CN116618663A - High-purity compact fine PtRh alloy spherical powder and preparation method thereof - Google Patents
High-purity compact fine PtRh alloy spherical powder and preparation method thereof Download PDFInfo
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- 239000000843 powder Substances 0.000 title claims abstract description 203
- 229910045601 alloy Inorganic materials 0.000 title claims abstract description 115
- 239000000956 alloy Substances 0.000 title claims abstract description 115
- 229910019017 PtRh Inorganic materials 0.000 title claims abstract description 83
- 238000002360 preparation method Methods 0.000 title claims abstract description 26
- 239000002131 composite material Substances 0.000 claims abstract description 91
- 239000002994 raw material Substances 0.000 claims abstract description 38
- 239000000463 material Substances 0.000 claims abstract description 33
- 238000000713 high-energy ball milling Methods 0.000 claims abstract description 30
- 239000002893 slag Substances 0.000 claims abstract description 27
- 229910004298 SiO 2 Inorganic materials 0.000 claims abstract description 19
- 238000003723 Smelting Methods 0.000 claims abstract description 18
- 239000011258 core-shell material Substances 0.000 claims abstract description 15
- 239000012670 alkaline solution Substances 0.000 claims abstract description 11
- 238000002156 mixing Methods 0.000 claims abstract description 10
- 238000011065 in-situ storage Methods 0.000 claims abstract description 8
- 238000000034 method Methods 0.000 claims description 58
- 238000000498 ball milling Methods 0.000 claims description 57
- 230000008569 process Effects 0.000 claims description 32
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 25
- 229910052760 oxygen Inorganic materials 0.000 claims description 25
- 239000001301 oxygen Substances 0.000 claims description 25
- 239000002245 particle Substances 0.000 claims description 25
- 239000007789 gas Substances 0.000 claims description 22
- 238000009616 inductively coupled plasma Methods 0.000 claims description 16
- 238000000227 grinding Methods 0.000 claims description 15
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 12
- 239000012159 carrier gas Substances 0.000 claims description 12
- 238000005406 washing Methods 0.000 claims description 9
- 239000003795 chemical substances by application Substances 0.000 claims description 7
- 238000001035 drying Methods 0.000 claims description 7
- 238000011049 filling Methods 0.000 claims description 7
- 238000004519 manufacturing process Methods 0.000 claims description 7
- 238000004886 process control Methods 0.000 claims description 7
- 230000005540 biological transmission Effects 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 6
- 230000007935 neutral effect Effects 0.000 claims description 6
- 238000012216 screening Methods 0.000 claims description 3
- 239000010948 rhodium Substances 0.000 description 53
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Substances [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 49
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 46
- 229910052814 silicon oxide Inorganic materials 0.000 description 46
- 229910052703 rhodium Inorganic materials 0.000 description 26
- 229910052697 platinum Inorganic materials 0.000 description 25
- 239000012071 phase Substances 0.000 description 24
- 239000000126 substance Substances 0.000 description 18
- 238000002844 melting Methods 0.000 description 16
- 230000008018 melting Effects 0.000 description 16
- 238000010438 heat treatment Methods 0.000 description 8
- 229910052751 metal Inorganic materials 0.000 description 8
- 239000002184 metal Substances 0.000 description 8
- 229910052755 nonmetal Inorganic materials 0.000 description 6
- 239000000047 product Substances 0.000 description 6
- 238000010791 quenching Methods 0.000 description 6
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- 239000007790 solid phase Substances 0.000 description 6
- 238000007711 solidification Methods 0.000 description 6
- 230000008023 solidification Effects 0.000 description 6
- 239000012535 impurity Substances 0.000 description 5
- 230000001788 irregular Effects 0.000 description 5
- 238000009832 plasma treatment Methods 0.000 description 5
- 239000000243 solution Substances 0.000 description 5
- 230000009471 action Effects 0.000 description 4
- 239000008367 deionised water Substances 0.000 description 4
- 229910021641 deionized water Inorganic materials 0.000 description 4
- 238000001914 filtration Methods 0.000 description 4
- 239000010410 layer Substances 0.000 description 4
- 229910000510 noble metal Inorganic materials 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 238000005275 alloying Methods 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 239000012467 final product Substances 0.000 description 3
- 238000005469 granulation Methods 0.000 description 3
- 230000003179 granulation Effects 0.000 description 3
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- 238000000889 atomisation Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
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- 230000000052 comparative effect Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
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- 238000009776 industrial production Methods 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- 239000008188 pellet Substances 0.000 description 2
- PXXKQOPKNFECSZ-UHFFFAOYSA-N platinum rhodium Chemical compound [Rh].[Pt] PXXKQOPKNFECSZ-UHFFFAOYSA-N 0.000 description 2
- 239000011241 protective layer Substances 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 229910000967 As alloy Inorganic materials 0.000 description 1
- 229910000629 Rh alloy Inorganic materials 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 238000009529 body temperature measurement Methods 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
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- 230000005494 condensation Effects 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
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- 238000000635 electron micrograph Methods 0.000 description 1
- 230000003628 erosive effect Effects 0.000 description 1
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- 238000002309 gasification Methods 0.000 description 1
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- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 239000010970 precious metal Substances 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
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- 238000001179 sorption measurement Methods 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/02—Making metallic powder or suspensions thereof using physical processes
- B22F9/04—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/06—Metallic powder characterised by the shape of the particles
- B22F1/065—Spherical particles
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/14—Treatment of metallic powder
- B22F1/142—Thermal or thermo-mechanical treatment
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/14—Treatment of metallic powder
- B22F1/145—Chemical treatment, e.g. passivation or decarburisation
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/16—Metallic particles coated with a non-metal
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C5/00—Alloys based on noble metals
- C22C5/04—Alloys based on a platinum group metal
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- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/02—Making metallic powder or suspensions thereof using physical processes
- B22F9/04—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling
- B22F2009/043—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling by ball milling
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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
Technical Field
The invention relates to high-purity compact fine PtRh alloy spherical powder and a preparation method thereof, belonging to the technical field of noble metal powder preparation.
