• 대한금속재료학회지
• /
• 제49권10호
• /
• pp.747-753
• /
• 2011

In order to improve the corrosion resistance of Fe-20Cr-1.7C-1Si hardfacing alloy without a loss of wear resistance, the effect of Ni addition was investigated. As expected, the corrosion resistance of the alloy increased with increasing Ni concentration. The wear resistance of the alloy did not decrease, even though the hardness decreased, up to Ni concentration of 5 wt.%. This was attributed to the fact that the decrease in hardness was counterbalanced by the strain-induced martensitic transformation. The wear resistance of the alloy, however, decreased abruptly with increases of the Ni concentration over 5 wt.%.

• Korean Chemical Engineering Research
• /
• 제52권5호
• /
• pp.678-687
• /
• 2014

The catalytic performance of silicon carbide supported nickel catalysts modified with or without second metal (Co, Cu and Zn) for the methanation of CO has been investigated in a fixed-bed reactor using a feed consisting of 25% CO and 75% $H_2$ without any diluent gas. It has been found that the introduction of Co species can clearly improve the catalytic activity of Ni/SiC catalyst, whereas the addition of Cu or Zn can result in a significant decrease in the catalytic activity. The characterizations by means of XRD, TEM, XPS, CO-TPD and $H_2$-TPR indicate that the addition of Co could decrease the particle size of active metal, increase active sites on the surface of methanation catalyst, improve the chemisorption of CO and enhance the reducibility of methanation catalysts. Additionally, the special interaction between Co species and Ni species is likely favorable for the dissociation of adsorbed CO on the surface of catalyst, and this may also contribute to the high activity of 5Co-Ni/SiC catalyst for CO methanation reaction. For 5Cu-Ni/SiC catalyst and 5Zn-Ni/SiC catalyst, Cu and Zn species could cover partial nickel particles and decrease the chemisorption amount of CO. These could be responsible for the low methanation activity. In addition, a 150h stability test under 2 MPa and $300^{\circ}C$ showed that 5Co-Ni/SiC catalyst was very stable for CO methanation reaction.

• 한국수소및신에너지학회논문집
• /
• 제17권3호
• /
• pp.248-254
• /
• 2006

The promotion effects of noble metals upon the activity and reducibility in steam methane reforming over $Ni/MgAl_2O_4$ catalysts were investigated. While $Ni/MgAl_2O_4$ catalysts require the pre-reduction by $H_2$, the noble metal-added catalysts show high catalytic activities without pre-treatment. According to $CH_4$-TPR, the addition of noble metal makes the $Ni/MgAl_2O_4$ catalyst easily reducible. The reduction degree of NiO in the noble metal-added catalysts after using at $650^{\circ}C$ without pre-reduction was $15{\sim}20%$, and was lower than that in the $H_2$-reduced $Ni/MgAl_2O_4$ catalyst(reduction degree=27%). The enhancement of the catalytic activity over noble metal-added catalysts results from easier reducibility by addition of noble metal and the synergy effect between noble metal and Ni.

• 반도체디스플레이기술학회지
• /
• 제13권3호
• /
• pp.51-55
• /
• 2014

Ni-CNT(Carbon Nanotubes) composite coating is often used for the surface treatment of mechanical/electronic devices to improve the properties of the Ni coating. For the Ni-CNT coating, the dispersion of CNT fibers is a critical process. In this study, ultrasonic treatment instead of the conventional ball milling was attempted as a dispersion method for the electroless Ni-CNT coating. SEM-EDX analysis was performed and contact angle, sheet resistance, and micro-hardness were measured. Results showed that the ultrasonic treatment was comparable to the ball milling, as a dispersion method, but the difference was negligible. However, combined ball milling and ultrasonic treatment(double treatment) showed much improved micro-hardness value, above 350Hv(close to the value obtained by the Ni-CNT electroplating). In addition, electroless Ni-CNT(double-treated) coatings formed on the thin Ni film deposited by the electroless plating(double coating) showed better mechanical properties. Thus, double treatment and double coating are suggested as an improved electroless Ni-CNT coating method.

