Formation Of Phase Research Articles

Growth and optimization of spray coated Cu2BaSnS4 thin films for solar photovoltaic application

Quaternary multicomponent Cu2BaSnS4 (CBTS) has emerged as a potential absorber material due to its abundant and nontoxic constituents, high absorption coefficient (10−4 cm−1) and suitable bandgap (1.5–2.0 eV) for the solar photovoltaic application. In this study, polycrystalline CBTS thin layers have been deposited by a typical spray pyrolysis technique on glass substrates using different substrate temperatures (Ts = 200, 250, 300 and 350 °C) followed by annealing in a sulfur-rich atmosphere at 550 °C under an argon flow. The (micro-)structural, compositional, and optical properties of both types of films have been studied. Analysis of x-ray diffractogram (XRD) patterns for all acquired films showed the presence of polycrystalline CBTS alongside various secondary phases, including Cu2SnS3 being predominant. Nonetheless, the XRD of the films deposited at 250 °C and annealed at 550 °C showed only the CBTS phase. Raman spectroscopy confirm the formation of the trigonal phase of CBTS. The presence of Cu, Ba, Sn and S in CBTS thin films was confirmed by X-ray photoelectron spectroscopy and Energy-dispersive X-ray spectroscopy. Scanning electron micrographs show a smooth and dense structure with enhanced crystallinity and improved uniformity. Overall, the physical properties of CBTS thin films were found to be spray deposition temperature dependent. An appropriate optical band gap of 1.6 to 1.8 eV and a compact structure indicate their prospective for solar cell applications.

Influence of multiphase microstructure on the strength and ductility of Nb–Zr–Ti–V refractory high entropy alloys

In this investigation, we focused on the lightweight Nb–Zr–Ti–V alloys as representative model alloys to explore improving mechanical properties of refractory high entropy alloys (RHEAs) through phase engineering. The alloys were deliberately designed with different element concentrations and varied cooling rates after homogenization treatment, resulting in formation of multiple secondary phases. Microstructures of prepared alloys were reported, revealing the decomposition of the BCC matrix into dual-BCC phases with increasing V content. We attribute this phenomenon to the substantial atomic size misfit between V and Zr. Additionally, a metastable FCC phase and an intermetallic Laves phase emerged at intermediate temperatures in Nb0.75ZrTiV0.75, influenced by the nonequilibrium condition during cooling and the enthalpic effect. Compression tests were performed to access mechanical characteristics of different phases. The dual-BCC phases, featuring granular or multilayer morphology, enhanced ductility of the alloy by facilitating dislocation movement at BCC interfaces. In contrast, the FCC and Laves phases, characterized by a needle-like morphology, increased strength of the alloy owing to their intrinsic hardness. Based on the current discovery and understanding on secondary phases in the Nb–Zr–Ti–V alloys, our future objective is to obtain a modulated microstructure with an appropriate combination of different phases to optimize strength and ductility simultaneously.

Effect of Temperature and Frequency on the Viscoelastic Behavior of Commercial 6082 (Al–Mg–Si) Alloy

<div>The viscoelastic response of pure Al and commercial 6082 and 6082-T6 (Al–Mg–Si) alloys is measured with dynamic–mechanical analyzer as a function of temperature (ranging from 35 to 425°C) and loading frequency (ranging from 0.01 to 100 Hz). The measured data (the storage modulus, loss modulus, and mechanical damping) are compared to available transmission electron microscopy and differential scanning calorimetry data, to ascertain whether unexplained variations of the viscoelastic behavior of the alloys can be correlated to phase transformations. The results suggest that some of these variations may be controlled by the formation and dissolution of metastable phases, such as Guinier–Preston (GP) zones and phases β″, β′, and B′. Indeed, GP zones and phase β″ have been reported to control other mechanical properties. However, due to the high complexity of the aging path of Al–Mg–Si alloys, with formation and dissolution reactions of many precipitate types overlapping along wide temperature intervals, further research is necessary to establish unequivocally the contribution of each individual phase transformation to the overall viscoelastic behavior. Finally, an internal friction peak related to grain boundary sliding is significantly smaller in the alloys compared to pure Al, probably because the precipitates pin the grain boundaries.</div>

Spark Plasma Sintering of Pure Titanium: Microstructure and Mechanical Characteristics.

