SummaryA timescale algorithm demonstrating a clock ensemble utilizing commercial atomic clocks and multiplexing equipment has been established at the University of Alabama to serve as a testbed for research and student training.

We investigate the structural, static, and dynamic magnetic properties of epitaxial Heusler Co2Fe(Ti0.5Al0.5) (CFTA) alloy thin films with thickness varying from 6 nm to 80 nm grown by sputter beam epitaxy on cubic MgO(001), MgAl2O4(001), and hexagonal Al2O3(112̄0) substrates. X-ray diffraction measurements indicate epitaxial growth of CFTA thin films with B2 chemical ordering, with cubic [001] and [220] CFTA axes normal to the cubic and hexagonal substrates, respectively. Microstructure analysis of films grown on MgO substrates reveals a uniformly oriented epitaxial crystal with small variations consistent with strain distortions, providing an explanation for the relatively large X-ray rocking curve values found. Meanwhile, films on Al2O3(112̄0) substrates reveal columnar growth with frequent in-plane grain rotations. A pronounced four-fold magnetocrystalline anisotropy is observed in epitaxial thin films grown on cubic substrates. A pronounced uniaxial anisotropy for films grown on Al2O3(112̄0) substrates is observed. A saturation magnetization of ∼5.0μB/f.u. (where f.u. represents formula unit) is obtained at room temperature, slightly smaller compared to the expected value based on the Slater-Pauling rule. Ferromagnetic resonance spectroscopy finds an effective damping parameter and inhomogeneous linewidth broadening comparable to those found in parent compound Co2FeAl, which suggests that Ti substitution can be achieved without negatively affecting the magnetic properties of the system.

The Co-Ti-Sn family of alloys from their half-to full-Heusler compositions are synthesized. Co1.5TiSn, a compound predicted by our theoretical calculations, is successfully synthesized in the L21 structure with cobalt vacancies in the tetrahedral sites. The saturated magnetic moment at 5 K is measured to be similar to 0.6 mu B/formula unit, consistent with density functional theory (DFT) predictions of half-metallicity in the compound. A cluster expansion-based analysis of the alloy system indicates the Co1.5TiSn compound to be nearly on the convex hull, within DFT accuracy. Our experimental realization of the Co1.5TiSn compound suggests that it is either kinetically or entropically stabilized. (c) 2022 Elsevier B.V. All rights reserved.

Elemental substitution by a different element is a well utilized technique of stabilizing a single-phase compound, in case the parent alloy is multi-phase, and this has been demonstrated specifically in a number of Heusler systems. This can, however, give an increased propensity for chemical disorder as well as adding complexity to synthesis and characterization.In this paper, we present the successful synthesis of a single-phase compound, Co2Fe1.25Ge0.75, by tuning the parent Co2FeGe stoichiometry (which exhibits multi-phase structure) rather than introducing a fourth element. The compound is found to crystallize in L21 structure (space group # 225). Magnetization measurements reveal Co2Fe1.25Ge0.75 has a saturation magnetization as high as 6.7 ± 0.1 μ B /f.u. at 5 K and a Curie temperature of 1135 ± 5 K – both being the highest reported to date for cubic full Heusler alloys to our knowledge. Thin films of Co2Fe1.25Ge0.75 deposited on Al2O3 (110) and MgAl2O4 (100) substrates show excellent expitaxial quality, among the reported for Heusler films to date, and exhibit magnetic properties comparable to bulk samples. First principle calculations suggest the system exhibits total energy minimum at the experimentally-observed lattice parameter. Furthermore, the calculations corroborate the observed enhancement in magnetization and point to the importance of on-site Coulomb interactions. While our novel approach of substitution led to the discovery of stable Co2Fe1.25Ge0.75 alloy with very high moment and Curie temperature that can be readily grown as a high-quality epitaxial thin film, making it a candidate for device applications, this approach can be taken as a new paradigm for the discovery of novel single-phase Heusler compounds with enhanced magnetic properties.

