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Effect of Silane Capping on the Dispersion and Combustion Characteristics of Sub-micrometer Boron Particles Loaded in Jet A-1
Energy & Fuels ( IF 5.3 ) Pub Date : 2018-09-20 00:00:00 , DOI: 10.1021/acs.energyfuels.8b02490
Pawan Kumar Ojha 1 , Srinibas Karmakar 1
Affiliation  

The present investigation deals with the surface modification of sub-micrometer boron particles with octadecyltrimethoxysilane (OTMS, a silane compound) to improve the dispersion stability of boron particles in liquid fuel. Characterizations of as-received and silane-coated boron particles in terms of the particle size, morphology, surface chemistry, ignition temperature, and oxidation profile have been conducted using typical material characterization methods, such as scanning electron microscopy, scanning transmission electron microscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis (TGA). The results show that the surfaces of as-received boron particles have been successfully functionalized via a condensation reaction of hydroxyl function groups (−OH) with OTMS molecules. The capping of OTMS on the boron surface makes the particle stable against air oxidation. The dispersion stabilities of OTMS-capped boron in Jet A-1 at particle loadings of 1, 5, and 10% are found out to be 20, 18, and 2 h, respectively. Ignition and combustion characteristics of as-received and silane-coated boron particles loaded in Jet A-1 at desired concentrations have been analyzed to understand the effect of silane coating. TGA, true color flame images, and spectroscopic results show that the burning process of OTMS-capped boron is slightly delayed in comparison to as-received boron. The droplet diameter regression profiles show smooth regression up to 70–80% of the droplet lifetime with some intermittent puffing with disruptions at a later stage in both of the particle cases. However, the intensity of disruption is stronger in the case of OTMS-capped boron because of the formation of a more compact shell inside the droplet as a result of the melting of the OTMS layer (particularly toward the end of the droplet lifetime). The micrographs of the combustion residue reveal that some tiny holes are present on the residue surface in the case of as-received boron, whereas multiple blow holes are there in the case of OTMS-capped boron. A blanket of silicon seems to cover the particle surface, which makes them stick together.

中文翻译:

硅烷封端对射流A-1中亚微米级硼粒子弥散和燃烧特性的影响

本研究涉及用十八烷基三甲氧基硅烷(OTMS,一种硅烷化合物)对亚微米级硼颗粒进行表面改性,以提高硼颗粒在液体燃料中的分散稳定性。已经使用典型的材料表征方法,如扫描电子显微镜,扫描透射电子显微镜,X,对粒径大小,形貌,表面化学,着火温度和氧化曲线进行了表征和硅烷包覆硼粒子的表征。射线光电子能谱和热重分析(TGA)。结果表明,通过羟基官能团(-OH)与OTMS分子的缩合反应,已成功接收了硼颗粒的表面。OTMS在硼表面的封盖使颗粒对空气氧化稳定。发现在颗粒载荷分别为1、5和10%时,OTMS包覆的硼在Jet A-1中的分散稳定性分别为20、18和2 h。已经分析了以期望的浓度负载在Jet A-1中的原样和硅烷涂覆的硼颗粒的点火和燃烧特性,以了解硅烷涂层的作用。TGA,真彩色火焰图像和光谱结果表明,与原样接收的硼相比,OTMS覆盖的硼的燃烧过程略有延迟。两种颗粒情况下,液滴直径的回归曲线均显示出高达70-80%的液滴寿命的平滑回归,并且在以后的阶段出现了间歇性的喷吹和破坏。然而,在OTMS封盖的硼中,破裂强度更强,这是因为OTMS层熔化(特别是在液滴寿命即将结束时),从而在液滴内部形成了更致密的壳。燃烧残留物的显微照片显示,在硼接收状态下,残留物表面存在一些小孔,而在OTMS封盖的硼情况下,存在多个气孔。一层硅似乎覆盖了粒子表面,这使它们粘在一起。燃烧残留物的显微照片显示,在硼接收状态下,残留物表面存在一些小孔,而在OTMS封盖的硼情况下,存在多个气孔。一层硅似乎覆盖了粒子表面,这使它们粘在一起。燃烧残留物的显微照片显示,在硼接收状态下,残留物表面存在一些小孔,而在OTMS封盖的硼情况下,存在多个气孔。一层硅似乎覆盖了粒子表面,这使它们粘在一起。
更新日期:2018-09-20
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