Ultrafine powder is mainly used as a raw material for deep processing high-tech products in the electronics industry, chemical industry, rocket and aerospace technology. The quality of its use mainly determines the characteristics of the dry powder itself. Different preparation methods and conditions and the properties of the powder vary greatly.
Chemical reduction method is the preparation of precious metals. The main method of ultrafine powder. Small parameter changes during the chemical reaction will cause differences in the average particle size of the powder and its distribution and powder morphology, and the reaction process must be adjusted and controlled. The first is how the precious metal particles form crystal nuclei from the liquid phase, and secondly how the particles grow around the crystal nuclei. Finally, how the metal particles collide with each other to coagulate and settle. These are closely related to the concentration of the solution, the temperature, the choice of the dispersant and the reducing agent, and the stirring and stirring strength. It is generally necessary to use the statistical process control method to establish measurement points for each process for data analysis and monitoring. Commonly used ultrafine precious metal powders are metal black and flake, powder, atomized powder, ground shiny powder and condensed or non-condensed powder. The performance indicators are shown in the table below.
Gold and gold alloy powder properties table
name
Component
Shake density
(g/mL)
Specific surface area
(m 2 /g)
Average thickness
(μm)
form
Superfine gold powder
Superfine gold powder
Superfine gold powder
Ultrafine gold palladium powder
Ultrafine gold palladium powder
Ultrafine gold palladium platinum powder
Ultrafine gold palladium platinum powder
Ultrafine gold palladium platinum powder
Au
Au
Au
75Au25Pd
70Au22.5Pd7.5Pt
70Au20Pd10Pt
60Au20Pd20Pt
40Au20Pd40Pt
6.5
6.0
7.0
1.55
14.5
1.5
2.2
2.0
0.55
0.63
0.48
4.7
4.5
5.0
3.5
8.0
1.8
3.2
1.45
1.3
1.2
1.1
1.3
1.3
Flaky or spherical
Flaky or spherical
Flaky or spherical
Alloy powder or dendritic powder
Alloy powder or dendritic powder
Alloy powder or dendritic powder
Alloy powder or dendritic powder
Alloy powder or dendritic powder

Ultrafine powder slurry is prepared thin wires of gold, gold-palladium and low gold paste, gold platinum, palladium, gold, silver-palladium conductor paste excellent properties of the main phase of conductive material, which can be used an aqueous solution of reducing thermal decomposition and Preparation. The thermal decomposition method firstly evaporates and dehydrates pure gold trichloride at 120 ° C, and then decomposes into gold chloride by long temperature to 160 ° C, and then slowly decomposes to 185-196 ° C to obtain an average particle size of 1-2. Mm gold powder. To obtain a finer gold powder, add an appropriate dispersing agent to the aqueous solution, slowly add oxalic acid to reduce with sufficient agitation, then settle to stand, and wash with hot water to remove excess dispersant, reducing agent, and reaction product. Finally, it is washed with alcohol for 2 to 3 times and dried at a low temperature. The average particle size is 0.1-0.5 μm, which is spherical. Scale-like ultrafine gold powder can also be obtained by other preparation methods. Ferrous sulfate can also be used to restore the same to obtain a good product.

H[AuCl 4 ]+3FeSO 4 →Au↓+Fe 2 (SO 4 )3+FeCl 3 +HCl

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