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Assignment #1 (Click for Solutions)

Question #1: Calculate the increase in surface area for the following conditions:

1. A spherical particle with a radius of 100 $\mu m$ to be reduced to a group of particles with 10 nm radius
2. A cylindrical wire with a radius of 100 $\mu m$ and a length of 100 $\mu m$ to be reduced to a group of wires with 10 nm radius and 100 nm length.
3. A cube particle with a length of 100 $\mu m$ to be reduced to a group of cubes with 10 nm length

Question #2: Estimate the ratio of surface to bulk atoms in following conditions:

1. Spherical clusters – for cluster of radii 1) 5 $\mu m$, 2) 500 nm, 3) 1 nm.
2. Cubic clusters – for cluster of length 1) 5 $\mu m$, 2) 500 nm, 3) 1 nm.

In typical metals the surface atom layer has a thickness of 2 $A\textsuperscript{o}$.

Question #3: The reaction for the deposition of $SiO_2$ on the surface is:

$SiH_4 (gas) + O_2 (gas) \rightarrow SiO_2 (solid) + 2 H_2 (gas)$

Gallium nitride (GaN) is an important wide-band-gap semiconductor. Propose a chemical reaction for the deposition of GaN.

Question #4: How long will it take for the spherical particles in Table 1 to settle, at their terminal velocities under free-settling conditions, through 2 m of water at 20$\textsuperscript{o}C$?

Question #5: Explain the applications of thin fi lms in the fields of energy and environment?