论文2013阅读次数 [1226] 发布时间 :2015-04-01 17:23:04
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8. Magnetic behavior of graphene sheets embedded carbon film originated from graphene nanocrystallite
Applied Physics Letters 102, 052402 (2013) (PDF-File)
Chao Wang and Dongfeng Diao
We found paramagnetic behavior at 300K of graphene sheets embedded carbon (GSEC) film, which is deposited under lowenergy electron irradiation in electron cyclotron resonance plasma. The origin of the magnetic properties of GSEC film is ascribed to the formation of graphene nanocrystallite. With higher irradiation energy, the size of nanocrystallite barely changed, while the density in GSEC film became higher, leading to a dramatically increase of saturation magnetization and residual magnetism. This finding indicates that GSEC film with higher magnetization can be expected, which has the potential for magnetic and spintronics applications.
7. Dangling bond induced cross-linking model in nanoscratched graphene layers
Surface &Coatings Technology 237，230（2013） (PDF-File)
Qi Zhang, Dongfeng Diao*, and Lei Yang.
Dangling bond induced cross-linking in an interlayer graphene during nanoscratch is simulated bymolecular dynamics method.The normal stress over 74 GPa leads to a broken hexagonal ring of the intralayer graphene, producing unstable dangling bonds which easily make up sp2 or sp3 between neighbor layers. The cross-linking density increaseswith increasing scratching depth, causing higher scratch hardness. The maximumscratch hardness is 90 GPa. The cross-linking is reversible after scratch when the normal stress is less than 90 GPa, beyond which the atoms from different graphene layers will be mixed together forming amorphous structure, making the scratch hardness decrease sharply. These results provide insights into the structural andmechanical properties of graphene based materials.
6. Coating NiTi archwires with diamond-like carbon films: reducing fluoride-induced corrosion and improving frictional properties
J Mater Sci: Mater Med 24, 2287 (2013) (PDF-File)
S.Y. Huang, J.J. Huang, T. Kang, Dongfeng Diao*, and Y.Z. Duan
This study aims to coat diamond-like carbon (DLC) films onto nickel–titanium (NiTi) orthodontic archwires. The film protects against fluoride-induced corrosion and will improve orthodontic friction. ‘Mirror-confinement-type electron cyclotron resonance plasma sputtering’ was utilized to deposit DLC films onto NiTi archwires. The influence of a fluoride-containing environment on the surface topography and the friction force between the brackets and archwires were investigated. The results confirmed the superior nature of the DLC coating, with less surface roughness variation for DLC-coated archwires after immersion in a high fluoride ion environment. Friction tests also showed that applying a DLC coating significantly decreased the fretting wear and the coefficient of friction, both in ambient air and artificial saliva. Thus, DLC coatings are recommended to reduce fluoride-induced corrosion and improve orthodontic friction.
5. Nanoindentation Behavior of Amorphous Carbon Films Containing Nanocrystalline Graphite and Diamond clusters Prepared by Radio Frequency Sputtering
Applied Surface Science 273, 816-823 (2013) (PDF-File)
Xue Fan, Dongfeng Diao*, Kenji Nose and T. Yoshida
Amorphous carbon (a-C) films were prepared by a radio-frequency sputtering method. Nano structures in the films were
controlled by changing the ion irradiation energy and deposition temperature. It was found that nanocrystalline graphite and diamond clusters were embedded in the pure amorphous structure with sizes of approximately 5 nm. a-C films contained nanocrystalline graphite clusters (a-C:NCG) were obtained with the ion energy ranging from 50 to 120 eV and temperature in 300–370 K. a-C film contained nanocrystalline diamond clusters (a-C:NCD) was obtained with 120 eV at 570 K. Nanoindentation behaviors of these carbon films were compared with pure amorphous structured carbon film. The percentage of elastic recoveries of a-C:NCD, a-C, and a-C:NCG films were obtained to be 81.9%, 84.3%, and 87.5%, respectively. Pop-in steps with about 3 nm displacement appeared in loading curves for a-C:NCG film, and 10 nm for a-C:NCD film. These results showed that the nanoindentation behaviors of amorphous carbon film containing cross-linked nanocrystalline graphite clusters is better than that of diamond clusters.
