Distribution Of Vanadium Research Articles

Interplay between vanadium distribution and microbial community in soil-plant system

Soil-plant system play an essential role in distribution and transformation of vanadium (V). V shapes the diversity of soil communities, while soil microorganisms mediate V transformation. Plants also absorb V from surrounding soil. However, the study of microbial response to V stress in different soil-plant compartments is limited, and the metabolic functions driving V transformation across these systems remain elusive. The study investigates the distribution of V in soil-plant systems nearby a V smelter. 16S rRNA sequencing and metagenomics are utilized to reveal the microbial adaptation and V transformation in bulk soil, rhizosphere, and endosphere. Bothriochloa ischaemum (L.) Keng. (BK) exhibits higher phytoextraction potential (TF = 0.74 ± 0.26). Environmental variables, including pH, V, OM, and AP, show significant (p < 0.05) influence in soil community composition, with homogeneous selection governing the assembly processes in bulk soil and rhizosphere, while stochastic process dominates endospheric assembly. Metagenomic investigation revealed a coordinated metabolic pathway between functional taxa in soil and plants, which lead to root uptake and translocation. V stress is mitigated through Nocardioide, Microvirga, and Solirubrobacter, putatively harboring V(V) reduction genes n arG and mtrC in soil. In rhizosphere, citrate synthase gltA and alkaline phosphatase phoD exhibit functional potential to facilitate formation of V-complexation to increase V mobility. In endoshere, endophytic Enterobacter further detoxifies V(V), and likely promotes V translocation through siderophore biosynthesis gene, iucA. These findings enhance our understanding on interplay between V and microbial community in soil-plant systems, which is instrumental in developing mitigation plan for V contaminated sites.

Spatial distribution of PAHs, nickel, and vanadium in sediments from a large coastal lagoon near a petroleum extraction area in the southern Gulf of Mexico

One of the world's crucial areas for crude oil exploration and extraction is the southern Gulf of Mexico, where Terminos Lagoon (TL) is located. Sediments from the TL region were used to assess the spatial patterns, origins, and ecotoxicological risks associated with 16 priority polycyclic aromatic hydrocarbons (PAHs; 3.1–248.9 ng⸳g−1 dry weight basis, dw) and trace metals (Ni = 11.0–104.0 mg⸳kg−1; V = 2.0–35.0 mg⸳kg−1 dw) linked to anthropogenic activities. Although origin indices based on PAHs and metals concentrations indicate no crude oil pollution in the region, sources of pyrogenic PAHs were identified. A chemometric approach demonstrated associations between organic matter and PAHs, and that metal accumulation depends mostly by the input of lithogenic materials. Ecotoxicological risk estimations showed a higher risk of possible adverse effects in sites near swamps and mangrove zones, highlighting the need of future monitoring. This study provides a reference for policymakers to conserve Mexico's largest coastal lagoon and other oil-impacted coastal areas worldwide.

Achieving strength-ductility synergy in LPBF Ti-6Al-8 V alloy through in situ alloying

This study utilized in situ alloying during laser powder bed fusion (LPBF) to create a novel Ti-6Al-8V (wt. %, Ti68) alloy. Pure vanadium nanoparticles were incorporated into Ti-6Al-4V feedstock at a concentration of 4 wt.%. The resulting Ti68 alloy displayed exceptional mechanical properties, including a ultimate tensile strength of 1163 ± 34 MPa and a fracture elongation of 13.1 ± 2.0 %. These improvements can be attributed to the unique microstructure of this alloy, characterized by a heterogeneous α’+β phase resulting from the uneven distribution of vanadium. This microstructure enables sustained plastic deformation through dislocation slip and twinning in α’ phase, as well as dislocation slip and stress-induced martensitic transformation in β phase.

