A new synthesis reaction of Ti3SiC2 from Ti/TiSi2/TiC powder mixtures through pulse discharge sintering (PDS) technique

Ti/TiSi₂/TiC powder mixtures with molar ratios of 1:1:4 (M1) and 1:1:3 (M2) were first employed for the synthesis of Ti₃SiC₂ through pulse discharge sintering (PDS) technique in a temperature range of 1100–1325 °C. It was found that Ti₃SiC₂ phase began to form at the temperature above 1200 °C and its purity did not show obvious dependence on the sintering temperature at 1225–1325 °C. The TiC contents in M2 samples is always lower than that of the M1 samples, and the lowest TiC contents in the M1 and M2 samples were calculated to be about 7 wt% and 5 wt% when the sintering was conducted at the temperature near 1300 °C for 15 minutes. The relative density of the M1 samples is always higher than 99% at sintering temperature above 1225 °C, indicating a good densification effect produced by the PDS technique. A solid-liquid reaction mechanism between Ti-Si liquid phase and TiC particles was proposed to explain the rapid formation of Ti₃SiC₂. Furthermore, it is suggested that Ti/TiSi₂/TiC powder can be regarded as a new mixture to fabricate ternary carbide Ti₃SiC₂. Received: 5 September 2001 / Accepted: 11 September 2001     

Fabrication of Monolithic Ti3SiC2 Ceramic Through Reactive Sintering of Ti/Si/2TiC

Fabrication of monolithic Ti₃SiC₂ has been investigated through the route of reactive sintering of Ti/Si/2TiC mixtures. Significant phase differences existed between the surface and the interior of as-synthesized products due to the evaporation of Si during the reaction process. The use of a 3Ti/SiC/C mixture as a powder bed could control the evaporation of Si and develop monolithic Ti₃SiC₂. A reaction model for the formation of Ti₃SiC₂ in the Ti/Si/2TiC system is discussed.On leave from     

Low temperature synthesis of Ti3 SiC2 from Ti/SiC/C powders

Abstract

Ternary carbide Ti₃ SiC₂ was first synthesised through a pulse discharge sintering (PDS) technique from mixtures of Ti, SiC, and C with different molar ratios. Sintering processes were conducted at 1200 – 1400°C for 15 – 60 min at a pressure of 50 MPa. The phase constituents and microstructures of the synthesised samples were analysed by X-ray diffraction (XRD) technique and observed by scanning electron microscopy (SEM). The results showed that, for samples sintered from 3Ti/SiC/C powder at 1200 – 1400°C, TiC is always the main phase and only little Ti₃ SiC₂ phase is formed. When the molar ratios Ti : SiC : C were adjusted to 3 : 1.1 : 2 and 5 : 2 : 1, the purity of Ti₃ SiC₂ in the synthesised samples was improved to about 93 wt-%. The optimum sintering temperature for Ti₃ SiC₂ samples was found to be in the range 1250 – 1300°C and all the synthesised samples contain platelike grains. The relative density of Ti₃ SiC₂ samples was measured to be higher than 99% at sintering temperatures above 1300?C. It is suggested that the PDS technique can rapidly synthesise ternary carbide Ti₃ SiC₂ with good densification at lower sintering temperature.     

Formation of Ti<Subscript>3</Subscript>SiC<Subscript>2</Subscript> from Ti-Si-TiC powders by pulse discharge sintering (PDS) technique

Ti/Si/TiC powder mixture with molar ratios of 2:2:3 were sintered at various temperatures from 700–1300 °C for 15 min by PDS technique. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used for the evaluation of phase composition in different samples for the understanding of the sintering mechanism for this system. Results showed that Ti₅Si₃ formed as the intermediate phase during sintering. The reaction between Ti₅Si₃ and TiC as well as Si induces the formation of Ti₃SiC₂, and TiSi₂ appears as the byproduct in this process. At temperature above 1000 °C, TiSi₂ reacts with TiC to form Ti₃SiC₂. High Ti₃SiC₂ phase content bulk material can be synthesized at 1300 °C for 15 min.     

