DC and AC Conductivity,Biosolubility and Thermal Properties of Mg-Doped Na2O–CaO–P2O5 Glasses

Bioactive glasses have recently been extensively used to replace, regenerate, and repair hard tissues in the human body because of their ability to bond with living tissue. In this work, the effects of replacing Na₂O with MgO on the electrical, biosolubility, and thermal properties of the target glass 10Na₂O–60P₂O₅–30CaO (in mol%) were investigated. The electrical properties of the glasses were studied with the impedance spectroscopy technique. At 473 K, DC conductivity values decreased from 4.21 × 10⁻¹¹ to 4.21 × 10⁻¹² S cm⁻¹ after complete substitution of MgO for Na₂O. All samples had a similar activation energy of the DC conduction process ~1.27 eV. Conduction mechanisms were found to be due to hop of ions: Na⁺, Mg²⁺_, and probable H⁺. FTIR analysis showed that, as the Mg content increased, the Q² unit (PO₂⁻) shifted towards higher wavenumbers. The proportion of Q³ unit (P₂O₅) decreased in the glass structure. This confirmed that the replacement of Na⁺ by Mg²⁺ was accompanied by concurrent polymerization of the calcium–phosphate glass network. The biosolubility test in the phosphate-buffered saline solution showed that the magnesium addition enhanced the biosolubility properties of Na₂O–CaO–P₂O₅ glasses by increasing their dissolution rate and supporting forming CaP-rich layers on the surface. The glass transition temperature increased, and thermal stability decreased substantially upon substitution of Na₂O by MgO.     

Semiempirical method for examining asynchronicity in metal–oxido-mediated C–H bond activation

The oxidation of substrates via the cleavage of thermodynamically strong C–H bonds is an essential part of mammalian metabolism. These reactions are predominantly carried out by enzymes that produce high-valent metal–oxido species, which are directly responsible for cleaving the C–H bonds. While much is known about the identity of these transient intermediates, the mechanistic factors that enable metal–oxido species to accomplish such difficult reactions are still incomplete. For synthetic metal–oxido species, C–H bond cleavage is often mechanistically described as synchronous, proton-coupled electron transfer (PCET). However, data have emerged that suggest that the basicity of the M–oxido unit is the key determinant in achieving enzymatic function, thus requiring alternative mechanisms whereby proton transfer (PT) has a more dominant role than electron transfer (ET). To bridge this knowledge gap, the reactivity of a monomeric Mn^IV–oxido complex with a series of external substrates was studied, resulting in a spread of over 10⁴ in their second-order rate constants that tracked with the acidity of the C–H bonds. Mechanisms that included either synchronous PCET or rate-limiting PT, followed by ET, did not explain our results, which led to a proposed PCET mechanism with asynchronous transition states that are dominated by PT. To support this premise, we report a semiempirical free energy analysis that can predict the relative contributions of PT and ET for a given set of substrates. These findings underscore why the basicity of M–oxido units needs to be considered in C–H functionalization.

