A scalable method of synthesizing hexagonal boron nitride (hBN) films and nanotubes by chemical vapor deposition (CVD) is provided. The method includes atmospheric pressure CVD of hBN on metallic growth substrates using solid boron sources and molecular nitrogen. The solid boron source can be in the form of powder, fragments, or platelets and placed upstream, on top, or below the growth substrate. The growth substrate can include Fe, Ni, Cr, Cu, and their alloys including various steels. The growth atmosphere includes nitrogen compounds, inert gases and hydrogen. The reaction can occur within a reaction vessel heated to 800 C.-1200 C. in less than 120 minutes with sequential cooling at a controlled rate. In laboratory testing, the hBN film exhibited improved protection against harsh corrosion over long periods and resistance to high-temperature oxidation in air.

GaAs IR window slabs having largest dimensions that are greater than 8 inches, and preferably greater than 12 inches, are grown using the Horizontal Gradient Freeze (HGF) method. Heat extraction is simplified by using a shallow horizontal boat that is only slightly deeper than the desired window thickness, thereby enabling growth of large slabs while also minimizing material waste and fabrication cost as compared to slicing and shaping thick plates from large, melt-grown boules. Single crystal seeds can be used to optimize the final orientation of the slabs and minimize secondary nucleation, thereby maximizing yield. A conductive doped GaAs layer can be applied to the IR window slab to provide EMI shielding. The temperature gradient during HGF can be between 1 C./cm and 3 C./cm, and the directional solidification can be at a rate of between 0.25 mm/h and 2.5 mm/h.

A scalable method of synthesizing hexagonal boron nitride (hBN) films and nanotubes by chemical vapor deposition (CVD) is provided. The method includes atmospheric pressure CVD of hBN on metallic growth substrates using solid boron sources and molecular nitrogen. The solid boron source can be in the form of powder, fragments, or platelets and placed upstream, on top, or below the growth substrate. The growth substrate can include Fe, Ni, Cr, Cu, and their alloys including various steels. The growth atmosphere includes nitrogen compounds, inert gases and hydrogen. The reaction can occur within a reaction vessel heated to 800 C.-1200 C. in less than 120 minutes with sequential cooling at a controlled rate. In laboratory testing, the hBN film exhibited improved protection against harsh corrosion over long periods and resistance to high-temperature oxidation in air.