Mo Elements Research Articles

High efficiency degradation of RhB by MIL-88A(Fe)/MoS2 activated persulfate and its mechanism

MoS2/MIL-88A(Fe) composite catalyst was prepared by in-situ formation method. The material was characterized by SEM, TEM, XRD and XPS, and the Rhodamine B(RhB) was activated and degraded by persulfate (PMS). The results showed that M-10/M1:2 had the best degradation effect on RhB, the rate constant was 0.66420 min-1, and the degradation rate could reach 1.89-14 times that of other doped composite catalysts. The SEM results showed that M-10 had the least sulfur content, fewer MoS2 flower layers and more exposed Mo4+ atoms, which improved the electron transfer efficiency and accelerated the degradation reaction. The XPS spectra before and after M-10/M1:2 reaction showed that the REDOX reaction of Fe3+/Fe2+ and Mo4+/Mo6+ on the catalyst surface played an important role in the activation of PMS. The results of free radical capture experiment and ESR test showed that the main active substances in M-10/M1:2/PMS reaction system were SO4•−, 1O2, •O2−, and •OH, which only played a role in the degradation of RhB. Finally, based on the ESR results of M-10/M1:2/PMS system and the changes of Fe and Mo elements in XPS characterization before and after the reaction, the degradation mechanism of M-10/M1:2/PMS system was proposed.

Effects of Co and Mo on the microstructure properties of GH4282 and the mechanical properties of metal bellows

Abstract In the present study, a new type of Ni-Cr-Co-Mo (GH4282) precipitation-hardening superalloy was prepared on the basis of GH4202 alloy. By adding Co and Mo elements to enhance the solution-strengthening effect, good creep resistance and toughness were obtained. The results show that the strength and microstructure stability of GH4282 alloy are significantly higher than those of traditional GH4202 alloy under the condition of 700~900°C. The precipitated phase of GH4282 alloy is dominated by γ′ phase, which contains M23C6, MC, and a small amount of M6C carbide. The precipitation is mainly distributed along the grain boundaries, and has good stability at temperatures below 900°C, which can effectively pin the grain boundaries. The thermal stability of the alloy is increased. The metal bellows made of GH4282 alloy have significantly higher fatigue life and high-temperature stability, the increase of Co and Mo element content leads to the enhancement of precipitation, and the combined effect of solution strengthening and precipitation strengthening leads to the above results.

Laser-Directed Energy Deposition of Ti-Mo Biomaterials: Influencing Mechanisms of Molybdenum on Microstructure and Performance

Ti-Mo alloys with variable molybdenum (Mo) contents were fabricated by the laser-directed energy deposition process. The in-depth influencing mechanisms of the Mo element on microstructure and performance were quantitatively analyzed by experiment and first-principal calculation. Increasing Mo content decreased the formation and cohesive energies and stabilized the 𝛽 phase. The grain refining efficiency was increased, and the relative grain size was decreased by increasing the Mo content. The MS temperature decreased, and the acicular martensite formed with increasing Mo content. Both the solid-solution hardening and fine grain strengthening effects had positive influences, while the 𝛽 phase softening effect had a negative influence on the hardness and wear performance with increasing Mo content.

Oxygen-rich combustion behaviors and mechanisms of a new Ni-Cr-based superalloy fabricated by selective laser melting

The mechanical and combustion behavior of a new Ni-Cr-based superalloy, fabricated by selective laser melting in an atmosphere with an oxygen concentration greater than 99.5 %, was investigated through the analysis of microstructural morphology, elements distribution and combustion kinetics. The results show that heat treatment eliminated the anisotropy of the as-built microstructures and improved the tensile strength. The studied superalloy can be ignited with a combustion threshold of about 2.5 MPa–3 MPa. The burning length and burning rate increase with the increase of pressure. The selective combustion of Al, Ti, Nb, Cr, Fe, Mo, and Cu elements occurred, resulting in the dissolution of γ′, γ", and δ precipitates and formation of holes at the grain boundaries in the heat-affected zone. The microstructures exhibit large elongated grains in the melting zone and column grains in the heat-affected zone along the heat dissipation direction. The combustion products are a mixture of oxides exhibiting dendritic structures in terms of selective combustion, density, and melting point. The findings from this study enhance our comprehension of the combustion process in nickel-based superalloys, offering valuable data and guidance for the advancement of new oxygen-rich combustion-resistant superalloys.

