• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.08a
• /
• pp.356-356
• /
• 2011

탄소나노튜브(CNT)는 기계적, 전기적, 열적성질이 매우 우수하여 다양한 응용이 기대되고 있다. CNT를 금속기판에 직접 합성시킬 경우 CNT와 금속기판의 계면에서 높은 전도성 및 물리적 접착 강도를 기대할 수 있어서, 전계방출(field emission) 소자 또는 방열(heat dissipation) 소자 등과 같은 CNT의 높은 전도성과 일차원적 구조를 이용하고자 하는 분야로의 응용가능성을 높일 수 있다. 본 연구에서는 CNT의 합성촉매로 주로 사용되고 있는 니켈을 주요 성분으로 함유하고 있는 Inconel, Hastelloy, Invar 등을 합성기판으로 선정하여, CNT의 합성 거동을 조사하였다. CNT 합성은 CVD방법을 이용하였으며, 아세틸렌가스를 원료가스로 이용하였다. 합성 전 기판의산화 전처리가 CNT합성 효율에 영향을 미치는 것을 확인하였으며, 이를 체계적으로 조사하기 위하여, 다양한 온도(425~725$^{\circ}C$) 구간에서 산화 전처리를 실시한 후 CNT의 합성 거동을 조사하였다. 산화과정에 의한 표면구조의 변화 및 표면에서 금속성분의 재배열이 CNT합성 효율 변화의 원인으로 사료되고 있으며, 이를 분석하기 위해서, AFM, XRD, EDS, SEM, TEM 등을 이용하였다. 본 연구결과는 향후 전자방출소자, X-ray source 및 방열소자 등의 응용에 유용할 것으로 기대된다.

• Journal of Welding and Joining
• /
• v.30 no.3
• /
• pp.51-56
• /
• 2012

Different microstructures in the weld zone of a metal structure including a fusion zone and heat affected zone are formed as compared to the base material. Thus, the mechanical properties in the weld zone are different from those in the base material. As the basic data for reliably understanding the structural characteristics of welded nuclear material, the mechanical properties in the weld zone and base material for a Zircaloy-4 strap and Hastelloy${(R)}$-X alloy strap are measured using an instrumented indentation technique (IIT) in this study.

• Progress in Superconductivity and Cryogenics
• /
• v.12 no.4
• /
• pp.20-23
• /
• 2010

In this study, the electromechanical property of REBCO coated conductor (CC) tape adopting a stainless steel substrate has been investigated. Sample was subjected to uniaxial tension and measured its mechanical properties at RT and 77 K. $I_c-{\varepsilon}_t$ relations was also studied in which the strain and stress corresponding to the 95% $I_c$ retention and reversible strain limit were measured. In addition, these results were compared to the case of conventional REBCO CC tape adopting a Hastelloy substrate. As a result, by adopting a stainless steel substrate comparable strength and good electromechanical property to Hastelloy one could be achieved.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2006.02a
• /
• pp.86-86
• /
• 2006

• 한국초전도학회:학술대회논문집
• /
• v.9
• /
• pp.392-396
• /
• 1999

Superconducting YBa$_2Cu_3O_{7-{\delta}}$(YBCO) thin films were grown on Hastelloy(Ni-Cr-Mo alloys) with CeO$_2$ buffer layer in-situ by pulsed laser deposition in a multi-target processing chamber. To apply superconducting property on power transmission line, we have deposited YBCO thin film on flexible metallic substrate. However, it is difficult to grow the YBCO films on flexible metallic substrates due to both interdiffusion problem between metallic substrate and superconducting overlayers and non-crystallization of YBCO on amorphous substrate. It is necessary to use a buffer layer to overcome the difficulties. We have chosen CeO$_2$ as a buffer layer which has cubic structure of 5.41 ${\AA}$ lattice parameter and only 0.2% of lattice mismatch with 3.82 ${\AA}$ of a-axis lattice parameter of YBCO on [110] direction of CeO$_2$ In order to enhance the crystallization of YBCO films on metallic substrates, we deposited CeO$_2$ buffer layers with varying temperature and 02 pressure. By XRD, it is observed that dominated film orientation is strongly depending on the deposition temperature of CeO$_2$ layer. The dominated orientation of CeO$_2$ buffer layer is changed from (200) to(111) by increasing the deposition temperature and this transition affects the crystallization of YBCO superconducting film on CeO$_2$ buffered Hastelloy.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.18 no.3
• /
• pp.383-393
• /
• 2020

