Equi-Biaxial Fatigue Behaviour of Magnetorheological Elastomers in Magnetic Fields

The equi-biaxial fatigue behaviour of silicone based magnetorheological elastomers (MREs) in external magnetic fields was studied. Wöhler curves relating fatigue life to stress amplitude and dynamic stored energy for MREs with a range of magnetic particle contents were derived. It was found that the fatigue life of MREs in magnetic fields was higher than that without magnetic fields. Under constant stress amplitude conditions, the presence of magnetic fields resulted in longer times for the samples to undergo large deformations and thus complex modulus (E*) decreased at a slower rate during the fatigue process, especially for low stress amplitudes. MRE samples tested in the presence of magnetic fields reached limiting values of E* at failure ranging from 1.28 MPa to 1.44 MPa. The application of magnetic fields was found to have negligible influence on the damping loss factor of MREs containing various volume fractions of carbonyl iron particles

Fabrication of Dielectric Elastomers with Improved Electromechanical Properties Using Silicone Rubber and Walnut Polyphenols Modified Dielectric Particles

In this work, polyphenolic extract from walnut green husks (denoted as walnut polyphenols), which is an abun-dant agroindustrial residue/waste, was used to modify barium titanate (BT) particles in the preparation of sili-cone rubber (SR) based dielectric elastomer (DE) composites with enhanced electromechanical performance.By employing walnut polyphenols modification, the dispersibility of BT particles in the SR matrix and the com-patibility between BT and SR were greatly improved, which resulted in enhanced mechanical performance ofthe DE composites. Dielectric property measurement showed that DE composites containing walnut polyphenolsmodified BT particles (WNBT) had higher dielectric constants and lower dielectric losses than that of DEs withunmodified BT particles. Furthermore, it was found that the walnut polyphenols modification resulted in de-creased dielectric loss tangent of the DE composites, suggesting an improved compatibility between the modifiedBT particles and SR. Finally, the static and dynamic electromechanical performance of the DE composites wereevaluated. The SR/5%WNBT composite achievedthehighest actuatedareastrainof 38% among the SRbasedcom-posites used in this work. Moreover, the actuated area strain of SR/WNBT composites exhibited excellent electro-mechanical stability during the application of cyclic voltage signals

Enhanced gas barrier properties of graphene oxide/rubber composites with strong interfaces constructed by graphene oxide and sulfur

Constructing strong interfacial interactions and complex filler networks is crucial to establishing high gas barrier properties in rubber composites. In this research, sulfur-graphene oxide (S-GO) hybrids were prepared by in situ growth of sulfur on the surfaces of GO sheets. The S-GO hybrids were also introduced into butadiene styrene rubber (SBR) using a green method of latex compounding. Results showed that sulfur could melt and spread on the surface of the GO during the crosslinking process at high temperatures. This process prevented the aggregation of GO and resulted in a fine dispersion of GO and complex filler networks in S-GO/SBR composites. More importantly, the sulfur particles on the GO surface not only aided the crosslinking of rubber molecules, but also chemically reacted with the GO radicals generated at high temperatures. This occurred by the homolytic cleavage of oxygen-containing groups, which thereby constructed covalent interfaces between the GO and SBR molecules. Due to these strong interfaces and complex filler networks, the tensile and tear strength of S-GO/SBR composites increased by 66.2% and 26.6%, respectively, when compared with conventional GO/SBR composites. The gas permeability coefficient of S-GO/SBR composites was decreased dramatically by 50.7% and 23.3% by comparison with that of pure SBR and GO/SBR composites, respectively. The apparent improvement demonstrated that the facile and effective method used in this research may open up new opportunities for the development of multifunctional rubber crosslinking agent as well as the fabrication of rubber composites with high performance

Enhanced covalent interface, crosslinked network and gas barrier property of functionalized graphene oxide/styrene-butadiene rubber composites triggered by thiol-ene click reaction

The high gas barrier property of a rubber composite is of great significance for reducing the exhaust gas emissions due to tire rolling resistance and hence the contribution this factor makes to environmental protection. Enhanced covalent interfaces and crosslinked networks are crucial to the gas barrier property of rubber composites. In this research, γ-mercaptopropyltriethoxysilane (MPS) modified GO (MGO)/styrene-butadiene rubber (SBR) composites were prepared by a synergetic strategy of latex compounding method and thiol-ene click reaction. It was found that the mercapto groups in MGO reacted with the vinyl groups in SBR molecules through thiol-ene click reaction during the crosslinking process at 150 °C, thus forming strong chemical interactions at the interface in the form of GO-MPS-rubber and enhanced crosslinked networks. Meanwhile, the strong interface promoted the dispersion of MGO in SBR. The uniform dispersion of MGO, strong interface between MGO and SBR molecules and enhanced crosslinked networks resulted in improved mechanical and gas barrier properties. When filling 5 phr fillers, the tensile strength and gas barrier properties of an MGO/SBR composite improved by 19.0% and 37.5%, respectively, relative to the comparing GO/SBR composite

Diaqua­(2,2′-bipyridine-6,6′-dicarboxyl­ato)nickel(II)

In the title compound, [Ni(C12H6N2O4)(H2O)2], the NiII atom (site symmetry 2) displays a distorted cis-NiN2O4 octa­hedral coordination geometry with two N atoms and two O atoms of the tetra­dentate 2,2′-bipyridine-6,6′-dicarboxyl­ate ligand in the equatorial plane and two water mol­ecules in axial positions. The complete dianionic ligand is generated by crystallographic twofold symmetry. In the crystal, a two-dimensional supra­molecular structure parallel to (001) is formed through O—H⋯O hydrogen-bond inter­actions between the coordinated water mol­ecules and the O atoms of nearby carboxyl­ate groups

Achieving Strong Chemical Interface and Superior Energy-Saving Capability at the Crosslinks of Rubber Composites Containing Graphene Oxide Using Thiol-Vinyl Click Chemistry

Rapidly developments in international transportation inevitably lead to an increase in the consumption of energy and resources. Minimizing the rolling resistance of tires in this scenario is a pressing challenge. To lower the rolling resistance of tires, enhancing the interaction between fillers and rubber molecules while improving the dispersion of fillers are required to reduce the internal mutual friction and viscous loss of rubber composites. In this study, graphene oxide (GO) was modified using γ-mercaptopropyltrimethoxysilane (MPTMS) with thiol groups. A modified GO/natural rubber (MGO/NR) masterbatch with a fine dispersion of MGO was then introduced into solution-polymerized styrene butadiene rubber (SSBR) to create an MGO/SiO2/SSBR composite. During the crosslinking process at high temperatures, a strong chemical interface interaction between the MGO and rubber molecules was formed by the thiol-vinyl click reaction. The MGO sheets also act as crosslinks to enhance the crosslinking network. The results showed that the rolling resistance of the MGO SiO2/SSBR composite was superior by 19.4% and the energy loss was reduced by 15.7% compared with that of the base SiO2/SSBR composite. Strikingly, the wear performance and wet skid resistance improved by 19% and 17.3%, respectively. These results showed a strong interface that not only improved rolling resistance performance but also contributed to balancing the “magic triangle” (the combination of wear resistance, fuel efficiency, and traction) properties of tires

