Barium chromate material and preparation method thereof

Abstract

The invention provides a barium chromate material and a preparation method thereof, and belongs to the technical field of energetic materials. The method includes; barium chromate is prepared by using a surfactant-free microemulsion method; wherein the surfactant-free microemulsion is a ternary system, and consists of water, ethanol and n-butyl alcohol. Compared with a traditional chemical precipitation method and a method for preparing the BaCrO4 material by adding a surfactant for regulation and control, the preparation method of the barium chromate provided by the invention does not need heating or other special condition control in the process of preparing the BaCrO4 material by using the surfactant-free microemulsion constructed by n-butyl alcohol, ethanol and water, is simple and easy to operate and low in cost, and is suitable for industrial production. And the used reagents are environment-friendly solvents, so that the method is green and environment-friendly.

Description

Technical Field

[0001] The present invention belongs to the technical field of energetic materials, and specifically relates to barium chromate or delay composition and its preparation. Background Art

[0002] Delay composition is a substance that realizes time control through a stable combustion reaction with a specific formula, and delay composition is widely used in civil fields at home and abroad. By optimizing the formula, burning rate regulator and preparation process of delay composition, the delay accuracy and burning rate stability of electric detonators can be improved. The delay accuracy refers to the accuracy of the delay time of delay composition and is an important index for evaluating the performance of delay composition.

[0003] The purity and particle size of delay composition have important effects on the burning rate, accuracy and mixing uniformity. As an important component of delay composition, the micro-nanoization and particle size control of barium chromate still face some challenges, especially in the selection and optimization of refinement methods. Microemulsion has many unique properties, such as: thermodynamic stability, isotropy, uniform size of dispersed phase droplets, large solubilization capacity, low viscosity, strong fluidity, etc. Microemulsion has been widely used in many fields due to its unique microstructure and physical and chemical properties, such as: preparation of nanomaterials, oil exploitation, fuels, daily chemicals, drug carriers, etc. In traditional microemulsions, surfactants are usually considered to be the main components constituting the interfacial film of microemulsions, and their content is generally above 10 wt%. For example, in the patent document 1 (publication number CN1923706A) published in 2007, Li et al. synthesized BaCrO 4 nanomaterials, specifically prepared dendritic BaCrO in cetyltrimethylammonium bromide (CTAB) / water / n-octane / n-butanol reverse microemulsion 4 ,this method has low reaction temperature, short reaction time, simple operation steps, high yield and good repeatability. And for the method of preparing BaCrO 4 using traditional microemulsions (SBMEs) as mentioned above, although it has been greatly improved compared with the traditional ball milling method, solid phase reaction method and polymer complex method which have disadvantages such as complex preparation process and long reaction time, it also needs to use surfactants, and after the reaction, deionized water and absolute ethanol are required for repeated washing many times to remove surfactants and co-surfactants, and these surfactants cannot be recycled and are prone to environmental pollution. In summary, problems such as the simplification of the post-reaction treatment process, cost, and environmental protection all affect the cost performance of this preparation method in actual industrial production to a certain extent. Summary of the Invention

[0004] 1. Problems to be Solved

[0005] One of the purposes of the present invention is to provide a process suitable for large-scale industrial production of barium chromate; the produced barium chromate can be used as delay composition.

[0006] 2. Technical solution

[0007] To solve the above problems, the technical solutions adopted by the present invention are as follows:

[0008] The first aspect of the present invention provides a method for preparing barium chromate, including; preparing barium chromate by surfactant-free microemulsion method;

[0009] Among them, the surfactant-free microemulsion is a ternary system and is composed of water, ethanol, and n-butanol;

[0010] Among them, the water is calculated based on the total amount of the aqueous solution containing barium salt and chromium salt, and the mass ratio of water, ethanol, and n-butanol is (2-6):(2-6):(1-5); the mass ratio of water, ethanol, and n-butanol is preferably (3-5):(3-5):(2-4); the mass ratio of water, ethanol, and n-butanol is further preferably (3.5-4.5):(3.5-4.5):(2.5-3.5);

[0011] Calculated by barium ion and chromium ion respectively, the molar ratio of the barium salt to the chromium salt is (0.5-2):1; the molar ratio of the barium salt to the chromium salt is preferably (0.5-1.5):1; the molar ratio of the barium salt to the chromium salt is further preferably (0.8-1.2):1.

