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Positron Annihilation Lifetime Spectroscopy (PALS)
Lecture 3 Part 1 Positron Annihilation Lifetime Spectroscopy (PALS) Principles and applications for nano science
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Positron Annihilation Lifetime Spectrometer (PALS)
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POSITRON SOURCES POSITRON-MATTER INTERACTION POSITRON ANNIHILATION LIFETIME SPECTROMETER (PALS) PALS APPLICATIONS on POLYMERS
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The decay of neutron-deficiency radio isotopes (β+), 22Na
POSITRON SOURCE The decay of neutron-deficiency radio isotopes (β+), 22Na Pair formation by high energy γ-rays
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22Na 22Ne + γ + β+ + υe Fig. 1 Decay scheme of a 22Na nucleus
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POSITRON-MATTER INTERACTION
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Source preparation and sandwich type sample prepapation
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POSITRON ANNIHILATION IN MATTER
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Defect Type Size Materials Atomic Vacancies 0.1 nm Metals Dislocations 1 nm - 10 mm Voids 0.1 nm - 1 mm Holes 0.1 nm - 10 mm Polymers
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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
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Energy window for stop Detector (0.51 MeV) for start (1.28 MeV) Fig. 8 Energy spectrum of 22Na detected by a multichannel analyzer of PAL spectrometer with the plastic detectors scintillator
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Fig. 9 Energy spectrum of 22Na detected by a multichannel analyzer of PAL spectrometer, after lower and upper level adjustment for start signals
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2ns 5ns 10ns 8ns 14ns FWHM Fig.10 The prompt curve for 60Co γ-rays, under 22Na window settings at the different delay times (2, 5, 8,10 and 14 ns)
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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 ps
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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 ns.
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Lifetime distribution of silicon sample τ1 = 120 ps, τ2 = 320 ps, and τ3 = 520 ps. (Math. lab.program, melt)
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Dose (kGy) τ1 (ns) I1 (%) τ2 (ns) I2 (%) τ3 (ns) I3 (%) 0.36±0.01
Table 1 Positron annihilation lifetime data of the PEf samples Dose (kGy) τ1 (ns) I1 (%) τ2 (ns) I2 (%) τ3 (ns) I3 (%) 0.36±0.01 78.0±0.1 1.05±0.05 10±0.1 3.10±0.10 12.0±0.2 1 82.0±0.1 1.03±0.03 7.4±0.1 2.90±0.10 10.6±0.2 52 81.0±0.1 1.10±0.10 7.8±0.2 3.00±0.20 11.0±0.2 98 0.35±0.01 79.0±0.1 0.98±0.05 8.8±0.1 12.0±0.1
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R is the average radius of the free volume holes. Ro is a constant =
The o-Ps lifetime, τo-Ps directly correlates with the radius of free volume holes and its intensity (Io-Ps) contains information 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 Ro-R
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Table 2 Radius of a free volumes and volumes
of PE-Foam polymers as a function of the dose Dose (kGy) Radius (Å), (τ3) Volume (Å3),(τ3) Radius (Å), (τ2) (Å3), (τ2) 3.70 212 1.74 22.1 1 3.57 190 1.71 21.0 52 3.64 202 1.82 25.2 98 1.63 18.1
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The correlation between free volume and gas separation properties in high molecular weight poly(methyl methacrylate) membranes, Ywu-Jang Fu et al. European Polymer Journal 43 (2007) 959–967
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The correlation between free volume and gas separation properties in high molecular weight poly(methyl methacrylate) membranes, Ywu-Jang Fu et al. European Polymer Journal 43 (2007) 959–967
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Dichloromethane Buthylacetate
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The correlation between free volume and gas separation properties in high molecular weight poly(methyl methacrylate) membranes, Ywu-Jang Fu et al. European Polymer Journal 43 (2007) 959–967 Butil asetat 996000 26
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Positron annihilation lifetime spectroscopy of molecularly imprinted hydroxyethyl methacrylate based polymers Nikolay Djourelov, Zeliha Ates, Olgun Güven, Marijka Misheva, Takenori Suzuki Polymer 48 (2007) 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
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Radiation Physics and Chemistry 76 (2007) 146–149
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
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Positron Annihilation Lifetime Spectroscopy (PALS)
Lecture 3 Part 2 Positron Annihilation Lifetime Spectroscopy (PALS) Principles and applications for nano science.
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Thermalization e+ (200 keV) Spur e- R М+ e- e- М+ e- М+ e+ (~ eV) М+
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) t ~ 1 ps
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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 ns, o-Ps – 142 ns. In Polymers o-Ps lifetime is quenched to some ns because of the pick-off annihilation.
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Methods of positron annihilation
Angular Correlation of Annihilation Radiation - ACAR 1274 keV t - PALS 511 keV t , E AMOC Positron Annihilation Lifetime Spectroscopy Coincidence Doppler Broadening Spectroscopy 22Na sample E1+E2- CDBS termalization e+ e- diffusion~ 100 nm 511 keV Doppler Broadening of Annihilation Line Aged MOmentum Correlation E DBAL
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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)
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Positron annihilation lifetime study of organic- inorganic hybrid materials prepared by irradiation
+ SiO2 (+ZrO2) These are some of the results for organic-inorganic hybrid prepared by gamma irradiation. It is Poly Di Methyl Siloxane with Silica or with Silica and Zirconia. For the samples without Zirconia we see one long lifetime with polymer like behavior which indicates that the organic inclusion is well dispersed in the PDMS matrix. For the samples with Zirconia we see two long-lived components with very strange behavior. Explain the figure. It was a real puzzle for us. 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
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TL9 MELT PORE SİZE CALCULATION ORIGIN /EXCEL
POZİTRON YOK OLMA YAŞAM SÜRESİ SPREKTROMETRESİNDE KULLANILAN PROGRAMLAR TL9 MELT PORE SİZE CALCULATION ORIGIN /EXCEL
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LT 9 programı kullanılarak elde edilen eğriler
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PALS POSITRONFIT PALFIT LT v.9
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Tao-Eldrup model Goworek-Gidley model
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Intensity1 dev. Intensity2 Intensity3 Lifetime1 Lifetime2 Lifetime3 27.375 55.428
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Continuous Distribution
More realistic presentation: continuous distribution CONTIN MELT LT v.9 In some cases discrete positron states are not acceptable and you may represent the lifetime as a continuous distribution. These are the used computer programs for extracting the lifetime information.
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Ödev Sorusu : p-Ps() Ps o-Ps()
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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