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Ice accumulation poses considerable challenges in transportation, notably in the domain of general aviation. The present study combines the strengths and limitations of conventional aircraft deicing techniques with the emerging trend toward all-electric aircraft. This study aims to utilize laser-induced graphene (LIG) technology to create a multifunctional surface, seamlessly integrating hydrophobic properties with efficient electrical heating to mitigate surface icing effectively. We investigated the utilization of a 10.6 μm CO2 laser for direct writing on polyimide (PI), a widely used insulating encapsulation material. From the thermomechanical perspective, our initial analysis using COMSOL Multiphysics software (V5.6) revealed that when the laser power P exceeds 5 W, the PI substrate experiences ablative damage. The experimental results show that when P ≤ 5 W, an increase in power has a positive impact on the quality, surface porosity, roughness reduction, line-spacing reduction, and water contact-angle enhancement of the graphene. Conversely, when P > 5 W, higher power negatively affects both the substrate and the graphene structure by inducing excessive ablation. However, it influences the graphene line height positively and is consistent with overall experimental–simulation congruence. Furthermore, the incorporation of high-quality graphene resulted in a surface that exhibited higher contact angles (CA > 120°), lower energy consumption, and higher heating efficiency compared to the use of traditional electrically heated materials for anti-icing applications. The potential applications of this one-step fabrication method extend across various industries, particularly aviation, marine engineering, and other ice-prone domains. Moreover, the method has extensive prospects for addressing pivotal challenges associated with ice formation and serves as an innovative and efficient anti-icing technology. [ABSTRACT FROM AUTHOR]

Flexible wearable sensors with high sensitivity, broad sensing range, and low detection accuracy have great potential applications in human motion online monitoring, human healthcare detection, and human–machine interface. However, high sensitivity and broad sensing range conflict, as the former requires conspicuous structural changes under microstrain while the latter requires complete morphology under large deformation. Herein, we report few-layer 2D Ti3C2Fx and 1D polypyrrole (PPy) nanowires with a sandwich stack structure transfer on polyacrylic acid (PAA) tape based on layer-by-layer (LBL) assemble technology. The 1D PPy nanowires enhance the strain sensor's interfacial adhesion and electron transmission channel, resulting in high sensitivity and a permissible detection range (0–50%). Under various applied force stimuli, the synergetic effect of Ti3C2Fx nanosheets (4.72 nm thickness) and PPy nanowires (diameter 20–50 nm) endows the stack structure with good electrical–mechanical performance, which is reflected by the sensor's high sensitivity (GF = 2950, ε = 50%; GF = 475, ε = 10%; GF = 22, ε = 0.1%). Such a flexible sensor with a permissible detection range (up to 50%), a low detection limit (0.1%), and reliable repeatability (>1500 cycles) has potential applications for human motion detection, clinical diagnosis, and healthcare monitoring. [ABSTRACT FROM AUTHOR]

Photoreduction of CO2 into CO, CH4 or hydrocarbons is attractive, due to environmental compatibility and economic feasibility. Optimizing the reaction engineering of CO2 reduction is an effective and general strategy that should be given special consideration. In this article, the photocatalytic CO2 reduction performances are originally investigated in a low vacuum in both dilute (10%) and pure CO2. We discover that the CH4 yield increased above one hundred times as the vacuum degree increased from barometric pressure to −80 kPa in dilute CO2. It also reveals long-term stability and good cycling performance in a low vacuum. The enhanced CO2 photoreduction performance in a low vacuum comes from better accumulation of photogenerated electrons, less intense Brownian movement of gas molecules in the environment and hindrance of the active site-blocking of gas molecules in the environment. Improved photocatalytic CO2 reduction in a low vacuum is further verified by Pt–TiO2 catalysts. This research presents a general route for producing clean fuels by photocatalytic CO2 reduction in a more effective way. [ABSTRACT FROM AUTHOR]

The hypersonic inward turning inlet has characteristics of high mass capture capability and compression capability, meanwhile it has direct influences on the design of the flight vehicle control ability and stability, therefore the design of forebody/inlet integration is of critical importance. In the paper, axi-symmetrical basic flow fields with controlled pressure distribution used for the designing of hypersonic inward turning inlet was established using the rotational method of characteristics. In combination of the streamline tracing technique, five forebodies/inward turning inlets were designed. The influences of different radial and circumferential positions on the inlet and forebody performances in longitudinal and course were studied numerically. The results show that the forebodies/inlets generate large aerodynamic forces and moments which influence both the flight vehicle control ability and stability. With the capture line being off from the center body, the performances of the flight vehicle static instability both longitudinal and lateral are improved; when the capture line changes in the circumferential direction, the degree of longitudinal static stability remains nearly unchanged; when the capture line is symmetrical about the longitudinal plane, mass flow ratio increases significantly compared to those with asymmetrical capture lines, but the penalty is the deterioration of the performance of course static stability. These conclusions presented in this paper have valuable contributions to the design of flight vehicles with high performance of handling and stability. [ABSTRACT FROM AUTHOR]

