🗊Презентация Crystal Defects and Noncrystalline Structure–Imperfection

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Crystal Defects and Noncrystalline Structure–Imperfection, слайд №1Crystal Defects and Noncrystalline Structure–Imperfection, слайд №2Crystal Defects and Noncrystalline Structure–Imperfection, слайд №3Crystal Defects and Noncrystalline Structure–Imperfection, слайд №4Crystal Defects and Noncrystalline Structure–Imperfection, слайд №5Crystal Defects and Noncrystalline Structure–Imperfection, слайд №6Crystal Defects and Noncrystalline Structure–Imperfection, слайд №7Crystal Defects and Noncrystalline Structure–Imperfection, слайд №8Crystal Defects and Noncrystalline Structure–Imperfection, слайд №9Crystal Defects and Noncrystalline Structure–Imperfection, слайд №10Crystal Defects and Noncrystalline Structure–Imperfection, слайд №11Crystal Defects and Noncrystalline Structure–Imperfection, слайд №12Crystal Defects and Noncrystalline Structure–Imperfection, слайд №13Crystal Defects and Noncrystalline Structure–Imperfection, слайд №14Crystal Defects and Noncrystalline Structure–Imperfection, слайд №15Crystal Defects and Noncrystalline Structure–Imperfection, слайд №16Crystal Defects and Noncrystalline Structure–Imperfection, слайд №17Crystal Defects and Noncrystalline Structure–Imperfection, слайд №18Crystal Defects and Noncrystalline Structure–Imperfection, слайд №19Crystal Defects and Noncrystalline Structure–Imperfection, слайд №20Crystal Defects and Noncrystalline Structure–Imperfection, слайд №21Crystal Defects and Noncrystalline Structure–Imperfection, слайд №22Crystal Defects and Noncrystalline Structure–Imperfection, слайд №23Crystal Defects and Noncrystalline Structure–Imperfection, слайд №24Crystal Defects and Noncrystalline Structure–Imperfection, слайд №25Crystal Defects and Noncrystalline Structure–Imperfection, слайд №26Crystal Defects and Noncrystalline Structure–Imperfection, слайд №27Crystal Defects and Noncrystalline Structure–Imperfection, слайд №28Crystal Defects and Noncrystalline Structure–Imperfection, слайд №29Crystal Defects and Noncrystalline Structure–Imperfection, слайд №30Crystal Defects and Noncrystalline Structure–Imperfection, слайд №31Crystal Defects and Noncrystalline Structure–Imperfection, слайд №32Crystal Defects and Noncrystalline Structure–Imperfection, слайд №33Crystal Defects and Noncrystalline Structure–Imperfection, слайд №34Crystal Defects and Noncrystalline Structure–Imperfection, слайд №35Crystal Defects and Noncrystalline Structure–Imperfection, слайд №36Crystal Defects and Noncrystalline Structure–Imperfection, слайд №37Crystal Defects and Noncrystalline Structure–Imperfection, слайд №38Crystal Defects and Noncrystalline Structure–Imperfection, слайд №39Crystal Defects and Noncrystalline Structure–Imperfection, слайд №40Crystal Defects and Noncrystalline Structure–Imperfection, слайд №41Crystal Defects and Noncrystalline Structure–Imperfection, слайд №42Crystal Defects and Noncrystalline Structure–Imperfection, слайд №43Crystal Defects and Noncrystalline Structure–Imperfection, слайд №44
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Слайды и текст этой презентации

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Chapter 4 Crystal Defects and Noncrystalline Structure–Imperfection
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Chapter 4 Crystal Defects and Noncrystalline Structure–Imperfection

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Crystal Defects and Noncrystalline Structure–Imperfection, слайд №2
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Forming a liquid solution of water and alcohol. Mixing occurs on the molecular scale.
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Forming a liquid solution of water and alcohol. Mixing occurs on the molecular scale.

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Point Defects – in the solid state are more predictable
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Point Defects – in the solid state are more predictable

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Crystal Defects and Noncrystalline Structure–Imperfection, слайд №5
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Point Defects in Alloys
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Point Defects in Alloys

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Solid solution of nickel in copper shown along a (100) plane. This is a substitutional solid solution with nickel atoms substituting for copper atoms on fcc atom sites.
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Solid solution of nickel in copper shown along a (100) plane. This is a substitutional solid solution with nickel atoms substituting for copper atoms on fcc atom sites.

