Hot-pressing Method Research Articles

Study on the effects of nano-copper addition on the properties of epoxy resin/graphite composite bipolar plates

Bipolar plates (BPs) are vital components in Proton Exchange Membrane Fuel Cells (PEMFCs), and their performance and cost significantly impact fuel cell stack efficiency and affordability. BPs require excellent conductivity, strength, and corrosion resistance depending on usage conditions. Common graphite and metal-based BPs offer good conductivity, but they have their drawbacks. Graphite lacks strength and is costly to process, while metal-based BPs need additional surface treatments to prevent corrosion. In recent years, composite bipolar plates have gained widespread attention due to their excellent conductivity, mechanical properties, and outstanding corrosion resistance. In this study, we used natural graphite flakes as the main conductive filler and nano-copper as the secondary conductive filler, with epoxy resin as the binder. The composite bipolar plate was prepared using a hot-pressing method. The study found that adding 1 wt% of nmCu can increase the conductivity of the composite BP by 75.2%, but it decreases the flexural strength by 26.84%. The prepared nmCu/G/EP composite BP exhibits an ASR of only 4.00 mΩ cm2 and a corrosion current density of 2.615 × 10−7 A/cm2, meeting the DOE 2025 expectations. After conducting Cu2+ leaching experiments on the prepared composite BP, single-cell performance testing showed a maximum power density of 0.556 W/cm2. This study expands the range of conductive fillers for composite BPs, no longer limited to carbon-based conductive fillers.

Regenerated products from leather industrial solid waste: Future perspective and current advances

The removal of chrome waste (CW) has been identified as a significant environmental problem due to chromium's toxicity. This study tried to make a regenerated flexible sheet (RFS) with a leather alternative effect from chrome waste powder (CWP), cardboard waste fiber (CBWF), and protein binder (PB) fabricated by the hydraulic wet and hot press method. The prepared RFS was characterized by its High-resolution scanning electron microscopy (HR-SEM), thermo gravimetric analysis (TGA), mechanical analysis, and biodegradation properties. The result showed the strong binding achieved with fiber/polymer membrane for RFS. In this regard, RFS with suitable mechanical properties such as tensile strength (37.54 ± 1.32 MPa), elongation at break (33.64 ± 0.52 %), flexibility (5.34 ± 0.67 %), water absorption (27.74 ± 1.56 %), and water desorption (27.46 ± 0.76 %) properties. RFS possessed the required mechanical properties for leather sheet production and it was also biodegradable. The study proves that these composites could be successfully used for the production of cost-effective leather goods and footwear production. Production of useful byproducts from waste is income generating and at the same time reduces environmental pollution and a feasible technology for waste recycling has been proved in this study.

Effects of carboxymethyl cellulose concentration on mechanical, viscoelastic properties, and thermal properties of starch/plant fiber foaming tableware materials with foam structure

In this study, a novel bio-based composite of starch/plant fiber foaming tableware material was prepared by the hot-pressing foaming method. The influence of the content of carboxymethyl cellulos (CMC) as a new type of film-forming agent filler on the properties of foam materials was systematically investigated. The results showed that the foam material with 10 wt% CMC had excellent cell morphology and uniform cell size (the average cell size reached the minimum value of 465.7 μm), relatively high porosity (57.01%), and excellent thermal insulation properties (thermal conductivity: 0.0541 W/m·K). The tensile strength of foam increased from 4.289 MPa for 0 wt% CMC to 5.714 MPa for 10 wt% CMC loading. Similarly, the flexural strength also increased from 11.609 MPa to 15.719 MPa for the foam material with 10 wt% CMC. The thermal stability and viscoelastic properties of the foam material reached the highest after adding 10 wt% CMC. In addition, the increase of CMC content is beneficial to improve the oil resistance and biodegradability of the material. The research shows that CMC is an effective filler to improve the properties of starch/plant fiber foaming tableware materials, which can greatly promote the development of bio-based polymer foam materials.

