Ceramic Additive Manufacturing Research Articles

Experimental demonstration and optimization of X-ray StaticCodeCT.

As the use of X-ray computed tomography (CT) grows in medical diagnosis, so does the concern for the harm a radiation dose can cause and the biological risks it represents. StaticCodeCT is a new low-dose imaging architecture that uses a single-static coded aperture (CA) in a CT gantry. It exploits the highly correlated data in the projection domain to estimate the unobserved measurements on the detector. We previously analyzed the StaticCodeCT system by emulating the effect of the coded mask on experimental CT data. In contrast, this manuscript presents test-bed reconstructions using an experimental cone-beam X-ray CT system with a CA holder. We analyzed the reconstruction quality using three different techniques to manufacture the CAs: metal additive manufacturing, cold casting, and ceramic additive manufacturing. Furthermore, we propose an optimization method to design the CA pattern based on the algorithm developed for the measurement estimation. The obtained results point to the possibility of the real deployment of StaticCodeCT systems in practice.

Lithography-based manufacturing of advanced ceramics for orthopaedic applications: A comparative tribological study

Ceramics long history in biomedical field is related to their high biocompatibility and mechanical properties. Precisely, for joint replacements, wear resistance is fundamental, so advanced ceramics as alumina and zirconia are preferred. Developments in ceramic additive manufacturing allow for dense ceramic parts with improved mechanical properties and shape accuracy.This paper focuses on the tribological analysis of stereolithography-manufactured components for orthopaedics. Alumina, yttria-stabilised zirconia, 10 and 20 wt% zirconia toughened alumina (ZTA) samples were analysed. The effect of surface finishing, microstructure and microhardness on wear was considered.Printing orientation does not significantly impact microhardness, wettability, and microporosity. However, some printing artefacts as the staircase effect were observed on spherical surfaces. Zirconia system presented high wear rates and friction coefficient, while alumina system showed more acceptable and stable values, with the formation of a self-mated tribofilm. ZTA composites presented the lowest wear volume and better mechanical and surface properties in general.

Preparation of High-Solid Filled Alumina Inks for Stereolithography 3D Printing Process

In ceramic additive manufacturing, it is important to fabricate parts with high solid contents to guarantee defect-free sintered parts. In stereolithography, low viscosity and especially shear-thinning behavior of the ink are the key factors in producing ceramic-resin parts. Therefore, there should be a correlation between solid loading and viscosity. In this study, Alumina-glass inks were printed using bottom-up and top-down approaches, and the rheological properties were investigated. The main objective of this study was to print a highly filled ceramic-resin part with a viscosity suitable for DLP printing. While use of suspensions with low viscosity was recommended for top-down digital light processing (DLP) printing, a new setup was designed to study the feasibility of the top-down approach for pastes for the top-down approach. According to the findings, ceramic-resin pastes with the solid content of maximum 75 wt% and viscosity of 47.64 Pa.s at the shear rate of 30 s-1 were easily printable via our hand-made top-down DLP printer. However, it was not possible to print inks with solid contents more than 60 wt% using the bottom-up DLP, mainly because the detachment force grew dramatically with an increase in viscosity.

A comprehensive study of dense zirconia components fabricated by additive manufacturing

Abstract Although additive manufacturing offers numerous potential advantages for fabricating functional, complex geometry zirconia parts with efficiency, industrial interest in practical applications is currently lacking. This potentially stems from the need for a more comprehensive investigation into the performance of additively manufactured zirconia components, which is essential for promoting and initializing industrial applications. The aim of this study is thus to provide a detailed evaluation of zirconia specimens fabricated by one of the most utilized ceramic additive manufacturing technologies, viz. digital light processing (DLP), with a range of typical zirconia components being printed. Key performance factors captured within include achievable density, surface quality measurements, dimensional accuracy, degree of shrinkage, and mechanical properties. The results of this work demonstrates that the performance of the DLP-prepared zirconia parts is comparable to those of conventionally fabricated zirconia. It is believed that this paper will serve as a good reference for academic and industrial communities interested in this rapidly expanding field.

