In-situ construction of grass-like hybrid architecture responsible for extraordinary corrosion performance: Experimental and theoretical approach

Despite the engineering potential by the co-existence of inorganic and organic substances to protect vulnerable metallic materials from corrosive environments,both their interaction and in-situ formation mechanism to induce the nature-inspired composite remained less understood.The present work used three distinctive mercaptobenzazole(MB)compounds working as corrosion inhibitors,such as 2-mercaptobenzoxazole(MBO),2-mercaptobenzothiazole(MBT),and 2-mercaptobenzimidazole(MBI)in a bid to understand how the geometrical structure arising from O,S,and N atoms affected the interaction toward inorganic layer.MB compounds that were used here to control the corrosion kinetics would be interacted readily with the pre-existing MgO layer fabricated by plasma electrolysis.This phenomenon triggered the nucleation of the root network since MB compounds were seen to be adsorbed actively on the defective surface through the active sites in MB compound.Then,the molecule with twin donor atoms adjacent to the mercapto-sites affected the facile growth of the grass-like structures with‘uniform’distribution via molecular self-assembly,which showed better corrosion performance than those with having dissimilar donor atoms with the inhibition efficiency(η)of 97%approximately.The formation mechanism underlying nucleation and growth behavior of MB molecule was discussed concerning the theoretical calculation of density functional theory.

Recent Advances in Multifunctional Reticular Framework Nanoparticles:A Paradigm Shift in Materials Science Road to a Structured Future

Porous organic frameworks(POFs)have become a highly sought-after research domain that offers a promising avenue for developing cutting-edge nanostructured materials,both in their pristine state and when subjected to various chemical and structural modifications.Metal–organic frameworks,covalent organic frameworks,and hydrogen-bonded organic frameworks are examples of these emerging materials that have gained significant attention due to their unique properties,such as high crystallinity,intrinsic porosity,unique structural regularity,diverse functionality,design flexibility,and outstanding stability.This review provides an overview of the state-of-the-art research on base-stable POFs,emphasizing the distinct pros and cons of reticular framework nanoparticles compared to other types of nanocluster materials.Thereafter,the review highlights the unique opportunity to produce multifunctional tailoring nanoparticles to meet specific application requirements.It is recommended that this potential for creating customized nanoparticles should be the driving force behind future synthesis efforts to tap the full potential of this multifaceted material category.

Advanced prediction of organic–metal interactions through DFT study and electrochemical displacement approach

Heterocyclic compounds are the promising biological compounds as nature-friendly for the corrosion protection of metallic surface.In this work,three heterocyclic compounds such as 1-azanaphthalene-8-ol(8-AN),2-methylquinoline-8-ol(8-MQ),and 8-quinolinol-5-sulfonic acid(8-QSA)were used as green compounds,and their anti-corrosion performance for AZ31 Mg in saline water was discussed on the basis of impedance interpretation and surface analysis.Findings found that the electrochemical performance was improved in the order of 8-AN>8-MQ>8-QSA,demonstrating the electron donor effect of N-heterocycles to form coordination complexes on the magnesium surface.From the electrochemical performance,the protective layer constructed at the optimal concentration reinforces the barrier against aggressive environments,with potential inhibition efficiency of 87.4%,99.0%,and 99.9%for 8-QSA,8-MQ,and 8-AN,respectively.Quantum chemical parameters and electron density distribution for free organic species in the absence and presence of Mg^(2+)cation were evaluated using density functional theory(DFT).Upon the formation of coordination complexes between organic compound and Mg^(2+),energy gap underwent change about ΔE=5.7 eV in the 8-AN/Mg^(2+)system.Furthermore,the adsorption of heterocyclic compounds on Mg surface reveals the formation of strong covalent bonds with Mg atoms,which further confirmed by the electron density difference and projected density of states analyses.Based on theoretical calculations,three inhibitors can adsorb on the metal surface in both parallel and perpendicular orientations via C,O and N atoms.In the parallel configuration,the C-Mg,N-Mg and O-Mg bond distances are between 2.11 and 2.25˚A,whereas the distances in the case of perpendicular adsorption are between 2.20 and 2.40˚A(covalent bonds via O and N atoms).The results indicated that parallel configurations are energetically more stable,in which the adsorption energies are-4.48 eV(8-AN),-4.28 eV(8-MQ)and-3.82 eV(8-QSA)compared to that of perpendicular adsorption(-3.65,-3.40,and-2.63 eV).As a result,experimental and theoretical studies were in well agreement and confirm that the nitrogen and oxygen atoms will be the main adsorption sites.

