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We successfully fabricated ZnO, Zn0.96Co0.04O, Zn0.95Co0.04Ce0.01O, Zn0.94Co0.04Ce0.02O, and Zn0.92Co0.04Ce0.04O nanoparticles and studied their room-temperature structure and magnetic properties. The X-rays diffraction (XRD) patterns of all the samples confirmed the presence of a wurtzite-type structure. XRD and Transmission Electron Microscopy (TEM) results showed that Zn2+ ions originally at tetrahedral sites were replaced by high-spin Co2+ and Ce3+ ions. This study also showed that with an increase in co-dopant concentration, the average grain size of the samples increased. We found that Zn0.96-xCo0.04CexO (x = 0.0, 0.1, 0.2, and 0.4) nanoparticles were ferromagnetic with a Curie temperature above 300 K. In addition, a large increase in ferromagnetism, i.e., high coercivity field, Hc, of 90Oe and remanent magnetization, Mr, of 0.25 × 10−2 emu/g, was observed for Zn0.96-xCo0.04CexO (x = 0.2) nanoparticles. The origins of ferromagnetism may be either due to the intrinsic nature of Co and Ce co-doped samples or to the presence of certain undetected spinel-type impurities in the samples. Also, it was concluded that Co and Ce incorporation are responsible for ferromagnetism in the doped sample. The doping generates oxygen vacancies, which trap charges and cause a rise in F-centers, resulting in exchange interactions with impurity atoms and increased magnetism. All these results showed that co-doped ZnO-based diluted magnetic semiconductors could be considered for spin-based electronics and optoelectronics devices.

We investigated the influence of oxygen vacancies (varying) on the structure and properties (dielectric and magnetic) of Co (fixed) and Mn (varied) co-doped ZnO nanoparticles (NPs) fabricated using the chemical precipitation technique. The oxygen vacancies in the lattice increased with an increase in dopants (Co, Mn) concentration. Annealing of the doped nanoparticles decreased their dielectric properties due to reduced grain boundaries caused by enhanced grain growth. Replacement of Zn ions with dopants in the lattice enhanced the samples' electrical conductivities due to the reduction in grain boundaries and increase of charge carriers. The co-doped nanoparticles annealed at 600 °C exhibited some hysteresis loop changes and became ferromagnetic (FM). The magnetization increased with an increase in dopants content in the ZnO matrix, while coercivity decreased. This shows that the properties of the doped samples are strongly related to the number of oxygen vacancies. These results demonstrated that the enhanced dielectric and magnetization responses of Co (fixed) and Mn (varied) co-doped ZnO nanoparticles are strongly correlated with the oxygen vacancies. The enhancement in optical, dielectric, and magnetic properties make transition metals (TM)-doped ZnO nanoparticles suitable for spintronics, and optoelectronic-based applications.

The ZnO, Zn0.96Mn0.04O, Zn0.95Mn0.04Co0.01O, Zn0.94Mn0.04Co0.02O and Zn0.92Mn0.04Co0.04O nanoparticles were synthesized by simple chemical precipitation technique. The effects of co-doping on the structure and magnetic properties of these nanoparticles were studied. The X-rays diffraction (XRD) scans were performed in the 2θ range of 20°–80°. The XRD patterns, at 300 K, of all the pure and co-doped ZnO samples confirmed the formation of wurtzite-type structure. X-ray diffraction and transmission scanning electron microscope analysis indicated that the high spin Co2+ and Mn2+ ions were substituted for the Zn2+ ions at tetrahedral sites. The average size of the nanoparticles were increased from 17 to 24 nm with the increase of dopants concentration. Moreover, Energy Dispersive X-ray spectroscopy (EDX) confirmed the synthesis results. All Zn0.96−xMn0.04Co x O (x = 0.0, 0.1, 0.2 and 0.4) nanoparticles samples were observed to be paramagnetic below 300 K. However, a large increase in the magnetization was observed below 40 K. This behavior, along with the negative value of the Curie–Weiss constant obtained from the linear fit to the susceptibility data below room temperature, indicated the ferromagnetic nature of the samples. The origin of ferromagnetism is likely to be the intrinsic characteristics of the Co and Mn doped samples. The high magnetization was noted for the 1 wt% Co co-doped Mn–ZnO annealed samples as compared to other samples with Co concentration above and below this threshold concentration.

