Shtansky Dmitry Vladimirovich

The fundamental and technological principles for the fabrication of hexagonal boron nitride nanostructures of various morphologies (nanotubes, nanoparticles, nanosheets with a high specific surface) using chemical vapor deposition (CVD) [CrystEngComm. 18 (2016) 6689–6699; Nano Res. 8 (2015) 2063–2072; J. Mater. Chem. A 3 (2015) 20749-20757], as well as BN-based nanohybrids by the plasma-chemical method were developed. The sequence of phase transformations occurring during the interaction of boric acid with ammonia in a temperature range of 25–1000 °C was studied.It was demonstrated that at room temperature boric acid reacts with ammonia to form an ammonium borate hydrate (NH4)2B4O7×4H2O. Its interaction with ammonia upon further heating at 550 °C for an hour leads to the formation of turbostratic BN. Nanocrystalline h-BN is obtained either during heating in ammonia at 550 °C for 24 hours or at 1,000 °C for an hour. This result is important for the development of novel cost-effective and scalable syntheses of h-BN nanostructures, such as nanosheets, nanoparticles, nanofibers, and nanofilms (Ceramics International 46 (2020) 19866-19872).

The “know-how” on the “Method for the preparation of heterogeneous BN/Cu nanoparticles in a microwave plasma installation and device for its implementation” (No. 40 −457-2015 OIC on 11/18/2015), “Method for the production of BN/Ag nanohybrid catalysts” (No. 14-457 −2017 OIS on 11/15/2017), “Method for obtaining heterogeneous Al/BN nanoparticles in a microwave plasma installation and a device for its implementation” (No. 11-457- 2018 ОIS on 19.10.2018), and “Method for producing nanocrystalline hexagonal boron nitride” No. 13-457- 2019 ОIS on 09.12.2019) were registered. The successful application of these methods and a comprehensive study of the materials obtained allowed us to establish the basic mechanisms and conditions for the formation of BN nanostructures with the established morphology. Preparation methods and application of BN-based nanoparticles, nanosheets, and nanohybrids were described [Nanoscale 10 (2018) 17477-17493].

Under the leadership of the project supervisor, various methods for the synthesis of nanohybrid materials based on h-BN for catalytic processes were developed. Efficient hybrid nanocatalysts were developed in the Ag/BN and CuNi/BN systems, and the work is underway with nanohybrids in the Pt/BN and Au/BN systems. A higher catalytic activity of nanomaterials obtained by the decomposition of metal salts was established compared with the CVD synthesis, in which cladding of metal nanoparticles on the surface of h-BN occurs [Beilstein J. Nanotechnol. 9 (2018) 250–261]. It was shown, both experimentally and theoretically (by DFT method), that the chemical state of the support surface has a significant effect on the content of catalytically active nanoparticles. The optimal content of boron oxide on the surface of h-BN formed during the preliminary heat treatment may significantly increase the concentration of Ag nanoparticles, which leads to an increase in the catalytic activity of the material in the oxidation of methanol reaction. A mechanism for the oxidation of methanol on Ag/BN structures was proposed, and energy barriers of its various stages were calculated [Catal. Sci. Technol. 8 (2018) 1652-1662]. The effect of the synthesis environment on the tendency of nanoparticles of noble metals and carriers to agglomeration was studied. The analysis of the activation schemes of nanohybrid catalysts based on defect-free h-BN nanostructures revealed the important role of the oxidation activation stage (exposure in an oxygen enriched medium) as compared to the reduction (aging in a hydrogen enriched medium) on the catalytic activity of the material in the CO oxidation reaction [J. Catal. 368 (2018) 217–227].

Resulting from the comprehensive study of the evolution of the structure of heterogeneous Ag/BN structures, it was found that the formation of silver nanoparticles over h-BN surfaces is accompanied by intermediate stages of the formation of nanocomposite polymer structures with Ag particles, as well as silver acetate. It was shown that these structures may be effectively used to control the content and size distribution of silver nanoparticles on the h-BN surface during low-temperature (up to 150°C) annealing. Varying the duration and temperature of annealing may also be used to control their morphology. It was also shown that the intermediate layer between the metal particle and the substrate plays an important role in increasing the catalytic properties of the Ag / BN system in the CO oxidation reaction. So, with the same content and size distribution of silver nanoparticles, enhanced properties are demonstrated by heterogeneous Ag / BN nanostructures containing a thin Ag-O-B transition layer [Catal. Sci. Technol. 9 (2019) 6460-6470].

