Carbon Black Network Research Articles

Strain Sensing Enhancement of 3D-printed Polyurethane through Surface Deposition of Carbon Black

Strain sensors for wearable electronics function by identifying mechanical deformations and translating into electrical signals. For optimal performance, electrical conductivity, electrical sensitivity, and flexibility are major properties of strain sensors. Polyurethane (PU) shows promise for custom strain sensors due to its high flexibility. Additionally, using digital light processing (DLP) 3D printing to shape PU is suitable for detecting body movements. Therefore, the aim of this study is developing 3D-printed PU to strain sensing devices, utilizing the surface coating method on 3D-printed PU with carbon black (CB) and polydimethylsiloxane (PDMS) to fabricate the (PDMS+CB)/CB/PU strain sensor. The conductive network of CB enhances sensitivity, while PDMS is incorporated to act as an adhesive for the durability of CB on the PU surface. The results of the experiment reveal a gauge factor of 6.04 with range from 1 to 10% elongation. The strain sensor of this study has high potential to use for strain sensing technology and is capable of detecting small body movements.

Structural Analysis of Cathode Slurry Under Flow Using New Probe for Rheo-Impedance Measurements

A battery slurry will experience a variety of shear stresses as it goes through the manufacturing process. The full characterization of a slurry for quality control is challenging due to the complex and changing relationship between active material particles, binder, and the carbon black conductive network as a function of these different shear environments. Rheology is a powerful tool for measuring suspension stability and the viscosity at different shear stresses. However, it cannot characterize the structure of the carbon black conductive network because the rheological properties are dominated by the larger active material particles. Poor distribution or aggregation of the carbon black additive will create an electrode with higher electrical resistance, resulting in more heat generation and a shorter cycle life. Electrochemical impedance spectroscopy is an information dense technique that probes the sample using an alternating current or potential at a range of frequencies. Amongst its many applications, EIS can discriminate between simultaneous events that take place over different time scales, such as the measurement of conductivity within a solid electrode vs the ionic conductivity of the electrolyte. Combining these techniques into a simultaneous measurement will characterize the rheological behavior and the structure of the carbon black conductive network under flow and temperature conditions that are relevant for a manufacturing environment. A novel probe for the simultaneous measurement of rheological properties and electrochemical impedance spectroscopy (Rheo-EIS) is herein presented. A structural analysis of Li-ion battery cathode slurries and carbon paste is used to demonstrate the technique.

Graphene oxide and carbon black synergistic coated cotton fabric for enhancing energy harvesting from water droplets

Hydrovoltaic generators (HGs), which harness sustainable energy directly from water flow have garnered tremendous interest worldwide due to their cost-effectiveness, eco-friendliness and potential for powering wearable electronics. However, current HGs generally suffer from poor ion selectivity and resistance matching resulting in low output current, limiting their application scenarios. Herein, a flexible cotton fabric based hydrovoltaic generator (CFHG) fabricated by successive modification with carbon black (CB) and graphene oxide (GO) is proposed, contributing to a simple yet effective performance improvement. Benefiting from the enhanced charge transfer efficiency, ion selectivity and fast capillary flow contributed by CB, GO and fiber network respectively, a considerable open-circuit voltage (Voc) of ∼0.75 V and a short-circuit current (Isc) of ∼8.7 μA are obtained when exposed to water droplets. Experimental results indicate that the power generation performance is influenced by various factors, including the amount of GO, cation size, liquid volume, polarity and pH, as well as temperature and humidity. Moreover, excellent flexibility and porosity of the CF substrate facilitate unconventional serial or parallel connections, providing sufficient power supply for commercial devices and wearable electronics. This research is highly significant for designing versatile power supplies for next-generation intelligent wearable electronics.

The effect of Li(Ni0.9Co0.05Mn0.05)O2 on improving electrical properties of semi-conductive LDPE/EVA/CB composites

The conductive mechanism of the semiconductor shielding layer between the conductive core and the insulation layer of high-voltage direct current (HVDC) cables includes tunneling and over-diffusion theories; however, the ethylene vinyl acetate copolymer (EVA) matrix in the semi-conductive composite material expands when heated, leading to a break in the carbon black (CB) conductive networks, which results in an increase in resistivity and the formation of the positive temperature coefficient (PTC) effect. The addition of materials with negative temperature coefficient (NTC) properties can weaken the PTC effect while absorbing some free electrons to enhance the suppression of space charge injection into the insulating layer. Li(Ni0.9Co0.05Mn0.05)O2 (NCM) was prepared by sol–gel method, which was melted and mixed with low-density polyethylene (LDPE), EVA, and CB, and pressed and molded to obtain modified semi-conductive composites. The semiconducting composites were measured by resistivity, thermal stimulation depolarizing current method (TSDC), and pulsed electroacoustic method (PEA). The results showed that the composites had the best performance when the NCM doping was 2 wt%.

