bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrically conductive composites of poly(urea‐formaldehyde) and cellulose filled with aluminum
Authors: Pinto Gabriel , Maaroufi Abdel‐Karim 
Published: November 2012

AbstractThis article addresses the preparation and characterization of composite materials obtained with compression molding of mixtures of aluminum powder and a commercial grade thermosetting resin of poly(urea‐formaldehyde) filled with α‐cellulose in powder form. The homogeneity of these composites was checked by the morphologies of the constituents (filler and matrix) by optical microscopy. The density of the composites was measured and compared with values calculated by assuming different void levels within the samples, to discuss the porosity effect, in connection with optical microscopy observations. Then, the dependence of electrical conductivity of the composites on volume fraction of the metal filler was investigated. The conductivity of the composites is <10−12 S/cm unless the metal content reaches the percolation threshold at a volume fraction of Vc = 38.6 vol%, beyond which the conductivity increases markedly by as much as nine orders of magnitude, indicating an insulator–conductor phase transition. The obtained results on electrical conductivity have been well interpreted with the statistical percolation theory. The deduced critical parameters, such as the threshold of percolation, Vc, the critical exponent, t, and the packing density coefficient, F, were in good accord with earlier studies. In addition, the hardness of samples remained almost constant with the increase of metal concentration. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers
Rheology and thermal behavior of polyamide reinforced with alumina whiskers
Authors: Abad María José , Ares Ana , Noguerol Rosalía , García Xoan , Cerecedo Carmen , Valcárcel Víctor , Caamaño J. Miguel , Guitián Francisco 
Published: November 2012

AbstractAlumina whiskers were melt‐mixed with polyamide 12 to obtain new composites with high performance properties and similar processability of neat polyamide. Three kinds of alumina whiskers were used to prepare composites (purified fibers, ribbon‐shaped fibers and silica‐coated fibers). The rheology, morphology and thermal behavior of composites were evaluated as function of the type of whisker and its amount in the samples. In terms of rheological properties, modulus and viscosity were enhanced as function of the amount of filler added. Good dispersion of alumina whiskers in PA12 and an optimal filler‐matrix interface were observed in morphological tests independently of the kind of fiber used. Studies on crystallization behavior indicated the nucleation action of whiskers, although the most important changes in crystalline state of PA12 were observed with ribbon‐shaped and silica‐coated fibers. Whiskers improved significantly the thermal stability of polyamide. But kinetics of degradation process studied using Coats‐Redfern method indicates that the best behavior wasobtained principally with ribbon‐shaped and silica‐coated whiskers. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers
The impact of creative tendency, academic performance, and self‐concept on creative science problem‐finding
Authors: Liu Mingxin , Hu Weiping , Adey Philip , Cheng Li , Zhang Xingli 
Published: November 2012

AbstractThis study was designed to address the impacts of science performance, science self‐concept, and creative tendency on the creative science problem‐finding (CSPF) ability of a sample of Chinese middle‐school students. Structural equation modeling was used to indicate that CSPF could be directly predicted by creative tendency and academic performance, and indirectly predicted by science self‐concept. The findings strongly support the idea that curiosity, imagination, and domain‐specific knowledge are important for CSPF, and science self‐concept could be mediated by knowledge that affects CSPF.
The preparation and properties of polystyrene/functionalized graphene nanocomposite foams using supercritical carbon dioxide
Authors: Li Chaoqun , Yang Guanghui , Deng Hua , Wang Ke , Zhang Qin , Chen Feng , Fu Qiang 
Published: November 2012

AbstractIn this work, polystyrene (PS)/functionalized graphene nanocomposite foams were prepared using supercritical carbon dioxide. Thermally reduced graphene oxide (TRG) and graphene oxide (GO) were incorporated into the PS. Subsequently, the nanocomposites were foamed with supercritical CO2. The morphology and properties of the nanocomposites and the nucleation efficiency of functionalized graphene in foaming PS are discussed. Compared with GO, TRG exhibited a higher nucleation efficiency and more effective cell expansion inhibition thanks to its larger surface area and better exfoliated structure. It is suggested that the factors that have a significant influence on the nucleation efficiency of TRG and GO originate from the differences in surface properties and chemical structure. Furthermore, PS/TRG nanocomposites and their nanocomposite foams also possess good electrical properties which enable them to be used as lightweight functional materials.© 2012 Society of Chemical Industry
Compatibilization of immiscible nylon 6/poly(vinylidene fluoride) blends using graphene oxides
Authors: Yang Jinghui , Feng Chenxia , Dai Jian , Zhang Nan , Huang Ting , Wang Yong 
Published: November 2012

