Papers by Keyword: Magnetic Measurement

Abstract: The aim of this study was to investigate the effect of the previously applied cold rolling and the latter heat treatment for the eutectoidal decomposition of δ-ferrite in 2507 type superduplex stainless steel (SDSS). The samples were cold rolled at seven different deformation rates which was followed by heat treatment at were 20, 700, 750, 800 and 850 °C temperatures. The rolled and heat treated samples were investigated by hardness tester, AC magnetometer and thermoelectric power measurement. The activation energy of the decomposition was determined by the Arrhenius equation through the results of the AC magnetometer measurement.

Abstract: For application in the magnetic material at high temperature, the equipment for the measurement of magnetic properties of hard magnetic material at elevated temperature has been developed. The temperature coefficient of remanence and coercive, demagnetization curves at different temperatures was measured by this equipment. The heating plate which using the mesh screen printer substrate method was designed to realize the accurate measurement in the quasi closed magnetic circuit .The temperature measuring range is from room temp. 500 °C.

Abstract: The magnetic properties and the crystal structure of the ball-milled Tb(Ni_0.95Fe_0.05)₃ compound have been studied by using magnetization measurements and X-ray diffraction (XRD). The results were compared with those obtained for the bulk compound prepared by arc-melting technique. The investigated sample is polycrystalline and crystallizes in the rhombohedral PuNi₃ type of crystal structure (space group R-3m). With the increase of the time milling (i.e. 1 h, 24 h and 48 h) a for-mation of grains less than 1μm and a reduction of magnetocaloric effect have been observed. The analysis of XRD patterns for ball-milled powders shows that after 48h milling time there is still visible a crystalline structure.

Abstract: The Co₃₈Ni₃₃Al₂₉ alloy as a potential ferromagnetic shape memory alloy was investigated. The method of preparation of the unidirectional solidified single-crystals from cast material is described. The high-temperature annealing and subsequent quenching was found to be necessary condition for the shape memory behavior. The martensitic transformation temperatures of annealed samples were about 200 K determined from magnetic measurement while as-cast sample did not exhibit any sharp transformation. All martensitic structures observed at room temperature by microscopic methods are thus stress induced. These results agree with pseudoelastic behavior observed in annealed and quenched samples.

Abstract: Nanostructured Co(OH)₂ thin films were synthesized by a simple solution growth process. In experiment, F^– and NH₃ were used as Co²⁺ ordination agents, and hydroxyl ions were supplied by ammonia hydroxide solution for the hydrolysis reaction. The results showed that the solution pH and F/Co ratio had great influences on the morphologies of the thin films. The Co(OH)₂ thin films were constructed with lots of Co(OH)₂ nanoflakes. Nanostructured Co3O4 thin films were prepared by annealing the Co(OH)₂ thin films at 400°C for 2 h. The magnetic properties of Co₃O₄ thin films were also investigated.

Abstract: Magnetic interactions may lead to errors in precision mass metrology. There are two factors named magnetic susceptibility and magnetic polarization which need to be determined before mass metrology. First four methods are compared and analyzed suitable range, requirement, uncertainty and note in comparison process. Then uncertainty factors are given out, and description of differences between normal weights and micro-gram standards are presented in the paper. It is easy to become magnetized if the weight is not well protected in manufacture or daily using. So it is important to control its safe and perform periodic self-verification on it.

Abstract: In the present work the microstructure and the strain induced phase transformation of a Lean Duplex Stainless Steel (LDSS) were studied. Sheet samples were cold rolled, the number of samples was nine; the applied deformation was up to 80%. The magnetization curves were measured by a single sheet tester-type magnetic property analyzer. The series of symmetrical minor hysteresis loops and the saturation loop were measured. Our novel data evaluation technique was applied for data evaluation of the magnetic measurements. This method is based on the multiphase-hyperbolic model of magnetization and it is called model based data evaluation (MBDE) technique. This method allowed us to separate the magnetic contribution of ferrite and martensite phases in the tested LDSS. Several new details of the kinetics of austenite→martensite strain induced phase transformation were clarified.

Abstract: Elaborated characterization tools play an important role for the further improvement of solar material and the development of solar cells. Besides the huge variety of highly advanced methods mainly based on optical and electrical measurements, the direct measurement of surface currents by the detection of their induced magnetic fields has gained less attention. The novel method current-analysis-by-inductive-coils (CAIC) based on an inductive coil detector and is reviewed and compared with already established methods, which are light-beam-induced-current (LBIC) and dark-lock-in-thermography (LIT). The detector reveals complementary information at high resolution. The LIT measurements depicted shunting defects in forward and reverse current. Because of the high spatial resolution of the CAIC measurement technique it was determinable that in some cases the positions of current sinks in the CAIC maps are not corresponding with the microstructure. The analyses of the superpositions reveals macroscopic precipitates like SiC and Si₃N₄ filaments and clusters as an origin of some of the shunts.

Abstract: Applied mechanical stress has a strong influence on magnetic properties of material. The aim of this paper is to discuss key technology of establishing an experimental platform for measuring magnetic properties of electrical sheet under tensile stress. Finally, measurement result of stress dependence of the magnetic characteristic under different applied stress is presented. Some conclusions about the stress-dependent magnetic behavior is also given in this paper.

Abstract: To receive monosized goethite (α-FeOOH) nanoparticles powders in the process of chemical precipitation of iron salt and alkali various surface active substances (SAS) with concentration of 0.3% were added to water: C12H25NaO4S (anion active), C12H38ClN (cation active) and EDTA – C10H14O8N2Na2 (complexon). It has been determined that the magnetic properties of the nanoparticles under investigation change in comparison with the nanoparticles obtained without SAS addition. In all the samples under study very interesting saturation magnetization temperature dependences have been obtained. They indicate the difference in goethite temperature phase transformations connected with various surface layers formed on the nanoparticles under SAS influence.