M1 Phase Research Articles

Interplay between boron doping and epitaxial relationships in VO2 films grown by laser ablation

We investigated the effect of boron doping on the functional and structural properties of VO2 thin films. Temperature-dependent measurements were performed on pure and boron-doped (0.5 and 1.3 at.%) VO2 films grown on Al2O3(0001) by Reactive Pulsed Laser Deposition. The transition temperature is initially reduced by the insertion of boron; decreasing from ca. 346 K in the case of the pure sample to 335 K for a 0.5 at.% boron amount. Further increase of the boron concentration leads to a slight decrease of the transition temperature (−2 K), a significantly broader hysteresis loop and a reduced resistivity contrast (less than 3 orders of magnitude). Raman spectroscopy and high-resolution X-ray diffraction were performed to elucidate the nature of the involved phases and their structure. A correlation was found between increasing the boron concentration and the formation of two peculiar in-plane epitaxial relationships, the VO2 films evolving from one to the other. We also evidenced the presence of the transient M2 phase in the highest doped sample.

Atomic scale analysis of Zn2+ storage in robust tunnel frameworks.

Realizing rapid and reversible Zn2+ storage at the cathode is imperative for the advancement of aqueous Zn-ion batteries (ZIBs), which offer an excellent option for large-scale electrochemical energy storage. However, owing to limitations of the structural stability of previously investigated frameworks, the Zn2+ storage processes remain unclear, thus hindering progress towards the above goal. Herein, we present the novel application of MoVTe oxide with an M1 phase (MVT-M1) as a potential cathode material for ZIBs. MVT-M1 features broad and robust tunnels that facilitate reversible Zn2+ insertion/extraction during cycling, as well as rich redox centers (Mo, V, and Te) to aid in charge redistribution, resulting in good performances in ZIBs. The exceptional resilience of MVT-M1 to high-energy electron beams allows for direct observation of Zn2+ insertion/extraction at the atomic scale within the tunnels for the first time using high-angle annular dark field scanning transmission electron microscopy; the storage location of zinc ions within the cathode is accurately determined layer by layer from the surface to the bulk phase by employing time-of-flight secondary ion mass spectrometry. Additionally, solvent molecules (H2O and methanol) are also found inside the tunnels along with Zn2+. Due to the broader heptagonal tunnels and Te ions in the hexagonal tunnels, MVT-M1 exhibits good cycling stability, outperforming MoVTe oxide with the M2 phase (no heptagonal tunnels) and MoV oxide with the M1 phase (no Te). These findings hold significant importance in advancing our understanding of the Zn2+ storage mechanism and enable the design of novel materials specifically optimized for efficient Zn2+ storage.

Effect of Sn on formation and transformation of VO2 phase

The role of stannum was investigated in formation and transformation of vanadium-dioxide phase in a deep perspective through characterization methods including Raman spectra, XRD, OM, SEM, UV–vis and electrochemical workstation. The result showed supersaturated stannum atoms could exist in SnxV2-xO5 as amorphous solid solution through non-equilibrium sputtering method, by which the unitary phase Sn-doped VO2 could be obtained under either thermal de-oxidation or thermal de-composition mechanism. Furthermore, cooperating stannum atoms with oxygen vacancies could regulate the formation of vanadium dioxide M1 or M2 phase, in turn engineer the phase transformation (M-R) temperature of VO2.

Beta rhythmicity in human motor cortex reflects neural population coupling that modulates subsequent finger coordination stability

Human behavior is not performed completely as desired, but is influenced by the inherent rhythmicity of the brain. Here we show that anti-phase bimanual coordination stability is regulated by the dynamics of pre-movement neural oscillations in bi-hemispheric primary motor cortices (M1) and supplementary motor area (SMA). In experiment 1, pre-movement bi-hemispheric M1 phase synchrony in beta-band (M1-M1 phase synchrony) was online estimated from 129-channel scalp electroencephalograms. Anti-phase bimanual tapping preceded by lower M1-M1 phase synchrony exhibited significantly longer duration than tapping preceded by higher M1-M1 phase synchrony. Further, the inter-individual variability of duration was explained by the interaction of pre-movement activities within the motor network; lower M1-M1 phase synchrony and spectral power at SMA were associated with longer duration. The necessity of cortical interaction for anti-phase maintenance was revealed by sham-controlled repetitive transcranial magnetic stimulation over SMA in another experiment. Our results demonstrate that pre-movement cortical oscillatory coupling within the motor network unknowingly influences bimanual coordination performance in humans after consolidation, suggesting the feasibility of augmenting human motor ability by covertly monitoring preparatory neural dynamics.

