Is Green Infrastructure Viable for Mitigating Pluvial Floods?A Retrospective Study of a Community Renovation Applying LID Principal and Practice in Zhenjiang City of China

Is GI(Green Infrastructure)viable to mitigate urban pluvial flood caused by extreme storm events?Limited research and planning have been undertaken in recent years,but little practice has been found in the real world.This retrospective study provides an example of mitigating pluvial flood by LID(Low Impact Development)principal and practices and transforming an old,ultra-dense low-income community into a climate change resilient community.The key findings include keeping flood control in mind when designing GI in the beginning;mimicking the sites’hydrologic characteristics as much as possible;outreaching to residences for maintenance issues from the beginning and monitoring the performance of GI facilities continuously.Technically,bioretention growing media with higher infiltration rate is specified that must be great than 150 mm/h in short term and 80 mm/h for long term;this paper chose low maintenance permeable pavement products avoiding clogging;and increasing parking space without compromising the design goals.

Wear-resistant Ag-MAX phase 3D interpenetrating-phase composites:Processing,structure,and properties

Electrical contact materials are generally Ag-or Cu-based composites and play a critical role in ensuring the reliability and efficiency of electrical equipments and electronic instruments.The MAX(M is an early transition metal,A is an element from III or IV main groups,and X is carbon or/and nitrogen)phase ceramics display a unique combination of properties and may serve as an ideal reinforcement phase for electrical contact materials.The biological materials evolved in nature generally exhibit three-dimensional(3D)interpenetrating-phase architectures,which may offer useful inspiration for the architectural design of electrical contact materials.Here,a series of bi-continuous Ag-Ti_(3)SiC_(2) MAX phase composites with high ceramic contents exceeding 50 vol.%and having micron-and ultrafine-scaled 3D interpenetrating-phase architectures,wherein both constituents were continuous and mutually interspersed,were exploited by pressureless infiltration of Ag melt into partially sintered Ti_(3)SiC_(2) scaffolds.The mechanical and electrical properties as well as the friction and wear performance of the composites were investigated and revealed to be closely dependent on the ceramic contents and characteristic structural dimensions.The composites exhibited a good combination of properties with high hardness over 2.3 GPa,high flexural strength exceeding 530 MPa,decent fracture toughness over 10 MPa·m^(1/2),and good wear resistance with low wear rate at an order of 10^(-5)mm^(3)/(N·m),which were much superior compared to the counterparts made by powder metallurgy methods.In particular,the hardness,electrical conductivity,strength,and fracture toughness of the composites demonstrated a simultaneous improvement as the structure was refined from micron-to ultrafine-scales at equivalent ceramic contents.The good combination of properties along with the facile processing route makes the Ag-Ti_(3)SiC_(2)3D interpenetrating-phase composites appealing for electrical contact applications.

Effect of exogenous flavins on the microbial corrosion by Geobacter sulfurreducens via iron-to-microbe electron transfer

Microbes can cause or accelerate metal corrosion,leading to huge losses in corrosion damages each year.Geobacter sulfurreducens is a representative electroactive bacterium in many soils,sediments,and wastew-ater systems.It has been confirmed to directly extract electrons from elemental metals.However,little is known about the effect of electron shuttles in G.sulfurreducens corrosion on stainless steel.In this study,we report that exogenous flavins promote iron-to-microbe electron transfer,accelerating micro-bial corrosion.G.sulfurreducens caused 1.3 times deeper pits and increased electron uptake(with 2 times increase of i_(corr))from stainless steel when riboflavin was added to the culture medium.OmcS-deficient mutant data suggest that G.sulfurreducens utilizes riboflavin as a bound-cofactor in outer membrane c-type cytochromes.The finding that,in the presence of microbes,riboflavin can substantially accelerate corrosion highlights the role of flavin redox cycling for enhanced iron-to-microbe electron transfer by G.sulfurreducens and provides new insights in microbial corrosion.

Enhanced pitting corrosion resistance of CoCrFeMnNi high entropy alloy in the presence of Desulfovibrio vulgaris via nitrogen doping

Corrosion-resistant high nitrogen high entropy alloys(HEAs)were manufactured by pressurized metal-lurgy.This work revealed the inhibitory effect of nitrogen on pitting corrosion of HEAs caused by sul-fate reducing bacterium Desulfovibrio vulgaris.Results indicated that HEA-0 N was susceptible to pitting corrosion and sulfidation under attack of D.vulgaris,whereas the addition of nitrogen significantly de-creased the pitting sensitivity.Pitting potentials of HEA-0.52 N and HEA-1.23 N increased by 133%and 171%,respectively compared to HEA-0 N in the presence of SRB.X-ray photoelectron spectroscopy results unveiled that nitrogen enriched in passive film and strengthened it by increasing fraction of Cr_(2)O_(3)and Fe^(3+)_(ox).Surface of the nitrogen-alloyed HEAs exhibited less defective passive films as revealed by Mott-Schottky results.Nitrogen doping provides a novel insight into the design of microbial corrosion resistant HEA.

