Hydrothermal synthesis of cobalt nanoparticles in supercritical water

Satoshi Ohara, Hidetsugu Hitaka, Jing Zhang, Mitsuo Umetsu, Takashi Naka, Tadafumi Adschiri

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


We report a new method to synthesize cobalt (Co) nanoparticles using supercritical hydrothermal synthesis. An important aspect of supercritical hydrothermal synthesis of nano particles is the ability to create a homogeneous reducing atmosphere by introducing H2 gas. Co aqueous solution with formic acid was pressurized to 30 MPa at room temperature and rapidly heated to 400 °C by mixing with supercritical water and then fed into a tubular reactor. The size of obtained Co nanoparticles was about 10nm and its particle size distribution was very narrow. The coercivity force at room temperature of the nanopartricles showed about 90Oe. In this study, another important aspect of supercritical hydrothermal synthesis is reported; that is, in-situ surface modification of Co nanoparticles with carboxylic acids during crystallization.

Original languageEnglish
Pages (from-to)635-638
Number of pages4
JournalFuntai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy
Issue number9
Publication statusPublished - 2007 Sep


  • Cobalt nanoparticles
  • Hydrothermal synthesis
  • Supercritical water
  • Surface modification

ASJC Scopus subject areas

  • Mechanical Engineering
  • Industrial and Manufacturing Engineering
  • Metals and Alloys
  • Materials Chemistry


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