• Journal of Powder Materials
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• v.18 no.5
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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.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.8
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• pp.508-513
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• 2017

Ultraviolet (UV) photodetectors are used in various industries and fields of research, including optical communication, flame sensing, missile plume detection, astronomical studies, biological sensors, and environmental research. However, general UV detectors that employ Schottky junction diodes and p-n junctions have high fabrication cost and low quantum efficiency. In this study, we investigated the characteristics of materials used to manufacture UV photodetectors in a low-cost solution process that requires easy fabrication of flexible substrates. We fabricated p-type NiO and n-type ZnO substrates with wide band gap by the sol-gel method and compared the characteristics of substrates prepared under different spin-coating and heat-treatment conditions.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.2
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• pp.170-174
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• 2023

Nickel oxide is a nonstoichiometric transparent conductive oxide with p-type conductivity, a wide-band energy gap of 3.4~4.0 eV, and excellent chemical stability, making it a very important candidate as a material for bipolar devices. P-type conductivity in Transparent Conductive Oxides (TCO) is controlled by the oxygen vacancy concentration. During the TCO film deposition process, additional oxygen diffusing into the NiO structure causes the formation of Ni 3p ions and Ni vacancies. This eventually affects the hole concentration of the p-type oxide thin film. In this work, the surface morphology and the electrical characteristics were confirmed in accordance with the annealing atmosphere of the nickel oxide thin film.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.121-121
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• 2003

NiO thin films are very attractive for use as an antiferromagnetic layer, p-type transparent conducting films, in electrochromic devices and functional sensor layer for chemical sensors, due to their excellent chemical stability, as well as optical, electrical and magnetic properties. In addition, (100)- and (111)-oriented NiO films can be used as buffer layers on which to deposit other oriented oxide films, such as c-axis-oriented perovskite-type ferromagnetic films and superconducting films, because of the similarity in symmetry of oxygen ion lattice and lattice constants between the NiO films and the oriented oxide films. Thus, controlling the crystallographic orientation and surface roughness of the NiO films for a buffer layer are very important.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.4
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• pp.322-327
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• 2003

Giant magnetoresistance(GMR) NiO multilayer, which has been used to reading head of highly dense magnetic recording, was fabricated, and oxidized in an air during 80 days to study the dependence of magnetoresistance properties on residual stress in the interfaces. The magnetoresistance ratio and the exchange biasing $field(H_{ex})$ of $NiO(60nm)/Ni_{81}Fe_{19}(5nm)/Co(0.7nm)/Cu(2nm)/Co(0.7nm)/Ni_{81}Fe_{19}(7nm)$ spin valves were increased from 4.9% to 7.3%, and 110 Oe to 170 Oe after natural oxidation in the atmosphere for 80 days, respectively. The sheet resistivity ${\rho}$ decreased from $28{\mu}{\Omega}m$ to $17{\mu}{\Omega}m$, but ${\Delta}p$ did not almost change after the oxidation. Therefore, the increase of MR ratio is due to the decrease in the sheet resistivity. the reduced resistance may result from the increase in the reflection of conduction electrons at the oxidized top surface. Also, the increase in the exchange biasing field is originated from the reduction of residual stress at the interface of $NiO/Ni_{81}Fe_{19}$ according as the aging time increases.

• 한국신재생에너지학회:학술대회논문집
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• 2005.11a
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• pp.667-672
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• 2005

In order to effectively utilize visible light in the photocatalytic reaction, nanaocomposite of Ni doped $TiO_2$ and $NiTiO_3$ powders were synthesized by mechanical alloying and heat treatment. About 5.4 wt% of $NiTiO_3$ with particle size less than 15nm was uniformly formed in the Ni-doped rutile $TiO_2$ matrix. The UV/VIS-DRS and PL investigation showed that the nanocompasite $TiO_2$ powders had a longer absorpt ion wavelength (600$\sim$650nm, 2.0$\sim$1.9eV) than that of Ni-doped $TiO_2$ or rutile $TiO_2$ powder. The carbon decomposition of 4-CP by the nanocompasite $TiO_2$ powders were higher than other $TiO_2$ (P-25).

