Carbon-based Fillers Research Articles

Multifunctional sensing mortar for masonry structures: first development and characterization

This study delves into the potential of self-monitoring masonry components constructed with specialized mortars containing conductive carbon-based fillers. The primary objective is to assess their ability to autonomously evaluate their structural integrity. These innovative masonry elements are designed to produce an integrated monitoring system within a structure. This system can effectively identify and respond to changes in structural performance, such as partial damage, crack propagation due to structural anomalies, or extreme loading events. The key to this self-monitoring capacity lies in the application of sensing mortars. These mortars can be used as the bedding material for masonry blocks. Through this approach, the study aims to preliminary characterize and explore the feasibility of cement-based smart mortars for intelligent masonry structures, aiming at diagnosing their own condition. Electromechanical tests on single components and more complex, though small scale, masonry elements allowed to achieve a first optimization of the materials and the building procedure, and to achieve a preliminary characterization of the mechanical, electrical and sensing behaviour. Compressive and bending tests have been coupled to electrical measurements through electrodes applied in the samples. The results of the work demonstrate the potential of the technology to be scaled to larger-scale structures.

Ionic liquid-modified carbon-based fillers and their polymer composites – A Raman spectroscopy analysis

Ionic liquid-modified carbon-based fillers and their polymer composites – A Raman spectroscopy analysis

Material properties characterization for the 4D printing of the hand orthosis utilized for cerebral palsy treatment

In addressing the challenges associated with spastic cerebral palsy, this paper explores the transformative potential of 3D printing and thermally-responsive shape memory polymers (SMPs) for designing innovative orthotic solutions. The investigation focuses on vat photopolymerization with digital light processing (DLP), specifically utilizing 3DM-IMPACT—a UV liquid shape memory photopolymer blended with carbon black. The composite material developed through this process aims to surpass limitations inherent in traditional orthotic materials, offering heightened adaptability and improved patient comfort. Central to the research objectives is the optimization of shape memory properties through the integration of carbon-based fillers and the reduction of the recovery temperature for enhanced usability. The results indicate that incorporating carbon black enhances the mechanical and shape memory properties of the samples to some degree, rendering it a prime candidate for the advancement of polymeric orthoses.

Effect of alternative carbon-based filler on rubber compounds properties

Instead of conventional carbon black, an alternative carbon filler (ACB) obtained in the pyrolysis process from tire waste was used for rubber compounds. The fillers were characterized using FTIR and TGA methods. The mechanical properties of the obtained rubber compounds and the influence of the fillers used on the vulcanization process, as well as the Payne effect, were examined. The results confirm the possibility of replacing conventional carbon black with an alternative carbon filler in rubber compounds.

Enhancing the thermal performance of polyethylene glycol phase change material with carbon-based fillers

New implementation of phase change materials (PCMs), such as Polyethylene Glycols (PEGs), can alleviate the overconsumption of natural resources and can also be applied in solar-thermal energy conversion applications due to their distinctive semi-crystalline structure. To further enhance the thermal properties of PCMs, carbon-based nanomaterials such as graphene nanoplatelets (GNPs) and milled carbon fibre (MCF) can be incorporated to fabricate PEG-based composites due to their high thermal conductivity. One of the possible drawbacks of the addition of carbon-based fillers is their aggregation at high loadings, leading to a possible reduction in the latent heat of PCM composites. Hence, this study explored the most appropriate loading level (5 wt.%) of carbon-based fillers with pristine PEGs to achieve optimal thermal performance. Specifically, PEG-based composites were synthesised with three fillers (GNPs, graphite and MCF) via a temperature-assisted ultrasonication method and rapid solidification. Then, Raman Spectroscopy was used to quantify the dispersion of fillers among the PEG matrices. The results showed that despite a 32.6 % reduction in enthalpy of fusion to 155.5 J g–1, the addition of 15 wt.% of MCF increased the thermal conductivity up to 0.67 W m–1 K–1, which was approximately 2.5 times higher than that of pristine PEG. Moreover, explanations were provided on the possible heat transfer mechanisms in different types of carbon-based fillers. PEG/MCF PCMs displayed good properties on latent heat, thermal conductivity, aggregation prohibition, volumetric heat capacity, phase change temperature and thermal stability, while PEG/graphite composites exhibited excellent performance on thermal diffusivity, phase change (melting) temperature, specific heat capacity and cyclability.

