Physics and Chemistry of Interfaces

This general yet comprehensive introduction to the field focuses on the essential concepts rather than specific details, on intuitive understanding rather than learning facts. The text reflects the many facets of this discipline by linking fundamentals with applications. The theory behind important concepts is backed by scientific-engineering aspects, as well as by a wide range of high-end applications. Examples of applications from biotechnology to microelectronics are used to illustrate the basic concepts. New to this third edition are topics as second harmonic generation spectroscopy, surface diffusion, atomic layer deposition, superlubricity, and bioadhesion. At the same time, the discussions of liquid surfaces, the Marangoni effect, electric double layers, measurement of surface forces, wetting, and adsorption have been updated. The number and variety of exercises are increased and the references are updated.

From the Contents:

• Introduction
• Liquid Surfaces
• Thermodynamics of Interfaces
• Charged Interfaces and the Electric Double Layer
• Surface Forces
• Contact Angle Phenomena and Wetting
• Solid Surfaces
• Adsorption
• Surface Modification
• Friction, Lubrication, and Wear
• Surfactants, Micelles, Emulsions, and Foams
• Thin Films on Surfaces of Liquids
• Solutions to Exercises
• Analysis of Diffraction Patterns

Preface XIII

1 Introduction1

2 Liquid Surfaces 5

2.1 Microscopic Picture of a Liquid Surface 5

2.2 Surface Tension 6

2.3 Equation of Young and Laplace 11

2.3.1 Curved Liquid Surfaces 11

2.3.2 Derivation of Young–Laplace Equation 13

2.3.3 Applying the Young–Laplace Equation 15

2.4 Techniques to Measure Surface Tension 16

2.5 Kelvin Equation 21

2.6 Capillary Condensation 24

2.7 Nucleation Theory 28

2.8 Summary 32

2.9 Exercises 33

3 Thermodynamics of Interfaces 35

3.1 Thermodynamic Functions for Bulk Systems 35

3.2 Surface Excess 36

3.3 Thermodynamic Relations for Systems with an Interface 40

3.3.1 Internal Energy and Helmholtz Energy 40

3.3.2 Equilibrium Conditions 41

3.3.3 Location of Interface 42

3.3.4 Gibbs Energy and Enthalpy 43

3.3.5 Interfacial Excess Energies 44

3.4 Pure Liquids 46

3.5 Gibbs Adsorption Isotherm 48

3.5.1 Derivation 48

3.5.2 System of Two Components 49

3.5.3 Experimental Aspects 51

3.5.4 Marangoni Effect 53

3.6 Summary 54

3.7 Exercises 55

4 Charged Interfaces and the Electric Double Layer 57

4.1 Introduction 57

4.2 Poisson–Boltzmann Theory of Diffuse Double Layer 58

4.2.1 Poisson–Boltzmann Equation 58

4.2.2 Planar Surfaces 59

4.2.3 The Full One-Dimensional Case 62

4.2.4 The Electric Double Layer around a Sphere 63

4.2.5 Grahame Equation 64

4.2.6 Capacitance of Diffuse Electric Double Layer 66

4.3 Beyond Poisson–Boltzmann Theory 67

4.3.1 Limitations of Poisson–Boltzmann Theory 67

4.3.2 Stern Layer 69

4.4 Gibbs Energy of Electric Double Layer 70

4.5 Electrocapillarity 72

4.5.1 Theory 73

4.5.2 Measurement of Electrocapillarity 75

4.6 Examples of Charged Surfaces 76

4.7 Measuring Surface Charge Densities 84

4.7.1 Potentiometric Colloid Titration 84

4.7.2 Capacitances 86

4.8 Electrokinetic Phenomena: the Zeta Potential 87

4.8.1 Navier–Stokes Equation 88

4.8.2 Electro-Osmosis and Streaming Potential 90

4.8.3 Electrophoresis and Sedimentation Potential 92

4.9 Types of Potential 95

4.10 Summary 97

4.11 Exercises 97

5 SurfaceForces 99

