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Two-dimensional (2D) ferromagnets have attracted significant interest for their potential in spintronic device miniaturization, especially since the discovery of ferromagnetic ordering in monolayer materials such as CrI3 and Fe3GeTe2 in 2017. This study presents a detailed investigation into the effects of the Hubbard U parameter, biaxial strain, and structural distortions on the magnetic characteristics of T″-phase VTe2. We demonstrate that setting the Hubbard U to 0 eV provides an accurate representation of the observed structural, magnetic, and electronic features for both bulk and monolayer T″-phase VTe2. The application of strain reveals two distinct ferromagnetic states in the monolayer T″-phase VTe2, each characterized by minor structural differences, but notably different magnetic moments. The T″-1 state, with reduced magnetic moments, emerges under compressive strain, while the T″-2 state, featuring increased magnetic moments, develops under tensile strain. Our analysis also compares the magnetic anisotropy between the T and T″ phases of VTe2, highlighting that the periodic lattice distortion in the T″-phase induces an in-plane anisotropy, which makes it a material with an easy-axis of magnetization. Monte Carlo simulations corroborate our findings, indicating a high Curie temperature of approximately 191 K for the T″-phase VTe2. Our research not only sheds light on the critical aspects of the VTe2 system but also suggests new pathways for enhancing low-dimensional magnetism, contributing to the advancement of spintronics and straintronics. [ABSTRACT FROM AUTHOR]

Internal photoemission of electrons (IPE) from large area one monolayer 2H‐MoS2 films synthesized on top of amorphous (a−) SiO2 or Al2O3 is used to determine the energy of the semiconductor valence band (VB) relative to the reference level of the insulator conduction band (CB). This allows us to compare the VB top energy in MoS2 to that of the (100)Si substrate crystal at the interface with the same insulator. Despite the CB in a–Al2O3 is found to be ≈1 eV below that in SiO2 as measured relative to the Si VB edge, the authors observe nearly no shift of the spectral threshold in the case of IPE from the MoS2 VB. This observation indicates violation of electroneutrality at the MoS2/a–Al2O3 interface causing an increase in barrier by ≈1 eV. This conclusion is supported by the much weaker field dependence of the IPE threshold at the MoS2/a–Al2O3 interface compared to the MoS2/a–SiO2 one, suggesting the presence of negative charges and/or interface dipoles. Therefore, the commonly accepted electron affinity rule (EAR) appears to be not appropriate to describe the band alignment at 2D/insulator interfaces. [ABSTRACT FROM AUTHOR]

Kerosene-fueled high velocity oxy-fuel (HVOF) spray was employed to deposit commercial Ti 2 AlC MAX phase powders onto Inconel 600 substrates. After optimizing three process parameters including flow rates of kerosene and oxygen as well as spray distance, a dense Ti 2 AlC coating with a very low decomposition was obtained. Using Rietveld phase analysis of the X-ray diffraction pattern, the weight percentage of Ti 2 AlC in the coating was determined to be 53.0%, which is not only far better than the coating deposited by plasma spray, but also is comparable with the optimum Ti 2 AlC coatings sprayed by H 2 -fueled HVOF and cold spray. This optimized Ti 2 AlC coating was further analyzed by a variety of techniques to probe its surface chemistry, morphology, cross-sectional microstructure, mechanical properties and salt fog corrosion resistance. [ABSTRACT FROM AUTHOR]

Plasma spraying was employed to spray commercial Ti 2 AlC MAX phase powders onto Inconel 600 substrates. Effects of different process parameters, including arc current, flow rates of primary Ar, secondary H 2 and carrier Ar, powder feedrate, spray distance as well as presence of cooling air on the backside on the substrate were systematically screened by evaluating the content of Ti 2 AlC in the coating through X-ray diffraction and Rietveld phase analysis. The highest content of the remaining Ti 2 AlC in the coating was achieved to be 26.0%. The coating with 26.0 wt% of Ti 2 AlC was further analyzed by a variety of techniques to probe its surface chemistry, morphology, cross-sectional microstructure, mechanical properties and salt fog corrosion resistance. [ABSTRACT FROM AUTHOR]

The surface‐enhanced Raman scattering (SERS) as a novel and efficient analytic technique to probe molecules has attracted tremendous attention. Semiconducting substrates have been widely investigated for their applications into SERS because of their easy integration with electronic devices. In this work, a wafer‐scale semiconducting MoS2 monolayer (2H‐MoS2‐ML) without additional treatment is used as the SERS substrate, which shows the naturally formed MoS2 ML has excellent chemical stability, high uniformity, and high sensitivity. It is found that the detection concentration limit can reach 1 × 10−8m and the enhancement factor is about 4.5 × 106 for the rhodamine 6G (R6G) under a 532 nm excitation laser, which is the highest SERS performance observed on 2H‐MoS2‐ML up to now. The experimental and computational studies reveal that the photo‐enhanced charge transfer coupled with molecule resonance contribute to remarkable SERS. In addition to R6G, 2H‐MoS2‐ML shows good SERS signals on the detection of amaranth and crystal violet too. The findings not only provide an insightful understanding of the mechanism for the improved SERS performance of semiconducting transition‐metal dichalcogenides (TMDs) MLs, but are helpful for the design of novel SERS substrates. It is expected that the wafer‐scale TMDs may find practical applications in SERS. [ABSTRACT FROM AUTHOR]

