钡-钨阴极的组织特性与热电子发射性能

王子玉; 尚吉花; 杨新宇; 张久兴

doi:10.11884/HPLPB202133.200335

钡-钨阴极的组织特性与热电子发射性能

doi: 10.11884/HPLPB202133.200335

合肥工业大学材料科学与工程学院，合肥 230009

基金项目: 国家自然科学基金项目（51501051）

详细信息

作者简介:
王子玉（1995—），男，硕士研究生，从事钡钨阴极材料研究

通讯作者:
杨新宇（1984—），男，副教授，主要从事功能材料研究

中图分类号: TF125
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出版历程
- 收稿日期: 2020-12-14
- 修回日期: 2021-03-21
- 网络出版日期: 2021-04-10
- 刊出日期: 2021-05-20

Microstructure characterization and thermionic emission performance of barium-tungsten cathode

School of Material Science and Engineering, Hefei University of Technology, Hefei 230009, China

摘要

摘要: 利用正交试验探讨了放电等离子技术工艺参数（温度、压力、保温时间）对钡-钨（Ba-W）阴极中的W的孔隙度的影响规律，获得了孔隙率在23%～30%内变化时所需要的最佳工艺参数。在此基础上，制备出了具有不同孔隙度的球形W基体和普通不规则的W基体。研究表明：球形多孔W颗粒间堆积、排列有序，无闭孔，孔径分布集中而均匀，在26.3%的孔隙度下中值孔径为1.41 μm；机械性能方面，球形钨粉基体维氏硬度低于传统普通不规则钨多孔体。在脉宽10 μs、频率1000 Hz的条件下，阴极脉冲发射电流密度随着孔隙度的增大，先增大后减小。当基体孔隙度为26.3%时，阴极电流发射密度最大，在1050 ℃，偏离点发射电流密度可达24.62 A/cm²，零场发射电流密度为7.62 A/cm²，功函数为1.95 eV。
- 放电等离子技术 /
- 钡-钨阴极 /
- 球形钨粉 /
- 孔隙度 /
- 热发射性能
Abstract: The effect of the parameters (sintering temperature, pressure, holding time) of spark plasma sintering technique on the W porosity of Ba-W cathode was studied by orthogonal method. When the W porosity varied in the range of 23%−30%, the corresponding process parameters were obtained. On this basis, the spherical and traditional irregular W matrix with different porosity were sintered. The results show that the spherical porous W particles were packed and arranged orderly, and the pore size distribution was concentrated and uniform. When the porosity of spherical W was 26.3%, the size of the median pore was 1.41 μm. The vickers hardness of spherical tungsten matrix was lower than that of conventional irregular tungsten matrix. Under the condition of pulse width 10 μs and frequency 1000 Hz, the impulse current density of Ba-W cathode increased at first and then decreased with the increase in porosity. The maximum current density belonged to the Ba-W cathode with the matrix porosity of 26.3%. At 1050 ℃, the off-point emission current density of Ba-W cathode reached 24.62 A/cm², the corresponding zero-field current density and workfunction were 7.62 A/cm² and 1.95 eV, respectively.
- spark plasma sintering /
- barium-tungsten cathode /
- spherical tungsten powders /
- porosity /
- thermionic emission property

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图 1 原料粉末与粒度分布

Figure 1. Two kinds of raw material powder and their particle size distribution

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图 2 放电等离子烧结曲线

Figure 2. Spark plasma sintering curves

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图 3 多孔体基体微观组织形貌

Figure 3. Microstructures of the porous tungsten matrix

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图 4 基体孔径分布

Figure 4. Pore size distribution of matrix

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图 5 基体维氏硬度

Figure 5. Vickers hardness of matrix

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图 6 浸渍基体微观组织形貌与元素分析

Figure 6. Microstructure and component analysis of the impregnated matrix

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图 7 阴极热发射性能伏安特性与肖特基曲线

Figure 7. Volt-ampere characteristics and Schottky curve of cathode thermal emission performance

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表 1 参数因素水平

Table 1. Parametric factor level

level	temperature/℃	holding time/min	pressure/MPa
1	1500	1	15
2	1600	2	20
3	1700	3	25

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表 2 正交试验方案及结果

Table 2. Orthogonal experimental results

number	A	B	C	error	porosity/%
1	1500	1	15	1	28.34
2	1500	2	20	2	25.33
3	1500	3	25	3	21.00
4	1600	2	15	3	22.05
5	1600	3	20	1	19.56
6	1600	1	25	2	21.97
7	1700	3	15	2	19.46
8	1700	1	20	3	18.15
9	1700	2	25	1	15.97

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表 3 正交试验极差分析

Table 3. Orthogonal experiment range analysis

	A	B	C	error
K	74.67	68.46	69.85	63.87
	63.58	63.35	63.04	66.76
	53.58	60.02	58.94	61.20
R	21.09	8.44	10.91	5.56

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表 4 正交试验方差分析，各因素偏方差和(S_A)、自由度(f )与置信度(α)

Table 4. Orthogonal experiment variance analysis，sum of variance(S_A)，degree of freedom(f ) and confidence (α) of each factor

source	S_A	f	F	α	degree
temperature（A）	74.20	2	14.39	0.1	high
holding Time（B）	12.05	2	2.34	0.25	low
pressure（C）	20.25	2	3.93	0.25	middle
error	5.16	2
SUM	111.66	8

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表 5 不同温度与孔隙度阴极偏离点电流密度

Table 5. Cathode deviation point values of different temperature and porosity

temperature/℃	J_devwith different spherical matrix cathode/（A·cm⁻²）
temperature/℃	23.4%	26.3%	30.5%
900	8.42	10.27	8.60
1000	10.66	14.77	11.43
1050	12.37	24.62	13.00
1100	13.95	33.07	14.56

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表 6 1050 ℃下各阴极J₀与Φ

Table 6. J₀ and Φ values of three cathodes after activated at 1050 ℃

activated temperature/℃	J₀/（A·cm⁻²）			Φ/eV
activated temperature/℃	23.4%	26.3%	30.5%	23.4%	26.3%	30.5%
1050	3.79	7.62	3.10	2.03	1.95	2.05

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