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1.
Azat D. Rakhimkulov S. M. Lomakin I. L. Dubnikova A. N. Shchegolikhin E. Ya Davidov R. Kozlowski 《Journal of Materials Science》2010,45(3):633-640
Studies of thermo-oxidative and fire-resistant properties of the polypropylene/multi-walled carbon nanotube composites (PP/MWCNT)
prepared by melt intercalation are discussed. The effective kinetic parameters of the PP/MWCNT thermo-oxidative decomposition
were computed according to the model-based kinetic analysis. The thermo-oxidative decomposition behavior of PP/MWCNT and stabilizing
effect caused by addition of MWCNT has been investigated by means of TGA and EPR spectroscopy. Comparative analysis of the
flammability characteristics for PP-clay/MWCNT nanocomposites was provided in order to emphasize the specific behavior of
the nanocomposites. 相似文献
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3.
Jimmie C. Oxley James L. Smith Matthew Porter Lindsay McLennan Kevin Colizza Yehuda Zeiri Ronnie Kosloff Faina Dubnikova 《Propellants, Explosives, Pyrotechnics》2016,41(2):334-350
The synthesis and decomposition of hexamethylene triperoxide diamine (HMTD) were studied. Mechanisms were proposed based on isotopic labeling and mass spectral interpretation of both condensed phase products and head‐space products. Formation of HMTD from hexamine appeared to proceed from dissociated hexamine as evident from scrambling of the 15N label when synthesis was carried out with equal molar labeled/unlabeled hexamine. Decomposition of HMTD was considered with additives and in the presence and absence of moisture. In addition to mass spectral interpretation, density functional theory (DFT) was used to calculate energy differences of transition states and the entropies of intermediates along different possible decomposition pathways. HMTD is destabilized by water and citric acid making purification following initial synthesis essential in order to avoid unanticipated violent reaction. 相似文献
4.
Yttrium aluminium garnet (YAG) powders substituted by neodymium Y3−xNdxAl5O12 (x = 0.1, 0.25, 0.35, 0.5, 0.6, 0.7, 0.8, 1.5, 2.0, 2.5, and 3.0) were prepared by a simple aqueous sol–gel method using aluminium nitrate nonahydrate, yttrium oxide, neodymium oxide as the starting materials and ethane-1,2-diol as complexing agent. The powders annealed at 1000 °C in air were characterized by X-ray diffraction (XRD) analysis, infrared (IR) spectroscopy and scanning electron microscopy (SEM). It was demonstrated, however, that the total substitution of yttrium by neodymium does not proceed in the YAG. Pure cubic garnet phase was formed only at low concentration of neodymium (x = 0.1, 0.25, 0.35, 0.5, 0.6, 0.7, 0.8 and 1.5). With further substitution, when the amount of neodymium was x = 2.0, 2.5 and 3.0 the main part of garnet phase transformed in to the perovskite neodymium aluminate (NdAlO3) phase. 相似文献
5.
Oxley J Smith J Brady J Dubnikova F Kosloff R Zeiri L Zeiri Y 《Applied spectroscopy》2008,62(8):906-915
A comparative study of the vibrational spectroscopy of peroxide-based explosives is presented. Triacetone triperoxide (TATP) and hexamethyl-enetriperoxide-diamine (HMTD), now commonly used by terrorists, are examined as well as other peroxide-ring structures: DADP (diacetone diperoxide); TPTP [3,3,6,6,9,9-Hexaethyl-1,2,4,5,7,8-hexaoxo-nonane (tripentanone triperoxide)]; DCypDp {6,7,13,14-Tetraoxadispiro [4.2.4.2]tetradecane (dicyclopentanone diperoxide)}; TCypDp {6,7,15,16,22,23-Hexaoxatrispiro[4.2.4.2.4.2] henicosane (tricyclopentanone triperoxide)}; DCyhDp {7,8,15,16-tetraoxadispiro [5.2.5.2] hexadecane (dicyclohexanone diperoxide)}; and TCyhTp {7,8,14,15,21,22-hexaoxatrispiro [5.2.5.2.5.2] tetracosane (tricyclohexanone triperoxide)}. Both Raman and infrared (IR) spectra were measured and compared to theoretical calculations. The calculated spectra were obtained by calculation of the harmonic frequencies of the studied compounds, at the density functional theory (DFT) B3LYP/cc-pVDZ level of theory, and by the use of scaling factors. It is found that the vibrational features related to the peroxide bonds are strongly mixed. As a result, the spectrum is congested and highly sensitive to minor changes in the molecule. 相似文献
6.