Electrochemical response of MgO/Co_(3)O_(4) oxide layers produced by plasma electrolytic oxidation and post treatment using cobalt nitrate

This work looked into the influence of the sealing treatment on the structural feature and electrochemical response of AZ31 Mg alloy coated via plasma electrolytic oxidation(PEO).Here,the inorganic layers produced by PEO in an alkaline-phosphate electrolyte were subsequently immersed for different periods in cold(60°C)and hot(100°C)aqueous solutions containing either 1 or 3 gr of cobalt nitrate hexahydrate in the presence of hydrogen peroxide as an initiator.The results showed that the sealing treatments in the hot solutions could trigger the hydration reactions of PEO coating which would largely assist the surface incorporation of Co_(3)O_(4)into the coating.In contrast,the sealing in cold solutions led to less compact coatings,which was attributed to the fact the hydration reactions would be restricted at 60°C.A nearly fully sealed coating with a porosity of~0.5%was successfully formed on the sample immersed in the hot solution containing 1 gr of cobalt nitrate hexahydrate.Thus,the electrochemical stability of this fully sealed coating was superior to the other samples as it had the lowest corrosion current density(4.71×10^(-10)A·cm^(-2))and the highest outer layer resistance(3.81×10^(7)Ω·cm^(2)).The composite coatings developed in this study are ideal for applications requiring high electrochemical stability.

Experimental and theoretical investigation of high-entropy-alloy/support as a catalyst for reduction reactions

Control of chemical composition and incorporation of multiple metallic elements into a single metal nanoparticle(NP)in an alloyed or a phase-segregated state hold potential scientific merit;however,developing libraries of such structures using effective strategies is challenging owing to the thermodynamic immiscibility of repelling constituent metallic elements.Herein,we present a one-pot interfacial plasma-discharge-driven(IP-D)synthesis strategy for fabricating stable high-entropy-alloy(HEA)NPs exhibiting ultrasmall size on a porous support surface.Accordingly,an electric field was applied for 120 s to enhance the incorporation of multiple metallic elements(i.e.,CuAgFe,CuAgNi,and CuAgNiFe)into ally HEA-NPs.Further,NPs were attached to a porous magnesium oxide surface via rapid cooling.With solar light as the sole energy input,the CuAgNiFe catalyst was investigated as a reusable and sustainable material exhibiting excellent catalytic performance(100%conversion and 99% selectivity within1 min for a hydrogenation reaction)and consistent activity even after 20 cycles for a reduction reaction,considerably outperforming the majority of the conventional photocatalysts.Thus,the proposed strategy establishes a novel method for designing and synthesizing highly efficient and stable catalysts for the convertion of nitroarenes to anilines via chemical reduction.

Tuning the reactivity of TiO_(2)layer with uniform distribution of Sub-5 nm Fe_(2)O_(3)particles via in situ voltage-assisted oxidation for robust catalytic reduction

The trade-off between efficiency and stability has limited the application of TiO_(2)as a catalyst due to its poor surface reactivity.Here,we present a modification of a TiO_(2)layer with highly stable Sub-5 nm Fe_(2)O_(3)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 Fe_(2)O_(3)NP embedded within porous TiO_(2)layer.Comprehensive surface characterizations with density functional theory demonstrated an improved electronic transition in TiO_(2)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 TiO_(2)layer due to uncoordinated electrons in Sub-5 nm Fe_(2)O_(3)NP/TiO_(2)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 TiO_(2)-based catalysts.This finding proposes a modified-electrochemical strategy enabling facile construction of TiO_(2)with nanoscale oxides extandable to other metal oxide systems.

