Recycled carbon fiber reinforced poly(butylene terephthalate) thermoplastic composites: fabrication,crystallization behaviors and performance evaluation

The thermoplastic composites based on poly(butylene terephthalate) (PBT) and recycled carbon fiber (RCF) were prepared through simple melt compounding by a twin‐screw extruder. An effective approach was utilized to clean and treat the RCF surface with a concentrated solution of nitric acid and then a solution of diglycidyl ether of bisphenol A as macromolecular coupling agent so as to improve the interfacial adhesion between the RCF and PBT matrix. As a result, the reinforcing potential of the RCF was enhanced substantially, and the mechanical properties, heat distortion temperature, and thermal stability of PBT could be significantly improved by incorporating this surface‐treated RCF. The morphologies of fracture surfaces indicated that the RCF achieved a homogeneous dispersion in the PBT matrix due to a good interfacial interaction between fiber and PBT. The investigations on the crystallization behaviors and kinetics demonstrated that the RCF acted as a nucleation agent for the crystallization of PBT, and the crystallization rate and nucleation density of PBT were increased remarkably due to the heterogeneous nucleating effect of RCF in the matrix. These features may be advantageous for the enhancement of mechanical properties, heat resistance, and processability of PBT‐based composites. This study may provide a design guide for carbon fiber‐reinforced PBT composites with a great potential as well as a low cost for industrial and civil applications. Copyright © 2012 John Wiley & Sons, Ltd.     

Dose rate dependence of cellulose triacetate dosimeter and radiochromic film dosimeter

The doses of γ-rays and electron beams were evaluated by Fricke dosimetry and the responses of cellulose triacetate dosimeter (CTA) and radiochromic film dosimeter (RCF) to the two types of radiations were compared to investigate their dose rate dependence. Both the change in absorbance at 280 nm of CTA and that in absorbance at 510 nm of RCF caused by γ-irradiation were larger than those by electron-irradiation, when the dosimeters were irradiated to the same dose. The results in this study suggest that the responses of CTA and RCF are dependent upon dose rate.     

Reductive catalytic fractionation of pine wood: elucidating and quantifying the molecular structures in the lignin oil

In-depth structural analysis of biorefined lignin is imperative to understand its physicochemical properties, essential for its efficient valorization to renewable materials and chemicals. Up to now, research on Reductive Catalytic Fractionation (RCF) of lignocellulose biomass, an emerging biorefinery technology, has strongly focused on the formation, separation and quantitative analysis of the abundant lignin-derived phenolic monomers. However, detailed structural information on the linkages in RCF lignin oligomers, constituting up to 50 wt% of RCF lignin, and their quantification, is currently lacking. This study discloses new detailed insights into the pine wood RCF lignin oil''s molecular structure through the combination of fractionation and systematic analysis, resulting in the first assignment of the major RCF-derived structural units in the ¹H–¹³C HSQC NMR spectrum of the RCF oligomers. Specifically, β-5 γ-OH, β-5 ethyl, β-1 γ-OH, β-1 ethyl, β-β 2x γ-OH, β-β THF, and 5-5 inter-unit linkages were assigned unambiguously, resulting in the quantification of over 80% of the lignin inter-unit linkages and end-units. Detailed inspection of the native lignin inter-unit linkages and their conversion reveals the occurring hydrogenolysis chemistry and the unambiguous proof of absence of lignin fragment condensation during proper RCF processing. Overall, the study offers an advanced analytical toolbox for future RCF lignin conversion and lignin structural analysis research, and valuable insights for lignin oil valorization purposes.

In-depth structural analysis of pine wood RCF lignin discloses new detailed insights into the RCF lignin oil''s molecular structure.     

Structure and microporous formation of cellulose/silk fibroin blend membranes: Part II. Effect of post-treatment by alkali

Blend membranes (RCF1) were prepared from mixture solution of cellulose and silk fibroin (SF) in cuoxam by coagulating with acetone–acetic acid (4:1 by volume). The blend membranes were subjected to post-treatment with 10% NaOH aqueous solution, and their structure and properties were characterized by FT-IR, X-ray diffraction, DSC, SEM and DMTA. In previous work, cellulose/SF blend membranes (RCF2) prepared by coagulating with 10% NaOH aqueous solution formed a microporous structure, in which the SF as a pore former was almost completely removed from the membrane. However, when the blend membranes RCF1 were immersed in 10% NaOH aqueous solution for post-treatment, a strong hydrogen bonding between cellulose and SF inhibited the removal of SF. Although alkali is a good solvent for SF, the blend membranes RCF1 such obtained from cellulose and SF were alkali resistant. The crystallinity and the mean pore size of the blend membranes slightly decreased with increasing post-treatment time. This work provided a cellulose/silk blend membrane, which can be used under alkaline medium.     

