Ultrahigh Resistance Research Articles

Ultrahigh tribocorrosion resistance of hydrogenated amorphous carbon coating via trace gradient W incorporation

In this work, we manipulated the trace gradient W incorporation combined with a increment top-layer thickness for the hydrogenated amorphous carbon (a-C:H) coating on thermally sprayed WC-based cermet. The tribocorrosion resistance of the modified a-C:H coating was investigated in terms of structural evolution during friction under 3.5wt.% NaCl solution. Regardless of introduction of gradient W doping, although the a-C:H coating maintained the sp2/sp3 atomic bond structure, the stress reduction and plasticity increase were obtained for coatings. Moreover, the stable open-circuit potential revealed that the tribocorrosion resistance of modified coating was significantly improved, as identified by the quite low wear rate and coefficient of friction at 1.46×10-8 mm3/N·m and COF of 0.067, respectively. Different with the traditional failure of worn-out and pitting corrosion of a-C:H coating in chloride solution, the designed robust interfaces and the functional top-layer enabled the coating to withstand longest sliding distance over 2100m at heavy contacting pressure of 1.67GPa. These observations offer the promising strategy to fabricate advanced carbon-based coatings with required extremely strong wear resistance and anticorrosion capability for mechanical components used in harsh marine environment.

Construction and Properties of Ultralow Thermal Conductivity and High Strength Zirconia Aerogel Composites by Freeze-Drying.

Zirconia aerogels possess significant applications, including their use catalyst carriers, thermal insulation materials, and thermal barrier coatings. This is due to their ultrahigh temperature resistance, high porosity, and low thermal conductivity. Nonetheless, the inherent challenges associated with ZrO2 aerogels, such as high brittleness, low compressive strength, and inadequate formability, restrict their potential applications. In this paper, with ultralow thermal conductivity and high strength zirconia aerogel composites with inorganic zirconium salt zirconium carbonate as the raw material, acetic acid as the solvent, polyvinylpyrrolidone (PVP) as the viscosity builder to stabilize the structure of the aerogel during the freeze-drying process. Additionally, yttrium nitrate hexahydrate (Y(NO3)3·6H2O) is employed as a phase stabilizer. The sol-gel method, in conjunction with the freeze-drying process, is utilized to fabricate ZrO2 aerogel composites with an optimized microstructure. The findings indicate that optimal process parameters are achieved with a PVP solution concentration of 2.0 wt % and a zirconium carbonate concentration of 20 wt %. The mechanical properties of the resulting composites reach up to 550 kPa, while the thermal insulation performance exhibits a temperature difference of 207 °C/cm and a thermal conductivity of 0.0504 W/(m·K). This advancement addresses the mechanical stability issues commonly associated with traditional ceramic aerogels and widely used elastic insulating materials, thereby enhancing their applicability as thermal insulation and heat preservation materials.

Improved oxidation and ablation resistance of SiCf/SiC-HfB2 composites: Role of oxygen-blocking scale and protection mechanism

To improve the oxidation and ablation resistance of SiCf/SiC composites, the as-synthesized ultrafine HfB2 powder was used as the modification phase to fabricate SiCf/SiC-HfB2 composites, and their oxidation and ablation behaviors were investigated. Compared with the unmodified SiCf/SiC composites, the oxidation resistance at 800–1500 °C and the ultra-high temperature ablation resistance of SiCf/SiC-HfB2 composites were significantly improved. After oxidation, a compact compound glass scale consisting of HfO2, HfSiO4 and Si-Hf-O glass was formed, providing the effective oxidation protection. A dual-phase oxide scale composed of HfO2 skeleton and Si-Hf-O glass was formed after ablation, exhibiting the high viscosity, the significant oxygen-blocking effect and resistance to gas flow scouring. The improved oxidation and ablation resistance of SiCf/SiC-HfB2 composites could be attributed to the effective protective role of oxygen-blocking scales formed during the oxidation and ablation processes.

Ultra-antiwetting Membrane for Hypersaline Water Crystallization in Membrane Distillation.