Polycarbosilane derived Ti3SiC2

Titanium silicon carbide (Ti₃SiC₂) ceramic was synthesized by in-situ reaction of metal titanium and polycarbosilane. Reaction mechanisms which lead to the formation of Ti₃SiC₂ were suggested on the basis of XRD analysis. The content of Ti₃SiC₂ reached 93% in products obtained from heating the Ti/polycarbosilane green compact at 1400 °C in Ar. The morphology and compositions of the products were examined by SEM equipped with EDX. The typical laminate structure of Ti₃SiC₂ particles with 1-4 μm in thickness and 4-15 μm in length was observed. EDX results showed that the atomic ratio of Ti:Si:C of grains is close to 3:1:2, which agrees with Ti₃SiC₂ composition.     

Synthesis of Ti3Si0.8Al0.4C1.8 solid solution from Ti-Si-Al-C powder mixture

In this study, free Ti/Si/Al/C powder mixtures with molar ratios of 3:0.8:0.4:1.8 were heated in argon with various schedules, in order to reveal the possibility for the synthesis of high Ti₃Si_0.8Al_0.4C_1.8 content powder. X-ray diffraction (XRD) was used for the evaluation of phase identities of the powder after different treatments. Scanning electron microscopy (SEM) was used to observe the morphology of the Ti₃Si_0.8Al_0.4C_1.8 solid solution. XRD results showed that predominantly single phase samples of Ti₃Si_0.8Al_0.4C_1.8 were prepared after heating at 1450 °C for 5 min in argon and the lattice parameters of Ti₃Si_0.8Al_0.4C_1.8 lay between those of Ti₃SiC₂ and Ti₃AlC₂. SEM observation showed that the grains of Ti₃Si_0.8Al_0.4C_1.8 solid solution exhibited a lamellar shape, which is a characteristic feature of Ti₃SiC₂ and Ti₃AlC₂.     

Ti<Subscript>3</Subscript>SiC<Subscript>2</Subscript>/TiC composites prepared by PDS

Synthesis of composite materials with improved mechanical properties is considered. Pulse discharge sintering (PDS) technique was utilized for consolidation and synthesis of double phase Ti₃SiC₂/TiC composites from the initial powders TiH₂/SiC/TiC. Scanning electron microscopy with energy-dispersive spectrometry (SEM with EDS) and X-ray diffractometry (XRD) were exploited for the analysis of the microstructure and composition of the sintered specimens. Mechanical tests showed high bending and compression strength and low Vickers hardness of Ti₃SiC₂-rich specimens. The reasons of this behaviour are in the features of the textured microstructure of Ti₃SiC₂ phase.     

原位生成TiC/Ti5Si3纳米复合材料的显微结构研究

研究了原位生成ＴｉＣ／ＴＩ５Ｓｉ３纳米复合材料的显微结构,实验结果表明,以ＳｉＣ和Ｔｉ原料,通过反应热压工艺可以原位合成ＴｉＣ／Ｔｉ５Ｓｉ２复合材料,其中的大部分ＴｉＣ粒子为纳米粒子,ＴｉＣ晶粒与Ｔｉ５Ｓｉ３晶粒的晶界上存在原子台阶,复合材料还含有少量Ｔｉ３ＳｉＣ２相,这些Ｔｉ３ＳｉＣ２相主要呈棒状分布在Ｔｉ５Ｓｉ３基体中,另有少量ＴｉｅＳｉＣ２相位震大的ＴｉＣ晶粒内。     

Wetting behaviour of laser textured Ti3SiC2 surface with micro-grooved structures

In the present paper, micro-grooved Ti₃SiC₂ surfaces with different roughness were fabricated by pulsed laser processing. The surface topography and chemical composition of smooth and micro-grooved surfaces were characterised. The wetting behaviours of smooth and micro-grooved Ti₃SiC₂ surfaces such as static contact angle, anisotropic wettability and contact angle evolution versus time were investigated. The experimental results show that micro-grooved structures can be efficiently fabricated on Ti₃SiC₂ surface by laser processing. The contact angle of micro-grooved surface was increased by 64.2° compared with that of smooth surface. The difference values of contact angles between perpendicular and parallel direction were <?10°. The wetting state of droplet on textured surface was close to Cassie–Baxter model.     

