نتایج جستجو برای: fluorine
تعداد نتایج: 7204 فیلتر نتایج به سال:
Oxynitride glasses are found as grain boundary phases in silicon nitride ceramics. They are effectively alumino-silicate glasses in which nitrogen substitutes for oxygen in the glass network, and this causes increases in glass transition and softening temperatures, viscosities (by two to three orders of magnitude), elastic moduli and microhardness. Calcium silicate-based glasses containing fluo...
Grafting of fluorine species on carbon nanostructures has attracted interest due to the effective modification of physical and chemical properties of the starting materials. Various techniques have been employed to achieve a controlled fluorination yield; however, the effect of contaminants is rarely discussed, although they are often present. In the present work, the fluorination of vertically...
Fluorine is the 13th most abundant element and, with other fluorine containing functional groups, is a most effective element in biological substances, pharmaceuticals, agrochemicals, liquid crystals, dyes, polymers and a wide range of consumer products. This reflects its resistance to metabolic change due to the strength of the C-F bond providing biological stability and the application of its...
1. INTRODUCTION Despite being largely absent from natural products and biological processes, fluorine plays a conspicuous and increasingly important role within pharmaceuticals and agro-chemicals, as well as in materials science. 1a−c Indeed, as many as 35% of agrochemicals and 20% of pharmaceuticals on the market contain fluorine. 1d Fluorine is the most electronegative element in the periodic...
Fluorinated compounds are synthesized in pharmaceutical research on a routine basis and many marketed compounds contain fluorine. The present review summarizes some of the most frequently employed strategies for using fluorine substituents in medicinal chemistry. Quite often, fluorine is introduced to improve the metabolic stability by blocking metabolically labile sites. However, fluorine can ...
This paper investigates how the thermal diffusion of boron in silicon is influenced by a high energy fluorine implant with a dose in the range 531014–2.331015 cm−2. Secondary Ion Mass Spectroscopy (SIMS) profiles of boron marker layers are presented for different fluorine doses and compared with fluorine profiles to establish the conditions under which thermal boron diffusion is suppressed. The...
In this study, the effects of fluorine treatment on surface properties, surface free energies, and dielectric constants of polyimide thin films were studied using X-ray photoelectron spectroscopy, contact angles, and dielectric characteristics, respectively. The glass transition temperature of fluorinated polyimide film gradually decreases with increasing fluorine pressure. The surface free ene...
the aim of conducting this research was to evaluate the viscosity change in the continuous casting of steel moldpowders by altering their chemical compositions, using hot stage microscope analysis. 4 low-fluorine samplescontaining such compositions as mno, fe2o3, li2o, tio2 and zno, as well as another fluorine-free samplecontaining a combination of fe2o3 and tio2, were prepared in this research...
Neutral fluorine (F i) lines are identified in the optical spectra of cool EHe stars. These are the first identification of F i lines in a star’s spectrum, and provide the first measurement of fluorine abundances in EHe stars. The results show that fluorine is overabundant in EHe stars. The overabundance of fluorine provides evidence for the synthesis of fluorine in these stars, that is discuss...
Fluorine-containing species can be extremely effective atmospheric greenhouse gases. We present fluorine budgets using organic and inorganic species retrieved by the ACE-FTS satellite instrument supplemented with output from the SLIMCAT 3-D chemical transport model. The budgets are calculated between 2004 and 2009 for a number of latitude bands: 70–30 N, 30–00 N, 00 N–30 S, and 30–70 S. At lowe...
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