Nanoparticles of antimony-doped tin oxide (ATO) were characterized for 0–33.3% Sb doping, both in aqueous dispersion and as dried powder. Antimony is incorporated in the cassiterite SnO2 structure of the ATO nanoparticles (d ≈ 7 nm) up to the highest doping levels, mainly as SbV, but with increasing Sb doping the SbIII content increases. We found adsorption of NH3 at the particle surface and evidence for the incorporation of nitrogen in the crystal lattice of the particles. The total nitrogen content increases with increasing Sb doping of the particles. Compact powder conductivity measurements show an increase in conductivity of ATO powder up to 13% Sb and a small decrease for higher Sb contents. Furthermore, we show that these particles can be used to prepare highly transparent conductive cross-linked ATO/acrylate nanocomposites with a continuous fractal particle network through the polymer matrix and a very low percolation threshold (ϕc ≈ 0.3 vol%).

The melting behavior, thermal stability, and glass-forming ability (GFA) of Cu84−xZrxAg8Al8 (x = 42 to 50) glassy alloys were investigated. The alloy with x = 46 exhibits the highest reduced glass transition temperature (Trg). However, the best GFA was obtained for alloy with x = 48 corresponding to the largest supercooled liquid region (ΔTx) and a deep eutectic composition. At the best GFA composition, full glassy samples with diameters of over 20 mm could be fabricated by injection copper mold casting and water quenching without flux. The underlying mechanism of the unusual GFA of the alloy is discussed.

High-energy synchrotron x-ray diffraction (XRD) has been used to quantify load transfer in bovine plexiform bone. By using both wide-angle and small-angle XRD, strains in the mineral as well as the collagen phase of bone were measured as a function of applied compressive stress. We suggest that a greater proportion of the load is borne by the more mineralized woven bone than the lamellar bone as the applied stress increases. With a further increase in stress, load is shed back to the lamellar regions until macroscopic failure occurs. The reported data fit well with reported mechanisms of microdamage accumulation in bovine plexiform bone.

Polarity effect on the interfacial reactions from high-density electric currents was investigated in a solder interconnect with a large disparity in the effective charge between the solder constituents. A reverse polarity effect was found where the intermetallic compound layer at the cathode grew significantly thicker than that at the anode under electric loading. Such an abnormal polarity effect was shown to result from electromigrations of Sn and Zn along opposite directions as dictated by the disparity in their effective charges. As Sn migrated to the anode under electron wind force, the resulting back stress drove Zn atoms to drift to the cathode. A kinetic analysis of the Zn mass transport explained the differential growth of the intermetallic compounds at the two electrodes, in good agreement with the experimental data.

We studied the effect of extended defects on electrical characteristics of Si doped n-type nonpolar a-plane GaN films. The n-type GaN layers were grown on co-loaded reduced defect density sidewall lateral epitaxial overgrowth (SLEO) a-plane GaN templates and high defect density planar a-plane GaN templates by metalorganic chemical vapor deposition (MOCVD). The highest conductivity value was observed at the carrier concentration of 1.05 × 1019 cm−3 as 261.12 cm2/Vs for SLEO a-GaN and 106.77 cm2/Vs for the planar a-plane GaN samples. At the same doping level, the carrier compensation for SLEO samples was ∼12% less than planar samples.

The effect of nanomaterials in platinum-decorated, multiwalled, carbon nanotube-based electrodes for amperometric glucose sensing was investigated by a comparative study with other carbon material-based electrodes such as graphite, glassy carbon, and multiwalled carbon nanotubes. Scanning and transmission electron microscopy and x-ray diffraction were used to investigate their morphologies and crystallinities. Electrochemical impedance spectroscopy was conducted to compare the electrochemical characteristics of these electrodes. The glucose-sensing results from the chronoamperometric measurements indicated that carbon nanotubes improve the linearity of the current response to glucose concentrations over a wide range, and that platinum decoration of the carbon nanotubes produces improved electrochemical performance with a higher sensitivity.

