阅读说明：本技术 一种钼掺杂的超细钨铜合金的冷冻干燥制备方法 (Freeze-drying preparation method of molybdenum-doped superfine tungsten-copper alloy ) 是由 马宗青 扈伟强 刘永长 于 2021-09-03 设计创作，主要内容包括：本发明提供了一种钼掺杂的超细钨铜合金的冷冻干燥制备方法,包括以下步骤：将可溶性的铜盐、钨酸铵盐、钼酸铵盐与表面活性剂一同加入去离子水中并超声处理,制备成溶液或者悬浊液；喷雾或直接倒入到液氮中进行预冻,收集预冻后的溶液或者悬浊液,放入冷冻干燥机中,进行去离子水的升华,得到前驱体粉末；将上述前驱体粉末进行两步煅烧,然后在还原性气氛中两步还原得到钨钼铜复合粉末；将得到的钨钼铜复合粉末进行预成型,烧结,得到超细的钨钼铜合金。本发明采用新颖的冷冻干燥法制备了超细的钨钼铜粉末,与传统的机械合金化等方法相比,冻干的超细钨钼铜粉末烧结活性高,因此相比文献烧结温度更低,保温时间更短,更节约能源。(The invention provides a freeze-drying preparation method of molybdenum-doped superfine tungsten-copper alloy, which comprises the following steps: adding soluble copper salt, ammonium tungstate, ammonium molybdate and a surfactant into deionized water together, and performing ultrasonic treatment to prepare a solution or a suspension; spraying or directly pouring into liquid nitrogen for prefreezing, collecting the prefreezed solution or suspension, placing into a freeze dryer, and sublimating with deionized water to obtain precursor powder; calcining the precursor powder in two steps, and then reducing the calcined precursor powder in a reducing atmosphere in two steps to obtain tungsten-molybdenum-copper composite powder; and performing and sintering the obtained tungsten-molybdenum-copper composite powder to obtain the superfine tungsten-molybdenum-copper alloy. The invention adopts a novel freeze-drying method to prepare the superfine tungsten-molybdenum-copper powder, and compared with the traditional mechanical alloying method and other methods, the freeze-dried superfine tungsten-molybdenum-copper powder has high sintering activity, so that compared with documents, the sintering temperature is lower, the heat preservation time is shorter, and the energy is saved.)

1. A freeze drying preparation method of molybdenum-doped superfine tungsten-copper alloy is characterized by comprising the following steps: the method comprises the following steps:

s1: adding soluble copper salt, ammonium tungstate, ammonium molybdate and a surfactant into deionized water together, and performing ultrasonic treatment to prepare a solution or a suspension;

s2: spraying the solution or the suspension or directly pouring the solution or the suspension into liquid nitrogen for prefreezing, collecting the prefreezed solution or suspension, putting the solution or the suspension into a freeze dryer with the freeze-drying temperature reaching the preset temperature of-100 to-65 ℃, maintaining the vacuum degree below 30Pa, and carrying out freeze drying for 10 to 30 hours to carry out sublimation of deionized water to obtain precursor powder;

s3: calcining the precursor powder in two steps, and then reducing the calcined precursor powder in a reducing atmosphere in two steps to obtain tungsten-molybdenum-copper composite powder;

s4: performing the obtained tungsten-molybdenum-copper composite powder, and then sintering at the temperature of 900-1200 ℃ for 1-6 h under normal pressure in a hydrogen atmosphere to finally obtain the ultrafine tungsten-molybdenum-copper alloy with the average grain size of 95-250 nm.

2. The method for freeze-drying preparation of molybdenum-doped ultra-fine tungsten-copper alloy as claimed in claim 1, wherein: in the step S1, the copper salt is one or more of copper nitrate trihydrate, copper sulfate and copper acetate; the ammonium tungstate is one or more of ammonium metatungstate and ammonium paratungstate; the ammonium molybdate is one or more of ammonium molybdate tetrahydrate, ammonium molybdate and ammonium heptamolybdate; the surfactant is one or two of polyethylene glycol and polyvinylpyrrolidone.

