CN116618663A - A kind of high-purity dense microfine PtRh alloy spherical powder and its preparation method - Google Patents

Abstract

The invention discloses a preparation method of high-purity compact fine PtRh alloy spherical powder, which comprises the steps of mixing sponge Pt and sponge Rh to obtain a premix A; adding Na to premix A ₂ B ₄ O ₇ And SiO ₂ Fully and uniformly mixing to obtain a ductile-brittle raw material system B; performing high-energy ball milling on the ductile-brittle material system B to obtain composite powder C; plasma in-situ smelting and sphericizing are carried out on the composite powder C to obtainComposite spherical powder D; the composite spherical powder D is a core-shell structure with a nonmetallic slag phase coated on the surface of PtRh alloy; and removing a nonmetallic slag phase in the composite spherical powder D by using an alkaline solution to obtain PtRh alloy spherical powder. The invention also discloses a high-purity compact fine PtRh alloy spherical powder with the granularity of 1-5 mu m, the average grain diameter of 2-4 mu m and the tap density of more than or equal to 7g/cm ³ The sphericity is more than or equal to 0.96, the sphericity rate is more than or equal to 98%, and the powder purity is more than or equal to 99.9%.

Description

A kind of high-purity dense microfine PtRh alloy spherical powder and its preparation method

technical field

The invention relates to a high-purity dense fine PtRh alloy spherical powder and a preparation method thereof, belonging to the technical field of precious metal powder preparation.

Background technique

Because PtRh alloy has the characteristics of corrosion resistance, oxidation resistance, creep resistance, electrical and thermal conductivity and strong catalytic activity, it is widely used in industrial fields such as glass fiber manufacturing, high temperature measurement, and reaction catalysis. Since Rh has a higher melting point, hardness, and high-temperature strength than Pt, the increase in Rh content can significantly improve the physical and chemical properties of PtRh alloys, but it also brings greater challenges to the processing of PtRh alloys.

The traditional preparation methods of PtRh alloy powder mainly include mechanical pulverization, atomization and electric spark discharge. The mechanical pulverization method is to obtain fine PtRh powder by means of cutting, fracturing, ball milling, etc., not only the process is time-consuming and energy-consuming, but also the shape of the obtained powder is irregular, which is difficult to apply to the near-net shape of PtRh parts; the atomization method is through the airflow The PtRh alloy melt is atomized by means of impact or centrifugal rotation to obtain spherical or quasi-spherical PtRh alloy powder. Its product has a wide particle size, poor sphericity, and generally has defects such as hollowness and bonding. The mechanical properties of parts obtained by using it as a raw material for near-net molding are generally poor. The spark discharge method is to form a high-temperature plasma ablation electrode through continuous discharge between PtRh alloy electrodes to obtain powder materials. Due to the local overheating of the electrode at the moment of discharge, a large amount of metal vapor generated will condense and adhere to the surface of the powder in the form of flocs, reducing the sphericity of the powder and causing the agglomeration of the powder. Therefore, the PtRh alloy prepared by the existing method cannot meet the requirement of near-net shape of the PtRh alloy in terms of fluidity, dispersibility and filling property.

In recent years, plasma spheroidization technology has been introduced into the field of PtRh alloy spherical powder preparation. This technology uses irregular shape PtRh alloy powder as raw material, and uses extremely high temperature of plasma to melt the powder, and the molten droplets are condensed into balls under the action of surface tension, and then rapidly cooled to obtain PtRh alloy spherical powder with regular shape. As the raw material of plasma spheroidization technology, irregular PtRh alloy powder needs to be obtained by alloy melting, ingot casting, segmentation, crushing and other methods. However, in the process of smelting and casting PtRh alloys, the composition segregation is common. Even if the size of the ingot is reduced, and multiple remelting + composition homogenization heat treatments are performed, the element composition of different positions inside the ingot is still different. This difference directly leads to the reduction of the uniformity of the composition of the irregular PtRh powder obtained after crushing, and finally affects the PtRh spherical powder obtained by spheroidization through composition heredity; in addition, the work hardening rate of the PtRh alloy increases with the Rh content in the alloy. The rise of the increase sharply, which makes the crushing of high Rh content (≥30wt%) PtRh alloy ingots extremely difficult, not only the crushing process consumes energy and time, but also easily introduces impurities; finally, although high-temperature plasma is beneficial to the raw material PtRh The rapid melting of the powder, but the extremely high temperature will inevitably lead to the burning loss and gasification of the alloy elements, especially the irregular powder with a particle size of less than 10 μm, the sharp position on the surface will be instantaneous when it enters the plasma high temperature zone. Vaporizes and is carried away by air currents. This phenomenon not only results in a final product composition that deviates from the original alloy design, but also results in a significant loss of precious metals. Therefore, although the plasma spheroidization technology can realize the preparation of PtRh alloy spherical powder, its existing problems cannot be ignored.

