Coupling between phase transitions and glassy magnetic behaviour in Heusler alloy Ni 50 Mn 34 In 8 Ga 8

Abstract: The transition sequence in the Heusler alloy Ni50Mn34In8Ga8 has been determined from measurements of elasticity, heat flow and magnetism to be paramagnetic austenite → paramagnetic martensite → ferromagnetic martensite at ∼335 and ∼260 K, respectively, during cooling. The overall pattern of elastic stiffening/softening and acoustic loss is typical of a system with bilinear coupling between symmetry breaking strain and the driving structural/electronic order parameter, and a temperature interval below the transition point in which ferroelastic twin walls remain mobile under the influence of external stress. Divergence between zero-field-cooling and field-cooling determinations of DC magnetisation below ∼220 K indicates that a frustrated magnetic glass develops in the ferromagnetic martensite. An AC magnetic anomaly which shows Vogel–Fulcher dynamics in the vicinity of ∼160 K is evidence of a further glassy freezing process. This coincides with an acoustic loss peak and slight elastic stiffening that is typical of the outcome of freezing of ferroelastic twin walls. The results suggest that local strain variations associated with the ferroelastic twin walls couple with local moments to induce glassy magnetic behaviour

Coupling between phase transitions and glassy magnetic behaviour in Heusler Alloy Ni50Mn34In8Ga8

The transition sequence in the Heusler alloy Ni50Mn34In8Ga8 has been determined from measurements of elasticity, heat flow and magnetism to be paramagnetic austenite → paramagnetic martensite → ferromagnetic martensite at ~335 and ~260 K, respectively, during cooling. The overall pattern of elastic stiffening/softening and acoustic loss is typical of a system with bilinear coupling between symmetry breaking strain and the driving order parameter in a temperature interval below the transition point in which ferroelastic twin walls remain mobile under the influence of external stress. Divergence between zero-field-cooling (ZFC) and field-cooling (FC) determinations of DC magnetisation below ~220 K indicates that a frustrated magnetic glass develops in the ferromagnetic martensite. An AC magnetic anomaly which shows Vogel-Fulcher dynamics in the vicinity of ~160 K is evidence of a further glassy freezing process. This coincides with an acoustic loss peak and slight elastic stiffening that is typical of the outcome of freezing of ferroelastic twin walls. The results indicate that local strain variations associated with the ferroelastic twin walls couple with local moments to induce glassy magnetic behaviour

Optical phonons, OH vibrations, and structural modifications of phlogopite at high temperatures: An in-situ infrared spectroscopic study

The thermal behavior of optical phonons and OH vibrations of phlogopite (a trioctahedral mica) was examined at temperatures up to 1000 K using in situ infrared spectroscopy. The results showed that with increasing temperature, O–K bands in phlogopite exhibited a relatively strong variation in frequency in a manner similar to those in muscovite. The work revealed that different types of OH bands (fundamentals and combinations) have very different thermal behavior or temperature dependence, and their absorption coefficients are commonly not constant on heating. OH combination bands that are associated with summation processes of multi-phonon interactions commonly show a decrease in their intensities on heating, but in contrast combination bands due to difference processes generally exhibit an increase. This means that temperature dependencies of their absorption coefficients need to be considered when using the Beer-Lambert law to determine or estimate OH contents or hydrogen concentrations at high temperatures. The results showed a structural anomaly associated with a discontinuity in the temperature derivative of the wavenumber of Al–O and Si–O vibrations and O–H stretching near 600 K. However, framework-related phonon modes in the FIR and MIR regions do not suggest a break of the original monoclinic structural symmetry in the investigated temperature region. The complex changes are attributed to temperature-induced alteration of local configuration involving TO4 tetrahedra and a possible change of the orientation of OH dipoles, in addition to a previously reported distortion of MO6 octahedra. Increasing temperature to 1000 K also causes partial dehydroxylation, as evidenced by the disappearance of the OH band near 3623 cm−1 and the decrease in OH band height and area of other OH bands. The study did not record the formation of H2O inside phlogopite as a result of partial dehydroxylation. The work offers new data and findings that have important implications in understanding the complex structural modifications and the behavior of phonon modes and the thermal stability of hydroxyls on approaching the dehydroxylation, as well as the way hydrogen is released from micas at high temperatures. Our data also show that phologpite becomes less transparent with increasing temperature suggesting a change of radiative properties and ability to transmit heat, which could be of interest for modeling thermal-transmission in crustal rocks

Optical phonons, OH vibrations, and structural modifications of phlogopite at high temperatures: An in-situ infrared spectroscopic study

