• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
• /
• pp.379.2-379.2
• /
• 2016

The Ni oxide/PVP nanofibers were synthesized by sol-gel and electrospinning technique. The obtained Ni oxide/PVP (polyvinylpyrrolidone) nanofibers were calcined to remove the PVP compound at 873 and 1173 K. The Ni oxide/PVP nanofibers were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The SEM images showed that the mat form was prepared by calcination of Ni oxide/PVP nanofibers at 873 K. And the crystal structure of Ni oxide at 1173 K was also confirmed by SEM images. XRD results shows the crystallinity of metallic Ni and NiO. TEM images also verified the crystal phase of Ni and Ni oxide. XP spectra revealed that the oxidation state of Ni to conclude the chemical composition of Cu oxide nanofibers.

• Journal of Electrochemical Science and Technology
• /
• 제9권2호
• /
• pp.93-98
• /
• 2018

$MnO_2$, a metal oxide used as an electrode material in electrochemical capacitors (EDLCs), has been applied in binary oxide and conducting polymer hybrid electrodes to increase their stability and capacitance. We developed a method for electrodepositing Mn-Ni oxide/PANI, Mn-Ni oxide/PEDOT, and Mn-Ni-Ru oxide/PEDOT films on carbon paper in a single step using a mixed bath. Mn-Ni oxide/PEDOT and Mn-Ni-Ru oxide/PEDOT electrodes used in an electro-osmotic pump (EOP) have shown better efficiency compared to Mn-Ni oxide and Mn-Ni oxide/PANI electrodes through testing in water as a pumping solution. EOP using a Mn-Ni-Ru oxide/PEDOT electrode was also tested in a 0.5 mM $Li_2SO_4$ solution as a pumping solution to confirm the effect of the $Li^+$ insertion/de-insertion reaction of Ruthenium oxide on the EOP. Experimental results show that the flow rate increases with the increase in current in a 0.5 mM $Li_2SO_4$ solution compared to that obtained when water was used as a pumping solution.

• Corrosion Science and Technology
• /
• 제7권3호
• /
• pp.145-151
• /
• 2008

Material degradation such as high temperature oxidation of metallic material is a severe problem in energy generation systems or manufacturing industries. The metallic materials are oxidized to form oxide films in high temperature environments. The oxide films act as diffusion barriers of oxygen and metal ions and thereafter decrease oxidation rates of metals. The metal oxidation is, however, accelerated by mechanical fracture and spalling of the oxide films caused by thermal stresses by repetition of temperature change, vibration and by the impact of solid particles. It is therefore very important to investigate mechanical properties and adhesion of oxide films in high temperature environments, as well as the properties in a room temperature environment. The oxidation tests were conducted for Ni and Ni-Co alloy under high temperature corrosive environments. The hardness distributions against the indentation depth from the top surface were examined at room temperature. Dynamic indentation tests were performed on Ni oxide films formed on Ni surfaces at room and high temperature to observe fractures or cracks generated around impact craters. As a result, it was found that the mechanical property as hardness of the oxide films were different between Ni and Ni-Co alloy, and between room and high temperatures, and that the adhesion of Ni oxide films was relatively stronger than that of Co oxide films.

• Journal of Electrochemical Science and Technology
• /
• 제3권4호
• /
• pp.178-184
• /
• 2012

A porous nickel (P-Ni) substrate was prepared by selective leaching of zinc from pressed pellets containing powders of Ni & Zn in 4 M NaOH solution. Anodic deposition of manganese oxide onto the porous Ni substrate ($MnO_x$/P-Ni) formed nano-flakes of manganese oxide layers as revealed in SEM studies. Pseudocapacitance of this oxide electrode was evaluated by cyclic voltammetry (CV) and chronopotentiometry (CHP) in 2 M NaOH solution. The specific capacitance of the Mn oxide electrode was as high as 1515 F $g^{-1}$, which was ten times higher than Mn oxide deposited on a flat Ni-ribbon. 80% of capacity was retained after 200 charge/discharge cycles. The system showed no loss of activity in dry form over period of days. The impedance studies indicated highly conducting $MnO_x$/P-Ni substance and the obtained specific capacitance from impedance data showed good agreement with the charge/discharge measurements.

• 한국재료학회지
• /
• 제12권3호
• /
• pp.220-224
• /
• 2002

The oxide scales formed on $Ni_3Al$-7.8%Cr-1.3%Zr-0.8%Mo-0.025%B after oxidation at 900, 1000 and 110$0^{\circ}C$ in air were studied using XRD, SEM, EPMA and TEM. The oxide scales consisted primarily of $NiO,\; NiAl_2O_4,\;{\alpha}-Al_2O_3,\; monoclinic-ZrO_2,\; and \;tetragonal-ZrO_2$. The outer layer of the oxide scale was rich in Ni-oxides, whereas the internal oxide stringers were rich in Al-oxides and $ZrO_2$. Within the above oxide scales, Cr and Mo tended to exist as dissolved ions.

