【摘要】 利用XPS,PLS,XRD,BET,TEM等现代分析手段,研究了本实验中制备的经镧和钡修饰的改性氧化铝涂层的热稳定性和改性机理,认为介稳态的γ相向介稳态的δ相和θ相转变和氧化铝颗粒的长大是改性涂层高温烧结的原因,镧和钡的加入可有效地抑制介稳态的氧化铝向热力学上稳定的α-Al2O3的转变,一定程度上提高了氧化铝的高温热稳定性。通过考察La3+与Ba2+在改性氧化铝涂层中的分布规律,提出掺杂离子进入氧化铝晶格缺陷的改性机理,并探讨了不同类型的缺陷的大小和浓度随温度的变化规律。更多还原

【Abstract】 Using γ-Al2O3 as the washcoat on the surface of cordierite monolith substrate is the absolutely necessary method in preparing automobile exhaust catalysts , and the thermal durability of the washcoat has been a scabrous problem for a long time. Utilizing such modern analysis methods as XPS, PLS, XRD, BET, TEM , a systematic research on thermal durability and modification mechanism of the lanthanum and barium modified γ-Al2O3 washcoat prepared in this experiment was presented. The research shows that the washcoat sintered at high temperature is ascribed to the phase transition of low-temperature spinel aluminas (γ-Al2O3) to high-temperature spinel aluminas (δ, θ-Al2O3) and growing up of the aluminas granule. The additive lanthanum and barium efficiently restrain the phase transition from spinel aluminas to corundum phase (α-Al2O3), which is stable in thermodynamics, thus to some extent heightens the thermal durability of aluminas at high temperature. By observing the dispersion rule of La3+ and Ba2+ in the modified wash-coat, the such modification mechanism as additive ions entering the defective configurations of aluminas crystal is proposed. And the rule, how the size and concentration of different kinds of defective configurations changed with the temperature, was also been discussed .更多还原