Alexander I. Titkov

A NiO-10YSZ/10YSZ half-cell for anode-supported solid oxide fuel cells (SOFCs) was fabricated using 3D inkjet printing and layer-by-layer laser treatment of printing compositions followed by thermal sintering by a co-firing method. The optimal granulometric composition and rheological characteristics of the printing compositions to fabricate the NiO-10YSZ (60:40 wt.%) anode support, NiO-10YSZ (40:60 wt.%) anode functional layer (AFL), and 10YSZ electrolyte were determined. Effects of the pore former and laser post-treatment on the morphology of the as-prepared anodes for the manufacture of SOFC anode supports were studied, and the optimum laser exposure for hybrid 3D printing was determined. A mechanism of influence of the exposure of laser post-treatment on the morphology of the NiO-10YSZ anode supports has been proposed. The mass content of 10YSZ and the number of layers were shown to affect the surface microstructure and the thickness of the thin-film electrolytes deposited on the surface of the anode supports. The hybrid inkjet 3D printing offers great opportunities as it allows a one-pot procedure to fabricate a NiO-10YSZ/10YSZ SOFC half-cell for SOFC anode supports.

In this work, a simple, inexpensive, and eco-friendly synthesis method of Cu−Ag microflakes has been developed. Firstly, Cu nanoparticles were synthesized by the reduction of copper nitrate in ethylene glycol at 180 °C in the presence of NaOH. The as-synthesized Cu powder was then dispersed in a mixture of ethyl alcohol and a dispersant followed by the mechanochemical treatment of the dispersion in a ball mill resulting in the formation of Cu flakes of approximately 0.2 μm thick and 2.7 μm lateral size. Next, by adding AgNO₃ dissolved in H₂O into the Cu particle dispersion, the bimetallic Cu−Ag microflakes were prepared. The particles so prepared were investigated by X-ray phase analysis and electron microscopy. It was shown that the Cu−Ag bimetallic particles were also flake-like in shape and similar in size to the original Cu microflakes. The effect of synthesis conditions, including parameters of mechanochemical processing, on thickness, size, and uniformity of the bimetallic microflakes was studied. The results obtained in this study were compared with those obtained by wet chemical synthesis alone. The flake-like Cu–Ag particles are supposed to be used in the manufacture of conductive pastes, adhesives, and composites for printed electronics.

An anode for solid oxide fuel cells (SOFCs) was fabricated using 3D inkjet printing and layer-by-layer laser treatment of compositions based on the NiO/YSZ system followed by thermal sintering. The samples were characterized by scanning electron microscopy and X-ray phase analysis. The study of the morphology of the as-prepared samples revealed the presence of both interlayer macroporosity and intralayer microporosity, which depends on the laser exposure during laser treatment. The use of graphite directly added to the printing composition as the pore former increased the intralayer porosity. The morphology and size of the pores were shown to be similar to those of the pore former. The microstructure and porosity of the anode support can be controlled by varying the laser exposure values and the graphite content of the ceramic composite, which in turn opens up great prospects for using these paste compositions and printing techniques for the manufacture of SOFC anode supports.

Hydroxyapatite, being the major mineral component of tooth enamel and natural bones, is a good candidate for bone tissue engineering applications. One of the promising approaches for manufacturing of three-dimensional objects is selective laser sintering/melting which enables the creation of a dense structure directly during 3D printing by adding material layer-by-layer. The effect of laser irradiation with a wavelength of 10.6 μm on the behavior of mechanochemically synthesized hydroxyapatite under different treatment conditions was studied for the first time in this work. It was shown that, in contrast to laser treatment, the congruent melting is impossible under conditions of a relatively slow rate of heating in a furnace. Depending on the mode of laser treatment, hydroxyapatite can be sintered or melted, or partially decomposed into the more resorbable calcium phosphates. It was found that the congruent selective laser melting of hydroxyapatite can be achieved by treating the dense powder layer with a 0.2 mm laser spot at a power of 4 W and at a scanning speed of 700 mm/s. Melting was shown to be accompanied by the crystallization of a dense monolayer of oxyhydroxyapatite while preserving the initial apatite crystal lattice. The thickness of the melted layer, the presence of micron-sized pores, and the phase composition can be controlled by varying the scanning speed and laser power. This set of parameters permits the use of selective laser melting technology for the production of oxyhydroxyapatite biodegradable implants with acceptable properties by 3D printing.

Silver nanoparticles (Ag NPs) of ~ 6 nm in size were synthesized by the reduction of silver 2-[2-(2-methoxyethoxy)ethoxy]acetate by benzyl alcohol acting both as the solvent and as the reducer. The as-synthesized Ag NPs were dispersed in a mixture of nontoxic solvents with different boiling temperatures (butanol and propylene glycol ethers) to prepare ink. The ink was spin-coated on polyimide films and processed with thermal and laser sintering. After thermal sintering, the silver films have a non-uniform structure and contain many voids, causing their resistivity to be quite high (28 µΩ×cm). Laser sintering of the Ag NPs inks spin-coated on a polyimide film using a fiber laser operating at a wavelength of 1.064 µm in a pulse-periodic mode results in a uniform film structure, almost without voids, with a lower resistivity of 2.3 µΩ×cm. Laser sintering in this case is a promising method to fabricate conductive patterns on various substrates, including polymer flexible ones.

In this article, conductive inks for inkjet printing with high content of silver nanoparticles with the addition of organic silver salt and polymer additives are developed and investigated. Silver nanoparticles are shown to be stably dispersed in a solvent and the presence of a silver salt and a polymeric surfactant ensures the viscosity necessary for printing. A print of test images is performed using a laboratory inkjet printer equipped with an industrial small-droplet printhead followed by annealing of printed patterns at 150–250°C, and their structural and electrical properties are investigated. Simultaneous presence of polymer additives and silver salt is found to influence the structure of the forming conductive layer and the conducting properties.