Vibrational study of CO, O, and H Adsorbed on the CoCrFeNi (110) High Entropy Alloy Surface.

The vibrational properties of CO, O, and H molecularly or dissociatively adsorbed on a CoCrFeNi(110) surface have been probed using high-resolution energy loss spectroscopy (HREELS) and modeled using density functional theory (DFT) calculations. Large (∼20 mm) single-crystal, quaternary face-centered cubic CoCrFeNi was synthesized via a modified Czochralski technique. We show strong evidence that CO adsorbs primarily on bridge and on-top sites in compositionally varied local environments, which reflect the random, multielemental surface composition inherent in a high entropy alloy.

Advancing Heteroanionicity in Zintl Phases: Crystal Structures, Thermoelectric and Magnetic Properties of Two Quaternary Semiconducting Arsenide Oxides, EuZnAsO and EuZnAsO.

Two novel quaternary oxyarsenides, EuZnAsO and EuZnAsO, were synthesized through metal flux reactions, and their crystal structures were established by single-crystal X-ray diffraction methods. EuZnAsO crystallizes in the orthorhombic space group , featuring polyanionic ribbons composed of corner-shared triangular [ZnAs] units, running along the [100] direction. The structure of EuZnAsO crystallizes in the monoclinic space group 2/ and its anionic substructure can be described as an infinite "ribbonlike" chain comprised of [ZnAs] trigonal-planar units, although the structural complexity here is greater and also amplified by disorder on multiple crystallographic positions.

It Runs in the BaAl Family: Relating the Structure and Properties of Middle Child LnCoGe (Ln = Pr, Nd, and Sm) to its Siblings LnCoGe and LnCoGe.

The BaAl prototype structure and its derivatives have been identified to host several topological quantum materials and noncentrosymmetric superconductors. Single crystals up to ∼3 mm × 3 mm × 5 mm of LnCoGe (Ln = Pr, Nd, and Sm) are obtained via flux growth utilizing Sn as metallic flux. The crystal structure is isostructural to the LuCoSi structure type in the crystallographic space group 2/.

CoCrFeNi High-Entropy Alloy as an Enhanced Hydrogen Evolution Catalyst in an Acidic Solution.

High-entropy alloys (HEAs) have intriguing material properties, but their potential as catalysts has not been widely explored. Based on a concise theoretical model, we predict that the surface of a quaternary HEA of base metals, CoCrFeNi, should go from being nearly fully oxidized except for pure Ni sites when exposed to O to being partially oxidized in an acidic solution under cathodic bias, and that such a partially oxidized surface should be more active for the electrochemical hydrogen evolution reaction (HER) in acidic solutions than all the component metals. These predictions are confirmed by electrochemical and surface science experiments: the Ni in the HEA is found to be most resistant to oxidation, and when deployed in 0.

Annihilation and Control of Chiral Domain Walls with Magnetic Fields.

The control of domain walls is central to nearly all magnetic technologies, particularly for information storage and spintronics. Creative attempts to increase storage density need to overcome volatility due to thermal fluctuations of nanoscopic domains and heating limitations. Topological defects, such as solitons, skyrmions, and merons, may be much less susceptible to fluctuations, owing to topological constraints, while also being controllable with low current densities.

Magnetic order and fluctuations in the quasi-two-dimensional planar magnet .

We use neutron scattering to investigate spin excitations in , which has a -axis incommensurate helical structure of the two-dimensional (2D) in-plane ferromagnetic (FM) ordered layers for . By comparing the wave vector and energy dependent spin excitations in helical ordered and paramagnetic , we find that Ni doping, while increasing lattice disorder in , enhances quasi-2D FM spin fluctuations. However, our band structure calculations within the combined density functional theory and dynamic mean field theory (DFT+DMFT) failed to generate a correct incommensurate wave vector for the observed helical order from nested Fermi surfaces.

Controllable organic magnetoresistance in polyaniline coated poly(p-phenylene-2,6-benzobisoxazole) short fibers.

Herein, we first report a tunable organic magnetoresistance (OMAR) effect in polyaniline (PANI) coated acid treated poly(p-phenylene-2,6-benzobisoxazole) (t-PBO) short fibers. This unique OMAR is interpreted using the paramagnetic nature of PBO molecules combined with the localization length a0 calculated from the wave-function shrinkage model and forward interference model.

Ir d-band derived superconductivity in the lanthanum-iridium system LaIr.

The electronic properties of the heavy metal superconductor [Formula: see text] are reported. The estimated superconducting parameters obtained from physical properties measurements indicate that [Formula: see text] is a BCS-type superconductor. Electronic band structure calculations show that Ir d-states dominate the Fermi level.

