Nanoscale Oxide Research Articles

Understanding the high-temperature oxidation resistance of heat-resistant austenitic stainless steel with gradient nanostructure

The underlying high-temperature oxidation mechanisms of the heat-resistant austenitic stainless steel with gradient nanostructured surface layer is revealed through systematic analysis of the microstructure and composition. Nanoscale oxide grains and high-density grain boundaries promoted the formation of pronounced spinel oxides, which suppressed elemental diffusion and CrO3 volatilization. High level of residual stress in the GNS layer facilitated the formation of high-density precipitates at the oxide/matrix interface and grain boundaries, which hindered the growth of oxide scale and reactive elements diffusion. The enhanced high-temperature oxidation resistance resulted from the synergistic combination of spinel oxides, precipitates, and high-density grain boundaries.

Aggregation, retention and transport of γ-MnO2 nanoparticles in water-saturated porous media: Impact on the immobility of thallium

Nano-scale Mn oxides can act as effective stabilizers for Tl in soil and sediments. Nevertheless, the comprehensive analysis of the capacity of MnO2 to immobilize Tl in such porous media has not been systematically explored. Therefore, this study investigates the impact of γ-MnO2, a model functional nanomaterial for remediation, on the mobility of Tl in a water-saturated quartz sand-packed column. The mechanisms involved are further elucidated based on the adsorption and aggregation kinetics of γ-MnO2. The results indicate that higher ionic strength (IS) and the presence of ion Ca(II) promote the aggregation of γ-MnO2, resulting from the reduced electrostatic repulsion between particles. Conversely, an increase in pH inhibits aggregation due to enhanced interaction energy. γ-MnO2 significantly influences Tl retention and mobility, with a substantial fraction of γ-MnO2-bound Tl transported through the column. This might be attributed to the high affinity of γ-MnO2 for Tl through ion exchange reactions and precipitation at the surface of γ-MnO2. The mobility of Tl in the sand column is influenced by the γ-MnO2 colloids, exhibiting either inhibition or promotion depending on the pH, IS, and cation type of the solution. In solutions with higher IS and Ca(II), the mobility of Tl decreases as γ-MnO2 colloids tend to aggregate, strain, and block, facilitating colloidal Tl retention in porous media. Although higher pH reduces the mobility of individual Tl, it promotes the mobility of γ-MnO2 colloids, facilitating a substantial fraction of colloidal-form Tl. Consequently, the optimal conditions for stabilizing Tl by γ-MnO2 involve either high IS and low pH or the presence of competitive cations (e.g., Ca(II)). These findings provide new insights into Tl immobilization using MnO2- and Mn oxide-based functional materials, offering potential applications in the remediation of Tl contamination in soil and groundwater.

Lead-bismuth eutectic corrosion resistance of TiAlN coating after N5+ ion irradiation

In this study, a Ti0.33Al0.67N coating with Cr as the transition layer was prepared by cathodic arc-ion plating. After irradiation with N5+ ions, the coating was exposed to lead-bismuth eutectic (LBE) at 450 °C for 3000 h. The effect of irradiation on the corrosion resistance of the coatings was also investigated. No evidence of an LBE corrosion attack was observed in either the irradiated or unirradiated coatings. Transmission electron microscopy images revealed that the nanoscale oxide layer on the surface of the titanium aluminum nitride coating was the main barrier to LBE corrosion. The unirradiated coating had a single oxide layer, whereas the irradiated coating had a double oxide layer. Irradiation also affects the coating adhesion by inducing stress. However, after the corrosion test, the adhesion of all coating samples unexpectedly increased and were almost at the same level. The coating exhibited excellent properties after irradiation and LBE corrosion; therefore, the coating can be applied in future nuclear reactors.

Innovations in nanomaterials: A paradigm shift in surface engineering for corrosion mitigation

The weight loss technique was utilized to examine the corrosion rates of mild steel in various aqueous solutions and operating conditions, both with and without an epoxy coating. It became out that the presence of salt and temperature increased the rate of corrosion while the pH level decreased. Significant reductions in corrosion rates occur in acidic conditions when coatings are present. In a saline solution, it did not work particularly well. Using X-ray diffraction, the diagnosis was acquired after a sol–gel method was used to create a MgO nanoparticle. The highest coating efficacy in an acidic solution was 96.9%, whereas the lowest coating efficacy in a saline solution devoid of nanoparticles was 29.8%. The performance of epoxy coatings in salty environments was improved by applying nanoscale magnesium oxide (MgO) up to a maximum value of 94%. Surface morphology was examined using the SEM test as well. A number of mathematical models were proposed to be employed in order to relate the corrosion rate to the operational state; a high correlation coefficient for the data advised that the polynomial interaction effect model be used.

