Cubic Phase Research Articles

Preparation and Physical Properties of Quaternary Mn2FeSi0.5Al0.5 Alloy Powders with Heusler and β-Mn Structures.

Manganese-based alloys with the composition Mn2FeZ (Z = Si, Al) have been extensively investigated in recent years due to their potential applications in spintronics. The Mn2FeSi alloy, prepared in the form of ingots, powders, or ribbons, exhibits either a cubic full-Heusler (L21) structure, an inverse-Heusler (XA) structure, or a combination of both. In contrast, the Mn2FeAl alloy has so far been synthesized only in the form of ingots, featuring a primitive cubic (β-Mn type) structure. This study focuses on the new quaternary Mn2FeSi0.5Al0.5 alloy synthesized from pure Mn, Fe, Si, and Al powders via mechanical alloying. The elemental powders were ball-milled for 168 h with a ball-to-powder ratio of 10:1, followed by annealing at 550 °C, 700 °C, and 950 °C for 8 h in an argon protective atmosphere. The results demonstrate that annealing at lower temperatures (550 °C) led to the formation of a Heusler structure with a lattice constant of 0.5739 nm. Annealing at 700 °C resulted in the coexistence of several phases, including the Heusler phase and a newly developed primitive cubic β-Mn structure. Further increasing the annealing temperature to 950 °C completely suppressed the Heusler phase, with the β-Mn structure, having a lattice constant of 0.6281 nm, becoming the dominant phase. These findings confirm the possibility of tuning the structure of Mn2FeSi0.5Al0.5 alloy powder-and thereby its physical properties-by varying the annealing temperature. The sensitivity of magnetic properties to structural changes is demonstrated through magnetization curves and zero-field-cooled/field-cooled curves in the temperature range of 5 K to 300 K.

Block Copolymer Electrolytes with Double Primitive Cubic Structures: Enhancing Solid-State Lithium Conduction via Lithium Salt Localization.

We present a strategy for enhancing Li+ conduction in block copolymer electrolytes by introducing trace amounts of Li salts into polystyrene-b-poly(ethylene oxide) (PS-b-PEO), wherein Li+ ions preferentially coordinate with the -OH end groups of the PEO chains, resulting in the formation of double primitive cubic (Im3̅m) structures. Compared with TFSI- anions in Li salts, smaller anions (PF6- and BF4-) could facilitate ion localization more effectively, expanding the salt concentration range for developing stable Im3̅m structures. The Im3̅m structures formed in PS-b-PEOs doped with LiBF4 at r = 0.013-0.02 (r ≡ [Li+]/[EO]) exhibited ionic conductivities several times higher than those doped at the conventional level (e.g., r = 0.06). The corresponding morphology factors were more than eight times higher than those of the lamellar-forming electrolytes. Notably, the activation energy value for Li+ conduction in PS-b-PEO with one Li+ ion per entire PEO chain was only 0.012 eV (by Vogel-Fulcher-Tammann), indicating that Li+ transport was less dependent on polymer relaxation. Furthermore, modifying the PEO chain ends with three -PO3H2 groups further strengthened the Li+-mediated end-end interactions and significantly extended the salt concentration range to form Im3̅m structures. In contrast, increasing the number of -OH end groups (such as diols and triols) had minimal effect on stabilizing the network morphologies.

Experimental and Theoretical Force Constants as Meaningful Indicator for Interatomic Bonding Characteristics and the Specific Case of Elemental Antimony.

