Articles de revues : « Carbon microfibrils »

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Thomas, Lynne, et Michael Jarvis. « Unravelling the nanostructure of cellulose microfibrils ». Acta Crystallographica Section A Foundations and Advances 70, a1 (5 août 2014) : C1321. http://dx.doi.org/10.1107/s2053273314086781.

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Cellulose is the most abundant naturally occurring polymer and has diverse applications in biology, energy and engineering. The cellulose nanostructure has implications on the mechanical strength of natural materials such as wood and nanocelluloses are also being used to create high-performance composite materials with properties comparable to aramid fibres and carbon nanotubes. The efficiency of breakdown of cellulose into ethanoic alcohols for biofuels is also strongly linked to the aggregation of cellulose fibres into microfibrils. Despite this, the nanostructure of cellulose microfibrils is not well understood. Neutron scattering is a powerful way to distinguish order and disorder in biological fibres, wherever the disordered regions are accessible to deuterium exchange. The aggregation of microfibrils in plant cell walls, coupled to the benefits of deuterium exchange and increased scattering contrast using neutrons gives rise to a small-angle Bragg reflection allowing the size of microfibrils to be deduced. Applying these measurements with a range of spectroscopic techniques and wide-angle X-ray and neutron scattering (WAXS, WANS) has enabled us to develop a model for the structure for the microfibrils of cellulose microfibrils in a range of plant species. The scattering data were consistent with 3nm fibrils with both hydrophobic and hydrophilic surfaces exposed. Disorder in chain packing and hydrogen bonding were shown to increase outwards from the microfibril centre. Axial disorder could be explained in terms of twisting of the microfibrils, with implications for their biosynthesis. The disorder aspects of these microfibrils are directly related to the mechanical strength of wood and the natural variation in microfibril angle reflects this. We will present the outcome of in-situ stretching measurements of cellulose microfibrils with insights into the mechanism of the absorption of strain to further probe this mechanical strength.

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Festucci-Buselli, Reginaldo A., Wagner C. Otoni et Chandrashekhar P. Joshi. « Structure, organization, and functions of cellulose synthase complexes in higher plants ». Brazilian Journal of Plant Physiology 19, n^o 1 (mars 2007) : 1–13. http://dx.doi.org/10.1590/s1677-04202007000100001.

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Annually, plants produce about 180 billion tons of cellulose making it the largest reservoir of organic carbon on Earth. Cellulose is a linear homopolymer of beta(1-4)-linked glucose residues. The coordinated synthesis of glucose chains is orchestrated by specific plasma membrane-bound cellulose synthase complexes (CelS). The CelS is postulated to be composed of approximately 36 cellulose synthase (CESA) subunits. The CelS synthesizes 36 glucose chains in close proximity before they are further organized into microfibrils that are further associated with other cell wall polymers. The 36 glucose chains in a microfibril are stabilized by intra- and inter-hydrogen bonding which confer great stability on microfibrils. Several elementary microfibrils come together to form macrofibrils. Many CESA isoforms appear to be involved in the cellulose biosynthetic process and at least three types of CESA isoforms appear to be necessary for the functional organization of CelS in higher plants.

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LIN, R. J. T., D. BHATTACHARYYA et S. FAKIROV. « INNOVATIVE MANUFACTURING OF CARBON NANOTUBE-LOADED FIBRILLAR POLYMER COMPOSITES ». International Journal of Modern Physics B 24, n^o 15n16 (30 juin 2010) : 2459–65. http://dx.doi.org/10.1142/s021797921006509x.

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The concept of microfibrillar composite (MFC) has been used to create a new type of polymer composites, in which the reinforcing microfibrils are loaded with carbon nanotubes (CNT). Polyamide 66 (PA66) has been melt blended with polypropylene in a twin screw extruder with and without CNT, and thereafter cold drawn to create a fibrillar state as well as to align the CNT in the PA66 microfibrils. The drawn bristles were compression moulded at 180°C to prepare MFC plates. The scanning electron microscope (SEM) observations indicate near perfect distribution of CNT in the reinforcing PA66 microfibrils. Although the fibrillated PA66 is able to improve the tensile stiffness and strength as expected from the MFC structure, the incorporation of CNT does not exhibit any further enhancing effect. It rather adversely affects the mechanical properties due to poor interface adhesion between the matrix and the reinforcing microfibrils with the presence of CNT, as demonstrated by SEM. However, the resulting highly aligned CNT within the MFC are expected to affect the physical and functional properties of these composites.

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Wang, Yu, Song Liu, Huihao Zhu, Huajian Ji, Guo Li, Zhou Wan, Yulu Ma et Linsheng Xie. « The Entangled Conductive Structure of CB/PA6/PP MFCs and Their Electromechanical Properties ». Polymers 13, n^o 6 (21 mars 2021) : 961. http://dx.doi.org/10.3390/polym13060961.

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In this work, carbon black (CB)/polyamide 6 (PA6)/polypropylene (PP) microfibrillar composites (MFCs) were fabricated through an extrusion (hot stretching) heat treatment process. The CB-coated conductive PA6 microfibrils with high aspect ratio were in situ generated as a result of the selective accumulation of CB at the interface. At the proper temperature, a 3D entangled conductive structure was constructed in the PP matrix, due to topological entanglement between these conductive microfibrils. This unique conductive structure provided the PP composites with a low electrical conductivity percolation threshold. Moreover, the electromechanical properties of conductive MFCs were investigated for the first time. A great stability, a high sensitivity and a nice reproducibility were achieved simultaneously for CB/PA6/PP MFCs. This work provides a universal and low-cost method for the conductive polymer composites’ (CPCs) fabrication as sensing materials.

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Zheng, Yunzhen, Daniel J. Cosgrove et Gang Ning. « High-Resolution Field Emission Scanning Electron Microscopy (FESEM) Imaging of Cellulose Microfibril Organization in Plant Primary Cell Walls ». Microscopy and Microanalysis 23, n^o 5 (24 août 2017) : 1048–54. http://dx.doi.org/10.1017/s143192761701251x.