Bio-corrosion behaviors and bio-compatibilities of TiNbZrTa and TiNbZrTaMo high entropy alloys

The bio-corrosion behavior and bio-compatibility of TiNbZrTa and TiNbZrTaMo high entropy alloys (HEAs) are crucial for their efficient maintenance during biological implantation. In this work, TiNbZrTa and TiNbZrTaMo HEAs were successfully prepared via vacuum melting, with a β-type titanium alloy Ti35Nb7Zr5Ta, exhibiting good biocompatibility used as a comparison. Due to the high entropy effect of equal atomic ratios, both TiNbZrTa and TiNbZrTaMo HEAs exhibit body-centered cubic (BCC) structure and lattice distortion compared to the β titanium alloy Ti35Nb7Zr5Ta. Mo elements contribute to the formation of a new BCC phase, resulting in a white matrix rich in Ta and Mo, and a dark second phase rich in Ti, Zr, and Nb. Electrochemical test results at 37 °C shown that TiNbZrTa has a wider and more stable passivation area than TiNbZrTaMo. The XPS results shown that formation of the passive film is related to the main elements added. Ti, Nb, Ta and Mo formed oxides via the solid-liquid interface and migrate inward, while Zr is formed at the passivation film/metal substrate interface and migrates outward, finally forming the layered structure of the passivation film. Additionally, the cytotoxicity test of mouse fiber cells was carried out to evaluate the biocompatibility of the HEAs. The results shown that the cell proliferation rate of TiNbZrTa and TiNbZrTaMo HEAs reached 0 and 1, respectively, with TiNbZrTa exhibiting better biocompatibility, as adding Mo reduced the cell proliferation rate. These findings may provide a method for predicting the bio-corrosion behavior and bio-compatibility of HEAs used for biological implantation.

VENDIAN-CAMBRIAN SEDIMENTARY PROVENANCE OF THE UPPER KALAR DEPRESSION (ALDAN SHIELD) ACCORDING TO GEOCHEMICAL DATA

There are presented the results of geochemical studies of the Vendian-Cambrian terrigenous rocks in the Upper Kalar depression– sandstones of the Silimkun formation, exposed in the floodplain of the Kilcheris River (left tributary of the China River), in the upper reaches of the Kemen River. The rocks are enriched in Sc, Cr, Nb, V, Co, Ni, as well as in Mo and heavy rare earth elements. This study demonstrates a rare pairwise correlation between Mo and Cr. A strong positive correlation of P with Nb, Ti and Fe is indicative of P sorption phenomena in alteration products of titanium minerals (e.g. leucoxene). It has been found that the sandstones of the Silimkun Formation were formed as a result of the destruction of granitoids of the Kalar massif – presumably granite porphyries and fine-grained porphyritic biotite granites. The influence of the gabbro-norites of the Chiney complex, enriched in trace elements commonly found in rocks, is less pronounced.

Optimisation of Mo doping to form NiCoMo ternary sulphides for high performance charge storage.

Multi-component synergy and the rational design of structures are effective methods for preparing electrode materials for high-performance energy storage devices. Transition metal-based hydroxides offer advantages such as a large specific surface area, large interlayer spacing, multiple redox states, and high theoretical capacity, making them commonly used as positive materials for supercapacitors. However, challenges like low conductivity and severe agglomeration limit their practical application. This study focuses on the preparation of Ni, Co, and Mo ternary transition metal hydroxides by incorporating the Mo element to optimize their structure. Furthermore, sulfide ions were utilized in an ion exchange process to replace hydroxides, resulting in the formation of NiCoMo ternary sulfide electrode materials. By adjusting the amount of Mo added, a spherical nanoneedle-shaped N2C1MS0.2-2 electrode material was successfully synthesized. This electrode exhibited a specific capacity of 2094 F g-1 at a current density of 1 A g-1. In addition, an asymmetric supercapacitor was assembled with activated carbon as the negative electrode and N2C1MS0.2-2 as the positive electrode, which had an energy density of 46.2 W h kg-1 at a power density of 800 W kg-1, a capacity retention of 89.7% and a coulombic efficiency of 97.8% after 10 000 cycles. This study provides a reference for the design and preparation of ternary sulphide electrode materials.

