Collection of 3D Printing(202312)
Al2O3-TiCp (AT) composites are frequently used as materials for metal cutting tools due to their superior mechanical properties. However, conventional sintering methods for AT materials have limitations in terms of energy consumption and cycle time. Therefore, in this study, direct additive manufacturing of AT composite ceramic materials was investigated using laser directed energy deposition technology. Effects of different TiCp ratios on the microstructure and mechanical properties of composite ceramic materials were explored. The results demonstrate that TiCp particles are uniformly distributed throughout the matrix of the fabricated samples, leading to refinement of Al2O3 grains. Stress induced by mismatch between the thermal expansion coefficients of TiCp and the Al2O3 matrix causes cracks to deflect and penetrates the particles, which consumes the crack extension energy and effectively suppresses the cracks in AT materials. Additionally, doping TiCp particles affects the molten pool by increasing the gas escape rate and improving the material density. However, high TiCp content aggravates the reaction with Al2O3 at high temperature, resulting in generation of gas and large pores in the composite material, which reduces the mechanical properties. Composites with TiCp mass fraction of 30% exhibit the best mechanical properties, with a relative density of 96.64%, microhardness and fracture toughness of 21.07 GPa and 4.29 MPa·m1/2.
Ceramic-based porous structures not only inherit the excellent properties of dense ceramic materials such as high-temperature resistance, electrical insulation, and chemical stability, but also have unique advantages similar to porous structures, including low density, high specific surface area, and low thermal conductivity. They show great potential in various applications, such as thermal insulation, bone tissue engineering, filtration and pollutants removal, and electronic components. However, there still exist some challenges for shaping complex geometries on the macro- scale and adjusting pore morphologies on the micro- and nano-scale through the conventional preparation strategy of ceramic-based porous structures. In recent decades, researchers have been devoting themselves to developing novel manufacturing techniques for ceramic-based porous structures. The direct-ink-writing 3D printing, as one of the representative additive manufacturing technologies, has become a current research hotspot, rapidly developing a series of mature theories and innovative methodologies for fabricating porous structures. In this work, the conventional strategies and additive manufacturing strategies for obtaining porous structures were firstly summarized. The direct-write assembly processes of pore structures were further introduced in detail, mainly including pseudoplastic ink formulation, solidification strategy, drying, and post-treatment. Meanwhile, the feasibility of direct-ink-writing 3D printing technologies combined with conventional manufacturing strategies in constructing ceramic-based hierarchical pore structures was analyzed emphatically. The new perspectives, developments, and discoveries of direct-ink-writing 3D printing technologies were further summarized in the field of manufacturing complex ceramic-based porous structures. In addition, the developments and challenges in the future were prospected according to the actual application status.
Silicon carbide (SiC) ceramics, as a high-performance structural-functional integrated material, are widely used in aerospace, nuclear industry and braking system. However, the conventional fabrication methods can not meet the increasing demands for large-scale and complex-structured SiC ceramics, such as engine nozzles, flaps and turbine blades. Binder jetting (BJ) 3D printing technology can overcome the traditional obstacle and provide a novel manufacturing roadmap. Here, we adopted this technique via SiC particle grading, optimized the particle size ratio based on gradation theory, and studied the influence of BJ printing on properties of SiC green body and as-sintered ceramic. For the particle-graded green body after BJ printing, SiC ceramics with a maximum flexural strength of (16.70±0.53) MPa was obtained after one precursor impregnation and pyrolysis (PIP) treatment, whose flexural strength was improved by 116% as compared with that BJ printed from a median diameter of 20 μm. SiC ceramics were further densified using liquid phase siliconization, with the density, flexural strength, elastic modulus, and fracture toughness reaching (2.655±0.001) g/cm3, (285±30) MPa, (243±12) GPa, and (2.54±0.02) MPa·m1/2, respectively. XRD results demonstrated that the sintered SiC ceramics were mainly composed of 3C structured-β-SiC. All results show that high-performance SiC ceramic materials are innovatively prepared by an efficient and reliable method, based on the combined techniques of particle grading, BJ printing, PIP and liquid silicon infiltration.
