•The PF filler in pores of IG-110 shrinks after irradiation.•The irradiated densified isostatic graphite has smaller change ratio of La.•The irradiation behavior depends on the initial graphitization ...degree of graphite.
Iso-molded nuclear graphite (IG-110) was infiltrated with phenol–formaldehyde (PF) resin to get the densified isostatic graphite with different bulk density (IG-110-PF, 1.86 g/cm3 and IG-110-PF-D, 1.91 g/cm3). The IG-110-PF and IG-110-PF-D samples were irradiated with 7 MeV Xe26+ to study their surface topography and microstructure evolution. The impregnation process of PF resin affects the initial graphitization degree of graphite, which lead to the difference in irradiation behavior. Due to the irradiation-induced graphitization, the PF filler (carbonized products of PF resin infiltrated into pores) in pores of IG-110 shrinks after irradiation, which confirmed by the smaller change ratio of crystallite size along the a-axis direction (La) in IG-110-PF and IG-110-PF-D after irradiation than IG-110. La of IG-110-PF-D decreased with the dose increase, resulting from the introduction of irradiation-induced in-plane defects, which is similar to IG-110.The increase in La of PF filler in IG-110-PF and decrease of increase rate in dislocation density after irradiation with surface irradiation dose of 0.02–0.11dpa, provide supporting evidence for the change of PF filler. The difference in irradiation behavior confirms that disordered structure of PF filler and initial crystallinity play an important role in microstructure evolution.
With the proposal of the two-carbon goal, energy conservation and emission reduction will become the focus of China’s energy system in the future for a long time to come. The establishment of a ...complete and efficient carbon traceability system will play an important role in promoting carbon emission reduction in the power system. Based on blockchain, this paper uses the consensus mechanism, time stamp, decentralization features, smart contract and other functions of blockchain, combined with the power flow calculation and the characteristics related to carbon emission and active power of the generator set, to obtain the corresponding carbon emission intensity of the generator set and carbon flow rate. It realizes the calculation and tracing of carbon emission flow in power distribution network and ensures the reliability of carbon traceability results, high efficiency of information transmission and transparency of traceability process. Firstly, based on the characteristics of the master-slave multi-chain structure in the consortium chain, In this paper, high-voltage substation nodes are the main chain nodes, and carbon flow tracing and calculation are carried out for the associated low-voltage substations, and the information of high-voltage or low-voltage substation nodes is guaranteed to be tamper-free through the hash anchoring method. The master-slave multi-chain model adopted in this paper is that the main chain adopts EA-DPoS (Evaluation and Agent-DPoS) algorithm, the slave chain adopts improved PBFT algorithm, and the comprehensive evaluation and reward and punishment mechanism are introduced to complete the consensus. Secondly, considering the security requirements of the power system data and the fact that some nodes of the distribution network do not have powerful computing resources comparable to those of the power grid company or major nodes, this paper encrypts and decrypts relevant data in the main chain node by combining the smart contract of blockchain. Meanwhile, cloud service providers with computing resources are responsible for generator power distribution combined with power flow calculation and carbon emission intensity calculation of the generator set. The power grid company adopts the cloud computing framework based on the double check mechanism to calculate the carbon flow rate while verifying the correct calculation results of the cloud service provider, and finally realizes the safe and accurate tracing of the carbon flow of the distribution network.
With the power data becoming more and more complex, it is of great significance to reduce the dimension and reconstruct the power data for the subsequent processing and application of power big data. ...This paper presents an algorithm based on variational mode decomposition (VMD) decomposition and orthogonal matching pursuit (OMP) reconstruction to reduce the dimension of power load data. Firstly, VMD method is used to decompose and filter the power load data; Secondly, K-means clustering algorithm is used to synthesize the decomposed data mode into a cluster center data set. Then, the data set is used as a dictionary; Thirdly, an OMP algorithm is proposed to select the elements to be reconstructed in the dictionary. And the corresponding data weights are given to reconstruct the load data with high-precision. As a result, the dimensionality of massive load data is reduced automatically. Finally, this paper builds a flexible load data dimensionality reduction model based on VMD method to verify the proposed method.
Two forms of fine-grained isotropic graphite, derived from mixed fillers by the isostatic pressing method, NG (filler with 100% natural graphite flake) and 75N25C-G (mixed filler with 75 wt.% natural ...graphite flake and 25 wt.% calcined coke) were prepared and irradiated with 7 MeV Xe26+ to investigate its irradiation behaviors. Grazing incidence X-ray diffraction and Raman spectra show that the initial graphitization degree of 75N25C-G is lower than that of NG, but the crystallite sizes are larger due to calcined coke in the filler particles. After irradiation, the stacking height of crystallite sizes along c-axis directions (Lc) of NG increased, and Lc of 75N25C-G decreased. This can be attributed to irradiation-induced catalytic graphitization of calcined coke, and is also the reason that the dislocation density of 75N25C-G increases slower than that of NG. After irradiation, the crystallite sizes along a-axis directions (La) of NG and 75N25C-G reduced, but this trend was more obvious in irradiated 75N25C-G; this was closely related to the change of the surface morphology. The results show that the effect of the content of natural graphite flakes in the filler on the initial graphitization degree determines the difference in microstructure evolution caused by irradiation.
