随着冷启动排放问题的日益严重,金属载体催化剂除了应用于摩托车和柴油机尾气催化燃烧外,不久将用于密耦型催化剂.然而,金属载体与活性涂层之间低的粘结力是制约金属载体催化剂发展的瓶颈.该文报导了一个3步工序:碱蚀预处理→950 ℃氧化→浸渍涂层并焙烧.超声波振动和高温急冷后超声波振动分别用于测定活性涂层的脱落率.结果表明,整体型金属载体起始负载达到10%,在经超声波振动后,脱落率为1.4%.与此同时,还发现经碱蚀后的FeCrAl合金表面存在许多大小不一的"坑".这些"坑"为后续的活性涂层起到钉扎作用.XRD分析可知,Fe-Cr固熔体在氧化层下面富集.SEM图象表明,煅烧后致密的氧化铝层在活性涂层和FeCrAl合金的界面形成,这极大地有益于增强活性γ-Al2O3涂层在FeCrAl合金箔材上的粘结力.
With increasing seriously problem of cold-start emission, metallic substrate catalyst, besides applied to catalytic combustion of motorcycle and diesel exhaust, will be also served as closed-coupled catalyst in the future. However, lower adhesion between metallic substrates and washcoat is the bottleneck problem restricting metallic substrate catalyst to develop. The paper reports a three-step procedure: alkali-etching pretreatment→oxidation at 950 ℃→coating impregnation and calcination. Ultrasonic vibration and ultrasonic vibration after quenching from high temperature tests were taken to examine weight loss of washcoat, respectively. The results showed that, initiative loading weight of monolithic metallic substrate reaches 10 wt%, and weight loss after ultrasonic vibration test is 1.4 wt%. Meanwhile, we also found that, in surface of FeCrAl alloy after etching pretreatment, there are many "pits" with different sizes which serves as pinning action for the loading washcoat. XRD analysis indicated that Fe-Cr solid solution concentrats under the oxide layer of FeCrAl alloy. SEM images indicated that after calcined, dense alumina layer forms at the interface between washcoat and FeCrAl alloy, which is greatly favourable to enhance the adhesion of the active γ-Al2O3 coating to FeCrAl foil material.
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