Volatilization of fluorine in a CaO–SiO2–CaF2-based system with the substitution of Na2O with K2O

Cuspidine-based systems are used to control the crystallization in mold fluxes, which is enabled by CaF₂ additions. However, excess CaF₂ increases the corrosion of casting machines. Therefore, Na₂O and K₂O are added to the mold flux system to ensure an optimized crystallization and lubrication ability of the flux with the CaF₂ content. This study investigated the effect of substituting Na₂O with K₂O on the volatilization of fluorine in a CaO–SiO₂–CaF₂-based slag system at high temperatures. The substitution of Na₂O with K₂O was performed at 5 mol% intervals. The volatilization was observed by thermogravimetric analysis under several isothermal conditions. The mass loss was measured at a heating rate of 5, 10, and 20 K/min. As the temperature increased, the volatilization of the mixed samples increased. The activation energy was calculated using the Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose methods. A kinetic analysis of the volatilization of fluorine was conducted using the calculated parameters and several known kinetic models. Consequently, the volatilization of the Na-rich sample was controlled by chemical reactions and that of the K-rich sample was identified to be controlled by a phase-boundary-controlled reaction. These results suggest that the addition of mixed alkali oxide promote the volatilization during the early stages of the reaction. From the post-experimental composition analyses, the remaining Na and K in the samples suggested a different mechanism for the Na and K volatilization. The volatilization of Na increased with time, whereas K volatilized easily during the beginning of the reaction.     

南极磷虾中氟的赋存形态及分析方法研究进展

南极磷虾资源储量巨大,营养价值丰富,但富氟问题是其在食品开发利用领域的"瓶颈"。如何选取合适的前处理方法以及快速、准确检测南极磷虾中的不同形态的氟含量成为亟需解决的关键问题。该文系统阐述国内外文献报道的南极磷虾及其产品中氟的赋存形态、氟的前处理方式、氟的分析检测方法,旨在为开发高精密度、高灵敏度的南极磷虾中氟化物的检测技术法提供参考价值。     

Perfluorocarbons in Chemical Biology

Perfluorocarbons, saturated carbon chains in which all the hydrogen atoms are replaced with fluorine, form a separate phase from both organic and aqueous solutions. Though perfluorinated compounds are not found in living systems, they can be used to modify biomolecules to confer orthogonal behavior within natural systems, such as improved stability, engineered assembly, and cell-permeability. Perfluorinated groups also provide handles for purification, mass spectrometry, and ¹⁹F NMR studies in complex environments. Herein, we describe how the unique properties of perfluorocarbons have been employed to understand and manipulate biological systems.     

Chemoenzymatic Asymmetric Synthesis of Pyridine-Based α-Fluorinated Secondary Alcohols

Fluoro-substituted and heteroaromatic compounds are valuable intermediates for a variety of applications in pharma- and agrochemistry and synthetic chemistry. This study investigates the chemoenzymatic preparation of chiral alcohols bearing a heteroaromatic ring with an increasing degree of fluorination in α-position. Starting from readily available picoline derivatives prochiral α-halogenated acyl moieties were introduced with excellent selectivity and 64–95 % yield. The formed carbonyl group was subsequently reduced to the corresponding alcohols using the alcohol dehydrogenase from Lactobacillus kefir, yielding an enantiomeric excess of 95–>99 % and up to 98 % yield.     

纳米ZnO/有机氟改性丙烯酸酯乳液的合成与表征

以纳米ZnO、甲基丙烯酸十二氟庚酯(DFMA)、甲基丙烯酸甲酯(MMA)、丙烯酸丁酯(BA)为原料,用半连续种子乳液聚合法制备纳米ZnO/有机氟改性聚丙烯酸酯,探索了合成工艺,然后将合成乳液用于亚麻织物的整理。采用FT-IR、XPS和SEM等方法对乳胶膜和整理后的织物进行表征分析。结果表明:当乳化剂质量分数为4%,引发剂质量分数为1.5%,反应温度为80℃,保温时间为60 min时,乳液的合成效果最好。合成的乳液具有良好的抗紫外性能,其乳胶膜的吸水率为8.64%。XPS和SEM测试结果显示,合成的复合乳液和织物相结合,提高了亚麻织物的疏水性。相比聚丙烯酸酯整理后的织物,经复合乳液整理后的亚麻织物对水的接触角提高了60.4°。     