We report the fabrication of micron-sized rodlike particles of nonstoichiometric Co and Ni ferrites by aging coprecipitated Fe(OH)2 and M(OH)2—where M is either Ni or Co—at 90 °C in the presence of an external magnetic field (B ≈ 405 mT). Potassium nitrate was used as a mild oxidant. Resultant particles were analyzed by means of electron microscopy, x-ray powder diffraction (XRD), magnetometry, energy dispersive x-ray (EDX) spectrometry, and atomic absorption spectroscopy. Rodlike particles of both types of ferrite exhibited a relatively uniform thickness, an average aspect ratio close to 10, and have a spinel crystalline structure. EDX spectrometry and atomic absorption spectroscopy confirmed the incorporation of Ni2+ and Co2+ in the respective ferrite particles. The incorporation of Co2+ led to non-negligible remanence and coercivity. The incorporation of Ni2+ led to a lower saturation magnetization, whereas the remanence and coercivity of the Ni ferrite were very low, still typical of a soft ferrimagnetic material. The mechanism of formation of the rodlike particles was investigated by the time-dependent observation of growing Ni ferrite rods.

The lattice parameters of magnesium solid-solution alloys with lithium, indium, and/or zinc have been determined via x-ray diffraction (XRD). Li decreased the axial ratio (c/a) of Mg from 1.624 to 1.6068 within 0–16 at.% Li. Indium increased the c/a of Mg to 1.6261 with increasing In toward 3.3 at.% while Zn showed no effect on c/a in the 0.2–0.7 at.% range. The effects were explained by electron overlap through the first Brillouin zone and by Vegard’s Law. A relationship was determined between electron concentration (e/a) and c/a as c/a = −15.6(e/a)2 + 60(e/a) − 55.8.

The high local temperature in flip-chip solder joints of microprocessors has raised concerns that the solder, a low melting temperature alloy, might locally liquefy and consequently cause failure of the microprocessors. This article reports a highly interesting electromigration behavior when the solder is in the molten state. A 6.3 × 103 A/cm2 electron current was applied to molten Sn3.5Ag solder at 255 °C through two Cu electrodes. The high current density caused rapid dissolution of the Cu cathode. The dissolved Cu atoms were driven by electrons to the anode side and precipitated out as a thick, and sometimes continuous, layer of Cu6Sn5. The applied current caused the dissolution rate of the Cu cathode to increase by one order of magnitude. A major difference between the electromigration in the solid and molten state was identified to be the presence of different countering fluxes in response to electromigration. For electromigration in the molten state, the back-stress flux, which was operative for electromigration in the solid state, was missing, and instead a countering flux due to the chemical potential gradient was present. An equation for the chemical potential gradient, dμ/dx, required to balance the electromigration flux was derived to be dμ/dx = N°z*eρJ, where N° is Avogadro’s number, z* is the effective charge of Cu, e is the charge of an electron, ρ is the resistivity of the solder, and J is the electron current density.

Four kinds of extruded Mg–X at.% Zn binary alloys (X = 1.9, 2.4, 3.0, and 3.4) were used to examine the effect of precipitate volume fraction on fracture toughness. All the alloys had fine grain sizes of 1–3 μm and fine sphere-shaped precipitates of 50–60 nm. The volume fraction of precipitates increased with additional zinc content. The results of mechanical property tests showed that the extruded Mg–2.4 at.% Zn alloy exhibited the best balance of strength and fracture toughness. One of the reasons was the different volume fraction of precipitates at the grain boundaries, which was the source of void formation. According to the fracture surface observations and ductile fracture model analysis, the volume fraction of precipitates of 2%–4% was shown to be enough to improve the fracture toughness for the fine-grained magnesium alloys; i.e., higher contents of zinc atoms were not needed to enhance the mechanical properties.

