Strong Repulsive Force Research Articles

Reversibly thermosecreting and convertible lubricative oil-in-water mixtures using multiple hydrogen bonding interactions

Achieving homogeneous oil and water mixing requires thorough droplet dispersions of both liquids. An additional component, such as a surfactant, particle, solvent or ion is normally required to stabilize the small liquid droplets by providing sufficiently low interfacial tensions or strong repulsive forces. Here we show that very stable oil-in-water mixtures can be created even at very high oil volume fractions by building multiple, high-strength hydrogen bonding interactions between water and a biocompatible and biodegradable oil trimethylolpropane trioleate, which make the oil molecules at the contact interface behave as pseudo-surfactants with ultrahigh interfacial activity. The resultant oil microdroplets can be reversibly thermosecreted from the continuous aqueous phase and lead to controllable formation/dissociation and switchable lubrication of the binary liquid mixture owing to the inherent thermal responsiveness of the intermolecular hydrogen bonding. Interestingly, although water is uncovered to possess a relatively poor lubricity, the liquid mixture yields an optimized lubrication that is even exceedingly comparable to pure oil at a water volume fraction as high as 80%.

Interactions Between [PdX4]2- (X=Cl, Br) Dianions in Presence of Counterions.

The interaction between two square palladium (II) dianions PdX4 2- (X=Cl, Br) is evaluated by crystal study and analyzed by quantum chemical means. The arrangement within the crystal between each pair of PdX4 2- neighbors is suggestive of a Pd⋅⋅⋅X noncovalent bond, which is verified by a battery of computational protocols. While the potential between these two bare dianions is computed to be highly repulsive, the introduction of even just two counterions makes this interaction attractive, as does the presence of a constellation of point charges. It is concluded that there is indeed a stabilizing Pd⋅⋅⋅X bond, but it is incapable of overcoming the strong coulombic repulsive force between two dianions. While the QTAIM, NBO, and NCI tools can indicate the presence of a noncovalent bond, they are unable to distinguish an attractive from a repulsive interaction.

“Tennis racket” hydrogel electrolytes to synchronously regulate cathode and anode of zinc-iodine batteries

Aqueous zinc-iodine (Zn-I2) batteries show great potential as energy storage candidates due to their high-safety and low-cost, but confronts hydrogen evolution reaction (HER) and dendrite growth at anode side and polyiodide shuttling at cathode side. Herein, “tennis racket” (TR) hydrogel electrolytes were prepared by the co-polymerization and co-blending of polyacrylamide (PAM), sodium lignosulfonate (SL), and sodium alginate (SA) to synchronously regulate cathode and anode of Zn-I2 batteries. “Gridline structure” of TR can induce the uniform transportation of Zn2+ ions through the coordination effect to hinder HER and dendrite growth at anode side, as well as hit I3− ions as “tennis” via the strong repulsion force to avoid shuttle effect at cathode side. The synergistic effect of TR electrolyte endows Zn-Zn symmetric battery with high cycling stability over 4500 h and Zn-I2 cell with the stably cycling life of 15000 cycles at 5 A g−1, outperforming the reported works. The practicability of TR electrolyte is verified by flexible Zn-I2 pouch battery. This work opens a route to synchronously regulate cathode and anode to enhance the electrochemical performance of Zn-I2 batteries.

Description of Short-Range Interactions of Carbon-Based Materials with a Combined AIREBO and ZBL Potential.

An accurate description of short-range interactions among atoms is crucial for simulating irradiation effects in applications related to ion modification techniques. A smooth integration of the Ziegler-Biersack-Littmark (ZBL) potential with the adaptive intermolecular reactive empirical bond-order (AIREBO) potential was achieved to accurately describe the short-range interactions for carbon-based materials. The influence of the ZBL connection on potential energy, force, and various AIREBO components, including reactive empirical bond-order (REBO), Lennard-Jones (LJ), and the torsional component, was examined with configurations of the dimer structure, tetrahedron structure, and monolayer graphene. The REBO component is primarily responsible for the repulsive force, while the LJ component is mainly active in long-range interactions. It is shown that under certain conditions, the torsional energy can lead to a strong repulsive force at short range. Molecular dynamics simulations were performed to study the collision process in configurations of the C-C dimer and bulk graphite. Cascade collisions in graphite with kinetic energies of 1 keV and 10 keV for primary knock-on atoms showed that the short-range description can greatly impact the number of generated defects and their morphology.

