Lutetium nitride powder with high crystallinity and a method for preparing the same

Abstract

The application provides a high-crystallinity lutetium nitride powder and a preparation method thereof. The preparation method of the lutetium nitride powder comprises the following steps: using a metal lutetium powder as a raw material, pressing the lutetium powder into a powder cake under high pressure, placing the powder cake in a crucible, pretreating the powder cake under high pressure in an NH3 environment for 3-5 hours, completing crushing in a planetary ball milling mode after discharging, and screening to obtain a screened powder; the screened powder is further heat-treated at a high temperature of 1000-1400 DEG C in an N2 environment for 4-8 hours, and the high-crystallinity lutetium nitride powder is obtained after screening. The lutetium nitride powder prepared by the application has high crystallinity, and the preparation process is simple, easy to break, low in operation cost, wide in process window, and suitable for large-scale industrial production. The prepared lutetium nitride can be widely used in the fields of high-performance mechanical parts, cutters, drill bits, precision parts, optics, electronics and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to lutetium nitride and a preparation method thereof, and particularly relates to a high-crystallinity lutetium nitride powder and a preparation method thereof. BACKGROUND

[0002] Lutetium is a silvery white metal with a metallic luster between iron and silver, and is the hardest and densest metal among rare earth elements. The melting point of lutetium is very high, which is 1663℃, and lutetium is relatively stable in air. The main use of lutetium metal is to be used as a catalyst for petroleum cracking, alkylation, hydrogenation and polymerization reactions, and lutetium can be used to manufacture certain special alloys, such as lutetium-aluminum alloy for neutron activation analysis. Lutetium nitride is a new type of material, which has high melting point, high hardness, high chemical stability, high thermal conductivity, good wear resistance and corrosion resistance, etc. These properties enable lutetium nitride to maintain stable hardness and strength under harsh conditions such as high temperature, high pressure and high speed, so that lutetium nitride has a wide application prospect in the manufacture of high-performance mechanical parts, cutting tools, drill bits and other precision components. In addition, lutetium nitride also has excellent properties such as high light transmittance and high electron mobility, so it also has a wide application in the fields of optics and electronics. Although the currently concerned "lutetium-hydrogen-nitrogen" ternary superconductor material has been proved to have no superconductivity even at 40 million atmospheres and a temperature as low as 2K (-271.15℃), it has directly promoted the research on the related physical properties of lutetium nitride, especially the research on the optical and electrical properties of lutetium nitride. Although lutetium nitride has shown excellent performance in some fields, the research on lutetium nitride still needs to be further deepened to solve the problems in the preparation process and performance optimization of lutetium nitride, and to expand the application field of lutetium nitride.

[0003] Due to the hard texture and high density of lutetium metal, it is difficult to directly nitride, so the production of lutetium nitride is difficult. At present, there are mainly two methods for preparing lutetium nitride: heat treatment method and physical vapor deposition method. The heat treatment method is to treat lutetium material at high temperature in a nitrogen atmosphere to form a lutetium nitride layer on the surface. This method is simple and easy to operate, but the thickness of the lutetium nitride layer prepared by this method is relatively thin, and the hardness is not high enough. In addition, direct nitriding will generate impurities, resulting in low product purity. The physical vapor deposition method is to place the metal lutetium target in a vacuum chamber, and through high-energy ion bombardment and nitrogen injection, a uniform lutetium nitride layer is formed on the surface. The lutetium nitride prepared by this method has high hardness and uniform thickness, but the equipment cost is high. SUMMARY

[0004] The purpose of the present application is to provide a high-crystallinity lutetium nitride powder and a preparation method thereof. The preparation method is simple, easy to break, low in operation cost, wide in process window, and suitable for large-scale industrial production; and the lutetium nitride powder obtained has high crystallinity.

[0005] The purpose of the present application is achieved in that:

[0006] The application discloses a preparation method of a high-crystallinity lutetium nitride powder.

[0007] (a) using a metal lutetium powder as a raw material, and pressing the lutetium powder into a powder cake under high pressure;

[0008] (b) placing the powder cake in a crucible and pre-treating the powder cake under high pressure in an NH3 environment for 3-5 hours, and then performing crushing in a planetary ball mill and sieving to obtain a sieved powder;

[0009] (c) heat-treating the sieved powder under a N2 environment at a high temperature of 1000-1400 DEG C for 4-8 hours, and then sieving to obtain the high-crystallinity lutetium nitride powder.

[0010] In the step (a), the metal lutetium powder cake is first vacuumized, and then pressed under a N2 environment; the high pressure used in the pressing is 300-400 MPa.

[0011] In the step (b), the pre-treatment temperature of the powder cake is 500-700 DEG C, and the heating rate is 20 DEG C / min; the pre-treatment pressure is 4-9 MPa of NH3 pressure.

[0012] In the step (b), the powder cake is crushed after the pre-treatment by filling N2 in a planetary ball mill.

