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Article

Established Model on Polycrystalline Graphene Oxide and Analysis of Mechanical Characteristic

by
Xu Xu
,
Chaoqi Xiong
,
Shaoping Mao
and
Wenjuan Yao
*
School of Mechanics and Engineering Science, Shanghai University, Shanghai 200444, China
*
Author to whom correspondence should be addressed.
Crystals 2022, 12(3), 382; https://doi.org/10.3390/cryst12030382
Submission received: 15 February 2022 / Revised: 7 March 2022 / Accepted: 9 March 2022 / Published: 12 March 2022
(This article belongs to the Special Issue 2D Crystalline Nanomaterials)
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Abstract

:
It may cause more novel physical effects that the combination with in-plane defects induced by grain boundaries (GBs) and quasi three-dimensional system induced by oxidation functional group. Different from those in blocks, these new physical effects play a significant role in the mechanical properties and transport behavior. Based on the configuration design, we investigate the in-plane and out-plane geometric deformation caused by the coupling of GBs and oxygen-containing functional groups and establish a mechanical model for the optimal design of the target spatial structure. The results show that the strain rate remarkably affect the tensile properties of polycrystalline graphene oxide (PGO). Under high oxygen content (R = 50%), with the increasing strain rate, the PGO is much closer to ductile fracture, and the ultimate strain and stress will correspondingly grow. The growth of temperature reduces the ultimate stress of PGO, but the ultimate strain remains constant. When the functional groups are distributed at the edge of the GBs, the overall strength decreases the most, followed by the distribution on the GBs. Meanwhile, the strength of PGO reaches the greatest value when the functional groups are distributed away from the GBs.

1. Introduction

Graphene is a two-dimensional material with single-layer atom thickness, composed of sp2 hybridized carbon atoms. Graphene has attracted extensive attention due to its excellent mechanical properties and unusual electrical properties. Graphene was first produced by Geim et al. in 2004 using a scotch tape method [1]. Chemical vapor deposition (CVD) [2,3] and exfoliation techniques [4,5] are most the common synthesis techniques. Large-scale prepared graphene using existing technology often has various defects, such as vacancy defects, dislocation defects, Stone-Wales defects, and so on. These defects affect the mechanical properties of graphene. In recent years, many research groups have investigated the regulation of defects on the physical properties of two-dimensional materials such as graphene [6,7,8,9,10,11,12]. Qin XM et al. studied the mechanical properties of graphene with vacancy defects and found that when the vacancy was 1 nm2, the failure strength decreased by about 16.1% [13]. Grain boundaries (GBs) can be regarded as a series of structures formed by a periodic arrangement of defects, and the GBs formed by Stone-Wales defects [14] are the most common. A carbon-carbon bond is rotated by 90° and six-membered rings are transformed into five-seven rings.
GBs greatly affect the mechanical properties of graphene. Because the GBs change the molecular structure of graphene, stress concentration occurs at the GBs when bearing load, which may reduce the mechanical properties of graphene. Several experimental studies reported degradation of the mechanical properties of graphene due to GBs [15]. Song Z et al. [16] studied the fracture process of polycrystalline graphene and discovered that the presence of GBs can reduce the strength of graphene by 50% or more, and cracks preferentially start at the junction of the GBs. Grantab et al. [17] found that the strength of GBs with large misorientation angles is close to that of perfect graphene. Liu et al. [18] found that the distribution of GB dislocations is, in addition to the misorientation angle, also an important factor in determining the failure strength. For GBs featuring a uniform dislocation distribution, a higher misorientation angle will yield a higher failure strength. For GBs with a non-uniform dislocation distribution, the failure strength decreases significantly. Lee et al. [19] believe that the GBs only reduced the strength of graphene slightly. Rasool et al. [20] also verified that the ultimate strength of high-tilt polycrystalline graphene (80~83 GPa) is close to the strength of perfect single-crystal graphene (90~94 GPa) by experiments. Therefore, the study of the influence of graphene defects has great scientific significance and practical value for the large-scale application of graphene in reality.
Graphene oxide (GO) is a graphene-derived compound with unique layered structure [21]. By connecting oxygen-containing functional groups such as hydroxyl, epoxy, and carboxyl groups on both sides of the graphene sheets, the dispersibility, hydrophilicity, and reactivity are improved significantly. This makes the graphene composite with other materials better, improving the mechanical properties. Oxidation of graphite followed by exfoliation to separate graphene layers is by far the most cost-effective and widely studied method for the commercial-scale production of graphene oxides [22]. Zhang Y et al. [23] studied the effects of polymer functional groups on GO/polymer interface structure, dynamics, and mechanical properties. It was found that the functional group polarity of the polymer can promote the affinity between polymer and GO. Chen et al. [24] uncovered the underlying mechanism that mixed solvent layers are formed steadily on the surface of GO sheet and screen the interactions between them and provided a facile method to prepare GO suspensions with high dispersion stability. Also, a recent report [25] described the molecular structure evolutions, dynamics, and mechanical properties of multilayer graphene oxide under different water contents through molecular dynamics.
Up until now, separate studies of polycrystalline graphene or GO have been relatively common, but a consideration of combining the two defects together has not been reported yet. Thus, this paper combined GBs and oxygen-containing functional groups and established a new polycrystalline graphene oxide (PGO) model. By studying the different distributions of functional groups, we revealed the effects of defects coupling on the mechanical properties of PGO, in order to make it possible to create unprecedented physical characteristics by using a mixed dimension (combination of sp2 and sp3) space design in the future.

