• Journal of IKEEE
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• v.25 no.3
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• pp.467-472
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• 2021

Stable operation of semiconductor devices is needed even at high temperatures. Among the structures of semiconductor devices, the area that can cause unstable electrical responses at high temperatures is the contact layer between the metal and the semiconductor. In this study, the effect of annealing conditions included in the process of forming a contact layer of nickel silicide(NiSix) on a p-type SiC layer on the specific contact resistance of the contact layer and the total resistance between the metal and the semiconductor was investigated. To this end, a series of electrodes for TLM (transfer length method) measurements were patterned on the 4 inch p-type SiC layer under conditions of changing annealing temperature of 1700 and 1800 ℃ and annealing time of 30 and 60 minutes. As a result, it was confirmed that the annealing conditions affect the resistance of the contact layer and the electrical stability of the device.

• Korean Chemical Engineering Research
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• v.56 no.6
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• pp.914-920
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• 2018

The intrinsic kinetic parameters of steam-methane reforming reactions over commercial nickel-based catalyst were determined. The reaction rate equations were derived from the reaction mechanism-based Langmuir-Hinshelwood chemisorption theory. As the experimental variables for the kinetic study, the reaction temperature ranged from 630 to $750^{\circ}C$ and the steam-to-carbon ratio also varied from 2.7 to 3.5. Based on the experimental data, the efficient optimization algorithm was used to determine the intrinsic kinetic parameters due to the high-dimensional objective function. It is confirmed that the parameter estimation results showed good agreement with the experimental values. Thus, this proposed mathematical reaction model can be used as the basic information to design a catalytic reactor and to optimize operating conditions.

• Journal of the Korean Society of Clothing and Textiles
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• v.44 no.6
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• pp.1154-1162
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• 2020

In this study, the soft textile actuator is produced for a smart wearable with the shape memory effects from linear shape memory alloys of Nickel and Titanium using the driving force through the fabrication process. The measurement model was designed to measure dynamic characteristics. The heating method, and memory shape of the linear shape memory alloy were set to measure the operating temperature. A shape memory alloy at 40.13℃, was used to heat the alloy with a power supply for the selective operation and rapid reaction speed. The required amount of current was obtained by calculating the amount of heat and (considering the prevention of overheating) set to 1.3 A. The fabrication process produced a soft textile actuator using a stitching technique for linear shape memory alloys at 0.5 mm intervals in the general fabric. The dynamic characteristics of linear shape memory alloys and actuators were measured and compared. For manufactured soft textile actuators, up to 0.8 N, twice the force of the single linear shape memory alloy, 0.38 N, and the response time was measured at 50 s.

• Nuclear Engineering and Technology
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• v.54 no.2
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• pp.627-636
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• 2022

In nuclear power plants and other nuclear facilities the removal of cobalt from radioactive liquid waste is needed to reduce the radioactivity concentration in effluents. In liquid wastes containing strong organic complexing agents such as EDTA cobalt removal can be problematic due to the high stability of the Co-EDTA complex. In this study, the removal of cobalt from NaNO₃ solutions using antimony oxide (Sb₂O₃) synthesized from potassium hexahydroxoantimonate was investigated in the absence and presence of EDTA. The uptake studies on the ion exchange material were conducted both in the dark (absence of UV-light) and under UV-C irradiation. Ca²⁺ or Ni²⁺ were included in the experiments as competing cations to test the selectivity of the ion exchanger. Results show that UV-C irradiation noticeably enhances the cobalt sorption efficiency on the antimony oxide. It was shown that nickel decreased the sorption of cobalt to a higher extent than calcium. Finally, the sorption data collected for Co²⁺ on antimony oxide was modeled using six different isotherm models. The Sips model was found to be the most suitable model to describe the sorption process. The Dubinin-Radushkevich model was further used to calculate the adsorption energy, which was found to be 6.2 kJ mol^-1.

