添加造孔剂法制备多孔陶瓷及其强度与孔径控制

采用添加造孔剂法制备了多孔陶瓷.系统地研究了造孔剂种类、粘结剂含量、球磨时间、烧结制度对多孔陶瓷强度及开口孔隙率的影响,以及钠长石含量对多孔陶瓷孔径分布的影响.结果表明,不同造孔剂对多孔陶瓷强度的影响不同.并且在球磨时间为12h之前,随着球磨时间的延长,多孔陶瓷的强度呈增加趋势.而随着钠长石含量的增加,多孔陶瓷的孔径呈减小的趋势.     

淀粉为造孔剂制备碳化硅多孔陶瓷

以微米碳化硅基体,氧化铝和氧化钇为烧结助剂,淀粉为造孔剂,采用无压烧结技术制备碳化硅多孔陶瓷.通过测试合成多孔陶瓷的密度、收缩率、力学强度以及扫描电子显微镜(SEM)和X-射线衍射(XRD)等研究了不同造孔剂含量对SiC粉体的力学性能、微观形貌和物相的影响.研究表明:随造孔剂含量的升高,碳化硅陶瓷密度和强度降低,气孔率增加,而造孔剂含量对碳化硅陶瓷的物相组成基本没有影响.     

SiC多孔陶瓷预成形坯的制备

本文采用真空烧结方法制备SiC多孔陶瓷预成形坯,研究了不同助烧结剂Al2O3-Y2O3、Si、Co和高岭土以及造孔剂羧甲基纤维素(CMC)含量对SiC多孔陶瓷预成形坯气孔率和形貌的影响。结果表明,多元助烧剂Al2O3-Y2O3有利于降低烧结温度和形成液相烧结,并有利于提高SiC多孔陶瓷的孔结构稳定性;羧甲基纤维素含量对烧结预成形坯气孔率和体积密度的影响较大,随着造孔剂CMC含量的增加,SiC多孔陶瓷的气孔率也相应地增加,其体积密度相应减少。     

以硅藻土为硅源制备硅酸钙多孔陶瓷

以硅藻土和碳酸钙为主要原料、淀粉为造孔剂、PVA为粘结剂,通过反应烧结制备了硅酸钙多孔陶瓷。研究了配比和烧结温度对样品体积收缩率、抗压强度和物相组成的影响。同时,也研究了造孔剂含量对气孔率和强度的影响。结果表明,收缩率随烧结温度的升高而增大,造孔剂含量与气孔率成正比、与抗压强度成反比。当碳酸钙含量为20 wt%,造孔剂含量为15 wt%时,在1250?C烧结可制备出气孔率为48.79%、抗压强度为12.2 MPa的多孔陶瓷。     

造孔剂种类及含量对高孔隙率多孔陶瓷性能的影响

本文以碳粉和淀粉为造孔剂制备高孔隙率多孔陶瓷,研究了造孔剂的种类和含量对多孔陶瓷气孔率、体积密度和力学性能的影响。结果表明:碳粉和淀粉造孔剂含量分别小于37.5%和25%时,多孔陶瓷形态结构完整,无破损。随着两种造孔剂含量增加,多孔陶瓷气孔率均呈增长趋势,体积密度和抗弯强度相应降低。当造孔剂的含量相同时,该体系中淀粉造孔剂的造孔效果优于碳粉造孔剂,其多孔陶瓷孔隙率最高可达33%、体积密度为1.7 g/cm3。但研究发现,碳粉造孔剂制备的多孔陶瓷强度高于淀粉造孔剂多孔陶瓷。     

氧化铝纤维对多孔陶瓷载体性能的影响

通过添加适量的塑性剂和造孔剂,采用挤压成型的方式制成了氧化铝纤维增强多孔陶瓷.探讨了不同烧结温度和不同纤维含量对于多孔陶瓷性能的影响.随着烧结温度的提高和纤维含量的增加,样品的线收缩率不断减小,而气孔率和抗折强度先增加后减小.在900℃烧结后,纤维含量4％时,材料最大抗折强度最高并达到4.19Mpa,比基体材料提高了35％.氧化铝纤维的加入有效地解决了多孔陶瓷开裂的问题.     