Stable Sb exhibits a rhombohedral structure, often referred to as distorted primitive cubic, with each Sb atom having three short and three longer first neighbor bonds. However, this crystal structure can also be interpreted as being layered, putting emphasis on only three short first neighbor bonds. Therefore, temperature-dependent extended X-ray absorption fine structure (EXAFS) spectroscopy is carried out at the Sb K-edge in order to obtain more detailed information on local structural and vibrational properties. Evaluation of the temperature-dependent bond lengths provides the temperature-dependent Peierls distortion while the temperature dependence of the variance of the interatomic distance distribution yields the EXAFS force constants. Ab initio density functional theory (DFT) calculations are used for determining projected force constants. Both EXAFS and DFT force constants are compared to those of other materials with different bonding characteristics, including two-center covalently bonded semiconductors, multicenter bonded IV-VI and V2VI3 compounds, and metallic Cu. Clearly, Sb exhibits characteristics of both localized covalent bonding and delocalized multicenter bonding. This suggests a continuous transition between these two bonding scenarios and adds to the understanding of bonding in elemental Sb in particular and in IV-VI and V2VI3 materials in general.

Physical properties of Pr3+ substituted zinc spinel (ZnPrxFe2−xO4) nanoferrites synthesized via sol–gel auto-combustion route

Spinel ferrites, a group of metal oxides, have garnered significant attention in the recent decade due to their high demand for numerous applications, including data storage and microwave device applications. In this context, we studied the effect of different doping concentrations of large Pr ions on the physicochemical properties of spinel lattice, such as dielectric and magnetic properties. In this research, we successfully fabricated a series of praseodymium ion-doped zinc spinel ferrites ZnPrxFe2-xO4 nanoparticles 0.00≤x≤0.20 via a simple and economical sol–gel auto-combustion approach. XRD (X-ray Diffraction Analysis) and FTIR investigations validate the presence of a cubical phase, with the crystallite size varying between 11 nm to 19 nm depending on the amount of Pr present. The Scherrer method, Williamson-Hall analysis (WH), and size-strain plot method (SSP) were investigated the correlation of crystalize size. The SSP approach has a better correlation coefficient than the WH method. Transmission electron microscopy TEM shows that the prepared material possessed the cubic and spherical symmetry. The significant variation in electrical parameters was discussed at an applied frequency ranging from 1 MHz to 3 GHz. The dielectric constant is approximately constant in low-frequency regions then relaxation peaks were observed at nearly 1.4 GHz and 2.2 GHz. The dielectric constant and complex dielectric constant of these samples dropped as the praseodymium content increased. Investigations regarding the magnetic properties were carried out using a vibrating sample magnetometer (VSM) at −23 k Oe to +23 k Oe. Low coercivity and relaxation peaks at high frequencies suggest that this material may be suitable for core materials, microwave technologies and recording media.

Free-standing arrays of BaTiO3 nanotubes for non-enzymatic glucose sensing & hydrophobic coating applications

BaTiO3 nanostructures have been considered as a promising candidates in recent past for energy and biomedical sectors owing to their excellent physiochemical properties, such as high dielectric constant, excellent piezoelectric property, good biocompatibility, non-linear optical characteristics etc. Present study reveals on free-standing arrays of BaTiO3 nanostructures, were fabricated by hydrothermal conversion of anodic TiO2 nanotubes. Morphological and structural information of the BaTiO3 nanotubes were done using FESEM and XRD studies. FESEM analysis revealed that the fabricated samples were having tubular morphology of average length and pore diameter of 4.63 μm and 290 nm respectively. Cubical perovskite crystalline phase of BaTiO3 was confirmed through XRD analysis. The BaTiO3 nanotube samples had shown a higher sensitivity of 44.43 μA mM−1 cm−2 and a faster response of 0.1 s for glucose detection. The fabricated BaTiO3 nanotubes film also showed a higher contact angle of 122.70°. Therefore, our present fabrication on Titanium foil study emphasizes on arrays of BaTiO3 nanotubes which will open up a new window in the development of various types of sensing and hydrophobic coating applications.

First moment of central values of some primitive Dirichlet L-functions with fixed order characters

We evaluate asymptotically the smoothed first moment of central values of families of primitive cubic, quartic and sextic Dirichlet L-functions, using the method of double Dirichlet series. Quantitative non-vanishing results for these L-values are also proved.

