CN1327046C - Monocrystalline Si3N4 nanometer belt and micro belt preparation method - Google Patents

Abstract

The present invention relates to a preparation method for single-crystal Si3N4 nanometer strips and single-crystal Si3N4 micron strips, which belongs to the technical field of material preparation. The present invention uses an organic precursor to synthesize the single-crystal Si3N4 nanometer strips and the single-crystal Si3N4 micron strips in a thermolysis mode; the present invention comprises the steps: 1, low-temperature crosslinking solidification: initial raw material is polysiloxane and is crosslinked and solidified under the preserved temperature of 240 to 290 DEG C in nitrogen or ammonia, and semitransparent SiCN solid in an amorphous state is obtained; 2, high-energy ball milling pulverization: semitransparent SiCN solid is milled in a high-energy ball mill and simultaneously a catalyst which is any one kind of FeCl2, Al, Cu, Ni and Fe and has 1 to 5 wt% using amount is introduced in the semi-transparent SiCN solid; 3, high-temperature pyrolysis: the high-temperature pyrolysis is carried out to mixtures after the high-energy ball milling, and the temperature is preserved under the pyrolysis temperature of 1250 to 1550 DEG C. The method has the advantages of simple technique, strong maneuverability and high synthesis product purity; the present invention can prepare lower-dimensional nanometer material such as nanometer wires, nanometer belts, nanometer rods, etc. with different patterns by simply controlling a plurality of key process parameters.

Description

Preparation method of single crystal Si3N4 nanoribbon and microribbon

technical field

The invention relates to a method for preparing single crystal Si ₃ N ₄ nano-belts and micro-belts, belonging to the technical field of material preparation.

Background technique

Nano ribbon material is a new type of functional material. Recently, represented by Professor Wang Zhonglin from the Georgia Institute of Technology in the United States, the nanoribbon structures of a series of broadband semiconductor systems such as zinc oxide, tin oxide, indium oxide, cadmium oxide, and gallium oxide were successfully synthesized by high-temperature solid gas phase method. These banded structures have high purity, high output, perfect structure, clean surface, and no internal defects, dislocations and stacking faults. They are an ideal single crystal linear sheet structure. Compared with carbon nanotubes and other nanowire structures, nanobelts are the only quasi-one-dimensional ribbon structure with controllable structure and no defects found so far, and have more unique and superior structures and physical properties than carbon nanotubes. . Carbon nanotubes are hard and highly conductive, characteristics that made them the darlings of nanoscience research in the 1990s. But carbon nanotubes suffer from defects when mass-produced. Electronic components with defective materials may experience an abnormal increase in temperature when current is passed through them. However, the synthesized semiconductor oxide nanoribbons do not have the stability problem of carbon nanotubes. At the same time, the purity of these ribbon-like structure materials can be as high as 95%, compared with that of carbon nanotubes, which is only about 70%. These advantages of nanoribbon may make it be put into industrial production earlier.

Low-dimensional Si ₃ N ₄ materials have high strength, light weight, good thermal shock and oxidation resistance, so they are widely used in many industrial fields. At the same time, Si ₃ N ₄ is also a semiconductor with a wide energy band (5.3ev). Its energy band can be lowered by means of doping to adjust its electrical and optical properties, so that it can be used in high temperature and high radiation environments. nanoelectronic devices. So far, according to the latest literature reports, only Japan's Bando et al. have synthesized single crystal Si ₃ N ₄ nanoribbons and microribbons by the high-temperature solid gas phase method, and there has been no report in China.

Contents of the invention

The object of the present invention is to propose a kind of equipment and synthesis process are simple, product yield is high, purity is high, and has good reproducibility to prepare single-crystal Si ₃ N ₄ nano-belts and micro-belts by pyrolysis of organic precursors Methods. The growth mechanism of nanoribbons and microribbons prepared by this method is different from the gas-solid (Vapor-Solid: VS) growth mechanism of Si ₃ N ₄ nanoribbons that have been reported. It is solid-liquid-gas-solid (Solid-Liquid-Gas-Solid: LSGS) mechanism. This mechanism is very beneficial to the doping of low-dimensional nanomaterials, so as to adjust their electrical and optical properties, and to prepare nanoelectronic devices that can be used in high temperature and high radiation environments.

