The three-dimensional nanostructured SiO2-based microshells of diatoms have been converted into nanocrystalline BaTiO3 via a series of shape-preserving reactions. The microshells, obtained as diatomaceous earth, were first exposed to a surfactant-induced dissolution/reprecipitation process [C.E. Fowler, et al., Chem. Phys. Lett.398, 414 (2004)] to enhance the microshell surface area, without altering the microshell shape. The SiO2 microshells were then converted into anatase TiO2 replicas via reaction with TiF4 gas and then humid oxygen. Hydrothermal reaction with a barium hydroxide-bearing solution then yielded three-dimensional nanocrystalline microshell replicas composed of BaTiO3. The enhanced surface area of the surfactant-treated microshells resulted in faster conversion into phase-pure BaTiO3 at 100 °C.

Light-induced metastability in hydrogenated nanocrystalline silicon (nc-Si:H) single-junction solar cells was studied systematically. First, we observed no light-induced degradation when the photon energy was lower than the band gap of the amorphous phase; degradation occurred when the energy was higher than the band gap in the amorphous phase. The light-induced degradation could be annealed away at an elevated temperature. We concluded that the light-induced defect generation occurred mainly in the amorphous phase. Second, forward current injection did not degrade the nc-Si:H cell performance. However, a reverse bias during light soaking enhanced the degradation. Third, the nc-Si:H cells made with an optimized hydrogen dilution profile showed minimal degradation although these cells had a high amorphous volume fraction. This indicated that the amorphous volume fraction was not the only factor determining the degradation. Other factors also played important roles in the nc-Si:H stability.

A controversial issue in mechanical property extractions from instrumented indentation applied load (P)–penetration depth (hs) curves concerns the possibility of finding more than one solid that essentially exhibits the same contact response. By recourse to finite element simulations of elastic-power law strain hardening solids, it was shown that for both the elasto-plastic and the fully plastic contact regimes it becomes possible to find an arbitrary number of solids whose P-hs curves are visually similar [L. Wang and S.I. Rokhlin, J. Mater. Res. 21, 995 (2006)]. Although this assertion supports prior findings [e.g., C.M. Cheng and Y.T. Cheng, J. Mater. Res. 14, 3493 (1999); K.K. Tho et al., Mater. Sci. Eng.A 390, 202 (2005); and J. Alkorta et al., J. Mater. Res.20, 432 (2005)], it apparently contradicts the work by Casals and Alcalá in which, through similar computational procedures and constitutive theory, it was shown that there can be “only” two solids with strictly the same P-hs curve [O. Casals and J. Alcalá, Acta Mater.53, 3545 (2005)]. The purpose of this comment is to reconcile the different views on the multiplicity of inferred properties that can be extracted from a single P-hs curve, as well as to address the issue of whether visually similar P-hs curves can be taken to be statistically identical both from analytical and experimental standpoints. Some considerations are also given regarding experiments performed with dual indenters.

Al85Ni9Nd4Co2 metallic glass/nanostructured ribbons and powders were used as starting materials for producing bulk amorphous/nanostructured Al-based alloys. Glassy ribbons were obtained by melt spinning at wheel surface velocities ranging from 5 to 37 m/s. The amorphous ribbons exhibited a supercooled liquid region of ∼20 K, a reduced glass transition temperature of ∼0.47 and γ ∼ 0.328. Mechanical alloying of the elemental powder mixture did not lead to amorphization. However, amorphous powders obtained by milling the glassy ribbons for 9 h exhibited a thermal stability similar to the initial ribbons. Isothermal differential scanning calorimetry measurements were used to determine the consolidation parameters of the glassy powders. Consolidation at 513 K by uniaxial hot pressing and hot extrusion indicated that the former method leads to bulk glassy samples, whereas the latter one yields nanostructured α-Al/glassy matrix composites.

Nanosized calcium hydroxyapatite particles were synthesized by the catalytic decomposition of urea with urease. The influence of the synthesis parameters, i.e., temperature and ratio of the reagents/urease concentrations, on the size and morphology of the hydroxyapatite particles were investigated. As reagents for the synthesis of hydroxyapatite, various amounts of CaCl2, NaH2PO4, urea, and urease were used. The urease-catalyzed decomposition of urea leads to the homogeneous precipitation of hydroxyapatite because of the release of OH− ions during the hydrolysis of urea. In the same process, CO32− ions are also released and incorporated into the crystal structure of the hydroxyapatite. In the temperature range from 30–40 °C, it was found that low crystalline carbonate hydroxyapatite was formed in all cases. It was found that decreasing the ratio of the concentrations of the reagents to the urease concentration leads to decrease in the particle size to below 100 nm and the morphology changes from leafy-like to spherical.

