A simple hydrothermal route to the eulytite phase of bismuth germanium oxide (E-BGO: Bi4(GeO4)3) that required no post-processing has been developed. The E-BGO material was isolated from a mixture of bismuth nitrate pentahydrate and a slight excess of germanium oxide in water under hydrothermal conditions (185 °C for 24 h). The resultant materials were characterized by powder x-ray diffraction, scanning electron microscopy, transmission electron microscopy, and luminescence measurements to verify the particle's phase (eulytite), morphology, size, and response to a variety of excitation energy sources, respectively. Photoluminescence spectroscopic response from E-BGO pellets indicated that the samples exhibited a strong emission peak consistent with an x-ray induced luminescence of a E-BGO single crystal (500 nm excited at 285 nm). Cathodoluminescent properties of the E-BGO displayed a broadband spectrum with a maximum at 487 nm. The growth process was consistent with a standard Oswald ripening and LaMer growth processes.

Ceramic wafers of alumina (Al2O3) were produced by tape casting of aqueous slurry followed by vacuum sintering. The binder system used to form the tape casting slurry is a copolymer of isobutylene and maleic anhydride, which is environmentally friendly, marketed under the name ISOBAM. The rheological properties of the slurries were studied by varying solid loading and binder addition level. Through the optimization of plasticizer addition, green tapes were casted with excellent plasticity and a thickness of 240–740 μm. The tapes displayed a post-sintering thickness of 150–660 μm. The morphologies, as well as the fracture surface and the as-sintered surface of the powder were examined using a scanning electron microscope (SEM). The in-line transmittance of the transparent unpolished Al2O3 wafers with a thickness of 660 μm was found to be 72% at a wave length of 5 μm and 26% at a wave length of 600 nm.

Cobalt crystals with hcp or hcp/fcc mixed structure were prepared by a solvothermal process based on the dosages of N2H4·H2O and the effect of crystal structure on their magnetic properties and Congo red (CR) removal abilities was studied. To our best knowledge, it is the first report on CR removal by micrometer and submicrometer sizes of Co crystals with the best CR removal ability reaching 694.4 mg g−1. For the hcp and fcc mixed structure, the degree of mixing can be clearly observed from the high-resolution transmission electron microscopy images. The micrometer and submicrometer sizes of Co crystals will be good for magnetic separation after CR removal.

From the view of tissue engineering, the deficiency in porosity has impeded further application of bacterial cellulose (BC) as a super biomaterial. In this study, we used a combination method consisting of acetic acid treatment and freeze-drying operation to improve the porous profile of BC, as well as a simple and fast method to measure the thickness, density, and porosity of BC. Results have shown a significant improvement in the porosity of the inner structure of BC treated with acetic acid and freeze-drying. Microscopic observation by scanning electron microscopy exhibited explicit evidences that more orderly porous layer-by-layer structures and more pores were formed along the cross section of modified BC as compared with the control. The enhancement of mechanical properties and crystallinity of modified BC was also demonstrated due to the improvement of material porosity in the particular extent from 50.3 to 76.43%. Cell culture of human fibroblast cells exhibited good cell viability on modified BC, suggesting that a better porous profile of BC on the surface and cross section helps facilitate cells to attach, as well as potentially promotes cells to grow in. These significant results may open the possibility of producing BC nanomaterials for tissue engineering with desirable properties.

New organic/inorganic mesoporous luminescent hybrid materials containing lanthanide (Eu, Tb) complexes chemically bonded to mesoporous SBA-15 [a kind of mesoporous silica with two-dimensional hexagonal (P6mm) structure] have been successfully synthesized by co-condensation of the modified hexafluoroacetylacetone (HFAASi) and tetraethoxysilane (TEOS) in the presence of Pluronic P123 surfactant as a template. The luminescent properties of these resulting mesoporous hybrid materials [denoted as Ln(HFAASi-SBA-15)3phen, Ln = Eu, Tb; phen = 1,10-phenanthroline] were characterized by Fourier transform infrared, small-angle powder x-ray diffraction, N2 adsorption measurements, transmission electron microscope, ultraviolet-visible diffuse reflection absorption spectra, and photoluminescent spectra, and the results exhibit that they all have uniformity in mesostructure and high surface area. Moreover, the mesoporous hybrid materials Eu(HFAASi-SBA-15)3phen and Tb(HFAASi-SBA-15)3phen exhibit the characteristic luminescence of Eu3+ and Tb3+, respectively, indicating that the effective intramolecular energy transfer between HFAASi and the lanthanide ions has been achieved.