The influence of V substitution for Co on the structural, electronic, magnetic, and mechanical properties of quaternary Heusler alloys Co 2-x V x FeSi ( $x = 0$ , 0.25, 0.50, 0.75, and 1) has been systematically investigated. The microstructural and the scanning profile using energy-dispersive X-ray analysis suggests the single-phase behavior in all alloys except for $x = 1$ . The X-ray diffraction analysis at room temperature reveals the $\text{L}2_{1}$ crystal structure promoting lattice expansion after V substitution. The low-temperature saturation magnetic moments, as determined from magnetization measurements, agree fairly well with our theoretical results and also obey the Slater–Pauling rule. Very high Curie temperature is also observed. The alloys are mechanically robust. First-principles calculation with the implementation of a Hubbard correction term (U) is observed to predict half-metallic behavior.

In this paper we report an experimental study of structural, magnetic, and mechanical properties of quaternary Heusler alloys Co2-xYxFeSi (Y = Co, Fe, Mn, Cr, V, Ti, or Sc, 0 <= x <= 1) and the experimental findings are supported by ab initio electronic structure calculations. The alloys were synthesized using an arc-melting technique. Single phase microstructures are observed for all alloys substituted with low-valence transition metals Y except Sc. X-ray powder diffraction patterns at room temperature show the presence of Heusler-like face-centered cubic crystal structure in all single phase specimens. The low-temperature saturation magnetic moments, as determined from magnetization measurements, agree fairly well with our theoretical results and also follow the Slater-Pauling rule of thumb for half-metals, a prerequisite for half-metallicity. The alloys are predicted to exhibit half-metallic ferromagnetism by ab initio electronic structure calculations using the GGA+U approach. All stable compounds are observed to have high Curie temperatures with linear dependence with the valence electrons concentration in the alloys. Relatively high hardness values are also measured, approaching 15.7 GPa for Ti-substituted material, highest among the values reported for Heuslers so far. All these properties strongly suggest the alloys are promising for the spintronic applications at room temperature and above.

In this study, we experimentally investigated quaternary Heusler alloys Co2-xVxFeGe with 0 <= x <= 1 prepared by arc melting and annealing, and showed that they are promising candidates for spintronics applications. Single phase microstructures were observed for V compositions from x = 0.25 to x = 0.625. Other V concentrations were multi-phased. All single phase samples had a face centered cubic crystal structure with a lattice constant that increased linearly with the V concentration. The low-temperature saturation magnetic moments were shown to obey the Slater-Pauling rule of thumb for half-metals, which is a prerequisite for half metallicity. All alloys had high Curie temperatures, which scaled linearly with the saturation magnetic moment, thereby facilitating applications at room temperature and above. Electrical transport measurements were performed to elucidate the electronic structures of the alloys. The temperature dependence of the electrical resistivity was analyzed and discussed in the framework of the two-current conduction model by considering the existence of an energy gap in the electronic spectrum around the Fermi level of the spin down sub-band. High mechanical hardness values were also observed.

Biofouling is a pivotal problem for polymeric membranes used in water treatment and reuse. Surface functionalization is a promising practice to improve the resistance of membranes to biofouling. Diverse materials, synthesis methods, and functionalization techniques will be needed to address different ap-plications. Herein, we employed a novel ultrasonic-assisted technique to functionalize polyvinylidene fluoride microfiltration membranes by silver-based metal-organic frameworks (AgMOFs). Polydopamine (PDA) coating was also used to carry out this surface modification. In this study, AgMOFs were syn-thesized and in-situ grafted on the membrane surface simultaneously using ultrasonication for the first time. Unlike the conventional methods in which AgMOFs are prone to be washed away, the AgMOFs synthesized by ultrasonic-assisted method strongly bonded with the PDA-coated membrane. In addition, the MOF-PDA membrane fabricated by this method showed more uniform and size-controlled AgMOFs on the membrane surface than other conventional methods with large MOF clusters. The AgMOF-functionalized membrane displayed enhanced static antibacterial activity and dynamic biofouling resistance compared to those of the PDA-coated and pristine membranes while in contact with the model bacteria, Escherichia coli and Staphylococcus aureus. These results were evidenced by a larger in-hibition zone area, a decline in viable cells observed in static antibacterial experiments, and more retained water flux in dynamic biofouling experiments. Altogether, our findings indicate that the in-situ synthesis of AgMOFs on membrane surfaces was successful by this facile and environmentally friendly method which can be considered in future studies with the purpose of surface modification for diverse applications. (C) 2022 Elsevier Ltd. All rights reserved.

