Effects of solvent system on tape casting of the BaSrTiO<Subscript>3</Subscript>-MgO-based dielectric ceramics containing B<Subscript>2</Subscript>O<Subscript>3</Subscript>

Ba_0.6Sr_0.4TiO₃-MgO-based ceramic slurries with B₂O₃ and Li₂CO₃ as sintering aid were prepared with different solvent systems for tape casting application. The effects of azeotropic mixtures of toluene–ethanol, methyl ethyl ketone (MEK)–ethanol and zeotrpic mixture of xylene–ethanol with a mass ratio of 50:50 on Ba_0.6Sr_0.4TiO₃-MgO-based nonaqueous suspensions with B₂O₃ and Li₂CO₃ as sintering aid were investigated by sedimentation test, rheological measurement, density measurement, and SEM analysis. Without organic additives added, suspensions prepared with the MEK–ethanol mixture present higher flowability with lower viscosity, but less stability because of the smaller viscosity and density of MEK. On the other hand, with organic additives added, the gel structure is formed in slurries prepared with the toluene–ethanol mixture and xylene–ethanol mixture, caused by the reaction of the functional hydroxyl group of PVB and dissociated borate in the slurries. While slurries prepared with the MEK–ethanol mixture were more stable, exhibiting nearly Newtonian flow behavior and significantly lower viscosity.     

Enhancing photovoltaic performance of photoelectrochemical solar cells with nano-sized ultra thin Sb2S3-sensitized layers in photoactive electrodes

Sb₂S₃-sensitized photoelectrochemical solar cells were prepared with photoactive electrodes containing thick and thin Sb₂S₃-sensitized layers, polyaniline hole conductor containing little amount of de-ionized water, and Pt counter electrodes. The device with the thin Sb₂S₃-sensitized layer shows much higher power conversion efficiency (3.78 %) than that of the device with the thick Sb₂S₃-sensitized layer (0.88 %). The FESEM and TEM images reveal that the device with the thin Sb₂S₃-sensitized layer is nanostructure, as that of the traditional quantum dot sensitized solar cell, while the device with the thick Sb₂S₃-sensitized layer is flat configuration. The photoactive electrode with the thin Sb₂S₃-sensitized layer shows higher light absorption, lower charge transfer resistance and longer electron lifetime compared with that of the one with the thick Sb₂S₃-sensitized layer, which results in higher photocurrent generation of the device.     

The properties of ion-implanted LiNbO3 waveguides measured by the RBS and ion beam etching stripping methods

Z-cut LiNbO₃ crystals were implanted at room temperature with 3.0 MeV O ions with a fluence of 6 × 10¹⁴ ions/cm². The effective refractive index of the guided mode was obtained by the prism coupling technique combined with mechanical stripping (ion beam etching) at room temperature. Surface layers, with thicknesses of 300, 630, 880, 1100, and 1500 nm, were removed. The channel spectra of LiNbO₃ waveguides with different etching depths were measured by the RBS technique. The damage profile of the LiNbO₃ waveguide was studied by dechannelling analysis with a multiple scattering function based on the channel spectrum. The refractive index profile was calculated based on the lattice damage ratio. The effective refractive index of the guided mode simulated by BPM showed good agreement with the experiment value.     

Silicon nitride-metal joints: phase equilibria in the systems Si3Ni4-Cr,Mo, W and Re

Phase diagrams in the ternaries Cr-Si-N, Mo-Si-N, W-Si-N and Re-Si-N are established. No ternary phase is found. Si₃N₄ coexist under argon at 1273 K with all binary Cr-silicides but not with chromium, with MoSi₂ and Mo₅Si₃ but not with Mo₃Si or molybdenum, with WSi₂, W₅Si₃ and tungsten, and with ReSi₂, Re₁₇Si₉ and rhenium. At 1673 K, Si₃N₄ is found in coexistence with Cr₅Si₃, MoSi₂, Mo₅Si₃, WSi₂, W₅Si₃, ReSi₂ and Re₁₇Si₉. The implications of these phase equilibria for joining silicon nitride with low thermal expansion metals are discussed.     