Pure and Zn0.98Ni0.02O nanostructures were prepared by the co-precipitation method. The effects of annealing in Argon (Ar) and oxygen (O2) environment on the structure, dielectric, electric and magnetic properties were investigated. The structural analysis from X-ray diffraction and energy dispersive X-ray results confirmed that all the nanoparticles samples indexed to hexagonal wurtzite ZnO structure. A significant decrease was observed in the dielectric constant (e r ) and dielectric loss (e′′) resulting from the incorporation of Ni into the ZnO lattice. Higher e r and e′′ were observed in the O2 annealed sample. Moreover, the AC electrical conductivity (α AC ) of the Ni doped ZnO sample increased in comparison with that of pure ZnO sample due to the increase of available charge carriers after replacement of Zn ions with Ni ions. The 2 wt% Ni-doped ZnO sample annealed in O2 and Ar environment revealed room temperature ferromagnetism (RTFM) behavior, but higher ferromagnetic was only observed in the O2 annealed sample. The origin of RTFM may originate from the exchange interaction between Ni 2+ and excess of O2 vacancy in Zn0.98Ni0.02O nanoparticles.

This review highlights the state of art progress in crucible designs which have been identified as showing potential for induction melting three groups of titanium alloys based on the systems; Ti–Al, Ti–Ni, as well as multicomponent Ti-based hydrogen storage alloys. Several important parameters for crucible design, including; crucible-melt interactions, thermodynamic stability, and, thermal shock resistance of different crucibles will be discussed. Based on the findings of the review, the selection criteria for identifying crucibles for melting titanium alloys were outlined and several specific promising solutions were suggested. Keywords: Titanium alloys, Induction melting, Crucible, Chemical stability, Thermal shock resistance

The properties of Ti–Al–Nb alloys strongly depend on alloy compositions and microstructures. Proper design of these important aspects requires detailed knowledge of the solidification sequences and liquidus projection. However, there are still some conflicts between previous experimental and calculated results about the liquidus projections in the composition range of Ti-(40–60)Al-(5–30)Nb and this has hindered Ti–Al–Nb alloy development. In this present work, we explicitly investigated the as-cast microstructures and phase constitution of 50 alloys with the composition range of Ti-(40–60)Al-(5–30)Nb and clarified the solidification sequences. We re-constructed the partial liquidus projection and found that the primary β phase region extend to just below 55 at.% Al content and the primary α phase region extend to just below 24 at.% Nb content. Moreover, it was observed that the invariant reaction between Liquid, β, α and γ phases is a peritectic reaction (Liquid+β+γ→α) and all the Liquid+β+γ, Liquid+β+α and Liquid+α+γ three-phase regions are of peritectic type. The present work provides essential information necessary for optimizing the Ti–Al–Nb thermodynamic database to accelerate alloy development.

A highly valuable co-precipitation technique was used for the preparation of ZnO, Zn0.98Al0.02O and Zn0.96Al0.02Ni0.02O semiconductor nanoparticles. X-ray diffraction and scanning electron microscopy measurements reveal that the samples are nano-columns with a hexagonal wurtzite crystal structure. A significant enhancement in dielectric constant resulted from the substitution of (Al, Ni) co-doped ZnO lattice while an opposite trend was observed for dielectric loss. With the substitution of both Al and Ni, the electrical conductivity was found to be increased in comparison with that of ZnO nanoparticles due to the increase of available charge carriers after replacement of Zn ions by Ni ions. The magnetic property measurements revealed well room-temperature ferromagnetism, RTFM (Diluted magnetic semiconductor behavior) for the Ni co-doped samples in comparison with that of single Al–ZnO. The origin of high ferromagnetic may arise from the metallic Ni and intrinsic property of the doped ZnO.

The effect of annealing temperature on the dielectric and magnetic properties of (Co, Zn) co-doped SnO2 nanoparticles under air/oxygen (O2) and argon (Ar) atmospheres at 600 °C have been systematically investigated. A significant decrease is observed in dielectric constant and dielectric loss resulting from the incorporation of Co and Zn into the SnO2 lattice. Higher dielectric constant and loss was observed in the O2 annealed sample. Moreover, the electrical conductivity of the (Co, Zn) co-doped SnO2 samples increased in comparison with that of pure SnO2 sample due to the increase of available charge carriers after replacement of Sn ions with Co and Zn ions. Room-temperature ferromagnetism (RTFM) was observed for both the O2 and Ar annealed (Co, Zn) co-doped SnO2 samples. However, the remanent magnetization (Mr) varied drastically for different environmental annealing processes with Mr = 0.412 and 0.20 memu/g for the O2 and Ar-annealed samples, respectively. The results show that the enhanced dielectric and magnetic properties of (Co, Zn) co-doped SnO2 sample is strongly correlated with the increase in O2 vacancies. These findings not only demonstrate that (Co, Zn) co-doped SnO2 samples show tunable RTFM, but also suggests that RTFM can be influenced by introduction of O2 vacancies during O2 annealing.

