Materials In Harsh Environments Research Articles

Electromagnetic wave absorption mechanism and wear corrosion characteristics of Ti3SiC2 MAX phase-doped Ni/AlN composite coating with core-shell structure based on laser cladding-induced pitaya-like multi-level heterogeneous interface

To satisfy the service requirements of wave-absorbing materials in harsh environments, it is important to design and manufacture corrosion-resistant composite-absorbing materials. According to the strategy of impedance matching and the dissipation behaviour of nickel-based alloys, AlN ceramics, and MAX-phase Ti3SiC2 multicomponent composite-regulated materials were studied. As an additive manufacturing technology, multilevel heterointerface composites with core–shell structures were obtained by laser cladding. The construction of a unique core–shell structure of a metal–ceramic and ceramic (core)–ceramic (shell) multi-level heterogeneous interface increased the interfacial relaxation and multiple dissipation and improved the impedance matching. The results enabled the N20M3 cladding coating to exhibit excellent microwave absorption characteristics, with a reflection loss of −32.84 dB at the ultra-thin thickness of 1.8 mm. Additionally, the composites exhibited excellent corrosion resistance, high hardness, and relatively good resistance to erosion wear. This work promotes the durability of wave-absorbing materials under severe conditions, as well as the integration of the efficient manufacturing of wave-absorbing materials.

Corrosion Monitoring Techniques in Subcritical and Supercritical Water Environments

A series of advanced equipment exposed to sub-/supercritical water environments at high temperatures, high pressures, and extreme water chemistry with high salt and dissolved oxygen content faces serious corrosion problems. Obtaining on-site corrosion data for typical materials in harsh environments is crucial for operating and maintaining related equipment and optimizing various corrosion prediction models. First, this article introduces the advantages and disadvantages, usage scenarios, and future development potential of several in situ monitoring technologies, including ultrasonic thickness measurement, the infrared thermography method, microwave imaging, eddy current detection, and acoustic emission. Considering the importance of electrochemical corrosion data in revealing microscale and nanoscale corrosion mechanisms, in situ testing techniques such as electrical resistance probes, electrochemical corrosion potential, electrochemical impedance spectroscopy, and electrochemical noise that can be applied to sub-/supercritical water systems were systematically discussed. The testing platform and typical data obtained were discussed with thick and heavy colors to establish a mechanical prediction model for corrosion behavior. It is of great significance to promote the development of corrosion monitoring techniques, such as breaking through testing temperature limitations and broadening the industrial application scenarios and maturity.

Corrosion and heat-resistant SiCN/C as lightweight fibers for microwave absorption and electromagnetic field shielding in Ku-band

SiCN fibers are usually combined with metals to increase the magnetic loss in electromagnetic field (EMF) shielding, but this results in high weight density, easy corrosion, difficult treatment, and high cost of the material. This study proposes the manufacturing of corrosion and heat-resistant ceramic lightweight fibers containing in-situ synthesized carbon nanostructures (SiCN/C) with excellent EMF shielding in Ku-band (12.4–18 GHz). The samples showed differential trends of EMF shielding effectiveness in terms of reflectance, transmittance, and absorption behavior. Compared to SiCN fibers, the EMF absorption was two times greater when carbon was added to the SiCN matrix. A minimum reflection coefficient (S11) of −12 dB was observed for SiCN/C fibers, meaning a high shielding efficiency with >90 % of the EMF energy shielded. On the other hand, SiCN fibers showed a minimum S11 of −7 dB, resulting in a protection of 80 % against EMF energy. Computational simulations clarified the better features of SiCN/C in electromagnetic shielding compared to SiCN, which was ascribed to enhanced conduction loss derived from conductive free carbon, and dipole and interfacial polarization loss generated by defects. The fibers were resistant to acidic and basic environments and oxidation of up to 600 °C. Moreover, the addition of carbon precursor represented a weight decrease of 17 % for SiCN/C compared to SiCN fibers. This research will afford an alternative solution for the manufacturing of SiCN/C fibers with EMF absorption properties that can be used as lightweight materials in harsh environments.

