• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2009.06a
• /
• pp.507-508
• /
• 2009

• Journal of the Korean Ceramic Society
• /
• v.52 no.6
• /
• pp.497-501
• /
• 2015

Inkjet printing is a widespread technology, offering advantages such as high-quality decoration, a continuous process, and the accurate direct reproduction of patterns or pictures. In inkjet printing technology, the dispersion stability of ceramic ink is one of the most important factors. In this study, the dispersion stability of blue $CoAl_2O_4$ ink for ceramic inkjet printing is systematically investigated. Blue $CoAl_2O_4$ pigment was synthesized by a solid-state reaction and then milled to less than 300nm in size. In order to investigate the influence of the viscosity on the dispersion stability, two types of $CoAl_2O_4$ ceramic inks (termed here Blue L and Blue H) were prepared using different volume ratios of ethylene glycol and ethanol. The Blue L and Blue H ink solutions contained cetyltrimethylammonium bromide(CTAB) as a dispersive agent. The viscosity, surface tension and jetting stability of the $CoAl_2O_4$ ceramic inks were analyzed using a rheometer, a surface tension meter and a dropwatcher. The dispersion stability of the $CoAl_2O_4$ ceramic ink was investigated by a multiple light-scattering method. Blue H, a ceramic ink with higher viscosity, showed much better dispersion stability than the Blue L ceramic ink.

• KSBB Journal
• /
• v.29 no.5
• /
• pp.385-391
• /
• 2014

In this study, the emulsion dispersion stability of optimizing storage temperature was investigated. The system was based on oil/water (O/W) emulsions. In order to evaluate the stability, mean diameter of droplet was measured as a function of temperature with various mixed hydrophilic lipophilic balance (HLB). In addition, the correlations between phase inversion temperature (PIT) and the optimum storage temperature were probed. In this system, majority of the smallest droplet was shown at temperature of $20^{\circ}C$ below PIT. Whether the temperature was increased or decreased from the optimum, size of the droplet increased. According to the mixed HLB, the particle size and optimum storage temperature were also affected. As the concentrations of surfactant were increased, the size of particle decreased with lower optimum temperature for storage. If the surfactant (4 wt%) were mixed with HLB, the optimum storage temperature was $21^{\circ}C$ for maintaining the size of smallest droplet at 108.3 nm in diameter. At above optimum condition, increased size of particle was observed approximately 4 % increases from 108.2 nm to 112.3 nm after 600 hours. The size of particle in emulsion was maintained stably without any considerable effect of Ostwald ripening phenomena at the optimum storage temperature with low polydispersity index.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.07a
• /
• pp.308-311
• /
• 2003

The mesoporous TiO2 film for the dye-sensitized solar cell was prepared by the spin coating using nano particle $TiO_2$ slurry. In order to obtain the good dispersion of nano size $TiO_2$ particles in slurry, the pH of solvent, the sort and quantity of solvent additive and the quantity of surfactant were adjusted. The experimental range of pH was $2\;{\sim}\;4$. The basic solvent for slurry was dilute $HNO_3$ and the solvent additives were ethylene glycol, propylene glycol and butylene glycol. The degree of particle dispersion was indirectly estimated by the viscosity of slurry and the microstructure after sintering. As results, the lower the pH of solvent was the lower the viscosity of the slurry became. The addition of ethylene glycol and propylene glycol to dilute $HNO_3$ brought about the lowering of viscosity and the enhancement of stability in slurry. The addition of surfactant lowered the viscosity of slurry. It was possible to obtain the homogeneous and uniformly dispersed mesoporous TiO2 film using the dilute HNO3 solvent of pH 2 with the addition of ethylene glycol, propylene glycol and neutral surfactant.

• Korean Journal of Materials Research
• /
• v.28 no.2
• /
• pp.82-88
• /
• 2018

Stable slurries of YSZ in aqueous suspension with added polymer dispersants, namely, poly-methacrylic acid ammonium salt (PMMA), poly-acrylic acid (PAA) and poly-acrylic-co-maleic acid (PAMA), were mixed with the monomolecular dispersants citric acid and oxalic acid. The dispersion properties of the suspension were investigated using PSA, viscosity, sedimentation, and FT-IR. The polymer dispersants and monomolecular dispersants were attached to the YSZ surface by the carboxylic group, as shown by the FTIR results. A stabilized aqueous suspension was obtained when the polymer dispersant and citric acid were mixed and compared to the use of citric acid alone as a dispersant agent. When the polymer dispersant and citric acid were mixed and milled through attrition milling, there was a smaller particle size compared to when the polymer dispersant alone was used as a dispersant agent. This study determined that the particle size of the mixed dispersant was affected by the properties of the monomolecular dispersant and that the stability of the suspension was affected by the polymer dispersant. However, when slurries of YSZ were mixed with oxalic acid, the particle bridging behavior was the result of the high degree of viscosity and the small sedimentation height.

