Glass-Ceramics Quiz

Fundamentals of Ceramic Materials

• The course is titled "Fundamentals of Ceramic Materials"
• Taught by Prof. Dr. Filiz Şahin
• Offered in the Fall of 2024-2025
• Held at the I.T.U Department of Metallurgical & Materials Engineering

Glass Raw Materials

• Raw materials for glass are oxides.
• Glass composition is given in terms of the percentage of each oxide.
• Basic materials for glass production are;
  • Quartz (Silicon dioxide (SiO2))
  • Soda (Sodium Carbonate (Na2CO3))
  • Limestone (Calcium Carbonate (CaCO3))
  • Potash (Potassium Carbonate (K2CO3))
  • Dolomite (Magnasium Calcium Carbonate (MgCa(CO3)2))
  • Crushed glass (25-30% of mixture)

Auxiliary Materials

• Auxiliary materials are added to base materials.
• Materials for glass discoloring and clarification (Manganese dioxide)
• Materials for coloring (metal oxides)
• Materials for opaque glass texture (Titanium and Zirconium oxides)

Composition of Glass

• When sand (SiO2) is mixed with metal oxides, melted at high temperatures, and cooled without crystallization, the product is glass.
• Adding soda (Na2CO3) lowers the melting point and viscosity, making it easier to work with.
• Lime (CaO) prevents dissolution in water.

Components of Glass

• Glass is used in many ways, so there is no single chemical composition.
• Three categories of substances in all glass:
  • Network Formers (SiO2, B2O3, P2O5): Make up the bulk of the glass.
  • Network Modifiers (Fluxes, Softeners: Na2CO3, K2CO3): Change the melting temperature.
  • Intermediate Oxides (Stabilizers): Strengthen the glass and improve chemical resistance (CaO, Al2O3).

Glass network formers, modifiers and intermediates

• Glass network formers form the interconnected backbone glass network.
• Glass network modifiers are present as ions to alter the glass network.
• Intermediate oxides can behave as network formers or modifiers depending on glass composition;
• They improve chemical resistance (especially Al2O3) and act as stabilizing agents (e.g., TiO2, ZrO2, CeO2).
• Each alkali ion creates one non-bridging oxygen.
• Reduced network connectivity decreases viscosity.
• Increased ionic conductivity reduces chemical resistance.

Glass Manufacturing

• The process of glass production has three stages;
  • Melting
  • Forming and Shaping
  • Annealing
  • Finishing

Glass Manufacturing - Melting

• Raw materials are mixed in proper proportions and fused in a furnace at 1800°C.
• CaCO3 + SiO2 → CaSiO3 + CO2
• Na2CO3 + SiO2 → Na2SiO3 + CO2
• Reducing agents are added to remove traces of ferrous compounds and carbon.

Glass Manufacturing - Forming and Shaping

• Molten glass is poured into molds.
• Shaping is done by blowing or pressing between rollers

Glass Manufacturing - Annealing

• Glass articles are cooled gradually to room temperature in different chambers with descending temperatures.
• This reduces internal strain.

Glass Manufacturing - Finishing

• Cleaning
• Grinding
• Polishing
• Cutting
• Sand Blasting

Characterization Techniques

• Structure: X-ray/electron/neutron diffraction, X-ray absorption spectroscopy (XAS), Raman spectroscopy, Nuclear magnetic resonance (NMR)
• Glass chemistry: Atomic emission spectroscopy (AES), Energy-dispersive X-ray spectroscopy (EDX), Infrared spectroscopy, X-ray photoelectron spectroscopy (XPS)
• Thermal analysis: Differential thermal analysis (DTA), Differential scanning calorimetry (DSC), Thermogravimetric analysis (TGA), Thermomechanical analysis (TMA)
• Electrical properties: Temperature-dependent electrical conductivity measurement, Impedance spectroscopy (AC conductivity), Electron paramagnetic resonance (EPR)
• Mechanical and rheological behavior: Indentation, Ultrasonic wave propagation, Fracture toughness test, 3/4-point bending test, Viscometry
• Optical properties: UV-Vis spectroscopy, Ellipsometry, Prism coupling, Optical fiber/waveguide transmission, Photoluminescence

Glass-Ceramics: Processing, Properties and Applications

• Enhancing mechanical properties of glasses with crystallization
• Controlled microstructure, crystalline phases (+residual glassy phase)

Nucleating Agents

• Nucleating agents promote heterogeneous nucleation.
• Nucleating agents increase the number of heterogeneous nucleation sites.
• Nucleating agents are composed of either metal elements (Au, Ag, Pt, Pd) or simple oxides (TiO2, ZrO2, P2O5, Ta2O5).

Glass-Ceramic Production

• Choice of the parent glass composition for desired crystalline phase.
• Synthesis of the glass via a melting process and shaping.
• Controlled crystallization (microstructure) of the glass.
• The composition determines the nature of the future crystalline phase(s), nucleation, growth, thermodynamics, and kinetics of the system.

