• 한국분말재료학회지
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• 제18권5호
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• pp.430-436
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• 2011

Joining of NiO-YSZ to 316 stainless steel was carried out with B-Ni2 brazing alloy (3 wt% Fe, 4.5 wt% Si, 3.2 wt% B, 7 wt% Cr, Ni-balance, m.p. 971-$999^{\circ}C$) to seal the NiO-YSZ anode/316 stainless steel interconnect structure in a SOFC. In the present research, interfacial (chemical) reactions during brazing at the NiO-YSZ/316 stainless steel interconnect were enhanced by the two processing methods, a) addition of an electroless nickel plate to NiO-YSZ as a coating or b) deposition of titanium layer onto NiO-YSZ by magnetron plasma sputtering method, with process variables and procedures optimized during the pre-processing. Brazing was performed in a cold-wall vacuum furnace at $1080^{\circ}C$. Post-brazing interfacial morphologies between NiO-YSZ and 316 stainless steel were examined by SEM and EDS methods. The results indicate that B-Ni2 brazing filler alloy was fused fully during brazing and continuous interfacial layer formation depended on the method of pre-coating NiO-YSZ. The inter-diffusion of elements was promoted by titanium-deposition: the diffusion reaction thickness of the interfacial area was reduced to less than 5 ${\mu}m$ compared to 100 ${\mu}m$ for electroless nickel-deposited NiO-YSZ cermet.

• 대한치과기공학회지
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• 제23권1호
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• pp.55-64
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• 2001

This study is focusing on the improvement of problems of Ti-6Al-4V alloy. A new Ti based alloy, Ti-15Sn-4Nb, have designed to examine any possibility of improving the mechanical properties and biocompatibility. Specimens of Ti alloys were melted in vacuum arc furnace and homogenized at $100^{\circ}C$ for 24h. All specimens were solution treated at $812^{\circ}C$ and aged at $500^{\circ}C$ for 10h. The corrosion resistance of Ti alloys was evaluated by potentiodynamic polarization test and immersion test inl%Lactic acid solutions. Ti-15Sn-4Nb system alloys showed Widmanstatten microstructure after solution treatment which is typical microstructure of ${\alpha}+{\beta}$ type Ti alloys. Analysing the corrosion resistance of Ti alloys, it was concluded that the passive films of Ti-15Sn-4Nb system alloys are more stable than that of Ti-6Al-4V alloys. Also, the corrosion resistance of Ti-15Sn-4Nb system alloys was improved with adding elements, Hf. It was analysed that the passive film of the Ti-15Sn-4Nb alloy which was formed in air atmosphere was consisted of TiO2, SnO and NbO through X-ray photoelectron spectroscopy(XPS) analysis.

• 전기화학회지
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• 제2권4호
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• pp.237-241
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• 1999

펄스전착법에 의한 구리박막의 특성과 via hole 충진 특성을 연구하였다. 특히 구리박막의 특성에 미치는 첨가제의 영향을 중점적으로 다루었다. 펄스 전류와 첨가제를 사용하여 전착한 구리박막은 83.4 MPa이하의 낮은 인장응력을 가졌으며 높은 Cu (111) 우선 배향성을 나타냈다. Superfilling에 의해 최고 $0.25{\mu}m, 6: 1$ 정도의 고 종횡비를 가지는 via hole에 결함 없이 성공적으로 충진할 수 있었으며 미세 구조를 관찰한 결과 쌍정에 의한 변형이 일어났음을 알 수 있었다. $500^{\circ}C$에서 1시간 동안 진공열처리를 했을 경우 두께의 $1\~2$배에 달하는 결정립을 가지는 bamboo구조를 나타냈으며 이때 전기비저항은 $1.8\~2.0{\mu}{\Omega}{\cdot}cm$을 나타냈다.

• 한국표면공학회지
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• 제42권4호
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• pp.161-168
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• 2009

Effects of TiN/Ti multilayer coating on the Ti-30Ta-xZr alloy surface were studied by using various experiments. The Ti-30Ta containing Zr (5, 10 and 15 wt%) were melted 10 times to improve chemical homogeneity by using a vacuum furnace. And then samples were homogenized for 24 hrs at $1000^{\circ}C$. The specimens were prepared for TiN/Ti coating by cutting and polishing. The prepared specimens were coated with TiN/Ti multilayers by using DC magnetron sputtering method. The analyses of coated surface and coated layer were carried out by field emission scanning electron microscope(FE-SEM), EDX, and X-ray diffractometer(XRD). From the microstructure and XRD analysis of Ti-30Ta-xZr alloys, The equiaxed structure was changed to needle-like structure with increasing Zr content. And $\alpha$-peak and elastic modulus increased as Zr content increased. The $\alpha$ and $\beta$ phase predominantly were found in the specimen containing high Zr content. According to the analysis of TiN/Ti coating layer, the surface defects and structures of Ti-30Ta-xZr were covered with TiN/Ti coating layer and surface roughness decreased.

