WO2021249304A1 - 一种石墨烯覆膜钡钨阴极及其制备方法 - Google Patents

一种石墨烯覆膜钡钨阴极及其制备方法 Download PDF

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WO2021249304A1
WO2021249304A1 PCT/CN2021/098369 CN2021098369W WO2021249304A1 WO 2021249304 A1 WO2021249304 A1 WO 2021249304A1 CN 2021098369 W CN2021098369 W CN 2021098369W WO 2021249304 A1 WO2021249304 A1 WO 2021249304A1
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graphene
cathode
barium tungsten
tungsten cathode
layer
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樊鹤红
包正强
梁田
许准
孙小菡
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东南大学
南京三乐集团有限公司
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
    • H01J1/02—Main electrodes
    • H01J1/13—Solid thermionic cathodes
    • H01J1/14—Solid thermionic cathodes characterised by the material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
    • H01J1/02—Main electrodes
    • H01J1/13—Solid thermionic cathodes
    • H01J1/20—Cathodes heated indirectly by an electric current; Cathodes heated by electron or ion bombardment
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
    • H01J9/02—Manufacture of electrodes or electrode systems
    • H01J9/04—Manufacture of electrodes or electrode systems of thermionic cathodes

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  • the invention relates to the technical field of microwave vacuum electronics, in particular to a graphene-coated barium tungsten cathode and a preparation method thereof.
  • Vacuum electronic devices represented by communication traveling wave tubes have been widely used in microwave communication systems such as radar communications and satellite communications because of their high frequency and high output power.
  • vacuum electronic devices due to their unique physical characteristics, vacuum electronic devices are showing , Medical CT, non-destructive testing, particle accelerators, free electron lasers, electron microscopes, electron beam exposure and other precision testing and preparation equipment have also played an important role.
  • the cathode's emission ability directly affects the performance indicators of the device and the system.
  • Hot cathode has significant advantages such as large emission current and long working life, and it is the most widely used. To further improve the emission capability of the cathode or to extend the life of the cathode is the development direction of the cathode.
  • the M-type cathode is a type of cathode with better emission capability and lifetime. It achieves a lower work function by coating a layer of osmium or iridium or ruthenium on the surface of the B-type or S-type cathode. Improve the emission ability, but the work function of the M-type cathode surface is closely related to the composition ratio of the cathode surface film layer. The optimal ratio should be maintained during the preparation and use process. Diffusion will cause changes in the cathode surface composition, resulting in changes in the work function of the cathode surface and changes in the emission current density under the same working conditions. The mutual diffusion between the cathode surface and the substrate during use affects the working stability of the M-type cathode And longevity.
  • the objective of the present invention is to provide a graphene-coated barium tungsten cathode with improved emission capability and working stability.
  • Another objective of the present invention is A method for preparing a graphene-coated barium tungsten cathode with a simple process is provided.
  • the graphene-coated barium tungsten cathode of the present invention includes a graphene layer and a B-type barium tungsten cathode layer, the upper surface of the B-type barium tungsten cathode layer is covered with a graphene layer, and the B-type barium tungsten cathode layer It is placed in a support tube, and a filament is arranged under the B-type barium tungsten cathode layer in the support tube to form a hot cathode.
  • the graphene layer is single-layer or double-layer graphene. It also includes a grid, and the grid is isolated from the graphene layer by an insulating dielectric layer or a vacuum.
  • the grid is ring-shaped or mesh-shaped.
  • Graphene coated barium tungsten cathode can be used as an electron source in hot cathode vacuum electronic devices and thermo-photocathode vacuum electronic devices.
  • the anode adopts a mesh structure, so that the cathode excitation light can enter the cathode from the back of the anode.
  • the cathode excitation light uses a wavelength shorter than 690 nanometers.
  • the method for preparing the above-mentioned graphene-coated barium tungsten cathode includes the following steps:
  • step (3) Place the graphene/TRT film obtained in step (2) on the temperature control table, place the B-type barium tungsten cathode on it, and control the temperature of the temperature control table to reach the TRT thermal stripping temperature.
  • the TRT loses its viscosity, and then remove the cathode.
  • the graphene is attached to the surface of the cathode to obtain a barium tungsten cathode coated with graphene.
  • the surface emission of the cathode can be adjusted by attaching a grid to the surface of the cathode.
  • the grid adopts a ring or mesh structure.
  • the grid and the cathode are isolated by an insulating layer medium or vacuum.
  • the voltage can realize the adjustment of the cathode emission ability.
  • the cathode emission capability can be adjusted by adjusting the grid voltage.
  • Figure 1 is a schematic diagram of the structure of the present invention
  • Fig. 2 is a schematic diagram of the structure of the grid of the present invention.
  • the raw materials can be directly purchased and used.
  • the graphene-coated barium tungsten cathode 6 and the positional relationship with the anode 7 are shown in Figure 1.
  • a graphene layer 1 is covered on the surface of the traditional B-type barium tungsten cathode 6.
  • the cathode 6 is supported by a support cylinder 3, and a hot wire is filled below.
  • the cathode 6 and the anode 7 may adopt a flat structure or a curved structure.
  • the graphene-coated barium tungsten cathode grid control structure and the schematic diagram of the positional relationship with the anode 7 are shown in Figure 2.
  • a grid 4 is added to the surface of the cathode 6 to adjust the surface emission of the cathode 6.
  • the grid 4 adopts a ring or mesh structure.
  • the electrode 4 and the cathode 6 are isolated by an insulating layer medium or vacuum.
  • the measured work function of the graphene-coated barium tungsten cathode 6 is not greater than 1.56 eV (Gong X, Fan H, Dong C, et al. Emission Performance of Graphene-Coated Ba-W Cathode, 2021 International Vacuum Electronics Conference, IEEE) .
  • Literature Work function distribution for a B cathode and an M cathode early in life. (From: TJGrant, Technical Digest, 1986 IEDM.
  • the work function of the B-type barium tungsten cathode is about 2.1 eV, and the work function of the M-type cathode is about 1.95 eV; the work function of the domestically-made Os-coated M-type cathode can reach about 1.87 eV; therefore, the present invention proposes
  • the emission performance of the graphene-coated barium tungsten cathode 6 is better than that of the B-type cathode (about 2.1 eV) and not inferior to the M-type cathode (about 1.9 eV).
  • the working life of the hot cathode can be doubled for every 10°C decrease in the working temperature of the hot cathode. Therefore, the low work function cathode 6 at the same emission current density corresponding to the decrease in the operating temperature can effectively increase the lifetime.
  • the intermediary transfer-heat release tape (TRT) dry transfer is a two-step transfer method to coat the barium tungsten cathode with graphene. In the case of using TRT-based graphene products, there is no need for the first transfer, as long as the direct dry transfer is sufficient.
  • the preparation of the graphene-coated barium tungsten cathode 6 specifically includes the following steps:
  • the graphene film is transferred from the substrate (such as a copper substrate) to the TRT by using the intermediary transfer method, and the TRT is covered on the side of the substrate where the graphene is grown, and then corroded by a solution (such as FeCl 3 solution) Remove the substrate while retaining the graphene on the TRT, and then wash the graphene-coated TRT in deionized water and then dry it;
  • a solution such as FeCl 3 solution
  • the second step place the graphene/TRT film on the temperature control table, place the B-type barium tungsten cathode on it, and control the temperature of the temperature control table to reach the TRT thermal stripping temperature.
  • the TRT loses its viscosity, and then the cathode is removed, and the graphene is attached.
  • a graphene-coated barium tungsten cathode 6 was obtained.

