Optimized compositions for bulk metallic glass (BMG) formation have been determined for the Cu−Hf binary and Cu−Hf−Al ternary systems. The Cu−Hf−Al BMG-forming composition region is identified to correlate with the (L → Cu10Hf7 + CuHf2 + CuHfAl) eutectic reaction. The eutectic temperature is reduced by nearly 50 K relative to that of the binary eutectic, demonstrating the significant role of the third element Al in stabilizing the liquid. The fragility parameter D* of the Cu55Hf45 binary and Cu49Hf42Al9 ternary supercooled liquid was determined from relaxation time measurements, indicating that Al incorporation also leads to a “stronger” liquid. The combination of these thermodynamic and kinetic effects is responsible for the dramatic enhancement of glass-forming ability from the Cu−Hf binary to the Cu−Hf−Al ternary.

The glass formation in Fe-rich ternary Fe-B-Nd and quaternary (Fe,B,Nd)96Nb4 alloys has been studied and the best ternary and quaternary glass formers are located at Fe67B23Nd10 and (Fe68B25Nd7)Nb4 with critical diameters of 1 and 4 mm, respectively. For (Fe,B,Nd)96Nb4 alloys, the competing phases with glass were identified by monitoring the microstructure change. Fe14Nd2B was discovered to be one competing phase, which is the principle magnetic phase for Nd-Fe-B hard magnets. Composites with uniformly distributed Fe14Nd2B were formed for quaternary alloys with a diameter of 1.5 to 3 mm. Bulk hard magnets could be obtained by directly annealing the composites in a compositional area. A hard magnet with a coercivity of 1,100 kAm−1 and a maximum energy product, (BH)max, of 33 kJm–3 was obtained at (Fe67B23Nd10)96Nb4 by annealing. The combination of hard magnetic properties and the large critical sample size may make these alloys a commercially viable candidate for industrial applications.

ZrO2 thin films containing silver nanoparticles were prepared using the sol-gel method with Ag to Zr molar ratios [Ag]/[Zr] = 0.11, 0.25, 0.43, 0.67, 1.00, 1.50, and 2.33. After dip coating on glass substrate, coated films were annealed at 200 and 300 °C in air. X-ray diffraction peaks corresponding to crystalline Ag were observed, but a specific peak corresponding to ZrO2 was not observed. At the molar ratio [Ag]/[Zr] = 0.25, the particle size of Ag distributed broadly centered at 17 nm for an annealing temperature of 200 °C and at 25 nm for 300 °C. The films annealed in air at 200 °C showed an absorption band centered at 450 nm because of the silver surface plasmon resonance, whereas films heated at 300 °C in air caused a red shift of the absorption to 500 nm. The absorption peak was analyzed using the effective dielectric function of Ag-ZrO2 composite films modeled with the Maxwell-Garnett expression.

In this article, the chemical and structural changes inside soda-lime glasses induced by femtosecond (fs) laser pulsing have been reported, based on transmission electron microscopy and electron energy loss spectroscopy studies. Under fs-laser interaction, Na-rich phases are formed, and Na nanoparticles are also precipitated around the Na-rich phases. These findings demonstrate how powerful and efficient the fs-laser pulsing and interaction can be in making novel microstructures in soda-lime silicate glass, and they bridge the gap between the macroscale property changes and nanometer-scale structures.

Metalorganic chemical vapor deposition was used to grow N-rich side GaNSb alloys under different growth conditions, and, for the first time, a considerable amount of Sb was incorporated into the GaNSb. The amount of Sb increased as the growth temperature decreased, but the maximal Sb content seemed to be limited by the solid solubility of Sb in GaN. Absorption spectroscopy of the GaNSb revealed a strong absorption band below the band gap of GaN. The below-band gap absorption extended to 0.8 eV, which makes GaNSb a promising material to serve as an infrared absorption layer on GaN.

