Radiation-induced processes on the silica-gel surface
Radiation-induced processes on the silica-gel surface
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DOI：
10.1039/df9613100203
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发表时间：
1961
期刊：
影响因子：
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通讯作者：
V. Kazansky;G. B. Pariisky;V. V. Voevodsky-V.
中科院分区：
文献类型：
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作者：
V. Kazansky;G. B. Pariisky;V. V. Voevodsky-V.
用Co/SUP60/源的伽马射线在真空中对热处理后的硅胶样品进行了辐照，并用电子自旋共振(ESR)方法进行了研究。在液氮温度照射下，硅胶表面羟基的键发生断裂，形成稳定在表层的氢原子。吸附的氢原子在-150℃和-120℃时与氧和乙烯发生化学作用，并在-150℃和-120℃观察到乙基自由基光谱。在液氮温度下照射的样品的氢原子信号伴随着一个由硅胶缺陷引起的复杂信号，该信号由至少四条不同的重叠线组成。在室温下辐照的样品中，F中心的形成发生在硅胶的表面和体相中。还观察到了极弱的超精细结构谱线，可能与奇电子与表面羟基氢原子相互作用引起的超精细分裂有关。在氧的作用下，光谱中出现了一条不对称谱线，可能是由于表面过氧化自由基的形成所致。由于这一信号的强度远高于更多辐照硅胶最初显示的强度，因此可以推断，不是所有在辐照过程中形成的缺陷都可以用ESR技术检测到。研究了辐射诱导的硅胶缺陷与各种气体之间的相互作用。这一结果与科恩和泰勒观察到的辐照硅胶的催化活性增加有关。(身份验证)？更少
Thermally pre-treated silica-gel samples were irradiated in vacuum by gamma-rays from a Co/sup 60/ source, and investigated by the electron spin resonancc (ESR) method. Scission of bonds in surface OH groups of silica-gel, leading to formation of hydrogen atoms stabilized in the surface layer, was shown to take place in samples irradiated at the liquid-nitrogen temperature. Adsorbed hydrogen atoms were highly reactive and interacted chemically with oxygen and ethylene at -150 and -120 deg C. An ethyl radical spectrum was observed in the latter case. The hydrogen-atom signal from samples irradiated at the liquid- nitrogen temperature was accompanied by a complex signal caused by silica-gel defects and consisting of at least four different superimposed lines. The formation of F-centers in samples irradiated at room temperature took place on the surface and in the bulk of silica-gel. Very weak lines of a hyperfine structure, possibly connected with hyperfine splitting due to interaction of odd electrons with hydrogen atoms of surface hydroxyl groupa were also observed. An asymmetric line probably caused by the formation of surface peroxide radicals appeared in the spectrum under the action of oxygen. Since the intensity of this signal was much higher than that shown initially by themore » irradiated silica-gel, it may be inferred that not all the defects formed during irradiation may be detected by thc ESR technique. Interactions between radiation-induced silicagel defects and various gases were studied. The results are of interest in connection with the increased catalytic activity of irradiated silica-gel, as observed by Cohn and Taylor. (auth)« less