5.1 Van der Waals Forces between Molecules 99

5.2 Van der Waals Force between Macroscopic Solids 103

5.2.1 Microscopic Approach 104

5.2.2 Macroscopic Calculation – Lifshitz Theory 107

5.2.3 Retarded Van der Waals Forces 112

5.2.4 Surface Energy and the Hamaker Constant 113

5.3 Concepts for the Description of Surface Forces 113

5.3.1 The Derjaguin Approximation 113

5.3.2 Disjoining Pressure 116

5.4 Measurement of Surface Forces 117

5.5 Electrostatic Double-Layer Force 120

5.5.1 Electrostatic Interaction between Two Identical Surfaces 120

5.5.2 DLVO Theory 125

5.6 Beyond DLVO Theory 127

5.6.1 Solvation Force and Confined Liquids 127

5.6.2 Non-DLVO Forces in Aqueous Medium 129

5.7 Steric and Depletion Interaction 130

5.7.1 Properties of Polymers 130

5.7.2 Force between Polymer-Coated Surfaces 131

5.7.3 Depletion Forces 134

5.8 Spherical Particles in Contact 135

5.9 Summary 140

5.10 Exercises 141

6 Contact Angle Phenomena and Wetting 143

6.1 Young’s Equation 143

6.1.1 Contact Angle 143

6.1.2 Derivation 144

6.1.3 Line Tension 148

6.1.4 Complete Wetting and Wetting Transitions 149

6.1.5 Theoretical Aspects of Contact Angle Phenomena 150

6.2 Important Wetting Geometries 153

6.2.1 Capillary Rise 153

6.2.2 Particles at Interfaces 155

6.2.3 Network of Fibers 156

6.3 Measurement of Contact Angles 158

6.3.1 Experimental Methods 158

6.3.2 Hysteresis in Contact Angle Measurements 159

6.3.3 Surface Roughness and Heterogeneity 161

6.3.4 Superhydrophobic Surfaces 163

6.4 Dynamics of Wetting and Dewetting 164

6.4.1 Spontaneous Spreading 164

6.4.2 Dynamic Contact Angle 166

6.4.3 Coating and Dewetting 170

6.5 Applications 172

6.5.1 Flotation 172

6.5.2 Detergency 173

6.5.3 Microfluidics 174

6.5.4 Electrowetting 176

6.6 Thick Films: Spreading of One Liquid on Another 176

6.7 Summary 179

6.8 Exercises 179

7 SolidSurfaces 181

7.1 Introduction 181

7.2 Description of Crystalline Surfaces 182

7.2.1 Substrate Structure 182

7.2.2 Surface Relaxation and Reconstruction 184

7.2.3 Description of Adsorbate Structures 186

7.3 Preparation of Clean Surfaces 187

7.3.1 Thermal Treatment 187

7.3.2 Plasma or Sputter Cleaning 188

7.3.3 Cleavage 189

7.3.4 Deposition of Thin Films 189

7.4 Thermodynamics of Solid Surfaces 190

7.4.1 Surface Energy, Surface Tension, and Surface Stress 190

7.4.2 Determining Surface Energy 193

7.4.3 Surface Steps and Defects 196

7.5 Surface Diffusion 198

7.5.1 Theoretical Description of Surface Diffusion 199

7.5.2 Measurement of Surface Diffusion 202

7.6 Solid–Solid Interfaces 205

7.7 Microscopy of Solid Surfaces 208

7.7.1 Optical Microscopy 208

7.7.2 Electron Microscopy 209

7.7.3 Scanning Probe Microscopy 211

7.8 Diffraction Methods 214

7.8.1 Diffraction Patterns of Two-Dimensional Periodic Structures 214

7.8.2 Diffraction with Electrons, X-Rays, and Atoms 216

7.9 Spectroscopic Methods 218

7.9.1 Optical Spectroscopy of Surfaces 218

7.9.2 Spectroscopy Using Mainly Inner Electrons 222

7.9.3 Spectroscopy with Outer Electrons 224

7.9.4 Secondary Ion Mass Spectrometry 225

7.10 Summary 226

7.11 Exercises 227

8 Adsorption 229

8.1 Introduction 229

8.1.1 Definitions 229

8.1.2 Adsorption Time 231

8.1.3 Classification of Adsorption Isotherms 232

8.1.4 Presentation of Adsorption Isotherms 234

8.2 Thermodynamics of Adsorption 235

8.2.1 Heats of Adsorption 235

8.2.2 Differential Quantities of Adsorption and Experimental Results 237

