[en] The aim of this study was to demonstrate the advantages and the method of application of the SHS process in the manufacture of (NiAl/Ni₃Al)/TiB₂ composites. A comparison was made between sinters manufactured by FAST/SPS using two different routes to process the substrates, which formed the composite matrix. The evaluation criteria were based on measurements of selected physical, mechanical, and tribological properties, and on microstructure examinations. The evaluation has indicated a preferable method for the manufacture of composites, where the SHS reaction takes place during compaction of the powder mixture. This produces a sinter characterized not only by the high degree of sintering, and high values of the Young’s modulus and HV1 hardness, but also by the satisfactory resistance to tribological wear. Additionally, the use of this process saves energy and reduces product-making cost, owing to a less expensive technique of making individual substrates.

[en] Highlights: • Ti matrix composite reinforced with high aspect ratio TiB fibers is prepared “in situ” successfully by casting. • Orientation of TiB fibers and their strengthening factor as a function of the extrusion ratio are modeled. • The breaking of the TiB fibers may be responsible for the overestimated strengthening factor by the model used. • Extrusion is an effective process for fiber realignment to obtain high strength for this Ti composite. According to shear-lag model, fibers orientation in composites reinforced with short fibers has a significant effect on their strength which can be predict in term of strengthening factor (C₀) of fibers. In this work, titanium matrix composite reinforced with TiB fibers was fabricated with enhanced mechanical performances using in situ technologies plus extrusion process. The value of TiB fibers C₀ in the as-cast composite was calculated to be very low (0.125). Increase of the strengthening factor of TiB fibers by extrusion was modeled based on a deformation model. The value of C₀ is calculated to be 0.442, 0.713 and 0.812 with extrusion ratio 1.5, 2.0 2.5, respectively. Tensile tests showed that extrusion process increased strength of the composite significantly. But C₀ was overestimated by this model with high extrusion ratios. The overestimating may be attributed to the broke of TiB fibers during extrusion.

[en] A method of hydrostatic hot extrusion of thick-walled, capillary tubes of Cu-Cr-Zr and of dispersive strengthened copper Cu+3.5 vol.%. TiB₂, is presented. The quality-evaluation of the produced tubes is done. (author). 2 refs, 1 fig., 5 tabs

[en] Highlights: • We proposed a series of transition metal borides (MBenes) monolayer as NRR catalysts. • MBenes exhibit metallic features and electrene characteristics for NRR activity. • Work function of the MBenes can be adopted as a descriptor for the NRR activity. Low-energy consumption and highly selective nitrogen reduction reaction (NRR) catalysts play an important role in solving the limitations of the traditional ammonia production. By means of first-principle calculations, we proposed a series of two-dimensional (2D) transition metal borides (MB) (M = Sc, Ti, V, Y, Zr, Nb, Mo, Hf, Ta and W) monolayer as NRR catalysts. These 2D MBenes exhibit high stability, metallic electronic band structures and the electrene characteristics which contribute to the NRR catalytic activity. Large amounts of active sites accelerate the NRR reaction, and the high selectivity towards NRR inhibits the HER process. We screened out four MBenes: TiB, YB, ZrB and MoB, with favorable limiting overpotentials of 0.64, 0.68, 0.65 and 0.68 V, respectively, which are promising for N₂ fixation applications. This work not only enriches the MBene family, but also provides a feasible strategy for the design of NRR catalysts.

[en] The values given in the literature for the enthalpy of the formation of titanium diboride, as obtained experimentally and by theoretical estimation, range between -32 and -74.4 kcal/mol. In this paper the authors use the method of direct synthesis from elements in a Calvet calorimeter to determine the enthalpy of formation, ΔHsub(f)⁰, sub(298), of titanium diboride with the composition Tisub(1.000+-0.002)Bsub(2.056+-0.006)Csub(0.009)Nsub(0.003), which was found to be -76.78+-0.83 kcal/mol. They calculate that ΔHsub(f,298) (TiBsub(2.056)=-76.14+-0.85 kcal/mol. The procedure employed makes it possible to carry out the titanium diboride synthesis reaction with the calorimeter at room temperature

[en] The effect of true porosity and the mean size of pores on hardness of sintered materials based on titanium diboride is investigated. It is established that the Rockwell hardness dependence on porosity is exponential. At equal porosity of 3+-1% the hardness reduces linearly with the growth of the mean size of pores

[en] Chambersite (Mn₃B₇O₁₃Cl)–Ti composites were fabricated using spark plasma sintering. The microstructure and phase composition of the composites were investigated along with the effects of chambersite on the mechanical properties and friction properties of Ti. The results show that chambersite reacts with Ti during sintering to form TiB, Ti_xO_y, and MnCl₂. The mechanical properties of the composites were optimal for the composite with 5 vol% chambersite. Chambersite helps to improve the friction properties of Ti: with increasing amount of chambersite added, the wear rate of the composites decreases. (paper)

[en] Hardness of TiB₂ films is studied within load wide range including low-loads (nanoindentation). Ratio of final depth of indenter penetration (following load relieving) to penetration total depth is shown to constitute for films 0.67 and 0.63 respectively. 9 refs., 3 figs

[en] This paper reports on investigation of the simultaneous formation and sintering of TiB₂. The resulting material showed an equigranular structure with grain sizes > 1μm. Coherent grain boundaries were frequently observed. A new phase was found in grain boundaries, and the b-axis of the base was as much as 1 1/2 times longer than that of TiB₂

[en] The settlements and the grain refining action of TiB₂ particles in the melt of electrolytic low-titanium aluminum (ELTA) with Al-4B addition were investigated. The results show that numerous fine TiB₂ particles will be formed when Al-4B master alloy is added into the melt of ELTA at the Ti/B mass ratio of 5:1. Because of their fine sizes, though there are also TiB₂ particle settlements, there will still be more TiB₂ particles being suspended in the melt of the ELTA with Al-4B addition than in the melt of the pure Al with Al-5Ti-1B addition at a given Ti addition level. These fine TiB₂ particles, together with the titanium atoms left in the melt, will form more heterogeneous nucleation sites during solidification of the melt, improving the grain refining efficiency and the fading-resisting ability obviously. Comparing with the method of adding Al-5Ti-1B into pure Al, the present method has advantages in resulting in the formation of fine TiB₂ particles and preventing their settlements