Positron Annihilation Lifetime Technique Research Articles

Characterization and application of LDH with chitosan composites investigated by positron annihilation lifetime spectroscopy and surface texture for the adsorption of methyl orange

With a rapid increase in industrial growth around the world, the demand for an entirely novel category of nanoparticles and technologies for wastewater treatment has become a key concern for environmental protection. Recently, hybrids of layered double hydroxides (LDH), particularly those containing LDH, have gained attention as potential nanoscale adsorbents for water treatment. Recent research has shown that LDH-containing composites are interesting versatile materials with the ability to be used in energy storage, photocatalysis, nanocomposites, and water treatment. In the current work, LDH-containing composites were utilized as adsorbents for the purpose of purifying water. The adsorbents investigated are Zn–Co–Fe/LDH/Chitosan-in situ sample preparation (LDH/CS1) and Zn–Co–Fe/LDH/Chitosan-ex situ sample preparation (LDH/CS2). Furthermore, LDH/CS1 and LDH/CS2 were investigated for wastewater treatment from methyl orange dye (MO) with various adsorption conditions. When the initial MO concentration was 20 mg/L and the amount of adsorbent was 0.1 g, the removal efficiency reached 72.8 and 91.7% for LDH/CS1 and LDH/CS2, respectively. The MO’s maximum adsorption capabilities are 160.78 and 165.89 mg/g for LDH/CS1 and LDH/CS2, respectively, which is much greater than that of comparable commercial adsorbents. MO adsorption onto LDH/CS1 and LDH/CS2 was best characterized by the pseudo-second-order kinetic model. The equilibrium adsorption data was followed by the Freundlich and Langmuir models. The adsorption is favorable as evidenced by the equilibrium parameter RL values for MO adsorption onto LDH/CS1 and LDH/CS2, which were 0.227 and 0.144, respectively. Using the free volume distribution method and the positron annihilation lifetime technique, the nanostructure of the materials was examined.

Humidity effect on the transport properties of per‐fluorinated sulfonic acid/PTFE proton exchange membranes: Positron annihilation study

AbstractThe positron annihilation lifetime (PAL) technique was used to investigate the yield and lifetime of positronium (Ps) in three different samples of per‐fluorinated sulfonic acid/polytetrafluoroethylene (PTFE) proton exchange membranes. The high probability of Ps formation enables the study of the hole volume size by the PAL technique and explains the mechanism of both methanol permeation and proton conductivity of the membranes in relation to the relative humidity (RH). The influence of various membrane parameters, including water uptake, proton conductivity, and mechanical properties, was studied. The concentration of water molecules and SO3−–H3O+groups is correlated with the ion exchange capacity (IEC) of the membranes where higher IEC leads to high absorbance of water. The proton conductivity is enhanced by increasing the IEC value of the membrane. The activation energies of decomposition temperature for the F‐950 membrane are the lowest (Eb = 2.856 and 1.030 eV for the 1st and 2nd decomposition peaks, respectively, implying that the membrane with high IEC is thermally less stable. With increasing the IEC of the membranes, the concentration of the water molecules/SO3 group increases. In addition, the proton conductivity of the membrane is positively influenced by increasing water content at high RH. The fact that the variations in hole volume size and both methanol permeability and proton conductivity are highly dependent on RH suggests that hole volume size plays an important role in many parameters of hydrated perfluorinated sulfonic acid/PTFE proton exchange membranes. The outcomes data were introduced and interpreted appropriately with a theoretical model and compared with the literature.

Effects of Interdomain and Intradomain Pores of Cu-Zn Ferrite Substituted with Nd Investigated Using Positron Annihilation Lifetime Technique

Positron annihilation lifetime spectroscopy at room temperature is used to investigate polycrystalline Cu-Zn ferrite samples substituted with Nd. Standard ceramic technique is used to prepare all investigated samples. The variation of positron annihilation parameters I1%, I2%, τ1, and τ2 are demonstrated with grain size, initial permeability, homogeneity of the samples, and electrical resistivity with Nd concentration. The important novel points are: (1) Intragranular pores are equal to the sum of intra- and interdomain pores. The lifetime τ1 is increased due to the decrease of the intradomain pores. The initial permeability and homogeneity are decreased with increasing the interdomain pores. The electrical resistivity is increased due to the increase of the interdomain pores.

