Carbon nanotubes (CNTs) have garnered significant attention in the fields of science, engineering, and medicine due to their numerous advantages. The initial step towards harnessing the potential of ...CNTs involves their macroscopic assembly. The present study employed a gentle and direct self-assembly technique, wherein controlled growth of CNT sheaths occurred on the metal wire’s surface, followed by etching of the remaining metal to obtain the hollow tubes composed of CNTs. By controlling the growth time and temperature, it is possible to alter the thickness of the CNTs sheath. After immersing in a solution containing 1 g/L of CNTs at 60 °C for 24 h, the resulting CNTs layer achieved a thickness of up to 60 µm. These hollow CNTs tubes with varying inner diameters were prepared through surface reinforcement using polymers and sacrificing metal wires, thereby exhibiting exceptional attributes such as robustness, flexibility, air tightness, and high adsorption capacity that effectively capture CO
2
from the gas mixture.
Water-coupled charge blasting is a promising technique to efficiently break rock masses. In this study, numerical models of double boreholes with water-coupled charge are established using LS-DYNA ...and are calibrated by the tests of rock masses subjected to explosion loads to examine its performance. The crack levels of rock mass induced by water-coupled charge blasting and air-coupled charge blasting are first compared. It is found that water-coupled charge blasting is more appropriate to fracture deep rock mass than air-coupled charge blasting. In addition, the effects of rock properties, water-coupled charge coefficients, and borehole connection angles on the performance of water-coupled charge blasting are investigated. The results show that rock properties and water-coupled charge coefficients can greatly influence the crack and fragmentation levels of rock mass induced by water-coupled charge blasting under uniform and non-uniform in-situ stresses. However, changing borehole-connection angles can only affect crack and fragmentation levels of rock mass under non-uniform in-situ stresses but barely affect those under uniform in-situ stresses. A formula is finally proposed by considering the above-mentioned factors to provide the design suggestion of water-coupled charge blasting to fracture rock mass with different in-situ stresses.
The problems associated with vibrations of viaducts and low-frequency structural noise radiation caused by train excitation continue to increase in importance. A new floating-slab track vibration ...isolator-non-obstructive particle damping-phononic crystal vibration isolator is proposed herein, which uses the particle damping vibration absorption technology and bandgap vibration control theory. The vibration reduction performance of the NOPD-PCVI was analyzed from the perspective of vibration control. The paper explores the structure-borne noise reduction performance of the NOPD-PCVIs installed on different bridge structures under varying service conditions encountered in practical engineering applications. The load transferred to the bridge is obtained from a coupled train-FST-bridge analytical model considering the different structural parameters of bridges. The vibration responses are obtained using the finite element method, while the structural noise radiation is simulated using the frequency-domain boundary element method. Using the particle swarm optimization algorithm, the parameters of the NOPD-PCVI are optimized so that its frequency bandgap matches the dominant bridge structural noise frequency range. The noise reduction performance of the NOPD-PCVIs is compared to the steel-spring isolation under different service conditions.
A comprehensive understanding of the dynamic frictional characteristics in rock joints under high normal load and strong confinement is essential for ensuring the safety of deep engineering ...construction and mitigating geological disasters. This study conducted shear experiments on rough rock joints under displacement-controlled dynamic normal loads, investigating the shear behaviors of joints across varying initial normal loads, normal loading frequencies, and normal loading amplitudes. Experimental results showed that the peak/valley shear force values increased with initial normal loads and normal loading frequencies but showed an initial increase followed by a decrease with normal loading amplitudes. Dynamic normal loading can either increase or decrease shear strength, while this study demonstrates that higher frequencies lead to enhanced friction. Increased initial normal loading and normal loading frequency result in a gradual decrease in joint roughness coefficient (JRC) values of joint surfaces after shearing. Positive correlations existed between frictional energy dissipation and peak shear forces, while post-shear joint surface roughness exhibited a negative correlation with peak shear forces through linear regression analysis. This study contributes to a better understanding of the sliding responses and shear mechanical characteristics of rock joints under dynamic disturbances.
The impact of cooling rate after solution heat treatment on exfoliation corrosion resistance of a Li-containing 7xxx aluminum alloy was investigated by accelerated immersion and electrochemical ...impedance spectroscopy test, optical microscope, electron backscatter diffraction and scanning transmission electron microscope. With the decrease of cooling rate from 1700 °C/s to 4 °C/s, exfoliation corrosion resistance of the aged specimens decreases with rating changing from EA to EC and the maximum corrosion depth increasing from about 169.4 µm to 632.1 µm. Exfoliation corrosion tends to develop along grain boundaries in the specimens with cooling rates higher than about 31 °C/s and along both grain boundaries and sub-grain boundaries in the specimens with lower cooling rates. The reason has been discussed based on the changes of the microstructure and microchemistry at grain boundaries and sub-grain boundaries due to slow cooling.