After our discovery of room temperature ferromagnetism in the (Co, Ni) co-doped SnO2 nanoparticles by co-precipitation method, we successfully annealed all (Co, Ni) co-doped SnO2 diluted magnetic nanoparticles in air at 800 °C. The effect of annealing on dielectric and magnetic properties of (Co, Ni) co-doped SnO2 diluted magnetic nanoparticles was investigated. The as-synthesized (Co, Ni) co-doped SnO2 nanoparticles were annealed in air at 800 °C for 2 h in an electric furnace. The dielectric constant and dielectric loss values of all (Co, Ni) co-doped SnO2 samples decrease whereas, the electrical conductivity value increased with an increase in Ni co-doped concentration. Room temperature ferromagnetic behavior was observed in (Co, Ni) co-doped SnO2 samples. Increasing the Ni content up to 2 % leads to an increase ferromagnetic behavior and beyond that the ferromagnetic behavior decreased. A comparative study shows that (Co, Ni) co-doped SnO2 nanoparticles annealed in air at 800 °C have an excellent dielectric, magnetic properties and higher electrical conductivity than that of the (Co, Ni) co-doped SnO2 annealed in air at 600 °C, indicating that these nanoparticles can be used for high frequency devices, ultrahigh dielectric materials and spintronics.

In this work, the dielectric and magnetic properties of (Co, Ni) co-doped SnO2 nanoparticles were studied using ac impedance spectroscopy and magnetic properties measurement system or quantum design superconducting quantum interference device. Results showed that dielectric constant (e r ), dielectric loss (e″), and ac electrical conductivity (σ AC ) are strongly frequency dependent. A decrease in frequency was accompanied with an increase in e r and e″ values, whereas, a decrease in the dielectric constant was observed with the increase of Ni co-doping concentration. It was found that the dielectric constant and dielectric loss values decrease, whilst AC electrical conductivity increases with increase in co-doping concentration. Magnetization measurements revealed that the Ni co-doped SnO2 samples exhibits room temperature ferromagnetism. The results illustrate that (Co, Ni) co-doped SnO2 nanoparticles have an excellent dielectric, magnetic properties, and high electrical conductivity than those of co-doped samples reported previously, indicating that these (Co, Ni) co-doped SnO2 materials can be suitable for the purpose of high frequency device and spintronic applications.

The magnetic, dielectric and electrical properties of (Co, Zn) co-doped SnO2 nanoparticles were investigated. The polycrystalline samples of (Co, Zn) co-doped SnO2 nanoparticles were prepared using a co-precipitation method. X-ray diffraction confirmed that the (Co, Zn) co-doped SnO2 powder samples have the same tetragonal structure as pure SnO2 nanoparticles. The magnetization measurements revealed that the Zn co-doped SnO2 samples exhibit room temperature ferromagnetism. Magnetic hysteresis loops were observed at room temperature with high coercivity H c of 85 Oe and remanent magnetization M r of 0.412 memu/g for 1 wt% Zn co-doped sample. A decrease in the dielectric constant was observed with an increase in Zn doping content and frequency, at room temperature. It was found that the dielectric constant and dielectric loss values decrease, while AC electrical conductivity increases with increase in doping concentration and frequency. This study demonstrates that the (Co, Zn) co-doped SnO2 materials can be used for applications in ultrahigh dielectric materials and spintronics.

The phase transformation sequences and phase equilibria in Ti-47Al-20Nb and Ti-47Al-22Nb (at.%) alloys were investigated through experiments and computational (CALculation of PHAse Diagrams) techniques. Experiments to study nonequilibria phase transformations involved quenching the alloys from high temperature followed by composition and microstructure characterization. The computed results show that with increase in temperature, the α + β + γ tie-triangle phase region shifts towards low Nb content. On the contrary, experimental results show that with increase in temperature the tie-triangle of α + β + γ moves towards high Nb content. These changes are attributed to the expansion of the α phase region and corresponding changes of the primary α, β and γ phase regions with increase in temperature. In the experimentally studied alloys, a part of the α phase transformed to γ phase by massive transformation and most of the β phase transformed to γ phase in high Nb content alloys.

With the purpose of obtaining compositionally uniform ingots during Ohno continuous casting of a dilute industrial aluminum alloy through eliminating segregation due to convection, a magnetic field strength required to damp natural convection and suppress macrosegregation was numerically determined. This was achieved by solving conservation equations of continuity, momentum, energy and Maxwell’s equations in order to predict the magnetic field effects on flow field (determining macrosegregation). The electromagnetic field was applied orthogonally to the natural convection flow. Through this approach, the optimum magnetic field strength required to damp natural convection and establish diffusion controlled solute transport of the alloy during solidification was established.