The effects of stearic acid on the high-energy ball milling of tin powder have been investigated. The mean crystallite sizes, microstrain, and phase transformations were examined using different techniques like x-ray diffraction (XRD), Rietveld refinement method, and differential scanning calorimetry (DSC). After 28 h of milling, the Rietveld analysis showed the stabilization of Sn mean crystallite sizes at around 50 nm. Due to the presence of oxygen in stearic acid, the milling process gradually produced an amorphous Sn oxide phase. The DSC thermogram of the sample milled for 28 h showed two exothermic peaks separated by an endothermic peak. Based on the DSC measurements, two samples were annealed at 240 and 350 °C for 20 min. The annealing at 240 °C confirmed the presence of an amorphous phase which crystallized in nanostructured tetragonal SnO phase. The annealing at 350 °C revealed the nucleation of nanostructured tetragonal SnO2 phase.

We investigated how changes in the method of supplying Sn and Fe carbon nanocoil (CNC) catalysts affected the results of chemical vapor deposition. The Sn/Fe catalysts were supplied using the following four materials: a thin Sn film, a drop-coated solution of Fe2O3, tetramethyltin (TMT) vapor, and ferrocene vapor. The CNC purity was evaluated using scanning electron microscopy. The CNC purity in the overall carbon deposit was also evaluated by analyzing the cross-section of the deposit. The CNC purity averaged over the overall carbon deposit was increased 1.5-fold by the TMT supply. We obtained a maximum CNC purity of 72% using a combination of TMT and ferrocene vapors, with Sn/Fe deposition on the substrate. Energy-dispersive x-ray spectroscopy analysis of the catalyst nanoparticles in the tips of the CNCs and carbon nanofibers (CNFs) revealed that there was a large difference in the Sn/Fe molar ratios for the angular- and round-type CNFs.

This research discussed how to synthesize submicrometer-sized TiC particulate reinforcement in the molten aluminum melt at low temperature via combustion synthesis by using in situ casting technique. A high temperature preheating treatment of Al–Ti–C pellets was carried out, by which the thermal explosion reaction of the pellets could take place in the pure aluminum melt at 750 °C. The synthesizing temperature of TiC particles was reduced by at least 150 °C compared with the conventional methods. In situ formed TiC particles were spherical in shape and were smaller than 1 µm in size due to the low melting temperature. The emergence of liquid aluminum phase led to the generation and accumulation of plenty of heat in the pellet in a short time due to the reactive diffusion of Al(l)–Ti(s). The formation mechanism of the submicrometer-sized TiC particles in the molten aluminum at low temperature was discussed in this research.

The stress relaxation and failure behavior of Ni/Sn–3.0Ag–0.5Cu/electroless nickel electroless palladium immersion gold flip-chip solder bumps undergoing electromigration (EM) at 150 °C under 1.5 × 104 A/cm2 was investigated in situ. Three modes of stress relaxation of Sn–3.0Ag–0.5Cu solder bumps were identified. At the cathode, voids and hollows with terrace morphology gradually formed to relieve the tensile stress; at the anode, especially around the current crowding corner, recrystallization of Sn grains and extrusion of hillocks occurred to relieve the compressive stress; in the solder bump, Sn grain boundary sliding that occurred to accommodate the diffusion creep was more pronounced with increasing EM time. Grain boundary sliding is considered to be an indispensable requisite for diffusion creep. The microstructural evolution of solder bumps at the last stage of lifetime was revealed, and the final EM-induced failure mode was the local fusion of a solder bump resulting from the crack formation-and-propagation at the cathode.

In nature, biological structures often exhibit complex geometries that serve a wide range of specific mechanical functions. One such example are the ammonites, a large group of extinct mollusks, which produced elaborate, fractal-like hierarchical suture interface patterns. This report experimentally explores the influence of hierarchical suture interface designs on mechanical behavior by taking advantage of additive manufacturing and its ability to fabricate complex geometries. In addition, structure/property relationships of additively manufactured multi-material prototypes are investigated. It is shown that increasing the order of hierarchy amplifies stiffness by more than an order of magnitude. Tensile strength can also be tailored by changing the order of hierarchy, which alters the normal to shear stress ratio of the interfacial layer. The addition of failure mechanisms with increased order of hierarchy also significantly increases the toughness. Therefore, hierarchical suture interfaces can be used to diversify the mechanical behavior of additively manufactured materials.

