Nanoscale Oxide Research Articles

Achieving strength-ductility synergy of ODS-FeCrAl alloys via heterostructured strategy

Oxide dispersion strengthened (ODS)-FeCrAl alloys are candidate structural materials for advanced nuclear reactor applications, which have excellent strength and radiation tolerance but low ductility. In this study, a novel ODS-FeCrAl heterostructured composite, reinforced with FCC-structured ODS-CoCrFeNiMn high-entropy particles, was prepared by using mechanical alloying and spark plasma sintering to achieve the strength-ductility synergy. The effect of different reinforcement contents (0, 10, 15 and 20 wt.%, designated as RC-0, RC-10, RC-15, and RC-20, respectively) on the microstructure and mechanical properties of the composites was investigated. The results showed that the unreinforced reference alloy, RC-0, consists of BCC-structured ODS-FeCrAl matrix and high-density oxides. In the RC-10, RC-15, and RC-20 composites, in addition to the ODS-FeCrAl matrix and nanoscale oxides, FCC-structured ODS-CoCrFeNiMn high-entropy reinforcement with ultrafine grain size and FCC transition layer with gradient grain size are observed. As the reinforcement content increases, the thickness of transition region increases. The composites show an increase in ultimate compressive strength and compressive strain with increasing reinforcement content in the following order: 2951 MPa/33.6%, 3169 MPa/40.0%, 3290 MPa/43.2%, and 3489 MPa/48.8%. And the compressive yield strength exhibits an initial increase and subsequent decrease, i.e. 1523 MPa (RC-0), 1680 MPa (RC-10), 1635 MPa (RC-15), and 1355 MPa (RC-20), respectively. The increase in yield strength is mainly attributed to hetero-deformation induced (HDI) strengthening and reinforcement hardening. The improvement in ductility is mainly attributed to the HDI work hardening and the suppression of microcrack formation and propagation at prior powder boundaries.

Comprehensive evaluation of corrosion resistance and biocompatibility of ultrafine-grained TiMoNb alloy for dental implants

To address the limited wear resistance observed in traditional titanium alloys, we have developed an ultrafine-grained equiatomic TiMoNb compositionally complex alloy (CCA) with exceptional wear resistance. However, there is a significant lack of in vitro and in vivo evaluation of the TiMoNb CCA for biomedical applications. In this study, we comprehensively evaluate the corrosion behavior, tribo-corrosion performance, biocompatibility, and osseointegration of the TiMoNb alloy. Our findings indicate that the alloy exhibits strong corrosion resistance and stable tribo-corrosion behavior, attributed to the presence of Ti-rich nanoscale precipitates that impede tribo-corrosion-induced shear deformation, along with a protective nanoscale oxide layer. Furthermore, in vitro and in vivo evaluations demonstrate the excellent biocompatibility of the TiMoNb alloy and reveal its ability to promote the regeneration of defective femurs and its favorable bone osseointegration capability. Overall, our study underscores the potential of the TiMoNb alloy as a promising material for dental implants and provides valuable insights into the tribo-corrosion mechanisms of ultrafine-grained alloys.

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.

Ultrasonic-assisted electrochemical strategy for ITO scraps recovery through anodic dissolution

The conversion of ITO scraps into oxide powders that can be employed to prepare targets is integral to the closed-loop utilization of scare metal indium. Herein, we present a novel route for electrochemical coupled ultrasonic recovery of ITO scraps, which averts the consumption of strong acids, alkalis and carbon containing reducing agents in traditional hydrometallurgical or pyrometallurgical recovery processes. In an ammonium salt solution, the ITO anode dissolves under the action of electrons: oxygen ions are oxidized, while metal ions are leached out, and then combines with hydroxide ions in the solution to form flocculent precipitates, which is attributed to the extremely low solubility product of indium hydroxide and tin hydroxide. The ultrasonic field can promote the mass transfer between the electrode and electrolyte interface, thereby accelerating the reaction process regulating the morphology and size of the product. After calcination, the precipitates become uniformly mixed nano-scale oxide powders with dimensions that meet the requirements for target preparation. The recycling strategy, with its green, straightforward operation, and feasible for scale-up, suggests potential industrial uses for recovering ITO scraps.

Depth-Resolved X-Ray Photoelectron Spectroscopy Evidence of Intrinsic Polar States in HfO2-Based Ferroelectrics.