The versatility of titanium (Ti) allows it to be employed in various industries, from aerospace engineering to medical technology, highlighting its significance in modern manufacturing and engineering processes. Spark plasma sintering (SPS) is currently being explored to enhance its properties further and broaden its application range. The current study focuses on exploring and optimizing the effect of SPS temperature (800, 900, 1000, 1100, 1200, and 1400 °C) on pure Ti sintered at 60 MPa in a controlled argon environment with a dwell time of 5 min. All the prepared samples were highly dense with a relative density above 99%, but exhibited significant variations in grain size (10 to 57 µm), tensile yield strength (488 to 700 MPa), ultimate tensile strength (597 to 792 MPa), and ductility (4 to 7%). A microstructural investigation was performed using XRD, SEM, and EDS to predict the influence of sintering temperature on the formation of different phases. The XRD patterns of all sintered samples showed the presence of single-phase α-Ti with hexagonally close-packed Ti. This work is a step forward in optimizing SPS-processed Ti's physical and mechanical properties for enhanced structural and biomedical applications.

Synergistic effect of Al2O3-decorated reduced graphene oxide on microstructure and mechanical properties of 6061 aluminium alloy

In this study, Al6061 alloy matrix composites reinforced Al2O3-decorated reduced graphene oxide (Al2O3/RGO) with 0.1, 0.3 and 0.5 weight present (wt%) were successfully fabricated using high energy ball milling and hot extrusion techniques. The microstructures of these Al2O3/RGO/Al6061 aluminum matrix composites (Al MMCs) were characterized. The results showed that Al2O3/RGO were uniformly distributed within the Al6061 matrix and tightly bonded to the matrix. Al2O3 encapsulation on RGO surface would prevent the formation of Al4C3 brittle phase in matrix, ensuring that there was no reaction between the reinforcement and the matrix Al6061. Tensile strength and Vickers hardness tests demonstrated that the mechanical properties of Al MMCs significantly increased with addition of Al2O3/RGOs. Remarkably, Al MMCs with 0.1 wt% reinforcement showed tensile yield and tensile strengths of 270 MPa and 286 MPa, respectively, which were 49% and 43% higher than those of pure Al6061 prepared using the same process. Furthermore, the 0.1 wt% Al2O3/RGO composite also showed the best plastic deformation capability in considering of the strength.

Enhancing the mechanical properties and thermal conductivity of Ti/AZ91 composites through integrated extrusion and rolling continuous deformation processing

With the increasing demand for highly integrated circuits to optimize energy efficiency, reduce weight, and improve mechanical properties, finding a Magnesium (Mg) matrix material with excellent mechanical strength and high thermal conductivity poses a significant challenge. In this work, titanium (Ti) particles were introduced into AZ91 (Mg-9Al-1Zn) alloy to fabricate Ti/AZ91 composites, employing a combination of stir casting, extrusion and rolling processes. This strategy simultaneously enhances the mechanical properties and thermal conductivity of the Ti/AZ91 composites compared with AZ91 alloy. The incorporation of Ti particles serves to refine grains, expediting the formation of Mg17Al12 phase within the Mg matrix. Optimal comprehensive mechanical properties are attained in 10 wt% Ti/AZ91 composite, exhibiting an ultimate tensile strength of 365 MPa, an elongation of 11.9 %, and a significantly low wear rate of 4.548×10−3 mm3/m. Notably, the 10 wt% Ti/AZ91 composite shows a 41.1 % reduction in wear rate relative to the AZ91 alloy, attributed to the incorporation of hard Ti particles. Furthermore, the thermal conductivity of the 2.5 wt% Ti/AZ91 composite exhibits a significant enhancement over that of the AZ91 alloy. Detailed discussions are provided on the fundamental mechanisms responsible for strengthening, wear resistance, and thermally conductive in Ti/AZ91 composites. These results highlight the substantial potential of Ti/AZ91 composites for lightweight structural applications, such as highly integrated circuits requiring excellent mechanical properties and high thermal conductivity.

