• Clean Technology
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• v.13 no.1 s.36
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• pp.34-45
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• 2007

Phase behavior of the ternary systems of water-insoluble simvastatin drug, which is well known to be effective drugs for hypercholesterolemia therapy, in solvent mixtures of dichloromethane and supercritical carbon dioxide was investigated to present a guideline of establishing operating conditions in the particle formation of the drugs by a supercritical anti-solvent recrystallization process utilizing dichloromethane as a solvent and carbon dioxide as an anti-solvent. The solubilities of simvastatin in the mixtures of dichloromethane and carbon dioxide were determined as functions of temperature, pressure and solvent composition by measuring the cloud points of the ternary mixtures at various conditions using a high-pressure phase equilibrium apparatus equipped with a variable-volume view cell. The solubility of the drug increased as the dichloromethane composition in solution and the system pressure increases at a fixed temperature. A lower solubility of the drug was obtained at a higher temperature. The second half of this work is focused on the particle formation of the simvastatin drug by a supercritical anti-solvent recrystallization process in a cylindrical high-pressure vessel equipped with an impeller. Microparticles of the simvastatin drug were prepared as functions of pressure (8 MPa to 12 MPa), temperature (303.15 K, 313,15 K), feed flow rate of carbon dioxide, and stirring speed (up to 3000 rpm), in order to observe the effect of those process parameters on the size and shape of the drug microparticles recrystallized.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.5
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• pp.175-180
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• 2016

ZnO nanoparticles were synthesized by aqueous preparation routes of a precipitation and a hydrothermal process. In the processes, the powders were formed by mixing aqueous solutions of Zn-nitrate hexahydrate ($Zn(NO_3)_2{\cdot}6H_2O$) with NaOH aqueous solution under controlled reaction conditions such as Zn precursor concentration, reaction pH and temperature. Single ZnO phase has been obtained under low Zn precursor concentration, high reaction pH and high temperature. The synthesized particles exhibited flakes (plates), multipods or rods morphologies and the crystallite sizes and shapes would be efficiently controllable by changing the processing parameters. The hydrothermal method showed advantageous features over the precipitation process, allowing the precipitates of single ZnO phase with higher crystallinity at relatively low temperatures below $100^{\circ}C$ under a wider pH range for the Zn precursor concentration of 0.1~1 M.

• The Journal of the Convergence on Culture Technology
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• v.9 no.3
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• pp.593-599
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• 2023

Nickel oxide (NiO) nanoparticles were successfully synthesized by a simple liquid phase process for producing ceramics powder using a precursor impregnated with a nickel(II) nitrate hexahydrate aqueous solution in an industrial pulp. The microfibrile structure of the precursor impregnated with nickel nitrate hexahydrate aqueous solution was confirmed by scanning electron microscope (SEM), and the crystal structure and particle size of nickel oxide (NiO) particles produced as the heat treatment temperature of the precursor were analyzed by X-ray diffraction (XRD) and SEM. As a result, it was confirmed through XRD and SEM analysis that the temperature at which the organic material of the precursor is completely thermally decomposed was 495-500℃, and the size and crystallinity of the nickel oxide particles produced increased as the heat treatment temperature increased. The size of the nickel oxide particles obtained by heat treatment at 500-800℃ for 1 hour was 50-200 nm. It was confirmed by XRD and SEM analysis that a NiO crystal phase was formed at a heat treatment temperature of 380℃, only a single NiO phase existed until 800℃.

• Korean Chemical Engineering Research
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• v.46 no.3
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• pp.626-632
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• 2008

The purpose of this study was to enhance gas exchange by producing hemosome, a hemoglobin microencapsulated with phospholipid of egg, and perfluorocarbone(PFC) emulsion solution. In the experiment, stable emulsion solution with 437 nm of mean particle size could be produced by Flusol-DA sonication, and shortening of emulsion time could be attained with higher stability as well. $0.8{\mu}m$ sized hemosome could be produced by microencapsulation of hemoglobin with phospholipid extracted from egg yolk. The pattern of oxygen saturation curve of hemosome was S shape, which is similar to that found in normal blood, and $P_{50}$ was measured to be 24 mmHg. The oxygen saturation in the mixed solution of hemosome and blood in 1:4(V/V%) ratio was similar to that of normal blood, and the same result was found in the mixed solution of PFC emulsion and blood in 1:4(V/V%) ratio.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.12 no.5
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• pp.229-233
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• 2002