[0013] In the step (b), the sieved powder is obtained by sieving the crushed powder cake using a 200-mesh sieve.

[0014] In the step (c), the sieved powder is heat-treated at a heating rate of 5 DEG C / min; the sintering is performed under normal pressure, and the N2 flow rate is 1-3 L / min.

[0015] In the step (c), the sieved powder is obtained by sieving the heat-treated powder using a 200-mesh sieve.

[0016] The high-crystallinity lutetium nitride powder prepared according to the above method has a crystallinity of greater than 99.9%.

[0017] In addition, the obtained high-crystallinity lutetium nitride powder is analyzed in terms of phase and crystallinity and characterized in terms of microscopic morphology by using X-ray diffraction (XRD) and a scanning electron microscope (SEM).

[0018] Compared with the prior art, the application has the following advantages:

[0019] Since the metal Lutetium is hard and dense, it is difficult to be directly nitrided. The application first vacuums the powder and makes Lutetium powder cake under high pressure in N2 environment to remove the oxygen attached to the surface of Lutetium powder particles, avoid the introduction of oxygen in the process of transferring to the sintering equipment, and further avoid the generation of impurities during sintering. Meanwhile, the high pressure can make the Lutetium powder particles deform and break. Then, the Lutetium powder is pretreated under high temperature, high pressure and NH3 atmosphere. The reaction between NH3 and Lutetium powder makes the Lutetium powder more brittle and finer, so as to change the hard texture of the Lutetium powder. Then, the Lutetium powder cake is broken by using planetary ball milling, so as to increase the specific surface area of the powder and prepare for the subsequent nitriding process. Finally, high-temperature heat treatment (i.e. high-temperature sintering) is carried out in N2 environment, and then the Lutetium nitride powder with high crystallinity is obtained.

[0020] The Lutetium nitride in the application has high crystallinity, and the preparation process is simple, easy to break, low in operation cost, wide in process window and suitable for large-scale industrial production. The prepared Lutetium nitride can be widely used in high-performance mechanical parts, cutters, drill bits and other precision parts, optics, electronics and other fields. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is the X-ray diffraction pattern of the Lutetium nitride powder prepared in Examples 1-4 and a standard sample.

[0022] Figure 2 is the scanning electron microscope image of the Lutetium nitride powder prepared in Example 1.

[0023] Figure 3 is the scanning electron microscope image of the Lutetium nitride powder prepared in Example 2. DETAILED DESCRIPTION

[0024] The following examples are used to further illustrate the application, but do not limit the application in any form.

[0025] Example 1

[0026] 1kg of metal Lutetium powder is weighed and pressed into a powder cake under 300MPa high pressure and N2 atmosphere. The powder cake is put into a crucible, and the sintering equipment is pressurized to 5MPa with NH3 at a rate of 20℃ / min to 500℃, pretreated for 5h, and then broken by planetary ball milling. Then, the sieved powder is put into the sintering equipment and heated to 1200℃ at a rate of 5℃ / min, and kept for 8h. The N2 flow rate is 3L / min. After sieving, the Lutetium nitride powder with high crystallinity is obtained.

[0027] The obtained Lutetium nitride powder is detected by XRD and SEM. The XRD pattern of the powder is as follows: Figure 1The XRD pattern of the prepared LuN powder is shown in Fig. 2. As can be seen from the figure, the prepared LuN powder is pure phase LuN, and the crystallinity of the powder is calculated by jade to be crystallinity = 99.99% compared with the XRD pattern of the standard sample (card No. PDF #15-0894). Figure 2 The SEM image of the powder is shown in Fig. 3. As can be seen from the figure, the particle size of the powder is 1-3 μm.

[0028] Example 2

[0029] 1 kg of metal Lu powder is weighed and pressed into a powder cake under a high pressure of 400 MPa and in a N2 atmosphere. The powder cake is put into a crucible, and the sintering equipment is charged with NH3 to 6 MPa, and heated to 600°C at a rate of 20°C / min, and pretreated for 5 h. After being discharged, planetary ball milling is performed to complete the crushing, and then the powder is sieved through a 200 mesh sieve. The sieved powder is put into the sintering equipment, and heated to 1300°C at a rate of 5°C / min, and kept for 8 h. The N2 flow rate is 3 L / min. After being discharged, the sieving is performed to obtain LuN powder with high crystallinity.

[0030] The XRD and SEM detection are performed on the prepared powder, and the crystallinity of the powder is calculated by jade to be crystallinity = 99.96%. The XRD pattern of the powder is shown in Fig. 4. Figure 1 The XRD pattern of the prepared LuN powder is shown in Fig. 2. As can be seen from the figure, the prepared LuN powder is pure phase LuN, and the crystallinity of the powder is calculated by jade to be crystallinity = 99.99% compared with the XRD pattern of the standard sample (card No. PDF #15-0894). Figure 3 The SEM image of the powder is shown in Fig. 3. As can be seen from the figure, the particle size of the powder is 1-3 μm.

