WO2012175007A1 - Nanoporous silicon fibre and the preparation process therefor - Google Patents

Abstract

Provided are a nanoporous fibre produced from glass fibre and a preparation process therefor. The preparation process uses glass fibre having a silica content of 45% - 85% as the raw material, and mainly comprises the step of salt decomposition and the step of acid soaking, producing a porous silicon fibre having a silica (SiO₂) content of up to 92% - 99% and excellent resistance to heat; at the same time, an irregular nanoporous structure thereof achieves good performance of thermal and acoustic isolation as well as sound absorption. This nanoporous silicon fibre is widely applied in fire-proofing, heat-preserving materials for construction, heat isolating material, and fire-proofing heat barrier material.

Description

 Description

 Nanoporous silicon fiber and preparation process thereof

Technical field

 The present invention relates to building materials, and more particularly to a nanoporous silicon fiber processed by using glass fibers and a preparation process thereof. technical background

 At present, with the rapid development of industrial facilities and residential construction, the demand for thermal insulation materials in the construction industry is very high, especially with the emphasis on energy conservation and environmental protection in all sectors of society, the requirements for thermal insulation, thermal insulation and sound insulation materials are more demanding. strict.

 Currently widely used insulation materials are organic polymer foaming resins (such as ps, pu foaming) and inorganic fibers (such as glass fiber, mineral fiber, etc.).

 Although the organic polymer foaming resin has light weight, good heat preservation effect and convenient construction, it has poor heat resistance, is flammable, and generates toxic gas when it is burned, so it has a fatal disadvantage.

 In the United States and other developed countries, inorganic fiber insulation materials have been widely used. Among the inorganic fibers are glass fibers and mineral fibers. Among them, the heat resistance temperature of the glass fiber is about 350 ° C, and the heat resistant temperature of the rock fiber is about 850 ° C. The heat retention and non-combustibility of these fibers are good. In addition, inorganic fibers include silicon fibers, ceramic fibers, etc. These fibers have a heat resistance temperature of up to 1000 °C and are therefore widely used in high temperature working environments. However, the disadvantage of this inorganic fiber insulation material is that the insulation performance is not as good as that of the organic polymer foam resin. Summary of the invention

Based on the technical problems and deficiencies of the prior art, the present invention aims to disclose a new technology for processing nanoporous silicon fibers by using glass fibers, that is, glass fibers as raw materials, and removing silica (Si0 ₂ ) from glass fibers. Substances other than the other components are precipitated to form nanoporous silicon fibers.

 The technical solution of the present invention is implemented as follows:

The invention adopts a process for preparing nanoporous silicon fibers by using glass fibers having a silica content of 45 to 85% as a raw material, and mainly comprises a step of salt decomposition and a step of acid soaking. Among them, the silica content is preferably 45 to 76.63%. Porosity of nanoporous silicon fibers produced when the content of Si0 _{2 in} glass fibers is less than 45% Too high to greatly reduce its mechanical strength, can not guarantee the required nanoporous silicon fiber; glass fiber

When the content of Si0 _{2 is} more than 76.63%, the porosity of the nanoporous silicon fiber produced is too low to greatly reduce its heat retention and sound absorbing property, and the content of 510 ₂ in the glass fiber used cannot be too high.

Said glass fibers are distributed in the silica (Si02) with a strong skeleton in the relative activity of these metal oxides Na ₂ 0- RO, such _{as: Na 2 0- CaO, Na 2} 0- B 2 0 3, Na 2 0—AI ₂ 0 ₃ , Na ₂ 0—MgO, etc., wherein R is an element of Group IIA or Group IIIA;

 The step of decomposing the salt is a stage of forming a fine nanopore on the surface of the fiber by utilizing a reaction of an ammonium salt with a highly reactive metal oxide on the surface of the glass fiber to convert the latter into a soluble salt;

 The chemical reaction equation is as follows:

