Dramatically Accelerating II-I Crystal Phase Transition of Polybutene­1 by In Situ Incorporation of H-Shape Long-Chain-Branching Structures.

This communication reports an effective strategy helping address the long-troubling melt processing issue of isotactic polybutene-1 (i-PB) caused by its extremely slow II-I crystal phase transition. The solution lies in a facile synthesis of i-PB containing H-shape long-chain-branching structures (LCB-i-PB) by applying a so-called ω-alkenylmethyldichlorosilane copolymerization-hydrolysis (ACH) chemistry to butene-1 polymerization with Ziegler-Natta or metallocene catalysts. It is evident that the H-shape LCB structures effectively enhance chain entanglements of i-PB and induce an over-the-board acceleration of the overall melt crystallization process including nucleation, form II crystallization, and form II-form I phase transition. As i-PB usually requires up to a week to reach equilibrium of the II-I phase transition, it is found that with LCB-i-PB such a transition is almost finished within as short as 24 h to even higher degrees.

The Shear-Accelerated II-I Phase Transition of Isotactic Poly(1-Butene).

The II-I phase transition of isotactic poly(1-butene) (iPBu) leads to improved mechanical performance. However, this will take several weeks and increase storage and processing costs. In this work, shear forces are introduced into the supercooled iPBu melt, and the effects of isothermal crystallization temperature (Tc) and shear temperature (Tshear) on crystallization and phase transition are explored. Shear-induced transcrystalline morphology of Form II with a significantly shortened crystallization induction period can be observed at relatively high Tc (105 °C). Besides, the shear-induced Form II can transit to Form I faster than the unsheared one. In addition, the phase transition rate increases as the Tshear decreases, with the fastest rate occurring at Tshear of 120 °C. The half transition time (t1/2) is measured as 6.3 h when Tc = 105 °C, Tshear = 120 °C, which is much shorter than the 20.7 h required for unsheared samples. The accelerated phase transition of iPBu can be attributed to the stretching of molecular chains, resulting from shear treatment. This study provides a quantitative analysis of the influence of the shear treatment and the Tshear on the II-I phase transition rate. It also presents a cost-effective and straightforward approach for expediting the phase transition process.

Effect of Retrogression with Different Cooling Ways on the Microstructure and Properties of T'/η' Strengthened Al-Zn-Mg-Cu Alloys.

Retrogression and re-aging (RRA) treatment has been proven to effectively overcome the trade-off between strength and corrosion resistance. Current research focuses on the heating rate, temperature, and holding time of retrogression treatment while ignoring the retrogression cooling ways. In this paper, the effects of RRA treatment with different retrogression cooling ways on the microstructure and properties of newly developed T'/η' strengthened Al-Zn-Mg-Cu alloys were investigated by performing tests on mechanical properties, intergranular corrosion (IGC) resistance, and electrochemical corrosion behavior. The results show that the mechanical properties of samples subject to RRA treatment with water-quenching retrogression (ultimate tensile strength, yield strength, and elongation of 419.2 MPa, 370.2 MPa, and 15.9, respectively) are better than those of air-cooled and furnace-cooled samples. The corrosion resistance of water-quenching (IGC depth of 162.2 µm, corrosion current density of 0.833 × 10-5 A/cm2) and furnace-cooled samples (IGC depth of 123.7 µm, corrosion current density of 0.712 × 10-5 A/cm2) is better than that of air-cooled samples. Microstructure characterization reveals that the effect of the retrogression cooling rate on mechanical properties is related to the size of T'/η' precipitates with grains as well as the proportion of T' and η', while the difference in corrosion resistance depends on the continuity of grain boundary precipitates (GBPs). With mechanical properties, corrosion resistance, and time cost taken into consideration, it is appropriate to select water quenching for retrogression. These findings offer valuable insights for further design to achieve superior performance in various applications.

The Role of Solidified Phases on the Hot Cracking of a Large-Size GH4742 Superalloy Ingot.

