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Dmitry Yu. Murzin - One of the best experts on this subject based on the ideXlab platform.
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Lactose oxidation over palladium catalysts supported on active Carbons and on Carbon Nanofibres
Research on Chemical Intermediates, 2009Co-Authors: Anton V. Tokarev, Arie J. Plomp, Johannes H. Bitter, Heidi Markus, Elena V. Murzina, Kari Eränen, Päivi Mäki-arvela, Dmitry Yu. MurzinAbstract:Liquid-phase lactose oxidation was investigated over supported Pd/C and Pd-Carbon Nanofibre catalysts, which were characterized by several methods. A complex relationship between catalyst activity and catalyst acidity was established, i.e. optimum catalyst acidity resulted in the highest activity in lactose oxidation. In-situ catalyst potential measurements during lactose oxidation gave information about the extent of accumulation of oxygen on the metal surface. These results could be correlated with catalyst deactivation, which was extensive over the most acidic catalysts at low reaction temperatures. Selectivity for the desired product, lactobionic acid, was a maximum of approximately 83% at 93% conversion. The main side-product was lactulose formed via isomerisation of lactose. Lower selectivity toward lactobionic acid was obtained when the rate of oxidation of lactose was low.
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Influence of Reaction Parameters on the Hydrogenolysis of Hydroxymatairesinol Over Carbon Nanofibre Supported Palladium Catalysts
Catalysis Letters, 2008Co-Authors: Heidi Bernas, Arie J. Plomp, Johannes H. Bitter, Dmitry Yu. MurzinAbstract:The influence of catalyst particle size, stirring rate, catalyst mass (0.2–0.6 g), reaction temperature (60–70 °C), and reactant concentration (1.3–4 mmol/L, with constant reactant/catalyst ratio) on the hydrogenolysis of the lignan hydroxymatairesinol (HMR) to matairesinol (MAT) was studied under hydrogen atmosphere using a Carbon Nanofibre supported palladium catalyst. When the temperature or HMR concentration was increased, the reaction rate increased as expected. However, the reaction rate was inversely dependent on the stirring rate, e.g., was influenced by external mass transfer, which was explained by the fact that the reaction rate decreases at higher hydrogen concentrations.
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dehydrogenation of hydroxymatairesinol to oxomatairesinol over Carbon Nanofibre supported palladium catalysts
Journal of Molecular Catalysis A-chemical, 2007Co-Authors: Heidi Markus, Arie J. Plomp, Johannes H. Bitter, Thomas Sandberg, Ville Nieminen, Dmitry Yu. MurzinAbstract:Abstract Dehydrogenation of the naturally occurring lignan hydroxymatairesinol to oxomatairesinol was performed over Carbon Nanofibre supported palladium catalysts (Pd/CNF) under nitrogen flow at 70 °C. To study the influence of support acidity on the catalyst performance, the amount of acid sites on the catalysts surface was varied by heat-treatment in nitrogen flow. It was concluded that both activity and selectivity to oxomatairesinol increased when the concentration of acid sites increased. The selectivity to oxomatairesinol was over 70% (at 4 h with 50% yield) when 2-propanol was used as solvent and the major by-product was 7-iso-propoxymatairesinol resulting from interactions with the solvent. In 2-pentanol, the selectivity increased to 90% (at 4 h with 50% yield). It was demonstrated that only one of the two diastereomers of hydroxymatairesinol preferentially yields oxomatairesinol. Quantum chemical calculations were performed as an attempt to explain this behaviour and to understand the role of acid sites.
Volker Altstädt - One of the best experts on this subject based on the ideXlab platform.
