• 한국세라믹학회지
• /
• 제41권1호
• /
• pp.81-85
• /
• 2004

점토를 이용한 나노 다공성 촉매 제조를 목적으로 $Ni^{2+}$ 이온으로 피복된 $SiO_2$ 나노 졸 입자를 2차원 충상점토 화합물의 층간에 삽입, 가교화 시켜 비표면적 및 다공도가 우수한 $NiO-SiO_2$ 가교화 점토($NiO-SiO_2$-PILM)를 합성하였다. 나노 크기의 실리카 졸 입자는 tetraethyl orthosilicate(TEOS)를 가수분해하여 합성하였고, 여기에 $Ni^{2+}$ 수용액을 첨가한 다음 NaOH 용액을 적정하여 $Ni^{2+}-SiO_2$ 혼합 나노 졸입자를 완성하였다. 이렇게 제조된 혼합 졸 용액을 1wt%의 점토 수분산액에 첨가하여 $60{\circ}C$에서 5h 이온교환 반응을 통해 층간에 삽입, 수세, 건조 후 $40^{\circ}C$에서 2시간 열처리 하므로써 다공성 가교화 점토를 제조하였다. 나노 졸 입자의 가교화에 따라 점토의 층간거리($d_{001}$)는 $45{\AA}$ 정도 크게 증가하였고 $600^{\circ}C$까지도 다공구조가 안정하게 유지되었다. 또한 질소 흡착-탈착 등온선 분석 결과 비표면적($S_{BET}$)이 최대 $760m^2/g$으로 다공 구조가 매우 잘 발달되어 있음을 확인하였고, $NiO-SiO_2$ 졸 가교화 점토의 경우 $NiO-SiO_2$ 나노입자가 층간에 이중층으로 배열되어 있음을 알 수 있었다.

• 한국세라믹학회지
• /
• 제33권4호
• /
• pp.411-417
• /
• 1996

Ultrafine NiO/YSZ (Yttria Stabilized Zirconia) powders were made by using a glycine nitrate process which is used as anode material for solid oxide fuel cells. The specific surface areas of synthesized NiO/YSZ powders were examined with controlling pH of a precursor solution and the content of glycine. The binding of glycine with metal nitrates occurring in the precursor solution was analyzed by using FTIR. The characteristics of synthesized powders were examined with X-ray diffraction(XRD) Brunauer Emmett Teller with N2 absorption. scanning electron microscopy (SEM). and transmission electron microscopy (TEM). Ultrafine NiO/YSZ powders of 15-18 m2/g were obtained through GNP when the content of glycine was controlled to 1 or 2 times the stoichiometric ratio in the precursor solutions. Strongly acid precursor solution increased the specific surface area of the synthesized powders. This is suggested to be the increased binding of metal nitrates and glycine under a strong acid solution of pH=0.5 that lets glycine consist of mainly the amine group of {{{{ { NH}`_{3 } ^{+ } }}. After sintering and reducing treatment of NiO/YSZ powders synthesized by GNP the Ni/YSZ pellet showed ideal microstructure where very fine Ni particles of 3-5 ${\mu}{\textrm}{m}$ were distributed uniformly and fine pore around Ni metal particles was formed. leading to anincrease of the triple phase boundary among gas Ni and YSZ.

• 한국분말재료학회지
• /
• 제30권6호
• /
• pp.484-492
• /
• 2023

In this study, Ni-Y₂O₃ powder was prepared by alloying recomposition oxidation sintering (AROS), solution combustion synthesis (SCS), and conventional mechanical alloying (MA). The microstructure and mechanical properties of the alloys were investigated by spark plasma sintering (SPS). Among the Ni-Y₂O₃ powders synthesized by the three methods, the AROS powder had approximately 5 nm of Y₂O₃ crystals uniformly distributed within the Ni particles, whereas the SCS powder contained a mixture of Ni and Y₂O₃ nanoparticles, and the MA powder formed small Y₂O₃ crystals on the surface of large Ni particles by milling the mixture of Ni and Y₂O₃. The average grain size of Y₂O₃ in the sintered alloys was approximately 15 nm, with the AROS sinter having the smallest, followed by the SCS sinter at 18 nm, and the MA sinter at 22 nm. The yield strength (YS) of the SCS- and MA-sintered alloys were 1511 and 1688 MPa, respectively, which are lower than the YS value of 1697 MPa for the AROS-sintered alloys. The AROS alloy exhibited improved strength compared to the alloys fabricated by SCS and conventional MA methods, primarily because of the increased strengthening from the finer Y₂O₃ particles and Ni grains.