AbstractA new strategy to compatibilize immiscible blends is proposed, using graphene oxide (GO) nanosheets taking advantage of their unique amphiphilic structures. When 0.5 or 1 wt% GOs were incorporated in immiscible nylon 6/poly(vinylidene fluoride) (PVDF) (90/10 wt%) blends, the dimension of PVDF dispersed particles was markedly reduced and became more uniform, revealing a well‐defined compatibilization effect of GOs on the immiscible blends. Correspondingly, the ductility of the compatibilized blends increased several times compared with uncompatibilized immiscible blends. In order to explore the underlying compatibilization mechanism, Fourier transform infrared and Raman spectra were applied to suggest that the edge polar groups of GOs can form hydrogen bonds with nylon 6 while the basal plane of GOs can interact with electron‐withdrawing fluorine on PVDF chains leading to the so‐called charge‐transfer C–F bonding. In this case, GOs exhibit favorable interactions with both nylon 6 and PVDF phase, therefore stabilizing the interface during GO migrations from PVDF/GO masterbatch to nylon 6 phase, which can minimize the interfacial tension and finally lead to compatibilization effects. Obviously, this work may open a broad prospect for GOs to be widely applied as a new compatibilizer in industrial fields. © 2012 Society of Chemical Industry
Synthesis of poly(lactic acid)‐based polyurethanes
Authors: Chen Szu‐Hsien , Tsao Ching‐Ting , Chou Hung‐Chia , Chang Chih‐Hao , Hsu Ching‐Te , Chuang Ching‐Nan , Wang Chih‐Kuang , Hsieh Kuo‐Huang 
Published: November 2012

AbstractPoly(lactic acid) (PLA) is a biodegradable aliphatic polyester, but its brittleness makes it unsuitable for many packaging and appliance applications. The goal of the work reported was to create novel poly(ester urethane)s that incorporate biodegradable poly(lactic acid) diols (PLA‐OHs) and good mechanical properties of increased molecular weight via crosslinked network formation for engineering plastics applications. Three kinds of polyols (PLA‐OHs, PLA‐OHs/poly(tetramethylene ether) glycol or PLA‐OHs/poly(butylene adipate) glycol (PBA)) and two kinds of diisocyanates (4,4‐diphenylmethane diisocyanate (MDI) or toluene 2,4‐diisocyanate (TDI)) were chosen for the soft and hard segments to compare their mechanical properties. In addition, 1,4‐butanediol and trimethylolpropane were each used as chain extender agents. Results showed the PLA/PBA‐polyurethanes (PLA/PBA‐PUs) of the MDI series and the PLA/PBA‐PUs of the TDI series had improved thermal stability and enhanced mechanical properties. Degradation behavior showed the PLA‐based polyurethanes could be degraded in phosphate‐buffered saline solution and enzyme solution. © 2012 Society of Chemical Industry
From high‐efficiency n‐type solar cells to modules exceeding 20% efficiency with aluminum‐based cell interconnection
Authors: Merkle Agnes , Schulte‐Huxel Henning , Blankemeyer Susanne , Feilhaber Ilka , Bock Robert , Steckenreiter Verena , Kajari‐Schroeder Sarah , Harder Nils‐Peter , Brendel Rolf 
Published: November 2012

