CN1270973C - Silica dioxide nanometer tube preparation method - Google Patents

Abstract

The present invention discloses a method for preparing silicon oxide nanotubes. The present invention has the steps: (1) normal butyl alcohol solvent is equally divided into two portions, the tetraethoxysilane is dissolved in one portion of the normal butyl alcohol solvent, and the quality concentration ranges from 2% to 8%; (2) the hydrochloric acid water solution with the concentration of 7.5% is dissolved in the other portion of the normal butyl alcohol solvent, the quality concentration of the chlorhydric acid water solution is 4% to 10% of that of the whole solution system; (3) under the ice bath condition, the rear mixture is added into the previous mixture, and the mixtures are kept to stir until the uniform mixing solution is obtained; (4) gel factors are added in the mixing solution, the quality concentration ranges from 1% to 6%, the mixing solution is slowly heated under stirring until the gel factors are completely dissolved; (5) the temperature of the mixing solution is cooled to the room temperature, the molecular gel is generated, is placed and is dried, and a SiO2 nanotube with white powder is obtained. The length of the SiO2 nanotube ranges between 2 and 18 micrometers, the diameter ranges between 200 and 500 nm, and the thickness of the tube wall ranges between 5 and 10 nm. Compared with the preparation method of the common nanotube, the SiO2 nanotube prepared by a template method has no need of expensive catalyst, and has less energy consumption.

Description

A method for preparing silica nanotubes

technical field

The invention belongs to the technical field of nanometer materials, and in particular relates to a method for preparing silicon dioxide nanotubes. In the method, the gel factor is aggregated and assembled in an organic solvent medium to form a fibrous aggregate, and the aggregate is used as a template to prepare silicon dioxide (SiO ₂ ) nanotubes.

Background technique

The different microstructures of materials greatly change the properties of materials, such as transport behavior, catalytic activity, separation, adsorption, storage and release kinetics, etc. Therefore, materials scientists usually focus on surface modification or changing the internal microstructure of materials, for example, hollow structures have very unique properties. Carbon nanotubes are the earliest synthesized nanomaterials with hollow structures. Its unique high conductivity, excellent strength, chemical selectivity and high elasticity make it an important member in the field of nanomaterials.

Following carbon nanotubes, many substances have been discovered one after another, such as boron nitride (BN), molybdenum disulfide (MoS ₂ ), tungsten disulfide (WS ₂ ), zirconia (ZrO ₂ ), silicon oxide (SiO ₂ ), Titanium oxide (TiO ₂ ) and the like can also form nanoscale diameter tubular structures. Depending on their diameter and structure, nanotube materials can be insulators, semiconductors, or exhibit metallic properties. Unique electrochemical properties allow them to be used as quantum tubes. The unique high specific surface area makes them have very important applications in energy storage, batteries, supercapacitors and energy conversion devices.

_SiO2 nanotubes have great potential application value in the fields of photovoltaic solar cells, photocatalytic materials, and electrode materials for rechargeable lithium batteries. The preparation of _SiO2 nanotubes has received extensive attention. Unlike the preparation of carbon nanotubes, which requires a lot of energy consumption (see Zhang Lide, Nanomaterials, Beijing: Chemical Industry Press, 2000, pp20-26.), silicon dioxide (SiO ₂ ) nanotubes can be prepared by template method, The method is simple and consumes less energy. That is, the precursor compound tetraethyl silicate (TEOS) is adsorbed on the template, undergoes sol/gel polymerization, and then the template material is ablated to obtain hollow nanotubes.

Contents of the invention

The object of the present invention is to provide a method for preparing silicon dioxide nanotubes, which does not need to use expensive catalysts and consumes less energy.

A method for preparing silicon dioxide nanotubes provided by the invention comprises the following steps in turn:

(1) The n-butanol solvent is equally divided into two parts, and ethyl orthosilicate is dissolved in one part of the n-butanol solvent, so that the mass concentration of the orthosilicate ethyl is 2 to 8% of the entire solution system;

(2) Dissolving the aqueous hydrochloric acid solution with a concentration of 7.5% in another part of n-butanol solvent, the mass concentration of the 7.5% aqueous hydrochloric acid solution is 4 to 10% of the entire solution system;

(3) Add the latter mixture to the former mixture under ice bath conditions, and keep stirring until a uniform mixed solution is obtained;

(4) Add gel factor in above-mentioned mixed solution, make its mass concentration be 1～6% of whole solution system, under stirring, heat slowly, until gel factor dissolves completely, wherein, the chemical molecular structure of gel factor The general formula is:

