MTE3203 Week 5 - Industrial ceramics and Glass

What does clay's layered structure give you?

Strong bonds within layers, weak bonds between them, so layers slide when wet. Weak interlayer bonds = plasticity. Same structure suspends in water, which is what makes slip casting possible.

In slip casting, what forms the wall of the part?

The porous plaster mould draws water out, building a solid skin against the wall. Once thick enough you pour the excess out. Cheap way to make hollow complex shapes.

What does firing actually accomplish?

A soft, shapeable material converts itself into a hard, refractory one. You shape something plastic, then heat converts it into phases stable far above the firing temperature.

Porcelain's three ingredients — what does each do?

Clay for plasticity, filler to cut shrinkage and vent gas, flux to bring the liquid down to a temperature at which a liquid appears for sintering

What triggers cement to set, and what are the two stages?

Water. It reacts, it doesn't dry. Setting over hours as interlocking crystals grow; hardening over months as strength keeps climbing.

Why reinforce concrete, why load it in compression, why manage heat in a big pour?

Tensile strength is about a tenth of compressive, so bending needs steel. Low toughness means tensile cracks run, while compression holds them shut. Hydration is exothermic and concrete insulates, so a thick pour cracks from thermal stress.

What defines a glass, and why is there no melting point?

A melt cooled too fast to crystallise. A melting point is where a lattice breaks down — no lattice, nothing to break, so you get a glass transition instead.

Zachariasen's rules reduce to one idea. What is it?

Oxygen bridging only two cations forces corner-sharing, and a corner is a hinge — the network can twist into disorder and stay fully bonded. Edges and faces are rigid, so the structure locks into a lattice.

Network formers, modifiers, intermediates — and what modifiers do to properties?

Formers build the network, modifiers break bridges, intermediates do either depending on context. Modifiers loosen the network: easier to melt and work, less durable and less thermal-shock resistant.

Why aluminium nitride for IC substrates?

It conducts heat but not electricity, and its thermal expansion nearly matches silicon — so the joint survives thermal cycling. That match is the decider.

Zachariasen's rules

1. No oxygen atom may be linked to more than two cations

2. The cation coordination number is small: 3 or 4.

3. Oxygen polyhedra share corners, not edges or faces.

4. At least three corners must be shared (for 3D networks) In general, all four rules should be satisfied for glass formation to occur.