Fine grained, three-phase ceramic composites that exhibit favorable toughness, hardness, and high room-temperature strength were evaluated for high-temperature mechanical stability. A 50vol%Al2O3–25vol%NiAl2O4–25vol%3 mol%yttria-stabilized tetragonal zirconia polycrystal (3Y–TZP) and a 33vol%Al2O3–33vol%NiAl2O4–33vol%3Y-TZP composite were compression creep tested at temperatures between 1350 and 1450 °C under constant stresses of 20–45 MPa. The three-phase microstructure effectively limited grain growth (average d0 = 1.3 μm, average df = 1.6 μm after 65% true strain). True strain rates were 10−4 to 10−6 s−1 with stress exponents n = 1.7 to 1.8 and a grain-size exponent p = 1.3. A method for compensating for grain growth is presented using stress jump tests. The apparent activation energy for high-temperature deformation for 50vol%Al2O3–25vol%NiAl2O4–25vol%3Y–TZP was found to be 373 kJ/mol-K.

In situ observation of the electrically induced crack growth and domain-structure evolution is carried out for [100]- and [101]-oriented 72%Pb(Mg1/3Nb2/3)O3–28% PbTiO3 (PMN–PT 72/28) ferroelectric single crystals under static (poling) and alternating electric fields. On the same poling electric field, domains are in the stable engineered domain state where four equivalent polarization variants coexist for [100]-oriented single crystal, while parallel lines representing the 71° domain boundaries appear for [101]-oriented one. Under the same cyclic electric field, the [100]-oriented single crystal shows much higher crack propagation resistance than that of a [101]-oriented crystal. Apart from the material aspects, such as crystallographic fracture anisotropy and non-180° domain boundary structure, crack boundary condition plays an important role in determining the crack propagation behavior.

The deformation behavior of the organic polymer matrix of the biocomposite nacre structure in abalone shell was investigated by in situ straining during transmission electron microscopy (TEM). We observed strong adhesion to mineral plates and high ductility of the organic matrix, confirming a crack-bridging toughening mechanism. In addition, direct observation of reversible mechanical behavior was made in the viscoelastic reformation of matrix ligaments after failure. Crystalline β-sheet structures identified through electron diffraction suggested the presence of protein structures similar to spider or cocoon silk, and the reversible mechanism was attributed to hydration-induced unfolding and refolding of domains in these silklike proteins. This work provides further insight into the molecular and nanoscale behavior of nacre organic matrix and its contribution to bulk mechanical performance.

The cubic nanocrystalline Li–Ti–O oxides were prepared by the solvothermal reaction of TiO2 and LiOH at 200 °C in water and aliphatic alcohols with different dielectric constants. The reaction in all solvents leads to the formation of white ternary compounds containing Li, Ti, and O. The actual Li content in the prepared materials increases with decreasing polarity of the used solvent. All prepared materials are crystalline, and their structure can be described using a spinel structural model. The structure of materials prepared at a relative dielectric constant (ϵr) value higher than 33 is characterized by Ti disorder when the Ti atoms are distributed between both types of the available octahedral sites with approximately the same probability. The tendency to form phases with Ti disorder decreases with decreasing ϵr of the solvent. All prepared materials are active toward electrochemical Li insertion. The observed specific capacity ranges between 60 and 150 mAh/g.

Cu–Zn is an important binary alloy system. In the interested temperature range from 300 to 1500 K, there are eight phases, liquid, Cu, β, β′, γ, δ, ϵ, and Zn phases. The thermodynamic descriptions of the Cu–Zn system are reassessed using the CALPHAD method. A new description of liquid phase and simplified description of body-centered cubic (bcc) phase are proposed. Good agreement has been found among the calculated thermodynamic properties, phase diagram, and the experimental information.

Dispersed uniform spherical silver particles were prepared in the absence of a protective colloid by rapidly mixing concentrated isoascorbic acid and silver-polyamine complex solutions. By varying the nature of the amine, temperature, concentration of reactants, silver/amine molar ratio, and the nature of the silver salt, it was possible to tailor the size of the resulting metallic particles in a wide range (80 nm to 1.3 μm). The silver spheres were formed by aggregation of nanosize subunits, the presence of which was detected by both electron microscopy and x-ray diffraction. Due to its simplicity, high metal concentration, and the absence of polymeric dispersants, the described method represents an advantageous route to manufacture cost-effectively dispersed uniform silver particles for electronic applications.

