This document summarizes a study that characterized the structure and explored the mechanical properties of carbon nanofibers produced through electrospinning polyacrylonitrile (PAN) polymer precursor. The study used electrospinning to produce PAN nanofibers, which were then oxidized and carbonized. Scanning electron microscopy was used to examine the fiber diameters and structures. The conclusions discussed how processing parameters like voltage, needle diameter, and distance between needle and drum impacted fiber formation and properties. Carbon nanofibers produced through this method showed potential for applications in areas like heat transfer and composite reinforcement.

1. Scheme of performed electospining machine
container with polymer power supply (0~6kV)
electric engine (0~1000 rpm/min) safty switch
drum container for sillicagel
INTRODUCTION
Carbon nanofibers, like other quasi-one-dimensional nanostructures such
as nanowires and nanotubes, have ecently been receiving increased attention.
This is due to their potential application as heat-management materials,
composite reinforcement, high-temperature catalysis, membrane-based
separation, and as components for nanoelectronics and photonics.
Carbon fibers are typically produced either by pyrolyzing fibers spun from
an organic precursor (e.g., polyacrylonitrile (PAN), or alternatively pitch),
or by chemical vapor deposition (CVD). The spinning method can only produce
microscale carbon fibers (diameter >5 lm). CVD can synthesize carbon fibers
with diameters ranging from several microns down to 10 nm.
Recently, carbon fibers were produced by pyrolyzing electrospun
nanofibers from PAN and from pitch with typical diameters of few hundreds
of nanometer and several microns, respectively. However, the structure and
the mechanical properties of carbon nanofibers produced from an electropsun
polymer precursor are largely unknown. The purpose of this paper is to
characterize the structure and to explore the modulus and strength of
electropsun PAN-derived carbon nanofibers.
MATERIALS & METHODS
Materials:
Research substrates: carbon nanofiber from polyacrylonitrile precursor (PAN).
Raw: PAN powder
Solvent: N,N-dimethylformamide (DMF)
Methods:
Methods of obtain carbon nanofiber:
To obtain carbon nanofiber were used electrospun methods.
The experimental electrospinning device was designed specifically to obtain this
type of nanofiber.
Reserch methods:
Scanning electron microscopy (SEM) - (Nova NanoSEM 200, FEI Co.
and Jeol JSM-5400) – for check diameters and structure of fiber after oxidation
and carbonization.
CONCLUSIONS:
1.The creating process of PAN nanofibers have the greatest impact: diameter of the needle,
and voltage.
- increase in voltage results the possibility of larger diameter needles.
- Insufficient large voltage causes the formation of droplets that stick formed fibers.
- too small diameter of the needle causes too much resistance flow and solidification of the
polymer inside the needle.
2. The distance from the drum to the needle:
- too small a distance causes the formation of an electric arc,
- too much distance does not allow to creation of the Taylor cone, the reason for this is
the falling voltage with distance, the drum - the needle
3. Third environmental Conditions
- effect of humidity on the process is indirect, too much moisture results the solidification
of the polymer in a solvent
1 2
3 4
5 6
1 2
3
4
5
6
RESULTS
Needle 0.45 mm Needle 0.60 mm
PANnanofibersPANnanofibersafteroxidationCarbonnanofibers
Selection of variables that affect the resulting fibers:
-Power supply: 6 kV (tested range of 1- 6kV)
-Diameter of needle: 0.45 mm (tested diameter of the needle 0.4, 0.45, 0.6, 1.2 mm)
-Distance from the needles of the cylinder:
2.5 cm (tested distance 1cm – 5cm)
- Reletive humidity 13% (optimal humidity: as small as possible)
-Temperature ambient (optimal temperature: not too high)
Designed device to obtain nanofibers by electrospinning method
The heating curve in function of time and temperature.