©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />PHYSICAL PROPERTIES OF MATERIALS...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Physical Properties Defined<br /...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Physical Properties in Manufactu...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Volumetric and Melting Propertie...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Density and Specific Gravity Def...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Why Density is Important<br />Im...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Thermal Expansion<br />Density o...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Coefficient of Thermal Expansion...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Thermal Expansion in Manufacturi...
Problem 4.2<br />A bridge built with steel girders is 500 m in length and 50 m in width.  Expansion joints are provided to...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Assume L1 = 500m at -35ºC<br />C...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Use formula 4.1<br />L2 – L1 = α...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Each expansion joint will contro...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Melting Characteristics for Elem...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Melting of Metal Alloys<br />Unl...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Melting of Alloys: Solidus and L...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Melting of Noncrystalline Materi...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Volume-to-Weight Changes<br />Fi...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Importance of Melting in Manufac...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Thermal Properties<br />Thermal ...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Specific Heat <br />The quantity...
Problem 4.5<br />With reference to Table 4.2, determine the quantity of heat required to increase the temperature of an al...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Use formula 4.2<br />H = CW(T2 –...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />The weight of aluminum is equal ...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Heat = (0.21cal/gºC)(103 cm3)(2....
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Why convert from cal to J?<br />
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Why convert from cal to J?<br />...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Volumetric Specific Heat <br />T...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Thermal Conductivity<br />Therma...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Thermal Diffusivity<br />The rat...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Thermal Properties in Manufactur...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Mass Diffusion<br />Movement of ...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Mass Diffusion<br />Figure 4.2  ...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Mass Diffusion in Manufacturing<...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Electrical Properties<br />Engin...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Electrical Properties<br />Movem...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Electrical Resistance<br />Resis...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Resistivity <br />Property that ...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Conductivity<br />Often more con...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Materials and Electrical Propert...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Semiconductors <br />A material ...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Electrical Properties in Manufac...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Electrochemistry<br />Field of s...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Terms in Electrochemical Process...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Electrolysis<br />The name given...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Electrolysis Example<br />Figure...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Chemical Reactions in the  Decom...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Chemical Reactions in the Decomp...
©2007 John Wiley & Sons, Inc.  M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Electrolysis in Manufacturing Pr...
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  1. 1. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />PHYSICAL PROPERTIES OF MATERIALS<br />Volumetric and Melting Properties<br />Thermal Properties<br />Mass Diffusion<br />Electrical Properties<br />Electrochemical Processes<br />
  2. 2. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Physical Properties Defined<br />Properties that define the behavior of materials in response to physical forces other than mechanical<br />Include: volumetric, thermal, electrical, and electrochemical properties<br />Components in a product must do more than simply withstand mechanical stresses<br />They must conduct electricity (or prevent conduction), allow heat to transfer (or allow its escape), transmit light (or block transmission), and satisfy many other functions<br />
  3. 3. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Physical Properties in Manufacturing<br />Important in manufacturing because they often influence process performance<br />Examples:<br />In machining, thermal properties of the work material determine the cutting temperature, which affects tool life<br />In microelectronics, electrical properties of silicon and how these properties can be altered by chemical and physical processes is the basis of semiconductor manufacturing<br />