I. L. Dubnikova S. M. Berezina Yu. M. Korolev G.‐M. Kim S. M. Lomakin 《应用聚合物科学杂志》2007,105(6):3836-3850
Nanocomposites polypropylene (PP) with 3 and 7 wt % of clay were prepared by melt mixing. Four types of maleic anhydride grafted PP (MAPP) in broad range of MA groups content (0.3–4 wt %) and molecular weights (MW) were used as polar compatibilizers. The effect of the MAPP kind on both the clay dispersion and miscibility with PP was studied. The mixed intercalated/exfoliated morphologies of nanocomposites in the presence of all studied compatibilizers were revealed by XRD and TEM. The oligomer compatibilizer with 4 wt % of MA groups increases the intercalation ability of polymer into clay galleries but this one has limited miscibility with PP and worsens crystalline structure of polymer matrix. The MAPPs with 0.3–1.3% of MA are characterized by the lower intercalation ability but well cocrystallize with PP. Maximum reinforcing effect is attained using high MW MAPP with 0.6% MA and for nanocomposite with 7 wt % (3.8 vol %) of clay it averages almost 1.7 times relative to neat PP and 1.3 times relative to noncompatibilized composite. Dynamic storage moduli of nanocomposites compatibilized by MAPPs with 0.3–1.3% of MA containing 7 wt % of clay increase up to 1.4–1.5 around 30–75°C and over the whole temperature range remain higher compared with both neat PP and uncompatibilized composite. On the contrary, the oligomer MAPP with 4 wt % of MA groups decreases the thermal–mechanical stability of nanocomposite at high temperature compared with both PP and uncompatibilized composites. The study of nanocomposites flammability showed that creating complex composites containing both layered silicate and relatively small amount of magnesium hydroxide can be a successful approach to reduce the combustibility of PP‐based nanocomposites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
7.
Anatoly Goifman Jenny Gun Faina Gelman Irina Ekeltchik Eckhard Worch Ovadia Lev 《Israel journal of chemistry》2006,46(1):17-26
The catalytic performance of pyrolyzed carbon-supported cobalt-nitrogen donor (CoN4) catalysts for the oxidation of thiol compounds by dioxygen in aqueous solution was studied. This paper continues our previous line of research, which was inspired by the electrocatalytic reduction of oxygen on pyrolyzed carbon-supported cobalt-porphyrins and related tetra-coordinated nitrogen donor-transition metal complexes (MeN4, where Me stands for a transition metal atom). Both pyrolyzed carbon-supported Co-imidazole and Co-porphyrin exhibited fast catalytic oxidation of the different thiols. The rate of oxidation of different thiols on the pyrolyzed CoN4 catalysts was compared to the homogeneous rate of oxidation using 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin Co(II) tetrasodium salt as catalyst. Based on the cobalt content, the heterogeneous catalysts always outperformed the homogeneous one, and at times even exhibited 4,100-fold better catalysis. The dependence of the catalytic rate of oxidation on the preparation temperature was investigated, showing an optimal catalysis at ˜650 °C for the cobalt-imidazole catalyst. The decrease in catalytic performance after heat treatment at elevated temperature was attributed to the formation of cobalt metal acting as a generator of carbon nanotubes. 相似文献
8.
