• Fibers and Polymers
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• v.5 no.4
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• pp.280-288
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• 2004

Split-type nylon/polyester microfiber and polyester microfiber fabrics possess drapeability, softness, bulkiness, and smoothness, so that they can be applied in various industrial fields. In particular, these fabrics are able to absorb various organic solvents, and can be used as clean room materials. To investigate the chemical affinity between solvents and the compositional materials of these fabrics, the contact angle of thermally pressed film fabrics was measured with different solvents. The thermally pressed nylon/polyester fabric films showed a chemical attraction to formamide. The sorption properties of the microfiber fabrics were investigated using a real time testing device, and these tests showed that the sorption behavior was more influenced by the structure of the fibrous assembly than by any chemical attraction. The effect of the fabric density, specific weight, and sample structure on the sorption capacity and rate was examined for various organic solvents. The sorption capacity was influenced by the density and the specific weight of the fibrous assembly, and knitted fabric showed a higher sorption capacity than woven fabric. However, the sorption rate was less affected in lower viscosity solvents. On applying Poiseuille's Law, the lower viscosity solvents showed higher initial sorption rates, and more easily penetrated into the fibrous assembly.

• Journal of the Korean Physical Society
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• v.73 no.10
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• pp.1535-1540
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• 2018

In this study, we prepared and characterized Nb-doped $Li_7La_3Zr_{2-x}O_{12}$ (LLZNO) powder and pellets with a cubic garnet structure by using a modified sol-gel synthesis and hot pressing. LLZNO powder with a very small grain size and cubic structure without secondary phases could be obtained by using a synthesis method in which Li and La sources in a propanol solvent were mixed together with Zr and Nb sources in 2-methoxy ethanol. A pure cubic phase LLZNO pellet could be fabricated from the prepared LLZNO and an additional 6-wt% of $Li_2CO_3$ powder by hot pressing at $1050^{\circ}C$ and 15.8 MPa. The hot-pressed LLZNO pellet with a relative density of 99% exhibited a very dense surface morphology. The total Li ionic conductivity of the hot-pressed LLZNO was $7.4{\times}10^{-4}S/cm$ at room temperature, which is very high level compared to other reported values. The activation energy for ionic conduction was estimated to be 0.40 eV.

• Bulletin of the Korean Chemical Society
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• v.32 no.1
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• pp.263-272
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• 2011

Highly luminescent and monodisperse InP quantum dots (QDs) were prepared by a non-organometallic approach in a non-coordinating solvent. Fatty acids with well-defined chain lengths as the ligand, a non coordinating solvent, and a thorough degassing process are all important factors for the formation of high quality InP QDs. By varying the molar concentration of indium to ligand, QDs of different size were prepared and their absorption and emission behaviors studied. By spin-coating a colloidal solution of InP QD onto a silicon wafer, InP QD thin films were obtained. The thickness of the thin films cured at 60 and $200^{\circ}C$ were nearly identical (approximately 860 nm), whereas at $300^{\circ}C$, the thickness of the thin film was found to be 760 nm. Different contrast regions (A, B, C) were observed in the TEM images, which were found to be unreacted precursors, InP QDs, and indium-rich phases, respectively, through EDX analysis. The optical properties of the thin films were measured at three different curing temperatures (60, 200, $300^{\circ}C$), which showed a blue shift with an increase in temperature. It was proposed that this blue shift may be due to a decrease in the core diameter of the InP QD by oxidation, as confirmed by the XPS studies. Oxidation also passivates the QD surface by reducing the amount of P dangling bonds, thereby increasing luminescence intensity. The dielectric properties of the thin films were also investigated by capacitance-voltage (C-V) measurements in a metal-insulator-semiconductor (MIS) device. At 60 and $300^{\circ}C$, negative flat band shifts (${\Delta}V_{fb}$) were observed, which were explained by the presence of P dangling bonds on the InP QD surface. At $300^{\circ}C$, clockwise hysteresis was observed due to trapping and detrapping of positive charges on the thin film, which was explained by proposing the existence of deep energy levels due to the indium-rich phases.