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AbstractWe have used field emission scanning electron microscopy (FESEM) to study the high-resolution organization of cellulose microfibrils in onion epidermal cell walls. We frequently found that conventional “rule of thumb” conditions for imaging of biological samples did not yield high-resolution images of cellulose organization and often resulted in artifacts or distortions of cell wall structure. Here we detail our method of one-step fixation and dehydration with 100% ethanol, followed by critical point drying, ultrathin iridium (Ir) sputter coating (3 s), and FESEM imaging at a moderate accelerating voltage (10 kV) with an In-lens detector. We compare results obtained with our improved protocol with images obtained with samples processed by conventional aldehyde fixation, graded dehydration, sputter coating with Au, Au/Pd, or carbon, and low-voltage FESEM imaging. The results demonstrated that our protocol is simpler, causes little artifact, and is more suitable for high-resolution imaging of cell wall cellulose microfibrils whereas such imaging is very challenging by conventional methods.

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Chen, Qian-ying, Jing Gao, Kun Dai, Huan Pang, Jia-zhuang Xu, Jian-hua Tang et Zhong-ming Li. « Nonlinear current-voltage characteristics of conductive polyethylene composites with carbon black filled pet microfibrils ». Chinese Journal of Polymer Science 31, n^o 2 (30 octobre 2012) : 211–17. http://dx.doi.org/10.1007/s10118-013-1203-1.

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Sun, Hui, Haijuan Kong, Haiquan Ding, Qian Xu, Juan Zeng, Feiyan Jiang, Muhuo Yu et Youfeng Zhang. « Improving UV Resistance of Aramid Fibers by Simultaneously Synthesizing TiO2 on Their Surfaces and in the Interfaces Between Fibrils/Microfibrils Using Supercritical Carbon Dioxide ». Polymers 12, n^o 1 (7 janvier 2020) : 147. http://dx.doi.org/10.3390/polym12010147.

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Aramid fibers with low density and high strength, modulus, and thermal resistance are widely used in applications such as bulletproof vests and cables. However, owing to their chemical structure, they are sensitive to ultraviolet light, which degrades the fibers’ useful mechanical properties. In this study, titanium dioxide (TiO2) nanoparticles were synthesized both on the aramid III fiber surface and in the interfacial space between the fibrils/microfibrils in supercritical carbon dioxide (scCO2) to improve the UV resistance of aramid fibers. The effects of scCO2 treatment pressure on the TiO2 structure, morphology, surface composition, thermal stability, photostability, and mechanical properties were investigated using Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, ultraviolet–visible spectroscopy, and single-fiber test. The results show that amorphous TiO2 formed on the fiber surface and the interface between fibrils/microfibrils, and decreased the photodegradation rate of the aramid III fiber. Moreover, this modification can also improve the tensile strength via treatment at low temperature and without the use of a solvent. The simple synthesis process in scCO2, which is scalable, is used for mild modifications with a green solvent, providing a promising technique for synthesizing metal dioxide on polymers.

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Ruben, George C., et Gordon H. Bokelman. « Freeze-dried and platinum-carbon replicated 35Å cellulose microfibrils are triple-stranded and left-hand twisted ». Proceedings, annual meeting, Electron Microscopy Society of America 44 (août 1986) : 58–61. http://dx.doi.org/10.1017/s0424820100142013.

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To contrast enhance unidirectional (45° angle) 15-18Å thick Pt/C coated cellulose specimens backed with 100-173Å thick carbon films, micrographs were contrast reversed on Kodak 7302 fine grain positive film. In addition to increasing the contrast of 10-20Å features, the Pt/C coated surfaces are now white and the molecular details are modulated on this background in blacks and shades of grey for easy structural interpretation. By shooting a tilt series at 10° intervals at 105X on a JEM 100CX at 80KV with a 5mm focal length and a 40μ objective aperture, a 6.6Å resolution and a 2710Å depth of field are achieved in the picture series. The tilt series is generally visualized stereoscopically and then a single image representing the correct 3-D structure is shown.

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Carvelli, Valter, Toru Fujii et Kazuya Okubo. « The effect of microfibrils cellulose modified epoxy on the quasi-static and fatigue behaviour of open hole carbon textile composites ». Journal of Composite Materials 52, n^o 24 (19 mars 2018) : 3365–80. http://dx.doi.org/10.1177/0021998318765623.

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The extensive experimental investigation aimed to assess the effects of hybrid epoxy resin with micro-fibrillated cellulose on tensile quasi-static and fatigue behaviour of open hole carbon plain weave composites. The hybridization of the matrix allowed an improved damage tolerance of the composite leading to increase of the quasi-static tensile strength and extension of the fatigue life. The enhanced mechanical performance of the notched composites was connected to the bridging effect of cellulose microfibrils preventing or delaying the cracks propagation in the matrix and along the fibres interface. The better distribution of the stress state was assessed by digital image correlation strain maps around the hole and the imparted fatigue damage was analysed by scanning electron microscope and X-ray micro-computed tomography visualizations.

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Carvelli, Valter, Andrea Betti et Toru Fujii. « Fatigue and Izod impact performance of carbon plain weave textile reinforced epoxy modified with cellulose microfibrils and rubber nanoparticles ». Composites Part A : Applied Science and Manufacturing 84 (mai 2016) : 26–35. http://dx.doi.org/10.1016/j.compositesa.2016.01.005.

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Fakirov, Stoyko, M. Zillur Rahman, Petra Pötschke et Debes Bhattacharyya. « Single Polymer Composites of Poly(Butylene Terephthalate) Microfibrils Loaded with Carbon Nanotubes Exhibiting Electrical Conductivity and Improved Mechanical Properties ». Macromolecular Materials and Engineering 299, n^o 7 (16 décembre 2013) : 799–806. http://dx.doi.org/10.1002/mame.201300322.

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Chen, Meiling, Chengguo Wang, Quan Gao, Yanxiang Wang, Min Jing et Wenli Wang. « Research on the multi-scale microstructure of polyacrylonitrile precursors prepared by a dry-jet wet spinning process ». High Performance Polymers 31, n^o 6 (19 juin 2018) : 662–70. http://dx.doi.org/10.1177/0954008318782731.