Phase Transition and Optical Properties of VO2 and Al: ZnO/VO2 Thin Films

Thermochromic Vanadium dioxide (VO2) has strong potential for smart window applications but its commercial scale usage is limited due to low visible light transmission. To address this issue, aluminum doped zinc oxide (AZO) anti-reflecting layer is integrated with VO2 layer in the present work. VO2 single layer and AZO/VO2 bilayer thin film samples were deposited by sputtering technique on quartz substrate. The single-phase growth of VO2 and AZO in single layer and bilayer thin film samples is confirmed by X-ray diffraction measurements. Monoclinic M1 phase of VO2 is detected in VO2 and AZO/VO2 thin film samples at room temperature. Monoclinic to rutile structural phase transition (SPT) in these samples is studied by performing temperature-dependent X-ray diffraction measurements. SPT in VO2 thin film samples is close to 68 °C and SPT temperature appears slightly lower in AZO/VO2 sample as compared to VO2 sample. Spectral transmittance measurement at room temperature showed significant improvement in the visible transmittance of AZO bilayer film than that of single layer VO2 thin film. These results demonstrate the possibility of integration of anti-reflecting layers such as AZO with VO2 layer for better visible transmittances suitable for large-scale smart window applications.

Investigation of tidal evolution in the Bohai Sea using the combination of satellite altimeter records and numerical models

Understanding secular tidal variability is fundamental for many practical purposes such as navigation, coastal engineering and flood warning. Observational tidal evolution is primarily based on coastal tide gauge records whose location and number are extremely limited. Tides undergo significant changes in the Bohai Sea mainly due to coastline changes induced by human activities while there are no publicly accessible long-term hourly tide gauges in the Bohai Sea. In this paper, we investigate secular tidal evolution of four major constituents (M2, S2, O1, and K1) in the Bohai Sea based on multi-satellite altimeter records and the numerical model. Both satellite results and model results indicate consistent feature of tidal changes for M2 tide in the Bohai Sea: M2 amplitudes remarkably increase in the Bohai Bay and Liaodong Bay while noticeably decrease in the Laizhou Bay; M2 phases significantly decrease in the Bohai Bay and Laizhou Bay while substantially increase in the south of the Liaodong Bay. The tidal changes of S2, K1, and O1 constituents revealed by multi-satellite altimeters and the numerical model are contradictory in many parts in the Bohai Sea. Such inconsistency may be related to residual mesoscale ocean variability in satellite results and the ignored contribution of water depth changes to tidal evolution in model results.

Determination of highly active and selective surface for the oxidative dehydrogenation of ethane over phase-pure M1 MoVNbTeOx catalyst

The original phase-pure M1 MoVNbTeOx catalyst was mechanically treated with stirring water for several days under ambient conditions to obtain particles with different sizes. The catalytic performance was significantly improved and stabilized after about 7 days of treatment. Among all the catalysts, the sample treated in water for 7 days can obtain 57.6 % ethane conversion and 0.79 kgC2H4/kgcat/h ethylene productivity while the original phase-pure M1 catalyst was only 19.2 % and 0.27 kgC2H4/kgcat/h at reaction temperature of 400 °C and contact time of 18.5 gcat·h/molC2H6. Meanwhile, the catalyst was systematically characterized and the results showed that there was essentially no difference in microstructure between the original and treated catalysts. TEM and SEM morphological characterizations presented that the particle size and aspect ratio of the catalysts changed significantly, in which the particle size of the catalyst become smaller and the proportion of basal surface was enhanced. The activity and selectivity of the catalysts exhibited a correlation with the amount and proportion of basal surface. It can be deducted that the basal surface is the most active and selective surface during oxidative dehydrogenation of ethane (ODHE) process, and the intrinsic activity based on the basal (001) plane of the catalyst remains stable after the mechanical treatment. Samples treated in water for 7 days showed excellent long-term stability in a 200 h stability test at reaction temperature of 440 °C and contact time of 9.3 gcat·h/molC2H6. The present work demonstrated that the differences in the catalytic properties of different M1 samples depend mainly on the amount and proportion of exposed basal surface, and the possibility of enhancing the activity of orthorhombic M1 phase by fragmentation method.