  4. 4. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Volumetric and Melting Properties<br />Properties related to the volume of solids and how the properties are affected by temperature <br />Includes: <br />Density<br />Thermal expansion<br />Melting point <br />
  5. 5. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Density and Specific Gravity Defined<br />Density = weight per unit volume <br />Typical units are g/cm3 (lb/in3) <br />Determined by atomic number and other factors such as atomic radius, and atomic packing<br />Specific gravity = density of a material relative to density of water and is a ratio with no units<br />
  6. 6. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Why Density is Important<br />Important consideration in material selection for a given application, but it is generally not the only property of interest<br />Strength is also important, and the two properties are often related in a strength‑to‑weight ratio, which is tensile strength divided by density<br />Useful ratio in comparing materials for structural applications in aircraft, automobiles, and other products where weight and energy are concerns<br />
  7. 7. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Thermal Expansion<br />Density of a material is a function of temperature<br />In general, density decreases with increasing temperature<br />Volume per unit weight increases with increasing temperature<br />Thermal expansion is the name for this effect of temperature on density<br />Measured by coefficient of thermal expansion <br />
  8. 8. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Coefficient of Thermal Expansion<br />Change in length per degree of temperature, such as mm/mm/C (in/in/F) <br />Length ratio rather than volume ratio because this is easier to measure and apply <br />Change in length for a given temperature change is: <br /> L2 ‑ L1 = L1 (T2 ‑ T1) <br /> where  = coefficient of thermal expansion; L1 and L2 are lengths corresponding respectively to temperatures T1 and T2<br />
  9. 9. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Thermal Expansion in Manufacturing<br />Thermal expansion is used in shrink fit and expansion fit assemblies<br />Part is heated to increase size or cooled to decrease size to permit insertion into another part<br />When part returns to ambient temperature, a tightly‑fitted assembly is obtained <br />Thermal expansion can be a problem in heat treatment and welding due to thermal stresses that develop in material during these processes<br />
  10. 10. Problem 4.2<br />A bridge built with steel girders is 500 m in length and 50 m in width. Expansion joints are provided to compensate for the change in length in the support girders as the temperature fluctuates. Each expansion joint can compensate for a maximum of 100mm of change in length. From historical records it is estimated that the minimum and maximum temperatures in the region will be -35ºC and 38ºC, respectively. What is the minimum number of expansion joints required?<br />
  11. 11. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Assume L1 = 500m at -35ºC<br />Coefficient of Thermal Expansion<br />α = 12 x 10-6/ºC for Steel Table 4.1 <br />
  12. 12. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Use formula 4.1<br />L2 – L1 = αL1(T2 – T1)<br />L2 - L1 = 12 x 10-6(500)(38-(-35))<br />L2 - L1 = 0.42 m<br />
  13. 13. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Each expansion joint will control 100mm = 0.1 m of expansion. 4 joints will provide 0.400 m of expansion. 5 joints will provide 0.500 m of expansion.<br />Therefore a minimum of 5 joints are needed for coverage of the total length.<br />
  14. 14. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Melting Characteristics for Elements<br />Melting pointTm of a pure element = temperature at which it transforms from solid to liquid state<br />The reverse transformation occurs at the same temperature and is called the freezing point<br />Heat of fusion = heat energy required at Tm to accomplish transformation from solid to liquid<br />
  15. 15. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Melting of Metal Alloys<br />Unlike pure metals, most alloys do not have a single melting point<br />Instead, melting begins at a temperature called the solidus and continues as temperature increases until converting completely to liquid at a temperature called the liquidus<br />Between the two temperatures, the alloy is a mixture of solid and molten metals <br />Exception: eutectic alloys melt (and freeze) at a single temperature<br />
  16. 16. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Melting of Alloys: Solidus and Liquidus<br />Figure 6.3 Phase diagram for the tin‑lead alloy system.<br />
  17. 17. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Melting of Noncrystalline Materials<br />In noncrystalline materials (glasses), a gradual transition from solid to liquid states occurs<br />The solid material gradually softens as temperature increases, finally becoming liquid at the melting point<br />During softening, the material has a consistency of increasing plasticity (increasingly like a fluid) as it gets closer to the melting point<br />
  18. 18. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Volume-to-Weight Changes<br />Figure 4.1 Changes in volume per unit weight (1/density) as a function of temperature for a hypothetical pure metal, alloy, and glass.<br />
