Ceramics quiz #4

Why are fining and annealing necessary when producing glass bottles?

Bottle needs to be able to withstand being slammed down so annealing allows for the raised edges of the bottom to withstand the roughness. Annealing basically reduces stress in formed glass.

Fining releases gas trapped within the glass to prevent weak spots.

List three process that can occur when light is “shined” on glass?

1. Refraction

2. Reflection

3. Scattering

Explain why some glass can “glow in the dark”?

When light is shined onto some glasses the electrons become excited and jump up an energy level. When they fall back down to their ground state, they release energy in the form of a photon.

List 5 things that can happen when a photon interacts with glass.

1. transmission

2. refraction

3. reflection

4. absorption

5. scattering

Approximate wavelength (in nm) of visible light

700 nm to 400 nm (red to violet)

Annealing

Slowly lowers temperature or glass starting at Tg and slowly lowering temperature so glass does not crack.

Fluxing

reduces processing temp slowly in order to resist cracking

Fining

homogeneous chemistry and temp to liberate bubbles.

Why is it necessary to anneal glass?

When glass is cooled from above Tg, stresses occur. Annealing glass heats the glass up to a working temperature (550 C) to relax stresses and allow the glass to cool stress-free.

How do you make glass?

1. Batch -

   1. Glass formers :(Ex: SiO2) + Conditional (Ex: Al2O5) mixed w/ glass former

   2. Modifiers: Control properties (Alkaline Earth (2nd)

   3. Fluxes: Lower processing temperature (1st on periodic table)

   4. Colorants: Transition metals, etc.

2. Mixing - Homogenize

3. Melt - Not too hot

4. Fining - Homogenize temp and remove air

5. Forming

6. Annealing - stress relief (around Tg or Tf)

7. Very slow cooling

What does "fining" of a melt involve?

removing bubbles

A material added to lower the melting temperature of glass is termed a...

Fluxing agent

What oxide is a good flux for a glass melt?

Na2O

Glass items prepared in layers of different colors that were carved to resemble a tree-dimensional paining is a style known as...

 

Cameo

Glass has a greater density than a crystal of the same composition.

False

The process of treating a glass to reduce internal stress is known as...

annealing

What is the process by which light is transmitted along an optical fiber?

internal reflection

Compared to the glass core, the refractive index of the classing of an optical fiber is always...

lower

A packet of electromagnetic energy best describes what?

A photon

A green beer bottle glass will likely transmit more light of which wavelength?

500 nm

Metals cannot be transparent because...

they have free electrons that absorb the light

By what process is light bent by glass?

Refraction

What is the approximate wavelength of visible light from red to blue?

700 nm - 400 nm