A flexible film laminated gradient index chalcogenide glass and a method of making the same

Abstract

This invention discloses a flexible, layered gradient refractive index chalcogenide glass, which is formed by stacking and sintering multiple layers of chalcogenide glass with different compositions. Each chalcogenide glass layer is composed of two base glasses with fixed compositions mixed in different molar ratios. The gradient refractive index chalcogenide glass is formed by stacking multiple layers of chalcogenide glass with different compositions sequentially in ascending order of the x-value, where x is the molar ratio of the two base glasses in each chalcogenide glass layer. This gradient refractive index chalcogenide glass allows for flexible control of the refractive index difference, achieving a refractive index difference of 0.05–0.48 in the 10 μm band. It exhibits excellent transmittance in the infrared band and strong chromatic aberration correction capability, making it a potentially valuable infrared material for applications in lightweight, compact infrared optical systems. The preparation method disclosed in this invention allows for flexible adjustment of the refractive index according to requirements, resulting in higher preparation efficiency and improved internal interface precision of the GRIN chalcogenide glass while shortening the preparation cycle.

Description

Technical Field

[0001] This invention belongs to the field of infrared glass material technology, specifically a gradient refractive index chalcogenide glass with flexible film stacking and its preparation method. Background Technology

[0002] In recent years, with the development and improvement of infrared detector technology and its processing technology, infrared optical systems have also developed rapidly and their applications are becoming increasingly widespread. However, this widespread application has also brought new challenges to the development of infrared thermal imaging systems. Diverse application scenarios require systems to be adaptable to various environments while simultaneously meeting the demands of miniaturization, lightweight design, and high quality, such as in portable weapon systems and unmanned aerial vehicles. To achieve better infrared imaging, multi-band or wide-band imaging is often necessary to improve imaging stability, enrich image details, and capture more information. However, wide-band or multi-band infrared optical systems place higher demands on chromatic aberration correction, and optical system designs using conventional homogeneous infrared materials often struggle to meet the requirements of miniaturization and lightweight design.

[0003] Gradient-index (GRIN) materials possess flexible optical properties, allowing for a controllable refractive index distribution within the material, creating a gradient change in a specific direction. This characteristic provides optical designers with additional design freedom, including chromatic aberration correction. Many GRIN optical materials exist in nature within the visible light band, such as those found in the human eye and fisheye. Currently, commercially available visible GRIN optical materials are primarily prepared using ion exchange and peak nanolayer extrusion methods, but commercially available GRIN materials for the infrared band are still unavailable.

[0004] Chalcogenide glasses are a common type of infrared optical material. Compared with traditional infrared crystal materials, chalcogenide glasses have a wider transmission band (covering short-wave, mid-wave, and long-wave infrared), a lower temperature coefficient of refractive index, a wider selection of refractive index / dispersion parameters, lower manufacturing costs, and their properties can be flexibly controlled through composition, making them ideal materials for preparing infrared GRIN optical materials. Since 2008, the US DARPA Strategic Science Agency has been developing GRIN chalcogenide glasses, but their use has been limited to the United States.

[0005] Currently, the main methods for preparing GRIN infrared chalcogenide glasses in the laboratory fall into three categories: ion exchange, gradient crystallization, and glass stacking. Ion exchange involves designing the composition and placing the glass in a suitable salt bath for ion exchange, introducing suitable migratable ions into the existing chalcogenide glass network. While ion exchange can create a continuously varying refractive index gradient, the refractive index change is small (<0.1), and the mechanical properties of the glass significantly decrease after immersion in the salt bath, affecting subsequent practical applications. Gradient crystallization involves controlling the precipitation of certain crystals in chalcogenide glasses through heat treatment and other methods. By interfering with the number and size of these crystals through external means, the refractive index can be controlled. Currently, there are reports of inducing crystallization changes in chalcogenide glasses through temperature heat treatment [ZL201710579672.6] and femtosecond laser induction, thereby achieving a gradient distribution of refractive index. However, the controllability of the refractive index distribution based on this method is weak, and the refractive index difference is small (<0.15).

[0006] The glass stacking method primarily controls the refractive index change by varying the composition of chalcogenide glasses. This is also the fabrication process adopted by the DARPA Strategic Science Agency in the United States. This approach can achieve a large refractive index difference (the maximum refractive index difference is 0.4). Based on this approach, two directions have been developed: the first is a method of hot-pressing bulk chalcogenide glasses with gradually varying compositions. In this method, as the number of stacked layers increases, the processes of melting and polishing the chalcogenide glasses separately require a significant amount of time. In addition, the processing quality and parallelism of both sides of each glass layer will affect the internal interface of the final GRIN chalcogenide glass. The other direction is a method of hot-pressing glass powder with gradually varying compositions [CN202111520507.6]. This method directly lays the powder layer by layer. This method makes it difficult to accurately guarantee the flatness and thickness of the interface, which will eventually lead to interface scattering and reflection, affecting the distribution of refractive index. Summary of the Invention

[0007] The technical problem to be solved by this invention is to provide a gradient refractive index chalcogenide glass with flexible film stacking and its preparation method. This gradient refractive index chalcogenide glass can flexibly control the change in refractive index difference, achieving a refractive index difference of 0.05-0.48 in the 10μm band. It exhibits excellent transmittance in the infrared band and strong chromatic aberration correction capability, making it a potentially valuable infrared material for lightweight infrared optical systems. The preparation method of this gradient refractive index chalcogenide glass can shorten the preparation cycle of GRIN chalcogenide glass and improve the internal interface precision of GRIN chalcogenide glass.