The effect of solidified phases on the hot cracking behaviour of a large-size GH4742 superalloy ingot produced using vacuum induction melting (VIM) is investigated in order to improve the quality of the final product. The results show that the solidification order of the ingot is γ matrix, MC carbide, η phase and γ' phase. Among them, the MC carbide and the η phase solidified in the mushy zone. The volume fraction of both the η phase and the MC carbide in the cracked zone is higher than that in the non-cracked zone, and a significant number of η phases are distributed near the hot cracks. The formation of solidified phases not only induces stress concentration at η phase/γ matrix interfaces but also reduces the ability of liquid feeding during solidification, thus promoting hot crack formation. It is believed that by controlling the segregation degree of both Nb and Ti, the volume fraction of η phases and MC carbides can be reduced to prevent hot cracking of the GH4742 superalloy VIM ingot.

Investigation on Mechanism of Microstructure Evolution during Multi-Process Hot Forming of GH4169 Superalloy Forging.

Typically, in the manufacturing of GH4169 superalloy forgings, the multi-process hot forming that consists of pre-deformation, heat treatment and final deformation is required. This study focuses on the microstructural evolution throughout hot working processes. Considering that δ phase can promote nucleation and limit the growth of grains, a process route was designed, including pre-deformation, aging treatment (AT) to precipitate sufficient δ phases, high temperature holding (HTH) to uniformly heat the forging, and final deformation. The results show that the uneven strain distribution after pre-deformation has a significant impact on the subsequent refinement of the grain microstructure due to the complex coupling relationship between the evolution of the δ phase and recrystallization behavior. After the final deformation, the fine-grain microstructure with short rod-like δ phases as boundaries is easy to form in the region with a large strain of the pre-forging. However, necklace-like mixed grain microstructure is formed in the region with a small strain of the pre-forging. In addition, when the microstructure before final deformation consists of mixed grains, dynamic recrystallization (DRX) nucleation behavior preferentially depends on kernel average misorientation (KAM) values. A large KAM can promote the formation of DRX nuclei. When the KAM values are close, a smaller average grain size of mixed-grain microstructure is more conductive to promote the DRX nucleation. Finally, the interaction mechanisms between δ phase and DRX nucleation are revealed.

Investigation of the stability of organic-inorganic halide perovskite thin films: Insight from experimental and simulation.

Herein, we investigated the stability of lead halide perovskites under ambient conditions after mixing the two cations Formamidinium (FA) and Cesium (Cs). The CsxFA1-xPbI3 perovskites solutions were prepared with different contents of x (0.0, 0.3, 0.5, 0.7 and 1.0) and deposited on substrates by spin-coating technique. The CsxFA1-xPbI3 films were, afterwards, characterized using the X-ray diffraction (XRD), UV-visible spectroscopy, photoluminescence (PL) spectra and scanning electron microscopy (SEM) to figure out their crystallinity, morphology, and optical properties. We noticed a stable perovskite structure for the mixed compounds unalike the pure FA and Cs films. The XRD analysis revealed, even after two weeks, the growth and good stability after two weeks of the desired black cubic α-phase perovskite structure in opposite to FAPbI3 and CsPbI3 which, respectively, showed faster degradation and transition into non-perovskite δ-phase and É£-phase no perovskite phases. The mixed perovskites Cs-FA also displayed a high absorbance especially for the ones with 30% of Cs and 70% of FA or 50% of each, with an excellent band gap energy ranging between 1.52 and 1.7 eV where FAPbI3 and CsPbI3 were showing a bandgap between 1.5 and 1.9 eV respectively. Moreover, the performance of the CsxFA1-xPbI3 based solar cells were simulated with SCAPS by using the band gaps obtained from the experimental study and after by varying the band gap, the thickness of the absorber layers and then different types of Electron Transport Layer (ETL). The simulation results revealed that the Cs0.3FA0.7PbI3 based solar cells had the highest higher efficiency around 22.36%.

Phase Behavior and Role of Organic Additives for Self-Doped CsPbI3 Perovskite Semiconductor Thin Films.