Arc erosion resistance of Al2O3–Cu/35Mo composites reinforced by trace graphene oxide

In this study, Al2O3–Cu/35Mo composites were prepared by rapid hot-press sintering-internal oxidation method, and the materials were modified by adding trace amounts of graphene oxide (GO). The results show that the relative densities of the composites are above 99%, the γ-Al2O3 generated by internal oxidation is diffusely distributed on the copper matrix. The incorporation of GO produced a small number of hard MoC particles at the interface, which facilitated the interfacial bonding of the composites. In the 30 V DC, 10–30 A electrical contact test, the anode mass of the composites increases, while the cathode mass decreases. And GO reduces the total mass loss of the electric contact by 63.6%, 38.9%, 51.3% and 20.9%, respectively. A comparison of the electrical contact properties of the two materials showed that the addition of GO dispersed the concentrated erosion of the arc. At 10 A and 30 A, the arc energy is reduced by 75.5% and 12.5%, respectively. With the gradual increase in electric current, GO makes the Al2O3–Cu/35Mo composites more stable during the electric contact process, improves the anti-welding ability of the contact and reduces contact resistance.

Sustainable Optimization of Mold Heating: A Dual Approach with SWARA and MARCOS Methods

There are many methods and raw materials in the manufacturing of fiber reinforced plastics (FRP) with hot press, such as Sheet Molding Compound (SMC), Bulk Molding Compound (BMC), and Prepreg fabrics. In most applications, it is commonly used to put the new dough into the mold without cooling the mold, press it again and cure it. Putting the mold into the dough without cooling causes the surface of the poured product to cure faster than the inner region, thus causing a structurally discontinuous structure in the product. Therefore, in more professional manufacturings, the mold is lowered to approximately 120 oC and the dough is put into the mold at this stage. However, this increases energy consumption and carbon emissions for the heating and cooling phases. In this study, the energy efficiency in the manufacturing of fiber reinforced plastics (FRP) produced by the hot press method was investigated. At the end of this study, by using alternative energy methods in manufacturing processes, results such as investment cost, depreciation expenses, reduction in invoices, and carbon emissions were achieved. In order to find the best alternative among these results, the criteria weights were determined with SWARA, and the founded alternatives ranked by the MARCOS method. As a result of this ranking, the best alternative was determined as a 40 kWh battery and a 25 kW solar panel option among the solar panel power and battery capacity alternatives.

Preparation of Wheat Straw Hot-Pressed Board through Coupled Dilute Acid Pretreatment and Surface Modification.

The production of wheat straw waste board materials encounters challenges, including inadequate inherent adhesiveness and the utilization of environmentally harmful adhesives. Employing a hot-pressed method for converting wheat straw into board materials represents a positive stride towards the resourceful utilization of agricultural wastes. This study primarily focuses on examining the influence of hot-pressing process conditions on the mechanical properties of wheat straw board materials pretreated with dilute acid. Additionally, it assesses the necessity of dilute acid treatment and optimizes the hot-pressing conditions to achieve optimal results at 15 MPa, 2 h, and 160 °C. Furthermore, a comprehensive process is developed for preparing wheat straw hot-pressed board materials by combining dilute acid pretreatment with surface modification treatments, such as glutaraldehyde, citric acid, and rosin. Finally, a thorough characterization of the mechanical properties of the prepared board materials is conducted. The results indicate a substantial improvement in tensile strength across all modified wheat straw board materials compared to untreated ones. Notably, boards treated with glutaraldehyde exhibited the most significant enhancement, achieving a tensile strength of 463 kPa, bending strength of 833 kPa, and a water absorption rate of 14.14%. This study demonstrates that combining dilute acid pretreatment with surface modification treatments effectively enhances the performance of wheat straw board materials, offering a sustainable alternative to traditional wood-based board materials.

Structural, Mechanical, and Barrier Properties of the Polyvinylidene Fluoride-Bacterial Nanocellulose-Based Hybrid Composite.