Ring expansion and isomerization in 1- and 2-methylene indene radicals and isomerizations among the three isomers of methyl indene were studied by the Becke three-parameter hybrid method with Lee-Yang-Parr correlation functional approximation (B3LYP). Structure, energy, and frequency calculations were carried out with the Dunning correlation consistent polarized doubleζ, (cc-pVDZ) basis set. In contrast to methyl cyclopentadiene, transition states for ring expansion starting from the molecule methyl indene could not be located. The potential energy surfaces for ring expansion in methylene indene radicals consist of several intermediates and transition states and involve two principal pathways. One pathway is associated with cleavage of the five-membered ring adjacent to the methylene group and formation of a six-membered ring. In the second pathway, the transition states of the first stage consist of a newly-formed three-membered ring fused to the original cyclopentadiene ring. In all cases, the reaction pathways leading to ring expansion include an intermediate that, via an additional transition state, produces an α- or (β-hydronaphthalene radical. The latter, by a fast H-atom ejection, forms naphthalene. The structure, energetics, and additional parameters on the potential energy surfaces are shown. Several transition states and intermediates are common to both ring expansion and isomerization, so that there are competing parallel pathways that determine the final distribution among the isomerization and ring expansion products. Potential energy surfaces for interisomerization among the various isomers of methyl indene were calculated, and several reaction pathways were suggested. 相似文献
9.
Anton Valkov Faina Nakonechny Marina Nisnevitch 《International journal of molecular sciences》2014,15(9):14984-14996
The photosensitizers Rose Bengal (RB) and methylene blue (MB), when immobilized in polystyrene, were found to exhibit high antibacterial activity in a continuous regime. The photosensitizers were immobilized by dissolution in chloroform, together with polystyrene, with further evaporation of the solvent, yielding thin polymeric films. Shallow reservoirs, bottom-covered with these films, were used for constructing continuous-flow photoreactors for the eradication of Gram-positive Staphylococcus aureus, Gram-negative Escherichia coli and wastewater bacteria under illumination with visible white light using a luminescent lamp at a 1.8 mW·cm−2 fluence rate. The bacterial concentration decreased by two to five orders of magnitude in separate reactors with either immobilized RB or MB, as well as in three reactors connected in series, which contained one of the photosensitizers. Bacterial eradication reached more than five orders of magnitude in two reactors connected in series, where the first reactor contained immobilized RB and the second contained immobilized MB. 相似文献
10.
Irina Dubnikova Evgeniya Kuvardina Vadim Krasheninnikov Sergey Lomakin Igor Tchmutin Sergey Kuznetsov 《应用聚合物科学杂志》2010,117(1):259-272
The effect of multiwalled carbon nanotube (MWCNT) dimensions and surface modification on the morphology, mechanical reinforcement, and electrical properties of PP‐based composites, prepared by melt mixing, has been studied. The MWCNTs of small (d < 10 nm) and large (d = 40–60 nm) diameters with various intrinsic aspect ratios (L/d) have been used as filler. Transmission electron microscopy and very cold neutrons (VCN) scattering showed that both as‐received and surface modified small diameter MWCNT(1)s exhibit a strong tendency to bundle or cluster together in melt compared to both long MWCNT(3)s and short MWCNT(2)s large diameter nanotubes. The fractions of isolated nanotubes are higher and the mass‐fractal dimensions are lower for thick MWCNT‐based nanocomposites. The nanotubes of all types are heterogeneous nucleation sites for PP crystallization. The tensile and DMA testing results revealed that both long thick MWCNT(3)s with L/d ≈ 300 and thin MWCNT(1)s with highest intrinsic L/d > 1000 exhibit similar reinforcing effects, because drastically decreasing the effective aspect ratio (L/d)eff of the thin flexibly nanotubes within polymer matrix. The nanocomposites based on the long large diameter MWCNT(3)s demonstrated the lowest percolation threshold equal to 1.5 vol % loading, highest dielectric and electromagnetic waves shielding properties. It was concluded that the choice of optimal diameter and length of MWCNTs is right approach to the improvement in the dispersion state and straightness of multiwelled carbon nanotubes in polymer melt as well as to enhancement of their efficiency as reinforcing and conductive nanosized filler. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献