Pressure retarded osmosis enhanced by micro-nano bubbles: Coupling effects of operation conditions and mass transfer resistance analyses

The concentration polarization is one of the bottlenecks of pressure retarded osmosis (PRO) for industrial-scale application. Micro-nano bubbles (MNBs) could form a strong repulsion and shear force on the membrane surface, thus, the degree of concentration polarization is reduced, and hence, both the water flux and power density could be increased. In this paper, the synergistic effects of MNBs with concentration, temperature, water and air flow rates, pressure, and spacers were investigated through membrane cell scale experiments. A numerical model with trans-membrane heat flux and MNBs effects is built and validated by the experiment results. The mechanism of strengthening effect of MNBs could be explained. A maximum promotion of 6.28 % was achieved for concentration combination of 0.171–1 mol/L. However, the promotion ratio of water flux was deceased significantly with higher temperature (<1 % for 45 °C) and higher pressure (nearly zero for 7 bar). The light MNBs would be pushed away from membrane under larger water flux with larger osmotic pressure difference. The variations of mass transfer resistances, and the thicknesses of boundary layers were discussed. Moreover, the key variables that have significant impacts on the metrics of PRO process were identified through partial least squares analysis.

New stable waterborne amorphous polylactic acid/organoclay nanocomposites prepared using emulsification solvent evaporation method

AbstractWater based polylactic acid (PLA)‐surface modified montmorillonite (MMt) nanocomposites as biobased formulations for paper coating were successfully developed using emulsification solvent evaporation method. Electrostatic and steric stabilization mechanisms have contributed to the production of stable emulsions up to 5 months at 23 ± 1°C, revealing strong repulsive forces generated between the nanoparticles as confirmed by zeta potential (ζ) and dynamic light scattering (DLS) analysis. MMt particles were fully encapsulated by PLA as demonstrated by transmission electron microscopy (TEM) micrographs. Meanwhile the film formation process highlighted the importance of emulsifier's type and solubility in the polymer matrix, as no films were obtained when sodium oleate was used alone compared with continuous, homogeneous, and free‐standing films obtained when the combination Tween 80 (80 wt%)—sodium oleate (20 wt%) was used. Scanning electron microscopy (SEM) micrographs of the cross‐section's surfaces showed homogeneous dispersion of the MMt particles with no clusters or agglomerates formed. Thermal analyses using differential scanning calorimetry and thermogravimetric analysis (DSC‐TGA) showed an overall reduction in the glass transition temperature (Tg) and the thermal stability of neat PLA, whoever this reduction was recovered when MMt was added due to the confinement effect. Thickened PLA and PLA/MMt emulsions using 1 wt% xanthan gum showed a non‐Newtonian behavior and shear thinning flow with suitable viscosity values for paper coating applications.Highlights Development of stable PLA/organoclay nanocomposite aqueous dispersions. Steric and electrostatic mechanisms provided excellent stability. Full encapsulation of organoclay platelets in nanometric PLA particles. Formation of free‐standing films from PLA/organoclay emulsions. Thickened PLA/organoclay emulsions using Xanthan gum for paper coatings.

Tuning Multipolar Mie Scattering of Particles on a Dielectric-Covered Mirror.

Optically resonant particles are key building blocks of many nanophotonic devices such as optical antennas and metasurfaces. Because the functionalities of such devices are largely determined by the optical properties of individual resonators, extending the attainable responses from a given particle is highly desirable. Practically, this is usually achieved by introducing an asymmetric dielectric environment. However, commonly used simple substrates have limited influences on the optical properties of the particles atop. Here, we show that the multipolar scattering of silicon microspheres can be effectively modified by placing the particles on a dielectric-covered mirror, which tunes the coupling between the Mie resonances of microspheres and the standing waves and waveguide modes in the dielectric spacer. This tunability allows selective excitation, enhancement, suppression, and even elimination of the multipolar resonances and enables scattering at extended wavelengths, providing transformative opportunities in controlling light-matter interactions for various applications. We further demonstrate with experiments the detection of molecular fingerprints by single-particle mid-infrared spectroscopy and with simulations strong optical repulsive forces that could elevate the particles from a substrate.

Oversaturating Liquid Interfaces with Nanoparticle‐Surfactants

AbstractAssemblies of nanoparticles at liquid interfaces hold promise as dynamic “active” systems when there are convenient methods to drive the system out of equilibrium via crowding. To this end, we show that oversaturated assemblies of charged nanoparticles can be realized and held in that state with an external electric field. Upon removal of the field, strong interparticle repulsive forces cause a high in‐plane electrostatic pressure that is released in an explosive emulsification. We quantify the packing of the assembly as it is driven into the oversaturated state under an applied electric field. Physiochemical conditions substantially affect the intensity of the induced explosive emulsification, underscoring the crucial role of interparticle electrostatic repulsion.

