We describe experiments on self-heating and melting of nanocrystalline silicon microwires using single high-amplitude microsecond voltage pulses, which result in growth of large single-crystal domains upon resolidification. Extremely high current densities (>20 MA/cm2) and consequent high temperatures (1700 K) and temperature gradients (1 K/nm) along the microwires give rise to strong thermoelectric effects. The thermoelectric effects are characterized through capture and analysis of light emission from the self-heated wires biased with lower magnitude direct current/alternating current voltages. The hottest spot on the wires consistently appears closer to the lower potential end for n-type microwires and to the higher potential end for p-type microwires. The experimental light emission profiles are used to verify the mathematical models and material parameters used for the simulations. Good agreement between experimental and simulated profiles indicates that these models can be used to predict and design optimum geometry and bias conditions for current-induced crystallization of microstructures.

The preparation and characterization of Fe3O4 microtubes by a polymer-based template approach were described. Fe3O4 tubes with diameter of 600 ± 50 nm and an average tube thickness of about 50 nm were fabricated after removing the electrospun polystyrene fiber template. The microtubes were composed of individual Fe3O4 nanocrystals. The synthesis process was ambient, generalizable, inexpensive, and nontoxic. The magnetite tubes thus fabricated behave with a saturation magnetization of 37 emu/g measured in the vibrating sample magnetometer. The microtubes prepared in this way might find potential applications in catalysis, magnetic fluid, and biological field.

Nanocrystalline silicon thin films were fabricated using a vacuum arc discharge technique. These thin films can be deposited on plastic substrates effectively when cooled by a cryogenic substrate holder. We used single crystal silicon wafers as both the electrodes to ignite the vacuum arc and the silicon ion source to deposit thin films. This resulted in nanocrystalline silicon clusters embedded in the amorphous silicon matrix. This thin film has highly crystalline volume (≈87%), which enhanced the absorption in wide range of wavelengths. Without ion implantation, the in situ doping of p- or n-type thin films can also be achieved. This thin film deposition process has its potential for fabricating thin film transistors and photovoltaic cells on plastic substrates at fairly low production costs.

The effect of the magnetic anisotropy and the dipolar interactions between NiFe magnetic layers and between nanowires on the magnetic properties of NiFe/Cu multilayered nanowire arrays electrodeposited into the nanopores of anodic aluminium oxide (AAO) templates with diameters of 35 and 200 nm has been studied. The variation of the aspect ratio (thickness/diameter) between the NiFe magnetic and Cu nonmagnetic layers influences the effective anisotropy field. The correlation between the measured hysteresis loops, with the applied field parallel and perpendicular to the multilayered nanowires’ axis, and the calculated effective anisotropy field, Heff, and saturation field, Hsat, shows that it is possible to tune the orientation of the magnetization axis with high accuracy. Two formulas, which include both the intra- and internanowire interactions, were proposed to calculate the saturation fields of multilayered nanowire arrays for the applied field parallel and perpendicular to the nanowires’ axis.

Single-crystalline p-type silicon nanowire (SiNW) arrays have been formed by electroless metal deposition on a silicon wafer piece in an ionic Ag/fluorhydric acid (HF) solution through selective etching. They display mechanical properties that are different from those of both bulk silicon and single SiNWs. As any practical application of these materials is likely to involve a large number of nanowires in close proximity to each other, it is necessary to understand the mechanical properties of SiNW arrays. In this work, as a first step to characterize their mechanical properties, the buckling instabilities of the surfaces formed by vertically aligned SiNWs have been studied by nanoindentation tests.

Regenerated silk fibroin (RSF) fibers were directly dry-spun from RSF aqueous solutions into air. To improve mechanical properties of fiber, the as-spun fibers were postdrawn in 80 vol.% ethanol aqueous solution, in which an immersion process was performed subsequently. With the increase in draw ratio, the fibers show substantial improvements of orientation and mechanical properties. Quantitative analysis of Fourier transform infrared spectroscopy indicates that the ratio of β-sheet to α-helix conformation increases sharply at the beginning of immersion process, then approaches a constant value after 90 min of immersion. All fibers exhibit very smooth surfaces. There is no obvious relationship between the pH of the spinning dope and the mechanical properties of the regenerated fibers. The breaking stress of the posttreated fiber is improved up to 301 MPa, which approaches that of degummed silk. The posttreated fiber is over three times the breaking energy of degummed silk.

