高技术陶瓷产品的精密注射成型制备技术的应用与发展

讨论了陶瓷粉末注射成型制备精密陶瓷部件这一新技术及其国内外发展状况。先进陶瓷精密注射成型的科学基础是现代高分子精密注塑理论和现代陶瓷制造技术,它将高分子流变学、陶瓷粉体技术、陶瓷工艺学和金属模具精密制造技术结合在一起。该技术突出的优点有:①可净近成型各种复杂形状的陶瓷零部件,使烧结后的陶瓷产品无需进行机加工或少加工,从而减少昂贵的陶瓷成本;②成型制品具有极高的尺寸精度和表面光洁度;③可实现微成型(Micro Injection Molding),制备μm-mm范围内的微型陶瓷零件;④成型过程机械化和自动化程度高,重复性好,便于规模化低成本生产。该技术已用于陶瓷发动机、通讯产业中光纤连接器插芯(Ferrule)、计算机工业中光盘盒磁盘驱动用陶瓷轴承和生物医学用陶瓷制品等精密陶瓷件的制造。随着微注射成型新技术的发展,微型陶瓷部件将应用于环境要求苛刻、结构复杂的MEMS系统。     

Development of matte finishes in electrostatic (EFB) and conventional hot dipping (CHDFB) fluidized bed coating process

This study focuses on the correlation between the thermo-rheological properties of a thermosetting powder coating system with its surface structure build-up. Epoxy powder coating systems, which displayed surface matting and surface wrinkling, were examined. Firstly, the evolution of the complex viscosity was correlated with the cure kinetic. Secondly, the structure build-up on the surface of the coatings was investigated with a combined SEM-CLA profilometry analysis at different stages of curing process for both EFB and CHDFB coating processes. Different finishes were found to characterize the films applied by using EFB and CHDFB coating processes as a result of the different way the film is heated by. Finally, a strict relationship of film morphology to the degree of conversion and to the evolution of the complex viscosity was found out for both EFB and CHDFB coating processes. The surface structure is built up after gelation point and continues to evolve after gelation with a full development of the film fine structure. Differences were observed in the surface structure build-up when different curing temperature was used, thereby indicating an influence of minimum viscosity on achievable finishing.     

浅析唐宋两代陶瓷艺术特点的差异

唐、宋两代都是中国历史上著名的盛世。由于其政治局势、社会环境、审美情趣的不同,也带来了它们陶瓷文化的迥然不同。本文试从唐宋陶瓷造型、釉色和陶瓷装饰等方面浅析其艺术特点上的差异。     

高温热机用陶瓷部件的研究与进展

本文着重讨论当前陶瓷基复合材料的在高温热机上的潜在应用情况,对陶瓷材料的要求及其在发动机上的使用趋势作了探讨,并就其目前最新工艺和制造方法作了探讨,对当前陶瓷发动机存在的问题进行了分析,认为仍需要对复合材料的界面以及高温使用的纤维加强进行研究,并就陶瓷材料部件在将来的发展作了预测。     

Development of a tribolelectric procedure for the measurement of mixing and drying in a vibrated fluidized bed

Fluidization of fine, pharmaceutical powders makes them easier to dry, coat and mix. Fine powders, however, are difficult to fluidize well with gas flow only. Vibration can often help achieve smooth fluidization at a lower gas flow. The objective of the present study was, thus, to develop reliable and quick experimental methods to characterize mixing and drying in vibrated fluidized beds of fine powders.Effective mixing is critical in many industrial applications and, in gas-solid fluidized beds, requires gas velocities greater than the minimum bubbling velocity (U_mb). There are a number of techniques available for determining U_mb. However, they often are impossible or impractical to use in an industrial application. A new measurement technique involving the use of triboelectric probes was developed. Signal characteristics obtained from sophisticated signal analysis were used to identify the minimum bubbling velocities. These predictions corresponded well with the values obtained from more traditional laboratory methods such as the bed pressure gradient.In a fluidized bed, particles hitting a metal probe will generate a small triboelectric current. Triboelectric probes are able to detect rapid changes in particle surface properties. Surface properties of the particles were modified by wetting the particles in a low shear mixer. This change was detected by triboelectric probes at various locations inserted throughout the bed. The water adsorbed on the particles will begin to evaporate when exposed to the gas stream and the surface properties of the particles will gradually return to their original dry state. The triboelectric probes were able to monitor this drying process. The effects of vibration amplitude on the mixing and drying rate of the bed were also determined.     

Densification behaviour and three-dimensional printing of Y2O3 ceramic powder by selective laser sintering

The selective laser sintering (SLS) of an yttria (Y₂O₃) ceramic powder was studied to understand both the effects of i) the initial yttria particle characteristics on the powder bed behaviour and ii) the process conditions (laser power, scanning speed, hatching space) on the sintering/melting of three-dimensionally printed objects. The roughness of the powder bed, a sensitive indicator of the layer bed quality, was determined through three-dimensional optical profilometry and the powder bed packing density was modelled using the discrete-element method. Complex shaped objects including spheres and open rings were successfully fabricated by the SLS three-dimensional printing. In addition, SLS cube-shaped samples were characterized by X-ray diffraction and scanning electron microscopy. The open pore volume fraction significantly decreased from 41% without a post-SLS heat treatment to 31% with a post-SLS heat treatment at 1750 °C for 20 h under secondary vacuum. Finally, an anisotropy in elastic properties has been highlighted, Young's modulus reaches 11 GPa in the stiffest direction.     

