夹层结构Cf-Si3N4复合材料微波介电响应机理研究

doi:10.15541/jim20160172

无机材料学报 ›› 2017, Vol. 32 ›› Issue (1): 86-90.DOI: 10.15541/jim20160172

夹层结构C_f-Si₃N₄复合材料微波介电响应机理研究

周伟^{1, 2}, 肖鹏², 罗衡^{2, 3}

(1. 湖南工业大学冶金与材料工程学院, 株洲 412008; 2. 中南大学粉末冶金国家重点实验室, 长沙 410083; 3. 中国工程物理研究院核物理与化学研究所, 绵阳 621900)

收稿日期:2016-03-23 修回日期:2016-04-26 出版日期:2017-01-20 网络出版日期:2016-12-15
作者简介:周伟(1986–), 男, 讲师. E-mail: chowvy@163.com
基金资助:
国家重点基础研究发展规划(973计划)(2011CB605804);国家自然科学基金(51604107);湖南省教育厅科学研究项目(16C0461)

Mechanism of Microwave Dielectric Response in Laminated C_f-Si₃N₄ Composites

ZHOU Wei^{1, 2}, XIAO Peng², LUO Heng^{2, 3}

(1. College of Metallurgy and Material Engineering, Hunan University of Technology, Zhuzhou 412008, China; 2. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China; 3. Innovation Research Team for Advanced Ceramics, Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang, 621900, China)

Received:2016-03-23 Revised:2016-04-26 Published:2017-01-20 Online:2016-12-15
About author:ZHOU Wei. E-mail: chowvy@163.com
Supported by:
State Key Development Program for Basic Research of China (2011CB605804);National Natural Science Foundation of China (51604107);Science Research Project of Hunan Provincial Department of Education(16C0461)

摘要/Abstract

摘要：

以短切炭纤维、氮化硅为原料, 采用凝胶注模工艺, 在1600℃、N₂气氛下无压烧结制备了夹层结构C_f-Si₃N₄复合材料。采用网络矢量分析仪测试了夹层结构C_f-Si₃N₄复合材料在X波段的介电响应行为, 并通过理论建模深入分析了该复合材料的微波介电响应机理。结果表明: 短切炭纤维呈二维分布的夹层结构, C_f-Si₃N₄复合材料介电常数随着炭纤维面密度增加存在“阈值”现象。通过修正Debye模型, 提出了夹层结构C_f-Si₃N₄复合材料在炭纤维形成导通网络后的介电响应理论模型, 揭示了夹层结构C_f-Si₃N₄复合材料介电损耗频散特性的机理。研究结果还表明, 在短切炭纤维刚刚形成导通网络时, 复合材料的弛豫时间存在较大分散性, 介电常数可采用多弛豫时间函数分段描述法。随着炭纤维面密度逐步增加, 弛豫时间的分散性减小, 分段弛豫时间函数演化成单一弛豫时间理论模型。

关键词: 夹层结构, Cf-Si3N4复合材料, 介电响应机理, 弛豫时间

Abstract:

Laminated C_f-Si₃N₄ composites were prepared by gelcasting followed by pressureless sintering at 1600℃ in N₂ atmosphere, using short carbon fiber, α-Si₃N₄ powder as starting materials. Microwave dielectric properties of C_f-Si₃N₄ composites were investigated in X-band using a network analyzer. Moreover, theoretical model regarding microwave dielectric responses was established by modification of Debye model, and the corresponding mechanism was discussed intensively. Results show that there exists percolation phenomenon in permittivity of laminated C_f-Si₃N₄ composites with surface density of short carbon fibers increasing due to formation of connected carbon fiber network. Additionally, the relaxation time of C_f-Si₃N₄ composites converges to multiple values immediately after carbon fibers network being formed, which results from inhomogeneity of microstructure, conductivity and coatings of short carbon fibers. And this dispersity can then weaken as surface density of short carbon fibers increasing. Consequently, the characteristic function of tangent loss evolves from multi-relaxation time model to uni-relaxation time model based on numerical analysis.

Key words: laminated Cf -Si3N4 composites, dielectric response, relaxation time

中图分类号:

TQ174

周伟, 肖鹏, 罗衡. 夹层结构C_f-Si₃N₄复合材料微波介电响应机理研究[J]. 无机材料学报, 2017, 32(1): 86-90.

ZHOU Wei, XIAO Peng, LUO Heng. Mechanism of Microwave Dielectric Response in Laminated C_f-Si₃N₄ Composites[J]. Journal of Inorganic Materials, 2017, 32(1): 86-90.

图/表 6

表1 Cf -Si3N4复合材料中短切炭纤维的面密度

Table1 Surface density of short carbon fibers inside Cf -Si3N4 composites

Samples	1#	2#	3#	4#	5#	6#
Surface density /(mg^.cm^-2)	0.3067	0.6134	0.7667	0.9201	1.2268	2.4530

图1 Cf-Si3N4复合材料的宏微观形貌

Fig. 1 Macro and micro morphology of Cf-Si3N4 composites(a) Macro morphology of Cf-Si3N4 composites, (b) Macro morphology of carbon fibers, and (c) Micro morphology of Cf-Si3N4 composites

图2 炭纤维不同面密度的夹层结构Cf -Si3N4复合材料(a)介电常数和(b)损耗角正切在X波段的频谱曲线

Fig. 2 (a)Permittivity and (b)dielectric loss tangent diagram of Cf -Si3N4 composites with different surface density chopped carbon fibers

图3 夹层结构Cf-Si3N4复合材料的介电常数Cole-Cole图

Fig. 3 Cole-Cole diagram of sandwich-structure Cf -Si3N4 composites

图4 损耗角正切随频率变化的实验结果与理论模型拟合曲线

Fig. 4 Experimental and theoretical curves of dielectric loss tangent vs frequency

图5 4#样品介电损耗角正切值分段拟合曲线

Fig. 5 Piecewise fitted curves of dielectric loss tangent of Cf -Si3N4 4#

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夹层结构C_f-Si₃N₄复合材料微波介电响应机理研究

Mechanism of Microwave Dielectric Response in Laminated C_f-Si₃N₄ Composites

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