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An understanding of the properties of polyacrylonitrile (PAN) precursors is an essential precondition for manufacturing high-performance carbon fibres, and the structure of the precursors has a direct and profound effect on the performance of carbon fibres. In this study, PAN precursors, formed in a multistage coagulation bath, were spun by a dry-jet wet spinning process, and the multi-scale microstructure and morphology of the precursors were investigated by separating the fibrils from the precursors. Scanning electron microscopy and high-resolution transmission electron microscopy were employed to examine the surface morphology, cross-sectional morphology and microstructure of the precursors. X-ray diffraction was used to characterize the crystal structure. The micropore sizes of the precursors were determined with nitrogen adsorption experiments; the adsorption increased after ultrasonic etching and decreased with an increase in the treated concentration. All the results demonstrated that the PAN precursors had a multi-scale microstructure, the precursors consisted of fibrils with diameters of 80–200 nm and the fibrils consisted of some microfibrils with diameters of 20–40 nm, including the periodic tissues with thicknesses of 16–30 nm perpendicular to the fibre axis.

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Razaina, Mat Taib, Dody Ariawan et Zainal Arifin Mohd Ishak. « Surface Characterization of Alkali Treated Kenaf Fibers by XPS and AFM ». Key Engineering Materials 694 (mai 2016) : 29–33. http://dx.doi.org/10.4028/www.scientific.net/kem.694.29.

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Kenaf fibers were immersed in 6% solution of sodium hydroxide (NaOH) for 1, 2, 3, 4 and 5 hours. The treated fibers were characterized with X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The XPS results showed that the alkali treatment increased the proportion of oxygen atoms on the fiber surface as indicated by the increase in oxygen-carbon ratio. An increase in C2 peak (C-OH bonds) was also observed suggesting the present of cellulose on the fiber surface. The decrease in C1 peak (C-C bonds) suggested that lignin was removed from the fiber surface following the alkali treatment. Scale-like structures were observed from the AFM topographic images to indicate the presence of cellulose microfibrils in the primary cell wall of the treated fiber. Alkali treated fiber surface showed lower mean surface roughness than the untreated fiber indicating smoother fiber surface. The fiber surface became relatively smooth after the alkali treatment due to the removal of non-cellulosic layer.

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Wang, Shan-Shan, Yong-He Han, Jia-Lian Chen, Da-Chun Zhang, Xiao-Xia Shi, Yu-Xuan Ye, Deng-Long Chen et Min Li. « Insights into Bacterial Cellulose Biosynthesis from Different Carbon Sources and the Associated Biochemical Transformation Pathways in Komagataeibacter sp. W1 ». Polymers 10, n^o 9 (31 août 2018) : 963. http://dx.doi.org/10.3390/polym10090963.

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Cellulose is the most abundant and widely used biopolymer on earth and can be produced by both plants and micro-organisms. Among bacterial cellulose (BC)-producing bacteria, the strains in genus Komagataeibacter have attracted wide attention due to their particular ability in furthering BC production. Our previous study reported a new strain of genus Komagataeibacter from a vinegar factory. To evaluate its capacity for BC production from different carbon sources, the present study subjected the strain to media spiked with 2% acetate, ethanol, fructose, glucose, lactose, mannitol or sucrose. Then the BC productivity, BC characteristics and biochemical transformation pathways of various carbon sources were fully investigated. After 14 days of incubation, strain W1 produced 0.040–1.529 g L−1 BC, the highest yield being observed in fructose. Unlike BC yields, the morphology and microfibrils of BCs from different carbon sources were similar, with an average diameter of 35–50 nm. X-ray diffraction analysis showed that all membranes produced from various carbon sources had 1–3 typical diffraction peaks, and the highest crystallinity (i.e., 90%) was found for BC produced from mannitol. Similarly, several typical spectra bands obtained by Fourier transform infrared spectroscopy were similar for the BCs produced from different carbon sources, as was the Iα fraction. The genome annotation and Kyoto Encyclopedia of Genes and Genomes analysis revealed that the biochemical transformation pathways associated with the utilization of and BC production from fructose, glucose, glycerol, and mannitol were found in strain W1, but this was not the case for other carbon sources. Our data provides suggestions for further investigations of strain W1 to produce BC by using low molecular weight sugars and gives clues to understand how this strain produces BC based on metabolic pathway analysis.

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Xu, Xiang-Bin, Zhong-Ming Li, Ming-Bo Yang, Shu Jiang et Rui Huang. « The role of the surface microstructure of the microfibrils in an electrically conductive microfibrillar carbon black/poly(ethylene terephthalate)/polyethylene composite ». Carbon 43, n^o 7 (juin 2005) : 1479–87. http://dx.doi.org/10.1016/j.carbon.2005.01.039.

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Di Giacomo, Raffaele, Chiara Daraio et Bruno Maresca. « Plant nanobionic materials with a giant temperature response mediated by pectin-Ca2+ ». Proceedings of the National Academy of Sciences 112, n^o 15 (30 mars 2015) : 4541–45. http://dx.doi.org/10.1073/pnas.1421020112.

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Conventional approaches to create biomaterials rely on reverse engineering of biological structures, on biomimicking, and on bioinspiration. Plant nanobionics is a recent approach to engineer new materials combining plant organelles with synthetic nanoparticles to enhance, for example, photosynthesis. Biological structures often outperform man-made materials. For example, higher plants sense temperature changes with high responsivity. However, these properties do not persist after cell death. Here, we permanently stabilize the temperature response of isolated plant cells adding carbon nanotubes (CNTs). Interconnecting cells, we create materials with an effective temperature coefficient of electrical resistance (TCR) of −1,730% K−1, ∼2 orders of magnitude higher than the best available sensors. This extreme temperature response is due to metal ions contained in the egg-box structure of the pectin backbone, lodged between cellulose microfibrils. The presence of a network of CNTs stabilizes the response of cells at high temperatures without decreasing the activation energy of the material. CNTs also increase the background conductivity, making these materials suitable elements for thermal and distance sensors.

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Pinto, Fátima, Ana Filipa Lourenço, Jorge F. S. Pedrosa, Lídia Gonçalves, Célia Ventura, Nádia Vital, Ana Bettencourt et al. « Analysis of the In Vitro Toxicity of Nanocelluloses in Human Lung Cells as Compared to Multi-Walled Carbon Nanotubes ». Nanomaterials 12, n^o 9 (22 avril 2022) : 1432. http://dx.doi.org/10.3390/nano12091432.

