Self-healing Characteristics Research Articles

Imparting Reprocessability, Quadruple Shape Memory, Self-Healing, and Vibration Damping Characteristics to a Thermosetting Poly(urethane-urea)

The advent of dynamic covalent bond chemistry (DCBC) has sparked renewed research interest in reprocessability of thermosetting polymers. However, combining reprocessability with stimuli-responsiveness remains a challenge for futuristic applications. Usually, a combination of complementary DCBCs is employed to integrate reprocessability with shape memory as well as self-healing (SH) attributes in a single polymeric system. In the present work, we report two-component poly(urethane-urea) (PUU) networks, with varied hard segment (HS) concentrations, that exhibit quadruple shape memory (QSM), efficacious vibration damping, thermally activated intrinsic SH as well as multiple cycles of thermal reprocessability. The component A is an isocyanate capped bi-soft segment blend of polybutadiene diol and polypropylene glycol, while the second component comprises an aromatic diamine chain extender solubilized in an oligomeric polyoxypropylene triol. The networks characterized through FTIR as well as small- and wide-angle X-ray scattering (SAXS and WAXD) revealed a phase-separated morphology with extensive hydrogen-bonding (H-bonding) interactions in the HS domains of the PUU networks. Dynamic mechanical analysis (DMA) measurements revealed broad dissipation factor (tan δ) vs temperature and frequency profiles of the networks, which could be leveraged for efficacious passive vibration damping applications. A dissociative mechanism of urethane and urea bond exchange, evidenced from temperature-dependent FTIR studies enabling facile stress relaxation, is proposed to be the mechanistic origin of the reprocessability and SH of the networks. A broad dissipation factor (tan δ) vs temperature profiles endowed the networks with QSM characteristics. We posit that the study is relevant for expanding the scope of DCBCs for development of reprocessable thermosetting polyurethanes with multiple smart functionalities.

Thermal effect on the geo-engineering characteristics of a rock salt.

Rock salt caverns are considered one of the best hosts to store oil, natural gas, radioactive and toxic wastes due to their low permeability, self-healing characteristics and wide distribution on the Earth. Stored nuclear waste in rock salts will radiate for many years. Therefore, the thermal energy and also temperature in the host environment will increase depending on time. In this study, P-wave velocity (Vp), Brazilian tensile strength (σt), uniaxial compression strength (σc) of Çankırı rock salt were investigated under different temperatures ranging from 20°C to 250°C since the temperature is a factor that causes changes in some physical and geo-mechanical properties of rocks. The acoustic emission technique was utilized during uniaxial compression strength tests, to monitor the crack accumulation. Additionally, X-ray micro-computed tomography technique was employed to observe the microstructure and determine the porosity of rock salt samples depending on the temperature. The Vp and the σt of Çankırı rock salt decrease with increasing temperatures of samples whereas the σc increases. The ductility of rock salt tends to increase with augmented temperature and the axial strain at the ultimate stress level is 2.96% at 20°C whereas it reaches up to 6.29% at 250°C. The AE activity of rock salt generates at the early stages of loading and AE count prominently increases with the increasing temperature of samples. Therefore, the stress levels of crack initiation (σi) and crack damage (σcd) thresholds were reached earlier than the previous one with each temperature increment. According to X-ray micro-CT images of rock salts, the number of cracks increased markedly in thermally treated rock salt samples and therewith the porosity increases from 1.12% to 2.73% with an increase in temperature from 50°C to 250°C.

Perovskite Grain-Boundary Manipulation Using Room-Temperature Dynamic Self-Healing "Ligaments" for Developing Highly Stable Flexible Perovskite Solar Cells with 23.8% Efficiency.