Na ₂ 0— RO+4N H ₄ N0 ₃ =2NaN0 ₃ +R(N0 ₃ ) ₂ +4NH ₃ +2H ₂ 0

Na ₂ 0 — RO+4N H ₄ CI=2NaCI+RCI ₂ +4NH ₃ +2H ₂ 0

 The salt used in the salt decomposition step is a mixture of ammonium nitrate and ammonium chlorate, and the mixing ratio of ammonium nitrate and ammonium chlorate is preferably 1: 0.1 to 0.6. The formation of nanopores is related to the concentration and decomposition temperature of the salt decomposing agent. The nanopores formed on the glass fibers are different depending on the concentration of the decomposing agent and the decomposition temperature. The suitable concentration of the salt decomposing agent is 0.8 to 12.5%. Suitable decomposition temperature is 100~500 °C.

 The acid immersion step is a step of completely precipitating the soluble salt of the fine nanopore produced in the salt decomposition step and obtaining a nanopore fiber having a pore depth and a desired pore diameter.

The process of forming nanopores on the surface of the fiber by acid soaking is to soak the fibers forming the nano-micropores on the surface during the decomposition of the salt in the pores of the surface of the expanded fiber in nitric acid or hydrochloric acid or sulfuric acid, thereby obtaining the nanometer having the desired pore depth and pore diameter. Hole fiber. When nitric acid is used, its concentration is 7 to 20%, its concentration is 15 to 30% when hydrochloric acid is used, and its concentration is 25 to 45% when sulfuric acid is used. The acid soaking of the present invention is preferably nitric acid

 When the glass fiber is immersed in sulfuric acid, a chemical reaction occurs to produce a sulfate which is not easily soluble in water. This salt is not easily washed out when it penetrates into the void of the nanoporous silicon fiber. The chemical reaction formula for the formation of sulfate is as follows:

Ca ²⁺ +S0 ₄ ² " ^→ CaS0 ₄

Mg ²⁺ + S0 ₄ ² " ^→ Mg S0 ₄ In addition, the mechanical strength of nanoporous silicon fibers produced by immersion with hydrochloric acid is significantly reduced, which greatly affects the practical application of nanoporous silicon fibers. Nitric acid and metal oxides when immersed in nitric acid The nitrate formed by the reaction is easily contained in water, so that the nitrate formed during the production process is easily washed away and the mechanical properties are good. The acid soaking process is a process in which the soluble substance diffuses in the solution. Therefore, to obtain a uniform and effective nanopore on the surface of the fiber, it is necessary to uniformly stir the mixture at a temperature of 50 to: L00 ° C for 1 to 5 hours.

 The above-mentioned acid-soaked fiber is washed in water at 50 to 100 ° C for 0.5 to 2 hours, and then the obtained nanoporous silicon fiber is dried at a temperature of 100 to 150 ° C, and then at 550 to 650 °. Heat treatment at C temperature stabilizes the formation of nanopores and increases the strength of the fibers. At this time, it should be noted that when the heat treatment temperature is too high, although the strength of the fiber can be increased, the formed nanopores shrink in a large amount; on the contrary, when the heat treatment temperature is too low, the number of micropores is excessively formed, and the fiber is reduced. strength.

The nanoporous silicon fiber can be obtained by the above method, and the porous silicon fiber having a silica (Si0 ₂ ) content of 92-99% is prepared by using glass fiber having a silica content of 45 to 85% as a raw material. Excellent heat resistance; At the same time, the nanoporous structure makes it have excellent thermal insulation and sound insulation.

 The diameter of the nanoporous silicon fiber: 0.5~20.0μΓΤΊ, length: 1.0mm or more, surface pore diameter: 3~200nm, pore depth of 10nm or more, porosity (nanopore volume per unit mass fiber): 0.1~0.2ml/ g, porosity (volume ratio of nanoporosity to fiber): 20 to 50%, thermal conductivity: 0.021 to 0.033 w/mm · k at 20 ° C, sound absorption coefficient: 0·65 to 1·00.

