Room-temperature ferromagnetic montmorillonite with layered structure and preparation method of room-temperature ferromagnetic montmorillonite

Abstract

The invention relates to room-temperature ferromagnetic montmorillonite with a layered structure and a preparation method thereof, the room-temperature ferromagnetic montmorillonite has oxygen vacancies and room-temperature ferromagnetism, and the oxygen vacancy concentration and the ferromagnetism are adjustable. The room-temperature ferromagnetic montmorillonite is prepared by adopting an extremely simple method, has adjustable ferromagnetism, and has industrial application prospects in the field of spinning electronic devices.

Description

Technical Field

[0001] The invention belongs to the technical field of inorganic chemistry, and in particular relates to a room temperature ferromagnetic montmorillonite with a layered structure and a preparation method thereof. Background Art

[0002] Traditional electronic devices control carriers based on the charge properties of electrons to process and transmit information, and then use the spin properties of electrons in magnetic materials to store information.

[0003] Spin field effect transistors use the spin properties of electrons in magnetic materials to make them move in a directional manner to construct spin transistors. Compared with traditional field effect transistors, they require less energy and are faster. Most semiconductor materials do not have ferromagnetism and are difficult to use to prepare spin field effect transistors. The Curie temperature of existing ferromagnetic materials is usually less than 200K, which is far below room temperature and is difficult to meet the temperature requirements of practical applications.

[0004] Materials based on s-block and p-block elements have the potential to develop ferromagnetism at relatively high temperatures due to their high spin wave stiffness. Montmorillonite (MMT), an aluminosilicate material composed of Al, Si and O elements, is widely used in industry due to its low price and stable properties. Using montmorillonite to prepare room-temperature ferromagnetic materials can greatly reduce costs, but there are still certain difficulties in preparing ferromagnetic montmorillonite and making its Curie temperature at room temperature. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a layered room-temperature ferromagnetic montmorillonite and a preparation method thereof in view of the deficiencies in the prior art. The room-temperature ferromagnetic montmorillonite can be used in spin electronic devices such as giant magnetoresistance sensors, spin field effect transistors, etc., and the preparation method is simple and efficient. Oxygen vacancies are introduced into the montmorillonite under an inert atmosphere to induce the montmorillonite to produce room-temperature ferromagnetism.

[0006] The invention provides a room-temperature ferromagnetic montmorillonite with a layered structure. The room-temperature ferromagnetic montmorillonite has oxygen vacancies and room-temperature ferromagnetism, and the oxygen vacancy concentration and the ferromagnetism are adjustable.

[0007] The present invention also provides a method for preparing the above-mentioned room temperature ferromagnetic montmorillonite with a layered structure, and the specific steps are as follows:

[0008] 1) Fully mixing montmorillonite with acid, and then centrifuging to separate solid and liquid to obtain acidic montmorillonite;

[0009] 2) The acidic montmorillonite obtained in step 1) is subjected to heat treatment to obtain a room temperature ferromagnetic montmorillonite with a layered structure.

[0010] According to the above scheme, the acid in step 1) is one or a mixture of formic acid, acetic acid, propionic acid, oxalic acid, and malonic acid, preferably acetic acid.

[0011] According to the above scheme, the mass volume ratio of montmorillonite to acid in step 1) is 1 g / 10-50 mL, and the mixing time of montmorillonite and acid is 10-60 min.

[0012] According to the above scheme, the centrifugal treatment process conditions in step 1) are: centrifugal speed 1500-10000 rpm, preferably 2000-6000 rpm, and centrifugal time 5-15 min.

[0013] According to the above scheme, the heat treatment process conditions in step 2) are: starting from room temperature under an inert atmosphere, at 5 to

[0014] The temperature is raised to 400-600°C at a heating rate of 10°C / min and kept at this temperature for 0.5-10 hours, preferably for 3-7 hours.

[0015] The present invention also includes the use of the above-mentioned room temperature ferromagnetic montmorillonite with a layered structure in the preparation of spin electronic devices (such as giant magnetoresistance sensors, spin field effect transistors, etc.).

[0016] The present invention mixes montmorillonite with acid and uses H + Replaced Na in montmorillonite + ,Ca 2+ The montmorillonite and the acid are separated by centrifugation to obtain acidic montmorillonite, and then the acidic montmorillonite is heat-treated in an inert atmosphere to break the Al-O-Si bond in the montmorillonite to generate oxygen vacancies. The generation of oxygen vacancies affects the electronic structure of the montmorillonite, causing the energy of the p orbital to change and induce spin coupling, thereby generating room temperature ferromagnetism. The oxygen vacancy concentration and ferromagnetism in montmorillonite can be controlled by adjusting the heat treatment temperature.

