镁铝质泡沫陶瓷过滤器的研制

研究了镁铝质泡陶瓷过滤器的成分，成型工艺，烧结工艺，性能及应用效果。实验结果表明，镁铝质泡沫陶瓷过滤器具有良好的应用前景。     

过滤熔融金属的陶瓷泡沫过滤器

引言随着科学技术的不断发展,对金属材料的综合性能提出越来越高的要求。大到制造巨型超音速飞行器的航天航空材料,小到制造薄壁易拉罐的材料,如超细铜芯线材料、高速运转的曲轴、气缸头材料、高压高流速的阀体材料等等。在熔炼及加工过程中,为了提高金属材料的延展性能、拉伸性能、光亮度等性能,先进工业国家都使用陶瓷泡沫过滤器对熔融状态的金属     

铸造用泡沫陶瓷过滤器的生产工艺

本文详细介绍了泡沫陶瓷过滤器的生产工艺,并简单介绍了其过滤机理。对海绵加工、浆料调节及产品烧结等生产工序分别作了阐述,并提出了生产过滤器的技术要求和铸造使用过程中的注意事项。     

锆刚玉—莫来石泡沫陶瓷过滤器的研究及应用

以氧化铝粉和锆英石粉为原料，通过反应烧结制成了锆刚玉－莫来石泡沫陶瓷过滤器，研究了锆英石对抗弯强放抗热震性的影响，对球墨铸铁和铸钢的过滤试验结果表明，过滤后的夹杂物减少，冲击韧性明显提高。     

MgO部分稳定ZrO2泡沫陶瓷的研究

报导ＭｇＯ部分稳定ＺｒＯ２泡沫陶瓷的研制和应用结果。ＭｇＯ－ＺｒＯ２泡沫陶瓷的烧结温度在１７３０－１７６０℃。烧结后以３００℃／ｈ的速度冷却可使ｔ－ＺｒＯ２沉淀粒子保持至室温。在１１００℃时效３ｈ可改善材料的抗弯强度和抗热震性能。ＭｇＯ－ＺｒＯ２泡沫陶瓷过滤高温合金的氧化物夹杂有良好的净化效果。     

泡沫陶瓷过滤器的研究现状和发展趋势

本文阐述了国内外铸造用泡沫陶瓷过滤器的材料成分、生产工艺和结构特点 ,着重介绍了它们的技术性能及其在液态铸造合金过滤净化中的应用效果 ,同时探讨了铸造用泡沫陶瓷过滤器在新世纪的市场前景和发展趋势。     

AS型泡沫陶瓷过滤器的研制

详细说明了用网状弹性聚氨基甲酸乙酯切片浸渍陶瓷料浆压制AS型泡沫陶瓷过滤器的工艺。采用非磷酸盐添加剂粘合,由碳化硅、氧化铝、硅胶及少量硅酸铝纤维制成的AS型泡沫陶瓷过滤器抗压强度可达1．65MPa而厚度仅为15mm,并且不会造成环境污染,完全可以满足过滤铁溶液的要求。     

汽车柴油机排气颗粒泡沫陶瓷过滤器的研制

着重论述了汽车柴油机排气颗粒泡沫陶瓷过滤器滤芯的性能要求，确定了泡沫陶瓷过滤器的配方、工艺和结构。所制得泡沫陶瓷的性能：抗弯强度为1．5MPa；膨胀系数为2．89×10－6／K－1；耐温性为1300℃．用此泡沫陶瓷做成的滤芯碳颗粒过滤效率为50％左右。根据台架试验与性能检测结果数据，集中讨论了工艺、添加剂和滤芯结构的影响。     

Al2O3基泡沫陶瓷的研究

以Al2O3和锆英石为主要原料制备了具较高强度及抗热震性的泡沫陶瓷并进行了性能研究与应用试验。结果表明：当锆英石含量为30%时,材料的抗弯强度最大,达3.84MPa;随锆英石含量的提高,抗热震性能增强;泡沫陶瓷的孔隙率与锆英石含量无关,为80-81%,泡沫陶瓷过滤器能有效滤除铸液中夹杂物。     

