CN100519477C - Method for preparing tantalum-aluminium-carbon ceramic by in-situ heat-pressing/solid-liquid phase reaction - Google Patents

Abstract

The present invention relates to the preparation technology of machinable layered ceramics, and in particular provides a method for preparing tantalum aluminum carbon (Ta ₄ AlC ₃ , Ta ₂ AlC and two-phase composite) ceramic block materials by in-situ hot pressing/solid-liquid phase reaction The method is characterized in that: using a certain stoichiometric ratio of Ta powder, Al powder and C powder as raw materials, the raw materials are ball milled for 5-15 hours, cold-pressed into a cake shape with a pressure of 10-20MPa, put into a graphite mold, and Heat to 1100°C-1600°C in a hot-press furnace with an inert gas (such as argon) as a protective gas (or under vacuum) at a heating rate of 2-50°C/min. In-situ hot pressing/solid-liquid phase reaction 0.5 -4 hours, hot pressing pressure is 20-40MPa. The present invention can synthesize high-purity, high-strength, and corrosion-resistant tantalum-aluminum-carbon block materials at relatively low temperatures in a short period of time; the ambient temperature of the materials obtained by the method of the present invention can range from room temperature to ultra-high temperatures greater than 1000°C. Use at high temperatures.

Description

A method for preparing tantalum-aluminum-carbon ceramics by in-situ hot pressing/solid-liquid phase reaction

technical field

The present invention relates to the preparation technology of machinable layered ceramics, and in particular provides a method for preparing tantalum aluminum carbon (Ta ₄ AlC ₃ , Ta ₂ AlC and two-phase composite) ceramic block materials by in-situ hot pressing/solid-liquid phase reaction method.

Background technique

Tantalum aluminum carbon (Ta ₄ AlC ₃ , Ta ₂ AlC and two-phase composite) bulk material is a new type of ternary layered material. It combines many advantages of ceramics and metals, including high modulus of ceramics (such as Ta ₄ AlC ₃ is 259GPa), anti-oxidation, corrosion resistance, etc.; at the same time, it has the properties of metal materials, high electrical conductivity, thermal conductivity , strong damage tolerance, etc. It has potential wide application prospects in high-tech fields such as aviation, aerospace, nuclear industry, fuel cells, electronic information, and ultra-high temperature structural parts. Although tantalum aluminum carbon (Ta ₄ AlC ₃ , Ta ₂ AlC and two-phase composite) bulk materials have such excellent properties, the difficulty in preparation limits the research on their properties and their applications. So far there is no report on the preparation of tantalum aluminum carbon (Ta ₄ AlC ₃ , Ta ₂ AlC and two-phase composite) bulk materials. Document 1 (Z. Metallkd. (German Journal of Metals) 71, 341 (1980)) studied the phase equilibrium relationship of Ta-Al-C system at 700 ° C and 1000 ° C. They found that Ta ₂ AlC and Ta ₅ Al ₃ C Two kinds of ternary carbides, but failed to obtain pure Ta ₂ AlC, and did not study its related properties. So far, there are no reports on bulk materials.

Contents of the invention

The invention first proposes a method for preparing tantalum-aluminum-carbon (Ta ₄ AlC ₃ , Ta ₂ AlC and two-phase composite) ceramic block materials by in-situ hot pressing/solid-liquid phase reaction. Among them, Ta ₄ AlC ₃ was discovered for the first time and its structure was determined through transmission electron microscope observation and theoretical calculation. The method uses Ta powder, Al powder and C powder as raw materials, and synthesizes high-purity, dense tantalum-aluminum-carbon (Ta ₄ AlC ₃ , Ta ₂ AlC and two-phase composite) bulk materials at a relatively low temperature in a short period of time.

Technical scheme of the present invention is as follows:

A method for preparing tantalum-aluminum-carbon ceramics by in-situ hot pressing/solid-liquid phase reaction, the method is characterized in that:

1) Raw material composition and ingredient range:

The stoichiometric ratio (ie molar ratio) of Ta ₂ AlC is Ta:Al:C=4:(0.8-2.5):(1.8-3.5) and Ta:Al:C=2:(0.8-2.5):(0.7 -1.5), the stoichiometric ratio of the synthesized Ta ₄ AlC ₃ and Ta ₂ AlC two-phase composites can be adjusted between the above two ratios.