Isogonal embeddings of interwoven and self-entangled honeycomb (hcb) nets and related interpenetrating primitive cubic (pcu) nets.

Two- and three-periodic vertex-transitive (isogonal) piecewise-linear embeddings of self-entangled and interwoven honeycomb nets are described. The infinite families with trigonal symmetry and edge transitivity (isotoxal) are particularly interesting as they have the Borromean property that no two nets are directly linked. These also lead directly to infinite families of interpenetrating primitive cubic nets (pcu) that are also vertex- and edge-transitive and have embeddings with 90° angles between edges.

CUBIC: A Versatile Cumate-Based Inducible CRISPRi System in Streptomyces.

Streptomyces, a genus of Gram-positive bacteria, is known as nature's medicine maker, producing a plethora of natural products that have huge benefits for human health, agriculture, and biotechnology. To take full advantage of this treasure trove of bioactive molecules, better genetic tools are required for the genetic engineering and synthetic biology of Streptomyces. We therefore developed CUBIC, a novel CUmate-Based Inducible CRISPR interference (CRISPRi) system that allows highly efficient and inducible gene knockdown in Streptomyces. Its broad application is shown by the specific and nondisruptive knockdown of genes involved in growth, development and antibiotic production in various Streptomyces species. To facilitate hyper-efficient plasmid construction, we adapted the Golden Gate assembly to achieve 100% cloning efficiency of the protospacers. We expect that the versatile plug-and-play CUBIC system will create new opportunities for research and innovation in the field of Streptomyces.

Influence of Cr doping on the structural, optical, and third-order nonlinear optical properties of ZnAl2O4 nanoceramics

In this research, Zn(1−x)CrxAl2O4 (x = 0.00, 0.05, 0.10, 0.20) nanoparticles were prepared by a simple and green chemistry synthesis using gelatin as a polymerization agent. X-ray diffraction technique and scanning electron microscopy imaging were used to analyze the structural and morphological properties of the samples. X-ray diffraction results revealed that all samples were polycrystalline and crystallized in a cubical spinel phase. With increasing the x from 0.00 to 0.20, the main Bragg peaks shift to smaller angles, and the crystallite size and energy bandgap of samples decrease as well. The nonlinear absorption coefficient, β, and nonlinear refractive index, n2, of Zn(1−x)CrxAl2O4 were meticulously studied by the Z-scan approach. The orders of n2 and β are 10−7 and 10−4 cm/W, respectively. The saturable absorption and the self-defocusing effect are the main factors in the appearance of β and n2, respectively. The experimental results confirmed that increasing the percentage of Cr caused nonlinear coefficients to increase.

Prediction of mechanical properties on perforated hollow sphere with different lattice arrangement

This paper investigates different lattice arrangements of perforated hollow sphere structure (PHSS) on their mechanical properties. For this new kind of hollow sphere structure, the outer sphere shells are perforated by several holes. This will open the inner sphere volume and embed with the epoxy-based adhesives to form syntactic metal foam. The numerical models of PHSS are developed by using Femap software for different lattice arrangements like body-centred cubic (BCC), face-centred cubic (FCC) and hexagonal. The simulation is conducted in MSC Marc software by applying quasi-static compression in order to determine the effective Young’s modulus and Poisson’s ratio values against the average density. Through this paper, it is found that the difference in lattice arrangements do not give significant effect on the Young’s modulus. However, in the case of size of perforation hole diameter, we can see the variation of Young’s modulus and Poisson’s ratio are significant. The results then are compared to the previous study of primitive cubic (PC).

Enhanced CO2 sorption properties in a polarizable [WO2F4]2--pillared physisorbent under direct air capture conditions.