The method for preparing single-crystal Si ₃ N ₄ nano-belts and micro-belts proposed by the present invention is characterized in that: the method uses an organic precursor to pyrolyze and synthesize single-crystal Si ₃ N ₄ nano-belts and micro-belts, including the following steps:

(1) Low-temperature cross-linking and curing: the initial raw material is polysilazane, which is kept in nitrogen or ammonia at 240-290°C for 0.4-4 hours for cross-linking and curing to obtain a translucent amorphous SiCN solid;

(2) High-energy ball milling: put the translucent SiCN solid into a nylon resin ball mill tank, perform dry ball milling in a high-energy ball mill, and introduce a catalyst while ball milling, so that the amorphous SiCN powder and the catalyst are evenly mixed;

(3) High-temperature pyrolysis: The mixture after high-energy ball milling is subjected to high-temperature pyrolysis, and kept at a pyrolysis temperature of 1250-1550°C for 1-8 hours to obtain low-dimensional nanomaterials with different shapes and chemical compositions. The protective atmosphere is _N2 gas or ammonia gas.

In the above preparation method, the catalyst in step 2 is any one of FeCl ₂ , Al, Cu, Ni, Fe.

In the above preparation method, the amount of catalyst used in the step 2 is 1-5wt%.

The present invention has the following advantages:

1) The equipment is simple and the cost is low;

2) The synthesis process is simple and highly controllable. Single crystal Si ₃ N ₄ nanoribbons and microribbons can be obtained by controlling some key process parameters in the synthesis process, and the process has high repeatability;

3) The synthetic product has high purity, and the synthesized ribbon structure has a smooth surface and no pollution;

4) The method for preparing single crystal nanobelts and microbelts of the present invention has very high flexibility in technology, and single crystal nanobelts of different chemical compositions can be obtained by regulating the chemical composition of the organic precursor at the molecular level;

5) The method for preparing single crystal nanobelts and microribbons of the present invention is very beneficial to doping the nanobelts, which is very beneficial for regulating the optical, electrical, thermal, magnetic and other properties of the nanobelts, and is a device for nanobelts provides the basis.

6) The method for preparing nanomaterials in the prior art can only synthesize low-dimensional nanomaterials of a single shape, while the method for preparing nanomaterials in the present invention can prepare low-dimensional nanomaterials of different shapes by simply controlling several key process parameters, such as nanowires, nanoribbons, and nanorods.

Description of drawings

Figure 1 SEM image of single crystal Si ₃ N ₄ nanoribbons synthesized from Polyureasilazane, catalyst FeCl ₂ , 1350°C pyrolysis temperature for 2 hours

Figure 2. The raw material is Polyureasilazane, the catalyst is Al, and the SEM image of the single crystal Si ₃ N ₄ micron band synthesized at 1450°C for 4 hours

Figure 3 SEM image of Al-doped single crystal Si ₃ N ₄ nanobelts synthesized from Polyureasilazane and Al[OCH(CH ₃ ) ₂ ] ₃ , catalyst FeCl ₂ at 1450°C for 2 hours

Figure 4. The raw material is Polysilazane, the catalyst is Fe, and the SEM image of single crystal Si ₃ N ₄ nanoribbons synthesized at 1450°C for 2 hours

Detailed ways

Below in conjunction with embodiment technical scheme of the present invention is described further:

Example 1

The initial raw material is liquid polyureasilazane (Polyureasilazane), which is kept at 260°C for 0.5 hours for cross-linking and solidification, and the protective atmosphere is 0.1MPa N ₂ gas to obtain a translucent amorphous SiCN solid. Put the translucent SiCN solid into a nylon resin ball mill tank and carry out dry ball milling in a high-energy ball mill. The abrasive material is Si ₃ N ₄ balls, and the ball milling time is 12 hours. While ball milling, 3wt% _FeCl2 powder was introduced as a catalyst, so that the amorphous SiCN powder was mixed with the catalyst evenly. Then 2 g of the mixture after high-energy ball milling was put into an alumina ceramic crucible for high-temperature pyrolysis in a tube furnace, and Si ₃ N ₄ single-crystal nanowires were synthesized at a pyrolysis temperature of 1350° C. for 2 hours. The protective atmosphere is 0.1MPa flowing _N2 gas, and the gas flow rate is 200ml/min. The synthesized Si ₃ N ₄ single crystal nanobelts are shown in Fig. 1 . The thickness and width of a single single crystal nanobelt are uniform, the average thickness is 20-40nm, the width is 400-600nm, and the length can reach several mm. The size of the nanowires is uniform, the surface is smooth, and there is no pollution.