3. The method for freeze-drying preparation of molybdenum-doped ultra-fine tungsten-copper alloy as claimed in claim 1, wherein: in step S1, the concentration of ammonium tungstate in the solution is: 0.01-0.2 g/mL; ammonium molybdate based on the molybdenum in tungsten molybdenum copper alloy: the tungsten atomic ratio is 5-40%; copper salt according to copper in tungsten molybdenum copper alloy: the mass ratio of (tungsten + molybdenum) is 10-30%; the mass of the surfactant is 2-20% of that of the ammonium tungstate salt.

4. The freeze-drying method for preparing molybdenum-doped ultra-fine tungsten-copper alloy as claimed in claim 3, wherein: in the step S1, the power of ultrasonic treatment is 100-200W, and the ultrasonic treatment time is 0.3-1 h.

5. The method for freeze-drying preparation of molybdenum-doped ultra-fine tungsten-copper alloy as claimed in claim 1, wherein: in step S3, two calcination steps are performed: calcining the mixture at the temperature of 180-240 ℃ and the temperature of 400-500 ℃ for 0.5-2 h by using flowing air respectively to remove the surfactant; two-step reduction: reducing the mixture by pure hydrogen for 1 to 3 hours at the temperature of 600 to 700 ℃ and 750 to 850 ℃.

6. The method for freeze-drying preparation of molybdenum-doped ultra-fine tungsten-copper alloy as claimed in claim 1, wherein: in the step S4, the tungsten-molybdenum-copper composite powder is placed into a die and preformed under the pressure of 5-20 MPa, and then the preformed sample is subjected to cold isostatic pressing under the pressure of 150-200 MPa.

Technical Field

The invention belongs to the technical field of composite material preparation, and particularly relates to a freeze-drying preparation method of molybdenum-doped superfine tungsten-copper alloy.

Background

The tungsten-copper alloy has the common excellent performance of tungsten and copper, has stronger mechanical and physical properties, good arc erosion resistance, good electric conduction and heat conduction performance, stronger microwave absorption capacity and the like, and is widely applied to the fields of electric contact materials, heat sink materials, electric spark processing materials, arc-resistant electrode materials, heavy electrical contact materials, radiator materials in high-density integrated circuits and the like. However, the tungsten-copper alloy is a composite material formed by combining tungsten particles with a body-centered cubic structure and copper with a face-centered cubic structure, and is called as a pseudo alloy, and the tungsten and the copper elements are not mutually solid-dissolved and cannot generate intermetallic compounds, and the tungsten alloy has poor mechanical properties due to the large grain size. These all result in alloys with structures and properties that are not compatible with the requirements of tungsten copper alloys for high technology applications, limiting their applications.

At present, most scholars add alloy elements such as Zn and Ag or second phase particles in the tungsten-copper alloy to improve the mechanical property, however, the alloy elements such as Zn and Ag and copper form solid solution, and the second phase particles are also distributed in the copper matrix. Since elemental copper is best thermally and electrically conductive, forming a solid solution or doping a second phase will sacrifice both the thermal and electrical conductivity of the tungsten copper alloy. Therefore, on the premise of little or even no sacrifice of the thermal conductivity and electrical conductivity of the tungsten-copper alloy, the research of refining W crystal grains from the perspective of tungsten and further improving the mechanical properties of the alloy is very important. The invention tries to add Mo element to refine W grains, Mo is also pseudo alloy with Cu and does not form solid solution, but W and Mo form solid solution. Currently, few studies on tungsten-molybdenum-copper alloys have been made, and the influence of Mo addition on tungsten-copper alloys has not been studied. The literature is summarized as follows: a method (CN107937748A) for preparing tungsten-molybdenum-copper composite material by high-current resistance sintering, the grain size of tungsten is larger than 1 μm; a method (CN 107326241B) for preparing tungsten-molybdenum-copper composite material by spark plasma sintering, the tungsten grain size is larger than 1 μm; a method for preparing tungsten-molybdenum-copper composite material by microwave sintering (CN 109207762A), the tungsten grain size is larger than 1 μm; a preparation method (CN 103194629A) of tungsten-molybdenum-copper composite material, wherein the grain size of tungsten is larger than 5 μm. The above patents all obtain tungsten molybdenum copper alloy with coarse grains by different sintering schemes through direct mixing or ball milling of tungsten molybdenum copper commercial powder. The W crystal grain size is more than micron, the mechanical property is far lower than that of W nanometer crystal, and the thick tungsten crystal grain still has huge optimization space.