Evolution of thermoelectric transport properties of Sb2Te3–Sb2Se3 solid-solution alloys depending on phase formation behavior

Sb2Te3-based alloys exhibit decent thermoelectric transport properties in the mid-temperature range above 550 K. However, the study on Sb2Te3 alloys has been limited in simple doping approach. Herein, evolution in the thermoelectric transport properties associated with the phase formation of solid solution alloys of Sb2(Te1−xSex)3 (x = 0, 0.25, 0.33, 0.5, 0.75, and 1.0) compositions is investigated to widen the strategy to solid solution alloying. A single phase of the Sb2Te3 rhombohedral structure formed from x = 0 to 0.5, whereas mixed phases with an orthorhombic structure of Sb2Se3 was observed at x = 0.75. The electrical conductivity weighted mobility were gradually decreased as Se content increases to x = 0.75. Consequently, the power factor was decreased gradually and significantly to 0.076 mW/mK2 for x = 0.75 (Sb2(Te0·25Se0.75)3) compared with 2.6 mW/mK2 of the pristine sample. The total thermal conductivity of 2.0 W/mK for the Sb2Te3 was significantly reduced gradually to 0.64 W/mK for x = 0.75 owing to simultaneous decrease in electrical and lattice thermal conductivities. The reduction in lattice thermal conductivity is mainly owing to the addition point defect scattering caused by the Se addition. Nevertheless, thermoelectric figure of merit zT of Sb2Te3 is gradually decreased from 0.64 to 0.11 for x = 0.75 at 650 K due to the degradation in electrical transport properties. Furthermore, the theoretical zT was estimated for all samples with varying carrier concentration based on single parabolic band model.

Computational thermodynamics-guided alloy design and phase stability in CoCrFeMnNi-based medium-and high-entropy alloys: An experimental-theoretical study

A computational thermodynamics approach has been employed to design CoCrFeMnNi-based medium- and high-entropy alloys (M/HEAs) with systematically varied compositions (Co((80-X)/2)Cr((80-X)/2)FeXMn10Ni10 with x = 30, 40, and 50 at.%) and phase stability. Since the formation of sigma phase, usually brittle and undesirable, is a common concern, when this class of alloys is subjected to elevated temperatures (600–1000 °C), predicting its formation becomes essential. Thus, its formation and the phase equilibria were studied using the CALPHAD method, and two empirical methods, namely, valence electron concentration (VEC) and paired sigma-forming element (PSFE). Isothermal aging treatments at 900–1100 °C for 20 h were performed, since CALPHAD and VEC/PSFE predictions diverged. Both prediction methods were compared with experimental characterization by a combination of scanning electron microscopy and high-energy synchrotron X-ray diffraction. The predictions from the VEC/PSFE and CALPHAD calculations (depending on the database used) were shown to be quite accurate.

Mechanical properties and microstructure of magnesium alloy with in situ formed Al2RE phases

The advancement of magnesium alloys has historically faced challenges due to their inherently low modulus and the inverse relationship between modulus and ductility. In this study, an Mg-15Gd-8Y–11Al-0.3Mn alloy containing Al2RE phases was developed through an in-situ synthesis process, exhibiting exceptional mechanical properties, including a high elastic modulus of 57.6 GPa coupled with a satisfactory elongation of 7.3 %. The findings indicate the presence of polygonal Al2RE phases of varying sizes within the alloy, with α-Mg observed in some Al2RE phases, forming a coherent interface. The grain size of the alloy was refined, and the dimensions of the Al2RE particles were reduced through the extrusion process. The effective strain transfer between α-Mg and Al2RE, facilitated by the coherent interface, endowed the alloy with commendable ductility, even at a substantial Al2RE volume fraction of 23 %. Furthermore, the formation of the Al2RE phase was identified as the key contributor to the alloy's enhanced modulus. This study provides novel insights for the engineering of high-modulus magnesium alloys, thereby paving the way into their broader industrial application.