Glass-Ceramic Production: Fabrication from glass batch

• Melting of glass
• Casting and cooling of molten glass
• Nucleation and grain growth to convert G/C

Glass-Ceramic Production: Fabrication from glass powder

• Sintering of glass powder during heating
• Cooling of the bulk

Glass-Ceramic - LAS (Lithium Aluminosilicate)

• Transparent
• Heat-resistant
• Low thermal expansion of coefficient (CTE)
• Colored with nucleating agents (TiO2, ZrO2)

Glass-Ceramic - MAS (Magnesium Aluminosilicate)

• High mechanical strength
• Excellent dielectric properties
• Good thermal stability
• Thermal shock resistance

Glass-Ceramic - MACOR®

• Machinable glass ceramics with nucleated fluoromica crystals in glass
• Aerospace industry
• Medical equipment
• Ultrahigh vacuum applications
• Welding
• Nuclear-related experiments

Glass-Ceramic - DICOR®

• Translucent and chemically durable.
• Contains tetrasilisic mica (KMg2.5AlSi4O10F2).
• Good strength.
• Ceria addition catches fluorescence.
• Used in dental crowns and inlays.

Glass-Ceramic - BIOVERIT I and BIOVERIT II

• Biocompatible
• Machinable
• Bioactivity
• Orthopedic surgery
• Middle ear implants

REFRACTORY MATERIALS

• Refractories are non-metallic inorganic materials capable of withstanding high temperatures and not degrading when in contact with corrosive liquids, gases and solids.
• Refractory insulators are used in high-temperature applications.

Properties of Refractory Materials

• Withstand high temperatures under high load (high creep resistance)
• High volume stability.
• Withstand sudden changes in temperature
• Low coefficient of thermal expansion
• High thermal shock resistance
• Withstand the action of molten metal, slag, glass, hot gases, etc.
• Withstand abrasive/wear/erosive forces
• Able to conserve heat
• Thermal conductivity
• Density and porosity (depending on dense or insulating requirements).

Manufacturing and Properties of Refractories

• Shaping Refractories by crushing, screening, mixing, and pressing into a mold, then drying and firing.
• Methods of crushing, grinding, screening, and batch weighting.

Physical properties of refractories

• Refractoriness
• Strength of refractories under load (RUL)
• Dimensional stability
• Porosity
• Thermal spalling
• Thermal expansion
• Thermal conductivity

Properties of Refractory Materials - Refractoriness

• Ability of a material to withstand heat without appreciable deformation or softening under service conditions
• Measured as the softening or melting temperature.
• Most refractory materials are mixtures of metallic oxides; they don't have a sharp melting point.

Pyrometric Cones Test (Seger Cone Test)

• Refractoriness is determined by comparing the behavior of a material sample in a furnace to a series of Seger Cones of standard dimensions.
• Seger cones melt or fuse at definite temperatures.
• Temperature at which fusion occurs is indicated by the cone's apex touching the base.

Physical Properties of Refractories - Strength of Refractories Under Load (RUL)

• Used to determine the temperatures at which a standard dimensioned refractory specimen undergoes 10% deformation using a constant load.

Physical Properties of Refractories - Dimensional Stability

• Resistance to volume change due to exposure to high temperatures over time.
• Dimensional change may be permanent or reversible, resulting in contraction or expansion.

Physical Properties of Refractories - Porosity

• Ratio of pore volume to bulk volume in a refractory.
• Can be due to manufacturing or deliberate incorporation.

Physical Properties of Refractories - Thermal Spalling

• Cracking, breaking or peeling of a refractory under high temperatures due to changes in temperature, leading to uneven expansion and contraction.

Physical Properties of Refractories - Thermal Expansion

• Expansion of a refractory material under prolonged heat exposure.
• Repeated expansion and contraction affect furnace lifetime.

Physical Properties of Refractories - Thermal Conductivity

• Ability to transmit heat
• A good heat conductivity is desirable for effective heat transmission.
• Dense refractories have high thermal conductivity due to absence of air voids.

Classification of Refractories

• Basicity of oxides
• Form
• Manufacturing process
• Method of application
• Special chemistry
• Insulating property

Refractories By Basicity

• Acidic refractories readily react with bases
• Basic refractories react with acids
• Neutral refractories have low reactivity

Refractories by Insulating Property

• Composite in nature, combining dense and insulating refractories
• Dense refractories positioned in front to withstand harsh conditions.
• Insulating refractories positioned behind to contain heat and prevent energy loss
• Main features are high porosity and low bulk density leading to low thermal conductivity, lower mechanical strength
• Designed for continuous use at high temperatures

Additional Information

• Several specific types of refractories (silica, aluminosilicate, magnesia, zircon) and their applications are detailed in the presentation.
• Raw materials, manufacturing processes, and properties for various types of refractories are discussed.

Test your knowledge on the properties and applications of glass-ceramics. This quiz covers essential aspects such as nucleating agents, thermal stability, and manufacturing processes. Perfect for students and professionals in materials science or ceramics engineering.