胶态无模快速成形陶瓷制件的应用及发展趋势

胶态无模快速成形陶瓷制件由于具有成形精度高、可机械加工能力好、能够制备大尺寸,复杂形状陶瓷制件等特点而备受关注。本文综述了近年来发展迅速的几种陶瓷胶态无模快速成型技术。着重介绍了各种技术的成形原理和方法、工艺过程及研究现状等,通过比较分析了不同快速成型制造技术在陶瓷零件制造中的特点及其存在的问题,对于陶瓷零件成形时不同成形技术的选择提出了一些参考意见,并结合课题组研究成果展望了胶态成形的发展趋势。     

激光增材制造超高温氧化物共晶陶瓷研究进展

超高温氧化物共晶陶瓷具有优异的高温强度、高温蠕变性能、高温结构稳定性以及良好的高温抗氧化和抗腐蚀性能, 成为1400 ℃以上高温氧化环境下长期服役的新型候选超高温结构材料之一, 在新一代航空航天高端装备热结构部件中具有重要的应用前景。基于熔体生长技术, 以选择性激光熔化和激光定性能量沉积为代表的激光增材制造技术具有一步快速近净成形大尺寸、复杂形状构件的独特优势, 近年来已发展成为制备高性能氧化物共晶陶瓷最具潜力的前沿技术。本文从工作原理、成形特点、技术分类等方面概述了基于熔体生长的两种典型激光增材制造技术, 综述了激光增材制造技术在超高温氧化物共晶陶瓷制备领域的研究现状和特点优势, 重点介绍了选择性激光熔化和激光定向能量沉积超高温氧化物共晶陶瓷在激光成形工艺、凝固缺陷控制、凝固组织演化、力学性能等方面的研究进展。最后, 指出了实现氧化物共晶陶瓷激光增材制造工程化应用亟需突破的关键瓶颈, 并对该领域未来的重点发展方向进行了展望。     

基于光固化技术增材制造陶瓷和金属的研究进展

增材制造是目前极具发展潜力的前沿技术之一。光固化增材技术作为增材制造的一个分支,具有高效、低能耗和成型精度高等优点,可解决传统工艺制备复杂结构金属和陶瓷存在的周期长、加工困难和成本高等问题,具有良好的经济和技术优势。光固化成型致密/多孔氧化物陶瓷已被广泛开发,并成功应用于微电子组件、光子晶体和骨科植入物等领域,但光固化非氧化物陶瓷和金属材料的应用基础理论和成型技术还未十分成熟,适宜于光固化工艺的陶瓷和金属浆料的制备仍面临很多挑战。本文综述了光固化增材制造氧化物陶瓷、非氧化物陶瓷和金属材料的研究进展,从浆料制备、光固化成型和后处理三个阶段分析了光固化增材制备三种材料的主要技术难点和可能的解决方案,最后指出了光固化陶瓷和金属材料的未来发展方向。     

熔融沉积纤维增强复合材料的研究进展

熔融沉积增材制造属于热塑性聚合物材料3D打印成型技术之一,具有原料广泛、制造成本低、个性化可定制等特点.随着制备工艺和技术的优化,近年来成型质量不断提高.同时,这种基于分层打印、逐层堆积的材料成型方式导致其力学强度偏低.发展适用于熔融沉积技术的纤维增强热塑性聚合物复合材料,利用纤维具有高比强度、高比模量的特性,可显著提高熔融沉积热塑性聚合物成型件的抗拉强度和拉伸模量等力学性能.然而,在熔融沉积纤维增强复合材料成型过程中,伴随着材料的流动与纤维取向、丝/层间结合、热量传导和残余应力等一系列复杂现象,明晰上述现象及其内在的关联性,是促进该技术应用和发展的关键.因此,近年来国内外研究者们主要从选择合适的纤维和优化制备工艺等方面不断尝试,并取得了丰硕的成果.用于熔融沉积纤维增强复合材料的纤维主要以短纤维和连续纤维两大类材料为主.短纤维复合材料发展较早、制备工艺相对简单;连续纤维复合材料成型件的力学性能相对较高.近年来,国内外研究者基于纤维增强复合材料的制备工艺、材料性能、成型机理等关键要素,聚焦于纤维含量、沉积角度、打印速度、喷嘴温度、层厚和化学助剂添加等工艺参数变化对成型件力学性能影响的相关研究,拟充分发挥纤维增强材料的技术优势,为制备较高力学性能和较好质量打印成型件提供可能.本文主要介绍了近年来国内外研究者在熔融沉积纤维增强复合材料方面的研究进展.从熔融沉积增材制造成型原理、纤维增强复合材料技术研究现状出发,介绍了短纤维和连续纤维增强复合材料的力学性能,以及工艺参数对增强复合材料力学性能的影响.最后,归纳了该技术仍存在的亟待解决的基础科学问题和关键技术问题,以及未来可能的研究方向.     