Wire-arc additive manufacture (WAAM) has great potential for manufacturing of Al-Cu components. However, inferior mechanical properties of WAAM deposited material restrict its industrial application. ...Inter-layer cold rolling and thermo-mechanical heat treatment (T8) with pre-stretching deformation between solution and aging treatment were adopted in this study. Their effects on hardness, mechanical properties and microstructure were analyzed and compared to the conventional heat treatment (T6). The results show that cold rolling increases the hardness and strengths, which further increase with T8 treatment. The ultimate tensile strength (UTS) of 513 MPa and yield stress (YS) of 413 MPa can be obtained in the inter-layer cold-rolled sample with T8 treatment, which is much higher than that in the as-deposited samples. The cold-rolled samples show higher elongation than that of as-deposited ones due to significant elimination of porosity in cold rolling; while both the T6 and T8 treatments decrease the elongation. The cold rolling and pre-stretching deformation both contribute to the formation of dense and dispersive precipitated
θ
′ phases, which inhibits the dislocation movement and enhances the strengths; as a result, T8 treatment shows better strengthening effect than the T6 treatment. The strengthening mechanism was analyzed and it was mainly related to work hardening and precipitation strengthening.
Non-pillar mining technology with automatically formed roadway is a new mining method without coal pillar reservation and roadway excavation. The stability control of automatically formed roadway is ...the key to the successful application of the new method. In order to realize the stability control of the roadway surrounding rock, the mechanical model of the roof and rib support structure is established, and the influence mechanism of the automatically formed roadway parameters on the compound force is revealed. On this basis, the roof and rib support structure technology of confined lightweight concrete is proposed, and its mechanical tests under different eccentricity are carried out. The results show that the bearing capacity of confined lightweight concrete specimens is basically the same as that of ordinary confined concrete specimens. The bearing capacity of confined lightweight concrete specimens under different eccentricities is 1.95 times higher than those of U-shaped steel specimens. By comparing the test results with the theoretical calculated results of the confined concrete, the calculation method of the bearing capacity for the confined lightweight concrete structure is selected. The design method of confined lightweight concrete support structure is established, and is successfully applied in the extra-large mine, Ningtiaota Coal Mine, China.
The study investigated the application of radiofrequency (RF)-sputtered TiO
2
coatings at various temperatures to enhance the hydrophobicity and corrosion resistance of Al6061 alloy. The research ...aimed to establish a correlation between the coating process and the resulting surface properties. Surface roughness and wettability were quantified with a surface profilometer and goniometer. Additionally, chemical boiling and salt spray corrosion tests were conducted to evaluate any topographical changes during these procedures. The analysis further involved the use of field-emission scanning electron microscopy (FESEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD) techniques to characterize the deposited coatings. The findings indicated that the TiO
2
coating applied at 500 °C exhibited the highest water contact angle and superior corrosion resistance compared to other temperatures. Surface characterization confirmed that this specific TiO
2
coating at 500 °C effectively delays corrosion due to its hydrophobic behavior, making it durable for industrial applications.
In practical applications, noble metal doping is often used to prepare high performance gas sensors, but more noble metal doping will lead to higher preparation costs. In this study, CeO
2
/ZnO-Pd ...with low palladium content was prepared by ultrasonic method with fast response and high selectivity for acetone sensing. With the same amount of palladium added, the selectivity coefficient of CeO
2
/ZnO-Pd is 1.88 times higher than that of the stirred sensor. Compared with the pure PdO-doped CeO
2
/ZnO-PdO material, the content of Pd in CeO
2
/ZnO-PdO is about 30% of that in CeO
2
/ZnO-PdO, but the selectivity coefficient for acetone is 2.56 times higher. The CeO
2
/ZnO-Pd sensor has a higher response (22.54) to 50×10
−6
acetone at 300 °C and the selectivity coefficient is 2.57 times that of the CeO
2
/ZnO sensor. The sensor has a sub-second response time (0.6 s) and still has a 2.36 response to 330×10
−9
of acetone. Ultrasonic doping makes Pd particles smaller and increases the contact area with gas. Meanwhile, the composition of n-p-n heterojunction and the synergistic effect of Pd/PdO improve the sensor performance. It shows that ultrasonic Pd doping provides a way to improve the utilization rate of doped metals and prepare highly selective gas sensors.
The macroscopic mechanical properties of rocks are significantly influenced by their microstructure. As a material bonded by mineral grains, the grain morphology of crystalline rock is the primary ...factor influencing the strength. However, most strength criteria neglect the strength variations caused by different grain characteristics in rocks. Furthermore, the traditional linear criteria tend to overestimate tensile strength and exhibit apex singularity. To address these shortcomings, a piecewise strength criterion that considers the grain size effect has been proposed. A part of an ellipse was employed to construct the envelope of the tensive-shear region on the meridian plane, to accurately reproduce the low tensile-compressive strength ratio. Based on the analysis of experimental data, both linear and exponential modification functions that account for grain size effects were integrated into the proposed criterion. The corresponding finite element algorithm has been implemented. The accuracy and applicability of the proposed criterion were validated by comparing with the experimental data.
