Friction and wear are two key factors that are detrimental at the nanoscale, because they are linked with surface forces. It is important to understand their mechanisms and to find ways to overcome them. At the macroscale lubricant are classically used to do so and are well understood. However, those lubricants cannot be readily used at the nanoscale and other lubrication methods must be found. In this paper I will focus on two new potential lubricants that were tested in Microelectromechanical Systems (MEMS): ionic liquid films and alcohol vapor. They are both very different and are not used in the same situations but they both show great potential. In fact, thanks to the alcohol vapor lubricant a device did not show signs of wear after 11 days of operation, whereas it failed within minutes in the absence of alcohol. No signs of wear were seen after 100 cycles of operation of a device with ionic liquid film but were observed in an uncoated device.
Tribochemical polishing is a technique that utilizes corrosive wear to polish surfaces. It involves chemically reacting the surface material with a corrosive medium like water or chemical reagent under sliding contact. The friction stimulates preferential dissolution of material at asperity peaks, making the surface very smooth after initial wear. It is effective when friction generates tribocorrosion products, mechanical stresses are low to avoid damage, and the corrosive medium is not too aggressive. Tribochemical polishing has been used to create smooth surfaces on materials like silicon nitride, silicon, and silicon carbide.
This textbook covers the wear of polymers and composites. It discusses key topics in polymer tribology including the factors that affect the friction and wear of polymers like sliding speed, temperature, load and surface roughness. It also examines the sliding mechanics of polymers such as the formation of transfer films, different wear regimes, flash temperature generation and the third body effect. Finally, it analyzes the fatigue wear of unfilled polymers under fluctuating loads and the influence of surface defects on wear. The book provides a comprehensive introduction to polymer tribology and the mechanisms that govern the wear of polymers.
Study of sliding wear rate of hot rolled steel specimen subjected to Zirconia...IJERA Editor
Wear is nothing but loss of material by usage. In a mechanical industry mechanical components will operate
under severe load, temperature and high speeds. Under such a type of situation, when metal to metal contact take
place the surfaces that comes in contact is subjected to wear. These should be considered as a serious affair in an
industry because if the process of wear continues it can reduce service life of the component and also to the
entire mechanical system to which the component has been used. In the light of the above the present work
mainly deals with the study of wear behavior of hot rolled steel with and without zirconia coating on the contact
surface and the effect of zirconia coating with varying thickness.
Tribochemical wear occurs due to chemical reactions between contacting surfaces that are accelerated by friction and heat. It is a complex wear mechanism that involves both mechanical and chemical processes. Flash temperatures generated during sliding can significantly increase reaction kinetics and lead to oxidation. Tribochemical wear can produce both protective surface layers that reduce wear, as well as abrasive debris. Effective ways to prevent tribochemical wear include using lubricants, hard coatings like DLC that form protective layers, and increasing the hardness of materials.
The document discusses various theories of adhesion including physical absorption, chemical bonding, diffusion, electrostatic, and mechanical interlocking theories. It explains that adhesion occurs due to molecular contact and surface forces between two materials. Adhesives are now commonly used in manufacturing across many industries like construction, automobiles, footwear, and more due to advantages like joining dissimilar materials and reducing weight.
Thermosetting and thermoplastic resins are the two main types of adhesives. Thermosetting adhesives harden permanently once heated, while thermoplastics soften when heated and reharden when cooled. Common thermosetting adhesives include phenol-formaldehyde, polyesters, and silicones. Thermoplastics include cellulose derivatives, starches, and polyvinyls. The strength of adhesive bonds depends on factors like the smoothness, thickness, and thermal expansion properties of the adhered surfaces as well as the degree of polymerization, polarity, and complexity of the adhesive molecule. Adhesives are applied through methods like brushing, rolling, spraying, or using reactive
This document discusses adhesion and surface phenomena in dentistry. It defines adhesion as the attachment between two dissimilar substances and describes the components of an adhesive junction. Adhesion can occur through mechanical, chemical, or physical bonding. The document outlines factors that affect adhesion such as surface energy, surface tension, wettability and contact angle. It also lists criteria for successful bonding and discusses the importance of adhesion for dental procedures like bonding restorations and sealing pits/fissures. Specific techniques for bonding to enamel and dentin are covered, including acid etching of enamel and the use of etchants, primers and bonding agents to create a hybrid layer for dentin bonding.
1. The document discusses the mechanisms of adhesion, which can be divided into chemical bonding and physical bonding. Chemical bonding involves primary bonds formed by electron sharing or exchange, and secondary bonds formed through mechanical linking. Physical bonding involves mechanical interlocking, diffusion, adsorption, and electrostatic forces.
2. Mechanical interlocking occurs when an adhesive penetrates pores and irregularities in a substrate to create a mechanical link. Diffusion bonding is caused by compatibility between polymer chains that allows for mixing and penetration. Adsorption bonding is through intermolecular attraction like van der Waals forces, requiring wetting of the substrate. Electrostatic bonding arises from separation of charges at interfaces, affecting polar adhesives.
Tribochemical polishing is a technique that utilizes corrosive wear to polish surfaces. It involves chemically reacting the surface material with a corrosive medium like water or chemical reagent under sliding contact. The friction stimulates preferential dissolution of material at asperity peaks, making the surface very smooth after initial wear. It is effective when friction generates tribocorrosion products, mechanical stresses are low to avoid damage, and the corrosive medium is not too aggressive. Tribochemical polishing has been used to create smooth surfaces on materials like silicon nitride, silicon, and silicon carbide.
This textbook covers the wear of polymers and composites. It discusses key topics in polymer tribology including the factors that affect the friction and wear of polymers like sliding speed, temperature, load and surface roughness. It also examines the sliding mechanics of polymers such as the formation of transfer films, different wear regimes, flash temperature generation and the third body effect. Finally, it analyzes the fatigue wear of unfilled polymers under fluctuating loads and the influence of surface defects on wear. The book provides a comprehensive introduction to polymer tribology and the mechanisms that govern the wear of polymers.
Study of sliding wear rate of hot rolled steel specimen subjected to Zirconia...IJERA Editor
Wear is nothing but loss of material by usage. In a mechanical industry mechanical components will operate
under severe load, temperature and high speeds. Under such a type of situation, when metal to metal contact take
place the surfaces that comes in contact is subjected to wear. These should be considered as a serious affair in an
industry because if the process of wear continues it can reduce service life of the component and also to the
entire mechanical system to which the component has been used. In the light of the above the present work
mainly deals with the study of wear behavior of hot rolled steel with and without zirconia coating on the contact
surface and the effect of zirconia coating with varying thickness.
Tribochemical wear occurs due to chemical reactions between contacting surfaces that are accelerated by friction and heat. It is a complex wear mechanism that involves both mechanical and chemical processes. Flash temperatures generated during sliding can significantly increase reaction kinetics and lead to oxidation. Tribochemical wear can produce both protective surface layers that reduce wear, as well as abrasive debris. Effective ways to prevent tribochemical wear include using lubricants, hard coatings like DLC that form protective layers, and increasing the hardness of materials.
The document discusses various theories of adhesion including physical absorption, chemical bonding, diffusion, electrostatic, and mechanical interlocking theories. It explains that adhesion occurs due to molecular contact and surface forces between two materials. Adhesives are now commonly used in manufacturing across many industries like construction, automobiles, footwear, and more due to advantages like joining dissimilar materials and reducing weight.
