Increasing Cr Content Research Articles

Chromium (VI)-Induced Alterations in Physio-Chemical Parameters, Yield, and Yield Characteristics in Two Cultivars of Mungbean (Vigna radiata L.).

Chromium (Cr) presently used in various major industries and its residues possess a potent environmental threat. Contamination of soil and water resources due to Cr ions and its toxicity has adversely affected plant growth and crop productivity. Here, deleterious effects of different levels of Cr (VI) treatments i.e., 0, 30, 60, 90, and 120 μM on two mungbean cultivars, Pusa Vishal (PV) and Pusa Ratna (PR), in hydroponic and pot conditions were evaluated. Germination, seedling growth, biomass production, antioxidant enzyme, electrolytic leakage, oxidative stress (hydrogen peroxide and malondialdehyde), and proline content were determined to evaluate the performance of both cultivars under hydroponic conditions for 15 days. The hydroponic results were further compared with the growth and seed yield attributes of both the genotypes in pot experiments performed over 2 years. Seedling growth, biomass production, total chlorophyll (Chl), Chl-a, Chl-b, nitrogen content, plant height, seed protein, and seed yield decreased significantly under the 120 μM Cr stress level. Activities of antioxidant enzymes superoxide dismutase, catalase, ascorbate peroxidase and peroxidase increased in the leaves following Cr exposure at 60–90 μM but declined at 120 μM. Cr-induced reductions in growth and seed yield attributes were more in the sensitive than in the tolerant cultivar. Cr accumulation in the roots, stems, leaves, and seeds increased with an increase in Cr concentrations in the pot conditions. Furthermore, for both cultivars, there were significant negative correlations in morpho-physiological characteristics under high Cr concentrations. Overall results suggest that (PR) is more sensitive to Cr stress (PV) at the seedling stage and in pot conditions. Furthermore, (PV) can be utilized to study the mechanisms of Cr tolerance and in breeding programs to develop Cr-resistant varieties.

Stress-induced transformation behavior in near-eutectic (AlNi2)70-xCo30Crx medium entropy alloys

The present investigation was an evaluation of the microstructure and mechanical properties in as-cast non-equiatomic medium entropy alloys (MEAs) (AlNi2)70-xCo30Crx (with x = 2.5, 10, 17.5, and 25 at.%), showing dual- or multi-phases structure (near-eutectic microstructure). The majority phase of developed MEAs was FCC (L12) phase and the minority phase was the ordered BCC (B2) phase. The t typical eutectic microstructure was formed in the matrix area of all MEAs and a little dendrite structure was identified in microscopic analysis. The dendrite structure changed from the B2 phase to the L12 phase with an increase in Cr contents. When the composition of Cr contents was 10% that consists of a fully eutectic structure, it showed the highest yield strength of 865.7 MPa together with excellent plastic strain. Interestingly, it was found that abnormal deformation behaviors were also observed in the stress-stain curve exhibiting two times of yielding phenomenon typically called “double-yielding”. Through TEM analysis, it was confirmed that the observed double-yielding phenomenon is related to the phase transformation from the B2 phase which constitutes the eutectic lamellar to L10 phases during compressive loading. In this study, we discussed detailed deformation mechanisms that can induce excellent mechanical properties of eutectic MEAs.

Effect of LCFeCr Alloy Additions on the Non-metallic Inclusion Characteristics in Ti-Containing Ferritic Stainless Steel

The influence of commercial low carbon ferrochromium (LCFeCr) additions on the inclusion characteristics in Ti-containing ferritic stainless steel was studied by laboratory experiment in this work. The inclusions in steel before and after the FeCr alloy additions were investigated through systematic samplings and microscopy investigations of the liquid steel. Different types of inclusions in the FeCr alloy and steel were detected and the evolution of the inclusion characteristics (e.g., composition, size, morphology, and number density) were investigated. The results showed that the Ti content decreased after the FeCr alloy additions. Furthermore, MnCr2O4 spinel inclusions originating from the FeCr alloys transformed into Ti2O3–Cr2O3-based liquid inclusions and Ti2O3-rich solid inclusions. They were formed due to the reactions between MnCr2O4 and TiN inclusions or dissolved Ti in molten steel. The ratio of Ti/Al in the steel melt has a direct influence on the evolution of inclusions from thermodynamic calculations. The addition of FeCr alloys caused an increased number density of these Ti2O3-containing inclusions and TiN inclusions up to 8 minutes from the time of alloy addition. The increased Cr content from 16 to 24 mass pct due to the FeCr additions can increase the critical N content to form TiN inclusions at a specific Ti content. Overall, this study has contributed to the understanding the behavior of inclusions from LCFeCr alloy during the alloying process in Ti-containing steel.

