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Highly ordered mesoporous silicon carbide ceramics with large surface areas and high stability

机译：具有高表面积和高稳定性的高度有序的介孔碳化硅陶瓷

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Highly ordered mesoporous silicon carbide ceramics have been successfully synthesized with yields higher than 75% via a one-step nanocasting process using commercial polycarbosilane (PCS) as a precursor and mesoporous silica as hard templates. Mesoporous SiC nanowires in two-dimensional (2D) hexagonal arrays (p6m) can be easily replicated from a mesoporous silica SBA-15 template. Small-angle X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM) images show that the SiC nanowires have long-range regularity over large areas because of the interwire pillar connections. A three-dimensional (3D) bicontinuous cubic mesoporous SiC structure (Ja3d) can be fabricated using mesoporous silica KIT-6 as the mother template. The structure shows higher thermal stability than the 2D hexagonal mesoporous SiC, mostly because of the 3D network connections. The major constituent of the products is SiC, with 12% excess carbon and 14% oxygen measured by elemental analysis. The obtained mesoporous SiC ceramics are amorphous below 1200 degrees C and are mainly composed of randomly oriented beta-SiC crystallites after treatment at 1400 degrees C. N-2-sorption isotherms reveal that these ordered mesoporous SiC ceramics have high Brunauer-Emmett-Teller (BET) specific surface areas (up to 720 m(2) g(-1)), large pore volumes (similar to 0.8 cm(3) g(-1)), and narrow pore-size distributions (mean values of 2.0-3.7 nm), even upon calcination at temperatures as high as 1400 degrees C. The rough Surface and high order of the nanowire arrays result from the strong interconnections of the SiC products and are the main reasons for such high surface areas. XRD, N-2-sorption, and TEM measurements show that the mesoporous SiC ceramics have ultrahigh stability even after re-treatment at 1400 degrees C under a N-2 atmosphere. Compared with 2D hexagonal SiC nanowire arrays, 3D cubic mesoporous SiC Shows superior thermal stability, as well as higher surface areas (590 m(2) g(-1)) and larger pore volumes (similar to 0.71 cm(3) g(-1)).
机译：高阶介孔碳化硅陶瓷已经成功地合成，通过一步一步的纳米浇铸工艺，使用市售聚碳硅烷（PCS）作为前体，并以介孔二氧化硅作为硬模板，合成了高于75％的产率。二维（2D）六边形阵列（p6m）的中孔SiC纳米线可以轻松地从中孔二氧化硅SBA-15模板复制。小角度X射线衍射（XRD）模式和透射电子显微镜（TEM）图像显示，由于线间柱连接，SiC纳米线在大面积上具有远距离规则性。可以使用介孔二氧化硅KIT-6作为母模板来制作三维（3D）双连续立方介孔SiC结构（Ja3d）。该结构比2D六角形介孔SiC具有更高的热稳定性，这主要是由于3D网络连接。产品的主要成分是SiC，通过元素分析测得的碳含量为12％，氧含量为14％。所得的介孔SiC陶瓷在1200℃以下为非晶态，并且主要由在1400℃处理后的无规取向的β-SiC微晶组成。N-2-吸收等温线表明，这些有序介孔SiC陶瓷具有较高的Brunauer-Emmett-Teller（ BET）比表面积（最大720 m（2）g（-1）），大孔体积（类似于0.8 cm（3）g（-1））和窄孔径分布（平均值为2.0-甚至在高达1400摄氏度的温度下煅烧时也能达到3.7 nm）。纳米线阵列的粗糙表面和高阶是由SiC产品的牢固互连造成的，并且是产生如此高表面积的主要原因。 XRD，N-2-吸收和TEM测量表明，即使在1400摄氏度的N-2气氛下进行了再处理，介孔SiC陶瓷也具有超高的稳定性。与2D六角形SiC纳米线阵列相比，3D立方介孔SiC显示出优异的热稳定性，以及更高的表面积（590 m（2）g（-1））和更大的孔体积（类似于0.71 cm（3）g（- 1））。

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