Membrane distillation (MD) has great potential in the management of hypersaline water for zero liquid discharge (ZLD) due to its high salinity tolerance. However, the membrane wetting issue significantly restricts its practical application. In this study, a composite membrane tailored for extreme concentrations and even crystallization of hypersaline water is synthesized by coating a commercial hydrophobic porous membrane with a composite film containing a dense polyamide layer, a cation exchange layer (CEL), and an anion exchange layer (AEL). When used in direct contact MD for treating a 100 g L-1 NaCl hypersaline solution, the membrane achieves supersaturation of feed solution and a salt crystal yield of 38.0%, with the permeate concentration at <5 mg L-1. The composite membrane also demonstrates ultrahigh antiwetting stability in 360 h of long-term operation. Moreover, ion diffusion analysis reveals that the ultrahigh wetting resistance of the composite membrane is attributed to the bipolar AEL and CEL that eliminate ion crossover. The literature review elucidates that the composite membrane is superior to state-of-the-art membranes. This study demonstrates the great potential of the composite membrane for direct crystallization of hypersaline water, offering a promising approach to filling the gap between reverse osmosis and conventional thermal desalination processes for ZLD application.

A ppb-level NO2 gas sensor with ultra-high concentration shock resistance characteristics based on In2O3-In2(MoO4)3

Metal oxides are widely used because of their simple structure, low price, and excellent gas-sensitive properties. But now, the metal oxide sensor faces two challenges. One is that when the detection limit of the sensor is low, it will be affected by a high concentration of gas and fail in practical applications. Second, the metal oxide sensor is susceptible to temperature changes, resulting in inaccurate measurement results. To address the above problems, the performance of metal oxides is enhanced through doping. Indium oxide doped with various levels of indium molybdate was prepared using a two-step hydrothermal method resulting in a composite material with an n-n heterostructure. The interaction formed by the n-n heterostructure enhances the redox reaction between NO2 gas and the sensor, and the unique nano cluster structure provides more active sites for the sensor, significantly improving the gas performance of the sensor towards NO2. Sensors based on In2(MoO4)3 with a doping ratio of 4 % (the sample IM3) showed excellent gas sensitivity. The lower and upper detection limits of the sensor are 200 ppb (response is 1.46) and 150 ppm (response is 515.94), respectively. And the sensor has good resistance to ultra-high concentration (10000 ppm) nitrogen dioxide (NO2) impact. In the range of 130–170°C, the temperature has a small and linear effect on the sensor response, which is very beneficial for temperature correction of gas sensors. The sensor prepared by In2(MoO4)3 doped In2O3 composite material has a good potential for application in engineering practice.

Ultrahigh corrosion resistance of Mg-Er alloys by two-layer barrier from oxide film and triangular prism-like Mg(OH)2

An ultrahigh corrosion resistance of Mg-Er alloys was achieved via a simple method by forming an Er2O3 oxide film using a high temperature treatment. The corrosion rate of Mg-8.1 wt% Er alloy with oxide film is only 0.12 mm/y in 3.5 wt% NaCl solution, even lower than that of high-purity magnesium. The triangular prism-like Mg(OH)2 was observed for the first time in corrosion field of Mg alloys, which was terrific compact and effectively hindered the further corrosion. A mechanism of two-layer barrier coming from the oxide film and triangular prism-like Mg(OH)2 was proposed to contribute the outstanding corrosion resistance.

Pseudo-bottle-brush decorated thin-film composite desalination membranes with ultrahigh mineral scale resistance.

High water recovery is crucial to inland desalination but is impeded by mineral scaling of the membrane. This work presents a two-step modification approach for grafting high-density zwitterionic pseudo-bottle-brushes to polyamide reverse osmosis membranes to prevent scaling during high-recovery desalination of brackish water. Increasing brush density, induced by increasing reaction time, correlated with reduced scaling. High-density grafting eliminated gypsum scaling and almost completely prevented silica scaling during desalination of synthetic brackish water at a recovery ratio of 80%. Moreover, scaling was effectively mitigated during long-term desalination of real brackish water at a recovery ratio of 90% without pretreatment or antiscalants. Molecular dynamics simulations reveal the critical dependence of the membrane's silica antiscaling ability on the degree to which the coating screens the membrane surface from readily forming silica aggregates. This finding highlights the importance of maximizing grafting density for optimal performance and advanced antiscaling properties to allow high-recovery desalination of complex salt solutions.

