Chromium-based coatings by atmospheric chemical vapor deposition at low temperature from Cr(CO)6

Cr-based coatings were grown under atmospheric pressure in different gaseous atmospheres (N2,H2, NH3) from the thermal decomposition of Cr(CO)6 at 300 °C in a cold-wall CVD reactor. Cr(CO)6 is a good candidate as precursor because of its low cost and its high volatility, which permits high flow rates. Original chromium oxycarbide and oxynitride coatings were deposited on steel. These phases were previously obtained by plasma-assisted CVD and low-pressure CVD, i.e., under nonequilibrium conditions. In the present work, the low deposition temperature likely accounts for their formation. We have investigated correlations between the growth conditions and their main chemical, structural and physical features. Preliminary results on the mechanical behavior of these Cr-based coatings are also reported

Nanocrystalline chromium-based coatings deposited by DLI-MOCVD under atmospheric pressure from Cr(CO)6

Nanocrystalline original Cr-based coatings were grown under atmospheric pressure by Direct Liquid Injection Metal Organic Chemical Vapor Deposition (DLI-MOCVD). The thin films were grown below 450 °C in a cold wall CVD reactor from solutions of Cr(CO)6 in toluene or THF injected and flash vaporized with or without NH3 addition prior to the deposition zone. Original nanocrystalline chromium oxycarbide and oxy-carbonitride phases were deposited on stainless steel substrates. The influence of injection parameters and conventional CVD conditions have been investigated on the main chemical, physical and structural characteristics of the coatings, as deduced from XRD, SEM, and EPMA analyses

Dépôt de carbures, nitrures et multicouches nanostructurées á base de chrome sous pression atmosphérique par dli-mocvd : nouveaux procédés et potentialités de ces revêtements métallurgiques

Des procédés atmosphériques de dépôt chimique en phase vapeur assisté par l'injection directe liquide (DLI-CVD), prometteurs pour traiter des pièces métalliques au défilé, ont permis l'élaboration à basse température de revêtements métallurgiques performants. Deux précurseurs organométalliques de chrome ont été employés dans différentes atmosphères : Cr (CO)6 pour des dépôts issus du système chimique Cr-O-N-C, et le bisbenzènechrome pour des monocouches de chrome métallique, de carbure (Cr-C) et de nitrure de chrome (CrN), ainsi que des multicouches CrN/Cr-C de bipériode 25 nm. Une approche thermodynamique a permis le calcul d'un nouveau diagramme ternaire Cr-N-C à 527°C, et l'étude de l'impact du solvant sur la nature et la qualité des dépôts en comparaison avec les systèmes chimiques sans solvant. Les propriétés des revêtements (dureté, adhérence, usure, corrosion) sont discutées en relation avec leur microstructure. Les revêtements multicouches nanostructurés CrN/Cr-C présentent des duretés et une tenue à l'usure prometteuses. ABSTRACT : Atmospheric MOCVD processes assisted by Direct Liquid Injection, attractive for on-line strip coating of metal pieces, were developped for the growth of advanced metallurgical coatings. Two chromium metal organic sources have been employed under various ambience : Cr (CO)6 for coatings in the Cr-O-N-C system, and bisbenzenechromium for metal chromium, carbide (Cr-C) and nitride chromium (CrN) monolayer and CrN/Cr-C multilayer coatings with a typical 25 nm biperiod. A thermodynamic approach has permited the calculation of a new ternary phase diagram in the Cr-C-N system and the study of the solvent impact on the nature of the coatings in comparison with chemical systems without solvent. Preliminary mechanical properties from scratch test, nanoindentation and residual stress measurements as well as tribological and corrosion behavior of the mono and multilayer Cr-based coatings are discussed in relation with their microstructure. Nanostructured CrN/Cr-C multilayer coatings exhibit promising hardness and wear resistance

Dépôt de carbures, nitrures et multicouches nanostructurées á base de chrome sous pression atmosphérique par dli-mocvd : nouveaux procédés et potentialités de ces revêtements métallurgiques

Des procédés atmosphériques de dépôt chimique en phase vapeur assisté par l'injection directe liquide (DLI-CVD), prometteurs pour traiter des pièces métalliques au défilé, ont permis l'élaboration à basse température de revêtements métallurgiques performants. Deux précurseurs organométalliques de chrome ont été employés dans différentes atmosphères : Cr (CO)6 pour des dépôts issus du système chimique Cr-O-N-C, et le bisbenzènechrome pour des monocouches de chrome métallique, de carbure (Cr-C) et de nitrure de chrome (CrN), ainsi que des multicouches CrN/Cr-C de bipériode 25 nm. Une approche thermodynamique a permis le calcul d'un nouveau diagramme ternaire Cr-N-C à 527°C, et l'étude de l'impact du solvant sur la nature et la qualité des dépôts en comparaison avec les systèmes chimiques sans solvant. Les propriétés des revêtements (dureté, adhérence, usure, corrosion) sont discutées en relation avec leur microstructure. Les revêtements multicouches nanostructurés CrN/Cr-C présentent des duretés et une tenue à l'usure prometteuses