The functionalization of C–H bonds is one of the most challenging synthetic transformations in chemistry, in part because of the inherent large bond dissociation-free energies (BDFEs) associated with C–H bonds (BDFE_C–H) (1, 2). Monomeric metal–oxido species can overcome these barriers and cleave C–H bonds in a diverse set of substrates. The utility of metal–oxido species is exemplified within the active sites of metalloenzymes, such as heme and nonheme Fe monooxygenases (3–6) and in related, synthetic Mn– (7–15), Co– (16), and Fe–oxido complexes (17–25). Even with the advances made with these natural and synthetic metal–oxido species, key mechanistic questions about which properties of the metal complexes contribute to productive C–H cleavage persist (26–30). Much of our current understanding of metal–oxido-mediated C–H bond activation is predicated on a relationship between ground-state thermodynamics and the height of the activation barrier. Reactions of metal–oxido species with organic substrates often show a correlation between variations in substrate C–H bond strength, (BDFE_C–H, Eq. 1, where C_G is a constant that is dependent on the reference electrode and solvent) and the log of the rate constant for C–H bond cleavage. Systems for which these correlations are highly linear are said to follow a linear free energy relationship or display Bell–Evans–Polanyi (BEP)-like correlations (31, 32).BDFEC–H= 23.06(E˚) + 1.37(pKa) + CG.[1]The ground-state thermodynamics for C–H bond cleavage are determined by comparing the BDFE_C–H of the C–H bond to be cleaved to that of the O–H bond formed in the resulting M^n-1–OH species; this BDFE_O–H value is obtained from the reduction potential of the M = O species and its basicity, in a manner analogous to Eq. 1 (1, 33). The relationship between BDFE_O–H, reduction potential and basicity can be conveniently represented using a thermodynamic square scheme that contains three limiting, mechanistic paths (Fig. 1) (26): 1) proton transfer/electron transfer (PT-ET); 2) electron transfer/proton transfer (ET-PT); and 3) synchronous, proton-coupled electron transfer (PCET). An important outcome of the approach of comparing BDFE values is the recognition that the basicity of the M–oxido unit can be a key contributor to C–H bond cleavage. This concept is exemplified by the high-valent Fe–oxido intermediate in cytochrome P450s (compound I). The reduced intermediate is highly basic, promoting the abstraction of H atoms from strong C–H bonds at relatively low, one-electron reduction potentials (34, 35).Open in a separate windowFig. 1.Thermodynamic square scheme for M–oxido complexes involved in C–H bond cleavage. For 1, E_1/2'' = −1.0 V; E_1/2 = −0.18 V; pK_a = 15; pK_a'' = 28.1(2); and BDFE_O–H = 87(2) kcal/mol (SI Appendix, Eq. S1). Values measured in DMSO at room temperature. Potentials are referenced to [Fe^III/IICp₂]^+/0.We have also shown that the basicity of the oxido ligand drives the reactivity of a low-valent Mn^III–oxido complex that is competent at cleaving C–H bonds, even though its reduction potential is less than −2.0 V versus [Fe^III/IICp₂]^+/0 (7). Our initial mechanistic suggestion for this Mn^III–oxido complex was a stepwise PT-ET pathway with proton transfer (PT) being rate limiting. However, subsequent kinetic studies on a related series of Mn^III–oxido complexes showed that electron transfer (ET) must also be involved in the rate-determining step (8). To reconcile these results, we proposed a mechanism with an imbalanced transition state, in which PT precedes ET (8). This type of asynchronous PCET mechanism (36) was examined computationally (37) and experimentally to explain the cleavage of C–H bonds with Co^III–oxido (16), Ru^IV–oxido (38), and Cu^III−O₂CAr complexes (39). The involvement of asynchronous PCET processes in the cleavage of C–H bonds by high-valent M–oxido complexes, such as Fe^IV/Mn^IV–oxido species, is still uncertain. In fact, most reactions have synchronous PCET mechanisms that follow the BEP principle (31, 32) and exhibit the correlations between the BDFE_C–H values of the substrates and the log of the second-order rate constants [log (k)]. However, C–H bond cleavage via an asynchronous PCET mechanism that is driven by the basicity of the M–oxido unit would be beneficial because reactivity could occur at lower redox potentials, while still achieving the efficiency that is often associated with PCET processes. We reasoned that this type of mechanism could occur if the high-valent M–oxido complex was relatively basic and could therefore favor mechanisms that involve PT-driven, asynchronous transition states. The high-valent Mn^IV–oxido complex [Mn^IVH₃buea(O)]⁻ (1) is a suitable candidate for testing this premise because it has a relatively high basicity, as gauged by its conjugate acid, [Mn^IVH₃buea(OH)], which has an estimated pK_a of ∼15 in DMSO (7).We report here the kinetic studies of 1 with a variety of substrates, and the results of these studies support the involvement of PT-dominated, asynchronous transition states and show the applicability of this type of mechanism in the cleavage of C–H bonds by high-valent M–oxido complexes. To further evaluate our findings, we developed a semiempirical free energy analysis to estimate the relative contributions from the free energies of PT and ET within an asymmetric transition state. This analysis supports the assertion that the observed reactivity of 1 is driven by the pK_a, leading to PT-controlled, asynchronous transition states for the substrates examined. Moreover, we demonstrate that this analysis is useful in predicting whether a PCET reaction will be synchronous or asynchronous based on reactivity and thermodynamic parameters. Our method deviates from traditional, BEP-like analyses, in that it examines the behavior of log (k) versus a linear combination of PT and ET terms, rather than bond strengths. The appropriate combination of these free energy terms is determined by the linearity of plots versus log (k).     

