The electrodeposition behaviors and magnetic properties of Ni-Co films

Ni-Co films with different compositions and microstructures were produced on ITO glasses by electrodeposition from sulphate bath at 25 °C. Cyclic voltammograms give a result that the increase in the Co²⁺ concentration displaces Ni-Co alloy oxidation peaks to negative potential with high Co current distributions. It is observed that the content of cobalt in the films increases from 22.42% to 56.09% as the molar ratio of CoSO₄/NiSO₄ varying from 0.015/0.085 to 0.045/0.055 in electrolyte. XRD patterns reveal that the structure of the films strongly depends on the Co content in the deposited films. The saturation magnetization (M_s) moves up from 144.84 kA m⁻¹ to 342.35 kA m⁻¹ and coercivity (H_c) falls from 15.27 kA m⁻¹ to 7.27 kA m⁻¹ with the heat treatment temperature increasing from 25 °C to 450 °C. The saturation magnetization (M_s) and coercivity (H_c) move up from 340.97 kA m⁻¹ and 7.98 kA m⁻¹ to 971.58 kA m⁻¹ and 18.62 kA m⁻¹ with the Co content increasing from 22.42% to 56.09% after annealing at 450.     

Skin permeation of d-limonene-based nanoemulsions as a transdermal carrier prepared by ultrasonic emulsification

Nanoemulsions can be used for transporting pharmaceutical phytochemicals in skin-care products because of their stability and rapid permeation properties. However, droplet size may be a critical factor aiding permeation through skin and transdermal delivery efficiency. We prepared d-limonene nanoemulsions with various droplet sizes by ultrasonic emulsification using mixed surfactants of sorbitane trioleate and polyoxyethylene (20) oleyl ether under different hydrophilic–lipophilic balance (HLB) values. Droplet size decreased with increasing HLB value. With HLB 12, the droplet size was 23 nm, and the encapsulated ratio peaked at 92.3%. Transmission electron microscopy revealed spherical droplets and the gray parts were d-limonene precipitation incorporated in spherical droplets of the emulsion system. Franz diffusion cell was used to evaluate the permeation of d-limonene nanoemulsion through rat abdominal skin; the permeation rate depended on droplet size. The emulsion with the lowest droplet size (54 nm) achieved the maximum permeation rate. The concentration of d-limonene in the skin was 40.11 μL/cm² at the end of 360 min. Histopathology revealed no distinct voids or empty spaces in the epidermal region of permeated rat skin, so the d-limonene nanoemulsion may be a safe carrier for transdermal drug delivery.     

Dynamics of gold clusters on amorphous carbon films induced by annealing in a transmission electron microscope

The change of the size distribution of Au clusters induced by annealing was studied in situ by transmission electron microscopy. Starting from statistically distributed Au clusters on a thin amorphous carbon film, “islands” are formed within a few months storage at room temperature, which consist of Au clusters with sizes <4 nm embedded in a thin Au film. These islands cover originally areas with sizes around 25 × 70 nm². If the temperature is increased in the transmission electron microscope two different processes can be clearly distinguished that lead to the coarsening of the cluster size distribution: cluster coalescence and (contactless) Ostwald ripening. The degree and rate of the coarsening are found to depend on the underlying surface (Au film or amorphous carbon) and the exposure to the high-flux high-energy electron beam, which can be estimated to lead to high-temperature excursions in a cluster on a 10⁻¹² s time scale. The experimental findings are confirmed by Monte-Carlo simulations using the many-body Gupta potentials in order to calculate the Au/Au interaction. Moreover, the results of MC simulations suggest an electron-beam induced formation of a “quasi-two-dimensional gas” of small highly mobile Au species on the Au film, which promotes Ostwald ripening.     

Removal of chloridazon by natural and ammonium kerolite samples

The adsorption of chloridazon (5-amino-4-chloro-2-phenylpyridazin-3(2H)-one) on natural and ammonium kerolite samples from aqueous solution at 10, 25 and 40 °C has been studied by using batch experiments. The experimental data points were fitted to the Langmuir equation in order to calculate the adsorption capacities (X_m) of the samples; two straight lines were obtained, which indicates that the adsorption process takes place in two different stages. Values for X_m1 (first stage) ranged from 1.1 × 10⁻² mol kg⁻¹ for natural kerolite at 40 °C up to 5.1 × 10⁻² mol kg⁻¹ for ammonium kerolite at 10 °C and the values for X_m2 (second stage) ranged from 9.1 × 10⁻² mol kg⁻¹ for natural kerolite at 40 °C up to 14 × 10⁻² mol kg⁻¹ for natural kerolite at 10 °C. The adsorption experiments showed on the one hand, that the ammonium kerolite is more effective than natural kerolite to adsorb chloridazon in the range of temperature studied and on the other hand, that the lower temperature, the more effective the adsorption of chloridazon on the adsorbents studied.     