• Journal of the Korean Ceramic Society
• /
• v.54 no.6
• /
• pp.478-483
• /
• 2017

The advantage of ceramic ink-jet printing technology is the accurate and fast printing process of digital images for various products. For digital ink-jet printing applications, ceramic ink requires proper viscosity and surface tension, along with dispersion stability of the inorganic pigments. The purpose of this study is the formulation of an environment-friendly ceramic ink with a water-based system; using nano-sized $CoAl_2O_4$ pigment as a raw material, ink should have dispersion stability to prevent nozzle clogging during ink-jet printing process. In addition, the surface tension of the ceramic ink was optimized with the polysiloxane surfactant according to the surface tension requirement (20 - 45 mN/m) for ceramic ink-jet printing; by adjusting the viscosity with poly ethylene oxide, jetting behavior of the ceramic ink was investigated according to changes in the physical features through drop watcher measurement.

• Journal of Powder Materials
• /
• v.11 no.6 s.47
• /
• pp.503-509
• /
• 2004

Dispersion stabilities and photocatalytic activities of rutile $TiO_{2}$ powders with unique nano-structure synthesized by homogeneous precipitation process at low temperature(HPPLT) have been investigated in the acrylic resin containing fluorostyrene in the range of 0~0.16 mole. Isoelectric point of $TiO_{2}$ in the acrylic resin placed in the neutral region whereas that of $TiO_{2}$ in the water placed in the acidic region, indicating that zeta potential and agglomeration of $TiO_{2}$ powder is strongly dependent on the pH and the type of solvent. To prepare an adhesion, an acrylic resin containing fluorostyrene was synthesized by a radical polymerization. The adhesion of coating layer was increased with increasing fluorostyrene's contents without changing the dispersion stabilities and degrading photocatalytic properties.

• Advances in nano research
• /
• v.2 no.2
• /
• pp.121-133
• /
• 2014

Polymer nanocomposites are advanced nanomaterials which exhibit dramatic improvements in various mechanical, thermal and barrier properties as compared with the neat polymer. Polystyrene/ alumina nanocomposites were prepared by an ultrasound-assisted solution casting method at filler loadings ranging from 0.2 to 2% and also at different ultrasonic frequencies, viz. 58 kHz, 192/58 kHz, 430 kHz, 470 kHz and 1 MHz. The composites were subjected to mechanical property tests (tensile and impact tests) and cavitation erosion tests to study the enhancement in functional properties. Filler dispersion in the polymer matrix was observed by SEM analysis. The effect of frequency on filler dispersion in the matrix was studied by SEM analysis and functional property enhancement of the composite material. The composites prepared at dual (high/ low) frequency (192/58 kHz) were found to show better property enhancement at low filler loadings as compared with neat polymer and also with composites prepared without ultrasound, thus reinforcing the finding that ultrasound-assisted synthesis is a promising method for the synthesis of nanocomposites.

• Korean Journal of Materials Research
• /
• v.27 no.9
• /
• pp.507-511
• /
• 2017

An optimum route to fabricate oxide dispersion strengthened ferritic superalloy with desired microstructure was investigated. Two methods of high energy ball milling or polymeric additive solution route for developing a uniform dispersion of $Y_2O_3$ particles in Fe-Cr-Al-Ti alloy powders were compared on the basis of the resulting microstructures. Microstructural observation revealed that the crystalline size of Fe decreased with increases in milling time, to values of about 15-20 nm, and that an FeCr alloy phase was formed. SEM and TEM analyses of the alloy powders fabricated by solution route using yttrium nitrate and polyvinyl alcohol showed that the nano-sized Y-oxide particles were well distributed in the Fe based alloy powders. The prepared powders were sintered at 1000 and $1100^{\circ}C$ for 30 min in vacuum. The sintered specimen with heat treatment before spark plasma sintering at $1100^{\circ}C$ showed a more homogeneous microstructure. In the case of sintering at $1100^{\circ}C$, the alloys exhibited densified microstructure and the formation of large reaction phases due to oxidation of Al.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.11a
• /
• pp.49-52
• /
• 2004

New hydrophobic alumina nanoparticles were synthesized from alumina powders which were hydrophilic nano-agglomerates with diameters from ${\mu}m$ to mm by surface modification. The synthesized hydrophobic alumina nanoparticles which were retreated with Oleic acid were analyzed by Fourier transform infrared spectrophotometer and transmission electron microscopy. Then transformer oil containing surface-modified alumina naonparticles were synthesized. The synthesized hydrophobic alumina nanoparticles were well-dispersed in transformer oil. The coefficient of viscosity and dielectric strength of the Nano-transformer oil were investigated with viscometer and high voltage experiment device. In this study, the thermal conductivity of Nano-transformer oil was investigated to reduce the oil temperature of transformer by transient hot-wire method.