CN108484161B

CN108484161B - Aluminum titanate composite material and preparation method thereof

Info

Publication number: CN108484161B
Application number: CN201810638924.2A
Authority: CN
Inventors: 徐培锋; 王振华
Original assignee: Shanghai Orient Material Technology Co ltd
Current assignee: Changzhou Chaotian New Material Co.,Ltd.
Priority date: 2018-06-20
Filing date: 2018-06-20
Publication date: 2020-11-03
Anticipated expiration: 2038-06-20
Also published as: CN108484161A

Abstract

The invention relates to an aluminum titanate composite material and a preparation method thereof, wherein the aluminum titanate composite material contains aluminum titanate and anorthite CaO & Al₂O₃·2SiO₂And cordierite Mg₂Al₄Si₅O₁₈The composite phase of (1).

Description

Aluminum titanate composite material and preparation method thereof

Technical Field

The invention relates to the field of ceramic materials, in particular to an aluminum titanate composite material and a preparation method thereof.

Background

Aluminum titanate is a novel material integrating low thermal expansion coefficient and high melting point, has high melting point (1860 +/-10 ℃), small thermal expansion coefficient (alpha <0.2 multiplied by 10E-6/° C), and even can generate negative expansion, and is the best high-temperature resistant material in the prior low-expansion material.

The aluminum titanate mainly takes ionic bonds and covalent bonds as bonding bonds, and crystal phases and air holes are arranged in the aluminum titanate from the aspect of microstructure and state, so that the aluminum titanate has the advantages of low heat conductivity, slag resistance, alkali resistance, corrosion resistance and non-infiltration to various metals and glass, which are not possessed by metal materials and high polymer materials, and therefore, the aluminum titanate has wide application in the harsh environments of wear resistance, high temperature resistance, alkali resistance, corrosion resistance and the like, and particularly the occasions requiring high thermal shock resistance.

In view of the excellent performance of the aluminum titanate material, the aluminum titanate material has wide application in the aspects of nonferrous metals, steel, automobiles, military industry, chemical engineering, medicine and the like; the material is often applied to metal cutting tools, dies, engine parts, cylinder linings, exhaust pipes, cylinder cover exhaust passages, supercharger volutes, turbine blades, turbine rotors and various heat insulation materials.

In addition, aluminum titanate is easy to decompose into oxides at the temperature of 1000-1200 ℃, and is decomposed violently at the temperature of 1100 ℃, microcracks can be generated due to the anisotropy of the triaxial expansion coefficient of the aluminum titanate material, so that the mechanical strength of the aluminum titanate material is poor, and the aluminum titanate material is applied on the basis of modification of the aluminum titanate material. Modifying aluminium titanate, primarily to suppress its heatThe main method is to add additives, and the common aluminum titanate modified additives are as follows: SiO 2₂、MgO、Fe₂O₃、ZrO₂、Li₂O、B₂O、Cr₂O₃、La₂O₃、CeO₂、SiC、Si₃N₄And FeTiO₃+Fe₂O₃And controlling the calcination conditions to improve the defects, so that the aluminum titanate composite ceramic material meets the requirements of good heat resistance, good thermal shock resistance and high mechanical strength. Among them, rare earth metal oxide modification is most commonly used. However, this modification method is costly, and requires a longer time for the solid phase reaction due to the lower activity of the oxide; because the addition amount is small, the solid phase reaction needs to be fully contacted, so that very strict requirements are provided for the uniformity of the mixture, the particle size distribution of each raw material powder and the particle size distribution among different raw materials, and the industrial large-scale stable production is not facilitated.

Currently, there are mainly 3 methods for synthesizing aluminum titanate: one, Al₂O₃And TiO₂A powder mixture, a solid phase method in which a solid phase reaction occurs by high temperature calcination; second, liquid phase method of metal alkoxide or metal salt hydrolysis product; and a gas phase method using VCD or the like. The synthesis preparation process of the solid phase method is simple, special equipment is not needed, although the high purity and the superfine degree can not be achieved, the method is a common preparation method, and the modification additive is added simply and efficiently, so that the method can be directly applied to powdery Al₂O₃And TiO₂The powder can be added during mixing.

