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Adding plasticizer is an efficient way to regulate the rheological behavior of ceramic paste and quality of green body in stereolithography-based additive manufacturing. The type and content of plasticizers (polyethylene glycol (PEG) and dibutyl phthalate (DBP)) had substantial effects on the rheological behavior and solid loading of ceramic paste, leading to varied macro / micro structure and strength of the green and sintered parts. DBP significantly reduced the viscosity and increased solid loading, and could adjust the flexibility of the green body by reducing the crosslinking density of UV curing system. PEG could inhibit crack initiation to some extent, but it was less effective for preventing cracking than DBP on ceramic parts with large-sized cross sections. It was concluded that DBP was more suitable as a plasticizer in alumina paste for SL additive manufacturing to form dense parts without defects. [ABSTRACT FROM AUTHOR]

The mechanical property of advanced ceramics by additive manufacturing through layer‐by‐layer processing and subsequent sintering has been employed as a key basis for optimizing the processing and developing future application. 3Y‐TZP ceramic was fabricated by stereolithography‐based additive manufacturing, and the mechanical properties were investigated by nanoindentation and microscratch testing. The microscopic mechanism and evolution of surface deformation and damage induced by scratching were revealed by scanning electron microscopy and surface interferometer. Results showed that the nanoindentation hardness and elastic modulus were comparable to those of conventional process. With the increase in the applied normal load, the scratch‐induced damage followed three sequential stages, that is, plastic plowing, microcracking and surface spalling. The magnitude of the microcracks nucleated during scratching depended on the applied normal load. Concerning the homogeneity and integrity with the sintered parts without delaminated cracks and pores, the evolution of surface damage was discussed in different stages. It was concluded that the layer‐by‐layer process did not affect the characteristic of microcracking evolution. [ABSTRACT FROM AUTHOR]

This paper considers two novel controller synthesis methodologies using a feedforward control structure for performing concentric self-servo track writing in hard disk drives. In the first methodology, it is assumed that a conventional causal track-following controller has been designed and a non-causal feedforward controller, which utilizes the stored error signal from writing the previous track, is designed using standard H\infty control synthesis techniques, in order to prevent the track errors from propagating and to achieve good disturbance attenuation. In the second methodology, both the track-following feedback controller and the feedforward controller are simultaneously designed via a mixed H2/H\infty control scheme, which involves the solution of a set of linear matrix inequalities and achieves good disturbance attenuation while preventing the propagation of track errors from the previous tracks. Simulation results confirm that the two proposed control synthesis methodologies prevent error propagation from the previously written tracks and significantly improve concentric self-servo track writing performance. [ABSTRACT FROM AUTHOR]

Improvement of the mechanical properties of advanced ceramics fabricated by additive manufacturing has been a prerequisite for their wide applications. In this work, zirconia-toughened alumina (ZTA) parts with a variety of yttria-stabilized zirconia (YSZ) content were fabricated by stereolithography (SL) technology, based on the appropriate self-holding ability of the viscoelastic paste and application of conformal contactless support strategy. Combining microstructural analysis and mechanical assessment by three-point bending and indentation tests, the influence of YSZ content on the SL process and subsequent mechanical properties was discussed. The results showed that the optimized matching of flexural strength (477.54 MPa) and fracture toughness (6.56 MPa m1/2) was acquired by ZTA ceramic with a YSZ content of 20 wt%. When the YSZ content reached 30 wt%, agglomerations formed and led to a negative influence on the properties of ZTA ceramics. It is confirmed that the combined contribution from the addition of YSZ on the improvement of mechanical property and influence of the SL process should be synthetically considered during the design of ceramic paste feedstock for such additive manufacturing. [ABSTRACT FROM AUTHOR]

The nanoscale plasticity phenomena in zirconia-toughened alumina (ZTA) ceramics with yttria-stabilized zirconia (YSZ) addition of 10% and 30% fabricated by additive manufacturing based on a stereolithography technique were explored in detail by nanoindentation and scanning electron microscopy. It was demonstrated that the initiation of nanoscale plasticity was attributed to the combined contributions from the generation of nanoscale shear deformation bands and localized microcracking at the indentations. Such localized plastic behavior underneath the nanoindenter was interpreted by maximum shear stress analysis. The response of the phase boundary during indentation was emphasized through crack propagation paths, and optimization of alumina–YSZ adaptation through component design and SL processing was expected. [ABSTRACT FROM AUTHOR]