The effect of additional elements on microstructure and mechanical properties of (TiCu)-based bulk metallic glasses (BMGs) has been systematically investigated. Based on the values of the heat of mixing between the additional elements and the major constituent elements Ti and Cu, small additions of elements having a positive heat of mixing with Cu and a negative heat of mixing with Ti are effective in forming nanoscale heterogeneities upon solidification and enhance the ductility. It is experimentally demonstrated that the selection of the minor elements in (TiCu)-based BMGs plays a crucial role to induce nanoscale heterogeneities and thus to control the deformation behavior of the bulk metallic glasses.

This study probes the relationship between the morphology of anodic titania (TiO2) layers grown on Ti foil substrates and their subsequent photoelectrochemical response in 0.5 M Na2SO4 supporting electrolyte. The effects of anodization variables (voltage and time) and anodization medium composition [water, glycerol, poly(ethylene glycol), ethylene glycol] along with fluoride ion concentration on the oxide layer of morphology and photoresponse are described. The degree of order of the self organized TiO2 nanotube arrays and the extent to which these arrays organize themselves over the entire substrate surface are key variables dictating the corresponding quality of the resultant photoresponse.

A thermal metalorganic atomic layer deposition (ALD) process was developed for the in situ, sequential growth of Pt/TaNx stacks for use as barrier/seed stacks for subsequent copper electroplating. Ultrathin platinum films were deposited by alternating pulses of (methylcyclopentadienyl)trimethylplatinum (MeCpPtMe3) and oxygen (O2) as co-reactants. An ALD process window was established and optimized by investigating saturation of Pt film-growth rate versus MeCpPtMe3 and O2 exposure as controlled by the length of reactant pulses and the duration of the inert gas purge cycles separating the reactant pulses. The resulting low-temperature (300 °C) ALD Pt process yielded uniform and continuous Pt films with typical carbon and oxygen impurity levels around, respectively, 2.5 and 1 at.%. Film conformality was nearly 100% in 120-nm trench structures with 11:1 aspect ratio.

Eutectic SnPb solder has been widely used in packaging for several decades. The stability of the interface between solder and under-bump metallization (UBM) is an important issue that has led to many studies. Even though Ni atoms dissolve much slower into SnPb solder than Cu, the intermetallic compound, Ni3Sn4, which forms when eutectic SnPb solder reacts with Ni(V)/Ti UBM, is not stable on Ti layer, creates V-rich zone, and causes spalling. To prevent the phenomenon, and the resulting reduction of mechanical reliability in solder joints, we propose the addition of a layer of Cu thin film to serve as a sacrificial layer. Both eutectic SnPb solder and composite solder (high-Pb solder with eutectic SnPb solder) were studied in severe reflow conditions to simulate the worst case of die attach and later reflow process. Cu film first was consumed completely to form a compound. Due to lower interfacial energy between Cu6Sn5 and Ni(V), the interface was stable and no spalling occurred. However, the same thickness of Cu was insufficient to prevent Ni from diffusing into solder or compound. Not only diffusion of Ni atoms was observed; Sn atoms also diffused into the Ni(V) layer. The Sn–Ni reaction caused the interface between the compound and Ni(V) to retreat into the Ni(V) layer. The compound was not stable at the interface, and spalling could be seen. Due to the interdiffusion of Ni and Sn, many Kirkendall voids were also observed at both side of the interface.

Platinum-iridium films (Ir = 0, 32, 46, 83, 100 at.%) were deposited on the nickel-base single crystal superalloy through magnetron sputtering. After annealing and aluminizing, the Pt-Ir modified aluminide coatings mainly consisted of PtAl2 and β-(Ni,Pt,Ir)Al phases. Hot corrosion resistance of Pt-Ir modified aluminide coatings with the different Ir contents were evaluated by exposure at 1173 K in the presence of the 90%Na2SO4 + 10%NaCl (wt%) salt deposits. The corrosion kinetics curves of the specimens were plotted up to 100 h heating time. The phase constitution, morphology of corrosion products, and element concentrations along the cross section were also measured. The lowest mass gain (0.299 mg/cm2, after 100 h) was observed for Pt-46Ir aluminide coating because the dense and continuous protective Al2O3 scale formed. Phase transformation from β-(Ni,Pt)Al to γ′-(Ni,Pt)3Al, characteristics of the scale, and protection by Pt/Ir enriched layer had the important effects on the hot corrosion behavior of modified aluminide coatings.

