The Influences of Oxygen Concentration and External Heating on Carbon Nanotube Growth in Diffusion Flame

Tight control of the carbon nanotube (CNT) synthesis process in flames remains a challenge due to the highly non-uniform gradient of flame thermochemical properties. The present study aims to establish a baseline model for flame-enhanced chemical vapor deposition (FECVD) synthesis of CNT and to analyze the CNT growth region at varying flame and furnace conditions. The numerical model comprises a computational fluid dynamics (CFD) simulation that is coupled with the CNT growth rate model to simulate the flow field within the furnace and the CNT growth respectively. Validation of the flame shape, flame length, and temperature profile are carried with a reasonable comparison to experimental measurements. A parametric study on the effects of furnace heating capacity and oxidizer concentration is conducted. The results of the CNT growth rate model reveal that there is a positive correlation between the heater power and CNT length. Supplying a higher concentration oxidizer at a fixed furnace power is predicted to result in further improvement in CNT length and high yield region. Flame structure analysis showed that with the heater turned on at 750 W (corresponding to heat flux of 21,713W/m2), the growth region expands twofold when oxygen concentration is increased from 19% to 24%. However, the growth region shrinks when the oxygen concentration is further increased to 27% which indicates depletion of carbon source for CNT growth due to excess oxygen. The finding of this research could guide and optimize the experiment of the flame-assisted CNT production in the future.

An Adaptive Power Controller of the Induction Crucible Furnace with a Conducting Ferromagnetic Crucible

A structural model of a high-frequency induction crucible furnace with a conducting ferromagnetic crucible is developed in the Simulink/Matlab environment based on investigations carried out by the authors. The inductor current was calculated using the inductor's resistance and inductance dependences on temperature, frequency, and current. An induction crucible furnace power control system structural model is designed based on the developed model. The output voltage pulse-frequency modulation is used as a furnace power control method. An adaptive power controller for the induction crucible furnace with a conducting ferromagnetic crucible is developed, which includes two channels for control of the power supply source frequency and voltage. It has been determined that the melting with the lowest energy expenditures is obtained in the case of using a power controller with two different adaptive control structures. The controller operates based on the frequency control principle and uses structures depending on the current temperature value. The use of the adaptive power controller with two control channels can significantly reduce the specific electric energy consumption in comparison with automatic frequency adjustment, in particular, by a factor of 1.45 for the IGT-1.6M industrial furnace.

Design and Implementation of Induction Coil for Case Hardening of a Carbon Steel Gear

This work includes a design of an induction coil as a guide to design an induction furnace as a part of a production line suitable for achieving case hardening of a CK-45 carbon steel gear in a mass production factory. Such a workpiece requires certain hardening profile in that the periphery including the gear teeth must be hardened for certain depth to withstand against corrosion, while the rest volume must be of low hardness in order to overcome mechanical stresses due to the coupled shaft. Induction heating technology adopted for achieving such a complex hardness profile in one workpiece. A numerical simulation intended to design the induction coil, then the induction furnace able to perform this hardening requirement. A three dimensional (3-D) electromagnetic-thermal coupled analysis using Finite Element Method (FEM) is intended to design this coil. This design must determine the required frequency, current, and temperature required for this process at certain required time. These parameters are the guide to build the suitable induction furnace power supply for this task. This work proves the truth that this simulation is quite accurate to implement a pioneer system.

Sources of Contaminants

This chapter describes the natural sources that produce background levels of chemical contaminants in environmental media and the generally much larger anthropogenic sources in terms of: primary releases; and secondary sources resulting from chemical reactions within environmental media. There are primary sources within residences (personal care products, pesticides, the smoking of cigarettes, and unvented kitchen and bathroom effluents and heaters), in and around communities (furnace, power plant, and motor vehicle effluents), and effluents from industrial and commercial activities. Secondary sources include reactions between primary pollutants and natural and anthropogenic components in the atmosphere, hydrosphere, and lithosphere.