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。     

基于光固化增材制造技术的陶瓷成形方法

目的 利用光固化增材制造技术成形复杂形状陶瓷零件。方法 以光敏树脂和陶瓷粉体混合得到氧化铝和氧化硅陶瓷浆料,浆料固体含量体积分数均超过55%。采用基于数字光处理技术的光固化增材制造设备,设计了一种栅栏式刮刀,可实现打印过程中高固含量浆料的均匀涂层和搅拌。光源波长为405 nm,面光源像素尺寸为50 μm,最小分层厚度为10 μm。在5 mW/cm2光强下分层曝光,分析在不同粉体的浆料固化性能,得到陶瓷坯体,经过脱脂烧结,完成陶瓷成形。结果 氧化硅浆料的透光性明显强于氧化铝浆料,氧化铝浆料的临界曝光强度更容易引发固化反应,测试件最小壁厚为0.2 mm,最小可成形孔为0.1 mm,并对氧化铝齿轮、螺钉、镂空摆件及氧化硅陶瓷型芯等复杂结构的陶瓷零件进行了验证。结论 基于光固化成形的增材制造可以实现高精度的复杂陶瓷零件成形,对拓展陶瓷成形方法具有重要意义。     

先进陶瓷成形技术现状及发展趋势

先进陶瓷材料因其优异的热、电、力、光学性能,而有着广泛应用。近年来,对先进陶瓷材料性能的要求越来越高,而成形技术则是阻碍陶瓷材料进一步发展的关键问题之一。对先进陶瓷的成形方法进行了一个汇总,包含传统方法以及近年新发展起来的工艺。传统成形方法总体来说有干法成形和湿法成形两大类,干法成形主要是压制成形法;而湿法成形大致可分为塑性成形和浆料成形两类。干法成形起步较早,目前应用最广;湿法成形自动化程度高,可用于更精细的陶瓷成形。近些年,陶瓷成形技术有了较大的发展,特别是陶瓷3D打印成形技术。可以预见,3D打印成形技术将是未来发展的趋势。     

可移动凹模对板材液压成形影响的研究

为了研究可移动凹模对板材液压成形的影响,进行了有无可移动凹模与不同可移动凹模加载方式(方式1与方式2)的板材液压成形试验.研究结果表明:比较有无可移动凹模对板材液压成形厚度分布的影响,在有可移动凹模时,成形零件厚度分布比较均匀,这种技术有利于提高板材的成形极限;没有可移动凹模,板材难于成形,尤其对于复杂零件;可移动凹模加载方式2比加载方式1更有利于板材厚度的均匀分布.     

基于光敏浆料的直写精细无模三维成型

配制了一种具有光敏特性的陶瓷浆料, 并用此浆料通过直写精细无模三维成型技术制备了线条直径为300μm的BaTiO3陶瓷基木堆结构. 系统地讨论了光敏浆料的配制方法、浆料直写无模成型的工作原理以及采用的烧结工艺. 制备过程中不同阶段的研究表明, 光敏浆料中的BaTiO₃纳米颗粒在烧结前未发生团聚, 从而保证挤压成型顺利进行; 烧结后样品成瓷效果好, 各向收缩均匀, 整体无变形、开裂. 该技术具有成型速度快、制造周期短、可用材料范围广等特点.     

陶瓷微器件的软刻蚀成形研究进展

软刻蚀技术是基于传统光刻蚀技术提出的一系列技术,包括微模塑、转移微模塑和毛细微模塑等,其共同特点是利用弹性模作为微结构转移元件,复制其他方法制备的原始模板的微结构,再用此弹性模进行微结构的成形。因其成本低廉、操作过程简单,为陶瓷微器件的制备提供了一种先进的净成形加工技术。其工艺步骤主要包括:弹性模的制备、浆料或陶瓷预聚体的制备、注模、干燥(交联固化)、脱模和烧结。本文按照制备工艺综述了软刻蚀技术成形陶瓷微器件的研究进展,着重讨论了影响微成形的关键因素,并对将来的研究方向进行了展望。     

