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The aim of this work is to highlight the correlation between treatment conditions, composition, and structure of reduced zinc oxide (ZnO:Zn) with optical and radioluminescence properties for the production of high yield scintillating powders. Purchased zinc oxide (ZnO) powders (≈0.35 ± 0.15 μm) were thermally reduced in Ar/H2 (3%) atmosphere at temperatures ranging between 600 (≈0.40 ± 0.17 μm) and 1000 °C (≈6.4 ± 1.6 μm), obtaining ZnO:Zn powders. The reduction degree, evaluated through energy dispersive spectroscopy, showed a linear increase from 0% up to 20% (800 °C sample), reaching a plateau condition at about 25% for the highest treatment temperatures (1000 °C sample). Structural analysis highlighted the existence of a threshold temperature, previously reported in the literature, around 800 °C, beyond which (i) the grain size remarkably increases, (ii) the shape changes from hexagonal to round-shaped, and (iii) the intensity of electron spin resonance (ESR)-active defects at g = 1.9596 decreases for a new resonance at g = 2.0105. Additionally, a substantial variation, from 5.63 ± 0.02 down to 5.2 ± 0.1 g/cm3, of the skeletal density and a slight contraction of the optical bandgap are observed. Unlike the structural properties, PL and x-ray radioluminescence showed a continuous increase of the green emission intensity, associated with ESR-active ionized oxygen vacancies and ESR non-active recombination centers, and of the PL defective lifetimes (33 ns < τfast < 88 ns, 395 ns < τslow < 930 ns). [ABSTRACT FROM AUTHOR]

Aim of the present study is to investigate how synthetic boehmite alumina (BA) nanoparticles modify the viscoleastic and fracture behaviour of linear low-density polyethylene. Nanocomposites containing up to 8 wt% of untreated and octyl silane-functionalized BA nanoparticles, were prepared by melt compounding and hot pressing. The BA nanoparticles were finely and unformly dispersed within the matrix according to scanning electron microscopy inspection. The results of quasi-static tensile tests indicated that nanoparticles can provide a remarkable stiffening effect at a rather low filler content. Short term creep tests showed that creep stability was significatively improved by nanofiller incorporation. Concurrently, both storage and loss moduli were enhanced in all nanocomposites, showing better result for surface treated nanoparticles. The plane-stress fracture toughness, evaluated by the essential work of fracture approach, manifested a dramatic increase (up to 64%) with the BA content, with no significant differences among the various types of BA nanoparticles. [ABSTRACT FROM AUTHOR]

Abstract: A multilayer catalyst consisting of a electrophoretically deposited thin film of carbon nanotubes (CNTs) on a substrate of carbon fibers, followed by a coating of polymer-derived silicon carbonitride (SiCN), which is then decorated with a monolayer of transition metals is shown to perform at the upperbound of the phenomemological prediction from an earlier work . A figure-of-merit for first order kinetics is equal to 4600Lmin−1 [NaBH4]−1 gmet −1, which is nearly 30 times the value reported in literature, is achieved. This high FOM is attributed to the CNT-thin film, as opposed to the thick CNT-paper used in previous work, thus needing merely 0.15wt% quantities of precious metals for effective catalysis. This new architecture corroborates the concepts that: (i) the catalytic activity derives mainly from the surface of the CNT substrate, and (ii) the silicon carbonitride interlayer is instrumental in dispersing the transition metals into a monolayer. The hydrogen generation rate (HGR) for zero order kinetics, which is obtained when [NaBH4]>0.03M, is measured to be 75Lmin−1 gmet −1, which is among the higher values reported in the literature. The present multilayer catalysts are able to perform without fading for many cycles, presumably because the bondings in the substrate are predominantly covalent. This feature adds further uniqueness to this multilayer catalyst. [Copyright &y& Elsevier]

