To replace ternary polymer with binary polymer, a novel bifunctional comonomer β-methylhydrogen itaconate (MHI) was synthesized to prepare poly(acrylonitrile-co-β-methylhydrogen itaconate) [P(AN-co-MHI)] copolymer used for carbon fiber precursor. The structural evolution and stabilization mechanism of P(AN-co-MHI) and polyacrylonitrile (PAN) during stabilization were studied by Fourier transform infrared spectroscopy, x-ray diffraction, differential scanning calorimetry, thermogravimetry, and kinetic investigation. The activation energy (Ea) of the stabilization reactions were calculated by Kissinger method and Ozawa method. The results show that the P(AN-co-MHI) exhibits a lower stabilization temperature than terpolymers containing similar chemistry component and a significantly improved stabilization performance compared with PAN homopolymer, such as lower cyclization temperature, lower Ea (85.36 kJ/mol), and larger extent of stabilization under the same condition, which is mainly attributed to the initiation of MHI comonomer through an ionic cyclization mechanism. The dehydrogenation of P(AN-co-MHI) is also promoted by the incorporation of comonomer MHI into PAN chains. Simultaneously, the rheological analysis shows that P(AN-co-MHI) possesses better spinnability than PAN, which is beneficial for preparation of high performance carbon fiber.

The long afterglow phosphor, CaWO4: Eu3+, is synthesized and the intensity and duration of its afterglow can be enhanced by the Ti4+ and Mg2+ incorporation. The x-ray diffraction patterns depict pure tetragonal CaWO4 of all samples. The emission spectra show the Eu3+ emission and the charge transfer (CT) emission of WO42−. The intensity of CT increases with the Mg2+ incorporation. The excitation spectra monitoring 616 nm exhibit the strongest CT band with Ti4+ incorporation. These results indicate that Mg2+ enhances the efficiency of CT emission of WO42− while the Ti4+ enhances the energy transfer rate from CT to Eu3+. Since the thermoluminescence (TL) curves do not imply a new trap, the enhancement of the afterglow results from the coreinforcement of CT efficiency and energy transfer rate.

Most biological materials are hierarchically structured composites that often possess exceptional mechanical properties. We show that nanoindentation can be a powerful tool for understanding the structure‑mechanical property relationship of biological materials and illustrate this for fish teeth and scales, not heretofore investigated at the nanoscale. Piranha and shark teeth consist of enameloid and dentin. Nanoindentation measurements show that the reduced modulus and hardness of enameloid are 4‑5 times higher than those of dentin. Arapaima scales are multilayered composites that consist of mineralized collagen fibers. The external layer is more highly mineralized, resulting in a higher modulus and hardness compared with the internal layer. Alligator gar scales are composed of a highly mineralized external ganoin layer and an internal bony layer. Similar design strategies, gradient structures, and a hard external layer backed by a more compliant inner layer are exhibited by fish teeth and scales and seem to fulfill their functional purposes.

Bulk metallic glasses (BMGs) are a promising class of engineering materials, but they can be difficult to machine due to high hardness and a metastable structure. Crystallization due to machining can have negative effects, such as a decreased load-bearing capacity of fabricated parts, and thus should be avoided. Here, a Zr-based BMG was machined using abrasive waterjet (AWJ), electrical discharge, ns-pulsed laser engraving, and conventional dry-milling techniques. Characterization of the processed material indicated that AWJ preserves the amorphous phase and provides the combination of speed and flexibility required to rapidly fabricate small three-dimensional parts, while the other techniques did not achieve these goals. As proof-of-principle, a screw, similar to an orthopedic implant, was rapidly machined from the BMG using AWJ.

The consolidation of crystalline powders to obtain dense microstructures is typically achieved through a combination of volume and grain boundary diffusion. In situ transmission electron microscopy was utilized to study neck formation between adjacent nickel particles during the early stages of sintering. It was found that the presence of carbon during consolidation of Ni lowers the reduction temperature of nickel oxides on the particle surface and therefore has the potential to accelerate consolidation. In the absence of carbon, the surface oxides remain present during the early stage of sintering and neck formation between particles is limited by self-diffusion of nickel through the oxide layer. This study provides direct experimental evidence that corroborates related earlier hypotheses of self-cleaning on the surface of the nanoparticles that precedes neck formation and growth.

