Question

5. Describe qualitatively the microstructural development that will occur upon slow cooling from of 1050 steel from 1600 °C to 20 °C.

6.

a). What are p-type semiconductors? What are their differences comparing with n-type semiconductors?

b). Moore’s law predicts the rapid and steady growth in the number of transistors contained on a single microcircuit chip. Why do engineers want to increase the number of transistors contained on a single microcircuit chip?

c). Even through silicon is abundant on the earth. What is the key reason that silicon wafers are so expensive?

d). Based on the semiconductor introduction video, if the thickness of a semiconductor wafer is ___ _ floor height, the Integrated Circuits are build on the top ____ floor(s).

7.

a). Among multiple components of a composite material, at least two components have to serve for specific functions. What are these two components? What are these two specific function?

b). Give an example of engineering application (not household items), where ceramics will be good materials to choose and high alloy steel will not be a good material to choose. Explain your reasons.

c). Give an example of engineering application (not household items), where polymers will be good materials to choose and composites will not be a good material to choose. Explain your reasons.

8.

a). Among many polymer processes, which processes can be usefor thermoplastics? Can they be used to process thermosetting polymers? Explain your reasons.

b). Engineering designers select thermosetting polymers to make electrical components. Explain why not use thermoplastic polymers.

c). PVC popes are widely used in commercial and residential construction, what does PVC stands for?

Answer 1

6.a.)

N-type semiconductor materials have been doped with elements which have spare electrons in their outer shells. This gives N-type silicon free electrons (which are negatively charged particals) which can move about at will - with the potential to create current.

P-type semiconductor materials have been doped in the opposite way, with elements that have too few electrons in their outer shells. Therefore the opposite of electrons - holes - are free to move about within the material - with the potential to create current.

p-type and n-type semiconductors are absolutely crucial to the construction of modern electronics. They are very useful because their conduction abilities can be easily controlled. Diodes and transistors, which are central to all sorts of modern electronics, require p-type and n-type semiconductors for their construction. The main difference between p-type and n-type semiconductor is that p-type semiconductors are made by adding impurities of Group-III elements to intrinsic semiconductors whereas, in n-type semiconductors, the impurities are Group-IV elements.