Dense ceramics with complex shape fabricated by 3D printing: A review

Journal of Advanced Ceramics 2021, 10(2): 0–0 https://doi.org/10.1007/s40145-020-0444-z ISSN 2226-4108 CN 10-1154/TQ Review Dense ceramics with complex shape fabricated by 3D printing: A review Zhe CHENa, Xiaohong SUNa,*, Yunpeng SHANGa,b, Kunzhou XIONGa,b, Zhongkai XUa, Ruisong GUOa, Shu CAIa, Chunming ZHENGb,* a School of Materials Science and Engineering, Key Laboratory of Advanced Ceramics and Machining Technology of Ministry of Education, Tianjin University, Tianjin 300072, China b School of Chemistry and Chemical Engineering, State Key Laboratory of Hollow-fiber Membrane Materials and Membrane Processes, Tiangong University, Tianjin 300387, China Received: July 1, 2020; Revised: December 7, 2020; Accepted: December 14, 2020 © The Author(s) 2020. Abstract: Three-dimensional (3D) printing technology is becoming a promising method for fabricating highly complex ceramics owing to the arbitrary design and the infinite combination of materials. Insufficient density is one of the main problems with 3D printed ceramics, but concentrated descriptions of making dense ceramics are scarce. This review specifically introduces the principles of the four 3D printing technologies and focuses on the parameters of each technology that affect the densification of 3D printed ceramics, such as the performance of raw materials and the interaction between energy and materials. The technical challenges and suggestions about how to achieve higher ceramic density are presented subsequently. The goal of the presented work is to comprehend the roles of critical parameters in the subsequent 3D printing process to prepare dense ceramics that can meet the practical applications. Keywords: 3D printing; dense ceramics; particle characteristics; process parameters 1 Introduction As one group of materials that are widely used in industries, ceramics have several characteristics like high hardness, superior strength, excellent hightemperature resistance, and outstanding wear resistance [1]. Unfortunately, it is these characteristics that make ceramics of complex shapes difficult to fabricate with conventional methods including dry pressing, injection molding, roll forming, and tape casting. On the one * Corresponding authors. E-mail: X. Sun, C. Zheng, hand, these traditional preparation techniques are relatively complex and time-consuming. On the other hand, it is not allowed to make ceramic parts with complex shapes, such as curved shapes or honeycomb structures. Besides, ceramic applications in modern production are subjected to many limitations because mold design and manufacturing, which has been widely used in ceramic industries, usually take a very long time. Therefore, there is an urgent need to find new technology to manufacture high-performance ceramics with complex shapes. The concept of additive manufacturing (AM) first appeared in 1892 and originated from a patented technology for making three-dimensional map models using a lamination www.springer.com/journal/40145 2 J Adv Ceram 2021, 10(2): 0–0 method in the United States [2]. 3D printing is a technique of rapid fabricating complex- shaped objects whereby 3D objects are built by depositing feedstock materials on each layer. With the growth of market demand and technological development, 3D printing is widely used in construction [3], medicine [4], aerospace [5], and other fields [6]. In 2014, WinSun company printed out a large residence in one day, reducing construction time and labor costs [7]. Both in fundamental researches and practical applications, selective laser sintering (SLS), selective laser melting (SLM), stereolithography (SLA) as well as direct inkjet writing (DIW) are the most studied methods of AM that have been widely used in industries so far. Many studies [8,9] confirm that 3D printing is extremely ideal for preparing complex structures, such as the commonly used hole structure. However, the porous ceramics prepared by this method often have great deficiencies in terms of ceramic density [10,11]. Data from several studies [12–14] show that the applications of 3D printed ceramics are often limited by their low density causing insufficient mechanical properties. In addition to affecting the mechanical properties of ceramics, the density of printed ceramics has a decisive effect on the functions of ceramics. It is worth noting that so far 3D printing technology has been used in the manufacture of functional ceramic devices such as piezoelectric ceramics and solid oxide fuel cells (SOFC), which has been widely studied in the energy field. At present, most of the 3D printing processes on the market that add binders or organic monomers are difficult to bypass the step of debinding or degreasing, which tends to reduce the density of the ceramic green body, because most of the binder or organic monomer will be discharged, leaving only the loose ceramic powder. Therefore, the densification process of 3D printed ceramics is mainly achieved during high-temperature sintering. There is a good correlation between the density of sintered ceramics and mechanical properties. Within a certain sintering temperature range, although the grains gradually grow, no obvious cracks are produced. At this time, the gradually increasing density leads to an increase in compressive strength, hardness, and elastic modulus. As the temperature continues to rise, the excessive growth of ceramic grains can lead to cracks. Due to crack propagation, the mechanical properties, including bending strength and modulus, will decrease sharply [15]. Strictly speaking, 3D printing is only one of the many steps in the preparation of ceramic devices. The performance of the final parts also depends on the formulation, sintering, and processing. The main objective of this review is to summarize the latest research advances in the realms of 3D printing technology for its possibility to fabricate high-density ceramics. The review offers important insights into the 3D printing mechanism and its technology for manufacturing highly dense ceramics. Especially, understanding the parameters that can affect the density of final products in different processes will conduce to the fabrication of ceramics with remarkable property. It also provides a comprehensive reference for researchers engaging in 3D printed ceramics. 2 Selective laser sintering Selective laser sintering (SLS), invented by Carl Deckard et al. in 1986 [16], is a 3D printing preparation approach using powder, in which three-dimensional parts are fabricated by sintering part of powder in a layered manner by means of a laser beam radiation. The SLS process is schematically illustrated in Fig. 1 [17]. In this process, a roller is first used to spread evenly powder materials on the entire bed, and then the laser beam moves on the powder bed at a certain scanning speed controlled. The laser beam interacts with the powder to generate high temperature quickly to achieve sintering. Once the sinter (...truncated)