Flexible perovskite solar cells (pero-SCs) are the best candidates to complement traditional silicon SCs in portable power applications. However, their mechanical, operational, and ambient stabilities are still unable to meet the practical demands because of the natural brittleness, residual tensile strain, and high defect density along the perovskite grain boundaries. To overcome these issues, a cross-linkable monomer TA-NI with dynamic covalent disulfide bonds, H-bonds, and ammonium is carefully developed. The cross-linking acts as "ligaments" attached on the perovskite grain boundaries. These "ligaments" consisting of elastomers and 1D perovskites can not only passivate the grain boundaries and enhance moisture resistance but also release the residual tensile strain and mechanical stress in 3D perovskite films. More importantly, the elastomer can repair bending-induced mechanical cracks in the perovskite film because of dynamic self-healing characteristics. The resultant flexible pero-SCs exhibit promising improvements in efficiency, and record values (23.84% and 21.66%) are obtained for 0.062and 1.004cm2 devices; the flexible devices also show overall improved stabilities with T90 >20000bending cycles, operational stability with T90 >1248h, and ambient stability (relative humidity=30%) with T90 >3000h. This strategy paves a new way for the industrial-scale development of high-performance flexible pero-SCs.

Crack width prediction of self-healing engineered cementitious composite using multi-expression programming

Concrete structures are prone to cracking due to environmental damage and/or tensile strain. Self-healing concrete has garnered scientific interest in recent years as it addresses the cracking problem and extends the service life of concrete structures. Engineered cementitious composite (ECC), a high-performance fiber-reinforced cement composite, is known to have some self-healing characteristics. However, the self-healing capability of ECC is characterized by the type and content of input parameters and is difficult to predict. This investigation utilised a multi-expression programming algorithm for the prediction of self-healing characteristics of ECC containing various admixtures. The database, containing 619 points, was extracted from literature containing crack width before self-healing (CB), limestone powder (LP), silica fume (SF), and fly ash (FA) as input parameters and crack width after self-healing as an output parameter. The performance of the developed model was evaluated based on various statistical indices and parametric analysis. The results showed that the developed model is robust and efficient in predicting the self-healing behavior of ECC containing various admixtures. Parametric and sensitivity analysis revealed that among the admixtures used, fly ash had the least impact and limestone powder had the highest impact on the self-healing capacity of ECC.

Solvent-free covalent MXene nanofluid: A new lubricant combining the characteristics of solid and liquid lubricants

A sole liquid lubricant or solid lubricant cannot cater to the demands of high-efficiency lubrication performance. From the standpoint of fusion of solid and liquid lubrication, solvent-free nanofluids are expected to be promising lubricants. In this work, solvent-free covalent MXene nanofluids were synthesized by grafting MXene with organosilane (KH560) and polyether amine oligomer (M2070) via covalent linkage. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, thermogravimetric analysis and rheological characterizations demonstrated that the MXene nanofluids were successfully synthesized and presented macroscopic fluidity at room temperature. Importantly, when used as a lubricant, the nanofluids perform well in friction-reduction and anti-wear properties even at high velocity (50 Hz), elevated temperature (100 °C), and heavy load (1100 N). The excellent tribological properties are ascribed to the nanofluids integrating the advantages of significantly improved load-bearing capacity and lubrication performance of the core nanomaterials, as well as liquid-like fluidity and self-healing characteristics of the organic shell. Moreover, the formation of 120–180 nm thick tribofilm on the worn steel surface was identified, which is significant in improving the lubrication performance. The above results suggest that the solvent-free MXene nanofluids should be a quite excellent candidate lubricant for integrating the advantages of solid and liquid lubricants and provide theoretical guidance for structural design of high-performance solvent-free nanofluid lubricants.

Preparation and Characterization of Poly(Acrylic Acid)-Based Self-Healing Hydrogel for 3D Shape Fabrication via Extrusion-Based 3D Printing.

