Homogeneous Single-phase Research Articles

Enhancing an internal electric field by a solid solution strategy for steering bulk-charge flow and boosting photocatalytic activity of Bi24O31ClxBr10–x

Constructing bismuth oxyhalide solid solutions with a single homogeneous phase have intrigued the research community; however, a deeper understanding of the intrinsic origin for improved bulk-charge separation is still unclear. Herein, a series of Bi24O31ClxBr10–x solid solutions with the same structural characteristics were synthesized by crystal structure regulation. Combining density functional theory calculation, Kelvin probe force microscopy, and zeta potential testing results, an enhanced internal electric field (IEF) intensity between [Bi24O31] and [X] layers was achieved by changing halogen types and ratios. This greatly facilitated bulk-charge separation and transfer efficiency, which is significant for the degradation of phenolic organic pollutants. Owing to the enhanced IEF intensity, the charge carrier density of Bi24O31Cl4Br6 was 33.1 and 4.7 times stronger than that of Bi24O31Cl10 and Bi24O31Br10, respectively. Therefore, Bi24O31Cl4Br6 had an optimal photoactivity for the degradation of bisphenol A, which was 6.21 and 2.71 times higher than those of Bi24O31Cl10 and Bi24O31Br10, respectively. Thus, this study revealed the intrinsic mechanism of the solid solution strategy for photocatalytic performance enhancement with respect to an IEF.

Microstructure and magnetocaloric property of homogeneous La(FexSi1−x)13 compounds fabricated by laser fusion using a powder mixture of Fe and LaySiz compounds

A highly homogeneous single-phase La(FexSi1−x)13 was obtained by the heat-treatment of a parent alloy produced by the laser fusion of a powder mixture of Fe and La-Si compounds. Rapid homogenization was promoted owing to the formation of a characteristic microstructure during laser fusion even at a high Fe concentration (e.g., x = 0.91). The selective oxidation of La during laser fusion was prevented by the reduction of oxides on the surface of Fe particles. The maximum of the magnetic entropy change (ΔSM) for the specimen heat-treated at 1323 K for 24 h was − 22 J/kg K under a magnetic field change of 1 T and the specimen heat-treated for a shorter duration of 2 h exhibited a ΔSM of − 18 J/kg K. Thus, the production of the parent alloy by the laser fusion of the powder mixture significantly decreased the heat-treatment duration for the formation of a highly homogenized La(FexSi1−x)13 compound at a high Fe concentration. Consequently, the laser fusion process followed by post-annealing is possible to selectively form fine structures made of the 1:13 phase, and such a feature will lead a way to 3D precision modeling of the regenerator-bed with using the highly homogeneous La(FexSi1−x)13.

Sensitivity of gas sensors enhanced by functionalization of hexabenzoperylene in solution-processed monolayer organic field effect transistors.

Solution-processed monolayer films consisting of unfunctionalized and functionalized hexabenzoperylenes in a single homogeneous phase have enabled highly sensitive detection of NH3 and NO2 on the basis of organic field effect transistors.

Catalyst Type Effects on Structure/Property Relations of Polypropylene Random Copolymers

AbstractPolypropylene (PP) random copolymers are an important class of commercial materials that can be tuned for a wide range of different applications. The structure–property relations are mainly discussed in this article focusing on two major influencing factors, the catalyst system and the type and amount of comonomer. Ziegler–Natta (ZN) catalyst systems still dominate the production of polypropylene and todays sixth‐generation ZN catalysts are based on postphthalate donor systems. Metallocene (MC) catalysts offer possibilities to exactly control the microstructure of the polymer even better. Mostly, ethylene is used as comonomer being randomly distributed for up to 7.3 mol% when using ZN catalysts. For single site catalysts, homogenous (single phase) materials can be achieved up to ethylene contents of 20.8 mol%. The incorporated comonomer reduces the crystallization speed and the lamellar thickness of the polymer thus affording soft and highly transparent materials. Random copolymers and terpolymers with higher α‐olefins only play a minor role but offer an additional possibility for property adjustments. PP random copolymers can also be varied in their performance through multistage polymerizations, altering the comonomer content and or the molecular weight in the different polymerization reactors.

A corrosion-resistant soft-magnetic high entropy alloy

In this paper, a soft-magnetic Fe40Co40Ni10Cr10 high entropy alloy (HEA) was designed and fabricated, and its microstructure, magnetic properties, corrosion resistance and mechanical properties have been systematically investigated. It is found that, this HEA is composed of single FCC structure and shows homogeneous compositional distribution. This HEA has good soft-magnetic properties as well as excellent corrosion resistance comparable to stainless steel. Besides, this HEA has high malleability with compressive plasticity of > 60% without fracture. The homogeneous compositional distribution and single FCC phase in this Cr-containing HEA is possibly the main reason for the combination of the above-mentioned properties. This work provides a novel route for designing functional HEAs with enhanced comprehensive material properties.

