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.

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.

Zn-0.7 wt.% Cu-hypoperitectic alloy was prepared in a graphite crucible under a vacuum atmosphere. Unidirectional solidification of the Zn-0.7 wt.% Cu-hypoperitectic alloy was carried out by using a Bridgman-type directional solidification apparatus under two different conditions: (i) with different temperature gradients (G = 3.85–9.95 K/mm) at a constant growth rate (41.63 μm/s) and (ii) with different growth rate ranges (G = 8.33–435.67 μm/s) at a constant temperature gradient (3.85 K/mm). The microstructures of the directionally solidified Zn-0.7 wt.% Cu-hypoperitectic samples were observed to be a cellular structure. From both transverse and longitudinal sections of the samples, cellular spacing (λ) and cell-tip radius (R) were measured. The effects of solidification-processing parameters (G and V) on the microstructure parameters (λ and R) were obtained by using a linear regression analysis. The present experimental results were also compared with the current theoretical and numerical models and similar previous experimental results.

Here we describe a simple method to produce boron nanoparticles with control over surface chemistry and dispersiblity in different solvents, with potential applications ranging from high energy density fuels to neutron capture therapy. The methodology should be adaptable to many hard materials; indeed, we have produced hydrocarbon-dispersible silicon nanoparticles using a procedure similar to that described below. The method, based on high-energy milling, with subsequent sedimentation to separate aggregates, produces gram quantities of nanoparticles in a narrow distribution of particle sizes centered around 50 nm, and should be readily scalable to industrial scale production.

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.

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.

Allotropic hexagonal-close-packed (hcp) → face-centered-cubic (fcc) transformations were reported in Group IVB elements titanium (Ti), zirconium (Zr), and hafnium (Hf) subjected to mechanical milling in a high-energy SPEX shaker mill. Although the transformation was observed in powders milled under regular conditions, no such phase transformation was observed when the powders were milled in an ultrahigh purity environment by placing the powder in a milling container under a high-purity argon atmosphere, which was in turn placed in an argon-filled glove box for milling. From a critical analysis of the results, it was concluded that the hcp → fcc phase transformation was, at least partially, due to pick-up of interstitial impurities by the powder during milling of these powders to the nanocrystalline state.

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.

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.