Synthesized monocrystalline nanodiamond (nD) particles are heat-treated at various temperatures to produce highly structured diamond crystals. The heat-treated nDs show different weight loss ratios during thermogravimetric analysis. The crystallinities of the heat-treated nDs are analyzed using Raman spectroscopy. The average particle sizes of the heat-treated nDs are measured by a dynamic light scattering (DLS) system and direct imaging observation methods. Moreover, individual dispersion behaviors of the heat-treated nD particles are investigated based on ultrasonic dispersion methods. The average particle sizes of the dispersed nDs according to the two different measurement methods show very similar size distributions. Thus, it is possible to produce highly crystallized nD powder particles by a heattreatment process, and the nD particles are relatively easy to disperse individually without any dispersant. The heattreated nDs can lead to potential applications such as in nanocomposites, quantum dots, and biomedical materials.

• Hansang Kwon(Department of materials system engineering, Pukyoung National University, 365 Sinseon-ro, Nam-gu, Busan 48547, Republic of Korea) Corresponding author
• Jehong Park(Department of R&D, Next Generation Materials Co., Ltd, 365 Sinseon-ro, Nam-gu, Busan 48547, Republic of Korea)
• Marc Leparoux(Laboratory of Advanced Materials Processing, EMPA-Swiss federal laboratories for materials science and technology, Feuerwerkerstrasse 39, 3602 Thun, Switzerland)