Search

\nHIGHLIGHTSPolymer nanocomposites are increasingly used in insulation applications for enhanced electrical properties. However, there are intricate parameters that control the properties of the polymer, and hence investigations are required. This paper attempts to correlate the electrical properties of Epoxy/Organically modified montmorillonite clay composites with the free volume resulting from the incorporation of the Organically modified montmorillonite clay filler of 2, 5, and 7 weight per cent (wt.%). Positron annihilation spectroscopy has been used to compute the fractional free volume and free volume. The free volume percentage is observed to increase with the incorporation of 2 and 5 wt.% and reduces at 7 wt.%. A similar trend is observed in the average size of free volume. The filler increases the AC electric breakdown strength by 20%, arc resistance by 5%, and comparative tracking index by 10% at 5 wt.%. Thermal conductivity is seen to increase marginally with the filler. The surfaces of the composites are hydrophilic at 2 and 7 wt.%, and at 5 wt.%, it is hydrophobic. Longer durations of water diffusion render the surfaces of the nanocomposites hydrophobic. Fourier transform infrared spectroscopy investigations reveal broadening of peak, increase in peak intensity and stretching of Si–O–Si bonds at 5 wt.% of filler due to exfoliation. An attempt has been made to understand the results of electrical parameters based on the results of positron annihilation lifetime spectroscopy and thermal conductivity. Water diffusion is minimal at 5 wt.% of OMMT.Highest CTI of 588 is achieved at 5 wt.%.Arc resistance of 400 s is achieved at 5 wt.%. OMMT.Proof tracking is higher at 5 wt.% of OMMT.Surface is hydrophobic at 5 wt.% OMMT.Water diffusion is minimal at 5 wt.% of OMMT.Highest CTI of 588 is achieved at 5 wt.%.Arc resistance of 400 s is achieved at 5 wt.%. OMMT.Proof tracking is higher at 5 wt.% of OMMT.Surface is hydrophobic at 5 wt.% OMMT. [ABSTRACT FROM AUTHOR]

Positron Annihilation Lifetime Spectroscopy (PALS) is sensitive to the material voids/free volume on the atomic scale. For this reason, this method has been used as a unique technology to measure the free volume and structural defects in polymers in recent years. In the present study, epoxy-matrix nanocomposites with different carboxylic acid functionalized multiwalled carbon nanotubes (COOH-MWCNTs) loadings (0.1-0.7 wt% at a step of 0.2) were fabricated, and the influence of COOH-MWCNTs loading on the prepared nanocomposites' free volume properties and tensile behavior were explored. The measurement of positron annihilation lifetime was done using a conventional synchronization system based on a 22Na radioactive source with 7 μCi activity. The detectors used in this work were fast plastic scintillators (type: NT-850) with ns time response. The results demonstrated that the tensile strength of the nanocomposites decreased with the increase in the lifetime of the ortho-positronium annihilation (increase in the radius and free volume) in the samples. The 0.3 wt% COOH-MWCNTs/epoxy nanocomposite showed the maximum tensile strength. Overall, the results of this work clearly revealed that there was a strong relationship between the tensile strength and free volume in the polymer nanocomposites.

This work is the first one that provides not only evidence for the existence of free volumes in the human stratum corneum but also focuses on comparing these experimental data, obtained through the unique positron annihilation lifetime spectroscopy (PALS) method, with theoretical values published in earlier works. The mean free volume of 0.269 nm was slightly lower than the theoretical value of 0.4 nm. The lifetime τ3 (1.83 ns with a coefficient of variation CV of 3.21%) is dependent on the size of open sites in the skin. This information was used to calculate the free volume radius R (0.269 nm with CV 2.14%), free volume size Vf (0.081 nm3 with CV 4.69%), and the intensity I3 (9.01% with CV 10.94%) to estimate the relative fractional free volume fv (1.32 a.u. with CV 13.68%) in human skin ex vivo. The relation between the lifetime of o-Ps (τ3) and the radius of free volume (R) was formulated using the Tao–Eldrup model, which assumes spherical voids and applies to sites with radii smaller than 1 nm. The results indicate that PALS is a powerful tool for confirming the existence of free volumes and determining their size. The studies also focused on describing the probable locations of these nanospaces in SC lipid bilayers. According to the theory, these play an essential role in dynamic processes in biological systems, including the diffusion of low-molecular-weight hydrophobic and moderately hydrophilic molecules. The mechanism of their formation has been determined by the molecular dynamics of the lipid chains. [ABSTRACT FROM AUTHOR]

Ceramic samples of Mn 1- x Zr x WO 4 (0.00 ≤ x ≤ 0.20) were prepared by a solid-state reaction to study changes in the structural, magnetic, and dielectric properties of multiferroic MnWO 4 caused by replacing Mn2+ ions with Zr4+ ions. The results indicate that Zr4+ replacement caused lattice deformation but did not affect the monoclinic lattice structure of any of the MnWO 4 samples. The concentration of vacancies, investigated by positron annihilation lifetime spectroscopy, increased with as the Zr4+ content x from 0.00 to 0.20. It was observed that Zr4+ replacement enhanced the dielectric constant of Mn 1- x Zr x WO 4 but slightly increased the dielectric loss. The magnetization and transition temperatures (T AF3 and T AF2) of the Mn 1- x Zr x WO 4 system were increased by the Zr4+ replacement, and the existing temperature range of the AF2 phase was extended upon the substitution of Zr4+ for Mn2+. This study demonstrated that the magnetic properties of Mn 1- x Zr x WO 4 were closely related to the vacancy concentration and lattice distortion. [ABSTRACT FROM AUTHOR]

In this work, the influence of aromatic rings on the local free volume of cured mixtures of acrylate epoxidized soybean oil (AESO) and vanillin dimethacrylate (VDM) was investigated. Cross-linking took place under the influence of UV light in the presence or absence of a photoinitiator. The local free volume and its homogeneity were characterized using the Positron Annihilation Lifetime Spectroscopy (PALS) technique. It was found that increasing the content of VDM, which contains aromatic rings, caused a decrease in the local free volume of the cured polymer network, with consequences for the diffusion properties of the polymer, which were tested for the case of water. Another consequence of increasing the content of VDM was a decrease in the conversion of double bonds in the finally cured samples, characterized by near-infrared spectroscopy (NIR). This finding illustrates a case where the decrease in free volume is not necessarily related to an increase in the crosslinking density of the polymer, but is a consequence of the presence of an increase in the occupied volume of aromatic rings in the volume of the polymer. [ABSTRACT FROM AUTHOR]