Light-Material Interactions Using Laser and Flash Sources for Energy Conversion and Storage Applications

This review provides a comprehensive overview of the progress in light-material interactions(LMIs),focusing on lasers and flash lights for energy conversion and storage applications.We discuss intricate LMI parameters such as light sources,interaction time,and fluence to elucidate their importance in material processing.In addition,this study covers various light-induced photothermal and photochemical processes ranging from melting,crystallization,and ablation to doping and synthesis,which are essential for developing energy materials and devices.Finally,we present extensive energy conversion and storage applications demonstrated by LMI technologies,including energy harvesters,sensors,capacitors,and batteries.Despite the several challenges associated with LMIs,such as complex mechanisms,and high-degrees of freedom,we believe that substantial contributions and potential for the commercialization of future energy systems can be achieved by advancing optical technologies through comprehensive academic research and multidisciplinary collaborations.

Effect of Ni Contents on the Microstructure and Mechanical Properties of Martensitic Stainless Steel Guide Roll by Centrifugal Casting

A novel process based on centrifugal casting was developed to produce martensitic stainless steel for guideroll materials. Centrifugal casting provides a lower production cost and less of the thermal cracking defects which normally occur in the overlaid welding process. In this study, the effects of Ni on the microstructure and mechanical properties of martensitic stainless steel were investigated. The results show that the addition of Ni resulted in a decrease in the volume fraction of delta ferrite and an increase in the volume fraction of the retained austenite, respectively. Moreover, a tensile strength of 1600 MPa with an elongation of 4% were obtained after tempering at 500℃ for 2 h. These values were higher than those obtained by using the conventional overlaid process.

Thin film processing and multiferroic properties of Fe-BaTiO_3 hybrid composite

Multiferroic bi-layer Fe/BaTiO3 （BTO） thin films were successfully deposited on Pt（200）/MgO（100） substrates using ion beam sputter deposition （1BSD）, and the mutiferroic properties were studied at room temperature. X-ray diffraction （XRD） analyses showed that BTO films were c-axis oriented and epitaxially grown on platinum coated MgO substrates, and （110） epitaxial Fe films were subsequently grown on （001） BTO films. Fe/BTO bi-layer films showed good ferroelectric and ferromagnetic properties at room temperature and the multiferroic coupling was observed, which should be attributed to the hybridization of Fe and Ti occurring at the ferromagnetic-ferroelectric interface.

HR-TEM and FIB-SEM characterization of formation of eutectic-like structure from amorphous GdAlO_3-Al_2O_3 system

The crystallization process of the eutectic composition of GdAlO_3-Al_2O_3 from the amorphous phase prepared by rapid-quenching of melt that leads to the formation of a cantaloupe skin-like microstructure was investigated using focused ion-beam scanning electron microscopy (FIB-SEM) and high-resolution transmission electron microscopy (HR-TEM).The amorphous films were heat-treated at temperatures between 1000 °C and 1500 °C for up to 30min to form the eutectic phases of GdAlO_3 and Al_2O_3.The GdAlO_3 and Al_2O_3 crystal phases that formed from the amorphous phase were identified by FIB-SEM and HR-TEM.Both components began to crystallize and grow from the amorphous phase separately at different temperatures.The formation process of these crystal phases was different from that of the ordinary eutectic microstructure solidified from the GdAlO_3-Al_2O_3 system.Therefore,the observed structure is termed "eutectic-like" for distinction.The microstructures formed from the amorphous phases at sufficiently high temperatures consisted of ultra-fine microstructures of individually crystallized components and were similar to ordinary eutectic microstructures.By heat-treating the amorphous films at 1500 °C for either 2 min,8min or 30min,the ultra-fine components of GdAlO_3 and Al_2O_3 were found to crystallize following a eutectic-like stage after 8min of heat treatment.

