CN1460658A - Method for preparing single-phase compact silicon titanium carbid block body material by using Al as adjuvant through hot-pressing reaction in situ - Google Patents

Abstract

A method for preparing single-phase dense titanium-silicon carbide bulk material by in-situ hot-pressing reaction with Al as an auxiliary agent. The method uses TiC, Ti, Si and Al as raw materials, and the molar ratio of the four raw materials is TiC:Ti:Si:Al=2:1:(0.95-1.05):(0.15-0.25). After the raw materials are mixed evenly, they are sintered in a hot-press furnace with an Ar atmosphere, the sintering temperature is 1200-1500° C., the holding time is 1-8 hours, and the pressure is 20-80 MPa. The content of Ti ₃ SiC ₂ in the product prepared by this method is as high as 98wt%, the material density is greater than 99%, the compressive strength reaches 800MPa, the three-point bending strength σ _b ≥ 420MPa, and K _IC ≥ 5MPa·m ^1/2 The process of the present invention Simple and suitable for industrial production.

Description

Method for preparing single-phase dense titanium-silicon carbide bulk material by in-situ hot-pressing reaction with Al as auxiliary agent

technical field

The invention relates to the preparation of ceramic materials, in particular to a method for preparing single-phase dense titanium-silicon carbide block materials by in-situ hot pressing reaction using Al as an auxiliary agent.

Background technique

Titanium silicon carbide (Ti ₃ SiC ₂ ) is an excellent high-temperature structural/functional material, which has electrical conductivity, thermal conductivity, high-temperature plasticity and processability like metal, and has high strength and low density like ceramics , Good high temperature stability and high temperature oxidation resistance. However, the synthesis of titanium silicon carbide is relatively difficult. Literature (1) Monatsh. Fur. Chem. 98, 1967. Using TiH ₂ , Si and graphite as raw materials, Ti ₃ SiC ₂ was synthesized by chemical reaction at 2000°C. Literature (2) J.Less.Common Metals.26, 1972. Literature (3) J.Mater.Sci.29, 1994. Use SiCl ₄ , TiCl ₄ , CCl ₄ , H ₂ and TiCl ₄ , SiCl ₄ , CH _4. Ti ₃ SiC ₂ films were prepared by vapor deposition method using H ₂ as raw material. Document (4) J.Eur.Ceram.Soc.5, 1989. Using Ti, Si and carbon black as raw materials, Ti ₃ SiC ₂ was synthesized by self-propagating high-temperature reaction, and there were a large number of impurity phases in the reaction product. Document (5) J.Amer.Ceram.Soc.78, 1995. Using Ti, Si and carbon black as raw materials, Ti ₃ SiC ₂ bulk material was prepared by arc melting method and post-annealing treatment, but the reaction product had high impurity content, The reaction temperature is difficult to precisely control. Document (6) J.Amer.Ceram.Soc.79, No.7, 1996. Using hot isostatic pressing process, using Ti, SiC and graphite as raw materials, prepared a dense single-phase Ti ₃ SiC ₂ bulk material, But the preparation process is quite complicated. Document (7) Z.Metallkd.91, No.11, 2000. Using Ti, Si and graphite as raw materials, and adding 4% NaF as a reaction aid, a Ti ₃ SiC ₂ block was prepared by hot pressing material, the product contains a large amount of TiC. Document (8) J.Eur.Ceram.Soc.22, 2002. Using a new process of spark plasma sintering (SPS), using Ti, Si and TiC as raw materials, a Ti ₃ SiC ₂ bulk material with a purity of 98% was obtained. But this process is not suitable for industrial production.

Contents of the invention

The object of the present _invention is to provide a method for preparing a single-phase dense _Ti3SiC2 bulk material, which is suitable for industrial scale production.

