Tribology and Mechanics of Magnetic Storage Devices

ISBN-13: 9780387946276 / Angielski / Twarda / 1996 / 1125 str.

Bharat Bhushan

Opis

Since January 1990, when the first edition ofthis first-of-a-kind book appeared, there has been much experimental and theoretical progress in the multi disciplinary subject of tribology and mechanics of magnetic storage devices. The subject has matured into a rigorous discipline, and many university tribology and mechanics courses now routinely contain material on magnetic storage devices. The major growth in the subject has been on the micro- and nanoscale aspects of tribology and mechanics. Today, most large magnetic storage industries use atomic force microscopes to image the magnetic storage components. Many companies use variations of AFMs such as friction force microscopes (FFMs) for frictional studies. These instruments have also been used for studying scratch, wear, and indentation. These studies are valuable in the fundamental understanding of interfacial phenomena. In the second edition, I have added a new chapter, Chapter 11, on micro and nanoscale aspects of tribology and mechanics of magnetic storage compo nents. This chapter presents the state of the art of the micro/nanotribology and micro/nanomechanics of magnetic storage components. In addition, typographical errors in Chapters 1 to 10 and the appendixes have been corrected. These additions update this book and make it more valuable to researchers of the subject. I am grateful to many colleagues and particularly to my students, whose work is reported in Chapter 11. I thank my wife, Sudha, who has been forbearing during the progress of the research reported in this chapter."

Spis treści

1. Introduction.- 1.1 Definition and History of Tribology.- 1.1.1 Definition.- 1.1.2 History.- 1.2 Industrial Significance of Tribology.- 1.3 Physics of Magnetic Recording.- 1.3.1 Basic Principle.- 1.3.2 Vertical Recording.- 1.3.3 Methods of Encoding Binary Information.- 1.3.4 Design Considerations.- Recording Density.- Reproduced Signal Amplitude.- Signal-to-Noise Ratio.- 1.4 Magnetic Data-Storage Systems.- 1.4.1 History of Magnetic Recording.- Storage Hierarchy.- 1.4.2 Examples of Modern Data-Storage Systems.- Tape Drives.- Floppy Disk (Diskette) Drives.- Rigid Disk Drives.- 1.4.3 Head Materials.- Permalloys.- Mu-Metal and Hy-Mu 800B.- Sendust Alloys.- Alfenol Alloys.- Amorphous Magnetic Alloys.- Ferrites.- Some Examples of Head Constructions.- 1.4.4 Media Materials.- Flexible Media.- Rigid Disks.- Functional Requirements.- 1.4.5 Manufacturing Processes of Magnetic Media.- Particulate Tapes.- Particulate Floppy Disks.- Rigid Disks.- References.- 2. Solid Surface Characterization.- 2.1 The Nature of Surfaces.- 2.2 Statistical Analysis of Surface Roughness.- 2.2.1 Average Roughness Parameters.- 2.2.2 Probability Distribution and Density Functions.- 2.2.3 Surface Height Distribution Function.- 2.2.4 Texture Descriptors.- 2.2.5 Distribution and Statistics of the Asperities and Valleys.- 2.2.6 Practical Considerations in Measurement of Roughness Parameters.- Long- and Short-Wavelength Filtering.- Measuring Length.- 2.3 Measurement of Surface Roughness.- 2.3.1 Mechanical Stylus Method.- Surface Mapping.- Measurement of Circular Surfaces.- Relocation.- Replication.- Sources of Errors.- 2.3.2 Optical Methods.- Taper-Sectioning Method.