Multifunctional conductive nanocomposites based on thermoplastic polycarbonate (PC), dodecylbenzenesulphonic acid doped polyaniline (PANI-DBSA) and bismuth sulfide (BS) with good thermal and dielectric properties have been fabricated using solution casting technique. In the present work, different percentages of PANI-DBSA were blended with PC-BS composite and their electrical and dielectric properties as well as microstructural features were experimentally investigated. Analysis of positron lifetime data yielded three components, and it was observed that the increase in positron lifetime parameter viz., o-Ps lifetime at the higher concentration of PANI-DBSA, and also increase in the ortho-positronium (o-Ps) intensity at lower weight percentages of the filler may be ascribed to the increase in the interfacial space by phase separation of PANI-DBSA, BS and PC polymer matrix, and the formation of additional cavities at the interfaces of PC/BS/PANI-DBSA conducting composite, respectively. A decrease in the o-Ps intensity on the increase in filler level may be the consequence of decrease in the number of free volume holes that are available for electron—positron annihilation, due to the aggregation of PANI-DBSA. These observations are corroborated by other experimental investigations, like X-ray diffraction, electron microscopy, infrared spectroscopy, differential scanning calorimetry and thermogravimetric analysis. Further, the effect of PANI-DBSA loading in PC-BS composite on the dielectric relaxation behavior has been studied over a wide range of frequencies, from 40 Hz up to 5 MHz. The presence of two semicircular arcs in the Cole–Cole plot of the composite confirms the existence of grain and grain boundary conduction in the nanocomposite. Good AC conductivity and permittivity, together with good thermal stability makes the PC/BS/PANI-DBSA conducting composite a potential candidate for electromagnetic interference shielding and energy storage applications. [ABSTRACT FROM AUTHOR]

Polyurethane-cement composite are widely used in modern civil engineering, and the method of adding diluent is often used to adjust the construction process to adapt to the engineering environment. Studies have shown that the addition of diluent impacts the performance of polyurethane-cement based composite surface coatings, but there have been few reports on the influence of diluent content on the mechanical properties and microstructure of the coatings. To address this, polyurethane coatings with different diluent contents were prepared, and positron annihilation lifetime spectroscopy was used to test the microstructure of the coatings. The tensile strength and elongation at rupture were tested using a universal material testing machine, and the fracture interface morphology of each coating was observed by scanning electron microscopy. Finally, the correlation between the microstructure parameters and the mechanical properties of the coating was analyzed using grey relation theory. The results demonstrated that with the increase in diluent content, (i) the average radius of the free volume hole (R) and the free volume fraction (FV) of the coating both showed a trend of first decreasing and then increasing. The value of R was between 3.04 and 3.24 Å, and the value of FV was between 2.08 and 2.84%. (ii) The tensile strength of the coating increased first and then decreased, while the elongation at rupture decreased first and then increased. Among them, the value of tensile strength was between 3.23 and 4.02 MPa, and the value of elongation at fracture was between 49.34 and 63.04%. In addition, the free volume in polymers plays a crucial role in facilitating the migration of molecular chain segments and is closely related to the macroscopic mechanical properties of polymers. A correlation analysis showed that the R value of the coating had the greatest influence on its tensile strength, while FV showed a higher correlation with the elongation at rupture. [ABSTRACT FROM AUTHOR]

The lifetime spectra of positrons annihilating in polymer matrices based on acrylated epoxidized soybean oil (AESO) and a mixture with vanillin-dimethacrylate (VDM) were measured. The chemical structure of the polymer series AESO and AESO-VDM was investigated by NIR spectroscopy. The semi-empirical quantum mechanical Tao-Eldrup model was used to estimate the sizes of individual free volumes in these matrices. Investigation of free-volume properties of polymer matrices based on natural oils, which are intended for the construction of amperometric biosensors, allows a better understanding of the relationship between the crosslinking densities of the matrices, i.e. microscopic characteristics, and the main operating parameters of the biosensors. The free volumes of the investigated matrices before, during and after the photopolymerization process were determined. The influence of vanillin-dimethacrylate (VDM) and photoinitiator (PI) on the final microstructural properties of the investigated matrices was evaluated. [ABSTRACT FROM AUTHOR]

This work is the first one that provides not only evidence for the existence of free volumes in the human stratum corneum but also focuses on comparing these experimental data, obtained through the unique positron annihilation lifetime spectroscopy (PALS) method, with theoretical values published in earlier works. The mean free volume of 0.269 nm was slightly lower than the theoretical value of 0.4 nm. The lifetime τ3 (1.83 ns with a coefficient of variation CV of 3.21%) is dependent on the size of open sites in the skin. This information was used to calculate the free volume radius R (0.269 nm with CV 2.14%), free volume size Vf (0.081 nm3 with CV 4.69%), and the intensity I3 (9.01% with CV 10.94%) to estimate the relative fractional free volume fv (1.32 a.u. with CV 13.68%) in human skin ex vivo. The relation between the lifetime of o-Ps (τ3) and the radius of free volume (R) was formulated using the Tao–Eldrup model, which assumes spherical voids and applies to sites with radii smaller than 1 nm. The results indicate that PALS is a powerful tool for confirming the existence of free volumes and determining their size. The studies also focused on describing the probable locations of these nanospaces in SC lipid bilayers. According to the theory, these play an essential role in dynamic processes in biological systems, including the diffusion of low-molecular-weight hydrophobic and moderately hydrophilic molecules. The mechanism of their formation has been determined by the molecular dynamics of the lipid chains.

A comparison of the results of studies on the influence of structural defects on the critical parameters of superconductivity has been made for the high-entropy alloy (NbTa) 0.67 (MoHfW) 0.33 and for the conventional superconducting magnet material Nb-47wt%Ti. Positron annihilation lifetime spectroscopy (PALS), electrical resistivity, magnetization and magnetic susceptibility measurements were used. In addition, X-ray powder diffraction studies were performed on the high-entropy alloy (NbTa) 0.67 (MoHfW) 0.33 . Due to the rapid cooling of the materials after melting in the arc furnace, they contain a higher concentration of structural defects compared to the heat-treated materials. Magnetic property measurements showed that both the critical temperatures T c and the upper critical fields μ 0 H c 2 of bulk superconductivity-related materials are improved in the presence of structural defects. [ABSTRACT FROM AUTHOR]

Positron annihilation lifetime spectroscopy (PALS) is a valuable technique to investigate defects in solids, such as vacancy clusters and grain boundaries in metals and alloys, as well as lattice imperfections in semiconductors. Positron spectroscopy is able to reveal the size, structure and concentration of vacancies with a sensitivity of 10−7. In the field of porous and amorphous systems, PALS can probe cavities in the range from a few tenths up to several tens of nm. In the case of polymers, PALS is one of the few techniques able to give information on the holes forming the free volume. This quantity, which cannot be measured with macroscopic techniques, is correlated to important mechanical, thermal, and transport properties of polymers. It can be deduced theoretically by applying suitable equations of state derived by cell models, and PALS supplies a quantitative measure of the free volume by probing the corresponding sub-nanometric holes. The system used is positronium (Ps), an unstable atom formed by a positron and an electron, whose lifetime can be related to the typical size of the holes. When analyzed in terms of continuous lifetimes, the positron annihilation spectrum allows one to gain insight into the distribution of the free volume holes, an almost unique feature of this technique. The present paper is an overview of PALS, addressed in particular to readers not familiar with this technique, with emphasis on the experimental aspects. After a general introduction on free volume, positronium, and the experimental apparatus needed to acquire the corresponding lifetime, some of the recent results obtained by various groups will be shown, highlighting the connections between the free volume as probed by PALS and structural properties of the investigated materials. [ABSTRACT FROM AUTHOR]