Thermodynamic simulation of atmospheric DLI-CVD processes for the growth of chromium-based hard coatings using bis(benzene)chromium as molecular source

Direct liquid injection (DLI) is a new technology particularly convenient for feeding CVD reactors with low volatility molecular precursors. Thus DLI-CVD can operate under atmospheric pressure and is a promising process for industrial applications requiring high precursor flow rates such as continuous deposition. In order to help the experimenter, a thermodynamic approach is particularly suitable for determining the chemistry of the process, i.e. the influence of the main growth parameters such as temperature, total pressure and initial gas phase composition on the nature of the deposited phases. A choice of the most explicit representations of the thermodynamic modelling describing the great trends resulting from the variation of experimental parameters is presented. Thermodynamic calculations in the Cr–C–H, Cr–N–C–H and Cr–C–Cl–H chemical systems were made to predict the atmospheric CVD growth of carbides, nitrides andmetal chromium coatings, respectively. Bis(benzene)chromium (BBC) was used as metalorganic precursor and the calculations simulated respectively the reactive gas phase mixtures BBC/solvent, BBC/NH3/solvent and BBC/C6Cl6/solvent. Even if a satisfactory agreement was found between experimental and theoretical tendencies, the deposition of metastable phases reveals that kinetics can play amajor role in such processes. Based on these results, chromium carbides, nitrides and metal coatings have been successfully deposited by DLI-CVD under atmospheric pressure either as single phased or nanostructured multilayer hard coatings

Multilayer chromium based coatings grown by atmospheric pressure direct liquid injection CVD

There is a great interest for multilayer hard coatings because they exhibit enhanced properties resulting from their nanostructuration. Such coatings are frequently constituted of carbide and nitride and are generally deposited under very low pressure by plasma and PVD processes. These vacuum techniques enable the growth of heterostructures with nanometric thick individual layers and sharp interfaces, which are two requirements for advanced performances. However, both to develop more economical processes and with the goal of continuous deposition applications, the CVD processes operating under atmospheric pressure are particularly attractive. In this paper we show that the combination of pulsed direct liquid injection and the use of metalorganic precursor (DLI-MOCVD) is a promising route for the growth of nanostructured multilayer coatings under atmospheric pressure. Chromium metal as well as chromium carbide and nitrides monolithic coatings have been deposited at 773 K by this process using liquid solution of bis(benzene) chromium as Cr molecular precursor. Then, CrCx/CrN nanostructured multilayer coatings with a bilayer period as low as 50 nm have been grown. Structural characterizations and preliminary mechanical properties of these metallurgical coatings are discussed

Effects of eight neuropsychiatric copy number variants on human brain structure

Many copy number variants (CNVs) confer risk for the same range of neurodevelopmental symptoms and psychiatric conditions including autism and schizophrenia. Yet, to date neuroimaging studies have typically been carried out one mutation at a time, showing that CNVs have large effects on brain anatomy. Here, we aimed to characterize and quantify the distinct brain morphometry effects and latent dimensions across 8 neuropsychiatric CNVs. We analyzed T1-weighted MRI data from clinically and non-clinically ascertained CNV carriers (deletion/duplication) at the 1q21.1 (n = 39/28), 16p11.2 (n = 87/78), 22q11.2 (n = 75/30), and 15q11.2 (n = 72/76) loci as well as 1296 non-carriers (controls). Case-control contrasts of all examined genomic loci demonstrated effects on brain anatomy, with deletions and duplications showing mirror effects at the global and regional levels. Although CNVs mainly showed distinct brain patterns, principal component analysis (PCA) loaded subsets of CNVs on two latent brain dimensions, which explained 32 and 29% of the variance of the 8 Cohen’s d maps. The cingulate gyrus, insula, supplementary motor cortex, and cerebellum were identified by PCA and multi-view pattern learning as top regions contributing to latent dimension shared across subsets of CNVs. The large proportion of distinct CNV effects on brain morphology may explain the small neuroimaging effect sizes reported in polygenic psychiatric conditions. Nevertheless, latent gene brain morphology dimensions will help subgroup the rapidly expanding landscape of neuropsychiatric variants and dissect the heterogeneity of idiopathic conditions

DÉPÔT DE CARBURES, NITRURES ET MULTICOUCHES NANOSTRUCTURÉES Á BASE DE CHROME SOUS PRESSION ATMOSPHÉRIQUE PAR DLI-MOCVD NOUVEAUX PROCÉDÉS ET POTENTIALITÉS DE CES REVÊTEMENTS MÉTALLURGIQUES