Study of Radiation-Induced Defects in p-Type Si1−xGex Diodes before and after Annealing

In this work, electrically active defects of pristine and 5.5 MeV electron irradiated p-type silicon–germanium (Si_1−xGe_x)-based diodes were examined by combining regular capacitance deep-level transient spectroscopy (C-DLTS) and Laplace DLTS (L-DLTS) techniques. The p-type SiGe alloys with slightly different Ge contents were examined. It was deduced from C-DLTS and L-DLTS spectra that the carbon/oxygen-associated complexes prevailed in the pristine Si_0.949Ge_0.051 alloys. Irradiation with 5.5 MeV electrons led to a considerable change in the DLT spectrum containing up to seven spectral peaks due to the introduction of radiation defects. These defects were identified using activation energy values reported in the literature. The double interstitial and oxygen complexes and the vacancy, di-vacancy and tri-vacancy ascribed traps were revealed in the irradiated samples. The interstitial carbon and the metastable as well as stable forms of carbon–oxygen (C_iO_i^* and C_iO_i) complexes were also identified for the electron-irradiated SiGe alloys. It was found that the unstable form of the carbon–oxygen complex became a stable complex in the irradiated and the subsequently annealed (at 125 °C) SiGe samples. The activation energy shifts in the radiation-induced deep traps to lower values were defined when increasing Ge content in the SiGe alloy.     

Amorphous–Crystalline Calcium Phosphate Coating Promotes In Vitro Growth of Tumor-Derived Jurkat T Cells Activated by Anti-CD2/CD3/CD28 Antibodies

A modern trend in traumatology, orthopedics, and implantology is the development of materials and coatings with an amorphous–crystalline structure that exhibits excellent biocopatibility. The structure and physico–chemical and biological properties of calcium phosphate (CaP) coatings deposited on Ti plates using the micro-arc oxidation (MAO) method under different voltages (200, 250, and 300 V) were studied. Amorphous, nanocrystalline, and microcrystalline statesof CaHPO₄ and β-Ca₂P₂O₇ were observed in the coatings using TEM and XRD. The increase in MAO voltage resulted in augmentation of the surface roughness R_a from 2.5 to 6.5 µm, mass from 10 to 25 mg, thickness from 50 to 105 µm, and Ca/P ratio from 0.3 to 0.6. The electrical potential (EP) of the CaP coatings changed from −456 to −535 mV, while the zeta potential (ZP) decreased from −53 to −40 mV following an increase in the values of the MAO voltage. Numerous correlations of physical and chemical indices of CaP coatings were estimated. A decrease in the ZP magnitudes of CaP coatings deposited at 200–250 V was strongly associated with elevated hTERT expression in tumor-derived Jurkat T cells preliminarily activated with anti-CD2/CD3/CD28 antibodies and then contacted in vitro with CaP-coated samples for 14 days. In turn, in vitro survival of CD4⁺ subsets was enhanced, with proinflammatory cytokine secretion of activated Jurkat T cells. Thus, the applied MAO voltage allowed the regulation of the physicochemical properties of amorphous–crystalline CaP-coatings on Ti substrates to a certain extent. This method may be used as a technological mechanism to trigger the behavior of cells through contact with micro-arc CaP coatings. The possible role of negative ZP and Ca²⁺ as effectors of the biological effects of amorphous–crystalline CaP coatings is discussed. Micro-arc CaP coatings should be carefully tested to determine their suitability for use in patients with chronic lymphoid malignancies.     

