Chapter_5_Solutions-_Study_Guide_for_Exam_2

The purification of hydrogen gas is possible by diffusion through a thin palladium sheet. Calculate the number of kilograms of hydrogen that pass per hour through a 2.8 mm thick sheet of palladium having and area of 0.72 m^2 at 500 C.  Assume a diffusion coefficient of 7.8 x 10^-8 m^2/s, that the concentrations at the high- and low- pressure sides of the plates are 3.4 and 0.58 kg/m^3 of hydrogen per cubic meter of palladium, and that steady-state conditions have been attained.

Determine the diffusion coefficient D for the diffusion of hydrogen into FCC iron at 800°C

The diffusion coefficients for species A in metal B are given at two temperatures: T (°C) D(m²/s) 1020 7.60E-17 1260 7.49E-16 (a) Determine the value of the activation energy Qd (in J/mol). i (b) Determine the value of Do. J/mol m²/s (Use scientific notation.) (c) What is the magnitude of D at 1170°C? m2/s (Use scientific notation.)

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Q(2): Answer the following (: 1. Are the materials that have a large particle size of their atoms diffusion through it faster, or are the materials that have a relatively small particle size, explain briefly? 2. How can the light be absorbed by color center? 3. The diffusion coefficients for zinc in copper at (500°C) and (700°C) are 2.4 x 1018 and 4.6 x 1018 m2/s, respectively. Determine the approximate time at 500°C that will produce the same diffusion result (in terms of concentration of Zn at some specific point in Cu) as a 8h heat treatment at (600°C). 4. Explain how is the equilibrium number of vacancies will change with temperature and activation energy?

Arrange the gases CO, N2 and CH4 in increasing order of adsorption on the surface of charcoal in a closed vessel. Give reasons also.

Determine the number of Frenkel and Schottky defects per cubic centimeter of a metal chloride at 40 deg Celcius. The energy for defect formation is 3.2 eV, and the density of the metal chloride is 7.80 g/mL at 40 deg Celcius.

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Carbon is allowed to diffuse through a steel plate 12 mm thick. The concentrations of carbon at the two faces are 0.87 and 0.42 kg C/m3 in Fe, which are maintained constant. If the preexponential and activation energy are 6.2 × 10-7 m2/s and 80,000 J/mol, respectively, compute the temperature (in K) at which the diffusion flux is 6.4 × 10-10 kg/m2-s.

A sheet of steel 1.8 mm thick has nitrogen atmospheres on both sides at 1200°C and is permitted to achieve a steady-state diffusion condition. The diffusion coefficient for nitrogen in steel at this temperature is 6 x 10-1" m²/s, and the diffusion flux is found to be 1.2 x 107 kg/m²-s. Also, it is known that the concentration of nitrogen in the steel at the high-pressure surface is 4 kg/m’. How far into the sheet from this high-pressure side will the concentration be 2.0 kg/m³? Assume a linear concentration profile.

Compute diffusion coefficients for the interdiffusion of carbon in both (a) a-iron (BCC) and (b) y-iron (FCC) at 975°C. Assume that Do for the interdiffusion of carbon in a-iron and in y-iron are 1.1 x 106 and 2.3 x 105 m²/s, respectively, and that Quare 80 and 148 kJ/mol, respectively. (a) (b) m²/s m²/s

Coprecipitation due to surface adsorption can be minimized by the following except: reducing the surface area, i.e precipitating under conditions where more nuclei are formed and small crystals resulted Carrying out a separation of ions that would be strongly adsorbed or replacing it with strongly absorbed ions lowering the oxidation number of metal ions so that it's charge reduced using hot solutions to reduce the amount of adsorption per unit area

We want to obtain a silicon semiconductor by doping with Aluminium. Find the value of the diffusion coefficient at a temperature of 756°C? Data: Diffusion coefficient of Al in Si (T = 500°C) = 2.69·10-22 cm2/s Diffusion coefficient of Al in Si (T = 1000°C) = 1.806·10-13 cm2/s D0 = 8 cm2/s; R = 8.314 J/mol K

Ab 29.

At room temperature (i.e., 300 K), a semiconductor made of gallium arsenide (GaAs) has an intrinsic electron concentration (ni) of 1.8×10^6 cm^-3 , an electron mobility (μe) of 8500 cm^2 V^1 s^-1 , and a hole mobility (μh) of 400 cm^2 V^-1 s^-1 . \ (a) Calculate the intrinsic electric conductivity and resistivity of GaAs at 300 K. (b) When GaAs is doped with an ionized donor concentration of 10^15 cm^-3 , where is the Fermi level? Calculate the electric conductivity of the doped GaAs. (c) If the semiconductor sample discussed in (b) is further doped with an ionized acceptor concentration of 9×10^14 cm^-3 , what is the free hole concentration and electric conductivity of the sample?

The band gap of gallium phosphide is 2.26 eV, which makes it appropriate for producing yellow LEDs, although the yellow color is rarely useful on its own (think a yellow laser pointer). One can alter the band gap of GaP, changing the emission color to red or green. Propose the ways to produce these two colors by (1) chemical (compositional) and (2) physical (non-compositional) modifications of the material.

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2. A three-point loading scheme for measuring the stress-strain behavior and flexural strength, σF, (stress at fracture) of brittle ceramics for rectangular and circular cross sections materials are shown below. 3FfL = πR³ 2bd2 (depending on the FfL The flexural strength σF, can be calculated as: σFƒ cross section shape). = Calculate the ceramic flexural strength when Fƒ=1030 N, L=3.5 cm and 2R=b=d=1 cm and define which structure is stronger. Show your work. Note when you calculate, don't forget to unit conversion! Ff R Compression Tension

Determine the number of Frenkel defects per cubic centimeter of a metal chloride at 40 deg Celcius. The energy for defect formation is 3.2 eV, and the density of the metal chloride is 6.50 g/mL at 40 deg Celcius.

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A first order reflection from the (123) planes of a cubic crystal was observed at an angle of e = 24.8 ° when X-rays of wavelength 154 pm were used. 1 h k? 1? d u? b? na = 2d sin e -= - hki (i) Determine the length of the side of the unit cell.

4. An alloy has an elastic modulus of 115 GPa. For the alloy, plastic deformation begins at a stress of 275 MPa. (a) If a sample of cross-sectional area 325 mm? is obtained from the alloy, determine the maximum load that may be applied on the sample without plastic deformation. (b) The original sample length is specified as 115 mm, what is the maximum length to which the sample can be stretched without plastic deformation.