ABSTRACTWe present the integrated development of back‐contacted solar cells and an adequate module interconnection for a high‐efficiency photovoltaic module. We report on a large area (125 × 125) mm2 back‐junction back‐contact n‐type solar cell metallized with aluminum having a total area conversion efficiency of 20.7%. To transfer the high conversion efficiency to the module, we use the laser welding process named aluminum‐based mechanical and electrical laser interconnection for module integration of these back‐contacted solar cells. We further analyze the impact of the busbars of our back‐junction back‐contact cells on the cell performance and report on optimization of the cell/module interface. The new cells have an adapted rear‐side geometry by omitting the emitter busbar. A proof‐of‐concept module consisting of these cells is presented. Copyright © 2012 John Wiley & Sons, Ltd.
Alternating, gradient, block, and block–gradient copolymers of ethylene and norbornene by Pd–Diimine‐Catalyzed “living” copolymerization
Authors: Xiang Peng , Ye Zhibin 
Published: November 2012

AbstractWe demonstrate, in this article, the facile synthesis of a broad class of low‐polydispersity ethylene–norbornene (E–NB) copolymers having various controllable comonomer composition distributions, including gradient, alternating, diblock, triblock, and block–gradient, through “living”/quasiliving E–NB copolymerization facilitated with a single Pd–diimine catalyst (1). This synthesis benefits from two remarkable features of catalyst 1, its high capability in NB incorporation and high versatility in rendering E–NB “living” copolymerization at various NB feed concentrations ([NB]0) while under an ethylene pressure of 1 atm and at 15 °C. At higher [NB]0 values between 0.42 and 0.64 M, E–NB copolymerization with 1 renders nearly perfect alternating copolymers. At lower [NB]0 values (0.11–0.22 M), gradient copolymers yield due to gradual reduction in NB concentration, with the starting chain end containing primarily alternating segments and the finishing end being hyperbranched polyethylene segments. Through two‐stage or three‐stage “living” copolymerization with sequential NB feeding, diblock or triblock copolymers containing gradient block(s) have been designed. This work thus greatly expands the family of E–NB copolymers. All the copolymers have controllable molecular weight and relatively low polydispersity (with polydispersity index below 1.20). Most notably, some of the gradient and block–gradient copolymers have been found to exhibit the characteristic broad glass transitions as a result of their possession of broad composition distribution. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013
Thermoresponsive NIPAM block copolymers containing densely grafted poly(vinyl ether) brushes synthesized by a combination of living cationic polymerization and RAFT polymerization
Authors: Minoda Masahiko , Shimizu Tatsuya , Miki Sadao , Motoyanagi Jin 
Published: November 2012

AbstractDiblock copolymers consisting of a multibranched polymethacrylate segment with densely grafted poly[2‐(2‐methoxyethoxy)ethyl vinyl ether] pendants and a poly(N‐isopropylacrylamide) segment were synthesized by a combination of living cationic polymerization and RAFT polymerization. A macromonomer having both a poly[2‐(2‐methoxyethoxy)ethyl vinyl ether] backbone and a terminal methacryloyl group was synthesized by living cationic polymerization. The sequential RAFT copolymerizations of the macromonomer and N‐isopropylacrylamide in this order were performed in aqueous media employing 4‐cyanopentanoic acid dithiobenzoate as a chain transfer agent and 4,4′‐azobis(4‐cyanopentanoic acid) as an initiator. The obtained diblock copolymers possessed relatively narrow molecular weight distributions and controlled molecular weights. The thermoresponsive properties of these polymers were investigated. Upon heating, the aqueous solutions of the diblock copolymers exhibited two‐stage thermoresponsive properties denoted by the appearance of two cloud points, indicating that the densely grafted poly[2‐(2‐methoxyethoxy)ethyl vinyl ether] pendants and the poly(N‐isopropylacrylamide) segments independently responded to temperature. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013
Emulsion polymerization of vinyl acetate using iodine‐transfer and RAFT radical polymerizations
Authors: Nomura Naoki , Shinoda Keiji , Takasu Akinori , Nagata Kenji , Inomata Katsuhiro 
Published: November 2012

AbstractThis study deals with control of the molecular weight and molecular weight distribution of poly(vinyl acetate) by iodine‐transfer radical polymerization and reversible addition‐fragmentation transfer (RAFT) emulsion polymerizations as the first example. Emulsion polymerization using ethyl iodoacetate as the chain transfer agent more closely approximated the theoretical molecular weights than did the free radical polymerization. Although 1H NMR spectra indicated that the peaks of α‐ and ω‐terminal groups were observed, the molecular weight distributions show a relatively broad range (Mw/Mn = 2.2–4.0). On the other hand, RAFT polymerizations revealed that the dithiocarbamate 7 is an excellent candidate to control the polymer molecular weight (Mn = 9.1 × 103, Mw/Mn = 1.48), more so than xanthate 1 (Mn = 10.0 × 103, Mw/Mn = 1.89) under same condition, with accompanied stable emulsions produced. In the Mn versus conversion plot, Mn increased linearly as a function of conversion. We also performed seed‐emulsion polymerization using poly(nonamethylene L‐tartrate) as the chiral polyester seed to fabricate emulsions with core‐shell structures. The control of polymer molecular weight and emulsion stability, as well as stereoregularity, is also discussed. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013
Molecular dynamics simulation of carbon nanostructures: The C60 buckminsterfullerene
Authors: László István , Zsoldos Ibolya 
Published: November 2012

AbstractMolecular dynamics calculations can reveal the physical and chemical properties of various carbon nanostructures or can help to devise the possible formation pathways. In our days the most well‐known carbon nanostructures are the fullerenes, the nanotubes, and the graphene. The fullerenes and nanotubes can be thought of as being formed from graphene sheets, i.e., single layers of carbon atoms arranged in a honeycomb lattice. Usually the nature does not follow the mathematical constructions. Although the first time the C60 and the C70 were produced by laser irradiated graphite, the fullerene formation theories are based on various fragments of carbon chains and networks of pentagonal and hexagonal rings. In the present article various formation pathways for the buckminsterfullerene C60 molecule will be presented. magnified image
Encapsulating graphene by ultra‐thin alumina for reducing process contaminations
Authors: Dauber Jan , Terrés Bernat , Trellenkamp Stefan , Stampfer Christoph 
Published: November 2012

AbstractWe discuss a fabrication process for making graphene devices based on encapsulated graphene for reducing contaminations during individual processing steps. A 3–5 nm alumina layer is deposited directly after exfoliating graphene, protecting it during the entire processing. We show that the visibility of the encapsulated graphene is sufficient to identify graphene flakes and Raman spectra exhibit the characteristic finger print. We perform transport measurements to study the sample quality and compare the results with graphene samples processed without an alumina layer. In particular we observe a higher yield and significantly reduced contact resistances for devices fabricated with the here presented method.magnified imageGraphene flake with metal (Cr/Au) contacts covered with an ultra‐thin (3–5 nm) oxidized aluminum layer (left) and without the layer (right).
On the low temperature microwave absorption anomaly in single‐wall carbon nanotubes
Authors: Karsa Anita , Quintavalle Dario , Forró László , Simon Ferenc 
Published: November 2012

AbstractThe low temperature microwave absorption anomaly reported by Corzilius et al. [Phys. Rev. B 75, 235416 (2007)] in single‐wall carbon nanotubes (SWCNTs) is revisited. It was originally reported that the microwave absorption of CVD grown SWCNTs shows an unexpected increase below ∼20 K (using flow cryostats) which depends on the microwave power. The original observation was made using the microwave cavity perturbation method while sweeping the microwave frequency. We reproduced this effect on arc‐discharge based SWCNTs, using static cryogenic conditions with cooled microwave cavities, and employing a stable frequency source locked to the cavity resonance. Our observation shows that the microwave absorption anomaly is robust against the tube type and the experimental conditions.
Optically induced spin echoes in a Tm2+ doped crystal
Authors: Moriyasu T. , Yamauchi T. , Kohmoto T. 
Published: November 2012

AbstractThe dynamics of the optically induced magnetization was observed by using polarization spectroscopy with the pump‐probe technique. We observed, as an alloptical manipulation of spin coherence in solids, the optically induced free induction decay and spin echoes in the ground state of the thulium ion doped in fluoride crystals.A vector model of the optically induced spin echoes for on‐resonant manipulation is considered. The application of spin echoes to solids is very important because of the possibility of the fast spin manipulation (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Preparation of high quality ZnSe nanowires dominated by excitonic emission
Authors: Fernandes Carlos , Ruda Harry , Saxena Ankur , Souza Christina de 
Published: November 2012

