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11/22/2017 10:05:29 PM
Posted: 9/4/2004 2:06:43 PM EST
[Last Edit: 9/4/2004 2:12:11 PM EST by scottryan]
Question 1:
Iron changes from body centered cubic to face centered cubic at 912°C. At this temperature the atomic radii of the iron atoms in the two structures are 1.26 Angstroms and 1.29 Angstroms respectively. What is the percent of volume change as the iron transforms. (Hint: remember the law of conservation of matter)

Quesiton 3:

An FCC metal powder which has a lattice parameter of 3.15 Angstroms was examined by X-Ray diffraction using Cu K(alpha, ave) incident radiation.

A) Calculate the value of 2 Theta angle necessary for observation of the (111) diffraction line.
B) Give the Miller indices and 2 Theta angle of the next higher angle line, if any
C) Give the miller indices and 2 Theta angle of the next lower angle line, if any.


Question 4:
Assuming that the wavelength of the X-rays in a diffractometer are from chromium (wavelength =2.29 Angstroms), compute the Bragg angle for the reflection of the X-Rays from the (211) planes of a body centered cubic iron crystal.

thanks
Scott
Link Posted: 9/4/2004 2:11:06 PM EST
That made my head hurt!
Link Posted: 9/4/2004 2:25:27 PM EST
Link Posted: 9/4/2004 7:42:41 PM EST
Anyone else got any info?
Link Posted: 9/4/2004 7:48:21 PM EST
There was a guy at the place that I take my car for oil changes that knows all that shit. He said look at what it got him. A job in a pit scraping dog guts off of oil pans so he could change the oil for people that can barely read.

Just pulling your leg. If you can wait till tuesday I'll ask some of my scientist and engineers at work.
Link Posted: 9/4/2004 7:51:36 PM EST
How about asking the professor, or one of his Pak/Chinese grad students?

This stuff is straight out of Met 309/310. If you don't know this stuff, TALK TO THE PROF teaching the class. If you are not getting it, you need to. There may be others in the same boat.

Don't let the prof ASSUME you know the stuff if you don't.

My thermo prof was 15 minutes late for class, and he stomped on in and pointed to me: "You! You know you don't need oxygen for an oxidation reaction to occur. Yes or No." Ummmm, yes. He went on down the line asking the same question.

Turns out one of his students got canned for incompetence in front of a senior management meeting, and he called up Pesic and screamed at him. I can imagine how that all went down....
Link Posted: 9/4/2004 9:25:35 PM EST
[Last Edit: 9/4/2004 10:12:03 PM EST by ROKIT88]
Q1 the lattice parameter gives you the side measurement of a cubic
structure:
side of FCC = 2*r*(2^(1/2))
side BCC = 4*r/(3^(1/2))
where 'r'=atomic radius
These formulae should be derived in your text.

You also need to know how many atoms are in each cube

FCC = 4 ( 8 1/8 pieces, 6 halves)
BCC = 2 (8 1/8 pieces, one whole center )


Now calculate the volume of FCC ( cube of side of FCC r=1.29)/4
" " " BCC " " " r=1.26)/2

This gives you the volume per atom of each structure.

Divide your FCC # by your BCC number and you have the volume change.

Good luck on the crystallography portion.

I can only assume the class is going to get more difficult, seek the professor's help as suggested above.


edited: because I can't visualize/count correctly
Link Posted: 9/5/2004 6:52:05 PM EST
[Last Edit: 9/5/2004 6:53:07 PM EST by scottryan]

Originally Posted By pogo:
How about asking the professor, or one of his Pak/Chinese grad students?



That is the problem, the professor is Chinese and the TAs are also and I can't understand him and everyone is pissed off. This is only the second week of the semester and I don't know what I am going to do?

I have never had this much trouble with a class. I have a 3.9 GPA.
Link Posted: 9/5/2004 8:35:29 PM EST
There should be a Teaching Enhancement Committee on your campus.

Basically, you TALK - no names taken - to a representative and their JOB is to look into the allegations and effect changes. At the U of Idaho this was taken pretty seriously when I got a heavyweight star prof from out behind his desk and in front of students again. The Pak grad student went back to his lab.

I would look into this.
Link Posted: 9/5/2004 8:49:38 PM EST
Ah yes, U Idaho physics recitation:

"I.... am...... not very excited for you."
--Ning Li as he handed back lab reports.

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