• The Journal of Korean Academy of Prosthodontics
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• v.45 no.5
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• pp.675-686
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• 2007

Statement of problem: Titanium nitride(TiN) coatings are the most general and popular coating method and used to improve the properties of metallic surface for industrial purposes. When TiN coating applied to the abutment screw, frictional resistance would be reduced, as a results, the greater preload and prevention of the screw loosening could be expected. Purpose: The purpose of this study was to investigate mechanical properties of TiN coated film of various coating thickness on the titanium alloy surface and to evaluate proper coating thickness. Material and method: 95 Titanium alloy (Ti-6Al-4V) discs of 15 mm in diameter and 3 mm in thickness were prepared for TiN coating and divided into 7 groups in this study. Acceding to coating deposition time (CDT) with TiN by using Arc ion plating, were divided into 7 groups : Group A (CDT 30min), Group B (CDT 60min), Group C (CDT 90min), Group D (CDT 120min), Group E (CDT 150min), Group F(CDT 180min) and Group G (no CDT) as a control group. TiN coating surface was observed with Atomic Force Microscope(AFM), field emission scanning electron microscopy(FE-SEM) and examined with scratch tester, wear tester. Result: 1. Coating thickness fir each coated group was increased in proportion to coating deposition time. 2. Surface of all coated groups except Group A was homogeneous and smooth. However, surface of none coated Group G had scratch. 3. Adhesion strength for each coated group was increased in proportion to coating deposition time. 4. Wear resistance for each coated group was increased in proportion to coating deposition time. 5. Surface roughness in Group A, B, C was increased in proportion to coating deposition time. But, surface roughness in Group D, E, F was showed decreased tendency in proportion to coating deposition time. Conclusion: According to coating deposition time, mechanical properties of TiN coated film were changed. It was considered that 120 minutes coating deposition time ($1.32{\mu}m$ in coating thickness) is necessary.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.551-556
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• 2018

The material normally used in hot dip galvanizing facilities is SM45C (carbon steel for mechanical structure, KS standard), mainly because of its price. During this process, the oxidation of the plating facility occurs due to the heat of the Zn fumes coming from the molten zinc. Since the cycle time of the current facilities is 6 months, much time and money are wasted. In this study, the corrosive properties of various materials (Inconel625, STS304, SM45C) were investigated by oxidation in a high temperature and Zn fumes environment. The possibility of applying the hot-dip galvanizing equipment was investigated for each material. The Zn fumes were generated by directly bubbling Ar gas into Zn molten metal in a 650 degree furnace. High-temperature, Zn fumes corrosion was conducted for 30 days. The sample was removed after 30 days and the oxidation of the surface was confirmed with EDS and SEM, and the corrosion properties were examined using potentiodynamic polarization tests.

• Journal of Microbiology and Biotechnology
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• v.22 no.9
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• pp.1193-1201
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• 2012

The analysis and quantification of ammonia-oxidizing bacteria (AOB) is crucial, as they initiate the biological removal of ammonia-nitrogen from sewage. Previous methods for analyzing the microbial community structure, which involve the plating of samples or culture media over agar plates, have been inadequate because many microorganisms found in a sewage plant are unculturable. In this study, to exclusively detect AOB, the analysis was carried out via denaturing gradient gel electrophoresis using a primer specific to the amoA gene, which is one of the functional genes known as ammonia monooxygenase. An AOB consortium (S1 sample) that could oxidize an unprecedented 100% of ammonia in 24 h was obtained from sewage sludge. In addition, real-time PCR was used to quantify the AOB. Results of the microbial community analysis in terms of carbon utilization ability of samples showed that the aeration tank water sample (S2), influent water sample (S3), and effluent water sample (S4) used all the 31 substrates considered, whereas the AOB consortium (S1) used only Tween 80, D-galacturonic acid, itaconic acid, D-malic acid, and $_L$-serine after 192 h. The largest concentration of AOB was detected in S1 ($7.6{\times}10^6copies/{\mu}l$), followed by S2 ($3.2{\times}10^6copies/{\mu}l$), S4 ($2.8{\times}10^6copies/{\mu}l$), and S3 ($2.4{\times}10^6copies/{\mu}l$).

