High-temperature Resistance Properties Research Articles

Failure criterion and damage evolution of high-strength geopolymer concrete under compression-shear composite loading after high temperatures

Geopolymer concrete (GPC) holds significant potential for building fire safety design due to its green, low-carbon, and high-temperature resistant properties. In practical applications, concrete structures often face multiaxial composite loads. Therefore, investigating the composite stress performance of high-strength geopolymer concrete (HGPC) after exposure to high temperatures is crucial for assessing structural damage and enhancing fire prevention measures. This paper examines the compressive shear performance of HGPC at various temperatures T (20°C, 200°C, 400°C, 600°C) and stress ratios k (0.15, 0.3, 0.45, 0.6). The study analyzes failure patterns, shear load-displacement curves, shear strengths and their components, and peak shear deformation. Failure criteria are proposed to describe the damage patterns of HGPC under compressive shear loading after high temperatures. Additionally, the damage evolution process is evaluated using the energy method. The results show that HGPC damage surfaces penetrate the coarse aggregate at room temperature under compression-shear composite loading but shift to the aggregate-mortar interface at 600°C. Shear stiffness, peak shear strength, and residual strength increase with higher stress ratios but decrease with rising temperatures. Temperature affects peak shear strength by over 95 %, significantly more than the stress ratio. The shear strength decreases more slowly than compressive strength up to 400°C but more rapidly beyond 400°C. The cohesive strength of HGPC decreases with increasing stress ratio under different temperatures, while contact friction strength exceeds 50 % of peak shear strength. Shear dilation strength generally increases, then decreases, peaking at k = 0.45. The failure criterion based on the modified twin shear unified strength theory aligns best with experimental results. Furthermore, an increased stress ratio retarded the development of damage evolution, which was first accelerated and then slowed with rising temperature.

Preparation of molybdenum disulfide/bentonite nanohybrid and its tribological properties as lubricant for water-based drilling fluids

In recent years, with the increase in energy demand and gradual scarcity of medium and shallow oil and gas resources, oil and gas exploration has shifted to special wells such as deep wells, ultra-deep wells, and extended reach wells. These complex wellbore structures inevitably increase the torque and friction between the casing and the drill pipe during drilling, which aggravates friction and wear, and leads to accidents such as drill sticking and drill breakage in severe cases. In this study, molybdenum disulfide/bentonite (MoS2/Bent) nanohybrids as drilling fluid lubricant were synthesized by hydrothermal method using sodium molybdate (Na2MoO4) and thiourea (CH4N2S) as raw materials and bentonite as carrier. The as-synthesized MoS2/Bent nanohybrid was characterized by X-ray powder diffractometer, transmission electron microscopy, Fourier transform infrared spectroscopy, and the high temperature resistance and tribological properties of MoS2/Bent nanohybrid were evaluated in base slurry. The results show that the friction coefficient of MoS2/Bent nanohybrid drilling fluid before aging is reduced by 74 % and the wear rate is reduced by 97 % compared with the base slurry. After high-temperature aging at 240 °C, the friction coefficient is reduced by 77 % and the wear rate is reduced by 90 %. The excellent friction reducing and antiwear performance is attributed to the formation of low shear strength MoS2 deposition film and oxide tribofilm on the surface of the friction pair during the rubbing process.

Waste coffee biochar and bi-oil composite modified rejuvenated asphalt: Preparation, characterization, and performance evaluation

In the realm of sustainable road construction, bio-oil has emerged as a promising and eco-friendly alternative for rejuvenating aged asphalt. Nevertheless, challenges arise due to poor stability, diminished performance at elevated temperatures, and limited anti-aging properties. This study introduces an innovative approach by blending biochar, obtained from the pyrolysis of waste coffee grounds, into bio-oil to create a composite modified regenerator. Initially, the study conducts a microscopic characterization of the biochar using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). Subsequently, the rheological properties of this composite rejuvenated asphalt are evaluated across low, moderate, and high-temperature ranges using bending beam rheometer (BBR), linear amplitude sweep (LAS), and multiple stress creep and recovery (MSCR) tests. Departing from the traditional emphasis on initial property restoration, it further delves into performance alterations after re-aging of rejuvenated asphalt through temperature sweep (TS) and Fourier transform infrared spectroscopy (FTIR) tests, providing a comprehensive assessment of the anti-aging characteristics of rejuvenated asphalt. Additionally, gel permeation chromatography (GPC) is employed to quantitatively analyze the changes in asphalt molecular weight distribution. The microscopic characterization reveals the development of a rough and porous structure within the biochar, facilitating enhanced adhesion and interaction between the rejuvenator and the asphalt binder. Moreover, bio-oil rejuvenated asphalt exhibits excellent low-temperature crack resistance and moderate-temperature fatigue resistance. Following the incorporation of biochar, notable enhancements in high-temperature rutting resistance and anti-aging properties are observed, validating the efficacy of the biochar with bio-oil composite modified regenerator. To achieve optimal performance outcomes, a biochar content of 6 % (as a proportion of aged asphalt), corresponding to a 1:1 ratio of biochar to bio-oil, is recommended. Under this condition, the properties of the composite modified rejuvenated asphalt demonstrate comparability to those of the original asphalt. In summary, this research underscores the potential for integrating waste coffee biochar material into infrastructure development, thereby promoting circular economy principles and advancing more sustainable construction practices.