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  • Manufacturing & Machinery (AREA)
  • Cold Cathode And The Manufacture (AREA)

Abstract

本发明公开了一种石墨烯覆膜钡钨阴极及其制备方法，所述石墨烯覆膜钡钨阴极包括石墨烯层和B型钡钨阴极层，B型钡钨阴极层的上表面覆石墨烯层，B型钡钨阴极层置于支撑筒内，支撑筒内的B型钡钨阴极层下设置灯丝。所述制备方法包括以下步骤：(1)制备B型钡钨阴极；(2)在衬底生长石墨烯一侧覆TRT，通过溶液腐蚀去除衬底，保留石墨烯，将覆有石墨烯的TRT清洗，烘干；(3)在温控台上放置石墨烯/TRT膜，B型钡钨阴极倒置其上，控制温度达到TRT热剥离温度，再将阴极取开，石墨烯附着在阴极表面。本发明有利于降低钡钨阴极表面逸出功，实测逸出功可达1.6eV以下，相比B型阴极，可以提升发射能力，或降低工作温度。

Description

一种石墨烯覆膜钡钨阴极及其制备方法 技术领域
本发明涉及微波真空电子技术领域，具体为一种石墨烯覆膜钡钨阴极及其制备方法。
背景技术
以通信行波管为代表的真空电子器件由于具有高频率、高输出功率等特点，已广泛用于雷达通信、卫星通信等微波通信系统中，此外由于具有独特的物理特性，真空电子器件在显示、医用CT、无损检测、粒子加速器、自由电子激光器、电子显微镜、电子束曝光等精密检测和制备设备中也发挥了重要的作用。
阴极作为真空微电子器件的电子源，其发射能力直接影响器件和系统的性能指标。热阴极拥有发射电流大、工作寿命长等显著优点，应用最为广泛。进一步提升阴极发射能力或延长阴极寿命是阴极一直的发展方向。
现有的热阴极中M型阴极是具有较好的发射能力和寿命的一类阴极，其通过在B型或S型阴极表面覆一层锇或铱或钌薄膜实现更低的逸出功，改善发射能力，但M型阴极表面逸出功和阴极表面膜层成分比例有很大关系，在制备和使用过程中要保持最佳比例，热态工作条件下阴极表面膜层和基底金属的互扩散会导致阴极表面成分的变化，造成阴极表面逸出功的变化和相同工作条件下发射电流密度的变化，在使用过程中的阴极表面和基底之间的互扩散影响了M型阴极工作稳定性和寿命。
发明内容
发明目的：为了改善阴极发射性能，并简化制备工艺，提升工作稳定性，本发明的目的是提供一种提升发射能力和工作稳定性的石墨烯覆膜钡钨阴极，本发明的另一目的是提供一种工艺简单的石墨烯覆膜钡钨阴极的制备方法。
技术方案：本发明所述的一种石墨烯覆膜钡钨阴极，包括石墨烯层和B型钡钨阴极层，B型钡钨阴极层的上表面覆石墨烯层，B型钡钨阴极层置于支撑筒内，支撑筒内的B型钡钨阴极层下设置灯丝，形成热阴极。
石墨烯层为单层或双层石墨烯。还包括栅极，栅极与石墨烯层之间通过绝缘介质层或真空进行隔离。栅极为环形或网状。
石墨烯覆膜钡钨阴极可以用于热阴极真空电子器件和热-光阴极真空电子器件中作为电子源。石墨烯覆膜钡钨阴极用于热-光综合发射真空电子器件中作为电子源时，阳 极采用网状结构，使阴极激励光可以从阳极背面入射阴极。石墨烯覆膜钡钨阴极用于热-光综合发射真空电子器件中作为电子源时，阴极激励光采用短于690纳米的波长。
上述石墨烯覆膜钡钨阴极的制备方法，包括以下步骤：
(1)制备B型钡钨阴极；
(2)在衬底生长石墨烯一侧覆TRT，然后通过FeCl 3腐蚀溶液腐蚀，去除衬底保留TRT上的石墨烯，将覆有石墨烯的TRT在去离子水中清洗，烘干；