This study presents an analysis of films which consist of two layers; one layer is PVDF as the matrix, along with fillers BaTiO3 (BT), and the second is one bacterial nanocellulose (BNC) filled with Fe3O4. The mass fraction of BT in PVDF was 5%, and the samples were differentiated based on the duration of the mechanical activation of BT. This innovative PVDF laminate polymer with environmentally friendly fillers aligns with the concept of circular usage, resulting in a reduction in plastic content and potential improvement of the piezoelectric properties of the entire composite. This work presents new, multifunctional "green" packaging materials that potentially could be a good alternative to specific popular materials used for this purpose. The synthesis of the films was carried out using the hot press method. Tensile tests, water vapor permeability examination, and structural analyses using SEM-EDS and FTIR have been conducted. The sample PVDF/BT20/BNC/Fe3O4 exhibited the best barrier properties (impermeability to water vapor), while the highest tensile strength and toughness were exhibited by the PVDF/BT5/BNC/Fe3O4 sample.

Hot-press melt-assembly anisotropic porous structure with enhanced radiative cooling

Passive daytime radiative cooling (PDRC) is a promising and sustainable technology, achieving subambient cooling of objects without electrical consumption. Current PDRC designs realize efficient cooling performance, but their complicated and expensive fabrication approaches remain a challenge. Herein, we present a simple, versatile, and effective morphology control method based on the hot-press melt-assembly approach for fabricating tunable anisotropic porous polymethyl methacrylate (PMMA) films with high-efficiency daytime radiative cooling capability. The abundant and disordered micro/nanopores in the PMMA films caused by localized melting and bonding of particles reinforce scattering of the incident sunlight. Apart from the high refractive index contrast between PMMA and air within the porous structure, the dispersed PMMA particles exhibit an apparent micro/nanoplatelet morphology after hot pressing, enhancing the backscattering of sunlight within a porous PMMA film and contributing to the high-performance subambient radiative cooling. Therefore, the porous PMMA film features an ultrahigh solar reflectance of 0.95 and strong mid-infrared thermal emittance of 0.93, allowing for a peak subambient cooling temperature reduction of 9.9 °C under a solar irradiance of 700 W/m2 with an average radiative cooling power of 98 W/m2 during the daytime. Furthermore, the hot-press melt-assembly method is a cost-effective and high-efficient process for fabricating the desirable micro/nanoporous structure, providing a practical and effective pathway toward a large-scale production for excellent passive radiative cooling.

Suppressed bipolar effect and high average ZTave in CuO-doped Bi0.46Sb1.54Te3 bulks with a large size

Currently, bismuth telluride-based zone-melted ingots dominate the commercial thermoelectric (TE) market. However, bismuth telluride-based zone-melted ingots with a layered lattice structure are brittle, posing challenges for their application in miniature devices. Their polycrystalline alloys have robust mechanical strength. However, the electrical conductivity of a p-type polycrystalline BiSbTe alloy bulk deteriorates. In the current study, the Bi0.46Sb1.54Te3 powder was from crushed zone-melted ingots. Large-sized polycrystalline (CuO)xBi0.46Sb1.54Te3 (x = 0, 0.003, 0.01, 0.03 and 0.1) bulks were prepared via the hot-pressing method under 65 MPa at 510°C for 15 min. The electrical conductivity was improved remarkably by the acceptor doping effect. The bipolar effect of the Seebeck coefficient and thermal conductivity at high temperatures was suppressed significantly due to increased majority carrier centration and enlarged bandgaps. Consequently, their TE performance (the dimensionless TE figure of merit, ZT) was significantly improved and the ZTmax and ZTave reached 1.4 and 1.27, respectively.

Microstructure, thermal/mechanical properties and corrosion behaviors of ternary and quaternary equimolar rare-earth monosilicates

