造孔剂及烧结温度对堇青石蜂窝多孔陶瓷的影响

【作者】 王浩；

【导师】 陈庆华； 夏开略；

【作者基本信息】 昆明理工大学 ， 材料工程（专业学位）， 2022， 硕士

【摘要】 堇青石蜂窝多孔陶瓷具有的孔隙率大、热膨胀系数低、抗热震性优异以及良好的化学稳定性等特性,使其在汽车尾气净化领域具有广泛的应用,如柴油机颗粒捕集器、汽油机颗粒捕集器以及催化剂载体等。目前堇青石蜂窝多孔陶瓷已经成为国内外环境工程材料领域的一个重要研究课题。同时随着汽车尾气排放标准的不断提高,对堇青石蜂窝多孔陶瓷的使用性能也提出更加的严苛要求。因此研究原料种类、粒径、化学组成和制备工艺等对堇青石蜂窝多孔陶瓷的影响以及如何制备出性能优异的堇青石蜂窝多孔陶瓷显得尤为重要。本研究采用一次烧成法制备堇青石蜂窝多孔陶瓷,以滑石、高岭土、氧化铝、氧化硅等为原料,使用挤压成型法和添加造孔剂法制备堇青石蜂窝多孔陶瓷。使用万能力学试验机、热膨胀仪等仪器对制备的堇青石蜂窝多孔陶瓷进行性能测试。本文在前人对堇青石蜂窝多孔陶瓷的研究基础上,研究了烧结温度、单一造孔剂的种类、含量以及复合造孔剂不同的配比及粒径对堇青石蜂窝多孔陶瓷的影响,研究结果如下:(1)研究了在不同的烧结温度下,堇青石蜂窝多孔陶瓷的物相组成、微观组织形貌、孔径分布及孔隙率、热膨胀系数等特性。研究发现,在烧结温度为1425℃时,烧结的堇青石蜂窝多孔陶瓷中只有堇青石相,此时样品30℃～800℃的热膨胀系数为0.9741×10-6·K-1,孔隙率、中值孔径和平均孔径分别为62.40%、24.21μm、21.90μm,孔与孔之间的连通性好,综合性能最优。(2)以马铃薯淀粉(PS)、玉米淀粉(CS)、石墨(G)、聚乙烯丙烯酸甲酯(PMMA)微球为造孔剂,研究了造孔剂的种类对堇青石蜂窝多孔陶瓷的影响。通过对制备的样品进行分析,造孔剂的改变不会影响堇青石蜂窝多孔陶瓷的物相组成,当马铃薯淀粉的使用量为主料的40 wt%时,制备的样品具有最低的热膨胀系数为0.5083×10-6 K-1,此时孔隙率为60.58%,中值孔径为24.06 μm,平均孔径为22.08 μm,而且孔径分布集中度高。综合造孔剂的来源、经济效益、制备样品的性能等因素,决定采用马铃薯淀粉为制备堇青石蜂窝多孔陶瓷过程中的造孔剂。(3)研究了单一造孔剂的使用量对堇青石蜂窝多孔陶瓷物相组成、微观组织相貌、孔隙率及孔径分布、抗压强度等特性的影响。结果表明,随着造孔剂的增加,样品的热膨胀系数先降低后升高,当造孔剂用量为主料的40wt%时,热膨胀系数最小。研究还发现,随着造孔剂使用量的增多,样品的中值孔径、平均孔径、孔隙率等逐渐增加,当造孔剂使用量超过40 wt%时,增速就变得平缓。同时,样品的抗压强度也随着造孔剂的使用量增加而降低。另外,当造孔剂的使用量超过主料的50wt%时,在干燥和烧结过程中堇青石蜂窝多孔陶瓷及生坯会出现开裂现象。通过对实验结果的分析,决定将制备堇青石蜂窝多孔陶瓷时造孔剂的使用量定为主料的40 wt%。(4)研究复合造孔剂中不同造孔剂的配比对堇青石蜂窝多孔陶瓷的影响。随着复合造孔剂中马铃薯淀粉含量的增加,堇青石蜂窝多孔陶瓷的孔隙率、中值孔径、平均孔径、比表面积等均出现不同程度的先增大后降低的现象,而堇青石蜂窝多孔陶瓷A向和B向的抗压强度会随着复合造孔剂中马铃薯淀粉的增加而降低,同时,石墨的引入增加了堇青石蜂窝多孔陶瓷的热膨胀系数。当复合造孔剂中马铃薯淀粉和石墨使用量均为主料的20 wt%时,堇青石蜂窝多孔陶瓷A向和B向的烧结收缩一样,此时制备的样品的综合性能也最优,所以决定将复合造孔剂中马铃薯淀粉和石墨的使用量均定为主料的20 wt%。(5)通过对马铃薯淀粉的筛分,研究了复合造孔剂中马铃薯淀粉的粒径以及集中度对堇青石蜂窝多孔陶瓷的影响,研究发现,随着马铃薯淀粉粒径的增加,堇青石蜂窝多孔陶瓷的中值孔径、平均孔径、热膨胀系数等不断增大,比表面积、抗压强度等则出现轻微的降低,但因为造孔剂的总使用量相同,这些变化的范围较小。同时也发现,使用的造孔剂的粒度分布越集中,所制备的堇青石蜂窝多孔陶瓷的孔径分布也越集中。更多还原

