Study of A Nanocrystalline Diamond for Composite Diamond Windows in THz TWTs

Author(s):  
Ming Q. Ding ◽  
Lili Li ◽  
Chengyi Hua ◽  
Jun Cai ◽  
Jinjun Feng
2004 ◽  
Vol 471-472 ◽  
pp. 52-58 ◽  
Author(s):  
Fang Hong Sun ◽  
Zhi Ming Zhang ◽  
H.S. Shen ◽  
Ming Chen

Nanocrystalline diamond films were deposited on Co-cemented carbide substrates using CH4/H2/Ar gas mixture by hot filament chemical vapor deposition (HFCVD) technique. The evidence of nanocrystallinity, smoothness and purity was obtained by characterizing the sample with scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM), high-resolution transmission electron microscopy (HR-TEM) and selected-area electron diffraction (SAED). A new process was used to deposit composite diamond films by a two-step chemical vapor deposition procedure including first the deposition of the rough polycrystalline diamond and then the smooth fine-grained nanocrystalline diamond. The results show that the film consists of nanocrystalline diamond grains with sizes range from 20 to 80 nm. The Raman spectroscopy, XRD pattern, HR-TEM image and SAED pattern of the films indicate the presence of nanocrystalline diamond. Surface roughness is measured as Ra<100nm by AFM. Smooth nanocrystalline diamond layers can be deposited on conventional microcrystalline diamond layers using a two-step chemical vapor deposition by regulating the deposition parameters. These composite diamond films with the multiplayer (nanocrystalline/microcrystalline) structure have low surface roughness and high adhesive strength on WC-Co substrates. The diamond-coated tools and drawing dies with these composite coatings display excellent performances in the practical application.


2006 ◽  
Vol 15 (4-8) ◽  
pp. 729-734 ◽  
Author(s):  
R. Ikeda ◽  
H. Tanei ◽  
N. Nakamura ◽  
H. Ogi ◽  
M. Hirao ◽  
...  

Author(s):  
Ying Yan ◽  
Xuelin Lei ◽  
Yun He

The effect of nanoscale surface texture on the frictional and wear performances of nanocrystalline diamond films under water-lubricating conditions were comparatively investigated using a reciprocating ball-on-flat tribometer. Although the untreated nanocrystalline diamond film shows a stable frictional state with an average friction coefficient of 0.26, the subsequent textured films show a beneficial effect on rapidly reducing the friction coefficient, which decreased to a stable value of 0.1. Furthermore, compared with the nanocrystalline diamond coating, the textured films showed a large decreasing rate of the corresponding ball wear rate from 4.16 × 10−3 to 1.15 × 10−3 mm3/N/m. This is due to the fact that the hydrodynamic fluid film composed of water and debris can provide a good lubrication environment, so the entire friction process has reached the state of fluid lubrication. Meanwhile, the surface texture can greatly improve the hydrophilicity of the diamond films, and as the texture density increases, the water contact angle decreases from 94.75° of the nanocrystalline diamond film to 78.5° of the textured films. The proper textured diamond film (NCD90) exhibits superior tribological properties among all tested diamond films, such as short run-in period, low coefficient of friction, and wear rate.


2012 ◽  
Vol 404 (6-7) ◽  
pp. 1643-1651 ◽  
Author(s):  
Karin Fromell ◽  
Pontus Forsberg ◽  
Mikael Karlsson ◽  
Karin Larsson ◽  
Fredrik Nikolajeff ◽  
...  

Author(s):  
Jean-Paul Mazellier ◽  
Cyril Di Giola ◽  
Pierre Legagneux ◽  
Clément Hébert ◽  
Emmanuel Scorsone ◽  
...  

MRS Bulletin ◽  
1998 ◽  
Vol 23 (9) ◽  
pp. 36-41 ◽  
Author(s):  
P. Keblinski ◽  
D. Wolf ◽  
F. Cleri ◽  
S.R. Phillpot ◽  
H. Gleiter

The low-pressure synthesis of rather pure nanocrystalline diamond films from fullerene precursors suggests that for a small enough grain size the diamond structure may be energetically preferred over graphite. Because of the small grain size of typically about 15 nm in these films, a significant fraction of the carbon atoms is situated in the grain boundaries (GBs). The surprisingly high wear resistance of these films even after the substrate is removed and their high corrosion resistance suggest that the grains are strongly bonded. Grain-boundary carbon is also believed to be responsible for the absorption and scattering of light in these films, for their electrical conductivity, and for their electron-emission properties. In spite of all these indications of a critical role played by GB carbon in achieving the remarkable properties of nanocrystalline diamond films, to date the atomic structures of the GBs are essentially not known.It is well-known that the electronic and optical properties of polycrystalline silicon films are significantly affected by the presence of GBs. For example GBs can provide active sites for the recombination of electron-hole pairs in photovoltaic applications. Also, in electronic devices such as thin-film transistors, GBs are known to play an important role. Because of silicon's strong energetic preference for sp3 hybridization over other electronic configurations, the structural disorder in silicon GBs is accommodated by a distortion of the tetrahedral nearestneighbor bonds and in the extreme by the creation of dangling bonds—that is, of three-coordinated Si atoms each having one unsaturated, bound electron in an otherwise more or less tetrahedrally coordinated environment.


2008 ◽  
Vol 205 (9) ◽  
pp. 2146-2153 ◽  
Author(s):  
Milan Kopecek ◽  
Lucie Bacakova ◽  
Jiri Vacik ◽  
Frantisek Fendrych ◽  
Vladimir Vorlicek ◽  
...  

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