Method for preparing hollow silicon dioxide fiber by using alginate fiber as template

Abstract

The invention discloses a method for preparing hollow silicon dioxide fibers by taking alginate fibers as a template, and relates to a preparation method of a biological template material, and the method realizes the preparation of the hollow silicon dioxide fibers with high morphology goodness of fit (greater than 92%) through vacuum-assisted acidification, sodium silicate in-situ conversion and high-temperature calcination processes. The method comprises the following steps: by taking natural alginate fiber (with the diameter of 10-30 microns) as a sacrificial template, adsorbing hydrochloric acid and sodium silicate by utilizing an internal honeycomb porous structure of the natural alginate fiber to react to generate silicic acid, and calcining at 1200 DEG C to form a hollow structure; the specific surface area of the obtained fiber reaches 420-680 m / g, and the obtained fiber has excellent mechanical performance and thermal stability and is suitable for the fields of high temperature resistance, heat insulation, drug sustained release, flexible electronic devices and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for preparing a biomimetic material, in particular to a method for preparing hollow silica fibers using seaweed fibers as templates. BACKGROUND

[0002] Hollow silica (quartz) fibers have good hardness and inertness, excellent mechanical properties, thermal properties and excellent barrier properties against corrosion and chemical attack. These properties make the material have better thermal / chemical stability, reusability and mechanical properties than traditional organic polymer hollow fibers, and thus have obvious advantages in the construction of electronic / optoelectronic devices and carrier materials and other applications.

[0003] At present, there are mainly the following methods for preparing hollow silica (quartz) fibers: Method 1: Template method is a traditional method for preparing hollow silica (quartz) fibers. In the template method, substances with different morphologies (such as fibrous, strip-shaped, tubular structure, columnar structure, double-chain type and disc-shaped) are used as the basis, and chemical growth method or physical deposition method is used to load SiO2, and finally the template is removed to obtain the desired structure. After years of research, the process is simple and easy to operate, and the product morphology is controllable, but it is relatively difficult to obtain multi-stage fibers with large aspect ratio, and this method is not easy to mass production, and it is difficult to completely remove the template. The above defects directly limit the application of the obtained material in many aspects, especially in the fields with high requirements for material strength and orientation, such as sensing, catalysis and biological separation of nanoscale fluid. For example, Zhang Hailian of Zhengzhou University used PVA electrospinning nanofibers as templates, tetraethyl orthosilicate (TEOS) as a silicon source, and adopted sol-gel reaction to construct Silica / PVA shell-core nanofibers, and finally removed PVA by burning to obtain hollow silica nanofibers composed of SiO2 small spheres. This method uses sol-gel method to generate silicon hydroxyl groups by hydrolyzing tetraethyl orthosilicate, which reacts with alcohol hydroxyl groups on PVA to form a small ball layer of SiO2 on the surface of PVA. However, the silicon hydroxyl groups generated by hydrolysis of tetraethyl orthosilicate tend to react with silicon hydroxyl groups rather than alcohol hydroxyl groups, which in turn leads to a low amount of deposition on the surface of PVA.

[0004] Method 2: Electrospinning is a new method for preparing hollow silica (quartz) fibers. This method can simply prepare nanofibers with a large aspect ratio and adjustable morphology. For example, Chinese invention patent CN202510601602.0 provides a kind of hollow silica nanofiber aerogel and its preparation method and application. The invention uses a coaxial electrospinning method to prepare hollow silica nanofibers, uses an organosilane crosslinking agent to improve the adhesion of hollow silica nanofibers, and prepares hollow silica nanofiber aerogel by vacuum freeze drying method. However, the diameter of the hollow silica (quartz) fiber prepared by this method is usually between 1-100 nanometers (nm), and it is difficult to obtain micron-sized hollow fibers.

[0005] Method 3: Coaxial spinning is another method for preparing hollow silica (quartz) fibers. For example, Chinese invention patent CN201210035457.7 provides a method for preparing hollow quartz fibers. The invention is to clean the quartz glass tube without impurities, bubbles and other defects and dry it. Then the standby quartz glass tube is loaded into the clamp of the pipe feeding device, heated to melt the quartz glass tube, and at the same time, high-pressure gas is blown into the tube to form a fine single hollow quartz fiber. The fiber surface is coated with a wetting agent by a coating device, and then the hollow quartz fiber is wound on a fiber winding drum, and finally dried and stored. The principle of this method is simple, but the technical parameters need to be strictly controlled, such as: (1) The silica content of the quartz glass tube should be greater than 99.95%; (2) The quartz glass tube cannot be bent and deformed, and cannot have bubbles and too many air lines; (3) The gas pressure of the molten quartz glass tube is controlled at 0.003Mpa~0.008Mpa; (4) The voltage of the pipe feeding device is controlled at 60V~70V; (5) The surface of the quartz fiber should be coated with a wetting agent; (6) The speed of the fiber winding drum should be controlled at 4000~4500 revolutions / second.

[0006] Therefore, this method greatly reduces the pass rate of the product. SUMMARY

[0007] The purpose of the present application is to provide a method for preparing hollow silica fibers using seaweed fibers as templates. The present application technically breaks through many problems existing in the prior art and makes up for its shortcomings. Seaweed fibers (diameter 10-30 μm) with adsorption properties are selected as templates, and sodium silicate reacts with hydrochloric acid adsorbed in seaweed fibers to generate silicic acid. In the next step, silicic acid is decomposed by heating calcination, and silica is generated in situ and sintered into shape. At the same time, seaweed fibers are decomposed by heat to form pores, and finally hollow silica fibers are generated.

