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12 pages, 3142 KiB

Open AccessArticle

Facile Synthesis of MXene/MnO₂ Nanocomposites for Efficient Removal of Radionuclide Uranium

by Ling Wang and Yi-Lin Liu

Crystals 2023, 13(5), 804; https://doi.org/10.3390/cryst13050804 - 11 May 2023

Cited by 3 | Viewed by 1275

The efficient removal of radionuclide uranium is crucial for sustainable nuclear energy and achieving a zero-carbon loop. In this study, we synthesized MXene/MnO₂ nanocomposites and evaluated their ability to adsorb and reduce uranium. The results showed that the nanocomposites achieved a uranium [...] Read more.

The efficient removal of radionuclide uranium is crucial for sustainable nuclear energy and achieving a zero-carbon loop. In this study, we synthesized MXene/MnO₂ nanocomposites and evaluated their ability to adsorb and reduce uranium. The results showed that the nanocomposites achieved a uranium removal rate of 99% and an adsorption capacity of 696 mg/g. Adsorption experiments were conducted under different conditions, including pH, cation, anion, and humic acid, and the uranium removal rate by the composite remained high at 91%, 70%, and 60% under the influence of pH = 4.97, 1.0 mM CaCl₂, and 20 mg/L humic acid, respectively. The XRD and SEM analyses revealed that the uranium element was removed by the reduction and fixation of the composite material. These findings indicate that the MXene/MnO₂ composite is an effective adsorption cleaning agent for the purification of radioactive nuclear wastewater, which has significant implications for pollution control. Full article

(This article belongs to the Special Issue Feature Paper in "Materials for Energy Applications" 2022–2023)

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12 pages, 2788 KiB

Open AccessArticle

Inelastic Neutron Scattering Study of Phonon Dispersion Relation in Higher Manganese Silicides

by Randy Belanger, James Patrick Clancy, Sheetal Jain, Zahra Yamani, Yu-Chih Tseng and Young-June Kim

Crystals 2023, 13(5), 741; https://doi.org/10.3390/cryst13050741 - 28 Apr 2023

Cited by 1 | Viewed by 2217

Abstract

We report inelastic neutron scattering (INS) measurements of the phonon dispersion relation in higher manganese silicides (HMSs). A large ingot of HMS is synthesized using a slow cooling method, which is found to have Mn

_{15}

Si

_{26}

as the primary phase. The [...] Read more.

We report inelastic neutron scattering (INS) measurements of the phonon dispersion relation in higher manganese silicides (HMSs). A large ingot of HMS is synthesized using a slow cooling method, which is found to have Mn

_{15}

Si

_{26}

as the primary phase. The sample is composed of highly oriented crystallites as confirmed by a neutron pole-figure study and thermal conductivity data. Our INS results are mostly consistent with earlier experimental and theoretical phonon studies in HMS, including the presence of a low-lying twisting mode. However, some discrepancies are also observed. Most notably, a 5 meV gap at the zone center and the softer dispersion relation of the low-lying twisting mode. We discuss the potential origins of these observations and their implications for the thermal properties of HMS. Full article

(This article belongs to the Special Issue Feature Paper in "Materials for Energy Applications" 2022–2023)

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12 pages, 4187 KiB

Open AccessArticle

Deep-Blue Organic Light-Emitting Diodes Employed Traditional Hole Transporting Material as Emitter for 31-Inch 4K Flexible Display

by Yan Xue, Qiong Nie, Xin Hou, Baolei Wang, Yanbo Chen, Yu Zhang and Lijuan Xiang

Crystals 2023, 13(4), 687; https://doi.org/10.3390/cryst13040687 - 17 Apr 2023

Cited by 1 | Viewed by 1304

Abstract

High-efficiency deep-blue organic light-emitting diodes (OLEDs) play a crucial role in realizing ultra-high-definition (UHD) flat-panel displays and reducing power consumption. Generally, most reported OLEDs with a Commission Internationale de L’Eclairage (CIE) y coordinate < 0.06 are achieved by traditional fluorescent deep-blue emitters. However, [...] Read more.

