The in vitro behaviors of the etched, electrochemically anodized, and hydroxyapatite (HA)-coated Ti6Al4V alloys were investigated through microstructural analysis, electrochemical measurements, and immersion tests in the Hank’s solution. A nanometer-scale, bonelike porous structure with a layer of TiO2 on top was formed during the anodization process. The surface of the coated substrate was composed of a thin TiO2 layer adjacent to the substrate, a thick monolithic HA on the outside, and a composite layer of TiO2 and HA in the middle. The anodization significantly improved the stability of the Ti6Al4V alloy in Hank’s solution due to a layer of TiO2 formed on the surface. The precoated HA further improved the stability of the Ti6Al4V alloy due to a composite layer of TiO2 and HA. The barrier layer of the composite of TiO2 and HA was suggested by the capacitive behavior of the HA-coated substrate in the electrochemical impedance spectroscopy. The electrochemical measurements implied a high tendency for the new formation of HA on the precoated HA and the anodized substrates, which was confirmed through the immersion tests. The newly formed HA on the anodized substrate was scattered over the entire surface. The newly formed HA on the HA-precoated surface mingled with the precoated HA, and gradually a new layer of HA was formed on top. These proved the favorable condition of the anodized surface as a prerequisite step for coating HA and the conductive promotion of new HA formation on the precoated surface. The new formation of HA during the immersion might suggest that artificial joints pretreated through anodization and HA coating could induce strong bonding to the bone due to the easy growth of new HA.

Flowerlike manganese oxide microspheres and cryptomelane-type manganese oxide nanobelts were selectively synthesized by a simple decomposition of KMnO4 under mild hydrothermal conditions without using template or cross-linking reagents. The effect of varying the hydrothermal times and temperatures on the nanostructure, morphology, compositional, and electrochemical properties of the obtained manganese oxides was investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) studies showed that the flowerlike manganese oxide microspheres could be obtained at relatively low hydrothermal temperatures, while high hydrothermal temperatures were favorable for the formation of cryptomelane-type manganese oxide nanobelts. A morphology and crystalline evolution of the nanostructures was observed as the hydrothermal temperature was increased from 180 to 240 °C. On the basis of changing the temperatures and hydrothermal reaction times, the formation mechanism of cryptomelane-type manganese oxide nanobelts is discussed. Cyclic voltammetry (CV) was used to evaluate the electrochemical properties of the obtained manganese oxide nanostructures, and the results show that the electrochemical properties depend on their shape and crystalline structure. This easily controllable, template-free, and environmentally friendly method has the potential for being used in syntheses of manganese oxide nanomaterials with uniform morphologies and crystal structures.

Hydrogenated nanocrystalline Si (nc-Si:H) thin films were prepared by plasma- enhanced chemical vapor deposition (PECVD). The films were deposited with a radio-frequency power of 100 W, while substrates were exposed to direct current (dc) biases in the range from 0 to −400 V. The effects of dc bias on the formation of nanoscale Si crystallites in the films and on their optical characteristics were investigated. The size of the Si crystallites in the films ranges from ∼1.9 to ∼4.1 nm. The relative fraction of the crystallites in the films reached up to ∼56.5% when a dc bias of −400 V was applied. Based on the variation in the structural, chemical, and optical features of the films with dc bias voltages, a model for the formation of nanostructures of the nc-Si:H films prepared by PECVD was suggested. This model can be utilized to understand the evolution in the size and relative fraction of the nanocrystallites as well as the amorphous matrix in the nc-Si:H films.