陶瓷制件层合速凝快速成型技术研究进展

着重介绍了层合速凝快速成型技术的原理及应用于陶瓷制件制造的研究现状,比较分析了其优缺点,并对今后该技术的发展作了展望.     

Fabrication of crescent-shaped ceramic microparticles based on single emulsion microfluidics

Ceramic microparticles have great potentials in various fields such as materials engineering, biotechnology, microelectromechanical systems, etc. Morphology of the microparticle performs an important role on their application. To date, it remains difficult to find an effective and controllable way for fabricating nonspherical ceramic microparticles with 3D features. This work demonstrates a method that combines UV light lithography and single emulsion opaque-droplet-templated microfluidic molding to prepare the crescent-shaped ceramic microparticles. By tailoring the intensity of UV light and flow rate of fluid, the shapes of microparticles are accordingly tuned. Therefore, varieties of crescent-shaped microparticles and their variations have been fabricated. After sintering, the crescent-shaped alumina ceramic microparticles were obtained. Benefitting from the light absorption and scattering behavior of most ceramic nanoparticles, this system can serve as a general platform to produce crescent-shaped microparticles made from different materials, and hold great potentials for applications in microrobotics, structural materials in MEMS, and biotechnology.     

古代窑炉对古代陶瓷发展的影响

我国古代窑炉经过了穴窑、馒头窑、龙窑、葫芦窑、阶级窑和蛋形窑等窑炉形制的发展转变,窑炉形制和结构的改进促进了窑炉烧成技术的提高,推动了我国同时期陶瓷的发展进程,形成了具有时代特色的陶瓷艺术面貌.     

Influence of powder characteristics on cold sintering of nano-sized ZnO with density above 99 %

Cold sintering parameters such as, temperature, pressure, aqueous phase, heating rate and dwelling time has been widely discussed in the literature but the role of starting powder with respective microstructure development is mostly overlooked. There is a need for understanding the effect of powder agglomerates and the role of inter particle friction on the densification behavior during cold sintering process. Present study encompasses investigation and optimization of these parameters for ZnO which enabled > 99 % of relative density with grain sizes below 200 nm. Additionally, role of external atmosphere was also studied to investigate its impact on densification during the process. All cold sintering experiments were carried out in a FAST/SPS device for studying aqueous phase evaporation and ensuring the reproducibility of process parameters. Microstructure characterization (scanning and transmission electron microscopy) showed – without any post heat treatment– defect free grain boundary structure opposite to what documented by previous studies.     

油相材料的物化性质对粉状乳化炸药贮存稳定性的影响

粉状乳化炸药的贮存稳定性是评价粉状乳化炸药质量的重要指标,是粉状乳化炸药研究的重要课题。研究了粉状乳化炸药贮存稳定性的影响因素,介绍了油相材料的物化性质对粉状乳化炸药贮存稳定性的影响。     

论工艺因素对氧化铝陶瓷零件形位公差尺寸的影响

本文尝试运用材料学过程理论对陶瓷制造过程进行了分析,进而总结分析了影响95%氧化铝陶瓷零件形位公差尺寸的工艺因素,讨论了陶瓷制造过程的能量分配问题和统筹兼顾问题。     

Design,fabrication of honeycomb-shaped 1–3 connectivity piezoelectric micropillar arrays for 2D ultrasound transducer application

As a core component of 2D ultrasound transducers, honeycomb-shaped 1–3 connectivity piezoelectric micropillar arrays have attracted enormous attention due to their unique performance and functionality. In this paper, honeycomb-shaped 1–3 connectivity piezoelectric micropillar arrays with a high aspect-ratio were designed and fabricated by means of deep X-ray lithography and powder injection molding in six steps: preparation of lost mold, powder-binder mixing, injection molding and demolding, removal of binders, and densification of powder. A polymer-based lost mold insert was generated by a synchrotron X-ray exposure and development process. The optimal volumetric ratio between the piezoelectric powder and binders was determined by torque rheology behavior, then they were homogeneously mixed with a twin extruder mixer. To fully fill in the micro-cavities of the lost mold, rheological properties of the mixture were analyzed with a capillary rheometer using different shear rates (50–5000 s⁻¹) and temperatures (140 °C, 150 °C, and 160 °C). After the mixture was completely injected, the lost mold was chemically dissolved in acetone and rinsed in methanol without bending or clustering of the micropillar arrays during evaporation. The binders in the injection molded portion were thermally decomposed using a continuous heating schedule of 200 °C, 390 °C, and 600 °C in argon gas under atmospheric conditions. Finally, the particles in the sample were densified into a coherent, solid mass by eliminating pores at 1300 °C. Based on the proposed micro-manufacturing process, defect-free honeycomb-shaped 1–3 connectivity piezoelectric micropillar arrays with a pattern dimension of 42 μm and aspect-ratio of 5 were successfully produced.