24小时热门版块排行榜

返回列表

当前主题已经存档。

luyunrosa

木虫 (小有名气)

应助: 4 (幼儿园)
金币: 3319.2
帖子: 198
在线: 61.3小时
虫号: 282731
注册: 2006-09-24
性别: MM
专业: 金属结构材料

[交流] Explain what is "EBSD"

Explain what is "ebsd"--electric backscatter diffraction. The materials is writing in English. it is good for beginner.

Section 1
Basics of EBSD
Principal system components
The principal components of an EBSD system
are
■ A sample tilted at 70° from the horizontal.
■ A phosphor screen which is fluoresced by
electrons from the sample to form the
diffraction pattern.
■ A sensitive charge coupled device (CCD)
video camera for viewing the diffraction
pattern on the phosphor screen.
■ A vacuum interface for mounting the
phosphor and camera in an SEM port. The
camera monitors the phosphor through a
lead glass screen in the interface, and the
phosphor can be retracted to the edge of
the SEM chamber when not in use.
■ Electronic hardware that controls the SEM,
including the beam position, stage, focus,
and magnification.
■ A computer to control EBSD experiments,
analyze the diffraction pattern and process
and display the results.
■ An optional electron detector mounted
below the phosphor screen for electrons
scattered in the forward direction from
the sample.

For EBSD, a beam of electrons is directed at a point of interest on a tilted crystalline sample in the SEM (Figure 2). The mechanism by which the
diffraction patterns are formed is complex, but the following model describes the principal features. The atoms in the material inelastically scatter a
fraction of the electrons, with a small loss of energy, to form a divergent source of electrons close to the surface of the sample. Some of these electrons are incident on atomic planes at angles which satisfy the
Bragg equation: nλ = 2d sin θ (1)
where n is an integer, λ is the wavelength of the electrons,
d is the spacing of the diffracting plane, and θ is
the angle of incidence of the electrons on the diffracting plane. These electrons are diffracted to form a set of paired large angle cones corresponding to each diffracting plane. When used to form an image on the
fluorescent screen, the regions of enhanced electron intensity between the cones produce the characteristic Kikuchi bands of the electron back
scattered diffraction pattern (Figure 3).
Figure 1: Components of an EBSD system
Figure 2: Formation of the diffraction pattern
Figure 3: A diffraction pattern from nickel collected

回复此楼