Anisotropic SmFeV Bulk Magnets with Enhanced Coercivity via Ball Milling Process.

Anisotropic bulk magnets of ThMn-type SmFeV with a high coercivity () were successfully fabricated. Powders with varying particle sizes were prepared using the ball milling process, where the particle size was controlled with milling time. A decrease in occurred in the heat-treated bulk pressed from large-sized powders, while heavy oxidation excessively occurred in small powders, leading to the decomposition of the SmFeV (1-12) phase.

A Review of Ultrafine-Grained Magnetic Materials Prepared by Using High-Pressure Torsion Method.

High-pressure torsion (HPT) is a severe plastic deformation technique where a sample is subjected to torsional shear straining under a high hydrostatic pressure. The HPT method is usually employed to create ultrafine-grained nano-structures, making it widely used in processing many kinds of materials such as metals, glasses, biological materials, and organic compounds. Most of the published HPT results have been focused on the microstructural development of non-magnetic materials and their influence on the mechanical properties.

Effects of Mg and Sb Substitution on the Magnetic Properties of Magnetic Field Annealed MnBi Alloys.

Rare-earth-free permanent magnets have attracted considerable attention due to their favorable properties and applicability for cost-effective, high-efficiency, and sustainable energy devices. However, the magnetic field annealing process, which enhances the performance of permanent magnets, needs to be optimized for different magnetic fields and phases. Therefore, we investigated the effect of composition on the crystallization of amorphous MnBi to the ferromagnetic low-temperature phase (LTP).

Beating Thermal Deterioration of Magnetization with Mn₄C and Exchange Bias in Mn⁻C Nanoparticles.

The magnetization of most materials decreases with increasing temperature due to thermal deterioration of magnetic ordering. Here, we show that Mn₄C phase can compensate the magnetization loss due to thermal agitation. The Mn⁻C nanoparticles containing ferrimagnetic Mn₄C and other Mn⁻C/Mn-O phases were prepared by using the traditional arc-discharge method.

In situ Observation of Phase Transformation in MnAl(C) Magnetic Materials.

The phase transformation in two modes, including both displacive and massive growth of τ-phase from ε-MnAl(C), was observed by transmission electron microscopy. The exact temperature range for different phase transformation modes was determined by magnetic measurements. The displacive growth of ε→τ in MnAl (or MnAlC) occurs at temperatures below 650 K (or 766 K), above which both modes coexist.

A Simple Analytical Model for Magnetization and Coercivity of Hard/Soft Nanocomposite Magnets.

We present a simple analytical model to estimate the magnetization (σ ) and intrinsic coercivity (H ) of a hard/soft nanocomposite magnet using the mass fraction. Previously proposed models are based on the volume fraction of the hard phase of the composite. However, it is difficult to measure the volume of the hard or soft phase material of a composite.

Enhanced luminescence of Cu-In-S nanocrystals by surface modification.

We have synthesized highly luminescent Cu-In-S nanocrystals by heating the mixture of metal carboxylates and alkylthiol under inert atmosphere. We modified the surface of CIS nanocrystals with zinc carboxylate and subsequent injection of alkylthiol. As a result of the surface modification, highly luminescent CIS@ZnS core/shell nanocrystals were synthesized.

Electrokinetic effects of charged nanoparticles in microfluidic Couette flow.

The behavior of Couette flow of nanofluids composed of negatively-charged nanoparticles dispersed in aqueous NaCl solutions is studied theoretically. The equation for calculating the Couette flow velocity profiles is derived. The induced electric fields and velocity profiles are calculated as a function of key parameters including nanoparticle size and volume fraction.

Round-robin test on thermal conductivity measurement of ZnO nanofluids and comparison of experimental results with theoretical bounds.

Ethylene glycol (EG)-based zinc oxide (ZnO) nanofluids containing no surfactant have been manufactured by one-step pulsed wire evaporation (PWE) method. Round-robin tests on thermal conductivity measurements of three samples of EG-based ZnO nanofluids have been conducted by five participating labs, four using accurate measurement apparatuses developed in house and one using a commercial device. The results have been compared with several theoretical bounds on the effective thermal conductivity of heterogeneous systems.

Study of micropart fabrication via 17-4 PH stainless nanopowder injection molding.

Micropart fabrication via 17-4 PH stainless nanopowder injection molding was investigated. The nanopowder was mixed with a binder that was based on wax to produce a feedstock composed of 45% powder and binder (the powder load). Initially, the fit and proper test was done before the micropart was made by making some bars of green samples, which the properties were examined after the sintering process.

Tailoring the morphology of CdSe nanocrystals by incorporation of Pb.

We have investigated the effects of Pb2+ addition on the morphological development of CdSe nanocrystals. We show that the addition of Pb ions in the initial precursor solution changed the morphology of CdSe nanocrystals to branched rods with high aspect ratio. The branched nanocrystals are mainly composed of wurzite phase grown along the [001] direction and the length of rods in each branched nanocrystal can be increased by increasing the amount of Pb2+ addition to accelerate the anisotropic growth of the nanocrystals.