用于浸渍阴极的钨海绵基体制备

Preparation of Porous Tungsten Matrix Used for Impregnated Dispenser Cathodes

微波真空电子器件广泛应用于卫星通信及未来军事前沿的高功率微波武器等方面,这些器件需要电流发射稳定、蒸发小、寿命长的浸渍阴极,进而对浸渍阴极钨海绵基体制备工艺提出了很高要求。本文首先利用分级技术对钨粉进行了分级,制备出流动性好颗粒均匀的钨粉。采用气体纯化与检测系统,可以除掉氢气中残余的氧和水,使氢气的露点降至-90℃以下,为制备无氧化的钨海绵基体提供良好的烧结气氛。采用真空去铜技术,制备出表面非常光洁,没有任何污渍和杂质沉淀的阴极基体,利用X射线能量色散谱(EDX)分析了制备的阴极基体断面,结果表明新方法达到了传统化学去铜及再高温去铜后的效果,新方法更节省时间,更环保。通过调节烧结时间和烧结气氛可以制备出微波器件所需的孔度适宜、闭孔率低的阴极基体,为制备低蒸发、长寿命微波器件的阴极打下基础。

Microwave vacuum electron devices are used in a wide variety of areas,such as radar,space technology and electron accelerator.The cathode is the core of the vacuum electron devices,and its performances directly determine the reliability and the lifetime of electron devices.Therefore,the development of vacuum electron devices put a high demand for porous tungsten matrix for impregnated dispenser cathode.In this work,the tungsten powder is classified by grading technology to realize uniform flow ability.Gas purification and detection system is used to remove residual oxygen and water in the hydrogen gas,and reduce the dew point of hydrogen to-90℃,which provides a good sintering atmosphere for preparing the non-oxidized tungsten sponge matrix.In order to overcome the drawbacks of chemical methods,a new method for copper removing is proposed.The tungsten copper alloy substrate is heated by a high frequency heating coil crucible localized firing at 1900 K.Thereby the copper in tungsten-copper alloy matrix is evaporated rapidly and deposited onto a condenser.The results show that this technology can remove copper effectively in a short time without furnace pollution or environmental pollution.By adjusting the sintering time and atmosphere,a cathode substrate with suitable pore size and low closed cell ratio for microwave devices can be prepared,which lays a foundation for preparing cathodes for low evaporation and long life microwave devices.