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Imperfections in Solids Conditions for substitutional solid solution (S.S.) Hume – Rothery rules 1. r (atomic radius) < 15% 2. Proximity in periodic table i.e., similar electronegativities 3. Same crystal structure for pure metals 4. Valency equality All else being equal, a metal will have a greater tendency to dissolve a metal of higher valency than one of lower valency (it provides more electrons to the “cloud”)
Описание слайда:
Imperfections in Solids Conditions for substitutional solid solution (S.S.) Hume – Rothery rules 1. r (atomic radius) < 15% 2. Proximity in periodic table i.e., similar electronegativities 3. Same crystal structure for pure metals 4. Valency equality All else being equal, a metal will have a greater tendency to dissolve a metal of higher valency than one of lower valency (it provides more electrons to the “cloud”)

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Imperfections in Solids Application of Hume–Rothery rules – Solid Solutions 1. Would you predict more Al or Ag to dissolve in Zn? 2. More Zn or Al in Cu?
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Imperfections in Solids Application of Hume–Rothery rules – Solid Solutions 1. Would you predict more Al or Ag to dissolve in Zn? 2. More Zn or Al in Cu?

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Imperfections in Solids Specification of composition weight percent
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Imperfections in Solids Specification of composition weight percent

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Wt. % and At. % -- An example
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Wt. % and At. % -- An example

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Converting Between: (Wt% and At%)
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Converting Between: (Wt% and At%)

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Interstitial solid solution applies to carbon in α-iron. The carbon atom is small enough to fit with some strain in the interstice (or opening) among adjacent Fe atoms in this important steel structure. [This unit-cell structure can be compared with that shown in Figure 3.4b.]
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Interstitial solid solution applies to carbon in α-iron. The carbon atom is small enough to fit with some strain in the interstice (or opening) among adjacent Fe atoms in this important steel structure. [This unit-cell structure can be compared with that shown in Figure 3.4b.]

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Random, substitution solid solution can occur in Ionic Crystalline materials as well. Here of NiO in MgO. The O2− arrangement is unaffected. The substitution occurs among Ni2+ and Mg2+ ions.
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Random, substitution solid solution can occur in Ionic Crystalline materials as well. Here of NiO in MgO. The O2− arrangement is unaffected. The substitution occurs among Ni2+ and Mg2+ ions.

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A substitution solid solution of Al2O3 in MgO is not as simple as the case of NiO in MgO. The requirement of charge neutrality in the overall compound permits only two Al3+ ions to fill every threeMg2+ vacant sites, leaving oneMg2+ vacancy.
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A substitution solid solution of Al2O3 in MgO is not as simple as the case of NiO in MgO. The requirement of charge neutrality in the overall compound permits only two Al3+ ions to fill every threeMg2+ vacant sites, leaving oneMg2+ vacancy.

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Iron oxide, Fe1−xO with x ≈ 0.05, is an example of a nonstoichiometric compound. Similar to the case of Figure 4.6, both Fe2+ and Fe3+ ions occupy the cation sites, with one Fe2+ vacancy occurring for every two Fe3+ ions present.
Описание слайда:
Iron oxide, Fe1−xO with x ≈ 0.05, is an example of a nonstoichiometric compound. Similar to the case of Figure 4.6, both Fe2+ and Fe3+ ions occupy the cation sites, with one Fe2+ vacancy occurring for every two Fe3+ ions present.

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Defects in Ceramic Structures
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Defects in Ceramic Structures

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Line Defects
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Line Defects

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Linear Defects (Dislocations) Linear Defects (Dislocations) Are one-dimensional defects around which atoms are misaligned Edge dislocation: extra half-plane of atoms inserted in a crystal structure b (the berger’s vector) is  (perpendicular) to dislocation line Screw dislocation: spiral planar ramp resulting from shear deformation b is  (parallel) to dislocation line
Описание слайда:
Linear Defects (Dislocations) Linear Defects (Dislocations) Are one-dimensional defects around which atoms are misaligned Edge dislocation: extra half-plane of atoms inserted in a crystal structure b (the berger’s vector) is  (perpendicular) to dislocation line Screw dislocation: spiral planar ramp resulting from shear deformation b is  (parallel) to dislocation line

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Edge Dislocation Edge Dislocation
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Edge Dislocation Edge Dislocation

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Definition of the Burgers vector, b, relative to an edge dislocation. (a) In the perfect crystal, an m× n atomic step loop closes at the starting point. (b) In the region of a dislocation, the same loop does not close, and the closure vector (b) represents the magnitude of the structural defect. For the edge dislocation, the Burgers vector is perpendicular to the dislocation line.
Описание слайда:
Definition of the Burgers vector, b, relative to an edge dislocation. (a) In the perfect crystal, an m× n atomic step loop closes at the starting point. (b) In the region of a dislocation, the same loop does not close, and the closure vector (b) represents the magnitude of the structural defect. For the edge dislocation, the Burgers vector is perpendicular to the dislocation line.

