In situinvestigation of the kinetics and microstructure during photopolymerization by positron annihilation technique and NIR-photorheology

Positron annihilation lifetime spectroscopy was used to study the free-volume parameters in various pure -, - and -cyclodextrins samples and, in the case of β-cyclodextrin, with inclusion of S-carvone and thymoquinone. The results clearly indicate the presence of long lifetime components related to Ps-formation. The data show that the addition of S-carvone to β-cyclodextrin results in a decrease of o-Ps lifetime that we ascribe to a reduction of free volume holes from 81.8 to 63.7 Å3. The long lifetime component disappears when thymoquinone is added to -cyclodextrin, indicating this substance acts as an o-Ps quencher. For all samples studied, a decrease in the long lifetime component values was observed with increasing source in situ time, a result that might be attributed to the irradiation of the sample by the 22Na positron source.

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In Situ Investigations on the Cross-Linking Process of the Epoxy Resin System DGEBA-DETA by Means of Positron Annihilation Lifetime Spectroscopy in Comparison with Infrared Spectroscopy

Materials Science Forum ◽

10.4028/www.scientific.net/msf.445-446.313 ◽

2004 ◽

Vol 445-446 ◽

pp. 313-315 ◽

Cited By ~ 4

Author(s):

Jörn Kanzow ◽

Vladimir Zaporojtchenko ◽

Hideki Nabika ◽

Minoru Mizuhata ◽

Shigehito Deki ◽

...

Keyword(s):

Infrared Spectroscopy ◽

Epoxy Resin ◽

Positron Annihilation ◽

Positron Annihilation Lifetime Spectroscopy ◽

Cross Linking ◽

Resin System ◽

Positron Annihilation Lifetime ◽

Epoxy Resin System ◽

The Cross

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In Situ Monitoring of Adsorption and Desorption of n-Heptane on Porous Silica by Positron Annihilation Lifetime Spectroscopy

Materials Science Forum ◽

10.4028/www.scientific.net/msf.733.207 ◽

2012 ◽

Vol 733 ◽

pp. 207-211 ◽

Cited By ~ 3

Author(s):

Radosław Zaleski ◽

Waldemar Dolecki ◽

Jacek Goworek

Keyword(s):

Positron Annihilation ◽

Porous Silica ◽

Positron Annihilation Lifetime Spectroscopy ◽

Intensity Change ◽

Adsorption And Desorption ◽

Positron Annihilation Lifetime ◽

Adsorption Desorption ◽

Kinetics Of ◽

Insight Into

Positron annihilation lifetime spectroscopy study of n-heptane adsorption and desorption on silica gel Si-60 gives insight into a free volume evolution during those processes. Analysis of the lifetime distribution allows to ascribe particular ortho-positronium components to silica walls, mesopores and n-heptane. Hysteresis loop of the intensities of the mesopore and n-heptane related components similar to classic adsorption/desorption isotherms is observed. Transition from an adsorbate multilayer structure to liquid when pores become completely filled, manifests itself as an intensity change. Kinetics of desorption and adsorption studies allows to determine the time of reaching the equilibrium by the Si 60–n-heptane system at various pressures.

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Positron Annihilation Lifetime Spectroscopy Application to In Situ Monitoring of n-Heptane Sorption in Mesopores

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.373.288 ◽

2017 ◽

Vol 373 ◽

pp. 288-294

Author(s):

Radosław Zaleski ◽

Marek Gorgol ◽

Agnieszka Kierys

Keyword(s):

Positron Annihilation ◽

Positron Annihilation Lifetime Spectroscopy ◽

Exponential Functions ◽

Spectra Analysis ◽

Time Constants ◽

Positron Annihilation Lifetime ◽

Cylindrical Pores ◽

Simplified Method ◽

Time Required

The dynamics of n-heptane adsorption and desorption on two silicas (Si-A and SBA-15) with different porosity was studied using positron annihilation lifetime spectroscopy (PALS). Simplified method of spectra analysis consisting in the summation of counts in the long-lived part of PALS spectra was used. It allowed to observe changes occurring in the minute time scale. The dependence of the number of counts on time could be fairly well approximated by exponential functions. It was found that the time required for reaching equilibrium in long cylindrical pores is up to ten times longer than in bell-mouthed interconnected ones. The longest time constants (ca. 5 min in Si-A and ca. 60 min in SBA-15) were observed for desorption in both samples.

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