Enhanced thermoelectric performance of copper iodide particles/nanowires composite in the low-temperature range.

Thermoelectric (TE) energy harvesting presents a viable method for reducing energy waste by transforming waste thermal energy into electricity. In this study, we fabricated copper iodide (CuI) composites using synthesized CuI nanowires (NWs) and particles to enhance TE performance in the low-temperature range. The Seebeck coefficient (S) was notably higher when a combination of CuI particles and NWs was used, reaching a maximum S of 1614.24 µV K-1 with a 60% NWs content at RT. Electrical conductivity (σ) exhibited an inverse correlation with S, with higher values detected when either particles or NWs were used only. The highest power factor (PF) of 128.44 µW m-1K-2 was recorded at RT with 60% NWs content, demonstrating improved TE performance. Thermal conductivity (κ) diminished when different material structures were employed, enhancing phonon scattering. The maximum figure of merit (ZT) achieved was ∼0.14 with 60% NWs content at 425 K, indicating the potential of this method for improving TE performance. This study offers valuable insights into optimizing TE performance using CuI composites, proposing a promising strategy for energy harvesting from low-temperature sources.

Highly porous thermoelectric composites with high figure of merit and low thermal conductivity from solution-synthesized porous Bi2Si2Te6 nanosheets.

Layer-structured Bi2Si2Te6 has garnered significant attention in the field of thermoelectrics due to its exceptional thermoelectric properties and unique structural characteristics. Enhancing the transport properties of composites by manipulating the thermal and electrical properties of materials through the fabrication of porous nanostructured materials has emerged as a promising strategy. This paper presents a study on enhancing the thermoelectric (TE) properties of Bi2Si2Te6 nanosheets (BST NSs) through nanostructuring and the fabrication of porous BST NSs (p-BST). The process involves Li intercalation and exfoliation to obtain BST NSs, followed by the creation of p-BST composites by introducing nanosized pores onto the surface of the NSs using high-power sonification for various durations. The incorporation of the porous structure effectively increases phonon scattering, leading to a decrease in the lattice thermal conductivity (κl) of the composite. The p-BST(2) composite demonstrates significantly low κ and enhanced thermoelectric figure of merit (ZT) values (∼0.63 W m-1 K-1 and ∼0.083) at room temperature. These results highlight the efficacy of porous structure preparation as a promising strategy for enhancing the thermoelectric performance of chalcogenide-based composites, offering potential solutions to environmental degradation and energy shortages.

Enhancing Dielectric Properties, Thermal Conductivity, and Mechanical Properties of Poly(lactic acid)-Thermoplastic Polyurethane Blend Composites by Using a SiC-BaTiO3 Hybrid Filler.

A composite of polymer blends-thermoplastic polyurethane (TPU) and poly(lactic acid) (PLA)-and BaTiO3-SiC was fabricated. BaTiO3 particles were used to improve the dielectric properties of the composite materials, whereas SiC was used to enhance thermal conductivity without altering the dielectric properties; notably, SiC has a good dielectric constant. The surfaces of the filler particles, BaTiO3 and SiC particles, were activated; BaTiO3 was treated with methylene diphenyl diisocyanate (MDI) and SiC's surface was subjected to calcination and acid treatment, and hybrid fillers were prepared via solution mixing. The surface modifications were verified using Fourier transform infrared spectroscopy (the appearance of OH showed acid treatment of SiC, and the presence of NH, CH2, and OH groups indicated the functionalization of BaTiO3 particles). After the extruded products were cooled and dried, the specimens were fabricated using minimolding. The thermal stability of the final composites showed improvement. The dielectric constant improved relative to the main matrix at constant and variable frequencies, being about fivefold for 40% BaTiO3-SiC-TPU-PLA composites. Upon inclusion of 40 wt.% MDI functionalized BaTiO3-SiC particles, an improvement of 232% in thermal conductivity was attained, in comparison to neat TPU-PLA blends.

