阅读说明：本技术 连续调控氧化锌陶瓷光吸收性质的方法、氧化锌陶瓷及制备方法 (Method for continuously regulating and controlling light absorption property of zinc oxide ceramic, zinc oxide ceramic and preparation method ) 是由 王泽岩 郑立仁 黄柏标 郑昭科 王朋 程合锋 刘媛媛 张倩倩 张晓阳 于 2021-09-10 设计创作，主要内容包括：本发明公开了一种连续调控氧化锌陶瓷光吸收性质的方法、氧化锌陶瓷及制备方法,将盛放有氧化锌粉体的模具置于等离子体烧结的炉膛中,抽真空,然后程序升温、烧结、程序降温,通过调节烧结温度和烧结压力来调控氧化锌陶瓷的光吸收性能。利用等离子体烧结技术的高温、缺氧和还原环境,以及等离子体烧结的脉冲电流,能够有效地在氧化锌陶瓷中通过控制烧结温度,引入大量的氧缺陷和间隙锌。通过调控烧结温度和压力,氧化锌陶瓷的颜色从原本的氧化锌的白色变成淡化色-黄色-暗黄色-红棕色。(The invention discloses a method for continuously regulating and controlling the light absorption property of zinc oxide ceramic, the zinc oxide ceramic and a preparation method thereof. By utilizing the high-temperature, oxygen-deficient and reducing environment of the plasma sintering technology and the pulse current of the plasma sintering, a large amount of oxygen defects and interstitial zinc can be effectively introduced into the zinc oxide ceramic by controlling the sintering temperature. By regulating and controlling the sintering temperature and pressure, the color of the zinc oxide ceramic is changed from the original white color of the zinc oxide to a lightened color, yellow, dark yellow and reddish brown.)

1. A method for continuously regulating and controlling the light absorption property of zinc oxide ceramic is characterized in that: the method comprises the following steps:

and placing the mold containing the zinc oxide powder in a hearth for plasma sintering, vacuumizing, then carrying out temperature programming, sintering and temperature programming, and regulating and controlling the light absorption performance of the zinc oxide ceramic by regulating the sintering temperature and the sintering pressure.

2. A preparation method of zinc oxide ceramic is characterized by comprising the following steps: the method comprises the following steps: selecting zinc oxide powder with a set specific surface area and a set diameter range;

and placing the mold containing the zinc oxide powder in a hearth for plasma sintering, vacuumizing, and then carrying out temperature programming, sintering and temperature programming to prepare the zinc oxide ceramic with the set color.

3. The method for continuously regulating the light absorption properties of the zinc oxide ceramic according to claim 1 or the method for preparing the zinc oxide ceramic according to claim 2, wherein: the specific surface area of the zinc oxide powder is 10-16m²(ii)/g, the particle diameter is 200nm-1 μm.

4. The method for continuously regulating the light absorption properties of the zinc oxide ceramic according to claim 1 or the method for preparing the zinc oxide ceramic according to claim 2, wherein: before the zinc oxide powder is put into a mould, calcining at the temperature of 450-550 ℃ for 1.5-2.5 h; preferably, the calcination temperature is 480-530 ℃, and the calcination time is 1.8-2.2 h; further preferably, the calcination temperature is 490-510 ℃, and the calcination time is 1.9-2.1 h; more preferably, the calcining temperature is 500 ℃, and the calcining time is 2 hours;

furthermore, the calcined zinc oxide powder is ball milled.

5. The method for continuously regulating the light absorption properties of the zinc oxide ceramic according to claim 1 or the method for preparing the zinc oxide ceramic according to claim 2, wherein: the air pressure value in the furnace chamber after vacuumizing is 0.1-10 MPa.

6. The method for continuously regulating the light absorption properties of the zinc oxide ceramic according to claim 1 or the method for preparing the zinc oxide ceramic according to claim 2, wherein: the temperature raising procedure of the programmed temperature raising is to raise the temperature raising rate of 100-200 ℃/min to 550-650 ℃ and to keep the temperature for 10-30min, the pressure is controlled to be 5.5-20Mpa, and then the temperature is raised to the sintering temperature at the temperature raising rate of 50-100 ℃/min.

