• The korean journal of orthodontics
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• v.25 no.2 s.49
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• pp.187-200
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• 1995

To estimate the characteristics of Korean Ni-Ti alloy orthodontic wire, this study investigated compositions, tensile properties, bending properties, heat treatment effects, and ion releasing degrees, and compared these characteristics to those of the imported Ni-Ti alloy wire. The results obtained are as follows ; 1. Ti and -Ni elements in ORTHOLLOY were in a range showing superelasticity, and there was a little difference in the Ni and Ti contents of ORTHOLLOY as compared with those of SENTALLOY. 2. The results of the tensile test concerning ORTHOLLOY exhibited a superelastic effect, indicating an area of a definite amount of stress in spite of the changes in the range from $2\%\;to\;8\%$ in the strain rate. 3. ORTHOLLOY presented higher load values than SENTALLOY in the same deflection values when the wire was tested in three-point bending. A load range displaying a superelastic effect was 80-l00g, 140-l80g, and 130-200g respectively, in wire diameters of 0.014', 0.016', and 0.018' 4. By heat treatments at $400^{\circ}C$ and at $500^{\circ}C$, a load range showing the effect of superelasticitly was lessened by the duration of the heat treatment time. The superelastic effect was destroyed as a result of the 10 minutes heat treatment at $600^{\circ}C$. 5. The quantity of the Ni ion released from ORTHOLLOY, tended to be greater than the amount of released Ni ion in SENTALLOY. The Co ion released was very little(<0.01ppm) in SENTALLOY and ORTHOLLOY irrespective of the lapse of time. Released Ni ions on the 1st day were at the maximum, and the releasing rate showed plateaus after three days. 6. The surface morphology of SENTALLOY was relatively regular irrespective of the lapse of rime, and the corrosion tendency was not observed. However, the surface morphology of ORTHOLLOY was rather irregular and shelved fitting corrosion after immersion.

• Bulletin of the Korean Chemical Society
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• v.23 no.1
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• pp.81-85
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• 2002

A new di-N-cyanoethylated 14-membered tetraaza macrocycle 1,8-bis(2-cyanoethyl)-3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetradecane $(L^2)$ and its nickel(II) complex $[NiL^2(OAc)]^+$ have been prepared. The square-planar complex $[NiL^2](C IO_4)_2$ can be prepared by addition of $HClO_4$ to a hot aqueous solution of $[NiL^2(OAc)]^+$ The Ni-N (tertiary amino group) bond distances $(2.008{\AA})$ of $[NiL^2](C IO_4)_2$ are relatively long, and the complex exhibits a d-d transition band at unusually long wavelength (ca. 515 nm). The complex $[NiL^2](C IO_4)_2$ rapidly reacts with acetate ion or ethylenediamine (en) to produce $[NiL^2(OAc)]^+$ or [Ni(en)_3]^{2+}$, respectively, and is readily decomposed in NaOH (0.01 M) solution. The chemical properties of $[NiL^2]^{2+}$ as well as its synthetic procedure are quite different from those for other related 14-membered tetraaza macrocyclic complexes. Effects of the N-cyanoethyl and C-methyl groups on the properties of $L^2$.

• Restorative Dentistry and Endodontics
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• v.23 no.2
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• pp.561-574
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• 1998

The purposes of this study were to observe the difference in the root canal wall after hand instrumentation or engine-driven Ni-Ti instrumentation under the scanning electron microscope, and to evaluate the apical leakage provided by continuous wave of canal filling technique with or without root canal sealer and smear layer. Twenty recently extracted human maxillary anterior teeth were instrumented with K-type files or engine-driven Ni-Ti files, Quantec series 2000$^{TM}$ and irrigated with 5.25% NaOCl alone or 15% EDT A and final flush of 5.25% NaOCl. After the instrumentation and flushing, teeth were split in half with a knife and a mallet. They were then examined with a scanning electron microscope Forty-four recently extracted human maxillary anterior teeth were divided into four groups with and without smear layer and then warm vertical canal filling using System-B with or without sealer. The extent of leakage was scored after immersion in India ink for 1 week. The results were as follows: 1. No significant difference of smear layer was observed between K-type file-instrumented group and engine-driven Ni-Ti file-instrumented group. 2. A group without smear layer showed significantly less apical leakage than a group with smear layer when sealer was used for the canal filling (p<0.01). 3. There was no significant difference between a group without sealer and smear layer and a group without sealer and with smear layer (p<0.01). 4. In groups without smear layer, a group with sealer showed significantly less apical leakage than a group without sealer (p<0.01). 5. When root canals were irrigated with NaOCl alone, a group with sealer showed significantly less apical leakage than a group without sealer (p<0.01).