Fine-grained polycrystalline MoTe2 with enhanced thermoelectric properties through iodine doping

Consisting of heavy elements and favorable electronic structure, MoTe2 has great potential as a good thermoelectric material for heat-to-electricity conversion. While some experimental work has been performed on the p-type version, n-type MoTe2 is theoretically predicted to have a great conversion efficiency and is crucial for eventual device functionality, yet has not been explored. Here, the preparation and thermoelectric properties of n-type iodine-doped nano-polycrystalline MoTe2 are currently reported. Nano-polycrystalline MoTe2 − xIx is obtained by ball milling and spark plasma sintering techniques. The composition, morphology and crystal structure of the prepared materials were analyzed by XRD and FESEM, which indicated a homogeneous single phase. The measured transport properties over the temperature range of 298–823 K indicate that iodine doping greatly enhances the carrier concentration and corresponding power factor, and drastically reducing the thermal conductivity. The ECR (Electrical conductivity ratios) carrier scattering analysis demonstrates that dislocation scattering is the main mechanism throughout the experimental temperature range. With the temperature and doping increasing, the thermal conductivity was reduced rapidly, and the minimum value was 1.19 Wm− 1 K− 1 at 673 K. The maximum value of the figure merit ZT ~ 0.16 over 673–750 K, which is much higher than other reported values. These excellent properties imply that MoTe2 will be an efficient candidate for thermoelectric applications.

An approach to design single BCC Mg-containing high entropy alloys for hydrogen storage applications

Mg is a lightweight element that can increase the gravimetric hydrogen storage capacity of high entropy alloys (HEAs). This work presents a new approach to design single-phase Mg-containing HEAs with attractive hydrogen storage properties. The design method is based on four calculated parameters (ϕ, VEC, ΔH∞¯ and ΔHfo¯) that allow us to find alloy compositions that form single body-centered cubic (BCC) solid solutions with high hydrogen affinity. The method was tested in the Mg–Al–Ti–Mn–Nb system and the Mg12Al11Ti33Mn11Nb33 alloy was selected among 1326 calculated compositions. This alloy was produced by high energy ball milling resulting in a homogeneous single-phase BCC alloy that absorbed 1.7 wt.% of H by forming a BCC monohydride. Despite its H uptake being H/M = 1, the gravimetric capacity of the lightweight Mg12Al11Ti33Mn11Nb33 alloy was comparable to refractory BCC-HEAs with H uptake of H/M = 2.

Velocity prediction of Cu/water nanofluid convective flow in a circular tube: Learning CFD data by differential evolution algorithm based fuzzy inference system (DEFIS)

The ability of the artificial intelligence (AI) of the differential evolution algorithm with a fuzzy inference system (DEFIS) in the prediction of fluid flow hydrodynamic is investigated. The DEFIS learns the CFD results in the convective flow of Cu/water nanofluid in a circular tube. The ANSYS-FLUENT CFD package is used. The thermal-chemical equilibrium conditions exist between the Cu nanoparticles and water. The homogenous single-phase CFD model can be considered by this assumption. The CFD simulations are done for several inlet velocities (i.e., 0.6, 0.7, 0.8, 0.9, and1). The DEFIS takes the x, and y coordinates and the inlet velocity as inputs to predict the nanofluid velocity at z-direction an output. The best intelligence of the DEFIS is tried by adjusting the input numbers, population numbers, and cross-over.The results displayed that for the best intelligence of the DEFIS (i.e., input number = 3, population number = 5, and cross-over =0.7), there is high compatibility between the results of the CFD and the DEFIS. At this condition, the DEFIS shows the ability to predict nanofluid velocity related to any inlet velocity independent of the CFD.