Host defense peptide-mimickingβ-peptide polymer displaying strong antibacterial activity against cariogenic Streptococcus mutans

Cariogenic Streptococcus mutans(S.mutans)is a leading cause of bacterial-induced oral diseases.Current strategies to kill bacteria based on Host defense peptide(HDP)mimicking polymers hold promise to treat oral bacterial infection.Here,we explore the impact of hydrophobic subunit and chain length variation on the antibacterial and antibiofilm activity ofβ-peptide polymers.The physicochemical and biological prop-erties,such as the toxicity,the antibacterial activity,and the effect on bacterial transcription ofβ-peptide polymers,were systematically investigated with numerous techniques.The results exhibited that the op-timalβ-peptide polymer has low toxicity towards human periodontal ligament fibroblasts,andβ-peptide polymers(especially P3)have more excellent antibacterial activity against S.mutans than metronidazole.In addition,β-peptide polymers inhibited the reversible and irreversible bacterial adhesion during the formation of biofilms.The polymer can promote biofilm dispersion by decreasing the hydrophobicity of bacterial cells after adhering to cell surfaces.Analysis of the transcriptome for S.mutans treated withβ-peptide polymers demonstrated thatβ-peptide polymers could reduce the cariogenicity of S.mutans by impacting the transcription of the energy and acid metabolism-related genes.β-peptide polymers are promising antimicrobial agents in clinical dentistry due to their high antibacterial efficiency and low tox-icity.

Enhanced Corrosion Resistance and Biofilm Inhibition of Functionally Graded TC4/TC4-5Cu Fabricated by Selective Laser Melting against Streptococcus mutans

Ti-6Al-4V(TC4)used in dentistry and orthopedics as implant biomaterial faces the risk of microbiologically influenced corrosion(MIC)owing to the residence of diverse oral microorganisms.Hereinto,Streptococcus mutans is a critical pathogenic microorganism that causes dental caries.This work investigated the corrosive effects of S.mutans on TC4 and functional gradient TC4/TC4-5Cu coupons fabricated by selective laser melting(SLM)through various electrochemical measurements,surface examination,observation of biofilm and corrosion analysis.The results indicated that the Cu-bearing alloy showed an inhibitory effect on the biofilms due to the release of Cu element,thereby reducing the corrosion rate of MIC.The corrosion current density(icorr)of TC4(11.7±0.8)nA cm−2 is higher than that of TC4/TC4-5Cu(7.4±0.4)nA cm−2 in the presence of S.mutans,while the maximum pit depth of TC4 is 1.6 times that of TC4/TC4-5Cu.Therefore,metal modification through Cu alloying is an effective strategy to improve the MIC resistance.

Toward a better understanding of microbiologically influenced corrosion caused by sulfate reducing bacteria

Sulfate reducing bacteria(SRB) are often the culprits of microbiologically influenced corrosion(MIC) in anoxic environments because sulfate is a ubiquitous oxidant. MIC of carbon steel caused by SRB is the most intensively investigated topic in MIC because of its practical importance. It is also because biogenic sulfides complicate mechanistic SRB MIC studies, making SRB MIC of carbon steel is a long-lasting topic that has generated considerable confusions. It is expedient to think that biogenic H_2S secreted by SRB acidifies the broth because it is an acid gas. However, this is not true because endogenous H_2S gets its H^+ from organic carbon oxidation and the fluid itself in the first place rather than an external source. Many people believe that biogenic H_2S is responsible for SRB MIC of carbon steel. However, in recent years,well designed mechanistic studies provided evidence that contradicts this misconception. Experimental data have shown that cathodic electron harvest by an SRB biofilm from elemental iron via extracellular electron transfer(EET) for energy production by SRB is the primary cause. It has been demonstrated that when a mature SRB biofilm is subjected to carbon source starvation, it switches to elemental iron as an electron source and becomes more corrosive. It is anticipated that manipulations of EET related genes will provide genetic-level evidence to support the biocathode theory in the future. This kind of new advances will likely lead to new gene probes or transcriptomics tools for detecting corrosive SRB strains that possess high EET capabilities.