Ti 2 AlN MAX-phase thin films have been deposited on MgO (1 1 1) substrates between 500 and 750 °C using DC reactive magnetron sputtering of a Ti 2 Al compound target in a mixed N 2 /Ar plasma. The composition, crystallinity, morphology and hardness of the thin films have been characterized by X-ray photoelectron spectroscopy, X-ray diffraction, atomic force microscopy and nano-indentation, respectively. The film initially forms a mixture of Ti, Al and (Ti,Al)N cubic solid solution at 500 °C and nucleates into polycrystalline Ti 2 AlN MAX phases at 600 °C. Its crystallinity is further improved with an increase in the substrate temperature. At 750 °C, a single-crystalline Ti 2 AlN (0 0 0 2) thin film is formed having characteristic layered hexagonal surface morphology, high hardness, high Young's modulus and low electrical resistivity. The mechanism behind the evolution of the microstructure with growth temperature is discussed in terms of surface energies, lattice mismatch and enhanced adatom diffusion at high growth temperatures. [ABSTRACT FROM AUTHOR]

• The magnetic properties of 2D chromium tellurides depend strongly on the structures. • Both the magnetic coupling and anisotropy can be tuned by bi-axial strains effectively. • The results can be well understood by the Cr-Cr direct exchange and second order perturbation theory. Two-dimensional (2D) chromium tellurides have attracted considerable research interest for their high Curie temperatures. Their magnetic properties have been found diverse in various experiments, the understanding of which however remains limited. In this work, we report that the magnetic ordering of ultrathin chromium tellurides is structure dependent and can be tuned by external strain. Based on first-principles calculations and Monte Carlo simulations, we show long-range stable magnetism with high and low Curie temperature, and short-range magnetism in 2D Cr 5 Te 8 , CrTe 2 , and Cr 2 Te 3 layers, respectively. We further find that ferromagnetic-to-antiferromagnetic transition can be realized by 2% compressive strain for CrTe 2 and 2% tensile strain for Cr 2 Te 3 , and their magnetic easy axis is tuned from out-of-plane to in-plane by the medium tensile and compressive strain. This strain dependent magnetic coupling is found to be related to Cr-Cr direct exchange and the change of magnetic anisotropy is understood by the atom and orbital resolved magnetic anisotropy energy and second order perturbation theory. Our results reveal the important roles of the structure and strain in determining the magnetic ordering in 2D chromium telluride, shedding light on understanding of the diverse magnetic properties observed in experiments. [ABSTRACT FROM AUTHOR]

Volatile organic compounds (VOCs) emitted from industrial processes, which are major emission sources of air pollutants, could cause significant impacts on air quality. However, studies on the comprehensive analysis from sources contributing to the health risk perspective regarding ambient VOCs in industrial cities are limited. In this study, VOC samples were collected from 15 April 2018 to 19 October 2018 in Changzhi, a typical industrial city in northern China, and a total of 57 VOCs were measured for analysis. The average VOC concentrations were 54.4 µg·m−3, with the highest concentrations in autumn (58.4 µg·m−3). Ambient VOCs in spring, summer and autumn were all dominated by alkanes (66.8%), with contributions of 70.3%, 66.3% and 63.8%, respectively. The top five concentrations of total VOCs were isopentane (19.0%), ethane (9.5%), n-butane (8.1%), benzene (7.9%) and propane (5.2%), indicating that vehicle exhaust and coal combustion are the main sources of VOCs. Source apportionment by principal component analysis showed that vehicle exhaust (27.5%) and coal combustion (23.5%) were the main sources of VOCs in Changzhi, followed by industrial production (17.4%), solvent evaporation (13.5%), liquefied petroleum gas/natural gas leaking (9.5%), and biogenic emissions (8.7%). Sources of coal combustion and vehicle exhaust contributed more VOCs than industrial production. The carcinogenic risks of benzene (3.4 × 10−5) and ethylbenzene (2.2 × 10−6) were higher than the limit levels (1 × 10−6). Coal combustion contributed most (25.3%) to the carcinogenic risks because of its high VOC emissions. In an industrial city such as Changzhi, vehicle exhaust and coal combustion have become major sources of ambient air VOCs owing to the increasingly stringent industrial standards. Therefore, VOCs from vehicle exhaust and coal combustion also need to take into account mitigation measures for VOCs from the perspective of source contribution to health risk. [ABSTRACT FROM AUTHOR]

