Cure behavior of colorful ZrO2 suspensions during Digital light processing (DLP) based stereolithography process

In this study, the light absorption of the pure ZrO₂ and three types of colorful ZrO₂ mixtures were investigated. It was found that the absorbance of colored ZrO₂ powder increases with the colorant content, and the yellow-colored powder has the strongest absorbance at the wavelength of 405 nm compared with the other two types of colored ZrO₂ powder. The cure behavior investigation on the ceramic suspensions of the above four types of ZrO₂ powders during DLP process shows that as the colorant content increases, the cure depth and excess cure width both decrease due to the ceramic absorbance. The cure depth of colored suspensions is linear with logarithm of incident energy, consistent with Beer-Lambert model, while the further research into the cure width shows that the excess cure width increases nonlinearly with logarithm of incident energy, which is inconsistent with Quasi-Beer-Lambert model. Additionally, colorful ZrO₂ accessories were successfully fabricated.     

Photocurable ceramic slurry using solid camphor as novel diluent for conventional digital light processing (DLP) process

This study presents the utility of solid camphor as a novel type of diluent for the preparation of photocurable ceramic slurries with sufficiently low viscosity at high solid loading (48 vol%), which can be applicable for the conventional digital light processing (DLP) process. The camphor addition remarkably decreased the viscosity of calcium phosphate (CaP) ceramic slurries without affecting their photopolymerization behavior. This approach could effectively mitigate the clogging of pores with residual slurries, and thus the porous structure of porous CaP scaffolds with 3D channels could be tightly controlled. Furthermore, the high densification of CaP frameworks after sintering at 1250 °C for 3 h could be achieved owing to the use of the high solid loading in the CaP slurry. The porous CaP scaffolds produced displayed high compressive strength (˜ 23.8 MPa) and modulus (˜ 276 MPa) at a high porosity of ˜ 50.6 vol%.     

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.     

Influence of resin composition on rheology and polymerization kinetics of alumina ceramic suspensions for digital light processing (DLP) additive manufacturing

Alumina ceramics with optimized microstructures and mechanical properties were obtained by the attractive digital lighting processing (DLP) additive manufacturing methodology in the present study. A acrylate-based resin system was designed for the alumina powders with a mean particle size of 0.5 μm. The influence of oligomer on the viscosity and polymerization kinetics of the ceramic suspensions has been elaborately discussed by rheology, curing depth and photo-DSC characterizations. The results indicated that the introduction of oligomer has improved the cross-linking density of resins and decreased the critical dose of energy for resin polymerization, which contributed to a tougher ceramic-resin slice with higher dimensional accuracy. Densifying processes including debinding and high temperature sintering of the ceramic parts were conducted according to the TG-DTA characterizations, alumina ceramics with uniform microstructures and eliminated delamination or intralaminar cracks were finally obtained. The flexural strength was 471 MPa for the ceramics obtained from the resin composition containing 20 wt% oligomer, Weibull modulus for the ceramics were determined to be 17.31 by evaluating thirty all sides polished ceramics, indicating the highly uniform property of the ceramics fabricated by DLP additive manufacturing.     

Effect of polystyrene addition on properties of porous Si3N4 ceramics fabricated by digital light processing

Porous Si₃N₄ ceramics with high strength and high transmittance have been widely used in the field of defense and military. Additive manufacturing (AM) technology is one of the effective means to fabricate porous Si₃N₄ ceramics. Nevertheless, it is difficult to prepare porous Si₃N₄ ceramics by using digital light processing (DLP) because of the large refractive index difference between Si₃N₄ powders and photosensitive resin. In this study, the effects of the amount of polystyrene (PS) powders on the properties of Si₃N₄ ceramic slurries and sintered ceramics were systematically discussed. The addition of PS reduced the overall refractive index of powders and increased the average particle size of powders, thus improving the cure depth of Si₃N₄ ceramic slurries from 11.0 ± 2.0 μm to 55.7 ± 1.8 μm. With the increase of PS content, the shrinkage and porosity of Si₃N₄ ceramics gradually increased, and the bulk density and flexural strength showed the opposite trend. The slurry with low viscosity (2.38 Pa٠s at a shear rate of 30 s⁻¹) and high cure depth (51.2 ± 4.6 μm) was obtained when the content of PS was 15 wt%, which met the thickness requirements for printing. The total porosity of Si₃N₄ ceramics reached the maximum values at 28.21 ± 2.58%. The addition of PS solved the problem of low cure depth of slurries, and PS as a pore-forming agent could help Si₃N₄ ceramics form porous structure. This research provides valuable insights into the fabrication of non-oxide ceramics with high refractive index using DLP technology.     

