Functional composite electrochemical coating Ni-Co-Al2O3 -an alternative to chromium plating

The physico-mechanical properties of composite electrochemical coatings (CEC) nickel-cobalt-aluminum oxide were investigated depending on the electrolyte parameters and electrolysis conditions. The previously developed low-concentration chloride electrolyte for nickel plating was used as an electrolyte to replace environmentally hazardous chromium plating electrolytes containing hexavalent chromium, which is prohibited by the laws of many countries. The wear resistance of the obtained CEC was determined on a three-ball friction machine. This made it possible to establish that the wear resistance of the CEC exceeds the wear of chrome coatings in dry friction mode by 2-2,5 times and is comparable to chromium in the friction mode with lubrication. In the dry friction mode, the higher wear resistance of the nickel-cobalt-alumina coating is explained only by the higher hardness of the latter. Probably, upon destruction of the coating, the particles of the alloying addition act as a solid lubricant, which causes an increase in the resistance of the CEC during wear. The microhardness of the CEC was determined using a PMT-3 microhardness tester and amounted to 6-25 GPa. The microhardness value was influenced by the concentration and properties of the dispersed phase, as well as the electrolysis conditions - the temperature and pH of the electrolyte, and the cathode current density. “Corrodcote” test was used in the study of corrosion. According to its data, the corrosion resistance of CEC is 2-3 times higher than the corrosion resistance of chromium deposits. The results obtained make it possible to recommend the developed functional CEC of nickel-cobalt-alumina instead of chromium coatings as corrosion- and wear-resistant.

Kinetics of Electrochemical Nanonucleation by Induced Codeposition of Iron Group Metals with Refractory Metals (W, Mo, Re)

It is shown that the earlier discovered features of the composition and properties of electrochemical coatings obtained by the induced codeposition from alloys of iron group metals (W, Mo, Re) such as nanocrystallinity (X-ray amorphism), macroscopic dimensional effects of microhardness and corrosion resistance, the effect of the volume current density on the properties and composition are a consequence of the fractality of the solutions of complexes (citrate, gluconate, etc.) in combination with the intensive interfacial exchange. In this case, the kinetics of nano-nucleation limits the size of the resulting alloy nucleus, as a result of which water molecules participate in the formation of coatings, leading to the incorporation of oxide-hydroxide inclusions into the solid phase and hydrogenation.

Сomposition, structure and functional properties of silver-tungsten composition electrochemistry coatings formed with the help of ultrasound

Influence of electrolyte composition and deposition parameters on the composition, structure, physicalmechanical and functional properties of composite silver-tungsten coatings was studied. It was shown that addition of sodium tungstate in electrolyte and application of ultrasound at the electroplating leads to formation of silver layers that contains tungsten oxides and demonstrates lower crystalline nucleus. Application of ultrasound vibration at the electrochemical deposition increases ability for plating process control and allows to optimize electrophysical and functional properties of composite electrochemical coatings, to make dense fine crystalline thin layers. Obtained layers demonstrate increased microhardness (by 10–50 %), wear resistance (1,5–2 times), corrosion resistance and improved contact electrical resistance. It is shown that application of ultrasound effect to electrodeposition allows increased level of permissible current density and provides.

Electrodeposition and Corrosion Properties of Nickel–Graphene Oxide Composite Coatings

Nickel-based composite electrochemical coatings (CEC) modified with multilayer graphene oxide (GO) were obtained from a sulfate-chloride electrolyte in the reverse electrolysis mode. The microstructure of these CECs was investigated by X-ray phase analysis and scanning electron microscopy. The corrosion-electrochemical behavior of nickel–GO composite coatings in a 0.5 M solution of H2SO4was studied. Tests in a 3.5% NaCl solution showed that the inclusion of GO particles into the composition of electrolytic nickel deposits makes their corrosion rate 1.40–1.50 times less.