Contents of the invention

The purpose of the present invention is to overcome the above-mentioned defects, provide a high-purity dense fine PtRh alloy spherical powder and its preparation method, and solve the problems of low composition uniformity, low purity and high loss rate of precious metals in the PtRh alloy spherical powder obtained by traditional preparation methods. Problem, the PtRh alloy spherical powder obtained in the present invention has a particle size of 1 to 5 μm, an average particle size of 2 to 4 μm, a tap density of ≥7 g/cm ³ , a sphericity of ≥0.96, a sphericity of ≥98%, and a powder purity of ≥99.9 %.

In order to realize the foregoing invention object, the present invention provides following technical scheme:

A preparation method of high-purity dense fine PtRh alloy spherical powder, comprising:

Mix the sponge Pt and the sponge Rh to obtain a premix A;

Add Na ₂ B ₄ O ₇ and SiO ₂ to the premixture A, and mix thoroughly to obtain the ductile-brittle raw material system B;

Perform high-energy ball milling on the ductile-brittle raw material system B to obtain composite powder C;

Perform plasma in-situ smelting and spheroidization treatment on the composite powder C to obtain a composite spherical powder D; the composite spherical powder D is a core-shell structure in which the non-metallic slag phase is coated on the surface of the PtRh alloy;

The non-metallic slag phase in the composite spherical powder D is removed by an alkaline solution to obtain a PtRh alloy spherical powder.

Further, the purity of the sponge Pt is ≥99.9wt%, and the purity of the sponge Rh is ≥99.9wt%;

In premixture A, the content of sponge Rh is 5wt%-50wt%, and the rest is sponge Pt.

Further, Na ₂ B ₄ O ₇ and SiO ₂ are added to the premixture A at a mass ratio of 1 to 4:1;

The total mass of Na ₂ B ₄ O ₇ and SiO ₂ is 4%-10% of the mass of the premixture A.

Further, the ductile-brittle raw material system B is subjected to high-energy ball milling using planetary high-energy ball milling equipment, and the ball milling parameters include:

The ball-to-material ratio is 5-3:1, the filling ratio is 10%-50%, the ball milling speed is 250-600r/min, the transmission ratio of revolution and rotation is 1:2-4, the ball diameter is 2-8mm, and the ball milling time is 2-10h. The material of the grinding ball and the inner lining of the ball milling tank is SiO ₂ .

Further, the ductile-brittle raw material system B was subjected to high-energy ball milling without adding a process control agent.

Further, the particle size range of the composite powder C is 1.5-7.5 μm.

Further, the method of performing high-energy ball milling on the ductile-brittle raw material system B to obtain the composite powder C is as follows:

Classify the powder obtained by high-energy ball milling of the ductile-brittle raw material system B, keep the powder within the required particle size range, and continue to carry out high-energy ball milling for the remaining powders, and repeat the above process until the particle size of all powders meets the required particle size range. Promptly obtain composite powder C;

The classification method is mechanical sieving or air classification.

Further, the process parameters for plasma in-situ smelting and spheroidization treatment of composite powder C are:

The power of the inductively coupled plasma torch is 20kW~50kW; the working gas is oxygen, and the flow rate of the working gas is 20slpm~40slpm; the side gas is oxygen, and the flow rate of the side gas is 100slpm~400slpm; the carrier gas is oxygen, and the flow rate of the carrier gas is 1slpm~10slpm; The system pressure for inductively coupled plasma torch operation is 50kPa-98kPa;

The powder feeding rate of composite powder C is 10g/min～80g/min.

Further, the alkaline solution is an aqueous solution of NaOH, KOH, Na ₂ CO ₃ or NaHCO ₃ , and the pH value of the alkaline solution is ≥9; after removing the non-metallic slag phase in the composite spherical powder D by using an excessive amount of alkaline solution, the The obtained product is repeatedly washed to neutrality, and the PtRh alloy spherical powder is obtained after drying;

The recovery rate of the PtRh alloy spherical powder is ≥98%, and the recovery rate is the ratio of the total mass of the platinum-rhodium alloy powder finally received to the total mass of the platinum sponge and rhodium sponge input initially, that is, the recovery ratio of the precious metal.

A high-purity dense fine PtRh alloy spherical powder obtained by the above-mentioned preparation method of the high-purity dense fine PtRh alloy spherical powder, the particle size range of the PtRh alloy spherical powder is 1-5 μm, and the average particle size is 2-4 μm , tap density ≥ 7g/cm ³ , sphericity ≥ 0.96, sphericity ≥ 98%, purity ≥ 99.9%.

