• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1295-1298
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• 2004

Selective Laser Sintering(SLS) method is one of Rapid Prototyping(RP) technologies. It is used to fabricate desirable part to sinter powder and stack the fabricated layer. To develop this SLS machine, it needs effective scanning path and the development of scanning device. This paper shows how to make fast scanning path with respect to scan spacing, laser beam size and scanning direction from 2-dimensional sliced file generated in commercial CAD/CAM software. Also, we develop the scanning device and its control algorithm to precisely follow the generated scanning path. Scanning path affects precision and total machining time of the final fabricated part. Sintering occurs using infrared laser which has high thermal energy. As a result, shrinkage and curling of the fabricated part occurs according to thermal distribution. Therefore, fast scanning path generation is needed to eliminate the factors of quality deterioration. It highly affects machining efficiency and prevents shrinkage and curling by relatively lessening the thermal distribution of the surface of sintering layer. To generate this fast scanning path, adaptive path generation is needed with respect to the shape of each layer, and not simply x, y scanning, but the scanning of arbitrary direction must be enabled. This paper addresses path generation method to focus on fast scanning, and development of scanning system and control algorithm to precisely follow generated path.

• Journal of the Korean Ceramic Society
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• v.27 no.8
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• pp.1020-1026
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• 1990

The effect of heating rate on the microstructural evolution during sintering of PZT ceramics has been investigated. In case of PZT powder compacts containing excess of PbO, fast heating caused incomplete rearrangement of solid grains in a liquid, resulting in lower density and inhomogeneous pore shape ; on contrary, slow heating resulted in better densification. In contrast, in case of compacts without excess PbO, the densification was enhanced by fast heating due to suppression of the grain growth.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.621-622
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• 2006

In this paper, we show some experimental results of binder-free WC sintered by Pulsed Electric Current Sintering (PECS) also known as Field Assisted Sintering Technology (FAST). These binder-free WC have extremely hardness and stiffness. However, these mechanical properties are dependent on the sintering condition, e.g., maximum temperature, applied pressure, etc. We show some relationship between mechanical properties and sintering condition to improve to sinter the binder-free WC.

• Journal of the Korean Ceramic Society
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• v.51 no.4
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• pp.344-349
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• 2014

$RuO_2$-based high frequency thick-film resistor paste was printed at the speed of 10, 100, 300 mm/sec on the AlN substrate, and then sintered at between 750 and $900^{\circ}C$. The sintered thick films were characterized in terms of printing and sintering conditions. With increasing printing speed, the thickness and roughness of sintered film increased. The resistance of the thick film resistor was reduced by increasing the printing speed from 10 to 100 mm/sec, but did not significantly change at 300 mm/sec speed. With increasing sintering temperature, the surface roughness and thickness of sintered resistor film decreased. The reduction rate was large in case of fast printed resistor. The resistance of the resistor increased up to $800^{\circ}C$ with sintering temperature, but again decreased at the higher sintering temperature.

• Journal of Powder Materials
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• v.5 no.4
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• pp.258-264
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• 1998

The initial sintering behaviour of the powder injection molded (PIMed) W-l5wt%Cu nanocomposite powder was investigated. The W-Cu nanocomposite powder was produced by the mechanochemical process consisting of high energy ball-milling and hydrogen reduction of W blue powder-CuO mixture. Solid state sintering of the powder compacts was conducted at $1050^{\circ}C$ for 2~10 hours in hydrogen at mosphere. The sintering behaviour was examined and discussed in terms of microstructural developments such as W-Cu aggregate formation, pore size distribution and W grain growth. The volume shrinkage of PIM specimen was slightly larger than that of PM(conventional PM specimen), being due to fast local densification in the PIM. Remarkable decrease of carbon and oxygen in the PIM enhanced local densification in the early stage of solid state sintering process with eliminating very fine pores less than 10 nm. In addition, such local densiflcation in the PIM is presumably responsible for mitigating of W-grain growth in the initial stage.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.25 no.2
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• pp.79-87
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• 2016