- Light-Sectioning Method.- Specular Reflection Methods.- Diffuse Reflection (Scattering) Methods.- Speckle Pattern.- Optical Interference Methods.- Digital Optical Profiler.- 2.3.3 Fluid Methods.- 2.3.4 Electrical Methods.- 2.3.5 Electron Microscopy Methods.- Reflection Electron Microscopy.- Integration of Backscattered Signal.- Stereomicroscopy.- 2.3.6 Scanning Tunneling Microscopy.- 2.3.7 Atomic Force Microscopy.- 2.3.8 Comparison of Measurement Methods.- 2.4 Measurement of Isolated Asperities.- 2.4.1 Optical Methods.- 2.4.2 Glide Test Methods.- 2.5 Physico-Chemical Characteristics of Surface Layers.- 2.5.1 Deformed Layer.- 2.5.2 Bielby Layer.- 2.5.3 Chemically-Reacted Layer.- 2.5.4 Physisorbed Layer.- 2.5.5 Chemisorbed Layer.- 2.5.6 Surface Tension, Surface Energy, and Wetting.- 2.5.7 Methods of Surface Characterization.- References.- 3. Contact between Solid Surfaces.- 3.1 Physical Properties of Polymers.- 3.1.1 Physical States of Polymers.- 3.1.2 Complex Modulus and Compliance.- 3.1.3 Creep and Relaxation Behavior.- 3.1.4 Temperature and Frequency Effects.- 3.2 Apparent and Real Area of Contact.- 3.3 Analysis of the Real Area of Contact.- 3.3.1 Elastic Contact.- 3.3.2 Limit of Elastic Deformation.- 3.3.3 Optimization of Mechanical Properties and Surface Roughness Parameters of Magnetic Media.- 3.3.4 Calculations of the Real Areas of Contact of Typical Particulate Magnetic Tapes.- Experimental Evidence of Elastic Contacts in Magnetic Tapes.- Changes in Contact Area Because of Tape-Surface Wear.- 3.3.5 Calculations of the Real Area of Contact of Typical Magnetic Rigid Disks.- Optimization of Relative Young’s Moduli of Thin-Film Composite Structure.- 3.4 Measurement of the Real Area of Contact.- 3.4.1 Review of Measurement Techniques.- Electrical-Contact Resistance.- Optical Techniques.- Ultrasonic Technique.- Neutrographic Technique.- Paints and Radioactive Traces.- 3.4.2 Comparison of Different Measurement Techniques.- Calculation for Overestimation of the Contact Area by Various Optical Techniques.- Feasibility of Phase-Contrast Microscopy.- Selection of Optimum Measurement Technique.- 3.4.3 Measurement of Typical Magnetic Tapes.- Test Apparatus and Procedure.- Results and Discussion.- References.- 4. Friction.- 4.1 Introduction.- 4.2 Need for Controlled Friction.- 4.3 Friction Theories.- 4.3.1 The Deformation (Hysteresis) Friction.- 4.3.2 The Adhesional Friction.- Real Area of Contact.- Adhesion Strength of Contacts.- Experimental Evidence of Tabor’s Classical Theory of Adhesion.- Chemical Effects in Adhesion.- Surface Free Energy Theory of Adhesion.- Grain Boundary Effects on Adhesion.- 4.3.3 Macroscopic Theory of Adhesion for Polymers in the Rubbery State.- 4.3.4 Sources of Stiction.- Meniscus/Viscous Effects.- Microcapillary-Evacuation Effect.- Changes in Surface Chemistry.- 4.3.5 Summary.- 4.4 Role of Physical Properties in Magnetic Tapes.- 4.4.1 Description of Reciprocating Friction Test Apparatus and Test Procedure.- Data Analysis.- 4.4.2 Description of Portable Reciprocating Friction Test Apparatus and Test Procedure.- 4.4.3 Effect of Temperature.- Tape-Drive Tests.- 4.4.4 Effect of Curing.- 4.4.5 Effect of Particle Loading.- 4.4.6 Effect of Magnetic-Particle Distribution.- 4.4.7 Effect of Surface Roughness.- 4.4.8 Effect of Humidity.- 4.4.9 Effect of Sliding Velocity.