Compared with the prior art, the present invention has at least one of the following beneficial effects:

(1) The present invention creatively proposes a method for preparing a high-purity dense fine PtRh alloy spherical powder. When the raw materials are ball milled and compounded for granulation, the ductile material system composed of sponge Pt and sponge Rh is added A certain proportion of Na ₂ B ₄ O ₇ and SiO ₂ brittle phase constitutes a "ductile-brittle" ball milling system. The addition of brittle phase not only makes the grinding and crushing efficiency of sponge Pt and sponge Rh higher, but also improves the grinding and crushing efficiency in the subsequent composite granulation process. Among them, it can adhere to the surface of the ductile metal phase, reduce the surface energy of the powder, and realize effective control of the particle size of the composite powder. At the same time, it is not necessary to introduce additional process control agents to control the particle size of the composite powder, which improves the product purity;

(2) The ball milling object of the present invention is ductile sponge Pt and sponge Rh simple substance, rather than PtRh alloy with higher mechanical properties, which greatly reduces the difficulty of ball milling, especially for ball milling of PtRh alloys with high Rh content, the difficulty of crushing is significantly reduced .

(3) The present invention limits the size of the composite powder by pre-classifying the composite powder obtained after ball milling and compound granulation, and the particle size of the composite powder sent into the plasma torch for alloying and spheroidization Control within a certain range, so that the plasma treatment process parameters have a better match with the particle size of the raw material powder, avoiding the situation that the small-size powder is severely burned and the large-size powder is not fully heated, and the product particle size is more Concentration, and the composite powder whose particle size does not meet the specifications after classification is returned to the ball milling step to continue processing, which improves the utilization rate of raw materials and at the same time, the spheroidization rate and sphericity of the final product are also higher.

(4) The present invention directly feeds the composite powder C containing Pt and Rh into the plasma torch, so that the alloying and spheroidization of the composite powder can be completed in one plasma treatment, which shortens the processing flow and reduces the cost and raw material loss, the product composition is uniform, and the powder yield is ≥98%.

(5) The present invention introduces Na ₂ B ₄ O ₇ and SiO ₂ into the composite powder to make the composite powder heat up more uniformly in the plasma torch, and preferentially melts Na ₂ B ₄ O ₇ and SiO ₂ to form glass The state melt will spontaneously float on the surface of the alloy melt to form a protective layer, avoiding the violent evaporation of Pt and Rh elements during the spheroidization process of the alloy smelting, ensuring the stability and consistency of the composition of the spherical alloy melt during the smelting process, and reducing the loss of raw materials.

(6) The present invention uses oxygen as the working medium in the plasma in-situ smelting and spheroidization process. Oxygen is used as a diatomic gas. After being excited in the plasma torch, the enthalpy value is higher than that of the monoatomic gas. At the same time, its own strong oxidation It is beneficial to the oxidation and slagging of non-Pt and Rh impurity phases in the composite powder C, and is dissolved in the glassy melt to improve the purity of the final product.

(7) Due to the existence of the core-shell structure of the powder during the plasma treatment process, a small amount of gasified powder material will condense on the surface of the non-metallic slag phase shell during the powder condensation process and be removed in the subsequent alkaline cleaning process , avoiding the generation of flocs on the surface of the PtRh alloy powder, and improving the fluidity and sphericity of the powder.

Description of drawings

Fig. 1 is the schematic diagram of the preparation method of spherical PtRh powder of the present invention;

Fig. 2 is the micromorphological figure of the high-purity dense microfine PtRh25 alloy spherical powder obtained in Example 2 of the present invention;

Fig. 3 is the particle size distribution figure of PtRh25 alloy spherical powder of the present invention;

Fig. 4 is the electronic micrograph of composite powder C composed of gray ductile phase (sponge Pt and sponge Rh) and white brittle phase (Na ₂ B ₄ O ₇ and SiO ₂ ) of the present invention;

Fig. 5 is an electron micrograph of the composite spherical powder of the core-shell structure "non-metallic slag phase-PtRh alloy" of the present invention.

Detailed ways

The following describes the present invention in detail, and the features and advantages of the present invention will become more clear and definite along with these descriptions.

The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as superior or better than other embodiments. While various aspects of the embodiments are shown in drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

The invention provides a method for preparing a high-purity dense fine PtRh alloy spherical powder with simple process, energy saving and high efficiency, and is suitable for industrial production. The high-purity dense fine PtRh alloy spherical powder prepared by the method of the present invention has high sphericity, It has the advantages of good dispersibility, fine particle size, uniform and stable composition, and high yield.

As shown in Figure 1, the preparation of the high-purity dense fine PtRh alloy spherical powder of the present invention comprises the following steps:

Step 1: Batching and mixing: using sponge Pt and sponge Rh as raw materials, according to the composition of the prepared PtRh alloy, the sponge Pt and sponge Rh are mixed according to the required ratio to obtain a premixture A, and Na ₂ B is added to the premixture A ₄ O ₇ and SiO ₂ and fully mixed to form a "ductile-brittle" raw material system B.

