The electron energy structure of self-assembled In(Ga)As/GaAs nanostructures, quantum dots, and quantum rings was studied with capacitance-voltage spectroscopy and one-dimensional numerical simulation using Poisson/Schrödinger equations. The electron energy levels in the quantum dots and quantum rings with respect to the electron ground state of the wetting layer were determined directly from capacitance-voltage measurements with a linear lever arm approximation. In the regime where the linear lever arm approximation was not valid anymore (after the charging of the wetting layer), the energy difference between the electron ground state of the wetting layer and the GaAs conduction band edge was obtained indirectly from a numerical simulation of the conduction band under different gate voltages, which led to the erection of complete electron energy levels of the nanostructures in the conduction band.

As the outer surface of a nanoporous carbon is treated with 16-mercaptohexadecanoic acid, the carbon particles can form a stable suspension in water. When the water phase is compressed, the liquid infiltration behavior in the nanopores becomes significantly different from that of untreated material, suggesting that the inner surface is also modified. After the treatment, the infiltration pressure does not decrease. Therefore, the surface-chain configurations at the inner and outer surfaces must be different, which explains the variations in infiltration pressure and volume.

We report on the preparation of a bioactive CaO–SiO2 monolithic scaffold with interconnected bimodal nanomacro porosity, which simulates the morphology of a natural trabecular bone, by a newly developed modified sol-gel process. This method inherently creates nanopores, whose average diameter can be tailored to approximately 5–20 nm by solvent exchange. To achieve interconnected macroporosity (pores ∼5–300 μm in size), a polymer [poly(ethylene oxide)] is added, which causes phase separation simultaneously with the sol-gel transition. High-resolution scanning electron microscopy and mercury intrusion porosimetry demonstrate a high degree of three-dimensional interconnectivity and sharp distributions of pore size. In vitro bioactivity tests in simulated body fluid (SBF) show bioactivity of the material after soaking for approximately 5 h, as verified by the formation of a hydroxyapatite layer deep into the scaffold structure. Analysis of the SBF after the reaction indicates the dissolution of the samples, another desired feature of temporary scaffolds for bone regeneration. MG63 osteoblast-like cells seeded on our sol-gel glass samples responded better to samples with nanopores enlarged by a solvent exchange process than to the one with normal nanopores. Thus, the benefits of the high surface area achieved by sol-gel and solvent exchange procedures are most clearly demonstrated for the first time.

Mg2Ni1-xCux (x = 0, 0.2, 0.4) and Mg2Ni1-yCoy (y = 0, 0.2, 0.4) were successfully synthesized via two steps: induction melting and then ball milling. The component and microstructure of the alloys were determined with x-ray diffraction (XRD) and scanning electron microscopy/x-ray energy-dispersive spectrometry (SEM/XEDS). Mg2Ni phase was observed in all 5 alloys. When the amount of Cu was increased, it led to the formation of phase from Mg2Cu to Cu11Mg10Ni9. Co2Mg was detected in the Co-containing alloys. The hydrogen absorption/desorption properties were tested with p-C-T measurement apparatus, and the results showed that the gaseous storage properties of the alloys were improved by the addition of Cu or Co.

To determine the optimum baking temperatures for nanopowder introduction, the variation of reflective spectrum of baked zinc oxide powders, which are used as pigments for thermal control coatings of spacecraft, has been investigated over the wavelength range of 0.225–2.5 μm after being baked at temperatures between 400 °C and 850 °C. It has been established that baking temperatures over 750 °C result in a reduction of spectral reflectance in the visible light spectrum region. This is due to the formation of absorption bands of intrinsic point defects and thus increasing the spectral reflectance in the near-infrared region. The optimum temperature is 650 °C at which the bleaching effect was observed long after heat treatment. Moreover, an increase in the reflection coefficient occurs in the regions of 380–450 nm and 1100–2500 nm in this case.

A linear relationship between the ratio of elastic work to the total indentation work and hardness to reduced modulus, i.e., We/Wt = λ H/Er, has been derived analytically and numerically in a number of studies and has been widely accepted. However, the scaling relationship between We/Wt and H/Er has recently been questioned, and it was found that λ is actually not a constant but is related to material properties. In this study, a new relationship between We/Wt and H/Er has been derived, which shows excellent agreement with numerical simulation and experimental results. We also propose a method for obtaining the elastic modulus and hardness of a material without invoking the commonly used Oliver and Pharr method. Furthermore, it is demonstrated that this method is less sensitive to tip imperfections than the Oliver and Pharr approach is.

