Self-healing Effect Research Articles

PH Stimuli-Responsive, Rapidly Self-healable Coatings Enhanced the Corrosion Resistance and Osteogenic Differentiation of Mg-1Ca Osteoimplant.

Mg-Ca alloys have emerged as a promising research direction for biomedical implants in the orthopedic field. However, their clinical use is deterred by their fast corrosion rate. In this work, a pH stimuli-responsive silk-halloysite (HNT)/phytic acid (PA) self-healing coating (Silk-HNT/PA) is constructed to slow down the corrosion rate of Mg-1Ca alloy and its cell viability and osteogenic differentiation ability are enhanced. The Silk-HNT/PA coating exhibits appealing active corrosion protection, by eliciting pH-triggerable self-healing effects, while simultaneously affording superior biocompatibility and osteogenic differentiation ability. Moreover, in vivo studies by histological analysis also demonstrate better osseointegration for the Silk-HNT/PA coated Mg-1Ca alloy. In summary, the Silk-HNT/PA coating in the present study has great potential in enhancing the biomedical utility of Mg alloys.

Linear and nonlinear nonparaxial loss-proof accelerating beams induced in a coherent atomic medium

(Objective) Owing to their unique properties, nonparaxial self-accelerating beams can potentially be used for several applications. Additionally, atomic vapors are of considerable interest in the observation of important optical and photonic phenomena. However, research on nonparaxial loss-proof accelerating beams in an atomic system has been limited to this end, this study performs a numerical analysis to demonstrate nonparaxial loss-proof accelerating beams in atomic vapor with linear and nonlinear susceptibilities. (Methods) These beams, as the eigenmodes of the Helmholtz equations with linear and nonlinear losses, can propagate robustly in an absorbing atomic system and preserve their beam shape owing to their enhanced self-healing effect. Such loss-proof beams can sustain the peak intensity and the structure of their main lobe region over large distances. Meanwhile, the under-healing and over-healing effects gradually attenuate and increase the intensity of the main lobe of the non-eigenmodes during propagation, respectively. Linear loss-proof beams also exhibit a nonparaxial accelerating Talbot effect. (Result) The results indicate that atomic vapor can serve as a promising medium for the generation of nonparaxial loss-proof accelerating beams in the future.

Effect of shape memory alloy fiber content and preloading level on the self-healing properties of smart cementitious composite (SMA-ECC)

Shape memory alloy (SMA) fibers are used in engineered cementitious composite (ECC) to achieve good self-healing properties in the newly developed smart cementitious material (SMA-ECC). This study focuses on the effect of SMA fiber content and preloading level on the self-healing properties of SMA-ECC through a two-stage four-point bending test. The self-healing effect was evaluated in terms of recovery of cracks, mechanical properties, and internal damage before and after self-healing. The results showed that the efficiency of the healing of cracks reduced with the increase in the width of the initial cracks. Cracks less than 50 µm width can be healed in SMA-ECC, while cracks larger than 200 µm width were the upper limit for the healing. The efficiency of the self-healing in terms of crack closure increased significantly with increasing SMA fiber content from 0.3% to 0.7% but did not change obviously when SMA fiber content increased from 0.7% to 1%. The recovery of flexural properties and damage decreased significantly with increasing preloading level. A high SMA fiber content was required for self-healing behavior at a high preloading level. At the pre-loading ratio of 50% and 70%, the recovery of flexural properties reached the maximum at the SMA fiber content of 0.7%. But at the pre-loading ratio of 90%, the recovery of flexural properties increased with increasing fiber content.