Aero-thermodynamic responses of a novel FGM sector disks using mathematical modeling and deep neural networks

Composite sector disks have extensive applications in aerospace industries, particularly when exposed to challenging conditions such as supersonic airflow and thermal environments. These applications leverage the superior properties of composite materials, including high strength-to-weight ratios, enhanced durability, and excellent thermal resistance, to meet the stringent requirements of aerospace operations. Multi-directional functionally graded (MD-FG) materials due to high-temperature resistance and other amazing properties in each direction have gotten plenty of attention recently. So, in this research, a thermoelasticity solution has been presented to study fundamental frequency traits of an MD-FG sector disk in supersonic airflow via both mathematics simulation and deep neural networks technique. For obtaining exact displacement fields, along with defining the changes of transverse shear strains along the system's thickness, the refined zigzag hypothesis is utilized. For obtaining the temperature-dependent equations, heat conduction relation and thermal boundary conditions of the MD-FG structure are presented. A coupled quasi-3D new refined theory (Q3D-NRT) and generalized differential quadrature method (GDQM) are presented for obtaining and solving the partial differential equations in the time-displacement domain. After obtaining the mathematics results, appropriate datasets are made for testing, training, and validation of the deep neural networks technique. Finally, the results have shown that aerodynamic pressure, temperature changes, Mach number, free stream speed, and air yaw angle have a major role in the stability/instability analyses of the thermally affected MD-FG sector disk in supersonic airflow. As an amazing outcome, increasing the sector angle, FG indexes, and temperature change lead to the reduction of the critical Mach number, and aerodynamic pressure associated with the flutter phenomenon.

Enhancement of thermo-oxidative stability of polyimide composites by functionalized polyimide film surface modification

Polyimide (PI) resin-based composites exhibit excellent high-temperature resistance, solvent resistance, and mechanical properties, making them have broad application prospects in various fields such as aviation, aerospace, and transportation. With the continuous development of new devices, the requirements for the service temperature and service life of materials are improved, so there is an urgent need to improve the thermo-oxidative stability of polyimide composites. In this work, PI films, aluminum-coated PI film, and copper-coated PI film with low oxygen permeability were used as surface oxygen barrier materials, and surface film modified polyimide composites were prepared. The results show that, compared with the unmodified composite materials, after aging at 350°C for 400 hours, the weight loss rates of the composites modified by three kinds of surface films all increased by more than 50%, and the bending strength retention rates of the composites respectively increased by 47%, 51%, 45%, and the interlaminar shear strength retention rates respectively increased by 107%, 82%, 78%, showing excellent thermo-oxidative stability.

Drawing on bionics, a flexible silica fiber paper is designed with high temperature resistance and hydrophobic properties

In this paper, a flexible silica fiber paper (SFP) made of silica ceramic with excellent high-temperature resistance was prepared. After modification with fluorosilane, the contact angle of the modified fiber paper with water was 153°. At the same time, the modified fiber paper maintains the superhydrophobic properties even after high-temperature heat treatment (150 ± 1° after treatment at 400 °C) and shows excellent hydrophobic performance at high temperatures. The produced ceramic inorganic fiber paper has good comprehensive properties and is a promising skin material for aircraft.