Thin film deposition using a plasma source with a hot refractory anode vacuum arc

Vacuum arc generated plasma was used to deposit metallic Al, Zn, and Sn coatings on glass substrates. An arc mode with a refractory anode and an expendable cathode (the “hot refractory anode vacuum arc”), overcomes macroparticle (MP) contamination experienced in other arc modes. I = 100–225 A arcs were sustained between a water-cooled coating source cathode and an anode, which was heated by the arc, separated from each other by a 10-mm gap, for times up to 150 s. The distance from the arc axis to the substrate (L) was 80–165 mm. Film thickness was measured with a profilometer. It was found that the deposition rate increased with time to a peak, and then decreased to a steady-state value. The peak occurred earlier when using short anode (9 mm long), e.g., with the Al cathode, L = 110 mm, and I = 200 A, the peak was at t _p = 15 s after arc ignition while with the long anode t _p = 45 s. t _p decreased with I, from 45 s with I = 100 A, to 10 s with I = 225 A with the short anode. The peak is believed to appear due to initial condensation of cathode material (including MPs) on the cold anode, and its subsequent evaporation as the anode heated. In the later HRAVA steady state, a balance between condensation and evaporation on the anode is established. The deposition rate peak was significant with low melting temperature Al and Zn cathodes, which produce many MPs, and negligible with Cu and Ti cathodes.     

Influence of Fe catalytic doping on the properties of TiO2 nanoparticles synthesized by microwave method

The present work focus on the development of an effective process for undoped and Fe doped TiO₂ powders production by microwave technique. The influence of Fe doping on the structure, phase, vibrational bands and optical properties of TiO₂ were discussed. The X-ray diffraction patterns of nanoparticles revealed a preferentially oriented (101) anatase phase for TiO₂ and transforms to rutile TiO₂ with Fe doping. Fourier transform infrared spectra analysis confirmed the phase transformation from anatase to rutile TiO₂ with Fe doping. The UV–visible spectra showed the increase in absorption band with Fe doping when compared with undoped TiO₂ nano particles, and optical band gap decreased slightly with Fe doping. SEM micrographs revealed spherical shaped grains of TiO₂ with high homogeneity, with a subsequent reduction in the agglomeration of particles with Fe doping suggesting its potential application for better photo catalytic activity.     

A New Highly Anisotropic Rh-Based Heusler Compound for Magnetic Recording

The development of high-density magnetic recording media is limited by superparamagnetism in very small ferromagnetic crystals. Hard magnetic materials with strong perpendicular anisotropy offer stability and high recording density. To overcome the difficulty of writing media with a large coercivity, heat-assisted magnetic recording was developed, rapidly heating the media to the Curie temperature T_c before writing, followed by rapid cooling. Requirements are a suitable T_c, coupled with anisotropic thermal conductivity and hard magnetic properties. Here, Rh₂CoSb is introduced as a new hard magnet with potential for thin-film magnetic recording. A magnetocrystalline anisotropy of 3.6 MJ m⁻³ is combined with a saturation magnetization of μ₀M_s = 0.52 T at 2 K (2.2 MJ m⁻³ and 0.44 T at room temperature). The magnetic hardness parameter of 3.7 at room temperature is the highest observed for any rare-earth-free hard magnet. The anisotropy is related to an unquenched orbital moment of 0.42 μ_B on Co, which is hybridized with neighboring Rh atoms with a large spin–orbit interaction. Moreover, the pronounced temperature dependence of the anisotropy that follows from its T_c of 450 K, together with a thermal conductivity of 20 W m⁻¹ K⁻¹, make Rh₂CoSb a candidate for the development of heat-assisted writing with a recording density in excess of 10 Tb in.⁻².     

Vortex behavior in Nb3Ge microbridges

We have fabricated Nb₃Ge microbridges, including those with variablethickness geometry, with submicrometer lengths, by means of plasma etching combined with lithographic techniques. The measuredI-V characteristic and the temperature variation of the critical current are consistent with that expected from the vortex concept. However, a deviation is observed in the microwave steps: the magnitude of the critical current oscillates with microwave power in a manner which agrees with an analog simulation based on the RSJ model. We have found a strong correlation between the bridge behavior and the film parametersT _c and ρ _n (normal resistivity). The critical current is reduced rapidly with a decrease inT _c and an increase in ρ _n , while in high-T _c and low-ρ _n bridges a linearI-V characteristic appears at low voltages. Taking into account the influence of pinning, we discuss the results in terms of vortex motion.     