The key role in the structure and properties of a novel CrNiTiMo high-entropy alloys films prepared by magnetron sputtering: Bias voltage

In this study, CrNiTiMo high-entropy alloys films were prepared on 304 stainless steel and silicon wafer substrates by direct current magnetron sputtering and the effects of bias voltages (0 to −200 V) on microstructure, chemical composition, hardness and corrosion resistance were investigated. The results showed that the surface of the CrNiTiMo HEAs films exhibited equiaxed nanoparticles and are composed of uniformly distributed Cr, Ni, Ti, and Mo elements. Meanwhile, the films developed a columnar structure and formed a biphasic structure with body-centered cubic solid solution and amorphous phases. The roughness decreased and then increased with increasing bias voltage, and the film deposited at −50 V had the lowest roughness (1.02 ± 01 nm), which also had a maximum hardness of approximately 9.52 ± 0.2 GPa and a maximum elastic modulus of approximately 187 ± 6 GPa. In addition, all films showed better corrosion resistance compared to 304 stainless steel substrates at 3.5 wt% NaCl solution. The corrosion current density (icorr) of the films decreased and then increased with increasing bias voltages and reached the lowest icorr of about 2.49 × 10−8A/cm2, indicating that the films deposited at a bias voltage of −50 V had the best corrosion resistance. These was attributed to the formation of the passivation films mainly composed of TiO2 and Cr2O3 and the improvement of the surface quality of the film as well as the refinement of the columnar structure and particles.

The Aspects of Dimensionality in the Analysis of Raman Spectra of 2D Materials

Two-dimensional crystals are a class of materials in which an individual layer is indefinitely extended in two dimensions. Each layer is the molecular unit in the crystalline lattice. The nature of interlayer/intermolecular interaction is poorly understood. However, it defines physical properties such as carrier mobility, thermal conductivity, photoluminescence, etc. The vibrational properties of 2D materials are described based on triperiodic space groups. However, the triperiodic space groups do not apply to the description of these structures. The 17 two-dimensional groups in triperiodic space groups do not allow the existence of a third dimension. Therefore, if structures are not planar, the approach is inappropriate. The way to describe such structures is using the diperiodic groups in three dimensions. The well-known 2D materials are graphite, graphene, chalcogenide of Ga, Mo, W, and other elements. The crystalline As2S3 belongs to a class of 2D materials. The unit cell contains two layers with ten atoms in each layer, and it is similar to a structure of metal chalcogenide (MoS(Se)2, WS(Se)2). A bond length of 2.24 A is within the layer, and 3.56 A is between the layers. This interlayer/intralayer bond length ratio (= 1.59) corresponds to a significant difference in bond strengths. Center-zone optical phonons in crystalline As2S3 have been investigated by Raman scattering in a wide temperature range for two polarizations in the layer plane (ac). The crystal's and individual layers' symmetry are different, defining different selection rules for optical phonons. According to the crystallographic data, crystal symmetry is monoclinic with 20 atoms in a unit cell and is P21/n (C2h 5). The axis b, perpendicular to the layers, is the only unique axis of the crystal. Therefore, all phonons in the ac plane should be indistinguishable. The layer symmetry is orthorhombic in the diperiodic space group in three dimensions, in which a, b, and c axes are axes of symmetry with a space group of Pnm21 (C2v 7). The intensity of Raman bands in the layer plane shows strong polarization dependence, indicating layer symmetry's dominance. Interlayer interaction is weak, and as a result, low-frequency Raman bands appear in the spectra. The position of these bands defines the strength of interlayer interaction. The data presented provides an understanding of the structural motives of 2D As2S3 and may predict the optical/electronic properties of similar 2D materials based on Raman spectra.

