Effect of TiO_(2)Addition on Properties of Al_(2)O_(3)Ceramics Prepared by Digital Light Printing(DL.P)

Ceramic slurry of 78 mass%solid loading was prepared using photosensitive acrylic resin and dispersant SP-710 as the liquid phase,Al_(2)O_(3) powder(d50=2.38μm)and TiO_(2) powder additive as the solid phase.Alumina ceramics were prepared by DLP,sintering for 4 h at 1450,1500,1550 or 1600℃,respectively.The effects of the TiO_(2) addition(0,1%,2%,3%and 5%,by mass)on the properties of the ceramics were studied.The results show that the addition of TiO_(2) can improve the sintering of Al_(2)O_(3) ceramics,significantly improve the densification,and reduce the sintering temperature.With the optimum TiO_(2) addition of 3%and the optimum sintering temperature of 1600℃,the obtained Al_(2)O_(3) ceramics have shrinkage of 15.7%,15.8%and 23.8%at the x axis,the y axis,and the z axis,respectively,the porosity of 2.4%,the bulk density of 3.74 g·cm-3 and the three-point bending strength of 251.1 MPa.Compared with the undoped alumina ceramics,the doped alumina ceramic has increased bulk density by 0.56 g·cm-3,decreased apparent porosity from 20.2%to 2.4%,and the three-point bending strength increases by 2.5 times.Therefore,the density and the strength of DLP prepared ceramics can be improved effectively by adding an appropriate amount of TiO_(2),and the performance of the DLP prepared ceramics is close to that of the pressed samples.Thus,it is hopeful to apply DLP in refractories field.

3D printing of calcium phosphate bioceramic with tailored biodegradation rate for skull bone tissue reconstruction

The bone regenerative scaffold with the tailored degradation rate matching with the growth rate of the new bone is essential for adolescent bone repair.To satisfy these requirement,we proposed bone tissue scaffolds with controlled degradation rate using osteoinductive materials(Ca-P bioceramics),which is expected to present a controllable biodegradation rate for patients who need bone regeneration.Physicochemical properties,porosity,compressive strength and degradation properties of the scaffolds were studied.3D printed Ca-P scaffold(3DS),gas foaming Ca-P scaffold(FS)and autogenous bone(AB)were used in vivo for personalized beagle skull defect repair.Histological results indicated that the 3DS was highly vascularized and well combined with surrounding tissues.FS showed obvious newly formed bone tissues.AB showed the best repair effect,but it was found that AB scaffolds were partially absorbed and degraded.This study indicated that the 3D printed Ca-P bioceramics with tailored biodegradation rate is a promising candidate for personalized skull bone tissue reconstruction.

Additive Manufacture of Ceramics Components by Inkjet Printing

In order to build a ceramic component by inkjet printing, the object must be fabricated through the interaction and solidification of drops, typically in the range of 10–100 p L. In order to achieve this goal, stable ceramic inks must be developed. These inks should satisfy specific rheological conditions that can be illustrated within a parameter space defined by the Reynolds and Weber numbers. Printed drops initially deform on impact with a surface by dynamic dissipative processes, but then spread to an equilibrium shape defined by capillarity. We can identify the processes by which these drops interact to form linear features during printing, but there is a poorer level of understanding as to how 2D and 3D structures form. The stability of 2D sheets of ink appears to be possible over a more limited range of process conditions that is seen with the formation of lines. In most cases, the ink solidifies through evaporation and there is a need to control the drying process to eliminate the "coffee ring" defect. Despite these uncertainties, there have been a large number of reports on the successful use of inkjet printing for the manufacture of small ceramic components from a number of different ceramics. This technique offers good prospects as a future manufacturing technique. This review identifies potential areas for future research to improve our understanding of this manufacturing method.

Digital Light Processing 3D-Printed Ceramic Metamaterials for Electromagnetic Wave Absorption

Combining 3D printing with precursor-derived ceramic for fabricating electromagnetic(EM) wave-absorbing metamaterials has attracted great attention. This study presents a novel ultraviolet-curable polysiloxane precursor for digital light processing(DLP) 3D printing to fabricate ceramic parts with complex geometry, no cracks and linear shrinkage. Guiding with the principles of impedance matching, attenuation, and effective-medium theory, we design a crosshelix-array metamaterial model based on the complex permittivity constant of precursor-derived ceramics. The corresponding ceramic metamaterials can be successfully prepared by DLP printing and subsequent pyrolysis process, achieving a low reflection coefficient and a wide effective absorption bandwidth in the X-band even under high temperature. This is a general method that can be extended to other bands, which can be realized by merely adjusting the unit structure of meta-materials. This strategy provides a novel and effective avenue to achieve “target-design-fabricating” ceramic metamaterials, and it exposes the downstream applications of highly efficient and broad EM wave-absorbing materials and structures with great potential applications.

