Monolithic Ti3SiC2 Research Articles

Effects of hydrogen-helium ions irradiation on Ti3SiC2-containing interphase or coating in SiCf/SiC

This work investigates the effects of irradiation on Ti3SiC2-containing interphase or coating in SiCf/SiC using a cooperative experiment involving H and He ions. SiC/TiC/Ti3SiC2/Ti5Si3Cx and SiC/Ti3SiC2 were irradiated at room temperature and then annealed at 320 °C for 24 h. Results showed the lattice swelling in all phases. With increasing irradiation dose, SiC and Ti5Si3Cx underwent amorphization, while TiC and Ti3SiC2 remained stable due to their ionic bonds. Annealing facilitated the migration of collision products and H, He ions to grain boundaries and phase interfaces, reducing lattice swelling rates of TiC and Ti3SiC2. The SiC/TiC interface displayed ion cluster accumulation, impacting the interface bonding strength, while the Ti3SiC2/Ti5Si3Cx interface exhibited the formation of cavities. Conversely, the TiC/Ti3SiC2 and SiC/Ti3SiC2 interfaces were stable. These findings indicate that interphase or coating containing Ti3SiC2 monolithic or TiC/Ti3SiC2 multilayered structures possess strong irradiation resistance.

A strong, machinable, and multifunctional Ti3SiC2-(Ti3SiC2-Cf) composite: Gradient architecture and mechanical properties

Ti3SiC2, as one of the most typical MAX ceramics, has been extensively studied as a potential high-temperature structural material. However, the restrictive relations between strength and toughness of Ti3SiC2 and Ti3SiC2-based materials have hampered their industrial applications. Herein, we reported the successful fabrication of Ti3SiC2–(Ti3SiC2–Cf) functionally graded materials (FGM) via hot-press sintering Ti3SiC2 and short Cf-derived preceramic papers. The microstructure evolution as well as the effect of sintering temperature on phase composition and interfacial reaction were investigated. Flexural strength and fracture toughness from ambient temperature to 1000 °C of the graded composites were determined to evaluate the mechanical performance. The results have shown that chemical reactions occurred between carbon fibers and Ti3SiC2 matrix, which leads to the formation of SiC interfaces with strong covalent bonds. The newly developed Ti3SiC2–(Ti3SiC2–Cf) graded composite materials exhibited excellent comprehensive performance as compared to that of monolithic Ti3SiC2. The flexural strength and fracture toughness of the graded composite at room temperature can be reached to 526 MPa and 7.46 MPa m1/2, respectively. However, there is no significant change in flexural strength and fracture toughness from RT to 1000 °C. The fracture micrographs also reveal that fiber breaking、pulling out and debonding are the primary mechanisms that contribute to the superior mechanical properties of composites. The exceptional performance demonstrated in Ti3SiC2–(Ti3SiC2–Cf) graded materials also makes them attractive choices for a variety of heatproof devices in aerospace sectors.

Fabrication of TiC coated short carbon fiber reinforced Ti3SiC2 composites: Process, microstructure and mechanical properties

The Cf/Ti3SiC2 composites were fabricated through spark plasma sintering (SPS) and hot isostatic pressing (HIP), TiC coated Cf and Ti3SiC2 powder were used as starting materials. The improved fracture toughness (KIC) and Vickers hardness (HV1) of the TiC coated Cf/Ti3SiC2 composite fabricated by SPS were 7.59 MPa·m1/2 and 7.28 GPa. On this foundation, taking the advantage of better sintering process of HIP, the highest KIC and HV1 achieved 8.32 MPa·m1/2 and 9.24 GPa with fiber content of 10 vol%, which increased by 40% and 65% compared with that of monolithic Ti3SiC2. The reasonable control of reactive interface is the main factor for the improved mechanical properties of the composites, the TiC coating effectively protected the fiber structure from interfacial reaction compared with that of the non-coated Cf/Ti3SiC2. Meanwhile, the artificially designed and weakly bonded TiC coated Cf can fully exert the toughening mechanisms like fiber pull-out and debonding.

Fabrication of SiCw/Ti3SiC2 composites with improved thermal conductivity and mechanical properties using spark plasma sintering

High strength SiC whisker-reinforced Ti3SiC2 composites (SiCw/Ti3SiC2) with an improved thermal conductivity and mechanical properties were fabricated by spark plasma sintering. The bending strength of 10 wt% SiCw/Ti3SiC2 was 635 MPa, which was approximately 50% higher than that of the monolithic Ti3SiC2 (428 MPa). The Vickers hardness and thermal conductivity (k) also increased by 36% and 25%, respectively, from the monolithic Ti3SiC2 by the incorporation of 10 wt% SiCw. This remarkable improvement both in mechanical and thermal properties was attributed to the fine-grained uniform composite microstructure along with the effects of incorporated SiCw. The SiCw/Ti3SiC2 can be a feasible candidate for the in-core structural application in nuclear reactors due to the excellent mechanical and thermal properties.

