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Articles 31 - 37 of 37

Full-Text Articles in Nanoscience and Nanotechnology

Atom Scale Characterization Of The Near Apex Region Of An Atomic Force Microscope Tip, Christopher J. Tourek, Sriram Sundararajan Oct 2010

Atom Scale Characterization Of The Near Apex Region Of An Atomic Force Microscope Tip, Christopher J. Tourek, Sriram Sundararajan

Mechanical Engineering Publications

Three-dimensional atom probe tomography (APT) is successfully used to analyze the near-apex regions of an atomic force microscope (AFM) tip. Atom scale material structure and chemistry from APT analysis for standard silicon AFM tips and silicon AFM tips coated with a thin film of Cu is presented. Comparison of the thin film data with that observed using transmission electron microscopy indicates that APT can be reliably used to investigate the material structure and chemistry of the apex of an AFM tip at near atomic scales.


An Alternative Method To Determining Optical Lever Sensitivity In Atomic Force Microscopy Without Tip-Sample Contact, Christopher J. Tourek, Sriram Sundararajan Jan 2010

An Alternative Method To Determining Optical Lever Sensitivity In Atomic Force Microscopy Without Tip-Sample Contact, Christopher J. Tourek, Sriram Sundararajan

Mechanical Engineering Publications

Force studies using atomic force microscopy generally require knowledge of the cantilever spring constants and the optical lever sensitivity. The traditional method of evaluating the optical lever sensitivity by pressing the tip against a hard surface can damage the tip, especially sharp ones. Here a method is shown to calculate the sensitivity without having to bring the tip into contact. Instead a sharpened tungsten wire is used to cause a point contact directly onto the cantilever and cause cantilever bending. Using beam theory, the sensitivity thus found can be converted to the equivalent sensitivity that would be obtained using the ...


Nanoscale Friction Switches: Friction Modulation Of Monomolecular Assemblies Using External Electric Fields, Kanaga Karuppiah Kanaga Subramanian, Yibo Zhou, L. Keith Woo, Sriram Sundararajan Oct 2009

Nanoscale Friction Switches: Friction Modulation Of Monomolecular Assemblies Using External Electric Fields, Kanaga Karuppiah Kanaga Subramanian, Yibo Zhou, L. Keith Woo, Sriram Sundararajan

Mechanical Engineering Publications

This paper presents experimental investigations to actively modulate the nanoscale friction properties of a self-assembled monolayer (SAM) assembly using an external electric field that drives conformational changes in the SAM. Such “friction switches” have widespread implications in interfacial energy control in micro/nanoscale devices. Friction response of a low-density mercaptocarboxylic acid SAM is evaluated using an atomic force microscope (AFM) in the presence of a DC bias applied between the sample and the AFM probe under a nitrogen (dry) environment. The low density allows reorientation of individual SAM molecules to accommodate the attractive force between the −COOH terminal group and ...


Obtaining A Relationship Between Process Parameters And Fracture Characteristics For Hybrid Co2 Laser∕Waterjet Machining Of Ceramics, Dinesh Kalyanasundaram, Pranav Shrotriya, Palaniappa A. Molian Jan 2009

Obtaining A Relationship Between Process Parameters And Fracture Characteristics For Hybrid Co2 Laser∕Waterjet Machining Of Ceramics, Dinesh Kalyanasundaram, Pranav Shrotriya, Palaniappa A. Molian

Mechanical Engineering Publications

A combined experimental and analytical approach is undertaken to identify the relationship between process parameters and fracture behavior in the cutting of a 1mm thick alumina samples by a hybrid CO2 laser∕waterjet (LWJ) manufacturing process. In LWJ machining, a 200W power laser was used for local heating followed by waterjet quenching of the sample surface leading to thermal shock fracture in the heated zone. Experimental results indicate three characteristic fracture responses: scribing, controlled separation, and uncontrolled fracture. A Green’s function based approach is used to develop an analytical solution for temperatures and stress fields generated in the workpiece ...


Method To Generate Surfaces With Desired Roughness Parameters, Yilei Zhang, Sriram Sundararajan Jul 2007

Method To Generate Surfaces With Desired Roughness Parameters, Yilei Zhang, Sriram Sundararajan

Mechanical Engineering Publications

A surface engineering method based on the electrostatic deposition of microparticles and dry etching is described and shown to be able to independently tune both amplitude and spatial roughness parameters of the final surface. Statistical models were developed to connect process variables to the amplitude parameters (center line average and root-mean-square) and a spatial parameter (autocorrelation length) of the final surfaces. Process variables include particle coverage, which affects both amplitude and spatial roughness parameters, particle size, which affects only spatial parameters, and etch depth, which affects only amplitude parameters. Correlations between experimental data and model predictions are discussed.


Generating Random Surfaces With Desired Autocorrelation Length, Yilei Zhang, Sriram Sundararajan Jan 2006

Generating Random Surfaces With Desired Autocorrelation Length, Yilei Zhang, Sriram Sundararajan

Mechanical Engineering Publications

A versatile surface processing method based on electrostatic deposition of particles and subsequent dry etching is shown to be able to tailor the autocorrelation length of a random surface by varying particle size and coverage. An explicit relation between final autocorrelation length, surface coverage of the particles, particle size, and etch depth is built. The autocorrelation length of the final surface closely follows a power law decay with particle coverage, the most significant processing parameter. Experimental results on silicon substrates agree reasonably well with model predictions.


The Effect Of Autocorrelation Length On The Real Area Of Contact And Friction Behavior Of Rough Surfaces, Yilei Zhang, Sriram Sundararajan Jan 2005

The Effect Of Autocorrelation Length On The Real Area Of Contact And Friction Behavior Of Rough Surfaces, Yilei Zhang, Sriram Sundararajan

Mechanical Engineering Publications

Autocorrelation length (ACL) is a surface roughness parameter that provides spatial information of surfacetopography that is not included in amplitude parameters such as root-mean-square roughness. This paper presents a relationship between ACL and the friction behavior of a rough surface. The influence of ACL on the peak distribution of a profile is studied based on Whitehouse and Archard’s classical analysis [Whitehouse and ArchardProc. R. Soc. London, Ser. A316, 97 (1970)] and their results are extended to compare profiles from different surfaces. The probability density function of peaks and the mean peak height of a profile are given as functions ...