Results 1 - 10 of 3164
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[en] High sphericity titanium carbide (TiC) powders with uniform distribution and favorable dispersity were obtained by thermal plasma treatment. By optimizing the process parameters, the spheroidization rate of TiC powders is almost 100%. During solidification process, a transformation from typical dendrite structure to cellular structure microstructure occurs with the increase of feeding speed. It ascribes to the decrease of heat absorbed from plasma torch, resulting in decreasing constitutional undercooling and improving solidified interface stability. Consequently, it promotes the formation of cellular structure. (paper)
[en] In this paper, we investigated the effect of titanium modification on microstructures and properties of carbidic austempered ductile iron (CADI) containing 3.72 wt.% C, 2.77 wt.% Si, and 0.51 wt.% Mn. The results showed that with the addition of 0.1 wt.% Ti, TiC particles were formed, and distributed in carbides and matrix. Microstructural observation indicated that the maximum diameter of graphite nodules decreased from 58 to 40 μm, and the shape of carbides transformed from network to fragmentation, which was related to the nucleation of the eutectic structure (γ + (Fe, Cr)3C) where TiC particles act as the nucleus. After isothermal quenching at 300 °C, the hardness of Ti-bearing CADI was 3.5 HRC higher than ordinary CADI, and the impact toughness was increased by 14.3%. Additionally, due to the decrease in exfoliation, the wear loss of Ti-bearing CADI was 14.8% lower than ordinary CADI during the block-on-ring wear test at the surface load of 300 N.
[en] In order to improve the wear resistance of hardmetal cutting tools, coatings of hard materials were established. Especially the production of multilayer coatings, which combine useful properties of different materials was a topic of industrial and academic research. The present work examined the possibilities of combining diamond as basic layer with protective CVD layers of TiC, TiN, Ti(C,N) and Al2O3. All these combinations could be realized and some showed quite good adherence under strain, which offers possibilities for technical applications. (author)
[en] A general method for measuring the average particle diameter of powders by means of the Fisher Sub-Sieve-Sizer using any sample mass is described. The method was experimentally tested on standard sub-sieve powders and applied to iron and titanium-carbide sub-micron powders
[en] The paper presents a thermodynamic analysis for predicting the conditions for the plasma synthesis of TiC powders. The paper also investigates the effects of feeding rate and molar ratio. The experimental results show that TiC powders are synthesized by thermal plasma and the average size of the TiC powders is less than 100 nm
[en] Quantum-chemical calculations (QCCs) are performed using the VASP program to determine the possibility of obtaining a MAX phase of Ti3AlC2 – хВх (0.5 ≤ х ≤ 2) composition. It is shown that the isomorphic substitution of C atoms for B atoms destabilizes the system but does not destroy it. Theoretical X-ray patterns are calculated according to the QCC data. Differences between the X-ray patterns of Ti3AlC2 and Ti3AlC2 – хВх (0.5 ≤ х ≤ 2) crystals are revealed, by which the substitution of C atoms for B atoms can be proved.
[en] One approach for the fabrication of ceramic-metal composites is based on the pressureless impregnation of a porous ceramic preform by a molten metal. Molten Cu does not react with TiC and the wetting angle is close to 90o. Nonetheless, molten Cu readily impregnates partially sintered TiC preforms. A model that describes the dependence of the critical contact angle for spontaneous impregnation by molten metals in partially sintered preforms on the level of densification and on the morphology of the particles was developed. For high aspect ratios of the particles forming the preform, wetting angles close to 90o still allow impregnation by the molten metal. The results of the model were confirmed by infiltration of partially sintered TiC preforms with molten Cu and by fabrication of the TiC/Cu composites with various ceramic-to metal ratios. Decreasing of the metal content in the composite from 50 vol.% to 10 vol.% leads to a hardness increase from 250 to 1800 HV, and to the decrease of the bending strength from 960 to 280 MPa. The resistivity of these TiC/Cu composites decreases from 142 ohm cm to 25 ohm cm. (author)
[en] An indirect method (a hybrid one in comparison with known PVD and CVD methods) for creation of hard transition metal carbide coatings with good adhesion to the substrate is presented, involving vacuum annealing of thin carbide-forming metal layers on high carbon steel substrates. A phenomenological diffusion model for the system layer/substrate which well fits the experiment is also presented. (author). 5 refs, 13 figs
[en] The optical reflectivities of face-centered-cubic TiC and ZrC have been measured in the range 1.0 less than or equal to hω less than or equal to 8.0 eV. In addition, the electronic-energy-band structures for these compounds have been calculated using a modified empirical-pseudopotential method, and the structures in the reflectivities derived from these band structures show approximate one-to-one correspondence to the structures in the data, with agreement to the order of 0.2 eV. Prominent structures in the measured reflectivities of both compounds are identified