粉末处理对陶瓷注射成形的影响

陶瓷注射成形是先进的陶瓷近净成形技术,可以高效成形形状复杂的陶瓷部件。而粉末处理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过程中的粉末处理步骤及其工艺优化。     

陶瓷注射成形中粘结剂的研究与进展

陶瓷粉末注射成形是先进的粉末近净成形技术,可以高效成形形状复杂的工艺部件.而粘结剂是陶瓷注射成形中最复杂和重要的环节.本文详细介绍了陶瓷注射成形的各种粘结剂组成,并对各种粘结剂的优缺点进行了比较.     

陶瓷注射成形技术进展

陶瓷粉末注射成形是从现代粉末注射成形技术中发展起来的一项新型成形技术。本文着重论述了陶瓷注射成形发展的历史、技术特点、工艺及进展情况，并介绍了CIM的典型产品和应用领域。     

陶瓷注射成形技术进展

陶瓷粉末注射成形是从现代粉末注射成形技术中发展起来的一项新型成形技术。本文着重论述了陶瓷注射成形发展的历史、技术特点、工艺及进展情况，并介绍了CIM的典型产品和应用领域。     

陶瓷粉末注射成型法制陶瓷粉末的煅烧处理

陶瓷粉末注射成型(ceramic injection molding,简称CIM)是一种新型陶瓷成型技术,在成型形状复杂的零件和精确控制零件尺寸上有着其它工艺无可比拟的优势.但工艺本身对粉末有着特殊的要求.本文研究了通过煅烧处理来改变粉末的粒度大小和颗粒的形状,发现经1250℃煅烧的粉末具有适合注射成型的颗粒形状和颗粒大小.     

氧化锆陶瓷注射成形工艺研究

研究了氧化锆陶瓷粉末注射成形工艺过程，包括粘结剂的选择、喂料粉末装载量的确定、混炼工艺及混炼扭矩的研究，注射压力、注射温度、保压压力、模具温度、注射速度等注射成形工艺对成形坯质量的影响，以及溶剂脱脂温度、样品厚度、粉末粒度及形藐等对溶剂脱脂速率的影响及后续热脱脂工艺，扶得了一条优化的注射成形工艺路线。     

陶瓷粉末注射成型计算机模拟研究与应用

本文介绍了计算机模拟软件在陶瓷粉末注射成型工艺中的应用现状,举例说明了C-Mold软件在陶瓷粉末注射成形工艺模拟薄体半球的填充,并与实验的实际情况做比较,以探讨陶瓷材料在充填过程中的现象。     

陶瓷注射成形技术及其研究进展

陶瓷注射成形(CIM)是一种近净尺寸成形工艺,适用于体积小、形状复杂、成形精度高的陶瓷结构件。笔者介绍了CIM的基本工艺过程,包括陶瓷粉体和粘结剂的选择、喂料制备、注射工艺和脱脂工艺。重点阐述了粘结剂的性能及分类、脱脂工艺研究进展以及微注射成形和低压注射成形新技术。最后对陶瓷注射成形的发展趋势进行了展望。     

氧化锆微型齿轮的粉末微注射成形数值模拟研究

微系统与其相关产品的蓬勃发展,使得市场对微型零件的需求急剧增加,而粉末微注射成形技术为其大规模生产提供了商业化的可能。重点研究了氧化锆陶瓷粉末-粘结剂微注射成形过程中三维充填模拟以及相关的实验验证。采用Power Law模型+Arrhenius模型,研究适于齿轮微注射成形用的注射温度。经研究发现,最适于齿轮微注射成形的注射温度为150℃。通过验证实验,Ansys-CFX软件模拟出来的结果能预测喂料的流变情况。     