[0012] According to the method for preparing barium chromate according to any one of the embodiments of the first aspect of the present invention, the surfactant-free microemulsion containing barium salt and chromium salt is subjected to stirring treatment

[0013] After the stirring treatment is completed, the product barium chromate is obtained by separation treatment.

[0014] According to the method for preparing barium chromate according to any one of the embodiments of the first aspect of the present invention, the time of the stirring treatment or the shaking treatment is 1-12 h; the time of the stirring treatment or the shaking treatment is preferably 1-10 h; the time of the stirring treatment or the shaking treatment is further preferably 1-5 h;

[0015] The temperature is 10°C to 40°C; the temperature is preferably 10°C to 35°C; the temperature is further preferably 15°C to 30°C.

[0016] According to the method for preparing barium chromate according to any one of the embodiments of the first aspect of the present invention, the steps include:

[0017] Preparing a surfactant-free microemulsion containing barium salt;

[0018] Preparing a surfactant-free microemulsion containing chromium salt;

[0019] Mix the two to obtain a surfactant-free microemulsion containing barium salt and chromium salt.

[0020] According to the method for preparing barium chromate according to any embodiment of the first aspect of the present invention, the preparation of the surfactant-free microemulsion containing barium salt includes:

[0021] Prepare an aqueous solution containing barium salt;

[0022] Mix the aqueous solution containing barium salt, ethanol, and n-butanol in a mass ratio of (2-6):(2-6):(1-5); the mass ratio of the aqueous solution containing barium salt, ethanol, and n-butanol is preferably (3-5):(3-5):(2-4); the mass ratio of the aqueous solution containing barium salt, ethanol, and n-butanol is further preferably (3.5-4.5):(3.5-4.5):(2.5-3.5).

[0023] According to the method for preparing barium chromate according to any embodiment of the first aspect of the present invention, the preparation of the surfactant-free microemulsion containing chromium salt includes:

[0024] Prepare an aqueous solution containing chromium salt;

[0025] Mix the aqueous solution containing chromium salt, ethanol, and n-butanol in a mass ratio of (2-6):(2-6):(1-5); the mass ratio of the aqueous solution containing chromium salt, ethanol, and n-butanol is preferably (3-5):(3-5):(2-4); the mass ratio of the aqueous solution containing chromium salt, ethanol, and n-butanol is further preferably (3.5-4.5):(3.5-4.5):(2.5-3.5).

[0026] According to the method for preparing barium chromate according to any embodiment of the first aspect of the present invention, in the surfactant-free microemulsion containing barium salt, calculated as barium ions, the molar concentration of the barium salt is 0.01-0.25 mol / L; the molar concentration of the barium salt is preferably 0.05-0.25 mol / L; the molar concentration of the barium salt is further preferably 0.0625-0.25 mol / L; the molar concentration of the barium salt is more preferably 0.08-0.25 mol / L;

[0027] In the surfactant-free microemulsion containing chromium salt, the molar concentration of the chromium salt is 0.01-0.125 mol / L; the molar concentration of the chromium salt is preferably 0.05-0.125 mol / L; the molar concentration of the chromium salt is further preferably 0.0625-0.125 mol / L;

[0028] The molar concentrations of the "barium salt and chromium salt" as described herein will affect the stability of the surfactant-free microemulsion to which they belong. At low molar concentrations, the difference between the two is not obvious. However, as the molar concentration increases, the stability of the surfactant-free microemulsion containing the barium salt is better. Based on this, when at a low concentration, there is no strict requirement for the addition direction of the surfactant-free microemulsion containing the barium salt and the surfactant-free microemulsion containing the chromium salt. However, when the molar concentration ≥ 0.0625 mol / L, it is recommended to add the surfactant-free microemulsion containing the barium salt to the surfactant-free microemulsion containing the chromium salt to mix the two.

