• The Korean Journal of Ceramics
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• v.2 no.4
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• pp.231-237
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• 1996

Mullite ceramics can be sintered by rf plasma sintering to densities as high as 97% compared to the theoretical density of the mullite, while SiC whisker-reinforced mullite matrix ceramic composites were not sintered by plasma sintering. Decomposition of mullite occurs in a superficial regins at the outside surface of the specimen by volatilization of SiO at elevated temperature by plasma. SiC whiskers were destroyed, and the matrix was converted to alumina from SiC-whisker reinforced mullite matrix ceramic composites during the plasma sintering. Accelerated volatilization from the SiC whisker in the mullite prevents sintering. The volatile species are mainly SiC and CO gas species. The effects of plasma on mullite and SiC-whisker reinforced mullite matrix composites are interpreted by thermodynamic simulation of the volatile species in the plasma environment. The thermodynamic results show that the decomposition will not occur during hot pressing.

• Journal of the Korean Ceramic Society
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• v.38 no.8
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• pp.687-692
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• 2001

Silicon nitride-La-silicon oxynitride ceramics were fabricated by Spark Plasma Sintering (SPS). The density, crystalline phase and microstructure were compared with those obtained by Hot Pressing (HP). The full density was achieved within 40 min by spark plasma sintering at 1$650^{\circ}C$, whereas the same result was required by hot pressing with a dwell time of 500 min at higher temperature. There were some differences in the microstructure and second phases in the sintered ceramics, which are attributed to the rapid densification in the spark plasma sintering. The fine and acicular grain microstructure appeared in spark plasma sintering.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.323-324
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• 2006

The nanostructure control of $Si_3N_4$ ceramics can be achieved by using fine starting powder and retardation of grain growth. The spark plasma sintering technique is useful to retard the grain growth by rapid heating. In the present work, the change of microstructure was investigated with emphasis on the particle size of starting powder, the amount of sintering additive and the heating schedule. The rapid heating by spark plasma sintering gave the fine microstructure consisting of equiaxed grains with the same size as starting particles. The spark plasma sintering of $Si_3N_4$ fine powder was effective to control the microstrucutre on nano-meter level.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.16 no.1
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• pp.38-42
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• 2006

Spark plasma sintering processes have been rapidly introduced recently to improve the quality and productivity of ceramic products and to solve the problem of environmental pollutions. Sintering temperatures and pressing pressures in the spark plasma sintering process are known to be the important factors highly affecting the quality of the ceramics. In this research, in order to see the effects of sintering temperatures and pressing pressures on the grain growth during the spark plasma sintering process of $Al_2O_3$ the grain growth processes associated with sintering temperatures and pressing pressures are simulated by the Monte Carlo method (MCM) and the finite element method (FEM). In this Part 1, the formulations for the simulation, which is the theoretical background of Part 2, are introduced.

• Journal of Powder Materials
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• v.19 no.2
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• pp.105-109
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• 2012

Magnetic properties and the microstructures of magnets prepared by spark plasma sintering were investigated in order to enhance magnetic properties by grain size control. Nd-Fe-B magnets were fabricated by the spark plasma sintering under 30 MPa at various temperatures. The grain size was effectively controlled by the spark plasma sintering and it was possible to make Nd-Fe-B magnets with grain size of 5.9 ${\mu}m$.

• Journal of Powder Materials
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• v.22 no.4
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• pp.283-288
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• 2015

Two sintering methods of a pressureless sintering and a spark-plasma sintering are tested to densify the Fe-TiC composite powders which are fabricated by high-energy ball-milling. A powder mixture of Fe and TiC is prepared in a planetary ball mill at a rotation speed of 500 rpm for 1h. Pressureless sintering is performed at 1100, 1200 and $1300^{\circ}C$ for 1-3 hours in a tube furnace under flowing argon gas atmosphere. Spark-plasma sintering is carried out under the following condition: sintering temperature of $1050^{\circ}C$, soaking time of 10 min, sintering pressure of 50 MPa, heating rate of $50^{\circ}C$, and in a vacuum of 0.1 Pa. The curves of shrinkage and its derivative (shrinkage rate) are obtained from the data stored automatically during sintering process. The densification behaviors are investigated from the observation of fracture surface and cross-section of the sintered compacts. The pressureless-sintered powder compacts show incomplete densification with a relative denstiy of 86.1% after sintering at $1300^{\circ}C$ for 3h. Spark-plasma sintering at $1050^{\circ}C$ for 10 min exhibits nearly complete densification of 98.6% relative density under the sintering pressure of 50 MPa.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.87-88
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• 2006