Optimization of Piezoresistive Response of Elastomeric Porous Structures Based on Carbon-Based Hybrid Fillers Created by Selective Laser Sintering.

Recently, piezoresistive sensors made by 3D printing have gained considerable interest in the field of wearable electronics due to their ultralight nature, high compressibility, robustness, and excellent electromechanical properties. In this work, building on previous results on the Selective Laser Sintering (SLS) of porous systems based on thermoplastic polyurethane (TPU) and graphene (GE)/carbon nanotubes (MWCNT) as carbon conductive fillers, the effect of variables such as thickness, diameter, and porosity of 3D printed disks is thoroughly studied with the aim of optimizing their piezoresistive performance. The resulting system is a disk with a diameter of 13 mm and a thickness of 0.3 mm endowed with optimal reproducibility, sensitivity, and linearity of the electrical signal. Dynamic compressive strength tests conducted on the proposed 3D printed sensors reveal a linear piezoresistive response in the range of 0.1-2 N compressive load. In addition, the optimized system is characterized at a high load frequency (2 Hz), and the stability and sensitivity of the electrical signal are evaluated. Finally, an application test demonstrates the ability of this system to be used as a real-time wearable pressure sensor for applications in prosthetics, consumer products, and personalized health-monitoring systems.

Design and optimization of a TiO2/RGO-supported epoxy multilayer microwave absorber by the modified local best particle swarm optimization algorithm

Abstract Microwave absorbers have many applications in medical, industrial, and military devices. Polymeric composites including carbon-based filler can be used as lightweight absorbers with high electromagnetic (EM) wave absorption performance. Hence, multilayer microwave absorbers were designed using titanium dioxide (TiO2)/reduced graphene oxide (RGO)/epoxy nanocomposites with different weight percentages manufactured using refluxing and annealing methods. The characterization of nanocomposite indicated thin layers of TiO2/RGO as divided sheets in epoxy. The EM properties of the nanocomposites were examined using the Nicolson-Ross-Weir (NRW) detection method. The S-parameters were measured using PNA-N5222A Microwave Network Analyzer. The multilayer absorber software was designed based on the modified local best particle swarm optimization algorithm by MATLAB software, in which the material and thickness of layers were optimized with two cost functions in X-band frequencies. The first cost function seeks to reach the best absorption bandwidth, and the second cost function seeks to reach the maximum average return loss (RL) of the frequency range of 8.2–12.4 GHz. A maximum bandwidth with an RL of less than −12.81 dB was obtained with a thickness of 2.4 mm. A maximum average RL of −22.1 dB was obtained with a thickness of 2.6 mm. The maximum absorption peak was observed with a thickness of 2.5 mm with −62.82 dB at a frequency of 10.86 GHz.

Electrical impedance-based evaluation of self-healing degree in cement composites with biological admixtures

The present study aims to explore the potential of using electrical impedance measurements for evaluating the self-healing degree in cement composites incorporating biological admixtures. Four different carbon-based conductive fillers such as carbon black, carbon nanotube, carbon fiber, and graphene were employed in the cementitious composites to ensure the electrical conductivity in the composite samples. The applicability of carbon-based fillers for evaluating self-healing degree was assessed by comparing the present electrical impedance-based evaluation with the self-healing degree quantitatively obtained from microscopic images and the regain in compressive strength. The samples containing carbon nanotube or graphene were shown to have satisfactory self-healing capacities, as evidenced by the restoration of electrical conductivity and the regain in compressive strength.

Thermally Conductive Molten Salt for Thermal Energy Storage: Synergistic Effect of a Hybrid Graphite-Graphene Nanoplatelet Filler.

Renewable energy technologies depend, to a large extent, on the efficiency of thermal energy storage (TES) devices. In such storage applications, molten salts constitute an attractive platform due to their thermal and environmentally friendly properties. However, the low thermal conductivity (TC) of these salts (<1W m-1 K-1) downgrades the storage kinetics. A commonly used method to enhance TC is the addition of highly conductive carbon-based fillers that form a composite material with molten salt. However, even that enhancement is rather limited (<9W m-1 K-1). In this study, the partial exfoliation of graphite to graphene nanoplatelets (GnP) in a molten salt matrix is explored as a means to address this problem. A novel approach of hybrid filler formation directly in the molten salt is used to produce graphite-GnP-salt hybrid composite material. The good dispersion quality of the fillers in the salt matrix facilitates bridging between large graphite particles by the smaller GnP particles, resulting in the formation of a thermally conductive network. The thermal conductivity of the hybrid composite (up to 44W m-1 K-1) is thus enhanced by two orders of magnitude versus that of the pristine salt (0.64W m-1 K-1).

