Application of thermomagnetometry to corrosion studies of archaeological iron

Summary Thermomagnetometry has been applied to mineralized archaeological iron samples and samples from accelerated corrosion tests. It has successfully quantified the degree of corrosion, measured by the loss of iron, as well as the amount of magnetite formed and water held in the corrosion and adhered soil layers. Thermomagnetometry, thermogravimetric analysis and differential scanning calorimetry have been applied to the reported corrosion products from archaeological iron. Fourier transform infra-red and Raman spectroscopies and X-ray diffraction analyses were undertaken on the residues and at intermediate heating stages, where the thermal analyses indicated, to identify the reaction products.     

Thermal Analysis of the Ferromagnetic Materials in the Region of Curie Temperature by Temperature-Modulated DTA

Thermal analysis has been employed to measure changes of the heat capacity of ferromagnetic materials such as alloys in the region of the Curie temperature. Thermal response for these materials is usually small in this region. The necessary increase in sensitivity was achieved by applying temperature modulation. Results obtained by this technique including temperature-modulated differential thermal analysis simultaneously with A.C. thermomagnetometry are presented.     

Synthesis of nickel base alloys for use as magnetic standards

The goal of this research is to prepare a series of alloys having sharp, reproducible magnetic transitions for calibrating temperature in thermogravimetry from the magnetic transition temperature of pure cobalt (1121°C) to below room temperature.Alloys in the Ni-Co and Ni-Cu systems were prepared by the thermal decomposition of coprecipitated oxalates in argon. The alloys were subsequently annealed under 5% hydrogen.Magnetic transition temperatures were measured using simultaneous thermomagnetometry/differential thermal analysis. Transition temperatures were corrected using well known meltingpoint standards. Magnetic transition temperatures along with precision are reported as a function of composition.     

Thermal Treatment of Iron-Copper Metastable Alloys

Mechanical alloying is a versatile technique for the solid state synthesis of many materials, including alloys such as iron-copper where the elements are immiscible under equilibrium conditions. The structural and magnetic state of these alloys, and their thermal stability, have been investigated by means of thermomagnetometry, DSC, X-ray diffraction and Mössbauer spectroscopy. Comparison of the thermomagnetometry curves for the various alloys together with analysis of intermediate reaction products enabled the individual thermal processes to be identified. The Curie temperature of the alloys was measured, and it was found that on heating the metastable alloys underwent phase segregation between 300-400°C.     

Advancing thermal analysis in response to the increasing demands

Thermal methods are relatively simple, fast, and versatile techniques which are constantly expanding and improving in order meet the demands of a growing technology. Three areas of research are discussed which have lead to an evolution in instrumentation. These are thin film technology, photochemical polymerization, and hazards evaluation. In addition to these changes, experimental advances based on simultaneous techniques, feedback control, and the analysis of heterogeneous kinetics are briefly described.     

Effects of TiN Coating of Iron Detected by Temperature Modulated Thermomagnetometry and Dilatometry

The aim of the present work is to find relation between the state of ceramic coating of iron and the physical properties of coated samples as a function of temperature. The iron samples coated by plasma assisted physical vapor deposition (PA PVD) with layers of TiN were investigated with new technique – temperature modulated thermomagnetometry (TM TMAG) and thermal dilatometry (TM DIL). From the irregular behavior of the thermal dilatation and magnetic susceptibility, the process of the coating degradation can be resolved. This revised version was published online in July 2006 with corrections to the Cover Date.