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Screw dislocation. The spiral stacking of crystal planes leads to the Burgers vector being parallel to the dislocation line.
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Screw dislocation. The spiral stacking of crystal planes leads to the Burgers vector being parallel to the dislocation line.

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Mixed dislocation. This dislocation has both edge and screw character with a single Burgers vector consistent with the pure edge and pure screw regions.
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Mixed dislocation. This dislocation has both edge and screw character with a single Burgers vector consistent with the pure edge and pure screw regions.

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Burgers vector for the aluminum oxide structure. The large repeat distance in this relatively complex structure causes the Burgers vector to be broken up into two (for O2−) or four (for Al3+) partial dislocations, each representing a smaller slip step. This complexity is associated with the brittleness of ceramics compared with metals. (From W. D. Kingery, H. K. Bowen, and D. R. Uhlmann, Introduction to Ceramics, 2nd ed., John Wiley & Sons, Inc., New York, 1976.)
Описание слайда:
Burgers vector for the aluminum oxide structure. The large repeat distance in this relatively complex structure causes the Burgers vector to be broken up into two (for O2−) or four (for Al3+) partial dislocations, each representing a smaller slip step. This complexity is associated with the brittleness of ceramics compared with metals. (From W. D. Kingery, H. K. Bowen, and D. R. Uhlmann, Introduction to Ceramics, 2nd ed., John Wiley & Sons, Inc., New York, 1976.)

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Imperfections in Solids Dislocations are visible in (T) electron micrographs
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Imperfections in Solids Dislocations are visible in (T) electron micrographs

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Dislocations & Crystal Structures
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Dislocations & Crystal Structures

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Planar Defects in Solids One case is a twin boundary (plane) Essentially a reflection of atom positions across the twinning plane. Stacking faults For FCC metals an error in ABCABC packing sequence Ex: ABCABABC
Описание слайда:
Planar Defects in Solids One case is a twin boundary (plane) Essentially a reflection of atom positions across the twinning plane. Stacking faults For FCC metals an error in ABCABC packing sequence Ex: ABCABABC

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Simple view of the surface of a crystalline material.
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Simple view of the surface of a crystalline material.

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A more detailed model of the elaborate ledgelike structure of the surface of a crystalline material. Each cube represents a single atom. [From J. P. Hirth and G. M. Pound, J. Chem. Phys. 26, 1216 (1957).]
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A more detailed model of the elaborate ledgelike structure of the surface of a crystalline material. Each cube represents a single atom. [From J. P. Hirth and G. M. Pound, J. Chem. Phys. 26, 1216 (1957).]

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Typical optical micrograph of a grain structure, 100×. The material is a low-carbon steel. The grain boundaries have been lightly etched with a chemical solution so that they reflect light differently from the polished grains, thereby giving a distinctive contrast. (From Metals Handbook, 8th ed., Vol. 7: Atlas of Microstructures of Industrial Alloys, American Society for Metals, Metals Park, OH, 1972.)
Описание слайда:
Typical optical micrograph of a grain structure, 100×. The material is a low-carbon steel. The grain boundaries have been lightly etched with a chemical solution so that they reflect light differently from the polished grains, thereby giving a distinctive contrast. (From Metals Handbook, 8th ed., Vol. 7: Atlas of Microstructures of Industrial Alloys, American Society for Metals, Metals Park, OH, 1972.)

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Simple grain-boundary structure. This is termed a tilt boundary because it is formed when two adjacent crystalline grains are tilted relative to each other by a few degrees (θ). The resulting structure is equivalent to isolated edge dislocations separated by the distance b/θ, where b is the length of the Burgers vector, b. (From W. T. Read, Dislocations in Crystals, McGraw-Hill Book Company, New York, 1953. Reprinted with permission of the McGraw-Hill Book Company.)
Описание слайда:
Simple grain-boundary structure. This is termed a tilt boundary because it is formed when two adjacent crystalline grains are tilted relative to each other by a few degrees (θ). The resulting structure is equivalent to isolated edge dislocations separated by the distance b/θ, where b is the length of the Burgers vector, b. (From W. T. Read, Dislocations in Crystals, McGraw-Hill Book Company, New York, 1953. Reprinted with permission of the McGraw-Hill Book Company.)