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Morphology and properties of injection-moulded Carbon-Nanofibre poly(etheretherketone) foams
Journal of Materials Science, 2009Co-Authors: Raquel Verdejo, Volker Altstädt, Philipp Werner, Jan Sandler, M. S. P. ShafferAbstract:Poly(ether ether ketone) (PEEK) is a high performance polymer that cannot usually be foamed reliably using conventional injection-moulding processes. Here, vapour-grown Carbon Nanofibres (CNFs) are introduced to stabilise the foaming process, and the resulting morphology of injection-moulded integral foams is investigated in detail. Different image analysis techniques revealed the positive effect of the nanofiller on the cellular structure. Electron microscopy confirmed a homogeneous dispersion of the Nanofibres in the cellular PEEK cores. The mechanical properties of the foam injection-moulded samples, in bending, showed an increase in yield strength and elastic modulus with Nanofibre loading fractions up to 15 wt%. Although the compressive properties of the foams were reduced as compared to the solid-polymer, the CNFs clearly offset this reduction in properties. Detailed differential scanning calorimetry (DSC) and dynamic mechanical analysis provide further evidence of an interaction between the matrix and the nanoscale filler.
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Carbon Nanofibre‐reinforced ultrahigh molecular weight polyethylene for tribological applications
Journal of Applied Polymer Science, 2007Co-Authors: Mathias C. Galetz, T. Blaβ, Holger Ruckdäschel, Jan Kurt Walter Sandler, Volker Altstädt, Uwe GlatzelAbstract:Carbon Nanofibre (CNF)-reinforced ultrahigh molecular weight polyethylene (UHMWPE) nanocomposites containing up to 10 wt % of Nanofibres were prepared by a novel solvent-assisted extrusion process using short chain oligomers to tailor the melt viscosity of the UHMWPE matrix. A detailed investigation of the resulting nanocomposite microstructure and of the static mechanical properties revealed that the Carbon Nanofibres lead to improved mechanical properties of the UHMWPE related to the wear performance of such systems. Unidirectional sliding tests against a 100Cr6 steel under dry conditions verified the significant potential of dispersed Carbon Nanofibres to reduce the wear rate of this polymer. In light of the promising results, a further optimization of the processing conditions of such UHMWPE nanocomposites is expected to yield interesting future nanocomposite materials even for demanding applications such as artificial knee implants. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4173–4181, 2007
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Carbon Nanofibre reinforced ultrahigh molecular weight polyethylene for tribological applications
Journal of Applied Polymer Science, 2007Co-Authors: Mathias C. Galetz, T. Blaβ, Holger Ruckdäschel, Jan Kurt Walter Sandler, Volker Altstädt, Uwe GlatzelAbstract:Carbon Nanofibre (CNF)-reinforced ultrahigh molecular weight polyethylene (UHMWPE) nanocomposites containing up to 10 wt % of Nanofibres were prepared by a novel solvent-assisted extrusion process using short chain oligomers to tailor the melt viscosity of the UHMWPE matrix. A detailed investigation of the resulting nanocomposite microstructure and of the static mechanical properties revealed that the Carbon Nanofibres lead to improved mechanical properties of the UHMWPE related to the wear performance of such systems. Unidirectional sliding tests against a 100Cr6 steel under dry conditions verified the significant potential of dispersed Carbon Nanofibres to reduce the wear rate of this polymer. In light of the promising results, a further optimization of the processing conditions of such UHMWPE nanocomposites is expected to yield interesting future nanocomposite materials even for demanding applications such as artificial knee implants. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4173–4181, 2007
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Tribological behaviour of Carbon-Nanofibre-reinforced poly(ether ether ketone)
Wear, 2004Co-Authors: Philipp Werner, Jan Kurt Walter Sandler, Volker Altstädt, Milos.p. Shaffer, Romy Jaskulka, Olaf Jacobs, Alan H. WindleAbstract:Abstract The influence of vapour-grown Carbon Nanofibres (CNF), of average diameter 150 nm, on the wear behaviour of semicrystalline poly(ether ether ketone) (PEEK) was investigated. Unidirectional sliding tests against two different counterpart materials (100Cr6 martensitic bearing steel, and X5CrNi18-10 austenitic stainless steel) were performed on injection moulded PEEK-CNF nanocomposites. The specific wear rates of the nanocomposites were measured as a function of filler loading fraction and the results are compared to a variety of commercial PEEK grades. Analysis of the wear behaviour, and examination of the wear surfaces, revealed a variety of effects compared to the control materials. Most importantly, the Carbon Nanofibres were found to reduce the wear rate of PEEK significantly. In the light of these promising results, combinations of Nanofibres with the conventional fillers, polytetrafluoroethylene and/or Carbon fibres, were explored; it was found that such optimised compounds can be used to tailor the wear properties of the PEEK-CNF compounds.
