Nanotribological Properties of Organic Boundary Lubricants: Langmuir Films Versus Self-Assembled Monolayers

1998 ◽  
Vol 120 (3) ◽  
pp. 489-495 ◽  
Author(s):  
Valery N. Bliznyuk ◽  
Mark P. Everson ◽  
Vladimir V. Tsukruk
Keyword(s):  
Friction Coefficient ◽  
Packing Density ◽  
Mechanical Stability ◽  
Normal Load ◽  
Langmuir Monolayers ◽  
Promising Alternative ◽  
Frictional Behavior ◽  
Self Assembling ◽  
Assembled Monolayers ◽  
Boundary Lubricants

Frictional characteristics of several types of boundary lubricants were tested using scanning probe microscopy (SPM). These include Langmuir monolayers of stearic acids (STA), their cadmium salts (STCd), self-assembling monolayers (SAMs) of alkylchlorsilanes, and complexes of STA with rigid naphthoylene benzimidazole (x-NBI) fragments. We observed that a Langmuir monolayer deposited on a silicon surface had a very low friction coefficient against a silicon nitride tip (about 0.01–0.05) but also low mechanical stability. SAMs were found to be much more stable but had the drawback of growth in the friction coefficient at high sliding velocities. Composite NBI/STA monolayers were much more stable and were not damaged by the highest normal load applied. The frictional behavior of different monolayers was analyzed in relation to their structural organization (the type of tethering to the surface and packing density). We introduced a figure of merit (FOM) parameter which allowed comparison of frictional properties of very different lubricant materials to those of the supporting substrate. For Langmuir monolayers the FOM increased strongly with surface packing density whereas for SAMs and x-NBI/STA complexes it possessed a maximum at surface densities in the range 3.5–4.5 molecules per nm2. Because of the possibility of tailoring the surface packing density of aliphatic tails in the complexes, they are a promising alternative to both LB films and SAMs. For such composite monolayers, the surface packing density can be optimized to give a desired frictional behavior.

scholarly journals Current Update of Collagen Nanomaterials—Fabrication, Characterisation and Its Applications: A Review

Pharmaceutics ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 316
Author(s):  
Samantha Lo ◽  
Mh Busra Fauzi
Keyword(s):  
Mechanical Stability ◽  
Health Management ◽  
Three Dimensional ◽  
Volume Ratio ◽  
Cartilage Regeneration ◽  
Nerve Tissue ◽  
Electrospinning Technique ◽  
Engineering Technology ◽  
Promising Alternative ◽  
Tissue Repair And Regeneration

Tissue engineering technology is a promising alternative approach for improvement in health management. Biomaterials play a major role, acting as a provisional bioscaffold for tissue repair and regeneration. Collagen a widely studied natural component largely present in the extracellular matrix (ECM) of the human body. It provides mechanical stability with suitable elasticity and strength to various tissues, including skin, bone, tendon, cornea and others. Even though exogenous collagen is commonly used in bioscaffolds, largely in the medical and pharmaceutical fields, nano collagen is a relatively new material involved in nanotechnology with a plethora of unexplored potential. Nano collagen is a form of collagen reduced to a nanoparticulate size, which has its advantages over the common three-dimensional (3D) collagen design, primarily due to its nano-size contributing to a higher surface area-to-volume ratio, aiding in withstanding large loads with minimal tension. It can be produced through different approaches including the electrospinning technique to produce nano collagen fibres resembling natural ECM. Nano collagen can be applied in various medical fields involving bioscaffold insertion or fillers for wound healing improvement; skin, bone, vascular grafting, nerve tissue and articular cartilage regeneration as well as aiding in drug delivery and incorporation for cosmetic purposes.