Thermosetting and thermoplastic resins are the two main types of adhesives. Thermosetting adhesives harden permanently once heated, while thermoplastics soften when heated and reharden when cooled. Common thermosetting adhesives include phenol-formaldehyde, polyesters, and silicones. Thermoplastics include cellulose derivatives, starches, and polyvinyls. The strength of adhesive bonds depends on factors like the smoothness, thickness, and thermal expansion properties of the adhered surfaces as well as the degree of polymerization, polarity, and complexity of the adhesive molecule. Adhesives are applied through methods like brushing, rolling, spraying, or using reactive
This document discusses adhesion and surface phenomena in dentistry. It defines adhesion as the attachment between two dissimilar substances and describes the components of an adhesive junction. Adhesion can occur through mechanical, chemical, or physical bonding. The document outlines factors that affect adhesion such as surface energy, surface tension, wettability and contact angle. It also lists criteria for successful bonding and discusses the importance of adhesion for dental procedures like bonding restorations and sealing pits/fissures. Specific techniques for bonding to enamel and dentin are covered, including acid etching of enamel and the use of etchants, primers and bonding agents to create a hybrid layer for dentin bonding.
1. The document discusses the mechanisms of adhesion, which can be divided into chemical bonding and physical bonding. Chemical bonding involves primary bonds formed by electron sharing or exchange, and secondary bonds formed through mechanical linking. Physical bonding involves mechanical interlocking, diffusion, adsorption, and electrostatic forces.
2. Mechanical interlocking occurs when an adhesive penetrates pores and irregularities in a substrate to create a mechanical link. Diffusion bonding is caused by compatibility between polymer chains that allows for mixing and penetration. Adsorption bonding is through intermolecular attraction like van der Waals forces, requiring wetting of the substrate. Electrostatic bonding arises from separation of charges at interfaces, affecting polar adhesives.
There are thousands of different adhesives that can be divided into three major types: thermoplastic adhesives, thermosetting adhesives, and rubber-resin blends. Some important adhesives include anaerobics, cyanoacrylates, toughened acrylics, epoxies, polyurethanes, silicones, phenolics, and polyimides. Each type of adhesive has different advantages and applications depending on the materials being bonded and service conditions.
Tribology is the science of interacting surfaces in relative motion. It describes everything that happens when things rub together, such as the effects of high and low friction. Tribology plays a role in mechanisms like gears and bearings. Lubrication is needed to reduce wear, remove heat and contamination, and lower friction to prevent wear. Recent tribology research includes improving journal bearing operation at heavy misalignment, tribological surface coatings, and lubrication and life of polymer rolling bearings. Research facilities like Argonne's Tribology Laboratory conduct advanced research on surface engineered materials, lubricants, fuels and additives using equipment like optical profilometers and multi-specimen testers.
The document discusses various types of coatings used for plastic films, paper, and metal foils. It describes common coating techniques like comma coating, reverse roll coating, and Myer bar coating. It also discusses surface treatment methods like corona treatment and plasma treatment that are used to increase adhesion of coatings. Barrier coatings used for paper are mentioned, which improve properties like printability, smoothness, gloss, and brightness.
Tribology is the study of friction, lubrication, and wear between interacting surfaces in relative motion. It helps improve machine reliability and reduce failures. Reynolds' equation, derived in 1886, quantifies fluid film lubrication and allows prediction of hydrodynamic, hydrostatic, and squeeze film mechanisms by modeling pressure as a function of coordinates and time. The equation assumes laminar flow of an incompressible Newtonian fluid with negligible inertia and pressure gradients in the film thickness direction.
This document discusses the applications of industrial tribology. It begins by defining tribology and the main causes of friction and wear between surfaces. It then discusses several industrial applications where tribology is important, including bearings, gears, cams, and automobile engines. For each application, the document discusses common failure mechanisms and how tribological principles can be applied to improve performance and reduce wear through methods like surface coatings, lubricants, and material selection. The document concludes by noting that understanding tribology can help conserve energy and that developing eco-friendly materials and lubricants can promote sustainability and reduce emissions.
This document discusses the role of tribology in engineering. Tribology comprises the science and technology of interacting surfaces in relative motion, including friction, lubrication, and wear. It is a vast and interdisciplinary field ranging from fundamental physics of surface contact to practical applications. The document emphasizes that tribologists should quantify the profitability of reducing friction and wear, for example through calculating potential cost savings from improved fuel efficiency. Active control of tribological systems using methods like liquid crystal lubricants may also help optimize friction and wear performance. Accuracy of tribological predictions remains limited by various factors.
Surface tension & wetting in dental materialsmohsen213
Surface tension and wetting play an important role in dental materials. Adhesion occurs through chemical or physical bonding between dissimilar surfaces or molecules. Cohesion refers to the attraction between like molecules and is responsible for surface tension, where surface molecules cling more strongly together due to fewer neighboring molecules. For an adhesive to wet a surface, its liquid form must enable bonds with the surface that are stronger than the surface's internal cohesive forces. The degree of wetting is indicated by the contact angle between a liquid drop and surface - low contact angles indicate high wettability. Etching a tooth surface increases its surface energy and roughness to promote wetting and bonding of dental resins through both chemical and mechanical mechanisms.
Wear is the process of material removal from solid surfaces that are in contact with each other due to sliding or rolling motion. It occurs on the surface of a component as a result of its motion relative to an adjacent working part and depends on factors like surface geometry, applied load, velocities, environment, and material properties. The main types of wear processes are abrasive wear, adhesive wear, surface fatigue, and erosive wear. Abrasive wear occurs when a harder surface rubs against a softer one.
Design Fabrication and Static Analysis of Single Composite Lap Jointijsrd.com
Mechanically fastened joints are critical parts in composite aircraft structures. The composite structural members are highly used in the following applications such as aerospace, automobiles, marine, architecture etc., In the past decades, Adhesive bonding is a practical joint method for joining composite materials which provide low shear and Tensile strength .To improve the strength material joint is to be used in the work. A Glass fibre Epoxy composite is to be fabricated by hand lay-up method. And experimentally results are to be obtained. The Experimental results are to be compared with Analytical and Numerical results. For numerical analysis ANSYS software is to be used.
Introduction to adhesive and adhesion, this powerpoint slide will explain you about what is an adhesive, advantage and disadvantage of joining using adhesive. In addition, you will understand the basics of adhesive theory i.e. the requirement of a good bond, good joint design, types of adhesives.
1. The document reports on an experimental lab test investigating wear and tribology using a pin-on-disc machine.
2. Tests were conducted with aluminum and steel pins under various loads and conditions to determine wear rate, friction, and other properties.
3. The results show that wear increases with higher load and dry conditions. Lubrication decreases wear. Surface treatments like nitriding and carburizing improve wear resistance by enhancing surface properties.
The document summarizes key points from a book on extreme tribology written by Professor Ahmed Abdelbary. It discusses tribology concepts like friction, wear, lubrication and how they operate under extreme conditions involving high loads, temperatures, or harsh environments. It provides brief summaries of the book's chapters which cover topics like tribo-material properties, lubrication challenges, simulation and modeling of tribo-systems operating under extreme conditions. The foreword written by Professor Klaus Friedrich recommends the book for engineers, researchers, and professors as it provides important instruction on wear which is rarely covered in sufficient detail during university studies.
“Wear of Polymers and Composites” is basically prepared to be used by senior and graduate students of tribology; yet, the author hops the current work be of interest to a larger pool of readership. The book, therefore, introduces fundamentals of polymer tribology and sliding mechanics. It establishes a link between the load parameters and wear response, and shows how they are important in determining the mechanism of fatigue wear.
This dissertation summarizes tribological research on polyurethane graphene composites. Experimental tests were conducted to analyze the wear rate and coefficient of friction of polyurethane (PU), PU with graphene (PUG), and PU with graphene and carbon (PUGC) composites under varying loads, speeds, and travel distances. The addition of graphene and carbon to PU was found to significantly reduce wear rate and coefficient of friction compared to unmodified PU. Microscopy images showed that graphene and carbon addition led to a smoother worn surface with less damage. Overall, the study demonstrated that graphene addition can improve the tribological properties of polyurethane composites.
