MWCNT-Reinforced Electrospun PAN Carbon Nanofibers Hit 1.9 S/cm at 1000C Carbonization

Polyacrylonitrile (PAN) is the standard precursor for carbon fibers globally — the same chemistry that produces aerospace structural fiber also produces the small-diameter carbon nanofibers (CNFs) used as battery and supercapacitor electrode substrates, conductive fabrics, and reinforcing fillers. The bottleneck has always been that PAN-derived carbon needs very high carbonization temperatures (1,500-2,500 °C) to develop graphitic structure with the electrical conductivity that downstream applications need. Energy costs scale steeply with temperature. A 2026 study from the University of Technology-Iraq and Al-Esraa University (Baghdad), published in the Iraqi Journal of Science, shows that incorporating Cheap Tubes 90% purity MWCNTs into the electrospinning precursor moves the graphitization improvement to a much lower carbonization temperature (1,000 °C in N₂) and triples the electrical conductivity at the same heat-treatment condition. Pre-carbonization, the MWCNT addition alone produces a 10¹¹× lift in precursor fiber conductivity (2.27×10^-11 → 0.7 S/cm). Post-carbonization, the CNF/CNT composite hits 1.9 S/cm — a 2.4× improvement over pure-PAN CNFs. The Raman D-band / G-band ratio drops from 1.22 to 1.15, confirming that the MWCNT template directs the PAN-derived carbon toward more ordered graphitic structure during the lower-temperature heat treatment.

Why Lower-Temperature Graphitization Matters

Conventional carbon fiber manufacture goes through three thermal stages: stabilization at 200-300 °C (oxidative crosslinking of PAN), carbonization at 800-1,500 °C (loss of non-carbon atoms, formation of turbostratic carbon), and graphitization at 2,000-3,000 °C (ordering of the carbon lattice into hexagonal graphite-like sheets). The graphitization step dominates the energy bill and equipment cost — few facilities can sustain 3,000 °C N₂ furnaces continuously. If the MWCNT precursor inclusion delivers comparable graphitization at 1,000 °C that you'd otherwise need 2,500 °C to achieve, the economics shift dramatically for distributed carbon-fiber manufacturing, sustainable carbon production from biomass-derived precursors, and small-scale specialty fiber R&D.

The Electrospinning + Carbonization Method

• Precursor solution: 10% w/v PAN (Mw 150,000 g/mol, Macklin China) dissolved in DMF (Sigma-Aldrich) on hot magnetic stirrer at 50 °C.
• MWCNT addition: Cheap Tubes MWCNTs (90% purity, 10-30 nm OD, 10-30 μm length) dispersed into the PAN/DMF solution by sonication.
• Electrospinning: high-voltage electrostatic field draws the polymer solution into ultrafine fibers collected on a grounded substrate.
• Thermal stabilization: 275 °C in air, oxidative crosslinking of PAN backbone.
• Carbonization: 1,000 °C in N₂ atmosphere, ~1 hour. Pyrolytic conversion of stabilized PAN to turbostratic carbon.
• Final product: free-standing carbon nanofiber mat. Compared head-to-head: PAN-only CNFs vs PAN/CNT-derived CNFs/CNTs under identical thermal protocol.

Materials and Methods

Cheap Tubes MWCNTs — cited in the materials section

From the paper's materials section (verbatim): “Multi-walled carbon nanotubes (MWCNTs) purchased from Cheap Tubes Company, USA with a length of 10-30 μm, outer diameter of 10-30 nm, and purity of 90% were used as reinforcement materials.”

Product clarification: the 10-30 nm diameter range plus the 90% purity grade together identify this as the Cheap Tubes Industrial Grade MWCNT 10-30 nm product line, not a research-grade SKU. The standard MWCNT catalog comes in 10-20 nm or 20-30 nm diameter ranges (not combined), while the 10-30 nm range is specific to the Industrial Grade line. For researchers reproducing this work, the matching product is in the Industrial Grade Carbon Nanotubes category.

The 90% purity grade is the Cheap Tubes standard research-grade specification — well-suited for high-temperature composite work because residual CCVD catalyst metals at this loading don't interfere with PAN pyrolysis chemistry. The 10-30 nm OD range overlaps the current Industrial Grade MWCNT 10-30 nm SKU and gives the right aspect ratio for percolation through the electrospun nanofiber network without disrupting the fiber-formation dynamics during electrospinning.

Characterization battery

• FE-SEM — fiber morphology, diameter distribution before and after MWCNT incorporation, before and after carbonization. ImageJ used for 50-fiber diameter measurements.
• FTIR — confirmation of PAN→carbon conversion (loss of nitrile C≡N stretch, emergence of aromatic C=C).
• XRD — presence of the (002) graphite peak as the marker of carbonization completeness.
• Raman — D-band / G-band intensity ratio (I_D/I_G) as the marker of graphitization quality.
• Electrical conductivity (EC): four-point probe measurement on the precursor and carbonized fiber mats.
• Water contact angle (WCA): surface hydrophilicity comparison across PAN precursor, PAN/CNT precursor, pure CNF, and CNF/CNT.

