Sang-Yeup Park

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James Marrow

University of Oxford

John Barry

Queen's University Belfast

Estela Blaisten-Barojas

George Mason University

David Seamon

Kansas State University

Petra Reinke

University of Virginia

Tomáš Dvořák

Academy of Performing Arts in Prague

Irina Kolesnik

Moscow State University

Iain Staffell

Imperial College London

amrit mandal

West Bengal University Of Technology

Prof. Mahendra S I N G H Sevda

Central Agricultural University (CAU), Imphal

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Papers by Sang-Yeup Park

Engineering thermally activated NiMoO4 nanoflowers and biowaste derived activated carbon-based electrodes for high-performance supercapatteries

Inorganic Chemistry Frontiers, 2019

NiMoO4 nanoflowers having pure crystalline phases with slight amorphous surface exhibited excelle... more

Si-Al-O-N 계에서 $Y_2O_3$ 첨가에 따른 상변화와 기계적 성질 = Phase changes and mechenical properties of Si-Al-O-N system with $Y_2O_3$ addition

Effect of Fluoride Additives on the Hydroxyapatite Laminate Composites

Ceramic transactions, Jul 6, 2011

Terahertz characterization of Y2O3-added AlN ceramics

Applied Surface Science, Dec 1, 2016

Abstract Terahertz optical and dielectric properties of AlN ceramics fabricated by hot pressed si... more Abstract Terahertz optical and dielectric properties of AlN ceramics fabricated by hot pressed sintering are investigated by THz time-domain spectroscopy in the frequency range of 0.2–3.5 THz. The measured properties of the pure AlN ceramic are compared with those of Y 2 O 3 -added AlN ceramic. Two prominent resonance modes, which are essentially responsible for the dielectric properties of the Y 2 O 3 -added AlN in terahertz regime, are characterized at ω TO1 / (2 π ) = 2.76 THz (92 cm −1 ) and ω TO2 / (2 π ) = 18.2 THz (605 cm −1 ) and are well described by the pseudo-harmonic oscillator model through theoretical fitting. The resonance ω TO1 at 2.76 THz is proposed to be due to the formation of a YAG (Y 3 Al 5 O 12 ) secondary phase in Y 2 O 3 -added AlN ceramic. From the experimental results, good correlation is observed between the prominent peak of YAG secondary phase at 2.76 THz and thermal conductivity. Additionally, there is a high correlation between densification and refractive index of AlN ceramics fabricated by hot pressed sintering.

Biocompatibility and the physical properties of bio-glass ceramics in the Na₂OCaO-SiO₂-P₂O5 system with CaF₂ and MgF₂ additives

Journal of Ceramic Processing Research, 2008

Biocompatibility of a new bio-glass composition was evaluated with the addition of fluorides, suc... more Biocompatibility of a new bio-glass composition was evaluated with the addition of fluorides, such as CaF2 and MgF2, for the substitution of Na2O in the conventional bio-glass composition (SiO2-CaO-Na2O-P2O5). Also, the physical properties of Na2OCaO-SiO2-P2O5 glass ceramics were investigated. When B2O3 (4 mol%) was added as a Na2O substitution, the thermal expansion coefficient was decreased in sintered samples (650-950 C). Compared to the low flexural strength (57 ± 3 MPa) and Vickers hardness (4.6 GPa) of sintered bio-glass ceramics without fluoride and B2O3 additions, new bio-glass ceramics substituted with 10 mol% MgF2 for Na2O showed more higher mechanical properties (flexural strength: 141 ± 5 MPa, Vickers hardness: 5.6 GPa). The thermal expansion coefficient of bio-glass ceramics due to the ion substitutions (Ca, Mg and B) was decreased from 16 × 10/ C to 9.4-10 × 10/ C (~400 C)

Effect of acetic acid in TiO2 paste on the performance of dye-sensitized solar cells

