【作者】 崔洪芝；

【导师】 王勇；

【作者基本信息】 中国石油大学 ， 化工过程机械， 2009， 博士

【摘要】 汽车尾气净化器载体和微粒捕集器过滤体(DPF)材料主要为堇青石和金属。堇青石载体的脆性大,强度低,使用寿命低。金属载体的强度高,但耐高温性差,且制备工艺复杂,催化剂涂层附着力差。无论是堇青石载体还是金属载体,都难以满足日益严苛的汽车尾气排放法规对催化剂载体的性能要求。Ni-Al、Fe-Al等金属间化合物材料具有强度高,耐高温性好,导电、导热率高等优异性能,是理想的汽车尾气净化器载体和微粒捕集器过滤体材料。本文率先提出采用Ni-Al等元素的自蔓延高温合成反应(SHS)工艺,在原位合成NiAl及其与陶瓷的复合材料的同时,获得所需要的多孔体,将材料的合成与孔洞的制取合二为一。该制备方法具有工艺简单,产品性能可控,成本低廉等特点,可获得性能系列化的多孔材料,以满足多种机动车型及不同使用环境对催化剂载体和DPF的要求,这对推广多孔NiAl基金属间化合物及其复合材料的工业化应用,促进其它体系金属间化合物多孔材料的开发等,具有重要意义。本文研究了Ni-Al金属间化合物多孔材料的反应合成工艺,分析了反应合成过程,物相及组织结构,孔隙形成机理以及性能。首先制备了Ni-Al金属间化合物多孔材料,详细论述了这种新型多孔材料的制备过程和影响参数;在此基础上,将反应合成工艺扩展至Ni+Al+B2O3+TiO2体系,通过原位反应获得了多孔NiAl/TiB2+Al2O3复合材料,以原位形成的TiB2+Al2O3陶瓷相,强化NiAl基体,并进一步提高其耐高温性。分别制备了两类复合孔型结构的多孔材料,一是大孔加小孔加微孔、小孔加微孔的蜂窝状结构,二是直通孔加小孔加微孔的壁流式结构。通过多种分析检测技术,研究了Ni-Al多孔材料的孔结构性能,其中包括多孔材料的孔隙率、孔径和压缩强度等三个重要性能参数,探讨了粉末配比、造孔剂含量等参数对多孔Ni-Al金属间化合物材料的孔结构性能的影响规律。同时,为降低多孔材料的制备成本,简化合成工艺,探索了等离子原位反应制备TiB2+Al2O3/FeAl复合材料的工艺,并分析其组织特征。研究结果表明:Ni-Al的SHS反应可按照预期设计进行,获得产物的典型物相为NiAl、Ni3Al、TiB2和Al2O3。NiAl相组织形态单一,为粗大的枝晶;Ni3Al相则为针片状形态;TiB2相颗粒细小,大部分尺寸小于5 m,呈规则的正方六面体或者六棱柱体,以10~20μm的团簇状镶嵌在块状Al2O3上,或分布在NiAl基体中;Al2O3相形态不规则,部分与NiAl基体混杂在一起,部分与TiB2簇团相伴生长。反应合成多孔材料的成孔机制包括物理机制和反应成孔机制两类。反应成孔机制可归结为Kirkendall效应,孔洞的形成源于Al元素的偏扩散,其形成的孔洞包括孔径与Al颗粒粒径相当的小孔和孔径十分细小的微孔。无外加造孔剂时,多孔材料孔隙率达到50%,孔洞为通孔,孔径尺寸为30～250 m,呈三维交错连通的网格状,孔道曲折、孔壁粗糙,具有大的比表面积,孔洞的壁面上还有相互连通的、孔径仅1.0～3.0 m的微孔,这些微孔穿通小孔的壁面,使反应合成的多孔材料的孔隙连通性更好,比表面积更大。添加尿素等造孔剂,获得了大孔材料,孔隙率高达85%,孔径范围0.2～3.0mm。在反应物粉末中加入有机粘结剂,挤出成型后,利用等离子引发原位反应,制备了具有直通孔结构的多孔NiAl材料和NiAl/TiB2+Al2O3复合材料,直通孔的壁面上同样具有微孔,孔径为0.5～2.0 m,这对满足柴油车DPF过滤体的需要尤为重要。并且反应合成的多孔材料均表现出良好的原坯形状相似性,制备工艺简单,有利于材料的批量化生产,加之具有独特的复合型孔洞结构,在过滤、环境催化等领域具有广泛的应用前景。更多还原