2. Model Establishment

Based on the principle of molecular dynamics, the ReaxFF potential function [26,27] obtained from the theory of quantum mechanics is chosen in this paper. NPT ensemble is used, and under this ensemble the total number of particles in the system, the pressure, and temperature of system remain constant. The Nose-Hoover thermostat is used for the temperature control and periodic boundary condition is used for box.
Two sheets of the same graphene are rotated at a certain angle, and then the edges are connected with five-membered, six-membered, and seven-membered rings. GBs are formed by periodic arrangement of carbon rings formed by non-six-membered rings. If two sheets of graphene rotate in opposite directions and at the same angle, the structure formed is symmetrical polycrystalline graphene. GBs of models can be described by the misorientation angle: θ = θL + θR (θL and θR are the rotation angles of the left and right parts, respectively). When θL = θR, symmetrical GBs are formed. Figure 1 shows the grain boundaries with a misorientation angle of 21.8° and 30°.
Based on the polycrystalline graphene model, the hydroxyl and epoxy functional groups were introduced to establish the PGO model. The functional groups are randomly and evenly distributed on both sides of the graphene sheet. The oxygen-containing functional groups’ densities, R, is an important definition of graphene oxide. It can be defined as R = N′/NC × 100%, where NC is the total number of carbon atoms and N′ is the number of carbon atoms connected with functional groups. This paper changes the parameter R of the model by adding or subtracting the number of hydroxyl and epoxy groups. As shown in Figure 2, two PGO models are established with a misorientation angle of 21.8° and 30°, respectively. The size of PGO model is 61.49 Å long, 63.90 Å wide, and R = 50%. The ratio of hydroxyl group to epoxy group is 1:1.
In order to study the effect of functional group distribution on the mechanical properties of PGO, three different PGO models were further established in this paper. As shown in Figure 3, (a) is the model in which the functional groups are distributed on GBs, (b) is the model in which the functional groups are distributed beside GBs, and (c) is the model in which the functional groups are distributed away from GBs. In Figure 3b,c, the functional groups distribute in a 61.1 Å × 6.03 Å area, which has the same size. Local functional groups densities R = 50%, the ratio of hydroxyl group to epoxy group is 1:1, which is the same as the functional groups’ full coverage model.

3. Results and Discussion

3.1. Model Validation

In order to verify the correctness of the simulation method and model, uniaxial tensile tests were carried out on graphene, polycrystalline graphene, and graphene oxide. Airebo force field was used for graphene and polycrystalline graphene, Reaxff force field was used for GO. Adopting the method described in the previous section, the stress-strain curves of the three models can be obtained. The results are shown in Figure 4.
The ultimate stress of the perfect graphene established in this paper is 126 GPa, compared with reference [28], the difference is about 8.03%, and it is consistent with the results obtained by most scholars [29,30,31]. The misorientation angle of polycrystalline graphene is 21.8°, the ultimate stress is 96 GPa, and the difference is about 8.57% compared with the reference [32]. The GO validation model established in this paper has the functional groups’ density as 2.44%, which is the same as the reference [33]. The ultimate stress of GO model is 96.18 GPa and the difference is about 12.56% compared with the reference. Due to the result of the comparison from the above set of figures, it can be considered that the molecular configuration of polycrystalline graphene oxide established in this paper is reasonable.
Figure 5 shows the stress-strain curve of GO with different functional groups densities. The ultimate stress is 82.2 GPa at a density of 5%. When it grows to 25%, the ultimate stress becomes 50.6 GPa.