Key Results

The 1.9 S/cm conductivity headline

The post-carbonization CNF/CNT composite measured 1.9 S/cm — a 2.4× improvement over the pure PAN-derived CNFs at the same 1,000 °C carbonization condition. The lift comes from two cooperative effects: (1) MWCNTs themselves are highly conductive carbon, so they raise the bulk conductivity directly; (2) the MWCNT inclusion templates the PAN-derived carbon to grow more graphitic structure around the CNT sidewalls, raising the conductivity of the matrix as well, not just adding the CNT's own contribution.

The 10¹¹× pre-carbonization lift

Before carbonization, pure PAN precursor fibers are essentially insulating: 2.27×10^-11 S/cm. Adding just enough Cheap Tubes MWCNT to the precursor solution lifts the precursor-fiber conductivity to 0.7 S/cm — an 11 orders of magnitude increase before any heat treatment. This means the MWCNT-loaded electrospun mat is conductive enough for downstream processing (e-textile electrodes, sensor substrates, low-power electronics) before the cost-intensive carbonization step. Many applications can use the precursor mat directly.

The graphitization-at-lower-temperature payoff

Raman spectroscopy shows the I_D/I_G ratio dropping from 1.22 (pure CNF) to 1.15 (CNF/CNT) at the same 1,000 °C carbonization condition. Lower I_D/I_G = larger sp² in-plane domains = better graphitic ordering. The MWCNT inclusion templates the PAN-derived carbon toward better graphitization at a lower temperature than pure PAN would require for equivalent ordering. For an industry where every 100 °C reduction in carbonization temperature is a meaningful energy-cost lever, this is the headline economic argument.

The hydrophilicity transformation

Water contact angle drops from 140° on the PAN precursor (hydrophobic, water beads up) to 18° on the CNF/CNT composite (highly hydrophilic, water spreads). This is meaningful for any aqueous-electrolyte application — supercapacitor electrodes, biosensor substrates, water-soluble drug delivery scaffolds, or aqueous battery chemistries. The PAN/CNT precursor (pre-carbonization) sits at 45°, and pure CNF lands at 40°. The CNF/CNT structure at 18° is the most hydrophilic of the four because the carbonization-induced oxygen defects on the CNT-templated regions plus the smaller fiber diameter conspire to maximize the surface-energy water interaction.

Why Cheap Tubes Industrial Grade MWCNT 10-30 nm Works for This Application

• 90% purity — the Cheap Tubes standard research-grade spec. Residual CCVD catalyst metals at this loading do not interfere with PAN pyrolysis chemistry but ensure consistent dispersion-and-templating behavior. (The paper's 90% purity match the current product spec exactly.)
• 10-30 nm outer diameter — corresponds to the Industrial Grade 10-30 nm SKU; right aspect ratio for percolation through the electrospun nanofiber network without disrupting fiber-formation dynamics during the high-voltage electrospinning process.
• 10-30 μm length — long enough for templating PAN-derived carbon into ordered graphitic structure during carbonization. Short tube fragments would not act as graphitization templates.
• DMF-dispersible — PAN dissolves in dimethylformamide, and the MWCNT has to disperse uniformly in the same solvent. Standard-grade Cheap Tubes MWCNT disperses cleanly in DMF under sonication without specialty surfactant systems.

Application Areas

• Battery anode and cathode current collectors — electrospun MWCNT-PAN CNFs are direct substitutes for copper / aluminum foil current collectors in flexible-format Li-ion, Na-ion, and Zn-ion cells.
• Supercapacitor electrodes — the high conductivity (1.9 S/cm), high hydrophilicity (18° WCA), and high specific surface area of the carbonized CNF/CNT mat are an excellent supercapacitor electrode substrate (especially for aqueous electrolytes).
• Smart fabric / e-textile electrodes — the precursor mat (pre-carbonization, 0.7 S/cm) is conductive enough for textile-integrated electrodes without needing the cost-intensive 1,000 °C carbonization step.
• Biomedical scaffolds — carbonized MWCNT-PAN nanofiber mats are used as biocompatible structural substrates for tissue engineering, neural interfaces, and bone-growth scaffolds.
• EMI shielding — the conductive carbonized mats serve as EMI shielding in flexible electronics packaging and shielded fabric.
• Catalysis supports — the high-surface-area carbonized CNF/CNT mats are substrates for transition-metal catalysts in hydrogen evolution, CO₂ reduction, and fuel cell research.

Order the Cheap Tubes MWCNTs Used in This Study

The multi-walled carbon nanotubes used by the University of Technology-Iraq team are available directly from Cheap Tubes. Order the matching SKU: Industrial Grade Multi Walled Carbon Nanotubes 10-30 nm. Other MWCNT diameter grades (8 nm, 8-15 nm, 20-30 nm, 30-50 nm, 50 nm) are available in the Multi Walled Carbon Nanotubes product category. Research and production volumes, SDS / TDS / CoA included, custom dispersions on request.

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