高铝粉煤灰制备陶瓷膜支撑体的性能研究

粉煤灰是电厂燃烧煤之后的固体废弃物,粉煤灰的高附加值应用是国家重点扶持的一个方向。采用高铝粉煤灰制备多孔陶瓷支撑体可以代替氧化铝多孔陶瓷在污水处理、固液分离等方面的应用,可以大大减少成本。以高铝粉煤灰为原料,分别使用淀粉和碱式碳酸镁作为造孔剂,羧甲基纤维素钠(CMC)为粘结剂,采用模压法成型,分别在1200~1500℃烧结下制备5组不同含量的多孔陶瓷样品,并测试其孔隙率、收缩率、气通量、水通量、抗折强度等性能。实验结果表明,烧结温度和造孔剂的种类和含量对多孔陶瓷的性能影响显著。碱式碳酸镁造孔作用明显优于淀粉,且随着造孔剂含量的增高,孔隙率、气通量、水通量逐渐升高,抗折强度略有降低。随着烧结温度的提高,气通量、水通量先升高后降低,在1350℃时达到最大值4854.24m~3/(m~2·h·bar)、48.61m~3/(m~2·h·bar)。综合考虑,造孔剂为20%碱式碳酸镁在1350℃温度下烧结2~3 h,作为多孔陶瓷支撑体性能最佳。     

SiC/莫来石复相多孔陶瓷气孔率和强度的影响因素

以煅烧高岭土、Al(OH)3粉末、SiC粉末为主要原料,以石墨为造孔剂制备了SiC/莫来石复相多孔陶瓷,研究了造孔剂含量、碳化硅颗粒粒径以及烧结温度对SiC/莫来石复相多孔陶瓷抗弯强度和气孔率的影响,并分别用XRD和SEM分析晶相组成和断面显微结构.结果表明:当SiC粒径为60 μm,造孔剂含量为15％时,在1400℃下保温3h制备的样品综合性能最佳,其孔隙率为30.3％,抗折强度达到58.0 MPa.     

无机盐/石英基复合相变储能材料多孔陶瓷基体的制备

以石英为骨料,钾长石为高温粘结剂,木炭为造孔剂制备无机盐/石英基复合相变储能材料用的微米孔石英多孔陶瓷基体,采用正交实验法系统研究了骨料颗粒粒度、造孔剂粒度、造孔剂含量、高温粘结剂含量及烧成温度对石英多孔陶瓷的显气孔率和抗折强度的影响.研究结果表明,影响石英多孔陶瓷抗折强度的最主要因素是长石含量,其次是骨料粒度和造孔剂粒度;影响石英多孔陶瓷显气孔率的主要因素是造孔剂含量.制备微米孔石英多孔陶瓷的优化配方和工艺是:石英、木炭和长石均过325目筛,三者质量比为7:2:1,烧成温度为1270f,保温时间为1h.该陶瓷具有以下优良的性能:显气孔率为55.12％,体积密度为1.14 g,/cm3,抗折强度为3.14 MPa,抗压强度为7.12 MPa,平均孔径为13.87 μm且孔径分布范围较窄,96％的气孔孔径在9～21 μm之间.     

Al2O3多孔陶瓷的制备和性能研究

采用乙基纤维素为成孔剂制备了Al2O3多孔陶瓷,探讨了工艺参数对其性能的影响。研究结果表明,造孔剂含量、球磨时间及烧结温度均对多孔陶瓷的气孔率和抗折强度有影响。烧结温度的升高使得气孔率降低,但变化不明显,抗折强度明显提高。随造孔剂含量的升高,使得气孔率逐渐上升,超过20％后变化趋于平稳。随着球磨时间的增加,试样呈现气孔率下降和抗折强度升高的趋势。以烧结温度为1580℃,造孔剂含量20％;球磨时间为2．5h的条件下,可获得高显气孔率、抗折强度较高的舢203多孔陶瓷。     

Porous mullite ceramics with enhanced compressive strength from fly ash-based ceramic microspheres: Facile synthesis,structure, and performance

Porous mullite ceramics are widely used in heat insulation owing to their high temperature and corrosion resistant properties. Reducing the thermal conductivity by increasing porosity, while ensuring a high compressive strength, is vital for the synthesis of high-strength and lightweight porous mullite ceramics. In this study, ceramic microspheres are initially prepared from pre-treated high-alumina fly ash by spray drying, and then used to successfully prepare porous mullite ceramics with enhanced compressive strength via a simple direct stacking and sintering approach. The influence of sintering temperature and time on the microstructure and properties of porous mullite ceramics was evaluated, and the corresponding formation mechanism was elucidated. Results show that the porous mullite ceramics, calcined at 1550 °C for 3 h, possess a porosity of 47%, compressive strength of 31.4 MPa, and thermal conductivity of 0.775 W/(m?K) (at 25 °C), similar to mullite ceramics prepared from pure raw materials. The uniform pore size distribution and sintered neck between the microspheres contribute to the high compressive strength of mullite ceramics, while maintaining high porosity.     

