Structure and properties of Cr–C/Ag films deposited by magnetron sputtering

Abstract

Cr–C/Ag thin films with 0–14 at.% Ag have been deposited by magnetron sputtering from elemental targets. The samples were analyzed by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) to study their structure and chemical bonding. A complex nanocomposite structure consisting of three phases; nanocrystalline Ag, amorphous CrCx and amorphous carbon is reported. The carbon content in the amorphous carbide phase was determined to be 32–33 at.% C, independent of Ag content. Furthermore, SEM and XPS results showed higher amounts of Ag on the surface compared to the bulk. The hardness and Young's modulus were reduced from 12 to 8 GPa and from 270 to 170 GPa, respectively, with increasing Ag content. The contact resistance was found to decrease with Ag addition, with the most Ag rich sample approaching the values of an Ag reference sample. Initial tribological tests gave friction coefficients in the range of 0.3 to 0.5, with no clear trends. Annealing tests show that the material is stable after annealing at 500 °C for 1 h, but not after annealing at 800 °C for 1 h. In combination, these results suggest that sputtered Cr–C/Ag films could be potentially applicable for electric contact applications

Influence of Nanoeffects on the Oxidation of Cr–C/Ag Thin Films Containing Silver Nanoparticles

“…The carbon concentration in the a‐CrC x phase was 32 to 34 at.%, which is similar to that of the crystalline carbide phase Cr 7 C 3 and also in good agreement with previous results obtained for Cr−C films . Within this a‐CrC x /a‐C matrix, there were 2 to 5 nm large metallic Ag nanoclusters embedded (according to the previous transmission electron microscopy results). There were no Cr nanoparticles or Cr−Ag nanoparticles observed.…”

“…Figure shows micrographs depicting the surfaces of as‐deposited films. Based upon the elemental contrast differences, it is obvious that the bright particles seen for samples B 2 to G 8 represent Ag NPs while the dark areas correspond to the amorphous a‐CrC x /a‐C matrix . Additionally, large numbers of surface particles are seen in the micrographs of samples B 2 to G 8, whereas no NPs are seen in micrograph of the Ag‐free sample A 0 .…”

“…The films were deposited and analyzed as previously described and only a brief summary will hence be given here. The sputtered Cr−C/Ag films were found to be nanocomposites with a ceramic matrix, which according to analysis of the C1s XPS spectra consisted of 60 to 70 % amorphous Cr−C (a‐CrC x ) and 30 to 40 % amorphous carbon (a‐C).…”

“…The addition of Ag to an otherwise ceramic material can e. g. reduce friction, improve the biocompatibility, give rise to a low electrical contact resistance, and increase the conductivity of the material . In particular, we recently showed that the addition of Ag to Cr−C films can greatly improve the electrical contact properties . In such materials, Ag typically forms surface nanoparticles, hereafter abbreviated as NPs, with sizes smaller than 50 nm .…”

Mechanical and tribological features of TaN(Ag-Cu) duplex nanocomposite coatings: their response to heat treatment

“…Values of coefficient of friction and wear rate of deposited TaN(Ag-Cu) coatings without and with heat-treatment are consigned in Table 4; the results of all tribological tests for the heat treated samples indicated a better anti-wear effect with increasing Ag-Cu content than the untreated ones. This improvement is linked to a surface enrichment of TaN with silver and copper nanoparticles, which have a solid lubricant effect that is more efficient than in untreated samples, as also explained by various authors [14,15], [34][35][36]. Figure 9 shows the wear tracks of C1 and C3 coatings, which after heat treatment are clearly smoother and shallower than as in the as produced condition (no heat treatment), decreasing removed material volume after tribological evaluation.…”