In this study, Cu 1− x Ho x FeO 2 nanoceramics were synthesized by sol-gel method to investigate the influence of the vacancy defects and Fe valence state tuning on the magnetic and dielectric properties of Cu 1− x Ho x FeO 2 nanoceramics. XRD and Raman analysis indicated that Cu 1− x Ho x FeO 2 nanoceramics with single-phase delafossite structure were synthesized by sol-gel method; Ho3+ ions had replaced the Cu ions in CuFeO 2 and resulted in lattice deformation. XPS analysis indicated that Ho3+ substitution could tune the Fe valence state, but did not cause significant change in oxygen vacancy concentration. The results of positron annihilation lifetime spectroscopy revealed that cation vacancies concentration in the interface region could be effectively tailored by Ho3+ substitution. The magnetic measurements indicated that Ho3+ substitution enhanced the magnetic transition temperatures and magnetization of Cu 1− x Ho x FeO 2 samples, which could be mainly attributed to the cation vacancies concentration in the interface region and Fe2+ concentration. Most interestingly, the Cu 1− x Ho x FeO 2 nanoceramics exhibited giant dielectric characteristic, which was attributed to the charge ordering of Fe3+ and Fe2+. [ABSTRACT FROM AUTHOR]

Friction stir welds were manufactured from aluminum alloy 2024-T3 and 7075-T6 workpieces under temperature control. Three control conditions, high-temperature, low-temperature and uncontrolled, were selected for each alloy based on the precipitation/dissolution temperatures of their strengthening phases, and the welds were characterized through positron annihilation lifetime spectroscopy and mechanical testing. For 2024, positron lifetimes and numerical simulation of the temperature profiles demonstrated that the S phase dissolution temperature was not achieved for any of the control conditions and hardness recovery upon cooling did not occur; however, for the low-temperature control (410°C), the S phase precipitated adjacent to the weld zone with the least extent of overaging, yielding the highest tensile strength of the three conditions. For 7075, dissolution of the η phase did not occur for the low-temperature (390°C) and the high-temperature (430°C) control conditions, and the low-temperature control produced the highest tensile strength due to the lesser degree of overaging of the strengthening phase. The uncontrolled condition for 7075, however, did achieve temperatures capable of dissolving the η phase, but due to the slow natural aging kinetics of 7075, a hardness recovery was not observed within the timeframe of this investigation. [ABSTRACT FROM AUTHOR]

Polyurethane-cement composite are widely used in modern civil engineering, and the method of adding diluent is often used to adjust the construction process to adapt to the engineering environment. Studies have shown that the addition of diluent impacts the performance of polyurethane-cement based composite surface coatings, but there have been few reports on the influence of diluent content on the mechanical properties and microstructure of the coatings. To address this, polyurethane coatings with different diluent contents were prepared, and positron annihilation lifetime spectroscopy was used to test the microstructure of the coatings. The tensile strength and elongation at rupture were tested using a universal material testing machine, and the fracture interface morphology of each coating was observed by scanning electron microscopy. Finally, the correlation between the microstructure parameters and the mechanical properties of the coating was analyzed using grey relation theory. The results demonstrated that with the increase in diluent content, (i) the average radius of the free volume hole (R) and the free volume fraction (FV) of the coating both showed a trend of first decreasing and then increasing. The value of R was between 3.04 and 3.24 Å, and the value of FV was between 2.08 and 2.84%. (ii) The tensile strength of the coating increased first and then decreased, while the elongation at rupture decreased first and then increased. Among them, the value of tensile strength was between 3.23 and 4.02 MPa, and the value of elongation at fracture was between 49.34 and 63.04%. In addition, the free volume in polymers plays a crucial role in facilitating the migration of molecular chain segments and is closely related to the macroscopic mechanical properties of polymers. A correlation analysis showed that the R value of the coating had the greatest influence on its tensile strength, while FV showed a higher correlation with the elongation at rupture.

Single crystal W is offered for Physics understanding of irradiation induced defects and their annealing as its structure is well defined and it is almost defect free. W(100) single crystal was neutron irradiated to a damage of 0.11 displacements per atom at 600 °C and subsequently isochronally annealed from 700 up to 1500 °C in 100 °C steps. Irradiation causes the formation of dislocation loops and vacancy clusters and a 45 % increase in hardness. After the annealing of 1500 °C the positron lifetime annihilation spectrum shows a defect free material and its hardness has been reverted to the pre-irradiation value and only clusters of Re, WRe and WOs2 have been detected by grazing incidence X-ray diffraction. The total line density of dislocations, number density of voids and their size versus annealing temperature have been determined. From hardness, the critical resolved stresses arising from dislocations and voids have been derived and correlated with their densities. The kinetics of defect annihilation versus annealing temperature is discussed.

Positron annihilation lifetime spectroscopy (PALS) has been used for the first time to investigate the microstructure of additively manufactured molybdenum. Despite the wide applicability of positron annihilation spectroscopy techniques to the defect analysis of metals, they have only been used sparingly to monitor the microstructural evolution of additively manufactured metals. Molybdenum and molybdenum with a dilute addition (0.1 wt%) of nano-sized silicon carbide, prepared via laser powder bed fusion (LPBF) at four different scan speeds: 100, 200, 400, and 800 mm/s, were studied by PALS and compared with electron backscatter diffraction analysis. The aim of this study was to clarify the extent to which PALS can be used to identify microstructural changes resulting from varying LPBF process parameters. Grain sizes and misorientation results do not correlate with positron lifetimes indicating the positrons are sampling regions within the grains. Positron annihilation spectroscopy identified the presence of dislocations and nano-voids not revealed through electron microscopy techniques and correlated with the findings of SiO2 nanoparticles in the samples prepared with silicon carbide. The comparison of results indicates the usefulness of positron techniques to characterize nano-structure in additively manufactured metals due to the significant increase in atomic-level information. [ABSTRACT FROM AUTHOR]

The aims of this systematic review are to explore the possibilities of using the positron annihilation lifetime spectroscopy (PALS) method in the pharmaceutical industry and to examine the application of PALS as a supportive, predictive method during the research process. In addition, the review aims to provide a comprehensive picture of additional medical and pharmaceutical uses, as the application of the PALS test method is limited and not widely known in this sector. We collected the scientific literature of the last 20 years (2002–2022) from several databases (PubMed, Embase, SciFinder-n, and Google Scholar) and evaluated the data gathered in relation to the combination of three directives, namely, the utilization of the PALS method, the testing of solid systems, and their application in the medical and pharmaceutical fields. The application of the PALS method is discussed based on three large groups: substances, drug delivery systems, and medical devices, starting with simpler systems and moving to more complex ones. The results are discussed based on the functionality of the PALS method, via microstructural analysis, the tracking of ageing and microstructural changes during stability testing, the examination of the effects of excipients and external factors, and defect characterization, with a strong emphasis on the benefits of this technique. The review highlights the wide range of possible applications of the PALS method as a non-invasive analytical tool for examining microstructures and monitoring changes; it can be effectively applied in many fields, alone or with complementary testing methods. [ABSTRACT FROM AUTHOR]