[0029] The method for preparing barium chromate according to any one of the embodiments of the first aspect of the present invention, wherein the barium salt includes but is not limited to barium chloride.

[0030] The method for preparing barium chromate according to any one of the embodiments of the first aspect of the present invention, wherein the chromium salt includes but is not limited to potassium chromate.

[0031] The second aspect of the present invention provides a delay composition, and the delay composition contains barium chromate.

[0032] The delay composition according to any one of the embodiments of the second aspect of the present invention, except for inevitable impurities, the mass ratio of barium chromate in the delay composition is 45-100%.

[0033] Alternatively, the mass ratio of barium chromate in the delay composition is 40-70%.

[0034] Alternatively, the mass ratio of barium chromate in the delay composition is 60%.

[0035] The delay composition according to any one of the embodiments of the second aspect of the present invention, the delay composition is barium chromate.

[0036] It should be noted that when the delay composition is the tungsten-based delay composition, it can be understood that the method for preparing barium chromate according to any one of the embodiments of the first aspect of the present invention is simultaneously the method for preparing the delay composition according to any one of the embodiments of the second aspect of the present invention.

[0037] The delay composition according to any one of the embodiments of the second aspect of the present invention, the barium chromate is prepared by the method for preparing barium chromate according to any one of the embodiments of the first aspect of the present invention.

[0038] The delay composition according to any one of the embodiments of the second aspect of the present invention, the delay composition is a tungsten-based delay composition.

[0039] Beneficial effects

[0040] (1) Compared with the traditional chemical precipitation method and the method of adding a surfactant for regulation and preparation of BaCrO 4For the preparation method of barium chromate provided by the present invention, a surfactant-free microemulsion composed of n-butanol, ethanol and water is used to prepare BaCrO 4 In the process of the material, no heating or other special condition control is required, the operation is simple and easy, the cost is low, and all the reagents used are environmentally friendly solvents, which is green and environmentally friendly. The preparation method of barium chromate provided by the present invention has the value of large-scale application and is suitable for large-scale industrial production of barium chromate.

[0041] (2) The preparation method of barium chromate provided by the present invention can prepare BaCrO with uniform morphology, small particle size and narrow particle size distribution. 4 Material, thus solving the disadvantages of uneven particle size and difficult-to-control morphology prepared by methods such as chemical precipitation. At the same time, the prepared BaCrO 4 Material has been experimentally verified to have good practical application value in delay charges.

[0042] (3) The preparation method of barium chromate provided by the present invention uses a surfactant-free microemulsion composed of n-butanol, ethanol and water to increase the solubility of chromate salt to 0.125 mol / L and the solubility of barium salt to 0.25 mol / L;

[0043] In the synthesis process of barium chromate, the highly soluble SFME can uniformly dissolve the barium salt and chromate salt as reactants in the microemulsion system, providing a more uniform reaction environment. This helps to control the progress of the reaction, making the collisions between reactant molecules more uniform and frequent, thus facilitating the synthesis of barium chromate nanomaterials with more uniform particle size and more regular morphology.

[0044] (4) The microenvironment inside the highly soluble SFME can be used as a template to guide the growth and assembly of materials. Therefore, different micro-solution systems have different dissolution and accommodation capabilities for different substances, and can synthesize materials in specific regions of the microemulsion to form materials with specific structures and functions. The preparation method of barium chromate provided by the present invention uses a surfactant-free microemulsion composed of n-butanol, ethanol and water, which can also improve the controllability of the particle size of the product barium chromate during the synthesis process.