From lab to field: Prussian blue frameworks as sustainable cathode materials.

Prussian blue and Prussian blue analogues have attracted increasing attention as versatile framework materials with a wide range of applications in catalysis, energy conversion and storage, and biomedical and environmental fields. In terms of energy storage and conversion, Prussian blue-based materials have emerged as suitable candidates of growing interest for the fabrication of batteries and supercapacitors. Their outstanding electrochemical features such as fast charge-discharge rates, high capacity and prolonged cycling life make them favorable for energy storage application. Furthermore, Prussian blue and its analogues as rechargeable battery anodes can advance significantly by the precise control of their structure, morphology, and composition at the nanoscale. Their tunable structural and electronic properties enable the detection of many types of analytes with high sensitivity and specificity, and thus, they are ideal materials for the development of sensors for environmental detection, disease trend monitoring, and industrial safety. Additionally, Prussian blue-based catalysts display excellent photocatalytic performance for the degradation of pollutants and generation of hydrogen. Specifically, their excellent light capturing and charge separation capabilities make them stand out in photocatalytic processes, providing a sustainable option for environmental remediation and renewable energy production. Besides, Prussian blue coatings have been studied particularly for corrosion protection, forming stable and protective layers on metal surfaces, which extend the lifespan of infrastructural materials in harsh environments. Prussian blue and its analogues are highly valuable materials in healthcare fields such as imaging, drug delivery and theranostics because they are biocompatible and their further functionalization is possible. Overall, this review demonstrates that Prussian blue and related framework materials are versatile and capable of addressing many technical challenges in various fields ranging from power generation to healthcare and environmental management.

Sustainable superhydrophobic and self-cleaning wood via wax within Epoxy/PDMS nano-composite coatings: Durability related to surface morphology

The stability of wood materials in harsh environments requires a durable superhydrophobic (SH) coating. In this paper, a sustainable SH coating, suitable for interior and exterior applications of wood, was produced by reinforcing with bio based carnauba-wax two matrices, i.e. Epoxy resin or polydimethylsiloxane (PDMS). Fluorine-free dodecyl-terminated silica nanoparticles (DDT-SiO2), prepared through a chemical procedure, have been used to increase the hydrophobicity of all coating formulations. A novel approach for the wood substrate preparation was proposed and tested. The results showed that long-term water-repellency of the SH coatings can be enhanced by solvent/ultrasonic pre-treatments, controlling the chemical and morphological characteristics of the wood substrate before coating. The formulation containing wax exhibited a contact angle of 172° and a sliding angle <3° when applied on a clean/micro-structured wood surface subjected to solvent pre-treatments. The PDMS-based coating displayed excellent durability to water impact test, 120 cycles outdoor weathering/aging and severe environments (i.e. chemicals, ultrasonic and sea-water) than Epoxy one. While wax decreased the transparency of Epoxy-based coatings, the synergistic effect on the durability of the coating was evident. The superior characteristics of non-wetting, mechanically durable and resistance to finger-touch test of wax-PDMS-DDT-SiO2 coating were attributed to the hierarchical structure caused by carnauba-wax self-assembly and interwoven morphology. In fact, the wax helps keep the “PDMS-NPs” lotus-like structures tightly connected, producing a robust surface. The self-cleaning test, carried out using commonly used liquids and colored water, confirmed the admirable performance of the PDMS-based coating, guaranteeing also aesthetic property. The surface treatment obtained can be considered “eco-friendly” as it is composed of vegetable carnauba-wax containing nanoparticles modified with non-fluorinated compounds.

