A wide range of heat treated iron-based alloys (steels and white cast irons) was subjected to wear test in laboratory mill with the aim of discovering the correlation between microstructure type and ...impact–abrasive wear resistance under corrosion. The role of microstructure and chemical composition was identified through analysis of wear behavior under a range of slurries (pH 1–14) and analysis of the worn surface. It was found that the best wear performance is achieved with martensitic structure in steels containing not less than 13wt% Cr. The results showed that austenitic Cr3Ni, Cr3Mn and Mn-based steels do not demonstrate significant advantages in wear resistance over low-alloyed steels having martensitic microstructure. It was found that high-chromium white cast irons have average wear resistance because of embrittlement due to the presence of coarse eutectic carbides in the structure. It was also noted that wear resistance depends both on corrosive resistance and deformation resistance. Deformation resistance seems to play a more important role because it can largely compensate for the lack of corrosion resistance. It was concluded that low-alloyed hypereutectoid steel having “martensite–austenite–carbides free” microstructure could be considered the most effective alloy for use in wear application, taking into account its low cost.
•Impact–abrasive–corrosive wear resistance is mainly determined by microstructure.•Tribo-chemical interaction depends on slurry's pH value.•Deformation-induced martensite transformation improves alloys wear behavior.•Carbide phases decrease the alloys wear resistance.
New belemnite species of the family Cylindroteuthididae are described from the Ryazanian and Valanginian sediments of the Nordvik Peninsula, namely
Arctoteuthis angusta
sp. nov. and
Boreioteuthis ...mirifica
sp. nov. The species
Lagonibelus necopinus
(Gustomesov, 1960), which was previously known only from the North Urals, was recognized for the first time in East Siberia, and the study of ontogenetic changes in the rostra of this species allowed substantiation of its subfamily and generic affiliation.
In the present work two arc weld cladded alloys A (C3Cr25Ni3Si3) and B (C5Cr40Ni40Si2BZr) were tested under solid particle erosion at higher temperature (500 °C and 800 °C). The alloys were cladded ...using flux-cored strips PL-AN-101 and PL-AN-111, respectively. Alloy A is hypo-eutectic with a γFe + carbide M7C3 eutectic and austenite matrix. Alloy B is hyper-eutectic comprising coarse columnar M7C3 carbide, graphite flakes and an inhomogeneous austenitic matrix. It was found that alloy A presented a lower erosion rate of 18–41% at 500 °C due to the energy-consuming mechanisms of erosion (ploughing and poly-deformation). Alloy B was eroded by a low-cycle mechanism of carbide cracking/chipping. By increasing the testing temperature to 800 °C, the erosion rate of the alloys increased by 4.2–6.7 times. The erosion mechanism of the alloys at 800 °C was the formation and abrupt spalling of a depressed defective subsurface layer consisting of carbide fragments. Alloy A performed with a lower erosion rate of 39–44% at 800 °C due to a lower thickness of the defective layer. Oxidation had a negligible effect on the erosion rate of any of the alloys. The erosion rate of the coatings decreased with the distance from the coating top due to refinement of the carbide M7C3 and graphite inclusions.
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•Cladded alloys C3Cr25Ni3Si3 and C5Cr40Ni40Si2BZr were erosion tested at 500 °C and 800 °C.•With the temperature increase, the erosion rate increased by 4.2–6.7 times for both alloys.•C3Cr25Ni3Si3 showed a better erosion resistance over C5Cr40Ni40Si2BZr.•Primary carbides and graphite flakes in C5Cr40Ni40Si2BZr facilitated the surface erosion.
This article presents the systematic data on the effects of carbon and boron on the microstructure and phase elemental composition of the hybrid multi-component alloys, containing (wt pct) ...5W–5Mo–5V–10Cr–2.5Ti–1Mn–1Si–Fe(balance). The nominal concentrations of boron were 1.5, 2.5 and 3.5 wt pct; at each boron level, the carbon content was 0.3, 0.7 and 1.1 wt pct. The following phases were identified in the alloys: (a) (W,Mo,V)-based borocarbide M
2
(B,C)
5
(primary particles and eutectic fibers), (b) Ti-rich carboboride M(C,B) (primary dispersions); (c) (Cr,Fe)-rich carboboride M
7
(C,B)
3
(eutectic lamellae); (d) boroncementite M
3
(C,B) (eutectic plates); (e) matrix. Boron was responsible for the M
2
(B,C)
5
formation while the M(C,B) was controlled by carbon. Boron and carbon change the eutectic carboboride type as follows: M
2
(B,C)
5
→ M
7
(C,B)
3
→ M
3
(C,B). Furthermore, B and C deplete the matrix by chromium enabling the pearlite/martensite structure instead of ferrite. A microstructural map is proposed to select the composition for a specific wear condition.