Ceramic-Metal Functionally Graded Materials (FGM) are of great interest for application as Thermal Barrier Coating (TBC) or Wear Resistant Coating (WRC). Spark Plasma Sintering (SPS) is a promising techniques for time-saving consolidation of laminated/graduated powder systems: SPS is a pressure-assisted electrical sintering method which directly applies a pulsed DC current as heat source. In the present work, production of $Al_2O_3-Ni$ FGMs by means of Spark Plasma Sintering is considered; effect of sintering condition on density, hardness and fracture toughness is studied. Problems correlated to this new processing technology are discussed.

• Journal of Powder Materials
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• v.11 no.1
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• pp.55-59
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• 2004

TiNi bodies were produced from (Ti＋Ni) powder mixture by spark-plasma sintering procerg. The sintering behavior was investigated through the measurement of change in density, densification rate, phase analysis and microstructure. Irrespective of heating rate, sintered bodies with above 97％ relative density could be obtained. TiNi with B2 structure was confirmed as the major phase and $Ti_2Ni,\;TiNi_3$, unreacted Ti, Ni as the second phase. Increase in heating rate suppressed a formation of intermediate phase during sintering process. Increase in holding time at sintering temperature led to a compositional homogenization.

• Journal of Powder Materials
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• v.27 no.4
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• pp.293-299
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• 2020

W₂C is synthesized through a reaction-sintering process from an ultrafine-W and WC powder mixture using spark plasma sintering (SPS). The effect of various parameters, such as W:WC molar ratio, sintering temperature, and sintering time, on the synthesis behavior of W₂C is investigated through X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) analysis of the microstructure, and final sintered density. Further, the etching properties of a W₂C specimen are analyzed. A W₂C sintered specimen with a particle size of 2.0 ㎛ and a relative density over 98% could be obtained from a W-WC powder mixture with 55 mol%, after SPS at 1700℃ for 20 min under a pressure of 50 MPa. The sample etching rate is similar to that of SiC. Based on X-ray photoelectron spectroscopy (XPS) analysis, it is confirmed that fluorocarbon-based layers such as C-F and C-F2 with lower etch rates are also formed.

• Journal of Powder Materials
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• v.22 no.5
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• pp.356-361
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• 2015

Fe-30 wt% TiC composite powders are fabricated by in situ reaction synthesis after planetary ball milling of (Fe, $TiH_2$, Carbon) powder mixture. Two sintering methods of a pressureless sintering and a spark-plasma sintering are tested to densify the Fe-30 wt% TiC composite powder compacts. Pressureless sintering is performed at 1100, 1200 and $1300^{\circ}C$ for 1-3 hours in a tube furnace under flowing argon gas atmosphere. Spark-plasma sintering is carried out under the following condition: sintering temperature of $1050^{\circ}C$, soaking time of 10 min, sintering pressure of 50 MPa, heating rate of $50^{\circ}C/min$, and in a vacuum of 0.1 Pa. The curves of shrinkage and its derivative (shrinkage rate) are obtained from the data stored automatically during sintering process. The densification behaviors are investigated from the observation of fracture surface and cross-section of the sintered compacts. The pressureless-sintered powder compacts are not densified even after sintering at $1300^{\circ}C$ for 3 h, which shows a relative denstiy of 66.9%. Spark-plasma sintering at $1050^{\circ}C$ for 10 min exhibits nearly full densification of 99.6% relative density under the sintering pressure of 50 MPa.