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Structure.questions_VI_answer - Show that Pauling’s first...

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MTLE-2100 Structure of Engineering Materials, Questions VI-Answer 1. Lead screens for the protection of personnel in x-ray diffraction laboratories are usually at least 1 mm thick. Calculate the transmission factor, I trans /I incident , of such a screen for Cu K α , Mo K α , and the shortest wavelengh radiation from a tube operated at 30,000 volts. ρ =11.34 g/cm 3 . λ μ / ρ μ x 0.1 I trans /I incident Cu K α 1.54Å 233.1 264.3 1.7E-115 Mo K α 0.711Å 122.8 139.3 3.3E-61 λ SWL (12400/30KV) 0.413 Å33 37.4 5.8E-17 (by extrapolation) 2. Calculate the breadth B (in degrees of 2 θ ) due to the small crystal effect alone, of the powder pattern lines of particles of diameter 1000, 750, 500 and 250 Å . Assume θ = 45 ° and λ = 1.5 Å . For particles 250 Å in diameter, calculate the breadth B for θ = 10, 45 and 80 ° . t= 0.9 λ /Bcos θ B . B= 0.9 λ /tcos θ B 1000 Å . 0.00191 rad. = 0.11 ° 750 Å . 0.00255 rad. = 0.15 ° 500 Å 0.00382 rad. = 0.22 ° 250 Å . 0.00764 rad. = 0.44 ° 250 Å . θ = 10 ° 0.00548 rad. = 0.31 ° 45 ° 0.44 ° 80 ° 0.0311 rad. = 1.78 ° 3. CsCl structure has Cl at corners of cubic cell and Cs at the body center position.
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Unformatted text preview: Show that Pauling’s first and second rules apply to the compound CsCl. r Cs+ = 1.67 Å , r Cl-= 1.81 Å . r/R = 1. 67 Å /1.81 Å =0.92. CN=8 is expected since the ratio is between 0.73—1.0. Strength of Cs +-Cl- bond = 1/8. Valence of anion, Cl, is one 1 = (CN around Cl) x (1/8). CN around Cl is 8. These are consistent with CsCl structure. 4. What is piezoelectricity? Applied electric field results in setting up an electric charge on the surface of a material. Conversely when an electric field is applied to the material, the material expands in one direction and contract in another direction. 5. What is the glass transition temperature? Temperature separating the super-cooled liquid state from glassy state. 6. What is a polymorphic transformation? Transformation between different crystal structures with the same chemical composition....
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  • Spring '08
  • Tomozawa
  • Glass, Glass transition, CsCl structure, small crystal effect, shortest wavelengh radiation, x-ray diffraction laboratories

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