Effect of Water Content in the Raw Material Mixture during Grinding on Alite Monoclinic Phase Formation

The article investigates the influence of the water content during grinding the raw material mixture on the formation of monoclinic phases M1 and M3 of alite using the Rietveld method. Four identical raw material mixtures were chosen, differing only in the water content for the grinding process. The milling process in a water environment in a PULVERISETTE 6 planetary mill was chosen for the preparation of the raw material mixture. Based on previous research in this area, a firing temperature of 1450 °C with soaking for 60 minutes was chosen. The results showed that the monoclinic M3 phase is predominantly formed. In contrast, the monoclinic M1 phase forms at lower firing temperatures than the M3 phase and with fewer crystallization nuclei due to less fine grinding. The results show that the amount of water used to grind the feedstock does not make any difference in the final amount of monoclinic M1 and M3 phases.

High Energy Storage Performance in La-Doped AgNbO3 Ceramics via Tape Casting.

AgNbO3-based Pb-free antiferroelectric (AFE) ceramics have attracted increasing interest owing to their excellent potential in energy storage applications. Herein, a high recoverable energy storage density (Wrec) of 7.62 J/cm3 is realized in La-doped AgNbO3 ceramics prepared via tape casting. The high Wrec is attributed to high breakdown strength Eb of 380 kV/cm induced by dense microstructure as well as fine grain size and enhanced AFE stability stemming from M2 phase and reduced tolerance factor t. The high Wrec exceeding 6 J/cm3 was maintained in a wide temperature range of 20-150 °C and exhibited frequency stability with less than 8% variation in a range of 1-200 Hz. The discharge energy density Wd exhibited temperature stability at 30-110 °C with less than 9% variation. Our research provides a good method for producing AgNbO3-based ceramics having high energy storage performances.

Nanocomposite catalysts of non-purified MoVNbTeOx with CeO2 or TiO2 for oxidative dehydrogenation of ethane

The phase-pure M1 of MoVNbTeOx has been demonstrated as a highly active catalyst for oxidative dehydrogenation of ethane (ODHE) reaction. However, the MoVNbTeOx without further purification shows poor catalytic performance so that the M2 phase has to be removed from the bulk material to approach the high purity of M1 phase. This work presents new discovery that the nanocomposite catalyst by adding CeO2 to the MoVNbTeOx using sol–gel method can effectively promote its catalytic performance. As a comparison, the sample combining TiO2 and MoVNbTeOx is also prepared which presents limited influence. The characterization results show that the enhanced catalyst performance can be attributed to the increased active species at the catalyst surface due to the addition of CeO2. This work would provide a new solution to greatly simplify the preparation procedure of MoVNbTeOx catalysts for the ODHE process and avoid the mass loss during the purification procedure.

Effect of Cr-substitution on vanadium dioxide thin films studied by soft X-ray magnetic circular dichroism

The tunability of magnetic properties of VO 2 has fascinated substantial attention in the first generation of spintronics-related applications such as read head sensors for hard disk drives and magnetic random-access memory. In this work, we focus on Cr doped VO 2 , V 1− x Cr x O 2 (0 ≤ x ≤ 0 . 3) (VCO) thin films and study the effect of Cr-substitution on the structural, electronic and magnetic properties. The VCO films were deposited on R-sapphire substrates using a pulse laser deposition method. Soft X-ray absorption spectroscopy (XAS) and soft X-ray magnetic circular dichroism (XMCD) studies of VCO thin films were performed to reveal and understand the origin of maTablegnetization and their enhancement with Cr-substitution. The XAS spectra suggest that the valences of V ions are in tetra and pentavalent states and Cr ions in the trivalent state. The XMCD spectra imply that the V and Cr ions are ferromagnetic at room temperature. These results also indicate that the VCO films are in the ferromagnetic insulating state and charge-ordered at the V and Cr sites. These results are consistent with the first principle density functional theory calculations. • XRD results suggest that a gradual structural change from the monoclinic M1 phase (0 ≤ x < 0.05) to triclinic T phase (0.05 ≤ x ≤ 0.20 to monoclinic M2 phase ( x > 0.20). • First Study to understand the origin of magnetization. • The VCO films are in the ferromagnetic insulating state and charge-ordered at the V and Cr sites, consistent with DFT. • The XMCD spectra indicate that the V and Cr ions are ferromagnetic at room temperature.

