## 4 Conclusions  
The method of ferrocene-toluene mixture pyrolysis in Ar flow at atmospheric pressure using a tubular quartz reactor proved to be an effective technology for the synthesis of the initial MWCNT. The graphene layers form the outer surface of the MWCNT. The distance between neighboring graphene layers is 0.34 nm. The internal diameter, external diameter and length of the MWCNTs are about 80 nm, 6-10 nm and 0.1-2 mm, respectively. The oxygen atom percentage (OH and H\({}_{2}\)O oxides) on the outer surface of the MWCNT using NEXAFS, XPS and Raman scattering methods was found to be 3%.  
It was found that the tungsten hexacarbonyl [W(CO)\({}_{6}\)] pyrolysis technique allows us to obtain nonstoichiometric WC\({}_{1\times}\) nanoparticles layers on the MWCNT surface. SEM, TEM, HRTEM, FFT, EDS and XRD studies show that a thick coating of pyrolytic tungsten carbide varies in the wide interval and is granular. All this suggests that coatings are not deposited as continuous thin layers covering the entire MWCNT surface, they become continuous only if grains increase sizes and coalesce at a relatively high initial concentration of W(CO)\({}_{6}\). The XPS, NEXAFS and Raman spectroscopy data indicated the oxidization of the tungsten carbide coatings in air and formation of the WO\({}_{3\times}\) coatings with a thickness of 3.3 nm. XPS and NEXAFS-spectroscopy results showed that the MWCNT surface was covered with tungsten carbide layer consisting of non-stoichiometric WC\({}_{1\times}\) nanoparticles. The MWCNT-(pyrolytic coating) interface structure was determined. It consists of three layers: a transition layer, in which MWCNT outer surface carbon atoms form bonds with coating layer tungsten atoms; a coating layer of WC\({}_{0.88}\) tungsten carbide; and an outer layer of WO\({}_{2.77}\) tungsten oxide. The nonstoichiometric WC\({}_{1\times}\) nanoparticle adhesion is provided by the chemical bonding between the carbon atoms of the MWCNT outer layer and the tungsten atoms of the coating. In the work, the MOCVD technology for the tungsten hexacarbonyl decomposition at a temperature of 300 \({}^{\circ}\)C was used, which allowed us to obtain the tungsten carbide coating with high adhesion to the MWCNT surface.  
**Supplementary Materials**: The following are available online at [[http://www.mdpi.com/2076-3417/10/14/4736/s1](http://www.mdpi.com/2076-3417/10/14/4736/s1)]([http://www.mdpi.com/2076-3417/10/14/4736/s1](http://www.mdpi.com/2076-3417/10/14/4736/s1)), Figure S1: a schematic illustration of the experimental setup for growing of the radial-oriented aligned MWCNTs, Figure S2: a schematic illustration of the experimental setup for synthesis of the WC\({}_{1,\text{w}}\)/MWCNTs nanocomposite, Figure S3: The processing stages scheme.  
**Author Contributions**: Conceptualization, D.S.; research supervision, writing--original draft, D.S., S.N. and V.S.; Synthesis of the nanocomposite samples, XRD measurement and its data interpretation, A.O., B.K., A.A. and I.V.; TEM, SEM and EDS measurements, S.G.; Raman spectroscopy measurements, S.I.; XPS and NEXAFS spectroscopy measurements and their data analysis, D.S., A.V., O.P., A.M., P.M., V.S. and S.N. All of the authors discussed the results and commented on the manuscript during its preparation. All authors have read and agreed to the published version of the manuscript.  
**Funding**: The reported study was funded by RFBR, project numbers 19-32-60018 and 18-33-00776, partially funded by RSF, project number 18-79-10227, the bilateral program RGBL at BESSY II, project number 2019-1-19107863, and the state research target for the G.A. Razuvaev Institute of Organometallic Chemistry of Russian Academy of Sciences (theme No. 45.8).  
**Acknowledgments**: Scientific research were performed at the Center for Studies in Surface Science of Research park of St. Petersburg State University and at the Centre of Collective Use at the Institute of Geology of Komi Science Centre of the Ural Branch of RAS.  
**Conflicts of Interest**: The authors declare no conflict of interest.