Search

In order to reduce the energy consumption of the reaction, the magnesium alloy samples were immersed directly into three conversion solutions and reacted for 9 hours at 60 ℃ and pH=12.0 used the chelating agent-assisted method by adding three chelating agents, ethylenediaminetetraacetic acid tetrasodium (EDTA-4Na), sodium citrate (SC) and potassium sodium tartrate (PST) to aluminum nitrate (Al(NO3)3) solution, and Mg-Al layered double hydroxides (LDHs) films doped with different chelating agents can be prepared on the surface of magnesium alloys. The microstructure, phase composition, and corrosion resistance of each LDHs film were analyzed by SEM, XRD, FT-IR, etc. The results show that the chelating agent-assisted method can successfully prepare LDHs films with typical layered structure on the surface of magnesium alloys under normal pressure and 60 ℃ environment; and three kinds of Mg-Al LDHs films obtained can effectively improve the corrosion resistance of magnesium alloys. Then, by comparing the structural properties of three different LDHs film layers, it is found that the Mg-Al-PST LDHs film prepared by adding PST has the highest density and the largest thickness, reaching up to 1.4 μm. The improvement effect of three coatings on the corrosion resistance of magnesium alloys is as follows: Mg-Al-PST LDHs > Mg-Al-SC LDHs > Mg-Al-EDTA LDHs; The magnesium alloy covered with the Mg-Al-PST LDHs film compared to the blank magnesium alloy, the corrosion current density decreases by about two orders of magnitude, and the total corrosion resistance increases by about one order of magnitude. And based on the analysis of the structure and properties of the obtained LDHs films, it can be seen that the chelating agent-assisted method can prepare Mg-Al LDHs films with better corrosion resistance in-situ on the surface of magnesium alloys under the lower energy consumption condition. The reason may be that the carboxyl group in the chelating agent can accelerate the deposition of Al3+ on the magnesium substrate and promote the substitution of some Mg2+ in Mg (OH)2 by Al3+ to form LDHs.

Concrete structures are at risk of fire and explosion effects during service. This paper mainly conducted static and dynamic mechanical test research of concrete after high temperature. Five different target temperatures and two cooling methods (air cooled with furnace and water cooled by immersion in water) were set to investigate its effects. Hydraulic servo machine and split Hopkinson pressure bar (SHPB) were used to obtain static and dynamic mechanical behavior, failure patterns, and mechanical characteristic parameters of concrete. The research results indicated that the compressive strength of concrete at 800°C was reduced by 77% and 67% under air-cooled and water-cooled methods, respectively. When the temperature was below 600°C, the compressive strength of water-cooled concrete was lower than that of the air-cooled specimen. The failure patterns of the concrete vary from a small amount of aggregate crushing at low strain rates to a large amount of coarse aggregate crushing at high strain rates. The increase in temperature weakens the dynamic increase factor (DIF) of concrete and causes a significant strain-softening phenomenon in the concrete stress–strain curve. By utilizing scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and X-ray computed tomography (X-CT) techniques, the microstructural features of concrete were obtained. The deterioration and enhancement mechanisms of the mechanical properties of concrete under high temperature and strain rates were studied by combining the results with static and dynamic mechanical properties analyses. Meanwhile, a dynamic constitutive model for concrete considering high-temperature influencing factors is established. [ABSTRACT FROM AUTHOR]

Purpose. To compare the differential diagnostic values of 18F-Alfatide II PET/CT between tuberculosis and lung cancer patients and in patients with sarcoidosis and common inflammation. Methods. Nine inflammation patients (4 tuberculosis, 3 sarcoidosis, and 2 common inflammation) and 11 lung cancer patients were included in this study. All patients underwent 18F-FDG and 18F-Alfatide II PET/CT within 2 weeks, followed by biopsy and surgery. The maximized standard uptake value (SUVmax) and the mean standard uptake value (SUVmean) were evaluated. Results. The active tuberculosis lesions showed a high accumulation of 18F-FDG, but varying degrees of accumulation of 18F-Alfatide II, including negative results. The SUVmax of 18F-Alfatide II in malignant lesions was significantly higher than that in tuberculosis (4.08 ± 1.51 versus 2.63 ± 1.34, P = 0.0078). Three patients with sarcoidosis showed negative results in 18F-Alfatide II PET/CT. Conclusions. The expression of αVβ3 is much lower in tuberculosis as compared to that in lung cancer, and accumulation of 18F-Alfatide II varied even in lesions of the same patient. The negative results of sarcoidosis patients led to the speculation that αVβ3 was not expressed in those lesions. [ABSTRACT FROM AUTHOR]