| 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.
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