Synthesis,microstructure and properties of (Ti1−x,Mox)2AlC phases

The reaction path of the (Ti_0.9, Mo_0.1)₂AlC phase from Ti, Al, TiC and Mo powder mixtures was investigated in detail ranging from 500 to 1450°C, and the results show that the reaction between Ti and Al produced Ti–Al intermetallics, and the reaction between Al and Mo formed Mo–Al intermetallics. And then the (Ti_0.9, Mo_0.1)₂AlC phase was formed by the reaction of Ti–Al, Mo–Al intermetallics, and TiC. At 1350°C for 2?h, a dense (Ti_0.9, Mo_0.1)₂AlC phase with purity was successfully fabricated. The Vickers hardness, flexural strength and fracture toughness were 5.48?GPa, 363.60?MPa and 5.78?MPa m^1/2, which were improved by 44, 34 and 136% for (Ti_0.80, Mo_0.20)₂AlC, respectively, compared with the single-phase Ti₂AlC.     

Crystallographic relations between Ti<Subscript>3</Subscript>SiC<Subscript>2</Subscript> and TiC

Ti₃SiC₂ is a so-called not-so-brittle ceramic that combines the merits of both metals and ceramics. However, many previous works demonstrated that its bonding nature and properties were strongly related to TiC. In this paper the crystallographic relations between Ti₃SiC₂ and TiC were established and described based on the transmission electron microscopy investigation on the Ti₃SiC₂/TiC interface in Ti₃SiC₂ based material. At Ti₃SiC₂/TiC interface, the following crystallographic relationships were identified: (111)TiC//(001)Ti₃SiC₂, (002) TiC//(104)Ti₃SiC₂, and [11ˉ0]TiC//[110]Ti₃SiC₂. Based on the above interfacial relations an interfacial structure model was established. The structure of Ti₃SiC₂ could be considered as two-dimensional closed packed layers of Si periodically intercalated into the (111) twin boundary of TiC_0.67 (Ti₃C₂). The intercalation resulted in the transformation from cubic TiC_0.67 to hexagonal Ti₃SiC₂. In the opposite case, de-intercalation of Si from Ti₃SiC₂ caused the transformation from hexagonal Ti₃SiC₂ to cubic TiC_0.67. Understanding the crystallographic relations between Ti₃SiC₂ and TiC is of vital importance in both understanding the properties and optimizing the processing route for preparing pure Ti₃SiC₂. Received: 10 February 2000 / Reviewed and accepted: 17 March 2000     

Synthesis and phase evolution of Si-C-Ti powder derived from poly(methylsilaacetylene) and Ti

Si-C-Ti powder was synthesized by reactive pyrolysis of poly(methylsilaacetylene)(PSCC) precursor mixed with metal Ti powder. Pyrolysis of PSCC/Ti mixture with certain atomic ratio was carried out in argon atmosphere between 1300 °C and 1500 °C. The metal-precursor reactions, and phase evolution were studied using X-ray diffraction and scanning electron microscopy equipped with EDX. Ti₃SiC₂ phase was obtained from reaction of PSCC and Ti for the first time. Ti₃SiC₂ formation started at 1300 °C and its amount increased significantly at 1400 °C. In addition, liquid formed by additive CaF₂ could promote the formation of Ti₃SiC₂ phase.     