The Influence of the Different Cementitious Material on Self-Healing of Microcracks in Shotcrete

Due to a particular construction process, the shotcrete structure is affected by external load, material aging, and external temperature during use, with cracks inevitably appearing. Cracks are formed from microstate gradually, and thus controlling the development of microcracks in the early phase can effectively improve the strength and impermeability of shotcrete. In this study, the method of laboratory experiment and analysis is adopted to study the effect of ettringite on achieving the self-healing effect of shotcrete. The test results show that: (1) after encountering water, ettringite effectively plays a microexpansion effect to fill the pores, helping shotcrete achieve the effect of waterproofing and self-healing, which is very suitable for single-layer lining structures with water seepage. (2) The content of ettringite is inversely proportional to the change law of pore structure. When the content of ettringite increases, the porosity and harmful pores proportion have a significant decrease. (3) Fly ash and mineral powder with a mixing amount of about 30% will not affect the strength of the concrete, while prolonging the time of the effect of ettringite, will effectively improve the impermeability of the shotcrete.

Two birds with one stone: Nanocontainers with synergetic inhibition and corrosion sensing abilities towards intelligent self-healing and self-reporting coating

A smart coating integrating high-performance self-healing and sensitive self-reporting abilities was developed based on mesoporous SiO2 nanoparticles (MSN) containing both 1,10-phenanthroline-5-amine (Phen-NH2) and cetyltrimethylammonium bromide (CTAB). In the obtained MSN-PC nanocontainers, Phen-NH2 functioned as both the corrosion inhibitor and the coloration species, while CTAB acted as not only the template agent but also the corrosion inhibitor. The synthesis of MSN-PC was achieved in a facile one-step process with high encapsulation degree, and both Phen-NH2 and CTAB exhibited the accelerated release behaviors from MSN-PC triggered by pH variation. Electrochemical impedance spectroscopy (EIS) measurement and quantum chemical calculation results confirmed the synergistic inhibition effect of Phen-NH2 and CTAB against the corrosion of steel substrate and thus a self-healing effect of the damaged coating. Compared with the blank epoxy coating, the healed epoxy coating containing 4 wt% of MSN-PC could increase the low frequency impedance modulus by more than 20 times after 120 h of immersion in 3.5 wt% NaCl solution, hence suppressing the corrosion activity on the exposed metal surface. In addition to the self-healing property, the generated Fe2+ ions from the anodic site of exposed steel surface could quickly react with the released Phen-NH2 from MSN-PC nanocontainers to produce a prominent red color, achieving the timely indication of coating damage within 20 min of salt spray test. The smart coating realized sensitive corrosion visualization while significantly delaying the corrosion degradation, which holds great potential for long-term corrosion protection.

Photothermal and pH dual-responsive self-healing coating for smart corrosion protection

• Sandwich-like rGO@MS-P-BTA microcapsules are designed to achieve both the pH-sensitive and photothermal-responsive actions. • rGO@MS-P-BTA microcapsules are incorporated into epoxy to prepare a self-healing coating. • The photothermal effect of rGO can not only activate the shape memory effect of epoxy, but also facilitate the release of BTA to suppress the corrosion activity. • PDMAEMA as a pH-driven “gatekeeper” realizes the controlled release of BTA. • The self-healing coating shows a fast healing effect and a prominent healing efficiency. A novel self-healing coating with photothermal and pH dual-responsive properties has been designed to protect carbon steel against corrosion by loading the stimuli-responsive microcapsules into a shape memory epoxy coating. The sandwich-like microcapsules were based on reduced graphene oxide/mesoporous silica (rGO@MS) assembled with a pH-responsive poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) layer, and were loaded with benzotriazole (BTA) inhibitors (abbreviated as rGO@MS-P-BTA). Under near-infrared (NIR) light irradiation, the prominent photothermal effect of rGO could not only elevate the coating temperature to activate the shape memory effect and close the coating scratch, but also facilitate the release of corrosion inhibitors to suppress the corrosion activity. Moreover, the PDMAEMA as a pH-driven “gatekeeper” realized the controlled release of BTA from microcapsules at acid conditions. The surface morphology analysis, electrochemical impedance spectroscopy (EIS), and scanning electrochemical microscopy (SECM) were performed to evaluate the self-healing performance of the composite coatings. The results showed that the combination of NIR light and pH-responsive self-healing effects endowed the coating with short healing time and prominent healing efficiency.