The three-dimensional (3D) printing of hydrogel is an issue of interest in various applications to build optimized 3D structured devices beyond 2D-shaped conventional structures such as film or mesh. The materials design for the hydrogel, as well as the resulting rheological properties, largely affect its applicability in extrusion-based 3D printing. Here, we prepared a new poly(acrylic acid)-based self-healing hydrogel by controlling the hydrogel design factors based on a defined material design window in terms of rheological properties for application in extrusion-based 3D printing. The hydrogel is designed with a poly(acrylic acid) main chain with a 1.0 mol% covalent crosslinker and 2.0 mol% dynamic crosslinker, and is successfully prepared based on radical polymerization utilizing ammonium persulfate as a thermal initiator. With the prepared poly(acrylic acid)-based hydrogel, self-healing characteristics, rheological characteristics, and 3D printing applicability are deeply investigated. The hydrogel spontaneously heals mechanical damage within 30 min and exhibits appropriate rheological characteristics, including G'~1075 Pa and tan δ~0.12, for extrusion-based 3D printing. Upon application in 3D printing, various 3D structures of hydrogel were successfully fabricated without showing structural deformation during the 3D printing process. Furthermore, the 3D-printed hydrogel structures exhibited excellent dimensional accuracy of the printed shape compared to the designed 3D structure.

Surface Modification of Transition Metal Dichalcogenide Nanosheets for Intrinsically Self-Healing Hydrogels with Enhanced Mechanical Properties.

Nanocomposites with enhanced mechanical properties and efficient self-healing characteristics can change how the artificially engineered materials' life cycle is perceived. Improved adhesion of nanomaterials with the host matrix can drastically improve the structural properties and confer the material with repeatable bonding/debonding capabilities. In this work, exfoliated 2H-WS2 nanosheets are modified using an organic thiol to impart hydrogen bonding sites on the otherwise inert nanosheets by surface functionalization. These modified nanosheets are incorporated within the PVA hydrogel matrix and analyzed for their contribution to the composite's intrinsic self-healing and mechanical strength. The resulting hydrogel forms a highly flexible macrostructure with an impressive enhancement in mechanical properties and a very high autonomous healing efficiency of 89.92%. Interesting changes in the surface properties after functionalization show that such modification is highly suitable for water-based polymeric systems. Probing into the healing mechanism using advanced spectroscopic techniques reveals the formation of a stable cyclic structure on the surface of nanosheets, mainly responsible for theimproved healingresponse. This work opens an avenue toward the development of self-healing nanocomposites where chemically inert nanoparticles participate in the healing network rather than just mechanically reinforcing the matrix by slender adhesion.

Study of Synthesis and Characterization of Pure Cus and Cufes Nanoparticles by Hydrothermal Method

Copper-based material has good electrical and optical properties but is not only physical properties and also good in antibacterial applications. Nano-structured CuS has potential value on high photocatalytic activity because of their suitable band gap and catalytic ability. CuS NP hydrogels had both adjustable physical properties and good injectable self-healing characteristics and excellent functionalities, concurrently including hemostatic ability, bacteria-killing capability, and cell migration and proliferation promotion. In vivo wound, healing, and histomorphological examinations of immunofluorescence staining in a mouse full-thickness wound model demonstrated good acceleration effects of these hydrogels for infected wound healing. A novel Chalcopyrite CuFeS nanocrystals are used as a Fenton reagent to degrade organic dyes without any additional source efficiently. Subsequently, the CuFeS2 nanocrystals/ biomass composite degradation column is made, continually degrading organic dyes. This paper demonstrates a comparative study of the synthesis and characterization of pure CuS and CuFeS nanoparticles using copper chloride, thiourea, ferric chloride and water solvent by straightforward hydrothermal methods. The synthesized material was characterized by an Xray diffraction (XRD), Scanning Electron Microscope (SEM), and Energy Dispersive X-ray spectrum (EDAX) techniques employed to study the nanostructure properties of the prepared sample. Crystallite size was determined by the Debye-Scherrer formula and found to be 15.5 nm and 20.55 nm, respectively. The EDAX spectrum showed a clear peak of present elements. An SEM image shows the morphology of the nanostructures. Optical analysis was done with UV and FTIR techniques. The pure CuS and CuFeS synthesized Tauc Relation and calculated nanomaterials bandgap came out to be 4.6eV and 4.4 eV, respectively.

