• Proceedings of the Materials Research Society of Korea Conference
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• 2000.11a
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• pp.168-168
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• 2000

• Proceedings of the Korean Magnestics Society Conference
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• 1995.05a
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• pp.86-87
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• 1995

• Journal of Korea Foundry Society
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• v.8 no.4
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• pp.437-445
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• 1988

The effect of interlamellar spacing on microstructural stability at high temperature was studied for unidirectionally solidified ternary $Ni\;/\;Ni_3Al-Ni_3$ Nb and binary $Ni-Ni_3Nb$ eutectic composite. The interlamellar spacing of both alloy systems were varied with the growth rate according to $"{\lambda}^2R=constant"$ relationship. As a result of isothermal heat treatments at high temperature it was considered that coarsening of lamellar structure was due to concentration gradient between the tip with a relatively small radius of curvature and the side of the thick lamellae with a larger radius of the opposite sign. Fault density was increased as the interlamellar spacing decreased. Therefore it is also considered that the higher coarsening rate of the specimen with the smaller interlamellar spacing was due to higher fault density. And the diference of coarsening rate between $Ni\;/\;Ni_3Al-Ni_3Nb$ and $Ni-Ni_3Nb$ eutectic composites was not observed when the interlamellar spacing was similar in size. This means that the presence of ${\gamma}'$ in ${\gamma}\;/\;{\gamma}'\;-{\delta}$ eutectic had no b arrier effect to diffusion through the ${\gamma}$ matrix.

• Restorative Dentistry and Endodontics
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• v.36 no.1
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• pp.1-11
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• 2011

Introduction: The aim of this paper is to discuss the mechanical and geometric features of Nickel-titanium (NiTi) rotary files and its clinical effects. NiTi rotary files have been introduced to the markets with their own geometries and claims that they have better ability for the root canal shaping than their competitors. The contents of this paper include the (possible) interrelationship between the geometries of NiTi file (eg. tip, taper, helical angle, etc) and clinical performance of the files as follows; - Fracture modes of NiTi rotary files - Non-cutting guiding tip and glide path - Taper and clinical effects - Cross-sectional area and clinical effects - Heat treatments and surface characteristics - Screw-in effect and preservation of root dentin integrity - Designs for reducing screw-in effect Conclusions: Based on the reviewed contents, clinicians may have an advice to use various brands of NiTi rotary instruments regarding their advantages which would fit for clinical situation.

• Journal of Powder Materials
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• v.8 no.1
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• pp.13-19
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• 2001

Ni and NiO particles were made by a combustion synthesis process. The characteristics of synthesized powders were investigated with various kinds and amounts of fuels such as urea, citric acid and glycine. Ni phase particles without NiO phase were obtained through combustion synthesis process in air atmosphere with-out further calcinations process, when the content of glycine was 2.44 times of the stoichiometric ratio in the precursor solution. Primary particle sizes of synthesized Ni and NiO particles were about 20∼30 nm.

• Journal of the Korean Magnetics Society
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• v.3 no.4
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• pp.310-313
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• 1993

The effect of Ni content in Cu underlayer on the magnetoresistance of Cu/Co artificial superlattice has been investigated. As the content of Ni increased, the preferred orientation of artificial superlattice changed from fec (100) to fcc (111) due to the change of the preferred orientation of the underlayer. When the content of Ni was 6 %, 26.7 % of magnetoresistance with 175 Oe of saturation field could be obtained in ${[Cu(19\AA)/Co(30\AA)]}_{20}|Cu-6%Ni(200\AA)/Si$.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.462-463
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• 2006

Monodispersed and nano-sized Ni powders were synthesized from aqueous nickel sulfate hexahydrate $(NiSO_4{\cdot}6H_2O)$ inside nonionic polymer network by using wet chemical reduction process. The sucrose was used as a nonionic polymer network source. The effect of reaction conditions such as the amount of sucrose and a various reaction temperature, nickel sulfate hexahydrate molarity. The influence of a nonionic polymer network on the particle size of the prepared Ni powders was characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), and particle size analysis (PSA). The results showed that the obtained Ni powders were strong by dependent of the reaction conditions. In particular, the Ni powders prepared inside a nonionic polymer network had smooth spherical shape and narrow particle size distribution.

• Journal of Applied Biological Chemistry
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• v.52 no.1
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• pp.28-32
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• 2009

The bacterial toxin, tolaasin, causes brown blotch disease on the cultivated mushrooms by collapsing fungal and fruiting body structure of mushroom. Cytotoxicity of tolaasin was evaluated by measuring hemolytic activity because tolaasins form membrane pores on the red blood cells and destroy cell structure. While we investigated the inhibitions of hemolytic activity of tolaasin by $Zn^{2+}$ and $Cd^{2+}$, we found that $Ni^{2+}$ is another antagonist to block the toxicity of tolaasin. $Ni^{2+}$ inhibited the tolaasin-induced hemolysis in a dose-dependent manner and its Ki value was $\sim10$ mM, implying that the inhibitory effect of $Ni^{2+}$ is stronger than that of $Cd^{2+}$. The hemolytic activity was completely inhibited by $Ni^{2+}$ at the concentration higher than 50 mM. The effect of $Ni^{2+}$ was reversible since it was removed by the addition of EDTA. When the tolaasin-induced hemolysis was suppressed by the addition of 20 mM $Ni^{2+}$, the subsequent addition of EDIA immediately initiated the hemolysis. Although the mechanism of $Ni^{2+}$ -induced inhibition on tolaasin toxicity is not known, $Ni^{2+}$ could inhibit any of fallowing processes of tolaasin action, membrane binding, molecular multimerization, pore formation, and massive ion transport through the membrane pore. Our results indicate that $Ni^{2+}$ inhibits the pore activity of tolaasin, the last step of the toxic process.

• Journal of the Korean Society for Heat Treatment
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• v.37 no.2
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• pp.79-85
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• 2024

The effects of annealing heat treatment and the addition of Cu element on the shape memory effect of the NiTi-based alloy were investigated by analyzing differential scanning calorimeter results and characterizing recovery rate through 3D scanning after Vickers hardness test. Through 3D scanning of impressions after Vickers hardness test, the strain recovery rates for specimens without annealing treatment and annealed specimens at 400, 450, and 500℃ were measured as 45.96%, 46.76%, 52.37%, and 43.57%, respectively. This is because as the annealing temperature increases, both B19' and NiTi₂ phases, which can impede martensitic transformation, are incorporated within the NiTi matrix. Particularly, additional phase transformation from R-phase to B19' observed in specimens annealed at 400 and 450℃ significantly contributes to the improvement in strain recovery rates. Additionally, the results regarding the Cu element content indicate that when the total content of Ni and Cu is below 49.6 at.%, the precipitation of fine B19' and NiTi₂ phases within the matrix can greatly influence the transformation enthalpy and temperature range, resulting in relatively lower strain recovery rates in NiTi alloys with a small amount of Cu element produced in this study.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.2
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• pp.275-282
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• 2002

Tensile residual stress happen by difference of coefficients of thermal expansion between fiber and matrix is one of the serious problems in metal matrix composite(MMC). In this study, TiNi fiber was used to solve the tensile residual stress as the reinforced material. TiNi fiber improves the tensile strength of composite by occurring compressive residual stress in matrix using shape memory effect of it. Pre-strain was added to generate compressive residual stress inside TiNi/A16061 composite. It was also evaluated the effect of compressive residual stress corresponding to pre-strains variation. AE technique was used to clarify the microscopic damage behavior at high temperature and the effect of pre-strain difference of TiNi/A16061 shape memory alloy composite.