In this study, we experimentally investigated quaternary Heusler alloys Co2−xVxFeGe with 0≤x≤1 prepared by arc melting and annealing, and showed that they are promising candidates for spintronics applications. Single phase microstructures were observed for V compositions from x=0.25 to x=0.625. Other V concentrations were multi-phased. All single phase samples had a face centered cubic crystal structure with a lattice constant that increased linearly with the V concentration. The low-temperature saturation magnetic moments were shown to obey the Slater–Pauling rule of thumb for half-metals, which is a prerequisite for half metallicity. All alloys had high Curie temperatures, which scaled linearly with the saturation magnetic moment, thereby facilitating applications at room temperature and above. Electrical transport measurements were performed to elucidate the electronic structures of the alloys. The temperature dependence of the electrical resistivity was analyzed and discussed in the framework of the two-current conduction model by considering the existence of an energy gap in the electronic spectrum around the Fermi level of the spin down sub-band. High mechanical hardness values were also observed.

The properties of Fe–Rh–Pd epitaxial thin films grown on MgO(001) were studied as a function of growth temperature. Films grown above 400°C exhibit a first-order antiferromagnetic to ferromagnetic magnetic phase transition with a transition temperature that decreases as the growth temperature is increased. The chemical order parameter computed from the ratio of intensities of the (001) and (002) diffraction peaks is nearly independent of the growth temperature, while the lattice constants change slightly. A comparison of our structural, magnetic, and electrical transport results with first-principle-based calculations as well as literature results indicates that the transition temperature of Fe–Rh-based alloy films depends sensitively on the lattice parameters and is of electronic origin. The transition temperature and its width can be tuned over a wide range by controlling the crystal structure via growth conditions or postdeposition annealing.

In this paper we report an experimental study of structural, magnetic, and mechanical properties of quaternary Heusler alloys ${\mathrm{Co}}_{2\ensuremath{-}x}{Y}_{x}\mathrm{FeSi}$ ($Y$ = Co, Fe, Mn, Cr, V, Ti, or Sc, $0\ensuremath{\le}x\ensuremath{\le}1$) and the experimental findings are supported by ab initio electronic structure calculations. The alloys were synthesized using an arc-melting technique. Single phase microstructures are observed for all alloys substituted with low-valence transition metals $Y$ except Sc. X-ray powder diffraction patterns at room temperature show the presence of Heusler-like face-centered cubic crystal structure in all single phase specimens. The low-temperature saturation magnetic moments, as determined from magnetization measurements, agree fairly well with our theoretical results and also follow the Slater-Pauling rule of thumb for half-metals, a prerequisite for half-metallicity. The alloys are predicted to exhibit half-metallic ferromagnetism by ab initio electronic structure calculations using the $\mathrm{GGA}+U$ approach. All stable compounds are observed to have high Curie temperatures with linear dependence with the valence electrons concentration in the alloys. Relatively high hardness values are also measured, approaching 15.7 GPa for Ti-substituted material, highest among the values reported for Heuslers so far. All these properties strongly suggest the alloys are promising for the spintronic applications at room temperature and above.