Nano-sized ZnO particles were successfully synthesized at low temperatures by a polymerized complex method via an organochemical route. The polymeric precursors could be prepared using Zn nitrate hexahydrate and a mixed solution of citric acid and ethylene glycol as a chelating agent and a reaction medium. The polymeric precursors were calcined at temperatures from 300 to $700^{\circ}C$ for 3 h, and evaluated for degree of crystallization process, thermal decomposition, surface morphology and crystallite size. The thermal decomposition and crystallization process were analyzed by TG-DTA, FI-IR and XRD. The morphology and crystallite size of the calcined particles were evaluated by scanning electron microscopy (SEM), transmittance electron microscopy (TEM) and Scherrer's equation. Crystallization of the ZnO particles was detected at $300^{\circ}C$ and entirely completed above $400^{\circ}C$. Particles calcined between 400 and $700^{\circ}C$ showed a uniform size distribution with a round shape. The average particle sizes calcined at $400^{\circ}C$ for 3 hour were 30~40nm showing an ordinary tendency to increase with the temperatures.

• Journal of Powder Materials
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• v.27 no.3
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• pp.233-240
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• 2020

Nano-sized ZnSe particles are successfully synthesized in an aqueous solution at room temperature using sodium borohydride (NaBH₄) and thioglycolic acid (TGA) as the reducing agent and stabilizer, respectively. The effects of the mass ratio of the reducing agent to Se, stabilizer concentration, and stirring time on the synthesis of the ZnSe nanoparticles are evaluated. The light absorption/emission properties of the synthesized nanoparticles are characterized using ultraviolet-visible (UV-vis) spectroscopy, photoluminescence (PL) spectroscopy, and particle size analyzer (PSA) techniques. At least one mass ratio (NaBH4/Se) of the reducing agent should be added to produce ZnSe nanoparticles finer than 10 nm and to absorb UV-vis light shorter than the ZnSe bulk absorption wavelength of 460 nm. As the ratio of the reducing agent increases, the absorption wavelengths in the UV-vis curves are blue-shifted. Stirring in the atmosphere acts as a deterrent to the reduction reaction and formation of nanoparticles, but if not stirred in the atmosphere, the result is on par with synthesis in a nitrogen atmosphere. The stabilizer, TGA, has an impact on the Zn precursor synthesis. The fabricated nanoparticles exhibit excellent photo-absorption/discharge characteristics, suggesting that ZnSe nanoparticles can be alloyed without the need for organic solutions or high-temperature environments.

• Korean Journal of Materials Research
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• v.21 no.6
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• pp.299-302
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• 2011

[ $WO_3$ ]powders were ball-milled with an alumina ball for 0-72 hours. $In_2O_3$ doped $WO_3$ was prepared by soaking ball-milled $WO_3$ in an $InCl_3$ solution. The mixed powder was annealed at $700^{\circ}C$ for 30 min in an air atmosphere. A paste for screen-printing the thick film was prepared by mixing the $WO_3$:In2O3 powders with ${\alpha}$-terpinol and glycerol. $In_2O_3$ doped $WO_3$ thick films were fabricated into a gas sensor by a screen-printing method on alumina substrates. The structural properties of the $WO_3$:$InO_3$ thick films were a monoclinic phase with a (002) dominant orientation. The particle size of the $WO_3$:$InO_3$ decreased with the ball-milling time. The sensing characteristics of the $In_2O_3$ doped $WO_3$ were investigated by measuring the electrical resistance of each sensor in the test-box. The highest sensitivity to 5 ppm $CH_4$ gas and 5 ppm $CH_3CH_2CH_3$ gas was observed in the ball-milled $WO_3$:$InO_3$ gas sensors at 48 hours. The response time of $WO_3$:$In_2O_3$ gas sensors was 7 seconds and recovery time was 9 seconds for the methane gas.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.9
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• pp.552-558
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• 2016

