the Korean Ceramic Society
In this study, the dielectric and polarization properties of manganese (Mn% = 0.0, 0.1, 0.2, 0.5)... more In this study, the dielectric and polarization properties of manganese (Mn% = 0.0, 0.1, 0.2, 0.5) doped (Pb 0.93 La 0.07)(Zr 0.82 Ti 0.18)O 3 (PLZT 7/82/18) anti-ferroelectric ceramics were studied for energy storage capacitor and pyroelectric applications. A systematic investigation demonstrated that the electric properties of PLZT 7/82/18 ceramics are affected significantly by the Mn-doping content. A maximum dielectric constant of ~2,128 at 1 kHz was found for 0.1% Mn-doped PLZT ceramics with a low dielectric loss of 0.018. The bipolar polarization versus electric field (P-E) hysteresis loops were traced for all compositions showing a typical anti-ferroelectric nature. The breakdown field was found to decrease with Mn-doping. The energy storage density and efficiency were found to be 460 J/cm 3 and ~63%, respectively, for 0.2% Mn-doped PLZT ceramics. The pyroelectric coefficient of PLZT ceramics shows an increase based on the amount of Mn-doping.
Korean Journal of Metals and Materials
ZnO/Ag/SnO 2 (ZAS) tri-layer films were prepared on glass substrates via RF and DC magnetron sput... more ZnO/Ag/SnO 2 (ZAS) tri-layer films were prepared on glass substrates via RF and DC magnetron sputtering, and then the influence of the thickness of the ZnO and SnO 2 layers on the optical and electrical properties of the ZAS films was investigated. As deposited ZnO 50 nm/Ag 10 nm/SnO 2 50 nm films showed a higher figure of merit, 1.08 × 10-2 Ω-1 , than the other films due to a high visible transmittance of 80.8% and a low resistivity of 1.21 × 10 −4 Ωcm. From the observed results, it can be concluded that the ZnO 50 nm/Ag 10 nm/SnO 2 50 nm tri-layer films can be used as a substitute for conventional transparent conducting oxide films in various opto-electrical applications.
Advanced materials (Deerfield Beach, Fla.), Jan 7, 2018
Following the celebrated discovery of graphene, considerable attention has been directed toward t... more Following the celebrated discovery of graphene, considerable attention has been directed toward the rich spectrum of properties offered by van der Waals crystals. However, studies have been largely limited to their 2D properties due to lack of 1D structures. Here, the growth of high-yield, single-crystalline 1D nanobelts composed of transition metal ditellurides at low temperatures (T ≤ 500 °C) and in short reaction times (t ≤ 10 min) via the use of tellurium-rich eutectic metal alloys is reported. The synthesized semimetallic 1D products are highly pure, stoichiometric, structurally uniform, and free of defects, resulting in high electrical performances. Furthermore, complete compositional tuning of the ternary ditelluride nanobelts is achieved with suppressed phase separation, applicable to the creation of unprecedented low-dimensional materials/devices. This approach may inspire new growth/fabrication strategies of 1D layered nanostructures, which may offer unique properties that...
Journal of the Korean Ceramic Society
As a case study on yttria stabilized zirconia ceramics, the sintering characteristics of submicro... more As a case study on yttria stabilized zirconia ceramics, the sintering characteristics of submicron powders and the granulation prepared by two-fluid spray drying of submicron particles were investigated. As-received powders of yttria stabilized zirconia particles were reduced to a uniform size of less than about 200 nm by repeated milling. Granulation size obtained by the two-fluid spray drying was affected by the organic matter and the primary particle size. Sintering behavior such as porosity, water absorption ratio, density, and transparency was influenced by processing conditions of the powder, and the discontinuous interfaces in a green body were reduced.
Journal of the Korean Ceramic Society
Bi 1/2 Na 1/2) 0.94 Ba 0.06 (Ti 1-x Nb x)O 3 (BNBTxNb) ceramics were investigated in terms of the... more Bi 1/2 Na 1/2) 0.94 Ba 0.06 (Ti 1-x Nb x)O 3 (BNBTxNb) ceramics were investigated in terms of the crystal structure as well as the ferroelectric, dielectric, and piezoelectric properties. While little change was observed in the microstructure except for a slight decrease in the average grain size, a significant change was noticed in the temperature dependence of dielectric and piezoelectric properties. It was shown that the property changes are closely related to the downward shift in the position of the ferroelectric-to-relaxor transition temperature with increasing amount of Nb doping. A special emphasis is put on the fact that Nb doping is so effective at decreasing the ferroelectric-to-relaxor transition temperature that even at no more than 2 at.% Nb addition, the transition temperature was already brought down slightly below room temperature, resulting in the birth of a large strain at 0.46 %, equivalent to S max /E max = 767 pm/V.
Korean Journal of Materials Research
In this study, nitrogen ions were implanted into STS 316L austenitic stainless steel by plasma im... more In this study, nitrogen ions were implanted into STS 316L austenitic stainless steel by plasma immersion ion implantation (PIII) to improve the corrosion resistance. The implantation of nitrogen ions was performed with bias voltages of −5, −10, −15, and −20 kV. The implantation time was 240 min and the implantation temperature was kept at room temperature. With nitrogen implantation, the corrosion resistance of 316 L improved in comparison with that of the bare steel. The effects of nitrogen ion implantation on the electrochemical corrosion behavior of the specimen were investigated by the potentiodynamic polarization test, which was conducted in a 0.5 M H 2 SO 4 solution at 70 o C. The phase evolution and texture caused by the nitrogen ion implantation were analyzed by an X-ray diffractometer. It was demonstrated that the samples implanted at lower bias voltages, i.e., 5 kV and 10 kV, showed an expanded austenite phase, γ N , and strong (111) texture morphology. Those samples exhibited a better corrosion resistance.
Korean Journal of Metals and Materials
Korean Journal of Materials Research, 2015
A simulation method to estimate microstructure dependent material properties and their influence ... more A simulation method to estimate microstructure dependent material properties and their influence on performance for a honeycomb structured SiC heating element has been established. Electrical and thermal conductivities of a porous SiC sample were calculated by solving a current continuity equation. ...
Journal of the European Ceramic Society, Sep 1, 2000
The eects of chromia (Cr 2 O 3) additions on the microstructural evolution and the mechanical pro... more The eects of chromia (Cr 2 O 3) additions on the microstructural evolution and the mechanical properties of alumina (Al 2 O 3) were investigated. When small amounts (<5 mol%) of Cr 2 O 3 were added in samples hot pressed at 1500 C, the grain size distribution became bimodal; large platelike grains were dispersed in a relatively small grained matrix. The large grains were composed of a core region that is free of Cr and a surrounding shell region rich in Cr. The interface between the core and the shell was composed of mis®t dislocations. The high diusion rate of Cr ions through the surface of alumina was attributed to this microstructural evolution. The mechanical properties of the specimens were strongly in¯uenced by this microstructural change. The fracture toughness and the¯aw tolerance (R-curve behavior) of Al 2 O 3 were improved markedly by the formation of the large platelike grains. The hardness and the elastic modulus also increased, however, the fracture strength decreased by the addition of Cr 2 O 3 .
Journal of the Korean Physical Society, 2015
ABSTRACT
Journal of Korean Powder Metallurgy Institute, 2012
Journal of Korean Powder Metallurgy Institute, 2011
Journal of the Korean institute of surface engineering, 2011