Relationships between arc plasma jet properties and plasma/liquid interaction mechanisms for the deposition of nanostructured ceramic coatings

Ceramic nanostructured coatings with intermediate thicknesses between 10 and 100 µm exhibit improved thermal and mechanical properties for thermal barrier coatings or wear resistant coatings. Such coatings comply with the technical requirements of aeronautical and automotive applications. This implies to develop deposition processes with high throughput and deposition rates promoting the formation of nanostructured coatings. The use of a liquid phase as a carrier medium of nanoparticles or of solution precursors has been shown to be of major interest when being injected within a thermal plasma jet. The as-sprayed materials can form ceramic nanostructured coatings provided the liquid injection encompassing the physicochemical properties of liquid and its injection method copes with the plasma properties. Especially the repeatability of the interaction phenomena between the liquid phase and the arc jet has a key role in the efficiency deposition so that some research efforts are devoted to stabilize the arc while a liquid jet is continuously injected within the plasma. Alternatively a pulsed arc plasma jet can be generated and associated with a time-phased injection of droplets. This paper presents the different issues related to the arc plasma properties produced by direct plasma torches including the arc instabilities and their influence on plasma/liquid interaction mechanisms leading to the formation of nanomaterials. A focus is made on pulsed plasma spraying associated with a synchronized injection of microsized droplets by means of an inkjet printing method.

Metal Oxide Nanostructure-Based Gas Sensor for Carbon Dioxide Detection

To increase the sensitivity and efficiency of a gas sensor, nanostructured ZnO and Co3O4 layers were obtained by hydrothermal synthesis directly on the electrode surface, eliminating the use of binders. Scanning electron microscope images showed that the resulting nanostructured coatings were characterised by good adhesion to the surface and high porosity, which opened up the possibility of their further use in the process of developing a gas sensor. The efficiency of the obtained nanostructured coatings and their sensitivity at room temperature to various concentrations of CO2 were determined. The resistance curves of the samples were obtained as a function of gas concentration in the chamber, for Co3O4 and ZnO nanostructures.

Design and simulation of mechanical press for testing of coining tools with nanostructured coatings

The present study proposes the design, simulation, and finite element analysis (FEA) of a mechanical press to test coining tools that contain nanostructured coatings. The designed mechanical testing press has a nominal force capacity of 800 kN with a ram stroke of 100 mm. CAD modeling of components, assemblies, and press structure is developed. The validation of the safety factor of the stress of the press is implemented by FEA analysis. Axisymmetric 2D FEA simulation is applied to determine the nanostructured coating behavior when subjected to high loads, the results are promising for future simulation studies on coatings. A displacement mechanism was designed for the test sheet, offering versatility and a variety of options for testing the coining tools as often as necessary under different load conditions. The final results of the machine operation simulation are satisfactory.