• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.682-683
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• 2006

Thermoelectric conversion efficiency of thermoelectric elements can be increased by using a structure combining n-type and p-type semiconductors. From the above point of view, attention was directed at ZnO as a candidate n-type semiconductor material and investigations were made. As the result, a dimensionless figure of merit ZT close to 0.28 (1073K) was obtained for specimens produced by the PCS (Pulse Current Sintering) method with addition of specified quantities of $TiO_2$, CoO, and $Al_2O_3$ to ZnO. It was found that the interstitial $TiO_2$ in the ZnO restrains the grain growth and CoO acts onto the bond between grains. The influence of the inclusion of $TiO_2$ and CoO onto the sintering behavior also was investigated.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.538-539
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• 2006

The influence of the internal current for the ZnO ceramics on the sintering behavior by pulse current sintering (PCS) method was investigated. To clear the dependence of inner current on the sintering behavior of ZnO ceramics, direct measurement of electric resistance of ZnO specimen under sintering by SPS device was carried out. It was observed that electric resistance of specimen decreases with increase in the temperature. The electric resistance begins to decrease from the low temperature of $200^{\circ}C$. The internal structure of sintered ZnO ceramics changed by the control of the internal current in the specimen using $Al_2O_3$ plate.

• Journal of Powder Materials
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• v.23 no.1
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• pp.1-7
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• 2016

Cu-Mn compacts are fabricated by the pulsed current activated sintering method (PCAS) for sputtering target application. For fabricating the compacts, optimized sintering conditions such as the temperature, pulse ratio, pressure, and heating rate are controlled during the sintering process. The final sintering temperature and heating rate required to fabricate the target materials having high density are $700^{\circ}C$ and $80^{\circ}C/min$, respectively. The heating directly progresses up to $700^{\circ}C$ with a 3 min holding time. The sputtering target materials having high relative density of 100% are fabricated by employing a uniaxial pressure of 60 MPa and a sintering temperature of $700^{\circ}C$ without any significant change in the grain size. Also, the shrinkage displacement of the Cu-Mn target materials considerably increases with an increase in the pressure at sintering temperatures up to $700^{\circ}C$.

• Korean Journal of Materials Research
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• v.31 no.5
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• pp.296-300
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• 2021

Al-Cr-Si ternary quench ribbons are fabricated using a single roll method and investigated for their structural and thermal properties. In particular, the sinterability is examined by pulse current sintering to obtain the following results. The Al₇₄Cr₂₀Si₆ composition becomes a quasicrystalline single phase; by reducing the amount of Cr, it becomes a two-phase mixed structure of Al phase and quasicrystalline phase. As a result of sintering of Al₇₄Cr₂₀Si₆, Al₇₇Cr₁₃Si₁₀ and Al₉₀Cr₆Si₄ compositions, the sintering density is increased with the large amount of Al phase; the sintering density is the highest in Al₉₀Cr₆Si₄ composition. In addition, as a result of investigating the effects of sintering temperature and pressurization on the sintered density of Al₉₀Cr₆Si₄, a sintered compact of 99% or more at 513 K and 500 MPa is produced. In particular, since the Al-Cr-Si ternary crystal is more thermally stable than the Al-Cr binary quaternary crystal, it is possible to increase the sintering temperature by about 100 K. Therefore, using an alloy of Al₉₀Cr₆Si₄ composition, a sintered compact having a sintered density of 99 % or more at 613 K and 250 MPa can be manufactured. It is possible to increase the sintering temperature by using the alloy system as a ternary system. As a result, it is possible to produce a sintered body with higher density than that possible using the binary system, and at half the pressure compared with the conventional Al-Cr binary system.

