• Transactions of Materials Processing
• /
• v.12 no.6
• /
• pp.588-596
• /
• 2003

The relationships between evolution of microstructure and mechanical properties of porous Al-3Si-2Mg-2Cu alloy after the foaming and various heat treating were investigated. The foamed alloy having various densities were manufactured by powder compact foaming and heat treated. Then compression test was performed with deformation rate of 0.5/s. The ultimate compression strength was not changed after solution heat treatment but the flow curve after ultimate strength showed very smooth and uniform plateau region. This change of flow curve means that the deformation mechanism is altered from brittle fracture to ductile deformation and the energy absorption property of Al foam is dramatically improved. The improvement of energy absorption without any detriment of mechanical properties is due to that the very brittle precipitation like Al-Cu and Al-Mg was uniformly dissolved in Al matrix after solution heat treatment. And various mechanical properties of Al alloy porous material were improved by 40% with aging of $200^{\circ}C$ and 50min. These improvements are ascribe to the various fine precipitates like $\Omega$ and $\theta$'.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.03a
• /
• pp.5-5
• /
• 2010

$(Na_{0.5}K_{0.5})NbO_3$ (NKN) ceramic with 1.5 mol% CuO added (NKNC) was well sintered even at a low temperature of $900^{\circ}C$ with the addition of ZnO. Most of the ZnO reacted with the CuO and formed the liquid phase that assisted the densification of the specimens at $900^{\circ}C$. A few $Zn^{2+}$ ions entered the matrix of the specimens and increased the coercive field ($E_c$) and $Q_m$ values of the specimens. High-piezoelectric properties of $k_p=0.37$, $Q_m=755$, and ${\varepsilon}_3\;^T/{\varepsilon}_0=327$ were obtained from the NKNC ceramics containing 1.0 mol% ZnO sintered at $900^{\circ}C$ for 2 h.

• International Journal of Advanced Culture Technology
• /
• v.3 no.2
• /
• pp.132-137
• /
• 2015

The purpose of this paper was to investigate the effects of solution treatment time and Sr-modification on the microstructure and property of the Al-Si piston alloy. It was found that as-cast microstructures of unmodified and Sr-modified Al-Si alloys consisted of a coarse acicular plate of eutectic Si, $Cu_3NiAl_6$ and $Mg_2Si$ phases in the ${\alpha}$-Al matrix but different in size and morphology. Both size and inter-particle spacing of Si particles were significantly changed by increasing of the solution treatment time. After a short solution treatment, the coarse acicular plate of the eutectic Si appears to be fragmented. Fully modified microstructure of Sr-modified alloy can reduce the solution treatment time to shorter compared to unmodified alloy. The maximum of a peak hardness value is found in the very short solution treatment of both Al-Si piston alloys. Compared to 10 h solution treatment, the solution treatment of 2-4 h is sufficient to achieve appropriate microstructures and hardness. The short solution treatment is very useful to increase the productivity and to reduce the manufacturing cost of the Al-Si piston alloys.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.16 no.3
• /
• pp.231-237
• /
• 2003

RE(Nd, Sm) elements doped (RE/Y)$_{1.8}$B $a_{2.4}$C $u_{3.4}$$O_{7-x}$ [(RE/Y)1.8] high $T_{c}$ superconductors were directionally grown by Top Seed Melt Growth(TSMG) process in air atmosphere. The (001)melt-textured N $d_{1.8}$B $a_{2.4}$C $u_{3.4}$ $O_{7-X}$(Nd1.8) seed crystals were used for achieving the c-axis alignment large grains perpendicular to surface of the samples. The (RE/Y)1.8 SEM micrographs of the melt-textured (RE/Y)1.8 samples revealed that the nonsuperconducting (RE/Y)211 inclusions are uniformly distributed in the superconducting (RE/Y)123 matrix except the region very close to the Nd seed crystal. The microstructure and superconducting properties were investigated by XRD, SEM, TEM and SQUID magnetometer. The Melt-textured (RE/Y)1.8 samples showed an onset $T_{c}$=91K and sharp superconducting transition. Also, the magnetization value of the (RE/Y)1.8 samples were compared with those of Y1.8 sample at 77 K. 77 K. 77 K. 77 K.K.

• Korean Journal of Crystallography
• /
• v.8 no.2
• /
• pp.132-137
• /
• 1997

The crystal structure of N,N'-di-tert-butoxycabonyl-2,7-diazabicyclo[3.3.0]oct-4-ene has been determined from single crystal x-ray diffraction study; C16H26N2O4, Triclinic, P1, a=11.119(1) Å, b=13.638(1) Å, c=6.214(1) Å, α=92.14(1)°, β=103.49(1)°, γ=73.35(1)°, V=877.4(2)Å3, T=293(2)K, Z=2, CuKα(λ=1.5418Å). The structure was solved by direct method and refined by full-matrix least squares to a final R=5.38% for 2389 unique observed F0>4σ(F0) reflections and 225 parameters.

• Korean Journal of Crystallography
• /
• v.8 no.2
• /
• pp.138-143
• /
• 1997

The crystal structure of isoimperatorin, f-[(3-methyl-2-butenyl)oxy]-7H-furo[3,2-g][1] benzopyran-7-one, has been determined from single crystal x-ray diffraction study; C16H14O4, Monoclinic, P21/c, a=8.865(1) Å, b=9.331(1) Å, c=16.156(1) Å, β=98.12(1)', V=1322.9(2) Å3, T=293(2)K, z=4, Cu Kα(λ=1.5418 Å). The structure was solved by direct method and refined by full-matrix least squares to a final R=5.72% for 1922 unique observed Fo>4o(F0) reflections and 182 parameters.

