A simple and efficient, one-pot approach for the synthesis of ether-linked diisoxazole derivatives has been developed through sequential reactions, which includes O-propargylation of 2-bromohomoallylic alcohols with propargyl bromide in the presence of sodium hydride in THF, and 1,3-dipolar cycloaddition by the addition of hydroximinoyl chlorides and triethylamine. This protocol provides some advantages such as high regioselectivity, easy operation and good product yields with a wide scope of substrates under mild conditions.
Abstract A facile procedure for the solid‐phase synthesis of cycloalkylphosphonates and 1‐cycloalkenylphosphonates in good yields and high purities using polystyrene‐supported phenylsulfonylmethylphosphonates with traceless sulfone linker strategy is described.
An efficient and mild protocol for the visible light-induced radical cascade difluoromethylation/cyclization of imidazoles with unactivated alkenes using easily accessible and bench-stable difluoromethyltriphenylphosphonium bromide as the precursor of the -CF
The A15 phase superconductor Nb3Al has been considered as an alternative to Nb3Sn for high field and large scale applications. However, to prepare a stoichiometric Nb3Al with fine grain structures is very difficult. High-energy ball milling is a solid state powder processing technique and is a very useful for preparing Nb-Al alloys (Nb3Al). The effects of ball milling time and annealing temperature on the formation of Nb3Al superconducting phase have been studied. Pure Nb and Al powders with stoichiometric ratio of Nb3Al were mixed and milled, and the charging and milling were performed in an inert atmosphere. Phase formation and structural evolution during high-energy ball milling have been examined by X-ray diffraction. Al disappeared and Nb peaks broadened after about one hour of milling. With increasing milling time, the peaks of Nb became considerably broader and intensities decreased, the Nb-Al solid solution phase was extensive when milled about 3 hours. In order to obtain Nb3Al superconducting phase, a subsequent anneal was required. We have annealed the as-milled powders at 800-900°C for different times to prepared Nb3Al superconducting alloy. The results indicated that Nb3Al with small amount of impurity phase can be obtained on annealing the Nb-Al solid solution phase and the superconducting transition temperature was about 15K, but it is difficult to obtain a homogeneous Nb3Al phase by annealing the amorphous powder.
Nickel foam is mainly used for the battery electrode materials specifically for MH-Ni batteries, which can be widely used in the portable computers, the mobile phones and the hybrid electric vehicle. It is important to study the mechanical properties. The effects of the porosity and model type of the open cell nickel foam on the tensile behavior were investigated. With the finite element method based on Kelvin model in this paper. The results show that the Kelvin model is more resistant to deformation than the Gibson-Ashby model and is closer to the experiment results, and the bearing capacity decreasing as the porosity increasing.
Very thin intrinsic amorphous silicon films (≪10 nm) are used for passivation studies of crystalline silicon. In this paper, a-Si:H layers are subjected to a variety of post-treatments. A hydrogen plasma treatment crystallizes the thin film almost instantaneously, significantly reducing the effective lifetime. Anneals in different atmospheres typically show similar results, which are highly dependent on the initial state of the a-Si/c-Si interface. Data will be discussed and conditions compared of thin intrinsic a-Si:H films that show changes in effective lifetime due to annealing. Films with initial low effective lifetimes can result in low or high lifetimes after annealing, while the opposite is also possible; films with high initial lifetime can result in low or high lifetime after annealing. Lastly, a minimum thickness of the intrinsic layer is needed for annealing to demonstrate a positive effect on the effective lifetime.
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