Method for adjusting band gap and / or color of metal oxide

Abstract

The invention provides a method for adjusting the band gap and / or color of a metal oxide. The method comprises the following steps: carrying out ball milling treatment on a metal oxide raw material to obtain a metal oxide product rich in lattice defect, preferably rich in oxygen vacancy; wherein the metal oxide raw material comprises one or more of a rare earth metal oxide and a titanium metal oxide. The method disclosed by the invention is simple to operate and mild in condition, and the product has the characteristics of adjustable band gap and color and is suitable for industrial large-scale production. In addition, the invention also provides a metal oxide rich in lattice defects.

Description

Technical Field

[0001] The present invention relates to the technical field of nanomaterials, and particularly relates to a ball milling method for adjusting the band gap and / or color of metal oxides. Background Art

[0002] Materials such as rare earth oxides and titanium group oxides are important inorganic functional materials. They exhibit extremely high application potential and value in many important fields such as photocatalysis, thermal catalysis, electrocatalysis, luminescent materials, and chemical mechanical polishing materials. However, these oxide materials usually appear white or light-colored close to white, with weak absorption of visible light, indicating that these materials have relatively wide optical and electronic band gaps. The band gap is highly correlated with the physical and chemical properties of the material such as the carrier migration rate, fluorescence properties, electron excitation and transition ability, conductivity, and catalytic activity. Therefore, the controllable adjustment of the band gap, especially the controllable synthesis of narrow-band gap and dark-colored rare earth oxides / titanium group oxides, is particularly important for the development of high-performance rare earth functional materials and titanium group metal functional materials.

[0003] Among them, the solid defect structure represented by oxygen vacancies and its accompanying behaviors such as metal valence state transformation, lattice distortion, and local disorder directly affect the above properties of the material. Therefore, controllably creating defect structures, understanding the nature of defect structures, especially revealing the abnormal physical and chemical properties that materials may exhibit at high / very high defect concentrations is particularly important for the development of high-performance rare earth functional materials and titanium group metal functional materials and for promoting the development of many basic research and application fields.

[0004] For band gap adjustment, a large number of past technologies mainly used doping and other means, which usually introduced impurities, affected the purity of the material, and had limited regulation, and the methods were difficult to industrialize and scale up. Since the first preparation and discovery of black titanium dioxide material by high-pressure hydrogen reduction method in 2011, methods such as laser irradiation and chemical reduction have been developed to synthesize black titanium dioxide. However, on the one hand, these methods still have problems such as weak industrial foundation, difficulty in large-scale preparation, non-uniform products, harsh conditions, high energy consumption, and large pollution. On the other hand, related research has not extended to other similar variable-valence oxides, such as variable-valence rare earth oxides. Summary of the Invention

[0005] In order to solve one of the above technical problems existing in the prior art, the present invention provides a method for adjusting the band gap and / or color of metal oxides by introducing lattice defects through a ball milling process. The method of the present invention can controllably introduce lattice defects such as oxygen vacancies into metal oxide raw materials through mechanical force, and regulate the band gap and / or color of metal oxide materials, with advantages such as good industrial foundation, good large-scale production capacity, uniform products, and high synthesis efficiency.

[0006] The first aspect of the present invention provides a method for adjusting the band gap and / or color of a metal oxide, comprising the following steps:

[0007] Ball-mill the metal oxide raw material to obtain a metal oxide product rich in lattice defects, preferably rich in oxygen vacancies; wherein the metal oxide raw material includes one or more of rare earth metal oxides and titanium group metal oxides.

[0008] According to some embodiments of the present invention, the ball-milling treatment is carried out under vacuum conditions. In some embodiments, the ball-milling treatment is carried out at a pressure of 0.1 kPa to 10 kPa, such as 0.1 kPa, 0.2 kPa, 0.5 kPa, 0.8 kPa, 1.0 kPa, 1.2 kPa, 1.5 kPa, 2 kPa, 5 kPa, 8 kPa, 10 kPa. In some embodiments, the ball-milling treatment is carried out at a pressure of 0.2 kPa to 5 kPa. In some embodiments, the ball-milling treatment is carried out at a pressure of 0.5 kPa to 2 kPa. In some embodiments, the ball-milling treatment is carried out at a pressure of 0.8 kPa to 1.2 kPa. In some embodiments, the degree of vacuum of the vacuum conditions is -90 kPa to -100 kPa, such as -90 kPa, -92 kPa, -95 kPa, -98 kPa, -100 kPa or any value therebetween. The present application does not make special limitations on the degree of vacuum during the ball-milling treatment. Those skilled in the art can obtain a metal oxide product rich in lattice defects by adjusting the degree of vacuum, ball-milling speed, ball-milling time, etc. For example, when the degree of vacuum is low, a metal oxide product rich in lattice defects can be obtained by appropriately increasing the ball-milling speed and / or ball-milling time. In addition, the controllable adjustment of the band gap and / or color of the metal oxide can be achieved by adjusting the ball-milling conditions.

