Papers by Author: Hai Ping Cui

Abstract: Nano-TiO2/micro-Cu composite particles were prepared by peptization method using Ti(OBu)4 and SnCl2•2H2O as the raw materials. The effect of the content of HNO3 on the morphology and composition was investigated. The results showed that when the mole ratio of HNO3 and Ti(OBu)4 was 0.5:1, about 100nm TiO2 of amorphous phase grew on the surface of Cu forming strawberry like particles. When the mole ratio of HNO3 and Ti(OBu)4 was 1:1, Cu powders were coated with TiO2 crystals of several nanometers in size, meanwhile particles of several microns in size was absorbed on the Cu surface, which can be easily removed by water cleaning. The possible mechanism was discussed in the end.

Abstract: Nano-TiO2/micro-Cu composite particles were prepared by hydrolysis of Ti(OBu)4 in abundant acidic aqueous solution and subsequent reflux in the presence of micron size Cu powders. The preparation process was optimized using response surface design with the degradation of TiO2/Cu particles to Methyl orange as target. The particle morphology and composition were characterized by FE-SEM, XPS and XRD. The photon absorption properties of composite particles was investigated by the UV-VIS DRS experiments, and the results show the photoabsorption property of composite particles is intermediate between TiO2 particles and Cu powders, showing cooperative effect by the combination of oxide semiconductor particles with metal substrate.

Abstract: 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.

Abstract: Molybdate conversion coatings were prepared on the anodized surfaces of aluminum alloy substrates, and the corrosion resistance in 3.5% NaCl solution was also investigated. The effects of the main parameters on the quality of the coatings were discussed. The morphology and chemical composition of the conversion coatings was examined by SEM and EDS. SEM observation showed that the coatings were composed of small sheet grains with tiny cracks between them. EDS analysis showed that the main element of the coatings was molybdenum. The results of polarization curve showed that the coatings effectively inhabited the pitting corrosion of aluminum alloy substrates. In the end the possible conversion mechanism was discussed.

Abstract: Amorphous titania coatings on copper particles were prepared by using tetrabutyl titanate to improve the anticorrosion property. The coated particles were characterized by SEM, EPMA and XRD. Experimental results showed that the resistance to oxidation of the coated copper particles depended on the stability and content of the sol. The proper pH value for the sol was about 4, and the ratio of tetrabutyl titanate and water was 1 to 2. The transmissivity of the etching solution of coated copper particles in 5% of H2SO4 was more than 80%, showing that the TiO2 coatings on copper particles exhibit an excellent corrosion resistance.

Abstract: Al2O3-Al2Cu3 multiphase coatings were prepared on the surface of steel by reactive flame spray. The binding strength, microhardness and abrasion quality of the coatings were measured and analyzed. The influence of the agglomerate size on the properties of the coatings was emphatically studied to choose suitable size range for Al-CuO reactive system. The results showed that coatings prepared by using –150∼+250 meshes agglomerates exhibited good mechanical properties.

Abstract: 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.

Abstract: 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.

Abstract: This research focus on the technology of copper chemical plating on Al-CuO agglomerated powders with the size of 150-200µm. Orthogonal design is employed to gain the optimized formula, and the quality of the cladding was analyzed by means of SEM and EPMA. The results show that the cladding is uniform and the Al-CuO powders are primarily coated by copper.

Abstract: The effects of two silane coupling agents (KH550, KH570) and three coupling agents of organic titanate (JSC, CT136 and NTC401) on the surface modification of superfine Al2O3 powders were tested and compared. The results showed that three coupling agents of organic titanate succeeded in modify the surface of Al2O3 particle from hydrophilic property to lipophilicity, while two silane coupling agents failed. The group changes of the surface were confirmed by IR spectrum, which also indicated that chemical absorption occurred between NTC401 and the powders surface, but for JSC and CT136 mainly occurred physical absorption. SEM photos of the powders showed that agglomeration-free particles could be obtained when the powders were treaded by NTC401. However, when treated by JSC or CT136 the powders tended to be secondly agglomerated. The proper coupling mechanism was analyzed, and it was thought that space structure of octahedral complex of titanium ion with six ligands could effectively impede agglomeration.