Abstract: The present disclosure generally relates to thermally conductive aligned materials for a variety of purposes, including as thermal interface materials for semiconductor devices or other applications. Certain aspects are directed to compositions comprising discontinuous fibers that may be substantially aligned, e.g., defining a substrate. The composition may also include a polymer or a phase change material in contact with at least some of the discontinuous fibers. The discontinuous fibers may include carbon fibers in some cases. In some cases, the discontinuous fibers are aligned so as to facilitate heat transfer, e.g., along the direction that the fibers are aligned. Other aspects are generally directed to devices using such compositions, methods of making such compositions, kits including such compositions, or the like.