High-entropy materials for thermoelectric applications: towards performance and reliability.

High-entropy materials (HEMs), including alloys, ceramics and other entropy-stabilized compounds, have attracted considerable attention in different application fields. This is due to their intrinsically unique concept and properties, such as innovative chemical composition, structural characteristics, and correspondingly improved functional properties. By establishing an environment with different chemical compositions, HEMs as novel materials possessing superior attributes present unparalleled prospects when compared with their conventional counterparts. Notably, great attention has been paid to investigating HEMs such as thermoelectrics (TE), especially for application in energy-related fields. In this review, we started with the basic definitions of TE fundamentals, the existing thermoelectric materials (TEMs), and the strategies adopted for their improvement. Moreover, we introduced HEMs, summarized the core effects of high-entropy (HE), and emphasized how HE will open up new avenues for designing high-entropy thermoelectric materials (HETEMs) with promising performance and high reliability. Through selecting and analyzing recent scientific publications, this review outlines recent scientific breakthroughs and the associated challenges in the field of HEMs for TE applications. Finally, we classified the different types of HETEMs based on their structure and properties and discussed recent advances in the literature.

Development of calcium phosphate-chitosan composites with improved removal capacity toward tetracycline antibiotic: Adsorption and electrokinetic properties.

Two eco-friendly and highly efficient adsorbents, namely brushite-chitosan (DCPD-CS), and monetite-chitosan (DCPA-CS) composites were synthesized via a simple and low-cost method and used for tetracycline (TTC) removal. The removal behavior of TTC onto the composite particles was studied considering various parameters, including contact time, pollutant concentration, and pH. The maximum TTC adsorption capacity was 138.56 and 112.48 mg/g for the DCPD-CS and DCPA-CS, respectively. Increasing the pH to 11 significantly enhanced the adsorption capacity to 223.84 mg/g for DCPD-CS and 205.92 mg/g for DCPA-CS. The antibiotic adsorption process was well-fitted by the pseudo-second-order kinetic and Langmuir isotherm models. Electrostatic attractions, complexation, and hydrogen bonding are the main mechanisms governing the TTC removal process. Desorption tests demonstrated that the (NH4)2HPO4 solution was the most effective desorbing agent. The developed composites were more efficient than DCPD and DCPA reference samples and could be used as valuable adsorbents of TTC from contaminated wastewater.

Recent Progress of Non-Isocyanate Polyurethane Foam and Their Challenges.

Polyurethane foams (PUFs) are a significant group of polymeric foam materials. Thanks to their outstanding mechanical, chemical, and physical properties, they are implemented successfully in a wide range of applications. Conventionally, PUFs are obtained in polyaddition reactions between polyols, diisoycyanate, and water to get a CO2 foaming agent. The toxicity of isocyanate has attracted considerable attention from both scientists and industry professionals to explore cleaner synthesis routes for polyurethanes excluding the use of isocyanate. The polyaddition of cyclic carbonates (CCs) and polyfunctional amines in the presence of an external blowing agent or by self-blowing appears to be the most promising route to substitute the conventional PUFs process and to produce isocyanate-free polyurethane foams (NIPUFs). Especially for polyhydroxyurethane foams (PHUFs), the use of a blowing agent is essential to regenerate the gas responsible for the creation of the cells that are the basis of the foam. In this review, we report on the use of different blowing agents, such as Poly(methylhydrogensiloxane) (PHMS) and liquid fluorohydrocarbons for the preparation of NIPUFs. Furthermore, the preparation of NIPUFs using the self-blowing technique to produce gas without external blowing agents is assessed. Finally, various biologically derived NIPUFs are presented, including self-blown NIPUFs and NIPUFs with an external blowing agent.

Design of antibacterial apatitic composite cement loaded with Ciprofloxacin: Investigations on the physicochemical Properties, release Kinetics, and antibacterial activity.

