Pure Water Environment Research Articles

Effect of various aging conditions and treatment methods on thermal degradation of coffee waste/epoxy composites

In composites containing lignocellulosic fillers, the chemical composition of the filler mostly determines the heat resistance. Based on the rules of green chemistry, new bio-based composites were developed from the waste of industrial crop product coffee (CW), and their thermal stability in different aging environments was examined by thermogravimetric analysis (TGA). Alkali (NaOH), microwave (MW), ultrasound (US), and alkali pretreatment followed by microwave (NaOH+MW) were applied to modify the CW. The effect of various applied treatment methods and environmental conditions such as UV radiation, water sorption, seawater, and hydrothermally agings on the thermal properties of the composites was investigated. Fourier-transform infrared spectroscopy (FTIR) and Field emission scanning electron microscopy (FE-SEM) were used in the characterization of composites. Among the environmental factors tested, seawater and hydrothermal aging affected the thermal resistance of the composites the most, while NaOH+MW affected it most among the processing methods. Although the thermal stability of unaged and UV-exposed MW-CW composites was found to be the highest, it was more affected by aging in seawater, pure water, and hydrothermal environments. As a result, MW was found to be more effective among the treatment methods in terms of thermal properties under UV conditions, confirming that the adoption of environmentally friendly methods and surface modification of the filler can provide superior composites.

Stainless steels as a solution for corrosion and erosion problems involving grains in agribusiness sector applications

Agricultural activities such as grain processing play a crucial role in Brazil's economy, contributing significantly to its gross domestic product (27.4% in 2021). The use of carbon steel equipment leads to considerable environmental and economic losses in agribusiness due to corrosion. This study explores the erosion-corrosion behavior of a dual-phase 11Cr and an 18Cr8Ni stainless steel (SS), compared to a mild (ASTM A36) and a high-strength carbon (AHSS) steel under conditions close to the agribusiness reality. The impact of corn particles as erosive component associated to pure water and chloride-containing environments was studied using a fog chamber, a topic until now unexplored in the literature. The methodology adopted is novel and explores the erosion-corrosion synergy in cumulative steps, aiming to shed light on the mechanisms of corrosion and wear that affect the materials in the agribusiness industry. The findings reveal that corn particles, despite their soft nature, can easily remove non-adherent corrosion products from the steel surface. In the deionized water medium, the impact of the soft particles can also shift the corrosion pattern of advanced high-strength steels from general corrosion to localized pitting damage reduzing the corrosion rates. The carbon and 11Cr steels showed the highest corrosion rates under the pure corrosion condition in both media. The erosion-corrosion process considerably reduced the corrosion rate, mainly in the deionized water medium for the carbon steels. An exception to this behavior was 18Cr8Ni steel, whose corrosion rates, however, were the lowest among the materials. Low-chromium stainless steel emerges as a cost-effective solution to erosion-corrosion challenges in the agribusiness segment.

Corrosion and stress corrosion behavior of CuCrZr alloy in high temperature pure water environment relevant to Japan's DEMO divertor

CuCrZr alloy is one of leading candidate of the cooling system of the Japan's DEMO divertor. Proposals of operating conditions resembles in-service light water reactors hence underlines the importance of water chemistry. The latter significantly affects corrosion behavior. To understand CuCrZr alloy's corrosion behavior, several 500-hr static water corrosion tests with various water conductivity and water chemistries (including dissolved oxygen 100ppb respectively dissolved hydrogen 1600 ppb) at 230 °C pure water were conducted. Additional creviced bent beam (CBB) tests in degassed water and in water with dissolved hydrogen 1600 ppb at 230 °C up to 1000 h were also conducted to investigate stress corrosion behavior. Results showed that the weight loss of coupons tested in oxygen dissolved water was tenfold than that of in degassed water; and the loss in degassed water is twenty times higher than that of in hydrogen dissolved water. Presence of pure copper precipitates on coupons tested in hydrogen dissolved water suggests the occurrence of hydrogen reduction. In degassed water, the weight loss at high water conductivity (0.3 μS/cm) was close to that of low water conductivity (≦0.1 μS/cm), suggesting that the effect brought by water conductivity was smaller than the effect brought by different water chemistries. All CBB test coupons show no cracks. Relatively deeper metal dissolution induced etching at grain boundaries were observed comparing with those coupons from static water corrosion tests. Combined factors of tensile stress and metal dissolution lead to a speculation that stress corrosion cracking might happen under other aggressive environments or testing methods.