The properties of rare-earth (RE) monosilicates can be regulated by solid solution engineering based on the mixture rule. The combination and number of RE principals are critical factors for better performances. In the present study, four single-phase equimolar multicomponent RE-monosilicate solid solutions including (Dy1/3Er1/3Yb1/3)2SiO5, (Ho1/3Er1/3Yb1/3)2SiO5, (Y1/4Er1/4Tm1/4Lu1/4)2SiO5 and (Dy1/4Er1/4Tm1/4Yb1/4)2SiO5 were synthesized by solid-state reaction and hot-pressing method. The microstructures, thermal and mechanical properties, and corrosion resistance to high-temperature water vapor were systematically investigated. Compared to the single-principal and ternary RE-monosilicates, the quaternary RE-monosilicates exhibited lower thermal conductivity of 1.32 Wm−1K−1 at 400 °C, matched thermal expansion coefficients (3.3 × 10−6/oC ∼ 5.8 × 10−6/oC from 200 °C to 1000 °C) with SiC, and much lower weight loss during water vapor corrosion. The results indicate that the increase of the RE element number can promote the grain growth, lower the thermal conductivity and thermal expansion coefficient, and enhance corrosion resistance.

Optimization of the Effect of Hydraulic Hot-Pressing-Process Parameters on Tensile Properties of Kapok Fiber Nonwoven Web Based on Taguchi Experimental Design

This paper investigates the effect of temperature on the physical properties of Kapok fiber web formed via the hot-pressing method. The kapok web was prepared using the Ashford drum carder. Test samples were subjected to heat treatment in a hydraulic hot-press under three different temperatures (160, 170, and 180°C), heating durations (5, 7.5, and 10 min), and pressures (500, 750, and 1000 psi). This study was conducted to clarify the tensile properties of kapok fabrics under optimal hot-press-forming process parameters such as temperature, heating time, and pressure; here, the Taguchi L27 orthogonal array experimental design was adopted for the optimization. The surface morphologies and tensile properties of kapok fabrics were investigated. The optimum combination of process factors was obtained through signal-to-noise (S/N) ratio analysis. Furthermore, analysis of variance was employed to determine the importance of the process parameter levels. Moreover, regression analysis was adopted to mathematically model the metamorphism of tensile properties with process parameters. A set of confirmation tests was also conducted, and the results verified the presented models. This study results showed that all three processing factors had significant influences on the tensile strength of the carded nonwoven kapok. The combination of hot-pressing parameters to obtain the optimum tensile strength was obtained as follows: 170°C temperature, 1000 psi pressure, and 10 min heating time.

Influence of Ti2SnC content on arc erosion resistance in Ag–Ti2SnC composites

Abstract In this work, an Ag–Ti2SnC composite was fabricated by the hot-pressing sintering method, and the erosion behavior of Ag–Ti2SnC with volume percentages of 10–40% was studied at a load voltage of 10 kV. The arc life and breakdown current were observed at about 31–36 ms and 39 A, respectively. The cathode spot traveled the fastest on the surface of the Ag–40 vol% Ti2SnC composite. Due to emission center model, the temperature of the minor protrusions on the cathode surface increased, resulting in Ag ions, Ti ions, and Sn ions being generated. Combining with the ionized oxygen, Ag2O, AgO, TiO2, and SnO2 were formed on the eroded Ag–Ti2SnC surface after arc erosion. The research results will broaden the application range of Ag–Ti2SnC electrical contact material and enrich the arc erosion mechanism.

Hot-Pressing Enhances Mechanical Strength of PEO Solid Polymer Electrolyte for All-Solid-State Sodium Metal Batteries.

Poly(ethylene oxide) (PEO)-based solid polymer electrolytes (SPEs) are widely utilized in all-solid-state sodium metal batteries (ASSSMBs) due to their excellent flexibility and safety. However, poor ionic conductivity and mechanical strength limit its development. In this work, an emerging solvent-free hot-pressing method is used to prepare mechanically robust PEO-based SPE, while sodium superionic conductors Na3Zr2Si2PO12 (NZSP) and NaClO4 are introduced to improve ionic conductivity. The as-prepared electrolyte exhibits a high ionic conductivity of 4.42×10-4 S cm-1 and a suitable electrochemical stability window (4.5V vs Na/Na+). Furthermore, the SPE enables intimate contact with the electrode. The Na||Na3V2(PO4)3@C ASSSMB delivers a high-capacity retention of 97.1% after 100 cycles at 0.5 C and 60°C, and exhibits excellent Coulombic efficiency (CE) (close to 100%). The ASSSMB with the 20µm thick electrolyte also demonstrates excellent cyclic stability. This study provides a promising strategy for designing stable polymer-ceramic composite electrolyte membranes through hot-pressing to realize high-energy-density sodium metal batteries.