Non-equilibrium defect chemistry in oxygen-rich zinc oxide nano-tetrapods synthesized using atmospheric pressure microplasma

We demonstrate the synthesis of zinc oxide (ZnO) nanoscale tetrapods (nTPs) using an atmospheric pressure microplasma with a metal wire as a sacrificial electrode.

Realization of Mg2+ intercalation in a thermodynamically stable layer-structured oxide.

Magnesium batteries have emerged as one of the considerable choices for next-generation batteries. Oxide compounds have attracted great attention as cathodes for magnesium batteries because of their high output voltages and ease of synthesis. However, a majority of the reported results are based on metastable nanoscale oxide materials. This study puts forward a thermodynamically stable layer-structured oxide K0.5MnO2 with an enlarged lattice spacing as a model cathode material employing optimized electrolytes, enabling Mg2+ intercalation into the K0.5MnO2 framework in a real magnesium battery directly using Mg foil as the anode. First-principles calculations implied that the enlarged layer spacing could decrease the migration energy barrier of Mg2+ in the layered oxide. This work can pave the way to understanding the fundamental intercalation behavior of Mg2+ in magnesium batteries.

Solid-state electrochemical oxidation with polyelectrolyte membrane stamps for micro-/nanoscale pattern formation on Au surfaces.

Nanoscale-patterned Au surfaces are promising for a wide range of applications from bio/chemical sensors to high-performance electrodes. However, pattern formation using conventional resist-based methods is complex, expensive, and environmentally unfriendly. Herein, we report a novel approach for pattern formation on Au surfaces using solid-state electrochemical treatment with polymer electrolyte membrane (PEM) stamps. During electrolysis, the patterned structure of the PEM stamp was transferred onto the Au surface to form micro- and nanoscale oxide patterns. X-ray analysis of the treated surface confirmed the formation of an oxide film on the Au surface, which was subsequently reduced to metallic Au after air exposure for several weeks. Although the pattern height decreased with air exposure, a patterned structure with a height of several hundred nanometers was maintained following oxide reduction. Reflectance spectroscopy revealed that the patterned Au surface exhibited sharp reflectance peaks, the intensities and positions of which strongly depended on the measurement angle, which are key characteristics of diffraction gratings. This fast and facile electrochemical treatment process is promising for the preparation of patterned Au surfaces that can be applied in optical gratings and localized surface plasmon resonance sensors.

A super magnetic porous biochar manufactured by potassium ferrate-accelerated hydrothermal carbonization for removal of tetracycline

Hydrothermal carbonization (HTC) is a promising and powerful technology for manufacturing magnetic biochar with abundant functional groups at relatively low temperature. Herein, K2FeO4-accelerated HTC of kelp was studied to manufacture high-performance magnetic biochar for eliminating tetracycline (TC) in aqueous solution. Nanoscale magnetic iron oxides were generated with abundant oxygen containing groups and porous structures as the HTC was performed at 300 °C. This magnetic biochar displayed 1245.43 mg/g adsorption capacity at 35 °C with 56.48 emu/g saturation magnetization. The adsorption was mostly ascribed to hydrogen bonding/coordination/cation exchange of oxygen functional groups and iron oxides. Moreover, K2FeO4-promoted HTC also exhibited good efficiency and generality for manufacturing potent magnetic biochars from different biowastes for eliminating TC in aqueous solution.

N-Carbon-Doped Binary Nanophase of Metal Oxide/Metal-Organic Framework for Extremely Sensitive and Selective Gas Response.

