Narrow Process Window Research Articles

Low-cost green antisolvent with an ultrawide processing window for efficient and stable perovskite solar cells

Antisolvent engineering is one of the most useful strategies to get high-efficiency perovskite solar cells (PSCs). Nevertheless, the most present commonly used effective antisolvents, such as chlorobenzene and diethyl ether, are toxic and expensive. Moreover, these antisolvents applied in PSCs are rather restricted due to their narrow processing window. Herein, we report a low-cost green antisolvent isopropanol (IPA) that displays ultrawide processing window, which dramatically enhances the reproducibility of PSCs. The highest power conversation efficiency of PSCs treated by IPA can reach as high as 24.8%. The origin of IPA effects is further disclosed by the intermolecular hydrogen-bonding force between IPA and DMF/DMSO, and the force can effectively remove DMF/DMSO in the spinning perovskite precursor film and helpfully enhance perovskite crystal growth with less carrier recombination as demonstrated by using various techniques. Our results here demonstrate a cheap green antisolvent for reproducible, high-efficient, stable PSCs and also provide an in-depth understanding the significant role of antisolvent in the fabrication of PSCs.

A novel approach to simultaneously modulate the processability and thermal performance of phthalonitrile resin through the strategic use of thioether bonds

Phthalonitrile (PN) resin is renowned for its absence of small molecule release during curing, high processing stability, and exceptional thermal stability, positioning it favorably in the realm of high-temperature resin applications. However, its narrow processing window and high melting point present challenges to its development and practical use. To address these limitations, this work synthesized PN prepolymers 4,4′-bis (sulfonylbiphenyl) thiophtalonitrile (BSPS) and 4,4′-bis(carbonylbiphenyl) thiophtalonitrile (BSPC) by introducing thioether bonds as a substitute for ether bonds, aiming to expand the prepolymers' processing window. Meanwhile, building upon the oxidation process of thioether to sulfone observed in pharmaceutical production, the potential for in-situ oxidation of thioether bonds during the curing of phthalonitrile prepolymers was investigated. A comprehensive analysis of the curing behavior, viscosity changes, and thermal stability was conducted using differential scanning calorimetry (DSC), rheological analysis, and thermogravimetric analysis (TGA). The DSC and rheological test results reveal that the experimental group prepolymers BSPS and BSPC exhibit lower melting points (BSPS 179 °C; BSPC 180 °C) and broader processing windows (BSPS 52 °C; BSPC 79 °C) than blank. Additionally, the thermal performance of resins show improvement over the blank, with BSPS achieving a decomposition temperature of up to 530 °C (Td5%). XPS analysis of the curing process confirmed that the enhanced thermal stability is attributable to the partial oxidation of thioether bonds into stable sulfone groups. This innovative structural approach allows for satisfactory processing performance in the initial stage, followed by a spontaneous transformation into a more robust and thermo-resistant structure post-shaping. This finding carries significant implications for the development of a balanced phthalonitrile system that harmonizes processing ease with superior thermal endurance.

Controlled Crystallization and Enhanced Performance of γ-CsPbI3 Perovskite Through Methylammonium Iodide-Assisted Coevaporation.

Cesium lead triiodide (CsPbI3) perovskites have garnered significant attention owing to their suitable bandgap for tandem silicon substrates and excellent chemical stability. However, γ-CsPbI3 prepared via low-temperature co-evaporation is limited by a narrow black phase processing window and random crystal orientation, hindering its optoelectronic performance and industrial applications. This study introduced trace amounts of methylammonium iodide (MAI) into the co-evaporation system, enhancing the crystallization process, promoting columnar grain growth, and stabilizing the γ-phase perovskite, resulting in films with improved structural integrity and reduced defect density. The optimal Pb/Cs ratio for achieving the best photoelectric performance shifted from 1:1 to 1.1:1 in the presence of MAI. Additionally, the incorporation of MAI allowed for more efficient longitudinal carrier transport, as evidenced by the enhanced photoluminescence (PL) intensity. The bandgap of CsPbI3 remained approximately at 1.7eV before the δ-phase transition, ensuring suitability for photovoltaic applications. Ultimately, a photovoltaic device with 12% efficiency is achieved in the p-i-n structure without additional post-annealing of the CsPbI3 perovskite films, demonstrating the practical benefits of MAI incorporation.