[0008] The object of the present application is achieved by the following technical solutions: A method for preparing hollow silica fibers using seaweed fibers as templates, the method comprising the following steps: (1) In a vacuum oven, seaweed fibers are soaked in a container containing hydrochloric acid aqueous solution, and then vacuum is started, with a relative vacuum degree of 10-30 KPa, so that the hydrochloric acid aqueous solution can penetrate into the grooves on the surface of the seaweed fibers and the irregular honeycomb porous structure inside, until there are no more bubbles rising in the container containing the hydrochloric acid aqueous solution; (2) The acidified seaweed fibers are taken out, the excess hydrochloric acid aqueous solution on the surface is removed, and then they are placed in a sodium silicate aqueous solution for at least 60 min to convert the sodium silicate into silicic acid on the surface of the seaweed fibers, and then taken out and placed for at least 24 h until surface dryness; 2Na2SiO3 +2HCl→H2SiO3+2NaCl (3) The seaweed fibers wrapped with silicic acid are placed in a high-temperature muffle furnace and slowly heated to 1200℃ at a heating rate of 1℃ / min to ablate the internal seaweed fibers, i.e. to obtain hollow silica fibers; H2SiO3→SiO2+H2O The raw material ratio for preparing the above-mentioned hollow silica fibers is as follows: Seaweed fibers (diameter 10-30 um) 100 parts; Hydrochloric acid aqueous solution (10%) 1-40 parts; Sodium silicate (modulus 1.5-3.5) 1-40 parts.

[0009] The outstanding effects of the present application are: 1. The hollow structure of the silica fibers is consistent with the template form, with a consistency of >92% (SEM image analysis); 2. The specific surface area reaches 420-680 m² / g (BET method test). BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 The hollow pores inside the hollow silica fibers in the present application. DETAILED DESCRIPTION

[0011] The present application will be described in detail below with reference to examples.

[0012] Example 1: ‌Acidification treatment: Take 100 parts of seaweed fibers with a diameter of 20 μm, soak them in 20 parts of 10% hydrochloric acid aqueous solution, and vacuum to a relative vacuum degree of 20 kPa until no bubbles are released.

[0013] Silica conversion: after draining, the fibers were immersed in 15 parts of a sodium silicate solution with a modulus of 2.0 for 60 min, then removed and left to dry at room temperature for 24 h.

[0014] High temperature calcination: heated at 1 °C / min to 1200 °C, held for 2 h, to obtain hollow silica fibers. SEM showed that the hollow structure of the fibers was complete, with a morphology coincidence degree of 93%, and a specific surface area of 502 m² / g.

[0015] Example 2: Acidification treatment: 100 parts of seaweed fibers with a diameter of 10 pm were immersed in 10 parts of a 10% hydrochloric acid aqueous solution, vacuumed to a relative vacuum degree of 15 kPa until no bubbles were released.

[0016] Silica conversion: after draining, the fibers were immersed in 20 parts of a sodium silicate solution with a modulus of 2.5 for 45 min, then removed and left to dry at room temperature for 15 h.

[0017] High temperature calcination: heated at 1 °C / min to 1200 °C, held for 3 h, to obtain hollow silica fibers. SEM showed that the hollow structure of the fibers was complete, with a morphology coincidence degree of 95%, and a specific surface area of 576 m² / g. Example 3: Acidification treatment: 100 parts of seaweed fibers with a diameter of 30 pm were immersed in 25 parts of a 10% hydrochloric acid aqueous solution, vacuumed to a relative vacuum degree of 30 kPa until no bubbles were released.

[0018] Silica conversion: after draining, the fibers were immersed in 22 parts of a sodium silicate solution with a modulus of 3.5 for 55 min, then removed and left to dry at room temperature for 24 h.

[0019] High temperature calcination: heated at 1 °C / min to 1200 °C, held for 5 h, to obtain hollow silica fibers. SEM showed that the hollow structure of the fibers was complete, with a morphology coincidence degree of 96%, and a specific surface area of 438 m² / g.

Claims

1. A method for preparing hollow silica fibers using seaweed fibers as a template, characterized by, The method comprises the following steps: (1) in a vacuum oven, seaweed fiber is soaked in a container containing hydrochloric acid aqueous solution, and then vacuum is started, the relative vacuum degree is 10-30 KPa, so that the hydrochloric acid aqueous solution can penetrate into the groove on the surface of the seaweed fiber and the irregular honeycomb porous structure inside, until there is no bubble rising in the container containing the hydrochloric acid aqueous solution; (2) take out the acidified seaweed fiber, remove the excess hydrochloric acid aqueous solution on the surface, then put it into sodium silicate aqueous solution, and place it for at least 60 min to convert sodium silicate into silicic acid on the surface of seaweed fiber, then take it out and place it for at least 24 h until it is surface dry; 2Na2SiO3 +2HCl→H2SiO3+2NaCl (3) the seaweed fiber wrapped with silicic acid is placed in a high temperature muffle furnace, and heated slowly to 1200℃ at a heating rate of 1℃ / min to ablate the internal seaweed fiber, i.e. to obtain hollow silica fiber; H2SiO3→SiO2+H2O The raw material ratio for preparing the above hollow silica fiber is as follows: Seaweed fiber (diameter 10-30 um) 100 parts; Hydrochloric acid aqueous solution (10%) 1-40 parts; Sodium silicate (modulus 1.5-3.5) 1-40 parts.

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