Inorganics

13 pages, 25374 KB

Open AccessArticle

Low-Temperature Formation of Aluminum Nitride Powder from Amorphous Aluminum Oxalate via Carbothermal Reduction

by Wenjing Tang, Yaling Yu, Zixuan Huang, Weijie Wang, Shaomin Lin, Ji Luo, Chenyang Zhang and Zhijie Zhang

Inorganics 2025, 13(10), 317; https://doi.org/10.3390/inorganics13100317 (registering DOI) - 25 Sep 2025

Abstract

Aluminum nitride (AlN) powder, a cornerstone material for advanced ceramics. This study examines the low-temperature formation of AlN crystals as well as their phase transformation by employing amorphous aluminum oxalate (AAO) as a novel precursor for carbothermal reduction, contrasting it with conventional aluminum [...] Read more.

Aluminum nitride (AlN) powder, a cornerstone material for advanced ceramics. This study examines the low-temperature formation of AlN crystals as well as their phase transformation by employing amorphous aluminum oxalate (AAO) as a novel precursor for carbothermal reduction, contrasting it with conventional aluminum hydroxide (Al(OH)₃). Through characterization using X-ray diffraction (XRD), scanning electron microscopy (SEM), High-Resolution Transmission Electron Microscope (HRTEM), ²⁷Al Magic-Angle Spinning Nuclear Magnetic Resonance (²⁷Al-MAS-NMR) energy-dispersive spectroscopy (EDS), and Fourier-transform infrared spectroscopy (FTIR), we unraveled the phase evolution pathways and the formation of AlN. Key findings reveal striking differences between the two precursors. When Al(OH)₃ was used, no AlN phase was detected at 1350 °C, and even at 1500 °C, the AlN obtained with significant residual alumina impurities. In contrast, the AAO precursor demonstrated exceptional efficiency: nano-sized α-Al₂O₃ formed at 1050 °C, followed by the emergence of AlN phases at 1200 °C, ultimately gaining the pure AlN at 1500 °C. The phase transformation sequence—Al(OH)₃ → γ-Al₂O₃ (950 °C) → (α-Al₂O₃ + δ-Al₂O₃) (1050 °C) → (AlN + α-Al₂O₃) (1200 °C~ 1350 °C) → AlN (≥1500 °C)—highlights the pivotal role of nano-sized α-Al₂O₃ in enabling low-temperature nano AlN synthesis. By leveraging the unique properties of AAO, we offer a transformative strategy for synthesizing nano-sized AlN powders, with profound implications for the ceramics industry. Full article

(This article belongs to the Special Issue New Advances into Nanostructured Oxides, 3rd Edition)

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10 pages, 2681 KB

Open AccessArticle

Theoretical Study on the Ortho–Para Reactivity Difference in Ru-Catalyzed Amination of Aminopyridines via η⁶-Coordination: Role of Meisenheimer Intermediate Coordination Ability

by Cheng Wang, Shuo-Qing Zhang and Xin Hong

Inorganics 2025, 13(10), 316; https://doi.org/10.3390/inorganics13100316 - 25 Sep 2025

Abstract

η⁶-Coordination catalysis has emerged as an effective strategy for activating electron-rich (hetero)arenes toward nucleophilic substitution. Recent experimental studies on Ru(II)-catalyzed amination of aminopyridines revealed a striking ortho–para reactivity difference, with ortho-substituted substrates undergoing efficient amination while para analogs [...] Read more.