4. Tribological Thermostability of Carbon Film with Vertically Aligned Grapheen Sheets
Tribology Letters 50, 305–311 (2013) (PDF-File)
Cheng Chen and Dongfeng Diao*
Tribological thermostability of carbon film with vertically aligned graphene sheets was studied with vertically aligned graphene
sheets was studied with annealing temperatures up to 1,750 C. The carbon film was deposited on silicon carbide substrate by electron cyclotron resonance plasma sputtering. Tribological thermostabilities of the carbon film in terms of friction coefficient, wear life, and nanoscratch depth were investigated by Pin-on-Disk tribometer and atomic force microscopy. The evolution of nanostructure of vertically aligned graphene sheets in the carbon film as a function of annealing temperature was examined by Raman spectroscopy and transmission electron microscopy. The results showed that the friction coefficient, wear life, and nanoscratch depth of the carbon film were thermally stable up to 1,250 C. When the annealing temperature was 1,500 C, the friction coefficient and the nanoscratch depth increased, the wear life decreased, but still all were of considerable values. These variations were attributed to the initiation of tubular-like structure originated from graphene sheets stacks. After annealing at 1,750 C, tribological performances degraded catastrophically due to the abundant formation of tubular-like structures and the appearance of a graphitic interlayer between the film and the substrate.
3. Potential of grapheme layer controlling nano-wear during C60 intrusion by molecular dynamics simulation
Wear 306, 248–253 (2013) (PDF-File)
Qi Zhang and Dongfeng Diao*
The intrusion process of a C60 (the smallest ball in nature) into a sliding contact space was simulated using the Molecular
Dynamics approach. The contact space consisted of upper and lower Si substrates layered by graphene with an included angle changing from 20o to 90o, andC60 just contacted with both the upper and lower substrates. A constant horizontal speed 3nm/ps was applied to the lower substrate, and the process of C60 breaking through the contact space was observed. During this process, the nano-wear of the substrate was evaluated by the number of dropped atoms from the substrates. The results showed the number of dropped atoms from the upper Si substrate was dependent on the initial included angle and the graphene layered positions. The potential that graphene can control nano-wear and realize no-wear of the surface was revealed, also the potential that graphene can control C60 intrusion into the sliding contact space was found.
2. Evolution of Maximum Contact Stresses in Amorphous Carbon Coated Silicon During Sliding Wear Against Si3N4Ball
ASME,Trans., Journal of Tribology 135, 021401-10 (2013) (PDF-File)
Tianxiao Cai, Pengyu Zhang and Dongfeng Diao*
The evolution of the maximum contact stresses in amorphous carbon coated silicon during sliding wear against a Si3N4 ball
was investigated. Amorphous carbon coating was prepared on a silicon substrate by the electron cyclotron resonance (ECR) plasma sputtering method. Surface morphologies of the coating and counterpart were measured by an atomic force microscope (AFM). The friction and wear behavior of the coating was studied by a ball-on-disk tribometer. The cross-sections of the wear tracks at different wear stages were observed with a scanning electron microscope (SEM). Maximum contact stresses with different coating thicknesses were calculated by the three-dimensional semi-analytical method (SAM). The results demonstrated that when taking surface asperities into consideration, maximum shear stress at the bonding interface and adjacent substrate showed a dramatic increase during wear and should be responsible for the initiation and propagation of the cracks observed at the final stage of sliding.
1. Frictional behavior of nanostructured carbon films
Friction 1, 63-71(2013) (PDF-File)
Dongfeng Diao*, Chao Wang, Xue Fan
We propose a new path for preparing nanostructured carbon films (NCFs) by
using electron cyclotron resonance
(ECR) plasma sputtering with ion–electron
hybrid irradiation for controlling the frictional behavior. The frictional behavior
of the NCF was measured by using a pin-on-disk tribometer with a nanoprobe displacement
sensor, and the transition curves of the friction coefficient and
microdisplacement of the NCFs were examined. The friction mechanism was
discussed by transmission electron microscopy (TEM) observation on the wear
track. From the results, we found a new method to prepare NCFs, which has the
potential to achieve low friction at the early stage of sliding contact. In
addition, the technology of ECR plasma with ion–electron hybrid irradiation
provides a new vision to rebuild a nanostructured surface from an original
surface for controlling the frictional behavior.
