A review of 3D printed porous ceramics

Three-dimensional (3D) printing of ceramics has gained widespread attentions in recent years. Many excellent reviews have reported the printing of ceramics. However, most of them focus on printing of dense ceramics or general ceramic aspects, there is no systematical review about 3D printing of porous ceramics. In this review paper, the 3D printing technologies for fabricating of porous ceramic parts are introduced, including binder jetting, selective laser sintering, direct ink writing, stereolithography, laminated object manufacturing, and indirect 3D printing processes. The techniques to fabricate hierarchical porous ceramics by integrating 3D printing with one or more conventional porous ceramics fabrication approaches are reviewed. The main properties of porous ceramics such as pore size, porosity, and compressive strength are discussed. The emerging applications of 3D printed porous ceramics are presented with a focus on the booming application in bone tissue engineering. Finally, summary and a perspective on the future research directions for 3D printed porous ceramics are provided.     

Direct ink writing of hierarchical porous ultra-high temperature ceramics (ZrB2)

An approach to producing hierarchical multi-scale porous ultra-high temperature ceramics (zirconium diboride, ZrB₂) using 3D printing has been developed. Porous ceramic filaments can be 3D printed via Direct Ink Writing (DIW) (paste extrusion). Millimeter scale porosity is created by the 3D printed scaffold filaments. We introduce 20-micron-scale porosity into the scaffold filaments with the addition of oil to produce capillary suspension paste inks. Micron-scale porosity is also developed by partial sintering of the ceramic. The rheological (flow) properties of the capillary suspension paste inks suitable for printing by extrusion through the needle of the 3D printer have been characterized. The samples are strengthened by partial sintering at high temperatures. Complex-shaped components can be printed and sintered into crack-free components, but distortion during drying and sintering lead to poor shape and tolerance control. X-ray tomography is used to characterize the internal structure of the printed components. Printed test bars measured in 4-point bend testing exhibit high strength to density ratio. Such materials potentially have applications as insulation near very high-temperature surfaces in aerospace applications.     

The fabrication of SiBCN ceramic components from preceramic polymers by digital light processing (DLP) 3D printing technology

We present a novel method to fabricate SiBCN ceramic components with complex shapes from preceramic polymers by using digital light processing (DLP) 3D printing technology in this research work. The photocurable precursor for 3D printing was prepared by blending high ceramic yield polyborosilazane with photosensitive acrylate monomers. The material formulation and printing parameters were optimized to fabricate complicated SiBCN ceramic components with high precision. The printed SiBCN ceramic materials were pyrolyzed at different temperatures, and retained their fine features after pyrolysis. Their microstructures were characterized by FTIR, XRD and TEM respectively. Furthermore, the thermal stability and mechanical properties of the SiBCN ceramic samples were investigated and discussed in detail. The 3D printed SiBCN ceramic material exhibited excellent thermal stability and resistance to high temperature oxidation up to 1500?°C.     

Study of alumina ceramic parts fabricated via DLP stereolithography using powders with different sizes and morphologies

Selecting suitable ceramic powders for the preparation of UV-curable ceramic suspensions, which are well suited for printing processes and production of high-performance ceramic components, is a crucial factor in the practical industrial application of digital light processing (DLP) stereolithography. Therefore, this study aims to provide a comprehensive evaluation of alumina ceramic parts fabricated via DLP stereolithography using a variety of alumina powders with varying sizes and morphologies. Experiments were conducted to examine the rheological response, recoating performance, and curing behavior of UV-curable alumina suspensions. Additionally, the thermal decomposition behavior of three-dimensional (3D)-printed green-bodies, as well as the physical and mechanical properties of 3D-printed sintered alumina components were thoroughly investigated. The best physical and mechanical performances were achieved by printing 55 vol% suspensions prepared using near-spherical AA04 alumina powders (median diameter .4 μm). This study elucidates the effects of ceramic particle size and morphology on the entire technological process of DLP-based ceramic stereolithography, thereby establishing the guidelines for the fabrication of high-performance 3D-printed ceramic objects in industrial and engineering production by selecting appropriate ceramic powders.     

