BS in Materials Engineering
Materials Engineering Department
Bamboo is a renewable natural composite with potential as both a construction and synthesis material. The components of bamboo are cellulosic vascular bundles imbedded within a lignin matrix that create a porous hierarchical structure. This structure has low density while maintaining high strength, toughness, and elasticity, but is susceptible to organic decay. A study was performed to evaluate the effect of varying bamboo culm age (1-3 years) and density (0.72-1.05 g/cm3) on the ability to control inorganic mineral precipitation to prevent degradation and preserve dimensional stability of the organic matrix. Internodal culm samples were immersed in solutions of sodium silicate, citric acid, and mineral water (NaSi:TCA:H2O) in volumetric ratios. Immersion periods varied from 30 seconds (evaporative precipitation) to 24 hours (acid-catalyzed soak diffusion). Water adsorption isotherms were modeled using Fick’s second law of diffusion and adsorption coefficients indicate that an evaporative precipitation treatment reduced the absorption coefficient of bamboo by 10%. Soak diffusion treatments increased the absorption coefficient and these results are representative of significant lignin leaching during processing and correlate to a reduction in total bamboo hydrophobicity negating the effects of the mineralization treatment. SEM analysis showed culms exposed to solutions of pH 6.5-7.3 showed limited mineralization, pH 8 evidenced mineral precipitations primarily within cell wells, and pH > 8.5 showed significant cellular decomposition and mineralization within pores. XRD analysis was performed that indicated the preservation of crystalline cellulose in evaporative precipitation treatments as well as peaks that correspond to sodium-rich feldspars and silica.