Abstract: We report the orientation control of crystalline Ge (111) and Ge (001) growth on SrTiO3 (100) substrate by adjusting the temperature of substrate. It is found that the substrate temperature plays an important role for the formation of crystalline Ge with different surface orientations and interfacial chemical configuration during the sputtering process. At 500°C, Ge (111) with good crystalline quality is formed, while Ge (001) is preferably grown on SrTiO3 substrate at 650°C. Our results show the possibility of manipulating the surface orientations during Ge growth on SrTiO3 by controlling the substrate temperatures. [Copyright &y& Elsevier]

We present a stoichiometry-dependent structural phase transition in SrRuO3 film on SrTiO3 substrate. The oxygen stoichiometry in the films was varied by changing the oxygen partial pressure P(O2) during the deposition process. For SrRuO3 films with P(O2) ≥ 60 mTorr, they exhibited a pseudo-orthorhombic structure with in-plane uniaxial magnetic anisotropy. On the other hand for films with P(O2) ≤ 45 mTorr, the tetragonal SrRuO3 phase with a perpendicular uniaxial magnetic anisotropy was stabilized at room temperature. The big difference in the magnetic anisotropy of these two SrRuO3 phases was shown to be closely linked to their respective RuO6 octahedral rotation patterns: the RuO6 octahedra rotate differently along the two orthogonal in-plane directions in the pseudo-orthorhombic phase, whereas in the tetragonal phase only octahedral rotations around z-axis are present and the octahedral tilts along the in-plane axes are diminished. First-principles calculations show that such a suppression of the RuO6 octahedra tilting in the tetragonal phase arises from the oxygen vacancies at the octahedral apex (along z-axis). This work demonstrates that the stoichiometry plays an important role in determining the octahedral rotations and tilts in the perovskite materials, which may induce new phases with distinctively different structural symmetry and physical property. [ABSTRACT FROM AUTHOR]

Abstract To alleviate the delamination of Ti 2 AlC-rich coating upon oxidation at 600 °C, a 270 μm thick TiC-Ti 2 AlC composite coating was prepared by plasma spraying the Ti 2 AlC MAX powders onto Inconel substrates. Thermal decomposition of Ti 2 AlC during spray introduced heavy content of TiC in the coating. These TiC-Ti 2 AlC coatings' morphology, crystalline structure and microstructure as a function of oxidation temperature from 200 to 1000 °C were investigated under scanning electron microscope, X-ray diffraction and optical microscope. The coating adhered strongly to the substrate throughout the entire temperature range without delamination, demonstrating decent oxidation resistance of the TiC-Ti 2 AlC composite coating and the viability of TiC as a beneficial secondary reinforcement phase. Highlights • TiC was introduced into Ti 2 AlC coating via thermal decomposition during plasma spray. • This TiC-Ti 2 AlC composite coating was adherent and oxidation resistant below 1000 °C. • TiC is effective in enhancing coating's hardness and circumvents delamination at 600 °C. [ABSTRACT FROM AUTHOR]

Isothermal oxidation of 100 μm Ti 2 AlC coatings deposited by kerosene-fuelled high velocity oxy-fuel spray have been carried out between 200 and 1000 °C for 5 h at 200 °C intervals. The development of coating’s crystalline phase, surface morphology and cross-sectional microstructure with respect to oxidation temperature has been investigated by X-ray diffraction with Rietveld phase analysis, optical microscope and scanning electron microscope. The coating maintained its phase composition and morphology till 400 °C, but was severely oxidized at 600 °C and above. A good temperature window for Ti 2 AlC would be below 1000 °C and avoid direct oxidation at 600 °C. [ABSTRACT FROM AUTHOR]

Exploring earth-abundant electrocatalysts with high activity and low-cost for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is vital to energy harvesting and storage, such as fuel cell and effective overall water splitting. Herein, novel heterostructures (Ni 3 S 2 /VS 2 ) without nitrogen (N) and with N doping are reported as superior electrocatalysts for the OER and HER, respectively. The heterostructure without doping shows enhanced OER performance with an extremely low overpotential (227 mV at 10 mA/cm 2 ) due to increased active sites and fantastic interfaces as well as unique structure. Moreover, N-doped Ni 3 S 2 /VS 2 (N-Ni 3 S 2 /VS 2 ) shows high electrocatalytic HER performance with a low HER overpotential (151 mV at 10 mA/cm 2 ), because the N-doping greatly improves conductivity and increases large amounts of catalytic active sites. Finally, we construct a two-electrode electrolyzer system (Ni 3 S 2 /VS 2 //N-Ni 3 S 2 /VS 2 ) and it achieves a current density of 10 mA/cm 2 at a low cell voltage of 1.648 V. Our findings demonstrate that structure design and doping can effectively improve the catalytic activities of nanomaterials for OER and HER. [ABSTRACT FROM AUTHOR]