Physical Properties of Polymer Concrete Utilizing Pahae Natural Zeolite, Corn Husk Fiber, and Polyurethane Resin Adhesives

This study aimed to determine the optimum composition in the manufacture of polymer concrete using Pahae natural zeolite, corn husk fiber, and polyurethane resin adhesives. This study used the hot-press method at 170℃ for 30 minutes. The compositions of zeolite and corn husk fiber tested were varied under three different additions of polyurethane resin of 15 g, 20 g, and 25 g, while the composition of sand was fixed at 60 g. The inclusion of corn husk fiber content reduces the density of the concrete and increases the porosity and water absorption. The physical properties analysis showed that the polymer concrete samples showed the highest density was 1.89 g/cm3 from 20 g of polyurethane resin and no addition of corn husk fiber; the highest porosity was 6.15% from 15 g of polyurethane resin and 10 g of corn husk fiber; and the highest water absorption was 5.85% from 15 g of polyurethane resin and 10 g of corn husk fiber. Because improved material quality and durability are linked to reduced water absorption rates in polymer concrete, the most favorable composition with minimal water absorption (0.51%) came from the sample utilizing 20 grams of polyurethane resin without incorporating corn husk fiber.

Improved thermoelectric performance of Bi2Te2.7Se0.3 with honey dispersion

Bi2Te3-based alloys are only commercial thermoelectric materials. While, currently, n-type Bi2Te[Formula: see text]Se[Formula: see text]-based alloys commonly have lower ZT values than those of p-type Bi[Formula: see text]Sb[Formula: see text]Te3 based alloys. In this paper, the influence of different amounts of dispersing honey on the thermoelectric performance of n-type Bi2Te[Formula: see text]Se[Formula: see text] alloys synthesized by the hydrothermal and hot-pressing methods was investigated. The carbon atoms contained in honey could increase lattice defects and grain boundary density effectively, and improved the Seebeck coefficient and suppress lattice thermal conductivity simultaneously. By adjusting the amount of honey, the maximum ZT value reached 0.82 at 423[Formula: see text]K, which was approximately 65% higher than that of the pristine Bi2Te2.7Se0.3.

Facile Synthesis of a Graphene Film with Ultrahigh Thermal Conductivity via a Novel Pressure-Swing Hot-Pressing Method

Facile Synthesis of a Graphene Film with Ultrahigh Thermal Conductivity via a Novel Pressure-Swing Hot-Pressing Method

A low-cost granular-medium hot quasi-isostatic pressing method for enhancing compressive properties of 3D printed structures

3D printed structures suffered weak bead-to-bead interfacial bonding due to the layer-by-layer manufacturing process. The hot isostatic pressing (HIP) method was effective in improving the micro-structures and enhancing the mechanical properties of 3D printed structures, but it was limited due to the high-cost device and process. Inspired by the HIP method, and aimed at improving the compressive properties of 3D printed thin-walled structures, this work proposed a low-cost granular-medium hot quasi-isostatic pressing (GMHQIP) method realized by the homemade equipment. The hot quasi-isostatic ambient pressure could be produced by pressing the granular medium in the high-temperature environment. The thin-walled structures treated by the GMHQIP method showed a more regular progressive deformation mode than non-treated structures. Compared to the non-treated structure, the specific energy absorption of thin-walled structures treated at 200 °C with 2 MPa for 8 h significantly increased by 170.4 % to the value of 4.95 J/g. The results indicated that the strength and toughness of 3D printed materials improved significantly after the GMHQIP treatment. The interfacial bonding of 3D printed structures was enhanced by using the GMHQIP method. This work offered a low-cost and efficient post-processing method for 3D printed structures to improve compressive properties.

Meltable Aluminum Molecular Rings with Fluorescence and Nonlinear Optical Properties.