Background
The PtRh alloy has the characteristics of corrosion resistance, oxidation resistance, creep resistance, high electric conduction and heat conduction, high catalytic activity and the like, and is widely applied to the industrial fields of glass fiber manufacturing, high-temperature measurement, reaction catalysis and the like. Because Rh has higher melting point, hardness and high-temperature strength than Pt, the improvement of Rh content can obviously improve the physicochemical properties of PtRh alloy, but also brings greater challenges to the processing of PtRh alloy.
The traditional preparation method of PtRh alloy powder mainly comprises a mechanical crushing method, an atomization method, an electric spark discharge method and the like. The mechanical crushing method is to obtain fine PtRh powder by means of cutting, fracturing, ball milling and the like, so that the process is time-consuming and energy-consuming, the obtained powder is irregular in form, and the method is difficult to apply to near-net forming of PtRh parts; the atomization method is to atomize PtRh alloy melt by airflow impact or centrifugal rotation to obtain spherical or spheroidic PtRh alloy powder. The product has the advantages of wide granularity, poor sphericity, common defects of hollowness, adhesion and the like, and the mechanical property of the part obtained by near net molding with the product as a raw material is generally poor. The spark discharge method is to form a high-temperature plasma erosion electrode by continuous discharge between PtRh alloy electrodes to obtain a powder material. Because the electrode is locally overheated at the moment of discharging, a large amount of generated metal vapor is condensed and then adhered to the surface of the powder in a flocculent manner, so that the sphericity of the powder is reduced and the agglomeration of the powder is also caused. Therefore, the PtRh alloy prepared by the prior method cannot meet the near-net forming requirement of the PtRh alloy in terms of fluidity, dispersibility and filling property.
In recent years, a plasma spheroidization technique has been introduced into the field of preparation of PtRh alloy spherical powders. The technology takes PtRh alloy powder with irregular forms as a raw material, melts the powder by utilizing the extremely high temperature of plasma, condenses and balls the molten drops under the action of surface tension, and rapidly cools to obtain PtRh alloy spherical powder with regular forms. As a raw material for the plasma spheroidization technique, irregular morphology PtRh alloy powder is required to be obtained by methods such as alloy melting, ingot casting, division, crushing, and the like. However, in the process of smelting an ingot, the PtRh alloy has the common condition of component segregation, and even if the size of the ingot is reduced and remelting and component homogenization heat treatment are carried out for a plurality of times, the elemental components at different positions in the ingot still have differences. The difference directly causes the uniformity of the components of the irregular PtRh powder obtained after crushing to be reduced, and the PtRh spherical powder obtained by spheroidization is finally influenced by the component genetics; in addition, the work hardening rate of PtRh alloy increases sharply along with the increase of Rh content in the alloy, which makes the breaking of PtRh alloy cast ingots with high Rh content (more than or equal to 30wt%) extremely difficult, and not only the breaking process consumes energy and time, but also impurities are extremely easy to introduce; finally, although the high temperature plasma is favorable for the rapid melting of the PtRh powder serving as a raw material, the extremely high temperature inevitably leads to burning and gasification of alloy elements, particularly irregular powder with granularity smaller than 10 mu m, and the sharp position of the surface of the powder can be gasified instantly when entering a high temperature region of the plasma and taken away by air flow. This phenomenon not only causes the final product composition to deviate from the original alloy design, but also causes a significant loss of precious metals. Therefore, although the plasma spheroidization technology can realize the preparation of PtRh alloy spherical powder, the problems of the PtRh alloy spherical powder still cannot be ignored.
Disclosure of Invention
The invention aims to overcome the defects and provide the high-purity compact fine PtRh alloy spherical powder and the preparation method thereof, which solve the technical problems of low component uniformity, low purity, high noble metal loss rate and the like of the PtRh alloy spherical powder obtained by the traditional preparation method, and the particle size of the PtRh alloy spherical powder obtained by the invention is 1-5 mu m, the average particle size is 2-4 mu m, and the tap density is 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%.
In order to achieve the above purpose, the present invention provides the following technical solutions:
a preparation method of high-purity compact fine PtRh alloy spherical powder comprises the following steps:
mixing the sponge Pt and the 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;
carrying out plasma in-situ smelting and sphericizing treatment on the composite powder C to obtain composite 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.
Further, the purity of the sponge Pt is more than or equal to 99.9 weight percent, and the purity of the sponge Rh is more than or equal to 99.9 weight percent;
in the premix A, the content of the sponge Rh is 5-50wt% and the rest is sponge Pt.