[0009] According to some embodiments of the present invention, the ball-milling treatment is carried out in a ball mill, and the revolution speed of the ball mill is 100 to 600 revolutions per minute, such as 100 revolutions per minute, 200 revolutions per minute, 300 revolutions per minute, 400 revolutions per minute, 500 revolutions per minute, 600 revolutions per minute or any value therebetween. In some embodiments, the revolution speed of the ball mill is 200 to 600 revolutions per minute. In some embodiments, the revolution speed of the ball mill is 300 to 500 revolutions per minute. In some embodiments, the rotation speed of the ball mill is 1.5 to 2.5 times the revolution speed, such as 1.5, 1.8, 2.0, 2.2 or 2.5 times.

[0010] According to some embodiments of the present invention, the time of the ball milling treatment is more than 1 hour. In some embodiments, the time of the ball milling treatment is 1 to 1000 hours, such as 1 hour, 3 hours, 5 hours, 7 hours, 10 hours, 20 hours, 30 hours, 50 hours, 70 hours, 100 hours, 120 hours, 150 hours, 200 hours, 300 hours, 400 hours, 500 hours, 600 hours, 700 hours, 800 hours, 900 hours, 1000 hours or any value therebetween. In some embodiments, the time of the ball milling treatment is 1 to 100 hours. In some embodiments, the time of the ball milling treatment is 50 to 300 hours.

[0011] According to some embodiments of the present invention, the color of the metal oxide raw material is white, yellow, blue or pink.

[0012] According to some embodiments of the present invention, the color of the metal oxide product rich in lattice defects is yellow, gray, blue - gray, blue, gray - black, brown, brown - gray, brown, brown - black or black.

[0013] According to some embodiments of the present invention, the color of the metal oxide raw material is white, light yellow or light pink, and the color of the metal oxide product rich in lattice defects is dark yellow, dark gray, blue - gray, dark blue, dark gray - black, brown, brown - gray, brown, brown - black or black.

[0014] According to some embodiments of the present invention, the rare earth metal includes one or more of cerium, neodymium, samarium, europium, dysprosium, holmium, thulium, ytterbium.

[0015] According to some embodiments of the present invention, the titanium group metal includes titanium and / or zirconium.

[0016] According to some embodiments of the present invention, the metal oxide raw material includes one or more of cerium dioxide, neodymium sesquioxide, samarium sesquioxide, europium sesquioxide, dysprosium sesquioxide, holmium sesquioxide, thulium sesquioxide, ytterbium sesquioxide, cerium - zirconium - oxygen solid solution, titanium dioxide and zirconium dioxide.

[0017] According to some embodiments of the present invention, the titanium dioxide includes rutile - type titanium dioxide and anatase - type titanium dioxide.

[0018] According to some embodiments of the present invention, the metal oxide raw material includes white or slightly light - yellow cerium dioxide and / or white titanium dioxide (such as anatase - type titanium dioxide), and the metal oxide product rich in lattice defects includes dark - colored (such as dark - gray) cerium dioxide and / or dark - colored (such as dark - gray) titanium dioxide (such as anatase - type titanium dioxide).

[0019] According to some embodiments of the present invention, the metal oxide raw material includes one or more of ytterbium sesquioxide that is white or slightly light greenish - white, thulium sesquioxide that is white or slightly light greenish - white, dysprosium sesquioxide that is white or slightly light yellowish - white, and holmium sesquioxide that is light yellowish - brown, and the metal oxide product rich in lattice defects includes one or more of ytterbium sesquioxide that is dark brown, thulium sesquioxide that is dark brown, dysprosium sesquioxide that is dark brown, and holmium sesquioxide that is dark brown.

[0020] According to some embodiments of the present invention, the metal oxide raw material includes neodymium sesquioxide that is light blue, and the metal oxide product rich in lattice defects includes neodymium sesquioxide that is grey.

[0021] According to some embodiments of the present invention, the metal oxide raw material includes cerium - zirconium - oxygen solid solution that is white and / or zirconia that is white, and the metal oxide product rich in lattice defects includes cerium - zirconium - oxygen solid solution that is tan and / or zirconia that is tan.

[0022] According to some embodiments of the present invention, the metal oxide raw material includes titanium dioxide that is white (such as rutile - type titanium dioxide), and the metal oxide product rich in lattice defects includes titanium dioxide that is blue - grey (such as dark blue - grey) (such as rutile - type titanium dioxide).

[0023] According to some embodiments of the present invention, the metal oxide raw material includes one or more of samarium sesquioxide that is light yellow and europium sesquioxide that is light pink, and the metal oxide product rich in lattice defects includes at least one of samarium sesquioxide that is yellow (such as dark yellow) and europium sesquioxide that is yellow (such as dark yellow).

