Search

This study describes the first, use of eco-friendly welan gum as a new depressant in galena-pyrite flotation separation. The depression mechanism were examined using micro-flotation and various characterization techniques. The selective depression performance of welan gum on pyrite was found to effectively enhance the galena/pyrite flotation separation index. Compared with the addition of NaBX alone, the grade of Pb in the produced concentrate increased by more than 28% (from 40.86% to 70.02%). And it was possible to recover 87.79% of galena and only 15.98% of pyrite. There was an accentuated increase in the electronegativity of the pyrite surface by more than ~ 8 mV after treatment with welan gum alone compared to an increase of ~ 1 mV for galena, which can be explained by the fact that welan gum selectively adsorbed on the pyrite surface in significant amounts. As a result, the subsequent adsorption of xanthate is prevented. This finding has been further proven by adsorption measurement results. The X-ray photoelectron spectroscopy and Time-of-Flight secondary ion mass spectrometry results indicated that the hydroxyl groups in welan gum showed acid – base interactions with the metal hydroxylated species anchored on the mineral surfaces, which may be the main driving force in the adsorption process. Differences in the amount of metal hydroxide on the mineral surface, as well as the electrical affinity of metal ions in metal hydroxide, contributed to the selective adsorption of welan gum. Therefore, welan gum can be regarded as a potential pyrite-depressant. [ABSTRACT FROM AUTHOR]

HfO 2 -based thin films have raised considerable interest in ferroelectric memory devices due to their thickness scalability and process compatibility with CMOS. Stress exhibits a significant influence on ferroelectric polarization in HfO 2 -based films. However, the effect of stress has yet to be clarified despite numerous efforts, and there has been a lack of systematic review to collate and discuss this effect. This paper briefly introduces how stress is characterized in HfO 2 -based polycrystalline films as basis. Then, the process in which stress affects ferroelectricity is carefully discussed. The paper subsequently elaborates both the effects of out of plane stress and in plane stress. Furthermore, the interaction between stress and other factors is presented. Finally, the up-to-date research on the effect of stress are summarized, and several further research challenges for researchers are provided. Given the ubiquitous stress during the chip manufacturing process, a detailed summary of the stress effect has technological implications for processing and applications of HfO 2 -based thin films. [ABSTRACT FROM AUTHOR]

Incorporating hydrogen into complex oxides holds promise for discovering exotic phenomena and novel functionalities by promoting couplings between ion and lattice/charge/spin/orbital degrees of freedom. Here, electrolyte gating‐driven hydrogenation is investigated in epitaxial brownmillerite SrFeO2.5 thin films in which the hydrogenation‐induced lattice distortion is qualitatively different from its counterpart SrCoO2.5. The achievable lattice expansion in hydrogenated SrFeO2.5 is weaker than in SrCoO2.5 and primarily occurs along the normal of the stacked octahedral FeO6 and tetrahedral FeO4 layers. Upon the substitution of Fe with Co, the lattice expansion monotonically increases with increase of Co/Fe ratio, implying an intrinsic difference in accommodating hydrogen between Fe‐ and Co‐based brownmillerites. Moreover, a net magnetic moment in hydrogenated SrFeO2.5 films is observed above room temperature, which gradually weakens with the increase of Co substitution, suggesting a stronger canted magnetism in Fe‐based hydrogenated brownmillerites. This work clarifies the electrolyte gating‐driven hydrogenation mechanisms in brownmillerite SrFeO2.5 epitaxial thin films and those with Co substitution, particularly the deterministic role of Co/Fe ratio in the evolution of structure and properties upon hydrogenation. [ABSTRACT FROM AUTHOR]

The control of oxygen vacancy channels (OVCs) in brownmillerite (BM) oxides has a substantial impact on tuning their physical and chemical properties. Here, we demonstrated a strain mechanism for directing the OVCs in BM-SrFeO2.5 (SFO) synthesized via a two-step process in which perovskite (P)-structured SrFeO3−δ (P-SFO3−δ) thin film is first prepared and then converted to the BM phase through the post-vacuum-annealing (PVA) treatment. The initial strain state for the first-step-prepared P-SFO3−δ thin films plays a determining role in the orientation of the OVCs of the final BM phase with the systematic manipulation of both chemical strain (lattice expansion) and epitaxial strain by tuning the oxygen deficiency and using different substrates, respectively. Larger tensile strains in the initial P-SFO3−δ thin films are inclined to facilitate the formation of BM with horizontal OVCs after PVA, while small tensile or compressive strains favor the vertical OVCs. Our results offer insights into the selective control of the orientation of the OVCs of BM-SrFeO2.5 thin films, which are of benefit to the design for functionalities related to the ion transport and migration. [ABSTRACT FROM AUTHOR]

Improving the endurance performance for hafnia-based ferroelectric thin films and devices is of considerable significance from both scientific and technological perspectives. Here, we obtained robust ferroelectricity in Hf0.5Zr0.5O2 (HZO) thin films without the need of the confinement from top electrodes by systematically optimizing the conditions and parameters for the post-deposition annealing (PDA) process. Compared with the post-metallization annealing (PMA) process, PDA is found to markedly improve the ferroelectric endurance performance. In particular, wake-up-free ferroelectric HZO thin films with an exceptional endurance performance (∼3 × 1010 cycles) are obtained by PDA processing conducted under an oxygen atmosphere, which is attributed to the suppression of oxygen deficiency in the HZO thin films and the inhibition of interfacial reaction layer that inevitably forms during annealing treatment for PMA processing. Our work offers insight into improving ferroelectricity and endurance for hafnia-based ferroelectric materials and devices. [ABSTRACT FROM AUTHOR]

Topological quad-domain textures in ferroelectric nanoislands have been considered as enablers for nanoelectric devices. However, the fabrication of ordered arrays of ferroelectric islands exhibiting this domain structure is a challenge. By using substrate patterning to create nucleation sites, highly ordered quad-domain ferroelectric polarization configurations were achieved in BiFeO3 nanoisland arrays. Reversible switching of the quad-domain between the center divergent state with highly conductive domain walls and the center convergent state with insulating domain walls can be realized, resulting in a resistance change with a large on/off ratio. This templated growth strategy enables the controllable fabrication of exotic topological domains and sheds light on their applications for configurable electronic devices. [ABSTRACT FROM AUTHOR]