Variable sensitivity multimaterial robotic e-skin combining electronic and ionic conductivity using electrical impedance tomography

Electronic skins (e-skins) aim to replicate the capabilities of human skin by integrating electronic components and advanced materials into a flexible, thin, and stretchable substrate. Electrical impedance tomography (EIT) has recently been adopted in the area of e-skin thanks to its robustness and simplicity of fabrication compared to previous methods. However, the most common EIT configurations have limitations in terms of low sensitivities in areas far from the electrodes. Here we combine two piezoresistive materials with different conductivities and charge carriers, creating anisotropy in the sensitive part of the e-skin. The bottom layer consists of an ionically conducting hydrogel, while the top layer is a self-healing composite that conducts electrons through a percolating carbon black network. By changing the pattern of the top layer, the resulting distribution of currents in the e-skin can be tuned to locally adapt the sensitivity. This approach can be used to biomimetically adjust the sensitivities of different regions of the skin. It was demonstrated how the sensitivity increased by 500% and the localization error reduced by 40% compared to the homogeneous case, eliminating the lower sensitivity regions. This principle enables integrating the various sensing capabilities of our skins into complex 3D geometries. In addition, both layers of the developed e-skin have self-healing capabilities, showing no statistically significant difference in localization performance before the damage and after healing. The self-healing bilayer e-skin could recover full sensing capabilities after healing of severe damage.

A rational design of a carbon black percolation network glass fibers for modeling an in situ self-reporting composite

The study proposed in this manuscript is aimed at developing a novel real-time monitoring system using carbon black (CB) as the primary sensing material which is nontoxic, highly sensitive, easily synthesizable, and durable at harsh environments. The percolation network characteristics are studied in order to determine a better approach to the existing prototypal model. Varying percentages of CB such as 5, 10, 15, and 20 wt% were added to a 10 wt% of surfactant solution. The solution is coated on a glass fiber (GF) strand and embedded in GF laminate to form a self-monitoring composite. A novel approach is developed where a pre-programmed setup is used to read out electrical resistance directly. The average resistance is found to be 227, 390, 589, and 842 kΩ for varying percentages of CB. 5wt% CB exhibits a higher gauge factor compared to the remaining proportions. It is characterized by studying the percolation network where many of the conductive pathways seemed to become disconnected on the application of load. The XRD characteristics confirmed the phase change in the material at (100) and (101/111) at 2θ = 24.45o and 2θ = 44.47o. A mathematical model is established using which stress in computed using the electrical resistance values obtained from the data acquisition module. This is used to continuously monitor the in situ behavior of any model subjected to external disturbances by self-reporting the data that is necessary for fault diagnosis.

BROADBAND DIELECTRIC CHARACTERIZATION OF CARBON BLACK–REINFORCED NATURAL RUBBER

ABSTRACT Natural rubber compounds reinforced with two different carbon blacks (N134 and N330) at various concentrations were characterized using very broadband dielectric spectroscopy from around 0.1 Hz to 0.3 THz using four different impedance and network analysis technologies. Percolation behavior was observed when the testing electrical frequency was below a certain range, which can be linked to the presence of percolated carbon black networks. When above a critical frequency level, the real part of AC conductivity or the permittivity tended to have a simple exponential relationship with the volume fraction of carbon black rather than a percolation-like behavior with the carbon black volume fraction and was no longer sensitive to carbon black networks. The AC conductivity derived via complex impedance was also strongly influenced by the choice of calculation model when the material was around or below the percolation threshold.

Achieving acceptable electromagnetic interference shielding in UHMWPE/ground tire rubber composites by building a segregated network of hybrid conductive carbon black

Polymeric composites with the hybrid filler network for high-performance electromagnetic interference (EMI) shielding brought increasing interest. Herein, UHMWPE/ground tire rubber (GTR)/conductive carbon black (CCB) (UGC) composites with a hybrid segregated structural CCB-GTR were constructed by solid-phase shear milling (S3M), mechanical blending, and compacted molding processes. The percolation behavior of electrical conductivity and EMI shielding effectiveness (SE) of composites was described using Sigmoidal/Growth models, and its EMI shielding mechanism was discussed. Results showed that the EMI SE of U30G70C20, U50G50C20, and U70G30C20 composites were found to be 37.5, 41.7, and 43.8 dB, respectively, due to constructing a hybrid network. The attenuation rate of microwave radiation is above 99.99%, and the shielding mechanism is mainly electrical loss. Moreover, the relationship between electrical conductivity and EMI SE is consistent with Sigmoidal/Growth models, indicating that Sigmoidal/Growth models can successfully predict the percolation threshold of the EMI SE of UGC composites.