Further, na is added to premix A 2 B 4 O 7 And SiO 2 The mass ratio of (2) is 1-4:1;
Na 2 B 4 O 7 and SiO 2 The total mass of the mixture is 4 to 10 percent of the mass of the premix A.
Further, the ductile-brittle material system B is subjected to high-energy ball milling by using planetary high-energy ball milling equipment, and the ball milling parameters comprise:
ball material ratio is 5-3:1, filling ratio is 10% -50%, ball milling rotating speed is 250-600 r/min, transmission ratio of revolution and rotation is 1:2-4, diameter of grinding ball is 2-8 mm, ball milling time is 2-10 h, and lining material of grinding ball and ball milling tank is SiO 2 。
Further, the ductile-brittle material system B was subjected to high energy ball milling without the addition of a process control agent.
Further, the particle size of the composite powder C is in the range of 1.5 to 7.5. Mu.m.
Further, the ductile-brittle material system B is subjected to high-energy ball milling, and the method for obtaining the composite powder C comprises the following steps:
classifying the powder obtained by performing high-energy ball milling on the ductile-brittle material system B, retaining the powder in the required particle size range, continuously performing high-energy ball milling on the rest powder, and continuously repeating the above process until the particle sizes of all the powder meet the required particle size range to obtain composite powder C;
the classification method is mechanical screening or air classification.
Further, the technological parameters of the plasma in-situ smelting and sphericizing treatment of the composite powder C are as follows:
the power of the inductively coupled plasma torch is 20kW to 50kW; the working gas is oxygen, and the flow rate of the working gas is 20slpm-40slpm; the side gas is oxygen, and the side gas flow 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 speed of the composite powder C is 10g/min-80g/min.
Further, the alkaline solution is NaOH, KOH, na 2 CO 3 Or NaHCO 3 The pH value of the alkaline solution is more than or equal to 9; removing nonmetallic slag phase in the composite spherical powder D by using an excessive alkaline solution, repeatedly washing the obtained product to be neutral, and drying to obtain PtRh alloy spherical powder;
the yield of the PtRh alloy spherical powder is more than or equal to 98 percent, and is the ratio of the total mass of the finally obtained platinum-rhodium alloy powder to the total mass of the initially input sponge platinum and sponge rhodium, namely the yield ratio of noble metals.
The high-purity compact fine PtRh alloy spherical powder is obtained by adopting the preparation method of the high-purity compact fine PtRh alloy spherical powder, the particle size range of the PtRh alloy spherical powder is 1-5 mu m, the average particle size is 2-4 mu m, and the tap density is 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 purity is more than or equal to 99.9%.
Compared with the prior art, the invention has at least one of the following beneficial effects:
(1) The invention creatively provides a preparation method of high-purity compact fine PtRh alloy spherical powder, which comprises the steps of adding a certain proportion of Na into a ductile material system formed by sponge Pt and sponge Rh when ball milling, crushing and composite granulating raw materials 2 B 4 O 7 SiO (silicon oxide) 2 The brittle phase forms a ductile-brittle ball milling system, and the addition of the brittle phase not only ensures that the grinding and crushing efficiency of the sponge Pt and the sponge Rh is higher, but also can be attached to the surface of the ductile metal phase in the subsequent composite granulation process, thereby reducing the surface energy of powder and realizing the effective control of the granularity of composite powderMeanwhile, no extra process control agent is needed to be introduced to control the granularity of the composite powder, so that the purity of the product is improved;
(2) The ball milling crushing objects of the invention are ductile sponge Pt and sponge Rh simple substance, but not PtRh alloy with higher mechanical property, so that the ball milling crushing difficulty is greatly reduced, and particularly the ball milling difficulty is remarkably reduced for PtRh alloy with high Rh content.
(3) The invention classifies the obtained composite powder after ball milling, crushing and composite granulating in advance, limits the size of the composite powder, controls the granularity of the composite powder which is sent into a plasma torch for alloying and spheroidizing within a certain range, ensures that the plasma treatment process parameters and the granularity of the raw material powder have better matching performance, avoids the condition that the powder with small size is seriously burnt and the powder with large granularity is not heated sufficiently, simultaneously ensures that the granularity of the product is more concentrated, and ensures that the ball milling step is continued for the composite powder with the granularity which does not meet the specification after classification, improves the utilization rate of the raw material, and ensures that the spheroidization rate and sphericity of the final product are higher.
(4) According to the invention, the composite powder C containing Pt and Rh simple substances is directly fed into the plasma torch, so that alloying and sphericizing of the composite powder are completed in one-time plasma treatment, the processing flow is shortened, the cost and raw material loss are reduced, the product components are uniform, and the powder yield is more than or equal to 98%.
(5) The invention introduces Na into the composite powder 2 B 4 O 7 SiO (silicon oxide) 2 The temperature of the composite powder in the plasma torch is increased more uniformly, and the Na which is melted preferentially 2 B 4 O 7 SiO (silicon oxide) 2 The formation of glassy state melt forms a protective layer on the surface of the alloy melt, so that severe evaporation of Pt and Rh elements in the alloy smelting spheroidization process is avoided, the stable and consistent components of the spherical alloy melt in the smelting process are ensured, and the raw material loss is reduced.
