We explore key mechanical responses of the layered microstructure found in selected parts of the exoskeletons (pronotum, leg and elytron) of Popillia japonica (Japanese beetle). Image analyses of exoskeleton cross-sections reveal four distinct layered regions. The load-bearing inner three regions (exocuticle, mesocuticle, and endocuticle) consist of multiple chitin-protein layers, in which chitin fibers align in parallel. The exocuticle and mesocuticle have a helicoidal structure, where the stacking sequence is characterized by a gradual rotation of the fiber orientation. The endocuticle has a pseudo-orthogonal structure, where two orthogonal layers are joined by a thin helicoidal region. The mechanics-based analyses suggest that, compared with the conventional cross-ply structure, the pseudo-orthogonal configuration reduces the maximum tensile stress over the exoskeleton cross-section and increases the interfacial fracture resistance. The coexistence of the pseudo-orthogonal and helicoidal structures reveals a competition between the in-plane isotropy and the interfacial strength in nature’s design of the biocomposite.

Focused ion beam machining was used to manufacture microcantilevers 30 μm by 3 μm by 4 μm with a triangular cross section in single crystal copper at a range of orientations between. These were imaged and tested using AFM/nanoindentation. Each cantilever was indented multiple times at a decreasing distance away from the fixed end. Variation of the beam’s behavior with loading position allowed a critical aspect ratio (loaded length:beam width) of 6 to be identified above which simple beam approximations could be used to calculate Young’s modulus. Microcantilevers were also milled within a single grain in a polycrystalline copper sample and electron backscattered diffraction was used to identify the direction of the long axis of the cantilever. The experimentally measured values of Young’s modulus and their variation with orientation were found to be in good agreement with the values calculated from the literature data for bulk copper.

It is yet unclear how far surface effects can dominate small volume creep deformation in the surface layer of a metallic solid. We report experimental results of the apparent activation volume of single, ultrafine-grained, and nanocrystalline Cu over a range of nanoscale displacements. The dependence of the apparent activation volume on the depth and grain size was determined using nanoindentation creep tests. The surface-affected deformation regimen, within which interfacial diffusion between the nanoindenter tip and the sample totally dominates the creep behavior, was quantitatively determined to be below ∼12 nm. As the initial creep depth is increased, the dominant mechanism is shifted from interfacial diffusion to grain-boundary diffusion as the contribution of the surface effects gradually vanishes when the indenter penetrates deeper into the sample (i.e., further away from the external surface).

We have investigated the fracture behavior of tetrahedral amorphous carbon films, with thicknesses 0.15 (ultrathin), 0.5 (thin), and 1.2 (thick) microns on silicon substrates. To that end, the systems were progressively loaded into a nanoindenter using a spherical tip, and surface and cross sections were subsequently examined using a focused ion beam miller at different loads. A transition was found as a function of film thickness: for ultrathin and thin films, cracking (radial and lateral) initiated in the silicon substrate and followed a similar path in the films. Thicker films, on the other hand, provided a higher level of protection to the substrate, and cracking (lateral and radial at the interface) was constrained to the film. The damage modes and the transition obtained differ from those that occur in thick coatings. Lateral cracks are highly dangerous, leading to delamination of thick films and to spallation when thinner films are used. The results have implications concerning the mechanical reliability of microelectromechanical systems.

The process of ultrathin Al-induced crystallization of amorphous Si (a-Si) has been investigated by using high-resolution transmission electron microscopy and Auger electron spectroscopic depth profiling. Ultrathin Al overlayers, with thicknesses of 2.0 and 4.5 nm, have been shown to be capable of inducing full crystallization of an a-Si bottom layer as thick as 40 nm at temperatures as low as 320 °C. After full crystallization of a-Si, the Al of the original 2.0-nm Al overlayer completely moved through the Si layer, leaving a high-purity, large-grained crystalline Si layer above it. Such movement of Al also occurs for the originally 4.5-nm Al overlayer, but in this case the crystallized Si layer is relatively fine-grained and contains ∼5.0 at.% of residual Al nanocrystals distributed throughout the layer. The observations have been interpreted on the basis of sites available for nucleation of crystalline Si in the microstructure of the Al/Si layer system upon annealing.