Improved Through-Plane Thermal Conductivity of Poly(dimethylsiloxane)Composites through the Formation of 3D Filler Foam Using Freeze-Casting and Annealing Processes.

The configuration of a continuous and oriented thermal pathway is essential for efficient heat dissipation in the oriented direction. Three-dimensional (3D) conductive filler structures provide a suitable approach for constructing continuous thermal pathways in polymer-based composites. The aluminum nitride/reduced graphene oxide/poly(dimethylsiloxane) (AlN/rGO/PDMS) composite material is made with a 3D foam structure and focuses on reducing GO and forming foam via polyvinyl alcohol (PVA). We analyze the successful fabrication of hybrid fillers and composites using various methods. The fabricated composite with a 3D network filler foam achieves a through-plane thermal conductivity of 1.43 W/mK and achieves 752% higher thermal conductivity compared to pure PDMS, which is superior to composites without 3D foam. The continuous 3D filler structure via freeze-drying and annealing processes provides efficient thermal dissipation in the through-plane direction pathway, which is critical for enhancing thermal conductivity. Therefore, this work produces a polymer composite material with improved thermal conductivity through various processes.

Interface engineering of CeO2 nanoparticle/Bi2WO6 nanosheet nanohybrids with oxygen vacancies for oxygen evolution reactions under alkaline conditions.

Because of the interactive combination synergy effect, hetero interface engineering is used way for advancing electrocatalytic activity and durability. In this study, we demonstrate that a CeO2/Bi2WO6 heterostructure is synthesized by a hydrothermal method. Electrochemical measurement results indicate that CeO2/Bi2WO6 displays not only more OER catalytic active sites with an overpotential of 390 mV and a Tafel slope of 117 mV dec-1 but also durability for 10 h (97.57%). Such outstanding characteristics are primarily attributed to (1) the considerable activities by CeO2 nanoparticles uniformly distributed on Bi2WO6 nanosheets and (2) the plentiful Bi-O-Ce and W-O-Ce species playing the role of strong couples between CeO2 nanoparticles and Bi2WO6 nanosheets and oxygen vacancy existence in CeO2 nanoparticles, which can improve the electrochemical active surface area (ECSA) and activity, and enhance the conductivity for OERs. This CeO2/Bi2WO6 consists of the heterojunction engineering that can open a modern method of thinking for high effective OER electrocatalysts.

Hollow CoFe-based hybrid composites derived from unique S-modulated coordinated transition bimetal complexes for efficient oxygen evolution from water splitting under alkaline conditions.

The oxygen evolution reaction (OER) is an important reaction in water splitting. However, the high cost and slow-rate catalysts hinder commercial applications. Although an important process for manufacturing of hollow structures, it is difficult to construct complicated hollow structures with an excellent and regulable shape for multi-component materials. In this study, we demonstrate that sulfur-Co,Fe bimetallic nitrogen carbon hollow composite hybrids (x-S-CoFe@NC) can be synthesized by regulating the amount of sulfur and using the hydrothermal method. For OER, 32-S-CoFe@NC exhibits excellent electrocatalytic activity with a low overpotential of 232 mV, which is higher than those of 0-S-CoFe@NC (270 mV), 23-S-CoFe@NC (247 mV), and RuO2 (243 mV) catalysts at 10 mA cm-2. In addition, with air as the cathode, a rechargeable Zn-air battery with outstanding long-life cycling stability for 80 hours based on 32-CoFe@NC + Pt/C is proposed. The advanced technique described here supplies a new route for preparing hollow transition bimetal carbon hybrids with an adjustable composite arrangement for electrocatalysis and water splitting.

Enhancement of the thermoelectric performance of Cu3SbSe4 particles by controlling morphology using exfoliated selenium nanosheets.

