Phase Synthesis Research Articles

Investigations on full-Heusler alloys Mn2TaAl and Mn2WAl for spintronic and thermoelectric applications

Investigations on full-Heusler alloys Mn2TaAl and Mn2WAl for spintronic and thermoelectric applications

Amplitude and Phase Synthesis at Cylindrical Apertures of Omnidirectional Dual-Reflector Antennas for Uniform Coverage

Amplitude and Phase Synthesis at Cylindrical Apertures of Omnidirectional Dual-Reflector Antennas for Uniform Coverage

Achieving excellent strength-ductility synergy in (Co, Cr)58Ni30Mo6Al6 high entropy alloys by suppressing intermetallic compounds and introducing nanoprecipitates

Precipitation hardening serves as a viable mechanism to enhance the strength of high/medium entropy alloys (H/MEAs). The nature of precipitates in HEAs varies based on the composition of multiple principal elements. In order to further enhance the performance of HEAs across different applications, it becomes imperative to exercise control over phase synthesis and suppress the precipitation of detrimental phases. In this investigation, we propose a strategy for regulating the precipitation of the second phase in (Co, Cr)58Ni30Mo6Al6 (Co/Cr ratio = 1, 1.5, 2, 3) HEAs. Through precise adjustment of atomic ratios, the detrimental σ and μ phases are effectively restrained, while coherent nanoprecipitates are achieved through subsequent aging treatment. These fine nanoscale coherent phases alter the mode of dislocation slip, transforming planar slip into cross-slip, thereby providing a novel mechanism for the strengthening of the alloy. This controlled elimination and precipitation of phase contributes to a hierarchical improvement in the mechanical tensile properties. The aged HEA exhibits exceptional characteristics, including a strength of 1.3 GPa and 31% plasticity at 298 K (1.67 GPa and 40% at 77 K).

Alternative lengthening of telomeres (ALT) cells viability is dependent on C-rich telomeric RNAs

Alternative lengthening of telomeres (ALT) is a telomere maintenance mechanism activated in ~10–15% of cancers, characterized by telomeric damage. Telomeric damage-induced long non-coding RNAs (dilncRNAs) are transcribed at dysfunctional telomeres and contribute to telomeric DNA damage response (DDR) activation and repair. Here we observed that telomeric dilncRNAs are preferentially elevated in ALT cells. Inhibition of C-rich (teloC) dilncRNAs with antisense oligonucleotides leads to DNA replication stress responses, increased genomic instability, and apoptosis induction selectively in ALT cells. Cell death is dependent on DNA replication and is increased by DNA replication stress. Mechanistically, teloC dilncRNA inhibition reduces RAD51 and 53BP1 recruitment to telomeres, boosts the engagement of BIR machinery, and increases C-circles and telomeric sister chromatid exchanges, without increasing telomeric non-S phase synthesis. These results indicate that teloC dilncRNA is necessary for a coordinated recruitment of DDR factors to ALT telomeres and it is essential for ALT cancer cells survival.

Non-Diffraction Self-Acceleration Beams With Customized Transverse Intensity Profiles Based on 3-D-Printed Meta-Structure

In this article, two 3-D-printed all-dielectric meta-structures that can produce diffraction-free self-acceleration beams with different transverse intensity profiles are proposed in the microwave frequency band. The first single-layer meta-structure, combining the Fourier lens phase and cubic phase distributions, is engineered to generate Airy beams with highly asymmetric transverse intensity profiles. In order to flexibly customize the propagation trajectory and transverse spot shape, Bessel-like beams with symmetric transverse profiles along arbitrary trajectories are realized by the second compact meta-structure based on phase synthesis. Calculating the phase mask of the metasurface is the most critical part. In this work, phase-modulated meta-structures can map the phase information to height distribution of the cube elements that can be precisely controlled. To verify the validity, two prototypes are printed and measured. From the beam intensities at different cross sections along the propagation trajectory, the oscillating multilobe intensity pattern of the 2-D Airy beam and the symmetric non-spreading central main lobe of the Bessel-like beam can be observed in simulation and measurement. Besides that, two kinds of beams have transverse acceleration behavior and self-reconstruction property. Therefore, the proposed meta-structures have great potential in numerous challenging fields, like microwave power transmission, secure communication, imaging, and detection.

