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Lecture 3 Part 1. Positron Annihilation Lifetime Spectroscopy (PALS) Principles and application s for nano science. Positron Annihilation Lifetime Spectrometer (PALS). POSITRON SOURCES POSITRON-MATTER INTERACTION POSITRON ANNIHILATION LIFETIME SPECTROMETER (PALS)

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Lecture 3

Part 1

Positron Annihilation Lifetime Spectroscopy

(PALS)

Principles and applications for nano science



POSITRON SOURCES

POSITRON-MATTER INTERACTION

POSITRON ANNIHILATION LIFETIME SPECTROMETER (PALS)

PALS APPLICATIONS on POLYMERS


  • POSITRON SOURCE

  • The decay of neutron-deficiency radio isotopes (β+), 22Na

  • Pair formation by high energy γ-rays


22 na 22 ne e fig 1 decay scheme of a 22 na nucleus
22Na 22Ne + γ + β+ + υeFig. 1 Decay scheme of a 22Na nucleus





HV; High Voltage power supply, SC; Plastic scintillator, PMT Base; Photomultiplier main base, PMT;

Photomultiplier tube, CFD; Constant fraction discriminator, FC; Fast coincidence, DB; Delay box,

TAC; Time to amplitude converter, ADC/MCA; Analogical to digital converter/Multi cannel analyzer,

22Na; Positron source within the sample.

Fig. 3 Flowchart for PAL spectrometer


Energy window Base; Photomultiplier main base, PMT;

for start

Detector

(1.28 MeV)

Energy window

for stop

Detector

(0.51 MeV)

Fig. 8 Energy spectrum of 22Na detected by a multichannel analyzer of PAL spectrometer with the plastic detectors scintillator


Fig. 9 Energy spectrum of 22Na detected by a multichannel analyzer ofPAL spectrometer, after lower and upper level adjustment for start signals


2ns analyzer of

5ns

8ns

10ns

14ns

FWHM

Fig.10 The prompt curve for 60Coγ-rays, under 22Na window settings at the different

delay times (2, 5, 8,10 and 14 ns)


Fig.11 The plot of delay time versus channel number analyzer of

The resolution of the instrument=ns/channel x FWHM

Resolution of PALS spectrometers are in the range of 190-250 ps


PAL spectra of polymers analyzer of

Fig. 13 Positron lifetime spectra of non-irradiated-PE-foam; (a) Count versus

channel number(b) Count versus time. One channel corresponds to 0.052 ns.


Lifetime distribution of silicon sample 1 120 ps 2 320 ps and 3 520 ps math lab program melt
Lifetime distribution of silicon sample analyzer ofτ1 = 120 ps, τ2 = 320 ps, and τ3 = 520 ps. (Math. lab.program, melt)



Ro-R analyzer of

The o-Ps lifetime, τo-Ps directly correlates with the radius of free volume holes and its intensity (Io-Ps) containsinformation about the free volume concentration (Jean, 1990). The average radius (R) of free volume holes on a quantum mechanical model developed by Tao (1972) and Eldrup et al. (1981) were proposed as follows:

R is the average radius of the free volume holes.

Ro is a constant =

= (1.66


Table 2 Radius of a free volumes and volumes analyzer of

of PE-Foam polymers as a function of the dose


The correlation between free volume and gas separation analyzer ofproperties in high molecular weight poly(methylmethacrylate) membranes,Ywu-Jang Fu et al. European Polymer Journal 43 (2007) 959–967


The correlation between free volume and gas separation analyzer ofproperties in high molecular weight poly(methylmethacrylate) membranes,Ywu-Jang Fu et al. European Polymer Journal 43 (2007) 959–967



The correlation between free volume and gas separation analyzer ofproperties in high molecular weight poly(methylmethacrylate) membranes,Ywu-Jang Fu et al. European Polymer Journal 43 (2007) 959–967

Butil asetat

996000

26


Positron annihilation lifetime spectroscopy of molecularly imprinted hydroxyethyl methacrylate based polymersNikolay Djourelov, Zeliha Ates, Olgun Güven, Marijka Misheva, Takenori SuzukiPolymer 48 (2007) 2692-2699

Free-volume hole radius (R)) for dry samples versus the type of crosslinking agent at different concentrations. Irradiated samples (D = 5 kGy)with 3:1 HEMA:glucose mole ratio; symbols : ▲, □, ◊, ♦ and ■ indicate 70, 30, 20, 10% and no crosslinking agent containing samples, respectively. NA indicates sample prepared without crosslinking agent.