The oxidation and decarburization behavior of 14.55 wt pct Cr-cast iron at 1273 K to 1423 K (1000 °C to 1150 °C) in a dry air atmosphere was studied. A gravimetric investigation showed that intensive ...oxidation of cast iron takes place at temperatures above 1273 K (1000 °C). It is found that oxidizing heating is accompanied by decarburization, which manifests itself in secondary and eutectic carbide dissolution. The volume fraction of carbides decreases with temperature and holding duration increasing. Decarburization results in the formation of a decarburized layer up to 4 mm in depth. A carbide-free layer in depth up to 100 μm appears in the free surface after 6 to 8 hours holding at 1373 K to 1423 K (1100 °C to 1150 °C). Preliminary activation energy calculations suggested that the eutectic carbide dissolution at the depths of 50 to 400 μm is controlled by carbon diffusion in austenite. The dissolution of eutectic carbides involves a capillarity-induced mechanism, which consists of formation and growth of capillary cavities inside carbides.
Bis(styryl) dye
bearing
-phenylazadithia-15-crown-5 ether receptor has been evaluated as a ratiometric fluorescent chemosensor for mercury (II) ions in living cells. In aqueous solution, probe
...selectively responds to the presence of Hg
via the changes in the emission intensity as well as in the emission band shape, which is a result of formation of the complex with 1:1 metal to ligand ratio (dissociation constant 0.56 ± 0.15 µM). The sensing mechanism is based on the interplay between the RET (resonance energy transfer) and ICT (intramolecular charge transfer) interactions occurring upon the UV/Vis (380 or 405 nm) photoexcitation of both styryl chromophores in probe 1. Bio-imaging studies revealed that the yellow (500-600 nm) to red (600-730 nm) fluorescence intensity ratio decreased from 4.4 ± 0.2 to 1.43 ± 0.10 when cells were exposed to increasing concentration of mercury (II) ions enabling ratiometric quantification of intracellular Hg
concentration in the 37 nM-1 μM range.
Problematic issues on creation and practical introduction of specific immune biologic prepa- rations for therapy and prophylaxis of natural-foci arbovirus infections - West Nile fever (WNF) and ...Crimean hemorrhagic fever (CHF), that are not available until now, are examined. Persistent natural foci of WNF and.CHF with epidemic manifestations have formed in Southern and North Caucasian Federal Districts of Russia. Markers of West Nile virus are being detected in central regions of Russia and Siberia, and the presence of fraction of population immune to this infection is also detected. Analysis, of literature sources that has been carried out forms a theoretical basis for creation ofnovel specific preparations for etiotropic, therapy and prophylaxis ofWNF and CHE. Use of blood from healthy donors with sufficiently high titers of class G immunoglobulins residing in certain subjects of Russian Federation in natural foci territories with the most intensive epidemic process is possible as raw material.
The natural flavonoid epigallocatechin gallate has a wide range of biological activities, including being capable of binding to nucleic acids; however, the mechanisms of the interactions of ...epigallocatechin gallate with DNA organized in chromatin have not been systematically studied. In this work, the interactions of epigallocatechin gallate with chromatin in cells and with nucleosomes and chromatosomes in vitro were studied using fluorescent microscopy and single-particle Förster resonance energy transfer approaches, respectively. Epigallocatechin gallate effectively penetrates into the nuclei of living cells and binds to DNA there. The interaction of epigallocatechin gallate with nucleosomes in vitro induces a large-scale, reversible uncoiling of nucleosomal DNA that occurs without the dissociation of DNA or core histones at sub- and low-micromolar concentrations of epigallocatechin gallate. Epigallocatechin gallate does not reduce the catalytic activity of poly(ADP-ribose) polymerase 1, but causes the modulation of the structure of the enzyme–nucleosome complex. Epigallocatechin gallate significantly changes the structure of chromatosomes, but does not cause the dissociation of the linker histone. The reorganization of nucleosomes and chromatosomes through the use of epigallocatechin gallate could facilitate access to protein factors involved in DNA repair, replication and transcription to DNA and, thus, might contribute to the modulation of gene expression through the use of epigallocatechin gallate, which was reported earlier.
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