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MnO x /Al 2 O 3 -carbon nanotubes (CNTs) composites prepared by hydrothermal method were characterized by XRD, SEM, TEM, TGA, BET, XPS and H 2 -TPR. Catalytic oxidation of chlorobenzene (CB) was conducted over the composites under gas hourly space velocity (GHSV) of 36000 h -1 and CB concentration of 2800 ppmv. For the catalyst with approximately 25 wt% CNTs and 10 at.% Mn, CB removal efficiencies reached up to 83.3 and 97.7% at 150 and 300°C, respectively. Moreover, no Cl species was detected over the used MnO x / Al 2 O 3 -CNTs catalyst implying that the release of chlorine element from the catalyst surface was facilitated by CNTs introduction.

The evolution and spatial distribution of internal random pore structure are key factors in damage mechanism and macro-mechanical properties of concrete material under freeze-thaw (F-T) environment. This paper was presented to discover the deterioration mechanism of concrete under F-T actions. Through the experiment, visual examination was employed to evaluate the surface damage; the degradation considering the mass loss and uniaxial compressive strength of concrete was statistically analyzed under F-T environment. Moreover, X-ray tomography was adopted to characterize the concrete internal structure subjected to F-T cycles. The specimens exposed to F-T environment were scanned at regular intervals. Coupled with CT test, the pore space was characterized in terms of porosity and pore distribution by image analysis. And the relationship between the pore structure and the F-T cycles was described quantitatively by the fractal theory. The results indicated that the fractal dimension of the pore structure presented "down-up" trend with the number of F-T cycles increasing. The pore structure evolution changed from chaos to order and then to a process of disorder. The results demonstrated that F-T cycles accelerated the generation of meso-damage in concrete, which leads to more severe damage under F-T cycles.

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In this study, the deterioration resistant of concrete with and without multi‐walled carbon nanotubes (MWCNTs) against combined freeze–thaw cycles and sulfate attack was studied, and concretes incorporating MWCNTs (i.e., 0.05, 0.10, and 0.15 wt%) as partial replacement of Portland cement were exposed to 5% sodium sulfate solution under freeze–thaw cycles. The performance, including compressive strength, relative dynamic elastic modulus, mass loss, microstructure, deterioration resistant coefficient of concretes were evaluated. Results show that when exposed to 5% sodium sulfate solution, MWCNTs could enhance the mechanical and durability properties of concrete subjected to combined freeze–thaw cycles and sulfate attack, regardless of the dosage of MWCNTs. The deterioration resistant of MWCNTs concrete was not increase with the increase dosage of MWCNTs. And the best resistance performance was obtained in concrete containing lower dosage of MWCNTs. In addition, MWCNTs could promote formation of hydration and corrosion products, and delay deterioration of concrete was demonstrated by SEM and thermogravimetric analysis.

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