• 한국재료학회지
• /
• 제10권10호
• /
• pp.715-720
• /
• 2000

MCFC 작동온도인 $650^{\circ}C$에서 음극의 creep과 소결에 의한 구조적 변형을 막기 위해 기계적 합금법에 의한 Ni-WC분말을 합금화하여 변형에 대한 저항성을 증대시키고자 하였다. 80시간동안 어트리션 밀링을 실시한 분말은 XRD 분석결과 결정규칙이 파괴된 비정질 상을 보였다. 제조된 분말은 적당한 점도의 슬러리로 제조후 테이프 캐스팅법에 의해 green sheet를 제조하였다. 제조된 박판의 두께는 0.9mm였고, 평균 기공 크기는 $3~5{\mu\textrm{m}}$, 기공율은 55%였다. 소결체의 XRD 분석결과 2차성은 생성되지 않았으며, SEM 및 dot-Mapping image를 통해 Ni matrix 안에 W 입자가 미세하고 균일하게 분포되어 있어 고용강화 및 분산강화를 통해 Ni 음극의 기계적 특성을 향상시킬 것으로 기대된다.

• 한국세라믹학회지
• /
• 제40권1호
• /
• pp.31-36
• /
• 2003

본 연구에서는 칩 인덕터용 코어 소재로 사용되는 NiCuZn-ferrite를 공침법을 이용하여 나노크기의 초미세 분말로 합성하고, 합성된 NiCuZn-ferrite의 하소 온도에 따른 저온소결 특성 및 전자기적 특성에 관하여 고찰하였다. 조성은 (N $i_{0.4-X}$C $u_{x}$Z $n_{0.6}$)$_{1+w}$(F $e_2$ $O_4$)$_{1-w}$에서 x 값을 0.2, w 값은 0.03으로 고정하였고, 하소는 30$0^{\circ}C$에서 7$50^{\circ}C$의 온도범위에서 진행하였다. 하소 후 90$0^{\circ}C$에서 소결한 시편의 특성을 측정한 결과, 공침법으로 합성한 NiCuZn-ferrite는 90$0^{\circ}C$의 저온에서 소결밀도 4.90g/㎤, 초기투자율 164, Q-factor 72임을 확인하였다. 또한, NiCuZn-ferrite의 미세구조는 하소온도가 증가함에 따라 입자가 커지고 불균일한 상태가 되며, 초기투자율 등의 ferrites의 전자기적 특성이 저하되었다.되었다.

• 한국분말재료학회지
• /
• 제1권1호
• /
• pp.79-84
• /
• 1994

The mechanism of activated sintering of tungsten powder was discussed in terms of diffusion and segregation of activator atoms at W grain boundaries. Shrinkage behaviours of W-0.2wt.% Ni, W-0.2wt.% Cu or pure W powder compacts during sintering at low temperatures of 900~ $1200^{\circ}C$ were investigated. It was found that the Cu additive inhibits sintering process causing lower densification than pure W compact while remarkable shrinkage occurred in the Ni added W powder. Such contrary effect was explained by comparing self diffusion processes along Ni or Cu segregated W boundaries in which Ni segregants enhance but Cu atoms retard the migration of W atoms at W boundaries.

• 한국표면공학회지
• /
• 제38권1호
• /
• pp.1-6
• /
• 2005

Ni-15at.% W coatings with film thicknesses of 20-40 ㎛ were electroplated on a steel substrate, and their oxidation behavior was investigated at 700 and 800℃ in air. For comparison, a pure Ni coating and a bulk Ni were also oxidized. The Ni-15at.%W coating displayed the worst oxidation resistance, due to the formation of less-protective NiO, Fe₂O₃, NiFe₂O₄ and NiWO₄. The corrosion behavior Ni-15at.%W coatings electroplated on a steel substrate was similarly investigated at 700 and 800℃ in the Ar-l%SO₂ atmosphere. For comparison, the uncoated steel substrate was also corrosion-tested in the Ar-l %SO₂ atmosphere. Severe scale spallation and the internal corrosion of the steel that occurred in the uncoated substrate were not observed in the coated specimen. However, it seemed that the Ni-15at.%W coating cannot be a potential candidate as a sulfidation-resistant coating, due to the formation of less-protective NiO, NiS, WO₃ and NiWO₄.

• 한국표면공학회:학술대회논문집
• /
• 한국표면공학회 2011년도 춘계학술대회 및 Fine pattern PCB 표면 처리 기술 워크샵
• /
• pp.201-201
• /
• 2011

크롬대체도금으로 개발 추진되고 있는 전기Ni-W합금도금피막은 경질크롬 도금피막보다도 고온에서 경도 및 내 산성이 우수하고, 유리성형용 금형으로 사용되고 있다. 최근 일본에서는 지금까지의 무전해Ni-W-P합금피막에 비해서 텅스텐, 인의 함유율이 높고, 질산 이외의 염산, 황산의 산성 환경과 암모니아, 수산화나트륨 등의 알칼리성 환경에서도 부식이나 변색이 생기지 않는 무전해Ni-W-P합금도금기술을 크롬도금을 대체하는 도금으로서 개발하고 있다.

