Preparation method of high-dispersion nano tungsten / rhenium / lanthanum oxide composite powder

Abstract

The application relates to a preparation method of a high-dispersion nano tungsten / rhenium / lanthanum oxide composite powder, and belongs to the field of functional materials. In the method, tungsten salt, rhenium salt, lanthanum salt, excess carbon source and fuel are subjected to a solution combustion synthesis reaction according to a certain molar ratio to obtain a WO2 / W18O49+ReO2 / ReO3+La2O3+C composite precursor. Then, the precursor is subjected to an oxidation reaction in air to obtain an intermediate product WO3+Re2O7+La2O3. The intermediate product is subjected to a reduction reaction in a hydrogen atmosphere to obtain a nano W+Re+La2O3 composite powder. In the application, carbon and lanthanum oxide dispersants are synchronously introduced in situ, the W-Re particle dispersity is improved, the carbon dispersant can be directly removed through calcination, and the method is safe and efficient. The prepared composite powder has low oxygen content, uniform tungsten particle size, and fine lanthanum oxide particles uniformly dispersed in a tungsten-rhenium matrix, which lays a foundation for the preparation of high-performance tungsten-rhenium alloys. The raw materials are cheap and easy to obtain, the equipment is simple, the process is fast and controllable, and the method is suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention belongs to the field of functional powder material preparation technology, specifically relating to a method for preparing highly dispersed nano-tungsten / rhenium / lanthanum oxide composite powder. Background Technology

[0002] Tungsten (W) is attractive in many engineering fields, including military applications, aerospace engineering, and the nuclear industry, due to its superior physical and mechanical properties. However, the further application of pure W is greatly limited by its low-temperature brittleness, relatively high ductile-brittle transition temperature (DBTT), high-temperature recrystallization brittleness, and low oxidation resistance at high temperatures. As a typical refractory metal alloy, tungsten-rhenium (W-Re) alloys exhibit superior high-temperature mechanical properties compared to pure W, such as better ductility, a lower ductile-brittle transition temperature, and high-temperature strength. Therefore, it has a wide range of high-temperature applications, including thermocouples, X-ray tubes, and plasma-oriented materials. In fact, high relative density and fine grain size are prerequisites for obtaining high-performance W-Re alloys. In particular, fine grain size not only improves the strength and plasticity of W-Re alloys but also significantly increases their fracture toughness and radiation resistance.

[0003] Refining W-Re powder particles to the nanoscale is a common method to lower sintering temperature and reduce grain size. However, nanoscale particles grow rapidly during sintering, resulting in poor grain refinement. Existing research has found that adding rare earth oxide (REO) particles (such as La2O3, Y2O3, and Lu2O3) is an effective method for refining grain size, especially La2O3, which makes a significant contribution to grain refinement. The preparation of W+Re+La2O3 alloy powder usually employs mechanical alloying methods, including high-energy grinding and mixing methods. These methods may produce undesirable characteristics, such as non-uniform composition, poor purity control, significant particle aggregation, high energy consumption, and long processing time. Furthermore, the large residual stress in the powder after ball milling can easily lead to rapid grain growth during subsequent sintering.

[0004] Based on the above considerations, this invention provides a method for preparing nano-tungsten / rhenium / lanthanum oxide (W+Re+La2O3) composite powder using solution combustion synthesis (SCS). Compared with mechanical alloying, the SCS method has several unprecedented advantages. It can utilize the exothermic reaction between metal salts (also known as oxidants) such as nitrates, sulfates, and carbonates and fuels (also known as reducing agents) such as urea, glycine, and starch to achieve a self-sustaining reaction, which is simple, rapid, energy-efficient, and environmentally friendly. Furthermore, this method can achieve uniform mixing at the molecular level, resulting in high purity and easy control over the particle size and distribution uniformity of W, Re, and La2O3, laying the foundation for the preparation of high-performance W+Re alloys. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing highly dispersed nano-tungsten / rhenium / lanthanum oxide composite powder, which addresses the shortcomings of the prior art. The prepared nano-tungsten / rhenium / lanthanum oxide composite powder has the characteristics of fine particles, uniform particle size and distribution. At the same time, the method is simple, highly controllable, short process and easy to implement.