Two important analytical means—theoretical bounds and homogenization techniques—have gained increasing attention and led to substantial progress in material research. Nevertheless, there is a lack of relating material microstructures to an entire theoretical bound and exploring the possibility of generating multiple microstructures for each property value. This paper aims to provide a microstructure diagram in relation to “bound B” constructed by translation and Weiner bounds. The inverse homogenization technique is used to seek for the optimal phase distribution within a base cell model to make the effective conductivity approach the “bound B” in two- or three-phase material cases. The design shows that the “bound B” is exactly attainable for two-phase composites even with single-length-scale microstructures. Although the multiphase translations bounds are well known to be asymptotically attainable on some parts, they still appear too roomy to be attained by single-length-scale composites. Our results showed a certain improvement in the attainability of single-length-scale structural composites when compared with new bounds established by [V. Nesi: Proc. R. Soc. Edinburgh Sect. A125, 1219 (1995)], [V. Cherkaev: Variational Methods for Structural Optimization (Springer Verlag, New York, 2000)], and (N. Albin et al.: Proc. R. Soc. London Ser. A463, 2031 (2007)]. Applicability of the translation bounds to the composites with high-contrast conductivities of phase compositions is also studied in this paper. Finally, we explore the multiple solutions to the optimal microstructures and categorize them into three classes in line with their topological resemblance, namely, spatially identical, unidirectionally identical, and bidirectionally different solutions.

We propose a parallel resistance model (PRM) in which total resistance (Rtotal) is given by the parallel connection of resistance of a filament (Rfila) and that of a film excluding the filament (Rexcl)—that is, 1/Rtotal = 1/Rfila + 1/Rexcl—to understand direct current (dc) electric properties of resistive random-access memory (ReRAM). To prove the validity of this model, the dependence of the resistance on temperature, R(T), and the relative standard deviation (RSD) of RHRS of Pt/NiO/Pt on the area of a top electrode, S, are investigated. It is clarified that both the R(T) and RSD depended on S, and all such dependencies can be explained by the PRM. The fact that Rtotal is decided by the magnitude relation between Rfila and Rexcl makes transport properties S-dependent and hinders the correct understanding of ReRAM. Smaller S is essential to observe the intrinsic transport properties of ReRAM filaments.

A combustion-synthesized AlN powder was investigated for use as a starting material in obtaining a high thermal conductivity AlN by microwave sintering followed by microwave reheating under a reducing atmosphere. Microwave sintering was found to proceed very quickly so that a density of 99.5% of theoretical with a thermal conductivity of 165 W/mK was achieved after sintering at 1900 °C for 5 min. The thermal conductivity could be improved by prolonging the soaking time, which is attributed to decreases in both oxygen content and secondary phases by evaporation and sublimation of the secondary phases. The reducing atmosphere was created by adding carbon particles to the AlN packing powder surrounding the specimen. The thermal conductivity could be significantly improved by microwave reheating of the sintered specimen under the reducing atmosphere. This is considered to be due to enhanced removal of the secondary phases by the reducing atmosphere. Sintering under the reducing atmosphere was found to retard densification because of the earlier removal of the secondary phases, thus resulting in a poor densification and a low thermal conductivity.

The present study shows that the as-melt-spun Zr28Y28Al22Co22 amorphous ribbon undergoes solid-state phase separation into Zr- and Y-rich regions when heated below the glass transition temperature (Tg). Dynamic mechanical measurements show that two types of low-temperature relaxation occur below Tg, and transmission electron microscopy observation confirms the solid-state phase-separated microstructure. The diffusion coefficient of solid-state phase separation is calculated by the measured separation distance.

A multiscale modeling approach applied to the stiffness prediction of polymers with high cross-link density is discussed. The material of focus in this work is the ionic polymer Nafion®. The approach applies rotational isomeric state theory in combination with a Monte Carlo methodology to develop a simulation model for polymer chain conformation. From this a large number of end-to-end chain lengths between cross links are generated; the probability density function of these lengths is estimated with the most appropriate Johnson family method. This estimation is used in a Boltzmann statistical thermodynamics approach to the multiscale prediction of stiffness. This work addresses the importance of the simulated polymer chain length in the generation of stable predictions. The multiscale prediction is found to be physically reasonable; the approach has the potential of serving as a first-order prediction tool for properties that are experimentally difficult or impossible to measure.

