Graphitic Carbon Nanofibers - Properties and Applications of Pyrograf III

By AZoNano

Table of Contents

Introduction
Pyrograf-III Properties
Pyrograf III Grades
Thermal Processing
Available product grades
Product forms
Advantages
Applications
Exclusive Features
About Pyrograf

Introduction

Pyrograf III is a highly fine, graphitic, patented yet economical carbon nanofiber. Pyrograf-III is offered in a diameter range from 70 – 200 nm and length more than 100 µm. Hence nanofibers have a size smaller than conventional milled or continous carbon fibers in the range 5 – 10 µm but considerably larger than carbon nanotubes (1-10 nm).

CNF is discontinuous fibrous reinforcement for engineered composites with an inherently low processing cost. When considering equivalent production volumes, CNF will have a cost that can be compared to E-glass on a per-pound basis yet its properties surpass those of glass and are equal to or more than expensive commercial carbon fiber. Since CNF is a discontinuous reinforcement, it can be incorporated into thermoplastics, elastomers and thermosets that are commercially available and can be presently used in high-volume molding processes without any definite novel manufacturing development.

Since CNF features exclusive intrinsic properties, especially its elastic modulus and strength, there may be a reduction in the material needed to produce a specific strength or stiffness, hence ensuring cost savings and net weight. Additionally the production process of CNF is very similar to carbon black, directly from a simple hydrocarbon source.

Pyrograf-III Properties

The property table shows the types and grades of Pyrograf III carbon nanofiber:

Table 1. Pyrograf III Properties

Nano- fiber Type Nano- fiber Grade N2Surface Area, (m2/gm) Dispersive Surface Energy, (mJ/m2) Moisture Content (%) Iron Content (ppm) PAH Content (mg PAH/g fiber) Density (lbs/ft3)
PR-19 PS 20-30 120-140 <5 <14,000 <1 2-4
PR-19 LHT <5 <14,000 <1 2-4
PR-19 HHT 15-25 265-285 <5 <100 <1 2-4
PR-24 PS 50-60 <5 <14,000 <1 2-4
PR-24 LHT <5 <14,000 <1 2-4
PR-24 HHT <5 <100 <1 2-4

Pyrograf III is a multifunctional material offering improved electrical conductivity over a broad range along with mechanical reinforcement of matrix materials. Shown below is the TEM image of the Pyrograf – III Nanofiber.

Figure 1. TEM Image of Pyrograf-III Nanofiber

Even though it is not possible to directly measure a number of properties by traditional methods, the physical characteristics of more graphitic forms of vapor-grown carbon fiber will tend towards single crystal graphite as shown in Pyrograf-I data.

Pyrograph III has an innovative structure, which can be referred to as stacked-cup carbon nanotubes (SCCNT). The graphene plane surface is offset from the fiber axis, which exposes the plane edges present on the interior and exterior surfaces of the carbon nanofibers. The following figures depict this unique stacked-cup structure.

Figure 2. Artistic Depiction of Pyrograf-II Stacked Cup Carbon Nanotubes

Figure 3. Cross-sectional view showing the internal structure of the Pyrograf product stacked-up carbon nanotubes.

Pyrograf III Grades

The following table shows the Pyrograf III grades:

Table 2. Pyrograf-III grades

PYROGRAF III GRADES:

PR-19-XT PR-24-XT
Production Full scale Full scale
Diameter, nanometers 100 to 200 60 to 150
Length, nanometers 30,000 to 100,000 30,000 to 100,000
Comments As grown material contains CVD carbon As grown material essentially free of CVD carbon

Thermal Processing

The properties of heat processed CNF is listed below:

  1. PS – pyrolytically stripped carbon fiber
    In this type, polyaromatic hydrocarbons are removed from the surface.
  2. LHT - Low heat treated carbon nanofiber
    The carbon fiber is heated to temperatures up to 1,500°C. Chemically vapor
    deposited carbon present on the Pyrograf surface is partially graphitized.
  3. HHT – High heat treated carbon nanofiber
    This carbon fiber is heated to temperatures up to 2,900°C. Chemically vapor deposited carbon present on the surface of Pyrograf is graphitized. A highly electrically conductive carbon nanofiber is created. Iron catalyst is removed from carbon nanofiber.

Available product grades

The product grades available are listed below:

  • PR-19-XT
    • PS – Pyrolytically stripped carbon nanofiber
    • LHT – Low heat treated carbon nanofiber
    • HT – High heat treated carbon nanofiber
  • PR-24-XT
    • PS – Pyrolytically stripped carbon nanofiber
    • LHT – Low heat treated carbon nanofiber
    • HT – High heat treated carbon nanofiber

Product forms

The different product forms of CNF are:

  • Bulk nanofiber shipped as free flowing powder
  • Masterbatch resins
  • Specialty papers

Advantages

The advantages of composites made from pyrograf nanofibers are:

  • Evenly conductive surfaces
  • Reduced cycle time
  • Low specific gravity
  • Low-cost composites
  • Static dissipation
  • Enable thin-walled modes
  • Class A surface finish
  • Low fiber loadings
  • Carbon cathodes and anodes

Applications

The applications of composites made from pyrograf nanofibers are:

Industrial applications

  • Silicon wafer production
  • Batteries and fuel cells
  • Disk drive components
  • Clean rooms

Automotive uses

  • Fuel systems
  • Mirror housings
  • Interior parts
  • Bumpers & fenders

Aerospace

  • Aircraft braking systems
  • Thermal management
  • EMI/RFI shielding
  • Light weight composites

Exclusive Features

The exclusive features of pyrograf nanofibers are:

Electrical properties

  • Improved electrical conductivity in composites at low carbon nanofiber loading
  • Minimal cost for electrically conductive and dissipative compound
  • Electrical conductivity without reduction in mechanical properties

Mechanical properties

  • Improved mechanical strength of polyolefins up to four times
  • Improved impact strength in polar resins
  • Modulus of rubber compounds is increased four times in high strain applications

Chemical properties

  • Chemical bonding to graphite planes in order to fine-tune composite properties
  • Reactive sulfur, oxygen and nitrogen sites on carbon nanofiber surfaces
  • Good interface between polymer matrices and carbon nanofibers

Thermal properties

  • Highest heat-transfer rate when compared to all known materials
  • Highly efficient thermal management composites

Adsorptive properties

  • Can remove radionucleides and heavy metals from ground water, water and wastewater
  • Highly adsorptive for organic materials

Figure 4. High resolution image showing the stacked cup structure of Pyrograf-III

About Pyrograf

Pyrograf Products, Inc. (PPI) is one of the leading producers of carbon nanofibers worldwide.

Pyrograf Products focuses on manufacturing high- quality, low-cost carbon nanofibers utilizing the proprietary and patented vapor grown carbon fiber (VGCF) process. Pyrograf-III, developed Applied Sciences, Inc. (ASI), is a versatile vapor grown carbon nanofiber with a wide range of applications.

This information has been sourced, reviewed and adapted from materials provided by Pyrograf.

For more information on this source, please visit Pyrograf.

Date Added: Aug 17, 2012 | Updated: Jun 11, 2013
Ask A Question

Do you have a question you'd like to ask regarding this article?

Leave your feedback
Submit