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In this work, Zn 1-x CoFe 2 Al x O 4 (x=0, 0.2, 0.4, 0.6, 0.8 and 1.0) ferrites were synthesized using the sol-gel method. XRD analysis was done and confirmed the formation of spinel structure, where the particle size and lattice parameter decrease with increase of aluminum concentration. This may be attributed to a shift of the bigger Al 3+ ions, from the tetrahedral to the octahedral sites, interchanging with smaller Zn 2+ ions and that consequently result to a decreased unit cell size. The Scanning Kelvin Probe Microscopy (SKPM) showed that the work function average ranges between 200 and 680 mV for the different concentration of aluminum in the samples. Fractural analysis indicated a small fracture between the samples of different ratios which can be attributed to the method used to prepare as well as the shifting of the Al 3+ ions. The UV-vis spectroscopy showed variation of energy gap with increasing aluminum concentration, and an increased optical absorbance as the Al 3+ ions were introduced in the samples.

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The spider silk fibers have unique high performance properties that make it a desirable model for artificial fibers and its performance under benign conditions has important implications for biomimicry. It has tensile strengths comparable to steel and some are nearly as elastic as rubber on a weight to weight basis. The spider spins its silk at ambient temperatures, low pressures and with water as solvent. Spiders are ectotherms and the ambient temperature affects the spinning speed and the mechanical and structural properties of the silk spun. The high cytocompatibility and low immunogenicity of spider silk fibers make them well suited for biomaterial products such as nerve conduits. Spider silk proteins have been shown to be soluble in ionic liquids, thus once soluble, they can be processed into new biomaterials such as films, gels, porous sponges, bone tissue engineering. The spider silk chains with a fixed molecular weight decreases exponentially with the UV irradiation time, since UV irradiation causes the chemical bonds in the protein chains to undergo cleavage. This paper reviews related literature on the spider silk spinning process, conditions and their effects on structure, mechanical properties of spider silk and its resistance to UV degradation. As a bonus, a brief review of the biotechnological production of recombinant spider silk us presented.