Papers by Maksim S Boldin
Journal of Advanced Ceramics
A glycine-nitrate self-propagating high-temperature synthesis (SHS) was developed to produce comp... more A glycine-nitrate self-propagating high-temperature synthesis (SHS) was developed to produce composite MgO-Gd2O3 nanopowders. The X-ray powder diffraction (XRD) analysis confirmed the SHS-product consists of cubic MgO and Gd2O3 phases with nanometer crystallite size and retains this structure after annealing at temperatures up to 1200 °C. Near full dense high IR-transparent composite ceramics were fabricated by spark plasma sintering (SPS) at 1140 °C and 60 MPa. The in-line transmittance of 1 mm thick MgO-Gd2O3 ceramics exceeded 70% in the range of 4–5 mm and reached a maximum of 77% at a wavelength of 5.3 mm. The measured microhardness HV0.5 of the MgO-Gd2O3 ceramics is 9.5±0.4 GPa, while the fracture toughness (KIC) amounted to 2.0±0.5 MPa·m1/2. These characteristics demonstrate that obtained composite MgO-Gd2O3 ceramic is a promising material for protective infra-red (IR) windows.
Russian Journal of Inorganic Chemistry, 2015
Izvestiya Vuzov. Poroshkovaya Metallurgiya i Funktsional’nye Pokrytiya (Proceedings of Higher Schools. Powder Metallurgy аnd Functional Coatings), 2015
Inorganic Materials: Applied Research, 2015
Russian Journal of Non-Ferrous Metals, 2014
The high temperature consolidation of nanopowders of pure tungsten carbide by electropulse plasma... more The high temperature consolidation of nanopowders of pure tungsten carbide by electropulse plasma sintering (spark plasma sintering) is investigated. The influence of the initial size of WC nanoparticles and their preparation modes on the density, structural parameters, and mechanical properties of tungsten car bide are investigated. Samples of high density nanostructured tungsten carbide with high hardness (to 31 GPa) and crack resistance (5.2 MPa m 1/2 ) are fabricated.
Technical Physics Letters, 2015
Ultrafine grained (UFG) tungsten carbide (WC) samples with high hardness (up to 34 GPa) and incre... more Ultrafine grained (UFG) tungsten carbide (WC) samples with high hardness (up to 34 GPa) and increased cracking resistance have been obtained by the method of spark plasma sintering (SPS). Initial pow ders have been prepared by two stage plasmachemical synthesis. The influence of the initial size of WC nano particles on the density, structural parameters, and mechanical properties of UFG tungsten carbide obtained by SPS has been studied. It is established that the phenomenon of accelerated sintering of WC powder is related to enhanced grain boundary diffusion.
Nanotechnologies in Russia, 2015
Ceramic materials based on Ca 0.5 Zr 2 (PO 4 ) 3 and NaFeNb(PO 4 ) 3 , structural analogs of NaZr... more Ceramic materials based on Ca 0.5 Zr 2 (PO 4 ) 3 and NaFeNb(PO 4 ) 3 , structural analogs of NaZr 2 (PO 4 ) 3 (NZP), were prepared by spark plasma sintering. At sintering temperatures of 1100-1200 and 880°C and sintering times of 12 and 3 min, the relative densities reached were 99.1 and 99.9%, respectively. According to X ray diffraction data, the sintering process caused no changes in phase composition. The ceramics had a dense, homogeneous microstructure and ranged in grain size from 0.5 to 2.5 µm.
ABSTRACT The structure and mechanical properties of nano- and ultradispersed mechanically activat... more ABSTRACT The structure and mechanical properties of nano- and ultradispersed mechanically activated heavy W-Ni-Fe and W-Ni-Fe-Co tungsten alloys (VNZh and VNZhK alloys, respectively) are studied. Mechanically activated nano- and ultradispersed charge powders are sintered by free sintering (thermally activated) and spark plasma sintering. The dependence of the density of the alloys made of the mechanically activated powders on the sintering temperature is found to have a nonmonotonic character with a maximum corresponding to the optimum sintering temperature. It is shown that an increase in the mechanical activation time and the acceleration of the milling bodies during mechanical activation lead to a decrease in the alloy particle size and the formation of nonequilibrium solid solutions and are accompanied by a decrease in the optimum sintering temperature of heavy tungsten alloys. Ultrahigh-strength tungsten alloys the mechanical properties of which are substantially higher than those of standard coarse-grained analogs are fabricated due to the optimization of the conditions of ball milling and high-rate spark plasma sintering of W-Ni-Fe powders.
Praseodymium and neodymium phosphates Ca 9 Ln(PO 4 ) 7 of the whitlockite structure were synthesi... more Praseodymium and neodymium phosphates Ca 9 Ln(PO 4 ) 7 of the whitlockite structure were synthesized in the form of powders via solid-phase reactions at high temperatures and in the form of ceramics using the two-step pressing + sintering process and one-step high-rate spark plasma sputtering (SPS) procedure. According to X-ray diffraction data, the phosphates were structural analogs of calcium phosphate, namely, of its low-temperature modification β-Ca 3 (PO 4 ) 2 , space group R3c. The particle size in the powders was 80-110 nm. The relative densities of the ceramics reached 99% when using SPS. The optimum conditions were found for obtaining high-density ceramics containing Pr and Nd. Their mechanical characteristics (microhardness, cracking resistance) were determined, and the microstructure was characterized.