The positron and mechanical parameters of a cold-worked aluminum alloy (3004) Using PALT, PADBT and HV**

Abstract In the present work, the influence of plastic deformation on the properties of a 3004 Al-alloy was studied with different techniques. Crystallite size, dislocation density, defect density, micro-strain, and stored dislocation energy are presented and compared for different three techniques. Methodology Many techniques for detecting defects have been developed, such as the positron annihilation lifetime technique (PALT), the positron annihilation Doppler broadening technique (PADBT), and the Vickers hardness test (HV). Implications The positron mean lifetime value of a non-deformed sample is 173±4.8 ps, which increases until the thickness reduction reaches a 10% deformation then saturated at saturation trapping of the positron in defect states with a mean of 221±5 ps. At an S-parameter of 0.3709±0.0031, a W-parameter of 0.5885±0.0057 was obtained at zero deformation: this decreases until saturation at 10% deformation. Findings A good correlation between the three techniques is observed for mean crystallite size. A good correlation was also noted between PALT and PADBT from 0 to 10% thickness reduction. HV has good correlations with PALT and PADBT from 0 to 6% thickness reduction: then a clear difference was found from 6 to 15% thickness reduction. Originality such results confirm the fact that the used technique can effects on the obtained results in some limitations.

Influence of nickel ion concentration on the free volume defects entrenched in an alkali sulphophosphate glass system by means of positron annihilation characterization technique

In this study we have evaluated the concentration of defect centers like voids, their size (up to nanoscale) and the fraction of free volume space integrated in Li2SO4−MgO−P2O5:NiO glass system as a function of NiO content. Positron annihilation lifetime (PAL) technique with 22Na positron source of radio activity 100 kBq is used for this study. The size, shape and the concentration of entrenched defects in the glass matrix are predicted to influence profoundly the physical properties of the glass. Cavity radius (R) and the entrenched free volume fraction (fv) are found to be the maximal in the sample doped with 0.8 mol% of NiO. This observation suggested that Ni2+ ions predominantly occupied octahedral positions (acted as modifiers along with SO42– ions) and induced large concentration of structural defects. The obtained information is found to be in concurrent with inferences drawn from dielectrics and spectroscopic studies of these glasses reported earlier.

Study of the nanostructure of γ‐irradiated high‐density polyethylene/carbon black composite and its durability as geomembrane

The degradation of the nearby generation of high‐density polyethylene (HDPE) loaded with 2.5% of carbon black (CB) content (ie, HDPE/CB composites) is studied experimentally with the end goal of radiation safety applications. The impact of various γ‐irradiation doses in the air on the nanostructure of free volume and durability has been researched. The free volume was evaluated utilizing the positron annihilation lifetime (PAL) technique while the durability was contemplated by measuring the mechanical properties such as strain, elongation at break, and tear resistance. The electrical conductivity was explored to demonstrate the impact of the irradiation dose on the conductivity of the samples. Surface morphology studies using a scanning electron microscope (SEM) showed the surface fracture of HDPE/CB composites for unirradiated and irradiated samples. The surface roughness of the HDPE/CB GMs increases with increasing the irradiation dose. Among various uses of HDPE/CB composites, sheets are liners of dumps used to dispose of interim storage for Low and Medium Level Waste of NORMs and TENORMs. HDPE Geomembrane liners proved its utilization from the results of present research of electrical, mechanical tests, and SEM morphology to have the required resistance to weather conditions.

Structure dependence of gamma ray irradiation effects on polyurethane and epoxy resin studied by PAL technique

Positron annihilation lifetime (PAL) technique has been employed tostudy the microstructural changes of polyurethane (PU), EUXIT 101and epoxy risen (EP), EUXIT 60 by Gamma-ray irradiation with thedose range (95.76 - 957.6) kGy. The size of the free volume hole andtheir fraction in PU and EP were determined from ortho-positroniumlifetime component and its intensity in the measured lifetime spectra.The results show that the irradiation causes significant changes in thefree volume hole size (Vh) and the fractional free volume (Fh), andthereby the microstructure of PU and EP. The results indicate thatthe γ-dose increases the crystallinity in the amorphous regions of PUand increase the cross-linking of EP.

Preparation of elastic polymer slices have the semiconductors properties for use in solar cells as a source of new and renewable energy

The present work aimed to prepare elastic polymer slices that have semiconductors properties for use in solar cells based on charge transfer (CT) complexation. For this purpose, first six derivatives of 1,8–naphthalimide fluorescent dyes were synthesized. Secondly, the synthesized fluorescent dyes were complexed with p–chloranil acceptor via CT interaction in methanol solvent. The obtained CT complexes were dispersed in poly(methyl methacrylate) (PMMA) matrixes using methylene chloride solvent at room temperature. The obtained polymer sheets were characterized by several spectroscopic and physicochemical techniques, such as IR and UV–vis spectroscopies; and SEM technique. The microstructural and morphological changes occurred in the sheets of the PMMA matrix blended with the CT products were observed using the positron annihilation Doppler broadening (PADB) and the positron annihilation lifetime (PAL) techniques. Finally, the photostability and the direct current (DC) electrical characteristics as a function of the temperature for the CT products dispersed in PMMA matrixes have been studied.

Physicochemical and Spectroscopic Study of Co(II), Ni(II), Cr(III), and Fe(III) Cholyltaurine Adducts

Physical spectroscopic characteristics of Co(II), Ni(II), Cr(III), and Fe(III) cholyltaurine adducts have been studied. IR and Raman spectra confirmed that the cholyltaurine compound acted as a mononegative bidentate chelating agent. Nitrogen atom of the NH group and O– of deprotonated sulphonate group acted as chelation sites towards the metal ions. UV-Vis spectra and magnetic moments block measurements confirmed that all complexes had the octahedral geometry. Water, Cl–, and NO3– acted as secondary chelates. The positron annihilation lifetime (PAL) technique was applied to investigate the structural changes of cholyltaurine ligand and its complexes. The results indicated that the average defect density in the studied ligand and its complexes was efficiently correlating with their molecular weight.

Determination of the activation enthalpy for migration of dislocations in plastically deformed 8006 Al-alloy by positron annihilation lifetime technique

The activation enthalpy for migration of dislocations of plastically deformed 8006 Al-alloy was investigated by positron annihilation lifetime technique. Plastic deformation using a hydraulic press produces mainly dislocations and may produce point defects. The type of defect was studied by isochronal annealing which determines the temperature range of recovery of each type. Only one type of defect (dislocations) was observed for the investigated sample and was found to be recovered within the range 455–700 K. Isothermal annealing by slow cooling was performed through this range and used in determination of the activation enthalpy of migration of dislocations which was found to be 0.26 ± 0.01 eV.

Synthesis, physicochemical characterization and anticancer screening of sulfa drug ruthenium complexes as anticancer agent

A new five complexes of ruthenium(III) sulfa drug compounds (sulfanilamide, SD1; sulfacetamide sodium; SD2; sulfadiazine, SD3; sulfamethoxazole, SD4; and sulfadimidine, SD5) were synthesized with Ru:SDn molar ratio of 1:2. The ruthenium(III) complexes were characterized by elemental analyses, IR, UV–vis. spectra, magnetic and thermal instruments. The results of the molar conductance measurements reveal that all the complexes have an electrolytic behavior. The infrared spectra show that the sulfa drug ligands (SD1, SD3, SD4 and SD5) act as a monobasic bidentate chelate through both nitrogen atoms of the anilino and sulfonamido groups. On the other hand, the SD2 ligand acts as monodentate toward Ru(III) ion via nitrogen atom of aniline group only because of sulfonamido group is deprotonated by sodium(I) ion. The spectroscopic results suggest octahedral geometry for all Ru(III) complexes. The molecular structures of the SDn ligands were also discussed using quantum chemical calculations. The kinetic thermodynamic parameters of the essential DTGmax decomposition steps were calculated. The images of scanning electron microscopy (SEM) and transmittance electron microscopy (TEM) show amorphous appearance for all Ru(III) complexes except for SD3 complex of a nano-sized structure that confirmed by the X-ray powder diffraction (XRD) patterns. The electron density and the defect structure of the ruthenium(III) complexes were investigated using the positron annihilation lifetime technique. The antimicrobial activities (bacteria and fungi) of the Ru(III) complexes were assessed in comparison with standers. The evaluation of cytotoxicity of Ru(III) complexes against HCT-116 cell line was performed.