[0008] The technical solution adopted by this invention to solve the above-mentioned technical problem is a flexible film-layered gradient refractive index chalcogenide glass. The gradient refractive index chalcogenide glass is formed by stacking and sintering multiple layers of chalcogenide glass with different compositions. Each of the different chalcogenide glass layers is composed of two base glasses with fixed compositions mixed in different molar ratios. The molar compositions of the two base glasses are expressed by chemical formulas as (M... b N 100-b ) 100-a S a and (M) b N 100-b ) 100-a Se a The molar composition of each chalcogenide glass layer is expressed by the chemical formula as x(M) b N 100-b ) 100-a S a -(1-x)(M b N 100-b ) 100-a Se a M and N are different elements, selected from one of the elements Ge, In, As, Ga, Sb, and Te, respectively. b N 100-b ) 100-a S a In the equation, a and b represent the molar ratios of S and M, respectively. b N 100-b ) 100-a Se a In the equation, a and b are the molar ratios of Se and M, respectively, 0 < a < 100, 0 ≤ b ≤ 100, and x is the molar ratio of the two base glasses in each chalcogenide glass layer, 0 ≤ x ≤ 1. The gradient refractive index chalcogenide glass is composed of multiple layers of chalcogenide glass with different compositions, stacked sequentially in ascending order of x value.

[0009] The two basic glass types selected in this invention (M) b N 100-b ) 100-a S a and (M) b N 100-b ) 100-a Se a With similar thermal properties, good glass-forming performance, good thermal stability, and large refractive index difference, it is suitable for subsequent preparation of mixed glass powders with different refractive indices. The stacked chalcogenide glass components are stacked in order of increasing x value, and are not prone to crystallization during subsequent sintering, reducing the impact on the refractive index distribution and transmittance of the prepared GRIN chalcogenide glass.

[0010] The GRIN chalcogenide glass prepared by this invention can achieve a large refractive index change, with a maximum refractive index difference Δn of 0.48 at the 10μm band. Furthermore, the refractive index difference can be flexibly changed according to actual needs to meet the design requirements of lightweight and miniaturized infrared optical systems.

[0011] A method for preparing gradient refractive index chalcogenide glass with the above-mentioned flexible film stacking involves ball milling and mixing two fixed base glass powders at different molar ratios to obtain mixed glass powders with different components. Organic binders are then added to the different mixed glass powders and ball milled to obtain multiple flexible composite films composed of organic binders and mixed glass powders. These flexible composite films are then rolled in a roller press to form large, uniform, and flat flexible composite films. The different flexible composite films are cut into the required shapes and stacked sequentially in a graphite mold according to their x-values ​​from low to high. The graphite mold is then placed in an electric spark sintering furnace for sintering, using high temperature to decompose the organic binder to obtain glass blocks. The glass blocks are then polished to finally obtain infrared-transparent GRIN chalcogenide glass.

[0012] To ensure the uniformity of the mixed glass powders and the effective bonding of the two base glass powders, the preparation method of this invention uses high-energy ball milling to allow the two base glass powders to mix and react in advance to obtain a flexible composite film; the roller press can ensure the thickness and flatness of the flexible composite film after rolling, meeting the preparation requirements of laminated GRIN chalcogenide glass.

[0013] This invention provides a method for preparing GRIN chalcogenide glass based on glass powder and organic binder. This method simplifies the existing bulk glass lamination method for preparing axial GRIN chalcogenide glass and achieves GRIN chalcogenide glass with performance similar to that of existing methods. By setting the molar ratio of two base glass powders, this invention can prepare powders with different refractive indices. Furthermore, the addition of an organic binder allows the mixed glass powders to adhere into a sheet-like flexible composite film. Compared to existing methods that use single-element raw materials to melt and quench glass of the same composition, this significantly shortens the preparation cycle. In addition, the chalcogenide glass composite film pressed by a roller press better ensures the thickness and flatness of each layer in the final GRIN sample, eliminating the tedious and difficult steps of high-precision grinding and polishing of bulk glass.

[0014] Preferably, the method for preparing the above-mentioned flexible film-laminated gradient refractive index chalcogenide glass specifically includes the following steps:

[0015] (1) Select two basic glasses, whose molar composition is expressed by chemical formula as (M b N 100-b ) 100-a S a and (M) b N100-b ) 100-a Se a M and N are different elements, selected from one of the elements Ge, In, As, Ga, Sb, and Te, respectively. b N 100-b ) 100-a S a In the equation, a and b represent the molar ratios of S and M, respectively. b N 100-b ) 100-a Se a In the equation, a and b are the molar ratios of Se and M, respectively, where 0 < a < 100 and 0 ≤ b ≤ 100. Determine the values ​​of a and b.

