• Journal of the Korean Ceramic Society
• /
• v.45 no.4
• /
• pp.220-225
• /
• 2008

Lead-free ferroelectric ceramics are widely researched today for industrial applications as sensors, actuators and transducers. Since $Pb(Zr_aTi_{1-a})O_3$-(PZT) has high Curie temperature($T_C$), high piezoelectric properties near its morphotropic phase boundary(MPB) composition and small temperature dependence electrical behavior, it has been used to commercial materials for wide temperature range and different application fields. According to the tolerance factor concept, since the $Bi^{3+}$ cation with 12-fold coordinate has a smaller ionic radius than 12-fold coordinate $Pb^{2+}$, most bismuth based perovskites possess a smaller tolerance factor. Therefore, MPBs with a higher $T_C$ may be expected in $Bi(Me^{3+})O_3PbTiO_3$ solid solutions. As in lead based perovskite systems, it is clear that we need to explore more materials in simple or complex bismuth based MPB systems. The objective of this study is to investigate the $Bi(Ni_{1_a}X_a)O_3-PbTiO_3(X=Ti^{4+},\;Nb^{5+})$ perovskite solid-solution. For improving the electronic conduction problem, the magnesium and manganese modified system was also studied.

• Journal of the Korean Society of Safety
• /
• v.24 no.4
• /
• pp.22-27
• /
• 2009

In this paper, the minuteness structure, piezoelectric, and dielectric characteristics of $0.95{Pb(Sb_{1/2}Nb_{1/2})_{0.02})_{0.02}(Ni_{1/3}Nb_{2/3})_{0.13}(Zr_{0.48}Ti_{0.52})_{0.85}}O_3+0.05Pb(CO_{1/2}W_{1/2})O_3+0.3%$ $MnO_2+0.3wt%$ CuO ceramics has been systematically investigated as a function of the sintering temperature after manufacturing the specimens with a general method. This study will be very helpful as basic data for developing ceramic materials, More study in a soon time for improving stability of temperature, effect of adds and stability and reality of frequency with improved production condition for specimens will give a powerful potentiality as a applied material of dielectric ceramics.

• The Journal of the Petrological Society of Korea
• /
• v.11 no.1
• /
• pp.17-28
• /
• 2002

This study has been designed to elucidate the petrography and geochemical characteristics of the Taeheung-ri lava in southeastern Jeju Island. The lava is divided into the alkaline basalt and tholeiitic basalt. More than 4 layers of tholeiitic basalt are overlain by layers of alkaline basalt. Compared with alkaline basalt, tholeiitic basalt has lower contents of $K_2O$, $P_2O_5$, Ba and Ta, but slight higher contents of $SiO_2$ and CaO. The contents of Ba and Rb of all basalts are enriched, but those of Ni and Cr are depleted compared with primitive mantle compositions. All basalts show inclined chondrite-normalized REE patterns with LREE enriched more than HREE and alkaline basalt has relatively higher. The basalts of this study area are plotted in the field of within plate basalt on the tectonomagmatic discrimination diagram. Tholeiitic basalt has higher ratios of Zr/Nb, Y/Nb, and $Al_2O_3/P_2O_5$ than alkaline basalt. Both tholeiitic and alkaline basalt are similar in their K/Ba ratios. The geochemical data suggest that the parental magma of both basalts might be produced by different degrees of partial melting of similar source mantle. The tholeiitic basalt formed by higher degree of partial melting than the alkaline basalt.

• Proceedings of the KIEE Conference
• /
• 1992.07b
• /
• pp.759-761
• /
• 1992

$0.10Pb(Sb_{1/2}Sn_{1/2})O_3-0.25PbTiO_3-0.65PbZrO_3+MnO_2(0.18mol%)$, NiO(0.15mol%) temary compound ceramics won fabricated by the mixed-oxide method. Noise properties of the pyroelectric infrared sensor were investigated with particle size of the raw materials and gain size of the specimens. Particle size were decreased and sintered density, voltage resposivity were increased with increasing the ball-mill times. The specimen ball-milled for a 80[hr] showed a good pop-corn noise properties.

• Journal of the Mineralogical Society of Korea
• /
• v.10 no.1
• /
• pp.60-73
• /
• 1997

The talc of the Daeheung, Pyeongan, and Cheongdang (Shinyang) talc deposits in the Yesan-Gongju-Cheongyang area is a hydrothermal alteration product of serpentinite originated from ultramafic rocks. The mineral assemblages in alteration zones are: serpentine, serpentine-talc, talc, talc-chlorite, talc-phlogopite-chlorite, and talc-tremolite-chlorite. Chemical distributions in both the Al2O3-FeO-MgO system and the immobile elements suggest that the serpentine-talc and talc rocks are the reaction product of ultramafic rocks and silicic hydrothermal solution without addition of other granitic components, whereas chlorite-, phlogopite-, and tremolite-bearing rocks are the metasomatic alteration product of serpentinite by hydrothermal solution affected by granitic gneiss. Discontinuities in the immobile element ratios of mineral assemblages are due to changes in their mineralogy. The relative contents of Al2O3, TiO2, Zr in the talc-phlogopite-chlorite and talc-tremolite-chlorite rocks increase irregularly with increasing phlogopite, tremolite, and/or chlorite contents in contrast to other ore types. But the relative contents of Cr, Ni, and Co are uniform in all the mineral assemblages. Chemistry of each mineral assemblage formed by steatitization of serpentinite suggests that Cr, Co, Ni, MgO, and Fe2O3 are relatively immobile during the alteration, whereas SiO2, Al2O3, CaO, and K2O are highly increased. The contents of chlorite, phlogopite, and tremolite in each mineral assemblage might be controlled by addition of Al2O3, K2O, and CaO, respectively. The high contents of other elements than immobile elements in the altered rocks as compared with unaltered rocks indicate that a large amount of elements were introduced from hydrothermal solution up to about 8∼41% in total mass showing maximum value in the talc-phlogopite-chlorite rock.