Characterization of Ti6Al4V implant surface treated by Nd:YAG laser and emery paper for orthopaedic applications

A more noble and biocompatible Ti alloy was achieved at fluence of 140 J cm⁻² where the implant indicated a higher degree of hardness (825HV), higher corrosion resistance (−0.21 V) and highest hydrophilicity (i.e. θ_c = 37°) compared with 70° of the control sample. These values corresponded to 58 and 39 mN m⁻¹ of surface tension respectively. The laser treated samples at 140 J cm⁻² showed higher wettability characteristics than mechanically roughened surface. Cell growth and their spreading condition in a specific area were analyzed by SEM and Image J Program software. Clearly, more cells were attached (1.2 × 10⁵) to and spread (488 μm²) over the surface at 140 J cm⁻² than in any other condition. Pathologically, the treated samples indicated no sign of infection.     

In-fiber Mach–Zehnder interferometer based on multi-mode fiber and up-taper for curvature sensing

A new type of curvature sensor comprises a stub of multi-mode fiber and an up-taper is proposed and demonstrated experimentally. The whole fabrication process is quite simple and the sensor head is cost effective. Measurement results show that it has a maximum curvature sensitivity of −61.877 nm/m⁻¹ at 1.1718 m⁻¹ (the highest value of reported papers among in-fiber Mach–Zehnder interferometers) and −9.2115 nm/m⁻¹ from 0.865 m⁻¹ to 1.1172 m⁻¹. Temperature sensitivity of 89.01 pm/°C within the range of 20–80 °C has also been achieved, which implies the possibility for measurement of temperature.     

Coarsening of mass-selected Au clusters on amorphous carbon at room temperature

Low-energy cluster beam deposition was used to deposit mass-selected Au_n clusters (n = 4, 6, 13 and 20) on amorphous carbon (a-C) substrates. The resulting samples were stored at room temperature under ambient conditions for time periods up to 32 months to analyze the coarsening behaviour of the clusters. Cluster-size distributions were measured in regular time intervals by transmission electron microscopy (TEM). The TEM experiments show a significant increase of the average cluster size with time analogous to classical surface Ostwald ripening (OR). The coarsening of Au clusters can be well described by steady-state diffusion-limited kinetics. The derived surface mass-transport diffusion coefficients at room temperature range between 1.1 and 3.8·10⁻²⁵ m² s⁻¹ for our samples. A detailed analysis of values suggests that, the rate of the surface OR for mass-selected Au_n clusters increases with the cluster size in the sequence: Au₄ ≈ Au₆ < Au₁₃ < Au₂₀ for the investigated range of Au clusters. Given that the initial, on-surface cluster-size distributions are nominally monodisperse, classical OR with cluster coarsening based only on the Gibbs-Thomson effect cannot explain the observed coarsening. The activation of the coarsening process is rationalized by initial variations of the cluster sizes due to the deposition process itself and/or the interaction of the clusters with the substrate. Moreover, the presence of initial deposited Au clusters as different isomers with slightly different chemical potential on the substrate, may also initiate the coarsening by surface OR. Furthermore, we find that the coarsening is most pronounced for the paucidispersed sample with Au_m (10 ? m ? 20) clusters. A possible explanation of this behaviour is the presence of an initial distribution of different cluster sizes directly after deposition.     

High surface area thermally stabilized porous iron oxide/silica nanocomposites via a formamide modified sol-gel process

Iron oxide/silica (Fe:Si as 1:10 atomic ratio) composite materials have been prepared by calcination for 3 h at different temperatures (400-900 °C) of xerogel precursor obtained via a formamide modified sol-gel process. The process involved TEOS and iron(III) nitrate, nitric acid and formamide. Genesis of the composite materials from the xerogel precursor has been investigated by TGA, DSC, FTIR, XRD, SEM and EDX. Results indicated that all the calcined composites are mainly composed of amorphous iron oxide dispersed as finely divided particles in amorphous silica matrixes. Nitrogen adsorption/desorption isotherms revealed a reversible type I of isotherms indicative of microporosity. However, high S_BET surface area and microsporosity were observed for the calcined composite materials (e.g. S_BET = 625 m² g⁻¹, and S_αs = 556 m² g⁻¹ for the composite calcined at 400 °C). Formation of the porous texture was discussed in terms of the action of formamide, which enhanced strengthening of the silica gel network during evaporation of the more volatile components within the composite body during the drying process.     

