We report that lightly abrading the surface of a commercial leaded brass results in the room temperature spontaneous growth of Pb whiskers and hillocks. The aspect ratios and submicron diameters of the whiskers that form render them easily dispersible in the atmosphere, with potentially serious health effects, especially for people that deal with leaded brass on a daily basis.

Based on a comparison of relationships between the energy dissipated during indentation and the ratio of hardness to elastic modulus, a procedure is outlined to determine hardness and elastic modulus from the ratio of the elastic to total energy dissipated during an indentation cycle for non-ideal indenters.

Gold nanoclusters were successfully deposited in the interior of TiO2 nanotubes fabricated as ordered arrays. This approach is a useful fabrication platform for miniature planar fuel cells, gas sensors, and heterogeneous catalysts. A pressure impregnation process was used to inject the titania and Au precursors into mesoporous alumina. After thermal treatment, Au nanoclusters were well-dispersed on the interior walls of nanotubular TiO2. The TiO2 nanotubes were shown by x-ray diffraction to be entirely anatase. Transmission electron microscopy imaging confirmed that 80% of the Au particles were 4.1 nm ± 2.0 nm in diameter. This material exhibited catalytic CO oxidation activity at low temperatures.

Nacre, the inner layer of mollusk shells is a composite made of platelets of mineral aragonitic calcium carbonate with a few weight percent organic material sandwiched in between. The organic and nanostructural nuances are often suggested to be the reason for the extreme toughness of nacre. Here we report the presence of interlocks between platelets of nacre from red abalone. We also report and show, using three-dimensional finite element modeling, that interlocks are the key mechanism for the high toughness and strength of nacre. The observed rotation between platelet layers, which were earlier reported as defects of structure, are necessary for the formation of interlocks.

Band-structure calculations of germanium carbide (GeC) show that it is a new indirect wide band gap semiconducting material, which crystallizes in both cubic and hexagonal phases. Through the density functional and total-energy technique in the generalized gradient approximation, the two polytypes 3C and 2H of GeC were studied. According to our calculations, it is a hard material with a percentage of covalency of about 80–90%. Important energy gaps were determined. The bulk modulus, density of states, and charge density were calculated. For the bulk modulus calculations, Murnaghan’s equation of state was used under elastic deformation to measure hardness. Our calculations showed that this semiconducting material crystallizes in zincblend (Eg = 1.76 eV) and wurtzite (Eg = 2.5 eV) structures.

The layered compounds MnPS3 and CdPS3 were exfoliated to form single molecular layers of Mn0.8PS3 and Cd0.8PS3 in suspension in water by ion exchange. The x-ray diffraction patterns of the two single-layer suspensions showed profound differences in some of the Bragg peaks, and we demonstrated that the differences are not due to the quality or size of the single layers, but are caused by structure factor modulations of the Warren tail for two-dimensional systems. We also demonstrated that the Cd or Mn vacancies generated in the exfoliation process are not ordered at long range, in contrast to an earlier report of vacancy ordering on intercalated MnPS3.

A dark red colored composite of C60 and (zinc, bismuth) borate glass was synthesized by solid-state reaction between C60 and frits of the glass at 650–700 °C in an argon atmosphere completely free from oxygen and moisture. An unusual change in color and the absorption spectrum of the glass upon composite formation with C60 indicated that the incorporated C60 underwent some sort of interaction with the glass. Such fullerene molecules bonded to relatively smaller units of bismuth-boron network, were extracted out by eluting a powdered sample with toluene. The composite itself and the toluene extract there of, were then characterized by ultraviolet–visible–near-infrared, infrared, and mass spectral studies. The results showed that the bismuth ions of the bismuth-boron network were bonded with the C60 cages through direct donation of their lone pair of electrons to the latter. The phenomenon of addition of boron to C60 via an “oxygen bridge,” which was observed in our earlier work, was also detected in this case. Studies on the nonlinear optical properties of the composite exhibited a moderate value of third order nonlinear susceptibility χ(3) (1.5 × 10−11 esu) and optical limiting properties of the composite. The result showed that the material had the prospect of being used in nonlinear optical devices.