Example 2

The initial raw material is liquid polyureasilazane (Polyureasilazane), which is kept at 260°C for 1 hour for cross-linking and solidification, and the protective atmosphere is 0.1MPa N ₂ gas to obtain a translucent amorphous SiCN solid. Put the translucent SiCN solid into a nylon resin ball mill tank and carry out dry ball milling in a high-energy ball mill. The abrasive material is Si ₃ N ₄ balls, and the ball milling time is 10 hours. While ball milling, 4.5wt% Al powder was introduced as a catalyst, so that the amorphous SiCN powder and the catalyst were evenly mixed. Then, 3 g of the mixture after high-energy ball milling was loaded into an alumina ceramic crucible for high-temperature pyrolysis in a tube furnace, and the Si ₃ N ₄ single crystal microribbons were synthesized at a pyrolysis temperature of 1450°C for 4 hours. The protective atmosphere is 0.1MPa flowing _N2 gas, and the gas flow rate is 200ml/min. The synthesized Si ₃ N ₄ single crystal microribbons are shown in Fig. 2 . The width and thickness of the single crystal microribbon are uniform, the thickness is about 200nm, the width can reach 6μm, and the length can reach several mm. The surface of the microribbon is smooth and free from pollution.

Example 3

Two kinds of polysilazanes (Polyureasilazane and Al[OCH(CH ₃ ) ₂ ] ₃ ) were used as the initial raw materials, the _latter being a solid powder. ₂ ] ₃ ) Mix evenly in a nylon resin ball mill tank at a ratio of 4:1, then heat at 270°C for 0.5 hours for cross-linking and solidification, and the protective atmosphere is 0.1MPa _N2 gas to obtain amorphous solid particles containing Al . The solid particles were put into a nylon resin ball mill tank and carried out dry ball milling in a high-energy ball mill. Si ₃ N ₄ balls were used as the abrasive, and the ball milling time was 13 hours. While ball milling, 3wt% Ni was introduced as a catalyst, so that the amorphous powder and the catalyst were evenly mixed. Then take 2 g of the mixture after high-energy ball milling and put it into an alumina ceramic crucible, carry out high-temperature pyrolysis in a tube furnace, and keep it at 1450°C for 2 hours to synthesize Si ₃ N ₄ single-crystal nanometers with Al doping. bring. The protective atmosphere is 0.1MPa flowing _N2 gas, and the gas flow rate is 200ml/min. The synthesized Si ₃ N ₄ single crystal nanobelts are shown in Fig. 3 . The thickness and width of the single single crystal ribbon structure are uniform, the thickness is about 80nm, and the surface of the micrometer ribbon is smooth and free of pollution.

Example 4

A liquid polysilazane (Polysilazane) was used as the initial raw material, and it was kept at 280°C for 0.4 hours for cross-linking and solidification, and the protective atmosphere was N ₂ gas of 0.1MPa to obtain a translucent amorphous SiCN solid. Put the translucent SiCN solid into a nylon resin ball mill tank and carry out dry ball milling in a high-energy ball mill. The abrasive material is Si ₃ N ₄ balls, and the ball milling time is 13 hours. 1wt% Fe was introduced as a catalyst during ball milling, so that the amorphous SiCN powder and the catalyst were evenly mixed. Then, 2 g of the mixture after high-energy ball milling was put into an alumina ceramic crucible for high-temperature pyrolysis in a tube furnace, and the single-crystal Si ₃ N ₄ nanobelts were synthesized at a pyrolysis temperature of 1450°C for 2 hours. The protective atmosphere is 0.1MPa flowing _N2 gas, and the gas flow rate is 200ml/min. The synthesized single crystal Si ₃ N ₄ nanobelts are shown in Fig. 4 . The thickness and width of a single nanoribbon are uniform, the thickness is about 60nm, the width is about 2um, and the length is several mm. The surface of the ribbon structure is smooth and free of pollution.

Claims (3)

1, single crystalline Si ₃N ₄The preparation method of nanobelt and micro belt is characterized in that: described method adopts organic precursor pyrolysis synthetic single crystal Si ₃N ₄Nanobelt and micro belt may further comprise the steps:

(1) crosslinked at low temperature solidifies: initial feed adopts polysilazane, and 240-290 ℃ of insulation carried out crosslinking curing in 0.4-4 hour in nitrogen or ammonia, obtained translucent non-crystalline state SiCN solid;

(2) high-energy ball milling is pulverized: translucent SiCN solid is packed in the nylon resin ball grinder, carry out dry ball milling and pulverize in high energy ball mill, introduce catalyzer in the time of ball milling, make that non-crystalline state SiCN powder and catalyst mix are even;

(3) high temperature pyrolysis: the mixture behind the high-energy ball milling is carried out high temperature pyrolysis, be incubated 1～8 hour under 1250～1550 ℃ of pyrolysis temperatures, can obtain the low-dimension nano material of different-shape and chemical ingredients, protective atmosphere is N ₂Gas or ammonia.

2, according to the described preparation method of claim 1, it is characterized in that: the catalyzer of described step 2 is FeCl ₂, any among Al, Cu, Ni, the Fe.

3, according to the described preparation method of claim 1, it is characterized in that: the catalyst levels of described step 2 is 1-5wt%.

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