Inclusion engineering in Co-based duplex entropic alloys

Co-based duplex entropic alloy is designed very recently to replace pure Co as a major component of the binder phase for cemented carbide cutting tools. This work aims to provide a fundamental study of oxide inclusion characteristics in the duplex fcc + hcp Co-based entropic alloys. It is found that the Co85−xCrxFe7.5Ni7.5 (x = 15, 30 at.%) alloys hold the highest liquidus (Tliq) and solidus (Tsol) temperatures, compare with the Co85−xCrxMn7.5Ni7.5 (x = 15, 30 at.%) and Co77.5−xCrxFe7.5Mn7.5Ni7.5 (x = 15, 30 at.%) alloys. For each grade, the increasing Cr content leads to a decrease of Tsol and Tliq temperatures. It is also noted that there is an approximate 100 °C of undercooling exists in each grade during the solidification. The stable oxide inclusion in the Co85−xCrxMn7.5Ni7.5 and Co77.5−xCrxFe7.5Mn7.5Ni7.5 alloys is the MnCr2O4 type, while Cr2O3 is the main stable inclusion in the Co85−xCrxFe7.5Ni7.5 alloy. Furthermore, the size range of the MnCr2O4 particles is larger than that of Cr2O3. The theoretical calculation shows that MnCr2O4 has a higher coagulation coefficient than Cr2O3 does. This is due to the influence of the thermo-physical parameters, i.e. the interfacial energy between the oxide and the alloy and the viscosity of liquid alloy. The theoretical calculation fits well with the experimental findings.

Differential strategies of two species of arbuscular mycorrhizal fungi in the protection of maize plants grown in chromium-contaminated soils.

Chromium (Cr) is a nonessential element for plants that is extremely toxic at high concentrations. Zea mays L. is a species of plant that has developed adaptive mechanisms to increase its tolerance and absorption capacity for this metal. One effective mechanism is to form associations with arbuscular mycorrhizal fungi (AMF), which help the plant cope with stress from heavy metals such as Cr. However, it is still not clear which species of AMF are more efficient as bioremediating agents for plants of agricultural importance. Here, we evaluated the effect of Gigaspora gigantea and Rhizophagus irregularis as protective agents of maize plants in soils contaminated with Cr at concentrations of 0, 48.5, 97 and 194mgkg-1 under greenhouse conditions. Maize tolerance to Cr was corroborated, as well as increased absorption of this element by plants associated with both species of AMF. G. gigantea caused an increase in nitrogen content and greater translocation of Cr to the aerial part of the plant; R. irregularis registered an increase in the formation of arbuscules and vesicles with increasing metal concentration and greater retention of Cr in the roots of the plants. Based on these results, we can conclude that the analyzed species of fungi use different strategies, with similar effectiveness, to enhance the absorption capacity of Cr by the plant and influence the differential deposition of this metal in various parts of the plant.

Preparation and electrochemical performance of Li 2 MnSiO 4 cathode material doped with chromium on manganese site

In this work, Li2Mn1–xCrxSiO4 cathode material was synthesized by the solid-phase doping method and two-step calcination. The appropriate calcination temperature can be obtained by TG-DTA curve. XRD, SEM and TEM tests show that the prepared Li2Mn1–xCrxSiO4 has a Pmn21 space group structure, and the particle size decreases from 570 to 140 nm with the increase of the doped Cr content. Cr doping enhances the structural stability of Li2Mn1–x CrxSiO4 and improves the electrochemical activity of the cathode. The results of XRD, EDS and XPS show that Cr3+ is successfully doped into the Li2MnSiO4 lattice, and the element distribution is uniform. The electrochemical results show that Li2Mn0.8Cr0.2SiO4 exhibits significantly enhanced cycle stability and discharge capability.