[0024] According to some embodiments of the present invention, the ball - milling treatment is carried out in a nylon - lined vacuum ball - milling container. In the present invention, the material of the vacuum ball - milling container includes, but is not limited to: nylon lining, zirconia lining, polytetrafluoroethylene lining, agate lining, silicon nitride lining, tungsten carbide lining, etc.

[0025] According to some embodiments of the present invention, the ball milling treatment is carried out in the presence of a ball milling medium. In some embodiments, the material of the ball milling medium is zirconia, agate, silicon nitride or tungsten carbide. In some embodiments, the ball milling medium is selected from one or more combinations of zirconia grinding balls with a diameter of 6-20 mm. In some embodiments, the ball milling medium is selected from the combination of zirconia grinding balls with a diameter of 5-8 mm and zirconia grinding balls with a diameter of 9-15 mm. In some embodiments, the mass ratio of the zirconia grinding balls with a diameter of 5-8 mm to the zirconia grinding balls with a diameter of 9-15 mm is (2-3):1. In some embodiments, the mass of the ball milling medium is 1-20 times, preferably 5-10 times, the total mass of the metal oxide raw materials.

[0026] According to some embodiments of the present invention, the ball milling treatment is carried out in a protective atmosphere. In some embodiments, the protective atmosphere includes at least one of nitrogen, helium and argon.

[0027] By the method of the present invention, it can be realized that after ball milling, cerium dioxide and titanium dioxide (anatase type) change from white to dark gray; ytterbium sesquioxide and thulium sesquioxide change from white or slightly light greenish white to brownish or dark brown; dysprosium sesquioxide and holmium sesquioxide change from white or slightly light yellowish white to brownish or dark brown; cerium zirconium oxide solid solution and zirconia change from white to brownish or dark brown; titanium dioxide (rutile type) changes from white to dark blue gray; samarium sesquioxide and europium sesquioxide change from light yellow or light pink to dark yellow; neodymium sesquioxide changes from light blue to gray.

[0028] The second aspect of the present invention provides a metal oxide rich in lattice defects, and the color of the metal oxide rich in lattice defects is yellow, gray, blue gray, blue, gray black, brown, brown gray, brown, brownish or black; the metal includes rare earth metals and / or titanium group metals.

[0029] According to some embodiments of the present invention, the metal includes one or more of cerium, neodymium, samarium, europium, dysprosium, holmium, thulium, ytterbium, titanium and zirconium.

[0030] According to some embodiments of the present invention, the metal oxide includes one or more of cerium dioxide, neodymium sesquioxide, samarium sesquioxide, europium sesquioxide, dysprosium sesquioxide, holmium sesquioxide, thulium sesquioxide, ytterbium sesquioxide, cerium zirconium oxide solid solution, titanium dioxide and zirconia.

[0031] According to some embodiments of the present invention, the metal oxide rich in lattice defects includes one or more of cerium dioxide in gray, neodymium sesquioxide in gray, samarium sesquioxide in yellow, europium sesquioxide in yellow, dysprosium sesquioxide in brown, holmium sesquioxide in brown, thulium sesquioxide in brown, ytterbium sesquioxide in brown, cerium-zirconium-oxygen solid solution in brown, zirconium dioxide in brown, rutile titanium dioxide in blue-gray, and anatase titanium dioxide in gray;

[0032] According to some embodiments of the present invention, the metal oxide rich in lattice defects includes one or more of cerium dioxide in dark gray, neodymium sesquioxide in dark gray, samarium sesquioxide in dark yellow, europium sesquioxide in dark yellow, dysprosium sesquioxide in dark brown, holmium sesquioxide in dark brown, thulium sesquioxide in dark brown, ytterbium sesquioxide in dark brown, cerium-zirconium-oxygen solid solution in dark brown, zirconium dioxide in dark brown, rutile titanium dioxide in dark blue-gray, and anatase titanium dioxide in dark gray

[0033] According to some embodiments of the present invention, the metal oxide rich in lattice defects is prepared by the method described in the first aspect.

[0034] In some embodiments, the metal oxide rich in lattice defects is cerium dioxide in dark gray. In some embodiments, the band gap value of the cerium dioxide in dark gray is not higher than 3.0 eV, preferably 1.8 eV to 3.0 eV, more preferably 1.8 eV to 2.5 eV.

[0035] In some embodiments, the metal oxide rich in lattice defects is rutile titanium dioxide in blue-gray. In some embodiments, the band gap value of the rutile titanium dioxide in blue-gray is not higher than 3.0 eV, preferably 2.2 eV to 2.8 eV.

[0036] The third aspect of the present invention provides the application of the metal oxide rich in lattice defects obtained by the method described in the first aspect or the metal oxide rich in lattice defects described in the second aspect in photocatalysis, thermal catalysis, luminescent materials, and magnetic materials.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] 1. The present invention realizes the preparation of dark rare earth oxides and dark titanium group metal oxides (such as dark cerium oxide, titanium oxide, ytterbium oxide, thulium oxide, etc.) through the ball milling method. At the same time, the controllable adjustment of structural parameters such as lattice defects and band gaps of the materials can be achieved by adjusting the ball milling conditions (such as ball milling speed and ball milling time), and the process is simple and suitable for industrial application.