The phase change of all-inorganic cesium lead halide (CsPbI3) thin film from yellow δ-phase to black γ-/α-phase has been a topic of interest in the perovskite optoelectronics field. Here, the main focus is how to secure a black perovskite phase by avoiding a yellow one. In this work, we fabricated a self-doped CsPbI3 thin film by incorporating an excess cesium iodide (CsI) into the perovskite precursor solution. Then, we studied the effect of organic additive such as 1,8-diiodooctane (DIO), 1-chloronaphthalene (CN), and 1,8-octanedithiol (ODT) on the optical, structural, and morphological properties. Specifically, for elucidating the binary additive-solvent solution thermodynamics, we employed the Flory-Huggins theory based on the oligomer level of additives' molar mass. Resultantly, we found that the miscibility of additive-solvent displaying an upper critical solution temperature (UCST) behavior is in the sequence CN:DMF > ODT:DMF > DIO:DMF, the trends of which could be similarly applied to DMSO. Finally, the self-doping strategy with additive engineering should help fabricate a black γ-phase perovskite although the mixed phases of δ-CsPbI3, γ-CsPbI3, and Cs4PbI6 were observed under ambient conditions. However, the results may provide insight for the stability of metastable γ-phase CsPbI3 at room temperature.

Effect of I-Phase on Microstructure and Corrosion Resistance of Mg-8.5Li-6.5Zn-1.2Y Alloy.

The effects of solid solution treatment duration on the corrosion behavior and microstructure behavior of the cast Mg-8.5Li-6.5Zn-1.2Y (wt.%) alloy were investigated. This study revealed that with the treatment time for solid solutions increasing from 2 h to 6 h, the amount of α-Mg phase gradually decreases, and the alloy presents a needle-like shape after solid solution treatment for 6 h. Meanwhile, when the solid solution treatment time increases, the I-phase content drops. Exceptionally, under 4 h of solid solution treatment, the I-phase content has increased, and it is dispersed uniformly over the matrix. What we found in our hydrogen evolution experiments is that the hydrogen evolution rate of the as-cast Mg-8.5Li-6.5Zn-1.2Y alloy following solid solution processing for 4 h is 14.31 mL·cm-2·h-1, which is the highest rate. In the electrochemical measurement, the corrosion current density (icorr) value of as-cast Mg-8.5Li-6.5Zn-1.2Y alloy following solid solution processing for 4 h is 1.98 × 10-5, which is the lowest density. These results indicate that solid solution treatment can significantly improve the corrosion resistance of the Mg-8.5Li-6.5Zn-1.2Y alloy. The I-phase and the α-Mg phase are the primary elements influencing the corrosion resistance of the Mg-8.5Li-6.5Zn-1.2Y alloy. The existence of the I-phase and the border dividing the α-Mg phase and ß-Li phase easily form galvanic corrosion. Although the I-phase and the boundary between the α-Mg phase and ß-Li phase will be corrosion breeding sites, they are more effective in inhibiting corrosion.

Effect of Deformation Parameters of an Initial Aged GH4169 Superalloy on Its Microstructural Evolution during a New Two-Stage Annealing.

This study aims to explore the effect of deformation parameters on microstructure evolution during the new two-stage annealing method composed of an aging treatment (AT) and a cooling recrystallization annealing treatment (CRT). Firstly, the hot compressive tests with diverse deformation parameters were finished for an initial aged deformed GH4169 superalloy. Then, the same two-stage annealing method was designed and carried out for the deformed samples. The results show that the deformation parameters mainly affect the grain microstructure during CRT by influencing the content, distribution and morphology of the δ phase after deformation. The reason for this is that there is an equilibrium of the content of the δ phase and Nb atom. When the deformation temperature is high, the complete dissolution behavior of the δ phase nuclei promotes the dispersion distribution of the δ phase with rodlike and needle-like shapes during AT. Thus, the fine and heterogeneous microstructure is obtained after annealing because the recrystallization nucleation is enhanced in those dispersed δ phases during CRT. However, when the retained content of δ phase nuclei is high after deformation, the clusters of intragranular δ phases will form during AT, resulting in the pinning of the motion for dislocation. The elimination of the mixed grain microstructure is slowed down due to the low static recrystallization (SRX) nucleation rate within the deformed grain.

Failure Analysis of a C-276 Alloy Pipe in a Controlled Decomposition Reactor.

