Scanning Electron Microscopy of Fibre Morphology

SEM imaging of textile fibres (accelerating voltage 1–15 kV, working distance 5–15 mm, secondary electron imaging for surface topography, backscattered electron imaging for atomic number contrast) provides high-resolution surface morphology characterisation essential for fibre identification, treatment verification, damage assessment, and failure analysis. Sample preparation: fibres mounted on aluminium stub with conductive carbon tape, sputter-coated with Au/Pd (80:20) 5–10 nm thickness using Quorum Q150R for >100 pA beam current at 10 kV — insufficient coating causes charging artefacts (bright streaks, image instability) at voltages >5 kV. Natural fibre morphology at key magnifications: wool scale structure (2,000×: scale edge angle 15–25°, scale height 300–500 nm; 10,000×: individual cell junctions visible) — Superwash-treated wool shows smooth, scaleless surface at 2,000× confirming proteolytic enzyme or chlorine scale removal; cotton convolutions (500×: reversal frequency 3–7/mm, lumen width 3–8 µm, wall thickness 4–8 µm for mature fibre — immature cotton wall <3 µm at 500×). Synthetic fibre cross-sections (fracture in liquid nitrogen then image fractured end at 90° orientation, 1,000–5,000×): PET circular (5,000×, diameter 10–25 µm), Coolmax 4DG grooved cross-section (4 channels, channel width 1–3 µm for moisture transport), hollow polyester (20–30% hollow by cross-section area measurement). Carbon fibre surface treatment verification (5,000×): oxidised carbon fibre shows nano-pit density 5–15 pits/µm², pit diameter 50–200 nm from surface etching versus untreated fibre featureless smooth surface — surface roughness (Ra) from AFM tapping mode: untreated carbon Ra = 3–5 nm, oxidised Ra = 8–15 nm correlating with improved epoxy wettability.