Synthesis and characterization of a series of nickel(ii) alkoxide precursors and their utility for Ni(0) nanoparticle production.

A series of nickel(ii) aryloxide ([Ni(OAr)(py)]) precursors was synthesized from an amide-alcohol exchange using [Ni(NR)] in the presence of pyridine (py). The H-OAr selected were the mono- and di-ortho-substituted 2-alkyl phenols: alkyl = methyl (H-oMP), iso-propyl (H-oPP), tert-butyl (H-oBP) and 2,6-di-alkyl phenols (alkyl = di-iso-propyl (H-DIP), di-tert-butyl (H-DBP), di-phenyl (H-DPhP)). The crystalline products were solved as solvated monomers and structurally characterized as [Ni(OAr)(py)], where x = 4: OAr = oMP (1), oPP (2); x = 3: OAr = oBP (3), DIP (4); x = 2: OAr = DBP (5), DPhP (6).

Magnetoresistive polyaniline-silicon carbide metacomposites: plasma frequency determination and high magnetic field sensitivity.

The Drude model modified by Debye relaxation time was introduced to determine the plasma frequency (ωp) in the surface initiated polymerization (SIP) synthesized β-silicon carbide (β-SiC)/polyaniline (PANI) metacomposites. The calculated plasma frequency for these metacomposites with different loadings of β-SiC nanoparticles was ranging from 6.11 × 10(4) to 1.

Manipulating the dimensional assembly pattern and crystalline structures of iron oxide nanostructures with a functional polyolefin.

Controlled crystalline structures (α- and γ-phase) and assembly patterns (1-D, 2-D and 3-D) were achieved in the synthesized iron oxide (Fe2O3) nanoparticles (NPs) using polymeric surfactant-polypropylene grafted maleic anhydride (PP-g-MA) with different concentrations. In addition, the change of the crystalline structure from the α- and γ-phase also led to the significantly increased saturation magnetization and coercivity.

Strengthened Magnetoresistive Epoxy Nanocomposite Papers Derived from Synergistic Nanomagnetite-Carbon Nanofiber Nanohybrids.

Novel papers based on epoxy nanocomposites with magnetite and carbon nanofiber (CNF) nanohybrids, without any surface modification to the nanofillers, show combined conductive, magnetic, and magnetoresistive properties. Negative magnetoresistance (MR) is observed in synthesized epoxy nanohybrid papers for the first time. These papers have potential applications for flexible electronics, magnetoresistive sensors, and the printing industry.

Magnetoresistive polyaniline/multi-walled carbon nanotube nanocomposites with negative permittivity.

Contrary to the observed positive giant magnetoresistance (GMR) in as-received multi-walled carbon nanotubes (MWNTs), pure polyaniline (PANI) synthesized with Cr(vi) as oxidant and MWNTs/PANI nanocomposites with ammonium persulfate (APS) as oxidant, a room temperature negative GMR of around -2% was reported in MWNTs/PANI nanocomposites with Cr(vi) as oxidant. Different from a frequency switch of permittivity from negative to positive in MWNTs/PANI nanocomposites with APS as oxidant, unique negative permittivity was observed in MWNTs/PANI nanocomposites with Cr(vi) as oxidant within the measured frequency range from 20 to 2 × 10(6) Hz. The obtained unique negative permittivity was explained by the plasma frequency from the Drude model, at which the permittivity changes from negative to positive and the material changes from a metamaterial to an ordinary dielectric medium.

One-pot synthesis of size- and morphology-controlled 1-D iron oxide nanochains with manipulated magnetic properties.

Polypropylene grafted maleic anhydride (PP-MA, 2500 g mole(-1)) has demonstrated its unique capability to synthesize 1-D ferromagnetic hard (292.7 Oe) γ-Fe2O3 nanochains made of ~24 nm nanoparticles vs. PP-MA with 8000 g mole(-1) for the synthesis of 1-D ferromagnetic soft (70.

Giant magnetoresistance in non-magnetic phosphoric acid doped polyaniline silicon nanocomposites with higher magnetic field sensing sensitivity.

Phosphoric acid doped conductive polyaniline (PANI) polymer nanocomposites (PNCs) reinforced with silicon nanopowders have been successfully synthesized using a facile surface initiated polymerization (SIP) method. The chemical structures of the nanocomposites are characterized using Fourier transform infrared (FT-IR) spectroscopy. The enhanced thermal stability of the silicon-PANI PNCs compared with pure PANI is obtained using thermogravimetric analysis (TGA).

