Metallic glass nanofilms

In this paper, we report for the first time the spontaneous formation of Zr-based metallic glass nanofilms by developed dynamic forced-shear-rupture technique of hat-shaped specimens. The obtained nanofilms have about 100 nm thickness and other two geometrical dimensions can reach micrometer scales. Their glassy nature and structural stability were solidly identified. It was found that electrons with the wavelength of less than 0.165 Å could make the metallic glass nanofilms transparent. Furthermore, it is clearly shown that shearbanding instability still afflicts such 100-nm-thick metallic glass nanofilms.

Size modification of Au nanoparticles induced by slow highly charged ions Ar-40(q+) irradiation

Size modification of Au nanoparticles (NPs), deposited on the Au-thick film surface and irradiated by slow highly charged ions (SHCI) 40Arq+ (3 6 q 6 12) with fixed low dose of 4.3 1011 ions/cm2 and various energy ranging from 74.64 to 290.64 keV at room temperature (293.15 K), was investigated by atomic force microscopy (AFM) and transmission electron microscopy (TEM). The effect of projectile kinetic energy on the modified size of NPs was explored by an appropriate choice of the fixed process parameters such as ion flux, irradiation temperature, incident angle, irradiation time, etc. The morphological changes of NPs were interpreted by models involving collisional mixing, Ostwald ripening (OR) and inverse Ostwald ripening (IOR) of spherical NPs on a substrate. A critical kinetic energy as well as a critical potential energy of the projectile in the Au NPs size modification process were observed.

Glass formation ability and mechanical properties of Ti40Cu40Zr10Ni10 alloy

Melt-spun ribbon and bulk samples in cylindrical rod form with diameter ranging from 2 mm to 4 mm of Ti40Cu40Zr10Ni10 alloy were prepared by melt-spinning technique and copper mould casting method, respectively. The microstructure, thermal stability and mechanical properties of the bulk samples were investigated. A completely glassy single phase is formed in the 2 mm rod sample. Increasing the diameter of the rod samples resulted in the formation of CuTi crystalline phase in the 3 mm and 4 mm rod samples.

Phase separation and crystallization in a melt-spun Ti45Zr35Ni17Cu3 alloy

Structure and crystallization behavior of amorphous and quasicrystalline Ti45Zr35Ni17Cu3 alloy have been studied. DSC trace of the amorphous alloy obtained during continuous heating to 1300 K shows distinctly an exothermic peak and two endothermic peaks.

Preparation of bioactive glass ceramic nanoparticles by combination of sol-gel and coprecipitation method

SiO2-CaO-P2O5 ternary bioactive glass ceramic nanoparticles were prepared via the combination of sol-gel and coprecipitation processes. Precursors of silicon and calcium were hydrolyzed in acidic solution and gelated in alkaline condition together with ammonium dibasic phosphate. Gel particles were separated by centrifugation, followed by freeze drying, and calcination procedure to obtain the bioactive glass ceramic nanoparticles. The investigation of the influence of synthesis temperature on the nanopartilce's properties showed that the reaction temperature played an important role in the crystallinity of nanoparticle. The glass ceramic particles synthesized at 55 degrees C included about 15% crystalline phase, while at 25 degrees C and 40 degrees C the entire amorphous nanopowder could be obtained.

Preparation and mechanical properties of a bulk icosahedral quasicrystalline Ti45Zr35Ni17Cu3 alloy

A bulk Ti45Zr35Ni17Cu3 alloy, which consisted of the icosahedral quasicrystalline phase, was prepared by mechanical alloying(MA) and subsequent pulse discharge sintering. Ti45Zr35Ni17Cu3 amorphous powders (with particle size < 50 mu m) were obtained after mechanical alloying for more than 150 h from the mixture of the elemental powder. The transformation temperature range from amorphous phase to the quasicrystalline phase was from 400 K to 900 K. The mechanical properties of the bulk quasicrystalline alloy have been examined at room temperature. The Vickers hardness and compressive fracture strength were 620 +/- 40 and 1030 +/- 60 MPa, respectively. The bulk quasicrystalline alloy exhibited the elastic deformation by the compressive test. The fracture mode was brittle cleavage fracture.

A novel route for the preparation of CdS nanocrystal-poly(acrylic acid) composites using gamma-radiation

CdS nanocrystals were synthesized through AOT/heptane/H2O reverse micelles. New stable reverse mikelles were obtained by adding an appropriate amount of acrylic. acid monomer, CdS nanocrystal-poly(acrylic acid) composites were synthesized by gamma-radiation with a reverse mi'celle route at room temperature. The US nanocrystals with narrow size distribution were, found to be dispersed homogeneously in the poly(acrylic acid) matrix. (C) 2002 Elsevier Science B.V. All rights reserved.

