• Korean Journal of Materials Research
• /
• v.16 no.3
• /
• pp.178-182
• /
• 2006

A single electro-discharge-sintering (EDS) pulse (1.0 kJ/0.7 g), from a $300{\mu}F$ capacitor, was applied to atomized spherical Ti-6Al-4V powder in a low vacuum to produce porous-surfaced implant compacts. A solid core surrounded by a porous layer was formed by a discharge in the middle of the compact. XPS (X-ray photoelectron spectroscopy) was used to study the surface characteristics of the implant material. C, O, and Ti were the main constituents, with smaller amounts of Al, V, and N. The implant surface was lightly oxidized and was primarily in the form of $TiO_2$ with a small amount of metallic Ti. A lightly etched EDS implant sample showed the surface form of metallic Ti, indicating that EDS breaks down the oxide film of the as-received Ti-6Al-4V powder during the discharge process. The EDS Ti-6Al-4V implant surface also contained small amounts of aluminum oxide in addition to $TiO_2$. However, V detected in the EDS Ti-6Al-4V implant surface, did not contribute to the formation of the oxide film..

• Applied Chemistry for Engineering
• /
• v.31 no.3
• /
• pp.291-298
• /
• 2020

ZITO/Ag/ZITO multilayer transparent electrodes at room temperature on glass substrates were prepared using RF/DC magnetron sputtering. Transparent conductive films with a sheet resistance of 9.4 Ω/㎡ and a transmittance of 83.2% at 550 nm were obtained for the multilayer structure comprising ZITO/Ag/ZITO (100/8/42 nm). The sheet resistance and transmittance of ZITO/Ag/ZITO multilayer films meant that they would be highly applicable for use in polymer-dispersed liquid crystal (PDLC)-based smart windows due to the ability to effectively block infrared rays (heat rays) and thereby act as an energy-saving smart glass. Effects of the thickness of the PDLC layer and the intensity of ultraviolet light (UV) on electro-optical properties, photopolymerization kinetics, and morphologies of difunctional urethane acrylate-based PDLC systems were investigated using new transparent conducting electrodes. A PDLC cell photo-cured using UV at an intensity of 2.0 mW/c㎡ with a 15 ㎛-thick PDLC layer showed outstanding off-state opacity, good on-state transmittance, and favorable driving voltage. Also, the PDLC-based smart window optimized in this study formed liquid crystal droplets with a favorable microstructure, having an average size range of 2~5 ㎛ for scattering light efficiently, which could contribute to its superior final performance.

• Korean Journal of Soil Science and Fertilizer
• /
• v.38 no.5
• /
• pp.238-246
• /
• 2005

We conducted this investigation to observe competitive adsorption phenomena among the heavy metals onto the available sorption sites of soil particle surfaces in sandy clay loam and clay soil collected from Nonsan city, Chungnam and Yoosung, Daejeon in Korea, respectively. Polluted and contaminated soils can often contain more than one heavy metal species, resulting in competition for available sorption sites among heavy metals in soils due to complex competitive ion exchange and specific sorption mechanism. And the adsorption characteristics of the heavy metals were reported that the selectivity for the sorption sites was closely related with electropotential and electro negativity carried by the heavy metals. The heavy metals were treated as single, binary and ternary systems as bulk solution phase. Adsorption in multi-element system was different from single-element system as Cr, Pb and Cd. The adsorption isotherms showed the adsorption was increased with increasing equilibrium concentrations. For binary and ternary systems, the amount of adsorption at the same equilibrium concentration was influenced by the concentration of individual ionic species and valence carried by the respective heavy metal. Also we found that the adsorption isotherms of Cd and Pb selected in this experiment were closely related with electronegativity and ionic potential regardless number of heavy metals in solution, while the adsorption of Cr carried higher valance and lower electro negativity than Cd and Pb was higher than those of Cd and Pb, indicating that adsorption of Cr was influenced by ionic potential than by electronegativity. Therefore adsorption in multi-element system could be influenced by electronegativity and ionic potential and valance for the same valance metals and different valance, respectively. But it still needs further investigation with respect to ionic strength and activity in multi-element system to verify sorption characteristics and reaction processes of Cr, especially for ternary system in soils.