3.2. The Effect of Strain Rate

Strain rate is a physical quantity indicating the deformation speed of materials. The research shows that strain rate has an important influence on the mechanical properties and deformation mechanism of materials. The ultimate stress is defined as the stress reached when the bond fracture occurs for the first time in PGO, and the maximum stress is defined as the maximum stress that can be achieved during the whole tensile process.
Figure 6 shows the dynamic fracture process of crack growth when PGO is tensioned at the strain rate of 1 × 10−5 fs−1, R = 50%, θ = 21.8°. At the beginning of the tensile phase, elastic deformation occurred in PGO, and the stress and strain increased linearly. When the strain reached 0.14 (Shown as Figure 6a), the breakage of the C-C bond occurred on the right side of GB and the load withstood the decrease instantaneously, and this part of the load was transmitted to other regions by PGO grid. PGO can continue to bear tensile loads after a fracture occurs due to the breakage and regeneration of chemical bonds during the tensile process of PGO. During the process of tension PGO to a strain of 0.26 (Figure 6b), multiple C-C bond fractures occurred at the edge of GB, resulting in a significant decrease in the load. When the strain reached 0.36 (Figure 6c), several small cracks expanded into a large crack, and PGO broke completely. In this process, the stress will fluctuate due to bond fracture and regeneration. The ReaxFF force field can reflect these changes in chemical bonds, so the stress-strain curve will oscillate irregularly after reaching the ultimate stress.
When the strain rate increased to 2.5 × 10−4 fs−1, the tensile stress-strain curve of PGO changed significantly. As shown in Figure 7, the stress-strain curve becomes smooth. Compared with the strain rate of 1 × 10−5 fs−1, there is no obvious cliff as in the decrease in stress. When the strain is 0.1 (Figure 7a), the C-C bond in some regions of PGO was broken. However, due to the regeneration of the bond, it did not cause too much impact on the whole. When the strain reaches 0.2 (Figure 7b), a large number of C-C bond fractures occur along the edge of the GB, and bond fractures also occur in some areas far away from the GB. After the strain exceeds 0.24 (Figure 7c), the fracture of C-C bonds at various places expands and develops into larger cracks. As the tension progresses, the remaining bonds that still bear the load gradually break. The overall load of the PGO decreases evenly until the PGO completely breaks. Due to the increase of strain rate, the carbon atoms in PGO cannot consume the work done by external force by changing their positions in a short time. The stress distribution in the whole system is uneven. When local stress concentration occurs and the tensile strength reaches the limit earlier, then the fracture occurs. Other parts will not have reached the strength limit and continue to bear the load, so the PGO will not break immediately. Therefore, the whole PGO model will not break immediately under the tension of a large strain rate, but will undergo tensile deformation for a period of time. The cracks everywhere will expand and develop, gradually lose the tensile capacity, and finally break completely.
Figure 8 shows the variation of tensile ultimate stress and ultimate strain of PGO with the strain rate. Take PGO with temperature 100 K, R = 50%, θ = 21.8° as an example, simulating six different strain rates. The results show that the ultimate tensile stress and ultimate tensile strain of PGO increase with the increase of strain rate. The strain rate increases from 1 × 10−5 fs−1 to 2.5 × 10−4 fs−1, and the ultimate stress increases by 13.97 GPa, about 37.26%, the ultimate strain increases by 0.042 and about 36.84%. The ultimate stress and ultimate strain growth rates are approximately the same, and both have approximately linear growth.

