发泡法、三维打印法、熔盐法制备多孔陶瓷

多孔陶瓷由于其广泛的应用前景而成为陶瓷领域的一个研究热点。综述了近年来多孔陶瓷制备研究的最新进展,重点概述了发泡法、三维打印法和熔盐法对多孔陶瓷的孔结构(孔尺寸、孔隙率和孔的连通性)及性能的影响。对所述3种方法制备的多孔陶瓷的孔径和孔隙率进行了对比,对其工艺的优缺点进行了总结,并在此基础上提出了多孔陶瓷制备过程中存在的问题和未来的发展方向。     

冷冻浇注制备多孔陶瓷的研究进展

冷冻浇注制备多孔陶瓷具有绿色经济、孔结构可控以及材料性能优良等优点,近年来受到国内外学者的广泛关注。本文在简单介绍冷冻浇注工艺原理的基础上,阐述了冷冻浇注工艺过程中孔结构的形成机理与条件,详细讨论了液相介质与冷冻条件对孔结构的影响,总结了冷冻浇注制备多孔陶瓷的材料体系以及典型工艺条件,最后指出冷冻浇注未来的研究方向是孔结构的有效控制及新型功能化多孔陶瓷的制备。     

凝胶注模成型法制备多孔羟基磷灰石陶瓷

采用凝胶注模成型工艺制备了多孔羟基磷灰石陶瓷,并通过X射线分析了多孔陶瓷的相成分,采用扫描电镜观测了孔隙结构和形貌.结果表明,所制备的多孔羟基磷灰石陶瓷的孔隙率均大于80%;孔隙尺寸主要分布在350～600μm,孔壁上存在孔径为60～190μm的贯通孔;X射线衍射证明烧结过程未引入异质成分.所制备的多孔羟基磷灰石陶瓷具有适宜的孔隙直径和孔隙率,且孔隙间具有良好的贯通性.     

包覆工艺制备多孔低介电氮化硅陶瓷的研究

以硅粉为原料,通过添加成孔剂球形颗粒,以聚乙烯醇作粘结剂,采用包覆工艺、干压成型,反应烧结制备了多孔氮化硅陶瓷,对比了包覆工艺对实验结果的影响.结果表明,采用包覆工艺较未采用包覆工艺制得的多孔氮化硅陶瓷有着更高的气孔率,宏观孔分布均匀,有较多的微孔,介电性能良好.     

先驱体转化法制备多孔陶瓷的发展现状

多孔陶瓷材料因其优异的性能在各种领域的应用越来越广泛,其制备方法也不断的发展.先驱体转化法制备多孔陶瓷是20世纪末才出现的一种新型工艺,它具有烧结温度低、成型工艺简单、所得制品强度高等优点,引起了科学技术界的广泛兴趣.根据所得多孔陶瓷的形态,先驱体转化法制备多孔陶瓷大致可分为两类:制备本征结构的多孔陶瓷,制备泡沫陶瓷.本文介绍了先驱体转化制备这两类多孔陶瓷的工艺、结构和性能的研究现状,以及其存在的急需解决的问题.     

天线罩用多孔氮化硅陶瓷的制备

采用反应烧结工艺,通过添加成孔剂的方法,制备出具有球形宏观孔的低密度多孔氮化硅陶瓷,研究了球形宏观孔和烧结工艺对多孔氮化硅陶瓷性能的影响.实验结果表明,与未添加成孔剂的样品相比,成孔剂的添加有效降低了材料的气孔率,使材料的介电常数ε'和介电损耗tanδ下降.孔的加入能促进针状氮化硅的生成,降低单位体积中产生的热量,防止...     

多孔陶瓷材料制备工

概述了多孔陶瓷的基本特征,分类,特性,性能,应用领域。详细介绍了多孔陶瓷的传统制备工艺与现代制备工艺的制备方法,优缺点以及适用范围等,以SiC多孔陶瓷为例作具体分析介绍。最后展望了多孔陶瓷材料的发展前景。     

碳化硅多孔陶瓷制备技术的研究进展

制备技术是获得高性能碳化硅多孔陶瓷的关键.综述了碳化硅合成方法和成孔方法对碳化硅多孔陶瓷一些主要的制备技术,主要包括烧成/烧结法、原位氧化反应结合法、反应烧结法、碳热还原法、先驱体转化法、化学气相渗透法等.介绍了各种方法的工艺过程,分析了优缺点,指出了今后发展的方向.     