高性能纤维表面改性研究进展

高性能纤维具有优异的性能,广泛用于宇航和军事领域,但是其与树脂基体之间的界面粘接性能较差,复合材料的层间剪切强度较低。针对这一复合材料体系,全面论述了提高其性能的几种方法以及各种方法的优缺点,其中包括纤维表面接枝、偶联、聚合物涂层、冷等离子体、γ射线辐射和超声波处理等,同时介绍了改性纤维的性能表征方法。     

改性TiO_2(TMG)表面修饰皮革及抗紫外性能研究

采用溶胶-凝胶法制备乙二醇表面改性的TiO_2,并与乙二醛构成复合鞣制剂,对皮革纤维进行表面修饰。采用UV-Vis、FTIR、XRD、TG/TGA及SEM等方法对改性TiO_2样品及改性TiO_2表面修饰皮革纤维进行性能检测。UV-Vis、XRD表征结果发现,乙二醇表面改性TiO_2保留一定的完整晶体构型及仍具有优良的紫外屏蔽性能,SEM结果证明,改性TiO_2成功修饰了纤维表面,具备一定的抗紫外能力,TMG-1[n(乙二醇):n(乙二醛)=1:1制备改性TiO_2]皮革抗紫外能力最强。     

改性TiO_2(TMG)表面修饰皮革及抗紫外性能研究

采用溶胶-凝胶法制备乙二醇表面改性的TiO_2,并与乙二醛构成复合鞣制剂,对皮革纤维进行表面修饰。采用UV-Vis、FTIR、XRD、TG/TGA及SEM等方法对改性TiO_2样品及改性TiO_2表面修饰皮革纤维进行性能检测。UV-Vis、XRD表征结果发现,乙二醇表面改性TiO_2保留一定的完整晶体构型及仍具有优良的紫外屏蔽性能,SEM结果证明,改性TiO_2成功修饰了纤维表面,具备一定的抗紫外能力,TMG-1[n(乙二醇):n(乙二醛)=1:1制备改性TiO_2]皮革抗紫外能力最强。     

微米稀土粉体表面改性技术研究

本文采用稀土粒子与蛇纹石粉体组成的微米复合粉体,研究了油酸、Span、硼酸酯对其的表面改性效果,确定了复合改性剂的复配配比为油酸∶Span∶硼酸酯=43.1∶24.1∶32.8。通过实验,得到了较优工艺条件:复合改性剂添加量5.8%,改性温度75℃,改性时间80min。改性后的微米稀土粉体表现出良好的亲油疏水性,提高了其在机油中的分散稳定性。     

氢氧化铝粉体表面化学改性的研究

综述了氢氧化铝粉体在应用领域存在的主要问题，解释了氢氧化铝粉体表面化学改性的机理。详细地介绍了国内外氢氧化铝粉体的表面化学改性的方法，主要包括酯化反应法、偶联剂法、表面活性剂吸附法以及聚合物包覆法。经研究表明，氢氧化铝粉体表面化学改性后扩宽了其应用领域，具有良好的前景。     

Preparation of broadband transparent Si3N4-SiO2 ceramics by digital light processing (DLP) 3D printing technology

Wave-transmitting materials are a kind of multi-functional materials that protect the normal operation of communication and guidance systems of spacecraft in harsh environments. In this paper, we fabricate a broadband microwave transparent Si₃N₄-SiO₂ composite ceramic with excellent performance through digital light processing (DLP) 3D printing technology. The influences of sintering temperature on the weight increase rate, density, dimensional shrinkage, phase composition, microstructure, bending strength and dielectric properties of Si₃N₄-SiO₂ ceramic were all systematically studied. The strength of Si₃N₄-SiO₂ ceramic sintered at 1350 ℃ was 77 ± 5 MPa. The relative permittivity of the ceramic is within the range of less than 4, and the loss tangent can be below 0.003. The 3D printed Si₃N₄-SiO₂ ceramic material exhibited excellent wave-transparent performance.     

