• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.10
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• pp.1155-1160
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• 2011

High-strength nickel-based super alloys have been widely used in aircraft engines, vessel engines, and turbine blades because of their high strength and excellent fatigue and oxidation resistance. In this study, tests were carried out to determine the total strain range and temperature for high-strength nickel-based super alloys. Prepared specimens of IN738LC were exposed to temperatures of $871^{\circ}C$ and $982^{\circ}C$ for 1,000.10,000 h. These specimens were subjected to tests of mechanical properties and microstructure observations. The changes in mechanical properties were related to changes in ${\gamma}$ according to the thermal exposure time.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.5
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• pp.45-50
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• 2010

Thermal analyses have been performed to study the effect of location of fuel ring and thermal barrier coatings in regenerative cooling channels in a full-scale combustor. For the effective cooling, the fuel ring has better be installed near axial location of the low expansion ratio and low heat flux, and branching of cooling channels is preferable. Also, the radiative cooled nozzle extension is thought to be reasonable for the cooling of combustor walls. Among the possible coatings, $Y_2O_3$ stabilized $ZrO_2$ coating and Ni/Cr coating have been adopted. Compared with Ni/Cr coating which has high oxidation resistance, $Y_2O_3$ stabilized $ZrO_2$ coating, one of ceramic coatings is found to be much effective to sustain the thermal survivability of combustion walls.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.3
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• pp.273-278
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• 2012

$ZrB_2$ has a melting temperature of $3245^{\circ}C$ and a low density of $6.1\;g/cm^3$, which makes this a candidate for application to ultra-high temperature over $2000^{\circ}C$. Beside these properties, $ZrB_2$ has excellent resistance to thermal shock and oxidation compared with other non-oxide engineering ceramics. This paper reviewed briefly 2 research examples, which are related to densification and properties of $ZrB_2$-based ceramics for ultra-high temperature applications. In the first section, the effect of $B_4C$ addition on the densification and properties of $ZrB_2$-based ceramics is shown. $ZrB_2$-20 vol.% SiC system was selected as a basic composition and $B_4C$ or C was added to this system in some extents. With sintered bodies, densification behavior and hightemperature (up to $1400^{\circ}C$) properties such as bending strength and hardness are examined. In the second section, the effect of the SiC size on the microstructures and physical properties is shown. $ZrB_2$-SiC ceramics are fabricated by using various SiC sources in order to investigate the grain-growth inhibition and the mechanical/thermal properties of $ZrB_2$-SiC.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.12
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• pp.1-9
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• 2003

In this paper, a novel Ni silicide technology with Cobalt interlayer and Titanium Nitride(TiN) capping layer for sub 100 nm CMOS technologies is presented, and the device parameters are characterized. The thermal stability of hi silicide is improved a lot by applying co-interlayer at Ni/Si interface. TiN capping layer is also applied to prevent the abnormal oxidation of NiSi and to provide a smooth silicidc interface. The proposed NiSi structure showed almost same electrical properties such as little variation of sheet resistance, leakage current and drive current even after the post silicidation furnace annealing at $700^{\circ}C$ for 30 min. Therefore, it is confirmed that high thermal robust Ni silicide for the nano CMOS device is achieved by newly proposed Co/Ni/TiN structure.

• Proceedings of the KIEE Conference
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• 2005.11a
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• pp.139-141
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• 2005

It is possble to study charge transfer property which is caused by height variation because we can see the organic materials barrier height and STM tip by organic materials energy band gap. Here, we investigated the negative differential resistance(NDR) and charge transfer property of self-assembled 4,4-Di(ethynylphenyl)-2'-nitro-1-(thioacetyl)benzene, which has been well known as a conducting molecule. Self-assembly monolayers(SAMs) were prepared on Au(111), which had been thermally deposited onto pre-treatment($H_{2}SO_{4}:H_{2}O_{2}$=3:1) Si. The Au substrate was exposed to a 1 mM/l solution of 1-dodecanethiol in ethanol for 24 hours to form a monolayer. After thorough rinsing the sample, it was exposed to a $0.1{\mu}M/1$ solution of 4,4-Di(ethynylphenyl)-2'-nitro-1-(thioacetyl)benzene in dimethylformamide(DMF) for 30 min and kept in the dark during immersion to avoid photo-oxidation. After the assembly, the samples were removed from the solutions, rinsed thoroughly with methanol, acetone, and $CH_{2}Cl_{2}$, and finally blown dry with $N_2$. Under these conditions, we measured electrical properties of self-assembly monolayers(SAMs) using ultra high vacuum scanning tunneling microscopy(UHV-STM). The applied voltages were from -1.50 V to -1.20 V with 298 K temperature. The vacuum condition is $6{\times}10^{-8}$ Torr. As a result, we found that NDR and charge transfer property by a little change of height when the voltage is applied between STM tip and electrode.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.6
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• pp.554-559
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• 2005