Self-Healing Polymer Electrolytes for Next-Generation Lithium Batteries

The integration of polymer materials with self-healing features into advanced lithium batteries is a promising and attractive approach to mitigate degradation and, thus, improve the performance and reliability of batteries. Polymeric materials with an ability to autonomously repair themselves after damage may compensate for the mechanical rupture of an electrolyte, prevent the cracking and pulverization of electrodes or stabilize a solid electrolyte interface (SEI), thus prolonging the cycling lifetime of a battery while simultaneously tackling financial and safety issues. This paper comprehensively reviews various categories of self-healing polymer materials for application as electrolytes and adaptive coatings for electrodes in lithium-ion (LIBs) and lithium metal batteries (LMBs). We discuss the opportunities and current challenges in the development of self-healable polymeric materials for lithium batteries in terms of their synthesis, characterization and underlying self-healing mechanism, as well as performance, validation and optimization.

Photoresponsive triple shape memory polymers with a self-healing function based on poly (lactic acid)/polycaprolactone blends

Self-healing shape memory polymers (SMPs) have considerablepotential in advanced manufacturing and biomedical fields. Polypyrrole (PPy) exhibits excellent photoconversion properties, which may be utilized in SMP formulation; however, its application in this regard has not been explored. In this study, PPy-filled polymer nanocomposites were prepared to investigate their shape memory and self-healing characteristics. First, poly(lactic acid) (PLA) and polycaprolactone (PCL) were blendedto form PLA/PCL shape memory matrices. An 80:20 PLA/PCL blend showed excellent triple-shape memory performance with shape recovery rates (Rr1, Rr2, and Rr3Rr) of 92%, 87%, and 93%, respectively PPy nanoparticles were then incorporated into the blend as photothermal conversion fillers to develop photoresponsive SMPs. SMPs. The resulting PLA/PCL/PPy nanocomposites exhibited elevated surface temperatures during near-infrared (NIR) irradiation, thus demonstrating the photoconversion effect. In addition, these nanocomposites showed reversible triple-shape change behavior and excellent self-healing efficiencies upon NIR exposure, owing to the controllable melting and recrystallization of the PLA and PCL phases. Furthermore, the material properties of severed nanocomposites were restored after self-healing. These results, in addition to the biocompatibility and simple fabrication process of these materials, therefore demonstrate the potential utility of PPy-filled SMPs in several applications, including soft robotics and biomedical devices.

Dual crosslinked injectable protein-based hydrogels with cell anti-adhesive properties

Currently, one of the most severe clinical concerns is post-surgical tissue adhesions. Using films or hydrogel to separate the injured tissue from surrounding tissues has proven the most effective method for minimizing adhesions. Therefore, by combining dual crosslinking with calcium ions (Ca2+) and tetrakis(hydroxymethyl) phosphonium chloride, we were able to create a novel, stable, robust, and injectable dual crosslinking hydrogel using albumin (BSA). This dual crosslinking has preserved the microstructure of the hydrogel network during the degradation process, which contributes to the hydrogel’s mechanical strength and stability in a physiological situation. At 60% strain, compressive stress was 48.81 kPa obtained. It also demonstrated excellent self-healing characteristics (within 25 min), tissue adhesion, excellent cytocompatibility, and a quick gelling time of 27 ± 6 s. Based on these features, the dual crosslinked injectable hydrogels might find exciting applications in biomedicine, particularly for preventing post-surgical adhesions.