We report the CO2 capture properties of an ultramicroporous physisorbent [Ni(WO2F4)(pyrazine)2]n, WO2F4-1-Ni, which crystallizes in I4/mcm (a = 9.91785(6) Å, c = 15.71516(9) Å) and its structure is solved using laboratory X-ray powder diffraction. The WO2F4 anion is acentric with polarizable WO bonds offering unique potential properties within a porous structure. Despite isostructural compounds being previously reported, the effect of this distorted anion on CO2 capture properties has not been studied. In this context, at a 400 ppm partial pressure of CO2 (applicable for direct air capture), this primitive cubic (pcu) network captures 0.934 mmolCO2 gsorbent-1 under dry conditions and 0.685 mmolCO2 gsorbent-1 at 75%RH, the highest capacity for a physisorbent reported to date.

Aggregation structure of chiral cubic liquid crystals revealed by X-ray diffraction utilizing a new algorithm.

Chiral aggregation structure spontaneously formed by achiral rodlike molecules, a long-time unsolved problem in liquid crystal science, has been clarified by applying a new crystallographic algorithm recently developed while utilizing aggregation characteristics of this type. Bicontinuously interwoven networks characterize it similarly to the neighboring Gyroid phase in a phase diagram against the alkyl chain length and temperature. However, the network connectivity is significantly different from the bicontinuous networks that have been either known for related compounds or assumed for this phase. The network is compatible with the homochiral arrangement of rodlike molecules with successive twists by a proper angle between adjacent junctions.

Equiatomic binary phases of Copper-Rare Earth Elements. An overview of monocuprides from first-principles calculations.

Equiatomic binary phases of copper with rare earth (RE) elements exhibit either primitive cubic ( ) or orthorhombic (Pnma) structures and in some cases both. By using density functional theory (DFT), we calculated the enthalpies of formation along the series of RE elements combined equimolarly with copper. For RE from Sc to Lu, the calculated enthalpies of formation fall in the range -49.8 kJ/mol for LuCu to -9.1 kJ/mol for the least thermodynamically stable CeCu. Except NdCu, all the other cubic or orthorhombic compounds exhibit lattice stability. Either forms of NdCu indicated lattice instability. Along the Sc-group, the hypothetical primitive cubic and orthorhombic forms of LuCu are found thermodynamically and mechanically stable. The overall trend of the formation enthalpies as a function of the Meyer Periodic Number is consistent with the energy trend of the 4 f-orbital filling as moving from Sc to Lu monocuprides. In addition, the calculated Gibbs free energies indicate that the thermodynamic stability is largely due to the entropic contributions. All standard DFT calculations were also repeated with DFT+U to better describe the correlation between the 5d-4f and 3d shells of RECu compounds. It has been found that DFT+U slightly affects the enthalpies of formation of RECu binaries. Moreover, DFT+U shifts up the f-band energies of RECu with light RE elements (such as La, Ce and Pr) and in contrast lowers them in the case of RECu with heavy RE elements from Nd to Lu.

Fluorescence-Responsive Detection of Ag(I), Al(III), and Cr(III) Ions Using Cd(II) Based Pillared-Layer Frameworks

Two Cd(II) based coordination polymers, {Cd3(btc)2(BTD-bpy)2]∙1.5MeOH∙4H2O}n (1) and [Cd2(1,4-ndc)2(BTD-bpy)2]n (2), where BTD-bpy = bis(pyridin-4-yl)benzothiadiazole, btc = benzene-1,3,5-tricarboxylate, and 1,4-ndc = naphthalene-1,4-dicarboxylate, were hydro(solvo)thermally synthesized. Compound 1 has a three-dimensional non-interpenetrating pillared-bilayer open framework with sufficient free voids of 25.1%, which is simplified to show a topological (4,6,8)-connected net with the point symbol of (324256)(344454628)(3442619728). Compound 2 has a three-dimensional two-fold interpenetrating bipillared-layer condense framework regarded as a 6-connected primitive cubic (pcu) net topology. Compounds 1 and 2 both exhibited good water stability and high thermal stability approaching 350 °C. Upon excitation, compounds 1 and 2 both emitted blue light fluorescence at 471 and 479 nm, respectively, in solid state and at 457 and 446 nm, respectively, in the suspension phase of H2O. Moreover, compounds 1 and 2 in the suspension phase of H2O both exhibited a fluorescence quenching effect in sensing Ag+, attributed to framework collapse, and a fluorescence enhancement response in sensing Al3+ and Cr3+, ascribed to weak ion-framework interactions, with high selectivity and sensitivity and low detection limit.

