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Interlayer Spacing (interlayer + spacing)
Selected AbstractsGraphite Oxide as a Photocatalyst for Hydrogen Production from WaterADVANCED FUNCTIONAL MATERIALS, Issue 14 2010Te-Fu Yeh Abstract A graphite oxide (GO) semiconductor photocatalyst with an apparent bandgap of 2.4,4.3,eV is synthesized by a modified Hummers' procedure. The as-synthesized GO photocatalyst has an interlayer spacing of 0.42,nm because of its moderate oxidation level. Under irradiation with UV or visible light, this GO photocatalyst steadily catalyzes H2 generation from a 20,vol % aqueous methanol solution and pure water. As the GO sheets extensively disperse in water, a cocatalyst is not required for H2 generation over the GO photocatalyst. During photocatalytic reaction, the GO loses some oxygen functional groups, leading to bandgap reduction and increased conductivity. This structural variation does not affect the stable H2 generation over the GO. The encouraging results presented in this study demonstrate the potential of graphitic materials as a medium for water splitting under solar illumination. [source] Molecular dynamics of the generation process of double-walled carbon nanotubes from peapodsHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 4 2006Yasushi Shibuta Abstract The generation process of a double-walled carbon nanotube (DWNT) from a "peapod" was studied by classical molecular dynamics simulation. Starting from a peapod structure, defined by five C60 molecules inside a (10,10) single-walled carbon nanotube (SWNT), polymerized fullerenes, a peanut-like structure and an almost nanotube-like structure were obtained under suitable conditions of temperature control. The mean distance between the two layers of the DWNT agreed with an experimental report that it is larger than the interlayer spacing found in multi-walled carbon nanotubes (MWNTs). In addition, the chirality dependence of the potential energy of a DWNT on the relative chirality of its constituent tubes was examined using a 6-12 Lennard-Jones potential. It was found that the potential energy depends only on the distance between the two layers, not on the relative chiralities. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(4): 254,264, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20115 [source] Polypropylene/clay nanocomposites prepared by in situ grafting-melt intercalation with a novel cointercalating monomerJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008Pingan Song Abstract Polypropylene (PP)/clay nanocomposites were prepared by melt-compounding PP with organomontmorillonite (OMT), using maleic anhydride grafted polypropylene (PP- g -MA) as the primary compatibilizer and N -imidazol- O -(bicyclo pentaerythritol phosphate)- O -(ethyl methacrylate) phosphate (PEBI) as the cointercalating monomer. X-ray diffraction patterns indicated that the larger interlayer spacing of OMT in PP was obtained due to the cointercalation monomer having a large steric volume and the d -spacing further increased with the addition of PP- g -MA, as evidenced by transmission electron microscopy. Thermogravimetric analysis revealed that the PEBI-containing PP nanocomposites exhibited better thermal stability than PEBI-free PP composites. Dynamic mechanical analysis demonstrated that the storage modulus was significantly enhanced, and the glass transition temperature (Tg) shifted slightly to low temperature with the incorporation of clay for PP/OMT hybrids. PEBI-containing PP/OMT composites gave a lower Tg value because of the strong internal plasticization effect of PEBI in the system. Cone calorimetry showed that the flame-retardancy properties of PP nanocomposites were highly improved with the incorporation of PEBI. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Rheological and Thermal Properties of Polylactide/Silicate Nanocomposites FilmsJOURNAL OF FOOD SCIENCE, Issue 2 2010Jasim Ahmed ABSTRACT:, Polylactide (DL)/polyethylene glycol/silicate nanocomposite blended biodegradable films have been prepared by solvent casting method. Rheological and thermal properties were investigated for both neat amorphous polylactide (PLA-DL form) and blend of montmorillonite (clay) and poly (ethylene glycol) (PEG). Melt rheology of the PLA individually and blends (PLA/clay; PLA/PEG; PLA/PEG/clay) were performed by small amplitude oscillation shear (SAOS) measurement. Individually, PLA showed an improvement in the viscoelastic properties in the temperature range from 180 to 190 °C. Incorporation of nanoclay (3% to 9% wt) was