Vacancy segregation and intrinsic coordination defects at (1 1 1) twist grain boundaries in diamond

High radiation damage resistance has become increasingly important for applications of functional materials in harsh environments. The high radiation damage resistance diamond cubic carbon is a unique material which is considered for radiation environments. Beyond the intrinsic radiation hardness of crystal, the interaction between point defects and interfaces (e.g., grain boundaries) increases resistance to radiation damage. In effect, grain boundaries act as sinks for point defects and promote their mutual annihilation. Furthermore, interfaces can be exploited to obtain controlled segregation of point defects, thus avoiding the degradation of material properties due to uncontrolled point defect segregation and coalescence.In the present work, we investigate the interaction between vacancies – as a radiation defect in the bulk crystal – and (1 1 1) twist grain boundaries in crystalline diamond using atomistic simulation with analytical bond order potential. Based on previous observations on structure–property relationships characterising the (1 1 1) twist grain boundaries, this work analyses the emergence of periodic segregation patterns, which are rationalised by the underlying interface structure and their periodic intrinsic coordination defect populations. This observation suggests that randomly distributed vacancies in bulk single crystals can form self-organised defect arrays in the grain boundary. The coordination defect content correlates with the interface sink efficiency, providing guidelines for designing interfaces with high sink efficiency.

A qualitative Assessment of the influence of gamma radiation and heating on aluminum using non-destructive examination

The environmental degradation of metals can pose a significant challenge as it can reduce the effectiveness and lifespan of the equipment. As such, there is a growing need for new non-destructive testing methods that can help assess the behavior of materials in harsh environments. This research proposes the use of the non-destructive Scanning Contact Potentiometry (SCP) technique as a real-time monitoring system to control metals that are affected by external factors like gamma radiation and heating conditions. The SCP technique allows for the measurement of localized electro-physical signals on the surface of a material, providing insights into the material's behavior and characteristics. By using SCP as a real-time monitoring system, it is possible to detect changes in the material's behavior and take appropriate actions before any significant damage occurs. The study's findings highlight the effects of gamma radiation and heat on aluminum specimens. The accelerated growth of Al2O3 on the surface of aluminum specimens exposed to doses of up to 400 kGy and 1000 kGy underlines the importance of careful monitoring and maintenance to prevent metal degradation. Similarly, the concurrent changes in mechanical characteristics and oxide development at 150 °C reveal the need for effective management of temperature exposure in industrial settings. This research can contribute to the development of more effective strategies for managing and maintaining industrial equipment and designing new materials, with potential benefits for a wide range of industries.

Enhanced mechanical properties and in vitro biocompatibility of TiMOVWCr high-entropy alloy synthesized by magnetron sputtering

This study proposes the synthesis of a high-entropy alloy (HEA) composed of TiMoVWCr and a new synthesis route specialized for high-entropy alloys (HEAs) using radio-frequency (RF) magnetron sputtering. The development of HEAs with diversification for various elements is paramount for bridging some limitations in the usage of materials in harsh environments. In developing HEA-preparation techniques, the emergence of a novel sputtering target system is promising for preparing a wide range of HEAs. Thus, a reproducible single target sputtering system is proposed for HEAs and is evaluated systematically. This new target-preparation technique aids in tailoring the elemental compositions to optimize the alloy for important mechanical and biomedical applications, e.g., titanium implants. Films are analyzed using X-ray diffraction (XRD), X-ray photoelectron spectroscopy, and field emission scanning electron microscopy cross-sectional thickness. XRD and valence electron concentration (VEC) data showed a body-centered cubic structure with a major peak orientation of (110). Additionally, this alloy exhibited a very high hardness (29.2 GPa (±1.5)), elastic modulus (321 ± 8.9 GPa), smooth surface, and good cell viability compared to CP-Ti. The remarkably high hardness and elastic modulus are compared with the literature. Further, the crystalline phase is obtained at room temperature (RT) without undergoing post-treatment.

Passivation behavior of Cr-modified rebar in simulated concrete pore solutions with different pH