CoLRIO: LiDAR-Ranging-Inertial Centralized State Estimation for Robotic Swarms

Collaborative state estimation using different heterogeneous sensors is a fundamental prerequisite for robotic swarms operating in GPS-denied environments, posing a significant research challenge. In this paper, we introduce a centralized system to facilitate collaborative LiDAR-ranging-inertial state estimation, enabling robotic swarms to operate without the need for anchor deployment. The system efficiently distributes computationally intensive tasks to a central server, thereby reducing the computational burden on individual robots for local odometry calculations. The server back-end establishes a global reference by leveraging shared data and refining joint pose graph optimization through place recognition, global optimization techniques, and removal of outlier data to ensure precise and robust collaborative state estimation. Extensive evaluations of our system, utilizing both publicly available datasets and our custom datasets, demonstrate significant enhancements in the accuracy of collaborative SLAM estimates. Moreover, our system exhibits remarkable proficiency in large-scale missions, seamlessly enabling ten robots to collaborate effectively in performing SLAM tasks. In order to contribute to the research community, we will make our code open-source and accessible at \url{https://github.com/PengYu-team/Co-LRIO}

The fabrication and properties of magnetorheological elastomers employing bio-inspired dopamine modified carbonyl iron particles

To obtain magnetorheological elastomers (MREs) with improved mechanical properties and exhibiting an enhanced magnetorheological (MR) effect, bio-inspired dopamine modification has been used to improve the functionality at the surface of carbonyl iron (CI) particles. Various techniques including x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to confirm that a polydopamine (PDA) layer of about 27.5 nm had been successfully deposited on the surface of the carbonyl iron particles prior to their inclusion in the MRE composites. The magnetic properties of PDA modified CI particles were shown to be almost the same as those for untreated CI particles. With the introduction of a PDA layer to the surfaces of the particles, both the tensile strength and the elongation at break of the MREs were improved. Furthermore, the MRE composites filled with PDA-coated CI particles exhibited lower zero-field storage moduli but higher magnetic field induced storage moduli when magnetization saturation was reached. The absolute and relative MR effect for the MREs reached 0.68 ± 0.002 MPa and 294% respectively, which were higher than those of MREs with pristine CI particles whose absolute and relative MR effect were 0.57 ± 0.02 MPa and 187% respectively. The findings of this work provide insights into enhanced fabrication of MREs with both improved mechanical properties and magneto-induced performance

Enhanced Fatigue and Durability of Carbon Black/natural rubber Composites Reinforced with Graphene Oxide and Carbon Nanotubes

Graphene oxide (GO) sheets and carbon nanotubes (CNTs) are of nanometer size and offer large shape factors which are beneficial in reducing crack propagation rates of composites when used in carbon black (CB) reinforced natural rubber (NR), thereby prolonging the service lives of rubber composites. In this research, CNT-CB/NR and GO-CB/NR composites were prepared by partially replacing CB with one-dimensional CNTs and two-dimensional flaky graphene oxide GO, respectively. The results showed that the complex filler dispersion in NR matrices was improved due to the isolation effect between the different fillers. The strain-induced crystallization (SIC) ability of CB/NR was effectively enhanced by the addition of both GO and CNT. The modulus at 100% strain and tear strength of the composites were also improved. More branching and deflections were observed at the crack tips of the composites and both effectively hindered crack propagation in the materials. Under uniaxial and multi-axial cyclic loading, the fatigue lives of CNT-CB/NR and GO-CB/NR composites greatly increased when compared with the fatigue lives of CB/NR composites. The GO-CB/NR composites exhibited evident advantages in respect of fatigue resistance and durability among the three composites

Influence of graphene oxide and carbon nanotubes on the fatigue properties of silica/styrene-butadiene rubber composites under uniaxial and multiaxial cyclic loading

The influence of equivalent replacement of silica (SiO2) by carbon nanotubes (CNT) or graphene oxide (GO) on the microstructure, mechanical and fatigue behaviors of SiO2/styrene-butadiene rubber (SBR) composites was investigated. Results showed that the synergistic effect between CNT (or GO) and SiO2 was beneficial for the filler network and improved the mechanical properties of SBR composites. Furthermore, the introduction of CNT (or GO) led to low crack growth rates and the crack propagation tips were easy to deflection. Under multiaxial fatigue conditions, the maximum engineering stress was determined to be a reliable fatigue life predictor for SBR composites