attributed by significant improvements in the elastic modulus (G,) of PLA/clay blend due to intercalation at higher temperature. Both dynamic modulii of PLA/PEG blend were significantly reduced with addition of 10% PEG. Rheometric measurement could not be conducted while PLA/PEG blends containing 25% PEG. A blend of PLA/PEG/clay (68/23/9) showed liquid-like properties with excellent flexibility. Thermal analysis of different clay loading films indicated that the glass transition temperatures (Tg) remained unaffected irrespective of clay concentration due to immobilization of polymer chain in the clay nanocomposite. PEG incorporation reduced the,Tg of the blend (PLA/PEG and PLA/PEG/clay) significantly. Both rheological and thermal analysis data supported plasticization and flexibility of the blended films. It is also interesting to study competition between PLA and PEG for the intercalation into the interlayer spacing of the clay. This study indicates that PLA/montmorillonite blend could serve as effective nano-composite for packaging and other applications. [source] PS/PMMA mixed polymer brushes on the surface of clay layers: Preparation and application in polymer blendsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2007Jian Zhang Abstract Polystyrene (PS) and poly(methyl methacrylate) (PMMA) mixed polymer brushes on the surface of clay layers were prepared by using in situ free radical polymerization. Free radical initiator molecules with two quaternary ammonium groups at both ends were intercalated into the interlayer spacing of clay layers. The amount of polymer brushes grafted on the surface of clay layers can be controlled by controlling the polymerization time. Thermogravimetric analysis, X-ray diffraction, and high-resolution transmission electron microscope results indicated successful preparation of the mixed polymer brushes on the surface of clay layers. The kinetics of the grafting of the monomers was also studied. The mixed polymer brushes on the surface of clay layers were used as compatibilizers in blends of PS and PMMA. In the blends, the intercalated clay particles tend to locate at the interface of two phases reducing the interfacial tension. In the meanwhile, PMMA homopolymer chains tend to intercalate into clay layers. The driving force for the intercalation is the compatibility between homo-PMMA chains and PMMA brushes on the surface of clay layers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5329,5338, 2007 [source] Preparation of functionalized montmorillonites and their application in supported zirconocene catalysts for ethylene polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2002Chengbin Liu Abstract Ethylene polymerization was carried out with zirconocene catalysts supported on montmorillonite (or functionalized montmorillonite). The functionalized montmorillonite was from simple ion exchange of [CH3O2CCH2NH3]+ (MeGlyH+) ions with interlamellar cations of layered montmorillonites. The functionalized montmorillonites [high-purity montmorillonite (MMT)-MeGlyH+] had larger interlayer spacing (12.69 Å) than montmorillonites without treatment (9.65 Å). The zirconocene catalyst system [Cp2ZrCl2/methylaluminoxane (MAO)/MMT-MeGlyH+] had much higher Zr loading and higher activities than those of other zirconocene catalyst systems (Cp2ZrCl2/MMT, Cp2ZrCl2/MMT-MeGlyH+, Cp2ZrCl2/MAO/MMT, [Cp2ZrCl]+[BF4]/MMT, [Cp2ZrCl]+[BF4],/MMT-MeGlyH+, [Cp2ZrCl]+[BF4],/MAO/MMT-MeGlyH+, and [Cp2ZrCl]+[BF4],/MAO/MMT). The polyethylenes with good bulk density were obtained from the catalyst systems, particularly (Cp2ZrCl2/MAO/MMT-MeGlyH+). MeGlyH+ and MAO seemed to play important roles for preparation of the supported zirconocenes and polymerization of ethylene. The difference in Zr loading and catalytic activity among the supported zirconocene catalysts is discussed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1892,1898, 2002 [source] Organoclay Nanocomposites from Ethylene,Acrylic Acid CopolymersMACROMOLECULAR MATERIALS & ENGINEERING, Issue 10 2006Sara Filippi Abstract Summary: A study of the structure,property relationships for nanocomposites prepared by melt compounding from ethylene,acrylic acid copolymers of varied composition and molecular architecture, and organoclays modified with different ammonium ions has been made by DSC, POM, SEM, TEM, WAXD, and rheological and mechanical tests. Within the series of clays investigated, the best levels of dispersion were displayed by those organically modified with quaternary ammonium ions containing two long alkyl tails. The relevant nanocomposites