多孔陶瓷的直写成型工艺研究进展

多孔陶瓷内部含有大量三维孔隙,具有轻质、高强、高比表面积、低导热系数等特性,但是多孔陶瓷的传统制备工艺对结构和性能的可控性较低,很难满足先进能源、航空航天、电子信息等领域的发展对多功能高性能材料的需求。直写成型工艺是一种制造成本低、材料使用性广、技术可拓展性高的3D打印工艺,不仅可以直接制备具有轻量化特点的多孔陶瓷,而且结合其他工艺可以实现多孔陶瓷的层级结构和多功能化,有望实现设计与制造、材料与器件、结构与功能的一体化。介绍了直写成型法3D打印多孔陶瓷的工艺原理,综述了直写成型法直接制备多孔陶瓷、直写成型结合乳液/泡沫法和冷冻干燥法制备层级多孔陶瓷的研究进展。由于工艺柔性高,直写成型法能够与其他方法良好融合,以制备具有特殊结构和性能的多孔材料,尤其是兼顾高强度、高孔隙率和形状可控性的层级多孔陶瓷。最后,总结了目前直写成型工艺制备多孔陶瓷的优势和不足,并对打印材料性能、打印设备和主要应用领域的发展进行了展望。     

烧成工艺制度对石英砂基多孔陶瓷材料孔结构及性能的影响

以节约粘土资源及开发新型节能建筑材料为目的,利用长江沿岸低品位石英砂开发研制多孔陶瓷.研究了烧成工艺对石英砂基多孔陶瓷孔结构及性能的影响,为新型隔热保温材料的开发提供了工艺参考依据.研究结果表明,利用长江沿岸低品位石英砂成功地研制出多孔陶瓷,其密度随烧结温度的升高或保温时间的延长而增大,气孔率则随烧结温度的升高或保温时间的延长而降低.从能耗、成本与性能3方面考虑,石英砂基多孔陶瓷较合理的制备工艺参数为烧结温度1100℃、保温时间60min.     

碳化硅多孔陶瓷的制备及研究进展

碳化硅多孔陶瓷具有抗腐蚀、抗热震性及低的热膨胀系数等特点,在冶金、化工、环保、航空、微电子等技术领域具有广泛的应用.综合阐述了制备碳化硅多孔陶瓷的主要工艺与制备过程,并对相关工艺的特点进行了分析,最后展望了碳化硅多孔陶瓷的发展趋势.     

Preparation of zirconium pyrophosphate bonded silicon nitride porous ceramics

Abstract

A new method for preparing high bending strength porous silicon nitride ceramics with controlled porosity was developed using a pressureless sintering technique, using zirconium pyrophosphate as a binder. The fabrication process was described in detail and the sintering mechanism of porous ceramics was analysed by an X-ray diffraction method. The microstructure and mechanical properties of the porous Si₃N₄ ceramics were investigated, as a function of the content of ZrP₂O₇. The resultant porous silicon nitride ceramics sintered at low temperature (1000 and 1100°C) showed fine micropore structure and a high bending strength. Porous silicon nitride ceramics with porosity of 34–47%, a bending strength of 40–114 MPa and a Young's modulus of 20–50 GPa were obtained.     

Effects of rheological properties on ice-templated porous hydroxyapatite ceramics

Freeze casting of aqueous suspension was investigated as a method for fabricating hydroxyapatite (HA) porous ceramics with lamellar structures. The rheological properties of HA suspensions employed in the ice-templated process were investigated systematically. Well aligned lamellar pores and dense ceramic walls were obtained successfully in HA porous ceramics with the porosity of 68–81% and compressive strength of 0.9–2.4 MPa. The results exhibited a strong correlation between the rheological properties of the employed suspensions and the morphology and mechanical properties of ice-templated porous HA ceramics, in terms of lamellar pore characteristics, porosities and compressive strengths. The ability to produce aligned pores and achieve the manipulation of porous HA microstructures by controlling the rheological parameters were demonstrated, revealing the potential of the ice-templated method for the fabrication of HA scaffolds in biomedical applications.     

