Page 235 - Manufacturing Engineering and Technology - Kalpakjian, Serope : Schmid, Steven R.

2l4 Chapter 8 Ceramics, Graphite, Diamond, and Nanomaterialsz Structure, General Properties, and Applications

QUALITATIVE PROBLEMS

8.l5. Explain Why ceramics are Weaker in tension than in 8.25. What is the difference between the structure of
compression. graphite and that of diamond? Is it important? Explain.
8.l6. What are the advantages of cermets? Suggest applica- 8.26. List and explain materials that are suitable for use as a
tions in addition to those given in this chapter. coffee cup.
8. I 1. Explain why the electrical and thermal conductivity of 8.27. Aluminum oxide and PSZ are described as White in
ceramics decreases with increasing porosity. appearance. Can they be colored? If so, how would you
8.l8. Explain Why the mechanical property data given in accomplish this?
Table 8.2 have such a broad range. What is the significance of 8.28. Why does the strength of a ceramic part depend on
this in engineering practice? its size?
8.l9. Describe the reasons that have encouraged the devel- 8.29. In old castles and churches in Europe, the glass
opment of synthetic diamond. windows display pronounced ripples and are thicker at the
8.20. Explain why the mechanical properties of ceramics bottom than at the top. Explain.
generally differ from those of metals. 8.30. Ceramics are hard and strong in both compression
8.2l. Explain how ceramics can be made tougher. and shear. Why, then, are they not used as nails or other
fasteners? Explain.
8.22. List and describe situations in which static fatigue can
be important. 8.3I. Perform an Internet search and determine the chem-
istry of glass used for (a) fiber-optic communication lines,
8.23. What properties are important in making heat-
(b) crystal glassware, and (c) high-strength glass fibers.
resistant ceramics for use on oven tops? Why?
8.32. Investigate and list the ceramics used for high-
8.24. A large variety of glasses is now available. Why is temperature superconductor applications.
this so?

QUANTITATIVE PROBLEMS

|]8.33. In a fully dense ceramic, UTS0 = 180 MPa and 8.37. A ceramic has /so = 0.80 W/mK. If this ceramic is
E0 = 300 GPa. What are these properties at 15% porosity shaped into a cylinder With a porosity distribution given by
for values of n = 4, 5, 6, and 7, respectively? P = 0.1(x/L)(1 - x/L), where x is the distance from one
|]8.34. Plot the UTS, E, and le values for ceramics as a end of the cylinder and L is the total cylinder length, plot
function of porosity Ii describe and explain the trends that the porosity as a function of distance, evaluate the average
you observe in their behavior. porosity, and calculate the average thermal conductivity.
|]8.35. What would be the tensile strength and the modu- |]8.38. It can be shown that the minimum Weight of a col-
umn which will support a given load depends on the ratio of
lus of elasticity of the ceramic in Problem 8.33 for porosities
of 20% and 40%, for the four n values given? the material’s stiffness to the square root of its density. Plot
this property for a ceramic as a function of porosity.
|]8.36. Calculate the thermal conductivities for ceramics
at porosities of 5%, 10%, and 20% for /eo = 0.7 W/m-K.

SYNTHESIS, DESIGN, AND PROIECTS

8.39. Make a list of the ceramic parts that you can find 8.4l. Describe applications in which a ceramic material
around your house or in your car. Give reasons why those with a near-zero coefficient of thermal expansion would be
parts are made of ceramics. desirable.
8.40. Assume that you are working in technical sales and 8.42. The modulus of elasticity of ceramics is typically
are fully familiar with all the advantages and limitations of maintained at elevated temperatures. What engineering appli-
ceramics. Which of the markets traditionally using nonce- cations could benefit from this characteristic?
ramic materials do you think ceramics can penetrate? What 8.43. List and discuss the factors that you would take into
would you like to talk about to your potential customers dur- account when replacing a metal component with a ceramic
ing your sales visits? What questions do you think they may component in a specific product.
ask you about ceramics?