The discovery of ferroelectricity in nanoscale hafnia-based oxide films has spurred interest in understanding their emergent properties. Investigation focuses on the size-dependent polarization behavior, which is sensitive to content and movement of oxygen vacancies. Though polarization switching and electrochemical reactions is shown to co-occur, their relationship remains unclear. This study employs X-ray photoelectron spectroscopy with depth sensitivity to examine changes in electrochemical states occurring during polarization switching. Contrasting Hf0.5Zr0.5O2 (HZO) with Hf0.88La0.04Ta0.08O2 (HLTO), a composition with an equivalent structure and comparable average ionic radius, electrochemical states are directly observed for specific polarization directions. Lower-polarization films exhibit more significant electrochemical changes upon switching, suggesting an indirect relationship between polarization and electrochemical state. This research illuminates the complex interplay between polarization and electrochemical dynamics, providing evidence for intrinsic polar states in HfO2-basedferroelectrics.

A New Approach to Single‐Step Fabrication of TiOx‐CeOx Nanoparticles

Mixed metal oxide (MMO) nanoparticles (NPs) are hybrids consisting of two or more nanoscale metal oxides. Advantages of MMO NPs over single metal oxides include improved catalytic activity, enhanced electrical and magnetic properties, and increased thermal stability due to the synergy of the different oxide components. This study presents a novel fabrication route for TiO2‐CeO2 NPs enriched with oxygen vacancies using a Haberland‐type gas aggregation cluster source. The NPs, deposited from different segmented Ti/Ce targets under varying O2 addition, were examined with respect to final composition, morphology, and Ti, Ce surface oxidation states. Particle formation mechanisms are proposed for the observed morphologies. Additionally, available O2 during deposition and its impact on the formation of defective sites were investigated. Defective sites in TiO2‐CeO2 NPs were analyzed using transfer to X‐ray photoelectron spectroscopy and transmission electron microscopy without contact to ambient oxygen. The incorporation of Ce to the target exhibits synergistic effects on the synthesis process. Segmented Ti/Ce targets enable the deposition of a broad range of mixed oxide NPs with diverse compositions and morphologies at considerably enhanced deposition rates, which is vital for practical applications. The presented fabrication approach is expected to be applicable for a broad variety of MMO NPs.

Degradation of the mechanical properties of NbMoTaW refractory high-entropy alloy in tension

The mechanical properties of the bcc refractory high-entropy alloy (RHEA) NbMoTaW with columnar and equiaxed microstructures and a nanoscale metal oxide layer on the grain boundaries are investigated at ambient temperatures (RT) to 1200 °C. Under compression, the alloy shows a yield strength, σy, of ⁓1390 ± 20 MPa at RT and retains a high yield strength, σy, of ⁓301.5 MPa at 1200 °C. However, in tension, the fracture strengths, σf, of both columnar and equiaxed microstructures are far lower - below 70 MPa - and the material fails in the elastic regime without showing any measurable ductility at all temperatures. The fracture mechanisms in tension transition from transgranular cleavage at RT to a mixture of transgranular and intergranular fracture at 800 °C to a complete intergranular fracture at 1200 °C due to selective weakening of the metal oxide layer on the grain boundaries driven by a structural change. The transition in the fracture mechanism in the equiaxed microstructure promotes extrinsic toughening at higher temperatures, resulting in a ⁓6.4 times higher fracture toughness (KIc ⁓10.3 MPa√m) at 1200 °C compared to that at RT. NbMoTaW is a well-known RHEA, but the poor tensile strength and fracture toughness measured in this study highlight the critical importance of investigating the mechanical properties of these high-temperature RHEAs in tension.

Lithium modulated spinel high entropy oxide anode of LIBs through microwave solvothermal method

Spinel structured high entropy oxides (HEO) with three-dimensional Li+ transport channel and two different Wyckoff sites show high theoretical capacities due to multiple hypervalent ions and abundant oxygen vacancies. However, the intrinsic poor electrical conductivity of oxides and the lack of low-energy-consumption synthesis methods remain problems. Herein, Li+ with low-electronegativity is introduced into (FeCoNiCrMn)3O4 through high-efficiency microwave-assisted solvothermal method. The nano-scale high entropy oxide particles with homogeneous distribution of elements are successfully obtained in a short time. The addition of Li+ in HEO not only increases the valence states of transition metal cations to increase the number of electron transfers, but also induces more oxygen vacancies, which facilitates Li ion storage and increases ionic conductivity. The Li induced lattice distortion together with the entropy stabilization mechanism alleviate the lattice stress, featuring the anode superior electrochemical stability. The anode HEO-15 with the optimal Li content shows the specific capacity of 452.8 mAh g-1 at a current density of 500 mA g-1 after 300 cycles for LIBs, much higher than that of HEO-0 (248.9 mAh g-1). This research provides an effective method to improve the lithium storage performance of HEO.