Performance Enhancement of Biopolyester Blends by Reactive Compatibilization with Maleic Anhydride-Grafted Poly(butylene succinate-co-adipate).

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a very promising biodegradable copolyester of high interest in food packaging. Its inherent brittleness and narrow processing window make it necessary to blend it with flexible biopolyesters, such as poly(butylene succinate-co-adipate) (PBSA). However, the resultant biopolyester blends are thermodynamically immiscible, which impairs their performance and limits their applications. This study is the first to explore the use of poly(butylene succinate-co-adipate) grafted with maleic anhydride (PBS-g-MAH) as a novel reactive additive to compatibilize PHBV/PBSA blends. The compatibilizer was prepared by a reactive melt-mixing process of PBSA and maleic anhydride (MAH) using dicumyl peroxide (DCP) as an organic radical initiator, achieving a grafting degree (Gd) of 5.4%. Biopolyester blend films were thereafter prepared via cast extrusion and their morphological, thermal, mechanical, and barrier properties were characterized. Compatibilization by PBSA-g-MAH was confirmed by observing an improved phase interaction and lower dispersed domain sizes in the blends with 15 wt% PBSA. These compatibilized PHBV/PBSA blends were thermally stable up to 285 °C, showed enhanced ductility and toughness, as well as providing an improved barrier against water and limonene vapors and oxygen. These findings suggest that the use of MAH-grafted biopolyesters can represent an effective strategy to improve the properties of biopolyester blends and open up new opportunities for the application of PHBV-based formulations for food packaging.

Enhancing 3D printability of polyhydroxybutyrate (PHB) and poly(3-hydroxybutyrate-co-3-hydroxy valerate) (PHBV) based blends through melt extrusion based-3D printing

Polyhydroxybutyrate (PHB) and poly (3-hydroxybutyrate-co-3-hydroxy valerate) (PHBV) possess favorable biological properties such as biocompatibility and biodegradability, making them suitable for various applications. However, their utility is limited by a narrow processing window due to low thermal stability and challenges in manipulating filament size during extrusion, attributed to poor melt strength. These issues result in irregularities such as discontinuous flow and incomplete deposition of melted PHB, significantly affecting 3D printing outcomes. To address these concerns, this study explores blending PHB and PHBV with poly (lactic acid) (PLA) and poly (butylene adipate-co-terephthalate) (PBAT) to enhance its processability and printability. Thermal analysis of all blends revealed three distinct degradation steps occurring at approximately 300, 360, and 400ºC, corresponding to PHB or PHBV, PLA, and PBAT, respectively. Moreover, the melting temperatures of PHB, PHBV, PLA, and PBAT were measured around 176, 173, 152, and 121ºC, respectively. It was observed that the polymer blends exhibited lower crystallization temperature and degree of crystallinity compared to PHB or PHBV. Assessing their 3D printability, neat PHB and PHBV filaments experienced fusion issues, poor flow during extrudate deposition, and significant warping, leading to 3D printing failures. In contrast, the blends displayed enhanced flowability and successfully produced high-quality specimens. Scanning electron microscope (SEM) analysis highlighted a phase separation morphology in the blends, showcasing uniform dispersion of PLA and PBAT within the PHB matrix.