27


Study on the microstructure and mechanical properties for epoxy resin/montmorillonite nanocomposites by positron

B. Wang and et al.

Radiation Physics and Chemistry 76 (2007) 146–149

31


Lecture 3 epoxy resin/montmorillonite nanocomposites by positron

Part 2

Positron Annihilation Lifetime Spectroscopy

(PALS)

Principles and applications for nano science.


t epoxy resin/montmorillonite nanocomposites by positron ~ 1 ps

Thermalization

  • ionization and excitation of atoms

  • free radicals

  • molecule dissociation

  • defects in crystalline structures

e+ (200 keV)

Spur

e-

R

М+

e-

e-

М+

e-

М+

e+ (~ eV)

М+

e-

R

e-

М+

R

R

e-

Terminal Spur (Blob)


What is Positronium? epoxy resin/montmorillonite nanocomposites by positrone++ e-=Ps

  • Hydrogen-like bound state of an electron and a positron.

  • Exists in two states: p-Ps() and o-Ps() (1:3)

  • In vacuum: p-Ps lives 0.125 ns, o-Ps – 142 ns.

  • In Polymers o-Ps lifetime is quenched to some ns because of the pick-off annihilation.


Methods of positron annihilation

epoxy resin/montmorillonite nanocomposites by positron- ACAR

1274 keV

511 keV

termalization

e+

22Na

E1+E2- CDBS

diffusion~ 100 nm

e-

511 keV

E1-511- DBAL

t ,E1-511 - AMOC

Angular

Correlation of

Annihilation

Radiation

Methods of positron annihilation

t - PALS

Positron

Annihilation

Lifetime

Spectroscopy

Coincidence

Doppler

Broadening

Spectroscopy

sample

Doppler

Broadening of

Annihilation

Line

Aged

MOmentum

Correlation


Crosslinking in molecularly imprinted polymers
Crosslinking in molecularly imprinted polymers epoxy resin/montmorillonite nanocomposites by positron

poly(2-hydroxyethyl methacrylate) (HEMA)

crosslinking agents:

diethylene glycol diacrylate (DEGDA)

polypropylene glycol dimethacrylate (PPGDMA, Mn=560)

triethylene glycol dimethacrylate (TEGDMA)

N. Djourelov, Z. Ateş, O. Güven, M. Misheva, T. Suzuki, Polymer 48 (2007) 2692-2699


Positron annihilation lifetime study of organic inorganic hybrid materials prepared by irradiation
Positron annihilation lifetime study of organic-inorganic hybrid materials prepared by irradiation

+ SiO2 (+ZrO2)

PDMS+Silica+Zirconia – 2 long-lived

components

PDMS+Silica – 1 long-lived component

N.Djourelov, T.Suzuki, M.Misheva, F.M.A.Margaça, I.M.Miranda Salvado, J Non-Crystalline Solids 351 (2005) 340–345


POZİTRON YOK OLMA YAŞAM SÜRESİ hybrid materials prepared by irradiation

SPREKTROMETRESİNDE

KULLANILAN PROGRAMLAR

  • TL9

  • MELT

  • PORE SİZE CALCULATION

  • ORIGIN /EXCEL


LT 9 programı kullanılarak elde edilen eğriler hybrid materials prepared by irradiation


PALS hybrid materials prepared by irradiation

  • POSITRONFIT

  • PALFIT

  • LT v.9


Tao eldrup model
Tao-Eldrup model hybrid materials prepared by irradiation

Goworek-Gidley model


Continuous distribution
Continuous Distribution hybrid materials prepared by irradiation

  • More realistic presentation: continuous distribution

  • CONTIN

  • MELT

  • LT v.9


Ödev Sorusu : hybrid materials prepared by irradiation

Nano boşlukları olan bir malzemenin pozitron yok olma yaşam süresi spektrometresi (PALS) ile incelenmesi sonucunda aşağıdaki spektrum elde edilmiştir. Bu malzemede bulunan (a) en büyük (b) en küçük boşluğun ve (c) sayısal olarak en fazla oranda bulunan boşluğun büyüklüğü kaç nm dir. NOT : Grafik verilerine ulaşmak için buraya tıklayınız : PALS ödev verileri

p-Ps()

Ps

o-Ps()


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