(6) In the plasma in-situ smelting and sphericizing treatment process, oxygen is used as a working medium, oxygen is used as diatomic gas, the enthalpy value after excitation in a plasma torch is higher than that of monoatomic gas, and meanwhile, the strong oxidizing property of the oxygen is beneficial to the oxidizing slagging of non-Pt and Rh impurity phases in the composite powder C and is dissolved in a glassy melt, so that the purity of a final product is improved.
(7) Because of the existence of the core-shell structure in the plasma treatment process, a small amount of gasified powder material in the powder condensation process is condensed on the surface of the nonmetallic slag phase shell and is removed in the subsequent alkaline washing process, so that the generation of floccules on the surface of PtRh alloy powder is avoided, and the fluidity and sphericity of the powder are improved.
Drawings
FIG. 1 is a schematic diagram of a method for producing spherical PtRh powder according to the present invention;
FIG. 2 is a diagram showing the microscopic morphology of the high-purity dense fine PtRh25 alloy spherical powder obtained in example 2 of the present invention;
FIG. 3 is a graph showing the particle size distribution of PtRh25 alloy spherical powder according to the present invention;
FIG. 4 shows the gray ductile phase (sponge Pt and sponge Rh) and the white brittle phase (Na) 2 B 4 O 7 SiO (silicon oxide) 2 ) Electron microscope photographs of the composite powder C;
FIG. 5 is an electron micrograph of a core-shell structured "nonmetallic slag phase-PtRh alloy" composite spherical powder of the present invention.
Detailed Description
The features and advantages of the present invention will become more apparent and clear from the following detailed description of the invention.
The word "exemplary" is used herein to mean "serving as an example, embodiment, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Although various aspects of the embodiments are illustrated in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated.
The invention provides a preparation method of high-purity compact fine PtRh alloy spherical powder, which is simple in process, energy-saving and efficient, and is suitable for industrial production.
As shown in fig. 1, the preparation of the high-purity compact fine PtRh alloy spherical powder of the present invention comprises the steps of:
step one: and (3) material mixing: the preparation method comprises the steps of taking sponge Pt and sponge Rh as raw materials, mixing the sponge Pt and the sponge Rh according to a required proportion according to the prepared PtRh alloy components to obtain a premix A, and adding Na into the premix A 2 B 4 O 7 SiO (silicon oxide) 2 And fully and uniformly mixed to form a ductile-brittle raw material system B.
Step two: ball milling, crushing and composite granulating: high-energy ball milling is carried out on a ductile-brittle raw material system B, components in the raw material system B are agglomerated and compounded again after being fully crushed in the ball milling process, specifically, ductile component sponge Pt and sponge Rh in the raw material system B are crushed and flaked in the ball milling process, and brittle component Na is formed 2 B 4 O 7 SiO (silicon oxide) 2 Directly crushing, continuously ball milling, agglomerating and compositing the flaky ductile component and the crushed brittle component to obtain spherical composite powder C containing four substances, and mechanically occluding ductile flaky Pt and Rh simple substances in the composite powder C to form a layered structure as shown in figure 4 so as to obtain the nominal component of the PtRh alloy powder to be prepared and brittle Na 2 B 4 O 7 SiO (silicon oxide) 2 The alloy is distributed at the interface between ductile Pt and Rh metal simple substance layers in a jogged mode, so that ductile Pt and Rh sheet simple substances are prevented from growing abnormally along with the extension of ball milling time;
step three: grading: classifying the ball-shaped composite powder C obtained by ball milling by a mechanical screening or air flow classifying method, reserving the composite powder C within the required granularity range, and returning the rest to the second step to continue high-energy ball milling;
step four: plasma in-situ smelting and sphericizing: and (3) feeding the spherical composite powder C obtained by grading into an inductively coupled plasma torch taking oxygen as working gas, and subjecting the composite powder to four stages of solid-phase heating, graded melting, alloy smelting spheroidization, quenching solidification in extremely short time to obtain the composite spherical powder with core-shell structural characteristics of 'nonmetallic slag phase-PtRh alloy'.
In the solid phase heating stage, due to the composite powderThe body C is in a ball shape and has a lamellar composite structure formed by mechanical occlusion of flaky Pt and Rh, so that compared with compact powder obtained by ingot breaking, the ball-shaped composite powder C has larger heating area and no sharp protruding part, the whole temperature rise is quicker and more uniform, and element burning loss caused by local (for example, sharp corner) severe temperature rise of the powder in the solid phase heating stage is avoided. The pellet is prepared from four raw materials, namely sponge Pt, sponge Rh and Na 2 B 4 O 7 And SiO 2 The shape of the composite powder formed after ball milling is pellet, the shape is determined by the basic principle of ball milling granulation, and the interior of the composite powder is not compact, but is formed by mechanical engagement and embedding of four raw materials.
Stage of classified melting due to Na 2 B 4 O 7 (melting point 878 ℃ C.) the melting point is far lower than that of SiO 2 (melting point 1723 ℃ C.), pt (melting point 1772 ℃ C.) and Rh (melting point 1966 ℃ C.), na in the pellet-shaped composite powder C after the uniform temperature rise 2 B 4 O 7 First melt Na 2 B 4 O 7 Is provided with fluxing SiO 2 The two brittle phases in the composite powder C form a glassy melt at a temperature far lower than the melting points of Pt and Rh, and permeate into a layered gap of the composite powder under the action of capillary force, so that the dissolution and adsorption of impurities introduced in the processing processes of early-stage powder ball milling and granulation and the like are realized, and the reactivity of the subsequent Pt and Rh alloying processes is improved.
