The Ni/Y2O3 catalyst showed high catalytic activity. Based on this, the aim of this study was to create Ni/Y2O3 nanocomposites powder with two innovative technologies, Ultrasonic Spray Pyrolysis (USP) and lyophilisation. In the USP process, thermal decomposition of the generated aerosols in an N2/H2 reduction atmosphere caused a complete decomposition of the nickel (II) nitrate to elemental Ni, which became trapped on the formed Y2O3 nanoparticles. The Ni/Y2O3 nanocomposite particles were captured via gas washing in an aqueous solution of polyvinylpyrrolidone (PVP) in collection bottles. PVP was chosen for its ability to stabilise nano-suspensions and as an effective cryoprotectant. Consequently, there was no loss or agglomeration of Ni/Y2O3 nanocomposite material during the lyophilisation process. The Ni/Y2O3 nanocomposite powder was analysed using ICP-MS, SEM-EDX, and XPS, which showed the impact of different precursor concentrations on the final Ni/Y2O3 nanocomposite particle composition. In a final step, highly concentrated Ni/Y2O3 nanocomposite ink (Ni/Y2O3 > 0.140 g/mL) and test coatings from this ink were prepared by applying them on a white matte photo paper sheet. The reflection curve of the prepared Ni/Y2O3 nanocomposite coating showed a local maximum at 440 nm with a value of 39% reflection. Given that Ni is located on the surface of the Ni/Y2O3 nanocomposite in the elemental state and according to the identified properties, tests of the catalytic properties of this coating will be performed in the future.

A coupled process of ultrasonic spray pyrolysis and lyophilisation was used for the synthesis of dried gold nanoparticles. Two methods were applied for determining their melting temperature: uniaxial microcompression and differential scanning calorimetry (DSC) analysis. Uniaxial microcompression resulted in sintering of the dried gold nanoparticles at room temperature with an activation energy of 26–32.5 J/g, which made it impossible to evaluate their melting point. Using DSC, the melting point of the dried gold nanoparticles was measured to be around 1064.3°C, which is close to pure gold. The reason for the absence of a melting point depression in dried gold nanoparticles was their exothermic sintering between 712 and 908.1°C.

Gold nanoparticles (AuNPs) have now been used in skin care creams for several years, with marketed anti-aging, moisturizing, and regenerative properties. Information on the harmful effects of these nanoparticles is lacking, a concern for the use of AuNPs as cosmetic ingredients. Testing AuNPs without the medium of a cosmetic product is a typical method for obtaining this information, which is mainly dependent on their size, shape, surface charge, and dose. As these properties depend on the surrounding medium, nanoparticles should be characterized in a skin cream without extraction from the cream’s complex medium as it may alter their physicochemical properties. The current study compares the sizes, morphology, and surface changes of produced dried AuNPs with a polyvinylpyrrolidone (PVP) stabilizer and AuNPs embedded in a cosmetic cream using a variety of characterization techniques (TEM, SEM, DLS, zeta potential, BET, UV–vis). The results show no observable differences in their shapes and sizes (spherical and irregular, average size of 28 nm) while their surface charges changed in the cream, indicating no major modification of their primary sizes, morphology, and the corresponding functional properties. They were present as individually dispersed nanoparticles and as groups or clusters of physically separated primary nanoparticles in both dry form and cream medium, showing suitable stability. Examination of AuNPs in a cosmetic cream is challenging due to the required conditions of various characterization techniques but necessary for obtaining a clear understanding of the AuNPs’ properties in cosmetic products as the surrounding medium is a critical factor for determining their beneficial or harmful effects in cosmetic products.

This study demonstrates the successful synthesis of Ni/Y2O3 nanocomposite particles through the application of ultrasound-assisted precipitation using the Ultrasonic Spray Pyrolysis technique. The particle size was predicted accurately using a modified equation, and they were collected in a water suspension with Polyvinylpyrrolidone (PVP) as the stabiliser. The presence of the Y2O3 core and Ni shell was confirmed with Transmission Electron Microscopy (TEM) and with electron diffraction. The TEM observations revealed the formation of round particles with an average diameter of 466 nm, while the lattice parameter on the Ni particle’s surface was measured to be 0.343 nm. The Ni/Y2O3 nanocomposite particle suspensions were lyophilized, to obtain a dried material that was suitable for embedding into a Polylactic acid (PLA) matrix. The resulting PLA/Ni/Y2O3 composite material was successfully extruded successfully, so that a 3D printed technology Fused Filament Fabrication could be used further for the production of tensile test tubes. The tensile tests showed that the addition of lyophilised Ni/Y2O3 into the PLA matrix decreased the tensile strength by 21.8 %, while the tensile modulus was not influenced. Dynamic Mechanical Analysis (DMA) showed that the addition of the Ni/Y2O3 particles increased the glass transition temperature by 5 °C, and increased the storage modulus in the glass transition range significantly. These findings demonstrate the potential for utilising Ni/Y2O3 nanocomposite particles in 3D printing applications, and warrant further exploration of their mechanical properties and potential applications in various fields.

This study demonstrates the successful synthesis of Ni/Y2O3 nanocomposite particles through the application of ultrasound-assisted precipitation using the ultrasonic spray pyrolysis technique. They were collected in a water suspension with polyvinylpyrrolidone (PVP) as the stabiliser. The presence of the Y2O3 core and Ni shell was confirmed with transmission electron microscopy (TEM) and with electron diffraction. The TEM observations revealed the formation of round particles with an average diameter of 466 nm, while the lattice parameter on the Ni particle’s surface was measured to be 0.343 nm. The Ni/Y2O3 nanocomposite particle suspensions were lyophilized, to obtain a dried material that was suitable for embedding into a polylactic acid (PLA) matrix. The resulting PLA/Ni/Y2O3 composite material was extruded, and the injection was moulded successfully. Flexural testing of PLA/Ni/Y2O3 showed a slight average decrease (8.55%) in flexural strength and a small decrease from 3.7 to 3.3% strain at the break, when compared to the base PLA. These findings demonstrate the potential for utilising Ni/Y2O3 nanocomposite particles in injection moulding applications and warrant further exploration of their properties and new applications in various fields.