Effect of phosphorus irradiation on the structural,electrical, and optical characteristics of ZnO thin films

Phosphorus irradiation at a low energy (50 keV) and at a dosage of 8×10¹⁴ ions/cm² was carried out on 〈002〉 ZnO films grown by using a pulsed laser deposition technique (Sample A). Subsequent rapid thermal annealing at 650 °C and 750 °C was performed to remove defects resulting from the irradiation (samples B and C, respectively). Atomic force microscopy was used to determine the root mean square roughness, which was 10.07, 8.66, and 9.31 nm for samples A, B, and C, respectively. Low-temperature photoluminescence measurements revealed increased deep-level defect peaks following irradiation; however, the subsequent annealing minimized the defects. Although the dominant donor-bound exciton peak verifies the n-type conductivity of the films, the free–electron–to–acceptor and donor-to-acceptor pair peaks in the irradiated samples confirm an increase in acceptor concentration.     

Small silver clusters at paramagnetic defects of silica surfaces: A density functional embedded-cluster study

We studied the interaction of small Ag_n clusters (n = 1–4) with paramagnetic defect centers of a dehydroxylated silica surface using an all-electron scalar relativistic density functional method. The surface and adsorption complexes on it were modeled with an accurate quantum mechanics/molecular mechanics (QM/MM) scheme of embedding QM clusters in an elastic polarizable environment, described at the molecular mechanics level (MM). We analyzed two types of frequent point defects as sites for trapping and growing of Ag clusters: a silicon atom with a dangling bond (E′ center), ≡ Si?, and a non-bridging oxygen center (NBO), ≡ Si–O?. The Ag clusters interact with these paramagnetic centers forming strong covalent metal-defect bonds. The high adsorption energy allows one to consider the NBO and E′ sites as traps of single Ag atoms and as centers of cluster growth. We also explored the effect of adsorption on observable electronic properties of the silver clusters and of the defects of the silica surface.     

Effects of power ultrasound on oxidation and structure of beef proteins during curing processing

The aim of this study was to evaluate the effects of power ultrasound intensity (PUS, 2.39, 6.23, 11.32 and 20.96 W cm⁻²) and treatment time (30, 60, 90 and 120 min) on the oxidation and structure of beef proteins during the brining procedure with 6% NaCl concentration. The investigation was conducted with an ultrasonic generator with the frequency of 20 kHz and fresh beef at 48 h after slaughter. Analysis of TBARS (Thiobarbituric acid reactive substances) contents showed that PUS treatment significantly increased the extent of lipid oxidation compared to static brining (P < 0.05). As indicators of protein oxidation, the carbonyl contents were significantly affected by PUS (P < 0.05). SDS–PAGE analysis showed that PUS treatment increased protein aggregation through disulfide cross-linking, indicated by the decreasing content of total sulfhydryl groups which would contribute to protein oxidation. In addition, changes in protein structure after PUS treatment are suggested by the increases in free sulfhydryl residues and protein surface hydrophobicity. Fourier transformed infrared spectroscopy (FTIR) provided further information about the changes in protein secondary structures with increases in β-sheet and decreases in α-helix contents after PUS processing. These results indicate that PUS leads to changes in structures and oxidation of beef proteins caused by mechanical effects of cavitation and the resultant generation of free radicals.     

Microstructures and nano mechanical properties of the metal tungsten film

The W film was prepared on 1045 steel by magnetron sputtering, with the thickness of 2 μm, its surface and cross-section morphologies were investigated with SEM, and the phase structure was analyzed with XRD. X-ray stress determinator was utilized to measure its residual stress, and the nano-hardness and elastic modulus of the film were surveyed by nano-indentation tester. The results show that the surface of W film is very compact and smooth; the particles arranged regularly, the granularity of the thin film is about 1 μm. The microcracks, cavities and desquamation were not found in the film and interface, and the bonding between the W film and substrate is well. The XRD results showed that the W film had a body-centered cubic structure, the lattice constant: a = 0.316 nm, the growth preferred orientations are (1 1 0) and (2 2 0). The compressive stress (−169 MPa) was found on the surface. The average nano-hardness and elastic modulus of W film are 15.22 GPa, 176.64 GPa, respectively, and the mechanical properties of W film are well.     