Goethite, ${\alpha}$-FeOOH have various applications such as absorbent, pigment and source for magnetic materials. Goethite particles were synthesized in a two step process, where $Fe(OH)_2$ were synthesized in nitrogen atmosphere using $FeSO_4$ as a raw material in the first process, and after that acicular goethite particles were obtained in an air oxidation process of $Fe(OH)_2$ in highly alkaline aqueous solution. Their phase and microstructure were investigated with XRD and FE-SEM. It was found that the morphology of goethite and the ratio of length-to-width (aspect ratio) of acicular goethite are dependent on the some factors such as R value ($OH^-/Fe^{2+}$), air flow rate and pH conditions. In particular, R value has the strongest influence on the synthesized goethite morphology. It is considered that the optimal value R is 4.5 because X-ray diffraction peaks of goethite have the highest intensity at that value. Morphology of goethite particles was controlled by air flow rates, showing that their size and aspect ratio are getting smaller and decrease, respectively as air flow rate increases. The largest goethite particle obtained is about 1,500 nm in length and 150 nm in diameter.

• Korean Journal of Materials Research
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• v.31 no.9
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• pp.481-487
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• 2021

ZnO particles are successfully synthesized at 150 ℃ for 30 min using zinc acetate as the Zn source and 1,4-butanediol as solvent using a relatively facile and convenient glycol process. The effect of ammonium hydroxide amounts on the growth behavior and the morphological evolution of ZnO particles are investigated. The prepared ZnO nanoparticle with hexagonal structure exhibits a quasi-spherical shape with an average crystallite size of approximately 30 nm. It is also demonstrated that the morphology of ZnO particles can be controlled by 1,4-butanediol with an additive of ammonium hydroxide. The morphologies of ZnO particles are changed sequentially from a quasi-spherical shape to a rod-like shape and a hexagonal rod shape with a truncated pyramidal tip, exhibiting preferential growth along the [001] direction with increasing ammonium hydroxide amounts. It is demonstrated that much higher OH^- amounts can produce a nano-tip shape grown along the [001] direction at the corners and center of the (001) top polar plane, and a flat hexagonal symmetry shape of the bottom polar plane on ZnO hexagonal prisms. The results indicate that the presence of NH⁴⁺ and OH^- ions in the solution greatly affects the growth behaviors of ZnO particles. A sharp near-band-edge (NBE) emission peak centered at 383 nm in the UV region and a weak broad peak in the visible region between 450 nm and 700 nm are shown in the PL spectra of the ZnO synthesized using the glycol process, regardless of adding ammonium hydroxide. Although the broad peak of the deep-level-emission (DLE) increases with the addition of ammonium hydroxide, it is suggested that the prominent NBE emission peaks indicate that ZnO nanoparticles with good crystallization are obtained under these conditions.

• Korean Journal of Applied Biomechanics
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• v.31 no.3
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• pp.183-188
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• 2021

Objective: The purpose of this study was to develop a stretchable joint motion sensor that is based on silver nano-particle. Through this sensor, it can be utilized as an equipment for rehabilitation and analyze joint movement. Method: In this study, precursor solution was created, after that, nozel printer (Musashi, Image master 350PC) was used to print on a circuit board. Sourcemeter (Keithley, Keithley-2450) was used in order to evaluate changes of electric resistance as the sensor stretches. In addition, the sensor was attached on center of a knee joint to 2 male adults, and performed knee flexion-extension in order to evaluate accurate analysis; 3 infrared cameras (100 Hz, Motion Master 100, Visol Inc., Korea) were also used to analyze three dimensional movement. Descriptive statistics were suggested for comparing each accuracy of measurement variables of joint motions with the sensor and 3D motions. Results: The change of electric resistance of the sensor indicated multiple of 30 times from initial value in 50% of elongation and the value of electric resistance were distinctively classified by following 10%, 20%, 30%, 40% of elongation respectively. Through using the sensor and 3D camera to analyze movement variable, it showed a resistance of 99% in a knee joint extension, whereas, it indicated about 80% in flexion phase. Conclusion: In this research, the stretchable joint motion sensor was created based on silver nanoparticle that has high conductivity. If the sensor stretches, the distance between nanoparticles recede which lead gradual disconnection of an electric circuit and to have increment of electric resistance. Through evaluating angle of knee joints with observation of sensor's electric resistance, it showed similar a result and propensity from 3D motion analysis. However, unstable electric resistance of the stretchable sensor was observed when it stretches to maximum length, or went through numerous joint movements. Therefore, the sensor need complement that requires stability when it comes to measuring motions in any condition.