Nanometer Control of Ruddlesden-Popper Interlayers by Thermal Evaporation for Efficient Perovskite Photovoltaics.

Solution-processed Ruddlesden-Popper (RP) interlayers in lead halide perovskite solar cells (PSCs) present processing challenges due to fast film formation and uncontrolled growth of phases and layer thickness at interfaces. In this work, an alternative, solvent-free, thermal co-evaporation process is developed to deposit RP interlayers. The method provides precise control on interlayer thickness and enables understanding its role on charge-carrier extraction. Studying RP film growth reveals the development of heterointerfaces when deposited on three-dimensional (3D) perovskite layers. This allows a large thickness window with an optimum between 20 nm and 40 nm to improve the optoelectronic properties of the underlying 3D perovskite. Solar cells using evaporated interlayers achieve power conversion efficiency of 21.6%, compared to 19.6% for untreated devices, driven by improvements in the open-circuit voltage and fill factor. This work sheds light on the importance of phase and thickness control of passivation layers, which ultimately determine the solar cell performance in state-of-the-art PSCs.

Performance improvement of glass-based lightweight aggregates through thermodynamic modelling design and lightweight mortar validation

To reduce environmental impact of sintered lightweight aggregates (LWAs), in this study, novel glass-based LWAs were produced from municipal solid wastes at 900 °C. The mix was designed by thermodynamic modelling to optimize the phase composition, liquid phase properties, and microstructure of the LWAs. Results demonstrated that the inclusion of incinerated sewage sludge ash (ISSA) increased the viscosity of the liquid phase, resulting in a refined pore structure characterized by smaller, more isolated pores, and thicker pore walls. Additionally, ISSA facilitated the formation of various crystalline phases (e.g. wollastonite) to stabilize the pore structure, thereby enhancing densification and matrix strength. Leaching behaviour tests confirmed the suitability of glass-based LWAs for environmentally safe lightweight products. Lightweight mortars incorporating developed LWAs exhibited a high 28-day compressive strength (up to 57.9 MPa) with a low density of 1688 kg/m3 and a low thermal conductivity of 1.0 W/(m·K). The energy simulation revealed substantial reductions in energy consumption when the lightweight mortars were utilized in the building compared with the reference building using normal-weight C30 concrete, underscoring its promising role in conserving energy and reducing carbon emissions.

Sustaining Surface Lithiophilicity of Ultrathin Li-Alloy Coating Layers on Current Collector for Zero-Excess Li-Metal Batteries.

Zero-excess Li-metal batteries (ZE-LMBs) have emerged as the ultimate battery platform, offering an exceptionally high energy density. However, the absence of Li-hosting materials results in uncontrolled dendritic Li deposition on the Cu current collector, leading to chronic loss of Li inventory and severe electrolyte decomposition, limiting its full utilization upon cycling. This study presents the application of ultrathin (≈50nm) coatings comprising six metallic layers (Cu, Ag, Au, Pt, W, and Fe) on Cu substrates in order to provide insights into the design of Li-depositing current collectors for stable ZE-LMB operation. In contrast to non-alloy Cu, W, and Fe coatings, Ag, Au, and Pt coatings can enhance surface lithiophilicity, effectively suppressing Li dendrite growth, thereby improving Li reversibility. Considering the distinct Li-alloying behaviors, particularly solid-solution and/or intermetallic phase formation, Pt-coated Cu current collectors maintain surface lithiophilicity over repeated Li plating/stripping cycles by preserving the original coating layer, thereby attaining better cycling performance of ZE-LMBs. This highlights the importance of selecting suitable Li-alloy metals to sustain surface lithiophilicity throughout cycling to regulate dendrite-less Li plating and improve the electrochemical stability of ZE-LMBs.