Step 2: Ball milling and compound granulation: Carry out high-energy ball milling on the "ductile-brittle" raw material system B. The ductile components sponge Pt and sponge Rh in B are broken and flaky, and the brittle components Na ₂ B ₄ O ₇ and SiO ₂ are directly broken, and after ball milling, the flaky ductile components and the broken brittle components are agglomerated and compounded to obtain Agglomerated composite powder C containing four substances, as shown in Figure 4, the ductile flake-like Pt and Rh elements in composite powder C mechanically interlock with each other to form a layered structure, achieving the required nominal composition of PtRh alloy powder, brittle Na ₂ B ₄ O ₇ and SiO ₂ are distributed in the interface between the ductile Pt and Rh metal element layers in the form of chimera, preventing the ductile Pt and Rh sheet-like elements from growing abnormally with the prolongation of ball milling time;

Step 3: Classification: classify the ball-shaped composite powder C obtained by ball milling by mechanical sieving or air-flow classification, retain the composite powder C within the required particle size range, and return the rest to step 2 to continue high-energy ball milling;

Step 4: Plasma in-situ smelting and spheroidization: Send the graded pellet-shaped composite powder C into an inductively coupled plasma torch with oxygen as the working gas, and the composite powder undergoes solid-phase heating and graded melting in a very short period of time , Alloy smelting spheroidization, quenching and solidification in four stages, and the composite spherical powder with core-shell structure characteristics of "non-metallic slag phase-PtRh alloy" is obtained.

In the solid phase heating stage, since the composite powder C is in the shape of pellets and has a layered composite structure formed by the mechanical interlocking of flaky Pt and Rh, compared with the dense powder obtained by crushing the ingot, the heating area of the pellet-shaped composite powder C Larger and no sharp protruding parts, the overall temperature rise is more rapid and uniform, avoiding the burning of elements caused by the sharp temperature rise of the powder part (such as at the sharp corner) during the solid phase heating stage. Pellet shape refers to the shape of composite powder formed by ball milling of four raw materials, namely sponge Pt, sponge Rh, Na ₂ B ₄ O ₇ and SiO ₂ . The basic principle of granulation determines that its interior is not dense, but formed by the mechanical interlocking and embedding of four raw materials.

In the stage of graded melting, since the melting point of Na ₂ B ₄ O ₇ (melting point 878°C) is much lower than that of SiO ₂ (melting point 1723°C), Pt (melting point 1772°C) and Rh (melting point 1966°C), the pellet-shaped compound after uniform heating In powder C, Na ₂ B ₄ O ₇ melts first, and the molten Na ₂ B ₄ O ₇ has the effect of fluxing SiO ₂ , so the two brittle phases in composite powder C are at a temperature far lower than the melting points of Pt and Rh. Form a glassy melt, and penetrate into the layered gap of the composite powder under the action of capillary force, realize the dissolution and adsorption of impurities introduced in the previous process of powder ball milling and granulation, and improve the reaction of the subsequent Pt and Rh alloying process active.

In the spheroidization stage of alloy smelting, as the temperature of the powder continues to rise to reach and exceed the melting point of Pt and Rh, each component of the powder is completely melted, and the liquid phase Pt and Rh have infinite solid solution characteristics, and spontaneously fuse into a spherical alloy melt under the action of surface tension. body, and under the joint action of diffusion and electromagnetic stirring, the composition of the alloy melt is homogenized; while the density of the glassy melt formed by melting Na ₂ B ₄ O ₇ and SiO ₂ is much lower than that of the PtRh alloy melt and is compatible with the alloy The melt is immiscible, so it spontaneously floats on the surface of the alloy melt to form a protective layer, avoiding the violent evaporation of Pt and Rh elements during the alloy smelting and spheroidizing process, and ensuring that the composition of the spherical alloy melt is stable and consistent during the smelting process.

In the quenching and solidification stage, the high-temperature droplet leaving the plasma torch is quenched and solidified under the huge temperature gradient with the environment, and the spherical alloy melt at the core of the droplet and the glassy melt wrapped around it are solidified respectively, and the result is shown in Figure 5. The “non-metallic slag phase-PtRh alloy” composite spherical powder with core-shell structure characteristics shown, where the non-metallic slag phase contains a glassy melt of a mixture of Na ₂ B ₄ O ₇ and SiO ₂ , and may also include a ball milling process In addition to a small amount of metal and non-metal impurities contained in the raw materials, these impurities are oxidized under the oxidizing atmosphere of the plasma torch, and the oxides formed will also be mixed into the non-metal slag phase.

Step 5: Alkali washing, water washing and drying. Put the "non-metallic slag phase-PtRh alloy" composite spherical powder with core-shell structure characteristics into an excessive amount of alkaline solution to remove the surface non-metallic slag phase, and then repeatedly wash the filtered PtRh alloy spherical powder with deionized water to medium After filtration and drying, high-purity dense fine PtRh alloy spherical powder is obtained.