were shown to possess mixed exfoliated and intercalated morphology. The spacing of the intercalated clay stacks, most of which comprise few silicate layers, was found to be independent of clay loading, in the range of 2,50 phr, and to change with the molecular architecture of the matrix polymer. An indication that the excess surfactant present in some of the clays, and the organic material added in others to expand the interlayer spacing, were expelled from the clay galleries during melt blending and acted as plasticisers for the matrix polymer, was obtained from WAXD and rheological characterisations. TEM micrograph of the nanocomposite of EAA1 with 11 phr of 15A. [source] Effect of Organic Modification on the Compatibilization Efficiency of Clay in an Immiscible Polymer BlendMACROMOLECULAR RAPID COMMUNICATIONS, Issue 20 2005Suprakas Sinha Ray Abstract Summary: This communication describes the effect of organic modifier miscibility with the matrices, and the effect of the initial interlayer spacing of the organoclay, on the overall morphology and properties of an immiscible polycarbonate/poly(methyl methacrylate) blend. By varying the organic-modifier-specific interactions with the blend matrices at the same time as changing the initial interlayer spacing of the organoclay, different levels of compatibilization were revealed. The evidence for the interfacial compatibilization of the organoclay was assessed by scanning electron microscopy observations and was supported by differential scanning calorimetry analyses. The effect on the level of clay exfoliation was also examined. Differential scanning calorimetry scans of virgin, montmorillonite, and various organically modified montmorillonite-compatibilized 40PC/60PMMA blends [source] Structural and electronic properties of few-layer graphenes from first-principlesPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2008J.-R. Huang Abstract The first-principles calculation method has been used to obtain structural and electronic properties of few-layer graphenes (FLG's) with and without a cross-film external electric potential, Vext. It is found that the AB stacking is more favorable than the AA stacking and the calculated layer spacing for the two-layer AB stacked FLG is only 2.725 Å, which is substantially reduced from that of the bulk graphite of 3.257 Å. The two-layer AB stacked FLG is found to exhibit a semi-metal,semiconductor transition under Vext qualitatively in agreement with previous studies. However, the energy gap, Eg, is not limited at 0.3 eV as obtained in previous first-principles calculation due to the reduced interlayer spacing. The threshold of the semi-metal,semiconductor transition is 0.04 Volts. Vext also induces Eg's in 3- and 4-layer AB stacked FLG's. However, in these FLG's the induced Eg's are small within 0.1 eV. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Poly(methyl methacrylate)/montmorillonite nanocomposites prepared by bulk polymerization and melt compoundingPOLYMER COMPOSITES, Issue 11 2009Krajnc, Matja This article focuses on structural, thermal, and mechanical properties of nanocomposites in dependence of preparation method and poly(methyl mathacrylate) (PMMA)/organically modified montmorillonite (OMMT) ratio. PMMA/OMMT nanocomposites were prepared by bulk polymerization and by melt compounding. Properties of nanocomposites of the same composition prepared by the two methods were compared. It was observed that nanocomposites prepared via melt compounding at 200°C had a highly oriented structure with lower interlayer spacing values than nanocomposites prepared via bulk polymerization. Two reasons for the observed smaller interlayer spacing obtained by melt compounding were identified. The first is enhanced PMMA penetration and/or formation between layers in the case of bulk polymerization, which was confirmed by determination of stronger interactions between OMMT and PMMA by Soxhlet extraction, infrared spectroscopy, and differential dynamic calorimery. The second reason for smaller interlayer spacing for nanocomposites prepared by melt compounding is organic modifier degradation during melt compounding process, which was confirmed by thermogravimetric analysis. Both reasons lead to the fracture of melt compounded nanocomposites on the OMMT-polymer interface, which was observed by scanning electron microscopy. For nanocomposites with disoriented structure and larger interlayer spacing prepared via bulk polymerization the fracture occurred in the polymer matrix. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] Use of different alkylammonium salts in clay surface modification for epoxy-based nanocompositesPOLYMER COMPOSITES, Issue 3 2009G. Ipek Nakas Layered silicates become widely used reinforcement material in the polymer nanocomposite production in recent years due to their high aspect ratio, ease of processing, and low cost. In this present study, the aim was to evaluate the usability of a raw clay source (Resadiye, Turkey) in the production of epoxy/clay nanocomposites and to investigate the effects of different surface modifiers. For this purpose, raw Na,montmorillonite clay was first purified and then surface modified by using different types of alkylammonium salts: tetramethyl ammonium bromide, benzyl triethyl ammonium bromide, dodecyl trimethyl ammonium bromide, hexadecyl trimethyl ammonium bromide, and octadecyl trimethyl ammonium bromide. Purification and surface modification of this clay were evaluated by using the following analyses; X-ray diffraction (XRD), cation exchange capacity (CEC), particle size distribution, and dissolved organic content. These analyses simply indicated that surface modification increased both interlayer spacing between the silicate layers and CEC of the clay. These improvements were directly proportional with the chain length of the surface modifier. Nanocomposite specimens were produced by adding 0.5 wt% surface modified clay into the epoxy matrix. These specimens were characterized by XRD, Si-mapping facility of SEM, and mechanical tests. XRD results indicated an exfoliated structure whereas Si-mapping showed the uniform distribution of clay particles in epoxy, leading to improved mechanical properties, for instance more than 100% increase in fracture toughness of the neat epoxy specimen. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] Preparation and characterization of polypropylene/solid-state organomodified montmorillonite nanocompositesPOLYMER COMPOSITES, Issue 4 2008Sun Yu-hai A novel organomodified montmorillonite prepared by solid-state method and its nanocomposites with polypropylene were studied. The interaction between modifying agent and montmorillonite was investigated by X-ray diffraction (XRD) analysis, contact angle determination, and Fourier-transform infrared spectroscopy. The results showed that the modifying agent behaves as an effective intercalating agent, enlarging the interlayer spacing of montmorillonite and making montmorillonite more hydrophobic. Polypropylene/solid-state organomodified montmorillonite composites were prepared by melt-mixing method. The dispersion of the silicates was investigated by XRD analysis and transmission electron microscopy. It was found that the nanocomposites are formed with solid-state organomodified montmorillonite and polypropylene. The thermogravimetric analysis and differential scanning calorimetry results showed that the organoclay could enhance the thermal stability and decrease the relative crystallinity of polypropylene. Mechanical and rheological tests indicated that the organoclay improves the mechanical properties but has no obvious effect on rheological properties of polypropylene. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers [source] Linear and nonlinear melt-state viscoelastic properties of polypropylene/organoclay nanocompositesPOLYMER ENGINEERING & SCIENCE, Issue 7 2008Ehssan Nazockdast Rheological behavior of polypropylene (PP)/organoclay nanocomposites varying in compatibilizer (PP- g -MA) and organoclay concentration was investigated. The samples were prepared by melt intercalation method in an internal mixer. The wide angle X-ray diffraction patterns and results of rheological measurements showed that the compatibilizer had strong influence in increasing the interlayer spacing. The observed low frequency liquid-like to solid-like transition and apparent yield stress in simple shear flows, along with convergence of transient shear stress to nonzero values in stress relaxation after the cessation of flow experiments, were found to be consistent with formation of a physical network in quiescent conditions which could be easily ruptured with applying low shear rates. The values of stress overshoot strain in flow reversal experiments were independent of shear rate, organoclay, and compatibilizer content. From the results of frequency sweep experiments in different nonlinear strain amplitudes it was shown that extended Cox-Merz analogy was valid in nonlinear dynamic deformations while the shear viscosity showed positive deviation from this analogy with higher deviations at lower shear rates. Results of storage modulus recovery and flow reversal experiments at different shear rates suggested that network structure is reformed with a much slower rate compared to the rotational relaxation of organoclay platelets. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source] Intercalation and exfoliation of talc by solid-state shear compounding (S3C) using pan-mill equipmentPOLYMER ENGINEERING & SCIENCE, Issue 4 2005Weiguo Shao The intercalation and exfoliation of talc have been realized by solid-state shear compounding (S3C) using pan-mill equipment that can exert fairly strong shear forces and has multifunctions such as pulverizing, mixing, and activation on materials. The structural features of pan-mill also show prospective in delaminating layered minerals. The morphology and structure of talc were investigated by using transmission electron microscopy (TEM) and X-ray diffraction (XRD). The characteristic peaks of talc interlayer spacing disappeared in the XRD pattern of PP/talc composite prepared by S3C, however, still remained in the XRD pattern of PP/talc prepared by the conventional mixing method. TEM confirms the intercalated and exfoliated structure of talc, and the well dispersion of talc in the PP matrix after talc and PP were co-milled. S3C is a new approach to prepare polymer/layered inorganic filler nanocomposite and has characteristics such as a simple process that needs neither organic ligands nor solvent. POLYM. ENG. SCI. 45:451,457, 2005. © 2005 Society of Plastics Engineers. [source] 2,4,6-Tris(methylthio)-1,3,5-triazine, 3-methyl-4,6-bis(methylthio)-1,3,5-triazine-2(3H)-thione, 1,3-dimethyl-4-methylthio-1,3,5-triazine-2,6(1H,3H)-dithione and 1,3,5-trimethyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trithioneACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2000Mark Greenberg The crystal structures of four isomers of C6H9N3S3 were determined. Their molecules tend to be planar, but the tendency is weakened when the number of formal N=C double bonds in the ring decreases. The structures of the triazine rings in the four compounds were found to be similar to their oxy analogues. All of the compounds form planar layer structures with similar interlayer spacing ranging from 3.41 to 3.60,Å. The molecular packing of each isomer is controlled by weak van der Waals interactions. [source] Effect of nanoclays on the dyeability of polypropylene nanocomposite fibresCOLORATION TECHNOLOGY, Issue 2 2008Lova Razafimahefa Polypropylene clay fibres loaded with different alkylammonium-modified montmorillonite were prepared using a melt spinning technique and relationships between the structure and properties of the nanopolypropylene fibres are discussed. Experiments carried out using transmission electron microscopy showed that the chemical structure of the organic modifier and the interlayer spacing of the clay induced different dispersions of the clay, thus improving accessibility of the nano fibre. It is known that nanoclays are effective and efficient sorbents for dyes. Therefore, the dyeing behaviour of the nano polypropylene fibres with two distinct acid dyes and a disperse dye was studied and the build-up of dyes, measured as colour yield, reported. The best results were obtained when the clay was well dispersed in nanopolypropylene fibres; that is, when maleated polypropylene was added as a compatibiliser and when disperse dye was used. Good wash fastness was then obtained. [source] Polymer,silicate nanocomposites produced by in situ atom transfer radical polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2004Hanying Zhao Abstract Polymer,silicate nanocomposites were synthesized with atom transfer radical polymerization (ATRP). An ATRP initiator, consisting of a quaternary ammonium salt moiety and a 2-bromo-2-methyl propionate moiety, was intercalated into the interlayer spacings of the layered silicate. Subsequent ATRP of styrene, methyl methacrylate, or n -butyl acrylate with Cu(I)X/N,N -bis(2-pyridiylmethyl) octadecylamine, Cu(I)X/N,N,N,,N,,N,-pentamethyldiethylenetriamine, or Cu(I)X/1,1,4,7,10,10-hexamethyltriethylenetetramine (X = Br or Cl) catalysts with the initiator-modified silicate afforded homopolymers with predictable molecular weights and low polydispersities, both characteristics of living radical polymerization. The polystyrene nanocomposites contained both intercalated and exfoliated silicate structures, whereas the poly(methyl methacrylate) nanocomposites were significantly exfoliated. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 916,924, 2004 [source] | |||||||||||||