Thermal desorption of hydrogen, deuterium and tritium from pyrolytic graphite
Thermal desorption of hydrogen, deuterium and tritium from pyrolytic graphite
复制标题
热解石墨中氢、氘和氚的热脱附
DOI：
10.1016/0022-3115(84)90459-8
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发表时间：
1984
影响因子：
3.1
通讯作者：
Kuniaki Watanabe
中科院分区：
文献类型：
--
作者：
K. Ashida;K. Ichimura;M. Matsuyama;Kuniaki Watanabe
采用质量分析热脱附谱沿着技术和X射线光电子能谱表面表征技术研究了氢、氘、氚注入热解石墨后的热释放。氢（或其同位素）离子注入到样品中，在室温下与5千伏的施加电压使用常规的离子枪。随后，将样品以各种温度斜坡加热至900° C以测量热解吸光谱。注入的氢（或其同位素）主要以H2形式脱附，少量以CH 4形式脱附.在重复注入-脱附循环的过程中，H2的脱附光谱逐渐变化，并在总剂量达到1× 1019 ion/cm 2后变得可重复，表明原始石墨因辐射损伤的形成/累积而发生改性。对于改性石墨，观察到三个脱附峰。第一个峰是由于在正常石墨晶格中的碳原子上捕获的氢原子的解吸。其他的对应于石墨中不同的被困氢原子。第一峰的脱附与注入量的关系符合二级动力学，表明脱附速率控制步骤是氢原子的表面缔合反应。三种氢同位素的活化能估计为44千卡/摩尔。但在频率因子上出现了同位素效应，其比值为H2：D2：T2 = 3：1.5：1。甲烷的脱附符合准一级动力学，脱附活化能为38 kcal/mol。
Thermal release of hydrogen, deuterium and tritium implanted into a pyrolytic graphite was studied by means of mass analyzed thermal desorption spectroscopy along with surface characterization by X-ray photoelectron spectroscopy. Hydrogen (or its isotopes) ions were implanted into the sample at room temperature with an applied voltage of 5 kV using a conventional ion gun. Subsequently, the sample was heated to 900° C with various temperature ramps to measure the thermal desorption spectra. The implanted hydrogen (or its isotopes) was predominantly desorbed as H 2 and in small amount as CH 4. The desorption spectra of H 2 changed gradually while repeating the implantation-desorption cycles and became reproducible after the total dose amounting to 1× 10 19 ion/cm 2, indicating that the virgin graphite is modified due to formation/accumulation of radiation damage. For the modified graphite, three desorption peaks were observed. The first peak is attributed to the desorption of hydrogen atoms trapped on the carbon atoms in the normal graphite lattice. The others correspond to differently trapped hydrogen atoms in the graphite. The desorption of the first peak obeyed the second order kinetics with respect to the amount of the implantation, indicating that the rate determining step is the surface association reaction of the hydrogen atoms. The activation energy was estimated as 44 kcal/mol for three hydrogen isotopes. However, the isotope effect appeared on the frequency factor: their ratio was estimated as H 2: D 2: T 2= 3: 1.5: 1. The desorption of methane obeyed the pseudo-first order kinetics with an activation energy of 38 kcal/mol.