Nanohybrid materials (Cu0.8Ni0.2)/BN were obtained, and their high catalytic activity in the reaction of methanol reforming and oxidation of carbon monoxide was demonstrated. It was shown that the methanol conversion starts at ~20 °C and is nearly completed at 320 °C.It was demonstrated that the (Ni0.2Cu0.8)/BN nanohybrids exhibit high catalytic stability and high selectivity for CO2 over the entire temperature range. No carbon monoxide was detected during the full methanol conversion. The possible mechanism of CO utilization during methanol reforming was proposed using ab initio calculations. It was also established that the onset temperature of catalytic CO oxidation is 100 °C and full conversion is completed at 200 °C [Chem. Eng. J. 395 (2020) 125109].

It was established that an increase in the content of silver nanoparticles on the surface of h-BN by their formation by the polyol method is nonlinear. For the first time, the catalytic stability of the Ag/BN nanohybrid catalysts in the CO oxidation reaction was studied. Thus, correlations between Ag content, particle size distribution and temperature of complete CO conversion allow us to conclude that AgNPs, which size is below the critical value (3 nm), have a decisive role in Ag/BN nanohybrid catalytic performance. Exceeding this time leads to an increase in the concentration of silver on the h-BN surface due to the growth of particles and does not contribute to an increase in the catalytic activity of the material. It was found that the high catalytic activity of the Ag/BN nanohybrids in the CO oxidation reaction persists for a long time, and its decline is associated with the partial sintering of the smallest silver nanoparticles [ChemCatChem 12(6) (2020) 1691-1698].

A cross-bar structure is employed to design a transparent p-n junction-based photodetector. The device consisting of aligned n-SnO2 and p-NiO nanofibers exhibits a high detectivity of 2.33×1013 Jones under the 250 nm illumination at −5 V, outperforming most state-of-art SnO2-based UV photodetectors. The device is also equipped with the self-powered functions due to a photovoltaic effect from the pn junction, resulting in a photocurrent of 10−10 A, responsivity of 30.29 mA W−1 at 0 V bias, and detectivity of 2.24×1011 Jones at 0.05 V bias.Moreover, the device is highly transparent (over 90% toward visible light) due to the wide band gap of photoactive materials and a well-designed cross-bar fiber structure [Advanced Electronic Materials 6 (2020) 1901048].

The developed BN nanostructureswere successfully utilized to fabricate lightweight yet high strength aluminum-based composite materials [Mater. Sci, Eng. A 642 (2015) 104-112; 681 (2017) 1-9]. It was shown that with the addition of only 1% of BN nanosheets, the tensile strength of the Al/BN composite reached 150 MPa, which is 70% higher than that of pure Al [Mater. Sci. Eng. A 745 (2019) 74-81]. A detailed description of diffusion-controlled phase transformations in Al/BN composites obtained by pulsed plasma sintering was presented [J. Alloys & Comp. 782 (2019) 875-880]. Al/BN composites with the tensile strength of 380 MPa at room temperature and 175 MPa at 500 °C were obtained. As compared to pure Al, the growth was 135 and 185%, respectively, which is higher than when using other types of the hardening phase (carbon tubes, Al2O3, SiC, ZrO2, B2O3 particles) [Materials & Design 141 (2018) 88-98]. It was also shown that by varying the energy of Ag ions in the range of 2–20 kV, it is possible to obtain Ag/BN nanohybrids with a crystalline or amorphous structure and a different distribution of Ag nanoparticles on the BN surface [Materials & Design 98 (2016) 167-173].

Obtaining antibacterial yet biocompatible and bioactive surfaces is an important task that the biological and biomedical community has been facing for many years already, but the problem has not yet been completely handled. Under the guidance of the project supervisor, new types of coatings with an antibacterial effect were developed [Applied Surface Science 330 (2015) 339; Colloids and Surfaces B: Biointerfaces 135 (2015) 158; Advanced Biomaterials and Devices in Medicine 1 (2015) 37; Journal of Biomedical Materials Research — Part B Applied Biomaterials, 105B (2017) 193-203; Mater. Sci. Eng. C 90 (2018) 289-299]. The results showed that there is an optimal range of antibacterial agent content and the type of its agglomeration, in which the films are biocompatible, bioactive and bactericidal. A kinetic model was developed for the deposition of coatings doped with Ag [Materials Letters 156 (2015) 118].