• Membrane and Water Treatment
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• v.11 no.4
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• pp.283-294
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• 2020

This work aims at studying the feasibility of continuous removal of mixed heavy metal ions from simulated zinc plating wastewaters by coupling a microbial fuel cell and a microbial electrolysis cell in batch and continuous modes. The discharging voltage of MFC increased initially from 0.4621 ± 0.0005 V to 0.4864 ± 0.0006 V as the initial concentration of Cr⁶⁺ increased from 10 ppm to 60 ppm. Almost complete removal of Cr⁶⁺ and low removal of Cu²⁺ occurred in MFC of the MFC-MEC-coupled system after 8 hours under the batch mode; removal efficiencies (REs) of Cr⁶⁺ and Cu²⁺ were 99.76% and 30.49%. After the same reaction time, REs of nickel and zinc ions were 55.15% and 76.21% in its MEC. Cu²⁺, Ni²⁺, and Zn²⁺ removal efficiencies of 54.98%, 30.63%, 55.04%, and 75.35% were achieved in the effluent within optimum HRT of 2 hours under the continuous mode. The incomplete removal of Cu²⁺, Ni²⁺ and Zn²⁺ ions in the effluent was due to the fact that the Cr⁶⁺ was almost completely consumed at the end of MFC reaction. After HRT of 12 hours, at the different sampling locations, Cr⁶⁺ and Cu²⁺ removal efficiencies in the cathodic chamber of MFC were 89.95% and 34.69%, respectively. 94.58%, 33.95%, 56.57%, and 75.76% were achieved for Cr⁶⁺, Cu²⁺, Ni²⁺ and Zn²⁺ in the cathodic chamber of MEC. It can be concluded that those metal ions can be removed completely by repeatedly passing high concentration of Cr⁶⁺ through the cathode chamber of MFC of the MFC-MEC-coupled system.

• Journal of Electrochemical Science and Technology
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• v.11 no.1
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• pp.60-67
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• 2020

In this study, copper (II) oxide powder for electroplating was prepared by recovering CuCl₂ from NaClO₃ type etching wastes via recovered non-sintering two step chemical reaction. In case of alkali copper carbonate [mCuCo₃·nCu(OH)₂], first reaction product, CuCo₃ is produced more than Cu(OH)₂ when the reaction molar ratio of sodium carbonate is low, since m is larger than n. As the reaction molar ratio of sodium carbonate increased, m is larger than n and Cu(OH)₂ was produced more than CuCO₃. In the case of m has same values as n, the optimum reaction mole ratio was 1.44 at the reaction temperature of 80℃ based on the theoretical copper content of 57.5 wt. %. The optimum amount of sodium hydroxide was 120 g at 80℃ for production of copper (II) oxide prepared by using basic copper carbonate product of first reaction. At this time, the yield of copper (II) oxide was 96.6 wt.%. Also, the chloride ion concentration was 9.7 mg/L. The properties of produced copper (II) oxide such as mean particle size, dissolution time for sulfuric acid, and repose angle were 19.5 mm, 64 second, and 34.8°, respectively. As a result of the hole filling test, it was found that the copper oxide (II) prepared with 120 g of sodium hydroxide, the optimum amount of basic hydroxide for copper carbonate, has a hole filling of 11.0 mm, which satisfies the general hole filling management range of 15 mm or less.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.98.1-98.1
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• 2018

소듐냉각 고속로 (SFR)는 원자력 발전의 가장 시급한 문제점으로 부각되고 있는 사용 후 핵연료를 재활용 하여 가동하는 원자로 이다. Generation IV로 명명되는 차세대 원자로 중에 하나로 국제 공동연구와 자체 연구를 통해 우리나라 고유의 기술이 축적되고 개발되고 있다. 현재 소듐냉각 고속로의 가장 큰 문제점 중의 하나는 금속핵연료와 피복관의 상호반응이다. 상호반응이 일어나면 공융현상을 일으켜 피복관의 녹는점이 낮아지고 피복관의 두께가 얇아져 원자로의 안전에 치명적인 위협이 된다. 이러한 문제를 해결하기 위해 전해도금 (electro-plating)을 활용하여 HT9 피복관 내면에 크롬을 도금하여 금속핵연료와 피복관의 상호반응을 억제하는 연구가 본 연구팀에서 진행되고 있다. 크롬과 전해도금을 코팅 물질과 코팅 방법으로 선정한 이유는 튜브 내면에 적용하기 용이하고 경제적인 코팅 방법이기 때문이다. 본 연구에서는 여러 가지 전해도금 인자 중 온도와 pulse 전류의 파형이 상호반응 방지 효과에 미치는 영향에 대하여 고찰하였다. 도금액의 온도를 $50{\sim}80^{\circ}C$, 전류 파형 중 on/off time을 1:1, 10:1, 1:10으로 하여 여러 HT9 시편을 도금하였고 모의 금속 핵연료 합금인 Ce-Nd와 확산 반응 실험을 수행하여 상호반응 방지 효과를 분석하였다. 광학현미경과 전자현미경을 이용한 미세구조 분석 결과 도금액의 온도가 $65^{\circ}C$ 이하인 시편에서는 미세균열이 심하게 발생하였고 그 균열을 통해서 물질이 확산하고 상호반응을 한다는 것이 관찰되었다. $65^{\circ}C$보다 높은 도금액의 온도에서 형성된 크롬막은 균열이 없고 상호반응 방지 효과가 좋은 것이 확인되었다. 특히 전류 파형의 on/off time이 1:1일 때 상호반응 방지 효과가 가장 좋은 것을 확인하였다. 이러한 결과는 크롬 전해도금의 코팅 조건이 상호반응 방지 효과에 매우 중요한 요인으로 작용한다는 것을 말해주고 있다.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.30 no.3
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• pp.367-376
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• 1997