Nanocrystalline LiCoO2 powders (10–50 nm) were synthesized by a citrate-nitrate combustion process followed by calcination at different temperatures (300–800 °C) in air. Thermogravimetric analyses indicated a sharp combustion at a low temperature of 225 °C, producing fine crystallites. Quantitative phase analyses from the x-ray diffractograms showed that while annealing at 500 °C produced mixed phases of cubic and rhombohedral LiCoO2, annealing at 800 °C resulted in single-phase rhombohedral LiCoO2. Electronic transitions related to the Co 3d bands were investigated by ultraviolet-visible reflectance spectra in absorbance mode and were ascribed to the Co 3d intra-band transition involving t2g and eg orbitals. The d-d transitions underwent a blue shift of about 0.3 eV as the cubic LiCoO2 transformed into the rhombohedral structure with band gap values of about 1.4 and 1.7 eV.

Ni60Nb40 metallic glass particles, prepared by mechanical alloying, were used to fabricate Al–30 wt% Ni60Nb40 metal matrix composites (MMCs) at 823 K by sintering, hot pressing, and hot extrusion. The Ni60Nb40 reinforcements remained amorphous in all the MMCs fabricated by the different methods. Compression tests revealed that the Young’s modulus and yield strength of the MMCs produced by hot-pressing and hot-extrusion are higher than those for the sintered specimens. Differential scanning calorimeter (DSC) annealing of the as-produced MMCs at 913 K revealed there are severe interfacial reactions between the Al matrix and the Ni60Nb40 reinforcements. The DSC isotherms indicate that the Al matrix reacts faster with Ni60Nb40 in the hot-pressed and hot-extruded MMCs than it does in the sintered material.

Lead ruthenate is used as a bifunctional electrocatalyst for both oxygen evolution and reduction and as a conducting component in thick-film resistors. It also has potential applications in supercapacitors and solid oxide fuel cells. However, thermodynamic properties of the compound have not been reported in the literature. The standard Gibbs energy of formation has now been determined in the temperature range from 873 to 1123 K using a solid-state cell incorporating yttria-stabilized zirconia (YSZ) as the electrolyte, a mixture of PbO + Pb2Ru2O6.5 + Ru as the measuring electrode, and Ru + RuO2 as the reference. The design of the measuring electrode is based on a study of phase relations in the ternary system Pb–Ru–O at 1123 K. For the reaction,

the standard enthalpy of formation and standard entropy at 298.15 K are estimated from the high-temperature measurements. An oxygen potential diagram for the system Pb–Ru–O is composed based on data obtained in this study and auxiliary information from the literature

Nanostructured thermally treated xerogels have been synthesized using a sol-gel process involving cerium (Ce) chloride heptahydrate and titanium (Ti) propoxide mixed in different Ce:Ti molar ratios. Structural features of the xerogels have been correlated with their photoluminescence (PL) response. The crystallite sizes in the samples lie in the nanorange. The x-ray diffraction and transmission electron microscopy results have confirmed the coexistence of CeO2 and TiO2 nanocrystallites in these xerogels. In general, a decrease in the CeO2 crystallite size and an increase in the TiO2 crystallite size are observed in the xerogels as a function of Ti content. Scanning electron microscopy results have evidenced the evolution of ordered structure in the xerogels as a function of TiO2 content. Although both of the phases (CeO2 and TiO2) have exhibited PL in ultraviolet and visible regions, the major luminescence contribution has been made by the CeO2 phase. The largest sized CeO2 crystallites in 1:1 thermally treated xerogel have led to its highest PL response. PL emission in the xerogels is assigned to their nanocrystalline nature and oxygen vacancy-related defects.

Properties and phase structures of lead-free piezoelectric ceramics 0.92Na0.5Bi0.5TiO3-0.08BaTiO3 (NBT-BT) modified with La2O3 have been studied. Because of the different valence and ionic radius between La3+ and the exchangeable A-site ions, the lattice distortion and arrangement in the modified compounds can be expected, which will directly influence the phase composition and electrical characteristics of NBT-BT. Differing from familiar frame of gradual variability going with adulteration, NBT-BT doping 0.2–1.0 at.% La2O3 presents an abnormal increase of dielectric constant and a dramatic vanish of piezoelectricity. Further study on the relaxor property and domain structure implies that it originates from a typical relaxor-to-antiferroelectric crossover phase transition. However, a larger addition of La2O3 could rejuvenate the ferroelectricity and piezoelectricity of NBT-BT, correlating well with the model of competing ferro- and antiferroelectric interactions and metastable intermediate phase behavior in the morphotropic phase boundary region of complex perovskites.

