The deep underground environment has complex geological conditions, which result in cement-based materials under the coupling conditions of high crustal stress, high pressure, and high temperature ...for the long-term. Thus, the mechanism of water transport is more complicated and often accelerates the deterioration of cement-based materials. In this study, the rules of water transport in mortar with an ultra-low w/b ratio under the coupling conditions of osmotic pressure, confining pressure, and temperature were systemically investigated based on a novel experimental device and low-field NMR technology. Experimental results showed that the saturation of the pore structure and penetration depth of mortar increased rapidly in the early stage (the first 10 min), and the water was mainly filled in nano-scale pores. Low-field NMR imaging technology could be applied to the visualization study of water transport in WPC mortar. With the increase of osmotic pressure and ambient temperature, the penetration rate of water in mortar was significantly increased, and the water was preferentially filled in nano-scale pores with pore sizes less than approximately 200 nm. The increase of confining pressure could improve the permeability of mortar to a certain extent due to the decrease in the penetration rate of water. For water transport in mortar with an ultra-low w/b ratio, the descending order of influence degree of different factors was osmotic pressure, confining pressure, and temperature.
AbstractThe aim of this research is to investigate the sorptivity and capillary coefficient in unsaturated concrete using the capillary water absorption experiment. The effects of water-binder ratio, ...fly ash content, and aggregate content on the water absorption performance in concrete are compared. The decrease of water-binder ratio, aggregate content, and the increase of the initial degree of water saturation can lead to a decrease in the water absorption ability. With the increase of fly ash content, the water absorption ability first decreases and then increases; the 40% fly ash content had the worst water absorption ability. To forecast the water transport process, an unsaturated flow theory was used to predict the water content distribution in concrete during transport, this theory can well reveal the water distribution in concrete during water transport and the law of water content distribution is consistent with that of the water absorption experimental.
•High-entropy rare-earth tantalate ferroelastic ceramics with ten different kinds of rare earths at the RE site are synthesized for the first time.•Compared with single rare-earth tantalates, the ...thermal conductivity of (10RE0.1)TaO4 is reduced by 16%–45% at 100 °C and 22%–45% at 800 °C. The thermal conductivity (1.0–2.2 W m−1 K−1, 100–1200 °C) of (10RE0.1)TaO4 is also lower than that of the currently reported high-entropy four-, five- and six-component rare-earth tantalates. This indicates that the high-entropy effect using ten rare earth elements has a significant improvement on the thermal properties of single rare-earth tantalates.•Lattice distortion and the formation mechanism of oxygen vacancies in rare-earth tantalates are reported for the first time. The phonon mean free path will be decreased by ferroelastic domains, lattice distortion associated with size and mass disorder, and point defect scattering, which target low-, mid- and high-frequency phonons, respectively, resulting in reduced thermal conductivity in the entire temperature range from 100 to 1200 °C.•(10RE0.1)TaO4, as an improved candidate for thermal barrier coatings materials, has a higher thermal expansion coefficient (10.5 × 10−6 K−1 at 1400 °C), lower Young's modulus (123 GPa) and enhanced high-temperature phase stability than that of single rare earth tantalates.
The primary purpose of this work is to optimize the thermophysical properties of rare-earth tantalate ceramics using the high-entropy effect. Here, the high-entropy rare-earth tantalate ceramic (Y0.1Nd0.1Sm0.1Gd0.1Dy0.1Ho0.1Er0.1Tm0.1Yb0.1Lu0.1)TaO4 ((10RE0.1)TaO4) is synthesized successfully. The lattice distortion and oxygen vacancy concentration are characterized firstly in the rare-earth tantalates. Notably, compared with single rare-earth tantalates, the thermal conductivity of (10RE0.1)TaO4 is reduced by 16%–45% at 100 °C and 22%–45% at 800 °C, and it also presents lower phonon thermal conductivity in the entire temperature range from 100 to 1200 °C. The phonon thermal conductivity (1.0–2.2 W m−1 K−1, 100–1200 °C) of (10RE0.1)TaO4 is lower than that of the currently reported high-entropy four-, five- and six-component rare-earth tantalates. This is the result of scattering by the ferroelastic domain, lattice distortion associated with size and mass disorder, and point defects, which target low-, mid- and high-frequency phonons. Furthermore, (10RE0.1)TaO4, as an improved candidate for thermal barrier coatings materials (TBCs), has a higher thermal expansion coefficient (10.5×10−6 K−1 at 1400 °C), lower Young's modulus (123 GPa) and better high-temperature phase stability than that of single rare-earth tantalates.
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•With an increase in bias voltage, the oxidation resistance of the NiCoCrAlYTa coating by arc ion plating significantly decreased although the coating became dense•Ta played a detrimental role on the ...oxidation behaviour at the latter stage of the oxidation process since it could accelerate the degradation of the protective Al2O3 layer.•The degradation of the Al2O3 layer could be a gradual evolution process without cracks or spallations.
The NiCoCrAlYTa coatings were prepared on the superalloy K423A by arc ion plating under different bias voltages from -50V to -150V, and the oxidation behaviour of these coatings was investigated at 1050°C for 100 h. The results showed that with an increase in bias voltage, the oxidation resistance of the coating significantly decreased although the coating became denser. Ta played a detrimental role on the oxidation behaviour at the latter stage of the oxidation process. The degradation mechanism of the protective Al2O3 layer and the oxidation model of the coating were discussed.