A Low-RCS Circularly Polarized Reflectarray Antenna With a Linearly Polarized Feed

A low-radar cross section (RCS) circularly polarized (CP) reflectarray antenna with a linearly polarized (LP) feed is designed. The out-of-band RCS of the reflectarray for both the TE and TM polarized incident waves is reduced by replacing its ground with an absorptive frequency selective reflector (AFSR). A systematic methodology based on synthesis of the equivalent circuit model (ECM) is presented to expedite the design of the AFSR. The unit phasing element of the reflectarray is designed in such a way that it exhibits minimum coupling between the two orthogonal reflected LP-field components. Moreover, during the reflectarray construction, a novel phase synthesis is used which takes into account possible lowest of the existing mutual coupling while providing quadrature phase difference between the orthogonal LP components with minimum phase error. The proposed design is fabricated using 14×14 phasing elements to experimentally validate the numerically simulated results. The performance of the reflectarray is compared with a conventional reflectarray without the AFSR. It is observed that when the reflectarray is integrated with the AFSR, its gain is reduced only by 1.16 dB. However, its out-of-band RCS is reduced significantly. The 8-dB RCS reduction bandwidth can be observed from 3.55-7.2 GHz (67.9%) and from 11.85-14.21 GHz (18.11%). Moreover, it provides peak co-pol CP gain of 21.62 dBi, aperture efficiency of 41%, and 1-dB gain-bandwidth from 8.68-8.95 GHz, respectively.

The effect of ZnO nanoparticles on nanomechanical behavior of Hydroxyapatite electrodeposited on NiTi biomedical alloy

This paper aims at surface characterization, chemical composition, and mechanical properties of Hydroxyapatite/ZnO (HA/ZnO) nanocomposite coatings on NiTi biomedical alloy. Morphological observations by FESEM and AFM techniques showed that ZnO NPs were responsible for a uniform, porous HA matrix. XRD analysis proved the pure HA phase synthesis in the presence of ZnO NPs; without them, there were other secondary CaP phases. XPS chemical state investigations firmly confirmed the presence of ZnO NPs by showing peaks at 531.05 eV (O ─ Zn bond) and 1021.82 eV (Zn ─ O bond). Nano-hardness test highlighted a significant enhancement in hardness of composite coating (0.37 GPa) compared to pure HA coating (0.19 GPa). The notable point was that HA/ZnO nanocomposite exhibited more plasticity than HA simple coating. This is beneficial as it provides a comfortable spot for cellular activities. Last but not least, the nano-scratch analysis revealed a great effect of ZnO inclusion on reducing friction coefficient by around 40%. The critical load was also much higher for HA/ZnO composite coating (91.4 mN) than HA coating (58.5 mN). Owing to higher plasticity and lower friction coefficient, HA/ZnO composite managed to ease the movement of the indenter tip on its surface, thereby suffering less shear stress.

Chemical resistance of celsian ceramics in acid and alkaline reagents

In the article, the chemical stability of celsian ceramics at different firing temperatures was investigated and the structural-phase features of the obtained samples before and after interaction with alkaline and acid media were studied.
 The technology of obtaining test samples was two-stage. The first stage was the synthesis of the celsian phase in a muffle furnace at a temperature of 1200 °C with a holding time of 2 hours and subsequent cooling together with the furnace. The second stage took place in a silitic furnace at temperatures of 1300, 1350 and 1400 °C with a set rate of 15 deg/min and holding at a maximum temperature of 4 hours. The chemical resistance of celsian ceramics was determined in relation to 20 % solutions of HCl and NaOH. The phase composition of the test samples was determined using the method of X-ray phase analysis (X-ray diffraction) using a DRON-3M diffractometer. The studies of the experimental samples microstructure and the surface morphology of their faults were carried out by the direct method of scanning electron microscopy using a scanning electron microscope PhenomPro.
 It was found that in relation to the 20 % solution of NaOH celsian ceramics was insoluble and has a value of alkali resistance in the range of 99.47—99.67 %. The study of microstructure and phase composition of celsian ceramics samples after treatment with 20 % NaOH solution showed that in all studied samples there was only a crystalline phase of celsian, the corrosion process didn’t occur. In relation to the 20 % HCl solution, the process of celsian ceramics corrosion was observed with the complete chemical interaction of the celsian phase with hydrochloric acid and the subsequent formation of the barium chloride dihydrate phase.