[0045] (5) The preparation method of barium chromate provided by the present invention uses a surfactant-free microemulsion composed of n-butanol, ethanol and water to increase the solubility of chromate salt and barium salt to 0.125 mol / L and 0.25 mol / L respectively; it is beneficial to produce more barium chromate with a lower solvent usage. Description of the Drawings

[0046] Figure 1 SEM image of barium chromate prepared for Example 1;

[0047] Figure 2 SEM image of barium chromate used in Example 2;

[0048] Figure 3 X-ray diffraction patterns of barium chromate prepared in Examples 1 and 2;

[0049] Figure 4 Particle size distribution diagrams of barium chromate used in Examples 2 and 3. Detailed implementation manners

[0050] The present disclosure can be more easily understood by referring to the following description in conjunction with the accompanying drawings and examples, all of which form a part of the present disclosure. It should be understood that the present disclosure is not limited to the specific products, methods, conditions or parameters described and / or illustrated herein. Further, the terms used herein are for the purpose of describing specific embodiments by way of example only and are not intended to be limiting, unless otherwise specified.

[0051] It should be noted that the terms used herein are only for describing the specific implementation manners and are not intended to limit the exemplary embodiments according to the present invention. It should be understood that the protection scope of the present invention is not limited to the specific specific embodiments described below; it should also be understood that the terms used in the embodiments of the present invention are for describing the specific specific embodiments and not for limiting the protection scope of the present invention. For the experimental methods without specific conditions indicated in the following specific implementation manners, they are generally carried out according to the conventional methods and conditions of molecular biology in the art, and such techniques and conditions are fully explained in the literature.

[0052] It should also be understood that, for the sake of clarity, certain features of the present disclosure may be described herein in the context of separate embodiments, but may also be provided in combination with each other in a single embodiment. That is, unless clearly incompatible or specifically excluded, each separate embodiment is considered combinable with any other embodiment, and such combination is considered to represent another different embodiment. On the contrary, for the sake of brevity, the various features of the present disclosure described in the context of a single embodiment may also be provided separately or in any sub-combination. Finally, although a specific embodiment may be described as part of a series of steps or part of a more general structure, each step or sub-structure itself may also be considered an independent embodiment.

[0053] Unless otherwise specified, it should be understood that each individual element in the list and each combination of the individual elements in the list will be interpreted as a different embodiment. For example, a list of embodiments represented as "A, B or C" should be interpreted as including embodiments "A", "B", "C", "A or B", "A or C", "B or C" or "A, B or C".

[0054] In this document, the endpoints and any values of the disclosed ranges are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this document. Unless the context clearly indicates otherwise, the singular forms "a", "an", and "the" as used herein include both singular and plural referents. Numerical ranges expressed by endpoints include all numerical values and fractions within the corresponding ranges, as well as the expressed endpoints, unless the context clearly states otherwise.

[0055] In this document, the reference to "substance" refers to at least one of such substance and its equivalents.

[0056] In this document, the precision is defined as:

[0057] where v 1 is the maximum value of the burning rate at this temperature, v 2 is the minimum value of the burning rate at this temperature, and v is the average value of the burning rate at this temperature.

[0058] When describing items by using conjunctive terms such as "…… and / or ……", the description should be understood to include any one of the associated listed items and all combinations of one or more of them.

[0059] Generally, the use of the term "about" indicates an approximate value that can vary according to the desired characteristics obtained from the disclosed subject matter, and will be interpreted in a context - dependent manner based on function. Therefore, those of ordinary skill in the art will be able to interpret a certain degree of difference on a case - by - case basis. In some cases, the number of significant digits used to express a specific value can be a representative technique for determining the difference allowed by the term "about". In other cases, the gradient in a series of values can be used to determine the range of differences allowed by the term "about". Further, all ranges in this disclosure are inclusive and combinable, and the reference to the values stated in the ranges includes each value within that range.

[0060] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this invention belongs; the terms used herein and / or include any and all combinations of one or more of the related listed items.

