P. V. Istomin

Siliciding of titanium carbides with gaseous SiO

Titanium carbides of different stoichiometries were silicided with gaseous SiO at 1350°C. A mechanical mixture of silicon and silicon dioxide was used as a reaction source of SiO. Ti3SiC2, TiSi2, and Ti5Si3 were the main reaction products, the phase composition of which strongly depended on the titanium carbide stoichiometry. The siliciding of carbides with a nearly stoichiometric carbon content resulted in the formation of Ti3SiC2, on the surface of which the other silicide phases, such as Ti5Si3 and TiSi2, began to form. For titanium carbides with a low carbon concentration, Ti5Si3 was the only siliciding product.

Preparation of biomorphic SiC

A carbon template has been silicided with gaseous SiO at 1350°C in vacuum using a mixture of silicon and silicon dioxide powders as a SiO source and pyrolyzed birch wood as a carbon template. The results demonstrate the feasibility of producing biomorphic SiC whose microstructure replicates the structure of the carbon template. The material thus obtained has a porosity of about 80% and an axial compressive strength of 35 MPa.

Preparation of Ti3SiC2 through reduction of titanium dioxide with silicon carbide

This paper describes the reduction of titanium dioxide with a mixture of silicon carbide and silicon powders at a temperature of 1550°C under vacuum. It has been shown that the use of the combined reductant enables the preparation of the ternary phase Ti3SiC2 through concurrent carboand silicothermic processes. The optimal compositions for Ti3SiC2 formation are TiO2 + (1.5–x)SiC + 2xSi with x = 0.4–0.5. The Ti3SiC2 yield then reaches 96 wt %.

Effect of chemical modification conditions on the sintering behavior of TiC powders

Dense ceramics have been produced from a chemically modified titanium carbide powder. Chemical modification was carried out by siliciding titanium carbide powder in a gaseous SiO atmosphere at 1350°C. This treatment produced a Ti3SiC2 layer (up to 19 wt %) on the surface of the TiC particles. Hot pressing at a temperature of 1600°C and pressures from 10 to 20 MPa ensured effective densification of the modified powders. The density of the resultant material reaches 4.8 g/cm3, with a residual porosity under 2%. Its bending strength and fracture toughness are 330 ± 50 MPa and 6.2 ± 0.6 MPa m1/2, respectively.

Reaction of metallic titanium with SiO gas

We have studied the silicidation of thin VT 1-00 titanium strips in a gaseous SiO atmosphere at 1350°C. The results demonstrate that silicidation produces a porous layer of Ti5Si3Ox particles on the surface of the titanium strips. This is accompanied by the incorporation of oxygen atoms into the crystal lattice of α-titanium, resulting in the formation of an α-Ti〈Oy〉 (0.1 ≤ y ≤ 0.5) solid solution. The thickness of the Ti5Si3Ox layer and the oxygen concentration in the α-titanium lattice depend on the silicidation rate and time.

Siliconization of titanium oxycarbides by silicon monoxide

Siliconization of titanium oxycarbides TiCxOy by gaseous SiO at 1350°C was studied. The reaction source of SiO was a powder mixture of silicon and silicon dioxide. It was found that the main siliconization product is Ti5Si3 and the siliconization of high-carbon (x > 0.70) oxycarbides also gives Ti3SiC2 and TiSi2.

Optimization of the Carbosilicothermic Synthesis of the Ti4SiC3 MAX Phase

We have studied the formation of the Ti4SiC3 MAX phase during the vacuum carbosilicothermic reduction of TiO2 with a combined reducing agent consisting of SiC and elemental Si and analyzed the effects of the synthesis temperature, heat treatment time, and percentage of elemental silicon in the starting mixture on the Ti4SiC3 yield. Optimal Ti4SiC3 synthesis conditions are as follows: temperature from 1550 to 1650°C, isothermal holding time of 360 min, and the starting-mixture composition TiO2 + 1.2SiC + 0.6Si. The Ti4SiC3 yield then reaches 92 wt %.

Silicidation of Tantalum Carbide and Zirconium Carbide Powders in a Gaseous SiO Environment

Tantalum carbide and zirconium carbide powders have been silicided in a gaseous SiO atmosphere at 1400°C. X-ray diffraction and energy dispersive X-ray microanalysis results demonstrate that the silicidation products are Ta5Si3 and TaSi2 in the case of TaC and ZrSi in the case of ZrC. The silicidation rate has been shown to influence the percentages of these silicides in the reaction products. The degree of silicidation reached in this study is about 20% in the case of TaC and about 16% in the case of ZrC.

Preparation of a SiC Fiber Textile Material

A textile material consisting of SiC fibers has been produced by siliciding carbon cloth in a gaseous SiO atmosphere. The reactive SiO source used was a mechanical mixture of silicon and silicon dioxide. The process was run at a temperature of 1400°C under dynamic vacuum. The results demonstrate the conceptual feasibility of using the process for producing SiC cloth reproducing the dimensions and shape of the parent carbon cloth.

Production of Ti3SiC2-based materials by SHS forced compaction of layered composite Ti–SiC

A new method of synthesizing ceramic composite materials based on Ti3SiC2 using non-powder reaction compositions of titanium and silicon carbide was developed. Aceramic composite with a Ti3SiC2–TiSi2 matrix reinforced with SiC particles was obtained by SHS forced compaction of a multilayer packet of regularly packed layers of titanium foil and polymer film filled with silicon carbide particles. The particulars of the phase composition and microstructure of the material obtained were investigated.