Ceramics International, 2012

Nanocrystalline TiO 2 films are considered as the most suitable photoelectrode for dye-sensitized... more Nanocrystalline TiO 2 films are considered as the most suitable photoelectrode for dye-sensitized solar cells (DSSCs). In the synthesis of TiO 2 paste, the effect of acetic acid on the properties of TiO 2 electrodes was investigated. The amount of acetic acid in the TiO 2 paste was varied from 1 mL to 30 mL. The synthesized TiO 2 pastes were deposited on fluorine-doped tin oxide (FTO) glass by doctor-blade method. The pore size was about 67.2 nm and pore volume was 79.34%. Photovoltaic measurements showed that the DSSC efficiency is limited by certain acetic acid content.

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In situ co-textured microstructure of alumina/alumina: Ca-hexaluminate multilayer composites

Ceramics International, 2001

Abstract In situ co-textured microstructure of alumina/alumina:Ca-hexaluminate multilayer composi... more Abstract In situ co-textured microstructure of alumina/alumina:Ca-hexaluminate multilayer composites has been investigated. Ca-hexaluminates, in situ grown in the presence of CaMgSiO 4 glass, showed a well-textured microstructure in Ca-hexaluminate/alumina multilayer composites. In situ texturing of Ca-hexaluminate was possible through the microstructure texturing of alumina using alumina platelets and CaMgSiO 4 glass. CaMgSiO 4 glass addition was effective for the in situ texturing of Ca-hexaluminates as well as the microstructure texturing of alumina. The in situ textured Ca-hexaluminate and alumina multilayer composites provide a well-controlled crack propagation because of crack shielding and crack deflection.

Phase formation and shape change of $Al_2O_3$ in silicate melts = 실리케이트 액상에서 알루미나의 입자 모양 변화와 새로운 상의 생성

Comparing Thermal and Chemical Decomposition of Up-Cycled Ammonium Paratungstate(APT)

Korean Journal of Materials Research, Jun 1, 2015

The possibility of using the chemical precipitation method of up-cycled ammonium paratungstate (A... more The possibility of using the chemical precipitation method of up-cycled ammonium paratungstate (APT) was studied and compared with the thermal decomposition method. WO 3 particles were synthesized by chemical precipitation method using a 1: 2 weight ratio of APT: Di-water. For thermal decomposition, APT powder was heated for 4h at 600 o C in air atmosphere. The reaction products were characterized by X-ray diffraction (XRD), X-ray fluorescence spectrometer (XRF), particle size analyzer (PSA), and field emission-scanning electron microscopy (FE-SEM). Thermogravimetric analysis (TGA) of the upcycled APT allowed for the identification of the sequence of decomposition and reduction reactions that occurred during the heat treatment. TGA data indicated a total weight loss of 10.78 % with the reactions completed in 658 o C. The XRD results showed that APT completely decomposed to WO 3 by thermal decomposition and chemical precipitation. The particle size of the synthesized WO 3 powders by thermal decomposition with 2 h of planetary milling was around 2 µm. During the chemical precipitation process, the particle size of the synthesized WO 3 powders showed a round-shape with ~0.6 µm size.

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Influence of a liquid phase on the microstructure development of Al2O3

Journal of Materials Science Letters, 1996

Mullite/zirconia laminate composites for high temperature application

Journal of The European Ceramic Society, Dec 1, 2000

Mullite/zirconia laminate composites were studied for a better understanding of crack formation a... more Mullite/zirconia laminate composites were studied for a better understanding of crack formation and crack propagation behavior at the interface of laminates. The laminate composites were fabricated by tape casting method and hot-pressing. It was demonstrated that the thermal mismatch stress was closely related to the crack formation and crack deflection behavior in the mullite/zirconia laminate composites. Two kinds of cracks were observed in zirconia layers; one is channel cracks in layers subjected to tensile stress, the other is the edge cracks in layers subjected to compressive stress. Among three forms of zirconia (monoclinic, tetragonal, cubic) tetragonal zirconia was effective to deflect the crack at the interface due to the stress induced tetra-mono phase transformation.

