Qijie Yan

A study of Fe-Ni-B ultrafine alloy particles produced by reduction with borohydride

Fe‐B, Fe‐Ni‐B, and Ni‐B ultrafine alloy particles have been prepared by reduction of metal ions in aqueous solution with borohydride. It is shown that iron and nickel contents in the particles can be easily varied by changing the Ni/(Ni+Fe) ratio in the aqueous solution; however, the boron content is constant when the concentration of the borohydride is kept constant. Several experimental results show that the alloy particles are amorphous. The scanning electron microscopic image indicates that the surface morphology of Fe35Ni15B26 alloy particles looks like cotton clusters. From the high‐resolution image, the average size of the high‐resolution image, the average size of the particles was determined to be about 30±5 nm and the fine structure of the particles indicates that there is an obvious boundary between the outer shell with a thickness of about 5 nm and the inner core with a diameter of about 20 nm. The particles are partially crystallized on the outer shell while the inner core is almost completel...

Carbon monoxide hydrogenation on Fe2O3/ZrO2 catalysts

Fe2O3/ZrO2 catalysts prepared by impregnation and coprecipitation methods were used for catalytic hydrogenation of CO. It was shown that the structure, reduction behavior of iron species, and catalytic properties of the catalysts were obviously affected by the preparation methods. For the Fe2O3/ZrO2 catalyst prepared by the impregnation method, the Fischer-Tropsch catalytic activity and the selectivity to light olefins were much higher than those of the corresponding catalyst prepared by the coprecipitation method, the formation of methane was suppressed and the selectivity to light olefins was enhanced. Various intermediates formed during the successive steps of reduction of the catalysts were studied by using temperature-programmed reduction combined with in situ Mössbauer spectroscopy. The role of zirconia in the catalysts was discussed.

Study on the structure and reduction behaviour of the iron–zirconium oxide system

The structures and reduction behaviour of iron–zirconium oxides prepared by the coprecipitation method have been studied using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), BET surface-area measurements and Mossbauer spectroscopy. The structure of the iron-zirconium oxides is severely affected by the composition. For iron-zirconium oxides with different iron contents, the chemical states of the Fe3+ cations are quite different, and hence the reduction behaviour of these Fe3+ cations is quite different too. The various intermediates formed during the successive reduction steps of the iron–zirconium oxides were determined using TPR combined with in situ Mossbauer spectroscopy. For the samples with low iron content (⩽ 20 atom%), Fe3+ cations were doped in the lattice of cubic zirconia and were difficult to reduce to Fe°. By contrast, for the samples with high iron content (≫ 70 atom%), Zr4+ cations were doped in the lattice of α-Fe2O3 and the reduction of the Fe3+ cations to Fe° was easier than that of the samples with low iron content.

Methane oxidative coupling over Na2WO4/SiO2

Methane oxidative coupling (MOC) was studied over Na2WO4/SiO2. The effect of Na2WO4 loading and reaction conditions on the catalytic behaviour was investigated. XRD, SEM, LRS and XPS have been used to study the catalyst morphology, Na2WO4 dispersity and surface oxygen species. These results were correlated with the catalytic activity and selectivity.

Very thin barium ferrite particles prepared by a novel technique: Ion exchange resin method

Very thin hexagonal barium ferrite particles have been prepared by a new method—ion exchange resin method. The exchanged resin when heated to 850 °C, transformed to the hexagonal ferrite BaFe12O19 as confirmed by x-ray diffraction. These particles show single-domain behavior with average diameter D=220 nm, average aspect ratio D/t=13, specific magnetization σ=71 emu/g and coercivity Hc=3800 Oe.