[0039] 2. The present invention provides dark rare earth metal oxides and dark titanium group metal oxides, such as dark gray cerium oxide, dark gray and dark blue-gray titanium oxide, dark gray neodymium sesquioxide, dark yellow samarium sesquioxide and europium sesquioxide, dark brown dysprosium sesquioxide, holmium sesquioxide, thulium sesquioxide and ytterbium sesquioxide, dark brown cerium-zirconium-oxygen solid solution, especially dark rare earth oxides such as dark ytterbium oxide and thulium oxide, which are reported for the first time. Description of the Drawings

[0040] Figure 1 It is a photograph of cerium dioxide samples with different colors prepared in Example 1.

[0041] Figure 2 It is an XRD pattern of the cerium dioxide sample prepared in Example 1.

[0042] Figure 3 It is a UV-vis diagram of the cerium dioxide sample prepared in Example 1.

[0043] Figure 4 It is a fluorescence spectrum of the cerium dioxide sample prepared in Example 1.

[0044] Figure 5 It is a TEM image of the cerium dioxide sample prepared in Example 1.

[0045] Figure 6 It is a band gap value diagram of the cerium dioxide sample prepared in Example 1.

[0046] Figure 7 It is a surface oxygen vacancy content characterization diagram of the cerium dioxide sample prepared in Example 1.

[0047] Figure 8 It is a bulk oxygen vacancy content characterization diagram of the cerium dioxide sample prepared in Example 1.

[0048] Figure 9 It is a photograph of titanium dioxide samples with different colors prepared in Example 2.

[0049] Figure 10 It is an XRD pattern of the titanium dioxide sample prepared in Example 2.

[0050] Figure 11 It is a UV-vis diagram of the titanium dioxide sample prepared in Example 2.

[0051] Figure 12 It is a band gap value diagram of the titanium dioxide sample prepared in Example 2.

[0052] Figure 13 It is a photograph of the titanium dioxide sample prepared in Example 3.

[0053] Figure 14It is a photo of the thulium oxide sample prepared in Example 4.

[0054] Figure 15 It is a photo of the ytterbium oxide sample prepared in Example 4.

[0055] Figure 16 It is a photo of the samarium oxide sample prepared in Example 5.

[0056] Figure 17 It is a photo of the europium oxide sample prepared in Example 5.

[0057] Figure 18 It is a photo of the dysprosium oxide sample prepared in Example 6.

[0058] Figure 19 It is a photo of the holmium oxide sample prepared in Example 6.

[0059] Figure 20 It is a photo of the neodymium oxide sample prepared in Example 7.

[0060] Figure 21 It is a photo of the zirconium oxide sample prepared in Example 8.

[0061] Figure 22 It is a photo of the cerium oxide sample prepared in Example 9.

[0062] Figure 23 It is a photo of the cerium oxide sample prepared in Comparative Example 1.

[0063] Figure 24 It is a photo of the cerium oxide sample prepared in Comparative Example 2. Detailed implementation manners

[0064] To make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below in conjunction with embodiments and the accompanying drawings. The specific embodiments described herein are only used to explain the present invention and do not constitute any limitation to the present invention.

[0065] Unless otherwise specified, the experimental methods used in the present invention are all conventional methods; the raw materials, reagents, instruments, etc. used, unless otherwise specified, can all be obtained through commercial channels.

[0066] The term "lattice defect" used herein refers to a region where the microscopic atomic arrangement of a substance is affected by crystal formation conditions, atomic thermal motion, impurity filling and other conditions, resulting in a structure deviating from the ideal crystal structure.

[0067] Preparation of cerium dioxide powder with controllable color and band gap within the range from white to dark gray in Example 1

[0068] Weigh 40 g of white cerium dioxide reagent powder into a 250 mL vacuum stainless steel ball milling jar with a nylon lining. Add 280 g of zirconia grinding balls with a diameter of 6 mm and 120 g of zirconia grinding balls with a diameter of 10 mm. Seal it in a glove box under an argon atmosphere, and then evacuate until the pressure in the ball milling jar is 1 kPa (vacuum degree -100 kPa). Fix the ball milling jar on a planetary ball mill, set the rotation speed of self-rotation to 800 revolutions per minute, and the revolution speed to 400 revolutions per minute. The operation mode is one-way intermittent operation, that is, fix the rotation direction. Every 30 minutes of operation, stop for 30 minutes to fully dissipate heat and protect the ball mill. Collect samples after ball milling for different times, and cerium dioxide nanoparticles with different degrees of gray can be obtained.