• Journal of Adhesion and Interface
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• v.25 no.1
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• pp.157-161
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• 2024

Amphiphilic gold nanoparticles, synthesized by the simultaneous binding of hydrophilic and hydrophobic ligands on their surfaces, find diverse applications in energy, bio, optical, electronic technologies, and various other fields. Particularly, these amphiphilic gold nanoparticles possess both hydrophilic and hydrophobic characteristics, enabling them to activate interface at the interface of immiscible fluids and form organized structures. The surface properties of gold nanoparticles play a crucial role in influencing the behaviors of amphiphilic gold nanoparticles at the interface of two fluids. Therefore, this study investigated the adsorption behaviors of gold nanoparticles at the organic solvent-water interface based on the surface characteristics of amphiphilic gold nanoparticles and the type of organic solvents. It was observed that the amount of adsorbed gold nanoparticles at the interface increased with the length of hydrocarbon chains in hydrophobic ligands and increased with shorter hydrocarbon chains in the organic solvent. Furthermore, using the Langmuir isotherm model, the study confirmed the formation of a monolayer by amphiphilic gold nanoparticles and obtained significant thermodynamic parameters simultaneously.

• Applied Chemistry for Engineering
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• v.21 no.3
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• pp.328-332
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• 2010

In this study, porous ZnO sphere and Cu-ZnO composite were synthesized by coprecipitation method in diethylene glycol solvent. The physicochemical properties of as-prepared composite materials were characterized by SEM, XRD, $N_2$-sorption and $H_2$-TPR. A series of porous Cu-ZnO with different Cu contents (0, 6.6, 21.3, 36.4, 54.6, 77.8 wt%) was investigated for CO oxidation activity in a fixed bed reactor system. With increasing Cu content in Cu-ZnO the surface area and micropore volume of Cu-ZnO are decreased and Cu (36.4 wt%)-ZnO shows higher activity for CO oxidation compared to the others.

• Clean Technology
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• v.17 no.4
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• pp.300-305
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• 2011

A mixture of supercritical carbon dioxide and a co-solvent was employed to strip a high-dose ion-implanted photoresist (HDIPR) from the surface of semiconductor wafers. The stripping efficiency was highly improved by the physical force generated from a ultrasonication tip inside the reactor. In addition, helium gas was injected in the reactor as a barrier gas before the introduction of pure supercritical $CO_2$ ($scCO_2$), which reduced the rinsing time significantly. The effect of co-solvents on the stripping efficiency was investigated. The wafer surfaces were analyzed by scanning electron microscopy and by an energy dispersive X-ray spectrometer.

• Journal of the Korean Electrochemical Society
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• v.15 no.3
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• pp.190-197
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• 2012

We employed the vinyl ethylene carbonate (VEC) as an electrolyte additive and investigated the effect of the electrolyte additive on the electrochemical performance in hybrid capacitor. The activated carbon was adopted as cathode material, and the $Li_4Ti_5O_{12}$ oxide was used as anode material. The electrolyte was prepared with the $LiPF_6$ salt in the mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate(EMC). We evaluated the electrochemical performance of the hybrid capacitor with increasing the amount of the VEC electrolyte additive, which is known as the remover of oxygen functional group and the stabilizer of the electrode by reducing the surface of electrode, and obtained the superior performance data especially at the addition of the VEC electrolyte additive of around 0.7 vol%. On the contrary, the addition of the VEC more than 0.7 vol% in the electrolyte leads to the degradation in electrochemical performance of hybrid capacitor, suggesting the increase of the side reaction from the excessive VEC additive. X-ray photoelectron spectroscopy (XPS) revealed that the addition of the VEC suppressed the formation of LiF component, which is known as the insulator, on the surface of electrode. The optimized addition of VEC exhibited the improved capacity retention around 82.7% whereas the bare capacitors without VEC additive showed the 43.2% of capacity retention after 2500 cycling test.

