Abstract:
The intent of this study was to thermally characterize glass – covered amorphous metal wires (GCAW) of compositions Co_{66}Fe_{4}Ni_{1}Si_{15}B_{14}, Co_{68.28}Fe_{4.32}Si_{12.5}B_{15}, and Fe_{77.5}Si_{7.5}B_{15} and Fe_{79}Si_{9}B_{12} amorphous ribbon, using differential scanning calorimetry (DSC), modulated® differential scanning calorimetry (MDSC®), and thermogravimetric analysis (TGA). The crystallization temperature of the GCAW was found to increase with additions of Co and Ni. The Curie temperature of FeSiB ribbon was easily found by DSC, while it was not visible in GCAW, indicating that the glass cladding acts as a barrier towards the detection of the Curie transition. Generally, the heat capacities measured by traditional DSC were lower than those determined by MDSC®. Neither instrumental parameters nor sample contact had any significant influence on the heat capacities of a silicon wafer measured with MDSC®. Additions of Co and Ni to the FeSiB composition decreased the relative heat capacity of the GCAW. Unusually high heat capacities were measured for the GCAW and typical glass fiber by both MSDC and traditional DSC, while normal heat capacities were measured for the amorphous ribbon and silicon. Experimental results suggest that this anomaly may be due to a contact issue pertaining to the aspect ratio, but at the present time it is otherwise unexplained. Both saturation magnetization and Curie temperature decreased with additions of Co and Ni. Two Curie temperatures were observed when the GCAW was heated to a temperature much greater than the crystallization temperature, the first corresponding to the amorphous metal and the second corresponding to the crystalline metal. The Néel temperature was also observed when the amorphous alloys were heated to ~800°C.