Energy storage performance and phase transition under high electric field in Na/Ta co-doped AgNbO3 ceramics

Lead-free antiferroelectric ceramics with high energy storage performance show great potential in pulsed power capacitors. However, poor breakdown strength and antiferroelectric stability are the two main drawbacks that limit the energy storage performance of antiferroelectric ceramics. Herein, high-quality (Ag1-xNax)(Nb1-xTax)O3 ceramics were prepared by the tape casting process. The breakdown strength was greatly improved as a result of the high density and fine grains, while the antiferroelectric stability was enhanced owning to the M2 phase. Benefiting from the synergistic improvement in breakdown strength and antiferroelectric stability, (Ag0.80Na0.20)(Nb0.80Ta0.20)O3 ceramic reveals a benign energy storage performance of Wrec = 5.8 J/cm3 and η = 61.7% with good temperature stability, frequency stability and cycling reliability. It is also found that the high applied electric field can promote the M2-M3 phase transition, which may provide ideas to improve the thermal stability of the energy storage performance in AgNbO3-based ceramics.

Importance of the donor unit on fluoranthene for selective detection of nitro aromatic explosives

In this work, two aggregation-induced emission enhancement (AIEE) materials encompassing phenyl (M1) and thiophene (T1) units flanked to fluoranthene were synthesized. We report a new packing polymorphic phase of M1 and the molecular interactions in the crystal lattice were stabilized by CH···π (2.882 Å) interactions. Single crystal X-ray diffraction (SXRD) studies revealed that high torsional angles of phenyl/thiophene unit on the fluoranthene endow weak π-π intermolecular interactions in the crystal lattice. The photophysical properties of M1 and T1 were explored in solution, solid-state and their AIEE phenomenon was studied in THF/water systems. Both the compounds show strong sky-blue emission at 453 nm (M1) and 460 nm (T1). The fluorescence lifetime and quantum yields are varied significantly in the aggregated form. The emission enhancement ascribed due to restricted intramolecular rotation (RIR) of thiophene/phenyl with central π-conjugated fluoranthene in the aggregation state. Distinct changes in the surface morphology, variation in the photophysical properties and energy levels by varying the THF/water ratios furnish its potential towards trace detection of different nitroaromatics. Both materials show high sensitivity and selectivity towards detection of Trinitrophenol (TNP), however, T1 showed a high quenching rate constant at fw = 90 % (KSV = 5.81 × 104 M−1) with LOD of 0.6 ppm at fw = 70 %. The observed fluorescence quenching is attributed due to photoinduced electron transfer from fluoranthene to nitroaromatics through static quenching process. The remarkable efficiency of these fluorescent probes were further explored towards the analysis of river/tap water samples, suggesting their high potential for use in field analysis.

Iron quantitative analysis of motor combined with bulbar region in M1 cortex may improve diagnosis performance in ALS.

To explore whether the combined analysis of motor and bulbar region of M1 on susceptibility-weighted imaging (SWI) can be a valid biomarker for amyotrophic lateral sclerosis (ALS). Thirty-two non-demented ALS patients and 35 age- and gender-matched healthy controls (HC) were retrospectively recruited. SWI and 3D-T1-MPRAGE images were obtained from all individuals using a 3.0-T MRI scan. The bilateral posterior band of M1 was manually delineated by three neuroradiologists on phase images and subdivided into the motor and bulbar regions. We compared the phase values in two groups and performed a stratification analysis (ALSFRS-R score, duration, disease progression rate, and onset). Receiver operating characteristic (ROC) curves were also constructed. ALS group showed significantly increased phase values in M1 and the two subregions than the HC group, on the all and elderly level (p < 0.001, respectively). On all-age level comparison, negative correlations were found between phase values of M1 and clinical score and duration (p < 0.05, respectively). Similar associations were found in the motor region (p < 0.05, respectively). On both the total (p < 0.01) and elderly (p < 0.05) levels, there were positive relationships between disease progression rate and M1 phase values. In comparing ROC curves, the entire M1 showed the best diagnostic performance. Combining motor and bulbar analyses as an integral M1 region on SWI can improve ALS diagnosis performance, especially in the elderly. The phase value could be a valuable biomarker for ALS evaluation. • Integrated analysis of the motor and bulbar as an entire M1 region on SWI can improve the diagnosis performance in ALS. • Quantitative analysis of iron deposition by SWI measurement helps the clinical evaluation, especially for the elderly patients. • Phase value, when combined with the disease progression rate, could be a valuable biomarker for ALS.

