Investigation on positron annihilation characteristics of CO2-exposed zeolite

Determination of Free-Volume Properties in Polymers Without Orthopositronium Components in Positron Annihilation Lifetime Spectroscopy

“…The four-lifetime analyzed lifetime and intensity results in those selected zeolites and molecular sieves are listed in Table . The results of Table are comparable to those existing data in zeolite systems. − It is noted that in the PATFIT analysis of PALS data, we have fixed the shortest lifetime τ 1 = 0.125 ns, which corresponds to the p -Ps lifetime so that the results for the other three lifetimes are more stable and consistent. We also attempted to constrain I 1 = 1/3 of o -Ps intensity in the PATFIT analysis.…”

“…This is likely because of the hydrates absorbed inside the cavities and some intergrain defect structures in those materials. Although some people have attempted to apply high temperature and pumping to remove hydrates and impurities from the inner surfaces, the PALS results are known not to be able to mirror the α,β cages’ sizes precisely. − In this study for the purpose of calibration τ 2 - R equation, instead of using ideal α,β cage sizes, we use the experimental o -Ps lifetimes (τ 3 and τ 4 ) according to eq to calculate the mean hole radii. For a real substrate with multicomponents of o -Ps lifetime, i , we calculate the mean radius from o -Ps lifetime R̅ by the following equation R̅ = ∑ i R i false( normalτ normalo − normalP normals false) · I i / ∑ i I i where R i (τ o -Ps ) and I i are the corresponding i th o -Ps lifetime according to eq and intensity, respectively.…”

Positron annihilation analysis of nanopores and growth mechanism of oblique angle evaporated TiO2 and SiO2 thin films and multilayers

“…The present work addresses this problem by using the positron annihilation spectroscopy (PAS) technique to analyze the actual porosity and pore size distribution in the interior of nanocolumns of TiO2 (𝑠 𝑡 ~0.1) and SiO2 (𝑠 𝑡 = 1) thin films and multilayers. This method is sensitive to lattice defects, grain interfaces and very small pores [19][20][21][22] and has been widely utilized for the characterization analysis of bulk [23][24][25] and layered materials [26,27]. In relation with the present work PAS would be sensitive to micropores as those expected to exist in the nanocolumns of thin films.…”

Pore structure characterization of supported polycrystalline zeolite membranes by positron annihilation spectroscopy

“…proven to be effective in quantifying the free-volume in polymers [18,19], micro/meso pores in silica [20], and cage and cavity size in zeolite crystals [21,22]. Recently, Yan and coworkers reported using PALS to obtain pore size and pore connectivity information in zeolite low-k films [23].…”