8.3 Adsorption Models 239

8.3.1 Langmuir Adsorption Isotherm 239

8.3.2 Langmuir Constant and Gibbs Energy of Adsorption 241

8.3.3 Langmuir Adsorption with Lateral Interactions 242

8.3.4 BET Adsorption Isotherm 243

8.3.5 Adsorption on Heterogeneous Surfaces 246

8.3.6 Potential Theory of Polanyi 247

8.4 Experimental Aspects of Adsorption from Gas Phase 249

8.4.1 Measuring Adsorption to Planar Surfaces 249

8.4.2 Measuring Adsorption to Powders and Textured Materials 251

8.4.3 Adsorption to Porous Materials 253

8.4.4 Special Aspects of Chemisorption 260

8.5 Adsorption from Solution 261

8.6 Summary 263

8.7 Exercises 264

9 SurfaceModification 267

9.1 Introduction 267

9.2 Physical and Chemical Vapor Deposition 268

9.2.1 Physical Vapor Deposition 268

9.2.2 Chemical Vapor Deposition 271

9.3 Soft Matter Deposition 275

9.3.1 Self-Assembled Monolayers 275

9.3.2 Physisorption of Polymers 279

9.3.3 Polymerization on Surfaces 282

9.3.4 Plasma Polymerization 285

9.4 Etching Techniques 287

9.5 Lithography 292

9.6 Summary 295

9.7 Exercises 296

10 Friction, Lubrication, and Wear 297

10.1 Friction 297

10.1.1 Introduction 297

10.1.2 Amontons’ and Coulomb’s Law 298

10.1.3 Static, Kinetic, and Stick-Slip Friction 300

10.1.4 Rolling Friction 302

10.1.5 Friction and Adhesion 303

10.1.6 Techniques to Measure Friction 304

10.1.7 Macroscopic Friction 306

10.1.8 Microscopic Friction 307

10.2 Lubrication 310

10.2.1 Hydrodynamic Lubrication 310

10.2.2 Boundary Lubrication 313

10.2.3 Thin-Film Lubrication 314

10.2.4 Superlubricity 315

10.2.5 Lubricants 317

10.3 Wear 318

10.4 Summary 321

10.5 Exercises 322

11 Surfactants, Micelles, Emulsions, and Foams 323

11.1 Surfactants 323

11.2 Spherical Micelles, Cylinders, and Bilayers 327

11.2.1 Critical Micelle Concentration 327

11.2.2 Influence of Temperature 329

11.2.3 Thermodynamics of Micellization 330

11.2.4 Structure of Surfactant Aggregates 332

11.2.5 Biological Membranes 334

11.3 Macroemulsions 336

11.3.1 General Properties 336

11.3.2 Formation 339

11.3.3 Stabilization 340

11.3.4 Evolution and Aging 344

11.3.5 Coalescence and Demulsification 346

11.4 Microemulsions 347

11.4.1 Size of Droplets 347

11.4.2 Elastic Properties of Surfactant Films 348

11.4.3 Factors Influencing the Structure of Microemulsions 350

11.5 Foams 352

11.5.1 Classification, Application, and Formation 352

11.5.2 Structure of Foams 353

11.5.3 Soap Films 355

11.5.4 Evolution of Foams 357

11.6 Summary 358

11.7 Exercises 359

12 Thin Films on Surfaces of Liquids 361

12.1 Introduction 361

12.2 Phases of Monomolecular Films 364

12.3 Experimental Techniques to Study Monolayers 367

12.3.1 Optical Microscopy 368

12.3.2 Infrared and Sum Frequency Generation Spectroscopy 369

12.3.3 X-Ray Reflection and Diffraction 370

12.3.4 Surface Potential 373

12.3.5 Rheologic Properties of Liquid Surfaces 376

12.4 Langmuir–Blodgett Transfer 381

12.5 Summary 383

12.6 Exercises 384

13 Solutions to Exercises 387

14 Analysis of Diffraction Patterns 413

14.1 Diffraction at Three-Dimensional Crystals 413

14.1.1 Bragg Condition 413

14.1.2 Laue Condition 414

14.1.3 Reciprocal Lattice 415

14.1.4 Ewald Construction 417

14.2 Diffraction at Surfaces 417

14.3 Intensity of Diffraction Peaks 419

Appendix A Symbols and Abbreviations 423

References 429

Index 453

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