Boundary characteristics in Heavily Deformed Metals

The potential of creating nanostructured metals by plastic deformation to very high strains is currently the subject of intensive research. An important part of this research concerns evolution of the characteristics of deformation induced boundaries, in particular boundary spacing and boundary misorientation. The aim of this paper is to give an overview of the present understanding of the relations between these characteristics, the microscopic deformation mechanisms and the macroscopic deformation mode.     

纳米材料(NSM)的制作方法及其应用

介绍了ＮＳＭ的主要制作方法，包括气相凝固法、机械合金化法和喷雾转化法等。并概述了ＮＳＭ在工业和尖端科学技术领域里的应用状况和前景。     

Surface modification of semiconductor photoelectrode for improved solar cell performance

The investigation is focused on the synthesis of nanostructured TiO₂–CuO admixed photoelectrode and its use as a photoelectrode of high-efficiency PEC solar cells for hydrogen production. TiO₂, in the nanostructured form, has been prepared by hydrolysis of titanium(IV) isopropoxide solution. An improvement in the nanostructured TiO₂ photoelectrode carried out in the present work corresponds to admixing CuO to improve the spectral response. In the present study, photo-electrochemical (PEC) and hydrogen evolution characteristics of new types of ns-TiO₂–CuO admixed/Ti septum-based semiconductor septum photo-electrochemical (SC-SEP PEC) solar cell has been studied. The CuO admixed ns-TiO₂ exhibited a high photocurrent and photovoltage of 18.6 mA/cm² and 680 mV, respectively. The ns-TiO₂–CuO electrode exhibited a higher hydrogen gas evolution rate of 14.00 l/h m².     

Cover Picture: Nanostructured Electrodes and the Low‐Temperature Performance of Li‐Ion Batteries (Adv. Mater. 1/2005)

The cover image shows a scanning electron micrograph of a commercially available track‐etch polycarbonate filter. This porous membrane serves as the host for the template‐synthesis of V₂O₅ nanowires of various diameters. Nanowires that are 70 nm in diameter are shown in the inset. Because V₂O₅ reversibly intercalates Li‐ions, it has potential for use as a cathode material in Li‐ion batteries. On p. 125, Sides and Martin report the use of these V₂O₅ nanowires as tools to investigate the poor low‐temperature performance of Li‐ion batteries.     

X-ray Diffraction Investigation of the Formation of Nanostructured Metastable Phases During Short-Duration Mechanical Alloying of Cu-Al Powder Mixtures

Mechanical alloying is a powder processing technique used to process materials farther from equilibrium state. This technique is mainly used to process difficult to alloy materials in which the solid solubility is limited, and to process materials where non-equilibrium phases cannot be produced at room temperature through conventional processing techniques. In the present work, mechanical alloying/milling of selected compositions in the Al-Cu binary alloy system was carried out at a ball-to-powder weight ratio (BPR) of 2 : 1, to investigate alloying and subsequent heat treatment on microstructural changes as a result of short milling times. Copper-aluminum powder mixtures containing 5, 20, and 40 wt% Al (11, 37, and 61 at% Al, respectively) were subjected to mechanical alloying, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC), after mechanical alloying and subsequent heat treatment. Nanometer-sized grains were observed in the as-milled crystalline powders in all compositions. Crystallite sizes were calculated using the Scherrer formula and found to be in the order of 10-20 nm after 360 minutes of milling time for all compositions. The XRD data show considerable solid solubility extension in these powders, and formation of intermetallic phases due to mechanical alloying and subsequent annealing. These changes are discussed in the context of the Al-Cu phase diagram.     

How light gets through periodically nanostructured metal films: a role of surface polaritonic crystals

The physical origin of the enhanced optical transmission of periodically structured films related to surface plasmon polaritons is discussed from first principles. The enhancement of transmission through smooth, randomly rough and periodically nanostructured films is considered. Analysis shows that any metal (or dielectric) nanostructured film can exhibit enhanced transmission in certain spectral ranges corresponding to surface plasmon (or phonon) polariton Bloch mode states on a periodic structure. Resonant tunnelling via these states is responsible for the transmission enhancement. The properties of surface polaritonic crystals are analogous to those of photonic crystals and can find numerous applications for scaling down optical devices to nanometric dimensions as well as for designing novel nanostructured materials whose optical properties are determined by surface polariton interaction in a periodic structure.     