Extreme mixing in nanoporous high-entropy oxides for highly durable energy storage

The ability to mix many different metal cations in a single-phase nanoscale oxide is critical for property adjusting and new material discovery. However, synthesizing multicomponent high-entropy oxides (HEOs) consisting of over ten metal cations remains a challenge due to dissimilarity and immiscibility among these elements. Herein, we explore the accommodation ability of Al3Ni-type and Al3Ti-type intermetallic phases and find that the Al3Ni-type phase is powerful to accommodate many different kinds metal elements. By chemically dealloying the Al from the multicomponent Al3Ni-type intermetallic phase, multicomponent spinel oxides such as 7-component (AlNiCoRuMoCrFe)3O4, 8-component (AlNiCoRuMoCrFeTi)3O4, 13-component (AlNiCoCrFeCuMoVTaNbHfZrTi)3O4, 16-component (AlNiCoCrFeCuMoTaNbHfZrTiRuVPdY)3O4 et al., with nanoporous structure and poor crystallity are obtained. As a case study, we find that when applied in Li-ion battery anode, our 16-component nanoporous HEO exhibits a high capacity of ∼1141.2 mAh g−1 after 290 cycles at 0.1 A g−1 and excellent cycling stability. This study greatly expands the composition space of nanoscale HEOs and provides an interesting route for new materials discovery.

Passivation Behavior of Chromium Alloyed High-Strength Rebar in Simulated Concrete Pore Solution

In this study, SEM, AFM, TEM, XPS, and electrochemical tests are used to study the passivation behavior of chromium alloyed high-strength rebar in simulated concrete pore (SCP) solutions with different pH values. The results show that after passivation in SCP solution with different pH values, the passivating film on the surface of the chromium alloyed rebar primarily consists of a layer of nanoscale oxide particles, which makes the passive film exhibit a p-n type semi-conductor, and the passive film presents a rhombohedral crystal structure. As the pH value of the SCP solution decreases, the nanoscale oxide particles on the surface of the rebar become denser, which leads to a reduction in the carrier density (Nq and Na) of the passive film and an increase in film resistance (R2) and charge transfer resistance (R3), thus increasing the corrosion resistance of the passive film. The passive film on the surface of the chromium alloyed high-strength rebar predominantly exhibits a three-layer structure, the outer passive film layer is composed of Fe oxides, the stable layer of the passive film is composed of Fe oxides and Cr oxides, and the growth layer of inner passive film is composed of Cr oxides. Compared with passivation 10 d in SCP solutions with pH 13.5 and pH 12.5, the passive film on the surface of the rebar has good stability at pH 10.5, which indicates that the addition of Cr is beneficial to promote the corrosion resistance of the rebar.

Oxide precipitation strengthening in Cu alloy modified with trace amounts of Nd during dynamic impact

In this study, three kinds of Cu-Nd alloys were prepared. The effect of Nd content on the dynamic impact behavior of the Cu-Nd alloys and its strengthening mechanism were studied. The results show that during the dynamic impact process, nano-scale oxide particles are precipitated in the alloy matrix, and a large number of cracks are formed along the grain boundaries, and the formation of shear bands and thermal grooves are also observed in local areas. With the increase of Nd content, the compressive strength of the alloys increases significantly, the grain size is refined, the number of twins increases, the grooves are much deeper and the number of the precipitated nano-oxide particles also increase significantly. In addition, due to the refinement of the grain size, the crack length is reduced. The increase of the alloy strength is mainly attributed to the nano-scale oxide precipitation strengthening and grain refinement strengthening.

Optical and Morphological Characterization of Nanoscale Oxides Grown in Low-Energy H+-Implanted c-Silicon

Optical and Morphological Characterization of Nanoscale Oxides Grown in Low-Energy H+-Implanted c-Silicon

Strain-driven magnetic transition of intercalated pressure-stabilized cobalt and cobalt oxide nanoparticles in linked graphene oxide nanoscale reactors

