• Journal of the Korean Ceramic Society
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• v.29 no.3
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• pp.211-215
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• 1992

Crack free PbTiO3 ceramics were produced by sol-gel processing using alkoxide, which has not been reported to be successful. The PbTiO3 gels were prepared from Ti alkoxide and lead acetate without any dopants. They were calcined at $600^{\circ}C$ and miled to produce fine PbTiO3 powder. It was pressed into discs and they were sintered at 110$0^{\circ}C$ for a few hours. The sintered ceramics were relativley hard and dense as having about 96% of theoretical density of PbTiO3. Fabrication of pure PbTiO3 ceramics by sol-gel processing is possibly due to their small grain size and uniform distribution of residual stress created during cubic-tetragonal transition over large number of small grains in fine grain PbTiO3 ceramics.

• Journal of the Korean Ceramic Society
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• v.32 no.1
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• pp.120-130
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• 1995

To analyze the mechanical property and the residual stress in functionally gradient materials(FGMs), disctype TZP/Ni-and TZP/SUS304-FGM were hot pressed using powder metallurgy compared with directly bonded materials which were fabricated by the same method. The continuous interface and the microstructure of FGMs were characterized by EPMA, WDS, optical microscope and SEM. By fractography, the fracture behavior of FGMs was mainly influenced by the defects which originated from the fabrication process. And the defectlike cracks in the FGMs induced by the residual stress have been shown to cause failure. This fact has well corresponded to the analysis of the residual stress distribution by Finite Element Method (FEM). The residual stress generated on the interface (between each layer, and matrix and second phase, respectively) were dominantly influenced on the sintering temperature and the material constants. As a consequence, the interfacial stability and the relaxation of residual stress could be obtained through compositional gradient.

• Resources Recycling
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• v.9 no.2
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• pp.18-25
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• 2000

Magnetic and physical properties of sintered bodies prepare from waste sintered barium hexaferrite magnets which were come from fabrication process of isotropic permanent magnets were investigated. The properties of the sintered bodies were characterized by XRD, XRF, SEM, and BH curve tracer. After the waste permanent magnets were milled and granulated, the granules of the waste permanent magnet powders and the commercial granules were mixed with various proportions, pressed, and sintered. although the magnetic properties were decreased gradually with the content of waste magnet powder, the magnetic characteristics of the sintered magnets at $1150~1200^{\circ}C$ were comparable to those required for isotropic permanent magnets.

• Progress in Superconductivity
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• v.1 no.2
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• pp.120-124
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• 2000

Ni-13%Cr and Ni-70%Cu alloy tapes were prepared by using high purity metal powders as starting materials. The Ni-13%Cr and the Ni-70%Cu mixtures were isostatically pressed, sintered, rolled and texture-annealed. SEM EDS analysis showed that copper and nickel atoms were completely mixed, while the alloying between the chromium powders and the nickel powders was incomplete. In spite of incomplete alloying between nickel and chromium powders, sharp cube-texture was developed for the Ni-13%Cr tape as well as the Ni-70%Cu tape.

• Journal of the Korean Chemical Society
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• v.16 no.6
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• pp.373-377
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• 1972

The analytical conditions for the fluorescence X-ray determination of small amount of cupper in solution were established. Copper in solution was extracted by diethyldithiocarbamate ethyl acetate and adsorbed by zinc powder. After drying, it was pressed to tablet under the pressure of $250Kg/cm^2.$$K_{\alpha}2(2{\theta}_{LiF} = 45.08^{\circ})$. The limit of detection was estimated to be about $10{\mu}g$ by the method of standard addition with an error of 10 %.