Disclosure of Invention

Aiming at the problems in the prior art, the invention aims to provide an aluminum titanate composite material with high strength and low expansion and a method for preparing the aluminum titanate composite material, which has simple process, low cost and easy industrial large-scale application.

In a first aspect, the present invention provides an aluminum titanate composite material comprising aluminum titanate, anorthite CaO. Al₂O₃·2SiO₂And cordierite Mg₂Al₄Si₅O₁₈The composite phase of (1).

According to the present invention, anorthite CaO. Al is contained in the aluminum titanate composite material₂O₃·2SiO₂And cordierite Mg₂Al₄Si₅O₁₈The two materials have the characteristics of high strength, low expansion coefficient and the like, so that the aluminum titanate composite material has excellent performances of high mechanical strength, good thermal stability, strong corrosion resistance, low thermal expansion coefficient and the like, not only preserves the advantages of the aluminum titanate, but also avoids the defects of the aluminum titanate, and lays a foundation for the wide application of the aluminum titanate composite material.

Preferably, in the aluminum titanate composite material, the content of aluminum titanate is 60-80% by mass, and anorthite CaO & Al₂O₃·2SiO₂10-20% of cordierite Mg₂Al₄Si₅O₁₈The content of (A) is 10-20%.

In a second aspect, the invention provides a preparation method of the aluminum titanate composite material, which is characterized in that alumina, titanium dioxide and diopside are used as raw materials, and the aluminum titanate composite material is prepared by solid-phase reaction sintering.

According to the invention, diopside CaMg (SiO) is used₃)₂As the modifying additive, the ingredients of each particle are the same regardless of the size, and diopside reacts with alumina to generate anorthite CaO. Al at high temperature₂O₃·2SiO₂And cordierite Mg₂Al₄Si₅O₁₈And obtaining the high-strength low-expansion aluminum titanate composite material.

Preferably, the preparation method comprises the following steps: mixing alumina powder, titanium dioxide powder and diopside powder to obtain a mixture; granulating the mixture to obtain granulated powder; molding the granulation powder to obtain a blank; and sintering the blank to obtain the aluminum titanate composite material.

Preferably, in the mixture, the weight percentages of the raw materials are as follows: 40-55% of alumina powder, 25-35% of titanium dioxide powder and 15-35% of diopside powder.

Preferably, the D50 of the alumina powder and/or the titanium dioxide powder is between 0.5 and 5um, preferably between 0.5 and 1.5um, and the D50 of the diopside powder is between 0.5 and 1.5um, preferably between 0.5 and 1 um.

Preferably, the granulating comprises: mixing and ball-milling the mixture with a 10% polyvinyl alcohol solution, 40-100% water, 0-0.1% sodium tripolyphosphate and 0-0.01% n-octanol, wherein the polyvinyl alcohol solution, the water, the sodium tripolyphosphate and the n-octanol are 5-15% (preferably 5-10%) of the weight of the mixture, so as to obtain slurry, and performing spray granulation on the slurry to obtain granulated powder.

Preferably, the particle size of the granulated powder is 50-150um, preferably 80-120 um, and the moisture content is 0.2-1%, preferably 0.5-1%.

Preferably, the forming comprises: and pressing and molding the granulated powder under the pressure of 8-20 MPa.

Preferably, in the firing, the firing temperature is 1450-1550 ℃ and the heat preservation time is 4-8 hours.

Preferably, in the firing, the temperature is raised from room temperature to 600 ℃ at 30 to 60 ℃/hr, from 600 ℃ to 1200 ℃ at 50 to 100 ℃/hr (preferably 60 to 100 ℃/hr), and from 1200 ℃ to the firing temperature at 50 to 100 ℃/hr (preferably 60 to 100 ℃/hr).

In a third aspect, the present invention provides a sagger made of the above aluminum titanate composite material.

Drawings

FIG. 1 is a scanning electron micrograph of an Alcalite titanate cordierite composite material prepared in example 1 of the present invention.

FIG. 2 is a scanning electron micrograph of the composite material prepared in comparative example 1.