In addition, the preparation process of the tungsten-molybdenum-copper alloy is worthy of exploration, and a thought is provided for providing the ultra-fine tungsten-molybdenum-copper powder with the ultra-high sintering activity by a newly developed freeze drying method. The basic principle of freeze drying is that the water in the material is frozen at low temperature, and then the ice crystal is directly converted into gaseous state for sublimation by vacuum pumping, so that the material is dehydrated to form solid particles. Namely, the freeze-drying method is utilized to convert ice into steam to remove the steam from the frozen solution under the high vacuum condition, and nano crystal grains and nano particles are directly precipitated. The method has the main advantages that the method is carried out at low temperature, the dried material keeps the original chemical components and physical properties, the grain size of the prepared powder is dozens of times smaller, the particle size distribution is extremely narrow, other elements can be effectively prevented from being introduced, and liquid evaporation or physical separation treatment is not needed. Freeze-drying has also been used to produce powders of tungsten carbide, pure tungsten, ODS tungsten, but the alloys produced from these powders are mainly used as structural materials with greater attention to mechanical properties. Compared with the powder, the tungsten, molybdenum and copper have great difference in composition and the microstructure of the sintered alloy is also great different.

Disclosure of Invention

The invention provides a freeze-drying preparation method of molybdenum-doped superfine tungsten-copper alloy aiming at the technical problems in the prior art, the superfine tungsten-molybdenum-copper powder is prepared by adopting a novel freeze-drying method, and compared with the traditional mechanical alloying method and other methods, the freeze-dried superfine tungsten-molybdenum-copper powder has high sintering activity, so that compared with the literature, the sintering temperature is lower, the heat preservation time is shorter, and the energy is saved.

The technical scheme adopted by the invention is as follows: a freeze drying preparation method of molybdenum-doped superfine tungsten-copper alloy comprises the following steps:

s1: adding soluble copper salt, ammonium tungstate, ammonium molybdate and a surfactant into deionized water together, and performing ultrasonic treatment to prepare a solution or a suspension;

s2: spraying the solution or the suspension or directly pouring the solution or the suspension into liquid nitrogen for prefreezing, collecting the prefreezed solution or suspension, putting the solution or the suspension into a freeze dryer with the freeze-drying temperature reaching the preset temperature of-100 to-65 ℃, maintaining the vacuum degree below 30Pa, and carrying out freeze drying for 10 to 30 hours to carry out sublimation of deionized water to obtain precursor powder;

s3: calcining the precursor powder in two steps, and then reducing the calcined precursor powder in a reducing atmosphere in two steps to obtain tungsten-molybdenum-copper composite powder;

s4: performing the obtained tungsten-molybdenum-copper composite powder, and then sintering at the temperature of 900-1200 ℃ for 1-6 h under normal pressure in a hydrogen atmosphere to finally obtain the ultrafine tungsten-molybdenum-copper alloy with the average grain size of 95-250 nm.

Specifically, in step S1, the copper salt is one or more of copper nitrate trihydrate, copper sulfate, and copper acetate; the ammonium tungstate is one or more of ammonium metatungstate and ammonium paratungstate; the ammonium molybdate is one or more of ammonium molybdate tetrahydrate, ammonium molybdate and ammonium heptamolybdate; the surfactant is one or two of polyethylene glycol and polyvinylpyrrolidone.