Wear-resistant Cu-based solid-solution-toughened Cr5Si3/CrSi metal silicide alloy with a microstructure consisting of predominantly the dual-phase primary dendrites with a Cr5Si3 core encapsulated by CrSi phase and a small amount of interdendritic Cu-based solid solution (Cuss) was designed and fabricated by the laser melting process using Cr–Si–Cu elemental powder blends as the precursor materials. The microstructure of the Cuss-toughened Cr5Si3/CrSi metal silicide alloy was characterized by optical microscopy, powder x-ray diffraction, and energy dispersive spectroscopy. The Cuss-toughened silicide alloys have excellent wear resistance and low coefficient of friction under room temperature dry sliding wear test conditions with hardened 0.45% C carbon steel as the sliding–mating counterpart.

Raman spectroscopy was used to determine the lattice expansion and stress distribution within the ion implanted layer in sapphire crystals. The crystals with the (1120) facewere implanted with 3.0 MeV H+ ions to doses of 3.3 × 1017 cm−2 and 4.8 × 1017 cm−2.The strain components and their variation with depth were analyzed by measuring the shift of the Raman peak on the cross-sectional basal plane. A continuum mechanics approach considered a model of a semi-infinite anisotropic elastic space subjected to the implantation-induced lattice expansion. The expansion and resulting compressive stresses were found to increase with depth, reaching a sharp maximum at the end of the ion range. The implantation-induced expansion coefficient was shown to be independent of the ion energy loss and implantation depth in sapphire. Such behavior was discussed in light of stopping and range of ions in matter data and defect production by nuclear collisions and ionization processes.

To understand the ceria–silica chemical mechanical polishing (CMP) mechanisms, we studied the effect of ceria slurry pH on silica removal and surface morphology. Also, in situ friction force measurements were conducted. After polishing; atomic force microscopy, x-ray photoelectron spectroscopy, and scanning electron microscopy were used to quantify the extent of the particle–substrate interaction during CMP. Our results indicate the silica removal by ceria slurries is strongly pH dependent, with the maximum occurring near the isoelectric point of the ceria slurry.

We examined the influence of the boundary plane on grain-boundary diffusion in Ni through a series of molecular dynamics simulations. A series of 〈010〉 ∑5 tilt boundaries, including several high symmetry and low symmetry boundary planes, were considered. The self-diffusion coefficient is a strong function of boundary inclination at low temperature but is almost independent of inclination at high temperature. At all temperatures, the self-diffusion coefficients are low when at least one of the two grains has a normal with low Miller indices. The grain boundary self-diffusion coefficient is an Arrhenius function of temperature. The logarithm of the pre-exponential factor in the Arrhenius expression was shown to be nearly proportional to the activation energy for diffusion. The activation energy for self-diffusion in a (103) symmetric tilt boundary is much higher than in boundaries with other inclinations. We discuss the origin of the boundary plane density–diffusion coefficient correlation.

A new type of bioactive materials, hydroxyapatite (HA)/α-wollastonite (α-Wol) composites, were prepared. The sintering behavior, phase evolution, and in vitro bioactivity of hydroxyapatite/α-wollastonite composites were examined. The properties of HA/α-Wol composites were quite different from those of HA ceramics or α-Wol ceramics. HA/α-Wol composites sintered 1300 °C for 2 h exhibited a dense microstructure consisting of grains in the range of 0.3–1.0 μm in diameter. During sintering, a complex phase evolution between HA and α-Wol was observed. At 1300 °C, the formation of the Si substituted HA and the additional α-tricalcium phosphate (TCP) were observed using Fourier transform infrared and x-ray diffraction analysis. Further heat treatment at 1350 °C transformed part of the HA and α-Wol into a new phase with the composition: Ca12P6Si2O31. The in vitro bioactivity of the HA/α-Wol composites with a weight ratio of 25:75 and 50:50 sintered at 1300 °C was better than that of α-Wol monophasic ceramics. This result revealed that the silica of α-Wol and the orthosilicate of Si substituted HA provided nucleation sites for the bonelike apatite layer. The phosphate present in the HA or α-TCP phases promoted the nucleation of a bonelike apatite layer on the surface of the composites. The dissolution rate of α-Wol phase in simulated body fluid was faster than α-TCP or HA phase. Therefore, HA/α-Wol composite is the bone replacement material of controllable bioactivity and degradation rate with relative content between HA and α-Wol phase.