• 한국표면공학회지
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• 제49권3호
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• pp.260-264
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• 2016

In this study, fractured surface morphology and mechanical properties of Ni-Cr-Mo alloys with various contents of Mo for dental material use have been evaluated by mechanical test. The alloys used were Ni-13Cr-xMo alloys with Mo contents of 4, 6, 8, and 10 wt.%, prepared by using a vacuum arc-melting furnace. Ni-13Cr-xMo alloys were used for mechanical test without heat treatment. The phase and microstructure of alloys using an X-ray diffraction (XRD) and optical microscopy (OM) were evaluated. To examine the mechanical properties of alloys according to microstructure changes, the tensile test and the hardness test were carried out using tensile tester. To understand the mechanism of Mo addition to Ni-Cr alloy on mechanical property, the morphology and fractured surfaces of alloys were investigated by field-emission scanning electron microscope (FE-SEM). As a result, 79Ni-13Cr-8Mo alloy was verified that the tensile strength and the hardness were better than others. Varying Mo content, the changes of microstructures of alloys were identified by OM and SEM and that of 79Ni-13Cr-8Mo alloy was proved fabricated well. Microstructures of alloys were changed depending on Mo content ratio. It has been observed that 8% alloy had the most suitable mechanical property for dental alloy.

• 자원리싸이클링
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• 제3권1호
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• pp.32-37
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• 1994

폐전지로부터 중금속 및 유가금속을 효과적으로 분리, 회수하기 위한 물리적, 화학적 처리기술을 개발함으로써 환경오염문제를 극소화하고 폐자원을 재활용하여 자원의 지속적인 확보와 공급에 기여하고자 이에 대한 기초연구로서 폐수은 전지의 수은제거를 위한 증류실험을 행하였다. 감압 증류실험시 폐전지내 수은은 노 내부온도 $150^{\circ}C$에서 증발되기 시작하여 이를 폐전지로부터 분리, 회수할 수 있었으며 $400^{\circ}C$ 이상에서는 유기물으 열분해가 진행되어 전지내 개스킷 등이 제거되었다. 폐전지의 증류시 내부압력, 반응온도 및 반응시간 등을 변화시키면서 그 영향을 조사하였으며 내부압력 20torr, $250^{\circ}C$에서 8시간 이상 증류실험한 결과 용출액의 수은 함량이 5ppb이하로 환경기준을 만족시켰고, 폐전지내 수은의 99.9%를 회수 할 수 있었다. 또한 전지의 사전 폐쇄없이 온도 증가속도를 $15^{\circ}C$/mm 이상으로, 가열하는 경우 내부 압력의 급격한 증가로 인하여 전지의 파열이 발생하였다.

• 한국전기전자재료학회논문지
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• 제20권7호
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• pp.594-599
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• 2007

[ $CulnS_2$ ] thin films were synthesized by sulfurization of Cu/In Stacked elemental layer deposited onto glass Substrates by vacuum furnace annealing at temperature $200^{\circ}C$. And structural and electrical properties were measured in order to certify optimum conditions for growth of the ternary compound semiconductor $CuInS_2$ thin films with non-stoichiometry composition. $CuInS_2$ thin film was well made at the annealed $200^{\circ}C$ of SLG/Cu/In/S stacked elemental layer which was prepared by thermal evaporator, and chemical composition of the thin film was analyzed nearly as the proportion of 1 : 1 : 2. Physical properties of the thin film were investigated at various fabrication conditions substrate temperature, annealing and temperature, annealing time by XRD, FE-SEM and Hall measurement system. The compositional deviations from the ideal chemical formula for $200^{\circ}C$ material can be conveniently described by non-molecularity$({\Delta}x=[Cu/In]-1)$ and non-stoichiometry $({\Delta}y=[{2S/(Cu+3In)}-1])$. The variation of ${\Delta}x$ would lead to the formation of equal number of donor and accepters and the films would behave like a compensated material. The ${\Delta}y$ parameter is related to the electronic defects and would determine the type of the majority charge carriers. Films with ${\Delta}y>0$ would behave as p-type material while ${\Delta}y<0$ would show n-type conductivity. At the sane time, carrier concentration, hall mobility and resistivity of the thin films was $9.10568{\times}10^{17}cm^{-3},\;312.502cm^2/V{\cdot}s\;and\;2.36{\times}10^{-2}\;{\Omega}{\cdot}cm$, respectively.

