Papers by Author: Sheng Ru Qiao

Abstract: Titanium Silicalite-1 (TS-1) zeolite was successfully synthesized through a mechanochemical assisted processing. In this method, an amorphous silica-titania precursor was firstly prepared through a mechanochemical treatment. TS-1 was then synthesized by the hydrothermal treatment of the silica-titania precursor with tetrapropylammonium bromide (TPABr) as the template. The results of the XRD, UV-vis, and FT-IR spectrum indicated that the titanium atom was incorporated into the amorphous silica-titania precursor during the grinding, and was also retained in the final TS-1 framework after the hydrothermal treatment. SEM image showed that the TS-1 appeared in a shape of elongated prism. The catalytic performance of TS-1 was examined by phenol hydroxylation with hydrogen peroxide as the oxidant. The results indicated that TS-1 synthesized by this method exhibited a good activity.

Abstract: Titanium Silicalite-1 (TS-1) was successfully synthesized from amorphous silica and titania powders by using a ball-milling method. In this method, amorphous fumed silica and anatase titania powders were ground in a planetary ball mill to produce a silica-titania precursor. The obtained precursor was then hydrothermally treated where TPABr was used as a template to obtain titanium silicalite-1 (TS-1). The XRD and UV-vis spectra indicate that the titanium in anatase with octahedral coordination is incorporated into the silica-titania precursor and the final TS-1 framework with a tetrahedral coordination. SEM image shows that TS-1 synthesized in this work appears in a shape of elongated prism with a dimension of about 3μm×1μm×0.2μm. This method gives a simple new approach to the synthesis of TS-1 using inexpensive silicon source, titanium source and template.

Abstract: Carbon fiber reinforced SiCN matrix composite (C/SiCN) was used in present investigation, its amorphous SiCN matrix was derived from the hexamethyldisilazane by chemical-liquid and vapor-infiltration into the carbon fiber weaving preform. The tension-tension fatigue was conducted at 1300°C in vaccum both for the as-received and 1500°C-annealed C/SiCN with 60Hz and 41MPa. The microstructure evolution of SiCN during fatigue was examined by X-Ray diffraction and transmission electron microscopy (TEM). The results indicate that pronounced crystallization takes place in the as-received C/SiCN during fatigue, and only β-SiC crystallites are detected within amorphous SiCN matrix, Si3N4 can’t be detected. This is different from the literature that reports that there isn’t any crystallization when C/SiCN is annealed at 1300°C under nitrogen or argon atmosphere. As for 1500°C-annealed C/SiCN, there isn’t any crystallization during fatigue, and it can be attributed to the phase stabilization in the SiCN matrix after annealing. Both vacuum and fatigue stress promote the crystallization course because they accelerate the decomposition of amorphous SiCN and atomic diffusion. Degradation – crystallization mechanism is used to explain the crystallization behavior of amorphous SiCN under condition of vacuum and tension-tension fatigue.

Abstract: Carbon fiber reinforced silicon carbonitride ceramic composite (C/SiCN) was prepared by rapid electro-thermal pyrolysis chemical vapor deposition using liquid hexamethyldisilazane as precursor. The density of C/SiCN is 1.75g/cm3 and with 15% porosity. Microstructure characteristics of C/SiCN were examined by transmission electron microscopy and scanning electron microscope equipped with energy dispersive spectrometer. The mechanical properties were characterized by three-point bending test. Microstructure observation displays a high degree of coalescence between SiCN matrix and fiber filaments, but there also exist plenty of micro-pores within fiber bundle. It is different from that of C/SiC composite made by chemical vapor infiltration. Mechanical test exhibits a mostly obvious nonlinear fracture behavior, which can be explained by typical toughening mechanism of long fiber-reinforced ceramic matrix composite.

Abstract: Alumina (Al2O3) coatings in the thickness of 10μm and 15μm were prepared on the 4043 Al-Si alloy substrates by electroplating technology. Multiple mechanical properties of alumina coatings were evaluated by various techniques: the long distance microscope, Charge Coupled Device microphotographics, acoustic emission and strain foils. For the electroplating alumina coatings, the in-plane tensile strength is 68.1 MPa, the cohesive strength is 96.2 MPa and the adhesive strength is over 22.7 MPa. Three different directional microcracks, which are relative to the tensile directional and corresponding to two fail modes in the alumina (coatings)/4043 Al-alloy (substrate) system, were found.

Abstract: The subsidence rate of nanometer particles in liquid is determined by their Brownian movement, liquid drag force and gravity. The paper utilized the relation between temperature and the Brownian movement that the Einstein’s Brownian motion equation reveals. One new method for temperature measurement is proposed which based on the subsidence rate of nanometer particles. The Einstein’s classical theory can connect with contemporary nanometer technology, it have new application.

Abstract: Mullite interlayer of the carbon fiber reinforced Si-C-N matrix composite (C/Si-C-N) was fabricated by liquid precursor impregnation and pyrolysis (PIP). The mixture of aluminium secbutoxide (A1OBu) and tetraethoxysilicate (TEOS) were used as starting materials. The monophase polymer gel used as mullite precursor could be formed from the mixture in the semi-closed air. A mullite interlayer with a thickness about 500nm is obtained at 850°C- 1200°C. The fiber/interlayer bonds are tight. The carbon fibers are not damaged in the fabrication procedure.

Abstract: Materials characterization is a crucial issue in the development and application of new materials. Materials characterization aims to mine and acquire characteristic information and their evolution in the materials. It mainly includes three important topics which are microstructural characterization, properties characterization, and environmental degradation. In this paper, characterization techniques about these topics were discussed for C/SiC composites and a characterization system was preliminarily established. All these characterization research and their results further the better understanding of the relationship between microstructure and properties and of the failure mechanisms in the C/SiC composites.

Abstract: By means of forced non-resonance under 3-point bending method, the internal frictions of 2D-C/SiC composites are carried out from 25°C to 400°C in air. The effects of temperature, amplitude and frequency on internal frictions have been analyzed. Results show that interface layer plays a dominant role to internal friction. When temperature increases from 25°C to 400°C, internal friction of 2D-C/SiC composite increases slightly, and storage modulus decreases monotonically. With frequency increases from 1Hz to 100Hz, internal friction reduces to a minimum around 10Hz, whereas above 50Hz it arises sharply. In amplitude scale from 0.5μm to 10μm, internal friction increases linearly with the increase of amplitude.