A neutron diffraction investigation of high valent doped barium ferrite with wideband tunable microwave absorption

The barium ferrite BaTixFe12−xO19 (x = 0.2, 0.4, 0.6, 0.8) (BFTO-x) ceramics doped by Ti4+ were synthesized by a modified sol—gel method. The crystal structure and magnetic structure of the samples were determined by neutron diffraction, and confirm that the BFTO-x ceramics were high quality single phase with sheet microstructure. With x increasing from 0.2 to 0.8, the saturation magnetization (Ms) decreases gradually but the change trend of coercivity (Hc) is complex under the synergy of the changed grain size and the magnetic crystal anisotropy field. Relying on the high valence of Ti4+, double resonance peaks are obtained in the curves of the imaginary part of magnetic conductivity (μ″) and the resonance peaks could move toward the low frequency with the increase of x, which facilitate the samples perform an excellent wideband modulation microwave absorption property. In the x = 0.2 sample, the maximum reflection loss (RL) can reach −44.9 dB at the thickness of only 1.8 mm, and the bandwidth could reach 5.28 GHz at 2 mm when RL is less than −10 dB. All the BFTO-x ceramics show excellent frequency modulation ability varying from 18 (x = 0.8) to 4 GHz (x = 0.4), which covers 81% of the investigated frequency in microwave absorption field. This work not only implements the tunable of electromagnetic parameters but also broadens the application of high-performance microwave absorption devices.

Enhanced Flotation Recovery of Fine Molybdenite Particles Using a Coal Tar-Based Collector

Low flotation efficiency has always been a problem in the separation of low-grade molybdenum ores because of the finely disseminated nature and crystal anisotropy of molybdenite. In this study, a novel kerosene–coal tar collector (KCTC) was prepared and used to explore the feasibility of improving the recovery of fine molybdenite particles. The results showed that KCTC achieved better attaching performance than that shown by kerosene, and the surface coverage and attaching rate constant were improved significantly, especially for finer particles of −38 + 20 μm. Compared with kerosene, KCTC showed more affinity for molybdenite particles and greater adsorbed amounts of KCTC on molybdenite particles were achieved. Moreover, the composite collector was shown to float single molybdenite particles of different sizes, and it was found that the recovery of molybdenite particles of different sizes, particularly in the case of those at −20 μm, was improved dramatically by KCTC. The flotation results of actual molybdenum ores further confirmed that KCTC was beneficial to flotation recovery and the selectivity of molybdenite. This indicated that KCTC is a potential collector for the effective flotation of low-grade deposits of molybdenum ores, and more studies should be conducted on further use in industrial practice.

Non-classical nucleation in vapor–liquid–solid growth of monolayer WS2 revealed by in-situ monitoring chemical vapor deposition

The very early nucleation stage of a transition metal dichalcogenide (TMD) was directly observed with in-situ monitoring of chemical vapor deposition and automated image analysis. Unique nucleation dynamics, such as very large critical nuclei and slow to rapid growth transitions, were observed during the vapor–liquid–solid (VLS) growth of monolayer tungsten disulfide (WS2). This can be explained by two-step nucleation, also known as non-classical nucleation, in which metastable clusters are formed through the aggregation of droplets. Subsequently, nucleation of solid WS2 takes place inside the metastable cluster. Furthermore, the detailed nucleation dynamics was systematically investigated from a thermodynamic point of view, revealing that the incubation time of metastable cluster formation follows the traditional time–temperature transformation diagram. Quantitative phase field simulation, combined with Bayesian inference, was conducted to extract quantitative information on the growth dynamics and crystal anisotropy from in-situ images. A clear transition in growth dynamics and crystal anisotropy between the slow and rapid growth phases was quantitatively verified. This observation supports the existence of two-step nucleation in the VLS growth of WS2. Such detailed understanding of TMD nucleation dynamics can be useful for achieving perfect structure control of TMDs.

A Neutron Diffraction Investigation of High Valent Doped Barium Ferrite With Super-wide Tunable Microwave Absorption

The Barium ferrite BaTixFe12-xO19 (x = 0.2, 0.4, 0.6, 0.8) ceramics doped by Ti4+ (BFTO-x) were synthesized by a modified sol-gel method. The crystal structure and magnetic structure of the samples were determined by neutron diffraction, and confirm that the BFTO-x ceramics were high quality single phase with sheet micro-structure. With x increasing from 0.2 to 0.8, the Ms decreases gradually but the change of Hc is complex under the synergy of the changed grain size and the magnetic crystal anisotropy field. Relying on the high valence of Ti4+, double resonance peaks are obtained in the curves of μ′′ and the resonance peaks could move towards the low frequency with the increase of x, which facilitate the samples perform an excellent wide-band modulation microwave absorption property. In the x = 0.2 sample, the maximum reflection loss can reach –44.9 dB at the thickness of only 1.8 mm, and the bandwidth could reach to 5.28 GHz at 2 mm when the RL is less than –10 dB. All the BFTO-x ceramics show excellent frequency modulation ability varying from 18 GHz (x = 0.8) to 4 GHz (x = 0.4), which covers 81% of the investigated frequency in microwave absorption field.

Nanoindentation in multi-modal map combinations: a correlative approach to local mechanical property assessment

A method is presented for the registration and correlation of property maps of materials, including data from nanoindentation hardness, Electron Back-Scattered Diffraction (EBSD), and Electron Micro-Probe Analysis (EPMA). This highly spatially resolved method allows for the study of micron-scale microstructural features, and has the capability to rapidly extract correlations between multiple features of interest from datasets containing thousands of data points. Two case studies are presented in commercially pure (CP) titanium: in the first instance, the effect of crystal anisotropy on measured hardness and, in the second instance, the effect of an oxygen diffusion layer on hardness. The independently collected property maps are registered using affine geometric transformations and are interpolated to allow for direct correlation. The results show strong agreement with trends observed in the literature, as well as providing a large dataset to facilitate future statistical analysis of microstructure-dependent mechanisms. Graphical abstract