Possible half-metallic behavior of Co2−xCrxFeGe Heusler alloys: Theory and experiment

This paper reports a combined experimental and theoretical study of structural, electronic, magnetic, and mechanical properties of quaternary Heusler alloys ${\mathrm{Co}}_{2\ensuremath{-}x}{\mathrm{Cr}}_{x}\mathrm{FeGe}$ prepared by arc-melting with Cr concentrations $0\ensuremath{\le}x\ensuremath{\le}1$. Single-phase microstructures are observed for Cr compositions from $x=0.25$ to $x=1$. Lower Cr concentrations are multiphased. X-ray diffraction patterns at room temperature reveal a face-centered cubic crystal structure in all single-phase samples. The low-temperature saturation magnetic moments, as determined from magnetization measurements, agree fairly well with our theoretical results and also obey the Slater-Pauling rule for half-metals, a prerequisite for half-metallicity. All alloys are observed to have high Curie temperatures that scale linearly with the saturation magnetic moments. Relatively high mechanical hardness values are also observed. First-principles calculations also predict a finite band gap in the minority spin channel of the alloys, increasing in size with increasing Cr concentration. Cr substitution brings the Fermi level toward the center of this gap while also increasing the majority spin density of states near the Fermi level. As a whole, ${\mathrm{Co}}_{2\ensuremath{-}x}{\mathrm{Cr}}_{x}\mathrm{FeGe}$ shows great promise as a half-metal with 100% spin polarization.

Experimental investigation on the erosion behavior in high-current vacuum arcs and resulting microparticles dynamics

Microparticles are an inevitable component of vacuum arcs. This paper focused on the dynamics of microparticle and erosion behavior in high-current vacuum arcs. The arc was sustained with AC 110 Hz between two butt CuCr alloy contacts with a diameter of 10 mm. An in situ microparticle diagnostic system suitable for vacuum arcs was developed. Three sources of microparticles were observed and the corresponding motion characteristics were obtained by our method. The influence of current and Cr content on erosion characteristics was investigated. The results indicate that the increase of Cr content contributes to inhibiting production of microparticles when the current is small. CuCr30 has the best effect of suppressing microparticle production among the three tested alloy materials under large current. The work of this paper helps with the understanding of microparticle behavior in high-current vacuum arcs and may provide a path for the design of a vacuum electrode.

Microstructures and properties of Fe1.25CoNi1.25CrxAl0.25 high-entropy alloys after cold-rolling and annealing

Microstructures and properties of Fe1.25CoNi1.25CrxAl0.25 (x=0.5, 0.75, 1) high-entropy alloys (HEAs) fabricated by copper mold suction casting were studied in this paper. The crystal structure of the alloy is composed of single-phase FCC solid solution, and the crystal structure does not change with the change of Cr content. The yield strength of as-cast alloys is below 200 MPa, and the elongation is above 50%. After cold-rolling and annealing, the strength and hardness of the alloy increase with the increase of Cr content. The comprehensive mechanical properties of the alloy with x=1 reach the best. The yield strength, tensile strength and elongation are 498 MPa, 770 MPa and 40%, respectively. The cubic texture of {001}<100> is the strongest texture of the specimen with x=0.5. The appropriate addition of Cr is beneficial to improve the corrosion resistance of the alloy. The alloy with x=0.75 has the best corrosion resistance in 0.5 mol/L H2SO4. The reduction of Cr content is advantageous to improve the soft magnetic properties of alloys, and Fe1.25CoCr0.5Ni1.25Al0.25 shows excellent magnetic properties. The Fe1.25CoCr0.5Ni1.25Al0.25 HEA, meanwhile, has good processability with the elongation over 50%.

