Hydrogen reduction of ammonium paratungstate (APT) into tungsten blue oxide (TBO)

The macromeritic tungsten powder was prepared by wet hydrogen reduction at medium temperature; the coarse powder of Ammonium paratungstate powder (APT) was used as raw material. It is obtained by evaporating and crystallizating adding alkalia metal salts in the solution of ammonium tungstate. The microstructure, phase composition and particle size of the macromeritic tungsten powder were investigated by SEM, XRD and test analysis sieves. The effects of kinds, contents of alkali metal salts and the temperature in the reduction were studied. The results revealed that ideal tungsten powder, with the good fluditity, spherical, integrate and well-distributed, could be obtained. The raw material is the solution of ammonium tungstate adding NaCl, Li2CO3 and KCl , the concentration of them are all 3g/L, and it is under the condition of 1000°C,180min in wet hydrogen atmosphere. The average particle size is 67μm, the maximum is 150μm, the biggest loose density is 13.41g/cm3, and the best powder flowability is 9s/50g.

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Sintering Behavior and Hardness of Tungsten Prepared by Hard Metal Sludge Recycling Process without Ammonium Paratungstate

Korean Journal of Metals and Materials ◽

10.3365/kjmm.2022.60.1.53 ◽

2022 ◽

Vol 60 (1) ◽

pp. 53-61

Author(s):

Hanjung Kwon ◽

Jung-Min Shin

Keyword(s):

Grain Size ◽

Tungsten Oxide ◽

Hydrogen Reduction ◽

Hard Metal ◽

High Energy ◽

Tungstic Acid ◽

Sintering Behavior ◽

Recycling Process ◽

Ammonium Paratungstate ◽

Tungsten Powders

In this paper, we suggest a novel recycling process for hard metal sludge that does not use ammonium paratungstate. Ammonia, which in the conventional recycling process is essential for removing sodium and crystallized tungstate, was not used in the novel process. Instead of ammonia, acid was used to remove the sodium and crystallized tungstate resulting in the formation of tungstic acid (H2WO4). Tungsten powders were successfully synthesized by hydrogen reduction of the tungstic acid through H2O decomposition, WO3 to WO2 reduction, and tungsten metal formation. The tungsten powders prepared from tungstic acid were spherical in shape and had a higher sintering density than the facet-shaped tungsten powders prepared from tungsten oxide. The spherical shape of the tungsten powders enhanced their sinterability and resulted in an increase in the size of grains. This is a result of the high diffusion rate of the atoms along the particle surfaces. Despite having a higher density, the hardness of the sintered tungsten was lower than that of tungsten from tungsten oxide. High energy milling effectively reduced grain size and improved hardness. The hardness of the tungsten prepared from milled tungstic acid was enhanced to a value (max. 471 HV) higher than the best previously reported value (389 HV). In sum, tungsten can be hardened, thereby improving its sinterability and reducing grain size, with tungstic acid prepared using the proposed recycling process.

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Synthesis and Magnetic Properties of Nanocrystalline Fe-Ni Alloys During Hydrogen Reduction of NiFe2O4

Korean Journal of Metals and Materials ◽

10.3365/kjmm.2011.49.1.052 ◽

2011 ◽

Vol 49 (01) ◽

pp. 52-57 ◽

Cited By ~ 3

Author(s):

Min Kyu Paek ◽

Kyung Hyo Do ◽

Mohamed Bahgat ◽

Jong Jin Pak

Keyword(s):

Magnetic Properties ◽

Hydrogen Reduction ◽

Ni Alloys

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Structural reconstruction of germanosilicate frameworks by controlled hydrogen reduction

Chemical Communications ◽

10.1039/c8cc09294j ◽

2019 ◽

Vol 55 (13) ◽

pp. 1883-1886 ◽

Cited By ~ 2

Author(s):

Yue Ma ◽

Hao Xu ◽

Xue Liu ◽

Mingming Peng ◽

Wenting Mao ◽

...

Keyword(s):

Metal Clusters ◽

Hydrogen Reduction ◽

Hydrogen Atmosphere ◽

Water Washing

Calcined UTL-type germanosilicate was firstly reduced in a hydrogen atmosphere at an appropriate temperature. Then, air-calcination and water-washing procedures were performed to remove the Ge metal clusters or crystals originated from the reduction of skeleton germanium(iv) to yield pure zeolite phase of two daughter structures analogous to IPC-2 and IPC-6.

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