Mechanical and Gamma Ray Absorption Behavior of PbO-WO3-Na2O-MgO-B2O3 Glasses in the Low Energy Range

The Makishima and Mackenzie model has been used to determine the mechanical properties of the PbO-WO₃-Na₂O-MgO-B₂O₃ glass system. The number of bonds per unit volume of the glasses (n_b) increases from 9.40 × 10²² to 10.09 × 10²² cm⁻³ as the PbO content increases from 30 to 50 mol%. The Poisson’s ratio (σ) for the examined glasses falls between 0.174 and 0.210. The value of the fractal bond connectivity (d) for the present glasses ranges from 3.08 to 3.59. Gamma photon and fast neutron shielding parameters were evaluated via Phy-X/PSD, while that of electrons were calculated via the ESTAR platform. Analysis of the parameters showed that both photon and electron attenuation ability improve with the PbO content. The fast neutron removal cross section of the glasses varies from 0.094–0.102 cm⁻¹ as PbO molar content reduced from 50–30 mol%. Further analysis of shielding parameters of the investigated glass system showed that they possess good potential to function in radiation protection applications.     

Microstructure Evolution in He-Implanted Si at 600 °C Followed by 1000 °C Annealing

Si single crystal was implanted with 230 keV He⁺ ions to a fluence of 5 × 10¹⁶/cm² at 600 °C. The structural defects in Si implanted with He at 600 °C and then annealed at 1000 °C were investigated by transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). The microstructure of an as-implanted sample is provided for comparison. After annealing, rod-like defects were diminished, while tangled dislocations and large dislocation loops appeared. Dislocation lines trapped by cavities were directly observed. The cavities remained stable except for a transition of shape, from octahedron to tetrakaidecahedron. Stacking-fault tetrahedrons were found simultaneously. Cavity growth was independent of dislocations. The evolution of observed lattice defects is discussed.     

Influence of Hydrated Lime on the Chloride-Induced Reinforcement Corrosion in Eco-Efficient Concretes Made with High-Volume Fly Ash

The main objective of this study was to analyze the influence that the addition of finely ground hydrated lime has on chloride-induced reinforcement corrosion in eco-efficient concrete made with 50% cement replacement by fly ash. Six tests were carried out: mercury intrusion porosimetry, chloride migration, accelerated chloride penetration, electrical resistivity, and corrosion rate. The results show that the addition of 10–20% of lime to fly ash concrete did not affect its resistance to chloride penetration. However, the cementitious matrix density is increased by the pozzolanic reaction between the fly ash and added lime. As a result, the porosity and the electrical resistivity improved (of the order of 10% and 40%, respectively), giving rise to a lower corrosion rate (i_CORR) of the rebars and, therefore, an increase in durability. In fact, after subjecting specimens to wetting–drying cycles in a 0.5 M sodium chloride solution for 630 days, corrosion is considered negligible in fly ash concrete with 10% or 20% lime (i_CORR less than 0.2 µA/cm²), while in fly ash concrete without lime, corrosion was low (i_CORR of the order of 0.3 µA/cm²) and in the reference concrete made with Portland cement, only the corrosion was high (i_CORR between 2 and 3 µA/cm²).     

Effects of non-steroidal anti-inflammatory drugs and prostaglandins on alkali secretion by rabbit gastric fundus in vitro