Controllable Degradable Plasma Electrolytic Oxidation Coated Mg Alloy for Biomedical Application

A controllable degradable coating on Mg alloy based on plasma electrolytic oxidation (PEO) process is reported for the first time. The reported results show that introduction of silica nanoparticles into PEO electrolytes leads to their reactive incorporation in coatings and thus influencing the degradation behavior. Dissolution of amorphous phases facilitates chemical reaction with components of simulated body fluid, resulting in self-healing effect via redeposition of insoluble conversion products. The dynamic balance between dissolution of the original coating and reconstruction of corrosion layer is mainly determined by the phase composition of the coating as well as the surrounding corrosive medium.

Self-healing of the bored helico-conical beam.

We investigate the dynamic evolution and self-healing properties of the bored helico-conical beams with different filter parameter S in this paper. The relative error coefficient, D, is utilized to judge the self-healing effect of the bored helico-conical beam. The result demonstrates that the self-healing effect of the bored beams will be perfect when D approaches to 0. We also discuss the influence of the filter parameter S on the effective self-healing distance theoretically and experimentally. The result demonstrates that the effective self-healing distance decreases exponentially with the increasing filter parameter S. Moreover, the corresponding transverse energy flows of the bored beams are analyzed. The experimental results of the dynamic evolution for the bored helico-conical beams agree with the simulation ones well.

Mechanism of Photocurrent Degradation and Contactless Healing in p-Type Mg-Doped Gallium Nitride Thin Films.

Light-induced degradation (LID) phenomenon is commonly found in optoelectronics devices. Self-healing effect in halide lead perovskite solar cells was investigated since the electrons and holes in the shallow traps could escape easily at room temperature. However, the degradation in the semiconductors could not easily recover at room temperature, and many of them needed annealing at temperatures in the several hundreds, which was not friendly to the integrated optoelectronic semiconductor devices. To solve this problem, in this work, LID effect of photocurrent in p-type Mg-doped gallium nitride thin films was investigated, and deep defect and vacancy traps played a vital role in the LID and healing process. This work provides a contactless way to heal the photocurrent behavior to its initial level, which is desirable in integrated devices.

Investigation of the macro performance, mechanism, and durability of multiscale steel fiber reinforced low-carbon ecological UHPC

China proposes a carbon peak by 2030 and carbon neutrality by 2060; reducing carbon dioxide emissions and capturing and using carbon dioxide has become a research focus. As a low-carbon ecological cement, sulphoaluminate cement (SAC) has gradually replaced ordinary Portland cement and has become a research hotspot. SAC has the advantages of high early strength, low CO2 emission, fast setting, and fast hardening. It is widely used in emergency repairs, rapid repairs, and offshore engineering. This paper developed a new low-carbon ecological ultra-high-performance concrete with high strength and excellent durability, namely sulfoaluminate cement-based reactive powder concrete (SACRPC). This work researched the effect of different scale steel fiber on macro performance (including rheological property, workability, and mechanical properties), durability, and micro/ nanostructure of SACRPC. Various characterization methods showed that the addition of mSF (micro steel fiber) improved the pore structure of the SACRPC, it was increased the porosity of the matrix, and provided enough space for the growth of hydration products AFt (ettringite), AH3 (gibbsite), and C-S-H (Calcium Silicate Hydrate); thus, it accelerated the hydration process of the SACRPC. The hydration products filled the pores of the SACRPC tightly bonded the fiber and the matrix. It was revealed that the multi-level and multiscale reinforced mechanism, namely hydration products, contributed to micro/nanostructure, mSF bridged micro-cracks, and MSF (macro steel fiber) prevented macro-cracks. In the sulfate erosion experiment, SO42- ions entered the matrix and occurred a chemical reaction; AFt regenerated on the surface and inside the SACRPC with a fibrous morphology and smaller crystals. The regenerated AFt filled the pores of the SACRPC and refined the pore structure. The whole process was similar to the self-healing effect of concrete. The unhydrated cement particles reacted with water and formed new hydration products that healed the cracks.

Fundamental Properties and Self-Healing Performance of Repair Mortar with Solid Capsules Made Using Inorganic Reactive Powder.

