Background technology
Mullite fiber is one type of hi-tech base mateiral in high-temperature technology field; Because of having a series of excellent properties; Comprise: hot strength, electrical insulating property and chemicalstability, low-thermal conductivity and the thermal expansivity (5.3 * 10 of HMP (1850 ℃), excellent high-temperature creep-resistant property, excellence
-6K), and good erosion resistance and high shear modulus, effect is very given prominence in the national economic development, and is closely bound up with the development of iron and steel, non-ferrous metal, building materials, the energy and new technological industry, is the important leverage of this type industry energy-saving consumption reduction.Therefore, mullite fiber has more and more come into one's own as a kind of lightening fire resistant material since coming out.In developed country, the refractory materials gross output value accounts for 0.1% of the output value in the national economy, and market outlook are boundless.
Along with improving constantly of scientific and technological level; The quickening of modernization of industry process; The application of high-performance mullite fiber no longer is confined on the traditional kiln and Thermal Equipment, and it will have more wide application in national defence and high-tech sector, and market capacity surpasses the demand of traditional industries.Like the application at space industry: American National space agency (NASA) adopts light-duty fiber to disintegrate the thermal insulation system problem in the space shuttle system that determined; Application in automobile industry: have excellent mechanical property owing to pass through mullite fiber enhanced aluminum magnesium alloy, successful Application on the motor car engine piston element.China's auto output surpassed 1,800 ten thousand in 2010, used the 0.2Kg fortifying fibre to calculate by every cover piston rod, and only this item ceramic fiber consumption can reach 3600 tons.
At present, in the production and research of mullite fiber, all adopt the mode of traditional resistance furnace heating to heat-treat; Heat mainly transmits through the mode of thermal conduction, thermal radiation and convection current from outside to inside, because the mullite fiber thermal conductivity is lower, so traditional heating mode efficient is lower; Temperature rise rate is slower, and required holding temperature up to 1300 ℃, about 3 hours of soaking time, whole intensification and insulating process generally need 8-10 hour; It is thus clear that production efficiency is low, the production cycle is long, energy consumption is big.Simultaneously, because the traditional way thermal treatment temp is high, soaking time is long, fiber crystal grain is grown up unusually, and fiber weakness fracture and powder phenomenon-tion are serious.In addition, traditional heating mode internal and external temperature gradient is bigger, and the material consistent performance is lower, is prone to the evil mind problem, and yield rate is low.
Therefore, reduce the mullite fiber thermal treatment temp, reduce soaking time; Shorten the production cycle; Enhance productivity, improve the mullite fiber performance, the green low-cost technology of preparing of development high-performance mullite fiber has important researching value and society and economic benefit.
Summary of the invention
Technical purpose of the present invention is to the above-mentioned state of the art; Provide a kind of efficient, energy-conservation, with low cost and be easy to the mullite fiber preparation method of industrialization; Utilize this preparation method comparatively fast to heat up, and in lesser temps, shorter soaking time the mullite synthesizing fiber.
The present invention realizes that the technical scheme that above-mentioned technical purpose adopts is: a kind of preparation method of mullite fiber is specially: the stoichiometric ratio according to each element in the mullite fiber chemical formula takes by weighing raw material, the configuration colloid; Then through becoming fibre, oven dry binder removal to process the mullite amorphous fiber; Again fiber is packed in the saggar of being processed by electromagnetic wave transparent material, then saggar is put into professional microwave oven, under air or oxygen atmosphere; Through adjustment microwave power control temperature rise rate; Heat temperature raising is cooled to room temperature at last to thermal treatment temp, obtains mullite fiber.
In the technique scheme:
The raw material that adopts during the colloid configuration can be simple substance, oxide compound, fluorochemical, nitride, bromide, muriate, nitrate salt, vitriol, the carbonate of respective element in the said mullite fiber chemical formula, also can be the precursor or the colloidal sol of desired raw material element.
Said one-tenth method for fiber includes but not limited to that high speed centrifugation gets rid of silk, hot gas flow high pressure spray silk, electrostatic spinning or melt drawing.
Said professional microwave oven can be selected from a kind of in net belt type microwave oven/kiln, push-plate type microwave oven/kiln, roller bed type microwave oven/kiln, shuttle-type microwave oven/kiln, box microwave oven/kiln and the bell-jar microwave oven/kiln; The microwave frequency of specialty microwave oven is generally 300MHz~300GHz, and preferred frequency is 2.45GHz, 5.8GHz, 0.915GHz or 24.15GHz.
Saggar by wave penetrate capability preferably material process, preferably by Al
2O
3, one or more the matrix material in the material such as BN processes.
In order to improve the performance of mullite fiber, preferably be incubated processing after heat temperature raising to the thermal treatment temp, soaking time is preferably 0.1~100h, further is preferably 0.1~1h.
In order to reduce thermal treatment temp, improve the performance of mullite fiber, can in raw material, add various solubility promoters, solubility promoter includes but not limited to aluminium powder, silica flour, SiO
2, V
2O
5, Bi
2O
3, CuO, Bi (NO
3)
3, Cu (NO
3)
2Deng in one or several mixing.
In order to improve temperature rise rate, keep the homogeneity in environment temperature field better, preferably in saggar, add auxilliary hot material.Auxilliary hot material can directly contact with sample and perhaps keep certain distance.
Auxilliary hot material includes but not limited to SiC, Co
2O
3, CuO, WO
3, MoS
2, PbS, CuFeS
2, WC and ZrO
2Deng in one or several mixture.
