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。     

氧化锆陶瓷注射成型溶剂脱脂行为的研究

以氧化锆陶瓷粉体为研究对象,采用低毒性、低成本的煤油作为有机脱脂溶剂,研究了注射成型生坯的溶剂脱脂行为,探索了时间、温度、固相体积分数和粘结剂体系对脱脂速率的影响,分别讨论了各因素影响脱脂速率的机理.结果表明:脱脂速率随温度升高而升高,随时间的延长而降低;脱脂初期扩散是控制性环节,温度是影响反应速率的主要因素,脱脂后期溶解成为控制性环节,浓度差成为影响反应速率的主要因素;注射坯体固相体积分数越高,脱脂速率越慢,粘结剂最终脱除率越低;用部分植物油取代石蜡的蜡-油基复合型粘结剂注射坯体的脱脂速率快于传统蜡基型的注射坯体,最终脱脂率也高于传统型的蜡基注射坯体.     

陶瓷注射成型粘结剂现状及发展趋势

本文重点介绍了陶瓷注射成型粘结剂的种类，特性及脱脂技术，比较了目前几种粘结剂体系的优缺点，指出了今后粘结剂发展方向和趋势。     

ZrO2陶瓷注射成型超临界CO2流体脱脂动力学研究

用传统扩散方程建立了描述ZrO2陶瓷注射成型超临界流体脱脂过程的传质模型,研究分析了陶瓷注射成型超临界流体脱脂行为和脱脂的动力学过程。研究结果表明：有机粘合剂的溶解和扩散是陶瓷注射成型超临界脱脂过程关键因素,其中扩散为控制步骤。当脱脂时间足够长,模型计算曲线与实验结果吻合。通过实验数据,利用简单的理论模型可以得到相应的扩散系数。利用传质模型可以预测陶瓷注射成型超临界脱脂过程传质速率和萃取动力学。     

Sialon陶瓷注射成型的溶剂脱脂研究

在Sialon陶瓷注射成型中,以蜡基粘结剂的溶剂脱脂为研究对象,考查了注射成型中溶剂脱脂工艺的脱脂温度、脱脂时间、试样厚度、溶剂加入方式及表面积与体积之比等参数对试样脱脂的影响,对溶剂脱脂过程中可溶组元的最大脱除率作了初步的分析,并用SEM观察了不同脱脂率的形貌的变化。结果表明：在40℃下采用纯的三氯乙烯对试样进行脱脂,当PW的脱出率在75%以上时,连通孔道基本形成,坯体在后续热脱脂和烧结中不会变形。     

陶瓷注射成型粘结剂现状及发展趋势

本文重点介绍了陶瓷注射成型粘结剂的种类、特性及脱脂技术;比较了目前几种粘结剂体系的优缺点,指出了今后粘结剂发展方向和趋势。     

空气阴极微生物燃料电池研究进展

微生物燃料电池（MFC）是一种利用微生物做催化剂,处理废水的同时能产电的新型污水处理技术,因其＂变废为宝＂的能力而得到快速的发展。其中,以空气做阴极的单室MFC,因其省却了不断添加阴极液的过程、提高功率输出的同时降低成本而受到越来越多的关注。单室MFC装置可以分为管状、立方体状和短臂型结构,空气阴极的结构组成包括膜、催化层、集电材料、基层和扩散层。膜和催化层通常用热压法进行结合。目前报道的研究结果表明,有扩散层时获得的功率密度更高。已研究的扩散层的粘结剂有PTEF、PDMS、EF以及Nafion。选择合适的构型、催化剂以及扩散层的层数和粘结剂对改善电池产电性能极为重要。如何将多个装置串联以扩大废水处理量、提高功率密度的同时提高电子回收率是需要进一步解决的问题。     

陶瓷注射成型中粘结剂的热脱脂特性评价

脱脂是陶瓷注射成型工艺的制约性步骤.通过热分析的方法研究了PW+EVA+SA的热特性.通过计算的方法和实测的方法得到粘结剂整体的热失重曲线,发现两者较为接近,继而提出了一个定量评价粘结剂脱脂特性的物理参量--脱脂惯量.通过对脱脂惯量的计算发现PW78%+EVA21%+SA1%粘结剂体系具有最好的脱脂特性.     

