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Effect of ball milling on hexagonal boron nitride (hBN) and development of Al-hBN nanocomposites by powder metallurgy route

Ghosh Arka, Shukla Uddeshya, Sahoo Nityananda, Ganguly Sourav, Shrivastava Pankaj, Kumar Lailesh, Alam Syed Nasimul

Materials Science Poland

2023

Vol. 41, No. 1

68--93

This study reports on the exfoliation of bulk hexagonal boron nitride (hBN) by high-energy ball milling and the development of Al-hBN (alumninum-hexagonal boron nitride) nanocomposites by the powder metallurgy (PM) route via the incorporation of the exfoliated hBN in the Al matrix as a nanoreinforcement. The effect of ball milling on the morphology, crystallite size, lattice strain, and thermal stability of hBN powder have also been reported in this paper. Commercially available bulk hBN was ball milled for up to 30 hours in a high-energy planetary ball mill in order to exfoliate the hBN. Although no new phases were formed during milling, which was confirmed by the XRD (x-ray powder diffraction) spectra, ball milling resulted in the attachment of functional groups like hydroxyl (OH) and amino (NH2) groups on the surface of the hBN, which was confirmed by FTIR (Fourier Transform Infrared Spectroscopy) analysis. HRTEM (high resolution transmission electron microscopy) analysis confirmed the synthesis of hBN having few atomic layers of hBN stacked together after 20 hours of milling. After 20 hours of milling, the hBN particle size was reduced from ~1 μm to ~400 nm, while the crystallite size of the 20-hourmilled hBN powder was found to be ~18 nm. Milling resulted in a flake-like structure in the hBN. Although milling involved both exfoliation as well as reagglomeration of the hBN particles, a significant decrease in the diameter of the hBN particles and their thickness was observed after a long period of milling. The average thickness of the 20-hour-milled hBN flakes was found to be ~32.61 nm. HRTEM analysis showed that the hexagonal structure of the milled hBN powder was maintained. Al-based nanocomposites reinforced with 1%, 2%, 3%, and 5% by weight hBN were fabricated by PM route. The Al-hBN powder mixtures were cold-compacted and sintered at 550◦C for 2 hours in argon (Ar) atmosphere. The maximum relative density of ~94.11% was observed in the case of Al-3 wt.% hBN nanocomposite. Al-3 wt.% hBN nanocomposite also showed a significant improvement in hardness and wear resistance compared to the pure Al sample that was developed in a similar fashion. The maximum compressive strength of ~999 MPa was observed in the case of Al-3 wt.% hBN nanocomposite and was approximately twice that of the pure Al sample developed in a similar fashion.

Effect of addition of Cu on the properties of eutectic Sn-Bi solder alloy

Alam S. N., Jindal N., Naithani N.

Materials Science Poland

2019

Vol. 37, No. 2

212--224

The present work reports the effect of Cu addition on the melting point, hardness and electrical resistivity of Sn-57 wt.% Bi eutectic solder alloy. Both binary eutectic Sn-57 wt.% Bi and ternary Sn-(57-x)Bi-xCu (x = 0.1, 0.3, 0.5, 0.7 and 1 wt.%) alloys containing various amounts of Cu were developed by melting casting route. The microstructure of the various solder alloys was analyzed using an optical microscope and a SEM. The variation in melting point, hardness and electrical resistivity of the Sn-Bi eutectic solder alloys with the addition of Cu was determined. The melting point of the eutectic Sn-Bi solder alloy was found to decrease up to the addition of 0.7 wt.% Cu. However, further addition of Cu led to an increase in the melting point of the alloy. Addition of Cu led to an increase in the hardness of the eutectic Sn-Bi solder alloy whereas the electrical resistivity of this alloy was found to increase up to the addition of 0.7 wt.% of Cu beyond which a decrease in the electrical resistivity was observed. A change in the microstructure of the solder alloy was observed when it was reheated above the melting temperature.

Badania właściwości termicznych elektrolitu BIVOX domieszkowanego La i ocena możliwości jego zastosowania w ogniwach paliwowych IT-SOFC

Paściak G., Chmielowiec J., Górecki L., Malinowski M.

Elektronika : konstrukcje, technologie, zastosowania

2015

Vol. 56, nr 10

19-22

Publikacja zawiera wyniki badań właściwości termicznych dwóch elektrolitów: referencyjnego – Bi4V2O11 (BIVOX) i Bi3.64V1.67O9.64 – domieszkowanego tlenkiem lantanu w ilości 4% wag. (BILAVOX.4). Oba elektrolity scharakteryzowano za pomocą różnicowej kalorymetrii skaningowej (DSC) i analizy termograwimetrycznej (TGA). Termiczne właściwości elektrolitów stałych BIVOX i BILAVOX.4 wyznaczono w atmosferach powietrza, argonu i gazu redukcyjnego – argon + 5% wodoru, przy narażaniu przez 5 i 20 godzin w temperaturach 400, 650 i 750°C. Uzyskane wyniki analizowano pod kątem możliwości zastosowania elektrolitu BILAVOX.4 w konstrukcji ogniwa paliwowego IT-SOFC (Intermediate Temperature Solid Oxide Fuel Cell).

Thermal properties of two electrolytes: reference – Bi4V2O11 (BIVOX) i Bi3.64V1.67O9.64 doped with lanthanum oxide at the quantity of 4% by weight (BILAVOX.4) were investigated. Both electrolytes were characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The thermal properties of BIVOX and BILAVOX. 4 were performed in air, argon and reducing – argon with 5% + hydrogen atmosphere during exposure to atmosphere for 5 hours and 20 hours in temperatures of 400, 650 and 750°C. The possibility of application of BILAVOX.4 electrolyte for the Intermediate Temperature Solid Oxide Fuel Cell (IT-SOFC) is discussed.