Abstract: We report further increase in the figure-of-merit (FOM) for hydrogen generation from NaBH4 than reported in an earlier paper , where a sub-nanometer layer of metal catalysts are deposited on carbon nanotube paper (CNT paper) that has been functionalized with polymer-derived silicon carbonitride (SiCN) ceramic film. Ternary, Ru–Pd–Pt, instead of the binary Pd–Pt catalyst used earlier, together with a thinner CNT paper is shown to increase the figure-of-merit by up to a factor of six, putting is above any other known catalyst for hydrogen generation from NaBH4. The catalysts are prepared by first impregnating the functionalized CNT-paper with solutions of the metal salts, followed by reduction in a sodium borohydride solution. The reaction mechanism and the catalyst efficiency are described in terms of an electric charge transfer, whereby the negative charge on the BH4 − ion is exchanged with hydrogen via the electronically conducting SiCN/CNT substrate . [ABSTRACT FROM AUTHOR]

Abstract: In this work, a powder metallurgy procedure for the preparation of bulk hydrogen storage alloys based on MgH2 is presented. To meet the requirements of high specific surface area, high porosity and microstructural stability, all desirable features for this sort of material, a powder mixture with the following composition MgH2–15Nb–2B–1C has been ball-milled to reduce down to a few nanometers the average crystallite size of the main components. Another effect of milling, conducted under a static air atmosphere, was the in situ formation of a limited (5% approx.) amount of MgO, that, as shown by recent literature studies, may beneficially influence both the microstructural stability of the hydride alloy and the kinetics of adsorption and desorption of hydrogen. The powder was subsequently consolidated by spark plasma sintering, a process that, thanks to the limited working temperature and pressure, should not change to a significant extent the nanostructure of the ball-milled powder. The stability against recrystallisation of the consolidated specimens was verified by a number of heating and cooling cycles, up to 100, simulating the temperature conditions involved with the adsorption–desorption cycles. At the end, the crystallite size of the Mg-hydride phase was still in the nanometric range, although an unwanted oxidation, due to air contamination of the furnace atmosphere, reduced significantly the content of the hydrogen storing phase. [Copyright &y& Elsevier]

Abstract: In this work, metallic tin, SiC and metallic zinc, were mixed with a copper containing alkali-lime-silica glass in order to investigate the precipitation process of colloidal copper-nanoparticles induced by external reducing agents. Metallic tin has been traditionally employed in copper reduction even by ancient glass makers, while SiC, although suggested from the literature, was not yet properly studied for this application. Moreover, metallic zinc was chosen on the basis of Ellingham’s diagrams and used for the first time for inducing copper reduction in glass. Samples with different reducing agent concentrations were prepared. The structural and optical properties of the samples were characterized by means of X-ray diffraction (XRD), UV–vis absorption and fluorescence spectroscopy. Moreover, the redox processes between the different reducing agents and cupric oxide were studied by means of differential scanning calorimetry (DSC). [Copyright &y& Elsevier]

A multitechnique approach, consisting of x-ray diffraction, differential thermal analysis, low frequency Raman scattering from the acoustic vibrations of nanoclusters, and transmission electron microscopy associated with selected area diffraction, has been used to study the nucleation and crystallization processes in SiO[sub 2]–Ga[sub 2]O[sub 3]–K[sub 2]O glasses. The specific aim was to determine the structure and the size distribution of nanoparticles embedded in the glass matrix. It has been found that nearly spherical nanocrystals of β-Ga[sub 2]O[sub 3], with a size of ∼2–3 nm, nucleate during thermal treatments at 900 °C. Crystallization was observed after annealing at higher temperature. The amount of the crystalline phase and the mean size of the nanocrystals increased with heat treatment, time and temperature. β-Ga[sub 2]O[sub 3] was the only crystalline phase to appear in all glass samples. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

