• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.1
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• pp.18-30
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• 1999

A heat transfer analysis for the two-dimensional (2-D) steady state using finite difference method (FDM) is performed to predict the thermal behavior of the primary first-wall (FW) system of fusion reactor under various geometric and thermo-hydraulic conditions, such as the beryllium (Be) armor thickness, pitch of cooling tube, and coolant velocity. The FW consists of authentic steel (type 316 stainless steel solution annealed) for cooling tubes, Cu for cooling tubes embedding material, and Be for a protective armor, based on the International Thermonuclear Experiment Reactor (ITER) report. The present 2-D analysis, the control volume discretized with hybrid grid (rectangular grid and polar grid) and Gauss-Seidel iteration method are adapted to solve the governing equations. In the present study, geometric and thermo-hydraulic parameters are optimized with consideration of several limitations. Consequently, it is suggested that the adequate pitch of cooling tube is 22-32mm, the beryllium armor thickness is 10-12mm, and that the coolant velocity is 4.5m/s-6m/s for $100^{\circ}C$ of inlet coolant temperature. The cooling tube should locate near beryllium armor. But, it would be better for locating the center of Cu wall, considering problems of material and manufacturing. Also, 2-D analysis neglecting the axial temperature distribution of cooling tube is appropriate, regarding the discretization error in axial direction.

• Journal of Powder Materials
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• v.20 no.4
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• pp.269-274
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• 2013

The present work investigated the dispersion behavior of $Y_2O_3$ particles into AISI 316L SS manufactured using laser cladding technology. The starting particles were produced by high energy ball milling in 10 min for prealloying, which has a trapping effect and homogeneous dispersion of $Y_2O_3$ particles, followed by laser cladding using $CO_2$ laser source. The phase and crystal structures of the cladded alloys were examined by XRD, and the cross section was characterized using SEM. The detailed microstructure was also studied through FE-TEM. The results clearly indicated that as the amount of $Y_2O_3$ increased, micro-sized defects consisted of coarse $Y_2O_3$ were increased. It was also revealed that homogeneously distributed spherical precipitates were amorphous silicon oxides containing yttrium. This study represents much to a new technology for the manufacture and maintenance of ODS alloys.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.2
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• pp.117-124
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• 2012

Alkaline electrolysis needs the electrode having a low overvoltage and good corrosion resistance in alkaline solution such as KOH and NaOH, for the oxygen and hydrogen production. The commercial materials such as SUS(stainless steel)-316, Ni and NiFe were evaluated for the electrode in alkaline electrolysis. The test solution for the alkaline electrolysis used 1~9M NaOH and 1~9M KOH. The voltage increased with an increase of current density in each solution. As for the 15wt.% (about 5M) NaOH, the voltage of the tested electrode under the current density of 1.8A/$cm^2$ showed the almost same value. The voltage over the current density of 1.8A/$cm^2$ deceased in the order: Ni${\fallingdotseq}$NiFe$cm^2$ showed the almost same value. The voltage over the current density of 1.8A/$cm^2$ deceased in the order: NiFe${\fallingdotseq}$SUS-316. From the results, it was estimated that NiFe and Ni was suitable as the electrode for the alkaline water electrolysis using NaOH and KOH electrolyte.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.6
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• pp.636-641
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• 2016

Alkaline water electrolysis is commercial hydrogen production technology. It is possible to operate MW scale plant. Because It used non-precious metal for electrode. But It has relatively low current density and low efficiency. In this study, research objective is development of anode for alkaline water electrolysis with low cost, high corrosion resistance and high efficiency. Stainless steel 316L (SUS 316L) was selected for a substrate of electrode. To improve corrosion resistance of substrate, Nickel (Ni) layer was electrodeposited on SUS 316L. Ni-Fe alloy was electrodeposited on the passivated Ni layer as active catalyst for oxygen evolution reaction(OER). We optimized preparation condition of Ni-Fe alloy electrodeposition by changing current density, electrodeposition time and composition ratio of Ni-Fe electrodeposition bath. This electrodes were electrochemically evaluated by using Linear sweep voltammetry (LSV) and Cyclic voltammetry (CV). The Ni-Fe alloy (Ni : Fe = 1 : 1) showed best activity of OER. The optimized electrode decreased overpotential about 40% at $100mA/cm^2$ compared with Ni anode.