• Applied Chemistry for Engineering
• /
• v.9 no.5
• /
• pp.704-709
• /
• 1998

Non-linear optical polymer based on poly (${\alpha}$-methylstyrene-co-maleic anhydride) (MSMA) substrate polymer was prepared by polymer reaction method and its thermal and electro-optic properties were examined. In the polymer reaction between MSMA substrate polymer and 2-[4-(4-nitrophenylazo)-N-ethylphenylamino]ethanol (DR1) chromophore, the degree of substitution of DR1 into MSMA was higher with the 4-dimethylaminopyridine (DMAP) as catalyst and 3-dicyclohexyl carbodiimide (DCC) as dehydrating agent (sample, MSMA-DC) than the one with just 4-dimethylaminopyridine as catalyst (sample, MSMA-D). The synthesized NLO polymer (MSMA-DC) exhibited electro-optic coefficient of 18 pm/V (632.8 nm) and glass transition temperature ($T_g$) of about $175^{\circ}C$.

• Applied Chemistry for Engineering
• /
• v.33 no.1
• /
• pp.50-57
• /
• 2022

Ti-In-Zn-O (TIZO)/Ag/TIZO multilayer transparent electrodes were prepared on glass substrates at room temperature using RF/DC magnetron sputtering. Obtained multilayer structure comprising TIZO/Ag/TIZO (10 nm/10 nm/40 nm) with the total thickness of 60 nm showed a transmittance of 86.5% at 650 nm and a sheet resistance of 8.1 Ω/□. The multilayer films were expected to be applicable for use in energy-saving smart window based on polymer-dispersed liquid crystal (PDLC) because of their transmittance properties to effectively block infrared rays (heat rays). We investigated the effects of the content ratio of prepolymer, the thickness of the PDLC coating layer, and the ultraviolet (UV) light intensity on electro-optical properties, and the surface morphology of polyester acrylate-based PDLC systems using new TIZO/Ag/TIZO transparent conducting electrodes. A PDLC cell with a thickness of 15 ㎛ PDLC layer photocured at an UV intensity of 1.5 mW/cm² exhibited good driving voltage, favorable on-state transmittance, and excellent off-haze. The LC droplets formed on the surface of the polymer matrix of the PDLC composite had a size range of 1 to 3 ㎛ capable of efficiently scattering incident light. Also, the PDLC-based smart window manufactured using TIZO/Ag/TIZO multi-layered transparent electrodes in this study exhibited a light brown, which will have an advantage in terms of aesthetics.

• Applied Chemistry for Engineering
• /
• v.18 no.1
• /
• pp.77-83
• /
• 2007

It is essential that second order nonlinear optical materials have low optical propagation losses in the wavelengths of second harmonic generation for practical applications in waveguides. Three dipolar chromophores substituted with nitro, cyano, and alkyl sulfone as an electron withdrawing group were prepared. The UV-Vis absorption spectra of the cyano and alkylsulfone chromophores showed a blue-shift compared to the nitro chromophore. The introduction of oxadiazole segment in the chromophore structure led to similar spectral shift. The blue-shift can produce low optical loses at second harmonics. The chromophores were successfully attached to a polyimide, yielding side chain polymers. The nonlinear optical property of the prepared optical polymers was determined by measuring electro-optic coefficient at 1.55 mm. The polymers exhibited high glass transition temperature of over $185^{\circ}C$ and thermal stability to $300^{\circ}C$ through differential scanning calorimeter analysis and thermal gravimetric analysis.

• Applied Chemistry for Engineering
• /
• v.17 no.2
• /
• pp.217-222
• /
• 2006

Polyimides have been investigated extensively and used widely over the past three decades because of their high performance properties such as excellent thermal, mechanical, and electrical properties. Polyimides are difficult to be processed because of the aromatic moieties, imide group, and insoluble nature in most organic solvents. The soluble polyimides were synthesized from 2,2,-bis(3-amino-4-hydroxyphenyl) hexafluoropropane (BAPAF) and 3,3,-diamino-4,4-dihydroxybyphenyl (HAB) as aromatic diamines and 4,4-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA), pyromellitic dianhydride (PMDA), 4,4-oxydiphthalic dianhydride (OPDA), 3,3,4,4-benzophenone tetracarboxylic dianhydride (BTDA) and 3,3,4,4-diphenylsulfone tetracarboxylic dianhydride (DSDA) as aromatic dianhydrides. The polyimides were characterized by NMR, FR-IR, TGA and the dielectric constant of the obtained polyimides was calculated from storage of electro-capacity. A novel photosensitive polyimide was synthesized by the reaction of polyimide, containing hydroxyl group and methacryloyl chloride using triethylamine. The good micro-pattern was obtained with photosensitive polyimide from the photolithographic technique.