The study of the evolution and metamorphosis of nanoparticles under high pressure and in nanoscale confinement is a rapidly developing field that promises a diverse range of fundamental research and application opportunities. Here, we demonstrate how a linked and strained graphene oxide (GO)-based confinement system, functioning as a nanoscale reactor at high pressures, allows the evolution of the magnetic properties of an in situ generated composite cobalt (Co) nanoparticle system and further enables the retention of such properties when the pressure of the system is returned to ambient. We posit that this phenomenon is due to an ‘induced pressure’ created by strain, on the flexible planes of the 2D GO system, created by the intercalated Co-based nanoparticles. For graphene/GO this strain is characterized by shifts in the Raman “G-band”. Specifically, the studied system comprises in situ generated Co-containing nanoparticles confined between linked GO layers upon pressurization between 0 and 25 GPa. After quenching to ambient pressure, each of these samples exhibited innate ferromagnetic behaviors, demonstrating that our confinement system can be used to ‘lock in’ phase changes created by the application of transient high pressure. Importantly, while the unpressurized sample exhibited antiferromagnetic Co3O4 nanoparticles of ∼4 nm size, the samples pressurized to 10 GPa and 25 GPa, presented ferromagnetic order on the shell of an antiferromagnetic core of Co3O4 and CoO.

Particle morphology and soil properties affect the retention of copper oxide nanoparticles in agricultural soils.

The interaction between nanoscale copper oxides (nano-CuOs) and soil matrix significantly affects their fate and transport in soils. This study investigates the retention of nano-CuOs and Cu2+ ions in ten typical agricultural soils by employing the Freundlich adsorption model. Retention of nano-CuOs and Cu2+ in soils was well fitted by the Freundlich model. The retention parameters (KD, KF, and N) followed an order of CuO NTs > CuO NPs > Cu2+, highlighting significant impact of nano-CuOs morphology. The KF and N values of CuO NPs/Cu2+ were positively correlated with soil pH and electrical conductivity (EC), but exhibited a weaker correlation for CuO NTs. Soil pH and/or EC could be used to predict KF and N values of CuO NPs or CuO NTs, with additional clay content should be included for Cu2+.The different relationship between retention parameters and soil properties may suggest that CuO NTs retention mainly caused by agglomeration, whereas adsorption and agglomeration were of equal importance to CuO NPs. The amendment of Ca2+ at low and medium concentration promoted retention of nano-CuOs in alkaline soils, but reduced at high concentration. These findings provided critical insights into the fate of nano-CuOs in soil environments, with significant implications for environmental risk assessment and soil remediation strategies.

Creation and Characterization of Nanoscale Ribbons on MoS2 by Atomic Force Microscope Nanolithography

The atomic force microscope (AFM) has been widely used for fabricating the nanoscale oxide ribbons on various materials surface. Herein, we first conducted local anodic oxidation (LAO) lithography on two-dimensional nanomaterial (2D), i.e. multilayer MoS2, using AFM. The correlation of patterning behavior on the MoS2 flakes between the lithography conditions was investigated. The height and full width half maximum (FWHM) increase linearly with increasing tip voltage, even at different tip speeds, which is consistent with the results obtained from the Cabrera-Mott oxidation theory. The size of the clear relation decreases linearly with increasing tip speed, indicating that longer tip writing patterns result in more oxidation. The formation mechanism of the patterned oxide lines is presented along with LAO reaction processes.The final LAO lithography products have been demonstrated to be MoO2 and MoO3 by micro-Raman spectroscopy. These results show that LAO lithography using AFM is an effective technique for nanofabrication of nanodevices.

Corrosion Protection Performance of PACC and PACC-Metal Oxides Nanocomposites Electropolymerized Coating of Low Carbon Steel

In the current study, a novel conductive polymer poly 6-((4 acetylphenyl) carbamoyl) cyclohex-3-ene-1-carboxylic acid (PACC) was created by polymerized 6-((4 acetylphenyl) carbamoyl) cyclohex-3-ene-1-carboxylic acid (ACC) monomer using the electropolymerization process. The resulting polymer was characterized using Fourier Transform Infrared Spectroscopy (FTIR). The ability of this polymer to protect the alloy from corrosion was studied at temperatures ranging between 298 and 328 K. The ability of these coatings to stop corrosion on the surface was assessed by measuring the corrosion potential (Ecorr) and the corrosion current (icorr) using a potentiostat. Adding nanoscale metal oxides (zirconium dioxide (ZrO2) and magnesium oxides (MgO)) enhanced the efficiency of this polymeric coating. The protection efficiency of the polymer alone was 77.5%; this efficiency increased to 85.0% and 99.7% in the presence of nano ZrO2 and MgO, respectively. Kinetic and thermodynamic parameters (Ea, H, and S) were calculated for uncoated and coated LCS. An atomic force microscope (AFM) studied the coating surface morphology. Electrochemical impedance spectroscopy (EIS) was used to evaluate the coating resistance.

