Process optimization and quality control are important issues in cold spraying and coating development. Because the cold spray processing is based on high kinetic energy by high particle velocities, online spray monitoring of particle inflight properties can be used as an assisting process tool. Particle velocities, their positions in the spray jet, and particle size measurements give valuable information about spraying conditions. This, in turn, improves reproducibility and reliability of coating production. This study focuses on cold spraying of Al6061 material and the connections between particle inflight properties and coating characteristics such as structures and mechanical properties. Furthermore, novel 2D velocity scan maps done with the HW CS2 online spray monitoring system are presented as an advantageous powder and spray condition controlling tool. Cold spray processing conditions were similar using different process parameters, confirmed with the online spray monitoring prior to coating production. Higher particle velocities led to higher particle deformation and thus, higher coating quality, denser structures, and improved adhesions. Also, deposition efficiency increased significantly by using higher particle velocities.

This research focused on using ground tire rubber (GTR) with different grain sizes as a replacement for the mineral aggregates used in a cement-based mixture suitable for extrusion-based Additive Manufacturing. The use of two types of GTR particles and the possibility to apply rubberized mixtures in advanced manufacturing technologies are the innovative aspects of this work. At the base of this strategy is the possibility of achieving cementitious aggregates, which would potentially be improved regarding some technological-engineering requirements (lightness, thermal-acoustic insulation, energy dissipation capacity, durability) and environmentally sustainable. The integration of waste tires into cement-based materials is a promising solution for the reuse and recycling of such industrial waste. In addition, this approach may involve a considerable reduction in the use of natural resources (sand, water, coarse mineral aggregates) needed for the building materials production. The purpose of the research was to investigate the effect of sand-GTR replacement on certain chemical-physical properties of mixtures (permeable porosity, surface wetness, and water sorptivity), closely related to material durability. Besides, the role of rubber on the printability properties of the fresh material was evaluated. GTR fillers do not alter the rheological properties of the cement material, which was properly extruded with better print quality than the reference mixture. Concerning chemical-physical characterization, the GTR powder-granules synergy promotes good compaction of the mixture, hinders the cracks propagation in the cement matrix, decreases the permeable porosity, improves the surface hydrophobicity and preserves optimal water permeability.

Additive manufacturing for cementitious materials represents the most attractive frontier in the modern context of Construction 4.0. In addition to the technological progress of printing systems, the development of functional and low environmental impact printable mixtures is one of the current challenges of digital fabrication in building and architectural fields. This paper proposes a preliminary physical-mechanical analysis on environmentally friendly mortars, compatible with the extrusion-based printing process, made up of recycling rubber aggregates deriving from end-of-life tires. In this study, two groups of rubber particle samples (0–1 mm rubber powder and 2–4 mm rubber granules) were used to partially/totally replace the mineral fraction of the reference printable mixture. Four tire rubber powder-granules proportions were investigated and control mortar (100% sand) was also prepared to compare its properties with those of the rubber-cement samples in terms of printability properties, mechanical strength, ductility, and structural isotropy. Based on the experimental results, the rubber aggregates increase the mixture fluidity, promoting better inter-layer adhesion than the neat mix. This leads to greater mechanical isotropy. As already investigated in other research works on Rubber-Concrete technology, the addition of rubber particles increases the ductility of the material but reduces its mechanical strength. However, by correctly balancing the fine and coarse rubber fraction, promising physical-mechanical performances were demonstrated.

Magnesium is one of the lightest structural metals used in different industrial sectors and many works in the literature have studied its reinforcement by filler addition. Basalt fibers are natural fillers that have good mechanical properties, excellent resistance to high temperatures, and lower cost than carbon fibers. Considering this, in recent years, they have been increasingly used in the production of composite materials with polymeric matrices. However, very little information is available in the literature about the use of basalt fibers as reinforcement in metal matrix composite materials. It is well known that the impregnation of fiber reinforcement affects the mechanical behavior of the composite materials. The aim of this study was to investigate the impregnation and the behavior of basalt fibers in a magnesium alloy composite material manufactured by a centrifugal casting technique.