Influence of the Al Content on the Properties of Mechanically Alloyed CoCrFeNiMnXAl20-X High-Entropy Alloys.

The equiatomic CoCrFeNiMn alloy prepared by mechanical alloying and spark plasma sintering underwent partial substitution of Mn by Al (5, 10 and 15 at.%) to determine its influence on mechanical properties and thermal stability. It was discovered that the higher the Al content, the higher the volume fraction of the hard phase with primitive cubic (PC) crystallographic lattice, which increases the hardness and strength of the alloys. The most promising mechanical properties have been achieved in the CoCrFeNiMn5Al15 alloy reaching the compressive yield strength (CYS) of 2135 ± 21 MPa and the ultimate compressive strength (UCS) of 2496 ± 21 MPa. All the prepared alloys showed good thermal stability as they maintained or only slightly reduced their initial hardness during the 100 h annealing at 800 °C. Furthermore, the higher the Al content, the higher the resistance against high-temperature oxidation. The oxidic layer changed its composition from Mn-oxides (CoCrFeNiMn15Al15 alloy) to Al-based oxides with exceptional protective properties.

Tailoring the self-assembly of lipid-based lyotropic liquid crystalline mesophases with biocompatible ionic liquid aqueous solutions

Interest in lipid-based lyotropic liquid crystalline nanoparticles (LCNPs) as drug delivery vehicles continues to grow, owing to their unique structural features. The structure of these particles can be controlled to suit specific applications, through tailoring the lipid composition and solvent conditions. Ionic liquids (ILs) are liquid salts comprising tailorable cations and anions, of which some are known to support the self-assembly of amphiphiles, and hence can be used as designer solvents for LCNPs. We employed dynamic light scattering, small angle X-ray scattering, and cryogenic transmission electron microscopy to examine the particle size and lyotropic liquid crystalline mesophase behavior of monoolein (MO)-based LCNPs in aqueous solutions containing 13 choline ILs with a selection of amino acid and carboxylate anions at 6 concentrations 20, 10, 5, 1, 0.33, and 0.16 wt%. Our results show the formation of LCNPs with various liquid crystalline nanostructures, including the inverse bicontinuous primitive cubic (Q2) phase with the Im3m crystallographic space group, the inverse hexagonal (H2), and the inverse discontinuous micellar cubic (I2) phases. The internal nanostructures of the MO nanoparticles depended on three main factors, the anion of the ILs, the IL concentration, and the pH of the solution. This study elucidates the potential application of IL solvents as a powerful tool to tailor the internal nanostructure of MO-based LCNPs, and advances the exploration of IL-enabled responsive LCNPs systems as prospective nanocarriers.

High Hardness and Wear Resistance in AlCrFeNiV High-Entropy Alloy Induced by Dual-Phase Body-Centered Cubic Coupling Effects.

High-entropy alloys (HEAs) with high hardness are promising materials for advanced industrial manufacturing. In this study, the AlCrFeNiV HEA was designed and successfully prepared using a plasma instantaneous process. The hardness test showed that AlCrFeNiV had a high hardness of 1076 ± 15 HV, which was much higher than those reported in the literature. The microstructure of AlCrFeNiV was composed of two different types of body-centered cubic (BCC) structures, BCC1 (Al, Cr, Fe, and Ni) and BCC2 (enriched V and Cr). A mixture of different BCC systems produced solution strengthening, which was responsible for the superior hardness. Moreover, the reciprocating sliding wear behavior of HEA against Al2O3 balls under dry and lubricated conditions at ambient temperature was investigated. The wear rates of AlCrFeNiV against Al2O3 under dry wear and lubrication were 17.2 × 10−5 mm3 N−1·m−1 and 12.4 × 10−5 mm3N−1·m−1, respectively, which were of the same order of magnitude as the wear rates of BCC HEAs. Regardless of the dry wear or wear with lubrication, the wear mechanism of the HEA was abrasive and delamination wear.

