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1.
Surface mechanical and tribological properties of a copolymer based on benzoyl-1,4-phenylene and 1,3-phenylene were evaluated using nanoprobe investigation techniques and compared to the properties obtained at the macroscale. These copolymers are commonly referred to as self-reinforced polymers (SRPs) because of their intrinsic high strength and modulus without addition of a reinforcing agent. Specimens were prepared by spin casting, solvent casting, and compression molding. Surface mechanical properties and film thickness were measured by nanoindentation and scratching techniques. Friction properties were found using lateral force microscopy (LFM), and surface topography was imaged by tapping mode atomic force microscopy (AFM). Macroscale friction testing revealed a kinetic coefficient of friction of 0.08 for SRP, approaching that of Teflon. Similarly low relative friction coefficients were obtained in nanoprobe measurements. Nanoindentation of SRP, polycarbonate (PC), and polyetherimide (PEI) demonstrated superior surface hardness and modulus of SRP copolymer thin films. 相似文献
2.
Keiji Hayashi Tomoki Shiraishi Kazuho Toyoda Fumiya Tanaka Taiga Mori Takumi Hata 《Computer Physics Communications》2011,(9):2032-2035
Laws of dynamic nano-friction (i.e., continuous wearless friction) were searched for under steady spatial distributions of the local quasi-temperature, by molecular dynamics (MD) simulations. The temperature control of the non-conservative model was carried out by extending the isothermal MD method using the Nosé–Poincaré thermostat. The results suggested that the threshold phenomenon characterizes sliding-velocity dependence of the nano-frictional force between crystal lattices constituting a nano-electromechanical system (NEMS). This phenomenon was turned out to be a universal feature, whether heat transfer to the environment exists or not. 相似文献
3.
This article investigates the tribological behavior of nanoparticles (NPs) of titanium dioxide anatase TiO2 (A), graphene, and TiO2 (A) + graphene added to the pure base oil group ΙΙ (PBO-GΙΙ). The morphology of these two nanostructures of TiO2 (A) and graphene was characterized by transmission electron microscopy (TEM). Oleic acid (OA) was blended as a surfactant into the formulation to help stabilize the NPs in the lubricant oil. A four-ball test rig was used to determine the tribological performance of six different samples, and an image acquisition system was used to examine and measure the wear scar diameter of the stationary balls. Field emission–scanning electron microscopy (FE-SEM) was used to examine the wear morphology. Energy-dispersive X-ray spectroscopy (EDX), element mapping, and Raman spectroscopy were employed to confirm the presence of (TiO2 (A) + graphene) and the formation of a tribolayer/film on the mating surfaces. Moreover, a 3D optical surface texture analyzer was utilized to investigate the scar topography and tribological performance. The experiments proved that adding (0.4?wt% TiO2 (A) + 0.2?wt% graphene) to the PBO-GΙΙ optimized its tribological behavior. These excellent results can be attributed to the dual additive effect and the formation of a tribofilm of NPs during sliding motion. Furthermore, the average reductions in the coefficient of friction (COF), wear scar diameter (WSD), and specific wear rate (SWR) were 38.83, 36.78, and 15.78%, respectively, for (0.4?wt% TiO2 (A) + 0.2?wt% graphene) nanolubricant compared to plain PBO-GΙΙ lubricant. 相似文献
4.
5.
Jen-Fin Lin Te-Hua Fang Cheng-Da Wu Ko-Han Houng 《Computational Materials Science》2007,40(4):480-484
The microcontact behavior of a copper asperity on a diamond plate was carried out using a molecular dynamics (MD) simulation with the parallel algorithms atom decomposition method. The results show that the dynamic frictional force had an oscillated behavior when the flat diamond plane slipped through the copper asperity. The contact load, contact area, dynamic frictional force, and dynamic frictional coefficient increased as the contact interference increased at a constant loading velocity. The dynamic frictional force and dynamic frictional coefficient increased as the sliding velocity increased. Furthermore, the microcontact behavior can be evaluated between a rigid smooth flat plane and a rigid smooth hemisphere to a deformable rough flat plane by combining the deformed behavior of the asperity obtained from MD results and the fractal and statistic parameters. 相似文献
6.