- 4.4.10 Friction Reduction by High-Frequency Oscillations.- 4.4.11 Summary.- 4.5 Role of Interlayer Pressure in Magnetic Tapes.- 4.5.1 Measurement of Creep Compliance and its Relationship to Friction.- Description of Creep Apparatus.- Test Procedure.- Results and Discussions.- Relationship between Creep Compliance and Friction.- 4.5.2 Friction of Tapes with and without Rough Backside.- 4.5.3 Effect of Tape Relaxation.- 4.5.4 Summary.- 4.6 Role of Chemical Properties in Magnetic Tapes.- 4.6.1 Polyurethane Chemistry.- 4.6.2 Thermomechanical Performance of Coatings.- 4.6.3 Chemical Changes of Coatings.- Experimental Procedure.- Results and Discussions.- 4.6.4 Effect of Binder Hydrolysis on the Drive Performance.- Measurement of Stiction.- 4.6.5 Summary.- 4.7 Role of Physical and Chemical Properties in Rigid Disks.- 4.7.1 Description of Various Techniques to Measure Friction/Stiction in Disk Drives.- 4.7.2 Effect of Disk and Head Slider Material Properties.- 4.7.3 Effect of Surface Roughness of Disk and Head Slider.- 4.7.4 Effect of Contact Start-Stops.- 4.7.5 Effect of Liquid Lubricant Film.- 4.7.6 Effect of Organic Adsorbants.- 4.7.7 Effect of Humidity and Temperature.- 4.7.8 Effect of Rest Period.- 4.7.9 Effect of Head Slider Area.- 4.7.10 Effect of Head Slider Load.- 4.7.11 Effect of Drive Acceleration/Velocity.- 4.7.12 Methods to Reduce Friction/Stiction.- 4.7.13 Summary.- References.- 5. Interface Temperature of Sliding Surfaces.- 5.1 Introduction.- 5.2 Thermal Analysis.- 5.2.1 Sliding of Equally Rough Surfaces (Low Stress).- Independent (Flash) Temperature Rise (?f) of an Asperity Contact.- Steady-State Interaction Temperature Rise (?i).- Partition of Heat.- Average Transient Temperature of an Interface.- 5.2.2 Sliding of a Rough Surface on a Smooth Surface (Low Stress).- Steady-State, Independent (Flash) Asperity-Contact Temperature Rise(?f).- Steady-State Interaction Temperature Rise (?i).- Partition of Heat.- Average Transient Temperature of an Interface.- 5.2.3 Transient Conditions.- 5.2.4 Temperature Variation Perpendicular to the Sliding Surface.- 5.2.5 Summary.- 5.3 Application of Analysis to Particulate Magnetic Media.- 5.3.1 Measurement of Thermophysical Properties of Heads and Medium Materials.- Magnetic-Head Materials.- Magnetic Medium Materials.- 5.3.2 Analytical Predictions for Particulate Magnetic Tapes.- Rough-Rough Surface Condition.- Rough-Smooth Surface Condition.- Magnetic Particle (with no Coating of Polymeric Binder) in Contact with the Head Surface.- Transient Conditions.- Temperature Variation Perpendicular to the Sliding Surface.- 5.3.3 Summary.- 5.4 Temperature Measurement of Particulate Magnetic Tapes.- 5.4.1 Tape Transport System.- 5.4.2 Infrared Measurement System.- Operating Equations for the Infrared Microscope.- Spot Size, Detector Response Time, and Temperature Error Interval of the Infrared Microscope.- AGA Thermovision 750.- 5.4.3 Determination of the Tape Radiative Properties.- 5.4.4 Friction Force Measurements.- 5.4.5 Temperature Measurements.- 5.4.6 Correlation of Predicted and Measured Asperity-Contact Temperatures.- 5.4.7 Summary.- References.- 6. Wear Mechanisms.- 6.1 Types of Wear Mechanics.- 6.1.1 Adhesive Wear.- 6.1.2 Abrasive Wear.- 6.1.3 Fatigue Wear.- Rolling Contact Fatigue.- Rolling/Sliding Contact Fatigue.- Sliding Contact Fatigue.- Static Fatigue.- 6.1.4 Impact Wear.- Erosion.