• Journal of the Mineralogical Society of Korea
• /
• v.19 no.3 s.49
• /
• pp.163-169
• /
• 2006

Mineralogy and geochemistry of the sediment core from the seamount (2710 m below the sea level) just south of the Antarctic Polar Front were examined to draw paleoceanographic information in glacial-interglacial cycles. Smectite was most abundant clay mineral associated with illite and chlorite. Its content was slightly higher below 170 cm, suggesting a boundary between isotope stage 4 and 5. Si, Zr, Cs, Th, REE, $K_{2}O$, and $Al_{2}O_{3}$ show complete antithetical distribution with respect to $CaCO_{3}$ through the core. $SiO_{2}$ maxima and $CaCO_{3}$ minima at depths of 24, 136, and 176 cm are probably correlated with massive influx of ice-rafted debris during the advance of Antarctic ice shelves. Ni, Cu, and Ba show rather little correlation with $SiO_{2}$, suggesting their relation to biogenic debris, precipitation from seawater, or hydrothermal input. Particularly, Ba maxima tend to lag $10{\sim}20cm$ after $SiO_{2}$ maxima, probably due to rapid increase of productivity following deglaciation.

• Nuclear Engineering and Technology
• /
• v.55 no.1
• /
• pp.156-168
• /
• 2023

This study investigates the high temperature oxidation behaviour of a Ni-20Cr-1.2Si (wt.%) alloy in steam from 1200 ℃ to 1350 ℃ by Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Diffraction (XRD). The results demonstrate that exposed Ni-based alloy developed a thin oxide scale, consisted mainly of Cr₂O₃. The oxidation kinetics obtained from the experimental results was applied to evaluate the hydrogen generation considering a simplified reactor core model with different cladding alloys following an unmitigated Loss-Of-Coolant Accident (LOCA) scenario in a hypothetical Small Modular Reactor (SMR). Overall, experimental data and simulations results show that both Fe-based and Ni-based alloys may enhance cladding survivability, delaying its melting, as well as reducing hydrogen generation under accident conditions compared to Zr-based alloys. However, a substantial neutron absorption occurs when Ni-based alloys are used as cladding for current uranium-dioxide fuel systems, even when compared to Fe-based alloys.

• Proceedings of the KIEE Conference
• /
• 1997.07d
• /
• pp.1326-1329
• /
• 1997

In this paper, PNN-PZN-PZT ceramics were fabricated with various mole ratio of the PZT[$Pb(Zr_{1/2}Tid_{1/2})O_3$]. PNN [$Pb(Ni_{1/3}Nb_{2/3})O_3$] and PZN[$Pb(Ni_{1/3}Nb_{2/3})O_3$ powders prepared by double calcination and PZT powders prepared by molten-salt synthesis method. The formation rate of perovskite phase in PNN-PZN-PZT ceramics could be obtained about 92% at PZT 0.3 mole ratio. The relative permittivity of specimen with PZT 0.3 mole ratio was shown 5,320 and appeared the relaxor ferroelectric feature. The maximum piezoelectric coefficient $d_{31}$ to be used for evaluation the displacement of piezoceramics in PNN-PZN-PZT ceramics was $324{\times}10^{-12}$(C/V) at the vicinity of morphotropic phase boundary and was larger than that of solid PZT ceramics($120{\times}10^{-12}C/V$).

• Proceedings of the KIEE Conference
• /
• 1997.07d
• /
• pp.1330-1332
• /
• 1997

In this paper, PNN-PZN-PZT ceramics were fabricated with various mole ratio of the PZT[$Pb(Zr_{1/2}Tid_{1/2})O_3$]. PNN [$Pb(Ni_{1/3}Nb_{2/3})O_3$] and PZN[$Pb(Ni_{1/3}Nb_{2/3})O_3$ powders prepared by double calcination and PZT powders prepared by molten-salt synthesis method. The formation rate of perovskite phase in PNN-PZN-PZT ceramics could be obtained about 92% at PZT 0.3 mole ratio. The relative permittivity of specimen with PZT 0.3 mole ratio was shown 5,320 and appeared the relaxor ferroelectric feature. The maximum piezoelectric coefficient $d_{31}$ to be used for evaluation the displacement of piezoceramics in PNN-PZN-PZT ceramics was $324{\times}10^{-12}$(C/V) at the vicinity of morphotropic phase boundary and was larger than that of solid PZT ceramics($120{\times}10^{-12}C/V$).

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.20 no.10
• /
• pp.3234-3242
• /
• 1996

This paper describes experimental results of modified small punch( MSP) test conducted to evaluate the fracure characteristics and mechanical properties of plasma sparayed zirconia ($ZrO_2$ stabilized with 8wt. % $Y_20_3$ : YSZ) NiCrAlY composite. The mixing ratios of YSZ/NiCrAlY were 0/100, 25/75, 50/50, 100/0 v.%. Test temperatures ranged from 293K to 1473K. This study is directed at development of thermal barrrier coating(TBC) system with superior heat resistance and mechanical properties. The microstructure and fracture process of the composite were examined by SEM and AE method. The mechanical properties of 100% YSZ were nearly independent of the temperatures tested in this study. In contrast, the NiCrAlY-containing composites showed a significant decrease of the mechanical properties above 1273K, showing a ductile- brittle transition behavior up to the temperature. Furthermore, it can seen that 25% YSZ/75% NiCrAlY composite gave the highest fracure strength and fracture energy among the mixing ratio tested over the temperature range.