Crystal structure and catalytic performance for direst oxidation of propylene to acrylic acid of MoVTeNbOx prepared by high-pressure hydrothermal synthesis

MoVTeNbOx catalysts were prepared through a high-pressure hydrothermal method, in which the crystalline structure and properties of the catalysts were tuned by varying the system pressure (0-12.0 MPa). Results showed that the system pressure had a significant influence on the structure and catalytic performance of MoVTeNbOx. Under 3.0 MPa, MoVTeNbOx prepared possessed the highest content of M1 phase (90.6%) and V5+ content (60.7%), exhibiting a uniform short and thick needle-like morphology. Also, it showed excellent selectivity (79.1%) and yield (52.8%) to acrylic acid at the catalytic temperature of 380°C. However, under 4.4 and 11.6 MPa, the characteristic peaks of M1 shifted to a certain extent and the morphology changed from short and thick to slender. As a result, the V5+ content of M1 (001) plane decreased, resulting in a remarkable decline of the selectivity to acrylic acid. Moreover, DFT simulation results showed that the anti-bond orbital energy of V-O bond is the highest under 3.0 MPa, while further increase of pressure leads to obvious extrusion between atoms in the internal structure of MoVTeNbOx. Moreover, it was clear that the lower the anti-bond orbital energy of V-O bond, the lower the selectivity to acrylic acid.

Probing Strain-Induced Effects on Performance of Low-Dimensional Hybrid Perovskites for Solar Energy Harvesting.

The application of strain to photovoltaics (PVs), thermoelectrics (TEs), and semiconductors often has substantial impacts on the fundamental properties governing the efficiency of these materials. In this work, we investigate two stable phases of hybrid organic-inorganic two-dimensional (2D) perovskites (2DPKs) and their response to the application of tensile and compressive strain of up to 5%. These 2D MAPbI3 analogues are known to exhibit strongly anisotropic properties and have been put forward as excellent candidates for application in mixed PV-TE devices. Our results, stemming from ab initio density functional theory calculations and investigation of transport properties through the Boltzmann transport equations, further elucidate the key properties contributing to the success of these materials. In particular, both the M1 and M2 phases exhibit stable structures between -5 and 5% biaxial strains. The M2 phase exhibits an excellent 23.8% power conversion efficiency under the application of 5% tensile strain. Furthermore, we analyze the effects of spin-orbit coupling on the band structures of both phases, revealing great potential for spintronic applications with the M2 phase, demonstrating Rashba coefficients up to 3.67 eV Å.

Te-doped MoV-Oxide (M1 phase) for ethane ODH. The role of tellurium on morphology, thermal stability and catalytic behaviour

Undoped and Te-doped MoV-Oxide (M1 phase) catalysts have been prepared hydrothermally (Te/Mo ratio in the synthesis gel from 0 to 0.17; and heat-treated at 400 or 600°C in N2 atmosphere), characterized by several physicochemical techniques and tested in the oxidative dehydrogenation (ODH) of ethane. The morphology and microporosity of the catalysts, the nature of V-species on the catalyst surface and the catalytic performance strongly depend on the composition and the heat-treatment temperature. When calcined at 400°C, the selectivity to ethylene decreases when the amount of tellurium increases, whereas when heat treated at 600°C, the selectivity to ethylene increases when the Te-loading increases. These trends have been explained on the basis of the good correlation between selectivity to ethylene and the concentration of V4+ species on the surface of catalysts, in which the most selective catalyst is that prepared with a Te/Mo ratio of 0.17 and heat-treated at 600°C.