7. The method for continuously regulating the light absorption properties of the zinc oxide ceramic according to claim 1 or the method for preparing the zinc oxide ceramic according to claim 2, wherein: the sintering temperature is 400-1100 ℃, preferably 400 ℃, 500 ℃, 600 ℃, 700 ℃, 800 ℃, 900 ℃, 1000 ℃ or 1100 ℃, the sintering time is 10-30min, and the sintering pressure is 11-70 MPa.

8. The method for continuously regulating the light absorption properties of the zinc oxide ceramic according to claim 1 or the method for preparing the zinc oxide ceramic according to claim 2, wherein: and applying an external mechanical pressure of 5.5-20MPa on the sample in the sintering process.

9. The method for continuously regulating the light absorption properties of the zinc oxide ceramic according to claim 1 or the method for preparing the zinc oxide ceramic according to claim 2, wherein: the cooling procedure in the procedure cooling process is as follows: firstly, the temperature is reduced to 650-450 ℃ at a cooling rate of 50-80 ℃/min, and then the temperature is naturally reduced to the room temperature.

10. A zinc oxide ceramic characterized by: the zinc oxide ceramic is prepared by the preparation method of the zinc oxide ceramic according to claim 2, and the light absorption band edge of the zinc oxide ceramic is continuously adjustable from 375nm to 600 nm.

Technical Field

The invention belongs to the technical field of spectroscopy and material science and engineering, and particularly relates to a method for continuously regulating and controlling the light absorption property of zinc oxide ceramic, the zinc oxide ceramic and a preparation method.

Background

The statements herein merely provide background information related to the present disclosure and may not necessarily constitute prior art.

The zinc oxide is used as an important oxide semiconductor, has a wider band gap (3.37eV), has the advantages of large exciton energy, high transparency, no toxicity, good biocompatibility and the like, and is widely applied to the fields of optoelectronic devices, piezoelectric sensors, gas detection and the like. However, the use of zinc oxide is limited due to its wide band gap, greatly reduced light utilization, low charge transport and poor conductivity.

Numerous studies have shown that the variation of the absorption edge of zinc oxide, mainly caused by defects in zinc oxide, mainly oxygen vacancies and interstitial zinc, forms defect levels in the energy band of zinc oxide, thus reducing the band gap of zinc oxide, changing the optical properties of zinc oxide and changing the position of its absorption edge; the existence of oxygen vacancy and other defects can change the chemical adsorption and chemical state of the surface of the zinc oxide material, and enhance the application of the zinc oxide material in the fields of carbon dioxide reduction and the like. In addition, the interstitial zinc defect can improve the conductivity of zinc oxide, because the interstitial zinc is a donor defect located near the conduction band bottom, and can improve the concentration of carriers.

At present, oxygen defects are mainly introduced into zinc oxide under the action of an oxygen-deficient environment and a reducing agent, but the inventor finds that the light absorption performance of the zinc oxide material is slightly changed by adopting the method, the color of the zinc oxide is basically light yellow, yellow or gray, and the change of the light absorption is limited; in addition, in the prior art, the interstitial zinc defects of the zinc oxide can only be introduced into the zinc oxide under the condition of high temperature and in the presence of zinc steam.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a method for continuously regulating and controlling the light absorption property of zinc oxide ceramic, the zinc oxide ceramic and a preparation method.

In order to achieve the purpose, the invention is realized by the following technical scheme:

in a first aspect, the invention provides a method for continuously regulating and controlling the light absorption property of zinc oxide ceramic, which comprises the following steps:

and placing the mold containing the zinc oxide powder in a hearth for plasma sintering, vacuumizing, then carrying out temperature programming, sintering and temperature programming, and regulating and controlling the light absorption performance of the zinc oxide ceramic by regulating the sintering temperature and the sintering pressure.

In some embodiments, the specific surface area of the zinc oxide powder is 10-16m²(ii)/g, the particle diameter is 200nm-1 μm.