Vanadium in a coastal Lagoon: distribution, sources, speciation, and ecological risks in sediments and water at Xiamen in China

ABSTRACT This study aimed to explore the spatial distribution, sources, contamination status, speciation, and risks of vanadium (V) in sediments and water from Yundang Lagoon (YL) at Xiamen in China. The concentration of V in YL water exhibited a similar distribution pattern, with an average concentration lower than the Chinese drinking water limit value. The V content in the sediments of various YL sampling sites varied significantly. The average V concentration in sediments was 108.28 mg/kg, ranging from 77.38 mg/kg to 151.20 mg/kg. Speciation investigations revealed that the largest amount of V was bound in the residual fraction, while the acid-soluble fraction had the lowest concentration in sediments. On average, the residual and acid-soluble fractions were 51.82% (ranging from 16.09% to 76.13%) and 1.22% (ranging from 0.16% to 2.60%), respectively. Enrichment factor values suggested minor anthropogenic enrichment of V in sediments. Correlation analysis indicated a weak correlation between silt and clay, while carbonate and Fe showed significant correlations with total V in sediments. This correlation suggests that concentrations of Fe and carbonate could favour V accumulation in YL sediments. Potential ecological risk values suggested no risk of V to aquatic biota in the study area.

Enhancement in the Electrocatalytic and Optoelectronic Performance of Cost-Effective Counter Electrode VO2 for Dye-Sensitized Solar Cell (DSSC)

Dye-sensitized solar cells (DSSCs) have garnered significant attention in the scientific community for more than two decades due to their cost-effectiveness, convenient manufacturability, little toxicity, and straightforward preparation methodology. In this study, we present a cost-effective alternative to the platinum electrode for DSSCs, which serves as the counter electrode. The utilization of vanadium oxide nanoparticles as counter electrodes (CEs) in DSSCs has been the subject of research due to its enhanced stability, cost-effectiveness, and favorable photovoltaic characteristics. The device has been fabricated in configuration of fluorine-doped tin oxide (FTO)||TiO2||ruthenium (II) dye (N719)||iodide—triiodide electrolyte||VO2 (counter electrode)||FTO and investigate their photovoltaic performance. The utilization of X-ray diffraction (XRD) analysis has provided insights into the crystalline properties of VO2, indicating that it exists in a crystalline phase with a crystalline size measuring 43.19 nm and a lattice strain of 1.68 × 10−3. The utilization of a field emission scanning electron microscope (FESEM) that is equipped with an energy dispersive X-ray spectrum reveals a dense microstructure characterized by a uniform distribution of vanadium (V) and oxygen (O) across the whole surface. The Raman spectroscopic examination of VO2 reveals the existence of many Raman bands, thereby confirming the presence of the monoclinic phase. Cyclic voltammetry measurements were employed to investigate the catalytic activity of the CE toward the electrolyte. The photovoltaic performance of the manufactured device was examined by I–V measurement, revealing a notable open circuit voltage (Voc) and efficient power conversion efficiency when compared to the other materials that were evaluated.

Leaching characteristics and solidification mechanism of vanadium in preparation of titanium-containing pellets using spent SCR catalyst

The spent SCR catalysts produced from flue gas denitrification are hazardous to the environment and human health. This study proposed a harmless strategy for utilizing the spent catalysts for manufacturing magnetite pellets, in which the mechanical properties of the spent catalyst pellets and the distribution of vanadium during heating were studied. The leaching characteristics and solidification mechanism of vanadium in magnetite pellets were investigated. The results confirmed that the pellets with 10 wt% spent catalysts have mechanical properties satisfactory for application as an ironmaking feedstock. After preheating and roasting the pellets, 91.2 wt% vanadium in spent catalysts was solidified. The leaching ratio of vanadium in spent catalyst pellets was less than 1 % under different pH, liquid-to-solid ratio, and leaching time conditions. Raman, XPS, XRD, and SEM analyses confirmed that the V2O5 started to liquefy at 700 °C, and 8.8 wt% of V2O5 was volatilized into the flue gas at 700–950 °C. The remaining vanadium oxides reacted with iron oxides to form FeVO4, Fe2VO4, and FeV2O4 at 700–1250 °C, leading to its consolidation in the pellets. The treatment of spent catalysts by the pelletizing process is a new technology with the advantages of low investment cost and controllable environmental risk. This new technology could not only solve the problem of spent catalysts utilization in the iron and steel industry but also provide a reference for the treatment of spent catalysts generated from flue gas denitrification in thermal power generation, waste incineration, and other industries.