• 한국수소및신에너지학회논문집
• /
• 제17권2호
• /
• pp.174-180
• /
• 2006

The eutectic Mg-23.5%Ni alloy was casted by melting and solidification. The powders of Mg-23.5%Ni and (Mg-23.5%Ni)-10% iron oxide were prepared by mechanical grinding of casted Mg-Ni alloy and casted Mg-Ni alloy+oxide, respectively. As milling time increases, hydriding and dehydriding rates of Mg-Ni and Mg-Ni-oxide alloy powders increase. The additions of iron oxide to Mg-Ni alloy and Mg-Ni-oxide increase hydriding rates and slightly decrease dehydriding rates.

• 한국재료학회지
• /
• 제14권4호
• /
• pp.281-286
• /
• 2004

The oxide scales formed on Ni-18W(at.%) coating that was electrodeposited on steel were investigated using XRD, SEM and TEM. The oxide scales consisted mainly of an outer NiO layer, and an inner thick ($NiWO_4$+NiO) mixed layer. The unoxidized coating below the oxide scale was rich in Ni and depleted in W, owing to the consumption of Wand the resultant Ni enrichment. The oxidation resistance of Ni-18W coating was poorer than that of the TiN coating, due to the formation of nonprotective NiWO$_4$. During oxidation, Ni and the substrate element of Fe diffused outward, while oxygen inward, according to the concentration gradients.

• Bulletin of the Korean Chemical Society
• /
• 제35권5호
• /
• pp.1305-1311
• /
• 2014

The nickel oxide, the most widely used cathode material for the molten carbonate fuel cell (MCFC), has several disadvantages including NiO dissolution, poor mechanical strength, and corrosion phenomena during MCFC operation. The surface modification of NiO with lanthanum maintains the advantages, such as performance and stability, and suppresses the disadvantages of NiO cathode because the modification results in the formation of $LaNiO_3$ phase which has high conductivity, stability, and catalytic activity. As a result, La-modified NiO cathode shows low NiO dissolution, high degree of lithiation, and mechanical strength, and high cell performance and catalytic activity in comparison with the pristine NiO. These enhanced physico-chemical and electrochemical properties and the durability in marine environment allow MCFC to marine application as a auxiliary propulsion system.

• 센서학회지
• /
• 제14권1호
• /
• pp.52-55
• /
• 2005

Ni oxide thin films with thermal sensitivity superior to Pt and Ni thin films were formed through annealing treatment after Ni thin films were deposited by a r.f. magnetron sputtering method. Resistivity values of Ni oxide thin films were in the range of $10.5{\mu}{\Omega}cm$ to $2.84{\times}10^{4}{\mu}{\Omega}cm$ according to the degree of Ni oxidation. Also temperature coefficient of resistance(TCR) values of Ni oxide thin films depended on the degree of Ni oxidation from 2,188 ppm/$^{\circ}C$ to 5,630 ppm/$^{\circ}C$ in the temperature range of $0{\sim}150^{\circ}C$. Because of the high linear TCR and resistivity characteristics, Ni oxide thin films exhibit much higher sensitivity to flow and temperature changes than pure Ni thin films and Pt thin films.

• Corrosion Science and Technology
• /
• 제3권5호
• /
• pp.198-208
• /
• 2004

Although there has been no general agreement on the mechanism of primary water stress corrosion cracking (PWSCC) as one of major degradation modes of Ni-base alloys in pressurized water reactors (PWR's), common postulation derived from previous studies is that the damage to the alloy substrate can be related to mass transport characteristics and/or repair properties of overlaid oxide film. Recently, it was shown that the oxide film structure and PWSCC initiation time as well as crack growth rate were systematically varied as a function of dissolved hydrogen concentration in high temperature water, supporting the postulation. In order to understand how the oxide film composition can vary with water chemistry, this study was conducted to characterize oxide films on Alloy 600 by an in-situ Raman spectroscopy. Based on both experimental and thermodynamic prediction results, Ni/NiO thermodynamic equilibrium condition was defined as a function of electrochemical potential and temperature. The results agree well with Attanasio et al.'s data by contact electrical resistance measurements. The anomalously high PWSCC growth rate consistently observed in the vicinity of Ni/NiO equilibrium is then attributed to weak thermodynamic stability of NiO. Redox-induced phase transition between Ni metal and NiO may undermine the integrity of NiO and enhance presumably the percolation of oxidizing environment through the oxide film, especially along grain boundaries. The redox-induced grain boundary oxide degradation mechanism has been postulated and will be tested by using the in-situ Raman facility.