This paper reports a combined experimental and theoretical study of structural, electronic, magnetic, and mechanical properties of quaternary Heusler alloys ${\mathrm{Co}}_{2\ensuremath{-}x}{\mathrm{Cr}}_{x}\mathrm{FeGe}$ prepared by arc-melting with Cr concentrations $0\ensuremath{\le}x\ensuremath{\le}1$. Single-phase microstructures are observed for Cr compositions from $x=0.25$ to $x=1$. Lower Cr concentrations are multiphased. X-ray diffraction patterns at room temperature reveal a face-centered cubic crystal structure in all single-phase samples. The low-temperature saturation magnetic moments, as determined from magnetization measurements, agree fairly well with our theoretical results and also obey the Slater-Pauling rule for half-metals, a prerequisite for half-metallicity. All alloys are observed to have high Curie temperatures that scale linearly with the saturation magnetic moments. Relatively high mechanical hardness values are also observed. First-principles calculations also predict a finite band gap in the minority spin channel of the alloys, increasing in size with increasing Cr concentration. Cr substitution brings the Fermi level toward the center of this gap while also increasing the majority spin density of states near the Fermi level. As a whole, ${\mathrm{Co}}_{2\ensuremath{-}x}{\mathrm{Cr}}_{x}\mathrm{FeGe}$ shows great promise as a half-metal with 100% spin polarization.

Produced water (PW) generation has been increasing recently due to the expansion of fossil fuel extraction and the aging of oil wells worldwide, especially in the United States. The adverse health risks, seismicity, and environmental impacts associated with PW have become a challenging concern. Therefore, there is increased demand for improved PW treatment and reuse management options. There are multiple methods for treating PW; this article focuses on treatment through membrane filtration. Moreover, this mini review aims to summarize statistics on PW abundance and trends in PW generation over time, to briefly call attention to health-related issues, highlight some treatment challenges, and mention the potential purposes for reuse with an emphasis on the United States, the largest generator of PW worldwide.

We report on the bulk properties of the Heusler alloy system Co2Fe1-xVxGe with 0⩽x⩽1 in steps of 0.125. We find single-phase alloys only for x=0.25 and x=0.375, both of which exhibit an L21 crystal structure. The alloys are found to be soft ferromagnets with high Curie temperatures (∼800K). Magnetization measurement shows the saturation magnetization to be 5.21 μB/f.u. and 4.78 μB/f.u. for Co2Fe0.75V0.25Ge and Co2Fe0.625V0.375Ge respectively, in good agreement with the values expected from a Slater-Pauling rule for half metals. In zero applied magnetic field, the resistivity versus temperature of these alloys does not display the usual T2 dependence at low temperatures indicative of electron-magnon scattering, another indirect suggestion of half metallicity. Our ab initio calculations also predict half-metallic character in the alloys after V substitution. The large exchange splitting between the occupied majority- and unoccupied minority-spin states leads to the Fermi level almost intersecting a peak in the V majority density of states. This leads to a markedly higher spin polarization upon V doping, making V an ideal dopant for achieving half-metallic behavior in Co2FeGe. Relatively high mechanical hardness values are also observed.

We performed combined experimental and theoretical studies of the effect of Cr substitution for Fe on the structural, magnetic, transport, electronic, and mechanical properties of Fe3-xCrxGe (0 <= x <= 1) intermetallic alloys. Single phase microstructures are observed for x <= 0.70. Higher Cr concentrations x <= 0.70 are multi-phased. A hexagonal D0(19) structure is found for all Cr concentrations, with the lattice parameters increasing systematically with an increasing Cr content. All the alloys in the series are found to be ferromagnets with large magnetization values of about 6 mu(B)/f.u. and high Curie temperature above room temperature. The low-temperature saturation magnetic moments agree fairly well with our theoretical results and also obey the Slater-Pauling rule. The density functional theory calculation reveals that Cr substitution energetically favours one of the Fe sites in Fe3Ge. The electrical resistivity measured over the temperature range from 5 K to 400 K shows metallic behavior, with a residual resistivity ratio that decreases with Cr content. Vicker's hardness values are observed to increase with increasing Cr content to approximately 5 GPa.

