• Journal of the Korean Electrochemical Society
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• v.22 no.4
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• pp.164-171
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• 2019

Nano-sized $SnO_2$ powders were synthesized via a solvent thermal reaction using $SnClO_4$, NaOH, and ethylene glycol at $150^{\circ}C$. TGA, SEM, FT-IR, XRD, and Potentiostat/Galvanostat were employed to investigate the chemical and electrochemical characteristics of the synthesized $SnO_2$. The structure of $SnO_2$ was amorphous, and when heat treated at $500^{\circ}C$, it was transformed into a crystalline structure. The morphology obtained by SEM micrographs of the as-synthesized $SnO_2$ showed powder features that had diameters ranging 100 to 200 nm. The electrochemical performance of the crystalline $SnO_2$ as a Li-air battery cathode was better than that of the amorphous $SnO_2$. The specific capacity of the crystalline $SnO_2$ was at least 350 mAh/g at 10 mA/g discharge rate. However, there was some capacity loss of all the cells during the consecutive cycles. Keywords : Lithium-Air Battery.

• Korean Chemical Engineering Research
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• v.57 no.2
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• pp.259-266
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• 2019

Tuning of electro-optical properties of nano-structured $SnO_2:Ga$ powders in a micro drop fluidized reactor (MDFR) was highly effective to enhance the activities of powders to be used as sensor materials. The tuning was conducted continuously in a facile one-step process during the formation of powders. The microscopic hydrodynamic forces affected the band gap structure and charge transfer of $SnO_2:Ga$ powders through the oxygen and interfacial tin vacancies by providing plausible pyro-hydraulic conditions, which resulted in the decrease in the electrical resistance of the materials. The analyses of room-temperature photoluminescence (PL) spectra and FT-IR exhibited that the tuning could improve the surface activities of $SnO_2:Ga$ powders by adjusting the excitation as well as separation of electrons and holes, thus maximizing the oxygen vacancies at the surface of the powders. The scheme of photocatalytic mechanism of $SnO_2:Ga$ powders was also discussed.

• Journal of Sensor Science and Technology
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• v.28 no.2
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• pp.127-132
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• 2019

In this study, the fabrication of through-silicon vias (TSVs) filled with SWNTs/Sn by utilizing surface/bulk micromachining and MEMS technologies is proposed. Tin (Sn) and single-walled nanotube (SWNT) powders are used as TSV interconnector materials in the development of a novel TSV at low temperature. The measured resistance of a TSV filled with SWNT/Sn powder is considerably reduced by increasing the fraction of Sn and is lower than that of a TSV filled with only Sn. This is because of a decrease in the surface scattering of electrons along with an increase in the grain size of sintered SWNTs/Sn. The proposed method is conducted at low temperatures (< $400^{\circ}C$) due to the low melting temperature of Sn; hence, the proposed TSVs filled with SWNTs/Sn can be utilized in CMOS based applications.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.869-873
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• 2002

$Cu_2ZnSnS_4$ (CZTS) thin film is one of the candidate materials for the solar cell. It has an excellent optical absorption coefficient as well as appropriate 1.4~1.5eV band gap. The purpose of this study is replacing a half of high-cost Indium(In) atoms with low-cost Zinc(Zn) atoms and the other half with low-cost Tin(Sn) atoms in the lattice of CIS. In annealing process of thin films deposited with mixture target, the thin films were appeared the peeling. The resistivity was decreased. Thin films were deposited on ITO glass substrates using a compound target which were made by $CU_2S$, ZnS, $SnS_2$ powder were sintered in the atmosphere of Al at room temperature by rf magnetron sputtering We investigated potentialities of a low-cost material for the solar cell by measuring of thin film composition, the structure and optical properties. We could get an appropriate $Cu_2ZnSnS_4$ composition A (112) preferred orientation was appeared without annealing temperature as shown in the diffraction peaks of the CIS cells and was available for photovoltaic thin film materials. The band gap increased from 1.4 to 1.7eV as the composition ratio of Zn/Sn.. The optical absorption coefficient of the thin film was above $10^4cm^{-1}$.

• Electronics and Telecommunications Trends
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• v.35 no.4
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• pp.1-10
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• 2020

Since the 1960s, semiconductor packaging technology has developed into electrical joining techniques using lead frames or C4 bumps using tin-lead solder compositions based on traditional reflow processes. To meet the demands of a highly integrated semiconductor device, high reliability, high productivity, and an eco-friendly simplified process, packaging technology was required to use new materials and processes such as lead-free solder, epoxy-based non cleaning interconnection material, and laser based high-speed processes. For next generation semiconductor packaging, the study status of two epoxy-based interconnection materials such as fluxing and hybrid underfills along with a laser-assisted bonding process were introduced for fine pitch semiconductor applications. The fluxing underfill is a solvent-free and non-washing epoxy-based material, which combines the underfill role and fluxing function of the Surface Mounting Technology (SMT) process. The hybrid underfill is a mixture of the above fluxing underfill and lead-free solder powder. For low-heat-resistant substrate applications such as polyethylene terephthalate (PET) and high productivity, laser-assisted bonding technology is introduced with two epoxy-based underfill materials. Fluxing and hybrid underfills as next-generation semiconductor packaging materials along with laser-assisted bonding as a new process are expected to play an active role in next-generation large displays and Augmented Reality (AR) and Virtual Reality (VR) markets.