The thermal transitions and the nonisothermal cold crystallization kinetics of poly(ethylene terephthalate) (PET) at constant heating rates were investigated using differential scanning calorimetry. It was found that the glass transition and crystallization temperature increased with the heating rates, while the melting temperature showed a little variation for the heating rates used. Crystallization and melting latent heats were remarkably constant, independent of the heating rate. Kinetics parameters were determined using Ozawa model. Two different kinetic regimes were identified, corresponding to primary and secondary crystallization, at low and high fractional crystallization, respectively, both following Ozawa’s model. Kinetics parameters were determined for the primary and secondary regimes; the pre-exponential constant (KT) and Ozawa’s exponent (m) decreased with increasing crystallization temperature. The combined kinetic parameter increased exponentially with temperature; activation energies were estimated using Arrhenius plots for the two PET crystallization regimes.

Near-stoichiometric compositions of Ba(B′1/3B″2/3)O3 (B′ = Mg, Co, or Zn and B″ = Nb or Ta) perovskite-type materials with nonstoichiometry on Ba and B′ positions were studied by room temperature Raman spectroscopy and transmission electron microscopy. The studied materials with 1:2 ratio of B-site cations belong to the family of perovskites that has tolerance factor larger than unity, indicating formation of a strained structure. This family of materials exhibits phase transition from a completely disordered phase having space group Pm-3m to a 1:2-ordered phase with space group P-3m1. Measured Raman spectra were attributed to the presence of 1:2-cation order and are characterized by the presence of seven modes, the strongest of which at 800 cm−1 originates from collective motion of oxygen octahedra. The appearance of a mode at 670 cm−1 in Co-containing samples was ascribed to the formation of a 1:1-ordered phase and was confirmed by selected-area electron diffraction.

The macroscopic electromechanical coupling properties of ferroelectric polycrystals are composed of linear and nonlinear contributions. The nonlinear contribution is typically associated with the extrinsic effects related to the creation and motion of domain walls. To quantitatively compare the macroscopic nonlinear properties of a lead zirconate titanate ceramic and the degree of domain orientation, in-situ neutron and high-energy x-ray diffraction experiments are performed and they provide the domain orientation density as a function of the external electric field and mechanical compression. Furthermore, the macroscopic strain under the application of external electrical and mechanical loads is measured and the nonlinear strain is calculated by means of the linear intrinsic piezoelectric effect and the linear intrinsic elasticity. The domain orientation density and the nonlinear strain show the same dependence on the external load. The scaling factor that relates to the two values is constant and is the same for both electrical and mechanical loadings.

Various compositions of Li1-2xCaxSi2N3 (x = 0–0.2) were synthesized by the reaction of Li3N, Si3N4, and Ca3N2 at temperatures of 1873–2073 K. Ca was incorporated into the LiSi2N3 host lattice to form a solid solution of Li1-2xCaxSi2N3. The activation energy for ionic conduction was decreased and ionic conductivity at room temperature was enhanced by Ca doping. At 298 K, the ionic conductivity of densified Li1-2xCaxSi2N3 (x = 0.075) ceramic reached 1.6 × 10−5 S m−1, almost four orders of magnitude higher than that of densified Li1-2xCaxSi2N3 (x = 0) ceramic (3.1 × 10−9 S m−1). The change in the LiSi2N3 framework upon Ca doping decreased the interaction between the ions and increased the number of defects in the structure, making it easier for mobile Li+ ions to migrate. Moreover, the incorporation of aliovalent substitutional Ca2+ ions in the LiSi2N3 lattice is expected to create Li+ vacancies (VLi) for charge compensation (Li1-2xCaxVLiSi2N3), thereby increasing the number of mobile Li+ ions.

We report that the hydrogen de/resorption of the 2LiBH4+MgH2 system was modified by introducing Ni nanoparticles. Dehydrogenation analysis revealed that the first-step dehydrogenation, i.e., the decomposition of MgH2, can be significantly promoted by adding a small amount of Ni because of the catalytic effect. However, the improvement of the second-step dehydrogenation, corresponding to the decomposition of LiBH4, needs the addition of a large amount of Ni, resulting in the formation of a Mg–Ni–B ternary alloy. Furthermore, the presence of the Mg–Ni–B ternary alloy allowed an increased reversible H-capacity, in which about 5.3 wt% of hydrogen can be rehydrogenated under 400 °C and 55 bar hydrogen pressure over 10 h, which is higher than that of the pristine 2LiBH4+MgH2 system (4.4 wt%).

