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81.
Arun K. Roy Samuel Pattnaik Rajani K. Samal Padma L. Nayak 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(8):1241-1249
The polymerization of acrylonitrile initiated by the redox system K2S2O8-citric acid catalyzed by Ag+ ion has been studied over the temperature range 35–50°C. The rate of polymerization is proportional to the square root of peroxydisulfate concentration. The initial rate increases with increasing citric acid concentration, but at relatively higher concentration of citric acid the rate decreases. The rate of polymerization also increases with increasing monomer concentration and temperature. The overall activation energy calculated from the Arrhenius plot was found to be 4.6 kcal/mole. On the basis of the observation, a suitable kinetic scheme has been proposed for the reaction. 相似文献
82.
The kinetics of the aqueous polymerization of acrylonitrile initiated by the chromic acid-1-propanol redox system was investigated under a nitrogen atmosphere. The rates of polymerization and the disappearance of Cr(VI) were measured. Chromic acid alone did not initiate the polymerization under deaerated and undeaerated conditions. Water-miscible organic solvents and neutral salts depress both the rate and the conversion. On the basis of the experimental observations of the dependence of the rate of polymerization Rp and the rate of disappearance of Cr(VI)-Rm on various variables, a suitable kinetic scheme was proposed and various rate and energy parameters evaluated. 相似文献
83.
The effects of time-periodic forcing in a few-mode model for zero-Prandtl-number convection with rigid body rotation is investigated.
The time-periodic modulation of the rotation rate about the vertical axis and gravity modulation are considered separately.
In the presence of periodic variation of the rotation rate, the model shows modulated waves with a band of frequencies. The
increase in the external forcing amplitude widens the frequency band of the modulated waves, which ultimately leads to temporally
chaotic waves. The gravity modulation, on the other hand, with small frequencies, destroys the quasiperiodic waves at the
onset and leads to chaos through intermittency. The spectral power density shows more power to a band of frequencies in the
case of periodic modulation of the rotation rate. In the case of externally imposed vertical vibration, the spectral density
has more power at lower frequencies. The two types of forcing show different routes to chaos.
相似文献
84.
One of the failure mechanisms in ductile materials is growth and coalescence of pre-existing voids. In view of this, we attempt to obtain atomistic insights into the prevailing mechanisms of void growth in a representative ductile material, namely Copper, using molecular dynamics simulations. In addition to shedding light on the observed length scale effects and dislocation mechanisms, we also elucidate how atomistic simulations can inform continuum-based models of failure and provide fodder for bridging different length scales. By performing a series of over 150 molecular dynamics simulations, we also try to decode the interplay between mechanical properties and void growth, and investigate the role of heterogeneity in void distribution (in terms of void size and placement) in affecting the strength of the material. Coupled with a comprehensive global sensitivity analysis technique, we explore configuration–property relationships in a subset of vast parameter space and highlight the importance of random nature of void distribution (along with some critical statistical parameters) in any successful theory of fracture. 相似文献
85.
Reduced Graphene Oxide–Ag3PO4 Heterostructure: A Direct Z‐Scheme Photocatalyst for Augmented Photoreactivity and Stability 下载免费PDF全文
A visible light driven, direct Z‐scheme reduced graphene oxide–Ag3PO4 (RGO–Ag3PO4) heterostructure was synthesized by means of a simple one‐pot photoreduction route by varying the amount of RGO under visible light illumination. The reduction of graphene oxide (GO) and growth of Ag3PO4 took place simultaneously. The effect of the amount of RGO on the textural properties and photocatalytic activity of the heterostructure was investigated under visible light illumination. Furthermore, total organic carbon (TOC) analysis confirmed 97.1 % mineralization of organic dyes over RGO–Ag3PO4 in just five minutes under visible‐light illumination. The use of different quenchers in the photomineralization suggested the presence of hydroxyl radicals ( . OH), superoxide radicals ( . O2?), and holes (h+), which play a significant role in the mineralization of organic dyes. In addition to that, clean hydrogen fuel generation was also observed with excellent reusability. The 4 RGO–Ag3PO4 heterostructure has a high H2 evolution rate of 3690 μmol h?1 g?1, which is 6.15 times higher than that of RGO. 相似文献
86.
Padma L. Nayak Rajani K. Samal 《Journal of polymer science. Part A, Polymer chemistry》1977,15(11):2603-2611
The kinetics of polymerization of acrylonitrile initiated by Cr(VI)–thiourea and Cr(VI)–ethylene thiourea have been studied at 35, 40, and 45°C in nitrogen. The rates of polymerization and of disappearance of Cr(VI) were measured. Chromic acid alone did not initiate the polymerization under deaerated and undeaerated conditions. On the basis of the experimental observation of the dependence of the rate of polymerization Rp, the rate of Cr(VI) disappearance, –Rm, etc., on various variables, a suitable kinetic scheme was proposed and various rate and energy parameters were evaluated. 相似文献
87.
88.
Sneha Samal Martin Stuchlík Iva Petrikova 《Journal of Thermal Analysis and Calorimetry》2018,131(2):1035-1040
Natural fabric such as flax and jute was considered in biaxial plain reinforcement in matrix of acrylic resin, and the composite is prepared in hand layup techniques. Fabric mass fraction of 7% was used in the matrix of composite. The samples were treated at r.t and 60 °C for the final fabrication. Scanning electron microscopy was carried out to support the microstructure effect of composite in terms of thermal change. Thermogravimetric and differential thermogravimetric analysis and residual compositional analysis with FTIR were carried out for the composite and matrix samples. The mechanical and viscoelastic properties, as well as the influence of frequency and fibers types, were evaluated, in flexural mode, by means of dynamical mechanical analysis. Glass transition (T g) and initial decomposition (T i) temperatures increase with incorporation of fibers into the matrix. While T i of flax and jute composite was similar, T g in case of flax improves than jute fabric-reinforced composite. This type of composites can be used in the automotive sector, in exterior and exterior components. 相似文献
89.
L.N. Patnaik N.C. Samal M. Senapati R. Mishra M.K. Rout 《European Polymer Journal》1983,19(7):605-606
The effects of substituents on the reaction of benzaldehydes with polyacrylonitrile radicals have been studied in terms of the multiparameter equations based on Swain and Lupton's Field and Resonance (F and R) components with the unique positional weighting factors f and r developed by Williams and Norrington. From the nature of the reaction constants, a polar transition state has been postulated. 相似文献
90.
The polymerization of acrylonitrile initiated by the vanadium(V)-thioglycollic acid redox system has been investigated in aqueous sulphuric acid under nitrogen over the range 30–45°. The polymerization is second order in monomer and first order in thioglycollic acid (TGA). The rate of vanadium(V) disappearance is proportional to (TGA) and [V(V)]. The effects of FeCl3, CuSO4 and acetic acid on the polymerization have been investigated. The proposed reaction scheme involves initiation by an organic free radical, produced by the interaction of V(V) with TGA and termination by V(V). Various rate parameters have been evaluated. 相似文献