Ruiqin Tan

Hydrothermal preparation of mesoporous TiO2 powder from Ti(SO4)2 with poly(ethylene glycol) as template

Mesoporous titania powder with anatase structure was prepared by hydrothermal synthesis from low-cost Ti(SO4)2 water solution with nontoxic poly ethylene glycol (PEG) as a templating agent. The templating pathway was suggested to use hydrogen bonding interaction between the hydrophilic surfaces of flexible rod- or worm-like micelles and the hydrothermal products of Ti(OH)4 to assemble an inorganic oxide framework. The mesoporous channel structures with diameters about 3 nm to 18 nm were achieved by adding appropriate amount of PEG with average moelcular weight of 200. The obtained powder showed good performance for the degradation of gaseous formaldehyde. These results suggested that hydrothermal synthesis with PEG templating provided a low-cost and convenient pathway to synthesis mesoporous TiO2 powder from water solution system.

Preparation of nanosized La2CuO4 perovskite oxide using an amorphous heteronuclear complex as a precursor at low-temperature

Nanosized LaCoO3 cobaltite oxide powder with perovskite structure was successfully synthesized at a relatively low calcination temperature using an amorphous heteronuclear complex, LaCo(DTPA)·6H2O, as a precursor. The precursor decomposed completely into cobaltite oxide above 400 °C according to the DTA and TGA results. XPS revealed that the decomposed species was composed of LaCoO3 cobaltite oxide after the precursor was calcined at 500 °C for 2 hours. XRD demonstrated that nanosized LaCoO3 crystalline powder with perovskite structure was formed after the calcination temperature increased to 600 °C. The grain size and the crystal size of LaCoO3 increased with the calcination temperature from 500 °C to 800 °C, and the heat-treatment time has a less obvious effect on the grain size and the crystal size. It is a useful way to synthesize nanosized perovskite oxides using an amorphous complex as a precursor. This method can be easily quantitatively controlled.

Study on the Poisoning Mechanism of Sulfur Dioxide for Perovskite La0.9Sr0.1CoO3 Model Catalysts

The reaction and poisoning mechanism of SO2 with La0.9Sr0.1CoO3 model catalysts have been investigated. The structure and the chemical states of the model catalysts have been studied by using AES, XPS and XRD techniques. The results indicated that SO2 diffused into the La0.9Sr0.1CoO3 film during poisoning. La2(SO4)3 species was formed on the surface of the film and La2(SO4)3, La2(SO3)3, La2O2SO4 and CoO species were found in the interior. The perovskite structure of La0.9Sr0.1CoO3 was destroyed by invasion of SO2. The concentration of sulfur in the film layer was related to the reaction temperature and time. After the sample was poisoned for a fairly long time, the distribution of sulfur in the La0.9Sr0.1CoO3 layer became homogeneous, suggesting that a dynamic equilibrium was achieved between the poisoning reaction and the decomposition of the sulfates. XRD and catalytic activity test results proved that the destruction of perovskite structure and the formation of sulfates were the main causes of deactivation.

Influence of PEG additive and precursor concentration on the preparation of LaCoO3 film with perovskite structure

Abstract LaCoO 3 thin films with perovskite structure were prepared on Si(111) substrate successfully by using an amorphous heteronuclear complex, LaCo(DTPA)·6H 2 O (DTPA, diethylenetriaminepentaacetic acid), as a precursor. X-Ray diffraction (XRD) results indicated that the crystalline sizes of LaCoO 3 films grew from 17.8 to 34.3 nm with the calcination temperature increasing from 550 to 800°C for 1 h and the crystalline sizes of LaCoO 3 films grew from 22.3 to 25.3 nm with the calcination time increasing from 1 to 6 h at 650°C. Auger electron spectroscopy (AES) depth profile analysis indicated that the composition of the thin film was homogenous with depth, the interface diffusion took place between LaCoO 3 layer and Si substrate. The thickness of LaCoO 3 thin film depended on the concentration of the precursor solution and could be described approximately by the following equation: d =0.580 c+ 0.285 c 2 . Scanning electron microscopy (SEM) indicated that the texture of the film was governed by the concentration of precursor solution. When the concentration of precursor solution was lower than 15%, a smooth film without microcrack was obtained. The texture of the film could be modified significantly by adding polyethylene glycol (PEG). But the thickness of the film was hardly influenced by the addition of PEG.