Ceramic based nanocomposite, in which nano-sized ceramics and metals were dispersed within matrix grains and/or at grain boundaries, were successfully fabricated in the ceramic/cerarnic and ceramic/metal composite systems such as /SiC, /, MgO/SiC, mullite/SiC, /SiC, /B, /W, /Mo, /Ni and /Mo systems. In these systems, the ceramiclceramic composites were fabricated from homogeneously mixed powders, powders with thin coatings of the second phases and amorphous precursor composite powders by usual powder metallurgical methods. The ceramiclmetal nanocomposites were prepared by combination of H2 reduction of metal oxides in the early stage of sinterings and usual powder metallurgical processes. The transmission electron microscopic observation for the /SiC nanocomposite indicated that the second phases less than 70nm were mainly located within matrix grains and the larger particles were dispersed at the grain boundaries. The similar observation was also identified for other cerarnic/ceramic and ceramiclmetal nanocornposites. The striking findings in these nanocomposites were that mechanical properties were significantly improved by the nano-sized dispersion from 5 to 10 vol% even at high temperatures. For example, the improvement in hcture strength by 2 to 5 times and in creep resistance by 2 to 4 orders was observed not only for the ceramidceramic nanocomposites but also for the ceramiclmetal nanocomposites with only 5~01%se cond phase. The newly developed silicon nitride/boron nitride nanocomposites, in which nano-sized hexagonal BN particulates with low Young's modulus and fracture strength were dispersed mainly within matrix grains, gave also the strong improvement in fracture strength and thermal shock fracture resistance. In presentation, the process-rnicro/nanostructure-properties relationship will be presented in detail. The special emphasis will be placed on the understanding of the roles of nano-sized dispersions on mechanical properties.
Background : The objective of this study was to make colloidal dispersion of the active compound was characterized nano-composite from radix of Angelica gigas Nakai using hot melt extrusion (HME). Therefore, food grade hydrophilic polymer matrices was used to disperse compound in aqueous media.
Methods and Results : Extrudate solid formulations (ESFs) mediated various HPMCs (hydroxypropyl methylcellulose) and Na-Alg polymer from ultrafine powder of radix of Angelica gigas Nakai was developed through physical crosslink method (HME) with ionization agent (treatment of acetic acid) and food grade polymer [HPMCs such as HP55, CN40H, AN6 and sodium alignate (Na-Alg)]. X-ray powder diffraction (XRD) analysis confirmed the amorphization of crystal compounds in extrudate solid formulations mediated HP55 (HP55-ESF). Differential scanning calorimetry (DSC) analysis indicated a lower enthalpy (ΔH = 10.62 J/g) of glass transition temperature (Tg) in HP55-ESF. Infrared fourier transform spectroscopy (FT-IR) reveled new functional groups produced in HP55-ESF. Phenolic compound, flavonoid (including decursin and decursinol angelate) and antioxidant activity increased at 5, 10 and 2 times in HP55-ESF. Water solubility (61.5%) nano size (323 ㎚) particle was achieved in the HP55-ESF.
Conclusion : Nano-composites have been developed utilizing melt-extruded solid dispersions technology by food grade polymer enhanced nano dispersion (< 500 ㎚) of active compound from radix of Angelica gigas Nakai with enhanced solubility and bioavailability. This nano-composites of radix of Angelica gigas Nakai developmental and marketed products to enable therapeutic performance.