In the alloy smelting spheroidization stage, as the powder is continuously heated to reach and exceed the melting points of Pt and Rh, all the components of the powder are completely melted, liquid phases Pt and Rh have infinite solid solution property, spontaneously fuse into spherical alloy melt under the action of surface tension, and complete homogenization of the components of the alloy melt under the combined action of diffusion and electromagnetic stirring; and melt Na 2 B 4 O 7 SiO (silicon oxide) 2 The density of the formed glassy melt is far lower than that of PtRh alloy melt and the glassy melt is not mutually soluble with the alloy melt, so that the glassy melt spontaneously floats on the surface of the alloy melt to form a protective layer, severe evaporation of Pt and Rh elements in the alloy smelting and spheroidizing process is avoided, and the stable and consistent components of the spherical alloy melt in the smelting process are ensured.
Quenching ofIn the solidification stage, the high-temperature molten drop separated from the plasma torch is subjected to quenching solidification under a huge temperature gradient with the environment, and the spherical alloy melt at the core part of the molten drop and the glassy melt wrapped outside are respectively solidified to obtain the composite spherical powder with core-shell structural characteristics of 'nonmetallic slag phase-PtRh alloy', as shown in figure 5, wherein the nonmetallic slag phase comprises Na 2 B 4 O 7 And SiO 2 The glassy melt of the mixture, which may also contain small amounts of metallic and non-metallic impurities contained in the ball milling process and in the feedstock, is oxidized in the oxidizing atmosphere of the plasma torch, and the oxides formed are incorporated into the non-metallic slag phase.
Step five: and (5) washing with alkali and drying. And (3) putting the composite spherical PtRh alloy powder with the core-shell structural characteristics into an excessive alkaline solution to remove the surface non-metal slag phase, repeatedly washing the filtered PtRh alloy spherical powder to be neutral by deionized water, filtering and drying to obtain the high-purity compact fine PtRh alloy spherical powder.
Preferably, in the first step, the purity of the raw material sponge Pt is more than or equal to 99.9wt%, the purity of the raw material sponge Rh is more than or equal to 99.9wt%, the content of the sponge Rh in the premix A is 5-50 wt%, and the rest is the sponge Pt.
Preferably, in step one, na 2 B 4 O 7 SiO (silicon oxide) 2 The total mass of the catalyst is 4 to 10 percent of the mass of the premix A, na 2 B 4 O 7 SiO (silicon oxide) 2 The mass ratio of (2) is 1-4:1. The proportion is favorable for fully crushing ductile powder in the ball milling process. Secondly, the formation of a plasma slag phase is facilitated, and finally, the removal of the slag phase in the alkaline washing process is facilitated. More specifically, the ratio takes into account SiO 2 At high temperature under Na 2 B 4 O 7 Solubility in SiO 2 Too high a ratio may result in insufficient dissolution in Na 2 B 4 O 7 A uniform melt cannot be formed. While Na is 2 B 4 O 7 Too high a ratio may not be effective in forming ductile-brittle grinding systems, siO 2 The effects of fully grinding and controlling the granularity of the powder are achieved in the system.
Preferably, in the second step, no process control agent is added in the ball milling and crushing and composite granulating process.
Preferably, in the second step, the ball milling crushing and composite granulating modes can adopt planetary high-energy ball milling, stirring high-energy ball milling or vibration high-energy ball milling, preferably planetary high-energy ball milling, wherein the ball milling parameters are ball material ratio of 5-3:1, filling ratio of 10-50%, ball milling rotating speed of 250-600 r/min, revolution and rotation transmission ratio of 1:2-4, grinding ball diameter of 2-8 mm, ball milling time of 2-10 h, and the grinding ball material and the lining material of a ball milling tank are SiO 2 。
Preferably, in the fourth step, the parameters of the plasma in-situ smelting and sphericizing treatment process are that the power of the inductively coupled plasma torch is 20kW to 50kW; the working gas is oxygen, and the flow is 20slpm-40slpm; the side gas is oxygen, and the flow 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 speed of the composite powder C is 10g/min-80g/min.
Preferably, in the fifth step, the alkaline solution is NaOH, KOH, na 2 CO 3 Or NaHCO 3 The PH value of the aqueous solution is more than or equal to 9; high-purity compact fine PtRh alloy spherical powder with particle size range of 1-5 μm, average particle diameter of 2-4 μm and tap density of more than or equal to 7g/cm 3 The sphericity is more than or equal to 0.96, sphericity rate is more than or equal to 98%, powder purity is more than or equal to 99.9%, and particle size distribution of PtRh alloy spherical powder is shown in figure 3.
The preparation method has the advantages of simple process, high production efficiency, no pollution to the environment and suitability for industrial production; the high-purity compact fine PtRh alloy spherical powder prepared by the method has the advantages of high sphericity, good dispersity and fine and uniform granularity, and can be used for manufacturing devices such as high-temperature thermocouples, glass fiber industrial temperature resistant parts, catalytic electrodes and the like.