A new amphiphile: octyl-β-D-glucopyranoside along with a single-source precursor, barium titanium methoxyethoxide, were used to develop a facile route for synthesis of BaTiO3, via either a hydrolytic or a nonhydrolytic method. The average particle size for the samples was on the order of 20 to 30 nm, while that for the control samples (without the amphiphile) ranged from 100 nm to several microns. The high-resolution transmission electron microscopy (HRTEM) images and selected-area electron- diffraction patterns revealed that these nanoparticles were single crystalline; the Raman active longitudinal optical modes observed in calcined (650 °C) samples at 718 and 304 cm−1 directly indicated the presence of tetragonal domains in an overall cubic lattice structure. Moreover, the one-step nonhydrolytic approach developed for the synthesis of BaTiO3 is fast, and it eliminates tedious steps such as prolonged refluxing and aging. Thermogravimetric and Fourier transform infrared (FTIR) analysis were performed to investigate the role of octyl-β-D-glucopyranoside in the evolution of the perovskite phase, grain size, and morphology. These techniques suggested that van der Waals type of interactions were present between the amphiphile and barium titanium methoxyethoxide oligomers, and in turn they led to the controlled growth of nanoparticles.

Porous magnesium with directional cylindrical pores (or “lotus-type” porous magnesium) was fabricated through the use of hydrogen decomposed from MgH2 powders during unidirectional solidification. Liquid magnesium was cast into a mold in which MgH2 powders were placed and was unidirectionally solidified, which achieved growth of pores elongated along the direction of solidification. The effect of the amount of the MgH2 powders on the pore structure (porosity, diameter, and number density of pores) and the change in the pore structure along the pore growth direction were clarified. The porosity and number density of pores increase with increasing amount of MgH2 powder, and the average diameter of pores decreases with increasing amount of MgH2 powder. The pore structure changes with the growth of pores along the solidification direction.

Rapid thermal annealing (RTA) processing under N2 and O2 ambient is suggested and characterized in this work for improvement of SiCOH ultra-low-k (k = 2.4) film properties. Low-k film was deposited by plasma-enhanced chemical vapor deposition (PECVD) with decamethylcyclopentasiloxane and cyclohexane precursors. The PECVD films were treated by RTA processing in N2 and O2 environments at 550 °C for 5 min, and k values of 1.85 and 2.15 were achieved in N2 and O2 environments, respectively. Changes in the k value were correlated with the chemical composition of C–Hx and Si–O related groups determined from the Fourier transform infrared (FTIR) analysis. As the treatment temperature was increased from 300 to 550 °C, the signal intensities of both the CHx and Si–CH3 peaks were markedly decreased. The hardness and modulus of the film processed by RTA have been determined as 0.44 and 3.95 GPa, respectively. Hardness and modulus of RTA-treated films were correlated with D-group [O2Si–(CH3)2] and T-group [O3Si–(CH3)] fractions determined from the FTIR Si–CH3 bending peak. The hardness and modulus improvement in this work is attributed to the increase of oxygen content in (O)x–Si–(CH3)y by rearrangement.

Subcritical cracking of thin glass films caused by stress-corrosion phenomena cannot be neglected when it comes to application and manufacturing processes that involve exposure to aqueous environments. A protocol is introduced to allow for a quantitative study of stress corrosion through channel cracking experiments. By this method, an exponential dependence of the crack propagation rate on the pH of the aqueous environment is revealed. Therefore, this behavior should be accounted for through the use of an appropriate pre-exponential factor in the expression of channel cracking rate. This factor should reflect the reduced crack resistance of the glass film caused by the weakening of the silica bonds behind the crack tip in the aqueous environment. A direct comparison between commercial slurries and reference solutions confirms that the crack resistance is a function of the pH of the ambient.

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%).