In this study, the enhanced passivation effect of Cr-modified rebar compared with carbon rebar has been explored with regard to the formation process of the passive film, which could provide a theoretical basis for the development and application of concrete materials in harsh environments. X-ray photoelectron spectroscopy and capacitance-potential method were used to investigate the composition, structural depth distribution, and semiconductive properties of passive films formed by Cr-modified rebar and carbon rebar in simulated concrete pore solutions with different pH. The kinetics of passive film growth and formation were analyzed by tracking tests of potentiostatic current transients and open circuit potential under natural aeration. The results show that the activation energy of Cr-modified rebar is lower at 14.59 kJ/mol, compared to carbon rebar's 25.36 kJ/mol. In the early stage, Cr-modified rebar can achieve a thinner, more stable initial film in a shorter time than carbon rebar. The rate of reduction of the initial thickening rate of the passive film on Cr-modified rebar is five times than that of carbon rebar per unit pH. The film growth rate after early stage of Cr-modified rebar decreases, whereas that of carbon steel increases, with decreasing pH. The passive film containing Cr oxide or hydroxide enhances the barrier effect of the oxide film to ion migration, and the re-dissociation of Fe oxide hinders the passivation process. This grants the thickness of the stable passive film of the two rebars changing oppositely and the Cr-modified rebar compared to carbon rebar enhance passivation with pH falling.

Highly elastic hard PECVD TiSiC:H/a-SiC:H coatings with enhanced erosion and corrosion resistance: The trampoline effect

Advanced protective coatings providing high resistance to solid particle erosion as well as corrosion require system designs that combine the controlled dissipation of impact energy with the suppressed diffusion of corrosive media. In the present work, we propose and investigate a coating architecture benefiting from a “trampoline” energy-damping effect in which a hard TiSiC:H layer on top of an elastic a-SiC:H underlayer is prepared by plasma enhanced chemical vapor deposition on aerospace-grade titanium (Ti6Al4V) alloy and stainless steel 410 (SS410) substrates provided with a Cr adhesion layer. In the first part of the work, we study the effect of hydrogen in the individual a-SiC:H films (determined by elastic recoil detection) on their morphology (using scanning electron microscopy) and the mechanical and tribological properties. The films exhibit a highly advantageous combination of properties such as high hardness (&amp;gt;20 GPa), high elastic recovery of up to 80%, low friction coefficient (μ = 0.15 against alumina counterpart), and excellent resistance to plastic deformation and elastic resilience, expressed by the hardness (H), reduced Young's modulus (Er), and the H/E, H3/Er2, and H2/Er ratios. In particular, the measured elastic strain-to-failure of the coatings reached an unusually high value of H/Er &amp;gt; 0.2, thus exceeding the super-elastic limit. Simultaneously, the a-SiC:H films provided an excellent corrosion and wear protection documented by a corrosion current that was found 103–104 times lower and a wear rate that was 34 times lower compared to the values for the bare SS410 substrate. When a top TiSiC:H layer (H = 30 GPa) was applied to complete a total thickness of 25 μm, the TiSiC:H/a-SiC:H system reduced the solid particle erosion rate (Al2O3 microparticles 50 μm in diameter, speed of 36 m/s, and 90° impact angle) by a factor of 37 for films exhibiting a composite H/E ratio of 0.26. The results of the present work show that hard and highly elastic a-SiC:H-based multilayer coating systems with selectively controlled mechanical, tribological, and corrosion properties are promising candidates for the protection of metallic materials in harsh environments.

Enabling Long-Lived Polymeric Room Temperature Phosphorescence Material in Abominable Solvent.

Long-lived polymeric room temperature phosphorescence (RTP) materials have drawn more attention due to their convenient preparation process and equally efficient phosphorescence performance in recent years. As the polymer matrix is sensitive to air and humidity, some non-covalent interactions in the matrix are easily decomposed in water or air, which means that it is difficult for this material to be stored stably for a long time in the atmospheric environment or under harsh conditions. In this work, polymer powder mBPipQ contains aromatic and piperidine rings that are designed and synthesized successfully. Then the polymer is uniformly dispersed into epoxy resin matrix to form long-lived polymeric RTP material with efficient afterglow properties. The stiff backbone structure of mBPip and dense molecular arrangement of epoxy resin provide a rigid environment to stabilize triplet excitons, the RTP performance is greatly enhanced. The lifetime of mBPipQ in epoxy resin is 2 times higher than that of small molecule chromophore in that one. Interestingly, after soaking in strong acid or alkali solution for 10 days, the material can still emit stable and efficient long-lived phosphorescence. It is thanks to the hard matrix after full curing, which can provide a protective layer to prevent external quenchers from interfering with phosphorescence emission. Utilizing the efficient phosphorescence emission and excellent abominable-solvent resistance of this RTP material, multilevel information encryption has been successfully demonstrated. This work broadens the application scope of polymeric RTP materials in harsh environments and provides a new idea for achieving efficient RTP emission.