High-strength thermal insulating porous mullite fiber-based ceramics

How to improve the strength of fibrous porous ceramics dramatically under the premise of no sacrificing its low density and thermal conductivity has remained a challenge in the high-temperature thermal insulation field. In this paper, a new kind of high-strength mullite fiber-based ceramics composed of interlocked porous mullite fibers was prepared by nanoemulsion electrospinning and dry pressing method. Results show that as to the porous ceramics with the same density (～ 0.8 g/cm³), the three-dimensional skeleton structure composed of porous mullite fibers was much denser than that composed of solid mullite fibers. Therefore, porous mullite fiber-based ceramics exhibited a higher compressive strength (5.53 MPa) than that of solid mullite fiber-based ceramics (3.21 MPa). In addition, porous mullite fiber-based ceramics exhibited a superior high-temperature heat insulation property because the porous structure in fibers could reduce the radiant heat conduction. This work provides new insight into the development of high-temperature thermal insulators.     

Development of ethylene glycol-based gelcasting for the preparation of highly porous SiC ceramics

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.     

Microstructure of TiO2 porous ceramics by freeze casting of nanoparticle suspensions

During freeze casting of TiO₂ porous ceramics, the porous architecture is strongly influenced by TiO₂ particle size, solids loading, and cooling temperature. This work investigates the influences of particle size, freezing substrate, and cooling temperature on the TiO₂ green bodies prepared by freeze casting. The results show that the lamellar channel width with 100 nm particles is larger than that of 25 nm particles, yet the ceramic wall thickness is noticeably decreased. The lamellar structure is more ordered when using a copper sheet than glass as its freezing substrate. A finer microstructure results when frozen at − 50 ℃ than − 30 ℃. Such porous materials have application potentials in a wide range of areas such as photocatalysis, solar cells, and pollutant removal and should be further studied.     

Digital light processing fabrication of porous cordierite ceramics from polysilxoane-based slurries

Herein, a pohotosentive polysiloxane (PSO)/talc/Al₂O₃ slurry was prepared for the digital light processing printing. Liquid photosensitive PSO was exploited as a triple-functioned material, acting both as the resin matrix, a high reactive Si source and a pore generator. Through adjusting the raw material components, polysiloxane can be sintered with talc and Al₂O₃ fillers after being pyrolyzed to 1200 ^oC while pores with variable diameters can be generated. Ternary component slurry prepared based on the above strategy possesses the characteristics of low viscosity, high reaction activity and good homogeneity. Sintering schedule of the printed thin-walled precursor was investigated to guarantee the morphology of cordierite product was consistent with the printed model. This work aims to provide a new strategy for DLP printing of MgO-Al₂O₃-SiO₂ ternary and other polymer derived ceramics.     

High-strength thermal insulating mullite nanofibrous porous ceramics

Mullite fibrous porous ceramics is one of the most commonly used high temperature insulation materials. However, how to improve the strength of the mullite fibrous porous ceramics dramatically under the premise of no sacrificing the low sample density has always been a difficult scientific problem. In this study, the strategy of using mullite nanofibers to replace the mullite micron-fibers was proposed to fabricate the mullite nanofibrous porous ceramics by the gel-casting method. Results show that mullite nanofibrous porous ceramics present a much higher compressive strength (0.837 MPa) than that of mullite micron-fibrous porous ceramics (0.515 MPa) even when the density of the mullite nanofibrous porous ceramics (0.202 g/cm³) is only around three quarters of that of the mullite micron-fibrous porous ceramics (0.266 g/cm³). The obtained materials that present the best combination of mechanical and thermal properties can be regarded as potential high-temperature thermal insulators in various thermal protection systems.     

Fabrication of wood-like porous silicon carbide ceramics without templates

The porous silicon carbide ceramics with wood-like structure have been fabricated via high temperature recrystallization process by mimicking the formation mechanism of the cellular structure of woods. Silicon carbide decomposes to produce the gas mixture of Si, Si₂C and SiC₂ at high temperature, and silicon gas plays a role of a transport medium for carbon and silicon carbide. The directional flow of gas mixture in the porous green body induces the surface ablation, rearrangement and recrystallization of silicon carbide grains, which leads to the formation of the aligned columnar fibrous silicon carbide crystals and tubular pores in the axial direction. The orientation degree of silicon carbide crystals and pores in the axial direction strongly depends on the temperature and furnace pressure such as it increases with increasing temperature while it decreases with increasing furnace pressure.     

