Pressureless sintering of submicron titanium carbide powders (original) (raw)
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Synthesis of Titanium Carbide by Means of Pressureless Sintering
Ceramics
In this study, titanium carbide was obtained by low-temperature pressureless (at pressure less than 1 MPa) sintering of a mixture of elementary titanium and graphite powders in a hot-pressing plant with a preliminary mechanical treatment of the initial mixture. The sintering was carried out at temperatures of 900 and 1000 °C in argon media. As a result, cubic modification (Fm3m) of titanium carbide was obtained. The content of impurities was about 12–13 wt.%
Sintering properties of submicron TiC powders from carbon coated titania precursor
2000
The sintering behavior of submicron titanium carbide (TiC) synthesized from carbon coated titania (TiO 2) precursor was investigated in TiC-Ni system. The densification was examined as functions of initial carbon content (30.95-34 wt.%) and Ni content (3-20 wt.%). The sintered density of TiC-Ni was markedly decreased with increased carbon content in the precursor. The amount of Ni had a relatively small influence on the densification of submicron TiC-Ni cermet compared with TiC (commercially available HCS)-Ni cermets. The results show that submicron TiC with only 3 wt.% Ni can be sintered to densities above 95% TD in flowing Ar+10H 2 at 1500 • C and below. The improvements in densification result from the capillary force increase since it is inversely dependent on the particle size. With decreased Ni content, the Vickers hardness increased and the fracture toughness decreased, as expected. However, the sufficient densification cannot be achieved for commercial HCS TiC powder sintered with Ni (<10 wt.%) under the same conditions. Therefore, both the Vickers hardness and fracture toughness decreased as the Ni content decreased. This was due to the increase of porosity in the sintered samples containing commercial TiC powder.
Advances in Materials Science and Engineering, 2010
Nearly fully dense carbides of zirconium, hafnium, and tantalum were obtained by pressureless sintering at 1950 • C with the addition of 5-20 vol% of MoSi 2 . Increasing the amount of sintering aid, the final density increased too, thanks to the formation of small amounts of liquid phase constituted by M-Mo-Si-O-C, where M is either Zr, Hf, or Ta. The matrices of the composites obtained with the standard procedure showed faceted squared grains; when an ultrasonication step was introduced in the powder treatment, the grains were more rounded and no exaggerated grains growth occurred. Other secondary phases observed in the microstructure were SiC and mixed silicides of the transition metals. Among the three carbides prepared by pressurless sintering, TaC-based composites had the highest mechanical properties at room temperature (strength 590 MPa, Young's modulus 480 GPa, toughness 3.8 MPa·m 1/2 ). HfC-based materials showed the highest sinterability (in terms of final density versus amount of sintering aid) and the highest high-temperature strength (300 MPa at 1500 • C).
Sintering and mechanical properties of TiB2-TiC-Ni using submicron borides and carbides
Materials Science and Engineering: A, 2016
A series of TiB 2-TiC-Ni composites were prepared to develop materials with enhanced mechanical properties for structural application. Submicron TiB 2-TiC powders were synthesized using a patented carbon coated precursor method. The composites had about 99% relative density after sintering at a temperature of 1550°C in flowing argon. TiB 2-TiC-Ni composites showed superior sintering and mechanical properties comparing with monolithic TiB 2 and TiC counterparts because of the enhanced microstructures. Phases, grain morphologies, pores sizes, sintering behaviors, and mechanical properties were correlated with the ratio of TiB 2 /TiC and Ni content. The plate like TiB 2 grains were observed in the composites. Toughening mechanism was determined as metallic binder plastics deformation, bridging, and debonding of the TiB 2 /TiC interface. TiB 2-TiC-Ni composites have good combinations of hardness and fracture toughness as 24.23 GPa, 7.41 • / , and 21.85 GPa, 8.44 • / , with Ni content of 5 and 10 wt%, respectively.
Sintering diagram of titanium carbide powders
Nanotechnologies in Russia, 2012
Sintering diagrams, which determine the dominating mechanism of powder sintering at a given temperature, the size of powder grains, and the neck between the grains, may be used to explain the experi ments on sintering and solve some practical problems concerning the sintering of metals and ceramics. In this work we have built sintering diagrams for titanium carbide powders of various dispersities. Using such dia grams, we have established that the dominating mechanisms of sintering titanium carbide micro and nanop owders are the surface and grain boundary diffusion of substance to the neck between the particles. It is found that the contribution of sintering basic mechanisms in the case of titanium carbide does not depend on the dispersity of powders.
