Abstract To design a lightweight and high-performance absorber, this work introduced a novel three-dimensional interconnected SiC foam with double-layer hollow skeleton (3D-ISF), which was prepared by depositing SiC, pyrolytic carbon, and SiC layer on interconnected carbon foam, followed by oxidation of carbon. SEM results showed the interconnected hollow structure had been successfully synthesized, which was beneficial for microwave absorbing efficiency, and numerous columnar SiC defects were observed and played a critical role in the microwave absorption properties. The electromagnetic performances of 3D-ISF-I and 3D-ISF-II were investigated in depth. With the increase of thickness of SiC layer, 3D-ISF-II exhibited a better microwave absorption property, which could be ascribed to the higher impedance matching ratio ( Z r ) and attenuation constant ( α ). The optimum reflection loss value of 3D-ISF-II could reach −45.649 dB while that of 3D-ISF-I was just −32.070 dB. There is no doubt that the prepared materials have tunable microwave absorbing properties, which can promote the development of SiC-based absorbing materials to a certain extent. Finally, it was confirmed that the Z r played a dominant role in 3D-ISF, which provided practical guidance for the design of porous materials.
In this study, a novel superhydrophobic coating consisting of SiC nanowires was created for the first time via atmospheric pressure chemical vapor deposition (APCVD) method. Results of the research indicated that the novel superhydrophobic coating was composed of countless β-SiC nanowires coated with methyl groups (-CH3) and it was proved that the SiC nanowires coating possessed superhydrophobic properties. In addition, the growth process of the nanowires coating was investigated on the basis of Vapor-Liquid-Solid mechanism, and a potential hydrophobic mechanism was proposed. The methyl groups on the surface of SiC nanowires reduced the overall surface free energy of the SiC nanowires coating which led to a increase in the contact angle of the SiC nanowires coating.
Chemical Vapor Deposition (CVD) is a suitable way to prepare silicon carbide (SiC) nanowires. The deposition temperature, gas velocity, and distribution of mixed gas components in the CVD tube are the primary factors affecting the final deposition rate. The influence of process parameters, consisting of deposition temperature, the flux of MTS, the flux of mixed gases and the ratio of Ar and H2, on deposition rate of SiC nanowires were calculated numerically. The process parameters achieved optimization by an orthogonal L9(3)4 test to get high deposition rate SiC nanowires. The optimal deposition rate for SiC nanowires is obtained under the following operating conditions: deposition temperature of 1473 K, flux of MTS of 5 mL/min, flux of mixed gases of 525 mL/min, and Ar : H2=1 : 1. Two calculation results were verified by the corresponding experimental results, which revealed the accurateness of the simulation results remarkably.
High-performance microwave absorption and being lightweight have become the foremost crucial factors in the practical application of mordern microwave adsorbers. In view of this, we presented the double-layer hollow reticulated SiC foam (DHRSF), which was planned to be used as a high-performance and lightweight microwave absorber. Reticulated carbon foam (RCF) obtained from the carbonization of melamine foam acted as the original reticulated template, where SiC, pyrolytic carbon (PyC), and SiC were sequentially deposited by chemical vapor deposition (CVD), chemical vapor infiltration (CVI), and CVD, respectively. DHRSF was then obtained by removing the carbon component during oxidation. The morphological results indicated that the special hollow and reticulated structures were fabricated successfully, which was considered to be the crucial factor for the microwave absorption. Numerous loose columnar SiC defects on the skeleton surfaces introduced a large number of trapping centers and interfaces to further improve the microwave absorption performances. The minimum reflection loss (RL) value of DHRSF could reach −41.39 dB at 7.2 GHz when the absorber thickness is 12 mm. It was also proven that all the minimum RL values are blow −20 dB at the thicknesses of 5–15 mm. Furthermore, the microwave absorption mechanism based on the special structures was discussed in detail, which provides a practical reference for the structure optimization of advanced microwave absorbers.
In order to investigate the gelled performance of low concentration Cr3+ crosslinking polymer,three gelled experiment simulating fields were designed in different dynamic conditions according to stir,circular flow and series flow in stainless steel screen meshes.The experimental results show that the low concentration Cr3+ crosslinking polymer has flowability as it is gelled in flow condition and through porous medium.
Prior research has explored the effects of engaging with real or virtual natural landscapes and listening to music during aerobic exercise on short-term affect, however, the specific differences in the improvement of short-term affect by different combinations of Virtual Reality (VR) and music rhythm require further investigation. The objective of this study is to investigate the effects of various combinations of VR and music on short-term mood, thereby providing a reference for future research on public fitness. This study recruited 132 valid participants (mean age 24.0 ± 0.9 years), with a gender distribution of 68 males and 64 females. Participants were randomly assigned to one of four groups: Visual-Music (V-M), Music-Visual (M-V), Visual-only (V), and Music-only (M). The exercise mode was 15 min of aerobic power cycling with 2 min of low-intensity power cycling intervals in the middle. After the exercise, the participants were asked to sit and then performed either a VR intervention or a music intervention for 15 min. The collected indicators included blood pressure, positive/negative affect, and heart rate variability indicators (RMSSD, SDNN, LF/HF). Data analysis included descriptive statistics, repeated measures ANOVA, and multifactor ANOVA. The effect of different VR and Music combined with exercise interventions on the improvement of short-term affect was analyzed based on the effect size (ɳp2) and combined with the significance p-value. Intra-group results showed that DBP, positive and negative affect, SDNN, RMSSD indicators in V-M group were significant differences (p < 0.05), while SBP, positive affect, negative affect, SDNN, RMSSD, LF/HF indicators in M-V group were significant differences (p < 0.05). Only SDNN and RMSSD indicators in M group had significant differences (p < 0.05), and only SBP and RMSSD indicators in V group had significant differences (p < 0.05). The results between groups showed that only SDNN and LH/HF groups had a significant difference (p < 0.05), other indicators had a trend of improvement or positive promotion to a certain extent, but the statistical difference was not significant (p > 0.05). Aerobic exercise with consistent intensity and the combined visual-auditory interventions (M-V and V-M) significantly improved blood pressure, and the short-term affect of physiological responses (LF/HF, SDNN, RMSSD), along with subjective affect measures, compared to other groups. These findings suggest that incorporating VR and music with exercise can effectively enhance short-term affect, recommending an integrated approach to aerobic exercise and relaxation through music and visual exposure to natural environments.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)