Preferably, in step 1, the purity of the raw material sponge Pt is ≥99.9wt%, the purity of the raw material sponge Rh is ≥99.9wt%, in the premixture A, the content of the sponge Rh is 5wt%-50wt%, and the rest is sponge Pt.

Preferably, in step 1, the total mass of Na ₂ B ₄ O ₇ and SiO ₂ is 4%-10% of the mass of pre-mixture A, and the mass ratio of Na ₂ B ₄ O ₇ and SiO ₂ is 1-4:1. This ratio is firstly beneficial to the full crushing of the ductile powder during the ball milling process. Secondly, it is also beneficial to the formation of the plasma slag phase, and finally it is also beneficial to the removal of the slag phase in the alkali cleaning process. More specifically, this ratio takes into account the solubility of SiO ₂ in Na ₂ B ₄ O ₇ at high temperature. If the ratio of SiO ₂ is too high, it will not be able to fully dissolve in Na ₂ B ₄ O ₇ and form a uniform melt. However, if the proportion of Na ₂ B ₄ O ₇ is too high, the ductile-brittle grinding system cannot be effectively formed, and SiO ₂ can fully grind and control the particle size of the powder in the system.

As a preference, in step 2, no process control agent is added in the ball milling and compound granulation process.

As a preference, in step 2, the ball mill crushing and compound granulation method can adopt planetary high-energy ball mill, stirring high-energy ball mill or vibratory high-energy ball mill, preferably planetary high-energy ball mill, and the ball-to-material ratio is preferably 5- 3:1, filling ratio 10%~50%, ball milling speed 250~600r/min, transmission ratio of revolution and rotation 1:2~4, ball diameter 2~8mm, ball milling time 2~10h, ball material and ball milling The lining material of the tank is SiO ₂ .

Preferably, in step 4, the parameters of the plasma in-situ smelting and spheroidization process are: the inductively coupled plasma torch power is 20kW-50kW; the working gas is oxygen, and the flow rate is 20slpm-40slpm; the side gas is oxygen, and the flow rate is 100slpm-400slpm; the carrier gas is oxygen, and the flow rate of the carrier gas is 1slpm-10slpm; the system pressure of the inductively coupled plasma torch is 50kPa-98kPa; the powder feeding rate of composite powder C is 10g/min-80g/min.

Preferably, in step five, the alkaline solution is an aqueous solution of NaOH, KOH, Na ₂ CO ₃ or NaHCO ₃ , the pH value of the solution is ≥ 9; the high-purity dense fine PtRh alloy spherical powder has a particle size range of 1-5 μm, The average particle size is 2-4 μm, tap density ≥ 7g/cm ³ , sphericity ≥ 0.96, sphericity ≥ 98%, powder purity ≥ 99.9%. The particle size distribution of PtRh alloy spherical powder is shown in Figure 3.

The preparation process of the present invention is simple, the production efficiency is high, the environment is not polluted, and is suitable for industrialized production; the high-purity dense fine PtRh alloy spherical powder prepared by the method of the present invention has high sphericity, good dispersibility, and fine and uniform particle size. Advantages, it can be used in the manufacture of high-temperature thermocouples, glass fiber industrial temperature-resistant parts, catalytic electrodes and other devices.

Embodiment 1: Preparation of PtRh10 alloy spherical powder

Step 1: Using sponge Pt with a purity of 99.9wt% and sponge Rh with a purity of 99.9wt% as raw materials, according to the composition of the prepared PtRh10 alloy, mix the sponge Pt and sponge Rh at a weight ratio of 9:1 to obtain a premixture A, and add the premixture Add 5% by mass of Na ₂ B ₄ O ₇ and SiO ₂ to A, the mass ratio of Na ₂ B ₄ O ₇ and SiO ₂ is 2:1, and mix well to form the "ductile-brittle" raw material system B;

Step 2: Perform high-energy ball milling on the "ductile-brittle" raw material system B by planetary high-energy ball milling, with a ball-to-material ratio of 3:1, a filling ratio of 25%, a ball milling speed of 400r/min, and a transmission ratio of revolution and rotation of 1:2 , the ball diameter is 6mm, the ball milling time is 7h, the ball material and the lining material of the ball mill tank are SiO ₂ , the ductile component sponge Pt and sponge Rh in the raw material system B are broken and flaky during the ball milling process, and the brittle component Na ₂ B ₄ O ₇ and SiO ₂ are directly crushed, and after ball milling, the flaky ductile components and the broken brittle components are reunited and compounded to obtain a spherical composite powder C containing four raw materials. The ductile flaky Pt, The Rh elements are mechanically occluded with each other to form a layered structure to achieve the required nominal composition of the PtRh10 alloy powder, and the brittle Na ₂ B ₄ O ₇ and SiO ₂ are distributed at the interface between the ductile Pt and Rh metal elements in the form of chimerism, preventing The ductile Pt and Rh flaky elements grow abnormally with the prolongation of the ball milling time, so no process control agent is added during the ball milling process;