Synthesis and luminescence characterization of Pr3+, Gd3+ co-doped SrF2 transparent ceramics

Pr³⁺, Gd³⁺ co-doped SrF₂ transparent ceramic, as the potential material for visible luminescent applications, was prepared by hot-pressing of precursor nanopowders. The microstructure, phase compositions, and in-line transmittance, as well as the photoluminescence properties were investigated systematically. Highly optical quality Pr,Gd:SrF₂ transparent ceramic with nearly pore-free microstructure was obtained at 800°C for 1.5 hours. The average in-line transmittance of the x at.% Pr, 6 at.% Gd:SrF₂ (x = 0.2, 0.5, 1.0, 2.0) transparent ceramics reached to 87.3 % in the infrared region. The photoluminescence spectra presented intense visible light emissions under the excitation of 444 nm, the main intrinsic emission bands located at 483 and 605 nm, which were attributed to the transitions of Pr³⁺: ³P₀ → ³H₄ and ¹D₂ → ³H₄, respectively. With the co-doping of Gd³⁺ ions, the emission intensity of the Pr:SrF₂ transparent ceramic was greatly enhanced. All the emission bands of x at.% Pr, 6 at.% Gd:SrF₂ transparent ceramics exhibited the highest luminescence intensity with the 1.0 at.% Pr³⁺ doping concentrations, whereas the lifetimes decreased dramatically with the Pr³⁺ doping contents increasing from 0.2 to 2.0 at.% due to its intense concentration quenching effect. The 1 at.% Pr, 6 at.% Gd:SrF₂ transparent ceramic is a promising material for visible luminescent device applications.     

高纯硫酸锰降氟研究

为解决高纯硫酸锰产品含氟量高的问题,生产无氟产品,本实验用降氟剂A和降氟剂B进行试验,比较两者的降氟效果,选择在经济和降氟效果上更优的降氟剂。降氟剂A的单位吸附量约为159.977mg/g,降氟剂B的单位吸附量为64.144mg/g;降氟剂A的再生除氟效果为73.013%,降氟剂B的再生除氟效果为96.5%。     

Biocompatible Cubic Boron Nitride: A Noncytotoxic Ultrahard Material

Cubic boron nitride (c-BN) has an ultrahardness and a large bandgap energy like diamond. In the last 30 years, most of the attention has been directed towards the mechanical and electronic applications of c-BN, while its biological potential has been overlooked. The authors report in vitro biocompatibility of high-quality c-BN films prepared by plasma-enhanced chemical vapor deposition using the chemistry of fluorine. c-BN films become superhydrophilic when chemical-treated in hydrogen and nitrogen plasmas with or without the impact of low-energy ions due to a marked increase in polar part of the surface free energy by removal of the fluorine atoms terminating c-BN surfaces. Satisfactory proliferation and differentiation of osteoblastic cells comparable with a control sample and a superhydrophilic nanocrystalline diamond film, and the formation of mineral deposits by biomineralization are confirmed on the superhydrophilic c-BN films with negative values of zeta potential. The results demonstrate a high potential of c-BN as a noncytotoxic ultrahard coating material for biological and biomedical applications.     

改型天然沸石净化高氟饮用水研究

以河南信阳上天梯优质斜发沸石为原料 ,研究了用盐酸、硫酸铝和高温方法活化天然沸石的工艺条件。用活化天然沸石处理后的含氟饮用水 ,基本可达到国家饮用水标准。     

基于数据挖掘的采场稳定性的知识获取与应用

利用数据挖掘技术，从已获得的大量有关采场稳定性的数据中，提取出可以理解的模式，从而有效地认识矿山采场稳定性的动态变化规律，发现新的知识，在此基础上，可以根据获得的现场资料，预测采场的稳定性。本文的实例研究证明，数据挖掘技术为分析和预测采场稳定性提供了一种很好的解决方法。