Research On Several New Self-propagating High-temperature Syntheses And Their Applications

Self-propagating high-temperature synthesis(SHS) is one of the most attractive technologies to manufacture the materials, which can be used in a lot of fields, such as ceramic materials, composite materials, functionally gradient materials(FGM) and surface modification.First, this paper discuses the method and principle of SHS and introduces the research situation of SHS and its development tendency on worldwide. Second, using SHS, ceramic-lined coating metal pipes were produced under the effect of centrifugal force. The effects of parameters on the properties of composite pipes were discussed. The microstructures of the ceramic-lined coating and mechanism of their joint were analyzed. The properties of composite pipes were measured. Third, a method was invented to produce the electric foam ceramic material of (Al2O3+TiB2) and (Al2O3+2Cr). The thermodynamics parameters were calculated, reaction temperatures and reaction velocities were measured. The effects of diluents(SiO2, Al2O3 and Ti) on material properties(compression strength, resistance to sudden heating, porosity and conductivity) were discussed. Forth, On the basis of calculating of the thermodynamics, joint technology of (Al2O3+TiB2) and Al was investigated under the condition of air atmosphere. FGM of (Al2O3+TiB2)/Al was produced and principle of producing FGM was discussed. The design method of temperature and component of FGM was established and microstructure and interface were analyzed. Finally, for the first time, the glassy and continuing ceramic coatings were prepared on the surfaces of cast iron, 1Cr18Ni9Ti, A3 and TiAl under the combining condition of SHS and laser with a small power.While the ceramic-lined coating metal pipes were produced, SiO2, Al2O3 and creamic-glass powder were added into the reactions as diluents. The results show that the density of the ceramic-lined coating increases and the porosity decreases with the increasing of centrifugal force; SiO2 and creamic-glass powder should be added at 5~10wt% to improve the density of the ceramic-lined coating; the micro-hardness of ceramic lined coatings are different in different fields(the hardness is higher in microstructure where there is more Al2O3, the hardness is lower where there is less Al2O3). And the ceramic-lined coating metal pipes are good at resistance to sudden heating under the temperature of 700.The foam ceramic materials of (Al2O3+TiB2) and (Al2O3+2Cr) produced by SHS can be adjusted its properties of electrical resistivity, strength and resistance to sudden heating by adding several kinds of diluents. The results show that: at room temperature the strength of (Al2O3+TiB2) is 2~5MPa and the strength of (Al2O3+2Cr) is l~3MPa; the porosity of (Al2O3+TiB2) and (Al2O3+2Cr) are 50~70% and the diameter are 0.1~0.5mm; the electrical resistivity range of(Al2O3+TiB2) is 1O'3 Q .m; the electrical resistivity of (Al2O3+TiB2) is (3.0- 5.0) X 10-4 O .m while adding Ti,; the electrical resistivity range of (Al2O3+2Cr) is 10-2 Q .m. When the per-heating reaction temperature is 298 K, the maximum measured temperature(Tc) of (Al2O3+TiB2) is 185O癈 and reaction velocity(Vp) range is 4~9mm/s. When the per-heating reaction temperature is 523 K and 10wt%Ti is added, the maximum reaction velocity is 11.8mm/s. With the increasing of SiO2 wt%, Vp is decreasing; when 5wt%SiO2 is added, the reaction velocity is 7.0mm/s.Under the condition of air atmosphere and 600 ~ 650C per-heating temperature, the foam ceramic material of (Al2O3+TiB2) was produced. The X-ray diffraction result shows that the sample is entirely reaction to formed the A12O3 and TiB2, but the porosity of materials is a little higher(about 4O~5O%). A ceramic-metal material of (Al2O3+TiB2)/Al was produced by SHS. The optimum interface strength of (Al2O3+TiB2)/Al and Al was obtained while (Al2O3+TIB2)/A1 system consists of 6O wt%Al. The results of FGM of (Al2O3+TiB2)/Al show that: the adiabatic temperature(Tad) of layers of FGM were designed at 600~650C per-heating temperature by adjusting the content of Al2O3 and...