Constraining the major pathways of vanadium incorporation into sediments underlying natural sulfidic waters

Vanadium (V) is a redox-sensitive trace metal. Interconversion between different vanadium species (e.g., VIII, VIV, VV) occurs rapidly in association with changes in redox conditions in natural environments. Different vanadium species exhibit variable geochemical behavior that impacts if and how they are sequestered into sediments, which makes vanadium a useful proxy for ancient ocean redox conditions. However, we still lack constraints on how different dissolved vanadium sink pathways impact distributions of vanadium in water column, pore waters, and sediments, especially in natural sulfidic settings. In the present study, we combined field and experimental data to constrain the major scavenging processes that influence the partitioning of vanadium between aqueous and solid phases to provide an improved picture of vanadium geochemical cycling under anoxic-sulfidic conditions. We find that in the sulfidic bottom waters and sediment pore waters of the Chesapeake Bay, vanadium concentrations are correlated with manganese (Mn) concentrations in both aqueous and solid phases. Our experimental results support our interpretation that elevated concentrations of vanadium in anoxic-sulfidic waters result from the release of vanadium due to desorption from and/or dissolution of Mn oxides in anoxic/sulfidic waters. While sorption of vanadium results in strongly adsorbed complexes on both Mn oxides and pyrite surfaces, vanadium preferentially sorbs to Mn oxides rather than to pyrite. Thus, the impact of Mn oxides on vanadium geochemistry is greater than that imposed by scavenging via sorption on pyrite, although both processes should be considered. Mn oxides also have a greater impact on vanadium geochemistry than reductive formation of solid V(OH)3 by H2S. Sorption of vanadium is sensitive to pH conditions (especially in anoxic waters), moderately sensitive to ionic strength, and weakly sensitive to phosphate concentrations. In addition, our results show that as waters become more sulfidic, dissolved V/Mn molar ratios increase, whereas solid phase V/Mn molar ratios decrease, indicating that the V/Mn molar ratio can be used to trace redox changes. Finally, we investigate the V/Mn record of black shales that span the Proterozoic and Phanerozoic to show a framework of utilizing this proxy with applicability to identify changes in redox conditions associated with both oxygenation and anoxic events in ancient oceans.

On the Interphase Distribution of Nickel(II) and Vanadium(IV) Ions in a System Based on PEG-1500

On the Interphase Distribution of Nickel(II) and Vanadium(IV) Ions in a System Based on PEG-1500

Microstructure and Mineral Phase Evolution of Vanadium Slag by Modulating the CaO/V2O5 Ratio

The slag mineral phase is reconstructed by adding CaO to the molten vanadium slag to obtain a slag with high metallurgical characteristics. In this paper, the effects of the CaO/V2O5 ratio on the microstructure of molten vanadium slag, the phase composition of vanadium slag, and the non-salt roasting-(NH4)2CO3 leaching performance of modified vanadium slag were comprehensively investigated. Molecular dynamics simulation was used to examine the microstructure of the simplified vanadium slag system (FeO-V2Ox-SiO2-CaO) at varied CaO/V2O5 ratios. The results show that V (3+, 4+, and 5+) in the molten vanadium slag is similar to the network former. The V-O structure is dominated by four-fold coordination, and V3+ and V5+ show rich coordination configurations. With the increased CaO content, the overall diffusivity of the system increases, and the network structure is destroyed by CaO. The addition of CaO realizes the mineral phase reconstruction of vanadium slag, and vanadium slag with a more concentrated vanadium distribution and a wider Ca distribution is obtained. The concentration of vanadium in vanadium spinel increases from 17% to 29.4%. A suitable CaO/V2O5 ratio reduces the dependence of the vanadium leaching recovery on the vanadium slag’s roasting temperature and duration.