[0016] (2) According to the chemical formula (M b N 100-b ) 100-a S a and (M) b N 100-b ) 100-a Se a The molar composition of the high-purity elemental raw materials M, N, S, and Se was calculated and weighed. Then, the raw materials for the two types of base glasses were mixed separately, placed into quartz tubes, and evacuated until the pressure inside the tubes was less than 1 × 10⁻⁶. -3 Pa, using a hydrogen-oxygen flame to melt and seal quartz tubes; place the melted quartz tubes separately into a swing furnace, heat to 550-950℃ for 8-12 hours, swing and melt for 10-30 hours, then remove from the furnace and cool by water for 2-3 seconds to obtain two types of pre-cooled and solidified glass columns; then place the two types of pre-cooled and solidified glass columns in an annealing furnace at 100-500℃ and hold for 2-6 hours, then control the cooling rate and cool to room temperature for 10-18 hours to obtain two types of glass columns;

[0017] (3) Take out the two types of glass columns from the quartz tube, grind the glass columns with a mortar and pestle for 10-20 minutes, and screen out the basic glass particles with a particle size of less than 100 mesh using a sieve with a 100-mesh aperture, and set them aside for later use.

[0018] (4) Use a ball mill to finely grind the basic glass particles to obtain basic glass powder with a particle size of less than 200 μm, and place it in a glass container for later use;

[0019] (5) Based on the chemical formula x(M) of each chalcogenide glass layer b N 100-b ) 100-a S a -(1-x)(M b N 100-b ) 100-a Se a0≤x≤1, determine multiple x values ​​from low to high, calculate the mass of the two basic glass powders required for the chalcogenide glass layer corresponding to different x values, and weigh them with a balance to obtain the raw materials for different chalcogenide glass layers;

[0020] (6) Place the weighed raw materials of different chalcogenide glass layers into ball mill jars respectively, and mix the two basic glass powders evenly using high-speed ball milling. The energy of the collision of the grinding balls causes the two basic glass powders to react and form a composition of x(M). b N 100-b ) 100-a S a -(1-x)(M b N 100-b ) 100-a Se a Mixed glass powders were obtained to produce mixed glass powders with different compositions;

[0021] (7) Add an organic binder to each mixed glass powder. The organic binder is added to each mixed glass powder by a mass percentage of 0.5-3%. After adding the organic binder, ball mill until the mixed glass powders adhere to each other to form a sheet-like flexible composite film, thus obtaining multiple flexible composite films.

[0022] (8) Place multiple flexible composite films into a roller press and roll them into large flexible composite films with uniform thickness and flatness to obtain multiple flexible composite films. Then cut the multiple flexible composite films into the required shapes and sizes according to the shape and size of the graphite mold, and stack them in the graphite mold in order from low to high according to the x value.

[0023] (9) Place the graphite mold in an electric spark sintering furnace and perform electric spark sintering on the sample in the graphite mold. Use high temperature to decompose the organic binder to obtain a glass block. Grind and polish the glass block to finally obtain infrared transparent GRIN chalcogenide glass.

[0024] Preferably, the difference in glass transition temperature between the two base glasses selected in step (1) is ≤30℃.

[0025] Preferably, the speed of fine grinding in step (4) is 250-500 rpm and the ball milling time is 5-30 min.

[0026] Preferably, in step (6), the rotation speed of the high-speed ball mill is 300-700 rpm, the number of ball milling cycles is 48-144, the total time of a single ball milling cycle is 15 min, of which the rotation time of a single ball milling cycle is 13 min and the stop time is 2 min.

[0027] Preferably, in step (7), the ball milling speed is 250-500 rpm, the ball milling cycle is 1-6, the total time of a single ball milling cycle is 15 min, of which the rotation time of a single ball milling cycle is 13 min and the stop time is 2 min.

[0028] To ensure the thickness and uniformity of the flexible composite film, preferably, the number of times each flexible composite film is repeatedly rolled in step (8) is 5-10 times, the temperature required for rolling is 50-150℃, and the thickness of each flexible composite film obtained by rolling is in the range of 100-200μm.

[0029] During sintering, sufficient temperature and high pressure are required to ensure the density of the sintered glass block. Therefore, as a preferred method, in step (9), the sample in the graphite mold is subjected to electric spark sintering in a nitrogen-protected environment. The maximum sintering temperature is 10-30°C higher than the softening temperature of the base glass with the higher softening temperature among the two base glasses. The sample is held at the maximum temperature for 10-30 minutes. In step (9), the maximum pressure used when the sample in the graphite mold is subjected to electric spark sintering is 30-80 MPa, and the pressure is held for 10-30 minutes.

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] (1) The gradient refractive index chalcogenide glass of the flexible film stack of the present invention adopts two base glasses (M) with similar thermal properties, good glass-forming performance, good thermal stability and large refractive index difference. b N 100-b ) 100-a S a and (M) b N 100-b ) 100-a Se a By adjusting the mixing ratio of the two base glass powders, GRIN chalcogenide glasses with a refractive index difference of 0.05-0.48 can be flexibly obtained. The gradient refractive index chalcogenide glass of this invention exhibits excellent transmittance in the infrared band and strong chromatic aberration correction capability, making it an infrared material with potential application value in lightweight and miniaturized infrared optical systems.