Further, before the zinc oxide powder is placed into a mold, the zinc oxide powder is calcined at the temperature of 450-550 ℃ for 1.5-2.5 h; preferably, the calcination temperature is 480-530 ℃, and the calcination time is 1.8-2.2 h; further preferably, the calcination temperature is 490-510 ℃, and the calcination time is 1.9-2.1 h; more preferably, the calcination temperature is 500 ℃ and the calcination time is 2 hours.

Organic matters and moisture in the zinc oxide powder can be removed through calcination so as to avoid influencing the performance of the ceramic, and meanwhile, the calcination time is not easy to be too long so as to avoid agglomeration.

Furthermore, the calcined zinc oxide powder is ball milled. The agglomerates of the zinc oxide powder are fully dispersed by ball milling.

In some embodiments, the pressure in the evacuated furnace is 0.1 to 10 MPa.

In some embodiments, the temperature raising procedure of the programmed temperature raising is to raise the temperature to 550-650 ℃ at a temperature raising rate of 100-200 ℃/min and to keep the temperature for 10-30min, the applied pressure is controlled to be 5.5-20MPa, and then the temperature is raised to the sintering temperature at a temperature raising rate of 50-100 ℃/min; the temperature rise rate cannot be too fast, in order to uniformly heat the powder, the prepared ceramic has good uniformity, and enough time is provided to form defects of uniform distribution in the ceramic.

In some embodiments, the sintering temperature is 400 ℃, 500 ℃, 600 ℃, 700 ℃, 800 ℃, 900 ℃, 1000 ℃ and 1100 ℃, the sintering time is 10-30min, and the sintering pressure is 11-70MPa, so that the ceramic can be quickly densified and uniform defect distribution can be formed in the ceramic.

Furthermore, in the temperature rise stage in the sintering process, the range of the applied mechanical pressure applied on the sample is 5.5-20MPa, so that the defects with uniform distribution can be produced in the powder under the condition that the ceramic is not compact.

In some embodiments, the cooling program of the temperature program process is: firstly, the temperature is reduced to 650-450 ℃ at a cooling rate of 50-80 ℃/min, and then the temperature is naturally reduced to the room temperature. The room temperature is the ambient temperature, the temperature range is generally 20-30 ℃, the influence of the temperature reduction rate on the defects is small, the defects are mainly formed in the heating section and the sintering section of the ceramic, and the temperature reduction stage mainly ensures that the ceramic does not crack or break.

In a second aspect, the present invention provides a method for preparing a zinc oxide ceramic, comprising the following steps:

selecting zinc oxide powder with a set specific surface area and a set diameter range;

and placing the mold containing the zinc oxide powder in a hearth for plasma sintering, vacuumizing, and then carrying out temperature programming, sintering and temperature programming to prepare the zinc oxide ceramic with the set color.

In some embodiments, the specific surface area of the zinc oxide powder is 10-16m²(ii)/g, the particle diameter is 200nm-1 μm.

Further, before the zinc oxide powder is placed into a mold, the zinc oxide powder is calcined at the temperature of 450-550 ℃ for 1.5-2.5 h; preferably, the calcination temperature is 480-530 ℃, and the calcination time is 1.8-2.2 h; further preferably, the calcination temperature is 490-510 ℃, and the calcination time is 1.9-2.1 h; more preferably, the calcination temperature is 500 ℃ and the calcination time is 2 hours.

Organic matters and moisture in the zinc oxide powder can be removed through calcination so as to avoid influencing the performance of the ceramic, and meanwhile, the calcination time is not easy to be too long so as to avoid agglomeration.

Furthermore, the calcined zinc oxide powder is ball milled. The agglomerates of the zinc oxide powder are fully dispersed by ball milling.

In some embodiments, the pressure in the evacuated furnace is 0.1 to 10 MPa.

In some embodiments, the temperature raising procedure of the programmed temperature raising is to raise the temperature to 550-650 ℃ at a temperature raising rate of 100-200 ℃/min and to keep the temperature for 10-30min, the pressure is controlled to be 5.5-20MPa, and then the temperature is raised to the sintering temperature at a temperature raising rate of 50-100 ℃/min.