Defect structure and electrical conduction behavior of Bi-based pyrochlores

Pyrochlore-type quaternary systems with the generic formula (Bi_1.5Zn_0.5)(Nb_0.5M_1.5)O₇ (BZNM, M=Ti, Sn, Zr, and Ce) have been synthesized by the standard solid-state reaction route. The study of positron annihilation lifetime spectra provides direct evidence for defect characterization for BZNM ceramics with different tetravalent element. The variation of the annihilation lifetime suggests that the defect structure undergoes significant changes. The defect structure is further described by means of the complex-defect model. Electrical conduction in the samples is expected to result mainly from the defects present in the lattice. Conduction measurement shows there are different conduction mechanisms. For temperatures less than 350 °C, electronic conduction dominates, while for temperatures greater than 350 °C, ionic conduction is dominant in the present system. The conduction mechanism includes the formation of charged defect dipoles, causing internal bias fields, creating oxygen vacancies that promote ionic conductivity.     

Proposal for a 4-channel all optical demultiplexer using 12-fold photonic quasicrystal

In this work, 12-fold photonic quasicrystal (PQC) with cross section equals to 138 μm² has been used to design a 4-channel optical demultiplexer. The size of structure promises its applications in optical integrated circuits (OICs) and also, wavelength division multiplexing (WDM) communication devices. Finite difference time domain (FDTD) method has been employed in order to investigate the structure's band gap and output waveforms of each channel. Four channels, with spacing less than 1 nm and cross-talk level better than ? 2.8 dB have been separated by introducing defects in L-shaped and line defect waveguides (LDWs) in the crystal's structure. It has been shown that, L-shaped waveguides (LWs) are quite more frequency selective than line defect waveguides. Also, it has been found that the exact tuning of the central wavelength of each channel is possible by making use of defects with different radiuses and sites in the waveguides.     

X-ray photoelectron spectroscopy of fast-frozen hematite colloids in aqueous solutions. 4. Coexistence of alkali metal (Na+, K+, Rb+, Cs+) and chloride ions

Colloidal suspensions of hematite in contact with aqueous solutions of 50 mM alkali metal chloride electrolytes (NaCl, KCl, RbCl, CsCl) were investigated by cryogenic X-ray photoelectron spectroscopy (XPS) and electrophoretic mobility. Suspension pH values were varied from 2 to 11 in order to evaluate effects of positively- and negatively-charged hematite surfaces. XPS revealed coexisting cations and chloride ions both below and above the point of zero charge. Concentration profiles of adsorbed cations point to a Hofmeister series in the order of Na⁺ > K⁺ > Rb⁺ ≈ Cs⁺. Binding energies of photoelectrons emitted from electrolyte ions increased with pH at roughly 0.04 eV per pH unit. This shift was attributed to variations in the surface electric potential of hematite. This effect, compounded by rises in aliphatic carbon signals with pH, called for referencing of all spectra to the 530.0 eV oxide component of the hematite O1s spectrum. This departure from the traditional use of the external C 1s 285.0 eV peak is hereby proposed for cryogenic XPS studies of interfacial reactions involving hematite.     