High-efficiency deep-blue organic light-emitting diodes (OLEDs) play a crucial role in realizing ultra-high-definition (UHD) flat-panel displays and reducing power consumption. Generally, most reported OLEDs with a Commission Internationale de L’Eclairage (CIE) y coordinate < 0.06 are achieved by traditional fluorescent deep-blue emitters. However, it is challenging to obtain deep-blue fluorescent OLEDs with a high external quantum efficiency (EQE) (reaching the theoretical limit of 5%). In this work, we have successfully employed a hole-transporting material for an emitter, which can increase the efficiency in deep-blue OLEDs. The device employed with the proposed hole-transporting material exhibits deep-blue emission peaks at 427.0 nm with CIE coordinates of (0.155, 0.051), a turn-on voltage (Von) of 4.5 V, and an EQE of 4.5%. The performance of the OLED can be improved by 5.0% by optimizing the device structure. Finally, the flexible display when using the OLED devices exhibited a high image quality. Full article

(This article belongs to the Special Issue Feature Paper in "Materials for Energy Applications" 2022–2023)

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12 pages, 5571 KiB

Open AccessArticle

Effect of Substrate Temperature on Variations in the Structural and Optical Properties of Cu₂O Thin Films Deposited via RF Magnetron Sputtering

by Jun-A Kim, Jung-Hwan Park, Sang-Geon Park, Chang-Sik Son, Young-Guk Son and Dong-Hyun Hwang

Crystals 2023, 13(4), 643; https://doi.org/10.3390/cryst13040643 - 09 Apr 2023

Cited by 2 | Viewed by 1776

Abstract

In the present study, Cu₂O films were deposited on a glass substrate via RF (radio frequency) magnetron sputtering under substrate temperature conditions that ranged from room temperature (RT, 25 °C) to 400 °C. The structural, compositional, and optical properties of the [...] Read more.

In the present study, Cu₂O films were deposited on a glass substrate via RF (radio frequency) magnetron sputtering under substrate temperature conditions that ranged from room temperature (RT, 25 °C) to 400 °C. The structural, compositional, and optical properties of the Cu₂O films were analyzed in relation to the experimental variables by applying various measurement methods. The substrate temperature was a crucial factor in shaping the structural, compositional, and optical properties of the Cu₂O films that were synthesized via RF-magnetron sputtering. Our findings revealed that the Cu₂O films exhibited a cubic structure, which was confirmed by XRD analysis. Specifically, the (111) and (200) planes showed different trends with respect to the substrate temperature. The intensity of the (111) peak increased at 250 °C, and above 300 °C, the preferred orientation of the (111) plane was maintained. The grain size, which was determined via FE-SEM, displayed a positive correlation with the substrate temperature. Additionally, XPS analysis revealed that the binding energy (BE) of the Cu₂O film sputtered at 400 °C was similar to that which was previously reported. Notably, the as-grown Cu₂O film demonstrated the highest transmittance (15.9%) in the visible region, which decreased with increasing substrate temperature. Furthermore, the energy band gap (E_g) of the Cu₂O films remained constant (2.51 eV) at low substrate temperatures (25 °C to 200 °C) but exhibited a slight increase at higher temperatures, reaching 2.57 eV at 400 °C. Full article

(This article belongs to the Special Issue Feature Paper in "Materials for Energy Applications" 2022–2023)

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11 pages, 2920 KiB

Open AccessArticle

Interlayer Investigations of GaN Heterostructures Integrated into Silicon Substrates by Surface Activated Bonding

by Shi Zhou, Shun Wan, Bo Zou, Yanping Yang, Huarui Sun, Yan Zhou and Jianbo Liang

Crystals 2023, 13(2), 217; https://doi.org/10.3390/cryst13020217 - 24 Jan 2023

Cited by 1 | Viewed by 1694

Abstract

Thinning the buffer layer thickness between the GaN epilayer and Si substrate without introducing large residual stress is persistently desired for GaN-on-Si devices to promote their thermal budgets and low-cost, multifunctional applications. In this work, the GaN-on-Si heterostructures were directly bonded at room [...] Read more.

