Lu3+/Yb3+ and Lu3+/Er3+ co-doped antimony selenide nanomaterials: synthesis,characterization, and electrical,thermoelectrical, and optical properties

Lu³⁺/Yb³⁺ and Lu³⁺/Er³⁺ co-doped Sb₂Se₃ nanomaterials were synthesized by co-reduction method in hydrothermal condition. Powder X-ray diffraction patterns indicate that the Ln_xLn^′_xSb_2−2xSe₃ Ln: Lu³⁺/Yb³⁺ and Lu³⁺/Er³⁺ crystals (x = 0.00 − 0.04) are isostructural with Sb₂Se₃. The cell parameters were increased for compounds upon increasing the dopant content (x). Scanning electron microscopy and transmission electron microscopy images show that co-doping of Lu³⁺/Yb³⁺ ions in the lattice of Sb₂Se₃ produces nanorods, while that in Lu³⁺/Er³⁺ produces nanoparticles, respectively. The electrical conductivity of co-doped Sb₂Se₃ is higher than that of the pure Sb₂Se₃ and increases with temperature. By increasing the concentration of Ln³⁺ions, the absorption spectrum of Sb₂Se₃ shows red shifts and some intensity changes. In addition to the characteristic red emission peaks of Sb₂Se₃, emission spectra of co-doped materials show other emission bands originating from f-f transitions of the Yb³⁺ ions.     

A green and facile one-pot synthesis of Ag–ZnO/RGO nanocomposite with effective photocatalytic activity for removal of organic pollutants

In this study, Ag–ZnO/reduced graphene oxide (Ag–ZnO/RGO) composite was synthesized by a green and facile one-step hydrothermal process. Aqueous suspension containing Ag and ZnO precursors with graphene oxide (GO) sheets was heated at 140 °C for 2 h. The morphology and structure of as-synthesized particles were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, and Photoluminescence (PL) spectroscopy which revealed the formation of composite of metal, metal oxide and RGO. It was observed that the presence of Ag precursor and GO sheets in the hydrothermal solution could sufficiently decrease the size of ZnO flowers. The hybrid nanostructure, with unique morphology, obtained from this convenient method (low temperature, less time, and less number of reagents) was found to have good photocatalytic and antibacterial activity. The perfect recovery of catalyst after reaction and its unchanged efficiency for cyclic use showed that it will be an economically and environmentally friendly photocatalyst.     

Optimization for allocating the explosive facilities in order to minimize the domino effect using nonlinear programming

Accidents caused by the domino effect in chemical plants or the petrochemical industry are generally more serious than any other accident. But it is difficult to examine the true factor because the domino effect is influenced by many nonlinear factors. The immediate causes of the domino effect are the peak overpressure, flying objects, and flame. Nonlinearity is inherent in all three causes. However, it is believed that a systematic and mathematical approach can minimize the incidence of the domino effect. We considered the case where there were n-explosive facilities in a given arbitrary rectangular facility site. This paper suggests the positions that can minimize the domino effect using a nonlinear approach. The method initiated an arbitrary number of facilities in addition to the original position, and can search for the position to minimize the domino effect. This paper presents a new computer-aided module, MiniFFECT (MINImization of domino eFFECT).     

Preparation of Mesoporous Ni–alumina Catalyst by One-step Sol–gel Method: Control of Textural Properties and Catalytic Application to the Hydrodechlorination of o-dichlorobenzene

Mesoporous Ni–alumina catalysts (Ni–alumina-pre and Ni–alumina-post) were synthesized by one-step sol–gel method using micelle complex comprising lauric acid and nickel ion as a template with metal source and using aluminum sec-butoxide as an aluminum source. The Ni–alumina catalysts showed relatively high surface areas (303 m²/g for Ni–alumina-pre and 331 m²/g for Ni–alumina-post) and narrow pore size distributions centered at ca. 4 nm. Highly dispersed Ni particles were observed in the Ni–alumina catalysts (ca. 5.2 nm for Ni–alumina-pre and ca. 6.8 nm for Ni–alumina-post) after reduction at 550 °C, while a catalyst prepared without a template (NiAl-comp) exhibited inferior porosity with large metal particles (ca. 12.3 nm). Mesoporous Ni–alumina catalysts with different porosity were obtained by employing different hydrolysis step of aluminum source. When aluminum source was hydrolyzed under the presence of micelle complex, a supported Ni catalyst with highly developed framework mesoporosity was obtained (Ni–alumina-post). On the other hand, when aluminum source was pre-hydrolyzed followed by mixing with micelle solution, the resulting catalyst (Ni–alumina-pre) retained high portion of textural porosity. It was revealed that the hydrolysis method employed in this research affected not only textural properties but also metal-support interaction in the Ni–alumina catalysts. It was also found that the Ni–alumina-pre catalyst exhibited weaker interaction between nickel and alumina than the Ni–alumina-post, leading to higher degree of reduction in the Ni–alumina-pre catalyst. In the hydrodechlorination of o-dichlorobenzene, the Ni–alumina catalysts exhibited better catalytic performance than the NiAl-comp catalyst, which was attributed to higher metal dispersion in the Ni–alumina catalysts. In particular, the Ni–alumina-pre catalyst showing 1.5 times higher degree of reduction and larger amounts of o-dichlorobenzene adsorption exhibited better catalytic performance than the Ni–alumina-post catalyst.     