• 한국재료학회지
• /
• 제17권2호
• /
• pp.86-90
• /
• 2007

The organic-capped Ba-Ti-O nanolayers were coated uniformly on spherical Ni particles for multilayer ceramic capacitor (MLCC) applications via the formation of Ti-hydroxide nano-coating layers and their subsequent reaction with Ba-stearate at $180^{\circ}C$. The capping of organic shell on oxide coating layer changed the hydrophilic surface structure into hydrophobic one, which significantly improved the dispersion behavior in hydrophobic solvents such as terpineol and butanol. In addition, the uniform coating of Ba-Ti-O layer was advantageous to prevent Ni oxidation. This method provides a useful chemical route to fabricate organic-soluble Ba-Ti-O coated Ni particles for a highly integrated passive component.

• Journal of Magnetics
• /
• 제14권2호
• /
• pp.75-79
• /
• 2009

Nickel (Ni) and ferrite ($Fe_3O_4$, $NiFe_2O_4$) nanoparticles were synthesized by LGC using both wire feeding (WF) and micron powder feeding (MPF) systems. Phase evolution and magnetic properties were then investigated. The Ni nanopowder included magnetic-ordered phases. The LGC synthesis yielded spherical particles with large coercivity while the abnormal initial magnetization curve for Ni indicated a non-collinear magnetic structure between the core and surface layer of the particles. Since the XRD pattern cannot actually distinguish between magnetite ($Fe_3O_4$) and maghemite (${\gamma}-Fe_2O_3$) as they have a spinel type structure, the phase of the iron oxide in the samples was unveiled by $M{\ddot{o}}ssbauer$ spectroscopy. The synthesized Ni-ferrite consisted of single domain particles, including an unusual ionic state. The synthesized nanopowder bore an active surface due to the defects that affected abnormal magnetic properties.

• 한국표면공학회지
• /
• 제45권3호
• /
• pp.97-105
• /
• 2012

The effects of pH, types of applied current, agitation method and time, additive on the amount of co-deposited $TiO_2$ particles in the matrix were investigated. The deposition rates increased with increasing pH values, while the volume fraction of $TiO_2$ particles and the size of agglomerated $TiO_2$ particles in the composite decreased. The volume fraction of $TiO_2$ particles in the composite decreased when pulsed current of 50% duty cycle was used. And the size of agglomerated $TiO_2$ particles in the nickel matrix of pulsed current was smaller than that of DC current specimen. The volume fraction of $TiO_2$ particles in the matrix decreased with longer time by air agitation, but in case of using magnetic bar, volume fraction in the same range of time was relatively constant. The volume fraction of the electrodeposited Ni-$TiO_2$ composite in the solution containing 0.01 M Dimethylamine borane (DMAB) increased slightly with increasing agitation time regardless of agitation methods. Thermal stability of the electrodeposited Ni-$TiO_2$ composite increased with lower pH at the temperature range of $200{\sim}800^{\circ}C$, and the results showed that the amount of co-deposited $TiO_2$ relies more on the deposition rate than zetapotential of $TiO_2$ particles.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
• /
• pp.422-425
• /
• 1999

Ultrafine NiO/YSZ (Yttria-Stabilized Zirconic) composite powders were prepared by using a glycine nitrate process (GNP) for anode material of solid oxide fuel cells. The specific surface areas of synthesized NiO/YSZ composite powders were examined with controlling pH of a precursor solution and the content of glycine. The binding of glycine with metal ions occurring in the precursor solution was analyzed by using FTIR. The characteristics of synthesized composite powders were examined with X-ray diffractometer, a BET method with $N_2$ absorption, scanning and transmission electron microscopies. Strongly acid precursor solution increased the specific surface area of the synthesized composite powders. This is suggested to be caused by the increased binding of metal ions and glycine under a strong acid solution of pH=0.5 that lets glycine consist of mainly the amine group of NH$_3$$^{+}$ After sintering and reducing treatment of NiO/YSZ composite powders synthesized by GNP, the Ni/YSZ pellet showed ideal microstructure very fine Ni Particles of 3-5${\mu}{\textrm}{m}$ were distributed uniformly and fine pores around Ni metal particles were formed, thus, leading to an increase of the triple phase boundary among gas, Ni and YSZ.Z.