Feasibility of Preparing Steel Slag–Ground Granulated Blast Furnace Slag Cementitious Materials: Synergistic Hydration, Fresh, and Hardened Properties

Steel slag and GBFS are wastes generated during the steel and iron smelting process, characterized by their considerable production rates and extensive storage capacities. After grinding, they are often used as supplementary cementitious materials. However, the intrinsic slow hydration kinetics of steel slag–GBFS cementitious material (SGM) when exposed to a pure water environment result in prolonged setting times and diminished early-age strength development. The incorporation of modifiers such as gypsum, clinker, or alkaline activators can effectively improve the various properties of SGM. This comprehensive review delves into existing research on the utilization of SGM, examining their hydration mechanisms, workability, setting time, mechanical strengths, durability, and shrinkage. Critical parameters including the performance of base materials (water-to-cement ratio, fineness, and composition) and modifiers (type, alkali content, and dosage) are scrutinized to understand their effects on the final properties of the cementitious materials. The improvement mechanisms of various modifiers on properties are discussed. This promotes resource utilization of industrial solid wastes and provides theoretical support for the engineering application of SGM.

Comparison of Mechanical Properties of Ductile/Brittle Epoxy Resin BFRP-AL Joints under Different Immersion Solutions.

The bonding properties of BFRP composites have been demonstrated in previous studies, satisfying the strength and durability criteria. In this paper, a further in-depth study is carried out to bond Basalt Fibre Reinforced Polymer (BFRP) to Aluminum Alloy 5052 using two bonding agents, Aralite® 2012 and Aralite® 2015, respectively. The salt sprays under 80 °C, 3.5% NaCl environment; 80 °C, 5% NaCl environment; and pure water environment are also considered for comparison. Experimental results show that joints created with Araldite® 2012 adhesives show higher average breaking strength (10.66 MPa at 720 h) and better ductility in a 5% NaCl environment. While the Araldite® 2015 adhesive joint exhibits a combination of tear failure and interface failure, along with thin-layer cohesion failure. In the SEM images of the two adhesive joints' failure, fiber pullout due to tension and damage at the interface between fiber and resin is apparent. To validate the experimental outcomes, water absorption testing, DSC, TGA-DTG, and FTIR experiments were conducted on dog-bone-shaped adhesive specimens to elucidate the results.

Experimental Study of Surface Damage of Stainless Steel Subjected to Cavitation Collapse in Aqueous Environment

With the aim of understanding cavitation damage of stainless steel under the effect of cavitation collapse in an aqueous environment, morphology, phase, chemical state, electrochemical, and other properties after cavitation and erosion are methodically examined. The obtained results indicate that the addition of metal ions in pure water strengthens the dynamic effect of cavitation collapse. When the cavitation collapses, it is capable of releasing a high temperature and transferring it to the surface of the stainless steel in a short time. Then, through the rapid cooling of the pure water environment, the martensitic structure is generated, but the presence of a massive amount of metal ions leads to a decrease in the speed of heat conduction and absorption of some heat. After the collapse of the bubble, the passivation film on the surface of the stainless steel incorporates into the creation of initial micropores. A concentration difference and a growth of the current density at the bottom of the hole, as well as a reduction in the pH value are detectable. Compared with pure water, 3.5% NaCl solution contains more free ions and its local current density is higher, so its corrosion resistance is worse.

WIRELESS POWER TRANSFER FOR UNDERWATER VEHICLES

Wireless power transfer (WPT) through magnetic resonance coupling (MRC) offers a safe and simple solution for underwater (UV) vehicles without being affected by water conductivity. Due to its ease of control in WPT systems, the most suitable topology is Serial-Serial (SS). In this study, square transmitting and receiving coils with dimensions of 40 cm - 40 cm were designed for 3.3 kW power transmission at 85 kHz. The design was studied in the air, pure water, and seawater environments. Three different cases were analyzed with ANSYS Maxwell 3D. The WPT system responded similarly in air and pure water environments. However, it was determined that the eddy current loss increased, the mutual inductance decreased, the coupling factor weakened, and the critical air gap decreased by about 0.2 cm in the seawater environment. The results showed that the WPT system's efficiency was similar for air and pure water but tolerably lower in the marine environment. Further, the health effects of the WPT design were examined through the ANSYS HFSS, in line with the IEEE standard and ICNIRP guidelines.

