High-Performance p-Type Bi2Te3-Based Thermoelectric Materials Enabled via Regulating Bi-Te Ratio.

Bi2Te3-based alloys, as the sole commercial thermoelectric (TE) material, play an irreplaceable role in the thermoelectric field. However, the low TE efficiency, poor mechanical properties, and high cost have limited its large-scale applications. Here, high-performance p-type Bi2Te3-based materials were successfully prepared by ball milling and hot pressing. The optimized p-type Bi0.55Sb1.45Te3 + 2.5 wt % Bi shows a peak zT value of 1.45 at 360 K, and the average zT value of up to 1.24 at 300-480 K, which is completely comparable with previously reported Bi2Te3-based alloys with excellent performance. Such performance mainly results from the enhanced electrical conductivity and decreased lattice thermal conductivity via regulating carrier and phonon transport. Furthermore, this material shows good mechanical properties, in which the Vickers hardness and compressive strength are up to 0.95 GPa and 94.6 MPa, respectively. Overall, both the thermoelectric and mechanical performance of the materials fabricated by our processing technology are quite competitive. This may enlighten researchers concentrating on Bi2Te3-based alloys, thus further promoting their industrial applications.

Nano-clay montmorillonite removes tetracycline in water: Factors and adsorption mechanism in aquatic environments.

In response to escalating environmental concerns surrounding antibiotic pollution, the utilization of calcium-montmorillonite minerals for tetracycline wastewater treatment is gaining prominence. This study systematically analyzed the physicochemical properties of calcium-montmorillonite through scanning electron microscope, contact angle analysis, X-ray diffraction, and Fourier transform infrared spectroscopy. It explored the adsorption efficacy and mechanisms for tetracycline removal, considering factors like initial pH, adsorption duration, concentration, and co-cations (Na+ and Ca2+). Under optimized conditions, achieving over 90% tetracycline removal with a maximum adsorption capacity of 526 mg/g, the study revealed competitive adsorption sites for coexisting cations. The Langmuir model best described the monolayer adsorption process, while kinetic studies favored the pseudo-first-order model. This research offers comprehensive insights into tetracycline adsorption on calcium-montmorillonite, emphasizing its potential as an efficient, cost-effective adsorbent for pharmaceutical wastewater treatment.

n-Type PVP/SWCNT Composite Films with Improved Stability for Thermoelectric Power Generation.

Single-walled carbon nanotubes (SWCNTs) are one of the promising thermoelectric materials in applications of powering wearable electronics. However, the electrical performance of n-type SWCNTs quickly decreases in air, showing a low stability, and low-cost and effective solutions to improving its stability are also lacking, all of which limit practical applications. In this study, we studied the stability of PVP/SWCNT composite films, where oxygen and moisture from air should be responsible for the decreased stability due to oxidation and hydration. In this case, we found that coating with a 0.20 g mL-1 PVP/0.002 g mL-1 PVDF layer on the surface of PVP/SWCNTs can prevent the penetration of oxygen and moisture from air, improving film stability, where there is almost no reduction in thermoelectric performance after they are exposed to air for 60 days. Based on the stable n-type PVP/SWCNT films, a thermoelectric generator was fabricated, where poly(dimethylsiloxane) (PDMS) was used to coat the surface of the thermoelectric leg to further improve its stability. This generator showed high output performance, which achieved an open-circuit voltage of 10.6 mV and a power density of 312.2 µW cm-2 at a temperature difference of 50 K. Particularly, it exhibited high stability, where the output performance kept almost unchanged after exposure to high-humidity air for 30 days. This coating technology is also applicable to other air-sensitive materials and promotes the development and application of thermoelectric materials and devices.

Adsorption Properties of Natural Zeolite Supported by Chitosan on Cd(II) in Micropolluted Irrigation Water.

This study utilized a 1% chitosan solution (dissolved in 2% acetic acid), with a chitosan-to-zeolite mass ratio of 0.005, to successfully prepare chitosan-loaded natural zeolite. The performance of chitosan-modified natural zeolite in the removal of low-concentration cadmium ions in the presence of micropollutants was investigated. The adsorbent was characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR), and scanning electron microscopy (SEM)/energy-dispersive spectroscopy (EDS) techniques. The impact of modified adsorbent dosage, pH value, contact time, temperature, and initial concentration on adsorption performance was discussed. Additionally, the adsorption kinetics, isotherms, and thermodynamics of cadmium on chitosan-modified zeolites were analyzed. The results indicated that the modified zeolite exhibited a dispersed and porous structure with increased surface area, average pore size, and total pore volume. Under the conditions of 25 °C, pH 6, a dosage of 8 g/L, and a 60 min adsorption reaction time, chitosan-loaded natural zeolite (CNZ) achieved a removal efficiency of over 94.51% for a 100 µg/L cadmium solution (in a 100 mL volume). The adsorption process followed the Langmuir model, suggesting monolayer adsorption. The adsorption kinetics followed a pseudo-second-order equation, indicating an exothermic process with an increase in entropy. Chitosan-loaded natural zeolite demonstrated improved adsorption capacity and effectively removed cadmium from water contaminated with micropollutants.