Self-healing cement composites are generally produced by using materials such as inorganic powders, bacteria pellets, and microcapsules. Among them, inorganic powder-type healing materials tend to decrease in healing performance over time because they react relatively quickly. Accordingly, this study encapsulated self-healing inorganic reactive powders in solid capsules (SC) in order to delay their reaction. The capsule surface was coated with a membrane to prevent moisture from permeating it. SC were utilized to provide the self-healing effect to the repair mortar. SC were mixed at three rates (0%, 5%, and 10%) by the binder mass of the repair mortar. The fundamental properties, including rheology, table flow, strength, and length change, and the self-healing performance of the self-healing repair mortar mixes were investigated. It was found that the rheological and mechanical properties of the repair mortar decreased slightly as the amount of SC increased. On the other hand, for a crack width of 0.25 mm and crack inducing age of 28 days, the healing performance of repair mortar specimens containing SC was at least 20 pt% better than that of plain repair mortar after a healing period of 28 days.

A New Self-Healing Triboelectric Nanogenerator Based on Polyurethane Coating and Its Application for Self-Powered Cathodic Protection.

With the increasing demand for carbon neutrality, the development of renewable and recycle green energy has attracted wide attention from researchers. A novel self-healing triboelectric nanogenerator (TENG) was constructed by applying a linear silicone-modified polyurethane (PU) coating as a triboelectric layer, which was obtained by reacting hydroxypropyl silicone oil and hexamethylene diisocyanate under the catalysis of Sn. The linear self-healing coating as the friction electrode could effectively alleviate the damages of TENG devices during long-term energy harvesting. When the triboelectric layer of the TENG device shows abrasion, the broken silicone-modified polyurethane polymer chains would gradually be cross-linked again through hydrogen bonding to achieve a self-healing effect. The entire self-healing process of the friction coating could be completed in 30 min at room temperature. The PU-based self-healing TENG exhibits an evident and stable output performance with a short-circuit current of 31.9 μA and output voltage of 517.5 V after multiple cutting-healing cycles, which could light 480 commercial LEDs. Besides, a self-powered cathodic protection system supplied by the self-healing TENG was constructed, which could transfer negative triboelectric charges to the protected metal surface to achieve an anti-corrosion effect by harvesting mechanical energy. Due to the self-healing characteristics of the TENG device as the power supply part, this intelligent system possesses great application potential in the long-term corrosion protection of multiple metal application industries, such as the marine industry.

Restructuring NiO to LiNiO2: Ultrastable and reversible anodes for lithium-ion batteries

The discovery of active materials with long-term stability for lithium-ion batteries has always been a major challenge in the energy storage industry. Recently, by using the self-healing effect of hydrogen bonding in polymeric structures, researchers have developed a good strategy to prevent the pulverization of high-capacity anode materials, including those based on Si. However, these anode materials still show limited lifetimes owing to the self-degradation of their structure. In this study, we first demonstrated the self-healing effect resulting from the restructuring of NiO nanomaterials to LiNiO2 with a highly stable capacity for lithium storage applications. The investigated NiO nanosheet anode showed a high initial discharge/charge capacity of 1434/1113 mAh g−1, which gradually degraded during the initial lithiation process. However, this capacity could be recovered with an acceptable cyclic performance. The stable high capacity of ∼ 750 mAh g−1 at 0.5 A g−1 could be restored to ∼ 1200 mAh g−1 at 0.1 A g−1. The ex situ X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy analyses of the healable cell were carried out to analyze the structural transformation of NiO into LiNiO2. This material showed stable cycling performance at 1.0 A g−1 for 1000 cycles and at 10.0 A g−1 for 10,000 cycles along with an immediately restored capacity at 0.1 A g−1, demonstrating its significant potential for application as a long-term stable and high-capacity active material in lithium storage systems. These results indicated the future prospects of LiNiO2 materials and this work proposes a novel strategy for developing a permanent anode for lithium storage systems.

