The spinning of hollow polyacrylonitrile fibres as a precursor for the formation of hollow carbon fibres

Hollow polyacrylonitrile (PAN) fibres were prepared as a precursor for hollow carbon fibres. The fibres were dry-jet wet spun from a DMF solution using water or a 50/50:water/DMF mixture as the coagulant both externally and internally. The effect of the spinning conditions on the fibre wall morphology and tensile properties was investigated by scanning electron microscopy and tensile testing and the knowledge gained from the early experiments was used to develop a pilot plant scale spinning rig. The rheological properties of the spinning solutions were investigated using steady shear flow rheometry, oscillatory rheometry and extensional rheometry, and the molecular weight of the PAN was determined using dilute solution rheometry. A simple model was proposed for the prediction of fibre diameters from the spinning conditions. This model was later used to predict the spinning conditions required to generate fibres of the target dimensions which were 25µm external diameter and 15µm internal diameter. The target dimensions were almost achieved but work was performed that showed that after carbonisation the fibres would have the required dimensions.Hollow polyacrylonitrile (PAN) fibres were prepared as a precursor for hollow carbon fibres. The fibres were dry-jet wet spun from a DMF solution using water or a 50/50:water/DMF mixture as the coagulant both externally and internally. The effect of the spinning conditions on the fibre wall morphology and tensile properties was investigated by scanning electron microscopy and tensile testing and the knowledge gained from the early experiments was used to develop a pilot plant scale spinning rig. The rheological properties of the spinning solutions were investigated using steady shear flow rheometry, oscillatory rheometry and extensional rheometry, and the molecular weight of the PAN was determined using dilute solution rheometry. A simple model was proposed for the prediction of fibre diameters from the spinning conditions. This model was later used to predict the spinning conditions required to generate fibres of the target dimensions which were 25µm external diameter and 15µm internal diameter. The target dimensions were almost achieved but work was performed that showed that after carbonisation the fibres would have the required dimensions

Distributional records, natural history notes, and conservation of some poorly known birds from southwestern Ecuador and northwestern Peru

Volume: 113Start Page: 108End Page: 11

Habitat associations of British breeding farmland birds

Capsule Territory distribution for ten species was most strongly positively influenced by the presence of hedges and woodland edge. Aims To describe and rank the importance of different habitat predictors on the distribution of bird territories. Methods We derived territory maps for ten bird species across 25 sites on English lowland farmland in 2002. We related habitat predictors to the distribution of these species using information theoretic methods. Results Habitat predictors were ranked as follows (numbers in parentheses indicate the number of species with a strong effect): hedge presence (8), boundary height (7), woodland edge (6), tree presence in boundary (4), brassica (mainly oil seed rape) (3), within-field vegetation height (3), boundary strip (3), boundary width (3), tilled fields (3), winter set-aside (2), ditch (1), winter stubble fields (1). Conclusions Non-cropped habitats had the most consistent positive effects across all ten species, with crop types and their margins exerting smaller effects