Improvement of brightness with Al2O3 passivation layers on the surface of InGaN/GaN-based light-emitting diode chips

In this study, sputtered 50, 70 and 90 nm thick Al₂O₃ thin films were evaluated as a passivation layer in the process of InGaN-based blue as LEDs (Light-Emitting Diodes) in order to improve the brightness of LED lamps. For packaged LED lamps, lamps with Al₂O₃ passivation layer had higher brightness than ones with SiO₂ passivation layer, and LED lamps with 90-nm Al₂O₃ passivation layer were the brightest among four kinds of lamps. Although lamps with Al₂O₃ passivation layer had a bias voltage 0.25 V at 20 mA forward current higher the lamps built with SiO₂ passivation layer, their brightness was improved about 13.6% higher than the conventional LEDs with no change in emitting wavelength.     

The effect of titanium addition on the microstructure,mechanical and tribological properties of Ni3Si alloys prepared by powder metallurgy method

Ni₃Si alloy with different content of titanium was fabricated by powder metallurgy method. The microstructures, hardness and tribological properties of the alloys were investigation. The results showed that pure Ni₃Si alloy was composed of β₁‐Ni₃Si phase and γ‐Ni₃₁Si₁₂ phase, and Ni₃Ti phase formed with titanium addition. The hardness of the alloy decreased with the increasing titanium content. The friction coefficient of pure Ni₃Si alloy increased with the increasing load, while the friction coefficient of the alloy with titanium addition decreased. The wear rates of the alloys were all increased with increasing load, and the alloy with 5 % titanium addition had the best wear resistance properties. The wear mechanisms of the alloys were abrasive wear at low load, and the wear mechanisms changed to oxidative wear at high load.     

Metal-semiconductor transition in Nb-doped ZnO thin films prepared by pulsed laser deposition

The structural, electrical and optical properties of Nb-doped ZnO films were investigated with different Nb contents (0, 0.15, 0.31, 0.46, 0.62, and 0.94 at.%) in this article. The film with 0.46 at.% Nb content showed the lowest resistivity of 8.95 × 10^− 4 Ω cm and high transmittance about 80% with high c-axis orientation. The undoped ZnO film showed a semiconducting behavior. And Nb-doped ZnO films showed a metal-semiconductor transition (MST), which was connected with localization of degenerate electrons. The films showed metallic conductivity at temperatures closer to the ambient temperature and semiconducting behavior at lower temperatures. It was noted that the NZO films with much lower Nb concentration of 0.15 at.% presented MST compared with other transparent conducting oxides films.     

Tensile deformation behavior of nano-sized Mo particles reinforced SnAgCu solders

In this work, tensile deformation of Sn-3.8Ag-0.7Cu (SAC387) solder and composite of SAC387 reinforced with nano-sized Mo particles have been studied with strain rates from 10⁻⁵ to 10⁻¹ s⁻¹ and temperatures of 25, 75 and 125 °C. It is found that the yield strength (σ_Y.S) and strain hardening exponent (n) are increased with the strain rate, but the n values decrease with increasing temperatures. The n values of the composite solder are also increased with the percentage of the Mo nano-particles (up to 1 wt.%) and thereafter decrease with further increasing of the Mo particle. The strain rate dependence of the Hollomon parameters is found to be stronger at higher temperatures for SAC387 solder, but it is weaker for the composite solders. Empirical equations for σ_Y.S and Hollomon parameters with strain rate and temperatures have been found for both SAC387 and composite solders. Finally, the fracture surfaces of the solders are examined.     

Diffuse ferroelectric phase transition in SrTiO<Subscript>3</Subscript>-BiScO<Subscript>3</Subscript> system ceramics

Ceramic samples of the (1−x)SrTiO₃-(x)BiScO₃ system with x = 0, 0.05, 0.1, 0.2, 0.3, 0.4, and 0.5 have been synthesized for the first time. X-ray diffraction data showed that the samples with x = 0.2, 0.3, and 0.4 at room temperature comprise the mixture of two phases: (i) cubic nonpolar phase with Pm3m structure and (ii) tetragonal polar phase with P4mm structure. The temperature dependences of permittivity and dielectric loss tangent of these samples exhibit anomalies characteristic of ferroelectrics with diffuse phase transitions.     

Development of an osmotically-driven pellet coated with acrylic copolymers (Eudragit® RS 30 D) for the sustained release of oxymatrine,a freely water soluble drug used to treat stress ulcers (I): in vitro and in vivo evaluation in rabbits

Purpose: To develop an osmotically-driven pellet coated with polymeric film for sustained release of oxymatrine (OMT), a freely water soluble drug.