陶瓷3D打印技术及材料研究进展

综述了陶瓷3D打印技术和材料的特性及其研究进展与应用现状,重点讨论了喷墨打印技术、熔化沉积成型技术、光固化成型技术、分层实体制造技术、激光选区熔化技术/激光选区烧结技术、三维打印成型技术、浆料直写成型技术的特性和研究进展,分析了磷酸三钙陶瓷、氧化铝陶瓷、陶瓷先驱体、SiC陶瓷、Si_3N_4陶瓷、碳硅化钛陶瓷的特性和应用现状,最后指出了陶瓷3D打印技术的发展方向是与传统陶瓷工艺相结合,实现陶瓷制品的快速生产及生物陶瓷制品、高性能陶瓷功能零件的制造。     

立体光固化快速成型工艺过程分析

作为一种离散堆积成型的成形方式,快速成型可以在无模具、刀具和工装的情况下,直接读取STL数据,快速制造出具有复杂形状的实体部件。本文简述了立体光固化快速成型技术的工艺过程并分析了工艺缺陷,最后指出快速成型技术的发展方向。     

增材制造压电陶瓷研究进展

压电陶瓷是一种可以实现机械信号和电信号相互转换的功能陶瓷。由压电陶瓷与有机相构成的复合材料具有不同的宏观连接方式, 这不仅决定了压电器件广泛的应用场合, 而且推动了压电陶瓷材料和器件多样化的成型技术发展。与传统成型技术相比, 增材制造技术的最大优势在于无需模具即可实现外形复杂的小批量样品快速成型, 这与多样化的压电陶瓷及其器件研发需求十分契合, 同时因其样品后续加工量少、原材料利用率高、无需切削液的特点, 得到了学术界和工业界的广泛关注。在陶瓷材料增材制造领域, 功能陶瓷和器件的研究仍在增长期。本文从不同增材制造技术角度, 探讨和对比现阶段无铅和含铅压电陶瓷增材制造的发展历史、原料制备、外形设计、功能特性检测及试样的应用, 并根据现阶段各增材制造技术的优、劣势对其未来进行了展望。     

等离子堆焊技术的研究进展

综述了等离子堆焊技术的原理、应用及最新研究状况,包括等离子沉积制造技术(plasma deposition manufacturing,PDM)、等离子激光复合堆焊技术(laser plasma hybrid surfacing,LPHS)等.概述了等离子沉积制造的技术特点,展示了运用PDM和LPHS技术直接成型高温合金GH163零件的一些研究结果.     

先驱体聚合物在陶瓷增材制造中的应用进展

先驱体陶瓷具有分子结构可设计、化学组成可调控、加工成型方便、力学性能优异、易于成型复杂构件、便于实现结构/功能一体化等优点,克服了传统粉末烧结制备陶瓷材料难于设计与成型的问题,对解决航空航天、国防尖端武器装备面临的材料瓶颈问题具有重要意义。在陶瓷增材制造技术的带动下,先驱体陶瓷的发展迎来了新的契机,增材制造先驱体陶瓷的研究得到了越来越多的关注。介绍了增材制造先驱体陶瓷的研究与应用进展,总结了各类陶瓷增材制造技术的优势和不足,并对先驱体陶瓷增材制造目前存在的问题与发展趋势进行了探讨和展望。     

陶瓷薄膜低温水溶液沉积评述

陶瓷薄膜的制备技术多种多样,如物理气相沉积、化学气相沉积、高温烧结和"溶胶-凝胶"法等.这些技术对制备条件都有较高的要求:如高温高真空等.近年发展起来的在低温条件下沉积陶瓷薄膜的技术为我们提供了一种设备简单,在接近室温、常压下可进行操作的方法.本文就这一新兴工艺及其机理进行了评述.     

