Effects of the Glass-Forming Ability and Annealing Conditions on Cocrystallization Behaviors via Rapid Solvent Removal: A Case Study of Voriconazole

The kinetic entrapment of molecules in an amorphous phase is a common obstacle to cocrystal screening using rapid solvent removal, especially for drugs with a moderate or high glass-forming ability (GFA). The aim of this study was to elucidate the effects of the coformer’s GFA and annealing conditions on the nature of amorphous phase transformation to the cocrystal counterpart. Attempts were made to cocrystallize voriconazole (VRC) with four structural analogues, namely fumaric acid (FUM), tartaric acid (TAR), malic acid (MAL), and maleic acid (MAE). The overall GFA of VRC binary systems increased with decreasing glass transition temperatures (Tgs) of these diacids, which appeared as a critical parameter for predicting the cocrystallization propensity such that a high-Tg coformer is more desirable. A new 1:1 VRC-TAR cocrystal was successfully produced via a supercooled-mediated re-cocrystallization process, and characterized by PXRD, DSC, and FTIR. The cocrystal purity against the annealing temperature displayed a bell-shaped curve, with a threshold at 40 °C. The isothermal phase purity improved with annealing and adhered to the Kolmogorov–Johnson–Mehl–Avrami kinetics. The superior dissolution behavior of the VRC-TAR cocrystal could minimize VRC precipitation upon gastric emptying. This study offers a simple but useful guide for efficient cocrystal screening based on the Tg of structurally similar coformers, annealing temperature, and time.

Effect of Electrode Material on the Crystallization of GeTe Grown by Atomic Layer Deposition for Phase Change Random Access Memory

The electrical switching behavior of the GeTe phase-changing material grown by atomic layer deposition is characterized for the phase change random access memory (PCRAM) application. Planar-type PCRAM devices are fabricated with a TiN or W bottom electrode (BE). The crystallization behavior is characterized by applying an electrical pulse train and analyzed by applying the Johnson–Mehl–Avrami kinetics model. The device with TiN BE shows a high Avrami coefficient (>4), meaning that continuous and multiple nucleations occur during crystallization (set switching). Meanwhile, the device with W BE shows a smaller Avrami coefficient (~3), representing retarded nucleation during the crystallization. In addition, larger voltage and power are necessary for crystallization in case of the device with W BE. It is believed that the thermal conductivity of the BE material affects the temperature distribution in the device, resulting in different crystallization kinetics and set switching behavior.

The Avrami Kinetics of Dynamic Recrystallization in Nickel-Niobium Alloys

The flow curves determined on a series of Ni-Nb alloys are analysed. Six alloys containing Ni–0.01, 0.1, 1, 2, 5 and 10 wt. % Nb with pure Ni were tested in torsion at various strain rates within the hot forging temperature range. Under these conditions, large strains were attained, which permitted steady state flow to take place. The double-differentiation method is employed to define the critical strain for the initiation of DRX, leading to the evaluation of the strain hardening and dynamic recovery parameters. The relations obtained are compared to ones determined earlier using a least squares approach. It is shown that the two sets of relations do not differ appreciably. These results are employed to predict the Avrami kinetics of a range of Ni-Nb alloys strained at different temperatures and strain rates. The Avrami time exponents all fall in the range 1.0 to 5.0. The dependence of the time of half-softening, t50, on Nb content, strain rate and temperature is also derived under the same conditions.

Applicability of zeolites in potassium and nitrate retention in different soil types

Environmental protection and sustainable agricultural production require the use of inexpensive and environmentally acceptable soil supplements. Objectives of this study were to investigate the influence of the addition of the natural zeolite ? clinoptilolite (NZ) and its iron(III)-modified form (FeZ) on the potassium and nitrate leaching from sandy, silty loam and silty clay soils. The zeolites were added in two amounts: 0.5 (FeZ) and 1.0 wt. % (NZ and FeZ). The experiments were carried out in columns organized in eight experimental systems containing unamended (control specimens) and amended soils. The concentration of K+ and NO3?N in the leachates was monitored during 7 days. The obtained results indicate that the K+ and NO3?N leaching mainly depends on the soil type and pH of the soil. The NZ and FeZ addition has the highest impact on the K+ retention in the acidic sandy soil. The highest NO3?N retention is obtained with FeZ in acidic silty loam soil. The K+ leaching kinetics for all the studied soils follow the Avrami kinetics model with the parameter n < 1. This study demonstrates that NZ and FeZ can be a good soil supplement for the K+ retention for all studied soils and in the NO3?N retention for silty loam and silty clay soils.

High-Temperature Deformation of Inconel 718PlusTM

Since its introduction in 2003, alloy 718PlusTM spurred a lot of interest owing to its increased maximum service temperature over conventional Inconel 718 (704 °C versus 650 °C), good formability, and weldability together with its moderate cost. Understanding the high-temperature deformation characteristics and microstructural evolution is still of interest to many. It is known that the service performance and hot-flow behavior of this alloy are a strong function of the microstructure, particularly the grain size. To develop precise microstructure evolution models and foresee the final microstructure, it is important to understand how and under which forming conditions softening and precipitation processes occur concurrently. In this work, the softening behavior, its mechanisms, and the precipitation characteristics of 718PlusTM were investigated in two parallel studies. While cylindrical compression tests were employed to observe the hot-flow behavior, the precipitation behavior and other microstructural phenomena such as particle coarsening were tracked via hardness measurements. A precipitation–temperature–time (PTT) diagram was reported, and modeling of the flow curves via hyperbolic sine model was discussed in the light of the PTT behavior. Both “apparent” approach and “physically based” approach are implemented and two different sets of parameters were reported for the latter. Finally, recovery and recrystallization kinetics are described via Estrin–Mecking and Bergstrom, and Avrami kinetics, respectively.

High Temperature Deformation of Inconel 718Plus™

Since its introduction in 2003, alloy 718Plus™ spurred a lot of interest owing to its increased maximum service temperature over conventional Inconel 718 (704°C vs 650°C), good formability and weldability together with its moderate cost. Understanding the high temperature deformation characteristics and microstructural evolution is still of interest to many. It is known that the service performance and hot-flow behavior of this alloy is a strong function of the microstructure, particularly the grain size. To develop precise microstructure evolution models and foresee the final microstructure, it is important to understand how and under which forming conditions softening and precipitation processes occur concurrently. In this work, the softening behavior, its mechanisms and the precipitation characteristics of 718Plus™ were investigated in two parallel studies. While cylindrical compression tests were employed to observe the hot-flow behavior, the precipitation behavior and other microstructural phenomena such as particle coarsening were tracked via hardness measurements. A PTT diagram was reported and modeling of the flow curves via hyperbolic sine model were discussed in the light of the PTT behavior. Both “apparent” approach and “physically based” approach are implemented and two different sets of parameters were reported for the latter. Finally, recovery and recrystallization kinetics are described via Estrin-Mecking and Bergstrom, and Avrami kinetics, respectively.