In this article, we report the unique microstructural characteristics of YBa2Cu3O7-x (YBCO)/BaSnO3 (BSO) nanocomposite thin films on LaAlO3 (LAO) substrates. The BSO secondary phase grows as self-assembled vertically aligned nanopillars uniformly distributed in the superconducting YBCO matrix. Detailed microstructure and strain studies including x-ray diffraction, cross-section and plan-view transmission electron microscopy, and geometric phase analysis reveal that, as the BSO doping concentration varied from 2 mol% to 20 mol%, the nanopillar density increased from 0.26 × 1011/cm2 to 1.44 × 1011/cm2 while the diameter of the nanopillars remains relatively constant (7–8 nm in diameter). The strain state of the YBCO matrix is affected by both lateral and vertical lattice strains; while, the BSO lattice is strongly tuned by YBCO rather than the substrate. A high-density array of dislocations in the order of 1013/cm2 was observed along the vertical heterogeneous interfaces throughout the YBCO film thickness for all doping concentrations.

A new technique for micropatterning Fe-based bulk metallic glass surfaces is reported. The transpassive dissolution process is utilized for a defined localized material removal when using a pulsed electrochemical micromachining process. By applying submicrosecond pulses between a work piece and a tool electrode, microholes of high aspect ratio and depth of up to 100 μm can be machined into the bulk glassy Fe65.5Cr4Mo4Ga4P12C5B5.5 alloy. Two potential electrolytes are identified for the machining process. For these electrolytes, different reaction mechanisms are discussed. The possibility of machining more complex structures is demonstrated for the most promising electrolyte, a methanolic H2SO4solution. The impact of the process parameters, pulse length and pulse voltage, on the machining gap and the surface quality of the machined structures is evaluated.

In spite of previous reports documented that many beneficial effects can be obtained by adding rare earth (RE) elements to Pb-free solders, this paper presents the risk of Sn whisker growth in the Sn–9Zn–0.5Ga Pb-free solders due to the addition of RE Pr. Results showed that solder microstructures are refined with the addition of trace amount of Pr. However, excessive Pr addition led to the formation of Pr–Sn intermetallic compounds (IMCs) and spontaneous growth of Sn whiskers on the IMC surfaces. It was found that the IMC size has a dramatic impact on whisker growth. Sn whiskers grew in slow-cooled solder with larger IMC particles are much longer and more prolific than that in fast-cooled solder with smaller IMC size. It was proposed that the driving force for whisker growth is originated from the oxidation of the RE-rich Pr–Sn IMCs. Our results indicated that the effects of RE on Pb-free solders should be reevaluated.

To improve the thermoelectric properties of LaCeFe3CoSb12 skutterudite materials, the LaCeFe3CoSb12 nanopowders of disordered structure were fabricated through a laser melting and quenching process and then were hot pressed into bulk pellets with the coexistence of ordered and disordered structures by mixing the disordered powders with the raw LaCeFe3CoSb12 crystalline materials. The results suggest that the introduced disordered structure can increase Seebeck coefficient from 57 to 179 μV/K while reduce thermal conductivity from 3.1 to 1.5 W/(m·K), although electrical conductivity can be decreased from 98,000 to 43,000 S/m, and consequently, figure of merit can be enhanced from 0.11 to 0.90 at 773 K. Therefore, fabricating a material with the coexistence of disordered and ordered structures can be considered as an effective way to obtain a high figure of merit, and this strategy can be also applied to other thermoelectric alloys.

Reciprocal space mapping using synchrotron-based x-ray diffraction has been used to study the effects of strain and strain relaxation in (111) oriented thin films of In2O3 on cubic Y-stabilized ZrO2 over a range of epilayer thicknesses between 35 and 420 nm. Maps around the epilayer (1026) reflection show that the 35-nm film is highly strained with a lateral periodicity close to that of the substrate, while the 420-nm film is almost completely relaxed. Analysis of the map for the former sample leads to an estimate of 0.31 for the Poisson ratio for In2O3. The mosaic spread deduced from transverse scans through the epilayer (444) and (666) reflections increases from 0.1° for the 35-nm-thick film to 0.3° for the 420-nm-thick film. These changes are discussed in relation to the morphological changes observed by atomic force microscopy.