[0069] The photographs of the cerium dioxide nanoparticles prepared in Example 1 and the test analysis results of X-ray diffraction spectrum (XRD), ultraviolet-visible absorption spectrum (UV-vis), fluorescence spectrum (Raman), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), and synchrotron radiation X-ray absorption spectrum (XAS) are as Figures 1 to 8 shown.

[0070] Figure 1 shows the color change of the samples after different ball milling times. From Figure 1 it can be seen that after ball milling for 1 h, the sample can be changed from white to gray, and with the extension of the ball milling time, the gray of the sample gradually deepens. Figure 2 is the XRD pattern of the samples after different ball milling times. All the diffraction peaks of the samples in this pattern correspond to the standard diffraction data of cerium dioxide. However, with the increase of the ball milling time, the full width at half maximum of each diffraction peak increases and the peak intensity weakens, indicating an increase in lattice defects. Figure 3 is the UV-vis pattern of the samples after different ball milling times. The results show that the absorption of the samples after ball milling in the visible band increases, and at the same time, the band gap changes. Figure 4 is the fluorescence pattern of the samples after different ball milling times. The results show that the fluorescence intensity of the samples and optical properties such as excitation and emission wavelengths change. Figure 5 is the TEM pattern of the samples after ball milling for different times. Figure a is the TEM pattern of the non-ball milled sample with a particle size of about 500 - 600 nm. Figures b to d are the TEM patterns of the samples after ball milling for 1 h, 10 h, and 100 h respectively. It can be seen that the particle size gradually decreases after ball milling, and the sample particles are gradually broken. After 100 h, the sample shows a nanoparticle morphology of 5 - 20 nm, and clear lattice fringes can be observed in Figures e and f, proving that the material particles still maintain good crystallinity. Figure 6 is the band gap value of the samples after different ball milling times. It can be seen that when ball milling for 1 - 1000 h, the band gap value is lower than that of the sample before ball milling, and the band gap value is the lowest when ball milling for 300 h. Figure 7XPS spectra of samples with different ball milling times and the fitted surface Ce 3+ / Ce 4+ ratio, the average valence state of the corresponding Ce, and the corresponding oxygen vacancy concentration and content. Figure a is the XPS spectrum of commercial cerium dioxide, which has a total of 10 peaks. The peaks corresponding to the blue curve are Ce 4+ corresponding peaks, and the peaks corresponding to the green curve are Ce 3+ corresponding peaks. Figure b is the XPS spectra of all samples. It can be seen that as the ball milling time prolongs, the intensity of the Ce 3+ corresponding peak at about 886 eV shows an obvious increase, indicating an increase in the Ce 3+ content on the material surface and the oxygen vacancy concentration. Figure c gives the specific calculation results. The left axis corresponds to the molar ratio of Ce 3+ on the material surface calculated by XPS to the total amount of Ce, and the right axis corresponds to the concentration of oxygen vacancies on the material surface with the red curve. As the ball milling time prolongs, the oxygen vacancy concentration on the material surface generally shows an increasing trend and becomes stable after 100 hours. Figure 8 XAS spectra of samples with different ball milling times and the fitted average valence state of bulk Ce and the corresponding oxygen vacancy concentration and content. Figure a is the XAS spectra of samples with different ball milling times, Figure b is the average valence state of Ce in the material bulk calculated, and Figure c is the oxygen vacancy content and concentration in the corresponding material bulk. From Figure 8 it can be seen that as the ball milling time prolongs, the oxygen vacancy content and concentration in the material bulk generally show an increasing trend and reach the maximum value at 300 hours.

[0071] Example 2 Preparation of Titanium Dioxide Powder with Controllable Color and Band Gap in the Range from White to Dark Blue-Grey

[0072] The difference from Example 1 is that: "40 g of white cerium dioxide reagent powder" is replaced with "40 g of white rutile titanium dioxide reagent powder".

[0073] Photographs of the titanium dioxide nanoparticles prepared in Example 2 and the characterization results of X-ray diffraction spectrum (XRD) and ultraviolet-visible absorption spectrum (UV-vis) are as Figures 9 to 11 shown.

[0074] Figure 9 shows the color changes of the samples after different ball milling times. From Figure 9 it can be seen that as the ball milling time prolongs, the samples first change from white to grey, and then the color changes to blue-grey. Figure 10 XRD patterns of samples with different ball milling times. All the diffraction peaks in the patterns correspond to the standard diffraction data of titanium dioxide. However, as the ball milling time increases, the full width at half maximum of each diffraction peak increases and the peak intensity weakens, indicating an increase in lattice defects. Figure 11UV-vis diagrams of samples with different ball-milling times. The results show that the light absorption of the samples after ball-milling increases in the visible band, and the band gap changes. Figure 12 Band gap values of samples with different ball-milling times. It can be seen that as the ball-milling time increases, the optical band gap of the material generally shows a decreasing trend.