Preparation and luminescence properties of ormosil material doped with Eu(TTA)(3)phen complex

The europium complex, Eu(TTA)(3)phen (TTA = thenoyltrifluoroacetone, phen = 1,10-phenanthroline) was successfully doped into organically modified silicate (ormosil) matrix-SiO2/(VTMOS+PMMA) (VTMOS = vinyltrimethoxysilane, PMMA = polymethylmethacrylate) via sol-gel process, and the luminescence properties of the resultant ormosil composite phosphors [ormosil: Eu(TTA)(3)phen were investigated compared with those of the pure Eu(TTA)(3)phen complex powder. The ormosil composite materials incorporated with Eu(TTA)(3)phen show the characteristic red emission of Eu3+ ion. The Eu3+ possesses fewer emission lines and longer lifetime in the hybrid phosphor than in the pure Eu(TTA)(3)phen complex. This has been explained from the viewpoint of the surrounding environment where the Eu3+ ion lies. (C) 2000 Elsevier Science B.V. All rights reserved.

Fabrication and electrochemical behavior of a sol-gel-derived carbon ceramic composite electrode entrapping 2 : 18-molybdodiphosphate

A new type of inorganic-organic hybrid material incorporating carbon powder and alpha -type 2:18-molybdodiphosphate (P2Mo18) in a methyltrimethoxysilane (MTMOS) based gel has been produced by a sol-gel process and used to fabricate a chemically modified electrode. The P2Mo18-doped carbon ceramic composite electrode was characterized using SEM and cyclic voltammetry. Square-wave voltammetry with an excellent sensitivity was exploited to conveniently investigate the dependence of current and half-wave potential (E-1/2) on pH. The chemically modified electrode has some advantages over the modified film electrodes constructed by the conventional methods, such as long-term stability, reproducibility, and especially repeatability of surface-renewal by simple polishing in the event of surface fouling or dopant leaching. In addition, the modified electrode shows a good catalytic activity for the electrochemical reduction of bromate in an acidic aqueous solution. (C) 2000 Elsevier Science B.V. All rights reserved.

Luminescent properties of organic-inorganic hybrid monoliths containing rare-earth complexes

Transparent organic-inorganic hybrid monoliths containing rare-earth complexes (Eu(TTA)(3)Phen, Tb(Sal)(3)) were prepared via the sol-gel technique. It could be observed by transmission electron microscopy that the fluorescent particles are distributed in the matrix at the microscopic level. The matrix is composed of organic-inorganic semiinterpenetrating networks, i.e., PHEMA-SiO2 system. The fluorescence emission spectra of samples are similar to those from corresponding powdered Eu(III) and Tb(III) complexes, and the half-widths of the strongest bands are less than 10 nm, which indicates that the monolith exhibits high fluorescence intensity and color purity. Furthermore, the fluorescence spectra exhibit no obvious change with decreasing nanoparticle size of the rare-earth complex. The fluorescence lifetimes of samples are longer than pure Eu(III), Tb(III) complexes, respectively. Samples irradiated with an UV lamp (365 nm) are still transparent but become bright red and green in color due to fluorescence of Eu(III) and Tb(III) complexes. (C) 2000 Elsevier Science B.V. All rights reserved.

Heat capacity enhancement and thermodynamic properties of nanostructured amorphous SiO2

The heat capacity of nanostructured amorphous SiO2 (na-SiO2) has been measured by adiabatic calorimetric method over the temperature range 9-354 K. TG and differential scanning calorimeter (DSC) were also employed to determine the thermal stability. Glass transition temperature (T-g) for the two same grain sizes with different specific surface of naSiO(2) samples and one coarse-grained amorphous SiO2 (ca-SiO2) sample were determined to be 1377, 1397 and 1320 K, respectively. The low temperature experimental results show that there are significant heat capacity (C-P) enhancements among na-SiO2 samples and ca-SiO2. Entropy, enthalpy, Gibbs free energy and Debye temperature (theta (D)) were obtained based on the low temperature heat capacity measurement of na-SiO2. The Cp enhancements of na-SiO2 were discussed in terms of configurational and vibrational entropy. (C) 2001 Elsevier Science B.V. All rights reserved.

Surface amorphous and crystalline microstructure by alloying zirconium using Nd : YAG pulsed laser

A novel composite coating was synthesized by laser alloying of zirconium nanoparticles on an austenite stainless steel surface using a pulsed Nd:YAG laser. The coating contained duplex microstructures comprising an amorphous phase and an austenitic matrix. A discontinuous zirconium-containing region formed at a depth of 16 mum below the surface. The amorphous phase was present in the zirconium-rich region, with the composition of zirconium ranging from 7.8 to 14.5 at. pet. The formation of the amorphous phase was attributed to the zirconium addition. The hardness, corrosion, and wear-corrosion resistance of the irradiated coating were evidently enhanced compared to those of the stainless steel.