Methods: Pellet containing OMT and sodium chloride (NaCl), an osmotically active agent, were prepared by extrusion/spheronization and then coated with acrylic copolymers (Eudragit^® RS 30 D) by the fluidized bed coating process. In vitro release and swelling behavior studies were employed to optimize and to evaluate the sustained-release behavior from the osmotically-driven pellets with film coated. Finally, in vivo evaluation in rabbits was employed to investigate the sustained plasma level of OMT and its active metabolite matrine.

Results: It was found that the F3 formulation, prepared with 20% NaCl and an 8% coating level, showed a continuous NaCl-induced water influx into the pellets providing a gradual sustained release of OMT for over 12?h. Finally, we confirmed that oral OMT with sustained release led to a gradual sustained plasma profile of both OMT, with a reduction in its bioavailability, and MT with an increase in the bioavailability compared with that of oral OMT with immediate release. Conclusions: The pharmaceutical parameters obtained suggested the potential usefulness of oral OMT with sustained release for the treatment of stress ulcers, as well as reducing the risk of MT-induced side effects.     

Stability of TaRhx as a potential diffusion barrier for Cu metallization: capacitance–voltage tests after bias temperature stress

Amorphous TaRh_x was integrated in metal oxide semiconductor (MOS) capacitors with Cu gate metallization (Al/Si/25 nm SiO₂/10 nm TaRh_x/Cu). The stability of TaRh_x diffusion barriers was investigated under bias temperature stress testing using capacitance–voltage (C–V) measurements. The stability of these capacitors was compared with similar capacitors with TaN_x as the diffusion barrier layer or with capacitors with no diffusion barrier. The electrical measurements were compared with compositional information obtained by backside secondary ion mass spectroscopy (SIMS) and transmission electron microscopy (TEM). Comparison of C–V measurements on capacitors with TaRh_x/Cu and TaRh_x/Al gate metallizations revealed that both mobile alkali ions and Cu⁺ contribute to the flatband voltage shift of the MOS capacitors. C–V measurements of capacitors with various barriers showed that the mobile ion concentration (Cu⁺) in the capacitors with TaRh_x diffusion barriers is reduced to 32 % of the value for capacitors with no diffusion barrier. In contrast, capacitors with TaN_x barriers showed the lowest mobile ion concentration among all the barrier types. Based on flatband voltage shift values, TaN_x barriers outperform TaRh_x barriers. However, if the percentage of deformed C–V curves is used as the reliability criterion, both barriers perform quite similarly. Compositional analysis data suggests that the concentrations of the diffused species are below the detection limits of SIMS and TEM. This work demonstrated the importance of employing electrical reliability tests for evaluation of potential diffusion barrier materials.     

Oxidation of Am(III) to Am(IV) with ozone in solutions of heteropolyanions

Oxidation of Am(III) in the presence of K₁₀P2W₁₇O₆₁ and K₈SiW₁₁O₃₉ (L) at 20dGC was studied by spectrophotometry. Am(III) is oxidized with ozone to Am(IV) only in the pH range 3.5–1.0. In the case of formation of a complex with Am: L = 1: 1, the reaction is approximately first-order with respect to the metal, and its rate decreases with a decrease in pH from 3.5 to 1.0. Am(IV) in solution in the presence of ozone is slowly reduced with products of water α-ray radiolysis, predominantly with ?₂?₂. The rate constant of the reaction of Am(IV) with ?₂?₂ was estimated.     

Structural, electrical and optical properties of Si doped ZnO films grown by atomic layer deposition

Si doped ZnO (SZO) films with various Si concentrations were deposited by atomic layer deposition at 300 °C using triethyzinc, tris(dimethylamino)silane and H₂O₂ as the precursors. The influences of Si doping concentration on structural, electrical and optical properties of ZnO films have been investigated. All the films exhibited a highly preferential c-axis orientation. A minimum resistivity of 9.2 × 10^?4 Ω cm, with a carrier concentration of 4.3 × 10²⁰ cm^?3 and a Hall mobility of 15.8 cm²/Vs, was obtained for SZO film prepared with the Si concentration of 2.1 at%. The increase of conductivity with Si doping was attributed to the presence of Si in +3 valence state acting as donor in ZnO and the increases of oxygen vacancies with Si concentration as proven by XPS measurements. The optical bandgap of SZO films initially increased from 3.25 to 3.55 eV with increasing of Si concentration to 2.1 at%, then decreased with further increase of Si concentration. The blue shift of band gap of SZO films with increasing carrier concentration can be explained by the Burstein-Moss (B-M) effects.     