Synthesis of Nano-Scale Molecular Iron Oxides as Photo-Catalyst for Molecular Transformations

Synthesis of Nano-Scale Molecular Iron Oxides as Photo-Catalyst for Molecular Transformations

Nanoscale oxide and γ' phase synergistically strengthened nickel-based alloys with varying Al/Ti ratios produced by HIP

In this paper, three nickel-based superalloys with different Al/Ti atomic ratios (1, 1.8 and 16), designated as ODS-1, ODS-1.8 and ODS-16, respectively, were prepared by mechanical alloying (MA) followed by hot isostatic pressing (HIP). The evolution of microstructure and tensile properties of the alloys under varying Al/Ti ratio was analyzed and discussed. The result showed that the size, type and constitution of oxides change with variation of Al/Ti ratio. The average size of the oxides decreases with increasing Al/Ti ratio, which is 15.8 nm for ODS-1, 13.8 nm for ODS-1.8 and 11.8 nm for ODS-16, respectively. The oxides in ODS-1 contain 21.4% Y4Zr3O12, 42.9% Y2TiO5, 21.4% YAM and 14.3% YAP. The oxides in ODS-1.8 consist of 23.5% Y4Zr3O12, 35.3% Y2TiO5, 17.6% YAM and 23.5% YAP. In contrast, only two types of oxides are formed in ODS-16, including 50% Y4Zr3O12 and 50% YAP. As the Al/Ti ratio is increased from 1 to 16, the percentage of Y-Al-O phase increases from 35.7% to 50%, while the proportion of Y-Ti-O phase decreases from 42.9% to 0%. Increasing Al/Ti ratio inhibits the formation of Y-Ti-O phase while promoting the generation of Y-Al-O particles. The finer oxide distribution in ODS-16 is considered to be the main reason for its finer grain size distribution. The bimodal distribution of the γ' phase can be found in all three alloys, but the bimodal distribution feature of the γ' phase in ODS-1 and ODS-1.8 is more significant than that in ODS-16. The average grain size decreases with increasing Al/Ti ratio. The tensile strength at 700 °C is reduced, but the ductility is improved with the increase of Al/Ti ratio. The influence of Al/Ti ratio on the formation of nanoscale oxides and γ' phases are revealed.

Amino Acid‐Mediated Formation of Zirconia Nanoparticles and their Transparent Dispersions

AbstractWe present a straightforward one‐pot hydrothermal method for the synthesis of zirconia nanodispersions, leading to the formation of stable sols. By simply varying the nature of the stabilizer used, one can obtain a large variety of objects with different sizes, shapes and crystallinities. Our results demonstrate the crucial role played by aliphatic amino acids both during the formation of the objects and after, since their interaction with the surface of the inorganic crystals influences strongly the optical properties and colloidal stability of the latter. Importantly, the versatility of this method allows for the introduction of different dopants, increasing substantially the scope of applications that can be achieved with such nanoscale oxides. The high transparencies and the easy dispersibility of nanoparticles in different liquid matrixes ensure the formation of zirconia‐based nanocomposites and ceramics with outstanding optical features for the orthopedic, dental, photonics and chemical sectors. This method can be easily scaled up, being already available for the production of high‐quality zirconia nanodispersions at the industrial level.

Unveiling deformation behavior and damage mechanism of irradiated high entropy alloys

The oxide dispersion strengthening (ODS) high entropy alloy (HEA) exhibits the high elevated temperature performance and radiation resistance due to severe atomic lattice distortion and oxide particles dispersed in matrix, which is expected to become the most promising structural material in the next generation of nuclear energy systems. However, microstructure and damage evolution of irradiated ODS HEA under loading remain elusive at submicron scale using the existing simulations owing to a lack of atomic-lattice-distortion information from a micromechanics description. Here, the random field theory informed discrete dislocation dynamics simulations based on the results of high-resolution transmission electron microscopy are developed to study the dislocation behavior and damage evolution in ODS HEA considering the influence of severe lattice distortion and nanoscale oxide particle. Noteworthy, the damage behavior shows an unusual trend of the decreasing-to-increasing transition with the continuous loading process. There are two main types of damage micromechanics generated in irradiated ODS HEA: the dislocation loop damage in which the damage is controlled by irradiation-induced dislocation loops and their evolution, the strain localization damage in which the damage comes from the dislocation multiplication in the local plastic region. The oxide particle hinders the dislocation movement in the main slip plane, and the lattice distortion induces the dislocation sliding to the secondary slip plane, which promotes the dislocation cross-slip and dislocation loop annihilation, and thus reduces the material damage in the elastic damage stage. These findings can deeply understand atomic-scale damage mechanism and guide the design of ODS HEA with high radiation resistance.