• 한국세라믹학회지
• /
• 제40권1호
• /
• pp.11-17
• /
• 2003

Ni-Mn 산화물 NTC 서미스터의 미세구조와 전기적 특성에 미치는 Zr $O_2$ 첨가의 효과를 연구하였다. Zr $O_2$를 포함하는 Ni-Mn-Zr 산화물 소결체의 주요 상은 입방정 스피넬 구조를 가지는 NiO-Mn$_3$ $O_4$-Zr $O_2$의 고용체와 정방정 결정구조를 가지는 Zr $O_2$ 상이였다. Zr $O_2$의 첨가량이 증가함에 따라 Ni-Mn-Zr산화물의 고용체를 형성하지 못하고 생성된 Zr $O_2$의 양이 증가하였다. NiO-Mn$_3$ $O_4$-Zr $O_2$ NTC 서미스터에 있어서 절대온도 역수(l/T)에 대한 로그 비저항(log $ho$)은 직선적인 관계가 있었고, 비저항, B$_{140}$320/정수 및 활성화 에너지는 Zr $O_2$ 함량이 증가함에 따라 크게 증가하였다.

• 한국환경농학회지
• /
• 제9권2호
• /
• pp.113-119
• /
• 1990

토양중(土壤中) Cr, Ni, Cd, Cu, Zn을 각각(各各) 0, 20, 50, 100, 200ppm첨가(添加)하고 무와 배추의 발아(發芽) 및 생육(生育)에 미치는 각(各) 중금속(重金屬)의 영향(影響)을 조사(調査)하였다. 무우와 배추의 발아(發芽)는 Ni와 Cr 200ppm첨가(添加) 토양(土壤)에서 심한 억제(抑制)를 받았으나 Cu, Cd, Zn 200 ppm첨가(添加) 토양(土壤)에서는 크게 영향(影響)을 받지 않았다. 5종(種)의 중금속(重金屬)이 무우와 배추의 생육(生育) 억제(抑制)에 미치는 영향(影響)은 Cr>Ni>Cd>Cu>Zn순(順)였으며 무우보다 배추가 더 크게 억제(抑制)를 받았다. 무우에 대하여 50%이상(以上) 심한 생육억제(生育抑制)를 보였던 각 중금속(重金屬)의 첨가농도(添加濃度) Cr가 20ppm, Ni, Cd과 Cu은 50ppm, Zn은 200ppm였으며, 배추에 대하여 Cr, Ni, Cd, Cu가 20ppm, Zn은 200ppm였다. 중금속(重金屬)에 의한 2가지 작물(作物)의 생육억제(生育抑制)는 토양중(土壤中) 퇴비(堆肥)와 석회(石灰)의 첨가(添加)에 의하여 현저(顯著)히 경감(輕減)되었다.

• 한국응용과학기술학회지
• /
• 제27권1호
• /
• pp.29-36
• /
• 2010

The effects of La addition to Ni/$CeO_2$ methane partial oxidation catalysts were investigated. Catalysts were prepared by the impregnation and urea methods. In the preparation of catalysts, La content was changed from 1 wt% to 3wt%. Catalysts that contain 2wt% La showed the highest methane conversion of about 80% and CO selectivity of 84% and $H_2$ selectivity of 70%. This result may be stemmed from that, when La content is 2wt%, a fluorite oxide-type structure is well formed and carbon deposition is also decreased. Among the catalysts, 2.5wt% Ni/Ce(La)Ox showed the highest catalytic activity. From the experiment of changing reaction temperature with 2.5wt% Ni/Ce(La)Ox catalyst, it was found that the optimum reaction temperature is $750^{\circ}C$ and at this temperature methane conversion was about 90%, CO and $H_2$ selectivities were 94 and 80%, respectively.

