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![(a) Chemical structure of monomers and polymers; (b) electrical power induced healing illustrated by optical images of the electrode [90]. Adapted with permission from Tiwari, N; Nanoscale; published by Royal Society of Chemistry, 2017.](publication/349526534/figure/fig2/AS:994363320590338@1614086098054/a-Chemical-structure-of-monomers-and-polymers-b-electrical-power-induced-healing.png)
(a) Chemical structure of monomers and polymers; (b) electrical power induced healing illustrated by optical images of the electrode [90]. Adapted with permission from Tiwari, N; Nanoscale; published by Royal Society of Chemistry, 2017.
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Nowadays, the self-healing approach in materials science mainly relies on functionalized polymers used as matrices in nanocomposites. Through different physicochemical pathways and stimuli, these materials can undergo self-repairing mechanisms that represent a great advantage to prolonging materials service-life, thus avoiding early disposal. Parti...
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... material presented a sheet resistance of 13.3 ohm/sq. Heat was generated internally applying a current of 12 V for 2 min to reach the temperature where r-DA occurs (120 °C), thus repairing a cut induced on the sheet [90] (Figure 6). Some of the authors of this review generated conductive nanocomposites that display self-healing properties via Diels-Alder reaction activated by Joule effect. ...
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Engineered living materials (ELMs) are the most relevant contemporary revolution in materials science and engineering. These ELMs aim to outperform current examples of "smart", active or multifunctional materials, enabling countless industrial and societal applications. The "living" materials facilitate unique properties, including autonomy, intell...
Citations
... 34 A Joule's effect heating system requires the presence of conductive particles, at least, to reach the electrical percolation threshold level. 35 The composition of the conductive particles can be very diverse; in addition to graphene nanoplatelets (GNPs), some studies use carbon nanotubes 36 and silver nanoparticles, 37 or include a thin electroconductive layer using physical vapor deposition techniques. 38,39 This technique is used to heat different elements, including fabrics. ...
Achieving proper dispersion of pigments, dyes, or other additives, such as microcapsules or nanoparticles, within printing pastes or textile coatings is crucial for obtaining a homogeneous result. In certain specialized applications, such as coloration technology, it is possible to use colorimetry tools, visual examination, and even artificial vision to identify defects. However, none of these techniques comprehensively map the specific additive distribution. This paper proposes a novel approach: monitoring the distribution of conductive particles (graphene nanoplatelets, referred to as GNPs) within an acrylic coating paste using the Joule’s effect. Four different dispersion systems (ultrasound mixer, blender, toroidal agitation, and three-roll mill) are employed. Thermographic images provide an accurate view of how conductive particles are distributed. This complements data from numerical values, such as the maximum and average temperatures recorded for each sample. In certain cases, relying solely on numerical values can be inadequate or insufficient, hence the novelty of this article emphasizing the significance of using the Joule’s effect to assess the distribution of conductive particles. Concerning the mixing systems, optimal dispersion of GNPs in distilled water is most effectively achieved using an ultrasound mixer, with enhanced uniformity as dispersion time increases. For mixing the components of the coating paste, the toroidal agitation method yields the best result. Employing the three-roll mill is discouraged for this application due to its propensity to induce phase separation.
... This property enables actuators' motion without any motors or external action. It finds applications in medicine [9], self-healing structures [10], soft robotics [11][12][13], and aerospace [14]. ...
Even though the influence of the printing direction on the mechanical properties of 3D-printed samples by fused filament fabrication is established in the literature, very little is known about mechanical and electrical coupling. In this study, electrically conductive polylactic acid filled with carbon black particles undergoes monotonic and repeated progressive tensile loading to better understand the influence of the printing direction on the electro-mechanical properties of three-dimensional-printed samples. The objective is to analyse the electro-mechanical behaviour of this composite for its potential application as an actuator. The classical laminate theory is also applied to evaluate the relevance of this theory in predicting the mechanical characteristics of this material. In addition, a comprehensive damage analysis is performed using acoustic emission, infrared thermog-raphy, scanning electron microscopy, and X-ray microcomputed tomography imaging. Results show that the degradation of the mechanical and electrical properties is highly influenced by the printing direction. The appearance and development of crazes in 0 • filaments are highlighted and quantified. The conclusions drawn by this study underline the interest in using longitudinal and unidirectional printing directions to improve the conductive path within the samples. Furthermore, the evolution of the resistance throughout the experiments emphasizes the need to control the implemented voltage in the design of future electro-thermally triggered actuators.