Laser remelted surface layers of a Cu-based metallic glass forming alloy have been produced with fully amorphous depths up to 350 μm for single track widths of around 1.3 mm and have been checked by transmission of synchrotron radiation. They have been subjected to indentation hardness and scratch testing, and the development of shear bands in both situations has been addressed. During the cross-sectional hardness indentation tests, Vickers values of over 735 HV2 have been found through the depth of the treated layer, and the scratch testing has revealed extremely low friction coefficient values (<0.02 at 10 N in single-pass and 0.02 at 18 N multi-pass regimes against a diamond stylus). The shear band formation has been related to both scratch test speed (strain rate) and load (contact stress) by methods such as atomic force microscopy measurements and subsequent surface roughness characterization by a height–height correlation function.

Ultrathin lanthanide (Nd, Pr, Eu, Sm) oxide films with functional dielectric properties down to 3.3 nm thickness were deposited by aqueous chemical solution deposition (CSD) onto hydrophilic SiO2/Si substrates. Precursor solutions were prepared from the oxides via an intermediate, solid Ln(III)citrate. A film heat treatment scheme was derived from thermogravimetric analysis of the precursor gels, showing complete decomposition by 600 °C. Crystalline phase formation in the films depended on the lanthanide, annealing temperature, and citric acid content in the precursor. Through variation of the precursor concentration and number of deposited layers, thickness series of uniform films were obtained down to ∼3 nm. The film uniformity was demonstrated both by atomic force microscopy and cross-section transmission electron microscopy. The lanthanide oxide films possessed good dielectric properties. It was concluded that aqueous CSD allows deposition of uniform ultrathin films and may be useful for the evaluation of new high-k candidate materials.

A thermogravimetric method was used to analyze intermediate processes involved in the formation and decomposition of AgNbO3and AgTaO3perovskites. Critical parameters that control the kinetics of the formation are associated with oxygen transport. The Nb2O5crystal structure has a capacity to trap molecular oxygen, which evolves during the decomposition of Ag2O that is present in a starting mixture. The formation of the perovskite phase involves a simultaneous reaction of three species: O2, Ag, and Nb2O5/Ta2O5. As the trapped molecular oxygen is in the immediate vicinity of the reaction site, the kinetics of the reaction is significantly accelerated. An absence of the molecular oxygen in the solid-state phase cannot be compensated for with an increase in a partial pressure of oxygen in the gas phase, that is, application of oxygen atmosphere.

Residual stresses in diamond films grown on WC–Co substrates have been investigated by Raman spectroscopy, x-ray diffraction (XRD), and curvature methods. Microcrystalline diamond films were deposited at 650–700 °C in a conventional hydrogen–methane environment by the microwave plasma-enhanced chemical vapor deposition technique. The film thickness, measured from cross-sectional micrographs taken by scanning electron microscopy, changed from 1.5 to 16.5 μm as the growth time increased from 1 to 12 h. The type and the magnitude of the total residual stress obtained from curvature and XRD measurements agreed very well in all of the samples and changed from tensile to compressive as film thickness increased. However, Raman spectroscopy results showed that all films exhibited compressive stress due to the domain size effect. Different methane fractions, varying from 1% to 3%, have been utilized for diamond growth, and the total residual stress increased as more methane was included.

