TiC-modified CNTs as reinforcing fillers for isotropic graphite produced from mesocarbon microbeads
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摘要: 采用无压放电等离子烧结技术，用纳米TiC改性多壁碳纳米管（MWCNTs），将纳米TiC改性后的碳纳米管（T-CNTs）掺杂到中间相炭微球（MCMB）中以制备高性能的各向同性石墨材料。利用X射线衍射（XRD）、扫描电子显微镜（SEM）、透射电子显微（TEM）等对T-CNTs和制备的石墨材料结构进行表征；并采用万能试验机、激光导热仪和热膨胀系数仪测试了制备石墨材料的力学性能和热学性能。结果表明，纳米TiC成功的附着在CNTs的表面。与未添加T-CNTs的各向同性石墨相比，T-CNTs/MCMB各向同性石墨材料其力学强度有显著的提高，材料的抗折强度提高了70%，石墨化度提高10%，热学性能也有不同程度的提高。
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关键词:
- 放电等离子烧结 /
- TiC改性多壁碳纳米管 /
- 中间相炭微球 /
- 各向同性石墨
Abstract: Multi-wall carbon nanotubes (CNTs) were modified by nano-TiC using a pressureless spark plasma sintering technology. The TiC-modified CNTs (T-CNTs) were added to mesocarbon microbeads (MCMBs) to prepare high performance isostatically pressed graphite materials. The structures of the T-CNTs and the prepared isotropic graphite materials were characterized by XRD, SEM and TEM. The mechanical and thermal properties of isotropic graphite reinforced by T-CNTs were measured by a micro-controlled electronic universal testing machine, laser thermal conductivity meter and thermal expansion coefficient meter. Results showed that the nano-TiC was successfully grown on the surface of CNTs. Compared with the isotropic graphite prepared from MCMBs without T-CNTs, the isotropic graphite with T-CNTs has a significant improvement in physical properties (density, open porosity and volume shrinkage). Its flexural strength and degree of graphitization increased by 70% and 10%, respectively, and the thermal properties were also improved to some degree. -
Figure 2. TEM images of T-CNTs. (a) Local morphology of T-CNTs. (b) Partial enlargement of TiC nanoblocks on T-CNTs. (c) Partial enlargement of TiC nanolayers on T-CNTs. The illustrations in (b) and (c) are the EDS spectra at the region illustrated by the red arrows.
Figure 4. Effect of the T-CNT content on the properties of composites; (a) The bulk density and volume shrinkage curves; (b) The open porosity of the composites; (c) The flexural strength of composites and (d) The stress-strain curves of composites.
Figure 5. Effect of the T-CNT content on thermal diffusivity and thermal conductivity of composites.
Figure 7. (a) XRD patterns of different T-CNT/MCMB graphite samples after graphitization and (b) the partial enlarged view of XRD patterns.
Figure 8. SEM images of the composite cross section. (a) Sectional morphology of MCMB sample. (b) Cross-sectional morphology of samples with 0.40% T-CNTs added. (c) Holes formed by the detachment of particles when they are broken (the dotted line in a) and (d) Smooth cleavage surface.
Figure 9. SEM images of the interface with T-CNTs. (a) SEM image of T-CNTs to prevent interparticle breaks. (b) A partial enlarged view of Fig. a; (c, d) EDS mapping in the dotted line in Fig. b. (e) Particles in the fracture. (f) The area labeled 2 in Fig. e is partially enlarged.
Table 1. Physical parameters of MCMBs.
D50(µm) TI(wt%) QI(wt%) Volatiles(wt%) Ash(wt%) 12 99.20 96.30 7.68 0.25 Note: *TI: Toluene insolubles. *QI: Quinoline insolubles. 
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Table 3. The combination properties of different samples.
Sample Density
(g·cm−3)Volume
shrinkage (%)Open
porosity (%)Flexural
strength (MPa)MCMB 1.796 32.86 14.56 14.29 MCMB with
0.40% CNTs1.827 34.39 11.59 19.46 MCMB with
0.40% T-CNTs1.848 35.98 8.48 24.58
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Table 4. CTE and isotropic ratios of graphite samples with different T-CNTs contents.
Sample CTE (10−6/K) Isotropy ratio Axial Radial MCMB 5.48 5.13 1.07 MCMB with 0.25% T-CNTs 5.08 4.93 1.03 MCMB with 0.40% T-CNTs 5.15 5.05 1.02
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Table 5. Degree of graphitization of CNT/MCMB graphite samples calculated by XRD results.
Sample 2θ (°) d002 (nm) Graphitization degree (%) MCMB 26.30 0.3385 64.0 MCMB with 0.25% CNTs 26.33 0.3382 67.4 MCMB with 0.40% CNTs 26.35 0.3379 70.9 MCMB with 0.70% CNTs 26.30 0.3385 64.0
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Table 6. Degree of graphitization of T-CNT/MCMB graphite samples calculated by XRD results.
Sample 2θ(°) d002(nm) Graphitization degree(%) MCMB 26.30 0.3385 64.0 MCMB with 0.10% T-CNTs 26.30 03385 64.0 MCMB with 0.25% T-CNTs 26.34 0.3380 69.8 MCMB with 0.40% T-CNTs 26.36 0.3377 73.3 MCMB with 0.75% T-CNTs 26.38 0.3375 75.6
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