... However, in practical applications, elastomers are often susceptible to environmental or external stresses which can lead to unexpected damage, cracks, and even macroscopic fractures, severely degrading their functionality and lifespan [1]. Self-healing elastomers, which have self-healing properties, can address these problems by fully or partially restoring in situ mechanical damages, thereby extending their service life and improving safety during use [2,3]. Consequently, self-healing elastomers have attracted tremendous attention over the past two decades as they can effectively alleviate environmental pollution, prolong the lifetime of products, and reduce costs [4][5][6][7]. ...
Self-healing elastomers refer to a class of synthetic polymers that possess the unique ability to autonomously repair from internal and external damages. In recent years, significant progress has been made in the field of self-healing elastomers. In particular, intrinsic self-healing elastomers have garnered a great deal of attention. This mini-review outlines recent advancements in the mechanisms, preparation methods, and properties of various intrinsic self-healing elastomers based on non-covalent bond systems, reversible covalent bond systems, and multiple dynamic bond composite systems. We hope that this review will prove valuable to researchers in order to facilitate the development of novel strategies and technologies for preparing high-performance self-healing elastomers for advanced applications.
... [41,47] Localized heating at cracks occurs due to the change of direction of the electric current at the tips of the crack, causing heat concentrations at the crack tips. [48,49] A high number of cracks in the sample during the flash SPS phase could lead to many localized hotspots with a higher rate of Nd-rich phase melting, potentially creating higher concentrations of this phase throughout the sample. Formation of an especially thick Nd-rich region is often associated with contaminants, such as oxygen, on the particle surface and Nd surface segregation. ...
Recycling of Nd–Fe–B magnets is an ongoing challenge regarding circular economy. State‐of‐the‐art magnet production methods, such as hot deformation, have limitations with respect to direct recycling of magnet scrap particles that differ from pristine melt‐spun Nd–Fe–B powder. Recent work has shown that a combination of presintering by field‐assisted sintering technology/spark plasma sintering (FAST/SPS) and hot deformation by flash spark plasma sintering (flash SPS) has the potential to directly produce Nd–Fe–B magnets from 100% scrap material. Both processes have the capability to adjust and monitor process parameters closely, resulting in recycled magnets with properties similar to commercial magnets but made directly from crushed and recycled Nd–Fe–B powder that partially or completely replaces pristine melt‐spun Nd–Fe–B powder. Herein, a systematic study is done inserting recycled magnet particles into a flash SPS deformed magnet, considering the effects of different weight percentages of scrap material of varied particle size fractions. In some cases, coercivity H cJ of >1400 kAm ⁻¹ and remanence B r of 1.1 T can be achieved with 20 wt% scrap material. The relationship between particle size fraction, oxygen uptake, and percentage of recyclate in a final magnet are all explored and discussed with respect to magnets made from pristine material.
... It is also one of the common and effective methods of introducing nanomaterials to promote the healing process through electric heating, namely the so-called Joule heating. [102][103][104][105][106][107] In essence, polymers are usually poor conductors of electricity, which can be combined with conductive nanomaterials in specific ways and form conductive channels. When the fabricated conductive composite material cracks, the resistance in the cracked area will sharply increase with the reduction of the cross-sectional area. ...