Positron trapping defects in free-volume investigation of Ge–Ga–S–CsCl glasses

Evolution of free-volume positron trapping defects caused by crystallization process in (80GeS2–20Ga2S3)100−х(СsCl)x, 0 ≤ x ≤ 15 chalcogenide-chalcohalide glasses was studied by positron annihilation lifetime technique. It is established that CsCl additives in Ge–Ga–S glassy matrix transform defect-related component spectra, indicating that the agglomeration of free-volume voids occurs in initial and crystallized (80GeS2–20Ga2S3)100−х(СsCl)x, 0 ≤ x ≤ 10 glasses. Void fragmentation in (80GeS2–20Ga2S3)85(СsCl)15 glass can be associated with loosing of their inner structure. Full crystallization in each of these glasses corresponds to the formation of defect-related voids. These trends are confirmed by positron-positronium decomposition algorithm. It is shown, that CsCl additives result in white shift in the visible regions in transmission spectra. The γ-irradiation of 80GeS2–20Ga2S3 base glass leads to slight long-wavelength shift of the fundamental optical absorption edge and decreasing of transmission speaks in favor of possible formation of additional defects in glasses and their darkening.

Dependence of alpha particle track diameter on the free volume holes size using positron annihilation lifetime technique

The alpha particle track diameter dependence of the free volume holes size (Vf) in DAM–ADC and CR-39 nuclear track detectors was investigated using positron annihilation lifetime technique. The effect of temperature on the alpha particle track diameter and free volume were also investigated in the T-range (RT-130°C). The obtained results revealed that the values of ortho-positronium lifetime τ3 and Vf increases while I3 slightly increases as T increases for the two detectors. The values of τ3, Vf and I3 are higher in CR-39 than DAM–ADC. The interpretation of obtained results is based on the fact that increasing T leads to significant enhancement of thermal expansion of the polymer matrix and consequently Vf increases. The track diameter increases as T increases. This can be explained by the fact that the increase in T increases the crystal size and Vf in the polymer. A relationship between Vf and the alpha particle track diameter was obtained. Moreover results of detector irradiation, along with free volume evaluation are addressed and thoroughly discussed.

A study of some properties for Li–Mn nanoparticles ferrite using positron annihilation lifetime technique

Nanoparticle samples of the composition Li(0.5–0.5x)MnxFe(2.5-0.5x)O4, (x = 0, 0.25, 0.5 and 0.75) are prepared with a sol–gel auto combustion method. The nano grain size is decreased with increasing the manganese content. The analysis of PAL spectra indicated the existence of cluster defects. There are different correlations between the lifetime parameters with the manganese content. The relative intensity I2 and the trapping rate қ are increased for samples with x = 0.25 & 0.75, and are decreased for the sample with x = 0.5 relative to the pure nano Li-ferrite. The electrical resistivity takes the same behavior as the G.S. by increasing Mn content. The size of the domain walls is decreased with Mn content for mono-grain Li ferrite samples.

Per-fluorinated sulfonic acid/PTFE copolymer studied by positron annihilation lifetime and gas permeation techniques

The mechanism of gas permeation in per-fluorinated sulfonic acid/PTFE copolymer Fumapem® membranes for polymer electrolyte fuel cells has been investigated from the viewpoint of free volume. Three different samples, Fumapem® F-950, F-1050 and F-14100 membranes with ion exchange capacity (IEC) = 1.05, 0.95 and 0.71 meq/g, respectively were used after drying. Free volume was quantified using the positron annihilation lifetime (PAL) technique and gas permeabilities were measured for O2 and H2 as function of temperature. Good linear correlation between the logarithm of the permeabilities at different temperatures and reciprocal free volume indicate that gas permeation in dry Fumapem® is governed by the free volume. Nevertheless permeabilities are much smaller than the corresponding flexible chain polymer with a similar free volume size due to stiff chains of the perfluoroethylene backbone.