• Applied Chemistry for Engineering
• /
• v.27 no.4
• /
• pp.449-454
• /
• 2016

In this study, highly monodispersed porous carbon microcapsules with a hollow core were synthesized using polystyrene (PS) beads as a hard template. The surface of PS was first modified with polyvinylpyrollidone (PVP) for the easy attachment of inorganic silica sol. After coating the surface of PVP modified PS microspheres with SBA-16 sol, the carbon microcapsules with a hollow macroporous core were fabricated through reverse replication method by filling carbon sources in the mesopores of silica mold. The hollow carbons having a mesoporous shell structure and narrow particle size distribution could be obtained after the carbonization of carbon source and the dissolution of silica mold by HF solution. The mesoporous characteristics and electrochemical properties of hollow carbon microcapsules were characterized by XRD, SEM, TEM, $N_2$ adsorption/desorption analysis and cyclic voltammetry. They showed the high electric conductivity and capability for use as efficient electro-materials such as a supercapacitor.

• Bulletin of the Korean Chemical Society
• /
• v.28 no.12
• /
• pp.2241-2247
• /
• 2007

A new series of chiral bent-shaped liquid crystals with an asymmetric central core based on 1,6- dihydroxynaphthalene and chiral terminal chain prepared from (S)-(?)-2-methyl-1-butanol, 1,6-naphthalene bis[4-(4-alkoxyphenyliminomethyl)]benzoates [N(1,6)-n-O-PIMB(n-2)*-(n-4)O (n = 8-11)] were synthesized. Their mesomorphic properties and phase structures were investigated by means of electro-optical, polarization reversal current, and second harmonic generation measurements in order to confirm the relationship between the molecular structure and phase structure. All odd n (n = 9 and 11) compounds, N(1,6)-9-O-PIMB7*-5O and N(1,6)-11-O-PIMB9*-7O exhibit antiferroelectric phase, whereas even n (n = 8 and 10) compounds was flexible, N(1,6)-10-O-PIMB8*-6O exhibits the ferroelectric phase but N(1,6)-8-O-PIMB6*-4O exhibits the antiferroelectric phase. These results come from the decrease of the closed packing efficiency within a layer and the lack of uniform interlayer interaction between adjacent layers, which were caused by the asymmetrical naphthalene central core. Thus, we concluded that the structure of central core as well as the terminal chain plays an important role for the emergence of particular polar ordering in phase structures.

• Bulletin of the Korean Chemical Society
• /
• v.29 no.1
• /
• pp.117-121
• /
• 2008

Pseudo-first-order rate constants (kobsd) have been measured spectrophotometrically for nucleophilic substitution reactions of 5-nitro-8-quinolyl benzoate (5) with alkali metal ethoxides, EtO?M+ (M+ = Li+, Na+ and K+) in anhydrous ethanol (EtOH) at 25.0 0.1 C. The plots of kobsd vs. [EtO?M+] exhibit upward curvatures, while the corresponding plots for the reactions of 5 with EtO?Na+ and EtO?K+ in the presence of complexing agents, 15-crown-5-ether and 18-crown-6-ether are linear with rate retardation. The reactions of 5 with EtO?Na+ and EtO?Li+ result in significant rate enhancements on additions of Na+ClO4, indicating that the M+ ions behave as a catalyst. The dissociated EtO and ion-paired EtOM+ have been proposed to react with 5. The second-order rate constants for the reactions with EtO (kEtO) and EtOM+ (kEtOM+) have been calculated from ion-pairing treatments. The kEtO and kEtOM+ values decrease in the order kEtONa+ > kEtOK+ > kEtOLi+ > kEtO, indicating that ion-paired EtOM+ species are more reactive than the dissociated EtO ion, and Na+ ion exhibits the largest catalytic effect. The M+ ions in this study form stronger complex with the transition state than with the ground state. Coordination of the M+ ions with the O and N atoms in the leaving group of 5 has been suggested to be responsible for the catalytic effect shown by the alkali metal ions in this study.