Pulse Plasma Sintering of NiAl-Al2O3 Composite Powder Produced by Mechanical Alloying with Contribution of Nanometric Al2O3 Powder

NiAl-Al2O3 composites, fabricated from the prepared composite powders by mechanical alloying and then consolidated by pulse plasma sintering, were presented. The use of nanometric alumina powder for reinforcement of a synthetized intermetallic matrix was the innovative concept of this work. Moreover, this is the first reported attempt to use the Pulse Plasma Sintering (PPS) method to consolidate composite powder with the contribution of nanometric alumina powder. The composite powders consisting of the intermetallic phase NiAl and Al2O3 were prepared by mechanical alloying from powder mixtures containing Ni-50at.%Al with the contribution of 10 wt.% or 20 wt.% nanometric aluminum oxide. A nanocrystalline NiAl matrix was formed, with uniformly distributed Al2O3 inclusions as reinforcement. The PPS method successfully consolidated NiAl-Al2O3 composite powders with limited grain growth in the NiAl matrix. The appropriate sintering temperature for composite powder was selected based on analysis of the grain growth and hardness of Al2O3 subjected to PPS consolidation at various temperatures. As a result of these tests, sintering of the NiAl-Al2O3 powders was carried out at temperatures of 1200 °C, 1300 °C, and 1400 °C. The microstructure and properties of the initial powders, composite powders, and consolidated bulk composite materials were characterized by SEM, EDS, XRD, density, and hardness measurements. The hardness of the ultrafine-grained NiAl-Al2O3 composites obtained via PPS depends on the Al2O3 content in the composite, as well as the sintering temperature applied. The highest values of the hardness of the composites were obtained after sintering at the lowest temperature (1200 °C), reaching 7.2 ± 0.29 GPa and 8.4 ± 0.07 GPa for 10 wt.% Al2O3 and 20 wt.% Al2O3, respectively, and exceeding the hardness values reported in the literature. From a technological point of view, the possibility to use sintering temperatures as low as 1200 °C is crucial for the production of fully dense, ultrafine-grained composites with high hardness.

Food seasoning-derived gel polymer electrolyte and pulse-plasma exfoliated graphene nanosheet electrodes for symmetrical solid-state supercapacitors

The symmetrical solid-state supercapacitors using graphene nanosheet electrodes and table salt-derived green gel polymer electrolyte which provide a stable energy storage device, and good electrochemical capability are introduced.

Influence of pulse plasma treatment on the phase composition and microhardness of detonation coatings based on Ti-Si-C

The paper considers the study results of the phase composition and microhardness of detonation coatings based on Ti-Si-C after exposure to pulsed plasma treatment. The CCDS2000 detonation complex was used to obtain the coatings. Coatings surface modification was carried out using pulsed plasma exposure (PPE). The detonation coatings were treated with varying the distance H (30 mm mode 1, 40 mm mode 2, 50 mm mode 3) from the plasmatron to the hardened surface. It is shown that the treated coatings are generally characterized by high microhardness compared to the original coating. It was determined that after treatment by pulsed plasma effects an increase in the intensity of all reflexes phase Ti3SiC2 was observed, and the appearance of reflexes (101, 102, 112, 204, 0016) phase Ti3SiC2 was found, which indicates the increase of the content of Ti3SiC2 phase. The change in the fraction of phases indicates a solid-phase transformation during pulsed-plasma activation. High hardness is observed on the coating surface treated according to mode 3 (50 mm) and as it approaches the surface of the substrate modes 2 (40 mm) and 1 (30 mm) the hardness decreases. It is established that the increase in the microhardness of detonation coatings after pulse-plasma treatment is associated with an increase in the content of Ti3SiC2 phases in the coatings, as well as an increase in the defects density in the modified layer.

The influence of pulse-plasma treatment on the phase composition and hardness of Fe-TiB2-CrB2 coatings

This work are presented the research results of pulse plasma treatment influence on the phase composition, hardness, roughness and element composition of coatings on the bases of Fe-TiB2-CrB2. The Fe-TiB2-CrB2 coating was deposited by detonation method. The following pulse-plasma treatment was used to modify the structure and properties of the surface layers of the sprayed coating. The results of mechanical experiments showed that the hardness of Fe-TiB2-CrB2 coating increased after the treatment. On the basis of the X-ray analysis, it has been established that the increase of coating hardness is connected with phase transformations in a surface layer, in particular, with formation of oxide phases and increase of carbide particles quantity.

Characterization of Al2O3 Samples and NiAl–Al2O3 Composite Consolidated by Pulse Plasma Sintering

The paper describes an investigation of Al2O3 samples and NiAl–Al2O3 composites consolidated by pulse plasma sintering (PPS). In the experiment, several methods were used to determine the properties and microstructure of the raw Al2O3 powder, NiAl–Al2O3 powder after mechanical alloying, and samples obtained via the PPS. The microstructural investigation of the alumina and composite properties involves scanning electron microscopy (SEM) analysis and X-ray diffraction (XRD). The relative densities were investigated with helium pycnometer and Archimedes method measurements. Microhardness analysis with fracture toughness (KIC) measures was applied to estimate the mechanical properties of the investigated materials. Using the PPS technique allows the production of bulk Al2O3 samples and intermetallic ceramic composites from the NiAl–Al2O3 system. To produce by PPS method the NiAl–Al2O3 bulk materials initially, the composite powder NiAl–Al2O3 was obtained by mechanical alloying. As initial powders, Ni, Al, and Al2O3 were used. After the PPS process, the final composite materials consist of two phases: Al2O3 located within the NiAl matrix. The intermetallic ceramic composites have relative densities: for composites with 10 wt.% Al2O3 97.9% and samples containing 20 wt.% Al2O3 close to 100%. The hardness of both composites is equal to 5.8 GPa. Moreover, after PPS consolidation, NiAl–Al2O3 composites were characterized by high plasticity. The presented results are promising for the subsequent study of consolidation composite NiAl–Al2O3 powder with various initial contributions of ceramics (Al2O3) and a mixture of intermetallic–ceramic composite powders with the addition of ceramics to fabricate composites with complex microstructures and properties. In composites with complex microstructures that belong to the new class of composites, in particular, the synergistic effect of various mechanisms of improving the fracture toughness will be operated.