Method for preparing infrared window material potassium bromide through hot pressing

Abstract

The invention discloses a method for preparing infrared window material potassium bromide through hot pressing. The method comprises the following steps: adhering a polyimide adhesive tape to the opposite surfaces of an upper mold and a lower mold of a hot press; a sleeve is arranged on the lower die, the ground potassium bromide powder is placed on the polyimide adhesive tape of the lower die, time, temperature and pressure are set, and after the temperature is increased to the preset temperature and kept for 30 min, the upper die starts to conduct pre-pressing at the first pressure for the first time and then conducts hot pressing at the second pressure for the second time; taking out the sleeve after hot pressing, and pushing out the potassium bromide film by using a reverse mold rod. The potassium bromide window sheet is prepared by adopting a hot pressing process, on one hand, at the temperature higher than 100 DEG C, the influence of water on potassium bromide is eliminated, the polyimide adhesive tape is pasted, the flowability among particles is improved, and the transparency of the potassium bromide window sheet is integrally improved; on the other hand, the potassium bromide particles are combined through pressure, and the mechanical performance of the potassium bromide window sheet is improved.

Description

Technical Field

[0001] This invention relates to the field of optical materials technology, and in particular to a hot pressing method for preparing potassium bromide as an infrared window material. Background Technology

[0002] Potassium bromide crystals are among the materials with the highest transmittance in the infrared spectrum and are often used as infrared window films. Therefore, potassium bromide windows are required to have high infrared transmittance and good mechanical properties. In existing technologies, potassium bromide windows are usually grown using the Czochralski method. The Czochralski method allows for easy observation of crystal growth and can grow high-quality crystals at a relatively fast growth rate. However, the Czochralski method has high equipment requirements, complex procedures, high costs, and the quality of potassium bromide windows is uncontrollable, making it unsuitable for large-scale applications.

[0003] Therefore, there is a lack of a simple and low-cost preparation process for potassium bromide, an infrared window material, in the existing technology. Summary of the Invention

[0004] To address the problems of high equipment requirements, complex procedures, high costs, and uncontrollable quality of potassium bromide windows in existing processes for preparing potassium bromide, the present invention aims to provide a method for hot-pressing to prepare potassium bromide as an infrared window material.

[0005] In a first aspect, the present invention provides a hot-pressing method for preparing potassium bromide as an infrared window material, comprising the following steps:

[0006] S1: Apply polyimide tape to the surfaces of the upper and lower molds of the hot press that are opposite each other;

[0007] S2: Set the sleeve in the lower mold, place the ground potassium bromide powder on the polyimide tape of the lower mold, set the time, temperature and pressure, heat up to the preset temperature and keep it for 30 minutes, then the upper mold starts to pre-press with the first pressure for the first time, and then hot-press with the second pressure for the second time.

[0008] S3: After hot pressing is completed, remove the sleeve and use the die-casting rod to push out the potassium bromide film.

[0009] Preferably, the particle size of the ground potassium bromide powder is no higher than 100 micrometers.

[0010] Preferably, the mold includes an upper mold and a lower mold, the diameter of which can be any one of 10cm, 3.5cm or 1.5cm.

[0011] Preferably, in order to eliminate the influence of moisture on the hot pressing process of potassium bromide window and improve the transparency of potassium bromide window, the preset temperature is 110-150℃.

[0012] Preferably, in order to ensure the surface flatness of the potassium bromide window, the first pressure is 0.5 MPa and the first time is 0.5-2 min.

[0013] Preferably, in order to increase the binding degree of potassium bromide particles and reduce the number and area of ​​pores between particles, the second pressure is 11-20 MPa; the second time is 60-240 min.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] (1) This invention uses a hot-pressing process to prepare potassium bromide windows. On the one hand, at a temperature above 100 degrees Celsius, the influence of moisture on potassium bromide is eliminated, and polyimide tape is adhered, increasing the fluidity between particles and improving the overall transparency of the potassium bromide window. On the other hand, pressure is used to bind the potassium bromide particles together, increasing the mechanical properties of the potassium bromide window.

[0016] (2) The preparation process of the present invention has low equipment requirements and does not require large machinery, so that potassium bromide windows with high permeability and good mechanical properties can be obtained.