Effect of dopants on the structural, optoelectronic and magnetic properties of pristine AgGaO3 perovskite: A first principles study

The structural, electronic and optical properties of pristine AgGaO3 and doped Ag1-xCrxGaO3 (x = 0.25, 0.50 and 0.75 at%) have been explored using first principle simulation based on density functional theory (DFT). The Perdew-Burke-Ernzerhof – Generalized Gradient Approximation (PBE-GGA) is used to optimize the geometry of pristine and Cr doped AgGaO3 systems. Structural analysis demonstrates that the calculated lattice parameters and unit cell volume decrease with the increase of Cr concentration. The incorporation of Cr at Ag sites significantly affects the electronic band gap of AgGaO3. All materials are found to be semiconductor with direct band gap values of 1.42 eV, 1.26 eV, 0.65 eV and 0.37 eV for pristine AgGaO3 and Cr doped Ag1−xCrxGaO3 (at x = 0.25, 0.50, 0.75 at%), respectively. The localized energy states of 75% Cr doped AgGaO3 play significant role to enhance optical conductivity. Further, Penn’s model is confirmed by observing the inverse relationship between the dielectric function and electronic band gap. The significant variations noted in electronic band gap as well as optical characteristics caused by the doping of Cr declares that the doped materials are more appropriate candidates for solar cell and optoelectronic like applications as compared to pristine AgGaO3. It is further established that magnetism is induced in all Cr doped perovskites. The net magnetic moment computed for each Cr atom is 3 μB. All doped systems are found to be ferromagnetic in nature.

Effect of La/Cr co-doping on dielectric dispersion of phase pure BiFeO3 nanoparticles for high frequency applications

Abstract Energy storage materials play a vital role in modern technology. A single device can perform multifunctions if fabricated using a multifunctional material like BiFeO3. For this purpose, a series of La and Cr doped BiFeO3 was synthesized using sol‒gel auto-combustion technique. A single phase rhombohedral distorted perovskite crystal structure related to bismuth ferrite with space group R3c (161) was confirmed from the X-ray diffraction patterns. Doping of La/Cr at Bi/Fe lattice sites in BiFeO3 did not affect the crystal symmetry of the parent compound. Morphological analysis exhibited homogeneous micro structures showing uniform distribution of multi-shaped grains with decreasing porosity and grain sizes with increasing Cr contents. These materials exhibited the conventional ferrite-like dielectric response, which gradually decreased with increasing frequency and lastly became constant in the high frequency regime. Impedance spectroscopy revealed the contribution of grains, grain boundaries and interfaces in electrical response of the samples. Frequency dependent electric modulus analysis confirmed the non-Debye type relaxation.

Chromium induced changes in growth and physiological attributes of Chicory (Cichorium intybus L), an important medicinal plant

This study was conducted to determine the impact of different concentrations (25, 37.5 and 50 mg kg-1 soil) of chromium (Cr) on growth, photosynthetic pigments, protein content, proline content, activities of antioxidant enzymes and seed yield of Cichorium intybus in a pot experiment. The results revealed that all the Cr treatments significantly (P &lt;/= 0.05) reduced the growth, photosynthetic pigments (chlorophyll a, chlorophyll b and total chlorophyll and carotenoids contents), protein content and seed yield in C. intybus. The activities of catalase (CAT), superoxide dismutase (SOD), peroxidase (POD) and proline content in C. intybus leaves increased significantly (P &lt;/= 0.05) with increasing levels of Cr treatments. Cr accumulation was found greater in the roots than in the shoots and enhanced with increasing Cr concentrations. Hence, C. intybus may serve as a bio-meter of Cr in Cr contaminated soils.

Thermodynamic, Thermal, and Structural Stability of Bimetallic MIL-53 (Al1–xCrx)