η⁶-Coordination catalysis has emerged as an effective strategy for activating electron-rich (hetero)arenes toward nucleophilic substitution. Recent experimental studies on Ru(II)-catalyzed amination of aminopyridines revealed a striking ortho–para reactivity difference, with ortho-substituted substrates undergoing efficient amination while para analogs are unreactive under identical conditions. Herein, we present a density functional theory investigation to elucidate the origin of this divergence. Computed free-energy profiles show that both substitution patterns follow a similar stepwise mechanism involving Ru-bound Meisenheimer intermediates and a proton-transfer relay, with C–N bond cleavage/rearomatization as the rate-determining step. However, the para pathway suffers from a substantially higher overall barrier, originating from the intrinsically less stable Meisenheimer intermediates. Energy decomposition analysis indicates that the decisive factor is weaker orbital interaction between the CpRu(II) fragment and the para-substituted Meisenheimer intermediate, whereas electrostatics and dispersion play negligible roles. These findings highlight the key role of metal–substrate orbital interactions in stabilizing dearomatized intermediates, offering mechanistic insights for rational design of η⁶-coordination catalysis with enhanced reactivity and selectivity. Full article

(This article belongs to the Special Issue Transition Metal Catalysts: Design, Synthesis and Applications)

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19 pages, 2194 KB

Open AccessArticle

Hidden Magnetic-Field-Induced Multiferroic States in A-Site-Ordered Quadruple Perovskites RMn₃Ni₂Mn₂O₁₂: Dielectric Studies

by Alexei A. Belik, Ran Liu and Kazunari Yamaura

Inorganics 2025, 13(10), 315; https://doi.org/10.3390/inorganics13100315 - 25 Sep 2025

Abstract

The appearance of spin-induced ferroelectric polarization in the so-called type-II multiferroic materials has received a lot of attention. The nature and mechanisms of such polarization were intensively studied using perovskite rare-earth manganites, RMnO₃, as model systems. Later, multiferroic properties were discovered [...] Read more.

The appearance of spin-induced ferroelectric polarization in the so-called type-II multiferroic materials has received a lot of attention. The nature and mechanisms of such polarization were intensively studied using perovskite rare-earth manganites, RMnO₃, as model systems. Later, multiferroic properties were discovered in some RFeO₃ perovskites and possibly in some RCrO₃ perovskites. However, R₂NiMnO₆ double perovskites have ferromagnetic structures that do not break the inversion symmetry. It was found recently that more complex magnetic structures are realized in A-site-ordered quadruple perovskites, RMn₃Ni₂Mn₂O₁₂. Therefore, they have the potential to be multiferroics. In this work, dielectric properties in magnetic fields up to 9 T were investigated for such perovskites as RMn₃Ni₂Mn₂O₁₂ with R = Ce to Ho and for BiMn₃Ni₂Mn₂O₁₂. The samples with R = Bi, Ce, and Nd showed no dielectric anomalies at all magnetic fields, and the dielectric constant decreases with decreasing temperature. The samples with R = Sm to Ho showed qualitatively different behavior when the dielectric constant started increasing with decreasing temperature below certain temperatures close to the magnetic ordering temperatures, T_N. This difference could suggest different magnetic ground states. The samples with R = Eu, Dy, and Ho still showed no anomalies on the dielectric constant. On the other hand, peaks emerged at T_N on the dielectric constant in the R = Sm sample from about 2 T up to the maximum available field of 9 T. The Gd sample showed peaks on dielectric constant at T_N between about 1 T and 7 T. Transition temperatures increase with increasing magnetic fields for R = Sm and decrease for R = Gd. These findings suggest the presence of magnetic-field-induced multiferroic states in the R = Sm and Gd samples with intermediate ionic radii. Dielectric properties at different magnetic fields are also reported for Lu₂NiMnO₆ for comparison. Full article

(This article belongs to the Special Issue Recent Progress in Perovskites)

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13 pages, 2257 KB

Open AccessArticle

Scalable High-Yield Exfoliation of Hydrophilic h-BN Nanosheets via Gallium Intercalation

by Sungsan Kang, Dahun Kim, Seonyou Park, Sung-Tae Lee, John Hong, Sanghyo Lee and Sangyeon Pak

Inorganics 2025, 13(10), 314; https://doi.org/10.3390/inorganics13100314 - 25 Sep 2025

Abstract

Hexagonal boron nitride (h-BN) possesses a unique combination of a wide bandgap, high thermal conductivity, and chemical inertness, making it a key insulating and thermal management material for advanced electronics and nanocomposites. However, its intrinsic hydrophobicity and strong interlayer van der Waals forces [...] Read more.

