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When detecting explosive traces by optical remote methods based on recording the vapors, it is essential to know the applicability limits of these techniques. The amount of a vaporized explosive depends on the vaporization kinetics, which, in turn, relies on the physicochemical properties of the explosive, film weight and thickness, ambient air temperature, and film temperature. In active detection techniques, the explosive film temperature on the surface of objects may be higher than the air temperature due to special heating devices. In this case, the questions on how the quantity of matter available for detection is about to change and how much energy has to be consumed to heat up the film can be answered by mathematical modeling. The mathematic model is based on the Hertz–Knudsen–Langmuir equation that describes the vaporization rate of matter with mass transfer between the surface and surrounding air, which is taken into account. In an elaboration of the mathematical model, we introduced previously the temperature difference between the film and ambient air, which is now taken into consideration. The basic parameters influencing the film vaporization rate, and their variation range, were identified. The kinetic parameters of vaporization of thin films of some explosives with a quantity of matter typical of a fingerprint were estimated. The weight of matter in air during vaporization of explosive thin films in a wide range of parameters under study was calculated. Conclusions were made of the applicability limits of the developed standoff detection methods for trace explosives. [ABSTRACT FROM AUTHOR]

Nanocomposite films of BiFeO3-Bi2Fe4O9 were fabricated on a sapphire substrate Al2O3 using the method of gas discharge high-frequency cathodic sputtering of a ceramic target with a stoichiometric composition in an oxygen atmosphere. The results of the film analysis using X-ray structural analysis, Raman scattering, XPS, and atomic force microscopy are presented. The lattice parameters, surface topography, chemical composition of the films, concentration, and average sizes of the crystallites for each phase were determined. It was shown that the ratio of the BiFeO3 to Bi2Fe4O9 phases in the obtained film is approximately 1:2. The sizes of the crystallites range from 15 to 17 nm. The optical and magnetic properties of the nanocomposite layers were studied, and the band gap width and magnetization hysteresis characteristic of ferromagnetic behavior were observed. The band gap width was found to be 1.9 eV for the indirect and 2.6 eV for the direct interband transitions. The magnetic properties are characterized by a hysteresis loop resembling a "wasp-waist" shape, indicating the presence of magnetic anisotropy. [ABSTRACT FROM AUTHOR]

The present review is concerned with the motion of aerosol particles, including that under the exposure to external fields, with special focus being put on the problems related to the similarity theory and invariants that manifest themselves as symmetry in physics. Research on the mechanics of aerosols is extremely important for managing environmental practices. Ultrasonic and electrostatic effects are used in technological processes for cleaning industrial aerosol emissions. In addition, aerosol systems are commonly used to prevent emergency situations (fire extinguishing, fog deposition). Understanding these processes requires knowledge of aerosol mechanics. At the same time, fundamental laws of particulate matter behavior have not been established until now, especially in the presence of external fields. In this paper, we consider the main similarity criteria that are applied for aerosol description. The motion of aerosol particles in the gravitational, electric, and ultrasonic fields is described. The results from studies into acoustic and electrostatic aerosol coagulations are presented herein. [ABSTRACT FROM AUTHOR]

The paper presents the results of characterization of the crystal structure, microstructure, dielectric and piezoelectric properties of PbFe 0.5 Nb 0.5 O 3 ceramics modified at the stage of synthesis by lithium carbonate. Due to a detailed analysis of relaxation processes and piezoelectric activity in the region of the ferroelectric to paraelectric state transition, conclusions are drawn about the optimal concentration of the modifier as well as, from the standpoint of mass production technology, the prospects for using such ceramics as targets for producing single-phase thin films of lead ferroniobate on Si substrates as part of a one-stage method of high-frequency cathodic deposition in O 2 atmosphere are shown. The features of the formation of C (U) dependences and the fatigue effect, which are manifested during cyclic field action on the obtained heterostructures, were studied. Image 1 • The Vogel-Fulcher type dielectric relaxation with a half a degree width was detected. • Piezoelectric activity of PFNL ceramics is retained above T C. • Single-phase polycrystalline textured PFN films on Si substrates were obtained. • The fatigue effects of the PFN film began to appear only after 107 switching cycles. [ABSTRACT FROM AUTHOR]

Detecting ferroelectricity at micro- and nanoscales is crucial for advanced nanomaterials and materials with complicated topography. Switching spectroscopy piezoresponse force microscopy (SSPFM), which involves measuring piezoelectric hysteresis loops via a scanning probe microscopy tip, is a widely accepted approach to characterize polarization reversal at the local scale and confirm ferroelectricity. However, the local hysteresis loops acquired through this method often exhibit unpredictable shapes, a phenomenon often attributed to the influence of parasitic factors such as electrostatic forces and current flow. Our research has uncovered that the deviation in hysteresis loop shapes can be caused by spontaneous backswitching occurring after polarization reversal. Moreover, we've determined that the extent of this effect can be exacerbated when employing inappropriate SSPFM waveform parameters, including duration, frequency, and AC voltage amplitude. Notably, the conventional 'pulse-mode' SSPFM method has been found to intensify spontaneous backswitching. In response to these challenges, we have redesigned SSPFM approach by introducing the positive up-negative down (PUND) method within the 'step-mode' SSPFM. This modification allows for effective probing of local piezoelectric hysteresis loops in ferroelectrics with reversible piezoresponse while removing undesirable electrostatic contribution. This advancement extends the applicability of the technique to a diverse range of ferroelectrics, including semiconductor ferroelectrics and relaxors, promising a more reliable and accurate characterization of their properties. [ABSTRACT FROM AUTHOR]