Synthesis and Spectroscopic Characterization of Potassium Polyfluoroalken‐1‐yltrifluoroborates

The potassium fluoroborates K[RCF=CFBF₃] (R = F, Cl (cis‐/trans‐mixture), trans‐C₄F₉, cis‐C₂F₅, cis‐C₆F₁₃, trans‐C₄H₉, trans‐C₆H₅) were prepared by fluoridation (methoxide‐fluoride substitution with K[HF₂]) of RCF=CFB(OMe)₂ and Li[RCF=CFB(OMe)₃] which were obtained from RCF=CFLi and B(OMe)₃. The K[RCF=CFBF₃] salts were characterized by their ¹H, ¹¹B, ¹⁹F NMR and IR spectra.     

The radiochemical and chemical characterization of marine sediments taken up from Cuba's northern and southern littoral

Journal of Radioanalytical and Nuclear Chemistry - Radioactive contamination factor (RCF) has been proposed as a suitable unit to measure the magnitude of radioactive contamination at global scale,...     

Hydrogen-Transfer Reductive Catalytic Fractionation of Lignocellulose: High Monomeric Yield with Switchable Selectivity

Lignin solubilization and in situ hydrogenolysis are crucial for reductive catalytic fractionation (RCF) of lignocellulose to aromatic monomers. In this study, we reported a typical hydrogen bond acceptor of choline chloride (ChCl) to tailor the hydrogen-donating environment of the Ru/C-catalyzed hydrogen-transfer RCF of lignocellulose. The ChCl-tailored hydrogen-transfer RCF of lignocellulose was conducted under mild temperature and low-pressure (<1 bar) conditions, which was applicable to other lignocellulosic biomass sources. We obtained an approximate theoretical yield of propylphenol monomer of 59.2 wt % and selectivity of 97.3 % using an optimal content of ChCl (10 wt %) in ethylene glycol at 190 °C for 8 h. When the content of ChCl in ethylene glycol was increased to 110 wt %, the selectivity of propylphenol switched toward propylenephenol (yield of 36.2 wt % and selectivity of 87.6 %). The findings in this work provide valuable information for transforming lignin from lignocellulose into value-added products.     

A technique for production of nanocrystalline cellulose with a narrow size distribution

Nanocrystalline cellulose (NCC) was prepared by sulfuric acid hydrolysis of microcrystalline cellulose. A differential centrifugation technique was studied to obtain NCC whiskers with a narrow size distribution. It was shown that the volume of NCC in different fractions had an inverse relationship with relative centrifugal force (RCF). The length of NCC whiskers was also fractionized by differential RCF. The aspect ratio of NCC in different fractions had a relatively narrow range. This technique provides an easy way of producing NCC whiskers with a narrow size distribution.     

The charge-charge flux-overlap model for the interpretation of atomic polar tensors and infrared intensities

The interpretation of infrared intensities using the concepts of atomic polar tensors divided according to contributions from charge-charge flux-overlap (CCFO) terms appears in general to be quite useful. Here we shall illustrate this analysis for the F and H atoms in chemically related molecules to show how their properties vary for CF, CH, OF and OH bonds as R varies in RCF, RCH and ROH molecules.     

A functionalized renewable carbon-based surface for sensor development

This paper describes the surface modification of glassy carbon (GC) electrodes with a bamboo-based renewable carbon (RC) before and after an acid functionalization procedure with a sulfonitric solution (1:3 HNO₃/H₂SO₄). The morphology and structural characterization indicate an increase of functional groups in the functionalized renewable carbon (RCF) surface. The enhanced electroanalytical properties of RC and RCF were evaluated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in two different setups, in the presence of the redox couple ([Fe(CN)₆]^3−/4−) and escitalopram (EST). The results revealed an enhancement for the electrochemical responses of both inorganic and organic compounds in the electrolyte. Therefore, the use of new carbon-based materials such as renewable carbon for development of electrochemical sensors brings a fresh approach to low-cost device development.

