Synthesis and characterization of bulk amorphous/nanocrystalline soft magnetic materials

Karataş, Mediha Merve
The aim of the study is to reach non-equilibrium cooling conditions and produce bulk glassy (Fe36Co36B19.2Si4.8Nb4)99.25Cu0.75 rod which has a good soft magnetic property and high electrical resistivity and to investigate its crystallization kinetics. The bulk metallic glass formation was achieved by arc melting and suction casting and it was confirmed by scanning electron microscopy (SEM), x-ray diffraction (XRD) and thermal analysis techniques. After characterizations, by isochronal and isothermal differential scanning calorimeter (DSC) analyses, crystallization kinetics of the alloy was investigated. From isochronal DSC analyses, activation energies for glass transition and crystallization events were determined by using different analytical methods such as Kissinger and Ozawa. The critical cooling rate was calculated from two approaches called Barandiaran and Colmenero and Liu et al. and results were compared. Numerous glass forming ability parameters such as Trg, ΔTx, and γ were estimated for the samples. High majority of parameters showed that the alloy is a good bulk glass former. The isothermal crystallization kinetics of the alloy was studied at temperatures chosen in above the first crystallization temperature. There were no crystallization signals detected in the isothermal DSC scans except for 585 ºC at 5 min holding. Although SEM showed featureless matrix, α-(FeCo) crystallites were distinguished in the XRD pattern and size of these crystallites was estimated by Scherrer equation. The magnetic and mechanical properties of the as cast and annealed alloys were compared. According to the obtained results, annealed alloys have higher saturation magnetization, lower coercive force and higher microhardness values than as cast alloys due to the presence of α-(FeCo) nanocrystalline structures within amorphous matrix.


Preparation and Characterization of Low Density Polyethylene/Ethylene Methyl Acrylate Glycidyl Methacrylate/Organoclay Nanocomposites
Coskunses, Fatma Isik; Yılmazer, Ülkü (Wiley, 2011-06-05)
The effects of organoclay type, compatibilizer, and the addition order of components during melt-blending process on the morphology and thermal, mechanical, and flow properties of ternary nanocomposites based on low-density polyethylene (LDPE) were investigated. As a compatibilizer, ethylene/methyl acrylate/glycidyl methacrylate (E-MA-GMA), as organoclays Cloisites (R) 15A, 25A, and 30B were used. All samples were prepared by a corotating twin screw extruder, followed by injection molding. The highest incre...
Synthesis and characterization of conducting polymers containing polypeptide and ferrocene side chains as ethanol biosensors
KESIK, Melis; Akbulut, Huseyin; SOYLEMEZ, Saniye; CEVHER, ŞEVKİ CAN; HIZALAN, Gonul; Udum, Yasemin Arslan; ENDO, Takeshi; YAMADA, Shuhei; Çırpan, Ali; Yağcı, Yusuf; Toppare, Levent Kamil (2014-01-01)
A novel approach for the fabrication of a biosensor from a conducting polymer bearing polypeptide segments and ferrocene moieties is reported. The approach involves the electrochemical copolymerization of the electroactive polypeptide macromonomer and independently prepared ferrocene imidazole derivative of dithiophene, on the electrode surface. The polypeptide macromonomer was synthesized by the simultaneous formation of N-carboxyanhydride (NCA) and ring opening polymerization of N-Boc-L-lysine (alpha-amin...
Synthesis and characterization of Ti-based bulk amorphous/naocrystalline alloys for engineering applications
Abdelal, Ali; Akdeniz, Mahmut Vedat; Department of Metallurgical and Materials Engineering (2004)
Amorphous and bulk amorphous metallic alloys are an intriguing class of structural materials and possess a range of interesting properties, including near theoretical strength, high hardness, extremely low damping characteristics, excellent wear properties, high corrosion resistance, low shrinkage during cooling and almost perfect as-cast surfaces with good potential for forming and shaping. In this study, new Ti-based bulk amorphous alloys are tried to be modeled and synthesized. For that purpose, electron...
Characterization of polylactide/poly(ethylene glycol) blends via direct pyrolysis mass spectrometry
Ozdemir, Esra; Tincer, Teoman; Hacaloğlu, Jale (2016-11-01)
In this study, melt blended poly(lactic acid) and poly(ethylene glycol), (PLA)/PEG samples involving 10, 15 and 20 wt% PEG were prepared and characterized by direct pyrolysis mass spectrometry technique in addition to classical techniques such differential scanning calorimetry, thermogravimetric analyses and mechanical tests. The incorporation of PEG resulted in consistent and significant decrease in the tensile strength and modulus, and reduction in endothermic melting peak of PLA due to the plasticizing e...
Investigation of as-quenched and tempered commercial steels by Magnetic Barkhausen Noise method
Gür, Cemil Hakan; Çam, İbrahim (Inderscience Publishers, 2006-01-01)
This study aims to characterise as-quenched and tempered steels by the Magnetic Barkhausen Noise method, and to contribute to optimisation of heat treatment processes. Identical austenitisation and quenching procedures were applied to SAE 1040 and SAE 4140 specimens to eliminate the effect of grain size. Samples were tempered at 200°C and 600°C for 2 hours. Microstructures were characterised by metallographic examinations and hardness measurements. Amplitude, position and frequency spectrum of signals were ...
Citation Formats
M. M. Karataş, “Synthesis and characterization of bulk amorphous/nanocrystalline soft magnetic materials,” M.S. - Master of Science, Middle East Technical University, 2016.