Ceramic additive manufacturing for enhanced piezocomposite transducers

Ceramic additive manufacturing for enhanced piezocomposite transducers

Research Progress on Extrusion and Jetting-based Ceramic Additive Manufacturing Technologies

Research Progress on Extrusion and Jetting-based Ceramic Additive Manufacturing Technologies

3Y-TZP DLP Additive Manufacturing: Solvent-free Slurry Development and Characterization

Vat photopolymerization (VP) stands out among ceramic additive manufacturing processes for its ability to print sub-100 micrometer complex features. One of the main challenges of this process is the preparation of a homogeneous and stable ceramic slurry with a high solid load and low viscosity. In this work, different dispersants and resins were tested, aiming to provide a solvent-free slurry suitable for DLP additive manufacturing. Disperbyk-111 and PEGDA 250 stood out in the tests, providing a 40 vol% ceramic slurry with no noticeable sedimentation and viscosity of 2.3 Pa.s at 30 s-1 despite the relatively high specific surface area (15 m2/g) of the 3Y-TZP powder used compared to powders usually used for VP slurries. The adsorption of Disperbyk-111 on ceramic particles surface was investigated by FTIR. Finally, ceramic bodies were 3D printed, debound and sintered at 1500 ºC for 2 h, confirming the ability to manufacture detailed dense ceramic parts.

Development of ceramic additive manufacturing: process and materials technology.

Ceramic additive manufacturing (C-AM) is highlighted as a technology that can overcome the inherent limitations of ceramics such as processability and formability. This process creates a structure by slicing a 3D model and stacking ceramic materials layer-by-layer without mold or machining. C-AM is a technology suitable for the era of multiple low-volume because it is more flexible than conventional methods for shape complexity and design modification. However, many barriers to practical use remain due to process speed, defects, and lack of knowledge. This review focuses on studies to overcome the limitations of C-AM in terms of process and materials. The C-AM process has been advanced through various studies such as model/equation-based parameter control and high-speed sintering using external energy. Besides, by improving and fusing existing technologies, high-precision high-speed printing technology has been improved. A variety of material studies have been made of manufacturing ceramic structures with superior properties using preceramic polymers and composite materials. Through these studies, C-AM has been applied to various fields such as medicine, energy, environment, machinery, and architecture. These continued growths and diverse results demonstrate the importance and potential of C-AM based ceramic manufacturing technology.

Synergy of solid loading and printability of ceramic paste for optimized properties of alumina via stereolithography-based 3D printing

The challenges associated with stereolithography-based ceramic additive manufacturing using high solid loading pastes are related to the printability of ultrathin layers and complex green bodies without auxiliary support structures directly underneath. In order to develop the strategy of conformal contactless support during additive manufacturing, the printability of alumina ceramic paste with a variety of solid loading, along with mechanical properties of the sintered parts fabricated by stereolithography process was investigated. A combination of scanning electron microscopy, micro-computed tomography scans and three-point bending tests were practiced systematically. The rheological behavior of ceramic paste was regulated distinctly by solid loading. As the solid loading increased, the degree of shrinkage decreased and the relative density increased for the sintered part. The sintered sample from 52 vol% ceramic paste presented the highest flexural strength with well densified microstructure. The research results promote property optimization of ceramic components fabricated by stereolithography method through material compositions and printability of ceramic paste, which simultaneously contributes to perfect support strategy for ceramic additive manufacturing.

Effect of graphite particles as additive on the curing behaviour of β-tricalcium phosphate suspensions and scaffold fabrication by digital light processing

Reducing the viscosity of high solid-loading ceramic suspensions and controlling the resolution of ceramic green parts produced by digital light processing (DLP) 3D printing are two important concerns in the ceramic additive manufacturing industry. The presence of ceramic particles within a photopolymerizable system leads to light scattering that reduces the resolution of the ceramic green scaffolds. This study introduced a graphite additive to solve these problems and focused on the effects of graphite concentration on the viscosity, curing behaviour and scaffold fabrication of β-TCP ceramic suspensions. As a result, it was found that an appropriate addition of graphite reduced the viscosity of the ceramic suspensions, and the light scattering decreased with the increase of graphite concentration. Both the cure depth (Cd) and excess width (Cex) also decreased with the increase of graphite concentration. But, graphite has a larger effect on the width curing than depth curing.

Ceramic Additive Manufacturing for the Rapid Prototyping of Mixed Potential Electrochemical Sensors

Ceramic electrochemical sensors play a major role in chemical analysis of gas species, and mixed potential sensors are attractive for their robustness in harsh environments such as automotive exhaust gases. A major challenge for rapid prototyping of ceramic chemical sensors is the high cost, high material waste, and low geometric flexibility of traditional screen printing and tape casting methods. While these two methods are suitable for mass production of thousands to millions of devices, they tend to be cost prohibitive for small scale rapid prototyping applications. Additive manufacturing techniques enable greater flexibility in working with small batches of materials, customized geometry, and shorter turnaround time.We will discuss efforts in the additive manufacturing of ceramic mixed potential sensors by extrusion of ceramic and conductor pastes onto zirconia laminates. [1] We evaluated the sensor performance to various test gases at the 100 PPM level including NOX, NH3, and C3H8, observing responses on the order of mV/100 ppm. Electrochemical techniques were employed to probe the effects of porosity on sensor response and evaluate the reproducibility of AM techniques. Finally, we will report on the printing of a ceramic gas sensor by extrusion of a ceramic paste to form the substrate instead of using a laminate substrate to demonstrate a complete device can be produced by AM techniques only.[1] Tsui, L.K.; Benavidez, A.; Evans, L.; Garzon, F.G. Prog. Additive Manuf. 2019, 4, 1, 13-21

