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Diamond and related materials 25건

  1. [해외논문]   Editorial Board   SCI SCIE


    Diamond and related materials v.81 ,pp. ii - ii , 2018 , 0925-9635 ,

    초록

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  2. [해외논문]   Fabrication of CdS quantum dot sensitized solar cells using nitrogen functionalized CNTs/TiO2 nanocomposites   SCI SCIE

    Zolfaghari-Isavandi, Zahra (Corresponding author.) , Shariatinia, Zahra
    Diamond and related materials v.81 ,pp. 1 - 15 , 2018 , 0925-9635 ,

    초록

    Abstract Effect of using nitrogen functionalized carbon nanotubes in photoanode materials of quantum dot sensitized solar cells (QDSSCs) was studied. Several SWCNT/TiO 2 , MWCNT/TiO 2 and N-doped MWCNT/TiO 2 nanocomposites were prepared including different weight percents (0.25–0.40wt%) of CNTs to TiO 2 . The nanocomposites were applied as the photoanodes of QDSSCs. All photoanodes were fabricated by CdS and ZnS doping using successive ionic layer adsorption and reaction (SILAR) method. The measured optical band gaps of all photoanodes were approximately equal to 2.5eV. The photoluminescence (PL) spectra of all photoanode nanocomposites illustrated four maxima at around 310, 365, 440 and 535nm plus two shoulders near 285 and 720nm which could be assigned to the emission bands of TiO 2 , CdS and ZnS nanoparticles (NPs) as well as CNTs. The highest power conversion efficiency (η) was measured under one illumination of sun (AM 1.5, 100mW/cm 2 ) for the 0.35% N-MWCNT loaded cell (1.78%) indicating 24.47% increase in the η value relative to that of the cell made up of bare TiO 2 (1.43%). The IPCE of 0.35% N-MWCNT was the greatest (~54% near 450nm) among other cells containing 0.35% of SWCNT and MWCNT indicating it can convert the most incident light into electrical energy due to the most loading of CdS quantum dots on the N-MWCNT. The electrochemical impedance spectroscopy (EIS) evidenced that the R s of the photoanode including 0.35%N-MWCNT (23.78Ω) was smaller than that of the blank photoanode (32.28Ω) and this was due to the increased charge transfer in the nanocomposite photoanode. Besides, a greater recombination resistance (R 2 ) was measured for the 0.35% N-MWCNT photoanode (494.2Ω) compared with that of the bare TiO 2 photoelectrode (206.8Ω). Highlights Several CNT/TiO 2 nanocomposites were applied as photoanodes of CdS QDSSCs. Composites were characterized by XRD, FE-SEM, EDS, ATR, UV–Vis, PL and Raman. The highest efficiency was measured for the cell made using 0.35% N-MWCNT. The optimized cell showed η=1.78%, V OC =0 0.545V, FF=0.48 and J SC =6 6.80mA.cm −2 . The highest IPCE (~54%) was measured for the cell fabricated by 0.35% N-MWCNT. Graphical abstract [DISPLAY OMISSION]

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  3. [해외논문]   Chemical structure and electrical characteristics of diamondlike carbon films   SCI SCIE

    Takabayashi, Susumu (Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan ) , Hayashi, Hiroyuki (Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan ) , Yang, Meng (Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan ) , Sugimoto, Rintaro (Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan ) , Ogawa, Shuichi (Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan ) , Takakuwa, Yuji (Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan)
    Diamond and related materials v.81 ,pp. 16 - 26 , 2018 , 0925-9635 ,

    초록

    Abstract The relationship between the chemical structure and electrical characteristics of diamondlike carbon (DLC) films has been clarified. The DLC films were formed in atmospheres with different ratios of methane to argon under the photoemission-assisted Townsend discharge. The dependence of the dielectric constant of the films on methane concentration in the synthesis was arch-like with a maximum. The breakdown strength was constant irrespective of the synthesis atmosphere and was approximately the same for both electrical polarizations. Raman spectra of the films were deconvoluted into five active bands. Raman analysis in conjunction with the sp 2 cluster model elucidated the DLC structure. The sp 2 cluster model comprises sp 2 clusters floating in a dielectric matrix sea. The sp 2 clusters were rather aliphatic for films formed in low methane concentration. The clusters grew to become aromatic with increasing methane concentration. Defects or dangling bonds increased similarly, but they were terminated with hydrogen for films formed in high methane concentration. The hydrogen-terminated bonds occupied large amounts of space in the DLC films, causing internal strain. The dielectric constant of the whole DLC film was determined by the size of sp 2 clusters, dielectric constant of the matrix sea material, and space volume induced by the hydrogen–carbon bonds. The breakdown strength was determined by the balance between the size of sp 2 clusters and density of dangling bonds in the matrix sea. However, because the dependences of these factors on methane concentration were opposing, the breakdown strength was approximately constant irrespective of methane concentration. Highlights Raman spectra of diamondlike carbon (DLC) films were analyzed with five bands. The sp 2 cluster model with the Raman analysis clarified the DLC structure. Electrical characteristics of the films can be elucidated by the sp 2 cluster model. Graphical abstract [DISPLAY OMISSION]