Quercetin-Coating Promotes Osteogenic Differentiation, Osseointegration and Anti-Inflammatory Properties of Nano-Topographic Modificated 3D-Printed Ti6Al4V Implant.

The capabilities of osseointegration and anti-inflammatory properties are of equal significance to the bio-inert titanium implant surface. Quercetin has proved its capacities of activating anti-inflammation through macrophage modulation and promoting osteogenic differentiation. Herein, we fabricated quercetin-coating on nano-topographic modificated 3D-printed Ti6Al4V implant surface. Subsequently the biological cells responses in vitro, anti-inflammatory and osseointegration performance in vivo were evaluated. In vitro studies indicated that quercetin-coating can enhance the adhesion and osteogenic differentiation of rBMSCs, while modulating the polarization of macrophages from M1 to M2 phase and improving the anti-inflammatory and vascular gene expression. Moreover, quercetin-loaded implants reduced the level of peri-implant inflammation and ameliorated new bone formation and rapid osseoinegration in vivo. Quercetin-coating might provide a feasible and favorable scheme for endowing 3D-printed titanium alloy implant surface with enhanced the rapid osseointegration and anti-inflammatory properties.

Exploring phase–amplitude coupling from primary motor cortex-basal ganglia–thalamus network model

The purpose of this study is to develop a primary motor cortex (M1)-basal ganglia–thalamus model capable of reproducing the physiological phenomenon of exaggerated phase–amplitude coupling (PAC) in Parkinson’s disease and exploring the potential sources of PAC anomalies in M1. The subthalamic nucleus (STN) phase-STN amplitude coupling, STN phase–M1 amplitude coupling, and M1 phase–M1 amplitude coupling are reproduced, where the phase frequencies are distributed in the beta band and the amplitude frequencies are distributed in the broad gamma band. We mainly study the impacts of thalamus →M1 connections and STN↔M1 bidirectional synaptic connections. Abnormal beta oscillations generated within the basal ganglia are found to be transmitted to M1 through the STN or thalamus and could be one of the potential sources of PAC-related beta oscillations in M1, thereby interfering with high-frequency signals in the motor cortex. Furthermore, the weakening of M1→STN leads to a shift of the oscillations of the STN from the high beta band to the low beta band, which is more consistent with pathological experiments, thus supporting the experimental results that the hyper-direct path from M1 to STN drives the beta oscillations of STN. Finally, the suppression effect of STN deep brain stimulation on PAC is investigated. As the stimulation frequency increases, the PAC modulation index within different regions gradually decreases, in general agreement with the trend of synchronization level and beta oscillation energy, indirectly indicating that PAC can be used as a feedback indicator of parkinsonian state.

Emergence of paraelectric, improper antiferroelectric, and proper ferroelectric nematic phases in a liquid crystal composed of polar molecules.

We have elaborated a theoretical approach for the description of polar nematic phases observed by Nishikawa etal. [Adv. Mater. 29, 1702354 (2017)0935-964810.1002/adma.201702354], their structures, and transitions between them. Specific symmetry contributions to the pair molecular potentials provide the molecular mechanisms responsible for the formation of proper and improper polarity on the macroscopic level. An improper antiferroelectric nematic M2 phase can arise between paraelectric nematic M1 and proper ferroelectric nematic MP in the temperature scale. The local polarization in M2 arises mostly due to the local splay deformation. The director distribution in M2 represents the conjugation of cylindrical waves with opposite splay and polarization signs. The director and polarization are parallel to the cylindrical domain axes in the middle of each cylinder but exhibit considerable (mostly radial) deformation on the periphery of each cylinder. Polarization vectors are mostly stacked antiparallel on the borders between the domains without the director disruption. The domain size decreases with the decreasing temperature, the percentage of the antiferroelectric decouplings increases, and M2 exhibits the first-order phase transition into proper ferroelectric MP. With the increasing temperature the domain size in the M2 phase increases, the domination of particular polar orientation of molecules reduces, and finally, the domain size diverges at particular temperature corresponding to the second-order phase transition from M2 to paraelectric M1. Variations of the polar and nonpolar orientational order parameters are estimated within each phase and between the phases. Our experimental and computer simulation results (also presented in the paper) fully support our theoretical findings.