Porous Piezoelectric Ceramics: Materials for Ultrasonic Flaw Detection and Medical Diagnostics

The key features of the piezoelectric materials for ultrasonic transducers are considered. A procedure is described for the fabrication of porous piezoelectric ceramics. It is shown that, owing to their high piezoelectric performance and ease of fabrication, porous ceramics may compete with lead niobate and piezoelectric composites in the fields of medical diagnostics and ultrasonic flaw detection.     

Forming and sintering of porous calcium-hexaaluminate ceramics with hydraulic alumina

We have developed a new eco-friendly fabrication process for porous ceramics using hydraulic alumina (HA) and water. In the present study, we fabricated porous calcium-hexaaluminate (CaAl₁₂O₁₉, CA6) ceramics using this new process. A boehmite gel 3-D network was formed by the hydration of HA in HA/CaCO₃ mixed slurry. The HA/CaCO₃ mixed slurry was hardened by the formation of this 3-D network. Even without the addition of an organic binder, green bodies containing the 3-D network demonstrated high compressive strength and retained their original shapes. Furthermore, the water acted as a fugitive material in the green bodies. Consequently, the open porosity of the CA6 ceramics could be controlled over a wide range of 42–62.7% by the addition of water (ratio of water to HA/CaCO₃ mixed powder: 0.4 to 1.6 by weight) without the use of organic fugitive materials. The results of evolved gas analysis-mass spectrometry measurements showed that the emissions from the hardened green body consisted mostly of water. Consequently, the new fabrication process for porous calcium-hexaaluminate ceramics was confirmed to be eco-friendly.     

Porous calcium phosphate ceramics prepared by coating polyurethane foams with calcium phosphate cements

Porous calcium phosphates have important biomedical applications such as bone defect fillers, tissue engineering scaffolds and drug delivery systems. While a number of methods to produce the porous calcium phosphate ceramics have been reported, this study aimed to develop a new fabrication method. The new method involved the use of polyurethane foams to produce highly porous calcium phosphate cements (CPCs). By firing the porous CPCs at 1200 °C, the polyurethane foams were burnt off and the CPCs prepared at room temperature were converted into sintered porous hydroxyapatite (HA)-based calcium phosphate ceramics. The sintered porous calcium phosphate ceramics could then be coated with a layer of the CPC at room temperature, resulting in high porosity, high pore interconnectivity and controlled pore size.     

Recent advances in 3D printing of porous ceramics: A review

3D printing, alongside the rapidly advancing field of porous ceramics, is quickly expanding the horizon of what is going to be possible in the future. In this paper, 3D printing technology is evaluated for its compatibility with porous ceramic materials, due to its competitive process in terms of speed and specific tooling, especially for good quality fabrication. The paper reviews the capabilities of these new technology techniques for the fabrication of porous ceramic. The basic technology is the 3D printing techniques, which are used to fabricate porous green ceramic parts that are later sintered. Different ceramic materials are evaluated and the classification of different powders according to their 3D printing quality as well as material aspects is examined. The evaluation of 3D printing process in terms of the powders’ physical properties such as particle size, flowability and wettability is also discussed. The relationship between the different 3D printing parameters and the final printing outcome are assessed.     

Controllable porosity hydroxyapatite ceramics as spine cage: fabrication and properties evaluation

A procedure was designed to prepare porosity-graded hydroxyapatite (HA) ceramics simulating the bimodal structure of natural bone, which could be used to build a cage that would promote the reconstruction of the anterior column after vertebrectomy or corpectomy in tumor and trauma surgery. HA ceramics with controllable pore size distribution and porosity were developed by using chitosan and Poly(vinyl alcohol) (PVA) as the pore-forming agents. HA ceramics with worthwhile properties such as a wide range of volume porosity (10-50%) and pore size (nanometer to 400 microm) can be obtained from this method, which allows the fabrication of HA ceramics with desirable porous characteristics simulating the bimodal natural bone architecture expected to provide advantages for bony fusion in the intervertebral foramina. When coated with chitosan-gelatin network, the bending strength of the porous HA ceramics significantly improved. The polymer network coated porous HA have potential application in the construction of cages for spinal operations.