Co–B films were synthesized through the solvent evaporation-assisted chemical reduction method by using a mixed-surfactant solution containing Span 40 and (1S)-(+)-10-camphorsulfonic acid. With the characterization of x-ray diffraction, selected-area electron diffraction, x-ray photoelectron spectroscopy, scanning electron micrography, and transmission electron micrography, the resulting Co–B films were identified to be amorphous alloys with mesoporous structure. The synergistic effect of two kinds of surfactants is essential for the formation of mesoporous structure. During liquid-phase cinnamaldehyde hydrogenation to cinnamyl alcohol, the mesoporous Co–B amorphous alloy films exhibited a much higher activity and better selectivity than the solid Co–B nanoparticles prepared by direct reduction of cobalt ions with borohydride. The enhanced activity is attributed to both the mesoporous and the film structure, which provides more Co active sites for the adsorption and diffusion of reactant molecules. The improved selectivity may be related to the difference in surface curvature.

A polypropylene-matrix composite material functionalized by nanoporous particulates was produced. When the temperature is relatively low, the matrix dominates the system behavior. When the temperature is relatively high, with a sufficiently large external pressure the polymer phase can be intruded into the nanopores, providing an energy absorption mechanism.

Zinc oxide (ZnO)/carbon-nanotubular-structures (CNTS) nanohybrids were grown using a three-step laser process. First, an ultraviolet (UV) laser (KrF) was used to deposit Co/Ni catalyst nanoparticles (NP) directly onto SiO2/Si substrates. Second, a random network of CNTS was grown onto these Co/Ni-catalyzed substrates by using the UV-laser ablation method. Finally, ZnO nanostructures were grown onto the CNTS template by means of the CO2 laser-induced chemical liquid deposition technique. While the laterally grown CNTS mainly consist of nanotube bundles featuring a high aspect ratio (diameter of ∼20 nm and length of up to several microns), the ZnO nanostructures were found to consist of various morphologies including nanorods, polypods, and nanoparticles with a size as small as 2 nm. The ZnO/CNTS nanohybrids were found to exhibit a polychromatic photoluminescent (PL) emission, at room temperature, comprising a narrow near-UV band centered around 390 nm, a broad visible to near infrared band (500–900 nm), and a relatively weak emission band centered around 1000 nm. These PL results are compared to those of individual components (CNTS and ZnO) and discussed in terms of carbon defect density and possible charge transfer between the ZnO nanocrystals and the carbon nanotubes.

The effects of Al incorporation and post-deposition annealing on the structural properties of C-Al-N thin films prepared by reactive unbalanced dc-magnetron sputtering were investigated using x-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and high-resolution transmission electron microscopy (HRTEM). XPS studies demonstrated the presence of abundant Al-N bonds in addition to C-C and N-C bonds. At low incorporations of Al and N, the films were found to be essentially amorphous. By Raman and HRTEM, the formation of ∼5 nm fullerene-like carbon nitride (FL-CNx) nanostructures in an amorphous (C, CNx) matrix was evidenced with increasing Al content in the films. Crystalline improvement of FL-CNx nanostructures was seen, as well as the precipitation of ∼3–4 nm face centered cubic (fcc-) AlN nanograins by thermal annealing at 500 °C or above. Through these improvements, C-Al-N nanocomposite thin films were achieved. The effects of the incorporated Al and annealing on stabilizing fcc-AlN nanograins and FL-CNx nanostructures are elucidated and explained through the use of thermodynamic considerations.