【Abstract】 The high porosity,low coefficient of thermal expansion,good thermal shock resistance and mechanical strength of cordierite honeycomb porous ceramics make it widely used in the field of automotive exhaust gas purification,such as diesel engine particle traps,gasoline engine particle traps and catalyst carriers.Concurrently,with the continuing improvement of automobile exhaust emission standards,the use of cordierite honeycomb porous ceramic performance requirements have been more rigorous.Consequently,it is highly significant to investigate the impact of raw material type,particle size,chemical composition and preparation process on cordierite honeycomb porous ceramics and how to prepare cordierite honeycomb porous ceramics with high porosity,high pore size concentration,low thermal expansion coefficient,high mechanical strength and low back pressure.In this study,cordierite honeycomb porous ceramics were prepared by primary firing method using talc,kaolin,aluminium oxide and silicon oxide as raw materials,and cordierite honeycomb porous ceramics were prepared by extrusion molding method and addition of porogenic agents.The prepared cordierite honeycomb porous ceramics were tested and observed using a universal mechanical testing machine,a thermal expansion meter and other instruments.The influence of sintering temperature,type and content of single consistent porogenic agents,and composite porogenic agents with different ratios and particle sizes on cordierite honeycomb porous ceramics was investigated in this paper,and the main research contents and results are as follows.:(1)The impact of various sintering temperatures on cordierite honeycomb porous ceramics was investigated.It was found that only cordierite phase was present in the sintered cordierite honeycomb porous ceramics at the sintering temperature of 1425℃.The coefficient of thermal expansion of the samples from 30℃ to 800℃ at this time was 0.9741×10-6·K-1,and the porosity,median pore size and average pore size were 62.40%,24.21 μm and 21.90μm,respectively,with good connectivity between the pores and the best overall performance.The best overall performance.(2)The effects of different porogenic agents on cordierite honeycomb porous ceramics were investigated using potato starch,corn starch,graphite and PMMA microspheres as porogenic agents.By analyzing the prepared samples,the change of porogenic agent does not affect the physical composition of cordierite honeycomb porous ceramics,and when the amount of potato starch used is 40 wt%of the main material,the prepared cordierite honeycomb porous ceramics have the lowest thermal expansion coefficient of 0.5083 × 10-6 K-1,at which the porosity is 60.58%,and the median pore size and average pore size are 24.06 μm,22.08 μm,high concentration of pore size distribution.Considering the source of pore-forming agent,economic benefits,performance of prepared samples and environmental pollution,it was decided to use potato starch as the pore-forming agent in the process of preparing cordierite honeycomb porous ceramics.(3)The effect of the amount of pore-forming agent on the cordierite honeycomb porous ceramics was studied.The test shows that the thermal expansion coefficient of the samples decreases with the addition of the porogenic agent and then rises,and the smallest thermal expansion coefficient is obtained at 40 wt%of the main material for the dosage of the porogenic agent.When the amount of pore-forming agent used was 40 wt%of the main material,the thermal expansion coefficient reached the lowest value.Moreover,the porosity,median pore diameter and average pore diameter of cordierite honeycomb porous ceramics progressively increased with the dosage of porogenic agents,but the growth rate became slow when the porogenic agent usage exceeded 40 wt%.Simultaneously,the compressive strength of the samples decreased with the increasing rate of pore-forming agent.In addition,when the amount of porogenic agent used exceeds 50 wt%of the main material,cordierite honeycomb porous ceramics and raw blanks crack during the drying and sintering process.Based on the performance of the cordierite honeycomb porous ceramics and the economic benefits in the preparation process,it is decided that the poreforming agent should be used in the preparation of the cordierite honeycomb porous ceramics at 40 wt%of the main material.(4)The effect of different porogenic ratios in the composite porogenic agent on cordierite honeycomb porous ceramics was investigated.The porosity,median pore size,mean pore size and specific surface area of cordierite honeycomb porous ceramics increase at the beginning and then all decrease to different degrees as the content of potato starch in the composite porogenic agent increases.The compressive strength of the ceramics in the A and B directions diminished with the increase of potato starch in the composite porosity agent.The coefficient of thermal expansion of cordierite honeycomb porous ceramics is increased by the admission of graphite.When the amount of potato starch and graphite used in the composite pore-forming agent is 20 wt%of the main material,the sintering shrinkage of the cordierite honeycomb porous ceramics in the A direction and the B direction is the same,and the comprehensive performance of the prepared sample is also the best at this time.Therefore,it was decided to set the usage amount of potato starch and graphite in the composite pore-forming agent as 20 wt%of the main material.(5)Through the screening of potato starch,the influence of the particle size and concentration of potato starch in the composite pore former on the cordierite honeycomb porous ceramics was studied.It was conclusively concluded that the median pore diameter,average pore diameter and thermal expansion coefficient of the samples were increasing with the increase of potato starch granule dimensions.While the specific surface area and compressive strength showed a slight decrease,but the range of these changes was small because of the same total amount of porogenic agent used.It is also found that the more concentrated the particle size distribution of the used pore-forming agent,the more concentrated the pore size distribution of the prepared cordierite honeycomb porous ceramics.更多还原