R-OCHN-X-NHCO-R

In the formula: R is -C ₁₇ H ₃₅ ; X is -C ₆ H ₄ -CH ₂ -C ₆ H ₄ -, -C ₆ H ₄ -, -C ₆ H ₁₂ - or -C ₆ H ₄ -OC ₆ H ₄ -;

(5) After cooling to room temperature to form a molecular gel, place it at room temperature for 7-10 days, then maintain it in a vacuum desiccator at 100-120°C for 4-6 hours, at 200-220°C for 2-3 hours, and finally at 500-220°C for 2-3 hours. Maintain at 550°C for 1.5 to 2 hours to obtain white powder SiO ₂ nanotubes.

The present invention proposes to prepare _SiO2 nanotubes using gelatin factor aggregates as templates. Gelation factors aggregate and self-assemble in water and non-aqueous media at very low concentrations through interactions such as hydrogen bonds to form fibrous aggregates, and finally gel the solvent to form a physical aggregation system. Our previous studies showed that the fibrous aggregates formed by gelling factors are actually bundles of several individual fibers. The diameter of the fiber bundle is between 50 and 500 nm. These fiber bundles will carry a small amount of positive charges, and orthoethyl silicate (TEOS) will be partially negatively charged. Under the interaction of charges, TEOS will gradually adsorb on the fiber bundles formed by the gelling factor. With the amount of adsorbed TEOS The increase of TEOS gradually wraps the outer surface of the fiber bundle. At room temperature, TEOS forms a stable gel system through sol/gel polymerization. Then the solvent in the system is removed under reduced pressure, and the organic matter in the system is removed by calcination. , prepared SiO ₂ nanotubes. Compared with the preparation method of the usual nanotubes, the preparation of SiO ₂ nanotubes by the template method does not require expensive catalysts and consumes less energy. For example, the preparation of carbon nanotubes is mainly a high-temperature reaction of arc discharge between graphite electrodes containing transition metal catalysts.

Description of drawings

Figure 1 is a fibrous aggregate formed by the aggregation and self-assembly of gelatin in an organic medium;

Figure 2 is a schematic diagram of preparing _SiO2 nanotubes with gel factor aggregates as a template, in which A is gel factor, (I) is a fibrous aggregate, (II) is Sol/Gel polymerization, calcined, (III) for SiO ₂ nanotubes;

Fig. 3 is the SEM photo of SiO _nanotubes stacked together;

Figure 4 is the SEM photograph of localized SiO ₂ nanotubes.

Detailed ways

Some small molecular organic compounds can gel water and most organic solvents at very low concentrations (mass fraction even lower than 1%), which is called molecular gel (Molecular gel). If the organic solvent is gelled, it is sometimes called organogel (Organogel). This type of organic compound is called gel factor (Gelator). During the process of heating and dissolving the gelling factor in an organic solvent, and then cooling to room temperature, the gelling factor spontaneously aggregates and assembles into an ordered Fibrous structure, these fibers can further form an entangled three-dimensional network structure, thereby gelling small solvent molecules. The molecular gel is a thermoreversible physical gel, which is different from the traditional "polymer hydrogel". The latter is a swollen body with a cross-linked structure formed by chemical bonds, which is insoluble and infusible when heated, and small molecules can penetrate or diffuse in it. The molecular gel has been described in detail in another patent application (Chinese patent application number: 02115941.6, June 6, 2002).

The chemical molecular structure general formula of gelatin factor is:

R-OCHN-X-NHCO-R

In the formula: R is -C ₁₇ H ₃₅ ; X is -C ₆ H ₄ -CH ₂ -C ₆ H ₄ -, -C ₆ H ₄ -, -C ₆ H ₁₂ - or -C ₆ H ₄ -OC ₆ H ₄ -.

According to the molecular structure general formula of above-mentioned gel factor, table 1 lists the molecular structure of 4 kinds of gel factors:

Table 1. Molecular structures of 4 gelatin factors R x AB -C ₁₇ H ₃₅ -C ₁₇ H ₃₅ 4,4'-Diaminodiphenyl methyl(4,4'-diaminobenzhydryl)1,3-bis(aminomethyl)benzol(1,3-xylylenedimethylamino)

CD -C ₁₇ H ₃₅ -C ₁₇ H ₃₅ 1,6-diaminohexanal(1,6-diaminodiamino)4,4'-Diaminodiphenylether(4,4'-diaminodiphenyl ether)