Joining of SiC ceramic-based materials with ternary carbide Ti3SiC2

The joining of two pieces of SiC-based ceramic materials (SiC or C_f/SiC composite) was conducted using Ti₃SiC₂ as filler in vacuum in the joining temperatures range from 1200 °C to 1600 °C. The similar chemical reactions took place at the interface between Ti₃SiC₂ and SiC or C_f/SiC, and became more complete with joining temperature increases, and with the consequent increased joining strengths of the SiC and C_f/SiC joints. Based on the XRD and SEM analyses, it turns out that two reasons are most important for the high joining strengths of the SiC and C_f/SiC joints. One is the development of layered Ti₃SiC₂ ceramic, which has plasticity in nature and can contribute to thermal stress relaxation of the joints; the other is the chemical reactions between Ti₃SiC₂ and the base materials which result in good interface bonding.     

Synthesis and some properties of Ti3SiC2 by hot pressing of titanium,silicon, and carbon powders Part 1 – Effect of starting composition on formation of Ti3SiC2 and observation of Ti3SiC2 crystal morphology

Abstract

Dense Ti₃SiC₂ bulk ceramic was synthesised by hot pressing of elemental titanium, silicon, and carbon powders. The effects of starting composition of the powders on the synthesis of pure Ti₃SiC₂ were examined. Phase identification was carried out by X-ray diffraction. Silicon content in the starting composition played an important role in formation of the final constituent phases in the composite. It was difficult to obtain the pure phase Ti₃SiC₂ because other thermodynamically stable reaction products such as TiC, TiSi₂, or Ti₅Si₃ were always present together with Ti₃SiC₂. The microstructure of samples was examined using scanning electron microscopy and transmission electron microscopy. Observations showed that the Ti₃SiC₂ matrix was composed of elongated, platelike, and equiaxial grains. It is suggested that the hexagonal crystal Ti₃SiC₂ exhibits anisotropic grain growth behaviour. The relative growth rates on different planes, therefore, endow Ti₃SiC₂ with several morphologies.     

Superhard pcBN tool materials with Ti<Subscript>3</Subscript>SiC<Subscript>2</Subscript> MAX-phase binder: Structure,properties, application

Superhard cutting tool materials were sintered in cBN–(Ti₃SiC₂–TiC) system via high pressure–high temperature method. Sintering was performed under the pressure 8 GPa in the 1400–2400°C temperature range. The initial mixtures of three compositions were chosen with 90, 80 and 60 vol % cBN. The mixtures were prepared by mixing cBN (1–3 μm) and Ti₃SiC₂–TiC (< 2 μm). It was found, that upon sintering, the compositions of the obtained samples differed from the initial mixtures in all cases as a result of chemical reactions. Microstructure observations, phase composition estimation, and mechanical properties of the obtained tool materials were carried out. The results indicate that both the varying cBN content and the applied sintering conditions have a direct effect on the structure, properties, and kinetics of reactions.     

Synthesis and microstructure of layered-ternary Ti2AlC ceramic by high energy milling and hot pressing

Fully dense and single-phase Ti₂AlC ceramic was successfully synthesized by a high energy milling and hot pressing using Ti, C and Al as starting materials. The effects of composition of the initial elemental powders and sintering temperatures on the purity and formation of Ti₂AlC were examined. The formation mechanism for the single-phase Ti₂AlC ceramics was investigated by XRD in details, which could be described as follows: the most of initial elements reacted to form TiC and Ti–Al intermetallics; the intermetallics and the residual Ti and Al transformed to TiAl phase; and finally the TiAl intermetallics and the TiC reacted to yield Ti₂AlC.     