Anaerobic microbiologically influenced corrosion mechanisms interpreted using bioenergetics and bioelectrochemistry： A review

Microbiologically influenced corrosion(MIC) is a major cause of corrosion damages, facility failures, and financial losses, making MIC an important research topic. Due to complex microbiological activities and a lack of deep understanding of the interactions between biofilms and metal surfaces, MIC occurrences and mechanisms are difficult to predict and interpret. Many theories and mechanisms have been proposed to explain MIC. In this review, the mechanisms of MIC are discussed using bioenergetics, microbial respiration types, and biofilm extracellular electron transfer(EET). Two main MIC types, namely EET-MIC and metabolite MIC(M-MIC), are discussed. This brief review provides a state of the art insight into MIC mechanisms and it helps the diagnosis and prediction of occurrences of MIC under anaerobic conditions in the oil and gas industry.

Microbiologically influenced corrosion behavior of S32654 super austenitic stainless steel in the presence of marine Pseudomonas aeruginosa biofilm

S32654 super austenitic stainless steel(SASS) is widely used in highly corrosive environments. However,its microbiologically influenced corrosion(MIC) behavior has not been reported yet. In this study, the corrosion behavior of S32654 SASS caused by a corrosive marine bacterium Pseudomonas aeruginosa was investigated using electrochemical measurements and surface analysis techniques. It was found that P. aeruginosa biofilm accelerated the corrosion rate of S325654 SASS, which was demonstrated by a negative shift of the open circuit potential(EOCP), a decrease of polarization resistance and an increase of corrosion current density in the culture medium. The largest pit depth of the coupons exposed in the P.aeruginosa broth for 14 days was 2.83 m, much deeper than that of the control(1.33 m) in the abiotic culture medium. It was likely that the P. aeruginosa biofilm catalyzed the formation of CrO_3, which was detrimental to the passive film, resulting in MIC pitting corrosion.

Antibacterial Performance of a Cu-bearing Stainless Steel against Microorganisms in Tap Water

Tap water is one of the most commonly used water resources in our daily life. However, the increasing water contamination and the health risk caused by pathogenic bacteria, such as Staphylococcus aureus and Escherichia coli have attracted more attention. The mutualism of different pathogenic bacteria may diminish antibacterial effect of antibacterial agents. It was found that materials used for making pipe and tap played one of the most important roles in promoting bacterial growth. This paper is to report the performance of an innovative type 304 Cu-bearing stainless steel(304Cu SS) against microbes in tap water. The investigation methodologies involved were means of heterotrophic plate count, contact angle measurements, scanning electron microscopy for observing the cell and subtract surface morphology,atomic absorption spectrometry for copper ions release study, and confocal laser scanning microscopy used for examining live/dead bacteria on normal 304 stainless steel and 304 Cu SS. It was found that the surface free energy varied after being immersed in tap water with polar component and Cu ions release.The results showed 304 Cu SS could effectively kill most of the planktonic bacteria(max 95.9% antibacterial rate), and consequently inhibit bacterial biofilms formation on the surface, contributing to the reduction of pathogenic risk to the surrounding environments.

Microbial corrosion resistance of a novel Cu-bearing pipeline steel

Microbiologically influenced corrosion(MIC) is becoming a serious problem for buried pipelines. Developing environmentally friendly strategies for MIC control is increasingly urgent in oil/gas pipeline industry.Copper(Cu) in steels can not only provide aging precipitation strengthening, but also kill bacterium,offering a special biofunction to steels. Based on the chemical composition of traditional X80 pipeline steel, two Cu-bearing pipeline steels(1% Cu and 2% Cu) were fabricated in this study. The microstructure,mechanical properties and antibacterial property against sulphate-reducing bacteria(SRB) and Pseudomonas aeruginosa(P. aeruginosa) were studied. It was found that the novel pipeline steel alloyed by 1%Cu exhibited acicular ferrite microstructure with nano-sized Cu-rich precipitates distribution in the matrix, resulting in better mechanical properties than the traditional X80 steel, and showed good MIC resistance as well. The pitting corrosion resistance of 1% Cu steel in as-aged condition was significantly better than that of X80 steel. A possible antibacterial mechanism of the Cu-bearing pipeline steel was proposed.

Effect of nitrogen on corrosion behaviour of a novel high nitrogen medium-entropy alloy CrCoNiN manufactured by pressurized metallurgy

A novel high nitrogen medium-entropy alloy CrCoNiN, which had higher strength and slightly lower ductility than CrCoNi alloy, was successfully manufactured by pressurized metallurgy. The microstructure and corrosion behaviour were investigated by microscopic, electrochemical and spectroscopic methods.The results indicated that nitrogen existed in the form of Cr_2N precipitates and uniformly distributed N atoms, and nitrogen alloying significantly refined the grain size. Besides, nitrogen enriched on the outmost surface of passive film and metal/film interface as ammonia(NH-_3 and NH_4^+) and CrN, respectively. The significant improvement of corrosion resistance of CrCoNiN was attributed to the lower metastable pitting susceptibility together with thicker, less defective and more compact passive film.