(3)在温控台上放置步骤(2)所得石墨烯/TRT膜，B型钡钨阴极倒置其上，控制温控台温度达到TRT热剥离温度，TRT失去粘性，再将阴极取开，石墨烯即附着在阴极表面，得到石墨烯覆膜钡钨阴极。
此外，还可通过在阴极表面附加栅极来对阴极表面发射进行调节，该栅极采用环形或网状结构，栅极与阴极之间通过绝缘层介质或真空进行隔离，通过调节该栅极的电压，可以实现对阴极发射能力的调节。
有益效果：本发明和现有技术相比，具有如下显著性特点：
1、有利于降低钡钨阴极表面逸出功，相比B型阴极，可以提升发射能力，或降低工作温度以延长阴极使用寿命；
2、相比M型阴极，采用石墨烯代替M型阴极的表面覆膜，有利于简化制备工艺、增强稳定性、降低成本。
3、在附加栅极的情况下，可以通过调节栅极电压调节阴极发射能力。
附图说明
图1是本发明的结构示意图；
图2是本发明栅极的结构示意图。
具体实施方式
下列实例中，原料均可直接购买使用。
石墨烯覆膜钡钨阴极6及与阳极7位置关系如图1，在传统B型钡钨阴极6表面覆一层石墨烯层1，阴极6由支撑筒3支撑，下方填充热丝。这里阴极6、阳极7可以采用平板型结构，亦可采用曲面结构。
石墨烯覆膜钡钨阴极栅控结构及与阳极7位置关系示意图如图2，在阴极6表面附加栅极4来对阴极6表面发射进行调节，该栅极4采用环形或网状结构，栅极4与阴极6之间通过绝缘层介质或真空进行隔离。
该石墨烯覆膜钡钨阴极6的实测逸出功不大于1.56eV(Gong X,Fan H,Dong C,et al. Emission Performance of Graphene-Coated Ba-W Cathode,2021 International Vacuum Electronics Conference,IEEE)。文献(Work function distribution for a B cathode and an M cathode early in life.(From:T.J.Grant,Technical Digest,1986 IEDM.
Figure PCTCN2021098369-appb-000001
1986IEEE.))表明B型钡钨阴极逸出功2.1eV左右，M型阴极逸出功为1.95eV左右；国产覆Os膜M型阴极的逸出功可达1.87eV左右；因此本发明所提出的石墨烯覆膜钡钨阴极6发射性能好于B型阴极(2.1eV左右)，不逊于M型阴极(1.9eV左右)。有经验表明，热阴极工作温度每降低10℃，工作寿命可提高一倍。因此，低逸出功阴极6在相同发射电流密度对应工作温度的下降可以有效提升寿命。
基于石墨烯制备的经验，钨基底上不适合直接生长石墨烯膜，因此需要采用转移的方式将石墨烯覆到钡钨阴极表面，但考虑到阴极的特殊性，要避免接触液体，因此，采用中介物转移-热释放胶带(TRT)干法转移的两步转移法进行钡钨阴极表面石墨烯覆膜。在使用TRT基底石墨烯成品的情况下，不需要第一步转移，只要直接干法转移即可。石墨烯覆膜钡钨阴极6的制备具体包括以下步骤：
第一步，采用中介物转移法将石墨烯膜从衬底(如铜基底)上转移到TRT上，在衬底生长石墨烯一侧覆TRT，然后通过溶液(如FeCl 3溶液)腐蚀的方法去除衬底同时保留下TRT上的石墨烯，接下来将覆有石墨烯的TRT在去离子水中清洗，然后烘干；
第二步，在温控台上放置石墨烯/TRT膜，B型钡钨阴极倒置其上，控制温控台温度达到TRT热剥离温度，TRT失去粘性，再将阴极取开，石墨烯即附着在阴极表面，得到了石墨烯覆膜钡钨阴极6。

Claims (8)

  1. 一种石墨烯覆膜钡钨阴极，其特征在于：包括石墨烯层(1)和B型钡钨阴极层(2)，所述B型钡钨阴极层(2)的上表面覆石墨烯层(1)，所述B型钡钨阴极层置于支撑筒内(3)，所述支撑筒(3)内的B型钡钨阴极层(2)下设置灯丝。
  2. 根据权利要求1所述的一种石墨烯覆膜钡钨阴极，其特征在于：所述石墨烯层(1)为单层或双层石墨烯。
  3. 根据权利要求1所述的一种石墨烯覆膜钡钨阴极，其特征在于：还包括栅极(4)，所述栅极(4)与石墨烯层(1)之间通过绝缘介质层(5)或真空进行隔离。
  4. 根据权利要求3所述的一种石墨烯覆膜钡钨阴极，其特征在于：所述栅极(4)为环形或网状。
  5. 根据权利要求1所述的一种石墨烯覆膜钡钨阴极，其特征在于：用于热-光综合发射真空电子器件中作为电子源时，阳极采用网状结构，使阴极激励光可以从阳极背面入射阴极。
  6. 根据权利要求1所述的一种石墨烯覆膜钡钨阴极，其特征在于：用于热-光综合发射真空电子器件中作为电子源时，阴极激励光采用短于690纳米的波长。
  7. 根据权利要求1所述的一种石墨烯覆膜钡钨阴极的制备方法，其特征在于包括以下步骤：
    (1)制备B型钡钨阴极；
    (2)在衬底生长石墨烯一侧覆TRT，然后通过腐蚀溶液腐蚀，去除衬底保留TRT上的石墨烯，将覆有石墨烯的TRT在去离子水中清洗，烘干；
    (3)在温控台上放置步骤(2)所得石墨烯/TRT膜，B型钡钨阴极倒置其上，控制温控台温度达到TRT热剥离温度，TRT失去粘性，再将阴极取开，石墨烯即附着在阴极表面，得到石墨烯覆膜钡钨阴极(6)。
  8. 根据权利要求7所述的一种石墨烯覆膜钡钨阴极的制备方法，其特征在于：所述腐蚀溶液为FeCl 3溶液。
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