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  • 1
    Online Resource
    Online Resource
    MDPI AG ; 2021
    In:  Materials Vol. 14, No. 2 ( 2021-01-19), p. 471-
    In: Materials, MDPI AG, Vol. 14, No. 2 ( 2021-01-19), p. 471-
    Abstract: Modeling of thermodynamic properties, like heat capacities for stoichiometric solids, includes the treatment of different sources of data which may be inconsistent and diverse. In this work, an approach based on the covariance matrix adaptation evolution strategy (CMA-ES) is proposed and described as an alternative method for data treatment and fitting with the support of data source dependent weight factors and physical constraints. This is applied to a Gibb’s Free Energy stoichiometric model for different magnesium sulfate hydrates by means of the NASA9 polynomial. Its behavior is proved by: (i) The comparison of the model to other standard methods for different heat capacity data, yielding a more plausible curve at high temperature ranges; (ii) the comparison of the fitted heat capacity values of MgSO4·7H2O against DSC measurements, resulting in a mean relative error of a 0.7% and a normalized root mean square deviation of 1.1%; and (iii) comparing the Van’t Hoff and proposed Stoichiometric model vapor-solid equilibrium curves to different literature data for MgSO4·7H2O, MgSO4·6H2O, and MgSO4·1H2O, resulting in similar equilibrium values, especially for MgSO4·7H2O and MgSO4·6H2O. The results show good agreement with the employed data and confirm this method as a viable alternative for fitting complex physically constrained data sets, while being a potential approach for automatic data fitting of substance data.
    Type of Medium: Online Resource
    ISSN: 1996-1944
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2487261-1
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  • 2
    In: Catalysis Today, Elsevier BV, Vol. 417 ( 2023-05), p. 113838-
    Type of Medium: Online Resource
    ISSN: 0920-5861
    RVK:
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2023
    detail.hit.zdb_id: 2012626-8
    detail.hit.zdb_id: 56797-8
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  • 3
    In: Crystals, MDPI AG, Vol. 13, No. 6 ( 2023-05-24), p. 863-
    Abstract: The control and prediction of morphological changes in annealed void microstructures is an essential and powerful tool for different semiconductor applications, for example, as part of the production of pressure sensors, resonators, or other silicon structures. In this work, with a focus on the void shape evolution of silicon, a novel simulation approach based on the level-set method is introduced to predict the continuous transformation of initial etched nano/micro-sized cylindrical structures at different annealing conditions. The developed model, which is based on a surface diffusion formulation and built in COMSOL Multiphysics® (Stockholm, Sweden), is introduced and compared to experimental literature data as well as with other analytical approaches. Some advantages of the presented model include the capability of simulating other materials under similar phenomena, the simulation of any possible initial geometry, and the visualization of intermediate steps during the annealing processing.
    Type of Medium: Online Resource
    ISSN: 2073-4352
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2661516-2
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  • 4
    Online Resource
    Online Resource
    MDPI AG ; 2023
    In:  Minerals Vol. 13, No. 10 ( 2023-09-22), p. 1238-
    In: Minerals, MDPI AG, Vol. 13, No. 10 ( 2023-09-22), p. 1238-
    Abstract: Frequency response (FR) analysis allows the characterization of gas diffusion occurring within a porous solid system. The shape of the pressure response curves obtained after a volume modulation in the reactor gives essential information about the gas adsorption and desorption properties of the porous material, e.g., zeolites, which is in contact with a certain gas environment, as well as information about the transport phenomena such as diffusion. In this work, a simulation model developed in COMSOL Multiphysics® is introduced to reproduce the experimental behavior of the tested solid/gas systems. This approach covers, for the first time, a coupling of computational fluid dynamics (CFD), porous media flow, and a customized mass adsorption/desorption function to simulate the behavior of real frequency response systems. The simulation results are compared to experimental data obtained from the interaction of propane in MFI zeolites as well as additional data from the literature to evaluate the model validity. Furthermore, a small variation study of the effect of simulation parameters such as the mass of the sample, bed porosity, or geometry is performed and analyzed. The essential advantage of this model with respect to other analytical approaches is to observe the spatial pressure and adsorption distribution (along with other local effects) of the gas within the porous material. Thus, local environments can be visualized, and non-idealities can, therefore, be detected in contrast to the general integral simulation approach.
    Type of Medium: Online Resource
    ISSN: 2075-163X
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2655947-X
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  • 5
    Online Resource
    Online Resource
    MDPI AG ; 2023
    In:  Minerals Vol. 13, No. 10 ( 2023-09-23), p. 1244-
    In: Minerals, MDPI AG, Vol. 13, No. 10 ( 2023-09-23), p. 1244-
    Abstract: Transient uptake curves for propane gas in a bed of HZSM-5 using a volumetric frequency response setup (batch system) were obtained. Thereby, a perturbation, such as a change in volume, was applied to the solid/gas system, and the resulting change in pressure was detected. Two cases of mass transfer limitations (bed diffusion control and micropore diffusion control) were compared, and it was concluded that, in the presented case, micropore diffusion is the rate-determining process. The obtained micropore diffusion coefficient for propane in HZSM-5 was, on average, about 1.2 × 10−10 m2 g−1, which is in good agreement with other frequency response studies shown by literature data. The homemade setup and the modeling presented in this work serve as the basis for ongoing numerical simulations.
    Type of Medium: Online Resource
    ISSN: 2075-163X
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2655947-X
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  • 6
    Online Resource
    Online Resource
    MDPI AG ; 2021
    In:  Mathematical and Computational Applications Vol. 26, No. 2 ( 2021-06-01), p. 43-
    In: Mathematical and Computational Applications, MDPI AG, Vol. 26, No. 2 ( 2021-06-01), p. 43-
    Abstract: The prediction and control of the transformation of void structures with high-temperature processing is a critical area in many engineering applications. In this work, focused on the void shape evolution of silicon, a novel algebraic model for the calculation of final equilibrium structures from initial void cylindrical trenches, driven by surface diffusion, is introduced. This algebraic model provides a simple and fast way to calculate expressions to predict the final geometrical characteristics, based on linear perturbation analysis. The obtained results are similar to most compared literature data, especially, to those in which a final transformation is reached. Additionally, the model can be applied in any materials affected by the surface diffusion. With such a model, the calculation of void structure design points is greatly simplified not only in the semiconductors field but in other engineering fields where surface diffusion phenomenon is studied.
    Type of Medium: Online Resource
    ISSN: 2297-8747
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2880856-3
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