PROVIDED BY EMAD BEHDAD

SPECIALIZED PROTECTION AND CORROSION OF MATERIALS

LECTURERSH.MONAJATI,PHD

JAFARI,PHDISLAMIC AZAD UNIVERSITY OF NAJAFABAD

BARANCH OF MATERIAL SCIENCE ENGINEERING

EDXRF WDXRF TXRF

INTRODUCTION X-ray Fluorescence (XRF)• 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)

Types of XRF instruments

• • 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

WHAT IS EDX ? • *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

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 energy shell

• 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

SCHEMATICS OF EDX

EXPERIMENTAL RESULTS OF EDX

Energy-dispersive spectrometers

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 amplitude

proportional to the energy.

Measuring the amplitude and counting produces the ED-spectrum.

What is the principle behind ED spectrometers?

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

DETECTOR AND CRYOSTAT

WHAT IS WDX ?• 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

Usage areas of wdx

• Identification of spectrally overlapped elements

• Detection of low concentration species (10-100 ppm)

• Analysis of low atomic number elements

• Oxidation and corrosion of metals

HOW WDX WORKS• 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 of wavelengths or energies.

• The crystal structure of sample diffracts the photons in principles of Bragg's law.

• Diffractions are then collected by a detector.

SCHEMATICS OF WDX EXPLANATION

(Non)-destructive

High accuracy

Excellent precision & long term stability

Good resolution & sensitivity

Multi-element analysis

Well-established technique

WHY WDX Some sample preparation

Qualified, experience staff

Expensive

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):

DIAGRAM AND CURVES WDS V.S EDS

TOTAL REFLECTION X-RAY FLUORESCENCE (TXRF)• Total reflection X-ray fluorescence analysis (TXRF) is basically an energy dispersive

• analytical technique in special excitation geometry.

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.

ADVANTAGES OF TXRF• • 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.

EXPERIMENTAL ANALYSIS RESULTS

Spectrum of a 3 μL mineral water sample, spiked with 1 ng/μL Ga asinternal standard element. Excitation in TXRF geometry with a multilayermonochromator by a Mo X-ray tube (50 kV, 10 mA, 1000 s measuring time).

PIXEPROVIDED BY

ZABIH ALLAH KHANSHA

Proton Induced X-ray Emission

INTERACTION BETWEEN MEV IONS AND A MATERIAL SURFACE.PROCESSES RELEVANT TO ION BEAM ANALYSIS

PROTON INDUCED X-RAY EMISSION

2-3 MeV

X-rays

DetectorSi(Li)

sample

REACTION PIXE BOX

PIXE USAGE 2004

Environmental & AtosphericArchaeology & ArtsBiomedicalmaterial & Earth Science

33%16%

24%

27%

JAME MOSQUE SLIMES PIXE ANALYSIS

SPECTRUMES PIXE SAMPLES LIVER BIOPSY

TYPICAL PIXE SPECTRUM OF NORMAL AND VARICOSE VEINS WITH 175MM MAYLAR ABSORBER IN FRONT OF SI(LI) DETECTOR

• QUESTIONS ? • THANKS FOR YOUR

ATTENTION