The electrical resistivity ρ of palladium (Pd) films prepared by using magnetron sputtering at different pressures φ ranging from 2 to 15 mTorr showed very different hydrogen (H)-induced response. This reaction is because the mean free path of the particles in vacuum changes substantially with φ, such that the structure of the deposits is altered accordingly. A film prepared at a moderate φ value of 6 mTorr has a moderate strength. After a few hydrogenation-dehydrogenation cycles, some cracks are generated because of the great difference in the specific volumes of the metal and hydride phases. Breathing of the cracks in subsequent switching cycles occurred, which led to the response gain of ρ, defined as the resistivity ratio of the dehydrogenated-to-hydrogenated states during a cycle, to increase to 17. This result demonstrates the attractiveness of using the Pd films in H2 detection application. The H-induced resistive response of the films prepared at other φ values was found to be much smaller.

A ternary system composed of Tb(DBM)3Phen (TbDP), Eu(DBM)3Phen (EuDP), and poly(N-vinylcarbazole) (PVK) was prepared with good thermal stability and the photoluminescence (PL) was studied. By comparing their emissions, it was found that energy transfer exists from PVK to lanthanide complexes in the ternary system. It also was found that the lifetime of 5D0 of Eu3+ in the ternary system is longer than that of the binary system of EuDP and PVK, but the lifetime of 5D4 of Tb3+ in the ternary system is shorter than that of the binary system of TbDP and PVK, showing evidence of energy transfer from TbDP to EuDP. Temperature-dependent PL spectra of the ternary system from 9 to 300 K further showed there is a change in energy transfer efficiencies from Tb3+ ions to Eu3+ ions at different temperature ranges, which not only is more evidence of energy transfer but also can be used as a temperature detector or a thermal-sensitive probe of a optical fiber sensor.

By using homogeneous electron-beam (EB) irradiation, rapid adhesion between nylon-6 film and polymethyl methacrylate (PMMA) was successfully developed. Effects of homogeneous irradiation of electron beam with low potential (HIEBL) on adhesive strength of different polymers without glue were investigated. HIEBL less than 0.216MJ kg−1 (MGy) increased the adhesive strength and its strain of composites constructed with nylon-6 film and PMMA, although additional HIEBL at more than 0.432 MGy apparently decreased the adhesive strain. HIEBL less than 0.432 MGy also enhanced the elasticity (dσ/dε)o of composites. To evaluate the influence of HIEBL on the adhesive strength, electron spin resonance signals that relate to dangling bonds were observed. Because EB irradiation generated dangling bonds in polymethyl methacrylate and nylon-6, dangling bonds probably acted reactive and bonding sites to each polymer at interface. Therefore, HIEBL enhanced the adhesive strength as well as elasticity of the composites.

In the present study, we compared cytotoxicity and cell uptake of silica nanoparticles with four different surface coatings generated through layer-by-layer self-assembly. Rabbit mesenchymal stem cells (rMSCs) were labeled with silica nanoparticles of different coatings including poly(ethyleneimine) (PEI), poly(allylamine hydrochloride) (PAH), poly(anetholesulfonic acid, sodium salt) (PAS), and dextran sulfate. The MTT [3-(4, 5-dimethylthiazol-2)-2, 5-diphenyl-2H-tetrazolium bromide] test was performed to quantify the cell biocompatibility. The cellular uptake of those silica nanoparticles was determined by flow cytometry and confocal laser scanning microscopy. The results showed that all examined silica nanoparticles were stable in aqueous phase with high monodispersity. Labeled rMSCs are unaffected in their viability, apoptosis, and differentiation capacities. The silica nanoparticle-coated synthetic polycations such as PEI or PAH have higher cell internalization than negatively charged polyelectrolytes. The ability to control cell uptake of different particles may have applications in cell labeling, cell separation, and other biomedical applications.

The effects of ruthenium (Ru)-oxidation states were investigated on Ru dissolution from PtRu thin-film electrodes, with the 200 cycles between 0.4 and 1.05 V (versus normal hydrogen electrode). The Ru-oxidation states of the PtRu thin films were systematically modified by an anodic (oxidation) treatment. The anodic-treated PtRu electrodes, whose methanol-oxidation activity was similar to untreated electrodes before the 200 cycles, showed a remarkable decrease in methanol oxidation after the cycles, because of the Ru dissolution from the PtRu surface. The results suggest that the Ru-oxide species are the origin of Ru dissolution in the PtRu alloy.

X-ray diffraction patterns, scanning electron microscopy images, and transmission electron microscopy images showed that one-dimensional GaN nanorods with [0001]-oriented single-crystalline wurtzite structures were grown on Al2O3 (0001) substrates by hydride vapor-phase epitaxy without a catalyst. The tip morphology of the GaN nanorods became flat with increasing temperature difference between the gas mixing and the substrate zones. The gas mixing temperature significantly affected the formation of the nanorods, and the substrate temperature influenced the morphology and the strain of the GaN nanorods near the GaN/Al2O3 heterointerface. The strain and the stress existing in the GaN layer near the heterointerface were decreased with increasing growth rate. The formation mechanisms of the GaN nanorods grown on the Al2O3 (0001) substrates are described on the basis of the experimental results.