Silicon carbide whiskers reinforced SiOC ceramics through digital light processing 3D printing technology

Polymer derived silicon oxycarbide ceramic materials and silicon carbide whiskers reinforced ceramic composite are prepared through digital light processing (DLP) 3D printing technology in the present work. A new type of UV-curable preceramic polymer is firstly synthesized and then two types of photopolymer resins with and without SiC whiskers as reinforcement are prepared. Due to the high curing rate and good fluidity of the resins, they are applied in DLP 3D printing and various 3D objects with complicated structures and high printing resolution have been printed. The derived ceramic materials show amorphous microstructure and there is no apparent porosity and cracking throughout the whole sample surface of the ceramic materials and the SiC whiskers are uniformly embedded in the ceramic matrix and remain intact and unaffected during the pyrolysis process. The SiC whiskers reduced the shrinkage and mass loss. More importantly, it significantly improves the mechanical performance of the derived ceramic materials in which the compressive strength increases from 77.5 ± 10.2 MPa to 98.4 ± 12.3 MPa. Benefiting from the easiness of the fabrication, high printing resolution and excellent mechanical performance, the derived ceramic materials have great potential applications in various areas.     

Fabrication of forsterite scaffolds with photothermal-induced antibacterial activity by 3D printing and polymer-derived ceramics strategy

Bacterial infection of the implanting materials is one of the greatest challenges in bone tissue engineering. In this study, porous forsterite scaffolds with antibacterial activity have been fabricated by combining 3D printing and polymer-derived ceramics (PDCs) strategy, which effectively avoided the generation of MgSiO₃ and MgO impurities. Forsterite scaffolds sintered in an argon atmosphere can generate free carbon in the scaffolds, which exhibited excellent photothermal effect and could inhibit the growth of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) in vitro. In addition, forsterite scaffolds have uniform macroporous structure, high compressive strength (>30 MPa) and low degradation rate. Hence, forsterite scaffolds fabricated by combining 3D printing and PDCs strategy would be a promising candidate for bone tissue engineering.     

3D printed ceramic phosphor and the photoluminescence property under blue laser excitation

An Al₂O₃/YAG: Ce³⁺ ceramic phosphor was fabricated for high-flux laser lighting using the digital lighting process (DLP)-based 3D printing method for the first time. The photocurable ceramic suspension for 3D printing was prepared by blending well-treated Al₂O₃/YAG: Ce³⁺ composite powders with photosensitive resin monomers and photo-initiators. The printing parameters, debinding and sintering processes were designed delicately to fabricated the dense sub-millimeter-sized cylinder ceramic with high dimensional accuracy. The ceramic showed excellent luminescence property under blue laser excitation with a threshold of 20.7 W/mm², higher than that prepared via dry-pressing followed by vacuum sintering. The luminescence properties and the microstructures of both ceramics were further comparatively investigated to find the possible interpretations for improvement of laser flux for the 3D-printed ceramic. The present work indicated that the new developed 3D printing method was promising for preparing luminescent ceramics for high-flux laser lighting in a rapid, effective, low-cost and precision-controlled manner.     

陶瓷增材制造(3D打印)技术研究进展

高性能陶瓷是现代技术发展和应用不可或缺的关键材料。常规的陶瓷制造技术难以满足对个性化、精细化、轻量化和复杂化的高端产品快速制造的需求。新兴的增材制造技术(3D打印)在高性能陶瓷的成型制造领域具有巨大的发展潜力,有望突破传统陶瓷加工和生产的技术瓶颈,为陶瓷关键零部件的应用开辟新的途径。本文针对陶瓷材料及其快速成型和后处理工艺,重点阐述了三维打印技术、光固化成型技术、选择性激光烧结技术等主流陶瓷增材制造技术的研究现状,并指出了目前存在的问题及发展趋势。     

基于浆料形态的陶瓷3D打印技术的浆料体系研究进展

3D打印技术因其操作简单便捷、成型快速灵活、可制备复杂结构的器件等优点,在精密陶瓷零件制造方面具有广泛应用。本文根据3D打印陶瓷的材料形态综述不同3D打印技术在陶瓷制备方面的特点,重点介绍了陶瓷3D打印成型技术中直写式3D打印、光固化3D打印、喷墨3D打印等技术所涉及的粘结剂、分散剂等组分的应用及作用机理,并对水基和非水基两种类型的添加剂组分进行总结和探讨,以期为3D打印技术制备高性能陶瓷样件提供参考。     

Effect of dispersants on structural integrity of 3D printed ceramics

Ceramic 3D printing based on stereolithography is an excellent alternative to overcome drawbacks of conventional subtractive manufacturing for 3D shape control. Optimization of photocurable ceramic slurry is one of the most essential conditions to achieve favorable 3D printed structures using SL. Homogeneity of ceramic particle dispersion in photocurable resin is particularly important to optimize ceramic suspension. Dispersant plays a significant role in increasing homogeneity. Dispersant in photocurable ceramic resin has an additional effect on photocurability and integrity of 3D printed green body. We herein discuss how dispersants influence 3D printing conditions based on stereolithography using various commercially available dispersants of BYK series such as BYK103, BYK111, BYK180, BYK182, and BYK2001. Both BYK111 and BYK180 showed better performances than others because of their lower volatilities under general temperature condition during a printing process. Both solubility and decomposition temperature of dispersants largely influenced the structural quality after washing and debinding processes. This study provides worthy information to design photocurable ceramic suspension for various types of ceramic materials.     

