Yi-nong Lu

Template-confined growth and structural characterization of amorphous carbon nanotubes

Porous anodic aluminum oxide templates with different channel structures have been synthesized and used to grow carbon nanotubes (CNTs) through the pyrolysis of ethylene at 700 °C. Aligned CNT arrays, Y-branched as well as novel dendriform CNTs have been obtained and well characterized by scanning electron microscopy and high-resolution transmission electron microscopy. The amorphous structure, irregular and quasi-hemispherical ends as well as the branched junction have been revealed in detail. The disordered structure of the carbon nanotubes was assigned to the lattice mismatch between alumina and carbon species. A growth mechanism mainly based on the space-limited and self-catalytic functions of template channels has been proposed accordingly.

Growth of carbon nanotubes with metal-loading mesoporous molecular sieves catalysts

Abstract Chemical vapor deposition (CVD) was employed to catalytically synthesize carbon nanotubes (CNTs) with Fe- or Fe/Co-loading M41S (MCM-41 or MCM-48) as catalysts and benzene as precursor at 650xa0°C. The experimental results indicated that the frameworks of the M41S host materials did not collapse after the synthesis process and well-graphitized curved CNTs ranging from 10 to 45xa0nm in diameter could be formed out of the pores of the M41S materials. The maximum yield of CNTs per hour was greater than 200% the weight of the catalyst. Quite a few helix-shaped CNTs were obtained with the structures clearly demonstrated by high-resolution electron microscopy. The good thermal stability and high productivity observed in this study suggested that the mesoporous molecular sieves could be a kind of promising supports for catalytically synthesizing CNTs.

Study on the densification of composite coating particles of α-Al2O3–SiO2

Abstract Composite coating particles consisting of alpha alumina cores (α-Al 2 O 3 , average particle size 0.26xa0μm) with outer homogeneous amorphous silica layer were prepared by the heterogeneous nucleation-and-growth processing. Densification of composite coating particles was studied at different sintering temperatures. Density of samples sintered at different temperatures was measured by the Archimedes method. Densification procedure of samples was observed and analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Based on the density of samples, XRD and SEM, densification procedure of samples is divided into two stages: one is the transient viscous flow of amorphous silica layer below 1350xa0°C, the other is mullitization of composite coating particles at 1500xa0°C.

Preparation of composite coating particles of α-Al2O3–SiO2 by heterogeneous nucleation-and-growth processing

In order to solve the difficult problem of heterogeneity of different components in the procedure of ceramic preparation, heterogeneous nucleation-and-growth processing is used to prepare the homogeneous distribution powders. Composite coating particles consisting of alpha alumina cores (average particle size 0.57 μm) with an outer amorphous silica layer are prepared by the heterogeneous nucleation-and-growth processing. The amorphous silica layer on cores is confirmed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and zeta-potential measurement. Effects of silica content in composite coating particles versus concentration of tetraethylorthosilicate (TEOS), pH value, reaction time and reaction temperature are studied.

Preparation of core/shell structure of α-Al(OH)3-SiO2 by heterogeneous nucleation-and-growth processing

In order to solve the difficult problem of heterogeneity of different components in the procedure of ceramic preparation, a novel processing (heterogeneous nucleation-and-growth processing) was used to prepare homogeneous distribution powders. Composite coating particles consisting of alpha aluminum hydroxide (α-Al(OH)3) cores (average particle size 0.42 μm) with outer homogeneous amorphous silica layer are prepared by heterogeneous nucleation-and-growth processing. Effects of silica content in composite coating particles versus concentration of silicon tetraethoxide (TEOS), pH value, time and temperature are studied. The homogeneous amorphous silica layer on cores is confirmed by X-ray diffraction, transmission electron microscopy and zeta potential measurement.

Fabrication of ultrafine mullite powders

Abstract In order to obtain fine mullite powders by a simple and inexpensive processing route gamma alumina (γ-Al2O3) is used as raw material, and the heterogeneous nucleation-and-growth process is chosen. Composite coating particles consisting of γ-Al2O3 cores with outer homogeneous amorphous silica layer are prepared by the heterogeneous nucleation-and-growth process in the ethanol suspension containing ammonia, tetraethylorthosilicate (TEOS) and γ-Al2O3. Ultrafine mullite powders (average particle size of 0.63xa0μm) were fabricated by calcined composite coating particles at 1400xa0°C for 2xa0h.

Fabrication of fine mullite powders by α-Al(OH)3-SiO2 core-shell structure precursors

Abstract In order to obtain fine mullite powders by a simple and inexpensive process, alpha aluminum hydroxide (α-Al(OH)3) was used as raw material, and heterogeneous nucleation-and-growth process was chosen for the preparation of powders. Composite coating particles consisting of α-Al(OH)3 cores with outer amorphous silica shell were prepared by heterogeneous nucleation-and-growth process in the ethanol suspension containing ammonia, tetraethylorthosilicate (TEOS) and α-Al(OH)3. Fine mullite powders (average particle size 0.67xa0μm) were fabricated by calcined composite coating particles at 1500xa0°C for 2xa0h.

Fabrication of composite coating particles with mullite stoichiometric ratio by a novel processing

In order to solve the difficult problem of heterogeneity of different components in the procedure of ceramic preparation, a novel processing (heterogeneous nucleation-and-growth processing) was used to prepare homogeneous distribution powders. Composite homogeneous coating particles with mullite stoichiometric ratio (consisting of alpha alumina cores (average particle size 0.26 μm) with an outer homogeneous amorphous silica layer) were prepared by the heterogeneous nucleation-and- growth processing. Effects of silica content in composite coating particles versus concentration of tetraethylorthosilicate (TEOS), pH value, reaction time and reaction temperature were studied. The homogeneous amorphous silica layer on cores was confirmed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and zeta potential measurement.

Fabrication of composite particles with core-shell structures by a novel processing

In order to solve the difficult problem of heterogeneity of different components in the procedure of ceramic preparation, novel processing (heterogeneous nucleation-and-growth processing) was used to prepare a homogeneous distribution of powders. Composite coated particles with core-shell structures were prepared by the heterogeneous nucleation-and-growth processing. The effects of silica content in composite coating particles versus concentration of tetraethylorthosilicate, pH value, reaction time and reaction temperature were studied. The amorphous silica shell on the cores was confirmed by X-ray diffraction, transmission electron microscopy and zeta potential measurement.