Strengths of Sapphire Crystals
THE strength of single crystals of entirely brittle materials should depend on the presence of stress raising flaws. Internally these could be formed by static dislocation arrays, voids or inclusions of foreign material. On the surface the flaws could be formed by mechanical damage or by surface steps as suggested by Marsh1.
The ultimate strength of solids
AbstractThere is an upper limit to the mechanical strength of any material under any particular test conditions. This limit is known as the ideal strength. The present paper attempts to define the ideal strength as closely as is presently possible. To this end, a brief account is first given of some of the highest strengths recorded experimentally. Then follows a short account of the published theoretical calculations of the ideal strength. Finally, the theoretical and experimental values are compared, and it is shown that in several instances these differ by less than a factor 2x. Resume Il existe une limite superieure de la resistance mecanique de tout rnateriau pour des conditions d'essai donnees. On donne a cette limite le nom de resistance ideale. Dans l'article, on tente de definir la resistance ideale de la maniere la plus precise qu'il soit possible de la faire avec les connaissances actuelles. A cette fin, on presente d'abord un sommaire de quelqu'unes des plus hautes resistances determinees expe...
Scaffolds Containing Spirulina sp. LEB 18 Biomass: Development, Characterization and Evaluation of In Vitro Biodegradation.
Polymer nanofibers are nanomaterials that can be used as scaffolds in tissue engineering. The objective of this study was to develop, characterize and evaluate the in vitro degradation of a biomaterial consisting of nanofibers produced from biodegradable and biocompatible polymers with potential applications as a scaffold for tissue regeneration and containing Spirulina sp. LEB 18 biomass as the bioactive compound. The polymers used were poly(hydroxybutyrate-co-hydroxyvalerate) and polycaprolactone. The polymeric solutions exhibited sufficiently high viscosity to produce uniform nanofibers with diameters between 335 and 617 nm. The applied conditions were as follows: a voltage of 25 kV, a distance from the capillary to the collector of 120 mm, a capillary diameter of 0.80 mm, and 12% polycaprolactone and a blend of 5% polycaprolactone and 10% poly(hydroxybutyrate-co-hydroxyvalerate). The biomass was incorporated into the nanofibers at a concentration of 3%, and the incorporation was confirmed using confocal microscopy. The nanofibers were characterized using differential scanning calorimetry and thermogravimetric analysis, which showed that the addition of biomass did not alter the thermal properties of the biomaterial. The addition of biomass improved the tensile strength and elongation of the scaffolds compared with those produced with polymers alone. A biodegradation assay showed enzymatic action toward the biomaterial, simulating the behavior of natural tissue. Based on the analysis, it was concluded that the scaffolds that were produced have the potential to be applied in the field of tissue regeneration as biomaterials with pharmacological properties.