Chemical Engineering Materials-- Failure of Metals : Fracture , Fatigue & CreepAjinkya Khandizod
This document discusses different types of metal failure including fracture, fatigue, and creep. It defines each type of failure and provides examples. Fracture can be ductile or brittle, with ductile fracture involving plastic deformation and brittle fracture occurring rapidly with little deformation. Fatigue is failure from fluctuating stresses over long periods and is a common cause of metal failure. Creep is plastic deformation that occurs over time at high temperatures. Environmental factors like thermal cycling and corrosion can enhance these failure mechanisms.
This book offers fundamentals and a comprehensive overview of tribology in sever conditions. It addresses a comprehensive coverage of classical tribology of solid contacts, friction mechanics, wear mechanisms and lubrication technologies. Characteristics of tribological systems operating under extreme conditions involving extraordinary loads, temperatures, speeds, and vacuum are discussed. Surface coating, surface treatment, and lubrication are argued considering the cutting-edge researches. In addition, tribology of automotive components is presented, as are tribological applications in many practical situations. The tribology of polymer composites, MEMS and NEMS are explored. A basic understanding of failure in tribological systems is covered. Various test methods used in evaluating wear are reviewed. Diverse techniques applied in predicting wear behavior by mathematical models, FE modeling and ANN approach are discussed.
types and applications of synthetic adhesivesAfzal Zubair
Synthetic adhesives are man-made adhesives that are designed and manufactured through industrial processes. They can be classified in several ways, including by the number of components needed, the structure of the adhesive polymer after curing, and the type of curing process. Some common types include one-component adhesives that cure with moisture and two-component adhesives that require mixing before curing. Synthetic adhesives are widely used for joining materials through gluing, for waterproofing objects, and in various industrial applications due to their superior mechanical and chemical properties compared to natural adhesives.
El documento habla sobre las competencias emprendedoras. Define las competencias emprendedoras como un conjunto de conocimientos, habilidades y actitudes necesarias para que una persona funcione efectivamente como emprendedor. Detalla algunos conocimientos clave como el estudio de mercados, la comercialización y el análisis financiero, así como habilidades importantes como aprovechar oportunidades, negociar, planificar y resolver problemas. Finalmente, destaca actitudes fundamentales para los emprendedores como la proactividad, la responsabilidad y la capacidad de asum
O documento fornece conselhos para empreendedores sobre como começar um negócio com pouco capital, aprender com erros, construir redes, encontrar inspiração e paixões, e ter paciência durante o processo de construção de um negócio.
There are thousands of different adhesives that can be divided into three major types: thermoplastic adhesives, thermosetting adhesives, and rubber-resin blends. Some important adhesives include anaerobics, cyanoacrylates, toughened acrylics, epoxies, polyurethanes, silicones, phenolics, and polyimides. Each type of adhesive has different advantages and applications depending on the materials being bonded and service conditions.
Tribology is the science of interacting surfaces in relative motion. It describes everything that happens when things rub together, such as the effects of high and low friction. Tribology plays a role in mechanisms like gears and bearings. Lubrication is needed to reduce wear, remove heat and contamination, and lower friction to prevent wear. Recent tribology research includes improving journal bearing operation at heavy misalignment, tribological surface coatings, and lubrication and life of polymer rolling bearings. Research facilities like Argonne's Tribology Laboratory conduct advanced research on surface engineered materials, lubricants, fuels and additives using equipment like optical profilometers and multi-specimen testers.
The document discusses various types of coatings used for plastic films, paper, and metal foils. It describes common coating techniques like comma coating, reverse roll coating, and Myer bar coating. It also discusses surface treatment methods like corona treatment and plasma treatment that are used to increase adhesion of coatings. Barrier coatings used for paper are mentioned, which improve properties like printability, smoothness, gloss, and brightness.
Tribology is the study of friction, lubrication, and wear between interacting surfaces in relative motion. It helps improve machine reliability and reduce failures. Reynolds' equation, derived in 1886, quantifies fluid film lubrication and allows prediction of hydrodynamic, hydrostatic, and squeeze film mechanisms by modeling pressure as a function of coordinates and time. The equation assumes laminar flow of an incompressible Newtonian fluid with negligible inertia and pressure gradients in the film thickness direction.
This document discusses the applications of industrial tribology. It begins by defining tribology and the main causes of friction and wear between surfaces. It then discusses several industrial applications where tribology is important, including bearings, gears, cams, and automobile engines. For each application, the document discusses common failure mechanisms and how tribological principles can be applied to improve performance and reduce wear through methods like surface coatings, lubricants, and material selection. The document concludes by noting that understanding tribology can help conserve energy and that developing eco-friendly materials and lubricants can promote sustainability and reduce emissions.
This document discusses the role of tribology in engineering. Tribology comprises the science and technology of interacting surfaces in relative motion, including friction, lubrication, and wear. It is a vast and interdisciplinary field ranging from fundamental physics of surface contact to practical applications. The document emphasizes that tribologists should quantify the profitability of reducing friction and wear, for example through calculating potential cost savings from improved fuel efficiency. Active control of tribological systems using methods like liquid crystal lubricants may also help optimize friction and wear performance. Accuracy of tribological predictions remains limited by various factors.
Surface tension & wetting in dental materialsmohsen213
Surface tension and wetting play an important role in dental materials. Adhesion occurs through chemical or physical bonding between dissimilar surfaces or molecules. Cohesion refers to the attraction between like molecules and is responsible for surface tension, where surface molecules cling more strongly together due to fewer neighboring molecules. For an adhesive to wet a surface, its liquid form must enable bonds with the surface that are stronger than the surface's internal cohesive forces. The degree of wetting is indicated by the contact angle between a liquid drop and surface - low contact angles indicate high wettability. Etching a tooth surface increases its surface energy and roughness to promote wetting and bonding of dental resins through both chemical and mechanical mechanisms.
Wear is the process of material removal from solid surfaces that are in contact with each other due to sliding or rolling motion. It occurs on the surface of a component as a result of its motion relative to an adjacent working part and depends on factors like surface geometry, applied load, velocities, environment, and material properties. The main types of wear processes are abrasive wear, adhesive wear, surface fatigue, and erosive wear. Abrasive wear occurs when a harder surface rubs against a softer one.
Design Fabrication and Static Analysis of Single Composite Lap Jointijsrd.com
Mechanically fastened joints are critical parts in composite aircraft structures. The composite structural members are highly used in the following applications such as aerospace, automobiles, marine, architecture etc., In the past decades, Adhesive bonding is a practical joint method for joining composite materials which provide low shear and Tensile strength .To improve the strength material joint is to be used in the work. A Glass fibre Epoxy composite is to be fabricated by hand lay-up method. And experimentally results are to be obtained. The Experimental results are to be compared with Analytical and Numerical results. For numerical analysis ANSYS software is to be used.
Introduction to adhesive and adhesion, this powerpoint slide will explain you about what is an adhesive, advantage and disadvantage of joining using adhesive. In addition, you will understand the basics of adhesive theory i.e. the requirement of a good bond, good joint design, types of adhesives.
1. The document reports on an experimental lab test investigating wear and tribology using a pin-on-disc machine.
2. Tests were conducted with aluminum and steel pins under various loads and conditions to determine wear rate, friction, and other properties.
3. The results show that wear increases with higher load and dry conditions. Lubrication decreases wear. Surface treatments like nitriding and carburizing improve wear resistance by enhancing surface properties.
The document summarizes key points from a book on extreme tribology written by Professor Ahmed Abdelbary. It discusses tribology concepts like friction, wear, lubrication and how they operate under extreme conditions involving high loads, temperatures, or harsh environments. It provides brief summaries of the book's chapters which cover topics like tribo-material properties, lubrication challenges, simulation and modeling of tribo-systems operating under extreme conditions. The foreword written by Professor Klaus Friedrich recommends the book for engineers, researchers, and professors as it provides important instruction on wear which is rarely covered in sufficient detail during university studies.