High-Power-Density and Excellent-Flexibility Thermoelectric Generator Based on All-SWCNTs/PVP Composites.

Flexible polymer/single-wall carbon nanotube (SWCNT) composites are a vital component for wearable/portable electronics, but the development of their n-type counterpart is laggard. Furthermore, little attention is paid to the interaction between SWCNT and polymers, especially the unconjugated polymers, as well as the conversion mechanism of conduction characteristics. Here, the n-type flexible SWCNTs/Polyvinyl Pyrrolidone (PVP) films are successfully fabricated, where the oxygen atoms in PVP interacted with SWCNT via hydrogen bonds, which can lower the energy barrier of electron tunneling, providing the pathway for the electron transfer. Furthermore, with the increasing synthesis temperature, the hydrogen bonds strengthened and the thermal activation energy further improved, both of which enhanced the electron-donating ability of PVP, resulting in a high-power-factor value of 260 µW m-1  K-2 . Based on the optimized SWCNTs/PVP films, a thermoelectric module is assembled, which achieved a power density of 400 µW cm-2 at a temperature difference of 56 K, coupled with excellent flexibility, showing a less than 1% variation of resistance after 5000 bending cycles. It shows the highest output-performance and the best flexibility among the reported SWCNT-based thermoelectric modules. This work provides significant insights into the interaction mechanism and performance optimization of hybrid thermoelectric composites, based on SWCNTs/unconjugated polymers.

Flexible Silica/MXene/Natural rubber film strain sensors with island chain structure for Healthcare monitoring.

The demand for flexible strain sensors with high sensitivity and durability has increased significantly. However, traditional sensors are limited in terms of their detection ranges and fabrications. In this work, a space stacking method was proposed to fabricate natural rubber (NR)/ Ti3C2Tx (MXene)/silica (SiO2) films that possessed exceptional electrical conductivity, sensitivity and reliability. The introduction of SiO2 into the NR/MXene composite enabled the construction of an "island-chain structure", which promoted the formation of conductive pathways and significantly improved the conductivity of the composite. Specifically, the electrical conductivity of the NR/MXene/10 wt%SiO2 composite was enhanced by about 200 times compared to that of the NR/MXene composite alone (from 0.07 to 13.4 S/m). Additionally, the "island-chain structure" further enhanced the sensing properties of the NR/MXene/10 wt%SiO2 composite, as evidenced by its excellent sensitivity (GF = 189.2), rapid response time (102 ms), and good repeatability over 10,000 cycles. The fabricated device demonstrates an outstanding mechanical sensing performance and can accurately detect human physiological signals. Specifically, the device serves as a strain detector, recognizing different strain signals by monitoring the movement of fingers, arms, and thighs. This study provides critical insights into composite manufacturing with exceptional conductivity, flexibility and stability, which are essential properties for creating high-performance flexible sensors.

Visualization of Deep Convolutional Neural Networks to Investigate Porous Nanocomposites for Electromagnetic Interference Shielding.

Constructing porous structures in electromagnetic interference (EMI) shielding materials is a common strategy to decrease the secondary pollution caused by the reflection of electromagnetic waves (EMWs). However, the lack of direct analysis methods makes it difficult to fully understand the effect of porous structures on EMI, hindering EMI composites' development. Furthermore, while deep learning techniques, such as deep convolutional neural networks (DCNNs), have significantly impacted material science, their lack of interpretability limits their applications to property predictions and defect detection tasks. Until recently, advanced visualization techniques provided an approach to reveal the relevant information behind DCNNs' decisions. Inspired by it, a visual approach for porous EMI nanocomposite mechanism studies is proposed. This work combines DCNN visualization with experiments to investigate EMI porous nanocomposites. First, a rapid and straightforward salt-leaked cold-pressing powder sintering method is employed to prepare high-EMI CNTs/PVDF composites with various porosities and filler loadings. Notably, the solid sample with 30 wt % loading maintains an ultrahigh shielding effectiveness of 105 dB. The influence of porosity on the shielding mechanism is discussed macroscopically based on the prepared samples. To determine the shielding mechanism, a modified deep residual network (ResNet) is trained on a dataset of scanning electron microscopy (SEM) images of the samples. The Eigen-CAM visualization of the modified ResNet intuitively shows that the amount and depth of the pores impact the shielding mechanisms and that shallow pore structures contribute less to EMW absorption. This work is instructive for material mechanism studies. Besides, the visualization has the potential as a porous-like structure marking tool.

Emerging Flexible Thermally Conductive Films: Mechanism, Fabrication, Application.