3D printing of ceramics: A review

Along with extensive research on the three-dimensional (3D) printing of polymers and metals, 3D printing of ceramics is now the latest trend to come under the spotlight. The ability to fabricate ceramic components of arbitrarily complex shapes has been extremely challenging without 3D printing. This review focuses on the latest advances in the 3D printing of ceramics and presents the historical origins and evolution of each related technique. The main technical aspects, including feedstock properties, process control, post-treatments and energy source–material interactions, are also discussed. The technical challenges and advice about how to address these are presented. Comparisons are made between the techniques to facilitate the selection of the best ones in practical use. In addition, representative applications of the 3D printing of various types of ceramics are surveyed. Future directions are pointed out on the advancement on materials and forming mechanism for the fabrication of high-performance ceramic components.     

Influence of number average molecular weight on the properties of 3D printed precursor ceramics

A deliberately selected end-capping agent was introduced into the precursor to form a low number average molecular weight precursor and meet the need for liquid crystal display (LCD) 3D printing. The influence of number average molecular weight on the photocuring properties of precursor and the physical properties of pyrolysis samples were studied in detail for the first time. The results proved that a relatively low number average molecular weight precursors had low ceramic yields after pyrolysis. As the number average molecular weight of the precursor decreased, the photocuring ability of the precursor photosensitive resin increased. With the decrease in the number average molecular weight of the precursor in the precursor photosensitive resin, the ceramic yield of 3D printed PDCs decreased from 58.4% to 30.2%, and the linear shrinkage increased from 27.2% to 40.3%. The bending strength of the LCD 3D printed specimen reached 61.5 ± 3.7 MPa. The low cost of precursor synthesis and equipment in this study points the way for the preparation of precursor non-oxide ceramic composites and can be conducive to the development and application of LCD 3D printing precursor ceramics.     

陶瓷部件3D 打印技术的研究进展

近年来,三维连续网络结构的陶瓷／金属复合材料由于兼具陶瓷材料的耐磨、高强、高硬、抗氧化、耐蚀及钢铁材料的导热性及良好的韧性受到人们的广泛关注。三维连续网络结构的陶瓷／金属复合材料的陶瓷结构的构建是制备复合材料的难题。3D打印技术突破了传统的加工模式,不依赖复杂模具和机械加工,并可根据材料不同的性能要求,开发出不同结构的陶瓷骨架,这将使陶瓷／金属复合材料领域发生巨大变化。本文介绍了陶瓷3D 打印技术的原理、分类、工艺特点及研究进展,并对3D打印技术未来的发展方向进行了展望。     

3D打印成型陶瓷零件坯体及其致密化技术

3D打印技术在陶瓷零件成型方面具有较大应用潜力,被认为是近净尺寸成型高性能复杂结构陶瓷零件的一种新途径。本文比较了陶瓷零件或其坯体的激光选区熔化、薄材叠加制造、熔融沉积造型、光固化、三维打印和激光选区烧结等不同3D打印工艺及其致密化手段的优势和不足,认为较低的相对密度和强度是阻碍3D打印陶瓷零件实现产品应用的主要障碍。本团队近年来采用造粒混合法制备出具有良好流动性的3D打印复合陶瓷粉体,再通过激光选区烧结(SLS)和冷等静压(CIP)技术分别进行坯体成型及均匀致密化处理,制备出了高性能、复杂结构的Al_2O_3致密陶瓷零件。本文回顾了这些工作,并补充介绍了溶解沉淀和溶剂蒸发这两种制备复合陶瓷粉体的新方法,利用SLS/CIP复合工艺进一步制造了ZrO_2、SiC、高白土等其它材质的复杂陶瓷零件,为3D打印陶瓷用于航空航天、医疗、艺术等领域奠定了基础。     

Additive manufacturing of ceramics: Advances,challenges, and outlook

Additive manufacturing (AM) of ceramics is relatively more challenging with respect to polymers and metals, owing to their high melting temperatures and inherent brittleness. Thus, this review aims to provide a comprehensive survey of recent AM technologies successfully employed to produce net shape ceramic components. In recent years, several techniques have been developed and the latest progress in this field are highlighted, as well as the current challenges in the complex shaped ceramic parts production via AM technologies. The state of the art concerning the various 3D printing processes applied to the fabrication of ceramic components is discussed with, for each method, the presentation of its advantages, disadvantages, and possible applications. The potential of AM for producing complex shape ceramic components and the challenges to overcome are discussed as well.     