An environmentally friendly route to prepare stable concentrated aqueous dispersions of silver nanoparticles is described. It was found that Arabic gum, a well known stabilizing agent, can also rapidly and completely reduce Ag2O to metallic silver in alkaline solutions (pH > 12.0) and elevated temperature (65 °C). The average size of the silver nanoparticles could be tailored from 10 to 30 nm by varying the experimental conditions. By hydrolyzing either enzymatically or chemically the polysaccharide, it was possible to isolate dispersed silver nanoparticles suitable for both biological and printable electronics applications. For the latter purpose, concentrated dispersions of silver particles were prepared and used for depositing thin uniform layers, which could be sintered into conductive films at low temperatures.

For a flexible electronic device integrating inorganic materials on a polymer substrate, the polymer can deform substantially, but the inorganic materials usually fracture at small strains. This paper describes an approach to make such a device highly stretchable. A polyimide substrate is first coated with a thin layer of an elastomer, on top of which SiNx islands are fabricated. When the substrate is stretched to a large strain, the SiNx islands remain intact. Calculations confirm that the elastomer reduces the strain in the SiNx islands by orders of magnitude.

Direct conversion of an amorphous carbon (C) film to capsules by gallium (Ga), and nickel and cobalt (NiCo) alloy particles upon heating is investigated in situ by transmission electron microscopy (TEM). Capsules are catalyzed in an NH3 atmosphere when the temperature is raised to 1050 °C. High resolution TEM reveals that graphene flakes initially nucleate at the surface of the catalysts, then segregate and transform into faceted multi-shell capsules upon continued heating. The solubility of carbon in the NiCo alloy particles can be differentiated from the solubility of carbon in Ga particles by the thickness of the walls. The C/Ga binary phase in nanoparticles is discussed regarding the formation of thin-walled carbon capsules.

Cobalt (15 at.%) doped bismuth vanadate, Bi4(V0.85Co0.15)2O11-δ (BICOVOX0.15), is known to have high oxygen ion conduction in the medium temperature range (400–600 °C). Small grain size may be important in stabilizing the highly conductive and disordered γ-phase at lower temperature. In this article, we report for the first time the synthesis of highly porous nanoscale BICOVOX powders by a solution combustion technique. The effects of fuel-to-oxidizer ratio, and postcombustion heat treatment temperature and time on the phase content and microstructure of the powders were investigated. As-combusted powders were revealed to be a mixture of Bi2O3, BiVO4, and γ-BICOVOX phases that were converted to phase pure γ-BICOVOX during heat treatment.

In this study, the dense films of well-crystallized ZnO nanocrystals were successfully prepared by direct spin-coating of the colloidal solution of ZnO nanoparticles derived from the microemulsion method. The average grain sizes in the films were reasonably controlled in the range from 6.5 to 34.3 nm by simply changing the annealing temperatures. The increase in band gap energies was found in the size region less than 13.3 nm, finally resulting in 3.47 eV for the average size of 6.5 nm. The photoluminescence spectra at room temperature showed intense ultraviolet (UV) emission with faint green luminescence. The Stokes shifts of the films were estimated to be one or two orders of magnitude smaller than those of the conventional ZnO nanocrystalline films, suggesting the well crystallization and slight amounts of lattice defects in the ZnO nanoparticles. These excellent features may be favorable to make high-performance optical application such as UV emitting devices.

A double-angle indenter model is proposed to determine the representative strain in the indentation process, and a new method is then developed aiming at the extraction of the yield strength and strain-hardening exponent from the surface layer of metals, because surface properties, especially in a small region, may differ from bulk ones and are sometimes closer to service properties such as fatigue strength, wear, and corrosion resistance. First, the isotropic metal was analyzed, the elastic modulus of which was fixed at 128 GPa, the yield strength was 50 to 200 MPa, and the strain-hardening exponent was 0.1 to 0.5. By introducing the yield strain to substitute the yield strength in the calculation, it was proved that the model can cover the majority of metals because the introduced weight parameter λ is independent of the yield strength and the elastic modulus, although it depends on the strain-hardening exponent to some extent. For the determination of yield strain εY (or yield strength Y), the precision is better for low C/E and low n, whereas for the determination of strain-hardening exponent n, the precision is better for high C/E and low εY. By using the double-angle indenter, the material constitutive relationship at the surface can be evaluated from just one indentation without any other measurements.