Specifically, in step S1, the concentration of ammonium tungstate in the solution is: 0.01-0.2 g/mL; ammonium molybdate based on the molybdenum in tungsten molybdenum copper alloy: the tungsten atomic ratio is 5-40%; copper salt according to copper in tungsten molybdenum copper alloy: the mass ratio of (tungsten + molybdenum) is 10-30%; the mass of the surfactant is 2-20% of that of the ammonium tungstate salt.

Specifically, in the step S1, the power of the ultrasonic treatment is 100 to 200W, and the ultrasonic treatment time is 0.3 to 1 hour.

Specifically, in step S3, two calcination steps are performed: calcining the mixture at the temperature of 180-240 ℃ and the temperature of 400-500 ℃ for 0.5-2 h by using flowing air respectively to remove the surfactant; two-step reduction: reducing the mixture by pure hydrogen for 1 to 3 hours at the temperature of 600 to 700 ℃ and 750 to 850 ℃.

Specifically, in the step S4, the tungsten-molybdenum-copper composite powder is placed in a mold and preformed under a pressure of 5 to 20MPa, and then the preformed sample is subjected to cold isostatic pressing under a pressure of 150 to 200 MPa.

Compared with the prior art, the invention has the beneficial effects that:

1. the invention adopts a novel freeze-drying method to prepare the superfine tungsten-molybdenum-copper powder, and compared with the traditional mechanical alloying method and other methods, the freeze-dried superfine tungsten-molybdenum-copper powder has high sintering activity, so that compared with documents, the sintering temperature is lower, the heat preservation time is shorter, and the energy is saved.

2. The prefreezing of the invention adopts liquid nitrogen, which is more convenient and faster than the process of preparing other powder by freeze drying, and the instant solidification of the solution also ensures that the solute stays at the original position.

3. The freeze-drying temperature of the invention is lower, which ensures that the tungsten-molybdenum-copper precursor powder can not be melted in the freeze-drying process, and also ensures that the powder can not be subjected to segregation in the freeze-drying process and the in-situ precipitation can ensure that the tungsten-molybdenum-copper elements are distributed more uniformly.

4. The tungsten crystal grains in the tungsten-molybdenum-copper alloy prepared by the invention are very fine, and the tungsten crystal grains in the tungsten-molybdenum-copper alloy in related documents are tens of times larger than those in the tungsten-molybdenum-copper alloy.

5. The invention greatly improves the mechanical property of the tungsten-molybdenum-copper alloy on the premise of not reducing too much electrical conductivity and thermal conductivity.

6. The invention can realize the preparation of the superfine nano powder and is also very suitable for preparing a large amount of composite nano powder in a single batch.

Drawings

FIG. 1 is an SEM picture of ultra-fine W-Mo-Cu composite powder obtained by freeze-drying in example 1 of the present invention;

FIG. 2 is an SEM photograph of an ultrafine W-Mo-Cu composite alloy obtained by sintering according to example 1 of the present invention;

FIG. 3 is an SEM picture of a W-Cu composite alloy of a comparative sample obtained by sintering in example 1 of the present invention;

FIG. 4 is an SEM picture of an ultrafine W-Mo-Cu composite alloy obtained by sintering in example 2 of the present invention.