  19. 19. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Importance of Melting in Manufacturing<br />Metal casting - the metal is melted and then poured into a mold cavity<br />Metals with lower melting points are generally easier to cast <br />Plastic molding - melting characteristics of polymers are important in nearly all polymer shaping processes<br />Sintering of powdered metals - sintering does not melt the material, but temperatures must approach the melting point in order to achieve the required bonding of powders<br />
  20. 20. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Thermal Properties<br />Thermal expansion, melting, and heat of fusion are thermal properties because temperature determines the thermal energy level of the atoms, leading to the changes in materials<br />Additional thermal properties:<br />Specific heat<br />Thermal conductivity<br />These properties relate to the storage and flow of heat within a substance<br />
  21. 21. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Specific Heat <br />The quantity of heat energy required to increase the temperature of a unit mass of material by one degree<br />To determine the energy to heat a certain weight of metal to a given temperature: <br /> H = C W (T2 ‑ T1) <br /> where H = amount of heat energy; C = specific heat of the material; W = its weight; and (T2 ‑ T1) = change in temperature<br />
  22. 22. Problem 4.5<br />With reference to Table 4.2, determine the quantity of heat required to increase the temperature of an aluminum block that is 10 cm x 10 cm x 10 cm from room temperature (21ºC) to 300ºC.<br />
  23. 23. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Use formula 4.2<br />H = CW(T2 – T1)<br />The Specific Heat of aluminum from Table 4.2 is C = 0.21Cal/gºC<br />
  24. 24. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />The weight of aluminum is equal to the Volume x Density<br />W = (10 cm3)(2.70 g/cm3)<br />
  25. 25. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Heat = (0.21cal/gºC)(103 cm3)(2.70 g/cm3)(300ºC - 21ºC)<br />Heat = 158,193 cal<br />Conversion: 1.0 cal = 4.184 J, so <br />Heat = 661,879 J<br />
  26. 26. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Why convert from cal to J?<br />
  27. 27. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Why convert from cal to J?<br />Calories is a unit of work; Joules is a unit of heat energy.<br />
  28. 28. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Volumetric Specific Heat <br />The quantity of heat energy required to raise the temperature of a unit volume of material by one degree<br />Density multiplied by specific heat C<br />Volumetric specific heat = C<br />
  29. 29. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Thermal Conductivity<br />Thermal conductivity of a material = capability to transfer heat through itself by the physical mechanism of thermal conduction<br />Thermal conduction = transfer of thermal energy within a material from molecule to molecule by purely thermal motions; no transfer of mass <br />Measure= coefficient ofthermal conductivityk. Units: J/s mm C (Btu/in hr F) <br />Coefficient of thermal conductivity is generally high in metals, low in ceramics and plastics <br />
  30. 30. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Thermal Diffusivity<br />The ratio of thermal conductivity to volumetric specific heat is frequently encountered in heat transfer analysis <br />
  31. 31. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Thermal Properties in Manufacturing<br />Important in manufacturing because heat generation is common in so many processes <br />In some cases, heat is the energy that accomplishes the process <br />Examples: heat treating, sintering of powder metals and ceramics<br />In other cases, heat is generated as a result of the process<br />Examples: cold forming and machining of metals<br />
  32. 32. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Mass Diffusion<br />Movement of atoms or molecules within a material or across a boundary between two materials in contact<br />Because of thermal agitation of the atoms in a material (solid, liquid, or gas), atoms are continuously moving about <br />In liquids and gases, where the level of thermal agitation is high, it is a free‑roaming movement <br />In metals, atomic motion is facilitated by vacancies and other imperfections in the crystal structure<br />
  33. 33. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Mass Diffusion<br />Figure 4.2 Mass diffusion: (a) model of atoms in two solid blocks in contact: (1) when two pieces are first brought together, each has its own compositions; (2) after time, an exchange of atoms occurs; and (3) eventually, a uniform concentration occurs. The concentration gradient dc/dx for metal A is plotted in (b).<br />
  34. 34. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Mass Diffusion in Manufacturing<br />Surface hardening treatments based on diffusion include carburizing and nitriding<br />Diffusion welding - used to join two components by pressing them together and allowing diffusion to occur across boundary to create a permanent bond <br />Diffusion is also used in electronics manufacturing to alter the surface chemistry of a semiconductor chip in very localized regions to create circuit details <br />
  35. 35. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Electrical Properties<br />Engineering materials exhibit a great variation in their capability to conduct electricity<br />Flow of electrical current involves movement of charge carriers ‑ infinitesimally small particles possessing an electrical charge <br />In solids, these charge carriers are electrons <br />In a liquid solution, charge carriers are positive and negative ions<br />
