Single step modification of micrometer-sized polystyrene particles by electromagnetic polyaniline and sorption of chromium(VI) metal ions from water

This article describes a single-step reproducible approach for the surface modification of micrometer-sized polystyrene (PS) core particles to prepare electromagnetic PS/polyaniline–Fe₃O₄ (PS/PANi–Fe₃O₄) composite particles. The electromagnetic PANi–Fe₃O₄ shell was formed by simultaneous seeded chemical oxidative polymerization of aniline and precipitation of Fe₃O₄ nanoparticles. The weight ratio of PS to aniline was optimized to produce core–shell structure. PS/PANi–Fe₃O₄ composite particles were used as adsorbent for the removal of Cr(VI) via anion-exchange mechanism. The composite particles possessed enough magnetic property for magnetic separation. The adsorption was highly pH dependent. Adsorption efficiency reached 100% at pH 2 in 120 min when 0.05 g of composite particles was mixed with 30 mL 5 mg L⁻¹ Cr(VI) solution. The adsorption isotherm fitted best with Freundlich model and maximum adsorption capacity approached 20.289 mg g⁻¹ at 323 K. The prepared composite was found to be an useful adsorbent for the removal of soluble Cr(VI) ions. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47524.     

Production scale plasma modification of polypropylene baselayer for improved water management properties

Through its hydrophobic properties, polypropylene (PP) offers unique potential as a functional fiber for a wide range of applications, for example, in nonwovens for hygiene applications or as a baselayer in sports textiles. Current work is focused on the modification of PP presently used in baselayers for sports textiles to increase the hydrophilicity by use of a production scale plant for low pressure plasma treatment. Attention was directed toward an increase in hydrophilicity and time stability of the achieved modification during storage. Changes in the fabric were characterized by sorption of the cationic dye (methylene blue), water retention value, water transport properties, Fourier transform infrared spectroscopy and color measurement. The obtained results indicate an improved wettability and wicking. The extent of modification decreased with storage time and parallel yellowing of treated samples was observed. This indicates chemical rearrangement of the products initially formed on the fiber surface. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41294.     

火焰层析成像的最新进展(英文)

To reduce greenhouse gas emissions from fossil fuel fired power plants,a range of new combustion technologies are being developed or refined,including oxy-fuel combustion,co-firing biomass with coal and fluidized bed combustion.Flame characteristics under such combustion conditions are expected to be different from those in normal air fired combustion processes.Quantified flame characteristics such as temperature distribution,oscillation frequency,and ignition volume play an important part in the optimized design and operation of the environmentally friendly power generation systems.However,it is challenging to obtain such flame characteristics particularly through a three-dimensional and non-intrusive means.Various tomography methods have been proposed to visualize and characterize flames,including passive optical tomography,laser based tomography,and electrical tomography.This paper identifies the challenges in flame tomography and reviews existing techniques for the quantitative characterization of flames.Future trends in flame tomography for industrial applications are discussed.     

High‐performance heat‐sink composites incorporating micron‐sized inorganic fillers and Sn/In metal particles

A novel thermal‐barrier composite system was developed by incorporating fusible metal particles in the epoxy matrix system. Using the latent heat of melting, the Sn/In metal particles having melting temperature at 125°C were imbedded in the polymer matrix to suppress the thermal shock and transient temperature variation. The high‐density metal particles were successfully dispersed in the polymer matrix without sinking by incorporating inorganic particles of aluminum nitride (AlN) and boron nitride (BN), which desirably facilitated the heat dissipation to give a high thermal conductivity at around 10 W/m‐K. Under the repeated melting and cooling cycles, the spherical shape of metal particles and the latent heat of melting were retained demonstrating the reversible thermal‐barrier capability of the developed composite system. Under the constant‐heating conditions, it was validated that the temperature rise was delayed by the endothermic melting of Sn/In particles. The developed composite system could find various applications since it could minimize damages caused by the repeated thermal fatigue and/or accidental thermal shock. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Catalytic activity of a reusable polymer‐anchored nickel(II)–phenanthroline complex on the oxidation of various organic substrates

A polymer‐anchored nickel(II)–phenanthroline complex [polyNi(II)–phen] was synthesized and used effectively as a reusable catalyst in various oxidation reactions in the presence of tert‐butylhydroperoxide as an oxidant in acetonitrile medium. The catalyst was characterized with elemental analysis, atomic absorption spectrometry (AAS), thermogravimetric analysis, scanning electron microscopy, and spectrometric methods such as diffuse reflectance spectroscopy, ultraviolet–visible spectroscopy, and Fourier transform infrared spectroscopy. The study of the effects of the time, temperature, oxidant, catalyst concentration, molar ratio of substrate to oxidant, and solvent in the oxidation of styrene individually gave the optimized reaction conditions. Under optimized conditions, the catalyst exhibited good conversions for the oxidation reactions of various olefins, alkanes, aromatic alcohols, and thioethers. The catalyst was easily recovered by simple filtration and reused for more than five times with consistent catalytic activity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Revisiting electrolyte thermodynamic models: Insights from molecular simulations

