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Polymer micro and nanocomposites: Structure, interactions, properties
Ja´nos Mo´czo,Be´la Puka´nszky 한국공업화학회 2008 Journal of Industrial and Engineering Chemistry Vol.14 No.5
The characteristics of all heterogeneous polymer systems including composites containing either micro or nanofillers are determined by four factors: component properties, composition, structure and interfacial interactions. The most important filler characteristics are particle size, size distribution, specific surface area and particle shape, while the main matrix property is stiffness. Segregation, aggregation and the orientation of anisotropic particles determine structure. Interfacial interactions lead to the formation of a stiff interphase considerably influencing properties. Interactions are changed by surface modification, which must be always system specific and selected according to its goal. Under the effect of external load inhomogeneous stress distribution develops around heterogeneities, which initiate local micromechanical deformation processes determining the macroscopic properties of the composites. In filled polymers the dominating deformation mechanism is usually debonding. Nanocomposites represent one of the new classes of materials, but further research and development is needed before they gain significant position in the market.
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Renner, Ká,roly,Henning, Sven,Mó,czó,, Já,nos,Yang, Min Soo,Choi, Hyoung Jin,Puká,nszky, Bé,la Wiley Subscription Services, Inc., A Wiley Company 2007 Polymer engineering and science Vol.47 No.8
<P>Polyamide/organophilic montmorillonite nanocomposites were prepared from two silicates with different organophilization resulting in strong and weak matrix/silicate adhesion, respectively; uncoated sodium montmorillonite was used as reference. The silicate content of the composites changed between 0 and 10 vol% in seven steps. Composite structure was characterized by X-ray diffraction and electron microscopy. Micromechanical deformation processes were followed by acoustic emission and volume strain measurements. The structure of the composites is more complicated than usually claimed; they contain individual silicate platelets, tactoids with different degree of intercalation, and larger particles. Elastic deformation and shear yielding dominates during the elongation of the specimens. The matrix polymer and the composites deform according to different mechanisms. Sound is emitted by cavitation in the former, while sound emitting processes are related tactoids and nonexfoliated particles in the composites. Acoustic events are generated mainly by the fracture of the particles. Matrix/silicate adhesion seems to be strong, debonding rarely takes place, and volume increase is initiated primarily by particle failure. The type and amount of the surfactant used for organophilization plays an important role in the determination of deformation processes and properties, since it influences both matrix/filler interaction and the inherent strength of the particles. POLYM. ENG. SCI., 47:1235–1245, 2007. © 2007 Society of Plastics Engineers</P>
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László Vanyorek,Ádám Prekob,EmÅke Sikora,Edina Reizer,Gábor Muránszky,Ferenc Kristály,Béla Viskolcz,Béla Fiser 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.79 No.-
Nitrogen-doped bamboo-like carbon nanotube (N-BCNT) coating was synthesized onto the surface ofzeolite beads by using Catalytic Chemical Vapour Deposition (CCVD) method to develop a “support onsupport” (SoS) system. These complex structured materials were used as supports during the preparationof hydrogenation catalysts. Rhodium, palladium and platinum nanoparticles were depositedhomogeneously onto the surface of the N-BCNTs of the SoS (final metal content 2 wt%). The catalyticactivity of these samples was compared in the hydrogenation of nitrobenzene. The Pt/N-BCNT-zeolitesample was the most active (182 mol nitrobenzene after 30 min). The activity of the other two catalysts at20 bar was well below this value, 99.5 mol after 60 min and 96 mol after 120 min for Pd and Rh,respectively. The aniline selectivity was different for the three catalysts and they facilitate the formationof various by-products (e.g. N-methylaniline, cyclohexylamine). The usage of the Pd and Pt/NBCNT-zeolite catalysts are more convenient, as only one main by-product was formed. It was confirmedthat the zeolite supported N-BCNTs are efficient catalyst supports in hydrogenation processes. Furthermore, by using this special SoS structure to support the catalytic metals the applicability iswidened and the catalyst removal is easier.
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Allelopathic Potential of Select Gymnospermous Trees
Jaime A. TEIXEIRA da SILVA,Javad KARIMI,Sasan MOHSENZADEH,,Judit DOBRÁNSZKI 강원대학교 산림과학연구소 2015 Journal of Forest Science Vol.31 No.2
Allelopathy is an ecological phenomenon that refers to the beneficial or harmful effects of one plant on another plant, both crop and weed species, by the release of organic chemicals (allelochemicals) from plant parts by leaching, root exudation, volatilization, residue decomposition in soil and other processes in both natural and agricultural systems. Allelopathy can affect many aspects of plant ecology including occurrence, growth, plant succession, the structure of plant communities, survival, dominance, diversity, and plant productivity. In this review, we describe the concept of allelopathy, some mechanisms of operation within plants and then focus on a select number of gymnospermous tree genera: Ephedra, Pinus, Taxus, Cedrus, Juniperus, Picea, Cunninghamia and Araucaria. Pinus, Taxus (yew) and Cedrus (cedar) trees have a strong negative allelopathic effect on the germination, growth, or development of other plant species in the forest community.
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