排序方式: 共有11条查询结果,搜索用时 281 毫秒
1.
氧化镁经机械粉碎后,形成具有高活性中心的新鲜表面。将一氧化碳、甲醛、甲醇分别吸附在氧化镁新鲜表面上,用ESR分别检测到CO_2~-,(CH_2O~-)(ads),和(CH_2~-)(ads)等负离子自由基的信号。而CO+H_2在氧化镁新鲜表面上反应形成了顺磁性的中间态,当温度升至573K时,该吸附态转变成两种新的吸附态:一种是甲醇形式的吸附态(OCH_2~-)(ads),该吸附态在温度大于643K时发生脱附;另一种是甲醛形式的吸附态(CH_2—O~-),该吸附态在温度大于823K时才脱附。最后,提出了CO+H_2在氧化镁新鲜表面上反应的可能机理。 相似文献
2.
3.
4.
5.
电子自旋共振(ESR)结合自旋探针方法研究高聚物体系已有大量报道,而目前应用于高聚物的拉伸过程研究仅限于静态测试,即样品先经拉伸后再被转入到ESR仪中测定。对一些具有快速松弛特性的材料研究,静态测试技术有着很大的误差和局限性。虽然可直接从国外引进ESR仪的拉伸裂置,但费用昂贵,同时由于设备结构复杂,拆装不能灵活,故使测定工作也受影响。 相似文献
6.
7.
8.
9.
10.
In the study of molecular motion of polymer by means of ESR in combination with spin probe, owing to that the ESR spectrum depicts only the behavior of spin probe, the information obtained is of indirect nature. Hence the relationship between them must first be investigated before any conclusion could be drawn. In this paper, two parameters T_R and C_R are introduced to characterize the changing of tumbling rate of spin probe, and the concept of rotation barrier of spin probe is proposed. It is considered that the magnitude of the rotation barrier is determined by the internal cavity size and distribution in polymer. When the temperature is raised, the size and distribution of the cavities change accordingly, thus the tumbling of spin probe changes gradually from a slower to a higher rate. 相似文献