• Proceedings of the Korean Magnestics Society Conference
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• 2000.09a
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• pp.381-388
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• 2000

By applying Current-applied Pressure-Assisted process, we could obtain full dense isotropic and anisotropic NdFeB magnets from rapidly quenched MQP-A powder. The Nd contents are found to play an important role during the CA-press and CA-deformation process. The (BH)$\sub$max/ of CA-pressed and CA-deformed magnets are 131 kJ/㎥(16.5 MGOe) and 352 kJ/㎥(44.2 MGOe), respectively. The texture of CA-deformed anisotropic NdFeB magnets with thickness reduction was investigated by pole figure, and the (006) texture was increase with the increase of thickness reduction. With the increment in thickness reduction from 50%, 60% to 80%, W$\sub$50/ decreases from 76$\^$$^{\circ}$/, 62.5$\^$$^{\circ}$/ to 17$\^$$^{\circ}$/, respectively.

• Journal of the Korean Ceramic Society
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• v.30 no.11
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• pp.941-948
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• 1993

The powder mixture of Si3N4-AlN-Y2O3, Si3N4-AlN-CeO2 and Si3N4-AlN-Y2O3-CeO2 system was hot-pressed at 175$0^{\circ}C$ for 2h in N2 to prepare $\alpha$-Sialon ceramics. The mechanical property and oxidation behaviour of the prepared $\alpha$-Sialon ceramics were investigated. At 120$0^{\circ}C$, oxidation resistance was best for the Y2O3 added $\alpha$-Sialon ceramics and oxidation rate increased when the amount of CeO2 increased. But when the mixture of Y2O3 and CeO2 added $\alpha$-Sialon ceramics showed a good oxidation resistance. Fracture toughness of (Y2O3＋CeO2) added $\alpha$-Sialon ceramics was higher than Y2O3 added $\alpha$-Sialon ceramics.

• Journal of the Korean Ceramic Society
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• v.29 no.2
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• pp.143-151
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• 1992

Partially stabilized alpha-sialon composition (X=0.1) powder was hot-pressed at 1800~200$0^{\circ}C$ for 0~90 min with 30 MPa. Sintering behavior, phase changes and mechanical properties for the specimens were studied. As sintering temperature was raised from 1800 to 190$0^{\circ}C$, the relative density tended to increase and reached 99% of theoretical at 190$0^{\circ}C$. However the amount of alpha-sialon decreased because alpha-sialon transformed to beta-Si3N4 and yttrium rich silicate glass. In the case of hot-pressing at 190$0^{\circ}C$ for various times, densification increased with sintering time and full densification above 99% of theoretical was attained by 30 min. The amount of alpha-sialon decreased with sintering time. The maximum strength of 825 MPa was obtained by hot-pressing at 190$0^{\circ}C$ for 60 min.

• Journal of Magnetics
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• v.5 no.4
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• pp.130-134
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• 2000

Using the current-applied pressure-assisted (CAPk) process, we could obtain fully dense isotropic and anisotropic NdFeB magnets from rapidly quenched MQP-A powder. The Nd content is found to play an important role during the current applied (CA)-pressing and CA-deformation processes. The $(BH)_max$ of CA-pressed and CA-deformed magnets are 131 kJ/$m^3$ (16.5 MGOe) and 352 kJ/$m^3$(44.2 MGOe), respectively. The change in texture of CA-deformed anisotropic NdFeB magnets with thickness reduction was investigated by pole figures and the (006) texture was found to increase with greater thickness reductions. As the thickness reduction increases from 50% to 60% to 80%, $W_50$ (the average angle of the contour with 50% intensity) decreases from $76^\circ$to $62.5^\circ$to $17^\circ$.

• Journal of the Korean Ceramic Society
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• v.39 no.2
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• pp.199-203
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• 2002

To investigate an effect of sintering atmosphere on microstructure and properties of metallic particle dispersed ceramic based composites, the powder mixtures of $Al_2O_3$/Fe-Ni, synthesized by chemical solution process, were hot-pressed under different atmospheres such as hydrogen or argon gas and different sintering temperature. Hot-pressed composite in a hydrogen atmosphere exhibited less reaction phase of $FeAl_2O_4$ and enhanced mechanical properties than that in an argon atmosphere. Furthermore, decreasing hot-pressing temperature produced a refinement of ceramic matrix and metallic dispersion particles as well as improvement of mechanical properties. The change of mechanical properties in the composites with different sintering conditions was explained by microstructural characteristics relating to reaction phase formation.