Magnesium alloys are potential biodegradable biomaterials in hard tissue implants. However, the fast degradation rate in the biological environment has hampered widespread applications. We propose to use a ZrO2 coating in conjunction with a Zr transition layer to improve the corrosion resistance of AZ91 magnesium alloy. X-ray photoelectron spectroscopy discloses that the coating is composed of ZrO2. The Vickers hardness measurement demonstrates that the surface hardness of the alloy is significantly enhanced. The electrochemical behavior of the coated sample is systematically evaluated by means of potentiodynamic polarization, open-circuit potential evolution, and electrochemical impedance spectroscopy. The electrochemical results indicate that the corrosion resistance of the coated alloy is enhanced significantly, and the electrode-controlled processes in a coated alloy–solution system are discussed.

The microstructures of exoskeletons from Homarus americanus (American lobster) and Callinectes sapidus (Atlantic blue crab) were investigated to elucidate the mechanical behavior of such biological composites. Image analyses of the cross-sectioned exoskeletons showed that the two species each have three well-defined regions across the cuticle thickness where the two innermost regions (exocuticle and endocuticle) are load bearing. These regions consist of mineralized chitin fibers aligned in layers, where a gradual rotation of the fiber orientation of the layers results in repeating stacks. The exocuticle and endocuticle of the two species have similar morphology, but different thicknesses, number of layers, and number of stacks. Mechanics-based analyses showed that the morphology of the layered structure corresponds to a nearly isotropic structure. The cuticles are inter-stitched with pore canal fibers, running transversely to the layered structure. Mechanics-based analyses suggested that the pore canal fibers increase the interlaminar strength of the exoskeleton.

Phases that are in equilibrium with BaR2CuO6+x (R=lanthanides and Y), such as the “green-phase” and “brown-phase” structural variants of BaR2CuO5 in bulk samples, are attractive choices for flux-pinning for coated conductor applications because of the guaranteed chemical stability. In films, high-temperature x-ray diffraction studies of Ba2RCu3O6+x superconductor deposited on SrTiO3 substrate using the trifluoroacetate solution method demonstrate that while BaNd2CuO5 (“brown-phase” structure) develops at 735 °C and 100 Pa pO2, neither BaGd2CuO5 nor Ba(Nd1/3Eu1/3Gd1/3)2CuO5 (both green-phase structure) form at these conditions. As a result, Ba2(Nd1/3Eu1/3Gd1/3)Cu3O6+x in thin films is in equilibrium with the brown-phase, and Ba2GdCu3O6+x is in equilibrium with Gd2O3 in the Ba–Gd–Cu–O system, in contrast to the bulk systems. Different phase relationships in the vicinity of the Ba2RCu3O6+x phase imply different phases are available for flux-pinning applications. These differences will need to be considered carefully in designing optimized superconducting coated conductors.

Fe-doped In2O3 nanocubes were synthesized by a solvothermal method. The lattice constant a decreases linearly as Fe doping concentration increases, and Raman scattering measurement proves the incorporation of Fe ions into the In2O3 crystal lattice. Mössbauer spectra show the presence of mixed valence of Fe ions instead of Fe3O4, while the sample is superparamagnetic. The products with an average diameter of 80 nm have a single-crystalline phase and appear as a square shape. Magnetic measurements confirm the superparamagnetic properties of the nanocubes, and electron paramagnetic resonance studies indicate Fe ions occupy different sites in the In2O3 matrix.

Metal-matrix composites are produced from Al powder and 30 vol% of icosahedral Al–Cu–Fe quasi-crystalline particles using a hot isostatic pressing technique. It is demonstrated that the initial icosahedral phase is transformed into the ω-Al70Cu20Fe10 tetragonal phase during the hot isostatic pressing (HIP) process. The mechanical properties of the composite were evaluated over the temperature range 293 to 773 K by performing compression tests at constant strain rate. The temperature dependence of the yield stress gives evidence of two temperature regimes with a transition temperature at approximately 423 K. Strain-rate sensitivity measurements support the change in rate-controlling deformation mechanisms at this temperature. It is proposed that cross-slip and/or climb mechanism control plastic flow. Finally, it is suggested that the phase transformation of the particle contributes positively to the improvement of the mechanical properties.