In some embodiments, the sintering time is 10-30min at 700 ℃, 800 ℃, 900 ℃, 1000 ℃ and 1100 ℃, and the sintering pressure is 11-70 MPa.

Furthermore, the applied mechanical pressure is 5.5-20MPa on the sample in the sintering process.

In some embodiments, the cooling program of the temperature program process is: firstly, the temperature is reduced to 650-450 ℃ at a cooling rate of 50-80 ℃/min, and then the temperature is naturally reduced to the room temperature. The room temperature is the ambient temperature, which is typically in the range of 20-30 ℃.

In a third aspect, the invention provides a zinc oxide ceramic prepared by the preparation method of the zinc oxide ceramic, wherein the light absorption band edge of the zinc oxide ceramic is continuously adjustable from 375nm to 600 nm.

The beneficial effects obtained by one or more of the above embodiments of the invention are as follows:

the invention can effectively introduce a large amount of oxygen defects and interstitial zinc in the zinc oxide ceramic by controlling the sintering temperature by fully utilizing the high-temperature, anoxic and reducing environment of the plasma sintering technology and the pulse current of the plasma sintering. In this process, the applied pressure causes densification of the ceramic while sintering in the mold and plasmaAn enclosed environment is formed between the upper pressure head and the lower pressure head. When the sintering temperature is higher than 900 ℃, the zinc element in the ceramic can be greatly separated from the lattice sites of the zinc oxide and enter the octahedral voids of the lattice of the zinc oxide. By regulating and controlling the sintering temperature and pressure, the color of the zinc oxide ceramic is changed from the original white color of the zinc oxide into a lightened color, yellow, dark yellow and reddish brown, and the carrier concentration of the zinc oxide ceramic is very obvious along with the change of the temperature. From 6.65X 10 at 700 deg.C¹⁴cm^-3To 1.63X 10 ℃ of 900 DEG C¹⁸cm^-3And 2.86X 10 at 1100 deg.C¹⁸cm^-3The electron mobility is also increased.

The light absorption band edge of the zinc oxide ceramic prepared by the method can continuously change and move from 375nm of pure powder to 600nm of long wavelength, and the light absorption performance of the zinc oxide ceramic is regulated and controlled in a wider waveband range.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.

FIG. 1 is a schematic temperature programmed graph of plasma sintering of zinc oxide ceramics prepared in examples 1-5 of the present invention;

FIG. 2 is a photograph of zinc oxide ceramics prepared in examples 1 to 5 of the present invention;

FIG. 3 is an electron scanning photograph of a cross-section of zinc oxide ceramic prepared in examples 1-5 of the present invention (a) sintering temperature is 700 ℃; (b) the sintering temperature is 800 ℃; (c) the sintering temperature is 900 ℃; (d) the sintering temperature is 1000 ℃; (e) the sintering temperature is 1100 ℃;

FIG. 4 is a graph of the diffuse reflectance of zinc oxide ceramics, both ultraviolet and visible, prepared in examples 1-5 of the present invention;

FIG. 5 is a band gap spectrum of zinc oxide ceramics prepared in examples 1 to 5 of the present invention;

FIG. 6 is a photograph of a real object of zinc oxide ceramic prepared in examples 1-7 of the present invention at different pressures and different temperatures;

FIG. 7 is a graph showing the band gap variation of zinc oxide ceramics prepared in examples 1-7 of the present invention at different pressures and different temperatures;

FIG. 8 is a graph of density variations for zinc oxide ceramics prepared according to examples 1-7 of the present invention at different pressures and different temperatures.

Detailed Description

It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

In order to make the technical solution of the present invention more clearly understood by those skilled in the art, the technical solution of the present invention will be described in detail below with reference to specific examples and comparative examples.

The test materials used in the following examples are all conventional in the art and are commercially available.

