• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1191-1192
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• 2006

Eventhough Fe-6.5 wt.% Si alloy shows excellent magnetic properties, magnetic components made of the alloy are not totally because of its extremely low ductility. In order to overcome this demerit of alloy, 6.7 wt.% Si alloy powders were produced by gas atomization and then post-processed to form magnetic cores. By doing so, the total core loss could be minimized by reducing both hysteresis and eddy current loss. From our experiments, we were able to achive a core loss of $390mW/cm^3$ at 0.1 T and 50 kHz through proper processes and a permeability $\mu_{eff}$ of 68 at low frequency.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2003.10a
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• pp.39-40
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• 2003

1) Using a developed high-frequency induction heated sintering method, the rapid densification of WC-Co hard materials was accomplished using ultra fine powders with 260 nm size within 1 minute. 2) The relative density of the composite was 99.5% for the applide pressure of 60MPa and the induced current for 90% output of total capacity. 3) The grain size of WC-Co hard materials is about 260nm and the average thickness of the binder phase determined is about 11nm. The fracture toughness and the hardness of this work 12 $MPa{\cdot}nm^2$, respectively. 4) Using pressureless sintering, we produced dense WC-Co hard materials with a relative density of 97% without applying pressure.

• Journal of Ginseng Research
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• v.19 no.2
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• pp.138-143
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• 1995

Currently, some food materials are disinfected by $\gamma$-irradiation (using Co-60) or ethylene oxide treatment. These treatments were applied to ginseng powder and the ginseng components such as ginsenosides, polyacetylenes and phenolic acids were analyzed by HPLC to determine any compositional changes due to irradiation. No appreciable difference was observed in the HPLC pattern of ginsenosides, polyacetylenes of ginseng powder after 10 key irradiation or ethylene oxide treatment (EO $CO_2$= 3 : 7, w/wfb) from those of untreated fresh ginseng powder when they were analyzed soon after treatments. When the ginseng powders were stored at room temperature for three years after the same treatment, the HPLC patterns of polyacetylenes and phenolic acid fraction showed appreciable change from those of fresh ginseng powder, however, the HPLC patterns of three year old samples did not show any appreciable difference.

• Korean Journal of Materials Research
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• v.9 no.3
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• pp.263-268
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• 1999

In this study, a new concept of aluminum-matrix composites and the possibility of in-situ processing are suggested, and preliminary results on AI- Ti system are presented. Fine powders of AI-lO% Ti were prepared by the gas atomization so that fine $Al_3Ti$ formed into flake shape. A 25v/o $Al_3Ti/Al$ composite sample was made by the pow­d er metallurgy process involving hot extrusion. Microstructure and mechanical behavior both at room temperature and high temperatures were analysed by OM, SEM, TEM and tension test. Microstructural characteristics and mechanical properties of the composites exhibited similar behavior to those of $SiC_w/2124$ composites. Merits and drawbacks of the $Al_3Ti/Al$ composites are discussed together with a possibility of further improvement.

• The Journal of Advanced Prosthodontics
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• v.15 no.4
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• pp.189-201
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• 2023

PURPOSE. The aim of this study was to investigate the mechanical properties of three-dimensional (3D) printed denture base resin incorporating microcapsules containing plant essential oils. MATERIALS AND METHODS. Denture base specimens containing up to 3% w/v essential oil microcapsule powders (MCPs), i.e., eucalyptus, geranium, lavender, menthol, and tea tree, in two resins (Detax and NextDent 3D+) were 3D printed using two printers (Asiga and NextDent 5100). The dispersion and interaction of the MCPs in the resin were assessed by SEM while the mechanical properties of the incorporated denture base including flexural strength (MPa), flexural modulus (MPa), Vickers hardness (VHN), and surface roughness (Ra) were also subsequently evaluated. Statistical analysis of any differences in mean values was determined using a two-way ANOVA with Tukey's post hoc testing (α = .05). RESULTS. The spherical shape of the MCPs was maintained during the mixing and polymerization/printing process. However, the Detax-Asiga group showed significant agglomeration of the MCPs even at the lowest MCP concentration levels (0.5% w/v). Overall, as the microcapsule concentration increased, the mean flexural strength decreased, though the menthol MCP groups remained compliant with the ISO standard. The flexural modulus and harness remained relatively unchanged, and the flexural modulus complied with the ISO standard regardless of the MCP concentration. Surface roughness increased with the addition of the MCPs but also remained below that required for clinical acceptance. CONCLUSION. Incorporation of microencapsulated plant essential oils into 3D printed denture base resin was successfully achieved. While incorporation negatively influenced flexural strength and surface roughness, little effect on flexural modulus and Vickers hardness was demonstrated.