Due to their versatility and accuracy, nanoindentation systems are increasingly used for the characterization of micron-sized particles. Single microbial cells (e.g., yeast cells) can be regarded as micron-sized, liquid-filled biological particles. Applying a nanoindentation system for the compressive testing of those cells offers many options, such as testing in liquid environment. However, diverse experimental problems have to be resolved, especially the visualization of the cells in liquid and the alignment of the surfaces between which the cell is compressed. Single yeast cells were tested using a nanoindenter equipped with a flat punch tip. The deformation behavior of the cells during loading as well as the shape recovery behavior during unloading was investigated. A bursting force was determined as the cell wall was failing at higher deformations. Moreover, the influence of the compression speed on the cell mechanical behavior was characterized.

A cellular automation (CA) model has successfully been used to model the development of microstructure of an aluminum alloy during solidification to produce detailed structure maps for the solidified alloys. More recently, the application of CA models to practical castings/solidification conditions has attracted increasing research interest. However, the determination of the calculation parameters of any model associated with nucleation is difficult. Accordingly, this work investigates the detailed effect of the six parameters of nucleation on microstructure formation and morphology as well as the grain size by cellular automaton-finite control volume method (CAFVM). The nucleation parameters can be determined or estimated by comparing the calculated and experimental results, which enables a more practical prediction of the microstructure (morphology and grain size).

The extruded Mg–Zn–Y–Zr plate was subjected to friction stir processing (FSP). FSP resulted in significant breakup and dispersion of bulky W-phase particles and remarkable grain refinement, thereby substantially enhancing superplasticity. Maximum superplasticity of 635% was achieved at 450 °C and a relatively high strain rate of 3 × 10−3 s−1. By comparison, the as-extruded sample did not exhibit superplasticity. Grain boundary sliding was identified to be the primary deformation mechanism in the FSP Mg–Zn–Y–Zr by superplastic data analyses and surfacial morphology observations. Furthermore, the superplastic deformation kinetics of the FSP Mg–Zn–Y–Zr is significantly faster than that of equal channel angular pressed (ECAP) magnesium alloys under both as-ECAP and annealing conditions.

Large area uniform nanoplates of molybdenum oxide (MoO3), a typical semiconductor material, have been synthesized under soft conditions by using carboxymethyl cellulose (CMC) as template. Under ambient condition, hydrolysis of ammonium molybdate into layered molybdenum oxide, and its subsequent inclusion of CMC polymers results in formation of lamellar CMC/molybdenum oxide hybrid. Calcinations of this lamellar hybrid at 500 °C lead to formation of large area uniform nanoplates of orthorhombic phase of MoO3. Scanning electron microscopy and transmission electron microscopy images show that these MoO3 nanoplates are regularly packed, about 100 nm in thickness and 10–100 μm in length. The mechanism of the hybrid reaction and the templating ability of CMC polymers have been extensively discussed. The oriented growth of short molybdenum oxide flakes into long-range ordered plates has been induced by CMC polymers because of the shrinking of CMC during the hybrid reaction. This is the first report that large area highly ordered molybdenum oxide nanometer materials have been obtained under soft reaction conditions.

The tailoring of cermet composition to improve tribological properties requires careful choice of the type of secondary carbide. To investigate this aspect, a number of sliding tests were carried out on baseline TiCN–20Ni cermet and TiCN–20wt%Ni–10 wt% XC cermets (X = W/Nb/Ta/Hf) at varying loads of 5N, 20N, and 50N against bearing steel. With these experiments, we attempted to answer some of the pertinent issues: (i) how does the type of secondary carbide (WC/NbC/TaC/HfC) influence friction and wear behavior, and is such influence dependent on load?; and (ii) how does the secondary carbide addition affect the stability and composition of the tribochemical layer under the selected sliding conditions? Our experimental results reveal that the added secondary carbides influence chemical interactions between different oxides and such interactions dominate the friction and wear behavior. A higher coefficient of friction (COF) range, varying from 0.75 to 0.64 was recorded at 5N; whereas the reduced COF of 0.46–0.52 was observed at 20N or 50N. The volumetric wear rate decreased with load and varied on the order of 10−6 to 10−7 mm3/Nm for the cermets investigated. The cermet containing HfC exhibited high friction and poor wear resistance. At low load (5N), the abrasion and adhesion of hard debris containing various oxides dominated the wear, and resulted in high friction and wear loss. In contrast, the more pronounced increase in friction-induced contact temperature (below 500 °C) and compaction of hard debris resulted in the formation of a distinct tribochemical layer at higher loads (20N and 50N). The formation of a dense tribolayer containing oxides of iron and/or titanium is responsible for the reduced friction and wear, irrespective of secondary carbides.