Detailed Description

In order to make the technical solutions of the present invention better understood, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

Example 1

(1) Adding 20g of ammonium metatungstate, 3.584g of ammonium molybdate tetrahydrate, 15.828g of copper nitrate trihydrate and 2g of surfactant polyvinylpyrrolidone (PVP) into 400ml of deionized water, and performing ultrasonic treatment for 1h under the power of 100W to prepare a solution;

(2) directly pouring the solution into liquid nitrogen for prefreezing, collecting the prefreezed solution, immediately putting the prefreezed solution into a freeze dryer with the freeze-drying temperature reaching the preset temperature of minus 80 ℃, starting a vacuum pump, maintaining the vacuum degree below 30Pa, and carrying out freeze drying for 24 hours to carry out sublimation of deionized water to obtain tungsten-molybdenum-copper precursor powder;

(3) calcining the precursor powder obtained by freeze-drying in the air at 200 ℃ and 500 ℃ for 1h respectively, and then reducing the precursor powder at 600 ℃ and 750 ℃ for 1.5h in a pure hydrogen atmosphere to obtain superfine tungsten-molybdenum-copper composite powder;

(4) and putting the obtained tungsten-molybdenum-copper composite powder into a mold, performing at 5MPa, maintaining the pressure for 5min, performing cold isostatic pressing at 200MPa for 30min, and sintering at 1050 ℃ under normal pressure in a hydrogen atmosphere for 4h to finally obtain the ultrafine (80W-20Mo) -20wtCu alloy.

By the freeze-drying preparation method of the molybdenum-doped superfine tungsten-molybdenum-copper alloy, superfine tungsten-molybdenum-copper composite nano powder with the average grain diameter of 30nm is obtained in step S3, the average grain size is small, the grain size distribution is narrowed, and the surface appearance is shown in figure 1. After sintering, the grain size of the tungsten-molybdenum-copper alloy is only about 100nm, the surface appearance is shown in figure 2, which is far smaller than the W grain (> 1 μm) of the tungsten-molybdenum-copper alloy in the literature, and the hardness of the tungsten-molybdenum-copper alloy is up to 560HV, and the conductivity is up to 32.5% IACS. In addition, we also prepared a comparative sample W-20wtCu tungsten copper alloy, the surface morphology of which is shown in FIG. 3, the grain size of which is about 200nm, the hardness of which is 495HV, and the electrical conductivity of which is 35.2% IACS. Therefore, the doping of Mo can obviously refine tungsten crystal grains in the tungsten-copper alloy, and greatly improve the hardness mechanical property of the alloy on the premise of not reducing the conductivity. On the other hand, compared with the pure tungsten copper alloy prepared by other processes in the literature, the pure tungsten copper alloy prepared by the freeze-drying method also has remarkable advantages in grain size.

Example 2

(1) Adding 20g of ammonium metatungstate, 3.584g of ammonium molybdate tetrahydrate, 7.034g of copper nitrate trihydrate, 1.5g of PVP (polyvinyl pyrrolidone) as a surfactant and 1.5g of polyethylene glycol (PEG) as a surfactant into 2000ml of deionized water, and performing ultrasonic treatment for 0.3h at the power of 200W to prepare a solution;

(2) spraying the solution into liquid nitrogen for prefreezing, collecting the prefreezed solution, immediately putting into a freeze dryer with freeze-drying temperature reaching preset temperature of-70 deg.C, opening a vacuum pump, maintaining vacuum degree below 30Pa, freeze-drying for 30 hr for sublimation of deionized water;

(3) calcining the precursor powder obtained by freeze-drying in the air at 180 ℃ and 400 ℃ for 2h respectively, and then reducing the precursor powder in a pure hydrogen atmosphere at 700 ℃ and 800 ℃ for 3h and 2h respectively to obtain superfine tungsten-molybdenum-copper composite powder;

(4) and putting the obtained tungsten-molybdenum-copper composite powder into a mold, performing under 20MPa and maintaining the pressure for 5min, then performing cold isostatic pressing under 150MPa for 30min, and finally performing normal-pressure sintering at 900 ℃ in a hydrogen atmosphere for 6h to finally obtain the ultrafine (80W-20Mo) -10wtCu alloy.

