CN1594216A

CN1594216A - Process for synthesizing high purity sialon material by coal-series kaolin

Info

Publication number: CN1594216A
Application number: CN 200410009293
Authority: CN
Inventors: 徐利华; 王体壮
Original assignee: University of Science and Technology Beijing USTB
Current assignee: University of Science and Technology Beijing USTB
Priority date: 2004-07-01
Filing date: 2004-07-01
Publication date: 2005-03-16
Anticipated expiration: 2024-07-01
Also published as: CN1260179C

Abstract

The invention provides a process for synthesizing high purity sialon material by coal-series kaolin which consists of, choosing kaolin with the total content of SiO2 and Al2O3 >=85%, fine grinding the raw material, drying at 100-800 deg. C for dehydration and pre-calcination, proportioning by experimental design, mixing by the ratio of carbon powder / raw material = 15-35/100, ball grinding at the presence of ethanol medium, drying, charging 2-10% of aqueous solution of polyvinyl alcohol into the dried raw material, agitating homogeneously, press forming under 10-30Mpa, drying at 50-200 deg. C, sintering in the atmosphere of flowing nitrogen, then cooling down to below 200 deg. C, and thermal insulating at 500-800 deg. C, removing free carbon.

Description

The method of the synthetic high-purity sialon material of a kind of Coaseries kaolin

Technical field

The invention belongs to technical field of new material preparation, the method for the synthetic high-purity sialon material of a kind of Coaseries kaolin particularly is provided, promptly adopt the method for grand (beta-Sialon) material of the synthetic Beta match of bast class mineral.

Background technology

Beta-Sialon is the most stable the most representative crystalline phase in the Sialon based material, it is typical hexagonal columnar crystal, have the excellent high-temperature over-all properties as characteristics such as: high rigidity, high-wearing feature, good thermal shock, corrosion-resistant and chemical stability height, thereby beta-Sialon is rising material.

At present, the preparation of high-purity beta-Sialon adopts high-purity expensive raw material as Si ₃N ₄, Al ₂O ₃, AlN, SiO ₂, high temperature (about 1700 ℃) hot pressing, self-propagating combustion silicon reduction, thermite reduction or carbothermic reductions synthetic (these method most literature all have report) such as Si powder, Al powder or carbon black, thereby synthetic cost is higher, complex process is unfavorable for the heavy industrialization application.It is the synthetic high-purity beta-Sialon (Materials ResearchBulletin 38 (2003) 663-674) of raw material with kaolin that human microwave sintering method is arranged, most literature has reported with kaolin to be the technology of raw material one-step synthesis beta-Sialon, but these technologies generate Al inevitably ₂O ₃, SiC, Si ₃N ₄And impurity such as AlN polytype, can not synthesize high-purity beta-Sialon.Up to the present, Shang Weijian is relevant is the patent report that material carbon thermal reduction nitriding prepares high-purity beta-Sialon material with the Coaseries kaolin.

Kaolinic main component is a kaolinite, and kaolinite is the coal measures mineral, belongs to triclinic(crystalline)system, often is finely divided crystal, and profile often is a sheet, granular and shaft-like, is divided into orderly kaolin and unordered kaolin two classes.High-quality kaolin is all in the Cenozoic and brown coal association, and forms in the lakes and marshes sedimentary environment of greenhouse experiment.China's kaolin resource is abundant, and deposit type is complete, and reserves are positioned at prostatitis, the world.So with kaolin is raw material, the high-purity beta-Sialon material of large-scale industrial production can be realized the purpose of high-performance, low cost, high added value material.

Summary of the invention

The objective of the invention is to: the method for the synthetic high-purity sialon material of a kind of Coaseries kaolin is provided, and is raw material with cheap kaolin, synthetic high-purity beta-Sialon material.

It is raw material that the present invention adopts with the coal series kaolinite, and by the high-purity beta-Sialon material of carbothermal reduction-nitridation method one step preparation, its concrete preparation method is as follows:

(1) chooses the chocolate Coaseries kaolin, make its main component SiO ₂Content is 35～65 quality % and Al ₂O ₃Content is 20～55 quality %, and SiO ₂And Al ₂O ₃Total content 85～95 quality %, the raw material fine grinding makes its particle diameter≤0.1mm;

(2) with raw material in 100～800 ℃ of following drying and dehydratings and pre-burning;

(3) by the test design batching, cry into the correction material, carbon dust/raw material is 15～35/100 mixing, under the ethanol medium, and normal temperature ball milling 1～50 hour, oven dry;

(4) the ball milling raw material of drying adds 2～10% polyvinyl alcohol water solution, makes polyvinyl alcohol account for 0.1～2.0% of batch mixing weight, stirs;

(5) be compression moulding under 10～30M β a at pressure, 50～200 ℃ of oven dry;

(6) said sample is put into atmosphere furnace, sintering under flowing nitrogen atmosphere, heat-up rate is 5～30 ℃/minute, is warmed up to 1350～1650 ℃, is incubated 1～6 hour, is cooled to then come out of the stove below 200 ℃.