Effect of sintering temperature on microstructure and properties of 3D printing polysilazane reinforced Al_(2)O_(3)core

Ceramic cores are the key intermediate components of hollow blades for aero-engine.Conventional processes,such as hot-press molding and gel film casting,face difficulties in fabricating complex-structured ceramic cores due to the complexity of moulds and long process cycles.Stereolithography 3D printing provides a new idea for the fabrication of complex-structured ceramic cores.The effect of sintering temperature on open porosity,bulk density,weight loss rate,shrinkage rate,flexural strength and microstructure of the Al_(2)O_(3)-based ceramic core doped with 10vol.%polysilazane(PSZ)was studied.The sintering mechanism of PSZ-reinforced ceramic cores was analyzed.Results show that the optimum sintering temperature of PSZ-reinforced ceramic cores is 1,450°C.At this temperature,the open porosity of the ceramic core is 36.60%,bulk density is 2.33 g·cm^(-3),weight loss rate is 22.11%,shrinkage rate along the X,Y,Z directions is 5.72%,5.01%,9.61%,respectively;the flexural strength is 28.794 MPa at 25°C and 13.649 MPa at 1,500°C.Properties of 3D printing PSZ-reinforced ceramic cores can meet the casting requirement of superalloy hollow blades,which is expected to promote the industrial application of 3D printing complex structure ceramic cores.

Preparation of PDOT:PSS Transparent Conductive Film Using Ink-Jet Printing

Flexible devices produced using organic materials have attracted the attention of many researchers. Important components of these flexible devices include transparent electrodes, which transmit visible light and possess conductivity. The present study improved the characteristics of a transparent conductive film that was made of poly(3, 4 ethylenedioxythiophene):poly(styrenesul-fonate) (PEDOT:PSS), an organic conductive material, and that had been prepared using ink-jet printing. To improve the resistance value and visible light transmittance of the film, the film substrate was first cleaned with ultraviolet/ozone treatment, and then the film was annealed after it was deposited on the substrate and dipped into a polar solvent. Consequently, the resistance value of the thin film decreased. However, the surface state of the film changed according to the treatment method and affected its visible light transmittance. Thus, the surface state of the film substrate, the annealing temperature after film deposition, and the dipping treatment with a polar solvent influenced the characteristics of a thin film.

Highly strengthening and toughening biomimetic ceramic structures fabricated via a novel coaxially printing

Additive manufacturing technology,by manipulating and emulating inherent multiscale,multi-material,and multifunctional structures found in nature,has created new opportunities for constructing heterogeneous structures associated with special properties and achieving ultra-high mechanical performance and reliability in ceramic composite materials.In this study,we have developed an innovative fabrication method designated as coaxial 3D printing for the synchronous construction of two constituents into ceramic composites with a tooth enamel biomimetic microstructure.Herein,the stiff silicate and flexible epoxy served as a strengthening bridge and toughening layer,respectively.The method differed from the traditional approach of randomly dispersing reinforcing components within a ceramic matrix.It allowed for the direct creation of an internally effective three-dimensional reinforcement network structure in ceramic composites.This process facilitated synergistic deformation and simultaneous enhancement of multiple materials and hierarchical structures.Owing to the uniform distribution of internal stress and effective block of microcrack propagation,the biomimetically structured silicate/epoxy ceramic composite has demonstrated much significant enhancement in mechanical properties,includingcompressive strength(48.8±3.12MPa),flexuralstrength(10.39±1.23MPa),andflexuraltoughness(218.7±54.6kJ/m^(3)),which was 0.5,2.1,and 47.5 times as high as those of the intrinsic brittle silicate ceramics,respectively.In-situ characterization and multiscale finite element simulation of microstructural evolution during three-point bending deformation further validated multiple-step features of the fracture process(silicate bridge fracture,interface detachment,epoxy extraction,and rupture),which benefited from interpenetrating structural features achieved by coaxial printing to accomplish with the complex propagating routines of the crack deflection in silicate ceramic composites.This coaxial 3D printing method paves the way for tailored toughening-strengthening designs for other brittle engineering ceramic materials.