The subnano free‐volume hole features of Nafion‐212 and poly(styrene sulfonic acid) grafted poly(ethylene‐co‐tetrafluoroethylene) polymer electrolyte membranes are investigated by using the positron annihilation lifetime spectroscopic analyses with three‐ and four‐component models (i.e., one‐ and two‐ortho‐positronium [o‐Ps] components). The four‐component model provides a more adequate description of free‐volume hole features for both membranes, in which the longer o‐Ps lifetime is assigned to the larger free volume hole sizes in the mobile side chains, while the shorter o‐Ps lifetime is associated with the smaller free volume hole sizes within the backbones (the rigid amorphous fractions and the crystalline‐amorphous interfaces) and the interfaces between the main chains and the side chains. The o‐Ps annihilation is found to occur primarily in the side chains. The subnano volume hole features revealed by the positron annihilation lifetime (PAL) spectra suggest the primary water uptake and conductance in the side chains and the possible presence of water molecules in the rigid amorphous fractions and the interfaces. Note that the three‐component model as usually reported in the literature may underestimate the lifetime and intensity of ortho‐positronium annihilation. [ABSTRACT FROM AUTHOR]

PMMA (Poly methyl methacrylate) composites have promising potential for applications in optics and dielectric energy storage. To investigate the effects of TeO 2 contents in PMMA in this respect, we studied their composites on light absorption in the UV visible range, structural analysis via X-ray diffraction, dielectric characteristics, and free volume behavior. We added up to approximately 7 % of the weight concentration of the TeO 2 micropowder to the PMMA matrix for effective dispersion because of the limitations of ultrasonic agitation. The XRD data demonstrate a widening of the peaks with a filler content of up to 4.8 % and agglomeration at 7 %, indicating TeO 2 particle contact. An increase in absorbance was observed in the UV visible spectrum of the PMMA/TeO 2 composites with increasing TeO 2 content up to 4.8 %. The dielectric constants exhibit a positive correlation with higher quantities of TeO 2 , and the polarization mechanism is interpreted by interface polarization and free volume. The free volume measured by positron annihilation lifetime spectroscopy (PALS) increases to 4.8 % but decreases to 7 %. The effect of the free volume within the matrix on the polarization distribution of TeO 2 influenced the dielectric constant and the loss factor, which increased to 4.8 % and then decreased to 7 % due to agglomeration. • Free volume behavior of PMMA/TeO 2 was investigated using the Positron Spectroscopy in both the glassy and molten phases. • The XRD spectrum reveals a broadened peak with TeO 2 content consistent with the free volume. • UV–visible absorbtion spectra aligns well with composite free volume. • Free volume quantity interpretes dielectric permitivity and loss factor using filler-matrix interface polarization. • PMMA/TeO 2 composites exhibit highly favorable dielectric characteristics, increasing the dielectric constant about 20 %. [ABSTRACT FROM AUTHOR]

Polymers are widely used today and the changes in their properties are investigated by different methods such as plasma irradiation. One of the most important methods for modifying polymers is cold plasma, by which the surface properties of the polymers can be changed under atmospheric pressure. In this study, the effect of plasma on Polystyrene (PS) and Polyamide 6 (PA6) samples was investigated. Surface and depth changes of the PS and PA6 have been investigated by various experimental techniques such as Fourier Transform Infrared (FTIR), X-ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), Contact Angle (CA), and Positron Annihilation Lifetime Spectroscopy (PALS). The results of Attenuated Total Reflectance (ATR)-FTIR show that the chemical bonds of PA6 have been changed, and preserved in PS in the depths. The XRD results show that there are no volume changes for chemical bands. The FESEM analysis results reveal that the plasma causes digging and creates roughness on the surface. The CA measurement confirms the FESEM results and points out an increase in hydrophobicity after plasma processing. The PALS results indicate that the free volumes of the matter are changed after plasma irradiation in the depths of PS and PA6. In addition, the plasma also causes changes in the micrometer depth. • One of the most important methods for modifying polymers is cold plasma. • The effect of plasma on Polystyrene (PS) and Polyamide 6 (PA6) samples was investigated by PALS. • The PALS results indicate that the free volumes of PS and PA are changed after plasma irradiation for the shallow depths. [ABSTRACT FROM AUTHOR]

• Heat capacities of quinuclidinium hexafluorophosphate were measured. • In this plastic crystal two solid-solid phase transitions were observed. • Defects in the mixtures doped with Li+ and Cl− ions expand largely. • Ionic conductivity and vacancy volume obey the cohen−turnbull free volume model. To study the phase behavior and role of defects in the ion conduction of a well-investigated plastic crystal electrolyte, we measured the low-temperature heat capacities of quinuclidinium hexafluorophosphate ([HQ]PF 6) plastic crystal and the defects of pure [HQ]PF 6 and its mixtures containing lithium ions and chloride ions. The heat capacities of the pure material show two solid‒solid phase transitions at room temperature and a low temperature. Positron annihilation lifetime spectroscopy (PALS) revealed the phase dependence of the defect size for both the pure material and the mixtures. The defects in these two mixtures expand largely to approximately 2 (with Li+) and 2.5 (with Cl−) times larger than those in the pure material. The relationships between the ionic conductivity and vacancy volume of the pure material and the mixtures obey the Cohen−Turnbull free volume model, which is also phase dependent. This work help elucidate defect-assisted ion transfer in organic ionic plastic crystals. [ABSTRACT FROM AUTHOR]

A comparison of the results of studies on the influence of structural defects on the critical parameters of superconductivity has been made for the high-entropy alloy (NbTa)0.67(MoHfW)0.33 and for the conventional superconducting magnet material Nb-47wt%Ti. Positron annihilation lifetime spectroscopy (PALS), electrical resistivity, magnetization and magnetic susceptibility measurements were used. In addition, X-ray powder diffraction studies were performed on the high-entropy alloy (NbTa)0.67(MoHfW)0.33. Due to the rapid cooling of the materials after melting in the arc furnace, they contain a higher concentration of structural defects compared to the heat-treated materials. Magnetic property measurements showed that both the critical temperatures Tc and the upper critical fields μ0Hc2 of bulk superconductivity-related materials are improved in the presence of structural defects.

In this study, the effects of different concentrations of pea protein concentrate (PPC) in the physical properties, porosity features, and oxidative stability of maltodextrin-based spray-dried microparticles containing orange essential oil (OEO, rich in limonene) were evaluated. The use of PPC resulted in spray-dried microparticles with encapsulation efficiencies of about 99 wt%, without visible pores, and relatively high glass transition temperature (66,4 °C) at Aw ∼ 0.3. The nitrogen adsorption and positron annihilation lifetime spectroscopy measurements showed that the increase of PPC concentration from 2.4 to 4.8 wt% (g of PPC/100 g of emulsion) did not affect the porosity features of the microparticles. These results were confirmed by the profiles of OEO retention and limonene oxide production, which were similar for both samples throughout four weeks of storage. Based on these results, we verified that the lower amount of PPC we tested can effectively protect the OEO during storage, showing that a relatively cheaper orange flavor powder can be produced using less protein.