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Cellulose micro/nanomaterials (CMNM), comprising cellulose microfibrils (CMF), nanofibrils (CNF), and nanocrystals (CNC), are being recognized as promising bio-nanomaterials due to their natural and renewable source, attractive properties, and potential for applications with industrial and economical value. Thus, it is crucial to investigate their potential toxicity before starting their production at a larger scale. The present study aimed at evaluating the cell internalization and in vitro cytotoxicity and genotoxicity of CMNM as compared to two multi-walled carbon nanotubes (MWCNT), NM-401 and NM-402, in A549 cells. The exposure to all studied NM, with the exception of CNC, resulted in evident cellular uptake, as analyzed by transmission electron microscopy. However, none of the CMNM induced cytotoxic effects, in contrast to the cytotoxicity observed for the MWCNT. Furthermore, no genotoxicity was observed for CNF, CNC, and NM-402 (cytokinesis-block micronucleus assay), while CMF and NM-401 were able to significantly raise micronucleus frequency. Only NM-402 was able to induce ROS formation, although it did not induce micronuclei. Thus, it is unlikely that the observed CMF and NM-401 genotoxicity is mediated by oxidative DNA damage. More studies targeting other genotoxicity endpoints and cellular and molecular events are underway to allow for a more comprehensive safety assessment of these nanocelluloses.

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Xu, Xiang-Bin, Zhong-Ming Li, Kun Dai et Ming-Bo Yang. « Anomalous attenuation of the positive temperature coefficient of resistivity in a carbon-black-filled polymer composite with electrically conductive in situ microfibrils ». Applied Physics Letters 89, n^o 3 (17 juillet 2006) : 032105. http://dx.doi.org/10.1063/1.2222339.

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Westbye, Peter, Christer Svanberg et Paul Gatenholm. « The effect of molecular composition of xylan extracted from birch on its assembly onto bleached softwood kraft pulp ». Holzforschung 60, n^o 2 (1 mars 2006) : 143–48. http://dx.doi.org/10.1515/hf.2006.023.

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Abstract The effect of the molecular structure of xylan on its assembly onto softwood kraft pulps was investigated. Various xylan-rich fractions were isolated from birch wood chips by different mild treatments using water (H2O), acetic acid (HAc) and sulfur dioxide (SO2). The isolation involved prehydrolysis followed by alkaline extraction, with only the time, temperature and medium in the prehydrolysis step varied. After separation, the fractions were neutralised (pH 7) and some material agglomerated and became insoluble. Dynamic light scattering measurements revealed differences in aggregate size among the different fractions. The fractions that agglomerated to the greatest extent contained less glucuronic acid and a higher amount of lignin. Such fractions adsorbed to a significantly higher extent (25.5% compared to 5.0% for the lowest soluble fraction) onto bleached softwood kraft pulps in experiments performed in autoclaves. The adsorption was carried out with fixed process parameters (100°C, pH 10, 120 min). The adsorption of various xylan fractions resulted in different surface morphology on cellulose microfibrils, as observed by AFM. Pulps treated with xylans that were soluble at pH 7 showed small differences from the control sample, which was treated in an autoclave without the addition of xylan. Pulps treated with xylans that agglomerated at pH 7 showed a greater difference in the amount of nanosized aggregates covering the surface. ESCA analysis of the chemical surface composition indicated that samples containing more lignin showed a greater shift towards carbon-carbon bonds. A novel sequence for a pulping process is suggested.

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Adnan, Azila, Giridhar Nair, Mark Lay et Janis Swan. « Bacterial Cellulose Synthesis by Gluconacetobacter xylinus : Enhancement via Fed-batch Fermentation Strategies in Glycerol Media ». Trends in Sciences 18, n^o 22 (31 octobre 2021) : 453. http://dx.doi.org/10.48048/tis.2021.453.

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Bacterial cellulose (BC) is an abundant polysaccharide, which is secreted by several genera of bacteria. It has remarkable characteristics, which include high purity, high tensile strength, high biocompatibility and non-toxic. The main feature that differentiates BC and plant cellulose (PC) is the absence of contaminants such as lignin, hemicellulose and pectin. However, the main drawbacks in producing BC are low yield and expensive carbon source. Due to that, this study was carried out to enhance BC volumetric productivity in fed-batch operation mode using glycerol as a carbon source. BC was produced in fill-and-draw and pulse-feed fed-batch cultures of Gluconacetobacter xylinus DSM 46604 in a 3-L bench-top bioreactor. The fed-batch fermentation trials were conducted in agitated and aerobic conditions at 30 ºC. For fill-and-draw fed-batch culture, a total of 24.2 g/L of BC accumulated in the bioreactor after 9 days, which corresponded to a yield and productivity of 0.2 g/g and 2.69 g/L/day, respectively. Pulse-feed fed-batch fermentation resulted in a yield and volumetric productivity of 0.38 g/g and 2.71 g/L/day, respectively. The pulse-feed fed-batch culture proved to be a better fermentation system for utilizing glycerol, which is a low-cost and abundant carbon source. HIGHLIGHTS Komagataeibacter species, which were formerly known as Acetobacter or Gluconacetobacter is one of the Gram-negative BC producers that secretes a large quantity of BC microfibrils extracellularly One of the main challenges in bacterial cellulose (BC) production is low productivity and high processing cost As fed-batch fermentation is one of the operation modes in bioprocess that can control the microbial growth rate, this operation mode is conducted to enhance the yield of BC, substrate consumption and also volumetric productivity Fill-and-draw and pulse feed fed-batch culture were conducted to enhance yield and volumetric productivity. The pulse-feed fed-batch culture resulted to be a favorable operation mode for utilizing glycerol, which is a low-cost and abundant carbon source GRAPHICAL ABSTRACT

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Sulaeman, Allyn P., Yang Gao, Tom Dugmore, Javier Remón et Avtar S. Matharu. « From unavoidable food waste to advanced biomaterials : microfibrilated lignocellulose production by microwave-assisted hydrothermal treatment of cassava peel and almond hull ». Cellulose 28, n^o 12 (28 juin 2021) : 7687–705. http://dx.doi.org/10.1007/s10570-021-03986-5.

