Lecture

Crystal Structure: Diffraction and Bragg's Law

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In course

MSE-101(a): Materials:from chemistry to properties

Ce cours permet l'acquisition des notions essentielles relatives à la structure de la matière, aux équilibres et à la réactivité chimique en liaison avec les propriétés mécaniques, thermiques, électriques et magnétiques des matériaux. ...

Description

This lecture covers the principles of diffraction, focusing on the observation of atomic arrangements using transmission electron microscopy and x-ray diffraction. It explains how to determine crystal structures by analyzing diffraction patterns and Miller indices. The lecture also discusses the organization of atoms in solids, including microstructures and composite materials.

Instructor

Véronique Michaud

Background: 1994 Habilitation à diriger des recherches ( INPG, France) 1991 PhD in Materials Engineering ( MIT, USA) 1987 Ingénieur Civil des Mines ( Ecole des Mines de Paris, France) Activities: Since January 2018: Associate Dean of Engineering, in charge of Education June 2012-Dec.2017: Head of the Materials Science and Engineering Section Since April 2017: Associate Professor at EPFL 2009-2017 : Professeur Titulaire at EPFL 1997-2009: Researcher at EPFL 1994-1997 : Chef de Travaux au laboratoire MSS-MAT, Ecole Centrale Paris (France) 1991-1994 : Post-doctoral research associate, MIT (USA) Author of about 300 publications of which 140 in peer-reviewed journals

Official source

Ontological neighbourhood

Earth science

Geology: Mineralogy

Related concepts (31)

Crystal structure

In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions, or molecules in a crystalline material. Ordered structures occur from the intrinsic nature of the constituent particles to form symmetric patterns that repeat along the principal directions of three-dimensional space in matter. The smallest group of particles in the material that constitutes this repeating pattern is the unit cell of the structure.

Fresnel diffraction

In optics, the Fresnel diffraction equation for near-field diffraction is an approximation of the Kirchhoff–Fresnel diffraction that can be applied to the propagation of waves in the near field. It is used to calculate the diffraction pattern created by waves passing through an aperture or around an object, when viewed from relatively close to the object. In contrast the diffraction pattern in the far field region is given by the Fraunhofer diffraction equation. The near field can be specified by the Fresnel number, F, of the optical arrangement.

Fraunhofer diffraction

In optics, the Fraunhofer diffraction equation is used to model the diffraction of waves when plane waves are incident on a diffracting object, and the diffraction pattern is viewed at a sufficiently long distance (a distance satisfying Fraunhofer condition) from the object (in the far-field region), and also when it is viewed at the focal plane of an imaging lens. In contrast, the diffraction pattern created near the diffracting object and (in the near field region) is given by the Fresnel diffraction equation.

Diffraction from slits

Diffraction processes affecting waves are amenable to quantitative description and analysis. Such treatments are applied to a wave passing through one or more slits whose width is specified as a proportion of the wavelength. Numerical approximations may be used, including the Fresnel and Fraunhofer approximations. Because diffraction is the result of addition of all waves (of given wavelength) along all unobstructed paths, the usual procedure is to consider the contribution of an infinitesimally small neighborhood around a certain path (this contribution is usually called a wavelet) and then integrate over all paths (= add all wavelets) from the source to the detector (or given point on a screen).

Composite material

A composite material (also called a composition material or shortened to composite, which is the common name) is a material which is produced from two or more constituent materials. These constituent materials have notably dissimilar chemical or physical properties and are merged to create a material with properties unlike the individual elements. Within the finished structure, the individual elements remain separate and distinct, distinguishing composites from mixtures and solid solutions.

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