Research on the thickness effect and micro-fracture mechanism of graphite sheets with layered structures

Qiu, Tian; Liang, LiHong

doi:10.1016/j.diamond.2024.110908

Cited by 3 publications

(1 citation statement)

References 79 publications

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“…This paper explores the physical, mechanical properties [ 19 , 20 , 21 , 22 ] and GF’s structural characteristics [ 23 ] depending on the rolling modes under identical conditions for obtaining material from natural graphite for their manufacture. The process of producing GFs involves several steps.…”

Section: Introductionmentioning

confidence: 99%

The Influence of Machining Conditions on the Orientation of Nanocrystallites and Anisotropy of Physical and Mechanical Properties of Flexible Graphite Foils

Shulyak,

Morozov,

Ivanov

et al. 2024

Nanomaterials

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The physical and mechanical properties and structural condition of flexible graphite foils produced by processing natural graphite with nitric acid, hydrolysis, thermal expansion of graphite and subsequent rolling were studied. The processes of obtaining materials and changing their characteristics has been thoroughly described and demonstrated. The structural transformations of graphite in the manufacture of foils were studied by X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM). A decrease in the average size of the coherent scattering regions (CSR) of nanocrystallites was revealed during the transition from natural graphite to thermally expanded graphite from 57.3 nm to 20.5 nm at a temperature of 900 °C. The rolling pressure ranged from 0.05 MPa to 72.5 MPa. The thickness of the flexible graphite foils varied from 0.11 mm to 0.75 mm, the density—from 0.70 to 1.75 g/cm3. It was shown that with an increase in density within these limits, the compressibility of the graphite foil decreased from 65% to 9%, the recoverability increased from 5% to 60%, and the resiliency decreased from 10% to 6%, which is explained by the structural features of nanocrystallites. The properties’ anisotropy of graphite foils was studied. The tensile strength increased with increasing density from 3.0 MPa (ρ = 0.7 g/cm3) to 14.0 MPa (ρ = 1.75 g/cm3) both in the rolling direction L and across T. At the same time, the anisotropy of physical and mechanical properties increased with an increase in density along L and T to 12% with absolute values of 14.0 MPa against 12.5 MPa at a thickness of 200 μm. Expressed anisotropy was observed along L and T when studying the misorientation angles of nanocrystallites: at ρ = 0.7 g/cm3, it was from 13.4° to 14.4° (up to 5% at the same thickness); at ρ = 1.3 g/cm3—from 11.0° to 12.8° (up to 7%); at ρ = 1.75 g/cm3—from 10.9° to 12.4° (up to 11%). It was found that in graphite foils, there was an increase in the coherent scattering regions in nanocrystallites with an increase in density from 24.8 nm to 49.6 nm. The observed effect can be explained by the coagulation of nanocrystallites by enhancing the Van der Waals interaction between the surface planes of coaxial nanocrystallites, which is accompanied by an increase in microstrains. The results obtained can help discover the mechanism of deformation of porous graphite foils. The obtained results can help discover the deformation mechanism of porous graphite foils. We assume that this will help predict the material behavior under industrial operating conditions of products based flexible graphite foils.

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Section: Introductionmentioning

confidence: 99%

The Influence of Machining Conditions on the Orientation of Nanocrystallites and Anisotropy of Physical and Mechanical Properties of Flexible Graphite Foils

Shulyak,

Morozov,

Ivanov

et al. 2024

Nanomaterials

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An approach based on gamma-ray transmission technique and artificial neural network for accurately measuring the thickness of various materials

Trang,

Linh,

Thanh

et al. 2024

Nucl Technol Radiat Prot

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This paper presents an approach based on the gamma-ray transmission technique and artificial neural network for accurately measuring the thickness of various materials in flat sheet form. The gamma-ray transmission system comprises a NaI(Tl) scintillation detector coupled with a 137Cs radioactive source. The artificial neural network model predicts the sample thickness through three input features: mass density, linear attenuation coefficient, and ln(R) - where R represents the ratio of areas under the 662 keV peak in spectra acquired from measurements with and without the sample. The artificial neural network model was trained using simulation data generated by MCNP6 code, facilitating the creation of comprehensive datasets covering diverse material types and thickness variations at a low cost. Hyperparameters of the artificial neural network model were defined by several optimization methods, such as hyperband-bayesian, tree-structured Parzen estimator, and random search, to establish an optimal artificial neural network architecture. Subsequently, the optimal artificial neural network model was deployed to predict the thickness of graphite, aluminum, copper, steel, and polymethyl methacrylate sheets, using input data obtained from the experiments. The results showed a good agreement between predicted and reference thicknesses, with a maximum relative deviation of 1.94 % and an average relative deviation of 0.52%.

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Friction in Adhesive Contact Between a Rough Hard Indenter and Smooth Soft Elastomer Layer

Lyashenko,

Pham,

Popov

2024

Machines

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The friction between a hard steel indenter and a soft elastomer is studied experimentally. To investigate the influence of roughness, a series of experiments was conducted utilizing an indenter with varying degrees of surface roughness. There is a strong adhesive interaction between the contacting bodies and the friction force is proportional to the real contact area. It has been shown that as the amplitude of roughness increases, the friction force initially rises due to the deformable elastomer filling the gaps between the roughness features, thereby increasing the real contact area. An increase in the roughness amplitude results in a more regular dependence of the friction force on the tangential displacement of the indenter. High-amplitude roughness prevents the propagation of elastic deformation waves (Schallamach waves) within the contact, which are responsible for the establishment of a “stick–slip” type of friction regime. The results of this study are of interest for technical applications in mechanical engineering, particularly those involving the production of rubber seals.

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Research on the thickness effect and micro-fracture mechanism of graphite sheets with layered structures

Cited by 3 publications

References 79 publications

The Influence of Machining Conditions on the Orientation of Nanocrystallites and Anisotropy of Physical and Mechanical Properties of Flexible Graphite Foils

The Influence of Machining Conditions on the Orientation of Nanocrystallites and Anisotropy of Physical and Mechanical Properties of Flexible Graphite Foils

An approach based on gamma-ray transmission technique and artificial neural network for accurately measuring the thickness of various materials

Friction in Adhesive Contact Between a Rough Hard Indenter and Smooth Soft Elastomer Layer

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