[0075] Preparation of titanium dioxide powder with controllable color and band gap in the range from white to dark gray in Example 3

[0076] The difference from Example 1 is that "40 g of white cerium dioxide reagent powder" is replaced by "40 g of white anatase titanium dioxide reagent powder".

[0077] The color changes of the samples after different ball-milling times are as Figure 13 shown.

[0078] Preparation of ytterbium oxide and thulium oxide powder with controllable color and band gap in the range from white to dark brown in Example 4

[0079] 1. The difference from Example 1 is that "40 g of white cerium dioxide reagent powder" is replaced by "40 g of white thulium oxide reagent powder". The color changes of the samples after different ball-milling times are as Figure 14 shown.

[0080] 2. The difference from Example 1 is that "40 g of white cerium dioxide reagent powder" is replaced by "40 g of white ytterbium oxide reagent powder". The color changes of the samples after different ball-milling times are as Figure 15 shown.

[0081] Preparation of europium oxide and samarium oxide powder with controllable color and band gap in the range from white to dark brown in Example 5

[0082] 1. The difference from Example 1 is that "40 g of white cerium dioxide reagent powder" is replaced by "40 g of white samarium oxide reagent powder." The color changes of the samples after different ball-milling times are as Figure 16 shown.

[0083] 2. The difference from Example 1 is that "40 g of white cerium dioxide reagent powder" is replaced by "40 g of white europium oxide reagent powder." The color changes of the samples after different ball-milling times are as Figure 17 shown.

[0084] Preparation of dysprosium oxide and holmium oxide powder with controllable color and band gap in the range from white or light yellow to dark brown in Example 6

[0085] 1. The difference from Example 1 is that "40 g of white cerium dioxide reagent powder" is replaced by "40 g of white dysprosium oxide reagent powder", and the color changes of the samples after ball-milling for 100 hours are as Figure 18 shown.

[0086] 2. The difference from Example 1 is that "40 g of white cerium dioxide reagent powder" is replaced with "40 g of pale yellow holmium oxide reagent powder", and the color change of the sample after ball milling for 100 hours is as Figure 19 shown.

[0087] Preparation of neodymium oxide powder with controllable color and band gap in the range of blue to gray in Example 7

[0088] The difference from Example 1 is that: "40 g of white cerium dioxide reagent powder" is replaced with "40 g of white neodymium oxide powder", and the color change of the sample after ball milling for 100 hours is as Figure 20 shown.

[0089] Preparation of zirconium oxide powder with controllable color and band gap in the range of white to dark brown in Example 8

[0090] The difference from Example 1 is that: "40 g of white cerium dioxide reagent powder" is replaced with "40 g of white zirconium dioxide reagent powder", and the color change of the sample after ball milling for 100 hours is as Figure 21 shown.

[0091] Preparation of cerium dioxide powder with controllable color and band gap in the range of white to dark gray in Example 9

[0092] 1. The difference from Example 1 is that the ball milling speed is adjusted to: the rotation speed is 400 revolutions per minute and the revolution speed is 200 revolutions per minute. The color change of the sample after ball milling for 1 hour is as shown in Figure A in Figure 22 , and the color change of the sample after ball milling for 10 hours is as shown in Figure C in Figure 22 .

[0093] 2. The difference from Example 1 is that the ball milling speed is adjusted to: the rotation speed is 600 revolutions per minute and the revolution speed is 300 revolutions per minute. The color change of the sample after ball milling for 1 hour is as shown in Figure A in Figure 22 , and the color change of the sample after ball milling for 10 hours is as shown in Figure C in Figure 22 .

[0094] 3. The difference from Example 1 is that "280 g of zirconia grinding balls with a diameter of 6 mm and 120 g of zirconia grinding balls with a diameter of 10 mm" is replaced with "28 g of zirconia grinding balls with a diameter of 6 mm and 12 g of zirconia grinding balls with a diameter of 10 mm", that is, the mass ratio of the ball milling raw material to the ball milling medium is 1:1, and the color change of the sample after ball milling for 1 hour is as shown in Figure B in Figure 22 .

[0095] 4. The difference from Example 1 is that "280 g of zirconia grinding balls with a diameter of 6 mm and 120 g of zirconia grinding balls with a diameter of 10 mm" is replaced by "140 g of zirconia grinding balls with a diameter of 6 mm and 60 g of zirconia grinding balls with a diameter of 10 mm", that is, the mass ratio of the ball-milling raw material to the ball-milling medium is 1:5. The color change of the sample after ball-milling for 1 hour is as Figure 22 shown in Figure B of

[0096] Preparation of Cerium Dioxide Powder with Color and Band Gap Controllable within the Range from White to Brownish Yellow in Comparative Example 1

[0097] The difference from Example 1 is that: the ball-milling atmosphere is air and the air pressure is 100 kPa. Specifically,

[0098] Weigh 40 g of white cerium dioxide reagent powder into a 250-ml nylon-lined vacuum stainless steel ball-milling jar, add 280 g of zirconia grinding balls with a diameter of 6 mm and 120 g of zirconia grinding balls with a diameter of 10 mm. Assemble the ball-milling jar in air, open the valve and fill it with compressed air to 100 kPa. Fix the ball-milling jar on a planetary ball mill, set the rotation speed of self-rotation to 800 revolutions per minute and the revolution speed to 400 revolutions per minute. The operation mode is one-way intermittent operation, that is, fix the rotation direction, stop for 30 minutes every 30 minutes of operation to fully dissipate heat and protect the ball mill. Collect samples at different ball-milling times. The color change of the samples after different ball-milling times is as Figure 23 shown.

