Scientists have predicted that carbon's immediate neighbors on the periodic chart, boron and nitrogen, may also form perfect nanotubes, since the advent of carbon nanotubes (CNTs) in 1991. First proposed then synthesized by researchers at UC Berkeley in the mid 1990's, the boron nitride nanotube (BNNT) has proven very difficult to make until now. Herein we provide an update on a catalyst-free method for synthesizing highly crystalline, small diameter BNNTs with a high aspect ratio using a high power laser under a high pressure and high temperature environment first discovered jointly by NASA/NIA/JSA. Progress in purification methods, dispersion studies, BNNT mat and composite formation, and modeling and diagnostics will also be presented. The white BNNTs offer extraordinary properties including neutron radiation shielding, piezoelectricity, thermal oxidative stability (> 800˚C in air), mechanical strength, and toughness. The characteristics of the novel BNNTs and BNNT polymer composites and their potential applications are discussed.

Inadequate dispersion of nanomaterials is a critical issue that significantly limits the potential properties of nanocomposites and when overcome, will enable further enhancement of material properties. The most common methods used to improve dispersion include surface functionalization, surfactants, polymer wrapping, and sonication. Although these approaches have proven effective, they often achieve dispersion by altering the surface or structure of the nanomaterial and ultimately, their intrinsic properties. Co-solvents are commonly utilized in the polymer, paint, and art conservation industries to selectively dissolve materials. These co-solvents are utilized based on thermodynamic interaction parameters and are chosen so that the original materials are not affected. The same concept was applied to enhance the dispersion of boron nitride nanotubes (BNNTs) to facilitate the fabrication of BNNT nanocomposites. Of the solvents tested, dimethylacetamide (DMAc) exhibited the most stable, uniform dispersion of BNNTs, followed by N,N-dimethylformamide (DMF), acetone, and N-methyl-2-pyrrolidone (NMP). Utilizing the known Hansen solubility parameters of these solvents in comparison to the BNNT dispersion state, a region of good solubility was proposed. This solubility region was used to identify co-solvent systems that led to improved BNNT dispersion in poor solvents such as toluene, hexane, and ethanol. Incorporating the data from the co-solvent studies further refined the proposed solubility region. From this region, the Hansen solubility parameters for BNNTs are thought to lie at the midpoint of the solubility sphere: 16.8, 10.7, and 9.0 MPa(1/2) for δd, δp, and δh, respectively, with a calculated Hildebrand parameter of 21.8 MPa(1/2).

One-dimensional (1D) nanostructures, such as nanowires, nanotubes, nanorods, and nanoribbons, have attracted significant attention stemming from the plethora of interesting size-dependent and, more importantly, structure-related properties resulting from confinement effects. In particular, the novel properties of 1D nanostructures of metals and metal oxides (binary and ternary) render them as prime candidates for a wide range of applications including the fabrication of nanoscale devices associated with solar cells, energy storage, fuel cells, molecular computing and information storage, medical imaging, diagnosis and detection, drug delivery, sensors and catalysis. Thus, it has been simultaneously necessary and critical to create synthetic protocols for the production of these materials which not only are reliable and reproducible, but also can generate compositionally pure, monodisperse, highly crystalline products of a desired 1D morphology. Solution-based methodologies have demonstrated significant advantages over other approaches, as they are facile, simple, flexible, 'green' by nature, and can be applied to a wide range of nanomaterials with diverse chemical compositions. Moreover, these methods can often be scaled so as to produce large quantities of products which are advantageous from an applications' standpoint. Herein, we present synthetic advances associated with solution-based approaches. Specifically solvothermal/hydrothermal, molten salt, electrospinning, template-directed, solution/one-pot, and sol-gel methodologies are discussed with the primary goal of achieving the reproducible synthesis of 1D motifs of metals, binary metal oxides, and ternary metal oxide systems.