For the first time, boron-doped TiCaPCON coatings were obtained, and their antibacterial activity was studied (Applied Surface Science 465 (2019) 486–497). It was shown that boron may be considered as an alternative to silver in antibacterial films. For the first time, Ag doped surfaces with a specific surface topography showing a high antibacterial activity were obtained by photolithography (Colloids and Surfaces B, 173 (2019) 719-724). Bioactive bio-soluble polymer nanofibers coated with TiCaPCON films were obtained, and their potential for bone tissue engineering was demonstrated (Applied Surface Science 479 (2019) 796-802).

It was shown for the first time that the concentration of ions released in a biological medium depends not only on the content of the bactericidal element in the coating, but also on the topography and surface roughness (ACS Applied Materials & Interfaces, 9 (2017) 4259-4271). The dependence of the bactericidal ions release on the degree of surface oxidation was also demonstrated. For the first time, the contribution of various bactericidal ions to the overall material bactericidal activity was established (ACS Applied Materials & Interfaces, 10 (2018) 24406-24420). The researchers managed to achieve a 100% bactericidal effect against Escherichia coli and Staphylococcus aureus strains with an extremely low concentration of Ag ions, 0.11 and 0.3 ppb, respectively.

New type of coatings decorated with metal nanoparticles were developed. It was shown that new materials effectively inhibit the growth of eight types of bacteria: Escherichia coli K261 and U20, Klebsiella pneumoniae B1079k/17-3, Acinetobacter baumannii B1280A/17, Staphylococcus aureus no. 839, Staphylococcus epidermidis i5189-1, Enterococcus faecium Ya-235: VanA and I-237: VanA, including antibiotic resistant ones. The bactericidal effect is achieved due to the intensive release of bactericidal ions, the generation of reactive oxygen species, and microgalvanic interaction. The results wee published in the high-ranking journal of the American Chemical Society (ACS Applied Materials & Interfaces 11 (2019) 28699-28719).

For the first time, the pulsed electrospark deposition technology was used to produce biocompatible and bioactive films with an antibacterial effect. The results were published in a number of Q1 journals: Surface and Coatings Technology, 302 (2016) 327-335; 309 (2017) 75-85; Ceramics International, 44 (2018) 3765-3774.

The method of plasma electrolytic oxidation (PEO) in electrolytes with particle additives was used to obtain hydroxyapatite-titanium dioxide coatings onto a Ti surface. Their microstructure and biological properties were studied in vitro (RSC Advances 6 (2016) 12688-12698). PEO coatings doped with hallotasite benzotriazole nanotubes on the AM50 magnesium alloy were also obtained (Corrosion Science 111 (2016) 753-769). For the first time, Ag/TiO2 and Pt/TiO2 coatings were obtained by a combination of microarc oxidation and ion implantation methods. The Ag-doped TiO2 coating exhibited a strong bactericidal effect against E. coli U20 (antibiotic-sensitive), E. coli K261 (antibiotic-resistant), S. aureus 839, and S. aureus 224/228 (methicillin-resistant) strains and inhibited the early stage of their biofilm formation. The Pt/TiO2 sample was effective toward E. coli U20 and antiadhesive for S. aureus 224/228 strains. The surface of TiO2-based coatings was adhesive for osteoblastic cells and able to maintain a high level of MC3T3-E1 cell proliferation [Applied Surface Science 516 (2020) 146068].

Another promising research area, actively developing under the guidance of the project supervisor, is plasma polymerization [Appl. Surf Sci. 435 (2018) 1220-1227] and surface functionalization of bio-soluble plasma polymers [Polymers 9 (2017) 736; Materials & Design, 132 (2017) 257-265]. To impart biosoluble polymer nanofibers with antibacterial characteristics, they were modified by the plasma polymerization of maleic anhydride and immobilization of gentamicin [Materials and Design 153 (2018) 60-70]. The immobilization of bioactive components using the grafting of platelet-rich blood plasma on COOH-modified fibers was shown to be a promising approach. Recently obtained results were published in the journal Nanomaterials 9 (2019) 637.

For the first time, BN nanoparticles with a petal-like surface were obtained by chemical vapor deposition and characterized as a promising anticancer drug-delivery system. The efficiency of nanocarriers against tumor cells with multidrug resistance was demonstrated [Applied Materials & Interface 7 (2015) 17217; ACS Applied Materials & Interfaces 9 (2017) 32498-32508]. An experimental and theoretical study of the chemical interaction of doxorubicin with BN(O) nanocarriers was carried out [J. Phys. Chem. C 122 (46) (2018) 26409-26418]. A method for the surface functionalization of BN nanoparticles with targeted legends for their targeted delivery to tumor cells was developed [J. Phys. Chem. C 121 (2017) 28096–28105].