Free-volume defects investigation of GeS2-Ga2S3-CsI chalcogenide glasses by positron annihilation spectroscopy

The transformation behavior of free-volume defect in (80GeS₂-20Ga₂S₃)_100-x (CsI)_x (x = 0, 5, 10, 15 mol%) chalcogenide glasses was studied by employing positron annihilation spectroscopic technique, which could reveal valuable information for in-depth understanding of nano-structural defects in glassy matrix. The results indicate that the structural changes caused by CsI additives can be adequately described by positron trapping modes determined with two-state model. The initial addition of CsI (x = 5 mol%) led to a void contraction, whereas, the void agglomeration occurred with the increase of CsI and the free-volume defects of the glasses were obviously reduced. The atomic density ρ is inversely proportional to the number of these defects. Meanwhile, the UV cut-off edge shifts toward short-wavelength with increasing of CsI. This study provides the valuable information of defects evolution in GeS₂-Ga₂S₃-CsI glasses.     

Experimental and simulated studies on the plastic mechanical characteristics of osteoporotic vertebral trabecular bone

Osteoporotic vertebral fractures present a major health care burden worldwide, thereby prompting vigorous investigation of the mechanical properties of vertebral bone. Because most vertebral fractures occur gradually and asymptomatically, they are thought to result from loading in daily activities rather than traumatic events. Hence, with respect to stress resistance, the elastic properties of osteoporotic vertebral trabecular bone have generated many studies. A large part of this data describes the linear elastic properties of the bone, with relatively less focus on the plastic mechanical characteristics which may be closely associated with load-induced fracture. We performed experimental and simulated studies of the plastic mechanical characteristics of osteoporotic trabecular bone using non-destructive technologies, rapid-prototyping (RP), and finite element (FE) analysis to build models based on high-resolution micro-computed tomography (micro-CT) data. Two-dimensional geometries for RP and FE models were derived from micro-CT scans of specimens from the central part of the lumbar vertebrae of aged female donors. A cubic specimen (6.5 mm) and a cylindrical specimen (7 mm in diameter and 5 mm long) were generated for the RP and FE models and analysed in place of real bone specimens. We performed simulated compression tests with the FE models to indirectly validate results of the experimental compression tests. To a remarkable degree, results obtained from experimental and simulated compression tests with the RP and FE models concurred. The results of this study support the use of RP technology and FE analysis in the non-destructive evaluation of the plastic mechanical characteristics of osteoporotic bone.     

Ultrasonic and mechanical soil washing processes for the removal of heavy metals from soils

In order to determine the optimal operating conditions of full-scale soil washing processes for the removal of heavy metals, the effect of high-power ultrasound on the conventional mechanical soil washing process was investigated in a large lab-scale 28 kHz sonoreactor. The soil samples were obtained from an abandoned railway station site in Seoul, Korea, which was contaminated with Cu (242.7 ± 40.0 mg/kg), Pb (441.3 ± 49.8 mg/kg), and Zn (358.0 ± 35.7 mg/kg). The treated concentrations of three heavy metal species in each process were compared with the regulation levels. It was found that higher performance, satisfying the regulation levels, was obtained in the ultrasonic/mechanical process due to the combined effects of macroscale mixing and microscale sonophysical effects. Moreover ultrasound played a more important role in less favorable conditions for the mechanical washing process (less acidic or less washing liquid conditions). Considering the application of the ultrasonic/mechanical soil washing process in real contaminated sites, the optimal conditions for the reactor with the bottom area of 15 × 15 cm² and the input ultrasound power of 250 W were determined as follows: (1) the amount of soil per an operation was a 300 g; (2) the ratio of soil and liquid was 1:3; (3) the concentration of acidic washing liquid was 0.5 M HCl.     

Synthesis and application of molecularly imprinted nanoparticles combined ultrasonic assisted for highly selective solid phase extraction trace amount of celecoxib from human plasma samples using design expert (DXB) software

