Manganese oxides have been synthesized by the interaction of Mn 2+ and Mn in the presence of nanoreactors: cetyltrimethylammonium bromide micelles that were not present in the final product composition. The synthesized substance is investigated using scanning electron microscopy, X-ray diffraction analysis, dynamic light scattering, the Brunauer-Emmett-Teller method, and the method of Barrett-Joyner-Halenda. It is determined that the substance under examination is a filamentous nanometer-scale material with a cross-section size up to 100 nm. The acute inhalation toxicity study is performed according to the interstate standard using the method of acute-toxicity class determination (ATC method) (OECD, Test no. 436:2008, IDT). The ATC method allows us to see that synthesized nanosized manganese oxide has an acute toxicity property when inhaled as an aerosol. Upon 4-h exposure to Wistar rats weighing 190 ± 10g, CL 50 is 0.12 mg/L. The clinical picture of acute intoxication is characterized by irritation, neurotoxic effects, and respiratory depression. According to CL 50 (>0.05-0.5), mg/L criterion, synthesized nanosized manganese oxide belongs to hazard class 2 in accordance with Globally Harmonized System of Classification and Labelling of Chemicals (GHS).

This paper describes a fire and explosion suppression formulation with increased flowability that ensures fast operation and high efficiency of an active explosion suppression system (complete fire and explosion suppression time = 2.25 ms; spraying capacity = over 98%). For the first time, the possibility of using mesoporous materials of different structures with high specific surface area as flow additives for these formulations has been reported. This also covers the results of an experimental study on the influence of various mesoporous silica materials used as additives on the rheological characteristics of a monoammonium phosphate (MAP)-based fire and explosion suppressant. Particular attention is paid to analysis of the results of the experiments in which the mesoporous materials are protected from moisture via poly(methylhydrosiloxane) hydrophobic modification. The study of the rheology of powders indicates that the flow parameters depend on the surface characteristics of silica nanoparticles and their size and concentration. The incorporation of superhydrophobized silica into MAP leads to a decrease in the cohesion force and an increase in the flow function ff (composition contact angle > 163°). The amount of superhydrophobic silica also affects the autoadhesion forces between particles. It has been established that the minimum resistance of a fire and explosion suppression powder to the flow occurs when modified nanoparticles with SBA-15-type structure are used as additives. The efficiency of hydrophobized silica materials as additives increases greatly with a decrease in the size of their particle agglomerates. The joint use of SBA-15 and Aerosil 380 silicas makes it possible to improve the rheological properties of the fire and explosion suppression formulation and to significantly increase its flowability.

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The method of manufacturing nanosized spherical superhydrophobic silica particles is reported. The efficiency of hydrophobized nanosilica (NS) as an additive to fire extinguishing powders (FEP) based on ammonium phosphates was evaluated. The effect of hydrophobization on the texture properties, size, and shape of the NS additive particles was studied. The surface of the fire extinguishing component is uniformly coated by spherical hydrophobized NS nanoparticles without a high-speed mixing procedure. NS additive provides a highly hydrophobic coating to the particles of the FEP + NS fire extinguishing powder. The apparent contact angle of the coated particles was found to be larger than 160°. The dynamic flow resistance of commercial and FEP + NS fire extinguishing powders was compared. The specific energy and aerated flow energy of the FEP + NS is relatively low, thus indicating a weak aerodynamic interaction between the particles in dynamic processes. It was established that the spraying resistance of FEP + NS is the lowest among the studied fire extinguishing powders (including commercial ones), so it is characterized by the best flowability.