Long-Term Observation of Mixing States and Sources of Vanadium-Containing Single Particles from 2020 to 2021 in Guangzhou, China.

The distribution of vanadium (V) in aerosols is commonly used to track ship exhaust emissions, yet the atmospheric abundance of V has been greatly reduced due to the implementation of a clean fuel policy. Recent research mainly discussed the chemical compositions of ship-related particles during specific events, yet few studies focus on the long-term changes of V in the atmosphere. In this study, a single-particle aerosol mass spectrometer was used to measure V-containing particles from 2020 to 2021 in Huangpu Port in Guangzhou, China. The long-term trend of the particle counts of V-containing particles declined annually, but the relative abundance of V-containing particles in the total single particles increased in summer due to the influence of ship emissions. Positive matrix factorization revealed that in June and July 2020, 35.7% of the V-containing particles were from ship emissions, followed by dust and industrial emissions. Furthermore, more than 80% of the V-containing particles were found mixing with sulfate and 60% of the V-containing particles were found mixing with nitrate, suggesting that the majority of the V-containing particles were secondary particles processed during the transport of ship emissions to urban areas. Compared with the small changes in the relative abundance of sulfate in the V-containing particles, the relative abundance of nitrate exhibited clear seasonal variations, with a high abundance in winter. This may have been due to the increased production of nitrate from high concentrations of precursors and a suitable chemical environment. For the first time, the long-term trends of V-containing particles in two years are investigated to demonstrate changes in their mixing states and sources after the clean fuel policy, and to suggest the cautious application of V as an indicator of ship emissions.

STUDY OF CONDITIONS FOR THE ASSOCIATED EXTRACTION OF VANADIUM AND GALLIUM DURING ALKALINE LEACHING OF RAW ALUNITE ORE

Alunite ore containing a significant amount of aluminum, iron oxide, titanium dioxide, and other valuable components (Ga – 0.003 wt%, V – 0.0315 wt.%) is the main raw material for the production of alumina and promising raw material for the production of gallium and vanadium. This paper studies the dynamics of the distribution of gallium and vanadium in the liquid phase during the dissolution of raw alunite in an alkaline solution are studied. The results have showed that alkali concentration, leaching temperature, liquid-to-solid ratio have a significant effect on the degree of extraction of these elements from solution. It has been found that when raw alunite ore is leached with a 5% NaOH solution (S:L=1:6) for 2 hours, the degree of extraction of Ga and V is, respectively, 50.2 and 59.23% of their total content in the rock

Thermodynamic analysis of vanadium distribution behavior in blast furnaces and basic oxygen furnaces

Abstract Production data from a vanadium (V)-containing titaniferous magnetite (VTM) smelting blast furnace (BF) ironmaking plant and a V-recovering basic oxygen furnace (BOF) shop were collected over a period of 1 year. The corresponding thermodynamics was analyzed in terms of V reduction in the BF operation and V oxidation in the BOF operation. The thermodynamic calculations were performed using the software Multi-Phase Equilibrium (MPE), in which generalized central atom model was introduced into the description of molten slag and applied for the slag database. The effects of operating conditions on V distribution ratios between slag and hot metal/semi-steel were analyzed and compared with the plant data. The simulated results could reproduce the variation of V distribution ratios with slag temperature and composition and provide the guidance for operators to control V distribution behavior for the better process operation.

Trace Elements in Olivine of Volcanic Rocks: Application to the Study of Magmatic Systems