A novel Ni40Co18Cr18Fe14Al5Ti5 high entropy alloy with superior mechanical properties and broad printing window via selective laser melting

3D printing technology has gained popularity in fabricating high-entropy alloys (HEAs) due to its inherent design adaptability and the capacity to create distinctive structural features. However, the field of 3D-printed HEAs has faced substantial challenges, primarily stemming from a narrow processing window and unsatisfactory mechanical properties. This study unveils a novel Ni40Co18Cr18Fe14Al5Ti5 HEA, suitable for selective laser melting (SLM) technology, showcasing a broad processing window and outstanding mechanical properties. The SLM-produced HEA exhibits near-full density and a hierarchical structure characterized by equiaxed grains without significant texture, cellular structures, and element segregation at cellular boundaries. Remarkably, this HEA demonstrates impressive mechanical performance across various printing parameters, highlighted by a yield strength of 811 MPa, an ultimate strength reaching 1071 MPa, and a tensile elongation of 29 % in the optimized sample. Microstructural analysis reveals that the synergistic effects of dislocation motion, stacking faults, and deformation-induced twinning contribute to the stable strain-hardening capability of the SLM-produced Ni40Co18Cr18Fe14Al5Ti5 HEA.

Hot-Casting Strategy Empowers High-Boiling Solvent-Processed Organic Solar Cells with Over 18.5% Efficiency.

Most top-rank organic solar cells (OSCs) are manufactured by the halogenated solvent chloroform, which possesses a narrow processing window due to its low-boiling point. Herein, based on two high-boiling solvents, halogenated solvent chlorobenzene (CB) and non-halogenated green solvent ortho-xylene (OX), preparing active layers with the hot solution is put forward to enhance the performance of the OSCs. In situ test and morphological characterization clarify that the hot-casting strategy assists in the fast and synchronous molecular assembly of both donor and acceptor in the active layer, contributing to preferable donor/acceptor ratio, vertical phase separation, and molecular stacking, which is beneficial to charge generation and extraction. Based on the PM6:BO-4Cl, the hot-casting OSCs with a wide processing window achieve efficiencies of 18.03% in CB and 18.12% in OX, which are much higher than the devices processed with room temperature solution. Moreover, the hot-casting devices with PM6:BTP-eC9 deliver a remarkable fill factorof 80.31% and efficiencyof 18.52% in OX, representing the record value among binary devices with green solvent. This work demonstrates a facile strategy to manipulate the molecular distribution and arrangement for boosting the efficiency of OSCs with high-boiling solvents.

Nucleation and property enhancement mechanism of robust and high-barrier PLA/CNFene composites with multi-level reinforcement structure

The demand for biopolymer-based green packaging has attracted growing attention because of its outstanding properties and consistency with clean environmental principle, unfortunately, its slow crystallization rate and narrow processing window are challenging. Inspired by combined functions in nanocellulose-based conductive hybrids, this work developed high-performance polylactic acid (PLA) composites using conductive cellulose nanofiber (CNFene). Interestingly, CNFene has multiple functions as highly graphitized carbon and abundant hydroxyl groups, delivering stimulating properties to PLA composites. As nucleating agents, 3 wt% CNFene has a carbon layer on the surface combined with a hydrogen bonding network synergistically enhancing the tensile and crystallization properties of PLA-C3, with a tensile strength of ∼ 53.7 MPa, crystallinity of ∼ 33.9 %, and 6.6 °C decrease in the cold crystallization temperature. Additionally, the compatibility between CNFene and PLA can form a multi-level “reinforcement” network structure, further improving thermal stability and barrier properties. The resultant PLA-C3 showed higher thermal decomposition onset temperature (T0), wider melt-processing window (197.6 °C) and extremely lower overall migration levels in ethanol (68.6 μg/kg) and isooctane (16.3 μg/kg), due to that improved interaction between CNFene and PLA positively affects crystallization ability and kinetic/mechanism of PLA to meet the requirements of industrial and green biopackaging applications.

Unlocking the Ambient Temperature Effect on FA-Based Perovskites Crystallization by In Situ Optical Method.

