CN102173463A - Method for preparing iron-based composite oxide Ca2Fe2O5 - Google Patents

Abstract

The invention discloses a method for preparing an iron-based composite oxide Ca2Fe2O5, which comprises the following steps of: uniformly mixing powdered CaCO3 and Fe2O3; grinding the mixed powder at a rotation speed of more than 1000 rpm for 3 to 10 h, and screening with a 60-mesh screen, and drying at 50 DEG C to obtain mechanical active powder; with alcohol with a moisture content of 3 percent as a ball milling medium, adding the mechanical active powder into a ball mill for ball milling; calcinating the mixed powder in a box-type high-temperature furnace; raising the temperature from the room temperature to 500 DEG C at a heating rate of 10 DEG C per minute; and then raising the temperature from 500 DEG C to 600 to 1000 DEG C at the heating rate of 5 DEG C per minute for calcinating for 24 hours. By making use of a high energy ball milling progressive heating principle, partial CaCO3 is decomposed to generate CaO on one hand, and on the other hand, the generated CaO can be transformed into Ca(OH)2 due to the existence of a small amount of water; such a mixing system of the CaCO3, the CaO and the Ca(OH)2 is beneficial to obtaining of pure Ca2Fe2O5.

Description

Iron-based composite oxides Ca 2Fe 2O 5The preparation method

Technical field

The invention belongs to chemical material field, be specifically related to a kind of semi-conductor iron-based composite oxides Ca ₂Fe ₂O ₅The preparation method.

Background technology

As far back as nineteen fifty-seven, Bertaut etc. have found Ca ₂Fe ₂O ₅, it is a kind of oxygen defect perofskite type oxide, is brownmillerite type oxide compound again.It is alternately to be made of one deck [FeO6] and one deck [FeO4].After finding brownmillerite, many experts and scholar have paid close attention to it, explore its new preparation technology path on the one hand; Its particular performances of R and D on the other hand is so that the use of daily production.The method for preparing brownmillerite the earliest is a solid reaction process, and in decades subsequently, people also make in this way continuing, and improve.The most commonly used in solid state reaction, the most successful technology is: CaCO ₃(99.95%), Fe ₂O ₃(99.998%) mixes by stoichiometric ratio, ground behind the 40min in air 1000 ℃ of (950 ℃) sintering 24 hours, be cooled to room temperature, grind, 1200 ℃ of (1180 ℃) sintering 24 hours, just can obtain single-phase Ca again ₂Fe ₂O ₅

When the development solid state reaction was sent out, people had also carried out the exploration-liquid phase method of other technologies, as citric acid-ir radiation method, citric acid method etc., but this class methods complex technical process, productive rate is low, makes that use is limited, so solid phase method is the emphasis that people study always.The development of high-energy ball-milling process has promoted solid reaction process to be used rapidly, reduces the solid phase reaction process time, simplifies technological process, reduces energy consumption of reaction.For adopting high-energy ball milling method, raw material prepares Ca with organism (oxalate, Citrate trianion) as some experts and scholars ₂Fe ₂O ₅(V.Berbenni, A.Marini, G.Bruni, C.Milanese.Solid state formation of calcium ferrites from thermal decomposition of mixtures Ca ₃(C ₆H ₅O ₇) ₂.4H ₂O-Fe ₂(C ₂O ₄) ₃.6H ₂O. The role of mechanical activation on the mechanism of the thermal decomposition and the temperature

Summary of the invention

Of the present inventionly be to provide a kind of cost lower, simple to operate, with CaCO ₃, Fe ₂O ₃Be raw material, the sensitization of high-energy ball milling machinery, low sintering iron-based composite oxides Ca ₂Fe ₂O ₅The preparation method.

For achieving the above object, the technical solution used in the present invention is:

1) at first, with pulverous CaCO ₃And Fe ₂O ₃Mass ratio according to 2: 1 mixes;

2) with mixed powder after grinding 3-10h, crossing 60 mesh sieves greater than 1000 rev/mins rotating speed, obtain the mechanical activation powder through 50 ℃ of oven dry;

3) adopting water content is that 3% alcohol is ball-milling medium, and the mechanical activation powder is added in the ball mill, and by the mechanical activation powder: abrading-ball: the quality of alcohol=1: 5: 1 compares ball milling;

4) powder mix is calcined in box High Temperature Furnaces Heating Apparatus, be warming up to 500 ℃ from room temperature, be warming up to 600-1000 ℃ of sintering 24 hours with 5 ℃/min temperature rise rate from 500 ℃ again with the temperature rise rate of 10 ℃/min.

