Study On The Preparation And Application Of Starch-based Carbonaceous Foam

Carbonaceous foam(CF)is a foam-like porous carbonaceous material.It has the characteristics of low density,high strength,easy processing,heat resistance,corrosion resistance,adjustable electrical and thermal conductivity,etc.It has shown great application potential in many fields such as chemical industry,aerospace and electronics.At present,the preparation of CF is mainly based on non-renewable pitches or synthetic resins.The preparation of CF from biomass raw materials is environmentally friendly and renewable,which is becoming a trend in the current research of CF.In this thesis,a typical polysaccharide(i.e.,starch)was used as raw material to prepare CF.The mechanism of transformation from starch to CF was revealed from multiple perspectives and scales,and structure-adjustable CF was obtained.The potential application of this starch-derived CF in the fields of phase change energy storage explored.The research in this thesis not only helps to broaden the choice of raw materials,but also provides inspiration for the preparation of CF from other polysaccharide-based biomass.It is also of great significance for the functionalization and high value-added utilization of biomass-based CF.In the first part of this thesis,CF with layered porous structure was prepared using starch as raw material.The effects of moisture,acid mixture,external pressure,exhaust,and heat transfer on the preparation of CF were discussed.The mechanism of conversion from starch to CF was revealed through multi-angle and cross-scale characterization and analysis of the reaction intermediates and products.The results show that the hydrogen bonding that is ubiquitous in polysaccharides is not the main factor affecting the preparation of CF.When preparing CF from polysaccharides,not only the molecular structure of the raw materials,but also the molecular conformation must be considered.To our knowledge,the effect of the molecular conformation of the raw materials has been rarely reported in the studies on the mechanism of CF formation.In addition to affecting the creep of the molecules when heated,the steric hindrance effects caused by the structure and conformation of the raw materials may also affect the activity and reaction order of various chemical reactions.This makes different starches have different thermal decomposition processes in the process of foaming and carbonization,which in turn leads to the differences in their carbon products.In the second part of this thesis,a novel thermal energy storage(TES)composite with dual functions of energy storage and temperature sensing was prepared.The starch-derived CF was used as the basic framework.Polypyrrole(PPy),a conductive polymer,was used as the thermal/electrical conduction enhancing medium,and an inorganic–organic phase change material(PCM)composite was used as the energy storage and resistance adjusting medium.The temperature change and energy storage process of the as-prepared CF-TES composite can be reflected in real time by electrical signals.Then,the formulation was optimized under the premise of ensuring a acceptable sensing function.Three samples with melting enthalpy change of 81.9(CF-PPy-PCM-1000-1),113.29(CF-PPy-PCM-8000-0)and 124.44(CF-PPy-PCM-20000-0)J/g were obtained.SEM characterization showed that the PCM in the composite was distributed on the cell wall of CF-PPy framework.Although there is still room to further increase the PCM load,this incompletely filled state also to some extent ensures that the PCM will not leak during the heat storage process.In summary,the mechanism of conversion from starch to CF was studied from multiple scales and angles,and composite materials were prepared using the obtained starch-derived CF.The potential application of these materials in the fields of thermal energy storage was discussed.The results of this thesis provide inspiration for the preparation of CF from renewable resources and the realization of high value-added utilization.