Piezoelectric and ferroelectric ceramics with a high Curie temperature (Tc) have attracted much attention owing to their applications in severe environments. In this work, phase structure and dielectric, ferroelectric, and piezoelectric properties of (0.975 − x)BiScO3-xPbTiO3-0.025Pb(Cd1/3Nb2/3)O3 (BS-xPT-PCN) ceramics (x = 0.58–0.64) were studied. A composition-induced structural transformation occurs from the rhombohedral to tetragonal phase through an intermediate monoclinic phase with the increasing PT concentration. The relationship between the structure and electrical properties of the system was discussed. The BS-xPT-PCN system near the morphotropic phase boundary (MPB) (x = 0.62) exhibits excellent piezoelectric and ferroelectric performances with d33 = 508 pC/N, kp = 56%, and Pr = 40 μC/cm2. The high-temperature piezoelectricity of the sample with MPB (x = 0.62) was characterized by an in situ XRD. The excellent thermal stability of the crystal structure and the piezoelectric property indicate that the BS-xPT-PCN system is a promising candidate for high-temperature piezoelectric applications.
The influence of Cu concentration on the selective catalytic reduction (SCR) of NO with ammonia (NH 3 -SCR) for copper-exchanged aluminosilicate zeolite catalysts (Cu-SSZ-13) was investigated. The results demonstrate that the SCR performance of the catalysts increases initially and decreases subsequently with an increase in Cu concentration in the low-temperature region (100−300 °C). The highest low-temperature SCR activity (lightoff temperature is 149 °C) is obtained in the Cu 0.100 -SSZ-13 catalyst, i.e., the concentration of the Cu salt solution reaches up to 0.100 mol/L. BET and XRD results illustrate that the concentration of the Cu salt solution does not have a significant effect on the structure of the samples. The NH 3 -TPD and H 2 -TPR outcomes demonstrate that the amount of Lewis acidity and isolated Cu 2+ on Cu-SSZ-13 catalysts increases as the CuCl 2 concentration increases from 0 to 0.125 mol/L. However, most of the H + in the Brønsted acid sites (Si−OH−Al) are replaced by isolated Cu 2+ , which limits the storage and transfer capacity of ammonia. As a result, the catalytic efficiency of Cu-SSZ-13 reduces with a further increase in CuCl 2 concentration.
Improving the utilization efficiency of visible sunlight and separation efficiency of photogenerated carriers are two important factors to enhance catalytic activity of photocatalyst. In this article, a tubular-hexagonal beta (β)-In2S3/In2O3...
Pt/SiO 2 -Al 2 O 3 catalysts were prepared by the traditional impregnation method (IM) and the strong electrostatic adsorption (SEA) process. Differences in particle size, surface chemical state, Pt adsorption site, ammonia oxidation activity, and thermal stability of Pt species were studied systematically. For the fresh catalyst of Pt/SiO 2 -Al 2 O 3 -IM (Pt/SiO 2 -Al 2 O 3 -IM-fresh), Pt species were dispersed unselectively on SiO 2 -Al 2 O 3 , and the large average size (6.6 nm) of Pt species could be observed in a bimodal distribution (ranges of 5.5−6.5 and 8.5−9.5 nm). After the hydrothermal treatment, the Pt size of the aged catalyst (Pt/SiO 2 -Al 2 O 3 -IM-aged) increased significantly, especially Pt particles on SiO 2 showed obvious agglomeration and some even increased to 40 nm. Conversely, for the catalyst prepared through the SEA process, Pt species of Pt/SiO 2 -Al 2 O 3 -SEA-fresh were selectively absorbed on Al 2 O 3 , the Pt particle size was in the range of 1.5−6.0 nm, and the average particle size was only 2.7 nm. After hydrothermal aging, Pt species did not show obvious agglomeration (the average particle size was 3.2 nm). Above all, Pt/SiO 2 -Al 2 O 3 -SEA presented better catalytic activity and thermal stability than Pt/SiO 2 -Al 2 O 3 -IM, i.e., the temperatures of 50% NH 3 conversion for the fresh and aged Pt/SiO 2 -Al 2 O 3 -SEA catalysts were 216 and 223 °C, respectively, much lower than those for Pt/SiO 2 -Al 2 O 3 -IM-fresh (228 °C) and Pt/SiO 2 -Al 2 O 3 -IM-aged (250 °C).
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