Papers by Author: Yong Huang

Abstract: Freeze casting is a useful forming technique to produce complex-shaped ceramic parts. The colloidal processing stage is an essential step for preparation of freeze casting slurries. In order to optimize freeze casting slurries, several processing additives, such as dispersant, binder, surfactant, and cryo-protectant are usually employed. Dispersion and suspension rheology of aqueous alumina/ zirconia slurries with 55 and 60 vol.% solid loading have been characterized in terms of the effect of organic additives, and the resulting microstructures of the freeze cast green and sintered materials examined.

Abstract: The effects of solid volume fraction (SVF) on the gelation of alumina suspensions for gelcasting, debonding and sintering of the green body were studied. It was found that with SVF rising, the gelation of alumina suspension delayed; and the strength of green body decreased. On the other hand, high SVF resulted in that polymerized acrylamide split at a relative low temperature. These phenomena manifest that the fast polymerization of monomers in high SVF alumina suspension was inhibited, and the flexibility of the gelcasting was improved. However, Excessive solid volume fraction was prone to a bad rheological behavior of alumina suspension, and deteriorated the microstructure and properties of sintered body.

Abstract: Rheological behaviors of alumina aqueous suspension were investigated, and some methods to modify the rheological behaviors of the suspensions were studied. It was found that there is a critical solid volume fraction for alumina aqueous suspensions. When the volume fraction reaches or exceeds the critical value the suspensions show shear thinning behaviors all along, while above which the rheological behaviors of alumina suspensions change from shear thinning to shear thickening.

Abstract: Zirconia suspensions with coarse particles were prepared and the rheogical behavior and sediment stability of such suspensions with different dispersants were studied. It was found that ZrO2 suspension stabilized with TAC (tri-ammonium citrate) has an obvious shear-thinning behavior and rapid settlement; In contrast, the suspension stabilized with arabic gum shows a shear-thickening behavior and hardly any settlement. Considering both fluidity and settlement stability, APA (ammonium-polyacrylate) was chosen as the dispersant to increase the solid volume fraction of ZrO2 suspension. Utilizing the above suspension, a kind of refractory nozzle for precision casting of a Cu-Cr alloy was prepared by gelcasting. Such nozzle has a very good resistance to thermal shock and flux scouring.

Abstract: In this paper, a W/O microemulsion system composed of cyclohexane / water / TritonX-100 / hexyl alcohol is adopted to prepare ultrafine spherical zirconia powder via the reaction between the precipitant and zirconium salt solved in the nano reactors. Furthermore, the powder’s surface characteristics and aqueous dispersibility that strongly depends on the post-treatment process are investigated thoroughly.

Abstract: As a good binder for aqueous Al2O3 suspensions tape-casting process, a commercial styrene-acrylic latex binder had been investigated. This paper studied on the rheological behaviors of the suspensions and drying process of aqueous slurries with latex binder system, and the research results indicated the rheological behaviors was affected by pH value, solid loading and dispersant (PAA-NH4) additives; and the drying speed of slurries was most decided by drying temperature and slurry coating thickness.

Abstract: In the industrialization of gelcasting, storage of ceramic slurry has been one of the key problems that must be solved. Except for sedimentation of ceramics particle, solidification properties of slurries were also affected after long-term storage. In this article, some factors in the process of slurry were discussed, and corresponding solution methods were put forward.

Abstract: Colloidal injection moulding of ceramics (CIMC) is a new ceramic forming technique that combines the advantages of gelcasting and injection moulding. It can inject nonplastic slurry into the mould and solidification course of ceramics slurry can be controlled by both temperature and pressure. Quick mixing technique ensures that ceramic slurry will not be solidified before casting. The equipment of CIMC was designed and developed. High performance ceramic components with complex shape have been manufactured by this equipment.

Abstract: Preparing Superconducting Bi-2223 films by dip-coating method is innovative and valuable. The advantages of this technique are low cost and precise stoichiometric. Controlling the evaporation of Pb efficiently can improve the formation of Bi-2223 phase. Textured BSCCO superconductors are studied and a mechanism for alignment of BSCCO grains addressed.

Abstract: The b–Si3N4 whisker randomly and unidirectionally reinforced Si3N4 composites were fabricated respectively. The high whisker alignment was obtained by extrusion processing. The R-curve behaviors were studied for the Si3N4 ceramics with addition of 3wt%, 5wt% and 10wt% b–Si3N4 whisker seeds respectively, and the effects of whisker orientation and content on the R-curve behaviors were analyzed and discussed. The ceramics with different whisker content and orientation showed well-defined R-curve behaviors. However, for the whisker random distribution, as its whisker content increased from 3wt% to 10wt%, the corresponding fracture toughness changed at an irregular trend; for the whisker unidirectional reinforcement, the fracture toughness in the direction perpendicular to whisker alignment was considerably improved, and most of indentation impressions tend to be very abnormal. The effects of whisker orientation and contents on the R-curve behaviors of the Si3N4 ceramics were further discussed.