Vibrio vulnificus is a gram-negative, halophilic, oxidase-positive, lactose-positive, motile, rod shaped bacterium that has been associated with primary septicemia and wound infection. Elucidating the growth and survival of V. vulnificus in ecological conditions is of great importance to develop sanitary measure against this microorganism. Thus we simulated the ecological conditions and evaluated the effect. About $10^5\;CFU/ml$ of V. vulnificus was inoculated to fresh water, brackish water $(1\%\;NaCl)$, sea water $(3\%\;NaCl)$, and bottom deposit solution. The same concentration of V. vulnificus was also inoculated to distilled water, $1\%\;NaCl$ solution and $3\%\;NaCl$ solution as controls. These were stored at 4, 15 and $25^{\circ}C$, respectively and were used to assess the effects of temperature and salinity on the survival of V. vulnificus. In fresh water V. vulnificus could not survive regardless of storage temperature. In case of brackish water and sea water survival time of V. vulnificus was the longest at $25^{\circ}C$, and the number of V. vulnificus was decreased most rapidly at $4^{\circ}C$. V. vulnificus survived longer in brackish water than in any other conditions. In bottom deposit solution containing brackish water, the survival time of V. vulnificus was longer and the rate of decline was slower than that in brackish water. These results indicate that both biological and physicochemical factors such as temperature and salinity could affect survival of V. vulnificus. V. vulnificus, damaged in normal fresh water, did not grow on TCBS agar of selective plating medium but grew on BHI agar plate; However, V. vulnificus was recovered by addition of salt and nutrient materials.

• Journal of the Korean Home Economics Association
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• v.42 no.3
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• pp.145-158
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• 2004

Experimental conditions for evaluating chitosan antibacterial activities were established. The chitosan antibacterial activities were measured against the Staphylococcus aureus and evaluated for their application to antibacterial textile finishing. The strain of Staphylococcus aureus used in this experiments was KCTC 1916. The chitosan antibacterial activities were estimated from the bacterial densities or ％reduction of bacteria in chitosan solutions and bacterial culture mixtures after incubation under specific conditions. Six parameters as follows were evaluated to optimize the experimental conditions for measuring antibacterial activities. The different combinations of mixtures according to the different ratios of chitosan solutions to the bacterial cultures showed different antibacterial activities. However, the chitosan antibacterial activities could be evaluated by comparing the data obtained from the same combinations of mixtures. The solvent influence on the chitosan solution antibacterial activities could be eliminated using control solution containing the same concentration of acetic acid. The initial pH of the chitosan -bacterial mixtures also affected the chitosan antibacterial activity; at a higher pH, higher activity in terms of ％reduction of bacteria was observed. In case of the bacterial solution without either the acetic acid or chitosan, the initial pH of the solution did not significantly affect bacterial growth. The ％ reduction of bacteria increased when contact times of bacteria with chitosan in the chitosan -bacterial mixture were expended upto 24 hours. However, the chitosan antibacterial activities could be successfully evaluated at contact time 0 where the chitosan-bacterial mixture was plated immediately after mixing and incubated to measure the bacterial number to 24 hours. Evaluating ％reduction of bacteria in the test mixtures after incubation were not changed when the inoculated bacterial concentrations were 2.3${\times}$10$\^$0/ml to 2.3${\times}$10$\^$6/ml. The optimal range of incubation time of the petri-Dish after plating the chitosan-bacterial mixture was 24 to 72 hours depending on the antibacterial activities of the test solutions.