AbstractA comprehensive model for the vapour liquid solid based growth of ZnSe nanowires is developed and applied to the optimisation of growth conditions for ZnSe nanowires. The model provided insight into the role of fluid dynamics and adatom incorporation, on the growth of nanowires. When applied experimentally, with appropriate conditions we show how high quality nanowires can be synthesized. In particular, such nanowires were shown to be dominated by excitonic emission with narrow linewidth attributed to free exciton and acceptor bound exciton emissions. The latter was shown to originate from VZn and related complexes, and as expected the emission is accompanied by strong LO phonon emission consistent with the high quality of the nanowires. This work can hence provide guidance for choice of growth conditions for exceptional quality ZnSe nanowires suitable for optoelectronic applications. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical properties of Er3+‐doped glasses for solar‐pumped lasers
Authors: Iwata Yasuyuki , Suzuki Takenobu , Ohishi Yasutake 
Published: November 2012

AbstractThe quantum efficiency (QE) of Er3+‐doped silicate, tellurite, phosphate and fluoride glasses have been examined under simulated sunlight excitation. The maximum of total QE, the sum of QE of 4S3/2, 4I11/2, 4I13/2→4I15/2 and 4S3/2→4I13/2 transition, is 75% and the maximum of QE1530, the QE of the 4I13/2→4I15/2 transition at 1530 nm, is 34% for 5.47×1019 cm‐3 Er3+‐doped fluoride glass. The figure of merit as laser media στ of silicate glass is 1.00×10‐22 cm2sec, which is the highest in 4 glasses. Although QE1530 of silicate is lower than fluoride, it is possible to compensate the low quantum efficiency to optimize the fiber laser design. Therefore Er3+‐doped fluoride and silicate glasses are expected to be promising candidates as solar‐pumped glass laser (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Polarization dependence of four‐wave mixing via biexcitons in CuCl microcavities
Authors: Matsuura S. , Mitsumori Y. , Kosaka H. , Edamatsu K. , Miyazaki K. , Kanatani Y. , Kim D. , Nakayama M. , Oohata G. , Oka H. , Ajiki H. , Ishihara H. 
Published: November 2012

AbstractWe studied the CuCl microcavity designed for the enhancement of the biexciton‐photon coupling, in terms of spectrally resolved four‐wave mixing. We observed the strong dependence of the spectrum on the polarization of the pump pulses and the polarization correlation between the pump pulses and the four‐wave mixing signal, suggesting that the biexciton state is successfully formed in the CuCl microcavity. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mn‐doping effect of photoluminescence on AgInS2
Authors: Paucar Raul , Miyamoto Umihito , Ohtani Naoki , Seo Takuya , Honjo Kazuhiro , Shim YongGu , Tokuda Takahiro , Yoshino Kenji , Wakita Kazuki 
Published: November 2012

AbstractThe effects of Mn‐doping on the photoluminescence spectra of AgInS2 bulk‐crystals grown by the hot‐press method have investigated by using a confocal microspectroscopy system. For Mn‐doped crystals, the emission peak located at 1.568 eV appears in addition to two peaks which exist on non‐doped samples. The lower energy peaks blow 1.8 eV are considered to be attributed to free‐to‐bound transition. We also examined temperature dependence of emission intensity of these peaks and obtained their activation energy. The energy values seem to correspond to energy levels related with the emissions because non‐doped and Mn‐doped samples indicated to be n‐type (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Acetylcholinesterase inhibitors: Modeling potential candidates
Authors: Kiametis Alessandra S. , Martins João B. L. , Romeiro Luiz A. S. , Gargano Ricardo 
Published: November 2012

AbstractAlzheimer's disease is the leading cause of dementia for elderly people. The main active therapeutic is supported on the increased levels of acetylcholine in the synaptic cleft, based on reversible inhibition of the acetylcholinesterase (AChE) enzyme. This article aims to propose possible inhibitor candidates for AChE, designed from nonisoprenoid lipids of cashew (Anacardium occidentale), and based on several electronic properties. These electronic properties were obtained through B3LYP/6‐311+G(2d,p) calculation level. Principal component analysis reveals that from the set of studied molecular structures a small group is correlated with donepezil, a drug with known biological activity. © 2012 Wiley Periodicals, Inc.