- Percussion.- 6.1.5 Corrosive Wear.- 6.1.6 Electrical-Arc-Induced Wear.- 6.1.7 Fretting and Fretting Corrosion.- 6.2 Head Wear.- 6.2.1 Head Body Wear.- Wear Mechanisms of Tape Heads.- Rigid Disk Head Sliders.- Magnetically Dead Layer in Ferrites.- Friction Polymers.- 6.2.2 Thin-Film Read-Write Gap Wear.- 6.2.3 Effect of Head/Tape Properties and Operating Parameters on Tape-Head Wear.- Head Material Hardness.- Head Material Grain Size.- Magnetic Particles.- Tape-Surface Roughness.- Isolated Asperities on Tape Surface.- Multiple Passes.- Tape Tension.- Tape Stiffness.- Sliding Speed.- Humidity.- 6.3 Medium Wear.- 6.3.1 Tape Wear.- Effect of Number of File Passes.- Effect of PVC.- Effect of Environment.- Summary.- 6.3.2 Rigid Disk Wear.- Particulate Disks.- Thin-Film Disks.- 6.4 Head-Medium Wear Studies using Autoradiographic Techniques.- 6.4.1 Head-Tape Interface.- Details of the Tape Drive and Neutron Activation of Ferrite Heads.- Preparation of Radioactive-Ferrite Standards.- Exposures of Tapes on X-Ray Films.- Optical Densitometer Measurements of X-Ray Films.- Measurement of the Average Mass of Radioactive Material on Tape and Drive-Component Surfaces.- Results and Discussions.- 6.4.2 Head-Disk Interface.- 6.5 Head-Tape Wear Studies In-Situ SEM.- 6.5.1 Description of Miniwear Test Apparatus.- 6.5.2 Results and Discussions.- 6.5.3 Summary.- 6.6 Tape-Path Component Wear.- 6.6.1 Description of Accelerated Flange Wear and Friction Test Apparatuses.- 6.6.2 Wear and Friction Data Using Different Flange Materials.- 6.6.3 Wear Data using Different Magnetic Tapes.- 6.6.4 Correlation of Accelerated Wear Data with Tape Drive.- References.- 7. Measurement Techniques of Head and Medium Wear.- 7.1 Head and Tape Wear.- 7.1.1 Accelerated Head Wear Test.- Screening Wear Resistance of Head Materials and Abrasivity of Tapes.- Screening Abrasivity of Magnetic Particles.- Screening Head Contours.- 7.1.2 Tape Durability Tests.- Loop Test.- Loose Debris Test.- Adherent Debris Test.- Abrasion Test.- 7.2 Head Slider and Rigid Disk Wear.- 7.2.1 Accelerated Wear Test.- Accelerated Durability Test.- Accelerated CSS Test.- Accelerated Flyability Test.- Accelerated Lubricant Persistence Studies.- Wear Measurement Techniques.- 7.2.2 Accelerated Corrosion Test.- EC Test.- ABE Test.- References.- 8. Lubrication Mechanisms and Lubricants.- 8.1 Regimes of Lubrication.- 8.1.1 Solid Lubrication.- 8.1.2 Fluid Lubrication.- Hydrostatic Lubrication.- Hydrodynamic Lubrication.- Elastohydrodynamic Lubrication.- Mixed Lubrication.- Boundary Lubrication.- 8.2 Types of Lubricants.- 8.2.1 Solid Lubricants.- Soft Materials.- Hard Materials.- 8.2.2 Liquid Lubricants.- Principal Classes of Lubricants.- Physical and Chemical Properties of Lubricants.- 8.3 Methods of Lubrication in Magnetic Media.- 8.3.1 Internal Versus Topical Lubrication.- 8.3.2 Solid Versus Liquid Lubrication.- 8.4 History of Lubricants for Magnetic Media.- 8.4.1 Tapes and Floppy Disks.- 8.4.2 Rigid Disks.- Particulate Disks.- Thin-Film Disks.- 8.5 Mechanisms of Lubrication in Magnetic Media.- 8.5.1 Tapes and Floppy Disks.- Lubricant Kinetics.- Lubrication by Fatty Acid Esters.- Effect of Humidity.- 8.5.2 Rigid Disks.- Shear Effect on Lubricant Performance.- 8.6 Stability Studies of Magnetic Tape and Floppy Disk Lubricants.- 8.6.1 Experimental Procedures.- 8.6.2 Materials Evaluated.