Processing and characterization of porous alumina scaffolds

Bioceramic materials are used for the reconstruction or replacement of the damaged parts of the human body. In this study an improved procedure is described for producing ceramic scaffolds with controlled porosity. Bioinert alumina ceramic was used to make porous scaffolds by using indirect fused deposition modeling (FDM), a commercially available rapid prototyping (RP) technique. Porous alumina samples were coated with hydroxyapatite (HAp) to increase the biocompatibility of the scaffolds. Initial biological responses of the porous alumina scaffolds were assessed in vitro using rat pituitary tumor cells (PR1). Both porous alumina and HAp coated alumina ceramics provided favorable sites for cell attachments in a physiological solution at 37 °C, which suggests that these materials would promote good bonding while used as bone implants in vivo. Based on these preliminary studies, similar tests were performed with human osteosarcoma cells. Cell proliferation studies show that both the ceramic materials can potentially provide a non-toxic surface for bone bonding when implanted in vivo.     

基于增材制造的陶瓷器型创新设计研究综述

通过梳理陶瓷领域的增材制造技术,并结合传统陶瓷的工艺过程及特点,探索增材制造技术对陶瓷器型创新的推进作用,并对未来发展趋势进行展望。基于陶瓷传统工艺过程,提炼传统器型的造型特点,就其存在的限制与问题进行分析;梳理目前陶瓷增材制造的技术发展脉络,探索不同增材制造技术的工艺特点及对陶瓷造型的影响,并结合陶瓷增材制造实例进行设计剖析,从创作方式和设计语言两方面阐述增材制造对于陶瓷器型的创新推进作用;最后对陶瓷增材制造技术进行未来展望。增材制造技术与陶瓷的结合,有力地推进了陶瓷器型的创新设计,使其突破了传统的设计限制,新的技术带来新的设计语言与创作形式,虽然目前仍处于发展阶段,但极具潜力。     

辽代陶瓷造型的设计学分析

目的对辽代陶瓷造型的设计学分析做宏观性的阐述。方法从设计学的视角出发,以辽代陶瓷造型为研究对象,从辽代陶瓷造型与分类、辽代陶瓷造型设计研究的必要性、辽代陶瓷造型的设计解析3个方面展开研究,注重对辽代陶瓷中的典型器进行成器之道的解构,注重对其造型的功能与审美进行设计原理的解读。结论辽代陶瓷是中原制瓷技术与辽人生活方式结合的时代产物,辽代陶瓷的形态设计丰富多源、民族特征鲜明,结构设计简单质朴、合理实用。辽代陶瓷的造型设计既是按照功能需求为人造物,也是按照美的规律为人造物。辽代陶瓷造型的产生发展与演变是辽代游牧文化变迁的物化形式,对它的研究既有历史反思性又有现实启迪性。     

Material Processing with a High Frequency Millimeter-Wave Source

A millimeter-wave beam based on a 15-kW, continuous-wave, 83-GHz gyrotron with superconducting magnets system is being investigated for use in material processing. The millimeter-wave beam can be focused to a few millimeters and manipulated quasi-optically and has been used in the following experiments: joining of ceramics (both similar and dissimilar materials), brazing of poled piezoelectric ceramics without significant heating and depoling, and coating of metals and polymers. Joining has been done directly and with reactive brazes. In coating, the beam's short wavelength and absorption depth permit effective ceramic-coating deposition on lower temperature materials, e.g., polymers and metals, without significant substrate heating, and localized deposition of coatings as well. Finally, the millimeter-wave source has been used in the efficient production of nanophase metal and ceramic powders, via a greatly accelerated modified polyol process producing smaller powders of greater uniformity. The results and implications of the various experiments will be discussed with some theoretical calculations and modeling.     