Substrate influence is a common problem when using instrumented indentation (also known as nanoindentation) to evaluate the mechanical properties of thin films. In this work, finite element analysis was used to develop an ad hoc model that predicts the substrate influence when testing thin dielectric films on silicon. The model was evaluated experimentally using three sets of films that were nominally the same except for thickness. Using the model significantly reduced the measurement error for the thinnest films (<250 nm) by accurately accounting for the influence of the substrate. The model also significantly reduced the measurement uncertainty, because properties were evaluated using larger indents that would normally be unduly affected by the substrate. The process for developing this model may be useful in developing other ad hoc models for analyzing film-substrate systems.

Microstructural characterization and crystallization kinetics of (1-x)TeO2-0.10CdF2-xPbF2 (x = 0.05, 0.10, and 0.15 in molar ratio) glasses were investigated using differential thermal analysis (DTA), x-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy/energy dispersive spectrometer (SEM/EDS), and absorbance spectroscopy techniques. For all of the glass compositions only one exothermic peak was observed on the DTA plots, and on the basis of the XRD and Raman spectrophotometry investigations it was understood that they refer to the formation of the α-TeO2 phase. SEM/EDS investigations revealed the presence of oriented needle-like α-TeO2 crystals in the 0.85TeO2-0.10CdF2-0.05PbF2 glass, rectangle-shaped α-TeO2 crystals in the 0.80TeO2-0.10CdF2-0.10PbF2 glass, and disoriented needle-like crystals in the 0.75TeO2-0.10CdF2-0.15PbF2 glass. DTA analyses were carried out at different heating rates, and the Avrami constants for all of the glasses were approximately 1. The activation energy calculations and SEM investigations demonstrated that the formation of the crystalline phases occurred via surface crystallization mechanism for all of the glasses. Activation energies for crystallization in these glasses were determined from the modified Kissinger plots and were found to vary between 67 and 183 kJ/mol. The addition of PbF2 as a network modifier into the glass structure contributes to the intensity of the Raman peaks change and forced the transition of the glass network from TeO4 trigonal bipyramid units to the TeO3 trigonal pyramid structural units.

We report on a novel biocompatible hierarchical TiO2 porous coating on the surface of Ti, processed via anodic oxidation. The coating consists of large (∼1–20 μm) pores on the microscale and nanotubes (∼50 nm diameter) on the nanoscale. This structure is exciting because of its potential application as a bioactive coating for Ti bone implants. Surface characterization of the coating showed nanotubes of relatively uniform diameter. The interface between TiO2 nanotubes and Ti, studied by transmission electron microscopy, was incoherent. The tubes were also somewhat interconnected.

In this work, the influence of SiO2 additions in leucite ceramics on the bulk linear thermal expansion coefficient (TEC) especially during the phase transition, has been studied. Thermal expansion and x-ray diffraction measurements at high temperatures were carried out to characterize the tetragonal-cubic phase transition. TEC for reference and SiO2-added leucite samples exhibited similar behavior as a function of temperature. Before and after the phase transition, the TEC values were similar to those observed in non-SiO2-added samples, whereas during the phase transition, a maximum TEC value was observed and it tends to decrease as the SiO2 addition increases. This behavior could be caused by the formation of an intermediate phase with an extremely high TEC (70 × 10–6 °C−1) during the phase transformation. Furthermore, the results suggest that as the intermediate phase is partially suppressed via SiO2 addition, the cubic phase can be partially stabilized at temperatures as low as 200 °C.

AlN codoped ZnO films were deposited on sapphire substrates at low temperature using a cosputter system under various N2/(N2 + Ar) flow ratios. To investigate the nitrogen function, the ratio of nitrogen ambient was varied during cosputtering. AlN codoped ZnO films with various crystallographic structures and bonding configurations were measured. With an adequate nitrogen atmosphere deposition condition and postannealing temperature at 450 °C, the p-type conductive behaviors of AlN codoped ZnO films were achieved due to the formation of Zn–N bonds. According to the low-temperature photoluminescence spectra, the binding energy (EA) of 0.16 eV for N acceptors can be calculated. Using time-resolved photoluminescence measurement, the carrier lifetime in AlN codoped ZnO films increases due to the reduction of oxygen vacancies caused by the occupation of adequate nitrogen atoms.

