Fabrication Of Sheath-core Phase Change Materials,and Regeneration And Carbonization Of Cellulose ?

The studies in this thesis are divided into two sections,(1)fabricated sheath-core structure polyacrylonitrile(PAN)/phase-changematerials(PCM)nano-fibers by co-axial electrospinning,explored their exothermic and endothermic behaviors.These works emphasized on the fabrication of sheath-core structure,the uniformity of the fibers and the sealing and performance of various types of PCMs.(2)The regeneration of cellulose I from its DMAc/Li Cl solution and the effects of polymorphs of the regenerated cellulose on its prolysis and carbonizaton.The details are listed below.PAN/PCM sheath/core structure nanofibers were fabricated by coaxial electro-spinning,the effects of spinning conditions on the morphologies of nano-fibers were explored,and it was observed that well encapsuled PCM could be obtained under certain spinning conditions.The phase change behaviors of the composite fibers were examined by DSC,and it was proved that the obtained nanofibers could well stabilize the sudden change of environmental temperature.Above studies proved that coaxial electrospinning could be used for the fabrication of sheath-core structured PCMs.Cellulose ? was regenerated from its DMAc / Li Cl solution through thermal induced gelations,the polymorphs of regenerated celluloseswere characterized by XRD and Raman spectrocopy,it was found that the crystallinity of the regenerated cellulose I could reach as high as 84.7%.The regeneration of cellulose I was found to depend on the gelation time and regenerated processes.By using this regeneration method,the regenerated cellulose I in aerogel form was fabricated,which proved that the propsed regeneration method was processable.The polymorphs of cellulose were considered to strongly affect its prolysis and carbonization.However,few experimental data proved it.Here,TGA was used to systematically studied the effect of the polymorphs of regenerated cellulose on its prolysis and char yield,and it was found that both the polymorphs of the regenerated cellulose and the addition of proper additives could strongly affect the char yield and prolysis kinectics of the regenerated cellulose.To be used as carbon precursor,the sequence of the polymorph of cellulose is in the order of cellulose ?> cellulose ?> amorphous.