A convenient strategy to synthesize highly tunable gelatin methacryloyl with very low gelation temperature

Gelatin methacryloyl (GelMA) is a polymeric derivative of gelatin (Gel) widely used in tissue engineering, as well as in wound dressing and drug delivery field. This work offers an alternative and convenient method for the synthesis and characterization of GelMA. In particular, the methacrylation was carried out under homogeneous single-phase reaction conditions, which allows of obtaining a good reproducibility of the derivatization degree of the polymer in a simple and fast way. The experimental conditions were adequately optimized to have the methacrylation of only ε-amino groups of lysine and hydroxylysine, as confirmed by FT-IR and 1H NMR analysis. The degree of derivatization of GelMA was determined using an internal standard applied to 1H NMR analysis. Based on these measurements, it was found that the optimized reaction proceeds to complete functionalization of ε-amino groups of lysine and hydroxylysine. The effect of the reaction conditions on the rheological properties of GelMA was investigated through temperature sweep experiments and compared with those of the polymer obtained under traditional heterogeneous reaction conditions. A significant difference was found in the gelation temperature of GelMA synthesized following the two different procedures. In particular, the proposed single-phase synthetic protocol gave a polymer which behaves like a solution when used at 10% w/v concentration and even at temperatures as low as 5 °C, whereas the polymer obtained with the classic biphasic procedure behaves like a gel within the same range of temperatures and when used at the same concentration. These results are particularly interesting as they could open GelMA to new applications particularly in the biomedical field.

Low-loss characteristics and sustained magneto-dielectric behaviour of cobalt ferrite nanoparticles over 1–6 GHz frequency range

Cobalt ferrite (CoFe2O4) nanoparticles were synthesized through the citrate precursor route. The XRD pattern confirmed the formation of a homogeneous single-phase spinel structure with an Fd3m space group. No impurities or unreacted constituents in the sample were observed. Analysis of the most prominent (311) peak of the XRD pattern revealed the crystallite size to be ~39 nm with lattice constant and interplanar spacing as ~8.374 Å and ~2.525 Å, respectively. Other key structural parameters, such as dislocation density, strain, X-ray density, and hopping lengths, were also obtained from XRD data. Structural parameters were refined by applying the full pattern fitting of the Rietveld method using the Pseudo-Voigt function. High-resolution images obtained from SEM and TEM confirmed the morphological characteristics and crystallite size of the CoFe2O4 nanoparticles. The hysteresis loop recorded over the applied external magnetizing field of −10 kOe to +10 kOe revealed a specific saturation magnetization, specific remanent magnetization, and coercivity value of ~64 emu/g, ~24 emu/g, and ~565 Oe, respectively. A remanence ratio ~0.374 signified magnetostatic interaction between CoFe2O4 nanoparticles and confirmed their multi-domain structure and soft magnetic nature. Investigations were carried out to obtain the variations in complex dielectric permittivity, complex magnetic permeability, dielectric and magnetic loss tangents, AC conductivity, and quality factor in 1–6 GHz frequency range. The CoFe2O4 nanoparticles exhibited low dielectric and magnetic loss tangents of 10−2 and 10−3 order, along with moderate values of relative permittivity and refractive index, i.e., 4.801 and 2.3, respectively. The sustained magneto-dielectric behaviour and low-loss characteristics suggest that CoFe2O4 nanoparticles can be suitably dispersed in a dielectric matrix and used to develop efficient substrate material for improved telemetry, telecommunications and radar systems of aerospace systems operating over the 1–6 GHz frequency range.

Fluorescence Aerosol Flow Tube Spectroscopy to Detect Liquid–Liquid Phase Separation

The phase behavior of atmospheric aerosol particles influences processes like gas-particle partitioning, solar light scattering, and cloud formation, ultimately affecting atmospheric air quality and climate. An important aspect of this phase behavior is whether an individual particle exists in a single homogeneous phase or undergoes liquid–liquid phase separation (LLPS). Herein, fluorescence aerosol flow tube (F-AFT) spectroscopy is developed to characterize LLPS in aerosolized submicron particles of 100–200 nm. A solvatochromic fluorescent probe molecule is incorporated into the particles. The link between its fluorescence emission and the local particle-phase chemical environment is used to determine the separation relative humidity (SRH) at which LLPS occurs. The LLPS behaviors of mixed organic/inorganic particles composed of polyethylene glycol (PEG), ammonium sulfate (AS), and sodium chloride (NaCl) are characterized. PEG/AS particles undergo LLPS at SRH values that vary with PEG composition. By comparison, PEG/NaCl particles continue as a single homogeneous phase to the RH of NaCl crystallization. The SRH values for the submicron particles are lower by >5% RH than those reported in the literature for supermicron particles deposited to substrate surfaces. Possible reasons for the differences are discussed, including kinetic and thermodynamic effects of system size and foreign substrate as well as observation time in the experimental apparatus.

Modeling cyclic voltammetry during solid electrolyte interphase formation: Baseline scenario of a dynamically evolving tunneling barrier resulting from a homogeneous single-phase insulating film.