Hydrogels pose unique challenges to nanoindentation including sample preparation, control of experimental parameters, and limitations imposed by mechanical testing instruments and data analysis originally intended for harder materials. The artifacts that occur during nanoindentation of hydrated samples have been described, but the material properties obtained from hydrated nanoindentation have not yet been related to the material properties obtained from macroscale testing. To evaluate the best method for correlating results from microscale and macroscale tests of soft materials, nanoindentation and unconfined compression stress-relaxation tests were performed on poly-2-hydroxyethyl methacrylate (pHEMA) hydrogels with a range of cross-linker concentrations. The nanoindentation data were analyzed with the Oliver–Pharr elastic model and the Maxwell–Wiechert (j = 2) viscoelastic model. The unconfined compression data were analyzed with the Maxwell–Wiechert model. This viscoelastic model provided an excellent fit for the stress-relaxation curves from both tests. The time constants from nanoindentation and unconfined compression were significantly different, and we propose that these differences are due to differences in equilibration time between the microscale and macroscale experiments and in sample geometry. The Maxwell–Wiechert equilibrium modulus provided the best agreement between nanoindentation and unconfined compression. Also, both nanoindentation analyses showed an increase in modulus with each increasing cross-linker concentration, validating that nanoindentation can discriminate between similar, low-modulus, hydrated samples.

Ultrafine eutectic-like microstructures of various rare earth (RE) oxide-Al2O3 systems were formed by use of amorphous phases. This new method uses a low migration rate in the amorphous phases. Mixtures of RE oxide (RE: Yb, Dy, Er, Ho, Gd, Sm, Eu) and Al2O3 powders with the eutectic compositions were melted and quenched rapidly to form the amorphous phases. A heat treatment of the amorphous phases of various eutectic systems at 1000 and 1300 °C, for 30 min, formed RE aluminum garnet (RE3Al5O12)/Al2O3 phases or RE aluminum perovskite (REAlO3)/Al2O3 phases. Scanning electron microscopy observation of these materials heat-treated at 1300 °C showed eutectic-like microstructures, in which crystals of eutectic component were entangled with each other. Furthermore, the microstructures were much finer than those of materials generally prepared from eutectic melts. In this study, it was confirmed that this method is useful for the formation of ultrafine eutectic-like microstructures for many eutectic systems.

Stoichiometric silicon carbide coatings the same as those used in the formation of TRISO (TRistructural ISOtropic) fuel particles were produced by the decomposition of methyltrichlorosilane in hydrogen. Fluidized bed chemical vapor deposition at around 1500 °C, produced SiC with a Young’s modulus of 362 to 399 GPa. In this paper we demonstrate the deposition of stoichiometric silicon carbide coatings with refined microstructure (grain size between 0.4 and 0.8 μm) and enhanced mechanical properties (Young’s modulus of 448 GPa and hardness of 42 GPa) at 1300 °C by the addition of propene. The addition of ethyne, however, had little effect on the deposition of silicon carbide. The effect of deposition temperature and precursor concentration were correlated to changes in the type of molecules participating in the deposition mechanism.

The electromigration behavior of the Cu/Au/SnAgCu/Cu combination was investigated under 103 A/cm2 of current stressing at ambient temperature. The Au layer, when it acts as a cathode, was consumed continuously, and no significant compound was found at the interface. Meanwhile, Cu6Sn5 was formed at the anodic Cu layer, and the thickness of the compound increased with increasing time. The Au atoms were found to be trapped in Cu6Sn5 within the solder matrix. The AuSn4 compound precipitated while attaching to Cu6Sn5 at the Cu6Sn5/solder interface. The thermomigration effect was found to be insignificant in this work as no obvious reaction occurred at the cathode/anode sides or in the solder matrix without current stressing.