图像法用于流化床颗粒混合特性的研究

利用基于相关的图像法速度测量技术,测量了小型二维气固流化床密相区颗粒运动速度分布.并提出了用颗粒速度不均匀指数来衡量流化床内颗粒的速度波动与混合.速度波动对于物料扩散与对流混合均十分重要.在流化床下部,颗粒运动速度往往低于床层表面,但速度不均匀指数则高于床层表面.在床层底部颗粒速度不均匀指数随流化床气泡产生而变化.床层内部混合以对流及扩散为主,而在床层表面,混合以对流为主.床层下部速度波动有利于颗粒在床内的扩散及对流混合.流化风量的增加可以增强颗粒的混合.针对这些结论,在流化床垃圾焚烧炉的设计中,对不同的组分选用不同的给料方式,可以促进物料在床内的混合.     

微机监控技术在混捏工艺中的应用

１引言混捏在炭素材料生产中占十分重要的地位,混捏过程就是把配料所得的各种炭素颗粒和粘结剂,在一定温度条件下搅拌、混合,得到具有一定塑性的糊料。在混捏过程中,各种颗粒的物料之间、物料与粘结剂之间相互作用,在机械搅拌和物理、化学吸附等作用下,使不同颗粒的...     

氮化硅陶瓷中压注塑成型技术(MPIM)研究及进展

首次采用中压注塑成型技术(MPIM)制得性能优良的氮化硅轴承球。研究了粘结剂配方、注塑成型、低缺陷排胶、气氛压力烧结等工艺参数对氮化硅轴承球致密度、力学性能、表面与微观形貌的影响。结果表明,喂料固含量55.51%、注塑速率5 cm/s、注塑温度90℃、注塑实际压力75 bar、超临界CO2萃取+热脱脂两步法排胶等工艺过程有效控制了氮化硅坯体的缺陷,制得了生坯致密度58.7%、烧结密度3.26 g/cm3、烧结致密度99.4%、抗弯强度843 MPa、无缺陷的氮化硅轴承球。MPIM是未来注塑成型技术发展的重点方向,具有广泛的应用前景。     

Effect of microcrystalline wax on the solvent debinding of the Sr-ferrite ceramics prepared by powder injection molding

Powder injection molding (PIM) opens new possibilities to process complex Sr-ferrite components for magnetic applications. In the present study, new binder system with the addition of microcrystalline wax (MW) was used for the Sr-ferrite powder injection molding. The optimum binder composition was determined based on rheological measurement, mircrostructure observation by SEM, thermal change by DSC and debinding process. The results indicated that MW with 10 vol.% addition in the binder system containing high density polyethylene (HDPE), paraffin wax (PW) and stearic acid (SA) decreases the defects of the green parts after solvent debinding because the distribution of the binder system between the Sr-ferrite particles becomes more homogeneous. Using the proper binder system containing MW, the defect-free and dense Sr-ferrite ceramics can be prepared after solvent and thermal debinding and sintering. Based on the experimental results, the effects of MW microcrystalline wax on the solvent debinding of the Sr-ferrite ceramics were detailed discussed.     

注射成型氧化铝陶瓷工艺研究

研究了氧化铝陶瓷注射成型工艺过程,包括粘结剂的选择、粉末装载量的确定及热脱脂工艺的研究。探讨了注射压力、注射温度和模具温度等注射成型工艺参数对试样性能的影响,得到了一条优化的氧化铝注射成型工艺路线。     

Surface modification of ceramic powders by titanate coupling agent for injection molding using partially water soluble binder system

In the conventional process of ceramic injection molding (CIM), wax-based binders could only be removed by thermal or organic solvent debinding. Recently, water solvent debinding, with its high efficiency and environmental acceptability, has appeared as a good alternative. In this study, zirconia powder modified by titanate coupling agent was applied in partially water soluble binder system for injection molding. In contrast to previous researches about titanate modification mainly focusing on rheological behavior and modification mechanism, investigations on the sintering behavior and densification process were also made in this study. Experimental results reveal that titanate modified powder exhibits densification temperature almost 100 °C lower than that required for the pure, original powder, giving rise to finer microstructure and therefore hopefully improved mechanically properties. It suggests a novel modification route to fabricate injection molded ceramic components using partially water soluble binder system.     

