Positron Annihilation Lifetime Spectroscopy Research Articles

Mechanism Insights in Anticorrosion Performance of Waterborne Epoxy Coatings Reinforced by PEI-Functionalized Boron Nitride Nanosheets.

Functionalized hexagonal boron nitride nanosheets (BNNSs) have arisen as compelling anticorrosive additives, yet the precise mechanism of their corrosion resistance enhancement in coatings remains unclear. Here, polyethylenimine functionalized BNNSs (PEI-BNNSs) with approximately 6-11 layers were prepared through a "one-step" method. Then, the PEI-BNNSs/Waterborne epoxy (WEP) composite coatings were incorporated via the waterborne latex blending method for the anticorrosion of the Q235 substrate. The impedance modulus (|Z|f = 0.01 Hz) of 0.5 wt % PEI-BNNSs/WEP composite coating soaked in 3.5 wt % NaCl solution for 35 days increased by 4 orders of magnitude compared to pure WEP coating, exhibiting exceptional long-term resistance against corrosion. The positron annihilation lifetime spectroscopy and corrosion product analysis demonstrated that the reinforced anticorrosion capabilities are not solely ascribed to the "tortuous path effect" arising from BNNSs impermeability. These mechanisms also encompass the reduction in free volume fraction and radius of the free volume cavities within the composite coating brought about by the PEI molecules. Additionally, the increase in coating adhesion, promoted by PEI, plays an important role in augmenting the barrier properties against corrosive agents. This study provided a full comprehension of the role played by functionalized BNNSs in fortifying the anticorrosion attributes of WEP coatings.

Correlation between positron annihilation lifetime and photoluminescence measurements for calcined Hydroxyapatite

Hydroxyapatite (HAp) Ca10(PO4)6(OH)2 is a compound that has stable chemical properties, composition, and an affinity for human bone. As a result, it can be used in odontology, cancer treatment, and orthopedic grafts to repair damaged bone. To produce calcined HAp at 600 °C with different pH values, a wet chemical precipitation method was employed. All synthesized HAp samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), photoluminescence (PL), Zeta potential, and positron annihilation lifetime spectroscopy (PALS). The XRD results revealed that all calcined HAp samples were formed in a hexagonal structure with a preferred (002) orientation at different pH values. The crystal size of the samples was determined using the Scherrer equation, which ranged from 16 to 25 nm. The SEM and TEM results showed that the morphology of the samples varied from nanorods to nanospheres and rice-like structures depending on the pH value of the sample. The PL measurements indicated that the blue and green emission peaks of HAp were due to defects (bulk, surface, and interface) in the samples, which created additional energy levels within the band gap. According to Zeta potential measurements, the charge carrier changed from a positive to negative value, ranging from 3.94 mV to − 2.95 mV. PALS was used to understand the relationship between the defects and the photoluminescence (PL) properties of HAp. Our results suggest that HAp nanoparticles have excellent potential for developing non-toxic biomedical and optical devices for phototherapy.

Investigating the effect of lead substitution on the optical, electrical, and photoresponse properties of Quasi-2D double perovskites

Quasi-2-dimensional (2D) halide perovskites have recently attracted attention due to their higher operational stability as alternatives to 3-dimensional (3D) perovskites having exceptional optoelectronic and charge transport properties. To reduce the lead content, here following the double perovskite approach lead is substituted with silver and bismuth simultaneously, and three quasi-2D perovskites, with general formula (C7H10N)2Pb(1-2x)AgxBixBr4, (0 ≤ x ≤ 0.5) were prepared. The optical studies show that the partially lead substituted sample has the lowest optical band gap, aptly supported by the theoretical calculations. The powder X-ray diffraction technique along with field-emission scanning electron microscopy suggests enhancement in crystallinity along with the decrease in grain boundaries with the substitution of lead. The improvement in crystallinity with concomitant reduction in grain boundaries has led to the decrease in point defects as identified from the positron annihilation lifetime spectroscopy and coincidence Doppler broadening analysis. The tuned band gap, improved crystal quality along with lower defects jointly contributed to the enhancement in electrical properties of the perovskites with varying lead percentages. Finally, the photoresponse of all the materials was studied after fabricating metal (Al)-semiconductor (MS) junction thin film photodetector devices.