Abstract: Developing catalysts to improve charge‐carrier transfer and separation is critical for efficient photocatalytic applications driven by low‐energy photons. van der Waals stacking of 2D materials has opened up opportunities to engineer heteromaterials for strong interlayer excitonic transition. However, fabrication of 2D heteromaterials with clean and seamless interfaces remains challenging. Here, a 2D tungsten carbide/tungsten trioxide (WC/WO3) heterogeneous hybrid in situ synthesized by a chemical engineering method has been reported. The hybrid comprises of layer‐by‐layer stacked WC and WO3 monolayers. The WC and specific interfacial interfaces between the WC and WO3 layers exhibit synergetic effects, promoting interfacial charge transfer and separation. Binderless WC performing platinum‐like behavior works as a potential substitute for noble metals and accelerates multielectron oxygen reduction, consequently speeding up the photocatalytic decomposition of organic compounds over the WO3 catalyst. The specific interfacial interaction between WC and WO3 layers potentially improves interfacial charge transfer from conduction band of WO3 to WC. In the absence of noble metals, the WC/WO3 hybrid as a catalyst exhibits distinct decomposition of organic compounds with vis–NIR light (λ = 400–800 nm). This finding provides a cost‐effective approach to capture low‐energy photons in environmental remediation applications. [ABSTRACT FROM AUTHOR]

Oxidation of commercial Ti 2 AlC MAX phase powders at 200–1000 °C has been investigated by XRD, XPS, SEM, STA and TGA coupled with FTIR. These powders are a mixture of Ti 2 AlC, Ti 3 AlC 2 , TiC and Ti 1.2 Al 0.8 . Oxidation at 400 °C led to disappearance of carbide phases from Ti 2p, Al 2p and C 1s XPS spectra. At 600 °C, powders changed from dark grey to light grey with a significant volume increase due to crack formation. Powders were severely oxidized by detecting rutile with minor anatase TiO 2 . At 800 °C, α-Al 2 O 3 was detected while anatase transformed into rutile TiO 2 . The cracks were healed and disappeared. At 1000 °C, the Ti 2 AlC powders were fully oxidized into rutile TiO 2 and α-Al 2 O 3 with a change of powder color from light grey to yellow. FTIR detected the release of C as CO 2 from 200 °C onwards but with additional CO above 800 °C. [ABSTRACT FROM AUTHOR]

We report 2D microporous carbon sheets with high surface area, derived from eggplant via simple carbonization and KOH activation, as low cost yet efficient bifunctional catalysts for high performance rechargeable zinc–air batteries. [ABSTRACT FROM AUTHOR]

Abstract: An in situ X-ray photoelectron emission investigation revealed that the size trend of the 2p3/2 binding-energy shift (BES) of Ni nanoclusters grown on SiO2 substrate follows the prediction of the bond order–length–strength (BOLS) correlation theory . Theoretical reproduction of the measurements turns out that the 2p3/2 binding energy of an isolated Ni atom is 850.51eV and its intrinsic bulk shift is 2.70eV. Findings confirmed that the skin-depth local strain and potential well quantum trapping induced by the shorter and stronger bonds between under-coordinated surface atoms provide perturbation to the Hamiltonian and hence dominate the size dependent BES. [Copyright &y& Elsevier]

• Cracks can be identified in nearly every Ti 2 AlC powder after oxidation for ≥1 h at 600 °C. • Longer oxidation duration at 600 °C lead to an increase in Ti 2 AlC powders' volume and weight. • Ti 2 AlC phase was still preserved but with strong TiO 2 and Al 2 O 3 after 16 hs at 600 °C. • DFT calculation showed that Ti 2 AlC slabs with surface terminated by Al 2 O 3 or TiO 2 is stable. • Oxygen inward diffusion into Ti-Al layer without Al out-diffusion at 600 °C cracks the Ti 2 AlC. Planar cracks tend to form in Al-containing M n+1 AX n phase materials after oxidation at an intermediate temperature range between 550 and 650 °C, although they have outstanding oxidation resistance beyond 1200 °C. Herein, Ti 2 AlC M n+1 AX n phase powders are employed as a model example to investigate such laminar cracks formation at 600 °C, accompanying with continuous volume expansion and weight increment with oxidation duration. Coupled with the crystallinity structure development during oxidation, density function theory calculation has been performed to elucidate the origin of such anomalous behavior at 600 °C for Ti 2 AlC, which can be applicable to other M n+1 AX n phase materials. [ABSTRACT FROM AUTHOR]