Example 1: preparation of PtRh10 alloy spherical powder
Step one: the sponge Pt with the purity of 99.9 weight percent and the sponge Rh with the purity of 99.9 weight percent are taken as raw materials, and the sponge Pt and the sponge Rh are taken according to the weight of the prepared PtRh10 alloy componentRatio 9:1 to obtain a premix A, adding 5% by mass of Na to the premix A 2 B 4 O 7 SiO (silicon oxide) 2 ，Na 2 B 4 O 7 SiO (silicon oxide) 2 The mass ratio of the raw materials is 2:1, and the raw materials are fully and uniformly mixed to form a ductile-brittle raw material system B;
step two: high-energy ball milling is carried out on a ductile-brittle material system B by adopting a planetary high-energy ball milling method, the ball material ratio is 3:1, the filling ratio is 25%, the ball milling rotating speed is 400r/min, the transmission ratio of revolution and rotation is 1:2, the diameter of a grinding ball is 6mm, the ball milling time is 7h, and the grinding ball material and the lining material of a ball milling tank are SiO 2 Ductile component sponge Pt and sponge Rh in raw material system B are crushed and flaked in the ball milling process, and brittle component Na 2 B 4 O 7 SiO (silicon oxide) 2 Directly crushing, continuously ball milling, agglomerating and compositing the flaky ductile component and the crushed brittle component to obtain spherical composite powder C containing four raw material substances, mechanically occluding ductile flaky Pt and Rh simple substances in the composite powder to form a layered structure, and obtaining the required preparation of nominal components of PtRh10 alloy powder and brittle Na 2 B 4 O 7 SiO (silicon oxide) 2 The alloy is distributed at the interface between ductile Pt and Rh metal simple substance layers in a jogged mode, so that ductile Pt and Rh sheet simple substances are prevented from growing abnormally along with the extension of the ball milling time, and therefore, a process control agent is not added in the ball milling process;
step three: classifying the ball-shaped composite powder C obtained by ball milling by using an ultrasonic vibration sieve, reserving the ball-shaped composite powder C with the granularity ranging from 1.5 mu m to 7.5 mu m, and returning the rest to the second step to continue high-energy ball milling;
step four: feeding the compound powder C obtained by grading into an inductively coupled plasma torch taking oxygen as working gas, wherein the power of the inductively coupled plasma torch is 40kW; the working gas is oxygen with the flow rate of 30slpm; the side gas is oxygen, and the flow is 300slpm; the carrier gas is oxygen, and the carrier gas flow is 8slpm; the system pressure for the operation of the inductively coupled plasma torch was 65kPa; the powder feeding speed of the spherical composite powder C with the particle size of 1.5-7.5 mu m is 40g/min, and the composite powder C is subjected to four stages of solid phase heating, graded melting, alloy smelting spheroidization, quenching solidification in a very short time to obtain the composite spherical powder with the core-shell structural characteristic of 'nonmetallic slag phase-PtRh 10 alloy'.
Step five: adding the non-metal slag phase-PtRh 10 alloy composite spherical powder with core-shell structural characteristics obtained in the step four into an excessive NaOH solution with PH=12 to remove the surface non-metal slag phase, repeatedly washing the filtered PtRh10 alloy spherical powder to be neutral by deionized water, filtering and drying to obtain high-purity compact fine PtRh10 alloy spherical powder, wherein the particle size range of the powder is 1-5 mu m, the average particle size is 2.8 mu m, and the tap density is 7.2g/cm 3 The sphericity is 0.97, the sphericity rate is 98.5%, and the powder purity is more than or equal to 99.93%.
Example 2: preparation of PtRh25 alloy spherical powder
Step one: the method comprises the steps of taking sponge Pt with the purity of 99.9wt% and sponge Rh with the purity of 99.9wt% as raw materials, and according to the prepared PtRh25 alloy components, mixing the sponge Pt and the sponge Rh according to the weight ratio of 3:1 to obtain a premix A, adding 8 mass percent of Na into the premix A 2 B 4 O 7 SiO (silicon oxide) 2 ，Na 2 B 4 O 7 SiO (silicon oxide) 2 The mass ratio of the raw materials is 5:2, and the raw materials are fully and uniformly mixed to form a ductile-brittle raw material system B;
step two: high-energy ball milling is carried out on a ductile-brittle material system B by adopting a planetary high-energy ball milling method, the ball material ratio is 5:1, the filling ratio is 20%, the ball milling rotating speed is 500r/min, the transmission ratio of revolution and rotation is 1:3, the diameter of a grinding ball is 4mm, the ball milling time is 5h, and the grinding ball material and the lining material of a ball milling tank are SiO 2 Ductile component sponge Pt and sponge Rh in raw material system B are crushed and flaked in the ball milling process, and brittle component Na 2 B 4 O 7 SiO (silicon oxide) 2 Directly crushing, continuously ball milling, agglomerating and compositing the flaky ductile component and the crushed brittle component to obtain spherical composite powder C containing four raw material substances, mechanically occluding ductile flaky Pt and Rh simple substances in the composite powder to form a layered structure, and obtaining the required preparation of nominal components of PtRh25 alloy powder and brittle Na 2 B 4 O 7 SiO (silicon oxide) 2 Is distributed at the interface between ductile Pt and Rh metal simple substance layers in a jogged modeThe ductile Pt and Rh flaky simple substances are prevented from growing abnormally along with the extension of the ball milling time, so that a process control agent is not added in the ball milling process;
step three: classifying the ball-shaped composite powder C obtained by ball milling by using an ultrasonic vibration sieve, reserving the ball-shaped composite powder C with the granularity ranging from 1.8 mu m to 4.8 mu m, and returning the rest to the second step to continue high-energy ball milling;
step four: feeding the compound powder C obtained by grading into an inductively coupled plasma torch taking oxygen as working gas, wherein the power of the inductively coupled plasma torch is 35kW; the working gas is oxygen with the flow rate of 25slpm; the side gas is oxygen, and the flow is 180slpm; the carrier gas is oxygen, and the carrier gas flow is 6slpm; the system pressure at which the inductively coupled plasma torch was operated was 90kPa; the powder feeding speed of the spherical composite powder C with the particle size of 1.8-4.8 mu m is 50g/min, and the composite powder C is subjected to four stages of solid phase heating, graded melting, alloy smelting spheroidization, quenching solidification in a very short time to obtain the composite spherical powder with the core-shell structural characteristic of 'nonmetallic slag phase-PtRh 25 alloy'.