Structure, vacancy, and physical properties of non-stoichiometric MnWO4 ceramics

Non-stoichiometric ceramic samples of Mn0.97WO4 and MnW0.97O4 were prepared by a solid-state reaction to study the effects of vacancies at different lattice positions on the structure and properties of MnWO4 materials caused by non-stoichiometric. Positron annihilation technology was introduced to study the vacancy characteristics of the MnWO4, Mn0.97WO4, and MnW0.97O4 ceramics. The results indicated that non-stoichiometric did not affect the monoclinic lattice structure of any of the MnWO4 samples, and had no obvious effect on the lattice parameters of the samples. The analysis of positron annihilation lifetime spectroscopy showed that W vacancies were the main defects in MnW0.97O4 samples, and Mn vacancies were favored in Mn0.97WO4 samples, the vacancies concentration for non-stoichiometric MnWO4 samples was higher than that of stoichiometric MnWO4. It was observed that the magnetization and transition temperatures of the non-stoichiometric MnWO4 system were increased, and the temperature range in which AF2 phase existed was enlarged. This study demonstrated that non-stoichiometric could enhance the magnetic properties of MnWO4, the effect of Mn vacancy on the properties of MnWO4 is higher than that of W vacancy. The intimate correlation between the vacancy defects and magnetic properties provides us strong evidence that the magnetic properties of MnWO4 can be enhanced by regulating vacancy defects.

Impact of chemical composition of soybean oil and vanillin-based photocross-linked polymers on parameters of electrochemical biosensors

Network properties on local free volume and biosensor parameters of polymers based on acrylated epoxidized soybean oil (AESO), a combination of AESO with vanillin dimethacrylate (VDM) in ratio 1:0.25 mol, and its combination with vanillin diacrylate (VDA) with the same molar ratio, used as laccase-holding matrixes for the construction of amperometric biosensors, were tested and compared. The formed polymer matrixes were investigated using Positron Annihilation Lifetime Spectroscopy (PALS) as bulk samples and applying electrochemical methods as sensor films. PALS results showed that the lifetime of the ortho-positronium component and corresponding intensity are almost similar for both polymers, indicating no significant difference from the point of view of their morphology. However, the cyclic voltammetric and chronoamperometric analysis demonstrated significant differences in the bioelecrodes’ operational parameters formed by the AESO:VDM polymer compared to AESO:VDA. The AESO:VDA-based bioelectodes were characterized with a twice higher affinity toward ABTS (KMapp = 0.158 ± 0.022 mM vs. 0.326 ± 0.043 mM). At the same time, their sensitivity was about twice less compared to AESO:VDM-based (902 A·M−1·m−2vs. 1608 A·M−1·m−2), and a start concentration of the linear frame was 7-folds higher (14 μM vs. 2 μM ABTS). It was shown early, that the operational parameters of amperometric biosensors are greatly dependent on morphological characteristics of polymer matrixes (e.g., crosslink density, cavities size, thermal expansion of free-volume hole, etc.). The matrix morphology affects on efficacity of physical diffusion of the substrate to the enzyme, and electroactive product toward the electrode, as well as provides a comfortable environment for the incorporated enzyme. Here, we describe the usage of polymer matrixes with the same morphological properties but different chemical compositions, analyzing the effect of chemical structure on the operational parameters of biosensors. Thus, it was demonstrated that the sensor operational parameters depend not only on the morphological properties of the polymer holding matrixes, providing enzyme fixation and substrate/product diffusion, but also on their chemical composition, which opens a possibility to adapt the biosensor characteristics according to the required needs of analysis.

Revisiting Metal-Organic Frameworks Porosimetry by Positron Annihilation: Metal Ion States and Positronium Parameters.