Copper antimony selenide (Cu3SbSe4), a ternary Cu-based material, is a promising p-type thermoelectric material. In this study, the morphology of Cu3SbSe4 particles was controlled using the shape of Se during the synthesis process. To this end, Se particles with a size of 20 µm were exfoliated to form nanosheets through an ultrasonication process without the oxidation of Se. The variation in the morphology of Cu3SbSe4 nanoparticles and nanosheets affected their grain size, thus affecting their electrical conductivity and lattice thermal conductivity owing to the phonon and electron scattering at the interface of the grains. By combining the effects of the morphological variation with the electrical and lattice thermal conductivity, the Cu3SbSe4 synthesized using Se nanosheets exhibited improved thermoelectric performance. The synthesized Cu3SbSe4 nanosheets achieved a maximum thermoelectric figure of merit value of 0.40, which was 1.41 times higher than that of Cu3SbSe4 nanoparticles.

Strongly Coupled Tin(IV) Sulfide-MultiWalled Carbon Nanotube Hybrid Composites and Their Enhanced Thermoelectric Properties.

Herein, tin(IV) sulfide (SnS2) and multiwalled carbon nanotube (MWCNT) composites are fabricated via a simple solution-mixing method in a hydrothermal reactor. SnS2 is closely coupled to the MWCNT surface, thus forming a coaxial nanostructure. Examination by X-ray photoelectron spectroscopy and scanning transmission electron microscopy indicates that the strong interface between SnS2 and the MWCNTs in the composite material is due to the formation of Sn-O and Sn-S bonds. In addition, an examination of the temperature-dependent thermoelectric (TE) properties demonstrates that the SnS2-MWCNT hybrid composite with 3 wt % MWCNTs exhibits the maximum power factor of ∼91.34 µW/(m·K2) at 500 K, which is ∼50 times larger than that of the pristine SnS2. These results highlight the fabrication and enhanced TE properties of hybrid composites via the coupling of SnS2 and MWCNTs.

Facile fabrication of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)-coated selenium nanowire/carbon nanotube composite films for flexible thermoelectric applications.

In this study, we synthesized a flexible thermoelectric composite film consisting of poly(3,4-ethylenedioxythiopene)-poly(4-styrenesulfonate)-coated selenium nanowires (PEDOT:PSS-coated Se NWs) and multi-walled carbon nanotubes (MWCNTs) via simple solution mixing. PEDOT:PSS-coated Se NWs were synthesized by coating PEDOT:PSS-on the surface of Se during the process of synthesizing Se NWs. Then, flexible PEDOT:PSS-coated Se/MWCNT composite films were synthesized by filtration. To verify the thermoelectric (TE) potential, the TE properties of the composite film with various MWCNT contents were investigated to determine the optimal conditions for improved TE performance. The maximum power factor of the composite film was ∼73.94 µW (m K2)-1, which is much higher than that of Se and PEDOT:PSS. This study suggests an approach to fabricate flexible inorganic/organic hybrid films with high TE performance.

Enhanced thermoelectric performance of UV-curable silver (I) selenide-based composite for energy harvesting.

Thermoelectric (TE) composites, with photocured resin as the matrix and Ag2Se (AS) as the filler, are synthesized by a digital-light-processing (DLP) based 3D printer. The mixture of diurethane dimethacrylate (DUDMA) and isobornyl acrylate (IBOA) is used as a UV-curable resin because of their low viscosity and high miscibility. Scanning electron microscopy (FE-SEM) images confirm that the filler retains its shape and remains after the UV-curing process. After completing curing, the mechanical and thermoelectric properties of the composite with different AS contents were measured. The addition of the AS filler increases the thermoelectric properties of the cured resin. When the AS contents increase by 30 wt.%, the maximum power factor was obtained (~ 51.5 µW/m·K2 at room temperature). Additionally, due to the phonon scattering effect between the interfaces, the thermal conductivity of composite is lower than that of pristine photoresin. The maximum thermoelectric figure of merit (ZT) is ~ 0.12, which is achieved with 30 wt.% of AS at 300 K with the enhanced power factor and reduced thermal conductivity. This study presents a novel manufacturing method for a thermoelectric composite using 3D printing.