Hypergolic Synthesis of Inorganic Materials by the Reaction of Metallocene Dichlorides with Fuming Nitric Acid at Ambient Conditions: The Case of Photocatalytic Titania

Hypergolic materials synthesis is a new preparative technique in materials science that allows a wide range of carbon or inorganic solids with useful properties to be obtained. Previously we have demonstrated that metallocenes are versatile reagents in the hypergolic synthesis of inorganic materials, such as γ-Fe2O3, Cr2O3, Co, Ni and alloy CoNi. Here, we go one step further by using metallocene dichlorides as precursors for the hypergolic synthesis of additional inorganic phases, such as photocatalytic titania. Metallocene dichlorides are closely related to metallocenes, thus expanding the arsenal of organometallic compounds that can be used in hypergolic materials synthesis. In the present case, we show that hypergolic ignition of the titanocene dichloride–fuming nitric acid pair results in the fast and spontaneous formation of titania nanoparticles at ambient conditions in the form of anatase–rutile mixed phases. The obtained titania shows good photocatalytic activity towards Cr(VI) removal (100% within 9 h), with the latter being dramatically enhanced after calcination of the powder at 500 °C (100% within 3 h). Notably, this performance was found to be comparable to that of commercially available P25 TiO2 under identical conditions. The cases of zirconocene, hafnocene and molybdocene dichlorides are discussed in this work, which aims to show the wider applicability of metallocene dichlorides in the hypergolic synthesis of inorganic materials (ZrO2, HfO2, MoO2).

Pr- and Sm-Substituted Layered Perovskite Oxide Systems for IT-SOFC Cathodes

In this study, the phase synthesis and electrochemical properties of A/A//A///B2O5+d (A/: Lanthanide, A//: Ba, and A//: Sr) layered perovskites in which Pr and Sm were substituted at the A/-site were investigated for cathode materials of Intermediate Temperature-Operating Solid Oxide Fuel cells (IT-SOFC). In the PrxSm1−xBa0.5Sr0.5Co2O5+d (x = 0.1–0.9) systems, tetragonal (x < 0.4) and orthorhombic (x ≥ 0.5) crystalline structures were confirmed according to the substitution amount of Pr, which has a relatively large ionic radius, and Sm, which has a small ionic radius. All of the layered perovskite oxide systems utilized in this study presented typical metallic conductivity behavior, with decreasing electrical conductivity as temperature increased. In addition, Pr0.5Sm0.5Ba0.5Sr0.5Co2O5+d (PSBSCO55), showing a tetragonal crystalline structure, had the lowest conductivity values. However, the Area-Specific Resistance (ASR) of PSBSCO55 was found to be 0.10 Ω cm2 at 700 °C, which is lower than those of the other compositions.

The development of methods for the research and synthesis of solid phases by the scientific school of Ya. A Ugai. Review

The scientific school founded by Yakov A. Ugai has existed at Voronezh State University for over fifty years. One of its focus areas has been the development of physics and chemistry for obtaining solid phases in systems with volatile components. This determined the necessity to develop methods for the investigation of vapour pressure (tensimetric methods). This article only focuses on some of the works by the VSU staff dedicated to the study and construction of P-T-x diagrams. This review analyses phase equilibria and the nature of the intermediate phases in the AIV – BV, AIV – BV – СV, and AIII – BVI systems.Owing to the special nature of the cation-cation and anion-anion bonds, these compounds have highly specific properties that make them promising materials (2D materials in particular). The article presents an overview of works devoted to the construction of P-T-x diagrams and the investigation of defect formation processes in binary and ternary systems based on AIVBV compounds. It should be emphasised that the known techniques needed updating due to the high values of vapour pressure. This allowed conducting experiments at pressures of about 35-40 atmospheres. The study of the AIII - BVI systems,on the contrary, is complicated by low values of vapour pressure over indium and gallium chalcogenides and the complex composition of the vapour. For such systems the auxiliary component method was developed. The possibilities of its application are wide and are not limited to AIIIBVI compounds. A new method for nonstoichiometry regulation was developed and applied using non-destructive selective chemical transport reactions (i.e. with the participation of an auxiliary component). This method is based on the introduction or removal of one of the sample components by means of a selective chemical transport reaction. In conclusion, the development of methods for the research and synthesis of intermediate phases with variable compositions (properties) was analysed based on the example of the discussed systems.

Synthesis and enantioseparation characteristics of a novel β-cyclodextrin chiral stationary phase based on diazotized silica in HPLC

A novel chiral selector polyacrylic acid-β-cyclodextrin (PAA-β-CD) was successfully prepared, then a facile synthesis of PAA-β-CD stationary phase based on diazotized silica was developed and characterized. Monodisperse silica microspheres were synthesized by a modified Stöber method. The obtained silica particles were functionalized by self-assembly positive charged photosensitive diazoresin (DR) and PAA-β-CD on the surface. The corresponding chiral stationary phase (CSP) was used in HPLC and the enantioseparation performance was investigated in both polar organic and reverse phase mode. Better separation abilities and excellent enantio-selectivities were obtained on PAA-β-CD CSP for antihistamine drugs in the acetonitrile and triethylammonium acetate buffer mobile phase. Abbreviations: AIBN: azodiisobutyronitrile; β-CD: b-cyclodextrin; β-CD-NH2: amino-β-CDcyclodextrin; β-CD-OTs: sulfonyl-b-cyclodextrin; CD: cyclodextrin; CSP: chiral stationary phase; DCC: dicyclohexyl carbimide; DR: diazoresin; MeOH: methanol; NMP: N-methyl pyrrolidone; PAA: polyacrylic acid; PAA-β-CD: polyacrylic acid-β-cyclodextrin; TEAA: triethylammonium acetate; TEOS: tetraethyl orthosilicate