• Journal of the Korean Ceramic Society
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• v.44 no.7
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• pp.343-348
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• 2007

Alumina/silver nanocomposites were fabricated using a soaking method through a sol-gel route to construct an intra-type nanostructure. The pulse electric-current sintering (PECS) technique was used to sinter the nanocomposites. Several specimens were annealed after sintering. The microstructure, mechanical properties, critical frontal process zone (FPZ) size, and thermo-mechanical properties of the nanocomposites were estimated. The relative densities of the specimens sintered at 1350 and $1450^{\circ}C$ were 95% and 99%, respectively. The maximum value of the three-point bending strength was found to be 780 MPa for the $2{\times}2{\times}10 mm$ specimen sintered at $1350^{\circ}C$. The fracture toughness of the specimen sintered at $1350^{\circ}C$ was measured to be $3.60 MPa{\cdot}m^{1/2}$ using the single-edge V-notched beam (SEVNB) technique. The fracture mode of the nanocomposites was transgranular, in contrast to the intergranular mode of monolithic alumina. The fracture morphology suggested that dislocations were generated around the silver nanoparticles dispersed within the alumina matrix. The specimens sintered at $1350^{\circ}C$ were annealed at $800^{\circ}C$ for 5 min, following which the maximum fracture strength became 810 MPa and the fracture toughness improved to $4.21 MPam^{1/2}$. The critical FPZ size was the largest for the specimen annealed at $800^{\circ}C$ for 5 min. Thermal conductivity of the alumina/silver nanocomposites sintered at $1350^{\circ}C$ was 38 W/mK at room temperature, which was higher than the value obtained with the law of mixture.

• Journal of Powder Materials
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• v.6 no.4
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• pp.301-306
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• 1999

Mechanical properties of oxide based materials could be improved by nanocomposite processing. To investigate optimum route for fabrication of nanocomposite enabling mass production, high energy ball milling and Pulse Electric Current Sintering (PECS) were adopted. By high energy ball milling, the $Al_2O_3$-based composite powder with dispersed Cu grains below 20 nm in diameter was successfully synthesized. The PECS method as a new process for powder densification has merits of improved sinterability and short sintering time at lower temperature than conventional sintering process. The relative densities of the $Al_2O_3$-5vol%Cu composites sintered at $1250^{\circ}C$ and $1300^{\circ}C$ with holding temperature of $900^{\circ}C$ were 95.4% and 95.7% respectively. Microstructures revealed that the composite consisted of the homogeneous and very fine grains of $Al_2O_3$ and Cu with diameters less than 40 nm and 20 nm respectively The composite exhibited enhanced toughness compared with monolithic $Al_2O_3$. The influence of the Cu content upon fracture toughness was discussed in terms of microstructural characteristics.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1012-1013
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• 2006

A technology of hardening porous materials of titan powders has been elaborated. The technology is based on passing alternating current with duration of ${\sim}10^{-1}{\ldots}10^1$ s through porous ($35{\ldots}40%$) blanks made by method of Sintering by Electric Discharge (SED) by passing a pulse of current with duration of ${\sim}10^{-5}{\ldots}10^{-3}$ s. The influence of technological regimes of porous blanks treatment on their structure and properties is investigated. Geometry and dimension of contact necks between powder particles of obtained samples are evaluated. Variations of porosity and strengths as well as microstructure of porous samples materials before and after treatment are investigated. Optimum range of treatment technological regimes is determined within which porosity of $30{\ldots}35%$ with maximum strength values.

• Korean Journal of Materials Research
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• v.10 no.9
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• pp.642-647
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• 2000

Nanocrystalline NiAl alloy containing 36at.%Al was synthesized by mechanical alloying (MA). Synthesized powder was sintered by a pulse electric current sintering (PECS) facility. Effecting parameters on the phase transformation were discussed in terms of cooling rate and time spent on heat treatment. The behavior of phase transformation for sintered parts was examined by differential scanning calorimetry (DSC) and X-ray diffraction (XRD) method. Microstructure was observed by scanning electron microscopy (SEM). Martensitic lattice parameter and volume fraction was calculated by direct comparison method in X-ray diffraction analysis.