Three-Dimensional Hexagonal Close-Packed Superlattices of Passivated Ag Nanocrystals

1997 ◽  
Vol 3 (S2) ◽  
pp. 431-432
Author(s):  
S. A. Harfenist ◽  
Z. L. Wang ◽  
R. L. Whetten ◽  
I. Vezmar ◽  
M. M. Alvarez ◽  
...  
Keyword(s):  
Carbon Film ◽  
Three Dimensional ◽  
Structure Characterization ◽  
Self Assembled Monolayers ◽  
Hexagonal Close Packed ◽  
Self Assembling ◽  
Transmission Electron ◽  
Assembled Monolayers ◽  
High Resolution Tem ◽  
Nanocrystal Superlattices

Silver nanocrystals passivated by dodecanethiol self-assembled monolayers were produced using an aerosol technique described in detail elsewhere [1]. Self-assembling passivated nanocrystal-superlattices (NCS's) involve self-organization into monolayers, thin films, and superlattices of size-selected nanoclusters encapsulated in a protective compact coating [2,3,4,5,6,7]. We report the preparation and structure characterization of three-dimensional (3-D) hexagonal close-packed Ag nanocrystal supercrystals from Ag nanocrystals of ˜4.5 nm in diameters. The crystallography of the superlattice and atomic core lattices were determined using transmission electron microscopy (TEM) and high-resolution TEM.SEM was used to image the nanocrystal superlattices formed on an amorphous carbon film of an TEM specimen grid (fig. la). The superlattice films show well shaped, sharply faceted, triangular shaped sheets. Figure lb depicts numerous Ag nanocrystal aggregates uniformly distributed over the imaging region. Inset in this figure is an enlargement of the boxed region at the edge of a supercrystal typifying the ordered nanocrystal packing.

The Dependence of the Friction Coefficient on the Size and Course of Sliding Speed

2014 ◽  
Vol 693 ◽  
pp. 305-310 ◽  
Author(s):  
Eva Labašová
Keyword(s):  
Friction Coefficient ◽  
Normal Load ◽  
Testing Machine ◽  
Current Component ◽  
Sliding Speed ◽  
Rectangular Shape ◽  
Coefficient Increase ◽  
The Coefficient Of Friction ◽  
Ring Method ◽  
Run Up

The coefficient of friction for the bronze material (CuZn25Al6) with insert graphite beds and other bronze material (CuSn12) are investigated in this paper. Friction coefficient was investigated experimentally by the testing machine Tribotestor`89 which uses the principle of the ring on ring method. The external fixed bushing was exposed to the normal load of the same size in all tests. Process of load was increased from level 50 N to 600 N during run up 300 s, after the run up the appropriate level of load was held. The internal bushing performed a rotational movement with constant sliding speed. The value of sliding speed was changed individually for every sample (v = 0.2 (0.3, 0.4) m.s-1). The forth test had a rectangular shape of sliding speed with direct current component 0.3 m.s-1 and the amplitude 0.1 m.s-1 period 300 s, the whole test took 2100 s. The obtained results reveal that friction coefficient increase with the increase of sliding speed.

Piston Ring-Cylinder Bore Friction Modeling in Mixed Lubrication Regime: Part II—Correlation With Bench Test Data

1999 ◽  
Vol 123 (1) ◽  
pp. 219-223 ◽  
Author(s):  
Ozgen Akalin ◽  
Golam M. Newaz
Keyword(s):  
Friction Coefficient ◽  
Test Data ◽  
Piston Ring ◽  
Normal Load ◽  
Test System ◽  
Mixed Lubrication ◽  
Contact Temperature ◽  
Bench Test ◽  
Crank Angle ◽  
Contact Width

A bench friction test system for piston ring and liner contact, which has high stroke length and large contact width has been used to verify the analytical mixed lubrication model presented in a companion paper (Part 1). This test system controls the speed, temperature and lubricant amount and records the friction force, loading force, crank angle signal and contact temperature data simultaneously. The effects of running speed, applied normal load, contact temperature and surface roughness on friction coefficient have been investigated for conventional cast-iron cylinder bores. Friction coefficient predictions are presented as a function of crank angle position and results are compared with bench test data. Analytical results correlated well with bench test results.

Tribological Behaviour of GFR Polymer Composites

2005 ◽  
Author(s):  
J. Quintelier ◽  
P. Samyn ◽  
P. De Baets ◽  
J. Degrieck
Keyword(s):  
Polymer Matrix Composites ◽  
Normal Load ◽  
Thin Polymer Film ◽  
Matrix Composites ◽  
Tribological Behaviour ◽  
Frictional Behavior ◽  
Glass Fiber Reinforced ◽  
Thin Polymer ◽  
Pin On Disc ◽  
The Coefficient Of Friction