Development of semi-crystalline polyurethane with self-healing and body temperature-responsive shape memory properties

Recently, polyurethane (PU) with multifunctionality has attracted significant attention in biomedical applications. This study reports semi-crystalline PUs with both shape memory and self-healing effects, which are composed of poly(ε-caprolactone) diol (PCL), isophorone diisocyanate (IPDI), and 1, 4-butanediol (BDO). The hard segment content greatly influences the structure, morphology and properties, and the increasing hard segment content promotes the phase separation and reduces the crystallizability of the soft segments. Herein, a new self-healing morphology of the semi-crystalline SMPUs is observed, and the self-healing mechanism is ascribed to the diffusion of soft segments and the stability of the hard domains. The relationship between the self-healing efficiency and the stability of hard domains is also explored. Furthermore, the shape memory mechanism of IPDI-based PU is clarified. Based on the partial melting state of the soft segment crystals, the PUs feature relatively good shape memory properties, and the response temperature can be designed as body temperature (37 °C). As the hard segment content increases, the value of shape fixity increases, while that of shape recovery decreases, which is related to hydrogen bonding between polymer chains. Considering the excellent biocompatibility, the as-designed semi-crystalline SMPUs are expected to be used as smart biomaterials in biomedical devices.

Thermal Dynamic Self-Healing Supramolecular Dopant Towards Efficient and Stable Flexible Perovskite Solar Cells.

Flexible perovskite solar cells (FPSCs) have attracted great attention due to their advantageous traits such as low cost, portability, light-weight, etc. However, mechanical stability is still the weak point in their practical application. Herein, we prepared efficient FPSCs with remarkable mechanical stability by a dynamic thermal self-healing effect, which can be realized by the usage of a supramolecular adhesive. The supramolecular adhesive, which was obtained by random copolymerization of acrylamide and n-butyl acrylate, is amphiphilic, has a proper glass transition temperature and a high density of hydrogen-bond donors and receptors, providing the possibility of thermal dynamic repair of mechanical damage in FPSCs. The adhesive also greatly improves the leveling property of the precursor solution on the hydrophobic poly[bis(4-phenyl)(2,4,6-trimethylphenyl)]amine (PTAA) surface. PSCs containing this adhesive achieve more than a 20 % power conversion efficiency (PCE) on flexible substrates and a 21.99 % PCE on rigid substrates (certified PCE of 21.27 %), with improved electron mobility and reduced defect concentration.

Multi-action self-healing coatings with simultaneous recovery of corrosion resistance and adhesion strength

In this study, a new self-healing strategy that can simultaneously recover the corrosion resistance and the adhesion strength of coatings was introduced. The coating was based on a shape memory epoxy resin containing ethylene vinyl acetate (EVA) microspheres loaded with Ce(NO3)3 inhibitors, and was cured at a relatively high temperature to facilitate the fusion of adjacent microspheres for a strengthened self-healing effect. The electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) results demonstrated that the shape memory effect of epoxy matrix, the filling of molten EVA microspheres as well as the release of Ce(NO3)3 inhibitors contributed synergistically to suppress the corrosion reaction at the coating damage. After healing, the low frequency impedance modulus of the coatings containing Ce(NO3)3-EVA microspheres was three orders of magnitude higher than that of the blank epoxy coating. The adhesion strength of the coatings containing Ce(NO3)3-EVA microspheres on the metal substrate was also largely repaired thanks to the strong bonding effect of the EVA microspheres.