The Preparation and Properties of a Ni-SiO2 Superamphiphobic Coating Obtained by Electrodeposition

Superamphiphobic coatings have shown great potential in many fields such as with their anti-corrosion, high-temperature resistance, self-cleaning, and drag reduction properties. However, due to the poor stability of their coatings, it is difficult to apply them on a large scale. In this paper, two kinds of SiO2 particles and nickel were co-deposited on the surface of steel to construct a micro/nano dual-scale structure by composite electrodeposition. The surface of the coating was then fluorinated with the low-surface-energy material 1H,1H,2H,2H-Perfluorodecyltriethoxysilane (AC-FAS) to prepare a Ni-SiO2 superamphiphobic coating. The coating has a water contact angle of 159° and an oil contact angle of 151°. The effect of nanoparticle concentration on the wettability and surface morphology of the coating was systematically studied. Comparative experiments revealed that the optimal micro/nanoparticle concentrations were 8 g/L of 20 nm SiO2 and 2 g/L of 1 μm SiO2. This preparation method greatly improves the corrosion resistance, wear resistance, chemical stability, and high-temperature resistance of the coating.

Composite Superhydrophobic Coating with Transparency and Thermal Insulation for Glass Curtain Walls.

In this paper, the preparation of a transparent superhydrophobic composite coating with a thermal insulation function using antimony-doped tin oxide (ATO) nanoparticles is proposed, which has advantages of being mass-producible and low-cost. In short, nanosilica and ATO are used as raw materials for constructing rough structures, and superhydrophobic coatings are obtained by mixing and adding binders after modification of each, which are then applied to the surface of various substrates by spraying to obtain a transparent superhydrophobic coating with a heat-insulating function. The specific role of each nanoparticle is discussed through comparative experiments that illustrate the mechanism by which the two particles construct rough structures. The coating achieves unique thermal insulation properties while possessing excellent superhydrophobicity (WCA of ∼163° and WSA of ∼3°) and high light transmission (∼70%). Heat-shielding experiments have demonstrated that the composite coating effectively reduces the room temperature by approximately 19% for the same irradiation time. The coating achieves a balanced improvement in visible transmittance, thermal insulation, and superhydrophobicity. In addition, the coating's self-cleaning properties, mechanical properties, chemical weathering resistance, high-temperature resistance, and anti-icing properties were verified through various experiments.

Rational construction of dicarbonous CB/CNT@PI composites toward low filler loading and low-frequency electromagnetic wave absorption.

With the application of low frequency radar and the demand for stealth of high temperature resistant components, it is increasingly urgent to develop absorbing materials with both low frequency and high temperature resistant properties. Here, we successfully prepared various carbon/polyimide composites as low-frequency electromagnetic wave absorbing materials by simple blending method. The well-designed mesh lap structure introduces a large amount of free space, further optimizing the impedance matching of the material. At the same time, the multiple loss mechanism formed by the combination of carbon black dominated polarization and carbon nanotube dominated conductive loss enhances the loss of incident electromagnetic wave. The results showed that only 10 wt% filler loading of the CB/CNT@PI is achieved in the low frequency range (1-4 GHz) with a minimum RL strength of - 18.3 dB, which has obvious advantages compared with other works in recent years. This study provides a way for the design and preparation of resin-based absorbing materials.

Nucleation Mechanism of Hexagonal Boron Nitride on Diamond (111) and Its Hydrogen-Terminated Surface: A DFT Study.

Hexagonal boron nitride (h-BN) has attracted significant attention due to its exceptional properties. Among various substrates used for h-BN growth, diamond emerges as a more promising substrate due to its high-temperature resistance and superior electrical properties. To reveal the nucleation mechanism of h-BN on the diamond (111) surface and the impact of hydrogenation treatment on this process, we explored the adsorption, diffusion, nucleation morphologies, and predicted nucleation pathways in this process using first-principles calculations based on density functional theory (DFT). Our results indicate that N positioned above the first layer of C and B positioned above the second layer of C enhance the stability of BN clusters. During the growth of BN clusters, there is a geometric transformation from chain-like structures to honeycomb-like structures. The proportion of unhybridized sp2 atoms within BN clusters and geometric symmetry significantly influence h-BN growth. Moreover, computational findings also suggest that to enhance the nucleation rate of h-BN it is essential to inhibit the formation of zigzag chain structures by BN clusters during the early stages of nucleation on a clean diamond surface. Additionally, hydrogenation treatment decreases the binding affinity of B and N on the substrate, facilitating atomic diffusion, and has been identified as an effective approach to facilitate nucleation. Furthermore, hydrogen-terminated diamond acts as an electron donor in the system, which profoundly affects the morphology of growing h-BN and the characteristics of the h-BN/diamond heterostructures. These conclusions are important to understanding and optimizing h-BN growth on diamond and provide a theoretical basis of the construction and application of the h-BN/diamond heterostructure.

