TWI458685B - Titanium dioxide nanopowder and manufacturing method thereof - Google Patents

Description

Titanium dioxide nano powder and method for producing same

The present invention relates to a method for producing a nano-powder, and more particularly to a method for producing a regular octahedral titanium dioxide nano-powder.

In recent years, the development of global nanotechnology has been in the ascendant. The successful development of many nano materials has improved people's lives and created unlimited business opportunities. Since the semiconductor energy level of titanium dioxide (TiO ₂ ) has a wide energy band, it is widely used as a multifunctional photocatalyst. Although the semiconductor level of zinc oxide also has a broad band, it may also be used as a multifunctional catalyst material, but its chemical stability is poor (for example, it is not resistant to acidic solutions). Therefore, most of the nano photocatalyst materials are mainly titanium dioxide, which is currently the most widely used nano material.

There are many manufacturing methods for titanium dioxide nano-powder, which can be mainly divided into physical methods and chemical methods. The physical method is the earliest manufacturing method, and uses a physical method such as a vapor phase condensation method and a high energy ball milling method to obtain a nano powder. The principle of the gas phase condensation method is to evaporate or volatilize the substance into a gas phase by various means, and nucleate by special technique condensation (such as liquid nitrogen) to obtain a nanometer powder. The powder produced by this method has high purity, uniform particle size distribution and controllable size, and is suitable for producing high melting point nano metal particles or nano particle films. The high-energy ball milling method uses the enormous energy of the ball mill to rotate and vibrate, and pulverizes the raw material into nano-sized particles. The advantages are simple operation and easy continuous production, and the disadvantage is that the particle size is not uniform and impurities are easily introduced. Chemical methods are another method of making nano-powders, and some chemical reactions are involved in the process. The chemical methods used to produce the nano-powder are mainly a precipitation method, a hydrolysis method, a sol-gel method, a hydrothermal method, a spray method, a redox method, a laser synthesis method, and an electrochemical manufacturing method. The above is only a rough classification. In the manufacturing process of titanium dioxide nanopowder, the above method may also be used in combination. For example, precipitation and spray methods often involve hydrolysis reactions and redox reactions; hydrothermal methods are often combined with sol-gel methods to produce nano-sized powders of different morphologies, such as nanowires, nanorods, nanotubes, Nano microspheres, etc.

Among the various methods for producing titanium dioxide nanopowder described above, the spray cracking method is one of the main processes for commercializing titanium dioxide nanopowder, and a nanometer powder having uniform particle size and stable quality can be obtained by this process. In addition, by using the sol-gel method and the hydrothermal method, various shapes of titanium dioxide nano-powder can be produced; and the nanometer size can be adjusted by controlling the pH value, hydrothermal temperature, reaction time and solution concentration of the reaction solution. . This is the most common method for obtaining diverse nanostructures.

With the rapid development of the technology industry, the application of various shapes of titanium dioxide nano-powder in various fields is also increasing. Usually, in the production of the regular octahedral titanium dioxide nanopowder, hydrothermal method, microemulsion method, template method and the like are used. However, the above methods require relatively expensive production equipment and are disadvantageous for large-scale and continuous production; in addition, the uniformity of the powder produced by these methods still needs to be improved. Therefore, there is a need to develop a method for producing a regular octahedral titanium dioxide nanopowder which is suitable for mass production, inexpensive to manufacture, and has a uniform particle size of the prepared titanium dioxide nanopowder.

In view of the above, an object of the present invention is to provide a method for producing a titanium dioxide nanopowder which can satisfy the above needs.

A first aspect of the present invention is a method for producing a titanium dioxide nanopowder comprising the steps of: (a) adding a titanium precursor and an alkaline chelating agent to water; and (b) adding an organic peptizing agent to the step (a). And (c) separating the product obtained in the step (c) to obtain a titanium dioxide nanopowder.

A second aspect of the present invention is a titanium dioxide nanopowder having a crystal form of a regular octahedron and a particle size of between 30 and 500 nm.

By the method of the present invention, a regular octahedral titanium dioxide nano-powder having a uniform particle size can be produced at a low cost, and the particle size distribution can be easily adjusted.

Other objects and advantages of the present invention will become apparent from the following detailed description and appended claims.

