Hollow glass microspheres and their preparation method and application

Abstract

The present invention belongs to the technical field of laser inertial confinement fusion (ICF), and specifically relates to a hollow glass microsphere, a preparation method and application thereof. In order to meet the requirements of the ICF field, the present invention provides a preparation method for millimeter-scale thin-walled hollow glass microspheres, comprising depositing a lithium-doped silicon-containing polymer coating on the surface of a polymer microsphere by chemical vapor deposition, and then removing the inner layer of polymer microspheres by high-temperature degradation under an inert gas to obtain lithium-doped silicon-containing polymer hollow microspheres; then oxidizing them to lithium-doped glass microspheres, and densifying and sintering them at 1000-1100°C, then reducing them to 350°C at a rate of 0.1-1°C / min, and then cooling them to room temperature with the furnace. The present invention realizes the preparation of hollow glass microspheres with high geometric symmetry, low surface roughness, high gas retention and pressure resistance, with a diameter of millimeter scale and a wall thickness of micrometer scale. The prepared hollow glass microspheres have potential application prospects in the field of ICF.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser inertial confinement fusion, and in particular relates to a hollow glass microsphere and a preparation method and application thereof. Background Art

[0002] Laser inertial confinement fusion (ICF) is one of the best ways to achieve controlled nuclear fusion. In the field of ICF, hollow microspheres serve as carriers of deuterium and tritium fuel, and their preparation is one of the key factors determining the success or failure of ICF experiments. Millimeter-scale, large-diameter, thin-walled glass microspheres play a vital role in ICF physics experiments due to their unique physical and chemical properties. ICF physics experiments involve a variety of extreme physical and chemical transformation processes such as microsphere ablation and implosion, and even tiny disturbances may cause experimental failure. The fluid dynamic instability caused by the quality of the microspheres is one of the main disturbance factors in ICF physics experiments and plays a decisive role in the success or failure of the physics experiments. Therefore, the millimeter-scale, thin-walled hollow glass microspheres used in ICF physics experiments must have extremely high geometric symmetry (including sphericity and wall thickness uniformity) and extremely low surface roughness. Furthermore, as carriers of deuterium-tritium fuel, the glass microspheres must also possess high pressure resistance and gas retention properties to ensure they can hold sufficient deuterium-tritium gas while preventing leakage during transport and storage. These stringent requirements pose significant challenges to the fabrication of millimeter-scale, thin-walled hollow glass microspheres.

[0003] Chinese patent CN 105906192 A, entitled "Tin liquid bubbling production process and device for hollow glass spheres," discloses a method for preparing millimeter-scale hollow glass spheres. However, this method requires converting a glass solution into glass bubbles by bubbling and cooling and solidifying to form hollow glass spheres. The prepared glass spheres are subject to multiple external influences such as buoyancy and surface tension, making it difficult to control the sphericity and surface quality of the glass spheres, and thus cannot meet the requirements of ICF physics experiments for target materials. Qi Xiaobo et al. (Journal of the Chinese Ceramic Society, 2010, 38: 718-724) reported a method for preparing large-diameter hollow glass microspheres based on dry gel particles. However, this method is highly susceptible to gravity during the sphere-forming process, resulting in a decrease in the sphericity and wall thickness uniformity of the microspheres. In addition, the diameter of the glass spheres prepared by this method is greatly dependent on the height of the microsphere preparation furnace, resulting in a significant limitation in the preparation of millimeter-scale hollow glass microspheres. Xu Wei et al. (Intense Laser and Particle Beams, 2015, 27:06-2008) reported a method for preparing hollow glass microspheres based on chemical vapor deposition (CVD)-oxidative sintering. This method deposits a silicon-containing polymer coating on the surface of a high-quality polymer microsphere (mandrel) via CVD. The mandrel is then removed in situ via oxidative sintering, while the silicon-containing polymer coating is oxidized to a silica shell, thereby producing glass microspheres with high geometric symmetry. Furthermore, this method can also produce millimeter-scale hollow glass microspheres by manipulating the mandrel diameter and coating wall thickness. However, the transformation of the silicon-containing polymer coating into a silica shell involves a series of physical and chemical reactions, including polymer cracking, oxidation, and shrinkage. These reactions easily lead to microstructural defects such as oxygen vacancies and hydroxyl groups in the silica shell, ultimately affecting the continuity of the silica network structure. This significantly reduces the gas retention and pressure resistance of the prepared hollow glass microspheres, making it difficult to prepare hollow glass microspheres that meet the requirements of ICF physics experiments. Therefore, how to achieve the preparation of hollow glass microspheres with high geometric symmetry, low surface roughness, high gas retention and pressure resistance with a diameter of millimeter scale and a wall thickness of micrometer scale is an important problem faced and urgently needs to be solved in the process of conducting laser inertial confinement fusion research experiments. Summary of the Invention

[0004] In order to meet the requirements of the laser inertial confinement fusion field and realize the preparation of hollow glass microspheres with high geometric symmetry, low surface roughness, high gas retention and pressure resistance, the present invention provides a millimeter-scale thin-walled hollow glass microsphere and a preparation method thereof.

[0005] The present invention first provides a method for preparing the hollow glass microspheres, comprising the following steps:

[0006] S1: Lithium-doped silicon-containing polymer coating is deposited on the surface of polymer microspheres by chemical vapor deposition;

[0007] S2: degrading the microspheres prepared in step S1 at high temperature under the protection of inert gas to remove the inner layer of polymer microspheres to obtain lithium-doped silicon-containing polymer hollow microspheres;

[0008] S3: oxidizing the lithium-doped silicon-containing polymer hollow microspheres obtained in step S2 to lithium-doped glass microspheres.

[0009] Furthermore, the present invention further comprises step S4: densifying and sintering the lithium-doped glass microspheres in step S3 at 1000-1100°C.

[0010] Furthermore, the present invention further comprises step S5: cooling the lithium-doped glass microspheres densified in step S4 to 350° C. at a rate of 0.1-1° C. / min, and then cooling them naturally to room temperature in the furnace.

[0011] Wherein, in step S1, the polymer microspheres include at least one of poly-α-methylstyrene microspheres, polystyrene microspheres, and polypropylene microspheres.

[0012] Preferably, the polymer microspheres have a diameter of 1.5 to 6 mm.

[0013] Wherein, in step S1, the chemical vapor deposition method is performed using a plasma enhanced chemical vapor deposition device.

[0014] In step S1, before the coating is deposited, the vacuum value is reduced to <5×10 -3 Pa; when the coating is deposited, working gases such as hydrogen, tetramethylsilane, trans-dibutene and n-butyllithium are introduced, the gas pressure is 5 to 20 Pa, the power of the 40.68 MHz radio frequency power supply is 10 to 30 W, and the deposition time is 10 to 100 hours.

[0015] Preferably, the polymer microspheres maintain random motion during deposition.

[0016] Wherein, in step S1, the lithium-doped silicon-containing polymer coating has a lithium content of 0.1 to 0.5 at.%, and a silicon content of 5 to 9 at.%.

[0017] Preferably, the lithium and silicon content is controlled by adjusting the gas flow rate. More preferably, the hydrogen, tetramethylsilane, trans-dibutene, and n-butyllithium gas flow rates are 9.5 sccm, 0.2-0.6 sccm, 0.2-0.25 sccm, and 0.1-0.3 sccm, respectively.

[0018] Wherein, in step S2, the inert gas is selected from at least one of nitrogen, argon, and helium.

[0019] In step S2, the high temperature degradation conditions are: slowly heating the temperature to 280-320°C at a heating rate of 0.5-5°C / min, and keeping the temperature for 5-20 hours to remove the inner layer of polymer microspheres.

[0020] Wherein, in step S3, the oxidation conditions are: gradually increasing the temperature from 280-320° C. to 400-650° C. at a heating rate of 0.5-2° C. / min, and keeping the temperature for 10-30 hours.

[0021] Wherein, in step S4, the densification sintering conditions are: heating to 1000-1100° C. at a rate of 0.5-2° C. / min and keeping the temperature for 5-15 hours.

[0022] The present invention also provides hollow glass microspheres prepared by the above preparation method.

[0023] Furthermore, the hollow glass microspheres have a diameter of 1 to 4 mm, a wall thickness of 2 to 20 μm, a sphericity greater than 99%, a wall thickness uniformity greater than 95%, a surface roughness less than 50 nm, an air retention half-life greater than 30 days, and an internal pressure resistance greater than 10 atm.

[0024] The present invention also provides the use of the hollow glass microspheres as deuterium-tritium fuel carriers in the field of laser inertial confinement fusion.

[0025] Beneficial effects: The method for preparing millimeter-scale thin-walled hollow glass microspheres of the present invention has the following advantages:

[0026] (1) A small amount of lithium is introduced into the silicon-containing polymer coating. The lithium element has the advantages of small atomic volume and good mobility, which effectively occupies the oxygen vacancy defects in the silica network structure, thereby reducing the oxygen vacancy defects and improving the gas retention and pressure resistance of the glass microspheres.

[0027] (2) By doping with lithium, the hardness and Young's modulus of the silicon-containing polymer can be effectively reduced, thereby softening the coating, effectively inhibiting the slagging phenomenon during the coating process, improving the coating quality, and reducing the surface roughness of the glass microspheres. This overcomes the problem that when using plasma chemical vapor deposition to prepare silicon-containing polymer coatings, the silicon-containing polymer coatings have high hardness and Young's modulus, resulting in brittle coatings and easy slagging of the coatings, which seriously affects the coating quality and ultimately causes an increase in the surface roughness of the glass microspheres.

[0028] (3) By increasing the microsphere densification sintering temperature to 1000-1100°C, which is higher than the strain point of lithium-doped silica, the present invention enables the effective migration of SiO2 molecules within the network structure, resulting in stress relaxation, thereby eliminating the stress in the silica shell. At the same time, the slow cooling process prevents the generation of new thermal stress. Through this process, the pressure resistance of the glass microspheres can be effectively improved.

[0029] (4) By increasing the microsphere densification sintering temperature to above 1000°C, the present invention can cause the hydroxyl groups in the silica network structure to undergo a dehydration reaction, thereby effectively reducing the hydroxyl defect content and improving the gas retention capacity and pressure resistance of the hollow glass microspheres. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is an optical image of the millimeter-scale thin-walled hollow glass microspheres prepared in Example 1 of the present invention;

[0031] Figure 2 This is a scanning electron microscope image of the millimeter-scale thin-walled hollow glass microspheres prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0032] The purpose of the present invention is to provide a method for preparing millimeter-scale thin-walled hollow glass microspheres in response to the requirements of the laser inertial confinement fusion field, thereby achieving the preparation of hollow glass microspheres with high geometric symmetry, low surface roughness, high gas retention and pressure resistance, with a diameter of millimeter scale and a wall thickness of micrometer scale.

[0033] The method for preparing millimeter-scale thin-walled hollow glass microspheres of the present invention is carried out in the following steps:

[0034] Step S1: A lithium-doped silicon-containing polymer coating is deposited on the surface of polymer microspheres with a diameter of 1.5 to 6 mm using a plasma enhanced chemical vapor deposition device. Before coating deposition, the device is evacuated to a vacuum of <5×10 -3 During coating deposition, the working gases (hydrogen, tetramethylsilane, trans-dibutene, and n-butyllithium) are introduced, with an internal pressure of 5 to 20 Pa. A 40.68 MHz RF power supply with a power of 10 to 30 W is used to generate plasma, and the deposition time is 10 to 100 hours. During coating, a microsphere motion device is used to induce random movement of the microspheres, effectively improving the uniformity of the coating.

[0035] In a preferred embodiment of the present invention, in step S1, the polymer microspheres include at least one of poly-α-methylstyrene microspheres, polystyrene microspheres, and polypropylene microspheres.

[0036] In a preferred embodiment of the present invention, the contents of lithium and silicon in the lithium-doped silicon-containing polymer coating in step S1 are controlled by adjusting the gas flow rate using a mass flow controller.

[0037] In a more preferred embodiment of the present invention, the lithium content in step S1 is 0.1 to 0.5 at.%, and the silicon content is 5 to 9 at.%.

[0038] Step S2: placing the microspheres prepared in step S1 in a crucible, placing it in a heating device, and introducing an inert gas as a protective gas; applying power and slowly heating the temperature to 280-320° C. at a heating rate of 0.5-5° C. / min, and keeping the temperature for 5-20 hours to remove the inner layer of polymer microspheres, thereby obtaining lithium-doped silicon-containing polymer hollow microspheres.

[0039] In a preferred embodiment of the present invention, the heating device in step S2 is a heating device capable of introducing inert and oxidizing gases, including at least one of a tube furnace and a box-type atmosphere furnace.

[0040] Step S3: Based on step S2, the atmosphere in the heating device is switched to oxygen, and the temperature is gradually increased from 280-320°C to 400-650°C at a heating rate of 0.5-2°C / min, and kept warm for 10-30 hours to oxidize the lithium-doped silicon-containing polymer microspheres into lithium-doped glass microspheres.

[0041] Step S4: Based on step S3, the temperature of the heating device is further increased to 1000-1100° C. at a rate of 0.5-2° C. / min, and kept at this temperature for 5-15 hours to densify the glass microspheres.

[0042] Step S5: Based on step S4, the temperature of the heating device is slowly reduced to 350°C at a rate of 0.1-1°C / min. The heating device is then allowed to cool naturally to room temperature. Millimeter-sized thin-walled hollow glass microspheres are obtained, having a diameter of 1-4 mm, a wall thickness of 2-20 μm, a sphericity greater than 99%, a wall thickness uniformity greater than 95%, a surface roughness less than 50 nm, an air retention half-life greater than 30 days, and an internal pressure resistance greater than 10 atm.

[0043] In the technical solution of the present invention, the process of high-temperature oxidation of the silicon-containing polymer coating to silica will undergo a series of physical and chemical reactions such as polymer cracking, recombination, oxidation, gas release, and volume shrinkage. These reactions can easily cause microstructural defects such as oxygen vacancies in the silica shell, ultimately affecting the continuity of the silica network structure and significantly reducing the gas retention and pressure resistance of the prepared hollow glass microspheres. Therefore, the method for preparing millimeter-scale thin-walled hollow glass microspheres disclosed in the present invention introduces a small amount of lithium into the silicon-containing polymer coating, utilizing the advantages of lithium's small atomic volume and good mobility to effectively occupy the oxygen vacancy defects in the silica network structure, thereby reducing oxygen vacancy defects and improving the gas retention and pressure resistance of the glass microspheres.

[0044] In the technical solution of the present invention, when using plasma chemical vapor deposition to prepare silicon-containing polymer coatings, due to their high hardness and Young's modulus, the coating is brittle and prone to coating slagging, which seriously affects the coating quality and ultimately increases the surface roughness of the glass microspheres. Therefore, the present invention effectively reduces the hardness and Young's modulus of the silicon-containing polymer through lithium doping, thereby softening the coating, effectively suppressing slagging during the coating process, improving the coating quality, and reducing the surface roughness of the glass microspheres.

[0045] In the technical solution of the present invention, the silicon-containing polymer coating contains a large amount of carbon and hydrogen elements. During the high-temperature oxidation sintering process, the carbon and hydrogen elements in the microsphere shell will be oxidized to gases such as CO2 and H2O, and released from the shell into the environment. This will cause the microspheres to shrink by approximately 80%. Excessive volume shrinkage can easily cause significant internal stress in the silica shell. In addition, the glass sphere sintering process involves multiple heating and holding steps. Due to the heat transfer differences between the inner and outer surfaces of the silica shell, the shell may generate certain thermal stresses. The presence of such stresses will seriously affect the mechanical properties of the silica shell, thereby reducing the compressive strength of the glass microspheres. Therefore, the disclosed method for preparing millimeter-scale thin-walled hollow glass microspheres increases the microsphere densification sintering temperature to 1000-1100°C, above the strain point of lithium-doped silica. This allows SiO2 molecules to migrate effectively within the network structure, resulting in stress relaxation and thus eliminating stress in the silica shell. At the same time, a slow cooling process prevents the generation of new thermal stresses. Through the above procedures, the pressure resistance of the glass microspheres can be effectively improved.

[0046] In the technical solution of the present invention, during the high-temperature oxidation process of the silicon-containing polymer coating into silica, the silica shell generates not only oxygen vacancy defects but also a large number of hydroxyl defects. These hydroxyl defects also affect the gas retention and pressure resistance of the hollow glass microspheres. Therefore, the disclosed method for preparing millimeter-scale, thin-walled hollow glass microspheres, by increasing the microsphere densification sintering temperature to above 1000°C, can dehydrate the hydroxyl groups in the silica network structure, effectively reducing the hydroxyl defect content and improving the gas retention and pressure resistance of the hollow glass microspheres.

[0047] In the technical solution of the present invention, the heating rate in step S2 is controlled between 0.5 and 5°C / min. This is mainly to avoid excessively high heating rates, which may cause the core shaft to thermally degrade too quickly, leading to the release of a large amount of small-molecule gases in a short period of time. Due to the limited diffusion rate of these small-molecule gases in the outermost silicon-containing polymer layer, a large amount of small-molecule gases may not be able to immediately diffuse out of the microspheres, causing a sharp increase in the gas pressure inside the microspheres and ultimately causing the microspheres to rupture. While too low a heating rate has no effect on the preparation of glass microspheres, it can reduce preparation efficiency.

[0048] In the technical solution of the present invention, the heating rate in steps S3 and S4 is controlled between 0.5 and 2°C / min. This is primarily because these two steps are critical stages in the oxidation of the silicon-containing polymer shell to a SiO2 shell. Chemical reactions occur within the shell, including the oxidation of C and H elements, the release of gases such as CO2 and H2O, the oxidation of Si elements, and the formation of a SiO2 network structure. Simultaneously, physical transformations such as microsphere volume shrinkage occur. These physical and chemical transformations are sensitive to reaction temperature. Excessively high heating rates can adversely affect these reactions, thereby reducing the quality of the glass spheres. On the other hand, excessively low heating rates can reduce production efficiency.

[0049] In the technical solution of the present invention, step S5 controls the cooling rate to be between 0.1 and 1° C. / min in order to avoid generating new thermal stress in the glass shell layer, which would result in a decrease in the pressure resistance of the glass ball.

[0050] Below with reference to specific embodiment, the scheme of the present invention will be explained. Those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. Where specific techniques or conditions are not indicated in the examples, they are carried out according to the techniques or conditions described in the literature in this area or according to the product instructions. Reagents or instruments used that do not indicate the manufacturer are conventional products that can be obtained commercially.

[0051] In the embodiment, the gas retention half-life is tracked and measured by using white light interferometry technology or Raman spectroscopy technology to measure the internal gas pressure of the inflated hollow glass microspheres.

[0052] Example 1 Preparation of millimeter-sized thin-walled hollow glass microspheres

[0053] Step S1: A lithium-doped silicon-containing polymer coating is deposited on the surface of poly-α-methylstyrene microspheres with a diameter of about 1.5 mm using a plasma-enhanced chemical vapor deposition device. Before coating deposition, the device is evacuated to a vacuum of <5×10 -3 Pa. Hydrogen, tetramethylsilane, trans-dibutene, and n-butyllithium were introduced through flow controllers, with gas flow rates of 9.5 sccm, 0.6 sccm, 0.2 sccm, and 0.3 sccm, respectively. The gas pressure was adjusted to 5 Pa using a plug valve. The power of the 40.68 MHz RF power supply was set to 10 W and turned on to generate plasma. The vacuum motor was started to drive the poly(α-methylstyrene) microspheres to roll in the sample tray. After 10 hours of deposition, a lithium-doped silicon-containing polymer coating with a lithium content of approximately 0.5 at.% and a silicon content of approximately 9 at.% was obtained.

[0054] Step S2: The microspheres prepared in step S1 were placed in a crucible in a tube furnace, and nitrogen was introduced as a protective gas. The temperature was slowly increased to 300°C at a rate of 0.5°C / min and maintained at this temperature for 5 hours to remove the inner layer of polymer microspheres, thereby obtaining lithium-doped hollow silicon-containing polymer microspheres.

[0055] Step S3: Based on step S2, the atmosphere in the tube furnace is switched to oxygen, and the temperature is gradually increased from 300°C to 400°C at a heating rate of 0.5°C / min, and kept warm for 10 hours to oxidize the lithium-doped silicon-containing polymer microspheres into lithium-doped glass microspheres.

[0056] Step S4: Based on step S3, the temperature of the tube furnace is further increased to 1000° C. at a rate of 0.5° C. / min and kept at this temperature for 5 hours to densify the glass microspheres.

[0057] Step S5: Based on step S4, the temperature of the tube furnace is slowly lowered to 350°C at a rate of 0.1°C / min. The tube furnace is then allowed to cool naturally to room temperature. Millimeter-sized thin-walled hollow glass microspheres are obtained, having a diameter of approximately 1 mm, a wall thickness of approximately 2 μm, a sphericity greater than 99%, a wall thickness uniformity greater than 95%, a surface roughness less than 50 nm, a gas retention half-life greater than 30 days, and an internal pressure resistance greater than 10 atm.

[0058] Example 2 Preparation of millimeter-sized thin-walled hollow glass microspheres

[0059] Step S1: A lithium-doped silicon-containing polymer coating is deposited on the surface of poly-α-methylstyrene microspheres with a diameter of about 4 mm using a plasma-enhanced chemical vapor deposition device. Before coating deposition, the device is evacuated to a vacuum of <5×10 -3 Pa. Hydrogen, tetramethylsilane, trans-dibutene, and n-butyllithium were introduced through flow controllers, with gas flow rates of 9.5 sccm, 0.4 sccm, 0.25 sccm, and 0.1 sccm, respectively. The gas pressure was adjusted to 10 Pa using a plug valve. The power of the 40.68 MHz RF power supply was set to 30 W and turned on to generate plasma. The vacuum motor was started to drive the poly(α-methylstyrene) microspheres to roll in the sample tray. After 100 hours of deposition, a lithium-doped silicon-containing polymer coating with a lithium content of approximately 0.1 at.% and a silicon content of approximately 5 at.% was obtained.

[0060] Step S2: The microspheres prepared in step S1 were placed in a crucible in a tube furnace, and nitrogen was introduced as a protective gas. The temperature was slowly increased to 300°C at a rate of 5°C / min and maintained at this temperature for 20 hours to remove the inner layer of polymer microspheres, thereby obtaining lithium-doped hollow silicon-containing polymer microspheres.

[0061] Step S3: Based on step S2, the atmosphere in the tube furnace is switched to oxygen, and the temperature is gradually increased from 300°C to 650°C at a heating rate of 2°C / min, and kept warm for 30 hours to oxidize the lithium-doped silicon-containing polymer microspheres into lithium-doped glass microspheres.

[0062] Step S4: Based on step S3, the temperature of the tube furnace is further increased to 1100° C. at a rate of 2° C. / min, and kept at this temperature for 15 hours to densify the glass microspheres.

[0063] Step S5: Based on step S4, the temperature of the tube furnace is slowly lowered to 350°C at a rate of 1°C / min. The tube furnace is then allowed to cool naturally to room temperature. Millimeter-sized, thin-walled hollow glass microspheres are obtained, having a diameter of approximately 2.5 mm, a wall thickness of approximately 20 μm, a sphericity greater than 99%, a wall thickness uniformity greater than 95%, a surface roughness less than 50 nm, a gas retention half-life greater than 30 days, and an internal pressure resistance greater than 10 atm.

[0064] Example 3 Preparation of millimeter-sized thin-walled hollow glass microspheres

[0065] Step S1: A lithium-doped silicon-containing polymer coating is deposited on the surface of polystyrene microspheres with a diameter of about 6 mm using a plasma enhanced chemical vapor deposition device. Before coating deposition, the device is evacuated to a vacuum of <5×10 -3 Pa. Hydrogen, tetramethylsilane, trans-dibutene, and n-butyllithium were introduced through flow controllers, with gas flow rates of 9.5 sccm, 0.5 sccm, 0.2 sccm, and 0.2 sccm, respectively. The gas pressure was adjusted to 20 Pa using a plug valve. The power of the 40.68 MHz RF power supply was set to 20 W and turned on to generate plasma. The vacuum motor was started to drive the poly(α-methylstyrene) microspheres to roll in the sample tray. After 50 hours of deposition, a lithium-doped silicon-containing polymer coating with a lithium content of approximately 0.3 at.% and a silicon content of approximately 7 at.% was obtained.

[0066] Step S2: The microspheres prepared in Step S1 were placed in a crucible in a box-type atmosphere furnace with argon as a protective gas. The crucible was then heated slowly to 300°C at a rate of 2°C / min and maintained at this temperature for 15 hours to remove the inner layer of polymer microspheres, thereby obtaining lithium-doped hollow silicon-containing polymer microspheres.

[0067] Step S3: Based on step S2, the atmosphere in the box-type atmosphere furnace is switched to oxygen, and the temperature is gradually increased from 300°C to 500°C at a heating rate of 1°C / min, and kept warm for 20 hours to oxidize the lithium-doped silicon-containing polymer microspheres into lithium-doped glass microspheres.

[0068] Step S4: Based on step S3, the temperature of the box-type atmosphere furnace is further increased to 1050° C. at a rate of 1° C. / min, and kept at this temperature for 10 hours to densify the glass microspheres.

[0069] Step S5: Based on step S4, the box-type atmosphere furnace temperature is slowly lowered to 350°C at a rate of 0.5°C / min. The box-type atmosphere furnace is then allowed to cool naturally to room temperature. Millimeter-sized thin-walled hollow glass microspheres are obtained, having a diameter of approximately 4 mm, a wall thickness of approximately 10 μm, a sphericity greater than 99%, a wall thickness uniformity greater than 95%, a surface roughness less than 50 nm, a gas retention half-life greater than 30 days, and an internal pressure resistance greater than 10 atm.

[0070] It should be noted that the specific features, structures, materials, or characteristics described in this specification may be combined in any suitable manner in any one or more embodiments. In addition, those skilled in the art may combine and combine the different embodiments and features of the different embodiments described in this specification without any contradiction.

Claims

1. A method for preparing hollow glass microspheres, characterized in that: The following steps are involved: S1: Lithium-doped silicon-containing polymer coating is deposited on the surface of polymer microspheres by chemical vapor deposition; S2: degrading the microspheres prepared in step S1 at high temperature under the protection of inert gas to remove the inner layer of polymer microspheres to obtain lithium-doped silicon-containing polymer hollow microspheres; S3: oxidizing the lithium-doped silicon-containing polymer hollow microspheres obtained in step S2 to lithium-doped glass microspheres; S4: densifying and sintering the lithium-doped glass microspheres in step S3 at 1000-1100° C.; S5: The lithium-doped glass microspheres densified in step S4 are cooled to 350° C. at a rate of 0.1-1° C. / min, and then cooled to room temperature naturally in the furnace.

2. The method for preparing hollow glass microspheres according to claim 1, wherein: In step S1, the polymer microspheres include at least one of poly-α-methylstyrene microspheres, polystyrene microspheres, and polypropylene microspheres.

3. The method for preparing hollow glass microspheres according to claim 1, wherein: In step S1, at least one of the following conditions is met: The polymer microspheres have a diameter of 1.5 to 6 mm; The chemical vapor deposition method is operated using a plasma enhanced chemical vapor deposition device; Before coating deposition, the vacuum value was reduced to <5×10 -3 Pa; During coating deposition, working gases including hydrogen, tetramethylsilane, trans-dibutene, and n-butyllithium were introduced at a pressure of 5-20 Pa, a 40.68 MHz RF power supply of 10-30 W, and a deposition time of 10-100 hours. The lithium-doped silicon-containing polymer coating has a lithium content of 0.1 to 0.5 at.%, and a silicon content of 5 to 9 at.%.

4. The method for preparing hollow glass microspheres according to claim 3, wherein: In the lithium-doped silicon-containing polymer coating, the contents of lithium and silicon are controlled by adjusting the gas flow rate.

5. The method for preparing hollow glass microspheres according to claim 1, wherein: In step S2, the inert gas is selected from at least one of nitrogen, argon, and helium; And / or, the high temperature degradation condition is: applying power and slowly heating the temperature to 280-320°C at a heating rate of 0.5-5°C / min, and keeping the temperature for 5-20 hours to remove the inner layer of polymer microspheres.

6. The method for preparing hollow glass microspheres according to claim 1, wherein: In step S3, the oxidation conditions are: gradually increasing the temperature from 280-320°C to 400-650°C at a heating rate of 0.5-2°C / min, and keeping the temperature for 10-30 hours.

7. The method for preparing hollow glass microspheres according to claim 1, wherein: In step S4, the densification sintering conditions are: heating to 1000-1100°C at a rate of 0.5-2°C / min and keeping the temperature for 5-15 hours.

8. Hollow glass microspheres prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the hollow glass microspheres according to claim 8 as deuterium-tritium fuel carriers in the field of laser inertial confinement fusion.

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