In this paper the surfaces of Al2O3 fine powders with average size of 500nm were modified by heterogeneous azeotropic distillation process. IR spectrums of the powders show that the distillation can effectively dehydrate hydrous Al2O3 powders, and succeed in substituting the hydrate water with butanol molecular. The dispersion of Al2O3 powders in epoxy resin is improved remarkably, which is observed by means of SEM. Experimental results show that abrasion property of
the resin filled with modified Al2O3 powders is improved.
Based on the SEM observation on cracks in lined ceramics of the composite pipes, the stress fields in lined ceramics were analyzed. The results indicated that there are the compressive field and heat stress field in lined ceramics, resulting in the existence of radial cracks and net cracks; besides being influenced by wall thickness of ceramic layer, the strength of compressive stress field is also dependent on bonding strength between metal and ceramics, and the strength of heat stress field is dependent on temperature gradient in lined ceramics during cooling of the ceramics.
The surface micro-topography of micro-WEDM is random, disordered and multi-scale and has been proved that it is fractal with the characteristic of self-affinity within a certain scale on the basic of the fractal geometry theory. According to the characterization of W-M fractal function, the principles of three evaluation methods about power spectrum method, structure function method and wavelet criterion have been described. The advantages and disadvantages of them evaluating the fractal property of the surface micro-topography of micro-WEDM have been compared in this paper. The experimental results indicate that the wavelet criterion is more stable and dependable than the other two methods, so the fractal dimension D of the surface micro-topography of micro-WEDM has been calculated using it. The result shows that the fractal dimension has the tendency of decrease with the increase of root mean square deviation (Sq) value while it is not absolutely monotonic, which can be used as a beneficial supplement to traditional evaluation parameters of surface roughness.
Micro wire electrical discharge machining (Micro-WEDM) is one key micro-processing technology for intricate micro parts. The surface texture is different with a single mechanical cutting surface and conventional spark-erosion formation machined surface. Assessment of the existing surface texture roughness parameters in terms of accuracy, or in the characterization of fine sense, can not meet the Micro-WEDM surface texture characterization needs. Through the analyses of surface autocorrelation function, structural shape ration, steepest attenuation autocorrelation function and surface texture direction, explicit the precise meaning of surface texture parameter characterization, make it really reflect the actual condition of Micro wire electrical discharge machining surface, modify Characterization Parameter algorithm, simplify the calculation process, make the results more accurate and more intuitive. Keywords: Micro wire electrical discharge machining; autocorrelation function; surface texture
Raspberry-like TiO2/Cu composite particles were prepared under mild conditions (75°C and
ambient pressure) by hydrolysis of Ti(OBu)4 in acidic aqueous solution and subsequent reflux in the
presence of micron size Cu powders. A 3-level and 4-factor design was employed to evaluate the effect of
the main parameters on the coating quality. TiO2 particles of approximate 100nm in size were found
coating on the surfaces of Cu powders to form raspberry-like structure. Ti and Cu element mainly existed
on the composite particle surface as the chemical state of Ti4+ and Cu2+. TG-DTA analysis showed the
TiO2 coating increased the thermal stability of Cu particles. The composite particles began oxidizing at
400°C while pure copper particles oxidized at 200°C.
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