Hexagonal boron nitride (h-BN) possesses a unique combination of a wide bandgap, high thermal conductivity, and chemical inertness, making it a key insulating and thermal management material for advanced electronics and nanocomposites. However, its intrinsic hydrophobicity and strong interlayer van der Waals forces severely limit exfoliation efficiency and dispersion stability, particularly in scalable liquid-phase processes. Here, we report a synergistic exfoliation strategy that integrates acid-induced hydroxylation with gallium (Ga) intercalation to achieve high-yield (>80%) production of ultrathin (<4 nm) hydrophilic h-BN nanosheets. Hydroxylation introduces abundant -OH groups, expanding interlayer spacing and significantly increasing surface polarity, while Ga intercalation leverages its native Ga₂O₃ shell to form strong interfacial interactions with hydroxylated basal planes. This oxide-mediated adhesion facilitates efficient layer separation under mild sonication, yielding nanosheets with well-preserved lateral dimensions and exceptional dispersion stability in polar solvents. Comprehensive characterization confirms the sequential chemical and structural modifications, revealing the crucial roles of hydroxylation-induced activation and Ga₂O₃ assisted wettability enhancement. This combined chemical activation–soft metallic intercalation approach provides a scalable, solution-processable route to high-quality h-BN nanosheets, opening new opportunities for their integration into dielectric, thermal interface, and multifunctional composite systems. Full article

(This article belongs to the Special Issue Physicochemical Characterization of 2D Materials)

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18 pages, 3204 KB

Open AccessArticle

Calcium Phosphate Ceramic Powders Prepared from Mechanochemically Activated Precursors

by Kostadinka Sezanova, Yordanka Tuparova, Pavletta Shestakova, Pavel Markov, Daniela Kovacheva and Diana Rabadjieva

Inorganics 2025, 13(10), 313; https://doi.org/10.3390/inorganics13100313 - 24 Sep 2025

Abstract

The chemical and structural similarity of calcium orthophosphates to hard tissues in the human body makes them suitable as biomaterials for bone implants, cements, injection systems, etc., for bone regeneration and reconstruction. Tetracalcium phosphate (Ca₄(PO₄)₂O, TTCP) is [...] Read more.

The chemical and structural similarity of calcium orthophosphates to hard tissues in the human body makes them suitable as biomaterials for bone implants, cements, injection systems, etc., for bone regeneration and reconstruction. Tetracalcium phosphate (Ca₄(PO₄)₂O, TTCP) is a promising component for such biomaterials due to its high calcium content and alkaline nature. The former makes it suitable for promoting mineralization, while the latter supports neutralization of the acidic environment, helping to prevent inflammation and improve the biocompatibility of the materials. However, it is the least used calcium orthophosphate due to the difficulties in its synthesis. This study examines the effect of high-energy mechanochemical activation on the phase evolution, particle morphology, and thermal behaviour of equimolar mixtures of Ca(OH)₂ and CaHPO₄, with the aim of optimizing precursor conditions for the synthesis of (TTCP)-rich ceramic materials. The results demonstrate that mechanochemical activation effectively induces structural disorder, promotes the formation of amorphous and nanocrystalline phases, and facilitates subsequent phase transitions upon calcination. The combined use of solid-state NMR, XRD, TEM, and thermal analysis provides a comprehensive understanding of the transformation pathways. Ultimately, 24 h of activation under the experimental conditions was identified as optimal for producing a precursor with a favorable phase composition for obtaining TTCP-rich ceramic materials after calcination at 1350 °C. Full article

(This article belongs to the Special Issue Featured Papers in Inorganic Materials 2025)

