• Journal of Powder Materials
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• v.16 no.1
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• pp.63-67
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• 2009

In order to investigate the effect of rapid solidification on the microstructure and the mechanical properties of Al-Zn-Mg system alloys, water atomization was carried out, since the water atomization beared the highest solidification rate among the atomization processes. The as atomized alloy powders consisted of fine grains less than 4 ${\mu}m$ in diameter, and the second particles were not detected on XRD. The microstructure as solidified was maintained even after the spark plasma sintering at the heating rate of 50 K/min. On the other hand, lower rate of 20 K/min induced a formation of $MgZn_2$ particles, resulting in strengthening of the matrix. The density was almost constant at the temperature above 698K. The sintering temperature above 698K had no effect on the strength of the sintered materials.

• Korean Journal of Materials Research
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• v.3 no.3
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• pp.276-281
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• 1993

In order to study the sintering kinetics of the ternery system, U-Ce-O, its shrinkage rate with time and temperature at the Ar atmoshpere were measured by using the dilatometer. At the sintering kinetics of U-Ce-O, sintering rate curve revealed bimodal and the first extreme point at bimodal curve was affected by the $UO_2$ the second one was due to the $CeO_2$. The sintering of $(U, Ce)O_2$ was delayed as increasing the $CeO_2$. At the same lOwt. % content, the highest sintering rate was observed at the $(U, Ce)O_2$ sample ball-milled for 4 hours.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.23 no.2
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• pp.77-79
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• 2014

There are several factors affected fractures of full contour zirconia (FCZ) dental prosthesis in laboratory process. First, residual moisture can cause zirconia cracks. Complete dry is requisite before zirconia sintering to prevent zirconia cracks. Second, slow cooling rate is essential to prevent cracks during zirconia sintering process. Cracks in bridge pontic area, thick dental implant prosthesis can be prevented by slow cooling rate such as 3 degree Celsius per minute during zirconia sintering. Third, slow heating rate and slow cooling rate during staining and glazing procedure is necessary to inhibit thermal shock of sintered dental zirconia. Lower preheat temperature of porcelain furnace is recommended. Finally, using diamond disc to open embrasure can lead cracks.

• Journal of Powder Materials
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• v.10 no.4
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• pp.270-274
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• 2003

Recently, the fabrication process of W-Cu nanocomposite powders has been researched to improve the sinterability by mechanochemical process (MCP), which consists of ball milling and hydrogen-reduction with W- and Cu-oxide mixture. However, there are many control variables in this process because the W oxides are hydrogen-reduced via several reduction stages at high temperature over 80$0^{\circ}C$ with susceptive reduction conditions. In this experiment, the W-15 wt%Cu nanocomposite powder was fabricated with the ball-milling and hydrogen-reduction process using W and CuO powder. The microstructure of the fabricated W-Cu nanocomposite powder was homogeneously composed of the fine W particles embedded in the Cu matrix. In the sintering process, the solid state sintering was certainly observed around 85$0^{\circ}C$ at the heating rate of 1$0^{\circ}C$/min. It is considered that the solid state sintering at low temperature range should occur as a result of the sintering of Cu phase between aggregates. The specimen was fully densified over 98% for theoretical density at 120$0^{\circ}C$ for 1 h with the heating rate of 1$0^{\circ}C$/min.

• Journal of the Korean Ceramic Society
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• v.31 no.7
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• pp.739-744
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• 1994

The B4C-C system was investigated to gain an understanding of the sintering behaviors of B4C. In order to get sintered density of 97% TD, sintering temperature of 225$0^{\circ}C$ was necessary. Since such a high temperature operation is actually difficult on a commercial basis, our objective was to examine the possibility of decreasing the sintering temperature by adding SiC. The addition of SiC in B4C increases the sintering rate about at 210$0^{\circ}C$ and results in a fine microstructure with more than 98% relative density on 55 wt% B4C-40wt% SiC-5 wt% C composition. The probability of liquid phase sintering was investigated, but the evidences of liquid phase formation were not observed with XRD and TEM observation. It was proposed that the addition of SiC and carbon to B4C reduce interface energy during sintering, which results in enhanced grain-boundary diffusion. Thus, the enhanced grain-boundary diffusion and retarded grain growth by SiC improve densification.

