---------------------------------------------------------------------

Read Class Handout Notes on Aerogel Manufacture "Aerogels"

Notation: <123> means page 123. thinking means you have to think about it.

1. Describe the chemical reactions in making Silica aerogels: (1) Hy______ (2) Co_____. Write down the chemical equations for TEOS. 2. What is a sol, and what is a gel? 3. What is an alcogel? 4. Why is supercritical drying important? What causes shrinkage of an aerogel upon drying? What is a supercritical fluid? 5. How much shrinkage is there for an alcogel if dried by supercritical fluid? and how much shrinkage by evaporation? What is a xerogel? 6. What are the two common precursors for making silica aerogel? Write down the chemical formulas. 7. What kind of catalysts are used in the gelation reactions? What size and shape of particles are formed typically? 8. What are the differences between the single-step and the two-step processes in making aerogels? Where can you buy this pre-polymerized stuff? 9. Which of the above two processes will give a more translucent gel? 10. How do you age an aerogel? Why do you have to age it? Usually how many hours are required? 11. What fluid is normally used for supercritical drying? What is the critical temperature of this fluid? What is the operating pressure? How long does it take to dry? 12. What is the recipe for making a single-step base-catalyzed silica aeogel? 13. Do you have an idea of what an aerogel is now? What applications are there? Why is it a nanomaterial? (Describe the size of the beads of silica and the pore size distribution). How strong can aerogels be? ---------------------------------------------------------------------