Atomic force microscopy (AFM) is an important technology that allows researchers to probe local surface properties at nanometer length scales. In addition to surface topography, the AFM can probe many types of tip-surface interactions (including adhesion and friction) to gain a better understanding of the chemical properties of surfaces. This thesis contains two experiments which utilize AFM to in addition to several other techniques to study (1) Self Assembled Monolayer (SAM) formation and corrosion and (2) intermolecular and surface/molecular effects on gramicidin film formation and molecular orientation. In the first experiment, N-octadecyltrichlorosilane (OTS) molecules were self-assembled onto silicon samples. We observed that OTS required a very short time (about 15 seconds) to complete the formation of the monolayer on surface. However, this SAM film was highly susceptible to corrosion by the strong oxidant (KMnO4), resulting in a chemical change to the film from hydrophobic functional groups (CH3) to hydrophilic functional groups (OH). In subsequent experiments, we observed that if the SAMs were formed using longer exposure times (about 24 hours), they were highly resistant to corrosion. Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Photoelectron Spectroscopy (XPS) also showed that the 24 hour growth SAM films were densely packed. These results indicate that SAM films based on organosilane molecules can protect the surface from corrosion, and further that more densely packed SAMs exhibit better anti-corrosion performance than less dense films. In the second experiment, the antibacterial peptide Gramicidin was used to study how intermolecular and surface energy properties can influence the aggregation and film formation of molecules on several surfaces. Gramicidin has a unique physical and chemical structure with hydrophobic side chain and hydrophilic ends. Here, we have used three different substrates (Silicon, Mica, and Graphite) to study intermolecular interactions, aggregation, and orientation of Gramicidin peptide. Langmuir-Blodgett methods were also used to study aggregation and molecular orientation at the solid-liquid interface.

Self assembled monolayer films (SAMs) deposited on silicon surfaces have gained considerable interest due to their ability to modify surface properties for advanced applications in sensors, MEMS, and NEMS devices. These molecular films are typically deposited on silicon surfaces from solution using a variety of solvents, which can influence the molecular packing and quality of the films. To better understand these effects, we have performed a systematic solvent effect study of the growth of n-Octadecyltrichlorosilane (OTS) on silicon substrates using chloroform, dichloromethane, toluene, benzene and hexadecane. The films were characterized using contact angle measurements, Fourier Transform Infrared Spectroscopy (FTIR), and Atomic Force Microscopy (AFM) to evaluate the SAM growth rate and film quality. Lateral Force Microscopy (LFM) and transmission FTIR were used to characterize the molecular packing. Finally, we used AFM to make adhesion measurements on the films and correlated these results with friction data. These techniques provide a means to characterize the local nanoscale packing of the films. The Hertzian contact model was used to model and describe the adhesion and friction result. Our results show that using hexadecane as the solvent produced OTS films with the highest density molecular packing. By comparing to Langmuir-Blodgett SAM film deposition methods, we show that it is the intermolecular interaction between the solvent molecules and OTS that determines this density. Thus, the structure and chemical properties of the solvent molecule strongly influences the molecular packing, quality, and performance of the SAM film.

This study aims to experimentally explore the possibility to join the two pieces of low-carbon steel and Cu-Ni alloy as the cladding material into a thick clad steel plate during a Friction Stir Lap Welding¡]FSLW¡^process without a probe. Two methods are employed to enhance the welding strength. Firstly, a layer of nickel is coated on the low-carbon steel to prevent it from oxidizing during the welding process. Secondly, the surface of the low-carbon steel is knurled to increase the contact area between the welding surfaces. Experimental results show that Ni-coating can effectively prevent the generation of oxidation and improve the welding strength. According to the tensile test using a plate of Cu-Ni alloy with a thickness of 4 mm, the welding strength of the clad steel plate with Ni-coating is about 2.3 times greater than that without Ni-coating. Moreover, according to the impact test, the clad steel plate with Ni-coating can absorb more impact energy than that without Ni-coating. This difference increases with increasing thickness of the plate. It is also found that the welding strength at the center of joints using the Ni-coating is greater than that at the substrate of copper-nickel alloy. For the clad steel plate with knurling, since it is difficult to fill the gap between the patterns of knurling, the increase in the contact area between the welding surfaces has been offset. Hence, the welding strength of the clad steel plate with knurling is less than that with Ni-coating.

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Thesis (M.S.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains x, 101 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 90-100).

Thesis (M.S.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains xi, 85 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 53).

Tungsten disulfide is a proven material as a low friction solid coating. The material is well characterized and has proven its capabilities the last century. Graphene is this centurys most promising material with electrical and mechanical properties. With it the 2D material revolution have started. In this thesis I present a feasible way to sputter tungsten disulfide on graphene as a substrate with little damage to the graphene from energetic particles and a straight forward method to quantize the damage before and after deposition. Further I investigate compositional changes in the sputtered films depending on processing pressure and how tungsten disulfide film thickness and the amount of graphene damage affects the materials low friction capabilities. It is shown that graphene is not a viable substrate for a low friction tungsten disulfide film and that tungsten disulfide is an excellent material for low friction coatings even down too a few nanometers and that the films behavior during load in the friction testing significantly depends on the processing pressure during sputtering.

