CN1278941C - A kind of Bi2Te3 nanocapsule and preparation method thereof - Google Patents

Abstract

The present invention discloses an Bi2Te3 nanometer capsule which is a seamless hollow capsule whose ratio of length to diameter is from 2 to 5. The Bi2Te3 nanometer capsule comprises the constituents of the atom percentage content: 39.8 to 40.3% of Bi and 59.7 to 60.2% of Te. The Bi2Te3 nanometer capsule is prepared by adopting a wet chemistry method. The Bi2Te3 nanometer capsule with hollow tube type structural is possible to improve the thermoelectric properties of semiconductors, and the Bi2Te3 nanometer capsule can be used for preparing thermoelectric material with high performance and is widely used in the fields of material, physics, chemistry, microelectronics, etc.

Description

A kind of Bi2Te3 nanocapsule and preparation method thereof

technical field

The invention relates to a semiconductor Bi ₂ Te ₃ nanocapsule and a preparation method thereof.

Background technique

Since the first discovery of carbon nanotubes (CNTs) by Japanese carbon chemist S. Lijima in 1991, people have conducted extensive and in-depth research on the synthesis, structure, performance and application of carbon nanotubes. Carbon nanotubes have a series of unique properties such as high chemical stability and high mechanical strength because of their unique one-dimensional hollow graphite sheet rolled into a seamless tubular structure (theoretical calculations show that its tensile strength is that of steel 100 times that of steel, but the density is only 1/6 of steel), and special electrical properties (according to the diameter and helicity of the pipe, it can be a better conductor than copper or a semiconductor). Carbon nanotubes are a class of materials with good application prospects, and have been widely used in many high-tech fields such as physics, chemistry, materials, and electronic technology.

Since _carbon nanotubes, other one _- dimensional tubular nanomaterials have attracted much attention due to _their special structures and wide _application prospects. Still can not meet the needs of multiple research and application fields, and more materials and types of nanotubes are still to be developed and studied.

Bi ₂ Te ₃ is one of the binary inorganic compounds with the largest atomic weight known so far. Bi ₂ Te ₃ -based alloys are currently the best room-temperature thermoelectric materials, and are used to make semiconductor refrigeration devices or thermoelectric power generation devices. Studies have shown that the nanometerization of materials (such as: superlattice, nanowires, etc.) can further improve the thermoelectric properties of Bi ₂ Te ₃ -based materials. There have been reports on the synthesis of Bi ₂ Te ₃ nanotubes by solvothermal or hydrothermal methods and their use in the preparation of high-performance thermoelectric materials.

Contents of the invention

The object of the present invention is to provide a Bi ₂ Te ₃ nanocapsule and a preparation method thereof in order to expand the application field of nanometer materials.

The Bi ₂ Te ₃ nanocapsule of the present invention is a seamless hollow capsule with a length-to-diameter ratio of 2 to 5, and its components and atomic percentages are:

Bi 39.8～40.3%,

Te 59.7-60.2%.

The diameter of the Bi ₂ Te ₃ nanocapsule is 50-200 nanometers, the wall thickness is 5-20 nanometers, and the length is 200-1000 nanometers.

The preparation method of Bi ₂ Te ₃ nanocapsules of the present invention adopts wet chemical method, and its steps are as follows:

1) Put the compound of Bi element and pure Te powder in the reaction vessel according to the atomic percentage ratio of Bi and Te, add deionized water 80 to 850 times the weight of Te, and stir and mix;

2) Add a complexing agent equivalent to 0.25 to 2.5 times the weight of Te to the above mixed solution, add an alkaline regulator to make the pH of the solution 12 to 14, and add a reducing agent equivalent to 0.5 to 3 times the weight of Te;

3) Heating to the set reaction temperature within the range of 55-85°C, after reacting for 6-100 hours, cooling to room temperature, and stopping stirring;

4) Collecting the solid reaction product in the reaction vessel, washing and drying to obtain the material of the present invention.

The compound of above-mentioned Bi element can be chloride, nitrate, vitriol or carbonate; Said alkaline conditioner can be NaOH or KOH; Complexing agent can adopt disodium ethylenediaminetetraacetic acid (hereinafter referred to as EDTA ); said reducing agent can be NaBH ₄ or KBH ₄ .

In the above preparation process, the stirring of the mixed solution starts from step 1) and continues until the end of the reaction. The reaction container used can be a glass container or an acid-resistant, alkali-resistant, heat-resistant plastic container.

The present invention has developed a new type of Bi ₂ Te ₃ nanocapsules, whose aspect ratio is significantly smaller than that of nanotubes. Its unique structure is expected to improve the semiconductor thermoelectric properties of Bi ₂ Te ₃ nanomaterials, and can be widely used in physics, chemistry, materials, Microelectronics and other fields.

Description of drawings

Figure 1 is the field emission scanning electron microscope and transmission electron microscope photographs of Bi ₂ Te ₃ nanocapsules synthesized at 85°C;

Figure 2 is the TEM and high-resolution electron micrographs of Bi ₂ Te ₃ nanocapsules synthesized at 55°C.

Detailed ways

Below in conjunction with embodiment the present invention is described in further detail.

Example 1

1) Add 200ml deionized water, 3.83g Te powder (about 30mmol, 99.99% purity, passed through a 30μm sieve), _6.31g BiCl3 (about 20mmol, analytically pure) in a glass beaker with a capacity of 800ml, The mixture was stirred with a magnetic stirrer at 120 rpm.