Metal-organic frameworks (MOFs) stand as pivotal porous materials with exceptional surface areas, adaptability, and versatility. Positron Annihilation Lifetime Spectroscopy (PALS) is an indispensable tool for characterizing MOF porosity, especially micro- and mesopores in both open and closed phases. Notably, PALS offers porosity insights independent of probe molecules, which is vital for detailed characterization without structural transformations. This study explores how metal ion states in MOFs affect PALS results. We find significant differences in measured porosity due to paramagnetic or oxidized metal ions compared to simulated values. By analyzing CPO-27(M) (M = Mg, Co, Ni), with identical pore dimensions, we observe distinct PALS data alterations based on metal ions. Paramagnetic Co and Ni ions hinder and quench positronium (Ps) formation, resulting in smaller measured pore volumes and sizes. Mg only quenches Ps, leading to underestimated pore sizes without volume distortion. This underscores the metal ions' pivotal role in PALS outcomes, urging caution in interpreting MOF porosity.

Synthesis and OER catalytic activity of quasi zeolitic imidazolate Framework-67 having two and three dimensional morphology

Zeolitic imidazolate framework-67 (ZIF-67), in two and three dimensional (2D/3D) morphologies have been synthesized at room temperature using different solvent media, and annealed at 350 and 920 °C to derive the modified ZIF-67 based catalysts. All the ZIF-67 based catalysts were characterized using powder X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, Scanning electron microscopy, Thermogravimetric analysis, N2 gas adsorption method, and Positron annihilation lifetime spectroscopy. It has been observed that catalytic activity of the ZIF-67 based catalysts towards oxygen evolution reaction (OER) depends on the morphology and annealing-induced modifications in active sites. Among different morphologies of as-synthesized ZIF-67, 2D ZIF-67 (nanosheet and disc like morphology) exhibits the best electrocatalytic activity in as-synthesized as well as in the annealed form in comparison to 3D ZIF-67 (rhombic dodecahedron) owing to their better electronic properties. All the types of ZIF-67 annealed at 920 °C show the lower Tafel slopes suggesting higher OER rate.

Positron annihilation lifetime spectroscopy of FeCr and FeCrAl oxide dispersion strengthened (ODS) alloys

Positron annihilation lifetime spectroscopy (PALS) was performed to characterize the interfacial nanostructure between the oxide particles and ferritic matrix in two types of oxide dispersion strengthened (ODS) alloys: FeCr dispersed with Y-Ti oxide nanoparticles and FeCrAl dispersed with Y-Al oxide nanoparticles. The spectra were precisely fitted and decomposed into three components with two trapping rates. Bulk lifetime approached the theoretical value of 107 ps by taking into account the positron trapping at two types of defects. Structural characterization was performed by coincidence Doppler broadening and high-resolution transmission electron microscopy (HRTEM), revealing that two-trapping defect clusters were closely associated with Y-Ti or Y-Al oxide particles. Trapping was not detected in the non-ODS alloys. Based on Kuramotos advanced theoretical work, the shorter annihilation lifetime (179–194 ps) could be ascribed to positron trapping at vacancies and divacancies localized under the misfit dislocations associated with Y-Ti or Y-Al oxide particles. The longer annihilation lifetime (301–323 ps) could be attributed to Ar-filled gas bubbles precipitated at the oxide particle-matrix interfaces. These results of PALS analyses were consistent with the HRTEM characterization.

Combinatory effects of nanocarbon- and radiation-induced networks on free-volume heterogeneity, nonisothermal crystallization, and electrorecovery

