阅读说明：本技术 可逆热致变色钼酸铋粉体的制备方法 (Preparation method of reversible thermochromic bismuth molybdate powder ) 是由 张良苗 朱田莉 王安 杨俊鑫 于 2019-09-16 设计创作，主要内容包括：本发明公开了一种可逆热致变色钼酸铋粉体的制备方法,其制备方法为：将铋盐、钼盐和掺杂元素按摩尔比称取一定量置于球磨罐中,加入适量有机溶剂湿法球磨1-24h,磨好的浆料过滤,置于80-150℃烘箱中干燥2-24h,使用压片机压片；压制好的薄片放入坩埚中,于马弗炉内300-400℃进行第一阶段热处理2-10h,继续升温至500-700℃进行第二阶段热处理2-24h,最后粉碎即可分别得到α、β、γ相钼酸铋热致变色粉体。本发明操作简单,易于工业化,所制备的钼酸铋粉体可以在不同温度下显示不同颜色,有希望用于温度识别指示或高温预警；同时粉体颜色变化随温度具有可逆性,可长期循环使用。(The invention discloses a preparation method of reversible thermochromic bismuth molybdate powder, which comprises the steps of weighing a certain amount of bismuth salt, molybdenum salt and doping elements according to a molar ratio, placing the bismuth salt, the molybdenum salt and the doping elements into a ball milling tank, adding a proper amount of organic solvent for wet ball milling for 1-24 hours, filtering the milled slurry, placing the slurry into an oven at 80-150 ℃ for drying for 2-24 hours, tabletting by using a tablet press, placing the pressed slices into a crucible, carrying out first-stage heat treatment for 2-10 hours at 300-400 ℃ in a muffle furnace, continuing to heat to 500-700 ℃ for second-stage heat treatment for 2-24 hours, and finally crushing to obtain α, β and gamma-phase bismuth molybdate thermochromic powder.)

1. A preparation method of reversible thermochromic bismuth molybdate powder is characterized by comprising the following steps:

a. mixing bismuth salt and molybdenum salt according to a molar ratio of 2: (1-6) weighing a certain amount of bismuth salt and molybdenum salt according to the proportion, then placing the bismuth salt and the molybdenum salt together in a ball milling tank for ball milling and mixing, and controlling the molar ratio of the doping elements to the bismuth to be 0-0.7 to obtain a mixed raw material;

b. adding an organic solvent into a ball milling tank, mixing the organic solvent with the mixed raw material prepared in the step a to obtain a wet material, controlling the filling ratio of the ball milling tank calculated according to the volume to be 60-80%, adding agate balls into the ball milling tank, and performing wet ball milling for 1-24 hours by using a ball mill to obtain mixed slurry;

c. b, filtering the mixed slurry ground in the step b, placing the intercepted solid in an oven at the temperature of 80-150 ℃ for drying for 2-24h, and then tabletting the solid by using a tabletting machine to obtain a flake material;

d. and c, placing the slices pressed in the step c into a crucible, placing the slices into a muffle furnace, performing low-temperature heat treatment for 2-10h at the first stage at the temperature of 300-400 ℃, continuously heating to the temperature of 500-700 ℃, performing solid-phase reaction heat treatment for 2-24h at the second stage, and crushing the generated solid-phase product to obtain α, β or gamma-phase bismuth molybdate thermochromic powder.

2. The method for preparing the reversible thermochromic bismuth molybdate powder of claim 1, comprising the following steps:

a. weighing a certain amount of bismuth salt and molybdenum salt according to the molar ratio of 1:3, 1:1 or 1:2 respectively, then placing the bismuth salt and the molybdenum salt together in a ball milling tank for ball milling and mixing, and controlling the molar ratio of the doping elements to bismuth to be 0-0.7 to obtain a mixed raw material;

b. adding an organic solvent into a ball milling tank, mixing the organic solvent with the mixed raw material prepared in the step a, controlling the filling ratio of the ball milling tank calculated according to the volume to be 60-80%, adding agate balls into the ball milling tank, and performing wet ball milling for 1-24 hours by using a ball mill to obtain mixed slurry;

c. b, filtering the mixed slurry ground in the step b, placing the intercepted solid in an oven at the temperature of 80-150 ℃ for drying for 2-24h, and then tabletting the solid by using a tabletting machine to obtain a flake material;

d. and c, placing the slices pressed in the step c into a crucible, placing the slices into a muffle furnace, performing low-temperature heat treatment for 2-10h at the first stage at the temperature of 300-400 ℃, continuously heating to the temperature of 500-650 ℃, performing solid-phase reaction heat treatment for 2-24h at the second stage, and crushing the generated solid-phase product to respectively obtain α, β or gamma-phase bismuth molybdate thermochromic powder.