• Journal of the Korean institute of surface engineering
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• v.35 no.1
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• pp.39-46
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• 2002

$Cu_2$$ZnSnS_4$(CZTS) thin film is one of the candidate materials for the solar cell. It has an excellent optical absorption coefficient as well as appropriate 1.4~1.5eV band gap. The purpose of this study is replacing a half of high-cost Indium(In) atoms with low-cost Zinc(Zn) atoms and the other half with low-cost Tin(Sn) atoms in the lattice of CIS. Thin films were deposited on ITO glass substrates using a compact target which were made by $Cu_2$S, ZnS, SnS$_2$ powder at room temperature by rf magnetron sputtering and were annealed in the atmosphere of Ar and $S_2$(g). We investigated potentialities of a low-cost material for the solar cell by measuring of thin film composition, the structure and optical properties. We could get an appropriate $Cu_2$$ZnSnS_4$ composition. Structure was coarsened with increasing temperature and (112), (200), (220), (312) planes appeared to conform to all the reflection Kesterite structure. A (112) preferred orientation was advanced with increasing the annealing temperature as shown in the diffraction peaks of the CIS cells and was available for photovoltaic thin film materials. The band gap increased from 1.51 to 1.8eV as the annealing temperature increased. The optical absorption coefficient of the thin film was about $10^4$$cm^{-1}$.

• Journal of Sensor Science and Technology
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• v.31 no.6
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• pp.455-460
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• 2022

Brush-like ZnO hierarchical nanostructures decorated with MgxZn1-xO (x = 0.1, 0.2, 0.3, 0.4, and 0.5) were fabricated and examined for application to a gas sensor. They were synthesized using vapor phase growth (VPG) on indium tin oxide (ITO) substrates. To generate electronic accumulation at ZnO surface, MgZnO nanoparticles were prepared by sol-gel method, and the ratio of Mg and Zn was adjusted to optimize the device for NO₂ gas detection. As the electrons in the accumulation layer generated by the heterojunction reacted faster and more frequently with the gas, the sensitivity and speed improved. When tested as sensing materials for gas sensors at 100 ppm NO₂ at 300℃, these MgZnO decorated ZnO nanostructures exhibited an improvement from 165 to 514 times compared to pristine ZnO. The response and recovery time of the MgZnO decorated ZnO samples were shorter than those of the pristine ZnO. Various analyzing techniques, including field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray powder diffraction (XRD) were employed to confirm the growth morphology, atomic composition, and crystalline information of the samples, respectively.

• Journal of the Korean Ceramic Society
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• v.53 no.4
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• pp.393-399
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• 2016

We have successfully fabricated 3D (3-dimensional) nanostructures of $TiO_2$ coated with a $g-C_3N_4$ layer via hydrothermal and sintering methods to enhance photoelectrochemical (PEC) performance. Due to the coupling of $TiO_2$ and $g-C_3N_4$, the nanostructures exhibited good performance as the higher conduction band of $g-C_3N_4$, which can be combined with $TiO_2$. To fabricate 3D nanostructures of $g-C_3N_4/TiO_2$, $TiO_2$ was first grown as a double layer structure on FTO (Fluorine-doped tin oxide) substrate at $150^{\circ}C$ for 3 h. After this, the $g-C_3N_4$ layer was coated on the $TiO_2$ film at $520^{\circ}C$ for 4 h. As-prepared samples were varied according to loading of melamine powder, with values of loading of 0.25 g, 0.5 g, 0.75 g, and 1 g. From SEM and TEM analysis, it was possible to clearly observe the 3D sample morphologies. From the PEC measurement, 0.5 g of $g-C_3N_4/TiO_2$ film was found to exhibit the highest current density of $0.12mA/cm^2$, along with a long-term stability of 5 h. Compared to the pristine $TiO_2$, and to the 0.25 g, 0.75 g, and 1 g $g-C_3N_4/TiO_2$ films, the 0.5 g of $g-C_3N_4/TiO_2$ sample was coated with a thin $g-C_3N_4$ layer that caused separation of the electrons and the holes; this led to a decreasing recombination. This unique structure can be used in photoelectrochemical applications.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.5
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• pp.191-198
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• 2018

SnSb alloy powders with excess Sn or Sb are fabricated by the high energy ball-milling of pure Sn and Sb powders with different Sn/Sb molar ratios, and then their material properties and lithium electrochemical performances are investigated. It is revealed by X-ray diffraction that SnSb alloys are successfully synthesized, and the powder size is decreased via ball-milling. Charge-discharge test using a coin-cell shows that the best result, in terms of the cyclability and the capacity after 50 cycles, comes from the electrode composed of Sn : Sb = 4 : 6, i.e. the capacity of $580mAh\;g^{-1}$ after 50 cycles. When the electrode is composed of Sn : Sb = 3 : 7, however, the capacity is noticeably decreased by the restrained Sn reaction with Li-ion. The pure SnSb alloy powders (Sn : Sb = 5 : 5) results in the second best performance. In the case of Sn-rich SnSb alloys, the initial capacity is relatively high, but the capacity is quickly fading after 20 cycles.

• Journal of Conservation Science
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• v.36 no.2
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• pp.123-142
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• 2020

We attempted an experimental study of lost-wax casting to reconstruct the Gilt-bronze pensive Bodhisattva; The main object we aimed to reconstruct was the Korean national treasure No.83, Gilt-bronze pensive Bodhisattva(Maitreya); thus, we scientifically analyzed and measured the alloy ratio and casting method. Initially, the alloy ratio we used during the preliminary experiment was Cu:Sn:Pb = 95.5:4.0:0.5; we then increased tin and lead by 2.5% to consider vaporization during the main experiment. After applying lost-wax casting, we realized that 30% rosin contributed to proper hardness after the wax hardness experiment. The microstructure revealed normal casting character(α-Cu, δ), and the results of the chemical analysis are identical to those of previous studies. The analysis of the mold suggests the presence of quartz powder for structural stability and fire-resistance along with other organic materials whose contribution is still unknown. We expect that our research will serve to provide basic data for advanced studies in the future.