Material Science All three families of materials (metals, polymers & ceramics) u
ID: 2074193 • Letter: M
Question
Material Science
All three families of materials (metals, polymers & ceramics) use thermal processing to change the shape and properties of materials in engineering components. This is accomplished by changing the internal structure, microstructure and composition of the material. One approach to moving atoms to new positions is by elevated temperature solid state diffusion .
Instructions- Fill in the empty blanks for the axes on plots on the concept map with the best choices from the word selection bank. Focused reading: Callister Ch. 5: Sec. 5.2 p. 142; Ch. 5 Summary p. 158 Diffusion of Solids Factors that affect A. Impurity Diffusion B. Grain Boundary Diffusion C. Interstitial Diffusion D. Vacancy Diffusion E. Surface Diffusion F. Pipeline Diffusion G. Self Diffusion Diffusion is mass transfer by translation of particles (atoms, molecules, or ions) 0-D Bulk Temperature Activation energy (Q) In diffusion, activation energy (Q) is the energy required to overcome an energy barrier Concentrationcold worked Factors that affect Diffusion in metal is 2. 5, 6. significant when T>Tm/2 (K) D= Doexp (-RT occurs by occurs by Net flow of Grain move along boundaries Sinters D: diffusion coefficient [m2 toward the Lowers lattice dislocationprovide locationAtom areas of lower energy by concentration recrystallization Microstructure Do: pre-exponential [m2/s] atom movement movementDiffusing diffusion Perticles Od: activation energy [Jmol or eVlatom R: gas constant [8.314 Wmol-K] T: absolute temperature [K] and grain adjacenti in between atom and atom and lattice sites lattice are lattice are element different Q interstitialExplanation / Answer
1.Vacancy Diffusion(A defect in which an atom is missing from one of the lattice sites is known as a "vacancy" defect.It is the simplest point defect.)
2.Interestitial Diffusion(Interstitials defects are a variety of crystallographic defects where atoms assume a normally unoccupied site in the crystal structure.)
3.Schottky Defect( In ionic crystals, the defect forms when oppositely charged ions leave their lattice sites, creating vacancies.)
4.Frenkel Defect(A Frenkel defect is a type of defect in crystalline solids wherein an atom is displaced from its lattice position to an interstitial site, creating a vacancy at the original site and an interstitial defect at the new location within the same element without any changes in chemical properties.)
5.Edge Dislocation(An edge dislocation is a defect where an extra half-plane of atoms is introduced midway through the crystal, distorting nearby planes of atoms.The dislocation has two properties, a line direction, which is the direction running along the bottom of the extra half plane, and the Burgers vector which describes the magnitude and direction of distortion to the lattice. In an edge dislocation, the Burgers vector is perpendicular to the line direction.)
6.Twin Boundaries(A twin boundary or composition surface separates the two crystals.It also results in increasing the net potential energy of the lattice makes it unstable and non uniformity of the properties will be present in the lattice.)
7.Stacking Fault(In crystallography, a stacking fault is a type of defect which characterizes the disordering of crystallographic planes.It also results in decreasing the interatomic distance,increasing the potential energyof the lattice.The most common example of stacking faults is found in close-packed crystal structures.FCC structures differ from HCP structures only in stacking order: both structures have close-packed atomic planes.