Energy storage in symmetric and asymmetric supercapacitors based in carbon cloth/polyaniline–carbon black nanocomposites

In this work, the construction of electrochemical capacitors using polyaniline–carbon black nanocomposites as electrode material is described. Symmetric and asymmetric cells were assembled. The active material was supported on carbon cloth acting as current collector as well. The electrolyte was H₂SO₄ 0.5 M, and the selected potential range was 1 V. The electrochemical behavior of the arrayed supercapacitors was studied by cyclic voltammetry and galvanostatic charge/discharge runs. At a constant current density of 0.3 A/g, a specific capacitance value of 1039 F/g was obtained for a symmetric assembly using both electrodes prepared with polyaniline and carbon black nanocomposites. When the set is asymmetric, being the positive electrode made of polyaniline and carbon black nanocomposites, the specific capacitance value is 1534 F/g. For the latter array, the specific power and energy density values are 300 W/kg and 426 Wh/kg at 0.3 A/g, and 13 700 W/kg and 28 Wh/kg at 13.7 A/g. These results suggest a good capacity of fast energy transfer. Moreover, this asymmetric supercapacitor demonstrated a high stability over 1000 cycles being the loss of only 5%. Copyright © 2015 John Wiley & Sons, Ltd.     

The rescheduling arc routing problem

In this paper, the rescheduling arc routing problem is introduced. This is a dynamic routing and scheduling problem that considers adjustments to an initial routing itinerary when one or more vehicle failures occur during the execution stage and the original plan must be modified. We minimize the operational and schedule disruption costs. Formulations based on mixed‐integer programming are presented to compare different policies in the rerouting phase. A solution strategy is developed when both costs are evaluated and it is necessary to find a solution quickly. Computational tests on a large set of instances compare the different decision‐maker policies.     

Behavior of poly(ethylene‐co‐olefin) polymers as elastomeric materials

The properties of two new ethylene‐α‐olefin copolymers, namely, ethylene–1‐hexene copolymer (EHC) and ethylene–1‐octadecene copolymers (EOC), synthesized via metallocene catalysts were evaluated. The copolymerization was carried out in an autoclave reactor with Et(Indenyl)₂ZrCl₂/methylaluminoxane as a catalyst system. These single‐site catalysts (metallocene type) allow one to obtain very homogeneous copolymers with excellent control of the molecular weight distribution and proportion of comonomer incorporation. So, copolymers with 18 mol % comonomer in the case of EHC and 12 mol % for EOC were shaped, and activities around 100,000 kg of polymer mol^?1 of Zr bar^?1 h^?1 were reached. The properties of these copolymers were compared with other commercial elastomers, such as ethylene–propylene copolymers synthesized by Ziegler–Natta catalysts and an ethylene–octene copolymer obtained via metallocene catalysts. The results show that these new copolymers, in particular, EOC, had excellent elastomeric properties. Furthermore, they had a relatively low viscosity, which implied a good response during processing. Moreover, the effectiveness of these copolymers as impact modifiers for polyolefins was also studied. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3008–3015, 2004     

Blends containing amphiphilic polymers IV. Poly(N‐1‐alkyl itaconamic acids) with poly(2‐vinylpyridine) and poly(4‐vinylphenol)

The phase behavior of blends containing Poly(N‐1‐alkyl itaconamic acids) (PNAIA) with Poly(2‐vinylpyrindine) (P2VPy) and Poly(4‐vinylphenol) (P4VPh) were analyzed by Diferential Scanning Calorimetry (DSC) and Fourier Transform Infrared Spectroscopy (FTIR). Miscibility over the whole range of compositions is observed in both systems. All the blends show thermograms exhibiting distinct single glass transition temperatures (T_g), which are intermediate to those of the pure components. The Calorimetric Analysis using Gordon Taylor, Couchman, and Kwei treatments allows conclusion that interactions between the components is favorable to the miscibility. FTIR analysis of the blends suggests that the driving force for miscibility is hydrogen bonding formation. The variation of the absorptions of the carbonyl groups of PNAIA and the hydroxyl groups of P4VPh allows one to attribute the miscibility to weak acid base like interactions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1245–1250, 2002; DOI 10.1002/app.10453     

