JP2018104779A - Method for manufacturing gold-loaded platinum powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing platinum powder making it possible to highly disperse gold on platinum particle surfaces.SOLUTION: A method for manufacturing high-disperse gold-loaded platinum powder includes: carrying out evaporation to dryness of solvent while stirring platinum powder and a gold compound solution under reduced pressure so that the metal compound is high-disperse loaded on particle surfaces of the platinum powder; and heat-treating the platinum powder having the gold compound loaded thereon at 560-650°C so that gold is high-disperse loaded on platinum particle surfaces.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing platinum powder, and more particularly to a method for obtaining a powder in which gold is dispersed and supported on platinum particles.

  As an application of platinum gold powder, there is an application for producing a conductive film, a heating element circuit, an electrode and the like of various electronic parts by making a paste. A general component structure of the paste includes platinum gold powder, an inorganic oxide such as a metal oxide or glass frit that serves as a binder for the substrate, and an organic vehicle. The paste is coated by means such as screen printing on an insulating substrate such as ceramics or an element, and then the coating layer is baked to form a conductive film, a heating element circuit, an electrode, and the like.

  Conventionally, it has been disclosed that a platinum gold powder is produced by mixing a platinum compound solution and a gold compound solution and reducing them in a wet manner (Patent Document 1). Patent Document 1 discloses a method for producing alloy fine particles in which Pt ions and Au ions are reduced by the action of a reducing agent in a liquid phase reaction system and precipitated as alloy fine particles made of a Pt—Au alloy. Yes.

Japanese Patent No. 5251227

    In the prior art, platinum and gold are alloyed, but depending on the application, a state where gold is highly dispersed on the surface of platinum particles may be preferable. When a coating layer containing platinum gold powder is baked to form an electrode or the like, if gold segregation occurs in the platinum gold powder, gold having a low melting point may sublimate.

  The present invention has been made in view of the above circumstances, and decomposes a gold compound into metal gold, and at the same time strengthens the bond between the surface of the platinum particle and gold so that gold is highly dispersed and supported on the surface of the platinum particle. An object of the present invention is to provide a method for producing gold-supported platinum powder.

  In order to achieve the above object, the present invention evaporates and evaporates the solvent while stirring the platinum powder and the gold compound solution under reduced pressure so that the gold compound is highly dispersed and supported on the surface of the platinum powder particles. And a step of heat-treating a platinum powder carrying a compound at 560 to 650 ° C. to carry gold in a highly dispersed manner on the surface of platinum particles.

  According to the configuration of the present invention, a gold-supported platinum powder that can disperse and support gold on the surface of the platinum particles by decomposing the gold compound into metal gold and at the same time strengthening the bond between the surface of the platinum particles and gold. The manufacturing method of can be provided.

The surface analysis result of the gold | metal | money of the particle | grain surface of Example 1 is shown. The surface analysis result of the gold | metal | money of the particle | grain surface of Example 2 is shown. The surface analysis result of the gold | metal | money of the particle | grain surface of Example 3 is shown. The surface analysis result of the gold | metal | money of the particle | grain surface of the comparative example 1 is shown. The surface analysis result of the gold | metal | money of the particle | grain surface of the comparative example 2 is shown. The surface analysis result of the gold | metal | money of the particle | grain surface of the comparative example 3 is shown.

  An embodiment of the present invention includes a step of evaporating and drying a solvent while stirring a platinum powder and a gold compound solution under reduced pressure so that the gold compound is highly dispersed and supported on the particle surface of the platinum powder, and the gold compound is supported. And a step of heat-treating the platinum powder at 560 to 650 ° C. so that the gold particles are highly dispersed and supported on the surface of the platinum particles.

  In the step of highly dispersing and supporting the gold compound on the surface of the platinum powder particle, the solvent is removed while stirring the platinum powder and chloroauric acid solution at 70 ° C. or less under reduced pressure, and the gold compound is coated on the surface of the platinum particle. . Through this step, the gold compound is supported in a highly dispersed manner on the surface of the platinum powder.

  In the heat treatment step, the powder in which the gold compound is coated on the surface of the platinum particles is heat treated in the atmosphere at a temperature of 560 to 650 ° C. The decomposition temperature of the gold compound is about 360 ° C. However, when a temperature near the decomposition temperature is applied, the precipitated gold aggregates and segregation of gold occurs. When heat treatment is performed at 560 to 650 ° C., which is higher than about 360 ° C. by 200 ° C. or more, the gold compound is decomposed to become metal gold, and at the same time, the bond between the platinum particle surface and gold is strengthened so be able to. In addition, when it heat-processes at the temperature over 650 degreeC, aggregation of platinum particles will progress and a coarse particle will produce | generate. When gold segregation occurs, gold having a low melting point may sublime.