A Raman spectrometer was used to probe the structure and luminescence of a range of europium-doped zirconia phosphors prepared by different routes. We have demonstrated that the synthesis method and precursor type have a strong influence on the structure and luminescence of the final phosphor product. Raman spectroscopy has also demonstrated the presence of local order around the dopant ions that is not apparent in x-ray diffraction (XRD) and corresponds with changes in luminescence. As europium concentration is increased from 1 mol% to 20 mol%, the long range structure (from XRD) changes from tetragonal to cubic. Raman spectroscopy, however, shows that the 1 mol% material has a localized structure similar to the monoclinic undoped zirconia. This localized symmetry can explain the differences observed previously in emission spectra.

A glass-ceramic (GC0) with nominal composition of 51.2% CaO–12.1% MgO–36.7% SiO2 (wt%) was synthesized. Then multiphase glass-ceramics of MGC1 and MGC2 were obtained by adding 1 and 2 wt% B2O3 to GC0 followed by thermal treatment. The bending strength of MGC1 was the highest, about 89.46 MPa, and the coefficient of thermal expansion was 10.67 × 10−6 °C−1, closer to that of Ti–6Al–4V alloy (10.03 × 10−6 °C−1). X-ray diffraction analysis confirmed that MGC1 was predominantly composed of akermanite, merwinite, and small amounts of dicalcium silicate crystalline phases. The bioactivity and cytocompatibility in vitro of MGC1 were detected by investigating the bonelike apatite-formation ability in simulated body fluid (SBF) and osteoblast morphology and viability. The results showed that MGC1 possessed bonelike apatite-formation ability in SBF and could release ionic products to significantly stimulate cell growth and viability. Furthermore, osteoblasts adhered and spread well on MGC1, indicating good bioactivity and potential cytocompatibility.

A diamondlike carbon (DLC) thin film was deposited onto a stainless steel substrate using a plasma-enhanced chemical vapor deposition (PECVD) process. Nanoindentation, coupled with focused-ion-beam (FIB) milling, was used to investigate contact-induced deformation and fracture in this coating system. Following initial elastic contact between the coating and the indenter and apparent plastic yield of the substrate, pop-ins were observed in the load–displacement curve, indicative of coating fracture. However, FIB cross-sectional images of indentations revealed the presence of ring, radial, and lateral cracks at loads much lower than the critical load for the first observed pop-ins. Finite element modeling was used, and the properties of the substrate and the film were calibrated by fitting the simulated load–displacement curves to experimental data. Then, based upon the experimental observations of damage evolution in this coating system, the stress distributions relevant to initiate ring, radial, and lateral cracks in the coating were ascertained. Furthermore, the effects of substrate yield stress and coating residual stress on the formation of these cracks were investigated.

A novel ZnO seedless chemical approach for density-controlled growth of ZnO nanowire (NW) arrays has been developed. The density of ZnO NWs is controlled by changing the precursor concentration. Effects of both growth temperature and growth time are also investigated. By this novel synthesis technique, ZnO NW arrays can grow on any substrate (polymer, glass, semiconductor, metal, and more) as long as the surface is smooth. This technique represents a new, low-cost, time-efficient, and scalable method for fabricating ZnO NW arrays for applications in field emission, vertical field effect transistor arrays, nanogenerators, and nanopiezotronics.

Commercially procured single-walled carbon nanotubes were dispersed in 2 wt% solution of sodium cholate and also in 1 wt% solution of sodium dodecyl sulfate. The absorption spectrum of the suspensions was studied in ultraviolet–visible–near-infrared (UV–vis–NIR) range. Two distinct bands, each containing three peaks, were observed in NIR range for both the suspensions. These peaks correspond to transitions between van Hove singularities E11 and E22 in the density of states of the semiconducting nanotubes. Comparing positions of the observed peaks with the empirical Kataura plot, the diameters and chiralities of the nanotubes were estimated. Using tight binding approximations, the diameter of the nanotubes was also estimated theoretically. Discrepancies between the theoretically calculated diameters and those obtained by empirical Kataura plots are found to be higher for E11 peaks. It has been suggested that the reason for this discrepancy is that the observed E11 peaks are blue-shifted due to Coulomb interactions and exciton formation.