     

全氟烷基亚磺酸盐的反应II. 一种合成N,N-双金氟烷基羟胺的新法

全氟烷基亚磺酸钠盐或银盐的水溶液, 与硝酸、亚硝酸或二氧化氮反应, 生成N,N-双全氟烷基羟胺, 产率中等, 并伴有全氟羧酸, 全氟酰胺和亚硝基全氟烷等副产物.     

Determining the geometry and magnetic parameters of fluorinated radicals by simulation of powder ESR spectra and DFT calculations: the case of the radical RCF2CF2* in nafion perfluorinated ionomers

The ESR spectrum of the chain-end radical RCF2CF2* detected in Nafion perfluorinated membranes exposed to the photo-Fenton reagent was accurately simulated by an automatic fitting procedure, using as input the hyperfine coupling tensors of the two F alpha and two F beta nuclei as well as the corresponding directions of the principal values from density functional theory (DFT) calculations. An accurate fit was obtained only for different orientations of the hyperfine coupling tensors for the two F alpha nuclei, indicating a nonplanar structure about the C alpha radical center. The fitted isotropic hyperfine splittings for the two F beta nuclei in the Nafion radical, 24.9 and 27.5 G, are significantly larger than those for the chain-end radical in Teflon (15 G), implying different radical conformations in the two systems. The excellent fit indicated that the geometry and electronic structure of free radicals can be obtained not only from single-crystal ESR spectroscopy, but also, in certain cases, from powder spectra, by combination with data from DFT calculations. The optimized structures obtained by DFT calculations for the CF3CF2CF2CF2* or CF3OCF2CF2* radicals as models provided additional support for the pyramidal structure determined from the spectral fit. Comparison and analysis of calculated and fitted values for the hyperfine splittings of the two F beta nuclei suggested that the radical detected by ESR in Nafion is ROCF2CF2*, which originates from attack of oxygen radicals on the Nafion side chain. The combination of spectrum fitting and DFT is considered important in terms of understanding the hyperfine splittings from 19F nuclei and the different conformations of fluorinated chain-end-type radicals RCF2CF2* in different systems, and also for elucidating the mechanism of Nafion fragmentation when exposed to oxygen radicals in fuel cell conditions.     

一种由全氟碘代烷合成全氟羧酸的新方法

本文报道全氟碘代烷在光氧化条件下生成相应酸羧的反应, 并对其机理进行了初步的探讨。以甲醇为溶剂, RFCF2I在Et3N存在下能顺利地进行光氧化反应, 反应完毕, 除去溶剂及Et3N即可分得全氟羧酸(RFCO2H), 反应操作简便, 收率较好, 无RFCF2H生成。     

Direct synthesis of fluorinated peroxides. V. The preparation of pentafluorosulfurperoxy esters by reactions of pentafluorosulfur hydroperoxide with acyl fluorides

The reaction of SF₅OOH with acyl fluorides in the presence of NaF has been investigated and found to yield new peroxy esters of the type RC(O)OOSF₅. An alternate method of synthesis using SF₅OOCl and acyl chlorides is discussed and the cesium fluoride catalyzed conversion of two of the esters to RCF(OF)OOSF₅ is described.     

INACTIVATION ACTION SPECTRA OF BACILLUS SUBTILIS SPORES IN EXTENDED ULTRAVIOLET WAVELENGTHS (50–300nm) OBTAINED WITH SYNCHROTRON RADIATION

Five types of Bacillus subtilis spores (UVR, UVS, UVP, RCE, and RCF) differing in repair and/or recombinational capabilities were exposed to monochromatic radiations at 13 wavelengths from 50 to 300 nm in vacuum. An improved biological irradiation system connected to a synchrotron radiation source was used to produce monochromatic UV radiation in this extended wavelength range with sufficient fluence to inactivate bacterial spores. From the survival curves obtained, the action spectra for the inactivation of the spores were depicted. Recombination-deficient RCE (recE) and RCF (recF) spores were more sensitive than the wild-type UVR spores in the entire range of wavelengths. This was considered to mean that DNA was the major target for the inactivation of the spores. Vacuum-UV radiations of 125-175 nm were effective in killing the spores, and distinct peaks of the sensitivity were seen with all types of the spores. Insensitivities at 190 and 100 nm were common to all five types of spores, indicating that these wavelengths were particularly impenetrant and absorbed by the outer layer materials. The vacuum-UV peaks centering at 150 nm were prominent in the spores defective in recombinational repair, while the far-UV peaks at around 235 and 270 nm were prominent in the UVS (uvrA ssp) and UVP (uvrA ssp polA) spores deficient in removal mechanisms of spore photoproducts. Thus, the profiles of the action spectra were explained by three factors; the penetration depth of each radiation in a spore, the efficiency of producing DNA damage that could cause inactivation, and the repair capacity of each type of spore.     