[0006] A method for preparing highly dispersed nano-tungsten / rhenium / lanthanum oxide composite powder includes the following specific steps:

[0007] (1) Preparation of tungsten oxide / rhenium oxide / lanthanum oxide / carbon composite powder by solution combustion synthesis: Tungsten salt, rhenium salt, lanthanum salt, excess carbon source, fuel and deionized water are mixed in a certain proportion to prepare an aqueous solution. The solution is placed on a temperature-controlled resistance furnace and heated and stirred. After evaporating the water until the solution becomes viscous, it is heated to a certain temperature to carry out the combustion synthesis reaction to obtain a uniformly mixed "WO2 / W" powder. 18 O 49 +ReO2 / ReO3+La2O3+C” composite precursor;

[0008] (2) Preparation of tungsten oxide / rhenium oxide / lanthanum oxide composite powder by calcination in air: The "WO2 / W" prepared in step (1) 18 O 49 The +ReO2 / ReO3+La2O3+C precursor was thoroughly ground and then calcined in air in a tube furnace. The easily oxidized WO2 / W 18 O 49 ReO2 / ReO3 are oxidized to WO3 and Re2O7 respectively; the highest oxidation state of La2O3 remains La2O3 after calcination, and C, which acts as a dispersant, reacts with oxygen to generate CO / CO2 gas, which is released and disappears, thus obtaining the "WO3+Re2O7+La2O3" composite intermediate product.

[0009] (3) Tungsten / rhenium / lanthanum oxide composite powder was prepared by hydrogen reduction reaction: The “WO3+Re2O7+La2O3” composite powder prepared in step (2) was placed in a tube furnace and calcined in a hydrogen atmosphere to carry out the reduction reaction. The easily reduced WO3 and Re2O7 were reduced to W and Re respectively, while the unreducible La2O3 was retained. Finally, after thorough grinding, “W+Re+La2O3” composite powder was obtained.

[0010] Further, the molar ratio of tungsten salt, rhenium salt, lanthanum salt, excess carbon source and fuel in step (1) is 1:(0.1~0.76):(0.06~0.34):(0.2~1.2):(14~25).

[0011] Further, the tungsten salt mentioned in step (1) is at least one of ammonium metatungstate, ammonium paratungstate, tungsten nitrate, and tungsten chloride.

[0012] Further, the rhenium salt mentioned in step (1) is at least one of ammonium rheniumate and ammonium perrheniumate; the lanthanum salt is at least one of lanthanum nitrate, lanthanum chloride, lanthanum carbonate and lanthanum sulfate.

[0013] Further, the carbon source mentioned in step (1) is at least one of glucose, sodium acetate, sucrose, fructose, starch and xylose.

[0014] Further, the fuel mentioned in step (1) is any one of glycine, glycine + citric acid, urea + citric acid, methanol + acetic acid, carbazide + thiourea, and ethylene glycol + acetic acid.

[0015] Further, the heating conditions described in step (1) are: temperature of 350-600℃ and time of 10-30min.

[0016] Furthermore, the calcination reaction conditions described in step (2) are as follows: heating rate of 3-12℃ / min, reaction temperature of 400-700℃, holding time of 1-5h, and cooling with the furnace after the reaction is completed.

[0017] Further, the hydrogen reduction reaction conditions described in step (3) are: heating rate of 3-12℃ / min, reaction temperature of 900-1100℃, holding time of 2-6h, hydrogen flow rate of 0.5-4L / min, and cooling with the furnace after the reaction is completed.

[0018] Furthermore, in step (3), the tungsten particles of the nano-tungsten / rhenium / lanthanum oxide composite powder have an average size of 50-300 nm and uniform particle size, and the lanthanum oxide particles are uniformly dispersed in the tungsten-rhenium matrix. The powder has a low oxygen content (0.33-0.56 wt.%).