Influence of Carbon Content on Ceramic Injection Molding of Reaction‐Bonded Silicon Carbide

Reaction‐bonded silicon carbide (RBSC) was prepared by ceramic injection molding (CIM) technique with feedstocks containing silicon carbide (SiC), a wax‐based organic system and different amounts of carbon black. As a critical effect of the reaction sintering process, carbon was introduced from the carbon black and the decomposition product of the organic polymers, respectively. This study described the influence of carbon content on the mixing and injection process firstly and then emphasized the debinding process since it played a large role in the process of the pyrolysis of organic. Results indicated that the preferable thermal debinding was performed in N₂ and the optimal performance was obtained for RBSC with 7 wt.% of carbon black, with the density of 2.98 g/cm³, apparent porosity of 0.24%, bending strength of 301.59 MPa and fracture toughness of 4.18 MPa·m^1/2.     

Aetiology of Defects in Large Ceramic Moldings

This study is an attempt to identify the causes of defects that appear in large ceramic injection molded bodies after sintering. It asks the question: are such defects established at the injection molding stage or are they caused by the debinding process or by sintering? Moldings with ascending thickness were prepared using a mold cavity with replaceable tool faceplates. Control over pressure during solidification was compared by using conventional molding and a novel molding technique that uses an insulated sprue. The organic vehicle is polyoxymethylene, which can be displaced by catalytic degradation in the solid state. This is a shrinking unreacted core process with a clearly defined reaction boundary in which there is no provision for particle movement in the liquid state. This study tracks the development of defects at each stage and concludes that the defects apparent after sintering have their origin in injection molding, even though they do not mature until a later stage.     

陶瓷的注射成型技术

陶瓷注射成型技术可解复杂形状的高性能陶瓷元件的大批量生产难题,并且产品尺寸精度高,表面条件好,论述了瓷注射成型工艺中粘结剂选取,注射成型,脱脂等步骤,并提出了将来的研究方向。     

Influence of injection temperature and pressure on the properties of alumina parts fabricated by low pressure injection molding (LPIM)

The quality of ceramics parts made by powder injection molding (PIM) method is influenced by a range of factors such as powder and binder characteristics, rheological behavior of feedstock, molding parameters and debinding and sintering conditions. In this study, to optimize the molding parameters, the effect of injection temperature and pressure on the properties of alumina ceramics in the LPIM process were thoroughly studied. Experimental tests were conducted on alumina feedstock with 60 vol% powder. Injection molding was carried out at temperatures and pressures of 70–100 °C and 0.1–0.6 MPa respectively. Results showed that increase in injection temperature and pressure and the resulting increase in flow rate leads to the formation of void which impairs the properties of molded parts. The SEM studies showed that injection at temperature of 100 °C results in evaporation of binder components. From the processing point of view, the temperature of 80 °C and pressure of 0.6 MPa seems to be the most suitable condition for injection molding. In addition, the effects of sintering conditions (temperature and time) on the microstructure and mechanical properties are discussed. The best final properties were found using injection molding under the above stated conditions, thermal debinding and sintering at 1700 °C during 3 h.     

Rheological and thermal debinding behaviors of silicon nitride in powder injection molding

In powder injection molding process, it is important to analyze the rheological and thermal debinding behaviors of feedstock, because they can directly affect the final quality of products. Therefore, for the silicon nitride based feedstocks, the rheological and thermal debinding behaviors were investigated and compared between feedstocks prepared with the combination of two types of powders and sintering aid ratios. At first, the optimal solids loading for each feedstock was determined based on the results of the torque rheometer experiment. The viscosity of the feedstocks was measured using the capillary rheometer, and rheological properties were evaluated with the Power Law-Arrhenius model. Silicon nitride (JPN) feedstock with 5 wt% yttria and 2 wt% alumina (JPN+5Y2A) had the highest moldability index among all feedstocks. The powders with sintering aid ratio of 5 wt% yttria and 2 wt% alumina made the feedstocks have a high moldability index. Thermogravimetric experiment was also performed to analyze the pyrolysis behavior of the feedstocks, and the apparent activation energies for each feedstock were obtained using Kissinger method with the thermogravimetric analysis results. Based on the results, the master decomposition curve (MDC) was developed, and the utility of MDC for optimizing the thermal debinding process was verified.