This paper focuses on the processes of the occurrence of magnetization during structure formation in samples of Ni₅₁Ti₄₉ alloy under deformation conditions. The possibility of the existence of a phase with an FCC (face-centered cubic) lattice in titanium nickelide has been demonstrated by electron microscopy and electron diffraction. It has been discovered that the interplanar distances of BCC₁₁₀ (body-centered cubic), FCC₁₁₁, and HCP₀₀₂ (hexagonal close packed) in the alloy under study have similar values, which indicates the possibility of their mutual polymorphic transformation. Based on the modular self-organization, a scheme of martensitic transformations in titanium nickelide from the B2 structure (BCC lattice) to the B19’ structure (HCP lattice) through an intermediate phase with an FCC lattice is proposed. It is shown that lenticular crystals appear in the Ni₅₁Ti₄₉ alloy under tensile deformation until rupture, which is accompanied by the onset of ferromagnetism. The effect of magnetization in Ni₅₁Ti₄₉ samples when immersed in liquid nitrogen has been also discovered. In this case, the reason for the appearance and disappearance of magnetization can be associated with microdeformation processes caused by direct and reverse martensitic transitions that occur during cooling and heating of the samples.

Nickel manganese oxide (NiMnO₃) combines magnetic and dielectric properties, making it a promising material for sensor and supercapacitor applications, as well as for catalytic water splitting. The efficiency of its utilization is notably influenced by particle size. In this study, we investigate the influence of thermal treatment parameters on the phase composition of products from alkali co-precipitation of nickel and manganese (II) ions and identify optimal conditions for synthesizing phase-pure nickel manganese oxide. Ultrafine nanoparticles of NiMnO₃ (with sizes as small as 2 nm) are obtained via liquid-phase ultrasonic dispersion, exhibiting a narrow size distribution. A systematic exploration of the solvent nature (water, N-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethylformamide) on the efficiency of ultrasonic dispersion of NiMnO₃ nanoparticles is provided. It is demonstrated that particle size is influenced not only by absorbed acoustic power, dependent on the physical properties of the used solvent (boiling temperature, gas solubility, viscosity, density) but also by the chemical stability of the solvent under prolonged ultrasonic treatment. Our findings provide insights for designing ultrasonic treatment protocols for nanoparticle dispersions with tailored particle sizes.

Focused ion beam (FIB) sample preparation for transmission electron microscopy is a well established technique. However there are some problems related with high-quality large-scale (over 10 um) sample preparation of thin foils. In this work we demonstrate the successful preparation of such samples on example of ferrite steel sample and present the refined lift-out preparation technique, which was applied here. All sample preparation has been carried out in conventional single-beam FIB Hitachi FB-2100 with additional low-kV Ar+ ion polishing.

The cyclic stability of superelasticity in compression in [001]_B2-oriented Ti_49.3Ni_50.7 single crystals is considered in this paper. The crystals were aged at 823 K for 1.0 h in air and helium. It has been experimentally shown that a two-layered surface thin film, consisting of a Ni-free oxide layer and a Ni-rich sublayer, appears after the oxidation at 823 K in air. The surface layers have a weak effect on the forward B2-R-B19’ martensitic transformation temperatures: T_R temperature increases by 4 K; M_s and M_f temperatures decrease by 6 K. The oxide layer does not affect either the superelasticity response during fatigue tests or the temperatures of reverse B19’-B2 martensitic transformation. The cracking of the surface oxide layer during fatigue tests was not found in [001]_B2-oriented single crystals aged in air. This is contributed by the relaxation of internal stresses. Such internal stresses are caused by both the formation of an oxide layer during aging and the matrix deformation at the stress-induced martensitic transformation. The main relaxation mechanisms of the internal stresses are the oriented growth of Ti₃Ni₄ precipitation near a thin surface film at aging in air, the formation of dislocations near the precipitation-matrix interface and a fine twinned B19’-martensite at fatigue tests.