◎Preparation of regular octahedral titanium dioxide nano-powder

The present invention mainly utilizes a sol-gel method and a hydrothermal method to produce a regular octahedral titanium dioxide nano-powder. Fig. 1 shows a method of producing the titanium dioxide nanopowder of the present invention. In step S1, a titanium precursor and an alkaline chelating agent are added to the water. The titanium precursor may be Titanium tetrachloride, titanium isopropoxide, titanium butoxide, or titanium alkoxide. The alkyl group of the titanium alkoxide may have 1 to 6 carbon atoms. The alkaline chelating agent can be an alcohol amine such as Triethanolamine. Step S1 can be carried out under an inert gas such as nitrogen or argon. Further, the reaction condition of the step S1 may be continued stirring at a temperature of 4 to 15 ° C for about 24 to 72 hours.

In step S2, an organic gum solvent is added to the mixture obtained in step S1. The organic peptizer may be an amine base such as diethylamine. Step S2 can be carried out under an inert gas such as nitrogen or argon. The reaction condition of the step S2 may be continued stirring at a temperature of from 3 to 100 ° C for about 24 to 72 hours.

In step S3, the mixture obtained in the step S2 is subjected to a hydrothermal reaction. The hydrothermal reaction can be continued for about 2 to 200 hours at a temperature of 50 to 300 °C. Hydrothermal method refers to a method of preparing a nanomaterial by using water as a solvent in a sealed pressure vessel. In general, substances that are not easily oxidized in a normal temperature-normal pressure environment undergo rapid oxidation reactions due to a high-temperature environment in a hydrothermal process. The hydrothermal reaction is a general term for performing chemical reactions in a fluid such as an aqueous solution or water vapor under high temperature and high pressure. The hydrothermal method provides the effect of the present invention in that the prepared powder has the advantages of uniform particle size distribution, light particle agglomeration and continuous production, and easy availability of a suitable stoichiometric ratio of nano-oxide powder. In the hydrothermal process, the process of nucleating crystal growth continues to grow into a larger crystal structure, thus allowing the nano oxide to have a specific crystal phase without the need for phase transfer to obtain a specific crystal phase. That is to say, a material having high crystallinity can be obtained without performing a high-temperature calcination treatment, so that it is possible to avoid the introduction of impurities and cause defects and the like, and the obtained powder has high sintering activity. In step S4, the product obtained in the step S3 is separated to obtain a titanium dioxide nanopowder. The method may further comprise drying the titanium dioxide nanopowder.

It has been found from the experimental results that when triethanolamine (alkaline chelating agent) is not added and only diethylamine (organic gel solvent) is added, the nanoparticles are less uniform in terms of specific morphology and their size is less uniform. Conversely, when triethanolamine and diethylamine are added at the same time, the nanoparticles will have a regular regular octahedral morphology and a uniform size.

In the hydrothermal method of step S3, the particle size of the titanium dioxide nanopowder varies with the time and temperature of the hydrothermal reaction. As shown by the results of the following examples, the higher the temperature of the hydrothermal reaction and the longer the time, the larger the particle size of the titanium dioxide nanopowder.

Example 1:

Add 100 mL of deionized water to the deionized water at a rate of 1 to several drops per second while stirring at a high speed (the molar ratio of the two is added to deionized water) Approximately 1 to 1), a titanium precursor solution can be obtained, and nitrogen or argon can be selectively introduced. Stirring is continued for about 24 to 72 hours; then the morphology controlled diethylamine is added and the temperature is raised to 100 ° C and stirring is continued for about 24 to 72 hours; then the temperature is increased to 230 to 270 ° C and continued Stir for about 2 to 72 hours.

For hydrothermal reaction. The obtained mixture is then collected by means of filtration or centrifugation or the like. The above powder is washed with deionized water at least three times to remove residual solvent, triethanolamine or diethylamine; and dried in an oven at a temperature between 60 and 500 ° C, thereby obtaining the regular octahedral titanium dioxide of the present invention. Nano powder. In this embodiment, by controlling the temperature and time of the hydrothermal reaction, nano-sized powders of different sizes can be obtained, and the results are shown in Table 1. According to different hydrothermal reaction conditions, the obtained nanometer powder has a particle size ranging from 30 to 50 nm, 50 to 100 nm, 50 to 200 nm, 100 to 300 nm, 200 to 400 nm, or 300 to 500 nm. Further, from the results of Table 1, it can be inferred that the larger the temperature of the hydrothermal reaction and the longer the time, the larger the particle size of the titanium dioxide nanopowder. Therefore, the present invention can adjust the particle size distribution of the regular octahedral titanium dioxide nanopowder by changing the time and temperature of the hydrothermal reaction.

