Papers by Author: Xue Feng Xu

Abstract: The inclusion complex of β-cyclodextrin (β-CD) and dibutyl phosphite (T304) was prepared by trituration. The tribological properties of the complex with different concentrations were investigated by a four-ball tester in the solution of polyethylene glycol-600 (PEG-600). The tribological test results showed that the complex exhibited better anti-friction and anti-wear properties than β-CD under different loads, and it was noted that the tribo-system showed the least friction coefficient when the concentration of the complex was 0.9%. It was proposed that the complex was decomposed into various molecular fragments and the T304 molecules were released under the friction condition. The XPS analytical results on the worn surfaces revealed that phosphide film formed by the released T304 played a major role and the iron alkoxide and carbon deposition films formed by the β-CD fragments had better anti-friction effect on the phosphide film surface. The interactions of different films resulted in the formation of a mixed boundary lubrication film.

Abstract: With butyl stearate (BS) as the core material and melamine-formaldehyde resin (MF) as the wall material, BS-MF resin microcapsules were synthesized under in situ polymerization method. The microcapsules were characterized using FTIR, SEM and other methods. The four-ball friction method was performed to test the tribological property of the microcapsules when polyethylene glycol was taken as the base fluid. The results showed that base fluid with 3% microcapsules had a friction coefficient as small as 0.053 and the wear scar diameter could be 0.326mm (4%) under 314N. The microcapsules were ruptured under the action of friction and then the reactive group formed physical adsorption film. The physical adsorption film, together with the subsequently formed friction polyester film, presented a synergistic lubricating effect.

Abstract: The complex of β-cyclodextrin (β-CD) and RC2540 dialkyl pentasulfide was synthesized and characterised by means of fourier transform infrared spectroscopy (FTIR), thermo-gravimetric analysis (TG) and scanning electron microscope (SEM). Then the friction and wear behavior of RC2540, β-CD and complex were studied by four-ball test using the mixture of PEG-600 and water as base fluid, and finally the lubrication mechanism of β-CD and the complex were analyzed using energy-dispersive X-ray spectroscopy (EDS). The experimental results revealed that the complex had formed well and had better antifriction and anti-wear property than β-CD. RC2540 in complex was released and the extreme pressure film was formed on the friction interface in the friction process. The β-CD molecules in complex were cracked into fragments, and the fragments with hydroxyl also formed lubricating film and fragments with no hydroxyl were mainly carbonized. The lubricating film of the complex had a better tribological performace due to the cooperation of the lubricating film of β-CD and extreme pressure film of RC2540.

Abstract: The grinding wheel will have a property of self-lubricating when the inclusion complexes of β-cyclodextrin (β-CD) and oleic acid are used as filler. The association constants and thermodynamic parameters of inclusion complex of β-CD and oleic acid were determined by competitive inclusion method in aqueous buffer solution (pH = 10.50, c = 0.025 mol/L) at different temperatures using phenolphthalein (PP) as a probe. Furthermore, the stoichiometric ratio of the complex was derived by equimolar series method. The results showed that the stoichiometric ratio of the complex was about 1:1 and the thermodynamic parameters of ΔG, ΔH and ΔS were all negative, which indicated that the formation of the inclusion complex was spontaneous, exothermic and enthalpy-driven. Thermogravimetric analysis revealed that the complex began to have a weight loss at 300°C and could withstand the hardening temperature of resin bond grinding wheel.

Abstract: A novel technology is studied in this paper to make photosensitive resin grinding wheel based on layered manufacturing technology. The bond strength among resin layers is analyzed. An effective measure is proposed to improve the bond strength among resin layers of the grinding wheel. We add magnetic abrasive particles into the liquid resin to get rough surface and increase contact area by action of magnetic force. Some experiments are curried out for testing shear strength of resin with magnetic abrasive under different conditions. Results show that this method had a significant effect in improving the bond strength among layers of new grinding wheel.

