CN1569626A

CN1569626A - Method of preparing nano-silicon carbide fiber

Info

Publication number: CN1569626A
Application number: CN 200410012271
Authority: CN
Inventors: 郭向云; 郝雅娟
Original assignee: Shanxi Institute of Coal Chemistry of CAS
Current assignee: Shanxi Institute of Coal Chemistry of CAS
Priority date: 2004-04-29
Filing date: 2004-04-29
Publication date: 2005-01-26
Anticipated expiration: 2024-04-29
Also published as: CN1260124C

Abstract

The invention discloses a method of preparing nano-silicon carbide fiber consisting of dissolving phenolic resin into absolute ethyl alcohol, charging rare-earth metal nitrate, acetate or chloridate to make it dissolved, dropping tetra ethyl ortho silicate into the solution, charging oxalate and hydrochloric acid, hydrolyzing at room temperature to obtain the carbon-silicon dyadic colloidal sols, charging hexamethylenetetramine, drying to obtain xerogel, elevating the temperature of the xerogel to 1200-1400 deg. C in argon gas protective atmosphere, cooling down to room temperature, subjecting the reaction product to air oxidation, expelling the non-reacted rare earth metallic oxide and silicon dioxide with nitric acid and hydrofluoric acid, finally washing, filtering, and drying to obtain the silicon carbide nano fiber.

Description

A kind of method for preparing SiC nano fiber

Technical field

The present invention relates to a kind of preparation method of SiC nano fiber, utilize the growth auxiliary agent of rare earth metal salt specifically, prepare the SiC nano fiber that a kind of length reaches up to a hundred microns as nanofiber.

Background technology

In recent years, one-dimensional nano structure material is because its unique light, electricity and mechanical property cause people's extensive concern.Wherein SiC nano fiber is a kind of semiconductor material with multiple excellent properties, have high heat conductivity, oxidation-resistance and high physical strength and chemical resistance, can in rigorous environment, use, therefore SiC nano fiber has the potential application prospect in fields such as nanostructure composite material and microelectronic devices.

At present, reported a lot of methods that prepare the one dimension silicon carbide nano material, comprised the carbon nanotube limited reactions, arc excitation, carbothermic reduction and chemical vapour deposition etc.For example, it is raw material with carbon nanotube and Polycarbosilane solution that Chinese patent (publication number CN 1436724A) discloses a kind of, adopts dipping and cracking technology to prepare a kind of method of silicon carbide nano bar.This method is with carbon nanotube atmospheric oxidation processing and soaks in nitric acid, after the washing oven dry, immersing concentration again is in the Polycarbosilane solution of 5wt%-30wt%, and ultrasonic separation, after the filtration, solid-liquid separation, the solid settlement thing is put into stove, under rare gas element, be heated to 1000～1300 ℃ of constant temperature, make the Polycarbosilane cracking of carbon nanotube adsorption, promptly get silicon carbide nano bar.The prepared silicon carbide nano bar caliber of this method is 10～40nm.Chinese patent (notification number 1281910) also discloses a kind of method for preparing nanometer silicon carbide whiskers with sol-gel method, clean carbonaceous colloidal sol and clean silicon sol were at room temperature stirred 24 hours by carbon and silicon mol ratio (3: 8), make binary carbon silicon sol, again 100-150 ℃ of dry 4-6 hour to the binary xerogel, or carry out supercritical drying, and obtain binary aerogel, carry out carbothermic reduction reaction then, slough carbon and silicon-dioxide at last, make pure nanometer silicon carbide whiskers.(Chemical Physical Letters, 329, (2000): 323-328) utilize mesoporous silicon oxide and the activity charcoal powder reaction that contains Fe nanometer particles, prepared beta-SiC nano-wire such as C.H.Liang.The mesoporous silica gel that at first prepares the ferri nano particle by sol-gel method with dried gel grinding powder, mixes with activity charcoal powder, and the carbon silicon mol ratio is 4.1.Then that this carbon silicon mixture is first at H ₂Under/Ar the atmosphere, 500 ℃ of constant temperature 4h are Fe nanometer particles with iron oxide reduction, then temperature are risen to 1400 ℃, and keep 2 hours under argon shield.Finally obtain silicon carbide nanometer line.Nanometer silicon carbide linear diameter with this method preparation is 20-50nm, and length is tens microns.