Titanium Carbide (TiC) Production by Mechanical Alloying
Powder Technology, 2018
This chapter presents the process for obtaining titanium carbides (TiC) from elemental powders of titanium dioxide, aluminum, and graphite by means of the mechanical alloying technique, using a semi-industrial attritor mill. Three grindings were performing: a wet, a dry, and a vacuum grinding. The mass relations between grinding elements and powders used were 20:1 to wet grinding and 40:1 to dry and vacuum grinding. Each grinding took 36 h with a control stop at 18 h. The samples were analyzed using X-ray diffraction analysis and the characteristics peak were detected on 2θ = 41, 60, 72, and 76°. Targets of TiC were produced using compaction and sintering processes. The particle size (between 200 nm and 1 μm) was measure using a scanning electron microscopy (SEM). After the milling process, the particle size showed a huge distribution. However, after the sintered process, the particle size (lower than 5 μm) distribution had a low dispersion and their shape trends to be spherical. It is necessary to highlight that the precursors used were low cost compared to the high cost and purity powders used for this purpose; so this method is an excellent alternative to implement as a low-cost industrial process.
Reactive processing of titanium carbide with titanium
Journal of Materials Science, 1984
The reactive sintering of titanium carbide with titanium metal was studied using mechanical mixtures of fine-grained powders heated in vacuum above the TiC-Ti eutectic temperature. Mixtures with bulk compositions of TiCo.94 to TIC0.63 yielded nonstoichiometric carbide with less than 0.5 wt % residual titanium metal after sintering, while residual metal was observed at higher titanium concentrations. The effects of time, temperature, and composition on Mohs hardness, final porosity and final grain-size were determined using a Box-Wilson experimental design. The experimental ranges studied were sintering times of 10 to 100 min, sintering temperatures of 1650 to 1850 ~ C, and compositions from TIC0.94 to TiCo.s8. Over these experimental ranges, the effects of time and temperature were small compared with those of composition. The Mobs hardness increased approximately linearly from two to nine with increasing percentage of titanium metal in the starting powder. The average grain size ranged from 15 to 70/~m, increasing with increasing time and temperature. For bulk compositions TiCo.94 to TiCo.7o grain growth was largely due to the conversion of titanium to substoichiometric carbide which grows epitaxially on the carbide grains. Substantial grain growth occurred for higher metal concentrations. The open porosity decreased from 28% to 16% as the amount of titanium metal in the starting powders was increased. Both the grain growth and the densification during reactive sintering of titanium-titanium-carbide mixtures were analysed in terms of a sintering model adapted from Kuczynski. A factor which empirically describes the behaviour of the system over a range of compositions was incorporated into the equations proposed by Kuczynski. Microstructural evidence and the activation energies for grain growth and densification all indicate that the rapid reaction between titanium metal and titanium carbide to form substoichiometric carbide occurs via shortcircuit diffusion of carbon out of the carbide grains along Ti2C platelets. Low sintered densities are attributed to the rapid formation of a solid titanium-carbide skeleton which prevents significant particle rearrangement in the eutectic liquid. Solution-precipitation processes do not appear to contribute significantly to the densification in this system.
The influence of sintering in nitrogen gas on the microstructure of a WC–VC–TiC–Co cemented carbide
International Journal of Refractory Metals and Hard Materials, 2008
This paper investigates the effects of nitrogen-sintering on the V-rich cubic phase grain size in a material with large additions of VC and TiC. Nitrogen transport is made the rate determining factor for the retardation of grain coarsening during sintering. A compacted sample comprising TiC, VC, WC and Co powders was sintered in 1 bar nitrogen gas.
Synthesis of titanium carbide nanopowders and production of porous materials on their basis
Nanotechnologies in Russia, 2011
A technology for the synthesis of titanium carbide nanopowders with a narrow particle size distri bution and a small concentration of impurities has been developed. Conditions for pressing and sintering tita nium carbide powders, which served as a basis for the creation of a porous material with an open porosity of up to 50%, have been determined. The ultimate bending strength of the porous material tended to decrease as the sintering temperature increased from 1250 to 1550°C, but it was still in the range of 66 to 95 MPa.
Nickel assisted sintering of Ti 3 SiC 2 powder under pressureless conditions
This investigation was aimed to study the effect of nickel addition on the sintering behaviour of Ti 3 SiC 2 powder under pressureless conditions. Nearly pure bulk Ti 3 SiC 2 ceramic with relative density of ∼98.5% was produced at 1500 • C by sintering of Ti 3 SiC 2 powder while using 1 wt.% nickel as a sintering aid. The activation energy of sintering of Ti 3 SiC 2 powder was determined to be 351 ± 5 kJ/mol, which was decreased slightly to 305 ± 10 kJ/mol when nickel (1 wt.%) was added. Sintering of Ti 3 SiC 2 powder was found to be controlled by mixed mode of mechanisms, i.e., the interface reactions and diffusion of Si atoms. The mechanism was changed to liquid phase sintering due to melting of Ni-based compounds in the sample sintered with Ni. The reaction of Ni with Ti 3 SiC 2 helped to decrease the grain growth rate. The hardness (Vickers), flexural strength and fracture toughness of the sintered Ti 3 SiC 2 -1Ni sample were found to be 3.4 GPa, 311 ± 22 MPa and 2.8-6.4 MPa m 1/2 , respectively.