Polyaniline (PANI) nanofibers were prepared electrochemically by a template-free method on different active substrates in aqueous solutions containing aniline and inorganic acid or organic acid. The influences of experimental parameters, such as polymerization potential, techniques of applied potential, electrolyte composition, and polymerization temperature, on the morphologies of the PANI nanofibers were systematically investigated. The PANI nanofibers obtained have promising applications in supercapacitors whose specific capacitance is as high as 1.21 × 103 F/g, which is the highest value possible using sulfuric acid (1.00 M H2SO4) as electrolyte. In addition, the formation mechanism of PANI nanofibers is discussed.

In this article, we present the vacuum ultraviolet-visible spectroscopic properties of NaRFPO4:Tb3+ (R = Gd and Y). Because the samples show intensive absorption near 172 nm and bright emission, the composition of the phosphors has been further optimized and an ideal phosphor NaGd0.3Y0.5Tb0.2FPO4 is obtained. This phosphor exhibits favorable characteristics such as a lower preparation temperature, an intensive emission under 172-nm excitation, a shorter decay time (τ1/10 = 8.7 ms) in comparison with the commercial green plasma display panel (PDP) phosphor Zn2SiO4:Mn2+ (τ1/10 = 10.8 ms), a good thermal stability for luminescence performance, and a uniform particle size around 2.3 μm. Hence, the phosphor NaGd0.3Y0.5Tb0.2FPO4 can be considered a promising green phosphor for use in PDPs.

An antigenic mimic of the Ebola glycoprotein was synthesized and tested for its ability to be recognized by an anti-Ebola glycoprotein antibody. Epitope-mapping procedures yielded a suitable epitope that, when presented on the surface of a nanoparticle, forms a structure that is recognized by an antibody specific for the native protein. This mimic-antibody interaction has been quantitated through ELISA and QCM-based methods and yielded an affinity (Kd = 12 × 10−6 M) within two orders of magnitude of the reported affinity of the native Ebola glycoprotein for the same antibody. These results suggest that the rational design approach described herein is a suitable method for the further development of protein-based antigenic mimics with potential applications in vaccine development and sensor technology.

Tungsten (W) fiber reinforced Zr47Ti13Cu11Ni10Be16Nb3 bulk metallic glass composite has been prepared by melt infiltration casting. Interfacial characteristics of the composite were analyzed by sessile drop technique, x-ray diffraction (XRD), scanning electron microscopy (SEM), electron probe x-ray microanalysis (EPMA), and nanoindenter. Results indicate that Zr47Ti13Cu11Ni10Be16Nb3 melt wets the W substrate, and the interfacial bond composed of a diffusion–dissolution layer between Zr47Ti13Cu11Ni10Be16Nb3 matrix and W fiber is in good condition. Due to these excellent interfacial characteristics, the mechanical properties of the composite are considerably enhanced with increasing volume fraction of W fiber. It was found that the compressive strength of 70% volume fraction of W fiber composite is 2.6 GPa, which is 58% higher than the value exhibited by the unreinforced matrix. At the same time, the reinforced matrix exhibits 13% plastic deformation when tested under quasi-static compression conditions. Instead of shear mode seen for the unreinforced matrix, the failure mode of the 70% volume fraction W fiber composite is mainly caused by fiber splitting and buckling. Also, the W fiber hinders localized shear bands from propagating and gives rise to multiple shear bands, which results in the enhancement of the compressive strength and plastic deformation.

The pyrochlore compositions Gd2–yNdyZr2O7 (y = 0.0, 0.1, 0.4, 0.6, 1.0, 1.4, 1.6, and 2.0) were synthesized, and their ionic conductivity was determined (100 Hz–15 MHz, 622–696 K). The direct-current (dc) conductivity (σdc) varies upon Nd substitution at the Gd site, and a peaking effect in σdc was observed around y = 1.0. This indicates that a significant increase in conductivity can be obtained at moderately high temperatures by suitable doping at the Gd site with isovalent rare-earth ions like Nd. The extent of oxygen ion disorder determined from x-ray diffraction was found to decrease with increasing Nd content. The dc conductivity obeys the Arrhenius relation σdcT = σ0 exp(−E/kBT). The activation energy E and the preexponential factor σ0, which is a measure of the concentration of the mobile species, increase while going from the ordered Nd2Zr2O7 to the least ordered Gd2Zr2O7. These two processes presumably lead to the peaking of σdc at an intermediate Nd content. Our results also suggest that the cooperative motion of mobile ions does not contribute much to the increase in activation energy in this compound.