氧化铝陶瓷直接凝固注模成型(DCC)工艺参数的研究

直接凝固注模成型(DCC)是利用陶瓷浆料粘度变化制备陶瓷坯体的先进成型方法,脱模时间长是限制其应用的主要问题.通过调整DCC工艺参数,减小充模前浆料的粘度以利于成形,而在充模后使浆料的粘度迅速增加,缩短脱模时间.将高固含量(体积分数为70%)低粘度的陶瓷浆料浇注到模具中,通过改变浆料的pH值或浆料离子浓度来改变其胶体化学行为,调节浆料流动性能;通过温度控制加速浆料凝固,使充模后10 min的浆料粘度与充模前浆料粘度比值达到13,3倍于传统浆料成型方法,充模后1 h即可得到有足够脱模强度的陶瓷坯体,效率显著提高.     

陶瓷注射成形中脱脂工艺及其新进展

陶瓷注射成形是先进的陶瓷近净成形技术,可高效成形形状复杂的陶瓷部件.而脱脂是陶瓷注射成形中最复杂和重要的环节.详细介绍了陶瓷注射成形各种脱脂工艺的脱脂原理,并对各种脱脂工艺的优缺点进行了比较.     

陶瓷增强铝合金互渗相复合材料的半固态设计和成形

目的 开发一种针对金属-陶瓷互渗相复合材料生产的高效方法,以提升该类材料在高温高负荷环境中的使用寿命和工作可靠性。方法 采用数值扫描技术研究了半固态成形过程,以铝合金为金属成分、氧化铝开孔体为陶瓷成分,制备了复合材料。通过模拟2种腔体（开放式和封闭式）的金属陶瓷压铸成形过程模拟不同的模腔设计,详细分析了腔体内的压力水平及其分布情况,探讨了压铸温度、金属液相体积分数等参数对材料成形质量的影响。结果 封闭模腔能够在成形过程中产生更加均匀的压力分布,有助于减少如气孔、未渗透区域等材料缺陷,并提高金属与陶瓷之间的互渗质量。与封闭模腔相比,开放模腔在控制材料均匀流动和确保渗透效果方面效果较差。结论 采用封闭模腔的半固态成形工艺能显著提升金属-陶瓷互渗相复合材料的整体质量和性能,有效减少成形缺陷,为高性能金属-陶瓷复合材料的制备提供了一种有效路径。     

特种陶瓷成型方法

成型技术是制备陶瓷材料的一个重要环节.特种陶瓷成型方法总的来说可分为干法成型和湿法成型两大类,干法成型包括钢模压制成型、等静压成型、超高压成型、粉末电磁成型等;湿法成型大致可分为塑性成型和胶态浇注成型两大类;近些年来固体无模成型技术在特种陶瓷的成型研究中也取得了较为快速的发展.对特种陶瓷的这些成型方法进行了简要介绍,指出了各种成型方法的优缺点,并展望了特种陶瓷成型方法的发展趋势.     

光学微结构的超精密加工技术

微结构光学元件在光电产品及光通讯产品中的应用日益广泛，采用多轴超精密机床加工光学微结构，可达到亚微米级形状精度和纳米级表面光洁度的高精度水平，详细介绍了光学自由曲面及光学微结构的超精密加工技术，并开发了适合超精加工微型槽和微透镜列阵的刀具轨迹自动生成软件。     

Freeforming of polymers

Rapid prototyping and freeform fabrication methods are being increasingly used as a stage in the design cycle of polymers. They also represent new ways of processing materials and particularly provide much closer coupling between materials synthesis and materials processing. Freeforming techniques also allow new combinations of materials to be formed, such as functional gradients, oriented composites, porous structures and devices.     