注射成形AlN-Y2O3陶瓷的结构与性能

采用粉末注射成形方法制备了具有高导热性能的AlN陶瓷导热材料, 研究了烧结温度对注射成形AlN陶瓷致密化的影响;研究了添加不同质量分数Y2O3对注射成形AlN陶瓷的晶界第二相、热导率和显微结构的影响. 结果表明在本实验研究条件下, 当烧结温度在1 850 ℃时, AlN的相对密度已经能够达到99.5%;Y2O3的添加量对AlN的晶界第二相的影响和传统AlN制备工艺中有较大的不同, 在Y2O3质量分数为3%时就有多余的Y2O3成为晶界相, 这主要是注射成形工艺中会引入大量的残碳造成的. 注射成形AlN陶瓷工艺中氧离子是否扩散进入晶格中对AlN陶瓷的热性能有一定影响. 当Y2O3质量分数为5%时, AlN中的晶界第二相主要为YN和Y2O3, 样品具有最高的热导率167.5 W/(m*K).     

The effect of water on the behaviour of alumina–paraffin suspensions for low-pressure injection moulding (LPIM)

The properties of ceramic powder–paraffin suspensions for low-pressure injection moulding (LPIM) is of critical importance to the successful production of high quality ceramic parts. Due to the high hygroscopicity of fine alumina powder, water introduced into the suspension at any stage of the production prior to sintering, may significantly influence its rheological behaviour and hence determine the process parameters as well as the properties of the sintered ceramics. In the industrial environment humidity cannot easily be avoided. Its effect is usually detrimental — it causes flocculation, which is usually the source of defects in sintered ceramics. However, according to the results of the present work, the effect can also be put to good use. Penetration of water into the as-moulded green parts facilitates binder removal and prevents defect formation during this processing step.     

纳米陶瓷复合材料制备工艺中nano-SiC与基体Al2O3粉末的均匀分散

本文探讨了用于增韧补强陶瓷基体的nano-SiC颗粒的液相分散工艺,研究结果表明:以乙醇和丙三醇的混和液作为分散介质,通过加入适当的表面活性剂,以及调节pH值可以制备出高分散、高稳定的纳米颗粒悬浮液,此法可获得理想的分散效果.     

特种陶瓷的制备工艺综述及其发展趋势

本文主要介绍了粉末陶瓷原料的制备技术、特种陶瓷成形工艺、烧结方法以及未来的发展趋势。目前,特种陶瓷中的粉末冶金陶瓷工艺已取得了很大进展,但仍有一些面临急需解决的问题。当前阻碍陶瓷材料进一步发展的关键之一是成形技术尚未完全突破。压力成形不能满足形状复杂性和密度均匀性的要求。多种胶体原位成形工艺,固体无模成形工艺以及气相成形工艺有望促使陶瓷成形工艺获得关键性突破。     

Preparation and indirect selective laser sintering of alumina/PA microspheres

Indirect selective laser sintering (SLS) is a promising additive manufacturing technique to produce ceramic parts with complex shapes in a two-step process. In the first step, the polymer phase in a deposited polymer/alumina composite microsphere layer is locally molten by a scanning laser beam, resulting in local ceramic particle bonding. In the second step, the binder is removed from the green parts by slowly heating and subsequently furnace sintered to increase the density. In this work, polyamide 12 and submicrometer sized alumina were used. Homogeneous spherical composite powders in the form of microspheres were prepared by a novel phase inversion technique. The composite powder showed good flowability and formability. Differential scanning calorimetry (DSC) was used to determine the thermal properties and laser processing window of the composite powder. The effect of the laser beam scanning parameters such as laser power, scan speed and scan spacing on the fabrication of green parts was assessed. Green parts were subsequently debinded and furnace sintered to produce crack-free alumina components. The sintered density of the parts however was limited to only 50% of the theoretical density since the intersphere space formed during microsphere deposition and SLS remained after sintering.     