Transparent alumina ceramics fabricated by 3D printing and vacuum sintering

Transparent alumina ceramics were fabricated using an extrusion-based 3D printer and post-processing steps including debinding, vacuum sintering, and polishing. Printable slurry recipes and 3D printing parameters were optimized to fabricate quality green bodies of varying shapes and sizes. Two-step vacuum sintering profiles were found to increase density while reducing grain size and thus improving the transparency of the sintered alumina ceramics over single-step sintering profiles. The 3D printed and two-step vacuum sintered alumina ceramics achieved greater than 99 % relative density and total transmittance values of about 70 % at 800 nm and above, which was comparable to that of conventional CIP processed alumina ceramics. This demonstrates the capability of 3D printing to compete with conventional transparent ceramic forming methods along with the additional benefit of freedom of design and production of complex shapes.     

Fabrication of complex shaped alumina parts by gelcasting on 3D printed moulds

Alumina ceramic components were produced using gelcasting and 3D printing techniques to generate the end product. The 3D printed mould made from (acrylonitrile butadiene styrene) ABS filament provides a convenient demoulding method by dissolution of the mould using acetone as a solvent. This process enables low cost production of complex shaped ceramic components. The effect of the suspension solid loading on the properties and microstructure of complex shaped alumina parts was investigated. The produced ceramic components had densities up to 99.0%, hardness of 18 GPa, flexural strength of 374 MPa and a fracture toughness of 3.8 MPa√m after sintering in air for 3 h, in good agreement with published values.     

Digital light processing-stereolithography three-dimensional printing of yttria-stabilized zirconia

Digital light processing (DLP)-stereolithography three-dimensional (3D) printing is a well known technique for fabricating components with complex geometries. However, the application of DLP 3D printing to functional ceramics such as 8 mol% yttria-stabilized zirconia (8YSZ), which is one of the most extensively used electrolyte materials for solid oxide fuel cells, is still a great challenge. Therefore, the fabrication of fully 8YSZ monoliths via DLP 3D printing was attempted herein, including the preparation of UV-curable ceramic suspensions, shaping of green bodies, and debinding and sintering. The results show that intact green bodies printed using a 30 vol% 8YSZ-photosensitive resin suspension with 0.1 wt% oleic acid as the dispersant under the optimized printing conditions was sufficiently dense without connected pores after vacuum debinding and sintering in air. The successful fabrication of 8YSZ monoliths with design flexibility via 3D printing provides a simple method for preparing functional ceramic components and may expand the application of 3D printing technology to the energy field.     

大壁厚3D打印SiO2陶瓷快速制备技术研究

选用复合分散剂制备低粘度陶瓷料浆,采用自主研发的陶瓷3D打印机,以DLP(digital light processing)工艺制备出了大壁厚(>3 mm)SiO₂空心内六角陶瓷部件,坯体精度均在50 μm内。分析了3D打印陶瓷素坯在空气气氛和氩气气氛下的热分解过程,研究了气氛对大壁厚(>3 mm)SiO₂陶瓷部件脱脂与烧结的影响。结合扫描电子显微镜(SEM)分析了大壁厚(>3 mm)3D打印SiO₂陶瓷坯体快速脱脂烧结的工艺,氩气气氛有利于大壁厚SiO₂陶瓷快速脱脂烧结。氩气气氛下,控制气流量,进行了大壁厚(>3 mm)SiO₂陶瓷部件的快速制备,脱脂烧结周期大大缩短,为21.8 h,较自国外某公司进口的料浆及其工艺的制备周期(以进口的该公司料浆及工艺制备的相同产品制备周期为283 h)缩短92.3%,较公开报道的3D打印相同工艺制备的SiO₂陶瓷空心叶片制备周期缩短82%以上。     

Optimization of mechanical properties of robocast alumina parts through control of the paste rheology

Robocasting, or Direct Ink Writing, can be used to create dense mono- or multi-materials ceramic parts using micro-extrusion of ceramic pastes through needles, whose position is controlled in 3D. Rheological properties of the ceramic pastes, printing parameters and thermal post processes (drying, debinding and sintering) are key parameters to control the quality of the printed parts. In this work, the rheological properties (including yield stress, shear-thinning behavior, storage/loss moduli and recovery time) of alumina pastes were characterized. Correlations were established between on one side the rheological properties and the printing conditions and on the other side the extrudability, the shape fidelity and the mechanical performance of the final parts. This paper thus defines an extended definition of printability, which includes functional requirements of the final parts in addition to the more classical processability criteria.