Thermoelectric Generator Using Polyaniline-Coated Sb2Se3/ß-Cu2Se Flexible Thermoelectric Films.

Herein, Sb2Se3 and ß-Cu2Se nanowires are synthesized via hydrothermal reaction and water evaporation-induced self-assembly methods, respectively. The successful syntheses and morphologies of the Sb2Se3 and ß-Cu2Se nanowires are confirmed via X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), and field emission transmission electron microscopy (FE-TEM). Sb2Se3 materials have low electrical conductivity which limits application to the thermoelectric generator. To improve the electrical conductivity of the Sb2Se3 and ß-Cu2Se nanowires, polyaniline (PANI) is coated onto the surface and confirmed via Fourier-transform infrared spectroscopy (FT-IR), FE-TEM, and XPS analysis. After coating PANI, the electrical conductivities of Sb2Se3/ß-Cu2Se/PANI composites were increased. The thermoelectric performance of the flexible Sb2Se3/ß-Cu2Se/PANI films is then measured, and the 70%-Sb2Se3/30%-ß-Cu2Se/PANI film is shown to provide the highest power factor of 181.61 µW/m·K2 at 473 K. In addition, a thermoelectric generator consisting of five legs of the 70%-Sb2Se3/30%-ß-Cu2Se/PANI film is constructed and shown to provide an open-circuit voltage of 7.9 mV and an output power of 80.1 nW at ΔT = 30 K. This study demonstrates that the combination of inorganic thermoelectric materials and flexible polymers can generate power in wearable or portable devices.

Developing Iron-Nickel Bimetallic Oxides with Nanocage Structures As High-Performance Bifunctional Catalysts via the Ensemble Effect from Nitrogen Sources.

Metal-air batteries will serve as renewable and ecofriendly energy-storage systems in the future because of their high theoretical energy-density performance and unlimited resources, using oxygen as fuel materials compared with commercial lithium-ion batteries. However, the unsuitable inactive reactions at the air-electrode interface (the oxygen reduction reaction and the oxygen evolution reaction) in the metal-air battery are major challenges. In this study, we report nitrogen (N)-doped iron (Fe) and nickel (Ni) bimetallic catalysts with a hollow structure (Fe-Ni nanocage) as outstanding bifunctional catalysts, which have not been reported previously. The open structure in the catalysts simultaneously has an active inner cavity and an outer shell; catalysts have a high active surface area, resulting in remarkable electrochemical performance. Furthermore, the electron transfer phenomenon due to the "ensemble effect" generates a higher catalyst activation. Nitrogen has a higher electronegativity than the metal cations, so doped nitrogen sources draw the electron into iron and nickel cations, and the deprived oxidation state of the metal cations accelerates the electrocatalytic performance.

Highly Thermal Conductive and Electrical Insulating Epoxy Composites with a Three-Dimensional Filler Network by Sintering Silver Nanowires on Aluminum Nitride Surface.

In this study, a new fabrication technique for three-dimensional (3D) filler networks was employed for the first time to prepare thermally conductive composites. A silver nanowire (AgNW)- aluminum nitride (AlN) (AA) filler was produced by a polyol method and hot-pressed in mold to connect the adjacent fillers by sintering AgNWs on the AlN surface. The sintered AA filler formed a 3D network, which was subsequently impregnated with epoxy (EP) resin. The fabricated EP/AA 3D network composite exhibited a perpendicular direction thermal conductivity of 4.49 W m-1 K-1 at a filler content of 400 mg (49.86 vol.%) representing an enhancement of 1973% with respect to the thermal conductivity of neat EP (0.22 W m-1 K-1). Moreover, the EP/AA decreased the operating temperature of the central processing unit (CPU) from 86.2 to 64.6 °C as a thermal interface material (TIM). The thermal stability was enhanced by 27.28% (99 °C) and the composites showed insulating after EP infiltration owing to the good insulation properties of AlN and EP. Therefore, these fascinating thermal and insulating performances have a great potential for next generation heat management application.