Additive manufacturing revolution in ceramic microsystems

PurposeThe purpose of this paper is to review possibilities of implementing ceramic additive manufacturing (AM) into electronic device production, which can enable great new possibilities.Design/methodology/approachA short introduction into additive techniques is included, as well as primary characterization of structuring capabilities, dielectric performance and applicability in the electronic manufacturing process.FindingsCeramic stereolithography (SLA) is suitable for microchannel manufacturing, even using a relatively inexpensive system. This method is suitable for implementation into the electronic manufacturing process; however, a search for better materials is desired, especially for improved dielectric parameters, lowered sintering temperature and decreased porosity.Practical implicationsRelatively inexpensive ceramic SLA, which is now available, could make ceramic electronics, currently restricted to specific applications, more available.Originality/valueCeramic AM is in the beginning phase of implementation in electronic technology, and only a few reports are currently available, the most significant of which is mentioned in this paper.

Postprocessing Study for the Controllable Structures of Ceramic Green Parts Realized by a Flexible Binder Jetting Printing (BJP) Solution

For indirect ceramic additive manufacturing (AM), green parts’ initial densities are low, limiting the postprocessing strengthening under atmospheric pressure. This study employed binder jetting printing (BJP) based on the polycondensation curing of urea‐formaldehyde resin to produce series of Al2O3 green specimens with controllable structures. Further, an integrated postprocessing procedure, including the sequential stages of presintering, ceramic slurry infiltration, and final sintering, was conducted on these green specimens with designed structural characteristics for verifying strengthening mechanism. Using a self‐developed BJP machine system and the related material which are flexible in process, this study printed green specimens with strong bonding (flexural strength above 6.84 MPa), additionally can regulate their initial densities within the wide range between 21.7%∼43.9%. Infiltrated with ceramic slurry, low‐density green specimens were significantly strengthened via final sintering, realizing final densities, flexural strength, and compressive strength of 73.2%, 43.15 MPa, and 331.17 MPa, respectively. In comparison, high‐density specimens performing poor infiltration obtained limited density increment after final sintering, but better mechanical properties and surface strengthening were realized, exhibiting final densities, flexural strength, comprehensive strength, surface roughness Ra, and Vickers hardness of 70.1%, 63.22 MPa, 450.18 MPa, 9.73 μm, and 4.58 GPa, respectively. In summary, this study is helpful to provide the technical reference for custom AM ceramic green parts and the postprocessing optimization.

Hydrothermal-Assisted Transient Binder Jetting of Ceramics for Achieving High Green Density

Ceramic additive manufacturing (AM) provides a freeform fabrication method for creating complex ceramic structures that have been extremely difficult to build by traditional manufacturing processes. However, ceramic structures made by AM processes usually exhibit a relatively low density, which is largely due to the use of a large amount of organic binder in shaping green bodies. In this research, we present a new ceramic AM process, named hydrothermal-assisted transient binder jetting (HTBJ), which utilizes a water-based hydrothermal mechanism to fuse particles, eliminating the use of binders in forming green bodies. A prototype system for the proposed HTBJ process is introduced. The effects of process parameters (such as layer thickness, printing passes, prepressing and final pressing pressure, and temperature) on the properties of achieved green parts are investigated. Experimental results indicate that, with optimized process parameters, HTBJ can achieve three-dimensional ceramic green parts with a high density of up to 90%.

Investigation of room‐temperature super‐stabilized suspension casting system mechanism

AbstractThe investigation of a novel gel‐casting system using a water‐soluble co‐polymer of isobutylene and maleic anhydride (trade name ISOBAM) to elucidate its nontraditional gelling mechanism is described. This system enables ceramic slurries to gel at low binder concentrations (0.3‐0.5 wt%), producing a dense, near‐net shaped green body with high solids loading, low organic content, low shrinkage, and moderate strength. The nature of the stabilizing bonds formed during gelation were investigated using Fourier‐transform infrared spectroscopy (FTIR), zeta potential, and rheological measurements which revealed that no covalent network was formed during gelation. It was concluded that the mechanism was based solely on weak interactions. As such, the ISOBAM casting system, and polymeric additive systems that behave similarly, represent a new class of near net‐shaped ceramic processing which could benefit a variety of applications, including ceramic additive manufacturing.