Embedding magnetic 3D carbon skeleton in SiCN ceramics for high-performance electromagnetic shielding

The electromagnetic (EM) characteristics of SiCN-based composite ceramics were adjusted by embedding magnetic 3D carbon skeleton (3D-CS) into SiCN ceramics through electroplating and polymer derivation. The distribution uniformity of carbon conductive networks and magnetic particles in composite ceramics were effectively improved profiting from the scheme adopted in this work. In addition, Ni distributed on CS catalyzed the in-situ formation of carbon nanowires (CNWs) in the matrix, and also coordinated the magnetic properties of the ceramics by reacting with Si to form Ni2Si. Benefiting from the embedding of conductive CS and dual role of Ni, the electromagnetic wave (EMW) absorption rate of composite ceramics was improved, and the electromagnetic shielding (EMS) performance was significantly enhanced. When the electroplating time was fixed at 50 min, the EMS value (SETotal) of the composite ceramics in the entire X-band was greater than 55 dB, indicating that more than 99.999% of EMWs are shielded. Beyond that, composite ceramics have excellent solvent (PH = 1 and PH = 14) resistance performance and are powerful candidates for EMS materials in harsh environments.

Large-Scale Fabrication of High-Performing Single-Crystal SiC Nanowire Sponges Using Natural Loofah

This study presents large-scale fabrication of single-crystal SiC nanowire (SiCnw) sponges through a carbothermal reduction approach using agricultural residue loofah, which is believed to be a perfect alternative to traditional petrochemical materials as the carbon source in industrial fabrication of SiC nanowires, without additional chemical C sources or catalysts. The single-crystal ultralong SiCnw are observed to have diverse morphologies with diameters of 50–400 nm, which possess a significant anisotropic and hierarchical microstructure with planar-aligned bamboo joints. A roughly 2 nm thick amorphous SiO2 layer is identified wrapping the crystalline 3C-SiC. The underlying vapor–solid mechanism is systematically investigated via thermodynamic calculations on the formation and interactions of SiO, CO, and SiC. Noteworthily, the fabricated loofah-based SiCnw sponge exhibits prominent high-temperature performance after thermal insulation tests of alcohol lamp flame and butane blowtorch flame, which is attributed to the stacking faults, SiO2 layer, SiC/SiO2 interface of the nanowires, and the overlength pathway in the porous aerogel–sponge domain synergetically acting as a phonon barrier to enhance phonon scattering, prolong phonon diffusion, and eventually reduce solid thermal conductivity in the sponge architecture. Our current work has great potential to be applied in the eco-friendly industrial preparation of high-performing SiCnw as thermal protection materials in harsh environments.

Fabrication of outstanding mechanical performance engineered poly (lactic acid)/thermoplastic poly(ester)urethane in-situ nanofiber composites with a large-scale industrial innovation methodology