Nonstoichiometric mixed ionic and electronic conductors (MIECs) find use as oxygen permeation membranes, cathodes in solid oxide fuel cells, oxygen storage materials in three-way catalysts, and chemoresistive gas sensors. Praseodymium–cerium oxide (PrxCe1−xO2−δ) solid solutions exhibit MIEC behavior in a relatively high and readily accessible oxygen partial pressure () regime and as such serve as model systems for investigating the correlation between thermodynamic and kinetic properties as well as exhibiting high performance figures of merit in the above applications. In this paper, we extend recently published results for Pr0.1Ce0.9O2−δ to include values of x = 0, 0.002, 0.008, 0.1, and 0.20 (in PrxCe1−xO2−δ) to test how both defect and transport parameters depend on Pr fraction. Important observed trends with increasing x include increases in oxygen ion migration energy and MIEC and reductions in vacancy formation and Pr ionization energies. The implications these changes have for potential applications of PrxCe1−xO2−δ are discussed.

KLa2Ti3O9.5 and KLa2Ti3O9.5:Er3+ nanocrystals were successfully synthesized using a hydrothermal method and a subsequent calcination treatment. The band gap (Eg) of the KLa2Ti3O9.5 nanocrystals was calculated to be about 2.56 eV by means of the reflectance diffusion technique. Under 980-nm excitation, the KLa2Ti3O9.5:Er3+ nanocrystals emitted intense green (2H11/2/4S3/2 → 4I15/2) and red (4F9/2 → 4I15/2) upconversion (UC) luminescence. In comparison with pure KLa2Ti3O9.5, the KLa2Ti3O9.5:Er3+ nanocrystals exhibited a higher activity for water splitting into H2 under simulated solar light irradiation. We suggest that the enhancement of photocatalytic activity is related to the Brunauer-Emmett-Teller (BET) surface area and UC luminescence of KLa2Ti3O9.5:Er3+.

Mesoporous titanium dioxide (TiO2) and lithium (Li)-doped TiO2 nanobelts were synthesized via a facile solvothermal process. The crystalline structure and morphology of the nanobelts were characterized in detail. The x-ray diffraction patterns, transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) images indicate that the nanobelts have uniform monoclinic geometry with a length of 3–4 μm and a width of 40–200 nm, the pores are also uniform with 5–7 nm in diameter. scanning electron microscopy and TEM studies demonstrate the as-prepared TiO2 nanobelts have varied morphologies that strongly depend on the volume ratio of the reaction medium and the pressure. Ultraviolet-visible diffuse reflectance spectroscopy was used to study the photocatalytic degradation of Malachite green over the lithium nanoparticle-loaded mesoporous TiO2 nanobelts. The doping of lithium does not change the crystalline phase but the results form infrared spectrums confirm that the Li+ ion incorporates into the lattice of TiO2 nanobelts, decomposes it by replacing Ti4+ and thus reduces the photocatalytic activity.

Two-micrometer-thick Pb0.97La0.02(Zr0.98Ti0.02)O3 (PLZT) antiferroelectric films, with the addition of different PbO insert layer, were successfully fabricated on LaNiO3/Si substrates through a sol–gel method, and their microstructure and the energy storage performance were investigated in detail. X-ray diffraction curves and scanning electron microscopy images indicated that all the PLZT films showed a strong (042)-preferred orientation and had a uniform surface microstructure. The electrical measurements illustrated that the capacitive density and saturation polarization values of the thick films were improved by the PbO insert layer. As a result, PLZT thick films with 0.4‐M/L PbO‐insert layer possessed an enhanced energy storage density and energy storage efficiency, which were 25.2 J/cm3 and 52.3% measured at 984 kV/cm, respectively. Moreover, after 106 switching, the Jreco values of the corresponding films were only declined from 17.5 to 16.1 J/cm3, indicating good fatigue endurance.

