Study of the phase transition ability of coal tar pitch and their coke products under the influence of temperature used to synthesise carbon composite materials

Using differential scanning calorimetry and thermogravimetric analysis showed the marking temperature of coal tar pitch is 107.8°C. The thermal decomposition of the pitch is divided into three main stages, corresponding to three phases α, β, γ, with a coke yield of 47% at 800°C. The change in the XRD diagram showed a clear transition from the amorphous state of carbon to the highly ordered crystalline structure of graphite after treatment at 2,200 and 2,700°С. The purity of the pitch sample and the structure of the CCC carbon-carbon composite material after heat treatment at 2,700°C were studied using scanning electron microscopy and energy-dispersive X-ray spectroscopy methods. The results showed that after heat treatment, the C content in the sample reached more than 99.5%, and the coke residues after graphitization were bound and connected to the carbon fabric into a mass of graphite material.

PITCH MEASUREMENT BY TRACEABLE ATOMIC FORCE MICROSCOPE

A Traceable Atomic Force Microscope (TAFM) to calibrate the pitch standards is presented. The TAFM consists of an atomic force microscope, a three-axis active compensation flexure stage, two laser interferometers, an L-shape mirror, a vibration isolator, and a super-Invar metrology frame. A test specimen is laid on the same plane of laser interferometers to eliminate the Abbe-offset. The displacements of X and Y axes are taken by the laser interferometers, the Z movement is controlled by AFM cantilever and the displacement is taken by a capacitance sensor while the flexure stage moves the specimen in X and Y axes motions. A water circulator is used to control the TAFM at 20°C. Measuring results of a standard pitch sample show that this TAFM can be used for measuring of pitch standards. A pitch standard with nominal value of 292 nm was served as a test sample. The combined standard uncertainty was 1.2 nm.

Numerical Modeling and Simulation of Electromagnetic Drying Processes

ABSTRACTElectromagnetic drying processes have been used in industrial applications for many years. New materials with different properties and structures have been recently developed which required the development of new drying systems capable of effectively drying the new materials. In this paper, we use Finite-Difference Time-Domain (FDTD) to model and simulate realistic electromagnetic drying processes including induction heating and RF drying. The power deposition patterns obtained from the FDTD code is also used in a finite-difference heat transfer code to evaluate the temperature distribution pattern and optimize rates of drying. Sample parameters used to analyze the RF drying and the induction heating processes include the sample conductivity, dielectric constant along with size, orientation and the geometric arrangement. Specifically, we analyzed the operating frequency, coil pitch, sample to coil diameter ratio, and the possible placement of multiple samples in an induction heating process. Effects investigated in a parallel plate RF drying system include: electrode spacing, electrode length and width, and the spacing between multiple samples. Results of electromagnetic power distributions and temperature patterns are presented.