The preparation process of the present invention is shown in Figure 2. The scanning electron microscope (SEM) photographs (Fig. 3, 4) of the prepared SiO ₂ nanotube samples clearly show that the SiO ₂ nanotubes vary in diameter and length. The length is 2-18 μm, the diameter is 200-500 nm, and the tube wall thickness is about 5-20 nm. In addition, it can be seen from the SEM photos that SiO ₂ nanotubes are translucent, which may be related to the characteristics of SiO ₂ . The flocs in the photo can only be amorphous SiO ₂ that has not been transformed into nanotubes, because after calcination at a high temperature of 500°C, it is impossible for organic matter to exist. This shows that in the preparation process, the amount of TEOS must be equivalent to the amount of gelatin aggregate template.

The following examples specifically illustrate the method of preparing SiO ₂ nanotubes using gelling factor aggregates as templates. As described in Table 2, the following examples use gelling factor A as the gelling agent. The remaining raw materials can be self-made or commercially available, but they must be refined or dried according to the experimental requirements.

Example 1:

Add 41mg tetraethyl orthosilicate and 429.5mg n-butanol in a small beaker, add 429.5mg n-butanol and 70mg concentration in another small beaker and be 7.5wt% hydrochloric acid aqueous solution, then under ice bath The latter mixture is added to the former mixture and stirring is maintained until a homogeneous mixed solution is obtained. Add this mixed solution into a test tube containing 30 mg of the above-mentioned gel factor, and slowly heat the test tube under stirring until the gel factor is completely dissolved. In this mixed liquid, the mass percentages of each component are: 3% gel factor; 4.1% tetraethyl orthosilicate; 85.9% n-butanol; 7% 7.5wt% hydrochloric acid.

After cooling to room temperature to form a molecular gel, keep it open at room temperature for 10 days, then keep it in a vacuum desiccator at 100°C for 4h, keep it in a tube furnace at 200°C for 3h, and finally keep it in a tube furnace at 500°C for 2h. White powder _SiO2 nanotubes were obtained.

Example 2:

Similar to the method of Example 1, change the mass percent of each component in the mixed solution to make it respectively: 1.5% gel factor; 2% tetraethyl orthosilicate; 90.4% n-butanol; 7.5wt% hydrochloric acid 6 %. Thereafter, after cooling to room temperature to form a molecular gel, it was left open at room temperature for 7 days, then maintained in a vacuum desiccator at 120°C for 5 hours, maintained in a tube furnace at 210°C for 2 hours, and finally in a tube furnace at 550°C Maintained for 1.5h to obtain white powder SiO ₂ nanotubes.

Example 3:

Similar to the method in Example 1, change the mass percent of each component in the mixed solution to make it respectively: 6% gel factor; 8% tetraethyl orthosilicate; 78% n-butanol; 7.5wt% hydrochloric acid 8 %. Thereafter, after cooling to room temperature to form a molecular gel, it was left open at room temperature for 8 days, then maintained in a vacuum desiccator at 110°C for 6 hours, maintained in a tube furnace at 220°C for 2 hours, and finally in a tube furnace at 520°C Maintained for 1.5h to obtain white powder SiO ₂ nanotubes.

Claims (1)

1, a kind of method for preparing the silica nanometer pipe may further comprise the steps successively:

(1) the propyl carbinol solvent being divided equally is two parts, and tetraethoxy is dissolved in a copy of it propyl carbinol solvent, and the mass concentration of tetraethoxy is 2～8%;

(2) be that 7.5% aqueous hydrochloric acid is dissolved in another part propyl carbinol solvent with concentration, the mass concentration of 7.5% aqueous hydrochloric acid is 4～10%;

(3) under condition of ice bath, back one mixture is joined in the last mixture, keep stirring until getting a uniform mixture;

(4) add the gel factor in above-mentioned mixing solutions, making its mass concentration is 1～6%, and under agitation, slowly heating is dissolved fully up to the gel factor, and wherein, the chemical molecular general structure of the gel factor is:

R-OCHN-X-NHCO-R

In the formula: R is-C ₁₇H ₃₅X is-C ₆H ₄-CH ₂-C ₆H ₄-,-C ₆H ₄-,-C ₆H ₁₂-or-C ₆H ₄-O-C ₆H ₄-;

(5) be cooled to after room temperature generates molecular gel, at room temperature placed 7～10 days, in 100～120 ℃ of vacuum driers, keep 4～6h then, keep 2 ~ 3h, keep 1.5～2h at 500～550 ℃ at last, obtain white powder SiO at 200～220 ℃ ₂Nanotube.

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