Microbiologically influenced corrosion of titanium caused by aerobic marine bacterium Pseudomonas aeruginosa

Microbiologically influenced corrosion(MIC) is a big threat to the strength and safety of many metallic materials used in different environments throughout the world. The metabolites and bioactivity of the microorganisms cause severe deterioration on the metals. In this study, MIC of pure titanium(Ti) was studied in the presence of a highly corrosive aerobic marine bacterium Pseudomonas aeruginosa. The results obtained from electrochemical test showed that Ti was corrosion resistant in the abiotic culture medium after 14 d, while the increased corrosion current density(i_(corr)) obtained from polarization curves and the decreased charge transfer resistance(R_(ct)) from electrochemical impedance spectroscopy(EIS)indicated the accelerated corrosion of Ti caused by P. aeruginosa biofilm. For further confirmation of the above results, the surface of Ti was investigated using scanning electron microscopy(SEM), confocal laser scanning microscopy(CLSM) and X-ray photoelectron spectroscopy(XPS). According to the XPS results, TiO_2 was formed in both abiotic and biotic conditions, while unstable oxide Ti_2O_3 was detected in the presence of P. aeruginosa, leading to the defects in the passive film and localized corrosion. Pitting corrosion was investigated with the help of CLSM, and the largest pit depth found on Ti surface immersed in P. aeruginosa was 1.2 μm. Ti was not immune to MIC caused by P. aeruginosa.

Effect of Cu Addition to 2205 Duplex Stainless Steel on the Resistance against Pitting Corrosion by the Pseudomonas aeruginosa Biofilm

The effect of copper addition to 2205 duplex stainless steel(DSS) on its resistance against pitting corrosion by the Pseudomonas aeruginosa biofilm was investigated using electrochemical and surface analysis techniques. Cu addition decreased the general corrosion resistance, resulting in a higher general corrosion rate in the sterile medium. Because DSS usually has a very small general corrosion rate, its pitting corrosion resistance is far more important. In this work, it was shown that 2205-3%Cu DSS exhibited a much higher pitting corrosion resistance against the P. aeruginosa biofilm compared with the 2205 DSS control, characterized by no significant change in the pitting potential and critical pitting temperature(CPT) values. The strong pitting resistance ability of 2205-3%Cu DSS could be attributed to the copper-rich phases on the surface and the release of copper ions, providing a strong antibacterial ability that inhibited the attachment and growth of the corrosive P. aeruginosa biofilm.

A novel Cu-bearing high-entropy alloy with significant antibacterial behavior against corrosive marine biofilms

The design of novel high-entropy alloys(HEAs)provides a unique opportunity for the development of structure-function integrated materials with high mechanical and antimicrobial properties.In this study,by employing the antibacterial effect of copper,a novel Al0.4CoCrCuFeNi HEA with broad-spectrum antibacterial and strong mechanical properties was designed.High concentrations of copper ions released from the HEA prevented growth and biofilm formation by biocorrosive marine bacterial species.These findings serve as a proof-of-concept for further development of unique HEA materials with high antimicrobial efficiency and mechanical properties,compared to conventional antibacterial alloys.

Enhanced antibacterial behavior of a novel Cu-bearing high-entropy alloy

Contact infection of bacteria and viruses has been a critical threat to human health. The worldwideoutbreak of COVID-19 put forward urgent requirements for the research and development of the selfantibacterial materials, especially the antibacterial alloys. Based on the concept of high-entropy alloys, thepresent work designed and prepared a novel Co_(0.4)FeCr_(0.9)Cu_(0.3) antibacterial high-entropy alloy with superior antibacterial properties without intricate or rigorous annealing processes, which outperform the antibacterial stainless steels. The antibacterial tests presented a 99.97% antibacterial rate against Escherichiacoli and a 99.96% antibacterial rate against Staphylococcus aureus after 24 h. In contrast, the classic antibacterial copper-bearing stainless steel only performed the 71.50% and 80.84% antibacterial rate, respectively. The results of the reactive oxygen species analysis indicated that the copper ion release and theimmediate contact with copper-rich phase had a synergistic effect in enhancing antibacterial properties.Moreover, this alloy exhibited excellent corrosion resistance when compared with the classic antibacterialstainless steels, and the compression test indicated the yield strength of the alloy was 1015 MPa. Thesefindings generate fresh insights into guiding the designs of structure-function-integrated antibacterial alloys.