Understanding the stability of porous materials, especially metal–organic frameworks (MOFs), is central to defining their applications in gas storage, separation, and catalysis. Herein, integrating high-temperature drop combustion calorimetry as well as simultaneous thermal and in situ structural analyses, we performed a comprehensive study on the thermodynamic, thermal, and structural stabilities of MOF in air. A family of MIL-53 (Al1–xCrx) with systematically tuned metal contents was intentionally chosen considering their unique property that H2BDC species serve as both coordinated linkers and guest species confined. The results suggest that as temperature increases, all samples underwent (1) a phase transition from the pore-filled Pnma to the Imma with empty pores, (2) structural degradation, and (3) complete oxidation (burning). At the same temperature, as the chromium (Cr) content increases, the thermal and structural stability of MIL-53 (Al1–xCrx) in air decreases. In contrast, interestingly, the intrinsic thermodynamic stability systematically increases as a function of Cr content, evidenced by the more exothermic enthalpies of formation, ranging from 92.8 ± 73.4 kJ/mol (slightly metastable) to −1593.2 ± 60.8 kJ/mol (stable). Such a phenomenon is likely due to enhanced H2BDC–MIL-53 guest–host interactions upon Cr substitution, which energetically neutralize the metastability of MIL-53 open frameworks. This study highlights that the thermal, structural, and energetic stabilities are different and have equal importance in governing the synthesis and applications of MOFs.

Facile synthesis of Cr-Co co-doped CdO nanowires for photocatalytic, antimicrobial, and supercapacitor applications

Pristine CdO and chromium (Cr)-cobalt (Co) co-doped CdO nanowires via a facile co-precipitation protocol were synthesized and characterized with different analytical techniques to investigate its physical, photocatalytic, antibacterial, and electrochemical properties. The co-doping of Cr-Co into CdO matrix and their structural variations were confirmed by X-ray diffraction (XRD) data. Fourier transform infrared (FTIR) and Raman spectra also confirmed the doping of Cr and Co ions. The energy bandgap was extracted by employing different methods using UV–vis results, exhibited redshift by decreasing Co contents and blue shift by increasing Cr concentration. Scanning electron microscopy (SEM) images confirmed the preparation of nanowires. The photocatalytic and antibacterial experiments results showed the higher photodegradation efficiency against methylene blue (MB) (99.5%), methyl orange (MO) (90.6%), rhodamine-B (RhB) (87.5%), safranin-O (SF) (87.5%), and methyl red (MR) dyes (99.99%), after 60 min of sunlight illumination and the higher zone of inhibition (ZOI) against Klebsiella pneumoniae and Staphylococcus aureus for optimal doped Cd0.90Co0.05Cr0.05O (Cd4) sample. The recyclability tests using Cd4 catalyst were exhibited higher stability up to 5th cycles. The higher ability to decompose dyes and kill bacteria is due to the generation of reactive species, confirmed by the radical trapping experiments. The electrochemical measurements were revealed that the Cd4 sample has a higher specific capacitance of 500 F/ g− 1 at 10 mV/s scan rate, excellent energy density 72 Wh/Kg, and greater power density of 4800 W kg− 1 at a current density of 0.1 A/g. Furthermore, the properties of CdO can be tuned by co-doping for making it a useful material for photocatalyst, supercapacitors electrodes, and antibacterial applications.

Structural and electrical properties of YMnO3 manganites: Influence of Cr ion doping

The crystalline samples of YMn1-xCrxO3 (x ​= ​0.0, 0.03) were synthesized by a conventional solid-state reaction technique. The single-phase wurtzite hexagonal structure with the P63cm space group was verified by X-ray diffraction (XRD) patterns accompanied by Rietveld refinement. The elevation of the Cr doping leads to a reduction in the crystallite size, although the lattice parameter has slightly improved as compared to pristine YMnO3. SEM analysis indicates a decrease in grain size from 1.35 to 1.26 ​μm with the increased Cr content in the crystal system. Almost similar Raman spectra are observed for both samples. The dielectric constant and loss tangent shows the normal dispersion due to the Maxwell–Wagner interfacial polarization. Furthermore, we discovered that Cr ion doping in YMnO3 doping increases the dielectric constant. The ac conductivity in the given frequency range is increased with frequency and explained by the hopping mechanism. The grain and grain boundary contributions are discussed using impedance and modulus spectroscopy, which shows the existence of non-Debye relaxation mechanisms. The electrical modulus analysis revealed that the grains play a major role in the conduction mechanism in these samples. The existence of hysteresis loops supports the presence of multiferroic properties in the samples.