Multiple cation-composited perovskites are demonstrated as a promising approach to improving the performance and stability of perovskite solar cells (PSCs). However, recipes developed for fabricating high-performance perovskites in laboratories are always not transferable in large-scale production, as perovskite crystallization is highly sensitive to processing conditions. Here, using an in situ optical method, the ambient temperature effect on the crystallization process in multiple cation-composited perovskites is investigated. It is found that the typical solvent-coordinated intermediate phase in methylammonium lead iodide (MAPbI3) is absent in formamidinium lead iodide (FAPbI3), and nucleation is almost completed in FAPbI3 right after spin-coating. Interestingly, it is found that there is noticeable nuclei aggregation in Formamidinium (FA)-based perovskites even during the spin-coating process, which is usually only observed during the annealing in MAPbI3. Such aggregation is further promoted at a higher ambient temperature or in higher FA content. Instead of the general belief of stress release-induced crack formation, it is proposed that the origin of the cracks in FA-based perovskites is due to the aggregation-induced solute depletion effect. This work reveals the limiting factors for achieving high-quality FA-based perovskite films and helps to unlock the existing narrow processing window for future large-scale production.

Phase-controlled molybdenum dioxide electrodes by RF reactive magnetron sputtering for achieving high-k rutile TiO2 dielectric

Molybdenum dioxide (MoO2) has recently garnered attention as a promising oxide electrode for next-generation dynamic random-access memory capacitors owing to its high work function, low resistivity, and good thermal stability. The formation of pure, reliable MoO2 films is a significant challenge because of their higher formation energy than that of non-conductive orthorhombic molybdenum trioxide (MoO3). Herein, we investigated the controlled growth of MoO2 films by manipulating the process pressure and oxygen-to-argon (O2/Ar) ratio using radio frequency reactive magnetron sputtering. By increasing the O2/Ar ratio at a fixed process pressure (pp), sputtered MoOx films were fabricated as metallic Mo, monoclinic MoO2, and orthorhombic MoO3. The MoO2 film with Mo/O atomic ratio of 0.5 was achieved in the narrow process window of O2/Ar ratio of 0.22 and pp = 3 mtorr. The MoO2 films exhibited a smooth surface morphology with a root mean square roughness of 0.34–0.68 nm. The resistivity of MoO2 film was 972 μΩ cm, which was decreased to 374–524 μΩ cm by rapid thermal annealing in N2 at 600 °C-800 °C. The phase-controlled MoO2 electrode led to the in-situ crystallization of high-k rutile TiO2 with a dielectric constant of 93 via local epitaxial growth. This might be attributed to the excellent coherence in the atomic arrangement and low lattice mismatch between the distorted rutile MoO2 (011) and rutile TiO2 (110) planes.

Process‐property relationship in polylactic acid composites reinforced by iron microparticles and 3D printed by fused filament fabrication

AbstractPolylactic acid (PLA) is the most widely used material in the fused filament fabrication (FFF) technique, which is a biocompatible thermoplastic. However, PLA's usefulness is limited by its narrow processing window and relatively low mechanical properties. Therefore, PLA composites have been developed to enhance its properties for FFF printing. A key challenge in producing composite parts via this method is to find the correlation between the mechanical properties of the parts and the process parameters. This knowledge is essential for optimizing the printing process to achieve the desired mechanical properties for composite parts industries such as aerospace, automotive, and medical, where high‐performance composite materials are crucial. The ability to control and predict the mechanical properties of FFF‐printed composite parts is critical for their successful integration into these industries. In this study, the effect of nozzle temperature (NT), printing speed (PS), and nominal porosity (POR) on the impact strength and specific impact strength of PLA/iron composites was examined using FFF. Response surface methodology (RSM) was used to optimize the experimental design. The results revealed that POR had the most significant effect on the impact resistance data, while NT had the least effect. Reducing the POR led to improved impact resistance in the samples. Multi‐objective optimization results showed that the lowest NT (190°C), the lowest POR (30%), and a PS of 50 mm/s were the optimal conditions for multiple objectives. RSM was also utilized to develop mathematical models of impact properties, focusing on varying NT, POR, and PS, which can be used to predict desired impact properties.Highlights Nominal porosity has the most influence on the impact strength of PLA/iron composites. Optimum values were temperature of 190°C, nominal porosity of 30%, and speed of 50 mm/s. RSM was effective in enhancing the mechanical properties of composite materials. RSM models provide a predictive tool for future FFF‐printed composite parts. Maximum impact strength of 4.44 kJ/m2 was achieved.