We report deposition and tribological studies of a chemisorbed UHMWPE (ultra-high-molecular-weight polyethylene) film on an Si surface. UHMWPE molecules containing carboxyl and hydroxyl chemical groups were chemisorbed onto an Si surface using an intermediate GPTMS SAM (glycidoxypropyltrimethoxy silane self-assembled monolayer) layer. The carboxyl and hydroxyl groups of UHMWPE molecules react with the terminal epoxy groups of GPTMS SAM during chemisorption. The resultant film (∼1.4 µm thick) has shown low coefficient of friction (∼0.1) and high wear life (exceeding 100,000 cycles) in a sliding test against a 4 mm diameter Si3N4 ball at a normal load of 0.3 N and a sliding velocity of 0.042 m/s measured on a micro-tribometer. In contrast, bare Si or GPTMS SAM modified Si has shown a higher coefficient of friction and failed within a few tens of sliding cycles. The high wear durability of the chemisorbed polymer film is attributed to the excellent adhesion of the UHMWPE film with the substrate due to chemisorption and to the good lubrication properties of UHMWPE molecules. This wear resistant film has potential applications in micro-electro-mechanical systems made of Si.

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.

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.

A thermodynamic study was carried out to resolve discrepancies in the enthalpy of formation and related parameters for lanthanum zirconate pyrochlore. The homogeneity field for single phase pyrochlore formation was determined to be ∼33–35 mol% La2O3 at 1500 °C. High-temperature oxide melt drop solution calorimetry was performed in sodium molybdate and lead borate solvents on three compositions ranging from La1.98Zr2.01O7 to La2.07Zr1.95O7. The enthalpy of formation from oxides at 25 °C, ΔH0f,ox, for stoichiometric lanthanum zirconate pyrochlore is −107.3 ± 5.1 kJ/mol, and the standard enthalpy of formation from elements, ΔH0f,el, is −4102.2 ± 6.0 kJ/mol. La2Zr2O7 pyrochlore was found by differential thermal analysis to be stable up to its melting point. The melting point and the fusion enthalpy of La2Zr2O7 pyrochlore were measured as 2295 ± 10 °C and ∼350 kJ/mol, respectively.

This article describes the synthesis and the characterization of a polyamide-12 filled with a nanostructured organic/inorganic titanoniobate hybrid material. The pristine oxide KTiNbO5 has been successfully organomodified by N-alkyl amines via an acido-basic reaction after a cationic exchange step as shown by x-ray diffraction. Transmission electron microscope study and scanning transmission electron microscope observations have been used to describe the change of morphology of the nanofillers before and after processing; the micronic aggregates were changed into single sheets and dispersed in the polymer. Thermomechanical properties of the composites have been determined, and their analyses with structure-properties models are consistent with the exfoliation of the organomodified titanoniobates.

Ultraviolet irradiation (λ = 248 nm) was used to photocatalyze a solution of the heteroleptic titanium alkoxide (OPy)2Ti(TAP)2 [where OPy = pyridine carbinoxide and TAP = 2,4,6 tris(dimethylamino)phenoxide], leading to the deposition of a titania-based thin film only in the exposed region. The effect of water addition to the (OPy)2Ti(TAP)2 pyridine solution on the properties of the final photodeposited film structure was examined by using vibrational spectroscopy and electron microscopy. Under consistent optical exposure conditions, the amount of water added altered the nanoscale porosity of the final material produced. Films deposited from a solution with a 1:1 H2O/Ti content exhibited surface pores ∼100 nm in diameter, whereas a 4:1 ratio yielded 10-nm pores, and material produced from a 8:1 solution appeared fully condensed. In addition, the effect of postdeposition thermal treatments on the nanostructure and chemistry of the photodeposited films was examined.