[0032] (2) The preparation method of this invention has significant advantages over existing methods: First, the method of adjusting the glass refractive index by mixing two powders allows for flexible adjustment of the refractive index according to requirements, resulting in high practical application value; Second, compared to the traditional method of adjusting the refractive index by adjusting the proportion of single raw materials, the preparation method of this invention can save more preparation time, especially when there are many layers; Third, the preparation method of this invention introduces an organic binder to bond the glass powder and roll it into a thin film, which can ensure the flatness of the internal interface of the GRIN chalcogenide glass and the thickness accuracy of each chalcogenide glass layer, compared to... Traditional glass grinding and polishing methods are simpler and more time-saving. The preparation method of this invention can shorten the preparation cycle of GRIN chalcogenide glass and improve the internal interface precision of GRIN chalcogenide glass. Fourth, the shape and size of the flexible composite film in the preparation method of this invention can be flexibly cut as needed, providing greater flexibility for the preparation of GRIN chalcogenide glass with different configurations. Fifth, the electric spark sintering (SPS) technology used in the preparation method of this invention can effectively improve the density of GRIN chalcogenide glass without destroying its layered structure. Compared with traditional melting methods, it also requires less time and has higher overall preparation efficiency. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the preparation process of the preparation method of the present invention;

[0034] Figure 2 This is a diagram showing the refractive index distribution of the GRIN chalcogenide glass in Example 1. Detailed Implementation

[0035] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0036] Example 1: A gradient refractive index chalcogenide glass with an 11-layer flexible film stack structure and a maximum refractive index difference Δn of 0.48 at the 10μm wavelength. This gradient refractive index chalcogenide glass is formed by stacking and sintering 11 layers of chalcogenide glass with different compositions. Each chalcogenide glass layer is composed of two base glasses with fixed compositions mixed in different molar ratios. The molar compositions of the two base glasses are expressed by chemical formulas as (M... b N 100-b ) 100-a S a and (M) b N 100-b ) 100-a Se a The molar composition of each chalcogenide glass layer is expressed by the chemical formula as x(M) b N 100-b ) 100-a S a -(1-x)(M b N 100-b )100-a Se a Where M is As, a = 60, b = 100, the molar composition of the two base glasses is represented by the chemical formulas As2S3 and As2Se3 (softening temperatures are 230℃ and 220℃ respectively). The molar composition of each chalcogenide glass layer is represented by the chemical formula xAs2S3-(1-x)As2Se3. The values ​​of x for the 11 chalcogenide glass layers are 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1 respectively. The 11 chalcogenide glass layers are stacked in order of increasing x value.

[0037] The process of preparing the gradient refractive index chalcogenide glass with flexible film stacking in Example 1 is as follows: Figure 1 As shown, the specific steps include:

[0038] (1) Preparation of As2S3 and As2Se3 base glasses by melt quenching method: Calculate and weigh high-purity elemental raw materials As, S, and Se according to the molar composition of the chemical formulas As2S3 and As2Se3 respectively. Then, mix the raw materials of the two base glasses separately, load them into quartz tubes, and evacuate the tubes until the pressure inside the tubes is less than 1×10⁻⁶. -3 Pa, using a hydrogen-oxygen flame to melt and seal quartz tubes; the melted quartz tubes are then placed in a swing furnace, heated to 650℃ for 12 hours, and swung and melted for 18 hours before being removed from the furnace and cooled by water for 3 seconds, resulting in two types of pre-cooled and solidified glass columns; the two types of pre-cooled and solidified glass columns are then placed in an annealing furnace at 170℃ and held for 4 hours, after which the cooling rate is controlled and the temperature is lowered to room temperature for 12 hours, resulting in two types of glass columns;

[0039] (2) Take out the two types of glass columns from the quartz tube, grind the glass columns with a mortar and pestle for 15 minutes, and screen out the basic glass particles with a particle size of less than 100 mesh using a sieve with a 100-mesh aperture for later use.

[0040] (3) Use a ball mill to finely grind the basic glass particles at a speed of 500 rpm for 10 min to obtain basic glass powder with a particle size of less than 200 μm, and place it in a glass container for later use.

[0041] (4) Based on the chemical formula xAs2S3-(1-x)As2Se3 for each chalcogenide glass layer, and the values ​​of x (0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1), the mass of the two basic glass powders required for the chalcogenide glass layer corresponding to different x values ​​was calculated, and weighed using a balance to obtain 11 sets of raw materials for the chalcogenide glass layer;

[0042] (5) The raw materials of the 11 groups of chalcogenide glass layers obtained by weighing were placed into ball mill jars respectively, and the two basic glass powders were mixed evenly by high-speed ball milling. The energy of the collision of the grinding balls caused the two basic glass powders to react and form a mixed glass powder with the composition xAs2S3-(1-x)As2Se3, resulting in 11 mixed glass powders with different compositions. The ball milling speed was 500 rpm, the ball milling cycle was 80, and the total time of a single ball milling cycle was 15 min. The rotation time of a single ball milling cycle was 13 min, and the stop time was 2 min.

[0043] (6) Weigh 0.995g of each mixed glass powder and add 0.005g of polytetrafluoroethylene (PTFE) as an organic binder, and then ball mill until the mixed glass powder adheres to form a sheet-like flexible composite film, to obtain 11 flexible composite films. The ball milling speed is 500rpm, the ball milling cycle is 2, the total time of a single ball milling cycle is 15min, the rotation time of a single ball milling cycle is 13min, and the stop time is 2min.

[0044] (7) Place 11 flexible composite films into a roller press and roll them into large flexible composite films with uniform thickness and flatness. During rolling, the flexible composite film needs to be heated to 80°C and a pressure of 0.5kN needs to be applied. Rolling is repeated 10 times. The thickness of each flexible composite film obtained by rolling is 100μm, and 11 flexible composite films are obtained.

[0045] (8) Cut 11 flexible composite films into circular pieces with a diameter of 15mm, and stack them in the graphite mold with an inner hole diameter that matches the x value from low to high.

