Dispersed Oxide Particles Research Articles

Experimental and simulation studies to optimize the mechanical alloying process of ODS-FeCrAl alloy powder

Oxide dispersion strengthened (ODS) FeCrAl alloy exhibits superior mechanical qualities at high temperatures and resistance to neutron irradiation, making it a highly promising material for accident-tolerant fuel cladding. The preparation of ODS-FeCrAl alloy powder by mechanical alloying can mix Y2O3 and FeCrAl alloy powder uniformly and promote the uniform dispersion of nanoscale oxide particles in the alloy matrix. The preparation of ODS-FeCrAl alloy powder by the mechanical alloying method is greatly influenced by the rotational speed. Therefore, this study uses a combination of experiments and numerical simulation to investigate the effects of different rotational speeds on the microscopic morphology, particle size and force of alloy powder during the ball milling process. The mechanically alloyed powder was subjected to XRD inspection to determine the optimum ball milling time at each rotational speed by means of the maximum lattice distortion, and then the powder micromorphology and particle size were analyzed. Then the forces on the powder and grinding ball during the ball milling process were analyzed by numerical simulation, and it was found that the collision force and normal force played a dominant role in the ball milling process. The combined experimental and simulation results determined that the ODS-FeCrAl alloy powder obtained by ball milling at 300 rpm for 35 h had the largest lattice distortion, fine grain size and uniform particle size, which achieved the best mechanical alloying effect.

Mechanical Behavior of Oxide Dispersion Strengthened Steel Directly Consolidated by Rotary Swaging.

Among the main benefits of powder-based materials is the possibility of combining different constituents to achieve enhanced properties of the fabricated bulk material. The presented study characterizes the micro- and sub-structures and related mechanical properties of ferritic steel strengthened with a fine dispersion of nano-sized Y2O3 oxide particles. Unlike the typical method of preparation via rolling, the material presented herein was fabricated by direct consolidation from a mixture of powders using the versatile method of hot rotary swaging. The mechanical properties were evaluated at room temperature and also at 1300 °C to document the suitability of the prepared steel for high-temperature applications. The results showed that the imposed shear strain, i.e., swaging ratio, is a crucial parameter influencing the microstructure and, thus, material behavior. The workpiece subjected to the swaging ratio of 1.4 already exhibited a sufficiently consolidated structure with ultra-fine grains and featured high room-temperature microhardness values (up to 690 HV0.5), as well as a relatively high maximum flow stress (~88 MPa) when deformed at the temperature of 1300 °C with the strain rate of 0.5 s-1. However, the dispersion of oxides within this sample exhibited local inhomogeneities. Increasing the swaging ratio to 2.5 substantially contributed to the homogenization of the distribution of the Y2O3 oxide particles, which resulted in increased homogeneity of mechanical properties (lower deviations from the average values), but their lower absolute values due to the occurrence of nucleating nano-sized recrystallized grains.

Scalable Photo-Responsive Physical Unclonable Functions via Particle Kinetics.

The increasing menace of counterfeiting and information theft underscores the urgent need for security platforms compatible with both micro- and nanoelectronics. Existing methods for anticounterfeiting labeling and cryptographic systems rely on unclonable patterns derived from the unpredictable variability of physical phenomena. However, these approaches impose limitations on the scalability of security components. Here we present a scalable platform for photoresponsive physically unclonable functions based on oxide particle kinetics in polymer solutions. The stochastic agglomeration process occurring during the formation of polymer films with dispersed oxide particles yields random patterns, with pixel sizes scalable from micro to nanoscales. We produce mechanically flexible and self-destructible optical unclonable function patterns utilizing oxide aggregates on a polymer film. Moreover, we establish a strategy for generating electrical unclonable patterns on a conducting polymer film. This involves covering the polymer film with an aggregate pattern mask, which serves as an ultraviolet-blocking layer for randomly exposing the film to ultraviolet ozone treatment. These unclonable patterns constitute robust and compact security systems, exhibiting effective resilience against machine-learning attacks (∼50% prediction error for training data sets of 1000). The developed scalable platforms for physically unclonable functions provide a hardware solution for robust cryptographic applications.

