Page 167 - Materials Chemistry, Second Edition

154 2 Solid-State Chemistry

18. Provide precedents for sol-gel syntheses using tetramethoxysilane, with references. Describe the
differences in experimental conditions and control over product morphology relative to using TEOS.
19. We have all seen cement trucks that have a distinctive rotating tank. Why is this constant rotation
necessary, and what would happen if the tank stopped rotating?
20. Why are coarse and fine aggregates needed for the overall strength of concrete?
21. Explain why the reaction of C2S with hydroxides occurs much slower than the C3S/hydroxide
reaction during cement hardening.
22. Suggest low- and high-temperature synthetic routes for AlN and BN ceramics.
23. How would you design smart glass-based intruder sensor, which would change color from clear to
bright red?
24. What are ‘chalcogenide glasses’? Describe some recent applications for these materials.
25. How would you design a smart glass windshield, which would self-repair itself after an automobile
crash?
26. Ancient colored glasses contained nanoparticles of Au and Cu. How were these synthesized (i.e.,
what metal salts were used, along with other experimental conditions required to yield nanosized
metal clusters)?
27. Explain why borosilicate glass is transparent to visible radiation and quartz is transparent to both
visible and UV radiation.
28. For metal oxide-based heterogeneous catalyst supports, describe the role of (1) surface hydroxyl
groups (concentration and speciation) and (2) Lewis acidity of the metal center on the chemisorption
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of transition metal catalysts. Cite various examples of surface-bound M and M nþ catalytic species.
29. Both homogeneous and heterogeneous catalysis offer distinct advantages and disadvantages. Though
a particular system is usually designed to be either homo- or heterogeneous in nature, there is
sometimes ambiguity regarding the exact nature of the active catalytic species. For instance, there
may be leaching of the transition metal species into solution, which may also involve “release and
capture” mechanisms. For a model system of your choosing (where leaching is a possibility), how
would you unambiguously determine whether the active catalytic species was heterogeneous or
homogeneous in nature?
30. For each of the following, determine the molecular and corresponding crystallographic point groups:
(a) a piece of 8.5 x11 paper (no lines), (b) staggered ferrocene, (c) eclipsed ferrocene, (d) hydrogen
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peroxide, (e) cyclopropane.
31. You are given a piece of golden-colored glass, and must add appropriate dopant(s) to yield a colorless
material. What dopant(s) are likely present, and which would you add? Explain.
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32. The lattice parameter of Ag is 0.4084 nm. Calculate the planar concentration (in units atoms/nm )of
atoms on the planes {100}, {110} and {111}.
33. The lattice parameter of Ge is 0.5659 nm. Calculate the number of atoms per unit length, that is the
linear atomic concentration (atoms per nm of length) along <100> and <110> directions.