Effects of Cr and Mo content on the microstructure and properties of Fe-based amorphous composite coatings by laser cladding

In this study, we successfully produced Fe-based amorphous composite coatings on the surface of 45 steel using laser cladding technology, and the impact of the relative content of Cr and Mo elements on the microstructure, hardness, and wear resistance of composite coatings has been investigated. The results show that the microstructure of the coating changes from dendrite to amorphous nanocrystalline when the content of Cr and Mo is 20 and 15 wt. %, respectively. However, when the Mo element continues to be added, elemental segregation will be caused, resulting in a large number of brittle Fe–Cr–Mo intermetallic compounds and MoSi2 ceramic phases in the coating. Therefore, the appropriate element ratio can not only increase the amorphous phase content in the coating but also prevent elemental segregation. Among the three types of amorphous composite coatings studied, the Fe45Cr20Mo15B10Si10 (wt. %) composite coating exhibited the most favorable performance, primarily due to its highest amorphous content (43.33%). Through the interaction of the amorphous phase, α-Fe, Fe–Cr solid solution, and a small proportion of intermetallic compounds, this coating achieved a hardness of 1282.8 HV0.2, approximately five times that of the 45 steel substrate, and demonstrated superior wear resistance.

Microstructure evolution and mechanical properties of Fe–Cr–B alloys with varying Mo additions

The continuously net-like morphology of borides accounts for the poor toughness of Fe–Cr–B wear-resistant alloys. To effectively modify the morphology of Fe2B, Mo element has been introduced in Fe–Cr–B alloys, and the microstructure evolution and mechanical properties have been systematically investigated. The results show Fe–Cr–B alloys are mainly composed of martensite, M2B, M23(B, C)6 and lamellar M3B2 after Mo addition. With the increase of Mo addition, the content of M3B2 increases gradually while that of M23(B, C)6 increases firstly and then decreases. Consequently, the net-like structure of M2B can be effectively broken to acquire the isolated bulk-like morphology, which is mainly attributed to the growth inhibition effect of lamellar structure M3B2. In addition, the hardness varies depending on the volume fraction of borides. However, the fracture toughness of Fe–Cr–B alloy can be dramatically improved by 34.3% with Mo addition increasing from 1 to 4%. Grain morphology modification of M2B plays the predominant role in the toughness improvement because the crack propagation path can be blocked. Furthermore, the lamellar M3B2 structure can effectively hinder the cracking propagation so as to improve the alloy's fracture toughness. Mo addition has been proved to be an effective way to modify the grain morphology of M2B hard phase.

Microstructures and Corrosion Behaviors of Non-Equiatomic Al0.32CrFeTi0.73(Ni1.50−xMox)(x = 0, 0.23) High-Entropy Alloy Coatings Prepared by the High-Velocity Oxygen Fuel Method

The non-equiatomic Al0.32CrFeTi0.73(Ni1.50−xMox) (x = 0, 0.23) high-entropy alloy (HEA) coatings were prepared by the high-velocity oxygen fuel (HVOF) method. The microstructures and corrosion behaviors of the HVOF-prepared coatings were investigated. The corrosion behaviors were characterized by polarization, EIS and Mott-Schottky tests under a 3.5 wt.% sodium chloride aqueous solution open to air at room temperature. The Al0.32CrFeTi0.73Ni1.50 coating is a simple BCC single-phase solid solution structure compared with the corresponding poly-phase composite bulk. The structure of the Al0.32CrFeTi0.73Ni1.27Mo0.23 coating, combined with the introduction of the Mo element, means that the (Cr,Mo)-rich sigma phase precipitates out of the BCC solid solution matrix phase, thus forming Cr-depleted regions around the sigma phases. The solid solution of large atomic-size Mo element causes the lattice expansion of the BCC solid solution matrix phase. Micro-hole and micro-crack defects are formed on the surface of both coatings. The growth of both coatings’ passivation films is spontaneous. Both passivation films are stable and Cr2O3-rich, P-type, single-layer structures. The Al0.32CrFeTi0.73Ni1.50 coating has better corrosion resistance and much less pitting susceptibility than the corresponding bulk. The corrosion type of the Mo-free coating is mainly pitting, occurring in the coating’s surface defects. The Al0.32CrFeTi0.73Ni1.27Mo0.23 coating with the introduction of Mo element increases pitting susceptibility and deteriorates corrosion resistance compared with the Mo-free Al0.32CrFeTi0.73Ni1.50 coating. The corrosion type of the Mo-bearing coating is mainly pitting, occurring in the coating’s surface defects and Cr-depleted regions.

