Chen Jian

Synthesis of high-purity Ti3SiC2 polycrystals by hot-pressing of the elemental powders

Abstract Synthesis of titanium silicon carbide (Ti3SiC2) from nonstoichiometric mixtures of the elemental Ti, Si, and active carbon powders (3Ti:1.2Si:2C) were investigated. The effects of temperature and time on the phase purity of the Ti3SiC2 were examined. Mechanical properties of high-purity Ti3SiC2 polycrystals were evaluated. The fracture toughness of materials was improved by laminate fracture and grain buckling.

Thermodynamic properties of Ti in Ag–Cu–Ti alloys

Abstract The titanium activities at dilution in Ag–Cu brazing alloys have been measured at 1273 K by an oxygen sensor. The equilibrium oxide phase formed by the reaction of Ti in the eutectic Ag–Cu melts with Al 2 O 3 crucible was TiO (solid). It was found that the Ti activity and activity coefficient in the eutectic Ag–Cu melts increase with the increment of Ti concentration and show a negative deviation from the ideal solution behavior at 1273 K. The Ti activity coefficient at infinite dilution is about 0.076 relative to pure solid Ti. Besides, the activity coefficient of Ti decreases with the increment of Cu concentration and increases with the increment of Ag concentration in Ag–Cu melts containing 1 wt.% Ti at 1273 K. Experimental results demonstrate that Sn decreases the activity coefficient of Ti in the Ag–Cu melts, probably due to its higher Ti solubility than Ag at the same temperature.

Mechanical properties and microstructure of a Si3N4/Ti3SiC2 multilayer composite

A new Si3N4/Ti3SiC2 laminated composite which was manufactured by the powder metallurgy method is presented. The work of fracture was measured in four-point bending at a crosshead speed of 0.05 mm/min. The results show that the mechanical properties of multilayered composites consisting of Ti3SiC2 layers in Si3N4 were significantly enhanced. Three-step toughening behaviors were found in the material. The crack deflection is regarded as a dominant toughening mechanism, meanwhile the unique microstructure and properties of Ti3SiC2 contributed to the improvement, thus preventing catastrophic failure.

In situ processing of TiN/Si3N4 composites by Ti-Si3N4 solid state reaction

Abstract Using an in situ synthesis method, TiN-Si 3 N 4 composites were successfully fabricated by heating mixed powder compacts of Ti and Si 3 N 4 in a nitrogen atmosphere. Mechanical properties with different Ti additions were tested. According to XRD analysis, the TiN and TiSi phases were formed during sintering. No other titanium suicides were found. The microstructure of this materials were investigated by SEM and EDS.

Mechanism of titanium deposition on Al2O3 ceramic surface by molten salt reaction

Abstract The mechanism of deposition of titanium on Al 2 O 3 ceramic surface by molten salt reaction has been studied. It is found that the thickness of the coatings increased with temperature and time, and there is a good linear relation between the layer thickness and the time. The deposition rate increased linearly with the initial concentration of potassium fluorotitanate in salt (K 2 TiF 6 %) 0 . It is estimated that the deposition process is controlled by interface reaction between molten salt and Al 2 O 3 substrate.

Mechanism of titanium coating on Si3N4 ceramics by molten salt reactions

Abstract Effects of reaction time, temperature and the initial concentration of potassium fluorotitanate on the deposition of titanium onto Si 3 N 4 ceramics by molten salt reactions have been studied. The composition of the coating layer deposited under different experimental conditions was determined by X-ray diffraction and AES. From the experimental results, the apparent activation energies at different temperature ranges were calculated. The mechanism of such process is proposed.