Summary of the invention

The purpose of this invention is to provide and a kind ofly can obtain the rare earth metal salt that utilizes that SiC nano fiber length reaches up to a hundred microns and prepare the method for SiC nano fiber as auxiliary agent.

The present invention realizes by following method:

1. with the resol of 1 weight part, be dissolved in the dehydrated alcohol of 3-5 weight part, add rare-earth metal nitrate, acetate or the muriate of 0.04-0.3 weight part then, stir and make it dissolving;

2. under continuous stirring condition, the tetraethoxy of 4-5 weight part is added dropwise in the above-mentioned solution, and adds the oxalic acid of 0.02-0.1 weight part and the hydrochloric acid of 0.04-0.1 weight part, under the room temperature hydrolysis 12-72 hour, obtain carbon silicon binary colloidal sol;

3. add the gelifying agent hexamethylenetetramine of 0.08-0.2 weight part in the carbon silicon binary colloidal sol, impel colloidal sol to solidify the formation gel,, obtain xerogel gel under 60-110 ℃ of condition dry 6-24 hour;

With xerogel under argon shield atmosphere, with 2-10 ℃/minute temperature rise rate, be warming up to 1200-1400 ℃, react after 3-20 hour, be cooled to room temperature;

With reaction product under 600-800 ℃, in the air oxidation 1-4 hour, remove unreacted rare-earth oxide and silicon-dioxide with nitric acid and hydrofluoric acid successively again, after washing, filter, oven dry, can obtain SiC nano fiber.

Aforesaid rare earth metal is cerium, lanthanum or praseodymium.

Utilize the length of the SiC nano fiber that the present invention prepares to be 100-200 μ m, diameter is 30-150nm.

The present invention has following advantage:

1, the inventive method is simple, and is easy to operate.

2, the length of Zhi Bei SiC nano fiber is 100-200 μ m, and diameter is 30-150nm.

Embodiment

Embodiment 1

1. take by weighing 12 gram resol, be dissolved in 35 milliliters of dehydrated alcohols, add 1.2 gram lanthanum nitrates then, stir and make it dissolving.

2. under continuous stirring condition, 50 milliliters of tetraethoxys are added dropwise in the above-mentioned solution, and add 0.25 gram oxalic acid and 1 milliliter of hydrochloric acid, hydrolysis is 12 hours under the room temperature, forms colloidal sol.

3. add 1 gram gelifying agent hexamethylenetetramine in the colloidal sol, impel colloidal sol to solidify the formation gel, gel under 110 ℃ of conditions dry 6 hours.

4. dried gel is put into tube type high-temperature furnace, feed argon gas, with 2 ℃/minute temperature rise rate, be warming up to 1250 ℃, isothermal reaction under argon shield, was cooled to room temperature after 10 hours.

With above-mentioned reaction product under 700 ℃, oxidation is 3 hours in the air, removes unreacted carbon, removes unreacted lanthanum trioxide and silicon-dioxide with nitric acid and hydrofluoric acid respectively successively again.After washing, filter, oven dry, can obtain SiC nano fiber.Its length is 100-120 μ m, and diameter is 80-100nm.

Embodiment 2

1. take by weighing 30 gram resol, be dissolved in 80 milliliters of dehydrated alcohols, add 1.2 gram Cerium II Chlorides then, stir and make it dissolving.

2. under continuous stirring condition, 100 milliliters of tetraethoxys are added dropwise in the above-mentioned solution, and add 1 gram oxalic acid and 2 milliliters of hydrochloric acid, hydrolysis is 24 hours under the room temperature, forms colloidal sol.

3. add 3 gram gelifying agent hexamethylenetetramines in the colloidal sol, impel colloidal sol to solidify the formation gel, gel under 100 ℃ of conditions dry 10 hours.

4. dried gel is put into tube type high-temperature furnace, feed argon gas, with 5 ℃/minute temperature rise rate, be warming up to 1200 ℃, isothermal reaction under argon shield, was cooled to room temperature after 20 hours.

