a. Relative permittivity at optical (visible) frequencies includes ONLY the foll

Question

a. Relative permittivity at optical (visible) frequencies includes ONLY the following polarizability component: (2) [dipolar; ionic: electronic; space-charge] b. Which ceramic fabrication method is the most likely used to fabricate toilet bowls: (2) [sinter+HIP; slip casting; doctor blade: chemical vapor deposition] c. The most precise control over stoichiometry is achieved from which thin film method: (2) [sputtering; thermal evaporation; atomic layer deposition] d. Reflection off an optical surface of a ceramic is primarily dependent on: (2) [absorption coefficient; refractive index; dispersion] e. In terms of their band structure, semiconductors and insulators are characterized by having relatively _____ band gap: (2) [large; small] f. A material which strains in response to an electric field is called a: (2) [dielectric; piezoelectric; pyroelectric] g. The process by which ceramic grains me together and density during heat treatment is called: (2) [pressing; sintering; viscous flow] h. The most important application of ionic conduction in ceramics is in: (2) [electrodes; batteries; windows] i. For normal ceramics which do not exhibit metallic conductivity, the resistivity _____ with decreasing temperature: (2) [decreases; increases; does not change] j. A ceramic with high permittivity will have _____ capacitance in a device: (2) [low; high; negligible] k. Superconducting ceramics like YBCO as magnetic materials are: (2) [ferromagnetic; antiferromagnetic; diamagnetic] l. The permittivity at optical frequencies will always be _____ that at microwave frequencies: (2) [greater than; less than; the same as] m. For infrared transmitting ceramics, the trade-off is always between infrared transmission and: (2) [thermal properties; refractive index; mechanical properties]

Explanation / Answer

1.  Electronic polarization occurs at even higher (i.e. optical) frequencies and is due to the displacement of the electron with respect to the nucleus.

2. Slip casting – here aqueous slurry of ceramic powder is
poured into plaster of Paris mold. As water begins to
move out due to capillary action, thick mass builds
along mold wall. It is possible to form solid piece by
pouring more slurry.

3. C

A method of depositing a thin metal-oxide film having a uniform thickness of about 200 A.

4. The factors that affect ceramic are the refractive index of the material, the angle of incident light and the surface topography.

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