Science Signaling, 2014
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Radiochemistry, 2014
Multicomponent oxides of pollucite structure, containing Cs and Ba, were synthesized as powders a... more Multicomponent oxides of pollucite structure, containing Cs and Ba, were synthesized as powders and ceramics. Their chemical compositions, Cs[MgAl 0.5 P 1.5 O 6 ] and Cs 0.875 Ba 0.125 [Li 0.125 Zn 0.875 Al 0.5 P 1.5 O 6 ], were modeled on the basis of the known structural features, taking into account the principles of iso-and heterovalent isomorphism of cations. From powdered samples synthesized using sol-gel process, a ceramic was prepared by spark plasma sintering (SPS). The sintering time was 3-4 min in the temperature interval 600-850°C. The relative densities were 97 and 99%. To evaluate the radiation resistance of the ceramics, the samples were irradiated with 132 Xe 26+ ions (E = 167 MeV) in the fluence interval from 6 × 10 10 to 1 × 10 13 cm -2 (ion flux density ~10 9 s -1 cm -2 ). The amorphization took place at fluences of (1.2-1.3) × 10 12 cm -2 . This fact suggests the decisive role of the ion energy loss for ionization in the generation of radiation defects. Conditions were found for the transition of the metamict form into the crystalline form on heating.
Proceedings of the National Academy of Sciences, 2006
Activation of mammalian innate and acquired immune responses must be tightly regulated by elabora... more Activation of mammalian innate and acquired immune responses must be tightly regulated by elaborate mechanisms to control their onset and termination. MicroRNAs have been implicated as negative regulators controlling diverse biological processes at the level of posttranscriptional repression. Expression profiling of 200 mi-croRNAs in human monocytes revealed that several of them (miR-146a͞b, miR-132, and miR-155) are endotoxin-responsive genes. Analysis of miR-146a and miR-146b gene expression unveiled a pattern of induction in response to a variety of microbial components and proinflammatory cytokines. By means of promoter analysis, miR-146a was found to be a NF-B-dependent gene. Importantly, miR-146a͞b were predicted to base-pair with sequences in the 3 UTRs of the TNF receptor-associated factor 6 and IL-1 receptor-associated kinase 1 genes, and we found that these UTRs inhibit expression of a linked reporter gene. These genes encode two key adapter molecules downstream of Toll-like and cytokine receptors. Thus, we propose a role for miR-146 in control of Toll-like receptor and cytokine signaling through a negative feedback regulation loop involving down-regulation of IL-1 receptor-associated kinase 1 and TNF receptor-associated factor 6 protein levels.
Journal of Sol-Gel Science and Technology, 2012
ABSTRACT Hexagonal barium titanate (HBT) thin films were prepared on borosilicate plate substrate... more ABSTRACT Hexagonal barium titanate (HBT) thin films were prepared on borosilicate plate substrates via sol–gel method using the dip-coating process. The structure, texture and morphology of the thin film were analyzed by X-ray diffraction, atomic force microscopy, nanoindentation technique, and transmission electron microscopy. The results showed that the thin film annealed at 700 °C crystallized with BaTiO3 hexagonal phase and traces of Ba2TiO4 (secondary phase). The nanoparticles and the RMS roughness of the sample treated at 700 °C presented high values when compared with those thermally treated at lower temperatures. The hardness and Youngs’ modulus of the thin films increased with increasing in grain size, and the thin film annealed at 700 °C with crystallite size about 10 nm presented multiple “pop-in” events during nano-indentation loading curves. The annealing temperature, growth size and surface roughness were discussed in connection with the HBT mechanical properties.
Journal of Experimental Medicine, 2008
Mammalian microRNAs are emerging as key regulators of the development and function of the immune ... more Mammalian microRNAs are emerging as key regulators of the development and function of the immune system. Here, we report a strong but transient induction of miR-155 in mouse bone marrow after injection of bacterial lipopolysaccharide (LPS) correlated with granulocyte/monocyte (GM) expansion. Demonstrating the suffi ciency of miR-155 to drive GM expansion, enforced expression in mouse bone marrow cells caused GM proliferation in a manner reminiscent of LPS treatment. However, the miR-155 -induced GM populations displayed pathological features characteristic of myeloid neoplasia. Of possible relevance to human disease, miR-155 was found to be overexpressed in the bone marrow of patients with certain subtypes of acute myeloid leukemia (AML). Furthermore, miR-155 repressed a subset of genes implicated in hematopoietic development and disease. These data implicate miR-155 as a contributor to physiological GM expansion during infl ammation and to certain pathological features associated with AML, emphasizing the importance of proper miR-155 regulation in developing myeloid cells during times of infl ammatory stress.
Journal of Experimental Medicine, 2011
Excessive or inappropriate activation of the immune system can be deleterious to the organism, wa... more Excessive or inappropriate activation of the immune system can be deleterious to the organism, warranting multiple molecular mechanisms to control and properly terminate immune responses. MicroRNAs (miRNAs), 22-nt-long noncoding RNAs, have recently emerged as key posttranscriptional regulators, controlling diverse biological processes, including responses to non-self. In this study, we examine the biological role of miR-146a using genetically engineered mice and show that targeted deletion of this gene, whose expression is strongly up-regulated after immune cell maturation and/or activation, results in several immune defects. Collectively, our findings suggest that miR-146a plays a key role as a molecular brake on inflammation, myeloid cell proliferation, and oncogenic transformation.
Journal of Biological Chemistry, 1995
Journal of Biological Chemistry, 1995
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Papers by Maksim S Boldin