The thermal behavior of optical phonons and OH vibrations of phlogopite (a trioctahedral mica) was examined at temperatures up to 1000 K using in situ infrared spectroscopy. The results showed that with increasing temperature, O–K bands in phlogopite exhibited a relatively strong variation in frequency in a manner similar to those in muscovite. The work revealed that different types of OH bands (fundamentals and combinations) have very different thermal behavior or temperature dependence, and their absorption coefficients are commonly not constant on heating. OH combination bands that are associated with summation processes of multi-phonon interactions commonly show a decrease in their intensities on heating, but in contrast combination bands due to difference processes generally exhibit an increase. This means that temperature dependencies of their absorption coefficients need to be considered when using the Beer-Lambert law to determine or estimate OH contents or hydrogen concentrations at high temperatures. The results showed a structural anomaly associated with a discontinuity in the temperature derivative of the wavenumber of Al–O and Si–O vibrations and O–H stretching near 600 K. However, framework-related phonon modes in the FIR and MIR regions do not suggest a break of the original monoclinic structural symmetry in the investigated temperature region. The complex changes are attributed to temperature-induced alteration of local configuration involving TO4 tetrahedra and a possible change of the orientation of OH dipoles, in addition to a previously reported distortion of MO6 octahedra. Increasing temperature to 1000 K also causes partial dehydroxylation, as evidenced by the disappearance of the OH band near 3623 cm−1 and the decrease in OH band height and area of other OH bands. The study did not record the formation of H2O inside phlogopite as a result of partial dehydroxylation. The work offers new data and findings that have important implications in understanding the complex structural modifications and the behavior of phonon modes and the thermal stability of hydroxyls on approaching the dehydroxylation, as well as the way hydrogen is released from micas at high temperatures. Our data also show that phologpite becomes less transparent with increasing temperature suggesting a change of radiative properties and ability to transmit heat, which could be of interest for modeling thermal-transmission in crustal rocks

Carbon-Coated Li3V2(Po4)3 Derived From Metal-Organic Framework As Cathode For Lithium-Ion Batteries With High Stability

Recently, Metal-Organic Frameworks (MOFs) derived carbon-based materials have attract wide interest in electrochemical devices due to their large surface area and favorable conductivity. In this work, instead of using MOFs for direct carbon sources, we employed vanadium metal-organic framework (MIL-101(V)) precursor as both carbon sources and vanadium sources for synthesizing carbon-coated Li3V2(PO4)3 nanocomposites (LVP@M-101). The electrochemical property of LVP@M-101 has been investigated as cathode electrode at a voltage of 3.0–4.8 vs Li+/Li, to compare with Li3V2(PO4)3 prepared using V2O5. It is shown that the composite material displays a remarkably improved electrochemical stability with a high reversible capacity of 113.1 and 105.8 mA h g−1 at the rate of 0.5C and 1C after 1000 cycles, together with a superior rate performance at various current densities from 0.1C to 10C. Moreover, we have applied ex-situ PXRD and EPR spectroscopy to investigate the lithiation/delithiation process of LVP@M-101 electrode. Through detailed characterizations and electrochemical tests, we believe that the novel nanocomposites LVP@M-101 retain the two-phase transition nature of Li3V2(PO4)3 and the enhanced cathodic performance in lithium-ion battery is largely due to its unique structural stability

Transcriptomic response of Ralstonia solanacearum to antimicrobial Pseudomonas fluorescens SN15-2 metabolites

To develop efficient biocontrol agents, it is essential to investigate the response of soil-borne plant pathogens to such agents. For example, the response of Ralstonia solanacearum, the tomato wilt pathogen, to antimicrobial metabolites of Pseudomonas fluorescens is unknown. Thus, we assessed the effects of P. fluorescens SN15-2 fermentation broth on R. solanacearum by transmission electron microscopy and transcriptome technology. RNA sequencing identified 109 and 155 genes that are significantly up-regulated and down-regulated, respectively, in response to P. fluorescens metabolites, many of which are associated with the cell membrane and cell wall, and with nucleotide acid metabolism, iron absorption, and response to oxidative stress. This study highlights the effectiveness of P. fluorescens metabolites against the tomato wilt pathogen, and helps clarify the underlying molecular mechanisms.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

One-Pot Synthesis of Co-Based Coordination Polymer Nanowire for Li-Ion Batteries with Great Capacity and Stable Cycling Stability

Abstract Nanowire coordination polymer cobalt–terephthalonitrile (Co-BDCN) was successfully synthesized using a simple solvothermal method and applied as anode material for lithium-ion batteries (LIBs). A reversible capacity of 1132 mAh g−1 was retained after 100 cycles at a rate of 100 mA g−1, which should be one of the best LIBs performances among metal organic frameworks and coordination polymers-based anode materials at such a rate. On the basis of the comprehensive structural and morphology characterizations including fourier transform infrared spectroscopy, 1H NMR, 13C NMR, and scanning electron microscopy, we demonstrated that the great electrochemical performance of the as-synthesized Co-BDCN coordination polymer can be attributed to the synergistic effect of metal centers and organic ligands, as well as the stability of the nanowire morphology during cycling