Evaluation of size of graphene sheet in anthracite by a temperature-programmed oxidation method
Evaluation of size of graphene sheet in anthracite by a temperature-programmed oxidation method
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DOI：
10.1021/ef030176x
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发表时间：
2004-09-01
期刊：
影响因子：
5.3
通讯作者：
Tomita, A
中科院分区：
文献类型：
--
作者：
Aso, H;Matsuoka, K;Tomita, A
为了评价含碳材料的平均层大小，准确的元素组成数据是必不可少的。然而，准确测定氢含量并非易事。在前文中，我们报道了程序升温氧化(TPO)技术适用于准确测定含碳物质有机部分的碳和氢的含量，并以三种中国无烟煤为例。在本研究中，我们试图根据TPO方法获得的元素分析数据来确定同一组无烟煤的结构。通过参考文献对氧、硫、氮、自由基等其他组分的含量进行了估算。三种无烟煤的平均层尺寸范围为2.1~3.7 nm，并与X射线衍射仪和高分辨电子显微镜的测定值进行了比较。TPO技术估计的大小比其他技术的大，这种差异归因于这些技术基于不同的理论和数学假设。这三种技术的结合提供了对这些材料结构的更全面的了解。除了平均结构外，还试图通过H2O、CO和CO2的TPO峰在500至800℃之间的温度区域的反卷积来获得更详细的信息。这些峰可以合理地分解为至少两个峰。由低温峰测得的H/C原子比小于由高温峰测得的H/C原子比。这可能是因为较小分子的氧化发生在较低的温度。
To evaluate the average layer size of carbonaceous material, it is essential to have its accurate elemental composition data. However, accurate determination of the hydrogen content is not easy. In the previous paper, we reported that a temperature-programmed oxidation (TPO) technique is suitable to accurately determine the amounts of carbon and hydrogen of the organic portion of carbonaceous material, using three Chinese anthracites as examples. In the present study, we attempt to determine the structure of the same set of anthracites on the basis of the elemental analysis data obtained by a TPO method. The contents of other components, such as oxygen, sulfur, nitrogen, and free radicals, were estimated by referring to the literature. The average layer sizes of the three anthracites range from 2.1 to 3.7 nm, and these values were compared with those estimated from XRD and HRTEM analysis. The size estimated from the TPO technique was larger than those from other techniques, and this discrepancy was attributed to the fact that these techniques are based on different theoretical and mathematical assumptions. The combination of these three techniques provided a more comprehensive understanding about the structure of these materials. In addition to the average structure, an attempt was made to obtain more detailed information through the deconvolution of TPO peaks of H2O, CO, and CO2 in the temperature region between 500 and 800 degreesC. The peaks could be reasonably resolved into at least two peaks. The H/C atomic ratio determined from the lower temperature peaks was smaller than that for the higher temperature peaks. This is likely because the oxidation of smaller size molecules takes place at lower temperatures.