• The korean journal of orthodontics
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• v.30 no.6 s.83
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• pp.731-738
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• 2000

The purpose of this study was to investigate the change of 3 point bending properties of various nickel titanium wires after recycling. Four Types of nickel-titanium (Align: martensitic type, NiTi, Optimalloy, Sentalloy: austenitic type) wires were divided to three groups: as-received condition (T0: control group), treated in artificial saliva for four weeks (T1) and autoclaved after being treated in artificial saliva (T2). Detrimental changes were observed for the selected mechanical properties in three point bending test. Loading force at 3mm deflection, unloading force at 3mm deflection, stress hysteresis, loading force at 1mm deflection, unloading force at 1mm deflection and stress hysteresis at 1mm deflection were calculated. The findings suggest that : 1. Align demonstrated statistically significant increase In loading force (p<0.05) and unloading force (p<0.01) at 3mm deflection after recycling(T2), but NiTi, Optimalloy and Sentalloy showed no statistically difference after recycling. 2. Align demonstrated statistically significant decrease in hysteresis(p<0.01) after recycling(T2) but NiTi, Optimalloy and Sentalloy showed no statistically significant difference after recycling. 3. All wires showed no statistically significant difference in loading force at 1mm deflection after recycling(T2). 4. Align demonstrated statistically significant decrease in unloading force in 1mm deflection (p<0.05) after recycling(T2) but NiTi, Optimalloy and Sentalloy showed no statistically difference after recycling 5. Loading force and unloading force of T1 showed no significant change compared with those of T0, but loading force and unloading force of T2 showed significant changes compared with those of T0(p<0.05, p<0.01 respectively). 6. Align demonstrated a tendency to lose some of this pseudoelasticity in T1 and pseudoplasticity and pseudoelasticity in T2.

• Journal of the Korean Ceramic Society
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• v.28 no.4
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• pp.329-337
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• 1991

The Ni-MgO composites were prepared by coprecipitation of NiO-MgO solid solutions and their selective reduction in a hydrogen atmosphere. We report on the measurements of both ac conductivity $\sigma$ ($\omega$, f) and dielectric constant $textsc{k}$'($\omega$, f) for the Ni-MgO composites in the frequency range from 10 Hz to 10 MHz at room temperature. The frequency exponents of conductivity and dielectric constant, x and y, are found to be x=0.98$\pm$0.05 and y=0.05$\pm$0.01. These results are in good agreement with a general scaling relation $\chi$-y=1, although these values are different from the theoretical predications. The dielectric constant exponent ($textsc{k}$' f-fc -s) is found to be s=0.62$\pm$0.07 with estimated percolation threshold fc=0.20$\pm$0.02.

• Journal of the Korean institute of surface engineering
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• v.30 no.4
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• pp.248-254
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• 1997

The sulfidation behavior of a sputter-deposited amorphous coating of 69.0%Nb-16.9Ni-11.9%Al-2.2%Si (at.%) has been investigated as a funtion of temperature.(973-1173K) in pure sulfur pressure of 0.01atm. The sulfidation kinetics of the casting obyed the parabolic rate low over the whole temperature ranges studied. The stlfidation rate increased with the temperature, as expected. The sulfide scale, the composition of which was $Al_2S_3,\;NbS_2,\;Ni_{3-x}S_2\;and\;FeCrS_4$, formed on the amorphous coating was primarily bilayered. Both the outer fastgrowing non-protective 4Al_2S_3$scale and the inner slowly-growing protective $NbS_2$,/TEX> scale and the inner slowly-growing protective $NbS_2$ scale had some Fe and Cr dissolution, which evidently came from the base substrate alloy of stainless steel type 304. Belows the coating, Kirkendall void formation was noticed. Nevertheless, a dramatic improvement of sulfidation resistance was achieved by sputter-depositing Nb-2 Ni-Al-Si layer on the stainless steel 304.

• Transactions of the Korean hydrogen and new energy society
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• v.8 no.3
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• pp.121-129
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• 1997