Thermal Properties of Surface-Modified and Cross-Linked Boron Nitride/Polyethylene Glycol Composite as Phase Change Material.

A thermally conductive phase change material (PCM) was fabricated using polyethylene glycol (PEG) and boron nitride (BN). However, the interfacial adhesion between the BN and the PEG was poor, hindering efficient heat conduction. Grafting polyvinyl alcohol (PVA) onto the surface of BN and cross-linking due to hydrogen bonding between the hydroxyl groups in PVA and oxygen atoms in PEG improved the wettability of fillers. By employing this strategy, we achieved a thermal conductivity value of 0.89 W/mK, a 286% improvement compared to the thermal conductivity of the pristine PEG (0.23 W/mK). Although the latent heat of composites decreased due to the mobility of the polymer chain, the value was still reasonable for PCM applications.

Incorporating MXene into Boron Nitride/Poly(Vinyl Alcohol) Composite Films to Enhance Thermal and Mechanical Properties.

Aggregated boron nitride (ABN) is advantageous for increasing the packing and thermal conductivity of the matrix in composite materials, but can deteriorate the mechanical properties by breaking during processing. In addition, there are few studies on the use of Ti3C2 MXene as thermally conductive fillers. Herein, the development of a novel composite film is described. It incorporates MXene and ABN into poly(vinyl alcohol) (PVA) to achieve a high thermal conductivity. Polysilazane (PSZ)-coated ABN formed a heat conduction path in the composite film, and MXene supported it to further improve the thermal conductivity. The prepared polymer composite film is shown to provide through-plane and in-plane thermal conductivities of 1.51 and 4.28 W/mK at total filler contents of 44 wt.%. The composite film is also shown to exhibit a tensile strength of 11.96 MPa, which is much greater than that without MXene. Thus, it demonstrates that incorporating MXene as a thermally conductive filler can enhance the thermal and mechanical properties of composite films.

Conductive PEDOT: PSS-Based Organic/Inorganic Flexible Thermoelectric Films and Power Generators.

We present a simple thermoelectric device that consists of a conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)-based inorganic/organic thermoelectric film with high thermoelectric performance. The PEDOT:PSS-coated Se NWs were first chemically synthesized in situ, and then mixed with an Ag precursor solution to produce the PEDOT:PSS-coated Ag2Se NWs. The PEDOT:PSS matrix was then treated with dimethyl sulfoxide (DMSO) prior to the production of flexible PEDOT:PSS-coated Ag2Se NW/PEDOT:PSS composite films with various weight fractions of Ag2Se via a simple drop-casting method. The thermoelectric properties (Seebeck coefficient, electrical conductivity, and power factor) of the composite films were then analyzed. The composite film with 50 wt.% NWs exhibited the highest power factor of 327.15 µW/m·K2 at room temperature. The excellent flexibility of this composite film was verified by bending tests, in which the thermoelectric properties were reduced by only ~5.9% after 1000 bending cycles. Finally, a simple thermoelectric device consisting of five strips of the proposed composite film was constructed and was shown to generate a voltage of 7.6 mV when the temperature difference was 20 K. Thus, the present study demonstrates that that the combination of a chalcogenide and a conductive composite film can produce a high-performance flexible thermoelectric composite film.

Fabrication of PEDOT:PSS/Ag2Se Nanowires for Polymer-Based Thermoelectric Applications.