Thinning the buffer layer thickness between the GaN epilayer and Si substrate without introducing large residual stress is persistently desired for GaN-on-Si devices to promote their thermal budgets and low-cost, multifunctional applications. In this work, the GaN-on-Si heterostructures were directly bonded at room temperature by surface activated bonding (SAB) and the therein residual stress states were investigated by confocal micro-Raman. The effects of thermal annealing process on the residual stress and interfacial microstructure in SAB fabricated GaN-on-Si heterostructures were also systematically investigated by in situ micro-Raman and transmission electron microscopy. It was found that a significant relaxation and a more uniform stress distribution was obtained in SAB bonded GaN-on-Si heterostructure in comparison with that of MOCVD grown sample; however, with increasing annealing temperature, the residual stresses at the SAB bonded GaN layer and Si layer evolute monotonically in different trends. The main reason can be ascribed to the amorphous layer formed at the bonding interface, which played a critical stress relaxation role and transformed into a much thinner crystallized interlayer without any observable structural defects after 1000 °C annealing. Full article

(This article belongs to the Special Issue Feature Paper in "Materials for Energy Applications" 2022–2023)

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22 pages, 3997 KiB

Open AccessArticle

Adsorption of Orange G Dye on Hydrophobic Activated Bentonite from Aqueous Solution

by Zohra Taibi, Kahina Bentaleb, Zohra Bouberka, Christel Pierlot, Maxence Vandewalle, Christophe Volkringer, Philippe Supiot and Ulrich Maschke

Crystals 2023, 13(2), 211; https://doi.org/10.3390/cryst13020211 - 24 Jan 2023

Cited by 3 | Viewed by 1556

Abstract

This report focusses on the modification of physical structure and chemical properties of a bentonite clay from the Hammam Boughrara region of the Maghnia district in western Algeria to maximize its adsorption capacity. The purified bentonite clay (called B) was modified, either by [...] Read more.

This report focusses on the modification of physical structure and chemical properties of a bentonite clay from the Hammam Boughrara region of the Maghnia district in western Algeria to maximize its adsorption capacity. The purified bentonite clay (called B) was modified, either by acid activation with 1M sulfuric acid (B-Act), or by intercalation with the cationic surfactant cetytrimethyl ammonium bromide (CTAB), applying a cation exchange capacity (CEC) of 100% (called B-CTAB). Modification of B was also introduced by combining these two steps consecutively, i.e., at first acid activation of B, followed by intercalation with CTAB (B-Act-CTAB). The B-Act-CTAB was obtained by H₂SO₄ (1M) acid activation, followed by co-adsorption of CTAB with 100% and 300% of the CEC of B-Act as precursor. In particular, a strong increase of surface area and pore volume of the modified bentonites was observed for B-Act (469.83 m²/g and 0.401 cm³g⁻¹), B-Act-CTAB100 (267.72 m²/g and 0.316 cm³ g⁻¹) and B-Act-CTAB300 (111.15 m²/g and 0.171 cm³g⁻¹), compared to B (31.79 m²/g and 0.074 cm³ g⁻¹) and B-CTAB (3.79 m²/g and 0.034 cm³ g⁻¹), respectively. The bentonite-based adsorbents were then used to evaluate the removal efficiency of an organic molecule, the azo dye Orange G (OG), as a model for a Persistent Organic Pollutant. Freundlich, Langmuir and Sips (Langmuir–Freundlich) models were applied to analyze equilibrium isotherms, showing a good correlation between experimental data and the Freundlich model. A good agreement was obtained between experimentally obtained kinetic adsorption data and the pseudo-second-order model, allowing to evaluate rate constants. B-Act-CTAB300 can be applied as a low-cost material for removal of azo dyes, since its adsorption capacity towards OG (102.80 mg/g) exceeds largely that of B-CTAB (31.49 mg/g) and B-Act-CTAB100 (12.77 mg/g). Full article