By the freeze-drying preparation method of the molybdenum-doped superfine tungsten-copper alloy, superfine tungsten-molybdenum-copper composite nano powder with the average grain diameter of 50nm is obtained in step S3, the average grain size is small, and the grain size distribution is narrowed. After sintering, the grain size of the obtained tungsten-molybdenum-copper alloy is only about 95nm, and the surface appearance is shown in figure 4, which is far smaller than the W grain (> 1 μm) of the tungsten-molybdenum-copper alloy in the literature. On the other hand, the hardness of the tungsten-molybdenum-copper alloy is as high as 393HV, and the electric conductivity is as high as 19.9% IACS. Therefore, compared with the traditional method, the freeze drying preparation method of the molybdenum-doped superfine tungsten-copper alloy has remarkable advantages in grain size, hardness and conductivity.

Example 3

(1) Adding 20g of ammonium paratungstate, 8.69g of ammonium heptamolybdate, 13.041g of copper nitrate trihydrate and 4g of surfactant PEG into 500ml of deionized water, and performing ultrasonic treatment for 0.5h under the power of 150W to prepare suspension;

(2) spraying the suspension into liquid nitrogen for prefreezing, collecting the prefreezed suspension, immediately putting the prefreezed suspension into a freeze dryer with the freeze-drying temperature reaching a preset temperature of-65 ℃, starting a vacuum pump, maintaining the vacuum degree below 30Pa, and freeze-drying for 10 hours to sublimate deionized water;

(3) calcining the precursor powder obtained by freeze-drying in the air at 240 ℃ and 500 ℃ for 0.5h respectively, and then reducing the precursor powder in a pure hydrogen atmosphere at 650 ℃ and 850 ℃ for 1h and 1.2h respectively to obtain superfine tungsten-molybdenum-copper composite powder;

(4) and putting the obtained tungsten-molybdenum-copper composite powder into a mold, performing under 10MPa and maintaining the pressure for 5min, then performing cold isostatic pressing under 160MPa for 30min, and finally performing normal-pressure sintering at 1000 ℃ in a hydrogen atmosphere for 5h to finally obtain the superfine (60W-40Mo) -15wtCu alloy.

By the freeze-drying preparation method of the molybdenum-doped superfine tungsten-copper alloy, the superfine tungsten-molybdenum-copper composite nano powder with the average grain diameter of 40nm is obtained in step S3, the average grain size is small, and the grain size distribution is narrowed. After sintering, the grain size of the obtained tungsten-molybdenum-copper alloy is only about 110nm, which is far smaller than the W grain (> 1 μm) of the tungsten-molybdenum-copper alloy in the literature. On the other hand, the hardness of the tungsten-molybdenum-copper alloy is up to 431HV, and the electric conductivity is up to 26.5% IACS. Therefore, compared with the traditional method, the freeze drying preparation method of the molybdenum-doped superfine tungsten-copper alloy has remarkable advantages in grain size, hardness and conductivity.

Example 4

(1) Adding 20g of ammonium metatungstate, 0.837g of ammonium molybdate, 18.73g of copper acetate and 0.4g of surfactant PVP into 1000ml of deionized water, and performing ultrasonic treatment for 0.8h under the power of 180W to prepare a solution;

(2) directly pouring the solution into liquid nitrogen for prefreezing, collecting the prefreezed solution, immediately putting the prefreezed solution into a freeze dryer with the freeze-drying temperature reaching the preset temperature of-85 ℃, starting a vacuum pump, maintaining the vacuum degree below 30Pa, and freeze-drying for 25 hours to sublimate deionized water;

(3) calcining the precursor powder obtained by freeze-drying in the air at 190 ℃ and 470 ℃ for 1.5h respectively, and then reducing the precursor powder in a pure hydrogen atmosphere at 620 ℃ and 780 ℃ for 1.2h and 3h respectively to obtain superfine tungsten-molybdenum-copper composite powder;

(4) and putting the obtained tungsten-molybdenum-copper composite powder into a mold, performing under 7MPa and maintaining the pressure for 5min, then performing cold isostatic pressing under 180MPa for 30min, and finally performing normal-pressure sintering at 1200 ℃ in a hydrogen atmosphere for 1h to finally obtain the superfine (95W-5Mo) -30wtCu alloy.