Surface modification of zinc oxide nanoparticles by aminopropyltriethoxysilane

Commercial zinc oxide nanoparticles (20–30 nm) were coated by aminopropyltriethoxysilane (APTES) under varying environments. Three different processes, acidic, basic and toluene were used. The effects of coating conditions (acidic, basic and toluene) on the grafting, structural and optical properties of these nanoparticles were studied. In the three cases, it was possible to control the coating and according to X-ray diffraction, BET, TEM and SEM results, it is clear that the APTES coating plays a role of growth inhibitor even at 800 °C. From diffuse reflectance measurements, one can notice that the grafting process did not modify the transmittance spectra of ZnO.     

Magnetic and structural properties of nanostructured (Fe65Co35)100−xCrx (x = 0, 10) powders prepared by mechanical alloying process

This work focuses on the preparation of nanostructured (Fe₆₅Co₃₅)_100−xCr_x (x = 0, 10) powders by mechanical alloying. The powders are milled for different milling times (up to 90 h). Characterizations of the milled powders were carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibratory sample magnetometer (VSM). It was observed that the formation of bcc-FeCo and bcc-FeCoCr phases were completely accomplished after 60 and 90 h of milling, respectively. The grain size decreases and the microstrain increases with increasing the milling time. In the initial stages of milling (up to 15 h) for the (Fe₆₅Co₃₅)₉₀Cr₁₀ powders, the saturation magnetization (M_s) decreased but further milling (up to 90 h) increased the M_s. However, the trend for coercivity was different and three stages were observed. An initial increasing stage (up to 15 h of milling), followed by a reducing middle stage (up to 60 h of milling) and then again an increasing final stage (up to 90 h milling). Besides, for the same milling time of 90 h, the addition of 10 at.% of Cr to Fe₆₅Co₃₅ powders leads to higher coercivity and lower saturation magnetization.     

Enhancement of gastrointestinal absorption of isoliquiritigenin by nanostructured lipid carrier

Isoliquiritigenin (ISL) has various pharmacological effects. Our previous studies demonstrated that the oral bioavailability of ISL was low and the concentration-time profiles of ISL exhibited double peaks after oral administration in rat, but the underlying mechanisms remained unknown. The objective of this study was to clarify the gastrointestinal (GI) absorptive characteristics of ISL using in situ intestinal perfusion model as well as explain double peaks phenomenon after oral administration and to evaluate the potential of using nanostructured lipid carrier (NLC) as an oral delivery carrier for poorly water soluble drugs. The results showed that the absorption percent in the stomach for 2 h was less than 10%, the absorption process of intestine was first-order process with passive diffusion mechanism, and the main absorptive segment was colon. Isoliquiritigenin-loaded nanostructured lipid carrier (ISL-NLC) could enhance oral absorption of ISL. The reason for the Double Peak Phenomenon following oral administration in ISL plasma concentrations versus time profiles is Variability of Absorption within different regions of the gut, very low absorption from the stomach, jejunum, duodenum and ileum compared with the absorption from the colon. A pharmacokinetic study was conducted in rats after a single dose oral administration of ISL at 20 mg/kg in the form of either ISL-NLC or isoliquiritigenin solution (ISL-Sol). The AUC _(0∼∞) values were 5.43 ± 0.67 μg h mL⁻¹ and 29.60 ± 2.88 μg h mL⁻¹ after administration of the ISL-Sol and ISL-NLC, respectively. The relative bioavailability of ISL-NLC to isoliquiritigenin was 545%. Our studies provide evidence that NLC are valuable as an oral delivery carrier to enhance the absorption of a poorly water soluble drug, ISL.