Green preparation of electrically conductive solution blow spun nanofibers from recycled polyethylene terephthalate via plasma-assisted oxidation-reduction

Simple and green strategy was described for the development of multifunctional polyester nanofibers (PNFs). Solution blow spinning (SBS) technology was applied to in situ immobilize nanocomposites of polyaniline (PANi) and silver nanoparticles (AgNPs) into plasma-treated polyester nanoscaled fibers prepared. The polyester nanofibers were prepared from recycled polyethylene terephthalate waste, which was exposed plasma-curing and a REDOX reaction in the presence of AgNO₃, aniline, and CH₃COONH₄. Plasma-catalyzed oxidative polymerization of aniline to polyaniline together with a reductive process of Ag⁺ to silver nanoparticles led to their enduring insoluble dispersion into the surface of polyester nanofibers. By taking the advantage of the PANi oxidation, AgNPs were precipitated from an aqueous medium of AgNPs. The morphological properties were investigated by various analytical techniques. The polyester fiber diameter was determined in the range of 450-650 nm. In addition, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were utilized to examine AgNPs, demonstrating diameters of 4-20 nm. The plasma-uncured AgNPs/PANi immobilized nanofibrous film displayed weak absorption bands at 399 nm and 403 nm upon increasing the concentration of AgNPs. On the other hand, the plasma-cured AgNPs/PANi immobilized nanofibers displayed strong absorption bands at 526 nm and 568 nm upon increasing the concentration of AgNPs. The AgNP-induced antimicrobial performance and the PANi-induced electrically conductivity were explored. The prepared PNFs showed high UV protection.

Magnetic Self-Healing Composites: Synthesis and Applications

Magnetic composites and self-healing materials have been drawing much attention in their respective fields of application. Magnetic fillers enable changes in the material properties of objects, in the shapes and structures of objects, and ultimately in the motion and actuation of objects in response to the application of an external field. Self-healing materials possess the ability to repair incurred damage and consequently recover the functional properties during healing. The combination of these two unique features results in important advances in both fields. First, the self-healing ability enables the recovery of the magnetic properties of magnetic composites and structures to extend their service lifetimes in applications such as robotics and biomedicine. Second, magnetic (nano)particles offer many opportunities to improve the healing performance of the resulting self-healing magnetic composites. Magnetic fillers are used for the remote activation of thermal healing through inductive heating and for the closure of large damage by applying an alternating or constant external magnetic field, respectively. Furthermore, hard magnetic particles can be used to permanently magnetize self-healing composites to autonomously re-join severed parts. This paper reviews the synthesis, processing and manufacturing of magnetic self-healing composites for applications in health, robotic actuation, flexible electronics, and many more.

Synthesis and Characterization of Supercapacitor Materials from Soy

Renewable resources and their byproducts are becoming of growing interest for alternative energy. Here, we have demonstrated the use of Arkansas’ most important crop, soy, as a carbon precursor for the synthesis of carbonized activated materials for supercapacitor applications. Different soy products (soymeal, defatted soymeal, soy flour and soy protein isolate) were converted into carbonized carbon and co-doped with phosphorus and nitrogen simultaneously, using a facile and time-effective microwave synthesis method. Ammonium polyphosphate was used as a doping agent which also absorbs microwave radiation. The surface morphology of the resulting carbonized materials was characterized in detail using scanning electron microscopy. X-ray photoelectron spectroscopy was also performed, which revealed the presence of a heteroelemental composition, along with different functional groups at the surface of the carbonized materials. Raman spectroscopy results depicted the presence of both a graphitic and defect carbon peak, with defect ratios of over one. The electrochemical performance of the materials was recorded using cyclic voltammetry in various electrolytes including acids, bases and salts. Among all the other materials, soymeal exhibited the highest specific capacitance value of 127 F/g in acidic electrolytes. These economic materials can be further tuned by changing the doping elements and their mole ratios to attain exceptional surface characteristics with improved specific capacitance values, in order to boost the economy of Arkansas, USA.