- 8.6.3 Catalytic Effect of Magnetic Oxides.- Oxidation Model.- Iron Oxide-Lubricant Interaction.- 8.6.4 Effect of Contaminants on Oxidation Stability.- 8.6.5 Effect of Additives on Oxidation Stability.- 8.6.6 Effect of Volatility on Oxidation Stability.- 8.6.7 Summary and Outlook.- 8.7 Volatility Studies of Rigid Disk Lubricants.- 8.7.1 Experimental Procedure.- 8.7.2 Volatilization Model.- 8.7.3 Results and Discussion.- References.- 9. Analysis and Measurement of Hydrodynamic Air Films.- 9.1 Lubrication Analysis.- 9.1.1 Head-Tape Interface.- Governing Equations.- Finite Difference Solution.- Finite Element Solution.- 9.1.2 Head-Floppy Disk Interface.- Single-Sided Recording.- Dual-Sided Recording.- 9.1.3 Head-Rigid Disk Interface.- Governing Equations.- Numerical Approach.- Analysis of Two-Rail Taper-Flat-Type Slider.- Analysis of Shaped-Rail Slider.- Analysis of Zero-Load Slider.- Analysis of Transverse Pressurized Contour (TPC) Slider.- 9.1.4 Surface Roughness Effects on Hydrodynamic Lubrication.- Lubrication Equations for Rough Surfaces.- Sheer-Film Analysis.- Squeeze Film Analysis.- Analysis of Head-Tape Interface.- Analysis of Head-Rigid Disk Interface.- Role of Surface Wear.- 9.2 Measurement of Air-Film Thickness.- 9.2.1 Principles of Measurement Techniques.- Optical Interference Technique.- Capacitance Technique.- Laser Doppler Interferometry.- 9.2.2 Measurement Results.- Head-Tape Interface.- Head-Rigid Disk Interface.- References.- 10. Surface Finishing of Ceramic Head Materials.- 10.1 Grinding and Lapping Processes.- 10.1.1 Grinding.- 10.1.2 Lapping.- Free Abrasive.- Fixed Abrasive.- 10.2 Residual Stresses.- 10.2.1 Measurement Techniques.- 10.2.2 Results.- 10.2.3 Discussion.- 10.3 Specific Energy.- 10.3.1 Grinding.- 10.3.2 Lapping.- 10.4 Interface Temperatures.- 10.4.1 Grinding.- Analysis.- Experimental Measurements.- 10.4.2 Lapping.- 10.5 Surface Finish and Morphology.- 10.5.1 Surface Finish.- 10.5.2 Morphology.- Grinding.- Lapping.- Chips.- Discussion.- 10.6 Alternate Methods of Finishing Ferrites.- 10.6.1 Chemo-Mechanical Lapping.- 10.6.2 Post Annealing.- Ni-Zn Ferrite.- Mn-Zn Ferrite.- 10.6.3 Lapping with Soft Abrasive.- 10.6.4 Precision Crack-Off Technique.- References.- 11. Micro/Nanotribology and Micro/Nanomechanics.- 11.1 Introduction.- 11.2 Origins and Significance of Micro/Nanotribology.- 11.3 Experimental Techniques.- 11.3.1 AFM/FFM.- 11.3.2 Tip/Cantilever Beam Construction.- 11.4 Surface Roughness.- 11.5 Friction and Adhesion.- 11.5.1 Nanoscale Friction.- 11.5.2 Microscale Friction and Adhesion.- Head-Slider Materials.- Magnetic Media.- Silicon.- 11.6 Scratching and Wear.- 11.6.1 Nanoscale Wear.- 11.6.2 Microscale Scratching.- 11.6.3 Microscale Wear.- 11.7 Indentation.- 11.7.1 Picoscale Indentation.- 11.7.2 Nanoscale Indentation.- 11.8 Detection of Material Transfer.- 11.9 Lubrication.- 11.9.1 Imaging of Lubricant Molecules.- 11.9.2 Measurement of Localized Lubricant Film Thickness.- 11.9.3 Nanodeformation, Adhesive Forces, and Molecular Conformation.- 11.9.4 Boundary Lubrication Studies.- 11.9.5 Langmuir-Blodgett (L-B) and Self-Assembled Monolayers.- 11.10 Nanofabrication/Nanomachining.- 11.11 Summary.- References.- Appendix A: Techniques for Measuring Mechanical Properties of Thin Films.- Appendix B: Surface Analytical Techniques.- Appendix C: Accelerated Friction and Wear Tests.- Name Index.