Development of Ag@Si composite sinter joining with ultra-high resistance to thermal shock test for SiC power device: Experiment validation and numerical simulation

Owing to its cost-effectiveness and low coefficient of thermal expansion (CTE), micron Si is incorporated into sintered Ag matrix to develop an Ag@Si composite sintering strategy. The Si integration helps reduce cost and alleviate CTE-mismatch of Ag-sintered die attachments. An innovative Ag@Si composite sintering structure is achieved by low-temperature and pressure-less sintering process, where a possibly slight diffusion of native SiO2 on the Si surface toward Ag is indicated by TEM observation, enabling the integration of Ag and Si into one continuous network. Owing to the robust well-bonded composite sintering, the Ag@Si joining strategy provides mechanical/microstructural reliability far beyond the pure Ag sinter joining, demonstrating significant prospects in high-temperature interconnection applications. During the harsh thermal cycling (−50–250 °C), the mitigating effect of the Si addition on CTE mismatch is manifested through the substantial suppression of microstructure deterioration in Ag@Si joint that occurs in pure-Ag-sintered joint, while the shear strength retention rate is doubled. Detailed investigation into the mechanism for elevated performance was conducted by material property and Missies stress analysis. The incorporation of Si helps modify the CTE, elastic properties, and stress distribution of Ag@Si-sintered material, synergistically contributing to the satisfactory joining reliability.

Transparent surface crystallized aluminosilicate glasses with an ultrahigh crack resistance

Overcoming inherent brittleness and poor crack resistance (CR) of inorganic glasses is crucial to widen their applications. By optimizing the thermal treatment scenarios, a transparent surface crystallized aluminosilicate glass with an ultrahigh CR (75.1 N) and high hardness (7.1 GPa) is fabricated. Compared with the as-prepared glass with the stoichiometric β-quartz s.s. composition (Li2O·Al2O3·2.5SiO2), a near 14 times enhancement in CR is exhibited, which could be one of the reported glasses with the highest CR. The evolution of phase compositions and morphologies with modifying thermal treatment protocols was revealed through characterization. And the processing parameter dependence behaviors of mechanical performances for these crystallized glasses is mainly ascribed to the alterations in grain size, preferred orientation, or fraction of β-spodumene s.s. and β-quartz s.s. crystal phases in the surface crystallized layer. These findings provide new insights for developing new transparent materials with ultrahigh crack resistance to fulfill the applications such as electronic screens.

Review on preparation technology of carbide resistant ultra-high temperature ceramic fiber

The rapid development of hyper-sonic vehicles has put forward an urgent demand for ultra-high temperature resistance ceramic fibers ceramic matrix composites. The properties of ultrahigh-temperature ceramic matrix composites made of carbon-based ultra-high temperature resistance ceramic fibers are excellent. Therefore, the preparation processes of several commonly used carbide-resistant ultrahigh-temperature ceramic fibers are described in detail. This review compares the advantages and disadvantages of five common methods (Molten-salt synthesis method, Chemical Vapor Reaction Method, Chemical Vapor Deposited method, Sol-Gel Method &amp; Polymer-Derived method) for preparing ceramic fibers, summarizes the preparation methods that should be used in the face of different preparation requirements, and evaluates the improvement and prospect of each method. Among them, the polymer-derived method, as the most difficult and effective preparation method, has been given great hope by material scientists.