Metal-organic frameworks (MOFs), which are highly ordered structures exhibiting sub-nanometer porosity, possess significant potential for diverse gas applications. However, their inherent insulative properties limit their utility in electrochemical gas sensing. This investigation successfully modifies the electrical conductivity of zeolitic imidazolte framework-8 (ZIF-8) employing a straightforward surface oxidation methodology. A ZIF-8 polycrystalline layer is applied on a wafer-scale oxide substrate and subjects to thermal annealing at 300°C under ambient air conditions, resulting in nanoscale oxide layers while preserving the fundamental properties of the ZIF-8. Subsequent exposure to NO2 instigates the evolution of an electrically interconnected structure with the formation of electron-rich dopants derived from the decomposition of nitrogen-rich organic linkers. The N-carbon-hybridized ZnO/ZIF-8 device demonstrates remarkable sensitivity (≈130ppm-1 ) and extreme selectivity in NO2 gas detection with a lower detection limit of 0.63ppb under 150°C operating temperature, surpassing the performance of existing sensing materials. The exceptional performances result from the Debye length scale dimensionality of ZnO and the high affinity of ZIF-8 to NO2 . The methodology for manipulating MOF conductivity through surface oxidation holds the potential to accelerate the development of MOF-hybridized conductive channels for a variety of electrical applications.

The Role of Surface Complexes in Ketene Formation from Fatty Acids via Pyrolysis over Silica: from Platform Molecules to Waste Biomass.

Fatty acids (FA) are the main constituents of lipids and oil crop waste, considered to be a promising 2G biomass that can be converted into ketenes via catalytic pyrolysis. Ketenes are appraised as promising synthons for the pharmaceutical, polymer, and chemical industries. Progress in the thermal conversion of short- and long-chain fatty acids into ketenes requires a deep understanding of their interaction mechanisms with the nanoscale oxide catalysts. In this work, the interactions of fatty acids with silica are investigated using a wide range of experimental and computational techniques (TPD MS, DFT, FTIR, in situ IR, equilibrium adsorption, and thermogravimetry). The adsorption isotherms of linear and branched fatty acids C1-C6 on the silica surface from aqueous solution have been obtained. The relative quantities of different types of surface complexes, as well as kinetic parameters of their decomposition, were calculated. The formation of surface complexes with a coordination bond between the carbonyl oxygens and silicon atoms in the surface-active center, which becomes pentacoordinate, was confirmed by DFT calculations, in good agreement with the IR feature at ∼1680 cm 1. Interestingly, ketenes release relate to these complexes' decomposition as confirmed by the thermal evolution of the absorption band (1680 cm-1) synchronously with the TPD peak of the ketene molecular ion. The established regularities of the ketenezation are also observed for the silica-induced pyrolysis of glyceryl trimyristate and real waste, rapeseed meals.

Flow and heat transfer characteristics of microencapsulated phase change material slurry in bonded triangular tubes for thermal energy storage systems

Three nanoscale metal oxides composed of nano TiO2, nano Al2O3, and nano MgO were added to the phase change microcapsule slurry for optimising the heat transfer behaviour. The thermal and rheological properties of the resulting microencapsulated phase change materials (MPCMs) and microencapsulated phase change material slurries (MPCSs) were characterized to determine the effects of added metal oxides in optimising the performance of MPCSs. The impacts of factors like metal oxides, concentrations, and flow rates on the heat transfer behaviour of MPCSs were investigated by forced convective heat transfer experiment with various working conditions. Compared to 6 wt% MPCSs, the heat transfer coefficients (hx) of 6 wt% slurries containing 1 wt% TiO2, 1 wt% Al2O3, and 1 wt% MgO increased by 4.0 %, 2.5 %, and 7.13 %, respectively. Nano-MgO showed the most significant heat transfer enhancement effect on MPCSs. Moreover, the heat transfer performance gradually enhanced as a function of the concentration for nano MgO. Overall, the addition of metal oxides enhanced heat transfer by increasing the thermal conductivity of the slurry, as well as improved the micro-convection effect. The proposed MPCSs are promising for applications in solar photovoltaic/thermal (PV/T) systems, chip cooling, thermal management, buildings, and automotive cooling.

Uncertainty and statistics of dislocation-oxide interactions on strength and creep failure of oxide dispersion strengthened steels

Oxide dispersion strengthening (ODS) steels exhibit excellent mechanical and creep properties due to the nanoscale oxide particles as barriers to dislocation motion, for the great application potentials to structural components of advanced nuclear power plants. However, the classical ODS model described by the Orowan mechanism or cutting mechanism only depends upon a single average size, ignoring uncertainty and statistics of dislocation-oxide interactions induced by the spatial and dimensional random distribution of oxide particles. When the oxide particle size is larger than the critical size to determine the interaction mechanism transformation from cutting to looping, the Orowan mechanism and cutting mechanism would exist simultaneously. Here we propose a modified ODS model for strength and creep rate considering the spatial distribution and size distribution of oxide particles, which is more consistent with the experimental result compared to the classical ODS model. In addition, the contribution of oxide particles to the yield strength and creep strength is evaluated quantitatively for various precipitate sizes and volume fractions. It is believed that this model provides an analytical framework to accurately predict the strength and creep rate of ODS steels.