In order to increase heat insulation effect, preferably saggar is put into attemperator, carry out microwave heating then.Insert lagging material between saggar and the attemperator inwall.Attemperator can be insulated tank, incubation chamber or insulation casket etc.Attemperator is to be processed by the good material of wave penetrate capability, preferably by Al
2O
3, one or more the matrix material in the material such as BN processes.Equally, the lagging material of between saggar and insulated tank inwall, inserting also is the good material of wave penetrate capability, is preferably Al
2O
3, one or more the matrix material in the material such as BN.
Process of cooling adopts and cools to room temperature with the furnace, perhaps adopts through the adjustment microwave power and is cooled to room temperature with certain rate of temperature fall.
Temperature rise rate among the preparation method of the present invention is preferably 5 ℃/min~200 ℃/min, further is preferably 10 ℃/min~80 ℃/min.Thermal treatment temp is generally 600 ℃~1700 ℃, further is preferably 750 ℃~1300 ℃.
Utilize the inventive method, can be according to the practical application needs, with the mullite fiber moulding or be processed into desired shape and the device of size.
The present invention utilizes microwave and mullite amorphous fiber directly to be coupled, and heat-up rate is fast, and sintering time is short; Help obtaining the mullite fiber that crystal grain is tiny, density is high; And the inside and outside thermally equivalent of material, can reduce the mullite fiber built-in thermal stress, reduce fiber weakness fracture and efflorescence ratio; The non-thermal effect of microwave can promote activated sintering in addition, improves molecular diffusion rate, reduces activation energy, can reduce the fiber thermal treatment temp.
Therefore, the present invention utilizes microwave method thermal treatment mullite fiber, and its beneficial effect is embodied in:
(1) promotes temperature rise rate in the mullite fiber heat treatment process, reduced thermal treatment temp, shortened soaking time, significantly promoted production efficiency;
(2) improve energy utilization rate, significantly reduced production cost, be easy to realize extensive industrialization;
(3) because the characteristic of the whole heating of microwave has promoted the mullite fiber uniformity in product performance, reduce fiber weakness fracture and powder phenomenon-tion, improved yield rate;
(4) because heat-up rate is fast, soaking time is short, can obtain the mullite fiber that crystal grain is tiny, density is high, and fiber following process property improves.
In sum, the low-cost mullite fiber preparation method of green provided by the invention be a kind of fast, efficient, energy-conserving and environment-protective, with low cost and be easy to realize the preparation method of scale operation.
Embodiment
Be described further below in conjunction with accompanying drawing and embodiment specific embodiments of the invention, it is pointed out that the following stated embodiment is intended to be convenient to understanding of the present invention, and it is not played any qualification effect.
Embodiment 1:
In the present embodiment, the chemical expression formula of mullite fiber is 3Al
2O
32SiO
2, concrete preparation method is following:
(1) takes by weighing 241.5g Aluminum Chloride Hexahydrate (AlCl
36H
2O), the 135g aluminium powder adds in the 400ml deionized water, stirs 20min with the rotating speed of 800rpm and makes mixed solution A, adds 480ml silicon sol (SiO then
2Content is 0.25g/ml), and 1% Z 150PH, being heated to 80 ℃, and fully stirring, the HCl adjusting pH that drips 1mol/L in the whipping process is 5 ± 1.Make colloidal sol after stirring 12h.
(2) colloidal sol becomes fibre to obtain colloid fiber through getting rid of silk;
(3) colloid fiber is heated to 500 ℃ with the temperature rise rate of 2 ℃/min, and thermal treatment 2h gets amorphous fiber;
(4) with the amorphous fiber that obtains in (3) through putting into professional microwave oven thermal treatment, sintering atmosphere is an air, the temperature rise rate with 10 ℃/min under the normal pressure is warming up to 1000 ℃, is incubated 30min then, furnace cooling promptly obtains polycrystalline mullite fibre afterwards.
The above-mentioned polycrystalline mullite fibre sample for preparing is carried out Measurement and analysis; Thing with the X-ray diffractometer analytic sample is mutually as shown in Figure 1; Can know by Fig. 1; Fiber is the mullite phase fully when the microwave treatment temperature is 1000 ℃, with the fracture apperance of sem observation sample, grain-size, and constitutional features, obtains Fig. 2.Can know the about 30nm of sample grain-size by Fig. 2, about 6~10 μ m of Fibre diameter, the fiber section is fine and close.
Embodiment 2:
Among the embodiment 2~8, the chemical expression formula of mullite fiber is identical with embodiment, and concrete preparation method is also basic identical with embodiment 1, and different is temperature rise rate, sintering temperature, and shown in the soaking time table 1 specific as follows.
The chemical expression formula and the processing condition of mullite fiber among table 1 embodiment 2~8
The above-mentioned polycrystalline mullite fibre sample for preparing is carried out Measurement and analysis, similar shown in Figure 1 with the thing of X-ray diffractometer analytic sample, be illustrated in that fiber is the mullite phase under the microwave treatment temperature shown in the table 1; With the fracture apperance of sem observation sample, grain-size, and constitutional features, obtain similar image shown in Figure 2, grain-size 30-60nm, Fibre diameter 6~10 μ m, the fiber section is fine and close.
Above-described embodiment specifies technical scheme of the present invention and beneficial effect; Be understood that the above is merely specific embodiment of the present invention; Be not limited to the present invention; All any modifications of in principle scope of the present invention, being made, replenish or be equal to replacement etc., all should be included within protection scope of the present invention.