MTC101T_Part 1.pdf

Introduction of materials chemistry (MTC101T) Dr. Tvarit Patel Department of Engineering and Physical Sciences IAR - Gandhinagar 1  What are Materials ?  Materials are probabl...

Introduction of materials chemistry (MTC101T) Dr. Tvarit Patel Department of Engineering and Physical Sciences IAR - Gandhinagar 1  What are Materials ?  Materials are probably more deep-seated in our culture than most of us realize. Transportation, housing, clothing, communication, recreation, and food production virtually every segment of our everyday lives is influenced to one degree or another by materials.  Historically, the development and advancement of societies have been intimately tied to the members’ ability to produce and manipulate materials to fill their needs. In fact, early civilizations have been designated by the level of their materials development (Stone Age, Bronze Age, Iron Age).  The development of many technologies that make our existence so comfortable has been intimately associated with the accessibility of suitable materials. 2  Types of Materials ?  Metals: – Strong, ductile – High thermal & electrical conductivity – Opaque, reflective.  Polymers/plastics: – Soft, ductile, low strength, low density – Thermal & electrical insulators – Optically translucent or transparent.  Ceramics: compounds of metallic & non-metallic elements (oxides, carbides, nitrides, sulfides) – Brittle, glassy, – Non-conducting (insulators) 3  Composite materials  A composite is composed of two (or more) individual materials, which come from the categories of metals, ceramics, and polymers.  The design goal of a composite is to achieve a combination of properties that is not displayed by any single material, and also to incorporate the best characteristics of each of the component materials. 4  Materials Science & Engineering  Sometimes it is useful to subdivide the discipline of materials science and engineering into materials science and materials engineering sub- disciplines.  “materials science” involves investigating the relationships that exist between the structures and properties of materials.  “materials engineering” is, on the basis of these structure–property correlations, designing or engineering the structure of a material to produce a predetermined set of properties. 5 The Materials Tetrahedron  Materials selection process 1. Application Determine required Properties Properties: mechanical, electrical, thermal, magnetic, optical, deteriorative. 2. Properties Identify candidate Material(s) Material: structure, composition. 3. Material Identify required Processing Processing: changes structure and overall shape ex: casting, sintering, vapor deposition, doping forming, joining, annealing. 6  Levels of Structure structure processing properties performance STRUCTURE (length scale) < 0.2 nm 7  Levels of Structure structure processing properties performance STRUCTURE (length scale) < 0.2 nm 0.2-10 nm 1 nm = ? 8  Atomic Arrangement: Ordered vs. Disordered Crystalline: atoms are arranged in a 3D, periodic array giving the material “long range order” stacking can effect properties (i.e. ductility) anisotropic materials hexagonal close-packed Non-crystalline or amorphous: atoms only have short-range, nearest neighbor order viscous materials (generally complex formulas) or rapid cooling isotropic materials 9  Levels of Structure structure processing properties performance STRUCTURE (length scale) < 0.2 nm 0.2-10 nm 1-1000 mm 1 nm = ? 10  Microstructure Single Crystal Polycrystalline the periodic arrangement of many small crystals or grains atoms extends throughout the small crystals misoriented with entire sample respect to on another difficult to grow, environment must several crystals are initiated and be tightly controlled grow towards each other anisotropic materials anisotropic or isotropic materials 11  Levels of Structure structure processing properties performance STRUCTURE (length scale) < 0.2 nm 1-100 nm 1-100 mm > 1 mm 1 nm = ? 12 Length Scales of Material Science Atomic – < 10-10 m Nano – 10-9 m Micro – 10-6 m Macro – > 10-3 m 13  Energy and Packing Non dense, random packing Energy typical neighbor bond length typical neighbor r bond energy Energy Dense, ordered packing typical neighbor bond length typical neighbor r bond energy Dense, ordered packed structures tend to have lower energies & thus are more stable. 14  Crystal Systems Unit cell: smallest repetitive unit which contains the complete lattice pattern of a crystal.  7 crystal systems of varying symmetry are known These systems are built by changing the lattice parameters: a, b, and c are the edge lengths , , and  are interaxial angles Fig. 3.4, Callister 7e. 15 Crystal Systems 16 Crystal Systems 17 Atomic arrangement 18 Space lattice 19 Symmetry 20 Crystal systems 21 Crystal systems 22 Crystal systems 23 Crystal systems 24 Crystal systems 25 Crystal systems 26 Crystal Plane 27 Equivalent Planes 28 Coordination Number 12 29 Linear Density 30