Micro/Nanotribology: State of the Art and Its Applications

Abstract

Abstract. Atomic force microscopy/friction force microscopy (AFM/FFM) techniques are increasingly used for tribological studies of engineering surfaces at scales, ranging from atomic and molecular to microscales. These techniques have been used to study surface roughness, adhesion, friction, scratching/wear, indentation, detection of material transfer, and boundary lubrication and for nanofabrication/nanomachining purposes. Measurement of atomic-scale friction of a freshly-cleaved highly-oriented pyrolytic graphite exhibited the same periodicity as that of corresponding topography. However, the peaks in friction am those in corresponding topography were displaced relative to each other. Variations in atomic-scale friction and the observed displacement has been explained by the variations in interatomic forces in the normal and lateral directions. Local variation in microscale friction is found to correspond to the local slope suggesting that a ratchet mechanism is responsible for this variation. Directionality in the friction is observed on both micro-and macro scales which results from the surface preparation and anisotropy in surface roughness. Microscale friction is generally found to be smaller than the macrofriction as there is less ploughing contribution in microscale measurements. Microscale friction is load dependent and friction values increase with an increase in the normal load approaching to the macrofriction at contact stresses higher than the hardness of the softer material. Wear rate for single-crystal silicon is negligible below 20 IlN and is much higher and remains approximately constant at higher loads. Elastic deformation at low loads is responsible for negligible wear. Mechanism of material removal on microscale is studied. At the loads used in the study, material is removed by the ploughing mode in a brittle manner without much plastic deformation. Most of the wear debris is loose. Evolution of the wear has also been studied using AFM. Wear is found to be initiated at nano scratches. AFM has been modified to obtain load-displacement curves and for measurement of nanoindentation hardness and Young's modulus of elasticity, with depth of indentation as low as I nm. Hardness of ceramics on nano scales is found to be higher than that on micro scale.Ceramics exhibit significant plasticity and creep on nanoscale. Scratching and indentation on nanoscales are the powerful ways to screen for adhesion and resistance to deformation of ultrathin films. Detection of material transfer on a nanoscale is possible with AFM. Boundary lubrication studies and measurement of lubricant-film thickness with a lateral resolution on a nanoscale have been conducted using AFM. Self-assembled monolayers and chemically-bonded lubricant fLIms with a mobile fraction are superior in wear resistance.

An in situ synchrotron XAS methodology for surface analysis under high temperature, pressure, and shear

“…Therefore, by reducing friction by 1%, the annual fuel consumption worldwide is projected to be reduced by 1 billion liters based on the total consumption in 2015 [2]. Furthermore, more than 1.0% saving in the Gross National Product (GNP) of many industrial counties, such as USA [3], UK [4] and China [5], can be achieved through a proactive practice of tribology that…”

Nanoscale friction and wear maps

“…In fact, several studies have shown that the tribology and mechanics of these devices are the limiting factors to the imminent broad-based impact of nanotechnology on our everyday lives (Maboudian & Howe 1997;Bhushan 1998Bhushan , 2003Bhushan , 2007a. Miniaturization and the subsequent development of devices for nanotechnology applications require better tribological performance of the system components and a fundamental understanding of the basic phenomena underlying friction, wear and lubrication on the micro-and nanoscale (Bhushan 1997(Bhushan , 1998(Bhushan , 1999a(Bhushan ,b, 2001(Bhushan , 2007a. The components used in the micro/ nanostructures are very light (of the order of a few micrograms) and operate under very light loads (of the order of a few micrograms to a few milligrams).…”

Ultrathin Wear‐Resistant Ionic Liquid Films for Novel MEMS/NEMS Applications

“…Adhesion, friction and wear at the nanometer size scale become critical and can be detrimental to the efficiency, power output and reliability of MEMS/NEMS devices. [1,2] For example, adhesion is the major cause of the failure of accelerometers used in automobile air bag triggering mechanisms [3] and in micromirror components of commercial digital light processing (DLP) equipment. [2,[4][5][6][7] Wear has been found to compromise the performance of NEMS-based atomic force microscopy (AFM) data storage systems.…”