Electro shape-memory polymers (eSMPs) are highly regarded for their ability to undergo preordained transformations in response to electrical cues, a feature intrinsically linked to the prevailing electrical conduction pathways and macromolecular configurations. Alterations through the introduction of nanoparticles or the implementation of crosslinking techniques can produce synergistic or antagonistic shifts in the free volume and nonisothermal crystallization behavior. To date, such effects have remained largely unexplored. In this study, we developed gamma radiation-processed eSMPs that exhibit superior electrorecovery capabilities (approximately 100% recovery at 7.5 V) intrinsically connected to the specific radiation dose administered. Furthermore, we examined the changes in the free volume, extensional viscosity, rheology, and nonisothermal crystallization of these electroconductive composites. Our findings highlight the necessity of a critical radiation dose for the induction of electroshape recovery, and evidence suggests that the radiation dose substantially reduces the crystallization temperature under nonisothermal conditions while simultaneously broadening the crystallization process, especially at high cooling rates. Analyses of extensional stress further underscored the critical role of radiation dose. Positron annihilation lifetime spectroscopy (PALS) studies revealed that both the NCB and radiation dose contribute to an overall reduction in the free-volume size.

Hardness Prediction of the Heat-Affected Zone in Multilayer Welded SUS316 Stainless Steel Based on Dislocation Density Change Behavior

The effects of strain hardening and recovery/recrystallization on the hardness of the heat-affected zone (HAZ) in multilayer welded austenitic stainless steel SUS316 were investigated in this study. The results revealed that strain hardening due to welding strain and softening due to recovery/recrystallization were the dominant factors affecting the hardness change in the HAZ during multilayer welding process. Furthermore, the relationship between the strain and dislocation density and that between the recovery/recrystallization and dislocation density were quantitatively investigated using positron annihilation lifetime spectroscopy. Based on these results, a new hardness prediction method based on the change in dislocation density in the HAZ during multilayer welding was proposed. The hardness values in the HAZ after the multilayer welding were predicted based on the simulated strain and thermal history, and the calculated hardness values agreed well with the measured results. This indicates that the newly proposed hardness prediction method based on the dislocation density change behavior in the HAZ during multilayer welding is valuable and effective for selecting the appropriate welding conditions before actual welding.

The effect of microstructure on recovery and recrystallization after annealing of two neutron irradiated ITER specification tungsten

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.

Highly permeable and selective polymer inclusion membrane for Li+ recovery and underlying enhanced mechanism

Polymer inclusion membrane (PIM) has become a potential alternative in efficient Li + separation from brines typically with Mg2+ and Li+, due to its exceptional stability and selectivity. However, the practical application of PIMs is still greatly restricted by its slow mass transfer and related unclear transport mechanism. Here, we fabricated an efficient PIM with tributyl phosphate (TBP) along with sodium tetraphenylborate (NaBPh4) as carriers and cellulose triacetate (CTA) as a polymer skeleton for highly selective and permeable Li + separation from high Mg2+/Li+ aqueous solutions, offering an initial flux of 3–20 times higher than other PIMs. With increasing TBP content in the PIM, a nonmonotonical trend (sharp increase-leveling off-slow decrease) of its initial flux was observed. The improvement of the solubility (compatibility) of NaBPh4 in CTA matrix by introducing TBP was demonstrated by scanning electron microscope (SEM) coupled with X-ray energy dispersive spectroscopy (EDS) images, which was highly consistent with binding energy simulation. X-ray diffraction (XRD) and positron annihilation lifetime spectroscopy (PALS) results verify that moderate TBP content in the PIM could enlarge the distance of polymer chains and enhance the initial flux of PIMs, while excessive TBP can occupy the free volume sites, leading to an adverse effect on the permeability. Our study provides valuable information on the compatibility effect on the mass transfer through the polymer matrix including PIMs, which exhibits prospect in a wide range of applications of metal separation.

ZnAl2O4:Er3+ Upconversion Nanophosphor for SPECT Imaging and Luminescence Modulation via Defect Engineering.