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AbstractLignocellulose based nanomaterials are emerging green biosolids commonly obtained from wood pulp. Alternative feedstocks, such as as unavoidable food waste, are interesting resources for nano/microfibers. This research reports the production and characterization of microfibrillated lignocellulose (MFLC) from cassava peel (CP) and almond hull (AH) via acid-free microwave-assisted hydrothermal treatment (MHT) at different temperatures (120–220 °C). During processing, the structural changes were tracked by ATR-IR, TGA, XRD, 13C CPMAS NMR, zeta potential, HPLC, elemental analysis (CHN; carbon, hydrogen and nitrogen), TEM and SEM analyses. The microwave processing temperature and nature of feedstock exerted a significant influence on the yields and properties of the MFLCs produced. The MFLC yields from CP and AH shifted by 15–49% and 31–73%, respectively. Increasing the MHT temperature substantially affected the crystallinity index (13–66% for CP and 36–62% for AH) and thermal stability (300–374 °C for CP and 300–364 °C for AH) of the MFLCs produced. This suggested that the MFLC from CP is more fragile and brittle than that produced from AH. These phenomena influenced the gelation capabilities of the fibers. AH MFLC pretreated with ethanol at low temperature gave better film-forming capabilities, while untreated and heptane pretreated materials formed stable hydrogels at solid concentration (2% w/v). At high processing temperatures, the microfibrils were separated into elementary fibers, regardless of pretreatment or feedstock type. Given these data, this work demonstrates that the acid-free MHT processing of CP and AH is a facile method for producing MFLC with potential applications, including adsorption, packaging and the production of nanocomposites and personal care rheology modifiers. Graphic abstract

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Missagia, Zélia Maria Velloso, Júlio Cesar dos Santos, Leandro José da Silva, Túlio Hallak Panzera, Juan Carlos Campos Rubio et Carlos Thomas. « Assessment of compacted-cementitious composites as porous restrictors for aerostatic bearings ». Proceedings of the Institution of Mechanical Engineers, Part L : Journal of Materials : Design and Applications 234, n^o 1 (12 septembre 2019) : 76–89. http://dx.doi.org/10.1177/1464420719874434.

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Cementitious composites reinforced with silica, silicon carbide or carbon microfibres are designed, manufactured, characterised and tested as porous restrictor for aerostatic bearings. Carbon microfibres are residues obtained from the cutting process of carbon fibre-reinforced polymers. Porosity, permeability, flexural strength and stiffness are quite relevant in the design of aerostatic porous bearings. A 3141 full factorial design is carried out to identify the effects of particle inclusion and water-to-cement ratio(w/c) factors on the physical and mechanical properties of cementitious composites. Higher density material is achieved by adding silicon carbide. Higher porosity is obtained at 0.28 w/c level when silica and silicon carbide are used. Carbon microfibres are not effective under bending loads. Higher compressive strength is reached especially when silica particles are combined with 0.33 or 0.35 w/c. According to the permeability coefficient values the cementitious composites consisted of CMF (0.28 w/c), silica (0.30 w/c) or silicon carbide (0.30 w/c) inclusions are promising as porous restrictor; however, carbon microfibre porous bearings achieved the lowest air gap variation under the tested working conditions.

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Zhang, Huiping, Lianlian Gao et Xijun Hu. « Preparation of microfibrous entrapped activated carbon composite ». Separation and Purification Technology 67, n^o 2 (juin 2009) : 149–51. http://dx.doi.org/10.1016/j.seppur.2009.03.023.

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Krasnikova, Irina V., Ilya V. Mishakov, Aleksey A. Vedyagin, Yury I. Bauman et Denis V. Korneev. « Surface modification of microfibrous materials with nanostructured carbon ». Materials Chemistry and Physics 186 (janvier 2017) : 220–27. http://dx.doi.org/10.1016/j.matchemphys.2016.10.047.

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Xu, Wei, Lei Xia, Xing‐hai Zhou, Peng Xi, Bo‐wen Cheng et Yu‐xia Liang. « Hollow carbon microfibres fabricated using coaxial centrifugal spinning ». Micro & ; Nano Letters 11, n^o 2 (février 2016) : 74–76. http://dx.doi.org/10.1049/mnl.2015.0346.

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Karwa, Amogh N., Virginia A. Davis et Bruce J. Tatarchuk. « Carbon Nanofiber Synthesis within 3-Dimensional Sintered Nickel Microfibrous Matrices : Optimization of Synthesis Conditions ». Journal of Nanotechnology 2012 (2012) : 1–14. http://dx.doi.org/10.1155/2012/396269.

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This study focuses on the process of optimization for carbon nanofiber synthesis at the exterior and the interior of 3-dimensional sintered nickel microfibrous networks. Synthesis of carbon nanofibers (CNF) by catalytic decomposition of acetylene (ethyne) was conducted at atmospheric pressure and short reaction times (10 min). Two factors evaluated during the study were (a) CNF quality (observed by SEM and Raman spectroscopy) and (b) rate of reaction (gravimetrically measured carbon yield). Independent optimization variables included redox faceting pretreatment of nickel, synthesis temperature, and gas composition. Faceting resulted in an 8-fold increase in the carbon yield compared to an untreated substrate. Synthesis with varying levels of hydrogen maximized the carbon yield (9.31 mg C/cm2catalyst). The quality of CNF was enhanced via a reduction in amorphous carbon that resulted from the addition of 20% ammonia. Optimized growth conditions that led to high rates of CNF deposition preferentially deposited this carbon at the exterior layer of the nickel microfibrous networks (570°C, 78% H2, 20% NH3, 2% C2H2, faceted Ni.). CNF growth within the 3-dimensional nickel networks was accomplished at the conditions selected to lower the gravimetric reaction rate (470°C, 10% H2, 88% N2, 2% C2H2, nonfaceted Ni).

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Bordjiba, Tarik, Mohamed Mohamedi, Lê H. Dao, Brahim Aissa et My Ali El Khakani. « Enhanced physical and electrochemical properties of nanostructured carbon nanotubes coated microfibrous carbon paper ». Chemical Physics Letters 441, n^o 1-3 (juin 2007) : 88–93. http://dx.doi.org/10.1016/j.cplett.2007.04.072.