An efficient preparation of new sulfonyl fluorides and lithium sulfonates

An efficient preparation of several polyfluoroalkanesulfonyl fluorides is reported. This method, based on the synthesis of polyfluoroalkyl trimethyl silanes (precursors of polyfluoroalkylsulfinates) as intermediates, allows the successive transformations to be carried out in one pot. Moreover, these sulfonyl fluorides can be obtained from the corresponding sulfinates by electrophilic fluorination. This original approach avoids isolation and purification of some thermally or hydrolytically unstable intermediates. A series of new sulfonyl fluorides have been thus prepared from halogenodifluoromethylated precursors RCF2X (X = F, Br; R = ArC(O), ArS(O)n(CF2)m; n = 0, 1, 2; m = 1, 2) and have been transformed into the corresponding lithium sulfonates, which have potential applications as electrolytes for lithium batteries.     

Electrochemically activated reaction of nucleophilic substitution in polyfluorovinyl halides under the action of the cyclopentadienylirondicarbonyl anion [CpFe(CO)2]−

The reaction of polyfluorovinyl halides RCF=CFX (R =t-C₄F₉, X = F, CI, or Br; R = Ph, X = F, Cl) with the [CpFe(CO)₂]^– anion has been studied by cyclic voltammetry and preparative-scale electrolysis. The electrochemical activation of vinyl halides made it possible to obtain the products of nucleophilic substitution for all substrates investigated independently of their configuration and the nature of the halogen.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1523–1528, June, 1996.     

Automatic fitting to 'powder' EPR spectra of coupled paramagnetic species employing Feynman's theorem

A previous automatic fitting procedure of EPR spectra has been extended with the purpose to characterise coupled paramagnetic complexes in powders and frozen solutions. The theoretical EPR spectra were obtained by matrix diagonalization of a general spin Hamiltonian. A least-squares fitting procedure using analytical derivatives of the calculated spectrum with respect to the spectroscopic, fine structure, nuclear quadrupole, electron-electron, and hyperfine coupling tensors was used to refine those parameters. The powder spectra of matrix isolated *CF3 and RCF2CF2* radicals, previously measured at low temperature, were reanalysed with this method. A theoretically modeled complex consisting of a Cu2+ ion, featuring an axially symmetric g-tensor and 63Cu hyperfine structure anisotropy, and a free radical located at different orientations, with respect to the symmetry axis of the Cu2+ ion, was examined in order to investigate the possibility to recover the magnetic parameters of the separate units and the magnetic couplings between them.     

高效液相色谱-质谱法分离鉴定天然红心鸭蛋黄中的红色素

采用薄层色谱、高效液相色谱-质谱-质谱(HPLC-MS-MS)及高分辨电子轰击质谱(EI-MS)方法,分离鉴定了天然红心鸭蛋（简称红心蛋）蛋黄中红色素的分子组成和结构。以甲醇-水(体积比为99.5∶0.5)为流动相,用C18柱从红心蛋的红色素中分离出4个峰。光电二极管阵列检测器(PDA)扫描图显示,4个峰均为单峰,最大吸收波长分别为482,488,496,501 nm。HPLC-MS-MS分析结果表明,红心蛋中的红色素的各个峰具有相同的相对分子质量(Mr=562),其二级质谱具有紫杉紫素(rhodoxan     

Electrochemical investigation of the redox properties of some polyfluorinated alkenes. The influence of electrode materials on the shape of polarization curves

The electrochemical reduction of a number of polyfluorovinyl halides RCF=CFX (R =t-C₄F₉, X = F, Cl, Br; R = Ph, X = F, Cl) has been studied by the cyclic voltammetry technique using various different electrodes. An unusual tendency toward hampering of the reduction was observed on going from X = F to a heavier halogen. Calculations of the energies of the molecular orbitals for these compounds were carried out by the AM I method. A mechanism of the reduction of polyfluorovinyl halides was suggested on the basis of correlations between the values of the reduction potentialsE ^Red and the LUMO energies.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1436–1445, June, 1996.