[0099] Preparation of Cerium Dioxide Powder with Color and Band Gap Controllable within the Range from White to Brownish Yellow in Comparative Example 2

[0100] The difference from Example 1 is that: the ball-milling atmosphere is oxygen and the air pressure is 100 kPa. Specifically,

[0101] Weigh 40 g of white cerium dioxide reagent powder into a 250-ml nylon-lined vacuum stainless steel ball-milling jar, add 280 g of zirconia grinding balls with a diameter of 6 mm and 120 g of zirconia grinding balls with a diameter of 10 mm. Assemble the ball-milling jar in air, open the valve to evacuate and then fill it with oxygen to 100 kPa. Repeat the operation of evacuation - filling with oxygen five times and then close the valve. Fix the ball-milling jar on a planetary ball mill, set the rotation speed of self-rotation to 800 revolutions per minute and the revolution speed to 400 revolutions per minute. The operation mode is one-way intermittent operation, that is, fix the rotation direction, stop for 30 minutes every 30 minutes of operation to fully dissipate heat and protect the ball mill. Collect samples at different ball-milling times. The color change of the samples after different ball-milling times is as Figure 24 shown.

[0102] The results of Comparative Example 1 and Comparative Example 2 show that the cerium dioxide prepared in an air or oxygen atmosphere will be yellowish or even reddish, while the cerium dioxide prepared in the oxygen-free atmosphere of Example 1 of the present application will turn gray.

[0103] The technical solution of the present invention is not limited to the limitations of the above specific embodiments. Any technical deformation made according to the technical solution of the present invention falls within the protection scope of the present invention.

Claims

1. A method for adjusting the band gap and / or color of a metal oxide, comprising the following steps: The metal oxide raw material is ball-milled to obtain a metal oxide product rich in lattice defects, preferably rich in oxygen vacancies; wherein the metal oxide raw material comprises one or more of rare earth metal oxides and titanium group metal oxides.

2. The method according to claim 1, characterized in that: The ball milling process is carried out under vacuum conditions; Preferably, the ball milling treatment is carried out at a pressure of 0.1 kPa to 10 kPa; Preferably, the ball milling treatment is carried out at a pressure of 0.2 kPa to 5 kPa; Preferably, the ball milling treatment is carried out at a pressure of 0.5 kPa to 2 kPa; Preferably, the ball milling treatment is performed under a pressure of 0.8 kPa to 1.2 kPa.

3. The method according to claim 1 or 2, characterized in that: The ball milling treatment is carried out in a ball mill, and the revolution speed of the ball mill is 100 to 600 rpm, preferably 200 to 600 rpm, more preferably 300 to 500 rpm; and / or, the rotation speed of the ball mill is 1.5 to 2.5 times the revolution speed; and / or, The ball milling treatment time is more than 1 hour; preferably 1 to 1000 hours, more preferably 10 to 100 hours.

4. The method according to any one of claims 1 to 3, characterized in that: The color of the metal oxide raw material is white, light yellow or light pink, and the color of the metal oxide product rich in lattice defects is yellow, gray, blue-gray, blue, gray-black, brown, brown-gray, brown, tan or black; Preferably, the color of the metal oxide raw material is white, light yellow or light pink, and the color of the lattice defect-rich metal oxide product is dark yellow, dark gray, blue-gray, dark blue, dark gray-black, brown, brown-gray, brown, tan or black.

5. The method according to any one of claims 1 to 4, characterized in that: The rare earth metal includes at least one of cerium, ytterbium, thulium, samarium and europium; and / or the titanium group metal includes titanium and / or zirconium; Preferably, the metal oxide raw material includes one or more of cerium dioxide, neodymium trioxide, samarium trioxide, europium trioxide, dysprosium trioxide, holmium trioxide, thulium trioxide, ytterbium trioxide, cerium-zirconium oxygen solid solution, titanium dioxide and zirconium dioxide; Preferably, the titanium dioxide includes rutile titanium dioxide and anatase titanium dioxide.

