Search

The additive manufacturing of piezoelectric ceramic Lead Zirconate Titanate (PZT) through paste extrusion 3D printing was demonstrated. Different paste compositions with varied water weight content were studied to find a composition suitable for printing. The pastes were evaluated in terms of their viscosities, yield stresses, and stability when aged. Furthermore, the material properties of the ceramics produced through paste extrusion were characterized and compared with those of ceramics fabricated through a conventional die pressing method. Paste extruded PZT with achieved densities as high as 94.9% of the theoretical density after sintering, which nearly matched the 95% density attained by the pressed samples. Upon poling, the paste extruded PZT piezoelectric ceramics attained piezoelectric coefficients and dielectric constants that were close to the values of die pressed samples. As near full density PZT ceramics were successfully fabricated through paste extrusion, this work paves the way for piezoelectric ceramics with application-driven geometry designs for sensors, actuators, and energy harvesters.

Aluminum nitride (AlN) ceramics have attracted broad interest due to their potential applications in electronics. Additive manufacturing of ceramic components are rapidly advancing, could provide a new way of manufacturing over conventional methods. Non-destructive testing of 3D printed ceramic samples is an important step for quality control in manufacturing. Here we show that AlN ceramics show strong optical second harmonic generation (SHG) signals due to its wurtzite crystal structure. Microscopic SHG imaging can also examine the microscopy domains in AlN ceramics with submicron spatial resolution. This technique has the potential to be applied as a non-destructive testing method for examining 3D printed AlN ceramic components.

In this work, we report on the novel fabrication of aluminum nitride (AlN) components using Binder Jetting (BJT) additive manufacturing (AM). The AlN constructs were subjected to post-fabrication thermal treatment by hot isostatic pressing (HIPing) for 8 hours at a pressure of 206 MPa and temperature of 1900 °C. This treatment resulted in a 60.1% relative density maximum densification for AlN. The BJT printed AlN specimens were analyzed using various characterization techniques. The purity, microstructure, and polycrystallinity of the AlN phase formed were confirmed by techniques that included x-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS), and high-resolution transmission electron microscopy (HRTEM). Second harmonic generation (SHG) microscopy showed polarization dependence and second harmonic signal at 470 nm, indicating the potential to produce thermal and optical-mechanical devices. Mechanical properties obtained by nanoindentation resulted in an elastic modulus of ~251 GPa when measured in fully dense, contiguous crystalline regions, corresponding to an apparent, porous bulk stiffness of ~90 GPa for the final, 60.1 % dense products. Finally, the laser flash method (LFM) was used to measure the thermal conductivity of the material as a function of temperature resulting in values from 4.82 W/mK to 3.17 W/mK for the temperature range from 23 °C to 500 °C, respectively.

Fine structures (ferroelectric domains), ferroelectricity and Second Harmonic Generation results were found and studied as a function of laser linearly and circularly polarization dependent polarized excitations in ferroelectric stoichiometric La 0.05 Li 0.85 NbO 3 nanocrystals ceramic material. Scanning Electron Microscope images are taken as a comparison to Second Harmonic Generation intensity profiles revealed fine structures. By using laser polar measured response we are able to find the angle orientation from 0° to 90° angles of ferroelectric domains with highly good definition contrast obtained in blue/gray colors. It shows ferroelectric hysteresis loops at room temperature with a polarization saturation of (0.247 μC/cm 2 ), remnant polarization of (0.15 μC/cm 2 ) and coercitivity field of (1.31 kV/cm). X-ray Diffraction, Atomic Force Microscope, Raman spectroscopy and X-ray Photoelectron Spectroscopy, revealed well formed of ferroelectric ABO 3 perovskite crystal structure, piezoelectric image response indicate ferroelectric pattern domain structure, new vibrations modes on LaO 6 , LiO 6 and NbO 6 octahedral sites and binding energies of electronic structure of La 57 , Nb 41 , O 8 , Li 3 from the surface of the ferroelectric stoichiometric La 0.05 Li 0.85 NbO 3 nanocrystals ceramic material, respectively.

Binder jetting additive manufacturing is an emerging technology with capability of processing a wide range of commercial materials, including metals and ceramics (316 SS, 420 SS, Inconel 625, Iron, Silica). In this project, aluminum oxide (Al2O3) powder was used for part fabrication. Various build parameters (e.g. layer thickness, saturation, particle size) were modified and different sintering profiles were investigated to achieve nearly full-density parts (~96%). The material's microstructure and physical properties were characterized. Full XRD, compression testing, and dielectric testing were conducted on all parts. Sintered alumina parts were achieved with an average compressive strength of 131.86 MPa (16 h sintering profile) and a dielectric constant of 9.47–5.65 for a frequency range of 20 Hz to 1 MHz. The complexity offered by additive processing aluminum oxide can be extended to the manufacturing of high value energy and environmental components for environmental systems (e.g. filters and membranes) or biomedical implants with integrated reticulated structures for improved osseointegration.

Fabrication of barium titanate (BaTiO 3 ) specimens was accomplished with binder jetting additive manufacturing, and build parameters (e.g., binder saturation and layer thickness) and sintering profiles were modified to optimize the density achieved and the crystal structures obtained in the 3D printed parts. Surface and cross sectional grain morphology was characterized by scanning electron microscopy (SEM) revealing grain growth on localized areas of BTO fabricated specimens after sintering. Crystal structure was analyzed by X-ray diffraction (XRD) where the presence of a hexagonal phase was observed for BaTiO 3 only when sintered at 1400 °C. The dielectric constant of the fabricated BaTiO 3 specimens sintered at 1260 °C was obtained by using a K u -band wave-guide and vector network analyzer setup in which the relative permittivity was measured from 8.6 to 6.23 for a frequency range of 12.4–18 GHz, respectively. When sintered at 1400 °C for 4 h, a density of 3.93 g/cm 3 was obtained, which corresponds to 65.2% of the theoretical density. Piezoelectric properties exhibited a d 33 value of 74.1 for specimens also sintered at 1400 °C. Results reported in this paper demonstrate the feasibility of BTO as a binder jetting material for 3D printed dielectric structures, ceramic capacitors and gas and pressure sensors.