B006902 - CERAMIC AND GLASS MATERIALS

Italian

Structure of ceramics. Close-Packed lattices, lattice sites, interstitial sites in HPC and FCC lattices. Stability of ionic crystals. Prediction of crystal structures. Defects in the crystals. Classification and thermodynamic treatment of defects. Description of the glass structure. Structural glass models. Classes of oxide and non-oxide glasses. Glass transition thermodynamics. Phase diagrams. Manufacturing and applications of ceramic and glass materials.

Handout and bibliographic material proposed by the teachers.

Knowledge and Understanding: the course aims to train students on the main theoretical aspects underlying the structural, mechanical, electrical and optical properties of glass and ceramics. Technological and industrial aspects concerning these materials will also be discussed and analysed.
Communication: ability to communicate with appropriate vocabulary the skills acquired during the course.
Critical thinking: critical ability in the analysis, for example, of the different models discussed for the description of glass and ceramic structures. Ability to evaluate the advantages and disadvantages of production processes of materials, also in relation to the different applications.

Courses required: General and Inorganic Chemistry.
Courses recommended: Physical Chemistry I, Experimental Physics.

Total number of hours for lectures: 48.

Oral exam aimed at verifying the knowledge acquired, the ability to reason on the knowledge acquired, the quality of exposure and the competence in the use of specialized vocabulary.

Introduction to the course. Classification of materials. Definitions of pottery. General properties of ceramic materials. Types of traditional ceramic materials.
Types of traditional ceramic materials (glass, cements and refractories). Notes on the classification of silicates.

Structure of crystalline ceramics: maximum packing lattices, HPC and FCC (lattice sites and unit cell).Close-Packed lattices: interstitial sites. Relationship between reticular sites and interstitial sites in FCC and HCP. Stability of ionic crystals. Madelung's constant: one-dimensional lattice, two-dimensional lattice, three-dimensional lattice. Repulsive energy in ionic crystals. Stability of ionic crystals: calculation of total energy. Prediction of crystalline structures: coordination number, coordination polyhedra. Pauling's rules. Examples of FCC and HCP structures and related discussion of the main characteristics. Polymorphism and polytype: the case of blende and wurtzite. Defects in ceramic materials. Defect classification. Thermodynamic treatment of defects. Concentration of Frenkel defects and concentration of Schottky defects. Linear defects: corner and screw dislocations. Burgers Vector. Surface and volume defects.

Introduction to glasses and glass definitions. Description of the glass structure: pair distribution function, radial distribution function and pair correlation function. The pair distribution function and the coordination number in mixed systems. Other structural parameters. Types of crystals based on the prevailing bond. Structural models of glasses: monoatomic CRN, CRN of oxides, CRN of non-oxide binary systems. The theory of topological constraints or Phillips-Thorpe stiffness. Crystallite model. Lattice trainers and lattice modifiers. Structural glass models: random close packing (RCP). Description of the model. Comparison between RCP and HCP/FCC. Structures with maximum degree of packaging. Polyhedra of Voronoi. Bernal's canonical cavities. Classes of glass: silica glass, boron oxide glasses; alkaline silico glasses and sodium calcium glasses. Boron-sodium glasses and phosphorus oxide glasses. Description of crystal and glass structures. Numerical models and experimental measurements. Classes of oxide glasses: single-component glasses, biphasic glasses with structure modifiers, glasses with multiple formers and structure modifiers. Classes of non-oxide glasses: Si and amorphous Ge, one-component chalcogenic glasses, chalcogenide and calcohalide glasses, metallic glasses.

Recalls of thermodynamics. Phase transitions: definitions. Thermodynamics of phase transitions: thermodynamic functions in liquid-crystal transitions.
Thermodynamics of phase transitions: thermodynamic functions in liquid-glass transitions. Crystal and glass formation: Time-temperature-transformation diagrams
Crystal and glass formation: free energy of crystallite formation, behavior as a function of the radius, definition of critical and supercritical nuclei, number of critical nuclei per unit volume, Turnbull approximation, nucleation rate.
Crystal and glass formation: crystal growth rate (derivation and general considerations). Trend of nucleation and growth rates as a function of temperature. Johnson-Mehl-Avrami equation. TTT diagrams and experimental measurements of Iv and u. Cooling rate for the formation of glasses in different materials. Critical cooling rate and maximum thickness. Considerations on the type of hardening.

Phase diagrams. Definition of phase, component, degrees of freedom. General considerations on phase diagrams. Gibbs phase rule: statement and proof. Examples of one component phase diagrams. Two-component phase diagrams. Leverage rule. Binary systems with eutectic. Phase diagrams of binary systems: peritectoid, eutectoid and monotectic invariant points.

Application aspects of glassy materials: the glass manufacturing process. Batch composition and calculation. The merger process. Viscosity and production process: definition of "working point", "softening point", "annealing point" and "strain point". Aging and annealing. Flat glass production: rolling, deep drawing and float process. Blown glass. Coated glasses. Safety glass: tempering and lamination. Photochromic glasses. Glass ceramic: characteristics and methods of obtaining. Examples of glass ceramics. Bioceramics: inert (or almost complete) bioceramics and bioactive ceramics. Stress shielding. Bioceramic composites. Glassy materials for radiotherapy.