[0046] (9) Place the filled graphite mold in an electric spark sintering furnace and perform electric spark sintering on the sample inside the graphite mold. This utilizes high-temperature decomposition of the organic binder. Specifically, after closing the furnace door, evacuate the furnace chamber until the vacuum level reaches 1×10⁻⁶. -3 Pa, the furnace temperature is rapidly raised to 220℃ within 400s, at which point the furnace pressure rapidly rises to 5kN. Then, the temperature is held for 300s while maintaining the pressure of 5kN. After the holding period, the temperature is slowly raised to 260℃ within 300s and the pressure is increased to 10kN. Then, the temperature and pressure are held for 600s. After rapid purging with nitrogen to cool down to room temperature, the glass block is removed.

[0047] (10) The two sides of the glass block were polished with 1000-mesh, 2000-mesh, 4000-mesh and 7000-mesh sandpaper and polishing powder respectively, and finally the 11-layer GRIN chalcogenide glass of Example 1 was obtained.

[0048] The GRIN chalcogenide glass sample from Example 1 was tested using a Fourier transform infrared spectroscopy (FTIR) instrument. The results showed that the sample maintained good transmittance in the mid-to-long-wave infrared range. The sample was cut and polished flat, and the cross-section was scanned using EDX and confocal Raman spectroscopy. Both methods characterized the refractive index distribution of the GRIN chalcogenide glass from Example 1 as a step-like pattern. Figure 2 As shown, the results indicate that the maximum refractive index difference Δn of this GRIN chalcogenide glass can reach 0.48 in the 10μm band.

[0049] Example 2: A gradient refractive index chalcogenide glass with a 6-layer flexible film stack and a maximum refractive index difference Δn of 0.35 at the 10μm wavelength. This gradient refractive index chalcogenide glass is formed by stacking and sintering 6 layers of chalcogenide glass with different compositions. Each chalcogenide glass layer is composed of two base glasses with fixed compositions mixed in different molar ratios. The molar compositions of the two base glasses are expressed by chemical formulas as (M... b N 100-b ) 100-a S a and (M) b N 100-b ) 100-a Se a The molar composition of each chalcogenide glass layer is expressed by the chemical formula as x(M) b N 100-b ) 100-a S a -(1-x)(M b N 100-b ) 100-a Se a Where M is Ge, N is As, a = 55, b = 100 / 3, the molar composition of the two base glasses can be expressed by chemical formulas as Ge 15 As 30 S 55 and Ge 15 As 30 Se 55 (The softening temperatures are 380℃ and 375℃, respectively), and the molar composition of each chalcogenide glass layer is expressed by the chemical formula xGe. 15 As 30 S 55 -(1-x)Ge 15 As 30 Se 55 The values ​​of x for the six chalcogenide glass layers are 0, 0.1, 0.2, 0.3, 0.4, and 0.55, respectively. The six chalcogenide glass layers are stacked in order of increasing x value.

[0050] The process for preparing the gradient refractive index chalcogenide glass with flexible film stacking in Example 2 is as follows: Figure 1As shown, the specific steps include:

[0051] (1) Ge was prepared by melt quenching method 15 As 30 S 55 and Ge 15 As 30 Se 55 Basic glass: according to the chemical formula Ge 15 As 30 S 55 and Ge 15 As 30 Se 55 The molar composition of the high-purity elemental raw materials Ge, As, S, and Se was calculated and weighed. Then, the raw materials for the two types of base glasses were mixed separately, placed into quartz tubes, and evacuated until the pressure inside the tubes was less than 1 × 10⁻⁶. -3 Pa, using a hydrogen-oxygen flame to melt and seal quartz tubes; the melted quartz tubes are then placed in a swing furnace, heated to 850℃ for 10 hours, and swung for 15 hours before being removed from the furnace and cooled by water for 3 seconds, resulting in two types of pre-cooled and solidified glass columns; the two types of pre-cooled and solidified glass columns are then placed in an annealing furnace at 320℃ and held for 4 hours, after which the cooling rate is controlled and the temperature is lowered to room temperature for 12 hours, resulting in two types of glass columns;

[0052] (2) Take out the two types of glass columns from the quartz tube, grind the glass columns with a mortar and pestle for 15 minutes, and screen out the basic glass particles with a particle size of less than 100 mesh using a sieve with a 100-mesh aperture for later use.

[0053] (3) Use a ball mill to finely grind the basic glass particles at a speed of 450 rpm for 20 min to obtain basic glass powder with a particle size of less than 200 μm, and place it in a glass container for later use.

[0054] (4) Based on the chemical formula xGe of each chalcogenide glass layer 15 As 30 S 55 -(1-x)Ge 15 As 30 Se 55 Given x values ​​of 0, 0.1, 0.2, 0.3, 0.4, and 0.55, calculate the mass of the two basic glass powders required for the chalcogenide glass layer corresponding to different x values, and weigh them using a balance to obtain 6 sets of raw materials for the chalcogenide glass layer.

[0055] (5) The raw materials of the 6 groups of chalcogenide glass layers obtained by weighing were placed into ball mill jars respectively, and the two basic glass powders were mixed evenly by high-speed ball milling. The energy of the collision of the grinding balls caused the two basic glass powders to react to form a composition of xGe. 15 As 30 S 55 -(1-x)Ge 15 As 30 Se 55 The mixed glass powder was used to obtain six different mixed glass powders. The ball milling speed was 500 rpm, the ball milling cycle was 60, the total time of a single ball milling cycle was 15 min, the rotation time of a single ball milling cycle was 13 min, and the stop time was 2 min.