Bioceramic scaffolds with excellent osteogenesis ability and degradation rate exhibit great potential in bone tissue engineering. Akermanite (Ca2MgSi2O7) has attracted much attention due to its good mechanical property, biodegradability and enhanced bone repair ability. Here, akermanite (Ca2MgSi2O7) scaffolds were fabricated by an extrusion-type 3D printing at room temperature and sintering under an inert atmosphere using printing slurry composed of a silicon resin as polymer precursor, and CaCO3 and MgO as active fillers. Furthermore, the differences in structure, compressive strength, in vitro degradation, and biological properties among akermanite, larnite (Ca2SiO4) and forsterite (Mg2SiO4) scaffolds were investigated. The results showed that the akermanite scaffold is similar to those of larnite and forsterite in 3D porous structure, and its compressive strength and degradation rate were between those of the larnite and forsterite scaffolds, but it showed a greater ability to stimulate osteogenic gene expression of rabbit bone marrow mesenchymal stem cells (rBMSCs) than both larnite and forsterite scaffolds. Hence, such 3D printed akermanite scaffold possesses great potential for bone tissue engineering.
As an emerging manufacturing technology, additive manufacturing technology, also known as 3D printing technology, has received extensive attention in recent years. Additive manufacturing technology has great potential in the industry of high-performance ceramics. It is expected to break the technical bottle neck of the traditional manufacturing technologies used for ceramic fabrication and greatly improve the flexibility of design and manufacturing of high-performance ceramics. This will provide a transformative impetus for the development of the manufacturing technology of the high-performance ceramic materials. Polymer-derived ceramics (PDCs) are a class of polymers obtained by chemical methods and can be transformed into ceramics by heat treatments, i.e., pyrolysis. Due to the good machinability and formability of the PDC materials themselves, the pre-forming of the designed target structures can be easily realized. These structures might not be possible with traditional ceramic manufacturing. Therefore, the combination of PDCs and additive manufacturing technology has attracted great attention from researchers. This review introduces characteristics of the additive manufacturing technology used for preceramics. Based on that, the present research status, trends and applications are also systematically described and discussed. The challenges and future directions of the additive manufacturing of polymer-derived ceramics are given for the guidance of future development.
Piezoelectric ceramic is a type of functional ceramic, which is able to convert the mechanical signal and the electronic signal mutually. Composed of piezoelectric ceramics and organic phase, piezoelectric composites have different kinds of connectivities, which not only determine the diverse applications of piezoelectric devices, but also promote the development of various shaping techniques in manufacturing piezoelectric materials and devices. In comparison with the traditional shaping methods, the most distinguishable advantage of additive manufacturing lies in its ability of quickly shaping a small batch of samples into geometrically complex designs without a mould, which makes it a highly suitable technique for investigating piezoelectric ceramics and its derivative devices in different kinds of connectivities. Meanwhile, the final additively manufactured samples require only tiny post-processing, have a high rate of utilization of the raw material and do not need cutting fluid during manufacturing. Due to the above-mentioned advantages, it attracts the widespread concerns from both academic and industrial communities. When focusing in the field of additive manufacturing ceramics, the data of scientific reports in additive manufacturing functional ceramics and devices prove that it is still in a growing period. In the perspective of different additive manufacturing techniques, this article discusses and compares additive manufacturing of both lead-free and lead-based piezoelectric ceramics in the aspects of their historical development of each technique, preparation of the raw materials, geometrical designs, measurement of functional properties, and applications of the printed samples, and forecasts the future development based on the current benefits and drawbacks of each additive manufacturing technique.
Inflammation in bone defect after being implanted scaffold is related to oxidative stress, which is caused mainly by higher concentration of hydrogen peroxide (H2O2). Manganese dioxide (MnO2) can catalyze H2O2 decomposition to decrease excessive H2O2 in the surrounding environment of scaffolds. Furthermore, the oxygen (O2) generated by the decomposition of H2O2 can alleviate the hypoxia caused by insufficient blood supply in bone defects, which is conducive to bone tissue regeneration. Here, a simple redox method was proposed to deposit MnO2 particles on the surface of 3D printed bioactive glass (BG) scaffolds for the preparation of BG-MnO2 composite scaffolds (BGM), which endows BG-MnO2 scaffolds with the ability of H2O2 scavenging and O2 supplying simultaneously. The results showed that the MnO2 content deposited on the surface of BGM scaffolds was increased with the increase of potassium permanganate concentration in the reaction solution, and the compressive strength of BGM scaffolds was increased with the increase of MnO2 content. However, porosity and degradation rate of these scaffolds with or without MnO2 remained the same. More importantly, BGM scaffolds can continuously catalyze the decomposition of H2O2 to produce O2 in H2O2 environment. When BGM with different Mn content scaffolds (BMG5 and BGM9) catalyzed the decomposition of H2O2 to produce O2 in 2 mmol/L H2O2 solution, the saturated oxygen concentration in the solution could reach 8.4 and 11 mg/L, respectively. In vitro cell experiments showed that BGM scaffolds could promote the proliferation and alkaline phosphatase activity of rabbit bone marrow mesenchymal stem cells. Hence, BGM scaffolds show great potential in bone regeneration.