FIG. 3 is a scanning electron micrograph of the composite material obtained in comparative example 2.

Detailed Description

The present invention is further described below in conjunction with the following embodiments and the accompanying drawings, it being understood that the drawings and the following embodiments are illustrative of the invention only and are not limiting thereof.

Disclosed herein is an aluminum titanate composite material containing calcium aluminum titanateA composite phase of feldspathic cordierite, specifically, comprising: aluminum titanate Al₂TiO₅Alcalite CaO. Al₂O₃·2SiO₂And cordierite Mg₂Al₄Si₅O₁₈。

In a preferred embodiment, the aluminum titanate composite material contains 60 to 80% by mass of aluminum titanate and anorthite CaO · Al₂O₃·2SiO₂10-20% of cordierite Mg₂Al₄Si₅O₁₈The content of (A) is 10-20%. The aluminum titanate composite material with the composition has the advantages of high strength and low expansion coefficient.

In one embodiment, the composite material has anorthite glass phase formed between aluminum titanate crystals and cordierite formed as elongated particles embedded in the aluminum titanate crystals.

The aluminum titanate composite material disclosed by the invention has excellent performances of high mechanical strength, good thermal stability, strong corrosion resistance, low thermal expansion coefficient and the like, for example, the mechanical strength is 12-22 MPa, the thermal shock resistance is 0-800 ℃ and is not cracked for 3 times, and the thermal expansion coefficient is-0.02-0.2 multiplied by 10E-6/DEG C.

In one embodiment, diopside CaMg (SiO) is utilized₃)₂Preparing the high-strength low-expansion aluminum titanate composite material. Specifically, alumina Al is added₂O₃Powder and titanium oxide TiO₂Mixing the powders by adding diopside CaMg (SiO)₃)₂And sintering the powder through high-temperature solid-phase reaction to generate a composite phase of the anorthite cordierite titanate.

Aluminum oxide Al₂O₃Powder and/or titanium dioxide TiO₂The D50 of the powder can be between 0.5-5 um, preferably between 0.5-1.5 um. The finer the powder is, the more favorable the solid phase reaction proceeds. Here, "D50" means the median or median particle size, i.e., the particle size corresponding to the cumulative percentage of particle size distribution of 50%.

Diopside CaMg (SiO)₃)₂The powder D50 can be between 0.5-1.5 um, preferably between 0.5-1 um. As a modifying additive, relatively finer particle sizes may facilitate firingAnd the density of the blank is improved, so that the strength of the blank is improved, the sintering temperature can be reduced to a great extent, and the heat preservation time of the highest temperature section is shortened.

Aluminum oxide Al₂O₃Powder, titanium dioxide TiO₂Powder, diopside CaMg (SiO)₃)₂The mass ratio of the powder can be (40-55): (25-35): (15-35). The anorthite cordierite composite material prepared by the mass ratio has the advantages of low expansion coefficient, high strength and good thermal stability, and can be used as a conventional ceramic material. In a particularly preferred embodiment, 50% by mass of alumina Al may be added₂O₃Powder, 35% by mass of TiO 2₂Mixing the powder with 15% by mass of diopside powder.

In the high-temperature solid-phase reaction sintering, the reaction temperature can be 1450-1550 ℃. The reaction time can be 4-8 hours. Because the aluminium calcium titanate feldspar cordierite system has good thermal stability and smooth crystal phase transition, the method is suitable for quick firing.

In one embodiment, the aluminum titanate composite material is produced by a molding process of granulation followed by dry pressing.

First, mixing is performed. Mixing alumina powder, titanium dioxide powder and diopside powder to obtain a powder mixture which is used as a raw material of the anorthite cordierite composite material. The mixing device can adopt a gravity-free mixing device or a colter type mixing device and the like. The mixing time may be 30 to 60 minutes.

Then, granulation was performed. The granulation method can be extrusion molding, spray granulation, and granulation by an edge runner mill. Different additives can be selected according to different granulation processes. For example, extrusion molding is generally carried out using hpmc (hydroxypropyl methylcellulose) as a binder, pva (polyvinyl alcohol) as a binder if spray granulation is used, and MC (methylcellulose) as a binder if granulation is carried out by a wheel mill.

