7. Which of the following is false: a. The coefficient of thermal expansion is larger if the bond energy is smaller b. Ceramics are generally ionic bonding c. Van der Waals bonding is generally stronger than covalent bonding d. The free electrons in metallic bonding is reason for electrical conductivity 8. Which of the following is true: a. Polymers are generally denser than ceramices b. Young's modulus of ceramics are similar to polymers c. Composites have higher tensile strength than metals d. Ceramics have low resistance to fracture than metals

7. Which of the following is false: a. The coefficient of thermal expansion is larger if the bond energy is smaller b. Ceramics are generally ionic bonding c. Van der Waals bonding is generally stronger than covalent bonding d. The free electrons in metallic bonding is reason for electrical conductivity 8. Which of the following is true: a. Polymers are generally denser than ceramices b. Young's modulus of ceramics are similar to polymers c. Composites have higher tensile strength than metals d. Ceramics have low resistance to fracture than metals

Elements Of Electromagnetics

7th Edition

ISBN:9780190698614

Author:Sadiku, Matthew N. O.

Publisher:Sadiku, Matthew N. O.

ChapterMA: Math Assessment

Section: Chapter Questions

Problem 1.1MA

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*.Cements are considered as ceramic types -1 a- traditional. b- advanced. *...Ceramics bonding are -2 a- covalent. C- mixed. b- ionic. * Metals are than Ceramics -3 a- harder. b- softer. .Metals have good ductility because -4 b- their low bonding strength. a- their bonds are nondirectional. .. Ceramics are bad electrical conductors because -5 b- they have low electronegativity. a- their valence electrons are restricted.
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What are valid reasons for adding Yttrium to the zirconia in the Thermal Barrier Coating (TBC) in a turbine blade? Select one or more: a. To match the thermal conductivity of the TBC to the metal substrate b. To increase the weight of the TBC c. To prevent a change of the crystallographic structure as the temperature changes d. To match the thermal conductivity of the TBC to the underlying oxide layer e. To avoid breakage during change in thermal conditions
Ceramics materials have high temperature .. . resistance due to إجابتك The attraction force of the metallic bonds is depended on إجابتك the principal regions of a .. . macrostructure are إجابتك A substitutional defect is introduced when إجابتك The solubility of carbon in austenite is greater than to that of ferrite is due to إجابتك
3. Metals have ............ thermal conductivity value compared to polymers. a. Low b. Very low c. High d. Medium 4. Determine the length of a copper wire that has a cross - sectional area as 8.1 mm2. The resistance and the electrical resistivity of the copper wire are 14 and 1.79 x 10-6 m. The length of a copper wire (in meters)
QUESTION 3: [Thin-walled Pressure Vessels] 1. A cylindrical pressure vessel is fabricated from steel plating that has a thickness of 20 mm. The diameter of the pressure vessel is 450 mm, and its length is 2.0 m. Determine the maximum internal pressure that can be applied if the longitudinal stress is limited to 140 MPa, and the circumferential stress is limited to 60 MPa. 2. A compound thin cylinder has a common diameter of 100 mm, and the inner cylinder has a thickness of 2,5 mm. The radial pressure between the two cylinders is 200 kPa and the difference between the two common diameters before shrinkage was 4,305x 10-3 mm. E = 200 GPa. Determine a. Thickness of the outer cylinder b. Resultant hoop stresses in both cylinders if the compound cylinder is subjected to an internal pressure of 180 kPa.
The theoretical failure strength is significantly higher than the empirical failure strength of polycrystalline materials, even when they are highly polished because: a) Polycrystalline materials have little or no capacity for plastic deformation, so they have lower failure stresses b) Plastic deformation in polycrystalline materials adsorbs energy which reduces their failure strength c)The energy needed to break the atomic bonds in crystal lattices is lower in polycrystalline materials as compared to in single crystals d)Polycrystalline materials contain internal discontinuities
Compression molding is a manufacturing process in which the molding material is preheated then placed in an open mold cavity where the compressive action of the punch forces the polymer into the desired shape as shown in the figure below. Based on your understanding of the behavior of polymers, which of the statements below regarding compression molding of polymers are accurate? Punch Cavity C. -Upper mold half Charge 41 (1) -Lower mold half Knock-out pin V, F |x.F (2) and (3) Molded part a. Lower operating temperatures are more desirable as they reduce viscosity making it easier to fill the cavity b. This process can only be used for thermosets as they can thermally cure from monomer state This process can be used for both thermosets and thermoplastics as they can both be thermally shaped d. This process is suitable for rubber, PVC and polymethyl methacrylate
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Question 1 You are working on a design team at a small orthopaedic firm. You have been asked to select a cobalt- chrome-molybdenum (CoCr) material that will not experience plastic deformation under a specific mechanical test, as follows... A tensile stress is applied along the long axis of a solid cylindrical rod that has a diameter of 10 mm. An applied load of some magnitude F produces a 7x10-³ mm change in diameter (see figure below, original shape is blue, elongated shape is unshaded). Q1G: If your design required using the new material to create a wire, what is the largest diameter that would lead to ductile behavior while still avoiding plastic deformation when exposed to the above loading conditions?
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