Preparation of Si3N4 ceramic based on digital light processing 3D printing and precursor infiltration and pyrolysis

The emergence of digital light processing (DLP) 3D printing technology creates favorable conditions for the preparation of complex structure silicon nitride (Si₃N₄) ceramics. However, the introduction of photosensitive resin also makes the Si₃N₄ ceramics prepared by 3D printing have low density and poor mechanical properties. In this study, high-density Si₃N₄ ceramics were prepared at low temperatures by combining DLP 3D printing with precursor infiltration and pyrolysis (PIP). The Si₃N₄ photocurable slurry with high solid content and high stability was prepared based on the optimal design of slurry components. Si₃N₄ green parts were successfully printed and formed by setting appropriate printing parameters. The debinding process of printed green parts was further studied, and the results showed that samples without defects and obvious deformation can be obtained by setting the heating rate at .1°C/min. The effect of the PIP cycle on the microstructure and mechanical properties of the Si₃N₄ ceramics was studied. The experimental results showed that the mass change and open porosity of the samples tended to be stable after eight PIP cycles, and the open porosity, density, and bending strength of the Si₃N₄ ceramics were 1.30% (reduced by 97%), 2.64 g/cm³ (increased by 43.5%), and 162.35 MPa.     

无机纳米粉体表面处理设备与工艺研究

研究了混合喷嘴的间隙大小、表面处理液浓度和处理时间对无机纳米粉体表面处理效果的影响,测试不同工艺参数下,纳米粉体在酒精溶液中的沉降时间,吸光度。实验结果表明:采用高浓度的表面处理液、小间隙的喷嘴和经过多次的处理,纳米粒子的粒径变小,分散性得到了改善。同时也研究了CaCO3/HDPE复合体系中,纳米CaCO3对复合材料性能的影响,结果表明,经过表面处理的纳米CaCO3在复合体系中分散基本均匀,起到增强增韧的作用。     

Effect of particle grading on the properties of photosensitive slurry and BaTiO3 piezoelectric ceramic via digital light processing 3D printing

To improve the density and piezoelectric constant of BaTiO₃ ceramics prepared by Digital Light Processing 3D printing, the properties of photosensitive slurry were investigated from the perspective of particle grading, and the nitrogen-air two-step debinding and sintering process on the relative density and electrical properties were explored. It was found that as the mass ratio of coarse particles increased, the viscosity, shear stress and cure depth of the slurry decreased. When the mass ratio of fine and coarse particles was 2:8 and sintered at 1350 °C, the ceramic had better performance, with relative density reaching 95.39 ± 0.63 %. The piezoelectric constant d₃₃ was 215 ± 13 pC/N, 29.52 % higher than the single-peak powder. The relative permittivity (ε_r) and polarization (P_r) were 978 and 16.656 μC/cm². Finally, BaTiO₃ ceramics with Triply Periodic Minimal Surface structures were prepared as piezoelectric sensors, which had the highest output voltage at the same displacement when the mass ratio was 2:8.     