Carbon-cement supercapacitors as a scalable bulk energy storage solution.

The large-scale implementation of renewable energy systems necessitates the development of energy storage solutions to effectively manage imbalances between energy supply and demand. Herein, we investigate such a scalable material solution for energy storage in supercapacitors constructed from readily available material precursors that can be locally sourced from virtually anywhere on the planet, namely cement, water, and carbon black. We characterize our carbon-cement electrodes by combining correlative EDS-Raman spectroscopy with capacitance measurements derived from cyclic voltammetry and galvanostatic charge-discharge experiments using integer and fractional derivatives to correct for rate and current intensity effects. Texture analysis reveals that the hydration reactions of cement in the presence of carbon generate a fractal-like electron-conducting carbon network that permeates the load-bearing cement-based matrix. The energy storage capacity of this space-filling carbon black network of the high specific surface area accessible to charge storage is shown to be an intensive quantity, whereas the high-rate capability of the carbon-cement electrodes exhibits self-similarity due to the hydration porosity available for charge transport. This intensive and self-similar nature of energy storage and rate capability represents an opportunity for mass scaling from electrode to structural scales. The availability, versatility, and scalability of these carbon-cement supercapacitors opens a horizon for the design of multifunctional structures that leverage high energy storage capacity, high-rate charge/discharge capabilities, and structural strength for sustainable residential and industrial applications ranging from energy autarkic shelters and self-charging roads for electric vehicles, to intermittent energy storage for wind turbines and tidal power stations.

EFFECTS OF SHEAR HISTORY ON THE MECHANICAL, ELECTRICAL, AND MICROSTRUCTURAL PROPERTIES OF PARTICLE-REINFORCED RUBBER

ABSTRACT The extent and nature of networks of carbon black particles in rubber compounds play a key role in determining the mechanical hysteresis and conductivity of rubber goods. It is well known that in uncrosslinked compounds, such networks display transient and time-dependent behavior when subjected to steps or ramps in shear and temperature (often called flocculation). This study probes the observed structural recoveries of carbon black networks following various levels of imposed shear strain histories. It is demonstrated that the level of shear experienced by the compound immediately before vulcanization can have a dramatic effect on the final dynamic mechanical properties of the subsequently vulcanized materials. Significant reductions in Payne effect occur when the timescales of shear-induced structural recovery, determined from rheological experiments, exceed the kinetics of vulcanization. Electrical conductivity/resistivity is also affected, especially for compounds formulated in the electrical percolation transition region. Furthermore, the microstructure of carbon black networks is tracked at different extents of recovery by using transmission electron microscopy thin section analysis and atomic force microscopy methodologies for particle network microstructure quantification. Evidence is found that relates flocculation to the progressive relaxation of shear-induced anisotropy of the carbon black micro dispersion.

Fabrication of styrene–butadienestyrene (SBS) matrix-based flexible strain sensors with brittle cellulose nanocrystal (CNC)/carbon black (CB) segregated networks

Strain sensors based on conductive polymer composites (CPCs) filled with carbon black (CB) are potential as wearable detection devices for mass production due to their low cost. However, it is still challenging to design sensors with low CB loading and the conductivity and sensitivity guaranteed. Herein, a Pickering emulsion template method was conducted to design the styrene–butadienestyrene (SBS) matrix-based strain sensors, in which a conducting structure of segregated cellulose nanocrystal (CNC)/carbon black (CB) networks was constructed, improving the conductivity and reducing the percolation threshold (φc) to ∼0.28 wt%. Besides, the CNC incorporation and defect construction in the networks greatly promote the sensitivity of the sensor, the maximum gauge factor (GF) determined is beyond 260 within the 200% strain. Moreover, the sensor can exhibit remarkable working durability and reproductivity. All these above favorable properties have empowered the strain sensor with superior applicability in detecting various human motions (finger bending, elbow bending, knee bending, neck rotation, cheek bulging, and swallowing).

