Ceramics Flashcards
Definition of a ceramic
Inorganic Materials made from metals and non-metals united by ionic and/or covalent bonds
What type of structure can a ceramic be
Can be crystalline, amorphous or a mixture of both
Categories of ceramics
Glasses, Clay Products, Refractories, Abrasives, Cements, Advanced Ceramics
What is ceramics applications?
Aerospace, Consumer Products, Automotive, Piezoelectrics, Medical (Bio-ceramics), Military
What is Annealing of glass?
Annealing of glass is the process of slowly cooling hot glass objects after they have been formed, to relieve residual internal stresses introduced during manufacture
What is Tempering of glass?
Puts surface of glass into compression to suppress crack growth from scratches at surface
Glass Forming Methods
Blowing of Glass Bottles, Pressing, Fiber Drawing, Sheet Drawing
Particulate Forming Methods
Hydroplastic Forming, Slip Casting, Powder pressing
How are a ceramics physical properties tested?
3 Point Bending Test
Mechanical properties test of brittle materials
Materials used in creation of glass
Fusion of sand (SiO2), soda (Na2CO3) & Lime (CaO)
Physical and chemical properties of Glass
Physical - Hard, elastic, brittle, non-conductor of electricity
Chemical - resistant to all but fluorine and strong bases
What is material added to glass to improve its resistance to breaking
5% Borax (Used in pyrex)
What is material added to glass to change its colour
Metal oxides or colloidal iron (Fe) & Sulfur (S)
What is material added to glass to increase its refractive index and density
Lead (Pb)
List the types of Glass
Flat Glass: made by a “float glass process”; molten glass is floated on a pool of molten tin while cooling. Commonly found in doors and windows.
Laminated Glass: used in windshields, two sheets of glass with plastic between them.
Tempered Safety glass: used in car side windows and designed to break into tiny pieces; potassium (K) replaces sodium (Na) on the surface.
What is laminated glass
Safety Glass consisting of two or more panes of glass with one or more layers of butyral (PVB) sandwiched between them and treated.
Glass panes can be basic float glass, tempered or heat strengthened panel
If glass is broken, fragments tend to adhere to the PVB interlayer thereby reducing the risk of injury from falling glass and helping to resist further impact or weather damage
What is tempered glass
Glass designed to break into tiny pieces. Rapidly cooled to create a high mechanical strength.
- Made in special heated furnaces, which heats the annealed glass to a uniform temperature of approximately 700ºC
- When glass is in the furnace, it is rapidly cooled
- rapid cooling puts the glass surface into a state of compression while the centre core remains in tension
- mechanical Strength of Tempered Glass = 4 x Mechanical strength of Annealed Glass
- When tempered glass is broken, all the stored energy is released at once and the glass breaks into small pieces.
What does CERAMIC stand for?
lol no idea
What is sheet forming
– continuous casting
– sheets are formed by floating the molten glass on a pool of molten tin
What is hydroplastic forming?
Particulate forming
Mill (grind and screen constituents: desired particle size
Extrude the mass (e.g. into a brick)
Dry and fire the formed piece
What is slip casting?
Particulate forming
Mill (grind and screen constituents: desired particle size
Mix with water and other constituents to form slip
Slip casting operation
Dry and file the cast piece
What is powder pressing?
Particulate forming
Used for both clay and non-clay compositions
What is sintering?
Particulate forming
Occurs during firing of a piece that has been powder pressed
Powder particles coalesce and reduction of pore size
What does the properties of ceramic materials depend on?
properties are significantly dependent on processing and as it relates to the level of porosity
• because the very unpredictable nature of ceramic defects, we do not simply add a factor of safety for tensile loading
– we may add compressive surface loads
– we often choose to avoid tensile loading at all – most ceramic loading of any significance is compressive (consider buildings, dams, bridges and roads!)
Why is glass transparent?
Glass contains a 3D network of atoms which lacks the repeated, orderly arrangement typical of crystalline materials.
Describe the breaking of glass
When a force is applied to glasses, this causes a deformation. This deformation may leave a visible mark or fracture the glass.
The deformation can be used to determine the direction and amount of force.
Initially, glass acts as an elastic surface and bends away when a force is applied.
When the force increases beyond its tensile strength, it cracks
Describe fractures by projectiles
Bullets are a projectile force (load) that can pass through glass.
Load side = entrance side
Unloaded side = exit side
As the bullet’s velocity decreases, the central hole becomes smaller, cracking patterns become simpler, and the exit hole becomes wider than the entrance hole.
When glass is shot by a bullet which side of the hole is wider? Load or unload?
Exit (unloaded) side is wider than the entry (load) side
How can the sequence of impacts be determined?
Since crack propagation is stopped by earlier cracks, the initial bullet hole can be distinguished from the latter bullet hole.
What is the plastic layers sandwiched between the glass layers in laminated glass?
Butyral (PVB)