... There are a lot of reports in which silver nanowires, carbon nanotubes, MXene, etc. were used to construct transparent conductive thin layers on the surface of healable Pus; therefore the acquired composites were endowed with the ability of Joule heating while still maintaining transparency (Fig. 15(e)). [105][106][107] In general, the introduction of nanomaterials into healable PUs can provide multiple stimuli-response mechanisms for triggering the healing process or promoting healing efficiency. Meanwhile, the influence on the inherited properties of PUs can be greatly reduced by reasonably designing the structure and combination form of nanomaterials. ...
As a kind of polymeric material with high flexibility and durability, polyurethanes (PUs) are widely used in industry, electronic products, construction, transportation and medical fields. The introduction of healing ability can greatly enhance the service lives and recyclability of PUs. Over the past decade, this dream has come closer to reality with the development of polymer networks containing dynamic bonds, which are capable of healing their physical properties and unique functions after damage to polyurethane materials. However, high chain mobility is frequently required to achieve restoration in healable PUs, which inevitably leads to degradation of intrinsic mechanical properties, especially the tensile stress and Young's modulus. Herein, the synthesis, mechanical properties, healing performance of intrinsic healable PUs based on different types of supramolecular interactions and reversible covalent bonds are discussed, aiming at summarizing some strategies to resolve the tradeoff between mechanical properties and healable performances. Moreover, various PU-based nanomaterials have been summarized to improve the mechanical properties, to facilitate the healing process by stimulation, and to endow them with special functions. Finally, the potential applications, challenges and prospects in the field of healable PU composites are also elaborated in the final part of this paper.
... The combination of SMP and 3D printing is often called 4D printing, the fourth dimension referring to time [5,[14][15][16]. 4D printing is a dynamic field of research where an abundance of applications have been imagined including medicine [17], self-healing structures [18] or space applications [19]. Soft robotics is also a domain that opens a wide range of applications in this field [20][21][22]. ...
... Consideration should be given to the possibility of conducting polymer nanocomposites with reversible dynamic bonds, as well as their energy activation for selfhealing by heating when an electric current flows (Joule effect) [19]. Flexible composites based on silicone rubber (SR)/carbon fiber(CF)@polydopamine (PDA) (SR/CF@PDA) have good interfacial adhesion in the structure of the material and filler (due to the adhesive properties of PDA) [20], which ensures flexibility without compromising electrical properties. Polyurethane-coated carbon fiber (CF) can be added to the process for producing thermoplastic polymer composites with improved thermal and mechanical properties, as well as durability, as an effective reinforcing filler and an improved crosslinking process. ...
The development of reliable and effective functional materials that can be used in various technological fields and environmental conditions is one of the goals of modern nanotechnology. Heating elements’ manufacturing requires understanding the laws of heat transfer under conditions of different supply voltages, as this expands the possibilities of such materials’ application. Elastomers based on silicon-organic compounds and polyurethane modified with multi-walled carbon nanotubes (MWCNTs) were studied at various concentrations of Ni/MgO or Co-Mo/MgO and voltages (220, 250, and 300 V). It was found that an increase in voltage from 220 to 300 V leads to an initial increase in specific power on one-third followed by a subsequent decrease in a specific power when switched on again to 220 V (for −40 °C) of up to ~44%. In turn, for a polyurethane matrix, an increase in voltage to 300 V leads to an initial peak power value of ~15% and a decrease in power when switched on again by 220 V (for −40 °C) to ~36% (Ni/MgO -MWCNT). The conducted studies have shown that the use of a polyurethane matrix reduces power degradation (associated with voltage surges above 220 V) by 2.59% for Ni/MgO–based MWCNT and by 10.42% for Co-Mo/MgO. This is due to the better heat resistance of polyurethane and the structural features of the polymer and the MWCNT. The current studies allow us to take the next step in the development of functional materials for electric heating and demonstrate the safety of using heaters at a higher voltage of up to 300 V, which does not lead to their ignition, but only causes changes in electrophysical parameters.