• Korean Journal of Metals and Materials
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• v.50 no.2
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• pp.152-158
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• 2012

The effect of current waveform on Cu filling into TSV (through-silicon via) and the bottom-up ratio of Cu were investigated for three dimensional (3D) Si chip stacking. The TSV was prepared on an Si wafer by DRIE (deep reactive ion etching); and its diameter and depth were 30 and $60{\mu}m$, respectively. $SiO_2$, Ti and Au layers were coated as functional layers on the via wall. The current waveform was varied like a pulse, PPR (periodic pulse reverse) and 3-step PPR. As experimental results, the bottom-up ratio by the pulsed current decreased with increasing current density, and showed a value of 0.38 on average. The bottom-up ratio by the PPR current showed a value of 1.4 at a current density of $-5.85mA/cm^2$, and a value of 0.91 on average. The bottom-up ratio by the 3-step PPR current increased from 1.73 to 5.88 with time. The Cu filling by the 3-step PPR demonstrated a typical bottom-up filling, and gave a sound filling in a short time.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2000.11a
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• pp.3-4
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• 2000

Many researchers are interested in the synthesis and characterization of carbon nitride and diamond-like carbon (DLq because they show excellent mechanical properties such as low friction and high wear resistance and excellent electrical properties such as controllable electical resistivity and good field electron emission. We have deposited amorphous carbon nitride (a-C:N) thin films and DLC thin films by shielded arc ion plating (SAIP) and evaluated the structural and tribological properties. The application of appropriate negative bias on substrates is effective to increase the film hardness and wear resistance. This paper reports on the deposition and tribological OLC films in relation to the substrate bias voltage (Vs). films are compared with those of the OLC films. A high purity sintered graphite target was mounted on a cathode as a carbon source. Nitrogen or argon was introduced into a deposition chamber through each mass flow controller. After the initiation of an arc plasma at 60 A and 1 Pa, the target surface was heated and evaporated by the plasma. Carbon atoms and clusters evaporated from the target were ionized partially and reacted with activated nitrogen species, and a carbon nitride film was deposited onto a Si (100) substrate when we used nitrogen as a reactant gas. The surface of the growing film also reacted with activated nitrogen species. Carbon macropartic1es (0.1 -100 maicro-m) evaporated from the target at the same time were not ionized and did not react fully with nitrogen species. These macroparticles interfered with the formation of the carbon nitride film. Therefore we set a shielding plate made of stainless steel between the target and the substrate to trap the macropartic1es. This shielding method is very effective to prepare smooth a-CN films. We, therefore, call this method "shielded arc ion plating (SAIP)". For the deposition of DLC films we used argon instead of nitrogen. Films of about 150 nm in thickness were deposited onto Si substrates. Their structures, chemical compositions and chemical bonding states were analyzed by using X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and infrared spectroscopy. Hardness of the films was measured with a nanointender interfaced with an atomic force microscope (AFM). A Berkovich-type diamond tip whose radius was less than 100 nm was used for the measurement. A force-displacement curve of each film was measured at a peak load force of 250 maicro-N. Load, hold and unload times for each indentation were 2.5, 0 and 2.5 s, respectively. Hardness of each film was determined from five force-displacement curves. Wear resistance of the films was analyzed as follows. First, each film surface was scanned with the diamond tip at a constant load force of 20 maicro-N. The tip scanning was repeated 30 times in a 1 urn-square region with 512 lines at a scanning rate of 2 um/ s. After this tip-scanning, the film surface was observed in the AFM mode at a constant force of 5 maicro-N with the same Berkovich-type tip. The hardness of a-CN films was less dependent on Vs. The hardness of the film deposited at Vs=O V in a nitrogen plasma was about 10 GPa and almost similar to that of Si. It slightly increased to 12 - 15 GPa when a bias voltage of -100 - -500 V was applied to the substrate with showing its maximum at Vs=-300 V. The film deposited at Vs=O V was least wear resistant which was consistent with its lowest hardness. The biased films became more wear resistant. Particularly the film deposited at Vs=-300 V showed remarkable wear resistance. Its wear depth was too shallow to be measured with AFM. On the other hand, the DLC film, deposited at Vs=-l00 V in an argon plasma, whose hardness was 35 GPa was obviously worn under the same wear test conditions. The a-C:N films show higher wear resistance than DLC films and are useful for wear resistant coatings on various mechanical and electronic parts.nic parts.