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이충훈,김정혁,Edward Joseph D. Castro,황용규 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.1
In this work, few-layer graphene (FLG) was successfully grown on polycrystalline Ni a large scale by using DC plasma enhanced chemical vapor deposition (DC PE-CVD), which may serve as an alternative route in large-scale graphene synthesis. The synthesis time had an effect on the quality of the graphene produced. The applied DC voltage, on the other hand, influenced the minimization of the defect densities in the graphene grown. We also present a method of producing a free-standing polymethyl methacrylate (PMMA)/graphene membrane on a FeCl<SUB>3(aq)</SUB> solution, which could then be transferred to the desired substrate.
Design of a Carbon-Nanotube Yarn Field Emitter for Micro-focus X-ray Generation
Hyun Suk Kim,Edward Joseph D. Castro,Choong Hun Lee 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.69 No.3
The field-emission (F-E) characteristics of multi-walled carbon-nanotube (MWCNT) yarn and its contribution to X-ray generation have been investigated in the current work. A dry spinning method was used to fabricateMWCNT yarn from superMWCNTs that had been fabricated by using microwave plasma-enhanced chemical vapor deposition (MW-PECVD). The F-E behavior of the MWCNT yarn followed the Fowler-Nordheim model. Compared to a MWCNT, the MWCNT yarn displayed a significant F-E capability in both the diode and the triode X-ray generation structures. The low-voltage F-E of the MWCNT yarn can be attributed to the field-enhancing effect of the yarn due to its shape and to the contribution of the high-aspect-ratio nanotubes that protrude from the sides of the yarn. The effect of filters on the development of X-ray images has also been demonstrated. The amount of exposure of the samples to X-rays was also manipulated. Results of this study indicate that the MWCNT yarn may be a good candidate for use in low-voltage F-E applications for X-ray imaging.
Optimum design for the carbon nanotube based micro-focus X-ray tube
Kim, Hyun Suk,Castro, Edward Joseph D.,Lee, Choong Hun Elsevier 2015 Vacuum Vol.111 No.-
<P><B>Abstract</B></P> <P>The current work reports the optimum design conditions of a direct current plasma enhanced chemical vapor deposition grown multi-walled carbon nanotube based micro-focus X-ray tube with dual focusing lens. Extensive simulations were performed in order to determine the configuration that would generate a desirable focal spot size. Several dimensions of the X-ray basic structure and the focusing lens were manipulated using a commercially available simulation package. A manipulation of the factors (i.e. geometric parameter, axial distances, and bias voltages variances) and their effects on the focal spot size were also analyzed. A remarkable reduction in the focal spot size was achieved at the anode target via simulation and high resolution images were obtained in a prototype X-ray generator through standard line pattern test.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A CNT-based micro-focus X-ray tube with dual focusing lens. </LI> <LI> A manipulation of the factors and its effect on the focal spot size analysis. </LI> <LI> A similar result via simulation and experimental for focal spot size. </LI> <LI> A high resolution image using a standard line pattern test. </LI> </UL> </P>