• 한국재료학회지
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• 제3권3호
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• pp.300-309
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• 1993

본 연구에서는 다공성 니켈재료의 원료분말로 활용될 수 있는 hollw 니켈금속분말 계조를 위한 니켈-흑연복합분말의 흑연코어 기화과정에 관하여 실험을 행하였다. 수증개-수소 혼합가스에 의한 복합분말중 흑연코어의 기화온도는 $800^{\circ}C$~$900^{\circ}C$였으며, 약 1시간의 기화반응에 의해 내부가 텅 빈 hollw니켈금속분말을 얻을 수 있었다. 흑연코어의 평균입도가 21$\mu\textrm{m}$인 82.2tw,% 니켈-17.87tw.5 흑연 복합분말로부터 제조된 hollw니켈금속분말을 100Kg/c$\textrm m^2$의 압력으로 압축, 성형한 성형체의 겉보기 기공도는 45%이었으며, 이성형체를 진공로에서 $1150^{\circ}C$ 의 온도로 1시간 소결하여 30%의 기공도와 소재내에 균질한 기공분포를 갖즌 소결체를 얻음으로써 다공성재료 제조시 hollow분말을 원료로 사용하여 재료 내의 기공에 관한 제반사항을 쉽게 조절할 수 있다는 가능성을 확인하였다.

• 한국재료학회지
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• 제22권10호
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• pp.513-518
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• 2012

Recently, automobile parts have been required to have high strength and toughness to allow for weight lightening or improved stability. But, traditional micro-alloyed steel cannot be applied in automobile parts. In this study, we considered the influence of quenching temperature and cooling rate for specimens fabricated by vacuum induction furnace. Directly quenched micro-alloyed steel for hot forging can be controlled according to its micro structure and the heat-treatment process. Low carbon steel, as well as alloying elements for improvement of strength and toughness, was used to obtain optimized conditions. After hot forging at $1,200^{\circ}C$, the ideal mechanical properties (tensile strength ${\geq}$ 1,000 MPa, Charpy impact value ${\geq}\;100\;J/cm^2$) can be achieved by using optimized conditions (quenching temperature : 925 to $1,050^{\circ}C$, cooling rate : ${\geq}\;5^{\circ}C/sec$). The difference of impact value according to cooling rate can be influenced by the microstructure. A fine lath martensite micro structure is formed at a cooling rate of over $5^{\circ}C/sec$. On the other hand, the second phase of the M-A constituent microstructure is the cause of crack initiation under the cooling rate of $5^{\circ}C/sec$.

• 한국표면공학회지
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• 제37권5호
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• pp.249-252
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• 2004

Effects of HA and TiN coating on the electrochemical characteristics of Ti-6AI-4V alloys for bone plates were investigated using various test methods. Ti-6AI-4V alloys were fabricated by using a vacuum induction furnace and bone plates were made by laser cutting and polishing. HA was made of extracted tooth sintered and then tooth ash was used as HA coating target. The TiN and HA film coating on the surface were carried on using electron-beam physical vapor deposition (EB-PVD) method. The corrosion behaviors of the samples were examined through potentiodynamic method in 0.9% NaCI solutions at $36.5\pm$$1^{\circ}C$ and corrosion surface was observed using SEM and XPS. The surface roughness of TiN coated bone plates was lower than that of tooth ash coated plates. The structure of TiN coated layer showed the columnar structure and tooth ash coated layer showed equiaxed and anisotrophic structure. The corrosion potential of the TiN coated specimen is comparatively high. The active current density of TiN and tooth ash coated alloy showed the range of about $1.0xl0^{-5}$ $A\textrm{cm}^2$, whereas that of the non-coated alloy was$ 1.0xl0^{-4}$ $A\textrm{cm}^2$. The active current densities of HA and TiN coated bone plates were smaller than that of non-coated bone plates in 0.9% NaCl solution. The pitting potential of TiN and HA coated alloy is more drastically increased than that of the non-coated alloy. The pit number and pit size of TiN and HA coated alloy decreased in compared with those of non-coated alloy. For the coated samples, corrosion resistance increased in the order of TiN coated, tooth ash coated, and non-coated alloy.