In this work molecular imprinted nanoparticles (MINPs) was synthesized and applied for ultrasonic assisted solid phase extraction of celecoxib (CEL) from human plasma sample following its combination by HPLC–UV. The MINPs were prepared in a non-covalent approach using methacrylic acid as monomer, CEL as template, ethylene glycol dimethacrylate as cross-linker, and 2,2-azobisisobutyronitrile (AIBN) as the initiator of polymerization. pH, volume of rinsing and eluent solvent and amount of sorbent influence on response were investigated using factorial experimental design, while optimum point was achieved and set as 250 mg sorbent, pH 7.0, 1.5 mL washing solvent and 2 mL eluent by analysis of results according to design expert (DX) software. At above specified conditions, CEL in human plasma with complicated matrices with acceptable high recoveries (96%) and RSD% lower than 10% was quantified and estimated.The proposed MISPE-HPLC–UV method has linear responses among peak area and concentrations of CEL in the range of 0.2–2000 μg L⁻¹, with regression coefficient of 0.98. The limit of detection (LOD) and quantification (LOQ) based on three and ten times of the noise of HPLC peaks correspond to blank solution were 0.08 and 0.18 μg L⁻¹, respectively.     

Highly sensitive hydrogen detection by medium energy Ne+ impact

Hydrogen atoms on solid surfaces were measured directly by elastic recoil detection analysis (ERDA) using medium energy (100–150 keV) Ne⁺ ions with an excellent sensitivity of (～ 1 × 10¹² H/cm²) without any absorber foils and time-of-flight techniques. An electrostatic toroidal analyzer acquired H⁺ ions with energy around 11 keV recoiled from Si(111)-1 × 1-H surfaces. The H⁺ fraction strongly depends upon emerging angle and takes a value more than 50% at the angle below 70° and a saturated value of 17% at the angle above 80° with respect to surface normal. We detected H atoms on the reduced TiO₂(110) exposed to water molecules at room temperature (2 L) and estimated the absolute amount of H to be ～ 2.0 × 10¹⁴ H/cm² corresponding to ～ 38% (～ 0.38 ML) of the bridging oxygen atoms.     

Study on the bias-dependent effects of proton-induced damage in CdZnTe radiation detectors using ion beam induced charge microscopy

The influence of damage induced by 2 MeV protons on CdZnTe radiation detectors is investigated using ion beam induced charge (IBIC) microscopy. Charge collection efficiency (CCE) in irradiated region is found to be degraded above a fluence of 3.3 × 10¹¹ p/cm² and the energy spectrum is severely deteriorated with increasing fluence. Moreover, CCE maps obtained under the applied biases from 50 V to 400 V suggests that local radiation damage results in significant degradation of CCE uniformity, especially under low bias, i. e., 50 V and 100 V. The CCE nonuniformity induced by local radiation damage, however, can be greatly improved by increasing the detector applied bias. This bias-dependent effect of 2 MeV proton-induced radiation damage in CdZnTe detectors is attributed to the interaction of electron cloud and radiation-induced displacement defects.     

Defect interactions in La0.3Sr0.7Fe(M′)O3−δ (M′ = Al,Ga) perovskites: Atomistic simulations and analysis of p(O2)-T-δ diagrams

Atomistic modelling showed that a key factor affecting the p(O₂) dependencies of point defect chemical potentials in perovskite-type La_0.3Sr_0.7Fe_1−xM′_xO_3−δ (M′ = Ga, Al; x = 0–0.4) under oxidizing conditions, relates to the coulombic repulsion between oxygen vacancies and/or electron holes. The configurations of A- and B-site cations with stable oxidation states have no essential influence on energetics of the mobile charge carriers, whereas the electrons formed due to iron disproportionation are expected to form defect pair clusters with oxygen vacancies. These results were used to develop thermodynamic models, adequately describing the p(O₂)-T-δ diagrams of La_0.3Sr_0.7Fe(M′)O_3−δ determined by the coulometric titration technique at 923–1223 K in the oxygen partial pressure range from 1 × 10^− 5 to 0.5 atm. The thermodynamic functions governing the oxygen intercalation process were found independent of the defect concentration. Doping with aluminum and gallium leads to increasing oxygen deficiency and induces substantial changes in the behavior of iron cations, increasing the tendencies to disproportionation and hole localization. Despite similar oxygen nonstoichiometry in the Al- and Ga-substituted ferrites at a given dopant content, the latter tendency is more pronounced in the case of aluminum-containing perovskites.     