With above-mentioned reaction product under 800 ℃, oxidation is 1 hour in the air, removes unreacted carbon, removes unreacted cerium oxide and silicon-dioxide with nitric acid and hydrofluoric acid respectively successively again.After washing, filter, oven dry, can obtain SiC nano fiber, its length is 100-120 μ m, diameter is 30-50nm.

Embodiment 3

1. take by weighing 40 gram resol, be dissolved in 120 milliliters of dehydrated alcohols, add 8 gram praseodymium nitrates then, stir and make it dissolving.

2. under continuous stirring condition, 150 milliliters of tetraethoxys are added dropwise in the above-mentioned solution, and add 3 gram oxalic acid and 2 milliliters of hydrochloric acid, hydrolysis is 48 hours under the room temperature, forms colloidal sol.

3. add 6 gram gelifying agent hexamethylenetetramines in the colloidal sol, impel colloidal sol to solidify the formation gel, gel under 60 ℃ of conditions dry 20 hours.

4. dried gel is put into tube type high-temperature furnace, feed argon gas, with 2 ℃/minute temperature rise rate, be warming up to 1350 ℃, isothermal reaction under argon shield, was cooled to room temperature after 5 hours.

With above-mentioned reaction product under 700 ℃, oxidation is 2 hours in the air, removes unreacted carbon, removes unreacted Praseodymium trioxide and silicon-dioxide with nitric acid and hydrofluoric acid respectively successively again.After washing, filter, oven dry, can obtain SiC nano fiber, its length is 130-150 μ m, diameter is 100-120nm.

Embodiment 4

1. take by weighing 50 gram resol, be dissolved in 150 milliliters of dehydrated alcohols, add 15 gram lanthanum acetates then, stir and make it dissolving.

2. under continuous stirring condition, 200 milliliters of tetraethoxys are added dropwise in the above-mentioned solution, and add 4 gram oxalic acid and 5 milliliters of hydrochloric acid, hydrolysis is 72 hours under the room temperature, forms colloidal sol.

3. add 10 gram gelifying agent hexamethylenetetramines in the colloidal sol, impel colloidal sol to solidify the formation gel, gel under 80 ℃ of conditions dry 24 hours.

4. dried gel is put into tube type high-temperature furnace, feed argon gas, with 10 ℃/minute temperature rise rate, be warming up to 1400 ℃, isothermal reaction under argon shield, was cooled to room temperature after 3 hours.

With above-mentioned reaction product under 600 ℃, oxidation is 4 hours in the air, removes unreacted carbon, removes unreacted lanthanum trioxide and silicon-dioxide with nitric acid and hydrofluoric acid respectively successively again.After washing, filter, oven dry, can obtain SiC nano fiber, its length is 180-200 μ m, diameter is 120-150nm.

Claims

1. method for preparing SiC nano fiber, it is characterized in that preparation process is as follows: (1). with the resol of 1 weight part, be dissolved in the dehydrated alcohol of 3-5 weight part, add rare-earth metal nitrate, acetate or the muriate of 0.04-0.3 weight part then, stir and make it dissolving;

(2). under continuous stirring condition, the tetraethoxy of 4-5 weight part is added dropwise in the above-mentioned solution, and adds the oxalic acid of 0.02-0.1 weight part and the hydrochloric acid of 0.04-0.1 weight part, under the room temperature hydrolysis 12-72 hour, obtain carbon silicon binary colloidal sol;

(3). add the gelifying agent hexamethylenetetramine of 0.08-0.2 weight part in the carbon silicon binary colloidal sol, impel colloidal sol to solidify the formation gel,, obtain xerogel gel under 60-110 ℃ of condition dry 6-24 hour;

(4). xerogel under argon shield atmosphere, with 2-10 ℃/minute temperature rise rate, is warming up to 1200-1400 ℃, reacts after 3-20 hour, be cooled to room temperature;

(5). with reaction product under 600-800 ℃, in the air oxidation 1-4 hour, remove unreacted rare-earth oxide and silicon-dioxide with nitric acid and hydrofluoric acid successively again, after washing, filter, oven dry, can obtain SiC nano fiber.

2. a kind of method for preparing SiC nano fiber as claimed in claim 1 is characterized in that described rare earth metal is cerium, lanthanum or praseodymium.