Rigid polyurethane foams (RPUFs) were modified with 0–15 wt.% turkey feather fibers (TFFs) produced from waste turkey feathers. One-shut free rising method was used for the production of TFFs-filled-RPUFs in a closed mold. The dependence of mechanical performance and water vapor permeability (WVP) feature of the final foams on TFFs loading was evaluated with free volume change. The free volume analysis was performed via Positron Annihilation Lifetime Spectroscopy (PALS), while the mechanical and WVP characteristics were determined with the use of the universal tester machines. PALS findings showed that the incorporation of TFFs with RPUF matrix caused the considerable diminishment in the free volume due to TFFs serving as a filling material and formation of strong secondary bonds between components. Moreover, tensile strength and extension of the foams decreased with the increasing of TFFs, which caused by the occurrence of noteworthy restriction on the spatial alignment and orientation capability of polyurethane chains due to the lack of sufficient free volume allowing the chains to move freely. As for the compression tests, all the TFFs-loaded RPUFs depicted substantially lower performance due to TFFs interfering with the ordered organization of isocyanate domains. Moreover, impact test results showed that the addition of TFFs into RPUF matrix brought about the insufficient impact energy delocalization throughout the matrix due to the restriction on the mobility of polymer chains. Additionally, the remarkable diminishment in WVP was recorded due to the reduction in the number of vacancies and constitution of keratin composed of roundly 60% of hydrophilic protein (especially cystine). All in all, this study established a strong links between free volume and characteristics of TFFs-loaded RPUFs. Graphical Abstract [ABSTRACT FROM AUTHOR]

The free volume in the amorphous phase of a simple carbon‐black‐filled peroxide cross‐linked isoprene rubber (IR) is investigated by positron annihilation lifetime spectroscopy to clarify the structural changes in the rubber phase by the carbon black (CB) fillers. The ortho‐positronium (o‐Ps) pick‐off annihilation lifetime measured in the rubber without CB is around 2.8 ns and is found to be almost constant even after CB filling. This result indicates that in a portion of the rubber phase the free volume remains similar in size to that in the cross‐linked IR without CB. The o‐Ps intensity drastically decreases from 37% without CB to 15% with a CB loading as high as 80 phr. This decline is revealed to exceed the contribution, which is expected only from the decrease in the fraction of the amorphous phase by CB addition, by a factor of 0.37 at the highest CB loading. The additional reduction is related to the generation of a bound rubber layer surrounding the CB fillers with low molecular‐chain mobility where positronium formation is inhibited. The decrease rate is found to represent the volume of this rigid rubber phase and strongly depend on the formation of the CB network structure. [ABSTRACT FROM AUTHOR]

The subnano level free‐volume hole features of poly(styrene sulfonic acid) (PSSA) grafted poly(ethylene‐co‐tetrafluoroethylene) polymer electrolyte membranes (ETFE‐PEMs) are investigated using positron annihilation lifetime spectroscopy (PALS). The hole sizes are formed mainly at the graft‐polymerization step and are not altered dramatically at the sulfonation. With increasing grafting degree, τ4, standing for the annihilation of ortho‐positronium (o‐Ps) in the larger free‐volume holes of the mobile amorphous layers and the PSSA grafts outside of the lamellae, decreases monotonously, whereas τ3, representing for that in the smaller free‐volume holes of the lamellar amorphous regions, the PSSA grafts, and the interface zones inside the lamellae, only shows a slight decrease. From the viewpoint of free‐volume hole sizes, gas molecules are predicted to pass dominantly through the mobile amorphous phases and the PSSA grafts outside of the lamellae. Specifically, the limited hole concentration induced by confining lamellae at the interfacial zones is observed. Thus, the obtained results are associated with a significant reduction of gas passing and the moderate or higher tensile strength for the ETFE‐PEMs in comparison to Nafion‐212. [ABSTRACT FROM AUTHOR]

Positron annihilation lifetime spectroscopy (PALS) is a valuable technique to investigate defects in solids, such as vacancy clusters and grain boundaries in metals and alloys, as well as lattice imperfections in semiconductors. Positron spectroscopy is able to reveal the size, structure and concentration of vacancies with a sensitivity of 10−7. In the field of porous and amorphous systems, PALS can probe cavities in the range from a few tenths up to several tens of nm. In the case of polymers, PALS is one of the few techniques able to give information on the holes forming the free volume. This quantity, which cannot be measured with macroscopic techniques, is correlated to important mechanical, thermal, and transport properties of polymers. It can be deduced theoretically by applying suitable equations of state derived by cell models, and PALS supplies a quantitative measure of the free volume by probing the corresponding sub-nanometric holes. The system used is positronium (Ps), an unstable atom formed by a positron and an electron, whose lifetime can be related to the typical size of the holes. When analyzed in terms of continuous lifetimes, the positron annihilation spectrum allows one to gain insight into the distribution of the free volume holes, an almost unique feature of this technique. The present paper is an overview of PALS, addressed in particular to readers not familiar with this technique, with emphasis on the experimental aspects. After a general introduction on free volume, positronium, and the experimental apparatus needed to acquire the corresponding lifetime, some of the recent results obtained by various groups will be shown, highlighting the connections between the free volume as probed by PALS and structural properties of the investigated materials.

The microstructure changes (such as micro defects and free volume, etc.) is a deep factor that determines the sustained release behavior of polymer film. However, there are few reports exploring the micro defects of sustained-release materials. Herein, we develop a facile method to non-destructive monitoring and sustained-release ethylene within chitosan. The comprehensive means of positron annihilation lifetime spectroscopy, atomic force microscopy and Raman spectrums are performed together to study the microstructures change of ethylene sustained-release and its mechanism. When ethylene is in chitosan film, it shows good ripening performance and mechanical properties. The sustained-release ethylene improves its bioavailability and can control the fruit-ripening on-demand. More importantly, the microstructural changes of cavities have a significant impact on the sustained release of ethylene, due to the creation of cavities, the free volume of positrons undergoes a process of increasing from less to more and then gradually decreasing, reaching a maximum at 120 h. Furthermore, the ethephon/chitosan film could on-demand control the ripening time of mangoes and bananas. Therefore, this research presents a comprehensive means to study of microstructure change monitoring and controllable sustained release, and provides the possibility to solve the problem of on-demand ripening of fruit and reducing pesticide residue. Sustained-release mechanism of ETH/CS film and its application in on-demand fruit ripening. [Display omitted] • A facile method to nondestructive monitoring and sustained-release ethylene within chitosan is successfully developed. • The sustained-release ethylene improves its bioavailability and can control the fruit-ripening on-demand. • PALS, AFM and Raman spectrums are performed together for non-destructive monitoring of ethylene sustained-release. • The influence rule of microstructure such as microdefects and free volume of positrons on the release of ethylene is found. [ABSTRACT FROM AUTHOR]