Strontium titanium silicates are possible oxide forms for immobilization of short lived fission products in radioactive waste. Through beta decay, strontium decays to yttrium, and then to zirconium. Therefore, not only the stability of Sr-loaded waste forms, but also that of a potential decay product series with charge-balance in a naturally occurring mineral or a ceramic is of fundamental importance. Strontium titanosilicate (SrTiSiO5) is the Sr-analogue of titanite (CaTiSiO5). To incorporate the reaction 3Sr2+ = 2Y3+ + vacancy in the titanite composition, Y-substituted Sr-analogues of titanite, (Sr1–xY2/3x)TiSiO5 (x = 0, 0.25, 0.5, 0.75) were prepared by high temperature synthesis and were found to form glass upon cooling. The Y-end-member (Y2/3TiSiO5, x = 1) crystallized to a mixture of Y2TiSiO7, TiO2, and SiO2 upon quenching in air. The enthalpies of formation of Y-substituted Sr-titanite glasses were obtained from drop solution calorimetry in a molten lead borate (2PbO·B2O3) solvent at 702 °C. The enthalpies of formation from constituent oxides are exothermic but become less so with increasing Y content. The thermodynamic stability of the Y-substituted Sr-analogue of crystalline titanite may become marginal with increasing yttrium content.

An all-oxide Al2O3-TiO2 ceramic multilayer composed of 10–100 nm thick alternating layers was fabricated using the reactive magnetron sputtering process. Microindentation tests were carried out on the multilayer ceramic followed by microstructural observations of the cross-sections of the indented sites to characterize the indentation response of the system. During the observations, it was noted that an extensive room temperature “deformation” occurred in the multilayer ceramic material. The material shows a thickness reduction of as much as ∼40% under a conical indenter at 300 mN of load without microcracking and dislocation-assisted deformation. The room temperature deformation mechanism is governed by the relative movement and rearrangement of the anisotropic nanoscale columnar grains along the intergranular boundaries containing elongated voids. The relative sliding along the intergranular boundaries, and the subsequent granular rotation under indentation were well captured by finite element simulation.

The poor wettability between ceramics and metals is a main obstacle in obtaining high-performance metal-matrix composites (MMCs) parts using direct metal laser sintering (DMLS). Rare earth (RE) elements, due to their unique physical and chemical properties, have high potential for improving laser processability of MMCs. In this work, a comparative study was performed to investigate the influence of RE–Si–Fe addition on microstructural features and mechanical properties of DMLS processed tungsten carbide (WC) particle reinforced Cu MMCs parts. It showed that by adding 3 wt% RE–Si–Fe, the WC reinforcing particles were refined, the particle dispersion state was homogenized, and the particle/matrix interfacial compatibility was enhanced. The RE–Si–Fe-containing WC/Cu MMCs parts possessed significantly elevated mechanical properties, i.e., densification level of 95.7%, microhardness of 417.6 HV, fracture strength of 201.8 MPa, and friction coefficient of 0.8. The metallurgical functions of the RE–Si–Fe additive for the improvement of DMLS quality of MMCs parts were discussed.

The massive spalling of Cu3Sn in the soldering reaction between high-Pb solders and Cu substrates was studied to identify the mechanism behind this rather interesting and frequently observed phenomenon. Four different alloys (99.5 Pb 0.5 Sn, 99 Pb 1S n, 97 Pb 3 Sn, and 95 Pb 5 Sn, in wt%) were soldered at 350 °C for durations ranging from 10 s to 600 min. At low Sn concentration (0.5 or 1 Sn), massive spalling occurred as early as 20 min. However, at high Sn concentration (3 or 5 Sn), massive spalling was not completed even after 600 min. To the best of our knowledge, these results are the most detailed observations ever reported on the sequence of events that occur during massive spalling. The Pb–Sn–Cu phase diagram is used to rationalize the phenomenon.

Two Fe-Al-Ti alloys with coherent αFe,Al (A2) + Fe2AlTi (L21) microstructures have been produced and the evolution of the microstructure with aging time has been studied by light optical and scanning electron microscopy and hardness measurements. The compressive flow strength, creep properties, brittle-to-ductile-transition temperatures (BDTT), and oxidation behavior of the alloys have been evaluated. The results show that the investigated alloys show good flow strength, high creep resistance, and good oxidation resistance. However, their BDDT is high compared to binary Fe-Al-based alloys and compared to other Fe-Al-Ti alloys no increase in creep resistance was achieved by generating coherent microstructures. The latter effect is due to the breakup of the coherent microstructures when the temperature varies because the compositions and consequently the volume fractions of the phases vary markedly depending on temperature.