A quantitative local analytical method with the application of inductively coupled plasma mass spectrometry with laser ablation (LA-ICP-MS) was tested at Vernadsky Institute for the determination of contents of trace elements (Cu, Zn, Co, Ni, Mn, Cr, Sc, V, Ca, Ti, Al, Y, and REE) in olivine. Olivine phenocrysts from volcanic rocks of various geological settings have been studied: island-arc basalts, mid-ocean ridge (MOR) basalts, and high-alkaline continental volcanic rocks. The contents of some elements (Ni, Co, Mn, Cr, Sc, and Zn) systematically vary during the evolution of the composition of olivine, and the concentration fields of these elements in olivine from different settings overlap one another. At the same time, the contents of some other elements (Ca, Al, Ti, V, and Cu) fundamentally differ in olivine from different geological settings. Copper content in olivine from oceanic tholeiites and highly alkaline continental volcanics is 1–3 ppm, which is systematically lower than copper content in olivine from island-arc basalts (3–9 ppm). The concentrations of vanadium in olivine in MOR basalts are higher than in island-arc and alkaline continental ones, which may be due to relatively more reduced crystallization conditions as more favorable for the incorporation of V3+ into the olivine structure. Variations in the distribution coefficients of trace elements between olivine and silicate melt (DOl/Melement) were determined for volcanic rocks from Kamchatka, the Bouvet Triple Junction, and Gaussberg volcano. It has been demonstrated that the unusually high values DOl/MNi of DOl/MNi = 50–150 previously identified for the lamproites of Gaussberg volcano indicate a mismatch between the composition of the quenched glass and the composition of the equilibrium melt for olivine phenocrysts. When using the bulk compositions of Gaussberg rocks, values of DOl/MNi = 11–21 were obtained, which correspond to experimental estimates for high-potassium rocks. The redox crystallization conditions of the studied rocks were estimated using several oxybarometers based on the distribution of vanadium between coexisting olivine and melt. These values were: ΔQFM= +0.6 to +1.5 for oceanic tholeiites of the Bouvet Triple Junction area, South Atlantic, and ΔQFM = +1.5 to +2.4 for Mutnovsky volcano, Kamchatka. Estimates of the redox crystallization conditions of the highly alkaline rocks of Gaussberg volcano significantly vary depending on which model is chosen: ΔQFM= +0.2 to +4.8, which may be due to the strong effect of K2O content in the melt involved in one of the models. The newly acquired analytical data confirmed the possibility of using contents of trace elements in olivine to characterize igneous systems from different geological settings and highlighted the need for additional experimental studies on the distribution of these elements between olivine and melt, especially in highly alkaline systems.

Site‐Preferences in the Mixed‐Valent Series FeMo1−nVnO4: Controlling the Formation of the α‐Polymorph and the Charge Localization

AbstractThe mixed‐valent, solid solution series FeMo1−nVnO4 (0≤n≤0.3) was synthesized and characterized by x‐ray diffraction, and thermal analysis. Assignments of individual Fe‐species stem from 57Fe‐Mössbauer spectroscopy and DFT‐calculations of the electric field gradients. The incorporation of smaller ions (FeIII, VV) represents an internal “chemical pressure” effect stabilizing the low‐temperature α‐polymorph with increasing n. The site‐preference and distribution of vanadium on individual Mo‐sites impacts the α→β transition temperatures around 650 K, and causes distinct differences in charge mobility in this hole‐doped semiconductor around 225 K. We assign the charge localization in α‐FeMo1−nVnO4 to enhanced electron‐phonon coupling within a polaronic scenario.

Distribution of niobium and vanadium in titanium tetrachloride production middlings

This paper describes the results of a study that looked at the distribution of niobium and vanadium at different stages of titanium slag and titanium tetrachloride production. The former is produced by smelting while the production of the latter is based on chlorination of titanium feedstock in molten alkali metal salts. Titanium feedstock was subjected to reduction smelting at 1.400&ndash;1.600 oC in the presence of carbonaceous reducing material. In this case, an AM grade of anthracite was used as such material. The resulting titanium slag was ground and dried and then it was subjected to chlorination at 700&ndash;820 oC in molten alkali metal salts in the presence of ground anthracite as the carbonaceous reducing material. The findings indicate that 99.9% of niobium and 84.9% of vanadium convert to the titanium slag produced through the smelting of ilmenite concentrate. The following distribution of niobium in the middlings can be observed at the following stage when the slag is chlorinated in molten salts to obtain titanium tetrachloride: 37% goes to the chlorinator tailings, 3% gets trapped in the dust chamber as part of chloride fumes, 1.8% gets settled in the melt of the settling chamber with a salt bath, and 58.2% gets accumulated as a solid deposit of titanium tetrachloride slurry at the first condensation stage. Out of the total amount of vanadium that is fed into the chlorinator with titanium feedstock, 13.9% goes to the tailings while 78.4% gets recovered as commercial titanium tetrachloride. During the following purification stage, 0.33% of vanadium remains in the purified titanium tetrachloride while the rest of it goes into the waste bottoms.

