Ceramic coatings with aluminum titanuate(Al2TiO5)were prepared on Ti-6Al-4V alloy using pulsed bi-polar Micro-arc Oxidation(MAO).The micromorphology and phase composition of the micro-arc-oxidition ...ceramic coatings on the titanium alloy were characterized by X-ray powder diffraction(XRD),and scanning electron microscopy(SEM)respectively.The results revealed that the distinct discharge channels and pores on the surface of the micro-arc-oxidition coatings appeared,and these channels were connected in the molten state.The elec-trolyte concentration was inversely proportional to the coating hardness;additionally,the coating prepared with sodium aluminate and sodium hypophosphite concentrations of 4 g/L and 0.5 g/L,respectively,was the most refined after high-temperature sintering,and it was demonstrated to better prevent oxidation.Increasing the electrolyte concentration coincided with fluctuating coating thermal shock resistance.The thermal shock resis-tance of the coating respectively prepared with sodium aluminate,and the sodium hypophosphite concentrations of 4 g/L and 0.5 g/L was the highest.Additionally,the high-concentration coatings performed significantly better than the low-concentration coatings.The oxidation resistance of the coating samples was also significantly higher than that of the TC4 titanium alloy substrate.The adhesion strength between the coatings and the substrate with and without the sealing treatment was measured by tensile tests.Then,the high-temperature oxidation perfor-mance of the coating samples with and without the sealing treatment was investigated by conducting a high-temperature oxidation experiment at a calcinating temperature of 500℃.The results indicate that the adhe-sion strength between the coatings and substrate was high for the as-prepared and sealed micro-arc oxidation samples regardless of whether they were calcined.The high-temperature oxidation mass increase curves for the sealed and unsealed coating samples calcined at 500℃for 500 h revealed that the high-temperature-oxidation-induced mass increase of the coating samples sealed with a sodium silicate solution was much lower than that of the titanium alloy substrate.Thus,the sealing treatment significantly improved the high-temperature oxidation resistance of the TC4 titanium alloy.Lastly,the high-temperature oxidation behavior at 500℃was analyzed and discussed.
The anode material plays a crucial role in the reliability and safety of Li-ion batteries. Among various of anode materials, Cr, Ti-based anode materials, including LiCrTiO
4
, Li
5
Cr
9
Ti
4
O
24
, ...and Li
5
Cr
7
Ti
6
O
25
, have caught much attention because of the obvious advantages, such as high potential plateau (about 1.55 V vs. Li/Li
+
) and minimum chance for the formation of solid electrolyte interphase film and dendritic lithium, which remarkably improves the and safety and cycling stability. Nonetheless, the poor ionic conductivity limits the large-scale applications. At present, many effective strategies have been used to enhance the electrochemical property, and several significant progresses have been also made. A comprehensive review of the recent progresses, including crystal structure, lithium storage mechanism, synthesis, modification, and morphology control, were summarized systematically. The critical challenges and future perspectives of Cr, Ti-based anode materials were highlighted.
In this study, we introduce a physical model of a three-dimensional (3D) guided wave sensor called 3D-CMUT, which is based on capacitive micro-machined ultrasonic transducers (CMUTs). This 3D-CMUT ...sensor is designed to effectively and simultaneously obtain 3D vibration information about ultrasonic guided waves in the out-of-plane (z-direction) and in-plane (x and y-directions). The basic unit of the 3D-CMUT is much smaller than the wavelength of the guided waves and consists of two orthogonal comb-like CMUT cells and one piston-type CMUT cell. These cells are used to sense displacement signals in the x, y, and z-directions. To ensure proper functioning of the 3D-CMUT unit, the resonant frequencies of the three composed cells are set to be identical by adjusting the microstructural parameters appropriately. Moreover, the same sensitivity in the x, y, and z-directions is theoretically achieved by tuning the amplification parameters in the external circuit. We establish a transient analysis model of the 3D-CMUT using COMSOL finite element simulation software to confirm its ability to sense multimode ultrasonic guided waves, including A0, S0, and SH0 modes. Additionally, we simulate the ball drop impact acoustic emission signal on a plate to demonstrate that the 3D-CMUT can not only utilize in-plane information for positioning but also out-of-plane information. The proposed 3D-CMUT holds significant potential for applications in the field of structural health monitoring (SHM).