Structural and optoelectronic properties of vacuum evaporated SnS thin films annealed in argon ambient

In this work, 650 nm polycrystalline SnS thin films were grown by thermal evaporation of high purity tin sulfide powder at 250 °C substrate temperature, followed by post deposition annealing at 200 °C and 300 °C for 2, 4 and 6 h, and at 400 °C for 2 and 4 h in argon ambient. The XRD pattern of the as-deposited and annealed SnS films led to the conclusion that the as-deposited films were polycrystalline in nature with preferentially oriented along (1 1 1) direction. The direct bandgap of all the films was found to be observed between 1.33 and 1.53 eV. Except for annealing at 400 °C all the films were nearly stoichiometric in nature, suggesting lower rate of desulfurization at that ambient. However, higher annealing temperature has resulted in the segregation of tin phase. All the films showed good absorption in the visible range. The as-deposited and annealed films showed p-type conductivity. Hall measurement revealed the carrier concentration and mobility ranging from 10¹⁵ to 10¹⁶ cm⁻³ and 0.8 to 31.6 cm² V⁻¹ s⁻¹ respectively. The photoconductivity measurements of all the SnS films were carried out by recording the lowering of resistance of the respective films with time under illumination.     

Structural evolution of electroless Ni-P coating on Al-12 wt.% Si alloy during heat treatment at high temperatures

The work is concerned with the high-temperature heat treatment of an Al-12 wt.% Si alloy coated by an electroless Ni-P layer. The electroless deposition took place on a pre-treated substrate in a bath containing nickel hypophosphite, nickel lactate and lactic acid. Resulting Ni-P deposit showed a thickness of about 8 μm. The coated samples were heat-treated at 200-550 °C/1-24 h. LM, SEM, EDS and XRD were used to investigate phase transformations. Adherence to the substrate was estimated from the scratch test and microhardness of the heat-treated layers was also measured. It is found that various phase transformations occur, as both temperature and annealing time increase. These include (1) amorphous Ni-P → Ni + Ni₃P, (2) Al + Ni → Al₃Ni, (3) Ni₃P → Ni₁₂P₅ + Ni, (4) Ni₁₂P₅ → Ni₂P + Ni, and (5) Al₃Ni + Ni → Al₃Ni₂. The formation of intermetallic phases, particularly Al₃Ni₂, leads to significant surface hardening, however, too thick layers of intermetallics reduce the adherence to the substrate. Based on the growth kinetics of the intermetallic phases, diffusion coefficients of Ni in Al₃Ni and Al₃Ni₂ at 450-550 °C are estimated as follows: D(Al₃Ni, 450 °C) ≈ 6 × 10⁻¹² cm² s⁻¹, D(Al₃Ni, 550 °C) ≈ 4 × 10⁻¹¹ cm² s⁻¹, D(Al₃Ni₂, 450 °C) ≈ 1 × 10⁻¹² cm² s⁻¹ and D(Al₃Ni₂, 550 °C) ≈ 1 × 10⁻¹¹ cm² s⁻¹. Mechanisms of phase transformations are discussed in relation to the elemental diffusion.     

Highly active Ce1−xCuxO2 nanocomposite catalysts for the low temperature oxidation of CO

A series of Ce_1−xCu_xO₂ nanocomposite catalysts with various copper contents were synthesized by a simple hydrothermal method at low temperature without any surfactants, using mixed solutions of Cu(II) and Ce(III) nitrates as metal sources. These bimetal oxide nanocomposites were characterized by means of XRD, TEM, HRTEM, EDS, N₂ adsorption, H₂-TPR and XPS. The influence of Cu loading (5-25 mol%) and calcination temperature on the surface area, particle size and catalytic behavior of the nanocomposites have been discussed. The catalytic activity of Ce_1−xCu_xO₂ nanocomposites was investigated using the test of CO oxidation reaction. The optimized performance was achieved for the Ce_0.80Cu_0.20O₂ nanocomposite catalyst, which exhibited superior reaction rate of 11.2 × 10⁻⁴ mmol g⁻¹ s⁻¹ and high turnover frequency of 7.53 × 10⁻² s⁻¹ (1% CO balanced with air at a rate of 40 mL min⁻¹, at 90 °C). No obvious deactivation was observed after six times of catalytic reactions for Ce_0.80Cu_0.20O₂ nanocomposite catalyst.     

