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REVIEW QUESTIONS

1. Define: a) Ceramics. b) Coordination number. c) Ions radius ratio.

2. What are the common characteristics of ceramics? 3. When can we say that the radius ratio of an ion is the critical radius ratio? 4. How can we judge that a certain ceramic is ionically bonded or covalently

bonded or both? and with what percentage? 5. Draw by differentiating between stable and unstable structures. 6. What are the primary types of atomic bonds in ceramics? 7. Compare between Traditional ceramics & Engineering Ceramics. 8. What are the factors affecting the packing of ions of ceramics? 9. Draw the unit cell and describe the following ceramic structures:

a) NaCl structure. b) CsCl structure. c) Perovskite structure. d) Ba flourite structure .

10. The zinc blende crystal structure is one that may be generated from close-packed planes of anions.

a) Will the stacking sequence for this structure be FCC or HCP? Why?

b) Will cations fill tetrahedral or octahedral positions? Why? c) What fraction of the positions will be occupied?

11. The corundum crystal structure, found for Al2O3, consists of an HCP arrangement of O2- ions; the Al3- ions occupy octahedral positions. What fraction of the available octahedral positions is filled with Al3- ions?

12. What is the anti-fluorite structure? What fraction of tetrahedral interstitial sites are occupied by cations?

SHEET2: CERAMICS STRUCTURES

BENHA UNIVERSITY M462 MATERIAL TECHNOLOGY BANHA FACULTY OF ENGINEERING 4TH YEAR MECHANICAL ENGINEERING MECHANICAL ENGINEERING DEPARTMENT DR. SALEH | ENG. ABDALLA MOHAMED

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13. Describe the perovskite structure. What fraction of octahedral interstitial sites are occupied by the tetravalent cations?

14. What is the spinel crystal structure? What is its best property? 15. Draw a section of graphite structure. Why are the layers of graphite able to

slide past each other easily?

PROPLEMS

1. Determine the coordination number for: SrO and RbCl. Ionic radii: Sr2+ = 0.127 nm, O2- = 0.132 nm, Rb+ = 0.149 nm, Cl- = 0.181 nm.

2. Predict CN for CsI, NiO, KI, and NiS. Ionic radii: Cs+ = 0.17, O2- = 0.14, I- = 0.22, Ni+2 = 0.069, K+ = 0.138 nm.

3. Calculate the density in gm/cm3 of: CsBr, NiO and CdO. Ionic radii: Cs+ = 0.165 nm, Br- = 0.196 nm, Ni2+ = 0.078 nm, Cd2+ = 0.103 nm, and O2- = 0.132 nm. CsBr CsCl structure and NiO & CdO Nacl structure.

4. Calculate the linear density in ions/nm in the [110] and [111] directions for BaO and CoO. Ionic radii: Ba2+ = 0.143 nm, Co2+ = 0.082 nm, O2- = 0.132 nm. BaO and CoO NaCl structure.

5. Calculate the planar density in ions/nm2 on the (111) and (110) planes for FeO and KBr. Ionic radii: Fe2+ = 0.087 nm, K+ = 0.133 nm, O2- = 0.132 nm, and Br- = 0.196 nm. FeO and KBr NaCl structure.

6. For each of the following crystal structures, represent the indicated plane, showing both anions and cations:

a) (100) plane for the rock salt crystal structure. b) (110) plane for the cesium chloride crystal structure. c) (110) plane for the perovskite crystal structure.

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