Three-Dimensional Numerical Modeling of an Ar-N_2 Plasma Arc Inside a Non-Transferred Torch

A three-dimensional numerical model is developed to study the behaviour of an argon-nitrogen plasma arc inside a non-transferred torch. In this model, both the entire cathode and anode nozzle are considered to simulate the plasma arc. The argon-nitrogen plasma arc is simulated for different arc currents and gas flow rates of argon. Various combinations of arc core radius and arc length, which correspond to a given torch power, are predicted. A most feasible combination of the same, which corresponds to an actual physical situation of the arc inside the torch, is identified using the thermodynamic principle of minimum entropy production for a particular torch power. The effect of the arc current and gas flow rate on the plasma arc characteristics and torch efficiency is explained. The effect of the nitrogen content in the plasma gas on the torch power and efficiency is clearly detected. Predicted torch efficiencies are comparable to the measured ones and the effect of the arc current and gas flow rate on predicted and measured efficiencies is almost similar. The efficiency of the torch, cathode and anode losses and core temperature and velocity at the nozzle exit are reported for five different cases.

Nitrogen-doped porous carbon nanofoams with enhanced electrochemical kinetics for superior sodium-ion capacitor

Many electrochemical energy storage devices,such as batteries,supercapacitors,and metal ion capacitors,rely on effective and inexpensive electrode materials.Herein,we have developed highly active nitrogen-doped porous carbon nanofoams(NPCNs-600-N)for sodium-ion capacitors(SICs).NPCNs-600-N have a highly porous framework,extended interlayer spacing(0.41 nm),and lots of surface functional groups.Accordingly,NPCNs-600-N achieves a high reversible capacity(301 mAh·g^(-1)at 0.05 A·g^(-1)),superior rate capability(112 mAh·g^(-1)at 5.00 A·g^(-1)),and ultra-stable cyclability.The excellent rate and cycling performance originate from the abundant active sites and porous architecture of NPCNs-600-N.Further-more,SICs device is constructed by employing the NPCNs-600-N as the battery-like anode and commercial superconductive carbon black as the capacitive cathode,which delivers high energy/power densities of 92 Wh·kg^(-1)/15984 W·kg^(-1)with a remarkable cyclability(93%reten-tion over 5000 cycles at 1.00 A·g^(-1)).The methodology of the work enables the simultaneous tuning of the porous architectures and surface function groups of carbon for high-performance SICs.