• Restorative Dentistry and Endodontics
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• v.48 no.1
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• pp.10.1-10.9
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• 2023

Objectives: This study compared the buckling resistance of 3 nickel-titanium (NiTi) retreatment file systems and the torque/force generated during retreatment. Materials and Methods: The buckling resistance was compared among the D-RaCe (DR2), HyFlex Remover, and Mtwo R25/05 retreatment systems. J-shaped canals within resin blocks were prepared with ProTaper NEXT X3 and obturated by the single-cone technique with AH Plus. After 4 weeks, 4 mm of gutta-percha in the coronal aspect was removed with Gates-Glidden drills. Retreatment was then performed using DR1 (size 30, 10% taper) followed by DR2 (size 25, 4% taper), HyFlex Remover (size 30, 7% taper), or Mtrwo R25/05 (size 25, 5% taper) (15 specimens in each group). Further apical preparation was performed with WaveOne Gold Primary. The clockwise torque and upward force generated during retreatment were recorded. After retreatment, resin blocks were examined using stereomicroscopy, and the percentage of residual filling material in the canal area was calculated. Data were analyzed using 1-way analysis of variance with the Tukey test. Results: The HyFlex Remover files exhibited the greatest buckling resistance (p < 0.05), followed by the Mtwo R25/05. The HyFlex Remover and Mtwo R25/05 files generated the highest maximum clockwise torque and upward force, respectively (p < 0.05). The DR1 and DR2 files generated the least upward force and torque (p < 0.05). The percentage of residual filling material after retreatment was not significantly different between file systems (p > 0.05). Conclusions: NiTi retreatment instruments with higher buckling resistance generated greater clockwise torque and upward force.

• Resources Recycling
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• v.12 no.6
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• pp.38-46
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• 2003

In this study, nano-sized Ni-ferrite and $Fe_2$$O_3$＋NiO powder was fabricated by spray pyrolysis process in the condition of 1kg/$\textrm{cm}^2$ air pressure using the Fe-Ni complex waste acid solution generated during the manufacturing process of shadow mask. The average particle size of the produced powder was below 100 nm. The effects of the reaction temperature, the concentration of raw material solution and the nozzle tip size on the properties of powder were studied. As the reaction temperature increased from $800 ^{\circ}C$ to $1100^{\circ}C$, the average particle size of the powder increased from 40 nm to 100 nm, the structure of the powder gradually became solid, yet the distribution of the particle size appeared more irregular. Along with the increase of the reaction temperature, the fraction of the Ni-ferrite phase were also on the rise, and the surface area of the powder was greatly reduced. As the concentration of Fe in solution increased from 20g/l to 200g/l, the average particle size of the powder gradually increased from 30 nm to 60 nm, while the distribution of the particle size appeared more irregular. Along with the increase of the concentration of solution, tie fraction of the Ni-ferrite phase was on the rise, and the surface area of the powder was greatly reduced. Along with the increase of the nozzle tip size, the distribution of the particle size appeared more irregular, yet the average particle size of the powder showed no significant change. As the nozzle tip size increased from 1 mm to 2 mm, the fraction of the Ni-ferrite phase showed no significant change, while the surface area of the powder slightly reduced. As the nozzle tip size increased to 3 mm and 5 mm, the fraction of the Ni-ferrite phase gradually reduced, and the surface area of the powder slightly increased.

• Restorative Dentistry and Endodontics
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• v.35 no.2
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• pp.88-95
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• 2010

