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Positron Annihilation Lifetime Spectroscopy (PALS)

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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Positron Annihilation Lifetime Spectroscopy (PALS)

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  1. Lecture 3 Part 1 Positron Annihilation Lifetime Spectroscopy (PALS) Principles and applications for nano science

  2. Positron Annihilation Lifetime Spectrometer(PALS)

  3. POSITRON SOURCES POSITRON-MATTER INTERACTION POSITRON ANNIHILATION LIFETIME SPECTROMETER (PALS) PALS APPLICATIONS on POLYMERS

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

  5. 22Na 22Ne + γ + β+ + υeFig. 1 Decay scheme of a 22Na nucleus

  6. POSITRON-MATTER INTERACTION

  7. Source preparation and sandwich type sample prepapation

  8. POSITRON ANNIHILATION IN MATTER

  9. 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

  10. 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

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

  12. 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)

  13. 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

  14. 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.

  15. Lifetime distribution of silicon sampleτ1 = 120 ps, τ2 = 320 ps, and τ3 = 520 ps. (Math. lab.program, melt)

  16. Table 1 Positron annihilation lifetime data of the PEf samples

  17. 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

  18. Table 2 Radius of a free volumes and volumes of PE-Foam polymers as a function of the dose

  19. 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

  20. 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

  21. Dichloromethane Buthylacetate

  22. 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

  23. 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

  24. 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

  25. Lecture 3 Part 2 Positron Annihilation Lifetime Spectroscopy (PALS) Principles and applications for nano science.

  26. 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)

  27. 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.

  28. - 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

  29. 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

  30. 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

  31. POZİTRON YOK OLMA YAŞAM SÜRESİ SPREKTROMETRESİNDE KULLANILAN PROGRAMLAR • TL9 • MELT • PORE SİZE CALCULATION • ORIGIN /EXCEL

  32. LT 9 programı kullanılarak elde edilen eğriler

  33. PALS • POSITRONFIT • PALFIT • LT v.9

  34. Tao-Eldrup model Goworek-Gidley model

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

  36. 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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