(This article belongs to the Special Issue Feature Paper in "Materials for Energy Applications" 2022–2023)

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14 pages, 3422 KiB

Open AccessArticle

Photocatalytic Dye Decomposition over CaMnO_3−δ and Pr_0.5Ca_0.5MnO₃: A Combined XPS and DFT Study

by Majid Ebrahimizadeh Abrishami, Mojtaba Mohammadi and Mohsen Sotoudeh

Crystals 2022, 12(12), 1728; https://doi.org/10.3390/cryst12121728 - 28 Nov 2022

Cited by 4 | Viewed by 1361

Abstract

In the field of environmental sustainability, the development of highly efficient photocatalytic under a wide wavelength range with band engineering is regarded as a promising strategy to enhance photocatalytic dye degradation. Here, we report on CaMnO_3−δ and Pr_0.5Ca_0.5MnO [...] Read more.

In the field of environmental sustainability, the development of highly efficient photocatalytic under a wide wavelength range with band engineering is regarded as a promising strategy to enhance photocatalytic dye degradation. Here, we report on CaMnO_3−δ and Pr_0.5Ca_0.5MnO₃ perovskite materials prepared by a sol-gel combustion method. From X-ray photoelectron spectroscopy (XPS), the particle surfaces of both compounds are oxygen deficient, while the surface hydroxyl and carbonyl groups’ adsorption on the surface of Pr_0.5Ca_0.5MnO₃ particles is more pronounced. FT-FIR spectroscopy has been used to investigate the covalent bonds and oxygen vacancy characteristics. Photocatalytic activities were investigated by the degradation of methylene blue and methyl orange under UV light. It was observed that both dye molecules are more degraded over CaMnO_3−δ. The underlying mechanisms behind the photoexcitation and degradation process are established via the Spin-polarized Density Functional Theory (DFT). Full article

(This article belongs to the Special Issue Feature Paper in "Materials for Energy Applications" 2022–2023)

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21 pages, 5018 KiB

Open AccessEditor’s ChoiceArticle

Multiscale Simulations for Defect-Controlled Processing of Group IV Materials

by Gaetano Calogero, Ioannis Deretzis, Giuseppe Fisicaro, Manuel Kollmuß, Francesco La Via, Salvatore F. Lombardo, Michael Schöler, Peter J. Wellmann and Antonino La Magna

Crystals 2022, 12(12), 1701; https://doi.org/10.3390/cryst12121701 - 24 Nov 2022

Cited by 3 | Viewed by 1990

Abstract

Multiscale approaches for the simulation of materials processing are becoming essential to the industrialization of future nanotechnologies, as they allow for a reduction in production costs and an enhancement of devices and applications. Their integration as modules of “digital twins”, i.e., a combined [...] Read more.

Multiscale approaches for the simulation of materials processing are becoming essential to the industrialization of future nanotechnologies, as they allow for a reduction in production costs and an enhancement of devices and applications. Their integration as modules of “digital twins”, i.e., a combined sequence of predictive chemical–physical simulations and trained black-box techniques, should ideally complement the real sequence of processes throughout all development and production stages, starting from the growth of materials, their functional manipulation and finally their integration in nano-devices. To achieve this framework, computational implementations at different space and time scales are necessary, ranging from the atomistic to the macro-scale. In this paper, we propose a general paradigm for the industrially driven computational modeling of materials by deploying a multiscale methodology based on physical–chemical simulations bridging macro, meso and atomic scale. We demonstrate its general applicability by studying two completely different processing examples, i.e., the growth of group IV crystals through physical vapor deposition and their thermal treatment through pulsed laser annealing. We indicate the suitable formalisms, as well as the advantages and critical issues associated with each scale, and show how numerical methods for the solution of the models could be coupled to achieve a complete and effective virtualization of the process. By connecting the process parameters to atomic scale modifications such as lattice defects or faceting, we highlight how a digital twin module can gain intrinsic predictivity far from the pre-assessed training conditions of black-box “Virtual Metrology” techniques. Full article

