Analysis Seminar

7/31/2019 Analysis Seminar

1/31

PROVIDED BY

EMAD BEHDAD

SPECIALIZED PROTECTION AND CORROSION OF MATERIALS

LECTURERSH.MONAJATI,PHD

JAFARI,PHD

ISLAMIC AZAD UNIVERSITY OF NAJAFABAD

BARANCH OF MATERIAL SCIENCE ENGINEERING

EDXRF WDXRF TXRF


2/31

Atoms in the sample are excited and emit characteristic x-rays

x-ray source

x-ray detector

Energy of characteristic x-rays Types of elements present (qualitative analysis)

Number of x-rays for each element concentration (quantitative analysis)


3/31

Tube excited XRF

Radio-isotope excited XRF

Secondary target Synchrotron,

Total reflection of x-ray florescence

Wavelength dispersive (WD-XRF)

Energy dispersive (ED-XRF)

Filter instruments (proportional counter)

Based on the excitation

Based on the detection


4/31

*Energy dispersive X-ray spectroscopy (EDS or EDX)

*Analytical technique used for the elemental analysis

*Technique used for chemical characterization of a sample

*Investigation of a sample *Analyzing X-rays emitted by the matter

*Full quantitative analysis showing the sample composition


5/31

HOW EDX WORKS ?

A high-energy beam of charged particles is focused into the

sample

Ground state(unexcited) electrons in sample are stimulated

Electrons are excited from lower energy shells to higher energyshell

The difference in energy between the shells may be released in

the form of an X-ray

The number and energy of the X-rays emitted from a specimen

can be measured by an energy dispersive spectrometer


6/31

SCHEMATICS OF EDX


7/31


8/31

The heart of an ED-spectrometer is a semi-conductor crystal (Si, Ge)

a high voltage is applied over the crystal (bias -600V)

and the crystal is cooled (e.g. at liquid nitrogen temperature)When x-rays enter the crystal electron-hole pairs are formed

the number is proportional to the energy of the x-ray

because of the bias the electrons are swept out of the crystal

For each photon an electric pulse is produced with an amplitudeproportional to the energy.

Measuring the amplitude and counting produces the ED-spectrum.

What is the principle behind ED spectrometers?


9/31

WHY EDX Fast

(Non)-destructive

Sample Area

Good precision, accuracy

Fair sensitivity

Multi-element analysis

Generally not portable

Some sample preparation required

Experienced staff

Moderately expensive


10/31


11/31

Wavelength dispersive X-ray spectroscopy (WDXRF or WDS)

A method used to count the number of X-rays

Reads or counts only the x-rays of a single wavelength

Element must be known

Often used in conjunction with EDS


12/31

Identification of spectrally overlapped elements

Detection of low concentration species (10-100 ppm)

Analysis of low atomic number elements

Oxidation and corrosion of metals


13/31

The WDX operates in much the same way as EDX.

Unlike the related technique of Energy dispersive X-ray

spectroscopy (EDX)WDX reads or counts only the x-rays

of a single wavelength, not producing a broad spectrum ofwavelengths or energies.

The crystal structure of sample diffracts the photons in

principles of Bragg's law.

Diffractions are then collected by a detector.


14/31


15/31

(Non)-destructive

High accuracy

Excellent precision & long term

stability

Good resolution & sensitivity

Multi-element analysis

Well-established technique

Some sample preparation

Qualified, experience staff

Expensive


16/31

Comparison of WD and ED X-ray Detectors

Most important advantages of WD: Higher resolution, sensitivity

Most important advantages of ED: Cheaper, faster (except for

multichannel WD) Other differences (more detailed comparison):


17/31

DIAGRAM AND CURVES WDS V.S EDS


18/31


19/31

TOTAL REFLECTION X-RAY FLUORESCENCE

(TXRF)

Total reflection X-ray fluorescence analysis (TXRF) is basically an energy dispersive

analytical technique in special excitation geometry.


20/31

USAGE AREAS OF TXRF

Total reflection X-ray fluorescence (TXRF) has become

increasingly popular in micro and trace elemental analysis.

It is being used in geology, biology, materials science, medicine,

forensics, archaeology, art history, and more.

Unlike the high incident angles (~ 40 ) used in traditional XRF,

TXRF involves very low incident angles.

These low angles allow the X-rays to undergo total reflection.


21/31

Background reduced.

Double excitation of sample by both the primary and the reflected beam.

No matrix effects.

Calibration and quantification independent from any sample matrix.

Simultaneous multi-element ultra-trace analysis.

Several different sample types and applications.

Excellent detection limits (ppt or pg) for all elements from sodium to plutonium.

Excellent dynamic range from ppt to percent.

Possibility to analyses the sample directly without chemical pretreatment.

Non destructive analysis.

Low running cost.


22/31

EXPERIMENTAL ANALYSIS RESULTS

Spectrum of a 3 L mineral water sample, spiked with 1 ng/L Ga asinternal standard element. Excitation in TXRF geometry with a multilayer

monochromator by a Mo X-ray tube (50 kV, 10 mA, 1000 s measuring

time).


23/31

PIXEPROVIDED BY

ZABIH ALLAH KHANSHA

MATERIAL SURFACE


24/31

MATERIAL SURFACE.

PROCESSES RELEVANT TO ION BEAM

ANALYSIS


25/31

2-3 MeV

X-rays

Detector

Si(Li)

sample


26/31

REACTION PIXE BOX


27/31

PIXE USAGE 2004

Environmental &Atospheric

Archaeology & Arts

Biomedical

material & Earth Science

33%16%

24%

27%


28/31

JAME MOSQUE SLIMES PIXE

ANALYSIS


29/31

SPECTRUMES PIXE SAMPLES LIVER

BIOPSY


30/31

TYPICAL PIXE SPECTRUM OF NORMAL AND VARICOSE

VEINS WITH 175MM MAYLAR ABSORBER IN FRONT OF

SI(LI) DETECTOR


31/31

QUESTIONS ?

THANKS FOR YOUR

ATTENTION

Documents

Analysis Seminar