A method for synthesizing metal nitride (oxide) by using low work function metal powder to enhance nitridation

Abstract

The present invention belongs to the field of material synthesis, and specifically relates to a method for synthesizing metal nitrides (oxides) by enhanced nitridation using low work function metal powders. The method comprises the following steps: (1) grinding and mixing low work function metal powders and metal oxides; (2) placing the mixed powders in a tube furnace for nitridation, introducing ammonia, heating the tube furnace to 600-850°C, the nitridation time is 1-10 hours, then naturally cooling to room temperature, and taking out the reaction product; (3) acid-washing the reaction product obtained in step (2), then filtering, washing with water, and drying to obtain metal nitrides (oxides). Compared with the traditional high-temperature ammonia gas flow nitridation method without adding metal powder, the present invention can synthesize metal nitrides (oxides) at a relatively low temperature and in a shorter time, and can synthesize metal nitrides (oxides) that cannot be synthesized by traditional nitridation methods.

Description

Technical Field

[0001] The invention belongs to the field of material synthesis, and in particular relates to a method for synthesizing metal nitride (oxide) by using low work function metal powder to enhance nitridation. Background Art

[0002] Metal nitrides (oxides) are widely used and can be used as ceramic materials, coating materials, catalytic materials, etc. Some of them have bright colors and can be used as dyes, and some metal nitrides (oxides) have excellent wide-spectrum absorption ability and have broad prospects in the study of photocatalysis (see reference: Coordination Chemistry Reviews 257 (2013) 1957-1969).

[0003] At present, the methods for synthesizing metal nitrides (oxides) are very limited. The mainstream method is to use ammonia flow to perform nitriding at high temperature to introduce nitrogen atoms into metal oxides. Because the covalent bond between metal atoms and oxygen atoms in most metal oxides is very strong, such as: ZrO2, SrTiO3, YTaO4, etc. The stronger the metal-oxygen bond, the longer the nitriding time required by the traditional high-temperature ammonia flow nitriding method (usually up to 20 to 50 hours), and the higher the nitriding temperature required (usually up to about 900 to 1200°C). For example: Even if SrTiO3 is nitrided for a long time at high temperature, the amount of nitrogen atoms doped into the SrTiO3 lattice is less than 0.5% (atomic ratio). In addition, there is a method that uses urea as a nitrogen source and performs a high-temperature reaction under a nitrogen flow, with a reaction temperature of up to 900°C. The amount of urea required for this method is relatively large, and it is easy to introduce impurity phases and carbon deposits (see literature: Inorg.Chem.2021,60,4852-4859). It can be seen that the development of a more efficient nitridation process is an important part of the field of metal nitride (oxide) synthesis, which has important scientific significance and practical value in terms of environment, economy, etc. Summary of the invention

[0004] In view of the limitations of existing nitridation methods, the present invention uses low work function metal powder to achieve enhanced nitridation of metal oxides, providing a new universal nitridation synthesis method with low reaction temperature, short reaction time, and applicable to the synthesis of many nitrides (oxides).

[0005] In order to achieve the above object, the technical solution of the present invention is as follows:

[0006] A method for synthesizing metal nitride (oxide) by nitriding low work function metal powder, the method comprising the following steps:

[0007] (1) grinding and mixing low work function metal powder and metal oxide;

[0008] (2) placing the mixed powder in a tube furnace for nitridation, introducing ammonia gas, raising the temperature of the tube furnace to 600-850° C., nitriding for 1-10 hours, then naturally cooling to room temperature, and taking out the reaction product;

[0009] (3) The reaction product obtained in step (2) is acid-washed, then filtered, washed with water, and dried to obtain a metal nitride (oxide).

[0010] In the above technical solution, preferably, the low work function metal is a metal having a work function value lower than 5 eV.

[0011] In the above technical solution, preferably, the low work function metal includes any one of Mg, Al, Zn and Zr.

