课程名称︰材料科学概论 课程性质︰系选修 课程教师︰吕宗昕 开课学院：工学院 开课系所︰化工系 考试日期（年月日）︰100/1/10 考试时限（分钟）：120 是否需发放奖励金：是 （如未明确表示，则不予发放） 试题 : 1. (a) Please describe the behavior of creep.(4 Points) (b) Please describe the major three steps of fatigue failure.(6 points) (c) Please draw figures to show the fracture behavior for highly ductile materials, moderately ductile materials, and brittle materials.(6 points) 2. A copper alloy gas a plane strain fracture toughness if 52 MPa, It is found fracture results at a stress of 430MPa when the maximum interal crack length us 3.2mm. Compute the stress in the same alloy when fracture will occur for a critical interal crack length of 4.5mm.(15 points) 3. Steady state creep rate data are listed as below for aluminum @ 1200 degree C creep rate: 10E-4 (1/s) at stress = 12MPa creep rate: 10E-6 (1/s) at stress = 4MPa Compute the steady state creep rate @ 800 degree C when stress =11MPa. The activation energy for creep is 320 kJ/mol. (15 points) 4. (a) What is the crystal structure name and indicate the position of each ion for BaTiO3. (6 points) (b) Please calculate the ideal density of BaTiO3. Atomic weights of Ba, Ti, O are 137.34, 47.90, and 15.9994, respectively. The lattice constant of BaTiO3 is 0.42 nm. (6 points) 5. A parallel plate capacitor has an area of 8 E-3 m^2 and a plate separation of 4 E-4 m. The applied voltage is 30V. The polarization of the inserted material is 3 E-6 C/m^2. Calculate the dielectric constand of the material, the capacitance of the capacitorm the stored charge on each plate, abd the dielectric displacement. 8.85 E-12 is given. (20 points) 6. (a) Please draw the band structures for conductors such as Cu and extrinsic p-type semiconductors. (8 points) (b) Please draw a phase diagram for Al2O3-Cr2O3. These two materials form complete solid solutions. m.p. of Al2O3 = 2045 and of Cr2O3 = 2275 degree C. (4 points) 7. Calculate the conductivity of the doped silicon @ 30 degree C when 3 E16 1/m^3 phosphorus is doped in silicon. The electrical condoctivity for pure silicon @ 30 degree C is 7.6 E-4 1/(ohm-m), amd the electrom and hole mobility are 0.18 and 0.064 m^2/v-s, and e= 1.6 E-19. (10%) ends -- 十年生死两茫茫　不思量　自难忘　千里孤坟　无处话凄凉 纵使相逢应不识　尘满面 鬓如霜 夜来幽梦忽还乡　小轩窗　正梳妆　相顾无言　唯有泪千行 料得年年肠断处 明月夜 短松冈 --

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