Preparation And Characterization Of Chitosan/Ceramics Composites With Lamellar Structure

Most of natural biological materials have excellent mechanical properties due tointricate layered structures. Templating is the one of the most effective means tofabricate the biomimetic laminated composites. Especially, the intricate structure ofnatural biological materials can be used as templates to obtain composites with similarstructure. But biological templates exists some problems, such as uncontrollablestructures and unable to industrial production, while synthetic templates become a newresearch hotspot due to its controllable structure.The controllable lamellar structure of chitosan hydrogel was used as the template toobtain the lamellar chitosan/creamics composites, and the the silica particles and theprecursor of hydroxyapatite were added into the chitosan solution to prepare thelamellar chitosan/silica composites and lamellar chitosan/hydroxyapatite composites.The lamellar structure characteristics of composites and its correspondence relationshipwith chitosan hydrogel templates have been analysised quantitatively. The applicationsof chitosan/silica composites in water treatment and chitosan/hydroxyapatite compositesin drug delivery field have been evaluated preliminary.The results show that chitosan hydrogel templates have controllable concentric lamellarstructure in the number range of1~77layers and in the thickness range of77.92μm~6mm. The chitosan/silica composites with silica content of50wt%,70wt%and90wt%were successfully copied the lamellar structure of chitosan hydrogel template.Thechitosan/silica composites have the same concentric lamellar structure with20layers aschitosan templates. The layer numbers have no relationship with the content ofinorganic matter, and can be regulated by changing the coagulation soaking time inNaOH solution and water. The averaged layer thickness of composite hydrogels is221.77μm similar to it of hydrogel template (222.50μm). The bending strength andmodulus of chitosan/silica composites in the direction perpendicular to layers are31.52MPa and4.21GPa respectively, and those parallel to layers are41.44MPa, and9.35GPa respectively, which are close to the mechanical properties of wood. Chitosan/silica composites after carbonization of carbon/silica composite of methyl orangeadsorption rate and adsorption capacity were65.45%and3.27mg/g, the adsorptionrate and adsorption capacity than coal ash zeolite and30.82%high17.80%. Thecarbon/silica composites were obtained by carbonized the composites and its adsorptionrate and capacity of methyl orange were65.45±1.79%and3.27±0.03mg/g respectively,which were higher than fly ash zeolite by17.80%and30.82%. The chitosan/hydroxyapatite composites with hydroxyapatite content of50wt%havesuccessfully copied the lamellar chitosan hydrogel template, and the number andthickness of layers are20and215.56μm, consist with chitosan hydrogel templates.Chitosan hydrogel templates induce and regulate the formation of hydroxyapatites, andfurther assembly them to form lamellar structure. The compression strength andmodulus of chitosan/hydroxyapatite composites were32.29±1.52MPa and1.09GParespectively close to the compact bone level. The sustainable release time of rifampicinfrom lamellar chitosan/hydroxyapatite composites is more than400h, increased by7times compared with lamellar chitosan materials.