[0061] The present invention will be described below through specific embodiments to make the technical solutions of the present invention easier to understand and master. However, the present invention is not limited thereto. The described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Therefore, they do not impose any limitations on the present invention. Those skilled in the art make some non-essential improvements and adjustments based on the content of the present invention, which all fall within the protection scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. In the following embodiments, unless otherwise specified, the experimental methods are all conventional methods; the reagents and materials, unless otherwise specified, can all be obtained from commercial channels. Specific Embodiment

[0063] In the following embodiments, for the preparation of the base charge of the delay composition, the method of manual mixing and sieving is adopted. Weigh 30 g of tungsten powder and 60 g of barium chromate, mix them evenly on paper, and after visually observing uniformity, sieve through a 100-mesh sieve for more than three times. After sieving and mixing, put it into an oven and dry it at 45 °C for 10 hours.

[0064] For the convenience of processing, the total accuracy S of the delay time is used to represent the magnitude of the delay accuracy.

[0065] The accuracy is defined as:

[0066]

[0067] where v 1 is the maximum value of the burning rate at this temperature, v 2 is the minimum value of the burning rate at this temperature, and v is the average value of the burning rate at this temperature. The temperature in the experiment is normal temperature (25 °C).

[0068] Prepare the delay body. The delay body shell material used for pressing the delay body is 2A12 aluminum alloy, and the specification dimensions are: inner diameter 3.50 mm, outer diameter 6.16 mm, and length 16.40 mm. The input end and the output end are both 60 mg of 601 water-resistant ignition charge, and the delay composition is pressed in 4 times, 110 mg each time.

[0069] Among them, the tungsten powder used: purchased from Nanjing University of Science and Technology Chemical Industry Co., Ltd., with an average particle size of 1.5 μm;

[0070] The barium chromate used: the average particle size is 1.45 μm (Example 2); the average particle size is 0.2 μm (Example 1).

[0071] Example 1

[0072] (1) Mix n-butanol, ethanol, and BaCl 2 solution at normal temperature and stir. The emulsion changes from turbid to transparent to obtain microemulsion A; among them, BaCl2 The molar concentration of the solution is 0.125 mol / L, and the mass ratio of n-butanol, ethanol, and BaCl 2 in the solution is 3:4:4.

[0073] (2) Mix n-butanol, ethanol, and K 2 CrO 4 solutions at room temperature, stir, and the emulsion changes from turbid to transparent to obtain microemulsion B; among them, the molar concentration of K 2 CrO 4 solution is 0.125 mol / L, and the mass ratio of n-butanol, ethanol, and K 2 CrO 4 in the solution is 3:4:4.

[0074] (3) Add microemulsion A to microemulsion B, stir at about 25 °C at room temperature for 2 h to obtain a solid precipitate, remove the supernatant, wash and dry to obtain barium chromate; among them, the mass ratio of microemulsion A to microemulsion B is 1:1.

[0075] Example 2

[0076] Refer to the preparation of tungsten-based delay charge base charge as described above, where the barium chromate is selected from Nanjing University of Science and Technology Science and Technology Chemical Co., Ltd., with an average particle size of 1.45 μm, and the barium chromate is prepared by ball milling after being synthesized by the precipitation method.

[0077] In addition, as Figure 1 and 2 shown, Figure 1 is the SEM image of the barium chromate prepared in Example 1 of this example, Figure 2 is the SEM image of the raw material barium chromate used in Example 2 of this example. It can be seen from the figure that there are obvious differences in the morphology and particle size of the raw material barium chromate, while the particle size and morphology of the barium chromate prepared under the SFME system are relatively uniform, and the particle size is significantly smaller than that of the raw material, indicating that the SFME method can effectively reduce the particle size of barium chromate and control the particle size distribution.

[0078] As Figure 3 shown, the figure is the XRD pattern of the barium chromate prepared in Example 1 and the raw material barium chromate used in Example 2 of this example. It can be seen from the figure that compared with the raw material barium chromate, the position of the diffraction characteristic peaks of the micro-nano barium chromate prepared through the SFME system remains basically unchanged, and there are no extra impurity peaks, indicating that its crystal form has not changed and the purity is relatively high.

