Facile and rapid synthesis of multiferroic TbMnO3 single crystalline

The pure single phase of multiferroic material TbMnO₃ powders were successfully synthesized by one-step molten salt synthesis (MSS) method in the NaCl–Na₂SO₄ eutectic salts at the temperature as low as 800 °C for 1 h. The temperature of synthesized high purity TbMnO₃ is limited in a very narrow range. Prolonging the sintering time will not have an effect on the purity of samples, and either lower or higher salt concentration is not conducive to form pure TbMnO₃. The obtained TbMnO₃ was indexed to an orthorhombically distorted perovskite phase. The as-prepared crystals exhibit uniform and regular rhombic-like morphology with an average size of about 2 μm in edge length and 1–2 μm in thickness. The elements Mn and Tb in TbMnO₃ exist dominantly as Mn³⁺ and Tb³⁺, respectively. The magnetic measurements of the TbMnO₃ powders exhibit antiferromagnetism. Because of the simplicity and generalizability of the MSS method, it is reasonable to expect that the MSS method could also be exploited in future works which involves the nanoscale investigation of ferroelectric, ferromagnetic and multiferroic materials.     

A novel magnetic random access memory design using square ring elements for the hard layer

The behavior of narrow permalloy square rings under the influence of a magnetic field was studied using magnetic force microscopy (MFM). Two stable states of opposite polarity at remanence and simple switching were observed. We propose a design for the hard layer of magnetic random access memory (MRAM) that uses these states in square rings for data storage.     

Effects of the magnetic field on the relaxation of small particle systems

We study the effect of a magnetic field on the thermal relaxation of non-interacting small monodomain particles with a distribution of anisotropy constants and random easy-axes directions. Numerical calculations of the relaxation curves for different distribution widths, and under different magnetic fields H and temperatures T, have been performed in the framework of a two-state approximation. We show how the obtained data can be analyzed in terms of an modified Tln(t/τ₀) scaling from which the field dependence of the mean relaxing energy barriers can be extracted, a microscopic information which is not easily obtainable by other methods.     

Bi-based superconductors prepared with addition of CoFe2O4 for the design of a magnetic probe

We have investigated the microstructure and the magnetoresistivity of bismuth based superconductor bulks added with nano-sized CoFe₂O₄ particles (10 nm in diameter). Samples were prepared through the solid state reaction (SSR) technique by addition of CoFe₂O₄ nanoparticles during the last step of heat treatment. Phase examination using X-ray diffraction (XRD), morphology investigation by scanning electron microscope (SEM), microstructure and local chemical composition analyses using transmission electron microscope (TEM) coupled with energy dispersive X-ray spectroscope (EDXS), electrical resistance versus temperature ρ(T) under applied magnetic fields (B) and electrical resistance versus B at 77 K, ρ(B), were carried out. The CoFe₂O₄ added sample shows a great magnetoresistance to weak magnetic field at the temperature of liquid nitrogen (77 K). This result is attractive for practical, because CoFe₂O₄ added samples can be utilized as active elements in magnetic fields sensor devices.     

Researches on Ni-P Alloys

Worldwide researches on Ni-P alloys have been briefly reviewed,including their corrosion resistance,crystallisation behaviour,amorphisation by ion implantation,and usage as underlayer for thin film magnet-ic media.     

磁力探伤缺陷显示膜

缺陷显示膜是一种新的磁力探伤显示材料,可以代替现有的磁粉和磁悬液,灵敏度高于干磁粉,接近磁悬液,A型试块可清晰显示.     

Isothermal oxidation behavior of FeCo–2V intermetallic alloy

Isothermal oxidation behavior and the nature of oxide layer formed during oxidation of FeCo–2V alloy were characterized in the temperature range of 500–600 °C. Oxidation kinetics of the alloy follows a parabolic rate law. SEM and XRD studies indicate the formation of an iron rich outer oxide layer and an inner solute rich layer containing cobalt and vanadium rich oxides. The oxidation mechanism of the FeCo–2V alloy is similar to that of low alloy steels. During the initial stages, preferential oxidation of iron and cobalt occurs at the alloy surface and leads to the formation of a solute rich inner layer. Continued oxidation occurs through oxidation of iron and cobalt at the outer layer and internal oxidation of inner layer. The iron rich oxide layer formed at the surface on oxidation of FeCo alloy is semi-conducting in nature and may not provide the necessary insulating barrier required at the surface to minimize eddy current losses during A.C. applications.     

An EPR investigation of electrospun polyaniline-polyethylene oxide blends

The EPR magnetic susceptibility behavior of the camphorsulfonic acid doped polyaniline (PANCSA) blends with polyethylene oxide (PEO) is reported in fibers and films. In particular, EPR investigations on electrospun (PANCSA)_0.72(PEO)_0.28 nanofibers, cast films of (PANCSA)_0.72(PEO)_0.28 and cast films of (PANCSA) were performed to investigate differences in the mesoscopic disorder as induced by the process of electrospinning. The changes observed in the Pauli susceptibility, EPR lineshape, EPR linewidth, and dc conductivity are interpreted as due to increased chain alignment in the fibers compared with the cast films.     

Nanoscale Studies of the Early Stages of Oxidation of a TiAl-Base Alloy

The strategy to perform nanoscale studies of the initial stages of oxidation of TiAl involved first gaining some information on the electronic structure of pure TiO₂ surfaces and then on TiAl surfaces before and after oxidation both in low- and high-oxygen potentials. Both materials were studied in atomically-cleaned states generated by repeated sputtering and heating. It was found that the oxygen vacancies created additional defect states in the band gap of stoichiometric TiO₂. The results obtained on TiO₂ were used as fingerprints to study the oxide nucleation. The results on the initial stages of oxidation of TiAl confirm the nucleation of Ti₂O₃ islands of nanometer size and monolayer height in a low-oxygen-pressure environment, whilst a TiO₂ layer developed in an atmospheric environment. The ledges on atomically-cleaned surfaces usually acted as nucleation sites.     

Effect of flame conditions on abrasive wear performance of HVOF sprayed nanostructured WC-12Co coatings

Nanostructured WC-12Co coatings were deposited by high velocity oxy-fuel (HVOF) spraying with an agglomerated powder. The effect of flame conditions on the microstructure of the nanostructured coatings was investigated. The wear properties of the coatings were characterized using a dry rubber-wheel wear test. The results show that the nanostructured WC-Co coatings consist of WC, W2C, W and an amorphous binder phase. The microstructure of the coating is significantly influenced by the ratio of oxygen flow to fuel flow. Under the lower ratio of oxygen/fuel flow, the nanostructured coating presents a relative dense microstructure and severe decarburization of WC phase occurs during spraying. With increasing ratio of oxygen/fuel flow, the bonding of WC particles in the coating becomes loose resulting from the original structure of feedstock and the decarburization of WC becomes less owing to limited heating to the powder. Both the decarburization of WC particles in spraying and the bonding among WC particles in the coatings affect the wear performance. The examination of the worn surfaces of the nanostructured coatings reveals that the dominant wear mechanisms would be spalling from the interface of WCCo splats when spray particles undergo a limited melting. While the melting state of the spray particles is improved,the dominant wear mechanisms become the plastic deformation and plowing of the matrix and spalling of WC particles from the matrix.