Oversaturating Liquid Interfaces with Nanoparticle-Surfactants.

Assemblies of nanoparticles at liquid interfaces hold promise as dynamic "active" systems when there are convenient methods to drive the system out of equilibrium via crowding. To this end, we show that oversaturated assemblies of charged nanoparticles can be realized and held in that state with an external electric field. Upon removal of the field, strong interparticle repulsive forces cause a high in-plane electrostatic pressure that is released in an explosive emulsification. We quantify the packing of the assembly as it is driven into the oversaturated state under an applied electric field. Physiochemical conditions substantially affect the intensity of the induced explosive emulsification, underscoring the crucial role of interparticle electrostatic repulsion.

Direct Evidence of Electric Double Layer (EDL) Repulsive Force Being Responsible for the Time-Dependent Behavior of Clay Gels in the Structural Rejuvenation Mode.

A strong EDL repulsive force is needed to accentuate the time-dependent behavior of charge and shape anisotropic clay gels at the stepdown shear rate. This force was strengthened by P2O74- adsorption, increasing the negative charge density of the clay particles. At the stepdown shear rate of 10 s-1, it is strong enough to disrupt the flow-aligned structure attained at 1000 s-1 and orient the particles to form more bonds. The resultant outcome is stepdown shear stress increasing with time until these structure disruption and bond formation processes reach an equilibrium state. The number of lower energy approach configurations (-ve face - +ve edge) for bonding is reduced by the strengthened EDL repulsive force, slowing the bonding process. The time to reach the equilibrium stepdown shear stress value increased initially and then decreased and became zero at a high negative charge density where the charge anisotropy of the particles no longer exists. The need of a sufficiently strong EDL repulsive force for the display of time-dependent behavior is true for all clay gels: Laponite, hectorite, NaMnt, sepiolite, and kaolin gels. The untreated NaMnt gel already displayed time-dependent behavior as its EDL repulsive force is sufficiently strong. The same EDL-control time-dependent behavior was obtained if pH was used to vary the negative charge density of the clay particles.

Experimental investigation on inter-particle settling dynamics of multiple spherical particles released side by side at intermediate Reynolds numbers

The settling of solid particles in fluid constitutes a fundamental and crucial aspect with applications spanning various natural phenomena and engineering processes, including sediment transport and wastewater treatments. This paper delves into an experimental investigation aimed at comprehending the settling dynamics and self-organization of multiple spherical particles settling side by side at intermediate Reynolds numbers. The study employs an electromagnetic release device, previously developed for controlled settling of particles under gravity, ensuring simultaneous release with zero initial rotation and velocity. This research captures settling trajectories and provides insight into the flow fields surrounding particles by utilizing particle tracking and particle image velocimetry. The experiments systematically investigate the influence of the settling patterns, the flow fields, the velocities of particles, and their dependence on Reynolds number Re (Re = 52–258), the number of particles n (n = 3–8), as well as the initial spacing between particles l0* (l0* = 0–2). The results consistently reveal a left–right symmetry about the centerline in settling patterns, flow fields, and particle rotations across all values of n, l0*, and Re. The final settling pattern exhibits distinct shapes dependent on l0*: a “V” or “M” shape for l0* &amp;lt; 0.2, a “concave-downward” shape for 0.2 &amp;lt; l0* &amp;lt; 2, and a “straight-line” shape for l0* ≥ 2. The lateral spread of particles increases with time, particularly pronounced with smaller l0* and larger Re, attributed to strong repulsive forces between neighboring particles. Correspondingly, the maximum of horizontal velocities reduces from outside to inside and increases with decreasing l0* and increasing Re. The inner vortices are smaller than the outer vortices, which causes the lateral spread. The vertical spread increases with n but remains insensitive to Re. The average terminal settling velocities for all particles in the array are consistently smaller than those for single particles, as a portion of kinetic energy contributes to horizontal motions.

Preparation and Characterization of Novel Polyelectrolyte Liposomes Using Chitosan Succinate Layered over Chitosomes: A Potential Strategy for Colon Cancer Treatment.