Pitzer and electrolyte nonrandom two‐liquid (eNRTL) models are the two most widely used electrolyte thermodynamic models. For aqueous sodium chloride (NaCl) solution, both models correlate the experimental mean ionic activity coefficient (γ_±) data satisfactorily up to salt saturation concentration, that is, ionic strength around 6 m. However, beyond 6 m, the model extrapolations deviate significantly and diverge from each other. We examine this divergence by calculating the mean ionic activity coefficient over a wide range of concentration based on molecular simulations and Kirkwood–Buff theory. The asymptotic behavior of the activity coefficient predicted by the eNRTL model is consistent with the molecular simulation results and supersaturation experimental data. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3728–3734, 2018     

Effect of extended defects in planar and pixelated CdZnTe detectors

We evaluated a spectroscopy-grade 15×15×7 mm³ CdZnTe (CZT) crystal with a high μτ-product, >10⁻² cm²/V, but impaired by microscopic extended defects, such as walls of dislocations, low-angle and sub-grain boundaries, and Te inclusions. First, we evaluated a planar detector fabricated from this crystal using a Micro-scale X-ray Detector Mapping (MXDM) technique. Then, we fabricated from the same crystal a pixel detector to study local non-uniformities of the electric field. The measured X-ray response maps confirmed the presence of non-uniformities in the charge transport, and they showed that the global- and local-distortions of the internal E-field correlated to the extended defects and space-charge buildup on the side surfaces.     

Modeling of high-k dielectric nanocomposites

In this paper, based on recent research on BaTiO₃ (BT) nanoparticles, BT/P(VDF-HFP) nanocomposites, frequency-dependent dielectric properties of such a material system with high energy density have been investigated as functions of the volume fraction of the nanoparticles at room temperature by several theoretical models. For single domain and single crystals of BT, a Debye type of dissipation and soft mode theory have been adopted to obtain a more precise frequency-dependent dielectric spectrum of BT. For nanodielectric composites, among the others, Wiener Rule, Lichtenecker model, Maxwell–Wagner model, Yamada, and modified Kerner model were applied to evaluate the frequency-dependent dielectric spectrum of nanocomposites. A simple rule of mixture for the dielectric loss tangent was obtained using Lichtenecker logarithmic rule. The results from theoretical calculations are compared with the experimental data. For the dielectric constant, Lichtenecker model, Maxwell–Wagner model, and Yamada model show reasonable agreements with the experimental data up to 50 % volume fraction of the nanoparticles. At the higher volume fraction of the nanoparticles, the experimental data show a decreasing trend of the dielectric constant of the composites due to an increase in porosity of the system. In this case, a three-phase model (nanoparticles/pores/matrix) was developed to predict dielectric properties of the system at higher volume fraction of the nanoparticles (up to 80 %). The results showed reasonable agreements for a wide range of frequency. This theoretical study provides an essential information on dielectric properties of polymer-based BT nanocomposites with a wide frequency range instead of the trial-and-error strategy of experiments and can be used for designing high energy density dielectric materials in the future.     

The Effects of Mn Substitution on Magnetization Reversal Properties in Gd0.7Ca0.3MnO3

Low temperature magnetization in polycrystalline Gd_0.7Ca_0.3Mn_1?x M _x O₃ (M=Cr, Ga, Ru; x=0, 0.2) has been investigated. The samples were prepared via the conventional solid state reaction method. For all the samples, the paramagnetic to ferrimagnetic (PM-FiM) transition temperature (say T _max) can be well defined from the temperature dependent ac susceptibility data. The negative magnetization suppresses due to 20 % Cr or Ga doping at the Mn site. On the other hand, below the compensation temperature (T _comp), the nature of the Ru doping sample is almost similar to that of undoped Gd_0.7Ca_0.3MnO₃. The nonmagnetic Ga doping drastically reduces magnetization and T _max shifts to a lower temperature. However, Ru and Cr doping increase the value of T _max. The network of canted Mn³⁺/Mn⁴⁺ moments changes with the substitution of Cr, Ga, and Ru at the Mn site giving rise to the variation of the internal magnetic moment. Thus, the antiparallel coupling of the Gd moments with Mn/M changes and affects the low temperature magnetization reversal properties.     

Low temperature crystallization of amorphous silicon carbide thin films for p–n junction devices fabrication

Metal induced crystallization technique was used to crystallize hydrogenated amorphous silicon carbide (a-SiC:H) thin films at low temperatures. Two types of substrates, silicon and silicon carbide were considered and the substrate effects on the final crystallized film were studied. About 200 nm a-SiC:H films were deposited and crystallized successfully on n-type Si and n-type 6H SiC substrates at a temperature of 600 °C. Fourier Transform Infrared (FTIR) spectroscopy and transmission electron microscopy (TEM) analysis confirmed the crystallization of a-SiC:H film. Current–voltage (I–V) and capacitance–voltage (C–V) measurement confirms the formation of p–n junction with rectification over five orders of magnitude from ?2 V to 2 V.