By the freeze-drying preparation method of the molybdenum-doped superfine tungsten-copper alloy, superfine tungsten-molybdenum-copper composite nano powder with the average grain diameter of 55nm is obtained in step S3, the average grain size is small, and the grain size distribution is narrowed. After sintering, the grain size of the obtained tungsten-molybdenum-copper alloy is only about 250nm, which is far smaller than the W grain (> 1 μm) of the tungsten-molybdenum-copper alloy in the literature. On the other hand, the hardness of the tungsten-molybdenum-copper alloy is as high as 320HV, and the electric conductivity is as high as 42.2% IACS. Therefore, compared with the traditional method, the freeze drying preparation method of the molybdenum-doped superfine tungsten-copper alloy has remarkable advantages in grain size, hardness and conductivity.

Example 5

(1) Adding 20g of ammonium metatungstate, 3.052g of ammonium molybdate tetrahydrate, 15.799g of copper acetate and 0.8g of surfactant PVP into 1500ml of deionized water, and performing ultrasonic treatment for 0.6h under the power of 120W to prepare a solution;

(2) directly pouring the solution into liquid nitrogen for prefreezing, collecting the prefreezed solution, immediately putting the prefreezed solution into a freeze dryer with the freeze-drying temperature reaching the preset temperature of-100 ℃, starting a vacuum pump, maintaining the vacuum degree below 30Pa, and freeze-drying for 20 hours to sublimate deionized water;

(3) calcining the precursor powder obtained by freeze-drying in the air at 210 ℃ and 430 ℃ for 1.2h respectively, and then reducing at 680 ℃ and 760 ℃ for 2h and 2h respectively in a pure hydrogen atmosphere to obtain superfine tungsten-molybdenum-copper composite powder;

(4) and putting the obtained tungsten-molybdenum-copper composite powder into a mold, performing at 15MPa, maintaining the pressure for 5min, performing cold isostatic pressing at 190MPa for 30min, and sintering at 1100 ℃ under normal pressure in a hydrogen atmosphere for 2h to finally obtain the superfine (90W-10Mo) -25wtCu alloy.

By the freeze-drying preparation method of the molybdenum-doped superfine tungsten-copper alloy, superfine tungsten-molybdenum-copper composite nano powder with the average grain diameter of 35nm is obtained in step S3, the average grain size is small, and the grain size distribution is narrowed. After sintering, the grain size of the obtained tungsten-molybdenum-copper alloy is only about 160nm, which is far smaller than the W grain (> 1 μm) of the tungsten-molybdenum-copper alloy in the literature. On the other hand, the hardness of the tungsten-molybdenum-copper alloy is as high as 472HV, and the electric conductivity is as high as 35.5% IACS. Therefore, compared with the traditional method, the freeze drying preparation method of the molybdenum-doped superfine tungsten-copper alloy has remarkable advantages in grain size, hardness and conductivity.

Example 6

(1) Adding 20g of ammonium metatungstate, 6.144g of ammonium molybdate tetrahydrate, 13.382g of copper sulfate, 1.2g of PVP (polyvinyl pyrrolidone) surfactant and 1.2g of PEG (polyethylene glycol) surfactant into 300ml of deionized water, and performing ultrasonic treatment for 0.9h at power of 140W to prepare a solution;

(2) directly pouring the solution into liquid nitrogen for prefreezing, collecting the prefreezed solution, immediately putting the prefreezed solution into a freeze dryer with the freeze-drying temperature reaching the preset temperature of-95 ℃, starting a vacuum pump, maintaining the vacuum degree below 30Pa, and freeze-drying for 15 hours to sublimate deionized water;

(3) calcining the precursor powder obtained by freeze-drying in the air at 230 ℃ and 480 ℃ for 0.8h respectively, and then reducing at 660 ℃ and 820 ℃ for 2.5h and 2.5h respectively in a pure hydrogen atmosphere to obtain superfine tungsten-molybdenum-copper composite powder;

(4) and putting the obtained tungsten-molybdenum-copper composite powder into a mold, performing under 10MPa and maintaining the pressure for 5min, then performing cold isostatic pressing under 175MPa for 30min, and finally performing normal-pressure sintering at 950 ℃ in a hydrogen atmosphere for 5h to finally obtain the superfine (70W-30Mo) -20wtCu alloy.