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Crystal Defects and Noncrystalline Structure–Imperfection, слайд №32
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Specimen for the calculation of the grain-size number, G is defined at a magnification of 100×. This material is a low-carbon steel similar to that shown in Figure 4.18. (From Metals Handbook, 8th ed., Vol. 7: Atlas of Microstructures of Industrial Alloys, American Society for Metals, Metals Park, OH, 1972.)
Описание слайда:
Specimen for the calculation of the grain-size number, G is defined at a magnification of 100×. This material is a low-carbon steel similar to that shown in Figure 4.18. (From Metals Handbook, 8th ed., Vol. 7: Atlas of Microstructures of Industrial Alloys, American Society for Metals, Metals Park, OH, 1972.)

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Optical Microscopy
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Optical Microscopy

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Optical Microscopy
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Optical Microscopy

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Crystal Defects and Noncrystalline Structure–Imperfection, слайд №36
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Determining Grain Size, using a micrograph taken at 300x We count 14 grains in a 1 in2 area on the (300x) image To report ASTM grain size we needed a measure of N at 100x not 300x We need a conversion method!
Описание слайда:
Determining Grain Size, using a micrograph taken at 300x We count 14 grains in a 1 in2 area on the (300x) image To report ASTM grain size we needed a measure of N at 100x not 300x We need a conversion method!

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For this same material, how many Grains would I expect /in2 at 100x? At 50x?
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For this same material, how many Grains would I expect /in2 at 100x? At 50x?

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Crystal Defects and Noncrystalline Structure–Imperfection, слайд №39
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Two-dimensional schematics give a comparison of (a) a crystalline oxide and (b) a non-crystalline oxide. The non-crystalline material retains short-range order (the triangularly coordinated building block), but loses long-range order (crystallinity). This illustration was also used to define glass in Chapter 1 (Figure 1.8).
Описание слайда:
Two-dimensional schematics give a comparison of (a) a crystalline oxide and (b) a non-crystalline oxide. The non-crystalline material retains short-range order (the triangularly coordinated building block), but loses long-range order (crystallinity). This illustration was also used to define glass in Chapter 1 (Figure 1.8).

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Bernal model of an amorphous metal structure. The irregular stacking of atoms is represented as a connected set of polyhedra. Each polyhedron is produced by drawing lines between the centers of adjacent atoms. Such polyhedra are irregular in shape and the stacking is not repetitive.
Описание слайда:
Bernal model of an amorphous metal structure. The irregular stacking of atoms is represented as a connected set of polyhedra. Each polyhedron is produced by drawing lines between the centers of adjacent atoms. Such polyhedra are irregular in shape and the stacking is not repetitive.

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A chemical impurity such as Na+ is a glass modifier, breaking up the random network and leaving nonbridging oxygen ions. [From B. E. Warren, J. Am. Ceram. Soc. 24, 256 (1941).]
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A chemical impurity such as Na+ is a glass modifier, breaking up the random network and leaving nonbridging oxygen ions. [From B. E. Warren, J. Am. Ceram. Soc. 24, 256 (1941).]

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Schematic illustration of medium-range ordering in a CaO–SiO2 glass. Edge-sharing CaO6 octahedra have been identified by neutron-diffraction experiments. [From P. H. Gaskell et al., Nature 350, 675 (1991).]
Описание слайда:
Schematic illustration of medium-range ordering in a CaO–SiO2 glass. Edge-sharing CaO6 octahedra have been identified by neutron-diffraction experiments. [From P. H. Gaskell et al., Nature 350, 675 (1991).]

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Summary Point, Line, Surface and Volumetric defects exist in solids. The number and type of defects can be varied and controlled T controls vacancy conc. amount of plastic deformation controls # of dislocations Weight of charge materials determine concentration of substitutional or interstitial point ‘defects’ Defects affect material properties (e.g., grain boundaries control crystal slip). Defects may be desirable or undesirable e.g., dislocations may be good or bad, depending on whether plastic deformation is desirable or not. Inclusions can be intention for alloy development
Описание слайда:
Summary Point, Line, Surface and Volumetric defects exist in solids. The number and type of defects can be varied and controlled T controls vacancy conc. amount of plastic deformation controls # of dislocations Weight of charge materials determine concentration of substitutional or interstitial point ‘defects’ Defects affect material properties (e.g., grain boundaries control crystal slip). Defects may be desirable or undesirable e.g., dislocations may be good or bad, depending on whether plastic deformation is desirable or not. Inclusions can be intention for alloy development

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