Alternative Process Routes to Manufacture Porous Ceramics—Opportunities and Challenges

Abstract

Porous ceramics can be realized by different methods and are used for various applications such as cross-flow membranes or wall-flow filters, porous burners, solar receivers, structural design elements, or catalytic supports. Within this paper, three different alternative process routes are presented, which can be used to manufacture porous ceramic components with different properties or even graded porosity. The first process route is based on additive manufacturing (AM) of macro porous ceramic components. The second route is based on AM of a polymeric template, which is used to realize porous ceramic components via replica technique. The third process route is based on an AM technology, which allows the manufacturing of multimaterial or multiproperty ceramic components, like components with dense and porous volumes in one complex-shaped component.

Porous Functional Graded Bioceramics with Integrated Interface Textures

“…While some techniques, such as direct foaming [15,18,27], freeze casting [19,28] or emulsion-forming [29,30], cannot easily be adapted to meet patient individual demands without changing various process parameters, additive manufacturing (AM) allows convenient customization as required. However, as direct AM of ceramic implants remains challenging [40], established ceramic manufacturing techniques indirectly utilizing computer-aided designing provide great opportunity to fulfill the current demands [31,32]. In this work, bi-layered bending bars were fabricated by joining two ceramic feedstocks containing varied amounts of 20 µm spherical pore formers (0-40 Vol%), which generated a well-defined porosity after the heat treatment inside each layer.…”

“…The density gradient ρ i (x,y,z) induces location-dependent properties M i (x,y,z) along the spatial directions (x,y,z) and thus perspective biomedical applications that cannot be achieved by common homogeneous porous ceramics, for which ρ i and M i are constant in volume [23][24][25]. Graded porosities were commonly achieved by modifying established fabrication techniques of homogeneous porous ceramics, including sacrificial templating [7,14,21,22,26], direct foaming [15,18,27], freeze casting [19,28], emulsion forming [29,30], replica technique [20,[31][32][33] and additive manufacturing (AM) [16,17,31,32]. Among the various mentioned processing routes, techniques utilizing computer-aided designing provide the highest potential to realize freely adjustable graded architectures with complex shapes [17,31], which are required for the fabrication of patient individual implants.…”

3D‐printed alumina‐based ceramics with spatially resolved porosity

“…The advantageous properties of porous ceramics, such as chemical inertness, corrosion, biocompatibility, and low density, make them superior candidates for applications that demand lightweight properties, acoustic/thermal insulation, high thermal shock resistance, and increased capillary activity 1 . It has been reported in 2019 that, more than 16,000 scientific articles about porous ceramics have been published 2 in the last 20 years. In recent years, the interest and demand on porous ceramics have increased particularly in bio‐based applications as porous ceramics may enable the impregnation of bone cells through open pores resulting in a bone growth on the biocompatible walls 3 .…”

Process Data-Based Knowledge Discovery in Additive Manufacturing of Ceramic Materials by Multi-Material Jetting (CerAM MMJ)

“…The droplet method offers advantages, as the material of the ceramic highly filled suspensions is deposited droplet by droplet, and thus the material is applied at a defined position in a spatially resolved manner. In addition to accurately separated areas, material gradients within a component can be realized [17][18][19]. Through the specific selection of materials, the modification of the starting powders as well as the targeted adjustment of the feedstock properties, the shrinkage behavior can be adjusted in a manner that permits defect-free co-sintering and final densities of up to 99% of the theoretical density can be achieved [13,14].…”