2(a) to 2(f) show scanning electron microscope (SEM) images of the regular octahedral titanium dioxide nano-powder obtained in the above embodiment, and FIG. 3 shows X-ray diffraction patterns thereof, or The hydrothermal reaction conditions corresponding to the curves are shown in Table 1. As is apparent from Fig. 2 and Fig. 3, the titanium dioxide nanopowder obtained in the above embodiment has a regular regular octahedron morphology and a uniform particle size. It can be seen from the results of Fig. 3 that the regular octahedral titanium dioxide nanopowder is an anatase crystal phase, and it has also been confirmed that the nano oxide grown by hydrothermal method is a substance having a specific crystal phase. Figure 4 uses a scanning electron microscope (SEM) to capture the microstructure of nanomaterials. It can be seen that the regular octahedral titanium dioxide nanopowders are arranged in a thin film. According to the manufacturing method of the present invention, a titanium dioxide nano-powder having a regular octahedral structure can be produced under the same synthetic framework, and the nanoparticle size can be controlled in various ranges between 30 nm and 500 nm, and is exhibited in each range. Good size uniformity. In the prior art, the titanium dioxide nano-powder developed by the M. Grätzel laboratory of the EPFL in Switzerland has only a small size range (15-30 nm), and the present invention is relatively different in synthesis. In a manner, a particle size range of more than 30 nm can be obtained.

◎Preparation of octahedral titanium dioxide nano film

The regular octahedral titanium dioxide nano-powders of different sizes prepared by the invention can be further used to prepare titanium dioxide nano-films of different sizes. The method is as follows: the normal octahedral titanium dioxide nano-powder prepared by the above method is added to water, an aqueous solvent or an oily solvent, and then added, for example, an organic small molecule, A dispersant of an oligomer or a polymer to form a slurry or a solution. Among them, anionic and cationic surfactants may be optionally added. Next, a regular octahedral titanium dioxide nano film is formed on the substrate by screen printing, spin coating, spray coating or the like.

Example 2:

Mixing 6g of the above-mentioned regular octahedral titanium dioxide nanopowder with 1mL of acetic acid, stirring for three minutes; adding 5mL of deionized water, stirring for 3 minutes to make it evenly mixed; then adding 15mL of ethanol, 20g of terpineol, and 30g of ethyl After the cellulose was stirred for 12 hours to be uniformly dispersed, the production of the regular octahedral titanium dioxide nano slurry was completed.

The above-mentioned regular octahedral titanium dioxide nano slurry is coated on a transparent conductive glass substrate by screen printing, and is sintered at a high temperature to remove organic substances, and the sintering temperature is between 300 and 600 ° C, and the sintering time is Between 1 and 5 hours; followed by cooling to room temperature, a regular octahedral titanium dioxide nanofilm can be formed on the substrate to a thickness of 1 to 10 microns, which can be used for transparent electrodes such as solar cells. The hardness of the film is between 3 and 6H pencil hardness. 4 is a scanning electron microscope image of a regular octahedral titanium dioxide nano film disposed on a substrate according to the above embodiment. The film made of the titanium dioxide nanopowder of the present invention is applied to a dye-sensitized solar cell, and has higher photoelectric conversion efficiency than the prior art. Table 2 shows the titanium dioxide nano film (HD30 of the present invention, whose hydrothermal reaction conditions are shown in Table 1) and the titanium dioxide nano film (NP) developed by the M. Grätzel laboratory of the Swiss Institute of Technology in Lausanne (EPFL). The result of the comparison. The results measured by the two films at the same thickness can be seen that since the nano-size of HD30 is larger than that of NP, the specific surface area is smaller than that of NP, and the dye in the dye-sensitive system is adsorbed on HD30. It is less than the NP, so that the short-circuit current density is small. However, because the HD30 has a better material quality and a higher open circuit voltage and fill factor, the conversion efficiency is higher than that of NP.