This work reports an "all-in-one" theranostic upconversion luminescence (UCL) system having potential for both diagnostic and therapeutic applications. Despite considerable efforts in designing upconversion nanoparticles (UCNPs) for multimodal imaging and tumor therapy, there are few reports investigating dual modality SPECT/optical imaging for theranostics. Especially, research focusing on in vivo biodistribution studies of intrinsically radiolabeled UCNPs after intravenous injection is of utmost importance for the potential clinical translation of such formulations. Here, we utilized the gamma emission from 169Er and 171Er radionuclides for the demonstration of radiolabeled ZnAl2O4:171/169Er3+ as a potent agent for dual-modality SPECT/optical imaging. No uptake of radio nanoformulation was detected in the skeleton after 4 h of administration, which evidenced the robust integrity of ZnAl2O4:169/171Er3+. Combining the therapeutics using the emission of β- particulates from 169Er and 171Er will be promising for the radio-theranostic application of the synthesized ZnAl2O4:169/171Er3+ nanoformulation. Cell toxicity studies of ZnAl2O4:1%Er3+ nanoparticles were examined by an MTT assay in B16F10 mouse melanoma cell lines, which demonstrated good biocompatibility. In addition, we explored the mechanism of UCL modulation via defect engineering by Bi3+ codoping in the ZnAl2O4:Er3+ upconversion nanophosphor. The UCL color tuning was successfully achieved from the red to the green region as a function of Bi3+ codoping concentrations. Further, we tried to establish a correlation of UCL tuning with the intrinsic oxygen and cation vacancy defects as a function of Bi3+ codoping concentrations with the help of electron paramagnetic resonance (EPR) and positron annihilation lifetime spectroscopy (PALS) studies. This study contributes to building a bridge between nature of defects and UC luminescence that is crucial for the design of advanced UCNPs for theranostics.

Statistical thermodynamics to assess probability of water channel formation in membrane

In this work, the probability of water channel formation was calculated for several polymeric materials, and with that information, the desalination capacity of each material was assessed. Using a 3D lattice model for a flat sheet, the Gibbs free energy change (ΔG) that results from the formation of the first water channel from the top to the bottom surface of the sheet was calculated as a function of the hydrophilicity/-phobicity of the polymeric material (w), the total fraction of water in the 3D lattice (x), and the thickness of the lattice (n). With this result, an equation was further derived to evaluate (xb) the fraction of water which is related to the channel formation, and (xb/x), the ratio of xb to x. It was found that the values of xb are closely related to the fractional free volume (FFV) measured by positron annihilation lifetime spectroscopy (PALS) and the percent free volume of percolated open spaces where water could pass through obtained by molecular dynamics simulation (MDS).These equations were then used to assess the usefulness of each material for making reverse osmosis membranes. When xb is too large, too many channels form, and those channels join to form large pores through which salt can pass, rendering reverse osmosis unsuccessful. On the other hand, when xb is too small, not enough water channels are formed, so reverse osmosis cannot occur then either. It was found that xb was too small for polyvinylidene fluoride (PVDF) and polyethersulfone (PES); suitable for cellulose acetate (CA), aromatic polyamide (APA) and aromatic polyamidehydrazide (APAH); and too large for cellophane (CE). This paper determines which circumstances allow water to form channels in a membrane, and it provides a novel method to assess a material's suitability for reverse osmosis.

Exploring the electrochemical properties of lithium-ion battery electrodes composed of vacancy-defective zinc-substituted magnetite nanocrystallites

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 Zn0.2Fe2.8O4. 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 Zn0.1Fe2.9O4 sample compared with the other two samples, Fe3O4 and Zn0.2Fe2.8O4. Electrochemical measurements show better reversibility, higher initial discharge capacity, and lower electrochemical impedance for the Zn0.1Fe2.9O4 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 (DLi+) increases with Zn2+ doping from 1.51 × 10–15 cm2s–1 for Fe3O4 to 3.25 × 10–13 cm2s–1 for Zn0.1Fe2.9O4, and 1.43 × 10–13 cm2s–1 for Zn0.2Fe2.8O4. The initial discharge capacities of the samples found to be about 1345.04 mAh g−1 for Fe3O4, 1435.82 mAh g−1 for Zn0.1Fe2.9O4, and 1063.72 mAh g−1 for Zn0.2Fe2.8O4 electrodes, respectively. During first few cycles, the discharge capacity decline faster as Zn content increases. The discharge capacity of the Zn0.2Fe2.8O4 electrode is stable at 410 mAhg−1 from the 60th to the 200th cycle, which is higher than the Fe3O4 electrode (150 mAhg−1) and the Zn0.1Fe2.9O4 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.