In one example, spray granulation is used. Putting the raw materials of the anorthite cordierite composite material into a ball mill, adding PVA (polyvinyl alcohol), water, sodium tripolyphosphate and n-octanol, and carrying out ball milling to obtain slurry. Wherein PVA is used as a binder, water is used as a slurry medium, sodium tripolyphosphate is used as a water reducing agent, and n-octanol is used as a defoaming agent.

In a preferred embodiment, 5 to 15% (e.g., 10%) PVA, 40 to 100% (e.g., 40%) water (preferably purified water), 0 to 0.1% (e.g., 0.1%) sodium tripolyphosphate, and 0 to 0.01% (e.g., 0.01%) n-octanol, based on 5 to 15% (e.g., 10%) by weight of the raw materials, are added and ball-milled to obtain a slurry. The ball milling time can be 0.5-8 hours.

In a preferred example, the slurry obtained is subjected to spray granulation while being stirred to obtain granulated powder. The particle size of the granulated powder can be 50-150 um. The moisture content of the granulated powder can be controlled to be 0.2-1.5%, preferably 0.5-1%, so as to facilitate dry pressing.

Then, the granulated powder is pressed and molded to obtain a green body. The pressing pressure can be 8-20 MPa. In one example, pressing is performed using an 800 ton bi-directional hydraulic press. The shape of the blank can be selected according to requirements, and is for example plate-shaped.

Subsequently, the green body is fired. The firing temperature can be 1450-1550 ℃. Because of the good thermal stability and smooth crystal phase transition of the anorthite titanate cordierite system, the crystal phase is suitable for quick firing, for example, the firing time can be 24 to 34 hours.

In one example, a stepwise temperature increase is employed, and the temperature increase rate is increased in sequence. For example, the temperature rise may be performed at the following temperature rise rate: the temperature is raised from room temperature to 600 ℃ at 30 to 60 ℃/hr (e.g., 50 ℃/hr), from 600 ℃ to 1200 ℃ at 60 to 100 ℃/hr (e.g., 80 ℃/hr), and from 1200 ℃ to the firing temperature (e.g., 1500 ℃) at 60 to 100 ℃/hr (e.g., 100 ℃/hr). The low temperature section adopts a slow temperature rise mode, which is beneficial to slow oxidation of organic matters in the embryo body and prevention of cracking, diopside is adopted as an additive of aluminum titanate, and the medium temperature section and the high temperature section are suitable for fast burning, thereby being beneficial to saving energy and increasing the productivity. And then, keeping the temperature for a period of time, such as 4 to 8 hours, at the sintering temperature. After firing, the material may be naturally cooled to room temperature.

The firing device can be a high-temperature shuttle kiln or the like. For example, the plate-shaped blank body can be placed on the furnace in a standing manner.

The traditional aluminum titanate modified additive is rare earth metal oxide, the cost is high, and longer solid phase reaction time is needed due to lower activity of the oxide; because the addition amount is small, the solid phase reaction needs to be fully contacted, so that very strict requirements are provided for the uniformity of the mixture, the particle size distribution of each raw material powder and the particle size distribution among different raw materials, and the industrial large-scale stable production is not facilitated.

In this embodiment, diopside CaMg (SiO) is used instead₃)₂The powder is used as a modifying additive, the components of each particle are the same no matter how fine the powder is, and diopside CaMg (SiO) is prepared at high temperature₃)₂Powder and surrounding alumina Al₂O₃Production of anorthite CaO & Al by powder reaction₂O₃·2SiO₂And cordierite Mg₂Al₄Si₅O₁₈Both of these materials have the characteristics of high strength, low expansion coefficient and the like. Diopside CaMg (SiO)₃)₂The aluminum titanate anorthite cordierite composite material obtained by the method has the excellent performances of high mechanical strength, good thermal stability, strong corrosion resistance, low thermal expansion coefficient and the like, not only preserves the advantages of aluminum titanate, but also avoids the defects of the aluminum titanate, and lays a foundation for the wide application of the aluminum titanate composite material. For example, the aluminum titanate composites of the present invention can be used to prepare saggers, particularly saggers for lithium batteries.