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Carbon-Nanofibre-reinforced poly(ether ether ketone) fibres
Journal of Materials Science, 2003Co-Authors: Jan Kurt Walter Sandler, Volker Altstädt, Alan H. Windle, Philipp Werner, Milos.p. ShafferAbstract:Nano-reinforced fibres were spun from a semicrystalline high-performance poly(ether ether ketone) containing up to 10 wt% vapour-grown Carbon Nanofibres using conventional polymer processing equipment. Mechanical tensile testing revealed increases in nanocomposite stiffness, yield stress, and fracture strength for both as-spun and heat-treated fibres. X-ray and differential scanning calorimetry analyses were performed in order to investigate both the orientation of Nanofibres within the polymer matrix and the matrix morphology. The Carbon Nanofibres were found to be well aligned with the direction of flow during processing. Significantly, the degree of crystallinity of the poly(ether ether ketone) matrix was found to increase with the initial addition of Nanofibres although the crystal structure was not affected. The measured increase in composite tensile modulus is compared to injection-moulded nanocomposite samples made from the same blends. The results highlight the need to characterise the matrix morphology when evaluating nanocomposite performance and hence deducing the intrinsic properties of the nanoscale reinforcement.
William I. Milne - One of the best experts on this subject based on the ideXlab platform.
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Deterministic cold cathode electron emission from Carbon Nanofibre arrays
Scientific Reports, 2014Co-Authors: Matthew T Cole, Pierre Legagneux, Laurent Gangloff, Kenneth B. K. Teo, Oliver Groening, William I. MilneAbstract:The ability to accurately design Carbon Nanofibre (CN) field emitters with predictable electron emission characteristics will enable their use as electron sources in various applications such as microwave amplifiers, electron microscopy, parallel beam electron lithography and advanced Xray sources. Here, highly uniform CN arrays of controlled diameter, pitch and length were fabricated using plasma enhanced chemical vapour deposition and their individual emission characteristics and field enhancement factors were probed using scanning anode field emission mapping. For a pitch of 10 µm and a CN length of 5 µm, the directly measured enhancement factors of individual CNs was 242, which was in excellent agreement with conventional geometry estimates (240). We show here direct empirical evidence that in regular arrays of vertically aligned CNs the overall enhancement factor is reduced when the pitch between emitters is less than half the emitter height, in accordance to our electrostatic simulations. Individual emitters showed narrow Gaussian-like field enhancement distributions, in excellent agreement with electric field simulations.
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In-situ deposition of sparse vertically aligned Carbon Nanofibres on catalytically activated stainless steel mesh for field emission applications
Diamond and Related Materials, 2012Co-Authors: William I. Milne, Matthew T Cole, Kenneth B. K. Teo, Kai Hou, Jamie H. Warner, J. S. Barnard, Kai Ying, Yan ZhangAbstract:Abstract We report on an inexpensive, facile and industry viable Carbon Nanofibre catalyst activation process achieved by exposing stainless steel mesh to an electrolyzed metal etchant. The surface evolution of the catalyst islands combines low-rate electroplating and substrate dissolution. The plasma enhanced chemical vapour deposited Carbon Nanofibres had aspect-ratios > 150 and demonstrated excellent height and crystallographic uniformity with localised coverage. The Nanofibres were well-aligned with spacing consistent with the field emission nearest neighbour electrostatic shielding criteria, without the need of any post-growth processing. Nanofibre inclusion significantly reduced the emission threshold field from 4.5 V/μm (native mesh) to 2.5 V/μm and increased the field enhancement factor to approximately 7000.
Jan Kurt Walter Sandler - One of the best experts on this subject based on the ideXlab platform.