Effect of W and Mo contents on the microstructural evolution and properties in the 9% Cr martensitic rotor steel during long-term aging at 630 °C

The evolution of tensile properties and microstructure in three 9% Cr martensitic rotor steel with varying contents of W and Mo elements is investigated after aging at 630 °C for different durations, with a primary focus on the characteristics of martensite laths and blocks, grain boundaries, dislocations, and precipitates. The results indicate that the presence of W and Mo elements not only influences the precipitation and coarsening behavior of Laves phases but also that of M23C6 carbides, which differs from conventional beliefs. The elevated content of Mo and reduced content of W in the steel leads to a reduction in the equilibrium Cr concentration, promoting enhanced precipitation of Cr atoms and increases nucleation sites of M23C6 carbides. During the aging treatment, the M23C6 carbides in the 2.0W0.5Mo steel exhibits the highest content and the lowest coarsening rate. The strength of 9% Cr martensitic rotor steel is primarily enhanced through dislocation strengthening and grain boundary strengthening. The presence of fine M23C6 carbides effectively immobilizes dislocations and interfaces, resulting in the exceptional stability of the microstructure in the 2.0W0.5Mo steel and a minimal reduction in yield strength.

Mechanical property and strengthening mechanism of ZrC nanoparticle dispersion-strengthened Mo containing FeCrAl alloys

Poor mechanical strength at high temperature is the key problem to limit the application of FeCrAl alloys as the candidates for the accident tolerant fuel (ATF) cladding in LWRs. Fe-13Cr-5Al (wt %) alloys were strengthened by adding solid solution element Mo and nanosized ZrC particles, and the strengthening mechanism was assessed by microstructure characterizations including TEM and EBSD. Fe-13Cr-5Al-2Mo-1ZrC alloy has the highest ultimate tensile strength (UTS) and an acceptable ductility at each tested temperature (Room temperature, 400 °C or 800 °C). Especially at 800 °C, the UTS of Fe-13Cr-5Al-2Mo-1ZrC alloy is about 124 MPa, which is 125 % and 34.7 % higher than that of raw Fe-13Cr-5Al (55 MPa) and Fe-13Cr-5Al-1ZrC alloys (89 MPa), respectively. Fe-13Cr-5Al-2Mo-1ZrC alloy has the highest hardness of 306.3 HV, which is 12.8 % higher than that of Fe-13Cr-5Al and 3.7 % higher than that of Fe-13Cr-5Al-1ZrC alloys, respectively. Furthermore, Fe-13Cr-5Al-2Mo-1ZrC samples maintain high strength and favorable ductility after annealing at 1000 °C for 20 h indicating their superior thermal stabilities. The excellent mechanical properties and superior thermal stabilities of Fe-13Cr-5Al-2Mo-1ZrC alloy were not only attributed to the dispersion strengthen by nanosized ZrC particles, the solid solution strengthening by Mo elements, but also the grain refinement structure promoted by the synergistic effects of Mo and ZrC additions.

Technology development of novel autogenous double pulse tungsten insert gas welding technique to evaluate the depth of penetration, micro segregation via machine learning and desirability function approach

The present research investigates the effect of process parameters on the microstructure, micro segregation, and material properties of the Autogenous Double Pulse Tungsten Inert Gas Welding (ADP-TIG) of Inconel 625. The optimization of the process parameter was evaluated by Response surface Methodology (RSM) Box Behnken method. In this article, the effects of the weld-bead geometry, weld centre (WC), weld interface (WI), and heat affected zone (HAZ) were evaluated through macro morphology, microstructure, SEM/EDAX, XRD, and micro hardness. The outcomes indicate that by employing a combination of high and low frequency pulsing in ADP-TIG, it is possible to regulate not only the dimensions of the weld-bead and penetration depth but also the HAZ. The ADP-TIG process has a low heat input, resulting in finer grains in the microstructure, reduced secondary phases, and a narrower HAZ. SEM images of alloy 625 confirms the depiction of fine equiaxed dendrites. The ADP-TIG process reduces secondary phase formation due to a reduction in Mo and Nb alloying elements. EDAX results also show that the micro segregation in the weld centre (WC) and weld interface (WI) is very less in the dendritic core region because of the lower heat Input. The XRD result confirms the presence of NbzNi, Cr₂Nb, Ni8Nb, Fe2Mo3 and FeNi phases. The maximum microhardness values in WC and WI are 290 HV and 280 HV, respectively. The impacts of ADP-TIG welding technique specifications on factors such as weld bead geometry, WC, WI, and HAZ have been thoroughly examined across a range of process parameters. Further the process parameters of ADP-TIG were optimized using a desirability function to achieve defect-free welds, followed by experimental validation. The desirability function results were then compared with a machine learning (ML) approach. The investigation aimed to assess ML algorithms' predictive capability for weldment outcomes. From the ML modelling results, Support Vector Machine (SVM) using the Radial Basis Function (RBF) kernel was identified as the superior strategy for accurately predicting Heat input, Mo segregation, and Nb segregation. Additionally, Gaussian process regression (GPR) with an RBF kernel was recommended for predicting the Width to Depth Ratio.