By the freeze-drying preparation method of the molybdenum-doped superfine tungsten-copper alloy, superfine tungsten-molybdenum-copper composite nano powder with the average grain diameter of 35nm is obtained in step S3, the average grain size is small, and the grain size distribution is narrowed. After sintering, the grain size of the obtained tungsten-molybdenum-copper alloy is only about 100nm, which is far smaller than the W grain (> 1 μm) of the tungsten-molybdenum-copper alloy in the literature. On the other hand, the hardness of the tungsten-molybdenum-copper alloy is as high as 515HV, and the electric conductivity is as high as 19.5 IACS. Therefore, compared with the traditional method, the freeze drying preparation method of the molybdenum-doped superfine tungsten-copper alloy has remarkable advantages in grain size, hardness and conductivity.

Example 7

(1) Adding 20g of ammonium metatungstate, 6.144g of ammonium molybdate tetrahydrate, 13.382g of copper sulfate, 1.2g of PVP (polyvinyl pyrrolidone) surfactant and 1.2g of PEG (polyethylene glycol) surfactant into 300ml of deionized water, and performing ultrasonic treatment for 0.9h at power of 140W to prepare a solution;

(2) directly pouring the solution into liquid nitrogen for prefreezing, collecting the prefreezed solution, immediately putting the prefreezed solution into a freeze dryer with the freeze-drying temperature reaching a preset temperature of-65 ℃, starting a vacuum pump, maintaining the vacuum degree below 30Pa, and freeze-drying for 15 hours to sublimate deionized water;

(3) calcining the precursor powder obtained by freeze-drying in the air at 230 ℃ and 480 ℃ for 0.8h respectively, and then reducing at 660 ℃ and 820 ℃ for 2.5h and 2.5h respectively in a pure hydrogen atmosphere to obtain superfine tungsten-molybdenum-copper composite powder;

(4) and putting the obtained tungsten-molybdenum-copper composite powder into a mold, performing under 10MPa and maintaining the pressure for 5min, then performing cold isostatic pressing under 175MPa for 30min, and finally performing normal-pressure sintering at 950 ℃ in a hydrogen atmosphere for 5h to finally obtain the superfine (70W-30Mo) -20wtCu alloy.

By adopting the freeze-drying preparation method of the molybdenum-doped superfine tungsten-copper alloy, the superfine tungsten-molybdenum-copper composite nano powder with the average grain diameter of 45nm is obtained in step S3, the average grain size is small, and the grain size distribution is narrowed. After sintering, the grain size of the obtained tungsten-molybdenum-copper alloy is only about 110nm, which is far smaller than the W grain (> 1 μm) of the tungsten-molybdenum-copper alloy in the literature. On the other hand, the hardness of the tungsten-molybdenum-copper alloy is up to 496HV, and the electric conductivity is up to 19.4% IACS. Therefore, compared with the traditional method, the freeze drying preparation method of the molybdenum-doped superfine tungsten-copper alloy has remarkable advantages in grain size, hardness and conductivity.

The present invention has been described in detail with reference to the embodiments, but the description is only illustrative of the present invention and should not be construed as limiting the scope of the present invention. The scope of the invention is defined by the claims. The technical solutions of the present invention or those skilled in the art, based on the teaching of the technical solutions of the present invention, should be considered to be within the scope of the present invention, and all equivalent changes and modifications made within the scope of the present invention or equivalent technical solutions designed to achieve the above technical effects are also within the scope of the present invention.