Nonlinear magnetoelastic effects in ultrathin epitaxial FCC Co(0 0 1) films:: an ab initio study

Those linear and nonlinear magnetoelastic coupling coefficients which determine the magnetostrictive stress and the strain-induced out-of-plane magnetic anisotropy in epitaxially grown FCC Co(0 0 1) films are calculated by the ab initio density functional electron theory. The nonlinear couplings have a strong effect on the change Δσ₁^m of the in-plane magnetostrictive stress resulting from a change of the magnetization direction from [0 1 0] to [1 0 0], but a negligibly small effect on the out-of-plane anisotropy e_MCA. The calculations confirm the experimental result that the measured out-of-plane anisotropy cannot be totally attributed to volume magnetoelastic effects. Estimates are given for the nonlinear magnetoelastic coupling coefficients m₁^γ,2 and m₂^γ,2.     

Application of ZnO nanorods loaded on activated carbon for ultrasonic assisted dyes removal: Experimental design and derivative spectrophotometry method

A method based on application of ZnO nanorods loaded on activated carbon (ZnO-NRs-AC) for adsorption of Bromocresol Green (BCG) and Eosin Y (EY) accelerated by ultrasound was described. The present material was synthesized under ultrasound assisted wet-chemical method and subsequently was characterized by FE-SEM, TEM, BET and XRD analysis. The extent of contribution of conventional variables like pH (2.0–10.0), BCG concentration (4–20 mg L⁻¹), EY concentration (3–23 mg L⁻¹), adsorbent dosage (0.01–0.03 g), sonication time (1–5 min) and centrifuge time (2–6 min) as main and interaction part were investigated by central composite design under response surface methodology. Analysis of variance (ANOVA) was adapted to experimental data and guide the best operational conditions mass by set at 6.0, 9 mg L⁻¹, 10 mg L⁻¹, 0.02 g, 4 and 4 min for pH, BCG concentration, EY concentration, adsorbent dosage, sonication and centrifuge time, respectively. At these specified conditions dye adsorption efficiency was higher than 99.5%. The suitability and well prediction of optimum point was tested by conducting five experiments and respective results revel that RSD% was lower than 3% and high quality of fitting was confirmed by t-test. The experimental data were best fitted in Langmuir isotherm equation and the removal followed pseudo second order kinetics. The experimentally obtained maximum adsorption capacities were estimated as 57.80 and 61.73 mg g⁻¹ of ZnO-NRs-AC for BCG and EY respectively from binary dye solutions. The mechanism of removal was explained by boundary layer diffusion via intraparticle diffusion.     

Modeling and deformation analyzing of InSb focal plane arrays detector under thermal shock

A higher fracture probability appearing in indium antimonide (InSb) infrared focal plane arrays (IRFPAs) subjected to the thermal shock test, restricts its final yield. In light of the proposed equivalent method, where a 32 × 32 array is employed to replace the real 128 × 128 array, a three-dimensional modeling of InSb IRFPAs is developed to explore its deformation rules. To research the damage degree to the mechanical properties of InSb chip from the back surface thinning process, the elastic modulus of InSb chip along the normal direction is lessened. Simulation results show when the out-of-plane elastic modulus of InSb chip is set with 30% of its Young’s modulus, the simulated Z-components of strain distribution agrees well with the top surface deformation features in 128 × 128 InSb IRFPAs fracture photographs, especially with the crack origination sites, the crack distribution and the global square checkerboard buckling pattern. Thus the Z-components of strain are selected to explore the deformation rules in the layered structure of InSb IRFPAs. Analyzing results show the top surface deformation of InSb IRFPAs originates from the thermal mismatch between the silicon readout integrated circuits (ROIC) and the intermediate layer above, made up of the alternating indium bump array and the reticular underfill. After passing through both the intermediate layer and the InSb chip, the deformation amplitude is reduced firstly from 2.23 μm to 0.24 μm, finally to 0.09 μm. Finally, von Mises stress criterion is employed to explain the causes that cracks always appear in the InSb chip.     