(Ni,Zn)Fe2O4 particle/organic hybrid was synthesized in situ from metalorganics below 100 °C. A mixture of nickel (II) acetylacetonate (NA), zinc acetylacetonate (ZA), and iron (III) 3-allylacetylacetonate (IAA) was hydrolyzed and polymerized yielding a spinel oxide particle/organic hybrid. X-ray diffraction analysis revealed that the crystallinity of spinel particles was dependent upon the hydrolysis conditions of NA-ZA-IAA. Nanocrystalline nickel zinc ferrite particles below 5 nm were uniformly dispersed in the organic matrix. The magnetization of hybrid increased with an increasing amount of water for hydrolysis. Nano-sized nickel zinc ferrite particle/organic hybrid showed a magnetization-applied field (BH) curve with no remanence above 40 K. The magnetization versus H/T curves from 40 to 100 K were superimposed on the same curve and satisfied the Langevin equation. The remanent magnetization and coercive field of the hybrid were 7.2 emu/g and 150 Oe, respectively, at 4.2 K. The absorption edge of the hybrid was blue-shifted compared with that of bulk ferrite.

Radio frequency (rf) magnetron sputtering is used to deposit Ti0.85Nb0.15O2 and Ti0.8Ta0.2O2 films on glass substrates at substrate temperatures (TS) ranging from ∼250 to 400 °C. The most conducting Nb-doped TiO2 films were deposited at TS = 370 °C, with conductivities of ∼60 S/cm, carrier concentrations of 1.5 × 1021 cm−3 and mobilities <1 cm2/V·s. The conductivity of the films was limited by the mobility, which was more than 10 times lower than the mobility for films deposited epitaxially on SrTiO3. The difference in properties is likely caused by the randomly oriented crystal structure of the films deposited on glass compared with biaxially textured films deposited on SrTiO3. The anatase phase could not be stabilized in the Ta-doped TiO2 films, likely because of the high dopant concentration.

Degradation of insulation resistance due to the formation of the Y2Ti2O7 (pyrochlore) phases in yttrium(Y)-doped BaTiO3 ceramics was investigated. The addition of Y2O3 and sintering aid SiO2 to the BaTiO3 ceramics caused the formation of barium-related BaSiO3 and titanium-related Y2Ti2O7 second phases. The appearance of the abnormally grown large pyrochlore grains with the increase of sintering temperature critically degraded insulation resistance at high temperatures. When the volume fraction of the pyrochlore phase increased, the resistance degradation was also observed although the grain size of the pyrochlore phase became smaller. The highly oxygen ionic conductive nature of the Y2Ti2O7 pyrochlore phase is supposed to accelerate electromigration of oxygen vacancies resulting in the resistance degradation. The formation of pyrochlore phase should be prevented to guarantee the high-temperature reliability of BaTiO3 bases ceramic capacitors.

The ideal strengths of metals and alloys at finite temperatures have been studied using the statistical moment method. The tensile and shear strengths of the body-centered cubic (bcc) transition metals like Mo and W (refractory metals), and ordered FeAl (B2) and Fe3Al (DO3) alloys are calculated as a function of the temperature. The orthogonal tight-binding method is used for bcc transition elements, while the universal binding-energy relation (UBER)-type of pairwise potentials, derived from ab initio density-functional theory, is used for the FeAl and Fe3Al alloys. We discuss the temperature dependence of the tensile and shear strengths of the metals and alloys in conjunction with those of the second-order elastic constants.

Cu–Ag alloy films prepared by magnetron cosputtering were characterized by using x-ray diffraction. A two-phase nanocrystalline structure of Cu grains supersaturated with Ag and Ag grains saturated with Cu was always observed. When alloying Ag with Cu or Cu with Ag, the grain sizes decreased dramatically, and the supersaturation increased with the amount of the alloying element. On annealing, the grain sizes of the Cu–Ag films increased and the solubilities decreased. To shed light on the mechanisms in play during the phase formation and subsequent phase changes, additional in situ real-time measurements were carried out using a high-intensity x-ray beam from the synchrotron at the European Synchrotron Radiation Facility in Grenoble, France. Based on the experimental findings, the phase formation and the subsequent changes during annealing are discussed.