As one of the most promising biodegradable materials, poly(lactic acid) (PLA) is seriously restricted by its notorious brittleness and weak heat distortion resistance. Hitherto, the possibility of effectively toughening PLA while simultaneously maintaining high strength and stiffness has hardly been realized on an industrial scale. In this work, an innovative industrial methodology was applied to manufacture high-performance engineered (95-x) poly(l-lactic acid)/5poly(d-lactic acid)/xthermoplastic poly(ester)urethane ((95-x)L/5D/xT) nanofiber composites. The in-situ formed TPU nanofibers (TNFs) combined with sterocomplex crystals (SCs) generating synergistic effects significantly improve the crystallization behavior and elasticity of melt. The compatibility between PLA matrix and TNFs in (95-x)L/5D/xT nanofiber composites was significantly reinforced by constructing bundle structures. The bundle structure is composed of rigid PLA hybrid crystals tightly bundled with a handle of oriented TNFs with good interfacial compatibility, bundle structures interlink with each other forming 3D strengthening-toughening bundle structures contributing to the mechanical performance. The notched Izod impact strength of 80L/5D/15T and 75L/5D/20T nanofiber composites prodigiously increase to 74.8 and 98.7 kJ/m2, which is 27.7 and 35.6 times higher than that of neat PLLA. Meanwhile, the nanofiber composites can maintain balanced tensile yield strength, good Young's modulus, and obtain advantaged heat distortion resistance of 1132 MPa at 100 °C. Compared with reported PLA/elastomer blends, neat biodegradable plastics, general-purpose and engineering plastics, the efficient industrial-scale manufactured 80L/5D/15T and 75L/5D/20T nanofiber composites possessing outstanding mechanical performance of super toughness, balanced strength, good Young’s modulus and advantaged heat distortion resistance. It has immense potential to substitute non-degradable petroleum-based engineering plastics as structural materials in harsh environments, thereby reducing CO2 emissions and reducing pollution caused by discarded non-degradable petroleum-based plastics.

Durability of Repair Metakaolin Geopolymeric Cement under Different Factors

Nowadays, energy saving, and green sustainability are influencing the development of all industries, including the construction industry. In recent years, geopolymeric cement and concrete have become hot topic materials as a replacement for traditional OPC; this work carried out orthogonal experiments to identify four potential factors affecting the basic properties of the metakaolin-geopolymeric cement specimens. The results showed that the metakaolin and activator contents were the two primary influencing factors. Given the importance of studying the durability of building restoration materials in harsh environments, this experiment focused on testing the bond strength, permeability resistance, sulphate corrosion resistance, and freeze-thaw resistance of metakaolin geopolymer pastes with different proportions of metakaolin dopant and alkali activator content. The findings are that durability of the formed specimens significantly improved when suitable metakaolin and activator contents were incorporated, and bond strength was also improved. Moreover, the microscopic tests, including SEM and FT-IR experiments, were used to better reflect the changing durability of pattern. The experiments showed that the best durability of the metakaolin geopolymeric cement was achieved when the ratio of metakaolin to cement was 1.5 and the ratio of activator to cementitious material was 0.3. It can be concluded that the appropriate content of metakaolin and activator can give the geopolymer excellent performance under harsh conditions, which will contribute to the wide application of geopolymer.

High radiation tolerance of electrocaloric (1-x)Pb(Mg1/3Nb2/3)O3–xPbTiO3

High radiation tolerance of functional materials in harsh environments is the key requirement for the operation of particle accelerators, medical devices, nuclear power plants, satellites, and spacecraft. Neutron and gamma (γ) radiation can seriously affect the functional properties of the irradiated materials and thus the performance of the entire device. In this work, the feasibility of using (1-x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 (PMN–100xPT) electrocaloric materials in applications where the material is exposed to high neutron and γ-radiation is investigated. For this purpose, three different compositions of PMN–100xPT ceramics (x = 0, 0.1, and 0.35) were prepared and their dielectric, ferroelectric and electrocaloric properties were investigated before and after neutron and γ-irradiation. The samples were irradiated with a neutron fluence of 1015 to 1017 neutrons cm−2 with an energy of 1 MeV, which exceeds the largest expected neutron irradiation in the European Council for nuclear Research (CERN) and simultaneously exposed to γ-irradiation. The neutron and γ-radiation partially affect the functional properties of the PMN–35PT, the ceramic with distinct ferroelectric and weakened relaxor features, with some differences observed in the domain switching behavior, measured by conventional polarization versus electric field (P–E) hysteresis, at the highest radiation dose of 1017 neutrons cm−2. In contrast, the functional properties of the irradiated PMN and PMN–10PT samples with relaxor behavior are quite similar to those of the pristine samples, therefore, we conclude that these materials can be used as working materials in EC coolers exposed to such harsh environments.