Mechanical properties of polycrystalline RuSr2GdCu2O8 superconductor

The main objective of this paper is to report the room temperature hardness and elastic modulus of the RuSr₂GdCu₂O₈ superconductor phase by instrumented indentation. Polycrystalline samples were produced by a solid state reaction technique. The samples were also characterized by scanning electron microscopy, X-ray diffraction and electrical resistivity measurements. The influence of porosity on the mechanical properties was avoided by considering only those indentations inside the grains. The hardness and elastic modulus were 8.6 GPa and 145 GPa, respectively. These values are comparable with those of Y-123. The indentation fracture toughness evaluated after conventional Vickers indentation was 1.9 MPa m^1/2.     

Kinetics of microplasma atmospheric ion generation correlated with discharge current

The conditions necessary for achieving a stable bipolar ion generation (in the order of 10⁶ ion/cm³) and lower ozone concentration (less than 50 ppb) using a surface discharge microplasma device (SMD) by adjusting the applied voltage and frequency were experimentally determined and investigated. Measurements of the discharge current characteristics of the SMD revealed saturation against the frequency (1.5–2.5 kHz, depending on the applied voltage). The ion and ozone concentrations both increased in step with the discharge current in the lower frequency region. The ion concentration reached equilibrium in the frequency range of 200–500 Hz, and the point of equilibrium within that range depended on the applied voltage. The ozone concentration did not reach equilibrium under our experimental conditions (ozone concentration < 100 ppb). The kinetics of the ion/ozone generation rate with a focus on the plasma reaction and recombination of bipolar ions is discussed.     

Mixed conductivity,stability and thermomechanical properties of Ni-doped La(Ga,Mg)O3−δ

Perovskite-type LaGa_0.65Mg_0.15Ni_0.20O_3−δ exhibiting oxygen transport comparable to that in K₂NiF₄-type nickelates was characterized as a model material for ceramic membrane reactors, employing mechanical tests, dilatometry, oxygen permeability and faradaic efficiency measurements, thermogravimetry (TG), and determination of the total conductivity and Seebeck coefficient in the oxygen partial pressure range from 10^− 15 Pa to 40 kPa. Within the phase stability domain which is similar to La₂NiO_4+δ, the defect chemistry of LaGa_0.65Mg_0.15Ni_0.20O_3−δ can be adequately described by the ideal solution model with oxygen vacancies and electron holes to be the only mobile defects, assuming that Ni²⁺ may provide two energetically equivalent sites for hole location. This assumption is in agreement with the density of states, estimated from thermopower, and the coulometric titration and TG data suggesting Ni⁴⁺ formation in air at T < 1150 K. The hole conductivity prevailing under oxidizing conditions occurs via small-polaron mechanism as indicated by relatively low, temperature-activated mobility. The ionic transport increases with vacancy concentration on reducing p(O₂) and becomes dominant at oxygen pressures below 10^− 7–10^− 5 Pa. The average thermal expansion coefficients in air are 11.9 × 10^− 6 and 18.4 × 10^− 6 K^− 1 at 370–850 and 850–1270 K, respectively. The chemical strain of LaGa_0.65Mg_0.15Ni_0.20O_3−δ ceramics at 1073–1123 K, induced by the oxygen partial pressure variations, is substantially lower compared to perovskite ferrites. The flexural strength determined by 3-point and 4-point bending tests is 167–189 MPa at room temperature and 85–97 MPa at 773–1173 K. The mechanical properties are almost independent of temperature and oxygen pressure at p(O₂) = 1–2.1 × 10⁴ Pa and 773–1173 K.