A novel diffusion bonding of 6063Al based on a mode of diffusion-migrating and suspension-broken of surface oxide film

The breaking of surface oxide film in a technology area of ultrasonic-assisted diffusion joining manufacturing of large-size structure components is a challenge. In this work, a novel method of breaking surface oxide film of Al alloys based on first diffusion-migrating and then suspension-broken was investigated. Diffusion bonding of 6063Al alloys was performed by Zn interlayer at temperature below 400 °C. The oxide film migrated away from the Al alloy base metal by solid phase diffusion at 360 °C, and remained in the joint as a nanoscale oxide film. When temperature increased to 390 °C, the oxide film suspended in the Zn–Al eutectic liquid phase were rapidly broken up into small fragments through an instantaneous ultrasonic action (only 0.3 s). The change of acoustic pressure in the liquid metal proved that the suspended continuous oxide film was broken by the micro-jet acted simultaneously on both sides of oxide film induced by the ultrasonic cavitation effect. Finally, the inter-diffusion between Zn and Al at 360 °C was promoted by a longer holding time to obtain the homogeneous joint composed by Zn–Al eutectoid phase containing oxide fragments, and had a higher strength than the base metal. The breaking of oxide film and joint homogenization were performed under pressure-less condition, which effectively avoided the squeezed-out of the liquid phase. This technology shows a great potential for manufacturing large-size joint of industrial products.

Tuning the reactivity of TiO2 layer with uniform distribution of Sub-5 nm Fe2O3 particles via in situ voltage-assisted oxidation for robust catalytic reduction

The trade-off between efficiency and stability has limited the application of TiO2 as a catalyst due to its poor surface reactivity. Here, we present a modification of a TiO2 layer with highly stable Sub-5 nm Fe2O3 nanoparticles (NP) by modulating its structure-surface reactivity relationship to attain efficiency-stability balance via a voltage-assisted oxidation approach. In situ simultaneous oxidation of the Ti substrate and Fe precursor using high-energy plasma driven by high voltage resulted in uniform distribution of Fe2O3 NP embedded within porous TiO2 layer. Comprehensive surface characterizations with density functional theory demonstrated an improved electronic transition in TiO2 due to the presence of surface defects from reactive oxygen species and possible charge transfer from Ti to Fe; it also unexpectedly increased the active site in the TiO2 layer due to uncoordinated electrons in Sub-5 nm Fe2O3 NP/TiO2 catalyst, thereby enhancing the adsorption of chemical functional groups on the catalyst. This unique embedded structure exhibited remarkable improvement in reducing 4-nitrophenol to 4-aminophenol, achieving approximately 99% efficiency in 20 ​min without stability decay after 20 consecutive cycles, outperforming previously reported TiO2-based catalysts. This finding proposes a modified-electrochemical strategy enabling facile construction of TiO2 with nanoscale oxides extandable to other metal oxide systems.

On the nanoscale oxide dispersion via in-situ atmospheric oxidation during laser powder bed fusion

In-situ oxidation during laser additive manufacturing (AM) is considered a more economical approach to producing AM oxide dispersion-strengthened (ODS) alloys. However, there is very few success in making AM ODS alloys with oxide density comparable to commercial ODS alloys made by conventional means. To explore the key mechanisms that prevent the high-density dispersion of nanoscale oxides during in-situ reactive AM, we investigated oxide dispersion by in-situ gas-phase reaction during laser powder bed fusion (LPBF) with respect to oxygen gettering elements with different oxygen affinity, getter concentration, atmospheric oxygen level, and laser parameters. Our results show that in-situ oxidation in a high-oxygen printing atmosphere during LPBF AM cannot effectively produce good-quality ODS steels, even when the amount of oxygen pick-up from the atmosphere into the melt pool is comparable to the oxygen level in commercial ODS alloys. We found that surface oxidation and oxide agglomeration in the melt pool prevent the high-density dispersion of nanoscale oxides. In addition, oxide agglomeration also contributes to a higher amount of manufacturing defects. Powder spattering plays a secondary impact on oxygen loss.