Characteristics Improvement of PEDOT:PSS Transparent Conductive Film Prepared by Ink-Jet Printing

Recently, a high-performance and low-priced transparent conductive film has been expected to be developed because flexible devices produced using organic materials have been actively studied. An indium tin oxide (ITO) thin film, which has been generally used as a material for a transparent conductive film, has problems, such as fragility to bending stress and depletion of the resource. The present study used poly(3, 4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS), an organic electroconductive material, and examined the improvement in the resistance value and visible light transmittance of a transparent conductive film produced using the ink-jet method. In previous studies, we reported that, to improve the resistance value and visible light transmittance of a thin film, it was effective to clean the film substrate with ultraviolet/ozone (UV/O3) treatment, anneal the film after it was deposited on the substance, and dip the annealed film into a polar solvent. Focusing on the thin film processing between printing operations, the present study improved resistance value and visible light transmittance by examining both the application methods of a polar solvent and the annealing time between printing operations. As a result, the resistance value and visible light transmittance of a PEDOT:PSS thin film were 390.4 Ω and 86.6%, respectively. This film was obtained by applying a polar solvent and performing annealing for 30 min between printing operations. The printing was performed three times.

Application of nonlinear color matching model to four-color ink-jet printing

Through discussing the color matching technology and its application in printing industry the conventional approaches commonly used in color matching, and the difficulties in color matching, a nonlinear color matching model based on two step learning is established by finding a linear model by learning pure color data first and then a nonlinear modification model by learning mixed color data. Nonlinear multiple regression is used to fit the parameters of the modification model. Nonlinear modification function is discovered by BACON system by learning mixture data. Experiment results indicate that nonlinear color conversion by two step learning can further improve the accuracy when it is used for straightforward conversion from RGB to CMYK. An improved separation model based on GCR concept is proposed to solve the problem of gray balance and it can be used for three to four color conversion as well. The method proposed has better learning ability and faster printing speed than other historical approaches when it is applied to four color ink jet printing.

The Effect of Silica Particle Size on the Performance of Color Ink-jet Printing Paper

In this paper,the effects of four sorts of silica with the particle size range of 4～10μm on coated paper properties and printing performance were studied.The results showed that the smaller particle size silica can provide the coated paper with higher density and contrast, better definition and good printing performance.

Printable,flexible ceramic fiber paper based on electrospinning

Based on the fact that it is challenging for the polymer flexible circuit substrates to meet the requirements of serving in high-temperature environments,this work proposed the idea of using printable ceramic fiber paper as a high-temperature flexible circuit substrate.A ceramic fiber paper with all ceramic components had been developed via electrospinning,solving the problems of low strength and severe strength drop at high temperatures of traditional ceramic fiber paper.The tensile strength of the prepared ceramic fiber paper is 2.63 MPa,and the reliable service temperature is 1200℃.Its bulk density is about 1.5 times that of traditional ceramic fiber paper.It can be printed with patterns by commercial inkjet printers like ordinary printing paper and has excellent printability.The feasibility of ceramic fiber paper as a flexible circuit substrate was verified by constructing a simple circuit.When the fiber paper is significantly bent,the circuit still forms a complete path,which proves that it has a strong application potential for high-temperature flexible circuit substrate and is expected to promote the development of flexible electronic devices serving at extreme high-temperature environments.

Manufacturing of ceramic cores:From hot injection to 3D printing

With the improvement of aero-engine performance,the preparation of hollow blades of single-crystal superalloys with complex inner cavity cooling structures is becoming increasingly urgent.The ceramic core is the key intermediate part of the preparation and has attracted wide attention.To meet this challenge,new technologies that can make up for the defects of long periods and high costs of fabricating complex structural cores by traditional hot injection technology are needed.Vat photopolymerization 3D printing ceramic technology has been applied to the core field to realize the rapid preparation of complex structural cores.However,the industrial application of this technology still needs further research and improvement.Herein,ceramic cores were prepared using traditional hot injection and vat photopolymerization 3D printing techniques using fused silica,nano-ZrO_(2),and Al_(2)O_(3) powders as starting materials.The 3D printed ceramic core has a typical layered structure with a small pore size and low porosity.Because of the layered structure,the pore area is larger than that of the hot injection ceramic core,the leaching performance has little effect(0.0277 g/min for 3D printing cores,0.298 g/min for hot injection cores).In the X and Y directions,the sintering shrinkage is low(2.7%),but in the Z direction,the shrinkage is large(4.7%).The fracture occurs when the inner layer crack expands and connects with the interlayer crack,forming a stepped fracture in the 3D-printed cores.The bending strength of the 3D printed core at high temperature(1500℃)is 17.3 MPa.These analyses show that the performance of vat photopolymerization 3D-printed ceramic cores can meet the casting requirements of single crystal superalloy blades,which is a potential technology for the preparation of complex structure ceramic cores.The research mode of 3D printing core technology based on the traditional hot injection process provides an effective new idea for promoting the industrial application of 3D printing core technology.