Single visit monolithic restoration can be proceed with digital workflow which consist of intraoral scanning, dental CAD(computer aided design) and restoration milling with CAM(Computer aided manufacturing). While zirconia has more than 900MPa of flexural strength compared with 400MPa for lithium disilicate, shortened fabricating time of lithium disilicate is considered to be a better choice for fabricating single visit full contour monolithic restoration. However, new zirconia materials which are TZI C(Dentsply Sirona) and LUXEN Enamel(Dental Max), new induction heating method of sintering furnace, and new sintering protocols for MoSi2 heating elements sintering furnace offer significantly reduction of full contour monolithic zirconia restoration fabrication time with greater translucency. These new developments lead single visit zirconia restoration in reality.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1256-1257
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• 2008

Dye-Sensitized Solar Cell(DSSC) is a new type of solar cell by using photocatalytic properties of $TiO_2$. The size and shape of $TiO_2$ particle are two of important parameters that are related to the characteristics of DSSC. And these can be changed by controlling $TiO_2$ sintering conditions especially temperature. The particles of $TiO_2$ are classified anatase and rutile. Anatase particles are created at low sintering temperature and rutile particles are created at high sintering temperature. Anatase particles have advantages such as increased surfaces that cause more attached dye molecules, and fast electron transportation. And rutile particles have advatages such as more efficient light scattering. Therefore, we studied characteristics of DSSC in this paper as $TiO_2$ sintering temperature is varied. As a result, we found that characteristics of DSSC are very good in the case that anatase and rutile particles are together and this sintering temperature is 450$^{\circ}C$.

• Journal of Powder Materials
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• v.20 no.6
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• pp.425-431
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• 2013

Microstructural and mechanical properties of Ni-YSZ fabricated using SPS processing have been investigated at various sintering temperatures. Our study shows samples to be applied as a SOFC anode have the proper porosity of 40% and high hardness when processed at $1100^{\circ}C$. These results are comparable to the values obtained at $100-200^{\circ}C$ higher sintering temperature reported by others. This result is important because when the fabrication processes are performed above $1100^{\circ}C$, the mechanical property starts to decrease drastically. This is caused by the fast grain coarsening at the higher temperature, which initiates a mismatch between thermal expansion coefficients of Ni and YSZ and induces cracks as well.

• Journal of the Korean Ceramic Society
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• v.34 no.4
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• pp.357-367
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• 1997

A fast process for producing pure silica glasses with the reproducibility of 100% by means of sintering of silica aerogels was optimized. The density of silica glasses synthesized by heat-treating upto 110$0^{\circ}C$ with the heating rate of 0.1$^{\circ}C$/min was 2.197 g/㎤. Synthetic silica glasses(5 mm thickness) exhibited the transmittance of 92% in the near IR range as well as they had the excellent mechanical properties such as flexural strength of 162 MPa and hardness of 778 kg/$\textrm{mm}^2$.

• Journal of Powder Materials
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• v.17 no.1
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• pp.13-22
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• 2010

The unique features of spark plasma sintering process are the possibilities of a very fast heating rate and a short holding time to obtain fully dense materials. $\beta$-SiC powder with 0, 2, 6, 10 wt% of $\alpha$-SiC particles (seeds) and 4 wt% of Al-B-C (sintering aids) were spark plasma sintered at $1700-1850^{\circ}C$ for 10 min. The heating rate, applied pressure and sintering atmosphere were kept at $100^{\circ}C/min$, 40 MPa and a flowing Ar gas (500 CC/min). Microstructural development of SiC as function of seed content and temperature during spark plasma sintering was investigated quantitatively and statistically using image analysis. Quantitative image analyses on the sintered SiC ceramics were conducted on the grain size, aspect ratio and grain size distribution of SiC. The microstructure of SiC sintered up to $1700^{\circ}C$ consisted of equiaxed grains. In contrast, the growth of large elongated SiC grains in small matrix grains was shown in sintered bodies at $1750^{\circ}C$ and the plate-like grains interlocking microstructure had been developed by increasing sintering temperature. The introduction of $\alpha$-SiC seeds into $\beta$-SiC accelerated the grain growth of elongated grains during sintering, resulting in the plate-like grains interlocking microstructure. In the $\alpha$-SiC seeds added in $\beta$-SiC, the rate of grain growth decreased with $\alpha$-SiC seed content, however, bulk density and aspect ratio of grains in sintered body increased.