A study of some properties for substituted Li-ferrite using positron annihilation lifetime technique

Positron annihilation lifetime spectroscopy (PALS) is used to investigate polycrystalline substituted Li-ferrite samples. The dray ceramic technique was used to prepare all investigated samples. The variation of positron annihilation parameters I1%, I2%, τ1, and τ2 has been demonstrated with porosity and the initial permeability against the ionic radii of substituted ions for Li ferrite. The grain size (G.S.) increased with increasing the ionic radii of the substituted ions for Li-ferrite. The correlation between I2 and τ2 has opposite behavior with the ionic radii of the substituted ions. Whereas the correlation between I1 and τ1; has nearly the same behavior with the ionic radii of the substituted ions except for V and Gd samples. There is mostly a direct correlation between the electrical resistivity and I2 values except for Sm sample with increasing the ionic radii of substituted ions.

Casting of Poly Hydroxybutarate/Poly (vinyl alcohol)Membranes for Proton Exchange Fuel Cells

Gamma irradiation was used efficiently for casting poly hydroxybutarate(PHB) and phosphorylated poly (vinyl alcohol)(PVA) with different ratios. The optimum gamma irradiation dose for attaining finally crosslinking was 10kGy. It was found that adding 0.5% phosphate-terminated silica nanoparticles (SiO2-P NPs) in the cast mixture was enough for membranes reinforcement. Membranes characterizations are carried out using FT-IR and tensile strength for examining their chemical and physical properties. Morphological properties of the casted membranes were studied using scanning electron microscope while their crystallinity was investigated using x-ray diffraction. Thermal characterization was performed using thermal gravimetric analysis. Water uptake and ion exchange capacity are determined as well. The prepared membranes' highest proton conductivity value was 8.6×10−2 S/cm while their free volume sizes were measured using positron annihilation lifetime technique (PALS). The casted membranes are strongly recommended to be used into the proton exchange membrane fuel cell (PEMFC) from performance and durability point of view.

Effect of Cu on the boron segregation at grain boundaries and vacancy-type defects in ultra-low carbon micro-alloy steels

By thermal neutron irradiation particle tracking autoradiography (PTA) technique, the development of boron segregation at grain boundaries in ultra-low carbon micro-alloy steels was investigated during cooling from 1150°C to 850°C, and the effect of Cu on boron segregation at grain boundaries was discussed. By positron annihilation lifetime(PAL) technique, the changes of vacancy-type defects with temperatures and the effect of Cu on vacancy-type defects in the cooling process were discussed. Results show that, the concentration of boron at grain boundaries increases rapidly at the beginning of the cooling; after that, it begins to decrease; and then, it increases gradually again. The addition of Cu not only increases the concentration of boron at grain boundaries but also speeds up the development process of boron segregation at grain boundaries. During the continuous cooling process, the addition of Cu significantly affects the change of vacancy-type defects with temperatures in ultra-low carbon micro-alloy steels.

Utility of positron annihilation lifetime technique for the assessment of spectroscopic data of some charge-transfer complexes derived from N-(1-Naphthyl)ethylenediamine dihydrochloride

In this work, structural, thermal, morphological, pharmacological screening and positron annihilation lifetime measurements were performed on the interactions between a N-(1-Naphthyl)ethylenediamine dihydrochloride (NEDA·2HCl) donor and three types of acceptors to characterize these CT complexes. The three types of acceptors include π-acceptors (quinol and picric acid), σ-acceptors (iodine) and vacant orbital acceptors (tin(IV) tetrachloride and zinc chloride). The positron annihilation lifetime parameters were found to be dependent on the structure, electronic configuration, the power of acceptors and molecular weight of the CT complexes. The positron annihilation lifetime spectroscopy can be used as a probe for the formation of charge-transfer (CT) complexes.

Correlation Coefficient between Vickers Hardness and Nuclear Technique

The aim of this work is to establish a correlation coefficient between the positron annihilation lifetime technique (PALS) and the Vickers hardness for the heat treatable aluminum alloys (6066, 6063).The potential of positron annihilation spectroscopy in the study of light alloys is illustrated with special regards to age hardening, severe plastic deformation, annealing and quenching in aluminum alloys. Vickers hardness is the standard method for measuring the hardness of metals, particularly those with extremely hard surfaces. Accordingly, a correlation coefficient of 90 % between τ and Hv is obtained. This correlation can help us to explain many behaviors of these alloys under deferent conditions.