Characterization and Applications of Metal Ferrite Nanocomposites

In recent years, nanosized spinel-type ferrites emerged as an important class of nanomaterials due to their high electrical resistivity, low eddy current loss, structural stability, large permeability at high frequency, high coercivity, high cubic magnetocrystalline anisotropy, good mechanical hardness, and chemical stability [...]

Comparison of Airborne Electromagnetic and Ground-based Resistivity Observations: Case Study Banda Aceh Basin

Airborne measurements are very useful to cover very large areas. Nine month after the Aceh Tsunami and Earthquake in 2004, BGR (Federal Institute for Geoscience and Natural Resources) conducted a fresh water supply exploration survey within a project called Helicopter Project Aceh (HELP ACEH). The helicopter-borne electromagnetic (HEM) device operates at five frequencies. The HEM can estimate the 1D resistivity models down to a depth of 150 m for the high electrical resistivity areas and 50 m for low electrical resistivity areas. In this paper, the airborne data of 2005 are compared with resistivity data acquired in Banda Aceh basin in 2018. The HEM output consists of 1D resistivity models derived by inversion of the processed data. These 1D resistivity models are compared with the 2D resistivity models derived from ground-based resistivity measurements. However, the 2D models on the ground are transformed into 1D resistivity models so it can be used for comparison. The transformation is conducted by averaging the resistivity values in the each layer, so every layer only has one resistivity value. Both methods are influenced by many factors. For example, resistivity on the ground is affected by local conditions. The airborne measurements are also influenced by objects that are at the surface of the ground. In some cases, the airborne resistivity models have some differences in absolute resistivity values, but they often have the same structural pattern compared with the ground-based resistivity models.

Interpretations and DFT Calculations for Polypropylene/Cupper Oxide Nanosphere

The electronic properties of polymers and polymers reacting with metal oxides can be studied using molecular modeling. Polypropylene (PP) is a synthetic, thermoplastic polymer with high electrical resistivity in this sense. The effect of the addition of metal oxides such as copper oxide (CuO) on the electronic properties of PP was investigated using a computational analysis based on density functional theory. To research PP electronic properties and PP/CuO nanocomposite, DFT theory at B3LYB/6-311g (d, p) level was chosen. The addition of nanosphere metal oxide increased the reactivity of the studied model structures for nanocomposite, according to the results of total dipole moment (TDM) and HOMO/LUMO bandgap energy calculations. Because of the interaction of metal oxide with the original polymer, the energy bandgap values decreased.

Enhanced Magnetic Properties of FeSiAl Soft Magnetic Composites Prepared by Utilizing PSA as Resin Insulating Layer

Thermosetting organic resins are widely applied as insulating coatings for soft magnetic powder cores (SMPCs) because of their high electrical resistivity. However, their poor thermal stability and thermal decomposition lead to a decrease in electrical resistivity, thus limiting the annealing temperature of SMPCs. The large amount of internal stress generated by soft magnetic composites during pressing must be mitigated at high temperatures; therefore, it is especially important to find organic resins with excellent thermal stabilities. In this study, we prepared SMPCs using poly-silicon-containing arylacetylene resin, an organic resin resistant to high temperatures, as an insulating layer. With 2 wt % PSA as an insulating layer and annealed at 700 °C for 1 h, the FeSiAl SMPCs achieved the best magnetic properties, including the lowest core loss of 184 mW/cm3 (measured at 0.1 T and 50 kHz) and highest permeability of 96.

High Thermal Stability of κ-Ga2O3 Grown by MOCVD

We report a high thermal stability of kappa gallium oxide grown on c-plane sapphire substrate by metal organic chemical vapor deposition. Kappa gallium oxide is widely known as a metastable polymorph transitioning its phase when subjected to a high temperature. Here, we show the kappa gallium oxide whose phase is stable in a high temperature annealing process at 1000 °C. These oxide films were grown at 690 °C under nitrogen carrier gas. The materials showed high electrical resistivity when doped with silicon, whereas the film conductivity was significantly improved when doped with both indium and silicon. This work provides a pathway to overcoming limitations for the advance in utilizing kappa gallium oxide possessing superior electrical characteristics.

Investigation of spray pyrolyzed cubic structured Cu doped SnS films

In this work undoped and Cu doped SnS film at 4% and 8% were deposited onto glass substrates by spray pyrolysis technique in order to investigate the effect of Cu doping on their physical properties. Surface investigations showed that Cu doping reduced the surface roughness of SnS films from 36.5 nm to 8.8 nm. XRD studies revealed that all films have recently solved large cubic phase of SnS (p-SnS) with a- lattice of 11.53 Å and Cu doping led to reduction in crystallite size from 229 Å to 198 Å. Additionally, all deposited films were found to be under compressive strain. Optical band gaps of SnS:Cu varied in the range of 1.83 eV-1.90 eV. Hall-effect measurements exhibited that all film have p-type conductivity with low hole concentration (~10 11 -10 12 cm -3 ) and high electrical resistivity (~10 4 -10 5 Ωcm).

Preventing Nugget Shifting in Joining of Dissimilar Steels via Resistance Element Welding: A Numerical Simulation.

Joining the advanced high strength steels and the conventional steels is a critical issue for the manufacturing of lightweight vehicles. Resistance element welding (REW) is an emerging joining method for dissimilar metals and alloys by applying an auxiliary rivet-like resistance element in resistance spot welding (RSW). In this study, an electrical-thermal-mechanical coupled REW model for high-strength dual-phase (DP) steel and Q235 steel was developed by considering contact resistances as functions of temperature and surface contacting area. The results show that the welding element in REW serves to concentrate the current flow and thus Joule heat generation at the faying interface between the element and workpiece. For welding DP600 and Q235 workpieces with a small thickness ratio (≤0.4) or a high electrical resistivity ratio (≥3), REW could effectively mitigate nugget shifting between workpieces and reducing the thermal excursion to electrode as compared to RSW. Adding well-designed insulation layers in REW could further concentrate the current within the welding element, and enables a large-sized nugget at a lower current. This study is significant because it provides a better understanding to the electrical-thermal-mechanical behaviors with interfacial contacts in REW and contributes to its further advance.

Phase transition regulation and piezoelectric performance optimization of fresnoite crystal for high temperature acceleration sensing

Fresnoite crystal, Ba2TiSi2O8 (BTS), is a potential candidate for high temperature piezoelectric sensing applications, due to high electrical resistivity and strong piezoelectric response at elevated temperatures. However, anomalies of electro-elastic...