This work aims to develop an injectable and antibacterial composite cement for bone substitution and prevention/treatment of bone infections. This cement is composed of calcium phosphate, calcium carbonate, bioactive glass, sodium alginate, and ciprofloxacin. The effect of ciprofloxacin on the microstructure, chemical composition, setting properties, cohesion, injectability, and compressive strength was investigated. The in vitro drug release kinetics and the antibacterial activity of ciprofloxacin-loaded composites against staphylococcus aureus and Escherichia coli pathogens were investigated. XRD and FTIR analysis demonstrated that the formulated cements are composed of a nanocrystalline carbonated apatite analogous to the mineral part of the bone. The evaluation of the composite cement's properties revealed that the incorporation of 3 and 9 wt% of ciprofloxacin affects the microstructural and physicochemical properties of the cement, resulting in a prolonged setting time, and a slight decrease in injectability and compressive strength. The in vitro drug release study revealed sustained release profiles over 18 days. The amounts of ciprofloxacin released per day (0.2 -15.2 mg/L) depend on the cement composition and the amount of ciprofloxacin incorporated. The antibacterial activity of ciprofloxacin-loaded cement composites attested to their effectiveness to inhibit the growth of Staphylococcus aureus and Escherichia coli.

Towards the application of carboxymethyl chitin/ionic liquid blend as polymer electrolyte membrane for aqueous batteries.

Carboxymethyl chitin (CMChit) has the potential to be used as a solid polymer electrolyte (SPE) based on its ionic conductivity value of the order of 10-6 S·cm-1 in self-standing membranes. In controlled humidity of 65RH%, carboxymethyl chitin based membrane blended with 1-Butyl-3-methylimidazolium acetate (BMIM[Ac]) ionic liquid (IL) (40 wt%) showed a threshold value of ionic conductivity in the order of 10-4 S·cm-1 and electrochemical stability was up to 2.93 V. The effects of the relative humidity and ionic liquid weight fraction on the ionic conductivity and structural changes were investigated in detail. Furthermore, the X-ray diffraction (XRD) diffractogram indicated a clear reduction of crystallinity of the CMChit. The Field-emission scanning electron microscopy (FESEM) observation of the cross-sections confirmed the homogeneity of the prepared blend. This electrolyte was tested in symmetric cells based on Zn//SPE//Zn and showed good reversibility and potential for application in proton-conducting batteries.

Formulation and characterization of hydroxyapatite-based composite with enhanced compressive strength and controlled antibiotic release.

A composite based on hydroxyapatite (HA) and chitosan (CS) combined with ciprofloxacin (CIP) was formulated by the solid-liquid mixing method. The optimization of the solid to the liquid ratio and the use of chitosan in a small amount (≤5 wt%) promoted the preparation of stable and rigid monoliths. A synergistic effect of CS and CIP contents on the compressive strength of the CIP-loaded composite was evidenced. The compressive strength of the fabricated biocomposite ranged in values from 1 to 6 MPa, comparable to those reported for cancellous bone. The improvement of the mechanical properties with the increase of the rate of organic components was correlated with the diminution of the surface area and the reduction in the pore volume of the specimens. On the other hand, the in vitro release experiments of the antibiotic indicated a sustained and controlled release of CIP over 10 days. Moreover, in vitro antibacterial tests performed on the biocomposite HA-CS5-CIP showed significant inhibition of Staphylococcus aureus and Escherichia coli pathogens. According to the showed results, the formulated composite with three-phase components could be a promising material for bone repair and local antibiotic release for the treatment of bone infections.

Li0.5Ni0.5Ti1.5Fe0.5(PO4)3/C Electrode Material for Lithium Ion Batteries Exhibiting Faster Kinetics and Enhanced Stability.