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Czarnecki, Jarema S., Simon Jolivet, Mary E. Blackmore, Khalid Lafdi et Panagiotis A. Tsonis. « Cellular Automata Simulation of Osteoblast Growth on Microfibrous-Carbon-Based Scaffolds ». Tissue Engineering Part A 20, n^o 23-24 (décembre 2014) : 3176–88. http://dx.doi.org/10.1089/ten.tea.2013.0387.

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Lu, Hailong, Lili Zhang, Jinxia Ma, Nur Alam, Xiaofan Zhou et Yonghao Ni. « Nano-Cellulose/MOF Derived Carbon Doped CuO/Fe3O4 Nanocomposite as High Efficient Catalyst for Organic Pollutant Remedy ». Nanomaterials 9, n^o 2 (16 février 2019) : 277. http://dx.doi.org/10.3390/nano9020277.

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Metal–organic framework (MOF)-based derivatives are attracting increased interest in various research fields. In this study, nano-cellulose MOF-derived carbon-doped CuO/Fe3O4 nanocomposites were successfully synthesized via direct calcination of magnetic Cu-BTC MOF (HKUST-1)/Fe3O4/cellulose microfibril (CMF) composites in air. The morphology, structure, and porous properties of carbon-doped CuO/Fe3O4 nanocomposites were characterized using SEM, TEM, powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), and vibrating sample magnetometry (VSM). The results show that the as-prepared nanocomposite catalyst is composed of Fe3O4, CuO, and carbon. Compared to the CuO/Fe3O4 catalyst from HKUST-1/Fe3O4 composite and CuO from HKUST-1, this carbon-doped CuO/Fe3O4 nanocomposite catalyst shows better catalytic efficiency in reduction reactions of 4-nitrophenol (4-NP), methylene blue (MB), and methyl orange (MO) in the presence of NaBH4. The enhanced catalytic performance of carbon-doped CuO/Fe3O4 is attributed to effects of carbon preventing the aggregation of CuO/Fe3O4 and providing high surface-to-volume ratio and chemical stability. Moreover, this nanocomposite catalyst is readily recoverable using an external magnet due to its superparamagnetic behavior. The recyclability/reuse of carbon-doped CuO/Fe3O4 was also investigated.

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Liu, Jian, Ying Yan et Huiping Zhang. « Adsorption dynamics of toluene in composite bed with microfibrous entrapped activated carbon ». Chemical Engineering Journal 173, n^o 2 (septembre 2011) : 456–62. http://dx.doi.org/10.1016/j.cej.2011.08.004.

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Fabia, Janusz, Jarosław Janicki, Czesław Ślusarczyk, Monika Rom, Tadeusz Graczyk et Andrzej Gawłowski. « Study of Structure of Polypropylene Microfibres Modified with Multi-Walled Carbon Nanotubes ». Fibres and Textiles in Eastern Europe 23, n^o 3(111) (30 avril 2015) : 38–44. http://dx.doi.org/10.5604/12303666.1151773.

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Smirnov, Maksim M., et Andrey R. Korabelnikov. « OBTAINING COMPOSITE FIBROUS MATERIALS BY ELECTROSPINNING FROM SOLUTIONS OF POLYMETHYL METHACRYLATE WITH THE ADDITION OF CARBON NANOTUBES ». Technologies & ; Quality 52, n^o 2 (2 juillet 2021) : 56–61. http://dx.doi.org/10.34216/2587-6147-2021-2-52-56-61.

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The article is devoted to the research and testing of a method for producing nonwoven material from nano- and microfibres saturated with carbon nanotubes by the method of electrospinning, the study of the effect of ultrasonic treatment of a polymer solution and the addition of carbon nanotubes on the properties of the solution and the morphology of the resulting material. As a result of the study, samples of materials were obtained from solutions of polymethylmethacrylate, treated and not treated with ultrasound, organoleptic and microscopic studies of the obtained samples were carried out. A decrease in the viscosity of a polymer solution treated with ultrasound and a significant decrease in the diameter of fibres obtained from such solutions were found.

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Liu, Jian, Ying Yan et Huiping Zhang. « Preparation of Microfibrous Entrapped Activated Carbon Composites and its Application for Benzene Adsorption ». Separation Science and Technology 49, n^o 13 (25 août 2014) : 2016–24. http://dx.doi.org/10.1080/01496395.2014.907318.

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Karwa, Amogh N., et Bruce J. Tatarchuk. « Aerosol filtration enhancement using carbon nanostructures synthesized within a sintered nickel microfibrous matrix ». Separation and Purification Technology 87 (mars 2012) : 84–94. http://dx.doi.org/10.1016/j.seppur.2011.11.026.

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Ribeiro Junior, Aluizio H., Sergio Luiz M. Ribeiro Filho, Filipe José V. Ribeiro, Juan Carlos Campos Rubio, Maikson LP Tonatto, Carlos Thomas, Fabrizio Scarpa et Tulio H. Panzera. « Statistical and numerical approaches of particulate reinforced polymers and their effect on the interlocking effect of hybrid composite joints ». Journal of Composite Materials 56, n^o 8 (27 février 2022) : 1267–85. http://dx.doi.org/10.1177/00219983211073511.

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Full factorial designs are conducted to identify the effects of the incorporation of microparticles of silica, Portland cement and carbon laminate wastes (carbon microfibres (CMF)), at 3, 6 and 9 wt% levels, on the mechanical performance of epoxy polymers and single carbon fibre joints at two grammage levels (200 and 600 g/m2). Particulate reinforced polymers (PRP) are characterised in tensile, compression, three-point bending and impact tests to better assess the influence of particles in the interlaminar region of hybrid composites composed of fibres and particles. The single joint test is performed to verify the presence of shear locking effect using particles between laminae. Compressive strength and modulus of PRPs increase when 3 wt% CMFs are added, revealing the most efficient level. The apparent shear strength is higher in composite joints made with 600 g/m2 grammage and CMF particles, promising reinforcement mechanisms for hybrid composites.

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Guomin Xu, Wenjian Guan et Xueni Sun. « Filtration Performance and Application of Activated Carbon Fiber Enhanced Microfibrous Entrapped Sorbent (ACF-MFES) ». Russian Journal of Physical Chemistry A 94, n^o 1 (janvier 2020) : 182–88. http://dx.doi.org/10.1134/s0036024420010070.