Synthesis and characterisation of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) multi-block copolymers comprising blocks of differing 3-hydroxyvalerate contents

Polyhydroxyalkanoates (PHAs) are attractive alternatives to commodity petroleum derived plastics, being bacterially derived, thermoprocessible and truly biodegradable under ambient conditions. However, the common short chain length PHAs - poly(3-hydroxybutyrate) (P3HB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) - are relatively stiff and brittle, and P3HB in particular has a narrow processing window. Block copolymer synthesis offers an opportunity to produce novel PHA materials comprised of different PHA phases, delivering a potential step-change improvement in PHA properties due to microphase separation. Therefore, this work demonstrates the synthesis and characterisation of novel high molecular weight PHBV-b-PHBV-b-PHBV block copolymers using isocyanate chemistry. High molecular weight, narrow compositional distribution, hydroxy-functionalised PHBV blocks of low (1 mol%) 3HV and high (67 mol%) 3HV contents were used as building blocks. The resulting block copolymers showed a very significant increase in elongation at break (to 76.0 %), as well as improved tensile toughness (to 15.0 MJ/m3) and tensile strength (to 18.5 MPa) compared to the starting materials or comparable blends. Based on the similarity in properties between the 1 mol% 3HV block copolymer products and their counterpart random copolymers, it is also shown that the introduction of urethane linkages had minimal effect on polymer properties. The morphologies of these novel PHBV materials were investigated, supporting the concept that the microphase separation of the different PHBV phases delivered these improved mechanical properties. This approach to PHA-b-PHA block copolymer synthesis offers an attractive generic platform for the production of novel biodegradable PHA materials for film and other applications.

Investigation on hot deformation behavior and quenching precipitation mechanism of 2195 Al-Li alloy

Al-Li alloys suffer from a narrow processing window. The hot deformation behavior of the ramp heating homogenized 2195 Al-Li alloy was investigated by hot compression test in the temperature range of 300–500 °C and strain rate range of 0.01–10 s−1, and the strain compensated Arrhenius constitutive relationship model and processing map of the alloy were established. The laws of Zener-Hollomon parameters on the age-hardening response and quenching sensitivity of the deformed alloy were analyzed. The quenching precipitation mechanism of the deformed alloy were revealed. The results showed that the hardness of the aged alloy tends to increase first and then decrease with increasing Z parameter, while the quenching sensitivity tends to decrease first and then increase. The quench-induced phases are precipitated under the induction of incoherent Al3Zr dispersoids within recrystallized grains. The boundary angle would affect the quenching precipitation behavior. It was also found that the types and amounts of second phases are significantly different between the homogenized and hot-deformed samples under slow cooling rate. The ramp heating homogenized 2195 Al-Li alloy after hot deformation at temperatures of 455–500 °C and strain rates below 1 s−1 possesses a lower flow stress, higher age-hardening response and smaller quenching sensitivity.

Joining of Aluminum and CFRP via Laser Powder Bed Fusion: Influence of Experimental Set-Up and Laser Processing on Microstructure and Mechanical Properties.