Enhanced oxidation resistance of ZrB2-MoSi2 coating through MoSi2-TaSi2 double-silicide alloying modifying

This study explored how MoSi2-TaSi2 ratios in silicide alloys influence the oxygen resistance of ZrB2-MoSi2-TaSi2 coatings, using self-propagating high-temperature synthesis and spark plasma sintering. The oxidative self-separation effect of TaSi2 and MoSi2 enhances nanoscale Zr and Ta oxide particle dispersion, forming a Zr-B-Ta-Si-O glass with optimal oxygen-blocking in the 50ZrB2-(MoSi2-10TaSi2) coating (ZMT10). Compared to ZrB2-MoSi2, ZMT10 showed 28.87 % and 48.21 % reductions in weight gain and oxygen penetration, increasing protection to 99.71 %. Excessive TaSi2 leads to Ta5+ dissolution, oxide aggregation, and a dendritic structure, facilitating oxygen diffusion and oxidation, raising the oxygen penetration in 50ZrB2-(MoSi2-30TaSi2) to 0.73 %, lowering protection to 99.18 %.

FORMATION OF TWO-PHASE ZONES DURING INTERNAL OXIDATION OF BINARY ALLOYS

In the paper the formation patterns of two-phase regions during the internal oxidation process in low-alloyed binary alloys is studied. The goal of the research is the creation of a mathematical model for the internal oxidation process, which is to describe the kinetics of formation and evolution of internal oxidation zones, the study of the patterns governing the two-phase zone formation during internal oxidation, the study of the space-time dynamics of the structural parameters of the two-phase area, namely the number of the oxide particles, their average radius and the phase volume, at different stages of the internal oxidation zone evolution. The two-phase process of diffusion saturation with light components applied to binary alloys is analyzed theoretically. The conditions for formation of disperse oxide particles are formulated. A mathematical model for the formation of two-phase areas as well as the numerical solution for the system of equations describing the kinet- ics of formation and evolution of the two-phase area for different values of the process parameters is proposed. The modeling and experiments demonstrate that the distribution of structural parameters of the two-phase area has complex, non-monotonous nature. The influence of the main parameters of the process on the kinetics of the formation of the two-phase area in a lightly-alloyed binary nickel-based alloy plate is also determined. All stages of the plate’s oxidation process are studied – from the inception of the particles to the coalescence of second-stage particles. The results of the work could be used for developing new technologies in thermal and chemical-thermal treatments for disperse strengthening of materials using internal oxidation, as a physical basis for seeking ways of providing certain distributions of the internal oxidation zone structural parameters, which are required to give the al- loy a necessary set of physical and mechanical properties. The comparison of the modeling and experimental results shows a good correlation, which allows them to be recommended for developing new technologies in disperse strengthening, new heat-resistant steels, disperse-strengthened magnetic materials and electrotechnical alloys.

The influence of ionic form and Cu2O particles on thermal stability of carboxylic cation exchangers

In this study the interaction of polymeric support with carboxylic groups and dispersed cuprous oxide particles on thermal and wetting properties of composite materials was investigated. Carboxylic cation exchangers (CCEs) in the Cu2+ form (macroporous, M and gel-type structure, G) was reacted with an ascorbic acid/NaOH solution to obtain hybrid ion exchangers containing Cu2O fine particles (over 20.0 wt% of Cu). The results of thermal analysis, under air and under N2, of CCEs with carboxylic groups in the H+ and Na+ form and obtained composites (M/H, M/Na, M/Na#Cu2O, M/H#Cu2O and G/H, G/Na, G/Na#Cu2O, G/H#Cu2O) were discussed. The TG/DTG curves shoved varied content of the hygroscopic water in examined materials, in the range of 4.05–22.55 wt%. It was found that similarly to M/Na and G/Na, M/Na#Cu2O and G/Na#Cu2O were stable until up to 450 °C, while M/H#Cu2O, G/H#Cu2O decomposed faster than M/H and G/H, below 200 °C. By X-ray diffraction and FTIR spectroscopy, Na2CO3, CuO, Cu2O and Cu0 were identified in the solid residues, whose mass reached 55.0 wt%. The obtained multifunctional, thermal stable and exceptionally rich in Cu2O composite materials are potential catalysts, sorbents and biocides.