Described CaCO ₃And Fe ₂O ₃Purity＞99%.

The present invention utilizes the gradual heating principle of high-energy ball milling, makes on the one hand portion C aCO ₃Decomposition obtains CaO, on the other hand because the existence of small amount of moisture makes the CaO that generates can be converted into Ca (OH) ₂, this CaCO ₃, CaO, Ca (OH) ₂Mixed system is beneficial to and obtains pure Ca ₂Fe ₂O ₅Obtain mixed powder behind the high-energy ball milling simultaneously, not only granularity is little, and these powder have unique chemical property and high activation energy.By the adjustment of ball milling time, sintering temperature, soaking time, can make material synthetic particle size difference under lower temperature, the Ca that the structure different colours is different ₂Fe ₂O ₅

Description of drawings

Fig. 1 is that the present invention calcines the Ca that obtains down at 800 ℃ the different ball milling times ₂Fe ₂O ₅Composite oxides XRD analysis figure, wherein ordinate zou is an intensity, is the X-coordinate diffraction angle number of degrees.

Embodiment

Below in conjunction with drawings and Examples the present invention is described in further detail.

Embodiment 1:1) at first, with the pulverous CaCO of purity＞99% ₃And Fe ₂O ₃Mass ratio according to 2: 1 mixes;

2) with mixed powder after grinding 3h, crossing 60 mesh sieves greater than 1000 rev/mins rotating speed, obtain the mechanical activation powder through 50 ℃ of oven dry;

3) adopting water content is that 3% alcohol is ball-milling medium, and the mechanical activation powder is added in the ball mill, and by the mechanical activation powder: abrading-ball: the quality of alcohol=1: 5: 1 compares ball milling;

4) powder mix is calcined in box High Temperature Furnaces Heating Apparatus, be warming up to 500 ℃ from room temperature, be warming up to 800 ℃ of sintering 24 hours with 5 ℃/min temperature rise rate from 500 ℃ again with the temperature rise rate of 10 ℃/min.

Embodiment 2: milling time step 2 in the present embodiment) is 5h, and the sintering temperature of step 4) is 600 ℃, and other step is with embodiment 1.

Embodiment 3: milling time step 2 in the present embodiment) is 8h, and the sintering temperature of step 4) is 900 ℃, and other step is with embodiment 1.

Embodiment 4: milling time step 2 in the present embodiment) is 10h, and the sintering temperature of step 4) is 1000 ℃, and other step is with embodiment 1.

Referring to Fig. 1, as seen from the figure, along with the lengthening of ball milling time, synthetic Ca ₂Fe ₂O ₅Amount increase.When the ball milling time is increased to 3h, obtain pure brownmillerite type Ca ₂Fe ₂O ₅Yet overlong time (＞3h) CaFe ₂O ₄Increase mutually.

Claims (2)

1. iron-based composite oxides Ca ₂Fe ₂O ₅The preparation method, it is characterized in that:

1) at first, with pulverous CaCO ₃And Fe ₂O ₃Mass ratio according to 2: 1 mixes;

2) with mixed powder after grinding 3-10h, crossing 60 mesh sieves greater than 1000 rev/mins rotating speed, obtain the mechanical activation powder through 50 ℃ of oven dry;

3) adopting water content is that 3% alcohol is ball-milling medium, and the mechanical activation powder is added in the ball mill, and by the mechanical activation powder: abrading-ball: the quality of alcohol=1: 5: 1 compares ball milling;

4) powder mix is calcined in box High Temperature Furnaces Heating Apparatus, be warming up to 500 ℃ from room temperature, be warming up to 600-1000 ℃ of sintering 24 hours with 5 ℃/min temperature rise rate from 500 ℃ again with the temperature rise rate of 10 ℃/min.

2. iron-based composite oxides Ca according to claim 1 ₂Fe ₂O ₅The preparation method, it is characterized in that: described CaCO ₃And Fe ₂O ₃Purity＞99%.

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