A new experimental measurement of residual stresses around Vickers′ indentations on the surface of the SiC/Al 2O 3 nanocomposites is proposed with the aid of a Raman microprobe. Results s how that the shifts of R...A new experimental measurement of residual stresses around Vickers′ indentations on the surface of the SiC/Al 2O 3 nanocomposites is proposed with the aid of a Raman microprobe. Results s how that the shifts of R lines in the fluorescence spectra va ry with the distance from the centre of indentation. The magnitude of load appli ed on the surface of the materials through the indenter influences the shifts of R lines to great extent. The luminescence of R lines of the materials before indenting is used to determine the residual stresses around the indentation in the materials, assuming that the stress tensor is transversely isotropic. Final ly, the term of hydrostatic stress is adopted to explain and compare different residual stresses around indentations with the increase of the indenting load an d the distance from the centre of indentations. <展开更多
The rheological behavior and gelcasting of composite suspensions of SiC and synthesized Al 2O 3-Y 2O 3-La 2O 3 powder as sintering aid were investigated. It was found that the rheological behavior of SiC particles cou...The rheological behavior and gelcasting of composite suspensions of SiC and synthesized Al 2O 3-Y 2O 3-La 2O 3 powder as sintering aid were investigated. It was found that the rheological behavior of SiC particles could be modified with a slightly oxidized surface that was similar to silica in colloidal behavior. The smaller the particles were, the more similar to silica the SiC powder was. The pH value of Al 2O 3-Y 2O 3-La 2O 3 synthesized powder slurry at isoelectric points (IEP) is higher than that of SiC powder. The dispersant PAA-NH 4 changes the IEP of both SiC and Al 2O 3-Y 2O 3-La 2O 3 powder slurry to higher pH values. The experimental results indicate that the composite suspension could possess satisfactory stability and lower viscosity at pH =10.1 and PAA-NH 4 as dispersant. The optimum solid loading was 550 0 in volume. Machinable green bodies with uniform complex shape are gained after molding.展开更多
A unique SiC whisker wheel was invented,in which the whiskers were aligned normally to the grinding wheel surface.In this paper,grindabilities of the SiC whisker wheel are investigated and compared with those of other...A unique SiC whisker wheel was invented,in which the whiskers were aligned normally to the grinding wheel surface.In this paper,grindabilities of the SiC whisker wheel are investigated and compared with those of other wheels of SiC grains,Al2O3 grains,as well as Al2O3 long and short fibres which were also aligned normally to the grinding wheel surface,respectively.The main research contents concern grinding characteristics of a directionally aligned SiC whisker wheel such as material-removal volume,wheel-wear rates,integrity of the ground surfaces,grinding ratios and grinding efficiency.Furthermore,grinding wheels of whiskers and fibres have a common disadvantage:they tend to load easily.The authors have proposed a simple method of loading-free grinding to overcome this propensity and investigate some related grinding characteristics under loading-free grinding conditions.展开更多
文摘A new experimental measurement of residual stresses around Vickers′ indentations on the surface of the SiC/Al 2O 3 nanocomposites is proposed with the aid of a Raman microprobe. Results s how that the shifts of R lines in the fluorescence spectra va ry with the distance from the centre of indentation. The magnitude of load appli ed on the surface of the materials through the indenter influences the shifts of R lines to great extent. The luminescence of R lines of the materials before indenting is used to determine the residual stresses around the indentation in the materials, assuming that the stress tensor is transversely isotropic. Final ly, the term of hydrostatic stress is adopted to explain and compare different residual stresses around indentations with the increase of the indenting load an d the distance from the centre of indentations. <
文摘The rheological behavior and gelcasting of composite suspensions of SiC and synthesized Al 2O 3-Y 2O 3-La 2O 3 powder as sintering aid were investigated. It was found that the rheological behavior of SiC particles could be modified with a slightly oxidized surface that was similar to silica in colloidal behavior. The smaller the particles were, the more similar to silica the SiC powder was. The pH value of Al 2O 3-Y 2O 3-La 2O 3 synthesized powder slurry at isoelectric points (IEP) is higher than that of SiC powder. The dispersant PAA-NH 4 changes the IEP of both SiC and Al 2O 3-Y 2O 3-La 2O 3 powder slurry to higher pH values. The experimental results indicate that the composite suspension could possess satisfactory stability and lower viscosity at pH =10.1 and PAA-NH 4 as dispersant. The optimum solid loading was 550 0 in volume. Machinable green bodies with uniform complex shape are gained after molding.
文摘A unique SiC whisker wheel was invented,in which the whiskers were aligned normally to the grinding wheel surface.In this paper,grindabilities of the SiC whisker wheel are investigated and compared with those of other wheels of SiC grains,Al2O3 grains,as well as Al2O3 long and short fibres which were also aligned normally to the grinding wheel surface,respectively.The main research contents concern grinding characteristics of a directionally aligned SiC whisker wheel such as material-removal volume,wheel-wear rates,integrity of the ground surfaces,grinding ratios and grinding efficiency.Furthermore,grinding wheels of whiskers and fibres have a common disadvantage:they tend to load easily.The authors have proposed a simple method of loading-free grinding to overcome this propensity and investigate some related grinding characteristics under loading-free grinding conditions.