• Korean Journal of Crystallography
• /
• v.6 no.1
• /
• pp.27-35
• /
• 1995

The crystal structure of 1-tert-butoxycarbonyl-4-[N-(tert-butoxycarbonyl)-N-(ethoxycarbonylmethyl)amino]-3-phenylsulfonylpyrrolidind [C24H36O8N2S] has been from single crystal x-ray diffraction study ; C24H36O8N2S triclinic, p1, a=11.363(8)Å, b=11.589(6)Å, c=11.013(10)Å,α=95.32(6)°,β=98.64(7)°,γ=79.57(5)°,V=1406.8(18)Å3, t=293K, Z=2, CuKα(λ=1.5418Å). The molecular structure was solved by diredt method and refined by full-matrix least squares to a final R=9.78% for 3621 unique observed [F≥4σ(F)] reflections and 703 paramenters.

• Korean Journal of Crystallography
• /
• v.6 no.2
• /
• pp.98-102
• /
• 1995

The crystal structure of -Ethyl-1,4-dihydro-7-methyl-1,8-naphthyridin-4-one-3-carboxylic acid [Nalicixic Acid] has been determined from single crystal X-ray diffraction study; C12H12N2O3, monoclinic, P21/c, a=8.910(2)Å, b=13.145(3)Å, c=9.370(3)Å, β =100.06(2)°, V=1080.6Å, T=293K, Z=4, CuKα(λ=1.5418Å). The molecular structure was solved by direct method and refined by full-matrix least squares to a final R=0.055 for 1555 unique observed [F0>4σ(F0)] reflections and 166 parameters. The conformation of the molecule is stabilized by an intramolecular O(17)-H(17)…O(14) hydrogen bond [2.525(2)Å, 144.3(10)°].

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.21 no.4
• /
• pp.347-360
• /
• 2015

Trace metals(As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Pb and Zn) concentrations in surface sediments of Jinhae bay in August of 2013 were measured to investigate the characteristics of trace metals distribution and to evaluate the metal pollution. Assessment for metal pollution was carried out using the sediment quality guidelines(SQGs) such as threshold effects level(TEL) and probable effects level(PEL) proposed by the ministry of onceans and fisheries(MOF) in Korea and geochemical assessment techniques(enrichment factor(EF) and geoaccumulation index ($I_{geo}$)). The mean concentration of trace metals in the sediments are as follows: 11.1 mg/kg for As, 0.52 mg/kg for Cd, 14.1 mg/kg for Co, 69.8 mg/kg for Cr, 57.2 mg/kg for Cu, 3.7 % for Fe, 0.064 mg/kg for Hg, 600 mg/kg for Mn, 40.1 mg/kg for Pb, 167.2 mg/kg for Zn. The spatial distributions of As, Co, Cr and Fe were not distinguished clearly in whole area. However, Cd, Hg, Pb and Zn were high in northern area of bay, and Cu and Mn were high in southeastern and eastern area of bay, respectively. The distribution pattern of trace metals, correlation matrix and R-mode factor analyses results revealed that the distribution of trace metals were mainly effected by the sediment grain size(Co, Cr and Fe), redox condition of sediments(Mn) and anthropogenic factors(As, Cd, Cu, Hg, Pb and Zn). Comparing the concentrations of several trace metals(As, Cd, Cr, Hg and Pb) with SQGs from Korea(TEL and PEL), the concentrations of Hg, Cd and Pb in sediment of northern area of bay were higher than TEL. EF and $I_{geo}$ values of As, Cd, Cu, Hg, Mn, Pb and Zn showed that these metals in sediments are enriched by anthropogenic activities in some areas, and pollution status for Cd, Hg and Pb in northern area and Cu in southeastern area of bay were concerned about current level, although those for As, Mn and Zn were not.

• Korean Journal of Environmental Agriculture
• /
• v.15 no.3
• /
• pp.372-382
• /
• 1996

In order to elucidate the relationship between the mobility of heavy metals in soil and their uptake by plants, the soil samples collected from the Mangyeong River area were analyzed for the contents and existing forms of the heavy metals and the correlation between the contents of heavy metals in the soil and those in various parts of rice plants therefrom. The soil samples were collectes from ten sites in the paddy fields in 1982 and 1990, respectively, and the analysis on heavy metals including Cd, Zn, Cu and Pb was performed. The results are as follows: Total contents of heavy metals in the samples of 1990 were higher than those of 1982. The extent of increase was that Cd, Zn, Cu and Pb were 3, 29, 59 and 8% in top soil and 8, 50, 91 and 8% in sub-soil, respectively. The order of increasing ratio was Cu > Zn > Pb > Cd and the variation of Cd content by sequentially different extraction was organically bound > dilute acid-extractable=Fe-Mn oxide bound > exchangeable > residual fractions and the content of Cd with organically bound was $46.62{\sim}48.08$ and $41.18{\sim}50.18%$ of total Cd in top and sub-soil, respectively. The ratios of immobile heavy metals, Cd, Pb, Cu and Zn, bound within an oxide or silicate matrix of Fe-Mn oxide in top-soil were 21.25, 35.98, 74.18 and 82.12%, respectively, and consequently their mobile ratios of exchangeable, dilute acid-extractable and organically bound were more than 17.88%. Those of mobile Cd, Pb, Cu and Zn were 78.25, 64.02, 25.82 and 17.88%, respectively. Except for Pb a correlation between the contents of Cd, Zn, and Cu of exchangeable and dilute acid-extractable in top-soil and those in leaf blade, stem and panicle axis was significant, but was not significant in sub-soil.