“Wear of Polymers and Composites” is basically prepared to be used by senior and graduate students of tribology; yet, the author hops the current work be of interest to a larger pool of readership. The book, therefore, introduces fundamentals of polymer tribology and sliding mechanics. It establishes a link between the load parameters and wear response, and shows how they are important in determining the mechanism of fatigue wear.
This dissertation summarizes tribological research on polyurethane graphene composites. Experimental tests were conducted to analyze the wear rate and coefficient of friction of polyurethane (PU), PU with graphene (PUG), and PU with graphene and carbon (PUGC) composites under varying loads, speeds, and travel distances. The addition of graphene and carbon to PU was found to significantly reduce wear rate and coefficient of friction compared to unmodified PU. Microscopy images showed that graphene and carbon addition led to a smoother worn surface with less damage. Overall, the study demonstrated that graphene addition can improve the tribological properties of polyurethane composites.
Chemical Engineering Materials-- Failure of Metals : Fracture , Fatigue & CreepAjinkya Khandizod
This document discusses different types of metal failure including fracture, fatigue, and creep. It defines each type of failure and provides examples. Fracture can be ductile or brittle, with ductile fracture involving plastic deformation and brittle fracture occurring rapidly with little deformation. Fatigue is failure from fluctuating stresses over long periods and is a common cause of metal failure. Creep is plastic deformation that occurs over time at high temperatures. Environmental factors like thermal cycling and corrosion can enhance these failure mechanisms.
This book offers fundamentals and a comprehensive overview of tribology in sever conditions. It addresses a comprehensive coverage of classical tribology of solid contacts, friction mechanics, wear mechanisms and lubrication technologies. Characteristics of tribological systems operating under extreme conditions involving extraordinary loads, temperatures, speeds, and vacuum are discussed. Surface coating, surface treatment, and lubrication are argued considering the cutting-edge researches. In addition, tribology of automotive components is presented, as are tribological applications in many practical situations. The tribology of polymer composites, MEMS and NEMS are explored. A basic understanding of failure in tribological systems is covered. Various test methods used in evaluating wear are reviewed. Diverse techniques applied in predicting wear behavior by mathematical models, FE modeling and ANN approach are discussed.
types and applications of synthetic adhesivesAfzal Zubair
Synthetic adhesives are man-made adhesives that are designed and manufactured through industrial processes. They can be classified in several ways, including by the number of components needed, the structure of the adhesive polymer after curing, and the type of curing process. Some common types include one-component adhesives that cure with moisture and two-component adhesives that require mixing before curing. Synthetic adhesives are widely used for joining materials through gluing, for waterproofing objects, and in various industrial applications due to their superior mechanical and chemical properties compared to natural adhesives.
El documento habla sobre las competencias emprendedoras. Define las competencias emprendedoras como un conjunto de conocimientos, habilidades y actitudes necesarias para que una persona funcione efectivamente como emprendedor. Detalla algunos conocimientos clave como el estudio de mercados, la comercialización y el análisis financiero, así como habilidades importantes como aprovechar oportunidades, negociar, planificar y resolver problemas. Finalmente, destaca actitudes fundamentales para los emprendedores como la proactividad, la responsabilidad y la capacidad de asum
O documento fornece conselhos para empreendedores sobre como começar um negócio com pouco capital, aprender com erros, construir redes, encontrar inspiração e paixões, e ter paciência durante o processo de construção de um negócio.
O documento fornece orientações para quem deseja abrir um negócio, discutindo comportamentos importantes como buscar oportunidades, estabelecer metas e planejar, além de detalhar os passos para desenvolver um plano de negócios abordando aspectos de marketing, vendas, operações, administração, jurídicos e financeiros. O autor disponibiliza seus contatos no final para apoiar interessados.
O documento apresenta a primeira aula de um curso de empreendedorismo ministrado pelo professor Nivaldo J Silva na UNISAL. A aula introduz o tema do empreendedorismo e discute conceitos como tipos de empreendedores, competências empreendedoras e a autoavaliação do perfil empreendedor. A ementa do curso é apresentada, assim como o método das aulas e sites recomendados para o empreendedor.
O documento discute o que é ser empreendedor, fornecendo definições de diversos autores e características-chave. Também aborda o processo empreendedor, incluindo identificar oportunidades, desenvolver planos de negócios, obter recursos e gerenciar o negócio. Finalmente, discute fatores que influenciam o empreendedorismo e mitos versus verdades sobre empreendedores.
O documento discute o empreendedorismo no contexto educacional. Ele descreve como as escolas estão desenvolvendo habilidades empreendedoras nos alunos, como iniciativa, autonomia e capacidade de lidar com desafios, para que se tornem profissionais competentes e capazes de enfrentar um mercado de trabalho em constante mudança. Projetos como feiras de empreendedorismo estudantil são citados como exemplos de como as escolas preparam os alunos para o mundo dos negócios.
O documento descreve a história do empreendedorismo ao longo dos séculos XVII-XX. No século XVII, os empreendedores assinavam contratos com governos para fornecer bens e serviços. Nos séculos XVIII-XIX, empreendedores e capitalistas foram diferenciados. Nos séculos XIX-XX, empreendedores eram vistos como administradores. O termo "empreendedorismo" surgiu em 1950 e o conceito de risco foi introduzido nas décadas de 1960-70.
O documento discute a importância crescente do empreendedorismo no Brasil e no mundo. Aborda como o empreendedorismo tem sido difundido no Brasil a partir da década de 1990 devido à estabilização econômica, globalização e altas taxas de desemprego. Também destaca iniciativas de apoio ao empreendedorismo no Brasil e experiências internacionais que demonstram os benefícios do empreendedorismo para o crescimento econômico.
The tribological properties of textured surfaces of brass and aluminum were compared with untextured surfaces of the same specimens. This was done to research the effect of micro-dimples and their geometry parameters in reducing the wear of samples tested under lubricated contact with a ball-on-flat reciprocating tribometer.
Reducing the hygroscopic swelling in MEMS sensor using different mold materia...IJECEIAES
Today, Hygroscopic swelling is one of the biggest challenging problem of Epoxy mold compound (EMC) in packaging with Microelectromechanical system (MEMS) devices. To overcome this hygroscopic swelling problem of EMC and guard the devices, MEMS devices are molded in this paper with different Mold Compound (MC) i.e. titanium and ceramic etc. during their interconnection with the board. Also, a comparatively performance analysis of this various mold compound with MEMS pressure sensor has been studied in this paper at 60% humidity, 140 mol/m 3 saturation concentration and 25 o C. It was observed that hygroscopic swelling does not take place in the titanium mold compound. But, titanium is very costly so we have to consider something cheaper material i.e. ceramic in this paper. The Hygroscopic swelling in Ceramic Mold Compound after 1 year is nearly 0.05 mm, which is very less than epoxy.
Tribology is the study of friction, wear, and lubrication, which is important for mechanical systems. It has become evident that high friction and wear account for over 6% of GDP loss through wasted resources. Tribology focuses on surface interactions and properties at micro and nano scales to understand and control friction and wear. Improved tribological knowledge through understanding concepts like contact mechanics, lubrication, and materials selection can reduce energy use, extend product lifetimes, and benefit the environment through potential savings.
Impact testing is an effective method to evaluate the fatigue resistance of coatings under cyclic loading conditions. The authors developed an impact testing procedure using a hard carbide ball that repetitively impacts coated specimens. Three HVOF thermal spray coatings on a P91 steel substrate - WC-CoCr, CrC-NiCr, and Ni20Cr - were tested. The WC-CoCr coating showed superior fatigue strength, sustaining impacts without cohesive delamination failure. In contrast, the brittle CrC-NiCr coating developed microcracks leading to total coating removal after 600,000 impacts. The impact testing results provide insight into coating failure mechanisms and guidance for optimizing coated components used in steam turbines.