The properties of Fe-Rh-Pd epitaxial thin films grown on MgO(001) were studied as a function of growth temperature. Films grown above 400◦C exhibit a first-order antiferromagnetic to ferromagnetic magnetic phase transition with a transition temperature that decreases as the growth temperature is increased. The chemical order parameter computed from the ratio of intensities of the (001) and (002) diffraction peaks is nearly independent of the growth temperature, while the lattice constants change slightly. A comparison of our structural, magnetic, and electrical transport results with first-principles-based calculations as well as literature results indicate that the transition temperature of Fe-Rhbased alloy films depends sensitively on the lattice parameters, and is of electronic origin. The transition temperature and its width can be tuned over a wide range by controlling the crystal structure via growth conditions or post-deposition annealing.

We synthesize the FexCa1-xTiSb series of alloys (0 < x < 1) through arc melting. On the cobalt-rich side, we successfully synthesize CoTiSb in the Clb half-Heusler crystal structure. At the Fe0.25Co0.75TiSb composition, we find the alloy to be composed of CoTiSb-rich grains with iron segregation at grain boundaries. At the prototypical half-Heusler composition Fe0.5Co0.5TiSb, we synthesize a single phase, comprised of equiaxed grains, showing signatures of a C1b crystal structure with a lattice constant of 0.5918 nm in X-ray diffraction data. Conductivity measurements indicate the Fe0.5Co0.5TiSb half-Heusler phase to be semiconducting with a small band gap of the order of 0.1 eV. A density functional theorybased cluster expansion study of the configurational order of Fe, Co in the half-Heusler structure shows mixing to be weakly unfavorable, indicating Fe/Co solid solution in the Fe0.5Co0.5TiSb alloy at all but very low temperatures, in agreement with the single phase with C1b symmetry found in experiments. Our calculations indicate the perfectly stoichiometric compound to be semi-metallic or metallic. However, an addition of 0.5 electrons results in a semiconducting state in agreement with experimental resistivity measurements and slight Fe-, Co-rich off-stoichiometry in the as-synthesized Fe0.5Co0.5TiSb sample. Further, our calculations indicate the nonmagnetic, ferromagnetic and antiferromagnetic states to be energetically within a few meV/atom of one another, consistent with the observation of extremely low magnetic moment. On the iron-rich side, at the Fe0.75Co0.25TiSb composition, we synthesize a two-phase mixture of the Fe0.5Co0.5TiSb phase and a secondary antimony-rich phase with composition roughly Sb1.8Ti1.5Fe, and at the FeTiSb composition, we find a two-phase mixture of a previously-reported Heusler-based Fe1.5TiSb phase and the antimony-rich phase. (C) 2019 Elsevier B.V. All rights reserved.

We report a detailed experimental and theoretical study of the effects of V substitution for Fe atom on the structural, magnetic, transport, electronic and mechanical properties of an off-stoichiometric Fe3-xVxGe intermetallic alloy series (0 <= x <= 1). Single phase microstructures are observed for x < 0.75, whereas higher V content alloys x >= 0.75 are multi-phased. Vanadium substitution is observed to induce a diffusionless martensitic phase transformation from a Heusler-like L2(1) structure to hexagonal DO19 structure, as corroborated by Differential Scanning Calorimetry results. The vanadium substitution is also found to decreases the grain size, inhibiting the grain growth by pinning the grain boundary migration. All the alloys in the series are found to be soft ferromagnets at 5 K with saturation magnetic moment and Curie temperature decreasing as V concentration increases. The low temperature saturation magnetic moment is in close agreement with the expected Slater-Pauling values for the L2(1) phases, while the hexagonal samples have markedly higher values of saturation moments. First-principle calculations agree with the experimental findings and reveal that V substitution energetically favours one of the Fe sites in Fe3Ge. The electrical resistivity measured over the temperature range from 5 K to 400 K shows negative temperature coefficient of resistivity at high temperatures with increasing the V concentration. Relatively high mechanical hardness values are also observed, with the values increasing with increasing V content. Vanadium substitution is found to play a central role in tuning the mechanical properties, stabilising the L2(1) structure, and shifting the martensitic transformation temperature to higher values from that of parent Fe3Ge. (c) 2020 Elsevier B.V. All rights reserved.