This work is aimed at a deeper understanding of the polarity-sensitive electro-optical response observed in a liquid crystal (LC) cell with asymmetric insertion of thin films of TiO[SUB2]-V[SUB2]O[SUB5] having a Ti/V atomic ratio of 1/1, prepared by sol-gel synthesis on a transparent indium tin oxide substrate. After preliminary structural characterization of the films, the electro-optical response of the liquid crystal cells containing a TiO[SUB2]-V[SUB2]O[SUB5] layer has been analyzed. The voltage thresholds of the Freedericksz transition are increased or decreased for anodic or the cathodic polarization, respectively, of the TiO[SUB2]-V[SUB2]O[SUB5] film. In such a way a polarity-sensitive electro-optical response is generated that has the same frequency as the field applied. Impedance and cyclic voltammetry measurements were performed on liquid crystal cells having TiO[SUB2]-V[SUB2]O[SUB5] films inserted as the electrode, for as-deposited films as well as for films annealed at 400 °C. The LC cell containing thermally annealed Ti/V 1/1 film showed a rectified square wave response instead of the usual impulsive one, quadratic versus electric field. On the contrary, the LC cell containing as-deposited Ti/V 1/1 film exhibits more complex electro-optical behavior with a weak asymmetric response. All the measurements suggest that charge redistribution of the ions, always present in the films, occurs during the intercalation-deintercalation processes induced by the voltage applied, and this is responsible for changes of the effective electric field that act on the liquid crystal layer. [ABSTRACT FROM AUTHOR]

Dissolution and gelation procedures have a great influence on gelation time, microstructure and mechanical properties of reconstituted collagen products. We have investigated the dissolution of atelocollagen in CO2/water solutions at low temperature (4 °C) at different CO2 pressures (0.3-0.9 MPa), as well as gelation kinetics and physico-chemical properties of the hydrogel obtained after CO2 removal. Compared to conventional methods, the CO2-assisted technique resulted in faster soluble collagen dissolution and faster gelation into transparent gels characterized by thin 10 nm fibrils. Electrophoresis and CD spectroscopy demonstrated that the process did not denature the soluble collagen. The possibility to obtain collagen dissolution and gelation without the use of chemical agent other than water and CO2 makes this process particularly appealing for biomedical applications. [ABSTRACT FROM AUTHOR]

Kenaf fibres of different aspect ratios (L/D = 30 and 160) were melt compounded in an internal mixer with two types of starch-grafted-polypropylene matrices (G906PF and G906PJ) at various loadings, i.e. 10, 20 and 30 wt%. The compound was then compression-moulded into plaques of 1-mm thickness. Thermal, rheological and dynamic mechanical properties of the composite samples were investigated by several techniques involving differential scanning calorimetry, thermogravimetric analysis, melt flow index, Vicat softening point and dynamic mechanical thermal analysis. The results indicated that both thermal and mechanical properties of the composites were remarkably improved by kenaf fibres. Loss modulus and loss factor showed a shift of peak transitions to higher temperatures. Finally, the properties of the investigated composite materials were not affected by the fibre aspect ratio. [ABSTRACT FROM AUTHOR]

Abstract: In this work, the deposition of copper phthalocyanine (CuPc) thin films by glow discharge-induced sublimation (GDS) is investigated. The physical properties of the deposited films are studied by FT-IR spectroscopy and nitrogen physisorption measurements. The gas/film interaction of the deposited coatings is tested by measuring their IR response and electrical conductivity in NO2- and NO-containing atmospheres. [Copyright &y& Elsevier]

In the search of new materials for electrodes in electrochromic devices and in asymmetric liquid crystal cells, some modified vanadium oxide thin films has been investigated. The new gels have been generated by the addition of 10% of bismuth (atomic ratio) to the precursors mixture. The sol–gel route started from metal alkoxides, vanadium oxo iso-propoxide and BiCl3 dissolved in ethanol (99%), to give the atomic ratio Bi/V=1:10.The crystallization temperature of such bulk gels has been found by DTA analysis to occur at 320 °C, while only seeds of a crystal phase are found after annealing the dip-coated films at 400 °C, identified as Bi4V6O21 (PDF card no. 33-222). Microscopic visual investigation and micro-Raman analysis were performed on the deposited films, “as grown” and “400 °C annealed”. Finally, the films have been tested as electrodes in asymmetric nematic liquid crystal (NLC) cells, to investigate the rectification effect. The electro-optic measurements were performed in modified nematic liquid crystal cells for both “as-deposited” and annealed films. The voltage dependence of the electro-optical response and the current flow have been analyzed at the same time in the voltage range −10/+10 V. A model based on the electrical interaction between both the indium tin oxide (ITO)-Bi/V oxide films and Bi/V oxide films–liquid crystal interfaces is proposed, to explain the electric and electro-optic asymmetric responses of the cells. [Copyright &y& Elsevier]