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  4. [해외논문]   Atmospheric-pressure chemical purification of detonation-synthesized nanodiamond by using perchloric acid: Intensive parametric study to control sp3/sp2carbon ratio   SCI SCIE

    Hong, Seung Pyo (Plasma Technology Research Center, National Fusion Research Institute, 37 Dongjangsan-ro, Gunsan-si, Jeollabuk-do 54004, Republic of Korea ) , Ha, Sang Wook (Plasma Technology Research Center, National Fusion Research Institute, 37 Dongjangsan-ro, Gunsan-si, Jeollabuk-do 54004, Republic of Korea ) , Lee, Seung Whan (Plasma Technology Research Center, National Fusion Research Institute, 37 Dongjangsan-ro, Gunsan-si, Jeollabuk-do 54004, Republic of Korea)
    Diamond and related materials v.81 ,pp. 27 - 32 , 2018 , 0925-9635 ,

    초록

    Abstract Controlled- and high-sp 3 /sp 2 carbon ratio of the detonation-synthesized nanodiamond (DND) may play a very important role in many applications. Here, we demonstrated an atmospheric-pressure process of chemical purification using perchloric acid (HClO 4 ) and intensively studied the control parameters including the reaction temperature, DND loading amount, and processing time. The sp 3 /sp 2 carbon ratio was characterized using UV-Raman spectroscopy (325nm) and is evaluated based on the intensity ratio ( I Dia / I G ) of the diamond peak and G band peak at 1325cm −1 and 1590cm −1 , respectively. Through the combination of control parameters, we successfully controlled the intensity ratio of I Dia / I G at the range from 0.28 to 1.5 and achieved 15.5% higher than compared with commercial DND. In addition, we also investigated the electrical conductivity of DND vs. intensity ratio of I Dia / I G and the results show that lower intensity ratio of I Dia / I G have higher electrical conductivity because of non-diamond carbon. Highlights Chemical purification of detonation-synthesized nanodiamond by using perchloric acid (HClO 4 ) The intensive parametric study to control sp 3 /sp 2 carbon ratio of detonation-synthesized nanodiamond The controlled- and high- sp 2 /sp 3 carbon ratio by chemical purification The controlled electrical conductivity based on sp 2 /sp 3 carbon ratio Graphical abstract [DISPLAY OMISSION]

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  5. [해외논문]   Growth and characterization of freestanding p+diamond (100) substrates prepared by hot-filament chemical vapor deposition   SCI SCIE

    Ohmagari, Shinya (Corresponding author.) , Yamada, Hideaki , Umezawa, Hitoshi , Tsubouchi, Nobuteru , Chayahara, Akiyoshi , Mokuno, Yoshiaki
    Diamond and related materials v.81 ,pp. 33 - 37 , 2018 , 0925-9635 ,

    초록

    Abstract Heavily B-doped p+diamond (100) thick films were grown by hot-filament chemical vapor deposition (HFCVD). Low resistivity ( 100μm). Freestanding crack-free films were prepared by removing the seed substrates via laser-cut and mechanical polishing processes. The X-ray diffraction rocking curve (004) spectrum showed the full-width at half maximum value of 25arcsec, equivalent to that of the seed substrates employed. Vertical Schottky barrier diodes showed clear rectifying actions with low leakage current level. Highlights Heavily boron-doped (p+) thick diamond films were prepared by hot-filament CVD Resistivity of 3mΩcm was demonstrated under high-rate growth (1–4μm/h) conditions XRD rocking curve (004) of freestanding p+substrates revealed good crystallinity Vertical Schottky diodes showed clear rectifying action with low leakage current Graphical abstract [DISPLAY OMISSION]

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  6. [해외논문]   Theoretical modelling for interface design and thermal conductivity prediction in diamond/Cu composites   SCI SCIE

    Yuan, Mengying (Corresponding authors. ) , Tan, Zhanqiu (Corresponding authors.) , Fan, Genlian , Xiong, Ding-Bang , Guo, Qiang , Guo, Cuiping , Li, Zhiqiang , Zhang, Di
    Diamond and related materials v.81 ,pp. 38 - 44 , 2018 , 0925-9635 ,