Fabrication of p-type Li-doped ZnO films by pulsed laser deposition

p-Type ZnO thin films have been realized via doping Li as acceptor by using pulsed laser deposition. In our experiment, Li₂CO₃ was used as Li precursor, and the growth temperature was varied from 400 to 600 °C in pure O₂ ambient. The Li-doped ZnO film prepared at 450 °C possessed the lowest resistivity of 34 Ω cm with a Hall mobility of 0.134 cm² V⁻¹ s⁻¹ and hole concentration of 1.37 × 10¹⁸ cm⁻³. X-ray diffraction (XRD) measurements showed that the Li-doped ZnO films grown at different substrate temperatures were of completely (0 0 2)-preferred orientation.     

Molecular dynamics and phase transitions in paramagnetic [Mn(H2O)6][SiF6] investigated by H NMR

The temperature dependences of ²H NMR spectra and spin-lattice relaxation time T₁ have been measured for paramagnetic [Mn(H₂O)₆][SiF₆]. The obtained ²H NMR spectra were simulated by considering the quadrupole interaction and paramagnetic shift. The variation of the spectra measured in phase III was explained by the 180° flip of water molecules. The activation energy E_a and the jumping rate at infinite temperature k₀ for the 180° flip of H₂O were obtained as 35 kJ mol⁻¹ and 4×10¹⁴ s⁻¹, respectively. The spectral change in phases I and II was ascribed to the reorientation of [Mn(H₂O)₆]²⁺ around the C₃ axis where the E_a and k₀ values were estimated as 45 kJ mol⁻¹ and 1×10¹³ s⁻¹, respectively. From the almost temperature independent and short T₁ value, the correlation time for electron-spin flip-flops, τ_e, and the exchange coupling constant J were obtained as 3.0×10⁻¹⁰ s and 2.9×10⁻³ cm⁻¹, respectively. The II-III phase transition can be caused by the onset of the jumping motion of [Mn(H₂O)₆]²⁺ around the C₃ axis.     

Characterization of single-crystalline In2O3 films deposited on Y-stabilized ZrO2 (1 0 0) substrates by MOCVD

Epitaxial In₂O₃ films have been deposited on Y-stabilized ZrO₂ (YSZ) (1 0 0) substrates by metalorganic chemical vapor deposition (MOCVD). The films were deposited at different substrate temperatures (450-750 °C). The film deposited at 650 °C has the best crystalline quality, and observation of the interface area shows a clear cube-on-cube epitaxial relationship of In₂O₃(1 0 0)||YSZ(1 0 0) with In₂O₃[0 0 1]||YSZ[0 0 1]. The Hall mobility of the single-crystalline In₂O₃ film deposited at 650 °C is as high as 66.5 cm² V⁻¹ s⁻¹ with carrier concentration of 1.5 × 10¹⁹ cm⁻³ and resistivity of 6.3 × 10⁻³ Ω cm. The absolute average transmittance of the obtained films in the visible range exceeds 95%.     

Ag-N doped ZnO film and its p-n junction fabricated by ion beam assisted deposition

Ag-N doped ZnO film was synthesized by ion beam assisted deposition and its electrical properties and annealing property were investigated. The films remained p-type even after annealing at 400 °C in air for 10 min. While the annealing temperature went up to 500 °C, the conduction type of these films shifted from p-type to n-type. The p-type ZnO film revealed low resistivity (0.0016 Ω cm), low Hall mobility (0.65 cm² V⁻¹ s⁻¹) and high carrier concentration (5.8 × 10²⁰ cm⁻³). ZnO p-n homojunction consisting of a p-type layer (Ag-N doped ZnO film) and an n-type layer (In-doped ZnO film) had been fabricated by ion beam assisted deposition. With electrical measurement, its current-voltage curve had a typical rectifying characteristic with current rectification ratio of 25 at bias ±5 V and a reverse current of 0.01 mA at −5 V. The depletion width was estimated 3.8 nm by using p-n junction equation.     

Simultaneous measurement of curvature and temperature based on PCF-based interferometer and fiber Bragg grating

A sensor head consisting of a photonic crystal fiber (PCF)-based Mach-Zehnder interferometer (MZI) and a fiber Bragg grating (FBG) is proposed and experimentally demonstrated for simultaneous measurement of curvature and temperature. The MZI fabricated by splicing a short length of PCF between two single-mode fibers with the air-hole structure that completely collapsed near the splicing points, is sensitive to fiber bending and surrounding temperature, while the FBG is only sensitive to the later. Simultaneous measurement of curvature and temperature is therefore obtained. Sensitivities of 4.06 nm/m^− 1 and 6.30 pm/°C are achieved experimentally for curvature and temperature, respectively. And the corresponding resolutions are 5.2 × 10^− 4 m^− 1 and 1.25 °C for curvature and temperature, respectively, based on the wavelength measurement resolution of 10 pm.     