(This article belongs to the Special Issue Feature Paper in "Materials for Energy Applications" 2022–2023)

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21 pages, 4396 KiB

Open AccessArticle

Predicting the Crystal Structure and Lattice Parameters of the Perovskite Materials via Different Machine Learning Models Based on Basic Atom Properties

by Sams Jarin, Yufan Yuan, Mingxing Zhang, Mingwei Hu, Masud Rana, Sen Wang and Ruth Knibbe

Crystals 2022, 12(11), 1570; https://doi.org/10.3390/cryst12111570 - 03 Nov 2022

Cited by 8 | Viewed by 3305

Abstract

Perovskite materials have high potential for the renewable energy sources such as solar PV cells, fuel cells, etc. Different structural distortions such as crystal structure and lattice parameters have a critical impact on the determination of the perovskite’s structure strength, stability, and overall [...] Read more.

Perovskite materials have high potential for the renewable energy sources such as solar PV cells, fuel cells, etc. Different structural distortions such as crystal structure and lattice parameters have a critical impact on the determination of the perovskite’s structure strength, stability, and overall performance of the materials in the applications. To improve the perovskite performance and accelerate the prediction of different structural distortions, few ML models have been established to predict the type of crystal structures and their lattice parameters using the basic atom characteristics of the perovskite materials. In this work, different ML models such as random forest (RF), support vector machine (SVM), neural network (NN), and genetic algorithm (GA) supported neural network (GA-NN) have been established, whereas support vector regression (SVR) and genetic algorithm-supported support vector regression (GA-SVR) models have been assessed for the prediction of the lattice parameters. The prediction model accuracy for the crystal structure classification is almost 88% in average for GA-NN whereas for the lattice constants regression model GA-SVR model gives ~95% in average which can be further improved by accumulating more robust datasets into the database. These ML models can be used as an alternative process to accelerate the development of finding out new perovskite material by providing valuable insight for the behaviours of the perovskite materials. Full article

(This article belongs to the Special Issue Feature Paper in "Materials for Energy Applications" 2022–2023)

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12 pages, 2387 KiB

Open AccessArticle

Study of the Thermal Properties and Lattice Disorder Effects in CdTe–Based Crystals: CdBeTe, CdMnTe, and CdZnTe

by Diksha Singh, Karol Strzałkowski, Ali Abouais and Amine Alaoui-Belghiti

Crystals 2022, 12(11), 1555; https://doi.org/10.3390/cryst12111555 - 31 Oct 2022

Cited by 5 | Viewed by 1550

Abstract

Mixed semiconductor ternary crystals were grown using the Bridgman–Stockbarger method. This is a high–temperature and high–pressure crystal growth method. Cd_1–xBe_xTe crystals were grown in the range of composition 0 < x < 0.1, such as 0.00, 0.01, 0.03, 0.05, [...] Read more.

Mixed semiconductor ternary crystals were grown using the Bridgman–Stockbarger method. This is a high–temperature and high–pressure crystal growth method. Cd_1–xBe_xTe crystals were grown in the range of composition 0 < x < 0.1, such as 0.00, 0.01, 0.03, 0.05, and 0.1. The main goal of this paper was to compare the thermal properties of CdBeTe with previously grown CdMnTe and CdZnTe–mixed ternary crystals. The photopyroelectric technique was applied to examine the thermal properties. The thermal diffusivity and effusivity values were obtained after testing all the samples, and the thermal conductivity was calculated then. As such, a complete thermal characterization of the crystals was carried out. For further characterization, the thermal conductivity versus composition was checked by applying the Sadao Adachi model. Thanks to that, we were able to determine the total thermal resistivity of the crystals and the additional resistivity which arises from the lattice disorder. As such, the disorder effects arising from substituting the native atom with a foreign one were characterized for all crystals. We were looking for the best substitution of the Cd atom in the CdTe matrix based on the compounds’ thermal properties. It turned out that Zn and Mn introduce a similar disorder, with Be being the highest one. Full article