[0017] (3) The preparation process of the present invention can produce potassium bromide windows of corresponding size and thickness as required.

[0018] (4) The preparation process of the present invention is simple, low in cost, and can be mass-produced, and has broad prospects. Detailed Implementation

[0019] The present application will be further described below with reference to specific embodiments.

[0020] It should be noted that terms such as "upper", "lower", "left", "right", and "middle" used in this specification are only for clarity of description and are not intended to limit the scope of implementation. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered as within the scope of this application.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the term “and / or” as used herein includes any and all combinations of one or more of the associated listed items.

[0022] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0023] As used herein, the term “about” is used to provide for the flexibility and imprecision associated with a given term, measure, or value. Those skilled in the art can readily determine the degree of flexibility for a particular variable.

[0024] As used herein, the term “at least one of…” is intended to be synonymous with “one or more of…”. For example, “at least one of A, B, and C” explicitly includes only A, only B, only C, and combinations thereof.

[0025] Concentration, amount, and other numerical data may be presented in range format herein. It should be understood that such range format is used solely for convenience and brevity and should be flexibly interpreted to include not only the values ​​explicitly stated as the limits of the range, but also all individual values ​​or subranges encompassed within the range, as if each value and subrange were explicitly stated. For example, a range of values ​​from about 1 to about 4.5 should be interpreted to include not only the explicitly stated limits of 1 to 4.5, but also individual numbers (such as 2, 3, 4) and subranges (such as 1 to 3, 2 to 4, etc.). The same principle applies to ranges that describe only a single value, such as “less than about 4.5,” which should be interpreted to include all the aforementioned values ​​and ranges. Furthermore, this interpretation should apply regardless of the breadth of the range or characteristic described.

[0026] Existing tableting molds suffer from rough surfaces due to insufficient manufacturing processes that fail to achieve the required precision. Potassium bromide powder exhibits significantly reduced fluidity during hot pressing. Therefore, this invention utilizes polyimide tape adhered to both the upper and lower molds to enhance fluidity and ensure the smooth hot pressing process of the potassium bromide powder.

[0027] The hot-pressing preparation method of potassium bromide as the infrared window material of the present invention includes the following steps:

[0028] S1: Weigh 0.5-2.5g of potassium bromide powder, grind the potassium bromide powder until the particle size is less than 100μm, select the appropriate mold, and stick the polyimide tape on the opposing surfaces between the upper and lower molds of the hot press.

[0029] S2: Place the sleeve on the lower mold, put the ground potassium bromide powder on the polyimide tape of the lower mold, heat to 110-150℃ and keep warm for 30 minutes, then pre-press with a pre-compression pressure of 0.5 MPa for 0.5-2 minutes.

[0030] S3: Pressurize to 11-20 MPa and hot press for 60-240 minutes.

[0031] S4: After hot pressing is completed, remove the sleeve and use the corresponding mold demolding rod to push out the potassium bromide film.

[0032] Example 1

[0033] The first aspect of this embodiment provides a hot-pressing process for potassium bromide infrared window materials, the process comprising the following steps:

[0034] S1: Weigh 0.5g of potassium bromide powder, grind the potassium bromide powder until the particle size is less than 100μm, install a mold with a diameter of 1.5cm, and stick polyimide tape to the opposing surfaces between the upper and lower molds of the hot press.

[0035] S2: Place the sleeve on the lower mold, put the ground potassium bromide powder on the polyimide tape of the lower mold, heat to 110℃ and keep warm for 30 minutes, then pre-press with a pre-compression pressure of 0.5 MPa for 0.5 minutes.

[0036] S3: Pressurize to 15 MPa and hot press for 60 minutes.

[0037] S4: After hot pressing is completed, remove the sleeve and use the corresponding mold demolding rod to push out the potassium bromide film. Then immediately conduct infrared performance testing on the potassium bromide film. The results are shown in Table 1.

[0038] Example 2

[0039] The first aspect of this embodiment provides a hot-pressing process for potassium bromide infrared window materials, the process comprising the following steps:

[0040] S1: Weigh 1.5g of potassium bromide powder, grind the potassium bromide powder until the particle size is less than 100μm, install a mold with a diameter of 3.5cm, and stick polyimide tape to the opposing surfaces between the upper and lower molds of the hot press.