[0017] The beneficial effects of the present invention are as follows: 1) The montmorillonite provided by the present invention has a layered structure and room temperature ferromagnetism, and the ferromagnetism is adjustable, and has industrial application prospects in the field of spin electronic devices. 2) The preparation method provided by the present invention has the characteristics of low raw material price, environmental friendliness and simple operation, and is suitable for large-scale preparation and production. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a SEM image of the product prepared by heat treatment at 550°C in Example 1;

[0019] Figure 2 This is the electron paramagnetic resonance (EPR) test graph of the raw material montmorillonite used in Example 1 and the product obtained by heat treatment at 550° C. at room temperature;

[0020] Figure 3 The XRD patterns of the raw material montmorillonite used in Example 1 and the products obtained at different heat treatment temperatures;

[0021] Figure 4 TEM image of the product prepared by heat treatment at 550°C in Example 1;

[0022] Figure 5 The XPS spectra of the raw material montmorillonite used in Example 1 and the product obtained by heat treatment at 550°C;

[0023] Figure 6 XPS O1s fine spectra of the raw material montmorillonite used in Example 1 and the product obtained by heat treatment at 550°C;

[0024] Figure 7 The hysteresis loop diagram of the raw material montmorillonite used in Example 1 and the product obtained by heat treatment at 550°C measured at room temperature (300K);

[0025] Figure 8 The electron paramagnetic resonance test graphs of the raw material montmorillonite used in Example 1 and the products obtained by heat treatment at different temperatures at room temperature;

[0026] Fig. 9 The raw material montmorillonite used in Example 1 and the products obtained by heat treatment at different temperatures are at room temperature (300K)

[0027] The hysteresis loop diagram of the measurement below;

[0028] Fig.10 The electron paramagnetic resonance (EPR) test graphs of the product obtained in Example 2 and the product obtained by heat treatment at 550° C. in Example 1 at room temperature. DETAILED DESCRIPTION

[0029] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below using embodiments in conjunction with the accompanying drawings.

[0030] Example 1

[0031] A series of layered room-temperature ferromagnetic montmorillonite were prepared by the following method. The specific steps are as follows: 7 portions of montmorillonite (K-10 montmorillonite) were prepared, each portion was 1 g, each portion was added to 30 mL of acetic acid, heated to 80°C in a water bath and stirred for 30 min, then placed in a centrifuge and centrifuged at 3000 rpm for 10 min to separate the solid and liquid to obtain a paste-like acidic montmorillonite, then, the temperature was increased from room temperature to a heat treatment temperature (the heat treatment temperatures were 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, and 600°C, respectively) under an inert atmosphere, kept warm for 3 hours, and naturally cooled to obtain 7 products.

[0032] Figure 1 The product prepared by heat treatment at 550°C in this embodiment (denoted as O v -MMT-550°C) from the SEM image, it can be seen that the product prepared in this embodiment is a layered structure formed by stacking multiple layers of nanosheets.

[0033] Figure 2 The electron paramagnetic resonance (EPR) test diagram of the raw material montmorillonite (MMT) used in this embodiment and the product obtained by heat treatment at 550°C at room temperature. It can be seen that the product obtained by heat treatment at 550°C in this embodiment has a g

[0034] A single peak appeared at the position of =1.99, proving the generation of oxygen vacancies.

[0035] Figure 3 The XRD diagrams of the raw material montmorillonite used in this embodiment and the products obtained at different heat treatment temperatures. It can be seen from the figure that the XRD peaks of the heat-treated product corresponding to the montmorillonite (002) and (006) crystal planes at 2θ=9.18° and 28.18° relative to the raw material montmorillonite are shifted to smaller angles, indicating that the interplanar spacing of the montmorillonite increases after heat treatment.

[0036] Figure 4 The product prepared by heat treatment at 550°C in this embodiment (denoted as O v -MMT-550℃) TEM image shows that the product is composed of multiple layers of nanosheets, with about 5 layers, a thickness of about 5nm, and a spacing of 1nm between each layer. Figure 1 It can be seen that the montmorillonite with oxygen vacancies prepared in this example has a layered structure.

[0037] Figure 5 The raw material montmorillonite (MMT) used in this example is the product obtained by heat treatment at 550°C (denoted as O in the figure). v -MMT) XPS test chart, Figure 6 This is the O1s fine spectrum of XPS. It can be seen from the figure that, compared with the raw material montmorillonite, the product obtained by heat treatment at 550°C simultaneously shows the peak of oxygen adsorption by Al oxygen vacancies and the peak of oxygen adsorption by Si oxygen vacancies, further proving that montmorillonite with oxygen vacancies has been prepared.