• Korean Chemical Engineering Research
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• v.49 no.2
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• pp.211-217
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• 2011

In this study, ion exchange membranes were prepared using high impact polystyrene(HIPS) with various crosslinking and sulfonation time. Degree of sulfonation(DS) of sulfonated HIPS(SHIPS) membrane was increased with sulfonation time and decreased with crosslinking time. The highest value of DS was 66%. Also, water uptake and ion exchange capacity(IEC) of SHIPS membrane were decreased with degree of crosslinking and increased with sulfonation time. Then their values were 35.2% and 1.55 meq/g, respectively. Electrical resistance and ion conductivity of the membranes were showed more excellent value with sulfonation time. The maximum value of electrical resistance and ion conductivity were $0.4\Omega{\cdot}cm^{2}$ and 0.1 S/cm, respectively. It is indicated that the SHIPS membrane has the higher performance compare with Nafion 117. Durability of SHIPS membranes in a organic solvent was increased with increasing crosslinking time. The surface roughness of HIPS membranes were confirmed with SEM that was become uneven surface with progressing sulfonation.

• Membrane Journal
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• v.26 no.1
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• pp.76-85
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• 2016

Fabrication of polysulfone (PSf) hollow fiber membranes was investigated for the separation of $N_2/NF_3$ gas mixtures, which are emitted from the display and the semiconductor industries. A combination of the non-solvent induced phase separation (NIPS) and the vapor-induced phase separation (VIPS) technique was applied to develop high flux hollow fiber membranes. Thin polymer layers were further coated onto the surface of the hollow fiber membranes by using polydimethylsiloxiane (PDMS) or Teflon AF1600(R), which contributes to improve the $N_2/NF_3$ selectivity. The $N_2/NF_3$ separation performances of our PSf hollow fiber membranes were determined by the intrinsic properties of coating materials. Especially, the PSf hollow fiber membrane coated with Teflon AF 1600(R) exhibited a higher $N_2/NF_3$ selectivity (> 14) with a slightly lower $N_2$ permeance (4.5 GPU), as compared to the commercial PSf counterparts. This feature provides a good potential as a membrane structure to separate $N_2/NF_3$.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.65-65
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• 2012

Copper zinc tin sulfide ($Cu_2ZnSnS_4$, CZTS) is a very promising material as a low cost absorber alternative to other chalcopyrite-type semiconductors based on Ga or In because of the abundant and economical elements. In addition, CZTS has a band-gap energy of 1.4~1.5eV and large absorption coefficient over ${\sim}10^4cm^{-1}$, which is similar to those of $Cu(In,Ga)Se_2$(CIGS) regarded as one of the most successful absorber materials for high efficient solar cell. Most previous works on the fabrication of CZTS thin films were based on the vacuum deposition such as thermal evaporation and RF magnetron sputtering. Although the vacuum deposition has been widely adopted, it is quite expensive and complicated. In this regard, the solution processes such as sol-gel method, nanocrystal dispersion and hybrid slurry method have been developed for easy and cost-effective fabrication of CZTS film. Among these methods, the hybrid slurry method is favorable to make high crystalline and dense absorber layer. However, this method has the demerit using the toxic and explosive hydrazine solvent, which has severe limitation for common use. With these considerations, it is highly desirable to develop a robust, easily scalable and relatively safe solution-based process for the fabrication of a high quality CZTS absorber layer. Here, we demonstrate the fabrication of a high quality CZTS absorber layer with a thickness of 1.5~2.0 ${\mu}m$ and micrometer-scaled grains using two different non-vacuum approaches. The first solution-processing approach includes air-stable non-toxic solvent-based inks in which the commercially available precursor nanoparticles are dispersed in ethanol. Our readily achievable air-stable precursor ink, without the involvement of complex particle synthesis, high toxic solvents, or organic additives, facilitates a convenient method to fabricate a high quality CZTS absorber layer with uniform surface composition and across the film depth when annealed at $530^{\circ}C$. The conversion efficiency and fill factor for the non-toxic ink based solar cells are 5.14% and 52.8%, respectively. The other method is based on the nanocrystal dispersions that are a key ingredient in the deposition of thermally annealed absorber layers. We report a facile synthetic method to produce phase-pure CZTS nanocrystals capped with less toxic and more easily removable ligands. The resulting CZTS nanoparticle dispersion enables us to fabricate uniform, crack-free absorber layer onto Mo-coated soda-lime glass at $500^{\circ}C$, which exhibits a robust and reproducible photovoltaic response. Our simple and less-toxic approach for the fabrication of CZTS layer, reported here, will be the first step in realizing the low-cost solution-processed CZTS solar cell with high efficiency.