Papers by Author: Xin Gang Yu

Abstract: Two kinds of high active coal gangue powder (ACGP) were prepared by heat treated and ball milled coal gangue. The density, fineness, Loss on ignition (LOI), activity and influence of the fineness of the two kinds of ACGP on the density and I/W (compressive strength to weight of the foam concrete specimens) of foam concrete were also studied in this paper. The results show that the density and I/W of the foam concrete were greatly affected by the fineness of ACGP. The finer of the ACGP, the lower density and higher I/W of the coal gangue foam concrete will be got. Based on the experimental results, a method to evaluate the activity of active powder used for cement admixture is proposed and the activity of the ACGP is also evaluated.

Abstract: The relationship among the composition, microstructure and strength of materials is always one of the hotspots for scholars of materials research. The influence of curing time on the compressive strength and flexural strength of the foam concrete with the cement, cement-slag and cement-steel slag as main binder respectively was studied in this paper. The microstructure of these foam concrete was analyzed by SEM and the mineral phases of the foam concrete was analyzed by XRD. The relationship among the binders, microstructure, mineral phases and strength of the foam concrete were explored and the reasons of why the strength of the cement foam concrete and cement-slag foam concrete is much higher than that of the cement-steel slag foam concrete are proposed.

Abstract: The pore structure and microstructure of the foam concrete was analyzed by scanning electron microscopy and light microscopy combined with digital image analysis. The results show that: (1) even-distributed fine and close pores resulting in high strength and low permeability; (2) uneven-distributed large size pores and open pores lead to low strength and high permeability; (3) light microscopy combined with digital image analysis is a cheap and convenient tool fitting for the pore structure analysis of the foam concrete; (4) scanning electron microscopy is very appropriate for the pore structure and microstructure analysis of the foam concrete.

Abstract: As a porous material, foam concrete can be manufactured not only into building materials with good heat insulation performance, but also into materials with good water permeability, and by properly controlling the size and shape of the pores, the foam concrete can be used as acoustic material to meet People's increasing demand for functional materials. Therefore, the development of foam concrete has a vast potential for future market. Though the setting time of foam concrete is one of the key technical parameters for the preparation of high performance foam concrete, there is no standard method for the testing of the foam concrete’s setting time. That militates against the development of foam concrete greatly. In this paper, two methods were used to measure the setting time of foam concrete. The results show that the offset value of the foam concrete’s initial setting time measured by the two different methods increases with the increasing of foam volume adding to the foam concrete which use the Portland cement and Portland cement-mineral admixture as binder. Finally, a prefer method to test the foam concrete’s initial setting time was selected.

Abstract: Light-yellow glass was prepared by coating silver film on the flat glass substrate surface with sol-gel dip-coating process. The chemical composition and the valence state of elements on the surface of silver thin film deposited on glass substrate were studied by X-ray photoelectron spectroscopy. Results show that: elements of Na, Mg, Ca exist in the form of their respective stable state, such as Na2O, MgO, CaO, when heat treated at 500°C for 0.5h; but Si is unstable, and exhibit stoichiometrical disturbances. Results of chemical composition and their content by weight percent of silver thin film surface reveal that minute of quantity silver on the glass surface can lead to the glass with light-yellow color. The transmission of light for the light-yellow glass, deep-yellow glass and the flat glass substrate was also analyzed by spectrophotometer, and the results indicate that the light-yellow glass is capable of absorbing UV rays heavily.

Abstract: The high performance coal gangue foam concrete with the dry density less than 440kg/m3, the thermal conductivity less than 0.085W/(m•K) and the compressive strength over 2.0 MPa was prepared. The microstructure of the coal gangue foam concrete was analyzed by SEM. The hydrates of the coal gangue foam concrete were detected by XRD, and the temperature stability of the coal gangue foam concrete was analyzed by DTA and DSC.

Abstract: ZrO2-CeO2 thin film was successfully prepared on 316L stainless steel by sol-gel process and the corrosion characteristics of the substrate coated with ZrO2-CeO2 thin film were evaluated through potentiodynamic polarization curve obtained in deaerated 15% H2SO4. The results show that, with the increase of CeO2 content, the corrosion rate of 316L stainless steel substrates coated with ZrO2-CeO2 thin film decreases. The surface morphology of the coating was observed by field scanning electron microscopy and the elements in the surface of coated substrate analyzed by FEM-EDX.

Abstract: The chemical composition and the valence state of elements on the surface of ZrO2 thin films deposited on glass substrates have been studied by X-ray photoelectron spectroscopy. Results show that: elements of Na, Mg, Zr, Ca exist in the form of their respective stable state, such as Na2O, MgO, ZrO2, CaO, when heat treated at 500°C for 0.5h; but Si is unstable, and exhibit stoichiometrical disturbances. Results of chemical composition and their content by atom percent of ZrO2 thin films surface reveal that: Si, and Ca diffuse from glass to the thin films in scale; Na diffuses few and Mg collects to the thin films surface. The diffusion of Mg2+ and Ca2+ from glass to ZrO2 thin films is negative diffusion.

Abstract: The influence of heat-treated temperature and the CeO2 content on the chemical composition and the valence state of elements on surface of ZrO2-CeO2 thin films deposited on metal substrates has been studied by X-ray photoelectron spectroscopy. Results show that: elements of Fe, Cr, Zr, Ce exist in the form of their respective stable state, such as Fe2O3, (Fe0.6Cr0.4)O3, ZrO2, CeO2, when heat treated at 600°C and 700°C for 2h respectively; with the increase of heat-treated temperature, the area of oxygen with O1s peak corresponding to value of bonding energy 529.28ev increases, but the area of oxygen with O1s peak corresponding to value of bonding energy 531.7ev decreases.

Abstract: X-ray diffraction (XRD) method to measure the residual stress existing in the metal substrate surface layer was introduced and the sol-gel ZrO2-CeO2 thin film was successfully prepared on SUS304 stainless steel substrate by dip-coating process. The macro residual stress existing in metal substrate was analyzed by XRD. It turns out that the compressive stress existing in the metal substrate surface layer increases with the increase of heat-treated temperature. Based on the above study, colored stainless steels of high quality were prepared by sol-gel process.