Ortho-positronium annihilation processes in Y zeolites under different environments by measurements of the energy spectra of the positron annihilation radiation

Measurements of the energy distribution of the positron annihilation radiation in Y zeolites are carried out to elucidate the various ortho-positronium annihilation processes that take place in these microporous materials and relate them to the ortho-positronium lifetime components observed by positron annihilation lifetime spectroscopy in earlier studies. Y zeolites with various Si/Al ratios in the range from 2.6 to 40 are investigated under a controlled atmosphere of N2 gas and after exposure to the atmosphere. The ortho-positronium annihilation modes are characterized by analyzing the γ-ray spectra through the use of the f3γ index, which represents the fraction of 3γ-annihilation, and the S parameter. The proportion of ortho-positronium self-annihilation is found to be no less than 15% in N2 gas, but drastically decreases by the physisorption of water molecules and possibly positronium spin exchange interaction with oxygen in the atmosphere. The presence of water molecules suppresses ortho-positronium intrinsic annihilation and, at the same time, promotes ortho-positronium pick-off annihilation in the pores. Similarly, the S parameter rises due to an increased contribution from para-positronium annihilation and ortho-positronium pick-off annihilation, which is also consistent with the physisorption of water and positronium spin exchange. In conjunction with the previously measured ortho-positronium lifetime components, the specific ortho-positronium annihilation sites and processes in these porous materials under different environments are determined and a complete picture of the ortho-positronium behavior in Y zeolites is obtained.Graphical abstractγ-ray energy spectra of Y zeolites with a Si/Al ratio = 2.6 measured in N2 gas and water-saturated zeolites

Proton pathways via free volumes: A positron annihilation lifetime spectroscopy (PALS) investigation of proton conductivity in SPEEK-PEG-TMOS composites

This study investigates the ionic conductivity and dielectric properties of SPEEK-PEG-TMOS solid-state polymer electrolytes across a broad frequency spectrum (0.1–1000 kHz). Proton transport mechanisms were explored over an extensive temperature range, and positron annihilation lifetime spectroscopy (PALS) was employed to elucidate the roles of free volumes in the transport mechanism. At elevated temperatures, sulfonic acid groups and free volume defects predominantly govern the conductivity in all polymer electrolytes. PEG incorporation significantly improved proton conductivity at low temperatures, while the presence of TMOS and higher PEG content have elevated conductivity at higher temperatures. Proton conductivity mechanisms at elevated temperatures are influenced by SPEEK's intrinsic proton conductivity, PEG's plasticizing effect, acid-base interactions, and the presence of free volumes. PALS analysis reveals temperature-dependent trends in the o-Ps lifetime, intensity, and free volume fraction, increasing linearly with temperature due to thermal expansion. PEG content modulated this trend, with lower PEG content samples displaying lower thermal expansion slopes, and higher PEG content samples exhibiting more substantial increases in hole-free volume. The o-Ps intensity displayed a temperature-dependent change attributed to PEG's thermal expansion limitations. These insights contributed to a comprehensive understanding of the intricate interplay between PEG content, thermal expansion, and free volume in SPEEK-PEG-TMOS composites. The study has implications for material science applications, particularly in the development of high-temperature, anhydrous proton-conductive systems.