Synthesis and application of stationary phase for DNA-affinity chromatographic analysis of unmodified and antisense oligonucleotide

The goal of the research was the synthesis and application of an oligonucleotide immobilized stationary phase for the analysis of unmodified and antisense oligonucleotides. The method for attaching these molecules to aminopropyl silica modified with pentanedioic acid was developed. Each step of the synthesis was carefully controlled with the application of spectroscopic, elemental, and chromatographic analyses. The oligonucleotide-based stationary phase was applied for the retention studies. Unmodified oligonucleotides of different complementarity to the molecule attached as a stationary phase, as well as antisense oligonucleotides, were tested. The comparative study upon complex optimization of oligonucleotide analysis in different liquid chromatography modes was performed. Results have shown that this stationary phase may be applied for oligonucleotide analysis in hydrophilic interaction liquid chromatography and ion exchange chromatography, but no unique sequence-based selectivity was obtained. Contrary results were observed for affinity chromatography, which allowed for specific separation of the complementary strands based on hydrogen bonding and stacking interactions, where the temperature was the main factor influencing the selectivity of the separation. Furthermore, the oligonucleotide-based stationary phase may be applied for comparative antisense oligonucleotide hybridization studies to a specific RNA sequence. All of the results have shown that affinity chromatography with oligonucleotide-based stationary phases is a powerful technique for the specific base recognition of polynucleotides.Graphical abstract

Ice Bath Assisted BiMn2O5(Mullite) Phase Synthesis, Structural and Compositional Analysis under Different Bi Concentration

In this work, ice bath assisted co-precipitation synthesis of nanostructured Bismuth Manganite (BiMn2O5) with varied bismuth concentration and their consequences on the structural properties have rationally been investigated for first time in reports. The novelty of this study is to primarily elucidate the crystalline phase formations and related structural as well as compositional changes while fabricating BiMn2O5 with different amount of Bi content up to 20% to compensate the volatile Bi during annealing process. Powder X-ray diffraction and Rietveld Refinement techniques evidently confirmed the formation of single-phase mullite-type orthorhombic perovskite structure for stoichiometric ratio; while increasing Bi content, a secondary phase sillenite (Bi24Mn2O40) was formed which also gradually increased with increase in bismuth in the precursor solution. Rod and cubic shaped morphologies were commonly observed and size of the particles shows particle size ranging between 45 nm and 120 nm with increase of bismuth content. The mixed morphology is inevitably due to the presence of the secondary phases due to increasing Bi content that are evident from the XRD results. Raman and Optical properties evidently confirmed the structural variation and changes in the band gap respectively owing to the increase in secondary phase evolution with excess bismuth content. X-ray photoelectron spectroscopy (XPS) studies confirmed the increment in Bi content and the coexistence of Mullite and Sillenite phases in the samples.

Magnetic Properties and Microstructure of Sm <sub>5</sub>Fe <sub>17</sub>-Based Composite Magnets

We have investigated synthesis, magnetic properties and microstructure of Sm5Fe17-based hard magnetic phase with a Sm20Fe70Ti10 composition. Ultrahigh coercivities, μ0Hc=7.18 T at room temperature and μ0Hc=8.86 T at 10 K, have been achieved. The room-temperature coercivity, determined from high-field pulse measurements, reaches 35% of the anisotropy field μ0Ha=20.7±0.8 T. Further, it is demonstrated that a coercivity of 2.18 T is maintained even at 500 K. The Curie temperature TC of Sm20Fe70Ti10 is 577 K and the calculated exchange stiffness parameter A is 7.72 pJ/m. Detailed transmission electron microscopy investigations show a two-phase microstructure consisting of the Sm5Fe17-based hard magnetic matrix phase with grain size below 200 nm and finer, below 100 nm, Fe2Ti grains. Majority of the Fe2Ti phase is located at the grain boundaries with some finer inclusions found also inside the 5:17 grains. Despite the high fraction of the Fe2Ti grains, nearly single-phase demagnetization loops are observed. In order to enhance Ms, the effect of Ti content on phase constitution, magnetic properties and microstructure was studied in detail. Ms increases and Hc decreases for the Ti-lean compositions.

