The continuous hydrothermal synthesis of nano-particulate ferrites in near critical and supercritical water

2001 ◽  
Vol 11 (5) ◽  
pp. 1408-1416 ◽  
Author(s):  
Albertina Cabañas ◽  
Martyn Poliakoff
Keyword(s):  
Hydrothermal Synthesis ◽  
Supercritical Water

Hydrothermal Synthesis of Potassium Hexatitanates under Subcritical and Supercritical Water Conditions and Its Application in Photocatalysis

2001 ◽  
Vol 13 (3) ◽  
pp. 842-847 ◽  
Author(s):  
Rosiyah Binti Yahya ◽  
Hiromichi Hayashi ◽  
Takako Nagase ◽  
Takeo Ebina ◽  
Yoshio Onodera ◽  
...  
Keyword(s):  
Hydrothermal Synthesis ◽  
Supercritical Water ◽  
Water Conditions

scholarly journals Hydrothermal Synthesis of Cobalt Nanoparticles in Supercritical Water

2007 ◽  
Vol 54 (9) ◽  
pp. 635-638 ◽  
Author(s):  
Satoshi Ohara ◽  
Hidetsugu Hitaka ◽  
Jing Zhang ◽  
Mitsuo Umetsu ◽  
Takashi Naka ◽  
...  
Keyword(s):  
Hydrothermal Synthesis ◽  
Supercritical Water ◽  
Cobalt Nanoparticles

Simulation of Nucleation, Growth, and Aggregation of Nonaparticles in Supercritical Water

2013 ◽  
Vol 316-317 ◽  
pp. 1071-1074
Author(s):  
Lu Zhou ◽  
Shu Zhong Wang ◽  
Hong He Ma
Keyword(s):  
Hydrothermal Synthesis ◽  
Rate Constant ◽  
Supercritical Water ◽  
Metal Oxide Nanoparticles ◽  
Operation Time ◽  
Growth Rate Constant ◽  
Synthesis Reaction ◽  
Synthesis Of Nanoparticles ◽  
Size Evolution ◽  
Nucleation Growth

A simulation model was developed for predicting the particle size evolution in hydrothermal synthesis of nanoparticles in supercritical water. Four elementary kinetic processes, including hydrothermal synthesis reaction, nucleation, growth, and aggregation, were involved based on the population balance equations (PBEs). The homogenous nucleation of metal oxide nanoparticles started at the operation time of 3.72μs. When the rate constant of hydrothermal synthesis reaction lnk increased from 2.8 to 6.16, the nucleation rate increased by three orders of magnitude (1021-1024particles/m3•s) and the nucleation period reduced from 0.2s to less than 0.02s. The APS decreased by approximately half when a ten-fold smaller growth rate constant was adopted in the range of 10-11-10-8.

The Aqueous Chemistry of Chromium(III) above 100 °C: Hydrothermal Synthesis of Chromium Spinels

1971 ◽  
Vol 49 (14) ◽  
pp. 2433-2441 ◽  
Author(s):  
T. W. Swaddle ◽  
J. H. Lipton ◽  
G. Guastalla ◽  
P. Bayliss
Keyword(s):  
Stainless Steel ◽  
Hydrothermal Synthesis ◽  
Molecular Oxygen ◽  
Supercritical Water ◽  
Perchloric Acid ◽  
Aqueous Chemistry ◽  
Hydrothermal Deposition ◽  
316 Stainless Steel ◽  
Chromium Vi ◽  
Hydrothermal Origin

The hydrothermal deposition of CrO(OH) from aqueous chromium(III) chloride, nitrate, and perchlorate, and of Cr3(SO4)2(OH)5•H2O and Cr(OH)SO4•2H2O(?) from aqueous chromium(III) sulfate, has been investigated. Aqueous chromium(III) is oxidized to chromium(VI) by 0.4 M perchloric acid above 225 °C, and by molecular oxygen above 250 °C. Aqueous chromium(III) can react at 300 °C with iron or steel, cobalt, and copper to produce FeCr2O4, CoCr2O4, and Cu2Cr2O4, respectively. CrO(OH) reacts with type 316 stainless steel at 440 °C in supercritical water of density 0.7 g cm−3 to yield (Fe,Ni)-Cr2O4, which is the "cubic Cr2O3" of Laubengayer and McCune. The spinels MCr2O4 (M = Mg, Mn, Fe, Co) can be made hydrothermally at ca. 300 °C from Cr(OH)3 and M(OH)2. This information is relevant to corrosion phenomena, and the possible hydrothermal origin of chromite deposits in serpentinized rocks.

Hydrothermal synthesis of zirconia nanocrystals in supercritical water

2004 ◽  
Vol 19 (8) ◽  
pp. 2230-2234 ◽  
Author(s):  
Yukiya Hakuta ◽  
Tomotugu Ohashi ◽  
Hiromichi Hayashi ◽  
Kunio Arai
Keyword(s):  
Hydrothermal Synthesis ◽  
Supercritical Water ◽  
Hydrothermal Reaction ◽  
Acetate Solution ◽  
Supercritical Conditions ◽  
Transmission Electron ◽  
Tetragonal Crystal ◽  
Tetragonal Crystal Structure ◽  
Zirconia Powders

Zirconia nanocrystals were prepared by hydrothermal reaction of 0.05 M zirconyl nitrate and zirconyl acetate solutions at supercritical conditions of 400 °C and30 MPa for 1.8 s reaction time. Characterization of products were performed byx-ray diffraction, transmission electron microscopy, and Brunauer–Emmett–Teller measurements. The product particles were compared with zirconia particles prepared by conventional hydrothermal synthesis routes and precipitation-calcination. From the results, zirconia powders prepared in supercritical water had higher crystallinity than those obtained by other methods. Product particles with tetragonal crystal structure with a mean diameter of 6.8 nm could be formed from 0.05 M zirconyl acetate solution in the presence of 0.1 M potassium hydroxide at supercritical conditions.

Sign in / Sign up

Export Citation Format

Share Document