3.3. The Effect of Temperature

Temperature is an important factor that affects the mechanical properties of materials. The mechanical properties of materials will show differences under different temperature conditions. Uniaxial tensile simulation of PGO at six temperatures from 100 K to 1250 K was carried out, including extreme low temperature (100 K), room temperature (300 K), high temperature (500 K, 750 K), and extreme high temperature (1000 K, 1250 K). As can be seen from Figure 9, during the tensile process of PGO, the elastic deformation process occurs first. At this time, there is no bond fracture in PGO, and the stress-strain curve changes almost linearly. When the tension continues, the C-C bond breaks in PGO, and PGO reaches the ultimate stress. At this time, the deformation is irreversible. PGO disperses the stress and continues to bear the tensile load by rearranging the position of carbon atoms. With the progress of tension, the load on the PGO continues to rise to the maximum load. At this time, the small cracks in PGO expand, and the bearing stress begins to decrease significantly until PGO is completely broken.
The mechanical property data of PGO obtained by simulation are listed in Table 1. Compared with room temperature (300 K), the ultimate stress at extreme low temperature (100 K) is increased by 12.86%; the maximum stress is increased by 3.16%. At extreme high temperature (1250 K), the ultimate stress is reduced by 37.27% and the maximum stress is reduced by 20.29%. In general, with the increase of temperature, the ultimate stress, maximum stress and Young’s modulus of PGO will decrease, but the maximum change of ultimate strain is only 0.015 and fluctuates between 0.105 and 0.120. Therefore, it can be considered that the ultimate strain will not be affected when the temperature changes.
Figure 10 reflects the changing trend of ultimate stress and maximum stress in PGO with the increase of temperature. It can be found that when the temperature increases, both the ultimate stress and maximum stress decrease, but the decline rate of maximum stress is significantly lower than the ultimate stress. It can also be seen from Figure 11 that the higher the maximum stress is, the higher the temperature, and the greater the difference between the ultimate stress and the maximum stress will be.
As shown in Figure 12, no vacancies are found in the structure at room temperature (Figure 12a). The removal of atoms (mainly functional groups, and few carbon atoms) can be observed when the temperature is 1250 K, which shows that the temperature greatly increases the energy of the atom. The energy required for the atom to leave the original position is reduced significantly, which directly leads to the reduction of tensile strength.

3.4. The Effect of Oxygen-Containing Functional Group Position

During the preparation of PGO, the positions of functional groups are randomly distributed, and the bond lengths and bond angles have certain differences. In order to study the effect of the distribution position of oxygen-containing functional groups in PGO on the mechanical properties, the same uniaxial tensile simulation was carried out for three PGO models with different distribution positions of functional groups. The oxygen-containing functional groups are distributed on the GB, beside the GB, and far away from the GB. The three functional group distribution models with misorientation angle of 21.8° are PGO-1, PGO-2, and PGO-3. The three functional group distribution models with misorientation angle of 30° are PGO-4, PGO-5, and PGO-6. Because the structure at the GB is different from that of normal graphene, the calculated functional groups density is local. The two models (PGO-2 and PGO-3, and PGO-5 and PGO-6) in which functional groups are distributed at the amorphous boundary, have the same functional group distribution area. The main parameters are shown in Table 2. The local functional groups densities are about 50%. The functional group is the combination of 50% epoxy group and 50% hydroxyl group. The established models are shown in Figure 13.
Figure 14 shows the tensile fracture state of three models with a misorientation angle of 21.8°, and Table 3 shows the uniaxial tensile data of PGO under different functional group distribution. It can be found that whether it is a misorientation angle of 21.8° or 30°, when the functional groups are distributed far away from the GB, the ultimate stress is the largest, followed by the distribution on the GB. When the functional groups are distributed at the edge of the GB, the ultimate stress that PGO can bear is the lowest. When the functional group is attached to the graphene sheet, it will change the graphene carbon bond from sp2 hybrid to weaker sp3 hybrid, and pull the connected carbon atoms out of the graphene plane, so as to convert the structure from two-dimensional plane structure to three-dimensional space structure, which further weakens the mechanical properties of graphene. When functional groups are distributed on the GB, the influence of GB and functional groups weaken the strength of graphene together. As shown in Figure 14a, the fracture occurs at the GB, but due to the high oxygen content (50%), when the fracture occurs at the GB, the functional groups distributed on the GB produce the regeneration of chemical bonds, buffering and dissipating the tensile energy to a certain extent. When the functional groups are distributed at the edge of the GB, the effect of this coupling still acts on the edge of the GB, as shown in Figure 14b, the fracture occurs at the edge of the GB at this time. Due to the loss of the buffer of functional groups, the ultimate stress will be lower than the PGO model, in which the functional groups are distributed at the GB. For the model in which the functional groups are distributed away from the GB, the two weak regions are far away and have no coupling effect. As shown in Figure 14c, the functional group region with lower strength will fracture first, but its ultimate stress is higher than the other two distribution models.