Step five: adding the nonmetal slag phase-PtRh 25 alloy composite spherical powder with the core-shell structural characteristics obtained in the step four into an excessive KOH solution with PH=13 to remove the surface nonmetal slag phase, repeatedly washing the filtered PtRh25 alloy spherical powder to be neutral by deionized water, filtering and drying to obtain high-purity compact fine PtRh25 alloy spherical powder with the granularity of 1.2-4.1 mu m, the average particle size of 3.1 mu m and the tap density of 7.1g/cm 3 The sphericity is 0.97, the sphericity rate is 98.8%, the powder purity is 99.92%, as shown in figure 2.
Example 3: preparation of PtRh48 alloy spherical powder
Step one: the method comprises the steps of taking sponge Pt with the purity of 99.9wt% and sponge Rh with the purity of 99.9wt% as raw materials, and according to the prepared PtRh48 alloy components, mixing the sponge Pt and the sponge Rh according to the weight ratio of 13:12 to obtain a premix A, adding 8% by mass of Na to the premix A 2 B 4 O 7 SiO (silicon oxide) 2 ，Na 2 B 4 O 7 SiO (silicon oxide) 2 The mass ratio of the mixture is 3:1, and the mixture is fully and uniformly mixed to form a ductile-brittle raw material bodyB is;
step two: high-energy ball milling is carried out on a ductile-brittle material system B by adopting a planetary high-energy ball milling method, the ball material ratio is 5:1, the filling ratio is 30%, the ball milling rotating speed is 500r/min, the transmission ratio of revolution and rotation is 1:4, the diameter of a grinding ball is 8mm, the ball milling time is 9h, and the grinding ball material and the lining material of a ball milling tank are SiO 2 Ductile component sponge Pt and sponge Rh in raw material system B are crushed and flaked in the ball milling process, and brittle component Na 2 B 4 O 7 SiO (silicon oxide) 2 Directly crushing, continuously ball milling, agglomerating and compositing the flaky ductile component and the crushed brittle component to obtain spherical composite powder C containing four raw material substances, mechanically occluding ductile flaky Pt and Rh simple substances in the composite powder to form a layered structure, and obtaining the required preparation of the nominal component of PtRh48 alloy powder and brittle Na 2 B 4 O 7 SiO (silicon oxide) 2 The alloy is distributed at the interface between ductile Pt and Rh metal simple substance layers in a jogged mode, so that ductile Pt and Rh sheet simple substances are prevented from growing abnormally along with the extension of the ball milling time, and therefore, a process control agent is not added in the ball milling process;
step three: classifying the ball-shaped composite powder C obtained by ball milling by using an ultrasonic vibration sieve, reserving the ball-shaped composite powder C with the granularity ranging from 2 mu m to 6 mu m, and returning the rest to the second step to continue high-energy ball milling;
step four: feeding the compound powder C obtained by grading into an inductively coupled plasma torch taking oxygen as working gas, wherein the power of the inductively coupled plasma torch is 50kW; the working gas is oxygen with the flow rate of 40slpm; the side gas is oxygen, and the flow is 400slpm; the carrier gas is oxygen, and the carrier gas flow is 10slpm; the system pressure at which the inductively coupled plasma torch was operated was 80kPa; the powder feeding speed of 2-6 mu m spherical composite powder C powder is 75g/min, and the composite powder C is subjected to four stages of solid phase heating, graded melting, alloy smelting spheroidization and quenching solidification in extremely short time to obtain the composite spherical powder with core-shell structural characteristics of 'nonmetallic slag phase-PtRh 48 alloy'.
Step five: adding the non-metal slag phase-PtRh 48 alloy composite spherical powder with core-shell structural characteristics obtained in the step four into excessive Na with PH=13 2 CO 3 Removing surface nonmetallic slag phase from the solution, repeatedly washing the filtered PtRh48 alloy spherical powder to be neutral by deionized water, filtering and drying to obtain high-purity compact fine PtRh48 alloy spherical powder with the particle size of 1.8-4.9 mu m, the average particle size of 3.2 mu m and the tap density of 7.15g/cm 3 The sphericity is 0.98, the sphericity rate is 98.3%, and the powder purity is more than or equal to 99.92%.