Structures and Luminescent Properties of Rare-Earth Metal–Organic Framework Series with Thieno[3,2b]thiophene-2,5-dicarboxylate

Four new rare-earth metal–organic frameworks containing thieno[3,2b]thiophene-2,5-dicarboxylate (ttdc2−) with general formulae [M2(DMF)4(ttdc)3] (M3+ = Y3+ for 1, La3+ for 2, Tb3+ for 3) and [M2(H2O)2(ttdc)3] (M3+ = Lu3+ for 4) were synthesized. Their crystal structures were determined by performing a single-crystal X-ray diffraction analysis. Coordination polymers 1–3 are based on the binuclear metal-carboxylate building units with the formulae {M2(DMF)4(OOCR)6}. The six-connected blocks in 1–3 form a three-dimensional network with the primitive cubic (pcu) topology. Coordination framework 4 is based on chains comprised by stretched pseudo-binuclear metal-carboxylate building units. The chains are interconnected in four directions with ttdc2− linkers forming the 3D framework. The luminescent properties were studied for the synthesized frameworks in the solid state. All the coordination frameworks show a broad blue emission band (λex = 380 nm) typical for intra-ligand electron transitions. The sensing properties of 3 dispersions in solutions were investigated in detail and the luminescent response (quenching) was discovered in the presence of cinnamaldehyde and quinoline in diluted solutions at concentrations of as low as 4 × 10−1 vol.% and 4 × 10−2 vol.% (~3 × 10−3 M), respectively.

The Propagation of Thermoelastic Waves in Different Anisotropic Media Using Matricant Method

Thermoelasticity is a generalization of classical theories of elasticity and thermal conductivity and describes a wide range of phenomenon. The theory can precisely predict the propagation of thermoelastics waves in case of an isotropic medium. However, the propagation of thermoelastic waves in the anisotropic medium is not fully understood. In this case, the theory of elasticity employs an approximate theory of temperature stress which does not take into consideration the interactions of temperature and deformations. In this paper, an analytical study has been carried out by using method of matricant to investigate the propagation of longitudinal elastic and heat waves in the anisotropic medium of a monoclinic, trigonal, hexagonal, and cubical crystal systems. In this article, a solution to the problem of the propagation of thermal waves and the propagation of a thermal wave along z -axis has been obtained. The attenuation coefficient and phase velocity of thermal waves for various materials are determined. Specifically, the problem of propagation of heat waves in one dimension has been solved.

Mixed‐Ligand Metal‐Organic Frameworks: Synthesis and Characterization of New MOFs Containing Pyridine‐2,6‐dimethanolate and Benzene‐1,4‐dicarboxylate Ligands

AbstractThe development of synthetic approaches towards new mixed‐ligand metal organic frameworks (MOFs) has been attracting considerable attention recently as they display fascinating properties due to the synergistic effect between the different ligands. Herein, the initial combination of pyridine‐2,6‐dimethanol (H2pdm) with benzene‐1,4‐dicarboxylic acid (H2bdc) has provided access to three new mixed‐ligand MOFs, [M3(bdc)2(Hpdm)2]n (MII=ZnII, 1; MnII, 2) and [Mn3(bdc)3(H2pdm)2]n (3). 1–3 are the first MOFs containing H2pdm in its neutral or anionic form. 1 and 2 are isostructural 2D MOFs with a square lattice (sql) framework topology, while 3 is a 3D MOF possessing a primitive cubic (pcu) topology. Dc magnetic susceptibility measurements for 3 demonstrate antiferromagnetic interactions between the MnII ions which is a combination of intra‐ and intertrimer exchange pathways.