(This article belongs to the Special Issue Feature Paper in "Materials for Energy Applications" 2022–2023)

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7 pages, 6356 KiB

Open AccessArticle

Laser Terahertz Emission Microscope for Imaging Grain Heterogeneity: A Case Study of CH₃NH₃PbI₃ Perovskite Semiconductors

by Zhaoyu Liu, Liang Luo, Joongmok Park, Richard H. J. Kim, Zhaoning Song, Deniz Turan, Mona Jarrahi, Yanfa Yan and Jigang Wang

Crystals 2022, 12(10), 1462; https://doi.org/10.3390/cryst12101462 - 17 Oct 2022

Cited by 1 | Viewed by 1495

Abstract

Strong terahertz (THz) emission from the methylammonium lead iodide (MAPbI₃) perovskite semiconductors has been observed following above-bandgap photoexcitation, yet local THz responses of crystalline microstructures are absent. We implement laser THz emission microscope (LTEM), yet-to-be applied to the perovskite semiconductors, as [...] Read more.

Strong terahertz (THz) emission from the methylammonium lead iodide (MAPbI₃) perovskite semiconductors has been observed following above-bandgap photoexcitation, yet local THz responses of crystalline microstructures are absent. We implement laser THz emission microscope (LTEM), yet-to-be applied to the perovskite semiconductors, as a novel and complementary tool to evaluate the electronic and grain heterogeneity of MAPbI₃ thin films. Two MAPbI₃ samples with different grain sizes are studied. Using this approach, we show that the one with a larger grain size gives more uniform THz radiation. More significant spatial THz intensity fluctuation is observed for the sample with a smaller grain size. Full article

(This article belongs to the Special Issue Feature Paper in "Materials for Energy Applications" 2022–2023)

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Review

Jump to: Research

18 pages, 3335 KiB

Open AccessReview

Li-Rich Layered Oxides: Structure and Doping Strategies to Enable Co-Poor/Co-Free Cathodes for Li-Ion Batteries

by Laura Silvestri, Arcangelo Celeste, Mariarosaria Tuccillo and Sergio Brutti

Crystals 2023, 13(2), 204; https://doi.org/10.3390/cryst13020204 - 23 Jan 2023

Cited by 3 | Viewed by 3028

Abstract

Lithium-rich layered oxides (LRLO) are a wide class of innovative active materials used in positive electrodes in lithium-ion (LIB) and lithium–metal secondary batteries (LMB). LRLOs are over-stoichiometric layered oxides rich in lithium and manganese with a general formula Li_1+xTM_1−xO [...] Read more.

Lithium-rich layered oxides (LRLO) are a wide class of innovative active materials used in positive electrodes in lithium-ion (LIB) and lithium–metal secondary batteries (LMB). LRLOs are over-stoichiometric layered oxides rich in lithium and manganese with a general formula Li_1+xTM_1−xO₂, where TM is a blend of transition metals comprising Mn (main constituent), Ni, Co, Fe and others. Due to their very variable composition and extended defectivity, their structural identity is still debated among researchers, being likely an unresolved hybrid between a monoclinic (mC24) and a hexagonal lattice (hR12). Once casted in composite positive electrode films and assembled in LIBs or LMBs, LRLOs can deliver reversible specific capacities above 220–240 mAhg⁻¹, and thus they exceed any other available intercalation cathode material for LIBs, with mean working potential above 3.3–3.4 V vs Li for hundreds of cycles in liquid aprotic commercial electrodes. In this review, we critically outline the recent advancements in the fundamental understanding of the physical–chemical properties of LRLO as well as the most exciting innovations in their battery performance. We focus in particular on the elusive structural identity of these phases, on the complexity of the reaction mechanism in batteries, as well as on practical strategies to minimize or remove cobalt from the lattice while preserving its outstanding performance upon cycling. Full article

(This article belongs to the Special Issue Feature Paper in "Materials for Energy Applications" 2022–2023)

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