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  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 31 (1985), S. 973-981 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Prior studies have demonstrated that char gasification rates vary with conversion, showing a maximum at an intermediate level. In this work experimentally determined char-air reaction rates and corresponding pore structures are compared to assess the applicability of a previously proposed random pore model and to extract pertinent chemical and physical parameters. Results on six different chars are presented and analyzed to obtain structure parameters, intrinsic kinetics, and activation energies. Agreement between two independent evaluations of the structure parameters demonstrates the degree of applicability of the random pore model and supports the view that rate variations with conversion are controlled by pore structural changes, even though overall rates also include contributions of intrinsic reactivity.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 31 (1985), S. 1725-1727 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 31 (1985), S. 957-964 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Six char samples generated from two coals were impregnated by solutions with different concentrations of Na2CO3 and /or K2CO3. The catalyst solution penetration was studied, the catalyst uptake was measured, and the effects of impregnation on the char pore structure were determined experimentally. The results indicate that the impregnated catalysts reside only on particle exteriors without significant penetration. The overall rate of reaction is therfore the combination of catalytic reaction on particle exteriors and noncatalytic reaction on the pore surfaces inside the particle. A kinetic model is presented that takes these findings into account.
    Additional Material: 8 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 31 (1985), S. 965-972 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Oxidation rates of Na2CO3- and K2CO3-impregnated char samples were measured in an isothermal kinetic control regime. The results were analyzed by a previously developed model to extract the intrinsic catalytic reactivities, freed from superimposed noncatalytic and structural effects. Although the overall catalyzed rates are only several times greater than their uncatalyzed counterparts, the intrinsic catalytic rates were found to be four orders of magnitude greater. The results further indicate that the function of the catalyst is to increase the number of active sites without affecting the activation energy. The overall reaction kinetics are demonstrated to contain the combined contributions of both catalytic and noncatalytic reactions, and in this context the effects of multiple catalysts as well as of the pore structure development during reaction can be understood and interpreted.
    Additional Material: 11 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 85-91 
    ISSN: 0887-6266
    Keywords: ferroelectricity ; piezoelectricity ; bilaminate ; nylon 11 ; PVF2 ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The ferroelectric and piezoelectric properties of a new class of polymer ferroelectric and piezoelectric materials, nylon 11/polyvinylidene fluoride (PVF2) bilaminate films, prepared by a co-melt-pressing method, is presented. The bilaminate films exhibit typical ferroelectric D-E hysteresis behavior with a remanent polarization, Pr, of about 75 mC/m2, which is higher than the value of 52 mC/m2 observed for PVF2 or nylon 11 films measured under the same conditions. The coercive field, Ec, of the bilaminate films is ∼ 78 MV/m, which is higher than that of either PVF2 or nylon 11 films. Measurements of the temperature dependence of the piezoelectric strain coefficient, d31, and the piezoelectric stress coefficient, e31, were also carried out. The bilaminate films exhibit a piezoelectric strain coefficient, d31, of 41 pC/N at room temperature, which is significantly higher than the PVF2 films (25 pC/N) and the nylon 11 films (3.1 pC/N). When the temperature is increased to 110°C, d31 of the bilaminate films reaches a maximum value of 63 pC/N, more than five times that of PVF2 (11 pC/N) and more than four times that of nylon 11 (14 pC/N) at the same temperature. The piezoelectric stress coefficient, e31, of the bilaminate films shows a value of 109 mC/m2 at room temperature, almost twice that of the PVF2 films (59 mC/m2) and about 18 times that of the nylon 11 films (6.2 mC/m2). Measurement of the temperature dependence of the hydrostatic piezoelectric coefficient, dh, of the bilaminate films also shows an enhancement with respect to the individual components, PVF2 and nylon 11. ©1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 26 (1994), S. 159-169 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rate constants are calculated for CH3 (+ Ar) ⇄ CH2 + H (+ Ar) at the limiting low-pressure, the limiting high-pressure, as well as the intermediate fall-off ranges. The results show that published experimental rate constants for methyl dissociation correspond to the fall-off region close to the low-pressure limit. At the low-pressure limit the activation energy is less than the bond dissociation energy, in agreement with experimental results. Forward and backward rate coefficients at the high-pressure limit are compared with other theoretical calculations. More theoretical and experimental work is necessary to understand the reverse reaction and its competing reactions, as well as the decomposition channel leading to CH + H2. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 7
    Publication Date: 2013-08-31
    Description: Efficient actuators that are lightweight, high performance and compact are needed to support telerobotic requirements for future NASA missions. In this work, we present a new class of electromechanically active polymers that can potentially be used as actuators to meet many NASA needs. The materials are graft elastomers that offer high strain under an applied electric field. Due to its higher mechanical modulus, this elastomer also has a higher strain energy density as compared to previously reported electrostrictive polyurethane elastomers. The dielectric, mechanical and electromechanical properties of this new electrostrictive elastomer have been studied as a function of temperature and frequency. Combined with structural analysis using x-ray diffraction and differential scanning calorimetry on the new elastomer, structure-property interrelationship and mechanisms of the electric field induced strain in the graft elastomer have also been investigated. This electroactive polymer (EAP) has demonstrated high actuation strain and high mechanical energy density. The combination of these properties with its tailorable molecular composition and excellent processability makes it attractive for a variety of actuation tasks. The experimental results and applications will be presented.
    Keywords: Nonmetallic Materials
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  • 8
    Publication Date: 2018-06-02
    Description: A piezoelectric polymeric blend system has been developed. The system contains two components: ferroelectric poly(vinylidene-trifluoroethylene) and graft elastomer. The remanent polarization, Pr, and the piezoelectric strain coefficient, d31, of the blends have been studied as a function of relative composition of the two components, temperature and frequency. Both blended copolymer and graft unit in the elastomer contribute to the total crystallinity of the blend-system, and hence to the remanent polarization and piezoelectricity. The piezoelectric strain coefficient, d31, of the blend systems shows dependence on both the remanent polarization and the mechanical stiffness, which in turn are determined by the fraction of the two components in the blends. This mechanism makes it possible for the piezoelectric strain response of the blend to be tailored by adjusting the relative composition. Although Pr of the copolymer is higher than that of the blends, the blend films containing 75 wt.% copolymer exhibit a higher d31 at room temperature, possibly due to their lower modulus. The blend films containing 50 wt.% copolymer exhibit a constant value of d31, from room temperature to 70 C.
    Keywords: Nonmetallic Materials
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