    초록

    Abstract Interface design is essential for diamond/Cu (Dia/Cu) composites to achieve high thermal conductivity (TC), due to the incompatibility between diamond particles and Cu matrix. In this work, a physical model was developed to theoretically reveal the effects of different interface layers on the TC of Dia/Cu composites. The results indicate that the thickness, intrinsic TC, phonon velocity and carbide transformation of interface layers and their solubility in Cu matrix greatly affect the thermal performance of the composites. Interface layers with nanoscale thickness (e.g. smaller than 200nm) are desirable to improve the TC of Dia/Cu. The carbide transformation affects the TC differently via varying the phonon mismatch between Dia/Cu and thermal resistance of interface layers. W-WC layer is the most favorable candidate to achieve high thermal performance, which agrees well with experimental results. This study supplies an overall but specific consideration for the interface design in Dia/Cu composites for the first time, and offers a fundamental guide for experiments of interface modification, which is also applicable for other matrix composites. Highlights A multi-layered interface physical model was developed to predict thermal conductivity. Effects of various interface layers on thermal conductivity of diamond/Cu composites were revealed. Conductivity is affected by layers’ thickness, conductivity, phonon velocity, carbide formation and solubility in Cu. Carbide transformation influences thermal conductivity via varying phonon mismatch and thermal resistance. Graphical abstract [DISPLAY OMISSION]

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  7. [해외논문]   Chameleon diamonds: Thermal processes governing luminescence and a model for the color change   SCI SCIE

    Byrne, Keal S. (Department of Mineral Sciences, Smithsonian Institution, Washington DC 20560, USA ) , Butler, James E. (Department of Mineral Sciences, Smithsonian Institution, Washington DC 20560, USA ) , Wang, Wuyi (Gemological Institute of America (GIA), New York, NY 10036, USA ) , Post, Jeffrey E. (Department of Mineral Sciences, Smithsonian Institution, Washington DC 20560, USA)
    Diamond and related materials v.81 ,pp. 45 - 53 , 2018 , 0925-9635 ,

    초록

    Abstract To date, the eponymous color-changing behavior of chameleon diamonds lacks an explanation in terms of an identified diamond defect structure or process. Well known, however, is that this color-change is driven by the influence of both light and heat. In this paper, we present observations of how luminescence emission in chameleon diamonds responds to temperature changes and optical pumping. Fluorescence, phosphorescence, and thermoluminescence experiments on a suite of natural chameleon diamonds reveal that a specific emission band, peaking near 550nm, may be stimulated by several different mechanisms. We have observed thermal quenching of the 550nm emission band with an activation energy of 0.135eV. The 550nm band is also observed in phosphorescence and thermoluminescence. Thermoluminescence spectra suggest the presence of low lying acceptor states at 0.7eV above the valence band. When excited with 270nm light, we observe emission of light in two broad spectral bands peaking at 500 and 550nm. We suggest that the 550nm emission band results from donor—acceptor pair recombination (DAPR) from low lying acceptor states at ca. 0.7eV above the valence band and donor states approximately 2.5 to 2.7eV above the valence band. We do not identify the structure of these defects. We propose a speculative model of the physics of the color change from ‘yellow’ to ‘green’ which results from increased broad-band optical absorption in the near-IR to visible due to transitions from the valence band into un-ionized acceptor states available in the ‘green’ state of the chameleon diamond. We report near-IR absorption spectra confirming the increased absorption of light in the near-IR to visible in the ‘green’ when compared to the ‘yellow’ state with a threshold at ca. 0.65eV, supporting the proposed model. Highlights Measured fluorescence and phosphorescence of chameleon diamonds Measured near IR absorption of a chameleon diamond in it ‘green’ and ‘yellow’ states Proposed a model for the physics of the color change in chameleon diamonds Graphical abstract [DISPLAY OMISSION]

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  8. [해외논문]   Preparation and cutting performance of ultra-smooth CVD composite diamond coated ladder-shape drilling tools   SCI SCIE

    Xiang, Daohui (Corresponding author.) , Guo, Zhenhai , Zhang, Lei , Feng, Haoren
    Diamond and related materials v.81 ,pp. 54 - 60 , 2018 , 0925-9635 ,