Influence of print settings on conductivity of 3D printed elastomers with carbon-based fillers

Flexible, elastomeric materials for 3D printing have attracted considerable interest due to their potential application in clothing, shoe manufacturing and orthopedics. At the same time, smart clothing is also moving closer to more mainstream applications; as such, it is of considerable interest to combine both the structural and smart functions 3D printing offers in one material. While smart functionalities may be incorporated in a textile in a variety of ways (e.g. using shape-memory polymers), the use of electronic components such as sensors and actuators allow smart response to a multitude of stimuli. This necessitates the use of conductive and flexible materials that offer reliable conductivity after printing and provide optically attractive results. It is known that print conditions influence electrical properties, but while the print parameters are well researched for hard materials, there is not as much research for flexible compounds. Here, we show the influence of print speed, temperature, infill orientation, layer thickness and print mode (i.e. time between printing of successive layers). It was found that the most influential parameters are print mode, infill orientation and print temperature. The differences in electrical properties between the three materials used in this test may be explained by differences in filler content. A preliminary study into the optimization of the shape of a printed conductive line on elastic textile shows that the overall length of the printed path needs to be adapted to the maximum stretch of the textile, while shape has little influence on conductivity.

Characterization and piezo-resistivity studies on graphite-enabled self-sensing cementitious composites with high stress and strain sensitivity

Carbon-based conductive fillers have recently been incorporated into a cement matrix to develop an intrinsic self-sensing concrete for data monitoring without the need for embedded, attached, or remote sensors while maintaining or improving its mechanical properties and durability. This paper studies cementitious composites filled with graphite as a novel self-sensing construction material. Experiments were systematically conducted to investigate the dispersion, chemical, mechanical, electroconductivity and piezo-resistivity properties of the composites. Experimental results showed an effective mixing with uniform dispersion of the graphite which acted as an inert filler in the mix and did not alter the microstructure of cement hydration products. Isothermal calorimetry, TGA and rheology tests showed good hydration and adequate workability of the composites with low graphite concentration (≤ 10%), while the effect of adding graphite on the compressive strength is insignificant for graphite concentrations of up to 10%. Monotonic and cyclic compressive test results indicated a repeatable piezo-resistivity performance for low graphite concentration cementitious composites whose stress sensitivity values vary from 0.75 to 7.25%/MPa, and strain sensitivity/gauge factor (GF) 150–1250 with some hysteresis. These combinations showed a stable and reliable piezo-resistivity and the ability to detect damage upon failure.

Commercial and recycled carbon-based fillers and fibers for self-sensing cement-based composites: Comparison of mechanical strength, durability, and piezoresistive behavior

The possible use of industrial by-products as carbon-based fillers and/or fibers to produce Multifunctional Cement-based Composites (MCC) with piezoresistive behavior for Structural Health Monitoring (SHM) was investigated. As fillers, Used Foundry Sand (UFS) and Gasification Char (GCH) were compared with commercial Graphene Nanoplatelets (GNP). As fibers, 6 mm-long recycled carbon fibers (RCF) were compared with virgin ones. Mortars were tested in terms of mechanical strength, water absorption, microstructure, and piezoresistive behavior. UFS and GCH are more effective than GNP in decreasing the mortar electrical resistivity (−30%), total porosity (−11%), water absorption (−27%) and in increasing the compressive strength (+10%). The combination of UFS with RCF in mortars provides the best results in terms of fluidity, strength, water absorption, and piezoresistive parameters. Generally, a lower mortar resistivity, even if with lower piezoresistivity properties, allows the use of cheaper instrumentation for SHM, thanks to the lower full scale and the better correlation strength between the change in resistivity with strain.