Improvement mechanism of Mo element on cracks, microstructure and properties of laser cladding WC-Ni60AA coating

To enhance the forming quality and mechanical properties of metal-based composite coatings, WC-Ni60AA composite coatings were prepared on the surface of 65Mn via laser cladding. The influence of Mo element addition on the forming quality, phases, microstructure, microhardness, and frictional wear of the coatings was systematically investigated. The wear mechanism of the composite coatings was analyzed in depth, with particular attention to the grain refinement mechanism and crack inhibition mechanism induced by Mo elements on the coatings. The results indicate that the coatings without Mo element exhibit numerous “Y-shaped” cracks on the surface, with dense cracks in the top part and sparse cracks in the bottom part, and the main crack deviates towards the laser scanning direction. Upon addition of Mo elements, the crack density of the coatings initially decreases and then increases, with complete elimination of coating cracks observed at an addition of 1.00 wt% Mo. Prior to Mo addition, the main phases in the coatings are γ-(Fe, Ni), Fe3W3C, W2C, and M23(C, B)6. After Mo addition, a new phase Mo2C appears in the coatings. The addition of Mo elements strengthens the grain boundaries of the coatings, refines the grains, and transforms the originally coarse cellular and dendritic structures into fine, dense equiaxed grains. The average hardness of the coatings initially decreases and then increases. The coating with 1.00 wt% Mo addition exhibits the highest average microhardness, minimal average friction coefficient, and wear rate, with the wear mechanism being abrasive wear and slight spalling wear. The oxide film formed by Cr2O3, NiO, and MoO3 in the coatings enhances the wear resistance of the coatings.

Investigations on corrosion resistance of steel coated with chromium-free ZTM conversion coating

Chromium–free conversion coatings based on Zr/Ti/Mo (ZTM) compounds via chemical conversion technology were investigated to improve the corrosion performance of SPCC-JISG 31 steels. A preliminary study was carried out to evaluate the influences of critical parameters, including the concentrations of active species Zr, Ti and Mo, and the conversion bath's pH, on the protective efficiency using a Statistical design of experiments (DoE) methodology. Passivation layer with compositional Mo, Ti and Zr elements has been employed on the steels by dipping in mixed solutions containing 17 g/l Na2MoO4, 1 g/l K2TiF6 and 7 g/l K2ZrF6 under pH = 5. The morphology and elemental analysis of Zr/Ti/Mo on surface of the steels was studied by the employment of scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS). Pull-off adhesion test was performed, indicating that the ZTM coatings enabled to increase the adhesion strength (6.0 MPa) of mild steel to the organic coating than that of traditional phosphate (ZrP) coating. The results of electrochemical impedance spectroscopy and the salt spray test (529 h) evidenced the higher corrosion resistance of the Zr/Ti/Mo coating compared with theconventional phosphate coating.

