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1.
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. 相似文献
2.
Margeaux A. Miller Prof. Dr. Ellen M. Sletten 《Chembiochem : a European journal of chemical biology》2020,21(24):3451-3462
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. 相似文献
3.
Dr. Timo Broese Dr. Peter Ehlers Dr. Peter Langer Dr. Jan von Langermann 《Chembiochem : a European journal of chemical biology》2021,22(23):3314-3318
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. 相似文献
4.
Guoqiang Yi Bingchu Mei Weiwei Li Jinghong Song Zuodong Liu Zhiwei Zhou Liangbi Su 《Journal of the American Ceramic Society》2020,103(1):279-286
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. 相似文献
5.
6.
Jason H. C. Yang Kungen Teii Chung-Chueh Chang Seiichiro Matsumoto Miriam Rafailovich 《Advanced functional materials》2021,31(4):2005066
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. 相似文献
7.
改型天然沸石净化高氟饮用水研究 总被引:10,自引:0,他引:10
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。 相似文献
8.
通过微观分析方法,在鄂尔多斯盆地白垩系钻孔岩样中首次发现方沸石类矿物。就地取材,对方沸石岩进行提纯和改性,制成多孔方沸石球,用于含氟水的处理,取得了明显的效果。对于100mL起始浓度3.00mg/L的含氟水,方沸石球较佳的水处理工艺条件为:用量1.5g,搅拌后静置48h,直径3mm。对于起始浓度3.00mg/L的含氟水,方沸石球一次水处理后氟离子浓度就低于国家标准。对于起始浓度3.00~10.00mg/L的含氟水,经方沸石球几次水处理后氟离子浓度也低于国家标准。方沸石球对氟离子吸附等温线符合Langmuir吸附等温式,为:qe=0.243ce/(1 0.433ce);吸附速度符合斑厄姆公式,为:dq/dt=4.482×10-3(qe-q)/t 0.176。用过的方沸石球再生处理后活性基本恢复,多次再生后除氟效果有所下降。 相似文献
9.
为探讨云南昭通氟中毒地区环境中氟的含量和分布规律以及氟的来源,在昭通镇雄和威信地区采集了160个煤、黄铁矿结核、煤矸石、黏土、玉米、辣椒、饮用水样品,用高温水解-氟离子选择电极法对样品中的氟进行了分析.结果表明:云南昭通氟中毒区晚二叠世龙潭组主采煤层C5煤含氟量低,平均含氟量为77.13 mg/kg;3个典型氟中毒病区民用煤的平均含氟量为72.56 mg/kg,稍低于中国煤炭平均含氟量〖BF〗(82 mg/kg), 与世界煤的平均值(80 mg/kg)〖BFQ〗接近.中毒区的煤主要为低氟煤,煤中的氟与灰分关系较为密切.中毒区的拌煤黏土中氟含量一般在367~2 435 mg/kg, 但以含氟量超过600 mg/kg的高氟拌煤黏土为主,平均含氟量为1 084.2 mg/kg.氟中毒区饮用水的含氟量一般低于0.35 mg/L,低于国家饮用水的要求(1.0 mg/L). 相似文献
10.
海水中微量氟的测定 总被引:7,自引:0,他引:7
孙红英 《广东有色金属学报》2002,12(1):68-71
用柠檬酸钠和EDTA来消除Al^3 ,Fe^3+等干扰离子的影响;采用标准加入法消除盐类对电位的影响;在pH=6.5时,用氟离子选择电极测海水中氟的电位。最后,通过格氏作图法测得海水中氟的含量。回收率为98%-105%。此方法分析快速、结果准确、可靠。 相似文献