• Journal of the Korean Ceramic Society
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• v.32 no.9
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• pp.1027-1032
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• 1995

SiC had been widely applied for mechanical sealing as a sealing material. SiC sintering is commonly made of reaction sintering, presureless sintering, and hot isostatic pressing (HIP) sintering. In this investigation, however, clay bonded sintering was used to avoide any complications of the special sintering methods as mentioned above. In order to prevent harmful SiC oxidation in the clay bonded sintering, clay and frit were used to form the SiC oxidation protecting layer and graphite was added to provide high solid lubricity. As a result, the material with 6% clay (clay 5.4% and frit 0.6%) and 2~4% graphite (45 mesh) sintered at 140$0^{\circ}C$ for 3 hours, showed the following physical properties; porosity 6%, static friction coefficient 0.15, kinematic coefficient 0.1,. and specific wear rate 4.8$\times$10-8 $\textrm{mm}^2$kgf-1. On the other hand, the flexural strength was 900kgf/$\textrm{cm}^2$. This tribological characteristic properties were similar to those of the reaction sintered SiC except the flexural strength.

• Journal of the Korean Ceramic Society
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• v.29 no.4
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• pp.265-272
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• 1992

Role of CaO in the sintering of 12Ce-TZP ceramics was studied. The addition of small amounts of CaO increase the densification rate of 12Ce-TZP by altering lattice defect structure and the diffusion coefficient of the rate controlling species, namely cerium and zirconium cations. CaO also inhibits grain growth during sintering and allows the sintering process to proceed to theoretical density by maintaining a high diffusion flux of vacancies from the pores to the grain boundaries. The inhibition of grain growth is accomplished by the segregation of solute at the grain boundaries, causing a decrease in the grain boundary mobility. The segregation of calcium was revealed by AES study.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.274-275
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• 2006

The sintering behavior of titanium-titanium nitride nanocomposite powders has been studied by dilatometry. Titanium. titanium nitride nanocomposite powders were produced by the reactive milling of micron sized titanium powder $(12\;{\mu}m)$ in nitrogen atmosphere. The Ti-TiN nanocomposite powders milled for various durations along with the initial micron sized Ti powders were then sintered in the temperature range of $450-1000^{\circ}C$ by a constant rate of heating $(10^{\circ}C/min)$. The linear shrinkage, shrinkage rate, activation energy for sintering and microstructure has been studied and discussed as a function of milling time.

• Electrical & Electronic Materials
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• v.1 no.1
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• pp.26-34
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• 1988

Sintered CdS/CdTe solar cells have been farbricated by coating a (Cd+Te) slurry on sintered CdS films followed by the sintering at 625.deg.C for one hour with various heating rates. When cadmium and tellurinm powders are used instead of CdTe powder to form CdS/CdTe junction, CdTe is formed in the temperature range of 290.deg.C-400.deg.C. The microstructure of the CdTe films depends strongly on the heating rate of the sintering due to the low melting temperature and the high vapor pressure of the elemental Cd and Te. An optimum heating rate obtain CdTe films with uniform and dense microstructure which, in turn, improves the efficiency of the sintered CdS/CdTe solar cells. All-polycrystalline CdS/CdTe solar cells with an efficiency of 9.57% under 50mW/cm$^{2}$ tungsten light have been farbricated by using a heating rate of 14.deg.C/min.

• Electrical & Electronic Materials
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• v.9 no.8
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• pp.836-850
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• 1996

In this study, we have analyzed structural analysis and measured ferroelectric characteristics of PZT thin films prepared by sol gel process with different sintering conditions and different Zr/Ti mot%. When the Zr mot% of PZT thin film was increased, it was found that the remanent. polarization and coercive field were decreased and increased, respectively. Also, the maxium dielectric constant of PZT(50/50) thin film was 786.8. We got double hysteresis(anti-fcrroelectric) curve from PbZrO$_{3}$ thin film. As heating rate goes up, pyrochlore phase of PZT thin film was decreased and dielectric and ferroelectric characteristics were improved. As a result of variation of sintering temperature and time 500.deg. C-800.deg. C and 5 sec.-8 hours, respectively, we got optimal sintering temperature and time. The optimium sintering temperature and time of conventional furnace method and rapid thermal processing method were 650.deg. C-700.deg. C for 30-60 minutes and 700.deg. C/20 seconds-2 minutes, respectively.