[0056] (6) Weigh 0.99g of each mixed glass powder and add 0.01g of polytetrafluoroethylene (PTFE) as an organic binder, and then ball mill until the mixed glass powder adheres to form a sheet-like flexible composite film, to obtain 6 flexible composite films. The ball milling speed is 500rpm, the ball milling cycle is 6, the total time of a single ball milling cycle is 15min, the rotation time of a single ball milling cycle is 13min, and the stop time is 2min.

[0057] (7) Place the 6 flexible composite films into a roller press and roll them into large flexible composite films with uniform thickness and flatness. During the rolling process, the flexible composite films need to be heated to 80°C and a pressure of 0.5kN is applied. The rolling is repeated 10 times. The thickness of each flexible composite film obtained by rolling is 100μm, and 6 flexible composite films are obtained.

[0058] (8) Cut the 6 flexible composite films into circular pieces with a diameter of 15mm, and stack them in the graphite mold with an inner hole diameter that matches the x value from low to high.

[0059] (9) Place the filled graphite mold in an electric spark sintering furnace and perform electric spark sintering on the sample inside the graphite mold. This utilizes high-temperature decomposition of the organic binder. Specifically, after closing the furnace door, evacuate the furnace chamber until the vacuum level reaches 1×10⁻⁶. -3 Pa, the furnace temperature is rapidly raised to 320℃ within 400s, at which point the furnace pressure rapidly rises to 4kN. Then, the temperature is held for 400s while maintaining the pressure of 4kN. After the holding period ends, the temperature is slowly raised to 410℃ within 300s and the pressure is increased to 9kN. Then, the temperature and pressure are held for 600s. After rapid purging with nitrogen to cool down to room temperature, the glass block is removed.

[0060] (10) The two sides of the glass block were polished with 1000-mesh, 2000-mesh, 4000-mesh and 7000-mesh sandpaper and polishing powder respectively, and finally the 6-layer structure of GRIN chalcogenide glass of Example 2 was obtained.

[0061] The GRIN chalcogenide glass sample from Example 2 was tested using a Fourier transform infrared spectroscopy (FTIR) instrument. The results showed that the sample maintained good transmittance in the mid-to-long-wave infrared range. The sample was cut open and polished flat, and the cross-section was scanned using EDX and confocal Raman spectroscopy. Both methods characterized the refractive index distribution of the GRIN chalcogenide glass from Example 2 as step-like, indicating that the maximum refractive index difference Δn of this GRIN chalcogenide glass at the 10 μm wavelength range can reach 0.35.

[0062] Example 3: A gradient refractive index chalcogenide glass with a 5-layer flexible film stack and a maximum refractive index difference Δn of 0.2 at the 10μm wavelength. This gradient refractive index chalcogenide glass is formed by stacking and sintering 5 layers of chalcogenide glass with different compositions. Each chalcogenide glass layer is composed of two base glasses with fixed compositions mixed in different molar ratios. The molar compositions of the two base glasses are expressed by chemical formulas (M...). b N 100-b ) 100-a S a and (M) b N 100-b ) 100-a Se a The molar composition of each chalcogenide glass layer is expressed by the chemical formula as x(M) b N 100-b ) 100-a S a -(1-x)(M b N 100-b ) 100-a Se a Where M is Ge, a = 200 / 3, b = 100, the molar composition of the two base glasses is represented by the chemical formulas GeS2 and GeSe2 (softening temperatures are 540℃ and 530℃ respectively), the molar composition of each chalcogenide glass layer is represented by the chemical formula xGeS2-(1-x)GeSe2, the values ​​of x corresponding to the 5 chalcogenide glass layers are 0, 0.25, 0.5, 0.75, and 1 respectively, and the 5 chalcogenide glass layers are stacked in order of increasing x value.

[0063] The process for preparing the gradient refractive index chalcogenide glass with flexible film stacking in Example 3 is as follows: Figure 1 As shown, the specific steps include:

[0064] (1) Preparation of GeS2 and GeSe2 base glasses by melt quenching method: Calculate and weigh high-purity elemental raw materials Ge, S, and Se according to the molar composition of the chemical formulas GeS2 and GeSe2, respectively. Then, mix the raw materials of the two base glasses separately, load them into quartz tubes, and evacuate the tubes until the pressure inside the tubes is less than 1×10⁻⁶. -3 Pa, using a hydrogen-oxygen flame to melt and seal quartz tubes; the melted quartz tubes were then placed in a swing furnace, heated to 950℃ for 10 hours, and swung and melted for 26 hours before being removed from the furnace and cooled by water for 2 seconds, resulting in two types of pre-cooled and solidified glass columns; the two types of pre-cooled and solidified glass columns were then placed in an annealing furnace at 350℃ and held for 6 hours, after which the cooling rate was controlled and the temperature was lowered to room temperature for 18 hours, resulting in two types of glass columns;

[0065] (2) Take out the two types of glass columns from the quartz tube, grind the glass columns with a mortar and pestle for 15 minutes, and screen out the basic glass particles with a particle size of less than 100 mesh using a sieve with a 100-mesh aperture for later use.

[0066] (3) Use a ball mill to finely grind the basic glass particles at a speed of 350 rpm for 25 min to obtain basic glass powder with a particle size of less than 200 μm, and place it in a glass container for later use.