In this work, we performed infrared reflectivity measurements of RETiTaO6 dielectric ceramics for rare-earth (RE) = Y, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Yb. The infrared spectra were analyzed through the four-parameter semi-quantum model based on two orthorhombic (aeschynite and euxenite) structures presented by the ceramics. We discerned the strongest phonon modes that contribute to the intrinsic dielectric behavior of the two families. Then the unloaded quality factors and the dielectric permittivities were estimated at the microwave region. The variations of the intrinsic dielectric response of both systems with RE ion substitution are discussed in terms of changes in their dielectric polarizabilities. It is proposed that the covalency of the RE–O bonds play an important role in the evolution of dielectric permittivity as well as in the sign of the temperature coefficient of the resonant frequency.

The indentation behavior of cold-rolled AA6061 Al alloy was investigated. Following the approach suggested by Tabor, indentation stress–indentation strain curves were constructed and analyzed. The indentation stress required to create the same indentation strain increases with an increase in the reduction of thickness, suggesting a strong effect of plastic deformation history on the deformation behavior of materials. Through the dislocation dynamics, the evolution of the dislocations underneath the indentation was correlated with the plastic deformation history and the indentation load. The plastic energy dissipated in indentation was then calculated and found to be proportional to the 3/2 power of the indentation load and the 3/4 power of the average dislocation density underneath the indentation. The ratio of the dissipated plastic energy to the total energy in the indentation was demonstrated to be a function of the deformation state in materials, independent of the indentation load.

Using an all-electron, full potential first-principles method, we have investigated the topology of charge density and elastic anisotropy of Ti3SiC2 polymorphs comparatively. By analyzing the charge density topology, it was found that the Ti–Si bonds are weaker in β than in α, resulting in a destabilizing effect and lower Young’s modulus in directions between a and c axes for β. On the other hand, the Si–C bonds (absent in α) are formed in β in the c direction. The formation of the Si–C bonds not only mitigates the destabilizing effect of the weaker Ti–Si bonds, but also results in larger Young’s modulus in the c direction. In contrast to the high elastic anisotrophy, the elastic anisotropy of Ti3SiC2 is very low.

The elastic properties of a nickel film approximately 800 nm thick were measured with nanoindentation, microtensile testing, atomic force acoustic microscopy (AFAM), and surface acoustic wave (SAW) spectroscopy. Values for the indentation modulus (220–223 GPa) and Young’s modulus (177–204 GPa) were lower than predicted for randomly oriented polycrystalline nickel. The observed behavior was attributed to grain-boundary effects in the nanocrystalline film. In addition, the different measurement results were not self-consistent when interpreted assuming elastic isotropy. Agreement was improved by adopting a transversely isotropic model corresponding to the film’s 〈111〉 preferred orientation and reducing the elastic moduli by 10–15%. The SAW spectroscopy results indicated that the film density was 1–2% lower than expected for bulk nickel, consistent with models for nanocrystalline materials. Similar reductions in modulus and density were observed for two additional films approximately 200 and 50 nm thick using AFAM and SAW spectroscopy. These results illustrate how complementary methods can provide a more complete picture of film properties.

Based on dimensional analysis and finite element computations, an energy-based representative strain for conical indentation in elastoplastic materials has been proposed to establish an explicitly one-to-one relationship between the representative stress σr, the indentation loading curvature C, and the ratio of reversible work We to total work Wt performed by the indenter, i.e., σr/C = F0(We/Wt), where σr is the flow stress corresponding to the representative strain. The relationship provides a very simple method to evaluate the representative stress σr from the three directly measurable quantities We, Wt, and C. Numerical examples and further theoretical analysis reveal that a unique, stable solution can be obtained from the present method for a wide range of material properties, including both highly plastic materials (e.g., Ni for which E/σy = 1070) and highly elastic materials (e.g., materials for which E/σy = 25 and n = 0.5), using indenters with different tip apex angles. Based on the representative strains and stresses given by two indenters with different tip apex angles, e.g., (σr,80, ϵr,80) and (σr,65, ϵr,65), the plastic properties of materials, i.e., the yield strength σy and strain hardening exponent n can be further determined.

