Study on resistance to high current electron beam bombardment of different types of graphite
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摘要: 石墨因组成元素的原子序数较低、熔点极高、导热性能优异、化学稳定性高及抗热冲击能力较强等诸多优点, 已成为相对论返波管中关键部件收集极的首选材料。对4种具有代表性的高纯石墨及其各自碳化钛涂层改性材料作为强流电子束二极管中的阳极进行了耐强流电子束性能考核。结果表明,4种石墨在电压为860 kV、电流为11 kA、脉宽为40 ns的电子束轰击下二极管的电流表现出明显的差异,石墨4#即使电子束脉冲作用167次,电流曲线也未表现出明显异常,而其他三种石墨的电流曲线均出现不同程度的尾蚀。通过石墨表面碳化钛涂层的烧蚀实验进一步验证了石墨的差异性,表明石墨的热导率对其抗烧蚀性能具有重要的影响。石墨的热导率越高,碳化钛熔融析出再结晶程度越低,说明石墨的抗烧蚀性能越好。石墨4#具有优异的耐电子束轰击性能,在相对论返波管收集极领域具有重要的应用前景。Abstract: In this paper, four typical types of high purity graphite and their titanium carbide coating modified materials were tested as anodes in high current electron beam diodes. The results show that the currents of the diodes were obviously different when the graphite anodes were under electron beam bombardment with voltage 860 kV, current 11 kA and pulse width 40 ns. The current curve for graphite 4# was normal even after interaction of 167 electron pulses while the other graphite current curves showed different degrees of tail erosion. The ablative experiments of titanium carbide coating on graphite further verified the difference of the graphite, indicating that the thermal conductivity of graphite has an important effect on its ablative resistance. The higher the thermal conductivity of graphite, the lower the degree of recrystallization of titanium carbide, the better the corrosion resistance of graphite. Therefore, graphite 4# has an excellent resistance to electron beam bombardment and would be promising for application as collector materials in relativistic traveling wave tubes.
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Key words:
- collector /
- graphite /
- electron beam bombardment /
- titanium carbide coating /
- thermal conductivity
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表 1 不同型号石墨的物理参数
Table 1. Physical parameters of different graphite
type density/
(g·cm−3)resistivity/
(10−5 Ω·m)bending
strength/GPacompressive
strength /GPathermal expansion
coefficient/(10−6 K−1)thermal conductivity/
(W·m−1·K−1)graphite 1# 1.89 1.88 72 147 8.09 70 graphite 2# 1.91 1.46 80 160 5.50 65 graphite 3# 1.84 1.76 100 148 5.25 95 graphite 4# 1.91 1.18 85 140 5.11 120 表 2 不同石墨物理参数的影响
Table 2. Effects of physical parameters of different graphite
influencing factor reference graphite type
(resistance to electron beam bombardment)whether it is main
influencing factorinfluence 1#
(poor)2#
(medium)3#
(good)4#
(excellent)density √ √ √ √ no ― resistivity ― √ √ ― no ― bending strength √ √ ― √ no ― compressive strength √ ― √ √ no ― thermal expansion coefficient √ √ √ √ yes the greater coefficient of thermal expansion,
the greater risk of particle sheddingthermal conductivity ― √ √ √ yes the higher thermal conductivity, the better
resistance to electron beam bombardment -
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