Injectable Supramolecular Hybrid Hydrogel Delivers IL-1β-Stimulated Exosomes to Target Neuroinflammation

Long-term neuroinflammation is a major barrier to neurological recovery after cerebral ischemia-reperfusion injury (CIRI). Here, a thermosensitive injectable supramolecular hybrid hydrogel is developed to sustainably deliver exosomes derived from interleukin-1β-stimulated bone marrow stromal cells (BMSCs) (βExos) with improved exosome production and anti-inflammatory capacity for neuroinflammation inhibition and neurological recovery. The supramolecular hydrogel displays self-healing and injectable features, along with high biocompatibility and tissue-like softness. The βExos effectively reduce the lipopolysaccharide-induced inflammatory responses in the immortalized mouse microglia (BV2) cell line, and the in situ formed hydrogel improves the exosome retention in the ischemic core area. More remarkably, in the middle cerebral artery occlusion in vivo model, glial scar formation and neuronal loss are significantly reduced by regulating neuroinflammation using the released βExos. Therefore, the combination of interleukin-1β-stimulated exosomes with injectable supramolecular hydrogel provides an appealing strategy for treating central nervous system diseases.

Condensation heat transfer on slippery lubricant-impregnated nanohole-arrayed stainless-steel surface

The condensation heat transfer performance of lubricant-impregnated surfaces has a competitive advantage owing to the improved mobility of droplets and self-healing characteristics. In this study, we fabricated the lubricant-impregnated surfaces featured with Teflon-coated anodized nanoporous oxide layer on stainless steel infused with Krytox GPL103 oil. The characterization shows that the droplet state on the surface changes from the pinning to slippery states (sliding angle α of 1.8 ± 0.3°) enabled by the presence of the lubricant oil. The condensation heat transfer performances of the lubricant-impregnated Teflon-coated anodized stainless-steel surface (L-T-AS) are investigated from the aspects of the surface wettability and droplet mobility, compared to that of Teflon-coated stainless-steel surface (T-S) and Teflon-coated anodized stainless-steel surface (T-AS). Whereas coalescence-induced droplet shedding and droplet sweeping are found on the T-S and T-AS, the shedding of discrete droplets and their sweeping without further coalescence are noticed on the L-T-AS. The heat transfer coefficient of the L-T-AS is 398.4% higher than that of the T-AS at the low subcooling temperature of 0.2 K. The heat transfer performance of the dropwise condensation of the L-T-AS has further been elucidated by the theoretical model considering the heat transfer rate through a single droplet associated with the density distribution function of the droplet.

High-performance self-healing composite ultrafiltration membrane based on multiple molecular dynamic interactions

The inevitable membrane damage during the use of separation membrane seriously affects the separation and purification effects. Herein, we first synthesized a novel poly(aryl ether sulfone) material containing boronic acid groups (PES-H2BO2) through molecular design, then PES-H2BO2 ultrafiltration membrane was prepared via non-solvent induced phase inversion method. Further, the PES-H2BO2 ultrafiltration membrane and polyvinyl alcohol (PVA) hydrogel were composited by hydrogen bonds and reversible boronate ester bonds between the two to fabricate a series of novel PVA hydrogel/PES-H2BO2 composite ultrafiltration membranes. Through the ultrafiltration experiment of polyacrylamide (PAM) solution, the flux and retention rate changes of the composite ultrafiltration membrane in the initial stage, damage stage, self-healing stage, and stabilization stage were tested and analyzed. The results confirmed that the composite membrane has the ability to rapidly restore the flux and retention rate to the pre-breakage levels through a self-healing effect within 15 min after being damaged, demonstrating their outstanding self-healing characteristics. The design strategy of fabricating composite ultrafiltration membrane with excellent self-healing performance by forming hydrogen bond and reversible boronate ester bond between hydrogel and membrane matrix in this study provides a convenient and feasible way for the design and preparation of high-performance self-healing separation membranes.