Effect of Fe3O4:RGO Ratios in Magnetic Nanocomposites Applied for Dye Discoloration

Nanocomposites of magnetite anchored on reduced graphene oxide with different magnetite:reduced graphene oxide mass ratios were synthesized and evaluated in indigo carmine photo Fenton discoloration. All nanocomposites are magnetic and showed comparable amounts of magnetite and hematite with a higher level of hematite for low iron contents. The highest value of 63.6 emu g-1 was obtained for the nanocomposite with the highest magnetite content. The nanocomposites presented high dispersion of iron oxide particles, at about 12 nm on reduced graphene oxide surface sheets. The samples also showed bandgap energies below that found for bulk magnetite, showing an important effect of reduced graphene oxide. The nanocomposite with an iron nitrate precursors mass ratio of 17:1 showed the best performance (99.7% of indigo carmine discoloration (2.1 × 10-5 mol L-1) at 30 min of reaction, hydrogen peroxide(2.3 × 10-1 mol L-1), and a catalyst dosage of 0.67 g L-1). Reusability tests were performed, and this nanocomposite was shown to be active for at least three recycles. X-ray photoelectron spectrum of Fe2p3/2 showed that the FeIII/FeII ratio was maintained even after three recycles (4 runs), meaning that reduced graphene oxide is responsible for stabilizing magnetite particles, thus maintaining its photocatalytic activity.

Initial contact and spreading of a non-Newtonian drop on a solid surface

In this work, the very initial contact and spreading of drops of two non-Newtonian fluids on a hydrophilic stainless-steel surface were comparatively investigated. The fluids employed were respectively a polymer solution of polyacrylamide (PAAm) and an aqua dispersion of fine graphene oxide (GO) particles. Experimental studies involved visualizing and characterizing the spreading width over time on the substrate surface. A more precise investigation into the initial contact and spreading of non-Newtonian pendant drops on a solid surface was performed through a home-made ultra-high-speed direct current (DC) electrical device with an acquisition frequency up to 1.25 MHz (time interval of 0.8 μs), a high-speed camera and a home-developed high-speed micro-particle image velocimetry (micro-PIV). The competing mechanisms of related forces: inertial, viscous, and capillary forces were probed to lead to different scaling laws.

ALUMINUM OXIDE IN VACUUM CONDENSATES BASED ON COPPER

Strengthening of copper and copper alloys with aluminum oxide particles is an important technological technique. Composite materials based on copper strengthened with aluminum oxide particles have a significant operating temperature range and better mechanical properties at elevated temperatures than age-hardening alloys. However, at moderate operating temperatures, the use of age-hardening alloys remains more economically justified. The main direction in the development of composites strengthened with oxide particles is the dispersion of the strengthening phase to sizes of several or one nanometer, which will bring their mechanical properties to the level of age-hardening alloys. However, dispersion leads to a significant increase not only in strength, but also in electrical resistance. The adverse effect on the electrical conductivity of dispersed particles will decrease with a decrease in the volume fraction of oxide, bringing the electrical conductivity closer to the level of copper. Based on an analysis of the materials of scientific research devoted to the production of dispersion-strengthened Cu–Al2O3 composites, it was concluded that the most significant progress in the dispersion of oxide particles with uniform distribution in the copper matrix of the composite was achieved using the method of electron beam evaporation and simultaneous deposition (condensation) of vapors of components in vacuum (EB–PVD). Structural studies of the morphology of aluminum oxide particles in dispersion-strengthened copper composites were carried out using methods such as: X-ray fluorescence analysis, transmission electron microscopy, and energy-dispersive X-ray spectroscopy (EDS). The average size of aluminum oxide particles in the studied dispersion-strengthened composites was in the range from 1.8 to 3 nm. In the work, the dependence of the specific electrical resistance of composites (ρ) on the oxide content was investigated. It was found that a decrease in the size of oxide particles leads to an increase in the electrical resistance of the dispersion-strengthened composite. The studies of the method of electron beam evaporation and subsequent condensation in vacuum, presented in the work, confirm the possibility of further dispersion of aluminum oxide particles with simultaneous narrowing of the distribution histogram. This opens up prospects for further improvement of vacuum dispersion-strengthened copper-based composites.