Microelectromechanical systems (MEMS) are a fast-growing field in microelectronics. MEMS are commonly used as actuators and sensors with a wide variety of applications in health care, automotives, and the military.
Adhesion is linked with surface forces like capillary pressure and is thus detrimental at the
nanoscale where body forces are negligible. It can lead to instant failure during fabrication and
operation but it can also lead to overtime failure because of induced friction and wear. However,
when it is possible, coating a device with hydrophobic materials reduces drastically that mechanism.
Understanding how adhesion works is crucial to design new systems and to enable new
technologies. Two models (JKR and DMT) are studied in this paper and model adhesion in different
cases. Photolithography and particularly the release step must be carefully designed to prevent
contamination and stiction. Materials must be chosen and designed wisely to prevent adhesion
failure during operation but lubricants can be used to reduce its impact as well as the impact of
friction and wear.
Steps towards mathematical modeling of microcasting process from mesoscopic p...Alexander Decker
This document summarizes steps towards mathematical modeling of microcasting from a mesoscopic point of view. It discusses that microcasting involves producing small metallic parts with high aspect ratios using molten metal cast into microstructured molds. The document then presents governing differential equations that can be used to model fluid flow in microcasting from a mesoscopic scale perspective. Specifically, it discusses that the Navier-Stokes equations can be applied given channel dimensions are far enough from molecular scales. Lastly, it provides classifications for channel size and discusses modeling approaches for multi-phase systems in microcasting.
Steps towards mathematical modeling of microcasting process from mesoscopic p...Alexander Decker
This document discusses steps towards developing a mathematical model of the microcasting process from a mesoscopic point of view. It begins by introducing microcasting and its applications. It then discusses structural dimensions in microcasting and challenges associated with decreasing size scales. The document outlines different scales (macro, meso, micro, nano) for modeling casting and solidification phenomena. It presents the governing differential equations needed to model fluid flow at the mesoscale level in microcasting. Finally, it discusses channel classification and indicates that flow channels in microcasting are typically in the range of mesochannels.
Design and Fabrication of wear Testing MachineIJMERJOURNAL
ABSTRACT: Wear is damage to a surface as a result of relative motion with respect to another substance. One key point is that wear is damage and it is not limited to loss of material from the surface. However, loss of material is definitely one way in which a part can experience wear. In the older definitions of wear there used to be a greater stress on the “loss of material” , however now-a-days the newer and more general definitions of wear is very natural to the design or device engineer , who thinks of wear in terms of a change to a part that effects its performance. The focus is on the change which may be translated to damage. The implication of this generalization will be further explored in the discussion of wear measures. A mass measurement does not measure displaced materials. In addition it is sensitive to wear debris and transferred material that becomes attached to the surface and can not be removed. This material does not necessarily have to be from the same surface; it can from the counter face as well.
Friction and wear are two key factors that are detrimental at the nanoscale, because they are
linked with surface forces. It is important to understand their mechanisms and to find ways to
overcome them. At the macroscale, lubricants are classically used to do so and are well understood. However, those lubricants cannot be readily used at the nanoscale and other lubrication methods must be found. In this paper I will focus on two new potential lubricants that were tested in Microelectromechanical Systems (MEMS): ionic liquid films and alcohol vapor. They are both very different and are not used in the same situations but they both show great potential. In fact, thanks to the alcohol vapor lubricant a device did not show signs of wear after 11 days of operation, whereas it failed within minutes in the absence of alcohol. No signs of wear were seen after 100 cycles of operation of a device with ionic liquid film but were observed in an uncoated device.
To ensure good adhesion between a 200 nm thick silicon dioxide layer and a 4.5 μm thick hardcoat polymeric coating, a better understanding of mechanisms of adhesion at this interface is needed. To reach this purpose, focus is placed on two axes: characterizing mechanical properties of materials composing the system and in parallel, finding an applicable and effective method to quantify adhesion. Small dimension of SiO2 thin film makes it challenging to accurately characterize it. Hence the use of both nano-indentation and AFM to attempt assessment of SiO2 thin film elastic modulus Ef; taking into account limitations and uncertainty associated with each technique. Elastic modulus of SiO2 thin film determined by nano-indentation is roughly 50 GPa on a wafer substrate and 15 GPa on a lens substrate. As for AFM, modulus measured is approximately 56 GPa on a wafer substrate and 22 GPa on a lens substrate. This highlights significant influence of substrate for both techniques. Impact on mechanical properties between SiO2 thin films under different intrinsic stresses was also investigated. Results suggest that higher density of SiO2 thin film leads to higher elastic modulus.
To quantify adhesion, micro-tensile and micro-compression tests were performed. Micro-tensile experiments give ultimate shear strengths of hardcoat-substrate interface ranging from 9 to 14 MPa. Values of energy release rates of SiO2 / Hardcoat, range from 0.1 J/m² to 0.5 J/m², depending on moduli values found on wafer or lens substrate.
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Seminar on Electrochemical Surface StructuringSRINJOY GUHA
This document presents information on electrochemical surface structuring techniques. It discusses electrochemical machining (ECM) and electrochemical micro machining (EMM), noting they are commonly used for surface structuring to enhance tribological properties. When ECM is applied at the micro scale, it is termed EEM. The document outlines techniques for controlling surface topography at the micrometer and nanometer scales using EMM and describes recent developments in EMM for titanium surface structuring, including oxide film laser lithography and producing well-defined multi-scale surface structures.
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The document discusses the history and development of tribology as a field of science. It begins by covering early understandings of friction from da Vinci to Reynolds' breakthrough on hydrodynamic lubrication in the late 19th century. It then defines tribology as the study of friction, wear, and lubrication between interacting surfaces. The document goes on to discuss practical objectives in tribology like minimizing friction and wear, and covers topics such as the laws of friction, wear mechanisms, and lubrication techniques like hydrostatic lubrication.
A CRITICAL REVIEW ON DIFFERENT TYPES OF WEAR OF MATERIALSIAEME Publication
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Understanding Inductive Bias in Machine LearningSUTEJAS
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Advanced control scheme of doubly fed induction generator for wind turbine us...IJECEIAES
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Introduction- e - waste – definition - sources of e-waste– hazardous substances in e-waste - effects of e-waste on environment and human health- need for e-waste management– e-waste handling rules - waste minimization techniques for managing e-waste – recycling of e-waste - disposal treatment methods of e- waste – mechanism of extraction of precious metal from leaching solution-global Scenario of E-waste – E-waste in India- case studies.
DEEP LEARNING FOR SMART GRID INTRUSION DETECTION: A HYBRID CNN-LSTM-BASED MODELgerogepatton
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Acquisition (SCADA)-based smart grids to facilitate real-time data gathering and control functionalities.
Robust Intrusion Detection Systems (IDS) are necessary for early threat detection and mitigation because
of the interconnection of these networks, which makes them vulnerable to a variety of cyberattacks. To
solve this issue, this paper develops a hybrid Deep Learning (DL) model specifically designed for intrusion
detection in smart grids. The proposed approach is a combination of the Convolutional Neural Network
(CNN) and the Long-Short-Term Memory algorithms (LSTM). We employed a recent intrusion detection
dataset (DNP3), which focuses on unauthorized commands and Denial of Service (DoS) cyberattacks, to
train and test our model. The results of our experiments show that our CNN-LSTM method is much better
at finding smart grid intrusions than other deep learning algorithms used for classification. In addition,
our proposed approach improves accuracy, precision, recall, and F1 score, achieving a high detection
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Presentation of IEEE Slovenia CIS (Computational Intelligence Society) Chapte...University of Maribor
Slides from talk presenting:
Aleš Zamuda: Presentation of IEEE Slovenia CIS (Computational Intelligence Society) Chapter and Networking.