• Cr/Cu CO-doped ZnO nanoparticles were synthesized by the sol-gel method. • XRD analysis of all Cr/Cu CO-doped ZnO nanoparticles show single phase (ZnO). • The refractive index results follow a similar trend to the shortest lifetime (τ1) and intensity (I1) values. • Refractive index (> 2) was calculated by using different models accurate within two decimal digits. • The antibacterial activities of Cr/Cu CO-doped ZnO NPs are not dependent on their composition. In this research, Cu/Cr codoped ZnO nanoparticles (Zn₀.₉₉₋ ₓ Cu₀.₀₁Cr x O) were prepared using the sol-gel technique. The dopant ratio was systematically varied, ranging from x = 0.01 to 0.05 in increments of 0.01. This variation allowed for an exploration of the impact of defects on the structural, microstructural, optical, and antibacterial properties of Cu/Cr-codoped ZnO nanoparticles. Structural analysis of the Zn₀.₉₉₋ ₓ Cu₀.₀₁Cr x O nanoparticles was conducted using X-ray diffraction. The findings confirmed the presence of a hexagonal wurtzite structure in the ZnCuCrO nanoparticles, as determined by the c/a ratios in the range of 1.6013 and 1.6039. The surface morphology, crystallite size, and nanoparticle shapes were determined through scanning electron microscopy. The nanoparticle elemental compositions were analyzed through electron dispersive spectroscopy. The optical characteristics of the samples were assessed using a UV spectrophotometer. The energy band gaps for the nanoparticles were computed, and we discussed how dopant elements and defects affected their optical properties. We determined the refractive index using five distinct models. Notably, the highest band gap was observed for Zn₀.₉ 4 Cu₀.₀₁Cr₀.₀ 5 O (E g =3.27 eV).Positron annihilation lifetime spectroscopy was employed to investigate the defect type, defect density, and crystal quality of Cu/Cr-codoped ZnO nanoparticles. The shortest lifetime τ1 obtained the highest value (0.181 ns) for Zn 0.97 Cu 0.01 Cr 0.02 O nanoparticles. Zn₀.₉₉₋ ₓ Cu₀.₀₁Cr x O NPs were assessed for their antibacterial effects on E. coli (gram-negative) and S. aureus (gram-positive). Cu/Cr codoped ZnO nanoparticles show potential as materials for optoelectronic and sensor applications due to their broad band gap (Eg > 3) and high refractive index (n > 2). [ABSTRACT FROM AUTHOR]

• The Positron Annihilation Lifetime Spectroscopy was utilized to examine the free volume behavior of PMMA-grafted-PEO and PMMA/PEO blend. • The impact of the free volume was focused on examining the structure-ionic conductivity of PEO-based copolymer. • PEO-based copolymers with PMMA reduce crystallinity and maintain fast segmental dynamics to enhance the conductivity. • PMMA-g-PEO exhibit highly favorable conductivity characteristics. • The Yahsi-Ulutas-Tav (YUT) theory is a highly promising model for interpreting ionic conductivity, specifically in relation to free volume. Recent research has focused on solid polymer electrolytes (SPEs) as the best liquid electrolyte replacements. Poly(ethylene oxide) (PEO) is the most frequent one because of its fast segmental movements in the free volume which controls lithium-ion transport between electrodes. Therefore, PEO-based copolymer electrolytes that can be tailored for mechanical strength and ionic conductivity are often studied. The most popular material is PEO chains containing PMMA because PEO transports ions, and PMMA has good mechanical properties. Further investigations on PEO-based solid polymer electrolytes (SPEs) have shown that chain designs with more nonlinear branches prevent crystallinity and maintain fast segmental dynamics. For this purpose, we worked on PEO-grafted-PMMA copolymers in which the free volume probed by positron annihilation lifetime spectroscopy considerably affects the structure-ionic conductivity relationship. Finally, we investigated the free volume theory of ionic condcutivity using Yahsi-Ulutas-Tav (YUT) theory. [Display omitted] [ABSTRACT FROM AUTHOR]

Efforts to utilize biopolymer membranes to diminish the carbon footprint of separation processes are ongoing. Herein, we report the fabrication of isosorbide (ISB)-based poly(arylene ether) biopolymer membranes, including ISB-based poly(arylene ether sulfone) (I-PAES) and ISB-based poly(arylene ether ketone) (I-PAEK) for gas separation. The robust mechanical properties and amorphous nature of ISB-based biopolymers allow for their application to gas separations. Both positron annihilation lifetime spectroscopy (PALS) and free volume analysis using density measurements reveal that replacing bisphenol A (BPA) in polysulfone (PSF) with ISB results in a significant reduction in free volume owing to the absence of bulky dimethyl groups and the presence of polar aliphatic ether groups. Substituting the sulfone group for a ketone group further decreased free volume. Solid-state CP/MAS 13C NMR analysis discloses that substituting ISB and replacing sulfonyl moieties with carbonyl groups restricts the rotational motion of internal rings, resulting in inhibited gas diffusion. Consequently, the I-PAEK membrane exhibited H 2 /CO 2 and H 2 /CH 4 selectivities more than three times and five times higher, respectively, compared to the PSF counterpart. Our present study demonstrates the feasibility of ISB-based poly(arylene ether) biopolymer membranes for gas separation. [Display omitted] • Isosorbide (ISB)-based biopolymer membranes are studied for gas separation. • PALS reveals that replacing bisphenol-A for ISB reduces the free volume in PSF. • The effect of ISB on chain mobility is identified by solid-state 13C NMR. • Replacing bisphenol-A for ISB increases H 2 /CO 2 , H 2 /CH 4 and CO 2 /CH 4 selectivity. • The ISB-based poly(arylene ether)s show improved H 2 separation efficiency. [ABSTRACT FROM AUTHOR]

The study of the recrystallization resistance of engineering grade tungsten (W) prior to and after neutron irradiation as well as subsequent thermal annealing provides valuable insight into neutron induced defect interactions and their kinetics as well as their correlation with recrystallization mechanisms. The outcome of such investigations would be of assistance for appropriate grade selection for a fusion reactor and the design of healing processes enabling the lifetime extension of fusion reactor components. Within this framework, samples from ITER specification W, forged bar and cold-rolled plate, were neutron irradiated to a dose of 0.18 dpa at 600 °C in the Material Test Reactor BR2, Mol, Belgium, and subsequently isochronally annealed from 700 to 1550 °C for 24 h with a 50 °C step with two non–irradiated counterparts. X-ray diffraction, optical microscopy and positron annihilation lifetime spectroscopy, combined with Vickers Hardness are used to correlate the recrystallization process and recovery mechanisms. It is found that the non-irradiated plate has a higher recrystallization resistance compared to that of the bar, with the former requiring 100 °C higher temperature for 24 h annealing time to recrystallize. Despite the irradiation induced dislocation loops and voids being of similar sizes and densities for both grades, the different initial microstructure affects the recrystallization process upon annealing, delaying it by 50 °C on the plate. Further in the plate a complete void dissolution is observed before recrystallization, which is not the case for the bar, for which the two effects occur at the same temperature. • Isochronal annealing up to 1550 °C of two neutron irradiated ITER specification tungsten. • Higher recrystallization resistance of cold-rolled tungsten compared to forged bar. • Recovery stages identified including dislocation annihilation and void dissolution. • Complete void dissolution occurs before recrystallization in cold-rolled tungsten. [ABSTRACT FROM AUTHOR]