Development of microstructure and properties within oxide dispersion strengthened steel directly consolidated by hot rotary swaging

Steels strengthened with fine oxides maintain favourable mechanical properties at high temperatures. This unique study evaluates the effects of direct consolidation of mechanically alloyed powders of ferritic steel and Y2O3 nanooxides by hot rotary swaging (multiple swaging ratios) on microstrutcures and mechancial properties of final rods. Direct consolidation of the steel powder by the proposed method was successful at the swaging ratio 1.0. However, the quality of consolidation improved with increasing the swaging ratio to 1.4, and finally to 1.8 (no visible pores). The microstructure of the rod processed with swaging ratio 1.8 exhibited homogeneous dispersion of oxide particles and featured ultra-fine (UF) grains, its average Vickers microhardness exceeded 700 HV1.

Time-Resolved Corrosion Behavior of Transition-Metal-Based High-Entropy Alloy in Saline and Phosphate Buffer Solutions

This study focuses on time-resolved surface modifications of a single-phase Ti25Zr25Nb15V15Ta20 high-entropy alloy (HEA) when immersed in 0.9 wt% NaCl and phosphate-buffer solutions (PBS) at 37 °C. A remarkable transition from high ionic diffusion to electron conduction was observed in PBS, whereas the existing conductivity in NaCl solution was further enhanced after 3 h of exposure. During in-situ testing, NaCl improved passivation conceived by the decrease in passivation-current density and increase in Tafel slope. Heterogeneously dispersed oxide particles with NaCl could have accounted for the moderate increase in conductivity while not affecting the capacitive behavior. The Tafel slope decreased after 2 h of immersion in PBS linked to K+ and P−3 accumulation on the surface. The pronounced change in the post-PBS treated sample was also revealed by a four-fold increase in HEA-electrolyte resistance. A visible decrease in the constant-phase-element parameter of the HEA-electrolyte interface after long-term PBS immersion indicated a rise in electrode conductivity and ionic build-up on the surface. The findings suggest that compared to PBS, the selected HEA has a faster passive-layer formation in NaCl with smaller changes in interface resistivity upon long-term immersion, which is promising for enhanced protein-adsorption rates and loading amount.

Catalytic Oxidation of VOC over Cobalt-Loaded Hierarchical MFI Zeolite

The zeolites ZSM-5 with different Si/Al ratios were modified with a buffer solution of HF and NH4F. This acidic treatment led to the obtaining of a material with secondary mesoporosity. The deposition of cobalt from an aqueous solution of cobalt acetate on the surface of treated samples generates the formation of different cobalt oxide species: bulk-like Co3O4 phases strongly interacting with the support, Co2+ in ion exchange positions (γ and β sites) and silicate-like phases. The mechanism of cobalt silicate phase formation is proposed here and includes a replacement of silanol groups and the bridging hydrogens by Co and the inclusion of the Co atoms in tetrahedral framework positions. The catalysts, obtained through use of the treated ZSM-5, exhibit higher activity in the reactions of propane, and n-hexane completes oxidation compared with the catalyst samples containing un-treated zeolite. Both the finer dispersion of metal oxide particles on the hierarchical sample and the presence of secondary mesoporosity improve the effectiveness of the active phase utilization via access to larger number of active sites.

Synthesized Nanoaluminum Oxide with Al2024 to Investigate Wear Behavior by Grey Relational Approach and ANN

Aluminum metal matrix composites (AMCs) have been employed in automobile manufacturing to reduce weight. Also this research concentrates on the tribological performances on the processed AMCs by the stir casting liquefying method. The aluminum alloy Al2024 was employed to nanoparticles of aluminum oxide for the preparation of AMCs with constant processing condition of stirring speed to produce the homogeneous dispersion. The processed composites were further investigated to identify the wear characteristics. Therefore, the dry sliding condition was achieved on the processed composites. The input parameters of dry sliding conditions are sliding distance, functional load, and sliding velocity, and the output characteristics are wear rate and coefficient of friction (COF). Those input parameters are framed by the Taguchi L9 array and parameters were further employed to optimize with grey relational analysis. From the L9 parameters, the better wear rate and COF were accumulated in the following parameter: 2,100 mm of sliding distance, 25 N of functional load, and 2.5 m/s of sliding velocity, respectively. Then the wear rates and COF values are subjected to produce the predicted responses with supporting of artificial neural network. Most of the predicted values are much higher than the actual wear response vales. The wear resistance of all the samples composed better performances with dispersion of nanoaluminum oxide particles on the Al2024 alloy.

