Study On Synthesis Of Silk Sericin/Calcium Carbonate Composite Material

Biological organisms produce organic-inorganic composite materials such as bone, teeth,diatoms, shells, etc. These composite materials have unique hierarchical structure and assemblymethods, so these materials have the remarkable mechanical properties of toughness, strength,stiffness and resistance to wearing due to their specific structures. Therefore, the features of thesecomposite materials attract a strong interest of materials scientist, which synthesize fine structure,excellent performance of the organic-inorganic composite materials by simulating the processof biomineralization, this is provide for a new way to the synthesis of new functional materials.In this paper, sericin protein was used as organic template, sericin protein/calcium carbonatecomposite materials were prepaped via double decomposition and carbonization, respectively. Inpreparation process, we studied different process parameters on the crystalline phase andmicrostructure of calcium carbonate via double decomposition, which included the sericinprotein concentration, molecular weight, reaction time, temperature, stirring rate, and pH. Andthen we studied calcium hydroxide concentration on morphology and crystal structures ofcalcium carbonate in the presence of sericin protein through carbonation method. On this basis,we preliminary study the formation mechanism of mineralized material.First, the sericin protein concentration and molecular weight of sericin protein influenced oncrystal growth of calcium carbonate. When the sericin concentration was1g/L, the thornspherical particles was prepared, with the sericin protein concentration increased, the sericinprotein concentration reached to1.5g/L, uniform cube particles was prepared by lamellar crystalassembled, with molecular weight of sericin protein increased, calcium carbonate crystalsevolved from the spindle to rod-like crystals, and crystal polymorphs are calcite. When themolecular weight of sericin protein was10～20kDa, the spindle crystals were obtained, whenthe molecular weight was30～50kDa, dumbbell-shaped crystals and flower crystal wereobtained, the molecular weight was100kDa, rod-like crystals were prepared. Second, the process parameters impacted on calcium carbonate crystal morphology and crystalstructure, the results showed that reaction time and temperature obviously affected on thecalcium carbonate crystal morphology and crystal structure. With the reaction time prolonged,calcium carbonate polymorphs gradually changed from calcite to mixture of calcite and vaterite,and the morphology of crystal evolved from disc-shaped particle to spherical crystal. At lowtemperature (20℃), calcium carbonate crystal was composed of thorn spherical and spindleparticles, and as the reaction temperature increased, calcium carbonate formed spherical crystal,and the crystal polymorphs was vaterite. With the stirring rate increased, the calcium carbonatemorphology was changed from irregular shape into the rod-like crystals. As the reaction pHincreased, the mixture of thorn spherical and cube particles gradually evolved into irregularaggregates.Third, sericin protein was selected as organic template, calcium carbonate was prepared bycarbonation method. Calcite crystal was obtained in different calcium hydroxide concentrations.The morphology of calcium carbonate formed the spindle-shaped crystals in the lowconcentration of calcium hydroxide (0.1mol/L～0.3mol/L), with the concentration of calciumhydroxide increased, calcium carbonate morphology gradually became irregular shape.We successfully synthesized rod, spherical, spindle-shaped crystals using sericin protein asorganic template through double decomposition and carbonization, which can be used in rubber,ink, paper and other industries.