Atmospheric MOCVD processes assisted by Direct Liquid Injection, attractive for on-line strip coating of metal pieces, were developped for the growth of advanced metallurgical coatings. Two chromium metal organic sources have been employed under various ambience : Cr (CO)6 for coatings in the Cr-O-N-C system, and bisbenzenechromium for metal chromium, carbide (Cr-C) and nitride chromium (CrN) monolayer and CrN/Cr-C multilayer coatings with a typical 25 nm biperiod. A thermodynamic approach has permited the calculation of a new ternary phase diagram in the Cr-C-N system and the study of the solvent impact on the nature of the coatings in comparison with chemical systems without solvent. Preliminary mechanical properties from scratch test, nanoindentation and residual stress measurements as well as tribological and corrosion behavior of the mono and multilayer Cr-based coatings are discussed in relation with their microstructure. Nanostructured CrN/Cr-C multilayer coatings exhibit promising hardness and wear resistance.Des procédés atmosphériques de dépôt chimique en phase vapeur assisté par l'injection directe liquide (DLI-CVD), prometteurs pour traiter des pièces métalliques au défilé, ont permis l'élaboration à basse température de revêtements métallurgiques performants. Deux précurseurs organométalliques de chrome ont été employés dans différentes atmosphères : Cr (CO)6 pour des dépôts issus du système chimique Cr-O-N-C, et le bisbenzènechrome pour des monocouches de chrome métallique, de carbure (Cr-C) et de nitrure de chrome (CrN), ainsi que des multicouches CrN/Cr-C de bipériode 25 nm. Une approche thermodynamique a permis le calcul d'un nouveau diagramme ternaire Cr-N-C à 527°C, et l'étude de l'impact du solvant sur la nature et la qualité des dépôts en comparaison avec les systèmes chimiques sans solvant. Les propriétés des revêtements (dureté, adhérence, usure, corrosion) sont discutées en relation avec leur microstructure. Les revêtements multicouches nanostructurés CrN/Cr-C présentent des duretés et une tenue à l'usure prometteuses

Chromium-based coatings by atmospheric chemical vapor deposition at low temperature from Cr(CO)6

International audienceCr-based coatings were grown under atmospheric pressure in different gaseous atmospheres (N2,H2, NH3) from the thermal decomposition of Cr(CO)6 at 300 °C in a cold-wall CVD reactor. Cr(CO)6 is a good candidate as precursor because of its low cost and its high volatility, which permits high flow rates. Original chromium oxycarbide and oxynitride coatings were deposited on steel. These phases were previously obtained by plasma-assisted CVD and low-pressure CVD, i.e., under nonequilibrium conditions. In the present work, the low deposition temperature likely accounts for their formation. We have investigated correlations between the growth conditions and their main chemical, structural and physical features. Preliminary results on the mechanical behavior of these Cr-based coatings are also reported

Dépôt de carbures, nitrures et multicouches nanostructurées à base de chrome sous pression atmosphérique par dli-mocvd (nouveaux procédés et potentialités de ces revêtements métallurgiques)

Des procédés atmosphériques de dépôt chimique en phase vapeur assisté par l'injection directe liquide (DLI-CVD), prometteurs pour traiter des pièces métalliques au défilé, ont permis l'élaboration à basse température de revêtements métallurgiques performants. Deux précurseurs organométalliques de chrome ont été employés dans différentes atmosphères : Cr (CO)6 pour des dépôts issus du système chimique Cr-O-N-C, et le bisbenzènechrome pour des monocouches de chrome métallique, de carbure (Cr-C) et de nitrure de chrome (CrN), ainsi que des multicouches CrN/Cr-C de bipériode 25 nm. Une approche thermodynamique a permis le calcul d'un nouveau diagramme ternaire Cr-N-C à 527C, et l'étude de l'impact du solvant sur la nature et la qualité des dépôts en comparaison avec les systèmes chimiques sans solvant. Les propriétés des revêtements (dureté, adhérence, usure, corrosion) sont discutées en relation avec leur microstructure. Les revêtements multicouches nanostructurés CrN/Cr-C présentent des duretés et une tenue à l'usure prometteusesAtmospheric MOCVD processes assisted by Direct Liquid Injection, attractive for on-line strip coating of metal pieces, were developped for the growth of advanced metallurgical coatings. Two chromium metal organic sources have been employed under various ambience : Cr (CO)6 for coatings in the Cr-O-N-C system, and bisbenzenechromium for metal chromium, carbide (Cr-C) and nitride chromium (CrN) monolayer and CrN/Cr-C multilayer coatings with a typical 25 nm biperiod. A thermodynamic approach has permited the calculation of a new ternary phase diagram in the Cr-C-N system and the study of the solvent impact on the nature of the coatings in comparison with chemical systems without solvent. Preliminary mechanical properties from scratch test, nanoindentation and residual stress measurements as well as tribological and corrosion behavior of the mono and multilayer Cr-based coatings are discussed in relation with their microstructure. Nanostructured CrN/Cr-C multilayer coatings exhibit promising hardness and wear resistance.TOULOUSE-ENSIACET (315552325) / SudocSudocFranceF