LPCVD and characterization of boron-containing pyrocarbon materials

International audiencePyrocarbon materials containing various amounts of boron have been prepared by LPCVD from BCl3–C3H8–H2 precursor mixtures. The growth rate is increased with respect to pure pyrocarbon deposition. By increasing BCl3 / (C3H8 + BCl3) ratio up to 85%, the incorporation of boron can reach 33 at.%. A small amount of boron (e.g. 8 at.%) highly enhances the anisotropy of pyrocarbon, as evidenced by optical microscopy, X-ray diffraction and transmission electron microscopy (selected area diffraction and lattice fringes techniques). X-ray photoelectron spectroscopy has shown that a large fraction of the boron atoms are included by substitution in the carbon layers, the remaining boron atoms belongs to a boron-rich amorphous part of the material. As boron content increases beyond 8 at.%, the anisotropy of the boron-rich pyrocarbon decreases, due to the limited growth and stacking of the carbon layers. Also, amorphous boron-rich regions are more and more abundant as the total amount of boron increases. The oxidation resistance of the C(B) materials is better than that of pure pyrocarbon. It is mainly due to the improvement of the structural organization for the low boron content materials and to the coating of the whole material with a stable boron oxide for materials with a higher boron content

Green gluing of tropical wood Part III: X-Ray Photoelectron Spectroscopy (XPS) and Fourier Transform Infrared Spectroscopy (FTIR) analysis of Frake and Ayous green wood's Glue line

Green gluing of tropical wood Part III: X-Ray Photoelectron Spectroscopy (XPS) and Fourier Transform Infrared Spectroscopy (FTIR) analysis of Frake and Ayous green wood’s Glue line. Emmanuel Njungab1,2, René Oum Lissouck2,4, 5Christine Labrugère, Ntede Ngah Hippolyte2, Régis Pommier3, Louis Max Ayina Ohandja2, Joseph Noah Ngamveng1 1 Laboratory of Macromolecular Chemistry (LCMA), Faculty of science, The University of Yaoundé 1, Cameroon. 2 Laboratory of Mechanics, Materials and Structures (LMMS), ENSP, The University of Yaoundé 1, Cameroon. 3 Institute of Mechanics and Engineering (I2M-GCE), The University of Bordeaux 1, France. 4 National Centre of Scientific Research (CNRS), UMR 5295, France. 5Centre de Caractérisation des Matériaux Avancés (ICMCB, CNRS-UPR), The Université of Bordeaux 1 Abstract: We have recently succeeded to bond two tropical african woods Ayous and Frake in the green state by the glulam technique using a one component (1C-PU) polyurethane adhesive. Durable bond line was achieved and succeeds to meet the structural standard requirement. Scanning electron microscopy performs on the glue line show a good embedding of the glue on the wood fibers. X-ray photoelectron spectroscopy also referred to as Electron spectroscopy for chemical analysis (ESCA) and Fourier transform infrared spectroscopy were used to investigate the interaction of both tropical woods with adhesive. Unlike theoretical expected urethane functional group, xps analysis indicated a high proportion of non hydrolyze urea group and hydrogen bonding of nitrogen (N) at 399,5 eV and 400,5 eV respectively. This foreseen that polyurea polymers and hydrogen bond are the most probable bond to strengthen the gluline. Key words: Green gluing, Tropical woods, Sanding, 1C-PU, XPS, FTIR, Polyure

Influence de l'évolution physico-chimique des fibres et de la zone interfaciale fibre/matrice sur le comportement mécanique des composites SiC/C/SiC et SiC/MAS-L après vieillissement thermique sous atmosphère contrôlée