On a Pin-on-Disc test rig with composite disc and steel pin tribological experiments were done on pultruded glass fiber reinforced polymer matrix composites plates. The wear and frictional behavior strongly depends on the structure. Also the normal load plays an important role in the frictional behavior, which is of greater importance than the speed. The formation of a thin polymer film onto the wear track results in a lowering of the coefficient of friction with 20%.

scholarly journals Experimental Study on the Transition between Static and Kinetic Frictions of Steel/Shale Pairs

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Qin Lian ◽  
Chunxu Yang ◽  
Jifei Cao
Keyword(s):  
Friction Coefficient ◽  
Normal Load ◽  
Critical Distance ◽  
Dynamic Friction ◽  
Stick Slip ◽  
Dynamic Friction Coefficient ◽  
The Coefficient Of Friction ◽  
The Difference ◽  
Stick Slip Motion ◽  
Insight Into

The transition between static and kinetic frictions of steel/shale pairs has been studied. It was found that the coefficient of friction decreased exponentially from static to dynamic friction coefficient with increasing sliding displacement. The difference between static and dynamic friction coefficients and the critical distance Dc under the dry friction condition is much larger than that under the lubricated condition. The transition from static to dynamic friction coefficient is greatly affected by the normal load, quiescent time, and sliding velocity, especially the lubricating condition. Maintaining continuous lubrication of the contact area by the lubricant is crucial to reduce or eliminate the stick-slip motion. The results provide an insight into the transition from static to dynamic friction of steel/shale pairs.

Synthesis, Self-Assembling and Redox Properties of 2-[(ω-Sulfanylalkyl)amino]-1,4-naphthoquinones

2006 ◽  
Vol 71 (9) ◽  
pp. 1383-1391 ◽  
Author(s):  
Maryte Kažemekaite ◽  
Vilma Railaite ◽  
Arunas Bulovas ◽  
Zita Talaikyte ◽  
Gediminas Niaura ◽  
...  
Keyword(s):  
Reduction Process ◽  
Spectroscopic Studies ◽  
Self Assembled Monolayers ◽  
Raman Spectroscopic ◽  
Self Assembling ◽  
Electrochemical Parameters ◽  
Surface Enhanced ◽  
Assembled Monolayers ◽  
Surface Enhanced Raman ◽  
Group Form

The newly synthesized 1,4-naphthoquinones linked via nitrogen atom to a short chain with terminal sulfanyl group form self-assembled monolayers on gold. The main electrochemical parameters of the monolayers were determined by cyclic voltammetry. Combined voltammetric and in situ Fourier-transform surface-enhanced Raman spectroscopic studies of the Au electrode modified with the title compounds clearly evidence that naphthoquinone group transforms into naphthalenediol during a reduction process.

Self Assembled Monolayers and Carbon Nanotubes: A Significant Tool’s for Modification of Electrode Surface

2020 ◽  
Vol 18 (9) ◽  
pp. 669-685
Author(s):  
Padmaker Pandey ◽  
Anamika Pandey ◽  
Shruti Singh ◽  
Nikhil Kant Shukla
Keyword(s):  
Carbon Nanotubes ◽  
Volume Ratio ◽  
Biological Molecules ◽  
Self Assembled Monolayers ◽  
Self Assembling ◽  
Biological Surfaces ◽  
Biological Recognition ◽  
Monomolecular Films ◽  
Assembled Monolayers ◽  
Interfacial Surfaces

A compromising and well-organized model system is needed for investigating the molecular behaviour of biomolecules as many transduction processes and biological recognition occur at biological surfaces. The application of techniques in interfacial surfaces like one molecule thick films has made a feasible and significant tool for modern scientific studies. Self Assembling Monolayers (SAMs) technology is a very useful means for producing monomolecular films of various biological molecules on different substrates. Carbon Nanotubes (CNTs) have length-to-diameter aspect ratio property which provides a large surface-to-volume ratio, making it an intensely capable material for biomolecular attachments. The incorporation of Carbon Nanotubes (CNTs) with biological systems forming functional assemblies has shown an explored area of research. Organo-sulfur mainly alkanethiol (CnH2n+1–SH) molecules get adsorbed onto CNTs. This phenomenon has grabbed a lot of attention because Self Assembling Monolayers (SAMs) of organo-sulfur compound acts as an example system for understanding important chemical, physical or biological processes.

Sign in / Sign up

Export Citation Format

Share Document