Review of Recent Advances in the Electrical/Mechanical Characteristics of Nanocomposites and Multi-scale Modeling of Nanocomposites

Nanocomposites have been considered innovative composite materials that have multi-functionality and high performance. Because the incorporation of nanoscale fillers may significantly improve the electrical, mechanical, and thermal properties of composites, numerous extensive studies on the characterization of nanocomposites with nanoscale fillers have been performed. In particular, the development of nanocomposites using carbon-based nanoscale fillers (e.g., carbon nanotubes, carbon black, graphene nanoplates) have attracted much interest in the composite field. This paper provides a review of recent advances in the electrical/mechanical characteristics of nanocomposites, which are essential for their practical applications. Furthermore, this paper revisits the recent research on multi-scale modeling, which is a promising approach for predicting the characteristics of nanocomposites. The current challenges and future development potentials for multi-scale modeling are also discussed.

Tribological performance of electrically conductive and self-lubricating polypropylene-ionic-liquid composites.

In this work, self-lubricating and electrically conductive polymers on a polypropylene (PP) matrix were prepared and investigated. These properties were obtained by additivating PP with carbon black (CB) and multi-walled carbon nanotubes (MWCNTs), in combination with a surface active ionic liquid (IL, trihexyltetradecylphosphonium docusate [P66614][DOC]). These polymeric composites are expected to achieve coefficients of friction (COFs) comparable to lubricated systems. Combined with electrical conductivity, these materials could be applied in electrically loaded tribosystems. The COF was reduced by up to 25% compared to that of plain PP, and high electrical conductivity and self-lubrication were achieved. Fundamental differences between the carbon-based fillers in their interaction with IL were investigated with high-resolution surface analysis (TEM, AFM) and Raman and ATR-FTIR spectroscopy. By varying the tribological test parameters, the application limits of self-lubrication were identified. It was demonstrated that the contact pressure has a strong influence on the COF. Therefore, this work points to potential applications in (e.g. 3D-printed) bearings and electrically loaded bearings where electrical conductivity and relatively low COFs are required.

A novel measurement system for self-sensing graphite-cement composites

Carbon-based conductive fillers have been incorporated into cement matrix to develop smart self-sensing materials with piezoresistive properties. However, accurately measuring the sensing property of the cement composite without compromising its mechanical performance is not easy to achieve in practical engineering. Therefore, in this study, a novel experimental setup for measuring the self-sensing properties of conductive fillers embedded cementitious composites was developed. This multi-functional measurement system is able to measure specimens under compressive and flexural stress with different loading profiles, apply various loading rates, obtain the electrical properties, and measure the strain using both LVDT and Particle Image Velocimetry (PIV) or Digital Image Correlation (DIC) techniques with all the data synchronised to one file sharing the same time stamp controlled by Python codes. In this study, the piezoresistivity and the performance on damage detection of the cementitious composites with low graphite concentration (5%) in a bulk form were investigated through monotonic compressive and flexural tests. Experiment results include the specimens’ stress, strain and Fractional Change in Resistivity (FCR). Data analysis showed that the set-up and methodology developed in this study are effective to test self-sensing cementitious composites, and the graphite-cement composites used in this study have a stable piezoresistivity and able to detect damage upon failure.

Development of polypropylene-based composites through fused filament fabrication: The effect of carbon-based fillers

• PP composites reinforced with carbonaceous fillers were developed using FFF. • Filaments of each material were processed, and a viable FFF process was optimized. • The effect of fillers was evaluated in terms of materials' thermo-physical properties. • The addition of fillers led to improvements of mechanical properties of FFF samples. Fused Filament Fabrication (FFF) is the most widespread additive manufacturing technique for polymeric materials. However, only a limited number of materials are available to be processed through this technique. Polypropylene and its composites are extremely versatile materials which are employed in a wide range of applications, but their use in FFF has not been much investigated due to issues related to adhesion and warping. In this work, composites having polypropylene as matrix and different carbonaceous fillers, namely carbon nanotubes and carbon fibers, were developed using FFF. Compounding, filament extrusion and FFF processes were successfully developed and optimized for each material. The materials were characterized in terms of their thermo-physical properties and the effect of the fillers on these properties was investigated. The addition of carbon fibers led to a significant improvement of mechanical properties, and a more moderate increase was observed in the case of carbon nanotubes addition.