A model to predict the thermodynamic stability of abiotic methane-hydrogen binary hydrates in a marine serpentinization environment

Abiotic methane (CH4) and hydrogen (H2), which are produced during marine serpentinization, provide abundant gas source for hydrate formation on ocean floor. However, previous models of CH4–H2 hydrate formation have generally focused on pure water environments and have not considered the effects of salinity. In this study, the van der Waals–Platteeuw model, which considered the effects of salinity on the chemical potentials of CH4, H2, and H2O, was applied in a marine serpentinization environment. The model uses an empirical formula and the Peng–Robinson equation of state to calculate the Langmuir constants and fugacity values, respectively, of CH4 and H2, and it uses the Pitzer model to calculate the activity coefficients of H2O in the CH4–H2–seawater system. The three-phase equilibrium temperature and pressure predicted by the model for CH4–H2 hydrates in pure water demonstrated good agreement with experimental data. The model was then used to predict the three-phase equilibrium temperature and pressure for CH4–H2 hydrates in a NaCl solutions, for which relevant experimental data are lacking. Thus, this study provides a theoretical basis for gas hydrate research and investigation in areas with marine serpentinization.

Fabrication of Supramolecular System Derived from Poly β-cyclodextrin Coupling Quinoline Dderivative and Its Fluorescence Sensing of Zinc Ion in Pure Water Environment.

Cyclodextrin (CD) is an important guest material owing to the water solubility and biocompatibility. In the paper, an organic small molecule was synthesized. According to supramolecular self-assembly, the organic molecule was bounded to the cavity of Poly β-cyclodextrin, which was characterized by IR, SEM and TEM et al. After self-assembly interaction, the morphology has changed obviously comparing with precursors. Simultaneously, the supramolecular self-assembly complex exhibited good water solubility. Moreover, By Gaussian calculation, the high binding activity between organic molecule and cyclodextrin was confirmed. By fluorescence investigation, the supramolecular system showed high fluorescence sensing activity for Zn2+ in pure water environment, which could track the dynamic change of Zn2+ in organisms. In addition, the supramolecular system exhibited low cytotoxicity. The work provided an interesting pathway for constructing water-soluble and low cytotoxic fluorescence sensor for Zn2+.

Four new coordination polymers with 2D → 2D interpenetrating networks and fluorescence quenching response to nitrobenzene

With the growing interests in two-dimensional (2D) materials, the rational assembly of new 2D coordination frameworks with functional properties have attracted extensive attentions. Four new isomorphic compounds with 2D → 2D interpenetrating structures, [M(cppp)2]n [M = Co (1), Cu (2), Ni (3) and Zn (4); Hcppp = 1- (4-carboxylphenyl)-3-(pyrid-4-yl) pyrazole] were rationally assembled through the reactions between suitable organic ligand (Hcppp) and metal nitrates. Compounds 1–4 were completely characterized by adsorption and desorption isotherms, elemental analysis, infrared spectroscopy, powder X-ray diffraction, scanning electron microscopy, single crystal X-ray diffraction and thermo-gravimetric analysis. The solid state fluorescence spectrum of compound 4 indicates an attractive blue luminescence behavior with a maximum emission peak at 473 nm, and the corresponding solvent-emulsions show turn-off fluorescence behavior to nitrobenzene (NB) in pure water environment. The quenching constant (KSV) and detection limit of compound 4 for electron-deficient NB reached 2.46×103 M−1 and 6.19×10–6 M, respectively. Notably, SEM and N2 adsorption-desorption isotherm indicated the block crystals of compound 4 after ultra-sonication can been effectively stripped into 2D lamellar structure, which can effectively provide recognition sites of π•••π interactions for NB. According to the experimental and theoretical simulation results, fluorescence quenching behavior of compound 4 by NB should be attributed to synergistic effects of competitive absorption between compound 4 and NB, Förster resonance energy transfer and photo-induced electron transfer. The fluorescence lifetimes of compound 4 in water and NB water dispersion indicate fluorescence sensing process was static.