The defect chemistry and electronic trapping energies in undoped single crystalline SrTiO 3 were examined by electrochemical impedance spectroscopy at low (25–160 °C) and intermediate (500–700 °C) temperatures. Electronic and ionic conductivity as well as chemical capacitance values were obtained with a transmission line equivalent circuit. Impedance spectroscopy at low temperatures was used to quantify trapping energies of main ionic defects. Particularly the chemical capacitance is shown to be a highly valuable, though hardly used tool for establishing a defect model based solely on electrochemical measurements. It is very sensitive for minority charge carriers and can thus unveil otherwise hardly accessible defect concentrations. The chemical capacitance analysis yields a valence dependent acceptor concentration in the ppm range for the investigated samples. Complementary positron annihilation lifetime spectroscopy (PALS) suggests existence of Ti vacancies and both methods (chemical capacitance and PALS) agree in their quantification of the corresponding vacancy concentration (6 ppm). Beyond successfully predicting acceptor defect concentrations in undoped SrTiO 3 , the method is sensitive for electronically relevant defects in sub-ppm concentrations. [ABSTRACT FROM AUTHOR]

This research is intended to compare degradation processes in light-cured (dimeth)acrylate-type polymer/filler dental composites affected to aging in dry-air and water-immersed mode. The positron annihilation lifetime (PAL) spectroscopy has been employed to study changes in atomic-deficient structure in these composites under aging. Under light-curing polymerization initiating crosslinking of monomer chains, fragmentation of free-volume holes in resin matrix dominates over enhanced fraction of trapped positrons, since filler–particles assemblies get to be more tightly covered by surrounding polymer causing disappearing of interfacial voids at the filler–polymer surface. Therefore, the PAL spectra-transforming trend in light-cured composites obeys inverse positron-to-Ps trapping conversion. In contrast, the PAL spectra-transforming trend in these restoratives under aging obeys direct Ps-to-positron trapping conversion. After dry-air aging, the observed changes in the density of annihilation sites are ascribed to a strong agglomeration of Ps-decay holes in polymer sub-system accompanied by weaker agglomeration and appearance of positron traps in filler–polymer sub-system. Under the water aging, the agglomeration of Ps-decaying holes in the polymer sub-system is suppressed due to absorbed water molecules, this effect being slightly revealed at lower polymerization. New positron traps are observed at the filler–polymer interfaces in all light-cured composites. The agglomerated Ps-decay holes in a polymer matrix and positron traps inside filler–particles assemblies and filler–polymer interfaces of artificially aged composites cause their progressive microcracking. [ABSTRACT FROM AUTHOR]

In this study, for the first time, the experimental technique of positron annihilation lifetime spectroscopy (PALS) has been applied to monitor in situ the microstructural changes of cellulose-based materials, i.e. paper, during water intake. For three different cellulose samples, bleached fine paper without filler, Kraft paper without filler, and a viscose fiber sheet, the mean positron lifetime Δ τ mean showed a strong increase with time in humid atmosphere, but exhibiting different trends depending on the type of sample. For all the cellulose samples investigated, the mean positron lifetime Δ τ mean shows an initial strong increase simultaneously occurring (t<10 h) to the mass increase of the samples due to water intake. Interestingly, the variations of Δ τ mean of the viscose fiber sheet and the Kraft paper sample both show a second increase on longer timescales (t>60 h in humid atmosphere) during which the mass increase of these samples has already been saturated. The results of this study show that by the means of PALS, water transport in paper can be reliably followed over a long timespan and it is even possible to distinguish between different types of cellulose materials. The second stage increase of the mean positron lifetime after long times in humid atmosphere for the Kraft paper sample and the pure viscose sheets even suggest that not only water intake itself can be monitored but also further atomistic processes in the material are accessible. [ABSTRACT FROM AUTHOR]

The aims of this systematic review are to explore the possibilities of using the positron annihilation lifetime spectroscopy (PALS) method in the pharmaceutical industry and to examine the application of PALS as a supportive, predictive method during the research process. In addition, the review aims to provide a comprehensive picture of additional medical and pharmaceutical uses, as the application of the PALS test method is limited and not widely known in this sector. We collected the scientific literature of the last 20 years (2002–2022) from several databases (PubMed, Embase, SciFinder-n, and Google Scholar) and evaluated the data gathered in relation to the combination of three directives, namely, the utilization of the PALS method, the testing of solid systems, and their application in the medical and pharmaceutical fields. The application of the PALS method is discussed based on three large groups: substances, drug delivery systems, and medical devices, starting with simpler systems and moving to more complex ones. The results are discussed based on the functionality of the PALS method, via microstructural analysis, the tracking of ageing and microstructural changes during stability testing, the examination of the effects of excipients and external factors, and defect characterization, with a strong emphasis on the benefits of this technique. The review highlights the wide range of possible applications of the PALS method as a non-invasive analytical tool for examining microstructures and monitoring changes; it can be effectively applied in many fields, alone or with complementary testing methods.

The cation and cation vacancy distributions in Zn2+ substituted maghemite (γ-Fe2 (1-x/3) ZnxO3, x = 0.0, 0.1, 0.2, 0.3 and 0.4) nanoparticles, which were synthesized directly via one pot room temperature co-precipitation method, were obtained by positron annihilation lifetime spectroscopy, coincidence Doppler broadening spectroscopy, and Rietveld refinement of XRD patterns. The analyses show that the substitution of small amounts of zinc ions for iron ones in maghemite (x ≤ 0.1) leads to an increase in the number of cation vacancies, while more substitutions cause to a decrease in cation vacancies. For the samples with x = 0.0 and 0.1, more of vacancies are placed at B sites, whereas for others they are placed at the A ones. [ABSTRACT FROM AUTHOR]

Single-phase Ni-Cu ferrite nanoparticles have been prepared by sol–gel method and exposed using an Am-Be source for time periods of one and two months. The effects of irradiation on structure and magnetic properties of prepared nanoparticles are investigated by X-ray diffraction, positron annihilation spectroscopy and vibrating sample magnetometer. The X-ray measurements showed that unirradiated and irradiated samples have cubic spinel structure and variation of structural parameters with irradiation is nonuniform. The positron annihilation measurements showed that the main effect of irradiation on samples is variation in momentum distribution of core electrons in metallic cations. The magnetic measurements represent that irradiation cause an increase in saturation magnetization and a decrease in coercivity. The increase in saturation magnetization is attributed to cation redistribution because of atomic displacement. The decrease in coercivity is attributed to the variation of magnetocrystalline anisotropy constant due to the effect of irradiation on the core electrons of cations. [ABSTRACT FROM AUTHOR]