Natrium super ionic conductor (NASICON) materials providing attractive properties such as high ionic conductivity and good structural stability are considered as very promising materials for use as electrodes for lithium- and sodium-ion batteries. Herein, a new high-performance electrode material, Li0.5Ni0.5Ti1.5Fe0.5(PO4)3/C, was synthesized via the sol-gel method and was electrochemically tested as an anode for lithium ion batteries, providing enhanced electrochemical performance as a result of nickel substitution into the lithium site in the LiTi2(PO4)3 family of materials. The synthesized material showed good ionic conductivity, excellent structural stability, stable long-term cycling performance, and improved high rate cycling performance compared to LiTi2(PO4)3. The Li0.5Ni0.5Ti1.5Fe0.5(PO4)3/C electrode delivered reversible capacities of about 93 and 68% of its theoretical one at current rates of 0.1 C (6.42 mA·g-1) after 100 cycles and 5 C (320.93 mA·g-1) after 1000 cycles, respectively. Theoretically, three Li+ ions can be inserted into the vacancies of the Li0.5Ni0.5Ti1.5Fe0.5(PO4)3/C structure. However, when the electrode is discharged to 0.5 V, more than three Li+ ions are inserted into the NASICON structure, leading to its structural transformation, and thus to an irreversible electrochemical behavior after the first discharge process.

Improved mechanical properties of k-carrageenan-based nanocomposite films reinforced with cellulose nanocrystals.

This work investigates the isolation of cellulose nanocrystals (CNC) from sugarcane bagasse (SCB) waste and the evaluation of their mechanical reinforcement capability for k-carrageenan biopolymer. The results from Atomic Force Microscopy and Transmission Electron Microscopy indicated the successful extraction of CNC from SCB following alkali, bleaching and acid hydrolysis treatments. The CNC displayed a needle-like structure with an average aspect ratio of 55. The surface functionality of the CNC was evaluated by Fourier Transform Infrared Spectroscopy and X-ray Photoelectron Spectroscopy measurements. X-ray diffraction studies showed that the as-extracted CNC exhibit cellulose I crystalline structure, with a crystallinity index of 80%. The obtained CNC were dispersed into k-carrageenan biopolymer matrix at various CNC contents (1, 3, 5 and 8 wt%) and the prepared films were further characterized. The incorporation of CNC decreased the light transmittance values but enhanced the mechanical properties compared with the neat k-carrageenan film. Empirical Halpin-Tsai model was used to predict the CNC dispersion within k-carrageenan matrix. The obtained nanocomposite films have the potential to be used as food packaging material.

Production of cellulose nanocrystals from vine shoots and their use for the development of nanocomposite materials.

In the present work, cellulose nanocrystals (CNC) were produced from vine shoots waste using chemical treatments followed by acid hydrolysis process. FTIR analysis confirmed that the non-cellulosic components were progressively removed during the chemical treatments, and the final obtained materials are composed of pure cellulose. AFM and TEM observations showed that the extracted CNC possess a needle-like shape with an average length of 456 nm and an average diameter of 14 nm, giving rise to an average aspect ratio of about 32. The as-extracted CNC exhibit a cellulose I structure with high crystallinity index (82%), as determined by XRD characterization. Importantly, the resulted CNC provide a higher thermal stability in comparison with CNC extracted from other resources, using the same extraction process. The isolated CNC's surface charge density was evaluated by XPS analysis and resulted in ~2.0 sulfate groups per 100 anhydroglucose units. In order to identify the reinforcing ability of the new extracted CNC, Carboxymethyl cellulose nanocomposite films were prepared with various CNC contents (1, 3, 5, 8 wt%) and their mechanical properties were investigated by uniaxial tensile test. The results showed that the as-extracted CNC displayed a higher reinforcing ability for nanocomposite materials.

New Redox Polymers that Exhibit Reversible Cleavage of Sulfur Bonds as Cathode Materials.

Two new cathode materials based on redox organosulfur polymers were synthesized and investigated for rechargeable lithium batteries as a proof-of-concept study. These cathodes offered good cycling performance owing to the absence of polysulfide solubility, which plagues Li/S systems. Herein, an aliphatic polyamine or a conjugated polyazomethine was used as the base to tether the redox-active species. The activity comes from the cleavage and formation of S-S or N-S bonds, which is made possible by the rigid conjugated backbone. The synthesized polymers were characterized through FTIR spectroscopy and thermogravimetric analysis (TGA). Galvanostatic measurements were performed to evaluate the discharge/charge cycles and characterize the performance of the lithium-based cells, which displayed initial discharge capacities of approximately 300 mA h g-1 at C/5 over 100 cycles with approximately 98 % Coulombic efficiency.