Millimeter Scale MEMS Air Turbine Generator by Winding Wire and Multilayer Magnetic Ceramic Circuit

This paper provides a new system and concept concerning to MEMS air turbine power generator. The generator was composed of the MEMS air turbine and the magnetic circuit. The magnetic circuit was fabricated by multilayer magnetic ceramic technology and achieved monolithic structure which included high permeability material and three di-mensional helical conductor patterns inside. Although the output power was micro watt class, some features were extracted by comparing to the simple winding wire type magnetic circuit. In the power density measurement, almost same output power density was extracted though the turn number of the winding wire type was more than that of monolithic type. Also the resistance of the conductor was quarter of the winding type. The maximum output voltage and the maximum power of the monolithic generator was 6.2 mV and 1.92 μVA respectively. The DC conductor resistance was 1.2 Ω. The energy density was 0.046 μVA/mm3. The appearance size of the monolithic type was 3.6, 3.4, 3.5 mm, length, width and height respectively.

Ceramic composites toughened by vat photopolymerization 3D printing technology

High strength and high toughness are mutually exclusive in structural materials.In ceramic materials,increasing toughness usually depends on the introduction of a ductile phase that reduces the strength and high-temperature stability of the material.In this work,vat photopolymerization 3D printing technology was used to achieve toughening of ceramic composite material.The friction sliding of the 3D-printed ceramic macrolayer structure results in effective energy dissipation and redistribution of strain in the whole structure,and macroscale toughening of the ceramic material is realized.In addition,the bridging and elongation of the crack in situ amorphous ceramic whiskers were significant microscopic toughening results,coupled with the toughening of the crack tip of nano-ZrO_(2).Multiscale collaborative toughening methods based on 3D-printed ceramics should find wide applications for materials in service at extreme high temperatures.

Digital light processing 3D printing of porous ceramics based on multi-materials additive manufacturing

1.Introduction Porous ceramics are widely used in many fields,including aerospace,electronics,medical materials,and biochemistry.They possess properties such as high-temperature resistance,corrosion resistance,good chemical stability,and large specific surface areas[1].Traditionally,porous ceramics are prepared using techniques such as partial sintering,pore-forming method,freeze-drying,tin plating,direct foaming,and recrystallization[2,3].However,it is challenging for these techniques to meet the requirements for complicated structures and rapid prototyping.

SLA打印制备融合TPMS氧化铝陶瓷支架结构优化设计研究

三周期最小表面(TPMS)结构具有优异的力学性能与生物医学性能,设计制造合适的TPMS骨支架结构能为骨修复、骨替代、骨愈合的临床治疗提供可能。本文基于人体骨组织结构参数分别设计了以P、G、D三种类型为主的TPMS支架及其不同融合系数K值影响下的融合TPMS支架,采用紫外立体光刻技术(SLA)打印制备了陶瓷生坯,通过脱脂与烧结后处理获得了成型氧化铝陶瓷支架,并对支架模型与成型陶瓷试样分别进行了有限元仿真与实验测试。结果表明:1)陶瓷支架具有相对光滑的表面与较高的成型精度,其整体形态与设计模型基本一致,侧面比顶面稍显粗糙。2)与单类型结构相比,融合TPMS结构支架表现出较好的抗压强度与应力分布。其中,当融合系数K=4时,P与G结构融合支架支架的力学性能最优,抗压强度为71.72 MPa,最大应力与平均应力分别为141.90和13.214 MPa;3)融合结构的渗透性均弱于单类型结构,且不同融合系数K值的结构支架渗透性也不同,结合数值模拟与实验数据,当融合系数K=1、2时,P与G结构、P与D结构融合支架渗透性表现较好。综上,当融合系数K=1时,P与G结构融合支架同时具备较优的力学性能和渗透性,适合作为人体骨支架结构类型。