Ageing behaviour and molecular/network structure evolution of EPDM/carbon black composites under compression and in thermal-oxidative environments

EPDM/carbon black (CB) composites were first prepared using sulfur as vulcanizing system, and the mechanical properties of EPDM/CB composites gradually increased with increasing CB content. Compressive stress-thermo oxidative ageing was performed in terms of three compressive stress levels and temperature conditions. During ageing process, two typical reactions of chains scission and crosslinking were deduced. On the one hand, degradation reaction of EPDM molecules occurred and unstable free radicals were produced under thermo/stress effect, which were oxidized to generate oxygenated compounds, leading to the increase of dangling chains ratio and the breakage of CB network with two-phase separation. On the other hand, the active free radicals were further consumed to initiate secondary crosslinking reaction, resulting in increase of crosslinking density and restriction of chains mobility. During the whole ageing process, the crosslinking reaction was dominant over chain scission reaction, resulting in the increase of crosslinking density and poor uniformity of network structure. Consequently, the surface/fractured surface morphologies of aged EPDM showed coarse features with obvious CB aggregates and the rupture of continuous CB network due to interfacial debonding, eventually leading to the remarkable deterioration of mechanical properties and decline of sealing resilience.

Free volume in carbon‐black‐filled isoprene rubber investigated by positron annihilation lifetime spectroscopy

AbstractThe free volume in the amorphous phase of a simple carbon‐black‐filled peroxide cross‐linked isoprene rubber (IR) is investigated by positron annihilation lifetime spectroscopy to clarify the structural changes in the rubber phase by the carbon black (CB) fillers. The ortho‐positronium (o‐Ps) pick‐off annihilation lifetime measured in the rubber without CB is around 2.8 ns and is found to be almost constant even after CB filling. This result indicates that in a portion of the rubber phase the free volume remains similar in size to that in the cross‐linked IR without CB. The o‐Ps intensity drastically decreases from 37% without CB to 15% with a CB loading as high as 80 phr. This decline is revealed to exceed the contribution, which is expected only from the decrease in the fraction of the amorphous phase by CB addition, by a factor of 0.37 at the highest CB loading. The additional reduction is related to the generation of a bound rubber layer surrounding the CB fillers with low molecular‐chain mobility where positronium formation is inhibited. The decrease rate is found to represent the volume of this rigid rubber phase and strongly depend on the formation of the CB network structure.

In situ coupled mechanical/electrical/WAXS/SAXS investigations on ethylene propylene diene monomer resin/carbon black nanocomposites

In situ coupled mechanical/electrical/WAXS/SAXS investigations on EPDM-based composite materials filled with carbon black (CB) have been performed under uniaxial tensile stretching. The time-resolved correlation between the electrical conductivity and the microstructural state of the composite reveals the mechanisms governing the structure/properties relationships with increasing deformation: orientation of the EPDM chains with reorganization of the CB network and ultimately, nano-cavitation. This involvement of different microstructural phenomena offers a comprehensive picture of the mechanisms underlying the non-monotonic evolution of the electrical conductivity with strain. At large deformations, the formation of nanovoids preceding the material fracture induces by a significant decrease in conductivity. Our study thus brings new light on the conductivity/strain relationships of carbon black filled elastomers. We envision potential applications in developing smart rubber materials where microstructural changes preceding material rupture can be monitored in situ by coupled electrical measurements. • SAXS/WAXS/Conductivity measurements were performed during deformation up to rupture. • The evolution of conductivity in EPDM-CB nanocomposites displays a maximum with extension ratio • Orientation of polymer chains and transverse interpenetration/contacting of CB occur first. • Then, cavitation limits and decrease conductivity at high extension ratios. • Conductivity measurements can be performed to detect cavitation in CB-filled elastomers.

Conductive polycarbonate composites prepared by a ternary polymer blend approach involving sea‐island‐type interfacial carbon black networks

AbstractTernary blends containing one major and two minor components are a common type of polymer blends, however, they have never been used to improve the electrical conductivity of polymer composites. Herein, polycarbonate (PC)/nylon‐poly(m‐xylene adipamide) (MXD6)/poly(ethylene terephthalate) (PET) (70/15/15) ternary blend is used to improve the conductivity of PC by forming sea‐island type interfacial carbon black (CB) networks. The phase change of PET from island to continuous structure, caused by the formation of CB networks at PET/MXD6 interface, is the key of success. The electrical percolation threshold of CB is much smaller than that in neat PC (only a ninth). Rheological investigation is carried out to confirm the formation of CB networks. The static mechanical properties of PC/MXD6/PET (70/15/15)‐2 vol% CB composite are evaluated by tensile testing, showing improved stiffness and strength, compared with the corresponding ternary blend, neat PC, and PC‐2 vol% CB composite.