[0019] The technology of this invention has the following advantages:

[0020] (1) The preparation method of highly dispersed nano-tungsten / rhenium / lanthanum oxide composite powder provided by the present invention can be selected and prepared by controlling parameters such as the type and ratio of raw materials, heating rate, hydrogen reduction temperature and time, thereby controlling the performance of the synthesized nano-tungsten / rhenium / lanthanum oxide composite powder and realizing its application in multiple fields.

[0021] (2) The solution combustion synthesis reaction in the preparation method provided by the present invention can achieve uniform mixing and dispersion of each component at the molecular level, and the large amount of gas released during the reaction can effectively prevent particle agglomeration, which is conducive to the final formation of nano tungsten / rhenium / lanthanum oxide composite powder with uniform loading and high dispersion of each component particle.

[0022] (3) The excess carbon source added in this invention undergoes an in-situ SCS reaction to obtain uniformly distributed carbon, which can act as a dispersant. This helps to suppress the coarsening and agglomeration of oxide particles, resulting in fine-sized and uniformly distributed WO3+Re2O7+La2O3 intermediate products, which provides a basis for the final synthesis of highly dispersed nano-tungsten / rhenium / lanthanum oxide composite powder.

[0023] (4) The La2O3 particles in the nano-tungsten / rhenium / lanthanum oxide composite powder synthesized by in-situ SCS reaction and hydrogen reduction in this invention are small in size and uniformly distributed, thus exhibiting good interfacial compatibility with the W-Re matrix, which is beneficial for obtaining better interfacial strength and uniform microstructure. (5) The dispersant (carbon) and rare earth oxide dispersion particles (lanthanum oxide) used in this invention are synthesized in-situ using inexpensive and readily available chemicals, eliminating the need for additional external introduction of carbon and lanthanum oxide, ensuring safety, efficiency, and avoiding external contamination.

[0024] (6) The preparation method provided by the present invention is time-saving, energy-saving, simple and low-cost, and has low equipment requirements, making it suitable for industrial production. Detailed Implementation

[0025] Example 1

[0026] Ammonium tungstate, ammonium rhenium oxide, lanthanum nitrate, glucose, and glycine + citric acid were weighed in a molar ratio of 1:0.43:0.26:0.5:16.9 and dissolved in a small amount of deionized water. The solution was stirred thoroughly with a glass rod until completely dissolved, forming a homogeneous aqueous solution. The mixed solution was heated in a temperature-controlled resistance furnace until the water evaporated and the solution became a brownish-brown viscous state. The solution was then held at 550°C for 10 minutes to induce a vigorous combustion synthesis reaction. The product after the reaction was completed was thoroughly ground to obtain a precursor powder. The prepared precursor powder was placed in a tube furnace for calcination, with both ends of the furnace tubes open. The temperature was increased to 500°C at a rate of 5°C / min and held for 2 hours. After cooling with the furnace, the product was ground to obtain a composite intermediate product of "WO3 + Re2O7 + La2O3". Finally, the composite powder was further reduced in a tube furnace under a hydrogen atmosphere, with the temperature increased to 1000℃ at a rate of 5℃ / min, held at that temperature for 4 hours, and then cooled with the furnace. The hydrogen flow rate was 2L / min. The prepared nano-tungsten / rhenium / lanthanum oxide composite powder had an average tungsten particle size of 240nm, uniform particle size, and rhenium and lanthanum oxide particles uniformly dispersed in the tungsten matrix. The powder had a low oxygen content (0.35wt.%).