• Laser Solutions
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• v.18 no.3
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• pp.1-5
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• 2015

A 3D printer based on laser powder deposition (LPD), also known as DED (direct energy deposition), has been developed for fabricating metal parts. The printer uses a ytterbium fiber laser (1070nm, 1kW) and is equipped with an Ar purge chamber, a three-dimensional translation stage and a powder feeding system composed of a powder chamber and delivery nozzles. To demonstrate the performance of the printer, a tapered cylinder of 320mm in height has been fabricated successfully using Ti-6Al-4V powders. The process parameters including the laser output power, the scan speed, and the powder feeding rate have been optimized. A 3D printed test specimen shows mechanical properties (yield strength, ultimate tensile strength, and elongation) exceeding the criteria to employed in a variety of Ti alloy applications.

• Food Science and Preservation
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• v.16 no.4
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• pp.525-533
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• 2009

To explore cattail pollen powder as a functional food ingredient, we analyzed the general components of pollen powder, tested changes in the physical properties of dough containing the powder, and investigated the process ability of powder-containing dough in bread making by adding 3%, 6%, or 9% by weight of pollen powder to wheat flour. Cattail pollen powder consisted of (all w/w) 12.7-13.2% water, 15.7-17.8% crude protein, 1.3% crude fat, 7.5-7.7% free sugar, 14.7-18.6% crude fiber, 3.4-4.9% pollen, and 49.7-55.9% soluble nitrogen-free extract (NFE). Analysis of the physical properties of dough mixed with pollen powder showed that as more pollen powder was added, the absorption rate increased, but dough stability decreased. With increasing levels of cattail pollen powder, the falling number decreased, and amylase activity increased. Fermentability was highest in dough made with 3% by weight of pollen powder, and the bread product made from such dough had the greatest volume. As more cattail pollen powder was added, the moisture activity in dough tended to decrease to a greater extent than seen in control dough, and this tendency increased with time. We found that longer storage periods were associated with greater hardness and springiness, which indicated degradation in product quality. Therefore, it is suggested that bread products containing cattail pollen powder should be consumed within 3 days of preparation. In a taste survey, bread baked with 3% (w/w) cattail pollen powder scored highest in all questionnaire items.

• Korean Journal of Metals and Materials
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• v.49 no.5
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• pp.395-399
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• 2011

In this study, micro gas sensors for ammonia gas were prepared by adopting MEMS technology and using a sol-gel process. Three types of sensors were prepared via different synthesis routes starting with W sol and Ru sol mixture. This mixture was deposited on a MEMS platform and the platform was subsegueny heated to a temperature of $350^{\circ}C$. The topography and crystal structure of the sensing film were studied using FE-SEM and XRD. The response of the gas sensor to $NH_3$ gas was examined at various operating temperatures and gas concentrations. The sensor response increased almost linearly with gas concentration and the best sensing response was obtained at $333^{\circ}C$ for 5.0 ppm $NH_3$ for the specimen prepared by coating $WO_3$ powders with the Ru sol mixture.

• Journal of the Korean institute of surface engineering
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• v.29 no.6
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• pp.829-833
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• 1996

Superconducting YBaCuO thin films were deposited on MgO (100) single crystal substrate by rf reactive sputtering method. Sputtering target was prepared by mixing the original powders of $Y_2O_3$, $BaCO_3$, and CuO at $830^{\circ}C$, and its composition was $YBa_2Cu_{3.3}O_x$ adding the excess CuO to compensate for the loss of Cu in the deposition process. The sputtering conditions for a high quality of YBCO thin film were: substrate temperature of 13$0^{\circ}C$; gas pressure of 10 mTorr; gas mixture ($O_2$: Ar =10: 90); distance of 2.5 inch; and rf power density of 4.87 W /$\textrm{cm}^2$. The deposition rate was 2.4~2.6 nm/min. From the RBS results, it was found that Cu and Ba contents in thin films decreased with the increase of substrate temperature. The increase of gas pressure resulted in significant deficiency of Ba elements.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.145-146
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• 2000

Primary emphasis was placed on the electrophoretic deposition of low voltage phosphor to indium-tin oxide-coated glass for the application of field emission display. The phosphor deposited by various parameters, such as deposition time and applied voltages was examined in detail. In addition, a comparison was made by analyzing luminance properties of the phosphor mixed with and without conducting $In_2O_3$ powder of less than 1um size. The measurement was performed as a function of $In_2O_3$ concentration from 3% to 15% by weight. The enhanced impact of indium powder mixing on the phosphor was clearly demonstrated by aging performance curve at 1000V excitation voltages with a current density of $1\;mA/cm^2$