We report on linear and nonlinear dielectric property measurements of BaTiO3–CoFe2O4 (BTO–CFO) ferroelectromagnetic nanocomposites and pure BaTiO3 and CoFe2O4 samples with scanning near-field microwave microscopy. The permitivity scanning image with spatial resolution on the micrometer scale shows that the nanocomposites have a very uniform quality with an effective dielectric constant ɛr = 140 ± 6.4 at 3.8 GHz and room temperature. The temperature dependence of dielectric permittivity shows that the Curie temperature of pure BTO was shifted by the clamping effect of the MgO substrate, whereas the Curie temperature shift of the BTO ferroelectric phase in BTO–CFO composites is less pronounced, and if it exists at all, would be mainly caused by the CFO. Nonlinear dielectric measurements of BTO–CFO show good ferroelectric properties from the BTO.

The present investigation reports for the first time a dramatic decrease in the sintering temperature of elemental W from the conventional temperature of ≥2500 °C to the modest temperature range of 1700–1790 °C by making the W powder nanostructured through high-energy mechanical milling (MM) prior to sintering. The crystallite size of the initial W powder charge with a particle size of 3–4 μm could be brought down to 8 nm by MM for 5 h in WC grinding media. Further milling resulted in a high level of WC contamination, which apparently was due to work hardening and the grain refinement of W. A sintered density as high as 97.4% was achieved by sintering cold, isostatically pressed nanocrystalline (8 nm) W powder at 1790 °C for 900 min. The microstructure of the sintered rods showed the presence of deformation bands, but no cracks, within a large number of W grains. The mechanical properties, when compared with the hardness and elastic modulus, of the sintered nano-W specimen were somewhat superior to those reported for the conventional sintered W.

ZnS:Mn cubes, microspheres, and nanospheres were prepared by the solvothermal synthesis approach. All samples possessed the same zinc blende structure. Surfactant cetyltrimethyl ammonium bromide (CTAB) exerts a major influence in directing the formation of these microstructures. By adding the CTAB into the reaction mixture, the cubes of the ZnS:Mn microstructures gradually dissolved to form larger microspheres. These microspheres are composed of an extensive growth of nanoparticles, which can be connected to each other. By increasing the concentrations of CTAB, these microspheres transformed into ZnS:Mn nanospheres. The photoluminescence emission showed a strong and broad peak centered at 594 nm for all samples due to the presence of 4T1 → 6A1 transition of the Mn2+ ion. A broad excitation peak centered at 263 and 327 nm is shown in all samples. Because the products show strong luminescent emissions and variety morphologies, they could be readily fabricated into devices for use in phosphor applications.

Al2O3 films are grown by atomic layer deposition (ALD) using trimethylaluminum and water as precursors on HF-last and NH3 plasma pretreatment Si substrates. The thickness, surface roughness, and density of Al2O3 films as well as the nature of their interlayers with Si substrates are characterized by x-ray reflectivity and spectroscopic ellipsometry techniques. The growth rates of Al2O3 films are 1.1 Å/cycle and 1.3 Å/cycle, respectively, on HF-last and NH3-plasma-nitrided surfaces. Al2O3 layer densities are rather independent of the number of growth cycles in all cases. The interfacial film thickness increases with the number of ALD cycles when deposited on an HF-last Si substrate. However, because SiOxNy inhibits oxygen diffusion, the interfacial film thickness is independent of the number of ALD cycles on the nitrided Si substrate.