Investigating Multiaxial Mullins Effect of Carbon-Black-Reinforced Elastomers Using Electrical Resistivity Measurements

The Mullins effect is commonly observed in the mechanical properties of elastomer/filler composites: The stress during unloading or second loading is considerably lower than the first loading stress. We measured the mechanical stresses and electrical conduction to investigate the Mullins effect in carbon-black (CB)-reinforced elastomers under various biaxial stretching. Imposing the small equibiaxial strain of 30% increases the electrical surface resistivity in the deformed state by more than 3 orders of magnitude, indicating the breakdown of the initial conductive percolated CB network. The resistivity of the relaxed unloaded states (ρS), representing the degree of residual destruction of the CB network, increases with the biaxial strain for small imposed deformation. However, ρS saturates at large deformations, indicating that the residual CB-network destruction does not increase further. The mechanical dissipation factor (Δ; the ratio of energy dissipation to input work) and ρS obtained at various degrees and types of deformation can be described by a single variable, i.e., the first invariant of deformation tensor. This indicates that the orthogonal strains cause the residual damage of the CB network and the internal mechanical damage.

An ultra-wide sensing range film strain sensor based on a branch-shaped PAN-based carbon nanofiber and carbon black synergistic conductive network for human motion detection and human–machine interfaces

A film sensor decorated with branch-shaped carbon nanofibers possessing extra branches achieves high sensitivity, good linearity, a wide sensing range, a fast response time, and great durability.

Thermoplastic Starch-Based Composite Reinforced by Conductive Filler Networks: Physical Properties and Electrical Conductivity Changes during Cyclic Deformation.

Conductive polymer composites (CPC) from renewable resources exhibit many interesting characteristics due to their biodegradability and conductivity changes under mechanical, thermal, chemical, or electrical stress. This study is focused on investigating the physical properties of electroconductive thermoplastic starch (TPS)–based composites and changes in electroconductive paths during cyclic deformation. TPS–based composites filled with various carbon black (CB) contents were prepared through melt processing. The electrical conductivity and physicochemical properties of TPS–CB composites, including mechanical properties and rheological behavior, were evaluated. With increasing CB content, the tensile strength and Young’s modulus were found to increase substantially. We found a percolation threshold for the CB loading of approximately 5.5 wt% based on the rheology and electrical conductivity. To observe the changing structure of the conductive CB paths during cyclic deformation, both the electrical conductivity and mechanical properties were recorded in parallel using online measurements. Moreover, the instant electrical conductivity measured online during mechanical deformation of the materials was taken as the parameter indirectly describing the structure of the conductive CB network. The electrical conductivity was found to increase during five runs of repeated cyclic mechanical deformations to constant deformation below strain at break, indicating good recovery of conductive paths and their new formation.

Reinforcing self-healing and Re-processable ionomers with carbon black: An investigation on the network structure and molecular mobility

While most self-healing elastomers are mechanically weak, using the most commonly used carbon black (CB) to reinforce self-healing elastomers has not been reported. The possible reason is that the introduction of carbon black will cause complex changes in molecular dynamics, which leads to unpredictable self-healing effects. Herein, carbon black is introduced into a self-healing ionomer based on brominated butyl rubber (BIIR) grafted with tert-butyl pyridine (BP). Interestingly, the hierarchical microstructure and multilevel molecular dynamics of ionomers are well regulated by the strong interfacial π-cation interactions between CB and ionic aggregates. The strong interfacial interaction leads to high content of bound rubber, uniform dispersion of CB and compact physical network. Although such structural change has negligible influence on the segmental motion, it enhances the relaxation time and activation energy of ionic clusters, and thus endows the ionomer with high mechanical properties. Meanwhile, the structural change leads to higher relaxation temperature, thereby increasing the self-healing temperature. Despite this fact, the healing efficiency can still be regulated between 50% and 100%, depending on the filler content and temperature. Moreover, the CB reinforced ionomer is re-processable and recyclable. This study demonstrates that CB reinforcement is feasible to improve the mechanical properties of self-healing elastomers.

The effect of a conductive polyaniline/carbon black composite on the performance of a semiconductive layer

In this study, conductive polyaniline (PANI) ribbons were introduced to a semiconductive layer to improve the conductivity stability of the layer during thermal expansion and enhance its ability to inhibit charge injection into the insulating layer. To maximise the effect of PANI, PANI and carbon black (CB) were preformed into a uniformly dispersed composite, which was then added to the polymer matrix of the semiconductive layer. The experimental results show that the resistivity of the semiconductive layer containing the PANI/CB composite is more stable during thermal expansion than that of the semiconductive layer only doped with CB. This is attributed to the conductive CB network being enhanced by the PANI ribbons. In addition, due to the unique conductivity mechanism and high dielectric constant of PANI, the semiconductive layer has a strong ability to inhibit space charge injection into the insulating layer.