A method for applying conductive inorganic tungsten bronze (NaxWO3) coatings over ceramic foams is presented. The general basis of bronze coating involves an intermediate layer between the ceramic surface and the redox external agent (liquid or gas phase). The intermediate layer is a multifunctional element and its function depends on the agents involved in redox reaction. The bronze film is formed either on the intermediate layer or in place of it. The initial melt included Na2WO4, WO3, and NaCl. The reticulated ceramic foams, made from pure alumina (Al2O3), were prepared by a standard impregnation method. In all depositions, the temperature was above the melting point of the Na2WO4/WO3 system. The effect of NaCl content on the final coating properties was investigated in the 10–40 mol% range. The best results were obtained with hydrogen reduction of 40% NaCl in the melt. The bronze crystals size in the coating was 0.8–1.6 μm. The bronze layer was continuous throughout the foam. The obtained coating has a bright yellow-gold color, consistent with a stoichiometric parameter value (x) of 0.85–0.95. The resistivity of coated foams decreased from above 12 Ω mm to below 1 Ω mm when the NaCl concentration in the melts increased from 10% to 40%, respectively, due to improved continuity of the bronze crystals. These highly conductive, bronze-coated alumina foams, can potentially serve as high-temperature electrodes in aggressive conditions.

YBa2Cu3Oy (YBCO) films produced by the ex situ conversion of BaF2-based precursors deposited by physical vapor deposition on ion-beam assisted deposited (IBAD) yttrium-stabilized zirconia (YSZ) and rolling-assisted biaxially textured substrates (RABiTS) templates are characterized by a bi-axially aligned, laminar grain structure that results from the anisotropic growth characteristics of the YBCO phase and its precipitation from a transient liquid phase during the conversion process. A bimodal microstructure characterizes these films and is defined by large, well-formed YBCO grains with Y2O3 precipitates in the bottom region of the film and small YBCO grains with a high density of stacking faults in the upper half. Ba2Cu3Oy or Ba–O–F/CuO second phase layers were often found between large YBCO grains in the bottom half of the films. YBCO grain sizes exceeded 50 μm within the plane of the film in some cases. Conversely, discrete secondary phases of Y2Cu2O5, Y2O3, and Ba2Cu3Oy/Ba–O–F could be found among the much smaller YBCO grains in the top portion of the bimodal structure. The dividing line of the bimodal structure was generally at one half of the film thickness, although exceptions to this trend were found. The highest critical current densities (Jc) and best film alignments for a given film thickness were found in samples where the layers of Ba2Cu3Oy or Ba–O–F were minimized or eliminated from the films. Samples quenched after partial conversion show the segregation of CuO to the top region of the film and the lateral growth of large YBCO grains from a precursor mix of Y2Cu2O5 and Ba–O–F. The data demonstrate that transient liquid phases are part of the conversion process of BaF2-based YBCO films. The control of both CuO segregation and the amount of liquid phases generated during the initial stages of phase formation is needed for optimizing the ex situ conversion process for high-Jc coated conductors.

Softening or melting behavior of the organically-modified siloxane hybrid gels and glasses in the system of RSiO3/2 and R2SiO2/2 (R: methyl and phenyl) has been investigated to obtain a new family of low-melting glasses. The RSiO3/2 and RSiO3/2–R2SiO2/2 gels showed softening temperatures around 50–100 °C. The softening temperature of RSiO3/2 single-component glasses, which were obtained by melting the corresponding gels at a temperature above the softening temperature, increased by heat-treatment at 200 °C, and finally showed no softening behavior. On the other hand, in the PhSiO3/2–Ph2SiO2/2 binary glasses, the softening temperatures showed a tendency to saturate after longer heat treatment over 200 h. These facts indicate that the present organically modified siloxane system will be a potential candidate for the low-melting glass.