Atomic stick–slip friction has been predicted by molecular dynamics simulation and observed in experiments. However, direct
quantitative comparison of the two has thus far not been possible because of the large difference between scanning velocities
accessible to simulations and experiments. In general, the slowest sliding speeds in MD simulations are at least five orders
of magnitude larger than the upper limit available to experimentalists. To take a step toward bridging this gap, we have applied
parallel replica dynamics, an accelerated molecular dynamics method, to the simulation of atomic stick–slip. The method allows
molecular simulations to run parallel in time in order to extend their duration, thereby enabling lower scanning velocities.
We show here that this method is able to predict atomic stick–slip friction accurately and efficiently at scanning speeds
several orders of magnitude slower than standard molecular dynamics simulations. The accuracy and usefulness of this method
is illustrated by correct prediction of the logarithmic dependence of friction on velocity. 相似文献
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8.
Raman spectroscopy has been used to study the confinement of octamethylcyclotetrasiloxane (OMCTS) and n-hexadecane between a prism and a lens at contact pressures of 40 MPa. Both lens and prism surfaces were optically smooth
but not atomically flat. A total internal reflection geometry was employed to provide the sensitivity needed to detect liquid
films of sub-nanometre thickness. For both liquids, the thickness of the residual film under load corresponded to less than
a monolayer of liquid. The Raman spectra of the confined liquids were identical or very similar to that of the bulk liquid.
Similar results were obtained for hexadecane confined between two surfaces coated with a Langmuir-Blodgett monolayer of a
fatty acid. We infer that the liquids do not form a boundary layer under these conditions but rather they are squeezed out
of the contact under the modest pressure applied. We ascribe the residual signal to liquid trapped in scratches or other defects
on the surfaces. 相似文献
9.
Yue-Rong Li Gavin Pereira Andreas Lachenwitzer Masoud Kasrai Peter R. Norton 《Tribology Letters》2007,27(3):245-253
X-ray absorption near-edge structure (XANES) spectroscopy has been used to characterize the chemistry of antiwear (AW) films
generated from mineral base oil containing a zinc dialkyl dithiophosphate additive. These films were formed on rubbed steel
surfaces with a reciprocating boundary contact using different sliding frequencies. The phosphorus L-edge XANES spectra show
that these films have slightly different chemical natures. Longer chain polyphosphates were present on the steel surface prepared
at the higher sliding frequencies. The surface morphology of these films was investigated using atomic force microscopy. These
images show that the surface morphology of the AW films changes with the sliding frequency. Round and bigger antiwear pads
were formed at a lower frequency while higher frequencies resulted in thinner films and flattened surfaces. Nanomechanical
properties of these antiwear films were investigated by nanoindentation measurement and the elastic moduli extracted from
force–displacement (f–d) curves are similar for all antiwear films, 100 ± 10 GPa. 相似文献
10.
A nanoscale study of the abrasive wear behaviour of a ductile monophasic metallic alloy (the stainless steel AISI 316L) is presented. By using atomic force microscopy (AFM) based techniques, particularly a diamond tip mounted on a stiff steel cantilever, the contact of a single abrasive asperity was simulated, and it was possible to determine accurately the load threshold below which no measurable wear occurs. It was observed that, once this nanoscale threshold for wear is overcome, the worn volume increases linearly with the load, as predicted by the Rabinowicz model. However, it was found that, although this critical threshold for measurable wear is most certainly related with the yield-onset of plastic deformation, it cannot be predicted by using directly a criterion based on the bulk microhardness. Hence, the results presented in this paper strongly indicate that indentation size effects play a crucial role on the response to abrasive wear at the asperity contact level. 相似文献