The purpose of this study was to compare the root canal shaping ability of 4 rotary NiTi instruments in simulated root canals. For the preparation of thirty two curved root canals, Mtwo instruments using "single length"technique, and Profile, ProTaper Universal, and K3 using crown-down technique (N = 8) were used. All canal samples were prepared by reaching an apical canal size of #30. Pre- and post-instrumentation digital images were recorded and an assessment of canal shape was determined using a computer image analysis program SigmaScan Pro (Systat Software Inc., San Jose, CA, USA). The changes of the dimension of inner walls of canals, (2) the changes of the dimension of outer walls of canals, and (3) the centering ratio were measured at 7 measuring points, and then data were statistically analyzed using one-way ANOVA and Duncan's test. The results were as below; 1. The root canal shaping ability of Profile was significantly faster than that of other rotary NiTi instruments (p < 0.05). 2. The deformation and fracture of all instruments used for this study were not experienced. 3. In the degree of changes of the dimension of inner walls of canals, Profile demonstrated the lowest changes of the dimension of inner walls of canals except at the measuring points of the 1 and 2 mm (p < 0.05). However, the ProTaper Universal showed the highest changes of the dimension of inner walls of canals at all measuring points (p < 0.05). 4. In the degree of changes of the dimension of outer walls of canals, Mtwo demonstrated the lowest changse of the dimension of outer walls of canals except at the measuring point of the 1 mm (p < 0.05). However, Profile exhibited the highest changes of the dimension of outer walls of canals at the measuring points of 3 and 4 mm and ProTaper Universal and K3 showed the largest changes of the dimension of outer walls of canals at the measuring points of 1, 2, 6, and 7 mm (p < 0.05). 5. In degree of centering ratio, Profile demonstrated the least centering ratio comparing with the centering ratio shown by other NiTi instruments at the measuring points of 1, 4, 5, and 6 mm. Results suggest that in the coronal part of canal preparation, active cutting files such as ProTaper Universal may efficiently flare the canal orifice and form a better taper, and in the apical part of the canal, files which have a better centering ability such as Profile may maintain the original canal curvature and reduce the shaping time.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1576-1578
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• 2004

The alumina membrane with nano sized pore was prepared from aluminum by anodic oxidation to apply for storage equipment, gas sensor and stamper. The pore size and cell size of the pores are controlled by anodic oxidation voltage. The alumina thickness was controlled by etching process using 0.2M $H_3PO_4$. The thickness of alumina on Si wafer was very accurately controlled by anodic oxidation time. Nickel with nano-sized grain was electroplated on the Au layer on silicon wafer. The fabricated pores on alumina membrane was the thickness of $7{\sim}10{\mu}m$ with straight nano-sized pore of 307${\sim}$120nm. The alumina by the etching process shows smooth surface. The size of Ni grain was 130nm and 250nm for 10mA/$cm^2$and 20mA/$cm^2$of electroplating currents, respectively.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.10
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• pp.1480-1488
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• 2003

Synthesis of carbon nanomaterials on a substrate coated with metal nitrates using an ethylene fueled inverse diffusion flame was illustrated. The effects of radial distance, residence time of the substrate, and hydrocarbon composition on the synthesis of carbon nanomaterials were investigated. The effects of catalyst metal particles were also studied using SUS304 substrates coated with Fe(NO$_3$)$_3$ (ferric nitrate, nonahydrate) and Ni(NO$_3$)$_2$(nickel nitrate, hexahydrate), and Cu substrate. Carbon nanomaterials, with diameters ranging from 30 - 70 nm, were observed on the substrate for both cases of using substrates only and using them with metal nitrates. In case of using the substrate with metal nitrates, the formation and growth of carbon nanomaterials were occurred in the lower temperature region than that of using the substrates only due to the easy activation of the metal particles coated on the surface of the substrates.

• Corrosion Science and Technology
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• v.13 no.2
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• pp.56-61
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• 2014

The purpose of this work is to investigate the effect of dissolved hydrogen concentration on crud deposition onto the fuel cladding surface in the simulated primary environments of a pressurized water reactor. Crud deposition tests were conducted in the dissolved hydrogen concentration range of 5~70 cc/kg at $325^{\circ}C$ for 14 days. Needle-shaped NiO deposits were formed in the hydrogen range of 5~25 cc/kg, while polygonal nickel ferrite deposits were observed at a hydrogen concentration above 35 cc/kg. However, the dissolved hydrogen content seems to have little effect on the amount of crud deposits.