• 한국재료학회지
• /
• 제28권9호
• /
• pp.495-498
• /
• 2018

Intermetallic compound matrix composites have been expected to be established as high temperature structural components. $Ni_3Al$ is a representative intermetallic alloy, which has excellent ductility even at room temperature by adding certain alloying elements. $Ni_3Al$ matrix composites with aluminum oxide particles, which are formed by the in-situ reaction between the alloy and aluminum borate whiskers, are fabricated by a powder metallurgical method. The addition of aluminum borate whiskers disperses the synthetic aluminum oxide particles during sintering and dramatically increases the strength of the composite. The uniform dispersion of reaction synthesized aluminum oxide particles and the uniform solution of boron in the matrix seem to play an important role in the improvement in strength. There is a dramatic increase in strength with the addition of the whisker, and the maximum value is obtained at a 10 vol% addition of whisker. The $Ni_3Al$ composite with 10 vol% aluminum oxide particles $0.3{\mu}m$ in size and with 0.1 wt% boron powder fabricated by the conventional powder metallurgical process does not have such high strength because of inhomogeneous distribution of aluminum oxide particles and of boron. The tensile strength of the $Ni_3Al$ with a 10 vol% aluminum borate whisker reaches more than twice the value, 930 MPa, of the parent alloy. No third phase is observed between the aluminum oxide and the matrix.

• Korean Chemical Engineering Research
• /
• 제48권6호
• /
• pp.776-783
• /
• 2010

수소생산을 위한 메탄의 부분산화용 촉매로 알루미나에 담지된 코발트와 니켈 촉매를 함침법으로 제조하였다. 메탄의 부분산화반응을 위한 이들 촉매의 반응활성은1기압, $CH_4/O_2=2.0$과 $450{\sim}650^{\circ}C$의 온도영역에서 조사하였다. 담지량이 다른 코발트촉매와 니켈촉매의 반응활성을 비교하고 코발트촉매에 니켈을 첨가한 이성분금속 촉매의 반응활성을 조사하였다. 그리고 코발트촉매와 니켈촉매에 첨가된 Ce와 La의 첨가효과를 조사하였다. 이들 촉매의 특성은 XRD와 SEM/EDX로 분석하였다. 코발트와 니켈은 10 wt%의 담지량이 적절한 것으로 나타났다. 이들 10 wt% 담지 코발트와 니켈촉매는 열역학적 평형값에 가까운 메탄의 전환율과 CO의 선택성을 나타내었으나 $H_2$의 선택성은 평형값보다 다소 낮게 나타났다. 코발트촉매에 니켈을 첨가한 이성분금속 촉매에서 $H_2$의 선택성은 증가하였으나 전환율을 고려하면 니켈을 첨가한 이점은 나타나지 않았다. 코발트촉매에서는 Ce의 첨가와 니켈촉매에서는La의 첨가로 메탄의 전환율과 수소의 선택성을 높일 수 있었다.

• 한국분말재료학회지
• /
• 제11권1호
• /
• pp.34-42
• /
• 2004

The effect of extrusion temperature on the microstructure and mechanical properties were studied in He-gas atomized $Al_{81-(x＋y)}Si_{19}Ni_xCe_y$ alloy powders and their extruded bars using SEM, tensile testing and thermal expansion testing. The extruded bar of $Al_{73}Si_{19}Ni_7Ce_1$ alloy consists of a mixed structure in which fine Si particles with a particle size below 20∼500nm and very fine $Al_3Ni,\;Al_3Ce$ compounds with a particle size below 200nm are homogeneously dispersed in Al martix with a grain size below 500nm. With increasing extrusion temperature, the microstructural scale was decreased. The ultimate tensile strength of the alloy bars has incresed with decreasing extrusion temperature from 500 to 35$0^{\circ}C$ and $Al_{73}Si_{19}Ni_7Ce_1$ alloy extreded at 35$0^{\circ}C$ shows a highest tensile strength of 810 MPa due to the fine namostructure. The addition of Ni and Ce decreased the coefficients of thermal expansion and the effects of extression temperature on the thermal expansion were not significant.