Fabrication of nano/microfiber scaffolds using a combination of rapid prototyping and electrospinning systems

Tissue‐engineered scaffolds require an adequate three‐dimensional (3‐D) structure for cell growth and attachment. Solid freeform fabrication can provide the interconnected pore to induce the cell ingrowth, and electrospinning technique can make the nanofiber web with high surface for cell attachment. In this study, 3‐D polycaprolactone (PCL) scaffolds were fabricated using a rapid prototyping plotting system coupled with an electrospinning apparatus. Scanning electron micrographs showed that these hybrid scaffolds had a regular microfiber structure with interconnected pores and a nanofiber distribution appropriate for cell attachment. Scaffolds were seeded with MG63 cells for in vitro study and implanted in the tibia of rabbit for in vivo study. The resulting structure also facilitated cell adhesion, proliferation, and differentiation as evidenced by biochemical analyses and confocal microscopy. The hybrid scaffolds also exhibited good biocompatibility and osteoconductivity in animal studies. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Chemical-looping combustion of syngas by means of spray-dried NiO oxygen carrier

Chemical-looping combustion (CLC) of syngas has a potential to generate power economically with achieving the inherent carbon dioxide capture. An oxygen carrier with high reactivity and excellent physical properties would make CLC technology more competitive. In this work, oxygen carrier with 70 wt% NiO was prepared by spray drying technique. The prepared oxygen carrier had excellent physical properties for fluidized-bed application of CLC process. The reactivity of the oxygen carrier in repeated reduction-oxidation was measured by thermogravimetric analyzer with simulated syngas. Oxygen carrier calcined at 1,100 °C showed high oxygen transfer capacity of 14.7 wt%, utilizing 98% of the transferable oxygen. Oxygen transfer capacity and oxygen transfer rate was increased with the increase of reaction temperature, and the highest oxygen transfer rate was observed when about half of the transferable oxygen reacted with syngas. The reduction rate of the syngas (mixture of H₂ and CO) appeared to be approximately the sum of the reaction rate of each fuel gas. The experimental results indicated that the spray-dried NiO oxygen carrier prepared in this work could be a good quality oxygen carrier for the CLC of syngas.     

Anti-reflective nano- and micro-structures on 4H-SiC for photodiodes

In this study, nano-scale honeycomb-shaped structures with anti-reflection properties were successfully formed on SiC. The surface of 4H-SiC wafer after a conventional photolithography process was etched by inductively coupled plasma. We demonstrate that the reflection characteristic of the fabricated photodiodes has significantly reduced by 55% compared with the reference devices. As a result, the optical response I _illumination/I _dark of the 4H-SiC photodiodes were enhanced up to 178%, which can be ascribed primarily to the improved light trapping in the proposed nano-scale texturing.     

Dispersion and flame retardancy of ethylene vinylacetate/layered silicate nanocomposites using the masterbatch approach for cable insulating material

Ethylene vinylacetate (EVA) copolymer-based nanocomposites with maleic anhydride-grafted ethylene-vinylacetate (EVAgMA) and organically modified clay (o-clay) were prepared in a twin screw extruder by following a two-step melt compounding method. EVAgMA/o-clay masterbatches with various clay contents up to 50 wt% were examined, after which the masterbatch with the highest clay content was melt compounded with EVA for the preparation of EVA/o-clay nanocomposites containing specific amounts of clay. Further morphological dispersion of the clay particles by highly polar EVA and shearing was confirmed in the EVA/o-clay nanocomposites by X-ray diffraction (XRD) and transmission electron microscopy (TEM). These morphologies led to increased thermal properties in air as well as a considerable decrease in heat release rate (HRR). EVA/o-clay/MDH nanocomposites were also prepared using a high clay-bearing masterbatch to confirm the synergistic flame retardancy of clay as a co-additive in EVA/MDH composites. EVA/o-clay/MDH nanocomposites prepared by substituting o-clay for MDH showed significantly lower and wider HRR during combustion compared to EVA/MDH composite.     

New Flower-Shaped Lead(II) Coordination Polymer at the Nano Scale: Synthesis, Structural Characterization and DFT Calculations of [Pb(o-phen)(N3)2] n Containing the Pb-(μ1,1-N3)(μ1,3-N3) Motif

A new nano-flower lead(II) azido coordination polymer from the ligand, orthophenanthroline (o-phen), [Pb(o-phen)(μ_1,1-N₃)(μ_1,3-N₃)] _n (1), was synthesized by a sonochemical method. Compound 1 was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), elemental analyses and IR spectroscopy. Single crystalline material was obtained using a heat gradient applied to a solution of the reagents. The structure of 1 is a coordination polymer of lead(II) containing the Pb-(μ_1,1-N₃)(μ_1,3-N₃) motif, formed of one-dimensional chains. The structure of the 1 was optimized by density functional theory. Structural parameters and IR spectra for 1 are consistent with the crystal structure. Pure phase PbO nanoparticles were obtained by thermolysis of 1 with oleic acid as a surfactant at 180 and 200 °C an air. PbO nanoparticles were characterized by XRD and SEM.