composite powders
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Fuel ◽  
2022 ◽  
Vol 310 ◽  
pp. 122313
Author(s):  
Daniel Hastings ◽  
Nikki Rodriguez ◽  
Holly McCann ◽  
Mirko Schoenitz ◽  
Edward L. Dreizin

Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 407
Author(s):  
Katarzyna Konopka ◽  
Justyna Zygmuntowicz ◽  
Marek Krasnowski ◽  
Konrad Cymerman ◽  
Marcin Wachowski ◽  
...  

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.


2021 ◽  
Author(s):  
Roberto Köferstein

Magnetoelectric (Sr0.5Ba0.5Nb2O6)1x(CoFe2O4)x (x = 0.2–0.6) composites were prepared by a one-pot softchemistrysynthesis using PEG400. Calcining at 700 ◦C resulted in nanocrystalline composite powders (dcryst. =24–30 nm) which were sintered between 1050 and 1200 ◦C to ceramic bodies with relative densities up to 98%.SEM investigations confirm the formation of composite ceramics with a 0–3 connectivity and variable grain sizesfrom 0.2 to 3.6 μm for sintering up to 1150 ◦C, while sintering at 1200 ◦C leads both to a change in themicrostructure and a considerable grain growth. Magnetic measurements at 300 K reveal ferrimagnetic behaviourwith saturation magnetization values smaller than bulk CoFe2O4 and coercivities between 790 and 160 Oe.Temperature-dependent impedance spectroscopy showed that the relative permittivities decrease both withrising frequency and CoFe2O4 fraction. The frequency dependence of the impedance can be well described usinga single RC circuit. Magnetoelectric measurements show the presence of pronounced field hystereses. Themaximum magnetoelectric coefficient (αME) depends both on the CoFe2O4 fraction (x) and sintering temperature.The composite with x = 0.3 exhibits the largest αME value of 37 μV Oe1 cm1 (@ 900 Hz). With rising frequencyof the AC driving field αME increases up to 300–400 Hz and is nearly constant until 1 kHz.


Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7906
Author(s):  
Walid Mohamed Daoush ◽  
Turki Saad Alkhuraiji ◽  
Abdulrahman Dohymish Alshammri

Polycrystalline cBN/copper composite abrasive particles were prepared by an electroless powder coating process. Ti metallization and tin/silver metallization techniques were used to improve the coating process by depositing an autocatalytic metallic layer on the surface of the cBN particles. Metallized, as well as un-metallized, cBN particles were further coated by copper using electroless deposition. Electroless copper coating of un-metallized and metallized cBN particles by 90 wt.% of copper were achieved. The surface morphology, the composition and the crystalline phase identifications of the metallized cBN particles, as well as the 10 wt.% cBN /copper composite powders, were investigated by field emission scanning electron microscopy, an energy-dispersive spectrometer and an X-ray diffractometer. The results show that the surface of the Ti metalized and tin/Ag-metallized cBN particles were covered by the nanosized Ti or Ag layer, respectively, which enhanced the deposition of the copper during the electroless deposition bath. The results also showed that the deposited layer on the metallized cBN particles was composed mainly of metallic copper. The produced 10 wt.% cBN/copper composite particles also underwent thermo-gravimetric analysis to investigate its stability at high temperature. It was revealed that the Ti-metallized cBN/copper composite powder has higher stability at 800 °C under the environmental conditions than the tin/silver-metallized and the un-metallized cBN/copper composite particles, respectively.


2021 ◽  
Author(s):  
Zuo Xiao ◽  
Yong Du ◽  
Qiufeng Meng ◽  
Lei Wang

Abstract The reduced graphene oxide/silver selenide nanowire (rGO/Ag2Se NW) composite powders were fabricated via a wet chemical approach, and then flexible rGO/Ag2Se NW composite film was prepared by a facile vacuum filtration method combined with cold-pressing treatment. A highest power factor of 228.88 μWm-1K-2 was achieved at 340 K for the cold-pressed rGO/Ag2Se NW composite film with 0.01 wt% rGO. The rGO/Ag2Se NW composite film revealed superior flexibility as the power factor retained 94.62% after bending for 500 times at a bending radius of 4 mm, which might be due to the interwoven network structures of Ag2Se NWs and pliability of rGO as well as nylon membrane. These results demonstrated the GO/Ag2Se NW composite film has a potential for preparation of flexible thermoelectric devices.


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