Comparative example 1:
the rest of the procedure is the same as in example 1, only Na is added 2 B 4 O 7 SiO of (2) 2 The amount is changed to 2% of the premix A, the formed glassy melt of the composite powder C cannot fully wrap Pt and Rh metals in the plasma treatment process, the formed nonmetallic slag phase cannot fully cover the metallic Pt and Rh phases, a large amount of platinum rhodium elements are gasified and lost, and the noble metal yield is reduced.
Comparative example 2:
the rest of the procedure is the same as in example 1, only Na is added 2 B 4 O 7 SiO of (2) 2 The amount is changed to 15% of the premix A, a large amount of low-melting-point brittle phase is added in the composite powder C, so that a large amount of energy is consumed by vaporization and melting of the nonmetallic phase in the plasma treatment process of the composite powder, metals Pt and Rh cannot be heated sufficiently, cannot be melted to form spheres, part of nonmetallic phase cannot float on the surface sufficiently to form a core-shell structure, finally the morphology of PtRh alloy powder cannot be changed, and nonmetallic impurities which cannot be melted are contained in the composite powder.
The invention has been described in detail in connection with the specific embodiments and exemplary examples thereof, but such description is not to be construed as limiting the invention. It will be understood by those skilled in the art that various equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its embodiments without departing from the spirit and scope of the present invention, and these fall within the scope of the present invention. The scope of the invention is defined by the appended claims.
What is not described in detail in the present specification is a well known technology to those skilled in the art.
Claims (10)
1. The preparation method of the high-purity compact fine PtRh alloy spherical powder is characterized by comprising the following steps:
mixing the sponge Pt and the 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;
carrying out plasma in-situ smelting and sphericizing treatment on the composite powder C to obtain composite 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.
2. The method for preparing the high-purity compact fine PtRh alloy spherical powder according to claim 1, wherein the purity of the sponge Pt is more than or equal to 99.9wt% and the purity of the sponge Rh is more than or equal to 99.9wt%;
in the premix A, the content of the sponge Rh is 5-50wt% and the rest is sponge Pt.
3. The method for producing a high purity dense fine PtRh alloy spherical powder according to claim 1, wherein Na is added to the premix A 2 B 4 O 7 And SiO 2 The mass ratio of (2) is 1-4:1;
Na 2 B 4 O 7 and SiO 2 The total mass of the mixture is 4 to 10 percent of the mass of the premix A.
4. The method for preparing high-purity dense fine PtRh alloy spherical powder according to claim 1, wherein the high-energy ball milling is performed on ductile-brittle material system B by using planetary high-energy ball milling equipment, and the ball milling parameters include:
ball-to-material ratio of 5-3:1 and filling ratio of 10% to the upper50 percent of ball milling rotating speed of 250-600 r/min, revolution and rotation transmission ratio of 1:2-4, grinding ball diameter of 2-8 mm, ball milling time of 2-10 h, and grinding ball and lining material of a ball milling tank are SiO 2 。
5. The method for producing a high-purity dense fine PtRh alloy spherical powder according to claim 1, wherein the ductile-brittle material system B is subjected to high-energy ball milling without adding a process control agent.
6. The method for producing a high-purity dense fine PtRh alloy spherical powder according to claim 1, wherein the particle size of the composite powder C is in the range of 1.5 to 7.5. Mu.m.
7. The preparation method of the high-purity compact fine PtRh alloy spherical powder according to claim 1, which is characterized in that the method for obtaining the composite powder C by performing high-energy ball milling on the ductile-brittle raw material system B is as follows:
classifying the powder obtained by performing high-energy ball milling on the ductile-brittle material system B, retaining the powder in the required particle size range, continuously performing high-energy ball milling on the rest powder, and continuously repeating the above process until the particle sizes of all the powder meet the required particle size range to obtain composite powder C;
the classification method is mechanical screening or air classification.
8. The method for preparing the high-purity compact fine PtRh alloy spherical powder according to claim 1, wherein the technological parameters of the plasma in-situ smelting and sphericizing treatment of the composite powder C are as follows:
the power of the inductively coupled plasma torch is 20kW to 50kW; the working gas is oxygen, and the flow rate of the working gas is 20slpm-40slpm; the side gas is oxygen, and the side gas flow 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 speed of the composite powder C is 10g/min-80g/min.
9. The method for preparing high-purity dense fine PtRh alloy spherical powder according to claim 1, wherein the alkaline solution is NaOH, KOH, na 2 CO 3 Or NaHCO 3 The pH value of the alkaline solution is more than or equal to 9; removing nonmetallic slag phase in the composite spherical powder D by using an excessive alkaline solution, repeatedly washing the obtained product to be neutral, and drying to obtain PtRh alloy spherical powder;
the yield of PtRh alloy spherical powder is more than or equal to 98 percent.
10. A high-purity compact fine PtRh alloy spherical powder is characterized in that the powder is obtained by adopting the preparation method of the high-purity compact fine PtRh alloy spherical powder as described in any one of claims 1 to 9, wherein the particle size range of the PtRh alloy spherical powder is 1-5 mu m, the average particle size is 2-4 mu m, and the tap density is 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 purity is more than or equal to 99.9%.
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