6. The method according to any one of claims 1 to 5, characterized in that: The metal oxide raw material comprises white cerium dioxide and / or white titanium dioxide such as anatase titanium dioxide, and the metal oxide product rich in lattice defects comprises gray, preferably dark gray cerium dioxide and / or gray, preferably dark gray titanium dioxide such as anatase titanium dioxide; or The metal oxide raw material includes one or more of white or white with slightly light green ytterbium trioxide, white or white with slightly light green thulium trioxide, white or white with slightly light yellow dysprosium trioxide, and light yellow holmium trioxide, and the lattice defect-rich metal oxide product includes one or more of dark brown ytterbium trioxide, dark brown thulium trioxide, dark brown dysprosium trioxide, and dark brown holmium trioxide; or The metal oxide raw material includes light blue neodymium trioxide, and the metal oxide product rich in lattice defects includes gray neodymium trioxide; or The metal oxide raw material includes a white cerium-zirconium-oxygen solid solution and / or white zirconium dioxide, and the lattice defect-rich metal oxide product includes a brown cerium-zirconium-oxygen solid solution and / or a brown zirconium dioxide; or The metal oxide raw material includes white titanium dioxide such as rutile titanium dioxide, and the lattice defect-rich metal oxide product includes bluish-grey, preferably dark bluish-grey titanium dioxide such as rutile titanium dioxide; or The metal oxide raw material includes at least one of light yellow samarium trioxide and light pink europium trioxide; the lattice defect-rich metal oxide product includes at least one of yellow, preferably dark yellow, samarium trioxide and yellow, preferably dark yellow, europium trioxide.

7. The method according to any one of claims 1 to 6, characterized in that: The ball milling treatment is carried out in the presence of ball milling media; Preferably, the ball milling medium is made of zirconium oxide, agate, silicon nitride or tungsten carbide; Preferably, the ball milling medium is selected from a combination of one or more zirconia grinding balls with a diameter of 6 to 20 mm; more preferably, the ball milling medium is selected from a combination of zirconia grinding balls with a diameter of 5 to 8 mm and zirconia grinding balls with a diameter of 9 to 15 mm; further preferably, the mass ratio of the zirconia grinding balls with a diameter of 5 to 8 mm to the zirconia grinding balls with a diameter of 9 to 15 mm is (2 to 3):1; Preferably, the mass of the ball milling medium is 1 to 20 times, more preferably 5 to 10 times, the total mass of the metal oxide raw material.

8. The method according to any one of claims 1 to 7, characterized in that: The ball milling process is carried out in a vacuum ball milling container; and / or, the ball milling process is carried out in a protective atmosphere; Preferably, the vacuum ball mill container is made of nylon lining, zirconium oxide lining, polytetrafluoroethylene lining, agate lining, silicon nitride lining or tungsten carbide lining; More preferably, the vacuum ball mill container is made of nylon lining; Preferably, the protective atmosphere comprises at least one of nitrogen, helium and argon.

9. A metal oxide rich in lattice defects, characterized in that: The color of the metal oxide rich in lattice defects is yellow, gray, blue-gray, blue, gray-black, brown, brown-gray, brown, tan or black; the metal includes rare earth metals and / or titanium group metals, preferably including one or more of cerium, neodymium, samarium, europium, dysprosium, holmium, thulium, ytterbium, titanium and zirconium; Preferably, the metal oxide includes one or more of cerium dioxide, neodymium trioxide, samarium trioxide, europium trioxide, dysprosium trioxide, holmium trioxide, thulium trioxide, ytterbium trioxide, cerium-zirconium oxygen solid solution, titanium dioxide and zirconium dioxide; Preferably, the lattice defect-rich metal oxide includes one or more of gray cerium dioxide, gray neodymium trioxide, yellow samarium trioxide, yellow europium trioxide, brown dysprosium trioxide, brown holmium trioxide, brown thulium trioxide, brown ytterbium trioxide, brown cerium-zirconium oxygen solid solution, brown zirconium dioxide, blue-gray rutile titanium dioxide, and gray anatase titanium dioxide; Preferably, the metal oxide rich in lattice defects includes one or more of dark gray cerium dioxide, dark gray neodymium trioxide, dark yellow samarium trioxide, dark yellow europium trioxide, dark brown dysprosium trioxide, dark brown holmium trioxide, dark brown thulium trioxide, dark brown ytterbium trioxide, dark brown cerium-zirconium oxygen solid solution, dark brown zirconium dioxide, dark blue-gray rutile titanium dioxide, and dark gray anatase titanium dioxide; Preferably, the band gap value of the dark grey cerium dioxide is not higher than 3.0 eV, preferably 1.8 eV to 3.0 eV, more preferably 1.8 eV to 2.5 eV; Preferably, the band gap value of the blue-gray rutile titanium dioxide is not higher than 3.0 eV, preferably 2.2 eV to 2.8 eV; Further preferably, the lattice defect-rich metal oxide is obtained by the method according to any one of claims 1-8.

10. Use of the lattice defect-rich metal oxide obtained by the method according to any one of claims 1 to 8 or the lattice defect-rich metal oxide according to claim 9 in photocatalysis, thermal catalysis, luminescent materials, and magnetic materials.

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