bluuebunny/crossref_metadata_2025_split huggingface dataset:
Melt Intercalation of PMMA into Organically-Modified Layered Silicate
Authors: Shen Z. , Simon G. P. , Cheng Y-B. 
Published: April 2011

ABSTRACTOrganic-inorganic hybrid nanocomposite materials of poly(methyl methacrylate) (PMMA) and organically-modified silicate (B34) systems have been prepared via melt intercalation with variation of tacticity and molecular weight as the main molecular variables. Only two of the PMMA samples (with the lowest glass transition temperatures) were able to undergo large-scale intercalation into B34, as seen by X-ray diffraction (XRD) and Infrared spectroscopy. The saturation weight ratio of PMMA to B34 was about 25:75 (wt%), deduced by a controlled differential scanning calorimetry (DSC) experiment. Two new absorption bands of PMMA-B34 hybrid in Fourier transform-infrared spectrometry (FTIR) were demonstrated for first time in this system and show a change in molecular interaction of bulk and intercalated PMMA. The degradation temperature of the PMMA-B34 hybrid is higher than that of PMMA alone, or a physical mixture of PMMA and silicate under an air or a nitrogen flow.
Calculating Phase Diagrams of Polymer-Clay Mixtures by Combining Density Functional and Self-Consistent Field Theory
Authors: Balazs Anna C. , Singh Chandralekha , Ginzburg Valeriy V. 
Published: April 2011

ABSTRACTWe analyze the thermodynamics of polymer-clay mixtures within the framework of density functional theory (DFT). The interaction potential between clay particles is calculated using the self-consistent field (SCF) method and is strongly dependent on the length and density of grafted short-chain organic modifiers. By combining the DFT and SCF techniques, we determine the role of the grafted chains on the equilibrium phase behavior of the mixtures.
Formation of Mesoscopic Polymer Dots by Rubbing Transfer
Authors: Sano M. , Okamura J. , Shinkai S. 
Published: April 2011

ABSTRACTRegularly spaced polymer dots are formed on a silicon surface by rubbing a thin polymer plate against the silicon substrate. Typically, the disk-shaped dots are 10 nm in height and 160 nm in diameter, and are separated by 340 nm from each other. It is found that the substrate temperature, the rubbing rate, the polymer viscoelasticity, and wettability against a substrate surface must be within a certain range to produce the aligned dots.
Covalent Attachment of a Single Dextran Polymer Between the Tip of an Atomic Force Microscope and a Gold Surface
Authors: Grandbois M. , Décor R. , Rief M. , Wagner A. , Mioskowski C. , Gaub Hermann 
Published: April 2011

ABSTRACTA method for covalent immobilization of a single dextran polymer between a gold surface and the tip of an atomic force microscope (AFM) is presented. Carboxymethylated dextran immobilized on gold by epoxythiol chemistry was activated with N-hydroxysuccinimide (NHS) and N-ethyl-N'-(dimethylaminopropyl) carbodiimide hydrochloride (EDC) in order to make the dextran polymer reactive for the amino groups present on the previously aminosilanized AFM tip. By measuring force vs extension curves we have shown that it is possible to catch such an activated dextran polymer with an AFM tip through the formation of a covalent bond. Dextran polymers were attached even without any detectable indentation of the tip in the dextran-coated gold surface. In this so-called fly-fishing mode, attachment of multiple dextran polymers, which typically occurs when the tip is indented into the surface, are efficiently avoided.
Integrating Organic Molecules to Silicon Surfaces
Authors: Zhu X.-Y. , Mulder J. A. , Hsung R. P. , Bergerson W. F. , Gasser A. , Nguyen A. 
Published: April 2011

ABSTRACTWe present a general strategy for the efficient assembly of organic molecules directly onto the silicon surface via Si-N and Si-O linkages. This is achieved from the reaction between an amine or an alcohol functional group and a chlorinated Si surface. The resulting organic monolayers are thermally stable. These methods are applicable for the assembly of a variety of functional organic molecules in both vacuum environment and solution phases.
Deposition of Nanocrystalline Tin (IV) Oxide Films on Organic Self-Assembled Monolayers
Authors: Supothina S. , Guire M. R. De , Niesen T. P. , Bill J. , Aldinger F. , Heuer A. H. 
Published: April 2011

ABSTRACTNanocrystalline thin films of tin (IV) oxide (cassiterite) have been deposited from aqueous solutions of tin (IV) chloride and hydrochloric acid at 80°C. Substrates were {100} single-crystal silicon wafers, with and without silanol-anchored, sulfonate-terminated organic self-assembled monolayers (SAMs). Using flowing solutions, films with thicknesses of up to 1 μtm have been grown, whereas the thickness of the films from static solutions is limited to about 80 nm. The films were characterized using transmission electron microscopy and Rutherford backscattering spectroscopy. The role of the flow rate and configuration of the deposition chamber is discussed.
Sol-Gel Synthesis And Characterization Of Molybdenum Oxide/Polypyrrole Hybrids
Authors: Dong W. , Dunn B. 
Published: April 2011

ABSTRACTMonolithic Mo oxide/polypyrrole hybrid aerogels and xerogels were successfully synthesized through sol-gel methods. The PPy formed appears to be β-substituted. A 100 fold increase in electrical conductivity was observed for the hybrids (4× 10–3 S/cm) as compared to the pristine MoO3 gels (2× 10–5 S/cm). An initial increase in Li+ intercalation capacity is also observed for the hybrid. The electrical conductivity and Li+ intercalation depend greatly on the concentration of Motrichloro alkoxide precursor and sol aging conditions. The hybrid aerogels have a density of 0.5 g/cc and a surface area of 120 m2/g. The as-formed gels are amorphous and crystallize to the orthorhombic MoO3 phase at 375°C.
Modifications Of Preceramic Polymers Suitable For Corrosion Resistant And High Temperature Coatings
Authors: Blum Y. D. , Chen H. P. , Macqueen D. B. , Johnson S. M. 
Published: April 2011

ABSTRACTLow-cost preceramic polymers have been developed and used for various coating and composite applications. These siloxane-based polymers can be tailored to be precursors to ceramics or remain as polymeric materials. Polyhydridomethylsiloxane (PHMS) serves as the base polymer, and it can be cured or modified by dehydrocoupling or a combination of hydrosilylation-dehydrocoupling reactions, both catalyzed by transition metal catalysts (Pt and Ru). The base polymer filled with various powders is used primarily for thick ceramic coatings. Modified polymers are used for low-temperature paint-like applications, especially where ambient curing is desirable. Both organic and inorganic modifications of PHMS for coating applications are discussed in this article. Paints containing such polymers and fillers are being evaluated for corrosion resistance and high-temperature applications.
Host-Guest Systems in the Development of Anticorrosive Polymeric Films
Authors: Estevão L. R. M. , Nascimento R. S. V. 
Published: April 2011

ABSTRACTInteractive dispersion-type LDPE/EVA films with anticorrosive properties were produced using host-guest systems of thermally stable volatile corrosion inhibitors (VCI) dicyclohexylammonium p-nitrobenzoate and phosphate, adsorbed on NaY zeolites and diatomaceous earths. Carbon steel specimens were either directly exposed to the inhibiting systems studied or wrapped with the additivated films. Accelerated corrosion tests were carried out where the inhibitive properties of the systems being studied were determined by mass loss of the test coupons. The influence of the mineral support on the volatility of the corrosion inhibitors was evaluated by TG/DTG techniques. The obtained results may be regarded as a confirmation of the hypothesis that VCI volatility may be controlled by their deposition on determined supports. Also, both VCIs had their efficiency enhanced by zeolites, and the phosphate greatly benefited from the use of diatomaceous earth.
Nanoscaled Filled Sol-Gel Hybrid Materials for Powder Coatings
Authors: Seneur S , Dutfurth C. , Muhle J. , Poppe A. , Schmidt H. 
Published: April 2011

ABSTRACTThe sol-gel process has been applied for the synthesis of inorganic-organic powder materials. For this purpose, low reactivity and, for reasons of comparison, nanoscaled sol-gel precursors and nanoscaled silica filler were used to synthesize a low molecular weight inorganic-organic composite which was meltable between 85°C and 100°C and curable at temperatures of 150°C - 200°C. The powders were used for electrostatic coating of aluminum sheets. The resulting coatings of the unfilled system exhibited excellent mechanical properties, e. g. a high abrasion resistance (weight losses between 6 mg and 10 mg per 1000 cycles by taber abrader test (ASTM D1044)) and high values for hardness (universal hardness (DIN 55676): 150 N/mm2). The hardness of the materials was increased up to 210 N/mm2 by the addition of silica, while the abrasion resistance remained unaffected.
High Surface Area Substrates for DNA Arrays
Authors: Glazer M. , Frank C. , Vinci R. P. , Mcgallo G. , Fidanza J. , Beecher J. 
Published: April 2011

ABSTRACTHigh-density, spatially addressable arrays of DNA probes offer a high-throughput approach to DNA sequence analysis that is likely to have a major impact on biological and genetic research. These arrays are comprised of short strands of immobilized DNA (“probe”) sequences prepared synthetically on a planar glass support. Samples of unknown, fluorescentlylabeled strands of “target' DNA can be analyzed by sequence-specific binding (“hybridization”) to the arrays in order to extract detailed sequence information. The detection sensitivity of these arrays is dependent on quantity and density of immobilized probe molecules on the surface, as well as the thermodynamics of nucleic acid hybridization. In this report, substrates with a porous, “3-dimensional” surface layer were investigated as a means of increasing the number of available probes, and therefore the amount of detectable bound target per unit area. Two methods for creating porous silica layers were investigated - a “subtractive” method and an “additive” method. For the systems investigated, the additive method, sol-gel processing, offered the most promising route for high density DNA arrays.
Lowering The Percolation Threshold In Carbon Blackfilled Polymer Composites
Authors: Grujnlan J. C. , Gerberich W. W. , Francis L. F. 
Published: April 2011

ABSTRACTIn an effort to lower the percolation threshold of carbon black-filled polymer composites, various polymer microstructures were examined. Composites prepared with a polyvinyl acetate (PVAc) latex and a poly(vinyl acetate – ethylene) water-dispersible powder showed a significantly lowered percolation threshold relative to an equivalently prepared composite that used a polyvinyl alcohol (PVA) solution to form the matrix phase. The percolation threshold of the dispersion-based composites occurred at 5 vol.% carbon black, while the equivalent solutionbased composite produced a threshold at 14 vol.%. By excluding the carbon black from regions occupied by polymeric particles, the dispersion-based composites lead to preferential aggregation of carbon black, as evidenced by SEM, and a lowered percolation threshold.
Dialkylenecarbonate-Bridged Polysilsesquioxanes: Hybrid Organic-Inorganic Sol-Gels with a Thermally Labile Bridging Group
Authors: Loy Douglas A. , Beach James V. , Baugher Brigitta M. , Assink Roger A. , Shea Kenneth J. , Tran Joseph , Small James H. 
Published: April 2011

ABSTRACTIn this paper, we introduce a new approach for altering the properties of bridged polysilsesquioxane xerogels using post-processing modification of the polymeric network. The bridging organic group contains latent functionalities that can be liberated thermally, photochemically, or by chemical means after the gel has been processed to a xerogel. These modifications can produce changes in density, solubility, porosity, and or chemical properties of the material. Since every monomer possesses two latent functional groups, the technique allows for the introduction of high levels of functionality in hybrid organic-inorganic materials. Dialkylenecarbonate-bridged polysilsesquioxane gels were prepared by the sol-gel polymerization of bis(triethoxysilylpropyl)carbonate (1) and bis(triethoxysilylisobutyl)-carbonate (2). Thermal treatment of the resulting non-porous xerogels and aerogels at 300–350°C resulted in quantitative decarboxylation of the dialkylenecarbonate bridging groups to give new hydroxyalkyl and olefinic substituted polysilsesquioxane monolithic xerogels and aerogels that can not be directly prepared through direct sol-gel polymerization of organotrialkoxysilanes.
A Study on The Phase Transformation and Exchange-Coupling of (Nd0 95La0 05)9 5FebalCo5Nb2B10.5 Nanocomposites
Authors: Chen Q. , Ma B. M. , Lu B. , Huang M. Q. , Laughlin D. E. 
Published: April 2011

ABSTRACTThe phase transformation and the exchange coupling in (Ndo095Lao005)9.5FebaICOsNb 2BI05 have been investigated. Nanocomposites were obtained by treating amorphous precursors at temperatures ranging from 650TC to 9500C for 10 minutes. The magnetic properties were characterized via the vibrating sample magnetometer (VSM). X-ray diffraction (XRD), thermomagnetic analysis (TMA), and transmission electron microscopy (TEM) were used to perform phase identification, measure grain size, and analyze phase distribution. The strength of the exchange coupling between the magnetically hard and soft phases in the corresponding nanocomposite was analyzed via the AM-versus-H plot. It was found that the remanence (Br), coercivity (Hci), and maximum energy product (BHmax) obtained were affected by the magnetic phases present as well as the grain size of constituent phases and their distribution. The optimal magnetic performance, BHm, occurred between 700°C to 750°C, where the crystallization has completed without excessive grain growth. TMA and TEM indicated that the system was composed of three phases at this point, Nd2(Fe Co) 14B, ca-Fe, and Fe3B. The exchange coupling interaction among these phases was consistently described via the AM-versus-H plot up to 750°C. The Br, Hci, and BHmax degraded severely when the thermal treatment temperature increased from 750°C. This degradation may be attributed to the grain growth of the main phases, from 45 to 68nm, and the development of precipitates, which grew from 5nm at 750°C to 12nm at 850°C. Moreover, the amount of the precipitates was found to increase with the thermal treatment temperatures. The precipitates, presumably borides, may cause a decrease in the amount of the a-Fe and Fe 3B and result in a redistribution of the Co in the nanocomposites. The increase of the Co content in the Nd 2(Fe Co) 14B may explain the increase of its Curie temperature with the thermal treatment temperatures. In this paper, we examine the impacts of these factors on the magnetic properties of (Ndo 95Lao 05)9 5FebaICosNb2B10.5 nanocomposite.
Magnetic Domain Observation on Melt-Spun Nd-Fe-B Ribbons Using Magnetic Force Microscopy
Authors: Gavrin A. , Sellers C. , Liouw S.H. 
Published: April 2011

ABSTRACTWe have used Magnetic Force Microscopy (MFM) to study the magnetic domain structures of melt-spun Nd-Fe-B ribbons. The ribbons are commercial products (Magnequench International, Inc. MQP-B and MQP-B+) with a thickness of approximately 20 microns. These materials have identical composition, Nd12.18B5.36Fe76.99Co5.46, but differ in quenching conditions. In order to study the distribution of domain sizes through the ribbon thickness, we have prepared cross-sectional samples in epoxy mounts. In order to avoid artifacts due to tip-sample interactions, we have used high coercivity CoPt coated MFM tips. Our studies show domain sizes typically ranging from 50-200 nm in diameter. This is in agreement with studies of similar materials in which domains were investigated in the plane of the ribbon. We also find that these products differ substantially in mean domain size and in the uniformity of the domain sizes as measured across the ribbon. While the B+ material shows nearly uniform domain sizes throughout the cross section, the B material shows considerably larger domains on one surface, followed by a region in which the domains are smaller than average. This structure is presumably due to the differing quench conditions. The region of coarse domains varies in thickness, disappearing in some areas, and reaching a maximum thickness of 2.75 µm in others. We also describe bulk magnetic measurements, and suggest that.
Applications of Rare-Earth Permanent Magnet Structures to Electrical Machinery
Authors: Leupold H.A. , Tilak A.S. , Marchand R.J. , Lagraffe D.A. 
Published: April 2011

ABSTRACTA variety of promising permanent magnet structures based upon the magic cylinder and magic mangle concepts are investigated with regard to their suitability for application to electrical generators and motors. Such structures feature high magnetic flux densities in large volumes relative to their masses and bulks as well as minimal stray fields and net magnetic moments. Magic mangles also afford small moments of inertia of their rotating elements thereby resulting in improved rotational responsiveness. One computer calculation showed that a small conventional electric generator can be replaced by a magic mangle with 70% more flux amplitude but with only one half the mass and bulk.
Small Brushless Dc-Motor With Sensorless Control - A Hollow Shaft Prototype
Authors: Hanitsch R. , Frenzel B. 
Published: April 2011

ABSTRACTThe features of the prototype with NdFeB-magnets will be presented and also the sensorless control strategy will be outlined. Measured and calculated data show good agreement. Focus will be on the magnetic circuit and the thermal behaviour and not on the control aspects of the motor. Specific parameters demonstrate the good quality of the drive system. A thermal analysis was also done in order to meet the requirements given by the medical specialists.
New series of Sm2TM17magnet materials for applications at temperatures up to 550°C
Authors: Chen Christina H. , Walmer Marlin S. , Walmer Michael H. , Liu Sam , Kuhl G. Edward , Simon Gerard K. 
Published: April 2011