Oxidation behavior of TiC-containing Ti<Subscript>3</Subscript>AlC<Subscript>2</Subscript> based material at 500–900 °C in air

The isothermal oxidation behavior of Ti₃AlC₂ based material containing 5 vol% TiC inclusion in air had been investigated at 500–900 °C by means of TGA, XRD, Raman spectroscopy and SEM/EDS. It was demonstrated that, although Ti₃AlC₂ based material exhibited good oxidation resistance at temperatures above 700 °C, anomalous oxidation with higher oxidation rate occurred at lower temperatures of 500 and 600 °C. This interesting phenomenon was due to the formation of microcracks associated with the stress developed within the scales, mainly consisting of anatase, and the volume expansion as Ti₃AlC₂ based material was directly exposed to air at those temperatures. Its oxidation, at temperatures investigated with the exception of 600 °C, generally obeyed a parabolic rate law. The weight gain data for the remaining temperatures were analyzed with an instantaneous parabolic rate constant method by assuming a parabolic rate law. The variations of instantaneous parabolic rate constant with time reflected the complexity of the oxidation behavior of Ti₃AlC₂ based material. These variations were discussed from the viewpoint of the formation of microcracks at 500 °C, and preferred oxidation of TiC inclusion in the initial oxidation and its subsequent depletion at 800 and 900 °C on the basis of X-ray diffraction, Raman spectroscopy, SEM scale morphology observation and composition analysis using EDS. In addition, the deleterious effect of TiC inclusion on the oxidation resistance of Ti₃AlC₂ based material was also investigated and discussed with comparison to monolithic Ti₃AlC₂, which was helpful to understand the discrepancies in reports on the oxidation of Ti₃AlC₂.     

Current Status in Layered Ternary Carbide Ti3SiC2, a Review

This article provides a review of current research activities that concentrate on Ti₃SiC₂. We begin with an overview of the crystal and electronic structures, which are the basis to understand this material. Followings are the synthetic strategies that have been exploited to achieve, and the formation mechanism of Ti₃SiC₂. Then we devote much attentions to the mechanical properties and oxidation/hot corrosion behaviors of Ti₃SiC₂ as well as some advances achieved recently. At the end of this paper, we elaborate on some new discoveries in the Ti₃SiC₂ system, and also give a brief discussion focused on the "microstructure -property" relationship.     

Thin Film Synthesis of Ti3SiC2 by Rapid Thermal Processing of Magnetron‐Sputtered Ti?C?Si Multilayer Systems

MAX phase coating could have interesting technical applications in many fields. This paper describes the synthesis of the M_n+1AX_n phase Ti₃SiC₂ by a rapid thermal annealing process of physical vapor deposited Ti? C? Si multilayer thin films on Si (100) and SiO₂ substrates. Annealing temperatures of 800–1000 °C affected the solid state reaction of titanium, carbon and silicon creating titanium‐carbides, ‐silicides, and Ti₃SiC₂. The film structures and chemical compositions were observed by grazing incidence X‐ray diffraction, transmission electron microscopy, and glow discharge optical emission spectroscopy. Analysis after the rapid thermal processing revealed the formation of the polycrystalline M_n+1AX_n phase Ti₃SiC₂ in coexistence with TiSi₂, TiC and Ti₅Si₃, even within a 0 s annealing process. This synthesis method has a high potential for the formation of MAX phases as a high temperature electrical contact material.     

Effect of Ti<Subscript>3</Subscript>SiC<Subscript>2</Subscript> addition on microwave absorption property of plasma sprayed Ti<Subscript>3</Subscript>SiC<Subscript>2</Subscript>/NASICON coatings

The work attempted to develop a kind of high temperature microwave absorption coating. The Ti₃SiC₂/NASICON composite coatings with different Ti₃SiC₂ concentrations were fabricated by atmospheric plasma spraying. The effect of Ti₃SiC₂ addition on phase, density, microstructure, dielectric property and microwave absorption property of as-sprayed coatings was investigated. Results show that the complex permittivity increases with increasing the content of Ti₃SiC₂ due to the enhanced space charge polarization, decreased porosity and increased conduction loss. When the content of Ti₃SiC₂ increases to 30 wt%, the coating exhibits the optimal microwave absorption property with a bandwidth (below ??5 dB) of 4.01 GHz and lowest reflection loss of ??12.4 dB at 9.63 GHz in 1.4 mm thickness. It indicates that the Ti₃SiC₂/NASICON composite coating can be a potential candidate for microwave absorption.