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19 pages, 4073 KB

Open AccessArticle

Single-Atom Cobalt-Doped 2D Graphene: Electronic Design for Multifunctional Applications in Environmental Remediation and Energy Storage

by Zhongkai Huang, Yue Zhang, Chunjiang Li, Liang Deng, Bo Song, Maolin Bo, Chuang Yao, Haolin Lu and Guankui Long

Inorganics 2025, 13(10), 312; https://doi.org/10.3390/inorganics13100312 - 24 Sep 2025

Abstract

Through atomic-scale characterization of a single cobalt atom anchored in a pyridinic N₃ vacancy of graphene (Co-N₃-gra), this study computationally explores three interconnected functionalities mediated by cobalt’s electronic configuration. Quantum-confined molecular prototypes extend prior bulk models, achieving a competitive catalytic [...] Read more.

Through atomic-scale characterization of a single cobalt atom anchored in a pyridinic N₃ vacancy of graphene (Co-N₃-gra), this study computationally explores three interconnected functionalities mediated by cobalt’s electronic configuration. Quantum-confined molecular prototypes extend prior bulk models, achieving a competitive catalytic activity for CO oxidation via Langmuir–Hinshelwood pathways with a 0.85 eV barrier. These molecular prototypes’ discrete energy states facilitate single-electron transistor operation, enabling sensitive detection of NO, NO₂, SO₂, and CO₂ through adsorption-induced conductance modulation. When applied to lithium–sulfur batteries using periodic Co-N₃-gra, cobalt sites enhance polysulfide conversion kinetics and suppress the shuttle effect, with the Li₂S₂→Li₂S step identified as the rate-limiting process. Density functional simulations provide atomic-scale physicochemical characterization of Co-N₃-gra, revealing how defect engineering in 2D materials modulates electronic structures for multifunctional applications. Full article

(This article belongs to the Special Issue Physicochemical Characterization of 2D Materials)

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11 pages, 578 KB

Open AccessArticle

Biophysical Characterization of Membrane Interactions of 3-Hydroxy-4-Pyridinone Vanadium Complexes: Insights for Antidiabetic Applications

by Luísa M. P. F. Amaral, Tânia Moniz and Maria Rangel

Inorganics 2025, 13(10), 311; https://doi.org/10.3390/inorganics13100311 - 24 Sep 2025

Abstract

The development of metallopharmaceuticals for diabetes treatment has garnered increasing attention due to its insulin-mimetic properties, particularly in vanadium complexes. In this study, we report the biophysical evaluation of a series of 3-hydroxy-4-pyridinone (3,4-HPO) vanadium complexes, designed to improve lipophilicity and biological cytocompatibility. [...] Read more.

The development of metallopharmaceuticals for diabetes treatment has garnered increasing attention due to its insulin-mimetic properties, particularly in vanadium complexes. In this study, we report the biophysical evaluation of a series of 3-hydroxy-4-pyridinone (3,4-HPO) vanadium complexes, designed to improve lipophilicity and biological cytocompatibility. Dynamic light scattering (DLS) was used to get insight on the size of the liposomes and Differential Scanning Calorimetry (DSC) was employed to investigate the interaction of these complexes with model biological membranes made from dimyristoylphosphatidylcholine (DMPC) unilamellar liposomes. The thermotropic phase behavior of the lipid bilayers was analyzed in the presence of vanadium complexes. The results reveal that the alkyl chain length of the 3,4-HPO ligands modulates membrane interaction of the respective vanadium compounds, with specific complexes inducing significant shifts in the lipid phase transition temperature (T_m), suggesting alterations in membrane fluidity and packing. These findings provide valuable insight into the membrane affinity of vanadium-based drug candidates and support their potential as next-generation antidiabetic agents. Full article

(This article belongs to the Special Issue New Trends in Vanadium Chemistry, Biochemistry, and Medicinal Chemistry, 2nd Edition)

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Inorganics, Volume 13, Issue 10 (October 2025) – 7 articles

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