• Journal of Surface Science and Engineering
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• v.50 no.4
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• pp.296-300
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• 2017

NiO nanofibers with Au nanoparticles were synthesized by sol-gel and electrospinning techniques, in which the reduction process by ultraviolet exposure is included for the growth of Au nanoparticles in the electrospinning solution. FE-SEM(Field Emission Scanning Electron Microscopy), TEM(Transmission Electron Microscopy) revealed that the synthesized nanofibers had the diameter of approximately 200 nm. X-ray diffraction showed the successful formation of Au-decorated NiO nanofibers. Gas sensing tests of Au-decorated NiO nanofibers were performed using reducing gases of CO, and $C_6H_6$, $C_7H_8$, $C_2H_5OH$. Compared to as-synthesized NiO nanofibers, the response of Au-loaded NiO nanofibers to CO gas was found to be about 3.4 times increased. On the other hand, the response increases were only 1.1-1.3 times for $C_6H_6$, $C_7H_8$, and $C_2H_5OH$.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.379.2-379.2
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• 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 Sensor Science and Technology
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• v.23 no.3
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• pp.211-215
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• 2014

The Pt-, Ni- and Cr-decorated tubular $SnO_2$ nanofibers for gas sensors were prepared by the electrospinning of polyvinylpyrrolidone (PVP) nanofibers containing Pt, Ni, and Cr precursors, the sputtering of $SnO_2$ on the electrospun PVP nanofibers, and the removal of sacrificial PVP parts by heat treatment at $600^{\circ}C$ for 2 h. Pt-decorated tubular $SnO_2$ nanofibers showed high response ($R_a/R_g=210.5$, $R_g$: resistance in gas, $R_a$: resistance in air) to 5 ppm $C_2H_5OH$ at $350^{\circ}C$ with negligible cross-responses to other interference gases (5 ppm trimethylamine, $NH_3$, HCHO, p-xylene, toluene and benzene). Cr-decorated tubular $SnO_2$nanofibers showed the selective detection of p-xylene at $400^{\circ}C$. In contrast, no significant selectivity to a specific gas was found in Ni-decorated tubular $SnO_2$ nanofibers. The selective and sensitive detection of gases using Pt-decorated and Cr-decorated tubular $SnO_2$ nanofibers were discussed in relation to the catalytic promotion of gas sensing reaction.

• Journal of Integrative Natural Science
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• v.11 no.1
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• pp.14-18
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• 2018

Nickel oxide nanofibers were synthesized by electrospinning with nickel(II) acetate tetrahydrate and polyvinylpyrrolidone and calcination process. The nanofiber shape was easily detected from the nanofibers with high Ni contents after calcined at $600^{\circ}C$ and the crystal structure of layer-by-layer growth was observed from SEM images at $900^{\circ}C$. XRD and TEM results showed metallic Ni and NiO structure were formed at nanofibers obtained at 600 and $900^{\circ}C$ and the crystallite size was calculated from 25 to 55 nm. The surface of nanofibers was fully oxidized from the deconvoluted Cu 2p and O 1s XPS spectra.

• Journal of the Semiconductor & Display Technology
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• v.3 no.1
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• pp.9-13
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• 2004

Carbon nanofibers (CNFs) with uniform diameter and controlled size were prepared from catalytic decomposition of $\textrm{C}_{2}\textrm{H}_{2}$ with Ni-MgO catalyst treated by mechanochemical (MC) process. The properties of Ni catalyst, such as size, distribution and morphology, can be governed by tuning grinding time in MC process. As a result, size and structure of CNFs can be tailored. The effect of grinding time to the as-grown CNFs was studied. CNFs with diameter from 10-70 nm were synthesized. CNFs with bundle formation sharing one tip and twisted CNFs were also synthesized with catalyst treated by MC process.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.2
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• pp.57-63
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• 2016

We developed a flexible and micro-thick electromagnetic interference (EMI) shielding nanofabric layer that also functions as a water resisting and heat sinking material. Electrospinning followed by a simple heat treatment process was carried on to produce the EMI-shielding Ni/C hybrid nanofibers. The ambient oxygen partial pressure ($pO_2$ = 0.1, 0.7, 1.3 Torr) applied during the heat treatment was varied in order to optimize the effectiveness of EMI-shielding by modifying the size and crystallinity of the magnetic Ni nanoparticles distributed throughout the C nanofibers. Permittivity and permeability of the nanofibers under the electromagnetic (EM) wave frequency range of 300 MHz~1 GHz were measured, which implied the EMI-shielding effectiveness (SE) optimization at $pO_2$ = 0.7 Torr during the heat treatment. The materials' heat diffusivity for both in-plane direction and vertical direction was measured to confirm the anisotropic thermal diffusivity that can effectively deliver and sink the local heat produced during device operations. Also, the nanofibers were aged at room temperature in oxygen ambient for water resisting function.

• Journal of the Korean Electrochemical Society
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• v.24 no.1
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• pp.1-6
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• 2021

In this study, new morphology of NCA cathode material for lithium ion batteries was obtained through the electrospinning method. The prepared NCA nanofibers formed a nano-bush structure, and the primary particles were formed on the surface of the nanofibers. The embossing primary particles increased the surface area thus increasing the reactivity of lithium ions. The nano-bush structure could shorten the Li+ diffusion path and improve the Li+ diffusion coefficient. Scanning electron microscopy (SEM) revealed that the synthesized material consisted of nanofibers. The surface area of the nanofibers increased by primary particles was measured using atomic force microscopy (AFM). X-ray diffraction (XRD) analysis was carried out to determine the structure of the NCA nanofibers.

• Proceedings of the Korean Ceranic Society Conference
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• 2003.04a
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• pp.93.2-93
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• 2003

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.30 no.6
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• pp.226-231
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• 2020

Polyvinyl pyrrolidone nanofibers including nickel, zinc, and iron precursors were fabricated via the electrospinning method. To convert as-spun nanofibers to Ni0.5Zn0.5Fe2O4 oxide nanof ibers which is capable of shielding an electromagnetic wave, heat treatment conditions were optimized. To obtain the heat treatment condition that can exclude amorphous carbon black and secondary crystal phase, samples were taken at each temperature while the calcination process and analyzed. According to the X-ray diffraction (XRD) analysis, the Ni0.5Zn0.5Fe2O4 crystal phase started to appear from 300℃, but it was confirmed through energy dispersive spectroscopy (EDS) analysis that heat treatment of 500℃ or more was required to remove most of the carbon black. When the calcination temperature exceeds 650℃, crystal nuclei starts to grow and the fiber surface condition becomes rough, so it was confirmed that the heat treatment conditions should be selectively determined according to the application field.

• 한국전기화학회:학술대회논문집
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• 2003.07a
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• pp.193-197
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• 2003

Mixture of $Ni(OH)_2-Mg(OH)_2$ used as the precurs was treated by mechnochemical(MC) and hand grinding process. Carbon nanofibers(CNF) were prepared using CVD process with the above prepared catalyst. CNFs with a uniform diameter were obtained with MC process treated catalyst, and the diameter could be controlled by tuning the grinding time. CNF bundles with close coalescence were produced with MC treated catalyst. After purification of CNFs and loading with Pt, they were used in fuel cell as the cathode catalyst support. The performance with carbon nanofibers prepared using ground mixture was found to be better than that prepared using unground mixture, which is attributed to the homogeneous CNFs with small diameter and specific interaction between Pt and CNFs.