The present invention will be described in detail by way of examples. It is also to be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the invention, and that certain insubstantial modifications and adaptations of the invention by those skilled in the art may be made in light of the above teachings. The specific process parameters and the like of the following examples are also only one example of suitable ranges, i.e., those skilled in the art can select the appropriate ranges through the description herein, and are not limited to the specific values exemplified below.

Performance testing

The mechanical strength of the obtained composite material is tested by adopting an anti-breaking strength tester, the expansion coefficient of the obtained composite material is tested by adopting a thermal expansion coefficient tester, and the thermal stability of the obtained composite material is tested by keeping the temperature of the obtained aluminum titanate composite material in an electric furnace at 1100 ℃ for 100 hours.

Example 1

1. Mixing materials: mixing 50 wt% of alumina (D50 is 0.5um), 35 wt% of titanium dioxide (D50 is 0.5um) and 15 wt% of diopside (D50 is 0.5um) for 30 minutes by a gravity-free mixing device to obtain a powder mixture, namely the raw material of the anorthite cordierite composite material.

2. And (3) granulation: putting raw materials of the anorthite cordierite composite material with certain mass into a ball mill, adding 10% PVA, 40% purified water, 0.1% sodium tripolyphosphate and 0.01% n-octanol by the weight of the raw materials, ball milling for half an hour, stirring the obtained slurry while performing spray granulation, controlling the particle size of the granulated powder to be 50-150 mu m, and controlling the water content to be 0.5-1.5%.

3. Molding: and pressing the granulated powder into a plate-shaped blank by using a 800-ton bidirectional hydraulic press.

4. And (3) firing: the plate-shaped blank plates are vertically placed by a high-temperature shuttle kiln to be installed in the kiln, and the temperature is raised at the following temperature raising speed:

FIG. 1 is a scanning electron micrograph of the anorthite cordierite composite obtained in example 1. The photograph shows that the crystal of the orthorhombic system of aluminum titanate is well developed, and the microcracks generated by the anisotropy of the expansion coefficient of the aluminum titanate crystals can be clearly seen. The low expansion of aluminum titanate is achieved by microcracks, where appropriate microcracks can act as toughening. Aluminum titanate itself is not strong because there are too many microcracks, so increasing strength reduces, rather than eliminates, microcracks. In fig. 1, the glass phase material between the crystals is anorthite, the large pieces are aluminum titanate, and the small pieces are cordierite. There is an anorthite glass phase between each crystal.

The caldron titanate cordierite composite material obtained by calculation comprises the following components in percentage by mass: 80% of aluminum titanate, 10% of anorthite and 10% of cordierite.

The test shows that the mechanical strength of the anorthite cordierite composite material obtained in the example 1 is 13MPa, the expansion coefficient is 0.2 multiplied by 10E < -6 >/DEG C, and the thermal stability is 1100 ℃ and the temperature is kept for 100 hours without abnormality.

Comparative example 1

The difference from example 1 is that in step 1, the weight percentages of alumina, titania and diopside are 55%, 35% and 10%, respectively.

FIG. 2 is a scanning electron micrograph of the composite material obtained in comparative example 1. The photograph shows that the crystal of the orthorhombic system of aluminum titanate is well developed, and the microcracks generated by the anisotropy of the expansion coefficient of the aluminum titanate crystals can be clearly seen. The glass phase material between the crystals is anorthite, the large blocks are aluminum titanate, and the small strips are cordierite. There is an anorthite glass phase between each crystal. The cracks produced were significantly wider, deeper and longer than in example 1. This is due to the significant reduction in anorthite glass phase and cordierite crystals, resulting in significantly larger and deeper microcracks. Through detection, the mechanical strength of the composite material obtained in the comparative example 1 is 9MPa, the expansion coefficient is 0.02 multiplied by 10E < -6 >/DEG C, and the product has a lower expansion coefficient and lower mechanical strength. The composite material obtained in comparative example 1 exhibited an increase in the coefficient of expansion from the original value of 0.02X 10E-6/deg.C to 4.8X 10E-6/deg.C after heat preservation at 1100 deg.C for 100 hours, indicating that a significant portion of the aluminum titanate had decomposed.