Step 3: Use an ultrasonic vibrating sieve to classify the ball-shaped composite powder C obtained by ball milling, retain the ball-shaped composite powder C with a particle size range of 1.5-7.5 μm, and return the rest to step 2 to continue high-energy ball milling;

Step 4: Send the classified composite powder C into an inductively coupled plasma torch with oxygen as the working gas, the power of the inductively coupled plasma torch is 40kW; the working gas is oxygen, and the flow rate is 30slpm; the side gas is oxygen, and the flow rate is 300slpm ; The carrier gas is oxygen, and the flow rate of the carrier gas is 8slpm; the system pressure of the inductively coupled plasma torch is 65kPa; After going through four stages of solid phase heating, graded melting, alloy smelting and spheroidization, and quenching and solidification within a short period of time, a composite spherical powder with core-shell structure characteristics of "non-metallic slag phase-PtRh10 alloy" was obtained.

Step 5: Put the composite spherical powder with core-shell structure characteristics "non-metallic slag phase-PtRh10 alloy" obtained in step 4 into excess NaOH solution of PH=12 to remove the surface non-metallic slag phase, and then filter the obtained The PtRh10 alloy spherical powder was repeatedly washed to neutral, filtered and dried to obtain high-purity and dense fine PtRh10 alloy spherical powder with a particle size range of 1-5μm, an average particle size of 2.8μm, and a tap density of 7.2g/ cm ³ , sphericity 0.97, spherical rate 98.5%, powder purity ≥99.93%.

Embodiment 2: the preparation of PtRh25 alloy spherical powder

Step 1: Using sponge Pt with a purity of 99.9wt% and sponge Rh with a purity of 99.9wt% as raw materials, according to the composition of the prepared PtRh25 alloy, mix the sponge Pt and sponge Rh in a weight ratio of 3:1 to obtain a premixture A, and add the premixture Add 8% by mass of Na ₂ B ₄ O ₇ and SiO ₂ to A, the mass ratio of Na ₂ B ₄ O ₇ and SiO ₂ is 5:2, and mix well to form the "ductile-brittle" raw material system B;

Step 2: Carry out high-energy ball milling on the "ductile-brittle" raw material system B by planetary high-energy ball milling. The ball-to-material ratio is 5:1, the filling ratio is 20%, the ball milling speed is 500r/min, and the transmission ratio of revolution and rotation is 1:3. , the ball diameter is 4mm, the ball milling time is 5h, the ball material and the lining material of the ball mill tank are SiO ₂ , the ductile component sponge Pt and sponge Rh in the raw material system B are broken and flaky during the ball milling process, and the brittle component Na ₂ B ₄ O ₇ and SiO ₂ are directly crushed, and after ball milling, the flaky ductile components and the broken brittle components are reunited and compounded to obtain a spherical composite powder C containing four raw materials. The ductile flaky Pt, The Rh elements are mechanically occluded to form a layered structure to achieve the required nominal composition of the PtRh25 alloy powder, and the brittle Na ₂ B ₄ O ₇ and SiO ₂ are distributed in the interface between the ductile Pt and Rh metal elements in the form of chimera, preventing The ductile Pt and Rh flaky elements grow abnormally with the prolongation of the ball milling time, so no process control agent is added during the ball milling process;

Step 3: Use an ultrasonic vibrating sieve to classify the ball-shaped composite powder C obtained by ball milling, retain the ball-shaped composite powder C with a particle size range of 1.8-4.8 μm, and return the rest to step 2 to continue high-energy ball milling;

Step 4: Send the classified composite powder C into an inductively coupled plasma torch with oxygen as the working gas, the power of the inductively coupled plasma torch is 35kW; the working gas is oxygen, and the flow rate is 25 slpm; the edge gas is oxygen, and the flow rate is 180 slpm ; The carrier gas is oxygen, and the flow rate of the carrier gas is 6slpm; the system pressure of the inductively coupled plasma torch is 90kPa; After going through four stages of solid phase heating, graded melting, alloy smelting spheroidization, and quenching and solidification within a short period of time, a composite spherical powder with core-shell structure characteristics of "non-metallic slag phase-PtRh25 alloy" was obtained.

Step 5: Put the composite spherical powder with the core-shell structure characteristic "non-metallic slag phase-PtRh25 alloy" obtained in step 4 into the excess KOH solution of PH=13 to remove the surface non-metallic slag phase, and then filter the obtained The PtRh25 alloy spherical powder was repeatedly washed to neutral, filtered and dried to obtain high-purity and dense fine PtRh25 alloy spherical powder with a particle size of 1.2-4.1 μm, an average particle size of 3.1 μm, and a tap density of 7.1 g/cm ^3. The sphericity is 0.97, the spherical rate is 98.8%, and the powder purity is 99.92%, as shown in Figure 2.