In-situ formed Ni2Si into lightweight SiC(rGO) nanocomposite PDCs to boost load bearing-microwave absorption integration for complex environments

As contemporary aerospace and radar-detecting technologies evolve, load bearing-microwave absorption integration of thermal protection materials for complex environment requirements are urgent. Well known for low density, good high-temperature resistance and superior tunable dielectric properties, polymer-derived ceramics (PDCs) promisingly meet most needs of high-performance aircraft thermal protection system (TPS). Aimed at promoting practical application, we integrate in-situ formed Ni2Si into lightweight SiC(rGO) nanocomposite PDCs via re-pyrolyzing coassembled nano-Ni/SiC(rGO)p/polycarbosilane-vinyltriethoxysilane-graphene oxide (PVG) blends to enhance their mechanical and electromagnetic wave (EMW) absorbing performances. Size effect on phase transition of Ni into Ni2Si (as brazing bonding agents) accompanied by volumetric expansion, ingeniously eliminates stretching stress from PVG precursor inward shrinkage for compact framework during re-pyrolysis. In-situ generated Ni/Ni2Si/C core-shell nanostructure (similar to nodular cast iron) has good chemical compatibility with β-SiC/SiOxCy/Cfree(rGO), thereby enables composites improved compactness and toughness. More interestingly, heterogeneous interfaces/defects among Ni, Ni2Si, carbon shell, β-SiC and SiOxCy/Cfree(rGO) matrix, effectively facilitate interfacial/dipole polarization for robust EMW absorption, and lightweight SiC(rGO, Ni2Si)Ni=4% nanocomposite PDCs exhibit outstanding fracture toughness of 6.56 MPa·m1/2 and high compressive strength of 119.25 MPa. Such composite with structure-function integration maintain stable under butane blowtorch at ∼1300 °C, shedding light on a new route to mass-manufacture aerospace vehicle components.

Performance of asphalt mixtures containing high reclaimed asphalt pavement and waste steel rolling oil

Reducing costs, dealing with environmental problems, and preserving more natural resources are among the main incentives for reusing asphalt instead of road reconstruction. However, asphalt reuse involves the addition of some modifiers to the asphalt mixture. In this respect, rejuvenators investigated in the previous studies did not perform properly against all failures. Besides, they had problems such as lacking access to the required amount for road construction and high production costs. Regarding the high-temperature resistance and antioxidant properties of the waste steel rolling oil (WSRO), for the first time, the effect of using this lubricant was investigated on the recovery of bitumen aging and the performance of asphalt mixture containing high amounts of reclaimed asphalt pavement (RAP). To this end, the conventional (penetration and softening point) tests and rotational viscosity test were conducted to determine the optimal amount of rejuvenator. In addition, FTIR and FESEM tests were carried out for chemical and morphological investigation. SCB and dynamic creep tests were performed on a balanced mix design to examine the performance against cracking and rutting. Moisture sensitivity was also investigated by performing an indirect tensile test. The results show that a uniform texture was created in the aged bitumen modified with WSRO, and there was a decrease in functional groups that represent the occurrence of aging. Therefore, WSRO can restore aging and improve rutting and cracking performance. Resistance to moisture sensitivity also improved. Overall, the results show a performance improvement in the mixture containing high RAP content mixed with WSRO as a waste rejuvenator. However, more studies encompassing rheological, economic and environmental aspects, are needed to conclude about the practical use of this material.

Photocurable comb polyamic acid for solvent-free direct ink writing with low dimensional shrinkage

Polyimides are high-performance organic polymers with excellent insulation, high-temperature resistance, and mechanical properties. However, their poor solubility makes it challenging to use them to prepare solvent-free high-performance photocurable polyimide inks with low dimensional shrinkage. In this study, photocurable comb polyamic acid resins were synthesized, and their solubility was examined based on density functional theory (DFT) calculations. Experiments showed that polyamic acid resins with specific topologies could be dissolved in photocurable monomers to prepare solvent-free photocured polyimide inks. A custom-made UV-assisted direct ink writing 3D printer was used to fabricate complex three-dimensional devices. Further heat treatment caused the polyamic acids to undergo dehydration and cyclization into rigid polyimide structures, and this process exhibited less than 6% dimensional shrinkage. The final material had a maximum storage modulus of 3.1 GPa (40 ℃) and a glass transition temperature of 204 ℃. The good comprehensive performance suggests great potential for aerospace applications.

Preparation and High-Temperature Resistance Properties of Phenolic Resin/Phosphate Hybrid Coatings.

In this study, a novel fabrication method was used to synthesize phenolic resin/phosphate hybrid coatings using aluminum dihydrogen phosphate (Al(H2PO4)3, hereafter denoted as Al), SC101 silica sol (Si) as the primary film-forming agent, and phenolic resin (PF) as the organic matrix. This approach culminated in the formation of Al+Si+PF organo-inorganic hybrid coatings. Fourier-transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) results confirmed the successful integration of hybrid structures within these coatings. The crystalline structure of the coatings post-cured at various temperatures was elucidated using X-ray diffraction (XRD). Additionally, the surface and cross-sectional morphologies were meticulously analyzed using scanning electron microscopy (SEM), offering insights into the microstructural properties of the coatings. The coatings' porosities under diverse thermal and temporal regimes were quantitatively evaluated using advanced image processing techniques, revealing a significant reduction in porosity to a minimum of 5.88% following a thermal oxidation process at 600 °C for 10 h. The antioxidant efficacy of the phosphate coatings was rigorously assessed through cyclic oxidation tests, which revealed their outstanding performance. Specifically, at 300 °C across 300 h of cyclic oxidation, the weight losses recorded for phosphate varnish and the phenolic resin-infused phosphate coatings were 0.15 mg·cm-2 and 0.09 mg·cm-2, respectively. Furthermore, at 600 °C and over an identical period, the weight reduction was noted as 0.21 mg·cm-2 for phosphate varnish and 0.085 mg·cm-2 for the hybrid coatings, thereby substantiating the superior antioxidation capabilities of the phenolic resin hybrid coatings in comparison to the pure phosphate varnish.

Fast Solution Blow Spinning of Lotus-Leaf-Inspired SiO2 Nanofiber Sponge for High Efficiency Purification.

Massive production of SiO2 nanofibers with both high durability and exceptional performance remains a significant challenge. Herein, a novel approach was introduced to achieve the massive production of SiO2 nanofibers with lotus-leaf-inspired surfaces by combining solution blowing spinning (SBS) and the polymer-derived ceramics method. Based on the SBS technique, three types of precursor nanofiber products were fast spined with methyl silsesquioxane polymer and polymethyl hydrogen siloxane employed as Si sources. The flow rate of the SBS spined Si-based ceramic nanofibers was enhanced to 20 mL·h-1. Furthermore, through the integration of hydrophobic-oleophilic SiO2 nanoparticles into the precursor solution, SiO2 nanofibers with lotus-leaf nanoprotrusion surfaces were fabricated. Nanoparticle-decorated SiO2 fibers demonstrated excellent hydrophobicity (138.3°), compression resilience (∼60%), proficiency in organic pollutant adsorption, high-temperature resistance (∼1100 °C), and outstanding thermal insulation properties (thermal conductivity of 0.0165 W·(m·K)-1).

Machining performance of micro-pit and micro-groove composite textured tools in tungsten alloy turning

Tungsten alloys are widely used in aerospace because of their high-temperature resistance, corrosion resistance, high strength, and other excellent comprehensive properties. But tungsten alloys are typical hard-to-machining materials. Surface micro-textures can improve friction properties, such as preparing micro-textures on the surface of cutting tools for tungsten alloys, which is expected to enhance the cutting performance of tungsten alloys. Still, the relevant cutting laws need to be further studied. A combination texture of micro-pit and micro-groove was designed, and the micro-textured tool surface was prepared by laser machining. Compared with non-textured tools, micro-pit and micro-groove composite textured tools can effectively improve the processing quality of tungsten alloys. It happened because textures on the tool’s surfaces enhance machining performance by reducing the actual contact area between the tool and the chip and storing lubrication medium. At the same time, comparative experiments of micro-textured tools and non-textured tools were carried out. The results showed that when cutting W93NiFe alloys with textured and non-textured tools, the maximum reduction in resultant cutting forces with textured tools was 9%. The maximum reduction in surface roughness was 39.3%, the surface burr height of the tungsten alloy workpiece was lower, the number of surface grooves was lesser, and the surface was more flat. The research results are significant in achieving the efficient processing and high-quality manufacturing of tungsten alloys.