The effects of non-steroidal anti-inflammatory drugs and prostaglandins E₂ and F_2α on the secretory and electrical activity of isolated rabbit fundic mucosa have been studied. Spontaneous acid secretion was inhibited by serosal side application of sodium thiocyanate (6×10⁻²M) and the resulting alkali secretion measured by pH stat tiration. Serosal side application of indomethacin (10⁻⁵M) or aspirin (3×10⁻³M) inhibited alkali secretion (0·55±0·06 to 0·12±0·06 μmol/cm²/h, n=6, p<0·01 and 0·28±0·06 to 0·11±0·03 μmol/cm²/h, n=7, p<0·02 respectively). Mucosal or serosal side prostaglandin E₂ (10⁻⁵ to 10⁻¹⁰M) and F_2α (10⁻⁴ to 10⁻¹⁰M) failed to alter the rate of alkalinisation but secretion was significantly increased by serosal side 16,16-dimethyl-prostaglandin E₂ (10⁻⁶M) (0·90±0·20 to 1·50±0·30 μmol/cm²/h, n=6, p<0·01). Serosal side application of 10⁻⁶M prostaglandin E₂ to fundic mucosae pretreated with either aspirin (5×10⁻³M) or indomethacin (10⁻⁵M), to reduce endogenous E₂ formation, also failed to alter alkali secretion. Pretreatment of the mucosa with 16,16-dimethyl-E₂ (10⁻⁶M) abolished the inhibitory effect of indomethacin (10⁻⁵M) on alkali secretion (n=6) but did not modify the secretory response to aspirin (3×10⁻³M) (fall in alkali secretion with aspirin = 81±11% and with aspirin plus 16,16-dimethyl-E₂ = 72±10%, n=7). In the doses used, none of the prostaglandins or non-steroidal anti-inflammatory drugs altered transmucosal potential difference or electrical resistance. These results show that the damaging agents, aspirin and indomethacin, both inhibit gastric alkali secretion but that modes of action may differ. The observation that prostaglandins, E₂ and F_2α failed to increase alkali production suggests that their protective activity against a variety of damaging agents as shown by others, may be mediated by another mechanism.     

Monolithic Integration of Nano-Ridge Engineered InGaP/GaAs HBTs on 300 mm Si Substrate

Nano-ridge engineering (NRE) is a novel method to monolithically integrate III–V devices on a 300 mm Si platform. In this work, NRE is applied to InGaP/GaAs heterojunction bipolar transistors (HBTs), enabling hybrid III-V/CMOS technology for RF applications. The NRE HBT stacks were grown by metal-organic vapor-phase epitaxy on 300 mm Si (001) wafers with a double trench-patterned oxide template, in an industrial deposition chamber. Aspect ratio trapping in the narrow bottom part of a trench results in a threading dislocation density below 10⁶∙cm⁻² in the device layers in the wide upper part of that trench. NRE is used to create larger area NRs with a flat (001) surface, suitable for HBT device fabrication. Transmission electron microscopy inspection of the HBT stacks revealed restricted twin formation after the InGaP emitter layer contacts the oxide sidewall. Several structures, with varying InGaP growth conditions, were made, to further study this phenomenon. HBT devices—consisting of several nano-ridges in parallel—were processed for DC and RF characterization. A maximum DC gain of 112 was obtained and a cut-off frequency f_t of ~17 GHz was achieved. These results show the potential of NRE III–V devices for hybrid III–V/CMOS technology for emerging RF applications.     

In-Situ TEM Annealing Observation of Helium Bubble Evolution in Pre-Irradiated FeCoNiCrTi0.2 Alloys

The FeCoNiCrTi_0.2 high-entropy alloys fabricated by vacuum arc melting method, and the annealed pristine material, are face centered cubic structures with coherent γ’ precipitation. Samples were irradiated with 50 keV He⁺ ions to a fluence of 2 × 10¹⁶ ions/cm² at 723 K, and an in situ annealing experiment was carried out to monitor the evolution of helium bubbles during heating to 823 and 923 K. The pristine structure of FeCoNiCrTi_0.2 samples and the evolution of helium bubbles during in situ annealing were both characterized by transmission electron microscopy. The annealing temperature and annealing time affect the process of helium bubbles evolution and formation. Meanwhile, the grain boundaries act as sinks to accumulate helium bubbles. However, the precipitation phase seems have few effects on the helium bubble evolution, which may be due to the coherent interface and same structure of γ’ precipitation and matrix.     