4. Conclusions

The strain rate greatly affects the mechanical properties of PGO under tension. When PGO stretched at low strain rate, brittle fracture is more likely to occur. However, due to the existence of functional groups and bond recombination, PGO can continue to bear the load until it is completely broken. When the strain rate increases, the tensile stress-strain curve of PGO is more like that of ductile material, and the ultimate stress and ultimate strain in the elastic stage increase linearly. When the temperature rises, the atomic thermal vibration in PGO increases, and the atoms can more easily overcome the constraints of the surrounding atoms and leave the original equilibrium position, resulting in being more prone to fracture under tension. The increase of temperature will reduce the ultimate stress and maximum stress of PGO, and the reduction trend of ultimate stress is greater than the maximum stress. The higher the temperature, the greater the difference between ultimate stress and maximum stress.
The distribution of functional groups will also affect the mechanical properties of PGO. When functional groups are distributed at the edge of GB, the effects of GB and functional groups are coupled to the edge area of grain boundary, and the fracture will occur at the edge of GB. In this case, PGO bears the lowest ultimate stress. When functional groups are distributed on the GB, the effects of GB and functional groups are coupled on the GB, and the fracture occurs in the center of the GB. Due to the existence of functional groups with a high oxygen content, the bond recombination during fracture will consume the work done by the external tensile force to achieve the buffer effect, so that the ultimate stress of this PGO model is higher than that model in which the functional groups are distributed at the edge of GB. When the functional groups are distributed far away from the GB, the weak region caused by the GB and functional groups do not affect each other, and the fracture will occur in the functional group distribution region with lower strength.

Author Contributions

X.X. carried out the work of literature research and study design in the early stage. C.X. and S.M. was responsible for the figure, data collection, and data analysis. W.Y. was mainly responsible for the final data summary and analysis as well as the writing of the article. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Key projects of the National Natural Science Foundation of China, grant number 11932010.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Conflicts of Interest

The authors declare no conflict of interest.

