Advanced Materials Research Vols. 476-478

Abstract: LiCl doped titania (TiO₂) hollow nanofibers were prepared by using polylactide (PLA) nanofibers as templates. The morphology and crystal structure of the TiO₂ hollow nanofibers were characterized by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The as-prepared LiCl doped TiO₂ hollow nanofibers exhibited a good humidity-sensing property. During the relative humidity (50%-95%) measurement, the response and recovery time is about 3 and 4 s, separately, with good linearity. The relationship between the humidity-sensing properties and the structure of the hollow nanofibers was also discussed. These distinguished and sensitive sensing performances make this material a good candidate in fabricating humidity sensors.

Abstract: μNear-infrared (NIR) emissions have been observed in Sm³⁺ doped low phonon energy heavy-metal-gallate glasses. The full-widths at half-maximum (FWHMs) of three fluorescence bands peaking at 960, 1038, and 1185 nm were derived to be 31, 36, and 42 nm, respectively, and the spontaneous transition probabilities were calculated to be 66, 16, and 6 s^-1. Maximum stimulated emission cross-sections ( σ_em) for NIR transition emissions were obtained to be 4.22´10^-22, 1.37´10^-22, and 0.71´10^-22 cm², respectively. Investigations on multi-channel NIR transition emissions of Sm³⁺, especially on the ~1.19 μm emission, which lies in the low-loss wavelength region of transmission window, are beneficial for potential applications in infrared optoelectronic devices.

Abstract: The electroless Ni-Plated technique was used to fabricate the coupled and activated Glass beads /Carbon Fiber. The microstructure of Ni-P-GBs/CFs was analyzed by IR, SEM, EDS, and the microwave absorption properties were characterized by Vector Network Analyzer. The results showed that Ni-p alloy layer is dense and continuous after electro less plating. When the mass ratio is 3:2(GB/CFs), and mass percent of mixed dusty materials is 22.5%, the average loss value is lower than -5 dB in the frequency range of 2～18 GHz, while the greatest loss value is up to -12.4dB in the 15.1 GHz.

Abstract: The effects of nitrogen annealing on the microstructure and magnetic properties of melt-spun Nd-Fe-Co-Zr-B alloy have been studied. It is shown that the ribbons annealed in purified argon atmosphere are composed of Nd2Fe14B and α-Fe phases, the microstructure of ribbons is homogeneous and fine-grained. The nitrogen-annealed ribbons are composed of Nd₂Fe₁₄B, NdBN₂ and α-Fe phases, the microstructure of ribbons is relatively heterogeneous and coarse-grained. The increase of nitrogen content in the annealing atmosphere can increase the volume fractions of NdBN₂ and α-Fe phases in the ribbons. The remanence, intrinsic coercivity and the maximum energy product of ribbons are decreased with increasing the nitrogen content in the annealing atmosphere.

Abstract: Gadolinium chelate and Quantum Dots (QDs) decorated single walled carbon nanotubes (SWNTs) nanohybrids (SWNT-Gd-QDs) were designed for dual-modal cellular imaging via magnetic resonance imaging (MRI) and optical imaging. The nanohybrids were prepared via a simple and novel layer-by-layer (LBL) assembly in combination with covalent connection strategy. The SWNT-Gd-QDs nanohybrids showed a strong near-infrared photoluminescence (PL) emission at room temperature and enhanced T1-weighted and T2-weighted MRI signals in water. Thus, the nanohybrids combine magnetic and fluorescent properties and can serve as dual-modal MRI/optical imaging contrast agent.

Abstract: Ag nanoparticles were successfully synthesized by hydrothermal method under the polyol system combined with traces of sodium chloride, Silver nitrate(AgNO3) and polyvinylpyrrolidone (PVP) acted as the silver source and dispersant respectively. The samples by this process were characterized via X-ray powder diffraction (XRD), Brunauer–Emmett–Teller (BET) adsorption equation, transmission electron microscopy (TEM) and the corresponding selected area electron diffraction (SAED) to determine the chemical composition, particle size, crystal structure and morphology. The experiment results indicate that the crystal structure of the samples is face centered cubic (FCC) structure as same as the bulk materials, The specific surface area is 24 m2/g, the particle size distribution ranging from10 to 50 nm, with an average particle size about 26 nm obtained by TEM and confirmed by XRD and BET results.

Abstract: Super resolution image reconstruction is a computational process of using multiple low-resolution observations to reconstruct a higher resolution image, which differs from improvement of optical devices. With magnification diversity among those low-resolution imagers, significant performance improvement, compared to traditional methods, is demonstrated. Results include fidelity metrics and simulated reconstructions. Performance improvement of super-resolution imaging systems with magnification diversity is studied in this paper.

Abstract: Oxide dispersion strengthened (ODS) ferritic steel which contains Y2O3 dispersion is one of the most promising candidates for fast neutron reactor cladding materials due to its excellent swelling resistance to neutron and superior creep resistance in high temperature. There are many ways to prepare ODS ferritic steel and the most commonly used method is mechanical alloying. However, ODS ferritic steel produced by the method of mechanical alloying is poor in the plasticity and impact property. Moreover, the anisotropies of structure and properties are obvious in the follow-up processing. In this paper, in order to reduce the cost, iron powder is used as raw material instead of ferritic steel powder. The complexing sol-gel method is adopted to prepare ODS iron-powder. There are many advantages of the sol-gel method such as the small size of disperse phase and the high uniformity. Besides, it is easy to control the conditions of reaction such as the water content, the bath temperature and the PH value. The gel-coated iron powder can be prepared under the appropriate environmental conditions. Then, we can obtain iron powder with Y2O3 dispersion after heating and reducing the gel-coated iron powder. By the spark plasma sintering(SPS), the ODS iron powder can be densified and we can observe the microstructure and test the performance. The results reveal the Y2O3 dispersion of ODS iron-powder by sol-gel method is uniform and the mechanical property is excellent.

Abstract: The influence of pre-sintering temperature and time, which ranged from 700 to 900°C and from 0.5 to 12h respectively, on the size and shape of the grains composed of YIG target were studied. The YIG precursors, of which the crystallization temperature was obtained by the DSC tests, were synthesized through the chemical co-precipitation method. According to the XRD, SEM and VSM measurement results, YIG powders pre-sintered at 750°C for 7hours, which temperature is lower than the crystallization temperature, can make the target with the highest density, good magnetic property, fine-grained and narrow grain size distribution.

Abstract: The electronic and optical properties of the lead sulfide are studied using first-principles calculations. The energy band structure and density of state of PbS are calculated. The results suggest that PbS exhibit a narrow band gap. The Mulliken analysis shows that the Pb-S bond is ionic. The dielectric function, absorption coefficient, reflectivity spectrum, refractive index and extinction coefficient are calculated for radiation up to 35eV. We have show that S (3p) electrons states and Pb (6p) electrons states play an important role in these transitions.