An APT investigation of an amorphous Cr-B-C thin film

A magnetron sputtered amorphous Cr-B-C thin film was investigated by means of atom probe tomography (APT). The film is constituted of two phases; a Cr-rich phase present as a few nanometer large regions embedded in a Cr-poor phase (tissue phase). The Cr-rich regions form columnar chains oriented parallel to the growth direction of the film. It was found that the Cr-rich regions have a higher B:C ratio than the Cr-poor regions. The composition of the phases was determined as approximately 35Cr-33B-30C and 15Cr-40B-42C (at%), respectively. The results suggest that this type of nanocomposite films has a more complex structure than previously anticipated, which may have an importance for the mechanical and electrical properties

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Ti-B-C nanocomposite coatings with a B content of 8-17 at.% have been deposited by magnetron sputtering from B4C, Ti, and C targets. X-ray diffraction, photoelectron spectroscopy, and electron microscopy show that the coatings consist of nanocrystalline (nc) TiC: B embedded in a matrix of amorphous (a) C, BCx, TiOx and BOx. The fraction of amorphous phase scales with the Ti concentration, where the matrix predominantly consists of free C with some BCx in coatings with a C/Ti ratio andgt; 1, while the matrix predominantly consists of BCx with some free C in coatings with a C/Ti ratio andlt; 1. nc-TiC:B/a-BCx/a-C coatings with low amount of free C exhibit a contact resistance comparable to the contact resistance of an Ag sputtered coating at loads of similar to 1 N against an Au probe, despite the O content of similar to 16 at.%.Funding Agencies|VINNOVA VINN Excellence Centre in Research and Innovation on Functional Nanoscale Materials, Fun-Mat||</p

Reactive sputtering of NbCx-based nanocomposite coatings : An up-scaling study

Nanocomposite Nb-C coatings, with a C/Nb ratio of 0.93-1.59, have been deposited by reactive sputtering in a commercial sputtering system where the C is supplied from an acetylene gas at deposition rates of up to 200 nm/min. The coatings are compared to non-reactively sputtered Nb-C coatings deposited from Nb and C targets in lab-scale equipment at deposition rates two orders of magnitude lower. X-ray diffraction, X-ray photoelectron spectroscopy, and electron microscopy are used to conclude that all coatings consist of nanoctystalline Nbc(x) grains (nc-NbCx) embedded in a matrix of amorphous C (a-C). The coating performance was evaluated in terms of their mechanical, tribological, and electrical properties. The chemical stability of the coatings was evaluated by exposure to a flowing mixture of corrosive gases. It is found that the coatings have comparable microstructure and performance to the coatings deposited by non-reactive sputtering. The high deposition rate and presence of different C-radicals on the coating surface during film growth for the reactively sputtered coatings are believed to result in a smaller NbCx grain size compared to the non-reactively sputtered coatings (reactive process: 10-3 nm, non-reactive process: similar to 75-3 nm). This difference results in a thinner a-C matrix of about 0.2 nm, which is not varying with C content for the reactively sputtered coatings. The thinner a-C matrix is reflected in coating properties, with a higher conductivity and slightly higher hardness. The coating richest in C content (C/Nb ratio 1.59) shows the lowest friction (0.23), wear rate (0.17 x 10(-6) mm(3)/mN), and contact resistance before (11 m Omega at 10 N) and after (30 m Omega at 10 N) the chemical stability test. These results imply that nc-NbCx/a-C coatings of this composition are a good candidate for electrical contact applications, and that up-scaling of the process is achievable

Reactive sputtering of NbCx-based nanocomposite coatings : An up-scaling study

Nanocomposite Nb-C coatings, with a C/Nb ratio of 0.93-1.59, have been deposited by reactive sputtering in a commercial sputtering system where the C is supplied from an acetylene gas at deposition rates of up to 200 nm/min. The coatings are compared to non-reactively sputtered Nb-C coatings deposited from Nb and C targets in lab-scale equipment at deposition rates two orders of magnitude lower. X-ray diffraction, X-ray photoelectron spectroscopy, and electron microscopy are used to conclude that all coatings consist of nanoctystalline Nbc(x) grains (nc-NbCx) embedded in a matrix of amorphous C (a-C). The coating performance was evaluated in terms of their mechanical, tribological, and electrical properties. The chemical stability of the coatings was evaluated by exposure to a flowing mixture of corrosive gases. It is found that the coatings have comparable microstructure and performance to the coatings deposited by non-reactive sputtering. The high deposition rate and presence of different C-radicals on the coating surface during film growth for the reactively sputtered coatings are believed to result in a smaller NbCx grain size compared to the non-reactively sputtered coatings (reactive process: 10-3 nm, non-reactive process: similar to 75-3 nm). This difference results in a thinner a-C matrix of about 0.2 nm, which is not varying with C content for the reactively sputtered coatings. The thinner a-C matrix is reflected in coating properties, with a higher conductivity and slightly higher hardness. The coating richest in C content (C/Nb ratio 1.59) shows the lowest friction (0.23), wear rate (0.17 x 10(-6) mm(3)/mN), and contact resistance before (11 m Omega at 10 N) and after (30 m Omega at 10 N) the chemical stability test. These results imply that nc-NbCx/a-C coatings of this composition are a good candidate for electrical contact applications, and that up-scaling of the process is achievable

Alkylammonium Cation Intercalation into Ti₃C₂ (MXene): Effects on Properties and Ion-Exchange Capacity Estimation

Ti₃C₂T_<i>x</i> MXene intercalated with Li⁺ ions was produced and ion-exchanged with a series of trimethylalkylammonium (AA) cations of increasing alkyl chain length. A discontinuous expansion in the MXene layer spacing was observed, attributed to complete packing of the interlayer space at a critical chain length. The latter was used to estimate the number of cations per Ti₃C₂ formula unit, which was found to be in good agreement with a similar quantification obtained from X-ray photoelectron spectroscopy, energy-dispersive spectroscopy, and elemental analysis. The system was also modeled using density functional theory and molecular dynamics, arriving at cation concentrations in the same range. The intercalated AA cations led to tunable increases in resistivity of the normally highly electrically conductive MXene and were investigated as interlayer pillars in electrochemical capacitors