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Gelcasting is a well-established colloidal processing method with a short forming time, high yields, high green capacity and low-cost machining, and has been used to prepare high-quality and complex-shaped dense/porous ceramic parts. In this article, we reviewed recent developments in gelcasting technology for ceramic preparation. For environmental pollution reduction during ceramic preparation by gelcasting, the development of low-toxic and nontoxic gelcasting systems is discussed. The occurrence and control of inner stress and surface-exfoliation in ceramic green bodies prepared by gelcasting are analyzed, and then some methods to control and eliminate the inner stress and surface-exfoliation in ceramic gelcast green bodies, especially for colloidal injection molding of ceramics (CIMC) are proposed. Finally, the applications of gelcasting for the fabrication of porous ceramics and complex-shaped ceramics (e.g., microbeads, rutile capacitor, thin-wall rutile tube, refractory nozzle) are summarized. 相似文献
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Masayoshi Fuji Yoshihiro Shiroki Hiroaki Takegami Hisao Suzuki Toyokazu Yokoyama 《Powder Technology》2007,172(1):57-62
Cordierite ceramic filters have been shown a potential candidate for a high temperature dust collection, owing to its very low thermal expansion coefficient characteristic as an attribute of excellent thermal shock resistance. It is preferable that a design of porous cordierite filter should have low pressure drop with high permeability while keeping the structural integrity. This study describes a simple and direct approach for fabricating a porous cordierite filter with honeycomb-type structure by introducing various non-through holes into mechanically foamed slurry, which is subsequently in-situ solidified by polymerization reaction. The gelcasting cordierite-based slurry was mechanically foamed in nitrogen-filled chamber. The resulting foamed slurry was cast directly into circular molds equipped with a cover having different number of pins. The gelled-bodies were carefully dried at 25 °C with a controlled humidity, followed by sintering under optimized condition. The dust collection performance, pressure drop, and gas permeability were evaluated as a function of the number of non-through holes in porous cordierite. Based on the results of the tests, the holey porous cordierite filter offered a better filter design for dust collection application. 相似文献
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Xing Du Lei Zhao Xuan He Xin Wang Weimin Qu Hui Chen Huan Chen Junjie Wang Zhongxing Lei 《Journal of Porous Materials》2016,23(2):381-388
Foam instability and long drying cycle limits the widespread use of foaming method. In this paper, a kind of porous mullite ceramic with thermal insulation–mechanical property trade-off were fabricated via novel ultrastable foam and improved gelcasting procedure. The solidification process and stability of foam slurry, as well as the thermal, mechanical property and pore structure of the porous mullite ceramics were investigated. The results showed that porous mullite ceramics with different bulk densities could be prepared via varying volume of foam which was stable enough to be maintained in slurry for a long time. The accelerated gelation rate as well as the gelation degree resulted in the improved gelcasting method led to a shortened period of drying and demould. The obtained pores, which were small, smooth, and unimodal distributed in size in porous mullite ceramics, contributed to achieving the trade-off between thermal insulation and mechanical property. 相似文献
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《Ceramics International》2020,46(6):7896-7902
Aqueous gelcasting is inappropriate for the preparation of highly porous ceramics, due to the large drying shrinkage of green bodies caused by the high surface tension of water. To solve this problem, non-aqueous gelcasting using organic solvents with much lower surface tension was developed. However, for most organic solvents, the precipitation polymerization of gels led to the low strength of green bodies, which was inconvenient for the fabrication of large size workpieces. In this work, a novel ethylene glycol-based gelcasting was developed to prepare highly porous SiC ceramics. Ethylene glycol induced the solution polymerization of gels and increased the strength of green bodies effectively. In addition, the high flexibility of the ethylene glycol-based gels could release the inner stress in the drying process. Highly porous SiC ceramics with large size were successfully prepared by the optimized gelcasting method. 相似文献
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《Ceramics International》2022,48(22):33058-33065
To further resource industrial solid waste, porous ceramics with high porosity were prepared by a gelcasting method using nickel slag and kaolin as raw materials and hydrophilic nontoxic SiO2 aerogel as a gelling agent. The effects of nickel slag content, dispersant and solid content on the properties and microstructure of porous ceramics were investigated in detail in terms of density, compressive strength, porosity, phase composition and micromorphology. The results confirmed that a certain amount of nickel slag can effectively improve the porosity of porous ceramics, while the addition of dispersant can promote the flow of the slurry, enhanced the denseness of the raw billet and significantly improved the compressive strength. However, its excessive use had a negative effect on the ceramic density and porosity. At the same time, the solid content played a key role in the performance of porous ceramics prepared by gelcasting, and too much solid content was also not conducive to the generation of pores. When the nickel slag content was 55%, the amount of dispersant was 2%, and the solid content was 60 vol%, the porous ceramic had a better overall performance, the density of the porous ceramic was 510 kg/m3, the compressive strength was 1.3 MPa, and the porosity reached 80.1%. The major crystalline phases of porous ceramics prepared by nickel slag were cordierite and anorthite. 相似文献