3. The method for preparing the reversibly thermochromic bismuth molybdate powder of claim 1, wherein: in the step a, the bismuth salt is any one salt or a mixed salt of any combination of bismuth oxide, bismuth nitrate, bismuth sulfate and bismuth chloride.

4. The method for preparing the reversibly thermochromic bismuth molybdate powder of claim 1, wherein: in the step a, the molybdenum salt is any one salt or a mixed salt of any combination of molybdenum oxide, molybdenum nitrate, molybdenum sulfate, molybdenum chloride and ammonium molybdate.

5. The method for preparing the reversibly thermochromic bismuth molybdate powder of claim 1, wherein: in the step a, the doping element is any one salt or a mixed salt of any combination of several salts of tungsten, iron, magnesium, calcium, vanadium, copper, manganese, nickel and zinc.

6. The method for preparing the reversibly thermochromic bismuth molybdate powder of claim 1, wherein: in the step a, if the doping element is X, the doping amount of the doping element calculated by molar ratio is X% ═ X/(X + Bi), where Bi is bismuth.

7. The method for preparing the reversibly thermochromic bismuth molybdate powder of claim 1, wherein: in the step b, the organic solvent is any one solvent or a mixture of at least several solvents selected from ethanol, ethylene glycol, n-butanol and acetone.

8. The method for preparing the reversibly thermochromic bismuth molybdate powder of claim 1, wherein: in the step b, the wet material ratio is carried out according to the proportion that 0.005mol of bismuth salt in the mixed raw material prepared in the step a is added with not less than 20ml of organic solvent.

9. The method for preparing the reversibly thermochromic bismuth molybdate powder of claim 1, wherein: in the step c, the drying temperature is 100-120 ℃, and the drying time is 5-16 h.

10. The method for preparing the reversibly thermochromic bismuth molybdate powder of claim 1, wherein: in the step d, the low-temperature heat treatment of the first stage is carried out at 350-400 ℃ for 4-6 h; the temperature is continuously increased to 600 ℃ and 700 ℃, and the second stage solid phase reaction heat treatment is carried out for 3-20 h.

Technical Field

The invention relates to a preparation method of a thermosensitive or thermosensitive material, in particular to a preparation method of a thermochromic material, which is applied to the technical field of preparation of inorganic functional materials.

Background

Thermochromic materials are materials that change color when heated to measure or indicate the surface of an objectSpecial temperature indicating materials for temperature and temperature distribution are also commonly referred to as heat-sensitive or temperature-sensitive materials. The thermochromic material is widely applied, such as being used as color-changing paper and color-changing ink to realize anti-counterfeiting marks; the coating is used as a thermochromic glass coating to realize building energy conservation; the device is used for detecting the overheating temperature of machine parts, such as an overtemperature alarm of a chemical reaction kettle, a petroleum cracking kettle and the like; can be used for daily articles such as color-changing clothes and color-changing plastics. The thermochromic material is mainly prepared from organic substances such as spiro, dianthrone, Schiff bases, fluoresceins and triphenylmethane color-changing microcapsules, and inorganic metal oxides such as Bi₂O₃、V₂O₅、MoO₃、Sm₃Fe₅O₁₂And the like. Although the organic color-changing material has bright color and more color change, the organic color-changing material is difficult to bear the high temperature of more than 200 ℃, is easy to age or decompose, loses the color-changing property, has poor light resistance, and can fade and lose efficacy quickly under the strong sunshine. Inorganic metal oxides are high temperature resistant and have good color change reversibility, so that development of non-toxic high temperature resistant inorganic thermochromic materials is imperative.

Bismuth molybdate is widely used as a common inorganic functional material, such as a photocatalyst, a gas sensor, an ion conductor and the like, and the crystal structure of bismuth molybdate at different temperatures is controversial, wherein the crystal structure of bismuth molybdate at the different temperatures is reported in the literature to be a low-temperature phase (orthogonal structure) below 320 ℃, a middle phase (tetragonal structure) at 520 ℃ and a high-temperature phase (monoclinic structure) at 640 ℃, the crystal structure of bismuth molybdate is reported to be α, β and gamma three crystal phases, the crystal phase of bismuth molybdate at the low temperature (about 300 ℃) is α and gamma, and the crystal phase at the high temperature (about 500 ℃) is β₂MoO₆Single crystal generation at 260 deg.C

The irreversible phase transition gamma → gamma' occurs at 645 ℃.

Many methods for preparing bismuth molybdate are applied, and many hydrothermal methods and coprecipitation methods are applied, for example, duyong arene (university of fertilizer industry, journal of the natural science), 2012,35 and 1500, adopt a coprecipitation method, ammonium molybdate and bismuth nitrate pentahydrate are used as raw materials, α and gamma crystalline phase bismuth molybdate nano powder are prepared by reacting at 250 ℃ for 24h, and Gopinathan Sankar et al (chem. mater.2003,15,146-153) adopt a hydrothermal method, nitric acid, ammonium molybdate and bismuth nitrate pentahydrate are used as raw materials, and α and gamma crystalline phase bismuth molybdate nano powder are prepared by hydrothermal reaction at 140 ℃ for 72 h.

Disclosure of Invention

In order to solve the problems of the prior art, the invention aims to overcome the defects of the prior art and provide a preparation method of reversible thermochromic bismuth molybdate powder, which utilizes bismuth salt and molybdenum salt to control the molar ratio of bismuth atoms to molybdenum atoms, carries out wet ball milling, drying, tabletting and sintering to finally synthesize bismuth molybdate powder with different crystal phases, wherein before and after heating, the nano-micron powder with α, β and gamma three crystal phases shows obvious color change from milky color to bright yellow color.

In order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method of reversible thermochromic bismuth molybdate powder comprises the following steps:

a. mixing bismuth salt and molybdenum salt according to a molar ratio of 2: (1-6) weighing a certain amount of bismuth salt and molybdenum salt according to the proportion, then placing the bismuth salt and the molybdenum salt together in a ball milling tank for ball milling and mixing, and controlling the molar ratio of the doping elements to the bismuth to be 0-0.7 to obtain a mixed raw material;

b. adding an organic solvent into a ball milling tank, mixing the organic solvent with the mixed raw material prepared in the step a to obtain a wet material, controlling the filling ratio of the ball milling tank calculated according to the volume to be 60-80%, adding agate balls into the ball milling tank, and performing wet ball milling for 1-24 hours by using a ball mill to obtain mixed slurry;

c. b, filtering the mixed slurry ground in the step b, placing the intercepted solid in an oven at the temperature of 80-150 ℃ for drying for 2-24h, and then tabletting the solid by using a tabletting machine to obtain a flake material;

d. and c, placing the slices pressed in the step c into a crucible, placing the slices into a muffle furnace, performing low-temperature heat treatment for 2-10h at the first stage at the temperature of 300-400 ℃, continuously heating to the temperature of 500-700 ℃, performing solid-phase reaction heat treatment for 2-24h at the second stage, and crushing the generated solid-phase product to obtain α, β or gamma-phase bismuth molybdate thermochromic powder.

As a preferred technical scheme, the preparation method of the reversible thermochromic bismuth molybdate powder comprises the following steps:

a. weighing a certain amount of bismuth salt and molybdenum salt according to the molar ratio of 1:3, 1:1 or 1:2 respectively, then placing the bismuth salt and the molybdenum salt together in a ball milling tank for ball milling and mixing, and controlling the molar ratio of the doping elements to bismuth to be 0-0.7 to obtain a mixed raw material;

b. adding an organic solvent into a ball milling tank, mixing the organic solvent with the mixed raw material prepared in the step a, controlling the filling ratio of the ball milling tank calculated according to the volume to be 60-80%, adding agate balls into the ball milling tank, and performing wet ball milling for 1-24 hours by using a ball mill to obtain mixed slurry;

c. b, filtering the mixed slurry ground in the step b, placing the intercepted solid in an oven at the temperature of 80-150 ℃ for drying for 2-24h, and then tabletting the solid by using a tabletting machine to obtain a flake material;

d. and c, placing the slices pressed in the step c into a crucible, placing the slices into a muffle furnace, performing low-temperature heat treatment for 2-10h at the first stage at the temperature of 300-400 ℃, continuously heating to the temperature of 500-650 ℃, performing solid-phase reaction heat treatment for 2-24h at the second stage, and crushing the generated solid-phase product to respectively obtain α, β or gamma-phase bismuth molybdate thermochromic powder.