[0012] In the above technical solution, preferably, the metal oxide includes any one of ZrO2, Ta2O5, HfO2, SrTiO3, SmTaO4, and Y2Zr2O7.

[0013] In the above technical solution, preferably, the mass ratio of the low work function metal powder to the metal oxide is 0.1 to 10:1.

[0014] In the above technical solution, preferably, in step (1), the low work function metal powder and the metal oxide are mixed mechanically by grinding in a mortar.

[0015] In the above technical solution, preferably, the mortar used to mix the low work function metal powder and the metal oxide is an agate mortar, a ceramic mortar, a glass mortar or a zirconia mortar.

[0016] In the above technical solution, preferably, in the step (2), the nitriding temperature is 600-800° C., and the nitriding time is 1-5 h.

[0017] In the above technical solution, preferably, the ammonia flow rate in step (2) is 50 to 5000 mL·g -1 ·min -1 .

[0018] In the above technical solution, preferably, in step (3), hydrochloric acid, sulfuric acid, nitric acid or perchloric acid with a concentration of 0.1 to 5 mol / L is used for pickling.

[0019] The beneficial effects of the present invention are:

[0020] The nitriding method of the present invention is simple, has strong universality and is applicable. Compared with the prior art, the metal powder assisted nitriding method of the present invention has the following advantages and characteristics:

[0021] 1. The method is more applicable and is suitable for the nitridation process of many difficult-to-nitridate metal oxides, such as SrTiO3 and Y2Zr2O7;

[0022] 2. The nitriding temperature is lower, 200-300℃ lower than the traditional nitriding method;

[0023] 3. The nitriding time is shorter and the energy consumption is lower. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a scanning electron microscope image of the nitrogen oxide Zr2ON2 synthesized in Example 1;

[0025] Figure 2 The XRD spectrum of the nitrogen oxide Zr2ON2 synthesized in Example 1;

[0026] Figure 3 The UV-Vis absorption spectrum of the nitrogen oxide Zr2ON2 synthesized in Example 1;

[0027] Figure 4 XRD spectrum of Ta3N5 synthesized in Example 2;

[0028] Figure 5 This is a scanning electron microscope image of Ta3N5 synthesized in Example 2;

[0029] Figure 6 XRD spectrum of the nitrogen oxide Hf2ON2 synthesized in Example 3;

[0030] Figure 7 The nitrogen oxide SrTiO synthesized in Example 4 3-x N y XRD spectrum of

[0031] Figure 8 The SrTiO synthesized in Example 4 3-x N y UV-Vis absorption spectrum of

[0032] Fig. 9 XRD spectrum of SmTaON2 synthesized in Example 5;

[0033] Fig.10 This is the UV-Vis absorption spectrum of SmTaON2 synthesized in Example 5;

[0034] Fig.11 The nitrogen-doped nitrogen oxide Y2Zr2O synthesized in Example 6 7-x N y UV-Vis absorption spectrum. DETAILED DESCRIPTION

[0035] The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0036] Example 1

[0037] 1) Mix Mg powder and ZrO2 (4 times the mass of Mg powder) and grind manually in an agate mortar for 30 min;

[0038] 2) Place the mixed powder in a corundum boat, place the boat in the central temperature control zone of a tube furnace, and use an ammonia gas flow rate of 5000 mL g -1 ·min -1 , at 1℃·min -1 The temperature was raised to 750°C and the nitridation reaction was carried out for 3 hours;

[0039] 3) Take out the nitrided powder, stir and wash it with 5 mol / L nitric acid, then wash it with water until it is neutral, and dry it to obtain Zr2ON2 solid powder.