Chitosan succinate is distinguished by its ability to shield the loaded drug from the acidic environment, localize and keep the drug at the colon site, and release the drug over an extended time at basic pH. The current study attempts to develop polyelectrolyte liposomes (PEL), using chitosan and chitosan succinate (CSSC), as a carrier for liposomal-assisted colon target delivery of 5 fluorouracil (5FU). The central composite design was used to obtain an optimized formulation of 5FU-chitosomes. The chitosan-coated liposomes (chitosomes) were prepared by thin lipid film hydration technique. After that, the optimized formulation was coated with CSSC, which has several carboxylic (COOH) groups that produce an anionic charge that interacts with the cation NH2 in chitosan. The prepared 5FU-chitosomes formulations were evaluated for entrapment efficiency % (EE%), particle size, and in vitro drug release. The optimized 5FU-chitosomes formulation was examined for particle size, zeta potential, in vitro release, and mucoadhesive properties in comparison with the equivalent 5FU-liposomes and 5FU-PEL. The prepared 5FU-chitosomes exhibited high EE%, small particle size, low polydispersity index, and prolonged drug release. PEL significantly limited the drug release at acidic pH due to the deprotonation of carboxylate ions in CSSC, which resulted in strong repulsive forces, significant swelling, and prolonged drug release. According to a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay, PEL treatment significantly decreased the viability of HT-29 cells. When compared to 5FU-liposome and 5FU-chitosome, the in vivo pharmacokinetics characteristics of 5FU-PEL significantly (p < 0.05) improved. The findings show that PEL enhances 5FU permeability, which permits high drug concentrations to enter cells and inhibits the growth of colon cancer cells. Based on the current research, PEL may be used as a liposomal-assisted colon-specific delivery.

Evaluation for water stability of bitumen mixture with multi-scale method

The interaction forces were investigated between matrix bitumen and four kinds of aggregates, including basalt, granite, limestone A, and limestone B in various pH solutions. The aim was to accurately evaluate the water damage resistance of bitumen mixtures at macroscopic and microscopic levels with a conjunctive method of boiling water tests, atomic force microscopy (AFM) colloidal probe technique, zeta potential measurements, and molecular dynamics simulation. Macroscopic evaluation was conducted through indoor water-boiled flaking rate tests to analyze the flaking rate and adhesion class of bitumen and aggregate. The microscopic forces were measured by AFM probe technique between bitumen and aggregate, zeta potential measurements were carried out and the extended Derjaguin-Landau-Verwey-Overbeek (DLVO) theory was employed to interpret the bitumen–aggregate interaction behaviors. Molecular dynamics simulations were considered to explain the interface binding tendency between bitumen and aggregate. The AFM force measurements showed that the long-range repulsion forces changed to attractive forces and high adhesive forces with the pH change from 4 to 6. However, the strong long-range repulsive forces were decreased, compounded with a relative low adhesion in the alkaline solution. The long-range force between granite and bitumen was a strong attraction, and adhesion was strong when the solution pH was 4, which is a more special phenomenon. It may be due to the electrostatic attraction between the positive charge on the granite surface and the negative charge on the bitumen surface. Zeta potential values of bitumen droplets and aggregate particles exhibited an overall decreasing trend with increasing solution pH, and the variation of surface potential value is consistent with the variation trend of long-range force between aggregate and bitumen. The microscopic forces between bitumen and aggregate measured by AFM were validated by molecular dynamics simulations, revealing a strong correlation between debonding work and interfacial forces. The results indicate that the adhesion between aggregates and bitumen in aqueous solution followed the order: limestone A > limestone B > basalt > granite, and alkaline conditions are not conducive to preventing water damage in bitumen mixtures. It provides insights into the water stability mechanism of bitumen-aggregate at macroscopic and microscopic scales, offering theoretical support for preventing water damage in bitumen pavements.

Exploring the role of surface hydrogenation in anti-friction of circular-textured amorphous carbon film from the atomic level and its dependence on textured shape

Hydrogenating the amorphous carbon (a-C) surface can achieve the ultra-low friction performance. However, the effect of surface hydrogenation on anti-friction of textured a-C surface, especially its dependence on different textured shapes, is still lack of study; the information on the complicated friction interfacial also remains unclear due to the limitation of in-situ characterization in experiment. Here, the friction behavior of circular-textured a-C film was investigated by reactive molecular dynamics simulations, and its dependence on the hydrogenated degree of textured a-C surface was mainly focused, in which the effect from textured shape was also comparatively studied. Results show that the anti-friction efficiency of the circular-textured a-C film strongly depends on the surface hydrogen content; when the surface H content is 31.0 %, the friction coefficient decreases by 97.5 %, which is attributed to the passivation effect of H atoms on the a-C surface, inhibiting the generation and crosslinking of unstable dangling bonds. Moreover, the migration of H atoms in the friction process provides a strong repulsive force, which also significantly reduces the shearing strength of the interface and the friction coefficient. In particular, further study discloses that the effect of textured shapes of a-C surface on friction behavior is also related with the surface H content; with the increase of H content, the textured shape of a-C surface, which exhibits the low-friction performance, transforms from rectangular to circular-textured one, and the corresponding low-friction mechanism also changes from the passivation of friction interface to H-induced repulsive effect. These results provide an effective way to develop an efficient a-C anti-friction system.

