SYNTHESIS OF SILICON CARBIDE BY FUEL-RICH COMBUSTION IN CERAMIC SURFACE BURNER

多孔陶瓷表面燃烧器是在多孔陶瓷板上沿表面形成火焰，在宽当量比范围内具有可燃性极限。如果甲烷-氧气混合物在高温下能够在相当富含燃料的当量比下燃烧，二氧化硅就可以转化为碳化硅。本文提出了表面燃烧器在碳化硅燃烧合成中的应用，并对其可行性进行了初步探讨。1)表面燃烧器采用蜂窝陶瓷组装而成，燃烧极限试验未观察到回火现象。2)燃烧器的富燃料燃烧当量比达到3.0，但碳烟生成量较大。3)附着在蜂窝表面的火焰当量比小于1.5W，而附着在蜂窝表面的火焰长度小于1.5w…当当量比大于1.5时，火焰长度增大。4)以31个物种的基元反应为基础，建立了化学反应动力学模型。分析结果表明，在当量比大于2.0的情况下，其组成和温度满足二氧化硅碳化反应所需的条件。5)在燃烧器富燃料火焰中，用一块石英玻璃在板坯上合成了一层碳化硅薄膜。然而，由于与燃烧热负荷相比，辐射热损失较大，样品不能保持足够高的反应温度，因此X射线衍射分析没有检测到产物的生成。事实表明，实现这一过程的一个关键因素应该是减少辐射热损失，而不是燃烧热负荷。这一事实意味着，实现这一目标的一个关键因素应该是减少板坯的辐射热损失并保持温度。较少

The porous ceramic surface burner, in which flame is formed along the surface on a porous ceramic plate, has flammability limit in wide region of equivalence ratio. If the combustion of a methane-oxygen mixture at high temperature can take place under a fairly fuel-rich equivalence ratio, silicon dioxide may be converted to silicon carbide. In the present study, an application of the surface burner to the combustion synthesis of silicon carbide was proposed and the possibility was investigated fundamentally. The following knowledge was obtained : 1) The surface burner was assembled by using ceramic honeycomb and flashback was not observed from the test of flammability limit. 2) The fuel-rich combustion of the burner achieved up to 3.0 in equivalence ratio, but soot generation became significant. 3) The thin flame attached on the surface of honeycomb in less equivalence ratio than 1.5 while the length of the flame attached on the surface of honeycomb in less equivalence ratio than 1.5 w … More hile the length of the flame was enlarged with elevation of the equivalence ratio beyond 1.5. 4) The chemical reaction kinetic model was analyzed on the basis of the elementary reactions with 31 species. The analytical result showed that the composition and temperature satisfied the condition required for the carbonizing reaction of silicon dioxide in the higher equivalence ratio than 2.0. 5) A piece of quartz glass was examined to synthesize a film of silicon carbide on the slab in the fuel-rich flame of the burner. However the production was not detected by XRD analysis because the sample could not maintain sufficiently high temperature necessary for the reaction due to large radiant heat loss compared with the combustion heat load. The fact means that a key factor for realizing this process should be to reduce the radiant heat loss compared with the combustion heat load. The fact means that a key factor for realizing should be to reduce the radiant heat loss from slabs and maintain temperature. Less