Defeating depolarizing fields with artificial flux closure in ultrathin ferroelectrics

Material surfaces encompass structural and chemical discontinuities that often lead to the loss of the property of interest in so-called dead layers. It is particularly problematic in nanoscale oxide electronics, where the integration of strongly correlated materials into devices is obstructed by the thickness threshold required for the emergence of their functionality. Here we report the stabilization of ultrathin out-of-plane ferroelectricity in oxide heterostructures through the design of an artificial flux-closure architecture. Inserting an in-plane-polarized ferroelectric epitaxial buffer provides the continuity of polarization at the interface; despite its insulating nature, we observe the emergence of polarization in our out-of-plane-polarized model of ferroelectric BaTiO3 from the very first unit cell. In BiFeO3, the flux-closure approach stabilizes a 251° domain wall. Its unusual chirality is probably associated with the ferroelectric analogue to the Dzyaloshinskii–Moriya interaction. We, thus, see that in an adaptively engineered geometry, the depolarizing-field-screening properties of an insulator can even surpass those of a metal and be a source of functionality. This could be a useful insight on the road towards the next generation of oxide electronics.

Biodiesel production by transesterification of low-cost feedstock (waste cooking oil) using mesoporous cubic-MgO nanocatalyst: Optimization using response surface methodology

Non-toxic nanoscale metal oxide structures are emerging as potential material in energy and environmental applications because of their enhanced and controllable properties. In this research work, MgO nanoparticles were synthesized by sol–gel method. The calcination temperature and time was optimized at 600°C, 2 hours. The obtained mesoporous MgO nanoparticles (size 15 nm) had a band gap of approximately 3.3 eV. MgO nanoparticles shows a zeta potential value of 17.3 mV, which is considered to be incipiently stable. Biodiesel production was carried out using cubic MgO nanoparticles. Response surface methodology (RSM) and one factor method was employed for the optimization of operating variables. RSM predicts 90% of biodiesel yield at optimal 1% (w/w) of catalyst, 16:1 methanol to oil molar ratio, 65°C of reaction temperature in 42 minutes which is also verified experimentally (89.5%). Biodiesel yield of approximately 92% is obtained using one factor method at higher reaction time of 2 hours, reaction temperature of 60°C with 12:1 methanol to oil molar ratio and 2% (w/w) of catalyst. The hexadecanoic acid, stearic acid, linoleic acid and oleic acid in the waste cooking oil gets transformed into hexadecanoic acid methyl ester, methyl stearate, 9,12-octadecadienoic acid methyl ester and 9-octadecenoic acid methyl ester during transesterification which is inferred from GC–MS spectrum. Transesterification reaction follows pseudo-first-order kinetics. MgO nanocatalyst when reused in the transesterification shows a yield of approximately 90% up to four cycles.

Toward a tunable fabrication of multifunctional iron-aluminum spinels via solution combustion synthesis: The effects of fuel, heating mode, and Fe:Al precursor ratio

The solid solutions of iron and aluminum spinels (hercynite, maghemite, magnetite, and γ-alumina) are promising materials for emerging technologies such as solar thermochemical fuel production and clean dehydrogenation of fossil fuels. Solution combustion synthesis (SCS) is an attractive technique for the fabrication of these materials as it has been used for synthesis of many nanoscale oxides. However, the design space of SCS is large with many synthesis parameters affecting the properties of the combustion products. To optimize the SCS of these materials, it is important to determine which parameters yield the best properties. In the present work, FeAlOx nanocomposites were obtained by SCS using iron nitrate and aluminum nitrate as precursors and oxidizers. Two fuels (citric acid and glycine), three Fe:Al molar ratios (1:2, 1:1, and 2:1) in the precursors, and three heating modes (hotplate, muffle furnace, and microwave oven) were compared. The products were characterized by X-ray diffraction analysis, scanning electron microscopy, Brunauer-Emmett-Teller surface area analysis, and laser diffraction particle size analysis. The fuel used had the largest impact on the combustion behavior and hence the material properties. The high combustion temperature of glycine allowed for the formation of an FeAl2O4/Fe3O4 solid solution, while the lower-temperature combustion of citric acid yielded Al-substituted γ-Fe2O3 with high amorphous content. With citric acid, the specific surface area as high as 200 m2/g was achieved. The effect of Fe:Al precursor ratio was clearly seen in variations of the lattice parameter, which demonstrated the ability to tune the phase composition. The heating mode had minor effects on material properties, but some differences were observed. All products obtained by SCS in a microwave oven had low specific surface areas compared to those obtained with a hotplate and a muffle furnace.