• 한국세라믹학회지
• /
• 제51권4호
• /
• pp.243-247
• /
• 2014

Spherical NiO-YSZ particles were synthesized by ultrasonic spray pyrolysis (USP). The morphology of the synthesized particles can be modified by controlling parameters such as precursor pH, carrier-gas flow-rate, and temperature of the heating zone. The synthesized spherical NiO-YSZ particles have rough surface morphology at high carrier-gas flow-rates due to rapid gas exhaustion and insufficient particle ordering. The Ni-YSZ cermet anode synthesized by ultrasonic spray pyrolysis at a flow rate of l L/min, with precursor solution at pH4, showed a higher maximum power density of 256 $mW/cm^2$ compared to a conventionally mixed Ni-YSZ anode (185 $mW/cm^2$) at $800^{\circ}C$. While the area-specific resistance of conventionally mixed Ni-YSZ anodes increases gradually with operation time (indicating performance degradation), the Ni-YSZ anode synthesized by USP does not exhibit any performance degradation, even after 500 h.

• 한국산업융합학회 논문집
• /
• 제25권6_2호
• /
• pp.1037-1045
• /
• 2022

In this study, nanoscale Al₂O3 ceramic particles were used due its exceptionally high hardness characteristics, chemical stability, and wear resistance properties. These nanoparticles will be used to investigate the optimal process conditions for the electro co-deposition of the Ni-Al₂O₃ composite coatings. A Watts bath electrolytic solution of a controlled composition along with a fixed agitation speed was used for this study. Whereas the current density, the pH value, temperature and concentration of the nano Al₂O₃ particles of the electrolyte were designated as the manipulative variables. The experimental design method was based on the orthogonal array to find the optimum processing parameters for the electro co-deposition of Ni-Al₂O₃ composite coatings. The result of confirmation experimental based on the optimal processing condition through the analysis of variance ; EDX analysis found that the ratio of alumina increased to 8.65 wt.% and subsequently the overall hardness increased to 983 Hv. Specially, alumina were evenly distributed on Nickel matrix and particles were embedded more firmly and finely in Nickel matrix.

• 한국재료학회지
• /
• 제29권5호
• /
• pp.328-335
• /
• 2019

Nb-doped $TiO_2$(NTO) coated NiCrAl alloy foam for hydrogen production is prepared using ultrasonic spray pyrolysis deposition(USPD) method. To optimize the size and distribution of NTO particles based on good physical and chemical stability, we synthesize particles by adjusting the weight ratio of the Nb precursor solution(5 wt%, 10 wt% and 15 wt%). The morphological, chemical bonding, and structural properties of the NTO coated NiCrAl alloy foam are investigated by X-ray diffraction(XRD), X-ray photo-electron spectroscopy(XPS), and Field-Emission Scanning Electron Microscopy(FESEM). As a result, the samples of controlled Nb weight ratio exhibit a common diffraction pattern at ${\sim}25.3^{\circ}$, corresponding to the(101) plane, and have chemical bonding(O-Nb=O) at 534 eV. The NTO particles with the optimum weight ratio of N (10 wt%) show a uniform distribution with a size of ~18.2-21.0 nm. In addition, they exhibit the highest corrosion resistance even in the electrochemical stability estimation. As a result, the introduction of NTO coated NiCrAl alloy foam by USPD improves the chemical stability of the NiCrAl alloy foam by protecting the direct electrochemical reaction between the foam and the electrolyte. Thus, the optimized NTO coating can be proposed for excellent protection of NiCrAl alloy foam for hydrocarbon-based steam methane reforming(SMR).