[0079] As Figure 4As shown in the figure, it is the particle size distribution diagram of barium chromate prepared in Example 1 and the raw material barium chromate used in this Example 2. It can be seen from the figure that the barium chromate prepared under the SFME system has a smaller particle size and a narrower particle size distribution, indicating that the SFME method can effectively reduce the particle size of barium chromate and control the particle size distribution.

[0080] Example 3

[0081] Refer to the preparation of tungsten-based delay composition base charge as described above, wherein the barium chromate is selected from the refined barium chromate prepared in Example 1, and the average particle size is 0.2 μm.

[0082] The average burning rate and delay accuracy of the delay compositions prepared in Examples 2 and 3 are shown in Table 1 in detail.

[0083]

[0084] It can be seen from Table 1 that the refined barium chromate can slow down the burning rate of the delay composition, making it contact with each component in the delay composition more fully, and the melting and solid-solid diffusion are more thorough, and it can participate in the burning of the delay composition more fully, improving the delay accuracy and burning stability.

[0085] Comparative Example 1

[0086] This comparative example is basically the same as Example 1, except that microemulsion B is added to microemulsion A.

[0087] It is found that when the microemulsion concentration ≥ 0.0625 mol / L, stratification will occur due to the long standing time.

[0088] The product homogeneity also decreases.

[0089] It is speculated that the reason is that the hydrophilic group -OH of the amphiphilic reagent ethanol faces the aqueous phase, and the lipophilic group extends into the oil phase, and the ethanol molecules are oriented in the interface. Also, because the -OH on ethanol is negatively charged and the non-polar group is positively charged, a positive electric potential difference with negative inside and positive outside is formed at the interface of the W / O type SFME droplet. Compared with microemulsion A, CrO in microemulsion B 4 2- is a large-volume ion with a low charge density, which may weaken the electrostatic repulsion, and will generate steric hindrance, weakening the stability of the interfacial film and causing droplet aggregation, reducing the emulsion stability.

[0090] Comparative Example 2

[0091] This comparative example is basically the same as Example 1, except that ethanol is replaced by isopropanol.

[0092] (1) Compared with the water / isopropanol / n-butanol microemulsion, the water / ethanol / n-butanol microemulsion is more suitable for applications that require rapid drying. Moreover, the water / ethanol / n-butanol microemulsion has better fluidity, facilitating processing and transportation.

[0093] (2) Compared with the water / isopropanol / n-butanol microemulsion, the water / ethanol / n-butanol microemulsion: has better solubility for barium salts and chromium salts, making it suitable for a variety of application scenarios.

[0094] (3) The toxicity of ethanol is lower than that of isopropanol, and it is more easily biodegradable. Therefore, the water / ethanol / n-butanol microemulsion has more advantages in terms of environmental protection and safety. The price of ethanol is usually lower than that of isopropanol, making the water / ethanol / n-butanol microemulsion more competitive in terms of cost.

[0095] Comparative Example 3

[0096] This comparative example is basically the same as Example 1, except that n-butanol is replaced by tetrachloroethylene.

[0097] Tetrachloroethylene is a volatile organic compound (VOC) with high toxicity and environmental hazards, which may pollute soil and water bodies.

[0098] It is more difficult to form a microemulsion with tetrachloroethylene, which is not conducive to the regulation and control of the process during the reaction. This can also be calculated through the formula and It can be calculated;

[0099] where S is the area of the single-phase region for forming the microemulsion, and χ ij is the Flory-Huggins parameter.

[0100] Comparative Example 4

[0101] This comparative example is basically the same as Example 1, except that n-butanol / ethanol is replaced by isopropanol / tetrachloroethylene.

[0102] (1) The water / isopropanol / tetrachloroethylene microemulsion: requires a longer drying time in applications.

[0103] The water / ethanol / n-butanol microemulsion: has a faster drying speed and is suitable for applications that require rapid drying.