B2O3-SiO2 is shown to act as a transient liquid phase sintering aid that reduces the sintering temperature of Nd:YAG ceramics to 1600 °C. 1 at.% Nd3xY3-3xAl5O12 (Nd:YAG) ceramics were doped with 0.34–1.35 mol% B2O3-SiO2 and sintered between 1100 and 1700 °C. Dilatometric measurements show that B2O3-SiO2 doping increases the densification rate during intermediate-stage sintering relative to SiO2-doped samples. B3+ content is reduced to <5 ppm in samples heated to 1500 °C, as determined by mass spectrometry. For B2O3-SiO2-doped samples, final stage densification and grain growth follow a more densifying sintering trajectory than SiO2-doped 1 at.% Nd:YAG ceramics because there is less SiO2 during final-stage densification. The increased densification kinetics during intermediate-stage sintering lead to highly transparent Nd:YAG ceramics when sintered at 1600 °C in either vacuum or oxygen. Thus, transparent Nd:YAG ceramics can be sintered without the need for expensive refractory metal vacuum furnaces or pressure-assisted densification.

Bi1.95La1.05TiNbO9 (BLTN-1.05) thin films were prepared on fused quartz substrates by pulsed laser deposition. The x-ray diffraction (XRD) analysis and atomic force microscope (AFM) surface morphology measurements were performed on the samples. The XRD pattern demonstrated that the films are single-phase perovskite structured and well crystallized. The AFM analysis indicated that the films have less rough surface. The fundamental optical constants were obtained through optical transmittance measurements. The nonlinear optical properties of BLTN thin films were measured by a single beam Z-scan technique under 1064 nm excitation. The real and imaginary parts of the third-order nonlinear optical susceptibility χ(3) of the film were measured to be 9.56 × 10−9 and −3.67 × 10−9 esu, respectively. The Z-scan results show that BLTN thin films have potential applications in nonlinear optics.

By measuring the ion concentration in a pressure-induced infiltration experiment on a hydrophobic Zeolite Socony Mobil-5, it is found that the nanopore wall has a strong ion repelling effect. When the initial ion concentration is relatively low, only water molecules can enter the nanopores. Once the initial ion concentration is relatively high, ions can infiltrate into the nanopores, but the effective ion concentration of the confined liquid is much lower.

A facile ethylene glycol–based solvothermal method was developed for the synthesis of lanthanide orthovanadate LnVO4 (Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Er, Tm, Yb, Lu) nanoparticles with relatively uniform size and morphologies. The LnVO4 nanoparticles ranged from 100 to 500 nm and changed from spheres to ellipses and platelet–shaped particles depending on the ionic size. Radius of the Ln ions affected crystal structure. The particles with larger ions form monoclinic-type structure for LaVO4 and with smaller ions form zircon-type structure for LnVO4 (Ln = Pr-Yb). A nucleation and aggregates formation mechanism of LnVO4 nanomaterials was proposed to illustrate the crystal growth. The morphologies of LnVO4 nanoparticles could be turned by pH value and molar ratio of reactants. Spherical LaVO4 and PrVO4 nanoparticles were obtained at pH 6, whereas elliptical nanoparticles were obtained at pH 3. Eu3+-, Dy3+-, and Sm3+-doped zircon-type YVO4 nanoparticles exhibit strong luminescence typical of doped ions.

Hierarchical ZnO/Si nanoheterostructure was prepared by growing oriented ZnO nanowire bundles onto the top of nanoporous silicon pillar array (NSPA) via a self-catalytic thermal evaporation and vapor-phase transport method. Samples were carefully characterized using field emission scanning electron microscopy, x-ray diffraction, and luminescence spectroscopy. One ultraviolet, one blue-green, and two red emission bands were observed in ZnO/NSPA, and the emission mechanism is discussed by developing a model-based energy band diagram. The origins of the ultraviolet and blue-green photoluminescence (PL) bands were attributed to the emission from the band edge transition and surface states of oxygen vacancies of ZnO, while two red PL bands originated from NSPA and could be well explained by the quantum confinement-luminescence center model. The realization of such all solid and wide wavelength nanodevice might be both meaningful for developing new concept lighting devices and potentially extended to fabricate hierarchical Si-based nanoheterostructures in fabricating other optoelectronic nanodevices.