In this study, we fabricated eutectic Au–Sn (Au–20 wt% Sn) flip-chip solder bumps from a single electroplating bath. After reflowing, the average diameter of the solder bump was approximately 80 μm. The (Ni,Au)3Sn2 phase was initially formed when the liquid Au–Sn solder reacted with the Ni UBM (under bump metallization). After aging at 150 °C, the (Ni,Au)3Sn2 intermetallic compound (IMC), which formed at the interface during reflow, was fully transformed into the (Au,Ni)Sn IMC due to the restricted supply of Ni atoms from the UBM to the interface. On the other hand, after aging at 250 °C for 1000 h, two IMC layers, (Au,Ni)Sn and (Ni,Au)3Sn2, were formed at the interface. The lower (Ni,Au)3Sn2 phase was formed when the (Au,Ni)Sn phase reacted with the Ni UBM. The interfacial (Au,Ni)Sn IMC grew with the preferential consumption of the available δ-phase in the solder matrix. Eventually, the ζ-phase covered most of the interfacial layer. In the bump shear tests, the Au–Sn/Ni joint aged at 150 °C fractured through the bulk of the solder, confirming the mechanical reliability of the interface. In contrast, the Au–Sn/Ni joint aged at 250 °C fractured along the interface, thereby demonstrating brittle failure, possibly a result of the brittle IMC layer at the interface.

Bis(2,2,6,6-tetramethyl-3,5-heptanedionato)zinc [Zn(TMHD)2] is a relatively uninvestigated precursor that was used in this work to grow highly c-axis-oriented ZnO films on Si(100). X-ray photoelectron spectroscopy studies before and after Ar ion sputtering indicated that surface carbon on several samples was reduced from as much as 34 at.% to much less than 1 at.% within the first 5 nm, indicating very clean Zn(TMHD)2 precursor decomposition. Microstructural and compositional analysis revealed columnar ZnO grains with domain widths of approximately half the total film thickness and a Zn-to-O atomic percent ratio indicative of stoichometric ZnO.

A bulk nanocrystalline (nc) Ni–Fe alloy was subjected to tensile deformation, which leads to grain growth. The nanoindentation study indicates that the hardness, H, and Young’s modulus, E, of the nc alloy before and after tensile deformation did not show a clear indentation-rate effect. However, the tensile deformation results in a decrease in the E values of about 15%, which might be attributed to the grain rotation, leading to texture development during the stress-induced grain growth.

This study investigated the electromigration behavior between Cu and Sn–9Zn solder under a current density of 1.0 × 103 A/cm2 for up to 230 h. The experimental results indicated that Cu5Zn8 was formed at the interface between Cu and the cathode side of the Sn–9Zn solder as well as in the bulk near the anode. Consumption of Cu was also observed for the Cu plating on the cathode side and anodic side, but with less compound formation and Cu consumption at the anode. The intermetallic compound layer on the cathode side was always thicker than that on the anode side after the same current-stressing time. The effect of chemical potential overwhelms electromigration in inducing Zn diffusion when a counterflow of electrons and chemical potential gradient exists. Voids formed at the Cu5Zn8–solder interface inside the solder regardless of the direction of current flow.

Novel magnetic cobalt ferrite nanostructures with curved surfaces (i.e., nanobowls and hollow nanospheres) in a periodic array have been fabricated by in situ reduction of a cobalt and iron salt solution mixture in the interstitial spaces of three-dimensional, close-packed, polystyrene sphere templates. The effect of the shape created by this nanostructure and magnetocrystalline anisotropy introduced by suitable annealing were used to tailor the coercivity to values relevant to high-density data-storage applications.

The accurate description of the indentation load–displacement relationship of an elastic sharp indenter indenting into an elastic half-space is critical for analyzing the nanoindentation data of superhard materials using the procedure proposed by Oliver and Pharr [J. Mater. Res.7, 1564 (1992)]. A further discussion on this issue is made in the present work to reconcile the apparent inconsistencies that have appeared between the experimental results reported by Lim and Chaudhri [Philos. Mag.83, 3427 (2003)] and the analysis performed by Fischer-Cripps [J. Mater. Res.18, 1043 (2003)]. It is found that the indenter size effect is responsible for this large discrepancy. Moreover, according to our analysis, we found that when the deformation of the indenter is significant, besides the errors caused by the Sneddon’s boundary condition as addressed by Hay et al. [J. Mater. Res.14, 2296 (1999)], the errors induced by the application of reduced modulus should be considered at the same time in correcting the modified Sneddon’s solution. In the present work, for the diamond indenter of 70.3° indenting into an elastic half-space with its Poisson’s ratio varying from 0.0 to 0.5 and the ratio of the Young’s modulus of the indented material to that of the diamond indenter, Ematerial/Eindenter, varying from 0 to 1, a set of new correction factors are proposed based on finite element analysis. The results reported here should provide insights into the analysis of the nanoindentation load–displacement data when using a diamond indenter to determine the hardness and Young’s modulus of superhard materials.