TITLE:
CVD Treatment of Carbon Fibers and Evaluation of Their Dispersion in CFRC
AUTHORS:
Chuang Wang, Bingliang Li, Lei Peng, Wenmin He, Liping Zhao, Kezhi Li
KEYWORDS:
Carbon Fiber, Chemical Vapor Deposition, Hydroxyethyl Cellulose, Dispersion
JOURNAL NAME:
Materials Sciences and Applications,
Vol.8 No.8,
August
18,
2017
ABSTRACT: Carbon-fiber-reinforced
cement-based (CFRC) composites is a promising functional material which can be used both in the military
and civil fields against electromagnetic interference. However, it is essential
to make carbon fibers dispersed uniformly during the preparation of CFRC. In
this work, short carbon fibers were treated through Chemical Vapor Deposition
(CVD) process at high temperature between 900°C and 1200°C under the
protection of diluted nitrogen gas N2 to modify the surface of carbon fibers to further strengthen the bonding between carbon fibers and cement matrix.
Natural gas (98% CH4) was used as a precursor. It was
decomposed to produce an uneven layer of pyrocarbon that was deposited on the
surface of carbon fibers. CVD-treated carbon fibers were pre-dispersed by using
ultrasonic wave. Both hydroxyethyl cellulose (HEC) and silicon fume were used
as dispersants and as admixtures. They helped CVD-treated carbon fibers
distribute uniformly. The mass fraction of HEC was around 1.78% in the aqueous
solution. Four methods, namely, the simulation experiment (SE) method, the
scanning electron microscopy (SEM) method, the fresh mixture (FM) method, and
the electrical resistivity measurement (ERM) method were, respectively, applied
to evaluate fiber dispersion degree. Each method indicated its own advantages
and disadvantages and it therefore catered for different conditions. Of the
four evaluation methods, the SE method was the most convenient way to determine
the pre-dispersion
state prior to the preparation of CFRC composites. This method was helpful for
predicting the subsequent dispersion state of carbon fibers in the cement
matrix because it economized a large quantity of raw materials and time.