Flexible Ag2Se NW/PEDOT:PSS thermoelectric composite films with different Ag2Se contents (10, 20, 30, 50, 70, and 80 wt.%) are fabricated. The Ag2Se nanowires are first fabricated with solution mixing. After that, Ag2Se NW/PEDOT:PSS composite film was fabricated using a simple drop-casting method. To evaluate the potential applications of the Ag2Se NW/PEDOT:PSS composite, their thermoelectric properties are analyzed according to their Ag2Se contents, and strategies for maximizing the thermoelectric power factor are discussed. The maximum room-temperature power factor of composite film (178.59 µW/m·K2) is obtained with 80 wt.% Ag2Se nanowires. In addition, the composite film shows outstanding durability after 1000 repeat bending cycles. This work provides an important strategy for the fabrication of high-performance flexible thermoelectric composite films, which can be extended to other inorganic/organic composites and will certainly promote their development and thermoelectric applications.

Thermal Properties of Binary Filler Hybrid Composite with Graphene Oxide and Pyrolyzed Silicon-Coated Boron Nitride.

To improve the thermal conductivity of a composite material, the filler dispersion and the interfacial adhesion between the filler and the matrix are important factors. A number of methods for satisfying these criteria are presented herein. Thus, graphene oxide (GO) is incorporated to enhance the dispersion state of surface-modified boron nitride (BN) by increasing the viscosity of the epoxy matrix and by providing steric hindrance. Meanwhile, polysilazane (PSZ) coating and thermolysis were used to enhance the wettability by providing structural similarity between the coating material and the epoxy matrix. Due to these strategies, the thermal conductivity was improved by 253% compared to that of the neat epoxy at a filler fraction of 40 wt %.

3D Interconnected Boron Nitride Networks in Epoxy Composites via Coalescence Behavior of SAC305 Solder Alloy as a Bridging Material for Enhanced Thermal Conductivity.

In this study, hybrid fillers of spherically shaped aggregated boron nitride (a-BN) attached with SAC305, were fabricated via simple stirring and the vacuum filtration method. a-BN was used as the primary conductive filler incorporated with epoxy resin, and these fillers were interconnected each other via the coalescence behavior of SAC305 during the thermal curing process. Based on controlled a-BN content (1 g) on 3 g of epoxy, the thermal conductivity of the composite filled with hybrid filler (a-BN:SAC305 = 1:0.5) reached 0.95 W/mK (33 wt%) due to the construction of the 3D filler network, whereas that of composite filled with raw a-BN was only 0.60 W/mK (25 wt%). The thermal conductivity of unfilled epoxy was 0.19 W/mK.

Quisqualis indica extract ameliorates low urinary tract symptoms in testosterone propionate-induced benign prostatic hyperplasia rats.

Benign prostate hyperplasia (BPH) is a common disease in old-age males, accounting for approximately 77% of morbidity within the age range of 40 to 70 years. It has been shown that morbidity increases with social graying. Quisqualis indica linn (QI) has been used to treat inflammation, stomach pain, and digestion problems. In this study, we evaluated the symptom-regulating effects of QI extract on a testosterone-induced BPH rat model. After inducing BPH in rats using testosterone propionate (TP) injection, we assessed basal intraurethral pressure (IUP) and increments of IUP elicited by electrical field stimulation (5 V, 5, 10, or 20 Hz) or phenylephrine (Phe) (0.01, 0.03, 0.1 mg/kg IV). To induce BPH, 8-week-old rats were subjected to a daily subcutaneous TP (3 mg/kg) injection for 4 weeks. Finasteride (Fina) (10 mg/kg PO) was administered to the rats in the first treatment, while QI (150 mg/kg PO) was administered to those in the second group. Blood pressure was measured together with IUP, after which low urinary tract (LUT), ventral prostate (VP), testicle, and corpus spongiosum were isolated and weighed. Basal IUPs for the Fina- and QI-treated groups were 87.6 and 86.8%, respectively. LUT and VP organ weights in the QI group were lower than those in the Fina group. However, the QI group showed significantly reduced electrical stimulated or Phe-induced IUP increment compared to the Fina and BPH groups. These results proved that QI can be beneficial for BPH symptoms by inhibiting 5α-reductase and consequently decreasing prostate and releasing urinary pressure.