Effects of Titanium-Implanted Dose on the Tribological Properties of 316L Stainless Steel

The effects of titanium (Ti) ion-implanted doses on the chemical composition, surface roughness, mechanical properties, as well as tribological properties of 316L austenitic stainless steel are investigated in this paper. The Ti ion implantations were carried out at an energy of 40 kV and at 2 mA for different doses of 3.0 × 10¹⁶, 1.0 × 10¹⁷, 1.0 × 10¹⁸, and 1.7 × 10¹⁸ ions/cm². The results showed that a new phase (Cr₂Ti) was detected, and the concentrations of Ti and C increased obviously when the dose exceeded 1.0 × 10¹⁷ ions/cm². The surface roughness can be significantly reduced after Ti ion implantation. The nano-hardness increased from 3.44 to 5.21 GPa at a Ti ion-implanted dose increase up to 1.0 × 10¹⁸ ions/cm². The friction coefficient decreased from 0.78 for un-implanted samples to 0.68 for a sample at the dose of 1.7 × 10¹⁸ ions/cm². The wear rate was slightly improved when the sample implanted Ti ion at a dose of 1.0 × 10¹⁸ ions/cm². Adhesive wear and oxidation wear are the main wear mechanisms, and a slightly abrasive wear is observed during sliding. Oxidation wear was improved significantly as the implantation dose increased.     

Preparation and Properties of (YCa)(TiMn)O3?δ Ceramics Interconnect of Solid Oxide Fuel Cells

(YCa)(TiMn)O_3–δ ceramics prepared using a reaction-sintering process were investigated. Without any calcination involved, the mixture of raw materials was pressed and sintered directly. Y₂Ti₂O₇ instead of YTiO₃ formed when a mixture of Y₂O₃ and TiO₂ with Y/Ti ratio 1/1 were sintered in air. Y₂Ti₂O₇, YTiO_2.085 and some unknown phases were detected in Y_0.6Ca_0.4Ti_0.6Mn_0.4O_3–δ. Monophasic Y_0.6Ca_0.4Ti_0.4Mn_0.6O_3–δ ceramics were obtained after 1400–1500 °C sintering. Dense Y_0.6Ca_0.4Ti_0.4Mn_0.6O_3–δ with a density 4.69 g/cm³ was observed after 1500 °C/4 h sintering. Log σ for Y_0.6Ca_0.4Ti_0.6Mn_0.4O_3–δ increased from –3.73 Scm^–1 at 350 °C to –2.14 Scm^–1 at 700 °C. Log σ for Y_0.6Ca_0.4Ti_0.4Mn_0.6O_3–δ increased from –2.1 Scm^–1 at 350 °C to –1.36 Scm^–1 at 700 °C. Increasing Mn content decreased activation energy E_a and increased electrical conductivity. Reaction-sintering process is proved to be a simple and effective method to obtain (YCa)(TiMn)O_3–δ ceramics for interconnects in solid oxide fuel cells.     

Structural Properties of Thin ZnO Films Deposited by ALD under O-Rich and Zn-Rich Growth Conditions and Their Relationship with Electrical Parameters

The structural, optical, and electrical properties of ZnO are intimately intertwined. In the present work, the structural and transport properties of 100 nm thick polycrystalline ZnO films obtained by atomic layer deposition (ALD) at a growth temperature (T_g) of 100–300 °C were investigated. The electrical properties of the films showed a dependence on the substrate (a-Al₂O₃ or Si (100)) and a high sensitivity to T_g, related to the deviation of the film stoichiometry as demonstrated by the RT-Hall effect. The average crystallite size increased from 20–30 nm for as grown samples to 80–100 nm after rapid thermal annealing, which affects carrier scattering. The ZnO layers deposited on silicon showed lower strain and dislocation density than on sapphire at the same T_g. The calculated half crystallite size (D/2) was higher than the Debye length (L_D) for all as grown and annealed ZnO films, except for annealed ZnO/Si films grown within the ALD window (100–200 °C), indicating different homogeneity of charge carrier distribution for annealed ZnO/Si and ZnO/a-Al₂O₃ layers. For as grown films the hydrogen impurity concentration detected via secondary ion mass spectrometry (SIMS) was 10²¹ cm⁻³ and was decreased by two orders of magnitude after annealing, accompanied by a decrease in Urbach energy in the ZnO/a-Al₂O₃ layers.     