Dispersing boron nitride nanosheets with carboxymethylated cellulose nanofibrils for strong and thermally conductive nanocomposite films with improved water-resistance

BNNS (boron nitride nanosheets)-CNF (cellulose nanofibrils) nanocomposite films have attracted increasing attention for advanced thermal management applications. However, the nanocomposite films reported so far generally suffer from unsatisfactory overall performance, especially for thermal conductivity and tensile strength. In this work, a nanocomposite film with excellent overall performance was prepared by using CCNF1.2 (carboxymethylated CNF with 1.2 mmol·g−1 carboxyl content) simultaneously as effective dispersant and reinforcement matrix for BNNS. The high aspect ratio of CCNF1.2 is primarily responsible for its excellent dispersion capability for BNNS, which provides strong steric hindrance repulsion force. Meanwhile, CCNF1.2 manifests the strongest hydrophobic-hydrophobic interactions with BNNS, and its carboxyl groups completely interact with the -OH of BNNS by hydrogen bonding. As a result, the BNNS-CCNF1.2 film (50 wt% BNNS) exhibits compacted aligned structure and superior comprehensive performance (125.0 MPa tensile strength, 17.3 W·m−1·K−1 in-plane thermal conductivity, and improved water resistance). This work demonstrates the effectiveness of CCNF in improving the overall performance of BNNS-CNF films and paves the way for their practical application in the advanced thermal management of next-generation electronic devices.

Performance evaluation of superconductive-assisted machining (SUAM) with superconducting tape and two permanent magnets

In this study, the repulsive force causing magnetic levitation for superconductive-assisted machining (SUAM) is calculated using the finite element method. Although bulk superconductors have been used for SUAM, here, we propose a magnetic levitation tool that uses superconducting tape. To obtain a stronger repulsive force, various models of a SUAM are designed and calculated. The results show that a strong repulsive force can be obtained by using two permanent magnets. In addition, even if the superconducting tape is rotated during stacking due to stacking errors, the repulsive force is not affected, indicating that there is no need to optimize the stacking method. Therefore, we expect that increasing the number of layers will generate a repulsive force that is greater than that obtained with bulk superconductors.

Controlled salinity water flooding and zeta potential: Insight into a novel enhanced oil recovery mechanism

Controlled salinity water flooding also known as engineered water flood has been tested as a potential enhanced oil recovery (EOR) method in laboratory as well as at pilot/field scale. However, there are cases seen where the method has failed to show its potential for EOR. Scientists believe that the lack of understanding of case specific underlying mechanism is the primary reason. Many of the literatures claims reduction of interfacial tension as the primary oil recovery mechanism; but recent findings highlighted that modification of electrical charges on rock surface with response to injection brine salinity has greater effect. In order to investigate the same and in search of more insightful mechanism, in this study we have designed and performed experiments with selected chemicals which can modify surface properties of sandstone and also the oil water interfacial tension. The electrical charge of the rock surface and oil–brine​ interfacial tension were modified by tuning salinity of injection water and adding surfactants (sodium dodecyl benzene sulfonate, SDBS and cetyltrimethylammonium bromide, CTAB). The electrical charge of the sandstone surfaces was quantified with zeta potential measurement. The oil recovery potential of the injection fluids was tested through laboratory core flooding experiments at controlled near reservoir conditions. Superposition of all the obtained results revealed that low salinity injection brine modifies the sandstone surface to higher negatively charged state than high salinity water. Therefore, with a negatively charged oil–brine interface it causes strong repulsive forces promoting detachment of residual oil and subsequent mobilization. The hypothesis is also proved by the fact that SDBS in spite of resulting in a lower interfacial tension reduction than CTAB yielded higher oil recovery. This is because of the negative zeta potential caused by SDBS to sandstone surface in comparison to the positive zeta potential observed in the case of CTAB.