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Carbon Nanofibre‐reinforced ultrahigh molecular weight polyethylene for tribological applications
Journal of Applied Polymer Science, 2007Co-Authors: Mathias C. Galetz, T. Blaβ, Holger Ruckdäschel, Jan Kurt Walter Sandler, Volker Altstädt, Uwe GlatzelAbstract:Carbon Nanofibre (CNF)-reinforced ultrahigh molecular weight polyethylene (UHMWPE) nanocomposites containing up to 10 wt % of Nanofibres were prepared by a novel solvent-assisted extrusion process using short chain oligomers to tailor the melt viscosity of the UHMWPE matrix. A detailed investigation of the resulting nanocomposite microstructure and of the static mechanical properties revealed that the Carbon Nanofibres lead to improved mechanical properties of the UHMWPE related to the wear performance of such systems. Unidirectional sliding tests against a 100Cr6 steel under dry conditions verified the significant potential of dispersed Carbon Nanofibres to reduce the wear rate of this polymer. In light of the promising results, a further optimization of the processing conditions of such UHMWPE nanocomposites is expected to yield interesting future nanocomposite materials even for demanding applications such as artificial knee implants. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4173–4181, 2007
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Carbon Nanofibre reinforced ultrahigh molecular weight polyethylene for tribological applications
Journal of Applied Polymer Science, 2007Co-Authors: Mathias C. Galetz, T. Blaβ, Holger Ruckdäschel, Jan Kurt Walter Sandler, Volker Altstädt, Uwe GlatzelAbstract:Carbon Nanofibre (CNF)-reinforced ultrahigh molecular weight polyethylene (UHMWPE) nanocomposites containing up to 10 wt % of Nanofibres were prepared by a novel solvent-assisted extrusion process using short chain oligomers to tailor the melt viscosity of the UHMWPE matrix. A detailed investigation of the resulting nanocomposite microstructure and of the static mechanical properties revealed that the Carbon Nanofibres lead to improved mechanical properties of the UHMWPE related to the wear performance of such systems. Unidirectional sliding tests against a 100Cr6 steel under dry conditions verified the significant potential of dispersed Carbon Nanofibres to reduce the wear rate of this polymer. In light of the promising results, a further optimization of the processing conditions of such UHMWPE nanocomposites is expected to yield interesting future nanocomposite materials even for demanding applications such as artificial knee implants. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4173–4181, 2007
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Tribological behaviour of Carbon-Nanofibre-reinforced poly(ether ether ketone)
Wear, 2004Co-Authors: Philipp Werner, Jan Kurt Walter Sandler, Volker Altstädt, Milos.p. Shaffer, Romy Jaskulka, Olaf Jacobs, Alan H. WindleAbstract:Abstract The influence of vapour-grown Carbon Nanofibres (CNF), of average diameter 150 nm, on the wear behaviour of semicrystalline poly(ether ether ketone) (PEEK) was investigated. Unidirectional sliding tests against two different counterpart materials (100Cr6 martensitic bearing steel, and X5CrNi18-10 austenitic stainless steel) were performed on injection moulded PEEK-CNF nanocomposites. The specific wear rates of the nanocomposites were measured as a function of filler loading fraction and the results are compared to a variety of commercial PEEK grades. Analysis of the wear behaviour, and examination of the wear surfaces, revealed a variety of effects compared to the control materials. Most importantly, the Carbon Nanofibres were found to reduce the wear rate of PEEK significantly. In the light of these promising results, combinations of Nanofibres with the conventional fillers, polytetrafluoroethylene and/or Carbon fibres, were explored; it was found that such optimised compounds can be used to tailor the wear properties of the PEEK-CNF compounds.
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Carbon-Nanofibre-reinforced poly(ether ether ketone) fibres
Journal of Materials Science, 2003Co-Authors: Jan Kurt Walter Sandler, Volker Altstädt, Alan H. Windle, Philipp Werner, Milos.p. ShafferAbstract:Nano-reinforced fibres were spun from a semicrystalline high-performance poly(ether ether ketone) containing up to 10 wt% vapour-grown Carbon Nanofibres using conventional polymer processing equipment. Mechanical tensile testing revealed increases in nanocomposite stiffness, yield stress, and fracture strength for both as-spun and heat-treated fibres. X-ray and differential scanning calorimetry analyses were performed in order to investigate both the orientation of Nanofibres within the polymer matrix and the matrix morphology. The Carbon Nanofibres were found to be well aligned with the direction of flow during processing. Significantly, the degree of crystallinity of the poly(ether ether ketone) matrix was found to increase with the initial addition of Nanofibres although the crystal structure was not affected. The measured increase in composite tensile modulus is compared to injection-moulded nanocomposite samples made from the same blends. The results highlight the need to characterise the matrix morphology when evaluating nanocomposite performance and hence deducing the intrinsic properties of the nanoscale reinforcement.