The solid electrolyte interphase (SEI) is an insulating film on anode surfaces in Li-ion batteries, which forms via the reaction of Li ions with reduced electrolyte species. The SEI leads to a reduction in the electrochemical current in heterogeneous electrochemical redox reactions at the electrode/electrolyte interface. Hence, the growth of the SEI is, in principle, self-limited. Toward our ultimate goal of an improved understanding of SEI formation, we develop a baseline quantitative model within Butler-Volmer electrode kinetics, which describes the cyclic voltammetry (CV) of a flat macroelectrode during SEI growth. Here, the SEI building up electrochemically during CV forms a homogeneous single-phase electronically insulating thin film due to the corresponding current. The model is based on a dynamically evolving electron tunneling barrier with increasing film thickness. Our objective is to provide a framework, which allows for both the qualitative, intuitive interpretation of characteristic features of CV measurements and the quantitative extraction of physicochemical parameters via model fitting. We also discuss the limitations of the baseline model and give a brief outlook for improvements. Finally, comparisons to exemplary CVs from the literature relevant to Li-ion battery science are presented.

A REVIEW ON NANOEMULSIONS: FORMULATION, COMPOSITION, AND APPLICATIONS

Nanoemulsions are sub-micron sized emulsions that are undergoing detailed assessment as potential drug carriers for enhancing the delivery of therapeutic agents. These are to date the most developed nanoparticulate systems for the systemic delivery of active pharmaceutical for controlled drug delivery as well as targeting. These are the thermodynamically durable isotropic system, in which two incompatible liquids (water and oil) are blended to form a single homogenous phase by utilizing a required quantity of surfactants to achieve mixing with a droplet diameter approaching roughly in the range of 0.5–100 μm. They find applications in various fields such as cosmetics as well as are adopted in various routes of administration.

Exploring the one-step synthesis of composite BiFeO3 based coatings

A one-step, annealing-free, and rapid aerosol assisted CVD method was used for the growth of composite BiFeO3 coatings. Through this method, an area of approximately 19 cm2 was coated in 7.5 min. Microstructural characterization by X-ray diffraction, Raman spectroscopy, and electron microscopy proved that BiFeO3 can be deposited onto amorphous and crystalline substrates. According to X-ray diffraction and Raman spectroscopy, small amounts of binary oxides of Bi and Fe were found in the samples; however, a more homogeneous BiFeO3 single phase was achieved using TiO2 coated borosilicate glass substrates. The samples exhibited a composite microstructure, which consisted of a thin layer of BiFeO3 (around 70 nm thick) covered by truncated and porous spherical particles of BiFeO3, Bi2O3, and Fe2O3 of several hundreds of nanometers of diameter. Findings suggested a rapid transformation of the precursor solution aerosols while traveling towards the substrate, which due to differences in size and volume, provoked variations in the composition and the development of irregular morphologies. Although the samples exhibited rough surfaces, the porous coatings offer the possibility of having materials with high-surface areas supported on inert substrates, which are attractive for applications involving surface reactions, such as photocatalysis or ambient remediation. The direct band gap of the samples exhibited values of 2.1 and 2.45 eV, reinforcing the feasible use of these materials in applications that could be triggered upon absorption of visible light.

Formation of large low shear velocity provinces through the decomposition of oxidized mantle

Large Low Shear Velocity Provinces (LLSVPs) in the lowermost mantle are key to understanding the chemical composition and thermal structure of the deep Earth, but their origins have long been debated. Bridgmanite, the most abundant lower-mantle mineral, can incorporate extensive amounts of iron (Fe) with effects on various geophysical properties. Here our high-pressure experiments and ab initio calculations reveal that a ferric-iron-rich bridgmanite coexists with an Fe-poor bridgmanite in the 90 mol% MgSiO3–10 mol% Fe2O3 system, rather than forming a homogeneous single phase. The Fe3+-rich bridgmanite has substantially lower velocities and a higher VP/VS ratio than MgSiO3 bridgmanite under lowermost-mantle conditions. Our modeling shows that the enrichment of Fe3+-rich bridgmanite in a pyrolitic composition can explain the observed features of the LLSVPs. The presence of Fe3+-rich materials within LLSVPs may have profound effects on the deep reservoirs of redox-sensitive elements and their isotopes.

Co-Amorphous Drug Formulations in Numbers: Recent Advances in Co-Amorphous Drug Formulations with Focus on Co-Formability, Molar Ratio, Preparation Methods, Physical Stability, In Vitro and In Vivo Performance, and New Formulation Strategies.