不同工艺制备ZrO2—Al2O3复合陶瓷超细粉体的研究

采用正滴定工艺，反滴定工艺和水解工艺来制备ＺｒＯ２－Ａｌ２Ｏ３系复合陶瓷超细粉体。研究了制备工艺对水合氧化锆凝胶的包裹状态，煅烧后粉体中ＺｒＯ２颗粒的弥散状态以及烧结体显微结构的影响。结果表明采用水解工艺，ＺｒＯ２颗粒能均匀弥散在Ａｌ２Ｏ３颗粒周围，最终获得均匀细晶的陶瓷烧结体；在反滴定工艺中，虽然水合氧化锆凝胶能较好包裹Ａｌ２Ｏ３颗粒，但由于Ａｌ２Ｏ３颗粒本身得不到有效分散，因此在烧结体中出现了     

Microstructure and properties evolution of silicon-based ceramic cores fabricated by 3D printing with stair-stepping effect control

A ceramic core is the key component in the manufacture of the hollow turbine blades of aeroengines. Compared with the traditional injection molding method, 3D printing is more suitable for manufacturing ceramic cores with a complex geometry at high precision. However, the stair-stepping effect is inevitable in the 3D printing process and affects the surface roughness and strength of the ceramic core. In this study, to explore the influence of nano-silica content on the microstructure and properties of the ceramic core, silicon-based ceramic cores were fabricated with the addition of nano-silica powder by digital light processing and subsequent sintering at 1200 °C. The results showed that the apparent porosity and pore size of the ceramic core gradually decreased as both the nano-silica powder content and bulk density increased. Meanwhile, the printing interlayer spacing was significantly reduced, resulting in a low surface roughness, high flexural strength, and creep-resistance. To simulate the entire casting process of a superalloy blade, the thermal deformation behavior of the ceramic core was observed by heating and cooling cycles performed in a thermal dilatometer at 1540 °C. The total linear shrinkage decreased as the nano-silica powder content increased, which was mainly due to the phase transformation of cristobalite and the densification of the ceramic core sintered at 1200 °C. The low surface roughness and linear shrinkage as well as high flexural strength of the ceramic core can contribute to the excellent quality of cast superalloy blades.     

Growth Mechanism of Monodispersed ZrO2 Particles

Monodispersed ZrO₂ seed particles which were prepared by hydrolysis of zirconium alkoxide solutions were allowed to grow by further addition of zirconium alkoxide and water under conditions in which new particles do not nucleate and grow. The particle growth mechanism is presumed to be a surface reaction in which the rate-determining step is a first-order polynuclearlayer growth mechanism. With this method of powder preparation, it is possible to precisely control the particle size, and it may be useful for applications in ceramic processing.     

UV Curable Systems for Tape Casting

The substitution of solvents by photopolymerizable binders in the tape casting process allows to achieve high ceramic loading and to eliminate the drying stage which is a critical step of the tape casting process. After the rapid UV polymerization of the resin, the high strength green tapes can be debinded and sintered. Ceramic suspensions containing alumina or zirconia powder, dispersant, UV curable binder and photoinitiator have been prepared. The use of a low viscosity organic vehicle allows to prepare low viscosity ceramic suspensions, containing about 50 vol% powder, which have a shear thinning behaviour. Because of the rapid attenuation of the incident light in UV curing systems containing ceramic particles it is important to estimate the thickness of the tape that can be treated. The effect of incident energy, of photoinitiator concentration and of powder volume fraction was studied. There is an optimal photoinitiator concentration which maximizes the cured depth and which depends on the volume fraction of solid. A theoretical model based on the Beer–Lambert’s law enables the prediction of cured depth for any volume fraction of solid. To prove the ability to manufacture ceramic sheets by tape casting, some suspensions were tape cast.     

New cellular ceramics from high alkane phase emulsified suspensions (HAPES)

Open porous mechanically stable ceramic foams are developed by a simple direct foaming process. The new processing route is based on the transition of a surfactant stabilized highly concentrated alkane phase homogeneously distributed in a stabilized aqueous ceramic powder suspension into high performance ceramic foams with porosities up to 90% and cell sizes ranging from 3 to 200 μm. The droplet size distribution of the high alkane phase emulsified suspensions (HAPES) is efficiently controlled by the stirring velocity during emulsification experimentally investigated for varying powder particle contents. Stable foams with tailored structural features can be prepared by adjusting the rheological characteristics of HAPES being dependent on the system and process parameters. The influence of the emulsification stirring velocity on the resulting HAPES droplet size is analysed on the basis of the Taylor model of mechanical shearing describing the stresses responsible for the fragmentation of the droplets.