Methanogenic archaea and sulfate reducing bacteria induce severe corrosion of steel pipelines after hydrostatic testing

Complex interactions within a microbial consortium can induce severe corrosion in oil pipelines.This study investigated the mechanism of microbiologically influenced corrosion(MIC)that led to failure of X52 steel pipelines after hydrostatic testing.Laboratory hydrostatic testing with untreated lake water and underground water were used to simulate and study the events that led to the actual corrosion.Biofilm analysis,weight loss,and several electrochemical measurements demonstrated rapid corrosion rates after hydrostatic testing.Analysis of microbial community structures revealed that methanogenic archaea and sulfate reducing bacteria(SRB),introduced by the hydrotest water,formed corrosive biofilms on X52 steel coupon surfaces that induced severe pitting.

Fabricating antibacterial CoCrCuFeNi high-entropy alloy via selective laser melting and in-situ alloying

A quasi-equiatomic CoCrFeCuNi high-entropy alloy(HEA) with a broad-spectrum antibacterial ability and good mechanical properties has been fabricated by selective laser melting(SLM) and in-situ alloying of a blend of pre-alloyed CoCrFeNi powder and Cu elemental powder.The as-built HEA alloy has a homogeneous distribution of Cu and presents a single FCC phase.Compared with the same HEA fabricated using the traditional ingot metallurgy(IM) process,the HEA alloy fabricated by SLM releases more Cu ions to prevent growth and biofilm formation by gram-negative Escherichia coli and gram-positive Staphylococcus aureus,which enhances the applicability of the HEA alloy in potential applications that requires antibacterial ability.The results of this study confirm the feasibility of combining the antibacterial CoCrFeCuNi HEA alloy and SLM technology in fabricating complex shaped parts or structures with a strong antibacterial ability to be used in medical application or other environments desired for antibacterial ability.

Enhanced resistance of 2205 Cu-bearing duplex stainless steel towards microbiologically influenced corrosion by marine aerobic Pseudomonas aeruginosa biofilms

An antibacterial 2205-Cu duplex stainless steel(DSS)was shown to inhibit the formation and growth of corrosive marine biofilms by direct contact with copper-rich phases and the release of Cu^(2+)ions from the2205-Cu DSS surface.In this work,the microbiologically influenced corrosion(MIC)resistance of 2205-Cu DSS in the presence of the corrosive marine bacterium Pseudomonas aeruginosa was investigated.The addition of copper improved the mechanical properties such as the yield strength,the tensile strength and the hardness of 2205 DSS.Electrochemical test results from linear polarization resistance(LPR),electrochemical impedance spectroscopy(EIS)and critical pitting temperature(CPT)measurements showed that 2205-Cu DSS possessed a larger polarization resistance(R_p),charge transfer resistance(R_(ct))and CPT values,indicating the excellent MIC resistance of 2205-Cu DSS against the corrosive P.aeruginosa biofilm.The live/dead staining results and the SEM images of biofilm confirmed the strong antibacterial ability of 2205-Cu DSS.The largest pit depth of 2205-Cu DSS was considerably smaller than that of 2205 DSS after 14 d in the presence of P.aeruginosa(2.2μm vs 12.5μm).2205-Cu DSS possessed a superior MIC resistance to regular 2205 DSS in the presence of aerobic P.aeruginosa.

Effect of organic silicon quaternary ammonium salts on mitigating corrosion of reinforced steel induced by SRB in mild alkaline simulated concrete pore solution

The corrosion damage of 20 SiMn steel by sulphate-reducing bacteria(SRB)and the mitigation effect of organic silicon quaternary ammonium salt(OSA)were studied in sterilized mild alkaline simulated concrete pore solution(STR)with different additions of SRB and OSA at pH 9.35 for 28 days.Uniform corrosion occurs in STR medium while slight localized corrosion is observed in STR+OSA medium,and localized pitting corrosion occurs in STR+SRB and STR+SRB+OSA media.The largest pit depth reduces from 36.70μm in STR+SRB medium to 3.31μm in STR+SRB+OSA medium due to the mitigation effect of OSA.The corrosion rate reflected by weight loss and electrochemical impedance spectroscopy(EIS)results presents the order of STR<STR+OSA<STR+SRB+OSA<STR+SRB,which also proves that the presence of SRB can accelerate corrosion in a carbonated medium.However,OSA as an efficient bacteriostatic agent can reduce the excessive growth of SRB and thus reduce corrosion.