  According to the present invention, an aqueous solution in which platinum powder having an average particle size of about 0.6 to 10 μm as a platinum raw material and gold chloride (III) acid, gold (I) sodium sulfite, or the like dissolved therein can be used as a gold compound. . Moreover, in the Example mentioned later, although the weight ratio of the gold in platinum powder was 1 wt%, the weight ratio of the gold in platinum powder can be changed by adjusting the compounding ratio of platinum powder and a gold compound. it can. In particular, it is preferable to use a chloroauric (III) acid solution from the viewpoints that impurities such as sodium and potassium do not remain, and thermal decomposition occurs at a low temperature.

Example 1
To 19.8 g of platinum powder with an average particle size of 9 μm, 18.9 g of chloroauric acid solution (1.06 wt%) was added and charged into an eggplant-shaped flask, and decompression and rotation by a motor were started. Soaked in a warm bath. The solvent was removed under the conditions of pressure: 4 × 103 Pa and rotation speed: 40 to 150 rpm. Further, in the eggplant flask, the mixture of the platinum powder and the chloroauric acid from which the solvent was removed was dried, and the chloroauric acid was highly dispersed and supported on the surface of the platinum particles. The drying conditions were 120 ° C. and 12 hours in the air.

  Next, the mixture was placed on an aluminum boat and heated in the atmosphere at 560 ° C. for 3 hours to decompose chloroauric acid and to carry highly dispersed gold on platinum.

  The mixture was pulverized by a pulverizer and classified with a sieve having an aperture of 53 μm to obtain spherical platinum powder on which gold was highly dispersed and supported.

(Examples 2 and 3)
Samples of Examples 2 and 3 were manufactured under the same conditions as in Example 1 except that the heating temperature in the heat treatment step was as follows.
Example 2: 600 ° C. for 3 hours Example 3: 650 ° C. for 3 hours

(Comparative Examples 1 and 2)
Samples of Comparative Examples 1 and 2 were produced under the same conditions as in Example 1 except that the heating temperature in the heat treatment step was as follows.
Comparative Example 1: 520 ° C. for 3 hours Comparative Example 2: 700 ° C. for 3 hours

(Comparative Example 3)
19.8 g of platinum powder with an average particle size of 9 μm is suspended in pure water, 18.9 g of chloroauric acid solution (1.06 wt%) is added, gold is reduced with a reducing agent (ascorbic acid), and platinum powder Gold was deposited on the surface of the particles.

  The composition of the obtained powder was measured by plasma emission spectroscopy. The particle size of the obtained powder was measured by a laser diffraction / scattering particle size distribution measuring method, and the particle size (D50) corresponding to an integrated value of the particle size distribution of 50% was determined as the average particle size.

  The distribution state of gold on the obtained powder particles was examined by surface analysis using EPMA (Electron Probe Microanalyzer). When a gold aggregate with a width of 1.0 μm or more is recognized in the surface analysis photograph, the distribution state is poor (with aggregation), and when such an aggregate is not recognized, the distribution state is good (in a highly dispersed state). Yes, no aggregation.)

  The properties of the obtained powder are shown in Table 1.

The surface analysis results (photos) of gold for the example powder and the comparative example powder are shown in FIGS. The magnification of the surface analysis photograph was adjusted so that the entire platinum particle could be accommodated in the entire photograph. In Examples 1 to 3, no gold aggregate having a width of 1.0 μm or more was observed (no gold aggregation), indicating that gold was highly dispersed. On the other hand, in Comparative Examples 1 and 3, aggregation of gold is observed. In Comparative Example 2, the average particle diameter is about 1.5 times that of Examples 1 to 3, and particle coarsening due to aggregation of platinum particles is observed.

Claims (1)

A step of evaporating and drying the solvent while stirring the platinum powder and the gold compound solution under reduced pressure, and supporting the gold compound on the particle surface of the platinum powder in a highly dispersed manner;
A step of heat-treating the platinum powder carrying the gold compound at 560 to 650 ° C. so that gold is highly dispersed and supported on the surface of the platinum particles;
A method for producing gold-dispersed platinum powder characterized by comprising: