A cost-effective, scalable and versatile method of preparing nano-ink without hazardous chemical precursors is a prerequisite for widespread adoption of printed electronics. Precursor-free synthesis by spark discharge is promising for this purpose. The synthesis of platinum nanoparticles (PtNPs) using a spark discharge under Ar, N2, and air has been investigated to prepare highly conductive nano-ink. The size, chemical composition, and mass production rate of PtNPs significantly depended on the carrier gas. Pure metallic PtNPs with sizes of 5.5 ± 1.8 and 7.1 ± 2.4 nm were formed under Ar and N2, respectively. PtNPs with sizes of 18.2 ± 9.0 nm produced using air consisted of amorphous oxide PtO and metallic Pt. The mass production rates of PtNPs were 53 ± 6, 366 ± 59, and 490 ± 36 mg/h using a spark discharge under Ar, N2, and air, respectively. It was found that the energy dissipated in the spark gap is not a significant parameter that determines the mass production rate. Stable Pt nano-ink (25 wt.%) was prepared only on the basis of PtNPs synthesized under air. Narrow (about 30 μm) and conductive Pt lines were formed by the aerosol jet printing with prepared nano-ink. The resistivity of the Pt lines sintered at 750 °C was (1.2 ± 0.1)·10−7 Ω·m, which is about 1.1 times higher than that of bulk Pt.

Elementary excitation spectra are investigated in a thin ferromagnetic film. The temperatures of stability of phase transitions “easy axis”–angular phase and “easy plane”–angular phase are obtained. It is shown that the reasons behind the formation of the angular phase is the presence of magnetoelastic interaction. The Curie temperature of the system under investigation is determined.

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Subject classification: 75.30.Kz In the paper we investigate phase transitions in temperature from the quadrupolar phase to the disordered phase in 2D isotropic and anisotropic non-Heisenberg ferromagnets. It is shown that in a 2D isotropic non-Heisenberg ferromagnet the long-range magnetic order is absent, whereas the quadrupolar phase is implemented in the anisotropic one. The temperature of the phase transition is determined. This system is compared with a 3D non-Heisenberg ferromagnet.

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We investigate the influence of dipole interaction on the phase transitions due to temperature variation in two-dimensional ferromagnets. The spectra of quasi-particles at the points of the phase transitions from "the easy-axis phase" to "the angular phase" and from "the easy-plane phase" to "the angular phase" are obtained. The temperatures of the phase transitions are found. The numerical evaluation of the temperature interval of angular phase existence is in good agreement with experimental data.