    초록

    Abstract The preparation of ultra-smooth composite diamond (USCD) coated ladder-shape drilling tools is studied. These are produced by growing microcrystalline diamond (MCD) and nanocrystalline diamond (NCD) layers employing the hot filament chemical vapor deposition (HFCVD) method on WC-Co parts. A double hot-wire arrangement apparatus is adopted, the complex shape tool is placed between upper tantalum wires and lower tantalum wires so that all parts of the tool can be coated with diamond. The drilling experiments are conducted for assessing the cutting performances of the MCD and USCD coated tools using carbon fiber reinforced plastics (CFRP) as the workpiece, the uncoated tool is also used in the drilling experiments for the sake of contrast. The results show that the MCD and USCD coated tools exhibit a better cutting performance than the uncoated one, besides, the USCD coated tool displays the best wear resistant. The workpiece is precisely machined with a smooth and bright surface by the USCD coated tool, and there are no defects such as crackle and burrs in the hole exit, the durability of the USCD coated tool and the processing quality of the workpiece have been greatly improved. Highlights Two types of diamond films (MCD and USCD films) are synthesized on WC-Co ladder-shape tools by HFCVD. Smaller friction coefficient for diamond coating on the WC-Co substrate is obtained by depositing nano-level USCD film. The drilling tests indicate that the USCD film can significantly improve the cutting performance of ladder-shape tools. Graphical abstract [DISPLAY OMISSION]

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  9. [해외논문]   Amorphous carbon nanocomposite films doped by titanium: Surface and sub-surface composition and bonding   SCI SCIE

    Zemek, J. (Institute of Physics of the Czech Academy of Sciences, Na Slovance 2, 182 21 Prague 8, Czech Republic ) , Houdkova, J. (Institute of Physics of the Czech Academy of Sciences, Na Slovance 2, 182 21 Prague 8, Czech Republic ) , Jiricek, P. (Institute of Physics of the Czech Academy of Sciences, Na Slovance 2, 182 21 Prague 8, Czech Republic ) , Jelinek, M. (Institute of Physics of the Czech Academy of Sciences, Na Slovance 2, 182 21 Prague 8, Czech Republic)
    Diamond and related materials v.81 ,pp. 61 - 69 , 2018 , 0925-9635 ,

    초록

    Abstract Hydrogen free Ti-doped amorphous carbon layers were prepared by dual beam pulsed laser deposition using two excimer lasers. The air-exposed surfaces were analyzed by high-energy resolved and angular-resolved core-level photoelectron spectroscopy, and were then step-by-step sputtered with an argon gas cluster ion beam (ArGCIB), which is known to be a very gentle technique with respect to changes in surface chemistry. The results show that the top surface of the sample and its sub-surface region differ in composition and in bonding. The top surface is enriched by oxygen-bearing species. Carbon-bearing species located on the surface are mostly in sp 3 hybridization. Titanium carbide clusters, TiC, are not directly exposed at the surface. They are embedded in a carbon network with dominating C sp 2 hybridization. Their interface is formed by a distinct carbon-rich titanium carbide with stoichiometry close to TiC 3 . The surface damage induced by ArGCIB was found to be minimal, verifiably affecting carbon atoms in the carbon network. Highlights The virgin surface of DLC:Ti films is enriched by C sp 3 , while C sp 2 is dominant in the sub-surface region. TiC clusters are embedded in a carbon network. The interface between TiC clusters and the carbon network is formed by TiC x , x~3. Sputtering DLC:Ti films with ArGCIB caused a structural damage in the carbon network. The results of an in-depth analysis by ArGCIB are in qualitative agreement with the ARXPS analysis. Graphical abstract [DISPLAY OMISSION]

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  10. [해외논문]   Direct growth of carbon nanofiber forest on nickel foam without any external catalyst   SCI SCIE

    Sridhar, Deepak (Corresponding author.) , Omanovic, Sasha , Meunier, Jean-Luc
    Diamond and related materials v.81 ,pp. 70 - 76 , 2018 , 0925-9635 ,

    초록

    Abstract Interest in the direct growth of carbon nanostructures on metal substrates is growing, especially in the field of supercapacitors, fuel cells, batteries and sensors. This paper presents results on the growth of carbon nanofibers (CNF) without the requirement of an external catalyst directly on nickel foam (Ni-foam) at a relatively low temperature of 400°C. Etching of Ni-foam leads to the growth of CNF forests covering entirely the internal surfaces of the Ni-foam, with CNF diameters that can be tuned between 78±32nm and 375±35nm through a change in the growth temperature between 400 and 700°C. Etching was found to be important to obtain a uniform surface CNF coverage and growth, particularly at higher temperatures. These CNF/Ni-foam composites yield 3D nano-scale internal forest structures in good contact with the micro-scale porosity of the metallic foam electrode. This work provides a foundation to use binderless CNF composite electrodes to obtain higher capacitance. Highlights Carbon nano fibers (CNF) are grown directly on nickel foam without using any external catalyst. The process temperature to grow densely covered CNF forest is as low as 400°C. Etching of nickel foam is essential for the dense CNF coverage, especially at the higher growth temperatures. The diameter of the CNF can be tuned by changing the growth temperature. Graphical abstract [DISPLAY OMISSION]

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