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IEEE Slovenia GRSS
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11TH INTERNATIONAL CONFERENCE ON ELECTRICAL, ELECTRONIC AND COMPUTING ENGINEERING
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The rivalry between prominent international actors for dominance over Central Asia's hydrocarbon
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referred to as the "New Great Game." This research centres on the power struggle, considering
geopolitical, geostrategic, and geoeconomic variables. Topics including trade, political hegemony, oil
politics, and conventional and nontraditional security are all explored and explained by the researcher.
Using Mackinder's Heartland, Spykman Rimland, and Hegemonic Stability theories, examines China's role
in Central Asia. This study adheres to the empirical epistemological method and has taken care of
objectivity. This study analyze primary and secondary research documents critically to elaborate role of
china’s geo economic outreach in central Asian countries and its future prospect. China is thriving in trade,
pipeline politics, and winning states, according to this study, thanks to important instruments like the
Shanghai Cooperation Organisation and the Belt and Road Economic Initiative. According to this study,
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governments. This success may be attributed to the effective utilisation of key tools such as the Shanghai
Cooperation Organisation and the Belt and Road Economic Initiative.
Comparative analysis between traditional aquaponics and reconstructed aquapon...bijceesjournal
The aquaponic system of planting is a method that does not require soil usage. It is a method that only needs water, fish, lava rocks (a substitute for soil), and plants. Aquaponic systems are sustainable and environmentally friendly. Its use not only helps to plant in small spaces but also helps reduce artificial chemical use and minimizes excess water use, as aquaponics consumes 90% less water than soil-based gardening. The study applied a descriptive and experimental design to assess and compare conventional and reconstructed aquaponic methods for reproducing tomatoes. The researchers created an observation checklist to determine the significant factors of the study. The study aims to determine the significant difference between traditional aquaponics and reconstructed aquaponics systems propagating tomatoes in terms of height, weight, girth, and number of fruits. The reconstructed aquaponics system’s higher growth yield results in a much more nourished crop than the traditional aquaponics system. It is superior in its number of fruits, height, weight, and girth measurement. Moreover, the reconstructed aquaponics system is proven to eliminate all the hindrances present in the traditional aquaponics system, which are overcrowding of fish, algae growth, pest problems, contaminated water, and dead fish.
Eric Nizeyimana's document 2006 from gicumbi to ttc nyamata handball play
Friction and wear in mems
1. Friction and Wear in MEMS: technology issues
and new potential lubrication methods
Friction and wear are two key factors that are detrimental at the nanoscale, because they are
linked with surface forces. It is important to understand their mechanisms and to find ways to
overcome them. At the macroscale lubricant are classically used to do so and are well understood.
However, those lubricants cannot be readily used at the nanoscale and other lubrication methods
must be found. In this paper I will focus on two new potential lubricants that were tested in
Microelectromechanical Systems (MEMS): ionic liquid films and alcohol vapor. They are both
very different and are not used in the same situations but they both show great potential. In fact,
thanks to the alcohol vapor lubricant a device did not show signs of wear after 11 days of operation,
whereas it failed within minutes in the absence of alcohol. No signs of wear were seen after 100
cycles of operation of a device with ionic liquid film but were observed in an uncoated device.
Introduction
From smartphones to cars to smart drugs, nanotechnology and microelectromechanical systems
(MEMS) have a wide range of applications and opportunities, such as accelerometers in airbags,
sensors and actuators. Yet we can only see the tip of the technology that is currently revolutionizing
our everyday life. Feynman’s visions1 are coming true but although we might swallow a camera,
we cannot swallow a nano surgeon robot yet. While there is no lack of ideas, there are a lot of
technological constraints to overcome to make them into a device.
1See R.P. Feynman, There’s plenty of room at the bottom, Caltech Engineering and Science, Vol. 23:5, pp.22-36,
1960
2. Friction and Wear in MEMS: technology issues and new potential lubrication methods 2
Both fabrication and reliable operations are limited by our current technology. Nanotribology
plays a major role in constraining MEMS: adhesion, friction and wear are three issues impacting
the industry. In this review, I focus on friction and wear during the operation of MEMS and on the
failure mechanisms they lead to. Even in devices designed and built with low-friction materials,
this issue still persists: we might need a higher voltage source than allowed by a design to overcome
static friction [1]. However, friction is also source of abrasive wear.
Even in MEMS with no contacting surfaces, wear (fluid erosion for example) limits the lifetime
of a device and thus renders a lot of technologies non-viable. Since, we cannot afford to change
MEMS in a complete device every other week, commercialized MEMS devices have non-moving
parts or very restricted motion. The study of those nanotribology issues can lead to the development
of more complex technologies such as nano/micro motors, and gear systems.
1 Current technology: limits and opportunities
MEMS are divided into four classes: class I MEMS without moving or impacting parts, class
II MEMS with moving parts but without rubbing or impacting surfaces, class III MEMS with
impacting parts but without rubbing parts, and finally class IV MEMS with rubbing parts. The
latter class of MEMS experiences the most friction and wear because of the rubbing natures of
those devices. When scaling down structures, the size dependence of forces renders surface forces
predominant over volume forces. This scaling effect leads to an aggravated importance of friction
and wear which drastically reduces performances and lifetime of MEMS [2].
During operation, MEMS can be exposed to different environments and conditions: some will
be used in a relatively humid environment, others will experience large accelerations or will be
3. Friction and Wear in MEMS: technology issues and new potential lubrication methods 3
exposed to chemicals. It is thus important to understand the failure mechanisms and their origins.
However, should we significantly reduce wear and friction, we would be able to build viable class
IV MEMS such as micromotors, microactuators and optical switches.
2 MEMS tribology
As discussed previously, MEMS applications are limited today by operation failure. The failure
mechanisms are scale dependent [3] and include friction and wear. As the dimensions of a device
reduce from 1 mm to 1 micron, the area gets a million times smaller and the volume a billion
times smaller. This implies that friction and surface tension are about a thousand times larger than
inertial or electromagnetic forces [4]. Friction, wear or contamination are known to alter MEMS
device performances or lead to their irreversible failure.
2.1 Friction
Several models have been developed to describe friction at the nanoscale for a single asperity on
a flat [1]. Each has its own domain of validity and limitations, but they show that friction is de-
pendent on the real area of contact and that, at the nanoscale, friction does not follow Coulomb’s
law and instead is proportional to velocity [3]. Adhesion is considered as a major contributor to
friction.
In Tambe and Bushan [3], dry, lubricated, hydrophilic and hydrophobic surfaces are studied
with different rest times, sliding velocities and environment conditions (relative humidity and tem-
perature). From the results presented in Figure 1, the authors infer that the scan size dependence of
friction is independent of velocity and that friction is proportional to the scan size. This property
4. Friction and Wear in MEMS: technology issues and new potential lubrication methods 4
is attributed to surface roughness.
Figure 1: Velocity dependence of the friction force for different scan sizes. Friction appears to be higher with
larger scan size for all velocities and the trend lines are parallel.[3]
It also appears that higher rest time leads to higher adhesion, especially in soft materials that
can conform to the asperities and thus have larger contact area. Higher relative humidity and lower
temperatures enables the condensation of water molecules on hydrophilic surfaces and thus leads
to higher adhesion, which causes more difficulty in sliding and thus higher friction. No significant
changes are observed on hydrophobic surfaces.