This study aims at understanding the effects of rotating magnetic field (RMF) on the fading effect of Al–5Ti–1B in commercial pure Al. The results indicate that fading effect is obvious after adding Al–5Ti–1B to Al with a holding time of 20 min. It is fair to claim that the fading effect can be eliminated to a great extent when RMF with magnetic flux densities of 6 and 12 mT is applied until the temperature decreases to 662 °C, which is mainly attributed to the homogeneous distribution of TiB2 particles caused by forced convection. However, refinement performance of pure Al by Al–5Ti–1B can be greatly weakened by RMF with an increase in magnetic flux density to 18 mT, since strong convection aggravates the agglomeration of TiB2 particles. In addition, the inoculated Al treated by a RMF of 6 mT until solidification exhibits a coarser solidification structure compared to that treated until the temperature decreased to 662 °C, which is mainly due to the prolongation of solidification time caused by Joule heat under RMF as proved by thermal analysis.

Electron-withdrawing halogen atoms are often bonded to the surface of carbon nanotubes to assist in the conversion from metallic to semiconducting properties. Single-walled carbon nanotubes (SWCNTs) were surface modified using UV photolysis with: (i) a broad band of wave lengths from approximately 250 to 400 nm having a maximum intensity at approximately 300 nm for photolysis of Cl2, (ii) low-pressure Hg lamps emitting 253.7 nm photons for photo-decomposition of HBr, and (iii) low-pressure Hg lamps emitting both 253.7 and 184.9 nm for photo-dissociation of HCl and HBr, respectively, and analyzed by x-ray photoelectron spectroscopy. Chlorine atoms adhered more readily than bromine atoms with the π-conjugation of the SWCNTs. The dominant increase with treatment was observed in the singly bonded chlorine moiety. Chlorine atoms, generated by UV photolysis of Cl2, produced a higher Cl saturation level of approximately 36 at.% than previously observed for multi-walled carbon nanotubes (13 at.%).The degree of chlorination depended on the amount of oxygen on the surface of the SWCNTs. Photo-dissociation of gaseous HCl and HBr showed lower amounts of halogenation on SWCNTs (approximately 5.8 at.% Cl and 2.5 at.% Br, respectively) than photolysis of Cl2.

To obtain a nanocrystalline surface layer, 316L stainless steel was treated by fast multiple rotation rolling (FMRR). The microstructure, after FMRR treatment and annealing treatment, was characterized by transmission electron microscopy and x-ray diffraction. Equiaxed nanocrystalline with the average grain size about 12 nm is obtained on the surface layer of FMRR sample. The investigation of thermal stability of the nanocrystalline layer indicates that the grains are still nanocrystalline and the average grain size is about 60 nm for annealing at 500 °C. In addition, the amount of α-martensite increases markedly as the annealing temperature increases from 300 to 500 °C. However, it begins to reduce at 600 °C due to the reversion transformation from martensite to austenite. After annealing at 400 °C, the microhardness of the annealed FMRR sample reaches a maximum value of about 660 HV, and it is four times higher than that of the original sample.

Stretchable transparent conductors are required for flexible and wearable electronics. This study demonstrates biaxially stretchable transparent conductors that use silver nanowire networks. The use of buckled nanowire networks has previously been reported to lend stretchability to the transparent conductor in a single axis. However, a nanowire network that is prestrained and then buckled out-of-plane biaxially shows a deterioration of the electrical conductivity after a single cycle of stretching and releasing the strain uniaxially. This has been attributed to the loss of good electrical contact between the nanowires. By hot pressing the out-of-plane buckled nanowires to obtain an in-plane wavy nanowire network with good wire-to-wire junctions, a biaxially stretchable transparent conductor that maintains good electrical conductivity with stretching up to 10% is demonstrated. The methods of prestraining the nanowire network to achieve out-of-plane buckled nanowires and hot pressing the out-of-plane buckled nanowires to obtain an in-plane wavy nanowire network with fused junctions are expected to be practical for other classes of percolative networks based on one-dimensional (1D) materials used in flexible and stretchable applications.

MTiO3 (M = Ca, Ni, and Zn) nanocrystals were prepared via a facile ethylene glycol-mediated synthesis route followed by calcination in air. The structures and morphologies of nanocrystals were characterized by x-ray diffraction, Raman spectroscopy, transmission electron microscopy, and scanning electron microscopy. The results indicated that CaTiO3 and NiTiO3 are orthorhombic phase, while the ZnTiO3 is orthorhombic phase. The activity of the CaTiO3 nanocrystals for water splitting into H2 was obviously higher than those of the NiTiO3 and ZnTiO3 nanocrystals, which could be attributed to the more negative conduction band position of CaTiO3 than NiTiO3 and ZnTiO3. The Brunauer–Emmett–Teller system-based surface areas of samples are 19.03, 21.13, and 4.17 m2/g for CaTiO3, NiTiO3, and ZnTiO3 nanocrystals, respectively. In addition, the activity of the CaTiO3 nanocrystals increased with increase in the sintering temperature of samples.