ОТЕЧЕСТВЕННЫЙ ОПЫТ ИССЛЕДОВАНИЯ В ОБЛАСТИ СТРОИТЕЛЬНЫХ МАТЕРИАЛОВ С ФУНКЦИЕЙ САМОВОССТАНОВЛЕНИЯ

The results of the analysis of scientific and technical literature, reflecting the experience of research of Russian scientists in the field of self-healing of building materials are shown. They are presented in publications included in international bibliographic and abstract databases. The tendency of changes in the number of publications over 10 years indicates an exponential growth in the interest of researchers in the ability of self-healing, most of the works (more than 50%) published in the field of materials science. The total number of publications by Russian authors over ten years devoted to self-healing is 206 works, of which 49% are in the field of materials science.
 An analysis of articles in publications included in international bibliographic and abstract databases published by domestic authors shows that methods of creating a material structure, which contains additional elements in the form of a reserve volume of a structure-forming substance, are proposed to implement the self-healing effect. Such elements are capsules or functional layers with a reducing agent, the destruction of which triggers the recovery (healing) process. Works are presented where the recovery effect is achieved due to the binder's own potential, which is not fully realized at the initial stage of structure formation. The authors have proposed the implementation of the self-healing effect in composites based on a hydraulic mineral binder (cement) and an organic binder (bitumen) or polymer. At the same time, in most cases, there is no mathematical description of self-healing mechanisms.

Reliability analysis for systems with self-healing mechanism under two different types of cumulative shocks

ABSTRACT System with self-healing mechanism has been successfully applied in many practical engineering fields. When we discuss the reliability performance of system subject to shocks, cumulative shocks have the greatest impact on most systems fields such as high-speed railway systems or civil structural components. In the present paper, we deal with two different types of cumulative shock models in discrete time with self-healing effect. We study a system with self-healing mechanism from a reliability point of view under these two shock models. The self-healing system will fail when the cumulative damage effect exceeds the given threshold. In the first model, there are shock events at instant of time , while in the second model at some time point there was no shock occurring event. Along with the work in this article, the system reliability formulas and the means and variances of their lifetimes are given under two different types shock models proposed, then simulation methods are adopted to analyze the reliability of the system for the second cumulative model. Finally, numerical examples and future researches are discussed.

Low-intensity-low-temperature stability assessment of perovskite solar cells operating on simulated Martian surface conditions.

Immigration to Mars, which is expected to be powered mainly by photovoltaics, is one of the greatest dreams of humanity. However, the extreme temperature difference and high-energy cosmic radiation on the surface of Mars make it difficult for conventional photovoltaics to operate steadily over time. With their advantages of being lightweight, having a high irradiation tolerance, and an outstanding power conversion efficiency (PCE), perovskite solar cells (PSCs) have shown themselves to be a promising candidate for Martian applications. In this study, we simulated the low-intensity-low-temperature (LILT) environment of the Mars surface, and monitored the in situ device performance of PSCs. Surprisingly, the device PCE was not only maintained at a high level but was even improved slightly. Further investigation revealed that the self-healing effect of perovskites under LILT conditions could be attributed to the light-induced decomposition of the perovskite film and the β-phase perovskite recrystallization process at the perovskite/hole transport layer interface. Interfacial β-phase perovskites are stable at low temperatures, which can facilitate charge extraction and protect the perovskite bulk from long-term light damage. This study demonstrated the feasibility of PSCs and provides a reference for Martian applications.

The anti-corrosion performance and catalytic passivation and sorptive corrosion inhibition self-healing of sulfonated aniline trimer modified basalt scale anti-corrosion coatings

• Dispersion of basalt flakes (BS) was enhanced by sulfonated aniline trimer (SAT). • Hydrogen bonded SAT acted release in response to pH. • SAT catalyzed the formation of composite passive films on the surface of steel. • The multi-functional coordination endowed the coatings self-healing effect. Basalt flake (BS) was the new type of natural lamellar material with high strength and hardness, chemical inertia, acid and alkali resistance. It was expected to be the excellent anti-corrosion coating filler. The poor compatibility between BS and polymer resin limited its application. The modification of BS by sulfonated aniline trimer (SAT) was realized by covalent grafting and hydrogen bond adsorption. The structure and function of the materials were studied through spectrum and energy spectrum, electrochemical experiments, theory methods of quantum chemistry and molecular dynamics. The modification of SAT promoted the compatibility of BS and polymer. The stable dispersion of BS was attributed to covalent anchoring via SAT. This promoting effect was evaluated and confirmed by the shielding ability of coatings to corrosive media. Hydrogen bonded SAT behaved pH responsive release and catalytic passivation and corrosion inhibition on steel, and its release at coating defects endowed the self-healing effect. The mechanism was the formation of dense oxide films and SAT adsorption films.