[0104] (2) The water / isopropanol / tetrachloroethylene microemulsion: shows poor solubility for substances such as barium salts and chromium salts;

[0105] The water / ethanol / n-butanol microemulsion: has better solubility for barium salts and chromium salts and is suitable for a variety of application scenarios.

[0106] (3) Water / isopropanol / perchloroethylene microemulsion: Perchloroethylene is highly toxic and long-term exposure may cause harm to health (such as liver damage, nervous system effects, etc.), and the toxicity of isopropanol is slightly higher than that of ethanol.

[0107] Water / ethanol / n-butanol microemulsion: Ethanol and n-butanol have low toxicity and high safety during use and storage.

[0108] (4) Water / isopropanol / perchloroethylene microemulsion: The production and treatment costs of perchloroethylene are high, and due to its environmental hazards, additional environmental protection treatment costs may be required.

[0109] Water / ethanol / n-butanol microemulsion: Ethanol and n-butanol have relatively low prices and are easily accessible, with low costs.

Claims

1. A method for preparing barium chromate, characterized in that: Including: preparing barium chromate by using a surfactant-free microemulsion method; Wherein, the surfactant-free microemulsion is a ternary system, and is composed of water, ethanol, and n-butanol; Wherein, the water is calculated as the sum of the aqueous solutions containing barium salt and chromium salt, and the mass ratio of water, ethanol and n-butanol is (3-4): (3-5): (2-4); Calculated based on barium ions and chromium ions respectively, the molar ratio of the barium salt to the chromium salt is (1-1.2):

1.

2. The method for preparing barium chromate according to claim 1, characterized in that: A surfactant-free microemulsion containing a barium salt and a chromium salt was subjected to a stirring treatment; After stirring, the product barium chromate is obtained by separation.

3. The method for preparing barium chromate according to claim 2, characterized in that: The stirring treatment time is 1 to 12 hours; The temperature is 10℃~40℃.

4. The method for preparing barium chromate according to any one of claims 1 to 3, characterized in that: Includes steps: preparing surfactant-free microemulsions containing barium salts; preparing surfactant-free microemulsions containing chromium salts; The two are mixed to obtain a surfactant-free microemulsion containing barium salt and chromium salt.

5. The method for preparing barium chromate according to claim 4, characterized in that: The preparation of the surfactant-free microemulsion containing barium salt comprises: preparing an aqueous solution containing a barium salt; An aqueous solution containing a barium salt, ethanol, and n-butanol are mixed in a mass ratio of (3-4):(3-5):(2-4).

6. The method for preparing barium chromate according to claim 5, characterized in that: The preparation of the surfactant-free microemulsion containing chromium salt comprises: preparing an aqueous solution containing a chromium salt; An aqueous solution containing a chromium salt, ethanol, and n-butanol are mixed in a mass ratio of (3-4):(3-5):(2-4).

7. The method for preparing barium chromate according to any one of claims 5 to 6, characterized in that: In the surfactant-free microemulsion containing the barium salt, the molar concentration of the barium salt is 0.01 to 0.25 mol / L, calculated as barium ions; In the surfactant-free microemulsion containing chromium salt, the molar concentration of the chromium salt is 0.01-0.125 mol / L calculated as chromium ions.

8. The method for preparing barium chromate according to claim 7, characterized in that: In the surfactant-free microemulsion containing the barium salt, the molar concentration of the barium salt is 0.01 to 0.25 mol / L, calculated as barium ions; In the surfactant-free microemulsion containing chromium salt, the molar concentration of the chromium salt is 0.01-0.125 mol / L calculated as chromium ions.

9. The method for preparing barium chromate according to claim 8, characterized in that: The surfactant-free microemulsion containing the barium salt is added to the surfactant-free microemulsion containing the chromium salt, and the two are mixed.

10. A delay medicine, characterized in that: The delay agent contains barium chromate, or the tungsten-based delay agent is barium chromate; The barium chromate is prepared according to any one of the methods described in claims 1 to 6; And / or, the delay agent is a tungsten-based delay agent.

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