Nucleation and growth behavior of coating film on Mg–Al–Zn alloy with different surface topographies via plasma electrolytic oxidation

This work was made to investigate how nucleation and growth behavior of the coating film were affected by surface topographies of Mg–Al–Zn alloy substrate during the initial stage of plasma electrolytic oxidation(PEO).To satisfy this end,a single substrate was prepared by mechanical treatment exhibiting rough and smooth regions with an equal area on the surface.The rough region with prominent hills and grooves induced the breakdown of passive film,which was indicated by an early appearance of plasma discharge on the rough region since nucleation of coating film occurred preferentially around the hills.However,the coating film grown on the grooves was somewhat thicker and more porous than the film grown on the hills and smooth regions.This was due to the fact that the growth of the coating film was found to be localized in the presence of rough region,which was in line with the discharge activities.Herein,the nucleation and growth behavior during the initial stage of PEO will be discussed schematically on the basis of microstructural interpretation.

Fabrication of branch-like Aph@LDH-MgO material through organic-inorganic hybrid conjugation for excellent anti-corrosion performance

Layered double hydroxides(LDH)frameworks have shown significant enhancement in stability and reusability,and their tailorable architecture brings new insight into the development of the next generation of hybrid materials,which attracted considerable attention in many fields over the years.One of the factors contributing to the widespread applicability of layered double hydroxides is their adaptable composition,which can accommodate a wide spectrum of potential anionic guests.This exceptional property makes the LDH system simple to adjust for various applications.However,most LDH systems are synthesized in situ in an autoclave at high temperatures and pressures that severely restrict the industrial use of such coating systems.In this study,LDH was directly synthesized on a magnesium alloy that had undergone plasma electrolytic oxidation(PEO)treatment in the presence of ethylenediaminetetraacetic acid,thereby avoiding the use of hydrothermal autoclave conditions.This LDH system was compared with a hybrid architecture consisting of organic-inorganic self-assembly.An organic layer was fabricated on top of the LDH film using 4-Aminophenol(Aph)compound,resulting in a smart hierarchical structure that can provide a robust Aph@LDH film with excellent anti-corrosion performance.At the molecular level,the conjugation characteristics and adsorption mechanism of Aph molecule were studied using two levels of theory as follows.First,Localized orbit locator(LOL)-πisosurface,electrostatic potential(ESP)distribution,and average local ionization energy(ALIE)on the molecular surface were used to highlight localization region,reveal the favorable electrophilic and nucleophilic attacks,and clearly explore the type of interactions that occurred around interesting regions.Second,first-principles based on density functional theory(DFT)was applied to study the hybrid mechanism of Aph on LDH system and elucidate their mutual interactions.The experimental and computational analyses suggest that the highπ-electron density and delocalization characteristics of the functional groups and benzene ring in the Aph molecule played a leading role in the synergistic effects arising from the combination of organic and inorganic coatings.This work provides a promising approach to design advanced hybrid materials with exceptional electrochemical performance.

Development of anti-corrosive coating on AZ31 Mg alloy subjected to plasma electrolytic oxidation at sub-zero temperature

Plasma electrolytic oxidation(PEO)is a promising surface treatment to generate adherent and thick anti-corrosive coating on light-weight metals(Al,Mg,Ti,etc.)using an eco-friendly alkaline electrolyte.High energy plasma,however,inevitably generates porous structures that limit their practical performance.The present study proposes a straight-forward simple method by utilizing sub-zero electrolyte(268 K)to alter the plasma characteristics during formation of the protective coating on AZ31 Mg alloy via PEO with a comparison to the electrolyte at room temperature(298 K).In refrigerated electrolyte,the formation of micro-defects is suppressed relatively at the expense of low coating growth,which is measured to be twice lower than that at 298 K due to the temperature-dependent soft plasma discharges contributing to the development of the present coating.As a consequence,corrosion resistance of the sample processed at 268 K is superior to that of 298K,implying that the effect of coating thickness is less dominant than that of compactness.This phenomenon is interpreted in relation to the ionic movement and oxide solidification controlled by soft plasma discharges arising from the temperature gradient between electrolyte and surface of the substrate during PEO.