Hygrothermal aging behavior and mechanism of multi-filler reinforced epoxy composites for steel structure coatings

The long-term hygrothermal resistance of epoxy-based composites plays a key role as an anti-corrosion and anti-wear coating for steel structures when exposed to complex service environments. The hygrothermal aging will cause an irreversible damage to the service performances of composites. In the present paper, the multi-fillers reinforced epoxy composites (MFREC) had been successfully prepared and have been given higher expectations for steel coatings. Its hygrothermal aging behavior was experimentally investigated through the immersion in distilled water (DW) and saline water (SW) at 20, 40, and 60 °C as long as 120 days. The moisture uptake, thermal properties, mechanical properties and microstructure analysis were tested to evaluate the long-term hygrothermal evolution. The research results showed that the quasi-equilibrium moisture uptake content (3.72%) of MFREC in SW was lower than that (4.14%) in DW owing to the preferential permeation and occupation effects of small ions (Na+, Cl−). Hygrothermal exposure led to a maximum degradation of tensile strength, elongation at break and glass transition temperature of MFREC, up to 38.2%, 46.6% and 20.8% in DW, and 34.5%, 40.8% and 18.4% in SW, respectively. This was because the epoxy matrix had generated relaxation and reinforced-fillers/epoxy interfaces had been destroyed, which can be verified by hydrogen bond increasing (maximum 75.2%) from infrared test, fiber pulling out from epoxy matrix (morphology analysis), elastic modulus decreasing (maximum 37.8%) from micro-hardness measurement and pore volume increasing (maximum 53.9%) from N2 adsorption test compared to unaged samples. Based on the Arrhenius theory, the long-term life prediction of MFREC tensile strength under three typical bridge service environments was conducted to evaluate the service time as coatings. It can be found that the stable strength retentions were 63.19% and 66.03% in the simulated pure water and marine environments, respectively. Furthermore, an additional strength degradation percentage up to 11.5% can be found for MFREC exposed to steel bridge coatings in southern as long as 3 years compared to the northern environment.

Naphthenic Acids Aggregation: The Role of Salinity

Naphthenic Acids (NA) are important oil extraction subproducts. These chemical species are one of the leading causes of marine pollution and duct corrosion. For this reason, understanding the behavior of NAs in different saline conditions is one of the challenges in the oil industry. In this work, we simulated several naphthenic acid species and their mixtures, employing density functional theory calculations with the MST-IEFPCM continuum solvation model, to obtain the octanol–water partition coefficients, together with microsecond classical molecular dynamics. The latter consisted of pure water, low-salinity, and high-salinity environment simulations, to assess the stability of NAs aggregates and their sizes. The quantum calculations have shown that the longer chain acids are more hydrophobic, and the classical simulations corroborated: that the longer the chain, the higher the order of the aggregate. In addition, we observed that larger aggregates are stable at higher salinities for all the studied NAs. This can be one factor in the observed low-salinity-enhanced oil recovery, which is a complex phenomenon. The simulations also show that stabilizing the aggregates induced by the salinity involves a direct interplay of Na+ cations with the carboxylic groups of the NAs inside the aggregates. In some cases, the ion/NA organization forms a membrane-like circular structural arrangement, especially for longer chain NAs.

Evolution of structural and mechanical properties of concrete exposed to high concentration CO2

There are many natural high concentration CO2 reservoirs in the deep subsurface worldwide, and there is a potential for CO2 leakage from deep CO2 reservoirs to shallower underground spaces. As a result, underground mining and tunnel construction may encounter zones with high concentration CO2, which raises concern of concrete carbonation. Concrete carbonation under low CO2 concentration may increase the strength of concrete, but concrete carbonation under high concentration CO2 may cause concrete damage. High concentration CO2 may significantly increase the carbonation rate of concrete, which causes the strength and service life of concrete to decrease. In order to investigate the effect of CO2 concentration on concrete carbonation, this paper studied the carbonation process of concrete samples in dry gas, pure water and 70% relative humidity (RH) environments with 100 kPa, 500 kPa and 1000 kPa CO2 partial pressures. The chemical compositions, pore structure and mechanical properties of the concrete samples were also studied. The results showed that the carbonation environment affected the crystallization process of carbonation products. The existence of water increased the level of concrete carbonation in pure water environment, and some C-S-H also reacted with CO2 to produce aragonite. Therefore, after 28 d carbonation of concrete in 100 kPa CO2, aragonite existed in pure water environment but did not exist in dry gas environment. For all carbonation environments, the compressive strength of concrete increased after carbonation in 100 kPa and 500 kPa CO2, but the compressive strength of concrete first increased and then decreased in pure water and 70% RH environment with 1000 kPa CO2. In summary, if the concentration of CO2 reaches a certain level (i.e., 1000 kPa partial pressure), the CO2-induced carbonation can eventually lead to concrete damage.

