Evaluation of Harmonic Structure Obtained in Mechanically Milled Powders and Pulse Plasma Sintered Compacts of Austenitic Steel

The paper describes an attempt to obtain harmonic structure (HS) in AISI308L steel. Harmonic structure is the term related to the microstructure fabricated by mechanical milling of metallic powders under soft milling conditions, resulting in the formation of plastically deformed, grain-refined shell and unchanged core. This microstructure can be preserved after successful powder compaction. The powders of AISI308L steel were milled under soft condition up to 50 h and then compacted by pulse plasma sintering at 900–1100 °C. For powders and compacts XRD, SEM and hardness measurements were applied as characterization techniques. The milling process resulted in austenite transformation into nanocrystalline ferrite and formation of grain refined outer layer. The applied pulse plasma sintering parameters allowed preservation of this microstructure and manufacturing of compacts with homogeneous distribution of elements, relative density above 95% and hardness in the range 167–185 HV, depending on sintering temperature. Simultaneously, the starting phase composition was restored, i.e., austenite with 12% contribution of ferrite. The crystallite size of austenite was about 20 nm and was significantly smaller then in starting powders.

New Nanosized (Gd3+, Sm3+) Co-doped Zinc Ferrite for Telecommunication Applications. Magnetic and Structural Properties.

Highly crystalline ZnFe1.98Sm0.01Gd0.01O4 nanoferrites were prepared by co-precipitation method for the first time. The nanoparticles were characterized using thermogravimetric and differential scanning calorimetry analysis (TGA and DSC), which shows the thermal behavior of the reagents mixture. XRD analysis confirms the formation of nanocrystalline ferrite phase with Fd3m space group, and the particle size was observed to be 11 nm . The FTIR reveals two based bands of absorption characterize the formation of the spinel structure. An exhaustive study of the magnetic properties, morphology, crystallinity and effects of co-doping Gd3 + and Sm3 + was presented in detail. The average crystallites size was observed to decrease for Gd3+ and Sm3+ co-doping. Magnetic measurements reveal weak ferrimagnetic behavior at low temperature and superparamagnetic at high temperature with a blocking temperature at 55 K.

Magneto-Optic Properties of Ultrathin Nanocrystalline Ferrite Garnet Films in the 8K to 300K Temperature Interval

A study of the initial stages of crystallization in RF magnetron-sputtered ferrite garnet films is reported, in which a series of ultrathin Bi2Dy1Fe4Ga1O12 layers is fabricated and characterized. The spectral and temperature dependencies of magnetic circular dichroism (MCD) of these films are studied in the temperature range from 300 K down to 8 K. Measured magneto-optical properties are reported in the spectral range between 300 and 600 nm. In ultrathin garnets at temperatures below 160 K, we found that between 360 and 520 nm, the spectral MCD dependencies were typical of bismuth-substituted garnets with high levels of gallium dilution in the tetrahedral sublattice. The MCD signal strength measured at its 440 nm peak grows linearly with reducing temperature between 160 K and 8 K. This observed temperature dependency of MCD differed dramatically from these measured in thicker (3.7 nm) nanocrystalline garnet films. The peak MCD signal at 440 nm in these 3.7 nm-thick samples grows linearly from 215 K down to 100 K, resembling the same dependency seen in 1.7 nm films. In thinnest layers of thickness 0.6 nm, no MCD signals were observed at any temperature in the range between 8 and 300 K.