  36. 36. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Electrical Properties<br />Movement of charge carriers is driven by the presence of electric voltage<br />And resisted by the inherent characteristics of the material, such as atomic structure and bonding between atoms and molecules<br /> Ohm's law: I = <br /> where I = current, A, E = voltage, V, and R = electrical resistance, <br />
  37. 37. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Electrical Resistance<br />Resistance in a uniform section of material (e.g., a wire) depends on its length L, cross‑sectional area A, and resistivity of the material r<br /> or <br /> where resistivity r has units of ‑m2/m or ‑m (‑in.)<br />
  38. 38. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Resistivity <br />Property that defines a material's capability to resist current flow <br />Resistivity is not a constant; it varies, as do so many other properties, with temperature <br />For metals, resistivity increases with temperature <br />
  39. 39. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Conductivity<br />Often more convenient to consider a material as conducting electrical current rather than resisting its flow<br />Conductivity of a material is simply the reciprocal of resistivity: <br /> Electrical conductivity = <br /> where conductivity has units of (‑m)‑1 or (‑in)‑1<br />
  40. 40. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Materials and Electrical Properties<br />Metals are the best conductors of electricity, because of their metallic bonding<br />Most ceramics and polymers, whose electrons are tightly bound by covalent and/or ionic bonding, are poor conductors <br />Many of these materials are used as insulators because they possess high resistivities <br />
  41. 41. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Semiconductors <br />A material whose resistivity lies between insulators and conductors<br />Most common semiconductor material is silicon, largely because of its abundance in nature, relative low cost, and ease of processing<br />What makes semiconductors unique is the capacity to significantly alter conductivities in their surface chemistries in very localized areas to fabricate integrated circuits <br />
  42. 42. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Electrical Properties in Manufacturing<br />Electric discharge machining - uses electrical energy in the form of sparks to remove material from metals <br />The important welding processes, such as arc welding and resistance spot welding, use electrical energy to melt the joint metal<br />Capacity to alter electrical properties of semiconductor materials is the basis for microelectronics manufacturing<br />
  43. 43. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Electrochemistry<br />Field of science concerned with the relationship between electricity and chemical changes, and the conversion of electrical and chemical energy<br />In a water solution, molecules of an acid, base, or salt are dissociated into positively and negatively charged ions<br />Ions are the charge carriers in the solution <br />They allow electric current to be conducted, playing the same role that electrons play in metallic conduction<br />
  44. 44. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Terms in Electrochemical Processes<br />Electrolyte - the ionized solution<br />Electrodes – where current enters and leaves the solution in electrolytic conduction<br />Anode - positive electrode<br />Cathode - negative electrode <br />The whole arrangement is called an electrolytic cell<br />
  45. 45. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Electrolysis<br />The name given to these chemical changes occurring in the solution<br />At each electrode, chemical reaction occurs, such as: <br />Deposition or dissolution of material<br />Decomposition of gas from the solution<br />
  46. 46. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Electrolysis Example<br />Figure 4.3 Example of electrolysis: decomposition of water; electrolyte = dilute sulfuric acid (H2SO4); electrodes = platinum and carbon (both chemically inert).<br />
  47. 47. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Chemical Reactions in the Decomposition of Water<br />The electrolyte dissociates into the ions H+ and SO4=<br />H+ ions are attracted to negatively charged cathode; upon reaching it they acquire an electron and combine into molecules of hydrogen gas <br /> 2H+ + 2e  H2 (gas) <br />
  48. 48. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Chemical Reactions in the Decomposition of Water<br />The SO4= ions are attracted to the anode, transferring electrons to it to form additional sulfuric acid and liberate oxygen<br /> 2SO4= ‑ 4e + 2 H2O  2H2SO4 + O2 <br />The product H2SO4 is dissociated into ions of and SO4= again and so the process continues <br />
  49. 49. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e<br />Electrolysis in Manufacturing Processes<br />Electroplating ‑ an operation that adds a thin coating of one metal (e.g., chromium) to the surface of a second metal (e.g., steel) for decorative or other purposes<br />Electrochemical machining ‑ a process in which material is removed from the surface of a metal part <br />Production of hydrogen and oxygen gases<br />

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