| 1. |
- Qadeer, Muhammad Ifran, et al.
(författare)
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High temperature magnetic properties of Sm-Co and Sm-Co/polyamide-12 materials : effects of temperature, particle size, and silanization
- 2013
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Ingår i: Journal of Materials Science. - : Springer Science and Business Media LLC. - 0022-2461 .- 1573-4803. ; 48:23, s. 8163-8170
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Tidskriftsartikel (refereegranskat)abstract
- There is an increasing demand for polymer-bonded magnets (PBM) in high temperature applications. While most research deals with high temperature properties of NdFeB-PBM, only a few studies consider Sm-Co PBM. Therefore, this study, on the thermal and magnetic properties of Sm-Co alloy powders and blends of these with polyamide-12 (PA12), was undertaken. Since the Sm-Co powders were the product of ball milling, they contained a variety of shapes and sizes. Studies on size fractions of these showed that the thermal stability and magnetic properties were improved as the particle size increased. It was suggested that higher residual strains and smaller crystallite sizes in the small particles were responsible for a decrease in the thermal stability and magnetic properties. In addition, energy dispersive X-ray spectroscopy revealed that the oxygen content increased with decreasing particle size (larger specific surface area) and higher oxygen content was possibly also responsible for a decrease in the magnetic properties. It was shown that, in general, the surface modification by silanization, using (3-aminopropyl)trimethoxsilane, increased the saturation magnetization and remanence of both the particles and the Sm-Co/PA12 composite. The silanization also improved the thermal stability of the particles.
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| 2. |
- Qadeer, Muhammad Ifran, et al.
(författare)
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Improved oxidation resistance of SmCo magnetic alloy powders by silanization
- 2013
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Ingår i: Progress in organic coatings. - : Elsevier BV. - 0300-9440 .- 1873-331X. ; 76:1, s. 94-100
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Forskningsöversikt (refereegranskat)abstract
- The thermal stability of Sm2Co17 powders coated with four different silanes was studied between 25 degrees C and 500 degrees C and isothermally at 400 degrees C. Thermogravimetry data indicated that the silane-based coatings provided improved oxidation resistance. The microstructural analysis of uncoated powders oxidized for 10 h at 400 degrees C revealed the formation of a featureless ca. 10 mu m thick shell, surrounding the unreacted core. The development of this shell was attributed to the inward diffusion of oxygen, decomposition of intermetallic phases and redistribution of alloying elements. The EDS elemental maps revealed that the shell was rich in O, Fe and Co, and depleted in Sm, Zr and Cu. In the presence of the silane-based coatings the thickness of the shell was reduced by more than 80% (to less than 2 mu m) and the redistribution of alloying elements was insignificant. Based on the thermogravimetric analysis at or above ca. 400 degrees C and the nnicrostructural analysis it was possible to assess the relative effectivity of the different silanes in preventing the oxidation of the SmCo powder. Methyltrimethoxysilane (MTMS), which also formed the thinnest coating, was the best silane. (3-Glycidyloxypropyl)trimethoxysilane, forming a thicker coating, was less effective than MTMS, but superior to the two amine-functionalized silanes ((3-aminopropyl)triethoxysilane and (3-aminopropyl)trimethoxysilane).
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| 3. |
- Qadeer, Muhammad Ifran, et al.
(författare)
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The Effect of Silanisation on Microstructural Stability and Magnetic Properties of the Intermetallic Sm2(Co, Fe, Cu, Zr)17
- 2011
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Ingår i: Materials Research Society Symposium Proceedings. - : Springer Science and Business Media LLC. - 0272-9172 .- 1946-4274. ; 1295, s. 443-448
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Tidskriftsartikel (refereegranskat)abstract
- The effects of silanising using the coupling agent γ-glycidoxpropyltrimethoxysilane on microstructural stability and magnetic properties of Sm-Co powder particles have been investigated. The silanisation provides structural stability by improving the oxidation resistance at 400oC for 10 hours. The untreated particles undergo microchemical changes by redistribution of alloying elements which mainly accumulate in parallel black and grey streaks in the interior of the particles. The silanised particles after heat treatment show coercivity of 836 Oe and the untreated particles show a much lower coercivity of 376 Oe. The difference in magnetic properties of uncoated particles is caused by diffusion of oxygen and microstructural instability.
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