Effect of the Mass Fraction of NiTi-TiB2 SHS-Particles on the Phase Composition, Structure, and Mechanical Properties of Inconel 625-NiTi-TiB2 Composites Produced by Direct Laser Deposition

This paper studies the impact of the mass fraction of NiTi-TiB₂ particles obtained by the method of self-propagating high-temperature synthesis (SHS) on the phase composition, structure, and mechanical properties of composites made by direct laser deposition from an Inconel 625-NiTiz-TiB₂ powder mixture. Composites were obtained from a powder mixture with the mass fraction of particles at 5-10 wt%, and they consisted of an Inconel 625 metal matrix wherein ceramic inclusions of titanium diboride TiB₂ were distributed. Increasing the mass fraction of SHS-produced NiTi particles from 30 to 95 wt% led to the emergence of a NiTi intermetallide phase in the matrix material as well as an increase in the average TiB₂ particle size and formation of their agglomerates. In addition, an increase in the microhardness of the materials was observed. The graph of tensile strength of Inconel 625-NiTi-TiB₂ samples has a parabolic shape with a maximum at 1000 MPa (when the mass fraction of SHS-produced NiTi-TiB₂ particles is at 30 wt%). A further increase in the mass fraction of NiTi-TiB₂ led to a decrease in the tensile strength down to 400 MPa. Here the deformation of samples decreases linearly as the ratio of composite particles in the initial mixture increases. From a comparative analysis of the results obtained, the optimal mass fraction of composite NiTi-TiB₂ particles in the Inconel 625-NiTi-TiB₂ powder mixture was found to be 5 wt%.

Modern Synthesis and Sintering Techniques of Calcium Copper Titanium Oxide (CaCu3Ti4O12) Ceramics and Its Current Trend in Prospective Applications: A Mini-Review

Calcium Copper Titanium Oxide (CaCu₃Ti₄O_12/CCTO) has grasped massive attention for its colossal dielectric constant in high operating frequencies and wide temperature range. However, the synthesis and processing of CCTO directly influence the material's properties, imparting the overall performance. Researchers have extensively probed into these downsides, but the need for a new and novel approach has been in high demand. Modern synthesis routes and advanced non-conventional sintering techniques have been employed to curb the drawbacks for better properties and performance. This review provides a short overview of the modern synthesis and sintering methods that utilize direct pulse current and electromagnetic waves to improve the material's electrical, optical, and dielectric properties in the best ways possible. In addition, the current application of CCTO as a photocatalyst under visible light and CuO's role in the efficient degradation of pollutants in replacement for other metal oxides has been reviewed. This research also provides a brief overview of using CCTO as a photoelectrode in zinc-air batteries (ZAB) to improve the Oxidation-reduction and evolution (ORR/OER) reactions.

Joining of Al2O3 Rods Using Microwaves and Employing Sic Particles as Adhesive

The joining of Al2O3 rods using SiC particles in a microwave field was examined. SiC with high microwave absorption characteristics is coated on the fracture surface of Al2O3 rods. Then, microwave irradiation is performed using a 2.45 GHz single-mode cavity and the Al2O3 rods are rapidly joined. Energy dispersive X-ray spectroscopy reveals that the substance generated on the joining surface comprises Al and O. It is believed that the SiC interacts with the microwave to generate microwave plasma and that the plasma melts the Al2O3 rods. Thus, the matrix melts and the fracture surfaces are joined.

Microwave Sintering of Titanium

Effective sintering of titanium requires the use of a high sintering temperature (≥1200 °C), preferably in high vacuum (< 10-2 Pa). This confines the heating and cooling rates to ~ 4 °C/min because of the limited thermal shock resistance of ceramic tube furnaces. Consequently, it leads to lengthy sintering cycles (10-12 hr). This work presents an assessment of microwave (MW) sintering of titanium. Titanium powders in the size ranges of <20 µm, 45-63 µm, and 100-150 µm were used to make green samples with compaction pressures ranging from 200-800 MPa. Sintering was carried out at 1200 °C for 2 hr in a 3 kW MW furnace with a 2.45 GHz multimode cavity under a vacuum of 2-6×10-3 Pa. The characteristics of MW heating of green titanium samples in vacuum are described in terms of the heating rate, vacuum fluctuations, and sparking discharge. The actual MW heating rate achieved from 350 °C to 1200 °C was 34 °C/min. The attendant densities are comparable to those attained by conventional vacuum sintering. Cross-sectional examinations revealed a fairly uniform pore distribution in MW-sintered samples made from either the coarse or fine titanium powder.