Co-amorphous drug delivery systems (CAMS) are characterized by the combination of two or more (initially crystalline) low molecular weight components that form a homogeneous single-phase amorphous system. Over the past decades, CAMS have been widely investigated as a promising approach to address the challenge of low water solubility of many active pharmaceutical ingredients. Most of the studies on CAMS were performed on a case-by-case basis, and only a few systematic studies are available. A quantitative analysis of the literature on CAMS under certain aspects highlights not only which aspects have been of great interest, but also which future developments are necessary to expand this research field. This review provides a comprehensive updated overview on the current published work on CAMS using a quantitative approach, focusing on three critical quality attributes of CAMS, i.e., co-formability, physical stability, and dissolution performance. Specifically, co-formability, molar ratio of drug and co-former, preparation methods, physical stability, and in vitro and in vivo performance were covered. For each aspect, a quantitative assessment on the current status was performed, allowing both recent advances and remaining research gaps to be identified. Furthermore, novel research aspects such as the design of ternary CAMS are discussed.

Systematic experimental search for Fe2YZ Heusler compounds predicted by ab-initio calculation

An extensive experimental investigation of Fe-based Heusler alloys has been performed in order to potentially prepare new materials which are tetragonally distorted and have large perpendicular magnetic anisotropy crucial not only for the STT-MRAM applications but also for magnetic shape memory devices. Based on criteria demanded for the MSM applications 25 Fe2YZ various compounds were selected for the synthesis using arc melting from more than 60 systems suggested theoretically. Only four compounds Fe2MnSn, Fe2NiSi, Fe2NiGe, and Fe3Ga were homogeneous single phase. None of the studied Fe-based materials exhibited the predicted tetragonal structure. Magnetic measurements confirmed that all investigated compounds are soft ferromagnets with no sign of a structural transition. Our results contradict the ab-initio calculations showing the limits of theoretical predictions by incomplete high throughput calculations as well as the limitations of the standard synthesis techniques.

The Texture and Structure of the Melt-Spun Co2MnAl-Type Heusler Alloy.

The structure of the Co2MnAl-type Heusler alloy in the form of a melt-spun ribbon was studied by electron microscopy, electron back-scattered diffraction (EBSD), and X-ray diffraction. The melt-spun ribbon consists of a homogeneous single-phase disordered Heusler alloy at the wheel side of the ribbon and an inhomogeneous single-phase alloy, formed by cellular or dendritic growth, at the free surface of the ribbon. Cellular growth causes the formation of an inhomogeneous distribution of the elemental constituents, with a higher Co and Al concentration in the centre of the cells or dendritic arms and a higher concentration of Mn at the cell boundaries. The EBSD analysis shows that the columnar crystals grow in the <111> crystal direction and are declined by about 10° against the direction of the spinning.

Investigation of entropy and turbulence characteristics of water based Al2O3, TiO2, and graphene-oxide nanoparticles in a triangular rod array

Entropy and turbulence characteristics are crucial for assessing the thermal–hydraulic performance of a nuclear reactor. Using the Finite Volume Method, this study investigates the turbulence behaviour and variation in entropy generation in a triangular rod array with water-based Al2O3, TiO2, and Graphene-Oxide nanoparticles. We also examine the effects of different volumes of nanofluids. Under forced turbulent conditions, numerical investigations were carried out assuming a homogeneous single phase mixture. The Reynolds number is varied from 20 × 103 to 80 × 103. The results are compared with traditional correlations which exhibit a precise alignment. By observing the results, it was found that as volume fractions of the coolants increase, the entropy decreases. On the contrary, with an increase in volume concentrations, however, turbulence kinetic energy was found increased.

Laser re-melting influence on isothermal oxidation behavior of electric current assisted sintered CoCrFeNi, CoCrFeNiAl0.5 and CoCrFeNiTi0.5Al0.5 high entropy alloys

In this study, it was aimed to determine the effect of laser re-melting on the oxidation behavior of high entropy alloys produced with electric current assisted sintering (ECAS). CoCrFeNi, CoCrFeNiAl0.5 and CoCrFeNiAl0.5Ti0.5 high entropy alloys (HEAs) were produced using ECAS. After the production of HEAs, the laser re-melting (LR) process was applied to the surface of sintered samples. Then, isothermal oxidation tests were carried out to HEAs at 1000 °C for 5, 25 and 75 h. Before and after the oxidation tests, the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) mapping analysis. The obtained results show that the LR process significantly improved the microstructural properties of ECAS-HEAs. More homogeneous microstructure, lower porosity and single-phase formations were observed in HEAs after LR. This has enabled a more stable microstructure compared to ECAS samples. After the oxidation tests, lower oxide layer thickness, lower oxide growth rates and lower inner oxide formation were obtained in laser re-melted HEAs. The presence of Al-rich phases enables the formation of alumina layer on the surface of HEAs. The best oxidation performance was obtained with laser re-melted CoCrFeNiAl0.5.