Study of Distributed Beamforming for Wireless Power Transfer in the Presence of RF Impairments

For an equivalent performance (sensitivity, communication range, computational capability, etc.), the energy efficiency of connected devices is continuously increasing. Providing the energy for such objects by the means of electromagnetic waves (wireless power transfer) becomes a feasible option in various scenarios, especially those in which the use of conventional energy resources (e.g. batteries) is unfeasible.This paper tackles a particular method of wireless power transfer, which is the distributed beamforming, i. e. the use of several sources, spatially distributed and which are coordinating together in order to maximize the power of the electromagnetic field in a particular location. Through simulation results, this paper highlights the robustness of this approach to different nonidealities, i.e. frequency and phase synthesis, phase noise and channel characteristics. A first experimental setup is also presented.

Synthesis and characterization of rectangular V2O5 microrods

Abstract In this work, rectangular vanadium pentoxide (V2O5) microrods were synthesized by the facile chemical route. For the crystal structure and morphology of the obtained microstructures, the material was characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM). The elemental composition spectra and elemental mapping of the V2O5 were studied by EDAX measurement. The results showed the successful synthesis of pure and crystalline orthorhombic phase of V2O5 rectangular microrods with appropriate elemental compositions.

Synthesis and Characterizations of Solid-Solution i-MAX Phase (W <sub>1/3</sub>Mo <sub>1/3</sub>R <sub>1/3</sub>) <sub>2</sub>AIC (R = Gd, Tb, Dy, Ho Er and Y) and Derivated i-MXene with Improved Electrochemical Properties

Synthesis and Characterizations of Solid-Solution i-MAX Phase (W <sub>1/3</sub>Mo <sub>1/3</sub>R <sub>1/3</sub>) <sub>2</sub>AIC (R = Gd, Tb, Dy, Ho Er and Y) and Derivated i-MXene with Improved Electrochemical Properties

Subsolidus structure of the ZnO–SrO–Al2O3–SiO2 system as a base for designing radio-transparent ceramics

Designing new materials with unique properties requires scientifically substantiated approaches to problem-solving. Applying a physical-chemical analysis of oxide systems to devise the formulation for a material makes it possible to determine the conditions of phase formation and assess the manufacturability of compositions. Given the enormous number of experiments required to build the state diagrams of multi-component oxide systems, the physical-chemical modeling is the most appropriate method to study their structure. This paper substantiates the selection of the basic oxide system ZnO‒SrO‒Al 2 O 3 ‒SiO 2 to design radio-transparent ceramics and reports the results of studying its subsolidus structure using modern data on splitting the system into elementary volumes. The main geometric-topological characteristics of the system's internal tetrahedra have been defined and analyzed; the minimum temperatures for melt occurrence have been calculated, as well as the eutectic compositions. To design radio-transparent ceramics with a predefined level of dielectric characteristics (e<10, tgd<10 -2 ), a region of the formulations has been selected within the tetrahedron SiO 2 –ZnAl 2 O 4 –ZnSiO 4 –SrAl 2 Si 2 O 8 concentrations, which ensure the synthesis of the target phases of willemite and strontium anorthite. By using the new data, heat-resistant polyphase ceramics have been obtained, whose dielectric characteristics (e=5.98‒8.96; tgd=0.004‒0.008) meet the requirements for radio transparent materials. The optimal ratio of phases (ZnSiO 4 :SrAl 2 Si 2 O 8= 1:1) has been established, which makes it possible to reduce dielectric permeability (e=5.98) and minimize dielectric losses (tgd=0.004). Scanning electron microscopy and X-ray analysis were used to determine the structural and phase features of the new ceramic materials

60 Years’ marine corrosion of aluminium alloy 24S (2024) from an historic aircraft wreck site: implications for conservation

ABSTRACT Aluminium alloys forming the remnants of Lockheed P38 of Antoine de Saint-Exupéry was identified as the 24S aluminium alloy developed in 1930s. After 60 years in sea water, thick corrosion layers composed of aluminium hydroxide, copper salts and nanometre pure copper particles. In addition, the ancient aluminium alloy has undergone a very important intergranular corrosion. After the synthesis of Al2Cu, Al7Cu2Fe and Al2CuMg intermetallic phases, the study of their electrochemical behaviour in NaCl medium explains the significant presence of pure copper, because all the phases undergo a dealloying process. Electrochemical impedance spectroscopy measurements show that the kinetic of dealloying is constant versus immersion time, and is not limited by diffusion which explains the complete formation of copper sponge in NaCl medium in the conditions of long-term corrosion on aluminium artefacts.