Nanocrystalline fiber cells of ZnO thin films doped with chromium: Synthesis, characterization and application for solar cells

In this work, we investigated the influence of Chromium (Cr) concentration 1.5 wt%Cr- 3.5 wt%Cr on the properties of zinc oxide (ZnO) thin films deposited by Dip-Coating technique. The structural, morphological and electrical properties of the obtained thin films are investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and by electrical measurements for testing solar cell performances. It was found that the doped films become more amorphous by increasing Cr concentrations. As a result, the surface morphology of ZnO thin films exhibits the formation of different structures of: nanofibers, nanofibrils and nanorods clearly distributed inside ZnO cells. Moreover, it was also observed that the n-type ZnO is inverted to p-type for 1.5 and 2.5 wt%Cr. The most suitable electrical parameters for this study were obtained for 1.5 wt%Cr doped ZnO solar cells and for 2.5 wt%Cr doped ZnO with an efficiency of 24.32% and 22.43%, respectively.

High magnetic coercive field in Ca‐Al‐Cr substituted strontium hexaferrite

The structural and magnetic properties of Sr0.67Ca0.33Fe9Al3−xCrxO19 submicrometric powders with substitution levels ranging from x = 0 up to x = 3, prepared by sol-gel synthesis method, have been investigated. The powders were characterized by high resolution synchrotron X-ray diffraction, scanning electron microscopy, powder neutron diffraction and MPMS-SQUID magnetometer. The structural analysis shows that upon Ca-substitution of SrFe12O19 at the Sr site and Al–Cr at the Fe sites, the magnetoplumbite structure is preserved, even for large levels of substitutions. The X-ray powder diffraction peak broadening and Williamson-Hall plots analyses indicate an increase of crystallites size and relaxation of the microstrain with increasing amounts of Chromium. The magnetic hysteresis loops reveal high coercivity fields at room temperature, with the highest value of HC = 1125 kA/m (1.41 T) obtained for Sr0.67Ca0.33Fe9Al2.5Cr0.5O19 powder interesting to develop free-Rare Earth high coercivity magnets. The saturation magnetization and remanence values increase monotonically with increasing Cr content while the switching field decreases. The structural Rietveld refinement of combined X-ray/neutron diffraction data shows the affinity of Al3+ and Cr3+ cations to migrate mainly towards (2a) Fe-Oh2 and (12k) Fe-Oh3 sites and only minor amounts is found on the (4f1) Fe-Oh1 octahedral sites. The structural observations corroborate the magnetic properties, demonstrating a correlation between the structure and magnetic properties in Ca–Al–Cr substituted strontium hexaferrite. The role of the particle size to maximize the coercivity properties is discussed.

Enhancement of multifunctional optoelectronic and spintronic applications of nanostructured Cr-doped SnO2 thin films by conducting microstructural, optical, and magnetic measurements

A chemical synthesis method was used to produce Cr-doped SnO2 nanoparticles. By using the TEM technique, the nanocrystalline nature of the Sn1-xCrxO2 (0.0 ≤ x ≤ 0.1) nanopowder was confirmed. With different Cr concentrations, the electron beam deposition technique was used to deposit a series of Sn1-xCrxO2 nanocrystalline thin films on a silica substrate. X-ray diffraction (XRD), atomic force microscopy (AFM), spectroscopic ellipsometry (SE), and vibrating sample magnetometry (VSM) techniques were used to examine the physical properties of the deposited films. The nanocrystalline nature of the Sn1-xCrxO2 (0.0 ≤ x ≤ 0.1) thin film was confirmed by XRD and AFM morphology measurements. The XRD spectrum of the Sn1-xCrxO2 nanocrystalline film demonstrated a tetragonal crystal structure with no detectable extra phases. The optical measurements showed that as the Cr content increases, the direct optical energy gap Eg decreases without any sign of solubility limit up to x ≤ 0.1. The decrease in Eg is attributed to the sp-d exchange interaction. Also, the spectral behavior of the refractive index dispersion of the Cr-doped SnO2 indicates that as the Cr dopant increases, the refractive index of the deposited film also increases, which is attributed to the increase in the polarizability. Moreover, as the Cr content raises the atomic number, the density of the deposited film increases from 1.43 × 1022 cm−3 for SnO2 to 1.57 × 1022 cm−3 for Sn0·9Cr0·1O2. Further, the behavior of the refractive index dispersion of the deposited film was revealed using a single oscillator model proposed by Wemple-DiDomenico (WDD). Our calculations revealed that as the Cr concentration increases, the value of oscillator energy Eo decreases owing to the decrease in Eg, whereas the value of dispersion energy Ed increases because of the chemical structural changes such as the lattice parameters. Finally, the magnetic studies revealed that incorporating a small fraction of Cr into SnO2 produces room temperature ferromagnetism in the film, which is gradually suppressed by a further increase in Cr doping. These findings indicate that the Cr-doped SnO2 film can be recommended for optoelectronic and spintronic device applications.