Distribution behavior of vanadium and titanium between hot metal and high titanium slag relevant to HIsmelt smelting condition

The HIsmelt process is well suited for smelting vanadium-titanium magnetite and has significant potential. In this paper, the vanadium and titanium distribution behavior at 1450 °C in the basicity range of 0.3–1.2 during HIsmelt smelting vanadium titano-magnetite was investigated experimentally for the first time. According to thermodynamic calculations combined with experimental validation, lower C content increases the activity coefficients of vanadium and titanium in the metal. Higher basicity decreases the activity coefficients of TiO2 and SiO2 in the slag, improves the distribution ratio of vanadium and titanium. Increasing C content and reducing basicity could increase the content of vanadium in the metal and TiO2 in the slag, which is favorable to vanadium extraction and titanium recovery. Furthermore, the V and Ti content in the hot metal increased significantly with rising smelting temperature. Higher smelting temperatures promote vanadium distribution into hot metal but not titanium distribution into slag. Finally, The Si and Ti distribution ratios have a positive connection according to the fitted models.

Distribution of Vanadium in the Surficial Sediments of Prydz Bay, Indian Sector of the Southern Ocean

ABSTRACT The study was carried out in seven stations to assess concentration levels of Vanadium (V) in sediments of the Prydz Bay, Indian sector of the Southern Ocean during the austral summer season. Sediment analysis showed that V concentration on the eastern side was extensively higher than on the western side of Prydz Bay. A significant observation was the high concentration of V concentration in fine sediment fraction than in total metal fraction. Vanadium concentration level on the western side varied from 19.4 to 45.5 mg/kg while it was 40.9–65.8 mg/kg on the eastern side of Prydz Bay. The prevailing petroleum-related activities coupled with fuel combustion processes at various research stations in the Antarctic subcontinent and the influence of sea ice cover interaction could be the reason for the high V concentration on the eastern side of Prydz Bay. A significant spatial variation in textural characteristics, elemental composition, and total organic carbon was observed with high concentration levels of total organic carbon (TOC), total nitrogen (TN), and total hydrogen (TH) in the eastern part of Prydz Bay. The statistical analysis revealed a strong positive correlation of V concentration with governing factors at p < .01 level.

Effect of Dimethyl Formamide (DMF) on Vanadium Reloading Over V-Ti SCR Catalyst

Active components reloading is critical process for the catalyst regeneration, which is limited by the low adsorption capacity and unwilling distribution of desired components to the catalyst surface. Herein we demonstrated that with dimethyl formamide(DMF) modification and sequentially reloading of vanadium, the traditional V-Ti SCR catalyst, which uses vanadium as the active components and titanium as the carrier, showed the significantly improved DeNOx performance, owing to the increased adsorption capacity and desired distribution of vanadium. When the DMF concentration was 6%, the adsorption capacity of the promoted catalyst was 3.58 and 6.57 mg/g under vanadyl ion concentrations of 1.5 and 3 g/L, respectively, 135 and 147% higher than that of the original catalyst. Adsorption kinetics demonstrated that the pseudo-second-order kinetic model better describes the process by which vanadyl ions adsorb onto the catalyst. In addition, the adsorption equilibrium indicated that Langmuir model was a closer fit for the vanadyl ion adsorption to the promoted catalyst. After DMF modification, the vanadyl ions were first adsorbed onto the functional groups on the catalyst surface, substantially increasing the vanadium loading on the catalyst surface while limiting the increase in vanadium content within the interior of catalyst, which was conducive to enhancing the DeNOx activity and reducing the increase in the SO2/SO3 conversion. When the vanadium adsorption capacity was 3.5 mg/g, the increase in the DeNOx activity of the promoted catalyst was 68.1% higher than that of the original catalyst, whereas the increase in SO2/SO3 conversion was 28.9% lower than that of the original catalyst. Thus, in the regeneration of SCR catalysts vanadium initial concentration and loading could be reduced.