Co-Dispersion Behavior of ZrB2–SiC–B4C–C Powders with Polyethyleneimine

The aqueous dispersion behavior of ZrB₂, SiC powders with B₄C and C as sintering aids was investigated. Well co-dispersed suspension can be obtained in acidic solutions in presence of polyethyleneimine (PEI). The adsorption of PEI on the powder surface was measured by thermal gravimetric (TG) analysis. Rheological measurements displayed the effect of dispersant on the flow behavior of as-prepared slurries. An optimum condition was obtained with 1 wt % PEI. The viscosity of 40 vol % ZrB₂–SiC–B₄C–C (ZSBC) suspension at 100 s⁻¹ was as low as 0.74 Pa·s, which was suitable for aqueous processing.     

Effects of Vanadium on the Structural and Optical Properties of Borate Glasses Containing Er3+ and Silver Nanoparticles

The erbium-vanadium co-doped borate glasses, embedded with silver nanoparticles (Ag NPs), were prepared to improve their optical properties for potential optical fiber and glass laser application. The borate glasses with composition (59.5–x) B₂O₃–20Na₂O–20CaO–xV₂O₅–Er₂O₃–0.5AgCl (x = 0–2.5 mol%) were successfully prepared by conventional melt-quenching method. The structural properties of glass samples were investigated by XRD, TEM and by Fourier transform infrared (FTIR) spectroscopy while optical properties were carried out by UV–Vis spectroscopy by measuring optical absorption and the emission properties were investigated by photoluminescence spectroscopy. The XRD patterns confirmed the amorphous nature of the prepared glass samples whilst the FTIR confirmed the presence of VO₄, VO₅, BO₃ and BO₄ vibrations. UV–Vis–NIR absorption spectra reveal eight bands which were located at 450, 490, 519, 540, 660, 780, 980, and 1550 nm corresponding to transition of ⁴F_5/2, ⁴F_7/2, ²H_11/2, ⁴S_3/2, ⁴F_9/2, ⁴I_9/2, ⁴I_11/2, and ⁴I_13/2, respectively. The optical band gap (E_opt), Urbach energy and refractive index were observed to decrease, increase and increase, respectively, to the addition of vanadium. Under 800 nm excitation, three emission bands were observed at 516, 580 and 673 nm, which are represented by ²H_11/2–⁴I_15/2, ⁴S_3/2–⁴I_15/2 and ⁴F_15/2–⁴I_15/2, respectively. The excellent features of achieved results suggest that our findings may provide useful information toward the development of functional glasses.     

Insight into Electrical and Dielectric Relaxation of Doped Tellurite Lithium-Silicate Glasses with Regard to Ionic Charge Carrier Number Density Estimation

We investigate the role of tellurite on a lithium-silicate glass 0.1 TeO₂ − 0.9 (Li₂O-2SiO₂) (LSTO) system proposed for the use in solid electrolyte for lithium ion batteries. The measurements of electrical impedance are performed in the frequency 100 Hz–30 MHz and temperature from 50 to 150 °C. The electrical conductivity of LSTO glass increases compared with that of Li₂O-2SiO₂ (LSO) glass due to an increase in the number of Li⁺ ions. The ionic hopping and relaxation processes in disordered solids are generally explained using Cole–Cole, power law and modulus representations. The power law conductivity analysis, which is driven by the modified Rayleigh equation, presents the estimation of the number of ionic charge carriers explicitly. The estimation counts for direct contribution of about a 14% increase in direct current conductivity in the case of TeO₂ doping. The relaxation process by modulus analysis confirms that the cations are trapped strongly in the potential wells. Both the direct current and alternating current activation energies (0.62–0.67 eV) for conduction in the LSO glass are the same as those in the LSTO glass.     