The spectroscopic properties of 3-hydroxyflavone (3-HF) molecules entrapped in films and in monoliths of sol–gel derived organically modified silicates (Ormosils) xerogels are studied by excitation and fluorescence spectroscopy as a function of the sol–gel precursors used for the synthesis. Different molar ratios of tetraethoxysilane (TEOS), methyltriethoxysilane (MTES) and phenyltriethoxysilane (PTES) as precursors are used for the sol preparation. Emission and excitation spectra in the ultraviolet–visible range and photo-degradation curves as a function of time are collected with a spectrofluorimeter. The 3-hydroxyflavone optical properties change in the different networks, owing to the effects of the chemical environment on the excited state intramolecular proton transfer and to the solubility of the dye molecules in the different sol–gel systems. It turns out that the spectroscopic features can be used to probe the chemical state of the dye molecules microenvironment. [Copyright &y& Elsevier]

Titania and titania/vanadia thin films were prepared via solgel process, starting from alcoholic solution of Ti (OBu) 4 for pure titania films and from Ti (OBu) 4 /VO(OPr i ) 3 for mixed oxide films. The main requirements of these materials for applications in electrochromic devices were investigated, i.e. high charge capacity and electrochemical stability. Microstructural and electrochemical characterizations were carried out both on gels and films leading to the following results: titania films showed a high electro-chemical stability associated with a good charge capacity, whereas mixed oxide systems displayed a high stability again but a lower intercalation/deintercalation charges. The first electro-optic measurements were also performed for two films with different Ti:V atomic ratio, to check the interaction with liquid crystals in modified nematic liquid crystal cells: the cell containing films poorer in vanadia give some rectification effect, but they have a very complex dependence on the applied potential and very slow relaxation times; on the contrary films richer in vanadia exhibits very good response in the liquid crystal cells, compared with another mixed conductivity oxides. [ABSTRACT FROM AUTHOR]

• Atmospheric pressure plasma (APP) deposition of ZnO:Al thin films have been studied. • Spray pyrolysis and plasma deposition methods were compared. • The APP was effective to produce thin films with good electrical properties. Pure and aluminum-doped zinc oxide thin films were produced with an atmospheric pressure plasma (APP) deposition process. Chemical, structural, morphological, electrical and optical analyses were carried out on samples coated with a plasma deposition process and with a spray pyrolysis process for comparison, respectively. The coatings were characterized by a compact layered structure of oxide islands, with a quite uniform distribution of Al in the network. Electrical measurements confirmed the active role and the dispersion of dopant in the zinc oxide network with an observed increase of conductivity even if high resistance values indicated a highly defective microstructure. In comparison to the spray pyrolysis coating the atmospheric pressure plasma coatings show a uniform substrate coverage and a higher chemical purity. [ABSTRACT FROM AUTHOR]

Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) nanocomposite films containing 0.25 wt % of Graphene Oxide (GO) nanoparticles were prepared by solution-casting and characterized by Differential Scanning Calorimetry (DSC), X-Rays Diffraction (XRD) and Positron Annihilation Lifetime Spectroscopy (PALS). Gas transport properties were analyzed in the 295–343 K interval using CO 2 , N 2 , D 2 and He. Neat PHBH films showed a semi-crystalline structure with lamellar crystalline domains of 30 ± 1 and 5 ± 1 nm size in the (020) and (002) direction, respectively. GO dispersion increases the PHBH crystalline fraction from 0.28 to 0.60 wt. % without changing the size of crystalline domains and the structure of the PHBH free volume. Nanocomposite films show mechanical properties similar to those of the neat PHBH film but improved gas barrier properties as consequence of the larger number density the of gas- impermeable crystalline domains. • Graphene oxide/3-hydroxybutyrate co-3-hydroxyhexanoate nanocomposite gas barrier. • Graphene Oxide/3-hydroxybutyrate co-3-hydroxyhexanoate free volume structure. • Graphene Oxide/3-hydroxybutyrate co-3-hydroxyhexanoate mechanical properties. • Measure of CO 2 , N 2 , D 2 , He diffusivity and solubility. [ABSTRACT FROM AUTHOR]