The effects of extrusion ratio and heat treatment on microstructures and tensile properties of a powder metallurgy Fe–22Mn steel

Powder metallurgy Fe–22Mn (wt.%) steel rods were fabricated by powder compact extrusion followed by heat treatment, and their microstructures and tensile properties were investigated. The microstructure of the as-extruded rods consisted of γ-austenite, ε-martensite, α'-martensite and a dispersion of ferrous manganese oxide (FMO) particles. By increasing the extrusion ratio from 9:1 to 16:1, the volume fractions of γ and ε increased significantly, while that of α' decreased significantly, which is due to more Mn atom diffused into the γ phase and improved its stability. This situation led to a significant decrease in yield strength without much change of the tensile strength and ductility. γ→ε and ε→α' transformations occurred during plastic deformation, resulting in a strengthening of the strain hardening capacity. The γ→ε transformation occurred only when the strain was <0.1, and beyond this strain, the volume fraction of γ decreased to a level that would not allow further phase transformation in γ. Annealing at 1200 °C for 1 h makes Fe atoms undergone segregation in FMOs, causing an obvious decrease of the hardness and Young’ s modulus of the FMO particles to a level lower than that of the matrix, which brings more severe damage to the ductility of the material.

Comparative Study of Physicochemical Characteristics and Catalytic Activity of Copper Oxide over Synthetic Silicon Oxide and Silicon Oxide from Rice Husk in Non-Oxidative Dehydrogenation of Ethanol

The article presents the results of comparative research on the physicochemical characteristics and catalytic activity of copper oxide supported on synthetic SiO2 and SiO2 (RH) from rice husk. SiO2 (RH) is more hydrophobic compared to SiO2, which leads to the concentration of copper oxide on its surface in the form of a “crust”, which is very important in the synthesis of low-percentage catalysts. According to SEM, XRD, and TPR-H2, the use of SiO2 (RH) as a carrier leads to an increase in the dispersion of copper oxide particles, which is the active center of ethanol dehydrogenation.

High-Pressure Die Casting: A Review of Progress from the EPSRC Future LiME Hub

This article provides an overview of high-pressure die casting (HPDC)-related research undertaken at the EPSRC Future LiME Hub between 2015–2022. The project aimed to identify the cause of variability in the tensile ductility of die-cast structures, and to develop novel processing techniques to address this issue. Variability in tensile ductility was related to the size of large pores and non-metallic inclusions. It was proposed that these non-metallic inclusions formed during the pyrolysis of commercial plunger lubricants in the shot sleeve, and that these large pores derived from dilatational strains introduced during semi-solid deformation. Processing parameters and die design were found to significantly influence the microstructure of die-cast products, and the subsequent variability in tensile ductility. To close, recent progress on the application of intensive melt shearing to HPDC is reviewed. Intensive melt shearing was found to induce significant grain refinement in both Al and Mg alloys due to the effective dispersion of native oxide particles, and the use of these particles as heterogeneous nucleation substrates. The presence of native oxide particles also enabled the use of novel heat treatment procedures that avoided conventional issues such as surface blistering and geometrical distortion.

Laser Additive Manufacturing of Oxide Dispersion-Strengthened Copper–Chromium–Niobium Alloys

Copper is a key material for cooling of thermally stressed components in modern aerospace propulsion systems, due to its high thermal conductivity. The use of copper materials for such applications requires both high material strength and high stability at high temperatures, which can be achieved by the concept of oxide dispersion strengthening. In the present work, we demonstrate the oxide reinforcement of two highly conductive precipitation-strengthened Cu-Cr-Nb alloys using laser additive manufacturing. Gas-atomized Cu-3.3Cr-0.5Nb and Cu-3.3Cr-1.5Nb (wt.%) powder materials are decorated with Y2O3 nanoparticles by mechanical alloying in a planetary mill and followed by consolidation by the laser additive manufacturing process of laser powder bed fusion (L-PBF). While dense specimens (&gt;99.5%) of reinforced and nonreinforced alloys can be manufactured, oxide dispersion-strengthened alloys additionally exhibit homogeneously distributed oxide nanoparticles enriched in yttrium and chromium next to Cr2Nb precipitates present in all alloys examined. Higher niobium contents result in moderate increase of the Vickers hardness of approx. 10 HV0.3, while the homogeneously dispersed nanometer-sized oxide particles lead to a pronounced increase of approx. 30 HV0.3 in material strength compared to their nonreinforced counterparts.