Effect of hexagonal-BN on phase transformation of additive-free Si_3N_4 /SiC nanocomposites prepared from amorphous precursor

Si3N4/SiC nanocomposites are well known and attractive for advanced ceramic applications due to excellent mechanlcal and thermal properties, which make them suitable for use in turbine engines, heat exchangers, and other sophisticated applications. However, without the presence of additives, the fabrication of Si3N4/SiC composites is difficult. The additives form a liquid phase during sintering and facilitate the densification of the composite. However, the additives present a drawback at high temperatures since they decrease the mechanical properties of the composites. Recently, Si3N4/SiC composites were fabricated via the polymer precursor route without any additives, using electric field assisted sintering （EFAS）. In this study, fully densified Si3N4/SiC nanocomposites incorporating hexagonal-BN were successfully fabricated by hot pressing without any additives at 1700 ℃ for 2 h under vacuum at a pressure of 50 MPa （via the amorphous precursor route）. Moreover, the incorporation of additives and h-BN is found to decrease the content of SiC. The phase transformation, densification, microstructure, and mechanical properties were discussed and presented.

Effect of Squeeze Cast Process Parameters on Fluidity of Hypereutectic Al-Si Alloy

The effects of processing variables on the fluidity of hypereutectic Al-Si alloy melt during squeeze casting were investigated.The maximum fluidity of Al-16.0%Si alloy during squeeze casting was obtained under the applied pressure of 30 MPa.The fluidity increased with superheat.The fluidity increased with silicon content in the range from 12.0% to 20.0%.That was decreased respectively by eutectic modification and primary silicon refinement.

Improving the electrochemical stability of AZ31 Mg alloy in a 3.5wt.%NaCl solution via the surface functionalization of plasma electrolytic oxidation coating

The unique interactions between hexadecanoic acid(HA)and albumin(ALB)molecules on the surface of the porous layer of AZ31 Mg alloy were exploited to fabricate a novel hybrid composite film with excellent electrochemical stability in a 3.5 wt.%Na Cl solution.Herein,the inorganic layer(IL)obtained by plasma electrolytic oxidation of AZ31 Mg alloy in an alkaline-phosphate-WO_(3)electrolyte was soaked in an organic solution composed of ALB and HA for 10 and 24 h at 60℃.Although albumin and HA may coexist on the same surface of IL,the higher reactivity of ALB molecules would prevent the formation of a thick layer of HA.The donor-acceptor complexes formed due to the unique interactions between ALB and/or HA and IL surface would reduce the area exposed to the corrosive species which in turn would efficiently protect the substrate from corrosion.The porous structure of the IL would provide preferable sites for the physical and chemical locking triggered by charge-transfer phenomena,leading to the inhomogeneous nucleation and crystal growth of a flowery flakes-like organic layer.DFT calculations were performed to reveal the primary bonding modes between the ALB,HA,and IL and to assess the mechanistic insights into the formation of such novel hybrid composites.

Origin of the synergistic effects of bimetallic nanoparticles coupled with a metal oxide heterostructure for accelerating catalytic performance

Precisely tuning bicomponent intimacy during reactions by traditional methods remains a formidable challenge in the fabrication of highly active and stable catalysts because of the difficulty in constructing well-defined catalytic systems and the occurrence of agglomeration during assembly.To overcome these limitations,a PtRuPNiO@TiO_(x)catalyst on a Ti plate was prepared by ultrasound-assisted low-voltage plasma electrolysis.This method involves the oxidation of pure Ti metal and co-reduction of strong metals at 3000◦C,followed by sonochemical ultrasonication under ambient conditions in an aqueous solution.The intimacy of the bimetals in PtRuPNiO@TiOx is tuned,and the metal nanoparticles are uniformly distributed on the porous titania coating via strong metal-support interactions by leveraging the instantaneous high-energy input from the plasma discharge and ultrasonic irradiation.The intimacy of PtRuPNiO@TiO_(x)increases the electron density on the Pt surface.Consequently,the paired sites exhibit a high hydrogen evolution reaction activity(an overpotential of 220 mV at a current density of 10 mA cm^(−2)and Tafel slope of 186 mV dec^(−1)),excellent activity in the hydrogenation of 4-nitrophenol with a robust stability for up to 20 cycles,and the ability to contrast stated catalysts without ultrasonication and plasma electrolysis.This study facilitates industrially important reactions through synergistic chemical interactions.