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 1995년도 추계학술강연 및 발표대회 강연 및 발표논문 초록집
• /
• pp.31-31
• /
• 1995

• 한국표면공학회:학술대회논문집
• /
• 한국표면공학회 2001년도 추계학술발표회 초록집
• /
• pp.56-56
• /
• 2001

Ni-W alloy deposit is one of the best alternatives to hard chromium plating because of its good mechanical properties (high hardness, high strength, and good wear resistance). Ni-W alloy is deposited from weakly acidic or alkaline electrolytic bath with nickel sulfate, sodium tungstate or APT, and some kinds of organic hydroxy-acid complex and ammonia salts. W content of the deposit can be changed from 0 to 5Owt% and the coating with high W content is more attracted. But, meanwhile, the deposited layers are always found high internal stress, which cause them to become brittle and to bond insufficiently with the substrate. On the second hand, as the W content is incresed, the current efficiency reduced, which results in large quantities of hydrogen evolution and then produces bubbles on surface and pitting appearance In this paper, the influence of some additives on Ni-W alloy electroplating was investigated by means of compositional analysis and SEM. The initial results showed that 2-butyne-1,4-diol was the best brightener for Ni-W plating process. It could brighten and level deposit, but decreased the cathodic current efficiency. Its optimum concentration range is from O.lgjL to 0.5gjL. Besides, three kinds of additives including 2-butyne-1,4-diol were examined with Dagguchi method.

• 한국전기화학회:학술대회논문집
• /
• 한국전기화학회 2003년도 춘계총회 및 학술발표회
• /
• pp.41-41
• /
• 2003

• 한국재료학회지
• /
• 제28권2호
• /
• pp.108-112
• /
• 2018

The present study demonstrates the effect of raw powder on the pore structure of porous W-Ni prepared by freeze drying of camphene-based slurries and sintering process. The reduction behavior of $WO_3$ and $WO_3-NiO$ powders is analyzed by a temperature programmed reduction method in Ar-10% H2 atmosphere. After heat treatment in hydrogen atmosphere, $WO_3-NiO$ powder mixture is completely converted to metallic W without any reaction phases. Camphene slurries with oxide powders are frozen at $-30^{\circ}C$, and pores in the frozen specimens are generated by sublimation of the camphene during drying in air. The green bodies are hydrogen-reduced at $800^{\circ}C$ and sintered at $1000^{\circ}C$ for 1 h. The sintered samples show large and aligned parallel pores to the camphene growth direction, and small pores in the internal wall of large pores. The strut between large pores, prepared from pure $WO_3$ powder, consists of very fine particles with partially necking between the particles. In contrast, the strut densification is clearly observed in the Ni-added W sample due to the enhanced mass transport in activation sintering.

• 한국표면공학회지
• /
• 제26권2호
• /
• pp.87-107
• /
• 1993

The grain size of the final products of WC-Co and WC-Ni composite powders is dependent on the size of the starting material and the conditions employed for the reduction and carburization. APT-Co and -Ni com-plex salts were prepared by the substitution reaction between ammonium ions in APT and the metal ions in Co(NO3)2 and Ni(NO3)2 solutions of different concentrations(0.1 to 0.7M) at $50^{\circ}C$ and the grain sizes of the com-plex salts was $0.54~0.76\mu\textrm{m}$. The complex which calcined the complex salts at $700^{\circ}$~80$0^{\circ}C$ for 60min. were 0.2~0.5$\mu\textrm{m}$. W-Co($5.92^{\circ}C$) and -Ni(6.95%) powders which reduced the complex oxides with H2d atmo-sphere(flow rate;600cc/min.) at $700^{\circ}$~$800^{\circ}C$ for 60min. were $0.5~0.6\mu\textrm{m}$. The mean grain sizes of WC-Co and WC-Ni composite powders which carburized both complex metals of W-Co and W-Ni at $800^{\circ}C$ for 60min. were $0.5~0.6\mu\textrm{m}$, and take place the coarsening of the grain above $800^{\circ}C$ and the optmium ratio of C3H8 and H2 was 0.2 for the control of the free carbon. The effect of Co contents on the particle sizes decreased from 0.4 to $0.25\mu\textrm{m}$ with increasing the content from 2.0 to 7.6w%. The activation energies on the reductions of oxides and the formations of carbides were as follows ; W-Co : Q = 8.7 kcal/mole, W-Ni : Q = 8.1 kcal/mole, WC-Co pow-der : Q = 17.8 kcal/mole, WC-Ni powder : Q = 16.6 kcal/mole.