... While the increase in elastic (Young's modulus) can be explained as being due to the addition of nanosilicas into the iPU matrix, the physical mechanisms that led to improvement of strain at break and toughness in nanocomposites remained still as open questions [130]. According to Odent et al. [58], imidazolium-functionalized polyurethane matrix reinforced by sulfonate-modified nanosilica improvements did not originate from the nature of the iPU matrix, but rather from the nanoparticles mobility during deformation, while ionic bonds break and reform with polymer chains as the nanoparticles move [131]. It was hypothesized that ionic nanocomposites dissipated strain energy through the dissociation of ionic crosslinks and nanoparticle motion [58]. ...
The ionic nanoparticle organic hybrids cover almost 20 year
of research however the substitution of the ionic canopy by
an ionic entangled polymer matrix was implemented only
recently, and can lead to the formulation of ionic nanocomposites.
The functionalization of nanoparticle surface by covalently
grafting a charged ligand (corona) interacting electrostatically
with the oppositely charged canopy (polymer
matrix) can promote dispersion state and stability which are
prerequisites for property "tuning", polymer reinforcement
and fabrication of high performance nanocomposites. Different
types of nanoparticle, shape (spherical or anisotropic),
loading, graft corona, polymer matrix type, charge density,
molecular weight, charge density can influence the nanoparticle
dispersion state, and can alter the rheological, mechanical,
electrical, self-healing and shape-memory behavior of
ionic nanocomposites. Such ionic nanocomposites can offer
new properties and design possibilities in comparison to
traditional polymer nanocomposites.1–3 However, to achieve
a technological breakthrough by designing and developing
such ionic nanomaterials, a synergy between experiments
and simulation methods is necessary in order to obtain a fundamental
understanding of the underlying physics and chemistry.
Although there are a few coarse-grained simulation
efforts to disclose the underlying physics, atomistic models
and simulations that could shed light on the interphase, effect
of polymer and nanoparticle chemistry on behavior, are
completely absent.
... To obtain a flexible heater, a polyurethane matrix was used [43]. However, most of these flexible heaters did not stretch [44], and the polyurethane matrix [45] showed a decrease in the heating power during stretching due to the destruction of the conductive network. ...
Of great importance in materials science is the design of effective functional materials that can be used in various technological fields. Nanomodified materials, which have fundamentally new properties and provide previously unrealized properties, have acquired particular importance. When creating heating elements and materials for deformation measurement, it is necessary to understand the patterns of heat release under conditions of mechanical deformation of the material, as this expands the potential applications of such materials. A study of elastomers modified with multi-walled carbon nanotubes (MWCNTs) has been carried at the MWCNTs concentration of 1–8 wt.%. The modes of heat release of nanomodified elastomers at a voltage of 50 V at different levels of tension are reported. The increment of the MWCNTs concentration to 7 wt.% leads to an increment in the power of heat emissions. It is worth noting the possibility of using the obtained elastomer samples with MNT as sensitive elements of strain sensors, which will allow obtaining information about physical and chemical parameters following the principles of measuring the change in electrical resistance that occurs during stretching and torsion. The changes in conductivity and heat emission under different conditions have been studied in parallel with Raman mapping and infrared thermography. The reported studies allow to make the next step to develop flexible functional materials for the field of electric heating and deformation measurement based on elastic matrices and nanoscale conductive fillers.
... They reported excellent electrically triggered healing efficiencies of the composites ranging from 94.79% to 96.15%. Furthermore, comprehensive reviews on electroactive 174 and magnetoactive 175 self-healable nanocomposites have been recently published, where other examples of shape memory self-healable materials can be found. ...
Electroactive and magnetoactive shape memory polymer nanocomposites (SMCs) are multistimuli-responsive smart materials that are of great interest in many research and industrial fields. In addition to thermoresponsive shape memory polymers, SMCs include nanofillers with suitable electric and/or magnetic properties that allow for alternative and remote methods of shape memory activation. This review discusses the state of the art on these electro- and magnetoactive SMCs and summarizes recently published investigations, together with relevant applications in several fields. Special attention is paid to the shape memory characteristics (shape fixity and shape recovery or recovery force) of these materials, as well as to the magnitude of the electric and magnetic fields required to trigger the shape memory characteristics.
