The adsorption of Hg-n (n = 1-3) on the Au-, Ag-, Cu-substituted Pd(1 1 1) surfaces as well as the PdM/gamma-Al2O3(1 1 0) (M = Au, Ag, Cu) surfaces has been investigated using spin-polarized density functional theory calculations. It is found that M-substituted Pd(1 1 1) surfaces show as good Hg adsorption capacity as the perfect Pd(1 1 1) at low Hg coverage, while the Hg adsorption capacity is only slightly weakened at high Hg coverage. On the basis of stepwise adsorption energies analysis, it is concluded that M-substituted Pd(1 1 1) surfaces can contribute to the binding of Hg atom on the surfaces at high Hg coverage. The electronic properties of the second metal atoms are the main factor contributes to the Hg adsorption capacity. Gas phase Pd-2 shows better Hg adsorption capacity than Pd-2/gamma-Al2O3, while PdM/gamma-Al2O3 can adsorb Hg more efficiently than bare PdM clusters. It suggests that the gamma-Al2O3 support can enhance the activity of PdM for Hg adsorption and reduces the activity of Pd-2. It is also found that Pd is the main active composition responsible for the interaction of mercury with the surface for PdM/gamma-Al2O3 sorbent. Taking Hg adsorption capacity and economic costs into account, Cu addition is a comparatively good candidate for Hg capture. (C) 2015 Elsevier B.V. All rights reserved.

•M-substituted Pd surfaces show good Hg adsorption capacity at low Hg coverage.•γ-Al2O3 can enhance the activity of bimetallic PdM for Hg adsorption.•Pd is the main active composition of PdM/γ-Al2O3 sorbent for Hg adsorption.•Cu addition is a better than Au and Ag for the Pd-based Hg adsorbents.

The dispersion-corrected density functional theory has been used to study the trivalent ions B, Al, Ga, and Fe incorporated SSZ-13-type zeolites. The associated structure and Brønsted/Lewis acidity change caused by the incorporation ions were comparatively studied. It was found that the smaller the radius differences of the incorporation ions are, the smaller the changes in the structure will be and the less acidity will be enhanced for the Brønsted sites. The trivalent Al is found to be the most favorable trivalent incorporation ion and Na is found to be the most favorable charge balanced ion for the synthesis of SSZ-13-type zeolites due to size comparability, which are in line with the experimental observation. The substitution energies which show the relative synthesis difficulty level were also applied for B, Al, Ga, and Fe incorporated zeolites and found that the difficulty decreases with order of Fe > B > Ga ≫ Al, also in good agreement with the experimental observations. Adsorption studies for the NH3 and pyridine molecules indicate that adsorption on the Brønsted acid sites is more stable than on the Lewis acid sites. The Brønsted acidity was found to follow the order of HAl-SSZ-13 > HGa-SSZ-13 ≈ HFe-SSZ-13 > HB-SSZ-13 where the Lewis acidity was found to follow the order of HGa-SSZ-13 ≈ HFe-SSZ-13 > HAl-SSZ-13 > HB-SSZ-13. Our results provide new insights for the synthesis of the SSZ-13-type zeolites and fundamental information for the zeolitic catalyst designation to enhance the catalytic performance.

Spin-polarized density functional theory calculations were carried out to investigate the adsorption of Hg-n (n = 1 - 3) on the perfect, step and vacancy-defective Pd(1 1 1) surfaces as well as the Pd/gamma-Al2O3( 1 1 0) surface. It is found that Hg atoms prefer to adsorb on the hollow sites on Pd(1 1 1) surfaces. The adsorption of Hg on the step and vacancy-defective Pd(1 1 1) surfaces is stronger than on the perfect Pd(1 1 1) surface, which indicates that the existence of vacancy and step defects can enhance the mercury adsorption activity of Pd adsorbents. As indicated by the calculated adsorption energies, the mercury adsorption on gamma-Al(2)O(3)is weak. The gamma-Al2O3 supported single Pd atom shows as good Hg adsorption activity as the perfect Pd(1 1 1) surface at low Hg coverage, while more coordination unsaturated active Pd atoms is needed to achieve high Hg adsorption capacity. In addition, it was also found that the Hg adsorption on Pd/gamma-Al2O3 weakens the binding of Pd to the gamma-Al2O3 surface. (C) 2014 Elsevier B.V. All rights reserved.

The microstructure and mechanical properties of AZ61-4Si magnesium alloy before and after equal channel angular processing (ECAP) were studied. Results show that the matrix α-Mg and divorced eutectic β-Mg17Al12 are refined and chinese script type Mg2Si phases are broken to dispersed particles after ECAP. The mechanical properties of the alloy after ECAP are significantly improved. After 4 passes of ECAP, the yield strength is increased from 50MPa to 109 MPa, tensile strength from 129MPa to 237MPa, elongation from 6% to 22%, and hardness from 61.2HBS to71.5HBS. The modification mechanism for microstructure and mechanical properties of the experimental alloy by ECAP was analyzed.