Low-temperature synthesis and properties of high-purity boron nitride microspheres

Boron nitride (BN) has excellent high temperature resistance, thermal conductivity, strong insulation, and wave-transparent properties. Spherical BN is an essential filler in polymer matrix composites due to good particle mobility and high filler content. In this paper, we present a large-scale preparation for BN microspheres with uniform particle size distribution in the range of 1.0–2.8 μm via solvothermal method at low cost and high yield (∼90%), which is two orders of magnitude lower than the diameter of the spherical BN prepared by other methods. BN microspheres can achieve good crystallinity (>70%) and high purity (>99.9%) at 800 °C. The temperature resistance study showed that the BN microspheres could maintain the dense particle morphology at 1200 °C. In addition, the prepared BN microspheres have good dielectric and thermal conductivity properties (dielectric constant ∼3.4, dielectric loss ∼2.0 × 10−3, and thermal conductivity of 9.8 W m−1 K−1), which show great potential in the field of wave-transparent and thermal conductive composites. The synthesis process of BN microspheres proposed in this study provides a new idea for the preparation of ceramic micro or nano materials by polymer-derived ceramics.

Multifunctional PVA/gelatin DN hydrogels with strong mechanical properties enhanced by Hofmeister effect

Due to the low mechanical strength, poor tensile property, and inability to work under extreme conditions, hydrogels encounter obstacles in their practical applications. It was found that the Hofmeister effect could strengthen and toughen the single hydrogel networks. Herein, poly (vinyl alcohol) (PVA)/gelatin dual-network (DN) hydrogels with strong mechanical properties were prepared and improved by Hofmeister effect using Na2SO4 as the salting-out solution. The hydrophilic anion SO42- induced a salting-out effect, which made the interplay in PVA and gelatin stronger, and the network structure more compact and stable. Moreover, the dual-assisted effect of freeze-thaw and freezing salting-out further enhanced the mechanical properties. The as-obtained DN hydrogel had excellent overall mechanical properties with a fracture tensile strain, a tensile strength and a toughness of 1281 %, 1.12 MPa and 7.19 MJ/m3, respectively. In addition, it had the ability to withstand weights more than 5000 times its own mass. The hysteresis energy, Young's modulus, and toughness recovery of the hydrogel reached 91.21 %, 97.36 %, and 97.47 % of the original values when the interval time was 180 min. Furthermore, after treatment with ethylene glycol /H2O solution, the hydrogel was given high temperature resistance, anti-freezing and moisturizing properties, while maintaining its good mechanical properties in a wide temperature range. The weight remained at 84.7 % and 71.45 % of the original weight after one week at 25 °C and 12 h at 60 °C, respectively. This kind of multifunctional DN hydrogel with high mechanical properties will find wider application in the field of flexible electronic devices.

Microwave absorbing performance of reduced graphene oxide @ alumina fabricated by atomic layer deposition method

In this work, a series of alumina coating reduced graphene oxide (RGO@Al2O3) composites with core-shell structure was synthesized by the atomic layer deposition (ALD) method. The alumina (Al2O3) thickness of the RGO@Al2O3 could be controlled by changing the number of ALD cycles. The microstructure, high-temperature resistance, and microwave absorbing properties of the composites were investigated in detail. The composite could provide excellent high-temperature resistance and microwave absorbing properties. The composite started decomposition at 620 °C. The maximum reflection loss value of the composite obtained by applying 200 Al2O3 deposition cycles is −14.2 dB at 15.7 GHz, and its effective absorption bandwidth reaches 5.0 GHz (13.0–18.0 GHz). The results show that the RGO@Al2O3 composite has the potential application in high-temperature microwave absorbing fields, due to excellent high-temperature resistance, reflection loss, and effective absorption bandwidth.

Experimental Study on the Characterization of Aging Resistance Properties of Optical Cables in the Hydrogen-Containing Downhole Environment.

The utilization of downhole optical cables has significantly enhanced the efficiency and reliability of oilfield production operations; however, the challenging high-temperature and high-pressure conditions prevalent in oil-gas fields markedly reduce the service lifespan of these optical cables. This limitation severely impedes their application and further development in subterranean environments. In this study, a qualitative analysis was conducted on the structural materials utilized in two types of optical cables to identify these materials and assess the high-temperature tolerance and aging resistance properties of the optical fibers incorporated within. It was discovered that hydrogen infiltration into the subterranean optical cables predominantly accounts for their operational failure. To address this issue, an optical loss testing platform was established, facilitating the execution of a high-temperature and high-pressure hydrogen permeation aging experiment on the optical fibers, allowing for the evaluation of the hydrogen resistance capabilities of the two types of optical fibers. The findings from this study provide a theoretical foundation and methodological guidance for the optimization of optical fibers, aiming to enhance their durability and functional performance in adverse environmental conditions encountered in oil-gas field applications.