The process of laser-induced brazing constitutes a potential option for connecting several ceramic components (n- and p-type ceramic bars and ceramic substrate) of a thermoelectric generator (TEG) unit. For the construction of the TEGs, TiOx and BxC were used as thermoelectric bars and AlN was used as substrate material. The required process time for joining is well below that of conventional furnace brazing processes and, furthermore, establishes the possibility of using a uniform filler system for all contacting points within the thermoelectric unit. In the work reported here, the application-specific optimization of the laser-joining process is presented as well as the adapted design of the thermoelectric modules. The properties of the produced bonding were characterized by using fatigue strength and microstructural investigations. Furthermore, the operational reliability of the modules was verified.

The mechanical and thermal behavior of nanoglasses (NGs) were studied with a focus on the effect of the microstructure. The thermal expansion was measured to track changes in excess free volume during heating. It was found that the excess free volume, which is initially more dominant in the interphase region between the denser amorphous particles, is partially lost as well as redistributed during annealing. This relaxation during heating causes the nanoglass to behave like a melt-spun ribbon after heating while remaining amorphous. Nanomechanical tests were used to probe the local incipient plasticity and the influence of the interphase region. This interphase appears to affect the mechanical response of the NGs by inhibiting the propagation of shear bands and thus offers a novel approach for the introduction of plasticity in bulk metallic glasses. The results suggest that the NGs consist of two distinct amorphous phases with different glass transition temperatures.

Silver-decorated titanium dioxide (Ag/TiO2) nanotube (NT) arrays were successfully prepared using a two-step synthesis route comprised of an anodic oxidation procedure followed by photochemical reduction using ultraviolet irradiation. The resulting Ag/TiO2 NT arrays were characterized using scanning electron microscopy, transmission electron microscopy, x-ray diffraction, and UV-vis diffusion reflectance spectrometry. The characterization results indicated that the silver decoration significantly enhanced the light absorption capability of the TiO2 NT arrays in the visible spectral range. The visible light photocatalytic activity of the subject NT arrays was investigated. The experimental results showed the photocatalytic activity of silver-decorated titanium dioxide Ag/TiO2 NT arrays to be dependent on the size of the silver particles. The improved visible light absorption can be attributed to plasmonic effects induced by particle size phenomenon. The Ag/TiO2 NT arrays exhibit promising application for photocatalytic degradation of dye solutions and pollutants in water using visible irradiation.

We describe an improved experimental approach for characterizing the elastic modulus and hardness of single microfibers through instrumented indentation. A sample mounting technique on a curved surface is presented that ensures contact between an unmodified fiber and substrate. The indentation analysis considers three separate corrections to the well-known Oliver and Pharr method: (i) overestimation of the projected contact area due to sample curvature, (ii) overestimation of projected contact area due to substrate curvature, and (iii) underestimation of fiber stiffness due to the structural compliance of the sample. The method is applied to four types of high performance ballistic fibers: KM2 Plus, Twaron, AuTx, and Dyneema; the results are presented according to both the modified analyses as well as the standard Oliver and Pharr analysis. The modified analyses resulted in an increase in the elastic modulus and hardness of up to 35 and 60%, respectively, compared to the Oliver–Pharr method. The technique has the potential to be applied to single microfilaments under various environmental conditions that may otherwise be compromised by traditional fiber mounting methods.

Mechanical properties of parts constructed with additive manufacturing (AM) technologies are highly influenced by raw material and process characteristics. It is widely assumed that a certain degree of anisotropy should be expected in AM parts due to their layer-upon-layer nature. Present work focuses on the PolyJet process, where each layer is built by selective jetting of photopolymers upon flat surfaces and subsequent UV radiation curing. An extensive experimental program was carried out to find out if the so-constructed parts present viscoelastic behavior and if their mechanical characteristics also depend on part orientation. Both hypotheses have been proven true, so a viscoelastic orthotropic-like behavior shall be expected in PolyJet manufactured part. Nevertheless, a significant improvement on material properties has been found for nearly vertical building orientations. This unexpected behavior is related to a shielding effect upon UV curing caused by support material.