2) Preparation process:

The raw materials are ball-milled for 5-15 hours, cold-pressed into cakes at a pressure of 10-20 MPa, put into graphite molds, and passed through inert gas (such as argon) as a protective gas (or under vacuum, the vacuum degree is higher than 10 ^{- 1} Pa) in a hot pressing furnace with a heating rate of 2-50°C/min (preferably 5-30°C/min) to 1100°C-1600°C (preferably 1350°C-1550°C) in-situ hot pressing/curing - liquid phase reaction for 0.5-4 hours (preferably 0.5-2 hours), hot pressing pressure is 20-40MPa (preferably 30-40MPa).

The features of the present invention are:

1. The selection of raw materials is simple, namely Ta powder, Al powder and C powder;

2. The existence of the liquid phase is used to promote the process of mass transfer and diffusion, so it can be synthesized at low temperature (below 1600°C) and in a short time (generally within two hours);

3. Through in-situ hot pressing/solid-liquid phase reaction, sintering and densification are performed simultaneously to obtain single-phase dense tantalum-aluminum-carbon (Ta ₄ AlC ₃ , Ta ₂ AlC and two-phase composite) bulk materials.

4. The ambient temperature of the material obtained by the method of the present invention can be used at an ultra-high temperature from room temperature to over 1000°C.

Description of drawings

Fig. 1 X-ray diffraction pattern of Ta ₄ AlC ₃ .

The scanning electron micrograph of the reaction product in Fig. 2.

TEM photograph of the reaction product in Fig. 3 .

Fig. 4 X-ray diffraction pattern of _{Ta 4} AlC ₃ and Ta ₂ AlC two-phase composite.

Transmission electron micrograph of the reaction product in Fig. 5.

Detailed ways

The present invention is described in detail below by way of examples.

Example 1.

180.95 grams of Ta powder, 13.49 grams of Al powder and 9.00 grams of C powder were ball-milled for 8 hours, cold-pressed into a cake under a pressure of 15 MPa, packed into a graphite mould, and passed through an inert gas (argon) as a heat shielding gas. In the press furnace, the temperature was raised to 1530°C at a rate of 10°C/min for in-situ hot pressing/solid-liquid phase reaction for 0.5 hours, and the hot pressing pressure was 30MPa. The obtained main reaction product is Ta ₄ AlC ₃ by X-ray diffraction analysis. Corresponding X-ray diffraction patterns, scanning electron micrographs, and transmission electron micrographs are listed in accompanying drawings 1-3 respectively.

Example 2.

180.95 grams of Ta powder, 14.84 grams of Al powder and 6.00 grams of C powder were ball milled for 12 hours, cold-pressed into a cake under a pressure of 10 MPa, packed into a graphite mold, and heated in a hot-press furnace with argon as a protective gas. The heating rate of 20°C/min was increased to 1450°C in situ hot pressing/solid-liquid phase reaction for 1 hour, and the hot pressing pressure was 35MPa. The obtained main reaction product is a two-phase composite material of Ta ₄ AlC ₃ and Ta ₂ AlC through X-ray diffraction analysis. The corresponding X-ray diffraction patterns are listed in accompanying drawing 4.

Example 3.

180.95 grams of Ta powder, 20.24 grams of Al powder and 6.00 grams of C powder were ball milled for 12 hours, cold-pressed into a cake under a pressure of 20 MPa, packed into a graphite mould, and heated under vacuum (vacuum degree is 10 ^-2 Pa) In the press furnace, the temperature was raised to 1350°C at a rate of 10°C/min for 2 hours of in-situ hot pressing/solid-liquid phase reaction, and the hot pressing pressure was 40MPa. The obtained main reaction product is Ta ₂ AlC by X-ray diffraction analysis. Corresponding transmission electron micrographs are on accompanying drawing 5.

Claims (1)

1. A method for preparing tantalum-aluminum-carbon ceramics by in-situ hot pressing/solid-liquid phase reaction, the method is characterized in that: 1) Raw material composition and ingredient range: Using Ta powder, Al powder and C powder as raw materials, synthesize single-phase Ta ₄ AlC ₃ , and the stoichiometric ratio of Ta ₂ AlC is Ta:Al:C=4:(0.8-2.5):(1.8-3.5) and Ta : Al: C = 2: (0.8-2.5): (0.7-1.5), synthesis: the stoichiometric ratio of Ta ₄ AlC ₃ and Ta ₂ AlC two-phase composite material is adjusted between the above two ratios; 2) Preparation process: The raw materials are ball milled for 5-15 hours, cold-pressed into cakes at a pressure of 10-20MPa, put into graphite molds, and heated at 2-50°C/min in a hot-press furnace with an inert gas as a protective gas or under vacuum. The heating rate is increased to 1100° C.-1600° C. in-situ hot pressing/solid-liquid phase reaction for 0.5-4 hours, and the hot pressing pressure is 20-40 MPa.

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