Flexural strength and Weibull analysis of Y-TZP fabricated by stereolithographic additive manufacturing and subtractive manufacturing

Digital light processing (DLP) is a relatively mature technology of ceramic additive manufacturing and is promising for fabricating zirconia-based dental restorations. It allows for manufacturing ceramic components with nearly unlimited geometries compared to traditional subtractive manufacturing technology. In order to explore its potential for fabricating dental prosthesis and determine its clinical indications, it is essential to investigate its microstructural characteristics and mechanical behavior. In this study, yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) fabricated by stereolithographic additive manufacturing, namely DLP acquired favorable flexural strength close to that of conventional subtractive-manufactured Y-TZP as indicated by uniaxial (three-point bending) and biaxial (ring on ring) tests, though the Weibull modulus of DLP-manufactured zirconia was lower than that of subtractive-manufactured zirconia. The strength predicting approach that uses effective area calculations was found to be applicable for both DLP-manufactured zirconia and subtractive-manufactured zirconia. Though both materials showed similar microstructures considering grain size and phase composition, significant differences in critical defects were observed.

Modeling sintering anisotropy in ceramic stereolithography of silica

In the domain of ceramic additive manufacturing, sintering is a key step for controlling the final shape and mechanical strength of a 3D object. The thermal treatment of the printed green objects has a high influence on the specimen density, debinding, and sintered microstructure. This work focuses on the shrinkage anisotropy phenomenon that occurs during sintering. We demonstrate by dilatometry and interrupted sintering microstructure analysis that this phenomenon originates from non-ideal particle packing between the printed layers, which generates an anisotropic porosity distribution at the mesoscale. Based on this, a sintering model is developed and specially adapted for the numerical prediction of the sintering anisotropy. This model is formulated in analytic equations that can easily identify all the model parameters and reproduce the experimental dimensional changes. This numerical tool can be of great assistance in the prediction of additive manufacturing object dimensional changes during sintering.

Ceramic Additive Manufacturing Methods Applied to Sintered Glass Components with Novel Properties

Ceramic Additive Manufacturing Methods Applied to Sintered Glass Components with Novel Properties

A photoacoustic imaging method for in-situ monitoring of laser assisted ceramic additive manufacturing

We propose an in-situ monitoring method of laser assisted ceramic additive manufacturing (AM) fabrication process using photoacoustic (PA) imaging technique. This method is potentially very practical and of low cost, as it can be easily implemented with little modification to the original AM system. A major advantage of this method is that it does not require any complex or expensive component to be installed, just need a microphone to be setup near the work-piece and a data processing program to analyse the acoustic data. By collecting the photoacoustic wave that produced by the laser scanning during the AM process, a spectrogram of the acoustic signal can be generated using short-time Fourier transform (STFT). The PA signal can be extracted by specifying the modulation frequency of the laser in the spectrogram. Combining with the scanning position of the laser beam, the PA image of the layer under processing can be obtained. Detection of two kinds of defects (metal defect and dried paste defect) have been demonstrated. Although there are many other kinds of possible defects in additive manufacturing processes, this method could be a practical and low cost way to monitor most of them with proper choice of parameters of the laser and detection system. The parameters of the system that can influence the PA image quality have also been discussed.

Controllable Ceramic Green‐Body Configuration for Complex Ceramic Architectures with Fine Features

AbstractFabrication of dense ceramic articles with intricate fine features and geometrically complex morphology by using a relatively simple and the cost‐effective process still remains a challenge. Ceramics, either in its green‐ or sintered‐form, are known for being hard yet brittle which limits further shape reconfiguration. In this work, a combinatorial process of ceramic robocasting and photopolymerization is demonstrated to produce either flexible and/or stretchable ceramic green‐body (Flex‐Body or Stretch‐Body) that can undergo a postprinting reconfiguration process. Secondary shaping may proceed through: i) self‐assembly‐assisted shaping and ii) mold‐assisted shaping process, which allows a well‐controlled ceramic structure morphology. With a proposed well‐controlled thermal heating process, the ceramic Sintered‐Body can achieve >99.0% theoretical density with good mechanical rigidity. Complex and dense ceramic articles with fine features down to 65 μm can be fabricated. When combined with a multi‐nozzle deposition process, i) self‐shaping ceramic structures can be realized through anisotropic shrinkage induced by suspensions' composition variation and ii) technical and functional multiceramic structures can be fabricated. The simplicity of the proposed technique and its inexpensive processing cost make it an attractive approach for fabricating geometrically complex ceramic articles with unique macrostructures, which complements the existing state of‐the‐art ceramic additive manufacturing techniques.