数据驱动的中温隔热陶瓷管件结构优化设计及性能评估

随着中温区电加热的电子产品和家电用品不断涌现,低成本的高效保温隔热材料研究日益成为热点。如何确保管路内部快速升温并避免外表温度大幅波动,有效提高能源利用率,是保温隔热材料领域的挑战。据此,本研究以低熔点玻璃助烧结的镁橄榄石、莫来石、珍珠岩和磷酸锌等复合物陶瓷为对象,从数据驱动的壁内多孔结构隔热管件优化设计出发,开展陶瓷隔热管件三维打印制造,通过显微结构和力学性能分析,并围绕管件的导热、隔热影响因素评估,系统考察了该类新型隔热管件的理化、力学和隔热性能及影响关系。结果表明,通过对沿管壁环绕的矩形大孔高度调控(400~1 200μm)、管腔内热源区的管壁倍增(1.2 mm×2 mm)以及有机微球造孔剂引入(~9%),同时通过烧结温度控制(700~750℃),可以显著改善热流出口区的温度水平(~20℃),并显著优于不锈钢真空隔热管的出口温度。研究结果表明,增材制造复合陶瓷管件具有优良的综合性能以及较低的原料成本,使得多孔陶瓷隔热管件在中温隔热领域具有广阔的应用前景。

氮化硅陶瓷光固化3D打印成形研究进展

与其他增材制造技术相比,光固化3D打印成形技术制备结构复杂、致密度高、表面精度高的陶瓷具有独特的优势,并逐步成为陶瓷增材制造领域的研究热点。然而,氮化硅陶瓷的高折射率和高吸光度等特征导致光固化成形困难,限制了其发展和应用。本文分别从光固化氮化硅陶瓷的浆料流变性能以及固化性能进行分析,总结归纳出氮化硅浆料在流变性能和固化性能方面面临的问题,进一步汇总了提升氮化硅陶瓷浆料光固化性能的研究工作,并对粉体改性、调控树脂组成等几种方法进行分析与探讨。最后,对氮化硅陶瓷光固化3D打印的未来发展趋势和方向进行了详细阐述。

颗粒级配对选区激光烧结打印结合常压固相烧结制备碳化硅陶瓷性能的影响

SiC陶瓷因其独特的热学、电学性能及优异的力学性能,被广泛应用于航空航天、核能、化工、半导体等国防与工业重大领域,但是传统的成型方法无法满足大尺寸复杂构件的制备需求。选区激光烧结(SLS)打印具有无需支撑、材料利用率高、加工效率高等优势,能高效成型复杂陶瓷结构零部件。本研究采用颗粒级配SiC的方法,系统研究了冷等静压(CIP)、前驱体浸渍热解(PIP)、CIP结合PIP后常压固相烧结等工艺对级配和中位径82μm未级配体系SiC陶瓷的影响。研究发现,级配粉末成型坯体的体积密度和抗弯强度比未级配坯体均提升了20%以上,级配体系CIP后常压固相烧结体的相对致密度达到了90%以上,实现了致密化烧结,而未级配体系烧结体的相对致密度仅为89%,这是由颗粒级配后坯体的堆积密度提升所致,且级配烧结体的抗弯强度(136.8 MPa)比未级配(99.4 MPa)提升了37%以上。采用多次重复PIP结合常压固相烧结的方法制备高致密的SiC陶瓷,发现SLS打印成型的坯体经四次PIP后致密度可达到CIP堆积致密的效果,但四次PIP后常压固相烧结体的体积密度仅为2.29 g/cm^(3),抗弯强度为59.6 MPa。

3D打印隔热材料研究进展

3D打印技术能够实现面向性能的设计以及非常规结构的制造,其在隔热领域的应用可以使材料具有更加精细、可控、定制化的结构与功能。当前,3D打印隔热材料技术仍处于快速迭代期,打印材料、结构设计和制造工艺等技术瓶颈尚待突破。本文对3D打印隔热材料的现状进行了综述,简要分析了在隔热材料制造方面较有前景的3D打印工艺,对比了各工艺的优缺点以及适用的材料类型,着重讨论了3D打印陶瓷、发泡混凝土、泡沫塑料和气凝胶材料在隔热领域的研究进展,最后总结了目前面临的技术挑战和未来的主要发展方向。