• Korean Journal of Materials Research
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• v.19 no.8
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• pp.443-446
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• 2009

This study develops a highly transparent ohmic contact scheme using indium oxide doped ZnO (IZO) as a current spreading layer for p-GaN in order to increase the optical output power of nitride-based lightemitting diodes (LEDs). IZO based contact layers of IZO, Ni/IZO, and NiO/IZO were prepared by e-beam evaporation, followed by a post-deposition annealing. The transmittances of the IZO based contact layers were in excess of 80% throughout the visible region of the spectrum. Specific contact resistances of $3.4\times10^{-4}$, $1.2\times10^{-4}$, $9.2\times0^{-5}$, and $3.6\times10^{-5}{\Omega}{\cdot}cm^2$ for IZO, Ni/Au, Ni/IZO, and NiO/IZO, respectively were obtained. The forward voltage and the optical output power of GaN LED with a NiO/IZO ohmic contact was 0.15 V lower and was increased by 38.9%, respectively, at a forward current of 20 mA compared to that of a standard GaN LED with an Ni/Au ohmic contact due to its high transparency, low contact resistance, and uniform current spreading.

• Polymer(Korea)
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• v.25 no.2
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• pp.218-225
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• 2001

The electroless plating of a metallic nickel on PAN-based carbon fiber surfaces was carried out to improve mechanical interfacial properties of the carbon fiber/epoxy resin composites which were unidirectionally fabricated by a prepregging method. In this work, the influence of Ni-P alloy concentration showing brittle-to-ductile transition was investigated on interlaminar shear strength (ILSS) and impact strength of the composites. The surface properties of carbon fibers were also measured by X-ray photoelectron spectroscopy (XPS). As the result, the $O_{ls}$ /$O_{ls}$ ratio or Ni and P amounts were increased with increasing electroless nickel plating time but the ILSS were not significantly improved. However, the impact properties was significantly improved in the presence of Ni-P alloy in the carbon fiber surface, resulting in an increase of the ductility of the composites.

• Journal of the Korean Magnetics Society
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• v.23 no.5
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• pp.149-153
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• 2013

The electronic structures of $TCr_2O_4$ (T = Fe, Co, Ni) spinel oxides have been investigated by employing synchrotron radiation-based soft X ray absorption spectroscopy (XAS). The measured 2p XAS spectra of transition-metal ions reveal that Cr ions are trivalent ($Cr^{3+}$), and all the T (T = Fe, Co, Ni) ions are divalent ($Fe^{2+}$, $Co^{2+}$, $Ni^{2+}$). It is also found that most of T (T = Fe, Co, Ni) ions occupy the A sites under the tetrahedral symmetry, while Cr ions occupy mainly the B sites under the octahedral symmetry. These findings show that the structures of $TCr_2O_4$ (T = Fe, Co, Ni) are very close to the normal spinel structures. Based on these findings, it is expected that Jahn-Teller (JT) effects are important in $FeCr_2O_4$ and $NiCr_2O_4$. In contrast, $CoCr_2O_4$ maintains the cubic structure without having the JT distortion since both $Cr^{3+}$ and $Co^{2+}$ ions are non-JT ions. This work suggests that the antiferromagnetic interaction between $Cr^{3+}$ and $T^{2+}$ ions plays an important role in determining the magnetic properties of $TCr_2O_4$ (T = Fe, Co, Ni).

• Journal of Korean Society of Water and Wastewater
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• v.28 no.2
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• pp.207-215
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• 2014

Wastewater containing heavy metals such as copper (Cu) and nickel (Ni) is harmful to humans and the environment due to its high toxicity. Crystallization in a fluidized bed reactor (FBR) has recently received significant attention for heavy metal removal and recovery. It is necessary to find optimum reaction conditions to enhance crystallization efficacy. In this study, the effects of crystallization reagent and pH were investigated to maximize crystallization efficacy of Cu-S and Ni-S in a FBR. CaS and $Na_2S{\cdot}9H_2O$ were used as crystallization reagent, and pH were varied in the range of 1 to 7. Additionally, each optimum crystallization condition for Cu and Ni were sequentially employed in two FBRs for their selective removal from the mixture of Cu and Ni. As major results, the crystallization of Cu was most effective in the range of pH 1-2 for both CaS and $Na_2S{\cdot}9H_2O$ reagents. At pH 1, Cu was completely removed within five minutes. Ni showed a superior reactivity with S in $Na_2S{\cdot}9H_2O$ compared to that in CaS at pH 7. When applying each optimum crystallization condition sequentially, only Cu was firstly crystallized at pH 1 with CaS, and then, in the second FBR, the residual Ni was completely removed at pH 7 with $Na_2S{\cdot}9H_2O$. Each crystal recovered from two different FBRs was mainly composed of CuxSy and NiS, respectively. Our results revealed that Cu and Ni can be selectively recovered as reusable resources from the mixture by controlling pH and choosing crystallization reagent accordingly.