Molecular dynamic simulation was used to study the melting behavior of gallium nitride (GaN) nanowires with the Stillinger-Weber potential. Our results reveal that the melting of the nanowires starts from the surface and rapidly extends to the inner regions of nanowires as temperature increases. The melting temperatures increase to saturation values ∼3100 and ∼2900 K when the diameters of nanowires are larger than 3.14 and 4.14 nm for the nanowires with [100]- and [110]-oriented lateral facets, respectively. The saturated values are close to the melting temperature of bulk GaN. The low melting temperature of GaN nanowires with small diameter may be associated with the large surfaces of nanowires.

One of the interests and challenges of nanoindentation is determining the shear stress at the onset of plastic yielding, which corresponds to dislocation nucleation. To extract this stress information from experimental load-displacement data, a spherical tip shape is usually assumed. However, it is well known that indenter tips have irregular shapes, especially at the small-length scales that are important for small loads. This will significantly affect the stress distribution under the indentation surfaces. In this work, an indenter tip shape is measured by atomic force microscopy. The measured indenter shape is input into a finite element analysis model for indentation simulations on 〈111〉-oriented single-crystal Al samples in the elastic regime. The resulting stresses, indentation force, and contact area are analyzed and compared to results from a fitted spherical indenter. The deviation of the assumed spherical indenter tip from the real measured indenter tip is studied.

Control of the low-temperature sintering of nanosilver particles was attained by dispersing and stabilizing nanosilver particles into a paste form using the selected organic binder systems. As demonstrated by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA), with the existing binder systems, undesirable premature coalescence of nanosilver particles was prevented and the metastable structure was retained until the binder burned out at relatively higher temperatures. Enhanced densification was achieved upon the binder burnout because at the relatively higher temperatures the densification mechanisms, e.g., grain-boundary or lattice diffusion, become more dominant. We propose that the onset of sintering, extent of densification, and final grain size can be controlled by either the size of the initial nanosilver particles or the binder systems with different burnout characteristics.

Thin films of Pb(Sc1/2Ta1/2)O3 (PST) were fabricated using an optimized chemical solution deposition procedure involving the de-hydration of scandium acetate and the addition of up to 30% excess lead in solution. The choice of substrate was found to impact the thermal induced stress in the films as confirmed by wafer bending and in-plane grazing angle x-ray diffraction measurements. The presence of either a compressive or a tensile in-plane stress led to a reduction in the temperature of the dielectric maximum, whereas the value of the dielectric maximum remained relatively unchanged; its value reduced by an order of magnitude compared with ceramic samples. It is concluded that mechanical stress alone is not the sole factor in the reduction of PST thin film permittivity. Microstructural features resulting from processing induced defects or an incomplete transformation to the relaxor state may be responsible for this commonly observed phenomenon.

The effects of niobium (Nb) addition on the glass-forming ability (GFA), crystallization behavior, and compressive mechanical property of iron (Fe)–boron (B)–yttrium (Y) alloys have been investigated. Among the (Fe71.2B24Y4.8)100−xNbx (x = 0, 2, 4, 6, 8) alloys investigated, (Fe71.2B24Y4.8)96Nb4 exhibits the highest GFA, enabling the formation of glassy rods with a maximum diameter of 7 mm, which is the largest among quaternary Fe-based alloys. The comparison of the crystallization behavior of the alloys shows that the formation of metastable Fe23B6 phase during crystallization in the (Fe71.2B24Y4.8)96Nb4 alloy can suppress the formation of other stable crystalline phases such as α-Fe, enhancing the stability of the glass phase. The present results show that the attainment of a significantly high GFA is possible even in a quaternary Fe-based alloy system by properly tailoring the competing crystalline phase by the modification of liquid chemistry.

Magnesium hydroxide nanoneedles and nanorods were synthesized by reverse precipitation in the presence of polyethylene glycol (MW 1000) at ambient temperature. The obtained magnesium hydroxide crystals were characterized in terms of morphology, particle size, crystal structure, and thermal stability by high-resolution transmission electron microscopy, x-ray diffraction, infrared spectroscopy, and thermogravimetric and differential thermal analysis. The experimental results show that the growth of magnesium hydroxide crystals and the dispersivity of the nanostructures were greatly influenced by polymer dispersant. The mechanism of the formation of magnesium hydroxide nanorods and nanoneedles was also proposed.