[0027] Example 2

[0028] Ammonium paratungstate, ammonium perrhenate, lanthanum chloride, starch, urea, and citric acid were weighed in a molar ratio of 1:0.25:0.08:0.3:18.3 and dissolved in a small amount of deionized water. The solution was stirred thoroughly with a glass rod until completely dissolved, forming a homogeneous aqueous solution. The mixed solution was heated in a temperature-controlled resistance furnace until the water evaporated and the solution became a brownish-brown viscous state. The solution was then held at 500°C for 15 minutes to induce a vigorous combustion synthesis reaction. The product after the reaction was completed was thoroughly ground to obtain a precursor powder. The prepared precursor powder was placed in a tube furnace for calcination, with both ends of the furnace tube open. The temperature was increased to 700°C at a rate of 7°C / min and held for 1 hour. After cooling with the furnace, the product was ground to obtain a composite intermediate product of "WO3+Re2O7+La2O3". Finally, the composite powder was further reduced in a tube furnace under a hydrogen atmosphere, with the temperature increased to 950°C at a rate of 10°C / min, held at that temperature for 3 hours, and then cooled with the furnace. The hydrogen flow rate was 3 L / min. The prepared nano-tungsten / rhenium / lanthanum oxide composite powder had an average tungsten particle size of 140 nm, uniform particle size, and rhenium and lanthanum oxide particles uniformly dispersed in the tungsten matrix. The powder had a low oxygen content (0.47 wt.%).

[0029] Example 3

[0030] Tungsten nitrate, ammonium rhenium sulfate, lanthanum sulfate, fructose, and carbazide + thiourea were weighed in a molar ratio of 1:0.66:0.32:0.8:22.4 and dissolved in a small amount of deionized water. The solution was stirred thoroughly with a glass rod until completely dissolved, forming a homogeneous aqueous solution. The mixed solution was heated in a temperature-controlled resistance furnace until the water evaporated and the solution became a brownish-brown viscous state. The solution was then held at 400°C for 20 minutes to induce a vigorous combustion synthesis reaction. The product after the reaction was completed was thoroughly ground to obtain a precursor powder. The prepared precursor powder was placed in a tube furnace for calcination, with both ends of the furnace tube kept open. The temperature was increased to 400°C at a rate of 3°C / min and held for 4 hours. After cooling with the furnace, the product was ground to obtain a composite intermediate product of "WO3 + Re2O7 + La2O3". Finally, the composite powder was further reduced in a tube furnace under a hydrogen atmosphere, with the temperature increased to 900℃ at a rate of 12℃ / min, held at that temperature for 2 hours, and then cooled with the furnace. The hydrogen flow rate was 4L / min. The prepared nano-tungsten / rhenium / lanthanum oxide composite powder had an average tungsten particle size of 50nm, uniform particle size, and rhenium and lanthanum oxide particles uniformly dispersed in the tungsten matrix. The powder had a low oxygen content (0.56wt.%).

[0031] Example 4

[0032] Tungsten chloride, ammonium perrhenate, lanthanum carbonate, sodium acetate, and ethylene glycol + acetic acid were weighed in a molar ratio of 1:0.12:0.08:0.95:24.3 and dissolved in a small amount of deionized water. The solution was stirred thoroughly with a glass rod until completely dissolved, forming a homogeneous aqueous solution. The mixed solution was heated in a temperature-controlled resistance furnace until the water evaporated and the solution became a brownish-brown viscous state. The solution was then held at 350°C for 30 minutes to induce a vigorous combustion synthesis reaction. The product after the reaction was completed was thoroughly ground to obtain a precursor powder. The prepared precursor powder was placed in a tube furnace for calcination, with both ends of the furnace tube open. The temperature was increased to 700°C at a rate of 8°C / min and held for 5 hours. After cooling with the furnace, the product was ground to obtain a composite intermediate product of "WO3 + Re2O7 + La2O3". Finally, the composite powder was further reduced in a tube furnace under a hydrogen atmosphere, with the temperature increased to 1100℃ at a rate of 12℃ / min, held for 5 hours, and then cooled with the furnace. The hydrogen flow rate was 2L / min. The prepared nano-tungsten / rhenium / lanthanum oxide composite powder had an average tungsten particle size of 300nm, uniform particle size, and rhenium and lanthanum oxide particles uniformly dispersed in the tungsten matrix. The powder had a low oxygen content (0.33wt.%).