Ni/Cr thin film is very interesting material as thin film resistors, filaments, and humidity sensors because their relatively large resistivity, more resistant to oxidation and a low temperature coefficient of resistance (TCR). These interesting properties of Ni/Cr thin films are dependent upon the preparation conditions including the deposition environment and subsequent annealing treatments. Ni/Cr thin films of 250 nm were deposited by DC magnetron sputtering on $Al_2O_3/Si$ substrate with 2-inch Ni/Cr (80/20) alloy target at room temperature for 45 minutes. Annealing treatments were performed at $400^{\circ}C,\;500^{\circ}C,\;and\;600^{\circ}C$ for 6 hours in air or $H_2$ ambient, respectively. The clear crystal boundaries without crystal growth and the densification were accomplished when the pores were disappeared in air ambient. Most of surface was oxidic including NiO, $Ni_2O_3$ and $Cr_xO_y$(x=1,2, y=2,3) after annealing in air ambient. The crystal growth in $H_2$ ambient was formed and stabilized by combination with each other due to the suppression of oxidized substance on film surface. Most oxidic Ni was restored when the oxidic Cr was present due to its stability in high-temperature $H_2$ ambient.

• Environmental Engineering Research
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• v.25 no.4
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• pp.614-621
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• 2020

Antibiotic pollution is one of the factors contributing to the spread of antibiotic-resistant bacteria in the environment. Advanced oxidation and irradiation processes have been introduced to eliminate antibiotics from water and wastewater. However, few studies have reported the toxic effects of residual antibiotics and their byproducts induced by a treatment system. In this study, we compared the efficacies of chemical (high-performance liquid chromatography (HPLC)) and biological (antimicrobial susceptibility test) assays for measuring the concentrations of residual antibiotics after gamma irradiation for degrading amoxicillin, cephradine, lincomycin, and tetracycline. The concentrations of residual antibiotics estimated using the two assay methods were almost identical, except cephradine. In the case of cephradine, inhibited bacterial growth was observed that was equivalent to twice the concentration measured by HPLC in the samples subjected to gamma irradiation. The observed inhibition of bacterial growth suggested the generation of potentially toxic intermediates following antibiotic degradation. These results indicate that biological and chemical assays should be used in concert for monitoring antibiotic contamination and the toxic derivatives of antibiotic degradation. The results demonstrate that these four antibiotics can be decomposed by 2.0 kGy gamma-irradiation without toxic effects of their byproducts.

• Textile Coloration and Finishing
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• v.25 no.2
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• pp.126-133
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• 2013

Although para-aramid fibers poss higher mechanical properties, they show very low resistance to sunlight exposure. This paper studied on the effect of nano-sol coated $TiO_2$ to improve the photo-stability of p-aramid fibers. Titanium dioxides were prepared by sol-gel method from titanium iso-propoxide at different R ratio ($H_2O$/titanium iso-propoxide). All samples were characterized by XRD, TEM and UV-vis spectrometer. The mechanical properties of p-aramid fabrics by $TiO_2$ nano-sol coating before and after sunlight irradiation were measured with tensile tester. XRD pattern of titanium dioxide particles was observed by mixing phase together with rutile and anatase type. The results showed, after sunlight irradiation, the decreased mechanical properties of the fiber. Furthermore, the sunlight irradiation obviously deteriorated the surface and defected areas of the fiber severely by photo-induced chain scission and end group oxidation in air.

• Journal of the Korean Vacuum Society
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• v.6 no.1
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• pp.28-35
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• 1997

Effects of rapid thermal annealing on the characteristics of Cu films deposited from the (hfac)Cu(VTMS) precursor and on the barrier properties of TiN layers were studied. By the post-annealing, the electrical characteristics of Cu/TiN and the microstructures of Cu films were significantly changed. The properties of Cu films were more sensitive to the annealing temperature than the annealing time. Sheet resistance started to increase above $400^{\circ}C$, and the interreaction between Cu and Ti and the oxidation of Cu layer were observed above $600^{\circ}C$. The grain growth of Cu with the (111) preferred orientation was found to be most pronounced at $500^{\circ}C$. It revealed that the optimum annealing conditions for MOCVD-Cu/PVD-TiN structures to enhance the electrical characteristics without degradation of TiN barriers were in the range of $400^{\circ}C$.

• Korean Journal of Materials Research
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• v.25 no.11
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• pp.636-641
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• 2015

Titanium has many special characteristics such as specific high strength, low elastic modulus, excellent corrosion and oxidation resistance, etc. Beta titanium alloys, because of their good formability and strength, are used for jet engines, and as turbine blades in the automobile and aerospace industries. Low cost beta titanium alloys were developed to take economic advantage of the use of low-cost beta stabilizers such as Mo, Fe, and Cr. Generally, adding a trace of boron leads to grain refinement in casted titanium alloys due to the pinning effect of the TiB phases. This study analyzed and evaluated the microstructural and mechanical properties after plastic deformation and heat treatment in boron-modified Ti-2Al-9.2Mo-2Fe alloy. The results indicate that a trace of boron addition made grains finer; this refinement effect was found to be maintained after subsequent processes such as hot forging and solution treatment. This can effectively reduce the number of required manufacturing process steps and lead to savings in the overall cost as well as low-cost beta elements.