Electrophoretic deposition of alumina,yttria, yttrium aluminium garnet and lutetium aluminium garnet

The electrophoretic deposition (EPD) method has been adapted for the deposition of ceramic green bodies from aqueous nanodispersions of alumina, yttria, yttrium aluminium garnet and lutetium aluminium garnet. These materials have been selected, since they are promising candidates for optically transparent ceramics. Films as well as cylindrical bodies have been successfully prepared by application of pulsed direct current (pDC) EPD. To guarantee constant deposition yield during pDC, a variant with variable pulse widths and pulse heights has been developed. The obtained green bodies were studied by surface area analysis, scanning electron microscopy, optical transmittance measurements, determination of pycnometric density and sintering behaviour. The effect of colloid-chemical dispersion properties on green and sintered ceramics is discussed as well. The green ceramics received are nanoporous and dense, providing excellent properties for further processing under mild conditions to optical materials. For comparison, EPD-formed green bodies were either processed directly to ceramic bodies or after additional compacting by hot-pressing in a piston-cylinder apparatus.     

电泳沉积技术制备铁电陶瓷薄膜的研究进展

综述了电泳沉积技术在制备铁电陶瓷薄膜方面的最新研究进展,讨论了陶瓷特性、电压、分散剂、热处理时间等因素对电泳沉积铁电薄膜性能的影响.最后展望了电泳沉积技术制备铁电陶瓷薄膜的进一步发展.     

METHODS FOR BRAZING CERAMIC AND METAL-CERAMIC JOINTS

Owing to improved manufacturing processes technical ceramics on the basis of oxide as well as nonoxide ceramics have gained an increasing technical potential. Among other joining techniques brazing has proved to be the most flexible joining process that can easily be adapted to various ceramic-metal-combinations. In order to induce a wetting reaction there are two different approaches. The more complicated process encircles a pre-metallization process and a subsequent brazing process. The less sophisticated process is the 'active brazing process' where special brazing alloys are employed that are able to wet ceramic base materials. Although both joining processes are very flexible there are restrictions regarding the filler metals to be used, the premetallization process and the actual (active-) brazing process.     

3D Printing of Ceramics with Controllable Green-Body Configuration Assisted by the Polyvinyl Alcohol-Based Physical Gels

Additive manufacturing of ceramics has received intense attention. In particular, 3D-printed ceramics with customized shapes are highly desirable in the chemical industry, aerospace, and biomedical engineering. Nevertheless, developing a simple and cost-effective process that shapes dense ceramics to complex geometries remains challenging because of the high hardness and low ductility of ceramic materials. Extrusion-based printing, such as direct ink writing (DIW), often requires supporting materials that pose additional difficulties during printing. Herein, a simple approach is developed to produce stretchable ceramic green bodies of zirconia and alumina for DIW. The ink is composed of polyvinyl alcohol (PVA) and an aqueous suspension of ceramic powders. Besides the colloidal network formed by the ceramic particles, PVA plays an important role in tuning the printability of the aqueous ink. Through a freeze-thaw process, PVA crystallizes to form physical networks. This strategy provides highly stretchable hydrogel green bodies that can be reprogrammed to complex geometries difficult for common DIW printing. The subsequent drying, debinding, and sintering processes produce ceramics with dense structures and fine mechanical properties. In short, this work demonstrates an efficient method for the DIW of ceramic parts that can be reprogrammed to complex geometries.     

Electrophoretic deposition applied to ceramic dental crowns and bridges

Electrophoretic deposition (EPD) was used as shaping technique for ceramic dental crowns and dental three-unit and four-unit bridges in the high loaded molar region. Because of esthetical aspects and their biocompatibility ceramics are the material of choice for dental applications. Allergic reactions or toxic tissue damages can be prevented largely by application of ceramic dental products. Zirconia in its tetragonal yttria stabilized polycrystal form (TZP) and alumina toughened zirconia (ATZ) offer highest strength combined with highest toughness. In this publication, the influence of the kind and the amount of dispersing agent on the rheological properties of the ceramic suspensions was investigated. For EPD plaster stumps which had been prepared for the dental crowns and bridges by the dental technician were coated with silver and were directly used as deposition electrodes. For optimisation of the removing step of the deposited crown or bridge cap from the plaster stumps organic temporary binders and organic intermediate layers were investigated. The dental parts were sintered either to full density or to porous ceramics for a subsequent glass infiltration step.