Microstructure Of Carbon Materials Research Articles

Tuning the Dielectric and Microwaves Absorption Properties of N-Doped Carbon Nanotubes by Boron Insertion.

It is of great significance to regulate the dielectric parameters and microstructure of carbon materials by elemental doping in pursuing microwave absorption (MA) materials of high performance. In this work, the surface electronic structure of N-doped CNTs was tuned by boron doping, in which the MA performance of CNTs was improved under the synergistic action of B and N atoms. The B,N-doped carbon nanotubes (B,N-CNTs) exhibited excellent MA performance, where the value of minimum reflection loss was −40.04 dB, and the efficient absorption bandwidth reached 4.9 GHz (10.5–15.4 GHz). Appropriate conductance loss and multi-polarization loss provide the main contribution to the MA of B,N-CNTs. This study provides a novel method for the design of CNTs related MA materials.

Molten metal chloride salt template synthesis of N/S co-doped porous carbon nanosheets for supercapacitors

Two-dimensional carbon nanosheets have recently become spotlight in the electrochemical energy storage fields. Herein, an effective and environmental-friendly strategy was developed to prepare ginkgo leaf derived N/S co-doped porous carbon nanosheets (PCNSs) using CaCl2/KCl molten salt as activating/template agent. The CaCl2/KCl as a green and non-toxic template can regulate the pore structure and microstructure of carbon materials. Benefiting from interconnected sheet-like morphology and plenty of heteroatoms (N, S, O) doping, the fabricated carbon-based supercapacitor exhibit good specific capacitance of 150.4 F g−1 at 0.05 A g−1 and splendid cycling performance with 94.2% capacity retention after 10,000 charge-discharge cycles at 1 A g−1.This facile and environmental-friendly activation strategy provides a new way of thinking for developing N, S-doped two-dimensional porous carbon nanosheets for high-performance energy storage devices.

Designing the effective microstructure of lignin-based porous carbon substrate to inhibit the capacity decline for SnO2 anode

As the traditional anode material of lithium-ion batteries, tin dioxide (SnO2) has the characteristics of a high theoretical capacity and stable crystal structure. However, the alloying/de-alloying reaction between tin and lithium ions causes volume expansion and continuously generates an SEI film, which causes the electrode to fall off the current collector and the capacity fade rapidly. Generally, a composite of carbon materials and SnO2 can alleviate the expansion and pulverization phenomena. However, the microstructure of carbon materials is complex and changeable, which makes it difficult to definitively state the influence mechanism of the microstructure on the lithium storage performance of composite materials. Here, three kinds of lignin-based porous carbons (LPCs) with different microstructural characteristics, along with a high graphitization, high specific surface area and hierarchical porosity, are obtained by regulating the process of gas exfoliation and in situ activation. Furthermore, a series of LPC/SnO2 composites are obtained by an ultrasonic dispersion and ball milling method. Electrochemical property results show that the hierarchical porous LPCs are more conducive to the dispersion/coating of SnO2 nanoparticles and that the reversible specific capacity of the electrode material increases from 64 to 620 mA h g−1, effectively mitigating the expansion and pulverization of SnO2 during the lithium storage process.

Correlation between the microstructure of carbon materials and their potassium ion storage performance

Alkali-metal ions storage in carbon materials is of great interests for developing high-performance anodes for batteries. While Li, Na ions storage has been extensively investigated, systematic studies on the correlation between K ions storage and carbon microstructure have rarely been conducted. The large radius of K ions leaves a legitimate question whether the charge storage sites for Li and Na ions are also active for K ions. Herein, electrospun carbon nanofibers are employed as model materials to explore the K-ion storage behaviors in carbon with representative microstructures. By combining in-situ characterization and theoretical calculations, three active sites have been unveiled, including (i) uptake of K-ion by defect sites; (ii) K ions adsorption on isolated graphene sheets in partially disordered carbon; (iii) K ions intercalation between graphene layers for carbon with a high degree of graphitization. A similar reversible capacity around 280 mAh/g is obtained for various carbon structures while their voltage profiles are highly disparate. Remarkably, it is found that non-graphitic carbon presents better rate capability and less temperature-dependence due to the faster ion diffusion. These findings offer new insights into the design of advanced carbon anode materials with tunable properties for K-ion batteries.

Nitrogen/sulfur co-doping assisted chemical activation for synthesis of hierarchical porous carbon as an efficient electrode material for supercapacitors

The microstructure of carbon materials in terms of its specific surface area and pore structure by its activation, are the key issues which determine the electrochemical performance of supercapacitors. In this work, we developed a particular chemical activation process assisted by nitrogen/sulfur co-doping for the preparation of hierarchical porous carbon materials with high specific surface area, aiming at improving the energy density of supercapacitors. The as-obtained hierarchical porous carbon materials exhibited both high Brunauer-Emmett-Teller surface area of up to 3652m2g−1 for more ions adsorption and high porosity (2.61cm3g−1) for rapid ion transport. Attributed to the synergistic effects of these two features, the porous carbon displays high gravimetric specific capacitance (324Fg−1) in KOH aqueous electrolyte with outstanding rate performance (73.3% capacitance retention at 100Ag−1). The symmetrical supercapacitor based on our hierarchical porous carbon displays a maximum specific energy of 9.76Whkg−1 and 94.5% retention over 10000 cycles at 15Ag−1. This synthesis strategy is facile, low-cost and industrialized, which provide a promising route to prepare the hierarchical porous carbon materials for energy storage and renewable delivery devices.

The Study of Carbon Materials Prepared by Zhaotong Anthracite under Ultra-High Temperature

In this paper, reporting a new way to directly prepare quality of carbon materials such as artificial graphite, like-graphitization carburant and senior carbonaceous reductant et al ,which is prepared from anthracite under ultra-high temperature without any other additional process and catalyst. The chemical composition of carbon materials was analysed ; the electrical resistivity was tested; the composition of phase and the graphitization degree was tested by XRD; the microstructure was characterized by SEM and the degree of crystallization and crystal defect was characterized by the Raman diffraction spectrum. At the same time, the graphitization method was discussed during ultra-high temperature. The results show that good carburant and carbonaceous reductant can be prepared by anthracite which was graphitization under ultra-high temperature ;The microstructure of carbon materials which was prepared by anthracite that was graphitization during ultra-high temperature is more ordered than that of raw anthracite, its graphitization degree also increase significantly; When the ultra-high graphitization temperature is above 2600 °C, carbon materials which is like to pure graphite have a small amount of structural defects and distortion; the high quality carbon materials prepared by graphitization method under ultra-high temperature ,it is a simple process with low cost and high added value, and its prospects of application is broad.