Infiltration studies were performed on uncoated nuclear graphite and isotropic pyrolytic carbon (PyC) coated graphite in molten FLiNaK salt at 650°C under argon atmosphere at 1, 3 and 5atm. Uncoated ...graphite shows weight gain more obviously than that of PyC coated graphite. Nuclear graphite with PyC coating exhibits excellent infiltration resistance in molten salt due to the small open porosity as conformed from scanning electron microscopy and mercury injection experiments.
Isotropic pyrolytic carbon (IPyC) prepared at 1300°C by chemical vapor deposition was implanted with 129Xe26+ ions to obtain a wide range of information and understanding about the coating materials ...in nuclear energy field. Microstructure of the pristine and ion-implanted IPyC on nuclear graphite substrate was firstly investigated using polarized light microscopy, scanning and transmission electron microscopy, X-ray diffraction, Raman spectroscopy, nanoindentation, and X-ray photoemission spectroscopy. It was demonstrated that the Xe ion irradiation resulted in concurrent changes in both physical and chemical structures of our standard polycrystalline sample. Influences of the thermal annealing temperature on the properties of the implanted IPyC at 500 and 1000°C were also studied. Ion-irradiation gave rise to the formation of structural deterioration along a and c axis, accompanying with the appearance of widespread clastic morphology among the irradiated zone of IPyC. There was a dose window that could be used to tune the mechanical properties of IPyC: the nanohardness and Young’s modulus increased after an irradiation, but decreased as the amorphization was reached.
Mesophase pitch based graphite foams with different thermal properties and cell structures were infiltrated with glass by pressureless infiltration to prepare potential alternative composites for ...cooling electronics. Microstructure, thermal diffusivity and coefficient of thermal expansion (CTE) of the obtained composites were investigated. It was demonstrated that there was excellent wettability of the graphite foam by molten glass, and the foam framework was retained well after infiltration, which could facilitate good heat transfer throughout the composites. The highest thermal diffusivity of the composites reached 202.80
mm
2/s with a density of 3.81
g/cm
3. And its CTE value was 4.53
ppm/K, much lower than the corresponding calculated result (7.46
ppm/K) based on a simple “rule of mixtures” without considering the space limitations of the graphite foams. Thus, the mechanical interlocking within the space limitations of the graphite network played a crucial role in limiting the thermal expansion of the glass. The CTEs of the graphite foam/glass composites varied from 4.53 to 7.40
ppm/K depending on the graphite foam density which varied from 0.82 to 0.48
g/cm
3. The CTEs were a good match to those of semiconductor chips and packaging materials.
Presented in this article are mechanical property and microstructural data for fluoride molten salt infiltrated graphite at high temperature. Four infiltration pressures (0 kPa, 450 kPa, 600 kPa, and ...1000 kPa) and two kinds of graphite (IG-110 and NG-CT-10) were used during molten salt infiltration. After fluoride molten salt infiltration, compression testing and tension testing were performed at 700 °C to determine compressive strength, tensile strength, softening coefficient, stress–strain curve, and absorbed energy. Utilizing scanning electron microscopy (SEM) applied to fracture fragments, SEM micrographs for the fracture surface of molten salt infiltrated graphite and virgin graphite were determined.
As a phase change material, Wood's alloy is infiltrated into the compressed expanded natural graphite (CENG) in an attempt to improve the thermal conductivity of the alloy. The thermal conductivity ...of the CENG/Wood's alloy composite depends on the bulk density of the CENG. Thermal conductivity of the composites can be 2.8–5.8 times than that of the Wood's alloy. On the other hand, the latent heat of the composites ranges from 29.27 to 34.20J/g. The graphite does not undergo a phase change, so the latent heat would be expected to be linear with the amount of Wood's alloy. The composites have a potential use in the heat sink of the electronic device.
► Compressed expanded natural graphite (CENG) improved the thermal performance of Wood's alloy. ► Thermal conductivity of the CENG/Wood's alloy composites is ∼5 times than that of the Wood's alloy. ► The latent heat would be expected to be linear with the amount of Wood's alloy. ► The composites have a potential use in the heat sink of the electronic device.
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