Additive-manufacturing-based joining methods enable tailored or even functionalized joints and allow for hybridization at small scales. The current study explored an innovative joining method for aluminum cast alloys (AlSi12) with thermoset carbon-fiber-reinforced polymers (CFRPs) via laser powder bed fusion (LPBF). The direct build-up of AlSi12 on a CFRP substrate proved to be challenging due to the dissimilar thermal properties of the considered materials, which led to substrate damage and low joint adhesion. These effects could be overcome by introducing an AlSi12 foil as an interlayer between the two joining partners, acting as a thermal barrier and further improving the AlSi12 melt wettability of the substrate. Within LPBF, the energy input in the form of volumetric laser energy density influenced both the porosity of the fused layers and the formation of thermally induced stresses due to the high cooling rates and different thermal expansion properties of the materials. While the AlSi12 volume density increased with a higher laser energy input, simultaneously increasing thermal stresses caused the debonding and deformation of the AlSi12 foil. However, within a narrow processing window of laser parameters, the samples achieved remarkably high shear strengths of τ > 20 MPa, comparable to those of conventional joining methods.

Tailoring microstructure and strength through selective remelting in laser powder bed fusion

Additive manufacturing provides new opportunities to manipulate local microstructure to enable strengthening pathways for austenitic stainless steels. Laser beam powder bed fusion techniques, however, are limited by their narrow process window, as compared to other additive manufacturing techniques. In this work, the use of layer-wise remelting is explored to expand the available process window in laser powder bed fusion to manipulate the microstructure and increase strength while minimizing porosity. Several single melt process conditions are considered for 316L stainless steel along with additional low energy and high energy remelts to evaluate the effect on grain morphology, texture, porosity, and hardness. Results demonstrate remelting as an effective approach to tune grain size and texture to achieve high hardness while reducing the overall porosity. While the data suggest that the optimal single melt process set results in the lowest porosity, remelting provides a pathway to reduce porosity for non-optimal process parameters, minimize grain growth, and increase strength.

Microstructure and Texture Evolution of the Magnesium Alloy ZMX210 during Rolling and Annealing.

The processability during massive deformation of magnesium-wrought products is hampered by the low formability of magnesium alloys. The research results of recent years demonstrate that rare earth elements as alloying elements improve the properties of magnesium sheets, such as formability, strength and corrosion resistance. The substitution of rare earth elements by Ca in Mg-Zn-based alloys results in a similar texture evolution and mechanical behaviour as RE-containing alloys. This work is an approach to understanding the influence of Mn as an alloying element to increase the strength of a Mg-Zn-Ca alloy. For this aim, a Mg-Zn-Mn-Ca alloy is used to investigate how Mn affects the process parameters during rolling and the subsequent heat treatment. The microstructure, texture and mechanical properties of rolled sheets and heat treatment at different temperatures are compared. The outcome of casting and the thermo-mechanical treatment are used to discuss how to adapt the mechanical properties of magnesium alloy ZMX210. The alloy ZMX210 behaves very similarly to the ternary Mg-Zn-Ca alloys. The influence of the process parameter rolling temperature on the properties of the ZMX210 sheets was investigated. The rolling experiments show that the ZMX210 alloy has a relatively narrow process window.

Phthalonitrile functionalized resoles – use of 2,3-dicyanohydroquinone as a versatile monomer for resins with very high thermal stability

In the aerospace industry, composite materials based on high-performance fibers and polymer matrices are widely used. Indeed, they can display very important mechanical and thermal properties with a very large density-to-stiffness balance. Usually, thermal protection systems are made from composite materials containing a char precursor for the polymer matrix. Temperature-resistant organic polymers are still quite rare and generally require very restrictive manufacturing and use processes. Recently, phthalonitriles have gained interest due to their very good thermostability and high char yield. However, phthalonitrile resins are generally solid at room temperature and often have a narrow processing window. In this work, synthesis methods allowing access to phthalonitrile resins were developed from 2,3-dicyanohydroquinone. These methods propose to consider together phenolic chemistry (phenolic reactive positions and aldehyde) and self-crosslinkable phthalonitrile chemistry (hydroxyl-mediated from phenolic and nitriles). It was thus possible to synthesize liquid resins at room temperature, leading to polymeric networks with a very high thermostability (temperature at 5% mass loss > 450 °C and char yield ≈ 70 %).