Effect of marine environment on the mechanical properties degradation and long-term creep failure of CFRP

The carbon fiber reinforced plastics (CFRP) has broad application prospect in the marine field, but its significate long-term performance and failure mechanism are still unclear. In this paper, the mechanical property degradation and creep failure mechanism of CFRP in marine environment were investigated by the molecular dynamics (MD) method. Based on the CFRP molecular model established in dry, pure water and salt immersion environment, the effect of service conditions on it in marine environment was explored. The results show that the marine environment can lead to a significant decrease in the mechanical properties of CFRP only in the vertical fiber direction, and the degradation extent increases with the increase of temperature. The effects of pure water immersion and salt immersion environment on its mechanical properties are basically the same. High stress level, hygrothermal environment and high temperature salt immersion environment will accelerate the creep failure of CFRP. Later, the creep failure mechanism of CFRP is analyzed from microstructure and microscopic energy. Microstructure analysis shows that water molecules could accelerate the movement of epoxy fragments and lead to CFRP failure. Microscopic energy analysis shows that the conversion process of strain energy and the decline of interface performance are the important reasons for creep failure. The finds of this paper introduce a new method to study the long-term performance of CFRP and can provide reference for the engineering application of CFRP in marine environment.

Microsecond molecular dynamics of methane\u2013carbon dioxide swapping in pure and saline water environment

This work aims at proposing the nondestructive methane-carbon dioxide (CH4–CO2) replacement mechanism as an ecofriendly energy production technique from the natural gas hydrate reserves in seafloor and permanently frozen grounds. Although the experimental data is widely available in literature, this replacement mechanism has not been elucidated at molecular level. In this contribution, we perform the microsecond level molecular dynamic simulations to evaluate two different CH4–CO2 replacement mechanisms: (i) direct CH4 displacement from hydrate structure, and (ii) dissociation of existing methane hydrate followed by a reformation of mixed CH4–CO2 hydrates. For this, we analyze CH4–CO2 replacement in three different modes i.e., CO2 as a replacing agent in (i) absence of free water molecules, (ii) presence of free water molecules, and (iii) presence of salt ions and free water molecules. Despite slow kinetics in the first mode, pure CO2 is observed to replace the methane more efficiently, while in the second mode, CO2 forms a new mixed hydrate layer on the existing seed crystal. However, in the third mode, salt ions help in destabilizing the methane hydrate and allow CO2 to form the hydrates. This proves that salt ions are favorable for CH4–CO2 replacement.

The highly improved hydrogen evolution performance of a 0D/0D MoP-modified P-doped Mn0.5Cd0.5S photocatalyst.

In this paper, we present a MoP/P-Mn0.5Cd0.5S photocatalytic material (PMOMCS-Px). A novel catalyst can efficiently split water into hydrogen without precious metals. In the sacrificial agent environment, the HER (hydrogen evolution rate) of PMOMCS-P5 was 4368.25 μmol g-1 h-1 which was 11.4 times greater than the HER of Mn0.5Cd0.5S (383.19 μmol g-1 h-1), and its hydrogen production performance was better than that of Pt/Mn0.5Cd0.5S (2.0 wt% Pt). Furthermore, the hydrogen evolution performance of PMOMCS-P5 under pure water conditions was also examined, and the HER of PMOMCS-P5 was 209.76 μmol g-1 h-1, which was 20.4 times that of Mn0.5Cd0.5S (10.29 μmol g-1 h-1). Its characterization proved that the introduction of the co-catalyst MoP and P doping inhibited the recombination of e- and h+, enhanced the reduction capacity, and reduced the hydrogen precipitation reaction overpotential of PMOMCS-Px, thus enhancing the hydrogen production performance of PMOMCS-Px. Therefore, an efficient and economical photocatalyst was prepared.

Effect of the third body layer formed at different temperature on fretting wear behavior of 316 stainless steel in the composite fretting motion of slip and impact

316 SS is a commonly used material for steam generator tube. The object of this investigation is to study the influence of temperature, which is 95 °C and 250 °C, on the formation of the third body layer (TBL), and the role of TBL on the fretting wear behavior of 316 SS. Thus, the fretting wear experiment between 316 SS tube and 316 SS plate was carried out in the composite fretting motion of slip and impact in pure water environment. The experiment time was set as 24 h, 48 h, 72 h and 120 h. The results show that at 95 °C, TBL is hard and attaches closely to the surface, which can lead to uniform abrasion and result severe microploughing between the base materials. While at 250 °C, the existence of thick TBL can avoid direct contact between base materials, and it can be easily deformed by shear forces due to its ductility, which acts as a lubricant and reducing volume loss and wear coefficient. Finally, we can conclude that temperature affects the formation mechanism and properties of TBL, thus changing the fretting wear behavior.