HiGtech är en projektgrupp på Högskolan i Gävle vilka konstruerar och bygger energisnåla tävlingsfordon. Ett av fordonen tävlar i Shell Eco Marathons prototypklass för bensindrivna förbränningsmotorer och drivs av en på högskolan konstruerad motor. Motorns effekt överförs till en kedjetransmission via en inköpt och modifierad centrifugalkoppling. Den nuvarande centrifugalkopplingen väger cirka 1,5 kg. Då en stor faktor för tävlingsresultatet är fordonets rullmotstånd, vilken beror av fordonets vikt, har målet med detta arbete varit att konstruera en specialanpassad centrifugalkoppling, vars vikt endast är hälften så stor som motorns nuvarande koppling. Experiment på motorn, en undersökning av befintliga centrifugalkopplingar samt en litteraturstudie har utförts vilket gav indata för konstruktionsarbetet. Centrifugalkopplingens diameter har optimerats med avseende på låg vikt, där massan av kopplingens nav, trumma och backar tagits fram och jämförts för olika diametrar. Backarnas massa har beräknats med en framtagen beräkningsmodell och navets samt trummans massor har tagits fram genom 3D-modellkoncept. Vidare har en centrifugalkoppling konstruerats av stål, anpassad för tävlingsfordonets motor med individuell justering av ingreppsvarvtalet för dess backar. Centrifugalkopplingens optimala diameter beräknades till 110 millimeter, vilket har resulterat i en totalvikt på den utvecklade kopplingen på cirka 730 g. En specifikationslista har tagits fram på lämpligt friktionsmaterial, dock krävs vidare tester för att säkerställa att önskad funktion uppnås på grund av vibrationer som kan uppstå, något som avgränsats bort i detta arbete. / HiGtech is a project group at the University of Gävle, in which students design and build energy efficient vehicles to compete with around the world. One of the vehicles is competing in the Shell Eco Marathon prototype class for gasoline-powered internal combustion engines and is driven by an on campus designed engine. The engine's power is transmitted to a chain transmission via a purchased and modified centrifugal clutch. The current centrifugal clutch weighs about 1.5 kg. An important factor for the outcome in the competition is the rolling resistance of the vehicle, which depends on its weight, the aim of this work has been to design a customized centrifugal clutch, whose weight is only half as large as the engine’s current clutch. Experiments on the engine, a survey of centrifugal clutches and a literature study has been performed which gave input for the design work. The diameter of the centrifugal clutch has been optimized for low weight, where the mass of the clutch hub, drum and shoes has been compared for the different diameters. The shoe mass has been calculated using a developed model and the hub and drum masses have been developed through a 3D model concept. Furthermore, a centrifugal clutch out of steel, adapted for the engine of the competing vehicle, has been developed, with individual adjustments of the engagement speed of its shoes. The optimal diameter of the centrifugal clutch was calculated to 110 millimeters, resulting in a total weight of the developed clutch of about 730 g. A list of specification has been developed for an appropriate choice of friction material, however, further testing is required to ensure that the desired functionality is achieved due to vibrations that may occur, this was however demarcated in this work.

As digital microfluidics has continued to mature since its advent in the early 1980's, an increase in new and novel applications of this technology have been developed. However, even as this technology has become more common place, a consensus on the physics and force models of the motion of the contact line between the fluid, substrate, and ambient has not been reached. This uncertainty along with the dependence of the droplet geometry on the force to cause its motion has directed much of the research at specific geometries and droplet actuation methods. The goal of this thesis is to help characterize the components of the friction force which opposes droplet motion as a one dimensional system model based upon simple system parameters independent from the actuation method. To this end, the force opposing the motion of a droplet under a thin rectangular glass cover slip was measured for varying cover slip dimensions (widths, length), gap height between the cover slip and substrate, and bulk droplet velocity. The stiffness of the droplet before droplet motion began, the force at which the motion initiated, and the steady-state force opposing the droplet motion were measured. The data was then correlated to hypothesized equations and compared to simple models accounting for the forces due to the contact angle hysteresis, contact line friction, and viscous losses. It was found that the stiffness, breakaway force, and steady-state force of the droplet could be correlated to with an error standard deviation of 8 %, 14%, and 10 % respectively. Much of the error was due to an unexpected height dependence for the breakaway and steady-state forces and testing error associated with the velocity. The models for the stiffness and breakaway force over predicted the results by 36% and 16% respectively. During testing, viii stability issues with the cover slip were observed and simple dye testing was conducted to visualize the droplet flow field.