The yttria stabilized zirconia, ZrO2 (Y2O3) has been widely used in dental prosthesis manufactured by CAD/CAM technique. This material is developed in the form of pre-sintered blocks, which are machined by extracting various customized prosthesis and generating a loss of about 30% of material. ZrO2(Y2O3) is notably a toughening for other ceramics, and has a high cost, so reusing discards these applications less noble, is strategically interesting. In this work the proposal is to recover discharges of ZrO2 (Y2O3) arising from prosthetic laboratories, reprocess them in order to reduce the particles size and subsequently sintering, demonstrating the potential use in applications less noble in dentistry. Discharges Residual of ZrO2-(Y2O3) were fragmented and then sieved to particle size separation. Powders of smaller than 63 μm were uniaxially pressed at different pressures. The compacts were characterized by the relative density showing green density of the order of 40%. After characterization, compacts were sintered at 1550°C-2h. The sintered material was characterized as its relative density and crystalline phases.

In this work, compacting powders of different ZrO2(Y2O3) are investigated relating the particle size, compaction pressure, and use of binders. Powders of ZrO2 stabilized with 3mol % Y2O3 with an average particle size of 0.15 to 0.7μm presence of both bonding and 0.15μm without addition of binder, were uniaxially compacted with pressures of 30 to 115MPa. Green density between 40% and 50% were obtained. The results indicate that powders sized less densification above 1400°C, while the larger sizes only after reaching full densification above 1500°C. Crystallographic characterization indicates that the powders have a percentage of monoclinic phases in the range of 15% to 26%, but only after sintering tetragonal phase is identified.

ZrO2(Y2O3)-based ceramics with coloring gradient can facilitate the development of dental prosthesis by the improvement of esthetic properties. In this work, ZrO2 powders with different particle sizes were investigated. White and yellow zirconia powders (TOSOH Corporation-Japan) were characterized by particles size distribution using nanoSight-LM20 analyzer. Furthermore, samples were characterized by X-Ray diffraction, Scanning Electron Microscopy and relative density. Compacts with two layers, one white and one yellow were uniaxially pressed at 80MPa and sintered at 1530°C-120min. The yellow-powder presented average particles size of 180±66nm, while the white-powder presented particles size of 198±73nm. After sintering, full dense ceramics with tetragonal phase were obtained. The linear shrinkage of the yellow and white-layer was 22.75% and 22.05% respectively. This difference in shrinkage is important in the machining of prostheses in ceramic CAD/CAM systems, because they lead to difficulties in adapting this customized prosthesis in patients.

In this work, the preparation of Al2O3-TiO2 ceramics by high-energy ball milling varying the molar fraction in 1:1 and 3:1 was investigated. The powder mixtures were processed in a planetary mill at 250rpm and a ball-to-powder weight ratio of 5:1, for 120min. Compacts were obtained by cold pressing at 100MPa. These specimens were heated at 1000◦C for 30min to promote the water evaporation, and subsequently sintered at 1500◦C for 240min. Samples were characterized by relative density and X-ray diffraction. Hardness and fracture toughness were determined by Vickers Indentation Method. The crystallite sizes were lower than 420 and 560Å in Al2O3-TiO2 and 3Al2O3-TiO2 powders, respectively. After sintering, XRD analysis indicates Al2TiO5 and Al2O3/Al2TiO5 as major crystalline phases for Al2O3-TiO2 and 3Al2O3-TiO2 compositions, respectively. The relative density of the Al2O3-TiO2 ceramics was higher than 90% in both compositions. However, hardness and fracture toughness results of 10.7GPa or 10.5GPa and 3.2MPa.m1/2 or 2.6MPa.m1/2 for Al2O3-TiO2 and 3Al2O3-TiO2 mixtures respectively, indicates that microstructure duplex composed by Al2O3 and Al2TiO5 grains lead to improvement of toughness of these ceramics.