Nanopowders are agglomerates of particles, nanoparticles, or nanoclusters. In contrast to nanopowders which tend to agglomerate to larger grains and where electron microscopy shows large particle sizes with a relatively broad size distribution, nanoparticles generally exhibit small sizes, well defined and regular shapes and have histograms with a narrow size distribution curve. https://www.alfa-chemistry.com/products/nanoparticles-nanopowders-55.htm