Effect of Powder on Tribological and Electrochemical Properties of Nylon 66 and Ultra-High Molecular Weight Polyethylene in Water and Seawater Environments

Polymer materials are used increasingly in marine machinery and equipment; their tribological properties and effect on the water environment have garnered significant attention. We investigate the effect of water or seawater environment containing powder on tribology and electrochemistry of polymer materials. A friction test involving nylon 66 (PA66) and an ultrahigh molecular weight polyethylene (UHMWPE) pin–disc (aluminum alloy) is performed in seawater or water with/without polymer powder, and the solution is analyzed electrochemically. The results show that the tribological properties of the UHMWPE improved by adding the powder to the solution, whereas the PA66 powder demonstrates abrasive wear in a pure water environment, which elucidates that the synergistic effect of powder and seawater on UHMWPE reduces the wear, and the synergistic effect of pure water and powder aggravates the wear. The results of electrochemical experiments show that after adding powder in the friction and wear tests, the powder can protect the pin by forming a physical barrier on the surface and reducing corrosion, and the changes are more obvious in seawater with powder in it. Through electrochemical and tribological experiments, the synergistic effect of solution environment and powder was proved.

Comparative Failure Study of Different Bonded Basalt Fiber-Reinforced Polymer (BFRP)-AL Joints in a Humid and Hot Environment.

Fiber-reinforced polymer (FRP) materials are increasingly used in automotive industrial fields to achieve lightweight. In order to study the influence of high temperature and high humidity on the bonding structure between different materials, this paper selects basalt fiber-reinforced resin composite materials (BFRP) and aluminum alloy (Al), and uses Araldite® 2012 and Araldite® 2014, two adhesives, to make single lap joints (SLJs). The aging test was carried out for 0 (unaged), 10, 20, and 30 days under the environment of 80 °C/95% relative humidity (RH) and 80 °C/pure water. In this work, simple Fickian law was used to simulate the hygroscopic change law of dumbbell specimens of two adhesives and BFRP in a pure water environment. It was discovered that Araldite® 2012 is most affected by moisture, but the time to reach the maximum water absorption in Araldite® 2014 was shorter than in Araldite® 2012. The failure strength of the joint was obtained through a quasi-static tensile experiment, and it was found that the Araldite® 2014 adhesive joint first increased and then decreased in a high temperature environment. The strength increased by 11.63% after 20 days of aging under an 80 °C/95%RH environment, and increased by 16.66% after 10 days of aging under an 80 °C/pure water environment, which indicates that post-curing reaction occurred. The strength of Araldite® 2012 joints showed a downward trend. After 30 days of aging, it reduced by 40.38% under an 80 °C/95%RH environment and 41.11% under an 80 °C/pure water environment. By observing the load-displacement curve, it was found that, as time increased, the slope of the curve decreased, indicating that the stiffness of the bonded joint decreased with time. The failure modes of the joints were analyzed by macroscopic images and microscopic SEM methods, and the results showed that the surface failure transitions from a mixed failure to a complete tear failure over time. The failure of the basalt fiber/resin interface was because the interaction between the epoxy resin in the adhesive and the epoxy resin in BFRP was greater than the force between the basalt fiber layer and the epoxy resin layer in the BFRP sheet.

Shear-Induced Interfacial Structural Conversion Triggers Macroscale Superlubricity: From Black Phosphorus Nanoflakes to Phosphorus Oxide.

As a new two-dimensional (2D) material, black phosphorus (BP) exhibits great potential for friction reduction. However, achieving macroscale superlubricity with a BP coating remains a great challenge. In this study, we designed a new lubrication system to achieve superlubricity with a BP coating at the macroscale, involving the formation of a BP coating with deposited BP nanoflakes, followed by water lubrication. Robust superlubricity with a coefficient of friction of 0.001 can be achieved on the BP coating in a pure water environment. The superlubricity mechanism is mainly attributed to the shear-induced interfacial structural conversion of BP to phosphorus oxide, leading to the formation of tribofilms on the friction pairs with extremely low shear strength. This finding provides a new strategy for achieving superlubricity of 2D material coatings at the macroscale, which has important implications for the development of novel superlubrication systems for industrial applications.