[0041] S2: Place the sleeve on the lower mold, put the ground potassium bromide powder on the polyimide tape of the lower mold, heat to 120℃ and keep warm for 30 minutes, then pre-press with a pre-compression pressure of 0.5 MPa for 2 minutes.

[0042] S3: Pressurize to 15 MPa and hot press for 120 minutes.

[0043] S4: After hot pressing, remove the sleeve and use the corresponding mold depressing rod to push out the potassium bromide film. Then, immediately perform infrared performance testing on the potassium bromide film. The results are shown in Table 1.

[0044] Comparative Example 1

[0045] The first aspect of this embodiment provides a potassium bromide hot-pressing process for infrared window materials, wherein the process is a potassium bromide cold-pressing process, and the process steps are as follows:

[0046] S1: Weigh 1.5g of potassium bromide powder, grind the potassium bromide powder until the particle size is less than 100μm, install a mold with a diameter of 3.5cm, and stick polyimide tape to the opposing surfaces between the upper and lower molds of the hot press.

[0047] S2: Put the sleeve on the lower mold, place the ground potassium bromide powder on the polyimide tape of the lower mold, and pre-compress it for 2 minutes with a pre-compression pressure of 0.5MPa.

[0048] S3: Pressurize to 15 MPa and cold press for 120 minutes.

[0049] S4: After cold pressing, remove the sleeve and use the corresponding mold casting rod to push out the potassium bromide film. Then, immediately perform infrared performance testing on the potassium bromide film. The results are shown in Table 1.

[0050] Comparative Example 2

[0051] The first aspect of this embodiment provides a potassium bromide hot-pressing process for infrared window materials. The process steps are as follows:

[0052] S1: Weigh 1.5g of potassium bromide powder, grind the potassium bromide powder until the particle size is less than 100μm, and install it into a mold with a diameter of 3.5cm.

[0053] S2: Place the mold sleeve on the lower mold, put the ground potassium bromide powder on the lower mold, heat to 120℃ and keep it at that temperature for 30 minutes, then pre-press it with a pre-pressing pressure of 0.5 MPa for 2 minutes.

[0054] S3: Pressurize to 15 MPa and hot press for 120 minutes.

[0055] S4: After hot pressing, remove the sleeve and use the corresponding mold depressing rod to push out the potassium bromide film. Then, immediately perform infrared performance testing on the potassium bromide film. The results are shown in Table 1.

[0056] Performance testing

[0057] The thickness and dimensions of the windows prepared in the examples and comparative examples were measured, and the infrared transmittance of the windows was tested. The results are shown in Table 1.

[0058] Table 1

[0059]

[0060]

[0061] The above embodiments are merely preferred embodiments of the present invention, but the implementation of the present invention is not limited to the above embodiments. Any changes, modifications, substitutions, or combinations made without departing from the spirit and principle of the present invention, such as various combinations of solutions in the embodiments, should be considered equivalent replacements and are all within the protection scope of the present invention.

Claims

1. A method for hot-pressing potassium bromide, an infrared window material, characterized in that, Includes the following steps: S1: Apply polyimide tape to the surfaces of the upper and lower molds of the hot press that are opposite each other; S2: Set the sleeve in the lower mold, place the ground potassium bromide powder on the polyimide tape of the lower mold, set the time, temperature and pressure, heat up to the preset temperature and keep it for 30 minutes, then the upper mold starts to pre-press with the first pressure for the first time, and then hot-press with the second pressure for the second time. S3: After hot pressing is completed, remove the sleeve and use the die-casting rod to push out the potassium bromide film.

2. The method as described in claim 1, characterized in that, The particle size of the ground potassium bromide powder is no higher than 100 micrometers.

3. The method as described in claim 1, characterized in that, The mold includes an upper mold and a lower mold, with a diameter of 10cm, 3.5cm or 1.5cm.

4. The method as described in claim 1, characterized in that, The preset temperature is 110-150℃.

5. The method as described in claim 1, characterized in that, The initial pressure is 0.5 MPa, and the initial time is 0.5-2 minutes.

6. The method as described in claim 1, characterized in that, The second pressure is 11-20 MPa; the second time is 60-240 min.

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