Your Answer : (Not Answered)

Correct Answer : B

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason accounts for both halves. The lower firing temperature lets pigments survive that would burn out or dissolve at glaze temperature, which is why onglaze offers reds, pinks and bright yellows underglaze cannot. But the decoration sits on the glaze rather than sealed beneath it, so it is exposed to cutlery, abrasion and dishwashing and wears away in time.

Your Answer : (Not Answered)

Correct Answer : C

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason is the cause. Raw lead compounds are soluble and readily absorbed, so they present a real hazard to the people preparing and applying the glaze. Fritting binds the lead into a glass in which it is far less available, and in many jurisdictions raw lead in a glaze is prohibited outright - the frit is the condition on which lead may still be used at all.

Your Answer : (Not Answered)

Correct Answer : D

Both are true and the reason gives the mechanism: combustion provides the reducing species as a by-product of running rich, whereas an electric kiln must have a gas introduced deliberately and its elements suffer for it.

Your Answer : (Not Answered)

Correct Answer : A

Correct answer: heat work, combining temperature and time

A cone bends when it has received enough thermal energy, which depends on how long it was held as well as how hot it got - the same integrated effect the ware itself experiences. That is why a cone is a better guide to whether a firing is complete than a thermocouple reading, which reports only the instantaneous temperature and says nothing about the soak.

Your Answer : (Not Answered)

Correct Answer : B

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason is the whole argument. Kiln furniture rides through the cycle with the ware and absorbs heat in proportion to its mass, so a heavy setting can consume more fuel than the ware itself. Lightweight cordierite and silicon carbide supports exist for that reason, and the ratio of ware to furniture is a standard measure of how well a kiln is being loaded.

Your Answer : (Not Answered)

Correct Answer : B

Both are true and the reason gives the mechanism: thermal mass sets the rate at which any kiln can be cycled, and removing the car leaves little but the ware itself to heat. The saving is in what is not heated rather than in better insulation.

Your Answer : (Not Answered)

Correct Answer : A

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason is the principle behind fast firing. Grain boundary migration has a higher activation energy than the diffusion that densifies, so raising the temperature quickly and holding briefly favours densification over coarsening. Passing rapidly through the low-temperature range where non-densifying surface diffusion dominates helps for the same reason.

Your Answer : (Not Answered)

Correct Answer : A

A grain boundary is a fast path for the diffusion that carries material into the pore, so a pore that stays on a boundary shrinks. Once the boundary sweeps past and leaves the pore behind, removal becomes extremely slow.

Your Answer : (Not Answered)

Correct Answer : C

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason gives the justification. Cracking in drying comes from differential shrinkage, so once shrinkage has ceased there is nothing to set up the stress and the remaining water can be driven off as fast as heat can be supplied. A good schedule is therefore slow and humid at first and hot and dry afterwards - and running it at one uniform rate wastes either time or product.

Your Answer : (Not Answered)

Correct Answer : B

Correct answer: plate-like clay particles sliding over a water film

Clay minerals are thin plates, and a film of water between them lets them slide past one another while surface tension holds them together. Both halves matter: the shape of the particles allows the sliding and the water film both lubricates and binds. Take the water away and the body is rigid; add too much and it flows.

Your Answer : (Not Answered)

Correct Answer : B

The first two are correct. The third is wrong, since equiaxed oxide particles give almost no green strength on their own and a binder has to be added. Plate-like clay particles are what give traditional bodies their green strength.

Your Answer : (Not Answered)

Correct Answer : C

Ageing allows entrained air to escape, lets the deflocculant act fully and stabilises the rheology. Freshly made slip commonly behaves differently from the same slip a day later. Production slips are held in agitated tanks for this reason.

Your Answer : (Not Answered)

Correct Answer : D

Correct answer: particle shape affects packing and flow behaviour

Equant particles pack densely and flow freely; plates and needles bridge, pack poorly and flow badly, and they orient during pressing so that the compact shrinks unevenly. Since packing determines green density and flow determines whether a die fills reproducibly, shape is a genuine process variable and not merely a description.

Your Answer : (Not Answered)

Correct Answer : D

It reports whatever passes through as one particle of that size, so a soft agglomerate is measured as though it were solid. Microscopy or a dispersion study is needed to tell the two apart. Agglomeration is invisible to an instrument that reports only size.

Your Answer : (Not Answered)

Correct Answer : A

Subtracting 1 from 25 gives 24, and dividing by the d50 of 5 gives 4.8. Span is a dimensionless measure of how broad a distribution is and allows powders of different average size to be compared. It says nothing about whether the distribution is symmetrical.

Your Answer : (Not Answered)

Correct Answer : C

The first two are correct. The third describes the opposite of coprecipitation, whose whole advantage is that mixing happens in solution at a scale no mechanical method can approach. Homogeneity at that scale is what shortens the later calcination.

Your Answer : (Not Answered)

Correct Answer : C

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason gives the mechanism. Shrinkage depends on local porosity, so a compact denser at one end than the other shrinks unevenly and warps - and the internal stress may crack it. A uniform but slightly lower density is preferable to a higher average with a gradient through it.

Your Answer : (Not Answered)

Correct Answer : B

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason gives the mechanism. The binder decomposes to gas which must escape through a body of low permeability, and heating too quickly generates it faster than it can leave. The pressure cracks or bloats the piece, so the burnout stage is held slow and is often the longest part of the schedule.

Your Answer : (Not Answered)

Correct Answer : D

A pressed compact of bare powder is far too fragile to survive handling between the press and the kiln. The binder is burnt out during firing and contributes nothing to the finished ceramic. Its only job is to hold the compact together until firing begins.

Your Answer : (Not Answered)

Correct Answer : C

Correct answer: alumina of the same purity as the powder

Milling media wear, and whatever they are made of ends up in the powder. For a high-purity product the only acceptable contaminant is more of the same material, so the media are made of it - which is why alumina and zirconia media exist despite costing far more than steel.