Air-breathing hypersonic flight vehicles are highly airframe/propulsion integrated, especially the outer and inner flows of the flight vehicles are very complicated and interact strongly with each other, considerable difficulties should be solved rationally in ground testing. Therefore, it is of great necessity to conduct researches on the related experimental methodology. This paper presents a brief analysis of main aerodynamic issues concerned with air-breathing hypersonic flight vehicles as well as associated experimental testing requirements, in which three typical types of experimental testing are focused on, they are performance testing of airframe/propulsion integrated vehicles, experiment of boundary layer transition with trips, and arc-heated facility testing of sharp leading edges. Besides, an overview of wind tunnel research methodologies both in China and abroad is included. This paper also provides critical similarity parameters that need to be ensured for the three types of experiments mentioned above, followed by an influence analysis of those key parameters that are difficult to achieve in ground testing. Based on the testing capability of the current test facilities, three typical wind tunnel experimental methods have been put forward, along with an effective method of acquiring accurate aerodynamic performance of the airframe/propulsion integrated vehicles in particular. The research materials presented should provide a useful guideline on the aerothermal and aerodynamic experimental research on hypersonic flight vehicles. [ABSTRACT FROM AUTHOR]

The pneumatic control wing rudder surface of a high-speed aircraft has a gap between the projectile and the wing rudder surface for flexibility. The existence of the gap leads to the entry of high-speed hot airflow as well as the strong separation and reattachment area at the root of the rudder shaft with high heat, high pressure, and high shear thermal environment. These severe environments require high thermal protection of the aircraft. Since the factors affecting the flow of the rudder gap are very complicated, accurate prediction of the thermal environment inside the gap is very difficult. At present, the traditional shock wave test of the wind tunnel is limited by the 2 mm diameter of the thin film heat flow sensor. Only limited measurement points can be arranged in the separation and reattachment area, and the peak of the heat flow cannot be captured, resulting in large differences between the calculation and the test. According to the characteristics of the thermal environment of the gap separation and reattachment area, this paper analyzes the feasibility of fine measurement regarding sensor selection, measurement point layout scheme, measurement, and data post-processing. Moreover, a distributed thermocouple fine measurement method is proposed to realize the use of spot heat measurement for the effect of surface heat. Aiming at the simplified model of the cylindrical body and the rudder surface, the fine thermal test of the rudder gap is completed, and the peak heat flow in the rudder interference zone is obtained. The effects of different gap heights, rudder angles, and angles of attack on the thermal environment of the rudder interference zone are studied experimentally. The experimental results show that the rudder gap interference on the missile body is mainly concentrated in the rudder axle interference zone. The thermal environment of the rudder axis interference zone increases with increasing gap height, rudder angle, and angle of attack. The comparison between the test results and the CFD calculation results shows that they are basically consistent, and the peak heat flow difference is within 10%. [ABSTRACT FROM AUTHOR]

Low-range light absorption and rapid recombination of photo-generated charge carriers have prevented the occurrence of effective and applicable photocatalysis for decades. Quantum dots (QDs) offer a solution due to their size-controlled photon properties and charge separation capabilities. Herein, well-dispersed interstitial nitrogen-doped TiO 2 QDs with stable oxygen vacancies (N-TiO 2-x -V O ) are fabricated by using a low-temperature, annealing-assisted hydrothermal method. Remarkably, electrostatic repulsion prevented aggregation arising from negative charges accumulated in situ on the surface of N-TiO 2-x -V O , enabling complete solar spectrum utilization (200-800 nm) with a 2.5 eV bandgap. Enhanced UV-vis photocatalytic H 2 evolution rate (HER) reached 2757 µmol g -1 h -1 , 41.6 times higher than commercial TiO 2 (66 µmol g -1 h -1 ). Strikingly, under visible light, HER rate was 189 µmol g -1 h -1 . Experimental and simulated studies of mechanisms reveal that V O can serve as an electron reservoir of photo-generated charge carriers on N-doped active sites, and consequently, enhance the separation rate of exciton pairs. Moreover, the negative free energy (-0.35 V) indicates more favorable thermodynamics for HER as compared with bulk TiO 2 (0.66 V). This research work paves a new way of developing efficient photocatalytic strategies of HER that are applicable in the sustainable carbon-zero energy supply., (© 2024 Wiley‐VCH GmbH.)

Photoreduction of CO 2 into CO, CH 4 or hydrocarbons is attractive, due to environmental compatibility and economic feasibility. Optimizing the reaction engineering of CO 2 reduction is an effective and general strategy that should be given special consideration. In this article, the photocatalytic CO 2 reduction performances are originally investigated in a low vacuum in both dilute (10%) and pure CO 2 . We discover that the CH 4 yield increased above one hundred times as the vacuum degree increased from barometric pressure to -80 kPa in dilute CO 2 . It also reveals long-term stability and good cycling performance in a low vacuum. The enhanced CO 2 photoreduction performance in a low vacuum comes from better accumulation of photogenerated electrons, less intense Brownian movement of gas molecules in the environment and hindrance of the active site-blocking of gas molecules in the environment. Improved photocatalytic CO 2 reduction in a low vacuum is further verified by Pt-TiO 2 catalysts. This research presents a general route for producing clean fuels by photocatalytic CO 2 reduction in a more effective way.