Progress in polymers and polymer composites used as efficient materials for EMI shielding

The explosive progress of electronic devices and communication systems results in the production of undesirable electromagnetic pollution, known as electromagnetic interference. The accumulation of electromagnetic radiation in space results in the malfunction of commercial and military electronic appliances, and it may have a negative impact on human health. Thus, the shielding of undesirable electromagnetic interference has become a serious concern of the modern society, and has been a very perspective field of research and development. This paper provides detailed insight into current trends in the advancement of various polymer-based materials with the effects of electromagnetic interference shielding. First, the theoretical aspects of shielding are outlined. Then, the comprehensive description of the structure, morphology and functionalization of the intrinsic conductive polymers, polymers filled with the different types of inorganic and organic fillers, as well as multifunctional polymer architectures are provided with respect to their conductive, dielectric, magnetic and shielding characteristics.

Controllable preparation of magnetic carbon nanocomposites by pyrolysis of organometallic precursors, similar molecular structure but very different morphology, composition and properties

Organometallic compounds were synthesized for solid-state pyrolysis to research the structure–property relationship between the precursors and the as-generated magnetic carbon nanocomposites.

Superiority of graphite coated metallic-nanoparticles over graphite coated insulating-nanoparticles for enhancing EMI shielding

A superior EMI shielding effectiveness (SE) for composites with a metallic(Ni)@graphite core and lower SE for a dielectric(MnO)@graphitic core of carbonaceous materials.

Galvanic Replacement Reaction Involving Core-Shell Magnetic Chains and Orientation-Tunable Microwave Absorption Properties

Electromagnetic (EM) wave absorption materials have attracted considerable attention because of EM wave pollution caused by the proliferation of electronic communication devices. One-dimentional (1D) structural magnetic metals have potential as EM absorption materials. However, fabricating 1D core-shell bimetallic magnetic species is a significant challenge. Herein, 1D core-shell bimetallic magnetic chains are successfully prepared through a modified galvanic replacement reaction under an external magnetic field, which could facilitate the preparation of 1D core-shell noble magnetic chains. By delicately designing the orientation of bimetallic magnetic chains in polyvinylidene fluoride, the composites reveal the decreased complex permittivity and increased permeability compared with random counterparts. Thus, elevated EM wave absorption perfromances including an optimal reflection loss of -43.5 dB and an effective bandwidth of 7.3 GHz could be achieved for the oriented Cu@Co sample. Off-axis electron holograms indicate that the augmented magnetic coupling and remarkable polarization loss primarily contribute to EM absorption in addition to the antenna effect of the 1D structure to scatter microwaves and ohmic loss of the metallic attribute. This work can serve a guide to construct 1D core-shell bimetallic magnetic nanostructures and design magnetic configuration in polymer to tune EM parameters and strengthen EM absorption properties.

Mechanistic insights into the optical limiting performance of carbonaceous nanomaterials embedded with core–shell type graphite encapsulated Co nanoparticles

Globular amorphous carbonaceous materials embedded with graphite encapsulated metallic Co-nanoparticles with a high degree of crystallinity are synthesized by pyrolysis and demonstrated as excellent candidates for optical limiters.

Facile fabrication of Co@C nanoparticles with different carbon-shell thicknesses: high-performance microwave absorber and efficient catalyst for the reduction of 4-nitrophenol

Co@C nanoparticles with different carbon-shell thicknesses can be used as a multifunctional material for a high-performance microwave absorber and as an efficient catalyst for the reduction of 4-nitrophenol.

Core–shell hybrid nanowires with Co nanoparticles wrapped in N-doped porous carbon for lightweight microwave absorption

One-dimensional core–shell structured nanowires with Co nanoparticles wrapped in N doped porous carbon were designed as a lightweight, thin and high-performance electromagnetic absorber.