Sliding friction properties of austenite- and martensite-based white cast iron containing 8.5% chromium

In this paper, the wear resistance and track of austenite- and martensitic-based white cast iron (AWCI and MWCI) containing 8.5% chromium have been investigated with micro-fricative wear tester, optical microscopy (OM), scanning electron microscopy with EDS (SEM–EDS), and 3D digital microscope. The results show that significant differences exist in the hardness (AWCI: HRC41.2, MWCI: HRC55.8) and impact toughness (AWCI: 28.6 J cm⁻², MWCI: 20.3 J cm⁻²) between as-forged AWCI and forged + heat-treated MWCI samples. At 20 N load, due to AWCIs’ low resistance matrices (pearlite and austenite), the wear performance is poor. The depth of the wear track in AWCI sample was 45.479 μm, lower than 70.810 μm in MWCI sample, indicating that the wear performance of AWCI sample was better than that of MWCI at 120 N. Additionally, associating with oxide film and wear debris on the samples’ surfaces, the sliding friction coefficient of AWCI increases with load increasing from 20 N to 60 N then decreases with load increasing from 60 N to 120 N, whereas the friction coefficient for MWCI decreases with load in the range of 20–60 N then increases with load increasing from 60 to 120 N.     

Characterization of transverse tensile, interlaminar shear and interlaminate fracture in CF/EP laminates with 10 wt% and 20 wt% silica nanoparticles in matrix resins

The transverse tensile properties, interlaminar shear strength (ILSS) and mode I and mode II interlaminar fracture toughness of carbon fibre/epoxy (CF/EP) laminates with 10 wt% and 20 wt% silica nanoparticles in matrix were investigated, and the influences of silica nanoparticle on those properties of CF/EP laminates were characterized. The transverse tensile properties and mode I interlaminar fracture toughness (G_IC) increased with an increase in nanosilica concentration in the matrix resins. However, ILSS and the mode II interlaminar fracture toughness (G_IIC) decreased with increasing nanosilica concentration, especially for the higher nanosilica concentration (20 wt%). The reduced G_IIC value is attributed to two main competing mechanisms; one is the formation of zipper-like pattern associated with matrix microcracks aligned 45° ahead of the crack tip, while the other is the shear failure of matrix. The ratio of G_IIC/G_IC decreased with the concentration of silica nanoparticles, comparable with similar CF/EP laminates with dispersed CNTs in matrix. Fractographic studies showed that interfacial failure between carbon fibre and epoxy resin occurred in the neat epoxy laminate, whereas a combination of interfacial failure and matrix failure occurred in the nanosilica-modified epoxy laminates, especially those with a higher nanosilica concentration (20 wt%).     

Structural,physical, and optical characterization of (Nd3+/Eu3+)-doped zinc-rich silica–borate glasses

In this study, zinc–silica–borate glass structures doped with rare earth (RE) oxides Eu₂O₃ and Nd₂O₃ were synthesized with classical melting–quenching technique. 60ZnO–10SiO₂–(30 – x)B₂O₃:xRE (x?=?0, 0.5, 1, 1.5 mol%) composition was chosen as the structure. The doping effect of two different rare earth oxides (individually) at different ratios was investigated according to the structural, physical, and optical properties of the glass structure. Structural properties of the synthesized glasses were determined with Fourier transform infrared (FTIR) device, and densities (ρ) and molar volumes (V_m) of the glasses were measured with Archimedes method, and optical properties were determined with UV–Visible (UV–Vis-NIR) device. FTIR results show that BO₃ units increased in all RE-doped glasses. While densities of the synthesized glasses varied between 3.755 and 3.941 g cm^??3, indirect bandgaps varied between 3.219 and 3.645 eV. The glass with the highest transmittance was the 1% Eu₂O₃-doped glass with a transmittance of 84%. While band edges shifted slightly toward short wavelengths in glasses doped with Nd₂O₃, they shifted to longer wavelengths in glasses doped with Eu₂O₃.