Microstructure and phase investigation of FeCrAl-Y2O3 ODS steels with different Ti and V contents

FeCrAl-based steels are considered promising materials for high-temperature nuclear applications. Over the past years, various compositions have been studied to assess their mechanical properties, structural integrity, and radiation damage resistance. However, the microstructure and phase composition of FeCrAl-ODS steels with the addition of different alloying elements are less commonly studied than pure FeCrAl alloys. The paper presents a novel research path for developing FeCrAl matrix ODS steels with Y2O3, Ti, and V additions. The materials synthesis consisted of mechanical alloying of pure metallic components with yttrium oxide in a planetary ball mill under an argon atmosphere. Titanium was added in the amount of 1.0 wt.% to both samples, while 0.5 wt.% of vanadium was added to one sample to verify its impact on the structural stability and hardness. The spark plasma sintering (SPS) technique was used to consolidate the powders. Afterward, the microstructure, chemical composition, phase composition, and hardness were assessed using SEM-EDS, EBSD, TEM-EDS, XRD, XRF, Nanoindentation, and Vickers microhardness. The experimental data reveal rather homogeneous powders after mechanical alloying and dense bulk samples after SPS. The microstructure observations show oxide particles and carbides on the grain boundaries and inside grains of the bcc matrix, which suggests elevated radiation damage resistance. The presence of nanoscale oxide particles (15–50 nm) in the matrix could significantly reduce the impact of aging embrittlement at high temperatures by affecting the chromium diffusion pathways in the ODS steel matrix. The addition of vanadium leads to an improvement of hardness to 4.83±0.43 GPa compared to 3.78±0.34 GPa for the sample without vanadium. Presented experimental results are promising in terms of research and development of FeCr and Al-based ODS materials tailored to operate under harsh conditions in generation IV fission reactors and fusion reactors.

A novel ODS high-entropy composite with improved strength and ductility

Body-centered cubic (BCC) structured high-entropy alloys (HEAs) usually exhibit excellent strength, thermal stability, irradiation tolerance and corrosion resistance but low ductility. In this study, a novel oxide dispersion strengthened (ODS) AlCrFeNi high entropy composite (with BCC-structure reinforced by face-centered cubic (FCC) ODS-CoCrFeNiMn HEA reinforcement was designed and prepared by mechanical alloying and spark plasma sintering. The effects of sintering temperatures (950 °C, 1000 °C, 1050 °C and 1100 °C) and reinforcement amount (5%, 10%,15% and 20%) on microstructure and mechanical properties were investigated. The results showed that the optimal sintering temperature of the ODS AlCrFeNi composites is 1100 °C. The hardness decreases with the increase of the reinforcement content (from 5% to 20%). Compared to the reference alloy (RA) without the addition of reinforcement, the compressive strain of the composite with 15% reinforcement (B–15%F) increases significantly from 8% (RA) to 18%, while the compressive strength increases from 2823 MPa (RA) to 3078 MPa. The B–15%F is composed of matrix, reinforcement and intermediate transition regions. The thickness of transition regions increases with increasing sintering temperature. The matrix consists of fine BCC FeCr phase and B2 NiAl phase, due to spinodal decomposition, together with high-density nanoscale oxides Y4Zr3O12 and a small amount of Y–Al–O. Surprisingly, the crystal structure of reinforcement transforms from FCC into the BCC during SPS. Meanwhile, the mutual diffusion of Al elements in the matrix and Co and Mn elements in the reinforcement also results in similar spinodal decomposition in the reinforcement. The domain size of spinodal decomposition in the reinforcement is coarser than that in the matrix. The reinforcement is mainly distributed on the prior particle boundaries (PPBs), which can effectively reduce/suppress the formation and propagation of micro-cracks along the PPBs, and thus improve both the strength and ductility of the composite.