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.
Highlights
The commercialization of short carbon fiber-reinforced cement composites (CFRC) has become possible with the development of relatively low-cost, pitch-based carbon fibers in recent years [1] [2] [3]
When they are added into cement substrate in this status, it can be concluded that the interracial adhesion between the fiber surface and cement is weaker due to smooth surface, the density of the Carbon-fiber-reinforced cement-based (CFRC) composite is lower, and the strength of the composite is not good
To improve the interfacial bonding between carbon fibers and cement matrix, carbon fibers were treated by Chemical Vapor Deposition (CVD) at high temperature
Summary
The commercialization of short carbon fiber-reinforced cement composites (CFRC) has become possible with the development of relatively low-cost, pitch-based carbon fibers in recent years [1] [2] [3]. Carbon fiber exhibits high elasticity, high modulus, less density, good electricity conductivity, and resistance to corrosion excellent reinforcement for composites. The effectiveness of the added fiber depends on the degree of fiber dispersion. Electrical resistivity measurement has been used to assess the degree of steel fiber dispersion [1] [10] [11], but little has been reported on the comparison of different methods, especially dispersion of carbon fibers after Chemical Vapor Deposition (CVD) treatment
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