Failure analysis was carried out on a ruptured C-276 pipe heated externally at 1050 °C, which had been used for a few months in a controlled decomposition reactor (CDR) system. To catch the decomposed perfluorinated compounds (PFCs, e.g., CF4, SF6, NF3, C3F8 and C4F8) present in the exhaust gas, the C-276 reactor was periodically purged with water mist, which caused a temperature gradient from the external to the inner surface of the pipe. The precipitation of large amounts of intermetallic compounds along the grain boundaries were found to be corroded preferentially. The internal surface of the used pipe was covered with many fine cracks. The corrosion and cracking of grain boundary precipitates accounted for the short service life of the C-276 pipe. Compositional measurements by electron probe micro-analyzer (EPMA) and phase identification by electron backscatter diffraction (EBSD) confirmed the presence of δ and µ phases in the ruptured pipe. The coarse intergranular precipitates were the δ phase (Mo7Ni7), which were enriched in Mo and Cr. Moreover, the fine precipitates dispersed intergranularly and intragranularly were the µ phase (Mo6Ni7), which were abundant in Mo and W. The numerous precipitates present in the matrix and along the grain boundaries were responsible for an obvious loss in the strength and ductility of the used C-276 pipe.

Multi-Dimensional Revealing the Influence Mechanism of the δ Phase on the Tensile Fracture Behavior of a Nickel-Based Superalloy on the Mesoscopic Scale.

As the key materials of aircraft engines, nickel-based superalloys have excellent comprehensive properties. Mircotensile experiments were carried out based on in situ digital image correlation (DIC) and in situ synchrotron radiation (SR) technique. The effects of the δ phase on the grain orientation, surface roughening, and strain localization were investigated. The results showed that the average kernel average misorientation (KAM) value of the fractured specimens increased significantly compared with that of the heat-treated specimens. The surface roughness decreased with an increasing volume fraction of the δ phase. The strain localization of specimens increased with the increasing ageing time. The size and volume fraction of voids gradually increased with the increase in plastic strain. Some small voids expanded into large voids with a complex morphology during micro-tensile deformation. The needle-like δ phase near the fracture broke into short rods, while the minor spherical δ phase did not break. The rod-like and needle-like δ phases provided channels for the propagation of the microcrack, and the accumulation of the microcrack eventually led to the fracture of specimens.

Investigation of Cation Exchange Behaviors of FAxMA1-xPbI3 Films Using Dynamic Spin-Coating.

In this study, we fabricated and characterized uniform multi-cation perovskite FAxMA1-xPbI3 films. We used the dynamic spin-coating method to control the cation ratio of the film by gradually increasing the FA+, which replaced the MA+ in the films. When the FA+ concentration was lower than xFA ~0.415 in the films, the stability of the multi-cation perovskite improved. Above this concentration, the film exhibited δ-phase FAPbI3 in the FAxMA1-xPbI3 films. The formation of δ-phase FAPbI3 disturbed the homogeneity of the photoluminescence spatial distribution and suppressed the absorption spectral bandwidth with the increasing bandgap. The precise control of the cation ratio of multi-cation perovskite films is necessary to optimize the energy-harvesting performance.

The Feasibility of Using Coxiella burnetii Avirulent Nine Mile Phase II Viable Bacteria as a Live Attenuated Vaccine Against Q fever.

This study aimed to explore if viable C. burnetii avirulent Nine Mile phase II (NMII) can elicit protective immunity against virulent NM phase I (NMI) infection. Interestingly, mice immunized with viable NMII elicited significant protection against NMI infection at different time points post-immunization. Viable NMII induced a dose-dependent NMI-specific IgG response in mice, but all doses of NMII-immunized mice conferred a similar level of protection. Comparing different routes of immunization indicated that intranasally immunized mice showed significantly higher levels of protection than other immunization routes. The observation that viable NMII induced a similar level of long-term protection against NMI challenge as the formalin-inactivated NMI vaccine (PIV) suggests that viable NMII bacteria can induce a similar level of long-term protection against virulent NMI challenge as the PIV. Viable NMII also induced significant protection against challenge with virulent Priscilla and Scurry strains, suggesting that viable NMII can elicit broad protection. Immune sera and splenocytes from viable NMII-immunized mice are protective against NMI infection, but immune serum-receiving mice did not control NMI replication. Additionally, viable NMII conferred a comparable level of protection in wild-type, CD4+ T cell-deficient, and CD8+ T cell-deficient mice, and partial protection in B cell-deficient mice. However, NMII-immunized T cell-deficient mice were unable to prevent C. burnetii replication. Thus, both B cells and T cells are required for viable NMII-induced protective immunity but T cells may play a critical role. Collectively, this study demonstrates the feasibility of using avirulent NMII as a live attenuated vaccine against human Q fever.