ABSTRACTA new series of Sm(CowFevCuxZry)zmagnet products with1Hcup to 13 kOe at 400°C has been developed. These magnets have low temperature coefficients ofiHcand a straight line B vs. H (extrinsic) demagnetization curve up to 550°C. A straight line extrinsic curve provides greater design flexibility and facilitates reduced size and weight of magnetic circuits. The straight line extrinsic demagnetization B curves are required for magnets used in dynamic applications. The maximum use temperature, defined here as TM, can be determined by finding the maximum temperature at which the B curve is a straight line. The results of this work show that increasing the Co content in the magnet enhances high temperature performance. A higher Co content provides a lower temperature coefficient β ofiHe. Magnets with Co content w = 0.65 have β = 0.26%C from 25°C to 300°C. Magnets with w = 0.82 have β = 0.116%C from 25°C to 300°C. The lower β results in a higher (BH)maxat high temperature, and a higher TM. The TMis 240°C for w = 0.65,330°C for w = 0.68, 400°C for w = 0.76, 490°C for w = 0.78, and 550°C for w = 0.82. By increasing the Co content and adjusting the content of other elements, along with appropriate changes of processing parameters, a new series of magnets has been developed for use at temperatures from 400°C to 550°C. Magnetic properties vs. temperature for the new series of magnets, in comparison to those of the best commercial magnets, are shown in this paper to illustrate the improvements which have been made. Magnetic properties at different temperatures vs. Co content for the series are also reported in this paper.
Hydrogenation Disproportionation Desorption Recombination Processes Applied to NdFeB-, SmFe- and SmCo-Type Alloys
Authors: Gutfleisch O. , Kubis M. , Handstein A. , Müller K.-H. , Schultz L. 
Published: April 2011

ABSTRACTRecent aspects of hydrogenation disproportionation desorption and recombination (HDDR) phenomena in NdFeB-, SmFe- and SmCo-type alloys are reviewed in this paper. The effects of additives on hydrogen sorption and magnetic properties are discussed. The possibilities of producing magnetically anisotropic NdFeB HDDR magnets by hot deformation or alternatively pre-aligning and compacting anisotropic powders are described. Current models for the inducement of magnetic anisotropy in NdFeB HDDR powder are summarized and it is shown that anisotropic powder can be produced from a ternary compound when using a modified processing route. The application of ‘extreme’ hydrogenation conditions, namely high hydrogen pressure or reactive milling in a hydrogen atmosphere at enhanced temperatures, allows the disproportionation of thermodynamically very stable compounds such as Sm2Fe17−xGax(x≥l), SmCo5or Sm2Co17. Reactive milling and subsequent recombination in vacuum lead to structures, of both the disproportionated and the recombined type, which are on a remarkably finer scale than those commonly observed for standard HDDR procedures. Exchange coupling between the nano-scaled grains can result in magnetically single phase behavior despite a multiphase microstructure and in particular for the Sm2Co17alloy, a remanence enhancement was observed after recombination at temperatures ≤700°C.
Magnetization Reversal In Melt-Ouenched NdFeB
Authors: Crew D.C. , Lewis L.H. , Mccormick P.G. , Street R. , Panchanathan V. 
Published: April 2011

ABSTRACTMelt-quenched NdFeB is an important modem permanent magnet material. However there still remains doubt as to the magnetization reversal mechanism which controls coercivity in material prepared by this processing route. To investigate this problem a new technique based on measurements of reversible magnetization along recoil curves has been used. The technique identifies the presence of free domain walls during magnetic reversal. For this study samples of isotropic (MQI), hot pressed (MQII) and die upset (MQIII) melt-quenched NdFeB were examined. The results indicate that in MQI free domain walls are not present during reversal and the reversal mechanism is most likely incoherent rotation of some form. Free domain walls are also not present during reversal in the majority of grains of MQII, even though initial magnetization measurements indicate that the grain size is large enough to support them. In MQIII free domain walls are present during reversal. These results are attributed to the reduced domain wall nucleation field in MQII compared with MQII and the increased dipolar interactions in MQIII.
Interferometry of Optical Second Harmonic Generation from Gd-Containing Langmuir-Blodgett Superstructures: Magneto-Induced Effects
Authors: Vishnevskaya E.I. , Didenko N.V. , Fedyanin A.A. , Khomutov G.B. , Murzina T V. , Nikulin A.A. , Aktsipetrov O.A. 
Published: April 2011

ABSTRACTNonlinear magneto-optical Kerr effect in Gd-containing Langmuir-Blodgett superstructures is studied by second harmonic generation (SHG) interferometry. The intensity of the regular magneto-induced second harmonic (SH) is found to be by a factor of about 2 larger than the intensity of the regular SH component of a non-magnetic origin. The phase shift between the magneto-induced and non-magnetic contributions to the nonlinear polarization is about 46° The intensity of the magnetization-independent hyper-Rayleigh scattering (HRS) is by two orders larger than that of mnagneto-induced HRS.