Example 1

A preparation method of zinc oxide ceramic with continuously adjustable light absorption properties comprises the following steps:

(1) commercial zinc oxide powder (specific surface area is 10-16 m)²Per g, particle size from 200nm to 1 μm) in air:

the alumina crucible is filled with 500 g, and the mixture is placed in a muffle furnace at 500 ℃ to be calcined for 2 hours, so that organic matters and water in the powder are removed, and the defect types of the ceramic are not influenced.

(2) And (2) performing ball milling dispersion on the powder obtained in the step (1), wherein the ball milling adopts bidirectional ball milling, the frequency is 20-50Hz, and the ball milling time is 10-30 min.

(3) Filling ceramic powder:

and (3) putting 2-5 g of the zinc oxide powder subjected to ball milling in the step (2) into a graphite die with a graphite paper lining and a diameter of 15mm, and manually compacting.

(4) Sintering zinc oxide ceramic:

placing the graphite mold in the step (3) between the pressure heads of the two graphite column electrodes, adjusting a mechanical pressure device, and fixing the graphite mold between an upper pressure head and a lower pressure head of the plasma sintering; closing the furnace door, opening a vacuum pump, removing air in the furnace chamber, starting heating when the air pressure value is 2Pa, measuring the temperature by using a K-type thermocouple, wherein the temperature measuring position of the thermocouple is a temperature measuring hole at the middle position of the graphite mold, and the distance from the sample is 5 mm; heating to 600 deg.C at a rate of 150 deg.C/min per minute and maintaining for 20min, controlling the pressure at 11Mpa, heating to 700 deg.C at a rate of 50 deg.C/min, increasing the pressure to 66Mpa, and maintaining at the corresponding temperature for 30 min; then the temperature is reduced to 500 ℃ at the speed of 80 ℃/min and kept for 10 min. In the whole sintering process, the mechanical pressure is maintained at 66 MPa; the mechanical pressure dropped to 0 within the last 1min, after which the temperature dropped to room temperature.

(5) Demolding and treating the ceramic:

and (4) releasing the pressure in the hearth, opening the furnace door after the air pressure in the hearth is the same as the atmospheric pressure, lifting the mechanical pressure device, and taking out the mold. Demoulding the ceramic from the mould, and then taking out the graphite wrapped outside the ceramic by using sand paper; cutting into 10 × 1mm size with a cutting machine³Then paraffin wax is removed by xylene at the time of cutting the ceramic.

Example 2

The same technical scheme as that of example 1 is adopted except that the step of increasing the temperature to 700 ℃ at a temperature increase rate of 50 ℃/min and increasing the pressure to 66MPa and keeping the temperature at the corresponding temperature for 30min is replaced with the step of increasing the temperature to 800 ℃ at a temperature increase rate of 50 ℃/min and increasing the pressure to 66MPa and keeping the temperature at the corresponding temperature for 30min in example 1.

Example 3

The procedure of example 1 was repeated except that "the subsequent temperature was raised to 700 ℃ at a temperature rise rate of 50 ℃/min and the pressure was raised to 66MPa, and the temperature was maintained at the corresponding temperature for 30 min" in example 1 was replaced with "the subsequent temperature was raised to 900 ℃ at a temperature rise rate of 50 ℃/min and the pressure was raised to 66MPa, and the temperature was maintained at the corresponding temperature for 30 min".

Example 4

The procedure of example 1 was repeated except that "the subsequent temperature was raised to 700 ℃ at a temperature rise rate of 50 ℃/min and the pressure was raised to 66MPa, and the temperature was maintained at the corresponding temperature for 30 min" in example 1 was replaced with "the subsequent temperature was raised to 1000 ℃ at a temperature rise rate of 50 ℃/min and the pressure was raised to 66MPa, and the temperature was maintained at the corresponding temperature for 30 min".

Example 5

The procedure of example 1 was repeated except that "the subsequent temperature was raised to 700 ℃ at a temperature rise rate of 50 ℃/min and the pressure was raised to 66MPa, and the temperature was maintained at the corresponding temperature for 30 min" in example 1 was replaced with "the subsequent temperature was raised to 1100 ℃ at a temperature rise rate of 50 ℃/min and the pressure was raised to 66MPa, and the temperature was maintained at the corresponding temperature for 30 min".

