Ceramics

Question 1

Definition of a ceramic

Answer 1

Inorganic Materials made from metals and non-metals united by ionic and/or covalent bonds

Question 2

What type of structure can a ceramic be

Answer 2

Can be crystalline, amorphous or a mixture of both

Question 3

Categories of ceramics

Answer 3

Glasses, Clay Products, Refractories, Abrasives, Cements, Advanced Ceramics

Question 4

What is ceramics applications?

Answer 4

Aerospace, Consumer Products, Automotive, Piezoelectrics, Medical (Bio-ceramics), Military

Question 5

What is Annealing of glass?

Answer 5

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

Question 6

What is Tempering of glass?

Answer 6

Puts surface of glass into compression to suppress crack growth from scratches at surface

Question 7

Glass Forming Methods

Answer 7

Blowing of Glass Bottles, Pressing, Fiber Drawing, Sheet Drawing

Question 8

Particulate Forming Methods

Answer 8

Hydroplastic Forming, Slip Casting, Powder pressing

Question 9

How are a ceramics physical properties tested?

Answer 9

3 Point Bending Test

Mechanical properties test of brittle materials

Question 10

Materials used in creation of glass

Answer 10

Fusion of sand (SiO2), soda (Na2CO3) & Lime (CaO)

Question 11

Physical and chemical properties of Glass

Answer 11

Physical - Hard, elastic, brittle, non-conductor of electricity
Chemical - resistant to all but fluorine and strong bases

Question 12

What is material added to glass to improve its resistance to breaking

Answer 12

5% Borax (Used in pyrex)

Question 13

What is material added to glass to change its colour

Answer 13

Metal oxides or colloidal iron (Fe) & Sulfur (S)

Question 14

What is material added to glass to increase its refractive index and density

Answer 14

Lead (Pb)

Question 15

List the types of Glass

Answer 15

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.

Question 16

What is laminated glass

Answer 16

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

Question 17

What is tempered glass

Answer 17

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.

Question 18

What does CERAMIC stand for?

Answer 18

lol no idea

Question 19

What is sheet forming

Answer 19

– continuous casting

– sheets are formed by floating the molten glass on a pool of molten tin

Question 20

What is hydroplastic forming?

Answer 20

Particulate forming
Mill (grind and screen constituents: desired particle size
Extrude the mass (e.g. into a brick)
Dry and fire the formed piece

Question 21

What is slip casting?

Answer 21

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

Question 22

What is powder pressing?

Answer 22

Particulate forming

Used for both clay and non-clay compositions

Question 23

What is sintering?

Answer 23

Particulate forming
Occurs during firing of a piece that has been powder pressed
Powder particles coalesce and reduction of pore size

Question 24

What does the properties of ceramic materials depend on?

Answer 24

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!)

Question 25

Why is glass transparent?

Answer 25

Glass contains a 3D network of atoms which lacks the repeated, orderly arrangement typical of crystalline materials.

Question 26

Describe the breaking of glass

Answer 26

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

Question 27

Describe fractures by projectiles

Answer 27

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.

Question 28

When glass is shot by a bullet which side of the hole is wider? Load or unload?

Answer 28

Exit (unloaded) side is wider than the entry (load) side

Question 29

How can the sequence of impacts be determined?

Answer 29

Since crack propagation is stopped by earlier cracks, the initial bullet hole can be distinguished from the latter bullet hole.

Question 30

What is the plastic layers sandwiched between the glass layers in laminated glass?

Answer 30

Butyral (PVB)