Claims

1. A method for preparing highly dispersed nano-tungsten / rhenium / lanthanum oxide composite powder, characterized in that... The preparation steps are as follows: (1) Preparation of tungsten oxide / rhenium oxide / lanthanum oxide / carbon composite powder by solution combustion synthesis: Tungsten salt, rhenium salt, lanthanum salt, excess carbon source, fuel and deionized water are mixed in a certain proportion to prepare an aqueous solution. The solution is placed on a temperature-controlled resistance furnace and heated and stirred. After evaporating the water until the solution becomes viscous, it is heated to a certain temperature to carry out the combustion synthesis reaction to obtain a uniformly mixed "WO2 / W" powder. 18 O 49 +ReO2 / ReO3+La2O3+C” composite precursor; the molar ratio of tungsten salt, rhenium salt, lanthanum salt, excess carbon source, and fuel is 1:(0.1~0.76):(0.06~0.34):(0.2~1.2):(14~25); (2) Preparation of tungsten oxide / rhenium oxide / lanthanum oxide composite powder by calcination in air: The "WO2 / W" prepared in step (1) 18 O 49 The +ReO2 / ReO3+La2O3+C precursor was thoroughly ground and then calcined in air in a tube furnace. The easily oxidized WO2 / W 18 O 49 ReO2 / ReO3 are oxidized to WO3 and Re2O7 respectively; the highest oxidation state of La2O3 remains La2O3 after calcination, and C, which acts as a dispersant, reacts with oxygen to generate CO / CO2 gas, which is released and disappears, thus obtaining the "WO3+Re2O7+La2O3" composite intermediate product. (3) Tungsten / rhenium / lanthanum oxide composite powder was prepared by hydrogen reduction reaction: The "WO3+Re2O7+La2O3" composite powder prepared in step (2) was placed in a tube furnace and calcined in a hydrogen atmosphere to carry out the reduction reaction. The easily reduced WO3 and Re2O7 were reduced to W and Re respectively, while the unreducible La2O3 was retained. Finally, after thorough grinding, the "W+Re+La2O3" composite powder was obtained. The hydrogen reduction reaction conditions are as follows: heating rate of 3-12 ℃ / min, reaction temperature of 900-1100 ℃, holding time of 2-6 h, hydrogen flow rate of 0.5-4 L / min, and cooling with the furnace after the reaction is completed. The nano-tungsten / rhenium / lanthanum oxide composite powder has an average tungsten particle size of 50–300 nm and uniform particle size, and lanthanum oxide particles are uniformly dispersed in the tungsten-rhenium matrix. The oxygen content of the powder is 0.33–0.56 wt.%.

2. The method for preparing a highly dispersed nano-tungsten / rhenium / lanthanum oxide composite powder as described in claim 1, characterized in that... The tungsten salt mentioned in step (1) is at least one of ammonium metatungstate, ammonium paratungstate, tungsten nitrate, and tungsten chloride.

3. The method for preparing a highly dispersed nano-tungsten / rhenium / lanthanum oxide composite powder as described in claim 1, characterized in that... The rhenium salt mentioned in step (1) is at least one of ammonium perrhenate and ammonium perrhenate; the lanthanum salt is at least one of lanthanum nitrate, lanthanum chloride, lanthanum carbonate and lanthanum sulfate.

4. The method for preparing a highly dispersed nano-tungsten / rhenium / lanthanum oxide composite powder as described in claim 1, characterized in that... The carbon source mentioned in step (1) is at least one of glucose, sodium acetate, sucrose, fructose, starch and xylose.

5. The method for preparing a highly dispersed nano-tungsten / rhenium / lanthanum oxide composite powder as described in claim 1, characterized in that... The fuel mentioned in step (1) is any one of glycine, glycine + citric acid, urea + citric acid, methanol + acetic acid, carbazide + thiourea, or ethylene glycol + acetic acid.

6. The method for preparing a highly dispersed nano-tungsten / rhenium / lanthanum oxide composite powder as described in claim 1, characterized in that... The heating conditions described in step (1) are: temperature of 350-600 ℃ and time of 10-30 min.

7. The method for preparing a highly dispersed nano-tungsten / rhenium / lanthanum oxide composite powder as described in claim 1, characterized in that... The calcination reaction conditions described in step (2) are: heating rate of 3-12 ℃ / min, reaction temperature of 400-700 ℃, holding time of 1-5 h, and cooling with the furnace after the reaction is completed.