2) Add 1 g of EDTA to the beaker, and add NaOH to make the pH value of the solution reach 12, and then add 2 g of NaBH ₄ .

3) Heating at a speed of 5°C/min until the solution temperature reaches 85°C and maintaining at this temperature.

4) Maintain a stirring speed of 120 rpm during the constant temperature reaction at 85° C., and cover the beaker with a plastic film to prevent excessive volatilization of the solvent.

5) Stop heating after reacting for 6 hours, and cool to room temperature naturally. The powdery reaction product in the beaker was collected, washed several times with deionized water, absolute ethanol and acetone in sequence, and dried under vacuum at room temperature to obtain Bi ₂ Te ₃ nanocapsules.

Using IRIS Intrepid II type XSP plasma emission spectrometry analysis, the results show that the atomic percentage of the synthesized nanocapsules is: 40.2% Bi and 59.8% Te. SIRION-FEI field emission scanning electron microscope and JEM-2010 transmission electron microscope were used to observe the shape of nanocapsules. As shown in Figure 1, the length of nanocapsules is between 200-800nm, the diameter is between 50-160nm, and the thickness of the tube wall is 8 ~ 10nm. The crystal structure of nanocapsules was analyzed by Rigaku-D/MAX-2550PC X-ray polycrystal diffractometer, and the result was a single-phase Bi ₂ Te ₃ structure.

Take 0.6g of the Bi ₂ Te ₃ nanocapsules synthesized by the above route, and press at 250°C, 50MPa, 30min under vacuum to obtain a disc-shaped sample with a diameter of 10mm and a thickness of about 1.2mm. After cutting, the electrical properties were measured at room temperature. The absolute value of the thermoelectric coefficient is 2.1×10 ^-4 V/K, and the resistivity is 2.5×10 ^-5 Ω·m, which has typical performance characteristics of thermoelectric materials.

Example 2

1) Add 450ml deionized water, 0.765g Te powder (about 6 mmol, 99.99% purity, passed through a 30 μm sieve), 1.58 g Bi(NO ₃ ) ₃ (about 4 mmol, Analytical purity), and stir the mixture with a magnetic stirrer at 100 rpm.

2) Heating at a rate of 5°C/min until the solution temperature reaches 55°C and maintaining at this temperature.

3) Add 1.9g EDTA to the beaker, and add KOH to make the pH value of the solution reach 14, and then add 2.3g KBH ₄ .

4) Maintain a stirring speed of 100 rpm during the constant temperature reaction at 55° C., and cover the beaker with a plastic film to prevent excessive solvent volatilization.

5) Stop heating after reacting for 100 hours, and cool to room temperature naturally. The powdery reaction product in the beaker was collected, washed several times with deionized water, absolute ethanol and acetone in sequence, and dried under vacuum at room temperature to obtain Bi ₂ Te ₃ nanocapsules.

Using IRIS Intrepid II type XSP plasma emission spectrometry analysis, the result shows that the atomic percentage content of the synthesized nanocapsule is: 39.9% Bi and 60.1% Te. JEM-2010 transmission electron microscope and JEOL-4000EX high-resolution transmission electron microscope were used to observe the shape of nanocapsules. As shown in Figure 2, the length of nanocapsules is between 300-1000nm, the diameter is between 80-200nm, and the thickness of the tube wall It is 5~8nm. The crystal structure of nanocapsules was analyzed by Rigaku-D/MAX-2550PC X-ray polycrystal diffractometer, and the result was a single-phase Bi ₂ Te ₃ structure.

Take 0.6g of the Bi ₂ Te ₃ nanocapsules synthesized by the above route, and press at 250°C, 50MPa, 30min under vacuum to obtain a disc-shaped sample with a diameter of 10mm and a thickness of about 1.2mm. The electrical properties were measured at room temperature after cutting. The absolute value of the thermoelectric coefficient is 1.4×10 ^-4 V/K, and the resistivity is 9.2×10 ^-6 Ω·m, which has typical performance characteristics of thermoelectric materials.

Claims (5)

1. Bi ₂Te ₃Nanocapsule is characterized in that it is that L/D ratio is 2～5 seamless hollow capsules, and its component and atomic percentage conc are:

Bi 39.8～40.3％，Te 59.7～60.2％。

2. Bi according to claim 1 ₂Te ₃Nanocapsule is characterized in that capsular diameter in 50～200 nanometers, wall thickness 5～20 nanometers, and length is in 200～1000 nanometers.

3. the described Bi of claim 1 ₂Te ₃The preparation method of nanocapsule, its step is as follows:

1) compound of Bi element and the pure Te powder ratio according to Bi and Te atomic percentage conc is placed in the reaction vessel, add the deionized water of 80～850 times of Te weight, and mix;

2) in above-mentioned mixed solution, add 0.25～2.5 times the complexing agent that is equivalent to Te weight, add alkaline conditioner and make the pH value of solution value be in 12～14, add 0.5～3 times the reductive agent that is equivalent to Te weight;

3) be heated to the interior setting temperature of reaction of 55～85 ℃ of scopes, react after 6～100 hours, cool to room temperature stops to stir;

4) collect the interior solid reaction product of reaction vessel, behind cleaning-drying, obtain Bi ₂Te ₃The nanocapsule material.

4. Bi according to claim 3 ₂Te ₃The preparation method of nanocapsule, the compound that it is characterized in that said Bi element is muriate, nitrate, vitriol or carbonate.

5. Bi according to claim 3 ₂Te ₃The preparation method of nanocapsule is characterized in that said reductive agent is NaBH ₄Or KBH ₄

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