UNIVERSIDADE FEDERAL DE SANTA CATARINA
Disciplina: FSC 3303 Tpicos Especiais em Fsica C: Introduo Difrao de Raios-X
Ano/Semestre: 2010/1
Professor: Carlos Eduardo Maduro de Campos
LISTA DE PROBLEMAS TEMA 2
1. What is the frequency (per second) and energy
1
Thermodynamic treatment of vacancies in elemental solid
If an elemental crystal of N atoms has n vacancies, then the number of ways the n
vacancies can be distributed is given as.
2
For ionic crystal of MX type, Schottky defects involve formation of equ
Diffraction basics
Equivalence of Laue equations and Braggs law
How is it that Braggs diffraction is also called Braggs reflection?
Diffraction under non-ideal conditions
Non ideal conditions and Integrated intensity
Because of experimental limitations, a
1
Basics of x-ray diffraction
X-rays: Electromagnetic radiation whose wavelength lies in the range of few Angstroms
Diffraction: A result of superposition of waves from scatters located on a 3D lattice.
Superposition principle: The resultant of a superpos
Assignments (taken from B D Cullitys, book)
Q. If the intensity ratio of (200) Bragg peak of Cr and (111) peak of Al is 0.5, calculate the relative
weight fraction of Cr and Al in the mixture.
Use the Wulff net given above to
Draw standard 111 stereographic projection of a cubic crystal. That is draw the poles
of all the possible cfw_100, cfw_110 and cfw_111 planes.
Note: Ashish Shekhar has taken the transparent sheets from me. You can take one
Braggs law in reciprocal space
The Braggs law can be rewritten as
2 is the angle between the incident and the
diffracted waves
2ddhl sin =
sin = (/dhkl)/2 = (1/dhkl)/(2/)
For all points P on the circle of radius 1/,
Bragg law is satisfied.
Combining the
Calculate the cohesive energy of copper (ccp structure) given the bond energy between two copper
atoms is 56.4 kJ/mol.
The surface of a solid has unsaturated bonds. Such unsaturated bonds give rise to surface energy
(Joule/m2) . Determine the surface ener
1
X-ray generation and detection
X-ray generation in laboratory
As a result, the metal target requires continuous cooling during x-ray generation.
2
Shortest wavelength radiation (min) emitted is determined by complete loss of the KE in
one single event.
1
Space groups
References:
1. Crystallogrpahy for Solid State Physics by A. R. Verma and O. N. Srivastava.
2. Introduction to Solids by L. V. Azaroff
3. Structure of Materials by Marc de Graef and Michael E Mc Henry
Space groups are derived by combining t
Silica and silicates
The formula of one unit is
(SiO4)4-
Linking of SiO4 tetrahedra (Compare this arrangement with those in the spharelite
Effective number of Si per unit =1
Effective number of O per unit is 4 x 1/2 = 2
The crystalline form of silica occu
Microscope
Magnification = v/u = (v-f)/f
Three lens system
Schematic of electron microscope
Electron microscopes exist because electron lens exists
These lenses are electromagnetic in nature (solenoid like)
Electron microscopes exists because
(i)
electron
1
Structure and characterization (MT-241)
Bonds and crystal structures
Bonding in solids, Cohesive energy for ionic and vanderWaals solids, simple
crystal structures of inorganic and metallic solids.
Geometrical crystallography
Lattice, Bravais lattices,
Chapter 4 Point defects and dislocations
I. Lattice impurities and vacancies
1. A point defect in a crystal is (i) the occupancy of a lattice sites by impurity atoms/ions or a voids (i.e. vacancy); or (ii) extra atoms/ions not in regular lattice positions
1
Crystal structure = lattice motif
Basis vectors and translation vectors
By selecting three non-coplanar basis vectors a, b and c lattice can be generated by
operating the translational operator T
T = u a + v b + w c (u, v w are integers, including 0 and
DETERMINATION OF ACTIVATION
ENERGY FOR THE OXIDATION OF NICKEL
Submitted by,
Bhaskar Sravan (07716)
R. Harini (07636)
Kumar Navin (07503)
AIM
To observe the microstructure of the oxide layer formed on the given sample of pure
Nickel and to calculate the p
Extrusion
an indirect-compression process.
forces developed by the reaction of the work piece (billet) with the container
and die reach substantially high values.
reaction of the billet with the container and die results in high compressive
stresses.
-eff
Forging
A billet is plastically deformed between two tools (dies) to obtain desired final configuration
Simple part geometry is transformed into a complex one
Role of Tools:
store the desired geometry
impart pressure on the deforming material through tool
Work Balance
A simple method for estimating the forces and energy involved
in some metal forming operations
Energy to complete an operation
= the ideal work required for shape change
in absence of friction and inhomogeneous flow (wi)
+
the work against fr
Dynamic recovery and recrystallization
Dynamic recovery
During dynamic recovery, the original grains get increasingly strained,
th
but the sub-boundaries remain more or less equiaxed
- the substructure is dynamic and re-adapts continuously to the
substruc
Microstructural
Microstructural heterogeneity due to alloying elements
Effect of solute atoms
Effect of second phase particles
Influence of alloying elements
Strong influence of alloying elements on the work hardening behaviour
th
depends on whether the e
Deformation twinning
In polycrystalline agreegates, the change in shape accompanying deformation
require the operation of several slip systems
Sudden localised shear process TWINNING involves a small but well
defined volume of the crystal
defined volume o
Theory of Work Hardening of Metals
Initial flow due to slip movement of dislocations
Subsequent hardening-due to hindrance in movement of dislocations
Other dislocations
Grain and subgrain boundaries
Solute atoms
atoms
Particles of a second phase
Surface