Embodiment 3: Preparation of PtRh48 alloy spherical powder

Step 1: Using sponge Pt with a purity of 99.9wt% and sponge Rh with a purity of 99.9wt% as raw materials, according to the composition of the prepared PtRh48 alloy, mix the sponge Pt and sponge Rh at a weight ratio of 13:12 to obtain a premixture A, and add the premixture to the premixture Add 8% by mass of Na ₂ B ₄ O ₇ and SiO ₂ to A, the mass ratio of Na ₂ B ₄ O ₇ and SiO ₂ is 3:1, and mix well to form the "ductile-brittle" raw material system B;

Step 2: Perform high-energy ball milling on the "ductile-brittle" raw material system B by planetary high-energy ball milling, with a ball-to-material ratio of 5:1, a filling ratio of 30%, a ball milling speed of 500r/min, and a transmission ratio of revolution and rotation of 1:4 , the ball diameter is 8mm, the ball milling time is 9h, the material of the ball and the inner lining of the ball mill is SiO ₂ , the ductile component sponge Pt and sponge Rh in the raw material system B are broken and flaked during the ball milling process, and the brittle component Na ₂ B ₄ O ₇ and SiO ₂ are directly crushed, and after ball milling, the flaky ductile components and the broken brittle components are agglomerated and compounded to obtain a spherical composite powder C containing four raw materials. The ductile flaky Pt, The Rh elements are mechanically occluded to form a layered structure to achieve the required nominal composition of the prepared PtRh48 alloy powder. The brittle Na ₂ B ₄ O ₇ and SiO ₂ are distributed in the interface between the ductile Pt and Rh metal element layers in the form of chimera, preventing The ductile Pt and Rh flaky elements grow abnormally with the prolongation of the ball milling time, so no process control agent is added during the ball milling process;

Step 3: Use an ultrasonic vibrating sieve to classify the spherical composite powder C obtained by ball milling, retain the spherical composite powder C with a particle size range of 2-6 μm, and return the rest to step 2 to continue high-energy ball milling;

Step 4: Send the classified composite powder C into an inductively coupled plasma torch with oxygen as the working gas, the power of the inductively coupled plasma torch is 50kW; the working gas is oxygen, and the flow rate is 40slpm; the side gas is oxygen, and the flow rate is 400slpm The carrier gas is oxygen, and the flow rate of the carrier gas is 10slpm; the system pressure of the inductively coupled plasma torch is 80kPa; After going through four stages of solid phase heating, graded melting, alloy smelting spheroidization, and quenching and solidification within a short period of time, a composite spherical powder with core-shell structure characteristics of "non-metallic slag phase-PtRh48 alloy" was obtained.

Step 5: Put the composite spherical powder with core-shell structure characteristics "non-metallic slag phase-PtRh48 alloy" obtained in step 4 into the excess Na ₂ CO ₃ solution with pH = 13 to remove the surface non-metallic slag phase, and then use deionized water The filtered PtRh48 alloy spherical powder was repeatedly washed until neutral, filtered and dried to obtain high-purity dense fine PtRh48 alloy spherical powder with a particle size of 1.8-4.9 μm, an average particle size of 3.2 μm, and a tap density of 7.15 μm. g/cm ³ , sphericity 0.98, spherical rate 98.3%, powder purity ≥ 99.92%.

Comparative example 1:

The rest of the steps are the same as in Example 1, except that the amount of SiO ₂ added with Na ₂ B ₄ O ₇ is changed to 2% of the premixture A. During the plasma treatment of the composite powder C, the formed glassy melt cannot fully Wrapping Pt and Rh metals, the formed non-metallic slag phase cannot fully cover the metal Pt and Rh phases, resulting in a large amount of gasification loss of platinum and rhodium elements and a decrease in the yield of precious metals.

Comparative example 2:

The remaining steps are the same as in Example 1, except that the amount of SiO ₂ added with Na ₂ B ₄ O ₇ is changed to 15% of that of premixture A, and a large amount of low-melting brittle phases are added to composite powder C, resulting in the composite powder being in the plasma During the treatment process, a large amount of energy is consumed by the evaporation and melting of the non-metallic phase. The metal Pt and Rh cannot be fully heated and cannot be melted to form a spherical shape. Part of the non-metallic phase cannot fully float on the surface to form a core-shell structure. The final PtRh alloy powder shape Unaltered and contains non-metallic impurities that cannot be melted.