Comparative example 2

The difference from example 1 is that in step 1, the weight percentages of alumina, titania and diopside are 40%, 20% and 40%, respectively.

FIG. 3 is a scanning electron micrograph of the composite material obtained in comparative example 2. The photographs show that the orthorhombic crystals of aluminum titanate are visible, the crystals have evidence of melting and the surface is covered with a layer of glass, and there are microcracks due to anisotropy of the coefficient of expansion of the aluminum titanate crystals, but in small numbers and in a fine size. The glass phase material between the crystals is anorthite, the large blocks are aluminum titanate, and the small strips are cordierite. There is an anorthite glass phase on the surface of each crystal and between the crystals. Because of the large amount of liquid phase, aluminum titanate and cordierite crystals tend to be dissolved in anorthite liquid phase, and the crystal surface is covered with liquid phase. Through detection, the mechanical strength of the composite material obtained in the comparative example 2 is 15MPa, and the expansion coefficient is 2.2 multiplied by 10E < -6 >/DEG C, so that the obtained product has high mechanical strength, but the expansion coefficient is large, the thermal shock property is poor, and the high temperature resistance is poor.

Claims

1. An aluminum titanate composite material characterized by containing aluminum titanate, anorthite CaO & Al₂O₃·2SiO₂And cordierite Mg₂Al₄Si₅O₁₈Wherein the content of aluminum titanate is 60 to 80% by mass, and anorthite CaO & Al₂O₃·2SiO₂10-20% of cordierite Mg₂Al₄Si₅O₁₈The content of (A) is 10-20%; the aluminum titanate composite material is prepared by taking alumina, titanium dioxide and diopside as raw materials and sintering through solid-phase reaction, wherein anorthite CaO & Al₂O₃·2SiO₂And cordierite Mg₂Al₄Si₅O₁₈Is generated by the reaction of diopside and alumina, anorthite glass phase is formed between aluminum titanate crystals, and cordierite is formed into strip-shaped particles and embedded in the aluminum titanate crystals; the weight percentage of each raw material is as follows: 40-55% of alumina powder, 25-35% of titanium dioxide powder and 15-35% of diopside powder.

2. A method of preparing the aluminum titanate composite of claim 1, comprising:

mixing alumina powder, titanium dioxide powder and diopside powder to obtain a mixture;

granulating the mixture to obtain granulated powder;

molding the granulated powder to obtain a blank; and

and sintering the blank to obtain the aluminum titanate composite material, wherein the sintering temperature is 1450-1550 ℃, and the heat preservation time is 4-8 hours.

3. The method according to claim 2, wherein D50 of the alumina powder and/or the titania powder is 0.5 to 5 μm, and D50 of the diopside powder is 0.5 to 1.5 μm.

4. The method according to claim 3, wherein D50 of the alumina powder and/or the titania powder is 0.5 to 1.5 μm, and D50 of the diopside powder is 0.5 to 1 μm.

5. The method of manufacturing according to claim 2, wherein the granulating comprises: mixing and ball-milling the mixture, 5-15% polyvinyl alcohol solution, 40-100% water, 0-0.1% sodium tripolyphosphate and 0-0.01% n-octanol, wherein the polyvinyl alcohol solution is 5-15% of the weight of the mixture, the water, the sodium tripolyphosphate and the n-octanol are relative to the weight of the mixture, so as to obtain slurry, and performing spray granulation on the obtained slurry, so as to obtain granulation powder; the grain size of the granulated powder is 50-150 microns, and the water content is 0.2-1%.

6. The method of manufacturing according to claim 2, wherein the forming includes: and pressing and molding the granulated powder under the pressure of 8-20 MPa.

7. The production method according to any one of claims 2 to 6, wherein the firing is performed at 30 to 60 ℃/hr from room temperature to 600 ℃, at 50 to 100 ℃/hr from 600 ℃ to 1200 ℃, and at 50 to 100 ℃/hr from 1200 ℃ to firing temperature.

8. A sagger, characterized in that, is made of the aluminum titanate composite material of claim 1.