Manipulating Composition And Properties Of Ceramics Via Solution Precursor Infiltration Technique

Liquid precursor infiltration technique is capable of introducing dopants with highhomogeneity, realizing surface modification, manufacturing of composite and gradientmaterials. By immersing green body with open porosities in the liquid containingmodifying components, the liquid would migrate along the interconnected porousstructure into the inerior part of the preform, achieving manipulation of thecomposition and properties of the material. This study is mainly focused onapplication of infiltration technique in several materials. Various ceramic materialswith obviously improved microstructure and properties have been fabricated. Theadvantages and disadvantages of both infiltration and the conventional ceramicprocessing technologies have also been contrastively studied.Firstly, ceramic parts have been developed by infiltrating aqueous solutionscontaining coloring ions into the water-debound green bodies prepared by ceramicinjection molding. Our strategy provided a general approach to the preparation ofcolored ceramics. The fabricated colored zirconia ceramics exhibits a macroscopiccore-shell structure with tunable thickness. Besides, the drying process influences theinfiltration rate by controlling the mass transferring mechanism. By adding ethanol tothe aqueous solution, the problem of applying infiltration to the hydrophobic greenbodies has been solved.ZTA composites have been prepared by cyclic infiltration and in-situ precipitationtechnique. The fabricated material contains fine-sized, well-distributed ZrO₂grainsthroughout the bulk matrix. Compared with the conventional ball-milling approach,infiltration prepared material successfully inhibits the abnormal grain growthphenomenon at a ZrO₂content （2.3vol%） lower than the previously reported criticalvalue （5vol%）. By adjusting the drying temperature after precipitation, thedecomposition behavior of zirconium-containing precipitates could be controlled,thereby adjusting the ZrO₂content introduced via infiltration.The next section investigates factors influencing the amount of exotic components,distribution profiles and so forth. It is found that reducing the solution concentration,diminishing the size of green body and imposing assisting mechanisms which favor the evacuation of entrapped gas within the green compact is beneficial for achieving ahigh infiltration efficiency and enhanced homogeneity. The results indicate thatinfiltration is especially suitable for doping small-sized ceramic green bodies withlow-content exotic elements, achieving good distribution homogeneity and precisecontrol of the introduced amount.The last part is focused on preparing translucent alumina ceramics via infiltrationand H2sintering. Different from the conventional strategies of introducing dopants inthe ball-milling stage, pure alumina preforms were infiltrated using aqueous nitratesolutions. Infiltration prepared composites exhibit much improved homogneity ofintroduced sintering additives and finer microstructure. The sample containing500ppm MgO has an average grain size of only approximately7μm, flexural strengthof about300MPa, exhibiting much enhanced optical properties over the ball-millingprepared counterpart. Triple doping proved to be more beneficial for achieving highertransmission properties.