Constructing a field-emission (FE) x-ray tube

该项目旨在建立一种制备内含金属丝的碳纳米管(CNTs)的技术。所获得的结果概述如下：1)场阳极生长(FAG)通常，场阳极生长的碳纳米管填充金属物质，但一些碳纳米管完全被一根铬丝填充，最长可达10-15μm。通常，在场阳极上生长的碳纳米管是从衬底垂直生长的，除了少数例外。典型的例外情况是：连接相邻碳纳米管的“桥接”碳纳米管和从厚碳纳米管侧面生长的“子”碳纳米管。2)场阴极生长这种类型的碳纳米管生长需要铁、镍或钴作为催化剂。这样生长的碳纳米管表面总是覆盖着金属纳米晶体，并且具有沿电场线直线生长的特点。后一个事实使我们能够制备所谓的“定向碳纳米管”，它可以作为电子束工具中的场电子源。最近，我们成功地将我们的定向碳纳米管应用于紧凑型X射线管的电子源，其结果将发表在4月23日的《应用物理快报》上。3)最新研究在该项目的最后阶段，我们注意到，像Fe、Ni和Co一样，钯(Pd)也能促进碳纳米管在场阳极上的生长。这种碳纳米管表面覆盖有Pd纳米晶。这种Pd纳米晶的氢封闭行为将很快在我们的实验室进行研究。

This project was aimed at establishing a technique to prepare carbon nanotubes (CNTs) having a metallic filament inside. The results obtained are outlined as follows.1) Field anode growth (FAG)Usually, FAG-grown CNTs are filled with a metallic matter, but some CNTs are completely filled with a Cr wire, lengthening up to 10-15 μm. In general, CNTs grown on field anodes undergo a straight growth from the substrate, with a few exceptions. Typical exceptional cases are ; "bridging" CNTs connecting the adjacent CNTs and "child" CNTs grown from the side face of thick CNTs.2) Field cathode growthThis type of CNT growth needs Fe, Ni or Co as catalyst. The CNTs thus grown are always topped with a metallic nanocrystal, and are characterized by straight growth along electric field lines. The latter fact enables us to prepare the so-called "aligned CNTs, " which can serve as the field-electron source in an electron-beam tool. Recently, we successfully applied our aligned CNTs to the electron source of a compact x-ray tube, the result of which is to be published in the April-23 issue of Applied Physics Letters.3) Newest researchIn the last stage of this project, we noticed that, like Fe, Ni and Co, palladium (Pd) catalytically promotes the CNT growth on field anodes. This sort of CNTs are capped with Pd nanocrystals. The hydrogen-occlusion behavior of such Pd nanocrystals will be soon investigated at our laboratory.