Spectroscopic, DFT study, and molecular docking investigation of N-(3-methylcyclohexyl)-2-phenylcyclopropane-1-carbohydrazide as a potential antimicrobial drug

Detailed theoretical molecular modeling, spectral (NMR, FT-IR, and UV–vis) analysis, electronic properties, and in silico biological study of N-(3-Methylcyclohexyl)-2-phenyl cyclopropane-1-carbohydrazide (PI2) has been studied in this present research using experimental and electronic structure theory calculations based on density functional theory (DFT). While the quantum calculations were done using DFT method at the B3LYP/6-31+G(d) level of theory, the characterization of PI2 was carried out with 1HNMR, UV-vs, and FT-IR spectroscopy. The major vibrations recorded for the studied compound were those of amide, CC, C–C, N–H, and C–H stretch. The UV–visible excited states calculation using Time Dependent Density Functional Theory (TD-DFT) showed the highest orbital contributions in S0 – S5 with π→π* assignment for all the studied phases. The visual study of weak interaction (NCI), nonlinear optics, and the natural bond orbital (NBO) results showed majorly a steric effect due to strong repulsive forces and van der Waals forces, a better NLO property in the studied compound as compared with urea (standard) and the intramolecular charge transfer in the studied compound showed the highest energy of stabilization of 66.79KCal/Mol for the donor – acceptor interaction of LP (1) N23 → π*C25 - O26 respectively. Molecular docking investigation of PI2 was achieved using six (6) target proteins from which two were gram negative; Escherichia coli (2NYU) and Pseudomonas aeruginosa (7CID), 2 g positive; Staphylococcus aureus (6P9J) and Streptococcus pyogenes (1MG1), one helminth; Ascaris lumbricoides (3FJU) and one fungus; Candida albican (6TZ6). The PI2 docked results were compared with the docked results obtained for the standard drugs (Ciprofloxacin, Albendazole, and Fluconazole). The studied structure showed the highest binding affinity of −8.5 kcal/Mol for 1MG1 as compared with −6.9 kcal/Mol for that of the standard drug. Finally, ADMET properties of PI2 were computed and the result showed a better drug property of the studied compound.

Novel neutron decay mode inside neutron stars

We explore the suggestion that the neutron lifetime puzzle might be resolved by neutrons decaying into dark matter through the process, n → χ χ χ, with χ having a mass one-third of the neutron. In particular, we examine the consequences of such a decay mode for the properties of neutron stars. Unlike an earlier suggested decay mode, in order to satisfy the constraints on neutron star mass and tidal deformability, there is no need for a strong repulsive force between the dark matter particles. This study suggests the possibility of having hot dark matter at the core of the neutron star and presents a possible mechanism of dark matter cooling, and examines the possible signal of neutrons decaying in this way inside the neutron star right after its birth.

Defeating hydrogen-induced grain-boundary embrittlement via triggering unusual interfacial segregation in FeCrCoNi-type high-entropy alloys

Metallic materials are mostly susceptible to hydrogen embrittlement (HE), which severely deteriorates their mechanical properties and causes catastrophic failures with poor ductility. In this study, we found that such a long-standing HE problem can be effectively eliminated in the Fex(CrCoNi)1-x face-centered-cubic (fcc) high-entropy alloys (HEAs) by triggering the localized segregation of Cr at grain boundaries (GBs). It was revealed that increasing the Fe concentration from 2.5 to 25 at. % leads to substantially improved HE resistance, i.e., the ductility loss decreases from 70% to 6%. Meanwhile, the fracture mode transformed from the intergranular to the transgranular mode. Multiscale microstructural analyses demonstrated that the Fe2.5Cr32.5Co32.5Ni32.5 and Fe25Cr25Co25Ni25 alloys show negligible differences in the phase structure, grain size, and grain-boundary (GB) character. However, interestingly, the near atomic-resolution elemental mapping revealed that an increased Fe concentration promotes the nanoscale Cr segregation at the GBs, which is primarily motivated by the strong repulsive force between Cr and Fe and the low self-binding energy of Cr. Such unusual interfacial segregation of Cr, which has not been reported before in the Fe25Cr25Co25Ni25 alloy, helps enhance the GBs’ cohesive strength and suppresses the local hydrogen segregation at GBs due to the deceased GB energy, leading to the outstanding HE resistance. These findings decipher the origins of the vastly-improved HE resistance in current FeCrCoNi-type HEAs, and meanwhile, provide new insight into the future development of novel high-performance structural alloys with extraordinary immunity to hydrogen-induced damages.