• Journal of the Korean Ceramic Society
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• v.37 no.4
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• pp.381-387
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• 2000

Si3N4/stainless steel 316 joints with Ni buffer layer were fabricated by direct active brazing method (DIB) using Ag-Cu-Ti brazing alloy only and double brazing method (DOB) using Ag-Cu brazing alloy with Si3N4 pretreated with Ag-Cu-Ti brazing alloy. For the joint brazed by DIB method, Ti was segregated at the Si3N4/brazing alloy interface, but was not enough to form a stable joint interface. In addition, large amounts of Ni-Ti inter-metallic compounds were formed in tehbrazing alloy near the joint interface, which could deplete the contents of Ti involved in the interfacial reaction. However, for the joint brazed by DOB method, segregation of Ti at the joint interface were enough to enhance the formation of stable interfacial reaction products such as TiN and Ti-Si-Ni-N-(Cu) multicompounds, which restricted the formation of Ni-Tio inter-metallic compounds in the brazing alloy during brazing with Ni buffer layer. Fracture strength of Si3N4/S.S 316 joints with Ni buffer layer was much improved by using DOB method rather than DIB method. It could be deduced that the differences of fracture strength of the joint with Ni buffer layer depending on brazing process adapted were directly affected by the formation of stable joint interface and the change in microstructure of the brazing alloy near the joint interface. It was found that fracture strength of Si3N4/S.S 316 joints with Ni buffer layer was gradually reduced as the thickness of interface. It was found that fracture strength of Si3N4/S.S 316 joints with Ni buffer layer was gradually reduced as the thickness of Ni buffer layer in the joint was increased from 0.1 mm to 10 mm. It seems to due to the increased residual stress in the joint as the thickness of Ni buffer layer is increased. The maximum fracture strength of Si3N4/S.S 316 joints with Ni buffer layer was 386 MPa, and the fracture of joint was originated at Si3N4/brazing alloy joint interface and propagated into Si3N4 matrix.

• Proceedings of the KAIS Fall Conference
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• 2000.10a
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• pp.30-33
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• 2000

최근 국내에서도 관 동맥 질환 환자의 수가 급증하고 있으며, 관 동맥 질환의 치료 방법인 관 동맥 성형 술은 관 동맥 stent의 도입에 의하여 보편화되어 국내에서 년간 5000개 이상의 stent가 시술되고 있다. 그러나 stent는 고가(1,200천원/개)로 전량 수입에 의존하고 있으며, 시술 후 사망까지 이를 수 있는 혈전에 의한 급성 페쇠와 재 협착이 문제점이다. 이를 위한 한가지 방법이 생체 적합성이 뛰어난 복합 stent의 개발인데 SiC나 Carbon을 coating한 stent는 시술 후 혈전 형성을 억제하는 것으로 알려져 있다. 특히 가장 순수한 Pyrolytic carbon은 hemocompatibility가 탁월하고 기밀 성이기 때문에 본 연구에서 그의 CVB-Kinetics를 연구코저 하는 것이다. methane으로부터 pyrolytic carbon의 CVD는 온도에 따라서 다양한 구조를 가지며 따라서 그의 mechanism도 다양하다는 것은 잘 알려져 있다. 더구나 광간(균질)반응과 표면(불균질)반응의 정량적 관계에 따라서도 다르다는 것도 확인되었다. 그러나 stainless steel 316L로 만든 stent는 12 - 15 %의 Ni과 2%의 Mo을 함유해서 금속성을 잃지 않는 저온(600℃)에서도 pyrolytic carbon의 속매적 CVD가 가능함을 그리고 SiC의 코팅에 적합한 buffer layer 역할을 함을 확인하였다. 그리하여 본 연구는 반응기 설계에 필요한 저온 촉매적 pyrolytic carbon의 CVD-kinetics의 연구결로 그의 mechanism과 함께 rate law 식을 유도, 확인하였으며 600℃, 90kPa에서 P/sub ch4//P/sub H2/=5:1과 체류시간 1.8 sec가 최적임을 발견하였다. 이때 석출속도 11.2 g-mol/g-cat.h 혹은 두께속도로 73 nm/sec를 나타내었다.메타놀-물 (1 : 1) 유출액에서 $(0.80\;{\mu}g)$ 검출되었다. 하면 morey eel내장에서 얻은 독물질도 DEAE-셀루로즈에서 ST-1 과 ST-2로 나누어지며, 이 ST-1의 TLC, HPLC 및 알루미나 컬럼상의 거동이 파랑비늘돔에서 얻은 ST-1의 그것과 같으므로 scaritoxin으로 보고한 ST-1은 ciguatoxin의 형태인 less polar cigutoxin (LPCTX) 으로 생각된다.에서 각각 대조구의 57, 413 및 315% 증진되었다. 거품의 열안정성은 15분 whipping시, pH 4.0(대조구, 30.2%) 및 5.0(대조구, 23.7%)에서 각각 $0{\sim}38.0$ 및 $0{\sim}57.0%$이었고 pH 7.0(대조구, 39.6%) 및 8.0(대조구, 43.6%)에서 각각 $0{\sim}59.4$ 및 $36.6{\sim}58.4%$이었으며 sodium alginate 첨가시가 가장 양호하였다. 전체적으로 보아 거품안정성이 높은 것은 열안정성도 높은 경향이며, 표면장력이 낮으면 거품형성능이 높아지고, 비점도가 높으면 거품안정성 및 열안정성이 높아지는 경향이 있었다.protocol.eractions between application agents that are developed using different languages. Dynamic agent invocation is accomplished by Java Native Interface(JNI) that links two heterogeneous methods, and by KQML language interface that facilitates the communications between heterogeneous agents. This scheme of dyna

• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.5
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• pp.297-305
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• 2006

The thermal ratcheting deformation at the reactor baffle and upper internal structure of the liquid metal reactor (LMR) can occur due to movement of the hot sodium free surface. In in-service inspection of reactor internals of LMR, a new inspection technique should be developed for the detection of the thermal ratcheting damage. In this study, an inspection technique using ultrasonic guided wave is proposed for the detection of the thermal ratcheting damage of cylindrical vessels. A 316L stainless steel cylindrical shell specimen has been prepared. The thermal ratchet structural tests were cyclically performed by heat-up up to $550^{\circ}C$ with steep temperature gradients along the axial direction after cool-down by cooling water. Ultrasonic guided wave propagation has been characterized by analysis of dispersion curve of the stainless steel plate. The zero-order antisymmetric $A_0$ guided wave has been selected as the optimal mode for detection of the ratcheting deformation. It is confirmed that the thermal ratcheting deformation can be detected by the measurement of transit time difference of circumferentially propagated $A_0$ guided waves.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.4
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• pp.562-572
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• 2005

Statement of problem : Titanium is widely used as an implant material lot artificial teeth. Also, studies on surface treatment to form a fine passive film on the surface of commercial titanium or its alloys and improving bioactivity with bone have been carried out. However, there is insufficient data about the biocompatibility of the implant materials in the body. Purpose: The purpose of this study was to examine whether the precipitation of apatite on titanium metal is affected by surface modification. Materials and methods: Specimens chemically washed for 2 minute in a 1:1:1.5 (in vol%) mixture of 48% HF 60% $HNO_3$ and distilled water. Specimens were then chemically treated with a solution containing 97% $H_2SO_4$ and 30% $H_2O_2$ at $40^{\circ}C$S for 1 hour, and subsequently heat-treated at $400^{\circ}C$ for 1 hour. All specimens were immersed in the HBSS with pH 7.4 at $36.5^{\circ}C$ for 15 days, and the surface were examined with TF-XRD, SEM, EDX and XPS. Also, commercial purity Ti specimens with and without surface treatment were implanted in the abdominal connective tissue of mice for 4 weeks. Conventional aluminium and stainless steel 316L were also implanted for comparison. Results and conclusions : The results obtained were summarized as follows. 1. An amorphous titania gel layer was formed on the titanium surface after the titanium specimen was treated with a $H_2SO_4$ and $H_2O_2$ solution. The average roughness was $2.175{\mu}m$ after chemical surface treatment. 2. The amorphous titania was subsequently transformed into anatase by heat treatment at $400^{\circ}C$ for 1 hour. 3. The average thickness of the fibrous capsule surrounding the specimens implanted in the connective tissue was $46.98{\mu}m$ in chemically-treated Ti, and 52.20, 168.65 and $100.95{\mu}m$ respectively in commercial pure Ti, aluminum and stainless steel 316L without any treatment.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.11
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• pp.1011-1020
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• 2017

This study was conducted to investigate the material properties of stainless steel 316L specimens of untreated and UNSM treated material, hydrogen attacked material(100 bar, $300^{\circ}C$ at 120 h) and UNSM treated hydrogen attacked material at room temperature. Results demonstrated that the hydrogen attacked materials showed a tendency toward a slightly decreased fatigue strength, while the hydrogen embrittlement effect was smaller than the S-N curve of conventional untreated material. As compared to untreated material, the fatigue limit of the UNSM treated material increased by 43.8%, while it was 57.1％ higher in the UNSM treated hydrogen attacked material than in untreated hydrogen attacked material. The plastic deformation layer was ${\sim}152{\mu}m$ thick, as confirmed by maps showing the level of local plastic deformation affected by the UNSM treatment in three ways: an image quality map, inverse pole figure map, and kernel average misorientation map captured via electron back scatter diffraction. Owing to hydrogen embrittlement, about 90％ of surface cracks were smaller than the average grain size of $35{\mu}m$.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.3
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• pp.333-340
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• 2010

This paper presents the distributions of the tensile and fracture properties of an alloy 82/182 dissimilar weld joint between an SA508 Gr.3 nozzle and F316L SS safe-end at ambient temperature. Tensile and J-R tests were conducted using specimens extracted from base metals, heat-affected zones (HAZs), buttering regions, and various regions of the weld metal. The results show that the root region of the weld has higher strength than the upper region. The yield and tensile strengths vary considerably within the root region of the weld. The buttering region had the lowest strengths. The strengths gradually increased as the F316L stainless steel weld boundary was approached. The variation of the strengths within the upper region of the weld is insignificant. The fracture toughness of the alloy 82/182 weld metal is less than those of both the base metals and both HAZs. Within the alloy 82/182 weld, the center of weld has a slightly lower fracture toughness than the weld boundary and buttering region, and the root region has greater toughness than the upper region of the weld.