 Compared with the prior art, the invention has the following significant advantages: the raw material cost is low, the process is simple, and the prepared nanoporous silicon fiber is superior in performance, and can be widely used in the field of fireproof building thermal insulation materials, thermal insulation materials and sound insulation materials. The most ideal high-tech cutting-edge material. DRAWINGS

 1 is a flow chart of a preparation process of the nanoporous silicon fiber of the present invention. detailed description

Example 1

 A process for preparing nanoporous silicon fibers by using glass fiber as a raw material, mainly comprising the steps of salt decomposition and the steps of acid soaking, specifically,

Glass fiber: Composition: 7Na ₂ 0— 23Β ₂ 0 ₃ — 70SiO ₂

 Diameter: Φ 7μηη

100 g of the above borosilicate glass fiber was placed in a mixed salt solution of ammonium hydroxide at a concentration of 7.9%, NH ₄ N0 ₃ : NH ₄ CI = 10:2, heated to 250 ° C, soaked for 10 minutes, and then taken out and dried; 70 ° C concentration Soaked in 11.7% nitric acid (HN0 ₃ ) solution for 2 h; further washed in boiling water for 30 min and then dried at 120 ° C for 15 min.

Finally, after heat treatment at 590 ° C for 5 min, the nanoporous silicon fiber was obtained after slowly cooling: Composition: Si0 ₂ - 96%

B ₂ 0 ₃ -3.5%

Na ₂ O-0.5%

 Diameter: Φ 49ηηη

 Softening temperature: 1470 °C Example 2

Glass fiber: Composition: 8Na ₂ 0-16CaO-76Si0 ₂

 Diameter: Φ 5μηη

 The above-mentioned soda lime glass fiber 100g was subjected to salt decomposition and acid immersion in the same process procedure as in Example 1, and the obtained fiber was washed in hot water at 70 ° C for 1.5 h, and then dried at 120 ° C. After 20 minutes, the heat treatment was carried out at a temperature of 550 ° C for 1 min, and then slowly cooled to obtain a silicon fiber having the following parameters.

Ingredients: Si0 ₂ -94%

 CaO-5.6%

Na ₂ 0— 0.4%

 Hole diameter: 064nm

 Softening temperature: 1350 ° C Example 3:

Glass fiber: Composition: 6MgO— 13B ₂ 0 ₃ — 12AI ₂ 0 ₃ — 69Si0 ₂

 Diameter: Φ 9μηη

100 g of the above Ε glass fiber was placed in a salt solution of 300 ° C (ie, NH ₄ NO ₃ :NH ₄ CI=10:3) at a concentration of 5% for 10 min, and then taken out to dry, followed by 15%. After immersing in nitric acid (HN0 ₃ ) solution for 3 hours, it is washed in Foshui for 30 min; then dried at 120 °C for 15 min, then heat-treated at 5 °C at 600 °C and slowly cooled. Silicon fiber:

Ingredients: Si0 ₂ — 98.5% AI ₂ O ₃ -0.9%

B ₂ 0 ₃ — 0.4%

 MgO-0.2%

 Hole diameter: Φ 59η m

 Softening temperature: 1560 ° C

It is seen as continuously to salt decomposition reaction is dissolved from the glass surface of the fiber-soluble component, thereby enhancing the Si0 ₂ content of the fiber, while raising the temperature of the heat-resistant and insulating properties of the fibers. Table 1 Heat transfer coefficient of the nanoporous silicon fiber and the existing material at different temperatures

Among them, the fiber specific gravity is 60 to: L80 kg/m ³ . It can be seen from Table 2 that the nanoporous silicon fiber prepared by the invention has much lower heat transfer coefficient than the thermal insulation material such as rock wool, and the nanoporous fiber has a heat resistance temperature of up to 1000 °C. The reason is that: in addition to the intersection of the nanoporous silicon fibers to form a void, the nanoporous silicon fiber itself has a lot of fine nanopores to greatly improve the heat resistance and heat resistance. Table 2 shows the relationship between the formation conditions of nanoporous silicon fibers and the relationship between fiber characteristics.

Wherein: A: Na ₂ 0—CaO— Si0 ₂ B: Na ₂ 0—B ₂ 0 ₃ —SiO Table 3 shows the sound absorption coefficient of the nanoporous silicon fiber

Among them, the specific gravity of the nanoporous silicon fiber is 130 kg/m ³ .

 It can be seen from Table 3 that the nanoporous silicon fiber produced by the process of the present invention has a high sound absorption rate and is an ideal sound absorbing material.

The present invention can use all glass fibers having a Si0 ₂ content of 45-85% as raw materials, preferably silicate glass fibers and borosilicate glass fibers, and the prepared nanoporous silicon fibers can be widely used as fireproof construction. Insulation materials, insulation materials, sound insulation materials. The above is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art within the technical scope of the present disclosure, according to the technical solutions of the present invention and Equivalent replacements or modifications of the inventive concept are intended to be included within the scope of the invention.

Claims

Claim

1. A process for preparing a nanoporous silicon fiber, comprising the steps of:

(1) Decomposition of salt: The glass fiber is placed in an ammonium salt solution and heated to react the relatively active metal oxide Na ₂ 0-RO distributed in the skeleton of the silica fiber of the glass fiber with an ammonium salt to form a soluble salt precipitate. And forming a plurality of nano-scale micropores on the surface of the glass fiber;

 The glass fiber has a silica content of 45 to 85%;

 Heating temperature is: 100~500 °C;

 Where R is an element of Group IIA or IIIA;

 (2) acid soaking: the fiber is further immersed in an acid solution, and continuously stirred to expand the nano-scale micropores on the surface of the fiber to obtain a suitable pore depth and pore diameter;

 The acid solution is nitric acid;

Temperature of the acid solution: 50~: L00 °C _;

 The concentration of the acid solution (mass ratio): the concentration of nitric acid, 7~20%;

 Soaking time: 1~5 hours;

 (3) washing, drying and heat treatment: the fiber is washed with water, dried, and then heat-treated at a high temperature to stabilize the formation of the nanopore and increase the strength of the fiber, and finally obtain the nanoporous silicon fiber; ,

 Washing water temperature: 50~: L00 °C;

 Washing time: 0.5~2 hours;

 Drying temperature: 100~150 °C;

 Heat treatment temperature: 550~650 °C;

 Heat treatment time: 0.5 to 5 minutes.

The content of the glass fiber of the step (1) is 45~76. 63%.

The preparation process of the nanoporous silicon fiber according to claim 1 or 2, wherein: in the step (1), the ammonium salt solution is a mixed solution of ammonium nitrate and ammonium chlorate, and the chemical reaction equation is as follows: : Na ₂ 0— RO+4NH ₄ N0 ₃ =2NaN0 ₃ +R(N0 ₃ ) ₂ +4NH ₃ +2H ₂ 0

Na ₂ 0 — RO+4NH ₄ CI=2NaCI+RCI ₂ +4NH ₃ +2H ₂ 0

 Wherein, the mixing ratio of ammonium nitrate and ammonium chlorate (mass ratio): 1 : 0.1 to 0.6;

 Concentration (mass ratio) of a mixed solution of ammonium nitrate and ammonium chlorate: 0.8 to 12.5%.

 4. The nanoporous silicon fiber prepared by the preparation process according to claim 1, wherein: the nanoporous silicon fiber is prepared by using glass fiber having a silica content of 45 to 85% as a raw material. a silicon fiber having a silica content of 92 to 99%;

 The diameter of the nanoporous silicon fiber: 0.5~20. 0μΓΤΊ

 Length of nanoporous silicon fiber: 1.0mm or more

 Nanoporous silicon fiber surface pore size: 3~200nm

 Hole depth: 10nm or more

 Porosity: 0. l~0. 2ml/g

 Porosity: 20~50%

 Thermal conductivity: 20 ° C, 0.021~0. 033w / 匪 · k

 Sound absorption coefficient: 0. 65~1. 00.

 The nanoporous silicon fiber prepared by the preparation process according to claim 4, wherein the nanoporous silicon fiber is prepared by using glass fiber having a silica content of 45 to 76.63% as a raw material.