Derivation of component aerosol direct radiative forcing at the top of atmosphere for clear-sky oceans

A two-step approach is proposed to derive component aerosol direct radiative forcing (ADRF) at the top of atmosphere (TOA) over global oceans from 60°S to 60°N for clear-sky condition by combining Terra CERES/MODIS-SSF shortwave (SW) flux and aerosol optical thickness (AOT) observations with the fractions of component AOTs from the GSFC/GOCART model. The derived global annual mean component ADRF is +0.08±0.17 W/m² for black carbon, −0.52±0.24 W/m² for organic carbon, −1.10±0.42 W/m² for sulfate, −0.99±0.37 W/m² for dust, −2.44±0.84 W/m² for sea salt, and −4.98±1.67 W/m² for total aerosols. The total ADRF has also been partitioned into anthropogenic and natural components with a value of −1.25±0.43 and −3.73±1.27 W/m², respectively. The major sources of error in the estimates have also been discussed. The analysis adds an alternative technique to narrow the large difference between current model-based and observation-based global estimates of component ADRF by combining the satellite measurement with the model simulation.     

High mobility W-doped In2O3 thin films: Effect of growth temperature and oxygen pressure on structural, electrical and optical properties

Highly conducting and transparent thin films of tungsten (W)-doped indium oxide were obtained using pulsed laser deposition to study the effect of growth temperature and oxygen pressure on structural, optical and electrical properties. The transparency of the films is seen to largely depend on the growth temperature. The electrical properties, however, are found to depend strongly on both the growth temperature and the oxygen pressure. High mobility (up to 358 cm² V⁻¹ s⁻¹), low resistivity (1.1 × 10⁻⁴ Ω cm), and relatively high transmittance (∼90%) tungsten-doped indium oxide films have been prepared at a growth temperature of 500 °C and an oxygen pressure of 1 × 10⁻⁶ bar.     

Production and corrosion resistance of NdFeBZr magnets with an improved response to thermal variations during sintering

This study describes an attempt to produce NdFeB magnets that are insensitive to the sintering temperature. It was found that addition of Zr to NdFeB magnets significantly augmented the thermal stability of this magnetic material during sintering at high temperature even at industrial scale. The best sintered magnets were produced by jet-milling the powder (to achieve an average 3.4 μm particle size), and then aligned, pressed and sintered under argon at 1100 °C for 3 h followed by appropriate heat treatment. The magnetic properties of the resulting magnets were: (BH)_m=403.8 kJ m⁻³ (±4.7 kJ m⁻³), B_r=1430 mT (±9 mT) and _iH_c=907 kA m⁻¹ (±12 kA m⁻¹). Large grain growth, in excess of 100 μm in the Zr-free magnets, was observed during sintering at 1100 °C. This did not occur in the presence of Zr. These observations imply that the sensitivity of this class of magnets to high sintering temperatures is greatly reduced by Zr addition. Corrosion resistance of NdFeB was therefore significantly improved by the addition of small amounts of Zr.     

Rate effect on mechanical properties of hydraulic concrete flexural-tensile specimens under low loading rates using acoustic emission technique

Acoustic emission (AE) waveform is generated by dislocation, microcracking and other irreversible changes in a concrete material. Based on the AE technique (AET), this paper focuses on strain rate effect on physical mechanisms of hydraulic concrete specimens during the entire fracture process of three point bending (TPB) flexural tests at quasi-static levels. More emphasis is placed on the influence of strain rate on AE hit rate and AE source location around peak stress. Under low strain rates, namely 0.77 × 10⁻⁷ s⁻¹, 1 × 10⁻⁷ s⁻¹ to 1 × 10⁻⁶ s⁻¹ respectively, the results show that the tensile strength increases as the strain rate increases while the peak AE hit rate decreases. Meanwhile, the specimen under a relatively higher strain rate shows a relatively wider intrinsic process zone in a more diffuser manner, lots of distributed microcracks relatively decrease stress intensity, thus delay both microcracking localization and macrocrack propagation. These phenomena can be attributed to Stéfan effect. In addition, further tests, namely the combination of AE monitoring and strain measuring systems was designed to understand the correlation between AE event activity and microfracture (i.e., microcracking and microcracking localization). The relative variation trend of cumulative AE events accords well with that of the load-deformation curve.