Abstract: We have prepared a new class of polymeric fibers and masses which are produced by precipitation from solutions of the polymer. The fibers and fiber masses have novel and useful characteristics. A fiber mass of this invention is a coherent, three-dimensional network of interconnected crystalline polymeric fibers and fiber bundles randomly arrayed in all directions. The fibers are smaller in diameter than can be consistently produced by conventional fiber drawing and spinning techniques.The novel fiber masses are produced from solutions of fiber-forming linear organic polymers having regularly repeated chain structures. The polymers are precipitated from these solutions by simultaneously cooling and agitating the polymer solution at vibrations in the sonic frequency range. The fiber masses may then be removed from the solvent or, in the case of a polymerizable solvent, a composite may be formed.

Abstract: Single crystals, useful as laser emission compounds, having the formula ARF.sub.4 wherein A is potassium, sodium, or lithium, and R is holmium, yttrium, erbium, or dysprosium are prepared by a direct congruent melt crystal growth process that yields crystals exhibiting substantially superior physical and chemical characteristics compared to those grown by conventional methods.