Rolling contact fatigue endurance of powder-extruded bearing steel

The mechanical and toughness properties and rolling contact fatigue endurance of powder-extruded bearing steel made from nitrogen atomized remelted turning powder in as-extruded and as-heat treated state are presented. The mechanical and toughness properties are comparable with those of wrought bearing steel. Rolling contact fatigue endurance was tested by the AXMAT method in as-extruded and as-spheroidizing annealed states depending on the austenitizing temperature, which ranged from 790 °C to 870 °C. Powder-extruded bearing steel in both states showed slightly higher hardness (63 HRC), higher contact fatigue resistance (L₁₀ = 80.7 and 55.2 million load cycles, respectively) in comparison with wrought steel (L₁₀ = 31.8 million load cycles). The results demonstrate the advantageous properties of powder-extruded bearing steel for high dynamic loading.     

A comprehensive investigation of dye–chitosan blended films for green chemistry applications

In this paper, the ability of chitosan film to remove dyestuff from wastewater was evaluated for environmental applications, using three commercial direct azo dyes. Two chitosan films were adopted: the standard one prepared following a well‐known procedure to form it, and a novel one, with a weakly acidic character. Moreover, to improve the adsorption process, the hydrophobic character of the films was investigated. The pH of the dye solutions was also changed, showing an excellent ability in dye removal at pH 12. The films were characterized by means of spectroscopic and morphologic methods to better understand the nature of interactions between dyes and chitosan chains. Swelling ratio measurements were also performed. All analyses suggest that all dyes showed a strong affinity to chitosan polymer chains, with the presence of extended hydrogen bonds and Van der Waals forces perturbing the chitosan network. Interestingly, very good results were obtained in recycling experiments related to the dyeing capacities of chitosan blended films in the presence of textiles. An ecofriendly application is thus presented in this paper. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45945.     

Antibacterial modification of nylon-6 nanofibers: structure,properties and antibacterial activity.

Antibacterial nylon 6 (PA6) nanofibers have been prepared in one-step procedure using Nanospider technology. Chlorhexidine (CHX), 1-dodecyltrimethylamonium bromide (DTAB) and benzyltrimethylamonium bromide (BTAB) have been used as antibacterial agents. Samples were characterized by a series of analytical and testing methods to investigate the surface chemistry, zeta potential, structure, morphology, phase composition, mechanical properties and antibacterial activity. Experimental characterization has been combined with molecular modeling to analyze the interaction of nanofibers with modifying molecules for better understanding the effect of nanofibers modification on their properties. Antibacterial modification of PA6 led to significant changes of zeta potential (from -31 mV for PA 6 up to -49 mV for PA6/BTAB), changes in phase composition (decrease of alpha phase content and increase of gamma phase content for PA6/BTAB and PA6/CHX) and to significant increase of fiber diameter for PA6/BTAB. Antibacterial modification resulted in the straightening of nanofibers and to higher permeability of nanofiber textile for all investigated samples. Tensile tests showed the the increase of Young modulus for all the investigated samples. All the modified samples: PA6/DTAB, PA6/BTAB and PA6/CHX exhibit good antibacterial activity.     

Friction Sensitivity of Nitramines. Part Ⅱ: Comparison with Thermal Reactivity（英）

The friction sensitivity (FS) of five linear and eight cyclic nitramines has been determined.Arrhenius parameters of non-autocatalyzed thermal decomposition of these nitramines were used for comparison...     

Friction Sensitivity of Nitramines. Part Ⅲ: Comparison with Detonation Performance（英）

The friction sensitivities (FS) of five linear and eight cyclic nitramines have been determined.These FS values were compared with the respective detonation velocities,D,and with the dimensionless ratio created by relating the heat of explosion,Qreal,to the activation energy,Ea,of non-autocatalyzed thermal decomposition of the explosives concerned.For the nitramaines studied,these comparisons show a general trend of FS decreasing with increasing energy content.