Hybrid zeolite-polyamide thin film nanocomposite (TFN) reverse osmosis membranes were synthesized by incorporating Linde type A (LTA)-type zeolite molecular sieve nanocrystals in the interfacial polymerization reaction used to form polyamide thin films. Nanocrystals were prepared with two different mobile cations (Na+ and Ag+) exchanged within the LTA crystal matrix. Incorporation of molecular sieve nanocrystals into polyamide thin films during interfacial polymerization was verified by infrared spectroscopy. Both TFN membranes exhibited higher water permeability, while maintaining similar salt rejection to pure polyamide thin film composite membranes. Nanocomposite thin films containing LTA nanocrystals in the silver form (AgA) produced a greater increase in water permeability than those in the sodium form (NaA). Furthermore, AgA-TFN membranes exhibited more hydrophilic and smooth interfaces, which appeared to inhibit adhesion of bacteria cells onto the membranes. The AgA nanocrystals exhibited significant bactericidal activity; however, when encapsulated within polyamide thin films the antimicrobial activity was significantly reduced.

The solid-phase epitaxial growth kinetics of amorphized (011) Si with application of in-plane uniaxial stress to magnitude of 0.9 ± 0.1 GPa were studied. Tensile stresses did not appreciably change the growth velocity compared with the stress-free case, whereas compression tended to retard the growth velocity to approximately one-half the stress-free value. The results are explained using a prior generalized atomistic model of stressed solid-solid phase transformations. In conjunction with prior observations of stressed solid-phase epitaxial growth of (001) Si, it is advanced that the activation volume tensor associated with ledge migration may be substrate orientation-dependent.

We show a drastically improved gas–solid reaction between NH3 and LiH by mechanical treatment for LiH, generating a hydrogen gas even at room temperature. The results of x-ray photoelectron spectroscopy showed that the mechanical pretreatment was effective in reducing a hydroxide phase from the surface of LiH. It was also possible to successfully recycle back LiNH2, which is the byproduct of this hydrogen desorption reaction, to LiH under 0.5-MPa H2 flow at 573 K. Thus, the LiH–NH3 system provides a recyclable H2 storage system to generate H2 at room temperature with 8.1 mass% and 4.5 kg/100 L hydrogen capacity.

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).

To explore potential applications of nanocomposites for microelectronic packaging, the thermal properties were investigated on newly developed nanocrystalline Al composites reinforced by AlN nanoparticles. It was found that the thermal conductivity (TC) is reduced with increasing AlN volume fraction (Vp), since connectivity of Al matrix is decreased by introduction of the nanoparticles. Although AlN nanoparticles introduce thermal resistance, they still have significant contribution to the TC of the composite as high-TC inclusion. Particularly, a percolation behavior of AlN nanoparticles is thought to occur with the threshold at 23–30%. Measurements at elevated temperatures (∼500 °C) show almost no distinct degradation of TC relative to room temperature. Moreover, the coefficient of thermal expansion (CTE) is remarkably lowered as Vp increases, e.g., from 26 × 10−6 to 13.9 × 10−6 K−1, by raising Vp to 39%. Therefore, the nanocomposites may be applicable as electronic packaging material, due to the combination of acceptable TC and low CTE.

We have developed a soft lithography-based process to create microscale patterns of silica on a diverse array of substrates. A sacrificial polymer layer was first patterned using a micromolding technique. A peptide was adsorbed on the substrate and the sacrificial layer was removed. The patterned peptide template then catalyzed the deposition of silica from a silicic acid solution. With this procedure, we have created both continuous and discontinuous silica patterns on metallic, ceramic, and polymer substrates.

The structure and the response of the effective electrical resistivity 〈ρ〉 in hydrogenation–dehydrogenation processes of palladium-coated/magnesium-nickel (Pd/Mg–Ni) films were investigated as functions of Mg-to-Ni ratio, substrate temperature, and thickness of Pd overcoat. Films of noncrystalline structures with various Mg-to-Ni ratios showed prominent hydrogen-(H-)induced switching effect of 〈ρ〉. A film is supposed to contain segregated noncrystalline regions of different Mg-to-Ni ratios. The regions of an Mg-to-Ni ratio close to 2 are responsible for the switching processes. At room temperature, a dehydrogenation process is much slower than a hydrogenation process. Crystallization hindered the H-induced switching effect of 〈ρ〉. The use of a thicker Pd overcoat accelerated the change of 〈ρ〉 in the initial hydrogenating process but diminished the contrast. Results led to some discussions on the mechanisms governing the switching effects.

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.