Key Engineering Materials Vols. 575-576

Abstract: The high-quality two sizes CdSe quantum dots (QDs) with nearly monodisperse size and shape were synthesized by the employed hot injection method with some modifications. The nanoparticles diameters were to be 2.6nm and 3.0nm respectively. To improve crystallization property and specific surface area of TiO₂ and to inhibit recombination processes of photoinduced electrons effectively, TiO₂-nano-SiO₂ hybrid films were prepared by adding proper meso-porous SiO₂ into TiO₂, in which the mass ratio of SiO₂ to TiO₂ was 5%. CdSe QDs were linked to TiO₂-nano-SiO₂ films using 3-mercaptopropionic acid to increase CdSe QDs adsorption. Two sizes CdSe QDs were achieved both to promote charge separation and to ensure the porper mobile pathway of free carriers. The J-V characterization showed that two sizes CdSe QDs co-sensitized TiO₂-nano-SiO₂ hybrid photoelectrodes had higher short circuit current density (J_SC) and open circuit voltage (V_OC), compared to one size CdSe QDs.

Abstract: Li_0.96Na_0.04Ni_1/3Co_1/3Mn_1/3O₂ with PEG400 or PEG2000 as additive was synthesized by coprecipitation method. Xray diffraction pattern reveals that both the products with PEG400 and PEG2000 are pure phase. Scanning Electron Microscopy shows that the average sizes of the powders are 100 nm and 80 nm, respectively. The sample with PEG 2000 has initial discharge capacity (205.8 Mah×g1) and the sample with PEG 400 exhibits good cycle performance with the capacity retention of 86.34 % after 90 cycles compared to that has no additive (167.6 mAh.g^-1 and 71.18 %) in the cut-off voltage of 2.0-4.5 V at 0.1 C rate. Therefore, PEG400 or PEG2000 as additive should improve the performance of Li_0.96Na_0.04Ni_1/3Co_1/3Mn_1/3O₂ cathode material.

Abstract: This study investigated the constitutive flow behavior and hot workability of in-situ 5wt% TiB₂ reinforced 7050 Al alloy matrix composite by hot compression experiments. Based on the experimental results of flow curves, a constitutive model describing the relationship of the flow stress, true strain, strain rate and temperature is proposed. Substantially, it is found the constitutive equation of flow stress is dependent on the strain, strain rate and temperature. The coefficients (E.g., α, n, Q and lnA) in the equation are functions of true strains. The results of the calculated values from constitutive equation are verified to well agree with the experimental values. Furthermore, the processing map of the composite is created in order to determine the hot processing domains. The optimum zones for hot workability and instability regions are identified. In instability domain, the microstructures display the main failure modes as the particle cracking and interface debonding.

Abstract: Biomorphic porous LaFeO₃ samples were prepared using aspen leaves as biotemplates. The structural and microscopy characterization has been carried out with X-ray diffraction, scanning electron microscopy and transmission electron microscopy. XRD patterns confirm thatLaFeO₃ shows perovskite phase with orthorhombic structure. The results of SEM and TEM revealed that the the obtained LaFeO₃ with hollow and porous structure. And the porous LaFeO₃ is composed of spherical particles with the size of 50-80 nm The gas sensing performance of as-prepared LaFeO₃ nanocrystlas was investigated. It is found that porous LaFeO₃ calcined at 700°C exhibit good sensitivity to acetone with rapid response.

Abstract: ZnS nanoparticles have been prepared by using 2, 3-dimercaptoethylthiopropanethiol (BES) as the coordinating modifier reagent to form Zn-thiol complex at low reaction temperatures. By controlling the experimental conditions, the diameter of the ZnS nanopaticles can be tuned from 43 nm to 115 nm. Systematic experiments were carried out to investigate the factors such as the amounts of the reagents (thiourea and BES) and the temperature, which have great influence on the sizes of the products. And when the content of BES is much higher, ZnS nanopaticles with mercapto surface modification were synthesized. In addition, massive blue shift in UV-vis spectra has been observed and the photoluminescence spectra of the ZnS show a strong emission at approximate 432 nm and 527 nm. Therefore, the preparation and properties studies of different ZnS sizes will offer great opportunities to explore the dependence of a material’s properties and find many interesting applications in the optical devices.

Abstract: A novel one-dimensional metal-organic coordination polymer, [Zn (NH₃)₂(BDC)]_n (BDC=1,4-benzenedicaboxylate), has been synthesized by solvent evaporation method through self-assembly of Zn (II) salts with terephthalic acid ligand in ammonia aqueous solution. Single crystal X-ray diffraction analysis indicated that each Zn (II) was coordinated by two nitrogen donors from two NH₃ and two oxygen counter donors from terephthalic acid ligand. The adjacent zigzag chains are arranged in a parallel fashion and linked by interchain hydrogen bonding interaction and π-π stacking interactions into higher-dimensional framework. The compound has also been characterized by CHN elemental analyses, Single crystal X-ray diffraction analysis, powder X-ray diffraction (PXRD) analysis, Fourier transform infrared (FT-IR) spectra, Thermalgravimetric-differential scanning calorimetric (TG-DSC) and Solid-state nuclear magnetic resonance (NMR), etc. Results showed that the framework of compound was stable at the temperature up to 246°C. The desolvated product [Zn (BDC)]_n, which was obtained by removal of molecular NH₃ from [Zn (NH₃)₂(BDC)]_n, can be transferred to the different skeleton structures through coordinating different small hydrogen-bond-forming molecules.

Abstract: In this work, a novel phenyleneethynylene derivative 4,4´-(2,5-dimethoxy-1,4-phenylene)bis(ethyne-2,1-diyl)dibenzoic acid (p-acid) was synthesized. Based on these we developed a simple and sensitive sandwich-type Uv-vis spectrum immunsensor for α-fetoprotein (AFP).

Abstract: Using Fe (NO₃)₃9H₂O, Y(NO₃)₃6H₂O and polyvinyl alcohol as the main raw material, the YFeO₃ nanoparticles were prepared by a microwave process. The YFeO₃ nanoparticles were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-visible diffuse reflectance spectroscopy (DRS). The results show that the perovskite structureYFeO₃ can be obtained, and the resulting product has a particle size of 70 nm and an optical band gap of 2.4 eV. The recovery of YFeO₃ photocatalysts was performed by the photocatalytic experiment of load YFeO₃. It is found that YFeO₃ nanocrystalline photocatalysts can be efficiently recovered by magnetic polymer film load.

Abstract: Rutile Ti_1xSn_xO₂ (0.2x<1) solid solutions had been prepared using a sol-hydrothermal method, which combined the conventional sol-gel process with hydrothermal method. Hybrid alkoxides of Ti⁴⁺ and Sn⁴⁺ were used as precursors in the sol-gel process and Sn⁴⁺ served as crystal-inducing agent during the formation of rutile crystal lattice in the hydrothermal process at 200°C. The microstructures and morphologies of nanoparticles were detected with XRD and TEM. Rutile Ti_1xSn_xO₂ solid solutions nanoparticles with well-distributed crystallite sizes about 10nm were obtained with Sn⁴⁺ content above 20mol% without any high temperature calcination. The oxygen sensitivity properties of Ti_1xSn_xO₂ solid solutions had also been investigated. It is proved Ti_1xSn_xO₂ solid solutions exhibited higher oxygen responses than single TiO₂ or SnO₂. A typical sample of Ti_0.5Sn_0.5O₂ presented the best sensitivity is approximately 6 under 400°C.