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Shao, Yan, Huiping Zhang et Ying Yan. « Adsorption dynamics of p-nitrophenol in structured fixed bed with microfibrous entrapped activated carbon ». Chemical Engineering Journal 225 (juin 2013) : 481–88. http://dx.doi.org/10.1016/j.cej.2013.03.133.

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Tao, Jingyuan, Biao Gao, Xuming Zhang, Jijiang Fu, Changjian Peng et Kaifu Huo. « Porous N-doped carbon microfibres derived from cattail as high-performance electrodes for supercapacitors ». International Journal of Nanomanufacturing 12, n^o 3/4 (2016) : 225. http://dx.doi.org/10.1504/ijnm.2016.079220.

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Drew, David M., E. Detlef Schulze et Geoffrey M. Downes. « Temporal variation in δ13C, wood density and microfibril angle in variously irrigated Eucalyptus nitens ». Functional Plant Biology 36, n^o 1 (2009) : 1. http://dx.doi.org/10.1071/fp08180.

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Wood can serve as a record of past climate, recording tree responses to changing conditions. It is also valuable in understanding tree responses to environment to optimise forest management. Stable carbon isotope ratios (δ13C), wood density and microfibril angle (MFA) are potentially useful wood property parameters for these purposes. The goal of this study was to understand how δ13C varied over time in response to cycles of soil drying and wetting and to variation in temperature in Eucalyptus nitens Deane & Maiden, in concert with wood density and MFA. δ13C increases did not necessarily occur when water stress was highest, but, rather, when it was relieved. Our hypothesis is that this was a result of the use of previously fixed carbohydrate reserves when growth and metabolic activity was resumed after a period of dormancy. MFA in particular showed concomitant temporal variation with δ13C. A peak in δ13C may not coincide temporally with an increase in water stress, but with a decrease, when higher growth rates enable the final incorporation of earlier stored photosynthate into mature wood. This has implications for using δ13C as a tool to understand past environmental conditions using radial measurements of wood properties. However, interpreting this data with other wood properties may be helpful for understanding past tree responses.

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Wang, Youling, et Mohamed Mohamedi. « Hierarchically organized nanostructured TiO2/Pt on microfibrous carbon paper substrate for ethanol fuel cell reaction ». International Journal of Hydrogen Energy 42, n^o 36 (septembre 2017) : 22796–804. http://dx.doi.org/10.1016/j.ijhydene.2017.07.138.

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Ponce de León, C., F. C. Walsh, C. J. Patrissi, M. G. Medeiros, R. R. Bessette, R. W. Reeve, J. B. Lakeman, A. Rose et D. Browning. « A direct borohydride–peroxide fuel cell using a Pd/Ir alloy coated microfibrous carbon cathode ». Electrochemistry Communications 10, n^o 10 (octobre 2008) : 1610–13. http://dx.doi.org/10.1016/j.elecom.2008.08.006.

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Wang, Feng, Xiaofang Qin, Lixia Yang, Shanmin Gao, Qingyao Wang et Zhenglong Yang. « Direct growth of carbon microfibres on SiO 2 particles by chemical vapour deposition from ethanol ». Micro & ; Nano Letters 13, n^o 10 (octobre 2018) : 1453–56. http://dx.doi.org/10.1049/mnl.2018.5068.

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Bosia, Federico, Emiliano Lepore, Noe T. Alvarez, Peter Miller, Vesselin Shanov et Nicola M. Pugno. « Knotted synthetic polymer or carbon nanotube microfibres with enhanced toughness, up to 1400 J/g ». Carbon 102 (juin 2016) : 116–25. http://dx.doi.org/10.1016/j.carbon.2016.02.025.

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Ferrari, V. J., A. P. Arquez et J. B. De Hanai. « Compósitos cimentícios de alto desempenho para aplicação como substrato de transição em vigas ». Revista ALCONPAT 6, n^o 1 (16 mars 2016) : 52–63. http://dx.doi.org/10.21041/ra.v6i1.115.

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Compuestos cementíceos de alto desempeño para su aplicación como sustrato de transición en vigasRESUMENEste estudio muestra el desarrollo y análisis del comportamiento de los materiales compuestos de cemento reforzado con fibras de alto rendimiento. El material descrito se desarrolló específicamente para su aplicación como sustrato de transición, o capa de reparación de la formación de la brida tensada vigas de hormigón reforzado con polímeros de flexión reforzado con fibras de carbono (PRFC). Diecinueve compuestos diferentes fueron producidos por el proceso de hibridación. Se varió la cantidad de fibras cortas y microfibras de acero. Para analizar el comportamiento de los ensayos de flexión en tres puntos materiales prismas se realizaron Jagged. La respuesta del material se analizó teniendo en cuenta parámetros de tenacidad a la flexión y (fractura). Materiales compuestos de alto rendimiento evidencia a través de un comportamiento pseudo- endurecimiento.Palabras clave: compuestos cementíceos; vigas de concreto; sustrato de transición. High performance cementitious compounds and their application as transition substrate for beamsABSTRACTThis study presents the development and analysis of the behavior of high performance cementitious compounds reinforced with fibers. The material described was specifically developed for its application as a transition substrate, meaning, a repair layer that forms the tensed span of the flexion reinforced concrete beams with carbon fiber reinforced polymers (CFRP). Nineteen different compounds were produced by the hybridization process. The volume of the short fibers and of the steel microfibers varied. To analyze the behavior of the flexural material, tests were done in three points in tests tubes with their notches. The response of the material was analyzed considering the tenacity parameters (to flexion and fracture). The high performance of the compounds through the behavior of pseudo-hardening was confirmed.Keywords: cementitious compounds; concrete beams; transition substrate. Compósitos cimentícios de alto desempenho para aplicação como substrato de transição em vigasRESUMONeste estudo apresenta-se o desenvolvimento e a análise do comportamiento de compuestos cementíceos de elevado desempeño reforzados com fibras. O material descrito foi especificamente desarrollado para aplicación como um sustrato de transición, ou seja, camada de reparo que forma o banzo traccionado de vigas de concreto reforçadas à flexão com polímeros reforzados com fibras de carbono (PRFC). Dezenove diferentes compuestos foram produzidos pelo processo de hibridização. Variou-se o volume de fibras curtas e de microfibras de aço. Para analisar o comportamiento do material à flexão, ensaios em três pontos em prismas entalhados foram realizados. A resposta do material foi analisada considerando-se parâmetros de tenacidade (flexional e ao fraturamento). Ficou evidenciado o elevado desempeño dos compuestos através de comportamiento de pseudo-encruamento.Palavras-chave: compuestos cementíceos; vigas de concreto; sustrato de transición.