As presented in Figure 2, the velocity dependence of friction is more complex. Some samples,
silicon (100), PDMS and Z-15 (perfluoropolyether lubricant) exhibit a decrease of the friction
force with higher velocities in the microscale but an increase in the nanoscale! Diamond-like
carbon (DLC), self-assembled monolayer hexadecanethiol (HDT) and Z-DOL (another perfluo-
ropolyether lubricant) are fairly independent of velocity in the microscale but HDT and Z-DOL
have an increasing friction with velocity whereas DLC’s friction force decreases with higher ve-
locity in the nanoscale. However, friction is significantly higher in the microscale than in the
5. Friction and Wear in MEMS: technology issues and new potential lubrication methods 5
nanoscale [3]. Friction is a source of wear, but friction can also result from wear [5]. As debris are
formed due to wear, third body interactions start appearing, leading to higher friction.
Figure 2: Evolution of the friction force for the different samples in the nano- and microscale as a function of
velocity. The different graphs show no consistent behavior from one material to another and from one scale
to another. [2]
Friction is often linked with stick-slip behavior, preventing smooth sliding. This property and
high values of the static coefficient of friction mean that of higher power or forces are required
to achieve steady state motion [1]. Friction by its nature leads to abrasive wear and to plastic
deformation, both leading to failure of a device.
2.2 Wear
Wear has multiple origins and is mostly attributed to adhesion and friction. It can be useful in
the macroscale, when polishing a surface with sand paper for example, but like fatigue it can
6. Friction and Wear in MEMS: technology issues and new potential lubrication methods 6
lead to catastrophic failure over time. This is especially true in the microscale, where, as already
discussed, surface energies and friction are dominant. Wear is linked with the smoothing out of
materials, the removal of materials and generally the alteration of the shape and properties of the
system.
Wear is the main reason why a lot of devices are not viable; without proper protection, some
will fail within minutes of operation [5]. This fact shows why wear needs to be assessed and il-
lustrates why today only MEMS with no rubbing surfaces are commercialized. Wear can lead to
different phenomena: one of the most common is the creation of debris [2, 5]. Debris will act as a
third body and will increase adhesion and friction. Debris are formed as asperities rub against the
opposing surface and are indicators of the local removal of a layer.
As layers are locally removed, other mechanisms can take place. For example, if the natural
silicon dioxide is locally peeled off [1, 5], the bare silicon surface will be exposed. Silicon sur-
faces have dangling bonds and if the passivation layer is not replenished fast enough, tribological
reactions will lead to chemical junctions between two silicon surfaces. Those junctions are strong
enough to pull out other silicon grains, further wearing out the device. Any factor that increases
friction or adhesion will also increase wear. For example, high relative humidity can lead to high
wear in silicon and silicon dioxide [1].
Although lubricants can be used to reduce wear, they are also subject to this triblogical phe-
nomenon. If the lubricant layer is not constantly replenished it will get worn out and rendered
useless over time [2, 5].
7. Friction and Wear in MEMS: technology issues and new potential lubrication methods 7
3 Ionic liquid films
Classically, lubricants have been used to reduce friction and wear. However lubricants must comply
with several requirements. Indeed, a lubricant must chemically bond to the device, be long-lasting
and withstand the same environments and conditions the device is exposed to. Two examples
of common lubricant are the perfluoropolyether (PEFE) Z-TETRAOL and PEFE Z-DOL which
are widely used for their excellent properties, in particular in the hard disk drive industry [3, 2].
However those lubricants are insulators and may not be suitable in every devices.
3.1 Principle
Like the two aforementioned lubricants, ionic liquid films are specifically designed to resist to
the regular operation of MEMS devices but are about twice as thin, from 0.5 nm to 2.5 nm dep-
dending on the treatment vs 1 nm to 7nm for the Z-TETRAOL [2]. They are strongly bonded to
the substrate by electrostatic interactions which offers good lubrication property in comparison to
classically covalently-bonded fluids. They show no volatility and a high decomposition tempera-
ture, which enables their use in a wide range of temperatures. Moreover, they exhibit great heat
transfer properties and, thanks to their ionic nature, they are conductors. This conducting property
has two major advantages: it enables electrical applications and also prevents charge build-up in
the devices, reducing the risk of electrical breakdown and arcing, further reducing wear.
At least one of the two ions is organic and one or both ions have a delocalized charge to pre-
vent the formation of a crystal lattice. When using imidazolium cations, the coefficient of friction
is reduced by the presence of long organic side chains. Oxygen-rich anions reduce wear.
Two ionic liquid films have been evaluated and compared to each other: 1-butyl-3-methylimidazolium
8. Friction and Wear in MEMS: technology issues and new potential lubrication methods 8
hexafluorophosphate (BMIM-PF6) and 1-butyl-3-methylimidazolium octyl sulfate (BMIM-OctSO4).
3.2 Results
The two ionic lubricants have been tested in different conditions and the results have been com-
pared to similar experiments on PEFE Z-TETRAOL. The two ionic lubricants have been either un-
treated, thermally treated or thermally treated and rinsed. The untreated sample is completely un-
bonded and the rinsed one is completely bonded whereas the not-rinsed sample is partially bonded.
For each of the six samples, surface potential has been measured using a Kelvin probe atomic
atomic force microscope (AFM) and adhesion, friction and wear have been studied using an AFM
[2]. The results are presented in Figure 3. The two ionic liquid films tested present approximately
the same behavior as the Z-TETRAOL. From this result, we can infer that the two ionic liquids are
fairly good lubricants.
However, the results show that the untreated lubricant in both cases leads to a worse behav-
ior than the bare silicon or silicon natural oxide (higher coefficient of friction). Indeed, as the
molecules are not bonded they are moving freely and are likely to form a meniscus on the AFM
tip and drastically increase adhesion and friction. Although the treated and rinsed samples exhibit
a better behavior regarding friction, they have the worst surface potential and thus the most sur-
face rearrangement (and wear), yet they have better results than the Z-TETRAOL. This can be
explained by the lack of mobile lubricant to replenish worn out immobile lubricant.
On the other hand, the partially bonded coatings show both the lowest coefficient of friction
and the lowest surface potential. They also have the lowest number of cycle dependency. These
coatings have similar results and appear to be very good lubricants.
9. Friction and Wear in MEMS: technology issues and new potential lubrication methods 9
Figure 3: Summary of the results: a. Comparison of the coefficient of friction of the different samples and
silicon. b. Comparison of the average surface potential of the different samples and silicon. c. Comparison
of the evolution of the coefficient of friction with the number of cycles for the different samples and silicon. [2]
The difference in surface potential between the two ionic liquid films and the Z-TETRAOL is
attributed to the build-up of charges in the Z-TETRAOL whereas charges are immediately dissi-
10. Friction and Wear in MEMS: technology issues and new potential lubrication methods 10
pated in the conducting ionic liquid films. Based on these findings, ionic liquid films show strong
potential as MEMS lubricants.
3.3 Limits
The ionic liquids show potential but they also have some shortcomings. In the experiments, only
a hundred cycles were taken into account for measuring wear and the BMIM-OctSO4 starts to
show wear after only 60 cycles in the best scenario of the partially bonded lubricant. However the
coefficients of friction of the Z-TETRAOl and the BMIM-PF6 are only studied over 100 cycles
and did not show signs of wear when they stopped the experiment [2]. Although Z-TETRAOL
has been extensively studied, the behavior of both ionic liquids has not been reported for longer
use. I believe they have a real potential, but 100 cycles might only represent a few minutes of
operation. Hence, wear of the ionic lubricants needs to be analyzed further to check if they really
meet anti-wear behavior criteria.
As mentioned, one interesting feature of the ionic liquids is their conducting property that en-
ables the use of lubricants in MEMS where insulating lubricants cannot be used. However and
conversely, ionic lubricants cannot be used in MEMS devices that require an insulator: a capaci-
tance for instance. Thus Z-TETRAOL remains a lubricant of choice in such cases and the industry
will have to carefully assess their choice of lubricants, especially in a MEMS device that requires
both behaviors.