Melt-grown oxide eutectic ceramics possess a large area of clean and firmly bonded phase interfaces through liquid-solid phase transformation, which makes them present excellent high-temperature properties such as strength retention, creep resistance, thermal stability, oxidation and corrosion resistance. As a result, directionally solidified oxide eutectic composite ceramics have been regarded as one of candidates for new generation of high temperature structural materials which can service above 1400 ℃ in oxidation environment for a long period. In recent years, laser additive manufacturing based on melt growth has developed into the most promising technique for preparing ultrahigh-temperature oxide eutectic ceramics due to its unique advantage in one-step fabricating highly dense parts with large sample size and complex shape. In this paper, laser additive manufacturing technology was summarized in terms of forming principle, technical features and classification. The research status and the encountered technical problems in additively manufacturing melt-grown oxide eutectic ceramics were reviewed. Moreover, the research progress on laser additive manufacturing oxide eutectic ceramics was introduced from the aspects of laser forming process, solidification defect control, solidification microstructure evolution, and mechanical properties. Finally, the key bottlenecks of realizing engineering applications of the laser 3D-printed oxide eutectic ceramics were pointed out, and the future development directions of this field were prospected. The focus of the future work can be summarized into four points: developing high-quality spherical eutectic ceramic powders, preparing large-scale eutectic parts with complex shapes, accurate controlling solidification defects, as well as strengthening and toughening eutectic composites.
At present, stereolithography 3D printing technology is widely used in ceramic additive manufacturing because of its high printing accuracy. Among them, the stereolithography ceramic slurry of non-oxide ceramics such as silicon carbide, silicon nitride, etc., has problems such as poor dispersion stability and low curing layer thickness because the incident light is difficult to penetrate and produce light curing reaction for printing high-solid-loading slurry. This is all because the refractive index and optical absorbance of the non-oxide ceramic printing material powder are relatively high. Therefore, printing and molding of high-solid-content non-oxide ceramics have become main challenges in stereolithography 3D printing, and the technology has attracted a large number of researchers to study its light-curing mechanism, powder control and other mechanisms. This paper systematically summarizes the research works of several non-oxide ceramics such as light-curing slurry preparation, light-curing molding, organic matter removal, and sintering densification. It also analyzes and discusses several methods of adjusting composition of photosensitive resin and modifying ceramic powder, and proposes innovative solutions to improve the slurry performance of non-oxide ceramics, optimize its light-curing printing, repair its densification defects and improve its performance. And the ultimate goal is to promote the advancement of high-precision preparation technology for light-curing additive manufacturing of large-size, complex-structure non-oxide ceramic parts.
Because of low thermal conductivity and weak physical and chemical stabilities, traditional “phosphor in silicone” color converters are precluded from high-power white LED applications. All-inorganic bulk luminescence materials not only can circumvent organic encapsulation, but also have higher thermal conductivity. However, those bulk materials are high in cost and very difficult to be shaped into three-dimensional structures. Here, based on amorphous silica nanoparticles, a slurry, containing (Gd,Y)AG:Ce phosphor powders and can be polymerized under UV light, were developed. Bulk (Gd,Y)AG:Ce-silica glass composites were prepared successfully through photo curing, debinding in air and pressureless sintering. Under excitation of blue light, these luminescence glass-ceramics exhibit broadband orange emission peaking at 575 nm with internal quantum efficiency higher than 90%. Our results show that the interfacial reaction between (Gd,Y)AG:Ce and silica glass is very weak, and thus the former can be well embedded into bulk silica glass. Such all-inorganic color converters were further used to fabricate high-power warm white LEDs with correlated color temperature smaller than 4500 K, color rendering index higher than 75, and luminous efficiency of 74 lm·W -1. Luminescence saturation threshold of the as-fabricated laser lighting device is as high as 2.84 W·mm-2, where its luminous flux can achieve 180 lm. Moreover, preparation of (Gd,Y)AG: Ce-silica glass composites is compatible to 3D printing technology, thus allowing the mass manufacturing of color converters with complex 3D structures, which may promote personalization and modularization of high-power white LEDs.