The invention provides a method for preparing single-phase dense titanium-silicon carbide bulk material by in-situ hot-pressing reaction, which is characterized in that: Al is used as an auxiliary agent and prepared according to the following steps: 1. TiC powder, Ti powder, Si Powder and Al powder are raw materials, and the four raw materials are compounded according to the molar ratio TiC:Ti:Si:Al=2:1:(0.95～1.05):(0.15～0.25); 2. After mixing the raw material powders evenly, place them in graphite In the mold, heat up to 1200-1500°C at a rate of 20-60°C/min in a hot-press furnace with Ar gas as a protective atmosphere, and heat press in situ for 1-8 hours at a pressure of 20-80 MPa.

The content of Ti ₃ SiC ₂ in the product prepared by this method can be determined by internal standard method, and its value is as high as 98wt%. The material density is determined by Archimedes, and its value is greater than 99%. Measured on the INSTRON-1195 million mechanical testing machine, the compressive strength of the material is ≥800MPa, the three-point bending strength σ _b ≥420MPa, and the K _IC ≥5MPa·m ^1/2 .

The essence of the present invention is to prepare Ti ₃ SiC ₂ material by means of a reactive hot pressing. Due to the low melting point of Al, at a lower temperature, Al will melt and form an Al-Si liquid phase alloy with Si, which promotes the reaction synthesis.

The innovation of the present invention lies in utilizing the low melting point of Al (660° C.) and the similarity in structure and performance of two similar compounds Ti ₃ SiC ₂ and Ti ₃ AlC ₂ . The Al-Si liquid phase alloy can promote the reaction synthesis and accelerate the sintering. At the same time, the doped Al is dispersed and dissolved in the matrix, which will not have a significant impact on the structure and performance of the material. Therefore, single-phase dense bulk materials can be obtained by hot-pressing sintering.

Description of drawings

Fig. 1 is the X-ray diffraction spectrum of the product Ti ₃ SiC ₂ sample prepared by this method.

Fig. 2 is a photograph of a Ti ₃ SiC ₂ bulk material with a diameter of 110 mm and a thickness of 10 mm prepared by this method.

Detailed ways

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

Example 1

150 g of mixed powder with a molar ratio of TiC:Ti:Si:Al=2:1:0.95:0.25 was put into a graphite mold and sintered under an Ar protective atmosphere. The heating rate is 50°C/min, the sintering temperature is 1300°C, the pressure is 30MPa, and the temperature is kept for 2 hours. The bulk material has a density of 99% and a Ti ₃ SiC ₂ content of 98.2 wt%. Compressive strength ≥800MPa, three-point bending strength σ _b ≥420MPa, K _IC ≥5 MPa·m ^1/2 .

Example 2

250 grams of mixed powder with a molar ratio of TiC:Ti:Si:Al=2:1:1.05:0.15 was put into a graphite mold and sintered under an Ar protective atmosphere. The heating rate is 50°C/min, the sintering temperature is 1400°C, the pressure is 60MPa, and the temperature is kept for 6 hours. The bulk material has a density of 99.8% and a Ti ₃ SiC ₂ content of 99.5 wt%. Compressive strength ≥800MPa, three-point bending strength σ _b ≥500MPa, K _IC ≥5MPa·m ^1/2 .

Claims (1)

1, the method for the single-phase fine and close silicon titanium-carbide block materials of a kind of in-situ hot pressing prepared in reaction is characterized in that this method is auxiliary agent with Al, and preparation according to the following steps:

1) with the TiC powder, the Ti powder, Si powder and Al powder are raw material; Mol ratio by four kinds of raw materials is TiC: Ti: Si: Al=2: 1: (0.95～1.05): (0.15～0.25); Batching

2) after raw material powder mixes, place graphite jig, in being connected with the hot pressing furnace of Ar gas as protective atmosphere, rise to 1200～1500 ℃ of in-situ hot pressings 1～8 hour with the temperature rise rate of 20～60 ℃/min, hot pressing pressure is 20～80MPa.

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