The corrosion behavior of Hastelloy C-276 was investigated to identify its applicability for carbon-anode-based oxide reduction (OR), in which Cl₂ and O₂ are simultaneously evolved at the anode. Under a 30 mL·min^-1 Cl₂ + 170 mL·min^-1 Ar flow, the corrosion rate was less than 1 g·m^-2·h^-1 up to 500℃, whereas the rate increased exponentially from 500 to 700℃. The effects of the Cl₂-O₂ composition on the corrosion rate at flow rates of 30 mL·min^-1 Cl₂, 20 mL·min^-1 Cl₂ + 10 mL·min^-1 O₂, and 10 mL·min^-1 Cl₂ + 20 mL·min^-1 O₂ with a constant 170 mL·min^-1 Ar flow rate at 600℃ was analyzed. Based on the data from an 8 h reaction, the fastest corrosion rate was observed for the 20 mL·min^-1 Cl₂ + 10 mL·min^-1 O₂ case, followed by 30 mL·min^-1 Cl₂ and 10 mL·min^-1 Cl₂ + 20 mL·min^-1 O₂. The effects of the chlorine flow rate on the corrosion rate were negligible within the 5-30 mL·min^-1 range. A surface morphology analysis revealed the formation of vertical scratches in specimens that reacted under the Cl₂-O₂ mixed gas condition.

• Journal of Mechanical Science and Technology
• /
• v.17 no.10
• /
• pp.1475-1484
• /
• 2003

The EDM processing characteristics of one of the nickel-based heat resistant alloys, Hastelloy- X, were investigated under the various EDM conditions and analyzed in terms of surface integrity. This alloy is commonly used as a material for the hot gas path component of gas turbines and it is difficult to machine by conventional machining methods. The primary EDM parameter which was varied in this study were the pulse-on time. Since the pulse-on time is one of the main factors that determines the intensity of the electrical discharge energy, it was expected that the machining ratio and the surface integrity of the specimens would be proportionally dependent on the pulse-on duration. However, experimental results showed that MRR (material removal rate) and EWR (electrode wear rate) behaved nonlinearly with respect to the pulse duration, whereas the morphological and metallurgical features showed rather a constant trend of change by the pulse duration. In addition the heat treating process affected the recast layer and HAZ to be recrystallized but softening occurred in recast layer only. A metallurgical evaluation of the microstructure for the altered material zone was also conducted.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.30 no.5
• /
• pp.479-483
• /
• 2010

9% nickel alloy steels used for LNG, cryogenic liquid, storage tank are welded with dissimilar Inconel or Hastelloy welding rod and the weldment shows similar characteristic with the dissimilar metal weld of low carbon steel and austenitic stainless steel. Band type indications are sometimes shown on the film during radiography test of the weldments. Thus this study identified whether the indications are non-relevant indications through material, radiographic test, ultrasonic test, liquid penetrant test and microstructure analysis and also proposed radiography film interpretation and cause of band type indications.

• Proceedings of the KIEE Conference
• /
• 1999.11d
• /
• pp.873-875
• /
• 1999

We have fabricated good quality superconducting $YBa_{2}Cu_{3}O_{7-\delta}$ thin films on Hastelloy(Ni-Cr-Mo alloys) metallic substrate with $CeO_2$ and $BaTiO_3$ buffer layers in-situ by pulsed laser deposition in a multi-target processing chamber. We have chosen $CeO_2$ as a buffer layer which has cubic structure of $5.41{\AA}$ lattice parameter and only 0.2% of lattice mismatch with YBCO. $CeO_2$ layer may be helpful for power transmission due to its conducting property. In order to enhance the crystallization of YBCO films on metallic substrates. we deposited $CeO_2$ and $BaTiO_3$ buffer layers at various temperatures. The YBCO superconducting tape fabricated with $BaTiO_3$ and $CeO_2$ buffer layers shows 85K of transition temperature and about $8.4{\times}10^4A/cm^2$ of critical current density at 77K.

• Nuclear Engineering and Technology
• /
• v.37 no.6
• /
• pp.537-556
• /
• 2005

A primary-pipe rupture accident is one of the design-basis accidents of a High-Temperature Gas-cooled Reactor (HTGR). When the primary-pipe rupture accident occurs, air is expected to enter the reactor core from the breach and oxidize in-core graphite structures. This paper describes an experiment and analysis of the air ingress phenomena and the method fur the prevention of air ingress into the reactor during the primary-pipe rupture accident. The numerical results are in good agreement with the experimental ones regarding the density of the gas mixture, the concentration of each gas species produced by the graphite oxidation reaction and the onset time of the natural circulation of air. A hydrogen production system connected to the High-Temperature Engineering Test Reactor (HTTR) Is being designed to be able to produce hydrogen by themo-chemical iodine-Sulfur process, using a nuclear heat of 10 MW supplied by the HTTR. The HTTR hydrogen production system is first connected to a nuclear reactor in the world; hence a permeation test of hydrogen isotopes through heat exchanger is carried out to obtain detailed data for safety review and development of analytical codes. This paper also describes an overview of the hydrogen permeation test and permeability of hydrogen and deuterium of Hastelloy XR.