Conventional acoustic systems exhibit a difficulty in sensing weak acoustic fault signals in complex mechanical vibration environments. Therefore, it is necessary to develop an acoustic sensing mode ...and a corresponding functional device with pressure amplification. This paper proposes a three-dimensional device, coupling gradient acoustic metamaterials (GAM) with phononic crystals (GAM–PC). The strong wave compression effect coupled with the phononic crystal equivalent medium mechanism is utilized to achieve the enhancement of weak acoustic signal perception at the target frequency. The superior amplification capability of the GAM–PC structure for the amplitude of loud signals is verified by numerical simulations and experiments. Moreover, the GAM–PC structure has a narrower bandwidth per slit, making it more frequency selective. Furthermore, the structure can separate different frequency components. This work is expected to be applied to signal monitoring in environments with strong noise.
Acoustic sensing systems play a critical role in identifying and determining weak sound sources in various fields. In many fault warning and environmental monitoring processes, sound-based sensing ...techniques are highly valued for their information-rich and non-contact advantages. However, noise signals from the environment reduce the signal-to-noise ratio (SNR) of conventional acoustic sensing systems. Therefore, we proposed novel nonlinear gradient-coiling metamaterials (NGCMs) to sense weak effective signals from complex environments using the strong wave compression effect coupled with the equivalent medium mechanism. Theoretical derivations and finite element simulations of NGCMs were executed to verify the properties of the designed metamaterials. Compared with nonlinear gradient acoustic metamaterials (Nonlinear-GAMs) without coiling structures, NGCMs exhibit far superior performance in terms of acoustic enhancement, and the structures capture lower frequencies and possess a wider angle acoustic response. Additionally, experiments were constructed and conducted using set Gaussian pulse and harmonic acoustic signals as emission sources to simulate real application scenarios. It is unanimously shown that NGCMs have unique advantages and broad application prospects in the application of weak acoustic signal sensing, enhancement and localization.
In the field of industrial structure detection, acoustic signals have been pivotal. A cost-effective and highly sensitive acoustic monitoring system that can enhance weak acoustic signals has always ...been an interesting topic in many research fields. However, environmental noise signals have consistently hindered the improvement of the signal-to-noise ratio (SNR) of traditional acoustic systems. In this work, we propose a structure (PC-Mie) that couples phononic crystal (PC) point defects and Mie resonance structures (Mies) to enhance weak effective signals from complex environments. Numerical simulations have confirmed that the PC-Mie exhibits superior sound pressure enhancement performance compared to each individual PC point defect and Mies. Moreover, the capability to amplify the sound pressure amplitude is related to the angle and position of the Mies at the center position. Simultaneously, the PC-Mie has a narrower bandwidth, giving the structure stronger frequency selectivity. Finally, the experiment proves that PC-Mie can function as an enhanced acoustic device or sensor to detect harmonic signals, verifying the validity of the PC-Mie structure for acoustically enhanced perception. Both numerical and experimental studies demonstrate that the PC-Mie can effectively enhance the energy of specific sound frequencies in complex air environments, making it suitable for collecting high-sensitivity acoustic signals. This research has significant implications for the development of weak acoustic signal detection technology and the application of self-powered sensors.