New understanding of extraction and separation of vanadium(IV), iron and titanium using iron powder induction-leaching and P204-P507 synergistic extraction

Herein, we investigated the induced-leaching behavior of hematite by iron powder after ammonium sulfate roasting vanadium titanomagnetite concentrate and develop a P204-P507 synergistic extraction method for separation of vanadium(IV), iron and titanium. The results showed that the effective selective separation of vanadium, iron and titanium could be obtained in which 97.39 % V and 88.62% Fe were dissolved into the solution and over 91.76% Ti was remained in leaching residue after leaching at 0.5 M H2SO4, 110 °C for 1 h, then added 10% iron powder and continue to leaching for 2 h. Tafel polarization curve and impedance spectroscopy both proved that iron powder could reduce the chemical reaction resistance and accelerate the ion transfer rate in the leachate. Based on the speciation analysis by Medusa software, the speciation distribution of vanadium, iron and titanium in the sulfuric acid system eventually exists in the form of VO2+ and Fe(Ⅱ) ions, while most of titanium precipitates to the leaching residue in the form of TiO2. The five stages countercurrent extraction test was carried out to confirm the prediction of McCabe-Thiele diagram, and the extraction efficiency of vanadium reached 98.13% under the condition of mixed extractant concentration of 15%, v(P204):v(P507) of 3, pH of 1.8 and phase ratio (O/A) of 2.0. The slope method proved that P204-P507 molecule could release two H+ ions for every vanadium ion extracted, which could be attributed to the cation exchange reaction. Finally, a high-titanium slag with a TiO2 content of 85.32% was obtained by alkaline leaching method.

РАСПРЕДЕЛЕНИЕ ХРОМА И ВАНАДИЯ В ДИФФУЗИОННОМ СЛОЕ СТАЛИ 35Х2Н3 ПРИ СОВМЕСТНОМ ТЕРМОДИФФУЗИОННОМ НАСЫЩЕНИИ

Termodiffusion saturation of the surface of alloys with two or more elements remains poorly understood despite the great practical and scientific interest that this method of chemical-thermal treatment represents. The simultaneous introduction of several elements can significantly reduce the processing time of products and obtain a multiphase composition on the surface of the product, which opens up wide opportunities for imparting unique technological and operational properties to products. The article describes the features of the distribution of chromium and vanadium during joint thermal diffusion saturation of steel X35CrNi2-3 at a temperature of 1000 °C. The proposed analysis technique is based on the possibilities of X-ray spectral microanalysis of diffusion layers on transverse microsections of the obtained samples. The elemental composition of the diffusion layer was monitored using a JEOL JSM-6460 LV universal scanning electron microscope. The microstructure was studied on an optical metallographic microscope Axio Observer D1.m. X-ray phase analysis was carried out on a Rigaku Ultima IV diffractometer. The hardness measurement was carried out on an FM-800 microhardness tester at a load of 100 g. Data were obtained on the qualitative and quantitative distribution of chromium and vanadium in the surface layer of steel. It is shown that the emerging diffusion coating has the following structure: a structureless outer layer, consisting mainly of chromium, vanadium carbides → a region of columnar crystals (experiencing γ→α transformation upon cooling), consisting mainly of their Cr1.0V0.4Fe0.3 solid solution → partially decarburized α-phase → base metal. The diffusion coefficients of chromium and vanadium are determined: in the α-phase DCr = 1.3·10–15 m2/s; DV = 1.8·10–14 m2/s; in the γ-phase DCr = 1.13·10–15 m2/s; DV = 1.3·10–15 m2/s. The microhardness of the outer surface layer was 1400–1980 H, the diffusion layer in the base metal was 630–790 HV, and the base metal was about 540–510 HV.