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Porous YSZ ceramics by water-based gelcasting 总被引:2,自引:0,他引:2
Gelcasting, as a novel method to form ceramic bodies, has been successfully developed to fabricate porous YSZ ceramics with an open porosity of 33.1–50.3%, mean pore size of 0.66–0.98 μm and the nitrogen permeability of 215–438 m3/m2.bar.h. In order to further illustrate the features of this water-based gelcasting process to prepare porous ceramics, the same YSZ powders were blended with the same additives, and then cold pressed and sintered at the same conditions employed for gelcasting process. Compared with the cold pressed samples, the gelcast bodies exhibit higher open porosity, lower closed porosity, relatively larger pore size and thus higher gas permeability. Therefore, the developed gelcasting process is a very effective method to fabricate porous ceramics for filters or supports. 相似文献
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Aqueous gelcasting of dense or cellular ceramics by using biopolymers as gel-formers, instead of monomers, is a promising technology mainly in terms of environmental aspects. The main difficulty of using biopolymer solutions in processing of cellular ceramics by foaming method is their high viscosity, which prevents the foaming capacity of the ceramic suspension. In this work, the procedure for preparing concentrated agarose solutions (4 wt.%) by dissolving under overpressure conditions was evaluated for the gelcasting of alumina foams, and the rheological behaviour of alumina suspensions containing agarose was studied. The viscosity of the gelling solution obtained under overpressure conditions was lower than that prepared by simply heating at 90 °C, thus providing high foaming capacity of the alumina suspensions and consequently manufacturing of highly porous ceramics (86–90%). The microstructure of alumina foams was typically composed of approximately spherical cells interconnected by circular windows. The use of different agarose concentrations in alumina suspensions effected the rheological conditions, which resulted in changes in the pore and window sizes of the resulting ceramics. Depending on agarose concentration (0.50–1.0 wt.% on a dry solids basis) in the starting (35 vol.%) alumina slurry, the mean pore size ranged from 529 to 375 μm, while the mean window size varied from 113 to 77 μm. 相似文献
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Preparation and characteristics of highly porous BN-Si3N4 composite ceramics by combustion synthesis
《Journal of the European Ceramic Society》2022,42(12):4835-4845
Nitride based ceramics are considered as a kind of promising material for structural and functional integration due to their robust structure, extreme environmental resistance and electromagnetically transparency. It is still challenging to prepare nitride based ceramics with homogeneous and controllable microstructure because of their low self-diffusion coefficient and difficulty in sintering. Here, we developed a gelcasting-SHS process by combining gelcasting forming and self-propagating high temperature synthesis (SHS) for the preparation of porous BN-Si3N4 composite ceramics. First, carbon residue problem in the gelcasting -SHS process was studied. Based on the result, porous BN-Si3N4 composite ceramics with high porosity (69.42 ~ 86.48%), high strength (21.7 ~ 81.0 MPa) and low dielectric constants (1.42 ~ 2.87) were synthesized. In addition, the thermal shock resistance of porous BN-Si3N4 composite ceramics until 1000 ℃ was evaluated. 相似文献
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Xuanyu Meng Jie Xu Jiatong Zhu Jia Zhao Mingyue Wei Runwu Yang Feng Gao 《Journal of the European Ceramic Society》2021,41(12):6010-6017
The potentially useful role of lanthanum zirconate (La2Zr2O7, LZO) porous bulk ceramics has been rarely explored thus far, much less the optimisation of its pore structure. In this study, LZO porous ceramics were successfully fabricated using a tert-butyl alcohol (TBA)-based gelcasting method, and the pore structures were tailored by varying the initial solid loading of the slurry. The as-prepared ceramics exhibited an interconnected pore structure with high porosity (67.9 %–84.2 %), low thermal conductivity (0.083–0.207 W/(m·K)), and relatively high compressive strength (1.56–7.89 MPa). The LZO porous ceramics with porosity of 84.2 % showed thermal conductivity as low as 0.083 W/(m·K) at room temperature and 0.141 W/(m·K) at 1200 °C, which is much lower than the counterparts fabricated from particle-stabilized foams owing to its unique pore structure with a smaller size, exhibiting better thermal insulating performance. 相似文献
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Gelcasting of Alumina Using Epoxy Resin as a Gelling Agent 总被引:1,自引:0,他引:1
Xiaojian Mao Shunzo Shimai Manjiang Dong Shiwei Wang 《Journal of the American Ceramic Society》2007,90(3):986-988
