Application of positron beams to the study of positronium-forming solids

Kobayashi, Yoshinori; Ito, Kenji; Oka, Toshitaka; He, Chunqing; Hamed, Mohamed; Suzuki, Ryoichi; Ohdaira, Toshiyuki

doi:10.1016/j.apsusc.2008.05.278

Cited by 25 publications

(23 citation statements)

References 47 publications

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“…Next, hybrid film-5, composite film-5, and the MSQ film were subjected to positron annihilation spectroscopy to investigate the formation of intramolecular void spaces and their size. Positron annihilation spectroscopy is quite useful for analyzing nanometer-sized pores; details regarding positron annihilation spectroscopy and its application for amorphous polymers are described elsewhere. − In the present experiments, the lifetime spectra of the samples were decomposed into three components. The longest lifetime (τ 3 ) corresponds to the pick-off annihilation of ortho -positronium ( o -Ps).…”

Section: Results and Discussionmentioning

confidence: 99%

Thermal Insulating Property of Silsesquioxane Hybrid Film Induced by Intramolecular Void Spaces

Hamada

Nakanishi

Okada

et al. 2021

ACS Appl. Polym. Mater.

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In the field of organic/inorganic hybrid polymers with the application as thermal insulating materials, ethylene-bridged polysilsesquioxane films are promising materials with enhanced thermal insulating properties due to the presence of intramolecular void spaces in their frameworks. With the aim of increasing the content in intramolecular void spaces to further enhance the thermal property of the resulting material, this paper describes the hydrosilylation reaction of hydrodimethyl-silylated oligomethylsilsesquioxane (MSQ-SiH) and octavinyl polyhedral oligomeric silsesquioxane (Vinyl-POSS) to produce a hybrid film with intramolecular void spaces, which was colorless and transparent due to the formation of covalent SiCCSi bonds. As a control experiment, a polymethylsilsesquixane (MSQ) film and an MSQ film containing 5 wt % of Vinyl-POSS (composite film-5) were prepared. Hybrid film-5 (prepared from MSQ-SiH and 5 wt % of Vinyl-POSS) exhibited lower density and thermal diffusivity (1.19 g/cm 3 and 1.21 × 10 −7 m 2 /s) than the MSQ film (1.34 g/cm 3 and 1.36 × 10 −7 m 2 /s) and composite film-5 (1.37 g/cm 3 and 1.58 × 10 −7 m 2 / s). Hybrid film-5 showed a 5% weight loss temperature (T d 5) and a 10% weight loss temperature (T d 10 ) of 382 and 453 °C, respectively, which were lower than those of the MSQ film (T d 5 of 436 °C and T d 10 of 481 °C) and higher than those of composite film-5 (T d 5 of 325 °C and T d 10 of 453 °C). Positron annihilation lifetime technique revealed that the hole volumes estimated from the value of the positronium lifetime component decreased in the order hybrid film-5 > MSQ film > composite film-5. Taken together, the results demonstrate that the thermal insulating property of the polysilsesquioxane film was improved by the formation of intramolecular void spaces around the POSS molecules.

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Section: Results and Discussionmentioning

confidence: 99%

Thermal Insulating Property of Silsesquioxane Hybrid Film Induced by Intramolecular Void Spaces

Hamada

Nakanishi

Okada

et al. 2021

ACS Appl. Polym. Mater.

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“…In particular, (i) S(E) increases and W(E) decreases at lower fluences (6.25 × 10 14 -3.13 × 10 15 ions/cm 2 ), while (ii) S(E) decreases and W(E) increases at higher fluences (2.5 × 10 16 -5.0 × 10 16 ions/cm 2 ) in the range up to 400 nm in a good agreement with the maximum penetration depth R max B = 400 nm after SRIM simulation; positron energy of 2-3 keV, showing the extreme values of S(E) and W(E), corresponds to a mean depth of 100-200 nm in consistent with the maximum damage R p V,B = 220 nm after SRIM simulation (Figure 2, top). A mean penetration depth of positrons (z m ) was estimated as z m = (40/ρ)E n , where z m is presented in nm, E the positron energy in keV, ρ is the density (1.18 g/cm 3 for PMMA), and n = 1.6 [50]. The results of variable-energy DBAL and PAL measurements at incident positron energy of 2.15 keV were found to be in consistence (Figure 2, bottom) [36].…”

Section: Positron Annihilation Spectroscopy Datamentioning

confidence: 99%

Ion-Irradiation-Induced Carbon Nanostructures in Optoelectronic Polymer Materials

Kavetskyy¹,

Степанов²

2016

Radiation Effects in Materials

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The recent results obtained on the ion-irradiation-induced carbon nanostructures in optoelectronic polymer materials exemplified by boron-ion-implanted polymethylmethacrylate " PMM" with an energy of keV, ion doses from . × to . × ions/ cm , and current density < μ"/cm are reviewed. The positron annihilation spectroscopy slow positron beam spectroscopy based on Doppler broadening of positron annihilation gamma rays as a function of incident positron energy and positron annihilation lifetime at a positron energy of . keV, and temperature-dependent positron annihilation lifetime spectroscopy , optical UV-visible spectroscopy, Raman spectroscopy, electrical current voltage measurements, and nanoindentation test are chosen as the main experimental tools for the investigation of low-energy ion-induced processes in " PMM". The formation of carbon nanostructures is confirmed for the samples irradiated with higher ion fluences > ions/cm and the experimental results of the comprehensive study are found to be in a good agreement with SRIM stopping and range of ions in matter simulation results.

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“…Because of poor sensitivity of most conventional techniques, positron annihilation gamma-ray energy spectroscopy (PAGES) and positron annihilation lifetime spectroscopy (PALS) based on variable-energy slow positron beams emerged as very useful techniques for thin films. These techniques have been successfully applied to the studies of various polymeric and porous silica films [1,2].…”

Section: Introductionmentioning

confidence: 99%