Formation of CaO-6Al2O3 and MgAl2O4 during dissolution of Al2O3 into CaMgSiO4 melt

Journal of Materials Science Letters, 1992

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Shape of MgAl2O4Grains in a CaMgSiAlO Glass Matrix

Journal of the American Ceramic Society, 1992

When sintered Al2O3 is annealed with CaMgSiAlO glass at 1600°C, polyhedral MgAl2O4 grains form an... more When sintered Al2O3 is annealed with CaMgSiAlO glass at 1600°C, polyhedral MgAl2O4 grains form and glass pockets are entrapped within the grains. After annealing for 13 h at 1600°C, the liquid pockets show a regular octahedron shape which is expected to represent the equilibrium shape. All grain surfaces in contact with the glass matrix show the same shape. The small grains, which must be shrinking, thus have the equilibrium shape, because their shrinkage shape is is identical to the equilibrium and growth shape. However, the octahedral shape also represents the growth shape for the growing large grains. The grains also form grain boundaries with neighboring grains.

High electrochemical capacitor performance of oxygen and nitrogen enriched activated carbon derived from the pyrolysis and activation of squid gladius chitin

Journal of Power Sources, 2018

• A novel O-and N-doped activated carbon is derived from squid gladius chitin. • The microporous ... more • A novel O-and N-doped activated carbon is derived from squid gladius chitin. • The microporous carbon is used for the fabrication of supercapacitor electrodes. • The supercapacitors demonstrated remarkable electrochemical performances. • The device shows long stability of ∼100% after 25,000 charge/discharge cycles.

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Mullite/zirconia laminate composites for high temperature application

Journal of the European Ceramic Society, 2000

Effect of grain orientation on abnormal grain growth in Ba-hexaferrite

Ceramics International, 2001

Abstract The nucleation and growth behavior of Ba-hexaferrite has been observed and explained in ... more Abstract The nucleation and growth behavior of Ba-hexaferrite has been observed and explained in terms of grain orientation due to liquid phase. It has been observed that the nuclei formation for abnormal grain growth was driven by the capillary force due to the liquid phase. A strong orientation of small grains was observed within abnormal grains in materials obtained using BaB 2 O 4 as a sintering aid. The microstructural orientation of Ba-hexaferrite observed in this study was in good agreement with the X-ray diffraction analysis based on the peak intensity of the (107) plane.

The effect of starting powder on the microstructure development of alumina–aluminum titanate composites

Ceramics International, 2003

The effect of starting powder on Al2TiO5 morphology and grain growth of Al2O3 was investigated in... more The effect of starting powder on Al2TiO5 morphology and grain growth of Al2O3 was investigated in alumina–aluminum titanate composites using Al2O3, TiO2 and calcined Al2TiO5 as starting powders. Depending on the composition of starting powders, various Al2TiO5 morphologies, such as rod-like, polyhedron-like, and irregular shape were observed. When Al2O3 and TiO2 were used as starting powder, the rod-like shape and the irregular shape of Al2TiO5 were observed. In the addition of calcined Al2TiO5 as starting powder, however, the polyhedron-like shape and the irregular shape of Al2TiO5 were observed. When the starting powder was consisted of Al2O3 and TiO2, alumina-aluminum titanate composites provided more narrow size distribution and smaller average size of Al2O3 grains compared to those consisting of Al2O3 and Al2TiO5.

Effect of acetic acid in TiO2 paste on the performance of dye-sensitized solar cells

Ceramics International, 2012

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Effect of fluoride additive on the mechanical properties of hydroxyapatite/alumina composites

Ceramics International, 2009

Abstract The effect of fluoride additives on the mechanical properties of hydroxyapatite/alumina ... more Abstract The effect of fluoride additives on the mechanical properties of hydroxyapatite/alumina composites was investigated. When MgF 2 (5 vol%) was added to hydroxyapatite/alumina composites, the decomposition of hydroxyapatite was suppressed due to the substitution of F − for OH − in the crystal structure. Comparing two additives, such as MgF 2 and CaF 2 , MgF 2 showed much more effective for the suppression of phase decomposition in the hydroxyapatite/alumina composites due to the enhanced substitution of F − for OH − . In the case of MgF 2 addition, a relatively high-mechanical properties (flexural strength: ∼170 MPa; Vickers hardness: ∼7 GPa) was obtained compared to MgF 2 -free composites.