Influence of Chromium Concentration on the Abrasive Wear of Ni-Cr-B-Si Coatings Applied by Supersonic Flame Jet (HVOF)

This research work studies the characteristics of wear and wear resistance of composite powder coatings, deposited by supersonic flame jet (HVOF), which contain composite mixtures Ni-Cr-B-Si having different chromium concentrations—9.9%, 13.2%, 14%, 16%, and 20%, at one and the same size of the particles and the same content of the remaining elements. The coating of 20% Cr does not contain B and Si. Out of each powder composite, coatings have been prepared without any preliminary thermal treatment of the substrate and with preliminary thermal treatment of the substrate up to 650 °C. The coatings have been tested under identical conditions of dry friction over a surface of solid, firmly-attached, abrasive particles using tribological testing device “Pin-on-disk”. Results have been obtained and the dependences of the hardness, mass wear, intensity of the wearing process, and absolute and relative wear resistance on the Cr concentration under identical conditions of friction. It has been found out that for all the coatings the preliminary thermal treatment of the substrate leads to a decrease in the wear intensity. Upon increasing Cr concentration the wear intensity diminishes and it reaches minimal values at 16% Cr. In the case of coatings having 20% Cr concentration, the wear intensity is increased, which is due to the absence of the components B and Si in the composite mixture, whereupon no inter-metallic structures are formed having high hardness and wear resistance. The obtained results have no analogues in the current literature and they have not been published by the authors.

Effect of niobium content on irradiation microstructure and hardening in FeCrAl-based alloys

• The evolution of dislocation loop with niobium content in FeCrAl alloys was discussed. • The formation of laves phase resulted in the decrease of Mo content and the increase of Cr content in the matrix of the FeCrAl alloys. • Nb addition increased nanoindentation hardness and reduced irradiation hardening in the FeCrAl alloys . Iron-chromium-aluminum (FeCrAl) alloys with different content of niobium (Nb)—0, 0.4 wt%, 0.8 wt%, and 1.2 wt%—were designed and prepared. All samples were then irradiated with 2.4 MeV Fe 2+ ion to the dose of 1 and 15 displacements per atom (dpa) at 400 °C. The formations of dislocation loops induced by self-ion irradiation in these alloys were investigated by transmission electron microscopy (TEM). Nano-indentation tests were used to assess the hardness and irradiation hardening of samples. For the samples before irradiation, the (Fe, Cr) 2 (Nb, Mo) Laves phases density and the nano-indentation hardness increased with increasing Nb content of the samples. After irradiation to 1 and 15 dpa, both of a /2<111> and a <100> dislocation loops were produced but no voids or αˊ phase were found in all samples. With increasing Nb content of the samples, the size of dislocation loops increased first and then decreased, while the total volume number density decreased and then increased. The fraction of a <100> dislocation loops increased first and then decreased with increasing Nb content, and increased with increasing irradiation dose. Dislocation networks and the amorphization of the Laves phases were observed in the samples with irradiation dose of 15 dpa. Irradiation hardening of Nb free samples was two to four times that of Nb containing samples, and the irradiation hardening increased with increasing Nb content of Nb containing samples. The experimental results indicate that the increase of Nb content in FeCrAl alloys can increase the density of Laves phases, leading to the decrease of Mo content and increase of Cr content in the matrix. The competition between the two types of solutes affects the nucleation and growth of the dislocation loops.