Crystal-liquid-glass, which combines the tunable properties of crystalline compounds with the processability of glasses, has emerged as a new class of materials for fabricating bulk-shapable devices in real applications. Inspired by the characteristics of deep eutectic solvent (DES) mixtures involving significant depressions in melting points compared to their neat constituent components, in this study, we designed and synthesized the first examples of meltable aluminum oxo clusters (AlOCs) via lattice doping with DESs at the molecular level. The abundant and strong hydrogen bonding between the aluminum molecular ring, DES components, and lattice solvents is postulated to be the root that affords melting point depressions and, thus, "melting" clusters. We prepared a transparent bubble-free glass film under autogenous pressure using a hot-press method. These cluster-based films exhibited luminescent and nonlinear optical properties similar to those of pristine crystalline compounds. Our study belongs to the interdisciplinary disciplines of chemistry and physics. It not only breaks the limitations of crystalline glass on metal and ligand types but also acts as a general guide for extending the range of meltable crystalline materials.

Toward a solid microneedle patch for rapid and enhanced local analgesic action.

Analgesic creams find widespread application as adjuncts for localized anesthesia prior to surgical procedures. Nevertheless, the onset of analgesic action is protracted due to the skin barrier's inherent characteristics, which necessitates prolonged intervals of patient and clinician waiting, consequently impinging upon patient compliance and clinician workflow efficiency. In this work, a biodegradable microneedles (MNs) patch was introduced to enhance the intradermal administration of lidocaine cream to achieve rapid analgesia through a minimally invasive and conveniently accessible modality. The polylactic acid (PLA) MNs were mass-produced using a simple hot-pressing method and served the purpose of creating microchannels across the skin's surface for rapid absorption of lidocaine cream. Optical and electron microscopes were applied to meticulously scrutinize the morphology of the fabricated MNs, and the comprehensive penetration tests involving dynamometer tests, evaluation on porcine cadaver skin, artificial film, optical coherence tomography (OCT), transepidermal water loss, and analysis on rats' skins, demonstrated the robust mechanical strength of PLA MNs for successful intradermal penetration. The behavioral pain sensitivity tests on living rats using Von Frey hair filaments revealed that the MN-assisted lidocaine treatment expeditiously accelerated the onset of action from 40 to 10min and substantially enhanced the efficacy of localized anesthesia. Furthermore, different treatment protocols encompassing the sequence of drug application relative to MN treatment, MN dimensions, and the frequency of MN insertions exhibited noteworthy influence on the resultant local anesthesia efficacy. Together, these results demonstrated that the lidocaine cream followed by diverse PLA MN treatments would be a promising strategy for rapid clinical local anesthesia with wide-ranging applications.

Biobased, self-healing, and recyclable polyurethane derived hydrogel-elastomer hybrids for efficient lubrication

Developing biobased hydrogel-elastomer hybrids with stable lubrication derived from self-healing and recyclable polymer matrix poses a key challenge in the field of medical devices. Herein, we reported a novel hydrogel-elastomer hybrid incorporating a tung oil (TO)-based, self-healing, and recyclable polyurethane (PU) substrate that exhibits exceptional hydrophilic and lubricating properties. Initially, a series of UV-curable PU elastomers containing dynamic hindered urea bonds (HUBs) derived from renewable TO were prepared. By adjusting the ratios of the cross-linking agent TO-based polyol and the chain-extending agent polytetramethyleneglycol, the mechanical and thermal properties of these elastomers could be tuned well. The as-prepared PU elastomers demonstrated remarkable dynamic properties, attributed to the dissociation and recombination of HUBs, enabling efficient self-healing and effective recycling through solvent or hot-pressing methods while preserving their mechanical properties. Furthermore, functional hydrogel-elastomer hybrids were obtained by applying UV-initiated polymerization method to generate hydrogel coatings onto the optimized PU elastomer surface. Compared to the pristine PU material, the resulting hydrogel-elastomer hybrids exhibited excellent lubricity in aqueous environments, resulting from the formation of a robust hydration layer facilitated by electrostatic forces. Overall, our current research work provides key design inspiration for developing next-generation medical devices from sustainable and recyclable functional biomaterials.