In the step a, the bismuth salt is preferably any one or a mixture of any two or more of bismuth oxide, bismuth nitrate, bismuth sulfate and bismuth chloride. Further preferred is bismuth oxide. Preferably, the molybdenum salt is any one salt or a mixed salt of any combination of molybdenum oxide, molybdenum nitrate, molybdenum sulfate, molybdenum chloride and ammonium molybdate. Further preferred is molybdenum oxide. Preferably, the doping element is any one salt or a mixed salt of any combination of tungsten, iron, magnesium, calcium, vanadium, copper, manganese, nickel and zinc. Further preferably any one salt or any combination of several salts of iron, vanadium and copper. When the doping element is X, the doping amount of the doping element calculated by a molar ratio is preferably X% ═ X/(X + Bi), where Bi is a bismuth element.

In the step b, the organic solvent is preferably any one solvent or a mixture of at least several solvents selected from ethanol, ethylene glycol, n-butanol and acetone. Particularly preferably, the organic solvent is any one of ethanol, ethylene glycol, n-butanol and acetone; or particularly preferably the organic solvent is a mixed solvent of ethanol and ethylene glycol, ethanol and n-butanol, ethanol and acetone, or ethylene glycol and n-butanol. The organic solvent is preferably ethanol. It is preferable to carry out the wet blending in a proportion of 0.005mol of bismuth salt in the mixed raw material prepared in the above step a to not less than 20ml of an organic solvent.

As a preferred technical scheme of the invention, in the step c, the drying temperature is preferably 100-120 ℃, and the drying time is preferably 5-16 h.

As a preferred technical scheme of the invention, in the step d, the low-temperature heat treatment of the first stage is preferably carried out at 350-400 ℃ for 4-6 h; preferably, the temperature is continuously raised to 600-700 ℃ to carry out the second-stage solid-phase reaction heat treatment for 3-20 h. The heat treatment process of the step d of the invention adopts a two-step method, wherein the first step of heat treatment at low temperature firstly removes surface adsorbed water and decomposes salts, and the second step of heat treatment is carried out in situ solid phase reaction to generate bismuth molybdate.

Compared with the prior art, the invention has the following obvious and prominent substantive characteristics and remarkable advantages:

1. the raw materials adopted by the method are non-toxic or low-toxic oxides or salts, so that the use of a large amount of acid and alkali in a liquid phase method is avoided, the environmental pollution is effectively avoided, the operation is simple, and the industrialization is easy;

2. the bismuth molybdate powder prepared by the method can display different colors at different temperatures, so that the bismuth molybdate powder is hopeful to be used for temperature identification indication or high-temperature early warning;

3. the bismuth molybdate powder prepared by the method has reversibility of color change along with temperature, and can be recycled for a long time.

Drawings

FIG. 1 is a comparative graph showing the color change of α -phase bismuth molybdate powder prepared by the method of the embodiment of the invention at 25-500 ℃ along with the temperature rise.

FIG. 2 is a graph of a visible reflectance spectrum of α -phase bismuth molybdate powder prepared by the method of the embodiment of the invention at a temperature of 175-300 ℃ along with a temperature rise.

FIG. 3 is a comparison graph of the color change of β -phase bismuth molybdate powder prepared by the second method of the present invention at 25-500 ℃ with the temperature increase.

FIG. 4 is a graph showing the color change of the gamma-phase bismuth molybdate powder prepared by the third method in the embodiment of the invention at 25-500 ℃ along with the temperature rise.

FIG. 5 is a comparison graph of colors of α phase bismuth molybdate powder doped with different metal elements prepared by the tetragonal method of the embodiment of the invention at 25 ℃ and 500 ℃.

Detailed Description

The above-described scheme is further illustrated below with reference to specific embodiments, which are detailed below: