A transparent ceramic fiber and its preparation method

Abstract

This invention discloses a transparent ceramic fiber and its preparation method. The preparation method includes: ball milling and mixing ceramic powder, photosensitive resin, dispersant, and initiator in a mass ratio of 81-84:13-16.5:0.8-4.2:0.3-0.8 to obtain a mixture; roller milling the mixture to obtain a ceramic slurry; extruding the ceramic slurry in a preheated extrusion device and curing it by passing it through a light source; and sintering the resulting shaped fiber filaments after debinding to obtain the transparent ceramic fiber. This invention enables the continuous extrusion preparation of ceramic fibers with high aspect ratio and low defects. The fiber length is controllable, with high roundness and controllable thickness, and the prepared diameter is ≤200μm. Through photocuring technology, the fiber surface is uniformly cured, which can improve the uniformity, density, and mechanical properties of the fiber. The fiber shape is self-rounded by surface tension, and the obtained fiber does not require post-processing such as polishing curved surfaces. The process is simple and has industrialization prospects.

Description

Technical Field

[0001] This invention relates to the field of chemical material preparation technology, specifically to a transparent ceramic fiber and its preparation method. Background Technology

[0002] The gain medium, as the heart of a laser, determines its output power and optical conversion efficiency. Fiber lasers, as laser gain media, offer advantages such as high stability, good beam quality, and high conversion efficiency, making them widely applicable in fields like medicine, information communication, and sensing. Currently, most fiber laser gain media are made of quartz glass / single crystal. Quartz glass possesses excellent optical properties, low loss, and high durability, meeting the requirements of many applications. However, its low thermal conductivity leads to spontaneous emission (ASE) during laser system operation, ultimately causing insufficient output power during prolonged operation. The development and application of single crystal fibers are limited by high energy consumption, high cost, complex fabrication, and especially the difficulty in achieving high doping concentrations. Therefore, it is necessary to research novel fiber laser gain media.

[0003] Transparent ceramics have proven to be an efficient and economical laser gain medium. A 2007 report showed a slope efficiency (η) as high as 65% for a 1 at.% Nd:YAG ceramic sample, attributed to the absence of a segregation coefficient in YAG ceramics, allowing for doping at higher levels than single crystals without doping loss. Furthermore, transparent ceramics possess high fracture toughness and a low fabrication temperature (1750–1850 °C), making them excellent candidates for gain media in fiber lasers.

[0004] However, there are currently few reports on transparent ceramic fibers. In 2011, Kim and Fair et al. at the U.S. Air Force Research Laboratory successfully fabricated ceramic fibers with a diameter of 30 μm using transparent ceramic materials, ushering in the era of transparent ceramic fibers. In 2017, they clad the ceramic fiber with SF57 glass and conducted laser experiments, achieving a maximum power of 0.7 W at 2091 nm, a slope efficiency of 7%, and a pump threshold of less than 500 mW. This verified the feasibility of using ceramic materials as gain media for fiber lasers. This experimental approach holds promise for developing fiber lasers towards smaller size, lighter weight, higher efficiency, and higher reliability.

[0005] Currently, the main methods for preparing ceramic fibers are liquid molding, including slip casting and 3D printing. Slip casting and gel casting, two colloidal molding processes, face challenges due to the surface tension of the slurry, making it difficult to inject into small-aperture plaster molds. This can even lead to voids in the green body, resulting in a rough surface. The length of the prepared ceramic fibers depends heavily on the mold design, limiting the production of long fibers; the maximum reported length is 113 mm. While 3D printing offers high precision, it is also limited by the model, making it unsuitable for long fiber preparation. These molding methods fall far short of the needs of ceramic fiber research and future industrial production. Therefore, developing reasonable manufacturing processes and improving production efficiency are urgent issues to be addressed in preparing high aspect ratio, long-distance ceramic fibers. Summary of the Invention

[0006] The technical problem to be solved by this invention is how to prepare long-distance transparent ceramic fibers.

[0007] The present invention solves the above-mentioned technical problems through the following technical means:

[0008] A method for preparing transparent ceramic fibers includes the following steps:

[0009] S1. Ceramic powder, photosensitive resin, dispersant and initiator are ball-milled and mixed to obtain a mixture; wherein the mass ratio of ceramic powder, photosensitive resin, dispersant and initiator is 81-84:13-16.5:0.8-4.2:0.3-0.8;

[0010] S2. The obtained mixture is roller-milled to obtain ceramic slurry;

[0011] S3. The obtained ceramic slurry is extruded in a preheated extrusion device and flows through a light source for curing to obtain shaped fiber filaments;

[0012] S4. After removing the glue from the obtained molded fiber filaments, sinter them to obtain the transparent ceramic fiber.

[0013] Preferably, in S1, the ceramic powder is one or a mixture of alumina powder, yttrium oxide powder, and magnesium oxide powder.

[0014] Preferably, the ceramic powder is a mixture of yttrium oxide powder and alumina powder in a molar ratio of 3:5.

[0015] Preferably, in S1, the photosensitive resin is one or a mixture of hydroxyethyl acrylate (HEA), 1,6-hexanediol diacrylate (HDDA), and trimethylolpropane triacrylate (TMPTA).

[0016] Preferably, in S1, the dispersant is one or a mixture of two of CPD01 and CPD02; the initiator is one or a mixture of two of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide TPO and tetradecyltrihexylphosphine bis(2,4,4-trimethylpentyl)hypophosphine CPI06.

[0017] Preferably, the initiator is a mixture of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide (TPO) and tetradecyltrihexylphosphine bis(2,4,4-trimethylpentyl)hypophosphine (CPI06), and the mass of tetradecyltrihexylphosphine bis(2,4,4-trimethylpentyl)hypophosphine (CPI06) is ≤ 2% of the mass of the photosensitive resin.

[0018] Preferably, in S2, a three-roll mill is used to perform 5-10 roller milling on the mixture under the conditions of a feed gap of 80-30μm and a rotation speed of 50-150r / min.

[0019] Preferably, in S2, a ceramic slurry with a viscosity of 8000-14000 cps is obtained by roller milling.

[0020] Preferably, in S3, the extrusion speed of the extrusion device is 1000-3000 mm / min, the slurry in the heating chamber is heated to 30-50°C, the nozzle diameter used at the extrusion outlet is 0.2-0.8 mm, and the light intensity of the light source is 30-100 mW.

[0021] Preferably, in S4, during the debinding process, the heating rate is 0.2-0.5℃ / min, the temperature is raised to 900-1100℃, and held for 2-4 hours; during the sintering process, the heating rate is 3℃ / min, the temperature is raised to 1780℃, and held for 2 hours.

[0022] Preferably, the purity of the ceramic powder is ≥99.99%.

[0023] Preferably, the amount of dispersant used is 1% to 5% of the mass of the ceramic powder.

[0024] Preferably, in S1, during the ball milling process, the ball milling speed is 300-400 r / min and the ball milling time is 2-4 h.

[0025] The present invention also proposes a transparent ceramic fiber, which is prepared by the aforementioned method for preparing transparent ceramic fibers.

[0026] This invention proposes a method for preparing transparent ceramic fibers by slurry extrusion and photocuring. The method involves ball milling selected ceramic powder, photosensitive resin, dispersant, and initiator to obtain a mixture. This mixture is then homogenized in a 3D roller mill to achieve a uniform slurry with a suitable viscosity. The resulting slurry is placed in an extrusion molding machine equipped with a photocuring lamp to obtain a shaped fiber preform. After debinding, a cellulose preform is obtained, which is then cured to obtain transparent ceramic fibers. This invention utilizes multiple roller milling steps after ball milling and extrusion photocuring instead of natural curing. It leverages the increased uniformity of the slurry after multiple roller milling steps, which can increase the uniformity and yield of the green body, thereby improving the quality of the ceramic. By curing and collecting the extruded slurry streamline as it falls, the upper limit of extruded fiber length can be exceeded. Furthermore, the strength of the preform can be precisely and freely controlled by adjusting the light intensity, reducing deformation during debinding and sintering.

[0027] This invention combines photopolymerization and extrusion molding technologies to achieve the liquid extrusion preparation of transparent ceramic fibers, solving problems such as high surface roughness and poor optical properties associated with traditional extrusion processes. It also enables stable long-distance fiber preparation, with advantages including, but not limited to: 1) Continuous extrusion preparation of ceramic fibers with high aspect ratio and low defects. Fiber length is controllable, with high roundness and thickness, and a prepared diameter ≤200μm. 2) Photopolymerization technology uniformly cures the fiber surface, improving fiber uniformity, density, and mechanical properties. 3) Surface tension is used to achieve self-circular fiber shape, eliminating the need for post-processing such as polishing curved surfaces. The process is simple and has promising industrialization prospects. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the apparatus used for extrusion photocuring preparation in an embodiment of the present invention;

[0029] Figure 2 The microstructure of the filament obtained in step three of embodiment 2 of the present invention;

[0030] Figure 3 This is a length diagram of the filament obtained in step three of embodiment 2 of the present invention;

[0031] Figure 4 This is a diagram showing the transparency of the fibers obtained after sintering in Example 2 of the present invention.

[0032] Figure 5 This is a morphology diagram of the fibers obtained after sintering in Example 2 of the present invention;

[0033] Figure 6 The image shows a micrograph of the fibers obtained after sintering in step four of Comparative Example 1 of this invention.

[0034] Figure 7 The microstructure of the shaped filament obtained in step two of Comparative Example 2 of this invention is shown.

[0035] Figure 8 This is a morphology diagram of the fibers obtained after sintering in Comparative Example 2 of the present invention.

[0036] Figure 9 This is a photograph of the product prepared in Example 1 of the present invention;

[0037] Figure 10 A micrograph of the fibers obtained after sintering in Example 1 of the present invention;

[0038] Figure 11 This is a physical image of the product prepared in Comparative Example 1 of the present invention;

[0039] Figure 12 This is a physical image of the product prepared in Comparative Example 3 of the present invention;

[0040] Figure 13 This is a physical image of the product prepared in Comparative Example 4 of the present invention. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0043] Unless otherwise specified in the embodiments, the techniques or conditions described in the literature in this field or in accordance with the product manual may be followed.

[0044] The following is a schematic diagram of the extrusion molding apparatus used. Figure 1 As shown, it includes a motor (specifically a stepper motor), an extrusion bolt, a feeding chamber, a slurry flow channel, and a heating system (specifically a heating bar). The stepper motor delivers torque to the extrusion bolt, which extrudes the slurry mixed in the feeding chamber into the nozzle in the slurry flow channel (the nozzle diameter is 0.35mm), forming a continuous slurry flow line. The heating system is responsible for controlling the temperature in the slurry flow channel to be constant. The slurry flow line is cured and formed after being irradiated by a curing light source (LED light source).

[0045] The manufacturer of the dispersant used is Jiaxing Raoji Technology Co., Ltd.

[0046] Example 1

[0047] This embodiment describes a method for preparing yttrium aluminum garnet transparent ceramic fibers by slurry extrusion photocuring, comprising the following steps:

[0048] Step 1, Ball Milling and Mixing: Weigh out ceramic powder, photosensitive resin, dispersant, and initiator according to a solid content of 83.64 wt.%. The ceramic powder is a mixture of yttrium oxide and alumina in a molar ratio of 3:5. The photosensitive resin is a mixture of HEA and HDDA in a mass ratio of 3:4, accounting for 13.07 wt.% of the total mass. CPD01 is used as the dispersant, at 3% of the ceramic powder mass. TPO is used as the initiator, at 6% of the photosensitive resin mass. The specific proportions of each raw material in this process are shown in the table below after conversion.

[0049]

[0050]

[0051] After weighing the raw materials, mix them in a planetary ball mill at 400 r / min for 3 h to obtain a mixture;

[0052] Step 2, roller milling: The mixture obtained in Step 1 is placed in a three-roll mill with a feed gap of 80μm and a discharge gap of 40μm. The mixture is milled for 5 rounds at 150r / min to obtain a ceramic slurry with a viscosity of 11000cps.

[0053] Step 3, extrusion photocuring molding: The ceramic slurry obtained in step 2 is introduced into the feeding chamber of the preheated 35℃ extrusion molding device, and a falling streamline is formed at an extrusion speed of 1500mm / min. It flows through the ring light source and is cured under a light intensity of 35mW to obtain the molded fiber filament.

[0054] Step 4, Debinding and Sintering: The filaments obtained in Step 3 are pre-fired in a muffle furnace at 0.3℃ / min to 1000℃ for 2 hours to remove organic matter, yielding a cellulose preform. Then, the temperature is increased to 1780℃ at 3℃ / min and held for 2 hours to obtain a dense sample of yttrium aluminum garnet transparent ceramic fiber, as shown in the micrograph. Figure 10 As shown, by Figure 10 It can be seen that there are some small pores on the sample surface; the actual object image is as follows. Figure 9 As shown, by Figure 9 It can be seen that the sample has a certain degree of transparency.

[0055] Example 2

[0056] This embodiment describes a method for preparing transparent alumina ceramic fibers by slurry extrusion and photocuring, comprising the following steps:

[0057] Step 1, Ball Milling and Mixing: Weigh out ceramic powder, photosensitive resin, dispersant, and initiator according to a solid content of 81.04 wt.%. The ceramic powder is 4N grade alumina powder; the photosensitive resin is a mixture of HEA, HDDA, and TMPTA in a 1:1:1 mass ratio, accounting for 16.21 wt.% of the total mass; CPD01 is used as the dispersant, at 3% of the ceramic powder mass; and a mixture of TPO and CPI06 in a 1:1 mass ratio is used as the initiator, at 2% of the photosensitive resin mass. The specific weighing ratios of each raw material in this process are shown in the table below.

[0058]

[0059] After weighing the raw materials, mix them in a planetary ball mill at 350 r / min for 4 h to obtain a mixture;

[0060] Step 2, roller milling: The mixture obtained in Step 1 is placed in a three-roll mill with a feed gap of 80μm and a discharge gap of 50μm. The mixture is milled at 150r / min for 7 rounds to obtain a ceramic slurry with a viscosity of 9000cps.

[0061] Step 3, Extrusion Photocuring: The ceramic slurry obtained in Step 2 is introduced into the feeding chamber of an extrusion molding device preheated to 35℃, forming a falling stream at an extrusion speed of 2100 mm / min, and flows through a ring light source. It is cured under a light intensity of 35 mW to obtain the molded fiber filament. Its surface morphology is shown in the figure below. Figure 2 As shown, by Figure 2 It can be seen that the obtained fiber filaments have high roundness and small radius (≤200μm), and their length can reach 30cm, such as Figure 3 As shown;

[0062] Step 4, Debinding and Sintering: The filaments obtained in Step 3 are pre-fired in a muffle furnace at 0.3℃ / min to 900℃ for 3 hours to remove organic matter, yielding a cellulose preform. Then, the temperature is increased to 1780℃ at 3℃ / min and held for 2 hours to obtain dense alumina transparent ceramic fibers, the morphology of which is shown in the figure below. Figure 5 As shown, by Figure 5 As can be seen, the fiber cross-section is dense, without any pores, and the surface is smooth. The actual transparent image is shown below. Figure 4 As shown, by Figure 4 It is known that it has transparent properties, and the text under the fibers is clearly visible.

[0063] Comparative Example 1

[0064] This comparative example demonstrates a method for preparing transparent alumina ceramic fiber slurry by extrusion photocuring, which includes the following steps:

[0065] Step 1, ball milling and mixing: Weigh out ceramic powder, photosensitive resin, dispersant and initiator according to a solid content of 86.38 wt.%. The ceramic powder is 4N grade alumina powder, the photosensitive resin is a mixture of HEA, HDDA and TMPTA in a mass ratio of 3:4:3, accounting for 10.5 wt.% of the total mass, the dispersant is CPD01, the amount is 3% of the mass of ceramic powder, and the initiator is a mixture of TPO and CPI06 in a mass ratio of 1:1, the amount is 5% of the mass of photosensitive resin.

[0066] After conversion, the specific weighing ratios of each raw material in this process are shown in the table below:

[0067]

[0068] After weighing the raw materials, mix them in a planetary ball mill at 400 r / min for 4 h to obtain a mixture;

[0069] Step 2, roller milling: The mixture obtained in Step 1 is placed in a three-roll mill with a feed gap of 60μm and a discharge gap of 50μm. The mixture is milled at 150r / min for 7 rounds to obtain a ceramic slurry with a viscosity of 9000cps.

[0070] Step 3, extrusion photocuring molding: The ceramic slurry obtained in step 2 is introduced into the feeding chamber of the preheated 35℃ extrusion molding device, and a falling streamline is formed at an extrusion speed of 2100mm / min. It flows through the ring light source and is cured under a light intensity of 35mW to obtain the molded fiber filament.

[0071] Step 4, Debinding and Sintering: The filaments obtained in Step 3 are pre-fired in a muffle furnace at 0.25℃ / min to 1100℃ for 3 hours to remove organic matter, yielding a cellulose preform. Then, the temperature is increased to 1780℃ at 3℃ / min and held for 2 hours to obtain a dense sample. The micrograph is shown below. Figure 6 As shown in the picture, the actual product is as follows. Figure 11 As shown, by Figure 6 and 11 It can be seen that its surface is relatively rough.

[0072] Comparative Example 2

[0073] This embodiment describes a method for photocuring yttrium aluminum garnet ceramic fiber slurry without roller milling, comprising the following steps:

[0074] Step 1, Ball Milling and Mixing: Weigh out ceramic powder, photosensitive resin, dispersant, and initiator according to a solid content of 83.64 wt.%. The ceramic powder is a mixture of yttrium oxide and alumina in a molar ratio of 3:5. The photosensitive resin is a mixture of HEA and HDDA in a mass ratio of 3:4, accounting for 13.07 wt.% of the total mass. CPD01 is used as the dispersant, at 3% of the ceramic powder mass. TPO is used as the initiator, at 6% of the photosensitive resin mass. The specific weighing ratios of each raw material in this process are shown in the table below.

[0075]

[0076] After weighing the raw materials, mix them in a planetary ball mill at 400 r / min for 3 h to obtain a mixture;

[0077] Step 2, Extrusion Photocuring: The ceramic slurry obtained in Step 1 is introduced into the feeding chamber of an extrusion molding device preheated to 35℃, forming a downward flow line at an extrusion speed of 2100 mm / min, and flows through a ring light source, curing under a light intensity of 35 mW to obtain the molded fiber filament; its microscopic image is shown below. Figure 7 As shown, by Figure 7 It can be seen that its roundness is not high and it has large pores;

[0078] Step 3, Debinding and Sintering: The filaments obtained in Step 2 are pre-fired in a muffle furnace at 0.3℃ / min to 1000℃ for 2 hours to remove organic matter, yielding a cellulose preform. Then, the temperature is increased to 1780℃ at 3℃ / min and held for 2 hours to obtain a dense sample. The microscopic image is shown below. Figure 8 As shown, by Figure 8 It can be seen that its roundness is not high.

[0079] Comparative Example 3

[0080] The only difference from Example 2 is that: the initiator used was a mixture of TPO and CPI06 in a 1:1 mass ratio, and the amount used was 5% of the mass of the photosensitive resin; the obtained fiber diameter was uneven, such as... Figure 12 As shown.

[0081] Comparative Example 4

[0082] The only difference from Example 2 is that it does not undergo roller milling; the resulting fibers are opaque, such as... Figure 13 As shown.

[0083] Figure 4 , Figure 9 , Figure 11 , Figure 12 The text in the image serves as the background for the photograph, making it easier to observe the transparency of the fibers.

[0084] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing transparent ceramic fibers, characterized in that: Includes the following steps: S1. Ceramic powder, photosensitive resin, dispersant, and initiator are ball-milled and mixed to obtain a mixture; wherein, the mass ratio of the ceramic powder, photosensitive resin, dispersant, and initiator is 81-84:13-16.5:0.8-4.2:0.3-0.8; the initiator is a mixture of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide and tetradecyltrihexylphosphine bis(2,4,4-trimethylpentyl)phosphine, and the mass of tetradecyltrihexylphosphine bis(2,4,4-trimethylpentyl)phosphine is ≤2% of the mass of the photosensitive resin; S2. The obtained mixture is roller-milled to obtain ceramic slurry; S3. The obtained ceramic slurry is extruded in a preheated extrusion device and flows through a light source for curing to obtain shaped fiber filaments; S4. After removing the glue from the obtained molded fiber filaments, sinter them to obtain the transparent ceramic fiber.

2. The method for preparing transparent ceramic fibers according to claim 1, characterized in that: In S1, the ceramic powder is one or a mixture of alumina powder, yttrium oxide powder, and magnesium oxide powder.

3. The method for preparing transparent ceramic fibers according to claim 1, characterized in that: In S1, the photosensitive resin is one or a mixture of hydroxyethyl acrylate, 1,6-hexanediol diacrylate, and trimethylolpropane triacrylate.

4. The method for preparing transparent ceramic fibers according to claim 1, characterized in that: In S1, the dispersant is one or a mixture of two of CPD01 and CPD02.

5. The method for preparing transparent ceramic fibers according to claim 1, characterized in that: In S2, a three-roll mill is used to perform 5-10 roller milling on the mixture under the conditions of a feed gap of 80-30μm and a rotation speed of 50-150r / min.

6. The method for preparing transparent ceramic fibers according to claim 1, characterized in that: In S2, a ceramic slurry with a viscosity of 8000-14000 cps is obtained by roller milling.

7. The method for preparing transparent ceramic fibers according to claim 1, characterized in that: In S3, the extrusion speed of the extrusion device is 1000-3000 mm / min, the slurry in the heating chamber is heated to 30-50°C, and the nozzle diameter used at the extrusion outlet is 0.2-0.8 mm; the light intensity of the light source is 30-100 mW.

8. The method for preparing transparent ceramic fibers according to any one of claims 1-7, characterized in that: In S4, during the glue removal process, the heating rate is 0.2-0.5℃ / min, the temperature is raised to 900-1100℃, and held for 2-4 hours; During the sintering process, the heating rate was 3℃ / min, the temperature was raised to 1780℃, and held for 2 hours.

9. A transparent ceramic fiber, characterized in that: It is prepared by the method of any one of claims 1-8 for the preparation of transparent ceramic fibers.

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