[0040] Figure 1 This is a scanning electron microscope image of the nitrogen oxide Zr2ON2 synthesized in Example 1. Figure 1 It can be seen that it presents the stacking morphology of nanoparticles; Figure 2 The XRD spectrum of the nitrogen oxide Zr2ON2 synthesized in Example 1 completely corresponds to the diffraction peak of the Zr2ON2 standard card (PDF#89-8344), proving that pure phase Zr2ON2 is synthesized; Figure 3 The UV-Vis absorption spectrum of the nitrogen oxide Zr2ON2 synthesized in Example 1 has an absorption edge extending to 500 nm and appears bright yellow.

[0041] Example 2

[0042] 1) Mix Al powder and Ta2O5 twice the mass of Al powder and grind manually in a ceramic mortar for 10 minutes;

[0043] 2) Place the mixed powder in a corundum boat, place the boat in the central temperature control zone of a tube furnace, and use an ammonia gas flow rate of 2000 mL g -1 ·min -1 , at 1℃·min -1 Raise the temperature to 800°C and carry out nitridation reaction for 5 hours;

[0044] 3) The nitrided powder is taken out, washed with 2 mol / L hydrochloric acid by stirring, then washed with water until neutral, and dried to obtain Ta3N5 solid powder.

[0045] Figure 4The XRD spectrum of Ta3N5 synthesized in Example 2 is completely consistent with the diffraction peak of the standard card (PDF#89-5200), which proves that the method for synthesizing Ta3N5 in Example 2 is effective;

[0046] Figure 5 This is a scanning electron microscope image of Ta3N5 synthesized in Example 2, which exhibits a nanoparticle morphology with a smooth surface.

[0047] Example 3

[0048] 1) Mix Zn powder and HfO2 with half the mass of Zn powder and grind manually in a zirconia mortar for 20 min;

[0049] 2) Place the mixed powder in a corundum boat, place the boat in the central temperature control zone of a tube furnace, and use an ammonia gas flow rate of 50 mL g -1 ·min -1 , at 2℃·min -1 The temperature was raised to 850°C and the nitridation reaction was carried out for 3 hours;

[0050] 3) Take out the powder sample after nitridation, stir and wash it with 0.5 mol / L perchloric acid, then wash it with water until it is neutral, and dry it to obtain Hf2ON2 solid powder.

[0051] Figure 6 : This is the XRD spectrum of the nitrogen oxide Hf2ON2 synthesized according to Example 3, which completely corresponds to the diffraction peak of the Hf2ON2 standard card (PDF#89-8346), proving that the rarely reported Hf2ON2 was synthesized according to Example 3.

[0052] Example 4

[0053] 1) Mix Mg powder and SrTiO3 twice the mass of Mg powder and grind manually in a glass mortar for 20 min;

[0054] 2) Place the mixed powder in a corundum boat, place the boat in the central temperature control zone of a tube furnace, and use an ammonia gas flow rate of 200 mL g -1 ·min -1 , at 10℃·min -1 Raise the temperature to 750°C and carry out nitridation reaction for 1 hour;

[0055] 3) Take out the nitrided powder, stir and wash it with 0.1 mol / L sulfuric acid, then wash it with water until it is neutral, and dry it to obtain SrTiO with high nitrogen content. 3-x N y Yellow solid powder.

[0056] Figure 7 The nitrogen oxide SrTiO synthesized in Example 4 3-x Ny The XRD spectrum of SrTiO3 is completely consistent with the diffraction peak of the SrTiO3 standard card (PDF#79-0174), indicating that the nitrogen oxide SrTiO 3-x N y The perovskite structure of the oxide precursor is still maintained; Figure 8 The SrTiO synthesized in Example 4 3-x N y The UV-Vis absorption spectrum of FIG. 1 shows that the absorption edge extends to 550 nm, which proves that the method of the embodiment effectively doped SrTiO 3 with nitrogen.