Freeform fabrication of functional aluminium prototypes using powder metallurgy

Freeform fabrication methods allow the direct formation of parts built layer by layer, under the control of a CAD drawing. Most of these methods form parts in thermoplastic or thermoset polymers, but there would be many applications for freeform fabrication of fully functional metal or ceramic parts. We describe here the freeforming of sinterable aluminium alloys. In addition, the building approach allows different materials to be positioned within a monolithic part for an optimal combination of properties. This is illustrated here with the formation of an aluminium gear with a metal-matrix composite wear surface.     

Design of a compact off-axis two-mirror freeform infrared imager with a wide field of view

With the development of modern precision optical fabrication and measurement technologies, optical freeform surfaces have been widely employed in different applications, especially in off-axis reflective optical systems. For an infrared optical system operating in the long-wavelength spectrum, compactness, brightness, and a wide field of view are key requirements for military surveillance or scene sensing. In this paper, we present an off-axis two-mirror freeform infrared imager with compactness and brightness. It has a large pupil of size 12?mm and a fast focal ratio of 2.2 over a wide 23° diagonal field of view, as well as good image quality. XY-polynomial freeform surfaces are applied to the viewing mirror and focusing mirror. The multiple degrees of freedom of optical freeform surfaces are very helpful for off-axis aberration correction and improving the optical performance over the entire pupil across the full field of view. The overall dimension of our designed freeform infrared imager is about 30?mm by 30?mm by 30?mm, which is elegantly miniaturized. The final designed results of a reflective freeform infrared imager are demonstrated and discussed in detail.     

基于快速成型技术的陶瓷零件无模制造

概述了几种近几年发展起来的陶瓷零件快速成型技术,着重介绍了它们的原理及应用于陶瓷零件制造的研究现状,比较分析了各种快速成型技术的优缺点及在产业化应用中存在的问题,并对今后该技术的发展进行了展望.     

电子束熔丝增材制造研究进展及展望

增材制造技术可以实现复杂三维结构件的快速制造,大幅度提高生产效率、减少材料损耗、降低生产成本.相比于电弧和激光增材制造技术,电子束熔丝增材制造凭借其制造成本低、加工效率高、材料利用率高等特点,逐渐成为增材制造领域的研究热点.从成形精度与缺陷调控、组织与性能特点、成形及其控制机理3个方面综合分析了国内外关于电子束熔丝增材...     

Voxelization and fabrication of freeform models

We present a volume graphics system for the generation of freeform models and synthesis of complex objects. A unique non-uniform rational B-spline (NURBS) volume representation and its voxelization algorithm are proposed. The forward difference technique is employed to speed up the voxelization process while the desired topological connectivity is preserved. For synthesis of our models and other three-dimensional objects, such as computed tomography images, voxel-based cutting tools are developed for the AutoCAD user interface. Volume rendering is applied to visualize the intermediate and final models. An isosurface is then extracted over the synthesized model and exported to a rapid prototyping machine as an STL file for fabrication. The approach taken in this system has been proven robust and efficient in modelling and fabrication of complex freeform models.     

Hybrid optical (freeform) components--functionalization of nonplanar optical surfaces by direct picosecond laser ablation

The performance of optical systems is typically improved by increasing the number of conventionally fabricated optical components (spheres, aspheres, and gratings). This approach is automatically connected to a system enlargement, as well as potentially higher assembly and maintenance costs. Hybrid optical freeform components can help to overcome this trade-off. They merge several optical functions within fewer but more complex optical surfaces, e.g., elements comprising shallow refractive/reflective and high-frequency diffractive structures. However, providing the flexibility and precision essential for their realization is one of the major challenges in the field of optical component fabrication. In this article we present tailored integrated machining techniques suitable for rapid prototyping as well as the fabrication of molding tools for low-cost mass replication of hybrid optical freeform components. To produce the different feature sizes with optical surface quality, we successively combine mechanical machining modes (ultraprecision micromilling and fly cutting) with precisely aligned direct picosecond laser ablation in an integrated fabrication approach. The fabrication accuracy and surface quality achieved by our integrated fabrication approach are demonstrated with profilometric measurements and experimental investigations of the optical performance.