Sustainable castor oil-based vitrimers: Towards new materials with reprocessability, self-healing, degradable and UV-blocking characteristics

Vitrimers with reversible cross-links are emerging promising sustainable materials with reprocessability and recyclability. Here, castor oil-based epoxy resin (EMCO) with epoxy group and carbon-carbon double bonds was prepared through a two-step process and then cured with itaconic acid (IA) through epoxy-acid ring-opening reaction and free radical polymerization to fabricate fully bio-based epoxy vitrimers containing reversible transesterification bond. The thermal-mechanical properties, reprocessability, repairability, and recyclability could be balanced by varying the molar ratio of EMCO to IA. When the carboxyl group/epoxy group molar ratio reached 1.0, the EMCO-IA1.0 vitrimer exhibited the highest tensile strength of 14.39 MPa and Tg of 52.95 °C. Moreover, the vitrimer can be effectively remodeled (2 h at 180 °C) to prepare films and self-healing thanks to a rapid and mild stress relaxation process (2.56 min at 110 °C) and low activation energy (60.94 kJ·mol−1). More significantly, EMCO-IA vitrimer could be degraded in ethanol solution and recycled to prepare films and also exhibited excellent UV blocking ability. Overall, the EMCO-IA vitrimer can achieve a highly efficient closed-loop recycling without significantly sacrificing the mechanical properties, which can extend the service life and facilitate the sustainable development of the castor oil-based polymeric material.

3D-Printed Photocurable Resin with Synergistic Hydrogen Bonding Based on Deep Eutectic Solvent

Vat polymerization, one of the 3D printing technologies, has been widely applied owing to its advantageous properties, such as high accuracy and surface quality. However, the applicability of this technology is limited to end-use product manufacturing, requiring advancements due to a gradual increase in the performance requirements and functional demands of the products. In this study, deep eutectic solvent-based photocurable resins (PCRs) with synergistic hydrogen bonding are synthesized using a facile and ecofriendly procedure to tune monomer proportions. The as-prepared PCRs, with ultralow viscosity and ultrahigh curing rate, are compatible with commercial liquid-crystal display printers. The 3D-printed parts with high optical transparency, stiffness, and thermal resistance exhibit humidity-dependent electrical conductivity and mechanical properties. In addition, the 3D-printed objects demonstrate self-healing features due to the synergistic effect of high-density hydrogen bonding in the microphase-separated polymer matrix. Moreover, different categories of structural assembly, from 2D to 3D and small to large, are demonstrated, and their solubility ensued in recycling and remolding. The synthesized PCRs are suitable for fabricating sacrificial molds, enabling the on-demand fabrication of precise multifunctional structures with various materials, which are otherwise incompatible with UV-based 3D printing, facilitating 3D printing by overcoming its material-selection limitations.

Research Progress of Sandwich-structured Flexible Energy Storage Dielectric Materials

Polymer dielectric materials show wide applications in smart power grids, new energy vehicles, aerospace, and national defense technologies due to the ultra-high power density, large breakdown strength, flexibility, easy processing, and self-healing characteristics. With the rapid development of integration, miniaturization and lightweight production of electronic devices, it is required to develop such storage and transportation dielectric system with larger energy storage density, higher charge and discharge efficiency, good thermostability and environmental friendly. However, the contradiction between dielectric constant and breakdown strength of dielectric materials are the key factors and bottleneck to obtain high performance dielectric materials. It is accepted that controlling charge distribution and inhibiting charge carrier injection are important to improve the energy storage characteristics of polymer dielectrics. In recent years, designing sandwich or stacking structured materials exhibits outstanding advantages in inhibiting charge injection and promoting polarization, thereby the permittivity and breakdown strength of polymer dielectrics can be simultaneously enhanced. Accordingly, this paper reviews the research progress of sandwich-structured polymer dielectric films in improving the energy storage performances from the perspectives of materials composition, structural design, and preparation methods. The influence of dielectric polarization, charge distribution, charge injection, interfacial barrier and electrical dendrite growth on the energy storage performance and the synergistic enhancement mechanisms in such sandwich-structured dielectric materials are systematically summarized, implying good development and vast application prospects. In brief, introducing easy polarization, wide-gap and deep-trap nanofillers has greater designability and regulation in the dielectric and breakdown properties. In addition, using the hard layer as the outer layer can reduce charge injection more effectively, achieving high breakdown resistance performance easily. Sandwich structure design also possesses advantages over other methods in maintaining good flexibility and dielectric stability of dielectric materials, thus becoming a hot-topic research area in recent years. In the future, it is necessary to combine low conductivity and high thermal conductivity of dielectric polymers to achieve high temperature energy storage and efficiency. Research on recyclable, self-repairing sandwich insulating films is good for the service life and safety of electronic components and will further expand the application of dielectric polymers. Finally, effective evaluation of sandwich-structured dielectric and energy storage performances through simulation and theoretical modeling is very helpful to reveal the breakdown and thermal failure mechanisms, and theoretically guide the design of polymer dielectric materials.