[0067] (4) Based on the chemical formula xGeS2-(1-x)GeSe2 of each chalcogenide glass layer, and the values ​​of x (0, 0.25, 0.5, 0.75, 1), calculate the mass of the two basic glass powders required for the chalcogenide glass layer corresponding to different x values, and weigh them with a balance to obtain the raw materials of 5 groups of chalcogenide glass layers.

[0068] (5) The raw materials of the five groups of chalcogenide glass layers obtained by weighing were placed into ball mill jars respectively, and the two basic glass powders were mixed evenly by high-speed ball milling. The energy of the collision of the grinding balls caused the two basic glass powders to react and form a mixed glass powder with the composition xGeS2-(1-x)GeSe2, resulting in five mixed glass powders with different compositions. The ball milling speed was 500 rpm, the ball milling cycle was 90, and the total time of a single ball milling cycle was 15 min. The rotation time of a single ball milling cycle was 13 min, and the stop time was 2 min.

[0069] (6) Weigh 0.99g of each mixed glass powder and add 0.01g of polytetrafluoroethylene (PTFE) as an organic binder, and then ball mill until the mixed glass powder adheres to form a sheet-like flexible composite film, to obtain 5 flexible composite films. The ball milling speed is 500rpm, the ball milling cycle is 6, the total time of a single ball milling cycle is 15min, the rotation time of a single ball milling cycle is 13min, and the stop time is 2min.

[0070] (7) Place the 5 flexible composite films into a roller press and roll them into large flexible composite films with uniform thickness and flatness. During the rolling process, the flexible composite films need to be heated to 80°C and a pressure of 1kN is applied. The rolling is repeated 10 times. The thickness of each flexible composite film obtained by rolling is 100μm, and 5 flexible composite films are obtained.

[0071] (8) Cut the five flexible composite films into circular pieces with a diameter of 15mm, and stack them in the graphite mold with an inner hole diameter that matches the x value from low to high.

[0072] (9) Place the filled graphite mold in an electric spark sintering furnace and perform electric spark sintering on the sample inside the graphite mold. This utilizes high-temperature decomposition of the organic binder. Specifically, after closing the furnace door, evacuate the furnace chamber until the vacuum level reaches 1×10⁻⁶. -3 Pa, the furnace temperature is rapidly raised to 420℃ in 400s, at which point the furnace pressure rises rapidly to 5kN. Then, the temperature is held for 300s while maintaining the pressure of 5kN. After the holding period, the temperature is slowly raised to 580℃ in 350s and the pressure is increased to 11kN. Then, the temperature and pressure are held for 650s. After rapid purging with nitrogen to cool down to room temperature, the glass block is removed.

[0073] (10) The two sides of the glass block were polished with 1000-mesh, 2000-mesh, 4000-mesh and 7000-mesh sandpaper and polishing powder respectively, and finally the 5-layer structure of GRIN chalcogenide glass of Example 3 was obtained.

[0074] The GRIN chalcogenide glass sample from Example 3 was tested using a Fourier transform infrared spectroscopy (FTIR) instrument. The results showed that the sample maintained good transmittance in the mid-to-long-wave infrared range. The sample was cut and polished flat, and the cross-section was scanned using EDX and confocal Raman spectroscopy. Both methods characterized the refractive index distribution of the GRIN chalcogenide glass from Example 3 as a step-like pattern. Figure 2 As shown, the results indicate that the maximum refractive index difference Δn of this GRIN chalcogenide glass can reach 0.2 in the 10μm band.

Claims

1. A flexible film laminated gradient index chalcogenide glass characterized in that, The gradient refractive index chalcogenide glass is formed by stacking and sintering multiple layers of chalcogenide glass with different compositions. Each chalcogenide glass layer is composed of two base glasses with fixed compositions mixed in different molar ratios. The molar compositions of the two base glasses are expressed by chemical formulas as (M... b N 100-b ) 100-a S a and (M) b N 100-b ) 100-a Se a The molar composition of each chalcogenide glass layer is expressed by the chemical formula as x(M) b N 100-b ) 100-a S a -(1-x)(M b N 100-b ) 100-a Se a M and N are different elements, selected from one of the elements Ge, In, As, Ga, Sb, and Te, respectively. b N 100-b ) 100-a S a In the equation, a and b represent the molar ratios of S and M, respectively. b N 100-b ) 100-a Se a In the equation, a and b are the molar ratios of Se and M, respectively, 0 < a < 100, 0 ≤ b ≤ 100, and x is the molar ratio of the two base glasses in each chalcogenide glass layer, 0 ≤ x ≤ 1. The gradient refractive index chalcogenide glass is composed of multiple layers of chalcogenide glass with different compositions, stacked sequentially in ascending order of x value.

2. A method of making the flexible film laminated gradient index chalcogenide glass of claim 1, characterized in that, The two-component fixed base glass powder is mixed by ball milling in different molar ratios to obtain a plurality of mixed glass powders with different components, and then an organic binder is added to each of the mixed glass powders and ball milled to obtain a plurality of flexible composite films of the organic binder and the mixed glass powder, and then the different flexible composite films are placed in a rolling machine to be rolled into a large piece of flexible composite film with uniform thickness and flatness, and then the flexible composite films are cut into the required shape and stacked in a graphite mold according to the size of the x value from low to high, and then the graphite mold is placed in an electric spark sintering furnace for sintering, and the organic binder is decomposed at high temperature to obtain a glass block, and the glass block is polished to obtain an infrared transparent GRIN chalcogenide glass.