According to the method of the present invention, the size limitation encountered in the preparation of titanium dioxide nanopowder by a single synthesis can be broken. The titanium dioxide nanopowder prepared by the invention can be more widely used in the preparation of a film in a dye-sensitized solar cell, and can be used to improve photoelectric conversion efficiency and practicality in film preparation.

The invention may be embodied in various specific forms without departing from the spirit and scope of the invention. The above-described embodiments are to be considered as illustrative and not restrictive, and the scope of the invention is defined by the scope of the appended claims It should be included in the scope of the present invention.

S1‧‧‧Adding titanium precursor and alkaline chelating agent to the water

S2‧‧‧Adding the organic gum solvent to the mixture obtained in step S1

S3‧‧‧ The hydrothermal reaction of the mixture obtained in step S2

S4‧‧‧ separating the product obtained in step S3 to obtain titanium dioxide nanopowder

Fig. 1 shows a method of producing the titanium dioxide nanopowder of the present invention.

Figure 2 shows a scanning electron microscope image of a regular octahedral titanium dioxide nanopowder prepared in accordance with the present invention. (a) a particle diameter of 30 to 50 nm; (b) a particle diameter of 50 to 100 nm; (c) a particle diameter of 50 to 200 nm; (d) a particle diameter of 100 to 300 nm; (e) a particle diameter of 200 to 400 nm; (f) The particle size is from 300 to 500 nm.

Figure 3 shows an X-ray diffraction pattern of a regular octahedral titanium dioxide nanopowder prepared in accordance with the present invention.

4 is a scanning electron microscope image of a regular octahedral titanium dioxide nano film disposed on a substrate, which is made of the regular octahedral titanium dioxide nano powder of the present invention.

S1‧‧‧Adding titanium precursor and alkaline chelating agent to the water

S2‧‧‧Adding the organic gum solvent to the mixture obtained in step S1

S3‧‧‧ The hydrothermal reaction of the mixture obtained in step S2

S4‧‧‧ separating the product obtained in step S3 to obtain titanium dioxide nanopowder

Claims (11)

A method for producing titanium dioxide nano powder, comprising the steps of: (a) adding a titanium precursor and an alkaline chelating agent to water, and the molar ratio of the titanium precursor to the alkaline chelating agent is 1:1. The alkaline chelating agent is triethanolamine; (b) an organic peptizing agent is added to the mixture obtained in the step (a), the organic peptizing agent is diethylamine; (c) (b) The resulting mixture is continuously stirred at a temperature of 50 to 300 ° C for 2 to 200 hours to carry out a hydrothermal reaction; and (d) the product obtained by the step (c) is separated to obtain a titanium oxide nanopowder. The method for producing a titanium dioxide nanopowder according to claim 1, further comprising drying the titanium dioxide nanopowder. The method for producing a titanium dioxide nanopowder according to claim 1, wherein the titanium precursor is Titanium tetrachloride, titanium isopropoxide, or titanium tetra-n-butoxide (titanium tetrapropoxide) Titanium butoxide). The method for producing a titanium dioxide nanopowder according to claim 1, wherein the titanium precursor is a titanium alkoxide. The method for producing a titanium dioxide nanopowder according to claim 4, wherein the alkyl group of the titanium alkoxide has 1 to 6 carbon atoms. The method for producing a titanium dioxide nanopowder according to claim 1, wherein the step (b) is carried out at a temperature of from 3 to 100 °C. The method for producing a titanium dioxide nanopowder according to claim 1, wherein the step (a) and/or the step (b) are carried out under an inert gas. The method for producing a titanium dioxide nanopowder according to claim 7, wherein the inert gas is nitrogen or argon. The method for producing the titanium dioxide nanopowder according to claim 1, further comprising continuously stirring the mixture obtained in the step (a) at a temperature of 4 to 15 ° C for about 24 to 72 hours. The method for producing a titanium dioxide nanopowder according to claim 1, further comprising continuously stirring the mixture obtained in the step (b) at a temperature of from 3 to 100 ° C for about 24 to 72 hours. A titanium dioxide nano-powder obtained by the method for producing a titanium dioxide nano-powder according to the first aspect of the invention, which has a crystal form of a regular octahedron and a particle size of between 30 and 500 nm.