【Abstract】 The current vehicle exhaust purifiers carrier and diesel particulate filter (DPF) substrate materials are mainly made from cordierite and metal materials. Cordierite carriers show high brittleness, low strength, and short life, and the metal carriers show high strength, but poor high temperature resistance and complicated fabricating process, poor adhesion of catalyst coating. Not only cordierite carrier but also metal carrier is difficult to meet the increasingly stricter vehicle exhaust emission regulation requiring for catalyst carrier performance. Ni-Al, Fe-Al intermetallic compounds possess high strength, high temperature resistance, good electrical conductivity and excellent thermal conductivity property; porous material made from above intermetallic compounds will be an ideal vehicle exhaust purifier carrier and diesel particulate filter (DPF) substrate materials. Originally the dissertation suggests that NiAl intermetallic compound and its composites be prepared by in-situ synthesis with self-propagating high temperature synthesis (SHS) technology, and the expected porous materials were produced simultaneously. The method is characterized with simple process, adjustable product properties and low cost etc.,therefore porous intermetallic compound materials with series of properties can be produced to meet the requirements for catalyst carriers and DPF for different vehicle type at varied utilizing environment. It has great significance for the promotion of porous NiAl intermetallic compounds and their industrial application,and for the enhancement of the research and development of other porous intermetallic compounds systems.The dissertation studied the reaction synthesis technology of porous NiAl intermetallic compounds, the process of reaction synthesis, phase and structure, pore formation mechanism and properties. Firstly porous NiAl intermetallic compound prepared by reaction synthesis technology using Ni-Al powders, the preparation process and influence parameters of the new type of inorganic porous materials were discussed in detail. On the basis, the reaction synthesis process was extended to the Ni+Al+B2O3+TiO2 system, and porous NiAl/TiB2+ Al2O3 composite materials were obtained through in-situ reaction, NiAl matrix was strengthened by the ceramic phases formed by in-situ reaction, and its temperature resistance was further improved. Two kinds of porous materials with compounded pore structure were prepared, the first type is honeycomb structure with two morphologies. One is macro-pore, small pore and micro-pore, the other is small pore and micro-pore. The second type is wall-flow structure of through-hole, small pore and micro-pore. Through a variety of analytical techniques, pore structure properties of porous NiAl intermetallic compound materials such as three important parameters of porosity, pore size and compressive strength were studied; influence rules of pore structure properties of porous NiAl intermetallic compounds by the ratio of powder and pore-forming agent were discussed. At the same time, synthesis process was simplified to reduce costs of porous materials. The process and structure properties of TiB2+Al2O3/FeAl composite materials produced by plasma in-situ reaction were explored.The result shows the SHS of Ni+Al reaction can be carried out in accordance with anticipated design, and the typical phases of obtained products are NiAl, Ni3Al, TiB2 and Al2O3. The morphology of NiAl phase structure is single coarse dendrite, and the Ni3Al is needle-plate shape; TiB2 particles are fine, mostly the size is less 5.0 m. TiB2 phase characterized with regular hexahedron or hexahedral cylinder laid in Al2O3 bulk in the clusters of 10~20μm, or distributed in the NiAl matrix. The morphology of Al2O3 is irregular, partly mixed with the NiAl matrix, partly accompanied with TiB2 clusters.The pore-forming mechanism of reaction synthesized porous materials comprises physical mechanism and reaction pore-forming mechanism. Reaction pore-forming mechanism is attributed to the Kirkendall effect, the formation of pores derive from partial diffusion of Al elements, So the small pores equivalent to the Al particles in size and micro-pores were formed, and the porosity reaches about 50% without pore-forming agent. The pore is through-pore, and pore size is between 30~250 m. The porous materials show connected three-dimensional network grid, twisted pore channel, rough pore wall and large specific surface area. There are micro-pores connected each other in the wall with pore size of only 1.0~3.0 m. These micro-pores penetrate through the wall, so that the connectivity of reaction synthesized porous materials becomes better, and the permeability and the specific surface area further increase. The Macroporous materials between 0.2~3.0mm were obtained by adding pore-forming agents such as urea, and the porosity reaches 85%. The porous NiAl and NiAl/TiB2+Al2O3 composites with straight through-pore were produced by plasma igniting in-situ reaction with reactant powders added with organic binder after extrusion molding. Similarly there are small pores and micro-pores on the wall of straight through-pore, with pore size of 0.5~3.0 m.This is extremely important to meet the requirements of DPF. And reactive synthesized porous materials have shown a good similarity to the shape of green samples. The preparation process is simple, easily leading to mass production, coupled with a unique compounded pore structure, so a wide range of applications can be found in the field of filters, environmental catalysis, and so on.更多还原