Photopolymerization 3D printing method is an effective means for the manufacturing of ceramics with highly complex-shaped structures and exceptional performance. The printed samples need to undergo heat treatment such as debinding and sintering before becoming usable final ceramic parts in various industrial applications, and the debinding process has a great impact on the properties of the printed ceramic parts. In this study, effect of the debinding process on physical properties and mechanical performance of the cordierite ceramics prepared by DLP photopolymerization 3D printing was studied, and defect suppression strategy was established accordingly. The effects of debinding atmosphere and heating rate on surface cracks and material elemental distribution of ceramic samples were compared and analyzed. The microstructure, size shrinkage, relative density, and mechanical performance such as bending strength of the sintered samples were also studied. It is found that the debinding atmosphere has the most significant influence on the properties of the sintered samples, in which the surface cracks can be significantly reduced, and the relative density, and bending strength can be increased when the debinding process is conducted in argon atmosphere at the optimized heating rate of 1 ℃/min. After debinding and sintering, the cordierite ceramic samples with a relative density of (94.6±0.3)% and a bending strength of (94.3±3.2) MPa was obtained. In conclusion, this study provides a scientific basis and technical reference for fabrication and application of cordierite ceramics based on photopolymerization 3D printing method.
Single crystal superalloy hollow blade is an important part of aero-engine, and its inner cavity structure is prepared by ceramic core. With the increase of thrust-weight ratio of aero-engine, the core structure is more and more complex. Traditional preparation technology is difficult to meet the requirements of complex core preparation. Stereolithography 3D printing of ceramic cores provides a feasible scheme for the preparation of complex cores. In order to improve the surface roughness of stereolithography 3D printed ceramic cores caused by step effect, this study used silicon-based core paste with solid content of 63% (in volume), and the cores of the green bodies were sintered at 1100 ℃ to 1300 ℃. Microstructure, element distribution, phase composition, surface morphology, and roughness of the silicon-based ceramic core were analyzed. It is found that printed surface of the core is smooth without obvious surface defects. Roughness of the printed surfaces of the sintered cores at 1100, 1200 and 1300 ℃ are 1.83, 1.24 and 1.44 μm, respectively. Their surface of lamellar stacking direction has lamellar structure characteristics, and microcracks appear between lamellar, and surface roughness of core sintered above 1200 ℃ meets the requirements (Ra≤2.0 μm) of hollow blade. Sintering temperatures affect the liquid content, mullite production, mullite formation morphology, and glass phase distribution of cores during the sintering process, and the surface roughness of stereolithography 3D-printed silicon ceramic cores is positively affected. Stereolithography 3D printing ceramic core technology combined with sintering process can produce a silicon-based ceramic core which surface roughness meets the requirements of an advanced hollow blade.
Debinding heat treatment process play an important role in forming quality of 3D printing ceramics. At present, the alumina green body prepared by light curing 3D printing is sintered after debinding in air. The final alumina ceramics may have defects such as micro cracks, resulting in poor mechanical properties. Direct heating and debinding in air may lead to cracks caused by reaction between resin and oxygen in green body. To avoid this situation, this work studies the printing heat treatment process of alumina ceramics based on digital light processing (DLP) technology. The alumina ceramic green body prepared by 3D printing was degreased either in air or in argon, and their macro morphologies were compared with each other. It is found that there are micro cracks in the alumina green body debinding in air. After being sintered in air, the alumina ceramics was obtained and their micro morphology and macro properties were characterized. Average grain size of alumina ceramics debinding in argon was larger than that directly debinding in air, while the grain structure was dense without obvious pore and impurity. Moreover, in terms of mechanical properties, alumina ceramics debinding in air have higher compressive strength. The highest density of alumina debinding in argon reaches 96.72%, and the compressive strength reaches 761.7 MPa, significantly improved as compared with the one debinding in air.
Gypsum is a common material for statues, building, and casting molds (alloys and ceramics). Due to the incomplete hydration reaction between water and gypsum, it is difficult to print high-strength gypsum products using 3D printing techniques such as Binder Jetting. To enhance its strength, the hydration reaction should be completely performed, which could be fulfilled by direct ink writing (DIW). However, the reaction in the gypsum paste for DIW is so fast that less time is left for operating a 3D printer. In this work, a printable gypsum paste with a reasonable setting time was developed to print 3D gypsum structures via direct ink writing. A retarder and a thickener were introduced into the paste to prolong its setting time for operating and tailor its rheological property for printing, respectively. The setting time, expansion and rheological properties of the pastes were tested by the Vicat apparatus, consistometer and rheometer, respectively. The results show that citric acid (CA) is a suitable retarder, although decreases its compressive strength due to the directional grown gypsum crystals resulting from the selective adsorption of CA on gypsum powder, while hydroxypropyl methylcellulose (HPMC) is an acceptable thickener, which affects forming flocculation structure in the paste, resulting in higher viscosity and shear modulus. Optimal amounts of CA and HPMC for the printable gypsum paste are 0.6% and 0.3% (in mass), respectively. Three-dimensional gypsum structures such as spider web and scaffold are successfully printed via direct ink writing, which compressive strength is around 20 MPa, much higher than that printed via Binder Jetting.