Electrochemical characterization and structural analysis of (In2O3)/(Fe2O3) nanocomposites for high-performance supercapacitors

This study presents a comprehensive investigation of the electrochemical characteristics and structural properties of novel nanocomposites with varying compositions of (In2O3)x/(Fe2O3)1-x, where x ranges from 1 to 0. These nanocomposites were synthesized using a versatile and cost-effective co-precipitation method. The crystallographic structure and morphology of the synthesized samples were thoroughly analyzed using Powder X-ray diffraction (PXRD) and Tunneling Electron Microscopy (TEM). Advanced analytical techniques were employed including Positron Annihilation Lifetime Spectroscopy (PALS) and Coincidence Doppler Broadening Spectroscopy (CDBS) to uncover critical insights into the structural and molecular properties of these nanocomposites. PALS analysis revealed valuable insights into the pore characteristics of the nanocomposites, while CDBS identified crucial molecular interactions within the materials. Electrochemical characterization of the nanocomposites is carried out using cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrochemical-impedance-spectroscopy (EIS) measurements. The (In2O3)0.3/(Fe2O3)0.7 nanocomposite exhibits a remarkable specific capacitance of 945 F g-1 at 1 A g-1 and exceptional rate performance, retaining 93.6% of its specific capacitance at a six-fold higher current density. Moreover, this nanocomposite electrode demonstrates outstanding cyclic stability, maintaining 92.1% of its specific capacitance even after 3000 GCD cycles at 8 A g-1. These findings suggest that the novel composition and integrated electrochemical properties of the (In2O3)0.3/(Fe2O3)0.7 nanocomposite hold great promise for enhancing the performance of next-generation electrochemical capacitors. This research contributes valuable insights into the design and development of advanced energy storage materials with applications in various high-performance energy storage devices.

Dynamically Reconstructed Triple-Copper-Vacancy Associates Confined in Cu Nanowires Enabling High-Rate and Selective CO2 Electroreduction to C2+ Products.

Electrochemically reconstructed Cu-based catalysts always exhibit enhanced CO2 electroreduction performance; however, it still remains ambiguous whether the reconstructed Cu vacancies have a substantial impact on CO2 -to-C2+ reactivity. Herein, Cu vacancies are first constructed through electrochemical reduction of Cu-based nanowires, in which high-angle annular dark-field scanning transmission electron microscopy image manifests the formation of triple-copper-vacancy associates with different concentrations, confirmed by positron annihilation lifetime spectroscopy. In situ attenuated total reflection-surface enhanced infrared absorption spectroscopy discloses the triple-copper-vacancy associates favor *CO adsorption and fast *CO dimerization. Moreover, density-functional-theory calculations unravel the triple-copper-vacancy associates endow the nearby Cu sites with enriched and disparate local charge density, which enhances the *CO adsorption and reduces the CO-CO coupling barrier, affirmed by the decreased *CO dimerization energy barrier by 0.4eV. As a result, the triple-copper-vacancy associates confined in Cu nanowires achieve a high Faradaic efficiency of over 80% for C2+ products in a wide current density range of 400-800mA cm-2 , outperforming most reported Cu-based electrocatalysts.

Annealing effects on the structural, positron annihilation parameters, and electrical properties of Fe2O3- PbO2-TeO2 glasses

This study focuses on the transformation of selected glasses consisting of 20Fe2O3–xPbO2–(80–x)TeO2 (where x = 5, 10, 15, 20, and 25 mol%) with varying concentrations of PbO2, into nanomaterials through annealing at a temperature close to the crystallization temperature (Tc). The physical and chemical properties of the resulting samples were investigated. The chemical structure was analyzed using Fourier Transform Infrared spectroscopy (FTIR), which revealed no significant chemical changes except for an increase in the concentration of PbO2. X-ray diffraction (XRD) was used to study the crystal structure. Improvements were seen with increasing PbO2 concentrations, and these improvements were further increased after the sample was annealed. Furthermore, positron annihilation lifetime (PAL) spectroscopy was used to study the microstructure, more precisely the size of vacancy-type defects. A correlation was established between the PAL and the properties of the samples. The size of the vacancy-type defects was confirmed by calculating the distribution of the long lifetime deduced from the PAL. In this work, the overall influence of PbO2 concentration and thermal treatment on the chemical and crystalline structures, electrical conductivity, and microstructure of the studied nanomaterials is highlighted. The results provide valuable insights into the relationship between the PAL and the properties of the samples and provide potential opportunities to tailor their properties for different applications.