Effect of Deformation Temperature on Microstructure and Mechanical Properties of AZ31 Mg Alloy Processed by Differential-Speed Rolling

A differential-speed rolling(DSR) was applied to AZ31 magnesium alloy sample at different rolling temperatures of 473,523,573,and 623 K with 1-pass and 2-pass operations.The microstructural evolution and mechanical properties of the deformed samples were investigated.The rolling temperature was found to be an important parameter affecting the microstructural development.After DSR at 473 K,the microstructure was more homogeneous than that obtained after deformation by equal-speed rolling(ESR).The fully recrystallized microstructures were generated after DSR at 573 and 623 K.As to mechanical properties,the yield strength(YS) and ultimate tensile strength(UTS) decreased monotonously with increasing rolling temperature.In contrast,the elongation of the DSR-deformed samples was improved as the rolling temperature increased.The strain hardening exponent(n) calculated by Hollomon equation increased with increasing the rolling temperature,which would explain an increase in the uniform elongation.

Fabrication of SiCw/Ti3SiC2 composites with improved thermal conductivity and mechanical properties using spark plasma sintering

High strength SiC whisker-reinforced Ti3SiC2 composites(SiCw/Ti3SiC2)with an improved thermal conductivity and mechanical properties were fabricated by spark plasma sintering.The bending strength of 10 wt%SiCw/Ti3SiC2 was 635 MPa,which was approximately 50%higher than that of the monolithic Ti3SiC2(428 MPa).The Vickers hardness and thermal conductivity(k)also increased by 36%and 25%,respectively,from the monolithic Ti3SiC2 by the incorporation of 10 wt%SiCw.This remarkable improvement both in mechanical and thermal properties was attributed to the fine-grained uniform composite microstructure along with the effects of incorporated SiCw.The SiCw/Ti3SiC2 can be a feasible candidate for the in-core structural application in nuclear reactors due to the excellent mechanical and thermal properties.

Laser dissimilar welding of CoCrFeMnNi-high entropy alloy and duplex stainless steel

High entropy alloys(HEAs)have superior mechanical properties that have enabled them to be used as structural materials in nuclear and aerospace applications.As a dissimilar joint design is required for these applications,we created a dissimilar joint between CoCrFeMnNi-HEA and duplex stainless steel(DSS)through laser beam welding;a technique capable of producing a sound joint between the two materials.Micro structure examination using SEM/EBSD/XRD analysis revealed that the weld metal(WM)exhibits an FCC phase regardless of the postweld heat treatment(PWHT)temperature(800 and 1000℃)without forming detrimental intermetallic compounds or microsegregation.The heat-affected zone of the CoCrFeMnNi-HEA showed CrMn oxide inclusions while that of the DSS showed no inclusions.Moreover,a lower hardness was recorded by the WM compared to the base metal after welding.After PWHT,the hardness of the WM,CoCrFeMnNi-HEA,and DSS decreased with an increase in the PWHT temperature.However,the decrease in the hardness of the HEA was more significant than in the WM and DSS.The cause for this reduction in hardness was attributed to recrystallization and grain growth.In addition,a strength of 584 MPa with low ductility was recorded after welding.The obtained strength was lower than that of the BMs,but comparable to that of the welded CoCrFeMnNi-HEA.The application of PWHT resulted in over a 20%increment in ductility,with only a marginal reduction in strength.The defo rmation mechanism in the as-weld joint was mainly dominated by dislocation while that for the PWHT joint was twinning.We propose laser beam offset welding as a technique to improve the mechanical properties of the dissimilar joint,which will be the subject of future studies.