Fabrication and characterization of porous CaSiO3 ceramics

Porous CaSiO₃ ceramics were prepared via a solid-state reaction method using CaCO₃ and SiO₂ as raw materials and active carbon as a pore-forming agent. The results indicated that porous CaSiO₃ ceramics could be obtained under a low sintering temperature of 1320?°C. The addition of active carbon significantly affected the volume density, microstructure, pore size distribution and mechanical strength of porous CaSiO₃ ceramics. With the increase of active carbon content, the volume density decreased, meanwhile the pore size and porosity increased gradually. Besides, the three-point bending tests demonstrated that the mechanical strength was decreased with increasing active carbon content. However, all the porous ceramics still exhibited high mechanical strength. These results implied that the increase of active carbon content not only enlarged the pore size and enhanced the porosity, but also kept a remarkable mechanical strength of porous CaSiO₃ ceramics. Therefore, these rationally designed CaSiO₃ porous ceramics will be a highly potential material in various applications due to its high mechanical strength, low sintering temperature and narrow pore size distribution.     

Fabrication of porous silicon carbide ceramics with high porosity and high strength

Unique porous SiC ceramics with a honeycomb structure were fabricated by a sintering-decarburization process. In this new process, first a SiC ceramic bonded carbon (SiC/CBC) is sintered in vacuum by spark plasma sintering, and then carbon particles in SiC/CBC are volatized by heating in air at 1000 °C without shrinkage. The honeycomb structure has at least two different sizes of pores; ∼20 μm in size resulting from carbon removal; and smaller open pores of 2.1 μm remaining in the sintered SiC shell. The total porosity is around 70% and the bulk density is 0.93 mg/m³. The bending and compressive strengths are 26 MPa, and 105 MPa, respectively.     

Preparation and characterization of porous mullite ceramics via foam-gelcasting

Porous mullite ceramics were prepared via foam-gelcasting using industrial grade mullite powder as the main raw materials, Isobam-104 as the dispersing and gelling agent, sodium carboxymethyl cellulose as the foam stabilizing agent, and triethanolamine lauryl sulfate as the foaming agent. The effects of processing parameters such as type and amount of additive, solid loading level and gelling temperature on rheological properties and gelling behaviors of the slurries were investigated. The green samples after drying at 100 °C for 24 h were fired at 1600 °C for 2 h, and the microstructures and properties of the resultant porous ceramic samples were characterized. Based on the results, the effects of foaming agent on the porosity level, pore structure and size and mechanical properties of the as-prepared porous mullite ceramics were examined. Porosity levels and pore sizes of the as-prepared samples increased with increasing the foaming agent content up to 1.0%, above which both porosity levels and pore sizes did not change. The compressive strength and flexural strength of the as-prepared sample with porosity of 76% and average pore size of 313 μm remained as high as 15.3±0.3 MPa and 3.7±0.2 MPa, respectively, and permeability increased exponentially with increasing the porosity.     

碳化硅-堇青石多孔陶瓷的制备及其性能

以碳化硅粉末、高岭土和滑石等为原料,按堇青石的化学计量比设计原料配比,制备了堇青石理论生成量分别为0、10%、15%、20%、100%的碳化硅-堇青石多孔陶瓷,测定了试样的抗折强度、显气孔率和热膨胀系数,并分别用XRD和SEM分析了试样的晶相组成和断面形貌。结果表明:与碳化硅多孔陶瓷相比,碳化硅-堇青石多孔陶瓷的抗折强度显著提高,热膨胀系数明显降低,但显气孔率有所降低。SEM分析结果表明:碳化硅-堇青石多孔陶瓷中碳化硅颗粒排列较紧密,断面呈“网格状”结构;而在多孔碳化硅陶瓷中,晶粒形貌清晰且排列较疏松,气孔平均孔径较大。