Baohuai Zhao

NO catalytic oxidation over an ultra-large surface area LaMnO3+δ perovskite synthesized by an acid-etching method

The perovskite oxides LaMnO3+δ were prepared by a citrate method and then etched by acid solution with different times. After etching, the perovskite structures of all the catalysts remained, the surface area enlarged apparently, and the NO catalytic oxidation activities were obviously promoted by increasing the etching time. Long-term experiments revealed the acceptable stability of the etched catalysts. The favorable activities of the etched LaMnO3+δ catalysts were mainly due to their high specific surface area, abundant activated oxygen species and vacancies, as well as the higher valence state of Mn ions resulting from the loss of La3+ in the perovskite structure.

Modification of MnCo2Ox catalysts by NbOx for low temperature selective catalytic reduction of NO with NH3

A series of MnCo2Ox catalysts modified with different Nb ratios were synthesized by co-precipitation and sol–gel method. The effects of niobia on the low-temperature NH3-SCR performances of the catalysts were investigated. The MnCo2O4 spinel phase was identified according to XRD and Raman results. Niobates including Mn2NbOx and Co2NbOx appeared with the increase of the Nb loading based on the Raman and H2-TPR results. Among the obtained catalysts, MnCo2Nb0.5Ox presented the best catalytic performance with a broad operation temperature window, high N2 selectivity and good H2O resistance. It was found that the addition of niobia weakened the redox properties of the catalysts to some extent, resulting in the decrease of NO conversion at 50 °C. This, as well as the enhanced surface acidity, inhibited the unselected oxidation of NH3 to N2O and increased the N2 selectivity over the modified catalysts. Consequently, the modification of MnCo2Ox catalyst by NbOx promoted the low-temperature NH3-SCR performance.

Structural and magnetic investigation of metastable alloy phases in Bi–Co multilayers

Abstract Bi–Co multilayers with a constant t Bi of 6.0 nm and a various t Co are prepared by alternate evaporation. The films grow into a new metastable rhombohederal phase for low t Co and metastable amorphous phases for large t Co . The influence of the structural evolution of the films from crystalline to amorphous on the magnetic properties of Bi–Co multilayers is investigated. Ferromagnetic properties are found in both the crystalline and the amorphous films, and that for amorphous alloy films are studied using Buschow’s model. The contribution of amorphous microstructure, i.e. the number of Bi neighbors surrounding Co atom and the degree of compositional short-range ordering in Bi–Co amorphous alloy films, to the magnetic properties are discussed in terms of heat of formation.

Improved activity and durability of Rh-based three-way catalyst under diverse aging atmospheres by ZrO 2 support

The catalytic activity and durability of Rh/ZrO2 catalyst were investigated compared with Rh/Al2O3 catalyst under diverse aging atmospheres, including lean, rich and lean-rich cyclic aging atmospheres, to simulate the real working conditions of three-way catalyst. Oxidation states and microstructures of rhodium species were investigated to correlate with the catalytic performance of the catalysts. The catalytic performance and durability of the Rh catalyst under diverse aging atmospheres were drastically enhanced by ZrO2 support. ZrO2 support was confirmed to be able to effectively inhibit rhodium sintering even under diverse aging conditions. It can also successfully keep Rh species in an active low-valence state on the surface of the catalyst. The superiority of ZrO2 support compared to Al2O3 was verified by the Rh-based monolith catalyst.

Nanoindentation study of Ni45Nb55 amorphous films prepared by ion beam assisted deposition

Abstract The mechanical properties of amorphous alloy films are of significance for their application. In the present work, the Ni 45 Nb 55 amorphous films of about 500 nm thick have been prepared by ion beam assisted deposition (IBAD). The hardness and elastic modulus of the amorphous films were investigated by nanoindentation tests. The experimental results revealed that amorphization of the films induced by IBAD resulted in the decrease of the hardness and elastic modulus. And the hardness and elastic modulus of the amorphous films were approximately 20% lower than those of the crystalline multilayer, respectively, which were interpreted according to the deformation mechanism and the free volume model.