TiAlSiCN coatings with extremely high thermal stability were obtained. The nanocomposite columnar coating structure does not undergo any structural changes upon annealing in vacuum up to 1,300 °C [Acta Mater. 83 (2015) 408-418]. The further surface modification of the TiAlSiCN coatings by deposition of a thin amorphous TiOx layer allowed researchers to increase the high-temperature oxidation resistance in air from 1,000 to 1,100 °C [Applied Surface Science 347 (2015) 713-718]. Multilayer coatings of SiBCN/TiAlSiCN and AlOx/TiAlSiCN with thermal stability up to 1,400 ° C and oxidation resistance up to 1,100 ° C were developed [Surf. Coat. Technol. 319 (2017) 277-285].

Studies aimed at obtaining nanocomposite self-lubricating coatings were delivered. MoSeC/TiAlSiCN nanocomposite coatings with a low coefficient of friction (< 0.1) and high wear resistance in the temperature range of 25-300 °C were developed.The coatings also showed excellent electrochemical characteristics in a H2SO4 solution at low polarization (< 0.5 V) and excellent tribological characteristics when tested in water [Applied Surface Science 327 (2015) 253-261]. The sequence of structural transformations during testing of MoCN-Ag nanocomposite coatings in the temperature range of 25-700 ° C was described.It was shown that a low coefficient of friction below 250 °C is associated with tribo-activated formation of carbon-containing nanofibers perpendicular to the load applied. Good self-lubricating characteristics at elevated temperatures are associated with an almost complete absence of wear and the formation of a thin tribo-activated MoOx layer [Materials & Design 93 (2016) 63-17]. Hard VCN-Ag coatings (hardness of 15-17 GPa) were developed, which withstand high elastic and plastic deformation without adhesive failure at the load of up to 1,000 N for 105 cycles without any brittle fracture [Surf. Coat. Technol. 331 (2017) 77-84]. It was shown, for the first time, that the simultaneous introduction of Nb and Ag overcomes the main disadvantages of TiCN coatings, such as a high friction coefficient at elevated temperatures and low heat resistance. Ag-doped coatings were highly resistant to high temperature oxidation and showed a self-healing effect due to the segregation of Ag metallic particles on defects (scratches, chips, pores and oxidation sites) [Appl. Surf Science 396 (2017) 110-120]. Spherical BN nanoparticles were shown to be promising additives to oil lubricants [Ceramics International 44 (2018) 6801-6809]. For the first time, the mechanical tests of hollow BN nanospheres in an electron microscope column were carried out. It was shown that BN particles are able to withstand a significant cyclic deformation (up to 30% of their outer diameter) and accumulate plastic deformation of up to 30% of compression deformation [Nanoscale 10 (2018) 8099]. The synergistic effect of the simultaneous addition of h-BN nanoplates and spherical W nanoparticles to a synthetic oil was demonstrated for the first time: the friction coefficient and wear rate reached minimum values. Molecular dynamics (MD) simulations and in situ TEM mechanical tests showed that the positive effect of adding spherical W NPs may be attributed to their rolling and sliding in the tribological contact zone. The formation of W/BN core/shell nanoparticles provides a superior macroscale lubricity [Tribology International 151 (2020) 106493].

For the first time, the new technology combining pulsed-arc evaporation (PAE) and electrospark deposition (ESD) in vacuum in a single technological cycle was developed. The excellent tribological properties of WC/a-C two-layer coatings are explained by the formation of a functional gradient structure with a smooth change in grain size and hardness from 3.6 GPa (Ti substrate) to 20 GPa (upper coating layer), increased strength and thickness of the electrospark deposited sublayer, which protects the substrate from plastic deformation, and a low coefficient of friction of the upper layer due to the formation of an amorphous structure with a high volume fraction of a-C phase providing good solid lubrication [Materials & Design 167 (2019) 107645]. In situ mechanical tests in an electron microscope column showed a high adhesive strength between the layers (the interface can withstand a load of 560 MPa). It was shown that in two-layer TiNbC coatings obtained by a combination of the ESD and PAE methods, the upper PAE layer provides wear protection for the less wear-resistant ESD sublayer. At the same time, a thick ESD underlayer with improved toughness prevents plastic deformation of the substrate under high loads [Surf. Coat. Technol. 385 (2020) 125422].