[0031] Example 3

[0032] 1 kg of metal Lu powder is weighed and put into a crucible. The sintering equipment is charged with NH3 to 4 MPa, and heated to 500°C at a rate of 20°C / min, and pretreated for 5 h. After being discharged, planetary ball milling is performed to complete the crushing, and then the sieving is performed through a 200 mesh sieve to obtain sieved powder. The sieved powder is put into the sintering equipment, and heated to 1200°C at a rate of 5°C / min, and kept for 8 h. The N2 flow rate is 3 L / min. After being discharged, the sieving is performed to obtain LuN powder. The XRD pattern of the powder is shown in Fig. 5. Figure 1 The XRD pattern of the prepared LuN powder is shown in Fig. 2. As can be seen from the figure, the prepared LuN powder is pure phase LuN, and the crystallinity of the powder is calculated by jade to be crystallinity = 99.99% compared with the XRD pattern of the standard sample (card No. PDF #15-0894).

[0033] Example 4

[0034] 1 kg of lutetium metal powder was weighed and placed in a crucible. The crucible was then placed in a sintering apparatus, and the temperature was increased to 1200 °C at a rate of 5 °C / min and held for 8 hours. The N2 flow rate was 3 L / min. After removing the powder from the furnace, it was sieved to obtain lutetium nitride powder. The XRD pattern of the powder is shown below. Figure 1 As shown in Example 4, the results show that there are impurity peaks at multiple locations on the horizontal axis, such as 29°~32° / 40° / 43° / 57° / 61°. These impurity peaks belong to lutetium trioxide (Lu2O3) and lutetium element, respectively, indicating that pure phase LuN could not be generated.

[0035] Example 5

[0036] 1 kg of lutetium metal powder was weighed and pressed into a powder cake under a high pressure of 300 MPa and a nitrogen atmosphere. The powder cake was placed in a crucible and then placed in a sintering apparatus. The temperature was increased to 1200 °C at a rate of 5 °C / min and held for 8 hours. The nitrogen flow rate was 3 L / min. After being removed from the furnace, the powder cake was crushed. The results showed that only the outer layer of the high-pressure pressed powder cake was nitrided, while the interior remained metallic, indicating incomplete nitriding.

Claims

1. A method for preparing a high-crystallinity lutetium nitride powder, characterized by comprising: The method comprises the following steps: ​ (a) using metal Lutetium powder as raw material, the Lutetium powder is pressed into a powder cake under high pressure; (b) the powder cake is placed in a crucible, pretreated for 3-5 hours under high pressure in NH3 environment, after being taken out of the furnace, the crushing is completed by planetary ball milling and sieving to obtain sieved powder; (c) the sieved powder is heat treated for 4-8 hours under high temperature of 1000-1400℃ in N2 environment, after being taken out of the furnace, sieving is performed to obtain Lutetium nitride powder with high crystallinity; in step (a), the metal Lutetium powder cake is first vacuumized, then pressed under N2 environment, the high pressure used in the pressing is 300-400MPa; in step (b), the pretreatment temperature of the powder cake in the crucible is 500-700℃, the heating rate is 20℃ / min; the pretreatment pressure is 4-9MPa of NH3 filling pressure.

2. The method for preparing lutetium nitride powder with high crystallinity according to claim 1, characterized in that, in step (b), after the pretreatment, the powder cake is crushed by filling N2 in the planetary ball milling tank.

3. The method of claim 1, wherein the high crystallinity lutetium nitride powder is prepared by the steps of: preparing a mixture of lutetium oxide and carbon; and heating the mixture at a temperature of 1,000°C to 1,500°C for 1 to 10 hours in a nitrogen atmosphere. in step (b), after the pretreatment crushing, sieving is performed with a 200 mesh sieve to obtain sieved powder.

4. The method of claim 1, wherein the high crystallinity lutetium nitride powder is prepared by the steps of: preparing a mixture of lutetium oxide and carbon; and heating the mixture at a temperature of 1,000°C to 1,500°C for 1 to 10 hours in a nitrogen atmosphere. in step (c), the heating rate of the heat treatment of the sieved powder is 5℃ / min; normal pressure sintering, the N2 flow rate is 1-3L / min.

5. The method of claim 1, wherein the high crystallinity lutetium nitride powder is prepared by the steps of: preparing a mixture of lutetium oxide and carbon; and heating the mixture at a temperature of 1,000°C to 1,500°C for 1 to 10 hours in a nitrogen atmosphere. in step (c), after the heat treatment, sieving is performed with a 200 mesh sieve.

6. Lutetium nitride powder with high crystallinity prepared by the method according to any one of the above claims 1-5.

7. The high crystallinity lutetium nitride powder according to claim 6, characterized by, the crystallinity of the Lutetium nitride powder is >99.9%.

Images