Injectable adhesive carboxymethyl chitosan-based hydrogels with self-mending and antimicrobial features for the potential management of periodontal diseases.

Treating periodontal diseases is a great challenge owing to the motion and wet conditions, bacterial infection, and tissue defects. Therefore, designing bioactive materials with outstanding wet-tissue adhesion, antimicrobial features, as well as favorable cell responses, is highly desirable to meet practical necessity. In this work, bio-multifunctional melatonin-loaded carboxymethyl chitosan/polyaldehyde dextran (CPM) hydrogels have been developed through the dynamic Schiff-base reaction. Our results demonstrate that the CPM hydrogels display injectability, structural stability, and high tissue adhesion in the wet and motional state, as well as self-healing features. In addition, the designed hydrogels show great antibacterial properties and excellent biocompatibility. The prepared hydrogels display a slow release of melatonin. Moreover, the in vitro cellular assay indicates that the developed hydrogels containing 10 mg per mL melatonin significantly promote cell migration. Thus, the synthesized bio-multifunctional hydrogels show great promise in the treatment of periodontal disease.

Dual conductive network sensors based on an MXene/PDES supramolecular elastomer and their performance

A dual conductive network strain sensor was prepared by simple UV-curing of a mixture of MXene and polymerizable deep eutectic solvent. This sensor had high-strength, while maintained the self-healing, anti-freezing, and high-adhesion features.

The effect of graphene nanoplatelet addition on the mechanical, durability and self-healing properties of engineered cementitious composites

Nanomaterial usage is an effective method to enhance the mechanical and durability properties of cementitious materials. Graphene Nanoplatelets (GNPs) are cost-efficient graphene-based nanomaterials that can exhibit graphene-like features. Although GNPs have been found to improve mechanical and durability properties, their effect on the self-healing behavior of cementitious materials, particularly Engineered Cementitious Composites (ECC), has not been examined in the literature studies. Therefore, this study aims to investigate the effects of GNP addition on mechanical, durability and self-healing behavior of ECC. During the study, the mechanical, durability, and self-healing characteristics of ECC with and without GNP were observed by using various mechanical and non-destructive test methods. Compression test, four-point bending test, resonance frequency test, ultrasonic pulse velocity test, sorptivity test, electrical impedance test and microscopic inspection were conducted. According to the test results, 0.05% GNP addition increased the compressive strength of ECC specimens. With the effect of GNP, first cracking strength, ultimate flexural strength and deformation values increased both for virgin and preloaded ECC specimens. The preloaded specimens with GNP performed similarly to virgin specimens under bending. The cracks of preloaded GNP specimens were either closed completely or extensively compared to control specimens. The crack numbers of GNP specimens after failure were also greater than that of control specimens. Accordingly, the flexural and self-healing behavior of the specimens improved with GNP addition. The effect of improvement by GNP addition was also evident in nondestructive tests. A considerable increment occurred in electrical resistance with GNP addition.