Investigation of Fe incorporation in LnCr2Al20 (Ln = La, Gd, Yb) with 57Fe Mössbauer and single crystal X-ray diffraction.

Crystal growth, structure determination, and magnetic properties of LnCr2Al(20-x)Fe(x) (Ln = La, Gd, Yb) adopting the CeCr2Al20 structure type with space group Fd3m, a ∼ 14.5 Å, are reported. Single crystal X-ray diffraction and Mössbauer spectroscopy are employed to fully characterize the crystal structure of LnCr2Al(20-x)Fe(x) (Ln = La, Gd, Yb).

Synthesis, structure, and properties of Ln2Ru3Al15 (Ln = Ce, Gd): comparison with LnRu2Al10 and CeRu4(Al,Si)(15.58).

Ln2Ru3Al15 (Ln = Ce, Gd) have been synthesized, and the competition between the growth of Ce2Ru3Al15 and CeRu2Al10 has been studied. The structure of Ce2Ru3Al15 was modified from the previously reported Ce2Ru3Al15 structure, and the structure of Gd2Ru3Al15 was determined for the first time. The magnetic and transport properties of Ln2Ru3Al15 were measured and compared to the properties of LnRu2Al10.

Morphology and phase controlled cobalt nanostructures in magnetic polypropylene nanocomposites: the role of alkyl chain-length in maleic anhydride grafted polypropylene.

A novel function of maleic anhydride grafted polypropylene (PP) with different backbone chain-lengths was demonstrated, i.e., in controlling the cobalt morphologies (dispersed polyhedral vs.

Microwave synthesized magnetic tubular carbon nanocomposite fabrics toward electrochemical energy storage.

Contrary to the helical carbon structure from pure cotton fabrics under microwave heating and radical oxidized ignition of nanoparticles from conventional heating, magnetic carbon tubular nanocomposite fabrics decorated with uniformly dispersed Co-Co(3)O(4) nanoparticles were successfully synthesized via a microwave heating process using cotton fabric and inorganic salt as precursors, which have shown better anti-corrosive performance and demonstrated great potential as novel electrochemical pseudocapacitor electrode.

Structural complexity meets transport and magnetic anisotropy in single crystalline Ln30Ru4Sn31 (Ln = Gd, Dy).

We present the structure of Ln(30)Ru(4+x)Sn(31-y) (Ln = Gd, Dy) and the anisotropic resistivity, magnetization, thermopower, and thermal conductivity of single crystal Ln(30)Ru(4+x)Sn(31-y) (Ln = Gd, Tb). Gd(30)Ru(4.92)Sn(30.

Magnetic carbon nanostructures: microwave energy-assisted pyrolysis vs. conventional pyrolysis.

Magnetic carbon nanostructures from microwave assisted- and conventional-pyrolysis processes are compared. Unlike graphitized carbon shells from conventional heating, different carbon shell morphologies including nanotubes, nanoflakes and amorphous carbon were observed. Crystalline iron and cementite were observed in the magnetic core, different from a single cementite phase from the conventional process.

Polyaniline stabilized magnetite nanoparticle reinforced epoxy nanocomposites.

Magnetic epoxy polymer nanocomposites (PNCs) reinforced with magnetite (Fe(3)O(4)) nanoparticles (NPs) have been prepared at different particle loading levels. The particle surface functionality tuned by conductive polyaniline (PANI) is achieved via a surface initiated polymerization (SIP) approach. The effects of nanoparticle loading, surface functionality, and temperature on both the viscosity and storage/loss modulus of liquid epoxy resin suspensions and the physicochemical properties of the cured solid PNCs are systematically investigated.

Synthesis, structure, and physical properties of Ln(Cu,Al,Ga)(13-x) (Ln = La-Pr, and Eu) and Eu(Cu,Al)(13-x).

Ln(Cu,Al,Ga)(13-x) (Ln = La-Pr, and Eu; x ~ 0.2) were synthesized by a combined Al/Ga flux. Single crystal X-ray and neutron diffraction experiments revealed that these compounds crystallize in the NaZn(13) structure-type (space group Fm3[overline]c) with lattice parameters of a ~ 12 Å, V ~ 1600 Å, and Z ~ 8.

Magnetic and transport properties of single crystal LnRu2Al10 (Ln = Pr, Gd, Yb).

Single crystals of LnRu(2)Al(10) (Ln = Pr, Gd, Yb) have been grown using the self-flux method, their structure has been determined by single crystal x-ray diffraction, and their magnetic and electronic transport properties have been studied. LnRu(2)Al(10) are members of the Y bFe(2)Al(10) structure type with space group Cmcm. PrRu(2)Al(10) displays paramagnetic behaviour down to 13.