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Carbon-Nanofibre-Filled Thermoplastic Composites
MRS Proceedings, 2001Co-Authors: Jan Kurt Walter Sandler, Volker Altstädt, Milos.p. Shaffer, Yeng Ming Lam, Alan H. Windle, Philipp Werner, Jacek Nastalczyk, G. Broza, Karl Schulte, Christian-andre KeunAbstract:Macroscopic poly(ether ether ketone) (PEEK) and polypropylene (PP) nanocomposites containing vapour-grown Carbon Nanofibres (CNF) were produced using standard polymer processing. Tensile tests revealed a linear increase in composite stiffness with Nanofibre content. A detailed DSC study verified that under standard processing conditions the degree of crystallinity and the crystalline structure of these semicrystalline thermoplastics were not affected by the Nanofibres. Nevertheless, we provide evidence that the nanoscale filler can alter the polymer morphology under certain conditions, an effect which needs to be considered when evaluating nanocomposite properties. Given the absence of morphological changes in the standard nanocomposites we were able to calculate the intrinsic Nanofibre modulus using short fibre theory; both distinctively different matrix systems show a similar effective Nanofibre modulus.
Matthew T Cole - One of the best experts on this subject based on the ideXlab platform.
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Deterministic cold cathode electron emission from Carbon Nanofibre arrays
Scientific Reports, 2014Co-Authors: Matthew T Cole, Pierre Legagneux, Laurent Gangloff, Kenneth B. K. Teo, Oliver Groening, William I. MilneAbstract:The ability to accurately design Carbon Nanofibre (CN) field emitters with predictable electron emission characteristics will enable their use as electron sources in various applications such as microwave amplifiers, electron microscopy, parallel beam electron lithography and advanced Xray sources. Here, highly uniform CN arrays of controlled diameter, pitch and length were fabricated using plasma enhanced chemical vapour deposition and their individual emission characteristics and field enhancement factors were probed using scanning anode field emission mapping. For a pitch of 10 µm and a CN length of 5 µm, the directly measured enhancement factors of individual CNs was 242, which was in excellent agreement with conventional geometry estimates (240). We show here direct empirical evidence that in regular arrays of vertically aligned CNs the overall enhancement factor is reduced when the pitch between emitters is less than half the emitter height, in accordance to our electrostatic simulations. Individual emitters showed narrow Gaussian-like field enhancement distributions, in excellent agreement with electric field simulations.
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In-situ deposition of sparse vertically aligned Carbon Nanofibres on catalytically activated stainless steel mesh for field emission applications
Diamond and Related Materials, 2012Co-Authors: William I. Milne, Matthew T Cole, Kenneth B. K. Teo, Kai Hou, Jamie H. Warner, J. S. Barnard, Kai Ying, Yan ZhangAbstract:Abstract We report on an inexpensive, facile and industry viable Carbon Nanofibre catalyst activation process achieved by exposing stainless steel mesh to an electrolyzed metal etchant. The surface evolution of the catalyst islands combines low-rate electroplating and substrate dissolution. The plasma enhanced chemical vapour deposited Carbon Nanofibres had aspect-ratios > 150 and demonstrated excellent height and crystallographic uniformity with localised coverage. The Nanofibres were well-aligned with spacing consistent with the field emission nearest neighbour electrostatic shielding criteria, without the need of any post-growth processing. Nanofibre inclusion significantly reduced the emission threshold field from 4.5 V/μm (native mesh) to 2.5 V/μm and increased the field enhancement factor to approximately 7000.