Yuqin Wan

Diameter Prediction for Electrospun Nanofibers

Models for jet velocity and fiber diameter of the electrospun fibers are given, respectively, by combing the mass conversation law with the force balance model in the electrospinning process.

Introduction to Nanofiber Materials: Characterization of nanofibers

Knowing the basic properties of nanofibers (such as morphology, molecular structure and mechanical properties) is crucial for the scientific understanding of nanofibers and for the effective design and use of nanofibrous materials. In order to evaluate and develop the manufacturing process, the composition, structure and physical properties must be characterized to decide whether the produced fibers are suitable for their particular application. Evaluation of the various production parameters in processes such as electrospinning is a critical step towards production of nanofibers commercially. Many common techniques used to characterize conventional engineering materials, as well as some not so common techniques, have been employed in the characterization of nanofibers. Table 6.1 shows the scales of fibers and the corresponding characterization techniques. To provide an overall understanding, some of the general characterization techniques for structural, chemical, mechanical, thermal and other properties will be introduced in this chapter. Structural characterization of nanofibers The morphological characterization techniques briefly discussed herein are: optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM) and scanning tunneling microscopy (STM). These methods characterize the morphology and determine fiber diameter, pore size and porosity, all of which are necessary to evaluate the various production parameters. The techniques for characterization of order/disorder of molecular structures using X-ray diffraction (XRD) are also covered in this section. Furthermore, mercury porosimetry, a special technique for porosity measurement, is introduced.

Inner-resonance in Rotor-Spun Composite Yarn Spinning Process

In this paper, a dynamic model was proposed for the rotor-spun composite yarn spinning process. The conditions for inner-resonance were obtained, which should be avoided in the spinning process.