A combined experimental and simulation study of multiphase bimetallic iodides semiconductor solar cell

The need of high quantum efficiency and stable semiconductor for the photovoltaics are always highly required. In this work, four phase containing multiphase bimetallic iodide (MPBI) compound was synthesized at room temperature by simple and novel chemical route. Synthesized compound was studied for structural, optical, and morphologic properties. The compound structural and phase confirmation was done by XRD, FT-IR, Raman spectroscopy and TEM studies. Optical properties such as absorption and emission characteristics were studied by UV-Visible spectroscopy and fluorescent spectroscopy respectively. The surface morphology and the elemental composition mapping was carried out using SEM and TEM methods. The detailed characterization inferred that high-temperature stable phase Ag4PbI6 was stabilized at room temperature along with AgI, PbI2 and Ag. From the obtained results, the mechanism of Ag4PbI6 phase formation is proposed and discussed. The synthesized semiconductor compound was studied for solar cell applications and obtained efficiency is 5.14 %. Further, the experimental solar cell results were verified using simulation results. This is one of the very few works which reports on room temperature stabilized high temperature stable Ag4PbI6 phase containing multiphase compound.

Mechanically Alloyed FeNi and Fe Powders Crystalline Size, Phase Formation, and Morphology: Investigation on Milling Time Impact

Mechanically Alloyed FeNi and Fe Powders Crystalline Size, Phase Formation, and Morphology: Investigation on Milling Time Impact

Phase Transformation of AlV55 Alloy at High Temperature

Vanadium–aluminum alloy is an important intermediate alloy for preparing aviation grade titanium alloys, and its product quality directly affects the finished product quality of titanium alloys. In this study, focusing on the problems of high powder content (19.8%) and low product yield in AlV55 alloy products, we conduct research on alloy quality control technology and implement a vanadium–aluminum alloy cooling crystallization control process. The research results indicate that there are three phases in AlV55 alloy, namely Al8V5, AlV, and Al2V3 phases. As the temperature decreases, the AlV phase gradually decomposes into Al8V5 phase and Al2V3 phase, and the proportion of Al8V5 phase is positively correlated with the fineness. Rapid cooling can reduce the formation of Al8V5 phase. The experimental results show that high-temperature water quenching can increase the proportion of vanadium–aluminum solid solution phase in the alloy from 19.03% to 31.76%, and reduce the fine powder rate to 13.2%, providing important product quality control means and technical support for the production of vanadium–aluminum alloys.

Chemical Reaction Modulated Low-Dimensional Phase Toward Highly Efficient Sky-Blue Perovskite Light-Emitting Diodes.

Blue perovskite light-emitting diodes (PeLEDs) are crucial avenues for achieving full-color displays and lighting based on perovskite materials. However, the relatively low external quantum efficiency (EQE) has hindered their progression towards commercial applications. Quasi-two-dimensional (quasi-2D) perovskites stand out as promising candidates for blue PeLEDs, with optimized control over low-dimensional phases contributing to enhanced radiative properties of excitons. Herein, the impact of organic molecular dopants on the crystallization of various n-phase structures in quasi-2D perovskite films. The results reveal that the highly reactive bis(4-(trifluoromethyl)phenyl)phosphine oxide (BTF-PPO) molecule could effectively restrain the formation of organic spacer cation-ordered layered perovskite phases through chemical reactions, simultaneously passivate those uncoordinated Pb2+ defects. Consequently, the prepared PeLEDs exhibited a maximum EQE of 16.6% (@ 490 nm). The finding provides a new route to design dopant molecules for phase modulation in quasi-2D PeLEDs.

Study of the influence of temperature and duration of chlorinating roasting on the extraction of gold from E-waste

In this work, based on experimental studies, the effect of roasting temperature and duration on the chlorination of gold from E-waste under low-temperature conditions was studied. It has been established that in the low-temperature range of 150-300 °C, the gold content in the residue shows a sharp decrease, reaching its minimum of 8 ppm at 250 °C. A further increase in temperature does not affect the gold content in the cinder. It has been shown that during chlorinating roasting above a temperature of 250 °C, side reactions should be expected to occur with the formation of additional phases representing chlorides of copper, iron and other elements. The results of SEM and XRD analyzes of the solid phase obtained after chlorinating roasting at a temperature of 250 °C and a roasting duration of 20 minutes showed the presence of copper and iron chlorides in them. Optimal technological parameters and modes of the process of chlorinating roasting of E-waste with gaseous chlorine have been established: temperature – 250 °С; roasting duration – 20 minutes; chlorine consumption is 1.5 times more than the stoichiometrically required amount (SRA) for gold chlorination. Under optimal roasting conditions, a high, up to ~97.6%, recovery of gold in the form of gold chloride (AuCl3) was achieved. The results of the experiments can be a basic basis and make it possible to conduct more representative experiments (scaling) in the future, taking into account the established optimal technological parameters. This will provide a chance to evaluate the possibility of extracting gold from E-waste of different types and compositions and to conduct further research on obtaining pure gold from the collected representative amount of gold sublimate AuCl3 by smelting.

