{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

sampleMT2solutions

# sampleMT2solutions - Sample Midterm MASC 310 Midterm II...

This preview shows pages 1–4. Sign up to view the full content.

Sample Midterm MASC 310 Midterm II Prof. Nutt CLOSED BOOK, CLOSED NOTES CALCULATORS ALLOWED SOLUTIONS

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Equations ( 29 ( 29 2 2 eff 1 erf 2 exp 8.31 J/mol 1 ln 1 x o s o d o T i T dC J D dx C C D x x C C x C C Dt x Dt Q D D RT R K F A σ σ ε ε ε = - = - = - - = - = = ° = = + = + ( 29 ( 29 ( 29 CRSS max 1 2 C cos cos %CW= 100% r o y y o y o d o Ic t E t k d A A A K Y a σ ε τ σ φ λ σ σ σ π - = = = + - × = % RA = A o - A f A o × 100 ε Tf = ln 100 100 - RA HYPERLINK "http://www.wiley.com/college/callister/0470125373/img_galleries/ch06/pages/c06tf02.htm" INCLUDEPICTURE "http://www.wiley.com/college/callister/0470125373/img_galleries/ch06/images/c06tf01.jpg" \* MERGEFORMATINET
1. Diffusion The strength of many oxide glasses can be improved tremendously by exchanging larger ions for smaller ions in the surface of the glass, a process called ion stuffing. For example, immersion of a lithia-alumina-silicate glass plate in molten potassium nitrate (KNO 3 ) at ~500°C for four hours allows the potassium ions to replace the smaller lithium ions in the glass near the surface, putting the surface in compression. Composition profiles show that the concentration of potassium at a depth of 20 μ m increases from 0 to about 10 weight percent. During immersion in the salt, the concentration of potassium is ~16 weight percent. Estimate the diffusion coefficient. This is a Fick’s Second Law problem, with solution 1 erf 2 x o s o C C x C C Dt - = - - The initial concentration of potassium in the glass is 0 weight percent (wt%) so that C o = 0.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 7

sampleMT2solutions - Sample Midterm MASC 310 Midterm II...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online