Synthesis and characterization of some Cr-Zr and Cr-Zr-O nanostructures

Abstract

The co-depositions of Cr-Zr and those of Cr-Zr-O coatings of 500 nm thick were made using magnetron sputtering in continuous mode, in a circular enclosure with a volume of 0.05 m3 evacuated prior to the deposition process under 10-6 mbar vacuum conditions. Silicon and Carbon substrates measuring 12x15mm were used for deposition. The topology of all of the CrZr and CrZrO2 coatings deposited on silicon and carbon substrates have been investigated by Scanning Electron Microscopy (SEM) at three magnifications: 1000x, 5000x and 10.000x. For all of the coatings deposited on Silicon substrates, at all three magnifications, was observed very smooth surfaces with only small topological elements. In some samples, few droplets of around 100nm can be observed. The appearance of particulates is caused by the arching events that occur at target surface during the deposition proces and are more pronounced during reactive sputtering. The coatings deposited on the Carbon substrate show more morphological features as these substrates have a lower grade surface polish finish as to sliced Silicon wafers; the deposited film tends to follow the substrate topology and cracks can be seen on the surface. Were investigated the mechanical properties of the samples of Cr+Zr, respectively Cr+Zr+O2 using The Bruker Hysitron TI 980 TriboIndenter which allows to extrapolate mechanical properties such Young’ s Modulus (YM) and Hardness (H). The experimental results obtained through nanoindentation studies, show: In the absence of oxygen during deposition ( Zr-Cr structures), the Young’s Modulus and Hardness are influenced by the concentration ratio of the two components Cr and Zr, i.e., there is the practical possibility of adjusting the two parameters YM and H by correspondingly changing the concentrations of the components of the structure . In the case of the Cr+Zr+O2 structures, for sample where the concentration of Chromium is maximum and the concentration of Zirconium is minimum, the presence of Oxygen causes a decrease for YM and respectively a decrease for H (in this case Cr-O bonds are predominant). In the case of sample in which the concentration of Zirconium is maximum and the concentration of Chromium is minimum, in the presence of Oxygen (now the bonds Zr-O being predominant), an increase for YM and an increase for H are observed. The crystalline structure was investigated using X-Ray Diffraction (XRD) method, using a setup composed of a diffractometer equipped with a Cu-Kα X-ray sourse, with a specific wavelength of 0.154nm, in a Bragg-Bretano type geometry. In the case of the Cr-Zr sample, diffractograms show that only the peaks corresponding to the Si substrate are visible, highlighting the amorphous character of the structure. Also, the measurements reveal the amorfous character of the Cr-Zr-O sample. In order to highlight the effect of the element Cr together with Zr and O, the diffractogram of the ZrO2 sample and diffractogram of Cr-Zr-O sample are examinated for comparison. Considering the application of these materials in dentistry, the 2 wide amorphous strips in the case of ZrO2 sample and amorfous character found in the case of Cr-Zr-O sample, could correspond to the adhesive used to attach the veneer to the tooth of such structures. From this perspective, it can be stated that the presence of the Cr element in the Cr-Zr-O structure widens the possibility of its use as an adhesive to attach the veneer to the tooth.