Microstructure and high-temperature tribological behaviours of nano-HfC reinforced Inconel 625 composite coating by plasma-transferred arc welding

The study involved plasma arc transfer welding (PTAW) for preparing coatings of Inconel 625 alloys that contained different amounts of nano-sized hafnium carbide (nano-HfC) particles. The impact of nano-HfC on the microstructure evolution and mechanical properties of PTAWed Inconel 625 were investigated. The research reveals that nano-HfC decomposes during the high-temperature plasma arc process and then react with O element to generate nano-HfO2. These HfO2 can serve as nucleation sites for MC carbides, which restricts the growth of secondary dendrite arms, leading to a more disordered grain growth direction. Simultaneously, the decomposition of HfC can increase the C/Nb ratio of the matrix, effectively suppressing Laves phase formation while encouraging the development of MC carbides. Compared with IN625, the wear rate of composites at room temperature and 600 °C were decreased. Notably, at 600 °C, the wear rate of the coating with 0.5 wt% HfC is the lowest among all the samples, as reflected by a noteworthy reduction in wear rate of 50 %. This is mainly attributed to the refinement of γ matrix, reduction of Laves phase as well as precipitation of the fine-sized MC carbides. This work illustrates that adding nano-HfC is an effective way to improve the wear resistance of the PTAWed Inconel 625.

The effect of CoPt3 sublayer on the formation of fct-L10 FePt nanoparticles in direct synthesis method

The smaller the size of magnetic nanoparticles is, the less their coercivity will be. The magnetic coercivity of FePt nanoparticles, in the compound ordered phase, known as fct-L10 FePt, is up to the order of tesla; however, the temperature of 600 °C, required for the formation of this phase, increases the size of FePt nanoparticles. In this research, fct-L10 FePt nanoparticles were fabricated using the direct synthesis method by Co-sputtering system. The presence of a CoPt3 sublayer resulted in the formation of a fct-L10 phase of FePt nanoparticles at 400 °C with a uniform surface distribution and mean size and standard deviation of 11 nm and 1.5 nm, respectively. The same as the other results of FePt/CoPt3, magnetic coercivity of fct-L10 FePt nanoparticles, with the mentioned size, reached to 3.0 kOe at room temperature, because of the presence of the CoPt3 sublayer.

Dielectric anisotropy in self-assembling MXene-based lyotropic nematic compounds

The formation of a lyotropic liquid crystal phase at the level of MXene-based aqueous dispersions due to the self-assembling capacity of these two-dimensional (2D) materials has been previously successfully reported. However, the influence of electrical external factors has been less studied in spite of the fact that understanding the electrical behaviour of 2D-based liquid crystal compounds is vital for fostering the development of new innovative applications. Consequently, within this paper, we report an in-depth evaluation of the dielectric properties of liquid crystalline phases in Ti3C2 MXene aqueous dispersions. The dependence on the low voltage of planar ε⊥′ to homeotropic ε∥′ orientational transition is emphasized and discussed, while the influence of the electric field frequency at the level of dielectric anisotropy is assessed in respect to various concentrations of MXene flakes within the same 2D-based compounds. Nonetheless, dielectric spectroscopy highlights the biphasic nature (containing both nematic and isotropic phases) of the studied aqueous Ti3C2 MXene inks visible up to 20% MXene. Above this concentration, the existence of a pure nematic phase in the dispersion of highMXene concentration (>20 wt%) was detected based on the evaluation of dielectric permittivity against various voltage values.