Compressive creep of SiC whisker/Ti3SiC2 composites at high temperature in air

AbstractThe compressive creep of a SiC whisker (SiCw) reinforced Ti3SiC2 MAX phase‐based ceramic matrix composites (CMCs) was studied in the temperature range 1100‐1300°C in air for a stress range 20‐120 MPa. Ti3SiC2 containing 0, 10, and 20 vol% of SiCw was sintered by spark plasma sintering (SPS) for subsequent creep tests. The creep rate of Ti3SiC2 decreased by around two orders of magnitude with every additional 10 vol% of SiCw. The main creep mechanisms of monolithic Ti3SiC2 and the 10% CMCs appeared to be the same, whereas for the 20% material, a different mechanism is indicated by changes in stress exponents. The creep rates of 20% composites tend to converge to that of 10% at higher stress. Viscoplastic and viscoelastic creep is believed to be the deformation mechanism for the CMCs, whereas monolithic Ti3SiC2 might have undergone only dislocation‐based deformation. The rate controlling creep is believed to be dislocation based for all the materials which is also supported by similar activation energies in the range 650‐700 kJ/mol.

Characterization of hot-pressed Ti3SiC2–SiC composites

The high-density Ti3SiC2-SiC composites with different SiC volume contents were fabricated by hot pressing technique under 35 MPa in a vacuum atmosphere at 1550 °C for 30 min. Microstructural observation showed that the distribution of SiC particulates in the Ti3SiC2 matrix was uniform which improved the hardness of Ti3SiC2–20 vol% SiC sample (13.9 GPa), compared to monolithic Ti3SiC2 (7.1 GPa). The sample containing 15 vol% SiC showed the highest flexural strength value, compared to the other Ti3SiC2-SiC samples and the monolithic Ti3SiC2. The fracture toughness of the Ti3SiC2-SiC samples was also lower than that of the monolithic Ti3SiC2 MAX phase.

Microstructures and Mechanical Behavior of Ti3SiC2/Al2O3-Ni Composites Synthesized by Pulse Discharge Sintering

High-purity Ti3SiC2 and Ti3SiC2/Al2O3-Ni composites with different Al2O3-Ni contents were fabricated using pulse discharge sintering (PDS) of a mechanical alloyed powder mixture. The synthesis process of monolithic Ti3SiC2 was studied through displacement temperature–time (DTT) curve, displacement rate–time and displacement rate–temperature diagrams obtained during the PDS process. It was found that TiCx and Ti5Si3Cy are the intermediate phases and the PDS process completed after 20 min at 1350 °C. The results showed that in Ti3SiC2/Al2O3-Ni composite, the Ni part of Al2O3-Ni leads to decomposition of Ti3SiC2 to TiCx, Ti5Si3Cy and Ni(Si)x. No evidence was detected in the reaction between Al2O3 and Ti3SiC2. The density and hardness of the composites are higher than monolithic Ti3SiC2 due to the production of reinforcing phases. The composite showed lower flexural strength and higher compressive strength than monolithic Ti3SiC2.

Influence of Cu on the mechanical and tribological properties of Ti3SiC2

Ti3SiC2/Cu composites with different contents of Cu were fabricated by mechanical alloying and spark plasma sintering method. The phase composition and structure of the composites were analyzed by X-ray diffractometry and scanning electron microscopy equipped with energy dispersive spectroscopy. The mechanical and tribological properties of Ti3SiC2/Cu composites were tested and analyzed compared with monolithic Ti3SiC2 in details. The results show that the Cu leads to the decomposition of Ti3SiC2 to produce TiCx, Ti5Si3Cy, Cu3Si, and TiSi2Cz. The friction coefficient and wear rate of the composites are lower than that of monolithic Ti3SiC2, which is ascribed to the fixing effect of hard TiCx, Ti5Si3Cy, and Cu3Si to inhibit the abrasive friction and wear. However, at elevated temperatures (ranging from room temperature to 600°C) the friction and wear of the composites are higher than those at room temperature. Plastic flowing and tribo-oxidation wear accompanied by material transference contribute to the increased friction and wear at elevated temperatures.