3. The method of making a flexible film laminated gradient index chalcogenide glass of claim 2, wherein, Specifically comprising the following steps: (1) Select two kinds of base glass, the molar composition is represented by the chemical formula as (M b N 100-b ) 100-a S a and (M b N 100-b ) 100-a Se a , wherein M and N are different elements, M and N are selected from one of Ge, In, As, Ga, Sb and Te elements, (M b N 100-b ) 100-a S a a and b in (M b N 100-b ) 100-a Se a a and b are the molar ratio of Se and M, respectively, 0 (2) According to the chemical formula (M b N 100-b ) 100-a S a and (M) b N 100-b ) 100-a Se a The molar composition of the high-purity elemental raw materials M, N, S, and Se was calculated and weighed. Then, the raw materials for the two types of base glasses were mixed separately, placed into quartz tubes, and evacuated until the pressure inside the tubes was less than 1 × 10⁻⁶. -3 Pa, using a hydrogen-oxygen flame to melt and seal quartz tubes; place the melted quartz tubes separately into a swing furnace, heat to 550-950℃ for 8-12 hours, swing and melt for 10-30 hours, then remove from the furnace and cool by water for 2-3 seconds to obtain two types of pre-cooled and solidified glass columns; then place the two types of pre-cooled and solidified glass columns in an annealing furnace at 100-500℃ and hold for 2-6 hours, then control the cooling rate and cool to room temperature for 10-18 hours to obtain two types of glass columns; (3) The two glass columns are taken out of the quartz tube, and each is preliminarily ground for 10-20 min using a mortar, and the base glass particles with a particle size of 100 mesh or less are sieved out using a sieve with a pore size of 100 mesh, and are reserved for use; (4) The base glass particles are finely ground using a ball mill to obtain base glass powder with a particle size of 200 μm or less, which is placed in a glass container for use; (5) according to the chemical formula x (M b N 100-b ) 100-a S a -(1-x) (M b N 100-b ) 100-a Se a , 0≤x≤1, determine a plurality of low to high x value, respectively, the mass of the two kinds of basic glass powder required for the corresponding chalcogenide glass layer of different x value is calculated, and the raw materials of different chalcogenide glass layers are weighed by a balance; (6) Put the weighed raw materials of different chalcogenide glass layers into ball milling jars respectively, and mix the two kinds of base glass powders uniformly by high-speed ball milling. The energy of the grinding balls collision makes the two kinds of base glass powders react to form mixed glass powders with components of x(M b N 100-b ) 100-a S a -(1-x)(M b N 100-b ) 100-a Se a , to obtain a plurality of mixed glass powders with different components; (7) An organic binder is added to each of the mixed glass powders, and the mass percentage of the organic binder in each of the mixed glass powders is 0.5-3%, and after the addition of the organic binder, the mixed glass powder is ball milled until it is adhered into a sheet-shaped flexible composite film, and a plurality of flexible composite films are obtained; (8) The plurality of flexible composite films are placed in a rolling machine to be rolled into a large piece of flexible composite film with uniform thickness and flatness, and then the plurality of flexible composite films are cut into the required shape and size according to the shape and size of the graphite mold, and are stacked in the graphite mold according to the size of the x value from low to high; (9) The graphite mold is placed in an electric spark sintering furnace, and the sample in the graphite mold is subjected to electric spark sintering, and the organic binder is decomposed at high temperature to obtain a glass block, and the glass block is polished to obtain an infrared transparent GRIN chalcogenide glass.

4. The method of making a flexible film laminated gradient index chalcogenide glass of claim 3, wherein, In step (1), the difference between the glass transition temperatures of the two selected base glasses is ≤ 30℃.

5. The method of making a flexible film laminated gradient index chalcogenide glass of claim 3, wherein, In step (4), the fine grinding speed is 250-500 rpm, and the ball milling time is 5-30 min.

6. The method of making a flexible film laminated gradient index chalcogenide glass of claim 3, wherein, In step (6), the high-speed ball milling speed is 300-700 rpm, the ball milling cycle is 48-144, and the total time of a single ball milling cycle is 15 min, wherein the rotation time of a single ball milling cycle is 13 min, and the stop time is 2 min.

7. The method of making a flexible film laminated gradient index chalcogenide glass of claim 3, wherein, In step (7), the ball milling speed is 250-500 rpm, the ball milling cycle is 1-6, and the total time of a single ball milling cycle is 15 min, wherein the rotation time of a single ball milling cycle is 13 min, and the stop time is 2 min.

8. The method of making a flexible film laminated gradient index chalcogenide glass of claim 3, wherein, In step (8), the number of repeated rollings of each flexible composite film is 5-10 times, and the required temperature during rolling is 50-150℃, and the thickness of each flexible composite film obtained by rolling is in the range of 100-200 μm.

9. The method of making a flexible film laminated gradient index chalcogenide glass of claim 3, wherein, In step (9), the sample in the graphite mold is subjected to electric spark sintering in a nitrogen-protected environment, the maximum temperature of sintering is 10-30℃ higher than the softening temperature of the basic glass with higher softening temperature, and the temperature is maintained for 10-30 min.

10. The method of making a flexible film laminated gradient index chalcogenide glass of claim 3, wherein, In step (9), the maximum pressure used for electric spark sintering of the sample in the graphite mold is 30-80 MPa, and the pressure is maintained for 10-30 min.

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