Effective thermal management is quite urgent for electronics owing to their ever-growing integration degree, operation frequency and power density, and the main strategy of thermal management is to remove excess energy from electronics to outside by thermal conductive materials. Compared to the conventional thermal management materials, flexible thermally conductive films with high in-plane thermal conductivity, as emerging candidates, have aroused greater interest in the last decade, which show great potential in thermal management applications of next-generation devices. However, a comprehensive review of flexible thermally conductive films is rarely reported. Thus, we review recent advances of both intrinsic polymer films and polymer-based composite films with ultrahigh in-plane thermal conductivity, with deep understandings of heat transfer mechanism, processing methods to enhance thermal conductivity, optimization strategies to reduce interface thermal resistance and their potential applications. Lastly, challenges and opportunities for the future development of flexible thermally conductive films are also discussed.

Scalable Flexible Phase Change Materials with a Swollen Polymer Network Structure for Thermal Energy Storage.

3D porous structural materials are proved to be enticing candidates for the fabrication of high-performance organic phase change materials (PCMs), but the stringent fabrication process and poor processability greatly hampered their commercialization. Herein, flexible leakage-proof composite PCMs with pronounced comprehensive performance are fabricated by a scalable polymer swelling strategy without using any solvent, in which the paraffin wax (PW) segment is confined in a robust flexible 3D polymer network, giving rise to the composite PCMs with excellent form stability even at 160 °C, a high latent heat energy storage density of 133.6 J/g, and an outstanding thermal conductivity of up to ∼5.11 W/mK. More importantly, the mass production of the flexible composite phase change fiber, film, and bulk products can be achieved by adopting mature processing technologies. These resultant composite PCMs exhibit promising thermal management ability to solve the overheating problem of electronics and high-efficiency solar-thermal energy conversion capacity.

Direct modification of polyketone resin for anion exchange membrane of alkaline fuel cells.

A kind of side-chain type anion exchange membranes (AEMs) with high ionic conductivity and good comprehensive stability was prepared via direct modification of commercial engineering plastic polyketone with diamines through Paal-Knorr reaction and quaternization reaction. It was found that the amount of diamine can effectively tune the microphase morphology and properties of the prepared quaternized functionalized-polyketone anion exchange membranes (QAFPK-AEMs). The tensile strength was increased from 18.6 MPa to 38.6 MPa, and the ion exchange capacity (IEC) was increased from 1.11 mmol/g to 2.71 mmol/g depending on the amount of added diamine. The QAFPK-1-6-AEM with the IEC of 1.43 mmol/g showed the highest hydroxide conductivity of 65 mS/cm at 25 °C and 96.8 mS/cm at 80 °C. The high ionic conductivity was achieved through the establishment of effective ionic channels, and it maintained 70% of the initial ionic conductivity after the 192 h treatment in 2 mol/L KOH (aq) at 80 °C. Moreover, a peak power density of 129 mW/cm2 was achieved when the assembled single cell with QAFPK-1-6-AEM was operated at 50 °C. Thus, the prepared QAFPK-AEMs showed great potential applications for the anion exchange membrane fuel cells (AEMFCs).

Multifunctional Thermal Management Materials with Excellent Heat Dissipation and Generation Capability for Future Electronics.

Thermal management materials (TMMs) used in electronic devices are crucial for future electronics and technologies such as flexible electronics and artificial intelligence (AI) technologies. As future electronics will work in a more complicated circumstance, the overheating and overcooling problems can exist in the same electronics while the common TMMs cannot meet the demand of thermal management for future electronics. In this work, nacre-mimetic graphene-based films with super flexibility and durability (in over 10,000 tensile cycles), excellent capability to dissipate excess heat (20.84 W/(m·K) at only 16-22 µm thickness), and outstanding heating performance to generate urgent heat for electronics under extremely cold conditions are fabricated by a facile solution casting method, and the fabricated composites are proved to be superior multifunctional TMMs for the thermal management in electronic chips. In addition, the application of the paper-like films with high in-plane thermal conductivity to a flexible heat spreader and film heater is demonstrated by simulation using a finite volume method, which shows the high importance of the in-plane thermal conductivity in thermal management of electronics.

Facile Method to Fabricate Highly Thermally Conductive Graphite/PP Composite with Network Structures.

Thermally conductive polymer composites have aroused significant academic and industrial interest for several decades. Herein, we report a novel fabrication method of graphite/polypropylene (PP) composites with high thermal conductivity in which graphite flakes construct a continuous thermally conductive network. The thermal conductivity coefficient of the graphite/PP composites is markedly improved to be 5.4 W/mK at a graphite loading of 21.2 vol %. Such a great improvement of the thermal conductivity is ascribed to the occurrence of orientations of crystalline graphite flakes with large particles around PP resin particles and the formation of a perfect thermally conductive network. The model of Hashin-Shtrikman (HS) is adopted to interpret the outstanding thermally conductive property of the graphite/PP composites. This work provides a guideline for the easy fabrication of thermally conductive composites with network structures.