Porous alumina ceramics with enhanced mechanical and thermal insulation properties based on sol-treated rice husk

To improve the properties of porous alumina ceramics, which were typically prepared by adding pore-forming agents, rice husk (RH) as pore-forming agent was pretreated with zirconia sol. The effects of sol-treatment on the thermal conductivity and compressive strength of the resultant ceramics were characterized. Furthermore, the pore size distribution, pore shape, microstructure, and phase evolution also were studied. The results showed that the RH pretreatment optimizes the microstructure of the ceramic pores. Moreover, complete morph-genetic RH is clearly observed in the pores, which is established as a key factor in improving the properties of the resultant ceramic. The thermal insulation properties are determined to significantly improve, although the thermal conductivity increases slightly with the increment of zirconia sol concentration from 5 to 10?wt%. Meanwhile, after sintering at 1550?°C, the compressive strength is significantly greater for the specimen prepared with 10?wt% zirconia sol-treated RH (65.56?MPa) than that with untreated RH (43.37?MPa). Hence, it was demonstrated that the use of zirconia sol-pretreated RH as a pore-forming agent could enhance the mechanical and thermal insulation properties of porous alumina ceramics.     

Preparation of near net size porous alumina-calcium aluminate ceramics by gelcasting-pore-forming agent processs

In the processing of porous ceramics, shrinkage from green body to sintered compact during drying and sintering is one of the key concerns which affect microstructure and properties of porous ceramics. Through releasing gases from the burning of the pore forming agents, and volume expansion from the formation of low density resultants during sintering, the sintering shrinkage can be effectively compensated and near net size preparation can be achieved. Herein, near net size porous alumina-calcium aluminate ceramics with controllable shrinkage have been prepared using a combination of gelcasting and pore-forming agent process by adjusting the amount of CaCO₃ and polymethyl methacrylate (PMMA) microspheres added. Al₂O₃ and CaCO₃ were used as raw materials, PMMA microspheres were used as pore-forming agent, isobutylene/maleic anhydride copolymer (Isobam104) was used as gelling agent and dispersing agent. The effects of the addition amounts of CaCO₃ and PMMA in the slurry on the phase composition, shrinkage, porosity, and strength of porous alumina-calcium aluminate ceramics were investigated. The results show that as the CaCO₃ addition amount increases from 0 to 20 wt%, the shrinkage of the samples gradually decreases from 7.3% to −1.4%, and the consequent porosity increases from 58% to 66%, while the compressive strength increases from 5.9 to 15.5 MPa. When PMMA content increases from 10 to 50 wt%, the shrinkage of the samples decreases first and then increases, the porosity increases from 51% to 74%, and the compressive strength decreases from 12.5 to 5.3 MPa. The mechanisms for controlling shrinkages during preparation of porous alumina-calcium aluminate ceramics can be attributed to the following aspects: on one hand, gas release from burning of PMMA and decomposition of CaCO₃ during sintering; on the other hand, volume expansion due to the formation of lower density calcium aluminates which come from the reactions between CaO and Al₂O₃. The near net size preparation technique is of great significance for the manufacture of porous ceramics since the subsequent machining cost can be effectively reduced.     

Recycling of waste red mud for fabrication of SiC/mullite composite porous ceramics

SiC/mullite composite porous ceramics were fabricated from recycled solid red mud (RM) waste. The porous ceramics were formed using a graphite pore forming agent, RM, Al(OH)₃ and SiC in the presence of catalysts. The influence of firing temperature and the pore-forming agent content on the mechanical performance, porosity and the microstructure of the porous SiC ceramics were investigated. Optimal preparation condition were determined by some testing. The results indicated that the flexural strength of specimens increased as a function of firing temperature and a reduction in graphite content, which concomitantly decreased porosity. The ceramic prepared under optimal conditions having 15?wt% graphite and sintered at 1350?°C, demonstrated excellent performance. Under optimal preparation conditions the flexural strength and porosity of the ceramic were 49.4?MPa and 31.4%, respectively. Scanning electron microscopy observation result showed that rod-shape mullite grains endowed the samples with high flexural strength and porosity. X-ray diffraction analysis indicated that the main crystallization phases of the porous ceramics were 6H-SiC, mullite, cristobalite and alumina. This work demonstrates that RM can be sucessfully reused as a new raw material for SiC/mullite composite porous ceramics.     

Effect of hydroxyapatite and tricalcium phosphate addition on protein foaming-consolidation porous alumina

Porous alumina-hydroxyapatite (HA) and alumina-tricalcium phosphate (TCP) composites have been fabricated to investigate the effect of HA and ??-TCP addition on protein foaming-consolidation derived porous alumina. HA and ??-TCP loadings along with yolk content, starch content, and sintering temperature were varied to modulate performance of the porous composites. The rheological behavior of slurry shifted from pseudoplastic flow to a Newtonian fluid with increasing yolk concentration. The foaming capacity of slurry increased with yolk addition. The addition of starch into slurry resulted in bigger pore size and avoided the porous bodies from cracks. The shrinkage of sintered bodies increased with increasing HA loading, but decreased with increasing ??-TCP loading. The compressive strength of porous alumina-HA body was found 2.9?MPa at 45.8% porosity and 20.4?MPa at 36.8% porosity. The increasing porosity of porous alumina-TCP body from 56.1 to 61.6% improved the compressive strength from 3.1 to 4.2?MPa. Increasing sintering temperature resulted in large grain size among powder particles, thus improving the compressive strength of porous bodies. Preliminary results of DF-1 cells culture on the surface of porous alumina and alumina-TCP samples are also reported.     

