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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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Presentation Transcript
slide1

Lecture 3

Part 1

Positron Annihilation Lifetime Spectroscopy

(PALS)

Principles and applications for nano science

slide3
POSITRON SOURCES

POSITRON-MATTER INTERACTION

POSITRON ANNIHILATION LIFETIME SPECTROMETER (PALS)

PALS APPLICATIONS on POLYMERS

slide4

POSITRON SOURCE

  • The decay of neutron-deficiency radio isotopes (β+), 22Na
  • Pair formation by high energy γ-rays
slide10

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

slide14

Energy window

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

slide15

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

slide16

2ns

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)

slide17

Fig.11 The plot of delay time versus channel number

The resolution of the instrument=ns/channel x FWHM

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

slide18

PAL spectra of polymers

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 sampleτ1 = 120 ps, τ2 = 320 ps, and τ3 = 520 ps. (Math. lab.program, melt)
slide21

Ro-R

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

slide22

Table 2 Radius of a free volumes and volumes

of PE-Foam polymers as a function of the dose

slide23

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

slide24

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

slide26

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

Butil asetat

996000

26

slide27

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

slide31

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

slide33

Lecture 3

Part 2

Positron Annihilation Lifetime Spectroscopy

(PALS)

Principles and applications for nano science.

slide34

t ~ 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)

slide35

What is Positronium?e++ 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

- 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

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

slide42

POZİTRON YOK OLMA YAŞAM SÜRESİ

SPREKTROMETRESİNDE

KULLANILAN PROGRAMLAR

  • TL9
  • MELT
  • PORE SİZE CALCULATION
  • ORIGIN /EXCEL
slide44
PALS
  • POSITRONFIT
  • PALFIT
  • LT v.9
tao eldrup model
Tao-Eldrup model

Goworek-Gidley model

continuous distribution
Continuous Distribution
  • More realistic presentation: continuous distribution
  • CONTIN
  • MELT
  • LT v.9
slide48

Ödev Sorusu :

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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