Hysteresis in Lanthanide Zirconium Oxides Observed Using a Pulse CV Technique and including the Effect of High Temperature Annealing

A powerful characterization technique, pulse capacitance-voltage (CV) technique, was used to investigate oxide traps before and after annealing for lanthanide zirconium oxide thin films deposited on n-type Si (111) substrates at 300 °C by liquid injection Atomic Layer Deposition (ALD). The results indicated that: (1) more traps were observed compared to the conventional capacitance-voltage characterization method in LaZrO_x; (2) the time-dependent trapping/de-trapping was influenced by the edge time, width and peak-to-peak voltage of a gate voltage pulse. Post deposition annealing was performed at 700 °C, 800 °C and 900 °C in N₂ ambient for 15 s to the samples with 200 ALD cycles. The effect of the high temperature annealing on oxide traps and leakage current were subsequently explored. It showed that more traps were generated after annealing with the trap density increasing from 1.41 × 10¹² cm⁻² for as-deposited sample to 4.55 × 10¹² cm⁻² for the 800 °C annealed one. In addition, the leakage current density increase from about 10⁻⁶ A/cm² at V_g = +0.5 V for the as-deposited sample to 10⁻³ A/cm² at V_g = +0.5 V for the 900 °C annealed one.     

Origin of Mangetotransport Properties in APCVD Deposited Tin Oxide Thin Films

Transparent conducting oxides (TCO) with high electrical conductivity and at the same time high transparency in the visible spectrum are an important class of materials widely used in many devices requiring a transparent contact such as light-emitting diodes, solar cells and display screens. Since the improvement of electrical conductivity usually leads to degradation of optical transparency, a fine-tuning sample preparation process and a better understanding of the correlation between structural and transport properties is necessary for optimizing the properties of TCO for use in such devices. Here we report a structural and magnetotransport study of tin oxide (SnO₂), a well-known and commonly used TCO, prepared by a simple and relatively cheap Atmospheric Pressure Chemical Vapour Deposition (APCVD) method in the form of thin films deposited on soda-lime glass substrates. The thin films were deposited at two different temperatures (which were previously found to be close to optimum for our setup), 590 °C and 610 °C, and with (doped) or without (undoped) the addition of fluorine dopants. Scanning Electron Microscopy (SEM) and Grazing Incidence X-ray Diffraction (GIXRD) revealed the presence of inhomogeneity in the samples, on a bigger scale in form of grains (80–200 nm), and on a smaller scale in form of crystallites (10–25 nm). Charge carrier density and mobility extracted from DC resistivity and Hall effect measurements were in the ranges 1–3 × 10²⁰ cm⁻³ and 10–20 cm²/Vs, which are typical values for SnO₂ films, and show a negligible temperature dependence from room temperature down to −269 °C. Such behaviour is ascribed to grain boundary scattering, with the interior of the grains degenerately doped (i.e., the Fermi level is situated well above the conduction band minimum) and with negligible electrostatic barriers at the grain boundaries (due to high dopant concentration). The observed difference for factor 2 in mobility among the thin-film SnO₂ samples most likely arises due to the difference in the preferred orientation of crystallites (texture coefficient).     

Enhancement of Bentonite Materials with Cement for Gamma-Ray Shielding Capability

The gamma-ray shielding ability of various Bentonite–Cement mixed materials from northeast Egypt have been examined by determining their theoretical and experimental mass attenuation coefficients, μ_m (cm²g⁻¹), at photon energies of 59.6, 121.78, 344.28, 661.66, 964.13, 1173.23, 1332.5 and 1408.01 keV emitted from ²⁴¹Am, ¹³⁷Cs, ¹⁵²Eu and ⁶⁰Co point sources. The μ_m was theoretically calculated using the chemical compositions obtained by Energy Dispersive X-ray Analysis (EDX), while a NaI (Tl) scintillation detector was used to experimentally determine the μ_m (cm²g⁻¹) of the mixed samples. The theoretical values are in acceptable agreement with the experimental calculations of the XCom software. The linear attenuation coefficient (μ), mean free path (MFP), half-value layer (HVL) and the exposure buildup factor (EBF) were also calculated by knowing the μ_m values of the examined samples. The gamma-radiation shielding ability of the selected Bentonite–Cement mixed samples have been studied against other puplished shielding materials. Knowledge of various factors such as thermo-chemical stability, availability and water holding capacity of the bentonite–cement mixed samples can be analyzed to determine the effectiveness of the materials to shield gamma rays.