Polystyrene Waste Recycling Process as an Alternative Antistatic Packaging Raw Material

Composite synthesis from styrofoam (polystyrene-based) was carried out by solvent blending method in which the solvent used was gasoline. The carbon black (CB) was used as filler comes from coconut shells. The samples were given a variation of filler composition: 0, 1, 3, and 5% of the total weight of the composite to be formed. In this method, stirring was carried out for at least 120 minutes (200 rpm in atmospheric conditions). The stirring process is carried out until the mixture becomes homogeneous, as indicated by the slurry formation. After that, the process continues to the printing stage using glass mold and drying in a windy room that is sufficiently exposed to sunlight for 3 days. The sample obtained is a composite measuring 8 cm x 8 cm. The tests carried out were the ATR-FTIR, SEM, conductivity, and mechanical tests. From the results of the ATR-FTIR test, there was no visible difference between the styrofoam before being treated with the composites, thus proving that the solvent had evaporated. The results of the SEM test show that there are lumps in the sample with higher filler concentrations, so it is possible to need additional time or stirring speed to distributed the filler evenly. Meanwhile, the conductivity test proved that the addition of carbon-based filler could increase the conductivity of the composites.

Development and characterization of active starch-based films incorporating graphene/polydopamine/Cu2+ nanocomposite fillers

With increasing environmental awareness and food safety concern worldwide, biodegradable active food packaging gained wide attention in recent years. Starch has been regarded as one of the most potential biomaterials to produce biodegradable films. However, relatively poor functional performance of starch-based films severely limits their application as food packaging materials. Carbon-based fillers can be used to enhance the functional attributes of starch-based films, but they are often difficult to incorporate because of their poor matrix dispersibility. In this study, we developed a simple green method to improve the dispersity of graphene in starch-based films by modifying the graphene surfaces using mussel-inspired polydopamine and copper ions. Spectroscopy and morphology analyses showed the surface of graphene was successfully modified. The addition of the nanocomposites positively influenced the microstructure of the starch-based films, as well as impacting their mechanical, barrier, and thermal properties. Additionally, the composite films exhibited antibacterial activity against food borne pathogens, suggesting promising potential of the films acting as active food packaging. Overall, the method developed in this study has the potential for optimizing and endowing extra properties of starch-based films so as to increase their application in biodegradable food packaging.

Sustainable, bio-based conductive materials from peanut waste for flexible electronics and tunable piezoresistive strain sensors

Sustainable engineering applications are of great significance in materials science because of limited natural resources. This study presents a sustainable, bio-based approach for the fabrication of flexible electronics and sensors by using peanut shell and skin as the precursors for conductive carbon-based fillers. Carbonized samples showed differences in terms of morphological, structural, and electrical properties. While peanut shell-based carbon showed higher crystallinity and morphology with multiple channels; peanut skin-based carbon showed stacked, layered morphology with smaller particle size. Elastic modulus of the samples increased, tensile strength, and tensile strain values were decreased for both composite sets. The electrical conductivity of the samples prepared by carbon from peanut shell showed lower percolation concentration. Both composites showed piezoresistive response under cycling loading/unloading and tunable piezoresistive sensors were shown to be sensitive to human motions including horizontal and vertical elbow movement and back and forth knee bending and squatting.

Paenibacillus mucilaginosus LT1906 exopolysaccharide-based composite aerogel for flexible strain sensor

Combination of the flexibility of polysaccharide-based aerogel with the conductivity and mechanical strength of carbon-based fillers is the ideal candidate for development of flexible strain sensors. In this study, exopolysaccharides (EPS) from Paenibacillus mucilaginosus (P.m) LT1906 was extracted. The microbial EPS and carbon nanotube (CNT) composite aerogel was fabricated. Using Na2CO3 as the deacetylation intensifier and BDDE as the cross-linker, EPS was constructed into the 3D interconnected porous structure physically compounded with CNT through facile freeze-drying technique. The resulting EPS/CNT composite aerogel can withstand a high compression strain of 70% and exhibits excellent fatigue resistance, with only 1.4% plastic deformation after 5000 cycles at 50% strain. It can also real-time test dynamic compression in the wide linear strain range of 0∼30%, with the low strain detection limit of 0.25%, sensitivity of 4.28 and the high resistance stability. Cyclable compressibility, high sensitivity and resistance stability have been verified in application trials in real-time and in-situ monitoring of human motions, especially subtle motion, thus suggesting feasibility of EPS/CNT composite aerogels in wearable strain sensors. The renewable and cost-effective microbe-derived polysaccharide as aerogel precursors will help to expand the application range of bio-polysaccharide aerogels.