Effect of nitrogen concentration on creep strength and microstructure of 9Cr-ODS ferritic/martensitic steel

9Cr oxide dispersion strengthened steels with slightly different nitrogen concentrations (0.0034 − 0.029 wt%) were prepared and their creep property at 973 K was investigated with microstructural characterization before and after the creep test. The creep strength decreased significantly as the nitrogen concentration increased. Microstructural observation revealed that, in the higher nitrogen concentration specimen, coarse Y-rich inclusions were found along the boundary between transformed ferrite region and residual ferrite region. The solubility difference of nitrogen in α and γ phase would induce the localized increment of nitrogen concentration in the boundary region during the austenitizing process, resulting in the thermodynamic destabilization and subsequent coarsening of the dispersed oxide particles. The rows of creep voids were found near the rupture part of the crept specimen, and their fraction increased with increasing nitrogen concentration. This suggests that the coarse inclusions were one of the main starting points of creep void formation, leading to premature fracture in the higher nitrogen specimen.

Effects of the Ball Milling Process on the Particle Size of Graphene Oxide and Its Application in Enhancing the Thermal Conductivity of Wood

To improve the dispersion of graphene oxide particles in wood for better thermal conductivity, this paper proposes the feasibility of obtaining graphene oxide with a smaller particle size using ball milling and its application in melamine resin-modified poplar veneer. The median diameter of multilayer graphene oxide was measured to learn the effects of different ball milling conditions on the particle size of graphene oxide, and the optimum ball milling process was chosen. In addition, the microscopic characterization of graphene oxide under the optimum ball milling process was carried out to investigate the microstructural changes in multilayer graphene after ball milling. Furthermore, the thermal conductivity of the graphene oxide/melamine resin-impregnated mixture modified veneer with the optimum ball milling process was also tested. The results show that, under the optimum ball milling process conditions of SDS wet ball milling with a vibration frequency of 30 Hz for 60 min, the particle size of the multilayer graphene was the smallest, and the median diameter could be reduced to 124 nm. Simultaneously, the thermal conductivity of the melamine resin-modified poplar veneer enhanced by the ball-milled graphene reached 0.405 W·m−1·K−1. In addition, it revealed that the number of graphene oxide layers was reduced to four after ball milling. However, the multilayer graphene was partially oxidized, the lamellar structure was destroyed and the crystallinity was reduced.

High-temperature creep properties of 9Cr-ODS tempered martensitic steel and quantitative correlation with its nanometer-scale structure

ABSTRACT The Japan Atomic Energy Agency (JAEA) has been developing 9Cr-oxide dispersion strengthened (ODS) tempered martensitic steel (TMS) as a candidate material for use in the fuel cladding tubes of sodium-cooled fast reactors (SFRs). The creep property is essential for the fuel cladding tube of SFR; the reliable prediction of in-reactor creep-rupture strength is critical for implementing the 9Cr-ODS TMS cladding tube in the SFR. This study investigated the quantitative correlation between the creep properties of 9Cr-ODS TMS at 700°C and the dispersions of nanosized oxides by analyzing the creep data and the material’s nanostructure. The possibility of deriving a formula for estimating the in-reactor creep properties of 9Cr-ODS TMSs based on an analysis of the nanostructure of neutron-irradiated 9Cr-ODS TMSs was also discussed. The creep properties of 9Cr-ODS TMS at 700°C closely correlated with the dispersion of nanosized oxide particles. The correlation between creep-rupture lives and nanosized oxide particle dispersion in 9Cr-ODS TMS was determined using existing creep models. The elucidation of correlation between the stress exponent of secondary creep rate and the nanostructure is essential to enhance future modeling reliability and formulation.