Effect of Minor Er Additions on the Microstructures and Mechanical Properties of Cast Al-Cu-Mg-Ag Alloys.

The microstructures and mechanical properties of novel cast Al-Cu-Mg-Ag alloys with and without minor additions of Er (0.09 and 0.2 wt %) are investigated by Vickers hardness tests, tensile tests, optical metallographic examination, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The results reveal that the Er addition decreases the hardness value of peak-aged Al-Cu-Mg-Ag alloy but has little influence on the time required for achieving the peak aging condition. Meanwhile, the Ω phase is suppressed in Er-added alloys, leading to a lower tensile strength at room temperature, which causes the (Mg, Ag, Er, V, Ti)-rich phase in the matrix in Er-added alloys. This blocky phase consumes available Mg and Ag atoms for Ω nucleation, leading to the low number density of Ω plates. The strength properties of Er-added alloys at 300 °C are found to be enhanced, which benefits from the pinning effect of the Al8Cu4Er phase on grain boundaries. Meanwhile, the brittle fracture of Er-added alloys at room temperature is directly associated with the Al8Cu4Er phase and the blocky (Mg, Ag, Er, V, Ti)-rich phase, which acts as the source of microcracks during deformation. In addition, no obvious grain refinement effect can be observed in Er-added alloys.

Quantitative Shape-Classification of Misfitting Precipitates during Cubic to Tetragonal Transformations: Phase-Field Simulations and Experiments.

The effectiveness of the mechanism of precipitation strengthening in metallic alloys depends on the shapes of the precipitates. Two different material systems are considered: tetragonal γ'' precipitates in Ni-based alloys and tetragonal θ' precipitates in Al-Cu-alloys. The shape formation and evolution of the tetragonally misfitting precipitates was investigated by means of experiments and phase-field simulations. We employed the method of invariant moments for the consistent shape quantification of precipitates obtained from the simulation as well as those obtained from the experiment. Two well-defined shape-quantities are proposed: (i) a generalized measure for the particles aspect ratio and (ii) the normalized λ2, as a measure for shape deviations from an ideal ellipse of the given aspect ratio. Considering the size dependence of the aspect ratio of γ'' precipitates, we find good agreement between the simulation results and the experiment. Further, the precipitates' in-plane shape is defined as the central 2D cut through the 3D particle in a plane normal to the tetragonal c-axes of the precipitate. The experimentally observed in-plane shapes of γ''-precipitates can be quantitatively reproduced by the phase-field model.

Drugs in phase I and phase II clinical trials for systemic sclerosis.

Introduction: Systemic sclerosis (SSc) is an autoimmune connective tissue disease that is characterized by excessive collagen deposition, vascular dysfunction, and fibrosis of cutaneous and visceral organs. Current therapeutic options are limited and provide only modest benefit.Areas covered: This review summarizes investigational agents in recent Phase I and II clinical trials evaluated for the treatment of SSc with a focus on skin in patients with early diffuse disease and interstitial lung disease. We performed a search on Pubmed and https://clinicaltrials.gov with keywords systemic sclerosis, Phase I clinical trial, and Phase II clinical trial to identify relevant studies from 2015 to 2019.Expert opinion: Therapeutic interventions in SSc should be guided by the level of disease activity and the degree of organ involvement. While most novel agents have failed to meet the primary endpoints of reducing skin thickening as measured by the modified Rodnan skin score, some have shown promise in improving the Composite Response Index for Clinical Trials in Early Diffuse Cutaneous Systemic Sclerosis (CRISS), reducing lung function decline, or improving patient-reported outcomes. However, most of the current evidence is based on small or open-label clinical trials. Well-designed, large, randomized, Phase III clinical trials are necessary to define the roles of investigational agents in treating SSc.

Treatment of non-metastatic castration-resistant prostate cancer: focus on apalutamide.