In this study, pure polylactic acid (PLA) and composite polylactic acid/ curcumin (PLA / Cur) were prepared by a suspension of ultrasonically agitated micrometersized curcumin powder, which was mixed with chloroform solvent under slow mechanical stirring and incorporated into the PLA. The resulting suspension was used to cast free-standing PLA / Cur composite films. The filler content was chosen to be 2.0 wt % curcumin. Physical properties (glass transition, temperature, mechanical and thermodynamic) were analyzed by Positron Annihilation Lifetime Spectroscopy (PALS), which is a unique tool for analyzing the defects of polymer materials. The free volume and holebility of PLA and PLA / Cur were studied in vacuum and temperature range of 283 to 353 K. Ortho-positronium (o Ps), life 3 ( ) , and intensity ( ) 3 I were measured as more sensitive parameters to determine free volume dimensions. The results of the thermodynamic property of PLA, examined with PALS technique, revealed a phase change of around 58 ºC. Also, an improvement was observed in the PLA / Cur structure with the addition of curcumin, by reducing nano-size defects. [ABSTRACT FROM AUTHOR]

Positron annihilation spectroscopy using lifetime and Doppler broadening allows the characterization of the lithiation state in LiCoO2 thin film used in cathode of lithium-ion batteries. The lifetime results reflect positron spillover because of the presence of graphite in between the oxide grains in real cathode Li-ion batteries. This spillover produces an effect in the measured positron parameters which are sensitive to delocalized electrons from lithium atoms as in Compton scattering results. The first component of the positron lifetime corresponds to a bulk-like state and can be used to characterize the state of charge of the cathode while the second component represents a surface state at the grain-graphite interface. [ABSTRACT FROM AUTHOR]

Liquid polymers are used in elastomeric compounds to modify their processing and final characteristics. The material is considered as a polymeric plasticizer and is used to substitute or supplement conventional plasticizer like paraffinic or aromatic oils, or hydrocarbon resins. Their plasticizing effect and contribution to the crosslinking in sulfur cured SSBR mixtures is studied. Aromatic oil, aliphatic resin and different liquid polymers, varied in type, molecular weight and microstructure are discussed. Different plasticizing effects are shown with corresponding curing torques and Shore hardness values. The free volume – measured by positron annihilation lifetime spectroscopy - increases or decreases according to the liquid polymer's incorporation in the main polymer.

Molecularly imprinted thin membranes for selective removal of tetracycline from real water samples were prepared using the radiation‐induced polymerization method. The chemical and physical characterization of the membranes was conducted by FTIR, XPS, AFM and SEM analyses. The effect of the template on the size and the size distribution of the pores in the membrane structure was investigated by positron annihilation lifetime spectroscopy (PALS) experiments. The presence of the template molecule causes the formation of larger cavities, which have a strong correlation to the molecular size of the template molecule. The density of the free volume holes in the imprinted network shows a significant increase due to the presence of the template molecule. The binding performances of the membranes were tested against various factors such as pH, time and initial concentration of template molecules. The specific selectivity of the membranes was investigated by cross‐reactivity experiments. The binding capacity of the imprinted membranes was obtained at 14.5 μmol g−1, with the highest imprinting factor (2.84) for tetracycline. The imprinting factor was obtained at 1.44, 1.25 and 1.57 for oxytetracycline hydrochloride, doxycycline hyclate and chlortetracycline, respectively. The binding capability of the imprinted membranes in real water samples was promising for the application of the membranes as a filter material for removal of tetracycline with high binding capacity. Tetracycline binding percentage of the membranes was determined at 92.4, 81.1., 75.0 and 68.7 for ultra‐pure water, tap water and natural water samples collected from different sources, respectively. [ABSTRACT FROM AUTHOR]

To realize efficient atmospheric CO2 chemisorption and activation, abundant Ti3+ sites and oxygen vacancies in TiO2 ultrathin layers were designed. Positron annihilation lifetime spectroscopy and theoretical calculations first unveil each oxygen vacancy is associated with the formation of two Ti3+ sites, giving a Ti3+-Vo-Ti3+ configuration. The Ti3+-Vo-Ti3+ sites could bond with CO2 molecules to form a stable configuration, which converted the endoergic chemisorption step to an exoergic process, verified by in-situ Fourier-transform infrared spectra and theoretical calculations. Also, the adjacent Ti3+ sites not only favor CO2 activation into COOH* via forming a stable Ti3+-C-O-Ti3+ configuration, but also facilitate the rate-limiting COOH* scission to CO* by reducing the energy barrier from 0.75 to 0.45 eV. Thus, the Ti3+-Vo-TiO2 ultrathinlayers could directly capture and photofix atmospheric CO2 into near-unity CO, with the corresponding CO2-to-CO conversion ratio of ca. 20.2%. [ABSTRACT FROM AUTHOR]

Single phase Zn2+-substituted magnetite nanocrystallites are synthesized via co-precipitation method and used as lithium-ion battery electrodes. The structural properties and vacancy distribution of nanoparticles are evaluated by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), and positron annihilation lifetime spectroscopy (PALS). The Rietveld refinement of the X-ray diffraction patterns shows that the lattice constant increases with Zn2+ content from 8.392 Å for magnetite to 8.448 Å for Zn 0.2 Fe 2.8 O 4. The XPS measurements show that cation vacancies increase with Zn content on the surface of nanoparticles. Positron annihilation lifetime spectra suggest more concentration of monovacancies and larger size of vacancy clusters in the Zn 0.1 Fe 2.9 O 4 sample compared with the other two samples, Fe 3 O 4 and Zn 0.2 Fe 2.8 O 4. Electrochemical measurements show better reversibility, higher initial discharge capacity, and lower electrochemical impedance for the Zn 0.1 Fe 2.9 O 4 electrode, which are attributed to the higher concentration of vacancy defects in its nanocrystallites. The electrochemical impedance spectroscopy (EIS) shows that the Li+ diffusion coefficient (D Li +) increases with Zn2+ doping from 1.51 × 10–15 cm2s–1 for Fe 3 O 4 to 3.25 × 10–13 cm2s–1 for Zn 0.1 Fe 2.9 O 4 , and 1.43 × 10–13 cm2s–1 for Zn 0.2 Fe 2.8 O 4. The initial discharge capacities of the samples found to be about 1345.04 mAh g−1 for Fe 3 O 4 , 1435.82 mAh g−1 for Zn 0.1 Fe 2.9 O 4 , and 1063.72 mAh g−1 for Zn 0.2 Fe 2.8 O 4 electrodes, respectively. During first few cycles, the discharge capacity decline faster as Zn content increases. The discharge capacity of the Zn 0.2 Fe 2.8 O 4 electrode is stable at 410 mAhg−1 from the 60th to the 200th cycle, which is higher than the Fe 3 O 4 electrode (150 mAhg−1) and the Zn 0.1 Fe 2.9 O 4 electrode (270 mAhg−1). This variance is explained by the cation vacancy concentration and the lattice constant of the samples. The impedance of the electrodes is also affected by the vacancy defects formed during the sample preparation. [Display omitted] • Single-phase Zn2+ substituted magnetite nanoparticles were synthesized via co-precipitation method at room temperature. • The vacancy distribution in nanoparticles due to substitution of Zn cation are measured by XPS and PALS respectively. • Discharge capacity of samples improved with Zn content which were explained based on lattice constant and cation vacancies. [ABSTRACT FROM AUTHOR]