Preparation and ablation behavior analysis of non-equimolar Cf/(Hf1/2Zr1/3Ti1/6)C composites under oxyacetylene flame with different heat fluxes

In this study, the synthesis of Cf/(Hf1/2Zr1/3Ti1/6)C non-equimolar middle-entropy composites was reported through precursor infiltration and pyrolysis processing for the first time. The pyrolysis process of the (Hf1/2Zr1/3Ti1/6)C precursor was examined by XRD, while the resultant ceramic was characterized by SEM, EDS, and TEM. The results showed that precursor-derived (Hf1/2Zr1/3Ti1/6)C powders were characterized by single-phase and uniformly distributed elements from microscale to nanoscale. The Cf/(Hf1/2Zr1/3Ti1/6)C composites exhibited a density of 2.741 g/cm3 and a porosity of 11.49 vol%. The various elements were uniformly distributed throughout the material. It also demonstrated outstanding mechanical properties, with a flexural strength of 219.34 MPa and a modulus of 24.82 GPa. At the heat flux of 3 MW/m2, the oxides after ablation were inadequate to fully envelop the substrate. When the heat flux increased to 4 MW/m2, a dense Hf-Zr-Ti-O multiphase oxide layer was formed on the surface of the sample, providing the internal Cf/(Hf1/2Zr1/3Ti1/6)C composites against further ablation. At the heat flux of 5 MW/m2, (Hf, Zr)TiO4 was severely consumed. Our research expands the application scope of non-equimolar middle-entropy composites in the domain of ultra-high temperature ablation resistance.

Facile preparation of SiC/ZrB2-SiC-Si coatings on Cf/SiC composites for ultrahigh temperature ablation resistance

A slurry method combined with silicon infiltration has good prospects in preparing ZrB2-SiC coatings yet remains a great challenge due to the unevenly distributed ZrB2 and heavily damaged substrate. Here we develop a SiC/ZrB2-SiC-Si bilayer coating on Cf/SiC by the slurry method and low-temperature silicon infiltration. The dense SiC inner layer promotes the interfacial bonding and inhibits the inward infiltration of Si; meanwhile, the liquid-gas co-existing siliconization restrains the ZrB2 aggregation and growth. The resultant coating presents high interfacial bonding of 15.6 MPa, can endure 5 ablation cycles for 600 s at 1900 °C. Especially, the coated Cf/SiC has high strength retention of 97.3 %.

Exceptional ultra-high temperature creep resistance of a [111]- oriented single crystal superalloy

There exists a gap in current academic knowledge regarding whether [111]-oriented single crystal (SX) superalloys maintain performance advantages related to anisotropy at ultra-high temperatures (UHT), defined as 1150 °C and above. To address the UHT anisotropy, a finely-designed [111]-oriented SX superalloy, enriched with 1.5 wt.% Re, has been developed. The present alloy demonstrated an impressive creep life exceeding 200 h under conditions of 1150 °C/137 MPa, setting a record in the existing literature. This remarkable property can be attributed to the effective utilization of conventional strengthening mechanisms, as evidenced by the interaction between phases and dislocations. Additionally, the advantageous anisotropy associated with the [111] orientation offers a solution to the trade-off between UHT creep resistance and material density.

Enhanced Wear and Corrosion Resistance of AZ91 Magnesium Alloy via Adherent Si-DLC Coating with Si-Interlayer: Impact of Biasing Voltage

Magnesium alloys are the lowest-density structural metals with a wide range of applications, such as aircraft skins, engine casings and automobile hubs. However, its low surface hardness and non-corrosion resistance in natural environments limit its wide range of applications. In this work, Si-DLC coatings (Si: 15 at.%) are fabricated on AZ91 alloy using a hollow cathode discharge combined with a DC bias voltage from 0 to −300 V to increase the deposition rate and modulate the structure and properties of the coatings. The Si interlayer with a thickness of around 0.6 µm is deposited first to enhance the adhesion. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy are used to investigate the effect of DC bias on the microstructure evolution of Si-DLC coatings. Meanwhile, corrosion and wear resistance of the coatings at various bias voltages have been investigated using electrochemical workstations and pin-on-desk wear testers. It is shown that the bias-free coating has a loose structure and is less resistant to corrosion and wear. The bias coating has a compact structure, small carbon cluster size, high chloride ion corrosion resistance, and high wear resistance against Al2O3 spheres. The corrosion potential of the coating bias at −300 V is −0.98 V, the corrosion current density is 1.35 × 10−6 A·cm−2, the friction coefficient is 0.08, and the wear rate is 10−8 orders of magnitude. The formation of SiC nanocrystals and high sp3-C, as well as the formation of transfer films on the surface of their counterparts, are the main reasons for the ultra-high wear resistance of the bias coatings. The wear rate, coefficient of friction, and corrosion rate of the coating are 0.0069 times, 0.2 times, and 0.0088 times that of the AZ91 alloy, respectively. However, the bias coating has only short to medium-term protection against the magnesium alloy and no long-term protection due to cracks caused by its high internal stress.