Using High Voltage Electrochemical Oxidation (HVEO) to obtain protective coatings, surface finishing on electronic materials

Electronics and microelectronic components such as printed circuit board, capacitors, CPU heat sinks, hard drive, etc. commonly encounter harsh environmental conditions during their operational lifetime. To protect the electronics materials from conditions like corrosion, wear, humidity and contaminants, aluminium protective coating materials can be used. However, the behavior of materials in harsh environments and their effect on the reliability of electronics in industrial products has been studied only very little. Moreover, the changes in the parameters (current density, temperature and time) of commonly used aluminium under various conditions remain largely unknown. In this paper, High Voltage Electrochemical Oxidation (HVEO) was used to produce a high microhardness of 440HV and high surface thickness of up to 44µm oxide coatings on aluminum alloy AMg2 (analogues of 5052-H32 alloy) for electronic components protection. The process was carried out in electrolyte of tartaric acid and sulfuric acid as an electrolyte under constant duration for each sample and various anodizing temperatures and current densities. The samples used in the study were aluminum used for commercial electronics devices designed for use in harsh conditions.

Visualizing time-dependent microstructural and chemical evolution during molten salt corrosion of Ni-20Cr model alloy using correlative quasi in situ TEM and in situ synchrotron X-ray nano-tomography

In situ monitoring of corrosion processes is important to fundamentally understand the kinetics and evolution of materials in harsh environments. A quasi in situ transmission electron microscopy technique was utilized to study microstructural and chemical evolution of a Ni-20Cr disc sample exposed to molten KCl-MgCl2 salt for 60 s in consecutive 20 s iterations. In situ synchrotron X-ray nano-tomography was performed to characterize the morphological evolution of a Ni-20Cr microwire exposed to molten KCl-MgCl2. Both techniques captured key corrosion events and revealed mechanisms at different time and length scales, potentially bringing greater insights and deeper understanding beyond conventional analysis.

Ultralight and heat-insulating mesoporous polyimide aerogels cross-linked with aminated SiO2 nanoparticles

Ideally, excellent heat-insulating material should have low thermal conductivity, low density, excellent resistance to high and low temperatures and good mechanical properties. But few materials can meet all the above requirements at the same time. Take polyimide (PI) aerogel as an example. Although it has the advantages of lightweight, good mechanical properties and excellent temperature resistance, the value of its thermal conductivity is often unsatisfactory. To solve this problem, a series of mesoporous polyimide aerogels using aminated SiO2 nanoparticles as cross-linker have been prepared. By changing the content of SiO2 and the synthetic methods, the key properties of PI aerogels such as the density and thermal conductivity were effectively tuned. These aerogels have low density, high specific modulus, significantly low thermal conductivity (~20 mW m−1 K−1), and excellent high temperature resistance. Their general properties (shrinkage, density, compression performances, specific surface area, pore size distribution, high temperature resistance) and their application potential as lightweight, high-performance thermal insulation materials in harsh environments are discussed.

Lightweight and Hydrophobic Three-Dimensional Wood-Derived Anisotropic Magnetic Porous Carbon for Highly Efficient Electromagnetic Interference Shielding.

Constructing multifunctional characteristics toward advanced electromagnetic interference shielding materials in harsh environments has become a development trend. Herein, the wood-derived magnetic porous carbon composites with a highly ordered anisotropic porous architecture were successfully fabricated through a pyrolysis procedure. The three-dimensional porous skeleton inherited from the wood stock serves as an electrically conductive network and incorporates magnetic Ni nanoparticles homogeneously and firmly embedded within the carbon matrix that can further improve the electromagnetic attenuation capacity. The optimized Ni/porous carbon (PC) composite exhibits an exceptional electromagnetic interference (EMI) shielding effectiveness of 50.8 dB at the whole X band (8.2-12.4 GHz) with a low thickness (2 mm) and an ultralow density (0.288 g/cm3) and simultaneously possesses an extraordinary compressive strength (11.7 MPa) and a hydrophobic water contact angle (152.1°). Our study provides an alternative strategy to utilize green wood-based materials to design multifunctional EMI shielding composites.