Numerical Study of Ti6Al4V Alloy Tube Heated by Super-Frequency Induction Heating.

Ti6Al4V alloys have a narrow processing window, which complicates temperature control, especially during large-scale production. Therefore, a numerical simulation and experimental study on the ultrasonic induction heating process of a Ti6Al4V titanium alloy tube were conducted to obtain stable heating. The electromagnetic and thermal fields in the process of ultrasonic frequency induction heating were calculated. The effects of the current frequency and current value on the thermal and current fields were numerically analyzed. The increase in current frequency enhances the skin and edge effects, but heat permeability was achieved in the super audio frequency range, and the temperature difference between the interior and exterior of the tube was less than 1%. An increase in the applied current value and current frequency caused an increase in the tube's temperature, but the influence of current was more prominent. Therefore, the influence of stepwise feeding, reciprocating motion, and stepwise feeding superimposed motion on the heating temperature field of the tube blank was evaluated. The coil reciprocating with the roll can maintain the temperature of the tube within the target temperature range during the deformation stage. The simulation results were validated experimentally, which demonstrated good agreement between the results. The numerical simulation method can be used to monitor the temperature distribution of Ti6Al4V alloy tubes during the super-frequency induction heating process. This is an economical and effective tool for predicting the induction heating process of Ti6Al4V alloy tubes. Moreover, online induction heating in the form of reciprocating motion is a feasible strategy for processing Ti6Al4V alloy tubes.

An integrated simulation model towards laser powder bed fusion in-situ alloying technology

The Laser Powder Bed Fusion (LPBF) in-situ alloying is a novel technology for preparing novel alloys efficiently. However, the narrow process window limit its application. A micro-scale integrated simulation model is designed and constructed based on the Discrete Element Method (DEM), the Finite Element Method (FEM), and Calculation of phase diagram (CALPHAD) method in the work. The equation of the methods are introduced. By defining the parameters such as composition inhomogeneity ω, the forming performance of LPBF in-situ alloying FeCoCrNi medium entropy alloys are predicted. The calculation results show that the hysteresis diffusion effect makes the mixing powders more challenging to be in-situ alloyed than conventional main component alloys. For the mixed powder beds consisting of 15–53 μm particles with equal mass ratio, the composition deviation on the micro-scale is within 2.5%, and the composition homogeneity reaches 98.9 %. Under a laser power of 150 W and a scanning speed of 500 mm/s, several laser remelting process are indispensable to eliminate unmelted elements. Experiments are carried out to verify the accuracy of the integrated simulation model, and the high-efficiency preparation experiment of non-equiatomic ratio medium entropy alloy was carried out by using the technology.

Preparation of phthalonitrile resins containing siloxane linkages with improved processability

To improve the processability of biphenyl phthalonitrile resin, a flexible siloxane structure was introduced into the phthalonitrile monomer through molecular design, which was then blended with a biphenyl monomer to prepare phthalonitrile alloy resins. When the ratio of phthalonitrile monomer containing flexible siloxane to biphenyl phthalonitrile monomer was 1:1, the processing window widened from 58 to 110°C, as compared to that of biphenyl phthalonitrile. Due to the introduction of the biphenyl structure into the phthalonitrile alloy resins, the initial decomposition temperature of the silicon-containing phthalonitrile resin increased from 385 to 516°C. More importantly, the phthalonitrile alloy resin exhibited a high bending strength (66 MPa) and bending modulus (3762 MPa), indicating that it could be potentially applied as high temperature structural composite matrices. Furthermore, it provides a new strategy for processing phthalonitrile resins with a high melting point and narrow processing window.