The evolution of Si-C-O Nicalon fibers and the fiber/matrix interfacial zone within MAS-L 2D-SiC/C/SiC and SiC/glass-ceramic composites, after aging at high temperature under various atmospheres (vacuum, argon or CO), was determined by TEM/EELS, AES, EPMA and XRD, and related to the mechanical tensile behavior of the material. The state of the interfacial bond is followed by micro-indentation tests (push-out). In the 2D-SiC/C/SiC composite, above 1200 °C under vacuum or argon, the disappearance of the pyrocarbon interphase and the crystallization of the fibers in sic after decomposition of the oxycarbon SiO2xC1x into CO and SiO gas, cause the mechanical properties of the material to fall. A CO atmosphere or a confinement of the composite under a SiC coating limits the degradation of the fibers by maintaining a CO back pressure within the material: 1) up to 1200 ° C, the modifications essentially take place on the surface of the fiber with growth of a mixed silica-carbon layer leading to plate traction curves; 2) from 1300 ° C under CO, the degradation of the fibers would be due to a majority gaseous emission in SiO. The weakening of the fiber/matrix bond leads to a decrease in the elastic limit in traction of the composite, the stress at break depending on the state of crystallization of the fiber. For the SiC/MAS-L composite, the fibers and the matrix practically do not evolve up to 1000 ° C under vacuum or argon. The interfacial zone sees the diffusion of the Si, Al and Mg elements of the matrix, strengthening the fiber/matrix bond and improving the mechanical properties of the material. Beyond 1100 ° C, the degradation of the composite is managed by the modifications of the matrix, which crystallizes in cordierite alpha and mullite under vacuum, and becomes vitreous under CO.L'évolution des fibres Si-C-O Nicalon et de la zone interfaciale fibre/matrice au sein des composites 2D-SiC/C/SiC et SiC/vitrocéramique MAS-L, après vieillissement à haute température sous diverses atmosphères (vide, argon ou CO), a été déterminée par TEM/EELS, AES, EPMA et XRD, et reliée au comportement mécanique en traction du matériau. L'état de la liaison interfaciale est suivi par des essais de micro-indentation (push-out). Dans le composite 2D-SiC/C/SiC, au-delà de 1200°C sous vide ou sous argon, la disparition de l'interphase de pyrocarbone et la cristallisation des fibres en sic après décomposition de l'oxycarbure SiO2xC1x en CO et SiO gazeux, provoquent la chute des propriétés mécaniques du matériau. Une atmosphère de CO ou un confinement du composite sous un revêtement de SiC limite la dégradation des fibres par le maintien d'une contre-pression de CO au sein du matériau: 1) jusqu'à 1200°C, les modifications ont essentiellement lieu en surface de fibre avec croissance d'une couche mixte silice-carbone conduisant à des courbes de traction à plateau; 2) à partir de 1300°C sous CO, la dégradation des fibres serait due à une émission gazeuse majoritaire en SiO. L'affaiblissement de la liaison fibre/matrice entraine une baisse de la limite élastique en traction du composite, la contrainte à rupture dépendant de l'état de cristallisation de la fibre. Pour le composite SiC/MAS-L, les fibres et la matrice n'évoluent pratiquement pas jusqu'à 1000°C sous vide ou sous argon. La zone interfaciale voit la diffusion des éléments Si, Al et Mg de la matrice, renforçant la liaison fibre/matrice et améliorant les propriétés mécaniques du matériau. Au-delà de 1100°C, la dégradation du composite est gérée par les modifications de la matrice, qui cristallise en cordiérite alpha et en mullite sous vide, et devient vitreuse sous CO

Influence de l'évolution physico-chimique des fibres et de la zone interfaciale fibre/matrice sur le comportement mécanique des composites SiC/C/SiC et SiC/MAS-L après vieillissement thermique sous atmosphère contrôlée

The evolution of Si-C-O Nicalon fibers and the fiber/matrix interfacial zone within MAS-L 2D-SiC/C/SiC and SiC/glass-ceramic composites, after aging at high temperature under various atmospheres (vacuum, argon or CO), was determined by TEM/EELS, AES, EPMA and XRD, and related to the mechanical tensile behavior of the material. The state of the interfacial bond is followed by micro-indentation tests (push-out). In the 2D-SiC/C/SiC composite, above 1200 °C under vacuum or argon, the disappearance of the pyrocarbon interphase and the crystallization of the fibers in sic after decomposition of the oxycarbon SiO2xC1x into CO and SiO gas, cause the mechanical properties of the material to fall. A CO atmosphere or a confinement of the composite under a SiC coating limits the degradation of the fibers by maintaining a CO back pressure within the material: 1) up to 1200 ° C, the modifications essentially take place on the surface of the fiber with growth of a mixed silica-carbon layer leading to plate traction curves; 2) from 1300 ° C under CO, the degradation of the fibers would be due to a majority gaseous emission in SiO. The weakening of the fiber/matrix bond leads to a decrease in the elastic limit in traction of the composite, the stress at break depending on the state of crystallization of the fiber. For the SiC/MAS-L composite, the fibers and the matrix practically do not evolve up to 1000 ° C under vacuum or argon. The interfacial zone sees the diffusion of the Si, Al and Mg elements of the matrix, strengthening the fiber/matrix bond and improving the mechanical properties of the material. Beyond 1100 ° C, the degradation of the composite is managed by the modifications of the matrix, which crystallizes in cordierite alpha and mullite under vacuum, and becomes vitreous under CO.L'évolution des fibres Si-C-O Nicalon et de la zone interfaciale fibre/matrice au sein des composites 2D-SiC/C/SiC et SiC/vitrocéramique MAS-L, après vieillissement à haute température sous diverses atmosphères (vide, argon ou CO), a été déterminée par TEM/EELS, AES, EPMA et XRD, et reliée au comportement mécanique en traction du matériau. L'état de la liaison interfaciale est suivi par des essais de micro-indentation (push-out). Dans le composite 2D-SiC/C/SiC, au-delà de 1200°C sous vide ou sous argon, la disparition de l'interphase de pyrocarbone et la cristallisation des fibres en sic après décomposition de l'oxycarbure SiO2xC1x en CO et SiO gazeux, provoquent la chute des propriétés mécaniques du matériau. Une atmosphère de CO ou un confinement du composite sous un revêtement de SiC limite la dégradation des fibres par le maintien d'une contre-pression de CO au sein du matériau: 1) jusqu'à 1200°C, les modifications ont essentiellement lieu en surface de fibre avec croissance d'une couche mixte silice-carbone conduisant à des courbes de traction à plateau; 2) à partir de 1300°C sous CO, la dégradation des fibres serait due à une émission gazeuse majoritaire en SiO. L'affaiblissement de la liaison fibre/matrice entraine une baisse de la limite élastique en traction du composite, la contrainte à rupture dépendant de l'état de cristallisation de la fibre. Pour le composite SiC/MAS-L, les fibres et la matrice n'évoluent pratiquement pas jusqu'à 1000°C sous vide ou sous argon. La zone interfaciale voit la diffusion des éléments Si, Al et Mg de la matrice, renforçant la liaison fibre/matrice et améliorant les propriétés mécaniques du matériau. Au-delà de 1100°C, la dégradation du composite est gérée par les modifications de la matrice, qui cristallise en cordiérite alpha et en mullite sous vide, et devient vitreuse sous CO

