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Consider a DVD similar to that of Problem 5.99. To protect sensitive information within the storage medium, a very thin film of reactive polymer is embedded within the polycarbonate at a distance d = 0.5 mm from the surface. The thin film can undergo a chemical reaction with oxygen during which it is converted from a transparent material to an opaque material, rendering the information unreadable. The chemical reaction begins when the oxygen concentration at the reactive polymer reaches
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Fundamentals of Heat and Mass Transfer
- 3. A block of pure iron needs to be converted to steel. The density of iron is 7.86x10^3kg/m^3, and the atomic weight is 0.0558kg/mol. The concentration of carbon at position A is 4x10^26 at/m^3. The carbon atomic weight is 0.012kg/mol. Carbon must be diffused into the iron to convert it to steel. It is desired to have 1025 atoms of carbon per m' at point B. Position A is 1mm from position B. Assume that you have 1m^3 of iron. You heat the material uniformly to 1200°C. Do, carton = 79x10 * m/sec, Ea = 83kJ/mol, and the density of carbon is 2260kg/m^3. (4pts) 1mm Fe block A What is Dearbon at 1200°C in m?/sec? i. ii. Calculate the FLUX (J) of carbon atoms in atoms per m²-sec at 1200°C? B.arrow_forwardIn an electrochemical cell, a metal anode lost 0.227 g while a total volume of 0.08149 L of hydrogen gas was produced. The temperature was 298 K and the barometric pressure was 745.4 mm Hg. At 298 K, the vapor pressure of water is 23.8 mm Hg. How many moles of hydrogen gas were collected?arrow_forwardIm absolutely lost and need help !arrow_forward
- Problem 3 An FCC iron-carbon alloy initially containing 0.35 wt% C is exposed to an oxygen-rich and virtually carbon- free atmosphere at 1400 K (1127 °C). Under these circumstances the carbon diffuses from the alloy and reacts at the surface with the oxygen in the atmosphere; that is, the carbon concentration at the surface position is maintained essentially at 0 wt% C. (This process of carbon depletion is termed decarburization.) At what position will the carbon concentration be 0.15 wt% after a 10-h treatment? The value of D at 1400 K is 6.9 x 10¹¹ m²/s.arrow_forwardDetermine the following 1. Determine what substance has a great strength? Calculate and demonstrate. 2. Determine the substance that has greater resilience? Calculate and demonstrate. 3. Determine which one of the samples have stronger molecular bonds? Give a brief explanation of your response. Draw diagrams as necessary.arrow_forwardA mechanism for hardening steel is called carburization. To achieve this process, the piece of steel is exposed to an atmosphere rich in hydrocarbon such as methane (CH4). Consider a steel with a carbide concentration of 0.25wt%, which must be treated at 950˚C. If the carbon concentration at the surface is suddenly increased to 1.20wt%, how long does it take for a penetration of 0.5mm from the surface to reach a concentration of 0.80wt%? . The diffusion coefficient for carbon in iron at this temperature is 1.6 x 10-11 m2s-1. Assume that the piece of steel is semi-finite. Use the table below.arrow_forward
- 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 methacrylatearrow_forward6. If we approximate the atmosphere to be 79% Nitrogen (N2) by volume and 21% oxygen (O2), estimate the density of air (kg/m3) and ppmv at 1 atmosphere and ambient temperatures of 40 C and 450 C. (Atomic weight of nitrogen=14)arrow_forwardParvinbhaiarrow_forward
- An optical fiber for telecommunication is made of SiO2 glass with a density of 3.2 (g/cm3). Given a 8 mm long and 10 µm diameter fiber. Calculate the number of atoms of Si in the fiber. Given: Avogadro's Number NA = 0.6023 x 1024 (atoms/mole) Molar mass: M(Si)=28.09 g/mole • M(0)=16 g/mole Select one: a. N(si atoms)=2.0153× 1016 b. N(Si atoms)=1.558 × 1016 C. N(Si atoms)=3.464x 1015 d. N(si atoms)=5.195 x 1012 e. N(Si atoms)=5.195 x 1015arrow_forwardVacancy diffusion vs interstitial diffusion (when they can happen?)arrow_forward1. You have ice at 263 K (-10.0 °C) and 1.0 atm. Whatvcould you do to make the ice sublime? 2. A sample of dry ice (solid CO2) is cooled to 173 K (-100.0 °C), and is set on a table at room temperature (298 K; 25 °C). At what temperature is the rate of sublimation and deposition the same (assume that pressure is held constant at 1 atm)?arrow_forward
- Refrigeration and Air Conditioning Technology (Mi...Mechanical EngineeringISBN:9781305578296Author:John Tomczyk, Eugene Silberstein, Bill Whitman, Bill JohnsonPublisher:Cengage Learning