正交设计优化粉煤灰-煤矸石质多孔陶粒的制备过程

以粉煤灰为主要原料,采用添加造孔剂法制备出了多孔陶粒。为了优化工艺参数,得到性能较好的粉煤灰多孔陶粒,通过正交试验设计,系统地研究了煤矸石的掺量、成孔剂、烧结温度对多孔陶粒的物理化学性能的影响,如气孔率、吸水率、抗压碎强度、物相组成和显微形貌等。研究结果表明,成孔剂是影响多孔陶粒性能的最主要因素。当煤矸石掺量20%、成孔剂15%,经1160℃烧成的多孔陶粒样品有着较大的抗压碎强度,显气孔率也达到58.22%。样品的晶相组成为钙长石,及少量的方石英和赤铁矿。其内部孔隙丰富,大孔与小孔交错分布,是一种兼具较高气孔率和较强力学强度的优质多孔陶瓷。     

高温烟气过滤用多孔陶瓷材料的研制

以氧化铝纤维和玻璃粉为主体材料,活性炭粉为造孔剂,通过半干压成型工艺制备了高温烟气过滤陶瓷.详细研究了玻璃粉含量、造孔剂含量以及烧成温度对材料过滤阻力、抗折强度、显气孔率等性能的影响,并对原料配方和烧成制度进行了优化,最优配方为:氧化铝70wt%、玻璃粉30wt%、外加造孔剂25wt%、羧甲基纤维素钠8wt%,最佳的烧成温度为1100 ℃,制得的高温烟气过滤陶瓷抗折强度8.9 MPa,过滤阻力95 Pa,显气孔率达59%.     

Design and formulation of polyurethane foam used for porous alumina ceramics

The present work studied a simple direct foaming method for preparation of porous alumina ceramics by expansion of a ceramic suspension based on polyurethane (PU) foam system. The effects of polyurethane formulas including catalyst composition, blowing agent content, NCO index and solid content on the samples properties were investigated. The results showed that the homogeneity, porosity and mechanical properties are various for different formulas. The dried green bodies showed diametrical compressive strength in the range of 0.39–1.25 MPa and were amenable to machining operations such as milling, drilling and lathing. Meanwhile, PU formulas play an important role in the microstructures and mechanical properties of green bodies and sintered ceramic foams. Pyrolytic removal of polyurethane skeleton followed by sintering at 1550 °C produced alumina bodies with open cell porosity 54–75% and diametrical compressive strength 1.39–28.47 MPa. Microstructure showed both large (200–300 μm) and small (50–100 μm) pores all with various sizes of windows. Based on the optimization of polyurethane formulation, the porous alumina foam with porosity of 64% and compressive strength of 25.26 MPa was prepared. This polyurethane foam system is easily available and low-cost, which could be widely applied in preparation of other porous ceramics, such as ZrO₂, SiO₂, etc.     

多孔低介电氧化硅陶瓷材料的制备

采用氧化硅为原料,木屑作为造孔剂制备了多孔的氧化硅陶瓷材料。借助于气孔率测试、抗弯强度测试、介电性能测试和SEM测试手段分析了造孔剂和烧结助剂的添加量对材料性能的影响。结果表明:加入BN作为添加剂烧成的氧化硅抗弯强度最大可达到14.80MPa。加入木屑作为造孔剂制备的陶瓷可以形成明显的气孔,气孔率最高可达到48.40%,介电常数最低可以达到3.0。     

凝胶注模法制备多孔羟基磷灰石陶瓷

采用凝胶注模法制备了多孔羟基磷灰石陶瓷,探讨了制备工艺对陶瓷显微结构和力学性能的影响。结果表明,以柠檬酸三铵C6H17O7N3为分散剂,最佳加入量(以粉料质量计算)为2%,最佳的球磨时间为5 h,球磨时最佳的水/粉料的质量比为1.5∶1,球磨时的最佳pH值为10,在1 200℃下烧成了HA多孔陶瓷。单体浓度10%的样品在1 200℃下2 h烧成的陶瓷,开孔率为39.87%,抗压强度为83.60 MPa,抗折强度为0.059 2 MPa;单体浓度15%的样品在1 200℃下3 h烧成的陶瓷,开孔率为39.59%,抗压强度为83.92 MPa,抗折强度为0.062 6 MPa。