Impact of RGD peptide density grafted onto polyethylene terephthalate on MC3T3 cell attachment

The aim of this study was to evaluate the impact of different densities on MC3T3 cells attachment onto polyethylene terephthalate (PET) film surfaces. Biomimetic modifications were performed by means of a three-step reaction procedure: creation of COOH functions onto PET surface, coupling agent grafting and finally immobilization of peptides. The originality of this work consist, in one hand on quantifying RGD peptides densities grafted onto PET, and on the other hand on studying MC3T3 cells responses after seeding on such biomimetic surfaces. After each functionnalization step, modifications were validated by several physicochemical techniques: X-Ray Photoelectron Spectroscopy permitted to prove the grafting and high-resolution β-imager coupled with use of radiolabelled amino acids served in evaluation of peptides densities. Moreover, this last technique permit us to ensure stability of binding between peptides and polymer. The efficiency of this new route for biomimetic modification of PET surface was demonstrated by measuring the adhesion at 15 hours of osteoblast like cells. Study of cellular comportment was realized by means of focal contact proteins (vinculin, actin) immunostaining

Surface modification of several carbon-based materials : comparison between CF4 rf plasma and direct F2-gas fluorination routes

Due to their extreme reactivity, fluorine and fluorinated gases may be used to modify the surface properties of numerous materials. In the following, the surface fluorination of some carbon-based compounds (graphite, graphitised carbon fibres, carbon blacks and elastomers)..

Suivi du greffage peptidique de biomatériaux par spectroscopie XPS

La biocompatibilité d'un matériel implantable est essentielle..

Suivi du greffage peptidique de biomatériaux par spectroscopie XPS

La biocompatibilité d'un matériel implantable est essentielle..

RGD nanodomains grafting onto titanium surface.

Titanium alloys exhibit excellent biocompatibility and corrosion resistance in the body fluid and possess mechanical properties similar of the bones' properties. When the loss of osseous is important in osseous surgery, large biomaterials are implanted and should be accepted by the organism. For increasing the biomaterials biocompatibility, biological compounds can be linked or deposited on the material surface making them biologically active. In order to study the tissue-implant interaction and to favor osteoblast-adhesion onto titanium, our work deals with the grafting of cell-binding peptides containing the Arginine-Glycine-Aspartic acid (RGD) sequence. In the present study, we focus on the elaboration of patterned biomaterial surfaces with highly functionalized nanodomains. The strategy of RGD peptide immobilization involves first the grafting if an amino-functional organosilane (APTES). Then, each of the free amino moieties were used as an initiator core for a dendrimer-like synthesis to multiply the number of free groups available for RGD immobilization on the material surface

Switchable hydrophobic-hydropholic fluorinated layer for offset processing

The use of heat-sensitive printing plate precursors has become very popular as one of the‘dry’ lithographic methods that have recently been proposed to comply with environmentalrequirements, A major problem associated with most ablative plates, however, is thegeneration of ablation particles that may contaminate the electronics and optics of thedevice. The objective of the present study is to provide a ‘processless’ method, through aplasma-enhanced fluorination (PEF) treatment involving a fluorinated gas [1]