FUNCTIONAL ELECTROCHEMICAL COATINGS IN DUAL-USE TECHNOLOGIES

Technological approaches to the application of functional electrochemical coatings in civil and military technologies are analyzed. It is shown that the existing technical solutions are aimed at solving the problems of strengthening and protection of surfaces and detoxification of environments from pollutants of natural and man-made origin. Electrochemical coatings based on the iron triad, doped with refractory metals, increase corrosion resistance, microhardness and wear resistance of surfaces. Doped with transition metals heteroxide coatings, which are synthesized by the method of plasma electrolytic oxidation on aluminum and titanium alloys have catalytic properties to neutralize toxic substances in the gas and liquid phases. Peculiarities of electrochemical formation of functional coatings on construction materials of different types are investigated. It is shown that cathodic deposition by direct and pulsed current on low-carbon steel and gray cast iron forms uniform ternary coatings of Fe-Mo-W and composite systems of Fe-Co-Mo (Fe-Co-W), which have increased corrosion resistance and mechanical properties compared to base metal material. The obtained thin-layer coatings are recommended for the restoration and strengthening of worn surfaces, in particular in the technology of repair of weapons and military equipment. It was found that plasma-electrolyte treatment of piston silumin in alkaline solutions based on diphosphates synthesized heteroxide systems that are active in reducing the number of toxic emissions of internal star engines and reducing hourly fuel consumption. It is shown that nanocomposite coatings on titanium show photocatalytic activity on the destruction of model pollutants. The obtained materials have a set of enhanced functional properties and are promising for use in industrial and repair production, including the security and defense sector.

Detonation nanodiamonds: from synthesis theory to application practice

The review is devoted to the current state of research and advances in the production and study of the properties of detonation nanodiamonds (DND), their application in technology and medicine. New data on the theory and practice of DND synthesis for the last 1–5 years are considered and systematized. It is shown that the zone of chemical reactions (ZCR) during the blust of explosive materials (EM) is decisive for the fractal pre-diamond structure formation, the final region of the nanodiamonds (1/3–3/4 of the diameter of the explosive charge) formation is determined. The possibility of predicting the DND yield and the influence of parameters on the synthesis process of nanodiamonds from individual EMs of binary and ternary compositions is shown, their optimal formulations are determined. The optimal ZCR width and the existence time of chemical reactions have been identified. The dependence of the DND yield on the nitrogen content in the EM was shown. The most effective method of DND purification and the possibility of obtaining graphite-diamond compositions of a given formulation are presented. The most informative indicators of nanodiamonds characterization are given. The magnetic properties of nanodiamonds are considered and the identity of the properties of DNDs from different EMs is shown. The characteristics of new compositions based on DND are indicated: electrochemical coatings (gold and chromium-diamond), thermal pastes, diamond-containing polymer filaments for a 3D printer, fuel compositions, enterosorbents, compatible with biosystems of the nanodiamond-drug composition.

Electrodeposition of Graphene Oxide Modified Composite Coatings Based on Nickel-Chromium Alloy

Composite electrochemical coatings (CECs) based on nickel-chromium alloy and modified with multilayer graphene oxide (GO) were obtained. The electrodeposition process of these coatings was studied in the potentiodynamic mode. The structure and the composition of nickel–chromium–GO CECs were studied by scanning electron microscopy and laser microspectral analysis. Nickel–chromium–GO CECs are dense and uniform. The carbon content in them increases when moving from the substrate to the surface. It was established that the addition of GO particles into the composition of electrolytic coatings with a nickel-chromium alloy results in the increase in their microhardness from 4423–5480 MPa to 6120–7320 MPa depending on the cathodic current density.

Nanocomposites for Enhanced Osseointegration of Dental and Orthopedic Implants Revisited: Surface Functionalization by Carbon Nanomaterial Coatings

Over the past few decades, carbon nanomaterials, including carbon nanofibers, nanocrystalline diamonds, fullerenes, carbon nanotubes, carbon nanodots, and graphene and its derivatives, have gained the attention of bioengineers and medical researchers as they possess extraordinary physicochemical, mechanical, thermal, and electrical properties. Recently, surface functionalization with carbon nanomaterials in dental and orthopedic implants has emerged as a novel strategy for reinforcement and as a bioactive cue due to their potential for osseointegration. Numerous developments in fabrication and biological studies of carbon nanostructures have provided various novel opportunities to expand their application to hard tissue regeneration and restoration. In this minireview, the recent research trends in surface functionalization of orthopedic and dental implants with coating carbon nanomaterials are summarized. In addition, some seminal methodologies for physicomechanical and electrochemical coatings are discussed. In conclusion, it is shown that further development of surface functionalization with carbon nanomaterials may provide innovative results with clinical potential for improved osseointegration after implantation.