Analysis of the Oxidation Behavior and Formation of an Extremely Thin Oxide Layer with a Novel Hot-Stamped Steel

This study investigates enhancing the high-temperature oxidation resistance of hot-stamped steels by adding the Cr/Mn/Si elements to form an extremely thin oxide layer. Under low oxygen partial pressure conditions and high Cr content in the matrix, the oxide layer of a 38Cr3MnNbVMo hot-rolled plate containing the Mo element and high Si content was further thinned to 0.6 μm after cooling at 900 °C for 5 min. The structure of the ultra-thin oxide layer consists of Fe3O4, Mn oxides, FeCr2O4, Cr2O3, and Fe2SiO4 oxides. Compared to other antioxidant elements, under low oxygen partial pressure conditions, Si is more prone to oxidation, forming ultra-thin (22 nm) Fe2SiO4 oxides at the matrix interface. Combined with Cr2O3, FeCr2O4, and Mn oxides, it collectively inhibits the mutual diffusion of external O ions and matrix Fe ions. Furthermore, the addition of the Mo element improves the oxidation resistance. The synergistic effect of multiple powerful oxidation-resistant elements and oxide products effectively inhibits the growth of the iron oxide scale, enhancing the oxidation resistance of hot-rolled, hot-stamped steel.

Solidification path and precipitation mechanism of a Ni-Cr-co-Mo based heat-resistant alloy

The solidification path and precipitation mechanism of the C-HRA-3 Ni-Cr-Co-Mo-based heat-resistant alloy are investigated by methods such as differential scanning calorimetry analysis, in-situ observations, quenching experiments, and scanning transmission electron microscopy. The results confirm that the primary solidification precipitates in the center of the C-HRA-3 alloy VAR ingot consist of Ti(C,N), M6C-M23C6 symbiotic phases, Ti(C,N)-M6C-M23C6 symbiotic phases and surrounding dispersed M6C and M23C6 carbides. The precipitation temperatures for Ti(C,N), M6C, and M23C6 are 1310 °C, 1280 °C, and 1230 °C, respectively. The C-HRA-3 alloy exhibits a wide solidification temperature range of 176 °C (1390 °C ∼ 1214 °C). Within 1390 °C ∼ 1355 °C, the γ phase grows vigorously, accompanied by a significant reduction in the fraction of liquid phase. At 1355 °C ∼ 1214 °C, the decrease in liquid phase fraction slows down, accompanied by significant enrichment of Mo, Cr, C and Ti elements. There is a clear functional relationship between the liquid phase percentage and temperature. M6C carbides undergo two heterogeneous nucleation mechanisms in the liquid phase. Due to the degradation of M6C carbides discharging Cr and C atoms, M23C6 carbides form at their edge. Dispersed M6C and M23C6 carbides nucleate at misfit dislocations around the symbiotic phases. Appropriately reducing the cooling rate during the stage above the precipitation temperature and increasing the cooling rate below the precipitation temperature can significantly reduce the volume percentage and size of the symbiotic phases.

Adsorption and separation performance of tungsten and molybdenum on modified zirconium based metal organic frameworks UiO-66-CTAB

A modified zirconium (Zr)-based metal organic framework (UiO-66-CTAB) was synthesized by solvothermal method, and used for the adsorption and separation of molybdenum (Mo) and tungsten (W). Under the optimized conditions, UiO-66-CTAB with uniform pore size and containing particles with tetrahedral cage structure could be obtained. UiO-66-CTAB showed BET surface area and micropore volume of 873.848 m2·g−1 and 0.403 cm3·g−1, respectively, with the particle size range of 200–300 nm. It acquired positive charge at pH < 7, thus it could get easily connected with the negatively charged Mo species. The material shows excellent adsorption of Mo and its effective separation from W in acidic solution. It is beneficial for separation at room temperature under the optimal contact time of 3 h. The adsorption capacity for Mo (QMo) was 355 mg·g−1 and the highest separation factor (βMo/W) was 51.4. Comprehensive analysis of XRD, SEM, FT-IR spectroscopy, XPS, and thermodynamic results indicate that the adsorption mechanism involved the selectivity of the effect of pore size, stronger affinity of the metal point Zr for Mo, and coordination interaction between the N atom of CTAB and Mo element, which allowed more Mo-homopoly acid ions to enter the cage and significantly hindered the entrance of W-homopoly acid ions into the UiO-66-CTAB. The adsorbent UiO-66-CTAB can be considered as a potential candidate for new and green adsorbent materials for the separation and recovery of W and Mo in the treatment of ores, wastes, and wastewater, which is beneficial for environmental protection.