However further work show that those lubricants have tremendous potential. As discussed
in this review, the BMIM-PF6 seems a good lubricant. Other studies have thus been conducted
with other fluorine containing anions and other cations. It appear that a combination of perfluo-
11. Friction and Wear in MEMS: technology issues and new potential lubrication methods 11
roalkylphosphate (FAP) as the anion with an imidazolium cation show even more potential and is
a more stable lubricant [6].
4 Alcohol adsorption
A less traditional way to reduce wear and friction is to use a vapor-phase lubrication. Depending
on the saturation pressure of lubricant, the coating replenishes itself over time until the system runs
out of vapor.
4.1 Principle
Alcohol adsorption lubrication is a potential new vapor-phase lubricant. The problem with classi-
cal lubricant is that they need to be conformally deposited on the substrate and chemical or physical
vapor deposition techniques cannot comply with this requirement. However, in vapor-phase lubri-
cation (VPL), such a coating is achieved by the adsorption of the gas molecule on the MEMS
surfaces [5].
Molecules can desorb from the surface, but as long as equilibrium is reached and the pressure
is maintained, another one will adsorb automatically and replenish the coating. One of the main
issues with VPL is the need for high temperatures or catalytic precursors to enable the coating.
However, alcohol presents interesting vapor pressure at ambient temperatures and can thus cir-
cumvent this issue.
Although the mechanism is not known, when using alcohol adsorption, high molecular weight
oligomers (a polymer comprised of only a few monomers) form during operation and further dras-
tically reduce friction and wear [5]. The wear protection mechanism is simple: alcohol molecules
12. Friction and Wear in MEMS: technology issues and new potential lubrication methods 12
adsorb on the surface and disrupt the equilibrium of strongly adsorbed water molecules, driving
their removal. Water is known to increase wear and friction in silicon and silicon dioxide. The
polymer formation is referred to as an in-situ lubrication method.
4.2 Results
The lubrication properties of alcohol adsorption were evaluated at the macroscale with a ball-on-
flat tribometer, at the microscale with a sidewall MEMS tribometer and at the nanoscale with an
AFM [5]. Although, the lubricant exhibited excellent properties in the three scales, I will focus
on the microscale. The different experiments were conducted with a constant alcohol-vapor pres-
sure and thus concentration in a stainless steel chamber. The MEMS device was coated with a
chemisorbed organic monolayer, rendering the surfaces hydrophobic.
The alcohol used in the experiments is pentan-1-ol (or 1-pentanol). To assess its influence on
Figure 4: isotherm thickness for pentan-1-ol. It appears that coverage is obtained at P/Psat=10%. [5]
the tribology, the authors determined the isotherm thickness. It appears that coverage is reached
when P/Psat = 10%, where P is the pressure and Psat is the vapor saturation pressure, and higher
ratios do not yield significantly better results, which are presented in Figure 4. The spectrum shows
that the water adsorption equilibrium is shifted and that water molecules are desorbing from the
13. Friction and Wear in MEMS: technology issues and new potential lubrication methods 13
surfaces whereas alcohol molecules are being adsorbed [5].
Then lifetime, defined as the number of cycles the device oscillates under a given load before
failure, was assessed by measuring the friction coefficient over time. Without the alcohol vapor,
the device fails in less than two minutes of operation ( 104 cycles), which reveals high wear and
friction. However at 95% of Psat, the device was turned off by the operator and did not show
wear. At 15% a device did not fail and had no sign of wear even after eleven days of operation,
but a liquid build-up was observed. Those results are presented in Figure 5. The liquid build-up is
Figure 5: a: Friction coefficient over time for 0%, 15% and 95% Psat. b: On the left a SEM image of the
device at 15% Psat after 108 cycles and on the right an unused device. In a, we can see that 15% is enough
to prevent failure. In b, we can observe a liquid build-up circled in white. [5]
circled in white in Figure 5.b and is attributed to high molecular weight oligomeric species. The
liquid deposits are observed near the tall asperities and do not dissolve in the alcohol. The same
formation is observed in the macroscale experiment and the authors have been able to determine
it was oligomeric species using TOF-SIMS spectroscopy and analyzing the peaks. The reaction
mechanism is not known, but the material is only formed in the contact region during sliding and
appears to further reduce friction and wear [5].
When alcohol vapor is no longer fed to the system, friction and wear revert back to their usual
14. Friction and Wear in MEMS: technology issues and new potential lubrication methods 14
behavior, indicating that the lubricant must be continuously replenished during operation. Unlike
typical solid coating, the alcohol lubricant does not change the device functionality, which is also
a great property.
4.3 Limits
Although alcohol adsorption shows tremendous potential in MEMS devices applications, some
points must be assessed. The liquid build-up in the microscale experiment has not been identified.
The authors believe it is the same oligomeric species as observed in the macroscale experiment, but
they are not certain of it [5]. This lubrication requires constant vapor feeding to the system during
operation. How can that be accomplished in common operation, by a customer for example? It also
means that it cannot be used in a MEMS device that requires a vacuum or a very specific pressure
to operate. Moreover, the vapor may affect the insulator permittivity of a capacitance. Hence, the
lifetime of MEMS is improved by four orders of magnitude with alcohol adsorption lubrication,
but this is not suited for all applications. Furthermore, the experiments were only conducted with
hydrophobic surface coatings. The surface energies of the hydrophobic surfaces may help the
alcohol vapor shift the water adsorption equilibrium and such good results may not be obtained
with hydrophilic surfaces. Further studies by the Dugger, Kim et al show that relative humidity
above 25-30% can drastically reduce the performance of the lubrication method in MEMS.
In a patent the authors obtained in 2011, they claim that a small pump could be built-in with
a supply that should last a long time [7], but they do not specify that time. They also claim that
polymers saturated with alcohol could provide a long lasting pentan-1-ol source. This has been
assessed in Dugger et al [8]. They found that such polymers can be thermally activated to deliver
15. Friction and Wear in MEMS: technology issues and new potential lubrication methods 15
the alcohol vapor in the system. Future work is needed to evaluate the integration of those polymers
in MEMS package and their lifetime.
Conclusion
Friction and wear are two very limiting factors in today’s technology. A lot of MEMS applications
are rendered non-viable because they involve sliding surfaces and might fail within minutes of
normal operation. Sliding, velocity, temperature, relative humidity and surface roughness are key
parameters that influence the tribology of MEMS. For these reasons, it is important to study the
failure mechanisms of such devices and to find ways to reduce them drastically. Usually friction
increases with velocity at the small scale, but it appears that this behavior is dependent on the
material and whether the system is at the nano- or the microscale.
Two new lubrication methods, ionic liquids films and alcohol adsorption, show great potential.
Both lubricants reduce friction and wear. The latter method even led to no wear after eleven days
of operation. Ionic liquid films appear as a good alternative to the classic Z-TETRAOL when
an insulating lubricant cannot be used, ionic liquids are conductors by nature. Moreover, those
lubricants can potentially reduce air emissions associated with hydrocarbon oxidation observed
in hydrocarbon based oils. They are considered ”green lubricants” [2]. However, the lifetime of
devices protected against friction and wear using this method must be studied further and over
longer periods of time.
Alcohol adsorption shifts the water adsorption equilibrium and tend to drive the removal of
water molecules, hence reducing wear in silicon and silicon dioxide for example. It also leads to
16. Friction and Wear in MEMS: technology issues and new potential lubrication methods 16
the formation of an olygomer build-up which further decreases wear. However, the behavior of
this lubrication method must be studied in the case of hydrophilic surfaces. For both lubricants, a
question must also be answered: how will the alcohol vapor be fed to the MEMS device or how
will the ionic liquid be replaced when completely worn out? The two proposed methods show
nonetheless incredible potential and might very well lead the way to viable class IV MEMS.
17. Friction and Wear in MEMS: technology issues and new potential lubrication methods 17
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