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El Waly, Bilal, Vincent Escarrat, Jimena Perez-Sanchez, Jaspreet Kaur, Florence Pelletier, Jorge Eduardo Collazos-Castro et Franck Debarbieux. « Intravital Assessment of Cells Responses to Conducting Polymer-Coated Carbon Microfibres for Bridging Spinal Cord Injury ». Cells 10, n^o 1 (5 janvier 2021) : 73. http://dx.doi.org/10.3390/cells10010073.

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The extension of the lesion following spinal cord injury (SCI) poses a major challenge for regenerating axons, which must grow across several centimetres of damaged tissue in the absence of ordered guidance cues. Biofunctionalized electroconducting microfibres (MFs) that provide biochemical signals, as well as electrical and mechanical cues, offer a promising therapeutic approach to help axons overcome this blind journey. We used poly(3,4-ethylenedioxythiophene)-coated carbon MFs functionalized with cell adhesion molecules and growth factors to bridge the spinal cord after a partial unilateral dorsal quadrant lesion (PUDQL) in mice and followed cellular responses by intravital two-photon (2P) imaging through a spinal glass window. Thy1-CFP//LysM-EGFP//CD11c-EYFP triple transgenic reporter animals allowed real time simultaneous monitoring of axons, myeloid cells and microglial cells in the vicinity of the implanted MFs. MF biocompatibility was confirmed by the absence of inflammatory storm after implantation. We found that the sprouting of sensory axons was significantly accelerated by the implantation of functionalized MFs after PUDQL. Their implantation produced better axon alignment compared to random and misrouted axon regeneration that occurred in the absence of MF, with a most striking effect occurring two months after injury. Importantly, we observed differences in the intensity and composition of the innate immune response in comparison to PUDQL-only animals. A significant decrease of immune cell density was found in MF-implanted mice one month after lesion along with a higher ratio of monocyte-derived dendritic cells whose differentiation was accelerated. Therefore, functionalized carbon MFs promote the beneficial immune responses required for neural tissue repair, providing an encouraging strategy for SCI management.

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Yang, Yi, Huiping Zhang, Haoxin Huang, Ying Yan et Xinya Zhang. « Degradation of m-cresol over iron loaded carbon nanotube microfibrous composite : Kinetic optimization and deactivation study ». Separation and Purification Technology 262 (mai 2021) : 118340. http://dx.doi.org/10.1016/j.seppur.2021.118340.

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Vallack, Nicola, et William W. Sampson. « Materials systems for interleave toughening in polymer composites ». Journal of Materials Science 57, n^o 11 (mars 2022) : 6129–56. http://dx.doi.org/10.1007/s10853-022-06988-1.

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AbstractWe review the literature describing the use of interleaves to increase interlaminar fracture toughness in fibre-reinforced polymer composites and hence to improve damage tolerance. From an analysis of data provided in the literature from the use of microfibre and nanofibre interleaves, we show that the performance of these widely researched systems is clearly differentiated when plotted against the mean coverage of the interleaf. Using a simple analysis, we suggest that this can be attributed to the influence of their porous architectures on the infusion of resin. We show also that the superior toughening performance of microfibre interleaves is only weakly influenced by the choice of fibre. We find also that the inclusion of carbon nanotubes within interleaves to deliver multifunctional composites can be optimised by using a hybrid system with microfibres. Graphical abstract

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Nabti, Zineb, Tarik Bordjiba, Sujittra Poorahong, Amel Boudjemaa, Ali Benayahoum, Mohamed Siaj et Khaldoun Bachari. « Free-standing and binder-free electrochemical capacitor electrode based on hierarchical microfibrous carbon–graphene–Mn3O4 nanocomposites materials ». Journal of Materials Science : Materials in Electronics 29, n^o 17 (16 juillet 2018) : 14813–26. http://dx.doi.org/10.1007/s10854-018-9618-7.

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Mota, Cesar, Mario Culebras, Andrés Cantarero, Antonio Madroñero, Clara Maria Gómez, Jose María Amo et Jose Ignacio Robla. « Effects of Gamma Irradiation on the Kinetics of the Adsorption and Desorption of Hydrogen in Carbon Microfibres ». Advances in Materials Physics and Chemistry 03, n^o 02 (2013) : 153–60. http://dx.doi.org/10.4236/ampc.2013.32021.

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Petrenko, Iaroslav, Adam P. Summers, Paul Simon, Sonia Żółtowska-Aksamitowska, Mykhailo Motylenko, Christian Schimpf, David Rafaja et al. « Extreme biomimetics : Preservation of molecular detail in centimeter-scale samples of biological meshes laid down by sponges ». Science Advances 5, n^o 10 (octobre 2019) : eaax2805. http://dx.doi.org/10.1126/sciadv.aax2805.

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Fabrication of biomimetic materials and scaffolds is usually a micro- or even nanoscale process; however, most testing and all manufacturing require larger-scale synthesis of nanoscale features. Here, we propose the utilization of naturally prefabricated three-dimensional (3D) spongin scaffolds that preserve molecular detail across centimeter-scale samples. The fine-scale structure of this collagenous resource is stable at temperatures of up to 1200°C and can produce up to 4 × 10–cm–large 3D microfibrous and nanoporous turbostratic graphite. Our findings highlight the fact that this turbostratic graphite is exceptional at preserving the nanostructural features typical for triple-helix collagen. The resulting carbon sponge resembles the shape and unique microarchitecture of the original spongin scaffold. Copper electroplating of the obtained composite leads to a hybrid material with excellent catalytic performance with respect to the reduction of p-nitrophenol in both freshwater and marine environments.

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