[0038] Figure 7 The raw material montmorillonite (MMT) used in this example is the product obtained by heat treatment at 550°C (denoted as O in the figure). v -MMT) room temperature MH curve, the MMT test graph is a straight line, while O v -MMT exhibits a hysteresis loop, proving that it has room temperature ferromagnetism. Figure 2It is confirmed that the montmorillonite containing oxygen vacancies prepared in this example has room temperature ferromagnetism.

[0039] Figure 8 The electron paramagnetic resonance test diagrams of the raw material montmorillonite (MMT) used in this embodiment and the products obtained by heat treatment at different temperatures at room temperature show that, in the range of 400-600°C, with the increase of heat treatment temperature, the oxygen vacancy concentration in the sample gradually increases, reaches the highest at 550°C, and then the oxygen vacancy concentration decreases.

[0040] Fig. 9 The room temperature MH curves of the raw material montmorillonite (MMT) used in this example and the products obtained by heat treatment at different temperatures show that within the range of 400-600°C, the ferromagnetism of the sample gradually increases with the increase of the heat treatment temperature, reaching the highest at 550°C, and then the ferromagnetism decreases. As the temperature increases from 400°C to 550°C, the saturation magnetization of the product increases from 0.004emu / g to 0.067emu / g, the residual magnetization increases from 0.001emu / g to 0.020emu / g, and the coercive force increases from 165mT to 337mT. When the temperature continues to rise to 600°C, the saturation magnetization decreases to 0.056emu / g, the residual magnetization decreases to 0.019emu / g, and the coercive force decreases to 262mT. Figure 8 This shows that the oxygen vacancy concentration and thus the ferromagnetism of the product can be controlled by adjusting the heat treatment temperature.

[0041] Example 2

[0042] A room temperature ferromagnetic montmorillonite with a layered structure has the following specific steps for its preparation: 1 g of montmorillonite is added to 30 mL of formic acid, heated to 80°C in a water bath and stirred for 30 minutes, then placed in a centrifuge and centrifuged at a speed of 3000 rpm for 10 minutes to separate the solid and liquid to obtain a paste-like acidic montmorillonite, then heated from room temperature to 550°C at a heating rate of 5°C / min in an inert atmosphere, kept warm for 3 hours, and naturally cooled to obtain the product.

[0043] Fig.10 This is the electron paramagnetic resonance (EPR) test diagram of the product obtained in this embodiment and the product obtained by heat treatment at 550°C in Example 1 at room temperature. By comparison, it can be seen that the EPR intensity of the product obtained by formic acid treatment is reduced compared with the product obtained by heat treatment at the same temperature as Example 1, indicating that its oxygen vacancy concentration is low.

Claims

1. A room temperature ferromagnetic montmorillonite with a layered structure, characterized in that: The room-temperature ferromagnetic montmorillonite has oxygen vacancies and room-temperature ferromagnetism, and the oxygen vacancy concentration and the ferromagnetism are adjustable.

2. The method for preparing the room temperature ferromagnetic montmorillonite with a layered structure according to claim 1, characterized in that: The specific steps are as follows: 1) Fully mixing montmorillonite with acid, and then centrifuging to separate solid and liquid to obtain acidic montmorillonite; 2) The acidic montmorillonite obtained in step 1) is subjected to heat treatment to obtain a room temperature ferromagnetic montmorillonite with a layered structure.

3. The method for preparing the room temperature ferromagnetic montmorillonite with a layered structure according to claim 2, characterized in that: Step 1) The acid is one or a mixture of formic acid, acetic acid, propionic acid, oxalic acid and malonic acid.

4. The method for preparing the room temperature ferromagnetic montmorillonite with a layered structure according to claim 2, characterized in that: Step 1) The mass volume ratio of the montmorillonite to the acid is 1 g / 10-50 mL, and the mixing time of the montmorillonite and the acid is 10-60 min.

5. The method for preparing the room temperature ferromagnetic montmorillonite with a layered structure according to claim 2, characterized in that: Step 1) The centrifugal treatment process conditions are: centrifugal speed 1500-10000 rpm, centrifugal time 5-15 min.

6. The method for preparing the room temperature ferromagnetic montmorillonite with a layered structure according to claim 2, characterized in that: Step 2) The heat treatment process conditions are: starting from room temperature in an inert atmosphere, heating to 400-600° C. at a heating rate of 5-10° C. / min, and keeping the temperature for 0.5-10 hours.

7. Use of the room temperature ferromagnetic montmorillonite with a layered structure as claimed in claim 1 in the preparation of spin electronic devices.

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