Instrumented indentation (referred to as nanoindentation at low loads and low depths) has now become established for the single point characterization of hardness and elastic modulus of both bulk and coated materials. This makes it a good technique for measuring mechanical properties of homogeneous materials. However, many composite materials are composed of material phases that cannot be examined in bulk form ex situ (e.g., carbides in a ferrous matrix, calcium silicate hydrates in cements, etc.). The requirement for in situ analysis and characterization of chemically complex phases obviates conventional mechanical testing of large specimens representative of these material components. This paper will focus on new developments in the way that nanoindentation can be used as a two-dimensional mapping tool for examining the properties of constituent phases independently of each other. This approach relies on large arrays of nanoindentations (known as grid indentation) and statistical analysis of the resulting data.

Polycrystalline HoGaMnO5, ErGaMnO5, and TmGaMnO5 oxides have been first prepared by soft chemistry procedures followed by high oxygen pressure treatments, to stabilize Mn4+ cations. Their crystal structures and magnetic behavior have been studied at room temperature and 5 K by neutron powder diffraction (NPD) data in complement with magnetization measurements. RGaMnO5 are orthorhombic, Pbam space group, and their crystal structures contain infinite chains of edge-sharing Mn4+O6 octahedra, interconnected by pyramidal Ga3+O5 and RO8 units. For R = Ho, a = 7.2810(4), b = 8.4526(4), and c = 5.6668(3) Å; for R = Er, a = 7.2575(3), b = 8.4357(3), and c = 5.6613(2) Å; and for R = Tm, a = 7.2438(3), b = 8.4124(3), and c = 5.6509(2) Å, at room temperature. Above 300 K the reciprocal magnetic susceptibility follows a Curie-Weiss law. In the paramagnetic region, a positive Weiss constant suggests the presence of ferromagnetic interactions, which have been investigated by low-temperature NPD for R = Er, Tm. The 5 K patterns show a detectable long-range magnetic ordering over the Mn and R positions, ferromagnetically aligned along the x-direction.

Integrating porous low-permittivity dielectrics into Cu metallization is one of the strategies to reduce power consumption, signal propagation delays, and crosstalk between interconnects for the next generation of integrated circuits. The porosity and pore structure of these low-k dielectric materials, however, also affect other important material properties in addition to the dielectric constant. In this paper, we investigate the impact of porogen loading on the stiffness and cohesive fracture energy of a series of porous organosilicate glass (OSG) thin films using nanoindentation and the double-cantilever beam (DCB) technique. The OSG films were deposited by plasma-enhanced chemical vapor deposition (PECVD) and had a porosity in the range of 7−45%. We show that the degree of porogen loading during the deposition process changes both the network structure and the porosity of the dielectric, and we resolve the contributions of both effects to the stiffness and fracture energy of the films. The experimental results for stiffness are compared with micromechanical models and finite element calculations. It is demonstrated that the stiffness of the OSG films depends sensitively on their porosity and that considerable improvements in stiffness may be obtained through further optimization of the pore microstructure. The cohesive fracture energy of the films decreases linearly with increasing porosity, consistent with a simple planar through-pore fracture mechanism.

The N-doped ZnO was prepared by heating a mixture of zinc nitrate hexahydrate [Zn(NO3)2·6 H2O] and ammonium salt at 623 K for 1 h in air. The mixture of zinc nitrate hydrate and ammonium salt formed a homogeneous molten salt at 623 K, and the homogeneous dispersion of the metal ions and ammonium ions contributed to the N-doping. In particular, when the mixture of zinc nitrate hydrate and ammonium acetate (CH3COONH4) was heated at 623 K, the doped amount of nitrogen was higher than with the mixture of zinc nitrate hydrate and NH4NO4. The acetate anion (CH3COO−) restricted the oxidation reaction of nitrate anion (NO3−). Furthermore, Al- and N-co-doped ZnO particles were obtained by heating the mixture of zinc nitrate hydrate, aluminum nitrate hydrate, and ammonium acetate. The Al and N co-doping effectively increased the doped amount of nitrogen. The spontaneous formation of ZnO lattice and the nitrogen source in the molten salt and the homogeneous dispersion of Zn2+ ions and Al3+ ions contributed to the increase in the amount of doped nitrogen.