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Flashcards in tf qs Deck (18)
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1

The glass transition temperature is the temperature at which the supercooled melt transforms to a fully ordered crystalline solid.

False

2

Recrystallization of metal alloys involves nucleation of new stress free grains in the cold worked
alloy resulting in a sharp decrease in hardness

True

3

Phase diagrams always give a correct indication of phases in a material no matter how it is
processed (e.g., whether or not it is cooled slowly or rapidly)

False

4

Al-Cu alloys are the only materials that can be precipitation hardened among all possible metal
alloy systems.

False

5

Quartz is the crystalline form of SiO2 that forms very easily by heat treating a piece of SiO2
glass for a few seconds at a temperature of ≈100 to 200°C.

False

6

An eutectoid transformation involves slow cooling of a molten alloy to form a solid containing a
mixture of two solid solutions.

False

7

Compared with metallic alloys glasses and ceramics show much more plastic deformation before they fracture.

False

8

Light emitting nanocrystals of semiconductor materials are called quantum dots.

True

9

The Pb-Sn phase diagram has a eutectic composition which melts at a temperature lower than
either pure Pb or pure Sn.

True

10

Precipitation hardening is the term used to describe the solidification of concentrated
solutions of salt particles precipitated in water.

False

11

Sintering is the process of cold pressing powders and heating the pressed pellet at a temperature below the melting point to get dense solid objects

True

12

Glass-ceramic products are made by heating (crystallizing) pre-shaped glasses.

True

13

Purification of electronic materials like silicon can be achieved by melting and directional solidification to partition the impurities between liquid and solid phases

True

14

Melting an impure electronic material and repeatedly freezing the melt in a ceramic boat in a normal furnace should purify the electronic material

False

15

Liquid immiscibility regions on a phase diagram can create micro or nanostructures useful for making Vycor (silica rich) glasses

True

16

An aerogel is an organic compound made from mixing solutions of polymers

False

17

A peritectic reaction on a phase diagram refers to the transformation of a solid solution (e.g., mullite) upon heating to a mixture of another solid (e.g., Al2O3) and a liquid solution

True

18

The transformation of austenite to pearlite at a temperature below ~727°C in a eutectoidcomposition always requires an incubation time for the nucleation process to commence

True