Abstract: In this paper, the adsorption characteristics of cationic polyelectrolyte PDADMAC on BGF particles and the Zeta potential of BGF particles have been investigated. A new type of composite abrasives slurry was obtained with cationic polyelectrolyte modified BGF particles and its polishing performance was studied. Experimental results showed that the Zeta potential of the modified BGF particles was changed from negative to positive and the maximum value (+35mv) was obtained when the adsorption saturation was achieved, and the adsorption capacity of SiO2 abrasives on BGF particles was improved significantly. The material removal rate was 469nm/min with the modified BGF/SiO2 composite abrasives slurry containing 5% SiO2 and 3% modified BGF particles, increasing by 47% and 89% than those of the unmodified BGF/SiO2 composite abrasives slurry (319nm/min) and the single silica abrasives slurry (248nm/min), respectively.

Abstract: In this paper, the adsorption characteristics of cationic polyelectrolyte PDADMAC on BGF particles and Zeta potential of BGF particles have been investigated. A new type of composite abrasive slurry was obtained with cationic polyelectrolyte modified BGF particles and its polishing performance was studied. Experimental results showed that the Zeta potential of the modified BGF particles was changed from negative to positive and the maximum value (+35mv) was obtained when the adsorption saturation was achieved, and the adsorption capacity of SiO₂ abrasives on BGF particles was improved significantly as well. The material removal rate was 469nm/min with the modified BGF/ SiO₂ composite abrasives slurry containing 5% SiO₂ and 3% modified BGF particles, increasing by 47% and 89% than those of the unmodified BGF/SiO2 composite abrasives slurry (319nm/min) and the single silica abrasives slurry (248nm/min), respectively.

Abstract: In order to increase the material removal rate of silicon wafer, composite abrasives slurry was used in CMP. Zeta potential of polymer particle was measured and interaction potential energy between silica abrasives and polymer particles in slurry were analyzed and calculated. Adsorptions between silica abrasives and polymer particles were observed with TEM. CMP experiments had been taken to analyze the effects of polishing parameters (the concentration of colloidal silica and polymer particle, the pressure and the speed of polishing) on the material removal rate. The mechanism of polymer particle in polishing was elaborated. Experimental results indicated that PS, PMMA and BGF polymer particles could adsorb silica abrasives in slurry. Silica shell/PS core, silica shell/PMMA core and silica shell/BGF core particles could be used to formulate composite abrasives slurries. The material removal rate with composite abrasives slurry was higher than that of single abrasive slurry. The maximum material removal rate was obtained with silica shell/BGF core composite abrasives slurry.

Abstract: In order to increase the material removal rate of silicon wafer, composite abrasives slurry was used in CMP. The mechanism of interaction between silica abrasives and polymer particles was analyzed. Small silica abrasives were seen to attach onto the surface of the polymer particles. Composite abrasives slurry was obtained by adding polymer particles into single abrasive slurry. Three key parameters, the concentration of colloidal silica, the concentration of polymer particle and the speed of polishing, which influence the material removal rate of silicon wafer were analyzed by Taguchi method and the optimal parameters were obtained. Experimental results indicated that the maximum material removed rate of 353nm/min was obtained when optimal craft parameters of 5% colloidal silica, 3% polymer particle, 50rpm plate and carrier rotation speed were selected.

Abstract: In this paper, mixed slurries containing silica abrasives and polystyrene (PS) polymer particles in deionized water at pH 10.5 have been evaluated for silicon wafer polishing. By applying the theory of electric double layer model, the effect of the particle interactions in mixed slurry is investigated. Zeta potential measurements and TEM images have been used to show the formation of composite particles. The polishing mechanism with composite particles slurries is discussed. Polishing experiments with the mixed slurries formed by coating smaller (~30nm) abrasives onto softer and larger (~2000nm) polymer particles have shown the superior characteristic with higher removal rate and high surface quality.