Some material can also carry out carbonization treatment after coming out of the stove, be incubated 1～4 hour down at 500～800 ℃ and slough uncombined carbon, obtains high-purity beta-Sialon material.

The invention has the advantages that: adopt the synthetic high rigidity that can satisfy the application requiring under the severe condition of carbothermal reduction-nitridation method cheaply, high-wearing feature, good thermal shock, corrosion-resistant and chemical stability is high, eco-friendly beta-Sialon material, can reduce raw materials cost, simplify production technique.

Description of drawings

Fig. 1 is the microstructure photograph of the prepared high-purity beta-Sialon material of the present invention.

Embodiment

Below introduce the specific embodiment of the present invention by description to embodiment.

Raw material is: Graphite Powder 99; 1000 order Al ₂O ₃, somewhere, China Shanxi kaolin, its main component sees the following form:

Title	??SiO ₂	??Al ₂O ₃	??CaO	??Fe ₂O ₃	??MgO	??Na ₂O	??K ₂O	??TiO ₂	Loss on ignition	Total amount
Title	??SiO ₂	??Al ₂O ₃	??CaO	??Fe ₂O ₃	??MgO	??Na ₂O	??K ₂O	??TiO ₂	Loss on ignition	Total amount	Datong District's soil	??49.32	??33.22	??1.87	??0.68	??0.20	??0.12	??0.27	??0.81	??15.20	??101.69

Embodiment 1:

Kaolin is finely ground to 200 powder materials;

Use chamber type electric resistance furnace 800 ℃ of following pre-burnings powder, be incubated 4 hours;

Add Al ₂O ₃Proofreading and correct the sial atomic ratio is 105/100, and carbon dust and raw material are mixed with 18/100;

Add an amount of ethanol, in aluminum oxide ball milling jar, use aluminum oxide abrading-ball ball milling 30 hours;

To expect to take out, suitably ethanol evaporation makes material be pulpous state, adds the SL dispersion agent, mixes 1 hour with stirrer, 85 ℃ of oven dry down;

The polyvinyl alcohol water solution of adding 1%, the quality percentage composition of the aqueous solution is 3%;

On DY-30 type electric tablet machine, be shaped to the cake of 12.6 with 15MP;

120 ℃ of oven dry;

Use molybdenum wire furnace, the high pure nitrogen flow velocity is 1.5l/min, and heat-up rate is 10 ℃/min, with 4 hours sintering of 1450 ℃ of insulations, naturally cools to 600 ℃ and closes nitrogen, and insulation is 2 hours in air, removes uncombined carbon.

Show that with X-ray analysis product is Si ₃Al ₃O ₃N ₅Be the beta-Sialon of Z=3, its content 〉=95%.

Embodiment 2:

Kaolin is finely ground to 400 powder materials;

On DY-30 type electric tablet machine, be shaped to the cake of 12.6 with 15MP;

120 ℃ of oven dry;

Claims

1, the method for the synthetic high-purity sialon material of a kind of Coaseries kaolin, adopting with the coal series kaolinite is raw material, by the high-purity beta-Sialon material of carbothermal reduction-nitridation method one step preparation, it is characterized in that: concrete preparation method is:

A, choose the chocolate Coaseries kaolin, make composition SiO ₂Content is 35～65 quality %, Al ₂O ₃Content is 20～55 quality %, and SiO ₂And Al ₂O ₃Total content 85～95 quality %, the raw material fine grinding makes its particle diameter≤0.1mm;

B, with raw material in 100～800 ℃ of following drying and dehydratings and pre-burning;

C, by test design batching, cry into the correction material, carbon dust/raw material is 15～35/100 to mix, under the ethanol medium, normal temperature ball milling 1～50 hour, oven dry;

The raw material that d, ball milling are dried, the polyvinyl alcohol water solution of adding 2～10% makes polyvinyl alcohol account for 0.1～2.0% of batch mixing weight, stirs;

E, be compression moulding under 10～30MPa at pressure, 50～200 ℃ of oven dry;

F, said sample is put into atmosphere furnace, sintering under flowing nitrogen atmosphere, heat-up rate is 5～30 ℃/minute, is warmed up to 1350～1650 ℃, is incubated 1～6 hour, is cooled to then come out of the stove below 200 ℃.

2, in accordance with the method for claim 1, it is characterized in that: carry out carbonization treatment after coming out of the stove, be incubated 1～4 hour down at 500～800 ℃ and slough uncombined carbon, obtain high-purity beta-Sialon material.