Androgen deprivation therapy (ADT) is an important component of systemic therapy in advanced prostate cancer; however, resistance to ADT is inevitable. Three large studies demonstrated the efficacy of novel androgen receptor (AR)-targeted therapies in prolonging metastasis-free survival and time to symptomatic progression in patients with non-metastatic castration-resistant prostate cancer (nmCRPC). Enzalutamide and apalutamide have been approved by the FDA in the nmCRPC setting. This review discusses the role of AR and ADT in prostate cancer, mechanism of ADT resistance and the nmCRPC stage. In addition, pharmacologic characteristics and clinical development of apalutamide, role of apalutamide in nmCRPC, and ongoing clinical studies of apalutamide in different stages of prostate cancer are discussed.

The δ Phase Precipitation of an Inconel 718 Superalloy Fabricated by Electromagnetic Stirring Assisted Laser Solid Forming.

Fabricating an Inconel 718 superalloy using electromagnetic stirring assisted laser solid forming (EMS-LSF) is a novel method to modify its microstructure and mechanical properties by consuming the Nb element in the γ phase to alleviate interdendritic segregation. The precipitate of the δ phase at 950 °C after EMS-LSF can help to achieve the uniform diffusion of Nb, and can also improve its mechanical properties. The precipitation behavior of the δ phase in an EMS-LSF Inconel 718 superalloy with different heat treatment processes has been investigated. The results show that the morphology of the δ phase changes from rod-like to a long-needle shape and tends to grow from the inter dendrite to the core dendrite with electromagnetic field intensity increasing, which is accompanied by the "cutting" and "dissolution" of the Laves phase. Through precipitation kinetics analysis, the precipitation rate of the δ phase is seen to increase with the electromagnetic field intensity increasing. Under a combination of electromagnetic stirring and laser solid forming, the microhardness of the Inconel 718 samples increased slightly due to the fact that a higher content of Nb was distributed in the core dendrite resulting from the serious convection of liquid metal, which can strengthen the matrix.

Study on Microstructure and Mechanical Properties of WC-10Ni3Al Cemented Carbide Prepared by Different Ball-Milling Suspension.

In this paper, WC-10Ni3Al cemented carbides were prepared by the powder metallurgy method, and the effects of ball-milling powders with two different organic solvents on the microstructure and mechanical properties of cemented carbides were studied. We show that the oxygen in the organic solvent can be absorbed into the mixed powders by ball-milling when ethanol (CH3CH2OH) is used as a ball-milling suspension. This oxygen leads to the formation of α-Al2O3 during sintering, which improves the fracture toughness, due to crack deflection and bridging, while the formation of η-phase (Ni3W3C) inhibits the grain growth and increases the hardness. Alternatively, samples milled using cyclohexane (C6H12) showed grain growth during processing, which led to a decrease in hardness. Therefore, the increase of oxygen content from using organic solvents during milling improves the properties of WC-Ni3Al composites. The growth of WC grains can be inhibited and the hardness can be improved without loss of toughness by self-generating α-Al2O3 and η-phase (Ni3W3C).

Single crystals of the filled Ti2N-type η-phase Ti3Zn3Ox (x = 1.07 and 1.23) prepared using a Bi flux.

Single crystals of the filled Ti2Ni-type Ti3Zn3Ox η-phase (cubic, space group Fd-3m) having {111} facets were obtained by heating Ti, Zn and ZnO with a Bi flux. The lattice parameter of a single crystal prepared at 800°C was 11.4990 (2) Å, which is close to that of Ti3Zn3O∼0.5 (a = 11.502 Å), as reported by Rogl & Nowotny [Monatsh. Chem. (1977), 108, 1167-1180]. The occupancies of the O1 (16c) and O2 (8a) sites were 1 and 0.071 (12), respectively, and the composition of the crystal was determined to be Ti3Zn3O1.04. A single crystal from the sample prepared at 650°C had the same structure type, with a lattice parameter of 11.5286 (2) Å. However, O atoms were situated at a new 32e site in addition to the original 16c and 8a sites, and the Zn-atom positions were split in accordance with the new O-atom site. The chemical formula Ti3Zn3O1.27 determined by X-ray diffraction occupancy refinement agreed with the chemical composition obtained for the cross section of the single crystal determined with an electron probe microanalyzer.