Effect of Silicate Addition on the Microstructure Texturing of Alumina Laminate Composites

Materials Science Forum, 2003

Effect of silicate compositions on the microstructure texturing of alumina laminate composites wa... more Effect of silicate compositions on the microstructure texturing of alumina laminate composites was investigated to enhance the damage tolerance behavior. The grain orientation of textured alumina layer was confirmed by XRD peaks at (006) plane and (1010) plane. Compared to the CaAl 2 Si 2 O 8 (anorthite) addition, the orientation angle in textured alumina layer showed more narrow distribution in the CaMgSiO 4 (monticellite) addition. From the indentation pattern, microstructure textured alumina laminates exhibited an effective crack deflection pattern at the interface of the textured/untextured laminates.

Engineering thermally activated NiMoO4 nanoflowers and biowaste derived activated carbon-based electrodes for high-performance supercapatteries

Inorganic Chemistry Frontiers, 2019

NiMoO4 nanoflowers having pure crystalline phases with slight amorphous surface exhibited excelle... more

Si-Al-O-N 계에서 $Y_2O_3$ 첨가에 따른 상변화와 기계적 성질 = Phase changes and mechenical properties of Si-Al-O-N system with $Y_2O_3$ addition

Effect of Fluoride Additives on the Hydroxyapatite Laminate Composites

Ceramic transactions, Jul 6, 2011

Terahertz characterization of Y2O3-added AlN ceramics

Applied Surface Science, Dec 1, 2016

Biocompatibility and the physical properties of bio-glass ceramics in the Na₂OCaO-SiO₂-P₂O5 system with CaF₂ and MgF₂ additives

Journal of Ceramic Processing Research, 2008

Effect of acetic acid in TiO2 paste on the performance of dye-sensitized solar cells

Ceramics International, 2012

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In situ co-textured microstructure of alumina/alumina: Ca-hexaluminate multilayer composites

Ceramics International, 2001

Phase formation and shape change of $Al_2O_3$ in silicate melts = 실리케이트 액상에서 알루미나의 입자 모양 변화와 새로운 상의 생성

Comparing Thermal and Chemical Decomposition of Up-Cycled Ammonium Paratungstate(APT)

Korean Journal of Materials Research, Jun 1, 2015

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Influence of a liquid phase on the microstructure development of Al2O3

Journal of Materials Science Letters, 1996

Mullite/zirconia laminate composites for high temperature application

Journal of The European Ceramic Society, Dec 1, 2000

Formation of CaO-6Al2O3 and MgAl2O4 during dissolution of Al2O3 into CaMgSiO4 melt

Journal of Materials Science Letters, 1992

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Shape of MgAl2O4Grains in a CaMgSiAlO Glass Matrix

Journal of the American Ceramic Society, 1992

High electrochemical capacitor performance of oxygen and nitrogen enriched activated carbon derived from the pyrolysis and activation of squid gladius chitin

Journal of Power Sources, 2018

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Mullite/zirconia laminate composites for high temperature application

Journal of the European Ceramic Society, 2000

Effect of grain orientation on abnormal grain growth in Ba-hexaferrite

Ceramics International, 2001

The effect of starting powder on the microstructure development of alumina–aluminum titanate composites

Ceramics International, 2003

Effect of acetic acid in TiO2 paste on the performance of dye-sensitized solar cells

Ceramics International, 2012

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Effect of fluoride additive on the mechanical properties of hydroxyapatite/alumina composites

Ceramics International, 2009

Effect of Silicate Addition on the Microstructure Texturing of Alumina Laminate Composites

Materials Science Forum, 2003

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