Searching for new oxides with low thermal conductivity and high thermal expansion coefficients (TECs) as thermal barrier coatings (TBCs) is vital for the development of highly efficient gas turbines ...and aeroengines. We report the densification sintering, high TECs, and low thermal conductivity of A4Ta2O9 (A = Ca, Mg) tantalates. The best sintering temperature of dense A4Ta2O9 ceramics was determined via an optical contact angle tester, and samples with a relative density of 99.8% were synthesized via spark plasma sintering (SPS). The hardness (9–10 GPa), Young's modulus (172.7–211.8 GPa) and fracture toughness (1.5–1.6 MPa m1/2) of the A4Ta2O9 ceramics are primarily affected by the bonding strength. Furthermore, we studied the thermal transport properties of A4Ta2O9. The low thermal conductivity (1.78–1.93 W m−1 K−1 at 900 °C), extraordinary phase stability, and high TECs (11.4–11.8 × 10−6 K−1 at 1200 °C) of A4Ta2O9 ceramics make them candidate TBCs with high operating temperatures.
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Combination treatment using bacteriophage and antibiotics is potentially an advanced approach to combatting antimicrobial-resistant bacterial infections. We have recently developed an ...inhalable powder by co-spray drying Pseudomonas phage PEV20 with ciprofloxacin. The purpose of this study was to assess the in vivo effect of the powder using a neutropenic mouse model of acute lung infection. The synergistic activity of PEV20 and ciprofloxacin was investigated by infecting mice with P. aeruginosa, then administering freshly spray-dried single PEV20 (106 PFU/mg), single ciprofloxacin (0.33 mg/mg) or combined PEV20-ciprofloxacin treatment using a dry powder insufflator. Lung tissues were then harvested for colony counting and flow cytometry analysis at 24 h post-treatment. PEV20 and ciprofloxacin combination powder significantly reduced the bacterial load of clinical P. aeruginosa strain in mouse lungs by 5.9 log10 (p < 0.005). No obvious reduction in the bacterial load was observed when the animals were treated only with PEV20 or ciprofloxacin. Assessment of immunological responses in the lungs showed reduced inflammation associating with the bactericidal effect of the PEV20-ciprofloxacin powder. In conclusion, this study has demonstrated the synergistic potential of using the combination PEV20-ciprofloxacin powder for P. aeruginosa respiratory infections.
Abstract
Alleviating cracks induced by the temperature rise in mass concrete has always been a research hotspot and engineering problem. In this study, a type of energy storage phase change ...low‐temperature rising concrete was designed and prepared to reduce the cracking risk of mass concrete. First, a type of energy storage coarse aggregate (ESA) was prepared using a semi‐dry method with cement and fly ash as matrix materials, mixed with carbon black (CB), carbon fiber (CF), and phase change material (PCM). Furthermore, the influence of these materials on the mechanical properties, microstructure, and pore structure of the ESA was studied. Subsequently, ESA was used to prepare phase change low‐temperature rising concrete, and its mechanical properties, thermal conductivity (TC), and internal temperature rise were investigated. The research results show that, except for the compressive strength of PCM‐15‐ESA, which is only 7% lower than that of the control, PC‐P0, other samples have no mechanical property deterioration. The double‐layer protection measures can effectively avoid the mechanical property deterioration of concrete induced by PCM leakage. The maximum internal temperature rise of concrete is reduced by 9.8°C, which greatly reduces the risk of cracking of concrete.
An autonomous emergency braking (AEB) algorithm for snow-asphalt joint pavement is proposed. Based on machine vision and kinetic analysis, we realize the identification of road information, including ...the road type, slope, and road section lengths. A new safety model, the reference velocity model, is proposed to solve the problem of determining the braking time on the joint pavement to achieve collision avoidance. In the asphalt section, we design the desired deceleration considering the comfort and safety, while in the snow section, we use the estimated maximum deceleration that the pavement can provide. To meet the desired deceleration requirement, we choose a single-neuron proportion integration differentiation (PID) controller with a Kalman filter. The joint simulation with CarSim and Simulink shows that the host vehicle successfully realizes collision avoidance in various working conditions and verifies the proposed AEB algorithm. Benefitting by the recognition of the forefront road conditions, our proposed model performs better than the traditional AEB model.
It is important to investigate the high-temperature mechanical properties and failure mechanisms of Gd2Zr2O7 ceramic materials for the development of novel thermal barrier coatings. Freestanding ...(Gd0.9Yb0.1)2Zr2O7 (GYbZ) coatings were prepared by supersonic plasma sprayed technique. A modified high-temperature in situ experimental system (up to 1500 °C) with the aid of digital image correlation technique was used to evaluate the fracture strength and flexural modulus of GYbZ coatings using three-point bending tests, and the fracture toughness was studied by single edge notched beam experiments. In addition, the extended finite element analysis was used to estimate the critical energy release rate of GYbZ coatings through the aforementioned experimental data. The effect of test temperature on the mechanical properties, cracking and fracture morphology of freestanding GYbZ coatings was discussed under bending loads. The results are useful for understanding high-temperature failure mechanisms of multilayered GYbZ thermal barrier coatings.
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