Structure of Materials, Part 3: Liquid Crystals, Defects, and Diffusion

Structure determines so much about a material:  its properties, its potential applications, and its performance within those applications.  This course is the finale in a three-part series from MIT’s Department of Materials Science and Engineering that explores the structure of a wide variety of materials with current-day engineering applications.  Taken together, these three courses provide similar content to MIT’s sophomore-level materials structure curriculum.

Part 3 begins with an exploration of quasi-, plastic, and liquid crystals.  Next, we will learn how properties of materials are influenced and can be modified by structural defects. We will show that point defects are present in all crystals at finite temperatures and how their presence governs diffusion in materials. Next, we will explore dislocations in materials.  We will introduce the descriptors that are used to describe dislocations, we will learn about dislocation motion and consider how dislocations dramatically affect the strength of materials.  Finally, we will explore how defects can be used to strengthen materials, and we will learn about the properties of other structural defects such as stacking faults and grain boundaries.

Part 1: Quasi, Plastic, and Liquid Crystals

• Quasi crystals
• An introduction to plastic and liquid crystals
• Liquid crystal descriptors
• Liquid crystal applications

Part 2: Introduction to Point Defects

• Thermodynamics of point defects
• Vacancies, interstitials, solid solutions and nonequilibrium defects

Part 3: Ionic Point Defects & Diffusion

• Kröger-Vink notation
• Extrinsic defects
• Diffusion

Part 4: Dislocations and Deformation

• Introduction to dislocations
• Elastic and plastic deformation
• Stress and strain
• Dislocation descriptors
• The Burgers vector
• Dislocation motion
• Resolved shear stress

Part 5: Strengthening & Surface Energy

• Strengthening Mechanisms
• Surface free energy
• Wulff shape

Part 6: 2-Dimensional Defects

• Surface defects
• Stacking faults
• Grain boundaries
• Surface reconstruction
• Linear defects in liquid crystals