金属双极板表面改性涂层的评价方法研究进展

理想的质子交换膜燃料电池（PEMFC）用金属双极板需要具备良好的耐蚀性和导电性,表面改性是解决金属双极板耐蚀性和导电性的主要途径之一。本文对金属双极板表面改性涂层的各种性能评价方法进行了归类、介绍、总结。表面改性金属双极板的性能评价方法主要有非原位的电化学腐蚀分析、界面接触电阻测量、表面形貌表征、组分分析以及原位的组装电池评价等,重点介绍了各种方法的基本原理、操作条件、结果分析以及应用情况等,发现电化学腐蚀分析的测试标准不统一、原位评估方法应用较少等问题,提出进一步分析测试参数影响并统一测试标准以及尽可能在电池运行环境中评估金属双极板性能的研究方向,期待后续研究能够尽快完善相关评价标准体系,促进行业规范有序发展。     

陶瓷砖抛光粉在混凝土中的应用研究

研究了陶瓷砖抛光粉对混凝土工作性能、力学性能和抗渗性能的影响,并分析了抛光粉对水泥净浆孔结构的影响。结果表明:陶瓷砖抛光粉替代水泥量为10%时,混凝土的工作性能最好且混凝土7d、28d强度均达到最大值;在替代量为15%时,抗渗性能最好,孔隙率达到最低;在一定的掺量范围内,陶瓷砖抛光粉有利于提高混凝土的工作性能、力学性能和抗渗性,细化浆体中的孔结构,对改善混凝土性能和结构有积极作用。     

表面改性玄武岩纤维滤料过滤性能研究

针对玄武岩纤维滤料表面改性后在常温及高温条件下过滤性能及表面形态开展研究。结果表明,在常温及高温条件下,滤料均呈现开始阶段过滤透气性好,阻力增加较慢,随着过滤过程的进行,滤料表面粉尘堆积,阻力增加变快的特点。相比于常温过程,过滤初始阶段由于滤料表面及浸渍纤维处理剂挥发消失,粉尘颗粒直接接触滤料表层直至纤维内部,以致滤料阻力增加速度更快,随着过滤过程的进行,阻力增加速度变慢,但过滤效率依然优秀。     

Evaluation of direct light processing for the fabrication of bioactive ceramic scaffolds: Effect of pore/strut size on manufacturability and mechanical performance

Bioactive ceramic scaffolds for bone regeneration consisting of a three-dimensional mesh of interpenetrating struts with square section were fabricated via Digital Light Processing (DLP). The ability of the technique to manufacture 3D porous structures from β-tricalcium phosphate (β-TCP) powders with different dimensions of struts and pores was evaluated, identifying the possibilities and limitations of the manufacturing process. Small pore sizes were found to seriously complicate the elimination of excess slurry from the scaffold’s innermost pores. The effect of the strut/pore size on the mechanical performance of the scaffolds under compressive stresses was also evaluated, but no significant influence was found. Under compressive stresses, the structures resulted weaker when tested perpendicularly to the printing plane due to interlayer shear failure. Interlayer superficial grooves are proposed as potential failure-controlling defects, which could also explain the lack of a Weibull size effect on the mechanical strength of the fabricated DLP scaffolds.     

Distribution of carbon contamination in oxide ceramics occurring during spark-plasma-sintering (SPS) processing: II - Effect of SPS and loading temperatures

Carbon contamination during the SPS processing was investigated in the spinel, alumina and zirconia. The carbon contamination changes with the SPS conditions and the target materials. At the high heating rate of 100?°C/min, the contamination occurred over the entire area in the spinel, but only around the surface areas in the alumina and zirconia. For the spinel, the contamination is sensitive to the SPS parameters, such as the heating rate and loading conditions, but less sensitive to the sintering temperature. This suggests that the carbon contamination was caused by evaporation of CO gas from the carbon paper/dies. At the high heating rates, the carbon evaporation is enhanced due to the rapid heating, and then, the evaporated CO gases are encapsulated into the closed pores during the heating process and remain in the matrix. The carbon contamination can be suppressed by a high temperature loading even at the high heating rate.     

化学镀镍及其前处理对空心陶瓷粉体润湿性的影响

给出了一种空心陶瓷粉体表面化学镀及其前处理工艺,采用透过高度法、红外光谱法对前处理和化学镀后粉体表面性能及在不同润湿相中的润湿性能进行了研究。实验结果表明:空心陶瓷粉体经粗化、化学镀处理后润湿性能有大幅提高,利于提高粉体与基体的结合强度;利用润湿性的变化可以考察其粗化处理程度。