Characterisation of graphene nanoplatelets reinforced hot pressed Ti3SiC2 ceramic

Ti3SiC2 based ceramic reinforced by 5 wt-% graphene nanoplatelets (GNPs) was prepared by hot pressing at 1550°C for 1 h under a uniaxial pressure load of 30 MPa. The effects of GNPs on the strengthening and toughening of the hot pressed Ti3SiC2 based ceramic were investigated. Comparing with t monolithic Ti3SiC2 ceramic, the flexural strength and facture toughness of the Ti3SiC2–GNP ceramic were significantly improved. The flexural strength and fracture toughness increased from 451.9 to 800.6 MPa, and from 6.23 to 9.67 MPa m1/2 respectively. The mechanism for these mechanical property improvements was attributed to the layered fracture of Ti3SiC2 grains, refined crystalline strengthening and GNP strengthening.

Friction and Wear of Ti<sub>3</sub>SiC<sub>2</sub>-Ag/Inconel 718 Tribo-Pair under a Hemisphere-on-Disk Contact

Room temperature friction and wear of Ti3SiC2-Ag sliding against Inconel 718 with a hemisphere-on-disc configuration were investigated in air. The effects of Ag content and TiAlN coating on Inconel 718 substrate were also included. Ti3SiC2/Inconel 718 tribo-pair showed high friction coefficient (0.6) and severe wear due to pullout of Ti3SiC2 grains was observed at a sliding speed of 1 m/s. Ti3SiC2-Ag composites had better tribological behavior than that of monolithic Ti3SiC2 in sliding against Inconel 718. At a sliding speed of 0.01 m/s, Ti3SiC2-Ag/Inconel 718 tribo-pairs exhibited moderate friction coefficient (0.32-0.4). At a sliding speed of 1 m/s, severe wear was not observed for Ti3SiC2-15vol.%Ag and Ti3SiC2-20vol.%Ag composites although the tribo-layer was not rich in Ag. When Ti3SiC2-Ag composites mated with TiAlN coating on Inconel 718 substrate, moderate friction coefficient (0.29-0.36) and low wear rate (10-6 mm3N-1m-1) were obtained at 0.01 m/s. A transition from mild wear to severe wear of Ti3SiC2-Ag composites at 0.1 m/s can be attributed to the ploughing effect by hard asperities on TiAlN coating.

Temperature-dependent thermal properties of a shape memory alloy/MAX phase composite: Experiments and modeling

A shape memory alloy/MAX phase composite, namely NiTi/Ti3SiC2 composite, was fabricated using spark plasma sintering at 1233K under 100MPa for 8min, from a NiTi/Ti3SiC2 powder mixture with a 50/50 v/v ratio. The thermal diffusivity was measured at both ambient and elevated temperatures up to 1224K using a laser flash analyzer. The specific heat at constant pressure was measured over the temperature range 300–600K using a differential scanning calorimeter. The thermal conductivity was then calculated from the thermal diffusivity, specific heat and density. To validate the experimental results, a survey of data on the thermal diffusivity, specific heat and thermal conductivity of monolithic NiTi and Ti3SiC2 was carried out. Finite-element modeling of a micromechanics-based representative volume element was carried out to predict the thermal conductivity of the NiTi/Ti3SiC2 composite. An agreement between the experimental and finite-element results was found.

Microstructure and properties of Al2O3-TiC-Ti3SiC2 composites fabricated by spark plasma sintering

Highly densified Al2O3-TiC-Ti3SiC2 composites were fabricated by spark plasma sintering technique and subsequently characterised. From fracture surface observation, it is found that Al2O3 is 0·2-0·4 μm, TiC is 1-1·5 μm and Ti3SiC2 is 1·5-5 μm in grain size. With the increase in Ti3SiC2 volume contents, Vickers hardness of the composites decreases because of the low hardness of monolithic Ti3SiC2. The fracture toughness rises remarkably when the contents of Ti3SiC2 increase, which is attributed to the pullout and microplastic deformation of Ti3SiC2 grains. At the same time, the flexural strength of the composites shows a considerable improvement as well. The electrical conductivity rises significantly as the Ti3SiC2 contents increase because of the formation of Ti3SiC2 network and the increase in conductive phase contents.

Oxidation Behavior of Ti3SiC2-SiC Ceramic Composites

The high temperature oxidation behaviors of the Ti3SiC2-SiC ceramic composites fabricated by in situ synthesis under hot isostatic pressing were studied by DSC. The results show that the growth of the oxide scales on Ti3SiC2-SiC ceramic composites obeys a parabolic law in air. The oxidation resistance at 1400°C is better than that at 1200°C for long time. The oxidation resistance of the Ti3SiC2-SiC ceramic composites is much higher than that of monolithic Ti3SiC2. The mechanism of oxidation of Ti3SiC2-SiC ceramic composites is discussed.