A water-soluble epoxy resin and hardener system for gelcasting of ceramics was developed. Polymerization of the system is a nucleophilic addition reaction, and not affected by oxygen. Therefore, this gelcasting system can be carried out in an air atmosphere. The ceramic slurries were prepared by mixing the aqueous premix solution of epoxy resin with alumina powder and dispersant. For cross-linking, a polyamine hardener was added. Both the rheological properties of the slurries and the gelling behaviors of the aqueous premix solutions were evaluated. The slurry with a solid loading of 80 wt% is optimized for gelcasting. The flexural strength of the sintered ceramics is 335±47 MPa with 98% of theoretical density. 相似文献
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Wenhao Li Xiaoyan Zhang Junjie Zhang Hanlin Shen Junjie Yang Ying Liu Jun Liu Shengen Zhang Jinlong Yang 《Journal of the American Ceramic Society》2022,105(5):3197-3210
Herein, a simple, versatile, and low-cost approach has been proposed to realize the green utilization of secondary aluminum dross, the hazardous solid waste, namely directly sintering dry-pressed green bodies from secondary aluminum dross to fabricate porous ceramics according to high-temperature foaming process spontaneously without adding spare foaming agents. Aluminum nitride (AlN) in secondary aluminum dross was employed to realize high-temperature foaming due to its oxidation, which makes traditional AlN and salts removal process needless. Moreover, near-zero shrinkage or even expansion during sintering of porous ceramics have occurred because in-situ foaming process together with the oxidation of Al particles well offset the sintering shrinkage. After sintering at 1400°C for 2 h, porous ceramics composed of α-Al2O3 and spinel phases with open porosity of 37.91%, sintering expansion rate of 1.13%, flexural strength of 45.67 MPa, and thermal conductivity of 0.97 W/(m·K) have been prepared. Cenospheres as pore-forming agents have been added to further improve the porosity, and alumina-based porous ceramics with open porosity of 28.39%–43.20% and flexural strength of 15.80–52.48 MPa have been obtained. This effective solution for recycling secondary aluminum dross could supply high-performance porous ceramics, which is expected to be applied in the fields of light-weight structural components and thermal insulations. 相似文献
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Xinshuang GuoZhufa Zhou Guilin MaShumei Wang Song ZhaoQiang Zhang 《Ceramics International》2012,38(1):713-719
Pore-gradient Al2O3 foams were produced by gelcasting using the epispastic polystyrene (EPS) sphere template. This approach allows the design of porous ceramics with degree of pore connectivity and height of gradient layers via appropriate selection of the sizes and numbers of spheres. The fabrication processing of open-cell porous ceramics limited by polymeric sponge template, sharp cracks at the strut edges and closed pores can be resolved by this approach. To achieve the optimal manufacturing conditions of maintaining integrity of the network, the effects of solid loads, height of the slurry and the pre-removal of the polymeric foam template on the struts of the ceramic foams were studied. The results revealed that 55 vol.% Al2O3 slurries with 0.5 wt.% ammonium polyacrylate kept good fluidity for casting and avoided the inner inordinate shrinkage. Different shrinkage behavior of the top and bottom of the sample was effectively reduced due to approximately same water vapor diffusion areas on the top and bottom. The integrity of dendritic solidification structure maintained perfectly through template pre-removed in dichloromethane compared with direct heating. 相似文献
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研究了分散剂的种类、用量、料浆pH值、球磨时间、有机单体含量等因素对氧化硅料浆性能的影响,制备出固相体积分数达42vol%,流变性能够满足凝胶注模工艺要求的二氧化硅料浆,并成功制备了复杂形状的二氧化硅坯体。对凝胶注模成形二氧化硅坯体低温烧结技术进行了研究,提出了素烧、浸渍工艺,有效地降低了二氧化硅坯体的烧成温度。实验表明:二氧化硅凝胶注模成形坯体在1200℃素烧,冷却后浸渍硅溶液,可在1300℃烧结。 相似文献
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面对日益匮乏的陶瓷原料,利用固体废弃物来制备发泡陶瓷已是当今趋势。以粉煤灰为主要原料,研究铬渣掺量、碎玻璃掺量和粉磨工艺对粉煤灰发泡陶瓷的影响。结果表明,掺入适量的铬渣可改善粉煤灰发泡陶瓷的性能,小掺量的碎玻璃对粉煤灰发泡陶瓷的性能影响较小。当原料配比为m(粉煤灰)∶m(铬渣)∶m(长石)∶m(碎玻璃)=60∶10∶20∶10时,采用湿法粉磨3 h,可以制得平均孔径为0.64 mm,体积密度为368.54 kg/m3,抗压强度为8.11 MPa的发泡陶瓷。 相似文献
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《Journal of the European Ceramic Society》2007,27(2-3):655-661
Grain-oriented ferroelectric ceramics have attracted more interest recently because they may provide near single crystal properties. In the present study, a novel process combining magnetic alignment and gelcasting was explored to prepare grain-oriented ferroelectric ceramics with different crystal structures. In a strong magnetic field, ceramic particles in slurry were aligned by the magnetic force and then locked in situ by polymerization via a gelcasting technique. This process was found effective for ferroelectric ceramics with a bismuth layer structure (Bi4Ti3O12) and tungsten bronze structure (Sr0.5Ba0.5Nb2O6). The sintered samples show highly anisotropic structure and enhanced physical properties. However for perovskite structured ferroelectric ceramics (BaTiO3), the green compact shows grain orientation, while after sintering the sample become random again.Thus for certain materials using the conventional ceramic processes, i.e., using conventional starting powders, gelcasting under strong magnetic fields (10 T) and pressure-less sintering, the preparation of dense grain-oriented ceramic materials is possible. 相似文献