$ZrV_{0.1}Mn_{0.7}Ni_{1.2}$ alloy ingot (bulk alloy) made by the arc melting was found to be consisting of mostly of $ZrV_{0.2}Mn_{0.98}Ni_{1.04}$ matrix alloy and $ZrV_{0.01}Mn_{0.13}Ni_{1.2}$ 2nd phase alloy. The former alloy had the form of the C15 type Laves alloy structure and the latter one had the intermetallic compound structure of $Zr_9Ni_{11}$. In order to investigate the effect of these two phases on the electrochemical charge-discharge characteristics of bulk $ZrV_[0.1}Mn_0.7}Ni_{1.2}$ alloy, the matrix and the 2nd phase alloys were fabricated separately by arc melting method and their electrochemical characteristics were studied and compared with the bulk alloy. It was found that the discharge capacity was the lowest of 160 mAh/g in the 2nd phase alloy. The matrix alloy exhibited 200 mAh/g. Both were lower than that of the bulk alloy of 250 mAh/g. The matrix and the bulk alloys showed a similar properties in the activation stage, the high rate dischargeability and the self discharge characteristics. Also a signigicant capacity decrease was observed after activation in both alloys. Whereas the 2nd phase alloy showed the very different characteristics. This alloy was found to be difficult to activate. However the capacity was remained constant after the activation. Also the self discharge rate was seen to be better than those of the matrix and the bulk alloys.

• Korean Journal of Soil Science and Fertilizer
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• v.33 no.6
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• pp.446-452
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• 2000

This study was carried out to investigate the effect of mine activity on paddy fields, agricultural water, and plants in the ruined Oksung Cu-Zn mine area. Soil samples collected from paddy fields adjacent to the Cu-Zn mine sites were sequentially extracted and determined the contents of heavy metals such as Cd, Zn, Cu, Pb, Cr and Ni. Distribution of exchangeable heavy metals in soils was 30.2% of Cd, 11.3% of Zn, 2.2% of Cu, 4.6% of Cr, 0.6% of Pb and 3.9% of Ni. Water soluble heavy metals were only detected with Zn. The contents of heavy metals in water collected from the mine were 0.01 of Cd, 27.35 of Zn, 4.86 of Cu, 1.04 of Pb, 0.03 of Cr and $0.08mg\;L^{-1}$ of Ni. while the contents in waler collected out of the mine were 16.67 of Zn, 0.59 of Cu, 0.49 of Pb, 0.05 of Cr and $0.06mg\;L^{-1}$ of Ni. On the other hand, agricultural water near mine area were 1.26 of Zn, 0.05 of Cu, 0.05 of Pb and $0.02mg\;L^{-1}$ of Ni. Both Cd and Cr were not detected in the agricultural water.

• Korean Journal of Metals and Materials
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• v.49 no.4
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• pp.298-303
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• 2011

Mg-23.5 wt%Ni-xwt%Cu (x = 2.5, 5 and 7.5) samples for hydrogen storage were prepared by melt spinning and crystallization heat treatment from a Mg-23.5 wt%Ni-5 wt%Cu alloy synthesized by the gravity casting method. They were then ground under $H_2$ to obtain a fine powder. Among these samples the Mg-23.5Ni-2.5Cu sample had the highest hydriding and dehydriding rates after activation. The Mg-23.5Ni-2.5Cu sample absorbed 3.59 and 4.01 wt%H for 10 and 60 min, respectively, at 573K under 12 bar $H_{2}$. The activated 88(87.5Mg-10Ni-2.5Cu)-$5Nb_{2}O_{5}-7NbF_{5}$ sample absorbed 2.93 wt%H for 10 min, and 3.14 wt%H for 60 min at 573K under 12 bar $H_{2}$.

• Korean Journal of Soil Science and Fertilizer
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• v.50 no.5
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• pp.383-390
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• 2017

Heavy metal contamination of soil might be a cause of serious concern due to the potential health impacts of consuming contaminated products. In this study, the total content of heavy metals (Cd, Cr, Cu, Ni, Pb, Zn, As, and Hg) in soils was analyzed, and the difference of heavy metal contents depending on crops, soil characteristics, and topography was compared in 169 greenhouse soils obtained from Gyeongnam Province. The concentrations of the heavy metals were $0.25mg\;kg^{-1}$ (ranged 0.01~0.44) for Cd, $28.94(0.53{\sim}72.63)mg\;kg^{-1}$ for Cr, $26.03(0.5{\sim}166.13)mg\;kg^{-1}$ for Cu, $14.91(1.27{\sim}33.22)mg\;kg^{-1}$ for Ni, $15.76(0.43{\sim}57.1)mg\;kg^{-1}$ for Pb, $119.72(6.33{\sim}239.39)mg\;kg^{-1}$ for Zn, $2.54(0.01{\sim}23.57)mg\;kg^{-1}$ for As, and $0.049(0.012{\sim}0.253)mg\;kg^{-1}$ for Hg in topsoils. The concentrations of Pb and As in topsoil were highest in green pepper and those of Cd, Cr, and Ni were highest in melon. In addition, the concentrations of Cr and Ni were highest in diluvial terrace compared with the other topographies. Higher concentrations of Cd, Cr, and Ni were found in silty clay loam and silt loam soils than sandy loam and loam soils.