Inter-particle interactions of alumina powders in UV-curable suspensions for DLP stereolithography and its effect on rheology,solid loading,and self-leveling behavior

For the UV-curable alumina suspensions used in digital light processing (DLP) stereolithography, optimizing the dispersant type is important for achieving low viscosity, high solid loading, and remarkable self-leveling behavior. However, the inter-particle interactions in UV-curable alumina suspensions dispersed using different dispersants are overlooked. Herein, the effect of inter-particle interactions on rheology, solid loading, and self-leveling behavior of UV-curable alumina suspensions was systematically investigated. Three different commercial dispersants were used: oleic acid (OA), alkane-acrylic phosphate ester (PM1590), and copolymer dispersant (BYK111). After dispersing, BYK111 endowed alumina powders with thicker adsorption polymer layer to provide stronger steric repulsion force and facilitated better wetting of alumina powers in the photocurable resin, resulting in a reduced network structure degree, which decreased the viscosity (1.04 Pa s at 30 s^?1); homogeneous packing of alumina powders, which enhanced the maximum solid loading (55 vol%); and inhibition of particle flocculation, which facilitated the spontaneous spreading of suspension.     

Gluconate action in the hydration of calcium aluminate cements: Theoretical study,processing of aqueous suspensions and hydration reactivation

Considering the production of stable CAC aqueous suspensions, this work addressed the action of gluconate anion as a Ca²⁺ complexing agent and retarder of CAC hydration. Using quantum simulations, the complexation energy of gluconate complexes was calculated. The pH range of stability for the complexes was estimated and aqueous suspensions containing CAC and sodium gluconate (NaG), stable up to 4 days at room temperature, were prepared. Afterwards, their hydration reactions were reactivated by adjusting the systems’ pH. Results of solidification kinetics and mineralogical characterisation highlighted that, after reactivation, calcium aluminate hydrates were formed. Thermodynamics simulations indicated that using NaG up to 1 wt% would not be deleterious to the systems refractoriness up to 1700 °C. These systems could be applied in less explored processing routes for CAC-based refractory compositions (e.g. slip casting, direct foaming and additive manufacturing), resulting in innovations to produce advanced refractory ceramics.     

The formation of core-sheath structure and its effects on thermal decomposition and crystallization of alumina fibers

Thermal decomposition is a critical process for fabricating alumina fibers using sol-gel methods. In this work, effects of preheating time on microstructure of prepared alumina fibers were studied. Results showed that core-sheath structure formed in the fibers when holding time exceeded 2 h at 400 °C. The fibers having core-sheath structure after thermal decomposition showed more residues, smaller crystal grain size and lower density. Thermal decomposition and densification of fibers were investigated. Results showed that core-sheath structure formed because fiber surface and core underwent different decomposition reactions due to the reduction in the number of gas channels on the fiber surface. This work provides a comprehensive study of thermal decomposition of precursor fibers and provides guidelines for developing appropriate calcination schedules.     

Study on fiber structure formation in wet spinning of aliphatic polyketone using aqueous solution of complex metal salts—Characteristics of solid structure formation in drying step and its effects on superdrawing step

Solid structure formation in the drying step for wet spinning of poly(1‐oxotrimethylene) using as a solvent an aqueous solution of complex metal salts of calcium chloride/zinc chloride was studied. Because the degree of structural densification and the crystal structure both differ depending on the drying temperature, the drying temperature had a major effect on the drawing behavior and the strength achieved after drawing. With higher drying temperature, the denseness increased due to smaller voids in the dried undrawn fiber, while there was also a tendency toward higher strength with respect to the draw ratio. However, an excessively high drying temperature altered the crystal structure from a rough crystalline form to a dense crystalline form and reduced both the maximum draw ratio and strength. Mechanical cleavage of the molecular chains occurred between the ethylene groups and carbonyl groups of the main chains in the drawing step. This cleavage made it possible to suppress the inhibition of drawing due to entanglement of the molecular chains, thereby enabling superdrawing to afford a high performance fiber. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 446–452, 2004