[0057] Example 5

[0058] 1) Zr powder and SmTaO4 with the same mass as Zr powder were mixed and manually ground in an agate mortar for 20 min;

[0059] 2) Place the mixed powder in a corundum boat, place the boat in the central temperature control zone of a tube furnace, and use an ammonia gas flow rate of 500 mL g -1 ·min -1 , at 5℃·min -1 The temperature was raised to 800°C and the nitridation reaction was carried out for 4 hours;

[0060] 3) The nitrided powder is taken out, washed with 0.2 mol / L hydrochloric acid by stirring, then washed with water until neutral, and dried to obtain a red SmTaON2 solid powder with a perovskite structure.

[0061] Fig. 9 The XRD spectrum of SmTaON2 synthesized in Example 5 shows that after nitridation, SmTaO4 is transformed into SmTaON2, and the nitrogen oxide SmTaON2 (PDF#47-1365) is effectively synthesized; Fig.10 This is the UV-Vis absorption spectrum of SmTaON2 synthesized in Example 5, and its absorption edge extends to 600nm, showing an orange-red color.

[0062] Example 6

[0063] 1) Mix a certain mass of Mg powder and half the mass of Y2Zr2O7 and grind them manually in a ceramic mortar for 20 min;

[0064] 2) Place the mixed powder in a corundum boat, place the boat in the central temperature control zone of a tube furnace, and use an ammonia gas flow rate of 1000 mL g -1 ·min -1 , at 2℃·min -1 Raise the temperature to 600°C and carry out nitridation reaction for 10 hours;

[0065] 3) Take out the nitrided powder, stir and wash it with 1 mol / L hydrochloric acid, then wash it with water until it is neutral, and dry it to obtain yellow Y2Zr2O with perovskite structure. 7-x N y Solid powder.

[0066] Fig.11 The nitrogen-doped nitrogen oxide Y2Zr2O synthesized in Example 6 7-x N y The UV-Vis absorption spectrum shows that compared with the absorption edge of 250nm of its oxide precursor Y2Zr2O7, its absorption edge extends to about 500nm, proving that Y2Zr2O7 is effectively doped according to the method of Example 6.

[0067] The above embodiments are only preferred embodiments of the present invention and are not intended to limit the implementation methods. The protection scope of the present invention shall be subject to the scope defined in the claims. Other different forms of changes or modifications may be made based on the above description. Obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for synthesizing metal nitrides or oxynitrides by nitriding low work function metal powders, characterized in that: The method comprises the following steps: (1) grinding and mixing low work function metal powder and metal oxide; (2) placing the mixed powder in a tube furnace for nitridation, introducing ammonia gas, raising the temperature of the tube furnace to 600-850° C., nitriding for 1-10 hours, then naturally cooling to room temperature, and taking out the reaction product; (3) acid-washing the reaction product obtained in step (2), followed by filtering, washing with water, and drying to obtain a metal nitride or nitrogen oxide; The low work function metal is selected from any one of Mg, Al, Zn and Zr; The metal oxide is selected from any one of ZrO2, Ta2O5, HfO2, SrTiO3, SmTaO4, and Y2Zr2O7.

2. The method according to claim 1, characterized in that The low work function metal is a metal with a work function value lower than 5 eV.

3. The method according to claim 1, characterized in that The mixing mass ratio of the low work function metal powder to the metal oxide is 0.1-10.

4. The method according to claim 1, characterized in that: In the step (1), the low work function metal powder and the metal oxide are mixed mechanically by grinding in a mortar.

5. The method according to claim 4, characterized in that The mortar used for mixing the low work function metal powder and the metal oxide is an agate mortar, a ceramic mortar, a glass mortar or a zirconia mortar.

6. The method according to claim 1, characterized in that In the step (2), the nitriding temperature is 600-800° C., and the nitriding time is 1-5 hours.

7. The method according to claim 1, characterized in that The ammonia flow rate in step (2) is 50 to 5000 mL·g -1 ·min -1 .

8. The method according to claim 1, characterized in that In the step (3), the acid washing is performed using hydrochloric acid, sulfuric acid, nitric acid or perchloric acid with a concentration of 0.1 to 5 mol / L.

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