Copper–tin (CuxSn1−x) nanocluster is a promising system for gas sensing applications, mainly because of its sensitivity and selectivity for H2S. In this work, pure Sn and Cu as well as composite CuxSn1−x nanoclusters were synthesized using the dc magnetron sputtering gas condensation technique. Nanoclusters with different Sn to Cu ratios were produced by changing the ratio of Sn and Cu in the target. The dependence of Sn, Cu, and CuxSn1−x nanoclusters’ size distribution on various source parameters, such as the inert gas flow rate and aggregation length, has been investigated in detail. The results show that as the inert gas flow rate increases, the mean nanocluster size increases for Sn, decreases for Cu, while increases and then decreases for CuxSn1−x. The results could be understood in terms of the contribution percentage of the nanocluster formation mechanism. Furthermore, this work demonstrates the ability of tuning the CuxSn1−x nanoclusters’ size and composition by a proper optimization of the source operation conditions.

The numerical approach of Lee et al. [Trans. Korean Soc. Mech. Eng., A28, 816–825 (2004)] to spherical indentation technique for property evaluation of hyperelastic rubber is enhanced. The Yeoh model is adopted as the constitutive form of rubber material because it can express well large deformation and cover various deformation modes with a simple form. We first determine the friction coefficient between a rubber specimen and a spherical indenter in a practical viewpoint and perform finite element simulations for a deeper indentation depth than that selected by Lee et al. [Trans. Korean Soc. Mech. Eng., A28, 816–825 (2004)]. An optimal data acquisition spot is selected, which features sufficiently large strain energy density and negligible frictional effect. We improve then two normalized functions mapping an indentation load–displacement curve onto a strain energy density–invariant curve, the latter of which gives the Yeoh model constants. The enhanced spherical indentation approach successfully produces the rubber material properties with an average error of less than 5%. The validity of our developed approach is verified by experimental evaluation of material properties with three kinds of rubber materials.

Quasicrystalline precipitates in ZrAlNiCuNb alloy were systematically studied by transmission electron microscopy. It was found that precipitates always contain various linear phason strains. By electron diffraction analysis, two types of linear phason strain with two different directions perpendicular to the incident beam described by strain matrices with only one nonzero element were identified. After measuring the deviations of diffraction spots and quantitatively fitting against their perpendicular components of the reciprocal lattice vectors, the phason strain matrices were obtained. Domain structures formed as a result of linear phason strain variants along directions with equal probability. Electron diffraction and high-resolution electron imaging provide supportive evidence of this result.

The ability of silver (Ag)-containing borate bioactive glass (BG) coatings to improve the biocompatibility and antibacterial properties of titanium (Ti) implants was investigated in vitro and in vivo in a rabbit tibial fracture model. Dense coatings of borate BG (thickness ≈ 20 μm) containing 0, 0.75, and 1.0 wt% Ag2O were prepared by depositing a layer of particles on Ti plates, followed by sintering at 900 °C. The as-prepared coatings had an adhesive strength of 10 ± 1 MPa, and when immersed in an aqueous phosphate (K2HPO4) solution, the coatings converted to hydroxyapatite, releasing Ag+ ions continuously for over 4 wk. After implantation of BG-coated Ti constructs in a rabbit tibial fracture model and of methicillin-resistant Staphylococcus aureus-induced osteomyelitis, the BG coating doped with 1.0 wt% Ag2O was most effective for the simultaneous eradication of the infection and fracture fixation. Implants coated with Ag-containing BG coatings could provide an approach for reducing implant-related bone infection.

Constitutive models that describe crystal microplasticity in a continuum framework can be envisaged as average representations of the dynamics of dislocation systems. Thus, their performance needs to be assessed not only by their ability to correctly represent stress–strain characteristics on the specimen scale but also by their ability to correctly represent the evolution of internal stress and strain patterns. Three-dimensional discrete dislocation dynamics (3D DDD) simulations provide complete knowledge of this evolution, and averages over ensembles of statistically equivalent simulations can therefore be used to assess the performance of continuum models. In this study, we consider the bending of a free-standing thin film. From a continuum mechanics point of view, this is a one-dimensional (1D) problem as stress and strain fields vary only in one dimension. From a dislocation plasticity point of view, on the other hand, the spatial degrees of freedom associated with the bending and piling up of dislocations are essential. We compare the results of 3D DDD simulations with those obtained from a simple 1D gradient plasticity model and a more complex dislocation-based continuum model. Both models correctly reproduce the nontrivial strain patterns predicted by 3D DDD for the microbending problem.