The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions should not be construed as limiting the present invention. Those skilled in the art understand that without departing from the spirit and scope of the present invention, various equivalent replacements, modifications or improvements can be made to the technical solutions and implementations of the present invention, all of which fall within the scope of the present invention. The protection scope of the present invention shall be determined by the appended claims.

The content that is not described in detail in the description of the present invention belongs to the well-known technology of those skilled in the art.

Claims (10)

1. A preparation method of high-purity dense fine PtRh alloy spherical powder, characterized in that, comprising: Mix the sponge Pt and the sponge Rh to obtain a premix A; Add Na ₂ B ₄ O ₇ and SiO ₂ to the premixture A, and mix thoroughly to obtain the ductile-brittle raw material system B; Perform high-energy ball milling on the ductile-brittle raw material system B to obtain composite powder C; Perform plasma in-situ smelting and spheroidization treatment on the composite powder C to obtain a composite spherical powder D; the composite spherical powder D is a core-shell structure in which the non-metallic slag phase is coated on the surface of the PtRh alloy; The non-metallic slag phase in the composite spherical powder D is removed by an alkaline solution to obtain a PtRh alloy spherical powder. 2. the preparation method of a kind of high-purity dense fine PtRh alloy spherical powder according to claim 1, is characterized in that, the purity of sponge Pt≥99.9wt%, the purity of sponge Rh≥99.9wt%; In premixture A, the content of sponge Rh is 5wt%-50wt%, and the rest is sponge Pt. 3. A method for preparing a high-purity dense fine PtRh alloy spherical powder according to claim 1, wherein the mass ratio of adding Na ₂ B ₄ O ₇ to SiO ₂ in the premixture A is 1 to 4 :1; The total mass of Na ₂ B ₄ O ₇ and SiO ₂ is 4%-10% of the mass of the premixture A. 4. the preparation method of a kind of high-purity dense microfine PtRh alloy spherical powder according to claim 1, is characterized in that, utilizes planetary high-energy ball mill equipment to carry out high-energy ball mill to ductile-brittle raw material system B, and ball mill parameter comprises: The ball-to-material ratio is 5-3:1, the filling ratio is 10%-50%, the ball milling speed is 250-600r/min, the transmission ratio of revolution and rotation is 1:2-4, the ball diameter is 2-8mm, and the ball milling time is 2-10h. The material of the grinding ball and the inner lining of the ball milling tank is SiO ₂ . 5. The method for preparing a high-purity dense fine PtRh alloy spherical powder according to claim 1, characterized in that the ductile-brittle raw material system B is subjected to high-energy ball milling without adding a process control agent. 6. The method for preparing a high-purity dense fine PtRh alloy spherical powder according to claim 1, characterized in that the particle size range of the composite powder C is 1.5-7.5 μm. 7. the preparation method of a kind of high-purity dense microfine PtRh alloy spherical powder according to claim 1, is characterized in that, ductile-brittle raw material system B is carried out high-energy ball milling, and the method for obtaining composite powder C is: Classify the powder obtained by high-energy ball milling of the ductile-brittle raw material system B, keep the powder within the required particle size range, and continue to carry out high-energy ball milling for the remaining powders, and repeat the above process until the particle size of all powders meets the required particle size range. Promptly obtain composite powder C; The classification method is mechanical sieving or air classification. 8. the preparation method of a kind of high-purity dense fine PtRh alloy spherical powder according to claim 1, is characterized in that, the processing parameter that composite powder C is carried out plasma in-situ smelting and spheroidization is: The power of the inductively coupled plasma torch is 20kW~50kW; the working gas is oxygen, and the flow rate of the working gas is 20slpm~40slpm; the side gas is oxygen, and the flow rate of the side gas is 100slpm~400slpm; the carrier gas is oxygen, and the flow rate of the carrier gas is 1slpm~10slpm; The system pressure for inductively coupled plasma torch operation is 50kPa-98kPa; The powder feeding rate of composite powder C is 10g/min～80g/min. 9. the preparation method of a kind of high-purity dense microfine PtRh alloy spherical powder according to claim 1, is characterized in that, alkaline solution is NaOH, KOH, Na ₂ CO ₃ or NaHCO ₃ aqueous solution, the alkaline solution The pH value is ≥ 9; after removing the non-metallic slag phase in the composite spherical powder D by using an excess alkaline solution, the obtained product is repeatedly washed to neutrality, and the PtRh alloy spherical powder is obtained after drying; The yield of PtRh alloy spherical powder is ≥98%. 10. A high-purity dense fine PtRh alloy spherical powder, characterized in that it is obtained by the preparation method of a high-purity dense fine PtRh alloy spherical powder according to any one of claims 1-9, the PtRh alloy spherical powder The particle size range of the body is 1-5 μm, the average particle size is 2-4 μm, the tap density is ≥7 g/cm ³ , the sphericity is ≥0.96, the sphericity rate is ≥98%, and the purity is ≥99.9%.