Morozov Nikolai S, Demchenko David V, Bukovsky Pavel O, Yakovenko Anastasiya A, Shulyak Vladimir A, Gracheva Alexandra V, Chebotarev Sergei N, Goryacheva Irina G, Avdeev Viktor V
Lomonosov Moscow State University, Moscow 119991, Russia.
Ishlinsky Institute for Problems in Mechanics RAS, Moscow 119526, Russia.
Nanomaterials (Basel). 2024 Sep 15;14(18):1499. doi: 10.3390/nano14181499.
This study investigates the tribological properties of graphite foils (GF) with densities of 1.0, 1.3, and 1.6 g/cm, produced from purified natural graphite of different particle sizes (40-80 μm, 160-200 μm, >500 μm). Surface roughness was measured after cold rolling and friction testing at static (0.001 mm/s) and dynamic conditions (0.1 Hz and 1 Hz). Results showed that static friction tests yielded similar roughness values ( ≈ 0.5-0.7 μm, ≈ 0.5-1.0 μm) across all densities and particle sizes. Dynamic friction tests revealed increased roughness ( from 0.7 to 3.5 μm, from 1.0 to 6.0-7.0 μm). Friction coefficients (µ) decreased with higher sliding speeds, ranging from 0.22 to 0.13. GF with 40-80 μm particles had the lowest friction coefficient (µ = 0.13-0.15), while 160-200 μm particles had the highest (µ = 0.15-0.22). Density changes had minimal impact on friction for the 40-80 μm fraction but reduced friction for the 160-200 μm fraction. Young's modulus increased with density and decreased with particle size, showing values from 127-274 MPa for 40-80 μm, 104-212 MPa for 160-200 μm, and 82-184 MPa for >500 μm. The stress-strain state in the graphite foil samples was simulated under normal and tangential loads. This makes it possible to investigate the effect of the anisotropy of the material on the stress concentration inside the sample, as well as to estimate the elasticity modulus under normal compression. Structural analyses indicated greater plastic deformation in GF with 40-80 μm particles, reducing coherent-scattering region size from 28 nm to 24 nm. GF samples from 160-200 μm and >500 μm fractions showed similar changes, expanding with density increase from 18 nm to 22 nm. Misorientation angles of GF nanocrystallites decreased from 30° to 27° along the rolling direction (RD). The coherent scattering regions of GF with 40-80 μm particles increased, but no significant changes in the coherent scattering regions were observed for the 160-200 μm and >500 μm fractions during dynamic friction tests. Microstrains and residual macrostresses in GF increased with density for all fractions, expanding under higher friction-induced loads. Higher values of both stresses indicate a higher level of accumulated deformation, which appears to be an additional factor affecting the samples during friction testing. This is reflected in the correlation of the results with the roughness and friction coefficient data of the tested samples.
本研究调查了由不同粒径（40 - 80μm、160 - 200μm、>500μm）的纯化天然石墨制成的密度为1.0、1.3和1.6 g/cm³的石墨箔（GF）的摩擦学性能。在冷轧后以及在静态（0.001 mm/s）和动态条件（0.1 Hz和1 Hz）下进行摩擦测试后测量了表面粗糙度。结果表明，所有密度和粒径的静态摩擦测试产生了相似的粗糙度值（≈0.5 - 0.7μm，≈0.5 - 1.0μm）。动态摩擦测试显示粗糙度增加（从0.7μm增加到3.5μm，从1.0μm增加到6.0 - 7.0μm）。摩擦系数（μ）随着滑动速度的提高而降低，范围从0.22到0.13。粒径为40 - 80μm的GF具有最低的摩擦系数（μ = 0.13 - 0.15），而粒径为160 - 200μm的GF具有最高的摩擦系数（μ = 0.15 - 0.22）。密度变化对40 - 80μm粒径部分的摩擦影响最小，但对160 - 200μm粒径部分的摩擦有降低作用。杨氏模量随密度增加而增加，随粒径减小而减小，40 - 80μm粒径的GF的杨氏模量值为127 - 274 MPa，160 - 200μm粒径的为104 - 212 MPa，>500μm粒径的为82 - 184 MPa。在法向和切向载荷下模拟了石墨箔样品中的应力 - 应变状态。这使得研究材料各向异性对样品内部应力集中的影响以及估计法向压缩下的弹性模量成为可能。结构分析表明，粒径为40 - 80μm的GF中塑性变形更大，相干散射区域尺寸从28 nm减小到24 nm。粒径为160 - 200μm和>500μm部分的GF样品显示出类似的变化，随着密度增加从18 nm扩展到22 nm。GF纳米微晶的取向差角沿轧制方向（RD）从30°减小到27°。粒径为40 - 80μm的GF的相干散射区域增加，但在动态摩擦测试期间，粒径为160 - 200μm和>500μm部分的相干散射区域未观察到显著变化。所有部分的GF中的微观应变和残余宏观应力随密度增加而增加，在更高的摩擦诱导载荷下扩展。这两种应力的较高值表明累积变形水平较高，这似乎是摩擦测试期间影响样品的另一个因素。这反映在结果与测试样品的粗糙度和摩擦系数数据的相关性中。