Example 6

This example prepares zinc oxide ceramics with different pressures, and the preparation method is the same as that of example 1, except that: in the step (4), the mechanical pressure is kept at 11MPa, and the sintering temperatures (the sintering temperature is the temperature corresponding to the temperature of 30min in example 1) are 400 ℃, 500 ℃, 600 ℃, 700 ℃, 800 ℃, 900 ℃, 1000 ℃ and 1100 ℃.

Example 7

This example is a supplement to and a comparison of examples 1-6:

in this embodiment, zinc oxide ceramics are prepared at different sintering temperatures (the sintering temperature is the temperature corresponding to the temperature maintained for 30min in embodiment 1), and the preparation method is the same as that of embodiment 1, except that: the sintering temperature in the step (4) is 400 ℃, 500 ℃ and 600 ℃ respectively.

Testing of the properties of the zinc oxide ceramics:

1. measurement of ultraviolet diffuse reflectance spectrum:

the light absorption of all samples was measured and recorded by an ultraviolet diffuse reflectance spectrometer (Shimadzu UV 2550 UV-vis spectrometer), and the results are shown in fig. 4, 5 and 7. The statistical results of the band gaps are shown in fig. 7.

2. And (3) test results:

the band gaps of the five samples of 700 deg.C, 800 deg.C, 900 deg.C, 1000 deg.C and 1100 deg.C prepared in examples 1-5 were changed from 3.20eV of the powder to 2.75eV, 2.56eV, 2.40eV, 2.31eV and 2.0eV, respectively, as shown in FIG. 5. As shown in fig. 2, the corresponding color changes to yellow-grayish yellow-yellowish gray-brownish red accordingly. As shown in FIG. 4, the absorption edge red-shifted from 387nm of the powder to 451nm, 484nm, 517nm, 537nm, and 620nm, respectively. The electron scanning photographs of the cross sections of the five samples are shown in FIG. 3, when the sintering temperature is lower than 900 ℃, a large number of voids exist in the ceramic, and the size of crystal grains is between 500nm and 1.2 μm; compared with 700 ℃, when the sintering temperature is 800 ℃, some crystal grains grow up, and the size of the crystal grains reaches about 2 mu m; at 900 ℃, the ceramic is basically and completely compact, and the size of crystal grains reaches 6-7 μm; as the size of the crystal grains of the ceramic is further increased to 10 μm and 30 μm with the increase of the temperature, the density of the ceramic is gradually increased, the concentration of oxygen vacancies is greatly increased, and after 900 ℃, the evaporation of zinc element is accelerated, the interstitial zinc entering the tetrahedron of the zinc oxide crystal lattice is greatly increased, and the color of the ceramic is gradually deepened. Examples 6 and 7 were performed in order to compare the change law of the color light absorption of ceramics under conditions of low sintering temperature and low mechanical pressure. The results are shown in fig. 6, 7 and 8.

As can be seen from FIG. 6, the color of the zinc oxide ceramic gradually changes with the increase of the calcination temperature, gradually deepens from white (400 ℃) to brown-red (1100 ℃) of the ceramic powder, and the change of the color of the ceramic under high mechanical pressure is larger, and the high mechanical pressure is more favorable for the generation of oxygen vacancies and the formation of defects by combining the change rule of the ceramic density under different pressures, as shown in FIG. 8. However, at higher temperatures, the effect of such high mechanical pressure on the densification of the ceramic is less, as shown in fig. 7, which is mainly that the volatilization of zinc element is dependent on temperature, the effect of pressure is less, but higher mechanical pressure can make the densification of the ceramic higher.

With the combination of the drawings 1-8, the preparation pressure of the zinc oxide ceramics with different colors and gradually changed light absorption can be realized within the range of 11-66Mpa, the change rule of the light absorption is obvious and controllable, and the prepared zinc oxide ceramics can stably exist in the air; the sintering temperature can be adjusted from 400 ℃ to 1100 ℃.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.