Intrusion-type deformation in epitaxial Ti3SiC2∕TiC0.67 nanolaminates

We investigate the deformation of epitaxial Ti3SiC2(0001)∕TiCx(111) (x∼0.67) nanolaminates deposited by magnetron sputtering. Nanoindentation and transmission electron microscopy show that the Ti3SiC2 layers deform via basal plane slip and intrusion into the TiC layers, suppressing kink-band and pile-up deformation behaviors analogous with monolithic Ti3SiC2. This remarkable response to indentation is due to persistent slip in the TiC layers and prevention of gross slip throughout the nanolaminate by the interleaving Ti3SiC2 layers. Hardness and Young’s modulus were measured as ∼15 and ∼240GPa, respectively.

Reaction Path and Microstructures of Ti<sub>3</sub>SiC<sub>2</sub>/SiC Composite by Spark Plasma Sintering

Ti3SiC2/20vol%SiC composite was synthesized by spark plasma sintering (SPS) under a pressure of 50MPa at 1350°C using Ti, Si and C as starting powders. The phase constituents and microstructures of the composite were investigated. X-ray diffraction (XRD) results demonstrated that Ti reacted with C to form TiC firstly, then TiSi2 formed from Ti and Si. The formation of Ti3SiC2 might come from two reactions. One was that TiSi2, Ti and TiC reacted directly to form monolithic Ti3SiC2. The other one was that TiSi2, Ti and C reacted to form Ti3SiC2 and SiC. The EPMA results showed that the main phases were Ti3SiC2 and SiC with a minor content of TiC as impurity. TiC particles less than 1μm in diameter distributed in SiC phase.

ＣＶＤ法による高機能セラミックス材料の開発

Chemical vapor deposition (CVD) has been commonly employed as a thin film processing, whereas thick films and bulk ceramic materials can be also obtained by modifying and optimizing CVD conditions and apparatus. The development of highly-functional bulk ceramic materials and thick films by CVD has been reviewed in this paper. Monolithic Ti3SiC2 bulk material was synthesized by CVD, and was identified as a machinable soft ceramic material. SiC and Si3N4 are hardly sinterable materials, thus sintering aids are inevitable to consolidate these powders. However, such aids would yield significant deterioration of their high-temperature performance. Thermal CVD can provide bulk bodies by enhancing deposition rates. CVD SiC bulk body was used to investigate intrinsic nature of SiC, particularly high-temperature oxidation mechanism. By introducing laser in CVD, the deposition rate was tremendously increased several 100 to 1000 times greater than that of conventional CVD. Laser CVD enabled one to realize thermal barrier coating of yttria stabilized zirconia (YSZ). This YSZ coating contained a large amount of nanopores being beneficial for thermal insulation. Plasma enhanced CVD produced characteristic Ru-C film, where Ru nano-particles dispersed in an amorphous C matrix. This film can be a promising catalytic electrode for oxygen sensors and fuel cells.

Cyclic Fatigue‐Crack Growth and Fracture Properties in Ti3SiC2 Ceramics at Elevated Temperatures

The cyclic fatigue and fracture toughness behavior of reactive hot‐pressed Ti3SiC2 ceramics was examined at temperatures from ambient to 1200°C with the objective of characterizing the high‐temperature mechanisms controlling crack growth. Comparisons were made of two monolithic Ti3SiC2 materials with fine‐ (3–10 μm) and coarse‐grained (70–300 μm) microstructures. Results indicate that fracture toughness values, derived from rising resistance‐curve behavior, were significantly higher in the coarser‐grained microstructure at both low and high temperatures; comparative behavior was seen under cyclic fatigue loading. In each microstructure, ΔKth fatigue thresholds were found to be essentially unchanged between 25° and 1100°C; however, there was a sharp decrease in ΔKth at 1200°C (above the plastic‐to‐brittle transition temperature), where significant high‐temperature deformation and damage are first apparent. The substantially higher cyclic‐crack growth resistance of the coarse‐grained Ti3SiC2 microstructure was associated with extensive crack bridging behind the crack tip and a consequent tortuous crack path. The crack‐tip shielding was found to result from both the bridging of entire grains and from deformation kinking and bridging of microlamellae within grains, the latter forming by delamination along the basal planes.

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.

Synthesis and high temperature mechanical properties of Ti3SiC2/SiC composite

A high density Ti3SiC2/20 vol % SiC composite was hot pressed under a uniaxial pressure of 45 MPa for 30 min in an Ar atmosphere at 1600 °C. The grain size of the Ti3SiC2/SiC composite was finer than that of monolithic Ti3SiC2, though the composite was hot pressed at a higher temperature, due to the dispersion of SiC particles in the Ti3SiC2 matrix. Room temperature fracture toughness of the composite and Vickers hardness were measured as 5.4 MPa m1/2 and 1080 kg mm−2, respectively. A higher flexure strength of the composite compared to that of monolithic Ti3SiC2 was measured both at room temperature and up to 1200 °C. At 1000 °C, the composite showed a lower oxidation rate than that of monolithic Ti3SiC2.