In the photoacoustic detection of breast cancer, the weak intensity and severe energy attenuation of photoacoustic signals excited by the breast tissue become an important factor limiting the ...efficient acquisition of the ultrasound transducer. To overcome this problem, we proposed a linear defect channel and bifurcated acoustic transmission channel models at the front of the ultrasonic transducers based on the phononic crystal bandgap characteristics and defect state structure. The results of numerical analyses and simulations carried out using COMSOL demonstrated that the photoacoustic signal transmission channel proposed could confine the acoustic energy within the defects, while achieving the directional transmission and local enhancement of the acoustic field of high-frequency breast photoacoustic signals. This design effectively reduces the signal transmission loss and amplifies the mammographic signal intensity, which is conducive to efficient acquisition. In addition, the directional transmission effect is found to be strongly dependent on frequency, which makes the channel have great frequency selectivity. Through the flexible modulation of the transmission path of the artificial acoustic structure, breast photoacoustic signals of specific frequencies can be exported in separate paths to reduce the interference of noise signals. This study combines biomedical tumor detection with phononic crystals to present a novel method for efficient acquisition and deep detection of acoustic signals in tissue photoacoustic detection from the signal perspective, which is conducive to improving the sensitivity of breast cancer detection.
Water environmental pollutants have become one of the most serious environmental issues, and the removal of various environmental pollution (dyes, phenols, pesticides, heavy metal ions, etc.) is of ...particular concern because of their toxicity and refractory. Compared to conventional eliminating routes, photoelectrocatalysis (PEC), is considered as a promising strategy since it combines the advantages of photocatalysis (PC) and electrocatalysis (EC). However, it still encounters bottlenecks of scarce reaction sites and low product selectivity, restricting its development toward practical applications. In recent years, various of g–C3N4–based composites were used for the remediation of these typical environmental pollutants. Given this situation, this review summarizes the latest progress in the design and preparation of novel g–C3N4–based composites and their PEC degradation different pollution in the water environment. Some removal mechanisms are briefly discussed, and the prospects are presented for further research.
Display omitted
•Water and wastewater can be effectively treated through g-C3N4 based composites.•Photoelectrocatalysis ability of g-C3N4 based composites result in desirable removal performance.•Various environmental pollution are summarized and discussed.•Prospects of g-C3N4 based composites are presented.
In this work, a phononic crystal gradient metamaterial structure (PCGMs) is proposed based on the strong wave compression effect coupled with equivalent medium theory to achieve enhancement and ...directional sensing of weak target acoustic signals. Compared with the conventional gradient structure, PCGMs exhibit superior acoustic enhancement performance and wider range of acoustic response capability. Numerical analysis and experimental validation consistently demonstrate that PCGMs can effectively enhance the target frequency signals in harmonic signals. This study breaks through the detection limit of acoustic sensing systems and provides a great method for engineering applications of weak acoustic signal perception.
It is necessary to construct hierarchically porous photocatalysts to ensure high light absorption and electrochemical kinetics in photocatalysis. Carbon nitride (g-C
3
N
4
) appears to be a favorable ...choice, especially the tunable hollow micro/nanostructure. However, the facile preparation of g-C
3
N
4
with hierarchical pores still faces challenge. Here, we firstly report a facile preparation of hierarchically porous g-C
3
N
4
with uniform organic microstructure as a soft template. The template is
in situ
formed in thiourea precursor solution, and its similar
π
-conjugated structure to g-C
3
N
4
makes it effective in modifying the condensation of g-C
3
N
4
. The layer thickness of the as-prepared g-C
3
N
4
is about 3–4 nm. And the resultant g-C
3
N
4
possesses hierarchical meso/macropores with a specific surface area of 27.34 m
2
g
−1
and pore volume of 0.18 cm
3
g
−1
, approximately 6.2 and 9.0 times, respectively, higher than that of the unmodified one. This favors the charge/mass transport process, hence rendering the catalyst a 2.4-fold enhancement in photodegrading organic pollutant with H
+
and ·O
2
−
as the predominant species. At the same time, the photostability can be guaranteed with only 20% loss of its efficiency after long-term use.