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Crystals 12 00382 g001 550
Figure 1. (a) Grain boundaries with misorientation angle of 21.8°; (b) grain boundaries with misorientation angle of 30°; (c) the cell used in modeling and the rotation mode.
Figure 1. (a) Grain boundaries with misorientation angle of 21.8°; (b) grain boundaries with misorientation angle of 30°; (c) the cell used in modeling and the rotation mode.
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Figure 2. (a) PGO model with misorientation angle of 21.8°; (b) PGO model with misorientation angle of 30°; (c) hydroxyl and epoxy functional groups used in this paper.
Figure 2. (a) PGO model with misorientation angle of 21.8°; (b) PGO model with misorientation angle of 30°; (c) hydroxyl and epoxy functional groups used in this paper.
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Crystals 12 00382 g003 550
Figure 3. (a) The model in which the functional groups are distributed on GBs; (b) the model in which the functional groups are distributed beside GBs; (c) the model in which the functional groups are distributed away from GBs.
Figure 3. (a) The model in which the functional groups are distributed on GBs; (b) the model in which the functional groups are distributed beside GBs; (c) the model in which the functional groups are distributed away from GBs.
Crystals 12 00382 g003
Crystals 12 00382 g004 550
Figure 4. (a) Stress-strain curves of perfect graphene; (b) stress-strain curves of polycrystalline graphene; (c) stress-strain curves of GO.
Figure 4. (a) Stress-strain curves of perfect graphene; (b) stress-strain curves of polycrystalline graphene; (c) stress-strain curves of GO.
Crystals 12 00382 g004
Crystals 12 00382 g005 550
Figure 5. Stress-strain curve of GO with different functional groups density.
Figure 5. Stress-strain curve of GO with different functional groups density.
Crystals 12 00382 g005
Crystals 12 00382 g006 550
Figure 6. Tensile stress-strain curve and dynamic fracture process of PGO under the strain rate of 1 × 10−5 fs−1. (a) PGO at strain of 0.14; (b) PGO at strain of 0.26; (c) PGO at strain of 0.36.
Figure 6. Tensile stress-strain curve and dynamic fracture process of PGO under the strain rate of 1 × 10−5 fs−1. (a) PGO at strain of 0.14; (b) PGO at strain of 0.26; (c) PGO at strain of 0.36.
Crystals 12 00382 g006
Crystals 12 00382 g007 550
Figure 7. Tensile stress-strain curve and dynamic fracture process of PGO under the strain rate of 2.5 × 10−4 fs−1. (a) PGO at strain of 0.1; (b) PGO at strain of 0.2; (c) PGO at strain of 0.24.
Figure 7. Tensile stress-strain curve and dynamic fracture process of PGO under the strain rate of 2.5 × 10−4 fs−1. (a) PGO at strain of 0.1; (b) PGO at strain of 0.2; (c) PGO at strain of 0.24.
Crystals 12 00382 g007
Crystals 12 00382 g008 550
Figure 8. Variation law of ultimate stress and ultimate strain of PGO under different strain rates.
Figure 8. Variation law of ultimate stress and ultimate strain of PGO under different strain rates.
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Crystals 12 00382 g009 550
Figure 9. Stress-strain curves of PGO under uniaxial tension at different temperatures.
Figure 9. Stress-strain curves of PGO under uniaxial tension at different temperatures.
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Crystals 12 00382 g010 550
Figure 10. Ultimate stress and maximum stress of PGO at different temperatures.
Figure 10. Ultimate stress and maximum stress of PGO at different temperatures.
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Crystals 12 00382 g011 550
Figure 11. Variation curve of difference between ultimate stress and maximum stress with temperature.
Figure 11. Variation curve of difference between ultimate stress and maximum stress with temperature.
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Crystals 12 00382 g012 550
Figure 12. Vacancies in the PGO structure at high temperature. (a) PGO tensile process under 300 K; (b) PGO tensile process under 1250 K.
Figure 12. Vacancies in the PGO structure at high temperature. (a) PGO tensile process under 300 K; (b) PGO tensile process under 1250 K.
Crystals 12 00382 g012
Crystals 12 00382 g013 550
Figure 13. Structure diagram of PGO model with different functional group distribution. (a) distributed on GB; (b) distributed at the edge of GB; (c) distributed away from GB.
Figure 13. Structure diagram of PGO model with different functional group distribution. (a) distributed on GB; (b) distributed at the edge of GB; (c) distributed away from GB.
Crystals 12 00382 g013
Crystals 12 00382 g014 550
Figure 14. Tensile fracture states of three functional group distribution models. (a) fracture state of PGO-1; (b) fracture state of PGO-2; (c) fracture state of PGO-3.
Figure 14. Tensile fracture states of three functional group distribution models. (a) fracture state of PGO-1; (b) fracture state of PGO-2; (c) fracture state of PGO-3.
Crystals 12 00382 g014
Table
Table 1. Uniaxial tensile results of PGO under different temperatures.
Table 1. Uniaxial tensile results of PGO under different temperatures.
Temperature (K)Ultimate Stress (GPa)Ultimate StrainMaximum Stress (GPa)Young’s Modulus (GPa)
10037.640.12048.31313.67
30033.510.11846.83283.98
50029.840.12044.17248.67
75026.440.12041.12220.33
100023.180.10538.25220.76
125021.020.11037.33191.09
Table
Table 2. Main parameters of three PGO models with different functional group distributions.
Table 2. Main parameters of three PGO models with different functional group distributions.
Numbers of Local Carbon AtomsMisorientation Angle (°)Oxygen ContentNumbers of Epoxy GroupNumbers of Hydroxyl
PGO-113321.849.6%2222
PGO-215421.849.4%2526
PGO-315421.849.4%2526
PGO-41183050.8%2020
PGO-51533049.7%2526
PGO-61533049.7%2526
Table
Table 3. Uniaxial tensile results using different models.
Table 3. Uniaxial tensile results using different models.
ModelTemperature (K)Ultimate Stress (GPa)Ultimate Strain
1PGO-130048.7010.1128
2PGO-230046.5200.1094
3PGO-330059.4880.1686
4PGO-150046.5840.1052
5PGO-250045.1460.1084
6PGO-350055.2590.1480
7PGO-430053.7850.1146
8PGO-530049.0540.1026
9PGO-630065.2710.1258
10PGO-450049.4400.0854
11PGO-550046.4290.1052
12PGO-650066.8860.1158
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Xu, X.; Xiong, C.; Mao, S.; Yao, W. Established Model on Polycrystalline Graphene Oxide and Analysis of Mechanical Characteristic. Crystals 2022, 12, 382. https://doi.org/10.3390/cryst12030382

AMA Style

Xu X, Xiong C, Mao S, Yao W. Established Model on Polycrystalline Graphene Oxide and Analysis of Mechanical Characteristic. Crystals. 2022; 12(3):382. https://doi.org/10.3390/cryst12030382

Chicago/Turabian Style

Xu, Xu, Chaoqi Xiong, Shaoping Mao, and Wenjuan Yao. 2022. "Established Model on Polycrystalline Graphene Oxide and Analysis of Mechanical Characteristic" Crystals 12, no. 3: 382. https://doi.org/10.3390/cryst12030382

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