Ultrahigh fatigue resistance achieved in additively manufactured aluminum alloy

Ultrahigh fatigue resistance achieved in additively manufactured aluminum alloy

Fatigue-resistant NiTi micropillars with small hysteresis fabricated by micro severe plastic deformation

Through compressing polycrystalline NiTi micropillars down to a 40% height reduction by nanoindentation equipment and subsequently manufacturing them by focused ion beam, cuboidal NiTi micropillars with a nanocrystal/nanolaminate heterostructure were obtained. Mechanical behavior and fatigue tests show that the heterostructured NiTi micropillars processed by micro severe plastic deformation (MSPD) have a large recoverable strain (4.5%), small hysteresis (4.3 MPa), and ultrahigh fatigue resistance (> 106 cycles) under a maximum applied stress of 2.5 GPa. These properties were attributed to the extreme grain refinement and homogeneous phase transformation occurring in the nanocrystals. The findings suggest that the MSPD holds great potential for fabricating superior materials for applications in small-scale engineering devices.

A skin-effect-inspired 3D solar evaporator for simultaneously achieving highly efficient steam generation and ultra-high salt resistance

A skin-effect-inspired solar evaporator (SEISE) with non-uniform porosity was designed to match thermal localization and water transport localization, thus simultaneously achieving excellent evaporation performance and ultra-high salt resistance.

Achieving ultra-high heat resistance of novel energetic materials through a hydrogen bonding and extended π-conjugation strategy

Two high-performance heat-resistant energetic materials were developed via a synergistic strategy of designing hydrogen bonding networks and expanding the π-conjugation system.

Ultrahigh compressive strength and heat resistance of polystyrene/polyphenylene oxide foams of supercritical carbon dioxide foaming

AbstractPolystyrene (PS) foam materials are lightweight, but suffer from poor compressive strength and heat resistance, among other problems, which limit their application. Herein, a method for preparing PS foam with high compressive strength and high heat resistance using supercritical CO2 is proposed. PS/polyphenylene oxide (PPO) blends were prepared using a corotating intermeshing twin‐screw extruder. The results showed that PPO exhibited excellent molecular‐level compatibility with PS, which substantially improved mechanical properties and heat resistance of PS. Foam samples of PS/PPO blends with the same expansion ratio were prepared via batch foaming experiments, and the compressive strength of different foams was determined at different temperatures. At room temperature, the compressive strength of the PS/PPO‐30% foam increased by 173% compared with pure PS foam. As the testing temperature increased from 30 to 120°C, the compressive strength of pure PS foams decreased rapidly. Nevertheless, PS/PPO foams maintained high compressive strength at high temperatures.

Achieving ultrahigh fatigue resistance of Al15(CoCrNi)85 medium-entropy alloy with deformable multicomponent BCC phases

The bending fatigue performance of the Al15(CoCrNi)85 medium-entropy alloy (MEA) with deformable multicomponent duplex BCC phases was investigated. The significantly enhanced fatigue resistance is attributed to the reduced cyclic strain localization, which originates essentially from the duplex BCC phases and the Al addition in the FCC matrix. Al addition in the FCC matrix might enhance the planar slip, which is beneficial for the reduction of the slip irreversibility of dislocations and the cyclic strain localization. The deformable duplex BCC phases with the semi-coherent interfaces efficiently coordinate the incompatible plastic deformation, which would help release the local stress concentration at the phase boundaries. By comparing to the widely used micro-electro-mechanical system (MEMS) material, the Al15(CoCrNi)85 MEA with superior fatigue performance might be accepted as a promising material for micromechanical parts in MEMS.